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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/28897-8.txt b/28897-8.txt new file mode 100644 index 0000000..dc040fc --- /dev/null +++ b/28897-8.txt @@ -0,0 +1,24571 @@ +The Project Gutenberg eBook, The Variation of Animals and Plants Under +Domestication, Volume II (of 2), by Charles Darwin + + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: The Variation of Animals and Plants Under Domestication, Volume II (of 2) + + +Author: Charles Darwin + + + +Release Date: May 20, 2009 [eBook #28897] + +Language: English + +Character set encoding: ISO-8859-1 + + +***START OF THE PROJECT GUTENBERG EBOOK THE VARIATION OF ANIMALS AND +PLANTS UNDER DOMESTICATION, VOLUME II (OF 2)*** + + +E-text prepared by Steven Gibbs, Keith Edkins, and the Project Gutenberg +Online Distributed Proofreading Team (http://www.pgdp.net) + + + +Transcriber's note: + + A few typographical errors have been corrected: they are listed + at the end of the text. The Errata on page viii, which were in + the original book, have been applied to this e-text. + + Page numbers within curly brackets (such as {iii} and {27} + have been included so that the reader might use the index. + + + + + +THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION. + +by + +CHARLES DARWIN, M.A., F.R.S., &c. + +IN TWO VOLUMES.--VOL. II. + +With Illustrations. + + + + + + + +LONDON: +John Murray, Albemarle Street. +1868. + +The right of Translation is reserved. + +London: Printed by William Clowes and Sons, Stamford Street, and Charing +Cross. + + + + +{iii} + +CONTENTS OF VOLUME II. + +CHAPTER XII. + +INHERITANCE. + +WONDERFUL NATURE OF INHERITANCE--PEDIGREES OF OUR DOMESTICATED +ANIMALS--INHERITANCE NOT DUE TO CHANCE--TRIFLING CHARACTERS +INHERITED--DISEASES INHERITED--PECULIARITIES IN THE EYE INHERITED--DISEASES +IN THE HORSE--LONGEVITY AND VIGOUR--ASYMMETRICAL DEVIATIONS OF +STRUCTURE--POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY DIGITS AFTER +AMPUTATION--CASES OF SEVERAL CHILDREN SIMILARLY AFFECTED FROM NON-AFFECTED +PARENTS--WEAK AND FLUCTUATING INHERITANCE: IN WEEPING TREES, IN DWARFNESS, +COLOUR OF FRUIT AND FLOWERS, COLOUR OF HORSES--NON-INHERITANCE IN CERTAIN +CASES--INHERITANCE OF STRUCTURE AND HABITS OVERBORNE BY HOSTILE CONDITIONS +OF LIFE, BY INCESSANTLY RECURRING VARIABILITY, AND BY REVERSION--CONCLUSION +... Page 1 + +CHAPTER XIII. + +INHERITANCE _continued_--REVERSION OR ATAVISM. + +DIFFERENT FORMS OF REVERSION--IN PURE OR UNCROSSED BREEDS, AS IN PIGEONS, +FOWLS, HORNLESS CATTLE AND SHEEP, IN CULTIVATED PLANTS--REVERSION IN FERAL +ANIMALS AND PLANTS--REVERSION IN CROSSED VARIETIES AND SPECIES--REVERSION +THROUGH BUD-PROPAGATION, AND BY SEGMENTS IN THE SAME FLOWER OR FRUIT--IN +DIFFERENT PARTS OF THE BODY IN THE SAME ANIMAL--THE ACT OF CROSSING A +DIRECT CAUSE OF REVERSION, VARIOUS CASES OF, WITH INSTINCTS--OTHER +PROXIMATE CAUSES OF REVERSION--LATENT CHARACTERS--SECONDARY SEXUAL +CHARACTERS--UNEQUAL DEVELOPMENT OF THE TWO SIDES OF THE BODY--APPEARANCE +WITH ADVANCING AGE OF CHARACTERS DERIVED FROM A CROSS--THE GERM WITH ALL +ITS LATENT CHARACTERS A WONDERFUL OBJECT--MONSTROSITIES--PELORIC FLOWERS +DUE IN SOME CASES TO REVERSION ... Page 28 + +CHAPTER XIV. + +INHERITANCE _continued_--FIXEDNESS OF CHARACTER--PREPOTENCY--SEXUAL +LIMITATION--CORRESPONDENCE OF AGE. + +FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO ANTIQUITY OF +INHERITANCE--PREPOTENCY OF TRANSMISSION IN INDIVIDUALS OF THE SAME FAMILY, +IN CROSSED BREEDS AND SPECIES; OFTEN STRONGER IN ONE SEX THAN THE OTHER; +SOMETIMES DUE TO THE SAME CHARACTER BEING PRESENT AND VISIBLE IN ONE BREED +AND LATENT IN THE OTHER--INHERITANCE AS LIMITED BY SEX--NEWLY-ACQUIRED +CHARACTERS IN OUR DOMESTICATED ANIMALS OFTEN TRANSMITTED BY ONE SEX ALONE, +SOMETIMES LOST BY ONE SEX ALONE--INHERITANCE AT CORRESPONDING PERIODS OF +LIFE--THE IMPORTANCE OF THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS +EXHIBITED IN DOMESTICATED ANIMALS; AS EXHIBITED IN THE APPEARANCE AND +DISAPPEARANCE OF INHERITED DISEASES; SOMETIMES SUPERVENING EARLIER IN THE +CHILD THAN IN THE PARENT--SUMMARY OF THE THREE PRECEDING CHAPTERS ... Page +62 + +{iv} + +CHAPTER XV. + +ON CROSSING. + +FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED BREEDS--WHEN +THE NUMBERS OF TWO COMMINGLING BREEDS ARE UNEQUAL, ONE ABSORBS THE +OTHER--THE RATE OF ABSORPTION DETERMINED BY PREPOTENCY OF TRANSMISSION, BY +THE CONDITIONS OF LIFE, AND BY NATURAL SELECTION--ALL ORGANIC BEINGS +OCCASIONALLY INTERCROSS; APPARENT EXCEPTIONS--ON CERTAIN CHARACTERS +INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE WHICH HAVE SUDDENLY +APPEARED IN THE INDIVIDUAL--ON THE MODIFICATION OF OLD RACES, AND THE +FORMATION OF NEW RACES, BY CROSSING--SOME CROSSED RACES HAVE BRED TRUE FROM +THEIR FIRST PRODUCTION--ON THE CROSSING OF DISTINCT SPECIES IN RELATION TO +THE FORMATION OF DOMESTIC RACES ... Page 85 + +CHAPTER XVI. + +CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES--INFLUENCE OF +DOMESTICATION ON FERTILITY. + +DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN CROSSED--VARIOUS +CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING AND SEXUAL +PREFERENCE--VARIETIES OF WHEAT SAID TO BE STERILE WHEN CROSSED--VARIETIES +OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND TOBACCO, RENDERED IN +SOME DEGREE MUTUALLY STERILE--DOMESTICATION ELIMINATES THE TENDENCY TO +STERILITY NATURAL TO SPECIES WHEN CROSSED--ON THE INCREASED FERTILITY OF +UNCROSSED ANIMALS AND PLANTS FROM DOMESTICATION AND CULTIVATION ... Page +100 + +CHAPTER XVII. + +ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL EFFECTS OF CLOSE +INTERBREEDING. + +DEFINITION OF CLOSE INTERBREEDING--AUGMENTATION OF MORBID +TENDENCIES--GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, AND +ON THE EVIL EFFECTS FROM CLOSE INTERBREEDING--CATTLE, CLOSELY INTERBRED; +HALF-WILD CATTLE LONG KEPT IN THE SAME +PARKS--SHEEP--FALLOW-DEER--DOGS--RABBITS--PIGS--MAN, ORIGIN OF HIS +ABHORRENCE OF INCESTUOUS MARRIAGES--FOWLS--PIGEONS--HIVE-BEES--PLANTS, +GENERAL CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING--MELONS, +FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND FOREST-TREES--ON THE INCREASED SIZE +OF HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY--ON CERTAIN PLANTS +WHICH EITHER NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, BUT ARE FERTILE, +BOTH ON THE MALE AND FEMALE SIDE, WHEN CROSSED WITH DISTINCT INDIVIDUALS +EITHER OF THE SAME OR ANOTHER SPECIES--CONCLUSION ... Page 114 + +{v} + +CHAPTER XVIII. + +ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED CONDITIONS OF LIFE: +STERILITY FROM VARIOUS CAUSES. + +ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE CONDITIONS OF +LIFE--STERILITY FROM CHANGED CONDITIONS, IN ANIMALS, IN THEIR NATIVE +COUNTRY AND IN MENAGERIES--MAMMALS, BIRDS, AND INSECTS--LOSS OF SECONDARY +SEXUAL CHARACTERS AND OF INSTINCTS--CAUSES OF STERILITY--STERILITY OF +DOMESTICATED ANIMALS FROM CHANGED CONDITIONS--SEXUAL INCOMPATIBILITY OF +INDIVIDUAL ANIMALS--STERILITY OF PLANTS FROM CHANGED CONDITIONS OF +LIFE--CONTABESCENCE OF THE ANTHERS--MONSTROSITIES AS A CAUSE OF +STERILITY--DOUBLE FLOWERS--SEEDLESS FRUIT--STERILITY FROM THE EXCESSIVE +DEVELOPMENT OF THE ORGANS OF VEGETATION--FROM LONG-CONTINUED PROPAGATION BY +BUDS--INCIPIENT STERILITY THE PRIMARY CAUSE OF DOUBLE FLOWERS AND SEEDLESS +FRUIT ... Page 145 + +CHAPTER XIX. + +SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS ON HYBRIDISM. + +ON THE EFFECTS OF CROSSING--THE INFLUENCE OF DOMESTICATION ON +FERTILITY--CLOSE INTERBREEDING--GOOD AND EVIL RESULTS FROM CHANGED +CONDITIONS OF LIFE--VARIETIES WHEN CROSSED NOT INVARIABLY FERTILE--ON THE +DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND VARIETIES--CONCLUSIONS +WITH RESPECT TO HYBRIDISM--LIGHT THROWN ON HYBRIDISM BY THE ILLEGITIMATE +PROGENY OF DIMORPHIC AND TRIMORPHIC PLANTS--STERILITY OF CROSSED SPECIES +DUE TO DIFFERENCES CONFINED TO THE REPRODUCTIVE SYSTEM--NOT ACCUMULATED +THROUGH NATURAL SELECTION--REASONS WHY DOMESTIC VARIETIES ARE NOT MUTUALLY +STERILE--TOO MUCH STRESS HAS BEEN LAID ON THE DIFFERENCE IN FERTILITY +BETWEEN CROSSED SPECIES AND CROSSED VARIETIES--CONCLUSION ... Page 173 + +CHAPTER XX. + +SELECTION BY MAN. + +SELECTION A DIFFICULT ART--METHODICAL, UNCONSCIOUS, AND NATURAL +SELECTION--RESULTS OF METHODICAL SELECTION--CARE TAKEN IN +SELECTION--SELECTION WITH PLANTS--SELECTION CARRIED ON BY THE ANCIENTS, AND +BY SEMI-CIVILISED PEOPLE--UNIMPORTANT CHARACTERS OFTEN ATTENDED +TO--UNCONSCIOUS SELECTION--AS CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR +DOMESTICATED ANIMALS CHANGED THROUGH THE ACTION OF UNCONSCIOUS +SELECTION--INFLUENCE OF DIFFERENT BREEDERS ON THE SAME SUB-VARIETY--PLANTS +AS AFFECTED BY UNCONSCIOUS SELECTION--EFFECTS OF SELECTION AS SHOWN BY THE +GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST VALUED BY MAN ... Page 192 + +{vi} + +CHAPTER XXI. + +SELECTION--_continued._ + +NATURAL SELECTION AS AFFECTING DOMESTIC PRODUCTIONS--CHARACTERS WHICH +APPEAR OF TRIFLING VALUE OFTEN OF REAL IMPORTANCE--CIRCUMSTANCES FAVOURABLE +TO SELECTION BY MAN--FACILITY IN PREVENTING CROSSES, AND THE NATURE OF THE +CONDITIONS--CLOSE ATTENTION AND PERSEVERANCE INDISPENSABLE--THE PRODUCTION +OF A LARGE NUMBER OF INDIVIDUALS ESPECIALLY FAVOURABLE--WHEN NO SELECTION +IS APPLIED, DISTINCT RACES ARE NOT FORMED--HIGHLY-BRED ANIMALS LIABLE TO +DEGENERATION--TENDENCY IN MAN TO CARRY THE SELECTION OF EACH CHARACTER TO +AN EXTREME POINT, LEADING TO DIVERGENCE OF CHARACTER, RARELY TO +CONVERGENCE--CHARACTERS CONTINUING TO VARY IN THE SAME DIRECTION IN WHICH +THEY HAVE ALREADY VARIED--DIVERGENCE OF CHARACTER, WITH THE EXTINCTION OF +INTERMEDIATE VARIETIES, LEADS TO DISTINCTNESS IN OUR DOMESTIC RACES--LIMIT +TO THE POWER OF SELECTION--LAPSE OF TIME IMPORTANT--MANNER IN WHICH +DOMESTIC RACES HAVE ORIGINATED--SUMMARY ... Page 224 + +CHAPTER XXII. + +CAUSES OF VARIABILITY. + +VARIABILITY DOES NOT NECESSARILY ACCOMPANY REPRODUCTION--CAUSES ASSIGNED BY +VARIOUS AUTHORS--INDIVIDUAL DIFFERENCES--VARIABILITY OF EVERY KIND DUE TO +CHANGED CONDITIONS OF LIFE--ON THE NATURE OF SUCH CHANGES--CLIMATE, FOOD, +EXCESS OF NUTRIMENT--SLIGHT CHANGES SUFFICIENT--EFFECTS OF GRAFTING ON THE +VARIABILITY OF SEEDLING-TREES--DOMESTIC PRODUCTIONS BECOME HABITUATED TO +CHANGED CONDITIONS--ON THE ACCUMULATIVE ACTION OF CHANGED CONDITIONS--CLOSE +INTERBREEDING AND THE IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE +VARIABILITY--CROSSING AS A CAUSE OF THE APPEARANCE OF NEW +CHARACTERS--VARIABILITY FROM THE COMMINGLING OF CHARACTERS AND FROM +REVERSION--ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH EITHER +DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE VARIABILITY +... Page 250 + +CHAPTER XXIII. + +DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS OF LIFE. + +SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE ACTION OF CHANGED +CONDITIONS, IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND IN THE STATE OF THE +TISSUES--LOCAL DISEASES--CONSPICUOUS MODIFICATIONS FROM CHANGED CLIMATE OR +FOOD, ETC.--PLUMAGE OF BIRDS AFFECTED BY PECULIAR NUTRIMENT, AND BY THE +INOCULATION OF POISON--LAND-SHELLS--MODIFICATIONS OF ORGANIC BEINGS IN A +STATE OF NATURE THROUGH THE DEFINITE ACTION OF EXTERNAL +CONDITIONS--COMPARISON OF AMERICAN AND EUROPEAN TREES--GALLS--EFFECTS OF +PARASITIC FUNGI--CONSIDERATIONS OPPOSED TO THE BELIEF IN THE POTENT +INFLUENCE OF CHANGED EXTERNAL CONDITIONS--PARALLEL SERIES OF +VARIETIES--AMOUNT OF VARIATION DOES NOT CORRESPOND WITH THE DEGREE OF +CHANGE IN THE CONDITIONS--BUD-VARIATION--MONSTROSITIES PRODUCED BY +UNNATURAL TREATMENT--SUMMARY ... Page 271 + +{vii} + +CHAPTER XXIV. + +LAWS OF VARIATION--USE AND DISUSE, ETC. + +NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE ORGANISATION--ON THE +EFFECTS OF THE INCREASED USE AND DISUSE OF ORGANS--CHANGED HABITS OF +LIFE--ACCLIMATISATION WITH ANIMALS AND PLANTS--VARIOUS METHODS BY WHICH +THIS CAN BE EFFECTED--ARRESTS OF DEVELOPMENT--RUDIMENTARY ORGANS ... Page +293 + +CHAPTER XXV. + +LAWS OF VARIATION, _continued_--CORRELATED VARIABILITY. + +EXPLANATION OF TERM--CORRELATION AS CONNECTED WITH +DEVELOPMENT--MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED SIZE +OF PARTS--CORRELATED VARIATION OF HOMOLOGOUS PARTS--FEATHERED FEET IN BIRDS +ASSUMING THE STRUCTURE OF THE WINGS--CORRELATION BETWEEN THE HEAD AND THE +EXTREMITIES--BETWEEN THE SKIN AND DERMAL APPENDAGES--BETWEEN THE ORGANS OF +SIGHT AND HEARING--CORRELATED MODIFICATIONS IN THE ORGANS OF +PLANTS--CORRELATED MONSTROSITIES--CORRELATION BETWEEN THE SKULL AND +EARS--SKULL AND CREST OF FEATHERS--SKULL AND HORNS--CORRELATION OF GROWTH +COMPLICATED BY THE ACCUMULATED EFFECTS OF NATURAL SELECTION--COLOUR AS +CORRELATED WITH CONSTITUTIONAL PECULIARITIES ... Page 319 + +CHAPTER XXVI. + +LAWS OF VARIATION, _continued_--SUMMARY. + +ON THE AFFINITY AND COHESION OF HOMOLOGOUS PARTS--ON THE VARIABILITY OF +MULTIPLE AND HOMOLOGOUS PARTS--COMPENSATION OF GROWTH--MECHANICAL +PRESSURE--RELATIVE POSITION OF FLOWERS WITH RESPECT TO THE AXIS OF THE +PLANT, AND OF SEEDS IN THE CAPSULE, AS INDUCING VARIATION--ANALOGOUS OR +PARALLEL VARIETIES--SUMMARY OF THE THREE LAST CHAPTERS ... Page 339 + +CHAPTER XXVII. + +PROVISIONAL HYPOTHESIS OF PANGENESIS. + +PRELIMINARY REMARKS--FIRST PART:--THE FACTS TO BE CONNECTED UNDER A SINGLE +POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION--THE DIRECT ACTION +OF THE MALE ELEMENT ON THE FEMALE--DEVELOPMENT--THE FUNCTIONAL INDEPENDENCE +OF THE ELEMENTS OR UNITS OF THE BODY--VARIABILITY--INHERITANCE--REVERSION. + +SECOND PART:--STATEMENT OF THE HYPOTHESIS--HOW FAR THE NECESSARY +ASSUMPTIONS ARE IMPROBABLE--EXPLANATION BY AID OF THE HYPOTHESIS OF THE +SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST PART--CONCLUSION ... Page +357 + +{viii} + +CHAPTER XXVIII. + +CONCLUDING REMARKS. + +DOMESTICATION--NATURE AND CAUSES OF VARIABILITY--SELECTION--DIVERGENCE AND +DISTINCTNESS OF CHARACTER--EXTINCTION OF RACES--CIRCUMSTANCES FAVOURABLE TO +SELECTION BY MAN--ANTIQUITY OF CERTAIN RACES--THE QUESTION WHETHER EACH +PARTICULAR VARIATION HAS BEEN SPECIALLY PREORDAINED ... Page 405 + +INDEX ... Page 433 + + * * * * * + +ERRATA. + + Vol. II., pp. 18, 232, 258, for Cratægus oxycantha, read oxyacantha. + ,, p. 98, 8 lines from top, for Dianthus armoria read armeria. + ,, ,, 156, 15 lines from bottom, for Casuarinus read Casuarius. + ,, ,, ,, 4 lines from bottom, for Grus cineria read cinerea. + ,, ,, 168, 11 lines from top, for Oesculus read Æsculus. + ,, ,, 300, 3 lines from top, for anastomising read anastomosing. + ,, ,, ,, foot-note, for Birckell read Brickell. + + * * * * * + + +{1} THE + +VARIATION OF ANIMALS AND PLANTS + +UNDER DOMESTICATION. + + * * * * * + +CHAPTER XII. + +INHERITANCE. + + WONDERFUL NATURE OF INHERITANCE--PEDIGREES OF OUR DOMESTICATED + ANIMALS--INHERITANCE NOT DUE TO CHANCE--TRIFLING CHARACTERS + INHERITED--DISEASES INHERITED--PECULIARITIES IN THE EYE + INHERITED--DISEASES IN THE HORSE--LONGEVITY AND VIGOUR--ASYMMETRICAL + DEVIATIONS OF STRUCTURE--POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY + DIGITS AFTER AMPUTATION--CASES OF SEVERAL CHILDREN SIMILARLY AFFECTED + FROM NON-AFFECTED PARENTS--WEAK AND FLUCTUATING INHERITANCE: IN WEEPING + TREES, IN DWARFNESS, COLOUR OF FRUIT AND FLOWERS, COLOUR OF + HORSES--NON-INHERITANCE IN CERTAIN CASES--INHERITANCE OF STRUCTURE AND + HABITS OVERBORNE BY HOSTILE CONDITIONS OF LIFE, BY INCESSANTLY + RECURRING VARIABILITY, AND BY REVERSION--CONCLUSION. + +The subject of inheritance is an immense one, and has been treated by many +authors. One work alone, 'De l'Hérédité Naturelle,' by Dr. Prosper Lucas, +runs to the length of 1562 pages. We must confine ourselves to certain +points which have an important bearing on the general subject of variation, +both with domestic and natural productions. It is obvious that a variation +which is not inherited throws no light on the derivation of species, nor is +of any service to man, except in the case of perennial plants, which can be +propagated by buds. + +If animals and plants had never been domesticated, and wild ones alone had +been observed, we should probably never have heard the saying, that "like +begets like." The proposition would have been as self-evident, as that all +the buds on the same tree are alike, though neither proposition is strictly +true. For, as has often been remarked, probably no two individuals are {2} +identically the same. All wild animals recognise each other, which shows +that there is some difference between them; and when the eye is well +practised, the shepherd knows each sheep, and man can distinguish a +fellow-man out of millions on millions of other men. Some authors have gone +so far as to maintain that the production of slight differences is as much +a necessary function of the powers of generation, as the production of +offspring like their parents. This view, as we shall see in a future +chapter, is not theoretically probable, though practically it holds good. +The saying that "like begets like" has in fact arisen from the perfect +confidence felt by breeders, that a superior or inferior animal will +generally reproduce its kind; but this very superiority or inferiority +shows that the individual in question has departed slightly from its type. + +The whole subject of inheritance is wonderful. When a new character arises, +whatever its nature may be, it generally tends to be inherited, at least in +a temporary and sometimes in a most persistent manner. What can be more +wonderful than that some trifling peculiarity, not primordially attached to +the species, should be transmitted through the male or female sexual cells, +which are so minute as not to be visible to the naked eye, and afterwards +through the incessant changes of a long course of development, undergone +either in the womb or in the egg, and ultimately appear in the offspring +when mature, or even when quite old, as in the case of certain diseases? Or +again, what can be more wonderful than the well-ascertained fact that the +minute ovule of a good milking cow will produce a male, from whom a cell, +in union with an ovule, will produce a female, and she, when mature, will +have large mammary glands, yielding an abundant supply of milk, and even +milk of a particular quality? Nevertheless, the real subject of surprise +is, as Sir H. Holland has well remarked,[1] not that a character should be +inherited, but that any should ever fail to be inherited. In a future +chapter, devoted to an hypothesis which I have termed pangenesis, an +attempt will be made to show the means by which characters of all kinds are +transmitted from generation to generation. + +{3} + +Some writers,[2] who have not attended to natural history, have attempted +to show that the force of inheritance has been much exaggerated. The +breeders of animals would smile at such simplicity; and if they +condescended to make any answer, might ask what would be the chance of +winning a prize if two inferior animals were paired together? They might +ask whether the half-wild Arabs were led by theoretical notions to keep +pedigrees of their horses? Why have pedigrees been scrupulously kept and +published of the Shorthorn cattle, and more recently of the Hereford breed? +Is it an illusion that these recently improved animals safely transmit +their excellent qualities even when crossed with other breeds? have the +Shorthorns, without good reason, been purchased at immense prices and +exported to almost every quarter of the globe, a thousand guineas having +been given for a bull? With greyhounds pedigrees have likewise been kept, +and the names of such dogs, as Snowball, Major, &c., are as well known to +coursers as those of Eclipse and Herod on the turf. Even with the Gamecock +pedigrees of famous strains were formerly kept, and extended back for a +century. With pigs, the Yorkshire and Cumberland breeders "preserve and +print pedigrees;" and to show how such highly-bred animals are valued, I +may mention that Mr. Brown, who won all the first prizes for small breeds +at Birmingham in 1850, sold a young sow and boar of his breed to Lord Ducie +for 43 guineas; the sow alone was afterwards sold to the Rev. F. Thursby +for 65 guineas; who writes, "she paid me very well, having sold her produce +for 300_l_., and having now four breeding sows from her."[3] Hard cash paid +down, over and over again, is an excellent test of inherited superiority. +In fact, the whole art of breeding, from which such great results have been +attained during the present century, depends on the inheritance of each +small {4} detail of structure. But inheritance is not certain; for if it +were, the breeder's art[4] would be reduced to a certainty, and there would +be little scope left for all that skill and perseverance shown by the men +who have left an enduring monument of their success in the present state of +our domesticated animals. + +It is hardly possible, within a moderate compass, to impress on the mind of +those who have not attended to the subject, the full conviction of the +force of inheritance which is slowly acquired by rearing animals, by +studying the many treatises which have been published on the various +domestic animals, and by conversing with breeders. I will select a few +facts of the kind, which, as far as I can judge, have most influenced my +own mind. With man and the domestic animals, certain peculiarities have +appeared in an individual, at rare intervals, or only once or twice in the +history of the world, but have reappeared in several of the children and +grandchildren. Thus Lambert, "the porcupine-man," whose skin was thickly +covered with warty projections, which were periodically moulted, had all +his six children and two grandsons similarly affected.[5] The face and body +being covered with long hair, accompanied by deficient teeth (to which I +shall hereafter refer), occurred in three successive generations in a +Siamese family; but this case is not unique, as a woman[6] with a +completely hairy face was exhibited in London in 1663, and another instance +has recently occurred. Colonel Hallam[7] has described a race of two-legged +pigs, "the hinder extremities being entirely wanting;" and this deficiency +was transmitted through three generations. In fact, all races presenting +any remarkable peculiarity, such as solid-hoofed swine, Mauchamp sheep, +niata cattle, &c., are instances of the long-continued inheritance of rare +deviations of structure. + +When we reflect that certain extraordinary peculiarities have {5} thus +appeared in a single individual out of many millions, all exposed in the +same country to the same general conditions of life, and, again, that the +same extraordinary peculiarity has sometimes appeared in individuals living +under widely different conditions of life, we are driven to conclude that +such peculiarities are not directly due to the action of the surrounding +conditions, but to unknown laws acting on the organisation or constitution +of the individual;--that their production stands in hardly closer relation +to the conditions than does life itself. If this be so, and the occurrence +of the same unusual character in the child and parent cannot be attributed +to both having been exposed to the same unusual conditions, then the +following problem is worth consideration, as showing that the result cannot +be due, as some authors have supposed, to mere coincidence, but must be +consequent on the members of the same family inheriting something in common +in their constitution. Let it be assumed that, in a large population, a +particular affection occurs on an average in one out of a million, so that +the _à priori_ chance that an individual taken at random will be so +affected is only one in a million. Let the population consist of sixty +millions, composed, we will assume, of ten million families, each +containing six members. On these data, Professor Stokes has calculated for +me that the odds will be no less than 8333 millions to 1 that in the ten +million families there will not be even a single family in which one parent +and two children will be affected by the peculiarity in question. But +numerous cases could be given, in which several children have been affected +by the same rare peculiarity with one of their parents; and in this case, +more especially if the grandchildren be included in the calculation, the +odds against mere coincidence become something prodigious, almost beyond +enumeration. + +In some respects the evidence of inheritance is more striking when we +consider the reappearance of trifling peculiarities. Dr. Hodgkin formerly +told me of an English family in which, for many generations, some members +had a single lock differently coloured from the rest of the hair. I knew an +Irish gentleman, who, on the right side of his head, had a small white lock +in the midst of his dark hair: he assured me that his grandmother had {6} a +similar lock on the same side, and his mother on the opposite side. But it +is superfluous to give instances; every shade of expression, which may +often be seen alike in parents and children, tells the same story. On what +a curious combination of corporeal structure, mental character, and +training, must handwriting depend! yet every one must have noted the +occasional close similarity of the handwriting in father and son, although +the father had not taught his son. A great collector of franks assured me +that in his collection there were several franks of father and son hardly +distinguishable except by their dates. Hofacker, in Germany, remarks on the +inheritance of handwriting; and it has even been asserted that English boys +when taught to write in France naturally cling to their English manner of +writing.[8] Gait, gestures, voice, and general bearing are all inherited, +as the illustrious Hunter and Sir A. Carlisle have insisted.[9] My father +communicated to me two or three striking instances, in one of which a man +died during the early infancy of his son, and my father, who did not see +this son until grown up and out of health, declared that it seemed to him +as if his old friend had risen from the grave, with all his highly peculiar +habits and manners. Peculiar manners pass into tricks, and several +instances could be given of their inheritance; as in the case, often +quoted, of the father who generally slept on his back, with his right leg +crossed over the left, and whose daughter, whilst an infant in the cradle, +followed exactly the same habit, though an attempt was made to cure +her.[10] I will give one instance which has fallen under my own +observation, and which is curious from being a trick associated with a +peculiar state of mind, namely, pleasurable emotion. A boy had the singular +habit, when pleased, of rapidly moving his fingers parallel to each other, +and, when much excited, of raising both hands, with the fingers still +moving, to the sides of his face on a level with the eyes; this boy, when +almost an old man, could still hardly resist this trick when much pleased, +but from its absurdity concealed it. He had eight children. Of these, a +girl, when {7} pleased, at the age of four and a half years, moved her +fingers in exactly the same way, and what is still odder, when much +excited, the raised both her hands, with her fingers still moving, to the +sides of her face, in exactly the same manner as her father had done, and +sometimes even still continued to do when alone. I never heard of any one +excepting this one man and his little daughter who had this strange habit; +and certainly imitation was in this instance out of the question. + +Some writers have doubted whether those complex mental attributes, on which +genius and talent depend, are inherited, even when both parents are thus +endowed. But he who will read Mr. Galton's able paper[11] on hereditary +talent will have his doubts allayed. + +Unfortunately it matters not, as far as inheritance is concerned, how +injurious a quality or structure may be if compatible with life. No one can +read the many treatises[12] on hereditary disease and doubt this. The +ancients were strongly of this opinion, or, as Ranchin expresses it, _Omnes +Græci, Arabes, et Latini in eo consentiunt_. A long catalogue could be +given of all sorts of inherited malformations and of predisposition to +various diseases. With gout, fifty per cent. of the cases observed in +hospital practice are, according to Dr. Garrod, inherited, and a greater +percentage in private practice. Every one knows how often insanity runs in +families, and some of the cases given by Mr. Sedgwick are awful,--as of a +surgeon, whose brother, father, and four paternal uncles were all insane, +the latter dying by suicide; of a Jew, whose father, mother, and six +brothers and sisters were all mad; and in some other cases several members +of the same family, during three or four successive generations, have +committed suicide. Striking instances {8} have been recorded of epilepsy, +consumption, asthma, stone in the bladder, cancer, profuse bleeding from +the slightest injuries, of the mother not giving milk, and of bad +parturition being inherited. In this latter respect I may mention an odd +case given by a good observer,[13] in which the fault lay in the offspring, +and not in the mother: in a part of Yorkshire the farmers continued to +select cattle with large hind-quarters, until they made a strain called +"Dutch-buttocked," and "the monstrous size of the buttocks of the calf was +frequently fatal to the cow, and numbers of cows were annually lost in +calving." + + Instead of giving numerous details on various inherited malformations + and diseases, I will confine myself to one organ, that which is the + most complex, delicate, and probably best-known in the human frame, + namely, the eye, with its accessory parts. To begin with the latter: I + have heard of a family in which parents and children were affected by + drooping eyelids, in so peculiar a manner, that they could not see + without throwing their heads backwards; and Sir A. Carlisle[14] + specifies a pendulous fold to the eyelids as inherited. "In a family," + says Sir H. Holland,[15] "where the father had a singular elongation of + the upper eyelid, seven or eight children were born with the same + deformity; two or three other children having it not." Many persons, as + I year from Mr. Paget, have two or three of the hairs in their eyebrows + (apparently corresponding with the vibrissæ of the lower animals) much + longer than the others; and even so trifling a peculiarity as this + certainly runs in families. + + With respect to the eye itself, the highest authority in England, Mr. + Bowman, has been so kind as to give me the following remarks on certain + inherited imperfections. First, hypermetropia, or morbidly long sight: + in this affection, the organ, instead of being spherical, is too flat + from front to back, and is often altogether too small, so that the + retina is brought too forward for the focus of the humours; + consequently a convex glass is required for clear vision of near + objects, and frequently even of distant ones. This state occurs + congenitally, or at a very early age, often in several children of the + same family, where one of the parents has presented it.[16] Secondly, + myopia, or short-sight, in which the eye is egg-shaped, and too long + from front to back; the retina in this case lies behind the focus, and + is therefore fitted to see distinctly only very near objects. This + condition is not commonly congenital, but comes on in youth, the + liability to it being well known to be transmissible from parent to + child. The change from the spherical to the ovoidal shape seems the + immediate {9} consequence of something like inflammation of the coats, + under which they yield, and there is ground for believing that it may + often originate in causes acting directly on the individual affected, + and may thenceforward become transmissible. When both parents are + myopic Mr. Bowman has observed the hereditary tendency in this + direction to be heightened, and some of the children to be myopic at an + earlier age or in a higher degree than their parents. Thirdly, + squinting is a familiar example of hereditary transmission: it is + frequently a result of such optical defects as have been above + mentioned; but the more primary and uncomplicated forms of it are also + sometimes in a marked degree transmitted in a family. Fourthly, + _Cataract_, or opacity of the crystalline lens, is commonly observed in + persons whose parents have been similarly affected, and often at an + earlier age in the children than in the parents. Occasionally more than + one child in a family is thus afflicted, one of whose parents or other + relation presents the senile form of the complaint. When cataract + affects several members of a family in the same generation, it is often + seen to commence at about the same age in each; _e.g._, in one family + several infants or young persons may suffer from it; in another, + several persons of middle age. Mr. Bowman also informs me that he has + occasionally seen, in several members of the same family, various + defects in either the right or left eye; and Mr. White Cooper has often + seen peculiarities of vision confined to one eye reappearing in the + same eye in the offspring.[17] + + The following cases are taken from an able paper by Mr. W. Sedgwick, + and from Dr. Prosper Lucas.[18] Amaurosis, either congenital or coming + on late in life, and causing total blindness, is often inherited; it + has been observed in three successive generations. Congenital absence + of the iris has likewise been transmitted for three generations, a + cleft-iris for four generations, being limited in this latter case to + the males of the family. Opacity of the cornea and congenital smallness + of the eyes have been inherited. Portal records a curious case, in + which a father and two sons were rendered blind, whenever the head was + bent downwards, apparently owing to the crystalline lens, with its + capsule, slipping through an unusually large pupil into the anterior + chamber of the eye. Day-blindness, or imperfect vision under a bright + light, is inherited, as is night-blindness, or an incapacity to see + except under a strong light: a case has been recorded, by M. Cunier, of + this latter defect having affected eighty-five members of the same + family during six generations. The singular incapacity of + distinguishing colours, which has been called _Daltonism_, is + notoriously hereditary, and has been traced through five generations, + in which it was confined to the female sex. + + With respect to the colour of the iris: deficiency of colouring matter + is well known to be hereditary in albinoes. The iris of one eye being + of a different colour from that of the other, and the iris being + spotted, are cases which have been inherited. Mr. Sedgwick gives, in + addition, on the {10} authority of Dr. Osborne,[19] the following + curious instance of strong inheritance: a family of sixteen sons and + five daughters all had eyes "resembling in miniature the markings on + the back of a tortoiseshell cat." The mother of this large family had + three sisters and a brother all similarly marked, and they derived this + peculiarity from their mother, who belonged to a family notorious for + transmitting it to their posterity. + + Finally, Dr. Lucas emphatically remarks that there is not one single + faculty of the eye which is not subject to anomalies; and not one which + is not subjected to the principle of inheritance. Mr. Bowman agrees + with the general truth of this proposition; which of course does not + imply that all malformations are necessarily inherited; this would not + even follow if both parents were affected by an anomaly which in most + cases was transmissible. + +Even if no single fact had been known with respect to the inheritance of +disease and malformations by man, the evidence would have been ample in the +case of the horse. And this might have been expected, as horses breed much +quicker than man, are matched with care, and are highly valued. I have +consulted many works, and the unanimity of the belief by veterinaries of +all nations in the transmission of various morbid tendencies is surprising. +Authors, who have had wide experience, give in detail many singular cases, +and assert that contracted feet, with the numerous contingent evils, of +ring-bones, curbs, splints, spavin, founder and weakness of the front legs, +roaring or broken and thick wind, melanosis, specific ophthalmia, and +blindness (the great French veterinary Hazard going so far as to say that a +blind race could soon be formed), crib-biting, jibbing, and ill-temper, are +all plainly hereditary. Youatt sums up by saying "there is scarcely a +malady to which the horse is subject which is not hereditary;" and M. +Bernard adds that the doctrine "that there is scarcely a disease which does +not run in the stock, is gaining new advocates every day."[20] So it {11} +is in regard to cattle, with consumption, good and bad teeth, fine skin, +&c. &c. But enough, and more than enough, has been said on disease. Andrew +Knight, from his own experience, asserts that disease is hereditary with +plants; and this assertion is endorsed by Lindley.[21] + +Seeing how hereditary evil qualities are, it is fortunate that good health, +vigour, and longevity are equally inherited. It was formerly a well-known +practice, when annuities were purchased to be received during the lifetime +of a nominee, to search out a person belonging to a family of which many +members had lived to extreme old age. As to the inheritance of vigour and +endurance, the English race-horse offers an excellent instance. Eclipse +begot 334, and King Herod 497 winners. A "cock-tail" is a horse not purely +bred, but with only one-eighth or one-sixteenth impure blood in his veins, +yet very few instances have ever occurred of such horses having won a great +race. They are sometimes as fleet for short distances as thoroughbreds, but +as Mr. Robson, the great trainer, asserts, they are deficient in wind, and +cannot keep up the pace. Mr. Lawrence also remarks, "perhaps no instance +has ever occurred of a three-part-bred horse saving his '_distance_' in +running two miles with thoroughbred racers." It has been stated by Cecil, +that when unknown horses, whose parents were not celebrated, have +unexpectedly won great races, as in the case of Priam, they can always be +proved to be descended on both sides, through many generations, from +first-rate ancestors. On the Continent, Baron Cameronn challenges, in a +German veterinary periodical, the opponents of the English race-horse, to +name one good horse on the Continent which has not some English race-blood +in his veins.[22] + +With respect to the transmission of the many slight, but {12} infinitely +diversified characters, by which the domestic races of animals and plants +are distinguished, nothing need be said; for the very existence of +persistent races proclaims the power of inheritance. + +A few special cases, however, deserve some consideration. It might have +been anticipated, that deviations from the law of symmetry would not have +been inherited. But Anderson[23] states that a rabbit produced in a litter +a young animal having only one ear; and from this animal a breed was formed +which steadily produced one-eared rabbits. He also mentions a bitch, with a +single leg deficient, and she produced several puppies with the same +deficiency. From Hofacker's account[24] it appears that a one-horned stag +was seen in 1781 in a forest in Germany, in 1788 two, and afterwards, from +year to year, many were observed with only one horn on the right side of +the head. A cow lost a horn by suppuration,[25] and she produced three +calves which had on the same side of the head, instead of a horn, a small +bony lump attached merely to the skin; but we here approach the doubtful +subject of inherited mutilations. A man who is left-handed, and a shell in +which the spire turns in the wrong direction, are departures from the +normal though a symmetrical condition, and they are well known to be +inherited. + + _Polydactylism._--Supernumerary fingers and toes are eminently liable, + as various authors have insisted, to transmission, but they are noticed + here chiefly on account of their occasional regrowth after amputation. + Polydactylism graduates[26] by multifarious steps from a mere cutaneous + appendage, not including any bone, to a double hand. But an additional + digit, supported on a metacarpal bone, and furnished with all the + proper muscles, nerves, and vessels, is sometimes so perfect, that it + escapes detection, unless the fingers are actually counted. + Occasionally there are several supernumerary digits; but usually only + one, making the total number six. This one may represent either a thumb + or finger, being attached to the inner or outer margin of the hand. + Generally, through the law of correlation, both hands and feet are + similarly affected. I have tabulated the cases recorded in various + works or privately communicated {13} to me, of forty-six persons with + extra digits on one or both hands and feet; if in each case all four + extremities had been similarly affected, the table would have shown a + total of ninety-two hands and ninety-two feet each with six digits. As + it is, seventy-three hands and seventy-five feet were thus affected. + This proves, in contradiction to the result arrived at by Dr. + Struthers,[27] that the hands are not more frequently affected than the + feet. + + The presence of more than five digits is a great anomaly, for this + number is not normally exceeded by any mammal, bird, or existing + reptile.[28] Nevertheless, supernumerary digits are strongly inherited; + they have been transmitted through five generations; and in some cases, + after disappearing for one, two, or even three generations, have + reappeared through reversion. These facts are rendered, as Professor + Huxley has observed, more remarkable from its being known in most cases + that the affected person had not married one similarly affected. In + such cases the child of the fifth generation would have only 1-32nd + part of the blood of his first sedigitated ancestor. Other cases are + rendered remarkable by the affection gathering force, as Dr. Struthers + has shown, in each generation, though in each the affected person had + married one not affected; moreover such additional digits are often + amputated soon after birth, and can seldom have been strengthened by + use. Dr. Struthers gives the following instance: in the first + generation an additional digit appeared on one hand; in the second, on + both hands; in the third, three brothers had both hands, and one of the + brothers a foot affected; and in the fourth generation all four limbs + were affected. Yet we must not over-estimate the force of inheritance. + Dr. Struthers asserts that cases of non-inheritance and of the first + appearance of additional digits in unaffected families are much more + frequent than cases of inheritance. Many other deviations of structure, + of a nature almost as anomalous as supernumerary digits, such as + deficient phalanges, thickened joints, crooked fingers, &c., are in + like manner strongly inherited, and are equally subject to intermission + with reversion, though in such cases there is no reason to suppose that + both parents had been similarly affected.[29] + + {14} + + Additional digits have been observed in negroes as well as in other + races of man, and in several of the lower animals. Six toes have been + described on the hind feet of the newt (_Salamandra cristata_), and, as + it is said, of the frog. It deserves notice from what follows, that the + six-toed newt, though adult, had preserved some of its larval + characters; for part of the hyoidal apparatus, which is properly + absorbed during the act of metamorphosis, was retained. In the dog, six + toes on the hinder feet have been transmitted through three + generations; and I have heard of a race of six-toed cats. In several + breeds of the fowl the hinder toe is double, and is generally + transmitted truly, as is well shown when Dorkings are crossed with + common four-toed breeds.[30] With animals which have properly less than + five digits, the number is sometimes increased to five, especially in + the front legs, though rarely carried beyond that number; but this is + due to the development of a digit already existing in a more or less + rudimentary state. Thus the dog has properly four toes behind, but in + the larger breeds a fifth toe is commonly, though not perfectly, + developed. Horses, which properly have one toe alone fully developed + with rudiments of the others, have been described with each foot + bearing two or three small separate hoofs: analogous facts have been + noticed with sheep, goats, and pigs.[31] + + The most interesting point with respect to supernumerary digits is + their occasional regrowth after amputation. Mr. White[32] describes a + child, three years old, with a thumb double from the first joint. He + removed the lesser thumb, which was furnished with a nail; but to his + astonishment it grew again, and reproduced a nail. The child was then + taken to an eminent London surgeon, and the newly-grown thumb was + wholly removed by its socket-joint, but again it grew and reproduced a + nail. Dr. Struthers mentions a case of partial regrowth of an + additional thumb, amputated when the child was three months old; and + the late Dr. Falconer communicated to me an analogous case which had + fallen under his own observation. A gentleman, who first called my + attention to this subject, has given me the following facts which + occurred in his own family. He himself, two brothers, and a sister were + born with an extra digit to each extremity. His parents were not + affected, and there was no tradition in the family, or in the village + in which the family had long resided, of any member having been thus + affected. Whilst a child, both additional toes, which were attached by + bones, were rudely cut off; but the stump of one grew again, and a + second operation was performed in his thirty-third year. + + {15} + + He has had fourteen children, of whom three have inherited additional + digits; and one of them, when about six weeks old, was operated on by + an eminent surgeon. The additional finger, which was attached by bone + to the outer side of the hand, was removed at the joint; the wound + healed, but immediately the digit began growing; and in about three + months' time the stump was removed for the second time by the root. But + it has since grown again, and is now fully a third of an inch in + length, including a bone; so that it will for the third time have to be + operated on. + + Now the normal digits in adult man and other mammals, in birds, and, as + I believe, in true reptiles, have no power of regrowth. The nearest + approach to this power is exhibited by the occasional reappearance in + man of imperfect nails on the stumps of his fingers after + amputation.[33] But man in his embryonic condition has a considerable + power of reproduction, for Sir J. Simpson[34] has several times + observed arms which had been cut off in the womb by bands of false + membrane, and which had grown again to a certain extent. In one + instance, the extremity was "divided into three minute nodules, on two + of which small points of nails could be detected;" so that these + nodules clearly represented fingers in process of regrowth. When, + however, we descend to the lower vertebrate classes, which are + generally looked at as representing the higher classes in their + embryonic condition, we find ample powers of regrowth. Spallanzani[35] + cut off the legs and tail of a salamander six times, and Bonnet eight + times, successively, and they were reproduced. An additional digit + beyond the proper number was occasionally formed after Bonnet had cut + off or had divided longitudinally the hand or foot, and in one instance + three additional digits were thus formed.[36] These latter cases appear + at first sight quite distinct from the congenital production of + additional digits in the higher animals; but theoretically, as we shall + see in a future chapter, they probably present no real difference. The + larvæ or tadpoles of the tailless Batrachians, but not the adults,[37] + are capable of reproducing lost members.[38] Lastly, as I have been + informed by Mr. J. J. Briggs and Mr. F. Buckland, when portions of the + pectoral and tail fins of various {16} fresh-water fish are cut off, + they are perfectly reproduced in about six weeks' time. + +From these several facts we may infer that supernumerary digits in man +retain to a certain extent an embryonic condition, and that they resemble +in this respect the normal digits and limbs in the lower vertebrate +classes. They also resemble the digits of some of the lower animals in the +number exceeding five; for no mammal, bird, existing reptile, or amphibian +(unless the tubercle on the hind feet of the toad and other tailless +Batrachians be viewed as a digit) has more than five; whilst fishes +sometimes have in their pectoral fins as many as twenty metacarpal and +phalangeal bones, which, together with the bony filaments, apparently +represent our digits with their nails. So, again, in certain extinct +reptiles, namely, the Ichthyopterygia, "the digits may be seven, eight, or +nine in number, a significant mark," says Professor Owen, "of piscine +affinity."[39] + +We encounter much difficulty in attempting to reduce these various facts to +any rule or law. The inconstant number of the additional digits--their +irregular attachment to either the inner or outer margin of the hand--the +gradation which can be traced from a mere loose rudiment of a single digit +to a completely double hand--the occasional appearance of additional digits +in the salamander after a limb has been amputated--these various facts +appear to indicate mere fluctuating monstrosity; and this perhaps is all +that can be safely said. Nevertheless, as supernumerary digits in the +higher animals, from their power of regrowth and from the number thus +acquired exceeding five, partake of the nature of the digits in the lower +vertebrate animals;--as they occur by no means rarely, and are transmitted +with remarkable strength, though perhaps not more strongly than some other +anomalies;--and as with animals which have fewer than five digits, when an +additional one appears it is generally due to the development of a visible +rudiment;--we are led in all cases to suspect, that, although no actual +rudiment can be detected, yet that a latent tendency to the formation of an +additional digit exists in all mammals, including man. On this view, as we +shall more plainly see in the {17} next chapter when discussing latent +tendencies, we should have to look at the whole case as one of reversion to +an enormously remote, lowly-organised, and multidigitate progenitor. + + * * * * * + +I may here allude to a class of facts closely allied to, but somewhat +different from, ordinary cases of inheritance. Sir H. Holland[40] states +that brothers and sisters of the same family are frequently affected, often +at about the same age, by the same peculiar disease, not known to have +previously occurred in the family. He specifies the occurrence of diabetes +in three brothers under ten years old; he also remarks that children of the +same family often exhibit in common infantile diseases the same peculiar +symptoms. My father mentioned to me the case of four brothers who died +between the ages of sixty and seventy, in the same highly peculiar comatose +state. An instance has been already given of supernumerary digits appearing +in four children out of six in a previously unaffected family. Dr. Devay +states[41] that two brothers married two sisters, their first-cousins, none +of the four nor any relation being an albino; but the seven children +produced from this double marriage were all perfect albinoes. Some of these +cases, as Mr. Sedgwick[42] has shown, are probably the result of reversion +to a remote ancestor, of whom no record had been preserved; and all these +cases are so far directly connected with inheritance that no doubt the +children inherited a similar constitution from their parents, and, from +being exposed to nearly similar conditions of life, it is not surprising +that they should be affected in the same manner and at the same period of +life. + + * * * * * + +Most of the facts hitherto given have served to illustrate the force of +inheritance, but we must now consider cases, grouped as well as the subject +allows into classes, showing how feeble, capricious, or deficient the power +of inheritance sometimes is. When a new peculiarity first appears, we can +never predict whether it will be inherited. If both parents from their +birth present {18} the same peculiarity, the probability is strong that it +will be transmitted to at least some of their offspring. We have seen that +variegation is transmitted much more feebly by seed from a branch which had +become variegated through bud-variation, than from plants which were +variegated as seedlings. With most plants the power of transmission +notoriously depends on some innate capacity in the individual: thus +Vilmorin[43] raised from a peculiarly coloured balsam some seedlings, which +all resembled their parent; but of these seedlings some failed to transmit +the new character, whilst others transmitted it to all their descendants +during several successive generations. So again with a variety of the rose, +two plants alone out of six were found by Vilmorin to be capable of +transmitting the desired character. + + The weeping or pendulous growth of trees is strongly inherited in some + cases, and, without any assignable reason, feebly in other cases. I + have selected this character as an instance of capricious inheritance, + because it is certainly not proper to the parent-species, and because, + both sexes being borne on the same tree, both tend to transmit the same + character. Even supposing that there may have been in some instances + crossing with adjoining trees of the same species, it is not probable + that all the seedlings would have been thus affected. At Moccas Court + there is a famous weeping oak; many of its branches "are 30 feet long, + and no thicker in any part of this length than a common rope:" this + tree transmits its weeping character, in a greater or less degree, to + all its seedlings; some of the young oaks being so flexible that they + have to be supported by props; others not showing the weeping tendency + till about twenty years old.[44] Mr. Rivers fertilized, as he informs + me, the flowers of a new Belgian weeping thorn (_Cratægus oxyacantha_) + with pollen from a crimson not-weeping variety, and three young trees, + "now six or seven years old, show a decided tendency to be pendulous, + but as yet are not so much so as the mother-plant." According to Mr. + MacNab,[45] seedlings from a magnificent weeping birch (_Betula alba_), + in the Botanic Garden at Edinburgh, grew for the first ten or fifteen + years upright, but then all became weepers like their parent. A peach + with pendulous branches, like those of the weeping willow, has been + found capable of propagation by seed.[46] Lastly, a weeping and almost + prostrate yew (_Taxus baccata_) was found in a hedge in Shropshire; it + was a male, but one branch bore female flowers, and produced berries; + these, {19} being sown, produced seventeen trees, all of which had + exactly the same peculiar habit with the parent-tree.[47] + + These facts, it might have been thought, would have been sufficient to + render it probable that a pendulous habit would in all cases be + strictly inherited. But let us look to the other side. Mr. MacNab[48] + sowed seeds of the weeping beech (_Fagus sylvanica_), but succeeded in + raising only common beeches. Mr. Rivers, at my request, raised a number + of seedlings from three distinct varieties of weeping elm; and at least + one of the parent-trees was so situated that it could not have been + crossed by any other elm; but none of the young trees, now about a foot + or two in height, show the least signs of weeping. Mr. Rivers formerly + sowed above twenty thousand seeds of the weeping ash (_Fraxinus + excelsior_), and not a single seedling was in the least degree + pendulous: in Germany, M. Borchmeyer raised a thousand seedlings, with + the same result. Nevertheless, Mr. Anderson, of the Chelsea Botanic + Garden, by sowing seed from a weeping ash, which was found before the + year 1780, in Cambridgeshire, raised several pendulous trees.[49] + Professor Henslow also informs me that some seedlings from a female + weeping ash in the Botanic Garden at Cambridge were at first a little + pendulous, but afterwards became quite upright: it is probable that + this latter tree, which transmits to a certain extent its pendulous + habit, was derived by a bud from the same original Cambridgeshire + stock; whilst other weeping ashes may have had a distinct origin. But + the crowning case, communicated to me by Mr. Rivers, which shows how + capricious is the inheritance of a pendulous habit, is that a variety + of another species of ash (_F. lentiscifolia_) which was formerly + pendulous, "now about twenty years old has long lost this habit, every + shoot being remarkably erect; but seedlings formerly raised from it + were perfectly prostrate, the stems not rising more than two inches + above the ground." Thus the weeping variety of the common ash, which + has been extensively propagated by buds during a long period, did not, + with Mr. Rivers, transmit its character to one seedling out of above + twenty thousand; whereas the weeping variety of a second species of + ash, which could not, whilst grown in the same garden, retain its own + weeping character, transmitted to its seedlings the pendulous habit in + excess! + + Many analogous facts could be given, showing how apparently capricious + is the principle of inheritance. All the seedlings from a variety of + the Barberry (_B. vulgaris_) with red leaves inherited the same + character; only about one-third of the seedlings of the copper Beech + (_Fagus sylvatica_) had purple leaves. Not one out of a hundred + seedlings of a variety of the _Cerasus padus_, with yellow fruit, bore + yellow fruit: one-twelfth of the seedlings of the variety of _Cornus + mascula_, with yellow fruit, came true:[50] and lastly, all the trees + raised by my father from a yellow-berried holly (_Ilex aquifolium_), + {20} found wild, produced yellow berries. Vilmorin[51] observed in a + bed of _Saponaria calabrica_ an extremely dwarf variety, and raised + from it a large number of seedlings; some of these partially resembled + their parent, and he selected their seed; but the grandchildren were + not in the least dwarfed: on the other hand, he observed a stunted and + bushy variety of _Tagetes signata_ growing in the midst of the common + varieties by which it was probably crossed; for most of the seedlings + raised from this plant were intermediate in character, only two + perfectly resembling their parent; but seed saved from these two plants + reproduced the new variety so truly, that hardly any selection has + since been necessary. + + Flowers transmit their colour truly, or most capriciously. Many annuals + come true: thus I purchased German seeds of thirty-four named + sub-varieties of one _race_ of ten-week stocks (_Matthiola annua_), and + raised a hundred and forty plants, all of which, with the exception of + a single plant, came true. In saying this, however, it must be + understood that I could distinguish only twenty kinds out of the + thirty-four named sub-varieties; nor did the colour of the flower + always correspond with the name affixed to the packet; but I say that + they came true, because in each of the thirty-six short rows every + plant was absolutely alike, with the one single exception. Again, I + procured packets of German seed of twenty-five named varieties of + common and quilled asters, and raised a hundred and twenty-four plants; + of these, all except ten were true in the above limited sense; and I + considered even a wrong shade of colour as false. + + It is a singular circumstance that white varieties generally transmit + their colour much more truly than any other variety. This fact probably + stands in close relation with one observed by Verlot,[52] namely, that + flowers which are normally white rarely vary into any other colour. I + have found that the white varieties of _Delphinium consolida_ and of + the Stock are the truest. It is, indeed, sufficient to look through a + nurseryman's seed-list, to see the large number of white varieties + which can be propagated by seed. The several coloured varieties of the + sweet-pea (_Lathyrus odoratus_) are very true; but I hear from Mr. + Masters, of Canterbury, who has particularly attended to this plant, + that the white variety is the truest. The hyacinth, when propagated by + seed, is extremely inconstant in colour, but "white hyacinths almost + always give by seed white-flowered plants;"[53] and Mr. Masters informs + me that the yellow varieties also reproduce their colour, but of + different shades. On the other hand, pink and blue varieties, the + latter being the natural colour, are not nearly so true: hence, as Mr. + Masters has remarked to me, "we see that a garden variety may acquire a + more permanent habit than a natural species;" but it should have been + added, that this occurs under cultivation, and therefore under changed + conditions. + + With many flowers, especially perennials, nothing can be more + fluctuating than the colour of the seedlings, as is notoriously the + case with verbenas, carnations, dahlias, cinerarias, and others.[54] I + sowed seed of twelve {21} named varieties of Snapdragon (_Antirrhinum + majus_), and utter confusion was the result. In most cases the + extremely fluctuating colour of seedling plants is probably in chief + part due to crosses between differently-coloured varieties during + previous generations. It is almost certain that this is the case with + the polyanthus and coloured primrose (_Primula veris_ and _vulgaris_), + from their reciprocally dimorphic structure;[55] and these are plants + which florists speak of as never come true by seed: but if care be + taken to prevent crossing, neither species is by any means very + inconstant in colour; thus I raised twenty-three plants from a purple + primrose, fertilised by Mr. J. Scott with its own pollen, and eighteen + came up purple of different shades, and only five reverted to the + ordinary yellow colour: again, I raised twenty plants from a bright-red + cowslip, similarly treated by Mr. Scott, and every one perfectly + resembled its parent in colour, as likewise did, with the exception of + a single plant, 73 grandchildren. Even with the most variable flowers, + it is probable that each delicate shade of colour might be permanently + fixed so as to be transmitted by seed, by cultivation in the same soil, + by long-continued selection, and especially by the prevention of + crosses. I infer this from certain annual larkspurs (_Delphinium + consolida_ and _ajacis_), of which common seedlings present a greater + diversity of colour than any other plant known to me; yet on procuring + seed of five named German varieties of _D. consolida_, only nine plants + out of ninety-four were false; and the seedlings of six varieties of + _D. ajacis_ were true in the same manner and degree as with the stocks + above described. A distinguished botanist maintains that the annual + species of Delphinium are always self-fertilised; therefore I may + mention that thirty-two flowers on a branch of _D. consolida_, enclosed + in a net, yielded twenty-seven capsules, with an average of 17.2 seed + in each; whilst five flowers, under the same net, which were + artificially fertilised, in the same manner as must be effected by bees + during their incessant visits, yielded five capsules with an average of + 35.2 fine seed; and this shows that the agency of insects is necessary + for the full fertility of this plant. Analogous facts could be given + with respect to the crossing of many other flowers, such as carnations, + &c., of which the varieties fluctuate much in colour. + + As with flowers, so with our domesticated animals, no character is more + variable than colour, and probably in no animal more so than with the + horse. Yet with a little care in breeding, it appears that races of any + colour might soon be formed. Hofacker gives the result of matching two + hundred and sixteen mares of four different colours with like-coloured + stallions, without regard to the colour of their ancestors; and of the + two hundred and sixteen colts born, eleven alone failed to inherit the + colour of their parents: Autenrieth and Ammon assert that, after two + generations, colts of a uniform colour are produced with certainty.[56] + +In a few rare cases peculiarities fail to be inherited, apparently from the +force of inheritance being too strong. I have been assured by breeders of +the canary-bird that to get a good {22} jonquil-coloured bird it does not +answer to pair two jonquils, as the colour then comes out too strong, or is +even brown. So again, if two crested canaries are paired, the young birds +rarely inherit this character:[57] for in crested birds a narrow space of +bare skin is left on the back of the head, where the feathers are up-turned +to form the crest, and, when both parents are thus characterised, the +bareness becomes excessive, and the crest itself fails to be developed. Mr. +Hewitt, speaking of Laced Sebright Bantams, says[58] that, "why this should +be so, I know not, but I am confident that those that are best laced +frequently produce offspring very far from perfect in their markings, +whilst those exhibited by myself, which have so often proved successful, +were bred from the union of heavily-laced birds with those that were +scarcely sufficiently laced." + +It is a singular fact that, although several deaf-mutes often occur in the +same family, and though their cousins and other relations are often in the +same condition, yet their parents are very rarely deaf-mutes. To give a +single instance: not one scholar out of 148, who were at the same time in +the London Institution, was the child of parents similarly afflicted. So +again, when a male or a female deaf-mute marries a sound person, their +children are most rarely affected: in Ireland out of 203 children thus +produced one alone was mute. Even when both parents have been deaf-mutes, +as in the case of forty-one marriages in the United States and of six in +Ireland, only two deaf and dumb children were produced. Mr. Sedgwick,[59] +in commenting on this remarkable and fortunate failure in the power of +transmission in the direct line, remarks that it may possibly be owing to +"excess having reversed the action of some natural law in development." But +it is safer in the present state of our knowledge to look at the whole case +as simply unintelligible. + + * * * * * + +With respect to the inheritance of structures mutilated by injuries or +altered by disease it is difficult to come to any {23} definite conclusion. +In some cases mutilations have been practised for a vast number of +generations without any inherited result. Godron has remarked[60] that +different races of man have from time immemorial knocked out their upper +incisors, cut off joints of their fingers, made holes of immense size +through the lobes of their ears or through their nostrils, made deep gashes +in various parts of their bodies, and there is no reason whatever to +suppose that these mutilations have ever been inherited. Adhesions due to +inflammation and pits from the small-pox (and formerly many consecutive +generations must have been thus pitted) are not inherited. With respect to +Jews, I have been assured by three medical men of the Jewish faith that +circumcision, which has been practised for so many ages, has produced no +inherited effect; Blumenbach, on the other hand, asserts[61] that in +Germany Jews are often born in a condition rendering circumcision +difficult, so that a name is here applied to them signifying "born +circumcised." The oak and other trees must have borne galls from primeval +times, yet they do not produce inherited excrescences; many other such +facts could be adduced. + +On the other hand, various cases have been recorded of cats, dogs, and +horses, which have had their tails, legs, &c., amputated or injured, +producing offspring with the same parts ill-formed; but as it is not at all +rare for similar malformations to appear spontaneously, all such cases may +be due to mere coincidence. Nevertheless, Dr. Prosper Lucas has given, on +good authorities, such a long list of inherited injuries, that it is +difficult not to believe in them. Thus, a cow that had lost a horn from an +accident with consequent suppuration, produced three calves which were +hornless on the same side of the head. With the horse, there seems hardly a +doubt that bony exostoses on the legs, caused by too much travelling on +hard roads, are inherited. Blumenbach records the case of a man who had his +little finger on the right hand almost cut off, and which in consequence +grew crooked, and his sons had the same finger on the same hand similarly +crooked. A soldier, fifteen years before his marriage, lost his left eye +from purulent ophthalmia, and his {24} two sons were microphthalmic on the +same side.[62] In all such cases, if truthfully reported, in which the +parent has had an organ injured on one side, and more than one child has +been born with the same organ affected on the same side, the chances +against mere coincidence are enormous. But perhaps the most remarkable and +trustworthy fact is that given by Dr. Brown-Séquard,[63] namely, that many +young guinea-pigs inherited an epileptic tendency from parents which had +been subjected to a particular operation, inducing in the course of a few +weeks a convulsive disease like epilepsy: and it should be especially noted +that this eminent physiologist bred a large number of guinea-pigs from +animals which had not been operated on, and not one of these manifested the +epileptic tendency. On the whole, we can hardly avoid admitting, that +injuries and mutilations, especially when followed by disease, or perhaps +exclusively when thus followed, are occasionally inherited. + +Although many congenital monstrosities are inherited, of which examples +have already been given, and to which may be added the lately recorded case +of the transmission during a century of hare-lip with a cleft-palate in the +writer's own family,[64] yet other malformations are rarely or never +inherited. Of these later cases, many are probably due to injuries in the +womb or egg, and would come under the head of non-inherited injuries or +mutilations. With plants, a long catalogue of inherited monstrosities of +the most serious and diversified nature could easily be given; and with +plants, there is no reason to suppose that monstrosities are caused by +direct injuries to the seed or embryo. + +_Causes of Non-inheritance._ + +A large number of cases of non-inheritance are intelligible on the +principle, that a strong tendency to inheritance does exist, but {25} that +it is overborne by hostile or unfavourable conditions of life. No one would +expect that our improved pigs, if forced during several generations to +travel about and root in the ground for their own subsistence, would +transmit, as truly as they now do, their tendency to fatten, and their +short muzzles and legs. Dray-horses assuredly would not long transmit their +great size and massive limbs, if compelled to live on a cold, damp +mountainous region; we have indeed evidence of such deterioration in the +horses which have run wild on the Falkland Islands. European dogs in India +often fail to transmit their true character. Our sheep in tropical +countries lose their wool in a few generations. There seems also to be a +close relation between certain peculiar pastures and the inheritance of an +enlarged tail in fat-tailed sheep, which form one of the most ancient +breeds in the world. With plants, we have seen that the American varieties +of maize lose their proper character in the course of two or three +generations, when cultivated in Europe. Our cabbages, which here come so +true by seed, cannot form heads in hot countries. Under changed +circumstances, periodical habits of life soon fail to be transmitted, as +the period of maturity in summer and winter wheat, barley, and vetches. So +it is with animals; for instance, a person whose statement I can trust, +procured eggs of Aylesbury ducks from that town, where they are kept in +houses and are reared as early as possible for the London market; the ducks +bred from these eggs in a distant part of England, hatched their first +brood on January 24th, whilst common ducks, kept in the same yard and +treated in the same manner, did not hatch till the end of March; and this +shows that the period of hatching was inherited. But the grandchildren of +these Aylesbury ducks completely lost their early habit of incubation, and +hatched their eggs at the same time with the common ducks of the same +place. + +Many cases of non-inheritance apparently result from the conditions of life +continually inducing fresh variability. We have seen that when the seeds of +pears, plums, apples, &c., are sown, the seedlings generally inherit some +degree of family likeness from the parent-variety. Mingled with these +seedlings, a few, and sometimes many, worthless, wild-looking plants +commonly appear; and their appearance may be attributed to the principle of +reversion. But scarcely a single seedling will be found {26} perfectly to +resemble the parent-form; and this, I believe, may be accounted for by +constantly recurring variability induced by the conditions of life. I +believe in this, because it has been observed that certain fruit-trees +truly propagate their kind whilst growing on their own roots, but when +grafted on other stocks, and by this process their natural state is +manifestly affected, they produce seedlings which vary greatly, departing +from the parental type in many characters.[65] Metzger, as stated in the +ninth chapter, found that certain kinds of wheat brought from Spain and +cultivated in Germany, failed during many years to reproduce themselves +truly; but that at last, when accustomed to their new conditions, they +ceased to be variable,--that is, they became amenable to the power of +inheritance. Nearly all the plants which cannot be propagated with any +approach to certainty by seed, are kinds which have long been propagated by +buds, cuttings, offsets, tubers, &c., and have in consequence been +frequently exposed during their individual lives to widely diversified +conditions of life. Plants thus propagated become so variable, that they +are subject, as we have seen in the last chapter, even to bud-variation. +Our domesticated animals, on the other hand, are not exposed during their +individual lives to such extremely diversified conditions, and are not +liable to such extreme variability; therefore they do not lose the power of +transmitting most of their characteristic features. In the foregoing +remarks on non-inheritance, crossed breeds are of course excluded, as their +diversity mainly depends on the unequal development of characters derived +from either parent, modified by the principles of reversion and prepotency. + +_Conclusion._ + +It has, I think, been shown in the early part of this chapter how strongly +new characters of the most diversified nature, whether normal or abnormal, +injurious or beneficial, whether affecting organs of the highest or most +trifling importance, are inherited. Contrary to the common opinion, it is +often sufficient for the inheritance of some peculiar character, that one +parent alone should possess it, as in most cases in which the rarer {27} +anomalies have been transmitted. But the power of transmission is extremely +variable: in a number of individuals descended from the same parents, and +treated in the same manner, some display this power in a perfect manner, +and in some it is quite deficient; and for this difference no reason can be +assigned. In some cases the effects of injuries or mutilations apparently +are inherited; and we shall see in a future chapter that the effects of the +long-continued use and disuse of parts are certainly inherited. Even those +characters which are considered the most fluctuating, such as colour, are +with rare exceptions transmitted much more forcibly than is generally +supposed. The wonder, indeed, in all cases is not that any character should +be transmitted, but that the power of inheritance should ever fail. The +checks to inheritance, as far as we know them, are, firstly, circumstances +hostile to the particular character in question; secondly, conditions of +life incessantly inducing fresh variability; and lastly, the crossing of +distinct varieties during some previous generation, together with reversion +or atavism--that is, the tendency in the child to resemble its +grand-parents or more remote ancestors instead of its immediate parents. +This latter subject will be fully discussed in the following chapter. + + * * * * * + + +{28} + +CHAPTER XIII. + +INHERITANCE _continued_--REVERSION OR ATAVISM. + + DIFFERENT FORMS OF REVERSION--IN PURE OR UNCROSSED BREEDS, AS IN + PIGEONS, FOWLS, HORNLESS CATTLE AND SHEEP, IN CULTIVATED + PLANTS--REVERSION IN FERAL ANIMALS AND PLANTS--REVERSION IN CROSSED + VARIETIES AND SPECIES--REVERSION THROUGH BUD-PROPAGATION, AND BY + SEGMENTS IN THE SAME FLOWER OR FRUIT--IN DIFFERENT PARTS OF THE BODY IN + THE SAME ANIMAL--THE ACT OF CROSSING A DIRECT CAUSE OF REVERSION, + VARIOUS CASES OF, WITH INSTINCTS--OTHER PROXIMATE CAUSES OF + REVERSION--LATENT CHARACTERS--SECONDARY SEXUAL CHARACTERS--UNEQUAL + DEVELOPMENT OF THE TWO SIDES OF THE BODY--APPEARANCE WITH ADVANCING AGE + OF CHARACTERS DERIVED FROM A CROSS--THE GERM WITH ALL ITS LATENT + CHARACTERS A WONDERFUL OBJECT--MONSTROSITIES--PELORIC FLOWERS DUE IN + SOME CASES TO REVERSION. + +The great principle of inheritance to be discussed in this chapter has been +recognised by agriculturists and authors of various nations, as shown by +the scientific term _Atavism_, derived from atavus, an ancestor; by the +English terms of _Reversion_, or _Throwing back_; by the French +_Pas-en-arrière_; and by the German _Rück-schlag_, or _Rück-schritt_. When +the child resembles either grandparent more closely than its immediate +parents, our attention is not much arrested, though in truth the fact is +highly remarkable; but when the child resembles some remote ancestor, or +some distant member in a collateral line,--and we must attribute the latter +case to the descent of all the members from a common progenitor,--we feel a +just degree of astonishment. When one parent alone displays some +newly-acquired and generally inheritable character, and the offspring do +not inherit it, the cause may lie in the other parent having the power of +prepotent transmission. But when both parents are similarly characterised, +and the child does not, whatever the cause may be, inherit the character in +question, but resembles its grandparents, we have one of the simplest cases +of reversion. We continually see another and even more simple case of +atavism, though not generally included under this head, namely, when {29} +the son more closely resembles his maternal than his paternal grandsire in +some male attribute, as in any peculiarity in the beard of man, the horns +of the bull, the hackles or comb of the cock, or, as in certain diseases +necessarily confined to the male sex; for the mother cannot possess or +exhibit such male attributes, yet the child has inherited them, through her +blood, from his maternal grandsire. + +The cases of reversion may be divided into two main classes, which, +however, in some instances, blend into each other; namely, first, those +occurring in a variety or race which has not been crossed, but has lost by +variation some character that it formerly possessed, and which afterwards +reappears. The second class includes all cases in which a distinguishable +individual, sub-variety, race, or species, has at some former period been +crossed with a distinct form, and a character derived from this cross, +after having disappeared during one or several generations, suddenly +reappears. A third class, differing only in the manner of reproduction, +might be formed to include all cases of reversion effected by means of +buds, and therefore independent of true or seminal generation. Perhaps even +a fourth class might be instituted, to include reversions by segments in +the same individual flower or fruit, and in different parts of the body in +the same individual animal as it grows old. But the two first main classes +will be sufficient for our purpose. + + * * * * * + +_Reversion to lost Characters by pure or uncrossed forms._--Striking +instances of this first class of cases were given in the sixth chapter, +namely, of the occasional reappearance, in variously-coloured pure breeds +of the pigeon, of blue birds with all the marks which characterise the wild +_Columba livia_. Similar cases were given in the case of the fowl. With the +common ass, as we now know that the legs of the wild progenitor are +striped, we may feel assured that the occasional appearance of such stripes +in the domestic animal is a case of simple reversion. But I shall be +compelled to refer again to these cases, and therefore will here pass them +over. + +The aboriginal species from which our domesticated cattle and sheep are +descended, no doubt possessed horns; but several hornless breeds are now +well established. Yet in these--for instance, {30} in Southdown sheep--"it +is not unusual to find among the male lambs some with small horns." The +horns, which thus occasionally reappear in other polled breeds, either +"grow to the full size, or are curiously attached to the skin alone and +hang loosely down, or drop off."[66] The Galloways and Suffolk cattle have +been hornless for the last 100 or 150 years, but a horned calf, with the +horn often loosely attached, is occasionally born.[67] + +There is reason to believe that sheep in their early domesticated condition +were "brown or dingy black;" but even in the time of David certain flocks +were spoken of as white as snow. During the classical period the sheep of +Spain are described by several ancient authors as being black, red, or +tawny.[68] At the present day, notwithstanding the great care which is +taken to prevent it, particoloured lambs and some entirely black are +occasionally dropped by our most highly improved and valued breeds, such as +the Southdowns. Since the time of the famous Bakewell, during the last +century, the Leicester sheep have been bred with the most scrupulous care; +yet occasionally grey-faced, or black-spotted, or wholly black lambs +appear.[69] This occurs still more frequently with the less improved +breeds, such as the Norfolks.[70] As bearing on this tendency in sheep to +revert to dark colours, I may state (though in doing so I trench on the +reversion of crossed breeds, and likewise on the subject of prepotency) +that the Rev. W. D. Fox was informed that seven white Southdown ewes were +put to a so-called Spanish ram, which had two small black spots on his +sides, and they produced thirteen lambs, all perfectly black. Mr. Fox +believes that this ram belonged to a breed which he has himself kept, and +which is always spotted with black and white; and he finds that Leicester +sheep crossed by rams of this breed always produce black lambs: he has gone +on recrossing these crossed sheep with pure white Leicesters during three +successive {31} generations, but always with the same result. Mr. Fox was +also told by the friend from whom the spotted breed was procured, that he +likewise had gone on for six or seven generations crossing with white +sheep, but still black lambs were invariably produced. + +Similar facts could be given with respect to tailless breeds of various +animals. For instance, Mr. Hewitt[71] states that chickens bred from some +Rumpless fowls, which were reckoned so good that they won a prize at an +exhibition, "in a considerable number of instances were furnished with +fully developed tail-feathers." On inquiry, the original breeder of these +fowls stated that, from the time when he had first kept them, they had +often produced fowls furnished with tails; but that these latter would +again reproduce rumpless chickens. + +Analogous cases of reversion occur in the vegetable kingdom; thus "from +seeds gathered from the finest cultivated varieties of Heartsease (_Viola +tricolor_), plants perfectly wild both in their foliage and their flowers +are frequently produced;"[72] but the reversion in this instance is not to +a very ancient period, for the best existing varieties of the heartsease +are of comparatively modern origin. With most of our cultivated vegetables +there is some tendency to reversion to what is known to be, or may be +presumed to be, their aboriginal state; and this would be more evident if +gardeners did not generally look over their beds of seedlings, and pull up +the false plants or "rogues" as they are called. It has already been +remarked, that some few seedling apples and pears generally resemble, but +apparently are not identical with, the wild trees from which they are +descended. In our turnip[73] and carrot-beds a few plants often +"break"--that is, flower too soon; and their roots are generally found to +be hard and stringy, as in the parent-species. By the aid of a little +selection, carried on during a few generations, most of our cultivated +plants could probably be brought back, without any great change in their +conditions of life, to a wild or nearly wild condition: Mr. Buckman has +effected this with the parsnip;[74] {32} and Mr. Hewett C. Watson, as he +informs me, selected, during three generations, "the most diverging plants +of Scotch kail, perhaps one of the least modified varieties of the cabbage; +and in the third generation some of the plants came very close to the forms +now established in England about old castle-walls, and called indigenous." + + * * * * * + +_Reversion in Animals and Plants which have run wild._--In the cases +hitherto considered, the reverting animals and plants have not been exposed +to any great or abrupt change in their conditions of life which could have +induced this tendency; but it is very different with animals and plants +which have become feral or run wild. It has been repeatedly asserted in the +most positive manner by various authors, that feral animals and plants +invariably return to their primitive specific type. It is curious on what +little evidence this belief rests. Many of our domesticated animals could +not subsist in a wild state; thus, the more highly improved breeds of the +pigeon will not "field" or search for their own food. Sheep have never +become feral, and would be destroyed by almost every beast of prey. In +several cases we do not know the aboriginal parent-species, and cannot +possibly tell whether or not there has been any close degree of reversion. +It is not known in any instance what variety was first turned out; several +varieties have probably in some cases run wild, and their crossing alone +would tend to obliterate their proper character. Our domesticated animals +and plants, when they run wild, must always be exposed to new conditions of +life, for, as Mr. Wallace[75] has well remarked, they have to obtain their +own food, and are exposed to competition with the native productions. Under +these circumstances, if our domesticated animals did not undergo change of +some kind, the result would be quite opposed to the conclusions arrived at +in this work. Nevertheless, I do not doubt that the simple fact of animals +and plants becoming feral, does cause some tendency to reversion to the +primitive state; though this tendency has been much exaggerated by some +authors. + +{33} + + I will briefly run through the recorded cases. With neither horses nor + cattle is the primitive stock known; and it has been shown in former + chapters that they have assumed different colours in different + countries. Thus the horses which have run wild in South America are + generally brownish-bay, and in the East dun-coloured; their heads have + become larger and coarser, and this may be due to reversion. No careful + description has been given of the feral goat. Dogs which have run wild + in various countries have hardly anywhere assumed a uniform character; + but they are probably descended from several domestic races, and + aboriginally from several distinct species. Feral cats, both in Europe + and La Plata, are regularly striped; in some cases they have grown to + an unusually large size, but do not differ from the domestic animal in + any other character. When variously-coloured tame rabbits are turned + out in Europe, they generally reacquire the colouring of the wild + animal; there can be no doubt that this does really occur, but we + should remember that oddly-coloured and conspicuous animals would + suffer much from beasts of prey and from being easily shot; this at + least was the opinion of a gentleman who tried to stock his woods with + a nearly white variety; and when thus destroyed, they would in truth be + supplanted by, instead of being transformed into, the common rabbit. We + have seen that the feral rabbits of Jamaica, and especially of Porto + Santo, have assumed new colours and other new characters. The best + known case of reversion, and that on which the widely-spread belief in + its universality apparently rests, is that of pigs. These animals have + run wild in the West Indies, South America, and the Falkland Islands, + and have everywhere acquired the dark colour, the thick bristles, and + great tusks of the wild boar; and the young have reacquired + longitudinal stripes. But even in the case of the pig, Roulin describes + the half-wild animals in different parts of South America as differing + in several respects. In Louisiana the pig[76] has run wild, and is said + to differ a little in form, and much in colour, from the domestic + animal, yet does not closely resemble the wild boar of Europe. With + pigeons and fowls,[77] it is not known what variety was first turned + out, nor what character the feral birds have assumed. The guinea-fowl + in the West Indies, when feral, seems to vary more than in the + domesticated state. + + With respect to plants run wild, Dr. Hooker[78] has strongly insisted + on what slight evidence the common belief in their power of reversion + rests. Godron[79] describes wild turnips, carrots, and celery; but + these plants in their cultivated state hardly differ from their wild + prototypes, except in the {34} succulency and enlargement of certain + parts,--characters which would be surely lost by plants growing in a + poor soil and struggling with other plants. No cultivated plant has run + wild on so enormous a scale as the cardoon (_Cynara cardunculus_) in La + Plata. Every botanist who has seen it growing there, in vast beds, as + high as a horse's back, has been struck with its peculiar appearance; + but whether it differs in any important point from the cultivated + Spanish form, which is said not to be prickly like its American + descendant, or whether it differs from he wild Mediterranean species, + which is said not to be social, I do not know. + + * * * * * + +_Reversion to Characters derived from a Cross, in the case of +Sub-varieties, Races, and Species._--When an individual having some +recognizable peculiarity unites with another of the same sub-variety, not +having the peculiarity in question, it often reappears in the descendants +after an interval of several generations. Every one must have noticed, or +heard from old people of children closely resembling in appearance or +mental disposition, or in so small and complex a character as expression, +one of their grandparents, or some more distant collateral relation. Very +many anomalies of structure and diseases,[80] of which instances have been +given in the last chapter, have come into a family from one parent, and +have reappeared in the progeny after passing over two or three generations. +The following case has been communicated to me on good authority, and may, +I believe, be fully trusted: a pointer-bitch produced seven puppies; four +were marked with blue and white, which is so unusual a colour with pointers +that she was thought to have played false with one of the greyhounds, and +the whole litter was condemned; but the gamekeeper was permitted to save +one as a curiosity. Two years afterwards a friend of the owner saw the +young dog, and declared that he was the image of his old pointer-bitch +Sappho, the only blue and white pointer of pure descent which he had ever +seen. This led to close inquiry, and it was proved that he was the +great-great-grandson of Sappho; so that, according to the common +expression, he had only 1-16th of her blood in his veins. Here it can +hardly be doubted that a character derived from a cross with an individual +of the same variety reappeared after passing over three generations. + +{35} + +When two distinct races are crossed, it is notorious that the tendency in +the offspring to revert to one or both parent-forms is strong, and endures +for many generations. I have myself seen the clearest evidence of this in +crossed pigeons and with various plants. Mr. Sidney[81] states that, in a +litter of Essex pigs, two young ones appeared which were the image of the +Berkshire boar that had been used twenty-eight years before in giving size +and constitution to the breed. I observed in the farmyard at Betley Hall +some fowls showing a strong likeness to the Malay breed, and was told by +Mr. Tollet that he had forty years before crossed his birds with Malays; +and that, though he had at first attempted to get rid of this strain, he +had subsequently given up the attempt in despair, as the Malay character +would reappear. + +This strong tendency in crossed breeds to revert has given rise to endless +discussions in how many generations after a single cross, either with a +distinct breed or merely with an inferior animal, the breed may be +considered as pure, and free from all danger of reversion. No one supposes +that less than three generations suffices, and most breeders think that +six, seven, or eight are necessary, and some go to still greater +lengths.[82] But neither in the case of a breed which has been contaminated +by a single cross, nor when, in the attempt to form an intermediate breed, +half-bred animals have been matched together during many generations, can +any rule be laid down how soon the tendency to reversion will be +obliterated. It depends on the difference in the strength or prepotency of +transmission in the two parent-forms, on their actual amount of difference, +and on the nature of the conditions of life to which the crossed offspring +are exposed. But we must be careful not to confound these cases of +reversion to characters gained from a cross, with those given under the +first class, in which characters originally common to _both_ parents, but +lost at some former period, reappear; for such characters may recur after +an almost indefinite number of generations. + +{36} + +The law of reversion is equally powerful with hybrids, when they are +sufficiently fertile to breed together, or when they are repeatedly crossed +with either pure parent-form, as with mongrels. It is not necessary to give +instances, for in the case of plants almost every one who has worked on +this subject from the time of Kölreuter to the present day has insisted on +this tendency. Gärtner has recorded some good instances; but no one has +given more striking cases than Naudin.[83] The tendency differs in degree +or strength in different groups, and partly depends, as we shall presently +see, on the fact of the parent-plants having been long cultivated. Although +the tendency to reversion is extremely general with nearly all mongrels and +hybrids, it cannot be considered as invariably characteristic of them; +there is, also, reason to believe that it may be mastered by long-continued +selection; but these subjects will more properly be discussed in a future +chapter on Crossing. From what we see of the power and scope of reversion, +both in pure races and when varieties or species are crossed, we may infer +that characters of almost every kind are capable of reappearance after +having been lost for a great length of time. But it does not follow from +this that in each particular case certain characters will reappear: for +instance, this will not occur when a race is crossed with another endowed +with prepotency of transmission. In some few cases the power of reversion +wholly fails, without our being able to assign any cause for the failure: +thus it has been stated that in a French family in which 85 out of above +600 members, during six generations, had been subject to night-blindness, +"there has not been a single example of this affection in the children of +parents who were themselves free from it."[84] + + * * * * * + +_Reversion through Bud-propagation--Partial Reversion, by segments in the +same flower or fruit, or in different parts of the {37} body in the same +individual animal._--In the eleventh chapter, many cases of reversion by +buds, independently of seminal generation, were given--as when a leaf-bud +on a variegated, curled, or laciniated variety suddenly reassumes its +proper character; or as when a Provence-rose appears on a moss-rose, or a +peach on a nectarine-tree. In some of these cases only half the flower or +fruit, or a smaller segment, or mere stripes, reassumed their former +character; and here we have with buds reversion by segments. Vilmorin[85] +has also recorded several cases with plants derived from seed, of flowers +reverting by stripes or blotches to their primitive colours: he states that +in all such cases a white or pale-coloured variety must first be formed, +and, when this is propagated for a length of time by seed, striped +seedlings occasionally make their appearance; and these can afterwards by +care be multiplied by seed. + +The stripes and segments just referred to are not due, as far as is known, +to reversion to characters derived from a cross, but to characters lost by +variation. These cases, however, as Naudin[86] insists in his discussion on +disjunction of character, are closely analogous with those given in the +eleventh chapter, in which crossed plants are known to have produced +half-and-half or striped flowers and fruit, or distinct kinds of flowers on +the same root resembling the two parent-forms. Many piebald animals +probably come under this same head. Such cases, as we shall see in the +chapter on Crossing, apparently result from certain characters not readily +blending together, and, as a consequence of this incapacity for fusion, the +offspring either perfectly resemble one of their two parents, or resemble +one parent in one part and the other parent in another part; or whilst +young are intermediate in character, but with advancing age revert wholly +or by segments to either parent-form, or to both. Thus young trees of the +_Cytisus adami_ are intermediate in foliage and flowers between the two +parent-forms; but when older the buds continually revert either partially +or wholly to both forms. The cases given in the eleventh chapter on the +changes which occurred during growth {38} in crossed plants of Tropæolum, +Cereus, Datura, and Lathyrus are all analogous. As however these plants are +hybrids of the first generation, and as their buds after a time come to +resemble their parents and not their grandparents, these cases do not at +first appear to come under the law of reversion in the ordinary sense of +the word; nevertheless, as the change is effected through a succession of +bud-generations on the same plant, they may be thus included. + +Analogous facts have been observed in the animal kingdom, and are more +remarkable, as they occur strictly in the same individual, and not as with +plants through a succession of bud-generations. With animals the act of +reversion, if it can be so designated, does not pass over a true +generation, but merely over the early stages of growth in the same +individual. For instance, I crossed several white hens with a black cock, +and many of the chickens were during the first year perfectly white, but +acquired during the second year black feathers; on the other hand, some of +the chickens which were at first black became during the second year +piebald with white. A great breeder[87] says, that a Pencilled Brahma hen +which has any of the blood of the Light Brahma in her, will "occasionally +produce a pullet well pencilled during the first year, but she will most +likely moult brown on the shoulders and become quite unlike her original +colours in the second year." The same thing occurs with Light Brahmas if of +impure blood. I have observed exactly similar cases with the crossed +offspring from differently coloured pigeons. But here is a more remarkable +fact: I crossed a turbit, which has a frill formed by the feathers being +reversed on its breast, with a trumpeter; and one of the young pigeons thus +raised showed at first not a trace of the frill, but, after moulting +thrice, a small yet unmistakably distinct frill appeared on its breast. +According to Girou,[88] calves produced from a red cow by a black bull, or +from a black cow by a red bull, are not rarely born red, and subsequently +become black. + +In the foregoing cases, the characters which appear with advancing age are +the result of a cross in the previous or some {39} former generation; but +in the following cases, the characters which thus reappear formerly +appertained to the species, and were lost at a more or less remote epoch. +Thus, according to Azara,[89] the calves of a hornless race of cattle which +originated in Corrientes, though at first quite hornless, as they become +adult sometimes acquire small, crooked, and loose horns; and these in +succeeding years occasionally become attached to the skull. White and black +bantams, both of which generally breed true, sometimes assume as they grow +old a saffron or red plumage. For instance, a first-rate black bantam has +been described, which during three seasons was perfectly black, but then +annually became more and more red; and it deserves notice that this +tendency to change, whenever it occurs in a bantam, "is almost certain to +prove hereditary."[90] The cuckoo or blue-mottled Dorking cock, when old, +is liable to acquire yellow or orange hackles in place of his proper +bluish-grey hackles.[91] Now, as _Gallus bankiva_ is coloured red and +orange, and as Dorking fowls and both kinds of bantams are descended from +this species, we can hardly doubt that the change which occasionally occurs +in the plumage of these birds as their age advances, results from a +tendency in the individual to revert to the primitive type. + + * * * * * + +_Crossing as a direct cause of Reversion._--It has long been notorious that +hybrids and mongrels often revert to both or to one of their parent-forms, +after an interval of from two to seven or eight, or according to some +authorities even a greater number of generations. But that the act of +crossing in itself gives an impulse towards reversion, as shown by the +reappearance of long-lost characters, has never, I believe, been hitherto +proved. The proof lies in certain peculiarities, which do not characterise +the immediate parents, and therefore cannot have been derived from them, +frequently appearing in the offspring of two breeds when crossed, which +peculiarities never appear, or appear with extreme rarity, in these same +breeds, as long as they are {40} precluded from crossing. As this +conclusion seems to me highly curious and novel, I will give the evidence +in detail. + + My attention was first called to this subject, and I was led to make + numerous experiments, by MM. Boitard and Corbié having stated that, + when they crossed certain breeds, pigeons coloured like the wild _C. + livia_, or the common dovecot, namely, slaty-blue, with double black + wing-bars, sometimes chequered with black, white loins, the tail barred + with black, with the outer feathers edged with white, were almost + invariably produced. The breeds which I crossed, and the remarkable + results attained, have been fully described in the sixth chapter. I + selected pigeons, belonging to true and ancient breeds, which had not a + trace of blue or any of the above specified marks; but when crossed, + and their mongrels recrossed, young birds were continually produced, + more or less plainly coloured slaty-blue, with some or all of the + proper characteristic marks. I may recall to the reader's memory one + case, namely, that of a pigeon, hardly distinguishable from the wild + Shetland species, the grandchild of a red-spot, white fantail, and two + black barbs, from any of which, when purely-bred, the production of a + pigeon coloured like the wild _C. livia_ would have been almost a + prodigy. + + I was thus led to make the experiments, recorded in the seventh + chapter, on fowls. I selected long-established, pure breeds, in which + there was not a trace of red, yet in several of the mongrels feathers + of this colour appeared; and one magnificent bird, the offspring of a + black Spanish cock and white Silk hen, was coloured almost exactly like + the wild _Gallus bankiva_. All who know anything of the breeding of + poultry will admit that tens of thousands of pure Spanish and of pure + white Silk fowls might have been reared without the appearance of a red + feather. The fact, given on the authority of Mr. Tegetmeier, of the + frequent appearance, in mongrel fowls, of pencilled or + transversely-barred feathers, like those common to many gallinaceous + birds, is likewise apparently a case of reversion to a character + formerly possessed by some ancient progenitor of the family. I owe to + the kindness of this same excellent observer the inspection of some + neck-hackles and tail-feathers from a hybrid between the common fowl + and a very distinct species, the _Gallus varius_; and these feathers + are transversely striped in a conspicuous manner with dark metallic + blue and grey, a character which could not have been derived from + either immediate parent. + + I have been informed by Mr. B. P. Brent, that he crossed a white + Aylesbury drake and a black so-called Labrador duck, both of which are + true breeds, and he obtained a young drake closely like the mallard + (_A. boschas_). Of the musk-duck (_A. moschata_, Linn.) there are two + sub-breeds, namely, white and slate-coloured; and these I am informed + breed true, or nearly true. But the Rev. W. D. Fox tells me that, by + putting a white drake to a slate-coloured duck, black birds, pied with + white, like the wild musk-duck, were always produced. + + We have seen in the fourth chapter, that the so-called Himalayan + rabbit, with its snow-white body, black ears, nose, tail, and feet, + breeds {41} perfectly true. This race is known to have been formed by + the union of two varieties of silver-grey rabbits. Now, when a + Himalayan doe was crossed by a sandy-coloured buck, a silver-grey + rabbit was produced; and this is evidently a case of reversion to one + of the parent varieties. The young of the Himalayan rabbit are born + snow-white, and the dark marks do not appear until some time + subsequently; but occasionally young Himalayan rabbits are born of a + light silver-grey, which colour soon disappears; so that here we have a + trace of reversion, during an early period of life, to the + parent-varieties, independently of any recent cross. + + In the third chapter is was shown that at an ancient period some breeds + of cattle in the wilder parts of Britain were white with dark ears, and + that the cattle now kept half wild in certain parks, and those which + have run quite wild in two distant parts of the world, are likewise + thus coloured. Now, an experienced breeder, Mr. J. Beasley, of + Northamptonshire,[92] crossed some carefully selected West Highland + cows with purely-bred shorthorn bulls. The bulls were red, red and + white, or dark roan; and the Highland cows were all of a red colour, + inclining to a light or yellow shade. But a considerable number of the + offspring--and Mr. Beasley calls attention to this as a remarkable + fact--were white, or white with red ears. Bearing in mind that none of + the parents were white, and that they were purely-bred animals, it is + highly probable that here the offspring reverted, in consequence of the + cross, to the colour either of the aboriginal parent-species or of some + ancient and half-wild parent-breed. The following case, perhaps, comes + under the same head: cows in their natural state have their udders but + little developed, and do not yield nearly so much milk as our + domesticated animals. Now there is some reason to believe[93] that + cross-bred animals between two kinds, both of which are good milkers, + such as Alderneys and Shorthorns, often turn out worthless in this + respect. + + In the chapter on the Horse reasons were assigned for believing that + the primitive stock was striped and dun-coloured; and details were + given, showing that in all parts of the world stripes of a dark colour + frequently appear along the spine, across the legs, and on the + shoulders, where they are occasionally double or treble, and even + sometimes on the face and body of horses of all breeds and of all + colours. But the stripes appear most frequently on the various kinds of + duns. They may sometimes plainly be seen on foals, and subsequently + disappear. The dun-colour and the stripes are strongly transmitted when + a horse thus characterised is crossed with any other; but I was not + able to prove that striped duns are generally produced from the + crossing of two distinct breeds, neither of which are duns, though this + does sometimes occur. + + The legs of the ass are often striped, and this may be considered as a + reversion to the wild parent-form, the _Asinus tæniopus_ of + Abyssinia,[94] which is thus striped. In the domestic animal the + stripes on the shoulder are occasionally double, or forked at the + extremity, as in certain zebrine {42} species. There is reason to + believe that the foal is frequently more plainly striped on the legs + than the adult animal. As with the horse, I have not acquired any + distinct evidence that the crossing of differently-coloured varieties + of the ass brings out the stripes. + + But now let us turn to the result of crossing the horse and ass. + Although mules are not nearly so numerous in England as asses, I have + seen a much greater number with striped legs, and with the stripes far + more conspicuous than in either parent-form. Such mules are generally + light-coloured, and might be called fallow-duns. The shoulder-stripe in + one instance was deeply forked at the extremity, and in another + instance was double, though united in the middle. Mr. Martin gives a + figure of a Spanish mule with strong zebra-like marks on its legs,[95] + and remarks, that mules are particularly liable to be thus striped on + their legs. In South America, according to Roulin,[96] such stripes are + more frequent and conspicuous in the mule than in the ass. In the + United States, Mr. Gosse,[97] speaking of these animals, says, "that in + a great number, perhaps in nine out of every ten, the legs are banded + with transverse dark stripes." + + Many years ago I saw in the Zoological Gardens a curious triple hybrid, + from a bay mare, by a hybrid from a male ass and female zebra. This + animal when old had hardly any stripes; but I was assured by the + superintendent, that when young it had shoulder-stripes, and faint + stripes on its flanks and legs. I mention this case more especially as + an instance of the stripes being much plainer during youth than in old + age. + + As the zebra has such conspicuously striped legs, it might have been + expected that the hybrids from this animal and the common ass would + have had their legs in some degree striped; but it appears from the + figures given in Dr. Gray's 'Knowsley Gleanings,' and still more + plainly from that given by Geoffroy and F. Cuvier,[98] that the legs + are much more conspicuously striped than the rest of the body; and this + fact is intelligible only on the belief that the ass aids in giving, + through the power of reversion, this character to its hybrid offspring. + + The quagga is banded over the whole front part of its body like a + zebra, but has no stripes on its legs, or mere traces of them. But in + the famous hybrid bred by Lord Morton,[99] from a chesnut, nearly + purely-bred, Arabian mare, by a male quagga, the stripes were "more + strongly defined and darker than those on the legs of the quagga." The + mare was subsequently put to a black Arabian horse, and bore two colts, + both of which, as formerly stated, were plainly striped on the legs, + and one of them likewise had stripes on the neck and body. + + The _Asinus Indicus_[100] is characterised by a spinal stripe, without + shoulder {43} or leg stripes; but traces of these latter stripes may + occasionally be seen even in the adult;[101] and Colonel S. Poole, who + has had ample opportunities for observation, informs me that in the + foal, when first born, the head and legs are often striped, but the + shoulder-stripe is not so distinct as in the domestic ass; all these + stripes, excepting that along the spine, soon disappear. Now a hybrid, + raised at Knowsley[102] from a female of this species by a male + domestic ass, had all four legs transversely and conspicuously striped, + had three short stripes on each shoulder, and had even some zebra-like + stripes on its face! Dr. Gray informs me that he has seen a second + hybrid of the same parentage similarly striped. + +From these facts we see that the crossing of the several equine species +tends in a marked manner to cause stripes to appear on various parts of the +body, especially on the legs. As we do not know whether the primordial +parent of the genus was striped, the appearance of the stripes can only +hypothetically be attributed to reversion. But most persons, after +considering the many undoubted cases of variously coloured marks +reappearing by reversion in crossed pigeons, fowls, ducks, &c., will come +to the same conclusion with respect to the horse-genus; and in this case we +must admit that the progenitor of the group was striped on the legs, +shoulders, face, and probably over the whole body, like a zebra. If we +reject this view, the frequent and almost regular appearance of stripes in +the several foregoing hybrids is left without any explanation. + + * * * * * + +It would appear that with crossed animals a similar tendency to the +recovery of lost characters holds good even with instincts. There are some +breeds of fowls which are called "everlasting layers," because they have +lost the instinct of incubation; and so rare is it for them to incubate +that I have seen notices published in works on poultry, when hens of such +breeds have taken to sit.[103] Yet the aboriginal species was of course a +good incubator; for with birds in a state of nature hardly any {44} +instinct is so strong as this. Now, so many cases have been recorded of the +crossed offspring from two races, neither of which are incubators, becoming +first-rate sitters, that the reappearance of this instinct must be +attributed to reversion from crossing. One author goes so far as to say, +"that a cross between two non-sitting varieties almost invariably produces +a mongrel that becomes broody, and sits with remarkable steadiness."[104] +Another author, after giving a striking example, remarks that the fact can +be explained only on the principle that "two negatives make a positive." It +cannot, however, be maintained that hens produced from a cross between two +non-sitting breeds invariably recover their lost instinct, any more than +that crossed fowls or pigeons invariably recover the red or blue plumage of +their prototypes. I raised several chickens from a Polish hen by a Spanish +cock,--breeds which do not incubate,--and none of the young hens at first +recovered their instinct, and this appeared to afford a well-marked +exception to the foregoing rule; but one of these hens, the only one which +was preserved, in the third year sat well on her eggs and reared a brood of +chickens. So that here we have the appearance with advancing age of a +primitive instinct, in the same manner as we have seen that the red plumage +of the _Gallus bankiva_ is sometimes reacquired by crossed and purely-bred +fowls of various kinds as they grow old. + +The parents of all our domesticated animals were of course aboriginally +wild in disposition; and when a domesticated species is crossed with a +distinct species, whether this is a domesticated or only tamed animal, the +hybrids are often wild {45} to such a degree, that the fact is intelligible +only on the principle that the cross has caused a partial return to the +primitive disposition. + +The Earl of Powis formerly imported some thoroughly domesticated humped +cattle from India, and crossed them with English breeds, which belong to a +distinct species; and his agent remarked to me, without any question having +been asked, how oddly wild the cross-bred animals were. The European wild +boar and the Chinese domesticated pig are almost certainly specifically +distinct: Sir F. Darwin crossed a sow of the latter breed with a wild +Alpine boar which had become extremely tame, but the young, though having +half-domesticated blood in their veins, were "extremely wild in +confinement, and would not eat swill like common English pigs." Mr. Hewitt, +who has had great experience in crossing tame cock-pheasants with fowls +belonging to five breeds, gives as the character of all "extraordinary +wildness;"[105] but I have myself seen one exception to this rule. Mr. +S. J. Salter,[106] who raised a large number of hybrids from a bantam-hen +by _Gallus Sonneratii_, states that "all were exceedingly wild." Mr. +Waterton[107] bred some wild ducks from eggs hatched under a common duck, +and the young were allowed to cross freely both amongst themselves and with +the tame ducks; they were "half wild and half tame; they came to the +windows to be fed, but still they had a wariness about them quite +remarkable." + +On the other hand, mules from the horse and ass are certainly not in the +least wild, yet they are notorious for obstinacy and vice. Mr. Brent, who +has crossed canary-birds with many kinds of finches, has not observed, as +he informs me, that the hybrids were in any way remarkably wild. Hybrids +are often raised between the common and musk duck, and I have been assured +by three persons, who have kept these crossed birds, that they were not +wild; but Mr. Garnett[108] observed that his female hybrids exhibited +"migratory propensities," of which there is not a vestige in the common or +musk duck. No case is {46} known of this latter bird having escaped and +become wild in Europe or Asia, except, according to Pallas, on the Caspian +Sea; and the common domestic duck only occasionally becomes wild in +districts where large lakes and fens abound. Nevertheless, a large number +of cases have been recorded[109] of hybrids from these two ducks, although +so few are reared in comparison with purely-bred birds of either species, +having been shot in a completely wild state. It is improbable that any of +these hybrids could have acquired their wildness from the musk-duck having +paired with a truly wild duck; and this is known not to be the case in +North America; hence we must infer that they have reacquired, through +reversion, their wildness, as well as renewed powers of flight. + +These latter facts remind us of the statements, so frequently made by +travellers in all parts of the world, on the degraded state and savage +disposition of crossed races of man. That many excellent and kind-hearted +mulattos have existed no one will dispute; and a more mild and gentle set +of men could hardly be found than the inhabitants of the island of Chiloe, +who consist of Indians commingled with Spaniards in various proportions. On +the other hand, many years ago, long before I had thought of the present +subject, I was struck with the fact that, in South America, men of +complicated descent between Negroes, Indians, and Spaniards, seldom had, +whatever the cause might be, a good expression.[110] Livingstone,--and a +more unimpeachable authority cannot be quoted,--after speaking of a +half-caste man on the Zambesi, described by the Portuguese as a rare +monster of inhumanity, remarks, "It is unaccountable why half-castes, such +as he, are so much more cruel than the Portuguese, but such is undoubtedly +the case." An inhabitant remarked to Livingstone, "God made white men, and +God made black men, but the Devil made half-castes."[111] When two races, +both {47} low in the scale, are crossed, the progeny seems to be eminently +bad. Thus the noble-hearted Humboldt, who felt none of that prejudice +against the inferior races now so current in England, speaks in strong +terms of the bad and savage disposition of Zambos, or half-castes between +Indians and Negroes; and this conclusion has been arrived at by various +observers.[112] From these facts we may perhaps infer that the degraded +state of so many half-castes is in part due to reversion to a primitive and +savage condition, induced by the act of crossing, as well as to the +unfavourable moral conditions under which they generally exist. + + * * * * * + +_Summary on the proximate causes leading to Reversion._--When purely-bred +animals or plants reassume long-lost characters,--when the common ass, for +instance, is born with striped legs, when a pure race of black or white +pigeons throws a slaty-blue bird, or when a cultivated heartsease with +large and rounded flowers produces a seedling with small and elongated +flowers,--we are quite unable to assign any proximate cause. When animals +run wild, the tendency to reversion, which, though it has been greatly +exaggerated, no doubt exists, is sometimes to a certain extent +intelligible. Thus, with feral pigs, exposure to the weather will probably +favour the growth of the bristles, as is known to be the case with the hair +of other domesticated animals, and through correlation the tusks will tend +to be redeveloped. But the reappearance of coloured longitudinal stripes on +young feral pigs cannot be attributed to the direct action of external +conditions. In this case, and in many others, we can only say that changed +habits of life apparently have favoured a tendency, inherent or latent in +the species, to return to the primitive state. + +It will be shown in a future chapter that the position of flowers on the +summit of the axis, and the position of seeds within the capsule, sometimes +determine a tendency towards reversion; and this apparently depends on the +amount of sap or nutriment which the flower-buds and seeds receive. The +position, also, of buds, either on branches or on roots, sometimes +determines, as was formerly shown, the transmission of the {48} proper +character of the variety, or its reversion to a former state. + +We have seen in the last section that when two races or species are crossed +there is the strongest tendency to the reappearance in the offspring of +long-lost characters, possessed by neither parent nor immediate progenitor. +When two white, or red, or black pigeons, of well-established breeds, are +united, the offspring are almost sure to inherit the same colours; but when +differently-coloured birds are crossed, the opposed forces of inheritance +apparently counteract each other, and the tendency which is inherent in +both parents to produce slaty-blue offspring becomes predominant. So it is +in several other cases. But when, for instance, the ass is crossed with _A. +Indicus_ or with the horse,--animals which have not striped legs,--and the +hybrids have conspicuous stripes on their legs and even on their faces, all +that can be said is, that an inherent tendency to reversion is evolved +through some disturbance in the organisation caused by the act of crossing. + +Another form of reversion is far commoner, indeed is almost universal with +the offspring from a cross, namely, to the characters proper to either pure +parent-form. As a general rule, crossed offspring in the first generation +are nearly intermediate between their parents, but the grandchildren and +succeeding generations continually revert, in a greater or lesser degree, +to one or both of their progenitors. Several authors have maintained that +hybrids and mongrels include all the characters of both parents, not fused +together, but merely mingled in different proportions in different parts of +the body; or, as Naudin[113] has expressed it, a hybrid is a living +mosaic-work, in which the eye cannot distinguish the discordant elements, +so completely are they intermingled. We can hardly doubt that, in a certain +sense, this is true, as when we behold in a hybrid the elements of both +species segregating themselves into segments in the same flower or fruit, +by a process of self-attraction or self-affinity; this segregation taking +place either by seminal or by bud-propagation. Naudin further believes that +the segregation of the two specific elements or essences is eminently +liable to occur in the male and female reproductive matter; and he thus +explains the almost {49} universal tendency to reversion in successive +hybrid generations. For this would be the natural result of the union of +pollen and ovules, in both of which the elements of the same species had +been segregated by self-affinity. If, on the other hand, pollen which +included the elements of one species happened to unite with ovules +including the elements of the other species, the intermediate or hybrid +state would still be retained, and there would be no reversion. But it +would, as I suspect, be more correct to say that the elements of both +parent-species exist in every hybrid in a double state, namely, blended +together and completely separate. How this is possible, and what the term +specific essence or element may be supposed to express, I shall attempt to +show in the hypothetical chapter on pangenesis. + +But Naudin's view, as propounded by him, is not applicable to the +reappearance of characters lost long ago by variation; and it is hardly +applicable to races or species which, after having been crossed at some +former period with a distinct form, and having since lost all traces of the +cross, nevertheless occasionally yield an individual which reverts (as in +the case of the great-great-grandchild of the pointer Sappho) to the +crossing form. The most simple case of reversion, namely, of a hybrid or +mongrel to its grandparents, is connected by an almost perfect series with +the extreme case of a purely-bred race recovering characters which had been +lost during many ages; and we are thus led to infer that all the cases must +be related by some common bond. + +Gärtner believed that only those hybrid plants which are highly sterile +exhibit any tendency to reversion to their parent-forms. It is rash to +doubt so good an observer, but this conclusion must I think be an error; +and it may perhaps be accounted for by the nature of the genera observed by +him, for he admits that the tendency differs in different genera. The +statement is also directly contradicted by Naudin's observations, and by +the notorious fact that perfectly fertile mongrels exhibit the tendency in +a high degree,--even in a higher degree, according to Gärtner himself, than +hybrids.[114] + +Gärtner further states that reversions rarely occur with {50} hybrid plants +raised from species which have not been cultivated, whilst, with those +which have been long cultivated, they are of frequent occurrence. This +conclusion explains a curious discrepancy: Max Wichura,[115] who worked +exclusively on willows, which had not been subjected to culture, never saw +an instance of reversion; and he goes so far as to suspect that the careful +Gärtner had not sufficiently protected his hybrids from the pollen of the +parent-species: Naudin, on the other hand, who chiefly experimented on +cucurbitaceous and other cultivated plants, insists more strenuously than +any other author on the tendency to reversion in all hybrids. The +conclusion that the condition of the parent-species, as affected by +culture, is one of the proximate causes leading to reversion, agrees fairly +well with the converse case of domesticated animals and cultivated plants +being liable to reversion when they become feral; for in both cases the +organisation or constitution must be disturbed, though in a very different +way. + +Finally, we have seen that characters often reappear in purely-bred races +without our being able to assign any proximate cause; but when they become +feral this is either indirectly or directly induced by the change in their +conditions of life. With crossed breeds, the act of crossing in itself +certainly leads to the recovery of long-lost characters, as well as of +those derived from either parent-form. Changed conditions, consequent on +cultivation, and the relative position of buds, flowers, and seeds on the +plant, all apparently aid in giving this same tendency. Reversion may occur +either through seminal or bud generation, generally at birth, but sometimes +only with an advance of age. Segments or portions of the individual may +alone be thus affected. That a being should be born resembling in certain +characters an ancestor removed by two or three, and in some cases by +hundreds or even thousands of generations, is assuredly a wonderful fact. +In these cases the child is commonly said to inherit such characters +directly from its grandparents or more remote ancestors. But this view is +hardly conceivable. If, however, we suppose that every character is derived +{51} exclusively from the father or mother, but that many characters lie +latent in both parents during a long succession of generations, the +foregoing facts are intelligible. In what manner characters may be +conceived to lie latent, will be considered in a future chapter to which I +have lately alluded. + + * * * * * + +_Latent Characters._--But I must explain what is meant by characters lying +latent. The most obvious illustration is afforded by secondary sexual +characters. In every female all the secondary male characters, and in every +male all the secondary female characters, apparently exist in a latent +state, ready to be evolved under certain conditions. It is well known that +a large number of female birds, such as fowls, various pheasants, +partridges, peahens, ducks, &c., when old or diseased, or when operated on, +partly assume the secondary male characters of their species. In the case +of the hen-pheasant this has been observed to occur far more frequently +during certain seasons than during others.[116] A duck ten years old has +been known to assume both the perfect winter and summer plumage of the +drake.[117] Waterton[118] gives a curious case of a hen which had ceased +laying, and had assumed the plumage, voice, spurs, and warlike disposition +of the cock; when opposed to an enemy she would erect her hackles and show +fight. Thus every character, even to the instinct and manner of fighting, +must have lain dormant in this hen as long as her ovaria continued to act. +The females of two kinds of deer, when old, have been known to acquire +horns; and, as Hunter has remarked, we see something of an analogous nature +in the human species. + +On the other hand, with male animals, it is notorious that the secondary +sexual characters are more or less completely lost when they are subjected +to castration. Thus, if the operation be performed on a young cock, he +never, as Yarrell states, crows {52} again; the comb, wattles, and spurs do +not grow to their full size, and the hackles assume an intermediate +appearance between true hackles and the feathers of the hen. Cases are +recorded of confinement alone causing analogous results. But characters +properly confined to the female are likewise acquired; the capon takes to +sitting on eggs, and will bring up chickens; and what is more curious, the +utterly sterile male hybrids from the pheasant and the fowl act in the same +manner, "their delight being to watch when the hens leave their nests, and +to take on themselves the office of a sitter."[119] That admirable observer +Réaumur[120] asserts that a cock, by being long confined in solitude and +darkness, can be taught to take charge of young chickens; he then utters a +peculiar cry, and retains during his whole life this newly acquired +maternal instinct. The many well-ascertained cases of various male mammals +giving milk, show that their rudimentary mammary glands retain this +capacity in a latent condition. + +We thus see that in many, probably in all cases, the secondary characters +of each sex lie dormant or latent in the opposite sex, ready to be evolved +under peculiar circumstances. We can thus understand how, for instance, it +is possible for a good milking cow to transmit her good qualities through +her male offspring to future generations; for we may confidently believe +that these qualities are present, though latent, in the males of each +generation. So it is with the game-cock, who can transmit his superiority +in courage and vigour through his female to his male offspring; and with +man it is known [121] that diseases, such as hydrocele, necessarily +confined to the male sex, can be transmitted through the female to the +grandson. Such cases as these offer, as was remarked at the commencement of +this chapter, the simplest possible examples of reversion; and they are +intelligible on the belief that characters common to the grandparent and +grandchild of the same sex are present, though latent, in the intermediate +parent of the opposite sex. + +The subject of latent characters is so important, as we shall see in a +future chapter, that I will give another illustration. {53} Many animals +have the right and left sides of their body unequally developed: this is +well known to be the case with flat-fish, in which the one side differs in +thickness and colour, and in the shape of the fins, from the other; and +during the growth of the young fish one eye actually travels, as shown by +Steenstrup, from the lower to the upper surface.[122] In most flat-fishes +the left is the blind side, but in some it is the right; though in both +cases "wrong fishes," which are developed in a reversed manner to what is +usual, occasionally occur, and in _Platessa flesus_ the right or left side +is indifferently developed, the one as often as the other. With gasteropods +or shell-fish, the right and left sides are extremely unequal; the far +greater number of species are dextral, with rare and occasional reversals +of development, and some few are normally sinistral; but certain species of +Bulimus, and, many Achatinellæ,[123] are as often sinistral as dextral. I +will give an analogous case in the great Articulate kingdom: the two sides +of Verruca[124] are so wonderfully unlike, that without careful dissection +it is extremely difficult to recognise the corresponding parts on the +opposite sides of the body; yet it is apparently a mere matter of chance +whether it be the right or the left side that undergoes so singular an +amount of change. One plant is known to me[125] in which the flower, +according as it stands on the one or other side of the spike, is unequally +developed. In all the foregoing cases the two sides of the animal are +perfectly symmetrical at an early period of growth. Now, whenever a species +is as liable to be unequally developed on the one as on the other side, we +may infer that the capacity for such development is present, though latent, +in the undeveloped side. And as a reversal of development occasionally +occurs in animals of many kinds, this latent capacity is probably very +common. + +The best yet simplest instances of characters lying dormant are, perhaps, +those previously given, in which chickens and {54} young pigeons, raised +from a cross between differently coloured birds, are at first of one +colour, but in a year or two acquire feathers of the colour of the other +parent; for in this case the tendency to a change of plumage is clearly +latent in the young bird. So it is with hornless breeds of cattle, some of +which acquire, as they grow old, small horns. Purely bred black and white +bantams, and some other fowls, occasionally assume, with advancing years, +the red feathers of the parent-species. I will here add a somewhat +different case, as it connects in a striking manner latent characters of +two classes. Mr. Hewitt[126] possessed an excellent Sebright gold-laced hen +bantam, which, as she became old, grew diseased in her ovaria, and assumed +male characters. In this breed the males resemble the females in all +respects except in their combs, wattles, spurs, and instincts; hence it +might have been expected that the diseased hen would have assumed only +those masculine characters which are proper to the breed, but she acquired, +in addition, well-arched tail sickle-feathers quite a foot in length, +saddle-feathers on the loins, and hackles on the neck,--ornaments which, as +Mr. Hewitt remarks, "would be held as abominable in this breed." The +Sebright bantam is known[127] to have originated about the year 1800 from a +cross between a common bantam and a Polish fowl, recrossed by a hen-tailed +bantam, and carefully selected; hence there can hardly be a doubt that the +sickle-feathers and hackles which appeared in the old hen were derived from +the Polish fowl or common bantam; and we thus see that not only certain +masculine characters proper to the Sebright bantam, but other masculine +characters derived from the first progenitors of the breed, removed by a +period of above sixty years, were lying latent in this hen-bird, ready to +be evolved as soon as her ovaria became diseased. + +From these several facts it must be admitted that certain characters, +capacities, and instincts may lie latent in an individual, and even in a +succession of individuals, without our being able to detect the least signs +of their presence. We have {55} already seen that the transmission of a +character from the grandparent to the grandchild, with its apparent +omission in the intermediate parent of the opposite sex, becomes simple on +this view. When fowls, pigeons, or cattle of different colours are crossed, +and their offspring change colour as they grow old, or when the crossed +turbit acquired the characteristic frill after its third moult, or when +purely-bred bantams partially assume the red plumage of their prototype, we +cannot doubt that these qualities were from the first present, though +latent, in the individual animal, like the characters of a moth in the +caterpillar. Now, if these animals had produced offspring before they had +acquired with advancing age their new characters, nothing is more probable +than that they would have transmitted them to some of their offspring, +which in this case would in appearance have received such characters from +their grandparents or more distant progenitors. We should then have had a +case of reversion, that is, of the reappearance in the child of an +ancestral character, actually present, though during youth completely +latent, in the parent; and this we may safely conclude is what occurs with +reversions of all kinds to progenitors however remote. + +This view of the latency in each generation of all the characters which +appear through reversion, is also supported by their actual presence in +some cases during early youth alone, or by their more frequent appearance +and greater distinctness at this age than during maturity. We have seen +that this is often the case with the stripes on the legs and faces of the +several species of the horse-genus. The Himalayan rabbit, when crossed, +sometimes produces offspring which revert to the parent silver-grey breed, +and we have seen that in purely bred animals pale-grey fur occasionally +reappears during early youth. Black cats, we may feel assured, would +occasionally produce by reversion tabbies; and on young black kittens, with +a pedigree[128] known to have been long pure, faint traces of stripes may +almost always be seen which afterwards disappear. Hornless Suffolk cattle +occasionally produce by reversion horned animals; and Youatt[129] asserts +that even in hornless individuals {56} "the rudiment of a horn may be often +felt at an early age." + +No doubt it appears at first sight in the highest degree improbable that in +every horse of every generation there should be a latent capacity and +tendency to produce stripes, though these may not appear once in a thousand +generations; that in every white, black, or other coloured pigeon, which +may have transmitted its proper colour during centuries, there should be a +latent capacity in the plumage to become blue and to be marked with certain +characteristic bars; that in every child in a six-fingered family there +should be the capacity for the production of an additional digit; and so in +other cases. Nevertheless there is no more inherent improbability in this +being the case than in a useless and rudimentary organ, or even in only a +tendency to the production of a rudimentary organ, being inherited during +millions of generations, as is well known to occur with a multitude of +organic beings. There is no more inherent improbability in each domestic +pig, during a thousand generations, retaining the capacity and tendency to +develop great tusks under fitting conditions, than in the young calf having +retained for an indefinite number of generations rudimentary incisor teeth, +which never protrude through the gums. + +I shall give at the end of the next chapter a summary of the three +preceding chapters; but as isolated and striking cases of reversion have +here been chiefly insisted on, I wish to guard the reader against supposing +that reversion is due to some rare or accidental combination of +circumstances. When a character, lost during hundreds of generations, +suddenly reappears, no doubt some such combination must occur; but +reversions may be constantly observed, at least to the immediately +preceding generations, in the offspring of most unions. This has been +universally recognised in the case of hybrids and mongrels, but it has been +recognised simply from the difference between the united forms rendering +the resemblance of the offspring to their grandparents or more remote +progenitors of easy detection. Reversion is likewise almost invariably the +rule, as Mr. Sedgwick has shown, with certain diseases. Hence we must +conclude that a tendency to this peculiar form of transmission is an +integral part of the general law of inheritance. {57} + + * * * * * + +_Monstrosities._--A large number of monstrous growths and of lesser +anomalies are admitted by every one to be due to an arrest of development, +that is to the persistence of an embryonic condition. If every horse or ass +had striped legs whilst young, the stripes which occasionally appear on +these animals when adult would have to be considered as due to the +anomalous retention of an early character, and not as due to reversion. +Now, the leg-stripes in the horse-genus, and some other characters in +analogous cases, are apt to occur during early youth and then to disappear; +thus the persistence of early characters and reversion are brought into +close connexion. + +But many monstrosities can hardly be considered as the result of an arrest +of development; for parts of which no trace can be detected in the embryo, +but which occur in other members of the same class of animals or plants, +occasionally appear, and these may probably with truth be attributed to +reversion. For instance: supernumerary mammæ, capable of secreting milk, +are not extremely rare in women; and as many as five have been observed. +When four are developed, they are generally arranged symmetrically on each +side of the chest; and in one instance a woman (the daughter of another +with supernumerary mammæ) had one mamma, which yielded milk, developed in +the inguinal region. This latter case, when we remember the position of the +mammæ in some of the lower animals on both the chest and inguinal region, +is highly remarkable, and leads to the belief that in all cases the +additional mammæ in woman are due to reversion. The facts given in the last +chapter on the tendency in supernumerary digits to regrowth after +amputation, indicate their relation to the digits of the lower vertebrate +animals, and lead to the suspicion that their appearance may in some manner +be connected with reversion. But I shall have to recur, in the chapter on +pangenesis, to the abnormal multiplication of organs, and likewise to their +occasional transposition. The occasional development in man of the +coccygeal vertebræ into a short and free tail, though it thus becomes in +one sense more perfectly developed, may at the same time be considered as +an arrest of development, and as a case of reversion. The greater frequency +of a monstrous kind of proboscis in the pig than in any other mammal, +considering the position of the pig {58} in the mammalian series, has +likewise been attributed, perhaps truly, to reversion.[130] + + When flowers which are properly irregular in structure become regular + or peloric, the change is generally looked at by botanists as a return + to the primitive state. But Dr. Maxwell Masters,[131] who has ably + discussed this subject, remarks that when, for instance, all the sepals + of a Tropæolum become green and of the same shape, instead of being + coloured with one alone prolonged into a spur, or when all the petals + of a Linaria become simple and regular, such cases may be due merely to + an arrest of development; for in these flowers all the organs during + their earliest condition are symmetrical, and, if arrested at this + stage of growth, they would not become irregular. If, moreover, the + arrest were to take place at a still earlier period of development, the + result would be a simple tuft of green leaves; and no one probably + would call this a case of reversion. Dr. Masters designates the cases + first alluded to as regular peloria; and others, in which all the + corresponding parts assume a similar form of irregularity, as when all + the petals in a Linaria become spurred, as irregular peloria. We have + no right to attribute these latter cases to reversion, until it can be + shown to be probable that the parent-form, for instance, of the genus + Linaria had had all its petals spurred; for a change of this nature + might result from the spreading of an anomalous structure, in + accordance with the law, to be discussed in a future chapter, of + homologous parts tending to vary in the same manner. But as both forms + of peloria frequently occur on the same individual plant of the + Linaria,[132] they probably stand in some close relation to each other. + On the doctrine that peloria is simply the result of an arrest of + development, it is difficult to understand how an organ arrested at a + very early period of growth should acquire its full functional + perfection;--how a petal, supposed to be thus arrested, should acquire + its brilliant colours, and serve as an envelope to the flower, or a + stamen produce efficient pollen; yet this occurs with many peloric + flowers. That pelorism is not due to mere chance variability, but + either to an arrest of development or to reversion, we may infer from + an observation made by Ch. Morren,[133] namely, that families which + have irregular flowers often "return by these monstrous growths to + their regular form; whilst we never see a regular flower realise the + structure of an irregular one." + + Some flowers have almost certainly become more or less completely + peloric through reversion. _Corydalis tuberosa_ properly has one of its + two nectaries colourless, destitute of nectar, only half the size of + the other, and {59} therefore, to a certain extent, in a rudimentary + state; the pistil is curved towards the perfect nectary, and the hood, + formed of the inner petals, slips off the pistil and stamens in one + direction alone, so that, when a bee sucks the perfect nectary, the + stigma and stamens are exposed and rubbed against the insect's body. In + several closely allied genera, as in Dielytra, &c., there are two + perfect nectaries, the pistil is straight, and the hood slips off on + either side, according as the bee sucks either nectary. Now, I have + examined several flowers of _Corydalis tuberosa_, in which both + nectaries were equally developed and contained nectar; in this we see + only the redevelopment of a partially aborted organ; but with this + redevelopment the pistil becomes straight, and the hood slips off in + either direction; so that these flowers have acquired the perfect + structure, so well adapted for insect agency, of Dielytra and its + allies. We cannot attribute these coadapted modifications to chance, or + to correlated variability; we must attribute them to reversion to a + primordial condition of the species. + + The peloric flowers of Pelargonium have their five petals in all + respects alike, and there is no nectary; so that they resemble the + symmetrical flowers of the closely allied Geranium-genus; but the + alternate stamens are also sometimes destitute of anthers, the + shortened filaments being left as rudiments, and in this respect they + resemble the symmetrical flowers of the closely allied genus, Erodium. + Hence we are led to look at the peloric flowers of Pelargonium as + having probably reverted to the state of some primordial form, the + progenitor of the three closely related genera of Pelargonium, + Geranium, and Erodium. + + In the peloric form of _Antirrhinum majus_, appropriately called the + "_Wonder_," the tubular and elongated flowers differ wonderfully from + those of the common snapdragon; the calyx and the mouth of the corolla + consist of six equal lobes, and include six equal instead of four + unequal stamens. One of the two additional stamens is manifestly formed + by the development of a microscopically minute papilla, which may be + found at the base of the upper lip of the flower in all common + snapdragons, at least in nineteen plants examined by me. That this + papilla is a rudiment of a stamen was well shown by its various degrees + of development in crossed plants between the common and peloric + Antirrhinum. Again, a peloric _Galeobdolon luteum_, growing in my + garden, had five equal petals, all striped like the ordinary lower lip, + and included five equal instead of four unequal stamens; but Mr. R. + Keeley, who sent me this plant, informs me that the flowers vary + greatly, having from four to six lobes to the corolla, and from three + to six stamens.[134] Now, as the members of the two great families to + which the Antirrhinum and Galeobdolon belong are properly pentamerous, + with some of the parts confluent and others suppressed, we ought not to + look at the sixth stamen and the sixth lobe to the corolla in either + case as due to reversion, any more than the additional petals in double + flowers in these same two families. But the case is different with the + fifth stamen in the peloric Antirrhinum, which {60} is produced by the + redevelopment of a rudiment always present, and which probably reveals + to us the state of the flower, as far as the stamens are concerned, at + some ancient epoch. It is also difficult to believe that the other four + stamens and the petals, after an arrest of development at a very early + embryonic age, would have come to full perfection in colour, structure, + and function, unless these organs had at some former period normally + passed through a similar course of growth. Hence it appears to me + probable that the progenitor of the genus Antirrhinum must at some + remote epoch have included five stamens and borne flowers in some + degree resembling those now produced by the peloric form. + + Lastly, I may add that many instances have been recorded of flowers, + not generally ranked as peloric, in which certain organs, normally few + in number, have been abnormally augmented. As such an increase of parts + cannot be looked at as an arrest of development, nor as due to the + redevelopment of rudiments, for no rudiments are present, and as these + additional parts bring the plant into closer relationship with its + natural allies, they ought probably to be viewed as reversions to a + primordial condition. + +These several facts show us in an interesting manner how intimately certain +abnormal states are connected together; namely, arrests of development +causing parts to become rudimentary or to be wholly suppressed,--the +redevelopment of parts at present in a more or less rudimentary +condition,--the reappearance of organs of which not a vestige can now be +detected,--and to these may be added, in the case of animals, the presence +during youth, and subsequent disappearance, of certain characters which +occasionally are retained throughout life. Some naturalists look at all +such abnormal structures as a return to the ideal state of the group to +which the affected being belongs; but it is difficult to conceive what is +meant to be conveyed by this expression. Other naturalists maintain, with +greater probability and distinctness of view, that the common bond of +connection between the several foregoing cases is an actual, though +partial, return to the structure of the ancient progenitor of the group. If +this view be correct, we must believe that a vast number of characters, +capable of evolution, lie hidden in every organic being. But it would be a +mistake to suppose that the number is equally great in all beings. We know, +for instance, that plants of many orders occasionally become peloric; but +many more cases have been observed in the Labiatæ and Scrophulariaceæ than +in any other order; and in one genus of the Scrophulariaceæ, namely +Linaria, no less {61} than thirteen species have been described in a +peloric condition.[135] On this view of the nature of peloric flowers, and +bearing in mind what has been said with respect to certain monstrosities in +the animal kingdom, we must conclude that the progenitors of most plants +and animals, though widely different in structure, have left an impression +capable of redevelopment on the germs of their descendants. + +The fertilised germ of one of the higher animals, subjected as it is to so +vast a series of changes from the germinal cell to old age,--incessantly +agitated by what Quatrefages well calls the _tourbillon vital_,--is perhaps +the most wonderful object in nature. It is probable that hardly a change of +any kind affects either parent, without some mark being left on the germ. +But on the doctrine of reversion, as given in this chapter, the germ +becomes a far more marvellous object, for, besides the visible changes to +which it is subjected, we must believe that it is crowded with invisible +characters, proper to both sexes, to both the right and left side of the +body, and to a long line of male and female ancestors separated by hundreds +or even thousands of generations from the present time; and these +characters, like those written on paper with invisible ink, all lie ready +to be evolved under certain known or unknown conditions. + + * * * * * + + +{62} + +CHAPTER XIV. + +INHERITANCE _continued_--FIXEDNESS OF CHARACTER--PREPOTENCY--SEXUAL +LIMITATION--CORRESPONDENCE OF AGE. + + FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO ANTIQUITY OF + INHERITANCE--PREPOTENCY OF TRANSMISSION IN INDIVIDUALS OF THE SAME + FAMILY, IN CROSSED BREEDS AND SPECIES; OFTEN STRONGER IN ONE SEX THAN + THE OTHER; SOMETIMES DUE TO THE SAME CHARACTER BEING PRESENT AND + VISIBLE IN ONE BREED AND LATENT IN THE OTHER--INHERITANCE AS LIMITED BY + SEX--NEWLY-ACQUIRED CHARACTERS IN OUR DOMESTICATED ANIMALS OFTEN + TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST BY ONE SEX + ALONE--INHERITANCE AT CORRESPONDING PERIODS OF LIFE--THE IMPORTANCE OF + THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS EXHIBITED IN DOMESTICATED + ANIMALS; AS EXHIBITED IN THE APPEARANCE AND DISAPPEARANCE OF INHERITED + DISEASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN IN THE + PARENT--SUMMARY OF THE THREE PRECEDING CHAPTERS. + +In the two last chapters the nature and force of Inheritance, the +circumstances which interfere with its power, and the tendency to +Reversion, with its many remarkable contingencies, were discussed. In the +present chapter some other related phenomena will be treated of, as fully +as my materials permit. + +_Fixedness of Character._ + +It is a general belief amongst breeders that the longer any character has +been transmitted by a breed, the more firmly it will continue to be +transmitted. I do not wish to dispute the truth of the proposition, that +inheritance gains strength simply through long continuance, but I doubt +whether it can be proved. In one sense the proposition is little better +than a truism; if any character has remained constant during many +generations, it will obviously be little likely, the conditions of life +remaining the same, to vary during the next generation. So, again, in +improving a breed, if care be taken for a length of time to exclude all +inferior individuals, the breed will obviously tend to become truer, as it +will not have been crossed during many generations by an inferior animal. +We have previously seen, {63} but without being able to assign any cause, +that, when a new character appears, it is occasionally from the first well +fixed, or fluctuates much, or wholly fails to be transmitted. So it is with +the aggregate of slight differences which characterise a new variety, for +some propagate their kind from the first much truer than others. Even with +plants multiplied by bulbs, layers, &c., which may in one sense be said to +form parts of the same individual, it is well known that certain varieties +retain and transmit through successive bud-generations their newly-acquired +characters more truly than others. In none of these, nor in the following +cases, does there appear to be any relation between the force with which a +character is transmissible and the length of time during which it has +already been transmitted. Some varieties, such as white and yellow +hyacinths and white sweet-peas, transmit their colours more faithfully than +do the varieties which have retained their natural colour. In the Irish +family, mentioned in the twelfth chapter, the peculiar tortoiseshell-like +colouring of the eyes was transmitted far more faithfully than any ordinary +colour. Ancon and Mauchamp sheep and niata cattle, which are all +comparatively modern breeds, exhibit remarkably strong powers of +inheritance. Many similar cases could be adduced. + +As all domesticated animals and cultivated plants have varied, and yet are +descended from aboriginally wild forms, which no doubt had retained the +same character from an immensely remote epoch, we see that scarcely any +degree of antiquity ensures a character being transmitted perfectly true. +In this case, however, it may be said that changed conditions of life +induce certain modifications, and not that the power of inheritance fails; +but in every case of failure, some cause, either internal or external, must +interfere. It will generally be found that the parts in our domesticated +productions which have varied, or which still continue to vary,--that is, +which fail to retain their primordial state,--are the same with the parts +which differ in the natural species of the same genus. As, on the theory of +descent with modification, the species of the same genus have been modified +since they branched off from a common progenitor, it follows that the +characters by which they differ from each other have varied whilst other +parts of the organisation have remained unchanged; and it might be argued +that {64} these same characters now vary under domestication, or fail to be +inherited, owing to their lesser antiquity. But we must believe structures, +which have already varied, would be more liable to go on varying, rather +than structures which during an immense lapse of time have remained +unaltered; and this variation is probably the result of certain relations +between the conditions of life and the organisation, quite independently of +the greater or less antiquity of each particular character. + +Fixedness of character, or the strength of inheritance, has often been +judged of by the preponderance of certain characters in the crossed +offspring between distinct races; but prepotency of transmission here comes +into play, and this, as we shall immediately see, is a very different +consideration from the strength or weakness of inheritance. It has often +been observed[136] that breeds of animals inhabiting wild and mountainous +countries cannot be permanently modified by our improved breeds; and as +these latter are of modern origin, it has been thought that the greater +antiquity of the wilder breeds has been the cause of their resistance to +improvement by crossing; but it is more probably due to their structure and +constitution being better adapted to the surrounding conditions. When +plants are first subjected to culture, it has been found that, during +several generations, they transmit their characters truly, that is, do not +vary, and this has been attributed to ancient characters being strongly +inherited; but it may with equal or greater probability be consequent on +changed conditions of life requiring a long time for their accumulative +action. Notwithstanding these considerations, it would perhaps be rash to +deny that characters become more strongly fixed the longer they are +transmitted; but I believe that the proposition resolves itself into +this,--that all characters of all kinds, whether new or old, tend to be +inherited, and that those which have already withstood all counteracting +influences and been truly transmitted, will, as a general rule, continue to +withstand them, and consequently be faithfully inherited. + +{65} + +_Prepotency in the Transmission of Character._ + +When individuals distinct enough to be recognised, but of the same family, +or when two well-marked races, or two species, are crossed, the usual +result, as stated in the previous chapter, is, that the offspring in the +first generation are intermediate between their parents, or resemble one +parent in one part and the other parent in another part. But this is by no +means the invariable rule; for in many cases it is found that certain +individuals, races, and species are prepotent in transmitting their +likeness. This subject has been ably discussed by Prosper Lucas,[137] but +is rendered extremely complicated by the prepotency sometimes running +equally in both sexes, and sometimes more strongly in one sex than in the +other; it is likewise complicated by the presence of secondary sexual +characters, which render the comparison of mongrels with their +parent-breeds difficult. + +It would appear that in certain families some one ancestor, and after him +others in the same family, must have had great power in transmitting their +likeness through the male line; for we cannot otherwise understand how the +same features should so often be transmitted after marriages with various +females, as has been the case with the Austrian Emperors, and as, according +to Niebuhr, formerly occurred in certain Roman families with their mental +qualities.[138] The famous bull Favourite is believed[139] to have had a +prepotent influence on the shorthorn race. It has also been observed[140] +with English race-horses that certain mares have generally transmitted +their own character, whilst other mares of equally pure blood have allowed +the character of the sire to prevail. + + The truth of the principle of prepotency comes out more clearly when + certain races are crossed. The improved Shorthorns, notwithstanding + that the breed is comparatively modern, are generally acknowledged to + possess great power in impressing their likeness on all other breeds; + and it is chiefly in consequence of this power that they are so highly + valued {66} for exportation.[141] Godine has given a curious case of a + ram of a goat-like breed of sheep from the Cape of Good Hope, which + produced offspring hardly to be distinguished from himself, when + crossed with ewes of twelve other breeds. But two of these half-bred + ewes, when put to a merino ram, produced lambs closely resembling the + merino breed. Girou de Buzareingues[142] found that of two races of + French sheep the ewes of one, when crossed during successive + generations with merino rams, yielded up their character far sooner + than the ewes of the other race. Sturm and Girou have given analogous + cases with other breeds of sheep and with cattle, the prepotency + running in these cases through the male side; but I was assured on good + authority in South America, that when niata cattle are crossed with + common cattle, though the niata breed is prepotent whether males or + females are used, yet that the prepotency is strongest through the + female line. The Manx cat is tailless and has long hind legs; Dr. + Wilson crossed a male Manx with common cats, and, out of twenty-three + kittens, seventeen were destitute of tails; but when the female Manx + was crossed by common male cats all the kittens had tails, though they + were generally short and imperfect.[143] + + In making reciprocal crosses between pouter and fantail pigeons, the + pouter-race seemed to be prepotent through both sexes over the fantail. + But this is probably due to weak power in the fantail rather than to + any unusually strong power in the pouter, for I have observed that + barbs also preponderated over fantails. This weakness of transmission + in the fantail, though the breed is an ancient one, is said[144] to be + general; but I have observed one exception to the rule, namely, in a + cross between a fantail and laugher. The most curious instance known to + me of weak power in both sexes is in the trumpeter pigeon. This breed + has been well known for at least 130 years: it breeds perfectly true, + as I have been assured by those who have long kept many birds: it is + characterised by a peculiar tuft of feathers over the beak, by a crest + on the head, by a most peculiar coo quite unlike that of any other + breed, and by much-feathered feet. I have crossed both sexes with + turbits of two sub-breeds, with almond tumblers, spots, and runts, and + reared many mongrels and recrossed them; and though the crest on the + head and feathered feet were inherited (as is generally the case with + most breeds), I have never seen a vestige of the tuft over the beak or + heard the peculiar coo. Boitard and Corbié[145] assert that this is the + invariable result of crossing trumpeters with any other breed: + Neumeister,[146] however, states that in Germany mongrels have been + obtained, though very rarely, which were furnished with the tuft and + would trumpet: but a pair of these mongrels with a tuft, which I + imported, never trumpeted. Mr. Brent states[147] that the crossed + offspring of a trumpeter were crossed {67} with trumpeters for three + generations, by which time the mongrels had 7-8ths of this blood in + their veins, yet the tuft over the beak did not appear. At the fourth + generation the tuft appeared, but the birds, though now having 15-16ths + trumpeter's blood, still did not trumpet. This case well shows the wide + difference between inheritance and prepotency; for here we have a + well-established old race which transmits it characters faithfully, but + which, when crossed with any other race, has the feeblest power of + transmitting its two chief characteristic qualities. + + I will give one other instance with fowls and pigeons of weakness and + strength in the transmission of the same character to their crossed + offspring. The Silk-fowl breeds true, and there is reason to believe is + a very ancient race; but when I reared a large number of mongrels from + a Silk-hen by a Spanish cock, not one exhibited even a trace of the + so-called silkiness. Mr. Hewitt also asserts that in no instance are + the silky feathers transmitted by this breed when crossed with any + other variety. But three birds out of many raised by Mr. Orton from a + cross between a silk-cock and a bantam-hen, had silky feathers.[148] So + that it is certain that this breed very seldom has the power of + transmitting its peculiar plumage to its crossed progeny. On the other + hand, there is a silk sub-variety of the fantail pigeon, which has its + feathers in nearly the same state as in the Silk-fowl: now we have + already seen that fantails, when crossed, possess singularly weak power + in transmitting their general qualities; but the silk sub-variety when + crossed with any other small-sized race invariably transmits its silky + feathers![149] + + The law of prepotency comes into action when species are crossed, as + with races and individuals. Gärtner has unequivocally shown[150] that + this is the case with plants. To give one instance: when _Nicotiana + paniculata_ and _vincæflora_ are crossed, the character of _N. + paniculata_ is almost completely lost in the hybrid; but if _N. + quadrivalvis_ be crossed with _N. vincæflora_, this later species, + which was before so prepotent, now in its turn almost disappears under + the power of _N. quadrivalvis_. It is remarkable that the prepotency of + one species over another in transmission is quite independent, as shown + by Gärtner, of the greater or less facility with which the one + fertilises the other. + + With animals, the jackal is prepotent over the dog, as is stated by + Flourens who made many crosses between these animals; and this was + likewise the case with a hybrid which I once saw between a jackal and + terrier. I cannot doubt, from the observations of Colin and others, + that the ass is prepotent over the horse; the prepotency in this + instance running more strongly through the male than through the female + ass; so that the mule resembles the ass more closely than does the + hinny.[151] The {68} male pheasant, judging from Mr. Hewitt's + descriptions,[152] and from the hybrids which I have seen, + preponderates over the domestic fowl; but the latter, as far as colour + is concerned, has considerable power of transmission, for hybrids + raised from five differently coloured hens differed greatly in plumage. + I formerly examined some curious hybrids in the Zoological Gardens, + between the Penguin variety of the common duck and the Egyptian goose + (_Tadorna Ægyptiaca_); and although I will not assert that the + domesticated variety preponderated over the natural species, yet it had + strongly impressed its unnatural upright figure on these hybrids. + + I am aware that such cases as the foregoing have been ascribed by + various authors, not to one species, race, or individual being + prepotent over the other in impressing it character on its crossed + offspring, but to such rules as that the father influences the external + characters and the mother the internal or vital organs. But the great + diversity of the rules given by various authors almost proves their + falseness. Dr. Prosper Lucas has fully discussed this point, and has + shown[153] that none of the rules (and I could add others to those + quoted by him) apply to all animals. Similar rules have been enounced + for plants, and have been proved by Gärtner[154] to be all erroneous. + If we confine our view to the domesticated races of a single species, + or perhaps even to the species of the same genus, some such rules may + hold good; for instance, it seems that in reciprocally crossing various + breeds of fowls the male generally gives colour;[155] but conspicuous + exceptions have passed under my own eyes. In sheep it seems that the + ram usually gives its peculiar horns and fleece to its crossed + offspring, and the bull the presence or absence of horns. + + In the following chapter on Crossing I shall have occasion to show that + certain characters are rarely or never blended by crossing, but are + {69} transmitted in an unmodified state from either parent-form; I + refer to this fact here because it is sometimes accompanied on the one + side by prepotency, which thus acquires the false appearance of unusual + strength. In the same chapter I shall show that the rate at which a + species or breed absorbs and obliterates another by repeated crosses, + depends in chief part on prepotency in transmission. + +In conclusion, some of the cases above given,--for instance, that of the +trumpeter pigeon,--prove that there is a wide difference between mere +inheritance and prepotency. This latter power seems to us, in our +ignorance, to act in most cases quite capriciously. The very same +character, even though it be an abnormal or monstrous one, such as silky +feathers, may be transmitted by different species, when crossed, either +with prepotent force or singular feebleness. It is obvious, that a +purely-bred form of either sex, in all cases in which prepotency does not +run more strongly in one sex than the other, will transmit its character +with prepotent force over a mongrelized and already variable form.[156] +From several of the above-given cases we may conclude that mere antiquity +of character does not by any means necessarily make it prepotent. In some +cases prepotency apparently depends on the same character being present and +visible in one of the two breeds which are crossed, and latent or invisible +in the other breed; and in this case it is natural that the character which +is potentially present in both should be prepotent. Thus, we have reason to +believe that there is a latent tendency in all horses to be dun-coloured +and striped; and when a horse of this kind is crossed with one of any other +colour, it is said that the offspring are almost sure to be striped. Sheep +have a similar latent tendency to become dark-coloured, and we have seen +with what prepotent force a ram with a few black spots, when crossed with +sheep of various breeds, coloured its offspring. All pigeons have a latent +tendency to become slaty-blue, with certain characteristic marks, and it is +known that, when a bird thus coloured is crossed with one of any other +colour, it is most difficult afterwards to eradicate the blue tint. A +nearly parallel case is offered by those black bantams which, as they grow +{70} old, develop a latent tendency to acquire red feathers. But there are +exceptions to the rule: hornless breeds of cattle possess a latent capacity +to reproduce horns, yet when crossed with horned breeds they do not +invariably produce offspring bearing horns. + +We meet with analogous cases with plants. Striped flowers, though they can +be propagated truly by seed, have a latent tendency to become uniformly +coloured, but when once crossed by a uniformly coloured variety, they ever +afterwards fail to produce striped seedlings.[157] Another case is in some +respects more curious: plants bearing peloric or regular flowers have so +strong a latent tendency to reproduce their normally irregular flowers, +that this often occurs by buds when a plant is transplanted into poorer or +richer soil.[158] Now I crossed the peloric snapdragon (_Antirrhinum +majus_), described in the last chapter, with pollen of the common form; and +the latter, reciprocally, with peloric pollen. I thus raised two great beds +of seedlings, and not one was peloric. Naudin[159] obtained the same result +from crossing a peloric Linaria with the common form. I carefully examined +the flowers of ninety plants of the crossed Antirrhinum in the two beds, +and their structure had not been in the least affected by the cross, except +that in a few instances the minute rudiment of the fifth stamen, which is +always present, was more fully or even completely developed. It must not be +supposed that this entire obliteration of the peloric structure in the +crossed plants can be accounted for by any incapacity of transmission; for +I raised a large bed of plants from the peloric Antirrhinum, artificially +fertilised by its own pollen, and sixteen plants, which alone survived the +winter, were all as perfectly peloric as the parent-plant. Here we have a +good instance of the wide difference between the inheritance of a character +and the power of transmitting it to crossed offspring. The crossed plants, +which perfectly resembled the common snapdragon, were allowed to sow +themselves, and, out of a hundred and twenty-seven seedlings, eighty-eight +proved to be common snapdragons, two were in an intermediate condition +between the peloric and normal state, {71} and thirty-seven were perfectly +peloric, having reverted to the structure of their one grandparent. This +case seems at first sight to offer an exception to the rule formerly given, +namely, that a character which is present in one form and latent in the +other is generally transmitted with prepotent force when the two forms are +crossed. For in all the Scrophulariaceæ, and especially in the genera +Antirrhinum and Linaria, there is, as was shown in the last chapter, a +strong latent tendency to become peloric; and there is also, as we have +just seen, a still stronger tendency in all peloric plants to reacquire +their normal irregular structure. So that we have two opposed latent +tendencies in the same plants. Now, with the crossed Antirrhinums the +tendency to produce normal or irregular flowers, like those of the common +Snapdragon, prevailed in the first generation; whilst the tendency to +pelorism, appearing to gain strength by the intermission of a generation, +prevailed to a large extent in the second set of seedlings. How it is +possible for a character to gain strength by the intermission of a +generation, will be considered in the chapter on pangenesis. + +On the whole, the subject of prepotency is extremely intricate,--from its +varying so much in strength, even in regard to the same character, in +different animals,--from its running either equally in both sexes, or, as +frequently is the case with animals, but not with plants, much stronger in +the one sex than the other,--from the existence of secondary sexual +characters,--from the transmission of certain characters being limited, as +we shall immediately see, by sex,--from certain characters not blending +together,--and, perhaps, occasionally from the effects of a previous +fertilisation on the mother. It is therefore not surprising that every one +hitherto has been baffled in drawing up general rules on the subject of +prepotency. + +_Inheritance as limited by Sex._ + +New characters often appear in one sex, and are afterwards transmitted to +the same sex, either exclusively or in a much greater degree than to the +other. This subject is important, because with animals of many kinds in a +state of nature, both high and low in the scale, secondary sexual +characters, not in {72} any way directly connected with the organs of +reproduction, are often conspicuously present. With our domesticated +animals, also, these same secondary characters are often found to differ +greatly from the state in which they exist in the parent-species. And the +principle of inheritance as limited by sex shows how such characters might +have been first acquired and subsequently modified. + + Dr. P. Lucas, who has collected many facts on this subject, shows[160] + that when a peculiarity, in no manner connected with the reproductive + organs, appears in either parent, it is often transmitted exclusively + to the offspring of the same sex, or to a much greater number of them + than of the opposite sex. Thus, in the family of Lambert, the horn-like + projections on the skin were transmitted from the father to his sons + and grandsons alone; so it has been with other cases of ichthyosis, + with supernumerary digits, with a deficiency of digits and phalanges, + and in a lesser degree with various diseases, especially with + colour-blindness, and a hæmorrhagic diathesis, that is, an extreme + liability to profuse and uncontrollable bleeding from trifling wounds. + On the other hand, mothers have transmitted, during several + generations, to their daughters alone, supernumerary and deficient + digits, colour-blindness, and other peculiarities. So that we see that + the very same peculiarity may become attached to either sex, and be + long inherited by that sex alone; but the attachment in certain cases + is much more frequent to one than the other sex. The same peculiarities + also may be promiscuously transmitted to either sex. Dr. Lucas gives + other cases, showing that the male occasionally transmits his + peculiarities to his daughters alone, and the mother to her sons alone; + but even in this case we see that inheritance is to a certain extent, + though inversely, regulated by sex. Dr. Lucas, after weighing the whole + evidence, comes to the conclusion that every peculiarity, according to + the sex in which it first appears, tends to be transmitted in a greater + or lesser degree to that sex. + + A few details from the many cases collected by Mr. Sedgwick,[161] may + be here given. Colour-blindness, from some unknown cause, shows itself + much oftener in males than in females; in upwards of two hundred cases + collected by Mr. Sedgwick, nine-tenths related to men; but it is + eminently liable to be transmitted through women. In the case given by + Dr. Earle, members of eight related families were affected during five + generations: these families consisted of sixty-one individuals, namely, + of thirty-two males, of whom nine-sixteenths were incapable of + distinguishing colour, and of twenty-nine females, of whom only + one-fifteenth were thus affected. {73} Although colour-blindness thus + generally clings to the male sex, nevertheless, in one instance in + which it first appeared in a female, it was transmitted during five + generations to thirteen individuals, all of whom were females. A + hæmorrhagic diathesis, often accompanied by rheumatism, has been known + to affect the males alone during five generations, being transmitted, + however, through the females. It is said that deficient phalanges in + the fingers have been inherited by the females alone during ten + generations. In another case, a man thus deficient in both hands and + feet, transmitted the peculiarity to his two sons and one daughter; but + in the third generation, out of nineteen grandchildren, twelve sons had + the family defect, whilst the seven daughters were free. In ordinary + cases of sexual limitation, the sons or daughters inherit the + peculiarity, whatever it may be, from their father or mother, and + transmit it to their children of the same sex; but generally with the + hæmorrhagic diathesis, and often with colour-blindness, and in some + other cases, the sons never inherit the peculiarity directly from their + fathers, but the daughters, and the daughters alone, transmit the + latent tendency, so that the sons of the daughters alone exhibit it. + Thus, the father, grandson, and great-great-grandson will exhibit a + peculiarity,--the grandmother, daughter, and great-granddaughter having + transmitted it in a latent state. Hence we have, as Mr. Sedgwick + remarks, a double kind of atavism or reversion; each grandson + apparently receiving and developing the peculiarity from his + grandfather, and each daughter apparently receiving the latent tendency + from her grandmother. + + From the various facts recorded by Dr. Prosper Lucas, Mr. Sedgwick, and + others, there can be no doubt that peculiarities first appearing in + either sex, though not in any way necessarily or invariably connected + with that sex, strongly tend to be inherited by the offspring of the + same sex, but are often transmitted in a latent state through the + opposite sex. + + Turning now to domesticated animals, we find that certain characters + not proper to the parent-species are often confined to, and inherited + by, one sex alone; but we do not know the history of the first + appearance of such characters. In the chapter on Sheep, we have seen + that the males of certain races differ greatly from the females in the + shape of their horns, these being absent in the ewes of some breeds, in + the development of fat in the tail in certain fat-tailed breeds, and in + the outline of the forehead. These differences, judging from the + character of the allied wild species, cannot be accounted for by + supposing that they have been derived from distinct parent-forms. There + is, also, a great difference between the horns of the two sexes in one + Indian breed of goats. The bull zebu is said to have a larger hump than + the cow. In the Scotch deer-hound the two sexes differ in size more + than in any other variety of the dog,[162] and, judging from analogy, + more than in the aboriginal parent-species. The peculiar colour called + tortoise-shell is very rarely seen in a male cat; the males of this + variety being of a rusty tint. A tendency to baldness in man before the + advent of old age is certainly inherited; and in the European, or at + least in the {74} Englishman, is an attribute of the male sex, and may + almost be ranked as an incipient secondary sexual character. + + In various breeds of the fowl the males and females often differ + greatly; and these differences are far from being the same with those + which distinguish the two sexes in the parent-species, the _Gallus + bankiva_; and consequently have originated under domestication. In + certain sub-varieties of the Game race we have the unusual case of the + hens differing from each other more than the cocks. In an Indian breed + of a white colour stained with soot, the hens invariably have black + skins, and their bones are covered by a black periosteum, whilst the + cocks are never or most rarely thus characterised. Pigeons offer a more + interesting case; for the two sexes rarely differ throughout the whole + great family, and the males and females of the parent-form, the _C. + livia_, are undistinguishable; yet we have seen that with Pouters the + male has the characteristic quality of pouting more strongly developed + than the female; and in certain sub-varieties[163] the males alone are + spotted or striated with black. When male and female English + carrier-pigeons are exhibited in separate pens, the difference in the + development of the wattle over the beak and round the eyes is + conspicuous. So that here we have instances of the appearance of + secondary sexual characters in the domesticated races of a species in + which such differences are naturally quite absent. + +On the other hand, secondary sexual characters which properly belong to the +species are sometimes quite lost, or greatly diminished, under +domestication. We see this in the small size of the tusks in our improved +breeds of the pig, in comparison with those of the wild boar. There are +sub-breeds of fowls in which the males have lost the fine flowing +tail-feathers and hackles; and others in which there is no difference in +colour between the two sexes. In some cases the barred plumage, which in +gallinaceous birds is commonly the attribute of the hen, has been +transferred to the cock, as in the cuckoo sub-breeds. In other cases +masculine characters have been partly transferred to the female, as with +the splendid plumage of the golden-spangled Hamburgh hen, the enlarged comb +of the Spanish hen, the pugnacious disposition of the Game hen, and as in +the well-developed spurs which occasionally appear in the hens of various +breeds. In Polish fowls both sexes are ornamented with a topknot, that of +the male being formed of hackle-like feathers, and this is a new male +character in the genus Gallus. On the whole, as far as I can judge, new +characters are more apt {75} to appear in the males of our domesticated +animals than in the females, and afterwards to be either exclusively or +more strongly inherited by the males. Finally, in accordance with the +principle of inheritance as limited by sex, the appearance of secondary +sexual characters in natural species offers no especial difficulty, and +their subsequent increase and modification, if of any service to the +species, would follow through that form of selection which in my 'Origin of +Species' I have called sexual selection. + +_Inheritance at corresponding periods of Life._ + +This is an important subject. Since the publication of my 'Origin of +Species,' I have seen no reason to doubt the truth of the explanation there +given of perhaps the most remarkable of all the facts in biology, namely, +the difference between the embryo and the adult animal. The explanation is, +that variations do not necessarily or generally occur at a very early +period of embryonic growth, and that such variations are inherited at a +corresponding age. As a consequence of this the embryo, even when the +parent-form undergoes a great amount of modification, is left only slightly +modified; and the embryos of widely-different animals which are descended +from a common progenitor remain in many important respects like each other +and their common progenitor. We can thus understand why embryology should +throw a flood of light on the natural system of classification, for this +ought to be as far as possible genealogical. When the embryo leads an +independent life, that is, becomes a larva, it has to be adapted to the +surrounding conditions in its structure and instincts, independently of +those of its parents; and the principle of inheritance at corresponding +periods of life renders this possible. + +This principle is, indeed, in one way so obvious that it escapes attention. +We possess a number of races of animals and plants, which, when compared +with each other and with their parent-forms, present conspicuous +differences, both in the immature and mature states. Look at the seeds of +the several kinds of peas, beans, maize, which can be propagated truly, and +see how they differ in size, colour, and shape, whilst the {76} full-grown +plants differ but little. Cabbages on the other hand differ greatly in +foliage and manner of growth, but hardly at all in their seeds; and +generally it will be found that the differences between cultivated plants +at different periods of growth are not necessarily closely connected +together, for plants may differ much in their seeds and little when +full-grown, and conversely may yield seeds hardly distinguishable, yet +differ much when full-grown. In the several breeds of poultry, descended +from a single species, differences in the eggs and chickens, in the plumage +at the first and subsequent moults, in the comb and wattles during +maturity, are all inherited. With man peculiarities in the milk and second +teeth, of which I have received the details, are inheritable, and with man +longevity is often transmitted. So again with our improved breeds of cattle +and sheep, early maturity, including the early development of the teeth, +and with certain breeds of fowl the early appearance of secondary sexual +characters, all come under the same head of inheritance at corresponding +periods. + +Numerous analogous facts could be given. The silk-moth, perhaps, offers the +best instance; for in the breeds which transmit their characters truly, the +eggs differ in size, colour, and shape;--the caterpillars differ, in +moulting three or four times, in colour, even in having a dark-coloured +mark like an eyebrow, and in the loss of certain instincts;--the cocoons +differ in size, shape, and in the colour and quality of the silk; these +several differences being followed by slight or barely distinguishable +differences in the mature moth. + +But it may be said that, if in the above cases a new peculiarity is +inherited, it must be at the corresponding stage of development; for an egg +or seed can resemble only an egg or seed, and the horn in a full-grown ox +can resemble only a horn. The following cases show inheritance at +corresponding periods more plainly, because they refer to peculiarities +which might have supervened, as far as we can see, earlier or later in +life, yet are inherited at the same period at which they first appeared. + + In the Lambert family the porcupine-like excrescences appeared in the + father and sons at the same age, namely, about nine weeks after {77} + birth.[164] In the extraordinary hairy family described by Mr. + Crawfurd,[165] children were produced during three generations with + hairy ears; in the father the hair began to grow over his body at six + years old; in his daughter somewhat earlier, namely, at one year; and + in both generations the milk teeth appeared late in life, the permanent + teeth being afterwards singularly deficient. Greyness of hair at an + unusually early age has been transmitted in some families. These cases + border on diseases inherited at corresponding periods of life, to which + I shall immediately refer. + + It is a well-known peculiarity with almond-tumbler pigeons, that the + full beauty and peculiar character of the plumage does not appear until + the bird has moulted two or three times. Neumeister describes and + figures a breed of pigeons in which the whole body is white except the + breast, neck, and head; but before the first moult all the white + feathers acquire coloured edges. Another breed is more remarkable: its + first plumage is black, with rusty-red wing-bars and a crescent-shaped + mark on the breast; these marks then became white, and remain so during + three or four moults; but after this period the white spreads over the + body, and the bird loses its beauty.[166] Prize canary-birds have their + wings and tail black: "this colour, however, is only retained until the + first moult, so that they must be exhibited ere the change takes place. + Once moulted, the peculiarity has ceased. Of course all the birds + emanating from this stock have black wings and tails the first + year."[167] A curious and somewhat analogous account has been + given[168] of a family of wild pied rooks which were first observed in + 1798, near Chalfont, and which every year from that date up to the + period of the published notice, viz. 1837, "have several of their brood + particoloured, black and white. This variegation of the plumage, + however, disappears with the first moult; but among the next young + families there are always a few pied ones." These changes of plumage, + which appear and are inherited at various corresponding periods of life + in the pigeon, canary-bird, and rook, are remarkable, because the + parent-species undergo no such change. + + Inherited diseases afford evidence in some respects of less value than + the foregoing cases, because diseases are not necessarily connected + with any change in structure; but in other respects of more value, + because the periods have been more carefully observed. Certain diseases + are communicated to the child apparently by a process like inoculation, + and the child is from the first affected; such cases may be here passed + over. Large classes of diseases usually appear at certain ages, such as + St. Vitus's dance in youth, consumption in early mid-life, gout later, + and apoplexy still later; and these are naturally inherited at the same + period. But even in diseases of this class, instances have been + recorded, as with St. Vitus's {78} dance, showing that an unusually + early or late tendency to the disease is inheritable.[169] In most + cases the appearance of any inherited disease is largely determined by + certain critical periods in each person's life, as well as by + unfavourable conditions. There are many other diseases, which are not + attached to any particular period, but which certainly tend to appear + in the child at about the same age at which the parent was first + attacked. An array of high authorities, ancient and modern, could be + given in support of this proposition. The illustrious Hunter believed + in it; and Piorry[170] cautions the physician to look closely to the + child at the period when any grave inheritable disease attacked the + parent. Dr. Prosper Lucas,[171] after collecting facts from every + source, asserts that affections of all kinds, though not related to any + particular period of life, tend to reappear in the offspring at + whatever period of life they first appeared in the progenitor. + + As the subject is important, it may be well to give a few instances, + simply as illustrations, not as proof; for proof, recourse must be had + to the authorities above quoted. Some of the following cases have been + selected for the sake of showing that, when a slight departure from the + rule occurs, the child is affected somewhat earlier in life than the + parent. In the family of Le Compte blindness was inherited during three + generations, and no less than thirty-seven children and grandchildren + were all affected at about the same age, namely seventeen or + eighteen.[172] In another case a father and his four children all + became blind at twenty-one years old; in another, a grandmother grew + blind at thirty-five, her daughter at nineteen, and three grandchildren + at the ages of thirteen and eleven.[173] So with deafness, two + brothers, their father and paternal grandfather, all became deaf at the + age of forty.[174] + + Esquirol gives several striking instances of insanity coming on at the + same age, as that of a grandfather, father, and son, who all committed + suicide near their fiftieth year. Many other cases could be given, as + of a whole family who became insane at the age of forty.[175] Other + cerebral affections sometimes follow the same rule,--for instance, + epilepsy and apoplexy. A woman died of the latter disease when + sixty-three years old; one of her daughters at forty-three, and the + other at sixty-seven: the latter had twelve children, who all died from + tubercular meningitis.[176] I mention this latter case because it + illustrates a frequent occurrence, namely, a change in the precise + nature of an inherited disease, though still affecting the same organ. + + {79} + + Asthma has attacked several members of the same family when forty years + old, and other families during infancy. The most different diseases, as + angina pectoris, stone in the bladder, and various affections of the + skin, have appeared in successive generations at nearly the same age. + The little finger of a man began from some unknown cause to grow + inwards, and the same finger in his two sons began at the same age to + bend inwards in a similar manner. Strange and inexplicable neuralgic + affections have caused parents and children to suffer agonies at about + the same period of life.[177] + + I will give only two other cases, which are interesting as illustrating + the disappearance as well as the appearance of disease at the same age. + Two brothers, their father, their paternal uncles, seven cousins, and + their paternal grandfather, were all similarly affected by a + skin-disease, called pityriasis versicolor; "the disease, strictly + limited to the males of the family (though transmitted through the + females), usually appeared at puberty, and disappeared at about the age + of forty or forty-five years." The second case is that of four + brothers, who when about twelve years old suffered almost every week + from severe headaches, which were relieved only by a recumbent position + in a dark room. Their father, paternal uncles, paternal grandfather, + and paternal granduncles all suffered in the same way from headaches, + which ceased at the age of fifty-four or fifty-five in all those who + lived so long. None of the females of the family were affected.[178] + +It is impossible to read the foregoing accounts, and the many others which +have been recorded, of diseases coming on during three or even more +generations, at the same age in several members of the same family, +especially in the case of rare affections in which the coincidence cannot +be attributed to chance, and doubt that there is a strong tendency to +inheritance in disease at corresponding periods of life. When the rule +fails, the disease is apt to come on earlier in the child than in the +parent; the exceptions in the other direction being vey much rarer. Dr. +Lucas[179] alludes to several cases of inherited diseases coming on at an +earlier period. I have already given one striking instance with blindness +during three generations; and Mr. Bowman remarks that this frequently +occurs with cataract. With cancer there seems to be a peculiar liability to +earlier inheritance: Mr. Paget, who has particularly {80} attended to this +subject, and tabulated a large number of cases, informs me that he believes +that in nine cases out of ten the later generation suffers from the disease +at an earlier period than the previous generation. He adds, "In the +instances in which the opposite relation holds, and the members of later +generations have cancer at a later age than their predecessors, I think it +will be found that the non-cancerous parents have lived to extreme old +ages." So that the longevity of a non-affected parent seems to have the +power of determining in the offspring the fatal period; and we thus +apparently get another element of complexity in inheritance. + +The facts, showing that with certain diseases the period of inheritance +occasionally or even frequently advances, are important with respect to the +general descent-theory, for they render it in some degree probable that the +same thing would occur with ordinary modifications of structure. The final +result of a long series of such advances would be the gradual obliteration +of characters proper to the embryo and larva, which would thus come to +resemble more and more closely the mature parent-form. But any structure +which was of service to the embryo or larva would be preserved by the +destruction at this stage of growth of each individual which manifested any +tendency to lose at too early an age its own proper character. + +Finally, from the numerous races of cultivated plants and domestic animals, +in which the seed or eggs, the young or old, differ from each other and +from their parent-species;--from the cases in which new characters have +appeared at a particular period, and afterwards have been inherited at the +same period;--and from what we know with respect to disease, we must +believe in the truth of the great principle of inheritance at corresponding +periods of life. + + * * * * * + +_Summary of the three preceding Chapters._--Strong as is the force of +inheritance, it allows the incessant appearance of new characters. These, +whether beneficial or injurious, of the most trifling importance, such as a +shade of colour in a flower, a coloured lock of hair, or a mere gesture; or +of the highest importance, as when affecting the brain or an organ so +perfect {81} and complex as the eye; or of so grave a nature as to deserve +to be called a monstrosity, or so peculiar as not to occur normally in any +member of the same natural class, are all sometimes strongly inherited by +man, the lower animals, and plants. In numberless cases it suffices for the +inheritance of a peculiarity that one parent alone should be thus +characterised. Inequalities in the two sides of the body, though opposed to +the law of symmetry, may be transmitted. There is a considerable body of +evidence showing that even mutilations, and the effects of accidents, +especially or perhaps exclusively when followed by disease, are +occasionally inherited. There can be no doubt that the evil effects of +long-continued exposure in the parent to injurious conditions are sometimes +transmitted to the offspring. So it is, as we shall see in a future +chapter, with the effects of the use and disuse of parts, and of mental +habits. Periodical habits are likewise transmitted, but generally, as it +would appear, with little force. + +Hence we are led to look at inheritance as the rule, and non-inheritance as +the anomaly. But this power often appears to us in our ignorance to act +capriciously, transmitting a character with inexplicable strength or +feebleness. The very same peculiarity, as the weeping habit of trees, +silky-feathers, &c., may be inherited either firmly or not at all by +different members of the same group, and even by different individuals of +the same species, though treated in the same manner. In this latter case we +see that the power of transmission is a quality which is merely individual +in its attachment. As with single characters, so it is with the several +concurrent slight differences which distinguish sub-varieties or races; for +of these, some can be propagated almost as truly as species, whilst others +cannot be relied on. The same rule holds good with plants, when propagated +by bulbs, offsets, &c., which in one sense still form parts of the same +individual, for some varieties retain or inherit through successive +bud-generations their character far more truly than others. + +Some characters not proper to the parent-species have certainly been +inherited from an extremely remote epoch, and may therefore be considered +as firmly fixed. But it is doubtful whether length of inheritance in itself +gives fixedness of character; {82} though the chances are obviously in +favour of any character which has long been transmitted true or unaltered, +still being transmitted true as long as the conditions of life remain the +same. We know that many species, after having retained the same character +for countless ages, whilst living under their natural conditions, when +domesticated have varied in the most diversified manner, that is, have +failed to transmit their original form; so that no character appears to be +absolutely fixed. We can sometimes account for the failure of inheritance +by the conditions of life being opposed to the development of certain +characters; and still oftener, as with plants cultivated by grafts and +buds, by the conditions causing new and slight modifications incessantly to +appear. In this latter case it is not that inheritance wholly fails, but +that new characters are continually superadded. In some few cases, in which +both parents are similarly characterised, inheritance seems to gain so much +force by the combined action of the two parents, that it counteracts its +own power, and a new modification is the result. + +In many cases the failure of the parents to transmit their likeness is due +to the breed having been at some former period crossed; and the child takes +after his grandparent or more remote ancestor of foreign blood. In other +cases, in which the breed has not been crossed, but some ancient character +has been lost through variation, it occasionally reappears through +reversion, so that the parents apparently fail to transmit their own +likeness. In all cases, however, we may safely conclude that the child +inherits all its characters from its parents, in whom certain characters +are latent, like the secondary sexual characters of one sex in the other. +When, after a long succession of bud-generations, a flower or fruit becomes +separated into distinct segments, having the colours or other attributes of +both parent-forms, we cannot doubt that these characters were latent in the +earlier buds, though they could not then be detected, or could be detected +only in an intimately commingled state. So it is with animals of crossed +parentage, which with advancing years occasionally exhibit characters +derived from one of their two parents, of which not a trace could at first +be perceived. Certain monstrosities, which resemble what naturalists call +the typical form of the group in question, {83} apparently come under the +same law of reversion. It is assuredly an astonishing fact that the male +and female sexual elements, that buds, and even full-grown animals, should +retain characters, during several generations in the case of crossed +breeds, and during thousands of generations in the case of pure breeds, +written as it were in invisible ink, yet ready at any time to be evolved +under the requisite conditions. + +What these conditions are, we do not in many cases at all know. But the act +of crossing in itself, apparently from causing some disturbance in the +organisation, certainly gives a strong tendency to the reappearance of +long-lost characters, both corporeal and mental, independently of those +derived from the cross. A return of any species to its natural conditions +of life, as with feral animals and plants, favours reversion; though it is +certain that this tendency exists, we do not know how far it prevails, and +it has been much exaggerated. On the other hand, the crossed offspring of +plants which have had their organisation disturbed by cultivation, are more +liable to reversion than the crossed offspring of species which have always +lived under their natural conditions. + +When distinguishable individuals of the same family, or races, or species +are crossed, we see that the one is often prepotent over the other in +transmitting its own character. A race may possess a strong power of +inheritance, and yet when crossed, as we have seen with trumpeter-pigeons, +yield to the prepotency of every other race. Prepotentcy of transmission +may be equal in the two sexes of the same species, but often runs more +strongly in one sex. It plays an important part in determining the rate at +which one race can be modified or wholly absorbed by repeated crosses with +another. We can seldom tell what makes one race or species prepotent over +another; but it sometimes depends on the same character being present and +visible in one parent, and latent or potentially present in the other. + +Characters may first appear in either sex, but oftener in the male than in +the female, and afterwards be transmitted to the offspring of the same sex. +In this case we may feel confident that the peculiarity in question is +really present though latent in the opposite sex; hence the father may +transmit through his daughter any character to his grandson; and the mother +{84} conversely to her granddaughter. We thus learn, and the fact is an +important one, that transmission and development are distinct powers. +Occasionally these two powers seem to be antagonistic, or incapable of +combination in the same individual; for several cases have been recorded in +which the son has not directly inherited a character from his father, or +directly transmitted it to his son, but has received it by transmission +through his non-affected mother, and transmitted it through his +non-affected daughter. Owing to inheritance being limited by sex, we can +see how secondary sexual characters may first have arisen under nature; +their preservation and accumulation being dependent on their service to +either sex. + +At whatever period of life a new character first appears, it generally +remains latent in the offspring until a corresponding age is attained, and +then it is developed. When this rule fails, the child generally exhibits +the character at an earlier period than the parent. On this principle of +inheritance at corresponding periods, we can understand how it is that most +animals display from the germ to maturity such a marvellous succession of +characters. + +Finally, though much remains obscure with respect to Inheritance, we may +look at the following laws as fairly well established. Firstly, a tendency +in every character, new and old, to be transmitted by seminal and bud +generation, though often counteracted by various known and unknown causes. +Secondly, reversion or atavism, which depends on transmission and +development being distinct powers: it acts in various degrees and manners +through both seminal and bud generation. Thirdly, prepotency of +transmission, which may be confined to one sex, or be common to both sexes +of the prepotent form. Fourthly, transmission, limited by sex, generally to +the same sex in which the inherited character first appeared. Fifthly, +inheritance at corresponding periods of life, with some tendency to the +earlier development of the inherited character. In these laws of +Inheritance, as displayed under domestication, we see an ample provision +for the production, through variability and natural selection, of new +specific forms. + + * * * * * + + +{85} + +CHAPTER XV. + +ON CROSSING. + + FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED + BREEDS--WHEN THE NUMBERS OF TWO COMMINGLING BREEDS ARE UNEQUAL, ONE + ABSORBS THE OTHER--THE RATE OF ABSORPTION DETERMINED BY PREPOTENCY OF + TRANSMISSION, BY THE CONDITIONS OF LIFE, AND BY NATURAL SELECTION--ALL + ORGANIC BEINGS OCCASIONALLY INTERCROSS; APPARENT EXCEPTIONS--ON CERTAIN + CHARACTERS INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE WHICH HAVE + SUDDENLY APPEARED IN THE INDIVIDUAL--ON THE MODIFICATION OF OLD RACES, + AND THE FORMATION OF NEW RACES, BY CROSSING--SOME CROSSED RACES HAVE + BRED TRUE FROM THEIR FIRST PRODUCTION--ON THE CROSSING OF DISTINCT + SPECIES IN RELATION TO THE FORMATION OF DOMESTIC RACES. + +In the two previous chapters, when discussing reversion and prepotency, I +was necessarily led to give many facts on crossing. In the present chapter +I shall consider the part which crossing plays in two opposed +directions,--firstly, in obliterating characters, and consequently in +preventing the formation of new races; and secondly, in the modification of +old races, or in the formation of new and intermediate races, by a +combination of characters. I shall also show that certain characters are +incapable of fusion. + +The effects of free or uncontrolled breeding between the members of the +same variety or of closely allied varieties are important; but are so +obvious that they need not be discussed at much length. It is free +intercrossing which chiefly gives uniformity, both under nature and under +domestication, to the individuals of the same species or variety, when they +live mingled together and are not exposed to any cause inducing excessive +variability. The prevention of free crossing, and the intentional matching +of individual animals, are the corner-stones of the breeder's art. No man +in his senses would expect to improve or modify a breed in any particular +manner, or keep an old breed true and distinct, unless he separated his +animals. The killing of inferior animals in each generation comes to the +{86} same thing as their separation. In savage and semi-civilised +countries, where the inhabitants have not the means of separating their +animals, more than a single breed of the same species rarely or never +exists. In former times, even in a country so civilised as North America, +there were no distinct races of sheep, for all had been mingled +together.[180] The celebrated agriculturist Marshall[181] remarks that +"sheep that are kept within fences, as well as shepherded flocks in open +countries, have generally a similarity, if not a uniformity, of character +in the individuals of each flock;" for they breed freely together, and are +prevented from crossing with other kinds; whereas in the unenclosed parts +of England the unshepherded sheep, even of the same flock, are far from +true or uniform, owing to various breeds having mingled and crossed. We +have seen that the half-wild cattle in the several British parks are +uniform in character in each; but in the different parks, from not having +mingled and crossed during many generations, they differ in a slight +degree. + +We cannot doubt that the extraordinary number of varieties and +sub-varieties of the pigeon, amounting to at least one hundred and fifty, +is partly due to their remaining, differently from other domesticated +birds, paired for life when once matched. On the other hand, breeds of cats +imported into this country soon disappear, for their nocturnal and rambling +habits render it hardly possible to prevent free crossing. Rengger[182] +gives an interesting case with respect to the cat in Paraguay: in all the +distant parts of the kingdom it has assumed, apparently from the effects of +the climate, a peculiar character, but near the capital this change has +been prevented, owing, as he asserts, to the native animal frequently +crossing with cats imported from Europe. In all cases like the foregoing, +the effects of an occasional cross will be augmented by the increased +vigour and fertility of the crossed offspring, of which fact evidence will +hereafter be given; for this will lead to the mongrels increasing more +rapidly than the pure parent-breeds. + +{87} + +When distinct breeds are allowed to cross freely, the result will be a +heterogenous body; for instance, the dogs in Paraguay are far from uniform, +and can no longer be affiliated to their parent-races.[183] The character +which a crossed body of animals will ultimately assume must depend on +several contingencies,--namely, on the relative numbers of the individuals +belonging to the two or more races which are allowed to mingle; on the +prepotency of one race over the other in the transmission of character; and +on the conditions of life to which they are exposed. When two commingled +breeds exist at first in nearly equal numbers, the whole will sooner or +later become intimately blended, but not so soon, both breeds being equally +favoured in all respects, as might have been expected. The following +calculation[184] shows that this is the case: if a colony with an equal +number of black and white men were founded, and we assume that they marry +indiscriminately, are equally prolific, and that one in thirty annually +dies and is born; then "in 65 years the number of blacks, whites, and +mulattoes would be equal. In 91 years the whites would be 1-10th, the +blacks 1-10th, and the mulattoes, or people of intermediate degrees of +colour, 8-10ths of the whole number. In three centuries not 1-100th part of +the whites would exist." + +When one of two mingled races exceeds the other greatly in number, the +latter will soon be wholly, or almost wholly, absorbed and lost.[185] Thus +European pigs and dogs have been largely introduced into the islands of the +Pacific Ocean, and the native races have been absorbed and lost in the +course of about fifty or sixty years;[186] but the imported races no doubt +were favoured. Rats may be considered as semi-domesticated animals. Some +snake-rats (_Mus alexandrinus_) escaped in the Zoological Gardens of +London, "and for a long time afterwards the keepers frequently caught +cross-bred rats, at first half-breds, afterwards with less and less of the +character of the snake-rat, till at length all traces of it +disappeared."[187] On the other hand, {88} in some parts of London, +especially near the docks, where fresh rats are frequently imported, an +endless variety of intermediate forms may be found between the brown, +black, and snake rat, which are all three usually ranked as distinct +species. + +How many generations are necessary for one species or race to absorb +another by repeated crosses has often been discussed;[188] and the +requisite number has probably been much exaggerated. Some writers have +maintained that a dozen, or score, or even more generations, are necessary; +but this in itself is improbable, for in the tenth generation there will be +only 1-1024th part of foreign blood in the offspring. Gärtner found,[189] +that with plants one species could be made to absorb another in from three +to five generations, and he believes that this could always be effected in +from six to seventh generations. In one instance, however, Kölreuter[190] +speaks of the offspring of _Mirabilis vulgaris_, crossed during eight +successive generations by _M. longiflora_, as resembling this latter +species so closely, that the most scrupulous observer could detect "vix +aliquam notabilem differentiam;"--he succeeded, as he says, "ad plenariam +fere transmutationem." But this expression shows that the act of absorption +was not even then absolutely complete, though these crossed plants +contained only the 1-256th part of _M. vulgaris_. The conclusions of such +accurate observers as Gärtner and Kölreuter are of far higher worth than +those made without scientific aim by breeders. The most remarkable +statement which I have met with of the persistent endurance of the effects +of a single cross is given by Fleischmann,[191] who, in reference to German +sheep, says "that the original coarse sheep have 5500 fibres of wool on a +square inch; grades of the third or fourth Merino cross produced about +8000, the twentieth cross 27,000, the perfect pure Merino blood 40,000 to +48,000." So that in this case common German sheep crossed twenty times +successively with Merinos have not by any means acquired wool as fine as +that of the pure breed. In all cases, the rate of absorption will {89} +depend largely on the conditions of life being favourable to any particular +character; and we may suspect that there would be under the climate of +Germany a constant tendency to degeneration in the wool of Merinos, unless +prevented by careful selection; and thus perhaps the foregoing remarkable +case may be explained. The rate of absorption must also depend on the +amount of distinguishable difference between the two forms which are +crossed, and especially, as Gärtner insists, on prepotency of transmission +in the one form over the other. We have seen in the last chapter that one +of two French breeds of sheep yielded up its character, when crossed with +Merinos, very much slower than the other; and the common German sheep +referred to by Fleischmann may present an analogous case. But in all cases +there will be during many subsequent generations more or less liability to +reversion, and it is this fact which has probably led authors to maintain +that a score or more of generations are requisite for one race to absorb +another. In considering the final result of the commingling of two or more +breeds, we must not forget that the act of crossing in itself tends to +bring back long-lost characters not proper to the immediate parent-forms. + +With respect to the influence of the conditions of life on any two breeds +which are allowed to cross freely, unless both are indigenous and have long +been accustomed to the country where they live, they will, in all +probability, be unequally affected by the conditions, and this will modify +the result. Even with indigenous breeds, it will rarely or never occur that +both are equally well adapted to the surrounding circumstances; more +especially when permitted to roam freely, and not carefully tended, as will +generally be the case with breeds allowed to cross. As a consequence of +this, natural selection will to a certain extent come into action, and the +best fitted will survive, and this will aid in determining the ultimate +character of the commingled body. + +How long a time it would require before such a crossed body of animals +would assume within a limited area a uniform character no one can say; that +they would ultimately become uniform from free intercrossing, and from the +survival of the fittest, we may feel assured; but the character thus +acquired would rarely or never, as we may infer from the several previous +{90} considerations, be exactly intermediate between that of the two +parent-breeds. With respect to the very slight differences by which the +individuals of the same sub-variety, or even of allied varieties, are +characterised, it is obvious that free crossing would soon obliterate such +small distinctions. The formation of new varieties, independently of +selection, would also thus be prevented; except when the same variation +continually recurred from the action of some strongly predisposing cause. +Hence we may conclude that free crossing has in all cases played an +important part in giving to all the members of the same domestic race, and +of the same natural species, uniformity of character, though largely +modified by natural selection and by the direct action of the surrounding +conditions. + +_On the possibility of all organic beings occasionally intercrossing._--But +it may be asked, can free crossing occur with hermaphrodite animals and +plants? All the higher animals, and the few insects which have been +domesticated, have separated sexes, and must inevitably unite for each +birth. With respect to the crossing of hermaphrodites, the subject is too +large for the present volume, and will be more properly treated in a +succeeding work. In my 'Origin of Species,' however, I have given a short +abstract of the reasons which induce me to believe that all organic beings +occasionally cross, though perhaps in some cases only at long intervals of +time.[192] I will here just recall the fact that many plants, though +hermaphrodite in structure, are unisexual in function;--such as those +called by C. K. Sprengel _dichogamous_, in which the pollen and stigma of +the same flower are matured at different periods; or those called by me +_reciprocally dimorphic_, in which the flower's own pollen is not fitted to +fertilise its own stigma; or again, the many kinds in which curious +mechanical contrivances exist, effectually preventing self-fertilisation. +There are, however, many hermaphrodite plants which are not in any way +specially constructed to favour intercrossing, but which nevertheless +commingle almost as freely as animals with separated sexes. This is the +case with cabbages, radishes, and onions, as I know from {91} having +experimented on them: even the peasants of Liguria say that cabbages must +be prevented "from falling in love" with each other. In the orange tribe, +Gallesio[193] remarks that the amelioration of the various kinds is checked +by their continual and almost regular crossing. So it is with numerous +other plants. + +Nevertheless some cultivated plants can be named which rarely intercross, +as the common pea, or which never intercross, as I have reason to believe +is the case with the sweet-pea (_Lathyrus odoratus_); yet the structure of +these flowers certainly favours an occasional cross. The varieties of the +tomato and aubergine (_Solanum_) and pimenta (_Pimenta vulgaris?_) are +said[194] never to cross, even when growing alongside each other. But it +should be observed that these are all exotic plants, and we do not know how +they would behave in their native country when visited by the proper +insects. + +It must also be admitted that some few natural species appear under our +present state of knowledge to be perpetually self-fertilised, as in the +case of the Bee Ophrys (_O. apifera_), though adapted in its structure to +be occasionally crossed. The _Leersia oryzoides_ produces minute enclosed +flowers which cannot possibly be crossed, and these alone, to the exclusion +of the ordinary flowers, have as yet been known to yield seed.[195] A few +additional and analogous cases could be advanced. But these facts do not +make me doubt that it is a general law of nature that the individuals of +the same species occasionally intercross, and that some great advantage is +derived from this act. It is well known (and I shall hereafter have to give +instances) that some plants, both indigenous and naturalised, rarely or +never produce flowers; or, if they flower, never produce seeds. But no one +is thus led to doubt that it is a general law of nature that phanerogamic +plants should produce flowers, and that these flowers should produce seed. +When they fail, we believe that such plants would perform their proper +functions under different conditions, or that they formerly did so and will +do so again. On analogous grounds, I believe that the few flowers {92} +which do not now intercross, either would do so under different conditions, +or that they formerly fertilised each other at intervals--the means for +effecting this being generally still retained--and they will do so again at +some future period, unless indeed they become extinct. On this view alone, +many points in the structure and action of the reproductive organs in +hermaphrodite plants and animals are intelligible,--for instance, the male +and female organs never being so completely enclosed as to render access +from without impossible. Hence we may conclude that the most important of +all the means for giving uniformity to the individuals of the same species, +namely, the capacity of occasionally intercrossing, is present, or has been +formerly present, with all organic beings. + + _On certain Characters not blending._--When two breeds are crossed + their characters usually become intimately fused together; but some + characters refuse to blend, and are transmitted in an unmodified state + either from both parents or from one. When grey and white mice are + paired, the young are not piebald nor of an intermediate tint, but are + pure white or of the ordinary grey colour: so it is when white and + common collared turtle-doves are paired. In breeding Game fowls, a + great authority, Mr. J. Douglas, remarks, "I may here state a strange + fact: if you cross a black with a white game, you get birds of both + breeds of the clearest colour." Sir R. Heron crossed during many years + white, black, brown, and fawn-coloured Angora rabbits, and never once + got these colours mingled in the same animal, but often all four + colours in the same litter.[196] Additional cases could be given, but + this form of inheritance is very far from universal even with respect + to the most distinct colours. When turnspit dogs and ancon sheep, both + of which have dwarfed limbs, are crossed with common breeds, the + offspring are not intermediate in structure, but take after either + parent. When tailless or hornless animals are crossed with perfect + animals, it frequently, but by no means invariably, happens that the + offspring are {93} either perfectly furnished with these organs or are + quite destitute of them. According to Rengger, the hairless condition + of the Paraguay dog is either perfectly or not at all transmitted to + its mongrel offspring; but I have seen one partial exception in a dog + of this parentage which had part of its skin hairy, and part naked; the + parts being distinctly separated as in a piebald animal. When Dorking + fowls with five toes are crossed with other breeds, the chickens often + have five toes on one foot and four on the other. Some crossed pigs + raised by Sir R. Heron between the solid-hoofed and common pig had not + all four feet in an intermediate condition, but two feet were furnished + with properly divided, and two with united hoofs. + + Analogous facts have been observed with plants: Major Trevor Clarke + crossed the little, glabrous-leaved, annual stock (_Matthiola_), with + pollen of a large, red-flowered, rough-leaved, biennial stock, called + _cocardeau_ by the French, and the result was that half the seedlings + had glabrous and the other half rough leaves, but none had leaves in an + intermediate state. That the glabrous seedlings were the product of the + rough-leaved variety, and not accidentally of the mother-plant's own + pollen, was shown by their tall and strong habit of growth.[197] In the + succeeding generations raised from the rough-leaved crossed seedlings, + some glabrous plants appeared, showing that the glabrous character, + though incapable of blending with and modifying the rough leaves, was + all the time latent in this family of plants. The numerous plants + formerly referred to, which I raised from reciprocal crosses between + the peloric and common Antirrhinum, offer a nearly parallel case; for + in the first generation all the plants resembled the common form, and + in the next generation, out of one hundred and thirty-seven plants, two + alone were in an intermediate condition, the others perfectly + resembling either the peloric or common form. Major Trevor Clarke also + fertilised the above-mentioned red-flowered stock with pollen from the + purple Queen stock, and about half the seedlings scarcely differed in + habit, and not at all in the red colour of the flower, from the + mother-plant, the other half bearing blossoms of a rich purple, closely + like those of the paternal plant. Gärtner crossed many white and + yellow-flowered species and varieties of Verbascum; and these colours + were never blended, but the offspring bore either pure white or pure + yellow blossoms; the former in the larger proportion.[198] Dr. Herbert + raised many seedlings, as he informed me, from Swedish turnips crossed + by two other varieties, and these never produced flowers of an + intermediate tint, but always like one of their parents. I fertilised + the purple sweet-pea (_Lathyrus odoratus_), which has a dark + reddish-purple standard-petal and violet-coloured wings and keel, with + pollen of the painted-lady sweet-pea, which has a pale cherry-coloured + standard, and almost white wings and keel; and from the same pod I + twice raised plants perfectly resembling both sorts; the greater number + resembling the father. So perfect was the resemblance, that I should + have thought there had {94} been some mistake, if the plants which were + at first identical with the paternal variety, namely, the painted-lady, + had not later in the season produced, as mentioned in a former chapter, + flowers blotched and streaked with dark purple. I raised grandchildren + and great-grandchildren from these crossed plants, and they continued + to resemble the painted-lady, but during the later generations became + rather more blotched with purple, yet none reverted completely to the + original mother-plant, the purple sweet-pea. The following case is + slightly different, but still shows the same principle: Naudin[199] + raised numerous hybrids between the yellow _Linaria vulgaris_ and the + purple _L. purpurea_, and during three successive generations the + colours kept distinct in different parts of the same flower. + + From such cases as the foregoing, in which the offspring of the first + generation perfectly resemble either parent, we come by a small step to + those cases in which differently coloured flowers borne on the same + root resemble both parents, and by another step to those in which the + same flower or fruit is striped or blotched with the two parental + colours, or bears a single stripe of the colour or other characteristic + quality of one of the parent-forms. With hybrids and mongrels it + frequently or even generally happens that one part of the body + resembles more or less closely one parent and another part the other + parent; and here again some resistance to fusion, or, what comes to the + same thing, some mutual affinity between the organic atoms of the same + nature, apparently comes into play, for otherwise all parts of the body + would be equally intermediate in character. So again, when the + offspring of hybrids or mongrels, which are themselves nearly + intermediate in character, revert either wholly or by segments to their + ancestors, the principle of the affinity of similar, or the repulsion + of dissimilar atoms, must come into action. To this principle, which + seems to be extremely general, we shall recur in the chapter on + pangenesis. + + It is remarkable, as has been strongly insisted upon by Isidore + Geoffroy St. Hilaire in regard to animals, that the transmission of + characters without fusion occurs most rarely when species are crossed; + I know of one exception alone, namely, with the hybrids naturally + produced between the common and hooded crow (_Corvus corone_ and + _cornix_), which, however, are closely allied species, differing in + nothing except colour. Nor have I met with any well-ascertained cases + of transmission of this kind, even when one form is strongly prepotent + over another, when two races are crossed which have been slowly formed + by man's selection, and therefore resemble to a certain extent natural + species. Such cases as puppies in the same litter closely resembling + two distinct breeds, are probably due to super-foetation,--that is, to + the influence of two fathers. All the characters above enumerated, + which are transmitted in a perfect state to some of the offspring and + not to others,--such as distinct colours, nakedness of skin, smoothness + of leaves, absence of horns or tail, additional toes, pelorism, dwarfed + structure, &c.,--have all been known to appear suddenly in individual + animals and plants. From this fact, and from the several slight, + aggregated differences which distinguish domestic races and species + from {95} each other, not being liable to this peculiar form of + transmission, we may conclude that it is in some way connected with the + sudden appearance of the characters in question. + +_On the Modification of old Races and the Formation of new Races by +Crossing._--We have hitherto chiefly considered the effects of crossing in +giving uniformity of character; we must now look to an opposite result. +There can be no doubt that crossing, with the aid of rigorous selection +during several generations, has been a potent means in modifying old races, +and in forming new ones. Lord Orford crossed his famous stud of greyhounds +once with the bulldog, which breed was chosen from being deficient in +scenting powers, and from having what was wanted, courage and perseverance. +In the course of six or seven generations all traces of the external form +of the bulldog were eliminated, but courage and perseverance remained. +Certain pointers have been crossed, as I hear from the Rev. W. D. Fox, with +the foxhound, to give them dash and speed. Certain strains of Dorking fowls +have had a slight infusion of Game blood; and I have known a great fancier +who on a single occasion crossed his turbit-pigeons with barbs, for the +sake of gaining greater breadth of beak. + +In the foregoing cases breeds have been crossed once, for the sake of +modifying some particular character; but with most of the improved races of +the pig, which now breed true, there have been repeated crosses,--for +instance, the improved Essex owes its excellence to repeated crosses with +the Neapolitan, together probably with some infusion of Chinese blood.[200] +So with our British sheep: almost all the races, except the Southdown, have +been largely crossed; "this, in fact, has been the history of our principal +breeds."[201] To give an example, the "Oxfordshire Downs" now rank as an +established breed.[202] They were produced about the year 1830 by crossing +"Hampshire and in some instances Southdown ewes with Cotswold rams:" now +the Hampshire ram was itself produced by repeated crosses between the +native {96} Hampshire sheep and Southdowns; and the long-woolled Cotswold +were improved by crosses with the Leicester, which latter again is believed +to have been a cross between several long-woolled sheep. Mr. Spooner, after +considering the various cases which have been carefully recorded, concludes +"that from a judicious pairing of cross-bred animals it is practicable to +establish a new breed." On the Continent the history of several crossed +races of cattle and of other animals has been well ascertained. To give one +instance: the King of Wurtemberg, after twenty-five years' careful +breeding, that is after six or seven generations, made a new breed of +cattle from a cross between a Dutch and Swiss breed, combined with other +breeds.[203] The Sebright bantam, which breeds as true as any other kind of +fowl, was formed about sixty years ago by a complicated cross.[204] Dark +Brahmas, which are believed by some fanciers to constitute a distinct +species, were undoubtedly formed[205] in the United States, within a recent +period, by a cross between Chittagongs and Cochins. With plants I believe +there is little doubt that some kinds of turnips, now extensively +cultivated, are crossed races; and the history of a variety of wheat which +was raised from two very distinct varieties, and which after six years' +culture presented an even sample, has been recorded on good authority.[206] + +Until quite lately, cautious and experienced breeders, though not averse to +a single infusion of foreign blood, were almost universally convinced that +the attempt to establish a new race, intermediate between two widely +distinct races, was hopeless: "they clung with superstitious tenacity to +the doctrine of purity of blood, believing it to be the ark in which alone +true safety could be found."[207] Nor was this conviction unreasonable: +when two distinct races are crossed, the offspring of the first generation +are generally nearly uniform in character; but even this sometimes fails to +be the case, especially with crossed dogs and fowls, the young of which +from the first are sometimes much {97} diversified. As cross-bred animals +are generally of large size and vigorous, they have been raised in great +numbers for immediate consumption. But for breeding they are found to be +utterly useless; for though they may be themselves uniform in character, +when paired together they yield during many generations offspring +astonishingly diversified. The breeder is driven to despair, and concludes +that he will never form an intermediate race. But from the cases already +given, and from others which have been recorded, it appears that patience +alone is necessary; as Mr. Spooner remarks, "nature opposes no barrier to +successful admixture; in the course of time, by the aid of selection and +careful weeding, it is practicable to establish a new breed." After six or +seven generations the hoped-for result will in most cases be obtained; but +even then an occasional reversion, or failure to keep true, may be +expected. The attempt, however, will assuredly fail if the conditions of +life be decidedly unfavourable to the characters of either +parent-breed.[208] + +Although the grandchildren and succeeding generations of cross-bred animals +are generally variable in an extreme degree, some curious exceptions to the +rule have been observed, both with crossed races and species. Thus Boitard +and Corbié[209] assert that from a Pouter and a Runt "a Cavalier will +appear, which we have classed amongst pigeons of pure race, because it +transmits all its qualities to its posterity." The editor of the 'Poultry +Chronicle'[210] bred some bluish fowls from a black Spanish cock and a +Malay hen; and these remained true to colour "generation after generation." +The Himalayan breed of rabbits was certainly formed by crossing two +sub-varieties of the silver-grey rabbit; although it suddenly assumed its +present character, which differs much from that of either parent-breed, yet +it has ever since been easily and truly propagated. I crossed some Labrador +and Penguin ducks, and recrossed the mongrels with Penguins; afterwards, +most of the ducks reared during three generations were nearly uniform in +character, being brown with a white crescentic mark on the lower part of +the breast, {98} and with some white spots at the base of the beak; so that +by the aid of a little selection a new breed might easily have been formed. +In regard to crossed varieties of plants, Mr. Beaton remarks[211] that +"Melville's extraordinary cross between the Scotch kale and an early +cabbage is as true and genuine as any on record;" but in this case no doubt +selection was practised. Gärtner[212] has given five cases of hybrids, in +which the progeny kept constant; and hybrids between _Dianthus armeria_ and +_deltoides_ remained true and uniform to the tenth generation. Dr. Herbert +likewise showed me a hybrid from two species of Loasa which from its first +production had kept constant during several generations. + +We have seen in the earlier chapters, that some of our domesticated +animals, such as dogs, cattle, pigs, &c., are almost certainly descended +from more than one species, or wild race, if any one prefers to apply this +latter term to forms which were enabled to keep distinct in a state of +nature. Hence the crossing of aboriginally distinct species probably came +into play at an early period in the formation of our present races. From +Rütimeyer's observations there can be little doubt that this occurred with +cattle; but in most cases some one of the forms which were allowed to cross +freely, will, it is probable, have absorbed and obliterated the others. For +it is not likely that semi-civilized men would have taken the necessary +pains to modify by selection their commingled, crossed, and fluctuating +stock. Nevertheless, those animals which were best adapted to their +conditions of life would have survived through natural selection; and by +this means crossing will often have indirectly aided in the formation of +primeval domesticated breeds. + +Within recent times, as far as animals are concerned, the crossing of +distinct species has done little or nothing in the formation or +modification of our races. It is not yet known whether the species of +silk-moth which have been recently crossed in France will yield permanent +races. In the fourth chapter I alluded with some hesitation to the +statement that a new breed, between the hare and rabbit, called leporides, +had been formed in France, and was found capable of propagating {99} +itself; but it is now positively affirmed[213] that this is an error. With +plants which can be multiplied by buds and cuttings, hybridisation has done +wonders, as with many kinds of Roses, Rhododendrons, Pelargoniums, +Calceolarias, and Petunias. Nearly all these plants can be propagated by +seed; most of them freely; but extremely few or none come true by seed. + +Some authors believe that crossing is the chief cause of variability,--that +is, of the appearance of absolutely new characters. Some have gone so far +as to look at it as the sole cause; but this conclusion is disproved by +some of the facts given in the chapter on Bud-variation. The belief that +characters not present in either parent or in their ancestors frequently +originate from crossing is doubtful; that they occasionally thus arise is +probable; but this subject will be more conveniently discussed in a future +chapter on the causes of Variability. + +A condensed summary of this and of the three following chapters, together +with some remarks on Hybridism, will be given in the nineteenth chapter. + + * * * * * + + +{100} + +CHAPTER XVI. + +CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES--INFLUENCE OF +DOMESTICATION ON FERTILITY. + + DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN + CROSSED--VARIOUS CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF + BREEDING AND SEXUAL PREFERENCE--VARIETIES OF WHEAT SAID TO BE STERILE + WHEN CROSSED--VARIETIES OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, + AND TOBACCO, RENDERED IN SOME DEGREE MUTUALLY STERILE--DOMESTICATION + ELIMINATES THE TENDENCY TO STERILITY NATURAL TO SPECIES WHEN + CROSSED--ON THE INCREASED FERTILITY OF UNCROSSED ANIMALS AND PLANTS + FROM DOMESTICATION AND CULTIVATION. + +The domesticated races of both animals and plants, when crossed, are with +extremely few exceptions quite prolific,--in some cases even more so than +the purely bred parent-races. The offspring, also, raised from such crosses +are likewise, as we shall see in the following chapter, generally more +vigorous and fertile than their parents. On the other hand, species when +crossed, and their hybrid offspring, are almost invariability in some +degree sterile; and here there seems to exist a broad and insuperable +distinction between races and species. The importance of this subject as +bearing on the origin of species is obvious; and we shall hereafter recur +to it. + +It is unfortunate how few precise observations have been made on the +fertility of mongrel animals and plants during several successive +generations. Dr. Broca[214] has remarked that no one has observed whether, +for instance, mongrel dogs, bred _inter se_, are indefinitely fertile; yet, +if a shade of infertility be detected by careful observation in the +offspring of natural forms when crossed, it is thought that their specific +distinction is proved. But so many breeds of sheep, cattle, pigs, dogs, and +poultry, have been crossed and recrossed in various ways, that any +sterility, if it had existed, would from being injurious {101} almost +certainly have been observed. In investigating the fertility of crossed +varieties many sources of doubt occur. Whenever the least trace of +sterility between two plants, however closely allied, was observed by +Kölreuter, and more especially by Gärtner, who counted the exact number of +seed in each capsule, the two forms were at once ranked as distinct +species; and if this rule be followed, assuredly it will never be proved +that varieties when crossed are in any degree sterile. We have formerly +seen that certain breeds of dogs do not readily pair together; but no +observations have been made whether, when paired, they produce the full +number of young, and whether the latter are perfectly fertile _inter se_; +but, supposing that some degree of sterility were found to exist, +naturalists would simply infer that these breeds were descended from +aboriginally distinct species; and it would be scarcely possible to +ascertain whether or not this explanation was the true one. + +The Sebright Bantam is much less prolific than any other breed of fowls, +and is descended from a cross between two very distinct breeds, recrossed +by a third sub-variety. But it would be extremely rash to infer that the +loss of fertility was in any manner connected with its crossed origin, for +it may with more probability be attributed either to long-continued close +interbreeding, or to an innate tendency to sterility correlated with the +absence of hackles and sickle tail-feathers. + +Before giving the few recorded cases of forms, which must be ranked as +varieties, being in some degree sterile when crossed, I may remark that +other causes sometimes interfere with varieties freely intercrossing. Thus +they may differ too greatly in size, as with some kinds of dogs and fowls: +for instance, the editor of the 'Journal of Horticulture, &c.,'[215] says +that he can keep Bantams with the larger breeds without much danger of +their crossing, but not with the smaller breeds, such as Games, Hamburgs, +&c. With plants a difference in the period of flowering serves to keep +varieties distinct, as with the various kinds of maize and wheat: thus +Colonel Le Couteur[216] remarks, "the Talavera wheat, from flowering much +earlier than any other kind, is sure to continue pure." In different parts +of {102} the Falkland Islands the cattle are breaking up into herds of +different colours; and those on the higher ground, which are generally +white, usually breed, as I am informed by Admiral Sulivan, three months +earlier than those on the lowlands; and this would manifestly tend to keep +the herds from blending. + +Certain domestic races seem to prefer breeding with their own kind; and +this is a fact of some importance, for it is a step towards that +instinctive feeling which helps to keep closely allied species in a state +of nature distinct. We have now abundant evidence that, if it were not for +this feeling, many more hybrids would be naturally produced than is the +case. We have seen in the first chapter that the alco dog of Mexico +dislikes dogs of other breeds; and the hairless dog of Paraguay mixes less +readily with the European races, than the latter do with each other. In +Germany the female Spitz-dog is said to receive the fox more readily than +will other dogs; a female Australian Dingo in England attracted the wild +male foxes. But these differences in the sexual instinct and attractive +power of the various breeds may be wholly due to their descent from +distinct species. In Paraguay the horses have much freedom, and an +excellent observer[217] believes that the native horses of the same colour +and size prefer associating with each other, and that the horses which have +been imported from Entre Rios and Banda Oriental into Paraguay likewise +prefer associating together. In Circassia six sub-races of the horse are +known and have received distinct names; and a native proprietor of +rank[218] asserts that horses of three of these races, whilst living a free +life, almost always refuse to mingle and cross, and will even attack each +other. + +It has been observed, in a district stocked with heavy Lincolnshire and +light Norfolk sheep, that both kinds, though bred together, when turned +out, "in a short time separate to a sheep;" the Lincolnshires drawing off +to the rich soil, and the Norfolks to their own dry light soil; and as long +as there is plenty of grass, "the two breeds keep themselves as distinct as +rooks and pigeons." In this case different habits of {103} life tend to +keep the races distinct. On one of the Faroe islands, not more than half a +mile in diameter, the half-wild native black sheep are said not to have +readily mixed with the imported white sheep. It is a more curious fact that +the semi-monstrous ancon sheep of modern origin "have been observed to keep +together, separating themselves from the rest of the flock, when put into +enclosures with other sheep."[219] With respect to fallow deer, which live +in a semi-domesticated condition, Mr. Bennett[220] states that the dark and +pale coloured herds, which have long been kept together in the Forest of +Dean, in High Meadow Woods, and in the New Forest, have never been known to +mingle: the dark-coloured deer, it may be added, are believed to have been +first brought by James I. from Norway, on account of their greater +hardiness. I imported from the island of Porto Santo two of the feral +rabbits, which differ, as described in the fourth chapter, from common +rabbits; both proved to be males, and, though they lived during some years +in the Zoological Gardens, the superintendent, Mr. Bartlett, in vain +endeavoured to make them breed with various tame kinds; but whether this +refusal to breed was due to any change in instinct, or simply to their +extreme wildness; or whether confinement had rendered them sterile, as +often occurs, cannot be told. + +Whilst matching for the sake of experiment many of the most distinct breeds +of pigeons, it frequently appeared to me that the birds, though faithful to +their marriage vow, retained some desire after their own kind. Accordingly +I asked Mr. Wicking, who has kept a larger stock of various breeds together +than any man in England, whether he thought that they would prefer pairing +with their own kind, supposing that there were males and females enough of +each; and he without hesitation answered that he was convinced that this +was the case. It has often been noticed that the dovecot pigeon seems to +have an actual aversion towards the several fancy breeds;[221] yet all have +{104} certainly sprung from a common progenitor. The Rev. W. D. Fox informs +me that his flocks of white and common Chinese geese kept distinct. + +These facts and statements, though some of them are incapable of proof, +resting only on the opinion of experienced observers, show that some +domestic races are led by different habits of life to keep to a certain +extent separate, and that others prefer coupling with their own kind, in +the same manner as species in a state of nature, though in a much less +degree. + + With respect to sterility from the crossing of domestic races, I know + of no well-ascertained case with animals. This fact, seeing the great + difference in structure between some breeds of pigeons, fowls, pigs, + dogs, &c., is extraordinary, in contrast with the sterility of many + closely allied natural species when crossed; but we shall hereafter + attempt to show that it is not so extraordinary as it at first appears. + And it may be well here to recall to mind that the amount of external + difference between two species will not safely guide us in foretelling + whether or not they will breed together,--some closely allied species + when crossed being utterly sterile, and others which are extremely + unlike being moderately fertile. I have said that no case of sterility + in crossed races rests on satisfactory evidence; but here is one which + at first seems trustworthy. Mr. Youatt,[222] and a better authority + cannot be quoted, states, that formerly in Lancashire crosses were + frequently made between longhorn and shorthorn cattle; the first cross + was excellent, but the produce was uncertain; in the third or fourth + generation the cows were bad milkers; "in addition to which, there was + much uncertainty whether the cows would conceive; and full one-third of + the cows among some of these half-breds failed to be in calf." This at + first seems a good case; but Mr. Wilkinson states,[223] that a breed + derived from this same cross was actually established in another part + of England; and if it had failed in fertility, the fact would surely + have been noticed. Moreover, supposing that Mr. Youatt had proved his + case, it might be argued that the sterility was wholly due to the two + parent-breeds being descended from primordially distinct species. + + I will give a case with plants, to show how difficult it is to get + sufficient evidence. Mr. Sheriff, who has been so successful in the + formation of new races of wheat, fertilised the Hopetoun with the + Talavera; in the first and second generations the produce was + intermediate in character, but in the fourth generation "it was found + to consist of many varieties; nine-tenths of the florets proved barren, + and many of the seeds seemed shrivelled abortions, void of vitality, + and the whole race was evidently verging to extinction."[224] Now, + considering how little these {105} varieties of wheat differ in any + important character, it seems to me very improbable that the sterility + resulted, as Mr. Sheriff thought, from the cross, but from some quite + distinct cause. Until such experiments are many times repeated, it + would be rash to trust them; but unfortunately they have been rarely + tried even once with sufficient care. + + Gärtner has recorded a more remarkable and trustworthy case: he + fertilised thirteen panicles (and subsequently nine others) on a dwarf + maize bearing yellow seed[225] with pollen of a tall maize having red + seed; and one head alone produced good seed, only five in number. + Though these plants are monoecious, and therefore do not require + castration, yet I should have suspected some accident in the + manipulation had not Gärtner expressly stated that he had during many + years grown these two varieties together, and they did not + spontaneously cross; and this, considering that the plants are + monoecious and abound with pollen, and are well known generally to + cross freely, seems explicable only on the belief that these two + varieties are in some degree mutually infertile. The hybrid plants + raised from the above five seed were intermediate in structure, + extremely variable, and perfectly fertile.[226] No one, I believe, has + hitherto suspected that these varieties of maize are distinct species; + but had the hybrids been in the least sterile, no doubt Gärtner would + at once have so classed them. I may here remark, that with undoubted + species there is not necessarily any close relation between the + sterility of a first cross and that of the hybrid offspring. Some + species can be crossed with facility, but produce utterly sterile + hybrids; others can be crossed with extreme difficulty, but the hybrids + when produced are moderately fertile. I am not aware, however, of any + instance quite like this of the maize with natural species, namely, of + a first cross made with difficulty, but yielding perfectly fertile + hybrids. + + The following case is much more remarkable, and evidently perplexed + Gärtner, whose strong wish it was to draw a broad line of distinction + between species and varieties. In the genus Verbascum, he made, during + eighteen years, a vast number of experiments, and crossed no less than + 1085 flowers and counted their seeds. Many of these experiments + consisted in crossing white and yellow varieties of both _V. lychnitis_ + and _V. blattaria_ with nine other species and their hybrids. That the + white and yellow flowered plants of these two species are really + varieties, no one has doubted; and Gärtner actually raised in the case + of both species one variety from the seed of the other. Now in two of + his works[227] he distinctly asserts that crosses between + similarly-coloured flowers yield more seed than between + dissimilarly-coloured; so that the yellow-flowered variety of either + species (and conversely with the white-flowered variety), when crossed + with pollen of its own kind, yields more seed than when crossed with + that of the white variety; and so it is when differently coloured + species are crossed. The general results may be seen in the Table at + the {106} end of his volume. In one instance he gives[228] the + following details; but I must premise that Gärtner, to avoid + exaggerating the degree of sterility in his crosses, always compares + the _maximum_ number obtained from a cross with the _average_ number + naturally given by the pure mother-plant. The white-variety of _V. + lychnitis_, naturally fertilised by its own pollen, gave from an + _average_ of twelve capsules ninety-six good seeds in each; whilst + twenty flowers fertilised with pollen from the yellow variety of this + same species, gave as the _maximum_ only eighty-nine good seed; so that + we have the proportion of 1000 to 908, according to Gärtner's usual + scale. I should have thought it possible that so small a difference in + fertility might have been accounted for by the evil effects of the + necessary castration; but Gärtner shows that the white variety of _V. + lychnitis_, when fertilised first by the white variety of _V. + blattaria_, and then by the yellow variety of this species, yielded + seed in the proportion of 622 to 438; and in both these cases + castration was performed. Now the sterility which results from the + crossing of the differently coloured varieties of the same species, is + fully as great as that which occurs in many cases when distinct species + are crossed. Unfortunately Gärtner compared the results of the first + unions alone, and not the sterility of the two sets of hybrids produced + from the white variety of _V. lychnitis_ when fertilised by the white + and yellow varieties of _V. blattaria_, for it is probable that they + would have differed in this respect. + + Mr. J. Scott has given me the results of a series of experiments on + Verbascum, made by him in the Botanic Gardens of Edinburgh. He repeated + some of Gärtner's experiments on distinct species, but obtained only + fluctuating results; some confirmatory, but the greater number + contradictory; nevertheless these seem hardly sufficient to overthrow + the conclusions arrived at by Gärtner from experiments tried on a much + larger scale. In the second place Mr. Scott experimented on the + relative fertility of unions between similarly and + dissimilarly-coloured varieties of the same species. Thus he fertilised + six flowers of the yellow variety of _V. lychnitis_ by its own pollen, + and obtained six capsules, and calling, for the sake of having a + standard of comparison, the average number of good seed in each one + hundred, he found that this same yellow variety, when fertilised by the + white variety, yielded from seven capsules an average of ninety-four + seed. On the same principle, the white variety of _V. lychnitis_ by its + own pollen (from six capsules), and by the pollen of the yellow variety + (eight capsules), yielded seed in the proportion of 100 to 82. The + yellow variety of _V. thapsus_ by its own pollen (eight capsules), and + by that of the white variety (only two capsules), yielded seed in the + proportion of 100 to 94. Lastly, the white variety of _V. blattaria_ by + its own pollen (eight capsules), and by that of the yellow variety + (five capsules), yielded seed in the proportion of 100 to 79. So that + in every case the unions of dissimilarly-coloured varieties of the same + species were less fertile than the unions of similarly-coloured + varieties; when all the cases are grouped together, the difference of + fertility is as 86 to 100. Some additional trials were made, and + altogether thirty-six similarly-coloured unions yielded thirty-five + good {107} capsules; whilst thirty-five dissimilarly-coloured unions + yielded only twenty-six good capsules. Besides the foregoing + experiments, the purple _V. phoeniceum_ was crossed by a rose-coloured + and a white variety of the same species; these two varieties were also + crossed together, and these several unions yielded less seed than _V. + phoeniceum_ by its own pollen. Hence it follows from Mr. Scott's + experiments, that in the genus Verbascum the similarly and + dissimilarly-coloured varieties of the same species behave, when + crossed, like closely allied but distinct species.[229] + + This remarkable fact of the sexual affinity of similarly-coloured + varieties, as observed by Gärtner and Mr. Scott, may not be of very + rare occurrence; for the subject has not been attended to by others. + The following case is worth giving, partly to show how difficult it is + to avoid error. Dr. Herbert[230] has remarked that variously-coloured + double varieties of the hollyhock (_Althæa rosea_) may be raised with + certainty by seed from plants growing close together. I have been + informed that nurserymen who raise seed for sale do not separate their + plants; accordingly I procured seed of eighteen named varieties; of + these, eleven varieties produced sixty-two plants all perfectly true to + their kind; and seven produced forty-nine plants, half of which were + true and half false. Mr. Masters of Canterbury has given me a more + striking case; he saved seed from a great bed of twenty-four named + varieties planted in closely adjoining rows, and each variety + reproduced itself truly with only sometimes a shade of difference in + tint. Now in the hollyhock the pollen, which is abundant, is matured + and nearly all shed before the stigma of the same flower is ready to + receive it;[231] and as bees covered with pollen incessantly fly from + plant to plant, it would appear that adjoining varieties could not + escape being crossed. As, however, this does not occur, it appeared to + me probable that the pollen {108} of each variety was prepotent on its + own stigma over that of all other varieties. But Mr. C. Turner of + Slough, well known for his success in the cultivation of this plant, + informs me that it is the doubleness of the flowers which prevents the + bees gaining access to the pollen and stigma; and he finds that it is + difficult even to cross them artificially. Whether this explanation + will fully account for varieties in close proximity propagating + themselves so truly by seed, I do not know. + + The following cases are worth giving, as they relate to monoecious + forms, which do not require, and consequently have not been injured by, + castration. Girou de Buzareingues crossed what he designates three + varieties of gourd,[232] and asserts that their mutual fertilisation is + less easy in proportion to the difference which they present. I am + aware how imperfectly the forms in this group were until recently + known; but Sageret,[233] who ranked them according to their mutual + fertility, considers the three forms above alluded to as varieties, as + does a far higher authority, namely, M. Naudin.[234] Sageret[235] has + observed that certain melons have a greater tendency, whatever the + cause may be, to keep true than others; and M. Naudin, who has had such + immense experience in this group, informs me that he believes that + certain varieties intercross more readily than others of the same + species; but he has not proved the truth of this conclusion; the + frequent abortion of the pollen near Paris being one great difficulty. + Nevertheless, he has grown close together, during seven years, certain + forms of Citrullus, which, as they could be artificially crossed with + perfect facility and produced fertile offspring, are ranked as + varieties; but these forms when not artificially crossed kept true. + Many other varieties, on the other hand, in the same group cross with + such facility, as M. Naudin repeatedly insists, that without being + grown far apart they cannot be kept in the least true. + + Another case, though somewhat different, may be here given, as it is + highly remarkable, and is established on excellent evidence. Kölreuter + minutely describes five varieties of the common tobacco,[236] which + were reciprocally crossed, and the offspring were intermediate in + character and as fertile as their parents: from this fact Kölreuter + inferred that they are really varieties; and no one, as far as I can + discover, seems to have doubted that such is the case. He also crossed + reciprocally these five varieties with _N. glutinosa_, and they yielded + very sterile hybrids; but those raised from the _var. perennis_, + whether used as the father or mother plant, were not so sterile as the + hybrids from the four other varieties.[237] So that the sexual {109} + capacity of this one variety has certainly been in some degree + modified, so as to approach in nature that of _N. glutinosa_.[238] + +These facts with respect to plants show that in some few cases certain +varieties have had their sexual powers so far modified, that they cross +together less readily and yield less seed than other varieties of the same +species. We shall presently see that the sexual functions of most animals +and plants are eminently liable to be affected by the conditions of life to +which they are exposed; and hereafter we shall briefly discuss the conjoint +bearing of this and other facts on the difference in fertility between +crossed varieties and crossed species. + +_Domestication eliminates the tendency to Sterility which is general with +Species when crossed._ + +This hypothesis was first propounded by Pallas,[239] and has been adopted +by several authors. I can find hardly any direct facts in its support; but +unfortunately no one has compared, in the case of either animals or plants, +the fertility of anciently domesticated varieties, when crossed with a +distinct species, with that of the wild parent-species when similarly +crossed. No one has compared, for instance, the fertility of _Gallus +bankiva_ and of the domesticated fowl, when crossed with a distinct species +of Gallus or Phasianus; and the {110} experiment would in all cases be +surrounded by many difficulties. Dureau de la Malle, who has so closely +studied classical literature, states[240] that in the time of the Romans +the common mule was produced with more difficulty than at the present day; +but whether this statement may be trusted I know not. A much more +important, though somewhat different, case is given by M. Groenland,[241] +namely, that plants, known from their intermediate character and sterility +to be hybrids between Ægilops and wheat, have perpetuated themselves under +culture since 1857, _with a rapid but varying increase of fertility in each +generation_. In the fourth generation the plants, still retaining their +intermediate character, had become as fertile as common cultivated wheat. + +The indirect evidence in favour of the Pallasian doctrine appears to me to +be extremely strong. In the earlier chapters I have attempted to show that +our various breeds of dogs are descended from several wild species; and +this probably is the case with sheep. There can no longer be any doubt that +the Zebu or humped Indian ox belongs to a distinct species from European +cattle: the latter, moreover, are descended from two or three forms, which +may be called either species or wild races, but which co-existed in a state +of nature and kept distinct. We have good evidence that our domesticated +pigs belong to at least two specific types, _S. scrofa_ and _Indica_, which +probably lived together in a wild state in South-eastern Europe. Now, a +widely-extended analogy leads to the belief that if these several allied +species, in the wild state or when first reclaimed, had been crossed, they +would have exhibited, both in their first unions and in their hybrid +offspring, some degree of sterility. Nevertheless the several domesticated +races descended from them are now all, as far as can be ascertained, +perfectly fertile together. If this reasoning be trustworthy, and it is +apparently sound, we must admit the Pallasian doctrine that long-continued +domestication tends to eliminate that sterility which is natural to species +when crossed in their aboriginal state. + +{111} + +_On increased Fertility from Domestication and Cultivation._ + +Increased fertility from domestication, without any reference to crossing, +may be here briefly considered. This subject bears indirectly on two or +three points connected with the modification of organic beings. As Buffon +long ago remarked,[242] domestic animals breed oftener in the year and +produce more young at a birth than wild animals of the same species; they, +also, sometimes breed at an earlier age. The case would hardly have +deserved further notice, had not some authors lately attempted to show that +fertility increases and decreases in an inverse ratio with the amount of +food. This strange doctrine has apparently arisen from individual animals +when supplied with an inordinate quantity of food, and from plants of many +kinds when grown on excessively rich soil, as on a dunghill, becoming +sterile; but to this latter point I shall have occasion presently to +return. With hardly an exception, our domesticated animals, which have long +been habituated to a regular and copious supply of food, without the labour +of searching for it, are more fertile than the corresponding wild animals. +It is notorious how frequently cats and dogs breed, and how many young they +produce at a birth. The wild rabbit is said generally to breed four times +yearly, and to produce from four to eight young; the tame rabbit breeds six +or seven times yearly, and produces from four to eleven young. The ferret, +though generally so closely confined, is more prolific than its supposed +wild prototype. The wild sow is remarkably prolific, for she often breeds +twice in the year, and produces from four to eight and sometimes even +twelve young at a birth; but the domestic sow regularly breeds twice a +year, and would breed oftener if permitted; and a sow that produces less +than eight at a birth "is worth little, and the sooner she is fattened for +the butcher the better." The amount of food affects the fertility even of +the same individual: thus sheep, which on mountains never produce more than +one lamb at a birth, when brought {112} down to lowland pastures frequently +bear twins. This difference apparently is not due to the cold of the higher +land, for sheep and other domestic animals are said to be extremely +prolific in Lapland. Hard living, also, retards the period at which animals +conceive; for it has been found disadvantageous in the northern islands of +Scotland to allow cows to bear calves before they are four years old.[243] + + Birds offer still better evidence of increased fertility from + domestication: the hen of the wild _Gallus bankiva_ lays from six to + ten eggs, a number which would be thought nothing of with the domestic + hen. The wild duck lays from five to ten eggs; the tame one in the + course of the year from eighty to one hundred. The wild grey-lag goose + lays from five to eight eggs; the tame from thirteen to eighteen, and + she lays a second time; as Mr. Dixon has remarked, "high-feeding, care, + and moderate warmth induce a habit of prolificacy which becomes in some + measure hereditary." Whether the semi-domesticated dovecot pigeon is + more fertile than the wild rock-pigeon _C. livia_, I know not; but the + more thoroughly domesticated breeds are nearly twice as fertile as + dovecots: the latter, however, when caged and highly fed, become + equally fertile with house pigeons. The peahen alone of domesticated + birds is rather more fertile, according to some accounts, when wild in + its native Indian home, than when domesticated in Europe and exposed to + our much colder climate.[244] + + With respect to plants, no one would expect wheat to tiller more, and + each ear to produce more grain, in poor than in rich soil; or to get in + poor soil a heavy crop of peas or beans. Seeds vary so much in number + {113} that it is difficult to estimate them; but on comparing beds of + carrots saved for seed in a nursery garden with wild plants, the former + seemed to produce about twice as much seed. Cultivated cabbages yielded + thrice as many pods by measure as wild cabbages from the rocks of South + Wales. The excess of berries produced by the cultivated Asparagus in + comparison with the wild plant is enormous. No doubt many highly + cultivated plants, such as pears, pineapples, bananas, sugar-cane, &c., + are nearly or quite sterile; and I am inclined to attribute this + sterility to excess of food and to other unnatural conditions; but to + this subject I shall presently recur. + +In some cases, as with the pig, rabbit, &c., and with those plants which +are valued for their seed, the direct selection of the more fertile +individuals has probably much increased their fertility; and in all cases +this may have occurred indirectly, from the better chance of the more +numerous offspring produced by the more fertile individuals having +survived. But with cats, ferrets, and dogs, and with plants like carrots, +cabbages, and asparagus, which are not valued for their prolificacy, +selection can have played only a subordinate part; and their increased +fertility must be attributed to the more favourable conditions of life +under which they have long existed. + + * * * * * + + +{114} + +CHAPTER XVII. + +ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL EFFECTS OF CLOSE +INTERBREEDING. + + DEFINITION OF CLOSE INTERBREEDING--AUGMENTATION OF MORBID + TENDENCIES--GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, + AND ON THE EVIL EFFECTS FROM CLOSE INTERBREEDING--CATTLE, CLOSELY + INTERBRED; HALF-WILD CATTLE LONG KEPT IN THE SAME + PARKS--SHEEP--FALLOW-DEER--DOGS--RABBITS--PIGS--MAN, ORIGIN OF HIS + ABHORRENCE OF INCESTUOUS MARRIAGES--FOWLS--PIGEONS--HIVE-BEES--PLANTS, + GENERAL CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING--MELONS, + FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND FOREST-TREES--ON THE INCREASED + SIZE OF HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY--ON + CERTAIN PLANTS WHICH EITHER NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, + BUT ARE FERTILE, BOTH ON THE MALE AND FEMALE SIDE, WHEN CROSSED WITH + DISTINCT INDIVIDUALS EITHER OF THE SAME OR ANOTHER SPECIES--CONCLUSION. + +The gain in constitutional vigour, derived from an occasional cross between +individuals of the same variety, but belonging to distinct families, or +between distinct varieties, has not been so largely or so frequently +discussed, as have the evil effects of too close interbreeding. But the +former point is the more important of the two, inasmuch as the evidence is +more decisive. The evil results from close interbreeding are difficult to +detect, for they accumulate slowly, and differ much in degree with +different species; whilst the good effects which almost invariably follow a +cross are from the first manifest. It should, however, be clearly +understood that the advantage of close interbreeding, as far as the +retention of character is concerned, is indisputable, and often outweighs +the evil of a slight loss of constitutional vigour. In relation to the +subject of domestication, the whole question is of some importance, as too +close interbreeding interferes with the improvement of old races, and +especially with the formation of new ones. It is important as indirectly +bearing on Hybridism; and perhaps on the extinction of species, when any +form has become so rare that only a few individuals {115} remain within a +confined area. It bears in an important manner on the influence of free +intercrossing, in obliterating individual differences, and thus giving +uniformity of character to the individuals of the same race or species; for +if additional vigour and fertility be thus gained, the crossed offspring +will multiply and prevail, and the ultimate result will be far greater than +otherwise would have occurred. Lastly, the question is of high interest, as +bearing on mankind. Hence I shall discuss this subject at full length. As +the facts which prove the evil effects of close interbreeding are more +copious, though less decisive, than those on the good effects of crossing, +I shall, under each group of beings, begin with the former. + +There is no difficulty in defining what is meant by a cross; but this is by +no means easy in regard to "breeding in and in" or "too close +interbreeding," because, as we shall see, different species of animals are +differently affected by the same degree of interbreeding. The pairing of a +father and daughter, or mother and son, or brothers and sisters, if carried +on during several generations, is the closest possible form of +interbreeding. But some good judges, for instance Sir J. Sebright, believe +that the pairing of a brother and sister is closer than that of parents and +children; for when the father is matched with his daughter he crosses, as +is said, with only half his own blood. The consequences of close +interbreeding carried on for too long a time, are, as is generally +believed, loss of size, constitutional vigour, and fertility, sometimes +accompanied by a tendency to malformation. Manifest evil does not usually +follow from pairing the nearest relations for two, three, or even four +generations; but several causes interfere with our detecting the evil--such +as the deterioration being very gradual, and the difficulty of +distinguishing between such direct evil and the inevitable augmentation of +any morbid tendencies which may be latent or apparent in the related +parents. On the other hand, the benefit from a cross, even when there has +not been any very close interbreeding, is almost invariably at once +conspicuous. There is reason to believe, and this was the opinion of that +most experienced observer Sir J. Sebright,[245] that the evil effects of +close interbreeding may be checked by the related individuals {116} being +separated during a few generations and exposed to different conditions of +life. + +That evil directly follows from any degree of close interbreeding has been +denied by many persons; but rarely by any practical breeder; and never, as +far as I know, by one who has largely bred animals which propagate their +kind quickly. Many physiologists attribute the evil exclusively to the +combination and consequent increase of morbid tendencies common to both +parents: that this is an active source of mischief there can be no doubt. +It is unfortunately too notorious that men and various domestic animals +endowed with a wretched constitution, and with a strong hereditary +disposition to disease, if not actually ill, are fully capable of +procreating their kind. Close interbreeding, on the other hand, induces +sterility; and this indicates something quite distinct from the +augmentation of morbid tendencies common to both parents. The evidence +immediately to be given convinces me that it is a great law of nature, that +all organic beings profit from an occasional cross with individuals not +closely related to them in blood; and that, on the other hand, +long-continued close interbreeding is injurious. + +Various general considerations have had much influence in leading me to +this conclusion; but the reader will probably rely more on special facts +and opinions. The authority of experienced observers, even when they do not +advance the grounds of their belief, is of some little value. Now almost +all men who have bred many kinds of animals and have written on the +subject, such as Sir J. Sebright, Andrew Knight, &c.,[246] have expressed +the strongest conviction on the impossibility of long-continued close +interbreeding. Those who have compiled works on agriculture, and have +associated much with breeders, such as the sagacious Youatt, Low, &c., have +strongly declared their opinion to the same effect. Prosper Lucas, trusting +largely to French authorities, has come to a similar conclusion. The +distinguished German agriculturist Hermann von Nathusius, who has written +the most able treatise on this subject which I have met with, concurs; and +as I shall have to quote from {117} this treatise, I may state that +Nathusius is not only intimately acquainted with works on agriculture in +all languages, and knows the pedigrees of our British breeds better than +most Englishmen, but has imported many of our improved animals, and is +himself an experienced breeder. + +Evidence of the evil effects of close interbreeding can most readily be +acquired in the case of animals, such as fowls, pigeons, &c., which +propagate quickly, and, from being kept in the same place, are exposed to +the same conditions. Now I have inquired of very many breeders of these +birds, and I have hitherto not met with a single man who was not thoroughly +convinced that an occasional cross with another strain of the same +sub-variety was absolutely necessary. Most breeders of highly-improved or +fancy birds value their own strain, and are most unwilling, at the risk, in +their opinion, of deterioration, to make a cross. The purchase of a +first-rate bird of another strain is expensive, and exchanges are +troublesome; yet all breeders, as far as I can hear, excepting those who +keep large stocks at different places for the sake of crossing, are driven +after a time to take this step. + +Another general consideration which has had great influence on my mind is, +that with all hermaphrodite animals and plants, which it might have been +thought would have perpetually fertilised themselves, and thus have been +subjected for long ages to the closest interbreeding, there is no single +species, as far as I can discover, in which the structure ensures +self-fertilisation. On the contrary, there are in a multitude of cases, as +briefly stated in the fifteenth chapter, manifest adaptations which favour +or inevitably lead to an occasional cross between one hermaphrodite and +another of the same species; and these adaptive structures are utterly +purposeless, as far as we can see, for any other end. + + With _Cattle_ there can be no doubt that extremely close interbreeding + may be long carried on, advantageously with respect to external + characters and with no manifestly apparent evil as far as constitution + is concerned. The same remark is applicable to sheep. Whether these + animals have gradually been rendered less susceptible than others to + this evil, in order to permit them to live in herds,--a habit which + leads the old and vigorous males to expel all intruders, and in + consequence often to pair with their own daughters, I will not pretend + to decide. The case of Bakewell's Long-horns, which were closely + interbred for a long period, has often been {118} quoted; yet Youatt + says[247] the breed "had acquired a delicacy of constitution + inconsistent with common management," and "the propagation of the + species was not always certain." But the Shorthorns offer the most + striking case of close interbreeding; for instance, the famous bull + Favourite (who was himself the offspring of a half-brother and sister + from Foljambe) was matched with his own daughter, granddaughter, and + great-granddaughter; so that the produce of this last union, or the + great-great-granddaughter, had 15-16ths, or 93.75 per cent. of the + blood of Favourite in her veins. This cow was matched with the bull + Wellington, having 62.5 per cent. of Favourite blood in his veins, and + produced Clarissa; Clarissa was matched with the bull Lancaster, having + 68.75 of the same blood, and she yielded valuable offspring.[248] + Nevertheless Collings, who reared these animals, and was a strong + advocate for close breeding, once crossed his stock with a Galloway, + and the cows from this cross realised the highest prices. Bates's herd + was esteemed the most celebrated in the world. For thirteen years he + bred most closely in and in; but during the next seventeen years, + though he had the most exalted notion of the value of his own stock, he + thrice infused fresh blood into his herd: it is said that he did this, + not to improve the form of his animals, but on account of their + lessened fertility. Mr. Bates's own view, as given by a celebrated + breeder,[249] was, that "to breed in and in from a bad stock was ruin + and devastation; yet that the practice may be safely followed within + certain limits when the parents so related are descended from + first-rate animals." We thus see that there has been extremely close + interbreeding with Shorthorns; but Nathusius, after the most careful + study of their pedigrees, says that he can find no instance of a + breeder who has strictly followed this practice during his whole life. + From this study and his own experience, he concludes that close + interbreeding is necessary to ennoble the stock; but that in effecting + this the greatest care is necessary, on account of the tendency to + infertility and weakness. It may be added, that another high + authority[250] asserts that many more calves are born cripples from + Shorthorns than from other and less closely interbred races of cattle. + + Although by carefully selecting the best animals (as Nature effectually + does by the law of battle) close interbreeding may be long carried on + with cattle, yet the good effects of a cross between almost any two + breeds is at once shown by the greater size and vigour of the + offspring; as Mr. Spooner writes to me, "crossing distinct breeds + certainly improves cattle for the butcher." Such crossed animals are of + course of no value to the breeder; but they have been raised during + many years in several {119} parts of England to be slaughtered;[251] + and their merit is now so fully recognised, that at fat-cattle shows a + separate class has been formed for their reception. The best fat ox at + the great show at Islington in 1862 was a crossed animal. + + The half-wild cattle, which have been kept in British parks probably + for 400 or 500 years, or even for a longer period, have been advanced + by Culley and others as a case of long-continued interbreeding within + the limits of the same herd without any consequent injury. With respect + to the cattle at Chillingham, the late Lord Tankerville owned that they + were bad breeders.[252] The agent, Mr. Hardy, estimates (in a letter to + me, dated May, 1861) that in the herd of about fifty the average number + annually slaughtered, killed by fighting, and dying, is about ten, or + one in five. As the herd is kept up to nearly the same average number, + the annual rate of increase must be likewise about one in five. The + bulls, I may add, engage in furious battles, of which battles the + present Lord Tankerville has given me a graphic description, so that + there will always be rigorous selection of the most vigorous males. I + procured in 1855 from Mr. D. Gardner, agent to the Duke of Hamilton, + the following account of the wild cattle kept in the Duke's park in + Lanarkshire, which is about 200 acres in extent. The number of cattle + varies from sixty-five to eighty; and the number annually killed (I + presume by all causes) is from eight to ten; so that the annual rate of + increase can hardly be more than one in six. Now in South America, + where the herds are half-wild, and therefore offer a nearly fair + standard of comparison, according to Azara the natural increase of the + cattle on an estancia is from one-third to one-fourth of the total + number, or one in between three and four; and this, no doubt, applies + exclusively to adult animals fit for consumption. Hence the half-wild + British cattle which have long interbred within the limits of the same + herd are relatively far less fertile. Although in an unenclosed country + like Paraguay there must be some crossing between the different herds, + yet even there the inhabitants believe that the occasional introduction + of animals from distant localities is necessary to prevent + "degeneration in size and diminution of fertility."[253] The decrease + in size from ancient times in the Chillingham and Hamilton cattle must + have been prodigious, for Professor Rütimeyer has shown that they are + almost certainly the descendants of the gigantic _Bos primigenius_. No + doubt this decrease in size may be largely attributed to less + favourable conditions of life; yet animals roaming over large parks, + and fed during severe winters, can hardly be considered as placed under + very unfavourable conditions. + + With _Sheep_ there has often been long-continued interbreeding within + the limits of the same flock; but whether the nearest relations have + been matched so frequently as in the case of Shorthorn cattle, I do not + know. The Messrs. Brown during fifty years have never infused fresh + blood into their excellent flock of Leicesters. Since 1810 Mr. Barford + has acted on the same principle with the Foscote flock. He asserts that + half a century {120} of experience has convinced him that when two + nearly related animals are quite sound in constitution, in-and-in + breeding does not induce degeneracy; but he adds that he "does not + pride himself on breeding from the nearest affinities." In France the + Naz flock has been bred for sixty years without the introduction of a + single strange ram.[254] Nevertheless, most great breeders of sheep + have protested against close interbreeding prolonged for too great a + length of time.[255] The most celebrated of recent breeders, Jonas + Webb, kept five separate families to work on, thus "retaining the + requisite distance of relationship between the sexes."[256] + + Although by the aid of careful selection the near interbreeding of + sheep may be long continued without any manifest evil, yet it has often + been the practice with farmers to cross distinct breeds to obtain + animals for the butcher, which plainly shows that good is derived from + this practice. Mr. Spooner sums up his excellent Essay on Crossing by + asserting that there is a direct pecuniary advantage in judicious + cross-breeding, especially when the male is larger than the female. A + former celebrated breeder, Lord Somerville, distinctly states that his + half-breeds from Ryelands and Spanish sheep were larger animals than + either the pure Ryelands or pure Spanish sheep.[257] + + As some of our British parks are ancient, it occurred to me that there + must have been long-continued close interbreeding with the fallow deer + (_Cervus dama_) kept in them; but on inquiry I find that it is a common + practice to infuse new blood by procuring bucks from other parks. Mr. + Shirley,[258] who has carefully studied the management of deer, admits + that in some parks there has been no admixture of foreign blood from a + time beyond the memory of man. But he concludes "that in the end the + constant breeding in-and-in is sure to tell to the disadvantage of the + whole herd, though it may take a very long time to prove it; moreover, + when we find, as is very constantly the case, that the introduction of + fresh blood has been of the very greatest use to deer, both by + improving their size and appearance, and particularly by being of + service in removing the taint of 'rickback,' if not of other diseases, + to which deer are sometimes subject when the blood has not been + changed, there can, I think, be no doubt but that a judicious cross + with a good stock is of the greatest consequence, and is indeed + essential, sooner or later, to the prosperity of every well-ordered + park." + + Mr. Meynell's famous foxhounds have been adduced, as showing that no + ill effects follow from close interbreeding; and Sir J. Sebright + ascertained from him that he frequently bred from father and daughter, + mother and {121} son, and sometimes even from brothers and sisters. Sir + J. Sebright, however, declares,[259] that by breeding _in-and-in_, by + which he means matching brothers and sisters, he has actually seen + strong spaniels become weak and diminutive lapdogs. The Rev. W. D. Fox + has communicated to me the case of a small lot of bloodhounds, long + kept in the same family, which had become very bad breeders, and nearly + all had a bony enlargement in the tail. A single cross with a distinct + strain of bloodhounds restored their fertility, and drove away the + tendency to malformation in the tail. I have heard the particulars of + another case with bloodhounds, in which the female had to be held to + the male. Considering how rapid is the natural increase of the dog, it + is difficult to understand the high price of most highly improved + breeds, which almost implies long-continued close interbreeding, except + on the belief that this process lessens fertility and increases + liability to distemper and other diseases. A high authority, Mr. + Scrope, attributes the rarity and deterioration in size of the Scotch + deerhound (the few individuals now existing throughout the country + being all related) in large part to close interbreeding. + + With all highly-bred animals there is more or less difficulty in + getting them to procreate quickly, and all suffer much from delicacy of + constitution; but I do not pretend that these effects ought to be + wholly attributed to close interbreeding. A great judge of rabbits[260] + says, "the long-eared does are often too highly bred or forced in their + youth to be of much value as breeders, often turning out barren or bad + mothers." Again: "Very long-eared bucks will also sometimes prove + barren." These highly-bred rabbits often desert their young, so that it + is necessary to have nurse-rabbits. + + With _Pigs_ there is more unanimity amongst breeders on the evil + effects of close interbreeding than, perhaps, with any other large + animal. Mr. Druce, a great and successful breeder of the Improved + Oxfordshires (a crossed race), writes, "without a change of boars of a + different tribe, but of the same breed, constitution cannot be + preserved." Mr. Fisher Hobbs, the raiser of the celebrated Improved + Essex breed, divided his stock into three separate families, by which + means he maintained the breed for more than twenty years, "by judicious + selection from the _three distinct families_."[261] Lord Western was + the first importer of a Neapolitan boar and sow. "From this pair he + bred in-and-in, until the breed was in danger of becoming extinct, a + sure result (as Mr. Sidney remarks) of in-and-in breeding." Lord + Western then crossed his Neapolitan pigs with the old Essex, and made + the first great step towards the Improved Essex breed. Here is a more + interesting case. Mr. J. Wright, well known as a breeder, crossed[262] + the same boar with the daughter, granddaughter, and + great-granddaughter, and so on for seven generations. The result was, + that in many instances the offspring failed to breed; in others they + produced few that lived; and of the latter many were idiotic, without + sense {122} even to suck, and when attempting to move could not walk + straight. Now it deserves especial notice, that the two last sows + produced by this long course of interbreeding were sent to other boars, + and they bore several litters of healthy pigs. The best sow in external + appearance produced during the whole seven generations was one in the + last stage of descent; but the litter consisted of this one sow. She + would not breed to her sire, yet bred at the first trial to a stranger + in blood. So that, in Mr. Wright's case, long-continued and extremely + close interbreeding did not affect the external form or merit of the + young; but with many of them the general constitution and mental + powers, and especially the reproductive functions, were seriously + affected. + + Nathusius gives[263] an analogous and even more striking case: he + imported from England a pregnant sow of the large Yorkshire breed, and + bred the product closely in-and-in for three generations: the result + was unfavourable, as the young were weak in constitution, with impaired + fertility. One of the latest sows, which he esteemed a good animal, + produced, when paired with her own uncle (who was known to be + productive with sows of other breeds), a litter of six, and a second + time a litter of only five weak young pigs. He then paired this sow + with a boar of a small black breed, which he had likewise imported from + England, and which boar, when matched with sows of his own breed, + produced from seven to nine young: now, the sow of the large breed, + which was so unproductive when paired with her own uncle, yielded to + the small black boar, in the first litter twenty-one, and in the second + litter eighteen young pigs; so that in one year she produced + thirty-nine fine young animals! + + As in the case of several other animals already mentioned, even when no + injury is perceptible from moderately close interbreeding, yet, to + quote the words of Mr. Coate, a most successful breeder (who five times + won the annual gold medal of the Smithfield Club Show for the best pen + of pigs), "Crosses answer well for profit to the farmer, as you get + more constitution and quicker growth; but for me, who sell a great + number of pigs for breeding purposes, I find it will not do, as it + requires many years to get anything like purity of blood again."[264] + +Before passing on to Birds, I ought to refer to man, though I am unwilling +to enter on this subject, as it is surrounded by natural prejudices. It has +moreover been discussed by various authors under many points of view.[265] +Mr. Tylor[266] has shown {123} that with widely different races, in the +most distant quarters of the world, marriages between relations--even +between distant relations--have been strictly prohibited. A few exceptional +cases can be specified, especially with royal families; and these have been +enlarged on in a learned article[267] by Mr. W. Adam, and formerly in 1828 +by Hofacker. Mr. Tylor is inclined to believe that the almost universal +prohibition of closely-related marriages has arisen from their evil effects +having been observed, and he ingeniously explains some apparent anomalies +in the prohibition not extending equally to the relations on both the male +and female side. He admits, however, that other causes, such as the +extension of friendly alliances, may have come into play. Mr. W. Adam, on +the other hand, concludes that related marriages are prohibited and viewed +with repugnance from the confusion which would thus arise in the descent of +property, and from other still more recondite reasons; but I cannot accept +this view, seeing that the savages of Australia and South America,[268] who +have no property to bequeath or fine moral feelings to confuse, hold the +crime of incest in abhorrence. + +It would be interesting to know, if it could be ascertained, as throwing +light on this question with respect to man, what occurs with the higher +anthropomorphous apes--whether the young males and females soon wander away +from their parents, or whether the old males become jealous of their sons +and expel them, or whether any inherited instinctive feeling, from being +beneficial, has been generated, leading the young males and females of the +same family to prefer pairing with distinct families, and to dislike +pairing with each other. A considerable body of evidence has already been +advanced, showing that the offspring from parents which are not related are +more vigorous and fertile than those from parents which are closely +related; hence any slight feeling, arising from the sexual excitement of +novelty or other cause, which led to the former rather than to the latter +unions, would be augmented through natural selection, and thus might become +instinctive; for those individuals which had an innate preference of this +kind would increase in number. It seems more probable, that degraded +savages should {124} thus unconsciously have acquired their dislike and +even abhorrence of incestuous marriages, rather than that they should have +discovered by reasoning and observation the evil results. The abhorrence +occasionally failing is no valid argument against the feeling being +instinctive, for any instinct may occasionally fail or become vitiated, as +sometimes occurs with parental love and the social sympathies. In the case +of man, the question whether evil follows from close interbreeding will +probably never be answered by direct evidence, as he propagates his kind so +slowly and cannot be subjected to experiment; but the almost universal +practice of all races at all times of avoiding closely-related marriages is +an argument of considerable weight; and whatever conclusion we arrive at in +regard to the higher animals may be safely extended to man. + + Turning now to Birds: in the case of the _Fowl_ a whole array of + authorities could be given against too close interbreeding. Sir J. + Sebright positively asserts that he made many trials, and that his + fowls, when thus treated, became long in the legs, small in the body, + and bad breeders.[269] He produced the famous Sebright Bantams by + complicated crosses, and by breeding in-and-in; and since his time + there has been much close interbreeding with these Bantams; and they + are now notoriously bad breeders. I have seen Silver Bantams, directly + descended from his stock, which had become almost as barren as hybrids; + for not a single chicken had been that year hatched from two full nests + of eggs. Mr. Hewitt says that with these Bantams the sterility of the + male stands, with rare exceptions, in the closest relation with their + loss of certain secondary male characters: he adds, "I have noticed, as + a general rule, that even the slightest deviation from feminine + character in the tail of the male Sebright--say the elongation by only + half an inch of the two principal tail-feathers--brings with it + improved probability of increased fertility."[270] + + Mr. Wright states[271] that Mr. Clark, "whose fighting-cocks were so + notorious, continued to breed from his own kind till they lost their + disposition to fight, but stood to be cut up without making any + resistance, and were so reduced in size as to be under those weights + required for the best prizes; but on obtaining a cross from Mr. + Leighton, they again resumed their former courage and weight." It + should be borne in mind that game-cocks before they fought were always + weighed, so that nothing was left to the imagination about any + reduction or increase of {125} weight. Mr. Clark does not seem to have + bred from brothers and sisters, which is the most injurious kind of + union; and he found, after repeated trials, that there was a greater + reduction in weight in the young from a father paired with his + daughter, than from a mother with her son. I may add that Mr. Eyton, of + Eyton, the well-known ornithologist, who is a large breeder of Grey + Dorkings, informs me that they certainly diminish in size, and become + less prolific, unless a cross with another strain is occasionally + obtained. So it is with Malays, according to Mr. Hewitt, as far as size + is concerned.[272] + + An experienced writer[273] remarks that the same amateur, as is well + known, seldom long maintains the superiority of his birds; and this, he + adds, undoubtedly is due to all his stock "being of the same blood;" + hence it is indispensable that he should occasionally procure a bird of + another strain. But this is not necessary with those who keep a stock + of fowls at different stations. Thus, Mr. Ballance, who has bred Malays + for thirty years, and has won more prizes with these birds than any + other fancier in England, says that breeding in-and-in does not + necessarily cause deterioration; "but all depends upon how this is + managed." "My plan has been to keep about five or six distinct runs, + and to rear about two hundred or three hundred chickens each year, and + select the best birds from each run for crossing. I thus secure + sufficient crossing to prevent deterioration."[274] + + We thus see that there is almost complete unanimity with + poultry-breeders that, when fowls are kept at the same place, evil + quickly follows from interbreeding carried on to an extent which would + be disregarded in the case of most quadrupeds. On the other hand, it is + a generally received opinion that cross-bred chickens are the hardiest + and most easily reared.[275] Mr. Tegetmeier, who has carefully attended + to poultry of all breeds, says[276] that Dorking hens, allowed to run + with Houdan or Crevecoeur cocks, "produce in the early spring chickens + that for size, hardihood, early maturity, and fitness for the market, + surpass those of any pure breed that we have ever raised." Mr. Hewitt + gives it as a general rule with fowls, that crossing the breed + increases their size. He makes this remark after stating that hybrids + from the pheasant and fowl are considerably larger than either + progenitor: so again, hybrids from the male golden pheasant and hen + common pheasant "are of far larger size than either parent-bird."[277] + To this subject of the increased size of hybrids I shall presently + return. + + With _Pigeons_, breeders are unanimous, as previously stated, that it + is absolutely indispensable, notwithstanding the trouble and expense + thus caused, occasionally to cross their much-prized birds with + individuals of another strain, but belonging, of course, to the same + variety. It deserves {126} notice that, when large size is one of the + desired characters, as with pouters,[278] the evil effects of close + interbreeding are much sooner perceived than when small birds, such as + short-faced tumblers, are valued. The extreme delicacy of the high + fancy breeds, such as these tumblers and improved English carriers, is + remarkable; they are liable to many diseases, and often die in the egg + or during the first moult; and their eggs have generally to be hatched + under foster-mothers. Although these highly-prized birds have + invariably been subjected to much close interbreeding, yet their + extreme delicacy of constitution cannot perhaps be thus fully + explained. Mr. Yarrell informed me that Sir J. Sebright continued + closely interbreeding some owl-pigeons, until from their extreme + sterility he as nearly as possible lost the whole family. Mr. + Brent[279] tried to raise a breed of trumpeters, by crossing a common + pigeon, and recrossing the daughter, granddaughter, + great-granddaughter, and great-great-granddaughter, with the same male + trumpeter, until he obtained a bird with 15/16ths of trumpeter's blood; + but then the experiment failed, for "breeding so close stopped + reproduction." The experienced Neumeister[280] also asserts that the + offspring from dovecotes and various other breeds are "generally very + fertile and hardy birds:" so again, MM. Boitard and Corbié,[281] after + forty-five years' experience, recommend persons to cross their breeds + for amusement; for, if they fail to make interesting birds, they will + succeed under an economical point of view, "as it is found that + mongrels are more fertile than pigeons of pure race." + + I will refer only to one other animal, namely, the Hive-bee, because a + distinguished entomologist has advanced this as a case of inevitable + close interbreeding. As the hive is tenanted by a single female, it + might have been thought that her male and female offspring would always + have bred together, more especially as bees of different hives are + hostile to each other; a strange worker being almost always attacked + when trying to enter another hive. But Mr. Tegetmeier has shown[282] + that this instinct does not apply to drones, which are permitted to + enter any hive; so that there is no _à priori_ improbability of a queen + receiving a foreign drone. The fact of the union invariably and + necessarily taking place on the wing, during the queen's nuptial + flight, seems to be a special provision against continued + interbreeding. However this may be, experience has shown, since the + introduction of the yellow-banded Ligurian race into Germany and + England, that bees freely cross: Mr. Woodbury, who introduced Ligurian + bees into Devonshire, found during a single season that three stocks, + at distances of from one to two miles from his hives, were crossed by + his drones. In one case the Ligurian drones must have flown over the + city of Exeter, and over several intermediate hives. On another + occasion several common black queens were crossed by Ligurian drones at + a distance of from one to three and a half miles.[283] + +{127} + +_Plants._ + + When a single plant of a new species is introduced into any country, if + propagated by seed, many individuals will soon be raised, so that if + the proper insects be present there will be crossing. With + newly-introduced trees or other plants not propagated by seed we are + not here concerned. With old-established plants it is an almost + universal practice occasionally to make exchanges of seed, by which + means individuals which have been exposed to different conditions of + life,--and this, as we have seen, diminishes the evil from close + interbreeding,--will occasionally be introduced into each district. + + Experiments have not been tried on the effects of fertilising flowers + with their own pollen during _several_ generations. But we shall + presently see that certain plants, either normally or abnormally, are + more or less sterile, even in the first generation, when fertilised by + their own pollen. Although nothing is directly known on the evil + effects of long-continued close interbreeding with plants, the converse + proposition that great good is derived from crossing is well + established. + + With respect to the crossing of individuals belonging to the same + sub-variety, Gärtner, whose accuracy and experience exceeded that of + all other hybridisers, states[284] that he has many times observed good + effects from this step, especially with exotic genera, of which the + fertility is somewhat impaired, such as Passiflora, Lobelia, and + Fuchsia. Herbert also says,[285] "I am inclined to think that I have + derived advantage from impregnating the flower from which I wished to + obtain seed with pollen from another individual of the same variety, or + at least from another flower, rather than with its own." Again, + Professor Lecoq asserts that he has ascertained that crossed offspring + are more vigorous and robust than their parents.[286] + + General statements of this kind, however, can seldom be fully trusted; + consequently I have begun a series of experiments, which, if they + continue to give the same results as hitherto, will for ever settle the + question of the good effects of crossing two distinct plants of the + same variety, and of the evil effects of self-fertilisation. A clear + light will thus also be thrown on the fact that flowers are invariably + constructed so as to permit, or favour, or necessitate the union of two + individuals. We shall clearly understand why monoecious and + dioecious,--why dimorphic and trimorphic plants exist, and many other + such cases. The plan which I have followed in my experiments is to grow + plants in the same pot, or in pots of the same size, or close together + in the open ground; to carefully exclude insects; and then to fertilise + some of the flowers with pollen from the same flower, and others on the + same plant with pollen from a distinct but adjoining plant. In many, + but not all, of these experiments, the crossed plants yielded much more + seed than the self-fertilised plants; and I have never seen the {128} + reversed case. The self-fertilised and crossed seeds thus obtained were + allowed to germinate in the same glass vessel on damp sand; and as the + seeds successively germinated, they were planted in pairs on opposite + sides of the same pot, with a superficial partition between them, and + were placed so as to be equally exposed to the light. In other cases + the self-fertilised and crossed seeds were simply sown on opposite + sides of the same small pot. I have, in short, followed different + plans, but in every case have taken all the precautions which I could + think of, so that the two lots should be equally favoured. Now, I have + carefully observed the growth of plants raised from crossed and + self-fertilised seed, from their germination to maturity, in species of + the following genera, namely, Brassica, Lathyrus, Lupinus, Lobelia, + Lactuca, Dianthus, Myosotis, Petunia, Linaria, Calceolaria, Mimulus, + and Ipomoea, and the difference in their powers of growth, and of + withstanding in certain cases unfavourable conditions, was most + manifest and strongly marked. It is of importance that the two lots of + seed should be sown or planted on opposite sides of the same pot, so + that the seedlings may struggle against each other; for if sown + separately in ample and good soil, there is often but little difference + in their growth. + + I will briefly describe the two most striking cases as yet observed by + me. Six crossed and six self-fertilised seeds of _Ipomoea purpurea_, + from plants treated in the manner above described, were planted as soon + as they had germinated, in pairs on opposite sides of two pots, and + rods of equal thickness were given them to twine up. Five of the + crossed plants grew from the first more quickly than the opposed + self-fertilised plants; the sixth, however, was weakly and was for a + time beaten, but at last its sounder constitution prevailed and it shot + ahead of its antagonist. As soon as each crossed plant reached the top + of its seven-foot rod its fellow was measured, and the result was that, + when the crossed plants were seven feet high, the self-fertilised had + attained the average height of only five feet four and a half inches. + The crossed plants flowered a little before, and more profusely than + the self-fertilised plants. On opposite sides of another _small_ pot a + large number of crossed and self-fertilised seeds were sown, so that + they had to struggle for bare existence; a single rod was given to each + lot: here again the crossed plants showed from the first their + advantage; they never quite reached the summit of the seven-foot rod, + but relatively to the self-fertilised plants their average height was + as seven feet to five feet two inches. The experiment was repeated in + the two following generations with plants raised from the + self-fertilised and crossed plants, treated in exactly the same manner, + and with nearly the same result. In the second generation, the crossed + plants, which were again crossed, produced 121 seed-capsules, whilst + the self-fertilised plants, again self-fertilised, produced only 84 + capsules. + + Some flowers of the _Mimulus luteus_ were fertilised with their own + pollen, and others were crossed with pollen from distinct plants + growing in the same pot. The seeds after germinating were thickly + planted on opposite sides of a pot. The seedlings were at first equal + in height; but when the young crossed plants were exactly half an inch, + the {129} self-fertilised plants were only a quarter of an inch high. + But this inequality did not continue, for, when the crossed plants were + four and a half inches high, the self-fertilised were three inches; and + they retained the same relative difference till their growth was + complete. The crossed plants looked far more vigorous than the + uncrossed, and flowered before them; they produced also a far greater + number of flowers, which yielded capsules (judging, however, from only + a few) containing more seeds. As in the former case, the experiment was + repeated in the same manner during the next two generations, and with + exactly the same result. Had I not watched these plants of the Mimulus + and Ipomoea during their whole growth, I could not have believed it + possible, that a difference apparently so slight, as that of the pollen + being taken from the same flower, and from a distinct plant growing in + the same small pot, could have made so wonderful a difference in the + growth and vigour of the plants thus produced. This, under a + physiological point of view, is a most remarkable phenomenon. + + * * * * * + + With respect to the benefit derived from crossing distinct varieties, + plenty of evidence has been published. Sageret[287] repeatedly speaks + in strong terms of the vigour of melons raised by crossing different + varieties, and adds that they are more easily fertilised than common + melons, and produce numerous good seed. Here follows the evidence of an + English gardener:[288] "I have this summer met with better success in + my cultivation of melons, in an unprotected state, from the seeds of + hybrids (_i.e._ mongrels) obtained by cross impregnation, than with old + varieties. The offspring of three different hybridisations (one more + especially, of which the parents were the two most dissimilar varieties + I could select) each yielded more ample and finer produce than any one + of between twenty and thirty established varieties." + + Andrew Knight[289] believed that his seedlings from crossed varieties + of the apple exhibited increased vigour and luxuriance; and M. + Chevreul[290] alludes to the extreme vigour of some of the crossed + fruit-trees raised by Sageret. + + By crossing reciprocally the tallest and shortest peas, Knight[291] + says, "I had in this experiment a striking instance of the stimulative + effects of crossing the breeds; for the smallest variety, whose height + rarely exceeded two feet, was increased to six feet; whilst the height + of the large and luxuriant kind was very little diminished." Mr. Laxton + gave me seed-peas produced from crosses between four distinct kinds; + and the plants thus raised were extraordinarily vigorous, being in each + case from one to two or three feet taller than the parent-forms growing + close alongside them. + + {130} + + Wiegmann[292] made many crosses between several varieties of cabbage; + and he speaks with astonishment of the vigour and height of the + mongrels, which excited the amazement of all the gardeners who beheld + them. Mr. Chaundy raised a great number of mongrels by planting + together six distinct varieties of cabbage. These mongrels displayed an + infinite diversity of character; "But the most remarkable circumstance + was, that, while all the other cabbages and borecoles in the nursery + were destroyed by a severe winter, these hybrids were little injured, + and supplied the kitchen when there was no other cabbage to be had." + + Mr. Maund exhibited before the Royal Agricultural Society[293] + specimens of crossed wheat, together with their parent varieties; and + the editor states that they were intermediate in character, "united + with that greater vigour of growth, which it appears, in the vegetable + as in the animal world, is the result of a first cross." Knight also + crossed several varieties of wheat,[294] and he says "that in the years + 1795 and 1796, when almost the whole crop of corn in the island was + blighted, the varieties thus obtained, and these only, escaped in this + neighbourhood, though sown in several different soils and situations." + + Here is a remarkable case: M. Clotzsch[295] crossed _Pinus sylvestris_ + and _nigricans_, _Quercus robur_ and _pedunculata, Alnus glutinosa_ and + _incana_, _Ulmus campestris_ and _effusa_; and the cross-fertilised + seeds, as well as seeds of the pure parent-trees, were all sown at the + same time and in the same place. The result was, that after an interval + of eight years, the hybrids were one-third taller than the pure trees! + + * * * * * + + The facts above given refer to undoubted varieties, excepting the trees + crossed by Clotzsch, which are ranked by various botanists as + strongly-marked races, sub-species, or species. That true hybrids + raised from entirely distinct species, though they lose in fertility, + often gain in size and constitutional vigour, is certain. It would be + superfluous to quote any facts; for all experimenters, Kölreuter, + Gärtner, Herbert, Sageret, Lecoq, and Naudin, have been struck with the + wonderful vigour, height, size, tenacity of life, precocity, and + hardiness of their hybrid productions. Gärtner[296] sums up his + conviction on this head in the strongest terms. Kölreuter[297] gives + numerous precise measurements of the weight and height of his hybrids + in comparison with measurements of both parent-forms; and speaks with + astonishment of their "_statura portentosa_," their "_ambitus + vastissimus ac altitudo valde conspicua_." Some exceptions to the rule + in the case of very sterile hybrids have, however, been noticed by + Gärtner and {131} Herbert; but the most striking exceptions are given + by Max Wichura,[298] who found that hybrid willows were generally + tender in constitution, dwarf, and short-lived. + + Kölreuter explains the vast increase in the size of the roots, stems, + &c., of his hybrids, as the result of a sort of compensation due to + their sterility, in the same way as many emasculated animals are larger + than the perfect males. This view seems at first sight extremely + probable, and has been accepted by various authors;[299] but + Gärtner[300] has well remarked that there is much difficulty in fully + admitting it; for with many hybrids there is no parallelism between the + degree of their sterility and their increased size and vigour. The most + striking instances of luxuriant growth have been observed with hybrids + which were not sterile in any extreme degree. In the genus Mirabilis, + certain hybrids are unusually fertile, and their extraordinary + luxuriance of growth, together with their enormous roots,[301] have + been transmitted to their progeny. The increased size of the hybrids + produced between the fowl and pheasant, and between the distinct + species of pheasants, has been already noticed. The result in all cases + is probably in part due to the saving of nutriment and vital force + through the sexual organs not acting, or acting imperfectly, but more + especially to the general law of good being derived from a cross. For + it deserves especial attention that mongrel animals and plants, which + are so far from being sterile that their fertility is often actually + augmented, have, as previously shown, their size, hardiness, and + constitutional vigour generally increased. It is not a little + remarkable that an accession of vigour and size should thus arise under + the opposite contingencies of increased and diminished fertility. + + It is a perfectly well ascertained fact[302] that hybrids will + invariably breed more readily with either pure parent, and not rarely + with a distinct species, than with each other. Herbert is inclined to + explain even this fact by the advantage derived from a cross; but + Gärtner more justly accounts for it by the pollen of the hybrid, and + probably its ovules, being in some degree vitiated, whereas the pollen + and ovules of both pure parents and of any third species are sound. + Nevertheless there are some well-ascertained and remarkable facts, + which, as we shall immediately see, show that the act of crossing in + itself undoubtedly tends to increase or re-establish the fertility of + hybrids. + +_On certain Hermaphrodite Plants which, either normally or abnormally, +require to be fertilised by pollen from a distinct individual or species._ + +The facts now to be given differ from those hitherto detailed, as the +self-sterility does not here result from long-continued, {132} close +interbreeding. These facts are, however, connected with our present +subject, because a cross with a distinct individual is shown to be either +necessary or advantageous. Dimorphic and trimorphic plants, though they are +hermaphrodites, must be reciprocally crossed, one set of forms by the +other, in order to be fully fertile, and in some cases to be fertile in any +degree. But I should not have noticed these plants, had it not been for the +following cases given by Dr. Hildebrand:[303]-- + + _Primula sinensis_ is a reciprocally dimorphic species: Dr. Hildebrand + fertilised twenty-eight flowers of both forms, each by pollen of the + other form, and obtained the full number of capsules containing on an + average 42.7 seed per capsule; here we have complete and normal + fertility. He then fertilised forty-two flowers of both forms with + pollen of the same form, but taken from a distinct plant, and all + produced capsules containing on an average only 19.6 seed. Lastly, and + here we come to our more immediate point, he fertilised forty-eight + flowers of both forms with pollen of the same form, taken from the same + flower, and now he obtained only thirty-two capsules, and these + contained on an average 18.6 seed, or one less per capsule than in the + former case. So that, with these illegitimate unions, the act of + impregnation is less assured, and the fertility slightly less, when the + pollen and ovules belong to the same flower, than when belonging to two + distinct individuals of the same form. Dr. Hildebrand has recently made + analogous experiments on the long-styled form of _Oxalis rosea_, with + the same result.[304] + +It has recently been discovered that certain plants, whilst growing in +their native country under natural conditions, cannot be fertilised with +pollen from the same plant. They are sometimes so utterly self-impotent, +that, though they can readily be fertilised by the pollen of a distinct +species or even distinct genus, yet, wonderful as the fact is, they never +produce a single seed by their own pollen. In some cases, moreover, the +plant's own pollen and stigma mutually act on each other in a deleterious +manner. Most of the facts to be given relate to Orchids, but I will +commence with a plant belonging to a widely different family. + + Sixty-three flowers of _Corydalis cava_, borne on distinct plants, were + fertilised by Dr. Hildebrand[305] with pollen from other plants of the + same species; and fifty-eight capsules were obtained, including on an + average {133} 4.5 seed in each. He then fertilised sixteen flowers + produced by the same raceme, one with another, but obtained only three + capsules, one of which alone contained any good seeds, namely, two in + number. Lastly, he fertilised twenty-seven flowers, each with its own + pollen; he left also fifty-seven flowers to be spontaneously + fertilised, and this would certainly have ensued if it had been + possible, for the anthers not only touch the stigma, but the + pollen-tubes were seen by Dr. Hildebrand to penetrate it; nevertheless + these eighty-four flowers did not produce a single seed-capsule! This + whole case is highly instructive, as it shows how widely different the + action of the same pollen is, according as it is placed on the stigma + of the same flower, or on that of another flower on the same raceme, or + on that of a distinct plant. + + With exotic Orchids several analogous cases have been observed, chiefly + by Mr. John Scott.[306] _Oncidium sphacelatum_ has effective pollen, + for with it Mr. Scott fertilised two distinct species; its ovules are + likewise capable of impregnation, for they were readily fertilised by + the pollen of _O. divaricatum_; nevertheless, between one and two + hundred flowers fertilised by their own pollen did not produce a single + capsule, though the stigmas were penetrated by the pollen-tubes. Mr. + Robinson Munro, of the Royal Botanic Gardens of Edinburgh, also informs + me (1864) that a hundred and twenty flowers of this same species were + fertilised by him with their own pollen, and did not produce a capsule, + but eight flowers fertilised by the pollen of _O. divaricatum_ produced + four fine capsules: again, between two and three hundred flowers of _O. + divaricatum_, fertilised by their own pollen, did not set a capsule, + but twelve flowers fertilised by _O. flexuosum_ produced eight fine + capsules: so that here we have three utterly self-impotent species, + with their male and female organs perfect, as shown by their mutual + fertilisation. In these cases fertilisation was effected only by the + aid of a distinct species. But, as we shall presently see, distinct + plants, raised from seed, of _Oncidium flexuosum_, and probably of the + other species, would have been perfectly capable of fertilising each + other, for this is the natural process. Again, Mr. Scott found that the + pollen of a plant of _O. microchilum_ was good, for with it he + fertilised two distinct species; he found its ovules good, for they + could be fertilised by the pollen of one of these species, and by the + pollen of a distinct plant of _O. microchilum_; but they could not be + fertilised by pollen of the same plant, though the pollen-tubes + penetrated the stigma. An analogous case has been recorded by M. + Rivière,[307] with two plants of _O. Cavendishianum_, which were both + self-sterile, but reciprocally fertilised each other. All these cases + refer to the genus Oncidium, but Mr. Scott found that _Maxillaria + atro-rubens_ was "totally insusceptible of fertilisation with its own + pollen," but fertilised, and was fertilised by, a widely distinct + species, viz. _M. squalens_. + + As these orchids had grown under unnatural conditions, in {134} + hot-houses, I concluded without hesitation that their self-sterility + was due to this cause. But Fritz Müller informs me that at Desterro, in + Brazil, he fertilised above one hundred flowers of the above-mentioned + _Oncidium flexuosum_, which is there endemic, with its own pollen, and + with that taken from distinct plants; all the former were sterile, + whilst those fertilised by pollen from any _other plant_ of the same + species were fertile. During the first three days there was no + difference in the action of the two kinds of pollen: that placed on the + stigma of the same plant separated in the usual manner into grains, and + emitted tubes which penetrated the column, and the stigmatic chamber + shut itself; but the flowers alone which had been fertilised by pollen + taken from a distinct plant produced seed-capsules. On a subsequent + occasion these experiments were repeated on a large scale with the same + result. Fritz Müller found that four other endemic species of Oncidium + were in like manner utterly sterile with their own pollen, but fertile + with that from any other plant: some of them likewise produced + seed-capsules when impregnated with pollen of widely distinct genera, + such as Leptotes, Cyrtopodium, and Rodriguezia! _Oncidium crispum_, + however, differs from the foregoing species in varying much in its + self-sterility; some plants producing fine pods with their own pollen, + others failing to do so; in two or three instances, Fritz Müller + observed that the pods produced by pollen taken from a distinct flower + on the same plant, were larger than those produced by the flower's own + pollen. In _Epidendrum cinnabarinum_, an orchid belonging to another + division of the family, fine pods were produced by the plant's own + pollen, but they contained by weight only about half as much seed as + the capsules which had been fertilized by pollen from a distinct plant, + and in one instance from a distinct species; moreover, a very large + proportion, and in some cases nearly all the seed produced by the + plant's own pollen, was embryonless and worthless. Some self-fertilized + capsules of a Maxillaria were in a similar state. + + Another observation made by Fritz Müller is highly remarkable, namely, + that with various orchids the plant's own pollen not only fails to + impregnate the flower, but acts on the stigma, and is acted on, in an + injurious or poisonous manner. This is shown by the surface of the + stigma in contact with the pollen, and by the pollen itself, becoming + in from three to five days dark brown, and then decaying. The + discolouration and decay are not caused by parasitic cryptogams, which + were observed by Fritz Müller in only a single instance. These changes + are well shown by placing on the same stigma, at the same time, the + plant's own pollen and that from a distinct plant of the same species, + or of another species, or even of another and widely remote genus. + Thus, on the stigma of _Oncidium flexuosum_, the plant's own pollen and + that from a distinct plant were placed side by side, and in five days' + time the latter was perfectly fresh, whilst the plant's own pollen was + brown. On the other hand, when the pollen of a distinct plant of the + _Oncidium flexuosum_, and of the _Epidendrum zebra_ (_nov. spec.?_), + were placed together on the same stigma, they behaved in exactly the + same manner, the grains separating, emitting tubes, and penetrating the + stigma, so that the two {135} pollen-masses, after an interval of + eleven days, could not be distinguished except by the difference of + their caudicles, which, of course, undergo no change. Fritz Müller has, + moreover, made a large number of crosses between orchids belonging to + distinct species and genera, and he finds that in all cases when the + flowers are not fertilised their footstalks first begin to wither; and + the withering slowly spreads upwards until the germens fall off, after + an interval of one or two weeks, and in one instance of between six and + seven weeks; but even in this latter case, and in most other cases, the + pollen and stigma remained in appearance fresh. Occasionally, however, + the pollen becomes brownish, generally on the external surface, and not + in contact with the stigma, as is invariably the case when the plant's + own pollen is applied. + + Fritz Müller observed the poisonous action of the plant's own pollen in + the above-mentioned _Oncidium flexuosum_, _O. unicorne, pubes_ (_?_), + and in two other unnamed species. Also in two species of Rodriguezia, + in two of Notylia, in one of Burlingtonia, and of a fourth genus in the + same group. In all these cases, except the last, it was proved that the + flowers were, as might have been expected, fertile with pollen from a + distinct plant of the same species. Numerous flowers of one species of + Notylia were fertilized with pollen from the same raceme; in two days' + time they all withered, the germens began to shrink, the pollen-masses + became dark brown, and not one pollen-grain emitted a tube. So that in + this orchid the injurious action of the plant's own pollen is more + rapid than with _Oncidium flexuosum_. Eight other flowers on the same + raceme were fertilized with pollen from a distinct plant of the same + species: two of these were dissected, and their stigmas were found to + be penetrated by numberless pollen-tubes; and the germens of the other + six flowers became well developed. On a subsequent occasion many other + flowers were fertilized with their own pollen, and all fell off dead in + a few days; whilst some flowers on the same raceme which had been left + simply unfertilised adhered and long remained fresh. We have seen that + in cross-unions between extremely distinct orchids the pollen long + remains undecayed; but Notylia behaved in this respect differently; for + when its pollen was placed on the stigma of _Oncidium flexuosum_, both + the stigma and pollen quickly became dark brown, in the same manner as + if the plant's own pollen had been applied. + + Fritz Müller suggests that, as in all these cases the plant's own + pollen is not only impotent (thus effectually preventing + self-fertilization), but likewise prevents, as was ascertained in the + case of the Notylia and _Oncidium flexuosum_, the action of + subsequently applied pollen from a distinct individual, it would be an + advantage to the plant to have its own pollen rendered more and more + deleterious; for the germens would thus quickly be killed, and, + dropping off, there would be no further waste in nourishing a part + which ultimately could be of no avail. Fritz Müller's discovery that a + plant's own pollen and stigma in some cases act on each other as if + mutually poisonous, is certainly most remarkable. + +We now come to cases closely analogous with those just {136} given, but +different, inasmuch as individual plants alone of the species are +self-impotent. This self-impotence does not depend on the pollen or ovules +being in a state unfit for fertilisation, for both have been found +effective in union with other plants of the same or of a distinct species. +The fact of these plants having spontaneously acquired so peculiar a +constitution, that they can be fertilised more readily by the pollen of a +distinct species than by their own, is remarkable. These abnormal cases, as +well as the foregoing normal cases, in which certain orchids, for instance, +can be much more easily fertilised by the pollen of a distinct species than +by their own, are exactly the reverse of what occurs with all ordinary +species. For in these latter the two sexual elements of the same individual +plant are capable of freely acting on each other; but are so constituted +that they are more or less impotent when brought into union with the sexual +elements of a distinct species, and produce more or less sterile hybrids. +It would appear that the pollen or ovules, or both, of the individual +plants which are in this abnormal state, have been affected in some strange +manner by the conditions to which they themselves or their parents have +been exposed; but whilst thus rendered self-sterile, they have retained the +capacity common to most species of partially fertilizing and being +partially fertilized by allied forms. However this may be, the subject, to +a certain extent, is related to our general conclusion that good is derived +from the act of crossing. + + Gärtner experimented on two plants of _Lobelia fulgens_, brought from + separate places, and found[308] that their pollen was good, for he + fertilised with it _L. cardinalis_ and _syphilitica_; their ovules were + likewise good, for they were fertilised by the pollen of these same two + species; but these two plants of _L. fulgens_ could not be fertilised + by their own pollen, as can generally be effected with perfect ease + with this species. Again, the pollen of a plant of _Verbascum nigrum_ + grown in a pot was found by Gärtner[309] capable of fertilising _V. + lychnitis_ and _V. Austriacum_; the ovules could be fertilised by the + pollen of _V. thapsus_; but the flowers could not be fertilised by + their own pollen. Kölreuter, also,[310] gives the case of three {137} + garden plants of _Verbascum phoeniceum_, which bore during two years + many flowers; these he successfully fertilised by the pollen of no less + than four distinct species, but they produced not a seed with their own + apparently good pollen; subsequently these same plants, and others + raised from seed, assumed a strangely fluctuating condition, being + temporarily sterile on the male or female side, or on both sides, and + sometimes fertile on both sides; but two of the plants were perfectly + fertile throughout the summer. + + It appears[311] that certain flowers on certain plants of _Lilium + candidum_ can be fertilised more easily by pollen from a distinct + individual than by their own. So, again, with the varieties of the + potato. Tinzmann,[312] who made many trials with this plant, says that + pollen from another variety sometimes "exerts a powerful influence, and + I have found sorts of potatoes which would not bear seed from + impregnation with the pollen of their own flowers, would bear it when + impregnated with other pollen." It does not, however, appear to have + been proved that the pollen which failed to act on the flower's own + stigma was in itself good. + + In the genus Passiflora it has long been known that several species do + not produce fruit, unless fertilised by pollen taken from distinct + species: thus, Mr. Mowbray[313] found that he could not get fruit from + _P. alata_ and _racemosa_ except by reciprocally fertilising them with + each other's pollen. Similar facts have been observed in Germany and + France;[314] and I have received two authentic accounts of _P. + quadrangularis_, which never produced fruit with its own pollen, but + would do so freely when fertilised in one case with the pollen of _P. + coerulea_, and in another case with that of _P. edulis_. So again, with + respect to _P. laurifolia_, a cultivator of much experience has + recently remarked[315] that the flowers "must be fertilised with the + pollen of _P. coerulea_, or of some other common kind, as their own + pollen will not fertilise them." But the fullest details on this + subject have been given by Mr. Scott:[316] plants of _Passiflora + racemosa_, _coerulea_, and _alata_ flowered profusely during many years + in the Botanic Gardens of Edinburgh, and, though repeatedly fertilised + by Mr. Scott and by others with their own pollen, never produced any + seed; yet this occurred at once with all three species when they were + crossed together in various ways. But in the case of _P. coerulea_, + three plants, two of which grew in the Botanic Gardens, were all + rendered fertile, merely by impregnating the one with pollen of the + other. The same result was attained in the same manner with _P. alata_, + but only with one plant out of three. As so many self-sterile species + have been mentioned, it may be stated that in the case of _P. + gracilis_, which is an annual, the flowers are nearly as fertile with + their own pollen as with that from a distinct plant; thus sixteen + flowers {138} spontaneously self-fertilised produced fruit, each + containing on an average 21.3 seed, whilst fruit from fourteen crossed + flowers contained 24.1 seed. + + Returning to _P. alata_, I have received (1866) some interesting + details from Mr. Robinson Munro. Three plants, including one in + England, have already been mentioned which were inveterately + self-sterile, and Mr. Munro informs me of several others which, after + repeated trials during many years, have been found in the same + predicament. At some other places, however, this species fruits readily + when fertilised with its own pollen. At Taymouth Castle there is a + plant which was formerly grafted by Mr. Donaldson on a distinct + species, name unknown, and ever since the operation it has produced + fruit in abundance by its own pollen; so that this small and unnatural + change in the state of this plant has restored its self-fertility! Some + of the seedlings from the Taymouth Castle plant were found to be not + only sterile with their own pollen, but with each other's pollen, and + with the pollen of distinct species. Pollen from the Taymouth plant + failed to fertilise certain plants of the same species, but was + successful on one plant in the Edinburgh Botanic Gardens. Seedlings + were raised from this latter union, and some of their flowers were + fertilised by Mr. Munro with their own pollen; but they were found to + be as self-impotent as the mother-plant had always proved, except when + fertilised by the grafted Taymouth plant, and except, as we shall see, + when fertilised by her own seedlings. For Mr. Munro fertilised eighteen + flowers on the self-impotent mother-plant with pollen from these her + own self-impotent seedlings, and obtained, remarkable as the fact is, + eighteen fine capsules full of excellent seed! I have met with no case + in regard to plants which shows so well as this of _P. alata_, on what + small and mysterious causes complete fertility or complete sterility + depends. + +The facts hitherto given relate to the much-lessened or completely +destroyed fertility of pure species when impregnated with their own pollen, +in comparison with their fertility when impregnated by distinct individuals +or distinct species; but closely analogous facts have been observed with +hybrids. + + Herbert states[317] that having in flower at the same time nine hybrid + Hippeastrums, of complicated origin, descended from several species, he + found that "almost every flower touched with pollen from another cross + produced seed abundantly, and those which were touched with their own + pollen either failed entirely, or formed slowly a pod of inferior size, + with fewer seeds." In the 'Horticultural Journal' he adds that, "the + admission of the pollen of another cross-bred Hippeastrum (however + complicated the cross) to any _one_ flower of the number, is almost + sure to check the fructification of the others." In a letter written to + me in 1839, Dr. Herbert says that he had already tried these + experiments during five consecutive years, and he subsequently repeated + them, with the same invariable result. {139} He was thus led to make an + analogous trial on a pure species, namely, on the _Hippeastrum + aulicum_, which he had lately imported from Brazil: this bulb produced + four flowers, three of which were fertilised by their own pollen, and + the fourth by the pollen of a triple cross between _H. bulbulosum_, + _reginæ_, and _vittatum_; the result was, that "the ovaries of the + three first flowers soon ceased to grow, and after a few days perished + entirely: whereas the pod impregnated by the hybrid made vigorous and + rapid progress to maturity, and bore good seed, which vegetated + freely." This is, indeed, as Herbert remarks, "a strange truth," but + not so strange as it then appeared. + + As a confirmation of these statements, I may add that Mr. M. + Mayes,[318] after much experience in crossing the species of Amaryllis + (Hippeastrum), says, "neither the species nor the hybrids will, we are + well aware, produce seed so abundantly from their own pollen as from + that of others." So, again, Mr. Bidwell, in New South Wales,[319] + asserts that _Amaryllis belladonna_ bears many more seeds when + fertilised by the pollen of _Brunswigia_ (_Amaryllis_ of some authors) + _Josephinæ_ or of _B. multiflora_, than when fertilised by its own + pollen. Mr. Beaton dusted four flowers of a Cyrtanthus with their own + pollen, and four with the pollen of _Vallota_ (_Amaryllis_) _purpurea_; + on the seventh day "those which received their own pollen slackened + their growth, and ultimately perished; those which were crossed with + the Vallota held on."[320] These latter cases, however, relate to + uncrossed species, like those before given with respect to Passiflora, + Orchids, &c., and are here referred to only because the plants belong + to the same group of Amaryllidaceæ. + + In the experiments on the hybrid Hippeastrums, if Herbert had found + that the pollen of two or three kinds alone had been more efficient on + certain kinds than their own pollen, it might have been argued that + these, from their mixed parentage, had a closer mutual affinity than + the others; but this explanation is inadmissible, for the trials were + made reciprocally backwards and forwards on nine different hybrids; and + a cross, whichever way taken, always proved highly beneficial. I can + add a striking and analogous case from experiments made by the Rev. A. + Rawson, of Bromley Common, with some complex hybrids of Gladiolus. This + skilful horticulturist possessed a number of French varieties, + differing from each other only in the colour and size of the flowers, + all descended from Gandavensis, a well-known old hybrid, said to be + descended from _G. Natalensis_ by the pollen of _G. + oppositiflorus_.[321] Mr. Rawson, after repeated trials, found that + none of the varieties would set seed with their own pollen, although + {140} taken from distinct plants of the same variety, which had, of + course, been propagated by bulbs, but that they all seeded freely with + pollen from any other variety. To give two examples: Ophir did not + produce a capsule with its own pollen, but when fertilised with that of + Janire, Brenchleyensis, Vulcain, and Linné, it produced ten fine + capsules; but the pollen of Ophir was good, for when Linné was + fertilised by it seven capsules were produced. This later variety, on + the other hand, was utterly barren with its own pollen, which we have + seen was perfectly efficient on Ophir. Altogether, Mr. Rawson, in the + year 1861, fertilised twenty-six flowers borne by four varieties with + pollen taken from other varieties, and every single flower produced a + fine seed-capsule; whereas fifty-two flowers on the same plants, + fertilised at the same time with their own pollen, did not yield a + single seed-capsule. Mr. Rawson fertilised, in some cases, the + alternate flowers, and in other cases all those down one side of the + spike, with pollen of other varieties, and the remaining flowers with + their own pollen; I saw these plants when the capsules were nearly + mature, and their curious arrangement at once brought full conviction + to the mind that an immense advantage had been derived from crossing + these hybrids. + + Lastly, I have heard from Dr. E. Bornet, of Antibes, who has made + numerous experiments in crossing the species of Cistus, but as not yet + published the results, that, when any of these hybrids are fertile, + they may be said to be, in regard to function, dioecious; "for the + flowers are always sterile when the pistil is fertilised by pollen + taken from the same flower or from flowers on the same plant. But they + are often fertile if pollen be employed from a distinct individual of + the same hybrid nature, or from a hybrid made by a reciprocal cross." + +_Conclusion._--The facts just given, which show that certain plants are +self-sterile, although both sexual elements are in a fit state for +reproduction when united with distinct individuals of the same or other +species, appear at first sight opposed to all analogy. The sexual elements +of the same flower have become, as already remarked, differentiated in +relation to each other, almost like those of two distinct species. + +With respect to the species which, whilst living under their natural +conditions, have their reproductive organs in this peculiar state, we may +conclude that it has been naturally acquired for the sake of effectually +preventing self-fertilisation. The case is closely analous with dimorphic +and trimorphic plants, which can be fully fertilised only by plants belong +to the opposite form, and not, as in the foregoing cases, in differently by +any other plant. Some of these dimorphic plants are completely sterile with +pollen taken from the same plant or from the same {141} form. It is +interesting to observe the graduated series from plants which, when +fertilised by their own pollen, yield the full number of seed, but with the +seedlings a little dwarfed in stature--to plants which when self-fertilised +yield few seeds--to those with yield none--and, lastly, to those in which +the plant's own pollen and stigma act on each other like poison. This +peculiar state of the reproductive organs, when occurring in certain +individuals alone, is evidently abnormal; and as it chiefly affects exotic +plants, or indigenous plants cultivated in pots, we may attribute it to +some change in the conditions of life, acting on the plants themselves or +on their parents. The self-impotent _Passiflora alata_, which recovered its +self-fertility after having been grafted on a distinct stock, shows how +small a change is sufficient to act powerfully on the reproductive system. +The possibility of a plant becoming under culture self-impotent is +interesting as throwing light on the occurrence of this same condition in +natural species. A cultivated plant in this state generally remains so +during its whole life; and from this fact we may infer that the state is +probably congenital. + +Kölreuter, however, has described some plants of Verbascum which varied in +this respect even during the same season. As in all the normal cases, and +in many, probably in most, of the abnormal cases, any two self-impotent +plants can reciprocally fertilize each other, we may infer that a very +slight difference in the nature of their sexual elements suffices to give +fertility; but in other instances, as with some Passifloras and the hybrid +Gladioli, a greater degree of differentiation appears to be necessary, for +with these plants fertility is gained only by the union of distinct +species, or of hybrids of distinct parentage. These facts all point to the +same general conclusion, namely, that good is derived from a cross between +individuals, which either innately, or from exposure to dissimilar +conditions, have come to differ in sexual constitution. + +Exotic animals confined in menageries are sometimes in nearly the same +state as the above-described self-impotent plants; for, as we shall see in +the following chapter, certain monkeys, the larger carnivora, several +finches, geese, and pheasants, cross together, quite as freely as, or even +more freely than, the individuals of the same species breed together. Cases +will, {142} also, be given of sexual incompatibility between certain male +and female domesticated animals, which, nevertheless, are fertile when +matched with any other individual of the same kind. + +In the early part of this chapter it was shown that the crossing of +distinct forms, whether closely or distantly allied, gives increased size +and constitutional vigour, and, except in the case of crossed species, +increased fertility, to the offspring. The evidence rests on the universal +testimony of breeders (for it should be observed that I am not here +speaking of the evil results of close interbreeding), and is practically +exemplified in the higher value of cross-bred animals for immediate +consumption. The good results of crossing have also been demonstrated, in +the case of some animals and of numerous plants, by actual weight and +measurement. Although animals of pure blood will obviously be deteriorated +by crossing, as far as their characteristic qualities are concerned, there +seems to be no exception to the rule that advantages of the kind just +mentioned are thus gained, even when there has not been any previous close +interbreeding. The rule applies to all animals, even to cattle and sheep, +which can long resist breeding in-and-in between the nearest +blood-relations. It applies to individuals of the same sub-variety but of +distinct families, to varieties or races, to sub-species, as well as to +quite distinct species. + +In this latter case, however, whilst size, vigour, precocity, and hardiness +are, with rare exceptions, gained, fertility, in a greater or less degree, +is lost; but the gain cannot be exclusively attributed to the principle of +compensation; for there is no close parallelism between the increased size +and vigour of the offspring and their sterility. Moreover it has been +clearly proved that mongrels which are perfectly fertile gain these same +advantages as well as sterile hybrids. + +The evil consequences of long-continued close interbreeding are not so +easily recognised as the good effects from crossing, for the deterioration +is gradual. Nevertheless it is the general opinion of those who have had +most experience, especially with animals which propagate quickly, that evil +does inevitably follow sooner or later, but at different rates with +different animals. No doubt a false belief may widely prevail like a +superstition; yet it is difficult to suppose that so many acute and +original {143} observers have all been deceived at the expense of much cost +and trouble. A male animal may sometimes be paired with his daughter, +granddaughter, and so on, even for seven generations, without any manifest +bad result; but the experiment has never been tried of matching brothers +and sisters, which is considered the closest form of interbreeding, for an +equal number of generations. There is good reason to believe that by +keeping the members of the same family in distinct bodies, especially if +exposed to somewhat different conditions of life, and by occasionally +crossing these families, the evil results may be much diminished, or quite +eliminated. These results are loss of constitutional vigour, size, and +fertility; but there is no necessary deterioration in the general form of +the body, or in other good qualities. We have seen that with pigs +first-rate animals have been produced after long-continued close +interbreeding, though they had become extremely infertile when paired with +their near relations. The loss of fertility, when it occurs, seems never to +be absolute, but only relative to animals of the same blood; so that this +sterility is to a certain extent analogous with that of self-impotent +plants which cannot be fertilised by their own pollen, but are perfectly +fertile with pollen of any other plant of the same species. The fact of +infertility of this peculiar nature being one of the results of +long-continued interbreeding, shows that interbreeding does not act merely +by combining and augmenting various morbid tendencies common to both +parents; for animals with such tendencies, if not at the time actually ill, +can generally propagate their kind. Although offspring descended from the +nearest blood-relations are not necessarily deteriorated in structure, yet +some authors[322] believe that they are eminently liable to malformations; +and this is not improbable, as everything which lessens the vital powers +acts in this manner. Instances of this kind have been recorded in the case +of pigs, bloodhounds, and some other animals. + +Finally, when we consider the various facts now given which plainly show +that good follows from crossing, and less plainly {144} that evil follows +from close interbreeding, and when we bear in mind that throughout the +whole organic world elaborate provision has been made for the occasional +union of distinct individuals, the existence of a great law of nature is, +if not proved, at least rendered in the highest degree probable; namely, +that the crossing of animals and plants which are not closely related to +beach other is highly beneficial or even necessary, and that interbreeding +prolonged during many generations is highly injurious. + + * * * * * + + +{145} + +CHAPTER XVIII. + +ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED CONDITIONS OF LIFE: +STERILITY FROM VARIOUS CAUSES. + + ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE CONDITIONS OF + LIFE--STERILITY FROM CHANGED CONDITIONS, IN ANIMALS, IN THEIR NATIVE + COUNTRY AND IN MENAGERIES--MAMMALS, BIRDS, AND INSECTS--LOSS OF + SECONDARY SEXUAL CHARACTERS AND OF INSTINCTS--CAUSES OF + STERILITY--STERILITY OF DOMESTICATED ANIMALS FROM CHANGED + CONDITIONS--SEXUAL INCOMPATIBILITY OF INDIVIDUAL ANIMALS--STERILITY OF + PLANTS FROM CHANGED CONDITIONS OF LIFE--CONTABESCENCE OF THE + ANTHERS--MONSTROSITIES AS A CAUSE OF STERILITY--DOUBLE + FLOWERS--SEEDLESS FRUIT--STERILITY FROM THE EXCESSIVE DEVELOPMENT OF + THE ORGANS OF VEGETATION--FROM LONG-CONTINUED PROPAGATION BY + BUDS--INCIPIENT STERILITY THE PRIMARY CAUSE OF DOUBLE FLOWERS AND + SEEDLESS FRUIT. + +_On the Good derived from slight Changes in the Conditions of Life._--In +considering whether any facts were known which might throw light on the +conclusion arrived at in the last chapter, namely, that benefits ensue from +crossing, and that it is a law of nature that all organic beings should +occasionally cross, it appeared to me probable that the good derived from +slight changes in the conditions of life, from being an analogous +phenomenon, might serve this purpose. No two individuals, and still less no +two varieties, are absolutely alike in constitution and structure; and when +the germ of one is fertilised by the male element of another, we may +believe that it is acted on in a somewhat similar manner as an individual +when exposed to slightly changed conditions. Now, every one must have +observed the remarkable influence on convalescents of a change of +residence, and no medical man doubts the truth of this fact. Small farmers +who hold but little land are convinced that their cattle derive great +benefit from a change of pasture. In the case of plants, the evidence is +strong that a great advantage is derived from exchanging seeds, tubers, +bulbs, and cuttings from one soil or place to another as different as +possible. {146} + + The belief that plants are thus benefited, whether or not well founded, + has been firmly maintained from the time of Columella, who wrote + shortly after the Christian era, to the present day; and it now + prevails in England, France, and Germany.[323] A sagacious observer, + Bradley, writing in 1724,[324] says, "When we once become Masters of a + good Sort of Seed, we should at least put it into Two or Three Hands, + where the Soils and Situations are as different as possible; and every + Year the Parties should change with one another; by which Means, I find + the Goodness of the Seed will be maintained for several Years. For Want + of this Use many Farmers have failed in their Crops and been great + Losers." He then gives his own practical experience on this head. A + modern writer[325] asserts, "Nothing can be more clearly established in + agriculture than that the continual growth of any one variety in the + same district makes it liable to deterioration either in quality or + quantity." Another writer states that he sowed close together in the + same field two lots of wheat-seed, the product of the same original + stock, one of which had been grown on the same land, and the other at a + distance, and the difference in favour of the crop from the latter seed + was remarkable. A gentleman in Surrey who has long made it his business + to raise wheat to sell for seed, and who has constantly realised in the + market higher prices than others, assures me that he finds it + indispensable continually to change his seed; and that for this purpose + he keeps two farms differing much in soil and elevation. + + With respect to the tubers of the potato, I find that at the present + day the practice of exchanging sets is almost everywhere followed. The + great growers of potatoes in Lancashire formerly used to get tubers + from Scotland, but they found that "a change from the moss-lands, and + _vice versâ_, was generally sufficient." In former times in France the + crop of potatoes in the Vosges had become reduced in the course of + fifty or sixty years in the proportion from 120-150 to 30-40 bushels; + and the famous Oberlin attributed the surprising good which he effected + in large part to changing the sets.[326] + + A well-known practical gardener, Mr. Robson[327] positively states that + he has himself witnessed decided advantage from obtaining bulbs of the + onion, tubers of the potato, and various seeds, all of the same kind, + from different soils and distant parts of England. He further states + that with {147} plants propagated by cuttings, as with the Pelargonium, + and especially the Dahlia, manifest advantage is derived from getting + plans of the same variety, which have been cultivated in another place; + or, "where the extent of the place allows, to take cuttings from one + description of soil to plant on another, so as to afford the change + that seems so necessary to the well-being of the plants." He maintains + that after a time an exchange of this nature is "forced on the grower, + whether he be prepared for it or not." Similar remarks have been made + by another excellent gardener, Mr. Fish, namely, that cuttings of the + same variety of Calceolaria, which he obtained from a neighbour, + "showed much greater vigour than some of his own that were treated in + exactly the same manner," and he attributed this solely to his own + plants having become "to a certain extent worn out or tired of their + quarters." Something of this kind apparently occurs in grafting and + budding fruit-trees; for, according to Mr. Abbey, grafts or buds + generally take on a distinct variety or even species, or on a stock + previously grafted, with greater facility than on stocks raised from + seeds of the variety which is to be grafted; and he believes this + cannot be altogether explained by the stocks in question being better + adapted to the soil and climate of the place. It should, however, be + added, that varieties grafted or budded on very distinct kinds, though + they may take more readily and grow at first more vigorously than when + grafted on closely allied stocks, afterwards often become unhealthy. + + I have studied M. Tessier's careful and elaborate experiments,[328] + made to disprove the common belief that good is derived from a change + of seed; and he certainly shows that the same seed may with care be + cultivated on the same farm (it is not stated whether on exactly the + same soil) for ten consecutive years without loss. Another excellent + observer, Colonel Le Couteur,[329] has come to the same conclusion; but + then he expressly adds, if the same seed be used, "that which is grown + on land manured from the mixen one year becomes seed for land prepared + with lime, and that again becomes seed for land dressed with ashes, + then for land dressed with mixed manure, and so on." But this in effect + is a systematic exchange of seed, within the limits of the same farm. + +On the whole the belief, which has long been held by many skilful +cultivators, that good follows from exchanging seed, tubers, &c., seems to +be fairly well founded. Considering the small size of most seeds, it seems +hardly credible that the advantage thus derived can be due to the seeds +obtaining in one soil some chemical element deficient in the other soil. As +plants after once germinating naturally become fixed to the same spot, it +might have been anticipated that they would show the good effects of a +change more plainly than animals, which continually wander about; and this +apparently is the {148} case. Life depending on, or consisting in, an +incessant play of the most complex forces, it would appear that their +action is in some way stimulated by slight changes in the circumstances to +which each organism is exposed. All forces throughout nature, as Mr. +Herbert Spencer[330] remarks, tend towards an equilibrium, and for the life +of each being it is necessary that this tendency should be checked. If +these views and the foregoing facts can be trusted, they probably throw +light, on the one hand, on the good effects of crossing the breed, for the +germ will be thus slightly modified or acted on by new forces; and on the +other hand, on the evil effects of close interbreeding prolonged during +many generations, during which the germ will be acted on by a male having +almost identically the same constitution. + +_Sterility from changed Conditions of Life._ + +I will now attempt to show that animals and plants, when removed from their +natural conditions, are often rendered in some degree infertile or +completely barren; and this occurs even when the conditions have not been +greatly changed. This conclusion is not necessarily opposed to that at +which we have just arrived, namely, that lesser changes of other kinds are +advantageous to organic beings. Our present subject is of some importance, +from having an intimate connexion with the causes of variability. +Indirectly it perhaps bears on the sterility of species when crossed: for +as, on the one hand, slight changes in the conditions of life are +favourable to plants and animals, and the crossing of varieties adds to the +size, vigour, and fertility of their offspring; so, on the other hand, +certain other changes in the conditions of life cause sterility; and as +this likewise ensues from crossing much-modified forms or species, we have +a parallel and double series of facts, which apparently stand in close +relation to each other. + +It is notorious that many animals, though perfectly tamed, {149} refuse to +breed in captivity. Isidore Geoffroy St. Hilaire[331] consequently has +drawn a broad distinction between tamed animals which will not breed under +captivity, and truly domesticated animals which breed freely--generally +more freely, as shown in the sixteenth chapter, than in a state of nature. +It is possible and generally easy to tame most animals; but experience has +shown that it is difficult to get them to breed regularly, or even at all. +I shall discuss this subject in detail; but will give only those cases +which seem most illustrative. My materials are derived from notices +scattered through various works, and especially from a Report, drawn up for +me by the kindness of the officers of the Zoological Society of London, +which has especial value, as it records all the cases, during nine years +from 1838-46, in which the animals were seen to couple but produced no +offspring, as well as the cases in which they never, as far as known, +coupled. This MS. Report I have corrected by the annual Reports +subsequently published. Many facts are given on the breeding of the animals +in that magnificent work, 'Gleanings from the Menageries of Knowsley Hall,' +by Dr. Gray. I made, also, particular inquiries from the experienced keeper +of the birds in the old Surrey Zoological Gardens. I should premise that a +slight change in the treatment of animals sometimes makes a great +difference in their fertility; and it is probable that the results observed +in different menageries would differ. Indeed some animals in our Zoological +Gardens have become more productive since the year 1846. It is, also, +manifest from F. Cuvier's account of the Jardin des Plantes,[332] that the +animals formerly bred much less freely there than with us; for instance, in +the Duck tribe, which is highly prolific, only one species had at that +period produced young. + + The most remarkable cases, however, are afforded by animals kept in + their native country, which, though perfectly tamed, quite healthy, and + allowed some freedom, are absolutely incapable of breeding. + Rengger,[333] who in Paraguay particularly attended to this subject, + specifies six quadrupeds in this condition; and he mentions two or + three others which most rarely {150} breed. Mr. Bates, in his admirable + work on the Amazons, strongly insists on similar cases;[334] and he + remarks, that the fact of thoroughly tamed native mammals and birds not + breeding when kept by the Indians, cannot be wholly accounted for by + their negligence or indifference, for the turkey is valued by them, and + the fowl has been adopted by the remotest tribes. In almost every part + of the world--for instance, in the interior of Africa, and in several + of the Polynesian islands--the natives are extremely fond of taming the + indigenous quadrupeds and birds; but they rarely or never succeed in + getting them to breed. + + The most notorious case of an animal not breeding in captivity is that + of the elephant. Elephants are kept in large numbers in their native + Indian home, live to old age, and are vigorous enough for the severest + labour; yet, with one or two exceptions, they have never been known + even to couple, though both males and females have their proper + periodical seasons. If, however, we proceed a little eastward to Ava, + we hear from Mr. Crawfurd[335] that their "breeding in the domestic + state, or at least in the half-domestic state in which the female + elephants are generally kept, is of every-day occurrence;" and Mr. + Crawfurd informs me that he believes that the difference must be + attributed solely to the females being allowed to roam the forests with + some degree of freedom. The captive rhinoceros, on the other hand, + seems from Bishop Heber's account[336] to breed in India far more + readily than the elephant. Four wild species of the horse genus have + bred in Europe, though here exposed to a great change in their natural + habits of life; but the species have generally been crossed one with + another. Most of the members of the pig family breed readily in our + menageries: even the Red River hog (_Potamochoerus penicillatus_), from + the sweltering plains of West Africa, has bred twice in the Zoological + Gardens. Here also the Peccary (_Dicotyles torquatus_) has bred several + times; but another species, the _D. labiatus_, though rendered so tame + as to be half-domesticated, breeds so rarely in its native country of + Paraguay, that according to Rengger[337] the fact requires + confirmation. Mr. Bates remarks that the tapir, though often kept tame + in Amazonia by the Indians, never breeds. + + Ruminants generally breed quite freely in England, though brought from + widely different climates, as may be seen in the Annual Reports of the + Zoological Gardens, and in the Gleanings from Lord Derby's menagerie. + + The Carnivora, with the exception of the Plantigrade division, + generally breed (though with capricious exceptions) almost as freely as + ruminants. Many species of Felidæ have bred in various menageries, + although imported from various climates and closely confined. Mr. + Bartlett, the present superintendent of the Zoological Gardens,[338] + remarks that the lion appears to breed more frequently and to bring + forth more young at a birth than any other species of the family. He + adds that the tiger has rarely bred; {151} "but there are several + well-authenticated instances of the female tiger breeding with the + lion." Strange as the fact may appear, many animals under confinement + unite with distinct species and produce hybrids quite as freely as, or + even more freely than, with their own species. On inquiring from Dr. + Falconer and others, it appears that the tiger when confined in India + does not breed, though it has been known to couple. The cheetah (_Felis + jubata_) has never been known by Mr. Bartlett to breed in England, but + it has bred at Frankfort; nor does it breed in India, where it is kept + in large numbers for hunting; but no pains would be taken to make them + breed, as only those animals which have hunted for themselves in a + state of nature are serviceable and worth training.[339] According to + Rengger, two species of wild cats in Paraguay, though thoroughly tamed, + have never bred. Although so many of the Felidæ breed readily in the + Zoological Gardens, yet conception by no means always follows union: in + the nine-year Report, various species are specified which were observed + to couple seventy-three times, and no doubt this must have passed many + times unnoticed; yet from the seventy-three unions only fifteen births + ensued. The Carnivora in the Zoological Gardens were formerly less + freely exposed to the air and cold than at present, and this change of + treatment, as I was assured by the former superintendent, Mr. Miller, + greatly increased their fertility. Mr. Bartlett, and there cannot be a + more capable judge, says, "it is remarkable that lions breed more + freely in travelling collections than in the Zoological Gardens; + probably the constant excitement and irritation produced by moving from + place to place, or change of air, may have considerable influence in + the matter." + + Many members of the Dog family breed readily when confined. The Dhole + is one of the most untameable animals in India, yet a pair kept there + by Dr. Falconer produced young. Foxes, on the other hand, rarely breed, + and I have never heard of such an occurrence with the European fox: the + silver fox of North America (_Canis argentatus_), however, has bred + several times in the Zoological Gardens. Even the otter has bred there. + Every one knows how readily the semi-domesticated ferret breeds, though + shut up in miserably small cages; but other species of Viverra and + Paradoxurus absolutely refuse to breed in the Zoological Gardens. The + Genetta has bred both here and in the Jardin des Plantes, and produced + hybrids. The _Herpestes fasciatus_ has likewise bred; but I was + formerly assured that the _H. griseus_, though many were kept in the + Gardens, never bred. + + The Plantigrade Carnivora breed under confinement much less freely, + without our being able to assign any reason, than other members of the + group. In the nine-year Report it is stated that the bears had been + seen in the Zoological Gardens to couple freely, but previously to 1848 + had most rarely conceived. In the Reports published since this date + three species have produced young (hybrids in one case), and, wonderful + to relate, the white Polar bear has produced young. The badger (_Meles + taxus_) has bred several times in the Gardens; but I have not heard of + this {152} occurring elsewhere in England, and the event must be very + rare, for an instance in Germany has been thought worth recording.[340] + In Paraguay the native Nasua, though kept in pairs during many years + and perfectly tamed, has never been known, according to Rengger, to + breed or show any sexual passion; nor, as I hear from Mr. Bates, does + this animal, or the Cercoleptes, breed in the region of the Amazons. + Two other plantigrade genera, Procyon and Gulo, though often kept tame + in Paraguay, never breed there. In the Zoological Gardens species of + Nasua and Procyon have been seen to couple; but they did not produce + young. + + As domesticated rabbits, guinea-pigs, and white mice breed so + abundantly when closely confined under various climates, it might have + been thought that most other members of the Rodent order would have + bred in captivity, but this is not the case. It deserves notice, as + showing how the capacity to breed sometimes goes by affinity, that the + one native rodent of Paraguay, which there breeds _freely_ and has + yielded successive generations, is the _Cavia aperea_; and this animal + is so closely allied to the guinea-pig, that it has been erroneously + thought to be the parent-form.[341] In the Zoological Gardens, some + rodents have coupled, but have never produced young; some have neither + coupled nor bred; but a few have bred, as the porcupine more than once, + the Barbary mouse, lemming, chinchilla, and the agouti (_Dasyprocta + aguti_), several times. This latter animal has also produced young in + Paraguay, though they were born dead and ill-formed; but in Amazonia, + according to Mr. Bates, it never breeds, though often kept tame about + the houses. Nor does the paca (_Coelogenys paca_) breed there. The + common hare when confined has, I believe, never bred in Europe;[342] + though, according to a recent statement, it has crossed with the + rabbit. I have never heard of the dormouse breeding in confinement. But + squirrels offer a more curious case: with one exception, no species has + ever bred in the Zoological Gardens, yet as many as fourteen + individuals of _S. palmarum_ were kept together during several years. + The _S. cinerea_ has been seen to couple, but it did not produce young; + nor has this species, when rendered extremely tame in its native + country, North America, been ever known to breed.[343] At Lord Derby's + menagerie squirrels of many kinds were kept in numbers, but Mr. + Thompson, the superintendent, told me that none had ever bred there, or + elsewhere as far as he knew. I have never heard of the English squirrel + breeding in confinement. But the species which has bred more than once + in the Zoological Gardens is the one which perhaps might have been + least expected, namely, the flying squirrel (_Sciuropterus volucella_): + it has, also, bred several times {153} near Birmingham; but the female + never produced more than two young at a birth, whereas in its native + American home she bears from three to six young.[344] + + Monkeys, in the nine-year Report from the Zoological Gardens, are + stated to unite most freely, but during this period, though many + individuals were kept, there were only seven births. I have heard of + one American monkey alone, the Ouistiti, breeding in Europe.[345] A + Macacus, according to Flourens, bred in Paris; and more than one + species of this genus has produced young in London, especially the + _Macacus rhesus_, which everywhere shows a special capacity to breed + under confinement. Hybrids have been produced both in Paris and London + from this same genus. The Arabian baboon, or _Cynocephalus + hamadryas_,[346] and a Cercopithecus have bred in the Zoological + Gardens, and the latter species at the Duke of Northumberland's. + Several members of the family of Lemurs have produced hybrids in the + Zoological Gardens. It is much more remarkable that monkeys very rarely + breed when confined in their native country; thus the Cay (_Cebus + azaræ_) is frequently and completely tamed in Paraguay, but + Rengger[347] says that it breeds so rarely, that he never saw more than + two females which had produced young. A similar observation has been + made with respect to the monkeys which are frequently tamed by the + aborigines in Brazil.[348] In the region of the Amazons, these animals + are so often kept in a tame state, that Mr. Bates in walking through + the streets of Parà counted thirteen species; but, as he asserts, they + have never been known to breed in captivity.[349] + +_Birds._ + + Birds offer in some respects better evidence than quadrupeds, from + their breeding more rapidly and being kept in greater numbers. We have + seen that carnivorous animals are more fertile under confinement than + most other mammals. The reverse holds good with carnivorous birds. It + is said[350] that as many as eighteen species have been used in Europe + for hawking, and several others in Persia and India;[351] they have + been kept in their native country in the finest condition, and have + been flown during six, eight, or nine years;[352] yet there is no + record of their having ever produced young. As these birds were + formerly caught whilst young, at great expense, being imported from + Iceland, Norway, and Sweden, there can {154} be little doubt that, if + possible, they would have been propagated. In the Jardin des Plantes, + no bird of prey has been known to couple.[353] No hawk, vulture, or owl + has ever produced fertile eggs in the Zoological Gardens, or in the old + Surrey Gardens, with the exception, in the former place on one + occasion, of a condor and a kite (_Milvus niger_). Yet several species, + namely, the _Aquila fusca_, _Haliætus leucocephalus_, _Falco + tinnunculus_, _F. subbuteo_, and _Buteo vulgaris_, have been seen to + couple in the Zoological Gardens. Mr. Morris[354] mentions as a unique + fact that a kestrel (_Falco tinnunculus_) bred in an aviary. The one + kind of owl which has been known to couple in the Zoological Gardens + was the Eagle Owl (_Bubo maximus_); and this species shows a special + inclination to breed in captivity; for a pair at Arundel Castle, kept + more nearly in a state of nature "than ever fell to the lot of an + animal deprived of its liberty,"[355] actually reared their young. Mr. + Gurney has given another instance of this same owl breeding in + confinement; and he records the case of a second species of owl, the + _Strix passerina_, breeding in captivity.[356] + + Of the smaller graminivorous birds, many kinds have been kept tame in + their native countries, and have lived long; yet, as the highest + authority on cage-birds[357] remarks, their propagation is "uncommonly + difficult." The canary-bird shows that there is no inherent difficulty + in these birds breeding freely in confinement; and Audubon says[358] + that the _Fringilla_ (_Spiza_) _ciris_ of North America breeds as + perfectly as the canary. The difficulty with the many finches which + have been kept in confinement is all the more remarkable as more than a + dozen species could be named which have yielded hybrids with the + canary; but hardly any of these, with the exception of the siskin + (_Fringilla spinus_), have reproduced their own kind. Even the + bullfinch (_Loxia pyrrhula_) has bred as frequently with the canary, + though belonging to a distinct genus, as with its own species.[359] + With respect to the skylark (_Alauda arvensis_), I have heard of birds + living for seven years in an aviary, which never produced young; and a + great London bird-fancier assured me that he had never known an + instance of their breeding; nevertheless one case has been + recorded.[360] In the nine-year Report from the Zoological Society, + twenty-four incessorial species are enumerated which had not bred, and + of these only four were known to have coupled. + + Parrots are singularly long-lived birds; and Humboldt mentions the + curious fact of a parrot in South America, which spoke the language of + {155} an extinct Indian tribe, so that this bird preserved the sole + relic of a lost language. Even in this country there is reason to + believe[361] that parrots have lived to the age of nearly one hundred + years; yet, though many have been kept in Europe, they breed so rarely + that the event has been thought worth recording in the gravest + publications.[362] According to Bechstein[363] the African _Psittacus + erithacus_ breeds oftener than any other species: the _P. macoa_ + occasionally lays fertile eggs, but rarely succeeds in hatching them; + this bird, however, has the instinct of incubation sometimes so + strongly developed, that it will hatch the eggs of fowls or pigeons. In + the Zoological Gardens and in the old Surrey Gardens some few species + have coupled, but, with the exception of three species of parrakeets, + none have bred. It is a much more remarkable fact that in Guiana + parrots of two kinds, as I am informed by Sir E. Schomburgk, are often + taken from the nests by the Indians and reared in large numbers; they + are so tame that they fly freely about the houses, and come when called + to be fed, like pigeons; yet he has never heard of a single instance of + their breeding.[364] In Jamaica, a resident naturalist, Mr. R. + Hill,[365] says, "no birds more readily submit to human dependence than + the parrot-tribe, but no instance of a parrot breeding in this tame + life has been known yet." Mr. Hill specifies a number of other native + birds kept tame in the West Indies, which never breed in this state. + + The great pigeon family offers a striking contrast with parrots: in the + nine-year Report thirteen species are recorded as having bred, and, + what is more noticeable, only two were seen to couple without any + result. Since the above date every annual Report gives many cases of + various pigeons breeding. The two magnificent crowned pigeons (_Goura + coronata_ and _Victoriæ_) produced hybrids; nevertheless, of the former + species more than a dozen birds were kept, as I am informed by Mr. + Crawfurd, in a park at Penang, under a perfectly well-adapted climate, + but never once bred. The _Columba migratoria_ in its native country, + North America, invariably lays two eggs, but in Lord Derby's menagerie + never more than one. The same fact has been observed with the _C. + leucocephala_.[366] + + Gallinaceous birds of many genera likewise show an eminent capacity for + breeding under captivity. This is particularly the case with pheasants; + yet our English species seldom lays more than ten eggs in confinement; + whilst from eighteen to twenty is the usual number in the wild + state.[367] With the Gallinaceæ, as with all other orders, there are + marked and {156} inexplicable exceptions in regard to the fertility of + certain species and genera under confinement. Although many trials have + been made with the common partridge, it has rarely bred, even when + reared in large aviaries; and the hen will never hatch her own + eggs.[368] The American tribe of Guans or Cracidæ are tamed with + remarkable ease, but are very shy breeders in this country;[369] but + with care various species were formerly made to breed rather freely in + Holland.[370] Birds of this tribe are often kept in a perfectly tamed + condition in their native country by the Indians, but they never + breed.[371] It might have been expected that grouse from their habits + of life would not have bred in captivity, more especially as they are + said soon to languish and die.[372] But many cases are recorded of + their breeding: the capercailzie (_Tetrao urogallus_) has bred in the + Zoological Gardens; it breeds without much difficulty when confined in + Norway, and in Russia five successive generations have been reared: + _Tetrao tetrix_ has likewise bred in Norway; _T. Scoticus_ in Ireland; + _T. umbellus_ at Lord Derby's; and _T. cupido_ in North America. + + It is scarcely possible to imagine a greater change in habits than that + which the members of the ostrich family must suffer, when cooped up in + small enclosures under a temperate climate, after freely roaming over + desert and tropical plains or entangled forests. Yet almost all the + kinds, even the mooruk (_Casuarius Bennettii_) from New Ireland, has + frequently produced young in the various European menageries. The + African ostrich, though perfectly healthy and living long in the South + of France, never lays more than from twelve to fifteen eggs, though in + its native country it lays from twenty-five to thirty.[373] Here we + have another instance of fertility impaired, but not lost, under + confinement, as with the flying squirrel, the hen-pheasant, and two + species of American pigeons. + + Most Waders can be tamed, as the Rev. E. S. Dixon informs me, with + remarkable facility; but several of them are short-lived under + confinement, so that their sterility in this state is not surprising. + The cranes breed more readily than other genera: _Grus montigresia_ has + bred several times in Paris and in the Zoological Gardens, as has _G. + cinerea_ at the latter place, and _G. antigone_ at Calcutta. Of other + members of this great order, _Tetrapteryx paradisea_ has bred at + Knowsley, a Porphyrio in Sicily, and the _Gallinula chloropus_ in the + Zoological Gardens. On the other hand, several {157} birds belonging to + this order will not breed in their native country, Jamaica; and the + Psophia, though often kept by the Indians of Guiana about their houses, + "is seldom or never known to breed."[374] + + No birds breed with such complete facility under confinement as the + members of the great Duck family; yet, considering their aquatic and + wandering habits, and the nature of their food, this could not have + been anticipated. Even some time ago above two dozen species had bred + in the Zoological Gardens; and M. Selys-Longchamps has recorded the + production of hybrids from forty-four different members of the family; + and to these Professor Newton has added a few more cases.[375] "There + is not," says Mr. Dixon,[376] "in the wide world, a goose which is not + in the strict sense of the word domesticable;" that is, capable of + breeding under confinement; but this statement is probably too bold. + The capacity to breed sometimes varies in individuals of the same + species; thus Audubon[377] kept for more than eight years some wild + geese (_Anser Canadensis_), but they would not mate; whilst other + individuals of the same species produced young during the second year. + I know of but one instance in the whole family of a species which + absolutely refuses to breed in captivity, namely, the _Dendrocygna + viduata_, although, according to Sir R. Schomburgk,[378] it is easily + tamed, and is frequently kept by the Indians of Guiana. Lastly, with + respect to Gulls, though many have been kept in the Zoological Gardens + and in the old Surrey Gardens, no instance was known before the year + 1848 of their coupling or breeding; but since that period the herring + gull (_Larus argentatus_) has bred many times in the Zoological Gardens + and at Knowsley. + + There is reason to believe that insects are affected by confinement + like the higher animals. It is well known that the Sphingidæ rarely + breed when thus treated. An entomologist[379] in Paris kept twenty-five + specimens of _Saturnia pyri_, but did not succeed in getting a single + fertile egg. A number of females of _Orthosia munda_ and of _Mamestra + suasa_ reared in confinement were unattractive to the males.[380] Mr. + Newport kept nearly a hundred individuals of two species of Vanessa, + but not one paired; this, however, might have been due to their habit + of coupling on the wing.[381] Mr. Atkinson could never succeed in India + in making the Tarroo silk-moth breed in confinement.[382] It appears + that a number of moths, especially the Sphingidæ, when hatched in the + autumn out of their proper season, {158} are completely barren; but + this latter case is still involved in some obscurity.[383] + +Independently of the fact of many animals under confinement not coupling, +or, if they couple, not producing young, there is evidence of another kind, +that their sexual functions are thus disturbed. For many cases have been +recorded of the loss by male birds when confined of their characteristic +plumage. Thus the common linnet (_Linota cannabina_) when caged does not +acquire the fine crimson colour on its breast, and one of the buntings +(_Emberiza passerina_) loses the black on its head. A Pyrrhula and an +Oriolus have been observed to assume the quiet plumage of the hen-bird; and +the _Falco albidus_ returned to the dress of an earlier age.[384] Mr. +Thomson, the superintendent of the Knowsley menagerie, informed me that he +had often observed analogous facts. The horns of a male deer (_Cervus +Canadensis_) during the voyage from America were badly developed; but +subsequently in Paris perfect horns were produced. + +When conception takes place under confinement, the young are often born +dead, or die soon, or are ill-formed. This frequently occurs in the +Zoological Gardens, and, according to Rengger, with native animals confined +in Paraguay. The mother's milk often fails. We may also attribute to the +disturbance of the sexual functions the frequent occurrence of that +monstrous instinct which leads the mother to devour her own offspring,--a +mysterious case of perversion, as it at first appears. + +Sufficient evidence has now been advanced to prove that animals when first +confined are eminently liable to suffer in their reproductive systems. We +feel at first naturally inclined to attribute the result to loss of health, +or at least to loss of vigour; but this view can hardly be admitted when we +reflect how healthy, long-lived, and vigorous many animals are under {159} +captivity, such as parrots, and hawks when used for hawking, chetahs when +used for hunting, and elephants. The reproductive organs themselves are not +diseased; and the diseases, from which animals in menageries usually +perish, are not those which in any way affect their fertility. No domestic +animal is more subject too disease than the sheep, yet it is remarkably +prolific. The failure of animals to breed under confinement has been +sometimes attributed exclusively to a failure in their sexual instincts: +this may occasionally come into play, but there is no obvious reason why +this instinct should be especially liable to be affected with perfectly +tamed animals, except indeed indirectly through the reproductive system +itself being disturbed. Moreover, numerous cases have been given of various +animals which couple freely under confinement, but never conceive; or, if +they conceive and produce young, these are fewer in number than is natural +to the species. In the vegetable kingdom instinct of course can play no +part; and we shall presently see that plants when removed from their +natural conditions are affected in nearly the same manner as animals. +Change of climate cannot be the cause of the loss of fertility, for, whilst +many animals imported into Europe from extremely different climates breed +freely, many others when confined in their native land are completely +sterile. Change of food cannot be the chief cause; for ostriches, ducks, +and many other animals, which must have undergone a great change in this +respect, breed freely. Carnivorous birds when confined are extremely +sterile; whilst most carnivorous mammals, except plantigrades, are +moderately fertile. Nor can the amount of food be the cause; for a +sufficient supply will certainly be given to valuable animals; and there is +no reason to suppose that much more food would be given to them, than to +our choice domestic productions which retain their full fertility. Lastly, +we may infer from the case of the elephant, chetah, various hawks, and of +many animals which are allowed to lead an almost free life in their native +land, that want of exercise is not the sole cause. + +It would appear that any change in the habits of life, whatever these +habits may be, if great enough, tends to affect in an inexplicable manner +the powers of reproduction. The result {160} depends more on the +constitution of the species than on the nature of the change; for certain +whole groups are affected more than others; but exceptions always occur, +for some species in the most fertile groups refuse to breed, and some in +the most sterile groups breed freely. Those animals which usually breed +freely under confinement, rarely breed, as I was assured, in the Zoological +Gardens, within a year or two after their first importation. When an animal +which is generally sterile under confinement happens to breed, the young +apparently do not inherit this power; for had this been the case, various +quadrupeds and birds, which are valuable for exhibition, would have become +common. Dr. Broca even affirms[385] that many animals in the Jardin des +Plantes, after having produced young for three or four successive +generations, become sterile; but this may be the result of too close +interbreeding. It is a remarkable circumstance that many mammals and birds +have produced hybrids under confinement quite as readily as, or even more +readily than, they have procreated their own kind. Of this fact many +instances have been given;[386] and we are thus reminded of those plants +which when cultivated refuse to be fertilised by their own pollen, but can +easily be fertilised by that of a distinct species. Finally, we must +conclude, limited as the conclusion is, that changed conditions of life +have an especial power of acting injuriously on the reproductive system. +The whole case is quite peculiar, for these organs, though not diseased, +are thus rendered incapable of performing their proper functions, or +perform them imperfectly. + + _Sterility of Domesticated Animals from changed conditions._--With + respect to domesticated animals, as their domestication mainly depends + on the accident of their breeding freely under captivity, we ought not + to expect that their reproductive system would be affected by any + moderate degree of change. Those orders of quadrupeds and birds, of + which the wild species breed most readily in our menageries, have + afforded us the greatest number of domesticated productions. Savages in + most parts of the world are fond of taming animals;[387] and if any of + these regularly produced {161} young, and were at the same time useful, + they would be at once domesticated. If, when their masters migrated + into other countries, they were in addition found capable of + withstanding various climates, they would be still more valuable; and + it appears that the animals which breed readily in captivity can + generally withstand different climates. Some few domesticated animals, + such as the reindeer and camel, offer an exception to this rule. Many + of our domesticated animals can bear with undiminished fertility the + most unnatural conditions; for instance, rabbits, guinea-pigs, and + ferrets breed in miserably confined hutches. Few European dogs of any + kind withstand without degeneration the climate of India; but as long + as they survive, they retain, as I hear from Mr. Falconer, their + fertility; so it is, according to Dr. Daniell, with English dogs taken + to Sierra Leone. The fowl, a native of the hot jungles of India, + becomes more fertile than its parent-stock in every quarter of the + world, until we advance as far north as Greenland and Northern Siberia, + where this bird will not breed. Both fowls and pigeons, which I + received during the autumn direct from Sierra Leone, were at once ready + to couple.[388] I have, also, seen pigeons breeding as freely as the + common kinds within a year after their importation from the Upper Nile. + The guinea-fowl, an aboriginal of the hot and dry deserts of Africa, + whilst living under our damp and cool climate, produces a large supply + of eggs. + + Nevertheless, our domesticated animals under new conditions + occasionally show signs of lessened fertility. Roulin asserts that in + the hot valleys of the equatorial Cordillera sheep are not fully + fecund;[389] and according to Lord Somerville,[390] the merino-sheep + which he imported from Spain were not at first perfectly fertile. It is + said[391] that mares brought up on dry food in the stable, and turned + out to grass, do not at first breed. The peahen, as we have seen, is + said not to lay so many eggs in England as in India. It was long before + the canary-bird was fully fertile, and even now first-rate breeding + birds are not common.[392] In the hot and dry province of Delhi, the + eggs of the turkey, as I hear from Dr. Falconer, though placed under a + hen, are extremely liable to fail. According to Roulin, geese taken + within a recent period to the lofty plateau of Bogota, at first laid + seldom, and then only a few eggs; of these scarcely a fourth were + hatched, and half the young birds died: in the second generation they + were more fertile; and when Roulin wrote they were becoming as {162} + fertile as our geese in Europe. In the Philippine Archipelago the + goose, it is asserted, will not breed or even lay eggs.[393] A more + curious case is that of the fowl, which, according to Roulin, when + first introduced would not breed at Cusco in Bolivia, but subsequently + became quite fertile; and the English Game fowl, lately introduced, had + not as yet arrived a its full fertility, for to raise two or three + chickens from a nest of eggs was thought fortunate. In Europe close + confinement has a marked effect on the fertility of the fowl: it has + been found in France that with fowls allowed considerable freedom only + twenty per cent. of the eggs failed; when allowed less freedom forty + per cent. failed; and in close confinement sixty out of the hundred + were not hatched.[394] So we see that unnatural and changed conditions + of life produce some effect on the fertility of our most thoroughly + domesticated animals, in the same manner, though in a far less degree, + as with captive wild animals. + + It is by no means rare to find certain males and females which will not + breed together, though both are known to be perfectly fertile with + other males and females. We have no reason to suppose that this is + caused by these animals having been subjected to any change in their + habits of life; therefore such cases are hardly related to our present + subject. The cause apparently lies in an innate sexual incompatibility + of the pair which are matched. Several instances have been communicated + to me by Mr. W. C. Spooner (well known for his essay on + Cross-breeding), by Mr. Eyton of Eyton, by Mr. Wicksted and othe + breeders, and especially by Mr. Waring of Chelsfield, in relation to + horses, cattle, pigs, foxhounds, other dogs, and pigeons.[395] In these + cases, females, which either previously or subsequently were proved to + be fertile, failed to breed with certain males, with whom it was + particularly desired to match them. A change in the constitution of the + female may sometimes have occurred before she was put to the second + male; but in other cases this explanation is hardly tenable, for a + female, known not to be barren, has been unsuccessfully paired seven or + eight times with the same male likewise known to be perfectly fertile. + With cart-mares, which sometimes will not breed with stallions of pure + blood, but subsequently have bred with cart-stallions, Mr. Spooner is + inclined to attribute the failure to the lesser sexual power of the + race-horse. But I have heard from the greatest breeder of race-horses + at the present day, through Mr. Waring, that "it frequently occurs with + a mare to be put several times during one or two seasons to a + particular stallion of acknowledged power, and yet prove barren; the + mare afterwards breeding at once with some other horse." These facts + are worth recording, as they show, like so many previous facts, on what + slight constitutional differences the fertility of an animal often + depends. + +{163} + +_Sterility of Plants from changed Conditions of Life, and from other +causes._ + +In the vegetable kingdom cases of sterility frequently occur, analogous +with those previously given in the animal kingdom. But the subject is +obscured by several circumstances, presently to be discussed, namely, the +contabescence of the anthers, as Gärtner has named a certain +affection--monstrosities--doubleness of the flower--much-enlarged +fruit--and long-continued or excessive propagation by buds. + + It is notorious that many plants in our gardens and hot-houses, though + preserved in the most perfect health, rarely or never produce seed. I + do not allude to plants which run to leaves, from being kept too damp, + or too warm, or too much manured; for these do not produce the + reproductive individual or flower, and the case may be wholly + different. Nor do I allude to fruit not ripening from want of heat, or + rotting from too much moisture. But many exotic plants, with their + ovules and pollen appearing perfectly sound, will not set any seed. The + sterility in many cases, as I know from my own observation, is simply + due to the absence of the proper insects for carrying the pollen to the + stigma. But after excluding the several cases just specified, there are + many plants in which the reproductive system has been seriously + affected by the altered conditions of life to which they have been + subjected. + + It would be tedious to enter on many details. Linnæus long ago + observed[396] that Alpine plants, although naturally laded with seed, + produce either few or none when cultivated in gardens. But exceptions + often occur: the _Draba sylvestris_, one of our most thoroughly Alpine + plants, multiplies itself by seed in Mr. H. C. Watson's garden, near + London; and Kerner, who has particularly attended to the cultivation of + Alpine plants, found that various kinds, when cultivated, spontaneously + sowed themselves.[397] Many plants which naturally grow in peat-earth + are entirely sterile in our gardens. I have noticed the same fact with + several liliaceous plants, which nevertheless grew vigorously. + + Too much manure renders some kinds utterly sterile, as I have myself + observed. The tendency to sterility from this cause runs in families; + thus, according to Gärtner,[398] it is hardly possible to give too much + manure to most Gramineæ, Cruciferæ, and Leguminosæ, whilst succulent + and bulbous-rooted plants are easily affected. Extreme poverty of soil + is less {164} apt to induce sterility; but dwarfed plants of _Trifolium + minus_ and _repens_, growing on a lawn often mown and never manured, + did not produce any seed. The temperature of the soil, and the season + at which plants are watered, often have a marked effect on their + fertility, as was observed by Kölreuter in the case of Mirabilis.[399] + Mr. Scott in the Botanic Gardens of Edinburgh observed that _Oncidium + divaricatum_ would not set seed when grown in a basket in which it + throve, but was capable of fertilisation in a pot where it was a little + damper. _Pelargonium fulgidum_, for many years after its introduction, + seeded freely; it then became sterile; now it is fertile[400] if kept + in a dry stove during the winter. Other varieties of pelargonium are + sterile and others fertile without our being able to assign any cause. + Very slight changes in the position of a plant, whether planted on a + bank or at its base, sometimes make all the difference in its producing + seed. Temperature apparently has a much more powerful influence on the + fertility of plants than on that of animals. Nevertheless it is + wonderful what changes some few plants will withstand with undiminished + fertility: thus the _Zephyranthes candida_, a native of the moderately + warm banks of the Plata, sows itself in the hot dry country near Lima, + and in Yorkshire resists the severest frosts, and I have seen seeds + gathered from pods which had been covered with snow during three + weeks.[401] _Berberis Wallichii_, from the hot Khasia range in India, + is uninjured by our sharpest frosts, and ripens its fruit under our + cool summers. Nevertheless I presume we must attribute to change of + climate the sterility of many foreign plants; thus the Persian and + Chinese lilacs (_Syringa Persica_ and _Chinensis_), though perfectly + hardly, never here produce a seed; the common lilac (_S. vulgaris_) + seeds with us moderately well, but in parts of Germany the capsules + never contain seed.[402] + + Some of the cases, given in the last chapter, of self-impotent plants, + which are fertile both on the male and female side when united with + distinct individuals or species, might have been here introduced; for + as this peculiar form of sterility generally occurs with exotic plants + or with endemic plants cultivated in pots, and as it disappeared in the + _Passiflora alata_ when grafted, we may conclude that in these cases it + is the result of the treatment to which the plants or their parents + have been exposed. + + The liability of plants to be affected in their fertility by slightly + changed conditions is the more remarkable, as the pollen when once in + process of formation is not easily injured; a plant may be + transplanted, or a branch with flower-buds be cut off and placed in + water, and the pollen will be matured. Pollen, also, when once mature, + may be kept for weeks or even months.[403] The female organs are more + sensitive, for Gärtner[404] found that dicotyledonous plants, when + carefully removed so that they did not in the least flag, could seldom + be fertilised; this occurred even with potted {165} plants if the roots + had grown out of the hole at the bottom. In some few cases, however, as + with Digitalis, transplantation did not prevent fertilisation; and + according to the testimony of Mawz, _Brassica rapa_, when pulled up by + its roots and placed in water, ripened its seed. Flower-stems of + several monocotyledonous plants when cut off and placed in water + likewise produce seed. But in these cases I presume that the flowers + had been already fertilised, for Herbert[405] found with the Crocus + that the plants might be removed or mutilated after the act of + fertilisation, and would still perfect their seeds; but that, if + transplanted before being fertilised, the application of pollen was + powerless. + + Plants which have been long cultivated can generally endure with + undiminished fertility various and great changes; but not in most cases + so great a change of climate as domesticated animals. It is remarkable + that many plants under these circumstances are so much affected that + the proportions and the nature of their chemical ingredients are + modified, yet their fertility is unimpaired. Thus, as Dr. Falconer + informs me, there is a great difference in the character of the fibre + in hemp, in the quantity of oil in the seed of the Linum, in the + proportion of narcotin to morphine in the poppy, in gluten to starch in + wheat, when these plants are cultivated on the plains and on the + mountains of India; nevertheless, they all remain fully fertile. + + _Contabescence._--Gärtner has designated by this term a peculiar + condition of the anthers in certain plants, in which they are + shrivelled, or become brown and tough, and contain no good pollen. When + in this state they exactly resemble the anthers of the most sterile + hybrids. Gärtner,[406] in his discussion on this subject, has shown + that plants of many orders are occasionally thus affected; but the + Caryophyllaceæ and Liliaceæ suffer most, and to these orders, I think, + the Ericaceæ may be added. Contabescence varies in degree, but on the + same plant all the flowers are generally affected to nearly the same + extent. The anthers are affected at a very early period in the + flower-bud, and remain in the same state (with one recorded exception) + during the life of the plant. The affection cannot be cured by any + change of treatment, and is propagated by layers, cuttings, &c., and + perhaps even by seed. In contabescent plants the female organs are + seldom affected, or merely become precocious in their development. The + cause of this affection is doubtful, and is different in different + cases. Until I read Gärtner's discussion I attributed it, as apparently + did Herbert, to the unnatural treatment of the plants; but its + permanence under changed conditions, and the female organs not being + affected, seem incompatible with this view. The fact of several endemic + plants becoming contabescent in our gardens seems, at first sight, + equally incompatible with this view; but Kölreuter believes that this + is the result of their transplantation. The contabescent plants of + Dianthus and Verbascum, found wild by Wiegmann, grew on a dry and + sterile bank. The fact that exotic {166} plants are eminently liable to + this affection also seems to show that it is in some manner caused by + their unnatural treatment. In some instances, as with Silene, Gärtner's + view seems the most probable, namely, that it is caused by an inherent + tendency in the species to become dioecious. I can add another cause, + namely, the illegitimate unions of reciprocally dimorphic or trimorphic + plants, for I have observed seedlings of three species of Primula and + of _Lythrum salicaria_, which had been raised from plants + illegitimately fertilised by their own-form pollen, with some or all + their anthers in a contabescent state. There is perhaps an additional + cause, namely, self-fertilisation; for many plants of Dianthus and + Lobelia, which had been raised from self-fertilised seeds, had their + anthers in this state; but these instances are not conclusive, as both + genera are liable from other causes to this affection. + + Cases of an opposite nature likewise occur, namely, plants with the + female organs struck with sterility, whilst the male organs remain + perfect. _Dianthus Japonicus_, a Passiflora, and Nicotiana, have been + described by Gärtner[407] as being in this unusual condition. + + _Monstrosities as a cause of Sterility._--Great deviations of + structure, even when the reproductive organs themselves are not + seriously affected, sometimes cause plants to become sterile. But in + other cases plants may become monstrous to an extreme degree and yet + retain their full fertility. Gallesio, who certainly had great + experience,[408] often attributes sterility to this cause; but it may + be suspected that in some of his cases sterility was the cause, and not + the result, of the monstrous growths. The curious St. Valery apple, + although it bears fruit, rarely produces seed. The wonderfully + anomalous flowers of _Begonia frigida_, formerly described, though they + appear fit for fructification, are sterile.[409] Species of Primulæ, in + which the calyx is brightly coloured, are said[410] to be often + sterile, though I have known them to be fertile. On the other hand, + Verlot gives several cases of proliferous flowers which can be + propagated by seed. This was the case with a poppy, which had become + monopetalous by the union of its petals.[411] Another extraordinary + poppy, with the stamens replaced by numerous small supplementary + capsules, likewise reproduces itself by seed. This has also occurred + with a plant of _Saxifraga geum_, in which a series of adventitious + carpels, bearing ovules on their margins, had been developed between + the stamens and the normal carpels.[412] Lastly, with respect to + peloric flowers, which depart wonderfully from the natural + structure,--those of _Linaria vulgaris_ seem generally to be more or + less sterile, whilst those before described of _Antirrhinum majus_, + when artificially fertilised with their own pollen, are perfectly {167} + fertile, though sterile when left to themselves, for bees are unable to + crawl into the narrow tubular flower. The peloric flowers of _Corydalis + solida_, according to Godron,[413] are barren; whilst those of Gloxinia + are well known to yield plenty of seed. In our greenhouse Pelargoniums, + the central flower of the truss is often peloric, and Mr. Masters + informs me that he tried in vain during several years to get seed from + these flowers. I likewise made many vain attempts, but sometimes + succeeded in fertilising them with pollen from a normal flower of + another variety; and conversely I several times fertilised ordinary + flowers with peloric pollen. Only once I succeeded in raising a plant + from a peloric flower fertilised by pollen from a peloric flower borne + by another variety; but the plant, it may be added, presented nothing + particular in its structure. Hence we may conclude that no general rule + can be laid down; but any great deviation from the normal structure, + even when the reproductive organs themselves are not seriously + affected, certainly often leads to sexual impotence. + + _Double Flowers._--When the stamens are converted into petals, the + plant becomes on the male side sterile; when both stamens and pistils + are thus changed, the plant becomes completely barren. Symmetrical + flowers having numerous stamens and petals are the most liable to + become double, as perhaps follows from all multiple organs being the + most subject to variability. But flowers furnished with only a few + stamens, and others which are asymmetrical in structure, sometimes + become double, as we see with the double gorse or Ulex, Petunia, and + Antirrhinum. The Compositæ bear what are called double flowers by the + abnormal development of the corolla of their central florets. + Doubleness is sometimes connected with prolification,[414] or the + continued growth of the axis of the flower. Doubleness is strongly + inherited. No one has produced, as Lindley remarks,[415] double flowers + by promoting the perfect health of the plant. On the contrary, + unnatural conditions of life favour their production. There is some + reason to believe that seeds kept during many years, and seeds believed + to be imperfectly fertilised, yield double flowers more freely than + fresh and perfectly fertilised seed.[416] Long-continued cultivation in + rich soil seems to be the commonest exciting cause. A double narcissus + and a double _Anthemis nobilis_, transplanted into very poor soil, have + been observed to become single;[417] and I have seen a completely + double white primrose rendered permanently single by being divided and + transplanted whilst in full flower. It has been observed by Professor + Morren that doubleness of the flowers and variegation of the leaves are + antagonistic states; but so many exceptions to the rule have lately + been recorded,[418] that, though general, it cannot be looked at as + invariable. {168} Variegation seems generally to result from a feeble + or atrophied condition of the plant, and a large proportion of the + seedlings raised from parents both of which are variegated usually + perish at an early age; hence we may perhaps infer that doubleness, + which is the antagonistic state, commonly arises from a plethoric + condition. On the other hand, extremely poor soil sometimes, though + rarely, appears to cause doubleness: I formerly described[419] some + completely double, bud-like, flowers produced in large numbers by + stunted wild plants of _Gentiana amarella_ growing on a poor chalky + bank. I have also noticed a distinct tendency to doubleness in the + flowers of a Ranunculus, Horse-chesnut, and Bladder-nut (_Ranunculus + repens_, _Æsculus pavia_, and _Staphylea_), growing under very + unfavourable conditions. Professor Lehman[420] found several wild + plants growing near a hot spring with double flowers. With respect to + the cause of doubleness, which arises, as we see, under widely + different circumstances, I shall presently attempt to show that the + most probable view is that unnatural conditions first give a tendency + to sterility, and that then, on the principle of compensation, as the + reproductive organs do not perform their proper functions, they either + become developed into petals, or additional petals are formed. This + view has lately been supported by Mr. Laxton,[421] who advances the + case of some common peas, which, after long-continued heavy rain, + flowered a second time, and produced double flowers. + + _Seedless Fruit._--Many of our most valuable fruits, although + consisting in a homological sense of widely different organs, are + either quite sterile, or produce extremely few seeds. This is + notoriously the case with our best pears, grapes, and figs, with the + pine-apple, banana, bread-fruit, pomegranate, azarole, date-palms, and + some members of the orange-tribe. Poorer varieties of these same fruits + either habitually or occasionally yield seed.[422] Most horticulturists + look at the great size and anomalous development of the fruit as the + cause, and sterility as the result; but the opposite view, as we shall + presently see, is more probable. + + _Sterility from the excessive development of the Organs of Growth or + Vegetation._--Plants which from any cause grow too luxuriantly, and + produce leaves, stems, runners, suckers, tubers, bulbs, &c., in excess, + sometimes do not flower, or if they flower do not yield seed. To make + European vegetables under the hot climate of India yield seed, it is + necessary to check their growth; and, when one-third grown, they are + taken up, and their stems and {169} tap-roots are cut or + mutilated.[423] So it is with hybrids; for instance, Prof. Lecoq[424] + had three plants of Mirabilis, which, though they grew luxuriantly and + flowered, were quite sterile; but after beating one with a stick until + a few branches alone were left, these at once yielded good seed. The + sugar-cane, which grows vigorously and produces a large supply of + succulent stems, never, according to various observers, bears seed in + the West Indies, Malaga, India, Cochin China, or the Malay + Archipelago.[425] Plants which produce a large number of tubers are apt + to be sterile, as occurs, to a certain extent, with the common potato; + and Mr. Fortune informs me that the sweet potato (_Convolvulus + batatas_) in China never, as far as he has seen, yields seed. Dr. Royle + remarks[426] that in India the _Agave vivipara_, when grown in rich + soil, invariably produces bulbs, but no seeds; whilst a poor soil and + dry climate leads to an opposite result. In China, according to Mr. + Fortune, an extraordinary number of little bulbs are developed in the + axils of the leaves of the yam, and this plant does not bear seed. + Whether in these cases, as in those of double flowers and seedless + fruit, sexual sterility from changed conditions of life is the primary + cause which leads to the excessive development of the organs of + vegetation, is doubtful; though some evidence might be advanced in + favour of this view. It is perhaps a more probable view that plants + which propagate themselves largely by one method, namely by buds, have + not sufficient vital power or organised matter for the other method of + sexual generation. + + Several distinguished botanists and good practical judges believe that + long-continued propagation by cuttings, runners, tubers, bulbs, &c., + independently of any excessive development of these parts, is the cause + of many plants failing to produce flowers and of others failing to + produce fertile flowers,--it is as if they had lost the habit of sexual + generation.[427] That many plants when thus propagated are sterile + there can be no doubt, but whether the long continuance of this form of + propagation is the actual cause of their sterility, I will not venture, + from the want of sufficient evidence, to express an opinion. + + That plants may be propagated for long periods by buds, without the aid + of sexual generation, we may safely infer from this being the case with + many plants which must have long survived in a state of nature. As I + have had occasion before to allude to this subject, I will here give + such cases as I have collected. Many alpine plants ascend mountains + beyond the height at which they can produce seed.[428] Certain species + of {170} Poa and Festuca, when growing on mountain-pastures, propagate + themselves, as I hear from Mr. Bentham, almost exclusively by bulblets. + Kalm gives a more curious instance[429] of several American trees, + which grow so plentifully in marshes or in thick woods, that they are + certainly well adapted for these stations, yet scarcely ever produce + seeds; but when accidentally growing on the outside of the marsh or + wood, are loaded with seed. The common ivy is found in Northern Sweden + and Russia, but flowers and fruits only in the southern provinces. The + _Acorus calamus_ extends over a large portion of the globe, but so + rarely perfects its fruit that this has been seen but by few + botanists.[430] The _Hypericum calycinum_, which propagates itself so + freely in our shrubberies by rhizomas and is naturalised in Ireland, + blossoms profusely, but sets no seed; nor did it set any when + fertilised in my garden by pollen from plants growing at a distance. + The _Lysimachia nummularia_, which is furnished with long runners, so + seldom produces seed-capsules, that Prof. Decaisne,[431] who has + especially attended to this plant, has never seen it in fruit. The + _Carex rigida_ often fails to perfect its seed in Scotland, Lapland, + Greenland, Germany, and New Hampshire in the United States.[432] The + periwinkle (_Vinca minor_), which spreads largely by runners, is said + scarcely ever to produce fruit in England;[433] but this plant requires + insect-aid for its fertilisation, and the proper insects may be absent + or rare. The _Jussiæa grandiflora_ has become naturalised in Southern + France, and has spread by its rhizomas so extensively as to impede the + navigation of the waters, but never produces fertile seed.[434] The + horse-radish (_Cochlearia armoracia_) spreads pertinaciously and is + naturalised in various parts of Europe; though it bears flowers, these + rarely produce capsules: Professor Caspary also informs me that he has + watched this plant since 1851, but has never seen its fruit; nor is + this surprising, as he finds scarcely a grain of good pollen. The + common little _Ranunculus ficaria_ rarely, and some say never, bears + seed in England, France, or Switzerland; but in 1863 I observed seeds + on several plants growing near my house. According to M. Chatin, there + are two forms of this Ranunculus; and it is the bulbiferous form which + does not yield seed from producing no pollen.[435] Other cases {171} + analogous with the foregoing could be given; for instance, some kinds + of mosses and lichens have never been seen to fructify in France. + + Some of these endemic and naturalised plants are probably rendered + sterile from excessive multiplication by buds, and their consequent + incapacity to produce and nourish seed. But the sterility of others + more probably depends on the peculiar conditions under which they live, + as in the case of the ivy in the northern parts of Europe, and of the + trees in the swamps of the United States; yet these plants must be in + some respects eminently well adapted for the stations which they + occupy, for they hold their places against a host of competitors. + +Finally, when we reflect on the sterility which accompanies the doubling of +flowers,--the excessive development of fruit,--and a great increase in the +organs of vegetation, we must bear in mind that the whole effect has seldom +been caused at once. An incipient tendency is observed, and continued +selection completes the work, as is known to be the case with our double +flowers and best fruits. The view which seems the most probable, and which +connects together all the foregoing facts and brings them within our +present subject, is, that changed and unnatural conditions of life first +give a tendency to sterility; and in consequence of this, the organs of +reproduction being no longer able fully to perform their proper functions, +a supply of organised matter, not required for the development of the seed, +flows either into these same organs and renders them foliaceous, or into +the fruit, stems, tubers, &c., increasing their size and succulency. But I +am far from wishing to deny that there exists, independently of any +incipient sterility, an antagonism between the two forms of reproduction, +namely, by seed and by buds, when either is carried to an extreme degree. +That incipient sterility plays an important part in the doubling of +flowers, and in the other cases just specified, I infer chiefly from the +following facts. When fertility is lost from a wholly different cause, +namely, from hybridism, there is a strong tendency, as Gärtner[436] +affirms, for flowers to become double, and this tendency is inherited. +Moreover it is notorious that with hybrids the male organs become sterile +before the female organs, and with double flowers the stamens first become +{172} foliaceous. This latter fact is well shown by the male flowers of +dioecious plants, which, according to Gallesio,[437] first become double. +Again, Gärtner[438] often insists that the flowers of even utterly sterile +hybrids, which do not produce any seed, generally yield perfect capsules or +fruit,--a fact which has likewise been repeatedly observed by Naudin with +the Cucurbitaceæ; so that the production of fruit by plants rendered +sterile through any other and distinct cause is intelligible. Kölreuter has +also expressed his unbounded astonishment at the size and development of +the tubers in certain hybrids; and all experimentalists[439] have remarked +on the strong tendency in hybrids to increase by roots, runners, and +suckers. Seeing that hybrid plants, which from their nature are more or +less sterile, thus tend to produce double flowers; that they have the parts +including the seed, that is the fruit, perfectly developed, even when +containing no seed; that they sometimes yield gigantic roots; that they +almost invariably tend to increase largely by suckers and other such +means;--seeing this, and knowing, from the many facts given in the earlier +parts of this chapter, that almost all organic beings when exposed to +unnatural conditions tend to become more or less sterile, it seems much the +most probable view that with cultivated plants sterility is the exciting +cause, and double flowers, rich seedless fruit, and in some cases +largely-developed organs of vegetation, &c., are the indirect +results--these results having been in most cases largely increased through +continued selection by man. + + * * * * * + + +{173} + +CHAPTER XIX. + +SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS ON HYBRIDISM. + + ON THE EFFECTS OF CROSSING--THE INFLUENCE OF DOMESTICATION ON + FERTILITY--CLOSE INTERBREEDING--GOOD AND EVIL RESULTS FROM CHANGED + CONDITIONS OF LIFE--VARIETIES WHEN CROSSED NOT INVARIABLY FERTILE--ON + THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND + VARIETIES--CONCLUSIONS WITH RESPECT TO HYBRIDISM--LIGHT THROWN ON + HYBRIDISM BY THE ILLEGITIMATE PROGENY OF DIMORPHIC AND TRIMORPHIC + PLANTS--STERILITY OF CROSSED SPECIES DUE TO DIFFERENCES CONFINED TO THE + REPRODUCTIVE SYSTEM--NOT ACCUMULATED THROUGH NATURAL SELECTION--REASONS + WHY DOMESTIC VARIETIES ARE NOT MUTUALLY STERILE--TOO MUCH STRESS HAS + BEEN LAID ON THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND + CROSSED VARIETIES--CONCLUSION. + +It was shown in the fifteenth chapter that when individuals of the same +variety, or even of a distinct variety, are allowed freely to intercross, +uniformity of character is ultimately acquired. Some few characters, +however, are incapable of fusion, but these are unimportant, as they are +almost always of a semi-monstrous nature, and have suddenly appeared. +Hence, to preserve our domesticated breeds true, or to improve them by +methodical selection, it is obviously necessary that they should be kept +separate. Nevertheless, through unconscious selection, a whole body of +individuals may be slowly modified, as we shall see in a future chapter, +without separating them into distinct lots. Domestic races have often been +intentionally modified by one or two crosses, made with some allied race, +and occasionally even by repeated crosses with very distinct races; but in +almost all such cases, long-continued and careful selection has been +absolutely necessary, owing to the excessive variability of the crossed +offspring, due to the principle of reversion. In a few instances, however, +mongrels have retained a uniform character from their first production. + +When two varieties are allowed to cross freely, and one is {174} much more +numerous than the other, the former will ultimately absorb the latter. +Should both varieties exist in nearly equal numbers, it is probable that a +considerable period would elapse before the acquirement of a uniform +character; and the character ultimately acquired would largely depend on +prepotency of transmission, and on the conditions of life; for the nature +of these conditions would generally favour one variety more than another, +so that a kind of natural selection would come into play. Unless the +crossed offspring were slaughtered by man without the least discrimination, +some degree of unmethodical selection would likewise come into action. From +these several considerations we may infer, that when two or more closely +allied species first came into the possession of the same tribe, their +crossing will not have influenced, in so great a degree as has often been +supposed, the character of the offspring in future times; although in some +cases it probably has had a considerable effect. + +Domestication, as a general rule, increases the prolificness of animals and +plants. It eliminates the tendency to sterility which is common to species +when first taken from a state of nature and crossed. On this latter head we +have no direct evidence; but as our races of dogs, cattle, pigs, &c., are +almost certainly descended from aboriginally distinct stocks, and as these +races are now fully fertile together, or at least incomparably more fertile +than most species when crossed, we may with much confidence accept this +conclusion. + +Abundant evidence has been given that crossing adds to the size, vigour, +and fertility of the offspring. This holds good when there has been no +previous close interbreeding. It applies to the individuals of the same +variety but belonging to different families, to distinct varieties, +sub-species, and partially even to species. In the latter case, though size +is often gained, fertility is lost; but the increased size, vigour, and +hardiness of many hybrids cannot be accounted for solely on the principle +of compensation from the inaction of the reproductive system. Certain +plants, both of pure and hybrid origin, though perfectly healthy, have +become self-impotent, apparently from the unnatural conditions to which +they have been exposed; and such plants, as well as others in their normal +state, can be stimulated to {175} fertility only by crossing them with +other individuals of the same species or even of a distinct species. + +On the other hand, long-continued close interbreeding between the nearest +relations diminishes the constitutional vigour, size, and fertility of the +offspring; and occasionally leads to malformations, but not necessarily to +general deterioration of form or structure. This failure of fertility shows +that the evil results of interbreeding are independent of the augmentation +of morbid tendencies common to both parents, though this augmentation no +doubt is often highly injurious. Our belief that evil follows from close +interbreeding rests to a large extent on the experience of practical +breeders, especially of those who have reared many animals of the kinds +which can be propagated quickly; but it likewise rests on several carefully +recorded experiments. With some animals close interbreeding may be carried +on for a long period with impunity by the selection of the most vigorous +and healthy individuals; but sooner or later evil follows. The evil, +however, comes on so slowly and gradually that it easily escapes +observation, but can be recognised by the almost instantaneous manner in +which size, constitutional vigour, and fertility are regained when animals +that have long been interbred are crossed with a distinct family. + +These two great classes of facts, namely, the good derived from crossing, +and the evil from close interbreeding, with the consideration of the +innumerable adaptations throughout nature for compelling, or favouring, or +at least permitting, the occasional union of distinct individuals, taken +together, lead to the conclusion that it is a law of nature that organic +beings shall not fertilise themselves for perpetuity. This law was first +plainly hinted at in 1799, with respect to plants, by Andrew Knight,[440] +and, not long afterwards, that sagacious observer Kölreuter, after showing +how well the Malvaceæ are adapted for {176} crossing, asks, "an id aliquid +in recessu habeat, quod hujuscemodi flores nunquam proprio suo pulvere, sed +semper eo aliarum suæ speciei impregnentur, merito quæritur? Certe natura +nil facit frustra." Although we may demur to Kölreuter's saying that nature +does nothing in vain, seeing how many organic beings retain rudimentary and +useless organs, yet undoubtedly the argument from the innumerable +contrivances, which favour the crossing of distinct individuals of the same +species, is of the greatest weight. The most important result of this law +is that it leads to uniformity of character in the individuals of the same +species. In the case of certain hermaphrodites, which probably intercross +only at long intervals of time, and with unisexual animals inhabiting +somewhat separated localities, which can only occasionally come into +contact and pair, the greater vigour and fertility of the crossed offspring +will ultimately prevail in giving uniformity of character to the +individuals of the same species. But when we go beyond the limits of the +same species, free intercrossing is barred by the law of sterility. + +In searching for facts which might throw light on the cause of the good +effects from crossing, and of the evil effects from close interbreeding, we +have seen that, on the one hand, it is a widely prevalent and ancient +belief that animals and plants profit from slight changes in their +condition of life; and it would appear that the germ, in a somewhat +analogous manner, is more effectually stimulated by the male element, when +taken from a distinct individual, and therefore slightly modified in +nature, than when taken from a male having the same identical constitution. +On the other hand, numerous facts have been given, showing that when +animals are first subjected to captivity, even in their native land, and +although allowed much liberty, their reproductive functions are often +greatly impaired or quite annulled. Some groups of animals are more +affected than others, but with apparently capricious exceptions in every +group. Some animals never or rarely couple: some couple freely, but never +or rarely conceive. The secondary male characters, the maternal functions +and instincts, are occasionally affected. With plants, when first subjected +to cultivation, analogous facts have been observed. We probably owe our +double flowers, rich seedless {177} fruits, and in some cases greatly +developed tubers, &c., to incipient sterility of the above nature combined +with a copious supply of nutriment. Animals which have long been +domesticated, and plants which have long been cultivated, can generally +withstand with unimpaired fertility great changes in their conditions of +life; though both are sometimes slightly affected. With animals the +somewhat rare capacity of breeding freely under confinement has mainly +determined, together with their utility, the kinds which have been +domesticated. + +We can in no case precisely say what is the cause of the diminished +fertility of an animal when first captured, or of a plant when first +cultivated; we can only infer that it is caused by a change of some kind in +the natural conditions of life. The remarkable susceptibility of the +reproductive system to such changes,--a susceptibility not common to any +other organ,--apparently has an important bearing on Variability, as we +shall see in a future chapter. + +It is impossible not to be struck with the double parallelism between the +two classes of facts just alluded to. On the one hand, slight changes in +the conditions of life, and crosses between slightly modified forms or +varieties, are beneficial as far as prolificness and constitutional vigour +are concerned. On the other hand, changes in the conditions greater in +degree, or of a different nature, and crosses between forms which have been +slowly and greatly modified by natural means,--in other words, between +species,--are highly injurious, as far as the reproductive system is +concerned, and in some few instances as far as constitutional vigour is +concerned. Can this parallelism be accidental? Does it not rather indicate +some real bond of connection? As a fire goes out unless it be stirred up, +so the vital forces are always tending, according to Mr. Herbert Spencer, +to a state of equilibrium, unless disturbed and renovated through the +action of other forces. + +In some few cases varieties tend to keep distinct, by breeding at different +periods, by great differences in size, or by sexual preference,--in this +latter respect more especially resembling species in a state of nature. But +the actual crossing of varieties, far from diminishing, generally adds to +the fertility of both the first union and the mongrel offspring. Whether +all {178} the most widely distinct domestic varieties are invariably quite +fertile when crossed, we do not positively know; much time and trouble +would be requisite for the necessary experiments, and many difficulties +occur, such as the descent of the various races from aboriginally distinct +species, and the doubts whether certain forms ought to be ranked as species +or varieties. Nevertheless, the wide experience of practical breeders +proves that the great majority of varieties, even if some should hereafter +prove not to be indefinitely fertile _inter se_, are far more fertile when +crossed, than the vast majority of closely allied natural species. A few +remarkable cases have, however, been given on the authority of excellent +observers, showing that with plants certain forms, which undoubtedly must +be ranked as varieties, yield fewer seeds when crossed than is natural to +the parent-species. Other varieties have had their reproductive powers so +far modified that they are either more or less fertile than are their +parents, when crossed with a distinct species. + +Nevertheless, the fact remains indisputable that domesticated varieties of +animals and of plants, which differ greatly from each other in structure, +but which are certainly descended from the same aboriginal species, such as +the races of the fowl, pigeon, many vegetables, and a host of other +productions, are extremely fertile when crossed; and this seems to make a +broad and impassable barrier between domestic varieties and natural +species. But, as I will now attempt to show, the distinction is not so +great and overwhelmingly important as it at first appears. + +_On the Difference in Fertility between Varieties and Species when +crossed._ + +This work is not the proper place for fully treating the subject of +hybridism, and I have already given in my 'Origin of Species' a moderately +full abstract. I will here merely enumerate the general conclusions which +may be relied on, and which bear on our present point. + +_Firstly_, the laws governing the production of hybrids are identical, or +nearly identical, in the animal and vegetable kingdoms. + +_Secondly_, the sterility of distinct species when first united, {179} and +that of their hybrid offspring, graduates, by an almost infinite number of +steps, from zero, when the ovule is never impregnated and a seed-capsule is +never formed, up to complete fertility. We can only escape the conclusion +that some species are fully fertile when crossed, by determining to +designate as varieties all the forms which are quite fertile. This high +degree of fertility is, however, rare. Nevertheless plants, which have been +exposed to unnatural conditions, sometimes become modified in so peculiar a +manner, that they are much more fertile when crossed by a distinct species +than when fertilised by their own pollen. Success in effecting a first +union between two species, and the fertility of their hybrids, depends in +an eminent degree on the conditions of life being favourable. The innate +sterility of hybrids of the same parentage and raised from the same +seed-capsule often differs much in degree. + +_Thirdly_, the degree of sterility of a first cross between two species +does not always run strictly parallel with that of their hybrid offspring. +Many cases are known of species which can be crossed with ease, but yield +hybrids excessively sterile; and conversely some which can be crossed with +great difficulty, but produce fairly fertile hybrids. This is an +inexplicable fact, on the view that species have been specially endowed +with mutual sterility in order to keep them distinct. + +_Fourthly_, the degree of sterility often differs greatly in two species +when reciprocally crossed; for the first will readily fertilise the second; +but the latter is incapable, after hundreds of trials, of fertilising the +former. Hybrids produced from reciprocal crosses between the same two +species, likewise sometimes differ in their degree of sterility. These +cases also are utterly inexplicable on the view of sterility being a +special endowment. + +_Fifthly_, the degree of sterility of first crosses and of hybrids runs, to +a certain extent, parallel with the general or systematic affinity of the +forms which are united. For species belonging to distinct genera can +rarely, and those belonging to distinct families can never, be crossed. The +parallelism, however, is far from complete; for a multitude of closely +allied species will not unite, or unite with extreme difficulty, whilst +other species, widely different from each other, can be crossed with +perfect facility. Nor does the difficulty depend on ordinary {180} +constitutional differences, for annual and perennial plants, deciduous and +evergreen trees, plants flowering at different seasons, inhabiting +different stations, and naturally living under the most opposite climates, +can often be crossed with ease. The difficulty or facility apparently +depends exclusively on the sexual constitution of the species which are +crossed; or on their sexual elective affinity, _i. e._ _Wahlverwandtschaft_ +of Gärtner. As species rarely or never become modified in one character, +without being at the same time modified in many, and as systematic affinity +includes all visible resemblances and dissimilarities, any difference in +sexual constitution between two species would naturally stand in more or +less close relation with their systematic position. + +_Sixthly_, the sterility of species when first crossed, and that of +hybrids, may possibly depend to a certain extent on distinct causes. With +pure species the reproductive organs are in a perfect condition, whilst +with hybrids they are often plainly deteriorated. A hybrid embryo which +partakes of the constitution of its father and mother is exposed to +unnatural conditions, as long as it is nourished within the womb, or egg, +or seed of the mother-form; and as we know that unnatural conditions often +induce sterility, the reproductive organs of the hybrid might at this early +age be permanently affected. But this cause has no bearing on the +infertility of first unions. The diminished number of the offspring from +first unions may often result, as is certainly sometimes the case, from the +premature death of most of the hybrid embryos. But we shall immediately see +that a law of an unknown nature apparently exists, which causes the +offspring from unions, which are infertile, to be themselves more or less +infertile; and this at present is all that can be said. + +_Seventhly_, hybrids and mongrels present, with the one great exception of +fertility, the most striking accordance in all other respects; namely, in +the laws of their resemblance to their two parents, in their tendency to +reversion, in their variability, and in being absorbed through repeated +crosses by either parent-form. + +Since arriving at the foregoing conclusions, condensed from my former work, +I have been led to investigate a subject which throws considerable light on +hybridism, namely, the fertility of {181} reciprocally dimorphic and +trimorphic plants, when illegitimately united. I have had occasion several +times to allude to these plants, and I may here give a brief abstract[441] +of my observations. Several plants belonging to distinct orders present two +forms, which exist in about equal numbers, and which differ in no respect +except in their reproductive organs; one form having a long pistil with +short stamens, the other a short pistil with long stamens; both with +differently sized pollen-grains. With trimorphic plants there are three +forms likewise differing in the lengths of their pistils and stamens, in +the size and colour of the pollen-grains, and in some other respects; and +as in each of the three forms there are two sets of stamens, there are +altogether six sets of stamens and three kinds of pistils. These organs are +so proportioned in length to each other that, in any two of the forms, half +the stamens in each stand on a level with the stigma of the third form. Now +I have shown, and the result has been confirmed by other observers, that, +in order to obtain full fertility with these plants, it is necessary that +the stigma of the one form should be fertilised by pollen taken from the +stamens of corresponding height in the other form. So that with dimorphic +species two unions, which may be called legitimate, are fully fertile, and +two, which may be called illegitimate, are more or less infertile. With +trimorphic species six unions are legitimate or fully fertile, and twelve +are illegitimate or more or less infertile. + +The infertility which may be observed in various dimorphic and trimorphic +plants, when they are illegitimately fertilised, that is, by pollen taken +from stamens not corresponding in height with the pistil, differs much in +degree, up to absolute and utter sterility; just in the same manner as +occurs in crossing distinct species. As the degree of sterility in the +latter case depends in an eminent degree on the conditions of life being +more or less favourable, so I have found it with illegitimate unions. It is +well known that if pollen of a distinct species be placed on the stigma of +a flower, and its own pollen be afterwards, even {182} after a considerable +interval of time, placed on the same stigma, its action is so strongly +prepotent that it generally annihilates the effect of the foreign pollen; +so it is with the pollen of the several forms of the same species, for +legitimate pollen is strongly prepotent over illegitimate pollen, when both +are placed on the same stigma. I ascertained this by fertilising several +flowers, first illegitimately, and twenty-four hours afterwards +legitimately, with pollen taken from a peculiarly coloured variety, and all +the seedlings were similarly coloured; this shows that the legitimate +pollen, though applied twenty-four hours subsequently, had wholly destroyed +or prevented the action of the previously applied illegitimate pollen. +Again, as, in making reciprocal crosses between the same two species, there +is occasionally a great difference in the result, so something analogous +occurs with dimorphic plants; for a short-styled cowslip (_P. veris_) +yields more seed when fertilised by the long-styled form, and less seed +when fertilised by its own form, compared with a long-styled cowslip when +fertilised in the two corresponding methods. + +In all these respects the forms of the same undoubted species, when +illegitimately united, behave in exactly the same manner as do two distinct +species when crossed. This led me carefully to observe during four years +many seedlings, raised from several illegitimate unions. The chief result +is that these illegitimate plants, as they may be called, are not fully +fertile. It is possible to raise from dimorphic species, both long-styled +and short-styled illegitimate plants, and from trimorphic plants all three +illegitimate forms. These can then be properly united in a legitimate +manner. When this is done, there is no apparent reason why they should not +yield as many seeds as did their parents when legitimately fertilised. But +such is not the case; they are all infertile, but in various degrees; some +being so utterly and incurably sterile that they did not yield during four +seasons a single seed or even seed-capsule. These illegitimate plants, +which are so sterile, although united with each other in a legitimate +manner, may be strictly compared with hybrids when crossed _inter se_, and +it is well known how sterile these latter generally are. When, on the other +hand, a hybrid is crossed with either pure parent-species, the sterility is +usually much lessened: and so it is when an illegitimate plant is +fertilised by {183} a legitimate plant. In the same manner as the sterility +of hybrids does not always run parallel with the difficulty of making the +first cross between the two parent species, so the sterility of certain +illegitimate plants was unusually great, whilst the sterility of the union +from which they were derived was by no means great. With hybrids raised +from the same seed-capsule the degree of sterility is innately variable, so +it is in a marked manner with illegitimate plants. Lastly, many hybrids are +profuse and persistent flowerers, whilst other and more sterile hybrids +produce few flowers, and are weak, miserable dwarfs; exactly similar cases +occur with the illegitimate offspring of various dimorphic and trimorphic +plants. + +Altogether there is the closest identity in character and behaviour between +illegitimate plants and hybrids. It is hardly an exaggeration to maintain +that the former are hybrids, but produced within the limits of the same +species by the improper union of certain forms, whilst ordinary hybrids are +produced from an improper union between so-called distinct species. We have +already seen that there is the closest similarity in all respects between +first illegitimate unions, and first crosses between distinct species. This +will perhaps be made more fully apparent by an illustration: we may suppose +that a botanist found two well-marked varieties (and such occur) of the +long-styled form of the trimorphic _Lythrum salicaria_, and that he +determined to try by crossing whether they were specifically distinct. He +would find that they yielded only about one-fifth of the proper number of +seed, and that they behaved in all the other above-specified respects as if +they had been two distinct species. But to make the case sure, he would +raise plants from his supposed hybridised seed, and he would find that the +seedlings were miserably dwarfed and utterly sterile, and that they behaved +in all other respects like ordinary hybrids. He might then maintain that he +had actually proved, in accordance with the common view, that his two +varieties were as good and as distinct species as any in the world; but he +would be completely mistaken. + +The facts now given on dimorphic and trimorphic plants are important, +because they show us, firstly, that the physiological {184} test of +lessened fertility, both in first crosses and in hybrids, is no safe +criterion of specific distinction; secondly, because we may conclude that +there must be some unknown law or bond connecting the infertility of +illegitimate unions with that of their illegitimate offspring, and we are +thus led to extend this view to first crosses and hybrids; thirdly, because +we find, and this seems to me of especial importance, that with trimorphic +plants three forms of the same species exist, which when crossed in a +particular manner are infertile, and yet these forms differ in no respect +from each other, except in their reproductive organs,--as in the relative +length of the stamens and pistils, in the size, form, and colour of the +pollen-grains, in the structure of the stigma, and in, the number and size +of the seeds. With these differences and no others, either in organisation +or constitution, we find that the illegitimate unions and the illegitimate +progeny of these three forms are more or less sterile, and closely resemble +in a whole series of relations the first unions and hybrid offspring of +distinct species. From this we may infer that the sterility of species when +crossed and of their hybrid progeny is likewise in all probability +exclusively due to differences confined to the reproductive system. We have +indeed been brought to a similar conclusion by observing that the sterility +of crossed species does not strictly coincide with their systematic +affinity, that is, with the sum of their external resemblances; nor does it +coincide with their similarity in general constitution. But we are more +especially led to this same conclusion by considering reciprocal crosses, +in which the male of one species cannot be united, or can be united with +extreme difficulty, with the female of a second species, whilst the +converse cross can be effected with perfect facility; for this difference +in the facility of making reciprocal crosses, and in the fertility of their +offspring, must be attributed either to the male or female element in the +first species having been differentiated with reference to the sexual +element of the second species in a higher degree than in the converse case. +In so complex a subject as Hybridism it is of considerable importance thus +to arrive at a definitive conclusion, namely, that the sterility which +almost invariably follows the union of distinct {185} species depends +exclusively on differences in their sexual constitution. + + * * * * * + +On the principle which makes it necessary for man, whilst he is selecting +and improving his domestic varieties, to keep them separate, it would +clearly be advantageous to varieties in a state of nature, that is to +incipient species, if they could be kept from blending, either through +sexual aversion, or by becoming mutually sterile. Hence it at one time +appeared to me probable, as it has to others, that this sterility might +have been acquired through natural selection. On this view we must suppose +that a shade of lessened fertility first spontaneously appeared, like any +other modification, in certain individuals of a species when crossed with +other individuals of the same species; and that successive slight degrees +of infertility, from being advantageous, were slowly accumulated. This +appears all the more probable, if we admit that the structural differences +between the forms of dimorphic and trimorphic plants, as the length and +curvature of the pistil, &c., have been co-adapted through natural +selection; for if this be admitted, we can hardly avoid extending the same +conclusion to their mutual infertility. Sterility moreover has been +acquired through natural selection for other and widely different purposes, +as with neuter insects in reference to their social economy. In the case of +plants, the flowers on the circumference of the truss in the guelder-rose +(_Viburnum opulus_) and those on the summit of the spike in the +feather-hyacinth (_Muscari comosum_) have been rendered conspicuous, and +apparently in consequence sterile, in order that insects might easily +discover and visit the other flowers. But when we endeavour to apply the +principle of natural selection to the acquirement by distinct species of +mutual sterility, we meet with great difficulties. In the first place, it +may be remarked that separate regions are often inhabited by groups of +species or by single species, which when brought together and crossed are +found to be more or less sterile; now it could clearly have been of no +advantage to such separated species to have been rendered mutually sterile, +and consequently this could not have been effected through natural +selection; but it may perhaps be argued, that, if a species were rendered +sterile with {186} some one compatriot, sterility with other species would +follow as a necessary consequence. In the second place, it is as much +opposed to the theory of natural selection, as to the theory of special +creation, that in reciprocal crosses the male element of one form should +have been rendered utterly impotent on a second form, whilst at the same +time the male element of this second form is enabled freely to fertilise +the first form; for this peculiar state of the reproductive system could +not possibly be advantageous to either species. + +In considering the probability of natural selection having come into action +in rendering species mutually sterile, one great difficulty will be found +to lie in the existence of many graduated steps from slightly lessened +fertility to absolute sterility. It may be admitted, on the principle above +explained, that it would profit an incipient species if it were rendered in +some slight degree sterile when crossed with its parent-form or with some +other variety; for thus fewer bastardised and deteriorated offspring would +be produced to commingle their blood with the new species in process of +formation. But he who will take the trouble to reflect on the steps by +which this first degree of sterility could be increased through natural +selection to that higher degree which is common to so many species, and +which is universal with species which have been differentiated to a generic +or family rank, will find the subject extraordinarily complex. After mature +reflection it seems to me that this could not have been effected through +natural selection; for it could have been of no direct advantage to an +individual animal to breed badly with another individual of a different +variety, and thus leave few offspring; consequently such individuals could +not have been preserved or selected. Or take the case of two species which +in their present state, when crossed, produce few and sterile offspring; +now, what is there which could favour the survival of those individuals +which happened to be endowed in a slightly higher degree with mutual +infertility and which thus approached by one small step towards absolute +sterility? yet an advance of this kind, if the theory of natural selection +be brought to bear, must have incessantly occurred with many species, for a +multitude are mutually quite barren. With sterile neuter insects we have +reason to {187} believe that modifications in their structure have been +slowly accumulated by natural selection, from an advantage having been thus +indirectly given to the community to which they belonged over other +communities of the same species; but an individual animal, if rendered +slightly sterile when crossed with some other variety, would not thus in +itself gain any advantage, or indirectly give any advantage to its nearest +relatives or to other individuals of the same variety, leading to their +preservation. I infer from these considerations that, as far as animals are +concerned, the various degrees of lessened fertility which occur with +species when crossed cannot have been slowly accumulated by means of +natural selection. + +With plants, it is possible that the case may be somewhat different. With +many kinds, insects constantly carry pollen from neighbouring plants to the +stigmas of each flower; and with some species this is effected by the wind. +Now, if the pollen of a variety, when deposited on the stigma of the same +variety, should become by spontaneous variation in ever so slight a degree +prepotent over the pollen of other varieties, this would certainly be an +advantage to the variety; for its own pollen would thus obliterate the +effects of the pollen of other varieties, and prevent deterioration of +character. And the more prepotent the variety's own pollen could be +rendered through natural selection, the greater the advantage would be. We +know from the researches of Gärtner that, with species which are mutually +sterile, the pollen of each is always prepotent on its own stigma over that +of the other species; but we do not know whether this prepotency is a +consequence of the mutual sterility, or the sterility a consequence of the +prepotency. If the latter view be correct, as the prepotency became +stronger through natural selection, from being advantageous to a species in +process of formation, so the sterility consequent on prepotency would at +the same time be augmented; and the final result would be various degrees +of sterility, such as occurs with existing species. This view might be +extended to animals, if the female before each birth received several +males, so that the sexual element of the prepotent male of her own variety +obliterated the effects of the access of previous males belonging to other +varieties; but we have no reason to believe, at least {188} with +terrestrial animals, that this is the ease; as most males and females pair +for each birth, and some few for life. + +On the whole we may conclude that with animals the sterility of crossed +species has not been slowly augmented through natural selection; and as +this sterility follows the same general laws in the vegetable as in the +animal kingdom, it is improbable, though apparently possible, that with +plants crossed species should have been rendered sterile by a different +process. From this consideration, and remembering that species which have +never co-existed in the same country, and which therefore could not have +received any advantage from having been rendered mutually infertile, yet +are generally sterile when crossed; and bearing in mind that in reciprocal +crosses between the same two species there is sometimes the widest +difference in their sterility, we must give up the belief that natural +selection has come into play. + +As species have not been rendered mutually infertile through the +accumulative action of natural selection, and as we may safely conclude, +from the previous as well as from other and more general considerations, +that they have not been endowed through an act of creation with this +quality, we must infer that it has arisen incidentally during their slow +formation in connection with other and unknown changes in their +organisation. By a quality arising incidentally, I refer to such cases as +different species of animals and plants being differently affected by +poisons to which they are not naturally exposed; and this difference in +susceptibility is clearly incidental on other and unknown differences in +their organisation. So again the capacity in different kinds of trees to be +grafted on each other, or on a third species, differs much, and is of no +advantage to these trees, but is incidental on structural or functional +differences in their woody tissues. We need not feel surprise at sterility +incidentally resulting from crosses between distinct species,--the modified +descendants of a common progenitor,--when we bear in mind how easily the +reproductive system is affected by various causes--often by extremely +slight changes in the conditions of life, by too close interbreeding, and +by other agencies. It is well to bear in mind such cases, as that of the +_Passiflora alata_, which recovered its self-fertility from {189} being +grafted on a distinct species--the cases of plants which normally or +abnormally are self-impotent, but can readily be fertilised by the pollen +of a distinct species--and lastly the cases of individual domesticated +animals which evince towards each other sexual incompatibility. + + * * * * * + +We now at last come to the immediate point under discussion: how is it +that, with some few exceptions in the case of plants, domesticated +varieties, such as those of the dog, fowl, pigeon, several fruit-trees, and +culinary vegetables, which differ from each other in external characters +more than many species, are perfectly fertile when crossed, or even fertile +in excess, whilst closely allied species are almost invariably in some +degree sterile? We can, to a certain extent, give a satisfactory answer to +this question. Passing over the fact that the amount of external difference +between two species is no sure guide to their degree of mutual sterility, +so that similar differences in the case of varieties would be no sure +guide, we know that with species the cause lies exclusively in differences +in their sexual constitution. Now the conditions to which domesticated +animals and cultivated plants have been subjected, have had so little +tendency towards modifying the reproductive system in a manner leading to +mutual sterility, that we have good grounds for admitting the directly +opposite doctrine of Pallas, namely, that such conditions generally +eliminate this tendency; so that the domesticated descendants of species, +which in their natural state would have been in some degree sterile when +crossed, become perfectly fertile together. With plants, so far is +cultivation from giving a tendency towards mutual sterility, that in +several well-authenticated cases, already often alluded to, certain species +have been affected in a very different manner, for they have become +self-impotent, whilst still retaining the capacity of fertilising, and +being fertilised by, distinct species. If the Pallasian doctrine of the +elimination of sterility through long-continued domestication be admitted, +and it can hardly be rejected, it becomes in the highest degree improbable +that similar circumstances should commonly both induce and eliminate the +same tendency; though in certain cases, with species having a peculiar +constitution, sterility might occasionally be thus {190} induced. Thus, as +I believe, we can understand why with domesticated animals varieties have +not been produced which are mutually sterile; and why with plants only a +few such cases have been observed, namely, by Gärtner, with certain +varieties of maize and verbascum, by other experimentalists with varieties +of the gourd and melon, and by Kölreuter with one kind of tobacco. + +With respect to varieties which have originated in a state of nature, it is +almost hopeless to expect to prove by direct evidence that they have been +rendered mutually sterile; for if even a trace of sterility could be +detected, such varieties would at once be raised by almost every naturalist +to the rank of distinct species. If, for instance, Gärtner's statement were +fully confirmed, that the blue and red-flowered forms of the pimpernel +(_Anagallis arvensis_) are sterile when crossed, I presume that all the +botanists who now maintain on various grounds that these two forms are +merely fleeting varieties, would at once admit that they were specifically +distinct. + +The real difficulty in our present subject is not, as it appears to me, why +domestic varieties have not become mutually infertile when crossed, but why +this has so generally occurred with natural varieties as soon as they have +been modified in a sufficient and permanent degree to take rank as species. +We are far from precisely knowing the cause; nor is this surprising, seeing +how profoundly ignorant we are in regard to the normal and abnormal action +of the reproductive system. But we can see that species, owing to their +struggle for life with numerous competitors, must have been exposed to more +uniform conditions during long periods of time, than have been domestic +varieties; and this may well make a wide difference in the result. For we +know how commonly wild animals and plants, when taken from their natural +conditions and subjected to captivity, are rendered sterile; and the +reproductive functions of organic beings which have always lived and been +slowly modified under natural conditions would probably in like manner be +eminently sensitive to the influence of an unnatural cross. Domesticated +productions, on the other hand, which, as shown by the mere fact of their +domestication, were not originally highly sensitive to changes in their +conditions of life, and which can now generally resist {191} with +undiminished fertility repeated changes of conditions, might be expected to +produce varieties, which would be little liable to have their reproductive +powers injuriously affected by the act of crossing with other varieties +which had originated in a like manner. + +Certain naturalists have recently laid too great stress, as it appears to +me, on the difference in fertility between varieties and species when +crossed. Some allied species of trees cannot be grafted on each other,--all +varieties can be so grafted. Some allied animals are affected in a very +different manner by the same poison, but with varieties no such case until +recently was known, but now it has been proved that immunity from certain +poisons stands in some cases in correlation with the colour of the hair. +The period of gestation generally differs much with distinct species, but +with varieties until lately no such difference had been observed. The time +required for the germination of seeds differs in an analogous manner, and I +am not aware that any difference in this respect has as yet been detected +with varieties. Here we have various physiological differences, and no +doubt others could be added, between one species and another of the same +genus, which do not occur, or occur with extreme rarity, in the case of +varieties; and these differences are apparently wholly or in chief part +incidental on other constitutional differences, just in the same manner as +the sterility of crossed species is incidental on differences confined to +the sexual system. Why, then, should these latter differences, however +serviceable they may indirectly be in keeping the inhabitants of the same +country distinct, be thought of such paramount importance, in comparison +with other incidental and functional differences? No sufficient answer to +this question can be given. Hence the fact that the most distinct domestic +varieties are, with rare exceptions, perfectly fertile when crossed, and +produce fertile offspring, whilst closely allied species are, with rare +exceptions, more or less sterile, is not nearly so formidable an objection +as it appears at first to the theory of the common descent of allied +species. + + * * * * * + + +{192} + +CHAPTER XX. + +SELECTION BY MAN. + + SELECTION A DIFFICULT ART--METHODICAL, UNCONSCIOUS, AND NATURAL + SELECTION--RESULTS OF METHODICAL SELECTION--CARE TAKEN IN + SELECTION--SELECTION WITH PLANTS--SELECTION CARRIED ON BY THE ANCIENTS, + AND BY SEMI-CIVILIZED PEOPLE--UNIMPORTANT CHARACTERS OFTEN ATTENDED + TO--UNCONSCIOUS SELECTION--AS CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR + DOMESTICATED ANIMALS CHANGED THROUGH THE ACTION OF UNCONSCIOUS + SELECTION--INFLUENCE OF DIFFERENT BREEDERS ON THE SAME + SUB-VARIETY--PLANTS AS AFFECTED BY UNCONSCIOUS SELECTION--EFFECTS OF + SELECTION AS SHOWN BY THE GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST + VALUED BY MAN. + +The power of Selection, whether exercised by man, or brought into play +under nature through the struggle for existence and the consequent survival +of the fittest, absolutely depends on the variability of organic beings. +Without variability nothing can be effected; slight individual differences, +however, suffice for the work, and are probably the sole differences which +are effective in the production of new species. Hence our discussion on the +causes and laws of variability ought in strict order to have preceded our +present subject, as well as the previous subjects of inheritance, crossing, +&c.; but practically the present arrangement has been found the most +convenient. Man does not attempt to cause variability; though he +unintentionally effects this by exposing organisms to new conditions of +life, and by crossing breeds already formed. But variability being granted, +he works wonders. Unless some degree of selection be exercised, the free +commingling of the individuals of the same variety soon obliterates, as we +have previously seen, the slight differences which may arise, and gives to +the whole body of individuals uniformity of character. In separated +districts, long-continued exposure to different conditions of life may +perhaps produce new races without the aid of selection; but to this +difficult subject {193} of the direct action of the conditions of life we +shall in a future chapter recur. + +When animals or plants are born with some conspicuous and firmly inherited +new character, selection is reduced to the preservation of such +individuals, and to the subsequent prevention of crosses; so that nothing +more need be said on the subject. But in the great majority of cases a new +character, or some superiority in an old character, is at first faintly +pronounced, and is not strongly inherited; and then the full difficulty of +selection is experienced. Indomitable patience, the finest powers of +discrimination, and sound judgment must be exercised during many years. A +clearly predetermined object must be kept steadily in view. Few men are +endowed with all these qualities, especially with that of discriminating +very slight differences; judgment can be acquired only by long experience; +but if any of these qualities be wanting, the labour of a life may be +thrown away. I have been astonished when celebrated breeders, whose skill +and judgment have been proved by their success at exhibitions, have shown +me their animals, which appeared all alike, and have assigned their reasons +for matching this and that individual. The importance of the great +principle of Selection mainly lies in this power of selecting scarcely +appreciable differences, which nevertheless are found to be transmissible, +and which can be accumulated until the result is made manifest to the eyes +of every beholder. + +The principle of selection may be conveniently divided into three kinds. +_Methodical selection_ is that which guides a man who systematically +endeavours to modify a breed according to some predetermined standard. +_Unconscious selection_ is that which follows from men naturally preserving +the most valued and destroying the less valued individuals, without any +thought of altering the breed; and undoubtedly this process slowly works +great changes. Unconscious selection graduates into methodical, and only +extreme cases can be distinctly separated; for he who preserves a useful or +perfect animal will generally breed from it with the hope of getting +offspring of the same character; but as long as he has not a predetermined +purpose to improve the breed, he may be said to be selecting {194} +unconsciously.[442] Lastly, we have _Natural selection_, which implies that +the individuals which are best fitted for the complex, and in the course of +ages changing conditions to which they are exposed, generally survive and +procreate their kind. With domestic productions, with which alone we are +here strictly concerned, natural selection comes to a certain extent into +action, independently of, and even in opposition to, the will of man. + + * * * * * + +_Methodical Selection._--What man has effected within recent times in +England by methodical selection is clearly shown by our exhibitions of +improved quadrupeds and fancy birds. With respect to cattle, sheep, and +pigs, we owe their great improvement to a long series of well-known +names--Bakewell, Colling, Ellman, Bates, Jonas Webb, Lords Leicester and +Western, Fisher Hobbs, and others. Agricultural writers are unanimous on +the power of selection: any number of statements to this effect could be +quoted; a few will suffice. Youatt, a sagacious and experienced observer, +writes,[443] the principle of selection is "that which enables the +agriculturist, not only to modify the character of his flock, but to change +it altogether." A great breeder of shorthorns[444] says, "In the anatomy of +the shoulder modern breeders have made great improvements on the Ketton +shorthorns by correcting the defect in the knuckle or shoulder-joint, and +by laying the top of the shoulder more snugly into the crop, and thereby +filling up the hollow behind it.... The eye has its fashion at different +periods: at one time the eye high and outstanding from the head, and at +another time the sleepy eye sunk into the head; but these extremes have +merged into the medium of a full, clear, and prominent eye with a placid +look." + +Again, hear what an excellent judge of pigs[445] says: "The legs {195} +should be no longer than just to prevent the animal's belly from trailing +on the ground. The leg is the least profitable portion of the hog, and we +therefore require no more of it than is absolutely necessary for the +support of the rest." Let any one compare the wild-boar with any improved +breed, and he will see how effectually the legs have been shortened. + +Few persons, except breeders, are aware of the systematic care taken in +selecting animals, and of the necessity of having a clear and almost +prophetic vision into futurity. Lord Spencer's skill and judgment were well +known; and he writes,[446] "It is therefore very desirable, before any man +commences to breed either cattle or sheep, that he should make up his mind +to the shape and qualities he wishes to obtain, and steadily pursue this +object." Lord Somerville, in speaking of the marvellous improvement of the +New Leicester sheep, effected by Bakewell and his successors, says, "It +would seem as if they had first drawn a perfect form, and then given it +life." Youatt[447] urges the necessity of annually drafting each flock, as +many animals will certainly degenerate "from the standard of excellence, +which the breeder has established in his own mind." Even with a bird of +such little importance as the canary, long ago (1780-1790) rules were +established, and a standard of perfection was fixed, according to which the +London fanciers tried to breed the several sub-varieties.[448] A great +winner of prizes at the Pigeon-shows,[449] in describing the Short-faced +Almond Tumbler, says, "There are many first-rate fanciers who are +particularly partial to what is called the goldfinch-beak, which is very +beautiful; others say, take a full-size round cherry, then take a +barley-corn, and judiciously placing and thrusting it into the cherry, form +as it were your beak; and that is not all, for it will form a good head and +beak, provided, as I said before, it is judiciously done; others take an +oat; but as I think the goldfinch-beak the handsomest, I would advise the +inexperienced fancier to get the head of a goldfinch, and keep it by him +for his observation." Wonderfully different as is the beak of the +rock-pigeon and goldfinch, undoubtedly, as far as {196} external shape and +proportions are concerned, the end has been nearly gained. + +Not only should our animals be examined with the greatest care whilst +alive, but, as Anderson remarks,[450] their carcases should be scrutinised, +"so as to breed from the descendants of such only as, in the language of +the butcher, cut up well." The "grain of the meat" in cattle, and its being +well marbled with fat,[451] and the greater or less accumulation of fat in +the abdomen of our sheep, have been attended to with success. So with +poultry, a writer,[452] speaking of Cochin-China fowls, which are said to +differ much in the quality of their flesh, says, "the best mode is to +purchase two young brother-cocks, kill, dress, and serve up one; if he be +indifferent, similarly dispose of the other, and try again; if, however, he +be fine and well-flavoured, his brother will not be amiss for breeding +purposes for the table." + +The great principle of the division of labour has been brought to bear on +selection. In certain districts[453] "the breeding of bulls is confined to +a very limited number of persons, who by devoting their whole attention to +this department, are able from year to year to furnish a class of bulls +which are steadily improving the general breed of the district." The +rearing and letting of choice rams has long been, as is well known, a chief +source of profit to several eminent breeders. In parts of Germany this +principle is carried with merino sheep to an extreme point.[454] "So +important is the proper selection of breeding animals considered, that the +best flock-masters do not trust to their own judgment, or to that of their +shepherds, but employ persons called 'sheep-classifiers,' who make it their +special business to attend to this part of the management of several +flocks, and thus to preserve, or if possible to improve, the best qualities +of both parents in the lambs." In Saxony, "when the lambs are weaned, each +in his turn is placed upon a table that his wool and form may be minutely +observed. {197} The finest are selected for breeding and receive a first +mark. When they are one year old, and prior to shearing them, another close +examination of those previously marked takes place: those in which no +defect can be found receive a second mark, and the rest are condemned. A +few months afterwards a third and last scrutiny is made; the prime rams and +ewes receive a third and final mark, but the slightest blemish is +sufficient to cause the rejection of the animal." These sheep are bred and +valued almost exclusively for the fineness of their wool; and the result +corresponds with the labour bestowed on their selection. Instruments have +been invented to measure accurately the thickness of the fibres; and "an +Austrian fleece has been produced of which twelve hairs equalled in +thickness one from a Leicester sheep." + +Throughout the world, wherever silk is produced, the greatest care is +bestowed on selecting the cocoons from which the moths for breeding are to +be reared. A careful cultivator[455] likewise examines the moths +themselves, and destroys those that are not perfect. But what more +immediately concerns us is that certain families in France devote +themselves to raising eggs for sale.[456] In China, near Shanghai, the +inhabitants of two small districts have the privilege of raising eggs for +the whole surrounding country, and that they may give up their whole time +to this business, they are interdicted by law from producing silk.[457] + +The care which successful breeders take in matching their birds is +surprising. Sir John Sebright, whose fame is perpetuated by the "Sebright +Bantam," used to spend "two and three days in examining, consulting, and +disputing with a friend which were the best of five or six birds."[458] Mr. +Bult, whose pouter-pigeons won so many prizes and were exported to North +America under the charge of a man sent on purpose, told me that he always +deliberated for several days before he matched each pair. Hence we can +understand the advice of an eminent fancier, who writes,[459] "I would here +particularly guard {198} you against having too great a variety of pigeons, +otherwise you will know a little of all, but nothing about one as it ought +to be known." Apparently it transcends the power of the human intellect to +breed all kinds: "it is possible that there may be a few fanciers that have +a good general knowledge of fancy pigeons; but there are many more who +labour under the delusion of supposing they know what they do not." The +excellence of one sub-variety, the Almond Tumbler, lies in the plumage, +carriage, head, beak, and eye; but it is too presumptuous in the beginner +to try for all these points. The great judge above quoted says, "there are +some young fanciers who are over-covetous, who go for all the above five +properties at once; they have their reward by getting nothing." We thus see +that breeding even fancy pigeons is no simple art: we may smile at the +solemnity of these precepts, but he who laughs will win no prizes. + +What methodical selection has effected for our animals is sufficiently +proved, as already remarked, by our Exhibitions. So greatly were the sheep +belonging to some of the earlier breeders, such as Bakewell and Lord +Western, changed, that many persons could not be persuaded that they had +not been crossed. Our pigs, as Mr. Corringham remarks,[460] during the last +twenty years have undergone, through rigorous selection together with +crossing, a complete metamorphosis. The first exhibition for poultry was +held in the Zoological Gardens in 1845; and the improvement effected since +that time has been great. As Mr. Baily, the great judge, remarked to me, it +was formerly ordered that the comb of the Spanish cock should be upright, +and in four or five years all good birds had upright combs; it was ordered +that the Polish cock should have no comb or wattles, and now a bird thus +furnished would be at once disqualified; beards were ordered, and out of +fifty-seven pens lately (1860) exhibited at the Crystal Palace, all had +beards. So it has been in many other cases. But in all cases the judges +order only what is occasionally produced and what can be improved and +rendered constant by selection. The steady increase of weight during the +last few years in our {199} fowls, turkeys, ducks, and geese is notorious; +"six-pound ducks are now common, whereas four pounds was formerly the +average." As the actual time required to make a change has not often been +recorded, it may be worth mentioning that it took Mr. Wicking thirteen +years to put a clean white head on an almond tumbler's body, "a triumph," +says another fancier, "of which he may be justly proud."[461] + +Mr. Tollet, of Betley Hall, selected cows, and especially bulls, descended +from good milkers, for the sole purpose of improving his cattle for the +production of cheese; he steadily tested the milk with the lactometer, and +in eight years he increased, as I was informed by him, the product in the +proportion of four to three. Here is a curious case[462] of steady but slow +progress, with the end not as yet fully attained: in 1784 a race of +silkworms was introduced into France, in which one hundred out of the +thousand failed to produce white cocoons; but now, after careful selection +during sixty-five generations, the proportion of yellow cocoons has been +reduced to thirty-five in the thousand. + +With plants selection has been followed with the same good results as with +animals. But the process is simpler, for plants in the great majority of +cases bear both sexes. Nevertheless, with most kinds it is necessary to +take as much care to prevent crosses as with animals or unisexual plants; +but with some plants, such as peas, this care does not seem to be +necessary. With all improved plants, excepting of course those which are +propagated by buds, cuttings, &c., it is almost indispensable to examine +the seedlings and destroy those which depart from the proper type. This is +called "roguing," and is, in fact, a form of selection, like the rejection +of inferior animals. Experienced horticulturists and agriculturists +incessantly urge every one to preserve the finest plants for the production +of seed. + +Although plants often present much more conspicuous variations than +animals, yet the closest attention is generally requisite to detect each +slight and favourable change. Mr. Masters relates[463] how "many a patient +hour was devoted," whilst he was {200} young, to the detection of +differences in peas intended for seed. Mr. Barnet[464] remarks that the old +scarlet American strawberry was cultivated for more than a century without +producing a single variety; and another writer observes how singular it was +that when gardeners first began to attend to this fruit it began to vary; +the truth no doubt being that it had always varied, but that, until slight +varieties were selected and propagated by seed, no conspicuous result was +obtained. The finest shades of difference in wheat have been discriminated +and selected with almost as much care, as we see in Colonel Le Couteur's +works, as in the case of the higher animals; but with our cereals the +process of selection has seldom or never been long continued. + +It may be worth while to give a few examples of methodical selection with +plants; but in fact the great improvement of all our anciently cultivated +plants may be attributed to selection long carried on, in part +methodically, and in part unconsciously. I have shown in a former chapter +how the weight of the gooseberry has been increased by systematic selection +and culture. The flowers of the Heartsease have been similarly increased in +size and regularity of outline. With the Cineraria, Mr. Glenny[465] "was +bold enough, when the flowers were ragged and starry and ill defined in +colour, to fix a standard which was then considered outrageously high and +impossible, and which, even if reached, it was said, we should be no +gainers by, as it would spoil the beauty of the flowers. He maintained that +he was right; and the event has proved it to be so." The doubling of +flowers has several times been effected by careful selection: the Rev. W. +Williamson,[466] after sowing during several years seed of _Anemone +coronaria_, found a plant with one additional petal; he sowed the seed of +this, and by perseverance in the same course obtained several varieties +with six or seven rows of petals. The single Scotch rose was doubled, and +yielded eight good varieties in nine or ten years.[467] The Canterbury bell +(_Campanula medium_) was doubled by careful selection in four +generations.[468] In four years Mr. Buckman,[469] by culture and {201} +careful selection, converted parsnips, raised from wild seed, into a new +and good variety. By selection during a long course of years, the early +maturity of peas has been hastened from ten to twenty-one days.[470] A more +curious case is offered by the beet-plant, which, since its cultivation in +France, has almost exactly doubled its yield of sugar. This has been +effected by the most careful selection; the specific gravity of the roots +being regularly tested, and the best roots saved for the production of +seed.[471] + +_Selection by Ancient and Semi-civilised People._ + +In attributing so much importance to the selection of animals and plants, +it may be objected that methodical selection would not have been carried on +during ancient times. A distinguished naturalist considers it as absurd to +suppose that semi-civilised people should have practised selection of any +kind. Undoubtedly the principle has been systematically acknowledged and +followed to a far greater extent within the last hundred years than at any +former period, and a corresponding result has been gained; but it would be +a great error to suppose, as we shall immediately see, that its importance +was not recognised and acted on during the most ancient times, and by +semi-civilised people. I should premise that many facts now to be given +only show that care was taken in breeding; but when this is the case, +selection is almost sure to be practised to a certain extent. We shall +hereafter be enabled better to judge how far selection, when only +occasionally carried on, by a few of the inhabitants of a country, will +slowly produce a great effect. + +In a well-known passage in the thirtieth chapter of Genesis, rules are +given for influencing, as was then thought possible, the colour of sheep; +and speckled and dark breeds are spoken of as being kept separate. By the +time of David the fleece was likened to snow. Youatt,[472] who has +discussed all the passages in relation to breeding in the Old Testament, +concludes that {202} at this early period "some of the best principles of +breeding must have been steadily and long pursued." It was ordered, +according to Moses, that "Thou shalt not let thy cattle gender with a +diverse kind;" but mules were purchased,[473] so that at this early period +other nations must have crossed the horse and ass. It is said[474] that +Erichthonius, some generations before the Trojan war, had many brood-mares, +"which by his care and judgment in the choice of stallions produced a breed +of horses superior to any in the surrounding countries." Homer (Book v.) +speaks of Æneas's horses as bred from mares which were put to the steeds of +Laomedon. Plato, in his 'Republic,' says to Glaucus, "I see that you raise +at your house a great many dogs for the chase. Do you take care about +breeding and pairing them? Among animals of good blood, are there not +always some which are superior to the rest?" To which Glaucus answers in +the affirmative.[475] Alexander the Great selected the finest Indian cattle +to send to Macedonia to improve the breed.[476] According to Pliny,[477] +King Pyrrhus had an especially valuable breed of oxen; and he did not +suffer the bulls and cows to come together till four years old, that the +breed might not degenerate. Virgil, in his Georgics (lib. iii.), gives as +strong advice as any modern agriculturist could do, carefully to select the +breeding stock; "to note the tribe, the lineage, and the sire; whom to +reserve for husband of the herd;"--to brand the progeny;--to select sheep +of the purest white, and to examine if their tongues are swarthy. We have +seen that the Romans kept pedigrees of their pigeons, and this would have +been a senseless proceeding had not great care been taken in breeding them. +Columella gives detailed instructions about breeding fowls: "Let the +breeding hens therefore be of a choice colour, a robust body, square-built, +full-breasted, with large heads, with upright and bright-red combs. Those +are believed to be the best bred which have five toes."[478] According to +Tacitus, the Celts attended to the races of their domestic animals; {203} +and Cæsar states that they paid high prices to merchants for fine imported +horses.[479] In regard to plants, Virgil speaks of yearly culling the +largest seeds; and Celsus says, "where the corn and crop is but small, we +must pick out the best ears of corn, and of them lay up our seed separately +by itself."[480] + +Coming down the stream of time, we may be brief. At about the beginning of +the ninth century Charlemagne expressly ordered his officers to take great +care of his stallions; and if any proved bad or old, to forewarn him in +good time before they were put to the mares.[481] Even in a country so +little civilised as Ireland during the ninth century, it would appear from +some ancient verses,[482] describing a ransom demanded by Cormac, that +animals from particular places, or having a particular character, were +valued. Thus it is said,-- + + Two pigs of the pigs of Mac Lir, + A ram and ewe both round and red, + I brought with me from Aengus. + I brought with me a stallion and a mare + From the beautiful stud of Manannan, + A bull and a white cow from Druim Cain. + +Athelstan, in 930, received as a present from Germany, running-horses; and +he prohibited the exportation of English horses. King John imported "one +hundred chosen stallions from Flanders."[483] On June 16th, 1305, the +Prince of Wales wrote to the Archbishop of Canterbury, begging for the loan +of any choice stallion, and promising its return at the end of the +season.[484] There are numerous records at ancient periods in English +history of the importation of choice animals of various kinds, and of +foolish laws against their exportation. In the reigns of Henry VII. and +VIII. it was ordered that the magistrates, at Michaelmas, should scour the +heaths and commons, and destroy all mares beneath a certain size.[485] Some +of our earlier kings passed laws against the slaughtering rams of any good +breed before they were seven years old, so that they {204} might have time +to breed. In Spain Cardinal Ximenes issued, in 1509, regulations on the +_selection_ of good rams for breeding.[486] + +The Emperor Akbar Khan before the year 1600 is said to have "wonderfully +improved" his pigeons by crossing the breeds; and this necessarily implies +careful selection. About the same period the Dutch attended with the +greatest care to the breeding of these birds. Belon in 1555 says that good +managers in France examined the colour of their goslings in order to get +geese of a white colour and better kinds. Markham in 1631 tells the breeder +"to elect the largest and goodliest conies," and enters into minute +details. Even with respect to seeds of plants for the flower-garden, Sir J. +Hanmer writing about the year 1660[487] says, in "choosing seed, the best +seed is the most weighty, and is had from the lustiest and most vigorous +stems;" and he then gives rules about leaving only a few flowers on plants +for seed; so that even such details were attended to in our flower-gardens +two hundred years ago. In order to show that selection has been silently +carried on in places where it would not have been expected, I may add that +in the middle of the last century, in a remote part of North America, Mr. +Cooper improved by careful selection all his vegetables, "so that they were +greatly superior to those of any other person. When his radishes, for +instance, are fit for use, he takes ten or twelve that he most approves, +and plants them at least 100 yards from others that blossom at the same +time. In the same manner he treats all his other plants, varying the +circumstances according to their nature."[488] + +In the great work on China published in the last century by the Jesuits, +and which is chiefly compiled from ancient Chinese encyclopædias, it is +said that with sheep "improving the breed consists in choosing with +particular care the lambs which are destined for propagation, in nourishing +them well, and in keeping the flocks separate." The same principles were +applied by the Chinese to various plants and fruit-trees.[489] An {205} +imperial edict recommends the choice of seed of remarkable size; and +selection was practised even by imperial hands, for it is said that the +Ya-mi, or imperial rice, was noticed at an ancient period in a field by the +Emperor Khang-hi, was saved and cultivated in his garden, and has since +become valuable from being the only kind which will grow north of the Great +Wall.[490] Even with flowers, the tree pæony (_P. moutan_) has been +cultivated, according to Chinese traditions, for 1400 years; between 200 +and 300 varieties have been raised, which are cherished like tulips +formerly were by the Dutch.[491] + +Turning now to semi-civilised people and to savages: it occurred to me, +from what I had seen of several parts of South America, where fences do not +exist, and where the animals are of little value, that there would be +absolutely no care in breeding or selecting them; and this to a large +extent is true. Roulin,[492] however, describes in Colombia a naked race of +cattle, which are not allowed to increase, on account of their delicate +constitution. According to Azara[493] horses are often born in Paraguay +with curly hair; but, as the natives do not like them, they are destroyed. +On the other hand, Azara states that a hornless bull, born in 1770, was +preserved and propagated its race. I was informed of the existence in Banda +Oriental of a breed with reversed hair; and the extraordinary niata cattle +first appeared and have since been kept distinct in La Plata. Hence certain +conspicuous variations have been preserved, and others have been habitually +destroyed, in these countries, which are so little favourable for careful +selection. We have also seen that the inhabitants sometimes introduce +cattle on their estates to prevent the evil effects of close interbreeding. +On the other hand, I have heard on reliable authority that the Gauchos of +the Pampas never take any pains in selecting the best bulls or stallions +for breeding; and this probably accounts for the cattle and horses being +remarkably uniform in character throughout the immense range of the +Argentine republic. + +Looking to the Old World, in the Sahara Desert "The Touareg is as careful +in the selection of his breeding Mahari {206} (a fine race of the +dromedary) as the Arab is in that of his horse. The pedigrees are handed +down, and many a dromedary can boast a genealogy far longer than the +descendants of the Darley Arabian."[494] According to Pallas the Mongolians +endeavour to breed the Yaks or horse-tailed buffaloes with white tails, for +these are sold to the Chinese mandarins as fly-flappers; and Moorcroft, +about seventy years after Pallas, found that white-tailed animals were +still selected for breeding.[495] + +We have seen in the chapter on the Dog that savages in different parts of +North America and in Guiana cross their dogs with wild Canidæ, as did the +ancient Gauls, according to Pliny. This was done to give their dogs +strength and vigour, in the same way as the keepers in large warrens now +sometimes cross their ferrets (as I have been informed by Mr. Yarrell) with +the wild polecat, "to give them more devil." According to Varro, the wild +ass was formerly caught and crossed with the tame animal to improve the +breed, in the same manner as at the present day the natives of Java +sometimes drive their cattle into the forests to cross with the wild +Banteng (_Bos sondaicus_).[496] In Northern Siberia, among the Ostyaks the +dogs vary in markings in different districts, but in each place they are +spotted black and white in a remarkably uniform manner;[497] and from this +fact alone we may infer careful breeding, more especially as the dogs of +one locality are famed throughout the country for their superiority. I have +heard of certain tribes of Esquimaux who take pride in their teams of dogs +being uniformly coloured. In Guiana, as Sir R. Schomburgk informs me,[498] +the dogs of the Turuma Indians are highly valued and extensively bartered: +the price of a good one is the same as that given for a wife: they are kept +in a sort of cage, and the Indians "take great care when the female is in +season to prevent her uniting with a dog of an inferior description." The +Indians told Sir Robert that, if a dog proved bad or useless, {207} he was +not killed, but was left to die from sheer neglect. Hardly any nation is +more barbarous than the Fuegians, but I hear from Mr. Bridges, the +Catechist to the Mission, that, "when these savages have a large, strong, +and active bitch, they take care to put her to a fine dog, and even take +care to feed her well, that her young may be strong and well favoured." + +In the interior of Africa, negroes, who have not associated with white men, +show great anxiety to improve their animals: they "always choose the larger +and stronger males for stock:" the Malakolo were much pleased at +Livingstone's promise to send them a bull, and some Bakalolo carried a live +cock all the way from Loanda into the interior.[499] Further south on the +same continent, Andersson states that he has known a Damara give two fine +oxen for a dog which struck his fancy. The Damaras take great delight in +having whole droves of cattle of the same colour, and they prize their oxen +in proportion to the size of their horns. "The Namaquas have a perfect +mania for a uniform team; and almost all the people of Southern Africa +value their cattle next to their women, and take a pride in possessing +animals that look high-bred." "They rarely or never make use of a handsome +animal as a beast of burden."[500] The power of discrimination which these +savages possess is wonderful, and they can recognise to which tribe any +cattle belong. Mr. Andersson further informs me that the natives frequently +match a particular bull with a particular cow. + +The most curious case of selection by semi-civilised people, or indeed by +any people, which I have found recorded, is that given by Garcilazo de la +Vega, a descendant of the Incas, as having been practised in Peru before +the country was subjugated by the Spaniards.[501] The Incas annually held +great hunts, when all the wild animals were driven from an immense circuit +to a central point. The beasts of prey were first destroyed as injurious. +The wild Guanacos and Vicunas were sheared; the old males and females +killed, and the others set at liberty. The various kinds of deer were +examined; the old males and females {208} were likewise killed; "but the +young females, with a certain number of males, selected from the most +beautiful and strong," were given their freedom. Here, then, we have +selection by man aiding natural selection. So that the Incas followed +exactly the reverse system of that which our Scottish sportsmen are accused +of following, namely, of steadily killing the finest stags, thus causing +the whole race to degenerate.[502] In regard to the domesticated llamas and +alpacas, they were separated in the time of the Incas according to colour; +and if by chance one in a flock was born of the wrong colour, it was +eventually put into another flock. + +In the genus Auchenia there are four forms,--the Guanaco and Vicuna, found +wild and undoubtedly distinct species; the Llama and Alpaca, known only in +a domesticated condition. These four animals appear so different, that most +professed naturalists, especially those who have studied these animals in +their native country, maintain that they are specifically distinct, +notwithstanding that no one pretends to have seen a wild llama or alpaca. +Mr. Ledger, however, who has closely studied these animals both in Peru and +during their exportation to Australia, and who has made many experiments on +their propagation, adduces arguments[503] which seem to me conclusive, that +the llama is the domesticated descendant of the guanaco, and the alpaca of +the vicuna. And now that we know that these animals many centuries ago were +systematically bred and selected, there is nothing surprising in the great +amount of change which they have undergone. + +It appeared to me at one time probable that, though ancient and +semi-civilised people might have attended to the improvement of their more +useful animals in essential points, yet that they would have disregarded +unimportant characters. But human nature is the same throughout the world: +fashion everywhere reigns supreme, and man is apt to value whatever he may +chance to possess. We have seen that in South America the niata cattle, +which certainly are not made useful by their shortened faces and upturned +nostrils, have been preserved. The Damaras of South Africa value their +cattle for uniformity {209} of colour and enormously long horns. The +Mongolians value their yaks for their white tails. And I shall now show +that there is hardly any peculiarity in our most useful animals which, from +fashion, superstition, or some other motive, has not been valued, and +consequently preserved. With respect to cattle, "an early record," +according to Youatt,[504] "speaks of a hundred white cows with red ears +being demanded as a compensation by the princes of North and South Wales. +If the cattle were of a dark or black colour, 150 were to be presented." So +that colour was attended to in Wales before its subjugation by England. In +Central Africa, an ox that beats the ground with its tail is killed; and in +South Africa some of the Damaras will not eat the flesh of a spotted ox. +The Kaffirs value an animal with a musical voice; and "at a sale in British +Kaffraria the low of a heifer excited so much admiration that a sharp +competition sprung up for her possession, and she realised a considerable +price."[505] With respect to sheep, the Chinese prefer rams without horns; +the Tartars prefer them with spirally wound horns, because the hornless are +thought to lose courage.[506] Some of the Damaras will not eat the flesh of +hornless sheep. In regard to horses, at the end of the fifteenth century +animals of the colour described as _liart pommé_ were most valued in +France. The Arabs have a proverb, "Never buy a horse with four white feet, +for he carries his shroud with him;"[507] the Arabs also, as we have seen, +despise dun-coloured horses. So with dogs, Xenophon and others at an +ancient period were prejudiced in favour of certain colours; and "white or +slate-coloured hunting dogs were not esteemed."[508] + +Turning to poultry, the old Roman gourmands thought that the liver of a +white goose was the most savoury. In Paraguay black-skinned fowls are kept +because they are thought to be more productive, and their flesh the most +proper for invalids.[509] In Guiana, as I am informed by Sir R. Schomburgk, +the aborigines will not eat the flesh or eggs of the fowl, but two {210} +races are kept distinct merely for ornament. In the Philippines, no less +than nine sub-varieties of the game cock are kept and named, so that they +must be separately bred. + +At the present time in Europe, the smallest peculiarities are carefully +attended to in our most useful animals, either from fashion, or as a mark +of purity of blood. Many examples could be given, two will suffice. "In the +Western counties of England the prejudice against a white pig is nearly as +strong as against a black one in Yorkshire." In one of the Berkshire +sub-breeds, it is said, "the white should be confined to four white feet, a +white spot between the eyes, and a few white hairs behind each shoulder." +Mr. Saddler possessed "three hundred pigs, every one of which was marked in +this manner."[510] Marshall, towards the close of the last century, in +speaking of a change in one of the Yorkshire breeds of cattle, says the +horns have been considerably modified, as "a clean, small, sharp horn has +been _fashionable_ for the last twenty years."[511] In a part of Germany +the cattle of the Race de Gfoehl are valued for many good qualities, but +they must have horns of a particular curvature and tint, so much so that +mechanical means are applied if they take a wrong direction; but the +inhabitants "consider it of the highest importance that the nostrils of the +bull should be flesh-coloured, and the eyelashes light; this is an +indispensable condition. A calf with blue nostrils would not be purchased, +or purchased at a very low price."[512] Therefore let no man say that any +point or character is too trifling to be methodically attended to and +selected by breeders. + + * * * * * + +_Unconscious Selection._--By this term I mean, as already more than once +explained, the preservation by man of the most valued, and the destruction +of the least valued individuals, without any conscious intention on his +part of altering the breed. It is difficult to offer direct proofs of the +results which follow from this kind of selection; but the indirect evidence +is abundant. In fact, except that in the one case man acts intentionally, +and in the other unintentionally, there is little difference between {211} +methodical and unconscious selection. In both cases man preserves the +animals which are most useful or pleasing to him, and destroys or neglects +the others. But no doubt a far more rapid result follows from methodical +than from unconscious selection. The "roguing" of plants by gardeners, and +the destruction by law in Henry VIII.'s reign of all under-sized mares, are +instances of a process the reverse of selection in the ordinary sense of +the word, but leading to the same general result. The influence of the +destruction of individuals having a particular character is well shown by +the necessity of killing every lamb with a trace of black about it, in +order to keep the flock white; or again, by the effects on the average +height of the men of France of the destructive wars of Napoleon, by which +many tall men were killed, the short ones being left to be the fathers of +families. This at least is the conclusion of those who have closely studied +the subject of the conscription; and it is certain that since Napoleon's +time the standard for the army has been lowered two or three times. + +Unconscious selection so blends into methodical that it is scarcely +possible to separate them. When a fancier long ago first happened to notice +a pigeon with an unusually short beak, or one with the tail-feathers +unusually developed, although he bred from these birds with the distinct +intention of propagating the variety, yet he could not have intended to +make a short-faced tumbler or a fantail, and was far from knowing that he +had made the first step towards this end. If he could have seen the final +result, he would have been struck with astonishment, but, from what we know +of the habits of fanciers, probably not with admiration. Our English +carriers, barbs, and short-faced tumblers have been greatly modified in the +same manner, as we may infer both from the historical evidence given in the +chapters on the Pigeon, and from the comparison of birds brought from +distant countries. + +So it has been with dogs; our present fox-hounds differ from the old +English hound; our greyhounds have become lighter; the wolf-dog, which +belonged to the greyhound class, has become extinct; the Scotch deer-hound +has been modified, and is now rare. Our bulldogs differ from those which +were formerly used for baiting bulls. Our pointers and Newfoundlands do not +{212} closely resemble any native dog now found in the countries whence +they were brought, These changes have been effected partly by crosses; but +in every case the result has been governed by the strictest selection. +Nevertheless there is no reason to suppose that man intentionally and +methodically made the breeds exactly what they now are. As our horses +became fleeter, and the country more cultivated and smoother, fleeter +fox-hounds were desired and produced, but probably without any one +distinctly foreseeing what they would become. Our pointers and setters, the +latter almost certainly descended from large spaniels, have been greatly +modified in accordance with fashion and the desire for increased speed. +Wolves have become extinct, deer have become rarer, bulls are no longer +baited, and the corresponding breeds of the dog have answered to the +change. But we may feel almost sure that when, for instance, bulls were no +longer baited, no man said to himself, I will now breed my dogs of smaller +size, and thus create the present race. As circumstances changed, men +unconsciously and slowly modified their course of selection. + +With race-horses selection for swiftness has been followed methodically, +and our horses can now easily beat their progenitors. The increased size +and different appearance of the English race-horse led a good observer in +India to ask, "Could any one in this year of 1856, looking at our +race-horses, conceive that they were the result of the union of the Arab +horse and the African mare?"[513] This change has, it is probable, been +largely effected through unconscious selection, that is, by the general +wish to breed as fine horses as possible in each generation, combined with +training and high feeding, but without any intention to give to them their +present appearance. According to Youatt,[514] the introduction in Oliver +Cromwell's time of three celebrated Eastern stallions speedily affected the +English breed; "so that Lord Harleigh, one of the old school, complained +that the great horse was fast disappearing." This is an excellent proof how +carefully selection must have been attended to; for without such care, all +traces of so small an infusion of Eastern blood would soon have been +absorbed and {213} lost. Notwithstanding that the climate of England has +never been esteemed particularly favourable to the horse, yet +long-continued selection, both methodical and unconscious, together with +that practised by the Arabs during a still longer and earlier period, has +ended in giving us the best breed of horses in the world. Macaulay[515] +remarks, "Two men whose authority on such subjects was held in great +esteem, the Duke of Newcastle and Sir John Fenwick, pronounced that the +meanest hack ever imported from Tangier would produce a finer progeny than +could be expected from the best sire of our native breed. They would not +readily have believed that a time would come when the princes and nobles of +neighbouring lands would be as eager to obtain horses from England as ever +the English had been to obtain horses from Barbary." + +The London dray-horse, which differs so much in appearance from any natural +species, and which from its size has so astonished many Eastern princes, +was probably formed by the heaviest and most powerful animals having been +selected during many generations in Flanders and England, but without the +least intention or expectation of creating a horse such as we now see. If +we go back to an early period of history, we behold in the antique Greek +statues, as Schaaffhausen has remarked,[516] a horse equally unlike a race +or dray horse, and differing from any existing breed. + +The results of unconscious selection, in an early stage, are well shown in +the difference between the flocks descended from the same stock, but +separately reared by careful breeders. Youatt gives an excellent instance +of this fact in the sheep belonging to Messrs. Buckley and Burgess, which +"have been purely bred from the original stock of Mr. Bakewell for upwards +of fifty years. There is not a suspicion existing in the mind of any one at +all acquainted with the subject that the owner of either flock has deviated +in any one instance from the pure blood of Mr. Bakewell's flock; yet the +difference between the sheep possessed by these two gentlemen is so great, +that they have the appearance of being quite different varieties."[517] I +have seen several analogous and {214} well-marked cases with pigeons: for +instance, I had a family of barbs, descended from those long bred by Sir J. +Sebright, and another family long bred by another fancier, and the two +families plainly differed from each other. Nathusius--and a more competent +witness could not be cited--observes that, though the Shorthorns are +remarkably uniform inn appearance (except in colouring), yet that the +individual character and wishes of each breeder become impressed on his +cattle, so that different herds differ slightly from each other.[518] The +Hereford cattle assumed their present well-marked character soon after the +year 1769, through careful selection by Mr. Tomkins,[519] and the breed has +lately split into two strains--one strain having a white face, and +differing slightly, it is said,[520] in some other points; but there is no +reason to believe that this split, the origin of which is unknown, was +intentionally made; it may with much more probability be attributed to +different breeders having attended to different points. So again, the +Berkshire breed of swine in the year 1810 had greatly changed from what it +had been in 1780; and since 1810 at least two distinct sub-breeds have +borne this same name.[521] When we bear in mind how rapidly all animals +increase, and that some must be annually slaughtered and some saved for +breeding, then, if the same breeder during a long course of years +deliberately settles which shall be saved and which shall be killed, it is +almost inevitable that his individual frame of mind will influence the +character of his stock, without his having had any intention to modify the +breed or form a new strain. + +Unconscious selection in the strictest sense of the word, that is, the +saving of the more useful animals and the neglect or slaughter of the less +useful, without any thought of the future, must have gone on occasionally +from the remotest period and amongst the most barbarous nations. Savages +often suffer from famines, and are sometimes expelled by war from their own +homes. In such cases it can hardly be doubted that they would save their +most useful animals. When the Fuegians {215} are hard pressed by want, they +kill their old women for food rather than their dogs; for, as we were +assured, "old women no use--dogs catch otters." The same sound sense would +surely lead them to preserve their more useful dogs when still harder +pressed by famine. Mr. Oldfield, who has seen so much of the aborigines of +Australia, informs me that "they are all very glad to get a European +kangaroo dog, and several instances have been known of the father killing +his own infant that the mother might suckle the much-prized puppy." +Different kinds of dogs would be useful to the Australian for hunting +opossums and kangaroos, and to the Fuegian for catching fish and otters; +and the occasional preservation in the two countries of the most useful +animals would ultimately lead to the formation of two widely distinct +breeds. + + * * * * * + +With plants, from the earliest dawn of civilisation, the best variety which +at each period was known would generally have been cultivated and its seeds +occasionally sown; so that there will have been some selection from an +extremely remote period, but without any prefixed standard of excellence or +thought of the future. We at the present day profit by a course of +selection occasionally and unconsciously carried on during thousands of +years. This is proved in an interesting manner by Oswald Heer's researches +on the lake-inhabitants of Switzerland, as given in a former chapter; for +he shows that the grain and seed of our present varieties of wheat, barley, +oats, peas, beans, lentils, and poppy, exceed in size those which were +cultivated in Switzerland during the Neolithic and Bronze periods. These +ancient people, during the Neolithic period, possessed also a crab +considerably larger than that now growing wild on the Jura.[522] The pears +described by Pliny were evidently extremely inferior in quality to our +present pears. We can realise the effects of long-continued selection and +cultivation in another way, for would any one in his senses expect to raise +a first-rate apple from the seed of a truly wild crab, or a luscious +melting pear from the wild pear? Alphonse De Candolle informs me that he +has lately seen on an ancient mosaic at Rome a representation of {216} the +melon; and as the Romans, who were such gourmands, are silent on this +fruit, he infers that the melon has been greatly ameliorated since the +classical period. + +Coming to later times, Buffon,[523] on comparing the flowers, fruit, and +vegetables which were then cultivated, with some excellent drawings made a +hundred and fifty years previously, was struck with surprise at the great +improvement which had been effected; and remarks that these ancient flowers +and vegetables would now be rejected, not only by a florist but by a +village gardener. Since the time of Buffon the work of improvement has +steadily and rapidly gone on. Every florist who compares our present +flowers with those figured in books published not long since, is astonished +at the change. A well-known amateur,[524] in speaking of the varieties of +Pelargonium raised by Mr. Garth only twenty-two years before, remarks, +"what a rage they excited: surely we had attained perfection, it was said; +and now not one of the flowers of those days will be looked at. But none +the less is the debt of gratitude which we owe to those who saw what was to +be done, and did it." Mr. Paul, the well-known horticulturist, in writing +of the same flower,[525] says he remembers when young being delighted with +the portraits in Sweet's work; "but what are they in point of beauty +compared with the Pelargoniums of this day? Here again nature did not +advance by leaps; the improvement was gradual, and, if we had neglected +those very gradual advances, we must have foregone the present grand +results." How well this practical horticulturist appreciates and +illustrates the gradual and accumulative force of selection! The Dahlia has +advanced in beauty in a like manner; the line of improvement being guided +by fashion, and by the successive modifications which the flower slowly +underwent.[526] A steady and gradual change has been noticed in many other +flowers: thus an old florist,[527] after describing the leading varieties +of the Pink which were grown in 1813, adds, "the pinks of those days would +now be scarcely grown as border-flowers." The improvement of {217} so many +flowers and the number of the varieties which have been raised is all the +more striking when we hear that the earliest known flower-garden in Europe, +namely at Padua, dates only from the year 1545.[528] + + * * * * * + +_Effects of Selection, as shown by the parts most valued by man presenting +the greatest amount of Difference._--The power of long-continued selection, +whether methodical or unconscious, or both combined, is well shown in a +general way, namely, by the comparison of the differences between the +varieties of distinct species, which are valued for different parts, such +as for the leaves, or stems, or tubers, the seed, or fruit, or flowers. +Whatever part man values most, that part will be found to present the +greatest amount of difference. With trees cultivated for their fruit, +Sageret remarks that the fruit is larger than in the parent-species, whilst +with those cultivated for the seed, as with nuts, walnuts, almonds, +chesnuts, &c., it is the seed itself which is larger; and he accounts for +this fact by the fruit in the one case, and by the seed in the other, +having been carefully attended to and selected during many ages. Gallesio +has made the same observation. Godron insists on the diversity of the tuber +in the potato, of the bulb in the onion, and of the fruit in the melon; and +on the close similarity in these same plants of the other parts.[529] + +In order to judge how far my own impression on this subject was correct, I +cultivated numerous varieties of the same species close to each other. The +comparison of the amount of difference between widely different organs is +necessarily vague; I will therefore give the results in only a few cases. +We have previously seen in the ninth chapter how greatly the varieties of +the cabbage differ in their foliage and stems, which are the selected +parts, and how closely they resembled each other in their flowers, +capsules, and seeds. In seven varieties of the radish, the roots differed +greatly in colour and shape, but no difference {218} whatever could be +detected in their foliage, flowers, or seeds. Now what a contrast is +presented, if we compare the flowers of the varieties of these two plants +with those of any species cultivated in our flower-gardens for ornament; or +if we compare their seeds with those of the varieties of maize, peas, +beans, &c., which are valued and cultivated for their seeds. In the ninth +chapter it was shown that the varieties of the pea differ but little except +in the tallness of the plant, moderately in the shape of the pod, and +greatly in the pea itself, and these are all selected points. The +varieties, however, of the _Pois sans parchemin_ differ much more in their +pods, and these are eaten and valued. I cultivated twelve varieties of the +common bean; one alone, the Dwarf Fan, differed considerably in general +appearance; two differed in the colour of their flowers, one being an +albino, and the other being wholly instead of partially purple; several +differed considerably in the shape and size of the pod, but far more in the +bean itself, and this is the valued and selected part. Toker's bean, for +instance, is twice-and-a-half as long and broad as the horse-bean, and is +much thinner and of a different shape. + +The varieties of the gooseberry, as formerly described, differ much in +their fruit, but hardly perceptibly in their flowers or organs of +vegetation. With the plum, the differences likewise appear to be greater in +the fruit than in the flowers or leaves. On the other hand, the seed of the +strawberry, which corresponds with the fruit of the plum, differs hardly at +all; whilst every one knows how greatly the fruit--that is, the enlarged +receptacle--differs in the several varieties. In apples, pears, and peaches +the flowers and leaves differ considerably, but not, as far as I can judge, +in proportion with the fruit. The Chinese double-flowering peaches, on the +other hand, show that varieties of this tree have been formed, which differ +more in the flower than in fruit. If, as is highly probable, the peach is +the modified descendant of the almond, a surprising amount of change has +been effected in the same species, in the fleshy covering of the former and +in the kernels of the latter. + +When parts stand in such close relation to each other as the fleshy +covering of the fruit (whatever its homological nature may be) and the +seed, when one part is modified, so generally is the other, but by no means +necessarily in the same degree. With {219} the plum-tree, for instance, +some varieties produce plums which are nearly alike, but include stones +extremely dissimilar in shape; whilst conversely other varieties produce +dissimilar fruit with barely distinguishable stones; and generally the +stones, though they have never been subjected to selection, differ greatly +in the several varieties of the plum. In other cases organs which are not +manifestly related, through some unknown bond vary together, and are +consequently liable, without any intention on man's part, to be +simultaneously acted on by selection. Thus the varieties of the stock +(Matthiola) have been selected solely for the beauty of their flowers, but +the seeds differ greatly in colour and somewhat in size. Varieties of the +lettuce have been selected solely on account of their leaves, yet produce +seeds which likewise differ in colour. Generally, through the law of +correlation, when a variety differs greatly from its fellow-varieties in +any one character, it differs to a certain extent in several other +characters. I observed this fact when I cultivated together many varieties +of the same species, for I used first to make a list of the varieties which +differed most from each other in their foliage and manner of growth, +afterwards of those that differed most in their flowers, then in their +seed-capsules, and lastly in their mature seed; and I found that the same +names generally occurred in two, three, or four of the successive lists. +Nevertheless the greatest amount of difference between the varieties was +always exhibited, as far as I could judge, by that part or organ for which +the plant was cultivated. + +When we bear in mind that each plant was at first cultivated because useful +to man, and that its variation was a subsequent, often a long subsequent, +event, we cannot explain the greater amount of diversity in the valuable +parts by supposing that species endowed with an especial tendency to vary +in any particular manner, were originally chosen. We must attribute the +result to the variations in these parts having been successively preserved, +and thus continually augmented; whilst other variations, excepting such as +inevitably appeared through correlation, were neglected and lost. Hence we +may infer that most plants might be made, through long-continued selection, +to yield races as different from each other in any character {220} as they +now are in those parts for which they are valued and cultivated. + +With animals we see something of the same kind; but they have not been +domesticated in sufficient number or yielded sufficient varieties for a +fair comparison. Sheep are valued for their wool, and the wool differs much +more in the several races than the hair in cattle. Neither sheep, goats, +European cattle, nor pigs are valued for their fleetness or strength; and +we do not possess breeds differing in these respects like the race-horse +and dray-horse. But fleetness and strength are valued in camels and dogs; +and we have with the former the swift dromedary and heavy camel; with the +latter the greyhound and mastiff. But dogs are valued even in a higher +degree for their mental qualities and senses; and every one knows how +greatly the races differ in these respects. On the other hand, where the +dog is valued solely to serve for food, as in the Polynesian islands and +China, it is described as an extremely stupid animal.[530] Blumenbach +remarks that "many dogs, such as the badger-dog, have a build so marked and +so appropriate for particular purposes, that I should find it very +difficult to persuade myself that this astonishing figure was an accidental +consequence of degeneration."[531] But had Blumenbach reflected on the +great principle of selection, he would not have used the term degeneration, +and he would not have been astonished that dogs and other animals should +become excellently adapted for the service of man. + +On the whole we may conclude that whatever part or character is most +valued--whether the leaves, stems, tubers, bulbs, flowers, fruit, or seed +of plants, or the size, strength, fleetness, hairy covering, or intellect +of animals--that character will almost invariably be found to present the +greatest amount of difference both in kind and degree. And this result may +be safely attributed to man having preserved during a long course of +generations the variations which were useful to him, and neglected the +others. + +I will conclude this chapter by some remarks on an important subject. With +animals such as the giraffe, of which {221} the whole structure is +admirably co-ordinated for certain purposes, it has been supposed that all +the parts must have been simultaneously modified; and it has been argued +that, on the principle of natural selection, this is scarcely possible. But +in thus arguing, it has been tacitly assumed that the variations must have +been abrupt and great. No doubt, if the neck of a ruminant were suddenly to +become greatly elongated, the fore limbs and back would have to be +simultaneously strengthened and modified; but it cannot be denied that an +animal might have its neck, or head, or tongue, or fore-limbs elongated a +very little without any corresponding modification in other parts of the +body; and animals thus slightly modified would, during a dearth, have a +slight advantage, and be enabled to browse on higher twigs, and thus +survive. A few mouthfuls more or less every day would make all the +difference between life and death. By the repetition of the same process, +and by the occasional intercrossing of the survivors, there would be some +progress, slow and fluctuating though it would be, towards the admirably +co-ordinated structure of the giraffe. If the short-faced tumbler-pigeon, +with its small conical beak, globular head, rounded body, short wings, and +small feet--characters which appear all in harmony--had been a natural +species, its whole structure would have been viewed as well fitted for its +life; but in this case we know that inexperienced breeders are urged to +attend to point after point, and not to attempt improving the whole +structure at the same time. Look at the greyhound, that perfect image of +grace, symmetry, and vigour; no natural species can boast of a more +admirably co-ordinated structure, with its tapering head, slim body, deep +chest, tucked-up abdomen, rat-like tail, and long muscular limbs, all +adapted for extreme fleetness, and for running down weak prey. Now, from +what we see of the variability of animals, and from what we know of the +method which different men follow in improving their stock--some chiefly +attending to one point, others to another point, others again correcting +defects by crosses, and so forth--we may feel assured that if we could see +the long line of ancestors of a first-rate greyhound, up to its wild +wolf-like progenitor, we should behold an infinite number of the finest +gradations, sometimes in one character and sometimes in another, but all +leading towards our {222} present perfect type. By small and doubtful steps +such as these, nature, as we may confidently believe, has progressed on her +grand march of improvement and development. + +A similar line of reasoning is as applicable to separate organs as to the +whole organisation. A writer[532] has recently maintained that "it is +probably no exaggeration to suppose that, in order to improve such an organ +as the eye at all, it must be improved in ten different ways at once. And +the improbability of any complex organ being produced and brought to +perfection in any such way is an improbability of the same kind and degree +as that of producing a poem or a mathematical demonstration by throwing +letters at random on a table." If the eye were abruptly and greatly +modified, no doubt many parts would have to be simultaneously altered, in +order that the organ should remain serviceable. + +But is this the case with smaller changes? There are persons who can see +distinctly only in a dull light, and this condition depends, I believe, on +the abnormal sensitiveness of the retina, and is known to be inherited. +Now, if a bird, for instance, received some great advantage from seeing +well in the twilight, all the individuals with the most sensitive retina +would succeed best and be the most likely to survive; and why should not +all those which happened to have the eye itself a little larger, or the +pupil capable of greater dilatation, be likewise preserved, whether or not +these modifications were strictly simultaneous? These individuals would +subsequently intercross and blend their respective advantages. By such +slight successive changes, the eye of a diurnal bird would be brought into +the condition of that of an owl, which has often been advanced as an +excellent instance of adaptation. Short-sight, which is often inherited, +permits a person to see distinctly a minute object at so near a distance +that it would be indistinct to ordinary eyes; and here we have a capacity +which might be serviceable under certain conditions, abruptly gained. The +Fuegians on board the {223} Beagle could certainly see distant objects more +distinctly than our sailors with all their long practice; I do not know +whether this depends on nervous sensitiveness or on the power of adjustment +in the focus; but this capacity for distant vision might, it is probable, +be slightly augmented by successive modifications of either kind. +Amphibious animals, which are enabled to see both in the water and in the +air, require and possess, as M. Plateau has shown,[533] eyes constructed on +the following plan: "the cornea is always flat, or at least much flattened +in front of the crystalline and over a space equal to the diameter of that +lens, whilst the lateral portions may be much curved." The crystalline is +very nearly a sphere, and the humours have nearly the same density as +water. Now, as a terrestrial animal slowly became more and more aquatic in +its habits, very slight changes, first in the curvature of the cornea or +crystalline, and then in the density of the humours, or conversely, might +successively occur, and would be advantageous to the animal whilst under +water, without serious detriment to its power of vision in the air. It is +of course impossible to conjecture by what steps the fundamental structure +of the eye in the Vertebrata was originally acquired, for we know +absolutely nothing about this organ in the first progenitors of the class. +With respect to the lowest animals in the scale, the transitional states +through which the eye at first probably passed, can by the aid of analogy +be indicated, as I have attempted to show in my 'Origin of Species.'[534] + + * * * * * + + +{224} + +CHAPTER XXI. + +SELECTION, _continued_. + + NATURAL SELECTION AS AFFECTING DOMESTIC PRODUCTIONS--CHARACTERS WHICH + APPEAR OF TRIFLING VALUE OFTEN OF REAL IMPORTANCE--CIRCUMSTANCES + FAVOURABLE TO SELECTION BY MAN--FACILITY IN PREVENTING CROSSES, AND THE + NATURE OF THE CONDITIONS--CLOSE ATTENTION AND PERSEVERANCE + INDISPENSABLE--THE PRODUCTION OF A LARGE NUMBER OF INDIVIDUALS + ESPECIALLY FAVOURABLE--WHEN NO SELECTION IS APPLIED, DISTINCT RACES ARE + NOT FORMED--HIGHLY-BRED ANIMALS LIABLE TO DEGENERATION--TENDENCY IN MAN + TO CARRY THE SELECTION OF EACH CHARACTER TO AN EXTREME POINT, LEADING + TO DIVERGENCE OF CHARACTER, RARELY TO CONVERGENCE--CHARACTERS + CONTINUING TO VARY IN THE SAME DIRECTION IN WHICH THEY HAVE ALREADY + VARIED--DIVERGENCE OF CHARACTER, WITH THE EXTINCTION OF INTERMEDIATE + VARIETIES, LEADS TO DISTINCTNESS IN OUR DOMESTIC RACES--LIMIT TO THE + POWER OF SELECTION--LAPSE OF TIME IMPORTANT--MANNER IN WHICH DOMESTIC + RACES HAVE ORIGINATED--SUMMARY. + +_Natural Selection, or the Survival of the Fittest, as affecting domestic +productions._--We know little on this head. But as animals kept by savages +have to provide their own food, either entirely or to a large extent, +throughout the year, it can hardly be doubted that, in different countries, +varieties differing in constitution and in various characters would succeed +best, and so be naturally selected. Hence perhaps it is that the few +domesticated animals kept by savages partake, as has been remarked by more +than one writer, of the wild appearance of their masters, and likewise +resemble natural species. Even in long-civilised countries, at least in the +wilder parts, natural selection must act on our domestic races. It is +obvious that varieties, having very different habits, constitution, and +structure, would succeed best on mountains and on rich lowland pastures. +For example, the improved Leicester sheep were formerly taken to the +Lammermuir Hills; but an intelligent sheep-master reported that "our coarse +lean pastures were unequal to the task of supporting such heavy-bodied +sheep; and they gradually dwindled away into less and less bulk: {225} each +generation was inferior to the preceding one; and when the spring was +severe, seldom more than two-thirds of the lambs survived the ravages of +the storms."[535] So with the mountain cattle of North Wales and the +Hebrides, it has been found that they could not withstand being crossed +with the larger and more delicate lowland breeds. Two French naturalists, +in describing the horses of Circassia, remark that, subjected as they are +to extreme vicissitudes of climate, having to search for scanty pasture, +and exposed to constant danger from wolves, the strongest and most vigorous +alone survive.[536] + +Every one must have been struck with the surpassing grace, strength, and +vigour of the Game-cock, with its bold and confident air, its long, yet +firm neck, compact body, powerful and closely pressed wings, muscular +thighs, strong beak massive at the base, dense and sharp spurs set low on +the legs for delivering the fatal blow, and its compact, glossy, and +mail-like plumage serving as a defence. Now the English game-cock has not +only been improved during many years by man's careful selection, but in +addition, as Mr. Tegetmeier has remarked,[537] by a kind of natural +selection, for the strongest, most active and courageous birds have +stricken down their antagonists in the cockpit, generation after +generation, and have subsequently served as the progenitors of their kind. + +In Great Britain, in former times, almost every district had its own breed +of cattle and sheep; "they were indigenous to the soil, climate, and +pasturage of the locality on which they grazed: they seemed to have been +formed for it and by it."[538] But in this case we are quite unable to +disentangle the effects of the direct action of the conditions of life,--of +use or habit--of natural selection--and of that kind of selection which we +have seen is occasionally and unconsciously followed by man even during the +rudest periods of history. + +Let us now look to the action of natural selection on special characters. +Although nature is difficult to resist, yet man often strives against her +power, and sometimes, as we shall see, with {226} success. From the facts +to be given, it will also be seen that natural selection would powerfully +affect many of our domestic productions if left unprotected. This is a +point of much interest, for we thus learn that differences apparently of +very slight importance would certainly determine the survival of a form +when forced to struggle for its own existence. It may have occurred to some +naturalists, as it formerly did to me, that, though selection acting under +natural conditions would determine the structure of all important organs, +yet that it could not affect characters which are esteemed by us of little +importance; but this is an error to which we are eminently liable, from our +ignorance of what characters are of real value to each living creature. + +When man attempts to breed an animal with some serious defect in structure, +or in the mutual relation of parts, he will either partially or completely +fail, or encounter much difficulty; and this is in fact a form of natural +selection. We have seen that the attempt was once made in Yorkshire to +breed cattle with enormous buttocks, but the cows perished so often in +bringing forth their calves, that the attempt had to be given up. In +rearing short-faced tumblers, Mr. Eaton says,[539] "I am convinced that +better head and beak birds have perished in the shell than ever were +hatched; the reason being that the amazingly short-faced bird cannot reach +and break the shell with its beak, and so perishes." Here is a more curious +case, in which natural selection comes into play only at long intervals of +time: during ordinary seasons the Niata cattle can graze as well as others, +but occasionally, as from 1827 to 1830, the plains of La Plata suffer from +long-continued droughts and the pasture is burnt up; at such times common +cattle and horses perish by the thousand, but many survive by browsing on +twigs, reeds, &c.; this the Niata cattle cannot so well effect from their +upturned jaws and the shape of their lips; consequently, if not attended +to, they perish before the other cattle. In Colombia, according to Roulin, +there is a breed of nearly hairless cattle, called Pelones; these succeed +in their native hot district, but are found too tender for the Cordillera; +in this case, natural selection {227} determines only the range of the +variety. It is obvious that a host of artificial races could never survive +in a state of nature;--such as Italian greyhounds,--hairless and almost +toothless Turkish dogs,--fantail pigeons, which cannot fly well against a +strong wind,--barbs with their vision impeded by their eye-wattle,--Polish +fowls with their vision impeded by their great topknots,--hornless bulls +and rams which consequently cannot cope with other males, and thus have a +poor chance of leaving offspring,--seedless plants, and many other such +cases. + +Colour is generally esteemed by the systematic naturalist as unimportant: +let us, therefore, see how far it indirectly affects our domestic +productions, and how far it would affect them if they were left exposed to +the full force of natural selection. In a future chapter I shall have to +show that constitutional peculiarities of the strangest kind, entailing +liability to the action of certain poisons, are correlated with the colour +of the skin. I will here give a single case, on the high authority of +Professor Wyman; he informs me that, being surprised at all the pigs in a +part of Virginia being black, he made inquiries, and ascertained that these +animals feed on the roots of the _Lachnanthes tinctoria_, which colours +their bones pink, and, excepting in the case of the black varieties, causes +the hoofs to drop off. Hence, as one of the squatters remarked, "we select +the black members of the litter for raising, as they alone have a good +chance of living." So that here we have artificial and natural selection +working hand in hand. I may add that in the Tarentino the inhabitants keep +black sheep alone, because the _Hypericum crispum_ abounds there; and this +plant does not injure black sheep, but kills the white ones in about a +fortnight's time.[540] + +Complexion, and liability to certain diseases, are believed to run together +in man and the lower animals. Thus white terriers suffer more than terriers +of any other colour from the fatal Distemper.[541] In North America +plum-trees are liable to a disease which Downing[542] believes is not +caused by insects; the kinds bearing purple fruit are most affected, "and +we have never known the green or yellow fruited varieties infected {228} +until the other sorts had first become filled with the knots." On the other +hand, peaches in North America suffer much from a disease called the +_yellows_, which seems to be peculiar to that continent, and "more than +nine-tenths of the victims, when the disease first appeared, were the +yellow-fleshed peaches. The white-fleshed kinds are much more rarely +attacked; in some parts of the country never." In Mauritius, the white +sugar-canes have of late years been so severely attacked by a disease, that +many planters have been compelled to give up growing this variety (although +fresh plants were imported from China for trial), and cultivate only red +canes.[543] Now, if these plants had been forced to struggle with other +competing plants and enemies, there cannot be a doubt that the colour of +the flesh or skin of the fruit, unimportant as these characters are +considered, would have rigorously determined their existence. + +Liability to the attacks of parasites is also connected with colour. It +appears that white chickens are certainly more subject than dark-coloured +chickens to the _gapes_, which is caused by a parasitic worm in the +trachea.[544] On the other hand, experience has shown that in France the +caterpillars which produce white cocoons resist the deadly fungus better +than those producing yellow cocoons.[545] Analogous facts have been +observed with plants: a new and beautiful white onion, imported from +France, though planted close to other kinds, was alone attacked by a +parasitic fungus.[546] White verbenas are especially liable to mildew.[547] +Near Malaga, during an early period of the vine-disease, the green sorts +suffered most; "and red and black grapes, even when interwoven with the +sick plants, suffered not at all." In France whole groups of varieties were +comparatively free, and others, such as the Chasselas, did not afford a +single fortunate exception; but I do not know whether any correlation +between colour and liability to disease was here observed.[548] In a former +chapter it was shown how curiously liable one variety of the strawberry is +to mildew. + +{229} + +It is certain that insects regulate in many cases the range and even the +existence of the higher animals, whilst living under their natural +conditions. Under domestication light-coloured animals suffer most: in +Thuringia[549] the inhabitants do not like grey, white, or pale cattle, +because they are much more troubled by various kinds of flies than the +brown, red, or black cattle. An Albino negro, it has been remarked,[550] +was peculiarly sensitive to the bites of insects. In the West Indies[551] +it is said that "the only horned cattle fit for work are those which have a +good deal of black in them. The white are terribly tormented by the +insects; and they are weak and sluggish in proportion to the white." + +In Devonshire there is a prejudice against white pigs, because it is +believed that the sun blisters them when turned out;[552] and I knew a man +who would not keep white pigs in Kent, for the same reason. The scorching +of flowers by the sun seems likewise to depend much on colour; thus, dark +pelargoniums suffer most; and from various accounts it is clear that the +cloth-of-gold variety will not withstand a degree of exposure to sunshine +which other varieties enjoy. Another amateur asserts that not only all +dark-coloured verbenas, but likewise scarlets, suffer from the sun; "the +paler kinds stand better, and pale blue is perhaps the best of all." So +again with the heartsease (_Viola tricolor_); hot weather suits the +blotched sorts, whilst it destroys the beautiful markings of some other +kinds.[553] During one extremely cold season in Holland all red-flowered +hyacinths were observed to be very inferior in quality. It is believed by +many agriculturists that red wheat is hardier in northern climates than +white wheat.[554] + +With animals, white varieties from being conspicuous are the most liable to +be attacked by beasts and birds of prey. In parts of France and Germany +where hawks abound, persons are advised not to keep white pigeons; for, as +Parmentier says, "it {230} is certain that in a flock the white always +first fall victims to the kite." In Belgium, where so many societies have +been established for the flight of carrier-pigeons, white is the one colour +which for the same reason is disliked.[555] On the other hand, it is said +that the sea-eagle (_Falco ossifragus_, Linn.) on the west coast of Ireland +picks out the black fowls, so that "the villagers avoid as much as possible +rearing birds of that colour." M. Daudin,[556] speaking of white rabbits +kept in warrens in Russia, remarks that their colour is a great +disadvantage, as they are thus more exposed to attack, and can be seen +during bright nights from a distance. A gentleman in Kent, who failed to +stock his woods with a nearly white and hardy kind of rabbit, accounted in +the same manner for their early disappearance. Any one who will watch a +white cat prowling after her prey will soon perceive under what a +disadvantage she lies. + +The white Tartarian cherry, "owing either to its colour being so much like +that of the leaves, or to the fruit always appearing from a distance +unripe," is not so readily attacked by birds as other sorts. The +yellow-fruited raspberry, which generally comes nearly true by seed, "is +very little molested by birds, who evidently are not fond of it; so that +nets may be dispensed with in places where nothing else will protect the +red fruit."[557] This immunity, though a benefit to the gardener, would be +a disadvantage in a state of nature both to the cherry and raspberry, as +their dissemination depends on birds. I noticed during several winters that +some trees of the yellow-berried holly, which were raised from seed from a +wild tree found by my father, remained covered with fruit, whilst not a +scarlet berry could be seen on the adjoining trees of the common kind. A +friend informs me that a mountain-ash (_Pyrus aucuparia_) growing in his +garden bears berries which, though not differently coloured, are always +devoured by birds before those on the other trees. This variety of the +mountain-ash would thus be more freely disseminated, and the yellow-berried +variety of the holly less freely, than the common varieties of these two +trees. + +{231} + +Independently of colour, other trifling differences are sometimes found to +be of importance to plants under cultivation, and would be of paramount +importance if they had to fight their own battle and to struggle with many +competitors. The thin-shelled peas, called _pois sans parchemin_, are +attacked by birds[558] much more than common peas. On the other hand, the +purple-podded pea, which has a hard shell, escaped the attacks of tomtits +(_Parus major_) in my garden far better than any other kind. The +thin-shelled walnut likewise suffers greatly from the tomtit.[559] These +same birds have been observed to pass over and thus favour the filbert, +destroying only the other kinds of nuts which grew in the same +orchard.[560] + +Certain varieties of the pear have soft bark, and these suffer severely +from boring wood-beetles; whilst other varieties are known to resist their +attacks much better.[561] In North America the smoothness, or absence of +down on the fruit, makes a great difference in the attacks of the weevil, +"which is the uncompromising foe of all smooth stone-fruits;" and the +cultivator "has the frequent mortification of seeing nearly all, or indeed +often the whole crop, fall from the trees when half or two-thirds grown." +Hence the nectarine suffers more than the peach. A particular variety of +the Morello cherry, raised in North America, is without any assignable +cause more liable to be injured by this same insect than other +cherry-trees.[562] From some unknown cause, the Winter Majetin apple enjoys +the great advantage of not being infested by the coccus. On the other hand, +a particular case has been recorded in which aphides confined themselves to +the Winter Nelis pear, and touched no other kind in an extensive +orchard.[563] The existence of minute glands on the leaves of peaches, +nectarines, and apricots, would not be esteemed by botanists as a character +of the least importance, for they are present or absent in closely related +sub-varieties, descended from the same parent-tree; yet there is good +evidence[564] that the {232} absence of glands leads to mildew, which is +highly injurious to these trees. + +A difference either in flavour or in the amount of nutriment in certain +varieties causes them to be more eagerly attacked by various enemies than +other varieties of the same species. Bullfinches (_Pyrrhula vulgaris_) +injure our fruit-trees by devouring the flower-buds, and a pair of these +birds have been seen "to denude a large plum-tree in a couple of days of +almost every bud;" but certain varieties[565] of the apple and thorn +(_Cratægus oxyacantha_) are more especially liable to be attacked. A +striking instance of this was observed in Mr. Rivers's garden, in which two +rows of a particular variety of plum[566] had to be carefully protected, as +they were usually stripped of all their buds during the winter, whilst +other sorts growing near them escaped. The root (or enlarged stem) of +Laing's Swedish turnip is preferred by hares, and therefore suffers more +than other varieties. Hares and rabbits eat down common rye before St. +John's-day-rye, when both grow together.[567] In the South of France, when +an orchard of almond-trees is formed, the nuts of the bitter variety are +sown, "in order that they may not be devoured by field-mice;"[568] so we +see the use of the bitter principle in almonds. + +Other slight differences, which would be thought quite unimportant, are no +doubt sometimes of great service both to plants and animals. The +Whitesmith's gooseberry, as formerly stated, produces its leaves later than +other varieties, and, as the flowers are thus left unprotected, the fruit +often fails. In one variety of the cherry, according to Mr. Rivers,[569] +the petals are much curled backwards, and in consequence of this the +stigmas were observed to be killed by a severe frost; whilst at the same +time, in another variety with incurved petals, the stigmas were not in the +least injured. The straw of the Fenton wheat is remarkably unequal in +height; and a competent observer believes that this variety is highly +productive, partly because the ears, from being distributed at various +heights above the ground, {233} are less crowded together. The same +observer maintains that in the upright varieties the divergent awns are +serviceable by breaking the shocks when the ears are dashed together by the +wind.[570] If several varieties of a plant are grown together, and the seed +is indiscriminately harvested, it is clear that the hardier and more +productive kinds will, by a sort of natural selection, gradually prevail +over the others; this takes place, as Colonel Le Couteur believes,[571] in +our wheat-fields, for, as formerly shown, no variety is quite uniform in +character. The same thing, as I am assured by nurserymen, would take place +in our flower-gardens, if the seed of the different varieties were not +separately saved. When the eggs of the wild and tame duck are hatched +together, the young wild ducks almost invariably perish, from being of +smaller size and not getting their fair share of food.[572] + +Facts in sufficient number have now been given showing that natural +selection often checks, but occasionally favours, man's power of selection. +These facts teach us, in addition, a valuable lesson, namely, that we ought +to be extremely cautious in judging what characters are of importance in a +state of nature to animals and plants, which have to struggle from the hour +of their birth to that of their death for existence,--their existence +depending on conditions, about which we are profoundly ignorant. + +_Circumstances favourable to Selection by Man._ + +The possibility of selection rests on variability, and this, as we shall +see in the following chapters, mainly depends on changed conditions of +life, but is governed by infinitely complex, and, to a great extent, +unknown laws. Domestication, even when long continued, occasionally causes +but a small amount of variability, as in the case of the goose and turkey. +The slight differences, however, which characterise each individual animal +and plant would in most, probably in all cases, suffice for the production +of distinct races through careful and prolonged selection. We see what +selection, though acting on mere individual differences, can effect when +families of cattle, sheep, {234} pigeons, &c., of the same race, have been +separately bred during a number of years by different men without any wish +on their part to modify the breed. We see the same fact in the difference +between hounds bred for hunting in different districts,[573] and in many +other such cases. + +In order that selection should produce any result, it is manifest that the +crossing of distinct races must be prevented; hence facility in pairing, as +with the pigeon, is highly favourable for the work; and difficulty in +pairing, as with cats, prevents the formation of distinct breeds. On nearly +the same principle the cattle of the small island of Jersey have been +improved in their milking qualities "with a rapidity that could not have +been obtained in a widely extended country like France."[574] Although free +crossing is a danger on the one side which every one can see, too close +interbreeding is a hidden danger on the other side. Unfavourable conditions +of life overrule the power of selection. Our improved heavy breeds of +cattle and sheep could not have been formed on mountainous pastures; nor +could dray-horses have been raised on a barren and inhospitable land, such +as the Falkland islands, where even the light horses of La Plata rapidly +decrease in size. Nor could the wool of sheep have been much increased in +length within the Tropics; yet selection has kept Merino sheep nearly true +under diversified and unfavourable conditions of life. The power of +selection is so great, that breeds of the dog, sheep, and poultry, of the +largest and least size, long and short beaked pigeons, and other breeds +with opposite characters, have had their characteristic qualities +augmented, though treated in every way alike, being exposed to the same +climate and fed on the same food. Selection, however, is either checked or +favoured by the effects of use or habit. Our wonderfully-improved pigs +could never have been formed if they had been forced to search for their +own food; the English racehorse and greyhound could not have been improved +up to their present high standard of excellence without constant training. + +As conspicuous deviations of structure occur rarely, the improvement of +each breed is generally the result, as already {235} remarked, of the +selection of slight individual differences. Hence the closest attention, +the sharpest powers of observation, and indomitable perseverance, are +indispensable. It is, also, highly important that many individuals of the +breed which is to be improved should be raised; for thus there will be a +better chance of the appearance of variations in the right direction, and +individuals varying in an unfavourable manner may be freely rejected or +destroyed. But that a large number of individuals should be raised, it is +necessary that the conditions of life should favour the propagation of the +species. Had the peacock been bred as easily as the fowl, we should +probably ere this have had many distinct races. We see the importance of a +large number of plants, from the fact of nursery gardeners almost always +beating amateurs in the exhibition of new varieties. In 1845 it was +estimated[575] that between 4000 and 5000 pelargoniums were annually raised +from seed in England, yet a decidedly improved variety is rarely obtained. +At Messrs. Carter's grounds, in Essex, where such flowers as the Lobelia, +Nemophila, Mignonette, &c., are grown by the acre for seed, "scarcely a +season passes without some new kinds being raised, or some improvement +affected on old kinds."[576] At Kew, as Mr. Beaton remarks, where many +seedlings of common plants are raised, "you see new forms of Laburnums, +Spiræas, and other shrubs."[577] So with animals: Marshall,[578] in +speaking of the sheep in one part of Yorkshire, remarks, "as they belong to +poor people, and are mostly in small lots, they never can be improved." +Lord Rivers, when asked how he succeeded in always having first-rate +greyhounds, answered, "I breed many, and hang many." This, as another man +remarks, "was the secret of his success; and the same will be found in +exhibiting fowls,--successful competitors breed largely, and keep the +best."[579] + +It follows from this that the capacity of breeding at an early age and at +short successive intervals, as with pigeons, rabbits, &c., facilitates +selection; for the result is thus soon made visible, and perseverance in +the work is encouraged. It can hardly be {236} accidental that the great +majority of the culinary and agricultural plants which have yielded +numerous races are annuals or biennials, which therefore are capable of +rapid propagation and thus of improvement. Sea-kale, asparagus, common and +Jerusalem artichokes, potatoes, and onions, alone are perennials. Onions +are propagated like annuals, and of the other plants just specified, none, +with the exception of the potato, have yielded more than one or two +varieties. No doubt fruit-trees, which cannot be propagated quickly by +seed, have yielded a host of varieties, though not permanent races; but +these, judging from pre-historic remains, were produced at a later and more +civilised epoch than the races of culinary and agricultural plants. + +A species may be highly variable, but distinct races will not be formed, if +from any cause selection be not applied. The carp is highly variable, but +it would be extremely difficult to select slight variations in fishes +whilst living in their natural state, and distinct races have not been +formed;[580] on the other hand, a closely allied species, the gold-fish, +from being reared in glass or open vessels, and from having been carefully +attended to by the Chinese, has yielded many races. Neither the bee, which +has been semi-domesticated from an extremely remote period, nor the +cochineal insect, which was cultivated by the aboriginal Mexicans, has +yielded races; and it would be impossible to match the queen-bee with any +particular drone, and most difficult to match cochineal insects. +Silk-moths, on the other hand, have been subjected to rigorous selection, +and have produced a host of races. Cats, which from their nocturnal habits +cannot be selected for breeding, do not, as formerly remarked, yield +distinct races in the same country. The ass in England varies much in +colour and size; but it is an animal of little value, bred by poor people; +consequently there has been no selection, and distinct races have not been +formed. We must not attribute the inferiority of our asses to climate, for +in India they are of even smaller size than in Europe. But when selection +is brought to bear on the ass, all is changed. Near Cordova, as I am +informed (Feb. 1860) by Mr. W. E. Webb, C.E., they are carefully bred, as +much as 200l. having been paid for a stallion ass, {237} and they have been +immensely improved. In Kentucky, asses have been imported (for breeding +mules) from Spain, Malta, and France; these "seldom averaged more than +fourteen hands high; but the Kentuckians, by great care, have raised them +up to fifteen hands, and sometimes even to sixteen. The prices paid for +these splendid animals, for such they really are, will prove how much they +are in request. One male, of great celebrity, was sold for upwards of one +thousand pounds sterling." These choice asses are sent to cattle-shows, one +day being given to their exhibition.[581] + +Analogous facts have been observed with plants: the nutmeg-tree in the +Malay archipelago is highly variable, but there has been no selection, and +there are no distinct races.[582] The common mignonette (_Reseda odorata_), +from bearing inconspicuous flowers, valued solely for their fragrance, +"remains in the same unimproved condition as when first introduced."[583] +Our common forest-trees are very variable, as may be seen in every +extensive nursery-ground; but as they are not valued like fruit-trees, and +as they seed late in life, no selection has been applied to them; +consequently, as Mr. Patrick Matthews remarks,[584] they have not yielded +distinct races, leafing at different periods, growing to different sizes, +and producing timber fit for different purposes. We have gained only some +fanciful and semi-monstrous varieties, which no doubt appeared suddenly as +we now see them. + +Some botanists have argued that plants cannot have so strong a tendency to +vary as is generally supposed, because many species long grown in botanic +gardens, or unintentionally cultivated year after year mingled with our +corn crops, have not produced distinct races; but this is accounted for by +slight variations not having been selected and propagated. Let a plant +which is now grown in a botanic garden, or any common weed, be cultivated +on a large scale, and let a sharp-sighted gardener look out for each slight +variety and sow the seed, and then, if distinct races are not produced, the +argument will be valid. + +{238} + +The importance of selection is likewise shown by considering special +characters. For instance, with most breeds of fowls the form of the comb +and the colour of the plumage have been attended to, and are eminently +characteristic of each race; but in Dorkings, fashion has never demanded +uniformity of comb or colour; and the utmost diversity in these respects +prevails. Rose-combs, double-combs, cup-combs, &c., and colours of all +kinds, may be seen in purely-bred and closely related Dorking fowls, whilst +other points, such as the general form of body, and the presence of an +additional toe, have been attended to, and are invariably present. It has +also been ascertained that colour can be fixed in this breed, as well as in +any other.[585] + + * * * * * + +During the formation or improvement of a breed, its members will always be +found to vary much in those characters to which especial attention is +directed, and of which each slight improvement is eagerly sought and +selected. Thus with short-faced tumbler-pigeons, the shortness of the beak, +shape of head and plumage,--with carriers, the length of the beak and +wattle,--with fantails, the tail and carriage,--with Spanish fowls, the +white face and comb,--with long-eared rabbits, the length of ear, are all +points which are eminently variable. So it is in every case, and the large +price paid for first-rate animals proves the difficulty of breeding them up +to the highest standard of excellence. This subject has been discussed by +fanciers,[586] and the greater prizes given for highly improved breeds, in +comparison with those given for old breeds which are not now undergoing +rapid improvement, has been fully justified. Nathusius makes[587] a similar +remark when discussing the less uniform character of improved Shorthorn +cattle and of the English horse, in comparison, for example, with the +unennobled cattle of Hungary, or with the horses of the Asiatic steppes. +This want of uniformity in the parts which at the time are undergoing +selection, chiefly depends on the strength of the principle of reversion +but it likewise depends to a certain extent on the continued {239} +variability of the parts which have recently varied. That the same parts do +continue varying in the same manner we must admit, for, if it were not so, +there could be no improvement beyond an early standard of excellence, and +we know that such improvement is not only possible, but is of general +occurrence. + +As a consequence of continued variability, and more especially of +reversion, all highly improved races, if neglected or not subjected to +incessant selection, soon degenerate. Youatt gives a curious instance of +this in some cattle formerly kept in Glamorganshire; but in this case the +cattle were not fed with sufficient care. Mr. Baker, in his memoir on the +Horse, sums up: "It must have been observed in the preceding pages that, +whenever there has been neglect, the breed has proportionally +deteriorated."[588] If a considerable number of improved cattle, sheep, or +other animals of the same race, were allowed to breed freely together, with +no selection, but with no change in their condition of life, there can be +no doubt that after a score or hundred generations they would be very far +from excellent of their kind; but, from what we see of the many common +races of dogs, cattle, fowls, pigeons, &c., which without any particular +care have long retained nearly the same character, we have no grounds for +believing that they would altogether depart from their type. + +It is a general belief amongst breeders that characters of all kinds become +fixed by long-continued inheritance. But I have attempted to show in the +fourteenth chapter that this belief apparently resolves itself into the +following proposition, namely, that all characters whatever, whether +recently acquired or ancient, tend to be transmitted, but that those which +have already long withstood all counteracting influences, will, as a +general rule, continue to withstand them, and consequently be faithfully +transmitted. + +_Tendency in Man to carry the practice of Selection to an extreme point._ + +It is an important principle that in the process of selection man almost +invariably wishes to go to an extreme point. Thus, in useful qualities, +there is no limit to his desire to breed certain {240} horses and dogs as +fleet as possible, and others as strong as possible; certain kinds of sheep +for extreme fineness, and others for extreme length of wool; and he wishes +to produce fruit, grain, tubers, and other useful parts of plants, as large +and excellent as possible. With animals bred for amusement, the same +principle is even more powerful; for fashion, as we see even in our dress, +always runs to extremes. This view has been expressly admitted by fanciers. +Instances were given in the chapters on the pigeon, but here is another: +Mr. Eaton, after describing a comparatively new variety, namely, the +Archangel, remarks, "What fanciers intend doing with this bird I am at a +loss to know, whether they intend to breed it down to the tumbler's head +and beak, or carry it out to the carrier's head and beak; leaving it as +they found it, is not progressing." Ferguson, speaking of fowls, says, +"their peculiarities, whatever they may be, must necessarily be fully +developed: a little peculiarity forms nought but ugliness, seeing it +violates the existing laws of symmetry." So Mr. Brent, in discussing the +merits of the sub-varieties of the Belgian canary-bird, remarks, "Fanciers +always go to extremes; they do not admire indefinite properties."[589] + +This principle, which necessarily leads to divergence of character, +explains the present state of various domestic races. We can thus see how +it is that race-horses and dray-horses, greyhounds and mastiffs, which are +opposed to each other in every character,--how varieties so distinct as +Cochin-China fowls and bantams, or carrier-pigeons with very long beaks, +and tumblers with excessively short beaks, have been derived from the same +stock. As each breed is slowly improved, the inferior varieties are first +neglected and finally lost. In a few cases, by the aid of old records, or +from intermediate varieties still existing in countries where other +fashions have prevailed, we are enabled partially to trace the graduated +changes through which certain breeds have passed. Selection, whether +methodical or unconscious, always tending towards an extreme point, +together with the neglect and slow extinction of the intermediate and +less-valued forms, is the key which unlocks the mystery how man has +produced such wonderful results. + +{241} + +In a few instances selection, guided by utility for a single purpose, has +led to convergence of character. All the improved and different races of +the pig, as Nathusius has well shown,[590] closely approach each other in +character, in their shortened legs and muzzles, their almost hairless, +large, rounded bodies, and small tusks. We see some degree of convergence +in the similar outline of the body in well-bred cattle belonging to +distinct races.[591] I know of no other such cases. + +Continued divergence of character depends on, and is indeed a clear proof, +as previously remarked, of the same parts continuing to vary in the same +direction. The tendency to mere general variability or plasticity of +organisation can certainly be inherited, even from one parent, as has been +shown by Gärtner and Kölreuter, in the production of varying hybrids from +two species, of which one alone was variable. It is in itself probable +that, when an organ has varied in any manner, it will again vary in the +same manner, if the conditions which first caused the being to vary remain, +as far as can be judged, the same. This is either tacitly or expressly +admitted by all horticulturists: if a gardener observes one or two +additional petals in a flower, he feels confident that in a few generations +he will be able to raise a double flower, crowded with petals. Some of the +seedlings from the weeping Moccas oak were so prostrate that they only +crawled along the ground. A seedling from the fastigate or upright Irish +yew is described as differing greatly from the parent-form "by the +exaggeration of the fastigate habit of its branches."[592] Mr. Sheriff, who +has been more successful than any other man in raising new kinds of wheat, +remarks, "A good variety may safely be regarded as the forerunner of a +better one."[593] A great rose-grower, Mr. Rivers, has made the same remark +with respect to roses. Sageret,[594] who had large experience, in speaking +of the future progress of fruit-trees, observes that the most important +principle is "that the more plants have departed from their original type, +the more they tend to depart from it." There is apparently much truth in +this {242} remark; for we can in no other way understand the surprising +amount of difference between varieties in the parts or qualities which are +valued, whilst other parts retain nearly their original character. + +The foregoing discussion naturally leads to the question, what is the limit +to the possible amount of variation in any part or quality, and, +consequently, is there any limit to what selection can effect? Will a +race-horse ever be reared fleeter than Eclipse? Can our prize-cattle and +sheep be still further improved? Will a gooseberry ever weigh more than +that produced by "London" in 1852? Will the beet-root in France yield a +greater percentage of sugar? Will future varieties of wheat and other grain +produce heavier crops than our present varieties? These questions cannot be +positively answered; but it is certain that we ought to be cautious in +answering by a negative. In some lines of variation the limit has probably +been reached. Youatt believes that the reduction of bone in some of our +sheep has already been carried so far that it entails great delicacy of +constitution.[595] But seeing the great improvement within recent times in +our cattle and sheep, and especially in our pigs; seeing the wonderful +increase in weight in our poultry of all kinds during the last few years; +he would be a bold man who would assert that perfection has been reached. +Eclipse perhaps may never be beaten until all our race-horses have been +rendered swifter, through the selection of the best horses during many +generations; and then the old Eclipse may possibly be eclipsed; but, as Mr. +Wallace has remarked, there must be an ultimate limit to the fleetness of +every animal, whether under nature or domestication; and with the horse +this limit has perhaps been reached. Until our fields are better manured, +it may be impossible for a new variety of wheat to yield a heavier crop. +But in many cases those who are best qualified to judge do not believe that +the extreme point has as yet been reached even with respect to characters +which have already been carried to a high standard of perfection. For +instance, the short-faced tumbler-pigeon has been greatly modified; +nevertheless, according to Mr. Eaton,[596] "the field is still as open for +fresh competitors as it was one hundred years ago." Over and over again it +has been said that {243} perfection had been attained with our flowers, but +a higher standard has soon been reached. Hardly any fruit has been more +improved than the strawberry, yet a great authority remarks,[597] "it must +not be concealed that we are far from the extreme limits at which we may +arrive." + +Time is an important element in the formation of our domestic races, as it +permits innumerable individuals to be born, and these when exposed to +diversified conditions are rendered variable. Methodical selection has been +occasionally practised from an ancient period to the present day, even by +semi-civilised people, and during former times will have produced some +effect. Unconscious selection will have been still more effective; for +during a lengthened period the more valuable individual animals will +occasionally have been saved, and the less valuable neglected. In the +course, also, of time, different varieties, especially in the less +civilised countries, will have been more or less modified through natural +selection. It is generally believed, though on this head we have little or +no evidence, that new characters in time become fixed; and after having +long remained fixed it seems possible that under new conditions they might +again be rendered variable. + +How great the lapse of time has been since man first domesticated animals +and cultivated plants, we begin dimly to see. When the lake-buildings of +Switzerland were inhabited during the Neolithic period, several animals +were already domesticated and various plants cultivated. If we may judge +from what we now see of the habits of savages, it is probable that the men +of the earlier Stone period--when many great quadrupeds were living which +are now extinct, and when the face of the country was widely different from +what it now is--possessed at least some few domesticated animals, although +their remains have not as yet been discovered. If the science of language +can be trusted, the art of ploughing and sowing the land was followed, and +the chief animals had been already domesticated, at an epoch so immensely +remote, that the Sanskrit, Greek, Latin, Gothic, Celtic, and Sclavonic +languages had not as yet diverged from their common parent-tongue.[598] + +{244} + +It is scarcely possible to overrate the effects of selection occasionally +carried on in various ways and places during thousands of generations. All +that we know, and, in a still stronger degree, all that we do not +know,[599] of the history of the great majority of our breeds, even of our +more modern breeds, agrees with the view that their production, through the +action of unconscious and methodical selection, has been almost insensibly +slow. When a man attends rather more closely than is usual to the breeding +of his animals, he is almost sure to improve them to a slight extent. They +are in consequence valued in his immediate neighbourhood, and are bred by +others; and their characteristic features, whatever these may be, will then +slowly but steadily be increased, sometimes by methodical and almost always +by unconscious selection. At last a strain, deserving to be called a +sub-variety, becomes a little more widely known, receives a local name, and +spreads. The spreading will have been extremely slow during ancient and +less civilised times, but now is rapid. By the time that the new breed had +assumed a somewhat distinct character, its history, hardly noticed at the +time, will have been completely forgotten; for, as Low remarks,[600] "we +know how quickly the memory of such events is effaced." + +As soon as a new breed is thus formed, it is liable through the same +process to break up into new strains and sub-varieties. For different +varieties are suited for, and are valued under, different circumstances. +Fashion changes, but, should a fashion last for even a moderate length of +time, so strong is the principle of inheritance, that some effect will +probably be impressed on the breed. Thus varieties go on increasing in +number, and history shows us how wonderfully they have increased since the +earliest records.[601] As each new variety is produced, the earlier, +intermediate, and less valuable forms will be neglected, and perish. When a +breed, from not being valued, is kept in small numbers, its extinction +almost inevitably follows sooner or later, either from accidental causes of +destruction or from close interbreeding; and this is an event which, in the +case of well-marked breeds, excites attention. The birth or production of a +new domestic race is so slow a process that it {245} escapes notice; its +death or destruction is comparatively sudden, is often recorded, and when +too late sometimes regretted. + +Several authors have drawn a wide distinction between artificial and +natural races. The latter are more uniform in character, possessing in a +high degree the character of natural species, and are of ancient origin. +They are generally found in less civilised countries, and have probably +been largely modified by natural selection, and only to a small extent by +man's unconscious and methodical selection. They have, also, during a long +period, been directly acted on by the physical conditions of the countries +which they inhabit. The so-called artificial races, on the other hand, are +not so uniform in character; some have a semi-monstrous character, such as +"the wry-legged terriers so useful in rabbit-shooting,"[602] turnspit dogs, +ancon sheep, niata oxen, Polish fowls, fantail-pigeons, &c.; their +characteristic features have generally been acquired suddenly, though +subsequently increased in many cases by careful selection. Other races, +which certainly must be called artificial, for they have been largely +modified by methodical selection and by crossing, as the English +race-horse, terrier-dogs, the English game-cock, Antwerp carrier-pigeons, +&c., nevertheless cannot be said to have an unnatural appearance; and no +distinct line, as it seems to me, can be drawn between natural and +artificial races. + +It is not surprising that domestic races should generally present a +different aspect from natural species. Man selects and propagates +modifications solely for his own use or fancy, and not for the creature's +own good. His attention is struck by strongly marked modifications, which +have appeared suddenly, due to some great disturbing cause in the +organisation. He attends almost exclusively to external characters; and +when he succeeds in modifying internal organs,--when for instance he +reduces the bones and offal, or loads the viscera with fat, or gives early +maturity, &c.,--the chances are strong that he will at the same time weaken +the constitution. On the other hand, when an animal has to struggle +throughout its life with many competitors and enemies, under circumstances +inconceivably complex and liable to change, modifications of the most +varied nature--in the internal organs as well as in external characters, in +the {246} functions and mutual relations of parts--will be rigorously +tested, preserved, or rejected. Natural selection often checks man's +comparatively feeble and capricious attempts at improvement; and if this +were not so, the result of his work, and of nature's work, would be even +still more different. Nevertheless, we must not overrate the amount of +difference between natural species and domestic races; the most experienced +naturalists have often disputed whether the latter are descended from one +or from several aboriginal stocks, and this clearly shows that there is no +palpable difference between species and races. + +Domestic races propagate their kind far more truly, and endure for much +longer periods, than most naturalists are willing to admit. Breeders feel +no doubt on this head; ask a man who has long reared Shorthorn or Hereford +cattle, Leicester or Southdown sheep, Spanish or Game poultry, tumbler or +carrier-pigeons, whether these races may not have been derived from common +progenitors, and he will probably laugh you to scorn. The breeder admits +that he may hope to produce sheep with finer or longer wool and with better +carcases, or handsomer fowls, or carrier-pigeons with beaks just +perceptibly longer to the practised eye, and thus be successful at an +exhibition. Thus far he will go, but no farther. He does not reflect on +what follows from adding up during a long course of time many, slight, +successive modifications; nor does he reflect on the former existence of +numerous varieties, connecting the links in each divergent line of descent. +He concludes, as was shown in the earlier chapters, that all the chief +breeds to which he has long attended are aboriginal productions. The +systematic naturalist, on the other hand, who generally knows nothing of +the art of breeding, who does not pretend to know how and when the several +domestic races were formed, who cannot have seen the intermediate +gradations, for they do not now exist, nevertheless feels no doubt that +these races are sprung from a single source. But ask him whether the +closely allied natural species which he has studied may not have descended +from a common progenitor, and he in his turn will perhaps reject the notion +with scorn. Thus the naturalist and breeder may mutually learn a useful +lesson from each other. + + * * * * * + +_Summary on Selection by Man._--There can be no doubt that {247} methodical +selection has effected and will effect wonderful results. It was +occasionally practised in ancient times, and is still practised by +semi-civilised people. Characters of the highest importance, and others of +trifling value, have been attended to, and modified. I need not here repeat +what has been so often said on the part which unconscious selection has +played: we see its power in the difference between flocks which have been +separately bred, and in the slow changes, as circumstances have slowly +changed, which many animals have undergone in the same country, or when +transported into a foreign land. We see the combined effects of methodical +and unconscious selection in the great amount of difference between +varieties in those parts or qualities which are valued by man, in +comparison with those which are not valued, and consequently have not been +attended to. Natural selection often determines man's power of selection. +We sometimes err in imagining that characters, which are considered as +unimportant by the systematic naturalist, could not be affected by the +struggle for existence, and therefore be acted on by natural selection; but +striking cases have been given, showing how great an error this is. + +The possibility of selection coming into action rests on variability; and +this is mainly caused, as we shall hereafter see, by changes in the +conditions of life. Selection is sometimes rendered difficult, or even +impossible, by the conditions being opposed to the desired character or +quality. It is sometimes checked by the lessened fertility and weakened +constitution which follow from long-continued close interbreeding. That +methodical selection may be successful, the closest attention and +discernment, combined with unwearied patience, are absolutely necessary; +and these same qualities, though not indispensable, are highly serviceable +in the case of unconscious selection. It is almost necessary that a large +number of individuals should be reared; for thus there will be a fair +chance of variations of the desired nature arising, and every individual +with the slightest blemish or in any degree inferior may be freely +rejected. Hence length of time is an important element of success. Thus, +also, propagation at an early age and at short intervals favours the work. +Facility in pairing animals, or their inhabiting a confined area, is +advantageous as a check to free crossing. Whenever and {248} wherever +selection is not practised, distinct races are not formed. When any one +part of the body or quality is not attended to, it remains either unchanged +or varies in a fluctuating manner, whilst at the same time other parts and +other qualities may become permanently and greatly modified. But from the +tendency to reversion and to continued variability, those parts or organs +which are now undergoing rapid improvement through selection, are likewise +found to vary much. Consequently highly-bred animals, when neglected, soon +degenerate; but we have no reason to believe that the effects of +long-continued selection would, if the conditions of life remained the +same, be soon and completely lost. + +Man always tends to go to an extreme point in the selection, whether +methodical or unconscious, of all useful and pleasing qualities. This is an +important principle, as it leads to continued divergence, and in some rare +cases to convergence of character. The possibility of continued divergence +rests on the tendency in each part or organ to go on varying in the same +manner in which it has already varied; and that this occurs, is proved by +the steady and gradual improvement of many animals and plants during +lengthened periods. The principle of divergence of character, combined with +the neglect and final extinction of all previous, less-valued, and +intermediate varieties, explains the amount of difference and the +distinctness of our several races. Although we may have reached the utmost +limit to which certain characters can be modified, yet we are far from +having reached, as we have good reason to believe, the limit in the +majority of cases. Finally, from the difference between selection as +carried on by man and by nature, we can understand how it is that domestic +races often, though by no means always, differ in general aspect from +closely allied natural species. + +Throughout this chapter and elsewhere I have spoken of selection as the +paramount power, yet its action absolutely depends on what we in our +ignorance call spontaneous or accidental variability. Let an architect be +compelled to build an edifice with uncut stones, fallen from a precipice. +The shape of each fragment may be called accidental; yet the shape of each +has been determined by the force of gravity, the nature {249} of the rock, +and the slope of the precipice,--events and circumstances, all of which +depend on natural laws; but there is no relation between these laws and the +purpose for which each fragment is used by the builder. In the same manner +the variations of each creature are determined by fixed and immutable laws; +but these bear no relation to the living structure which is slowly built up +through the power of selection, whether this be natural or artificial +selection. + +If our architect succeeded in rearing a noble edifice, using the rough +wedge-shaped fragments for the arches, the longer stones for the lintels, +and so forth, we should admire his skill even in a higher degree than if he +had used stones shaped for the purpose. So it is with selection, whether +applied by man or by nature; for though variability is indispensably +necessary, yet, when we look at some highly complex and excellently adapted +organism, variability sinks to a quite subordinate position in importance +in comparison with selection, in the same manner as the shape of each +fragment used by our supposed architect is unimportant in comparison with +his skill. + + * * * * * + + +{250} + +CHAPTER XXII. + +CAUSES OF VARIABILITY. + + VARIABILITY DOES NOT NECESSARILY ACCOMPANY REPRODUCTION--CAUSES + ASSIGNED BY VARIOUS AUTHORS--INDIVIDUAL DIFFERENCES--VARIABILITY OF + EVERY KIND DUE TO CHANGED CONDITIONS OF LIFE--ON THE NATURE OF SUCH + CHANGES--CLIMATE, FOOD, EXCESS OF NUTRIMENT--SLIGHT CHANGES + SUFFICIENT--EFFECTS OF GRAFTING ON THE VARIABILITY OF + SEEDLING-TREES--DOMESTIC PRODUCTIONS BECOME HABITUATED TO CHANGED + CONDITIONS--ON THE ACCUMULATIVE ACTION OF CHANGED CONDITIONS--CLOSE + INTERBREEDING AND THE IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE + VARIABILITY--CROSSING AS A CAUSE OF THE APPEARANCE OF NEW + CHARACTERS--VARIABILITY FROM THE COMMINGLING OF CHARACTERS AND FROM + REVERSION--ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH + EITHER DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE + VARIABILITY. + +We will now consider, as far as we can, the causes of the almost universal +variability of our domesticated productions. The subject is an obscure one; +but it may be useful to probe our ignorance. Some authors, for instance Dr. +Prosper Lucas, look at variability as a necessary contingent on +reproduction, and as much an aboriginal law, as growth or inheritance. +Others have of late encouraged, perhaps unintentionally, this view by +speaking of inheritance and variability as equal and antagonistic +principles. Pallas maintained, and he has had some followers, that +variability depends exclusively on the crossing of primordially distinct +forms. Other authors attribute the tendency to variability to an excess of +food, and with animals to an excess relatively to the amount of exercise +taken, or again to the effects of a more genial climate. That these causes +are all effective is highly probable. But we must, I think, take a broader +view, and conclude that organic beings, when subjected during several +generations to any change whatever in their conditions, tend to vary; the +kind of variation which ensues depending in a far higher degree on the +nature or constitution of the being, than on the nature of the changed +conditions. {251} + +Those authors who believe that it is a law of nature that each individual +should differ in some slight degree from every other, may maintain, +apparently with truth, that this is the fact, not only with all +domesticated animals and cultivated plants, but likewise with all organic +beings in a state of nature. The Laplander by long practice knows and gives +a name to each reindeer, though, as Linnæus remarks, "to distinguish one +from another among such multitudes was beyond my comprehension, for they +were like ants on an ant-hill." In Germany shepherds have won wagers by +recognising each sheep in a flock of a hundred, which they had never seen +until the previous fortnight. This power of discrimination, however, is as +nothing compared to that which some florists have acquired. Verlot mentions +a gardener who could distinguish 150 kinds of camellia, when not in flower; +and it has been positively asserted that the famous old Dutch florist +Voorhelm, who kept above 1200 varieties of the hyacinth, was hardly ever +deceived in knowing each variety by the bulb alone. Hence we must conclude +that the bulbs of the hyacinth and the branches and leaves of the camellia, +though appearing to an unpractised eye absolutely undistinguishable, yet +really differ.[603] + +As Linnæus has compared the reindeer in number to ants, I may add that each +ant knows its fellow of the same community. Several times I carried ants of +the same species (_Formica rufa_) from one ant-hill to another, inhabited +apparently by tens of thousands of ants; but the strangers were instantly +detected and killed. I then put some ants taken from a very large nest into +a bottle strongly perfumed with assafoetida, and after an interval of +twenty-four hours returned them to their home; they were at first +threatened by their fellows, but were soon recognised and allowed to pass. +Hence each ant certainly recognises, independently of odour, its fellow; +and if all the ants of the same community have not some countersign or +watchword, they must present to each other's senses some distinguishable +character. + +{252} + +The dissimilarity of brothers or sisters of the same family, and of +seedlings from the same capsule, may be in part accounted for by the +unequal blending of the characters of the two parents, and by the more or +less complete recovery through reversion of ancestral characters on either +side; but we thus only push the difficulty further back in time, for what +made the parents or their progenitors different? Hence the belief[604] that +an innate tendency to vary exists, independently of external conditions, +seems at first sight probable. But even the seeds nurtured in the same +capsule are not subjected to absolutely uniform conditions, as they draw +their nourishment from different points; and we shall see in a future +chapter that this difference sometimes suffices greatly to affect the +character of the future plant. The less close similarity of the successive +children of the same family in comparison with human twins, which often +resemble each other in external appearance, mental disposition, and +constitution, in so extraordinary a manner, apparently proves that the +state of the parents at the exact period of conception, or the nature of +the subsequent embryonic development, has a direct and powerful influence +on the character of the offspring. Nevertheless, when we reflect on the +{253} individual differences between organic beings in a state of nature, +as shown by every wild animal knowing its mate; and when we reflect on the +infinite diversity of the many varieties of our domesticated productions, +we may well be inclined to exclaim, though falsely as I believe, that +Variability must be looked at as an ultimate fact, necessarily contingent +on reproduction. + +Those authors who adopt this latter view would probably deny that each +separate variation has its own proper exciting cause. Although we can +seldom trace the precise relation between cause and effect, yet the +considerations presently to be given lead to the conclusion that each +modification must have its own distinct cause. When we hear of an infant +born, for instance, with a crooked finger, a misplaced tooth, or other +slight deviation of structure, it is difficult to bring the conviction home +to the mind that such abnormal cases are the result of fixed laws, and not +of what we blindly call accident. Under this point of view the following +case, which has been carefully examined and communicated to me by Dr. +William Ogle, is highly instructive. Two girls, born as twins, and in all +respects extremely alike, had their little fingers on both hands crooked; +and in both children the second bicuspid tooth in the upper jaw, of the +second dentition, was misplaced; for these teeth, instead of standing in a +line with the others, grew from the roof of the mouth behind the first +bicuspids. Neither the parents nor any other member of the family had +exhibited any similar peculiarity. Now, as both these children were +affected in exactly the same manner by both deviations of structure, the +idea of accident is at once excluded; and we are compelled to admit that +there must have existed some precise and sufficient cause which, if it had +occurred a hundred times, would have affected a hundred children. + +We will now consider the general arguments, which appear to me to have +great weight, in favour of the view that variations of all kinds and +degrees are directly or indirectly caused by the conditions of life to +which each being, and more especially its ancestors, have been exposed. + +No one doubts that domesticated productions are more variable than organic +beings which have never been removed from their {254} natural conditions. +Monstrosities graduate so insensibly into mere variations that it is +impossible to separate them; and all those who have studied monstrosities +believe that they are far commoner with domesticated than with wild animals +and plants;[605] and in the case of plants, monstrosities would be equally +noticeable in the natural as in the cultivated state. Under nature, the +individuals of the same species are exposed to nearly uniform conditions, +for they are rigorously kept to their proper places by a host of competing +animals and plants; they have, also, long been habituated to their +conditions of life; but it cannot be said that they are subject to quite +uniform conditions, and they are liable to a certain amount of variation. +The circumstances under which our domestic productions are reared are +widely different: they are protected from competition; they have not only +been removed from their natural conditions and often from their native +land, but they are frequently carried from district to district, where they +are treated differently, so that they never remain during a considerable +length of time exposed to closely similar conditions. In conformity with +this, all our domesticated productions, with the rarest exceptions, vary +far more than natural species. The hive-bee, which feeds itself and follows +in most respects its natural habits of life, is the least variable of all +domesticated animals, and probably the goose is the next least variable; +but even the goose varies more than almost any wild bird, so that it cannot +be affiliated with perfect certainty to any natural species. Hardly a +single plant can be named, which has long been cultivated and propagated by +seed, that is not highly variable; common rye (_Secale cereale_) has +afforded fewer and less marked varieties than almost any other cultivated +plant;[606] but it may be doubted whether the variations of this, the least +valuable of all our cereals, have been closely observed. + +Bud-variation, which was fully discussed in a former chapter, shows us that +variability may be quite independent of seminal reproduction, and likewise +of reversion to long-lost ancestral characters. No one will maintain that +the sudden appearance {255} of a moss-rose on a Provence-rose is a return +to a former state, for mossiness of the calyx has been observed in no +natural species; the same argument is applicable to variegated and +laciniated leaves; nor can the appearance of nectarines on peach-trees be +accounted for with any probability on the principle of reversion. But +bud-variations more immediately concern us, as they occur far more +frequently on plants which have been highly cultivated during a length of +time, than on other and less highly cultivated plants; and very few +well-marked instances have been observed with plants growing under strictly +natural conditions. I have given one instance of an ash-tree growing in a +gentleman's pleasure-grounds; and occasionally there may be seen, on beech +and other trees, twigs leafing at a different period from the other +branches. But our forest trees in England can hardly be considered as +living under strictly natural conditions; the seedlings are raised and +protected in nursery-grounds, and must often be transplanted into places +where wild trees of the kind would not naturally grow. It would be esteemed +a prodigy if a dog-rose growing in a hedge produced by bud-variation a +moss-rose, or a wild bullace or wild cherry-tree yielded a branch bearing +fruit of a different shape and colour from the ordinary fruit. The prodigy +would be enhanced if these varying branches were found capable of +propagation, not only by grafts, but sometimes by seed; yet analogous cases +have occurred with many of our highly cultivated trees and herbs. + +These several considerations alone render it probable that variability of +every kind is directly or indirectly caused by changed conditions of life. +Or, to put the case under another point of view, if it were possible to +expose all the individuals of a species during many generations to +absolutely uniform conditions of life, there would be no variability. + +_On the Nature of the Changes in the Conditions of Life which induce +Variability._ + +From a remote period to the present day, under climates and circumstances +as different as it is possible to conceive, organic beings of all kinds, +when domesticated or cultivated, have {256} varied. We see this with the +many domestic races of quadrupeds and birds belonging to different orders, +with gold-fish and silkworms, with plants of many kinds, raised in various +quarters of the world. In the deserts of northern Africa the date-palm has +yielded thirty-eight varieties; in the fertile plains of India it is +notorious how many varieties of rice and of a host of other plants exist; +in a single Polynesian island, twenty-four varieties of the bread-fruit, +the same number of the banana, and twenty-two varieties of the arum, are +cultivated by the natives; the mulberry-tree in India and Europe has +yielded many varieties serving as food for the silkworm; and in China +sixty-three varieties of the bamboo are used for various domestic +purposes.[607] These facts alone, and innumerable others could be added, +indicate that a change of almost any kind in the conditions of life +suffices to cause variability--different changes acting on different +organisms. + +Andrew Knight[608] attributed the variation of both animals and plants to a +more abundant supply of nourishment, or to a more favourable climate, than +that natural to the species. A more genial climate, however, is far from +necessary; the kidney-bean, which is often injured by our spring frosts, +and peaches, which require the protection of a wall, have varied much in +England, as has the orange-tree in northern Italy, where it is barely able +to exist.[609] Nor can we overlook the fact, though not immediately +connected with our present subject, that the plants and shells of the +arctic regions are eminently variable.[610] Moreover, it does not appear +that a change of climate, whether more or less genial, is one of the most +potent causes of variability; for in regard to plants Alph. De Candolle, in +his 'Géographie {257} Botanique,' repeatedly shows that the native country +of a plant, where in most cases it has been longest cultivated, is that +where it has yielded the greatest number of varieties. + +It is doubtful whether a change in the nature of the food is a potent cause +of variability. Scarcely any domesticated animal has varied more than the +pigeon or the fowl, but their food, especially that of highly-bred pigeons, +is generally the same. Nor can our cattle and sheep have been subjected to +any great change in this respect. But in all these cases the food probably +is much less varied in kind than that which was consumed by the species in +its natural state.[611] + +Of all the causes which induce variability, excess of food, whether or not +changed in nature, is probably the most powerful. This view was held with +regard to plants by Andrew Knight, and is now held by Schleiden, more +especially in reference to the inorganic elements of the food.[612] In +order to give a plant more food it suffices in most cases to grow it +separately, and thus prevent other plants robbing its roots. It is +surprising, as I have often seen, how vigorously our common wild plants +flourish when planted by themselves, though not in highly manured land. +Growing plants separately is, in fact, the first step in cultivation. We +see the converse of the belief that excess of food induces variability in +the following statement by a great raiser of seeds of all kinds.[613] "It +is a rule invariably with us, when we desire to keep a true stock of any +one kind of seed, to grow it on poor land without dung; but when we grow +for quantity, we act contrary, and sometimes have dearly to repent of it." + +In the case of animals the want of a proper amount of exercise, as +Bechstein has remarked, has perhaps played, independently of the direct +effects of the disuse of any particular organ, an important part in causing +variability. We can see in a vague manner that, when the organised and +nutrient fluids of the body are not used during growth, or by the wear and +tear of the tissues, {258} they will be in excess; and as growth, +nutrition, and reproduction are intimately allied processes, this +superfluity might disturb the due and proper action of the reproductive +organs, and consequently affect the character of the future offspring. But +it may be argued that neither an excess of food nor a superfluity in the +organised fluids of the body necessarily induces variability. The goose and +the turkey have been well fed for many generations, yet have varied very +little. Our fruit-trees and culinary plants, which are so variable, have +been cultivated from an ancient period, and, though they probably still +receive more nutriment than in their natural state, yet they must have +received during many generations nearly the same amount; and it might be +thought that they would have become habituated to the excess. Nevertheless, +on the whole, Knight's view, that excess of food is one of the most potent +causes of variability, appears, as far as I can judge, probable. + +Whether or not our various cultivated plants have received nutriment in +excess, all have been exposed to changes of various kinds. Fruit-trees are +grafted on different stocks, and grown in various soils. The seeds of +culinary and agricultural plants are carried from place to place; and +during the last century the rotation of our crops and the manures used have +been greatly changed. + +Slight changes of treatment often suffice to induce variability. The simple +fact of almost all our cultivated plants and domesticated animals having +varied in all places and at all times, leads to this conclusion. Seeds +taken from common English forest-trees, grown under their native climate, +not highly manured or otherwise artificially treated, yield seedlings which +vary much, as may be seen in every extensive seed-bed. I have shown in a +former chapter what a number of well marked and singular varieties the +thorn (_Cratægus oxyacantha_) has produced; yet this tree has been +subjected to hardly any cultivation. In Staffordshire I carefully examined +a large number of two British plants, namely, _Geranium phæum_ and +_Pyrenaicum_, which have never been highly cultivated. These plants had +spread spontaneously by seed from a common garden into an open plantation; +and the seedlings varied in almost every single character, both in their +flowers and foliage, to a degree which {259} I have never seen exceeded; +yet they could not have been exposed to any great change in their +conditions. + +With respect to animals, Azara has remarked with much surprise,[614] that, +whilst the feral horses on the Pampas are always of one of three colours, +and the cattle always of a uniform colour, yet these animals, when bred on +the unenclosed estancias, though kept in a state which can hardly be called +domesticated, and apparently exposed to almost identically the same +conditions as when they are feral, nevertheless display a great diversity +of colour. So again in India several species of fresh-water fish are only +so far treated artificially, that they are reared in great tanks; but this +small change is sufficient to induce much variability.[615] + +Some facts on the effects of grafting, in regard to the variability of +trees, deserve attention. Cabanis asserts that when certain pears are +grafted on the quince, their seeds yield more varieties than do the seeds +of the same variety of pear when grafted on the wild pear.[616] But as the +pear and quince are distinct species, though so closely related that the +one can be readily grafted and succeeds admirably on the other, the fact of +variability being thus caused is not surprising; we are, however, here +enabled to see the cause, namely, the different nature of the stock with +its roots and the rest of the tree. Several North American varieties of the +plum and peach are well known to reproduce themselves truly by seed; but +Downing asserts,[617] "that when a graft is taken from one of these trees +and placed upon another stock, this grafted tree is found to lose its +singular property of producing the same variety by seed, and becomes like +all other worked trees;"--that is, its seedlings become highly variable. +Another case is worth giving: the Lalande variety of the walnut-tree leafs +between April 20th and May 15th, and its seedlings invariably inherit the +same habit; whilst several other varieties of the walnut leaf in June. Now, +if seedlings are raised from the May-leafing Lalande variety, grafted on +another May-leafing variety, though both stock and graft have the same +early habit of leafing, yet the seedlings leaf at various times, {260} even +as late as the 5th of June.[618] Such facts as these are well fitted to +show, on what obscure and slight causes variability rests. + + I may here just allude to the appearance of new and valuable varieties + of fruit-trees and of wheat in woods and waste places, which at first + sight seems a most anomalous circumstance. In France a considerable + number of the best pears have been discovered in woods; and this has + occurred so frequently, that Poiteau asserts that "improved varieties + of our cultivated fruits rarely originate with nurserymen."[619] In + England, on the other hand, no instance of a good pear having been + found wild has been recorded; and Mr. Rivers informs me that he knows + of only one instance with apples, namely, the Bess Poole, which was + discovered in a wood in Nottinghamshire. This difference between the + two countries may be in part accounted for by the more favourable + climate of France, but chiefly from the great number of seedlings which + spring up there in the woods. I infer that this is the case from a + remark made by a French gardener,[620] who regards it as a national + calamity that such a number of pear-trees are periodically cut down for + firewood, before they have borne fruit. The new varieties which thus + spring up in the woods, though they cannot have received any excess of + nutriment, will have been exposed to abruptly changed conditions, but + whether this is the cause of their production is very doubtful. These + varieties, however, are probably all descended[621] from old cultivated + kinds growing in adjoining orchards,--a circumstance which will account + for their variability; and out of a vast number of varying trees there + will always be a good chance of the appearance of a valuable kind. In + North America, where fruit-trees frequently spring up in waste places, + the Washington pear was found in a hedge, and the Emperor peach in a + wood.[622] + + With respect to wheat, some writers have spoken[623] as if it were an + ordinary event for new varieties to be found in waste places; the + Fenton wheat was certainly discovered growing on a pile of basaltic + detritus in a quarry, but in such a situation the plant would probably + receive a sufficient amount {261} of nutriment. The Chidham wheat was + raised from an ear found _on_ a hedge; and Hunter's wheat was + discovered _by_ the roadside in Scotland, but it is not said that this + latter variety grew where it was found.[624] + +Whether our domestic productions would ever become so completely habituated +to the conditions under which they now live, as to cease varying, we have +no sufficient means for judging. But, in fact, our domestic productions are +never exposed for a great length of time to uniform conditions, and it is +certain that our most anciently cultivated plants, as well as animals, +still go on varying, for all have recently undergone marked improvement. In +some few cases, however, plants have become habituated to new conditions. +Thus Metzger, who cultivated in Germany during many years numerous +varieties of wheat, brought from different countries,[625] states that some +kinds were at first extremely variable, but gradually, in one instance +after an interval of twenty-five years, became constant; and it does not +appear that this resulted from the selection of the more constant forms. + + * * * * * + +_On the Accumulative Action of changed Conditions of Life._--We have good +grounds for believing that the influence of changed conditions accumulates, +so that no effect is produced on a species until it has been exposed during +several generations to continued cultivation or domestication. Universal +experience shows us that when new flowers are first introduced into our +gardens they do not vary; but ultimately all, with the rarest exceptions, +vary to a greater or less extent. In a few cases the requisite number of +generations, as well as the successive steps in the progress of variation, +have been recorded, as in the often-quoted instance of the Dahlia.[626] +After several years' culture the Zinnia has only lately (1860) begun to +vary in any great degree. "In the first seven or eight years of high +cultivation the Swan River daisy (_Brachycome iberidifolia_) kept to its +original colour; it then varied into lilac and purple and other minor +shades."[627] Analogous facts have been recorded with the Scotch rose. In +discussing the variability of plants several experienced horticulturists +have spoken to the {262} same general effect. Mr. Salter[628] remarks, +"Every one knows that the chief difficulty is in breaking through the +original form and colour of the species, and every one will be on the +look-out for any natural sport, either from seed or branch; that being once +obtained, however trifling the change may be, the result depends upon +himself." M. de Jonghe, who has had so much success in raising new +varieties of pears and strawberries,[629] remarks with respect to the +former, "There is another principle, namely, that the more a type has +entered into a state of variation, the greater is its tendency to continue +doing so; and the more it has varied from the original type, the more it is +disposed to vary still farther." We have, indeed, already discussed this +latter point when treating of the power which man possesses, through +selection, of continually augmenting in the same direction each +modification; for this power depends on continued variability of the same +general kind. The most celebrated horticulturist in France, namely, +Vilmorin,[630] even maintains that, when any particular variation is +desired, the first step is to get the plant to vary in any manner whatever, +and to go on selecting the most variable individuals, even though they vary +in the wrong direction; for the fixed character of the species being once +broken, the desired variation will sooner or later appear. + +As nearly all our animals were domesticated at an extremely remote epoch, +we cannot, of course, say whether they varied quickly or slowly when first +subjected to new conditions. But Dr. Bachman[631] states that he has seen +turkeys raised from the eggs of the wild species lose their metallic tints +and become spotted with white in the third generation. Mr. Yarrell many +years ago informed me that the wild ducks bred on the ponds in St. James's +Park, which had never been crossed, as it is believed, with domestic ducks, +lost their true plumage after a few generations. An excellent +observer,[632] who has often reared birds from the eggs of the wild duck, +and who took precautions {263} that there should be no crossing with +domestic breeds, has given, as previously stated, full details on the +changes which they gradually undergo. He found that he could not breed +these wild ducks true for more than five or six generations, "as they then +proved so much less beautiful. The white collar round the neck of the +mallard became much broader and more irregular, and white feathers appeared +in the ducklings' wings." They increased also in size of body; their legs +became less fine, and they lost their elegant carriage. Fresh eggs were +then procured from wild birds; but again the same result followed. In these +cases of the duck and turkey we see that animals, like plants, do not +depart from their primitive type until they have been subjected during +several generations to domestication. On the other hand, Mr. Yarrell +informed me that the Australian dingos, bred in the Zoological Gardens, +almost invariably produced in the first generation puppies marked with +white and other colours; but these introduced dingos had probably been +procured from the natives, who keep them in a semi-domesticated state. It +is certainly a remarkable fact that changed conditions should at first +produce, as far as we can see, absolutely no effect; but that they should +subsequently cause the character of the species to change. In the chapter +on pangenesis I shall attempt to throw a little light on this fact. + + * * * * * + +Returning now to the causes which are supposed to induce variability. Some +authors[633] believe that close interbreeding gives this tendency, and +leads to the production of monstrosities. In the seventeenth chapter some +few facts were advanced, showing that monstrosities are, as it appears, +occasionally thus caused; and there can be no doubt that close +interbreeding induces lessened fertility and a weakened constitution; hence +it may lead to variability: but I have not sufficient evidence on this +head. On the other hand, close interbreeding, if not carried to an +injurious extreme, far from causing variability, tends to fix the character +of each breed. + +It was formerly a common belief, still held by some persons, that the +imagination of the mother affects the child in {264} the womb.[634] This +view is evidently not applicable to the lower animals, which lay +unimpregnated eggs, or to plants. Dr. William Hunter, in the last century, +told my father that during many years every woman in a large London +Lying-in Hospital was asked before her confinement whether anything had +specially affected her mind, and the answer was written down; and it so +happened that in no one instance could a coincidence be detected between +the woman's answer and any abnormal structure; but when she knew the nature +of the structure, she frequently suggested some fresh cause. The belief in +the power of the mother's imagination may perhaps have arisen from the +children of a second marriage resembling the previous father, as certainly +sometimes occurs, in accordance with the facts given in the eleventh +chapter. + + * * * * * + +_Crossing as a Cause of Variability._--In an early part of this chapter it +was stated that Pallas[635] and a few other naturalists maintain that +variability is wholly due to crossing. If this means that new characters +never spontaneously appear in our domestic races, but that they are all +directly derived from certain aboriginal species, the doctrine is little +less than absurd; for it implies that animals like Italian greyhounds, +pug-dogs, bull-dogs, pouter and fantail pigeons, &c., were able to exist in +a state of nature. But the doctrine may mean something widely different, +namely, that the crossing of distinct species is the sole cause of the +first appearance of new characters, and that without this aid man could not +have formed his various breeds. As, however, new characters have appeared +in certain cases by bud-variation, we may conclude with certainty that +crossing is not necessary for variability. It is, moreover, almost certain +that the breeds of various animals, such as of the rabbit, pigeon, duck, +&c., and the varieties of several plants, are the modified descendants of a +single wild species. Nevertheless, it is probable that the crossing of two +forms, when one or both have long been domesticated or cultivated, adds to +the variability of the offspring, independently of the commingling of the +characters derived from the two parent-forms; and this implies {265} that +new characters actually arise. But we must not forget the facts advanced in +the thirteenth chapter, which clearly prove that the act of crossing often +leads to the reappearance or reversion of long-lost characters; and in most +cases it would be impossible to distinguish between the reappearance of +ancient characters and the first appearance of new characters. Practically, +whether new or old, they would be new to the breed in which they +reappeared. + + Gärtner declares,[636] and his experience is of the highest value on + such a point, that, when he crossed native plants which had not been + cultivated, he never once saw in the offspring any new character; but + that from the odd manner in which the characters derived from the + parents were combined, they sometimes appeared as if new. When, on the + other hand, he crossed cultivated plants, he admits that new characters + occasionally appeared, but he is strongly inclined to attribute their + appearance to ordinary variability, not in any way to the cross. An + opposite conclusion, however, appears to me the more probable. + According to Kölreuter, hybrids in the genus Mirabilis vary almost + infinitely, and he describes new and singular characters in the form of + the seeds, in the colour of the anthers, in the cotyledons being of + immense size, in new and highly peculiar odours, in the flowers + expanding early in the season, and in their closing at night. With + respect to one lot of these hybrids, he remarks that they presented + characters exactly the reverse of what might have been expected from + their parentage.[637] + + Prof. Lecoq[638] speaks strongly to the same effect in regard to this + same genus, and asserts that many of the hybrids from _Mirabilis + jalapa_ and _multiflora_ might easily be mistaken for distinct species, + and adds that they differed in a greater degree, than the other species + of the genus, from _M. jalapa_. Herbert, also, has described[639] the + offspring from a hybrid Rhododendron as being "as _unlike all others_ + in foliage, as if they had been a separate species." The common + experience of floriculturists proves that the crossing and recrossing + of distinct but allied plants, such as the species of Petunia, + Calceolaria, Fuchsia, Verbena, &c., induces excessive variability; + hence the appearance of quite new characters is probable. M. + Carrière[640] has lately discussed this subject: he states that + _Erythrina cristagalli_ had been multiplied by seed for many years, but + had not yielded any varieties: it was then crossed with the allied _E. + herbacea_, and "the resistance was now overcome, and varieties were + produced with flowers of extremely different size, form, and colour." + + From the general and apparently well-founded belief that the crossing + {266} of distinct species, besides commingling their characters, adds + greatly to their variability, it has probably arisen that some + botanists have gone so far as to maintain[641] that, when a genus + includes only a single species, this when cultivated never varies. The + proposition made so broadly cannot be admitted; but it is probably true + that the variability of cultivated monotypic genera is much less than + that of genera including numerous species, and this quite independently + of the effects of crossing. I have stated in my 'Origin of Species,' + and in a future work shall more fully show, that the species belonging + to small genera generally yield a less number of varieties in a state + of nature than those belonging to large genera. Hence the species of + small genera would, it is probable, produce fewer varieties under + cultivation than the already variable species of larger genera. + + Although we have not at present sufficient evidence that the crossing + of species, which have never been cultivated, leads to the appearance + of new characters, this apparently does occur with species which have + been already rendered in some degree variable through cultivation. + Hence crossing, like any other change in the conditions of life, seems + to be an element, probably a potent one, in causing variability. But we + seldom have the means of distinguishing, as previously remarked, + between the appearance of really new characters and the reappearance of + long-lost characters, evoked through the act of crossing. I will give + an instance of the difficulty in distinguishing such cases. The species + of Datura may be divided into two sections, those having white flowers + with green stems, and those having purple flowers with brown stems: now + Naudin[642] crossed _Datura lævis_ and _ferox_, both of which belong to + the white section, and raised from them 205 hybrids. Of these hybrids, + every one had brown stems and bore purple flowers; so that they + resembled the species of the other section of the genus, and not their + own two parents. Naudin was so much astonished at this fact, that he + was led carefully to observe both parent-species, and he discovered + that the pure seedlings of _D. ferox_, immediately after germination, + had dark purple stems, extending from the young roots up to the + cotyledons, and that this tint remained ever afterwards as a ring round + the base of the stem of the plant when old. Now I have shown in the + thirteenth chapter that the retention or exaggeration of an early + character is so intimately related to reversion, that it evidently + comes under the same principle. Hence probably we ought to look at the + purple flowers and brown stems of these hybrids, not as new characters + due to variability, but as a return to the former state of some ancient + progenitor. + + Independently of the appearance of new characters from crossing, a few + words may be added to what has been said in former chapters on the + unequal combination and transmission of the characters proper to the + two parent-forms. When two species or races are crossed, the offspring + of {267} the first generation are generally uniform, but subsequently + they display an almost infinite diversity of character. He who wishes, + says Kölreuter,[643] to obtain an endless number of varieties from + hybrids should cross and recross them. There is also much variability + when hybrids or mongrels are reduced or absorbed by repeated crosses + with either pure parent-form; and a still higher degree of variability + when three distinct species, and most of all when four species, are + blended together by successive crosses. Beyond this point Gärtner,[644] + on whose authority the foregoing statements are made, never succeeded + in effecting a union; but Max Wichura[645] united six distinct species + of willows into a single hybrid. The sex of the parent-species affects + in an inexplicable manner the degree of variability of hybrids; for + Gärtner[646] repeatedly found that when a hybrid was used as the + father, and either one of the pure parent-species, or a third species, + was used as the mother, the offspring were more variable than when the + same hybrid was used as the mother, and either pure parent or the same + third species as the father: thus seedlings from _Dianthus barbatus_ + crossed by the hybrid _D. chinensi-barbatus_ were more variable than + those raised from this latter hybrid fertilised by the pure _D. + barbatus_. Max Wichura[647] insists strongly on an analogous result + with his hybrid willows. Again Gärtner[648] asserts that the degree of + variability sometimes differs in hybrids raised from reciprocal crosses + between the same two species; and here the sole difference is, that the + one species is first used as the father and then as the mother. On the + whole we see that, independently of the appearance of new characters, + the variability of successive crossed generations is extremely complex, + partly from the offspring partaking unequally of the characters of the + two parent-forms, and more especially from their unequal tendency to + revert to these same characters or to those of more ancient + progenitors. + + * * * * * + +_On the Manner and on the Period of Action of the Causes which induce +Variability._--This is an extremely obscure subject, and we need here only +briefly consider, firstly, whether inherited variations are caused by the +organisation being directly acted on, or indirectly through the +reproductive system; and secondly, at what period of life or growth they +are primarily caused. We shall see in the two following chapters that +various agencies, such as an abundant supply of food, exposure to a +different climate, increased use or disuse of parts, &c., prolonged during +several generations, certainly modify either the whole organisation or +certain organs. This direct action of changed conditions perhaps comes into +play much more frequently than can be proved, and it is at least clear that +in all cases of {268} bud-variation the action cannot have been through the +reproductive system. + + With respect to the part which the reproductive system takes in causing + variability, we have seen in the eighteenth chapter that even slight + changes in the conditions of life have a remarkable power in causing a + greater or less degree of sterility. Hence it seems not improbable that + being generated though a system so easily affected should themselves be + affected, or should fail to inherit, or inherit in excess, characters + proper to their parents. We know that certain groups of organic beings, + but with exceptions in each group, have their reproductive systems much + more easily affected by changed conditions than other groups; for + instance, carnivorous birds more readily than carnivorous mammals, and + parrots more readily than pigeons; and this fact harmonizes with the + apparently capricious manner and degree in which various groups of + animals and plants vary under domestication. + + Kölreuter[649] was struck with the parallelism between the excessive + variability of hybrids when crossed and recrossed in various + ways,--these hybrids having their reproductive powers more or less + affected,--and the variability of anciently cultivated plants. Max + Wichura[650] has gone one step farther, and shows that with many of our + highly cultivated plants, such as the hyacinth, tulip, auricula, + snapdragon, potato, cabbage, &c., which there is no reason to believe + have been hybridized, the anthers contain many irregular pollen-grains, + in the same state as in hybrids. He finds also in certain wild forms, + the same coincidence between the state of the pollen and a high degree + of variability, as in many species of Rubus; but in _R. cæsius_ and + _idæus_, which are not highly variable species, the pollen is sound. It + is also notorious that many cultivated plants, such as the banana, + pine-apple, breadfruit, and others previously mentioned, have their + reproductive organs so seriously affected as to be generally quite + sterile; and when they do yield seed, the seedlings, judging from the + large number of cultivated races which exist, must be variable in an + extreme degree. These facts indicate that there is some relation + between the state of the reproductive organs and a tendency to + variability; but we must not conclude that the relation is strict. + Although many of our highly cultivated plants may have their pollen in + a deteriorated condition, yet, as we have previously seen, they yield + more seed, and our anciently domesticated animals are more prolific, + than the corresponding species in a state of nature. The peacock is + almost the only bird which is believed to be less fertile under + domestication than in its native state, and it has varied in a + remarkably small degree. From these considerations it would seem that + changes in the conditions of life lead either to sterility or to + variability, or to both; and not that sterility induces variability. On + the whole it is probable that any cause affecting the organs of + reproduction would likewise affect their product,--that is, the + offspring thus generated. + + {269} + + The period of life at which the causes that induce variability act, is + another obscure subject, which has been discussed by various + authors.[651] In some of the cases, to be given in the following + chapter, of modifications from the direct action of changed conditions, + which are inherited, there can be no doubt that the causes have acted + on the mature or nearly mature animal. On the other hand, + monstrosities, which cannot be distinctly separated from lesser + variations, are often caused by the embryo being injured whilst in the + mother's womb or in the egg. Thus I. Geoffroy St. Hilaire[652] asserts + that poor women who work hard during their pregnancy, and the mothers + of illegitimate children troubled in their minds and forced to conceal + their state, are far more liable to give birth to monsters than women + in easy circumstances. The eggs of the fowl when placed upright or + otherwise treated unnaturally frequently produce monstrous chickens. It + would, however, appear that complex monstrosities are induced more + frequently during a rather late than during a very early period of + embryonic life; but this may partly result from some one part, which + has been injured during an early period, affecting by its abnormal + growth other parts subsequently developed; and this would be less + likely to occur with parts injured at a later period.[653] When any + part or organ becomes monstrous through abortion, a rudiment is + generally left, and this likewise indicates that its development had + already commenced. + + Insects sometimes have their antennæ or legs in a monstrous condition, + and yet the larvæ from which they are metamorphosed do not possess + either antennæ or legs; and in those cases, as Quatrefages[654] + believes, we are enabled to see the precise period at which the normal + progress of development has been troubled. But the nature of the food + given to a caterpillar sometimes affects the colours of the moth, + without the caterpillar itself being affected; therefore it seems + possible that other characters in the mature insect might be indirectly + modified through the larvæ. There is no reason to suppose that organs + which have been rendered monstrous have always been acted on during + their development; the cause may have acted on the organisation at a + much earlier stage. It is even probable that either the male or female + sexual elements, or both, before their union, may be affected in such a + manner as to lead to modifications in organs developed at a late period + of life; in nearly the same manner as a child may inherit from his + father a disease which does not appear until old age. + + In accordance with the facts above given, which prove that in many + cases a close relation exists between variability and the sterility + following from changed conditions, we may conclude that the exciting + cause often acts at the earliest possible period, namely, on the sexual + elements, before impregnation has taken place. That an affection of the + female sexual element may induce variability we may likewise infer as + probable from the occurrence of bud-variations; for a bud seems to be + the analogue of an ovule. But the male element is apparently much + oftener affected by changed {270} conditions, at least in a visible + manner, than the female element or ovule; and we know from Gärtner's + and Wichura's statements that a hybrid used as the father and crossed + with a pure species gives a greater degree of variability to the + offspring, than does the same hybrid when used as the mother. Lastly, + it is certain that variability may be transmitted through either sexual + element, whether or not originally excited in them, for Kölreuter and + Gärtner[655] found that when two species were crossed, if either one + was variable, the offspring were rendered variable. + + * * * * * + +_Summary._--From the facts given in this chapter, we may conclude that the +variability of organic beings under domestication, although so general, is +not an inevitable contingent on growth and reproduction, but results from +the conditions to which the parents have been exposed. Changes of any kind +in the conditions of life, even extremely slight changes, often suffice to +cause variability. Excess of nutriment is perhaps the most efficient single +exciting cause. Animals and plants continue to be variable for an immense +period after their first domestication; but the conditions to which they +are exposed never long remain quite constant. In the course of time they +can be habituated to certain changes, so as to become less variable; and it +is possible that when first domesticated they may have been even more +variable than at present. There is good evidence that the power of changed +conditions accumulates; so that two, three, or more generations must be +exposed to new conditions before any effect is visible. The crossing of +distinct forms, which have already become variable, increases in the +offspring the tendency to further variability, by the unequal commingling +of the characters of the two parents, by the reappearance of long-lost +characters, and by the appearance of absolutely new characters. Some +variations are induced by the direct action of the surrounding conditions +on the whole organisation, or on certain parts alone, and other variations +are induced indirectly through the reproductive system being affected in +the same manner as is so common with organic beings when removed from their +natural conditions. The causes which induce variability act on the mature +organism, on the embryo, and, as we have good reason to believe, on both +sexual elements before impregnation has been effected. + + * * * * * + + +{271} + +CHAPTER XXIII. + +DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS OF LIFE. + + SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE ACTION OF CHANGED + CONDITIONS IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND IN THE STATE OF + THE TISSUES--LOCAL DISEASES--CONSPICUOUS MODIFICATIONS FROM CHANGED + CLIMATE OR FOOD, ETC.--PLUMAGE OF BIRDS AFFECTED BY PECULIAR NUTRIMENT, + AND BY THE INOCULATION OF POISON--LAND-SHELLS--MODIFICATIONS OF ORGANIC + BEINGS IN A STATE OF NATURE THROUGH THE DEFINITE ACTION OF EXTERNAL + CONDITIONS--COMPARISON OF AMERICAN AND EUROPEAN TREES--GALLS--EFFECTS + OF PARASITIC FUNGI--CONSIDERATIONS OPPOSED TO THE BELIEF IN THE POTENT + INFLUENCE OF CHANGED EXTERNAL CONDITIONS--PARALLEL SERIES OF + VARIETIES--AMOUNT OF VARIATION DOES NOT CORRESPOND WITH THE DEGREE OF + CHANGE IN THE CONDITIONS--BUD-VARIATION--MONSTROSITIES PRODUCED BY + UNNATURAL TREATMENT--SUMMARY. + +If we ask ourselves why this or that character has been modified under +domestication, we are, in most cases lost in utter darkness. Many +naturalists, especially of the French school, attribute every modification +to the "monde ambiant," that is, to changed climate, with all its +diversities of heat and cold, dampness and dryness, light and electricity, +to the nature of the soil, and to varied kinds and amount of food. By the +term definite action, as used in this chapter, I mean an action of such a +nature that, when many individuals of the same variety are exposed during +several generations to any change in their physical conditions of life, +all, or nearly all the individuals, are modified in the same manner. A new +sub-variety would thus be produced without the aid of selection. + +I do not include under the term of definite action the effects of habit or +of the increased use and disuse of various organs. Modifications of this +nature, no doubt, are definitely caused by the conditions to which the +beings are subjected; but they depend much less on the nature of the +conditions than on the laws of growth; hence they are included under a +distinct head in the {272} following chapter. We know, however, far too +little of the causes and laws of variation to make a sound classification. +The direct action of the conditions of life, whether leading to definite or +indefinite results, is a totally distinct consideration from the effects of +natural selection; for natural selection depends on the survival under +various and complex circumstances of the best-fitted individuals, but has +no relation whatever to the primary cause of any modification of structure. + +I will first give in detail all the facts which I have been able to +collect, rendering it probable that climate, food, &c., have acted so +definitely and powerfully on the organisation of our domesticated +productions, that they have sufficed to form new sub-varieties or races, +without the aid of selection by man or of natural selection. I will then +give the facts and considerations opposed to this conclusion, and finally +we will weigh, as fairly as we can, the evidence on both sides. + +When we reflect that distinct races of almost all our domesticated animals +exist in each kingdom of Europe, and formerly even in each district of +England, we are at first strongly inclined to attribute their origin to the +definite action of the physical conditions of each country; and this has +been the conclusion of many authors. But we should bear in mind that man +annually has to choose which animals shall be preserved for breeding, and +which shall be slaughtered. We have also seen that both methodical and +unconscious selection were formerly practised, and are now occasionally +practised by the most barbarous races, to a much greater extent than might +have been anticipated. Hence it is very difficult to judge how far the +difference in conditions between, for instance, the several districts in +England, could have sufficed without the aid of selection to modify the +breeds which have been reared in each. It may be argued that, as numerous +wild animals and plants have ranged during many ages throughout Great +Britain, and still retain the same character, the difference in conditions +between the several districts could not have modified in so marked a manner +the various native races of cattle, sheep, pigs, and horses. The same +difficulty of distinguishing between selection and the definite effects of +the conditions of life, is encountered in a still higher degree when we +compare closely allied natural {273} forms, inhabiting two countries, such +as North America and Europe, which do not differ greatly in climate, nature +of soil, &c., for in this case natural selection will inevitably and +rigorously have acted during a long succession of ages. + + From the importance of the difficulty just alluded to, it will be + advisable to give as large a body of facts as possible, showing that + extremely slight differences in treatment, either in different parts of + the same country, or during different seasons, certainly cause an + appreciable effect, at least on varieties which are already in an + unstable condition. Ornamental flowers are good for this purpose, as + they are highly variable, and are carefully observed. All + floriculturists are unanimous that certain varieties are affected by + very slight differences in the nature of the artificial compost in + which they are grown, and by the natural soil of the district, and by + the season. Thus, a skilful judge, in writing on Carnations and + Picotees,[656] asks "where can Admiral Curzon be seen possessing the + colour, size, and strength which it has in Derbyshire? Where can + Flora's Garland be found equal to those at Slough? Where do + high-coloured flowers revel better than at Woolwich and Birmingham? Yet + in no two of these districts do the same varieties attain an equal + degree of excellence, although each may be receiving the attention of + the most skilful cultivators." The same writer then recommends every + cultivator to keep five different kinds of soil and manure, "and to + endeavour to suit the respective appetites of the plants you are + dealing with, for without such attention all hope of general success + will be vain." So it is with the Dahlia:[657] the Lady Cooper rarely + succeeds near London, but does admirably in other districts; the + reverse holds good with other varieties; and again, there are others + which succeed equally well in various situations. A skilful + gardener[658] states that he procured cuttings of an old and well-known + variety (pulchella) of Verbena, which from having been propagated in a + different situation presented a slightly different shade of colour; the + two varieties were afterwards multiplied by cuttings, being carefully + kept distinct; but in the second year they could hardly be + distinguished, and in the third year no one could distinguish them. + + The nature of the season has an especial influence on certain varieties + of the Dahlia: in 1841 two varieties were pre-eminently good, and the + next year these same two were pre-eminently bad. A famous amateur[659] + asserts that in 1861 many varieties of the Rose came so untrue in + character, "that it was hardly possible to recognise them, and the + thought was not seldom entertained that the grower had lost his tally." + The same amateur[660] states that in 1862 two-thirds of his Auriculas + produced central trusses of flowers, and these are remarkable from not + keeping true; {274} and he adds that in some seasons certain varieties + of this plant all prove good, and the next season all prove bad; whilst + exactly the reverse happens with other varieties. In 1845 the editor of + the 'Gardener's Chronicle'[661] remarked how singular it was that this + year many Calceolarias tended to assume a tubular form. With + Heartsease[662] the blotched sorts do not acquire their proper + character until hot weather sets in; whilst other varieties lose their + beautiful marks as soon as this occurs. + + Analogous facts have been observed with leaves: Mr. Beaton asserts[663] + that he raised at Shrubland, during six years, twenty thousand + seedlings from the Punch Pelargonium, and not one had variegated + leaves; but at Surbiton, in Surrey, one-third, or even a greater + proportion, of the seedlings from this same variety were more or less + variegated. The soil of another district in Surrey has a strong + tendency to cause variegation, as appears from information given me by + Sir F. Pollock. Verlot[664] states that the variegated strawberry + retains its character as long as grown in a dryish soil, but soon loses + it when planted in fresh and humid soil. Mr. Salter, who is well known + for his success in cultivating variegated plants, informs me that rows + of strawberries were planted in his garden in 1859, in the usual way; + and at various distances in one row, several plants simultaneously + became variegated, and what made the case more extraordinary, all were + variegated in precisely the same manner. These plants were removed, but + during the three succeeding years other plants in the same row became + variegated, and in no instance were the plants in any adjoining row + affected. + + The chemical qualities, odours, and tissues of plants are often + modified by a change which seems to us slight. The Hemlock is said not + to yield conicine in Scotland. The root of the _Aconitum napellus_ + becomes innocuous in frigid climates. The medicinal properties of the + Digitalis are easily affected by culture. The Rhubarb flourishes in + England, but does not produce the medicinal substance which makes the + plant so valuable in Chinese Tartary. As the _Pistacia lentiscus_ grows + abundantly in the South of France, the climate must suit it, but it + yields no mastic. The _Laurus sassafras_ in Europe loses the odour + proper to it in North America.[665] Many similar facts could be given, + and they are remarkable because it might have been thought that + definite chemical compounds would have been little liable to change + either in quality or quantity. + + The wood of the American Locust-tree (_Robinia_) when grown in England + is nearly worthless, as is that of the Oak-tree when grown at the Cape + of Good Hope.[666] Hemp and flax, as I hear from Dr. Falconer, flourish + and yield plenty of seed on the plains of India, but their fibres are + brittle {275} and useless. Hemp, on the other hand, fails to produce in + England that resinous matter which is so largely used in India as an + intoxicating drug. + + The fruit of the Melon is greatly influenced by slight differences in + culture and climate. Hence it is generally a better plan, according to + Naudin, to improve an old kind than to introduce a new one into any + locality. The seed of the Persian Melon produces near Paris fruit + inferior to the poorest market kinds, but at Bordeaux yields delicious + fruit.[667] Seed is annually brought from Thibet to Kashmir,[668] and + produces fruit weighing from four to ten pounds, but plants raised from + seed saved in Kashmir next year give fruit weighing only from two to + three pounds. It is well known that American varieties of the Apple + produce in their native land magnificent and brightly-coloured fruit, + but in England of poor quality and a dull colour. In Hungary there are + many varieties of the Kidney-bean, remarkable for the beauty of their + seeds, but the Rev. M. J. Berkeley[669] found that their beauty could + hardly ever be preserved in England, and in some cases the colour was + greatly changed. We have seen in the ninth chapter, with respect to + wheat, what a remarkable effect transportal from the North to the South + of France, and reversely, produced on the weight of the grain. + +When man can perceive no change in plants or animals which have been +exposed to a new climate or to different treatment, insects can sometimes +perceive a marked change. The same species of cactus has been carried to +India from Canton, Manilla, Mauritius, and from the hot-houses of Kew, and +there is likewise a so-called native kind, formerly introduced from South +America; all these plants are alike in appearance, but the cochineal insect +flourishes only on the native kind, on which it thrives prodigiously.[670] +Humboldt remarks[671] that white men "born in the torrid zone walk barefoot +with impunity in the same apartment where a European, recently landed, is +exposed to the attacks of the _Pulex penetrans_." This insect, the too +well-known chigoe, must therefore be able to distinguish what the most +delicate chemical analysis fails to distinguish, namely, a difference +between the blood or tissues of a European and those of a white man born in +the country. But the discernment of the chigoe is not so surprising as it +at first appears; for {276} according to Liebig[672] the blood of men with +different complexions, though inhabiting the same country, emits a +different odour. + + Diseases peculiar to certain localities, heights, or climates, may be + here briefly noticed, as showing the influence of external + circumstances on the human body. Diseases confined to certain races of + man do not concern us, for the constitution of the race may play the + more important part, and this may have been determined by unknown + causes. The Plica Polonica stands, in this respect, in a nearly + intermediate position; for it rarely affects Germans, who inhabit the + neighbourhood of the Vistula, where so many Poles are grievously + affected; and on the other hand, it does not affect Russians, who are + said to belong to the same original stock with the Poles.[673] The + elevation of a district often governs the appearance of diseases; in + Mexico the yellow fever does not extend above 924 mètres; and in Peru, + people are affected with the _verugas_ only between 600 and 1600 mètres + above the sea; many other such cases could be given. A peculiar + cutaneous complaint, called the _Bouton d'Alep_, affects in Aleppo and + some neighbouring districts almost every native infant, and some few + strangers; and it seems fairly well established that this singular + complaint depends on drinking certain waters. In the healthy little + island of St. Helena the scarlet-fever is dreaded like the Plague; + analogous facts have been observed in Chili and Mexico.[674] Even in + the different departments of France it is found that the various + infirmities which render the conscript unfit for serving in the army, + prevail with remarkable inequality, revealing, as Boudin observes, that + many of them are endemic, which otherwise would never have been + suspected.[675] Any one who will study the distribution of disease will + be struck with surprise at what slight differences in the surrounding + circumstances govern the nature and severity of the complaints by which + man is at least temporarily affected. + +The modifications as yet referred to have been extremely slight, and in +most cases have been caused, as far as we can judge, by equally slight +changes in the conditions. But can it be safely maintained that such +changed conditions, if acting during a long series of generations, would +not produce a marked effect? It is commonly believed that the people of the +United States differ in appearance from the parent Anglo-Saxon race; and +selection cannot have come into action within so short a period. A good +observer[676] states that a general absence of fat, {277} a thin and +elongated neck, stiff and lank hair, are the chief characteristics. The +change in the nature of the hair is supposed to be caused by the dryness of +the atmosphere. If immigration into the United States were now stopped, who +can say that the character of the whole people would not be greatly +modified in the course of two or three thousand years? + + The direct and definite action of changed conditions, in + contradistinction to the accumulation of indefinite variations, seems + to me so important that I will give a large additional body of + miscellaneous facts. With plants, a considerable change of climate + sometimes produces a conspicuous result. I have given in detail in the + ninth chapter the most remarkable case known to me, namely, that in + Germany several varieties of maize brought from the hotter parts of + America were transformed in the course of only two or three + generations. Dr. Falconer informs me that he has seen the English + Ribston-pippin apple, a Himalayan oak, Prunus and Pyrus, all assume in + the hotter parts of India a fastigate or pyramidal habit; and this fact + is the more interesting, as a Chinese tropical species of Pyrus + naturally has this habit of growth. Although in these cases the changed + manner of growth seems to have been directly caused by the great heat, + we know that many fastigate trees have originated in their temperate + homes. In the Botanic Gardens of Ceylon the apple-tree[677] "sends out + numerous runners under ground, which continually rise into small stems, + and form a growth around the parent-tree." The varieties of the cabbage + which produce heads in Europe fail to do so in certain tropical + countries.[678] The _Rhododendron ciliatum_ produced at Kew flowers so + much larger and paler-coloured than those which it bears on its native + Himalayan mountain, that Dr. Hooker[679] would hardly have recognised + the species by the flowers alone. Many similar facts with respect to + the colour and size of flowers could be given. + + The experiments of Vilmorin and Buckman on carrots and parsnips prove + that abundant nutriment produces a definite and inheritable effect on + the so-called roots, with scarcely any change in other parts of the + plant. Alum directly influences the colour of the flowers of the + Hydrangea.[680] Dryness seems generally to favour the hairyness or + villosity of plants. Gärtner found that hybrid Verbascums became + extremely woolly when grown in pots. Mr. Masters, on the other hand, + states that the _Opuntia leucotricha_ "is well clothed with beautiful + white hairs when grown in a damp heat; but in a dry heat exhibits none + of this peculiarity."[681] Slight variations of many kinds, not worth + specifying in detail, are retained only as {278} long as plants are + grown in certain soils, of which Sageret[682] gives from his own + experience some instances. Odart, who insists strongly on the + permanence of the varieties of the grape, admits[683] that some + varieties, when grown under a different climate or treated differently, + vary in an extremely slight degree, as in the tint of the fruit and in + the period of ripening. Some authors have denied that grafting causes + even the slightest difference in the scion; but there is sufficient + evidence that the fruit is sometimes slightly affected in size and + flavour, the leaves in duration, and the flowers in appearance.[684] + + With animals there can be no doubt, from the facts given in the first + chapter, that European dogs deteriorate in India, not only in their + instincts but in structure; but the changes which they undergo are of + such a nature, that they may be partly due to reversion to a primitive + form, as in the case of feral animals. In parts of India the turkey + becomes reduced in size, "with the pendulous appendage over the beak + enormously developed."[685] We have seen how soon the wild duck, when + domesticated, loses its true character, from the effects of abundant or + changed food, or from taking little exercise. From the direct action of + a humid climate and poor pasture the horse rapidly decreases in size in + the Falkland Islands. From information which I have received, this + seems likewise to be the case to a certain extent with sheep in + Australia. + + Climate definitely influences the hairy covering of animals; in the + West Indies a great change is produced in the fleece of sheep, in about + three generations. Dr. Falconer states[686] that the Thibet mastiff and + goat, when brought down from the Himalaya to Kashmir, lose their fine + wool. At Angora not only goats, but shepherd-dogs and cats, have fine + fleecy hair, and Mr. Ainsworth[687] attributes the thickness of the + fleece to the severe winters, and its silky lustre to the hot summers. + Burnes states positively[688] that the Karakool sheep lose their + peculiar black curled fleeces when removed into any other country. Even + within the limits of England, I have been assured that with two breeds + of sheep the wool was slightly changed by the flocks being pastured in + different localities.[689] It has been asserted on good authority[690] + that horses kept during several years in the deep coal-mines of Belgium + become covered with velvety hair, almost like that on the mole. These + cases probably stand in close relation to the natural change of coat in + winter and summer. Naked varieties of several domestic animals have + occasionally appeared; but there is no reason to {279} believe that + this is in any way related to the nature of the climate to which they + have been exposed.[691] + + It appears at first sight probable that the increased size, the + tendency to fatten, the early maturity and altered forms of our + improved cattle, sheep, and pigs, have directly resulted from their + abundant supply of food. This is the opinion of many competent judges, + and probably is to a great extent true. But as far as form is + concerned, we must not overlook the equal or more potent influence of + lessened use on the limbs and lungs. We see, moreover, as far as size + is concerned, that selection is apparently a more powerful agent than a + large supply of food, for we can thus only account for the existence, + as remarked to me by Mr. Blyth, of the largest and smallest breeds of + sheep in the same country, of Cochin-China fowls and Bantams, of small + Tumbler and large Runt pigeons, all kept together and supplied with + abundant nourishment. Nevertheless there can be little doubt that our + domesticated animals have been modified, independently of the increased + or lessened use of parts, by the conditions to which they have been + subjected, without the aid of selection. For instance, Prof. + Rütimeyer[692] shows that the bones of all domesticated quadrupeds can + be distinguished from those of wild animals by the state of their + surface and general appearance. It is scarcely possible to read + Nathusius's excellent 'Vorstudien,'[693] and doubt that, with the + highly improved races of the pig, abundant food has produced a + conspicuous effect on the general form of the body, on the breadth of + the head and face, and even on the teeth. Nathusius rests much on the + case of a purely bred Berkshire pig, which when two months old became + diseased in its digestive organs, and was preserved for observation + until nineteen months old; at this age it had lost several + characteristic features of the breed, and had acquired a long, narrow + head, of large size relatively to its small body, and elongated legs. + But in this case and in some others we ought not to assume that, + because certain characters are lost, perhaps through reversion, under + one course of treatment, therefore that they had been at first directly + produced by an opposite course. + + In the case of the rabbit, which has become feral on the island of + Porto Santo, we are at first strongly tempted to attribute the whole + change--the greatly reduced size, the altered tints of the fur, and the + loss of certain characteristic marks--to the definite action of the new + conditions to which it has been exposed. But in all such cases we have + to consider in addition the tendency to reversion to progenitors more + or less remote, and the natural selection of the finest shades of + difference. + + The nature of the food sometimes either definitely induces certain + peculiarities, or stands in some close relation with them. Pallas long + ago asserted that the fat-tailed sheep of Siberia degenerated and lost + their enormous tails when removed from certain saline pastures; and + recently {280} Erman[694] states that this occurs with the Kirgisian + sheep when brought to Orenburgh. + + It is well known that hemp-seed causes bullfinches and certain other + birds to become black. Mr. Wallace has communicated to me some much + more remarkable facts of the same nature. The natives of the Amazonian + region feed the common green parrot (_Chrysotis festiva_, Linn.) with + the fat of large Siluroid fishes, and the birds thus treated become + beautifully variegated with red and yellow feathers. In the Malayan + archipelago, the natives of Gilolo alter in an analogous manner the + colours of another parrot, namely, the _Lorius garrulus_, Linn., and + thus produce the _Lori rajah_ or King-Lory. These parrots in the Malay + Islands and South America, when fed by the natives on natural vegetable + food, such as rice and plantains, retain their proper colours. Mr. + Wallace has, also, recorded[695] a still more singular fact. "The + Indians (of S. America) have a curious art by which they change the + colours of the feathers of many birds. They pluck out those from the + part they wish to paint, and inoculate the fresh wound with the milky + secretion from the skin of a small toad. The feathers grow of a + brilliant yellow colour, and on being plucked out, it is said, grow + again of the same colour without any fresh operation." + + Bechstein[696] does not entertain any doubt that seclusion from light + affects, at least temporarily, the colours of cage-birds. + + It is well known that the shells of land-mollusca are affected by the + abundance of lime in different districts. Isidore Geoffroy St. + Hilaire[697] gives the case of _Helix lactea_, which has recently been + carried from Spain to the South of France and to the Rio Plata, and in + both these countries now presents a distinct appearance, but whether + this has resulted from food or climate is not known. With respect to + the common oyster, Mr. F. Buckland informs me that he can generally + distinguish the shells from different districts; young oysters brought + from Wales and laid down in beds where "_natives_" are indigenous, in + the short space of two months begin to assume the "native" character. + M. Costa[698] has recorded a much more remarkable case of the same + nature, namely, that young shells taken from the shores of England and + placed in the Mediterranean, at once altered their manner of growth and + formed prominent diverging rays, like those on the shells of the proper + Mediterranean oyster. The same individual shell, showing both forms of + growth, was exhibited before a society in Paris. Lastly, it is well + known that caterpillars fed on different food sometimes either + themselves acquire a different colour or produce moths different in + colour.[699] + + {281} + + It would be travelling beyond my proper limits here to discuss how far + organic beings in a state of nature are definitely modified by changed + conditions. In my 'Origin of Species' I have given a brief abstract of + the facts bearing on this point, and have shown the influence of light + on the colours of birds, and of residence near the sea on the lurid + tints of insects, and on the succulency of plants. Mr. Herbert + Spencer[700] has recently discussed with much ability this whole + subject on broad and general grounds. He argues, for instance, that + with all animals the external and internal tissues are differently + acted on by the surrounding conditions, and they invariably differ in + intimate structure. So again the upper and lower surfaces of true + leaves, as well as of stems and petioles, when these assume the + function and occupy the position of leaves, are differently + circumstanced with respect to light, &c., and apparently in consequence + differ in structure. But, as Mr. Herbert Spencer admits, it is most + difficult in all such cases to distinguish between the effects of the + definite action of physical conditions and the accumulation through + natural selection of inherited variations which are serviceable to the + organism, and which have arisen independently of the definite action of + these conditions. + +Although we are not here concerned with organic beings in a state of +nature, yet I may call attention to one case. Mr. Meehan,[701] in a +remarkable paper, compares twenty-nine kinds of American trees, belonging +to various orders, with their nearest European allies, all grown in close +proximity in the same garden and under as nearly as possible the same +conditions. In the American species Mr. Meehan finds, with the rarest +exceptions, that the leaves fall earlier in the season, and assume before +falling a brighter tint; that they are less deeply toothed or serrated; +that the buds are smaller; that the trees are more diffuse in growth and +have fewer branchlets; and, lastly, that the seeds are smaller--all in +comparison with the corresponding European species. Now, considering that +these trees belong to distinct orders, it is out of the question that the +peculiarities just specified should have been inherited in the one +continent from one progenitor, and in the other from another progenitor; +and considering that the trees inhabit widely different stations, these +peculiarities can hardly be supposed to be of any special {282} service to +the two series in the Old and New Worlds; therefore these peculiarities +cannot have been naturally selected. Hence we are led to infer that they +have been definitely caused by the long-continued action of the different +climate of the two continents on the trees. + +_Galls._--Another class of facts, not relating to cultivated plants, +deserves attention. I allude to the production of galls. Every one knows +the curious, bright-red, hairy productions on the wild rose-tree, and the +various different galls produced by the oak. Some of the latter resemble +fruit, with one face as rosy as the rosiest apple. These bright colours can +be of no service either to the gall-forming insect or to the tree, and +probably are the direct result of the action of the light, in the same +manner as the apples of Nova Scotia or Canada are brighter coloured than +English apples. The strongest upholder of the doctrine that organic beings +are created beautiful to please mankind would not, I presume, extend this +view to galls. According to Osten Sacken's latest revision, no less than +fifty-eight kinds of galls are produced on the several species of oak, by +Cynips with its sub-genera; and Mr. B. D. Walsh[702] states that he can add +many others to the list. One American species of willow, the _Salix +humilis_, bears ten distinct kinds of galls. The leaves which spring from +the galls of various English willows differ completely in shape from the +natural leaves. The young shoots of junipers and firs, when punctured by +certain insects, yield monstrous growths like flowers and cones; and the +flowers of some plants become from the same cause wholly changed in +appearance. Galls are produced in every quarter of the world; of several +sent to me by Mr. Thwaites from Ceylon, some were as symmetrical as a +composite flower when in bud, others smooth and spherical like a berry; +some protected by long spines, others clothed with yellow wool formed of +long cellular hairs, others with regularly tufted hairs. In some galls the +internal structure is simple, but in others it is highly complex; thus M. +Lucaze-Duthiers[703] has figured in the common ink-gall no less than seven +concentric layers, composed of distinct tissue, {283} namely, the +epidermic, sub-epidermic, spongy, intermediate, and the hard protective +layer formed of curiously thickened woody cells, and, lastly, the central +mass abounding with starch-granules on which the larvæ feed. + +Galls are produced by insects of various orders, but the greater number by +species of Cynips. It is impossible to read M. Lucaze-Duthier's discussion +and doubt that the poisonous secretion of the insect causes the growth of +the gall, and every one knows how virulent is the poison secreted by wasps +and bees, which belong to the same order with Cynips. Galls grow with +extraordinary rapidity, and it is said that they attain their full size in +a few days;[704] it is certain that they are almost completely developed +before the larvæ are hatched. Considering that many gall-insects are +extremely small, the drop of secreted poison must be excessively minute; it +probably acts on one or two cells alone, which, being abnormally +stimulated, rapidly increase by a process of self-division. Galls, as Mr. +Walsh[705] remarks, afford good, constant, and definite characters, each +kind keeping as true to form as does any independent organic being. This +fact becomes still more remarkable when we hear that, for instance, seven +out of the ten different kinds of galls produced on _Salix humilis_ are +formed by gall-gnats (_Cecidomyidæ_) which, "though essentially distinct +species, yet resemble one another so closely that in almost all cases it is +difficult, and in some cases impossible, to distinguish the full-grown +insects one from the other."[706] For in accordance with a wide-spread +analogy we may safely infer that the poison secreted by insects so closely +allied would not differ much in nature; yet this slight difference is +sufficient to induce widely different results. In some few cases the same +species of gall-gnat produces on distinct species of willows galls which +cannot be distinguished; the _Cynips fecundatrix_, also, has been known to +produce on the Turkish oak, to which it is not properly attached, exactly +the same kind of gall as on the European oak.[707] These latter facts +apparently prove that the nature of the poison is a much more powerful +{284} agent in determining the form of the gall than the specific character +of the tree which is acted on. + +As the poisonous secretion of insects belonging to various orders has the +special power of affecting the growth of various plants;--as a slight +difference in the nature of the poison suffices to produce widely different +results;--and lastly, as we know that the chemical compounds secreted by +plants are eminently liable to be modified by changed conditions of life, +we may believe it possible that various parts of a plant might be modified +through the agency of its own altered secretions. Compare, for instance, +the mossy and viscid calyx of a moss-rose, which suddenly appears through +bud-variation on a Provence-rose, with the gall of red moss growing from +the inoculated leaf of a wild rose, with each filament symmetrically +branched like a microscopical spruce-fir, bearing a glandular tip and +secreting odoriferous gummy matter.[708] Or compare, on the one hand, the +fruit of the peach, with its hairy skin, fleshy covering, hard shell and +kernel, and on the other hand one of the more complex galls with its +epidermic, spongy, and woody layers, surrounding tissue loaded with starch +granules. These normal and abnormal structures manifestly present a certain +degree of resemblance. Or, again, reflect on the cases above given of +parrots which have had their plumage brightly decorated through some change +in their blood, caused by having been fed on certain fishes, or locally +inoculated with the poison of a toad. I am far from wishing to maintain +that the moss-rose or the hard shell of the peach-stone or the bright +colours of birds are actually due to any chemical change in the sap or +blood; but these cases of galls and of parrots are excellently adapted to +show us how powerfully and singularly external agencies may affect +structure. With such facts before us, we need feel no surprise at the +appearance of any modification in any organic being. + + I may, also, here allude to the remarkable effects which parasitic + fungi sometimes produce on plants. Reissek[709] has described a + Thesium, affected by an Oecidium, which was greatly modified, and + assumed some of the {285} characteristic features of certain allied + species, or even genera. Suppose, says Reissek, "the condition + originally caused by the fungus to become constant in the course of + time, the plant would, if found growing wild, be considered as a + distinct species or even as belonging to a new genus." I quote this + remark to show how profoundly, yet in how natural a manner, this plant + must have been modified by the parasitic fungus. + +_Facts and Considerations opposed to the belief that the Conditions of Life +act in a potent manner in causing definite Modifications of Structure._ + +I have alluded to the slight differences in species when naturally living +in distinct countries under different conditions; and such differences we +feel at first inclined, probably to a limited extent with justice, to +attribute to the definite action of the surrounding conditions. But it must +be borne in mind that there are a far greater number of animals and plants +which range widely and have been exposed to great diversities of +conditions, yet remain nearly uniform in character. Some authors, as +previously remarked, account for the varieties of our culinary and +agricultural plants by the definite action of the conditions to which they +have been exposed in the different parts of Great Britain; but there are +about 200 plants[710] which are found in every single English county; these +plants must have been exposed for an immense period to considerable +differences of climate and soil, yet do not differ. So, again, some birds, +insects, other animals, and plants range over large portions of the world, +yet retain the same character. + + Notwithstanding the facts previously given on the occurrence of highly + peculiar local diseases and on the strange modifications of structure + in plants caused by the inoculated poison of insects, and other + analogous cases; still there are a multitude of variations--such as the + modified skull of the niata ox and bulldog, the long horns of Caffre + cattle, the conjoined toes of the solid-hoofed swine, the immense crest + and protuberant skull of Polish fowls, the crop of the pouter-pigeon, + and a host of other such cases--which we can hardly attribute to the + definite action, in the sense before specified, of the external + conditions of life. No doubt in every case there must have been some + exciting cause; but as we see innumerable individuals exposed to nearly + the same conditions, and one alone is affected, we may conclude that + the constitution of the individual is of far higher {286} importance + than the conditions to which it has been exposed. It seems, indeed, to + be a general rule that conspicuous variations occur rarely, and in one + individual alone out of many thousands, though all may have been + exposed, as far as we can judge, to nearly the same conditions. As the + most strongly marked variations graduate insensibly into the most + trifling, we are led by the same train of thought to attribute each + slight variation much more to innate differences of constitution, + however caused, than to the definite action of the surrounding + conditions. + + We are led to the same conclusion by considering the cases, formerly + alluded to, of fowls and pigeons, which have varied and will no doubt + go on varying in directly opposite ways, though kept during many + generations under nearly the same conditions. Some, for instance, are + born with their beaks, wings, tails, legs, &c., a little longer, and + others with these same parts a little shorter. By the long-continued + selection of such slight individual differences, which occur in birds + kept in the same aviary, widely different races could certainly be + formed; and long-continued selection, important as is the result, does + nothing but preserve the variations which appear to us to arise + spontaneously. + + In these cases we see that domesticated animals vary in an indefinite + number of particulars, though treated as uniformly as is possible. On + the other hand, there are instances of animals and plants, which, + though exposed to very different conditions, both under nature and + domestication, have varied in nearly the same manner. Mr. Layard + informs me that he has observed amongst the Caffres of South Africa a + dog singularly like an arctic Esquimaux dog. Pigeons in India present + nearly the same wide diversities of colour as in Europe; and I have + seen chequered and simply barred pigeons, and pigeons with blue and + white loins, from Sierra Leone, Madeira, England, and India. New + varieties of flowers are continually raised in different parts of Great + Britain, but many of these are found by the judges at our exhibitions + to be almost identical with old varieties. A vast number of new + fruit-trees and culinary vegetables have been produced in North + America: these differ from European varieties in the same general + manner as the several varieties raised in Europe differ from each + other; and no one has ever pretended that the climate of America has + given to the many American varieties any general character by which + they can be recognised. Nevertheless, from the facts previously + advanced on the authority of Mr. Meehan with respect to American and + European forest-trees, it would be rash to affirm that varieties raised + in the two countries would not in the course of ages assume a + distinctive character. Mr. Masters has recorded a striking fact[711] + bearing on this subject: he raised numerous plants of _Hybiscus + Syriacus_ from seed collected in South Carolina and the Holy Land, + where the parent-plants must have been exposed to considerably + different conditions; yet the seedlings from both localities broke into + two similar strains, one with obtuse leaves and purple or crimson + flowers, and the other with elongated leaves and more or less pink + flowers. + + {287} + + We may, also, infer the prepotent influence of the constitution of the + organism over the definite action of the conditions of life, from the + several cases given in the earlier chapters of parallel series of + varieties,--an important subject, hereafter to be more fully discussed. + Sub-varieties of the several kinds of wheat, gourds, peaches, and other + plants, and to a certain limited extent sub-varieties of the fowl, + pigeon, and dog, have been shown either to resemble or to differ from + each other in a closely corresponding and parallel manner. In other + cases, a variety of one species resembles a distinct species; or the + varieties of two distinct species resemble each other. Although these + parallel resemblances no doubt often result from reversion to the + former characters of a common progenitor; yet in other cases, when new + characters first appear, the resemblance must be attributed to the + inheritance of a similar constitution, and consequently to a tendency + to vary in the same manner. We see something of a similar kind in the + same monstrosity appearing and reappearing many times in the same + animal, and, as Dr. Maxwell Masters has remarked to me, in the same + plant. + +We may at least conclude thus far, that the amount of modification which +animals and plants have undergone under domestication, does not correspond +with the degree to which they have been subjected to changed circumstances. +As we know the parentage of domesticated birds far better than of most +quadrupeds, we will glance through the list. The pigeon has varied in +Europe more than almost any other bird; yet it is a native species, and has +not been exposed to any extraordinary change of conditions. The fowl has +varied equally, or almost equally, with the pigeon, and is a native of the +hot jungles of India. Neither the peacock, a native of the same country, +nor the guinea-fowl, an inhabitant of the dry deserts of Africa, has varied +at all, or only in colour. The turkey, from Mexico, has varied but little. +The duck, on the other hand, a native of Europe, has yielded some +well-marked races; and as this is an aquatic bird, it must have been +subjected to a far more serious change in its habits than the pigeon or +even the fowl, which nevertheless have varied in a much higher degree. The +goose, a native of Europe and aquatic like the duck, has varied less than +any other domesticated bird, except the peacock. + +Bud-variation is, also, important under our present point of view. In some +few cases, as when all the eyes or buds on the same tuber of the potato, or +all the fruit on the same plum-tree, or all the flowers on the same plant, +have suddenly varied in the same manner, it might be argued that the {288} +variation had been definitely caused by some change in the conditions to +which the plants had been exposed; yet, in other cases, such an admission +is extremely difficult. As new characters sometimes appear by +bud-variation, which do not occur in the parent-species or in any allied +species, we may reject, at least in these cases, the idea that they are due +to reversion. Now it is well worth while to reflect maturely on some +striking case of bud-variation, for instance that of the peach. This tree +has been cultivated by the million in various parts of the world, has been +treated differently, grown on its own roots and grafted on various stocks, +planted as a standard, against a wall, and under glass; yet each bud of +each sub-variety keeps true to its kind. But occasionally, at long +intervals of time, a tree in England, or under the widely-different climate +of Virginia, produces a single bud, and this yields a branch which ever +afterwards bears nectarines. Nectarines differ, as every one knows, from +peaches in their smoothness, size, and flavour; and the difference is so +great, that some botanists have maintained that they are specifically +distinct. So permanent are the characters thus suddenly acquired, that a +nectarine produced by bud-variation has propagated itself by seed. To guard +against the supposition that there is some fundamental distinction between +bud and seminal variation, it is well to bear in mind that nectarines have +likewise been produced from the stone of the peach; and, reversely, peaches +from the stone of the nectarine. Now is it possible to conceive external +conditions more closely alike than those to which the buds on the same tree +are exposed? Yet one bud alone, out of the many thousands borne by the same +tree, has suddenly without any apparent cause produced a nectarine. But the +case is even stronger than this, for the same flower-bud has yielded a +fruit, one-half or one-quarter a nectarine, and the other half or +three-quarters a peach. Again, seven or eight varieties of the peach have +yielded by bud-variation nectarines: the nectarines thus produced, no +doubt, differ a little from each other; but still they are nectarines. Of +course there must be some cause, internal or external, to excite the +peach-bud to change its nature; but I cannot imagine a class of facts +better adapted to force on our minds the conviction that what we call the +external conditions of life are quite insignificant in {289} relation to +any particular variation, in comparison with the organisation or +constitution of the being which varies. + +It is known from the labours of Geoffroy St. Hilaire, and recently from +those of Dareste and others, that eggs of the fowl, if shaken, placed +upright, perforated, covered in part with varnish, &c., produce monstrous +chickens. Now these monstrosities may be said to be directly caused by such +unnatural conditions, but the modifications thus induced are not of a +definite nature. An excellent observer, M. Camille Dareste,[712] remarks +"that the various species of monstrosities are not determined by specific +causes; the external agencies which modify the development of the embryo +act solely in causing a perturbation--a perversion in the normal course of +development." He compares the result to what we see in illness: a sudden +chill, for instance, affects one individual alone out of many, causing +either a cold, or sore-throat, rheumatism, or inflammation of the lungs or +pleura. Contagious matter acts in an analogous manner.[713] We may take a +still more specific instance: seven pigeons were struck by +rattle-snakes;[714] some suffered from convulsions; some had their blood +coagulated, in others it was perfectly fluid; some showed ecchymosed spots +on the heart, others on the intestines, &c.; others again showed no visible +lesion in any organ. It is well known that excess in drinking causes +different diseases in different men; but men living under a cold and +tropical climate are differently affected:[715] and in this case we see the +definite influence of opposite conditions. The foregoing facts apparently +give us as good an idea as we are likely for a long time to obtain, how in +many cases external conditions act directly, though not definitely, in +causing modifications of structure. + + * * * * * + +_Summary._--There can be no doubt, from the facts given in the early part +of this chapter, that extremely slight changes in {290} the conditions of +life sometimes act in a definite manner on our already variable +domesticated productions; and, as the action of changed conditions in +causing general or indefinite variability is accumulative, so it may be +with their definite action. Hence it is possible that great and definite +modifications of structure may result from altered conditions acting during +a long series of generations. In some few instances a marked effect has +been produced quickly on all, or nearly all, the individuals which have +been exposed to some considerable change of climate, food, or other +circumstance. This has occurred, and is now occurring, with European men in +the United States, with European dogs in India, with horses in the Falkland +Islands, apparently with various animals at Angora, with foreign oysters in +the Mediterranean, and with maize grown in Europe from tropical seed. We +have seen that the chemical compounds secreted by plants and the state of +their tissues are readily affected by changed conditions. In some cases a +relation apparently exists between certain characters and certain +conditions, so that if the latter be changed the character is lost--as with +cultivated flowers, with some few culinary plants, with the fruit of the +melon, with fat-tailed sheep, and other sheep having peculiar fleeces. + +The production of galls, and the change of plumage in parrots when fed on +peculiar food or when inoculated by the poison of a toad, prove to us what +great and mysterious changes in structure and colour may be the definite +result of chemical changes in the nutrient fluids or tissues. + +We have also reason to believe that organic beings in a state of nature may +be modified in various definite ways by the conditions to which they have +been long exposed, as in the case of American trees in comparison with +their representatives in Europe. But in all such cases it is most difficult +to distinguish between the definite results of changed conditions, and the +accumulation through natural selection of serviceable variations which have +arisen independently of the nature of the conditions. If, for instance, a +plant had to be modified so as to become fitted to inhabit a humid instead +of an arid station, we have no reason to believe that variations of the +right kind would occur more frequently if the parent-plant inhabited a +station a little more {291} humid than usual. Whether the station was +unusually dry or humid, variations adapting the plant in a slight degree +for directly opposite habits of life would occasionally arise, as we have +reason to believe from what we know in other cases. + +In most, perhaps in all cases, the organisation or constitution of the +being which is acted on, is a much more important element than the nature +of the changed conditions, in determining the nature of the variation. We +have evidence of this in the appearance of nearly similar modifications +under different conditions, and of different modifications under apparently +nearly the same conditions. We have still better evidence of this in +closely parallel varieties being frequently produced from distinct races, +or even distinct species, and in the frequent recurrence of the same +monstrosity in the same species. We have also seen that the degree to which +domesticated birds have varied, does not stand in any close relation with +the amount of change to which they have been subjected. + +To recur once again to bud-variations. When we reflect on the millions of +buds which many trees have produced, before some one bud has varied, we are +lost in wonder what the precise cause of each variation can be. Let us +recall the case given by Andrew Knight of the forty-year-old tree of the +yellow magnum bonum plum, an old variety which has been propagated by +grafts on various stocks for a very long period throughout Europe and North +America, and on which a single bud suddenly produced the red magnum bonum. +We should also bear in mind that distinct varieties, and even distinct +species,--as in the case of peaches, nectarines, and apricots,--of certain +roses and camellias,--although separated by a vast number of generations +from any progenitor in common, and although cultivated under diversified +conditions, have yielded by bud-variation closely analogous varieties. When +we reflect on these facts we become deeply impressed with the conviction +that in such cases the nature of the variation depends but little on the +conditions to which the plant has been exposed, and not in any especial +manner on its individual character, but much more on the general nature or +constitution, inherited from some remote progenitor, of the whole group of +allied beings to which the plant belongs. We are thus driven to conclude +that in most {292} cases the conditions of life play a subordinate part in +causing any particular modification; like that which a spark plays, when a +mass of combustibles bursts into flame--the nature of the flame depending +on the combustible matter, and not on the spark. + +No doubt each slight variation must have its efficient cause; but it is as +hopeless an attempt to discover the cause of each as to say why a chill or +a poison affects one man differently from another. Even with modifications +resulting from the definite action of the conditions of life, when all or +nearly all the individuals, which have been similarly exposed, are +similarly affected, we can rarely see the precise relation between cause +and effect. In the next chapter it will be shown that the increased use or +disuse of various organs, produces an inherited effect. It will further be +seen that certain variations are bound together by correlation and other +laws. Beyond this we cannot at present explain either the causes or manner +of action of Variation. + +Finally, as indefinite and almost illimitable variability is the usual +result of domestication and cultivation, with the same part or organ +varying in different individuals in different or even in directly opposite +ways; and as the same variation, if strongly pronounced, usually recurs +only after long intervals of time, any particular variation would generally +be lost by crossing, reversion, and the accidental destruction of the +varying individuals, unless carefully preserved by man. Hence, although it +must be admitted that new conditions of life do sometimes definitely affect +organic beings, it may be doubted whether well-marked races have often been +produced by the direct action of changed conditions without the aid of +selection either by man or nature. + + * * * * * + + +{293} + +CHAPTER XXIV. + +LAWS OF VARIATION--USE AND DISUSE, ETC. + + NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE ORGANISATION--ON + THE EFFECTS OF THE INCREASED USE AND DISUSE OF ORGANS--CHANGED HABITS + OF LIFE--ACCLIMATISATION WITH ANIMALS AND PLANTS--VARIOUS METHODS BY + WHICH THIS CAN BE EFFECTED--ARRESTS OF DEVELOPMENT--RUDIMENTARY ORGANS. + +In this and the two following chapters I shall discuss, as well as the +difficulty of the subject permits, the several laws which govern +Variability. These may be grouped under the effects of use and disuse, +including changed habits and acclimatisation--arrests of +development--correlated variation--the cohesion of homologous parts--the +variability of multiple parts--compensation of growth--the position of buds +with respect to the axis of the plant--and lastly, analogous variation. +These several subjects so graduate into each other that their distinction +is often arbitrary. + +It may be convenient first briefly to discuss that co-ordinating and +reparative power which is common, in a higher or lower degree, to all +organic beings, and which was formerly designated by physiologists as the +_nisus formativus_. + + Blumenbach and others[716] have insisted that the principle which + permits a Hydra, when cut into fragments, to develop itself into two or + more perfect animals, is the same with that which causes a wound in the + higher animals to heal by a cicatrice. Such cases as that of the Hydra + are evidently analogous with the spontaneous division or fissiparous + generation of the lowest animals, and likewise with the budding of + plants. Between these extreme cases and that of a mere cicatrice we + have every gradation. Spallanzani,[717] by cutting off the legs and + tail of a Salamander, got in the course of three months six crops of + these members; so that 687 perfect bones were reproduced by one animal + during one season. At whatever {294} point the limb was cut off, the + deficient part, and no more, was exactly reproduced. Even with man, as + we have seen in the twelfth chapter, when treating of polydactylism, + the entire limb whilst in an embryonic state, and supernumerary digits, + are occasionally, though imperfectly, reproduced after amputation. When + a diseased bone has been removed, a new one sometimes "gradually + assumes the regular form, and all the attachments of muscles, + ligaments, &c., become as complete as before."[718] + + This power of regrowth does not, however, always act perfectly: the + reproduced tail of a lizard differs in the forms of the scales from the + normal tail: with certain Orthopterous insects the large hind legs are + reproduced of smaller size:[719] the white cicatrice which in the + higher animals unites the edges of a deep wound is not formed of + perfect skin, for elastic tissue is not produced till long + afterwards.[720] "The activity of the _nisus formativus_," says + Blumenbach, "is in an inverse ratio to the age of the organised body." + To this may be added that its power is greater in animals the lower + they are in the scale of organisation; and animals low in the scale + correspond with the embryos of higher animals belonging to the same + class. Newport's observations[721] afford a good illustration of this + fact, for he found that "myriapods, whose highest development scarcely + carries them beyond the larvæ of perfect insects, can regenerate limbs + and antennæ up to the time of their last moult;" and so can the larvæ + of true insects, but not the mature insect. Salamanders correspond in + development with the tadpoles or larvæ of the tailless Batrachians, and + both possess to a large extent the power of regrowth; but not so the + mature tailless Batrachians. + + Absorption often plays an important part in the repairs of injuries. + When a bone is broken, and does not unite, the ends are absorbed and + rounded, so that a false joint is formed; or if the ends unite, but + overlap, the projecting parts are removed.[722] But absorption comes + into action, as Virchow remarks, during the normal growth of bones; + parts which are solid during youth become hollowed out for the + medullary tissue as the bone increases in size. In trying to understand + the many well-adapted cases of regrowth when aided by absorption, we + should remember that most parts of the organisation, even whilst + retaining the same form, undergo constant renewal; so that a part which + was not renewed would naturally be liable to complete absorption. + + Some cases, usually classed under the so-called _nisus formativus_, at + first appear to come under a distinct head; for not only are old + structures reproduced, but structures which appear new are formed. + Thus, after inflammation "false membranes," furnished with + blood-vessels, lymphatics, and nerves, are developed; or a foetus + escapes from the Fallopian tubes, and falls into the abdomen, "nature + pours out a quantity of plastic lymph, which forms itself into + organised membrane, richly supplied with blood-vessels," and the foetus + is nourished for a time. In certain cases of {295} hydrocephalus the + open and dangerous spaces in the skull are filled up with new bones, + which interlock by perfect serrated sutures.[723] But most + physiologists, especially on the Continent, have now given up the + belief in plastic lymph or blastema, and Virchow[724] maintains that + every structure, new or old, is formed by the proliferation of + pre-existing cells. On this view false membranes, like cancerous or + other tumours, are merely abnormal developments of normal growths; and + we can thus understand how it is that they resemble adjoining + structures; for instance, that "false membrane in the serous cavities + acquires a covering of epithelium exactly like that which covers the + original serous membrane; adhesions of the iris may become black + apparently from the production of pigment-cells like those of the + uvea."[725] + + No doubt the power of reparation, though not always quite perfect, is + an admirable provision, ready for various emergencies, even for those + which occur only at long intervals of time.[726] Yet this power is not + more wonderful than the growth and development of every single + creature, more especially of those which are propagated by fissiparous + generation. This subject has been here noticed, because we may infer + that, when any part or organ is either greatly increased in size or + wholly suppressed through variation and continued selection, the + co-ordinating power of the organisation will continually tend to bring + all the parts again into harmony with each other. + +_On the Effects of the Increased Use and Disuse of Organs._ + +It is notorious, and we shall immediately adduce proofs, that increased use +or action strengthens muscles, glands, sense-organs, &c.; and that disuse, +on the other hand, weakens them. I have not met with any clear explanation +of this fact in works on Physiology. Mr. Herbert Spencer[727] maintains +that when muscles are much used, or when intermittent pressure is applied +to the epidermis, an excess of nutritive matter exudes from the vessels, +and that this gives additional development to the adjoining parts. That an +increased flow of blood towards an organ leads to its greater development +is probable, if not certain. Mr. Paget[728] thus accounts for the long, +thick, and dark-coloured hair which occasionally grows, even in young +children, near old-standing inflamed surfaces or fractured bones. When +Hunter {296} inserted the spur of a cock into the comb, which is well +supplied with blood-vessels, it grew in one case in a spiral direction to a +length of six inches, and in another case forward, like a horn, so that the +bird could not touch the ground with its beak. But whether Mr. Herbert +Spencer's view of the exudation of nutritive matter due to increased +movement and pressure, will fully account for the augmented size of bones, +ligaments, and especially of internal glands and nerves, seems doubtful. +According to the interesting observations of M. Sedillot,[729] when a +portion of one bone of the leg or fore-arm of an animal is removed and is +not replaced by growth, the associated bone enlarges till it attains a bulk +equal to that of the two bones, of which it has to perform the functions. +This is best exhibited in dogs in which the tibia has been removed; the +companion bone, which is naturally almost filiform and not one-fifth the +size of the other, soon acquires a size equal to or greater than the tibia. +Now, it is at first difficult to believe that increased weight acting on a +straight bone could, by alternately increased and diminished pressure, +cause nutritive matter to exude from the vessels which permeate the +periosteum. Nevertheless, the observations adduced by Mr. Spencer,[730] on +the strengthening of the bowed bones of rickety children, along their +concave sides, leads to the belief that this is possible. + +Mr. H. Spencer has also shown that the ascent of the sap in trees is aided +by the rocking movement caused by the wind; and the sap strengthens the +trunk "in proportion to the stress to be borne; since the more severe and +the more repeated the strains, the greater must be the exudation from the +vessels into the surrounding tissue, and the greater the thickening of this +tissue by secondary deposits."[731] But woody trunks may be formed of hard +tissue without their having been subjected to any movement, as we see with +ivy closely attached to old walls. In all these cases, it is very difficult +to disentangle the effects of long-continued selection from those +consequent on the increased action or movement of the part. Mr. H. +Spencer[732] acknowledges this difficulty, and gives as an instance the +spines {297} or thorns of trees, and the shells of nuts. Here we have +extremely hard woody tissue without the possibility of any movement to +cause exudation, and without, as far as we can see, any other directly +exciting cause; and as the hardness of these parts is of manifest service +to the plant, we may look at the result as probably due to the selection of +so-called spontaneous variations. Every one knows that hard work thickens +the epidermis on the hands; and when we hear that with infants long before +their birth the epidermis is thicker on the palms and soles of the feet +than on any other part of the body, as was observed with admiration by +Albinus,[733] we are naturally inclined to attribute this to the inherited +effects of long-continued use or pressure. We are tempted to extend the +same view even to the hoofs of quadrupeds; but who will pretend to +determine how far natural selection may have aided in the formation of +structures of such obvious importance to the animal? + + That use strengthens the muscles may be seen in the limbs of artisans + who follow different trades; and when a muscle is strengthened, the + tendons, and the crests of bone to which they are attached, become + enlarged; and this must likewise be the case with the blood-vessels and + nerves. On the other hand, when a limb is not used, as by Eastern + fanatics, or when the nerve supplying it with nervous power is + effectually destroyed, the muscles wither. So again, when the eye is + destroyed the optic nerve becomes atrophied, sometimes even in the + course of a few months.[734] The Proteus is furnished with branchiæ as + well as with lungs: and Schreibers[735] found that when the animal was + compelled to live in deep water the branchiæ were developed to thrice + their ordinary size, and the lungs were partially atrophied. When, on + the other hand, the animal was compelled to live in shallow water, the + lungs became larger and more vascular, whilst the branchiæ disappeared + in a more or less complete degree. Such modifications as these are, + however, of comparatively little value for us, as we do not actually + know that they tend to be inherited. + + In many cases there is reason to believe that the lessened use of + various organs has affected the corresponding parts in the offspring. + But there is no good evidence that this ever follows in the course of a + single generation. It appears, as in the case of general or indefinite + variability, that several generations must be subjected to changed + habits for any appreciable result. Our domestic fowls, ducks, and geese + have almost lost, not {298} only in the individual but in the race, + their power of flight; for we do not see a chicken, when frightened, + take flight like a young pheasant. Hence I was led carefully to compare + the limb-bones of fowls, ducks, pigeons, and rabbits, with the same + bones in the wild parent-species. As the measurements and weights were + fully given in the earlier chapters, I need here only recapitulate the + results. With domestic pigeons, the length of the sternum, the + prominence of its crest, the length of the scapulæ and furcula, the + length of the wings as measured from tip to tip of the radius, are all + reduced relatively to the same parts in the wild pigeon. The wing and + tail feathers, however, are increased in length, but this may have as + little connection with the use of the wings or tail, as the lengthened + hair on a dog with the amount of exercise which the breed has + habitually taken. The feet of pigeons, except in the long-beaked races, + are reduced in size. With fowls the crest of the sternum is less + prominent, and is often distorted or monstrous; the wing-bones have + become lighter relatively to the leg-bones, and are apparently a little + shorter in comparison with those of the parent-form, the _Gallus + bankiva_. With ducks, the crest of the sternum is affected in the same + manner as in the foregoing cases: the furcula, coracoids, and scapulæ + are all reduced in weight relatively to the whole skeleton: the bones + of the wings are shorter and lighter, and the bones of the legs longer + and heavier, relatively to each other, and relatively to the whole + skeleton, in comparison with the same bones in the wild-duck. The + decreased weight and size of the bones, in the foregoing cases, is + probably the indirect result of the reaction of the weakened muscles on + the bones. I failed to compare the feathers of the wings of the tame + and wild duck; but Gloger[736] asserts that in the wild duck the tips + of the wing-feathers reach almost to the end of the tail, whilst in the + domestic duck they often hardly reach to its base. He remarks, also, on + the greater thickness of the legs, and says that the swimming membrane + between the toes is reduced; but I was not able to detect this latter + difference. + + With the domesticated rabbit the body, together with the whole + skeleton, is generally larger and heavier than in the wild animal, and + the leg-bones are heavier in due proportion; but whatever standard of + comparison be taken, neither the leg-bones nor the scapulæ have + increased in length proportionally with the increased dimensions of the + rest of the skeleton. The skull has become in a marked manner narrower, + and, from the measurements of its capacity formerly given, we may + conclude, that this narrowness results from the decreased size of the + brain, consequent on the mentally inactive life led by these + closely-confined animals. + + We have seen in the eighth chapter that silk-moths, which have been + kept during many centuries closely confined, emerge from their cocoons + with their wings distorted, incapable of flight, often greatly reduced + in size, or even, according to Quatrefages, quite rudimentary. This + condition of the wings may be largely owing to the same kind of + monstrosity which often affects wild Lepidoptera when artificially + reared from the cocoon; or it may {299} be in part due to an inherent + tendency, which is common to the females of many Bombycidæ, to have + their wings in a more or less rudimentary state; but part of the effect + may probably be attributed to long-continued disuse. + +From the foregoing facts there can be no doubt that certain parts of the +skeleton in our anciently domesticated animals, have been modified in +length and weight by the effects of decreased or increased use; but they +have not been modified, as shown in the earlier chapters, in shape or +structure. We must, however, be cautious in extending this latter +conclusion to animals living a free life; for these will occasionally be +exposed during successive generations to the severest competition. With +wild animals it would be an advantage in the struggle for life that every +superfluous and useless detail of structure should be removed or absorbed; +and thus the reduced bones might ultimately become changed in structure. +With highly-fed domesticated animals, on the other hand, there is no +economy of growth; nor any tendency to the elimination of trifling and +superfluous details of structure. + +Turning now to more general observations, Nathusius has shown that, with +the improved races of the pig, the shortened legs and snout, the form of +the articular condyles of the occiput, and the position of the jaws with +the upper canine teeth projecting in a most anomalous manner in front of +the lower canines, may be attributed to these parts not having been fully +exercised. For the highly-cultivated races do not travel in search of food, +nor root up the ground with their ringed muzzles. These modifications of +structure, which are all strictly inherited, characterise several improved +breeds, so that they cannot have been derived from any single domestic or +wild stock.[737] With respect to cattle, Professor Tanner has remarked that +the lungs and liver in the improved breeds "are found to be considerably +reduced in size when compared with those possessed by animals having +perfect liberty;"[738] and the reduction of these organs affects the +general shape of the body. The cause of the reduced lungs in highly-bred +animals which take little exercise is {300} obvious; and perhaps the liver +may be affected by the nutritious and artificial food on which they largely +subsist. + + It is well known that, when an artery is tied, the anastomosing + branches, from being forced to transmit more blood, increase in + diameter; and this increase cannot be accounted for by mere extension, + as their coats gain in strength. Mr. Herbert Spencer[739] has argued + that with plants the flow of sap from the point of supply to the + growing part first elongates the cells in this line; and that the cells + then become confluent, thus forming the ducts; so that, on this view, + the vessels in plants are formed by the mutual reaction of the flowing + sap and cellular tissue. Dr. W. Turner has remarked,[740] with respect + to the branches of arteries, and likewise to a certain extent with + nerves, that the great principle of compensation frequently comes into + play; for "when two nerves pass to adjacent cutaneous areas, an inverse + relation as regards size may subsist between them; a deficiency in one + may be supplied by an increase in the other, and thus the area of the + former may be trespassed on by the latter nerve." But how far in these + cases the difference in size in the nerves and arteries is due to + original variation, and how far to increased use or action, is not + clear. + + In reference to glands, Mr. Paget observes that "when one kidney is + destroyed the other often becomes much larger, and does double + work."[741] If we compare the size of the udders and their power of + secretion in cows which have been long domesticated, and in certain + goats in which the udders nearly touch the ground, with the size and + power of secretion of these organs in wild or half-domesticated + animals, the difference is great. A good cow with us daily yields more + than five gallons, or forty pints of milk, whilst a first-rate animal, + kept, for instance, by the Damaras of South Africa,[742] "rarely gives + more than two or three pints of milk daily, and, should her calf be + taken from her, she absolutely refuses to give any." We may attribute + the excellence of our cows, and of certain goats, partly to the + continued selection of the best milking animals, and partly to the + inherited effects of the increased action, through man's art, of the + secreting glands. + + It is notorious, as was remarked in the twelfth chapter, that + short-sight is inherited; and if we compare watchmakers or engravers + with, for instance, sailors, we can hardly doubt that vision + continually directed towards a near object permanently affects the + structure of the eye. + + Veterinarians are unanimous that horses become affected with spavins, + splints, ringbones, &c., from being shod, and from travelling on hard + roads, and they are almost equally unanimous that these injuries are + transmitted. Formerly horses were not shod in North Carolina, and it + has been asserted that they did not then suffer from these diseases of + the legs and feet.[743] + +{301} + +Our domesticated quadrupeds are all descended, as far as is known, from +species having erect ears; yet few kinds can be named, of which at least +one race has not drooping ears. Cats in China, horses in parts of Russia, +sheep in Italy and elsewhere, the guinea-pig in Germany, goats and cattle +in India, rabbits, pigs, and dogs in all long-civilised countries, have +dependent ears. With wild animals, which constantly use their ears like +funnels to catch every passing sound, and especially to ascertain the +direction whence it comes, there is not, as Mr. Blyth has remarked, any +species with drooping ears except the elephant. Hence the incapacity to +erect the ears is certainly in some manner the result of domestication; and +this incapacity has been attributed by various authors[744] to disuse, for +animals protected by man are not compelled habitually to use their ears. +Col. Hamilton Smith[745] states that in ancient effigies of the dog, "with +the exception of one Egyptian instance, no sculpture of the earlier Grecian +era produces representations of hounds with completely drooping ears; those +with them half pendulous are missing in the most ancient; and this +character increases, by degrees, in the works of the Roman period." Godron +also has remarked that "the pigs of the ancient Egyptians had not their +ears enlarged and pendent."[746] But it is remarkable that the drooping of +the ears, though probably the effect of disuse, is not accompanied by any +decrease in size; on the contrary, when we remember that animals so +different as fancy rabbits, certain Indian breeds of the goat, our petted +spaniels, bloodhounds, and other dogs, have enormously elongated ears, it +would appear as if disuse actually caused an increase in length. With +rabbits, the drooping of the much elongated ears has affected even the +structure of the skull. + +The tail of no wild animal, as remarked to me by Mr. Blyth, is curled; +whereas pigs and some races of dogs have their tails much curled. This +deformity, therefore, appears to be the result of domestication, but +whether in any way connected with the lessened use of the tail is doubtful. + +{302} + +The epidermis on our hands is easily thickened, as every one knows, by hard +work. In a district of Ceylon the sheep have "horny callosities that defend +their knees, and which arise from their habit of kneeling down to crop the +short herbage, and this distinguishes the Jaffna flocks from those of other +portions of the island;" but it is not stated whether this peculiarity is +inherited.[747] + +The mucous membrane which lines the stomach is continuous with the external +skin of the body; therefore it is not surprising that its texture should be +affected by the nature of the food consumed, but other and more interesting +changes likewise follow. Hunter long ago observed that the muscular coat of +the stomach of a gull (_Larus tridactylus_) which had been fed for a year +chiefly on grain was thickened; and, according to Dr. Edmondston, a similar +change periodically occurs in the Shetland Islands in the stomach of the +_Larus argentatus_, which in the spring frequents the corn-fields and feeds +on the seed. The same careful observer has noticed a great change in the +stomach of a raven which had been long fed on vegetable food. In the case +of an owl (_Strix grallaria_) similarly treated, Menetries states that the +form of the stomach was changed, the inner coat became leathery, and the +liver increased in size. Whether these modifications in the digestive +organs would in the course of generations become inherited is not +known.[748] + +The increased or diminished length of the intestines, which apparently +results from changed diet, is a more remarkable case, because it is +characteristic of certain animals in their domesticated condition, and +therefore must be inherited. The complex absorbent system, the +blood-vessels, nerves, and muscles, are necessarily all modified together +with the intestines. According to Daubenton, the intestines of the domestic +cat are one-third longer than those of the wild cat of Europe; and although +this species is not the parent-stock of the domestic animal, yet, as +Isidore Geoffroy has remarked, the several species {303} of cats are so +closely allied that the comparison is probably a fair one. The increased +length appears to be due to the domestic cat being less strictly +carnivorous in its diet than any wild feline species; I have seen a French +kitten eating vegetables as readily as meat. According to Cuvier, the +intestines of the domesticated pig exceed greatly in proportionate length +those of the wild boar. In the tame and wild rabbit the change is of an +opposite nature, and probably results from the nutritious food given to the +tame rabbit.[749] + + * * * * * + +_Changed Habits of Life, independently of the Use or Disuse of particular +Organs._--This subject, as far as the mental powers of animals are +concerned, so blends into instinct, on which I shall treat in a future +work, that I will here only remind the reader of the many cases which occur +under domestication, and which are familiar to every one--for instance the +tameness of our animals--the pointing or retrieving of dogs--their not +attacking the smaller animals kept by man--and so forth. How much of these +changes ought to be attributed to inherited habit, and how much to the +selection of individuals which have varied in the desired manner, +irrespectively of the special circumstances under which they have been +kept, can seldom be told. We have already seen that animals may be +habituated to a changed diet; but a few additional instances may here be +given. + +In the Polynesian Islands and in China the dog is fed exclusively on +vegetable matter, and the taste for this kind of food is to a certain +extent inherited.[750] Our sporting dogs will not touch the bones of game +birds, whilst other dogs devour them with greediness. In some parts of the +world sheep have been largely fed on fish. The domestic hog is fond of +barley, the wild boar is said to disdain it; and the disdain is partially +inherited, for some young wild pigs bred in captivity showed an aversion +for this grain, whilst others of the same brood relished it.[751] One of my +relations bred some young pigs from {304} a Chinese sow by a wild Alpine +boar; they lived free in the park, and were so tame that they came to the +house to be fed; but they would not touch swill, which was devoured by the +other pigs. An animal when once accustomed to an unnatural diet, which can +generally be effected only during youth, dislikes its proper food, as +Spallanzani found to be the case with a pigeon which had been long fed on +meat. Individuals of the same species take to new food with different +degrees of readiness; one horse, it is stated, soon learned to eat meat, +whilst another would have perished from hunger rather than have partaken of +it.[752] + +The caterpillars of the _Bombyx hesperus_ feed in a state of nature on the +leaves of the _Café diable_, but, after having been reared on the +Ailanthus, they would not touch the _Café diable_, and actually died of +hunger.[753] + +It has been found possible to accustom marine fish to live in fresh water; +but as such changes in fish, and other marine animals, have been chiefly +observed in a state of nature, they do not properly belong to our present +subject. The period of gestation and of maturity, as shown in the earlier +chapters,--the season and the frequency of the act of breeding,--have all +been greatly modified under domestication. With the Egyptian goose the rate +of change in the season has been recorded.[754] The wild drake pairs with +one female, the domestic drake is polygamous. Certain breeds of fowls have +lost the habit of incubation. The paces of the horse, and the manner of +flight in certain breeds of the pigeon, have been modified, and are +inherited. The voice differs much in certain fowls and pigeons. Some breeds +are clamorous and others silent, as in the Call and common duck, or in the +Spitz and pointer dog. Every one knows how dogs differ from each other in +their manner of hunting, and in their ardour after different kinds of game +or vermin. + +With plants the period of vegetation is easily changed and is inherited, as +in the case of summer and winter wheat, barley, {305} and vetches; but to +this subject we shall immediately return under acclimatisation. Annual +plants sometimes become perennial under a new climate, as I hear from Dr. +Hooker is the case with the stock and mignonette in Tasmania. On the other +hand, perennials sometimes become annuals, as with the Ricinus in England, +and as, according to Captain Mangles, with many varieties of the +heartsease. Von Berg[755] raised from seed of _Verbascum phoenicium_, which +is usually a biennial, both annual and perennial varieties. Some deciduous +bushes become evergreen in hot countries.[756] Rice requires much water, +but there is one variety in India which can be grown without +irrigation.[757] Certain varieties of the oat and of our other cereals are +best fitted for certain soils.[758] Endless similar facts could be given in +the animal and vegetable kingdoms. They are noticed here because they +illustrate analogous differences in closely allied natural species, and +because such changed habits of life, whether due to use and disuse, or to +the direct action of external conditions, or to so-called spontaneous +variation, would be apt to lead to modifications of structure. + + * * * * * + +_Acclimatisation._--From the previous remarks we are naturally led to the +much disputed subject of acclimatisation. There are two distinct questions: +Do varieties descended from the same species differ in their power of +living under different climates? And secondly, if they so differ, how have +they become thus adapted? We have seen that European dogs do not succeed +well in India, and it is asserted,[759] that no one has succeeded in there +keeping the Newfoundland long alive; but then it may be argued, probably +with truth, that these northern breeds are specifically distinct from the +native dogs which flourish in India. The same remark may be made with +respect to different breeds of sheep, of which, according to Youatt,[760] +not one brought "from a torrid climate lasts out the second year," in the +Zoological Gardens. But sheep are capable of some degree of +acclimatisation, for Merino sheep bred at the Cape of Good Hope have been +found {306} far better adapted for India than those imported from +England.[761] It is almost certain that the breeds of the fowl are +descended from the same species; but the Spanish breed, which there is good +reason to believe originated near the Mediterranean,[762] though so fine +and vigorous in England, suffers more from frost than any other breed. The +Arrindy silk-moth introduced from Bengal, and the Ailanthus moth from the +temperate province of Shan Tung, in China, belong to the same species, as +we may infer from their identity in the caterpillar, cocoon, and mature +states;[763] yet they differ much in constitution: the Indian form "will +flourish only in warm latitudes," the other is quite hardy and withstands +cold and rain. + + Plants are more strictly adapted to climate than are animals. The + latter when domesticated withstand such great diversities of climate, + that we find nearly the same species in tropical and temperate + countries; whilst the cultivated plants are widely dissimilar. Hence a + larger field is open for inquiry in regard to the acclimatisation of + plants than of animals. It is no exaggeration to say that with almost + every plant which has long been cultivated varieties exist, which are + endowed with constitutions fitted for very different climates; I will + select only a few of the more striking cases, as it would be tedious to + give all. In North America numerous fruit-trees have been raised, and + in horticultural publications,--for instance, in Downing,--lists are + given of the varieties which are best able to withstand the severe + climate of the northern States and Canada. Many American varieties of + the pear, plum, and peach are excellent in their own country, but until + recently hardly one was known that succeeded in England; and with + apples,[764] not one succeeds. Though the American varieties can + withstand a severer winter than ours, the summer here is not hot + enough. Fruit-trees have originated in Europe as in America with + different constitutions, but they are not here much noticed, as the + same nurserymen do not supply a wide area. The Forelle pear flowers + early, and when the flowers have just set, and this is the critical + period, they have been observed, both in France and England, to + withstand with complete impunity a frost of 18° and even 14° Fahr., + which killed the flowers, whether fully expanded or in bud, of all + other kinds of pears.[765] This power in the flower of resisting cold + and afterwards producing fruit does not invariably depend, as we know + on good authority,[766] on general constitutional vigour. + + {307} + + In proceeding northward, the number of varieties which are enabled to + resist the climate rapidly decreases, as may be seen in the list of the + varieties of the cherry, apple, and pear, which can be cultivated in + the neighbourhood of Stockholm.[767] Near Moscow, Prince Troubetzkoy + planted for experiment in the open ground several varieties of the + pear, but one alone, the _Poire sans Pepins_, withstood the cold of + winter.[768] We thus see that our fruit-trees, like distinct species of + the same genus, certainly differ from each other in their + constitutional adaptation to different climates. + + With the varieties of many plants, the adaptation to climate is often + very close. Thus it has been proved by repeated trials "that few if any + of the English varieties of wheat are adapted for cultivation in + Scotland;"[769] but the failure in this case is at first only in the + quantity, though ultimately in the quality, of the grain produced. The + Rev. J. M. Berkeley sowed wheat-seed from India, and got "the most + meagre ears," on land which would certainly have yielded a good crop + from English wheat.[770] In these cases varieties have been carried + from a warmer to a cooler climate; in the reverse case, as "when wheat + was imported directly from France into the West Indian Islands, it + produced either wholly barren spikes or furnished with only two or + three miserable seeds, while West Indian seed by its side yielded an + enormous harvest."[771] Here is another case of close adaptation to a + slightly cooler climate; a kind of wheat which in England may be used + indifferently either as a winter or summer variety, when sown under the + warmer climate of Grignan, in France, behaved exactly as if it had been + a true winter wheat.[772] + + Botanists believe that all the varieties of maize belong to the same + species; and we have seen that in North America, in proceeding + northward, the varieties cultivated in each zone produce their flowers + and ripen their seed within shorter and shorter periods. So that the + tall, slowly maturing southern varieties do not succeed in New England, + and the New English varieties do not succeed in Canada. I have not met + with any statement that the southern varieties are actually injured or + killed by a degree of cold which the northern varieties withstand with + impunity, though this is probable; but the production of early + flowering and early seeding varieties deserves to be considered as one + form of acclimatisation. Hence it has been found possible, according to + Kalm, to cultivate maize further and further northwards in America. In + Europe, also, as we learn from the evidence given by Alph. De Candolle, + the culture of maize has extended since the end of the last century + thirty leagues north of its former boundary.[773] On the authority of + the great Linnæus,[774] I may quote an {308} analogous case, namely, + that in Sweden tobacco raised from home-grown seed ripens its seed a + month sooner and is less liable to miscarry than plants raised from + foreign seed. + + With the Vine, differently from the maize, the line of practical + culture has retreated a little southward since the middle ages;[775] + but this seems due to commerce, including that of wine, being now freer + or more easy. Nevertheless the fact of the vine not having spread + northward shows that acclimatisation has made no progress during + several centuries. There is, however, a marked difference in the + constitution of the several varieties,--some being hardy, whilst + others, like the muscat of Alexandria, require a very high temperature + to come to perfection. According to Labat,[776] vines taken from France + to the West Indies succeed with extreme difficulty, whilst those + imported from Madeira, or the Canary Islands, thrive admirably. + + Gallesio gives a curious account of the naturalisation of the Orange in + Italy. Daring many centuries the sweet orange was propagated + exclusively by grafts, and so often suffered from frosts that it + required protection. After the severe frost of 1709, and more + especially after that of 1763, so many trees were destroyed that + seedlings from the sweet orange were raised, and, to the surprise of + the inhabitants, their fruit was found to be sweet. The trees thus + raised were larger, more productive, and hardier than the former kinds; + and seedlings are now continually raised. Hence Gallesio concludes that + much more was effected for the naturalisation of the orange in Italy by + the accidental production of new kinds during a period of about sixty + years, than had been effected by grafting old varieties during many + ages.[777] I may add that Risso[778] describes some Portuguese + varieties of the orange as extremely sensitive to cold, and as much + tenderer than certain other varieties. + + The peach was known to Theophrastus, 322 B.C.[779] According to the + authorities quoted by Dr. F. Rolle,[780] it was tender when first + introduced into Greece, and even in the island of Rhodes only + occasionally bore fruit. If this be correct, the peach, in spreading + during the last two thousand years over the middle parts of Europe, + must have become much hardier. At the present day different varieties + differ much in hardiness: some French varieties will not succeed in + England; and near Paris, the _Pavie de Bonneuil_ does not ripen its + fruit till very late, even when grown on a wall; "it is, therefore, + only fit for a very hot southern climate."[781] + + I will briefly give a few other cases. A variety of _Magnolia + grandiflora_, raised by M. Roy, withstands cold several degrees lower + than that which any other variety can resist. With camellias there is + much difference in hardiness. One particular variety of Noisette rose + withstood the severe frost of 1860 "untouched and hale amidst a + universal destruction of other {309} Noisettes." In New York the "Irish + yew is quite hardy, but the common yew is liable to be cut down." I may + add that there are varieties of the sweet potato (_Convolvulus + batatas_) which are suited for warmer, as well as for colder, + climates.[782] + +The plants as yet mentioned have been found capable of resisting an unusual +degree of cold or heat, when fully grown. The following cases refer to +plants whilst young. In a large bed of young Araucarias of the same age, +growing close together and equally exposed, it was observed,[783] after the +unusually severe winter of 1860-61, that, "in the midst of the dying, +numerous individuals remained on which the frost had absolutely made no +kind of impression." Dr. Lindley, after alluding to this and other similar +cases, remarks, "Among the lessons which the late formidable winter has +taught us, is that, even in their power of resisting cold, individuals of +the same species of plants are remarkably different." Near Salisbury, there +was a sharp frost on the night of May 24th, 1836, and all the French beans +(_Phaseolus vulgaris_) in a bed were killed except about one in thirty, +which completely escaped.[784] On the same day of the month, but in the +year 1864, there was a severe frost in Kent, and two rows of +scarlet-runners (_P. multiflorus_) in my garden, containing 390 plants of +the same age and equally exposed, were all blackened and killed except +about a dozen plants. In an adjoining row of "Fulmer's dwarf bean" (_P. +vulgaris_), one single plant escaped. A still more severe frost occurred +four days afterwards, and of the dozen plants which had previously escaped +only three survived; these were not taller or more vigorous than the other +young plants, but they escaped completely, with not even the tips of their +leaves browned. It was impossible to behold these three plants, with their +blackened, withered, and dead brethren all round them, and not see at a +glance that they differed widely in constitutional power of resisting +frost. + +This work is not the proper place to show that wild plants {310} of the +same species, naturally growing at different altitudes or under different +latitudes, become to a certain extent acclimatised, as is proved by the +different behaviour of their seedlings when raised in England. In my +'Origin of Species' I have alluded to some cases, and I could add others. +One instance must suffice: Mr. Grigor, of Forres,[785] states that +seedlings of the Scotch fir (_Pinus sylvestris_), raised from seed from the +Continent and from the forests of Scotland, differ much. "The difference is +perceptible in one-year-old, and more so in two-year-old seedlings; but the +effects of the winter on the second year's growth almost uniformly makes +those from the Continent quite brown, and so damaged, that by the month of +March they are quite unsaleable, while the plants from the native Scotch +pine, under the same treatment, and standing alongside, although +considerably shorter, are rather stouter and quite green, so that the beds +of the one can be known from the other when seen from the distance of a +mile." Closely similar facts have been observed with seedling larches. + + Hardy varieties would alone be valued or noticed in Europe; whilst + tender varieties, requiring more warmth, would generally be neglected; + but such occasionally arise. Thus Loudon[786] describes a Cornish + variety of the elm which is almost an evergreen, and of which the + shoots are often killed by the autumnal frosts, so that its timber is + of little value. Horticulturists know that some varieties are much more + tender than others: thus all the varieties of the broccoli are more + tender than cabbages; but there is much difference in this respect in + the sub-varieties of the broccoli; the pink and purple kinds are a + little hardier than the white Cape broccoli, "but they are not to be + depended on after the thermometer falls below 24° Fahr.:" the Walcheren + broccoli is less tender than the Cape, and there are several varieties + which will stand much severer cold than the Walcheren.[787] + Cauliflowers seed more freely in India than cabbages.[788] To give one + instance with flowers: eleven plants raised from a hollyhock, called + the _Queen of the Whites_,[789] were found to be much more tender than + various other seedlings. It may be presumed that all tender varieties + would succeed better under a climate warmer than ours. With + fruit-trees, it is well known that certain varieties, for instance of + the peach, stand forcing in a hot-house better than others; and this + shows {311} either pliability of organisation or some constitutional + difference. The same individual cherry-tree, when forced, has been + observed during successive years gradually to change its period of + vegetation.[790] Few pelargoniums can resist the heat of a stove, but + _Alba multiflora_ will, as a most skilful gardener asserts, "stand + pine-apple top and bottom heat the whole winter, without looking any + more drawn than if it had stood in a common greenhouse; and _Blanche + Fleur_ seems as if it had been made on purpose for growing in winter, + like many bulbs, and to rest all summer."[791] There can hardly be a + doubt that the _Alba multiflora_ pelargonium must have a widely + different constitution from that of most other varieties of this plant; + it would probably withstand even an equatorial climate. + + We have seen that according to Labat the vine and wheat require + acclimatisation in order to succeed in the West Indies. Similar facts + have been observed at Madras: "two parcels of mignonette-seed, one + direct from Europe, the other saved at Bangalore (of which the mean + temperature is much below that of Madras) were sown at the same time: + they both vegetated equally favourably, but the former all died off a + few days after they appeared above ground; the latter still survive, + and are vigorous healthy plants." So again, "turnip and carrot seed + saved at Hyderabad are found to answer better at Madras than seed from + Europe or from the Cape of Good Hope."[792] Mr. J. Scott, of the + Calcutta Botanic Gardens, informs me that seeds of the sweet-pea + (_Lathyrus odoratus_) imported from England produce plants, with thick, + rigid stems and small leaves, which rarely blossom and never yield + seed; plants raised from French seed blossom sparingly, but all the + flowers are sterile; on the other hand, plants raised from sweet-peas + grown near Darjeeling in Upper India, but originally derived from + England, can be successfully cultivated on the plains of India; for + they flower and seed profusely, and their stems are lax and scandent. + In some of the foregoing cases, as Dr. Hooker has remarked to me, the + greater success may perhaps be attributed to the seeds having been more + fully ripened under a more favourable climate; but this view can hardly + be extended to so many cases, including plants, which, from being + cultivated under a climate hotter than their native one, become fitted + for a still hotter climate. We may therefore safely conclude that + plants can to a certain extent become accustomed to a climate either + hotter or colder than their own; although these latter cases have been + more frequently observed. + +We will now consider the means by which acclimatisation may be effected, +namely, through the spontaneous appearance of varieties having a different +constitution, and through the effects of use or habit. In regard to the +first process, there is no evidence that a change in the constitution of +the {312} offspring necessarily stands in any direct relation with the +nature of the climate inhabited by the parents. On the contrary, it is +certain that hardy and tender varieties of the same species appear in the +same country. New varieties thus spontaneously arising become fitted to +slightly different climates in two different ways; firstly, they may have +the power, either as seedlings or when full-grown, of resisting intense +cold, as with the Moscow pear, or of resisting intense heat, as with some +kinds of Pelargonium, or the flowers may withstand severe frost, as with +the Forelle pear. Secondly, plants may become adapted to climates widely +different from their own, from flowering and fruiting either earlier or +later in the season. In both these cases the power of acclimatisation by +man consists simply in the selection and preservation of new varieties. But +without any direct intention on his part of securing a hardier variety, +acclimatisation may be unconsciously effected by merely raising tender +plants from seed, and by occasionally attempting their cultivation further +and further northwards, as in the case of maize, the orange, and the peach. + +How much influence ought to be attributed to inherited habit or custom in +the acclimatisation of animals and plants is a much more difficult +question. In many cases natural selection can hardly have failed to have +come into play and complicated the result. It is notorious that mountain +sheep resist severe weather and storms of snow which would destroy lowland +breeds; but then mountain sheep have been thus exposed from time +immemorial, and all delicate individuals will have been destroyed, and the +hardiest preserved. So with the Arrindy silk-moths of China and India; who +can tell how far natural selection may have taken a share in the formation +of the two races, which are now fitted for such widely different climates? +It seems at first probable that the many fruit-trees, which are so well +fitted for the hot summers and cold winters of North America, in contrast +with their poor success under our climate, have become adapted through +habit; but when we reflect on the multitude of seedlings annually raised in +that country, and that none would succeed unless born with a fitting +constitution, it is possible that mere habit may have done nothing towards +their acclimatisation. On the other hand, when we {313} hear that Merino +sheep, bred during no great number of generations at the Cape of Good +Hope--that some European plants raised during only a few generations in the +cooler parts of India, withstand the hotter parts of that country much +better than the sheep or seeds imported directly from England, we must +attribute some influence to habit. We are led to the same conclusion when +we hear from Naudin[793] that the races of melons, squashes, and gourds, +which have long been cultivated in Northern Europe, are comparatively more +precocious, and need much less heat for maturing their fruit, than the +varieties of the same species recently brought from tropical regions. In +the reciprocal conversion of summer and winter wheat, barley, and vetches +into each other, habit produces a marked effect in the course of a very few +generations. The same thing apparently occurs with the varieties of maize, +which, when carried from the Southern to the Northern States of America, or +into Germany, soon become accustomed to their new homes. With vine-plants +taken to the West Indies from Madeira, which are said to succeed better +than plants brought directly from France, we have some degree of +acclimatisation in the individual, independently of the production of new +varieties by seed. + +The common experience of agriculturists is of some value, and they often +advise persons to be cautious in trying in one country the productions of +another. The ancient agricultural writers of China recommend the +preservation and cultivation of the varieties peculiar to each country. +During the classical period, Columella wrote, "Vernaculum pecus peregrino +longe præstantius est."[794] + +I am aware that the attempt to acclimatise either animals or plants has +been called a vain chimæra. No doubt the attempt in most cases deserves to +be thus called, if made independently of the production of new varieties +endowed with a different constitution. Habit, however much prolonged, +rarely produces any effect on a plant propagated by buds; it apparently +acts only through successive seminal generations. {314} The laurel, bay, +laurestinus, &c., and the Jerusalem artichoke, which are propagated by +cuttings or tubers, are probably now as tender in England as when first +introduced; and this appears to be the case with the potato, which until +recently was seldom multiplied by seed. With plants propagated by seed, and +with animals, there will be little or no acclimatisation unless the hardier +individuals are either intentionally or unconsciously preserved. The +kidney-bean has often been advanced as an instance of a plant which has not +become hardier since its first introduction into Britain. We hear, however, +on excellent authority,[795] that some very fine seed, imported from +abroad, produced plants "which blossomed most profusely, but were nearly +all but abortive, whilst plants grown alongside from English seed podded +abundantly;" and this apparently shows some degree of acclimatisation in +our English plants. We have also seen that seedlings of the kidney-bean +occasionally appear with a marked power of resisting frost; but no one, as +far as I can hear, has ever separated such hardy seedlings, so as to +prevent accidental crossing, and then gathered their seed, and repeated the +process year after year. It may, however, be objected with truth that +natural selection ought to have had a decided effect on the hardiness of +our kidney-beans; for the tenderest individuals must have been killed +during every severe spring, and the hardier preserved. But it should be +borne in mind that the result of increased hardiness would simply be that +gardeners, who are always anxious for as early a crop as possible, would +sow their seed a few days earlier than formerly. Now, as the period of +sowing depends much on the soil and elevation of each district, and varies +with the season; and as new varieties have often been imported from abroad, +can we feel sure that our kidney-beans are not somewhat hardier? I have not +been able, by searching old horticultural works, to answer this question +satisfactorily. + +On the whole the facts now given show that, though habit does something +towards acclimatisation, yet that the spontaneous appearance of +constitutionally different individuals is a far more effective agent. As no +single instance has been recorded, either with animals or plants, of +hardier individuals {315} having been long and steadily selected, though +such selection is admitted to be indispensable for the improvement of any +other character, it is not surprising that man has done little in the +acclimatisation of domesticated animals and cultivated plants. We need not, +however, doubt that under nature new races and new species would become +adapted to widely different climates, by spontaneous variation, aided by +habit, and regulated by natural selection. + +_Arrests of Development: Rudimentary and Aborted Organs._ + + These subjects are here introduced because there is reason to believe + that rudimentary organs are in many cases the result of disuse. + Modifications of structure from arrested development, so great or so + serious as to deserve to be called monstrosities, are of common + occurrence, but, as they differ much from any normal structure, they + require here only a passing notice. When a part or organ is arrested + during its embryonic growth, a rudiment is generally left. Thus the + whole head may be represented by a soft nipple-like projection, and the + limbs by mere papillæ. These rudiments of limbs are sometimes + inherited, as has been observed in a dog.[796] + + Many lesser anomalies in our domesticated animals appear to be due to + arrested development. What the cause of the arrest may be, we seldom + know, except in the case of direct injury to the embryo within the egg + or womb. That the cause does not generally act at a very early + embryonic period we may infer from the affected organ seldom being + wholly aborted,--a rudiment being generally preserved. The external + ears are represented by mere vestiges in a Chinese breed of sheep; and + in another breed, the tail is reduced "to a little button, suffocated, + in a manner, by fat."[797] In tailless dogs and cats a stump is left; + but I do not know whether it includes at an early embryonic age + rudiments of all the caudal vertebræ. In certain breeds of fowls the + comb and wattles are reduced to rudiments; in the Cochin-China breed + scarcely more than rudiments of spurs exist. With polled Suffolk + cattle, "rudiments of horns can often be felt at an early age;"[798] + and with species in a state of nature, the relatively greater + development of rudimentary organs at an early period of life is highly + characteristic of such organs. With hornless breeds of cattle and + sheep; another and singular kind of rudiment has been observed, namely, + minute dangling horns attached to the skin alone, and which are often + shed and grow again. With hornless goats, according to Desmarest,[799] + {316} the bony protuberances which properly support the horns exist as + mere rudiments. + + With cultivated plants it is far from rare to find the petals, stamens, + and pistils represented by rudiments, like those observed in natural + species. So it is with the whole seed in many fruits; thus near + Astrakhan there is a grape with mere traces of seeds, "so small and + lying so near the stalk that they are not perceived in eating the + grape."[800] In certain varieties of the gourd, the tendrils, according + to Naudin, are represented by rudiments or by various monstrous + growths. In the broccoli and cauliflower the greater number of the + flowers are incapable of expansion, and include rudimentary organs. In + the Feather hyacinth (_Muscari comosum_) the upper and central flowers + are brightly coloured but rudimentary; under cultivation the tendency + to abortion travels downwards and outwards, and all the flowers become + rudimentary; but the abortive stamens and pistils are not so small in + the lower as in the upper flowers. In the _Viburnum opulus_, on the + other hand, the outer flowers naturally have their organs of + fructification in a rudimentary state, and the corolla is of large + size; under cultivation, the change spreads to the centre, and all the + flowers become affected; thus the well-known Snow-ball bush is + produced. In the Compositæ, the so-called doubling of the flowers + consists in the greater development of the corolla of the central + florets, generally accompanied with some degree of sterility; and it + has been observed[801] that the progressive doubling invariably spreads + from the circumference to the centre,--that is, from the ray florets, + which so often include rudimentary organs, to those of the disc. I may + add, as bearing on this subject, that, with Asters, seeds taken from + the florets of the circumference have been found to yield the greatest + number of double flowers.[802] In these several cases we have a natural + tendency in certain parts to become rudimentary, and this under culture + spreads either to, or from, the axis of the plant. It deserves notice, + as showing how the same laws govern the changes which natural species + and artificial varieties undergo, that in a series of species in the + genus Carthamus, one of the Compositæ, a tendency in the seeds to the + abortion of the pappus may be traced extending from the circumference + to the centre of the disc: thus, according to A. de Jussieu,[803] the + abortion is only partial in _Carthamus creticus_, but more extended in + _C. lanatus_; for in this species two or three alone of the central + seeds are furnished with a pappus, the surrounding seeds being either + quite naked or furnished with a few hairs; and lastly, in _C. + tinctorius_, even the central seeds are destitute of pappus, and the + abortion is complete. + + With animals and plants under domestication, when an organ disappears, + leaving only a rudiment, the loss has generally been sudden, as with + hornless and tailless breeds; and such cases may be ranked as inherited + monstrosities. But in some few cases the loss has been gradual, and + {317} has been partly effected by selection, as with the rudimentary + combs and wattles of certain fowls. We have also seen that the wings of + some domesticated birds have been slightly reduced by disuse, and the + great reduction of the wings in certain silk-moths, with mere rudiments + left, has probably been aided by disuse. + + With species in a state of nature, rudimentary organs are so extremely + common that scarcely one can be named which is wholly free from a + blemish of this nature. Such organs are generally variable, as several + naturalists have observed; for, being useless, they are not regulated + by natural selection, and they are more or less liable to reversion. + The same rule certainly holds good with parts which have become + rudimentary under domestication. We do not know through what steps + under nature rudimentary organs have passed in being reduced to their + present condition; but we so incessantly see in species of the same + group the finest gradations between an organ in a rudimentary and + perfect state, that we are led to believe that the passage must have + been extremely gradual. It may be doubted whether a change of structure + so abrupt as the sudden loss of an organ would ever be of service to a + species in a state of nature; for the conditions to which all organisms + are closely adapted usually change very slowly. Even if an organ did + suddenly disappear in some one individual by an arrest of development, + intercrossing with the other individuals of the same species would + cause it to reappear in a more or less perfect manner, so that its + final reduction could only be effected by the slow process of continued + disuse or natural selection. It is much more probable that, from + changed habits of life, organs first become of less and less use, and + ultimately superfluous; or their place may be supplied by some other + organ; and then disuse, acting on the offspring through inheritance at + corresponding periods of life, would go on reducing the organ; but as + most organs could be of no use at an early embryonic period, they would + not be affected by disuse; consequently they would be preserved at this + stage of growth, and would remain as rudiments. In addition to the + effects of disuse, the principle of economy of growth, already alluded + to in this chapter, would lead to the still further reduction of all + superfluous parts. With respect to the final and total suppression or + abortion of any organ, another and distinct principle, which will be + discussed in the chapter on pangenesis, probably takes a share in the + work. + + With animals and plants reared by man there is no severe or recurrent + struggle for existence, and the principle of economy will not come into + action. So far, indeed, is this from being the case, that in some + instances organs, which are naturally rudimentary in the + parent-species, become partially redeveloped in the domesticated + descendants. Thus cows, like most other ruminants, properly have four + active and two rudimentary mammæ; but in our domesticated animals, the + latter occasionally become considerably developed and yield milk. The + atrophied mammæ, which, in male domesticated animals, including man, + have in some rare cases grown to full size and secreted milk, perhaps + offer an analogous case. The hind feet of dogs include rudiments of a + fifth toe, and in certain large breeds these toes, though still + rudimentary, become considerably developed {318} and are furnished with + claws. In the common Hen, the spurs and comb are rudimentary, but in + certain breeds these become, independently of age or disease of the + ovaria, well developed. The stallion has canine teeth, but the mare has + only traces of the alveoli, which, as I am informed by the eminent + veterinary Mr. G. T. Brown, frequently contain minute irregular nodules + of bone. These nodules, however, sometimes become developed into + imperfect teeth, protruding through the gums and coated with enamel; + and occasionally they grow to a third or even a fourth of the length of + the canines in the stallion. With plants I do not know whether the + redevelopment of rudimentary organs occurs more frequently under + culture than under nature. Perhaps the pear-tree may be a case in + point, for when wild it bears thorns, which though useful as a + protection are formed of branches in a rudimentary condition, but, when + the tree is cultivated, the thorns are reconverted into branches. + +Finally, though organs which must be classed as rudimentary frequently +occur in our domesticated animals and cultivated plants, these have +generally been formed suddenly, through an arrest of development. They +usually differ in appearance from the rudiments which so frequently +characterise natural species. In the latter, rudimentary organs have been +slowly formed through continued disuse, acting by inheritance at a +corresponding age, aided by the principle of the economy of growth, all +under the control of natural selection. With domesticated animals, on the +other hand, the principle of economy is far from coming into action, and +their organs, although often slightly reduced by disuse, are not thus +almost obliterated with mere rudiments left. + + * * * * * + + +{319} + +CHAPTER XXV. + +LAWS OF VARIATION, _continued_--CORRELATED VARIABILITY. + + EXPLANATION OF TERM--CORRELATION AS CONNECTED WITH + DEVELOPMENT--MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED + SIZE OF PARTS--CORRELATED VARIATION OF HOMOLOGOUS PARTS--FEATHERED FEET + IN BIRDS ASSUMING THE STRUCTURE OF THE WINGS--CORRELATION BETWEEN THE + HEAD AND THE EXTREMITIES--BETWEEN THE SKIN AND DERMAL + APPENDAGES--BETWEEN THE ORGANS OF SIGHT AND HEARING--CORRELATED + MODIFICATIONS IN THE ORGANS OF PLANTS--CORRELATED + MONSTROSITIES--CORRELATION BETWEEN THE SKULL AND EARS--SKULL AND CREST + OF FEATHERS--SKULL AND HORNS--CORRELATION OF GROWTH COMPLICATED BY THE + ACCUMULATED EFFECTS OF NATURAL SELECTION--COLOUR AS CORRELATED WITH + CONSTITUTIONAL PECULIARITIES. + +All the parts of the organisation are to a certain extent connected or +correlated together; but the connexion may be so slight that it hardly +exists, as with compound animals or the buds on the same tree. Even in the +higher animals various parts are not at all closely related; for one part +may be wholly suppressed or rendered monstrous without any other part of +the body being affected. But in some cases, when one part varies, certain +other parts always, or nearly always, simultaneously vary; they are then +subject to the law of correlated variation. Formerly I used the somewhat +vague expression of correlation of growth, which may be applied to many +large classes of facts. Thus, all the parts of the body are admirably +coordinated for the peculiar habits of life of each organic being, and they +may be said, as the Duke of Argyll insists in his 'Reign of Law,' to be +correlated for this purpose. Again, in large groups of animals certain +structures always co-exist; for instance, a peculiar form of stomach with +teeth of peculiar form, and such structures may in one sense be said to be +correlated. But these cases have no necessary connexion with the law to be +discussed in the present chapter; for we do not know that {320} the initial +or primary variations of the several parts were in any way related; slight +modifications or individual differences may have been preserved, first in +one and then in another part, until the final and perfectly co-adapted +structure was acquired; but to this subject I shall presently recur. Again, +in many groups of animals the males alone are furnished with weapons, or +are ornamented with gay colours; and these characters manifestly stand in +some sort of correlation with the male reproductive organs, for when the +latter are destroyed these characters disappear. But it was shown in the +twelfth chapter that the very same peculiarity may become attached at any +age to either sex, and afterwards be exclusively transmitted by the same +sex at a corresponding age. In these cases we have inheritance limited by, +or correlated with, both sex and age; but we have no reason for supposing +that the original cause of the variation was necessarily connected with the +reproductive organs, or with the age of the affected being. + +In cases of true correlated variation, we are sometimes able to see the +nature of the connexion; but in most cases the bond is hidden from us, and +certainly differs in different cases. We can seldom say which of two +correlated parts first varies, and induces a change in the other; or +whether the two are simultaneously produced by some distinct cause. +Correlated variation is an important subject for us; for when one part is +modified through continued selection, either by man or under nature, other +parts of the organisation will be unavoidably modified. From this +correlation it apparently follows that, with our domesticated animals and +plants, varieties rarely or never differ from each other by some single +character alone. + +One of the simplest cases of correlation is that a modification which +arises during an early stage of growth tends to influence the subsequent +development of the same part, as well as of other and intimately connected +parts. Isidore Geoffroy St. Hilaire states[804] that this may constantly be +observed with monstrosities {321} in the animal kingdom; and +Moquin-Tandon[805] remarks, that, as with plants the axis cannot become +monstrous without in some way affecting the organs subsequently produced +from it, so axial anomalies are almost always accompanied by deviations of +structure in the appended parts. We shall presently see that with +short-muzzled races of the dog certain histological changes in the basal +elements of the bones arrest their development and shorten them, and this +affects the position of the subsequently developed molar teeth. It is +probable that certain modifications in the larvæ of insects would affect +the structure of the mature insects. But we must be very careful not to +extend this view too far, for, during the normal course of development, +certain members in the same group of animals are known to pass through an +extraordinary course of change, whilst other and closely allied members +arrive at maturity with little change of structure. + +Another simple case of correlation is that with the increased or decreased +dimensions of the whole body, or of any particular part, certain organs are +increased or diminished in number, or are otherwise modified. Thus +pigeon-fanciers have gone on selecting pouters for length of body, and we +have seen that their vertebræ are generally increased in number, and their +ribs in breadth. Tumblers have been selected for their small bodies, and +their ribs and primary wing-feathers are generally lessened in number. +Fantails have been selected for their large, widely-expanded tails, with +numerous tail-feathers, and the caudal vertebræ are increased in size and +number. Carriers have been selected for length of beak, and their tongues +have become longer, but not in strict accordance with the length of beak. +In this latter breed and in others having large feet, the number of the +scutellæ on the toes is greater than in the breeds with small feet. Many +similar cases could be given. In Germany it has been observed that the +period of gestation is longer in large-sized than in small-sized breeds of +cattle. With our highly-improved animals of all kinds the period of +maturity has advanced, both with respect to the full growth of the body and +the period of reproduction; and, in correspondence with this, the teeth are +now developed earlier than formerly, so that, {322} to the surprise of +agriculturists, the ancient rules for judging the age of an animal by the +state of its teeth are no longer trustworthy.[806] + +_Correlated Variation of Homologous Parts._--Parts which are homologous +tend to vary in the same manner; and this is what might have been expected, +for such parts are identical in form and structure during an early period +of embryonic development, and are exposed in the egg or womb to similar +conditions. The symmetry, in most kinds of animals, of the corresponding or +homologous organs on the right and left sides of the body, is the simplest +case in point; but this symmetry sometimes fails, as with rabbits having +only one ear, or stags with one horn, or with many-horned sheep which +sometimes carry an additional horn on one side of their heads. With flowers +which have regular corollas, the petals generally vary in the same manner, +as we see in the same complicated and elegant pattern, on the flowers of +the Chinese pink; but with irregular flowers, though the petals are of +course homologous, this symmetry often fails, as with the varieties of the +_Antirrhinum_ or snapdragon, or that variety of the kidney-bean (_Phaseolus +multiflorus_) which has a white standard-petal. + +In the vertebrata the front and hind limbs are homologous, and they tend to +vary in the same manner, as we see in long and short-legged, or in thick +and thin-legged races of the horse and dog. Isidore Geoffroy[807] has +remarked on the tendency of supernumerary digits in man to appear, not only +on the right and left sides, but on the upper and lower extremities. Meckel +has insisted[808] that, when the muscles of the arm depart in number or +arrangement from their proper type, they almost always imitate those of the +leg; and so conversely the varying muscles of the leg imitate the normal +muscles of the arm. + +In several distinct breeds of the pigeon and fowl, the legs and the two +outer toes are heavily feathered, so that in the trumpeter pigeon they +appear like little wings. In the feather-legged bantam the "boots" or +feathers, which grow from the outside of the leg and generally from the two +outer toes, have, {323} according to the excellent authority of Mr. +Hewitt,[809] been seen to exceed the wing-feathers in length, and in one +case were actually nine and a half inches in length! As Mr. Blyth has +remarked to me, these leg-feathers resemble the primary wing-feathers, and +are totally unlike the fine down which naturally grows on the legs of some +birds, such as grouse and owls. Hence it may be suspected that excess of +food has first given redundancy to the plumage, and then that the law of +homologous variation has led to the development of feathers on the legs, in +a position corresponding with those on the wing, namely, on the outside of +the tarsi and toes. I am strengthened in this belief by the following +curious case of correlation, which for a long time seemed to me utterly +inexplicable, namely, that in pigeons of any breed, if the legs are +feathered, the two outer toes are partially connected by skin. These two +outer toes correspond with our third and fourth toes. Now, in the wing of +the pigeon or any other bird, the first and fifth digits are wholly +aborted; the second is rudimentary and carries the so-called +"bastard-wing;" whilst the third and fourth digits are completely united +and enclosed by skin, together forming the extremity of the wing. So that +in feather-footed pigeons, not only does the exterior surface support a row +of long feathers, like wing-feathers, but the very same digits which in the +wing are completely united by skin become partially united by skin in the +feet; and thus by the law of the correlated variation of homologous parts +we can understand the curious connection of feathered legs and membrane +between the two outer toes. + +Andrew Knight[810] has remarked that the face or head and the limbs vary +together in general proportions. Compare, for instance, the head and limbs +of a dray and race-horse, or of a greyhound and mastiff. What a monster a +greyhound would appear with the head of a mastiff! The _modern_ bulldog, +however, has fine limbs, but this is a recently-selected character. From +the measurements given in the sixth chapter, we clearly see that in all the +breeds of the pigeon the length of the beak and the size of the feet are +correlated. The view which, as before explained, seems the most probable +is, that disuse in all cases tends {324} to diminish the feet, the beak +becoming at the same time through correlation shorter; but that in those +few breeds in which length of beak has been a selected point, the feet, +notwithstanding disuse, have through correlation increased in size. + +With the increased length of the beak in pigeons, not only the tongue +increases in length, but likewise the orifice of the nostrils. But the +increased length of the orifice of the nostrils perhaps stands in closer +correlation with the development of the corrugated skin or wattle at the +base of the beak; for when there is much wattle round the eyes, the eyelids +are greatly increased or even doubled in length. + +There is apparently some correlation even in colour between the head and +the extremities. Thus with horses a large white star or blaze on the +forehead is generally accompanied by white feet.[811] With white rabbits +and cattle, dark marks often co-exist on the tips of the ears and on the +feet. In black and tan dogs of different breeds, tan-coloured spots over +the eyes and tan-coloured feet almost invariably go together. These latter +cases of connected colouring may be due either to reversion or to analogous +variation,--subjects to which we shall hereafter return,--but this does not +necessarily determine the question of their original correlation. If those +naturalists are correct who maintain that the jaw-bones are homologous with +the limb-bones, then we can understand why the head and limbs tend to vary +together in shape and even in colour; but several highly competent judges +dispute the correctness of this view. + +The lopping forwards and downwards of the immense ears of fancy rabbits is +in part due to the disuse of the muscles, and in part to the weight and +length of the ears, which have been increased by selection during many +generations. Now, with the increased size and changed direction of the +ears, not only has the bony auditory meatus become changed in outline, +direction, and greatly in size, but the whole skull has been slightly +modified. This could be clearly seen in "half-lops"--that is, in rabbits +with one ear alone lopping forward--for the opposite sides of their skulls +were not strictly symmetrical. This seems to me a curious instance of +correlation, between hard {325} bones and organs so soft and flexible, as +well as so unimportant under a physiological point of view, as the external +ears. The result no doubt is largely due to mere mechanical action, that +is, to the weight of the ears, on the same principle that the skull of a +human infant is easily modified by pressure. + +The skin and the appendages of hair, feathers, hoofs, horns, and teeth, are +homologous over the whole body. Every one knows that the colour of the skin +and that of the hair usually vary together; so that Virgil advises the +shepherd to look whether the mouth and tongue of the ram are black, lest +the lambs should not be purely white. With poultry and certain ducks we +have seen that the colour of the plumage stands in some connexion with the +colour of the shell of the egg,--that is, with the mucous membrane which +secretes the shell. The colour of the skin and hair, and the odour emitted +by the glands of the skin, are said[812] to be connected, even in the same +race of men. Generally the hair varies in the same way all over the body in +length, fineness, and curliness. The same rule holds good with feathers, as +we see with the laced and frizzled breeds both of fowls and pigeons. In the +common cock the feathers on the neck and loins are always of a particular +shape, called hackles: now in the Polish breed, both sexes are +characterised by a tuft of feathers on the head; but through correlation +these feathers in the male always assume the form of hackles. The wing and +tail-feathers, though arising from parts not homologous, vary in length +together; so that long or short winged pigeons generally have long or short +tails. The case of the Jacobin-pigeon is more curious, for the wing and +tail feathers are remarkably long; and this apparently has arisen in +correlation with the elongated and reversed feathers on the back of the +neck, which form the hood. + +The hoofs and hair are homologous appendages; and a careful observer, +namely Azara,[813] states that in Paraguay horses of various colours are +often born with their hair curled and twisted like that on the head of a +negro. This peculiarity is strongly inherited. But what is remarkable is +that the hoofs of these horses "are absolutely like those of a mule." The +hair also of the mane and tail is invariably much shorter than usual, being +only from four {326} to twelve inches in length; so that curliness and +shortness of the hair are here, as with the negro, apparently correlated. + +With respect to the horns of sheep, Youatt[814] remarks that "multiplicity +of horns is not found in any breed of much value: it is generally +accompanied by great length and coarseness of the fleece." Several tropical +breeds of sheep, which are clothed with hair instead of wool, have horns +almost like those of a goat. Sturm[815] expressly declares that in +different races the more the wool is curled the more the horns are spirally +twisted. We have seen in the third chapter, where other analogous facts +have been given, that the parent of the Mauchamp breed, so famous for its +fleece, had peculiarly shaped horns. The inhabitants of Angora assert[816] +that "only the white goats which have horns wear the fleece in the long +curly locks that are so much admired; those which are not horned having a +comparatively close coat." From these cases we may conclude that the hair +or wool and the horns vary in a correlated manner. Those who have tried +hydropathy are aware that the frequent application of cold water stimulates +the skin; and whatever stimulates the skin tends to increase the growth of +the hair, as is well shown in the abnormal growth of hair near old inflamed +surfaces. Now, Professor Low[817] is convinced that with the different +races of British cattle thick skin and long hair depend on the humidity of +the climate which they inhabit. We can thus see how a humid climate might +act on the horns--in the first place directly on the skin and hair, and +secondly by correlation on the horns. The presence or absence of horns, +moreover, both in the case of sheep and cattle, acts, as will presently be +shown, by some sort of correlation on the skull. + +With respect to hair and teeth, Mr. Yarrell[818] found many of the teeth +deficient in three hairless "_Ægyptian_" dogs, and in a hairless terrier. +The incisors, canines, and premolars suffered most, but in one case all the +teeth, except the large tubercular molar on each side, were deficient. With +man several striking cases have been recorded[819] of inherited baldness +with {327} inherited deficiency, either complete or partial, of the teeth. +We see the same connexion in those rare cases in which the hair has been +renewed in old age, for this has "usually been accompanied by a renewal of +the teeth." I have remarked in a former part of this volume that the great +reduction in the size of the tusks in domestic boars probably stands in +close relation with their diminished bristles, due to a certain amount of +protection; and that the reappearance of the tusks in boars, which have +become feral and are fully exposed to the weather, probably depends on the +reappearance of the bristles. I may add, though not strictly connected with +our present point, that an agriculturist[820] asserts that "pigs with +little hair on their bodies are most liable to lose their tails, showing a +weakness of the tegumental structure. It may be prevented by crossing with +a more hairy breed." + +In the previous cases deficient hair, and teeth deficient in number or +size, are apparently connected. In the following cases abnormally redundant +hair, and teeth either deficient or redundant, are likewise connected. Mr. +Crawfurd[821] saw at the Burmese Court a man, thirty years old, with his +whole body, except the hands and feet, covered with straight silky hair, +which on the shoulders and spine was five inches in length. At birth the +ears alone were covered. He did not arrive at puberty, or shed his milk +teeth, until twenty years old; and at this period he acquired five teeth in +the upper jaw, namely four incisors and one canine, and four incisor teeth +in the lower jaw; all the teeth were small. This man had a daughter, who +was born with hair within her ears; and the hair soon extended over her +body. When Captain Yule[822] visited the Court, he found this girl grown +up; and she presented a strange appearance with even her nose densely +covered with soft hair. Like her father, she was furnished with incisor +teeth alone. The King had with difficulty bribed a man to marry her, and of +her two children, one, a boy fourteen months old, had hair growing out of +his ears, with a beard and moustache. This strange peculiarity had, +therefore, been inherited for three generations, with the molar teeth +deficient in the grandfather and mother; whether {328} these teeth would +likewise fail in the infant could not be told. Here is another case +communicated to me by Mr. Wallace on the authority of Dr. Purland, a +dentist: Julia Pastrana, a Spanish dancer, was a remarkably fine woman, but +she had a thick masculine beard and a hairy forehead; she was photographed, +and her stuffed skin was exhibited as a show; but what concerns us is, that +she had in both the upper and lower jaw an irregular double set of teeth, +one row being placed within the other, of which Dr. Purland took a cast. +From the redundancy of the teeth her mouth projected, and her face had a +gorilla-like appearance. These cases and those of the hairless dogs +forcibly call to mind the fact, that the two orders of mammals--namely, the +Edentata and Cetacea--which are the most abnormal in their dermal covering, +are likewise the most abnormal either by deficiency or redundancy of teeth. + +The organs of sight and hearing are generally admitted to be homologous, +both with each other and with the various dermal appendages; hence these +parts are liable to be abnormally affected in conjunction. Mr. White Cowper +says "that in all cases of double microphthalmia brought under his notice +he has at the same time met with defective development of the dental +system." Certain forms of blindness seem to be associated with the colour +of the hair; a man with black hair and a woman with light-coloured hair, +both of sound constitution, married and had nine children, all of whom were +born blind; of these children, five "with dark hair and brown iris were +afflicted with amaurosis; the four others, with light-coloured hair and +blue iris, had amaurosis and cataract conjoined." Several cases could be +given, showing that some relation exists between various affections of the +eyes and ears; thus Liebreich states that out of 241 deaf-mutes in Berlin, +no less than fourteen suffered from the rare disease called pigmentary +retinitis. Mr. White Cowper and Dr. Earle have remarked that inability to +distinguish different colours, or colour-blindness, "is often associated +with a corresponding inability to distinguish musical sounds."[823] + +{329} + +Here is a more curious case: white cats, if they have blue eyes, are almost +always deaf. I formerly thought that the rule was invariable, but I have +heard of a few authentic exceptions. The first two notices were published +in 1829, and relate to English and Persian cats: of the latter, the Rev. +W. T. Bree possessed a female, and he states "that of the offspring +produced at one and the same birth, such as, like the mother, were entirely +white (with blue eyes) were, like her, invariably deaf; while those that +had the least speck of colour on their fur, as invariably possessed the +usual faculty of hearing."[824] The Rev. W. Darwin Fox informs me that he +has seen more than a dozen instances of this correlation in English, +Persian, and Danish cats; but he adds "that, if one eye, as I have several +times observed, be not blue, the cat hears. On the other hand, I have never +seen a white cat with eyes of the common colour that was deaf." In France +Dr. Sichel[825] has observed during twenty years similar facts; he adds the +remarkable case of the iris beginning, at the end of four months, to grow +dark-coloured, and then the cat first began to hear. + +This case of correlation in cats has struck many persons as marvellous. +There is nothing unusual in the relation between blue eyes and white fur; +and we have already seen that the organs of sight and hearing are often +simultaneously affected. In the present instance the cause probably lies in +a slight arrest of development in the nervous system in connection with the +sense-organs. Kittens during the first nine days, whilst their eyes are +closed, appear to be completely deaf; I have made a great clanging noise +with a poker and shovel close to their heads, both when they were asleep +and awake, without producing any effect. The trial must not be made by +shouting close to their ears, for they are, even when asleep, extremely +sensitive to a breath of air. Now, as long as the eyes continue closed, the +iris is no doubt blue, for in all the kittens which I have seen this colour +remains for some time after the eyelids open. Hence, if we suppose the +development of the organs of sight and hearing to be arrested at the stage +of the closed eyelids, the eyes would {330} remain permanently blue and the +ears would be incapable of perceiving sound; and we should thus understand +this curious case. As, however, the colour of the fur is determined long +before birth, and as the blueness of the eyes and the whiteness of the fur +are obviously connected, we must believe that some primary cause acts at an +early period. + +The instances of correlated variability hitherto given have been chiefly +drawn from the animal kingdom, and we will now turn to plants. Leaves, +sepals, petals, stamens, and pistils are all homologous. In double flowers +we see that the stamens and pistils vary in the same manner, and assume the +form and colour of the petals. In the double columbine (_Aquilegia +vulgaris_), the successive whorls of stamens are converted into +cornucopias, which are enclosed within each other and resemble the petals. +In hose-and-hose flowers the sepals mock the petals. In some cases the +flowers and leaves vary together in tint: in all the varieties of the +common pea, which have purple flowers, a purple mark may be seen on the +stipules. In other cases the leaves and fruit and seeds vary together in +colour, as in a curious pale-leaved variety of the sycamore, which has +recently been described in France,[826] and as in the purple-leaved hazel, +in which the leaves, the husk of the nut, and the pellicle round the kernel +are all coloured purple.[827] Pomologists can predict to a certain extent, +from the size and appearance of the leaves of their seedlings, the probable +nature of the fruit; for, as Van Mons remarks,[828] variations in the +leaves are generally accompanied by some modification in the flower, and +consequently in the fruit. In the Serpent melon, which has a narrow +tortuous fruit above a yard in length, the stem of the plant, the peduncle +of the female flower, and the middle lobe of the leaf, are all elongated in +a remarkable manner. On the other hand, several varieties of Cucurbita, +which have dwarfed stems, all produce, as Naudin remarks with surprise, +leaves of the same peculiar shape. Mr. G. Maw informs me that all the +varieties of the scarlet Pelargoniums which have contracted or imperfect +leaves have contracted flowers: the difference between {331} "Brilliant" +and its parent "Tom Thumb" is a good instance of this. It may be suspected +that the curious case described by Risso,[829] of a variety of the Orange +which produces on the young shoots rounded leaves with winged petioles, and +afterwards elongated leaves on long but wingless petioles, is connected +with the remarkable change in form and nature which the fruit undergoes +during its development. + +In the following instance we have the colour and form of the petals +apparently correlated, and both dependent on the nature of the season. An +observer, skilled in the subject, writes,[830] "I noticed, during the year +1842, that every Dahlia, of which the colour had any tendency to scarlet, +was deeply notched--indeed to so great an extent as to give the petals the +appearance of a saw; the indentures were, in some instances, more than a +quarter of an inch deep." Again, Dahlias which have their petals tipped +with a different colour from the rest are very inconstant, and during +certain years some, or even all the flowers, become uniformly coloured; and +it has been observed with several varieties,[831] that when this happens +the petals grow much elongated and lose their proper shape. This, however, +may be due to reversion, both in colour and form, to the aboriginal +species. + + * * * * * + +In this discussion on correlation, we have hitherto treated of cases in +which we can partly understand the bond of connexion; but I will now give +cases in which we cannot even conjecture, or can only very obscurely see, +what is the nature of the bond. Isidore Geoffroy St. Hilaire, in his work +on Monstrosities, insists,[832] "que certaines anomalies coexistent +rarement entr'elles, d'autres fréquemment, d'autres enfin presque +constamment, malgré la différence très-grande de leur nature, et +quoiqu'elles puissent paraître _complètement indépendantes_ les unes des +autres." We see something analogous in certain diseases: thus I hear from +Mr. Paget that in a rare affection of the {332} renal capsules (of which +the functions are unknown), the skin becomes bronzed; and in hereditary +syphilis, both the milk and the second teeth assume a peculiar and +characteristic form. Professor Rolleston, also, informs me that the incisor +teeth are sometimes furnished with a vascular rim in correlation with +intra-pulmonary deposition of tubercles. In other cases of phthisis and of +cyanosis the nails and finger-ends become clubbed like acorns. I believe +that no explanation has been offered of these and of many other cases of +correlated disease. + +What can be more curious and less intelligible than the fact previously +given, on the authority of Mr. Tegetmeier, that young pigeons of all +breeds, which when mature have white, yellow, silver-blue, or dun-coloured +plumage, come out of the egg almost naked; whereas pigeons of other colours +when first born are clothed with plenty of down? White Pea-fowls, as has +been observed both in England and France,[833] and as I have myself seen, +are inferior in size to the common coloured kind; and this cannot be +accounted for by the belief that albinism is always accompanied by +constitutional weakness; for white or albino moles are generally larger +than the common kind. + +To turn to more important characters: the niata cattle of the Pampas are +remarkable from their short foreheads, upturned muzzles, and curved lower +jaws. In the skull the nasal and premaxillary bones are much shortened, the +maxillaries are excluded from any junction with the nasals, and all the +bones are slightly modified, even to the plane of the occiput. From the +analogical case of the dog, hereafter to be given, it is probable that the +shortening of the nasal and adjoining bones is the proximate cause of the +other modifications in the skull, including the upward curvature of the +lower jaw, though we cannot follow out the steps by which these changes +have been effected. + +Polish fowls have a large tuft of feathers on their heads; and their skulls +are perforated by numerous holes, so that a pin can be driven into the +brain without touching any bone. That this deficiency of bone is in some +way connected with the tuft of feathers is clear from tufted ducks and +geese likewise having {333} perforated skulls. The case would probably be +considered by some authors as one of balancement or compensation. In the +chapter on Fowls, I have shown that with Polish fowls the tuft of feathers +was probably at first small; by continued selection it became larger, and +then rested on a fleshy or fibrous mass; and finally, as it became still +larger, the skull itself became more and more protuberant until it acquired +its present extraordinary structure. Through correlation with the +protuberance of the skull, the shape and even the relative connexion of the +premaxillary and nasal bones, the shape of the orifice of the nostrils, the +breadth of the frontal bone, the shape of the post-lateral processes of the +frontal and squamosal bones, and the direction of the bony cavity of the +ear, have all been modified. The internal configuration of the skull and +the whole shape of the brain have likewise been altered in a truly +marvellous manner. + +After this case of the Polish fowl it would be superfluous to do more than +refer to the details previously given on the manner in which the changed +form of the comb, in various breeds of the fowl, has affected the skull, +causing by correlation crests, protuberances, and depressions on its +surface. + +With our cattle and sheep the horns stand in close connexion with the size +of the skull, and with the shape of the frontal bones; thus Cline[834] +found that the skull of a horned ram weighed five times as much as that of +a hornless ram of the same age. When cattle become hornless, the frontal +bones are "materially diminished in breadth towards the poll;" and the +cavities between the bony plates "are not so deep, nor do they extend +beyond the frontals."[835] + + * * * * * + +It may be well here to pause and observe how the effects of correlated +variability, of the increased use of parts, and of the accumulation through +natural selection of so-called spontaneous variations, are in many cases +inextricably commingled. We may borrow an illustration from Mr. Herbert +Spencer, who remarks that, when the Irish elk acquired its gigantic horns, +weighing above one hundred pounds, numerous co-ordinated {334} changes of +structure would have been indispensable,--namely, a thickened skull to +carry the horns; strengthened cervical vertebræ, with strengthened +ligaments; enlarged dorsal vertebræ to support the neck, with powerful +fore-legs and feet; all these parts being supplied with proper muscles, +blood-vessels, and nerves. How then could these admirably co-ordinated +modifications of structure have been acquired? According to the doctrine +which I maintain, the horns of the male elk were slowly gained through +sexual selection,--that is, by the best-armed males conquering the +worse-armed, and leaving a greater number of descendants. But it is not at +all necessary that the several parts of the body should have simultaneously +varied. Each stag presents individual differences, and in the same district +those which had slightly heavier horns, or stronger necks, or stronger +bodies, or were the most courageous, would secure the greater number of +does, and consequently leave a greater number of offspring. The offspring +would inherit, in a greater or less degree, these same qualities, would +occasionally intercross with each other, or with other individuals varying +in some favourable manner; and of their offspring, those which were the +best endowed in any respect would continue multiplying; and so onwards, +always progressing, sometimes in one direction, and sometimes in another, +towards the present excellently co-ordinated structure of the male elk. To +make this clear, let us reflect on the probable steps, as shown in the +twentieth chapter, by which our race and dray-horses have arrived at their +present state of excellence; if we could view the whole series of +intermediate forms between one of these animals and an early unimproved +progenitor, we should behold a vast number of animals, not equally improved +in each generation throughout their entire structure, but sometimes a +little more in one point, and sometimes in another, yet on the whole +gradually approaching in character to our present race or dray-horses, +which are so admirably fitted in the one case for fleetness and in the +other for draught. + +Although natural selection would thus[836] tend to give to the {335} male +elk its present structure, yet it is probable that the inherited influence +of use has played an equal or more important part. As the horns gradually +increased in weight, the muscles of the neck, with the bones to which they +are attached, would increase in size and strength; and these parts would +react on the body and legs. Nor must we overlook the fact that certain +parts of the skull and the extremities would, judging by analogy, tend from +the first to vary in a correlated manner. The increased weight of the horns +would also act directly on the skull, in the same manner as, when one bone +is removed in the leg of a dog, the other bone, which has to carry the +whole weight of the body, increases in thickness. But from the facts given +with respect to horned and hornless cattle, it is probable that the horns +and skull would immediately act on each other through the principle of +correlation. Lastly, the growth and subsequent wear and tear of the +augmented muscles and bones would require an increased supply of blood, and +consequently an increased supply of food; and this again would require +increased powers of mastication, digestion, respiration, and excretion. + +_Colour as Correlated with Constitutional Peculiarities._ + +It is an old belief that with man there is a connexion between complexion +and constitution; and I find that some of the best authorities believe in +this to the present day.[837] Thus Dr. Beddoe by his tables shows[838] that +a relation exists between liability to consumption and the colour of the +hair, eyes, and skin. It has been affirmed[839] that, in the French army +which invaded Russia, soldiers having a dark complexion, from the {336} +southern parts of Europe, withstood the intense cold better than those with +lighter complexions from the north; but no doubt such statements are liable +to error. + +In the second chapter on Selection I have given several cases proving that +with animals and plants differences in colour are correlated with +constitutional differences, as shown by greater or less immunity from +certain diseases, from the attacks of parasitic plants and animals, from +burning by the sun, and from the action of certain poisons. When all the +individuals of any one variety possess an immunity of this nature, we +cannot feel sure that it stands in any sort of correlation with their +colour; but when several varieties of the same species, which are similarly +coloured, are thus characterised, whilst other coloured varieties are not +thus favoured, we must believe in the existence of a correlation of this +kind. Thus in the United States purple-fruited plums of many kinds are far +more affected by a certain disease than green or yellow-fruited varieties. +On the other hand, yellow-fleshed peaches of various kinds suffer from +another disease much more than the white-fleshed varieties. In the +Mauritius red sugar-canes are much less affected by a particular disease +than the white canes. White onions and verbenas are the most liable to +mildew; and in Spain the green-fruited grapes suffered from the +vine-disease more than other coloured varieties. Dark-coloured pelargoniums +and verbenas are more scorched by the sun than varieties of other colours. +Red wheats are believed to be hardier than white; whilst red-flowered +hyacinths were more injured during one particular winter in Holland than +other coloured varieties. With animals, white terriers suffer most from the +distemper, white chickens from a parasitic worm in their tracheæ, white +pigs from scorching by the sun, and white cattle from flies; but the +caterpillars of the silk-moth which yield white cocoons suffered in France +less from the deadly parasitic fungus than those producing yellow silk. + +The cases of immunity from the action of certain vegetable poisons, in +connexion with colour, are more interesting, and are at present wholly +inexplicable. I have already given a remarkable instance, on the authority +of Professor Wyman, of all the hogs, excepting those of a black colour, +suffering severely in Virginia from eating the root of the _Lachnanthes +tinctoria_. {337} According to Spinola and others,[840] buckwheat +(_Polygonum fagopyrum_), when in flower, is highly injurious to white or +white-spotted pigs, if they are exposed to the heat of the sun, but is +quite innocuous to black pigs. By two accounts, the _Hypericum crispum_ in +Sicily is poisonous to white sheep alone; their heads swell, their wool +falls off, and they often die; but this plant, according to Lecce, is +poisonous only when it grows in swamps; nor is this improbable, as we know +how readily the poisonous principle in plants is influenced by the +conditions under which they grow. + +Three accounts have been published in Eastern Prussia, of white and +white-spotted horses being greatly injured by eating mildewed and +honeydewed vetches; every spot of skin bearing white hairs becoming +inflamed and gangrenous. The Rev. J. Rodwell informs me that his father +turned out about fifteen cart-horses into a field of tares which in parts +swarmed with black aphides, and which no doubt were honeydewed, and +probably mildewed; the horses, with two exceptions, were chesnuts and bays +with white marks on their faces and pasterns, and the white parts alone +swelled and became angry scabs. The two bay horses with no white marks +entirely escaped all injury. In Guernsey, when horses eat fools' parsley +(_Æthusa cynapium_) they are sometimes violently purged; and this plant +"has a peculiar effect on the nose and lips, causing deep cracks and +ulcers, particularly on horses with white muzzles."[841] With cattle, +independently of the action of any poison, cases have been published by +Youatt and Erdt of cutaneous diseases with much constitutional disturbance +(in one instance after exposure to a hot sun) affecting every single point +which bore a white hair, but completely passing over other parts of the +body. Similar cases have been observed with horses.[842] + +We thus see that not only do those parts of the skin which bear white hair +differ in a remarkable manner from those bearing {338} hair of any other +colour, but that in addition some great, constitutional difference must +stand in correlation with the colour of the hair; for in the +above-mentioned cases, vegetable poisons caused fever, swelling of the +head, as well as other symptoms, and even death, to all the white or +white-spotted animals. + + * * * * * + + +{339} + +CHAPTER XXVI. + +LAWS OF VARIATION, _continued_--SUMMARY. + + ON THE AFFINITY AND COHESION OF HOMOLOGOUS PARTS--ON THE VARIABILITY OF + MULTIPLE AND HOMOLOGOUS PARTS--COMPENSATION OF GROWTH--MECHANICAL + PRESSURE--RELATIVE POSITION OF FLOWERS WITH RESPECT TO THE AXIS OF THE + PLANT, AND OF SEEDS IN THE CAPSULE, AS INDUCING VARIATION--ANALOGOUS OR + PARALLEL VARIETIES--SUMMARY OF THE THREE LAST CHAPTERS. + +_On the Affinity of Homologous Parts._--This law was first generalised by +Geoffroy Saint Hilaire, under the expression of _La loi de l'affinité de +soi pour soi_. It has been fully discussed and illustrated by his son, +Isidore Geoffroy, with respect to monsters in the animal kingdom,[843] and +by Moquin-Tandon, with respect to monstrous plants. When similar or +homologous parts, whether belonging to the same embryo or to two distinct +embryos, are brought during an early stage of development into contact, +they often blend into a single part or organ; and this complete fusion +indicates some mutual affinity between the parts, otherwise they would +simply cohere. Whether any power exists which tends to bring homologous +parts into contact seems more doubtful. The tendency to complete fusion is +not a rare or exceptional fact. It is exhibited in the most striking manner +by double monsters. Nothing can be more extraordinary than the manner, as +shown in various published plates, in which the corresponding parts of two +embryos become intimately fused together. This is perhaps best seen in +monsters with two heads, which are united, summit to summit, or face to +face, or, Janus-like, back to back, or obliquely side to side. In one +instance of two heads united almost face to face, but a little obliquely, +four ears were developed, and on one side a perfect face, which was +manifestly formed by the union of two {340} half-faces. Whenever two bodies +or two heads are united, each bone, muscle, vessel, and nerve on the line +of junction seems to seek out its fellow, and becomes completely fused with +it. Lereboullet,[844] who carefully studied the development of double +monsters in fishes, observed in fifteen instances the steps by which two +heads gradually became fused into one. In this and other such cases, no +one, I presume, supposes that the two already formed heads actually blend +together, but that the corresponding parts of each head grow into one +during the further progress of development, accompanied as it always is +with incessant absorption and renovation. Double monsters were formerly +thought to be formed by the union of two originally distinct embryos +developed upon distinct vitelli; but now it is admitted that "their +production is due to the spontaneous divarication of the embryonic mass +into two halves;"[845] this, however, is effected by different methods. But +the belief that double monsters originate from the division of one germ, +does not necessarily affect the question of subsequent fusion, or render +less true the law of the affinity of homologous parts. + +The cautious and sagacious J. Müller,[846] when speaking of Janus-like +monsters, says, that "without the supposition that some kind of affinity or +attraction is exerted between corresponding parts, unions of this kind are +inexplicable." On the other hand, Vrolik, and he is followed by others, +disputes this conclusion, and argues from the existence of a whole series +of monstrosities, graduating from a perfectly double monster to a mere +rudiment of an additional digit, that "an excess of formative power" is the +cause and origin of every monstrous duplicity. That there are two distinct +classes of cases, and that parts may be doubled independently of the +existence of two embryos, is certain; for a single embryo, or even a single +adult animal, may produce doubled organs. Thus Valentin, as quoted by +Vrolik, injured the caudal extremity of an embryo, and three days +afterwards it produced rudiments of a double pelvis and of double hind +limbs. {341} Hunter and others have observed lizards with their tails +reproduced and doubled. When Bonnet divided longitudinally the foot of the +salamander, several additional digits were occasionally formed. But neither +these cases, nor the perfect series from a double monster to an additional +digit, seem to me opposed to the belief that corresponding parts have a +mutual affinity, and consequently tend to fuse together. A part may be +doubled and remain in this state, or the two parts thus formed may +afterwards through the law of affinity become blended; or two homologous +parts in two separate embryos may, through the same principle, unite and +form a single part. + +The law of the affinity and fusion of similar parts applies to the +homologous organs of the same individual animal, as well as to double +monsters. Isidore Geoffroy gives a number of instances of two or more +digits, of two whole legs, of two kidneys, and of several teeth becoming +symmetrically fused together in a more or less perfect manner. Even the two +eyes have been known to unite into a single eye, forming a cyclopean +monster, as have the two ears, though naturally standing so far apart. As +Geoffroy remarks, these facts illustrate in an admirable manner the normal +fusion of various organs which during an early embryonic period are double, +but which afterwards always unite into a single median organ. Organs of +this nature are generally found in a permanently double condition in other +members of the same class. These cases of normal fusion appear to me to +afford the strongest support in favour of the present law. Adjoining parts +which are not homologous sometimes cohere; but this cohesion appears to +result from mere juxtaposition, and not from mutual affinity. + +In the vegetable kingdom Moquin-Tandon[847] gives a long list of cases, +showing how frequently homologous parts, such as leaves, petals, stamens, +and pistils, as well as aggregates of homologous parts, such as buds, +flowers, and fruit, become blended into each other with perfect symmetry. +It is interesting to examine a compound flower of this nature, formed of +exactly double the proper number of sepals, petals, stamens, and pistils, +with each whorl of organs circular, and with no trace left of the {342} +process of fusion. The tendency in homologous parts to unite during their +early development, Moquin-Tandon considers as one of the most striking laws +governing the production of monsters. It apparently explains a multitude of +cases, both in the animal and vegetable kingdoms; it throws a clear light +on many normal structures which have evidently been formed by the union of +originally distinct parts, and it possesses, as we shall see in a future +chapter, much theoretical interest. + + * * * * * + +_On the Variability of Multiple and Homologous Parts._--Isidore +Geoffroy[848] insists that, when any part or organ is repeated many times +in the same animal, it is particularly liable to vary both in number and +structure. With respect to number, the proposition may, I think, be +considered as fully established; but the evidence is chiefly derived from +organic beings living under their natural conditions, with which we are not +here concerned. When the vertebræ, or teeth, or rays in the fins of fishes, +or feathers in the tails of birds, or petals, stamens, pistils, and seeds +in plants, are very numerous, the number is generally variable. The +explanation of this simple fact is by no means obvious. With respect to the +variability in structure of multiple parts, the evidence is not so +decisive; but the fact, as far as it may be trusted, probably depends on +multiple parts being of less physiological importance than single parts; +consequently their perfect standard of structure has been less rigorously +enforced by natural selection. + + * * * * * + +_Compensation of Growth, or Balancement._--This law, as applied to natural +species, was propounded by Goethe and Geoffroy St. Hilaire at nearly the +same time. It implies that, when much organised matter is used in building +up some one part, other parts are starved and become reduced. Several +authors, especially botanists, believe in this law; others reject it. As +far as I can judge, it occasionally holds good; but its importance has +probably been exaggerated. It is scarcely possible to distinguish between +the supposed effects of such compensation of growth, and the effects of +long-continued selection, which {343} may at the same time lead to the +augmentation of one part and the diminution of another. There can be no +doubt that an organ may be greatly increased without any corresponding +diminution in the adjoining parts. To recur to our former illustration of +the Irish elk, it may be asked what part has suffered in consequence of the +immense development of the horns? + +It has already been observed that the struggle for existence does not bear +hard on our domesticated productions; consequently the principle of economy +of growth will seldom affect them, and we ought not to expect to find +frequent evidence of compensation. We have, however, some such cases. +Moquin-Tandon describes a monstrous bean,[849] in which the stipules were +enormously developed, and the leaflets apparently in consequence completely +aborted; this case is interesting, as it represents the natural condition +of _Lathyrus aphaca_, with its stipules of great size, and its leaves +reduced to mere threads, which act as tendrils. De Candolle[850] has +remarked that the varieties of _Raphanus sativus_ which have small roots +yield numerous seed, valuable from containing oil, whilst those with large +roots are not productive in this latter respect; and so it is with +_Brassica asperifolia_. The varieties of the potato which produce tubers +very early in the season rarely bear flowers; but Andrew Knight,[851] by +checking the growth of the tubers, forced the plants to flower. The +varieties of _Cucurbita pepo_ which produce large fruit yield, according to +Naudin, few in number; whilst those producing small fruit yield a vast +number. Lastly, I have endeavoured to show in the eighteenth chapter that +with many cultivated plants unnatural treatment checks the full and proper +action of the reproductive organs, and they are thus rendered more or less +sterile; consequently, in the way of compensation, the fruit becomes +greatly enlarged, and, in double flowers, the petals are greatly increased +in number. + +With animals, it has been found difficult to produce cows which should +first yield much milk, and afterwards be capable of {344} fattening well. +With fowls which have large topknots and beards the comb and wattles are +generally much reduced in size. Perhaps the entire absence of the oil-gland +in fantail pigeons may be connected with the great development of their +tails. + + * * * * * + +_Mechanical Pressure as a Cause of Modifications._--In some few cases there +is reason to believe that mere mechanical pressure has affected certain +structures. Every one knows that savages alter the shape of their infants' +skulls by pressure at an early age; but there is no reason to believe that +the result is ever inherited. Nevertheless Vrolik and Weber[852] maintain +that the shape of the human head is influenced by the shape of the mother's +pelvis. The kidneys in different birds differ much in form, and St. +Ange[853] believes that this is determined by the form of the pelvis, which +again, no doubt, stands in close relation with their various habits of +locomotion. In snakes, the viscera are curiously displaced, in comparison +with their position in other vertebrates; and this has been attributed by +some authors to the elongation of their bodies; but here, as in so many +previous cases, it is impossible to disentangle any direct result of this +kind from that consequent on natural selection. Godron has argued[854] that +the normal abortion of the spur on the inner side of the flower in +Corydalis, is caused by the buds being closely pressed at a very early +period of growth, whilst under ground, against each other and against the +stem. Some botanists believe that the singular difference in the shape both +of the seed and corolla, in the interior and exterior florets in certain +compositous and umbelliferous plants, is due to the pressure to which the +inner florets are subjected; but this conclusion is doubtful. + +The facts just given do not relate to domesticated productions, and +therefore do not strictly concern us. But here is a more appropriate case: +H. Müller[855] has shown that in {345} short-faced races of the dog some of +the molar teeth are placed in a slightly different position from that which +they occupy in other dogs, especially in those having elongated muzzles; +and as he remarks, any inherited change in the arrangement of the teeth +deserves notice, considering their classificatory importance. This +difference in position is due to the shortening of certain facial bones, +and the consequent want of space; and the shortening results from a +peculiar and abnormal state of the basal cartilages of the bones. + +_Relative Position of Flowers with respect to the Axis, and of Seeds in the +Capsule, as inducing Variation._ + + In the thirteenth chapter various peloric flowers were described, and + their production was shown to be due either to arrested development, or + to reversion to a primordial condition. Moquin-Tandon has remarked that + the flowers which stand on the summit of the main stem or of a lateral + branch are more liable to become peloric than those on the sides;[856] + and he adduces, amongst other instances, that of _Teucrium + campanulatum_. In another Labiate plant grown by me, viz. the + _Galeobdolon luteum_, the peloric flowers were always produced on the + summit of the stem, where flowers are not usually borne. In + Pelargonium, a _single_ flower in the truss is frequently peloric, and + when this occurs I have during several years invariably observed it to + be the central flower. This is of such frequent occurrence that one + observer[857] gives the names of ten varieties flowering at the same + time, in every one of which the central flower was peloric. + Occasionally more than one flower in the truss is peloric, and then of + course the additional ones must be lateral. These flowers are + interesting as showing how the whole structure is correlated. In the + common Pelargonium the upper sepal is produced into a nectary which + coheres with the flower-peduncle; the two upper petals differ a little + in shape from the three lower ones, and are marked with dark shades of + colour; the stamens are graduated in length and upturned. In the + peloric flowers, the nectary aborts; all the petals become alike both + in shape and colour; the stamens are generally reduced in number and + become straight, so that the whole flower resembles that of the allied + genus Erodium. The correlation between these changes is well shown when + one of the two upper petals alone loses its dark mark, for in this case + the nectary does not entirely abort, but is usually much reduced in + length.[858] + + {346} + + Morren has described[859] a marvellous flask-shaped flower of the + Calceolaria, nearly four inches in length, which was almost completely + peloric; it grew on the summit of the plant, with a normal flower on + each side; Prof. Westwood also has described[860] three similar peloric + flowers, which all occupied a central position on the flower-branches. + In the Orchideous genus, Phalænopsis, the terminal flower has been seen + to become peloric. + + In a Laburnum-tree I observed that about a fourth part of the racemes + produced terminal flowers which had lost their papilionaceous + structure. These were produced after almost all the other flowers on + the same racemes had withered. The most perfectly pelorised examples + had six petals, each marked with black striæ like those on the + standard-petal. The keel seemed to resist the change more than the + other petals. Dutrochet has described[861] an exactly similar case in + France, and I believe these are the only two instances of pelorism in + the laburnum which have been recorded. Dutrochet remarks that the + racemes on this tree do not properly produce a terminal flower, so + that, as in the case of the Galeobdolon, their position as well as + their structure are both anomalies, which no doubt are in some manner + related. Dr. Masters has briefly described another leguminous + plant,[862] namely, a species of clover, in which the uppermost and + central flowers were regular or had lost their papilionaceous + structure. In some of these plants the flower-heads were also + proliferous. + + Lastly, Linaria produces two kinds of peloric flowers, one having + simple petals, and the other having them all spurred. The two forms, as + Naudin remarks,[863] not rarely occur on the same plant, but in this + case the spurred form almost invariably stands on the summit of the + spike. + + The tendency in the terminal or central flower to become peloric more + frequently than other flowers, probably results from "the bud which + stands on the end of a shoot receiving the most sap; it grows out into + a stronger shoot than those situated lower down."[864] I have discussed + the connection between pelorism and a central position, partly because + some few plants are known normally to produce a terminal flower + different in structure from the lateral ones; but chiefly on account of + the following case, in which we see a tendency to variability or to + reversion connected with the same position. A great judge of + Auriculas[865] states that when an Auricula throws up a side bloom it + is pretty sure to keep its character; but that if it grows from the + centre or heart of the plant, whatever the colour of the edging ought + to be, "it is just as likely to come in any other class as in the one + to which it properly belongs." This is so notorious a {347} fact, that + some florists regularly pinch off the central trusses of flowers. + Whether in the highly improved varieties the departure of the central + trusses from their proper type is due to reversion, I do not know. Mr. + Dombrain insists that, whatever may be the commonest kind of + imperfection in each variety, this is generally exaggerated in the + central truss. Thus one variety "sometimes has the fault of producing a + little green floret in the centre of the flower," and in central blooms + these become excessive in size. In some central blooms, sent to me by + Mr. Dombrain, all the organs of the flower were rudimentary in + structure, of minute size, and of a green colour, so that by a little + further change all would have been converted into small leaves. In this + case we clearly see a tendency to prolification--a term which, I may + explain to those who have never attended to botany, means the + production of a branch or flower, or head of flowers, out of another + flower. Now Dr. Masters[866] states that the central or uppermost + flower on a plant is generally the most liable to prolification. Thus, + in the varieties of the Auricula, the loss of their proper character + and a tendency to prolification, and in other plants a tendency to + prolification and pelorism, are all connected together, and are due + either to arrested development, or to reversion to a former condition. + + The following is a more interesting case; Metzger[867] cultivated in + Germany several kinds of maize brought from the hotter parts of + America, and he found, as has been previously described, that in two or + three generations the grains became greatly changed in form, size, and + colour; and with respect to two races he expressly states that in the + first generation, whilst the lower grains on each head retained their + proper character, the uppermost grains already began to assume that + character which in the third generation all the grains acquired. As we + do not know the aboriginal parent of the maize, we cannot tell whether + these changes are in any way connected with reversion. + + In the two following cases, reversion, as influenced by the position of + the seed in the capsule, evidently acts. The Blue Imperial pea is the + offspring of the Blue Prussian, and has larger seed and broader pods + than its parent. Now Mr. Masters, of Canterbury, a careful observer and + a raiser of new varieties of the pea, states[868] that the Blue + Imperial always has a strong tendency to revert to its parent-stock, + and the reversion "occurs in this manner: the last (or uppermost) pea + in the pod is frequently much smaller than the rest; and if these small + peas are carefully collected and sown separately, very many more, in + proportion, will revert to their origin, than those taken from the + other parts of the pod." Again M. Chaté[869] says that in raising + seedling stocks he succeeds in getting eighty per cent. to bear double + flowers, by leaving only a few of the secondary branches to seed; but + in addition to this, "at the time of extracting the seeds, the upper + portion of the pod is separated and {348} placed aside, because it has + been ascertained that the plants coming from the seeds situated in this + portion of the pod, give eighty per cent. of single flowers." Now the + production of single-flowering plants from the seed of double-flowering + plants is clearly a case of reversion. These latter facts, as well as + the connection between a central position and pelorism and + prolification, show in an interesting manner how small a + difference--namely a little greater freedom in the flow of sap towards + one part of the same plant--determines important changes of structure. + + * * * * * + +_Analogous or Parallel Variation._--By this term I wish to express that +similar characters occasionally make their appearance in the several +varieties or races descended from the same species, and more rarely in the +offspring of widely distinct species. We are here concerned, not as +hitherto with the causes of variation, but with the results; but this +discussion could not have been more conveniently introduced elsewhere. The +cases of analogous variation, as far as their origin is concerned, may be +grouped, disregarding minor subdivisions, under two main heads; firstly, +those due to unknown causes having acted on organic beings with nearly the +same constitution, and which consequently vary in an analogous manner; and +secondly, those due to the reappearance of characters which were possessed +by a more or less remote progenitor. But these two main divisions can often +be only conjecturally separated, and graduate, as we shall presently see, +into each other. + + Under the first head of analogous variations, not due to reversion, we + have the many cases of trees belonging to quite different orders which + have produced pendulous and fastigate varieties. The beech, hazel, and + barberry have given rise to purple-leaved varieties; and as Bernhardi + has remarked,[870] a multitude of plants, as distinct as possible, have + yielded varieties with deeply-cut or laciniated leaves. Varieties + descended from three distinct species of Brassica have their stems, or + so-called roots, enlarged into globular masses. The nectarine is the + offspring of the peach; and the varieties of both these trees offer a + remarkable parallelism in the fruit being white, red, or yellow + fleshed--in being clingstones or freestones--in the flowers being large + or small--in the leaves being serrated or crenated, furnished with + globose or reniform glands, or quite destitute of glands. It should be + remarked that each variety of the nectarine has not derived its + character from a corresponding variety of the peach. The several + varieties also of a closely allied genus, namely the apricot, differ + from each other in nearly the same parallel manner. There is no reason + {349} to believe that in any of these cases long-lost characters have + reappeared, and in most of them this certainly has not occurred. + + Three species of Cucurbita have yielded a multitude of races, which + correspond so closely in character that, as Naudin insists, they may be + arranged in an almost strictly parallel series. Several varieties of + the melon are interesting from resembling in important characters other + species, either of the same genus or of allied genera; thus, one + variety has fruit so like, both externally and internally, the fruit of + a perfectly distinct species, namely, the cucumber, as hardly to be + distinguished from it; another has long cylindrical fruit twisting + about like a serpent; in another the seeds adhere to portions of the + pulp; in another the fruit, when ripe, suddenly cracks and falls into + pieces; and all these highly remarkable peculiarities are + characteristic of species belonging to allied genera. We can hardly + account for the appearance of so many unusual characters by reversion + to a single ancient form; but we must believe that all the members of + the family have inherited a nearly similar constitution from an early + progenitor. Our cereal and many other plants offer similar cases. + + With animals we have fewer cases of analogous variation, independently + of direct reversion. We see something of the kind in the resemblance + between the short-muzzled races of the dog, such as the pug and + bulldog; in feather-footed races of the fowl, pigeon, and canary-bird; + in horses of the most different races presenting the same range of + colour; in all black-and-tan dogs having tan-coloured eye-spots and + feet, but in this latter case reversion may possibly have played a + part. Low has remarked[871] that several breeds of cattle are + "sheeted,"--that is, have a broad band of white passing round their + bodies like a sheet; this character is strongly inherited and sometimes + originates from a cross; it may be the first step in reversion to an + original or early type, for, as was shown in the third chapter, white + cattle with dark ears, feet, and tip of tail formerly existed, and now + exist in a feral or semi-feral condition in several quarters of the + world. + + Under our second main division, namely, of analogous variations due to + reversion, the best cases are afforded by animals, and by none better + than by pigeons. In all the most distinct breeds sub-varieties + occasionally appear coloured exactly like the parent rock-pigeon, with + black wing-bars, white loins, banded tail, &c.; and no one can doubt + that these characters are simply due to reversion. So with minor + details; turbits properly have white tails, but occasionally a bird is + born with a dark-coloured and banded tail; pouters properly have white + primary wing-feathers, but not rarely a "sword-flighted" bird, that is, + one with the few first primaries dark-coloured, appears; and in these + cases we have characters proper to the rock-pigeon, but new to the + breed, evidently appearing from reversion. In some domestic varieties + the wing-bars, instead of being simply black, as in the rock-pigeon, + are beautifully edged with different zones of colour, and they then + present a striking analogy with the wing-bars in certain natural + species of the same family, such as _Phaps chalcoptera_; and this may + probably be accounted for by {350} all the forms descended from the + same remote progenitor having a tendency to vary in the same manner. + Thus also we can perhaps understand the fact of some Laugher-pigeons + cooing almost like turtle-doves, and of several races having + peculiarities in their flight, for certain natural species (viz. _C. + torquatrix_ and _palumbus_) display singular vagaries in this respect. + In other cases a race, instead of imitating in character a distinct + species, resembles some other race; thus certain runts tremble and + slightly elevate their tails, like fantails; and turbits inflate the + upper part of their oesophagus, like pouter-pigeons. + + It is a common circumstance to find certain coloured marks persistently + characterising all the species of a genus, but differing much in tint; + and the same thing occurs with the varieties of the pigeon: thus, + instead of the general plumage being blue with the wing-bars black, + there are snow-white varieties with red bars, and black varieties with + white bars; in other varieties the wing-bars, as we have seen, are + elegantly zoned with different tints. The Spot pigeon is characterised + by the whole plumage being white, excepting the tail and a spot on the + forehead; but these parts may be red, yellow, or black. In the + rock-pigeon and in many varieties the tail is blue, with the outer + edges of the outer feathers white; but in one sub-variety of the + monk-pigeon we have a reversed variation, for the tail is white, except + the outer edges of the outer feathers, which are black.[872] + + With some species of birds, for instance with gulls, certain coloured + parts appear as if almost washed out, and I have observed exactly the + same appearance in the terminal dark tail-bar in certain pigeons, and + in the whole plumage of certain varieties of the duck. Analogous facts + in the vegetable kingdom could be given. + + Many sub-varieties of the pigeon have reversed and somewhat lengthened + feathers on the back part of their heads, and this is certainly not due + to reversion to the parent-species, which shows no trace of such + structure; but when we remember that sub-varieties of the fowl, turkey, + canary-bird, duck, and goose, all have topknots or reversed feathers on + their heads; and when we remember that scarcely a single large natural + group of birds can be named, in which some members have not a tuft of + feathers on their heads, we may suspect that reversion to some + extremely remote form has come into action. + + Several breeds of the fowl have either spangled or pencilled feathers; + and these cannot be derived from the parent-species, the _Gallus + bankiva_; though of course it is possible that an early progenitor of + this species may have been spangled, and a still earlier or a later + progenitor may have been pencilled. But as many gallinaceous birds are + spangled or pencilled, it is a more probable view that the several + domestic breeds of the fowl have acquired this kind of plumage from all + the members of the family inheriting a tendency to vary in a like + manner. The same principle may account for the ewes in certain breeds + of sheep being hornless, like the females of some other hollow-horned + ruminants; it may account for certain domestic cats having + slightly-tufted ears, like those of the lynx; and for the skulls of + domestic rabbits often differing from each {351} other in the same + characters by which the skulls of the various species of the genus + Lepus differ. + + I will only allude to one other case, already discussed. Now that we + know that the wild parent of the ass has striped legs, we may feel + confident that the occasional appearance of stripes on the legs of the + domestic ass is due to direct reversion; but this will not account for + the lower end of the shoulder-stripe being sometimes angularly bent or + slightly forked. So, again, when we see dun and other coloured horses + with stripes on the spine, shoulders, and legs, we are led, from + reasons formerly given, to believe that they reappear from direct + reversion to the wild parent-horse. But when horses have two or three + shoulder-stripes with one of them occasionally forked at the lower end, + or when they have stripes on their faces, or as foals are faintly + striped over nearly their whole bodies, with the stripes angularly bent + one under the other on the forehead, or irregularly branched in other + parts, it would be rash to attribute such diversified characters to the + reappearance of those proper to the aboriginal wild horse. As three + African species of the genus are much striped, and as we have seen that + the crossing of the unstriped species often leads to the hybrid + offspring being conspicuously striped--bearing also in mind that the + act of crossing certainly causes the reappearance of long-lost + characters--it is a more probable view that the above-specified stripes + are due to reversion, not to the immediate wild parent-horse, but to + the striped progenitor of the whole genus. + +I have discussed this subject of analogous variation at considerable +length, because, in a future work on natural species, it will be shown that +the varieties of one species frequently mock distinct species--a fact in +perfect harmony with the foregoing cases, and explicable only on the theory +of descent. Secondly, because these facts are important from showing, as +remarked in a former chapter, that each trifling variation is governed by +law, and is determined in a much higher degree by the nature of the +organisation, than by the nature of the conditions to which the varying +being has been exposed. Thirdly, because these facts are to a certain +extent related to a more general law, namely, that which Mr. B. D. +Walsh[873] has called the "Law of _Equable Variability_," or, as he +explains it, "if any given character is very variable in one species of a +group, it will tend to be variable in allied species; and if any given +character is perfectly constant in one species of a group, it will tend to +be constant in allied species." + +This leads me to recall a discussion in the chapter on Selection, in which +it was shown that with domestic races, which are {352} now undergoing rapid +improvement, those parts or characters which are the most valued vary the +most. This naturally follows from recently selected characters continually +tending to revert to their former less improved standard, and from their +being still acted on by the same agencies, whatever these may be, which +first caused the characters in question to vary. The same principle is +applicable to natural species, for, as stated in my 'Origin of Species,' +generic characters are less variable than specific characters; and the +latter are those which have been modified by variation and natural +selection, since the period when all the species belonging to the same +genus branched off from a common progenitor, whilst generic characters are +those which have remained unaltered from a much more remote epoch, and +accordingly are now less variable. This statement makes a near approach to +Mr. Walsh's law of Equable Variability. Secondary sexual characters, it may +be added, rarely serve to characterise distinct genera, for they usually +differ much in the species of the same genus, and are highly variable in +the individuals of the same species; we have also seen in the earlier +chapters of this work how variable secondary sexual characters become under +domestication. + +_Summary of the three previous Chapters, on the Laws of Variation._ + +In the twenty-third chapter we have seen that changed conditions +occasionally act in a definite manner on the organisation, so that all, or +nearly all, the individuals thus exposed become modified in the same +manner. But a far more frequent result of changed conditions, whether +acting directly on the organisation or indirectly through the reproductive +system being affected is indefinite and fluctuating variability. In the +three latter chapters we have endeavoured to trace some of the laws by +which such variability is regulated. + +Increased use adds the size of a muscle, together with the blood-vessels, +nerves, ligaments, the crests of bone to which these are attached, the +whole bone and other connected bones. So it is with various glands. +Increased functional activity strengthens the sense-organs. Increased and +intermittent pressure thickens the epidermis; and a change in the nature of +the food sometimes modifies the coats of the stomach, and increases or +{353} decreases the length of the intestines. Continued disuse, on the +other hand, weakens and diminishes all parts of the organisation. Animals +which during many generations have taken but little exercise, have their +lungs reduced in size, and as a consequence the bony fabric of the chest, +and the whole form of the body, become modified. With our anciently +domesticated birds, the wings have been little used, and they are slightly +reduced; with their decrease, the crest of the sternum, the scapulæ, +coracoids, and furcula, have all been reduced. + +With domesticated animals, the reduction of a part from disuse is never +carried so far that a mere rudiment is left, but we have good reason to +believe that this has often occurred under nature. The cause of this +difference probably is that with domestic animals not only sufficient time +has not been granted for so profound a change, but that, from not being +exposed to a severe struggle for life, the principle of the economy of +organisation does not come into action. On the contrary, we sometimes see +that structures which are rudimentary in the parent-species become +partially redeveloped in their domesticated progeny. When rudiments are +formed or left under domestication, they are the result of a sudden arrest +of development, and not of long-continued disuse with the absorption of all +superfluous parts; nevertheless they are of interest, as showing that +rudiments are the relics of organs once perfectly developed. + +Corporeal, periodical, and mental habits, though the latter have been +almost passed over in this work, become changed under domestication, and +the changes are often inherited. Such changed habits in any organic being, +especially when living a free life, would often lead to the augmented or +diminished use of various organs, and consequently to their modification. +From long-continued habit, and more especially from the occasional birth of +individuals with a slightly different constitution, domestic animals and +cultivated plants become to a certain extent acclimatised, or adapted to a +climate different from that proper to the parent-species. + +Through the principle of correlated variability, when one part varies other +parts vary,--either simultaneously, or one after the other. Thus an organ +modified during an early embryonic period affects other parts subsequently +developed. When an {354} organ, such as the beak, increases or decreases in +length, adjoining or correlated parts, as the tongue and the orifice of the +nostrils, tend to vary in the same manner. When the whole body increases or +decreases in size, various parts become modified; thus with pigeons the +ribs increase or decrease in number and breadth. Homologous parts, which +are identical during their early development and are exposed to similar +conditions, tend to vary in the same or in some connected manner,--as in +the case of the right and left sides of the body, of the front and hind +limbs, and even of the head and limbs. So it is with the organs of sight +and hearing; for instance, white cats with blue eyes are almost always +deaf. There is a manifest relation throughout the body between the skin and +its various appendages of hair, feathers, hoofs, horns, and teeth. In +Paraguay, horses with curly hair have hoofs like those of a mule; the wool +and the horns of sheep vary together; hairless dogs are deficient in their +teeth; men with redundant hair have abnormal teeth, either deficient or in +excess. Birds with long wing-feathers usually have long tail-feathers. When +long feathers grow from the outside of the legs and toes of pigeons, the +two outer toes are connected by membrane; for the whole leg tends to assume +the structure of the wing. There is a manifest relation between a crest of +feathers on the head and a marvellous amount of change in the skull of +various fowls; and in a lesser degree, between the greatly elongated, +lopping ears of rabbits and the structure of their skulls. With plants, the +leaves, various parts of the flower, and the fruit, often vary together in +a correlated manner. + +In some cases we find correlation without being able even to conjecture +what is the nature of the connexion, as with various correlated +monstrosities and diseases. This is likewise the case with the colour of +the adult pigeon, in connexion with the presence of down on the young bird. +Numerous curious instances have been given of peculiarities of +constitution, in correlation with colour, as shown by the immunity of +individuals of some one colour from certain diseases, from the attacks of +parasites, and from the action of certain vegetable poisons. + +Correlation is an important subject; for with species, and in a lesser +degree with domestic races, we continually find that {355} certain parts +have been greatly modified to serve some useful purpose; but we almost +invariably find that other parts have likewise been more or less modified, +without our being able to discover any advantage in the change. No doubt +great caution is necessary in coming to this conclusion, for it is +difficult to overrate our ignorance on the use of various parts of the +organisation; but from what we have now seen, we may believe that many +modifications are of no direct service, having arisen in correlation with +other and useful changes. + +Homologous parts during their early development evince an affinity for each +other,--that is, they tend to cohere and fuse together much more readily +than other parts. This tendency to fusion explains a multitude of normal +structures. Multiple and homologous organs are especially liable to vary in +number and probably in form. As the supply of organised matter is not +unlimited, the principle of compensation sometimes comes into action; so +that, when one part is greatly developed, adjoining parts or functions are +apt to be reduced; but this principle is probably of much less importance +than the more general one of the economy of growth. Through mere mechanical +pressure hard parts occasionally affect soft adjoining parts. With plants +the position of the flowers on the axis, and of the seeds in the capsule, +sometimes leads, through a freer flow of sap, to changes of structure; but +these changes are often due to reversion. Modifications, in whatever manner +caused, will be to a certain extent regulated by that co-ordinating power +or _nisus formativus_, which is in fact a remnant of one of the forms of +reproduction, displayed by many lowly organised beings in their power of +fissiparous generation and budding. Finally, the effects of the laws, which +directly or indirectly govern variability, may be largely influenced by +man's selection, and will so far be determined by natural selection that +changes advantageous to any race will be favoured and disadvantageous +changes checked. + +Domestic races descended from the same species, or from two or more allied +species, are liable to revert to characters derived from their common +progenitor, and, as they have much in common in their constitutions, they +are also liable under changed conditions to vary in the same manner; from +these {356} two causes analogous varieties often arise. When we reflect on +the several foregoing laws, imperfectly as we understand them, and when we +bear in mind how much remains to be discovered, we need not be surprised at +the extremely intricate manner in which our domestic productions have +varied, and still go on varying. + + * * * * * + + +{357} + +CHAPTER XXVII. + +PROVISIONAL HYPOTHESIS OF PANGENESIS. + + PRELIMINARY REMARKS.--FIRST PART:--THE FACTS TO BE CONNECTED UNDER A + SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION--THE + DIRECT ACTION OF THE MALE ELEMENT ON THE FEMALE--DEVELOPMENT--THE + FUNCTIONAL INDEPENDENCE OF THE ELEMENTS OR UNITS OF THE + BODY--VARIABILITY--INHERITANCE--REVERSION. + + SECOND PART:--STATEMENT OF THE HYPOTHESIS--HOW FAR THE NECESSARY + ASSUMPTIONS ARE IMPROBABLE--EXPLANATION BY AID OF THE HYPOTHESIS OF THE + SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST PART--CONCLUSION. + +In the previous chapters large classes of facts, such as those bearing on +bud-variation, the various forms of inheritance, the causes and laws of +variation, have been discussed; and it is obvious that these subjects, as +well as the several modes of reproduction, stand in some sort of relation +to each other. I have been led, or rather forced, to form a view which to a +certain extent connects these facts by a tangible method. Every one would +wish to explain to himself, even in an imperfect manner, how it is possible +for a character possessed by some remote ancestor suddenly to reappear in +the offspring; how the effects of increased or decreased use of a limb can +be transmitted to the child; how the male sexual element can act not solely +on the ovule, but occasionally on the mother-form; how a limb can be +reproduced on the exact line of amputation, with neither too much nor too +little added; how the various modes of reproduction are connected, and so +forth. I am aware that my view is merely a provisional hypothesis or +speculation; but until a better one be advanced, it may be serviceable by +bringing together a multitude of facts which are at present left +disconnected by any efficient cause. As Whewell, the historian of the +inductive sciences, remarks:--"Hypotheses may often be of service to +science, when they involve a certain portion of incompleteness, and even of +error." Under this point of view I venture to advance the hypothesis of +Pangenesis, which {358} implies that the whole organisation, in the sense +of every separate atom or unit, reproduces itself. Hence ovules and +pollen-grains,--the fertilised seed or egg, as well as buds,--include and +consist of a multitude of germs thrown off from each separate atom of the +organism. + +In the First Part I will enumerate as briefly as I can the groups of facts +which seem to demand connection; but certain subjects, not hitherto +discussed, must be treated at disproportionate length. In the Second Part +the hypothesis will be given; and we shall see, after considering how far +the necessary assumptions are in themselves improbable, whether it serves +to bring under a single point of view the various facts. + +PART I. + +Reproduction may be divided into two main classes, namely, sexual and +asexual. The latter is effected in many ways--by gemmation, that is by the +formation of buds of various kinds, and by fissiparous generation, that is +by spontaneous or artificial division. It is notorious that some of the +lower animals, when cut into many pieces, reproduce so many perfect +individuals: Lyonnet cut a Nais or freshwater worm into nearly forty +pieces, and these all reproduced perfect animals.[874] It is probable that +segmentation could be carried much further in some of the protozoa, and +with some of the lowest plants each cell will reproduce the parent-form. +Johannes Müller thought that there was an important distinction between +gemmation and fission; for in the latter case the divided portion, however +small, is more perfectly organised; but most physiologists are now +convinced that the two processes are essentially alike.[875] Prof. Huxley +remarks, "fission is little more than a peculiar {359} mode of budding," +and Prof. H. J. Clark, who has especially attended to this subject, shows +in detail that there is sometimes "a compromise between self-division and +budding." When a limb is amputated, or when the whole body is bisected, the +cut extremities are said to bud forth; and as the papilla, which is first +formed, consists of undeveloped cellular tissue like that forming an +ordinary bud, the expression is apparently correct. We see the connection +of the two processes in another way; for Trembley observed that with the +hydra the reproduction of the head after amputation was checked as soon as +the animal began to bud.[876] + +Between the production, by fissiparous generation, of two or more complete +individuals, and the repair of even a very slight injury, we have, as +remarked in a former chapter, so perfect and insensible a gradation, that +it is impossible to doubt that they are connected processes. Between the +power which repairs a trifling injury in any part, and the power which +previously "was occupied in its maintenance by the continued mutation of +its particles," there cannot be any great difference; and we may follow Mr. +Paget in believing them to be the selfsame power. As at each stage of +growth an amputated part is replaced by one in the same state of +development, we must likewise follow Mr. Paget in admitting "that the +powers of development from the embryo are identical with those exercised +for the restoration from injuries: in other words, that the powers are the +same by which perfection is first achieved, and by which, when lost, it is +recovered."[877] Finally, we may conclude that the several forms of +gemmation, and of fissiparous generation, the repair of injuries, the +maintenance of each part in its proper state, and the growth or progressive +development of the whole structure of the embryo, are all essentially the +results of one and the same great power. + +_Sexual Generation._--The union of the two sexual elements seems to make a +broad distinction between sexual and asexual reproduction. But the +well-ascertained cases of Parthenogenesis prove that the distinction is not +really so great as it at first appears; for ovules occasionally, and even +in some cases {360} frequently, become developed into perfect beings, +without the concourse of the male element. J. Müller and others admit that +ovules and buds have the same essential nature. Certain bodies, which +during their early development cannot be distinguished by any external +character from true ovules, nevertheless must be classed as buds, for +though formed within the ovarium they are incapable of fertilisation. This +is the case with the germ-balls of the Cecidomyide larvæ, as described by +Leuckart.[878] Ovules and the male element, before they become united, +have, like buds, an independent existence.[879] Both have the power of +transmitting every single character possessed by the parent-form. We see +this clearly when hybrids are paired _inter se_, for the characters of +either grandparent often reappear, either perfectly or by segments, in the +progeny. It is an error to suppose that the male transmits certain +characters and the female other characters; though no doubt, from unknown +causes, one sex sometimes has a stronger power of transmission than the +other. + +It has been maintained by some authors that a bud differs essentially from +a fertilised germ, by always reproducing the perfect character of the +parent-stock; whilst fertilised germs become developed into beings which +differ, in a greater or less degree, from each other and from their +parents. But there is no such broad distinction as this. In the eleventh +chapter, numerous cases were given showing that buds occasionally grow into +plants having new and strongly marked characters; and varieties thus +produced can be propagated for a length of time by buds, and occasionally +by seed. Nevertheless, it must be admitted that beings produced sexually +are much more liable to vary than those produced asexually; and of this +fact a partial explanation will hereafter be attempted. The variability in +both cases is determined by the same general causes, and is governed by the +same laws. Hence new varieties arising from buds cannot be distinguished +from those arising from seed. Although bud-varieties usually retain their +character during {361} successive bud-generations, yet they occasionally +revert, even after a long series of bud-generations, to their former +character. This tendency to reversion in buds is one of the most remarkable +of the several points of agreement between the offspring from bud and +seminal reproduction. + +There is, however, one difference between beings produced sexually and +asexually, which is very general. The former usually pass in the course of +their development from a lower to a higher grade, as we see in the +metamorphoses of insects and in the concealed metamorphoses of the +vertebrata; but this passage from a lower to a higher grade cannot be +considered as a necessary accompaniment of sexual reproduction, for hardly +anything of the kind occurs in the development of Aphis amongst insects, or +with certain crustaceans, cephalopods, or with any of the higher vascular +plants. Animals propagated asexually by buds or fission are on the other +hand never known to undergo a retrogressive metamorphosis; that is, they do +not first sink to a lower, before passing on to their higher and final +stage of development. But during the act of asexual production or +subsequently to it, they often advance in organisation, as we see in the +many cases of "alternate generation." In thus speaking of alternate +generation, I follow those naturalists who look at the process as +essentially one of internal budding or of fissiparous generation. Some of +the lower plants, however, such as mosses and certain algæ, according to +Dr. L. Radlkofer,[880] when propagated asexually, do undergo a +retrogressive metamorphosis. We can to a certain extent understand, as far +as the final cause is concerned, why beings propagated by buds should so +rarely retrogress during development; for with each organism the structure +acquired at each stage of development must be adapted to its peculiar +habits. Now, with beings produced by gemmation,--and this, differently from +sexual reproduction, may occur at any period of growth,--if there were +places for the support of many individuals at some one stage of +development, the simplest plan would be that they should be multiplied by +gemmation at that stage, and not that they should first retrograde in their +development to an earlier or simpler structure, which might not be fitted +for the surrounding conditions. + +{362} + +From the several foregoing considerations we may conclude that the +difference between sexual and asexual generation is not nearly so great as +it at first appears; and we have already seen that there is the closest +agreement between gemmation, fissiparous generation, the repair of +injuries, and ordinary growth or development. The capacity of fertilisation +by the male element seems to be the chief distinction between an ovule and +a bud; and this capacity is not invariably brought into action, as in the +cases of parthenogenetic reproduction. We are here naturally led to inquire +what the final cause can be of the necessity in ordinary generation for the +concourse of the two sexual elements. + +Seeds and ova are often highly serviceable as the means of disseminating +plants and animals, and of preserving them during one or more seasons in a +dormant state; but unimpregnated seeds or ova, and detached buds, would be +equally serviceable for both purposes. We can, however, indicate two +important advantages gained by the concourse of the two sexes, or rather of +two individuals belonging to opposite sexes; for, as I have shown in a +former chapter, the structure of every organism appears to be especially +adapted for the concurrence, at least occasionally, of two individuals. In +nearly the same manner as it is admitted by naturalists that hybridism, +from inducing sterility, is of service in keeping the forms of life +distinct and fitted for their proper places; so, when species are rendered +highly variable by changed conditions of life, the free intercrossing of +the varying individuals will tend to keep each form fitted for its proper +place in nature; and crossing can be effected only by sexual generation, +but whether the end thus gained is of sufficient importance to account for +the first origin of sexual intercourse is very doubtful. Secondly, I have +shown, from the consideration of a large body of facts, that, as a slight +change in the conditions of life is beneficial to each creature, so, in an +analogous manner, is the change effected in the germ by sexual union with a +distinct individual; and I have been led, from observing the many +widely-extended provisions throughout nature for this purpose, and from the +greater vigour of crossed organisms of all kinds, as proved by direct +experiments, as well as from the evil effects of close interbreeding when +long {363} continued, to believe that the advantage thus gained is very +great. Besides these two important ends, there may, of course, be others, +as yet unknown to us, gained by the concourse of the two sexes. + +Why the germ, which before impregnation undergoes a certain amount of +development, ceases to progress and perishes, unless it be acted on by the +male element; and why conversely the male element, which is enabled to keep +alive for even four or five years within the spermatheca of a female +insect, likewise perishes, unless it acts on or unites with the germ, are +questions which cannot be answered with any certainty. It is, however, +possible that both sexual elements perish, unless brought into union, +simply from including too little formative matter for independent existence +and development; for certainly they do not in ordinary cases differ in +their power of giving character to the embryo. This view of the importance +of the quantity of formative matter seems probable from the following +considerations. There is no reason to suspect that the spermatozoa or +pollen-grains of the same individual animal or plant differ from each +other; yet Quatrefages has shown in the case of the Teredo,[881] as did +formerly Prevost and Dumas with other animals, that more than one +spermatozoon is requisite to fertilise an ovule. This has likewise been +clearly proved by Newport,[882] who adds the important fact, established by +numerous experiments, that, when a very small number of spermatozoa are +applied to the ova of Batrachians, they are only partially impregnated and +the embryo is never fully developed: the first step, however, towards +development, namely, the partial segmentation of the yelk, does occur to a +greater or less extent, but is never completed up to granulation. The rate +of the segmentation is likewise determined by the number of the +spermatozoa. With respect to plants, nearly the same results were obtained +by Kölreuter and Gärtner. This last careful observer found,[883] after +making successive trials on a Malva with more and more pollen-grains, that +even thirty grains did not fertilise a single seed; but when forty grains +were applied to the {364} stigma, a few seeds of small size were formed. +The pollen-grains of Mirabilis are extraordinarily large, and the ovarium +contains only a single ovule; and these circumstances led Naudin[884] to +make the following interesting experiments: a flower was fertilised by +three grains and succeeded perfectly; twelve flowers were fertilised by two +grains, and seventeen flowers by a single grain, and of these one flower +alone in each lot perfected its seed; and it deserves especial notice that +the plants produced by these two seeds never attained their proper +dimensions, and bore flowers of remarkably small size. From these facts we +clearly see that the quantity of the peculiar formative matter which is +contained within the spermatozoa and pollen-grains is an all-important +element in the act of fertilisation, not only in the full development of +the seed, but in the vigour of the plant produced from such seed. We see +something of the same kind in certain cases of parthenogenesis, that is, +when the male element is wholly excluded; for M. Jourdan[885] found that, +out of about 58,000 eggs laid by unimpregnated silk-moths, many passed +through their early embryonic stages, showing that they were capable of +self-development, but only twenty-nine out of the whole number produced +caterpillars. Therefore it is not an improbable view that deficient bulk or +quantity in the formative matter, contained within the sexual elements, is +the main cause of their not having the capacity of prolonged separate +existence and development. The belief that it is the function of the +spermatozoa to communicate life to the ovule seems a strange one, seeing +that the unimpregnated ovule is already alive and continues for a +considerable time alive. We shall hereafter see that it is probable that +the sexual elements, or possibly only the female element, include certain +primordial cells, that is, such as have undergone no differentiation, and +which are not present in an active state in buds. + +_Graft-hybrids._--When discussing in the eleventh chapter the curious case +of the _Cytisus adami_, facts were given which render it to a certain +degree probable, in accordance with the belief of some distinguished +botanists, that, when the tissues of two plants {365} belonging to distinct +species or varieties are intimately united, buds are afterwards +occasionally produced which, like hybrids, combine the characters of the +two united forms. It is certain that when trees with variegated leaves are +grafted or budded on a common stock, the latter sometimes produces buds +bearing variegated leaves; but this may perhaps be looked at as a case of +inoculated disease. Should it ever be proved that hybridised buds can be +formed by the union of two distinct vegetative tissues, the essential +identity of sexual and asexual reproduction would be shown in the most +interesting manner; for the power of combining in the offspring the +characters of both parents, is the most striking of all the functions of +sexual generation. + +_Direct Action of the Male Element on the Female._--In the chapter just +referred to, I have given abundant proofs that foreign pollen occasionally +affects the mother-plant in a direct manner. Thus, when Gallesio fertilised +an orange-flower with pollen from the lemon, the fruit bore stripes of +perfectly characterised lemon-peel: with peas, several observers have seen +the colour of the seed-coats and even of the pod directly affected by the +pollen of a distinct variety; so it has been with the fruit of the apple, +which consists of the modified calyx and upper part of the flower-stalk. +These parts in ordinary cases are wholly formed by the mother-plant. We +here see the male element affecting and hybridising not that part which it +is properly adapted to affect, namely the ovule, but the partially +developed tissues of a distinct individual. We are thus brought half-way +towards a graft-hybrid, in which the cellular tissue of one form, instead +of its pollen, is believed to hybridise the tissues of a distinct form. I +formerly assigned reasons for rejecting the belief that the mother-plant is +affected through the intervention of the hybridised embryo; but even if +this view were admitted, the case would become one of graft-hybridism, for +the fertilised embryo and the mother-plant must be looked at as distinct +individuals. + +With animals which do not breed until nearly mature, and of which all the +parts are then fully developed, it is hardly possible that the male element +should directly affect the female. But we have the analogous and perfectly +well-ascertained case of the male element of a distinct form, as with the +{366} quagga and Lord Morton's mare, affecting the ovarium of the female, +so that the ovules and offspring subsequently produced by her when +impregnated by other males are plainly affected and hybridised by the first +male. + +_Development._--The fertilised germ reaches maturity by a vast number of +changes: these are either slight and slowly effected, as when the child +grows into the man, or are great and sudden, as with the metamorphoses of +most insects. Between these extremes we have, even within the same class, +every gradation: thus, as Sir J. Lubbock has shown,[886] there is an +Ephemerous insect which moults above twenty times, undergoing each time a +slight but decided change of structure; and these changes, as he further +remarks, probably reveal to us the normal stages of development which are +concealed and hurried through, or suppressed, in most other insects. In +ordinary metamorphoses, the parts and organs appear to become changed into +the corresponding parts in the next stage of development; but there is +another form of development, which has been called by Professor Owen +metagenesis. In this case "the new parts are not moulded upon the inner +surface of the old ones. The plastic force has changed its course of +operation. The outer case, and all that gave form and character to the +precedent individual, perish and are cast off; they are not changed into +the corresponding parts of the new individual. These are due to a new and +distinct developmental process," &c.[887] Metamorphosis, however, graduates +so insensibly into metagenesis, that the two processes cannot be distinctly +separated. For instance, in the last change which Cirripedes undergo, the +alimentary canal and some other organs are moulded on pre-existing parts; +but the eyes of the old and the young animal are developed in entirely +different parts of the body; the tips of the mature limbs are formed within +the larval limbs, and may be said to be metamorphosed from them; but their +basal portions and the whole thorax are developed in a plane actually at +right angles to the limbs and thorax of the larva; and this {367} may be +called metagenesis. The metagenetic process is carried to an extreme degree +in the development of some Echinoderms, for the animal in the second stage +of development is formed almost like a bud within the animal of the first +stage, the latter being then cast off like an old vestment, yet sometimes +still maintaining for a short period an independent vitality.[888] + +If, instead of a single individual, several were to be thus developed +metagenetically within a pre-existing form, the process would be called one +of alternate generation. The young thus developed may either closely +resemble the encasing parent-form, as with the larvæ of Cecidomyia, or may +differ to an astonishing degree, as with many parasitic worms and with +jelly-fishes; but this does not make any essential difference in the +process, any more than the greatness or abruptness of the change in the +metamorphoses of insects. + +The whole question of development is of great importance for our present +subject. When an organ, the eye for instance, is metagenetically formed in +a part of the body where during the previous stage of development no eye +existed, we must look at it as a new and independent growth. The absolute +independence of new and old structures, which correspond in structure and +function, is still more obvious when several individuals are formed within +a previous encasing form, as in the cases of alternate generation. The same +important principle probably comes largely into play even in the case of +continuous growth, as we shall see when we consider the inheritance of +modifications at corresponding ages. + +We are led to the same conclusion, namely, the independence of parts +successively developed, by another and quite distinct group of facts. It is +well known that many animals belonging to the same class, and therefore not +differing widely from each other, pass through an extremely different +course of development. Thus certain beetles, not in any way remarkably +different from others of the same order, undergo what has been called a +hyper-metamorphosis--that is, they pass through an early stage wholly +different from the ordinary grub-like larva. In the same sub-order of +crabs, namely, the Macroura, as Fritz {368} Müller remarks, the river +cray-fish is hatched under the same form which it ever afterwards retains; +the young lobster has divided legs, like a Mysis; the Palæmon appears under +the form of a Zoea, and Peneus under the Nauplius-form; and how wonderfully +these larval forms differ from each other, is known to every +naturalist.[889] Some other crustaceans, as the same author observes, start +from the same point and arrive at nearly the same end, but in the middle of +their development are widely different from each other. Still more striking +cases could be given with respect to the Echinodermata. With the Medusæ or +jelly-fishes Professor Allman observes, "the classification of the Hydroida +would be a comparatively simple task if, as has been erroneously asserted, +generically-identical medusoids always arose from generically-identical +polypoids; and on the other hand, that generically-identical polypoids +always gave origin to generically-identical medusoids." So, again, Dr. +Strethill Wright remarks, "in the life-history of the Hydroidæ any phase, +planuloid, polypoid, or medusoid, may be absent."[890] + +According to the belief now generally accepted by our best naturalists, all +the members of the same order or class, the Macrourous crustaceans for +instance, are descended from a common progenitor. During their descent they +have diverged much in structure, but have retained much in common; and this +divergence and retention of character has been effected, though they have +passed and still pass through marvellously different metamorphoses. This +fact well illustrates how independent each structure must be from that +which precedes and follows it in the course of development. + +_The Functional Independence of the Elements or Units of the +Body._--Physiologists agree that the whole organism consists of a multitude +of elemental parts, which are to a great extent independent of each other. +Each organ, says Claude Bernard,[891] {369} has its proper life, its +autonomy; it can develop and reproduce itself independently of the +adjoining tissues. The great German authority, Virchow,[892] asserts still +more emphatically that each system, as the nervous or osseous system, or +the blood, consists of an "enormous mass of minute centres of action.... +Every element has its own special action, and even though it derive its +stimulus to activity from other parts, yet alone effects the actual +performance of its duties.... Every single epithelial and muscular +fibre-cell leads a sort of parasitical existence in relation to the rest of +the body.... Every single bone-corpuscle really possesses conditions of +nutrition peculiar to itself." Each element, as Mr. Paget remarks, lives +its appointed time, and then dies, and, after being cast off or absorbed, +is replaced.[893] I presume that no physiologist doubts that, for instance, +each bone-corpuscle of the finger differs from the corresponding corpuscle +in the corresponding joint of the toe; and there can hardly be a doubt that +even those on the corresponding sides of the body differ, though almost +identical in nature. This near approach to identity is curiously shown in +many diseases in which the same exact points on the right and left sides of +the body are similarly affected; thus Mr. Paget[894] gives a drawing of a +diseased pelvis, in which the bone has grown into a most complicated +pattern, but "there is not one spot or line on one side which is not +represented, as exactly as it would be in a mirror, on the other." + +Many facts support this view of the independent life of each minute element +of the body. Virchow insists that a single bone-corpuscle or a single cell +in the skin may become diseased. The spur of a cock, after being inserted +into the eye of an ox, lived for eight years, and acquired a weight of 306 +grammes, or nearly fourteen ounces.[895] The tail of a pig has been grafted +into the middle of its back, and reacquired sensibility. Dr. Ollier[896] +inserted a piece of periosteum from the bone of a young dog under the skin +of a rabbit, and true bone was developed. A multitude of similar facts +could be given. The {370} frequent presence of hairs and of perfectly +developed teeth, even teeth of the second dentition, in ovarian +tumours,[897] are facts leading to the same conclusion. + +Whether each of the innumerable autonomous elements of the body is a cell +or the modified product of a cell, is a more doubtful question, even if so +wide a definition be given to the term, as to include cell-like bodies +without walls and without nuclei.[898] Professor Lionel Beale uses the term +"germinal matter" for the contents of cells, taken in this wide +acceptation, and he draws a broad distinction between germinal matter and +"formed material" or the various products of cells.[899] But the doctrine +of _omnis cellula e cellulâ_ is admitted for plants, and is a widely +prevalent belief with respect to animals.[900] Thus Virchow, the great +supporter of the cellular theory, whilst allowing that difficulties exist, +maintains that every atom of tissue is derived from cells, and these from +pre-existing cells, and these primarily from the egg, which he regards as a +great cell. That cells, still retaining the same nature, increase by +self-division or proliferation, is admitted by almost every one. But when +an organism undergoes a great change of structure during development, the +cells, which at each stage are supposed to be directly derived from +previously-existing cells, must likewise be greatly changed in nature; this +change is apparently attributed by the supporters of the cellular doctrine +to some inherent power which the cells possess, and not to any external +agency. + +Another school maintains that cells and tissues of all kinds may be formed, +independently of pre-existing cells, from plastic lymph or blastema; and +this it is thought is well exhibited in the repair of wounds. As I have not +especially attended to histology, it would be presumptuous in me to express +an opinion on the two opposed doctrines. But every one appears to admit +that the body consists of a multitude of "organic units,"[901] {371} each +of which possesses its own proper attributes, and is to a certain extent +independent of all others. Hence it will be convenient to use indifferently +the terms cells or organic units or simply units. + +_Variability and Inheritance._--We have seen in the twenty-second chapter +that variability is not a principle co-ordinate with life or reproduction, +but results from special causes, generally from changed conditions acting +during successive generations. Part of the fluctuating variability thus +induced is apparently due to the sexual system being easily affected by +changed conditions, so that it is often rendered impotent; and when not so +seriously affected, it often fails in its proper function of transmitting +truly the characters of the parents to the offspring. But variability is +not necessarily connected with the sexual system, as we see from the cases +of bud-variation; and although we may not be able to trace the nature of +the connexion, it is probable that many deviations of structure which +appear in sexual offspring result from changed conditions acting directly +on the organisation, independently of the reproductive organs. In some +instances we may feel sure of this, when all, or nearly all the individuals +which have been similarly exposed are similarly and definitely affected--as +in the dwarfed and otherwise changed maize brought from hot countries when +cultivated in Germany; in the change of the fleece in sheep within the +tropics; to a certain extent in the increased size and early maturity of +our highly-improved domesticated animals; in inherited gout from +intemperance; and in many other such cases. Now, as such changed conditions +do not especially affect the reproductive organs, it seems mysterious on +any ordinary view why their product, the new organic being, should be +similarly affected. + +How, again, can we explain to ourselves the inherited effects of the use or +disuse of particular organs? The domesticated duck flies less and walks +more than the wild duck, and its limb-bones have become in a corresponding +manner diminished and increased in comparison with those of the wild duck. +A horse is trained to certain paces, and the colt inherits similar +consensual movements. The domesticated rabbit becomes tame from close +confinement; the dog intelligent from associating with man; the retriever +is taught to fetch and carry: and these {372} mental endowments and bodily +powers are all inherited. Nothing in the whole circuit of physiology is +more wonderful. How can the use or disuse of a particular limb or of the +brain affect a small aggregate of reproductive cells, seated in a distant +part of the body, in such a manner that the being developed from these +cells inherits the characters of either one or both parents? Even an +imperfect answer to this question would be satisfactory. + +Sexual reproduction does not essentially differ, as we have seen, from +budding or self-division, and these processes graduate through the repair +of injuries into ordinary development and growth; it might therefore be +expected that every character would be as regularly transmitted by all the +methods of reproduction as by continued growth. In the chapters devoted to +inheritance it was shown that a multitude of newly-acquired characters, +whether injurious or beneficial, whether of the lowest or highest vital +importance, are often faithfully transmitted--frequently even when one +parent alone possesses some new peculiarity. It deserves especial attention +that characters appearing at any age tend to reappear at a corresponding +age. We may on the whole conclude that in all cases inheritance is the +rule, and non-inheritance the anomaly. In some instances a character is not +inherited, from the conditions of life being directly opposed to its +development; in many instances, from the conditions incessantly inducing +fresh variability, as with grafted fruit-trees and highly cultivated +flowers. In the remaining cases the failure may be attributed to reversion, +by which the child resembles its grandparents or more remote progenitors, +instead of its parents. + +This principle of Reversion is the most wonderful of all the attributes of +Inheritance. It proves to us that the transmission of a character and its +development, which ordinarily go together and thus escape discrimination, +are distinct powers; and these powers in some cases are even antagonistic, +for each acts alternately in successive generations. Reversion is not a +rare event, depending on some unusual or favourable combination of +circumstances, but occurs so regularly with crossed animals and plants, and +so frequently with uncrossed breeds, that it is evidently an essential part +of the principle of inheritance. We know that {373} changed conditions have +the power of evoking long-lost characters, as in the case of some feral +animals. The act of crossing in itself possesses this power in a high +degree. What can be more wonderful than that characters, which have +disappeared during scores, or hundreds, or even thousands of generations, +should suddenly reappear perfectly developed, as in the case of pigeons and +fowls when purely bred, and especially when crossed; or as with the zebrine +stripes on dun-coloured horses, and other such cases? Many monstrosities +come under this same head, as when rudimentary organs are redeveloped, or +when an organ which we must believe was possessed by an early progenitor, +but of which not even a rudiment is left, suddenly reappears, as with the +fifth stamen in some Scrophulariaceæ. We have already seen that reversion +acts in bud-reproduction; and we know that it occasionally acts during the +growth of the same individual animal, especially, but not exclusively, when +of crossed parentage,--as in the rare cases described of individual fowls, +pigeons, cattle, and rabbits, which have reverted as they advanced in years +to the colours of one of their parents or ancestors. + +We are led to believe, as formerly explained, that every character which +occasionally reappears is present in a latent form in each generation, in +nearly the same manner as in male and female animals secondary characters +of the opposite sex lie latent, ready to be evolved when the reproductive +organs are injured. This comparison of the secondary sexual characters +which are latent in both sexes, with other latent characters, is the more +appropriate from the case recorded of the Hen, which assumed some of the +masculine characters, not of her own race, but of an early progenitor; she +thus exhibited at the same time the redevelopment of latent characters of +both kinds and connected both classes. In every living creature we may feel +assured that a host of lost characters lie ready to be evolved under proper +conditions. How can we make intelligible, and connect with other facts, +this wonderful and common capacity of reversion,--this power of calling +back to life long-lost characters? {374} + +PART II. + +I have now enumerated the chief facts which every one would desire to +connect by some intelligible bond. This can be done, as it seems to me, if +we make the following assumptions; if the first and chief one be not +rejected, the others, from being supported by various physiological +considerations, will not appear very improbable. It is almost universally +admitted that cells, or the units of the body, propagate themselves by +self-division or proliferation, retaining the same nature, and ultimately +becoming converted into the various tissues and substances of the body. But +besides this means of increase I assume that cells, before their conversion +into completely passive or "formed material," throw off minute granules or +atoms, which circulate freely throughout the system, and when supplied with +proper nutriment multiply by self-division, subsequently becoming developed +into cells like those from which they were derived. These granules for the +sake of distinctness may be called cell-gemmules, or, as the cellular +theory is not fully established, simply gemmules. They are supposed to be +transmitted from the parents to the offspring, and are generally developed +in the generation which immediately succeeds, but are often transmitted in +a dormant state during many generations and are then developed. Their +development is supposed to depend on their union with other partially +developed cells or gemmules which precede them in the regular course of +growth. Why I use the term union, will be seen when we discuss the direct +action of pollen on the tissues of the mother-plant. Gemmules are supposed +to be thrown off by every cell or unit, not only during the adult state, +but during all the stages of development. Lastly, I assume that the +gemmules in their dormant state have a mutual affinity for each other, +leading to their aggregation either into buds or into the sexual elements. +Hence, speaking strictly, it is not the reproductive elements, nor the +buds, which generate new organisms, but the cells themselves throughout the +body. These assumptions constitute the provisional hypothesis which I have +called Pangenesis. Nearly {375} similar views have been propounded, as I +find, by other authors, more especially by Mr. Herbert Spencer;[902] but +they are here modified and amplified. + +{376} + +Before proceeding to show, firstly, how far these assumptions are in +themselves probable, and secondly, how far they connect and explain the +various groups of facts with which we are concerned, it may be useful to +give an illustration of the hypothesis. If one of the simplest Protozoa be +formed, as appears under the microscope, of a small mass of homogeneous +gelatinous matter, a minute atom thrown off from any part and nourished +under favourable circumstances would naturally reproduce the whole; but if +the upper and lower surfaces were to differ in texture from the central +portion, then all three parts would have to throw off atoms or gemmules, +which when aggregated by mutual affinity would form either buds or the +sexual elements. Precisely the same view may be extended to one of the +higher animals; although in this case many thousand gemmules must be thrown +off from the various parts of the body. Now, when the leg, for instance, of +a salamander is cut off, a slight crust forms over the wound, and beneath +this crust the uninjured cells or units of bone, muscle, nerves, &c., are +supposed to unite with the diffused gemmules of those cells which in the +perfect leg come next in order; and these as they become slightly developed +unite with others, and so on until a papilla of soft cellular tissue, the +"budding leg," is formed, and in time a perfect leg.[903] Thus, that +portion of the leg which had {377} been cut off, neither more nor less, +would be reproduced. If the tail or leg of a young animal had been cut off, +a young tail or leg would have been reproduced, as actually occurs with the +amputated tail of the tadpole; for gemmules of all the units which compose +the tail are diffused throughout the body at all ages. But during the adult +state the gemmules of the larval tail would remain dormant, for they would +not meet with pre-existing cells in a proper state of development with +which to unite. If from changed conditions or any other cause any part of +the body should become permanently modified, the gemmules, which are merely +minute portions of the contents of the cells forming the part, would +naturally reproduce the same modification. But gemmules previously derived +from the same part before it had undergone any change, would still be +diffused throughout the organisation, and would be transmitted from +generation to generation, so that under favourable circumstances they might +be redeveloped, and then the new modification would be for a time or for +ever lost. The aggregation of gemmules derived from every part of the body, +through their mutual affinity, would form buds, and their aggregation in +some special manner, apparently in small quantity, together probably with +the presence of gemmules of certain primordial cells, would constitute the +sexual elements. By means of these illustrations the hypothesis of +pangenesis has, I hope, been rendered intelligible. + + * * * * * + +Physiologists maintain, as we have seen, that each cell, though to a large +extent dependent on others, is likewise, to a certain extent, independent +or autonomous. I go one small step further, and assume that each cell casts +off a free gemmule, which is capable of reproducing a similar cell. There +is some analogy between this view and what we see in compound animals and +in the flower-buds on the same tree; for these are distinct individuals +capable of true or seminal reproduction, yet have parts in common and are +dependent on each other; thus {378} the tree has its bark and trunk, and +certain corals, as the Virgularia, have not only parts, but movements in +common. + +The existence of free gemmules is a gratuitous assumption, yet can hardly +be considered as very improbable, seeing that cells have the power of +multiplication through the self-division of their contents. Gemmules differ +from true ovules or buds inasmuch as they are supposed to be capable of +multiplication in their undeveloped state. No one probably will object to +this capacity as improbable. The blastema within the egg has been known to +divide and give birth to two embryos; and Thuret[904] has seen the zoospore +of an alga divide itself, and both halves germinate. An atom of small-pox +matter, so minute as to be borne by the wind, must multiply itself many +thousand-fold in a person thus inoculated.[905] It has recently been +ascertained[906] that a minute portion of the mucous discharge from an +animal affected with rinderpest, if placed in the blood of a healthy ox, +increases so fast that in a short space of time "the whole mass of blood, +weighing many pounds, is infected, and every small particle of that blood +contains enough poison to give, within less than forty-eight hours, the +disease to another animal." + +The retention of free and undeveloped gemmules in the same body from early +youth to old age may appear improbable, but we should remember how long +seeds lie dormant in the earth and buds in the bark of a tree. Their +transmission from generation to generation may appear still more +improbable; but here again we should remember that many rudimentary and +useless organs are transmitted and have been transmitted during an +indefinite number of generations. We shall presently see how well the +long-continued transmission of undeveloped gemmules explains many facts. + +As each unit, or group of similar units throughout the body, casts off its +gemmules, and as all are contained within the smallest egg or seed, and +within each spermatozoon or pollen-grain, their number and minuteness must +be something {379} inconceivable. I shall hereafter recur to this +objection, which at first appears so formidable; but it may here be +remarked that a cod-fish has been found to produce 4,872,000 eggs, a single +Ascaris about 64,000,000 eggs, and a single Orchidaceous plant probably as +many million seeds.[907] In these several cases, the spermatozoa and +pollen-grains must exist in considerably larger numbers. Now, when we have +to deal with numbers such as these, which the human intellect cannot grasp, +there is no good reason for rejecting our present hypothesis on account of +the assumed existence of cell-gemmules a few thousand times more numerous. + +The gemmules in each organism must be thoroughly diffused; nor does this +seem improbable considering their minuteness, and the steady circulation of +fluids throughout the body. So it must be with the gemmules of plants, for +with certain kinds even a minute fragment of a leaf will reproduce the +whole. But a difficulty here occurs; it would appear that with plants, and +probably with compound animals, such as corals, the gemmules do not spread +from bud to bud, but only through the tissues developed from each separate +bud. We are led to this conclusion from the stock being rarely affected by +the insertion of a bud or graft from a distinct variety. This non-diffusion +of the gemmules is still more plainly shown in the case of ferns; for Mr. +Bridgman[908] has proved that, when spores (which it should be remembered +are of the nature of buds) are taken from a monstrous part of a frond, and +others from an ordinary part, {380} each reproduces the form of the part +whence derived. But this non-diffusion of the gemmules from bud to bud may +be only apparent, depending, as we shall hereafter see, on the nature of +the first-formed cells in the buds. + +The assumed elective affinity of each gemmule for that particular cell +which precedes it in the order of development is supported by many +analogies. In all ordinary cases of sexual reproduction the male and female +elements have a mutual affinity for each other: thus, it is believed that +about ten thousand species of Compositæ exist, and there can be no doubt +that if the pollen of all these species could be, simultaneously or +successively, placed on the stigma of any one species, this one would elect +with unerring certainty its own pollen. This elective capacity is all the +more wonderful, as it must have been acquired since the many species of +this great group of plants branched off from a common progenitor. On any +view of the nature of sexual reproduction, the protoplasm contained within +the ovules and within the sperm-cells (or the "spermatic force" of the +latter, if so vague a term be preferred) must act on each other by some law +of special affinity, either during or subsequently to impregnation, so that +corresponding parts alone affect each other; thus, a calf produced from a +short-horned cow by a long-horned bull has its horns and not its horny +hoofs affected by the union of the two forms, and the offspring from two +birds with differently coloured tails have their tails and not their whole +plumage affected. + +The various tissues of the body plainly show, as many physiologists have +insisted,[909] an affinity for special organic substances, whether natural +or foreign to the body. We see this in the cells of the kidneys attracting +urea from the blood; in the worrara poison affecting the nerves; upas and +digitalis the muscles; the Lytta vesicatoria the kidneys; and in the +poisonous matter of many diseases, as small-pox, scarlet-fever, +hooping-cough, glanders, cancer, and hydrophobia, affecting certain +definite parts of the body or certain tissues or glands. + +The affinity of various parts of the body for each other during {381} their +early development was shown in the last chapter, when discussing the +tendency to fusion in homologous parts. This affinity displays itself in +the normal fusion of organs which are separate at an early embryonic age, +and still more plainly in those marvellous cases of double monsters in +which each bone, muscle, vessel, and nerve in the one embryo, blends with +the corresponding part in the other. The affinity between homologous organs +may come into action with single parts, or with the entire individual, as +in the case of flowers or fruits which are symmetrically blended together +with all their parts doubled, but without any other trace of fusion. + +It has also been assumed that the development of each gemmule depends on +its union with another cell or unit which has just commenced its +development, and which, from preceding it in order of growth, is of a +somewhat different nature. Nor is it a very improbable assumption that the +development of a gemmule is determined by its union with a cell slightly +different in nature, for abundant evidence was given in the seventeenth +chapter, showing that a slight degree of differentiation in the male and +female sexual elements favours in a marked manner their union and +subsequent development. But what determines the development of the gemmules +of the first-formed or primordial cell in the unimpregnated ovule, is +beyond conjecture. + +It must also be admitted that analogy fails to guide us towards any +determination on several other points: for instance, whether cells, derived +from the same parent-cell, may, in the regular course of growth, become +developed into different structures, from absorbing peculiar kinds of +nutriment, independently of their union with distinct gemmules. We shall +appreciate this difficulty if we call to mind, what complex yet symmetrical +growths the cells of plants yield when they are inoculated by the poison of +a gall-insect. With animals various polypoid excrescences and tumours are +now generally admitted[910] to be the direct product, through +proliferation, of normal cells which have become abnormal. In the regular +growth and repair of bones, the tissues undergo, as Virchow remarks,[911] a +whole series of permutations and substitutions. "The cartilage-cells may be +{382} converted by a direct transformation into marrow-cells, and continue +as such; or they may first be converted into osseous and then into +medullary tissue; or lastly, they may first be converted into marrow and +then into bone. So variable are the permutations of these tissues, in +themselves so nearly allied, and yet in their external appearance so +completely distinct." But as these tissues thus change their nature at any +age, without any obvious change in their nutrition, we must suppose in +accordance with our hypothesis that gemmules derived from one kind of +tissue combine with the cells of another kind, and cause the successive +modifications. + +It is useless to speculate at what period of development each organic unit +casts off its gemmules; for the whole subject of the development of the +various elemental tissues is as yet involved in much doubt. Some +physiologists, for instance, maintain that muscle or nerve-fibres are +developed from cells, which are afterwards nourished by their own proper +powers of absorption; whilst other physiologists deny their cellular +origin; and Beale maintains that such fibres are renovated exclusively by +the conversion of fresh germinal matter (that is the so-called nuclei) into +"formed material." However this may be, it appears probable that all +external agencies, such as changed nutrition, increased use or disuse, &c., +which induced any permanent modification in a structure, would at the same +time or previously act on the cells, nuclei, germinal or formative matter, +from which the structures in question were developed, and consequently +would act on the gemmules or cast-off atoms. + +There is another point on which it is useless to speculate, namely, whether +all gemmules are free and separate, or whether some are from the first +united into small aggregates. A feather, for instance, is a complex +structure, and, as each separate part is liable to inherited variations, I +conclude that each feather certainly generates a large number of gemmules; +but it is possible that these may be aggregated into a compound gemmule. +The same remark applies to the petals of a flower, which in some cases are +highly complex, with each ridge and hollow contrived for special purposes, +so that each part must have been separately modified, and the modifications +transmitted; consequently, separate gemmules, according to our hypothesis, +{383} must have been thrown off from each cell or part. But, as we +sometimes see half an anther or a small portion of a filament becoming +petaliform, or parts or mere stripes of the calyx assuming the colour and +texture of the corolla, it is probable that with petals the gemmules of +each cell are not aggregated together into a compound gemmule, but are +freely and separately diffused. + + * * * * * + +Having now endeavoured to show that the several foregoing assumptions are +to a certain extent supported by analogous facts, and having discussed some +of the most doubtful points, we will consider how far the hypothesis brings +under a single point of view the various cases enumerated in the First +Part. All the forms of reproduction graduate into each other and agree in +their product; for it is impossible to distinguish between organisms +produced from buds, from self-division, or from fertilised germs; such +organisms are liable to variations of the same nature and to reversion of +character; and as we now see that all the forms of reproduction depend on +the aggregation of gemmules derived from the whole body, we can understand +this general agreement. It is satisfactory to find that sexual and asexual +generation, by both of which widely different processes the same living +creature is habitually produced, are fundamentally the same. +Parthenogenesis is no longer wonderful; in fact, the wonder is that it +should not oftener occur. We see that the reproductive organs do not +actually create the sexual elements; they merely determine or permit the +aggregation of the gemmules in a special manner. These organs, together +with their accessory parts, have, however, high functions to perform; they +give to both elements a special affinity for each other, independently of +the contents of the male and female cells, as is shown in the case of +plants by the mutual reaction of the stigma and pollen-grains; they adapt +one or both elements for independent temporary existence, and for mutual +union. The contrivances for these purposes are sometimes wonderfully +complex, as with the spermatophores of the Cephalopoda. The male element +sometimes possesses attributes which, if observed in an independent animal, +would be put down to instinct guided by sense-organs, as when the {384} +spermatozoon of an insect finds its way into the minute micropyle of the +egg, or as when the antherozoids of certain algæ swim by the aid of their +ciliæ to the female plant, and force themselves into a minute orifice. In +these latter cases, however, we must believe that the male element has +acquired its powers, on the same principle with the larvæ of animals, +namely by successive modifications developed at corresponding periods of +life: we can hardly avoid in these cases looking at the male element as a +sort of premature larva, which unites, or, like one of the lower algæ, +conjugates, with the female element. What determines the aggregation of the +gemmules within the sexual organs we do not in the least know; nor do we +know why buds are formed in certain definite places, leading to the +symmetrical growth of trees and corals, nor why adventitious buds may be +formed almost anywhere, even on a petal, and frequently upon healed +wounds.[912] As soon as the gemmules have aggregated themselves, +development apparently commences, but in the case of buds is often +afterwards suspended, and in the case of the sexual elements soon ceases, +unless the elements of the opposite sexes combine; even after this has +occurred, the fertilised germ, as with seeds buried in the ground, may +remain during a lengthened period in a dormant state. + +The antagonism which has long been observed,[913] though exceptions +occur,[914] between active growth and the power of sexual +reproduction--between the repair of injuries and gemmation--and with +plants, between rapid increase by buds, rhizomes, &c., and the production +of seed, is partly explained by the gemmules not existing in sufficient +numbers for both processes. {385} But this explanation hardly applies to +those plants which naturally produce a multitude of seeds, but which, +through a comparatively small increase in the number of the buds on their +rhizomes or offsets, yield few or no seed. As, however, we shall presently +see that buds probably include tissue which has already been to a certain +extent developed or differentiated, some additional organised matter will +thus have been expended. + +From one of the forms of Reproduction, namely, spontaneous self-division, +we are led by insensible steps to the repair of the slightest injury; and +the existence of gemmules, derived from every cell or unit throughout the +body and everywhere diffused, explains all such cases,--even the wonderful +fact that, when the limbs of the salamander were cut off many times +successively by Spallanzani and Bonnet, they were exactly and completely +reproduced. I have heard this process compared with the recrystallisation +which occurs when the angles of a broken crystal are repaired; and the two +processes have this much in common, that in the one case the polarity of +the molecules is the efficient cause, and in the other the affinity of the +gemmules for particular nascent cells. + +Pangenesis does not throw much light on Hybridism, but agrees well with +most of the ascertained facts. We may conclude from the fact of a single +spermatozoon or pollen-grain being insufficient for impregnation, that a +certain number of gemmules derived from each cell or unit are required for +the development of each part. From the occurrence of parthenogenesis, more +especially in the case of the silk-moth, in which the embryo is often +partially formed, we may also infer that the female element includes nearly +sufficient gemmules of all kinds for independent development, so that when +united with the male element the gemmules must be superabundant. Now, as a +general rule, when two species or races are crossed reciprocally, the +offspring do not differ, and this shows that both sexual elements agree in +power, in accordance with the view that they include the same gemmules. +Hybrids and mongrels are generally intermediate in character between the +two parent-forms, yet occasionally they closely resemble one parent in one +part and the other parent in another part, or even in their whole +structure: nor is this difficult to understand on {386} the admission that +the gemmules in the fertilised germ are superabundant in number, and that +those derived from one parent have some advantage in number, affinity, or +vigour over those derived from the other parent. Crossed forms sometimes +exhibit the colour or other characters of either parent in stripes or +blotches; and this may occur in the first generation, or through reversion +in succeeding bud and seminal generations, as in the several instances +given in the eleventh chapter. In these cases we must follow Naudin,[915] +and admit that the "essence" or "element" of the two species, which terms I +should translate into the gemmules, have an affinity for their own kind, +and thus separate themselves into distinct stripes or blotches; and reasons +were given, when discussing in the fifteenth chapter the incompatibility of +certain characters to unite, for believing in such mutual affinity. When +two forms are crossed, one is not rarely found to be prepotent in the +transmission of character over the other; and this we can explain only by +again assuming that the one form has some advantage in the number, vigour, +or affinity of its gemmules, except in those cases, where certain +characters are present in the one form and latent in the other. For +instance, there is a latent tendency in all pigeons to become blue, and, +when a blue pigeon is crossed with one of any other colour, the blue tint +is generally prepotent. When we consider latent characters, the explanation +of this form of prepotency will be obvious. + +When one species is crossed with another it is notorious that they do not +yield the full or proper number of offspring; and we can only say on this +head that, as the development of each organism depends on such +nicely-balanced affinities between a host of gemmules and developing cells +or units, we need not feel at all surprised that the commixture of gemmules +derived from two distinct species should lead to a partial or complete +failure of development. With respect to the sterility of hybrids produced +from the union of two distinct species, it was shown in the nineteenth +chapter that this depends exclusively on the reproductive organs being +specially affected; but why these organs should be thus affected we do not +know, any more than {387} why unnatural conditions of life, though +compatible with health, should cause sterility; or why continued close +interbreeding, or the illegitimate unions of dimorphic and trimorphic +plants, induce the same result. The conclusion that the reproductive organs +alone are affected, and not the whole organisation, agrees perfectly with +the unimpaired or even increased capacity in hybrid plants for propagation +by buds; for this implies, according to our hypothesis, that the cells of +the hybrids throw off hybridised cell-gemmules, which become aggregated +into buds, but fail to become aggregated within the reproductive organs, so +as to form the sexual elements. In a similar manner many plants, when +placed under unnatural conditions, fail to produce seed, but can readily be +propagated by buds. We shall presently see that pangenesis agrees well with +the strong tendency to reversion exhibited by all crossed animals and +plants. + +It was shown in the discussion on graft-hybrids that there is some reason +to believe that portions of cellular tissue taken from distinct plants +become so intimately united, as afterwards occasionally to produce crossed +or hybridised buds. If this fact were fully established, it would, by the +aid of our hypothesis, connect gemmation and sexual reproduction in the +closest manner. + +Abundant evidence has been advanced proving that pollen taken from one +species or variety and applied to the stigma of another sometimes directly +affects the tissues of the mother-plant. It is probable that this occurs +with many plants during fertilisation, but can only be detected when +distinct forms are crossed. On any ordinary theory of reproduction this is +a most anomalous circumstance, for the pollen-grains are manifestly adapted +to act on the ovule, but in these cases they act on the colour, texture, +and form of the coats of the seeds, on the ovarium itself, which is a +modified leaf, and even on the calyx and upper part of the flower-peduncle. +In accordance with the hypothesis of pangenesis pollen includes gemmules, +derived from every part of the organisation, which diffuse themselves and +multiply by self-division; hence it is not surprising that gemmules within +the pollen, which are derived from the parts near the reproductive organs, +should sometimes be able to affect the same parts, whilst still undergoing +development, in the mother-plant. {388} + +As, during all the stages of development, the tissues of plants consist of +cells, and as new cells are not known to be formed between, or +independently of, pre-existing cells, we must conclude that the gemmules +derived from the foreign pollen do not become developed merely in contact +with pre-existing cells, but actually penetrate the nascent cells of the +mother-plant. This process may be compared with the ordinary act of +fertilisation, during which the contents of the pollen-tubes penetrate the +closed embryonic sack within the ovule, and determine the development of +the embryo. According to this view, the cells of the mother-plant may +almost literally be said to be fertilised by the gemmules derived from the +foreign pollen. With all organisms, as we shall presently see, the cells or +organic units of the embryo during the successive stages of development may +in like manner be said to be fertilised by the gemmules of the cells, which +come next in the order of formation. + +Animals, when capable of sexual reproduction, are fully developed, and it +is scarcely possible that the male element should affect the tissues of the +mother in the same direct manner as with plants; nevertheless it is certain +that her ovaria are sometimes affected by a previous impregnation, so that +the ovules subsequently fertilised by a distinct male are plainly +influenced in character; and this, as in the case of foreign pollen, is +intelligible through the diffusion, retention, and action of the gemmules +included within the spermatozoa of the previous male. + +Each organism reaches maturity through a longer or shorter course of +development. The changes may be small and insensibly slow, as when a child +grows into a man, or many, abrupt, and slight, as in the metamorphoses of +certain ephemerous insects, or again few and strongly marked, as with most +other insects. Each part may be moulded within a previously existing and +corresponding part, and in this case it will appear, falsely as I believe, +to be formed from the old part; or it may be developed within a wholly +distinct part of the body, as in the extreme cases of metagenesis. An eye, +for instance, may be developed at a spot where no eye previously existed. +We have also seen that allied organic beings in the course of their +metamorphoses sometimes attain nearly the same structure after passing +{389} through widely different forms; or conversely, after passing through +nearly the same early forms, arrive at a widely different termination. In +these cases it is very difficult to believe that the early cells or units +possess the inherent power, independently of any external agent, of +producing new structures wholly different in form, position, and function. +But these cases become plain on the hypothesis of pangenesis. The organic +units, during each stage of development, throw off gemmules, which, +multiplying, are transmitted to the offspring. In the offspring, as soon as +any particular cell or unit in the proper order of development becomes +partially developed, it unites with (or to speak metaphorically is +fertilised by) the gemmule of the next succeeding cell, and so onwards. +Now, supposing that at any stage of development, certain cells or +aggregates of cells had been slightly modified by the action of some +disturbing cause, the cast-off gemmules or atoms of the cell-contents could +hardly fail to be similarly affected, and consequently would reproduce the +same modification. This process might be repeated until the structure of +the part at this particular stage of development became greatly changed, +but this would not necessarily affect other parts whether previously or +subsequently developed. In this manner we can understand the remarkable +independence of structure in the successive metamorphoses, and especially +in the successive metageneses of many animals. + +The term growth ought strictly to be confined to mere increase of size, and +development to change of structure.[916] Now, a child is said to grow into +a man, and a foal into a horse, but, as in these cases there is much change +of structure, the process properly belongs to the order of development. We +have indirect evidence of this in many variations and diseases supervening +during so-called growth at a particular period, and being inherited at a +corresponding period. In the case, however, of diseases which supervene +during old age, subsequently to the ordinary period of procreation, and +which nevertheless are sometimes inherited, as occurs with brain and heart +complaints, we {390} must suppose that the organs were in fact affected at +an earlier age and threw off at this period affected gemmules; but that the +affection became visible or injurious only after the prolonged growth of +the part in the strict sense of the word. In all the changes of structure +which regularly supervene during old age, we see the effects of +deteriorated growth, and not of true development. + +In the so-called process of _alternate generation_ many individuals are +generated asexually during very early or later stages of development. These +individuals may closely resemble the preceding larval form, but generally +are wonderfully dissimilar. To understand this process we must suppose that +at a certain stage of development the gemmules are multiplied at an unusual +rate, and become aggregated by mutual affinity at many centres of +attraction, or buds. These buds, it may be remarked, must include gemmules +not only of all the succeeding but likewise of all the preceding stages of +development; for when mature they have the power of transmitting by sexual +generation gemmules of all the stages, however numerous these may be. It +was shown in the First Part, at least in regard to animals, that the new +beings which are thus at any period asexually generated do not retrograde +in development--that is, they do not pass through those earlier stages, +through which the fertilised germ of the same animal has to pass; and an +explanation of this fact was attempted as far as the final or teleological +cause is concerned. We can likewise understand the proximate cause, if we +assume, and the assumption is far from improbable, that buds, like +chopped-up fragments of a hydra, are formed of tissue which has already +passed through several of the earlier stages of development; for in this +case their component cells or units would not unite with the gemmules +derived from the earlier-formed cells, but only with those which came next +in the order of development. On the other hand, we must believe that, in +the sexual elements, or probably in the female alone, gemmules of certain +primordial cells are present; and these, as soon as their development +commences, unite in due succession with the gemmules of every part of the +body, from the first to the last period of life. + +The principle of the independent formation of each part, in {391} so far as +its development depends on the union of the proper gemmules with certain +nascent cells, together with the superabundance of the gemmules derived +from both parents and self-multiplied, throws light on a widely different +group of facts, which on any ordinary view of development appears very +strange. I allude to organs which are abnormally multiplied or transposed. +Thus gold-fish often have supernumerary fins placed on various parts of +their bodies. We have seen that, when the tail of a lizard is broken off, a +double tail is sometimes reproduced, and when the foot of the salamander is +divided longitudinally, additional digits are occasionally formed. When +frogs, toads, &c., are born with their limbs doubled, as sometimes occurs, +the doubling, as Gervais remarks,[917] cannot be due to the complete fusion +of two embryos, with the exception of the limbs, for the larvæ are +limbless. The same argument is applicable[918] to certain insects produced +with multiple legs or antennæ, for these are metamorphosed from apodal or +antennæless larvæ. Alphonse Milne-Edwards[919] has described the curious +case of a crustacean in which one eye-peduncle supported, instead of a +complete eye, only an imperfect cornea, out of the centre of which a +portion of an antenna was developed. A case has been recorded[920] of a man +who had during both dentitions a double tooth in place of the left second +incisor, and he inherited this peculiarity from his paternal grandfather. +Several cases are known[921] of additional teeth having been developed in +the palate, more especially with horses, and in the orbit of the eye. +Certain breeds of sheep bear a whole crowd of horns on their foreheads. +Hairs occasionally appear in strange situations, as within the ears of the +Siamese hairy family; and hairs "quite natural in structure" have been +observed "within the substance of the brain."[922] As many as five spurs +have been seen on both legs in certain Game-fowls. In the Polish fowl the +male is ornamented with a topknot of hackles {392} like those on his neck, +whilst the female has one of common feathers. In feather-footed pigeons and +fowls, feathers like those on the wing arise from the outer side of the +legs and toes. Even the elemental parts of the same feather may be +transposed; for in the Sebastopol goose, barbules are developed on the +divided filaments of the shaft. + +Analogous cases are of such frequent occurrence with plants that they do +not strike us with sufficient surprise. Supernumerary petals, stamens, and +pistils, are often produced. I have seen a leaflet low down in the compound +leaf of _Vicia sativa_ converted into a tendril, and a tendril possesses +many peculiar properties, such as spontaneous movement and irritability. +The calyx sometimes assumes, either wholly or by stripes, the colour and +texture of the corolla. Stamens are so frequently converted, more or less +completely, into petals, that such cases are passed over as not deserving +notice; but as petals have special functions to perform, namely, to protect +the included organs, to attract insects, and in not a few cases to guide +their entrance by well-adapted contrivances, we can hardly account for the +conversion of stamens into petals merely by unnatural or superfluous +nourishment. Again, the edge of a petal may occasionally be found including +one of the highest products of the plant, namely the pollen; for instance, +I have seen in an Ophrys a pollen-mass with its curious structure of little +packets, united together and to the caudicle by elastic threads, formed +between the edges of an upper petal. The segments of the calyx of the +common pea have been observed partially converted into carpels, including +ovules, and with their tips converted into stigmas. Numerous analogous +facts could be given.[923] + +I do not know how physiologists look at such facts as the foregoing. +According to the doctrine of pangenesis, the free and superabundant +gemmules of the transposed organs are developed in the wrong place, from +uniting with wrong cells or aggregates of cells during their nascent state; +and this would follow from a slight modification in the elective affinity +of such cells, or possibly of certain gemmules. Nor ought we to feel much +surprise at the affinities of cells and gemmules varying {393} under +domestication, when we remember the many curious cases given, in the +seventeenth chapter, of cultivated plants which absolutely refuse to be +fertilised by their own pollen or by that of the same species, but are +abundantly fertile with pollen of a distinct species; for this implies that +their sexual elective affinities--and this is the term used by +Gärtner--have been modified. As the cells of adjoining or homologous parts +will have nearly the same nature, they will be liable to acquire by +variation each other's elective affinities; and we can thus to a certain +extent understand such cases as a crowd of horns on the heads in certain +sheep, of several spurs on the leg, and of hackles on the head of the fowl, +and with the pigeon the occurrence of wing-feathers on their legs and of +membrane between their toes; for the leg is the homologue of the wing. As +all the organs of plants are homologous and spring from a common axis, it +is natural that they should be eminently liable to transposition. It ought +to be observed that when any compound part, such as an additional limb or +an antenna, springs from a false position, it is only necessary that the +few first gemmules should be wrongly attached; for these whilst developing +would attract others in due succession, as in the regrowth of an amputated +limb. When parts which are homologous and similar in structure, as the +vertebræ in snakes or the stamens in polyandrous flowers, &c., are repeated +many times in the same organism, closely allied gemmules must be extremely +numerous, as well as the points to which they ought to become united; and, +in accordance with the foregoing views, we can to a certain extent +understand Isid. Geoffroy St. Hilaire's law, namely, that parts, which are +already multiple, are extremely liable to vary in number. + +The same general principles apply to the fusion of homologous parts; and +with respect to mere cohesion there is probably always some degree of +fusion, at least near the surface. When two embryos during their early +development come into close contact, as both include corresponding +gemmules, which must be in all respects almost identical in nature, it is +not surprising that some derived from one embryo and some from the other +should unite at the point of contact with a single nascent cell or +aggregate of cells, and thus give rise to a single part or organ. For +instance, two embryos might thus come to have on their {394} adjoining +sides a single symmetrical arm, which in one sense will have been formed by +the fusion of the bones, muscles, &c., belonging to the arms of both +embryos. In the case of the fish described by Lereboullet, in which a +double head was seen gradually to fuse into a single one, the same process +must have taken place, together with the absorption of all the parts which +had been already formed. These cases are exactly the reverse of those in +which a part is doubled either spontaneously or after an injury; for in the +case of doubling, the superabundant gemmules of the same part are +separately developed in union with adjoining points; whilst in the case of +fusion the gemmules derived from two homologous parts become mingled and +form a single part; or it may be that the gemmules from one of two +adjoining embryos alone become developed. + + * * * * * + +Variability often depends, as I have attempted to show, on the reproductive +organs being injuriously affected by changed conditions; and in this case +the gemmules derived from the various parts of the body are probably +aggregated in an irregular manner, some superfluous and others deficient. +Whether a superabundance of gemmules, together with fusion during +development, would lead to the increased size of any part cannot be told; +but we can see that their partial deficiency, without necessarily leading +to the entire abortion of the part, might cause considerable modifications; +for in the same manner as a plant, if its own pollen be excluded, is easily +hybridised, so, in the case of a cell, if the properly succeeding gemmules +were absent, it would probably combine easily with other and allied +gemmules. We see this in the case of imperfect nails growing on the stumps +of amputated fingers,[924] for the gemmules of the nails have manifestly +been developed at the nearest point. + +In variations caused by the direct action of changed conditions, whether of +a definite or indefinite nature, as with the fleeces of sheep in hot +countries, with maize grown in cold countries, with inherited gout, &c., +the tissues of the body, according to the doctrine of pangenesis, are +directly affected by the new conditions, and consequently throw off +modified gemmules, which are transmitted with their newly acquired +peculiarities to the offspring. On any ordinary view it is unintelligible +how changed {395} conditions, whether acting on the embryo, the young or +adult animal, can cause inherited modifications. It is equally or even more +unintelligible on any ordinary view, how the effects of the long-continued +use or disuse of any part, or of changed habits of body or mind, can be +inherited. A more perplexing problem can hardly be proposed; but on our +view we have only to suppose that certain cells become at last not only +functionally but structurally modified; and that these throw off similarly +modified gemmules. This may occur at any period of development, and the +modification will be inherited at a corresponding period; for the modified +gemmules will unite in all ordinary cases with the proper preceding cells, +and they will consequently be developed at the same period at which the +modification first arose. With respect to mental habits or instincts, we +are so profoundly ignorant on the relation between the brain and the power +of thought that we do not know whether an inveterate habit or trick induces +any change in the nervous system; but when any habit or other mental +attribute, or insanity, is inherited, we must believe that some actual +modification is transmitted;[925] and this implies, according to our +hypothesis, that gemmules derived from modified nerve-cells are transmitted +to the offspring. + +It is generally, perhaps always, necessary that an organism should be +exposed during several generations to changed conditions or habits, in +order that any modification in the structure of the offspring should ensue. +This may be partly due to the changes not being at first marked enough to +catch the attention, but this explanation is insufficient; and I can +account for the fact, only by the assumption, which we shall see under the +head of reversion is strongly supported, that gemmules derived from each +cell before it had undergone the least modification are transmitted in +large numbers to successive generations, but that the gemmules derived from +the same cells after modification, naturally go on increasing under the +same favouring conditions, until at last they become sufficiently numerous +to overpower and supplant the old gemmules. + +Another difficulty may be here noticed; we have seen that {396} there is an +important difference in the frequency, though not in the nature, of the +variations in plants propagated by sexual and asexual generation. As far as +variability depends on the imperfect action of the reproductive organs +under changed conditions, we can at once see why seedlings should be far +more variable than plants propagated by buds. We know that extremely slight +causes,--for instance, whether a tree has been grafted or grows on its own +stock, the position of the seeds within the capsule, and of the flowers on +the spike,--sometimes suffice to determine the variation of a plant, when +raised from seed. Now, it is probable, as explained when discussing +alternate generation, that a bud is formed of a portion of already +differentiated tissue; consequently an organism thus formed does not pass +through the earlier phases of development, and cannot be so freely exposed, +at the age when its structure would be most readily modified, to the +various causes inducing variability; but it is very doubtful whether this +is a sufficient explanation of the difficulty. + +With respect to the tendency to reversion, there is a similar difference +between plants propagated from buds and seed. Many varieties, whether +originally produced from seed or buds, can be securely propagated by buds, +but generally or invariably revert by seed. So, also, hybridised plants can +be multiplied to any extent by buds, but are continually liable to +reversion by seed,--that is, to the loss of their hybrid or intermediate +character. I can offer no satisfactory explanation of this fact. Here is a +still more perplexing case: certain plants with variegated leaves, phloxes +with striped flowers, barberries with seedless fruit, can all be securely +propagated by the buds on cuttings; but the buds developed from the roots +of these cuttings almost invariably lose their character and revert to +their former condition. + +Finally, we can see on the hypothesis of pangenesis that variability +depends on at least two distinct groups of causes. Firstly, on the +deficiency, superabundance, fusion, and transposition of gemmules, and on +the redevelopment of those which have long been dormant. In these cases the +gemmules themselves have undergone no modification; but the mutations in +the above respects will amply account for much fluctuating {397} +variability. Secondly, in the cases in which the organisation has been +modified by changed conditions, the increased use or disuse of parts, or +any other cause, the gemmules cast off from the modified units of the body +will be themselves modified, and, when sufficiently multiplied, will be +developed into new and changed structures. + + * * * * * + +Turning now to Inheritance: if we suppose a homogeneous gelatinous +protozoon to vary and assume a reddish colour, a minute separated atom we +aid naturally, as it grew to full size, retain the same colour; and we +should have the simplest form of inheritance.[926] Precisely the same view +may be extended to the infinitely numerous and diversified units of which +the whole body in one of the higher animals is composed; and the separated +atoms are our gemmules. We have already sufficiently discussed the +inheritance of the direct effects of changed conditions, and of increased +use or disuse of parts, and, by implication, the important principle of +inheritance at corresponding ages. These groups of facts are to a large +extent intelligible on the hypothesis of pangenesis, and on no other +hypothesis as yet advanced. + +A few words must be added on the complete abortion or suppression of +organs. When a part becomes diminished by disuse prolonged during many +generations, the principle of economy of growth, as previously explained, +will tend to reduce it still further; but this will not account for the +complete or almost complete obliteration of, for instance, a minute papilla +of cellular tissue representing a pistil, or of a microscopically minute +nodule of bone representing a tooth. In certain cases of suppression not +yet completed, in which a rudiment occasionally reappears through +reversion, diffused gemmules derived from this part must, according to our +view, still exist; hence we must suppose that the cells, in union with +which the rudiment was formerly developed, in these cases fail in their +affinity for such gemmules. But in the cases of complete and final abortion +the gemmules themselves no doubt have perished; nor is this {398} in any +way improbable, for, though a vast number of active and long-dormant +gemmules are diffused and nourished in each living creature, yet there must +be some limit to their number; and it appears natural that gemmules derived +from an enfeebled and useless rudiment would be more liable to perish than +those derived from other parts which are still in full functional activity. + +With respect to mutilations, it is certain that a part may be removed or +injured during many generations, and no inherited result follow; and this +is an apparent objection to the hypothesis which will occur to every one. +But, in the first place, a being can hardly be intentionally mutilated +during its early stages of growth whilst in the womb or egg; and such +mutilations, when naturally caused, would appear like congenital +deficiencies, which are occasionally inherited. In the second place, +according to our hypothesis, gemmules multiply by self-division and are +transmitted from generation to generation; so that during a long period +they would be present and ready to reproduce a part which was repeatedly +amputated. Nevertheless it appears, from the facts given in the twelfth +chapter, that in some rare cases mutilations have been inherited, but in +most of these the mutilated surface became diseased. In this case it may be +conjectured that the gemmules of the lost part were gradually all attracted +by the partially diseased surface, and thus perished. Although this would +occur in the injured individual alone, and therefore in only one parent, +yet this might suffice for the inheritance of a mutilation, on the same +principle that a hornless animal of either sex, when crossed with a perfect +animal of the opposite sex, often transmits its deficiency. + +The last subject that need here be discussed, namely Reversion, rests on +the principle that transmission and development, though generally acting in +conjunction, are distinct powers; and the transmission of gemmules and +their subsequent development show us how the existence of these two +distinct powers is possible. We plainly see this distinction in the many +cases in which a grandfather transmits to his grandson, through his +daughter, characters which she does not, or cannot, possess. Why the +development of certain characters, not necessarily in any way connected +with the reproductive organs, should be confined to one sex alone--that is, +why certain cells in one sex {399} should unite with and cause the +development of certain gemmules--we do not in the least know; but it is the +common attribute of most organic beings in which the sexes are separate. + +The distinction between transmission and development is likewise seen in +all ordinary cases of Reversion; but before discussing this subject it may +be advisable to say a few words on those characters which I have called +latent, and which would not be classed under Reversion in its usual sense. +Most, or perhaps all, the secondary characters, which appertain to one sex, +lie dormant in the other sex; that is, gemmules capable of development into +the secondary male sexual characters are included within the female; and +conversely female characters in the male. Why in the female, when her +ovaria become diseased or fail to act, certain masculine gemmules become +developed, we do not clearly know, any more than why when a young bull is +castrated his horns continue growing until they almost resemble those of a +cow; or why, when a stag is castrated, the gemmules derived from the +antlers of his progenitors quite fail to be developed. But in many cases, +with variable organic beings, the mutual affinities of the cells and +gemmules become modified, so that parts are transposed or multiplied; and +it would appear that a slight change in the constitution of an animal, in +connection with the state of the reproductive organs, leads to changed +affinities in the tissues of various parts of the body. Thus, when male +animals first arrive at puberty, and subsequently during each recurrent +season, certain cells or parts acquire an affinity for certain gemmules, +which become developed into the secondary masculine characters; but if the +reproductive organs be destroyed, or even temporarily disturbed by changed +conditions, these affinities are not excited. Nevertheless, the male, +before he arrives at puberty, and during the season when the species does +not breed, must include the proper gemmules in a latent state. The curious +case formerly given of a Hen which assumed the masculine characters, not of +her own breed but of a remote progenitor, illustrates the connexion between +latent sexual characters and ordinary reversion. With those animals and +plants which habitually produce several forms, as with certain butterflies +described by Mr. Wallace, in which three female forms and {400} the male +exist, or as with the trimorphic species of Lythrum and Oxalis, gemmules +capable of reproducing several widely-different forms must be latent in +each individual. + +The same principle of the latency of certain characters, combined with the +transposition of organs, may be applied to those singular cases of +butterflies and other insects, in which exactly one half or one quarter of +the body resembles the male, and the other half or three quarters the +female; and when this occurs the opposite sides of the body, separated from +each other by a distinct line, sometimes differ in the most conspicuous +manner. Again, these same principles apply to the cases given in the +thirteenth chapter, in which the right and left sides of the body differ to +an extraordinary degree, as in the spiral winding of certain shells, and as +in the genus Verruca among cirripedes; for in these cases it is known that +either side indifferently may undergo the same remarkable change of +development. + +Reversion, in the ordinary sense of the word, comes into action so +incessantly, that it evidently forms an essential part of the general law +of inheritance. It occurs with beings, however propagated, whether by buds +or seminal generation, and sometimes may even be observed in the same +individual as it advances in age. The tendency to reversion is often +induced by a change of conditions, and in the plainest manner by the act of +crossing. Crossed forms are generally at first nearly intermediate in +character between their two parents; but in the next generation the +offspring generally revert to one or both of their grandparents, and +occasionally to more remote ancestors. How can we account for these facts? +Each organic unit in a hybrid must throw off, according to the doctrine of +pangenesis, an abundance of hybridised gemmules, for crossed plants can be +readily and largely propagated by buds; but by the same hypothesis there +will likewise be present dormant gemmules derived from both pure +parent-forms; and as these latter retain their normal condition, they +would, it is probable, be enabled to multiply largely during the lifetime +of each hybrid. Consequently the sexual elements of a hybrid will include +both pure and hybridised gemmules; and when two hybrids pair, the +combination of pure gemmules derived from the one hybrid with the pure +gemmules of the same parts derived from the other would {401} necessarily +lead to complete reversion of character; and it is, perhaps, not too bold a +supposition that unmodified and undeteriorated gemmules of the same nature +would be especially apt to combine. Pure gemmules in combination with +hybridised gemmules would lead to partial reversion. And lastly, hybridised +gemmules derived from both parent-hybrids would simply reproduce the +original hybrid form.[927] All these cases and degrees of reversion +incessantly occur. + +It was shown in the fifteenth chapter that certain characters are +antagonistic to each other or do not readily blend together; hence, when +two animals with antagonistic characters are crossed, it might well happen +that a sufficiency of gemmules in the male alone for the reproduction of +his peculiar characters, and in the female alone for the reproduction of +her peculiar characters, would not be present; and in this case dormant +gemmules derived from some remote progenitor might easily gain the +ascendency, and cause the reappearance of long-lost characters. For +instance, when black and white pigeons, or black and white fowls, are +crossed,--colours which do not readily blend,--blue plumage in the one +case, evidently derived from the rock-pigeon, and red plumage in the other +case, derived from the wild jungle-cock, occasionally reappear. With +uncrossed breeds the same result would follow, under conditions which +favoured the multiplication and development of certain dormant gemmules, as +when animals become feral and revert to their pristine character. A certain +number of gemmules being requisite for the development of each character, +as is known to be the case from several spermatozoa or pollen-grains being +necessary for fertilisation, and time favouring their multiplication, will +together account for the curious cases, insisted on by Mr. Sedgwick, of +certain diseases regularly appearing in alternate generations. This +likewise holds good, more or less strictly, with other weakly inherited +modifications. Hence, as I have heard it remarked, certain diseases appear +actually to gain strength by the intermission of a generation. The +transmission of dormant gemmules during many successive generations is +hardly in itself more improbable, as {402} previously remarked, than the +retention during many ages of rudimentary organs, or even only of a +tendency to the production of a rudiment; but there is no reason to suppose +that all dormant gemmules would be transmitted and propagated for ever. +Excessively minute and numerous as they are believed to be, an infinite +number derived, during a long course of modification and descent, from each +cell of each progenitor, could not be supported or nourished by the +organism. On the other hand, it does not seem improbable that certain +gemmules, under favourable conditions, should be retained and go on +multiplying for a longer period than others. Finally, on the views here +given, we certainly gain some clear insight into the wonderful fact that +the child may depart from the type of both its parents, and resemble its +grandparents, or ancestors removed by many generations. + +_Conclusion._ + +The hypothesis of Pangenesis, as applied to the several great classes of +facts just discussed, no doubt is extremely complex; but so assuredly are +the facts. The assumptions, however, on which the hypothesis rests cannot +be considered as complex in any extreme degree--namely, that all organic +units, besides having the power, as is generally admitted, of growing by +self-division, throw off free and minute atoms of their contents, that is +gemmules. These multiply and aggregate themselves into buds and the sexual +elements; their development depends on their union with other nascent cells +or units; and they are capable of transmission in a dormant state to +successive generations. + +In a highly organised and complex animal, the gemmules thrown off from each +different cell or unit throughout the body must be inconceivably numerous +and minute. Each unit of each part, as it changes during development, and +we know that some insects undergo at least twenty metamorphoses, must throw +off its gemmules. All organic beings, moreover, include many dormant +gemmules derived from their grandparents and more remote progenitors, but +not from all their progenitors. These almost infinitely numerous and minute +gemmules must be included in each bud, ovule, spermatozoon, and +pollen-grain. Such an admission will be declared impossible; but, as +previously {403} remarked, number and size are only relative difficulties, +and the eggs or seeds produced by certain animals or plants are so numerous +that they cannot be grasped by the intellect. + +The organic particles with which the wind is tainted over miles of space by +certain offensive animals must be infinitely minute and numerous; yet they +strongly affect the olfactory nerves. An analogy more appropriate is +afforded by the contagious particles of certain diseases, which are so +minute that they float in the atmosphere and adhere to smooth paper; yet we +know how largely they increase within the human body, and how powerfully +they act. Independent organisms exist which are barely visible under the +highest powers of our recently-improved microscopes, and which probably are +fully as large as the cells or units in one of the higher animals; yet +these organisms no doubt reproduce themselves by germs of extreme +minuteness, relatively to their own minute size. Hence the difficulty, +which at first appears insurmountable, of believing in the existence of +gemmules so numerous and so small as they must be according to our +hypothesis, has really little weight. + +The cells or units of the body are generally admitted by physiologists to +be autonomous, like the buds on a tree, but in a less degree. I go one step +further and assume that they throw off reproductive gemmules. Thus an +animal does not, as a whole, generate its kind through the sole agency of +the reproductive system, but each separate cell generates its kind. It has +often been said by naturalists that each cell of a plant has the actual or +potential capacity of reproducing the whole plant; but it has this power +only in virtue of containing gemmules derived from every part. If our +hypothesis be provisionally accepted, we must look at all the forms of +asexual reproduction, whether occurring at maturity or as in the case of +alternate generation during youth, as fundamentally the same, and dependent +on the mutual aggregation and multiplication of the gemmules. The regrowth +of an amputated limb or the healing of a wound is the same process +partially carried out. Sexual generation differs in some important +respects, chiefly, as it would appear, in an insufficient number of +gemmules being aggregated within the separate sexual elements, and probably +in the presence of certain primordial cells. The development of each being, +including all the {404} forms of metamorphosis and metagenesis, as well as +the so-called growth of the higher animals, in which structure changes +though not in a striking manner, depends on the presence of gemmules thrown +off at each period of life, and on their development, at a corresponding +period, in union with preceding cells. Such cells may be said to be +fertilised by the gemmules which come next in the order of development. +Thus the ordinary act of impregnation and the development of each being are +closely analogous processes. The child, strictly speaking, does not grow +into the man, but includes germs which slowly and successively become +developed and form the man. In the child, as well as in the adult, each +part generates the same part for the next generation. Inheritance must be +looked at as merely a form of growth, like the self-division of a +lowly-organised unicellular plant. Reversion depends on the transmission +from the forefather to his descendants of dormant gemmules, which +occasionally become developed under certain known or unknown conditions. +Each animal and plant may be compared to a bed of mould full of seeds, most +of which soon germinate, some lie for a period dormant, whilst others +perish. When we hear it said that a man carries in his constitution the +seeds of an inherited disease, there is much literal truth in the +expression. Finally, the power of propagation possessed by each separate +cell, using the term in its largest sense, determines the reproduction, the +variability, the development and renovation of each living organism. No +other attempt, as far as I am aware, has been made, imperfect as this +confessedly is, to connect under one point of view these several grand +classes of facts. We cannot fathom the marvellous complexity of an organic +being; but on the hypothesis here advanced this complexity is much +increased. Each living creature must be looked at as a microcosm--a little +universe, formed of a host of self-propagating organisms, inconceivably +minute and as numerous as the stars in heaven. + + * * * * * + + +{405} + +CHAPTER XXVIII. + +CONCLUDING REMARKS. + + DOMESTICATION--NATURE AND CAUSES OF VARIABILITY--SELECTION--DIVERGENCE + AND DISTINCTNESS OF CHARACTER--EXTINCTION OF RACES--CIRCUMSTANCES + FAVOURABLE TO SELECTION BY MAN--ANTIQUITY OF CERTAIN RACES--THE + QUESTION WHETHER EACH PARTICULAR VARIATION HAS BEEN SPECIALLY + PREORDAINED. + +As summaries have been added to nearly all the chapters, and as, in the +chapter on pangenesis, various subjects, such as the forms of reproduction, +inheritance, reversion, the causes and laws of variability, &c., have been +recently discussed, I will here only make a few general remarks on the more +important conclusions which may be deduced from the multifarious details +given throughout this work. + +Savages in all parts of the world easily succeed in taming wild animals; +and those inhabiting any country or island, when first invaded by man, +would probably have been still more easily tamed. Complete subjugation +generally depends on an animal being social in its habits, and on receiving +man as the chief of the herd or family. Domestication implies almost +complete fertility under new and changed conditions of life, and this is +far from being invariably the case. An animal would not have been worth the +labour of domestication, at least during early times, unless of service to +man. From these circumstances the number of domesticated animals has never +been large. With respect to plants, I have shown in the ninth chapter how +their varied uses were probably first discovered, and the early steps in +their cultivation. Man could not have known, when he first domesticated an +animal or plant, whether it would flourish and multiply when transported to +other countries, therefore he could not have been thus influenced in his +choice. We see that the close adaptation of the reindeer and camel to +extremely cold and hot countries has not prevented their domestication. +Still less {406} could man have foreseen whether his animals and plants +would vary in succeeding generations and thus give birth to new races; and +the small capacity of variability in the goose and ass has not prevented +their domestication from the remotest epoch. + +With extremely few exceptions, all animals and plants which have been long +domesticated, have varied greatly. It matters not under what climate, or +for what purpose, they are kept, whether as food for man or beast, for +draught or hunting, for clothing or mere pleasure,--under all these +circumstances domesticated animals and plants have varied to a much greater +extent than the forms which in a state of nature are ranked as one species. +Why certain animals and plants have varied more under domestication than +others we do not know, any more than why some are rendered more sterile +than others under changed conditions of life. But we frequently judge of +the amount of variation by the production of numerous and diversified +races, and we can clearly see why in many cases this has not occurred, +namely, because slight successive variations have not been steadily +accumulated; and such variations will never be accumulated when an animal +or plant is not closely observed, or much valued, or kept in large numbers. + +The fluctuating, and, as far as we can judge, never-ending variability of +our domesticated productions,--the plasticity of their whole +organisation,--is one of the most important facts which we learn from the +numerous details given in the earlier chapters of this work. Yet +domesticated animals and plants can hardly have been exposed to greater +changes in their conditions than have many natural species during the +incessant geological, geographical, and climatal changes of the whole +world. The former will, however, commonly have been exposed to more sudden +changes and to less continuously uniform conditions. As man has +domesticated so many animals and plants belonging to widely different +classes, and as he certainly did not with prophetic instinct choose those +species which would vary most, we may infer that all natural species, if +subjected to analogous conditions, would, on an average, vary to the same +degree. Few men at the present day will maintain that animals and plants +were created with a tendency to vary, which long remained dormant, in order +that fanciers in after ages might {407} rear, for instance, curious breeds +of the fowl, pigeon, or canary-bird. + +From several causes it is difficult to judge of the amount of modification +which our domestic productions have undergone. In some cases the primitive +parent-stock has become extinct, or cannot be recognised with certainty +owing to its supposed descendants having been so much modified. In other +cases two or more closely allied forms, after being domesticated, have +crossed; and then it is difficult to estimate how much of the change ought +to be attributed to variation. But the degree to which our domestic breeds +have been modified by the crossing of distinct natural forms has probably +been exaggerated by some authors. A few individuals of one form would +seldom permanently affect another form existing in much greater numbers; +for, without careful selection, the stain of the foreign blood would soon +be obliterated, and during early and barbarous times, when our animals were +first domesticated, such care would seldom have been taken. + +There is good reason to believe that several of the breeds of the dog, ox, +pig, and of some other animals, are respectively descended from distinct +wild prototypes; nevertheless the belief in the multiple origin of our +domesticated animals has been extended by some few naturalists and by many +breeders to an unauthorised extent. Breeders refuse to look at the whole +subject under a single point of view; I have heard one, who maintained that +our fowls were the descendants of at least half-a-dozen aboriginal species, +protest that he was in no way concerned with the origin of pigeons, ducks, +rabbits, horses, or any other animal. They overlook the improbability of +many species having been domesticated at an early and barbarous period. +They do not consider the improbability of species having existed in a state +of nature which, if like our present domestic breeds, would have been +highly abnormal in comparison with all their congeners. They maintain that +certain species, which formerly existed, have become extinct or unknown, +although the world is now so much better known. The assumption of so much +recent extinction is no difficulty in their eyes; for they do not judge of +its probability by the facility or difficulty of the extinction of other +closely allied wild forms. Lastly, {408} they often ignore the whole +subject of geographical distribution as completely as if its laws were the +result of chance. + +Although from the reasons just assigned it is often difficult to judge +accurately of the amount of change which our domesticated productions have +undergone, yet this can be ascertained in the cases in which we know that +all the breeds are descended from a single species, as with the pigeon, +duck, rabbit, and almost certainly with the fowl; and by the aid of analogy +this is to a certain extent possible in the case of animals descended from +several wild stocks. It is impossible to read the details given in the +earlier chapters, and in many published works, or to visit our various +exhibitions, without being deeply impressed with the extreme variability of +our domesticated animals and cultivated plants. I have in many instances +purposely given details on new and strange peculiarities which have arisen. +No part of the organisation escapes the tendency to vary. The variations +generally affect parts of small vital or physiological importance, but so +it is with the differences which exist between closely allied species. In +these unimportant characters there is often a greater difference between +the breeds of the same species than between the natural species of the same +genus, as Isidore Geoffroy has shown to be the case with size, and as is +often the case with the colour, texture, form, &c., of the hair, feathers, +horns, and other dermal appendages. + +It has often been asserted that important parts never vary under +domestication, but this is a complete error. Look at the skull of the pig +in any one of the highly improved breeds, with the occipital condyles and +other parts greatly modified; or look at that of the niata ox. Or again, in +the several breeds of the rabbit, observe the elongated skull, with the +differently shaped occipital foramen, atlas, and other cervical vertebræ. +The whole shape of the brain, together with the skull, has been modified in +Polish fowls; in other breeds of the fowl the number of the vertebræ and +the forms of the cervical vertebræ have been changed. In certain pigeons +the shape of the lower jaw, the relative length of the tongue, the size of +the nostrils and eyelids, the number and shape of the ribs, the form and +size of the oesophagus, have all varied. In certain quadrupeds the length +of the intestines has been much increased or {409} diminished. With plants +we see wonderful differences in the stones of various fruits. In the +Cucurbitaceæ several highly important characters have varied, such as the +sessile position of the stigmas on the ovarium, the position of the carpels +within the ovarium, and its projection out of the receptacle. But it would +be useless to run through the many facts given in the earlier chapters. + +It is notorious how greatly the mental disposition, tastes, habits, +consensual movements, loquacity or silence, and the tone of voice have +varied and been inherited with our domesticated animals. The dog offers the +most striking instance of changed mental attributes, and these differences +cannot be accounted for by descent from distinct wild types. New mental +characters have certainly often been acquired, and natural ones lost, under +domestication. + +New characters may appear and disappear at any stage of growth, and be +inherited at a corresponding period. We see this in the difference between +the eggs of various breeds of the fowl, and in the down on chickens; and +still more plainly in the differences between the caterpillars and cocoons +of various breeds of the silk-moth. These facts, simple as they appear, +throw light on the characters which distinguish the larval and adult states +of natural species, and on the whole great subject of embryology. New +characters are liable to become attached exclusively to that sex in which +they first appeared, or they may be developed in a much higher degree in +the one than the other sex; or again, after having become attached to one +sex, they may be partially transferred to the opposite sex. These facts, +and more especially the circumstance that new characters seem to be +particularly liable, from some unknown cause, to become attached to the +male sex, have an important bearing on the acquirement by animals in a +state of nature of secondary sexual characters. + +It has sometimes been said that our domestic productions do not differ in +constitutional peculiarities, but this cannot be maintained. In our +improved cattle, pigs, &c., the period of maturity, including that of the +second dentition, has been much hastened. The period of gestation varies +much, but has been modified in a fixed manner in only one or two cases. In +{410} our poultry and pigeons the acquirement of down and of the first +plumage by the young, and of the secondary sexual characters by the males, +differ. The number of moults through which the larvæ of silk-moths pass, +varies. The tendency to fatten, to yield much milk, to produce many young +or eggs at a birth or during life, differs in different breeds. We find +different degrees of adaptation to climate, and different tendencies to +certain diseases, to the attacks of parasites, and to the action of certain +vegetable poisons. With plants, adaptation to certain soils, as with some +kinds of plums, the power of resisting frost, the period of flowering and +fruiting, the duration of life, the period of shedding the leaves and of +retaining them throughout the winter, the proportion and nature of certain +chemical compounds in the tissues or seeds, all vary. + +There is, however, one important constitutional difference between domestic +races and species; I refer to the sterility which almost invariably +follows, in a greater or less degree, when species are crossed, and to the +perfect fertility of the most distinct domestic races, with the exception +of a very few plants, when similarly crossed. It certainly appears a +remarkable fact that many closely allied species which in appearance differ +extremely little should yield when united only a few, more or less sterile +offspring, or none at all; whilst domestic races which differ conspicuously +from each other, are when united remarkably fertile, and yield perfectly +fertile offspring. But this fact is not in reality so inexplicable as it at +first appears. In the first place, it was clearly shown in the nineteenth +chapter that the sterility of crossed species does not closely depend on +differences in their external structure or general constitution, but +results exclusively from differences in the reproductive system, analogous +with those which cause the lessened fertility of the illegitimate unions +and illegitimate offspring of dimorphic and trimorphic plants. In the +second place, the Pallasian doctrine, that species after having been long +domesticated lose their natural tendency to sterility when crossed, has +been shown to be highly probable; we can scarcely avoid this conclusion +when we reflect on the parentage and present fertility of the several +breeds of the dog, of Indian and European cattle, sheep, and pigs. Hence it +would be unreasonable to expect that races formed under domestication {411} +should acquire sterility when crossed, whilst at the same time we admit +that domestication eliminates the normal sterility of crossed species. Why +with closely allied species their reproductive systems should almost +invariably have been modified in so peculiar a manner as to be mutually +incapable of acting on each other--though in unequal degrees in the two +sexes, as shown by the difference in fertility between reciprocal crosses +in the same species--we do not know, but may with much probability infer +the cause to be as follows. Most natural species have been habituated to +nearly uniform conditions of life for an incomparably longer period of time +than have domestic races; and we positively know that changed conditions +exert an especial and powerful influence on the reproductive system. Hence +this difference in habituation may well account for the different action of +the reproductive organs when domestic races and when species are crossed. +It is a nearly analogous fact, that most domestic races may be suddenly +transported from one climate to another, or be placed under widely +different conditions, and yet retain their fertility unimpaired; whilst a +multitude of species subjected to lesser changes are rendered incapable of +breeding. + +With the exception of fertility, domestic varieties resemble species when +crossed in transmitting their characters in the same unequal manner to +their offspring, in being subject to the prepotency of one form over the +other, and in their liability to reversion. By repeated crosses a variety +or a species may be made completely to absorb another. Varieties, as we +shall see when we treat of their antiquity, sometimes inherit their new +characters almost, or even quite, as firmly as species. With both, the +conditions leading to variability and the laws governing its nature appear +to be the same. Domestic varieties can be classed in groups under groups, +like species under genera, and these under families and orders; and the +classification may be either artificial,--that is, founded on any arbitrary +character,--or natural. With varieties a natural classification is +certainly founded, and with species is apparently founded, on community of +descent, together with the amount of modification which the forms have +undergone. The characters by which domestic varieties differ from each +other are more {412} variable than those distinguishing species, though +hardly more so than with certain protean species; but this greater degree +of variability is not surprising, as varieties have generally been exposed +within recent times to fluctuating conditions of life, are much more liable +to have been crossed, and are still in many cases undergoing, or have +recently undergone, modification by man's methodical or unconscious +selection. + +Domestic varieties as a general rule certainly differ from each other in +less important parts of their organisation than do species; and when +important differences occur, they are seldom firmly fixed; but this fact is +intelligible if we consider man's method of selection. In the living animal +or plant he cannot observe internal modifications in the more important +organs; nor does he regard them as long as they are compatible with health +and life. What does the breeder care about any slight change in the molar +teeth of his pigs, or for an additional molar tooth in the dog; or for any +change in the intestinal canal or other internal organ? The breeder cares +for the flesh of his cattle being well marbled with fat, and for an +accumulation of fat within the abdomen of his sheep, and this he has +effected. What would the floriculturist care for any change in the +structure of the ovarium or of the ovules? As important internal organs are +certainly liable to numerous slight variations, and as these would probably +be inherited, for many strange monstrosities are transmitted, man could +undoubtedly effect a certain amount of change in these organs. When he has +produced any modification in an important part, it has generally been +unintentionally in correlation with some other conspicuous part, as when he +has given ridges and protuberances to the skulls of fowls, by attending to +the form of the comb, and in the case of the Polish fowl to the plume of +feathers on the head. By attending to the external form of the +pouter-pigeon, he has enormously increased the size of the oesophagus, and +has added to the number of the ribs, and given them greater breadth. With +the carrier-pigeon, by increasing, through steady selection, the wattles on +the upper mandible, he has greatly modified the form of the lower mandible; +and so in many other cases. Natural species, on the other hand, have been +modified exclusively for their own good, to fit them for infinitely {413} +diversified conditions of life, to avoid enemies of all kinds, and to +struggle against a host of competitors. Hence, under such complex +conditions, it would often happen that modifications of the most varied +kinds, in important as well as in unimportant parts, would be advantageous +or even necessary; and they would slowly but surely be acquired through the +survival of the fittest. Various indirect modifications would likewise +arise through the law of correlated variation. + +Domestic breeds often have an abnormal or semi-monstrous character, as the +Italian greyhound, bulldog, Blenheim spaniel, and bloodhound amongst +dogs,--some breeds of cattle and pigs, several breeds of the fowl, and the +chief breeds of the pigeon. The differences between such abnormal breeds +occur in parts which in closely-allied natural species differ but slightly +or not at all. This may be accounted for by man's often selecting, +especially at first, conspicuous and semi-monstrous deviations of +structure. We should, however, be cautious in deciding what deviations +ought to be called monstrous: there can hardly be a doubt that, if the +brush of horse-like hair on the breast of the turkey-cock had first +appeared on the domesticated bird, it would have been considered a +monstrosity; the great plume of feathers on the head of the Polish cock has +been thus designated, though plumes are common with many kinds of birds; we +might call the wattle or corrugated skin round the base of the beak of the +English carrier-pigeon a monstrosity, but we do not thus speak of the +globular fleshy excrescence at the base of the beak of the male _Carpophaga +oceanica_. + +Some authors have drawn a wide distinction between artificial and natural +breeds; although in extreme cases the distinction is plain, in many other +cases an arbitrary line has to be drawn. The difference depends chiefly on +the kind of selection which has been applied. Artificial breeds are those +which have been intentionally improved by man; they frequently have an +unnatural appearance, and are especially liable to loss of excellence +through reversion and continued variability. The so-called natural breeds, +on the other hand, are those which are now found in semi-civilised +countries, and which formerly inhabited separate districts in nearly all +the European kingdoms. They have been rarely acted on by man's {414} +intentional selection; more frequently, it is probable, by unconscious +selection, and partly by natural selection, for animals kept in +semi-civilised countries have to provide largely for their own wants. Such +natural breeds will also, it may be presumed, have been directly acted on +to some extent by the differences, though slight, in the surrounding +physical conditions. + +It is a much more important distinction that some breeds have been from +their first origin modified in so slow and insensible a manner, that if we +could see their early progenitors we should hardly be able to say when or +how the breed first arose; whilst other breeds have originated from a +strongly-marked or semi-monstrous deviation of structure, which, however, +may subsequently have been augmented by selection. From what we know of the +history of the racehorse, greyhound, gamecock, &c., and from their general +appearance, we may feel nearly confident that they were formed by a slow +process of improvement: and with the carrier-pigeon, as well as with some +other pigeons, we know that this has been the case. On the other hand, it +is certain that the ancon and mauchamp breeds of sheep, and almost certain +that the niata cattle, turnspit and pug-dogs, jumper and frizzled fowls, +short-faced tumbler pigeons, hook-billed ducks, &c., and with plants a +multitude of varieties, suddenly appeared in nearly the same state as we +now see them. The frequency of these cases is likely to lead to the false +belief that natural species have often originated in the same abrupt +manner. But we have no evidence of the appearance, or at least of the +continued procreation, under nature, of abrupt modifications of structure; +and various general reasons could be assigned against such a belief: for +instance, without separation a single monstrous variation would almost +certainly be soon obliterated by crossing. + +On the other hand, we have abundant evidence of the constant occurrence +under nature of slight individual differences of the most diversified +kinds; and thus we are led to conclude that species have generally +originated by the natural selection, not of abrupt modifications, but of +extremely slight differences. This process may be strictly compared with +the slow and gradual improvement of the racehorse, greyhound, and gamecock. +As every detail of structure in each species is closely adapted to its +general {415} habits of life, it will rarely happen that one part alone +will be modified; but the co-adapted modifications, as formerly shown, need +not be absolutely simultaneous. Many variations, however, are from the +first connected by the law of correlation. Hence it follows that even +closely-allied species rarely or never differ from each other by some one +character alone; and this same remark applies to a certain extent to +domestic races; for these, if they differ much, generally differ in many +respects. + +Some naturalists boldly insist[928] that species are absolutely distinct +productions, never passing by intermediate links into each other; whilst +they maintain that domestic varieties can always be connected either with +each other or with their parent-forms. But if we could always find the +links between the several breeds of the dog, horse, cattle, sheep, pigs, +&c., the incessant doubts whether they are descended from one or several +species would not have arisen. The greyhound genus, if such a term may be +used, cannot be closely connected with any other breed, unless, perhaps, we +go back to the ancient Egyptian monuments. Our English bulldog also forms a +very distinct breed. In all these cases crossed breeds must of course be +excluded, for the most distinct natural species can thus be connected. By +what links can the Cochin fowl be closely united with others? By searching +for breeds still preserved in distant lands, and by going back to +historical records, tumbler-pigeons, carriers, and barbs can be closely +connected with the parent rock-pigeon; but we cannot thus connect the +turbit or the pouter. The degree of distinctness between the various +domestic breeds depends on the amount of modification which they have +undergone, and especially on the neglect and final extinction of the +linking, intermediate, and less valued forms. + +It has often been argued that no light is thrown, from the admitted changes +of domestic races, on the changes which natural species are believed to +undergo, as the former are said to be mere temporary productions, always +reverting, as soon as they become feral, to their pristine form. This +argument has been well combated by Mr. Wallace;[929] and full details were +given in the thirteenth chapter, showing that the tendency to reversion in +feral {416} animals and plants has been greatly exaggerated, though no +doubt to a certain extent it exists. It would be opposed to all the +principles inculcated in this work, if domestic animals, when exposed to +new conditions and compelled to struggle for their own wants against a host +of foreign competitors, were not in the course of time in some manner +modified. It should also be remembered that many characters lie latent in +all organic beings ready to be evolved under fitting conditions; and in +breeds modified within recent times the tendency to reversion is +particularly strong. But the antiquity of various breeds clearly proves +that they remain nearly constant as long as their conditions of life remain +the same. + +It has been boldly maintained by some authors that the amount of variation +to which our domestic productions are liable is strictly limited; but this +is an assertion resting on little evidence. Whether or not the amount in +any particular direction is fixed, the tendency to general variability +seems unlimited. Cattle, sheep, and pigs have been domesticated and have +varied from the remotest period, as shown by the researches of Rütimeyer +and others, yet these animals have, within quite recent times, been +improved in an unparalleled degree; and this implies continued variability +of structure. Wheat, as we know from the remains found in the Swiss +lake-habitations, is one of the most anciently cultivated plants, yet at +the present day new and better varieties occasionally arise. It may be that +an ox will never be produced of larger size or finer proportions than our +present animals, or a race-horse fleeter than Eclipse, or a gooseberry +larger than the London variety; but he would be a bold man who would assert +that the extreme limit in these respects has been finally attained. With +flowers and fruit it has repeatedly been asserted that perfection has been +reached, but the standard has soon been excelled. A breed of pigeons may +never be produced with a beak shorter than that of the present short-faced +tumbler, or with one longer than that of the English carrier, for these +birds have weak constitutions and are bad breeders; but the shortness and +length of the beak are the points which have been steadily improved during +at least the last 150 years; and some of the best judges deny that the goal +has yet been reached. We may, also, reasonably suspect, from what {417} we +see in natural species of the variability of extremely modified parts, that +any structure, after remaining constant during a long series of +generations, would, under new and changed conditions of life, recommence +its course of variability, and might again be acted on by selection. +Nevertheless, as Mr. Wallace[930] has recently remarked with much force and +truth, there must be both with natural and domestic productions a limit to +change in certain directions; for instance, there must be a limit to the +fleetness of any terrestrial animal, as this will be determined by the +friction to be overcome, the weight to be carried, and the power of +contraction in the muscular fibres. The English racehorse may have reached +this limit; but it already surpasses in fleetness its own wild progenitor, +and all other equine species. + +It is not surprising, seeing the great difference between many domestic +breeds, that some few naturalists have concluded that all are descended +from distinct aboriginal stocks, more especially as the principle of +selection has been ignored, and the high antiquity of man, as a breeder of +animals, has only recently become known. Most naturalists, however, freely +admit that various extremely dissimilar breeds are descended from a single +stock, although they do not know much about the art of breeding, cannot +show the connecting links, nor say where and when the breeds arose. Yet +these same naturalists will declare, with an air of philosophical caution, +that they can never admit that one natural species has given birth to +another until they behold all the transitional steps. But fanciers have +used exactly the same language with respect to domestic breeds; thus an +author of an excellent treatise says he will never allow that carrier and +fantail pigeons are the descendants of the wild rock-pigeon, until the +transitions have "actually been observed, and can be repeated whenever man +chooses to set about the task." No doubt it is difficult to realise that +slight changes added up during long centuries can produce such results; but +he who wishes to understand the origin of domestic breeds or natural +species must overcome this difficulty. + +The causes inducing and the laws governing variability have been so lately +discussed, that I need here only enumerate the leading points. As +domesticated organisms are much more {418} liable to slight deviations of +structure and to monstrosities, than species living under their natural +conditions, and as widely-ranging species vary more than those which +inhabit restricted areas, we may infer that variability mainly depends on +changed conditions of life. We must not overlook the effects of the unequal +combination of the characters derived from both parents, nor reversion to +former progenitors. Changed conditions have an especial tendency to render +the reproductive organs more or less impotent, as shown in the chapter +devoted to this subject; and these organs consequently often fail to +transmit faithfully the parental characters. Changed conditions also act +directly and definitely on the organisation, so that all or nearly all the +individuals of the same species thus exposed become modified in the same +manner; but why this or that part is especially affected we can seldom or +never say. In most cases, however, of the direct action of changed +conditions, independently of the indirect variability caused by the +reproductive organs being affected, indefinite modifications are the +result; in nearly the same manner as exposure to cold or the absorption of +the same poison affects different individuals in various ways. We have +reason to suspect that an habitual excess of highly nutritious food, or an +excess relatively to the wear and tear of the organisation from exercise, +is a powerful exciting cause of variability. When we see the symmetrical +and complex outgrowths, caused by a minute atom of the poison of a +gall-insect, we may believe that slight changes in the chemical nature of +the sap or blood would lead to extraordinary modifications of structure. + +The increased use of a muscle with its various attached parts, and the +increased activity of a gland or other organ, lead to their increased +development. Disuse has a contrary effect. With domesticated productions +organs sometimes become rudimentary through abortion; but we have no reason +to suppose that this has ever followed from mere disuse. With natural +species, on the contrary, many organs appear to have been rendered +rudimentary through disuse, aided by the principle of the economy of +growth, and by the hypothetical principle discussed in the last chapter, +namely, the final destruction of the germs or gemmules of such useless +parts. This difference may be partly {419} accounted for by disuse having +acted on domestic forms for an insufficient length of time, and partly from +their exemption from any severe struggle for existence, entailing rigid +economy in the development of each part, to which all species under nature +are subjected. Nevertheless the law of compensation or balancement +apparently affects, to a certain extent, our domesticated productions. + +We must not exaggerate the importance of the definite action of changed +conditions in modifying all the individuals of the same species in the same +manner, or of use and disuse. As every part of the organisation is highly +variable, and as variations are so easily selected, both consciously and +unconsciously, it is very difficult to distinguish between the effects of +the selection of indefinite variations, and the direct action of the +conditions of life. For instance, it is possible that the feet of our +water-dogs, and of the American dogs which have to travel much over the +snow, may have become partially webbed from the stimulus of widely +extending their toes; but it is far more probable that the webbing, like +the membrane between the toes of certain pigeons, spontaneously appeared +and was afterwards increased by the best swimmers and the best +snow-travellers being preserved during many generations. A fancier who +wished to decrease the size of his bantams or tumbler-pigeons would never +think of starving them, but would select the smallest individuals which +spontaneously appeared. Quadrupeds are sometimes born destitute of hair, +and hairless breeds have been formed, but there is no reason to believe +that this is caused by a hot climate. Within the tropics heat often causes +sheep to lose their fleeces, and on the other hand wet and cold act as a +direct stimulus to the growth of hair; it is, however, possible that these +changes may merely be an exaggeration of the regular yearly change of coat; +and who will pretend to decide how far this yearly change, or the thick fur +of arctic animals, or as I may add their white colour, is due to the direct +action of a severe climate, and how far to the preservation of the best +protected individuals during a long succession of generations? + +Of all the laws governing variability, that of correlation is the most +important. In many cases of slight deviations of structure as well as of +grave monstrosities, we cannot even {420} conjecture what is the nature of +the bond of connexion. But between homologous parts--between the fore and +hind limbs--between the hair, hoofs, horns, and teeth--we can see that +parts which are closely similar during their early development, and which +are exposed to similar conditions, would be liable to be modified in the +same manner. Homologous parts, from having the same nature, are apt to +blend together and, when many exist, to vary in number. + +Although every variation is either directly or indirectly caused by some +change in the surrounding conditions, we must never forget that the nature +of the organisation which is acted on essentially governs the result. +Distinct organisms, when placed under similar conditions, vary in different +manners, whilst closely-allied organisms under dissimilar conditions often +vary in nearly the same manner. We see this in the same modification +frequently reappearing at long intervals of time in the same variety, and +likewise in the several striking cases given of analogous or parallel +varieties. Although some of these latter cases are simply due to reversion, +others cannot thus be accounted for. + +From the indirect action of changed conditions on the organisation, through +the impaired state of the reproductive organs--from the direct action of +such conditions (and this will cause the individuals of the same species +either to vary in the same manner, or differently in accordance with slight +differences in their constitution)--from the effects of the increased or +decreased use of parts,--and from correlation,--the variability of our +domesticated productions is complicated in an extreme degree. The whole +organisation becomes slightly plastic. Although each modification must have +its proper exciting cause, and though each is subjected to law, yet we can +so rarely trace the precise relation between cause and effect, that we are +tempted to speak of variations as if they spontaneously arose. We may even +call them accidental, but this must be only in the sense in which we say +that a fragment of rock dropped from a height owes its shape to accident. + + * * * * * + +It may be worth while briefly to consider the results of the exposure to +unnatural conditions of a large number of animals of the same species, +allowed to cross freely, with no selection of any {421} kind; and +afterwards to consider the results when selection is brought into play. Let +us suppose that 500 wild rock-pigeons were confined in their native land in +an aviary, and fed in the same manner as pigeons usually are; and that they +were not allowed to increase in number. As pigeons propagate so rapidly, I +suppose that a thousand or fifteen hundred birds would have to be annually +killed by mere chance. After several generations had been thus reared, we +may feel sure that some of the young birds would vary, and the variations +would tend to be inherited; for at the present day slight deviations of +structure often occur, but, as most breeds are already well established, +these modifications are rejected as blemishes. It would be tedious even to +enumerate the multitude of points which still go on varying or have +recently varied. Many variations would occur in correlation, as the length +of the wing and tail feathers--the number of the primary wing-feathers, as +well as the number and breadth of the ribs, in correlation with the size +and form of the body--the number of the scutellæ, with the size of the +feet--the length of the tongue, with the length of the beak--the size of +the nostrils and eyelids and the form of lower jaw in correlation with the +development of wattle--the nakedness of the young with the future colour of +the plumage--the size of the feet and beak, and other such points. Lastly, +as our birds are supposed to be confined in an aviary, they would use their +wings and legs but little, and certain parts of the skeleton, such as the +sternum and scapulæ and the feet, would in consequence become slightly +reduced in size. + +As in our assumed case many birds have to be indiscriminately killed every +year, the chances are against any new variety surviving long enough to +breed. And as the variations which arise are of an extremely diversified +nature, the chances are very great against two birds pairing which have +varied in the same manner; nevertheless, a varying bird even when not thus +paired would occasionally transmit its character to its young; and these +would not only be exposed to the same conditions which first caused the +variation in question to appear, but would in addition inherit from their +one modified parent a tendency again to vary in the same manner. So that, +if the conditions decidedly tended to induce some particular variation, all +the birds might {422} in the course of time become similarly modified. But +a far commoner result would be, that one bird would vary in one way and +another bird in another way; one would be born with a little longer beak, +and another with a shorter beak; one would gain some black feathers, +another some white or red feathers. And as these birds would be continually +intercrossing, the final result would be a body of individuals differing +from each other slightly in many ways, yet far more than did the original +rock-pigeons. But there would not be the least tendency to the formation of +distinct breeds. + +If two separate lots of pigeons were to be treated in the manner just +described, one in England and the other in a tropical country, the two lots +being supplied with different food, would they, after many generations had +passed, differ? When we reflect on the cases given in the twenty-third +chapter, and on such facts as the difference in former times between the +breeds of cattle, sheep, &c., in almost every district of Europe, we are +strongly inclined to admit that the two lots would be differently modified +through the influence of climate and food. But the evidence on the definite +action of changed conditions is in most cases insufficient; and, with +respect to pigeons, I have had the opportunity of examining a large +collection of domesticated birds, sent to me by Sir W. Elliot from India, +and they varied in a remarkably similar manner with our European birds. + +If two distinct breeds were to be confined together in equal numbers, there +is reason to suspect that they would to a certain extent prefer pairing +with their own kind; but they would likewise intercross. From the greater +vigour and fertility of the crossed offspring, the whole body would by this +means become interblended sooner than would otherwise have occurred. From +certain breeds being prepotent over others, it does not follow that the +interblended progeny would be strictly intermediate in character. I have, +also, proved that the act of crossing in itself gives a strong tendency to +reversion, so that the crossed offspring would tend to revert to the state +of the aboriginal rock-pigeon. In the course of time they would probably be +not much more heterogeneous in character than in our first case, when birds +of the same breed were confined together. {423} + +I have just said that the crossed offspring would gain in vigour and +fertility. From the facts given in the seventeenth chapter there can be no +doubt of this; and there can be little doubt, though the evidence on this +head is not so easily acquired, that long-continued close interbreeding +leads to evil results. With hermaphrodites of all kinds, if the sexual +elements of the same individual habitually acted on each other, the closest +possible interbreeding would be perpetual. Therefore we should bear in mind +that with all hermaphrodite animals, as far as I can learn, their structure +permits and frequently necessitates a cross with a distinct individual. +With hermaphrodite plants we incessantly meet with elaborate and perfect +contrivances for this same end. It is no exaggeration to assert that, if +the use of the talons and tusks of a carnivorous animal, or the use of the +viscid threads of a spider's web, or of the plumes and hooks on a seed may +be safely inferred from their structure, we may with equal safety infer +that many flowers are constructed for the express purpose of ensuring a +cross with a distinct plant. From these various considerations, the +conclusion arrived at in the chapter just referred to--namely, that great +good of some kind is derived from the sexual concourse of distinct +individuals--must be admitted. + +To return to our illustration: we have hitherto assumed that the birds were +kept down to the same number by indiscriminate slaughter; but if the least +choice be permitted in their preservation and slaughter, the whole result +will be changed. Should the owner observe any slight variation in one of +his birds, and wish to obtain a breed thus characterised, he would succeed +in a surprisingly short time by carefully selecting and pairing the young. +As any part which has once varied generally goes on varying in the same +direction, it is easy, by continually preserving the most strongly marked +individuals, to increase the amount of difference up to a high, +predetermined standard of excellence. This is methodical selection. + +If the owner of the aviary, without any thought of making a new breed, +simply admired, for instance, short-beaked more than long-beaked birds, he +would, when he had to reduce the number, generally kill the latter; and +there can be no doubt that he would thus in the course of time sensibly +modify his {424} stock. It is improbable, if two men were to keep pigeons +and act in this manner, that they would prefer exactly the same characters; +they would, as we know, often prefer directly opposite characters, and the +two lots would ultimately come to differ. This has actually occurred with +strains or families of cattle, sheep, and pigeons, which have been long +kept and carefully attended to by different breeders without any wish on +their part to form new and distinct sub-breeds. This unconscious kind of +selection will more especially come into action with animals which are +highly serviceable to man; for every one tries to get the best dog, horse, +cow, or sheep, and these animals will transmit more or less surely their +good qualities to their offspring. Hardly any one is so careless as to +breed from his worst animals. Even savages, when compelled from extreme +want to kill some of their animals, would destroy the worst and preserve +the best. With animals kept for use and not for mere amusement, different +fashions prevail in different districts, leading to the preservation, and +consequently to the transmission, of all sorts of trifling peculiarities of +character. The same process will have been pursued with our fruit-trees and +vegetables, for the best will always have been the most largely cultivated, +and will occasionally have yielded seedlings better than their parents. + +The different strains, just alluded to, which have been raised by different +breeders without any wish for such a result, and the unintentional +modification of foreign breeds in their new homes, both afford excellent +evidence of the power of unconscious selection. This form of selection has +probably led to far more important results than methodical selection, and +is likewise more important under a theoretical point of view from closely +resembling natural selection. For during this process the best or most +valued individuals are not separated and prevented crossing with others of +the same breed, but are simply preferred and preserved; but this inevitably +leads during a long succession of generations to their increase in number +and to their gradual improvement; so that finally they prevail to the +exclusion of the old parent-form. + +With our domesticated animals natural selection checks the production of +races with any injurious deviation of {425} structure. In the case of +animals kept by savages and semi-civilised people, which have to provide +largely for their own wants under different circumstances, natural +selection will probably play a more important part. Hence such animals +often closely resemble natural species. + +As there is no limit to man's desire to possess animals and plants more and +more useful in any respect, and as the fancier always wishes, from fashion +running into extremes, to produce each character more and more strongly +pronounced, there is a constant tendency in every breed, through the +prolonged action of methodical and unconscious selection, to become more +and more different from its parent-stock; and when several breeds have been +produced and are valued for different qualities, to differ more and more +from each other. This leads to Divergence of Character. As improved +sub-varieties and races are slowly formed, the older and less improved +breeds are neglected and decrease in number. When few individuals of any +breed exist within the same locality, close interbreeding, by lessening +their vigour and fertility, aids in their final extinction. Thus the +intermediate links are lost, and breeds which have already diverged gain +Distinctness of Character. + +In the chapters on the Pigeon, it was proved by historical details and by +the existence of connecting sub-varieties in distant lands that several +breeds have steadily diverged in character, and that many old and +intermediate sub-breeds have become extinct. Other cases could be adduced +of the extinction of domestic breeds, as of the Irish wolf-dog, the old +English hound, and of two breeds in France, one of which was formerly +highly valued.[931] Mr. Pickering remarks[932] that "the sheep figured on +the most ancient Egyptian monuments is unknown at the present day; and at +least one variety of the bullock, formerly known in Egypt, has in like +manner become extinct." So it has been with some animals, and with several +plants cultivated by the ancient inhabitants of Europe during the neolithic +period. In Peru, Von Tschudi[933] found in certain tombs, apparently prior +to the dynasty of the Incas, two kinds of maize not now known in the +country. With our flowers and culinary vegetables, {426} the production of +new varieties and their extinction has incessantly recurred. At the present +time improved breeds sometimes displace at an extraordinarily rapid rate +older breeds; as has recently occurred throughout England with pigs. The +Long-horn cattle in their native home were "suddenly swept away as if by +some murderous pestilence," by the introduction of Short-horns.[934] + +What grand results have followed from the long-continued action of +methodical and unconscious selection, checked and regulated to a certain +extent by natural selection, is seen on every side of us. Compare the many +animals and plants which are displayed at our exhibitions with their +parent-forms when these are known, or consult old historical records with +respect to their former state. Almost all our domesticated animals have +given rise to numerous and distinct races, excepting those which cannot be +easily subjected to selection--such as cats, the cochineal insect, and the +hive-bee,--and excepting those animals which are not much valued. In +accordance with what we know of the process of selection, the formation of +our many races has been slow and gradual. The man who first observed and +preserved a pigeon with its oesophagus a little enlarged, its beak a little +longer, or its tail a little more expanded than usual, never dreamed that +he had made the first step in the creation of the pouter, carrier, and +fantail-pigeon. Man can create not only anomalous breeds, but others with +their whole structure admirably co-ordinated for certain purposes, such as +the race-horse and dray-horse, or the greyhound. It is by no means +necessary that each small change of structure throughout the body, leading +towards excellence, should simultaneously arise and be selected. Although +man seldom attends to differences in organs which are important under a +physiological point of view, yet he has so profoundly modified some breeds, +that assuredly, if found wild, they would be ranked under distinct genera. + +The best proof of what selection has effected is perhaps afforded by the +fact that whatever part or quality in any animal, and more especially in +any plant, is most valued by man, that part or quality differs most in the +several races. This result is well seen by comparing the amount of +difference {427} between the fruits produced by the varieties of the same +fruit-tree, between the flowers of the varieties in our flower-garden, +between the seeds, roots, or leaves of our culinary and agricultural +plants, in comparison with the other and not valued parts of the same +plants. Striking evidence of a different kind is afforded by the fact +ascertained by Oswald Heer,[935] namely, that the seeds of a large number +of plants,--wheat, barley, oats, peas, beans, lentils, poppies,--cultivated +for their seed by the ancient Lake-inhabitants of Switzerland, were all +smaller than the seeds of our existing varieties. Rütimeyer has shown that +the sheep and cattle which were kept by the earlier Lake-inhabitants were +likewise smaller than our present breeds. In the middens of Denmark, the +earliest dog of which the remains have been found was the weakest; this was +succeeded during the Bronze age by a stronger kind, and this again during +the Iron age by one still stronger. The sheep of Denmark during the Bronze +period had extraordinarily slender limbs, and the horse was smaller than +our present animal.[936] No doubt in these cases the new and larger breeds +were generally introduced from foreign lands by the immigration of new +hordes of men. But it is not probable that each larger breed, which in the +course of time supplanted a previous and smaller breed, was the descendant +of a distinct and larger species; it is far more probable that the domestic +races of our various animals were gradually improved in different parts of +the great Europæo-Asiatic continent, and thence spread to other countries. +This fact of the gradual increase in size of our domestic animals is all +the more striking as certain wild or half-wild animals, such as red-deer, +aurochs, park-cattle, and boars,[937] have within nearly the same period +decreased in size. + +The conditions favourable to selection by man are,--the closest attention +being paid to every character,--long-continued perseverance,--facility in +matching or separating animals,--and especially a large number being kept, +so that the inferior individuals may be freely rejected or destroyed, and +the better ones preserved. When many are kept there will also be a {428} +greater chance of the occurrence of well-marked deviations of structure. +Length of time is all-important; for as each character, in order to become +strongly pronounced, has to be augmented by the selection of successive +variations of the same nature, this can only be effected during a long +series of generations. Length of time will, also, allow any new feature to +become fixed by the continued rejection of those individuals which revert +or vary, and the preservation of those which inherit the new character. +Hence, although some few animals have varied rapidly in certain respects +under new conditions of life, as dogs in India and sheep in the West +Indies, yet all the animals and plants which have produced strongly marked +races were domesticated at an extremely remote epoch, often before the dawn +of history. As a consequence of this, no record has been preserved of the +origin of our chief domestic breeds. Even at the present day new strains or +sub-breeds are formed so slowly that their first appearance passes +unnoticed. A man attends to some particular character, or merely matches +his animals with unusual care, and after a time a slight difference is +perceived by his neighbours;--the difference goes on being augmented by +unconscious and methodical selection, until at last a new sub-breed is +formed, receives a local name, and spreads; but, by this time, its history +is almost forgotten. When the new breed has spread widely, it gives rise to +new strains and sub-breeds, and the best of these succeed and spread, +supplanting other and older breeds; and so always onwards in the march of +improvement. + +When a well-marked breed has once been established, if not supplanted by +still improving sub-breeds, and if not exposed to greatly changed +conditions of life, inducing further variability or reversion to long-lost +characters, it may apparently last for an enormous period. We may infer +that this is the case from the high antiquity of certain races; but some +caution is necessary on this head, for the same variation may appear +independently after long intervals of time, or in distant places. We may +safely assume that this has occurred with the turnspit-dog which is figured +on the ancient Egyptian monuments, with the solid-hoofed swine[938] +mentioned by Aristotle, with five-toed fowls {429} described by Columella, +and certainly with the nectarine. The dogs represented on the Egyptian +monuments, about 2000 B.C., show us that some of the chief breeds then +existed, but it is extremely doubtful whether any are identically the same +with our present breeds. A great mastiff sculptured on an Assyrian tomb, +640 B.C., is said to be the same with the dog still imported into the same +region from Thibet. The true greyhound existed during the Roman classical +period. Coming down to a later period, we have seen that, though most of +the chief breeds of the pigeon existed between two and three centuries ago, +they have not all retained to the present day exactly the same character; +but this has occurred in certain cases in which improvement was not +desired, for instance in the case of the Spot or the Indian ground-tumbler. + +De Candolle[939] has fully discussed the antiquity of various races of +plants; he states that the black-seeded poppy was known in the time of +Homer, the white-seeded sesamum by the ancient Egyptians, and almonds with +sweet and bitter kernels by the Hebrews; but it does not seem improbable +that some of these varieties may have been lost and reappeared. One variety +of barley and apparently one of wheat, both of which were cultivated at an +immensely remote period by the Lake-inhabitants of Switzerland, still +exist. It is said[940] that "specimens of a small variety of gourd which is +still common in the market of Lima were exhumed from an ancient cemetery in +Peru." De Candolle remarks that, in the books and drawings of the sixteenth +century, the principal races of the cabbage, turnip, and gourd can be +recognised; this might have been expected at so late a period, but whether +any of these plants are absolutely identical with our present sub-varieties +is not certain. It is, however, said that the Brussels sprout, a variety +which in some places is liable to degeneration, has remained genuine for +more than four centuries in the district where it is believed to have +originated.[941] + + * * * * * + +In accordance with the views maintained by me in this work and elsewhere, +not only the various domestic races, but the {430} most distinct genera and +orders within the same great class,--for instance, whales, mice, birds, and +fishes--are all the descendants of one common progenitor, and we must admit +that the whole vast amount of difference between these forms of life has +primarily arisen from simple variability. To consider the subject under +this point of view is enough to strike one dumb with amazement. But our +amazement ought to be lessened when we reflect that beings, almost infinite +in number, during an almost infinite lapse of time, have often had their +whole organisation rendered in some degree plastic, and that each slight +modification of structure which was in any way beneficial under excessively +complex conditions of life, will have been preserved, whilst each which was +in any way injurious will have been rigorously destroyed. And the +long-continued accumulation of beneficial variations will infallibly lead +to structures as diversified, as beautifully adapted for various purposes, +and as excellently co-ordinated, as we see in the animals and plants all +around us. Hence I have spoken of selection as the paramount power, whether +applied by man to the formation of domestic breeds, or by nature to the +production of species. I may recur to the metaphor given in a former +chapter: if an architect were to rear a noble and commodious edifice, +without the use of cut stone, by selecting from the fragments at the base +of a precipice wedge-formed stones for his arches, elongated stones for his +lintels, and flat stones for his roof, we should admire his skill and +regard him as the paramount power. Now, the fragments of stone, though +indispensable to the architect, bear to the edifice built by him the same +relation which the fluctuating variations of each organic being bear to the +varied and admirable structures ultimately acquired by its modified +descendants. + +Some authors have declared that natural selection explains nothing, unless +the precise cause of each slight individual difference be made clear. Now, +if it were explained to a savage utterly ignorant of the art of building, +how the edifice had been raised stone upon stone, and why wedge-formed +fragments were used for the arches, flat stones for the roof, &c.; and if +the use of each part and of the whole building were pointed out, it would +be unreasonable if he declared that nothing had been {431} made clear to +him, because the precise cause of the shape of each fragment could not be +given. But this is a nearly parallel case with the objection that selection +explains nothing, because we know not the cause of each individual +difference in the structure of each being. + +The shape of the fragments of stone at the base of our precipice may be +called accidental, but this is not strictly correct; for the shape of each +depends on a long sequence of events, all obeying natural laws; on the +nature of the rock, on the lines of deposition or cleavage, on the form of +the mountain which depends on its upheaval and subsequent denudation, and +lastly on the storm or earthquake which threw down the fragments. But in +regard to the use to which the fragments may be put, their shape may be +strictly said to be accidental. And here we are led to face a great +difficulty, in alluding to which I am aware that I am travelling beyond my +proper province. An omniscient Creator must have foreseen every consequence +which results from the laws imposed by Him. But can it be reasonably +maintained that the Creator intentionally ordered, if we use the words in +any ordinary sense, that certain fragments of rock should assume certain +shapes so that the builder might erect his edifice? If the various laws +which have determined the shape of each fragment were not predetermined for +the builder's sake, can it with any greater probability be maintained that +He specially ordained for the sake of the breeder each of the innumerable +variations in our domestic animals and plants;--many of these variations +being of no service to man, and not beneficial, far more often injurious, +to the creatures themselves? Did He ordain that the crop and tail-feathers +of the pigeon should vary in order that the fancier might make his +grotesque pouter and fantail breeds? Did He cause the frame and mental +qualities of the dog to vary in order that a breed might be formed of +indomitable ferocity, with jaws fitted to pin down the bull for man's +brutal sport? But if we give up the principle in one case,--if we do not +admit that the variations of the primeval dog were intentionally guided in +order that the greyhound, for instance, that perfect image of symmetry and +vigour, might be formed,--no shadow of reason can be assigned for the +belief that variations, alike in nature and the result {432} of the same +general laws, which have been the groundwork through natural selection of +the formation of the most perfectly adapted animals in the world, man +included, were intentionally and specially guided. However much we may wish +it, we can hardly follow Professor Asa Gray in his belief "that variation +has been led along certain beneficial lines," like a stream "along definite +and useful lines of irrigation." If we assume that each particular +variation was from the beginning of all time preordained, the plasticity of +organisation, which leads to many injurious deviations of structure, as +well as that redundant power of reproduction which inevitably leads to a +struggle for existence, and, as a consequence, to the natural selection or +survival of the fittest, must appear to us superfluous laws of nature. On +the other hand, an omnipotent and omniscient Creator ordains everything and +foresees everything. Thus we are brought face to face with a difficulty as +insoluble as is that of free will and predestination. + + * * * * * + + +{433} + + INDEX. + + ABBAS Pacha, a fancier of fantailed pigeons, i. 206. + ABBEY, Mr., on grafting, ii. 147; + on mignonette, ii. 237. + ABBOTT, Mr. Keith, on the Persian tumbler pigeon, i. 150. + ABBREVIATION of the facial bones, i. 73. + ABORTION of organs, ii. 315-318, 397. + ABSORPTION of minority in crossed races, ii. 87-89, 174. + ACCLIMATISATION, ii. 305-315; + of maize, i. 322. + ACERBI, on the fertility of domestic animals in Lapland, ii. 112. + _Achatinella_, ii. 53. + _Achillea millefolium_, bud variation in, i. 408. + _Aconitum napellus_, roots of, innocuous in cold climates, ii. 274. + _Acorus calamus_, sterility of, ii. 170. + ACOSTA, on fowls in South America at its discovery, i. 237. + _Acropera_, number of seeds in, ii. 379. + ADAM, Mr., origin of _Cytisus Adami_, i. 390. + ADAM, W., on consanguineous marriages, ii. 123. + ADAMS, Mr., on hereditary diseases, ii. 7. + ADVANCEMENT in scale of organisation, i. 8. + _Ægilops triticoides_, observations of Fabre and Godron on, i. 313; + increasing fertility of hybrids of, with wheat, ii. 110. + _Æsculus flava_ and _rubicunda_, i. 392. + _Æsculus pavia_, tendency of, to become double, ii. 168. + _Æthusa cynapium_, ii. 337. + AFFINITY, sexual elective, ii. 180. + AFRICA, white bull from, i. 91; + feral cattle in, i. 85; + food-plants of savages of, i. 307-309; + South, diversity of breeds of cattle in, i. 80; + West, change in fleece of sheep in, i. 98. + _Agave vivipara_, seeding of, in poor soil, ii. 169. + AGE, changes in trees, dependent on, i. 387. + AGOUTI, fertility of, in captivity, ii. 152. + AGRICULTURE, antiquity of, ii. 243. + _Agrostis_, seeds of, used as food, i. 309. + AGUARA, i. 26. + AINSWORTH, Mr., on the change in the hair of animals at Angora, ii. 278. + AKBAR Khan, his fondness for pigeons, i. 205; ii. 204. + _Alauda arvensis_, ii. 154. + ALBIN, on "Golden Hamburgh" fowls, i. 247; + figure of the hook-billed duck, i. 277. + ALBINISM, i. 111, ii. 17. + ALBINO, negro, attacked by insects, ii. 229. + ALBINOES, heredity of, ii. 9. + ALBINUS, thickness of the epidermis on the palms of the hands in man, ii. + 297. + ALCO, i. 31, ii. 102. + ALDROVANDI, on rabbits, i. 104; + description of the nun pigeon, i. 156; + on the fondness of the Dutch for pigeons in the seventeenth century, i. + 205; + notice of several varieties of pigeons, i. 207-210; + on the breeds of fowls, i. 247; + on the origin of the domestic duck, i. 278. + ALEFIELD, Dr., on the varieties of peas and their specific unity, i. 326; + on the varieties of beans, i. 330. + ALEXANDER the Great, his selection of Indian cattle, ii. 202. + ALGÆ, retrogressive metamorphosis in, ii. 361; + division of zoospores of, ii. 378. + ALLEN, W., on feral fowls, i. 237; ii. 33. + ALLMAN, Professor, on a monstrous _Saxifraga geum_, ii. 166; + on the development of the Hydroida, ii. 368. + ALMOND, i. 337; + antiquity of, ii. 429; + bitter, not eaten by mice, ii. 232. + _Alnus glutinosa_ and _incana_, hybrids of, ii. 130. + ALPACA, selection of, ii. 208. + _Althæa rosea_, i. 378, ii. 107. + _Amaryllis_, ii. 139. + _Amaryllis vittata_, effect of foreign pollen on, i. 400. + AMAUROSIS, hereditary, ii. 9. + AMERICA, limits within which no useful plants have been furnished by, i. + 310; + colours of feral horses in, i. 60-61; + North, native cultivated plants of, i. 312; + skin of feral pig from, i. 77; + South, variations in cattle of, i. 88, 92. + _Amygdalus persica_, i. 336-344, 374. + {434} + AMMON, on the persistency of colour in horses, ii. 21. + _Anagallis arvensis_, ii. 190. + ANALOGOUS variation, i. 409, ii. 348-352; + in horses, i. 55; + in the horse and ass, i. 64; + in fowls, i. 243-246. + _Anas boschas_, i. 277, ii. 40; + skull of, figured, i. 282. + _Anas moschata_, ii. 40. + "ANCON" sheep of Massachusetts, i. 100, ii. 103. + ANDALUSIAN fowls, i. 227. + ANDALUSIAN rabbits, i. 105. + ANDERSON, J., on the origin of British sheep, i. 94; + on the selection of qualities in cattle, ii. 196; + on a one-eared breed of rabbits, i. 108; + on the inheritance of characters from a one-eared rabbit and + three-legged bitch, ii. 12; + on the persistency of varieties of peas, i. 329; + on the production of early peas by selection, ii. 201; + on the varieties of the potato, i. 330-331; + on crossing varieties of the melon, i. 399; + on reversion in the barberry, i. 384. + ANDERSON, Mr., on the reproduction of the weeping ash by seed, ii. 19; + on the cultivation of the tree pæony in China, ii. 205. + ANDERSSON, Mr., on the Damara, Bechuana, and Namaqua cattle, i. 88; + on the cows of the Damaras, ii. 300; + selection practised by the Damaras and Namaquas, ii. 207; + on the use of grass-seeds and the roots of reeds as food in South + Africa, i. 309. + _Anemone coronaria_, doubled by selection, ii. 200. + ANGINA pectoris, hereditary, occurring at a certain age, ii. 79. + ANGLESEA, cattle of, i. 80. + ANGOLA sheep, i. 95. + ANGORA, change in hair of animals at, ii. 278; + cats of, i. 45, 47; + rabbits of, i. 106, 120. + ANIMALS, domestication of, facilitated by fearlessness of man, i. 20; + refusal of wild, to breed in captivity, ii. 149; + compound, individual peculiarities of, reproduced by budding, i. 374; + variation by selection in useful qualities of, ii. 220. + ANNUAL plants, rarity of bud-variation in, i. 408. + ANOMALIES in the osteology of the horse, i. 50. + ANOMALOUS breeds of pigs, i. 75; + of cattle, i. 89. + _Anser albifrons_, characters of, reproduced in domestic geese, i. 288. + _Anser ægyptiacus_, i. 282; ii. 68. + _Anser canadensis_, ii. 157. + _Anser cygnoides_, i. 237. + _Anser ferus_, the original of the domestic goose, i. 287; + fertility of cross of, with domestic goose, i. 288. + ANSON, on feral fowls in the Ladrones, i. 238. + ANTAGONISM between growth and reproduction, ii. 384. + _Anthemis nobilis_, bud-variation in flowers of, i. 379; + becomes single in poor soil, ii. 167. + ANTHEROZOIDS, apparent independence of, in algæ, ii. 384. + ANTHERS, contabescence of, ii. 165-166. + ANTIGUA, cats of, i. 46; + changed fleece of sheep in, i. 98. + _Antirrhinum majus_, peloric, i. 365; ii. 59, 70, 166; + double-flowered, ii. 167; + bud-variation in, i. 381. + ANTS, individual recognition of, ii. 251. + APES, anthropomorphous, ii. 123. + APHIDES, attacking pear-trees, ii. 231; + development of, ii. 361-362. + APOPLEXY, hereditary, occurring at a certain age, ii. 78. + APPLE, i. 348-350; + fruit of, in Swiss lake-dwellings, i. 317; + rendered fastigate by heat in India, i. 361; + bud-variation in the, i. 376; + with dimidiate fruit, i. 392-393; + with two kinds of fruit on the same branch, i. 392; + artificial fecundation of, i. 401; + St. Valéry, i. 401; ii. 166; + reversion in seedlings of, ii. 31; + crossing of varieties of, ii. 129; + growth of the, in Ceylon, ii. 277; + Winter Majetin, not attacked by _coccus_, ii. 231; + flower-buds of, attacked by bullfinches, ii. 232; + American, change of when grown in England, ii. 275. + APRICOT, i. 344-345; + glands on the leaves of, ii. 231; + analogous variation in the, ii. 348. + _Aquila fusca_, copulating in captivity, ii. 154. + _Aquilegia vulgaris_, i. 365; ii. 330. + ARAB boarhound, described by Harcourt, i. 17. + _Arabis blepharophylla_ and _A. Soyeri,_ effects of crossing, i. 400. + _Aralia trifoliata_, bud-variation in leaves of, i. 382. + ARAUCARIAS, young, variable resistance of, to frost, ii. 309. + ARCHANGEL pigeon, ii. 240. + ARCTIC regions, variability of plants and shells of, ii. 256. + _Aria vestita_, grafted on thorns, i. 387. + ARISTOPHANES, fowls mentioned by, i. 246. + ARISTOTLE, on solid-hoofed pigs, i. 75; + domestic duck unknown to, i. 277; + on the assumption of male characters by old hens, ii. 51. + {435} + ARNI, domestication of the, i. 82. + ARREST of development, ii. 315-318. + ARTERIES, increase of anastomosing branches of, when tied, ii. 230. + ARU islands, wild pig of, i. 67. + ARUM, Polynesian varieties of, ii. 256. + _Ascaris_, number of eggs of, ii. 379. + ASH, varieties of the, i. 360; + weeping, i. 361; + simple-leaved, i. 362; + bud-variation in, i. 382; + effects of graft upon the stock in the, i. 394; + production of the blotched Breadalbane, _ibid._; + weeping, capricious reproduction of, by seed, ii. 19. + _Asinus Burchellii_, i. 64. + _Asinus hemionus_, ii. 43. + _Asinus indicus_, ii. 42-43, 48. + _Asinus quagga_, i. 64. + _Asinus tæniopus_, ii. 41; + the original of the domestic ass, i. 62. + ASPARAGUS, increased fertility of cultivated, ii. 113. + ASS, early domestication of the, i. 62; + breeds of, _ibid._; + small size of, in India, _ibid._; + stripes of, i. 62-63; ii. 351; + dislike of to cross water, i. 181; + reversion in, ii. 41-43, 47; + hybrid of the, with mare and zebra, ii. 42; + prepotency of the, over the horse, ii. 67-68; + crossed with wild ass, ii. 206; + variation and selection of the, ii. 236. + ASSYRIAN sculpture of a mastiff, i. 17. + ASTERS, ii. 20, 316. + ASTHMA, hereditary, ii. 8, 79. + ATAVISM. _See_ Reversion. + ATHELSTAN, his care of horses, ii. 203. + ATKINSON, Mr., on the sterility of the Tarroo silk-moth in confinement, + ii. 157. + AUBERGINE, ii. 91. + AUDUBON, on feral hybrid ducks, i. 190; ii. 46; + on the domestication of wild ducks on the Mississippi, i. 278; + on the wild cock turkey visiting domestic hens, i. 292; + fertility of _Fringilla ciris_ in captivity, ii. 154; + fertility of _Columba migratoria_ and _leucocephala_ in captivity, ii. + 155; + breeding of _Anser canadensis_ in captivity, ii. 157. + AUDUBON and Bachman, on the change of coat in _Ovis montana_, i. 99; + sterility of _Sciurus cinerea_ in confinement, ii. 152. + AURICULA, effect of seasonal conditions on the, ii. 273; + blooming of, ii. 346. + AUSTRALIA, no generally useful plants derived from, i. 310; + useful plants of, enumerated by Hooker, i. 311. + AUSTRIA, heredity of character in emperors of, ii. 65. + AUTENRIETH, on persistency of colour in horses, ii. 21. + AVA, horses of, i. 53. + _Avena fatua_, cultivability of, i. 313. + AYEEN Akbery, pigeons mentioned in the, i. 150, 155, 185, 205, 207, 208. + AYRES, W. P., on bud-variation in pelargoniums, i. 378. + _Azalea indica_, bud-variation in, i. 377. + AZARA, on the feral dogs of La Plata, i. 27; + on the crossing of domestic with wild cats in Paraguay, i. 45; + on hornlike processes in horses, i. 50; + on curled hair in horses, i. 54; ii. 205, 325; + on the colours of feral horses, i. 60, 61; ii. 259; + on the cattle of Paraguay and La Plata, i. 82, 86, 89; ii. 250; + on a hornless bull, ii. 205; + on the increase of cattle in South America, ii. 119; + on the growth of horns in the hornless cattle of Corrientes, ii. 39; + on the "Niata" cattle, i. 90; + on naked quadrupeds, ii. 279; + on a race of black-skinned fowls in South America, i. 258; ii. 209; + on a variety of maize, i. 321. + + BABINGTON, C. C., on the origin of the plum, i. 345; + British species of the genus _Rosa_, i. 366; + distinctness of _Viola lutea_ and _tricolor_, i. 368. + BACHMANN, Mr., on the turkey, ii. 262. + _See also_ Audubon. + BADGER, breeding in confinement, ii. 151. + "BAGADOTTEN-TAUBE," i. 141. + BAILY, Mr., on the effect of selection on fowls, ii. 198; + on Dorking fowls, ii. 238. + BAIRD, S., on the origin of the turkey, i. 292. + BAKER, Mr., on heredity in the horse, ii. 11; + on the degeneration of the horse by neglect, ii. 239; + orders of Henrys VII. and VIII. for the destruction of undersized + mares, ii. 203. + BAKEWELL, change in the sheep effected by, ii. 198. + BALANCEMENT, ii. 342-344; + of growth, law of, i. 274. + BALDHEAD, pigeon, i. 151. + BALDNESS, in man, inherited, ii. 73-74; + with deficiency in teeth, ii. 326-327. + BALLANCE, Mr., on the effects of interbreeding on fowls, ii. 125; + on variation in the eggs of fowls, i. 248. + _Ballota nigra_, transmission of variegated leaves in, i. 383. + BAMBOO, varieties of the, ii. 256. + BANANA, variation of the, i. 372; ii. 256, 258; + bud-variation in the, i. 377; + sterility of the, ii. 268. + BANTAM fowls, i. 230; + Sebright, origin of, ii. 96; + sterility of, ii. 101. + BARB (Pigeon), i. 144-146, 210; ii. 227; + {436} + figure of, i. 145; + figure of lower jaw of, i. 164. + BARBS, of wheat, i. 314. + BARBERRY, dark or red-leaved variety, i. 362; ii. 19; + reversion in suckers of seedless variety, i. 384. + BARBUT, J., on the dogs of Guinea, i. 25; + on the domestic pigeons in Guinea, i. 186; + fowls not native in Guinea, i. 237. + BARKING, acquisition of the habit of, by various dogs, i. 27. + BARLEY, wild, i. 313; + of the lake-dwellings, i. 317-318; + ancient variety of, ii. 429. + BARNES, Mr., production of early peas by selection, ii. 201. + BARNET, Mr., on the intercrossing of strawberries, i. 351; + dioeciousness of the Hautbois strawberry, i. 353; + on the scarlet American strawberry, ii. 200. + BARTH, Dr., use of grass-seeds as food in Central Africa, i. 308. + BARTLETT, A. D., on the origin of "Himalayan" rabbits by intercrossing, + i. 109; + on the feral rabbits of Porto Santo, i. 114; + on geese with reversed feathers on the head and neck, i. 288; + on the young of the black-shouldered peacock, i. 290; + on the breeding of the Felidæ in captivity, ii. 150. + BARTRAM, on the black wolf-dog of Florida, i. 22. + BATES, H. W., refusal of wild animals to breed in captivity, ii. 150, + 152; + sterility of American monkeys in captivity, ii. 153; + sterility of tamed guans, ii. 156. + BATRACHIA, regeneration of lost parts in, ii. 15. + BEACH, raised, in Peru, containing heads of maize, i. 320. + BEAK, variability of, in fowls, i. 258; + individual differences of, in pigeons, i. 160; + correlation of, with the feet in pigeons, i. 171-174. + BEALE, Lionel, on the contents of cells, ii. 370; + on the multiplication of infectious atoms, ii. 378; + on the origin of fibres, ii. 382. + BEANS, i. 330; + of Swiss lake-dwellings, i. 319; + varieties of, produced by selection, ii. 218; + French and scarlet, variable resistance of to frost, ii. 309, 314; + superiority of native seed of, ii. 314; + a symmetrical variation of scarlet, ii. 322; + experiments on kidney, i. 330; + with monstrous stipules and abortive leaflets, ii. 343. + BEARD, pigeon, i. 151. + BEARS, breeding in captivity, ii. 151. + BEASLEY, J., reversion in crossed cattle, ii. 41. + BEATON, D., effect of soil upon strawberries, i. 353; + on varieties of pelargonium, i. 364, ii. 274, 311; + bud-variation in _Gladiolus colvillii_, i. 382; + cross between Scotch kail and cabbage, ii. 98; + hybrid gladiolus, ii. 139; + constant occurrence of new forms among seedlings, ii. 235; + on the doubling of the compositæ, ii. 316. + BECHUANA cattle, i. 88. + BECK, Mr., constitutional differences in pelargoniums, i. 364. + BECKMANN, on changes in the odours of plants, ii. 274. + BECKSTEIN, on the burrowing of wolves, i. 27; + "Spitz" dog, i. 31; + origin of the Newfoundland dog, i. 42; + crossing of domestic and wild swine, i. 66; + on the Jacobin pigeon, i. 154, 209; + notice of swallow-pigeons, i. 156; + on a fork-tailed pigeon, i. 157; + variations in the colour of the croup in pigeons, i. 184; + on the German dove-cot pigeon, i. 185; + fertility of mongrel pigeons, i. 192; + on hybrid turtle-doves, i. 193; + on crossing the pigeon with _Columba oenas_, _C. palumbus_, _Turtur + risoria_, and _T. vulgaris_, i. 193; + development of spurs in the silk-hen, i. 256; + on Polish fowls, i. 257, 264; + on crested birds, i. 257; + on the Canary-bird, i. 295, ii. 22, 161; + German superstition about the turkey, i. 293; + occurrence of horns in hornless breeds of sheep, ii. 30; + hybrids of the horse and ass, ii. 68; + crosses of tailless fowls, ii. 92; + difficulty of pairing dove-cot and fancy pigeons, ii. 103; + fertility of tame ferrets and rabbits, ii. 112; + fertility of wild sow, _ibid._; + difficulty of breeding caged birds, ii. 154; + comparative fertility of _Psittacus erithacus_ in captivity, ii. 155; + on changes of plumage in captivity, ii. 158; + liability of light-coloured cattle to the attacks of flies, ii. 229; + want of exercise a cause of variability, ii. 257; + effect of privation of light upon the plumage of birds, ii. 280; + on a sub-variety of the monk-pigeon, ii. 350. + BEDDOE, Dr., correlation of complexion with consumption, ii. 335. + BEDEGUAR gall, ii. 284. + BEE, persistency of character of, ii. 236, 254; + intercrossing, ii. 126; + conveyance, of pollen of peas by, i. 329. + BEE-OPHRYS, self-fertilisation of, ii. 91. + BEECH, dark-leaved, i. 362, ii. 19; + fern-leaved, reversion of, i. 382; + weeping, non-production of by seed, ii. 19. + BEECHEY, horses of Loochoo Islands, i. 53. + BEET, i. 326; + increase of sugar in, by selection, ii. 201. + {437} + _Begonia frigida_, singular variety of, i. 365; + sterility of, ii. 166. + BELGIAN rabbit, i. 106. + BELL, T., statement that white cattle have coloured ears, i. 85. + BELL, W., bud-variation in _Cistus tricuspis_, i. 377. + BELLINGERI, observations on gestation in the dog, i. 30; + on the fertility of dogs and cats, ii. 112. + BELON, on high-flying pigeons in Paphlagonia, i. 209; + varieties of the goose, i. 289. + BENGUELA, cattle of, i. 88. + BENNETT, Dr. G., pigs of the Pacific islands, i. 70, 87; + dogs of the Pacific islands, i. 87; + varieties of cultivated plants in Tahiti, ii. 256. + BENNETT, Mr., on the fallow deer, ii. 103. + BENTHAM, G., number and origin of cultivated plants, i. 306; + cereals all cultivated varieties, i. 312; + species of the orange group, i. 334-335; + distinctions of almond and peach, i. 338; + British species of _Rosa_, i. 366; + identity of _Viola lutea_ and _tricolor_, i. 368. + _Berberis vulgaris_, i. 384, ii. 19. + _Berberis Wallichii_, indifference of, to climate, ii. 164. + BERJEAN, on the history of the dog, i. 16, 18. + BERKELEY, G. F., production of hen-cocks in a strain of game-fowls, i. + 253. + BERKELEY, M. J., crossing of varieties of the pea, i. 397; + effect of foreign pollen on grapes, i. 400; + on hybrid plants, ii. 131; + analogy between pollen of highly-cultivated plants and hybrids, ii. + 268; + on Hungarian kidney-beans, ii. 275; + failure of Indian wheat in England, ii. 307; + bud developed on the petal of a _Clarkia_, ii. 384. + BERNARD, inheritance of disease in the horse, ii. 10. + BERNARD, C., independence of the organs of the body, ii. 368-369; + special affinities of the tissues, ii. 380. + BERNHARDI, varieties of plants with laciniated leaves, ii. 348. + _Bernicla antarctica_, i. 288. + BERTERO, on feral pigeons in Juan Fernandez, i. 190. + _Betula alba_, ii. 18. + BEWICK, on the British wild cattle, i. 84. + BIBLE, reference to breeding studs of horses in, i. 54; + references to domestic pigeons in the, i. 205; + indications of selection of sheep in the, ii. 201; + notice of mules in the, ii. 202. + BIDWELL, Mr., on self-impotence in _Amaryllis_, ii. 139. + BIRCH, weeping, i. 387, ii. 18. + BIRCH, Dr. S., on the ancient domestication of the pigeon in Egypt, i. + 205; + notice of bantam fowls in a Japanese encyclopædia, i. 230, 247. + BIRCH, Wyrley, on silver-grey rabbits, i. 109-110. + BIRDS, sterility caused in, by change of conditions, ii. 153-157. + BLADDER-NUT, tendency of the, to become double, ii. 168. + BLAINE, Mr., on wry-legged terriers, ii. 245. + BLAINVILLE, origin and history of the dog, i. 15-16; + variations in the number of teeth in dogs, i. 34; + variations in the number of toes in dogs, i. 35; + on mummies of cats, i. 43; + on the osteology of solid-hoofed pigs, i. 75; + on feral Patagonian and N. American pigs, i. 77. + "BLASS-TAUBE," i. 156. + BLEEDING, hereditary, ii. 7, 8; + sexual limitation of excessive, ii. 73. + BLENDING of crossed races, time occupied by the, ii. 87. + BLINDNESS, hereditary, ii. 9; + at a certain age, ii. 78; + associated with colour of hair, ii. 328. + BLOODHOUNDS, degeneration of, caused by interbreeding, ii. 121. + BLUMENBACH, on the protuberance of the skull in Polish fowls, i. 257; + on the effect of circumcision, ii. 23; + inheritance of a crooked finger, ii. 23; + on badger-dogs and other varieties of the dog, ii. 220; + on _Hydra_, ii. 293; + on the "nisus formativus," ii. 294. + BLYTH, E., on the Pariah dog, i. 24; + hybrids of dog and jackal, i. 32; + early domestication of cats in India, i. 43; + origin of domestic cat, _ib._; + crossing of domestic and wild cats, i. 44; + on Indian cats resembling _Felis chaus_, i. 45; + on striped Burmese ponies, i. 58; + on the stripes of the ass, i. 63; + on Indian wild pigs, i. 66; + on humped cattle, i. 79, 80; + occurrence of _Bos frontosus_ in Irish crannoges, i. 81; + fertile crossing of zebus and common cattle, i. 83; + on the species of sheep, i. 94; + on the fat-tailed Indian sheep, i. 96; + origin of the goat, i. 101; + on rabbits breeding in India, i. 112; + number of tail-feathers in fantails, i. 146; + Lotan tumbler pigeons, i. 150; + number of tail-feathers in _Ectopistes_, i. 159; + on _Columba affinis_, i. 183; + pigeons roosting in trees, i. 181; + on _Columba leuconota_, i. 182; + on _Columba intermedia_ of Strickland, i. 184; + variation in colour of croup in pigeons, i. 184-185, 197; + voluntary domestication of rock-pigeons in India, i. 185; + feral pigeons on the Hudson, i. 190; + {438} + occurrence of sub-species of pigeons, i. 204; + notice of pigeon-fanciers in Delhi, &c., i. 206; + hybrids of _Gallus Sonneratii_ and the domestic hen, i. 234; + supposed hybridity of _Gallus Temminckii_, i. 235; + variations and domestication of _Gallus bankiva_, i. 235-236, 237; + crossing of wild and tame fowls in Burmah, i. 236; + restricted range of the larger gallinaceous birds, i. 237; + feral fowls in the Nicobar islands, i. 238; + black-skinned fowls occurring near Calcutta, i. 256; + weight of _Gallus bankiva_, i. 272; + degeneration of the turkey in India, i. 294, ii. 278; + on the colour of gold-fish, i. 296; + on the Ghor-Khur (_Asinus indicus_), ii. 42; + on _Asinus hemionus_, ii. 43; + number of eggs of _Gallus bankiva_, ii. 112; + on the breeding of birds in captivity, ii. 157; + co-existence of large and small breeds in the same country, ii. 279; + on the drooping ears of the elephant, ii. 301; + homology of leg and wing feathers, ii. 323. + BOETHIUS on Scotch wild cattle, i. 85. + BOITARD and Corbié, on the breeds of pigeons, i. 132; + Lille pouter pigeon, i. 138; + notice of a gliding pigeon, i. 156; + variety of the pouter pigeon, i. 162; + dove-cot pigeon, i. 185; + crossing pigeons, i. 192-193, ii. 97, 126; + sterility of hybrids of turtle-doves, i. 193; + reversion of crossed pigeons, i. 197, ii. 40; + on the fantail, i. 208, ii. 66; + on the trumpeter, ii. 66; + prepotency of transmission in silky fantail, ii. 67, 69; + secondary sexual characters in pigeons, ii. 74; + crossing of white and coloured turtle-doves, ii. 92; + fertility of pigeons, ii. 112. + BOMBYCIDÆ, wingless females of, ii. 299. + _Bombyx hesperus_, ii. 304. + _Bombyx Huttoni_, i. 302. + _Bombyx mori_, i. 300-304. + BONAFOUS, on maize, i. 320, 321. + BONAPARTE, number of species of Columbidæ, i. 133; + number of tail-feathers in pigeons, i. 158; + size of the feet in Columbidæ, i. 174; + on _Columba guinea_, i. 182; + _Columba turricola_, _rupestris_, and _Schimperi_, i. 184. + _Bonatea speciosa_, development of ovary of, i. 403. + BONAVIA, Dr., growth of cauliflowers in India, ii. 310. + BONES, removal of portions of, ii. 296; + regeneration of, ii. 294; + growth and repair of, ii. 381-382. + BONNET, on the salamander, ii. 15, 341, 358, 385; + theory of reproduction, ii. 385. + BORCHMEYER, experiments with the seeds of the weeping ash, ii. 19. + BORECOLE, i. 323. + BORELLI, on Polish fowls, i. 247. + BORNEO, fowls of, with tail-bands, i. 235. + BORNET, E., condition of the ovary in hybrid _Cisti_, i. 389; + self-impotence of hybrid _Cisti_, ii. 140. + BORROW, G., on pointers, i. 42. + BORY de Saint-Vincent, on gold-fish, i. 297. + _Bos_, probable origin of European domestic cattle from three species of, + i. 83. + _Bos frontosus_, i. 79, 81-82. + _Bos indicus_, i. 79. + _Bos longifrons_, i. 79, 81. + _Bos primigenius_, i. 79-81, 119. + _Bos sondaicus_, ii. 206. + _Bos taurus_, i. 79. + _Bos trochoceros_, i. 81. + BOSC, heredity in foliage-varieties of the elm, i. 362. + BOSSE, production of double flowers from old seed, ii. 167. + BOSSI, on breeding dark-coloured silkworms, i. 302. + BOUCHARDAT, on the vine disease, i. 334. + BOUDIN, on local diseases, ii. 276; + resistance to cold of dark-complexioned men, ii. 335. + "BOULANS," i. 137. + "BOUTON d'Alep," ii. 276. + BOWEN, Prof., doubts as to the importance of inheritance, ii. 3. + BOWMAN, Mr., hereditary peculiarities in the human eye, ii. 8-10; + hereditary cataract, ii. 79. + BRACE, Mr., on Hungarian cattle, i. 80. + _Brachycome iberidifolia_, ii. 261. + BRACTS, unusual development of, in gooseberries, i. 355. + BRADLEY, Mr., effect of grafts upon the stock in the ash, i. 394; + effect of foreign pollen upon apples, i. 401; + on change of soil, ii. 146. + "BRAHMA Pootras," a new breed of fowls, i. 245. + BRAIN, proportion of, in hares and rabbits, i. 126-129. + BRANDT, origin of the goat, i. 101. + _Brassica_, varieties of, with enlarged stems, ii. 348. + _Brassica asperifolia_, ii. 343. + _Brassica napus_, i. 325. + _Brassica oleracea_, i. 323. + _Brassica rapa_, i. 325, ii. 165. + BRAUN, A., bud-variation in the vine, i. 375; + in the currant, i. 376; + in _Mirabilis jalapa_, i. 382; + in _Cytisus adami_, i. 388; + on reversion in the foliage of trees, i. 382; + spontaneous production of _Cytisus purpureo-elongatus_, i. 390; + reversion of flowers by stripes and blotches, ii. 37; + excess of nourishment a source of variability, ii. 257. + {439} + BRAZIL, cattle of, i. 88. + BREAD-FRUIT, varieties of, ii. 256; + sterility and variability of, ii. 262. + BREE, W. T., bud-variation in _Geranium pratense_ and _Centaurea cyanus_, + i. 379; + by tubers in the dahlia, i. 385; + on the deafness of white cats with blue eyes, ii. 329. + BREEDING, high, dependent on inheritance, ii. 3-4. + BREEDS, domestic, persistency of, ii. 246, 428-429; + artificial and natural, ii. 413-414; + extinction of, ii. 425; + of domestic cats, i. 45-47; + of pigs produced by crossing, i. 78; + of cattle, i. 86-87, 91-93; + of goats, i. 101. + BREHM, on _Columba amaliæ_, i. 183. + BRENT, B. P., number of mammæ in rabbits, i. 106; + habits of the tumbler pigeon, i. 151; + Laugher pigeon, i. 155; + colouring of the kite tumbler, i. 160; + crossing of the pigeon with _Columba oenas_, i. 193; + mongrels of the trumpeter pigeon, ii. 66; + close interbreeding of pigeons, ii. 126; + opinion on Aldrovandi's fowls, i. 247; + on stripes in chickens, i. 249-250; + on the combs of fowls, i. 253; + double-spurred Dorking fowls, i. 255; + effect of crossing on colour of plumage in fowls, i. 258; + incubatory instinct of mongrels between non-sitting varieties of fowls, + ii. 44; + origin of the domestic duck, i. 277; + fertility of the hook-billed duck, _ibid._; + occurrence of the plumage of the wild duck in domestic breeds, i. 280; + voice of ducks, i. 281; + occurrence of a short upper mandible in crosses of hook-billed and + common ducks, i. 281; + reversion in ducks produced by crossing, ii. 40; + variation of the canary-bird, i. 295; + fashion in the canary, ii. 240; + hybrids of canary and finches, ii. 45. + BRICKELL, on raising nectarines from seed, i. 340; + on the horses of North Carolina, ii. 300. + BRIDGES, Mr., on the dogs of Tierra del Fuego, i. 39; + on the selection of dogs by the Fuegians, ii. 207. + BRIDGMAN, W. K., reproduction of abnormal ferns, i. 383, ii. 379. + BRIGGS, J. J., regeneration of portions of the fins of fishes, ii. 15. + BROCA, P., on the intercrossing of dogs, i. 31-32; + on hybrids of hare and rabbit, i. 105; + on the rumpless fowl, i. 259; + on the character of half-castes, ii. 47; + degree of fertility of mongrels, ii. 100; + sterility of descendants of wild animals bred in captivity, ii. 160. + BROCCOLI, i. 323; + rudimentary flowers in, ii. 316; + tenderness of, ii. 310. + BROMEHEAD, W., doubling of the Canterbury bell by selection, ii. 200. + BROMFIELD, Dr., sterility of the ivy and _Acorus calamus_, ii. 170. + _Bromus secalinus_, i. 314. + BRONN, H. G., bud-variation in _Anthemis_, i. 379; + effects of cross-breeding on the female, i. 404; + on heredity in a one-horned cow, ii. 12, 13; + propagation of a pendulous peach by seed, ii. 18; + absorption of the minority in crossed races, ii. 88; + on the crossing of horses, ii. 92; + fertility of tame rabbits and sheep, ii. 112; + changes of plumage in captivity, ii. 158; + on the dahlia, ii. 261. + BRONZE period, dog of, i. 18. + BROWN, G., variations in the dentition of the horse, i. 50. + BROWN-SÉQUARD, Dr., inheritance of artificially-produced epilepsy in the + guinea-pig, ii. 24. + _Brunswigia_, ii. 139. + BRUSSELS Sprouts, i. 323, ii. 429. + _Bubo maximus_, ii. 154. + BUCKLAND, F., on oysters, ii. 280; + number of eggs in a codfish, ii. 379. + BUCKLE, Mr., doubts as to the importance of inheritance, ii. 3. + BUCKLEY, Miss, carrier-pigeons roosting in trees, i. 181. + BUCKMAN, Prof., cultivation of _Avena fatua_, i. 313; + cultivation of the wild parsnip, i. 326, ii. 201, 277; + reversion in the parsnip, ii. 31. + BUCKWHEAT, injurious to white pigs, when in flower, ii. 337. + BUD and seed, close analogy of, i. 411. + BUD-REVERSION, ii. 37. + BUDS, adventitious, ii. 384. + BUD-VARIATION, i. 373-411, ii. 254, 287-288, 291; + contrasted with seminal reproduction, i. 373; + peculiar to plants, i. 374; + in the peach, i. 340, 374; + in plums, i. 375; + in the cherry, _ibid._; + in grapes, _ibid._; + in the gooseberry, currant, pear, and apple, i. 376; + in the banana, camellia, hawthorn, _Azalea indica_, and _Cistus + tricuspis_, i. 377; + in the hollyhock and pelargonium, i. 378; + in _Geranium pratense_ and the chrysanthemum, i. 379; + in roses, i. 367, 379-381; + in sweet williams, carnations, pinks, stocks, and snapdragons, i. 381; + in wall-flowers, cyclamen, _Oenothera biennis_, _Gladiolus colvillii_, + fuchsias, and _Mirabilis jalapa_, i. 382; + in foliage of various trees, i. 382-384; + in cryptogamic plants, i. 383; + by suckers in _Phlox_ and barberry, i. 384; + by tubers in the potato, _ibid._; + in the dahlia, i. 385; + by bulbs in hyacinths, _Imatophyllum miniatum_, and tulips, i. 385; + in _Tigridia conchiflora_, i. 386; + {440} + in _Hemerocallis_, _ibid._; + doubtful cases, i. 386-387; + in _Cytisus Adami_, i. 387-394; + probable in _Æsculus rubicunda_, i. 392; + summary of observations on, 406. + BUFFON, on crossing the wolf and dog, i. 32; + increase of fertility by domestication, ii. 111; + improvement of plants by unconscious selection, ii. 216; + theory of reproduction, ii. 375. + _Bulimus_, ii. 53. + BULL, apparent influence of, on offspring, ii. 68. + BULLACE, i. 345. + BULLDOG, recent modifications of, i. 42. + BULLFINCH, breeding in captivity, ii. 154; + attacking flower-buds, ii. 232. + BULT, Mr., selection of pouter pigeons, ii. 197. + "BÜNDTNERSCHWEIN," i. 67. + BUNTING, reed, in captivity, ii. 158. + BURDACH, crossing of domestic and wild animals, i. 66; + aversion of the wild boar to barley, ii. 303. + BURKE, Mr., inheritance in the horse, ii. 10. + _Burlingtonia_, ii. 135. + BURMAH, cats of, i. 47. + BURMESE ponies, striped, i. 58, 59. + BURNES, Sir A., on the Karakool sheep, i. 98, ii. 278; + varieties of the vine in Cabool, i. 333; + hawks, trained in Scinde, ii. 153; + pomegranates producing seed, ii. 168. + BURTON Constable, wild cattle at, i. 84. + "BURZEL-TAUBEN," i. 150. + BUSSORAH carrier, i. 141. + _Buteo vulgaris_, copulation of, in captivity, ii. 154. + BUTTERFLIES, polymorphic, ii. 399-400. + BUZAREINGUES, Girou de, inheritance of tricks, ii. 6. + + CABANIS, pears grafted on the quince, ii. 239. + CABBAGE, i. 323-326; + varieties of, i. 323; + unity of character in flowers and seeds of, i. 323-324; + cultivated by ancient Celts, i. 324; + classification of varieties of, _ibid._; + ready crossing of, _ibid._, ii. 90, 91, 98, 130; + origin of, i. 325; + increased fertility of, when cultivated, ii. 113; + growth of, in tropical countries, ii. 277. + CABOOL, vines of, i. 333. + CABRAL, on early cultivation in Brazil, i. 311. + CACTUS, growth of cochineal on, in India, ii. 275. + CÆSAR, _Bos primigenius_ wild in Europe in the time of, i. 81; + notice of fowls in Britain, i. 246; + notice of the importation of horses by the Celts, ii. 203. + CAFFRE fowls, i. 230. + CAFFRES, different kinds of cattle possessed by the, i. 88. + "CÁGIAS," a breed of sheep, i. 95. + CALCEOLARIAS, i. 364; ii. 147; + effects of seasonal conditions on, ii. 274; + peloric flowers in, ii. 346. + "CALONGOS," a Columbian breed of cattle, i. 88. + CALVER, Mr., on a seedling peach producing both peaches and nectarines, + i. 341. + CALYX, segments of the, converted into carpels, ii. 392. + CAMEL, its dislike to crossing water, i. 181. + _Camellia_, bud-variations in, i. 377; + recognition of varieties of, ii. 251; + variety in, hardiness of, ii. 308. + CAMERON, D., on the cultivation of Alpine plants, ii. 163. + CAMERONN, Baron, value of English blood in race-horses, ii. 11. + _Campanula medium_, ii. 200. + CANARY-BIRD, i. 295; + conditions of inheritance in, ii. 22; + hybrids of, ii. 45; + period of perfect plumage in, ii. 77; + diminished fertility of, ii. 161; + standard of perfection in, ii. 195; + analogous variation in, ii. 349. + CANCER, heredity of, ii. 7, 8, 79. + CANINE teeth, development of the, in mares, ii. 318. + _Canis alopex_, i. 29. + _Canis antarcticus_, i. 20. + _Canis argentatus_, ii. 151. + _Canis aureus_, i. 29. + _Canis cancrivorus_, domesticated and crossed in Guiana, i. 23. + _Canis cinereo-variegatus_, i. 29. + _Canis fulvus_, i. 29. + _Canis Ingæ_, the naked Peruvian dog, i. 23. + _Canis latrans_, resemblance of, to the Hare Indian dog, i. 22; + one of the original stocks, i. 26. + _Canis lupaster_, i. 25. + _Canis lupus_, var. _occidentalis_, resemblance of, to North American + dogs, i. 21; + crossed with dogs, i. 22; + one of the original stocks, i. 26. + _Canis mesomelas_, i. 25, 29. + _Canis primævus_, tamed by Mr. Hodgson, i. 26. + _Canis sabbar_, i. 25. + _Canis simensis_, possible original of greyhounds, i. 33. + _Canis thaleb_, i. 29. + _Canis variegatus_, i. 29. + CANTERBURY Bell, doubled by selection, ii. 200. + CAPE of Good Hope, different kinds of cattle at the, i. 88; + {441} + no useful plants derived from the, i. 310. + CAPERCAILZIE, breeding in captivity, ii. 156. + _Capra ægagrus_ and _C. Falconeri_, probable parents of domestic goat, i. + 101. + CAPSICUM, i. 371. + CARDAN, on a variety of the walnut, i. 356; + on grafted walnuts, ii. 259-260. + CARDOON, ii. 34. + _Carex rigida_, local sterility of the, ii. 170. + CARLIER, early selection of sheep, ii. 204. + CARLISLE, Sir A., inheritance of peculiarities, ii. 6, 8; + of polydactylism, ii. 13. + "CARME" pigeon, i. 156. + CARNATION, bud-variation in, i. 381; + variability of, i. 370; + striped, produced by crossing red and white, i. 393; + effect of conditions of life on the, ii. 273. + CARNIVORA, general fertility of, in captivity, ii. 150. + CAROLINE Archipelago, cats of, i. 47. + CARP, ii. 236. + CARPELS, variation of, in cultivated cucurbitaceæ, i. 359. + CARPENTER, W. B., regeneration of bone, ii. 294; + production of double monsters, ii. 340; + number of eggs in an _Ascaris_, ii. 379. + _Carpinus betulus_, i. 362. + _Carpophaga littoralis_ and _luctuosa_, i. 182. + CARRIER pigeon, i. 139-142; + English, i. 139-141; + figured, i. 140; + skull figured, i. 163; + history of the, i. 211; + Persian, i. 141; + Bussorah, _ibid._; + Bagadotten, skull figured, i. 163; + lower jaw figured, i. 165. + CARRIÈRE, cultivation of the wild carrot, i. 326; + intermediate form between the almond and the peach, i. 338; + glands of peach-leaves, i. 343; + bud-variation in the vine, i. 375; + grafts of _Aria vestita_ upon thorns, i. 387; + variability of hybrids of _Erythrina_, ii. 265. + CARROT, wild, effects of cultivation on the, i. 326; + reversion in the, ii. 31; + run wild, ii. 33; + increased fertility of cultivated, ii. 113; + experiments on the, ii. 277; + acclimatisation of the, in India, ii. 311. + _Carthamus_, abortion of the pappus in, ii. 316. + CARTIER, cultivation of native plants in Canada, i. 312. + CARYOPHYLLACEÆ, frequency of contabescence in the, ii. 165. + CASPARY, bud-variation in the moss-rose, i. 380; + on the ovules and pollen of _Cytisus_, i. 388-389; + crossing of _Cytisus purpureus_ and _C. laburnum_, i. 389; + trifacial orange, i. 391; + differently-coloured flowers in the wild _Viola lutea,_ i. 408; + sterility of the horse-radish, ii. 170. + CASTELNAU, on Brazilian cattle, i. 88. + CASTRATION, assumption of female characters caused by, ii. 51-52. + _Casuarius bennettii_, ii. 156. + CAT, domestic, i. 43-48; + early domestication and probable origin of the, i. 43-44; + intercrossing of with wild species, i. 44-45; + variations of, i. 45-48; + feral, i. 47, ii. 33; + anomalous, i. 48; + polydactylism in, ii. 14; + black, indications of stripes in young, ii. 55; + tortoiseshell, ii. 73; + effects of crossing in, ii. 86; + fertility of, ii. 111; + difficulty of selection in, ii. 234, 236; + length of intestines in, ii. 302; + white with blue eyes, deafness of, ii. 329; + with tufted ears, ii. 350. + CATARACT, hereditary, ii. 9, 79. + CATERPILLARS, effect of changed food on, ii. 280. + CATLIN, G., colour of feral horses in North America, i. 61. + CATTLE, European, their probable origin from three original species, i. + 79-82; + humped, or Zebus, i. 79-80; + intercrossing of, i. 83, 91-93; + wild, of Chillingham, Hamilton, Chartley, Burton Constable, and + Gisburne, i. 84, ii. 119; + colour of feral, i. 84-85, ii. 102; + British breeds of, i. 86-87; + South African breeds of, i. 88; + South American breeds of, i. 89, ii. 205; + Niata, i. 89-91, ii. 205, 208, 332; + effects of food and climate on, i. 91-92; + effects of selection on, i. 92-93; + Dutch-buttocked, ii. 8; + hornless, production of horns in, ii. 29-30, 39; + reversion in, when crossed, ii. 41; + wildness of hybrid, ii. 45; + short-horned, prepotency of, ii. 65; + wild, influence of crossing and segregation on, ii. 86; + crosses of, ii. 96, 104, 118; + of Falkland islands, ii. 102; + mutual fertility of all varieties of, ii. 110; + effects of interbreeding on, ii. 117-119; + effects of careful selection on, ii. 194, 199; + naked, of Columbia, ii. 205; + crossed with wild banteng in Java, ii. 206; + with reversed hair in Banda Oriental, ii. 205; + selection of trifling characters in, ii. 209; + fashion in, ii. 210; + similarity of best races of, ii. 241; + unconscious selection in, ii. 214; + effects of natural selection on anomalous breeds of, ii. 226-227; + light-coloured, attacked by flies, ii. 229, 336; + Jersey, rapid improvement of, ii. 234; + effects of disuse of parts in, ii. 299; + rudimentary horns in, ii. 315; + supposed influence of humidity on the hair of, ii. 326; + {442} + white spots of, liable to disease, ii. 337; + supposed analogous variation in, ii. 349; + displacement of long-horned by short-horned, ii. 426. + CAULIFLOWER, i. 323; + free-seeding of, in India, ii. 310; + rudimentary flowers in, ii. 316. + CAVALIER pigeon, ii. 97. + _Cavia aperea_, ii. 152. + CAY (_Cebus azaræ_), sterility of, in confinement, ii. 153. + _Cebus azaræ_, ii. 153. + _Cecidomyia_, larval development of, ii. 283, 360, 367; + and _Misocampus_, i. 5. + CEDARS of Lebanon and Atlas, i. 364. + CELERY, turnip-rooted, i. 336; + run wild, ii. 33. + CELL-THEORY, ii. 370. + _Celosia cristata_, i. 365. + CELSUS, on the selection of seed-corn, i. 318, ii. 203. + CELTS, early cultivation of the cabbage by the, i. 324; + selection of cattle and horses by the, ii. 202-203. + _Cenchrus_, seeds of a, used as food, i. 309. + _Centaurea cyanus_, bud-variation in, i. 379. + CEPHALOPODA, spermatophores of, ii. 383. + _Cerasus padus_, yellow-fruited, ii. 19. + _Cercoleptes_, sterility of, in captivity, ii. 152. + _Cercopithecus_, breeding of a species of, in captivity, ii. 153. + CEREALS, i. 312-313; + of the Neolithic period in Switzerland, i. 317; + adaptation of, to soils, ii. 305. + _Cereus_, ii. 38. + _Cereus speciosissimus_ and _phyllanthus_, reversion in hybrids of, i. + 392. + _Cervus canadensis_, ii. 158. + _Cervus dama_, ii. 120. + CETACEA, correlation of dermal system and teeth in the, ii. 328. + CEYLON, cats of, i. 46; + pigeon-fancying in, i. 206. + _Chamærops humilis_, crossed with date palm, i. 399. + CHAMISSO, on seeding bread-fruit, ii. 168. + CHANNEL islands, breeds of cattle in, i. 80. + CHAPMAN, Professor, peach-trees producing nectarines, i. 341. + CHAPUIS, F., sexual peculiarities in pigeons, i. 162, ii. 74; + effect produced by first male upon the subsequent progeny of the + female, i. 405; + sterility of the union of some pigeons, ii. 162. + CHARACTERS, fixity of, ii. 239; + latent, ii. 51-56, 399-400; + continued divergence of, ii. 241; + antagonistic, ii. 401. + CHARDIN, abundance of pigeons in Persia, i. 205. + CHARLEMAGNE, orders as to the selection of stallions, ii. 203. + CHARTLEY, wild cattle of, i. 84. + CHATÉ, reversion of the upper seeds in the pods of stocks, ii. 347-348. + CHATIN, on _Ranunculus ficaria_, ii. 170. + CHAUNDY, Mr., crossed varieties of cabbage, ii. 130. + CHEETAH, general sterility of, in captivity, ii. 151. + _Cheiranthus cheiri_, i. 382. + CHERRIES, i. 347-348; + bud-variation in, i. 375; + white Tartarian, ii. 230; + variety of, with curled petals, ii. 232; + period of vegetation of, changed by forcing, ii. 311. + CHEVREUL, on crossing fruit-trees, ii. 129. + CHICKENS, differences in characters of, i. 249-250; + white, liable to gapes, ii. 228, 336. + CHIGOE, ii. 275. + CHILE, sheep of, i. 95. + CHILLINGHAM cattle, identical with _Bos primigenius_, i. 81; + characters of, i. 83-84. + CHILOE, half-castes of, ii. 46. + CHINA, cats of, with drooping ears, i. 47; + horses of, i. 53; + striped ponies of, i. 59; + asses of, i. 62; + notice of rabbits in, by Confucius, i. 103; + breeds of pigeons reared in, i. 206; + breeds of fowls of, in fifteenth century, i. 232, 247; + goose of, i. 237. + CHINCHILLA, fertility of, in captivity, ii. 152. + CHINESE, selection practised by the, ii. 204-205; + preference of the, for hornless rams, ii. 209; + recognition of the value of native breeds by the, ii. 313. + CHINESE, or Himalayan rabbit, i. 108. + "CHIVOS," a breed of cattle in Paraguay, i. 89. + CHOUX-RAVES, i. 323. + CHRIST, H., on the plants of the Swiss Lake-dwellings, i. 309, 318; + intermediate forms between _Pinus sylvestris_ and _montana_, i. 363. + CHRYSANTHEMUM, i. 379. + _Chrysotis festiva_, ii. 280. + CINERARIA, effects of selection on the, ii. 200. + CIRCASSIA, horses of, ii. 102. + CIRCUMCISION, ii. 23. + CIRRIPEDES, metagenesis in, ii. 366. + _Cistus_, intercrossing and hybrids of, i. 336, 389, ii. 140. + _Cistus tricuspis_, bud-variation in, i. 377. + CITRONS, i. 334-335. + "_Citrus aurantium fructu variabili_," i. 336. + _Citrus decumana_, i. 335. + _Citrus lemonum_, i. 336. + {443} + _Citrus medica_, i. 335-336. + CLEFT palate, inheritance of, ii. 24. + CLEMENTE, on wild vines in Spain, i. 332. + CLERMONT-TONNERRE, on the St. Valery apple, i. 401. + CLAPHAM, A., bud-variation in the hawthorn, i. 377. + "CLAQUANT," i. 138. + "CLAQUERS" (pigeons), i. 156. + CLARK, G., on the wild dogs of Juan de Nova, i. 27; + on striped Burmese and Javanese ponies, i. 59; + breeds of goats imported into the Mauritius, i. 101; + variations in the mammæ of goats, i. 102; + bilobed scrotum of Muscat goat, _ibid._ + CLARK, H. J., on fission and gemmation, ii. 359. + CLARKE, R. T., intercrossing of strawberries, i. 352. + CLARKE, T., hybridisation of stocks, i. 399, ii. 93. + CLARKSON, Mr., prize-cultivation of the gooseberry, i. 355. + CLASSIFICATION, explained by the theory of natural selection, i. 11. + CLIMATE, effect of, upon breeds of dogs, i. 37; + on horses, i. 52, 53; + on cattle, i. 91, 92; + on the fleece of sheep, i. 98, 99; + on seeds of wheat, i. 316; + on cultivated cabbages, i. 325; + adaptation of maize to, i. 322. + CLIMATE and pasture, adaptation of breeds of sheep to, i. 96-97. + CLIMATE and soil, effects of, upon strawberries, i. 353. + CLINE, Mr., on the skull in horned and hornless rams, ii. 333. + CLOS, on sterility in _Ranunculus ficaria_, ii. 170. + CLOTZSCH, hybrids of various trees, ii. 130. + CLOVER, pelorism in, ii. 340. + COATE, Mr., on interbreeding pigs, ii. 122. + COCCUS of apple trees, ii. 231. + COCHIN fowls, i. 227, 250, 252, 260-261; + occipital foramen of, figured, i. 261; + section of skull of, figured, i. 263; + cervical vertebra of, figured, i. 267. + COCHINEAL, persistence of, ii. 236; + preference of, for a particular cactus, ii. 275. + _Cochlearia armoracia_, ii. 170. + COCK, game, natural selection in, ii. 225; + spur of, grafted on the comb, ii. 296; + spur of, inserted into the eye of an ox, ii. 369; + effect of castration upon the, ii. 51-52. + COCK'S-COMB, varieties of the, i. 365. + COCOONS, of silkworms, variations in, i. 302-303. + CODFISH, bulldog, i. 89; + number of eggs in the, ii. 379. + _Coelogenys paca_, ii. 152. + COLIN, prepotency of the ass over the horse, ii. 67-68; + on cross-breeding, ii. 97; + on change of diet, ii. 304. + COLLINSON, Peter, peach-tree producing a nectarine, i. 340. + COLORATION, in pigeons, an evidence of unity of descent, i. 195-197. + COLOUR, correlation of, in dogs, i. 28-29; + persistence of, in horses, i. 50; + inheritance and diversity of, in horses, i. 55; + variations of, in the ass, i. 62-63; + of wild or feral cattle, i. 85; + transmission of, in rabbits, i. 107; + peculiarities of, in Himalayan rabbits, i. 111; + influence of, ii. 227-230; + correlation of, in head and limbs, ii. 324; + correlated with constitutional peculiarities, ii. 335-338. + COLOUR and odour, correlation of, ii. 325. + COLOUR-BLINDNESS, hereditary, ii. 9; + more common in men than in women, ii. 72-73; + associated with inability to distinguish musical sounds, ii. 328. + COLOURS, sometimes not blended by crossing, ii. 92. + _Columba affinis_, Blyth, a variety of _C. livia_, i. 183. + _Columba amaliæ_, Brehm, a variety of _C. livia_, i. 183. + _Columba guinea_, i. 182. + _Columba gymnocyclus_, Gray, a form of _C. livia_, i. 184. + _Columba gymnophthalmos_, hybrids of, with _C. oenas_, i. 193; + with _C. maculosa_, i. 194. + _Columba intermedia_, Strickland, a variety of _C. livia_, i. 184. + _Columba leucocephala_, ii. 155. + _Columba leuconota_, i. 182, 195. + _Columba littoralis_, i. 182. + _Columba livia_, ii. 29, 40; + the parent of domestic breeds of pigeons, i. 183; + measurements of, i. 134; + figured, i. 135; + skull figured, i. 163; + lower jaw figured, i. 164, 168; + scapula figured, i. 167. + _Columba luctuosa_, i. 182. + _Columba migratoria_ and _leucocephala_, diminished fertility of, in + captivity, ii. 155. + _Columba oenas_, i. 183; + crossed with common pigeon and _C. gymnophthalmos_, i. 193. + _Columba palumbus_, i. 193, ii. 350. + _Columba rupestris_, i. 182, 184, 195. + _Columba Schimperi_, i. 184. + _Columba torquatrix_, ii. 350. + _Columba turricola_, i. 184. + COLUMBIA, cattle of, i. 88. + COLUMBINE, double, i. 365, ii. 330. + {444} + COLUMBUS, on West Indian dogs, i. 23. + COLUMELLA, on Italian shepherd's dogs, i. 23; + on domestic fowls, i. 231, 247, ii. 202, 429; + on the keeping of ducks, i. 277; + on the selection of seed-corn, i. 318; + on the benefits of change of soil to plants, ii. 146; + on the value of native breeds, ii. 313. + COLZA, i. 325. + COMB, in fowls, variations of, i. 253-254; + sometimes rudimentary, ii. 315. + COMPENSATION, law of, i. 274. + COMPENSATION of growth, ii. 342-344. + COMPLEXION, connexion of, with constitution, ii. 335. + COMPOSITÆ, double flowers of, i. 365, ii. 167, 316. + CONCEPTION, earlier in Alderney and Zetland cows than in other breeds, i. + 87. + CONDITIONS of life, changed, effect of, ii. 418-419; + on horses, i. 52; + upon variation in pigeons, i. 212-213; + upon wheat, i. 315-316; + upon trees, i. 361; + in producing bud-variation, i. 408; + advantages of, ii. 145-148, 176-177; + sterility caused by, ii. 148-165; + conducive to variability, ii. 255-261, 394; + accumulative action of, ii. 261-263; + direct action of, ii. 271-292. + CONDOR, breeding in captivity, ii. 154. + CONFINEMENT, effect of, upon the cock, ii. 52. + CONFUCIUS, on the breeding of rabbits in China, i. 103. + CONOLLY, Mr., on Angora goats, ii. 326. + CONSTITUTIONAL differences in sheep, i. 96-97; + in varieties of apples, i. 349-350; + in pelargoniums, i. 364; + in dahlias, i. 370. + CONSTITUTIONAL peculiarities in strawberries, i. 353; + in roses, i. 367. + CONSUMPTION, hereditary, ii. 8; + period of appearance of, ii. 77; + correlated with complexion, ii. 335. + CONTABESCENCE, ii. 165-166. + _Convolvulus batatas_, ii. 169, 309. + _Convolvulus tricolor_, bud-variation in, i. 408. + COOPER, Mr., improvement of vegetables by selection, ii. 204. + COOPER, White, hereditary peculiarities of vision, ii. 9; + association of affections of the eyes with those of other systems, ii. + 328. + CORALS, bud-variation in, i. 374; + non-diffusion of cell-gemmules in, ii. 379. + CORBIÉ. _See_ Boitard. + CORNEA, opacity of, inherited, ii. 9. + _Cornus mascula_, yellow-fruited, ii. 19. + CORRELATION, ii. 319; + of neighbouring parts, ii. 320; + of change in the whole body and in some of its parts, ii. 321; + of homologous parts, ii. 322-331; + inexplicable, ii. 331-333; + commingling of, with the effects of other agencies, ii. 333-335. + CORRELATION of skull and limbs in swine, i. 73; + of tusks and bristles in swine, i. 76; + of multiplicity of horns and coarseness of wool in sheep, i. 95; + of beak and feet in pigeons, i. 172-173; + between nestling down and colour of plumage in pigeons, i. 194; + of changes in silkworms, i. 304; + in plants, ii. 219; + in maize, i. 323; + in pigeons, i. 167-171, 218; + in fowls, i. 274-275. + CORRESPONDING periods, inheritance at, ii. 75-80. + CORRIENTES, dwarf cattle of, i. 89. + CORRINGHAM, Mr., influence of selection on pigs, ii. 198. + CORSICA, ponies of, i. 52. + "CORTBECK" (pigeon) of Aldrovandi, i. 209. + _Corvus corone_ and _C. cornix_, hybrids of, ii. 94. + _Corydalis_, flower of, ii. 304. + _Corydalis cava_, ii. 132-133. + _Corydalis solida_, sterile when peloric, ii. 167. + _Corydalis tuberosa_, peloric by reversion, ii. 58-59. + _Corylus avellana_, i. 357. + COSTA, A., on shells transferred from England to the Mediterranean, ii. + 280. + "COUVE TRONCHUDA," i. 323. + COW, inheritance of loss of one horn in the, ii. 12, 23; + amount of milk furnished by the, ii. 300; + development of six mammæ in, ii. 317. + COWSLIP, ii. 21, 182. + CRACIDÆ, sterility of the, in captivity, ii. 156. + CRANES, fertility of, in captivity, ii. 156. + _Cratægus oxyacantha_, i. 363, ii. 18, 232, 258, 377. + _Cratægus monogyna_, i. 364. + _Cratægus sibirica_, i. 364. + CRAWFURD, J., Malasian cats, i. 47; + horses of the Malay Archipelago, i. 49; + horses of Japan, i. 53; + occurrence of stripes in young wild pigs of Malacca, i. 76; + on a Burmese hairy family with deficient teeth, ii. 77, 327; + Japanese origin of the bantam, i. 230; + game fowls of the Philippine islands, i. 232; + hybrids of _Gallus varius_ and domestic fowl, i. 234; + domestication of _Gallus bankiva_, i. 236; + feral fowls in the Pellew islands, i. 238; + history of the fowl, i. 246; + history of the domestic duck, i. 277; + domestication of the goose, i. 287; + cultivated plants of New Zealand, i. 312; + {445} + breeding of tame elephants in Ava, ii. 150; + sterility of _Goura coronata_ in confinement, ii. 155; + geese of the Philippine islands, ii. 162. + CREEPERS, a breed of fowls, i. 230. + CRESTED fowl, i. 227; + figured, i. 229. + "CRÈVE-COEUR," a French sub-breed of fowls, i. 229. + CRISP, Dr., on the brains of the hare and rabbit, i. 126. + CROCKER, C. W., singular form of _Begonia frigida_, i. 365-366, ii. 166; + sterility in _Ranunculus ficaria_, ii. 170. + CROCUS, ii. 165. + CROSS-BREEDING, permanent effect of, on the female, i. 404. + CROSSING, ii. 85-144, 173-192; + a cause of uniformity, ii. 85-90, 173; + occurs in all organised beings, ii. 90-92; + some characters not blended by, ii. 92-95, 173; + modifications and new races produced by, ii. 95-99; + causes which check, ii. 100-109; + domestication and cultivation favourable to, ii. 109-113, 189; + beneficial effects of, ii. 114-131, 174-176; + necessary in some plants, ii. 131-140, 175-176, 423; + summary of subject of, ii. 140-144; + of dogs with wolves in North America, i. 21-22; + with _Canis cancrivorus_ in Guiana, i. 23; + of dog with wolf, described by Pliny and others, i. 24; + characters furnished by, brought out by reversion in the progeny, ii. + 34-36; + a direct cause of reversion, ii. 39-47, 48; + a cause of variability, ii. 264-267. + CRUSTACEA, macrourous, differences in the development of the, ii. 368. + CRUSTACEAN with an antenna-like development of the eye-peduncle, ii. 391. + CRYPTOGAMIC plants, bud-variation in, i. 383. + CUBA, wild dogs of, i. 27. + "CUCKOO," sub-breeds of fowls, i. 244. + CUCUMBER, variation in number of carpels of, i. 359; + supposed crossing of varieties of the, i. 400. + _Cucumis momordica_, i. 360. + _Cucumis sativa_, i. 359. + _Cucurbita_, dwarf, correlation of leaves in, ii. 330. + _Cucurbita maxima_, i. 357, 359. + _Cucurbita moschata_, i. 357, 359. + _Cucurbita pepo_, i. 357, ii. 108; + varieties of, i. 358; + relation in size and number of fruit of, ii. 343. + CUCURBITACEÆ, i. 357-360; + supposed crossing of, i. 399; + Naudin's observations on hybrids of, ii. 172; + acclimatisation of, ii. 313. + "CULBUTANTS" (pigeons), i. 150. + CULTIVATION of plants, origin of, among savages, i. 309-310; + fertility increased by, ii. 111-113. + CUNIER, on hereditary night-blindness, ii. 9. + CURRANTS, of Tierra del Fuego, i. 309; + bud-variation in, i. 376. + CURTIS, Mr., bud-variation in the rose, i. 381. + CUVIER, on the gestation of the wolf, i. 29; + the odour of the jackal, an obstacle to domestication, i. 30; + differences of the skull in dogs, i. 34; + external characters of dogs, i. 35; + elongation of the intestines in domestic pigs, i. 73, ii. 303; + fertility of the hook-billed duck, i. 277; + number of digits, ii. 13; + hybrid of ass and zebra, ii. 42; + breeding of animals in the Jardin des Plantes, ii. 149; + sterility of predaceous birds in captivity, ii. 154; + facility of hybridisation in confinement, ii. 160. + CYANOSIS, affection of fingers in, ii. 332. + CYCLAMEN, bud-variation in, i. 382. + _Cynara cardunculus_, ii. 34. + _Cynips fecundatrix_, ii. 283. + _Cynocephalus hamadryas_, ii. 153. + _Cyprinus auratus_, i. 296-297. + _Cyrtanthus_, ii. 139. + _Cyrtopodium_, ii. 134. + _Cytisus Adami_, ii. 364; + its bud-variation, i. 387-389, 406, ii. 37; + seedlings from, i. 388; + different views of its origin, i. 389-390; + experiments in crossing _C. purpureus_ and _laburnum_ to produce, i. + 389; + its production by M. Adam, i. 390; + discussion of origin of, i. 396. + _Cytisus alpino-laburnum_, ovules and pollen of, i. 389; + origin of, i. 390. + _Cytisus alpinus_, i. 388. + _Cytisus laburnum_, i. 387, 389, 390, 396. + _Cytisus purpureo-elongatus_, ovules and pollen of, i. 389; + production of, i. 390. + _Cytisus purpureus_, i. 387, 388, 389, 390, 396. + + DAHLBOM, effects of food on hymenoptera, ii. 281. + DAHLIA, i. 369-370, ii. 147; + bud-variation by tubers in the, i. 385; + improvement of, by selection, ii. 216; + steps in cultivation of, ii. 261; + effect of conditions of life on, ii. 273; + correlation of form and colour in, ii. 331. + DAISY, hen and chicken, i. 365; + Swan River, ii. 261. + DALBRET, varieties of wheat, i. 314. + DALIBERT, changes in the odours of plants, ii. 274. + DALLY, Dr., on consanguineous marriages, ii. 122. + DALTONISM, hereditary, ii. 9. + DAMARAS, cattle of, i. 88, ii. 207-208. + {446} + DAMSON, i. 347. + DANDOLO, Count, on silkworms, i. 301. + DANIELL, fertility of English dogs in Sierra Leone, ii. 161. + DANISH Middens, remains of dogs in, i. 18. + DAPPLING in horses, asses, and hybrids, i. 55. + DARESTE. C., on the skull of the Polish fowl, i. 262; + on the production of monstrous chickens, ii. 289; + co-existence of anomalies, ii. 331; + production of double monsters, ii. 340. + DARVILL, Mr., heredity of good qualities in horses, ii. 11. + DARWIN, C., on _Lepus magellanicus_, i. 112; + on the wild potato, i. 330; + dimorphism in the polyanthus and primrose, ii. 21. + DARWIN, Dr., improvement of vegetables by selection, ii. 204. + DARWIN, Sir F., wildness of crossed pigs, ii. 45. + D'ASSO, monogynous condition of the hawthorn in Spain, i. 364. + _Dasyprocta aguti_, ii. 152. + Date-palm, varieties of the, ii. 256; + effect of pollen of, upon the fruit of _Chamærops_, i. 299. + _Datura_, ii. 38; + variability in, ii. 266. + _Datura lævis_ and _stramonium_, reversion in hybrids of, i. 392. + _Datura stramonium_, ii. 67. + DAUBENTON, variations in the number of mammæ in dogs, i. 35; + proportions of intestines in wild and domestic cats, i. 48, ii. 302. + DAUDIN, on white rabbits, ii. 230. + DAVY, Dr., on sheep in the West Indies, i. 98. + DAWKINS and Sandford, early domestication of _Bos longifrons_ in Britain, + i. 81. + DEAF-MUTES, non-heredity of, ii. 22. + DEAFNESS, inheritance of, ii. 78. + DEBY, wild hybrids of common and musk ducks, ii. 46. + DE CANDOLLE, Alph., number and origin of cultivated plants, i. 306-307, + 371; + regions which have furnished no useful plants, i. 310; + wild wheat, i. 312-313; + wild rye and oats, i. 313; + antiquity of varieties of wheat, i. 316; + apparent inefficacy of selection in wheat, i. 318; + origin and cultivation of maize, i. 320, ii. 307; + colours of seeds of maize, i. 321; + varieties and origin of the cabbage, i. 324-325; + origin of the garden-pea, i. 326; + on the vine, i. 332, ii. 308; + cultivated species of the orange group, i. 335; + probable Chinese origin of the peach, i. 337; + on the peach and nectarine, i. 340, 342; + varieties of the peach, i. 342; + origin of the apricot, i. 344; + origin and varieties of the plum, i. 345; + origin of the cherry, i. 347; + varieties of the gooseberry, i. 354; + selection practised with forest-trees, i. 361; + wild fastigate oak, i. 361; + dark-leaved varieties of trees, i. 362; + conversion of stamens into pistils in the poppy, i. 365; + variegated foliage, i. 366; + heredity of white hyacinths, i. 371, ii. 20; + changes in oaks dependent on age, i. 387; + inheritance of anomalous characters, ii. 19; + variation of plants in their native countries, ii. 256; + deciduous bushes becoming evergreen in hot climates, ii. 305; + antiquity of races of plants, ii. 429. + DE CANDOLLE, P., non-variability of monotypic genera, ii. 266; + relative development of root and seed in _Raphanus sativus_, ii. 343. + DECAISNE, on the cultivation of the wild carrot, i. 326; + varieties of the pear, i. 350; + inter-crossing of strawberries, i. 351; + fruit of the apple, i. 401; + sterility of _Lysimachia nummularia_, ii. 170; + tender variety of the peach, ii. 308. + DEER, assumption of horns by female, ii. 51; + imperfect development of horns in a, on a voyage, ii. 158. + DEER, fallow, ii. 103. + DEERHOUND. Scotch, difference in size of the sexes of, ii. 73; + deterioration of, ii. 121. + DEGENERATION of high-bred races, under neglect, ii. 239. + DE JONGHE, J., on strawberries, i. 352, ii. 243; + soft-barked pears, ii. 231; + on accumulative variation, ii. 262; + resistance of blossoms to frost, ii. 306. + DELAMER, E. S., on rabbits, i. 107, 112. + _Delphinium ajacis_, ii. 21. + _Delphinium consolida_, ii. 20-21. + _Dendrocygna viduata_, i. 182, ii. 157. + DENTITION, variations of, in the horse, i. 50. + DEODAR, i. 364. + DESMAREST, distribution of white on dogs, i. 29; + cat from the Cape of Good Hope, i. 47; + cats of Madagascar, i. 47; + occurrence of striped young in Turkish pigs, i. 76; + French breeds of cattle, i. 80; + horns of goats, i. 102; + on hornless goats, ii. 315. + DESOR, E., on the Anglo-Saxon race in America, ii. 276. + DESPORTES, number of varieties of roses, i. 367. + DEVAY, Dr., singular case of albinism, ii. 17; + on the marriage of cousins, ii. 122; + on the effects of close interbreeding, ii. 143, 263. + DEVELOPMENT and metamorphosis, ii. 388-389. + DEVELOPMENT, arrests of, ii. 315-318. + DEVELOPMENT, embryonic, ii. 366-368. + {447} + D'HERVEY-Saint-Denys, L., on the ya-mi, or imperial rice of the Chinese, + ii. 205. + DHOLE, fertility of the, in captivity, ii. 151. + DIABETES, occurrence of, in three brothers, ii. 17. + _Dianthus_, contabescent plants of, ii. 165-166; + hybrid varieties of, ii. 267. + _Dianthus armeria_ and _deltoides_, hybrids of, ii. 98. + _Dianthus barbatus_, i. 381. + _Dianthus caryophyllus_, i. 381. + _Dianthus japonicus_, contabescence of female organs in, ii. 166. + DICHOGAMOUS plants, ii. 90. + DICKSON, Mr., on "running" in carnations, i. 381; + on the colours of tulips, i. 386. + _Dicotyles torquatus_ and _labiatus_, ii. 150. + DIEFFENBACH, dog of New Zealand, i. 26; + feral cats in New Zealand, i. 47; + polydactylism in Polynesia, ii. 14. + _Dielytra_, ii. 59. + DIET, change of, ii. 303-304. + _Digitalis_, properties of, affected by culture, ii. 274; + poison of, ii. 380. + DIGITS, supernumerary, ii. 57; + analogy of, with embryonic conditions, ii. 16; + fusion of, ii. 341. + DIMORPHIC plants, ii. 166; + conditions of reproduction in, ii. 181-184. + DIMORPHISM, reciprocal, ii. 90. + DINGO, i. 25; + variation of, in colour, i. 28; + half-bred, attempting to burrow, i. 28; + attraction of foxes by a female, i. 31; + variations of, in confinement, ii. 263. + DIOECIOUSNESS of strawberries, i. 353. + DISEASES, inheritance of, ii. 7-8; + family uniformity of, ii. 57; + inherited at corresponding periods of life, ii. 77-80; + peculiar to localities and climates, ii. 276; + obscure correlations in, ii. 331-332; + affecting certain parts of the body, ii. 380; + occurring in alternate generations, ii. 401. + DISTEMPER, fatal to white terriers, ii. 227. + DISUSE and use of parts, effects of, ii. 295-303, 352-353, 418-419; + in the skeleton of rabbits, i. 124-128; + in pigeons, i. 171-177; + in fowls, i. 270-274; + in ducks, i. 284-286; + in the silk-moth, i. 300-304. + DIVERGENCE, influence of, in producing breeds of pigeons, i. 220. + DIXON, E. S., on the musk duck, i. 182; + on feral ducks, i. 190; + on feral pigeons in Norfolk Island, i. 190; + crossing of pigeons, i. 192; + origin of domestic fowls, i. 230; + crossing of _Gallus Sonneratii_ and common fowl, i. 234; + occurrence of white in the young chicks of black fowls, i. 244; + Paduan fowl of Aldrovandi, i. 247; + peculiarities of the eggs of fowls, i. 248; + chickens, i. 249-250; + late development of the tail in Cochin cocks, i. 250; + comb of lark-crested fowls, i. 256; + development of webs in Polish fowls, i. 259; + on the voice of fowls, i. 259; + origin of the duck, i. 277; + ducks kept by the Romans, i. 278; + domestication of the goose, i. 287; + gander frequently white, i. 288; + breeds of turkeys, i. 293; + incubatory instinct of mongrels of non-sitting races of fowls, ii. 44; + aversion of the dove-cot pigeon to pair with fancy birds, ii. 103; + fertility of the goose, ii. 112; + general sterility of the guans in captivity, ii. 156; + fertility of geese in captivity, ii. 157; + white peafowl, ii. 332. + DOBELL, H., inheritance of anomalies of the extremities, ii. 14; + non-reversion to a malformation, ii. 36. + DOBRIZHOFFER, abhorrence of incest by the Abipones, ii. 123. + DOGS, origin of, i. 15; + ancient breeds of, i. 17, ii. 429; + of neolithic, bronze and iron periods in Europe, i. 18-19, ii. 427; + resemblance of to various species of canidæ, i. 21; + of North America compared with wolves, i. 21-22; + of the West Indies, South America, and Mexico, i. 23, 31; + of Guiana, i. 23; + naked dogs of Paraguay and Peru, _ibid._ and 31; + dumb, on Juan Fernandez, i. 27; + of Juan de Nova, i. 27; + of La Plata, i. 27; + of Cuba, i. 27; + of St. Domingo, i. 28; + correlation of colour in, i. 28-29; + gestation of, i. 29-30; + hairless Turkish, i. 30, ii. 227; + inter-crossing of different breeds of, i. 31; + characters of different breeds of, discussed, i. 34-37; + degeneration of European, in warm climates, i. 36, 38; ii. 278, 305; + liability to certain diseases in different breeds of, i. 36 and _note_; + causes of differences of breeds discussed, i. 37-43; + catching fish and crabs in New Guinea and Tierra del Fuego, i. 39; + webbing of the feet in, i. 39; + influence of selection in producing different breeds of, i. 39, 43; + retention of original habits by, i. 182; + inheritance of polydactylism in, ii. 14; + feral, ii. 33; + reversion in fourth generation of, ii. 34; + of the Pacific Islands, ii. 87, 220, 303; + mongrel, ii. 92-93; + comparative facility of crossing different breeds of, ii. 102; + fertility of, ii. 111, 151; + inter-breeding of, ii. 120-121; + selection of, among the Greeks, ii. 202, 209; + among savages, ii. 206-207; + unconscious selection of, ii. 211-212; + valued by the Fuegians, ii. 215; + climatal changes in hair of, ii. 278; + production of drooping ears in, ii. 301; + {448} + rejection of bones of game by, ii. 303; + inheritance of rudiments of limbs in, ii. 315; + development of fifth toe in, ii. 317; + hairless, deficiency of teeth in, ii. 326; + short-faced, teeth of, ii. 345; + probable analogous variation in, ii. 349; + extinction of breeds of, ii. 425. + DOMBRAIN, H. H., on the auricula, ii. 346-347. + DOMESTICATION, essential points in, ii. 405-406; + favourable to crossing, ii. 109-110; + fertility increased by, ii. 111-113, 174. + DOMESTICATED animals, origin of, ii. 160-161; + occasional sterility of, under changed conditions, ii. 161-162. + DONDERS, Dr., hereditary hypermetropia, ii. 8. + DORKING fowl, i. 227, 261; + furcula of, figured, i. 268. + DORMOUSE, ii. 152. + DOUBLE FLOWERS, ii. 167-168, 171-172; + produced by selection, ii. 200. + DOUBLEDAY, H., cultivation of the filbert pine strawberry, i. 354. + DOUGLAS, J., crossing of white and black game-fowls, ii. 92. + DOWNING, Mr., wild varieties of the hickory, i. 310; + peaches and nectarines from seed, i. 339-340; + origin of the Boston nectarine, i. 340; + American varieties of the peach, i. 343; + North American apricot, i. 344; + varieties of the plum, i. 346; + origin and varieties of the cherry, i. 347-348; + "twin cluster pippins," i. 349; + varieties of the apple, i. 350; + on strawberries, i. 351, 353; + fruit of the wild gooseberry, i. 355; + effects of grafting upon the seed, ii. 26; + diseases of plum and peach trees, ii. 227-228; + injury done to stone fruit in America by the "weevil," ii. 231; + grafts of the plum and peach, ii. 259; + wild varieties of pears, ii. 260; + varieties of fruit-trees suitable to different climates, ii. 306. + _Draba sylvestris_, ii. 163. + DRAGON, pigeon, i. 139, 141. + "DRAIJER" (pigeon), i. 156. + DRINKING, effects of, in different climates, ii. 289. + DROMEDARY, selection of, ii. 205-206. + DRUCE, Mr., inter-breeding of pigs, ii. 121. + DU CHAILLU, fruit-trees in West Africa, i. 309. + DUCHESNE on _Fragaria vesca_, i. 351, 352, 353. + DUFOUR, Léon, on _Cecidomyia_ and _Misocampus_, i. 5. + DUCK, musk, retention of perching habit by the, i. 182; + feral hybrid of, i. 190. + DUCK, penguin, hybrid of, with Egyptian goose, ii. 68. + DUCK, wild, difficulty of rearing, ii. 233; + effects of domestication on, ii. 278. + DUCKS, breeds of, i. 276-277; + origin of, i. 277; + history of, _ibid._; + wild, easily tamed, i. 278-279; + fertility of breeds of, when crossed, i. 279; + with the plumage of _Anas boschas_, i. 280; + Malayan penguin, identical in plumage with English, i. 280; + characters of the breeds of, i. 281-284; + eggs of, i. 281; + effects of use and disuse in, i. 284-286, ii. 298; + feral, in Norfolk, i. 190; + Aylesbury, inheritance of early hatching by, ii. 25; + reversion in, produced by crossing, ii. 40; + wildness of half-bred wild, ii. 45; + hybrids of, with the musk duck, ii. 45-46; + assumption of male plumage by, ii. 51; + crossing of Labrador and penguin, ii. 97; + increased fertility of, by domestication, ii. 112; + general fertility of, in confinement, ii. 157; + increase of size of, by care in breeding, ii. 199; + change produced by domestication in, ii. 262. + DUMÉRIL, Aug., breeding of _Siredon_ in the branchiferous stage, ii. 384. + DUN-coloured horses, origin of, i. 59. + DUREAU de la Malle, feral pigs in Louisiana, ii. 33; + feral fowls in Africa, _ibid._; + bud-variation in the pear, i. 376; + production of mules among the Romans, ii. 110. + _Dusicyon sylvestris_, i. 23. + DUTCH rabbit, i. 107. + DUTCH roller pigeon, i. 151. + DUTROCHET, pelorism in the laburnum, ii. 346. + DUVAL, growth of pears in woods in France, ii. 260. + DUVAL-Jouve, on _Leersia oryzoides_, ii. 91. + DUVERNOY, self-impotence in _Lilium candidum_, ii. 137. + DZIERZON, variability in the characters and habits of bees, i. 298. + + EARLE, Dr., on colour-blindness, ii. 72, 328. + EARS, of fancy rabbits, i. 106; + deficiency of, in breeds of rabbits, i. 108; + rudimentary, in Chinese sheep, ii. 315; + drooping, ii. 301; + fusion of, ii. 341. + EATON, J. M., on fancy pigeons, i. 148, 153; + variability of characters in breeds of pigeons, i. 161; + reversion of crossed pigeons to coloration of _Columba livia_, i. 198; + on pigeon-fancying, i. 206, 215-216; + on tumbler-pigeons, i. 209, ii. 242; + carrier-pigeon, i. 211; + effects of interbreeding on pigeons, ii. 126; + properties of pigeons, ii. 197-198; + death of short-faced tumblers in the egg, ii. 226; + {449} + Archangel pigeon, ii. 240. + ECHINODERMATA, metagenesis in, ii. 367. + _Ectopistes_, specific difference in number of tail-feathers in, i. 159. + _Ectopistes migratorius_, sterile hybrids of, with _Turtur vulgaris_, i. + 193. + EDENTATA, correlation of dermal system and teeth in the, ii. 328. + EDGEWORTH, Mr., use of grass-seeds as food in the Punjab, i. 309. + EDMONSTON, Dr., on the stomach in _Larus argentatus_ and the raven, ii. + 302. + EDWARDS and COLIN, on English wheat in France, ii. 307. + EDWARDS, W. F., absorption of the minority in crossed races, ii. 87. + EDWARDS, W. W., occurrence of stripes in a nearly thoroughbred horse, i. + 57; + in foals of racehorses, i. 59. + EGGS, of fowls, characters of, i. 248; + variations of, in ducks, i. 281; + of the silkmoth, i. 301. + EGYPT, ancient dogs of, i. 17-18; + ancient domestication of the pigeon in, i. 204; + absence of the fowl in ancient, i. 246. + EGYPTIAN goose, hybrids of, with penguin duck, i. 282. + EHRENBERG, Prof., multiple origin of the dog, i. 16; + dogs of Lower Egypt, i. 25; + mummies of _Felis maniculata_, i. 43. + ELEMENT, male, compared to a premature larva, ii. 384. + ELEMENTS of the body, functional independence of the, ii. 368-371. + ELEPHANT, its sterility in captivity, ii. 150. + ELK, Irish, correlations in the, ii. 333-334. + ELLIOT, Sir Walter, on striped horses, i. 58; + Indian domestic and wild swine, i. 66; + pigeons from Cairo and Constantinople, i. 132; + fantail pigeons, i. 146; + Lotan tumbler pigeons, i. 150; + a pigeon uttering the sound _Yahu_, i. 155; + _Gallus bankiva_ in Pegu, i. 236. + ELLIS, Mr., varieties of cultivated plants in Tahiti, ii. 256. + ELM, nearly evergreen Cornish variety of the, i. 363, ii. 310; + foliage-varieties of the, i. 362. + ELM, weeping, i. 361; + not reproduced by seed, ii. 19. + _Emberiza passerina_, ii. 158. + EMBRYOS, similarity of, i. 12; + fusion of, ii. 339. + ENGEL, on _Laurus sassafras_, ii. 274. + ENGLAND, domestication of _Bos longifrons_ in, i. 81; + selection of horses in, in mediæval times, ii. 203; + laws against the early slaughter of rams in, ii. 203. + EPHEMERIDÆ, development of the, ii. 366. + _Epidendrum cinnabarinum_ and _E. zebra_, ii. 134. + EPILEPSY, hereditary, ii. 8, 78. + ERDT, disease of the white parts of cattle, ii. 337. + ERICACEÆ, frequency of contabescence in the, ii. 165. + ERICHTHONIUS, an improver of horses by selection, ii. 202. + ERMAN, on the fat-tailed Kirghisian sheep, i. 98, ii. 280; + on the dogs of the Ostyaks, ii. 206. + _Erodium_, ii. 59. + _Erythrina Crista-galli_ and _E. herbacea_, hybrids of, ii. 265. + ESQUILANT, Mr., on the naked young of dun-coloured pigeons, i. 170. + ESQUIMAUX dogs, their resemblance to wolves, i. 21; + selection of, ii. 206. + EUDES-DESLONGCHAMPS, on appendages under the jaw of pigs, i. 75-76. + _Euonymus Japonicus_, i. 383. + EUROPEAN cultivated plants, still wild in Europe, i. 307. + EVANS, Mr., on the Lotan tumbler pigeon, i. 150. + EVELYN, pansies grown in his garden, i. 368. + EVEREST, R., on the Newfoundland dog in India, i. 36, ii. 305; + degeneration of setters in India, i. 38; + Indian wild boars, i. 66. + EWES, hornless, ii. 350. + EXTINCTION of domestic races, i. 221. + EYES, hereditary peculiarities of the, ii. 8-10; + loss of, causing microphthalmia in children, ii. 24; + modification of the structure of, by natural selection, ii. 222-223; + fusion of, ii. 341. + EYEBROWS, hereditary elongation of hairs in, ii. 8. + EYELIDS, inherited peculiarities of the, ii. 8. + EYTON, Mr., on gestation in the dog, i. 30; + variability in number of vertebræ in the pig, i. 74; + individual sterility, ii. 162. + + _Faba vulgaris_, i. 330. + FABRE, observations on _Ægilops triticoides,_ i. 313. + _Fagus sylvatica_, ii. 19. + FAIRWEATHER, Mr., production of double flowers from old seed, ii. 167. + _Falco albidus_, resumption of young plumage by, in captivity, ii. 158. + _Falco ossifragus_, ii. 230. + _Falco subbuteo_, copulating in captivity, ii. 154. + _Falco tinnunculus_, breeding in captivity, ii. 154. + {450} + FALCONER, Dr., sterility of English bulldogs in India, i, 38; + resemblance between _Sivatherium_ and Niata cattle, i. 89; + selection of the silkworm in India, i. 301; + fastigate apple-trees in Calcutta, i. 361; + reproduction of a supernumerary thumb after amputation, ii. 14; + fertility of the dhole in captivity, ii. 151; + fertility of English dogs in India, ii. 161; + sterility of the tiger in captivity, ii. 151; + turkeys at Delhi, ii. 161; + on Indian cultivated plants, ii. 165; + Thibet mastiff and goat, ii. 278. + FALCONS, sterility of, in captivity, ii. 153. + FALKLAND Islands, horses of the, i. 52-53, 61; + feral pigs of the, i. 77; + feral cattle of the, i. 82, 86; + feral rabbits of the, i. 112. + FALLOW deer, ii. 103, 120. + FANTAIL pigeons, i. 146-148, ii. 227; + figured, i. 147; + furcula of, figured, i. 167; + history of, i. 208; + absence of oil-gland in, ii. 344. + FAROE Islands, pigeons of the, i. 183. + FASHION, influence of, in breeding, ii. 240. + FASTIGATE trees, ii. 277, 348. + FAUNAS, geographical differences, of, i. 10. + "FAVOURITE" bull, ii. 65, 118. + FEATHERS, homologous variation in, ii. 325. + FEET, of pigeons, individual differences of, i. 160; + correlations of external characters in, i. 170-171. + FEET and beak, correlation of, in pigeons, i. 171-174. + FELIDÆ, fertility of, in captivity, ii. 150. + _Felis bubastes_, i. 43. + _Felis caffra_, i. 44. + _Felis caligulata_, i. 43. + _Felis chaus_, i. 43-44. + _Felis jubata_, ii. 151. + _Felis lybica_, i. 44. + _Felis maniculata_, i. 43. + _Felis manul_, i. 45. + _Felis ornata_, i. 45. + _Felis sylvestris_, i. 44. + _Felis torquata_, i. 45. + FEMALE, affected by male element, ii. 365, 387-388. + FEMALE flowers, in male panicle of maize, i. 321. + FENNEL, Italian variety of, i. 326. + FERAL cats, i. 47; + cattle, i. 86; + rabbits, i. 111-115; + Guinea fowl, i. 294; + animals and plants, reversion in, ii. 32-34, 47. + FERGUSON, Mr., supposed plurality of origin of domestic fowls, i. 231; + chickens of black game-fowls, i. 244; + relative size of eggs of fowls, i. 248; + yolk of eggs of game-fowls, i. 249; + early pugnacity of game-cocks, i. 250; + voice of the Malay fowl, i. 259; + effects of interbreeding on fowls, ii. 124; + selection in Cochin China fowls, ii. 196; + on fashion in poultry, ii. 240. + FERNANDEZ, on Mexican dogs, i. 23. + FERNS, reproduction of abnormal forms of, by spores, i. 383; + non-diffusion of cell-gemmules in, ii. 379. + FERRETS, ii. 111, 151, 206. + FERTILISATION, artificial, of the St. Valery apple, i. 350. + FERTILITY, various degrees of, in sheep, i. 97; + unlimited mutual, of breeds of pigeons, i. 192-194; + comparative of mongrels and hybrids, ii. 100-101, 178-180; + influence of nourishment on, ii. 111; + diminished by close interbreeding, ii. 118, 175; + reduced, of Chillingham wild cattle, ii. 119; + of domesticated varieties when crossed, ii. 189. + _Festuca_, species of, propagated by bulblets, ii. 170. + FILBERTS, spared by tomtits, ii. 231. + FILIPPI, on the breeding of branchiferous tritons, ii. 384. + FINCHES, general sterility of, in captivity, ii. 154. + FINNIKIN (pigeon), i. 156. + FINNOCHIO, i. 326. + FIR, Scotch, acclimatisation of, ii. 310. + FISH, Mr., advantage of change of soil to plants, ii. 147. + FISHES, regeneration of portions of fins of, ii. 15; + variability of, when kept in tanks, ii. 259; + marine, living in fresh water, ii. 304; + double monsters of, ii. 340. + FISSION and gemmation, ii. 358. + FITCH, Mr., persistency of a variety of the pea, i. 329. + FITTEST, survival of the, i. 6. + FITZINGER, origin of sheep, i. 94; + African maned sheep, i. 96. + FIXEDNESS of character, conditions of, discussed, ii. 62-64. + FLAX, found in the Swiss lake-dwellings, i. 317; + climatal difference in products of, ii. 274. + FLEECE, fineness of, in Austrian merinos, ii. 197. + FLEISCHMANN, on German sheep crossed with merinos, ii. 88-89. + "FLORENTINER-TAUBE," i. 142-143. + FLOUNDER, ii. 53. + FLOURENS, crossing of wolf and dog, i. 32; + prepotency of the jackal over the dog, ii. 67; + hybrids of the horse and ass, ii. 68; + breeding of monkeys in Europe, ii. 153. + {451} + FLOWER-GARDEN, earliest known, in Europe, ii. 217. + FLOWERS, capricious transmission of colour-varieties in, ii. 20-21; + tendency to uniformity in striped, ii. 70; + scorching of, dependent on colour, ii. 229; + change in, caused by conditions of life, ii. 273; + rudimentary, ii. 316; + relative position of, to the axis, ii. 345. + FOETATION, abdominal, ii. 294. + FOLEY, Mr., wild varieties of pears, ii. 260. + FOLIAGE, inherited peculiarities of, i. 362; + variegation, of, i. 366; + bud-variation in, i. 382-384. + FOOD, influence of, on the pig, i. 72; + on cattle, i. 91; + excess of, a cause of variability, ii. 257. + FORBES, D., on Chilian sheep, i. 95; + on the horses of Spain, Chili, and the Pampas, i. 52. + _Formica rufa_, ii. 251. + FORTUNE, R., sterility of the sweet potato in China, ii. 169; + development of axillary bulbs in the yam, _ibid._ + FOWL, common, breeds of, i. 225-230; + supposed plurality of origin, i. 230; + early history of, i. 231-233; + causes of production of breeds of, i. 233; + origin of from _Gallus bankiva_, i. 236-239, 245; + feral, notices of, i. 237-238; + reversion and analogous variation in, i. 239-246, ii. 35, 38, 39, 40, + 349, 350; + "cuckoo" sub-breeds of, i. 244; + history of, i. 246-247; + structural characters of, i. 247-250; + sexual peculiarities of, i. 251-257, ii. 74; + external differences of, i. 257-260; + differences of breeds of, from _G. bankiva_, i. 260; + osteological characters of, i. 260-270; + effects of disuse of parts in, i. 270-274, ii. 298; + feral, i. 190, ii. 33; + polydactylism in, ii. 14; + fertility of, increased by domestication, ii. 112, 167; + sterility of, under certain conditions, ii. 162; + influence of selection on, ii. 196, 198, 209, 210; + evils of close interbreeding of, ii. 124-125; + crossing of, ii. 95, 96, 97; + prepotency of transmission in, ii. 67; + rudimentary organs in, ii. 315; + crossing of non-sitting varieties of, ii. 43-44; + homology of wing and leg feathers in, ii. 323; + hybrids of, with pheasants and _Gallus Sonneratii_, ii. 45; + black-skinned, ii. 209-210; + black, preyed upon by the osprey in Iceland, ii. 230; + five-toed, mentioned by Columella, ii. 429; + rumpless, tailed chickens produced by, ii. 31; + Dorking, crosses of, ii. 93; + form of comb and colour of plumage in, ii. 238; + game, crossing of white and black, ii. 92; + five-spurred, ii. 391; + Spanish, liable to suffer from frost, ii. 306; + Polish, peculiarities of skull of, ii. 332-333. + FOX, sterility of, in captivity, ii. 151. + FOX, S. Bevan, races of bees, i. 298. + FOX, W. Darwin, gestation of the dog, i. 30; + "Negro" cat, i. 46; + reversion of sheep in colour, ii. 30; + period of gestation in the pig, i. 74; + young of the Himalayan rabbit, i. 109; + crossing of wild and domestic turkeys, i. 292; + reversion in crossed musk ducks, ii. 40; + spontaneous segregation of varieties of geese, ii. 104; + effects of close interbreeding upon bloodhounds, ii. 121; + deafness of white cats with blue eyes, ii. 329. + FOXHOUNDS, i. 40, ii. 120. + _Fragaria chiloensis_, i. 351. + _Fragaria collina_, i. 351. + _Fragaria dioica_ of Duchesne, i. 353. + _Fragaria elatior_, i. 351. + _Fragaria grandiflora_, i. 351. + _Fragaria vesca_, i. 351. + _Fragaria virginiana_, i. 351. + _Fraxinus excelsior_, i. 360, 362, ii. 19. + _Fraxinus lentiscifolia_, ii. 19. + FRIESLAND cattle, probably descended from _Bos primigenius_, i. 81. + FRILLBACK (pigeon), i. 155; + Indian, i. 153. + _Fringilla ciris_, ii. 154. + _Fringilla spinus_, ii. 154. + FRIZZLED fowls, i. 230; + horses, i. 54. + FROG, polydactylism in the, ii. 14. + FRUIT, seedless, ii. 168. + FRUIT-TREES, varieties of, occurring wild, i. 310. + FRY, Mr., on fertile hybrid cats, i. 44; + on feral fowls in Ascension, i. 238. + FUCHSIAS, origin of, i. 364; + bud-variation in, i. 382. + _Fuchsia coccinea_ and _fulgens_, twin seed produced by crossing, i. 391. + FUEGIANS, their superstition about killing young water-fowl, i. 310; + selection of dogs by the, ii. 207; + their comparative estimation of dogs and old women, ii. 215; + their power of distant vision, ii. 223. + FUNGI, parasitic, ii. 284-285. + FURCULA, characters and variations of the, in pigeons, i. 167; + alteration of, by disuse, in pigeons, i. 175; + characters of, in fowls, i. 268. + FUSION of homologous parts, ii. 393. + + GAIT, inheritance of peculiarities of, ii. 6. + GALAPAGOS Archipelago, its peculiar fauna and flora, i. 9. + _Galeobdolon luteum_, pelorism in, ii. 59, 345. + {452} + GALLS, ii. 282-284. + GALL-GNATS, ii. 283. + GALL-LIKE excrescences not inherited, ii. 23. + GALLINACEOUS birds, restricted range of large, i. 237; + general fertility of in captivity, ii. 155. + _Gallinula chloropus_, ii. 156. + _Gallinula nesiotis_, i. 287. + GALTON, Mr., fondness of savages for taming animals, i. 20, ii. 160; + cattle of Benguela, i. 88; + on hereditary talent, ii. 7. + GALLESIO, species of oranges, i. 334, 335, 336; + hybridisation of oranges, i. 336; + persistency of races in the peach, i. 339; + supposed specific distinctions of peach and nectarine, i. 340; + Bizzaria orange, i. 391; + crossing of red and white carnations, i. 393; + crossing of the orange and lemon, i. 399, ii. 365; + effect of foreign pollen on maize, i. 400; + spontaneous crossing of oranges, ii. 91; + monstrosities a cause of sterility in plants, ii. 166; + seeding of ordinarily seedless fruits, ii. 168; + sterility of the sugar cane, ii. 169; + tendency of male flowers to become double, ii. 171; + effects of selection in enlarging fruit, &c., ii. 217; + variation of the orange tree in North Italy, ii. 256; + naturalisation of the orange in Italy, ii. 309. + _Gallus æneus_, a hybrid of _G. varius_ and the domestic fowl, i. 235. + _Gallus bankiva_, probable original of domestic fowls, i. 233, 236-239, + 245; + game-fowl, nearest to, i. 226; + crossed with _G. Sonneratii_, i. 234; + its character and habits, i. 235-236, ii. 109; + differences of various breeds of fowls from, i. 260; + occipital foramen of, figured, i. 261; + skull of, figured, i. 262; + cervical vertebra of, figured, i. 267; + furcula of, figured, i. 268; + reversion to, in crossed fowls, ii. 39-40; + hybrid of, with _G. varius_, i. 235, ii. 40; + number of eggs of, ii. 112. + _Gallus ferrugineus_, i. 226. + _Gallus furcatus_, i. 234. + _Gallus giganteus_, i. 235. + _Gallus Sonneratii_, characters and habits of, i. 233; + hybrids of, i. 234, ii. 45. + _Gallus Stanleyi_, hybrids of, i. 234. + _Gallus Temminckii_, probably a hybrid, i. 235. + _Gallus varius_, character and habits of, i. 234; + hybrids and probable hybrids of, i. 234-235. + GAMBIER, Lord, his early cultivation of the pansy, i. 368. + GAME-FOWL, i. 226, 250, 251, 252. + GAPES, ii. 228. + GARCILAZO de la Vega, annual hunts of the Peruvian Incas, ii. 207. + GARNETT, Mr., migratory propensities of hybrid ducks, ii. 45. + GARROD, Dr., on hereditary gout, ii. 7. + GASPARINI, a genus of pumpkins, founded on stigmatic characters, i. 359. + GAUDICHAUD, bud-variation in the pear, i. 376; + apple tree with two kinds of fruit on branch, i. 392. + GAUDRY, anomalous structure in the feet of horses, i. 50. + GAY, on _Fragaria grandiflora_, i. 351; + on _Viola lutea_ and _tricolor_, i. 368; + on the nectary of _Viola grandiflora_, i. 369. + GAYAL, domestication of the, i. 82. + GAYOT, _see_ Moll. + GÄRTNER, on the sterility of hybrids, i. 192, ii. 101; + acquired sterility of varieties of plants when crossed, i. 358; + sterility in transplanted plants, and in the lilac in Germany, ii. 164; + mutual sterility of blue and red flowers of the pimpernel, ii. 190; + supposed rules of transmission in crossing plants, ii. 68; + on crossing plants, ii. 98, 127, 130, 131; + on repeated crossing, ii. 267; + absorption of one species by another, when crossed, ii. 88; + crossing of varieties of the pea, i. 397; + crossing maize, ii. 105; + crossing of species of _Verbascum_, ii. 93, 105; + reversion in hybrids, ii. 36, 49, 50; + of _Cereus_, i. 392; + of _Tropæolum majus_ and _minus_, i. 392; + variability of hybrids, ii. 265; + variable hybrids from one variable parent, ii. 270; + graft hybrid produced by inosculation in the vine, i. 395; + effect produced by grafts on the stock, i. 394, ii. 278; + tendency of hybrid plants to produce double flowers, ii. 171; + production of perfect fruit by sterile hybrids, ii. 172; + sexual elective affinity, ii. 180; + self-impotence in _Lobelia_, _Verbascum_, _Lilium_, and _Passiflora_, + ii. 136-137; + on the action of pollen, ii. 108; + fertilisation of _Malva_, i. 402-403, ii. 363; + prepotency of pollen, ii. 187; + prepotency of transmission in species of _Nicotiana_, ii. 67; + bud-variation in _Pelargonium zonale_, i. 375; + in _Oenothera biennis_, i. 382; + in _Achillæa millefolium_, i. 408; + effect of manure on the fertility of plants, ii. 163; + on contabescence, ii. 165-166; + inheritance of plasticity, ii. 241; + villosity of plants, ii. 277. + GEESE (_anseres_) general fertility of, in captivity, ii. 157. + GEGENBAUR, on the number of digits, ii. 13. + GEMMATION and fission, ii. 358. + {453} + GEMMULES, or cell-gemmules, ii. 374, 378-381, 384. + GENET, fertility of the, in captivity, ii. 151. + GENERATION, alternate, ii. 361, 367, 390. + GENERATION, sexual, ii. 359-364. + GENIUS, inheritance of, ii. 7. + _Gentiana amarella_, ii. 168. + GEOFFROY Saint-Hilaire, production of monstrous chickens, ii. 289; + "_Loi de l'affinité de soi pour soi_," ii. 339; + compensation of growth, ii. 342. + GEOFFROY Saint-Hilaire, Isid., origin of the dog, i. 66; + barking of a jackal, i. 27; + period of gestation and odour of the jackal, i. 30; + anomalies in the teeth of dogs, i. 34; + variations in the proportions of dogs, i. 35; + webbed feet of Newfoundland dogs, i. 39; + crossing of domestic and wild cats, i. 44; + domestication of the arni, i. 82; + supposed introduction of cattle into Europe from the East, _ibid._; + absence of interdigital pits in sheep, i. 95; + origin of the goat, i. 101; + feral geese, i. 190; + ancient history of the fowl, i. 246; + skull of the Polish fowl, i. 262; + preference of the Romans for the liver of white geese, i. 289; + polydactylism, ii. 12; + assumption of male characters by female birds, ii. 51; + supernumerary mammæ in women, ii. 58; + development of a proboscis in the pig, _ibid._; + transmission and blending of characters in hybrids, ii. 94; + refusal of animals to breed in captivity, ii. 149; + on the Guinea pig, ii. 152; + silkworms producing white cocoons, ii. 199; + on the carp, ii. 236; + on _Helix lactea_, ii. 280; + on monstrosities, ii. 254; + injury to the embryo a cause of monstrosity, ii. 269; + alteration in the coat of horses in coal mines, ii. 278; + length of the intestines in wild and tame animals, ii. 302-303; + inheritance of rudimentary limbs in the dog, ii. 315; + correlation in monstrosities, ii. 320; + supernumerary digits in man, ii. 322; + co-existence of anomalies, ii. 331; + fusion of homologous parts, ii. 341-342; + presence of hairs and teeth in ovarian tumours, ii. 370; + development of teeth on the palate in the horse, ii. 391. + GEOGRAPHICAL differences of faunas, i. 10. + GEOLOGICAL succession of organisms, i. 11. + _Geranium_, ii. 59. + _Geranium phæum_ and _pyrenaicum_, ii. 258. + _Geranium pratense_, i. 379. + GERARD, asserted climatal change in Burgundian bees, i. 297. + GERARDE, on varieties of the hyacinth, i. 370. + GERSTÄCKER, on hive-bees, i. 299. + GERVAIS, Prof., origin of the dog, i. 16; + resemblance of dogs and jackals, i. 24; + taming of the jackal, i. 26; + number of teeth in dogs, i. 34; + breeds of dogs, i. 36; + on tertiary horses, i. 51; + biblical notices of horses, i. 55; + species of _Ovis_, i. 94; + wild and domestic rabbits, i. 103; + rabbits from Mount Sinai and Algeria, i. 105; + earless rabbits, i. 108; + batrachia with doubled limbs, ii. 391. + GESTATION, period of, in the dog, wolf, &c, i. 29-30; + in the pig, i. 74; + in cattle, i. 87, ii. 321; + in sheep, i. 97. + GESTURES, inheritance of peculiarities in, ii. 6. + "GHOONDOOKS" a sub-breed of fowls, i. 229. + GHOR-KHUR, ii. 42. + GILES, Mr., effect of cross-breeding in the pig, i. 404. + GIRAFFE, co-ordination of structure of, ii. 221. + GIRARD, period of appearance of permanent teeth in dogs, i. 35. + GIROU de Buzareingues, inheritance in the horse, ii. 10; + reversion by age in cattle, ii. 38; + prepotency of transmission of character in sheep and cattle, ii. 66; + on crossing gourds, ii. 108. + GISBURNE, wild cattle at, i. 84. + _Gladiolus_, i. 364; + self-impotence of hybrids of, ii. 139. + _Gladiolus colvillii_, bud-variation in, i. 382. + GLANDS, compensatory development of, ii. 300. + GLASTONBURY thorn, i. 364. + GLENNY, Mr., on the _Cineraria_, ii. 200. + GLOEDE, F., on strawberries, i. 353. + GLOGER, on the wings of ducks, ii. 298. + "GLOUGLOU" (pigeon), i. 154. + _Gloxiniæ_, peloric, i. 365, ii. 167. + GMELIN, on red cats, at Tobolsk, i. 47. + GOAT, i. 101-102, ii. 33; + polydactylism in the, ii. 14; + sexual differences in horns of, ii. 73; + valued by South Africans, ii. 207; + Thibet, ii. 278; + amount of milk and development of udders in the, ii. 300; + hornless, rudimentary bony cores in, ii. 316; + Angora, ii. 326. + GODRON, odour of the hairless Turkish dog, i. 30; + differences in the skull of dogs, i. 34; + increase of breeds of horses, i. 51; + crossing of domestic and wild swine, i. 66; + on goats, i. 101-102; + colour of the skin in fowls, i. 258; + bees of north and south of France, i. 297; + introduction of the silkworm into Europe, i. 300; + variability in the silkworm, i. 304; + supposed species of wheat, i. 312-314; + on _Ægilops triticoides_, i. 313; + variable presence of barbs in grasses, i. 314; + {454} + colours of the seeds of maize, i. 321; + unity of character in cabbages, i. 323; + correlation of colour and odour, i. 325; + effect of heat and moisture on the cabbage, i. 325; + on the cultivated species of _Brassica_, i. 325; + on the Rouncival and sugar peas, i. 327; + variation in the numbers of peas in the same pod, i. 328; + wild vines in Spain, i. 332; + on raising peaches from seed, i. 339; + supposed specific distinctness of peach and nectarine, i. 340; + nectarine producing peaches, i. 341; + on the flower of _Corydalis_, i. 344; + origin and variations of the plum, i. 345; + origin of the cherry, i. 347; + reversion of single-leaved strawberries, i. 353; + five-leaved variety of _Fragaria collina_, i. 353; + supposed immutability of specific characters, i. 358-359; + varieties of _Robinia_, i. 361; + permanency of the simple-leaved ash, i. 362; + non-inheritance of certain mutilations, ii. 23; + wild turnips, carrots, and celery, ii. 33; + pre-potency of a goat-like ram, ii. 66; + benefit of change of soil to plants, ii. 146; + fertility of peloric flowers of _Corydalis solida_, ii. 167; + seeding of ordinarily seedless fruit, ii. 168; + sexual sterility of plants propagated by buds, &c., ii. 169; + increase of sugar in beet-root, ii. 201; + effects of selection in enlarging particular parts of plants, ii. 217; + growth of the cabbage in the tropics, ii. 277; + rejection of bitter almonds by mice, ii. 232; + influence of marshy pasture on the fleece of sheep, ii. 278; + on the ears of ancient Egyptian pigs, ii. 301; + primitive distinctness of species, ii. 415; + solid hoofed swine, ii. 429. + GOETHE, on compensation of growth, ii. 342. + GOLDFISH, i. 296-297, ii. 236. + GOMARA, on South American cats, i. 46. + GONGORA, number of seeds in the, ii. 379. + GOOSE, ancient domestication of, i. 287; + sacred to Juno in Rome, _ibid._; + inflexibility of organisation of, i. 288; + skull perforated in tufted, i. 288; + characters of breeds and sub-breeds of, i. 288-289; + variety of, from Sebastopol, i. 289, ii. 392; + feral in La Plata, i. 190; + Egyptian, hybrid of, with penguin duck, ii. 68; + spontaneous segregation of varieties of, ii. 104; + fertility of, increased by domestication, ii. 112; + decreased fertility of, in Bogota, ii. 161; + sterility of, in the Philippine Islands, ii. 162; + selection of, ii. 204; + white, preference of the Romans for the liver of, ii. 209; + persistency of character in, ii. 254; + Egyptian, change in breeding season of, ii. 304. + GOOSEBERRY, i. 354-356; + bud-variation in the, i. 376; + Whitesmith's, ii. 232. + GÖPPERT, on monstrous poppies, ii. 166. + GOSSE, P. H., feral dogs in Jamaica, i. 28; + feral pigs of Jamaica, i. 77-78; + feral rabbits of Jamaica, i. 112; + on _Columba leucocephala_, i. 183; + feral Guinea fowl in Jamaica, i. 190; + reproduction of individual peculiarities by gemmation in a coral, i. + 374; + frequency of striped legs in mules, ii. 42. + GOULD, Dr., on hereditary hæmorrhage, ii. 7. + GOULD, John, origin of the turkey, i. 292. + _Goura coronata_ and _Victoriæ_, hybrids of, i. 194, ii. 155. + GOURDS, i. 357; + crossing of varieties of, ii. 108; + ancient Peruvian variety of, ii. 429. + GOUT, inheritance of, ii. 7; + period of appearance of, ii. 77. + GRABA, on the pigeon of the Faroe islands, i. 183. + GRAFTING, ii. 147; + effects of, ii. 259, 278; + upon the stock, i. 394-395; + upon the variability of trees, ii. 259; + changes analogous to bud-variation produced by, i. 387, 389. + GRAFT-HYBRIDS, i. 390-391, 394-397, ii. 364-365. + GRAPES, bud-variation in, i. 375; + cross of white and purple, i. 393; + green, liable to disease, ii. 336; + effect of foreign pollen on, i. 400. + GRASSES, seeds of, used as food by savages, i. 307-309. + GRAY, Asa, superior wild varieties of fruit-trees, i. 310; + cultivated native plants of North America, i. 312, 357; + non-variation of weeds, i. 317; + supposed spontaneous crossing of pumpkins, i. 399; + pre-ordination of variation, ii. 432; + progeny of husked form of maize, i. 320; + wild intermediate forms of strawberries, i. 352. + GRAY, G. R., on _Columba gymnocyclus_, i. 184. + GRAY, J. E., on _Sus pliciceps_, i. 70; + on a variety of the gold-fish, i. 297; + hybrids of the ass and zebra, ii. 42-43; + on the breeding of animals at Knowsley, ii. 149; + on the breeding of birds in captivity, ii. 157. + GREENE, J. Reay, on the development of the echinodermata, ii. 367. + GREENHOW, Mr., on a Canadian web-footed dog, i. 39. + GREENING, Mr., experiments on _Abraxas grossulariata_, ii. 280. + GREGSON, Mr., experiments on _Abraxas grossulariata_, ii. 280. + GREY, Sir George, preservation of seed-bearing plants by the Australian + savages, i. 310; + {455} + detestation of incest by Australian savages, ii. 123. + GREYHOUNDS, sculptured on Egyptian monuments, and in the Villa of + Antoninus, i. 17; + modern breed of, i. 41; + crossed with the bulldog, by Lord Orford, ii. 95; + co-ordination of structure of, due to selection, ii. 221-222; + Italian, ii. 227. + GREYNESS, inherited at corresponding periods of life, ii. 77. + GRIEVE, Mr., on early-flowering dahlias, i. 370. + GRIGOR, Mr., acclimatisation of the Scotch fir, ii. 310. + GROOM-NAPIER, C. O., on the webbed feet of the otter-hound, i. 40. + "GROSSES-GORGES" (pigeons), i. 137. + GROUND-TUMBLER, Indian, i. 150. + GROUSE, fertility of, in captivity, ii. 156. + GRÖNLAND, hybrids of _Ægilops_ and wheat, ii. 110. + _Grus montigresia_, _cinerea_, and _Antigone_, ii. 156. + GUANACOS, selection of, ii. 207. + GUANS, general fertility of, in captivity, ii. 156. + GUELDER-ROSE, ii. 185. + GUELDERLAND fowls, i. 230. + GUIANA, selection of dogs by the Indians of, ii. 206. + GUINEA FOWL, i. 294; + feral in Ascension, and Jamaica, i. 190, ii. 33; + indifference of to change of climate, ii. 161. + GUINEA pig, ii. 24, 152. + GÜLDENSTADT, on the jackal, i. 25. + GULL, herring, breeding in confinement, ii. 157. + GULLS, general sterility of, in captivity, ii. 157. + _Gulo_, sterility of, in captivity, ii. 152. + GÜNTHER, A., on tufted ducks and geese, i. 274; + on the regeneration of lost parts in batrachia, ii. 15. + GURNEY, Mr., owls breeding in captivity, ii. 154; + appearance of "black-shouldered" among ordinary peacocks, i. 291. + + HABIT, influence of, in acclimatisation, ii. 312-315. + HABITS, inheritance of, ii. 395. + HÄCKEL, on cells, ii. 370; + on the double reproduction of medusæ, ii. 384; + on inheritance, ii. 397. + HACKLES, peculiarities of, in fowls, i. 254. + HAIR, on the face, inheritance of, in man, ii. 4; + peculiar lock of, inherited, ii. 5; + growth of, under stimulation of skin, ii. 326; + homologous variation of, ii. 325; + development of, within the ears and in the brain, ii. 391. + HAIR and teeth, correlation of, ii. 326-328. + HAIRY family, corresponding period of inheritance in, ii. 77. + HALF-CASTES, character of, ii. 46. + HALF-LOP rabbits, figured and described, i. 107-108; + skull of, i. 119. + _Haliætus leucocephalus_, copulating in captivity, ii. 154. + HALLAM, Col., on a two-legged race of pigs, ii. 4. + HAMBURGH fowl, i. 227, 261; + figured, i. 228. + HAMILTON, wild cattle of, i. 84. + HAMILTON, Dr., on the assumption of male plumage by the hen pheasant, ii. + 51. + HAMILTON, F. Buchanan, on the shaddock, i. 335; + varieties of Indian cultivated plants, ii. 256. + HANCOCK, Mr., sterility of tamed birds, ii. 155-157. + HANDWRITING, inheritance of peculiarities in, ii. 6. + HANMER, Sir J., on selection of flower seeds, ii. 204. + HANSELL, Mr., inheritance of dark yolks in duck's eggs, i. 281. + HARCOURT, E. V., on the Arab boar-hound, i. 17; + aversion of the Arabs to dun-coloured horses, i. 55. + HARDY, Mr., effect of excess of nourishment on plants, ii. 257. + HARE, hybrids of, with rabbit, i. 105; + sterility of the, in confinement, ii. 152; + preference of, for particular plants, ii. 232. + HARE-LIP, inheritance of, ii. 24. + HARLAN, Dr., on hereditary diseases, ii. 7. + HARMER, Mr., on the number of eggs in a codfish, ii. 379. + HARVEY, Mr., monstrous red and white African bull, i. 91. + HARVEY, Prof., singular form of _Begonia frigida_, i. 365-366; + effects of cross-breeding on the female, i. 404; + monstrous saxifrage, ii. 166. + HASORA wheat, i. 313. + HAUTBOIS strawberry, i. 353. + HAWKER, Col., on call or decoy ducks, i. 281. + HAWTHORN, varieties of, i. 360-364; + pyramidal, i. 361; + pendulous hybridised, ii. 18; + changes of, by age, i. 364, 387; + bud-variation in the, i. 377; + flower buds of, attacked by bullfinches, ii. 232. + HAYES, Dr., character of Esquimaux dogs, i. 21-22. + HAYWOOD, W., on the feral rabbits of Porto Santo, i. 114. + HAZEL, purple-leaved, i. 362, 395, ii. 330. + HEAD of wild boar and Yorkshire pig, figured, i. 72. + {456} + HEAD and limbs, correlated variability of, ii. 323. + HEADACHE, inheritance of, ii. 79. + HEARTSEASE, i. 368-369; + change produced in the, by transplantation, i. 386; + reversion in, ii. 31, 47; + effects of selection on, ii. 200; + scorching of, ii. 229; + effects of seasonal conditions on the, ii. 274; + annual varieties of the, ii. 305. + HEAT, effect of, upon the fleece of sheep, i. 98. + HEBER, Bishop, on the breeding of the rhinoceros in captivity, ii. 150. + HEBRIDES, cattle of the, i. 80; + pigeons of the, i. 183. + HEER, O., on the plants of the Swiss lake-dwellings, i. 309, ii. 215, + 427; + on the cereals, i. 317-319; + on the peas, i. 326; + on the vine growing in Italy in the bronze age, i. 332. + _Helix lactea_, ii. 280. + _Hemerocallis fulva_ and _flava_, interchanging by bud-variation, i. 386. + HEMLOCK yields no conicine in Scotland, ii. 274. + HEMP, differences of, in various parts of India, ii. 165; + climatal difference in products of, ii. 274. + HEMPSEED, effect of, upon the colour of birds, ii. 280. + HERMAPHRODITE flowers, occurrence of, in Maize, i. 321. + HEN, assumption of male characters by the, ii. 51, 54; + development of spurs in the, ii. 318. + "HENNIES," or hen-like male fowls, i. 252. + HENRY, T. A., a variety of the ash produced by grafting, i. 394; + crossing of species of _Rhododendron_ and _Arabis_, i. 400. + HENSLOW, Prof., individual variation in wheat, i. 314; + bud-variation in the Austrian bramble rose, i. 381; + partial reproduction of the weeping ash by seed, ii. 19. + HEPATICA, changed by transplantation, i. 386. + HERBERT, Dr., variations of _Viola grandiflora_, i. 368; + bud-variation in camellias, i. 377; + seedlings from reverted _Cytisus Adami_, i. 388; + crosses of Swedish and other turnips, ii. 93; + on hollyhocks, ii. 107; + breeding of hybrids, ii. 131; + self-impotence in hybrid hippeastrums, ii. 138-139; + hybrid _Gladiolus_, ii. 139; + on _Zephyranthes candida_, ii. 164; + fertility of the crocus, ii. 165; + on contabescence, ii. 165; + hybrid _Rhododendron_, ii. 265. + HERCULANEUM, figure of a pig found in, i. 67. + HERON, Sir R., appearance of "black-shouldered" among ordinary peacocks, + i. 290-291; + non-inheritance of monstrous characters by goldfish, i. 296; + crossing of white and coloured Angora rabbits, ii. 92; + crosses of solid-hoofed pigs, ii. 93. + _Herpestes fasciatus_ and _griseus_, ii. 151. + HEUSINGER, on the sheep of the Tarentino, ii. 227; + on correlated constitutional peculiarities, ii. 337. + HEWITT, Mr., reversion in bantam cocks, i. 240; + degeneration of silk fowls, i. 243; + partial sterility of hen-like male fowls, i. 252; + production of tailed chickens by rumpless fowls, i. 259; + on taming and rearing wild ducks, i. 278-279, ii. 233, 262-263; + conditions of inheritance in laced Sebright bantams, ii. 22; + reversion in rumpless fowls, ii. 31; + reversion in fowls by age, ii. 39; + hybrids of pheasant and fowl, ii. 45, 68; + assumption of male characters by female pheasants, ii. 51; + development of latent characters in a barren bantam hen, ii. 54; + mongrels from the silk-fowl, ii. 67; + effects of close interbreeding on fowls, ii. 124-125; + on feathered-legged bantams, ii. 323. + HIBBERT, Mr., on the pigs of the Shetland Islands, i. 70. + HIGHLAND cattle, descended from _Bos longifrons_, i. 81. + HILDEBRAND, Dr., on the fertilisation of _Orchideæ_, i. 402-403; + occasional necessary crossing of plants, ii. 90; + on _Primula sinensis_ and _Oxalis rosea_, ii. 132; + on _Corydalis cava_, ii. 132-133. + HILL, R., on the Alco, i. 31; + feral rabbits in Jamaica, i. 112; + feral peacocks in Jamaica, i. 190; + variation of the Guinea fowl in Jamaica, i. 294; + sterility of tamed birds in Jamaica, ii. 155, 157. + HIMALAYA, range of gallinaceous birds in the, i. 237. + HIMALAYAN rabbit, i. 107, 108-111; + skull of, i. 120. + HIMALAYAN sheep, i. 95. + HINDMARSH, Mr., on Chillingham cattle, i. 84. + "HINKEL-TAUBE," i. 142-143. + HINNY and mule, difference of, ii. 67-68. + _Hipparion_, anomalous resemblance to in horses, i. 50. + _Hippeastrum_, hybrids of, ii. 138-139. + HIVE-BEES, ancient domestication of, i. 297; + breeds of, i. 298; + smaller when produced in old combs, i. 297; + variability in, i. 298; + crossing of Ligurian and common, i. 299. + "HOCKER-TAUBE," i. 141. + HOBBS, Fisher, on interbreeding pigs, ii. 121. + HODGKIN, Dr., on the attraction of foxes by a female Dingo, i. 31; + {457} + origin of the Newfoundland dog, i. 42; + transmission of a peculiar lock of hair, ii. 5. + HODGSON, Mr., domestication of _Canis primævus_, i. 26; + development of a fifth digit in Thibet mastiffs, i. 35; + number of ribs in humped cattle, i. 79; + on the sheep of the Himalaya, i. 95; + presence of four mammæ in sheep, _ibid._; + arched nose in sheep, i. 96; + measurements of the intestines of goats, i. 102; + presence of interdigital pits in goats, _ibid._; + disuse a cause of drooping ears, ii. 301. + HOFACKER, persistency of colour in horses, i. 51, ii. 21; + production of dun horses from parents of different colours, i. 59; + inheritance of peculiarities in handwriting, ii. 6; + heredity in a one-horned stag, ii. 12; + on consanguineous marriages, ii. 123. + HOG, Red River, ii. 150. + HOGG, Mr., retardation of breeding in cows by hard living, ii. 112. + HOLLAND, Sir H., necessity of inheritance, ii. 2; + on hereditary diseases, ii. 7; + hereditary peculiarity in the eyelid, ii. 8; + morbid uniformity in the same family, ii. 17; + transmission of hydrocele through the female, ii. 52; + inheritance of habits and tricks, ii. 395. + HOLLY, varieties of the, i. 360, 362; + bud-reversion in, i. 384; + yellow-berried, ii. 19, 230. + HOLLYHOCK, bud-variation in, i. 378; + non-crossing of double varieties of, ii. 107; + tender variety of the, ii. 310. + HOMER, notice of Geese, i. 287; + breeding of the horses of Æneas, ii. 202. + HOMOLOGOUS parts, correlated variability of, ii. 322-331, 354-355; + fusion of, ii. 393; + affinity of, ii. 339-342. + HOOFS, correlated with hair in variation, ii. 325. + HOOK-BILLED DUCK, skull figured, i. 282. + HOOKER, Dr. J. D., forked shoulder-stripe in Syrian asses, i. 63; + voice of the cock in Sikkim, i. 259; + use of Arum-roots as food, i. 307; + native useful plants of Australia, i. 311; + wild walnut of the Himalayas, i. 356; + variety of the plane tree, i. 362; + production of _Thuja orientalis_ from seeds of _T. pendula_, i. 362; + singular form of _Begonia frigida_, i. 365; + reversion in plants run wild, ii. 33; + on the sugar-cane, ii. 169; + on Arctic plants, ii. 256; + on the oak grown at the Cape of Good Hope, ii. 274; + on _Rhododendron ciliatum_, ii. 277; + stock and mignonette, perennial in Tasmania, ii. 305. + HOPKIRK, Mr., bud-variation in the rose, i. 381; + in _Mirabilis jalapa_, i. 382; + in _Convolvulus tricolor_, i. 408. + HORNBEAM, heterophyllous, i. 362. + HORNED fowl, i. 229; + skull figured, i. 265. + HORNLESS cattle in Paraguay, i. 89. + HORNS of sheep, i. 95; + correlation of, with fleece in sheep, ii. 326; + correlation of, with the skull, ii. 333; + rudimentary in young polled cattle, ii. 315; + of goats, i. 102. + HORSES, in Swiss lake-dwellings, i. 49; + different breeds of, in Malay Archipelago, i. 49; + anomalies in osteology and dentition of, i. 50; + mutual fertility of different breeds, i. 51; + feral, i. 51; + habit of scraping away snow, i. 53; + mode of production of breeds of, i. 54; + inheritance and diversity of colour in, i. 55; + dark stripes in, i. 56-61, ii. 351; + dun-coloured, origin of, i. 59; + colours of feral, i. 60-61; + effect of fecundation by a Quagga on the subsequent progeny of, i. + 403-404; + inheritance of peculiarities in, ii. 10-11; + polydactylism in, ii. 14; + inheritance of colour in, ii. 21; + inheritance of exostoses in legs of, ii. 23; + reversion in, ii. 33, 41; + hybrids of, with ass and zebra, ii. 42; + prepotency of transmission in the sexes of, ii. 65; + segregation of, in Paraguay, ii. 102; + wild species of, breeding in captivity, ii. 150; + curly, in Paraguay, ii. 205, 325; + selection of, for trifling characters, ii. 209; + unconscious selection of, ii. 212-213; + natural selection in Circassia, ii. 225; + alteration of coat of, in coal-mines, ii. 278; + degeneration of, in the Falkland Islands, ii. 278; + diseases of, caused by shoeing, ii. 300; + feeding on meat, ii. 305; + white and white-spotted, poisoned by mildewed vetches, ii. 337; + analogous variations in the colour of, ii. 349; + teeth developed on palate of, ii. 391; + of bronze period in Denmark, ii. 427. + HORSE-CHESNUT, early, at the Tuileries, i. 362; + tendency to doubleness in, ii. 168. + HORSE-RADISH, general sterility of the, ii. 170. + "HOUDAN," a French sub-breed of fowls, i. 229. + HOWARD, C., on an Egyptian monument, i. 17; + on crossing sheep, ii. 95, 120. + HUC, on the Emperor Khang-hi, ii. 205; + Chinese varieties of the bamboo, ii. 256. + HUMBOLDT, A., character of the Zambos, ii. 47; + parrot speaking the language of an extinct tribe, ii. 154; + on _Pulex penetrans_, ii. 275. + HUMIDITY, injurious effect of, upon horses, i. 53. + HUMPHREYS, Col., on Ancon sheep, i. 100. + HUNGARIAN cattle, i. 80. + {458} + HUNTER, John, period of gestation in the dog, i. 29; + on secondary sexual characters, i. 179; + fertile crossing of _Anser ferus_ and the domestic goose, i. 288; + inheritance of peculiarities in gestures, voice, &c., ii. 6; + assumption of male characters by the human female, ii. 51; + period of appearance of hereditary diseases, ii. 78; + graft of the spur of a cock upon its comb, ii. 296; + on the stomach of _Larus tridentatus_, ii. 302; + double-tailed lizards, ii. 341. + HUNTER, W., evidence against the influence of imagination upon the + offspring, ii. 264. + HUTTON, Capt., on the variability of the silk moth, i. 303; + on the number of species of silkworms, i. 300; + markings of silkworms, i. 302; + domestication of the rock-pigeon in India, i. 185; + domestication and crossing of _Gallus bankiva_, i. 236. + HUTCHINSON, Col., liability of dogs to distemper, i. 35. + HUXLEY, Prof., on the transmission of polydactylism, ii. 13; + on unconscious selection, ii. 194; + on correlation in the mollusca, ii. 320; + on gemmation and fission, ii. 359; + development of star-fishes, ii. 366. + HYACINTHS, i. 370-371; + bud-variation in, i. 385; + graft-hybrid by union of half bulbs of, i. 395; + white, reproduced by seed, ii. 20; + red, ii. 229, 336; + varieties of, recognisable by the bulb, ii. 251. + HYACINTH, feather, ii. 185, 316. + _Hyacinthus orientalis_, i. 370. + _Hybiscus syriacus_, ii. 286. + HYBRIDS, of hare and rabbit, i. 105; + of various species of _Gallus_, i. 234-236; + of almond, peach, and nectarine, i. 339; + naturally produced, of species of _Cytisus_, i. 390; + from twin-seed of _Fuchsia coccinea_ and _fulgens_, i. 391; + reversion of, i. 392-394, ii. 36, 48-50; + from mare, ass, and zebra, ii. 42; + of tame animals, wildness of, ii. 44-46; + female instincts of sterile male, ii. 52; + transmission and blending of characters in, ii. 92-95; + breed better with parent species than with each other, ii. 131; + self-impotence in, ii. 138-140; + readily produced in captivity, ii. 151. + HYBRIDISATION, singular effects of, in oranges, i. 336; + of cherries, i. 347; + difficulty of, in _Cucurbitæ_, i. 358; + of roses, i. 366. + HYBRIDISM, ii. 178-191; + the cause of a tendency to double flowers, ii. 171; + in relation to pangenesis, ii. 385. + HYBRIDITY in cats, i. 44-45; + supposed of peach and nectarine, i. 342. + _Hydra_, i. 374, ii. 293, 359. + HYDRANGEA, colour of flowers of, influenced by alum, ii. 277. + HYDROCELE, ii. 52. + HYDROCEPHALUS, ii. 295. + _Hypericum calycinum_, ii. 170. + _Hypericum crispum_, ii. 227, 337. + HYPERMETAMORPHOSIS, ii. 367. + HYPERMETROPIA, hereditary, ii. 8. + + ICHTHYOPTERYGIA, number of digits in the, ii. 16. + _Ilex aquifolium_, ii. 19. + IMAGINATION, supposed effect of, on offspring, ii. 263. + _Imatophyllum miniatum_, bud-variation in, i. 385. + INCEST, abhorred by savages, ii. 123-124. + INCUBATION, by crossed fowls of non-sitting varieties, ii. 43-44. + INDIA, striped horses of, i. 58; + pigs of, i. 66, 67, 76; + breeding of rabbits in, i. 112; + cultivation of pigeons in, i. 205-206. + INDIVIDUAL variability in pigeons, i. 158-160. + INGLEDEW, Mr., cultivation of European vegetables in India, ii. 169. + "INDISCHE Taube," ii. 144. + INHERITANCE, ii. 1-84, 371-373, 395, 397-402; + doubts entertained of by some writers, ii. 3; + importance of to breeders, 3-4; + evidence of, derived from statistics of chances, 5; + of peculiarities in man, 5-7, 12-16; + of disease, 7-8, 17; + of peculiarities in the eye, 8-10; + of deviations from symmetry, 12; + of polydactylism, 12-16; + capriciousness of, 17-22, 27; + of mutilations, 22-24; + of congenital monstrosities, 24; + causes of absence of, 24-26; + by reversion or atavism, 28-61; + its connexion with fixedness of character, 62-64; + affected by prepotency of transmission of character, 65-71; + limited by sex, 71-75; + at corresponding periods of life, 75-80; + summary of the subject of, 80-84; + laws of, the same in seminal and bud varieties, i. 409; + of characters in the horse, i. 10-11; + in cattle, i. 87; + in rabbits, i. 107; + in the peach, i. 339; + in the nectarine, i. 340; + in plums, i. 347; + in apples, i. 350; + in pears, i. 351; + in the pansy, i. 369; + of primary characters of _Columba livia_ in crossed pigeons, i. 201; + of peculiarities of plumage in pigeons, i. 160-161; + of peculiarities of foliage in trees, i. 362; + effects of, in varieties of the cabbage, i. 325. + INSANITY, inheritance of, ii. 7, 78. + INSECTS, regeneration of lost parts in, ii. 15, 294; + agency of, in fecundation of larkspurs, ii. 21; + effect of changed conditions upon, ii. 157; + sterile neuter, ii. 186-187; + {459} + monstrosities in, ii. 269, 391. + INSTINCTS, defective, of silkworms, i. 304. + INTERBREEDING, close, ill effects of, ii. 114-131, 175. + INTERCROSSING, of species, as a cause of variation, i. 188; + natural, of plants, i. 336; + of species of Canidæ and breeds of dogs, i. 31-33; + of domestic and wild cats, i. 44-45; + of breeds of pigs, i. 71, 78; + of cattle, i. 83; + of varieties of cabbage, i. 324; + of peas, i. 326, 329-330; + of varieties of orange, i. 336; + of species of strawberries, i. 351-352; + of _Cucurbitæ_, i. 357-358; + of flowering plants, i. 364; + of pansies, i. 368. + INTERDIGITAL pits, in goats, i. 102. + INTERMARRIAGES, close, ii. 122-123. + INTESTINES, elongation of, in pigs, i. 73; + relative measurements of parts of, in goats, i. 102; + effects of changed diet on, ii. 302. + _Ipomoea purpurea_, ii. 128. + IRELAND, remains of _Bos frontosus_ and _longifrons_ found in, i. 81. + IRIS, hereditary absence of the, ii. 9; + hereditary peculiarities of colour of the, ii. 9-10. + IRISH, ancient, selection practised by the, ii. 203. + IRON period, in Europe, dog of, i. 18. + ISLANDS, oceanic, scarcity of useful plants on, i. 311. + ISLAY, pigeons of, i. 183. + ISOLATION, effect of, in favour of selection, ii. 233-234. + ITALY, vine growing in, during the bronze period, i. 332. + IVY, sterility of, in the north of Europe, ii. 170. + + JACK, Mr., effect of foreign pollen on grapes, i. 400. + JACKAL, i. 24, 27, 30; + hybrids of, with the dog, i. 32; + prepotency of, over the dog, ii. 67. + JACOBIN pigeon, i. 154, 208. + JACQUEMET-BONNEFORT, on the mulberry, i. 334. + JAGUAR, with crooked legs, i. 17. + JAMAICA, feral dogs of, i. 28; + feral pigs of, i. 77; + feral rabbits of, i. 112. + JAPAN, horses of, i. 53. + JAPANESE pig (figured), i. 69. + JARDINE, Sir W., crossing of domestic and wild cats, i. 44. + JARVES, J., silkworm in the Sandwich islands, i. 301. + JAVA, Fantail pigeon in, i. 148. + JAVANESE ponies, i. 53, 59. + JEMMY BUTTON, i. 309. + JENYNS, L., whiteness of ganders, i. 288; + sunfish-like variety of the goldfish, i. 297. + JERDON, J. C., number of eggs laid by the pea-hen, ii. 112; + origin of domestic fowl, i. 237. + JERSEY, arborescent cabbages of, i. 323. + JESSAMINE, i. 394. + JEITTELES, Hungarian sheep-dogs, i. 24; + crossing of domestic and wild cats, i. 44. + JOHN, King, importation of stallions from Flanders by, ii. 203. + JOHNSON, D., occurrence of stripes on young wild pigs in India, i. 76. + JORDAN, A., on Vibert's experiments on the vine, i. 332; + origin of varieties of the apple, i. 350; + varieties of pears found wild in woods, ii. 260. + JOURDAN, parthenogenesis in the silk moth, ii. 364. + JUAN DE NOVA, wild dogs on, i. 27. + JUAN FERNANDEZ, dumb dogs on, i. 27. + _Juglans regia_, i. 356-357. + JUKES, Prof., origin of the Newfoundland dog, i. 42. + JULIEN, Stanislas, early domestication of pigs in China, i. 68; + antiquity of the domestication of the silk-worm in China, i. 300. + JUMPERS, a breed of fowls, i. 230. + JUNIPER, variations of the, i. 361, 364. + _Juniperus suecica_, i. 361. + _Jussiæa grandiflora_, ii. 170. + JUSSIEU, A. de, structure of the pappus in _Carthamus_, ii. 316. + + KAIL, Scotch, reversion in, ii. 32. + "KALA-PAR" pigeon, i. 142. + KALES, i. 323. + KALM, P., on maize, i. 322, ii. 307; + introduction of wheat into Canada, i. 315; + sterility of trees growing in marshes and dense woods, ii. 170. + "KALMI Lotan," tumbler pigeon, i. 151. + KANE, Dr., on Esquimaux dogs, i. 21. + KARAKOOL sheep, i. 98. + KARKEEK, on inheritance in the horse, ii. 10. + "KARMELITEN Taube," i. 156. + KARSTEN on _Pulex penetrans_, ii. 275. + KATTYWAR horses, i. 58. + KEELEY, R., pelorism in _Galeobdolon luteum_, ii. 59. + KERNER on the culture of Alpine plants, ii. 163. + KESTREL, breeding in captivity, ii. 154. + "KHANDÉSI," i. 141. + KHANG-HI, selection of a variety of rice by, ii. 205. + KIANG, ii. 43. + KIDD, on the canary bird, i. 77, ii. 275. + KIDNEY Bean, i. 371; + varieties of, ii. 256, 275. + {460} + KIDNEYS, compensatory development of the, ii. 300; + fusion of the, ii. 341; + shape of, in birds, influenced by the form of the pelvis, ii. 344. + KING, Col., domestication of rock doves from the Orkneys, i. 184, 185. + KING, P. S., on the Dingo, i. 21, 28. + KIRBY and Spence, on the growth of galls, ii. 283. + KIRGHISIAN sheep, i. 98. + KITE, breeding in captivity, ii. 154. + KLEINE, variability of bees, i. 298. + KNIGHT, Andrew, on crossing horses of different breeds, i. 51; + crossing varieties of peas, i. 326, ii. 129; + persistency of varieties of peas, i. 329; + origin of the peach, i. 338; + hybridisation of the morello by the Elton cherry, i. 347; + on seedling cherries, _ibid._; + variety of the apple not attacked by coccus, i. 349; + intercrossing of strawberries, i, 351, 352; + broad variety of the cock's comb, i. 365; + bud variation in the cherry and plum, i. 375; + crossing of white and purple grapes, i. 393; + experiments in crossing apples, i. 402, ii. 129; + hereditary disease in plants, ii. 11; + on interbreeding, ii. 116; + crossed varieties of wheat, ii. 130; + necessity of intercrossing in plants, ii. 175; + on variation, ii. 256, 257; + effects of grafting, i. 387, ii. 278; + bud-variation in a plum, ii. 289; + compulsory flowering of early potatoes, ii. 343; + correlated variation of head and limbs, ii. 323. + KNOX, Mr., breeding of the eagle owl in captivity, ii. 154. + KOCH, degeneracy in the turnip, i. 325. + KOHLRABI, i. 323. + KÖLREUTER, reversion in hybrids, i. 392, ii. 36; + acquired sterility of crossed varieties of plants, i. 358, ii. 101; + absorption of _Mirabilis vulgaris_ by _M. longiflora_, ii. 88; + crosses of species of _Verbascum_, ii. 93, 107; + on the hollyhock, ii. 107; + crossing varieties of tobacco, ii. 108; + benefits of crossing plants, ii. 130, 131, 175-176; + self-impotence in _Verbascum_, ii. 136, 141; + effects of conditions of growth upon fertility in _Mirabilis_, ii. 164; + great development of tubers in hybrid plants, ii. 172; + inheritance of plasticity, ii. 241; + variability of hybrids of _Mirabilis_, ii. 265; + repeated crossing a cause of variation, ii. 267-268; + number of pollen-grains necessary for fertilization, ii. 363. + "KRAUSESCHWEIN," i. 67. + KROHN, on the double reproduction of Medusæ, ii. 384. + "KROPF-TAUBEN," i. 137. + + LABAT, on the tusks of feral bears in the West Indies, i. 77; + on French wheat grown in the West Indies, ii. 307; + on the culture of the vine in the West Indies, ii. 308. + LABURNUM, Adam's, see _Cytisus Adami_; + oak-leaved, reversion of, i. 382; + pelorism in the, ii. 346; + Waterer's, i. 390. + LACHMANN, on gemmation and fission, ii. 358. + _Lachnanthes tinctoria_, ii. 227, 336. + LACTATION, imperfect, hereditary, ii. 8; + deficient, of wild animals in captivity, ii. 158. + LADRONE islands, cattle of, i. 86. + LAING, Mr., resemblance of Norwegian and Devonshire cattle, i. 82. + LAKE-DWELLINGS, sheep of, i. 94, ii. 427; + cattle of, ii. 427; + absence of the fowl in, i. 246; + cultivated plants of, i. 309, ii. 427, 429; + cereals of, i. 317-319; + peas found in, i. 326; + beans found in, i. 330. + LAMARE-PIQUOT, observations on half-bred North American wolves, i. 22. + LAMBERT, A. B., on _Thuja pendula_ or _filiformis_, i. 362. + LAMBERT family, ii. 4, 76. + LAMBERTYE on strawberries, i. 351, 352; + five-leaved variety of _Fragaria collina_, i. 353. + LANDT, L., on sheep in the Faroe islands, ii. 103. + LA PLATA, wild dogs of, i. 27; + feral cat from, i. 47. + LARCH, ii. 310. + LARKSPURS, insect agency necessary for the full fecundation of, ii. 21. + _Larus argentatus_, ii. 157. + _Larus tridactylus_, ii. 302. + LASTERYE, merino sheep in different countries, i. 99. + LATENT characters, ii. 51-56. + LATHAM, on the fowl not breeding in the extreme north, ii. 161. + _Lathyrus_, ii. 38. + _Lathyrus aphaca_, ii. 343. + _Lathyrus odoratus_, ii. 20, 91, 93, 311, 393. + LA TOUCHE, J. D., on a Canadian apple with dimidiate fruit, i. 392-393. + "LATZ-TAUBE," i. 154. + LAUGHER pigeon, i. 155, 207. + _Laurus sassafras_, ii. 274. + LAWRENCE, J., production of a new breed of fox-hounds, i. 40; + occurrence of canines in mares, i. 50; + on three-parts-bred horses, i. 54; + on inheritance in the horse, ii. 10-11. + LAWSON, Mr., varieties of the potato, i. 330. + LAXTON, Mr., bud-variation in the gooseberry, i. 376; + crossing of varieties of the pea, i. 397-398; + {461} + double-flowered peas, ii. 168. + LAYARD, E. L., resemblance of a Caffre dog to the Esquimaux breed, i. 25, + ii. 286; + crossing of the domestic cat with _Felis Caffra_, i. 44; + feral pigeons in Ascension, i. 190; + domestic pigeons of Ceylon, i. 206; + on _Gallus Stanleyi_, i. 234; + on black-skinned Ceylonese fowls, i. 256. + LE COMPTE family, blindness inherited in, ii. 78. + LECOQ, bud-variation in _Mirabilis jalapa_, i. 382; + hybrids of _Mirabilis_, i. 393, ii. 169, 265; + crossing in plants, ii. 127; + fecundation of _Passiflora_, ii. 137; + hybrid _Gladiolus_, ii. 139; + sterility of _Ranunculus ficaria_, ii. 170; + villosity in plants, ii. 277; + double asters, ii. 316. + LE COUTEUR, J., varieties of wheat, i. 313-315; + acclimatisation of exotic wheat in Europe, i. 315; + adaptation of wheat to soil and climate, i. 316; + selection of seed-corn, i. 318; + on change of soil, ii. 147; + selection of wheat, ii. 200; + natural selection in wheat, ii. 233; + cattle of Jersey, ii. 234. + LEDGER, Mr., on the Llama and Alpaca, ii. 208. + LEE, Mr., his early culture of the pansy, i. 368. + _Leersia oryzoides_, ii. 91. + LEFOUR, period of gestation in cattle, i. 87. + LEGS, of fowls, effects of disuse on, i. 270-272; + characters and variations of, in ducks, i. 284-288; + fusion of, ii. 341. + LEGUAT, cattle of the Cape of Good Hope, i. 88. + LEHMANN, occurrence of wild double-flowered plants near a hot spring, ii. + 168. + LEIGHTON, W. A., propagation of a weeping yew by seed, ii. 19. + LEITNER, effects of the removal of anthers, ii. 167. + LEMMING, ii. 152. + LEMOINE, variegated _Symphytum_ and _Phlox_, i. 384. + LEMON, i. 334, 335; + orange fecundated by pollen of the, i. 399. + LEMURS, hybrid, ii. 153. + LEPORIDES, ii. 98-99, 152. + LEPSIUS, figures of ancient Egyptian dogs, i. 17; + domestication of pigeons in ancient Egypt, i. 204. + _Leptotes_, ii. 134. + _Lepus glacialis_, i. 111. + _Lepus magellanicus_, i. 112. + _Lepus nigripes_, i. 108. + _Lepus tibetanus_, i. 111. + _Lepus variabilis_, i. 111. + LEREBOULLET, double monsters of fishes, ii. 340. + LESLIE, on Scotch wild cattle, i. 85. + LESSON, on _Lepus magellanicus_, i. 112. + LEUCKART on the larva of Cecidomyidæ, ii. 360. + LEWIS, G., cattle of the West Indies, ii. 229. + LHERBETTE and Quatrefages, on the horses of Circassia, ii. 102, 225. + LIEBIG, differences in human blood, according to complexion, ii. 276. + LIEBREICH, occurrence of pigmentary retinitis in deaf-mutes, ii. 328. + LICHENS, sterility in, ii. 171. + LICHTENSTEIN, resemblance of Bosjesman's dogs to _Canis mesomelas_, i. + 25; + Newfoundland dog at the Cape of Good Hope, i. 36. + LILACS, ii. 164. + LILIACEÆ, contabescence in, ii. 165. + _Lilium candidum_, ii. 137. + LIMBS, regeneration of, ii. 376-377. + LIMBS and head, correlated variation of, ii. 323. + LIME, effect of, upon shells of the mollusca, ii. 280. + LIME tree, changes of by age, i. 364, 387. + LIMITATION, sexual, ii. 71-75. + LIMITATION, supposed, of variation, ii. 416. + _Linaria_, pelorism in, ii. 58, 61, 346; + peloric, crossed with the normal form, ii. 70; + sterility of, ii. 166. + _Linaria vulgaris_ and _purpurea_, hybrids of, ii. 94. + LINDLEY, John, classification of varieties of cabbages, i. 324; + origin of the peach, i. 338; + influence of soil on peaches and nectarines, i. 340; + varieties of the peach and nectarine, i. 343; + on the New Town pippin, i. 349; + freedom of the Winter Majetin apple from coccus, i. 349; + production of monoecious Hautbois strawberries by bud-selection, i. + 353; + origin of the large tawny nectarine, i. 375; + bud-variation in the gooseberry, i. 376; + hereditary disease in plants, ii. 11; + on double flowers, ii. 167; + seeding of ordinarily seedless fruits, ii. 168; + sterility of _Acorus calamus_, ii. 170; + resistance of individual plants to cold, ii. 309. + LINNÆUS, summer and winter wheat regarded as distinct species by, i. 315; + on the single-leaved strawberry, i. 353; + sterility of Alpine plants in gardens, ii. 163; + recognition of individual reindeer by the Laplanders, ii. 251; + growth of tobacco in Sweden, ii. 307. + LINNET, ii. 158. + _Linota cannabina_, ii. 158. + {462} + LINUM, ii. 165. + LION, fertility of, in captivity, ii. 150, 151. + LIPARI, feral rabbits of, i. 113. + LIVINGSTONE, Dr., striped young pigs on the Zambesi, i. 77; + domestic rabbits at Loanda, i. 112; + use of grass-seeds as food in Africa, i. 308; + planting of fruit-trees by the Batokas, i. 309; + character of half-castes, ii. 46; + taming of animals among the Barotse, ii. 160; + selection practised in South Africa, ii. 207, 209. + LIVINGSTONE, Mr., disuse a cause of drooping ears, ii. 301. + LIZARDS, reproduction of tail in, ii. 294; + with a double tail, ii. 341. + LLAMA, selection of, ii. 208. + LLOYD, Mr., taming of the wolf, i. 26; + English dogs in northern Europe, i. 36; + fertility of the goose increased by domestication, i. 288; + number of eggs laid by the wild goose, ii. 112; + breeding of the capercailzie in captivity, ii. 156. + LOANDA, domestic rabbits at, i. 112. + _Loasa_, hybrid of two species of, ii. 98. + _Lobelia_, reversion in hybrids of, ii. 392; + contabescence in, ii. 166. + _Lobelia fulgens_, _cardinalis_, and _syphilitica_, ii. 136. + LOCKHART, Dr., on Chinese pigeons, i. 206. + LOCUST-TREE, ii. 274. + LOISELEUR-DESLONGCHAMPS, originals of cultivated plants, i. 307; + Mongolian varieties of wheat, i. 313; + characters of the ear in wheat, i. 314; + acclimatisation of exotic wheat in Europe, i. 315; + effect of change of climate on wheat, i. 316; + on the supposed necessity of the coincident variation of weeds and + cultivated plants, i. 317; + advantage of change of soil to plants, ii. 146. + _Lolium temulentum_, variable presence of barbs in, i. 314. + LONG-TAILED sheep, i. 94, 95. + LOOCHOO islands, horses of, i. 53. + LORD, J. K., on Canis latrans, i. 22. + "LORI RAJAH," how produced, ii. 280. + _Lorius garrulus_, ii. 280. + "LOTAN," tumbler pigeon, i. 150. + LOUDON, J. W., varieties of the carrot, i. 326; + short duration of varieties of peas, i. 329; + on the glands of peach-leaves, i. 343; + presence of bloom on Russian apples, i. 349; + origin of varieties of the apple, i. 350; + varieties of the gooseberry, i. 354; + on the nut tree, i. 357; + varieties of the ash, i. 360; + fastigate juniper (_J. suecica_), i. 361; + on _Ilex aquifolium ferox_, i. 362; + varieties of the Scotch fir, i. 363; + varieties of the hawthorn, _ibid._; + variation in the persistency of leaves on the elm and Turkish oak, i. + 363; + importance of cultivated varieties, _ibid._; + varieties of _Rosa spinosissima_, i. 367; + variation of dahlias from the same seed, i. 370; + production of Provence roses from seeds of the moss rose, i. 380; + effect of grafting the purple-leaved upon the common hazel, i. 395; + nearly evergreen Cornish variety of the elm, ii. 310. + LOW, G., on the pigs of the Orkney islands, i. 70. + LOW, Prof., pedigrees of greyhounds, ii. 3; + origin of the dog, i. 10; + burrowing instinct of a half-bred Dingo, i. 28; + inheritance of qualities in horses, i. 51; + comparative powers of English race-horses, Arabs, &c., i. 54; + British breeds of cattle, i. 80; + wild cattle of Chartley, i. 84; + effect of abundance of food on the size of cattle, i. 91; + effects of climate on the skin of cattle, i. 92, ii. 326; + on interbreeding, ii. 116; + selection in Hereford cattle, ii. 214; + formation of new breeds, ii. 244; + on "sheeted" cattle, ii. 349. + LOWE, Mr., on hive bees, i. 299. + LOWE, REV. Mr., on the range of _Pyrus malus_ and _P. acerba_, i. 348. + "LOWTAN" tumbler pigeon, i. 150. + _Loxia pyrrhula_, ii. 154. + LUBBOCK, Sir J., developments of the Ephemeridæ, ii. 366. + LUCAS, P., effects of cross-breeding on the female, i. 404; + hereditary diseases, ii. 7, 78-79; + hereditary affections of the eye, ii. 9-10; + inheritance of anomalies in the human eye and in that of the horse, ii. + 10, 11; + inheritance of polydactylism, ii. 13; + morbid uniformity in the same family, ii. 17; + inheritance of mutilations, ii. 23; + persistency of cross-reversion, ii. 35; + persistency of character in breeds of animals in wild countries, ii. + 64; + prepotency of transmission, ii. 65, 68; + supposed rules of transmission in crossing animals, ii. 68; + sexual limitations of transmission of peculiarities, ii. 72-73; + absorption of the minority in crossed races, ii. 88; + crosses without blending of certain characters, ii. 92; + on interbreeding, ii. 116; + variability dependent on reproduction, ii. 250; + period of action of variability, ii. 260; + inheritance of deafness in cats, ii. 329; + complexion and constitution, ii. 335. + LUCAZE-DUTHIERS, structure and growth of galls, ii. 282-284. + LUIZET, grafting of a peach-almond on a peach, i. 338. + {463} + LÜTKE, cats of the Caroline Archipelago, i. 47. + LUXURIANCE, of vegetative organs, a cause of sterility in plants, ii. + 168-171. + LYONNET, on the scission of _Nais_, ii. 358. + _Lysimachia nummularia_, sterility of, ii. 170. + _Lythrum_, trimorphic species of, ii. 400. + _Lythrum salicaria_, ii. 183; + contabescence in, ii. 166. + _Lytta vesicatoria_, affecting the kidneys, ii. 380. + + _Macacus_, species of, bred in captivity, ii. 153. + MACAULAY, Lord, improvement of the English horse, ii. 213. + MCCLELLAND, Dr., variability of fresh-water fishes in India, ii. 259. + MCCOY, Prof., on the dingo, i. 26. + MACFAYDEN, influence of soil in producing sweet or bitter oranges from + the same seed, i. 335. + MACGILLIVRAY, domestication of the rock-dove, i. 185; + feral pigeons in Scotland, i. 190; + number of vertebræ in birds, i. 266; + on wild geese, i. 287; + number of eggs of wild and tame ducks, ii. 112. + MACKENZIE, Sir G., peculiar variety of the potato, i. 330. + MACKENZIE, P., bud-variation in the currant, i. 376. + MACKINNON, Mr., horses of the Falkland islands, i. 52; + feral cattle of the Falkland islands, i. 86. + MACKNIGHT, C., on interbreeding cattle, ii. 118. + MACNAB, Mr., on seedling weeping birches, ii. 18; + non-production of the weeping beech by seed, ii. 19. + MADAGASCAR, cats of, i. 47. + MADDEN, H., on interbreeding cattle, ii. 118. + MADEIRA, rock pigeon of, i. 184. + _Magnolia grandiflora_, ii. 308. + MAIZE, its unity of origin, i. 320; + antiquity of, _ibid._; + with husked grains said to grow wild, _ibid._; + variation of, i. 321; + irregularities in the flowers of, i. 321; + persistence of varieties, _ibid._; + adaptation of to climate, i. 322, ii. 307; + acclimatisation of, ii. 313, 347; + crossing of, i. 400, ii. 104-105; + extinct Peruvian varieties of, ii. 425. + MALAY fowl, i. 227. + MALAY Archipelago, horses of, i. 53; + short-tailed cats of, i. 47; + striped young wild pigs of, i. 76; + ducks of, i. 280. + MALE, influence of, on the fecundated female, i. 397-406; + supposed influence of, on offspring, ii. 68. + MALE flowers, appearance of, among female flowers in maize, i. 321. + MALFORMATIONS, hereditary, ii. 79. + _Malva_, fertilisation of, i. 402, ii. 363. + _Mamestra suasa_, ii. 157. + MAMMÆ, variable in number in the pig, i. 74; + rudimentary, occasional full development of, in cows, i. 87, ii. 317; + four present in some sheep, i. 95; + variable in number in rabbits, i. 106; + latent functions of, in male animals, ii. 52, 317; + supernumerary and inguinal, in women, ii. 57. + MANGLES, Mr., annual varieties of the heartsease, ii. 305. + MANTELL, Mr., taming of birds by the New Zealanders, ii. 161. + MANU, domestic fowl noticed in the Institutes of, i. 246. + MANURE, effect of, on the fertility of plants, ii. 163. + MANX cats, i. 46, ii. 66. + MARCEL de Serres, fertility of the ostrich, ii. 156. + MARIANNE islands, varieties of _Pandanus_ in, ii. 256. + MARKHAM, Gervase, on rabbits, i. 104, ii. 204. + MARKHOR, probably one of the parents of the goat, i. 101. + MARQUAND, cattle of the channel islands, i. 80. + MARRIMPOEY, inheritance in the horse, ii. 10. + MARROW, vegetable, i. 357. + MARRYATT, Capt., breeding of asses in Kentucky, ii. 237. + MARSDEN, notice of _Gallus giganteus_, i. 235. + MARSHALL, Mr., voluntary selection of pasture by sheep, i. 96; + adaptation of wheats to soil and climate, i. 316; + "Dutch-buttocked" cattle, ii. 8; + segregation of herds of sheep, ii. 103; + advantage of change of soil to wheat and potatoes, ii. 146; + fashionable change in the horns of cattle, ii. 210; + sheep in Yorkshire, ii. 235. + MARSHALL, Prof., growth of the brain in microcephalous idiots, ii. 389. + MARTENS, E. Von, on _Achatinella_, ii. 53. + MARTIN, W. C. L., origin of the dog, i. 16; + Egyptian dogs, i. 18; + barking of a Mackenzie River dog, i. 27; + African hounds in the Tower menagerie, i. 32; + on dun horses and dappled asses, i. 55; + breeds of the horse, i. 49; + wild horses, i. 51; + Syrian breeds of asses, i. 62; + asses without stripes, i. 63; + effects of cross-breeding on the female in dogs, i. 404; + striped legs of mules, ii. 42. + MARTINS, defective instincts of silkworms, i. 304. + MARTINS, C., fruit trees of Stockholm, ii. 307. + {464} + MASON, W., bud-variation in the ash, i. 382. + MASTERS, Dr., reversion in the spiral-leaved weeping willow, i. 383; + on peloric flowers, ii. 58; + pelorism in a clover, ii. 346; + position as a cause of pelorism, ii. 345, 347. + MASTERS, Mr., persistence of varieties of peas, i. 329; + reproduction of colour in hyacinths, ii. 20; + on hollyhocks, ii. 107; + selection of peas for seed, ii. 199-200; + on _Opuntia leucotricha_, ii. 286; + reversion by the terminal pea in the pod, ii. 347. + MASTIFF, sculptured on an Assyrian monument, i. 17, ii. 429; + Tibetan, i. 35-36, ii. 278. + MATTHEWS, Patrick, on forest trees, ii. 237. + _Matthiola annua_, i. 399, ii. 20. + _Matthiola incana_, i. 381, 399. + MAUCHAMP, merino sheep, i. 100. + MAUDUYT, crossing of wolves and dogs in the Pyrenees, i. 24. + MAUND, Mr. crossed varieties of wheat, ii. 130. + MAUPERTUIS, axiom of "least action," i. 12. + MAURITIUS, importation of goats into, i. 101. + MAW, G., correlation of contracted leaves and flowers in pelargoniums, + ii. 330, 331. + MAWZ, fertility of _Brassica rapa_, ii. 165. + _Maxillaria_, self-fertilised capsules of, ii. 134; + number of seeds in, ii. 379. + _Maxillaria atro-rubens_, fertilisation of, by _M. squalens_, ii. 133. + MAYES, M., self-impotence in _Amaryllis_, ii. 139. + MECKEL, on the number of digits, ii. 13; + correlation of abnormal muscles in the leg and arm, ii. 322. + MEDUSÆ, development of, ii. 368, 384. + MEEHAN, Mr., comparison of European and American trees, ii. 281. + _Meleagris mexicana_, i. 292. + _Meles taxus_, ii. 151. + MELONS, i. 359-360; + mongrel, supposed to be produced from a twin-seed, i. 391; + crossing of varieties of, i. 399, ii. 108, 129; + inferiority of, in Roman times, ii. 216; + changes in, by culture and climate, ii. 275; + serpent, correlation of variations in, ii. 330; + analogous variations in, ii. 349. + MEMBRANES, false, ii. 294-295. + MÉNÉTRIES, on the stomach of _Strix grallaria_, ii. 302. + MENINGITIS, tubercular, inherited, ii. 78. + METAGENESIS, ii. 366. + METAMORPHOSIS, ii. 366. + METAMORPHOSIS and development, ii. 388, 389. + METZGER, on the supposed species of wheat, i. 312-313; + tendency of wheat to vary, i. 315; + variation of maize, i. 321-322; + cultivation of American maize in Europe, i. 322, ii. 347; + on cabbages, i. 323-325; + acclimatisation of Spanish wheat in Germany, ii. 26; + advantage of change of soil to plants, ii. 146; + on rye, ii. 254; + cultivation of different kinds of wheat, ii. 261. + MEXICO, dog from, with tan spots on the eyes, i. 29; + colours of feral horses in, i. 61. + MEYEN, on sending of bananas, ii. 168. + MICE, grey and white, colours of, not blended by crossing, ii. 92; + rejection of bitter almonds by, ii. 232; + naked, ii. 279. + MICHAUX, F., roan-coloured feral horses of Mexico, i. 61; + origin of domestic turkey, i. 292; + on raising peaches from seed, i. 339. + MICHEL, F., selection of horses in mediæval times, ii. 203; + horses preferred on account of slight characters, ii. 209. + MICHELY, effects of food on caterpillars, ii. 280; + on _Bombyx hesperus_, ii. 304. + MICROPHTHALMIA, associated with defective teeth, ii. 328. + MIDDENS, Danish, remains of dogs in, i. 18, ii. 427. + MIGNONETTE, ii. 237, 311. + MILLET, i. 371. + MILLS, J., diminished fertility of mares when first turned out to grass, + ii. 161. + MILNE-EDWARDS, on the development of the crustacea, ii. 368. + MILNE-EDWARDS, A., on a crustacean with a monstrous eye-peduncle, ii. + 391. + _Milvus niger_, ii. 154. + _Mimulus luteus_, ii. 128. + MINOR, W. C., gemmation and fission in the Annelida, ii. 358. + _Mirabilis_, fertilisation of, ii. 363; + hybrids of, ii. 131, 169, 265. + _Mirabilis jalapa_, i. 382, 393. + _Mirabilis longiflora_, ii. 88. + _Mirabilis vulgaris_, ii. 88. + _Misocampus_ and _Cecidomyia_, i. 5. + MITCHELL, Dr., effects of the poison of the rattlesnake, ii. 289. + MITFORD, Mr., notice of the breeding of horses by Erichthonius, ii. 202. + MOCCAS Court, weeping oak at, ii. 18. + MOGFORD, horses poisoned by fool's parsley, ii. 337. + MÖLLER, L., effects of food on insects, ii. 281. + MOQUIN-TANDON, original form of maize, i. 320; + variety of the double columbine, i. 365; + {465} + peloric flowers, ii. 58-59, 61; + position as a cause of pelorism in flowers, ii. 345; + tendency of peloric flowers to become irregular, ii. 70; + on monstrosities, ii. 254; + correlation in the axis and appendages of plants, ii. 321; + fusion of homologous parts in plants, ii. 339, 341-342; + on a bean with monstrous stipules and abortive leaflets, ii. 343; + conversion of parts of flowers, ii. 392. + MOLE, white, ii. 332. + MOLL and Gayot, on cattle, i. 80, ii. 96, 210. + MOLLUSCA, change in shells of, ii. 280. + MONKE, Lady, culture of the pansy by, i. 368. + MONKEYS, rarely fertile in captivity, ii. 153. + MONNIER, identity of summer and winter wheat, i. 315. + MONSTER, cyclopean, ii. 341. + MONSTERS, double, ii. 339-340. + MONSTROSITIES, occurrence of, in domesticated animals and cultivated + plants, i. 366, ii. 254; + due to persistence of embryonic conditions, ii. 57; + occurring by reversion, ii. 57-60; + a cause of sterility, ii. 166-167; + caused by injury to the embryo, ii. 269. + MONTEGAZZA, growth of a cock's-spur inserted into the eye of an ox, ii. + 369. + MONTGOMERY, E., formation of cells, ii. 370. + MOOR, J. H., deterioration of the horse in Malasia, i. 53. + MOORCROFT, Mr., on Hasora wheat, i. 313; + selection of white-tailed yaks, ii. 206; + melon of Kaschmir, ii. 275; + varieties of the apricot cultivated in Ladakh, i. 345; + varieties of the walnut cultivated in Kaschmir, i. 356. + MOORE, Mr., on breeds of pigeons, i. 148, 156, 208, 209, 211. + MOORUK, fertility of, in captivity, ii. 156. + MORLOT, dogs of the Danish Middens, i. 18; + sheep and horse of the bronze period, ii. 427. + _Mormodes ignea_, ii. 53. + MOROCCO, estimation of pigeons in, i. 205. + MORREN, C., on pelorism, ii. 58; + in _Calceolaria_, ii. 346; + non-coincidence of double flowers and variegated leaves, ii. 167. + MORRIS, Mr., breeding of the Kestrel in captivity, ii. 154. + MORTON, Lord, effect of fecundation by a quagga on an Arab mare, i. + 403-404. + MORTON, Dr., origin of the dog, i. 16; + hybrid of zebra and mare, ii. 42. + _Morus alba_, i. 334. + MOSCOW, rabbits of, i. 106, 120; + effects of cold on pear-trees at, ii. 307. + MOSSES, sterility in, ii. 171; + retrogressive metamorphosis in, ii. 361. + MOSS-ROSE, probable origin of, from _Rosa centifolia_, i. 379; + Provence roses produced from seeds of, i. 380. + MOSTO, Cada, on the introduction of rabbits into Porto Santo, i. 113. + MOTTLING of fruits and flowers, i. 400. + MOUFFLON, i. 94. + MOUNTAIN-ASH, ii. 230. + MOUSE, Barbary, ii. 152. + "MÖVEN-TAUBE," i. 148. + MOWBRAY, Mr., on the eggs of game fowls, i. 248; + early pugnacity of game cocks, i. 251; + diminished fecundity of the pheasant in captivity, ii. 155. + MOWBRAY, Mr., reciprocal fecundation of _Passiflora alata_ and + _racemosa_, ii. 137. + MULATTOS, character of, ii. 46. + MULBERRY, i. 334, ii. 256. + MULE and hinny, differences in the, ii. 67-68. + MULES, striped colouring of, ii. 42; + obstinacy of, ii. 45; + production of, among the Romans, ii. 110; + noticed in the Bible, ii. 202. + MÜLLER, Fritz, reproduction of orchids, ii. 134-135; + development of crustacea, ii. 368; + number of seeds in a _maxillaria_, ii. 379. + MÜLLER, H., on the face and teeth in dogs, i. 34, 73, ii. 345. + MÜLLER, J., production of imperfect nails after partial amputation of the + fingers, ii. 15; + tendency to variation, ii. 252; + atrophy of the optic nerve consequent on destruction of the eye, ii. + 297; + on Janus-like monsters, ii. 340; + on gemmation and fission, ii. 358; + identity of ovules and buds, ii. 360; + special affinities of the tissues, ii. 380. + MÜLLER, Max, antiquity of agriculture, ii. 243. + MULTIPLICITY of origin of pigeons, hypotheses of, discussed, i. 188-194. + MUNIZ, F., on Niata cattle, i. 90. + MUNRO, R., on the fertilisation of orchids, ii. 133; + reproduction of _Passiflora alata_, ii. 138. + "MURASSA" pigeon, i. 144. + MURPHY, J. J., the structure of the eye not producible by selection, ii. + 222. + _Mus alexandrinus_, ii. 87-88. + _Musa sapientum_, _Chinensis_ and _Cavendishii_, i. 377. + _Muscari comosum_, ii. 185, 316. + MUSCLES, effects of use on, ii. 297. + MUSK duck, feral hybrid of, with the common duck, i. 190. + {466} + MUSMON, female, sometimes hornless, i. 95. + MUTILATIONS, inheritance or non-inheritance of, ii. 22-24, 397. + MYATT, on a five-leaved variety of the strawberry, i. 353. + MYOPIA, hereditary, ii. 8. + MYRIAPODA, regeneration of lost parts in, ii. 15, 294. + + NAILS, growing on stumps of fingers, ii. 394. + NAIS, scission of, ii. 358. + NAMAQUAS, cattle of the, i. 88, ii. 207. + NARCISSUS, double, becoming single in poor soil, ii. 167. + NARVAEZ, on the cultivation of native plants in Florida, i. 312. + _Nasua_, sterility of, in captivity, ii. 152. + "NATAS," or Niatas, a South American breed of cattle, i. 89-91. + NATHUSIUS, H. von, on the pigs of the Swiss lake-dwellings, i. 68; + on the races of pigs, i. 65-68; + convergence of character in highly-bred pigs, i. 73, ii. 241; + causes of changes in the form of the pig's skull, i. 72-73; + changes in breeds of pigs by crossing, i. 78; + change of form in the pig, ii. 279; + effects of disuse of parts in the pig, ii. 299; + period of gestation in the pig, i. 74; + appendages to the jaw in pigs, i. 76; + on _Sus pliciceps_, i. 70; + period of gestation in sheep, i. 97; + on Niata cattle, i. 89; + on short-horn cattle, ii. 118; + on interbreeding, ii. 116; + in the sheep, ii. 120; + in pigs, ii. 122; + unconscious selection in cattle and pigs, ii. 214; + variability of highly selected races, ii. 238. + NATO, P., on the Bizzaria orange, i. 391. + NATURAL selection, its general principles, i. 2-14. + NATURE, sense in which the term is employed, i. 6. + NAUDIN, supposed rules of transmission in crossing plants, ii. 68; + on the nature of hybrids, ii. 48-49; + essences of the species in hybrids, ii. 386, 401; + reversion of hybrids, ii. 36, 49-50; + reversion in flowers by stripes and blotches, ii. 37; + hybrids of _Linaria vulgaris_ and _purpurea_, ii. 94; + pelorism in _Linaria_, ii. 58, 346; + crossing of peloric _Linaria_ with the normal form, ii. 70; + variability in _Datura_, ii. 266; + hybrids of _Datura lævis_ and _stramonium_, i. 392; + prepotency of transmission of _Datura stramonium_ when crossed, ii. 67; + on the pollen of _Mirabilis_ and of hybrids, i. 389; + fertilisation of _Mirabilis_, ii. 363; + crossing of _Chamærops humilis_ and the date palm, i. 399; + cultivated Cucurbitaceæ, i. 357-360, ii. 108; + rudimentary tendrils in gourds, ii. 316; + dwarf _Cucurbitæ_, ii. 330; + relation between the size and number of the fruit in _Cucurbita pepo_, + ii. 343; + analogous variation in _Cucurbitæ_, ii. 349; + acclimatisation of Cucurbitaceæ, ii. 313; + production of fruit by sterile hybrid Cucurbitaceæ, ii. 172; + on the melon, i. 360, ii. 108, 275; + incapacity of the cucumber to cross with other species, i. 359. + NECTARINE, i. 336-344; + derived from the peach, i. 337, 339-342; + hybrids of, i. 339; + persistency of characters in seedling, i. 340; + origin of, _ibid._; + produced on peach trees, i. 340-341; + producing peaches, i. 341; + variation in, i. 342-343; + bud-variation in, i. 374; + glands in the leaves of the, ii. 231; + analogous variation in, ii. 348. + NECTARY, variations of, in pansies, i. 369. + NEES, on changes in the odour of plants, ii. 274. + "NEGRO" cat, i. 46. + NEGROES, polydactylism in, ii. 14; + selection of cattle practised by, ii. 207. + NEOLITHIC period, domestication of _Bos longifrons_ and _primigenius_ in + the, i. 81; + cattle of the, distinct from the original species, i. 87; + domestic goat in the, i. 101; + cereals of the, i. 317. + NERVE, optic, atrophy of the, ii. 297. + NEUMEISTER, on the Dutch and German pouter pigeons, i. 138; + on the Jacobin pigeon, i. 154; + duplication of the middle flight feather in pigeons, i. 159; + on a peculiarly coloured breed of pigeons, "Staarhalsige Taube," i. + 161; + fertility of hybrid pigeons, i. 192; + mongrels of the trumpeter pigeon, ii. 66; + period of perfect plumage in pigeons, ii. 77; + advantage of crossing pigeons, ii. 126. + NEURALGIA, hereditary, ii. 79. + NEW ZEALAND, feral cats of, i. 47; + cultivated plants of, i. 311. + NEWFOUNDLAND dog, modification of, in England, i. 42. + NEWMAN, E., sterility of Sphingidæ under certain conditions, ii. 158. + NEWPORT, G., non-copulation of _Vanessæ_ in confinement, ii. 157; + regeneration of limbs in myriapoda, ii. 294; + fertilisation of the ovule in batrachia, ii. 363. + NEWT, polydactylism in the, ii. 14. + NEWTON, A., absence of sexual distinctions in the Columbidæ, i. 162; + production of a "black-shouldered" pea-hen among the ordinary kind, i. + 291; + on hybrid ducks, ii. 157. + NGAMI, Lake, cattle of, i. 88. + "NIATA" cattle, i. 89-91; + resemblance of to _Sivatherium_, i. 89; + {467} + prepotency of transmission of character by, ii. 66. + "NICARD" rabbit, i. 107. + NICHOLSON, Dr., on the cats of Antigua, i. 46; + on the sheep of Antigua, i. 98. + _Nicotiana_, crossing of varieties and species of, ii. 108; + prepotency of transmission of characters in species of, ii. 67; + contabescence of female organs in, ii. 166. + _Nicotiana glutinosa_, ii. 108. + NIEBUHR, on the heredity of mental characteristics in some Roman + families, ii. 65. + NIGHT-BLINDNESS, non-reversion to, ii. 36. + NILSSON, Prof., on the barking of a young wolf, i. 27; + parentage of European breeds of cattle, i. 80, 81; + on _Bos frontosus_ in Scania, i. 81. + NIND, Mr., on the dingo, i. 39. + "NISUS formativus," i. 293, 294, 355. + NITZSCH, on the absence of the oil-gland in certain Columbæ, i. 147. + NON-INHERITANCE, causes of, ii. 24-26. + "NONNAIN" pigeon, i. 154. + NORDMANN, dogs of Awhasie, i. 25. + NORMANDY, pigs of, with appendages under the jaw, i. 75. + NORWAY, striped ponies of, i. 58. + NOTT and Gliddon, on the origin of the dog, i. 16; + mastiff represented on an Assyrian tomb, i. 17; + on Egyptian dogs, i. 18; + on the Hare-Indian dog, i. 22. + _Notylia_, ii. 135. + NOURISHMENT, excess of, a cause of variability, ii. 257. + NUMBER, importance of, in selection, ii. 235. + _Numida ptilorhyncha_, the original of the Guinea-fowl, i. 294. + NUN pigeon, i. 155; + known to Aldrovandi, i. 207. + NUTMEG tree, ii. 237. + + OAK, weeping, i. 361, ii. 18, 241; + pyramidal, i. 361; + Hessian, i. 361; + late-leaved, i. 363; + variation in persistency of leaves of, i. 363; + valueless as timber at the Cape of Good Hope, ii. 274; + changes in, dependent on age, i. 387; + galls of the, ii. 282. + OATS, wild, i. 313; + in the Swiss lake-dwellings, i. 319. + OBERLIN, change of soil beneficial to the potato, ii. 146. + ODART, Count, varieties of the vine, i. 333, ii. 278; + bud-variation in the vine, i. 375. + ODOUR and colour, correlation of, ii. 325. + _Oecidium_, ii. 284. + _Oenothera biennis_, bud-variation in, i. 382. + OGLE, W., resemblance of twins, ii. 252. + OIL-GLAND, absence of, in fantail pigeons, i. 147, 160. + OLDFIELD, Mr., estimation of European dogs among the natives of + Australia, ii. 215. + OLEANDER, stock affected by grafting in the, i. 394. + OLLIER, Dr., insertion of the periosteum of a dog beneath the skin of a + rabbit, ii. 369. + _Oncidium_, reproduction of, ii. 133-135, 164. + ONIONS, crossing of, ii. 90; + white, liable to the attacks of fungi and disease, ii. 228, 336. + _Ophrys apifera_, self-fertilisation of, ii. 91; + formation of pollen by a petal in, ii. 392. + _Opuntia leucotricha_, ii. 277. + ORANGE, i. 334-336; + crossing of, ii. 91; + with the lemon, i. 399, ii. 365; + naturalisation of, in Italy, ii. 308; + variation of, in North Italy, ii. 256; + peculiar variety of, ii. 331; + Bizzaria, i. 391; + trifacial, _ibid._ + ORCHIDS, reproduction of, i. 402, 403; ii. 133-135. + ORFORD, Lord, crossing greyhounds with the bulldog, i. 41. + ORGANISMS, origin of, i. 13. + ORGANISATION, advancement in, i. 8. + ORGANS, rudimentary and aborted, ii. 315-318; + multiplication of abnormal, ii. 391. + ORIOLE, assumption of hen-plumage by a male in confinement, ii. 158. + ORKNEY islands, pigs of, i. 70; + pigeons of, i. 184. + ORTHOPTERA, regeneration of hind legs in the, ii. 294. + _Orthosia munda_, ii. 157. + ORTON, R., on the effects of cross-breeding on the female, i. 404; + on the Manx cat, ii. 66; + on mongrels from the silk-fowl, ii. 67. + OSBORNE, Dr., inherited mottling of the iris, ii. 10. + OSPREY, preying on Black-fowls, ii. 230. + OSTEN-SACKEN, Baron, on American oak galls, ii. 282. + OSTEOLOGICAL characters of pigs, i. 66, 67, 71-74; + of rabbits, i. 115-130; + of pigeons, i. 162-167; + of ducks, i. 282-284. + OSTRICH, diminished fertility of the, in captivity, ii. 156. + OSTYAKS, selection of dogs by the, ii. 206. + OTTER, ii. 151. + "OTTER" sheep of Massachusetts, i. 100. + OUDE, feral humped cattle in, i. 79. + OUISTITI, breed in Europe, ii. 153. + {468} + OVARY, variation of, in _Cucurbita moschata_, i. 359; + development of, independently of pollen, i. 403. + _Ovis montana_, i. 99. + OVULES and buds, identity of nature of, ii. 360. + OWEN, Capt., on stiff-haired cats at Mombas, i. 46. + OWEN, Prof. R., palæontological evidence as to the origin of dogs, i. 15; + on _Bos longifrons_, i. 81; + on the skull of the "Niata" cattle, i. 89, 90; + on fossil remains of rabbits, i. 104; + on the significance of the brain, i. 124; + on the number of digits in the Ichthyopterygia, ii. 16; + on metagenesis, ii. 366; + theory of reproduction and parthenogenesis, ii. 375. + OWL, eagle, breeding in captivity, ii. 154. + OWL pigeon, i. 148; + African, figured, i. 149; + known in 1735, i. 209. + _Oxalis_, trimorphic species of, ii. 400. + _Oxalis rosea_, ii. 132. + OXLEY, Mr., on the nutmeg tree, ii. 237. + OYSTERS, differences in the shells of, ii. 280. + + PACA, sterility of the, in confinement, ii. 152. + PACIFIC islands, pigs of the, i. 70. + PADUA, earliest known flower garden at, ii. 217. + PADUAN fowl of Aldrovandi, i. 247. + _Pæonia moutan_, ii. 205. + PÆONY, tree, ancient cultivation of, in China, ii. 205. + PAMPAS, feral cattle on the, i. 85. + _Pandanus_, ii. 256. + PANGENESIS, hypothesis of, ii. 357-404. + _Panicum_, seeds of, used as food, i. 309; + found in the Swiss lake-dwellings, i. 317. + PANSY, i. 368-370. + PAPPUS, abortion of the, in _Carthamus_, ii. 316. + PAGET, on the Hungarian sheep dog, i. 24. + PAGET, inheritance of cancer, ii. 7; + hereditary elongation of hairs in the eyebrow, ii. 8; + period of inheritance of cancer, ii. 79-80; + on _Hydra_, ii. 293; + on the healing of wounds, ii. 294; + on the reparation of bones, _ibid._; + growth of hair near inflamed surfaces or fractures, ii. 295; + on false membranes, _ibid._; + compensatory development of the kidney, ii. 300; + bronzed skin in disease of supra-renal capsules, ii. 331; + unity of growth and gemmation, ii. 359; + independence of the elements of the body, ii. 369; + affinity of the tissues for special organic substances, ii. 380. + PALLAS, on the influence of domestication upon the sterility of + intercrossed species, i. 31, 83, 193, ii. 109; + hypothesis that variability is wholly due to crossing, i. 188, 374, ii. + 250, 264; + on the origin of the dog, i. 16; + variation in dogs, i. 33; + crossing of dog and jackal, i. 25; + origin of domestic cats, i. 43; + origin of Angora cat, i. 45; + on wild horses, i. 52, 60; + on Persian sheep, i. 94; + on Siberian fat-tailed sheep, ii. 279; + on Chinese sheep, ii. 315; + on Crimean varieties of the vine, i. 333; + on a grape with rudimentary seeds, ii. 316; + on feral musk-ducks, ii. 46; + sterility of Alpine plants in gardens, ii. 163; + selection of white-tailed yaks, ii. 206. + _Paradoxurus_, sterility of species of, in captivity, ii. 151. + PARAGUAY, cats of, i. 46; + cattle of, i. 89; + horses of, ii. 102; + dogs of, ii. 102; + black-skinned domestic fowl of, i. 232. + PARALLEL variation, ii. 348-352. + PARAMOS, woolly pigs of, i. 78. + PARASITES, liability to attacks of, dependent on colour, ii. 228. + PARIAH dog, with crooked legs, i. 17; + resembling the Indian wolf, i. 24. + PARISET, inheritance of handwriting, ii. 6. + PARKER, W. K., number of vertebræ in fowls, i. 266. + PARKINSON, Mr., varieties of the hyacinth, i. 370. + PARKYNS, Mansfield, on _Columba guinea_, i. 183. + PARMENTIER, differences in the nidification of pigeons, i. 178; + on white pigeons, ii. 230. + PARROTS, general sterility of, in confinement, ii. 155; + alteration of plumage of, ii. 280. + PARSNIP, reversion in, ii. 31; + influence of selection on, ii. 201; + experiments on, ii. 277; + wild, enlargement of roots of, by cultivation, i. 326. + PARTHENOGENESIS, ii. 359, 364. + PARTRIDGE, sterility of, in captivity, ii. 156. + PARTURITION, difficult, hereditary, ii. 8. + _Parus major_, ii. 231. + _Passiflora_, self-impotence in species of, ii. 137-138; + contabescence of female organs in, ii. 166. + _Passiflora alata_, fertility of, when grafted, ii. 188. + PASTURE and climate, adaptation of breeds of sheep to, i. 96, 97. + PASTRANA, Julia, peculiarities in the hair and teeth of, ii. 328. + PATAGONIA, crania of pigs from, i. 77. + PATAGONIAN rabbit, i. 105. + {469} + PATERSON, R., on the Arrindy silk moth, ii. 306. + PAUL, W., on the hyacinth, i. 370; + varieties of pelargoniums, i. 378; + improvement of pelargoniums, ii. 216. + _Pavo cristatus_ and _muticus_, hybrids of, i. 290. + _Pavo nigripennis_, i. 290-291. + "PAVODOTTEN-TAUBE," i. 141. + PEACH, i. 336-344; + derived from the almond, i. 337; + stones of, figured, _ibid._; + contrasted with almonds, i. 338; + double-flowering, i. 338-339, 343; + hybrids of, i. 339; + persistency of races of, _ibid._; + trees producing nectarines, i. 340-341; + variation in, i. 342-343, ii. 256; + bud-variation in, i. 374; + pendulous, ii. 18; + variation by selection in, ii. 218; + peculiar disease of the, ii. 228; + glands on the leaves of the, ii. 231; + antiquity of the, ii. 308; + increased hardiness of the, _ibid._; + varieties of, adapted for forcing, ii. 310; + yellow-fleshed, liable to certain diseases, ii. 336. + PEACH-ALMOND, i. 338. + PEAFOWL, origin of, i. 290; + japanned or black-shouldered, i. 290-291; + feral, in Jamaica, i. 190; + comparative fertility of, in wild and tame states, ii. 112, 268; + white, ii. 332. + PEARS, i. 350; + bud-variation in, i. 376; + reversion in seedling, ii. 31; + inferiority of, in Pliny's time, ii. 215; + winter nelis, attacked by aphides, ii. 231; + soft-barked varieties of, attacked by wood-boring beetles, ii. 231; + origination of good varieties of, in woods, ii. 260; + Forelle, resistance of, to frost, ii. 306. + PEAS, i. 326-330; + origin of, 326; + varieties of, 326-329; + found in Swiss lake-dwellings, i. 317, 319, 326-329; + fruit and seeds figured, i. 328; + persistency of varieties, i. 329; + intercrossing of varieties, i. 330, 397, ii. 129; + effect of crossing on the female organs in, i. 398; + double-flowered, ii. 168; + maturity of, accelerated by selection, ii. 201; + varieties of, produced by selection, ii. 218; + thin-shelled, liable to the attacks of birds, ii. 231; + reversion of, by the terminal seed in the pod, ii. 347. + PECCARY, breeding of the, in captivity, ii. 150. + PEDIGREES of horses, cattle, greyhounds, game-cocks, and pigs, ii. 3. + PEGU, cats of, i. 47; + horses of, i. 53. + PELARGONIUMS, multiple origin of, i. 364; + zones of, i. 366; + bud-variation in, i. 378; + variegation in, accompanied by dwarfing, i. 384; + pelorism in, ii. 167, 345; + by reversion, ii. 59; + advantage of change of soil to, ii. 147; + improvement of, by selection, ii. 216; + scorching of, ii. 229; + numbers of, raised from seed, ii. 235; + effects of conditions of life on, ii. 274; + stove-variety of, ii. 311; + correlation of contracted leaves and flowers in, ii. 330-331. + _Pelargonium fulgidum_, conditions of fertility in, ii. 164. + "PELONES," a Columbian breed of cattle, i. 88. + PELORIC flowers, tendency of, to acquire the normal form, ii. 70; + fertility or sterility of, ii. 166-167. + PELORIC races of _Gloxinia speciosa_ and _Antirrhinum majus_, i. 365. + PELORISM, ii. 58-60, 345-346. + PELVIS, characters of, in rabbits, i. 122-123; + in pigeons, i. 166; + in fowls, i. 268; + in ducks, i. 284. + PEMBROKE cattle, i. 81. + PENDULOUS trees, i. 361, ii. 348; + uncertainty of transmission of, ii. 18-19. + PENGUIN ducks, i. 280, 282; + hybrid of the, with the Egyptian goose, i. 282. + PENNANT, production of wolf-like curs at Fochabers, i. 37; + on the Duke of Queensberry's wild cattle, i. 84. + _Pennisetum_, seeds of, used as food in the Punjab, i. 309. + _Pennisetum distichum_, seeds of, used as food in Central Africa, i. 308. + PERCIVAL, Mr., on inheritance in horses, ii. 10; + on horn-like processes in horses, i. 50. + _Perdix rubra_, occasional fertility of, in captivity, ii. 156. + PERIOD of action of causes of variability, ii. 269. + PERIOSTEUM of a dog, producing bone in a rabbit, ii. 369. + PERIWINKLE, sterility of, in England, ii. 170. + PERSIA, estimation of pigeons in, i. 205; + carrier pigeon of, i. 141; + tumbler pigeon of, i. 150; + cats of, i. 45-47; + sheep of, i. 94. + _Persica intermedia_, i. 338. + PERSISTENCE of colour in horses, i. 50; + of generic peculiarities, i. 111. + PERU, antiquity of maize in, i. 320; + peculiar potato from, i. 331; + selection of wild animals practised by the Incas of, ii. 207-208. + "PERÜCKEN-TAUBE," i. 154. + PETALS, rudimentary, in cultivated plants, ii. 316; + producing pollen, ii. 392. + PETUNIAS, multiple origin of, i. 364; + double-flowered, ii. 167. + "PFAUEN-TAUBE," i. 146. + _Phacochoerus Africanus_, i. 76. + _Phalænopsis_, pelorism in, ii. 346. + PHALANGES, deficiency of, ii. 73. + {470} + _Phaps chalcoptera_, ii. 349. + _Phaseolus multiflorus_, ii. 309, 322. + _Phaseolus vulgaris_, ii. 309. + _Phasianus pictus_, i. 275. + _Phasianus Amherstiæ_, i. 275. + PHEASANT, assumption of male plumage by the hen, ii. 51; + wildness of hybrids of, with the common fowl, ii. 45; + prepotency of the, over the fowl, ii. 68; + diminished fecundity of the, in captivity, ii. 155. + PHEASANTS, golden and Lady Amherst's, i. 275. + PHEASANT-FOWLS, i. 244. + PHILIPEAUX, regeneration of limbs in the salamander, ii. 376. + PHILIPPAR, on the varieties of wheat, i. 314. + PHILIPPINE Islands, named breeds of game fowl in the, i. 232. + PHILLIPS, Mr., on bud-variation in the potato, i. 385. + _Phlox_, bud-variation by suckers in, i. 384. + PHTHISIS, affection of the fingers in, ii. 332. + PICKERING, Mr., on the grunting voice of humped cattle, i. 79; + occurrence of the head of a fowl in an ancient Egyptian procession, i. + 246; + seeding of ordinarily seedless fruits, ii. 168; + extinction of ancient Egyptian breeds of sheep and oxen, ii. 425; + on an ancient Peruvian gourd, ii. 429. + PICOTEES, effect of conditions of life on, ii. 273. + PICTET, A., oriental names of the pigeon, i. 205. + PICTET, Prof., origin of the dog, i. 15; + on fossil oxen, i. 81. + PIEBALDS, probably due to reversion, ii. 37. + PIGEAUX, hybrids of the hare and rabbit, ii. 99, 152. + PIGEON à cravate, i. 148. + PIGEON Bagadais, i. 142, 143. + PIGEON coquille, i. 155. + PIGEON cygne, i. 143. + PIGEON heurté, i. 156. + PIGEON Patu plongeur, i. 156. + PIGEON Polonais, i. 144. + PIGEON Romain, i. 142, 144. + PIGEON tambour, i. 154. + PIGEON Turc, i. 139. + PIGEONS, origin of, i. 131-134, 180-204; + classified table of breeds of, i. 136; + pouter, i. 137-139; + carrier, i. 139-142; + runt, i. 142-144; + barbs, i. 144-146; + fantail, i. 146-148; + turbit and owl, i. 148-149; + tumbler, i. 150-153; + Indian frill-back, i. 153; + Jacobin, i. 154; + trumpeter, i. 154; + other breeds of, i. 155-157; + differences of, equal to generic, i. 157-158; + individual variations of, i. 158-160; + variability of peculiarities characteristic of breeds in, i. 161; + sexual variability in, i. 161-162; + osteology of, i. 162-167; + correlation of growth in, i. 167-171, ii. 321; + young of some varieties naked when hatched, i. 170, ii. 332; + effects of disuse in, i. 172-177; + settling and roosting in trees, i. 181; + floating in the Nile to drink, i. 181; + Dovecot, i. 185-186; + arguments for unity of origin of, i. 188-204; + feral in various places, i. 190, ii. 33; + unity of coloration in, i. 195-197; + reversion of mongrel, to coloration of, _C. livia_, i. 197-202; + history of the cultivation of, i. 205-207; + history of the principal races of, i. 207-212; + mode of production of races of, i. 212-224; + reversion in, ii. 29, 47; + by age, ii. 38; + produced by crossing in, ii. 40, 48; + prepotency of transmission of character in breeds of, ii. 66-67; + sexual differences in some varieties of, ii. 74; + period of perfect plumage in, ii. 77; + effect of segregation on, ii. 86; + preferent pairing of, within the same breed, ii. 103; + fertility of, increased by domestication, ii. 112, 155; + effects of interbreeding and necessity of crossing, ii. 125-126; + indifference of, to change of climate, ii. 161; + selection of, ii. 195, 199, 204; + among the Romans, ii. 202; + unconscious selection of, ii. 211, 214; + facility of selection of, ii. 234; + white, liable to the attacks of hawks, ii. 230; + effects of disuse of parts in, ii. 298; + fed upon meat, ii. 304; + effect of first male upon the subsequent progeny of the female, i. 405; + homology of the leg and wing feathers in, ii. 323; + union of two outer toes in feather-legged, _ibid._; + correlation of beak, limbs, tongue, and nostrils in, ii. 324; + analogous variation in, ii. 349-350; + permanence of breeds of, ii. 429. + PIGS, of Swiss lake-dwellings, i. 67-68; + types of, derived from _Sus scrofa_ and _Sus indica_, i. 66-67; + Japanese (_Sus pliciceps_, Gray), figured, i. 69; + of Pacific islands, i. 70, ii. 87; + modifications, of skull in, i. 71-73; + length of intestines in, i. 73, ii. 303; + period of gestation of, i. 74; + number of vertebræ and ribs in, i. 74; + anomalous forms, i. 75-76; + development of tusks and bristles in, i. 76; + striped young of, i. 76-77; + reversion of feral, to wild type, i. 77-78, ii. 33, 47; + production and changes of breeds of, by intercrossing, i. 78; + effects produced by the first male upon the subsequent progeny of the + female, i. 404; + two-legged race of, ii. 4; + {471} + polydactylism in, ii. 14; + cross-reversion in, ii. 35; + hybrid, wildness of, ii. 45; + monstrous development of a proboscis in, ii. 57; + disappearance of tusks in male under domestication, ii, 74; + solid hoofed, ii. 429; + crosses of, ii. 93, 95; + mutual fertility of all varieties of, ii. 110; + increased fertility by domestication, ii. 111; + ill effects of close interbreeding in, ii. 121-122; + influence of selection on, ii. 198; + prejudice against certain colours in, ii. 210, 229, 336; + unconscious selection of, ii. 214; + black Virginian, ii. 227, 336; + similarity of the best breeds of, ii. 241; + change of form in, ii. 279; + effects of disuse of parts in, ii. 299; + ears of, ii. 301; + correlations in, ii. 327; + white, buck-wheat injurious to, ii. 337; + tail of, grafted upon the back, ii. 369; + extinction of the older races of, ii. 426. + PIMENTA, ii. 91. + PIMPERNEL, ii. 190. + PINE-APPLE, sterility and variability of the, ii. 262. + PINK, Chinese. 322. + PINKS, bud-variation in, i. 381; + improvement of, ii. 216. + _Pinus pumilio_, _Mughus_, and _nana_, varieties of _P. sylvestris_, i. + 363. + _Pinus sylvestris_, i. 363, ii. 310; + hybrids of, with _P. nigricans_, ii. 130. + PIORRY, on hereditary disease, ii. 7, 78. + _Pistacia lentiscus_, ii. 274. + PISTILS, rudimentary, in cultivated plants, ii. 316. + PISTOR, sterility of some mongrel pigeons, i. 192; + fertility of pigeons, ii. 112. + _Pisum arvense_ and _sativum_, i. 326. + PITYRIASIS versicolor, inheritance of, ii. 79. + PLANCHON, G., on a fossil vine, i. 332; + sterility of _Jussiæa grandifiora_ in France, ii. 170. + PLANE tree, variety of the, i. 362. + PLANTIGRADE carnivora, general sterility of the, in captivity, ii. 151. + PLANTS, progress of cultivation of, i. 305-312; + cultivated, their geographical derivation, i. 311; + crossing of, ii. 98, 99, 127; + comparative fertility of wild and cultivated, ii. 112-113; + self-impotent, ii. 131-140; + dimorphic and trimorphic, ii. 132, 140; + sterility of, from changed conditions, ii. 163-165; + from contabescence of anthers, ii. 165-166; + from monstrosities, ii. 166-167; + from doubling of the flowers, ii. 167-168; + from seedless fruit, ii. 168; + from excessive development of vegetative organs, ii. 168-171; + influence of selection on, ii. 199-201; + variation by selection, in useful parts of, ii. 217-219; + variability of, ii. 237; + variability of, induced by crossing, ii. 265; + direct action of change of climate on, ii. 277; + change of period of vegetation in, ii. 304-305; + varieties of, suitable to different climates, ii. 306; + correlated variability of, ii. 330-331; + antiquity of races of, ii. 429. + PLASTICITY, inheritance of, ii. 241. + PLATEAU, F., on the vision of amphibious animals, ii. 223. + _Platessa flesus_, ii. 53. + PLATO, notice of selection in breeding dogs by, ii. 212. + PLICA polonica, ii. 276. + PLINY, on the crossing of shepherd's dogs with the wolf, i. 24; + on Pyrrhus' breed of cattle, ii. 202; + on the estimation of pigeons among the Romans, i. 205; + pears described by, ii. 215. + PLUM, i. 345-347; + stones figured, i. 345; + varieties of the, i. 345-346, ii. 219; + bud-variation in the, i. 375; + peculiar disease of the, ii. 227; + flower-buds of, destroyed by bullfinches, ii. 232; + purple-fruited, liable to certain diseases, ii. 336. + PLUMAGE, inherited peculiarities of, in pigeons, i. 160-161; + sexual peculiarities of, in fowls, i. 251-255. + PLURALITY of races, Pouchet's views on, i. 2. + _Poa_, seeds of, used as food, i. 308; + species of, propagated by bulblets, ii. 170. + PODOLIAN cattle, i. 80. + POINTERS, modification of, i. 42; + crossed with the foxhound, ii. 95. + POIS sans parchemin, ii. 231. + POITEAU, origin of _Cytisus Adami_, i. 390; + origin of cultivated varieties of fruit-trees, ii. 260. + POLISH fowl, i. 227, 250, 254, 256-257, 262; + skull figured, i. 262; + section of skull figured, i. 263; + development of protuberance of skull, i. 250; + furcula figured, i. 268. + POLISH, or Himalayan rabbit, i. 108. + POLLEN, ii. 363-364; + action of, ii. 108; + injurious action of, in some orchids, ii. 134-135; + resistance of, to injurious treatment, ii. 164; + prepotency of, ii. 187. + POLLOCK, Sir F., transmission of variegated leaves in _Ballota nigra_, i. + 383; + on local tendency to variegation, ii. 274. + POLYANTHUS, ii. 21. + POLYDACTYLISM, inheritance of, ii. 12-16; + significance of, ii. 16-17. + _Polyplectron_, i. 255. + PONIES, most frequent on islands and mountains, i. 52; + Javanese, i. 53. + POOLE, Col., on striped Indian horses, i. 58, 59; + {472} + on the young of _Asinus indicus_, ii. 43. + POPLAR, Lombardy, i. 361. + PÖPPIG, on Cuban wild dogs, i. 27. + POPPY, found in the Swiss lake-dwellings, i. 317, 319; + with the stamens converted into pistils, i. 365; + differences of the, in different parts of India, ii. 165; + monstrous, fertility of, ii. 166; + black-seeded, antiquity of, ii. 429. + PORCUPINE, breeding of, in captivity, ii. 152. + PORCUPINE family, ii. 4, 76. + _Porphyrio_, breeding of a species of, in captivity, ii. 156. + PORTAL, on a peculiar hereditary affection of the eye, ii. 9. + PORTO Santo, feral rabbits of, i. 112. + _Potamochoerus penicillatus_, ii. 150. + POTATO, i. 330-331; + bud-variation by tubers in the, i. 384-385; + graft-hybrid of, by union of half-tubers, i. 395; + individual self-impotence in the, ii. 137; + sterility of, ii. 169; + advantage of change of soil to the, ii. 146; + relation of tubers and flowers in the, ii. 343. + POTATO, sweet, sterility of the, in China, ii. 169; + varieties of the, suited to different climates, ii. 309. + POUCHET, M., his views on plurality of races, i. 2. + POUTER pigeons, i. 137-139; + furcula figured, i. 167; + history of, i. 207. + POWIS, Lord, experiments in crossing humped and English cattle, i. 83, + ii. 45. + POYNTER, Mr., on a graft-hybrid rose, i. 396. + PRAIRIE wolf, i. 22. + PRECOCITY of highly-improved breeds, ii. 321. + PREPOTENCY of pollen, ii. 187. + PREPOTENCY of transmission of character, ii. 65, 174; + in the Austrian emperors and some Roman families, ii. 65; + in cattle, ii. 65-66; + in sheep, ii. 66; + in cats, _ibid._; + in pigeons, ii. 66-67; + in fowls, ii. 67; + in plants, _ibid._; + in a variety of the pumpkin, i. 358; + in the jackal over the dog, ii. 67; + in the ass over the horse, _ibid._; + in the pheasant over the fowl, ii. 68; + in the penguin duck over the Egyptian goose, _ibid._; + discussion of the phenomena of, ii. 69-71. + PRESCOTT, Mr., on the earliest known European flower-garden, ii. 217. + PRESSURE, mechanical, a cause of modification, ii. 344-345. + PREVOST and Dumas, on the employment of several spermatozoids to + fertilise one ovule, ii. 363. + PRICE, Mr., variations in the structure of the feet in horses, i. 50. + PRICHARD, Dr., on polydactylism in the negro, ii. 14; + on the Lambert family, ii. 77; + on an albino negro, ii. 229; + on Plica polonica, ii. 276. + PRIMROSE, ii. 21; + double, rendered single by transplantation, ii. 167. + _Primula_, intercrossing of species of, i. 336; + contabescence in, ii. 166; + hose and hose, i. 365; + with coloured calyces, sterility of, ii. 166. + _Primula sinensis_, reciprocally dimorphic, ii. 132. + _Primula veris_, ii. 21, 109, 182. + _Primula vulgaris_, ii. 21, 109. + PRINCE, Mr., on the intercrossing of strawberries, i. 352. + _Procyon_, sterility of, in captivity, ii. 152. + PROLIFICACY, increased by domestication, ii. 174. + PROPAGATION, rapidity of, favourable to selection, ii. 297. + PROTOZOA, reproduction of the, ii. 376. + _Prunus armeniaca_, i. 344-345. + _Prunus avium_, i. 347. + _Prunus cerasus_, i. 347, 375. + _Prunus domestica_, i. 345. + _Prunus insititia_, i. 345-347. + _Prunus spinosa_, i. 345. + PRUSSIA, wild horses in, i. 60. + _Psittacus erithacus_, ii. 155. + _Psittacus macoa_, ii. 155. + _Psophia_, general sterility of, in captivity, ii. 157. + PTARMIGAN fowls, i. 228. + _Pulex penetrans_, ii. 275. + PUMPKINS, i. 357. + PUNO ponies of the Cordillera, i. 52. + PURSER, Mr. on _Cytisus Adami_, i. 389. + PUSEY, Mr., preference of hares and rabbits for common rye, ii. 232. + PUTSCHE and Vertuch, varieties of the potato, i. 330. + PUVIS, effects of foreign pollen on apples, i. 401; + supposed non-variability of monotypic genera, ii. 266. + _Pyrrhula vulgaris_, ii. 232; + assumption of the hen-plumage by the male, in confinement, ii. 158. + PYRRHUS, his breed of cattle, ii. 202. + _Pyrus_, fastigate Chinese species of, ii. 277. + _Pyrus acerba_, i. 348. + _Pyrus aucuparia_, ii. 230. + _Pyrus communis_, i. 350, 376. + _Pyrus malus_, i. 348, 376. + _Pyrus paradisiaca_, i. 348. + _Pyrus præcox_, i. 348. + + QUAGGA, effect of fecundation by, on the subsequent progeny of a mare, i. + 403-404. + QUATREFAGES, A. de, on the burrowing of a bitch to litter, i. 77; + {473} + selection in the silkworm, i. 301; + development of the wings in the silkmoth, i. 303, ii. 298; + on varieties of the mulberry, i. 334; + special raising of eggs of the silkmoth, ii. 197; + on disease of the silkworm, ii. 228; + on monstrosities in insects, ii. 269, 391; + on the Anglo-Saxon race in America, ii. 276; + on a change in the breeding season of the Egyptian goose, ii. 304; + fertilisation of the _Teredo_, ii. 363; + tendency to similarity in the best races, ii. 241; + on his "_tourbillon vital_," ii. 61; + on the independent existence of the sexual elements, ii. 360. + _Quercus cerris_, i. 363. + _Quercus robur_ and _pedunculata_, hybrids of, ii. 130. + QUINCE, pears grafted on the, ii. 259. + + RABBITS, domestic, their origin, i. 103-105; + of Mount Sinai and Algeria, i. 105; + breeds of, i. 105-111; + Himalayan, Chinese, Polish, or Russian, i. 108-111, ii. 97; + feral, i. 111-115; + of Jamaica, i. 112; + of the Falkland islands, i. 112; + of Porto Santo, i. 112-115, ii. 103, 279; + osteological characters of, i. 115-129; + discussion of modifications in, i. 129-130; + one-eared, transmission of peculiarity of, ii. 12; + reversion in feral, ii. 33; + in the Himalayan, ii. 41; + crossing of white and coloured Angora, ii. 92; + comparative fertility of wild and tame, ii. 111; + high-bred, often bad breeders, ii. 121; + selection of, ii. 204; + white, liable to destruction, ii. 230; + effects of disuse of parts in, ii. 298; + skull of, affected by drooping ears, ii. 301; + length of intestines in, ii. 303; + correlation of ears and skull in, ii. 324-325; + variations in skull of, ii. 350; + periosteum of a dog producing bone in, ii. 369. + RACE-HORSE, origin of, i. 54. + RACES, modification and formation of, by crossing, ii. 95-99; + natural and artificial, ii. 245; + Pouchet's views on plurality of, i. 2; + of pigeons, i. 207-212. + RADISHES, i. 326; crossing of, ii. 90; + varieties of, ii. 217-218. + RADCLYFFE, W. F., effect of climate and soil on strawberries, i. 354; + constitutional differences in roses, i. 367. + RADLKOFER, retrogressive metamorphosis in mosses and algæ, ii. 361. + RAFFLES, Sir Stamford, on the crossing of Javanese cattle with _Bos + sondaicus_, ii. 206. + RAM, goat-like, from the Cape of Good Hope, ii. 66. + RANCHIN, heredity of diseases, ii. 7. + RANGE of gallinaceous birds on the Himalaya, i. 237. + _Ranunculus ficaria_, ii. 170. + _Ranunculus repens_, ii. 168. + RAPE, i. 325. + _Raphanus sativus_, ii. 343. + RASPBERRY, yellow-fruited, ii. 230. + RATTLESNAKE, experiments with poison of the, ii. 289. + RAVEN, stomach of, affected by vegetable diet, ii. 302. + RAWSON, A., self-impotence in hybrids of _Gladiolus_, ii. 139-140. + RÉ, Le Compte, on the assumption of a yellow colour by all varieties of + maize, i. 321. + RÉAUMUR, effect of confinement upon the cock, ii. 52; + fertility of fowls in most climates, ii. 161. + REED, Mr., atrophy of the limbs of rabbits, consequent on the destruction + of their nerves, ii. 297. + REGENERATION of amputated parts in man, ii. 14; + in the human embryo, ii. 15; + in the lower vertebrata, insects, and myriapoda, _ibid._ + REINDEER, individuals recognised by the Laplanders, ii. 251. + REGNIER, early cultivation of the cabbage by the Celts, i. 324. + REISSEK, experiments in crossing _Cytisus purpureus_ and _laburnum_, i. + 389; + modification of a _Thesium_ by _Oecidium_, ii. 284. + RELATIONS, characters of, reproduced in children, ii. 34. + RENGGER, occurrence of jaguars with crooked legs in Paraguay, i. 17; + naked dogs of Paraguay, i. 23, 31, ii. 93, 102; + feral dogs of La Plata, i. 27; + on the aguara, i. 26; + cats of Paraguay, i. 46, ii. 86, 151; + dogs of Paraguay, ii. 87; + feral pigs of Buenos Ayres, i. 77; + on the refusal of wild animals to breed in captivity, ii. 149; + on _Dicotyles labiatus_, ii. 150; + sterility of plantigrade carnivora in captivity, ii. 152; + on _Cavia aperea_, ii. 152; + sterility of _Cebus azaræ_ in captivity, ii. 153; + abortions produced by wild animals in captivity, ii. 158. + REPRODUCTION, sexual and asexual, contrasted, ii. 361; + unity of forms of, ii. 383; + antagonism of, to growth, ii. 384. + _Reseda odorata_, ii. 237. + RETINITIS, pigmentary, in deaf-mutes, ii. 328. + REVERSION, ii. 28-29, 372-373, 396, 398-402; + in pigeons, ii. 29; + in cattle, ii. 29-30; + in sheep, ii. 30; + in fowls, ii. 31; + in the heartsease, _ibid._; + in vegetables, _ibid._; + in feral animals and plants, ii. 32-34; + to characters derived from a previous cross in man, dogs, pigeons, + pigs, and fowls, ii. 34-35; + {474} + in hybrids, ii. 36; + by bud-propagation in plants, ii. 36-38; + by age in fowls, cattle, &c., ii. 38-39; + caused by crossing, ii. 39-51; + explained by latent characters, ii. 51-56; + producing monstrosities, ii. 57; + producing peloric flowers, ii. 58-60; + of feral pigs to the wild type, i. 77-78; + of supposed feral rabbits to the wild type, i. 104, 111, 115; + of pigeons, in coloration, when crossed, i. 197-202; + in fowls, i. 239-246; + in the silkworm, i. 302; + in the pansy, i. 369; + in a pelargonium, i. 378; + in Chrysanthemums, i. 379; + of varieties of the China rose in St. Domingo, i. 380; + by buds in pinks and carnations, i. 381; + of laciniated varieties of trees to the normal form, i. 382; + in variegated leaves of plants, i. 383-384; + in tulips, i. 386; + of suckers of the seedless barberry to the common form, i. 384; + by buds in hybrids of _Tropæolum_, i. 392; + in plants, i. 409; + of crossed peloric snapdragons, ii. 71; + analogous variations due to, ii. 349-351. + REYNIER, selection practised by the Celts, ii. 202-203. + RHINOCEROS, breeding in captivity in India, ii. 150. + _Rhododendron_, hybrid, ii. 265. + _Rhododendron ciliatum_, ii. 277. + _Rhododendron Dalhousiæ_, effect of pollen of _R. Nuttallii_ upon, i. + 400. + RHUBARB, not medicinal when grown in England, ii. 274. + _Ribes grossularia_, i. 354-356, 376. + _Ribes rubrum_, i. 376. + RIBS, number and characters of, in fowls, i. 267; + characters of, in ducks, i. 283-284. + RICE, Imperial, of China, ii. 205; + Indian varieties of, ii. 256; + variety of, not requiring water, ii. 305. + RICHARDSON, H. D., on jaw-appendages in Irish pigs, i. 76; + management of pigs in China, i. 68; + occurrence of striped young in Westphalian pigs, i. 76; + on crossing pigs, ii. 95; + on interbreeding pigs, ii. 122; + on selection in pigs, ii. 194. + RICHARDSON, Sir John, observations on the resemblance between North + American dogs and wolves, i. 21-22; + on the burrowing of wolves, i. 27; + on the broad feet of dogs, wolves, and foxes in North America, i. 40; + on North American horses scraping away the snow, i. 53. + _Ricinus_, annual in England, ii. 305. + RIEDEL, on the "Bagadotte" pigeon, i. 141; + on the Jacobin pigeon, i. 154; + fertility of hybrid pigeons, i. 192. + RINDERPEST, ii. 378. + RISSO, on varieties of the orange, i. 336, ii. 308, 331. + RIVERS, Lord, on the selection of greyhounds, ii. 235. + RIVERS, Mr., persistency of characters in seedling potatoes, i. 331; + on the peach, i. 338, 339; + persistency of races in the peach and nectarine, i. 339, 340; + connexion between the peach and the nectarine, i. 340; + persistency of character in seedling apricots, i. 344; + origin of the plum, i. 345; + seedling varieties of the plum, i. 346; + persistency of character in seedling plums, i. 347; + bud-variation in the plum, i. 375; + plum, attacked by bullfinches, ii. 232; + seedling apples with surface-roots, i. 349; + variety of the apple found in a wood, ii. 260; + on roses, i. 366-367; + bud-variation in roses, i. 379-381; + production of Provence roses from seeds of the moss-rose, i. 380; + effect produced by grafting on the stock in jessamine, i. 394; + in the ash, i. 394; + on grafted hazels, i. 395; + hybridisation of a weeping thorn, ii. 18; + experiments with the seed of the weeping elm and ash, ii. 19; + variety of the cherry with curled petals, ii. 232. + RIVIÈRE, reproduction of _Oncidium Cavendishianum_, ii. 133. + ROBERTS, Mr., on inheritance in the horse, ii. 10. + ROBERTSON, Mr., on glandular-leaved peaches, i. 343. + ROBINET, on the silkworm, i. 301-304, ii. 197. + _Robinia_, ii. 274. + ROBSON, Mr., deficiencies of half-bred horses, ii. 11. + ROBSON, Mr., on the advantage of change of soil to plants, ii. 146-147; + on the growth of the verbena, ii. 273; + on broccoli, ii. 310. + ROCK pigeon, measurements of the, i. 134; + figured, i. 135. + RODENTS, sterility of, in captivity, ii. 152. + _Rodriguezia_, ii. 134, 135. + RODWELL, J., poisoning of horses by mildewed tares, ii. 337. + ROHILCUND, feral humped cattle in, i. 79. + ROLLE, F., on the history of the peach, ii. 308. + ROLLER-PIGEONS, Dutch, i. 151. + ROLLESTON, Prof., incisor teeth affected in form in cases of pulmonary + tubercle, ii. 332. + ROMANS, estimation of pigeons by, i. 205; + breeds of fowls possessed by, i. 231, 247. + {475} + ROOKS, pied, ii. 77. + _Rosa_, cultivated species of, i. 366. + _Rosa devoniensis_, graft-hybrid produced by, on the white Banksian rose, + i. 396. + _Rosa indica_ and _centifolia_, fertile hybrids of, i. 366. + _Rosa spinosissima_, history of the culture of, i. 367. + ROSELLINI, on Egyptian dogs, i. 17. + ROSES, i. 366-367; + origin of, i. 364; + bud-variation in, i. 379-381; + Scotch, doubled by selection, ii. 200; + continuous variation of, ii. 241; + effect of seasonal conditions on, ii. 273; + noisette, ii. 308; + galls of, ii. 284. + ROUENNAIS rabbit, i. 105. + ROULIN, on the dogs of Juan Fernandez, i. 27; + on South American cats, i. 46; + striped young pigs, i. 77; + feral pigs in South America, i. 78, ii. 33; + on Columbian cattle, i. 88, ii. 205, 226; + effects of heat on the hides of cattle in South America, i. 92; + fleece of sheep in the hot valleys of the Cordilleras, i. 98; + diminished fertility of these sheep, ii. 161; + on black-boned South American fowls, i. 258; + variation of the guinea-fowl in tropical America, i. 294; + frequency of striped legs in mules, ii. 42; + geese in Bogota, ii. 161; + sterility of fowls introduced into Bolivia, ii. 162. + ROY, M., on a variety of _Magnolia grandiflora_, ii. 308. + ROYLE, Dr., Indian varieties of the mulberry, i. 334; + on _Agave vivipara_, ii. 169; + variety of rice not requiring irrigation, ii. 305; + sheep from the Cape in India, ii. 306. + _Rubus_, pollen of, ii. 268. + RUDIMENTARY organs, i. 12, ii. 315-318. + RUFZ de Lavison, extinction of breeds of dogs in France, ii. 425. + RUMINANTS, general fertility of, in captivity, ii. 150. + RUMPLESS fowls, i. 230. + RUNTS, i. 142-144; + history of, i. 210; + lower jaws and skull figured, i. 164-165. + RUSSIAN or Himalayan rabbit, i. 108. + RÜTIMEYER, Prof., dogs of the Neolithic period, i. 19; + horses of Swiss lake-dwellings, i. 49; + diversity of early domesticated horses i. 51; + pigs of the Swiss lake-dwellings, i. 65, 67-68; + on humped cattle, i. 80; + parentage of European breeds of cattle, i. 80, 81, ii. 427; + on "Niata" cattle, i. 89; + sheep of the Swiss lake-dwellings, i. 94, ii. 427; + goats of the Swiss lake-dwellings, i. 101; + absence of fowls in the Swiss lake-dwellings, i. 246; + on crossing cattle, ii. 98; + differences in the bones of wild and domesticated animals, ii. 279; + decrease in size of wild European animals, ii. 427. + RYE, wild, De Candolle's observations on, i. 313; + found in the Swiss lake-dwellings, i. 319; + common, preferred by hares and rabbits, ii. 232; + less variable than other cultivated plants, ii. 254. + + SABINE, Mr., on the cultivation of _Rosa spinosissima_, i. 367; + on the cultivation of the dahlia, i. 369-370, ii. 261; + effect of foreign pollen on the seed-vessel in _Amaryllis vittata_, i. + 400. + ST. ANGE, influence of the pelvis on the shape of the kidneys in birds, + ii. 344. + ST. DOMINGO, wild dogs of, i. 28; + bud-variation of dahlias in, i. 385. + ST. HILAIRE, Aug., milk furnished by cows in South America, ii. 300; + husked form of maize, i. 320. + ST. JOHN, C., feral cats in Scotland, i. 47; + taming of wild ducks, i. 278. + ST. VALERY apple, singular structure of the, i. 350; + artificial fecundation of the, i. 401. + ST. VITUS' Dance, period of appearance of, ii. 77. + SAGERET, origin and varieties of the cherry, i. 347-348; + origin of varieties of the apple, i. 350; + incapacity of the cucumber for crossing with other species, i. 359; + varieties of the melon, i. 360; + supposed twin-mongrel melon, i. 391; + crossing melons, ii. 108, 129; + on gourds, ii. 108; + effects of selection in enlarging fruit, ii. 217; + on the tendency to depart from type, ii. 241; + variation of plants in particular soils, ii. 278. + SALAMANDER, experiments on the, ii. 293, 341; + regeneration of lost parts in the, ii. 15, 376, 385. + _Salamandra cristata_, polydactylism in, ii. 14. + SALISBURY, Mr., on the production of nectarines by peach-trees, i. 341; + on the dahlia, i. 369-370. + _Salix_, intercrossing of species of, i. 336. + _Salix humilis_, galls of, ii. 282, 283. + SALLÉ, feral guinea-fowl in St. Domingo, i. 294. + SALMON, early breeding of male, ii. 384. + SALTER, Mr., on bud-variation in pelargoniums, i. 378; + in the Chrysanthemum, i. 379; + transmission of variegated leaves by seed, i. 383; + bud-variation by suckers in _Phlox_, i. 384; + application of selection to bud-varieties of plants, i. 411; + accumulative effect of changed conditions of life, ii. 262; + on the variegation of strawberry leaves, ii. 274. + SALTER, S. J., hybrids of _Gallus Sonneratii_ and the common fowl, i. + 234, ii. 45; + {476} + crossing of races or species of rats, ii. 87-88. + SAMESREUTHER, on inheritance in cattle, ii. 10. + SANDFORD. _See_ DAWKINS. + SAP, ascent of the, ii. 296. + _Saponaria calabrica_, ii. 20. + SARDINIA, ponies of, i. 52. + SARS, on the development of the hydroida, ii. 368. + SATIATION of the stigma, i. 402-403. + _Saturnia pyri_, sterility of, in confinement, ii. 157. + SAUL, on the management of prize gooseberries, i. 356. + SAUVIGNY, varieties of the goldfish, i. 296. + SAVAGES, their indiscriminate use of plants as food, i. 307-310; + fondness of, for taming animals, ii. 160. + SAVI, effect of foreign pollen on maize, i. 400. + _Saxifraga geum_, ii. 166. + SAYZID MOHAMMED MUSARI, on carrier-pigeons, i. 141; + on a pigeon which utters the sound "Yahu," i. 155. + SCANDEROONS (pigeons), i. 142, 143. + SCANIA, remains of _Bos frontosus_ found in, i. 81. + SCAPULA, characters of, in rabbits, i. 123; + in fowls, i. 268; + in pigeons, i. 167; + alteration of, by disuse, in pigeons, i. 175. + SCARLET fever, ii. 276. + SCHAAFFHAUSEN, on the horses represented in Greek statues, ii. 213. + SCHACHT, H., on adventitious buds, ii. 384. + SCHLEIDEN, excess of nourishment a cause of variability, ii. 257. + SCHOMBURGK, Sir R., on the dogs of the Indians of Guiana, i. 19, 23, ii. + 206; + on the musk duck, i. 182; + bud-variation in the Banana, i. 377; + reversion of varieties of the China rose in St. Domingo, i. 380; + sterility of tame parrots in Guiana, ii. 155; + on _Dendrocygna viduata_, ii. 157; + selection of fowls in Guiana, ii. 209. + SCHREIBERS, on _Proteus_, ii. 297. + _Sciuropterus volucella_, ii. 152. + _Sciurus palmarum_ and _cinerea_, ii. 152. + SCLATER, P. L., on _Asinus tæniopus_, i. 62, ii. 41; + on _Asinus indicus_, ii. 42; + striped character of young wild pigs, i. 70; + osteology of _Gallinula nesiotis_, i. 287; + on the black-shouldered peacock, i. 290; + on the breeding of birds in captivity, ii. 157. + SCHMERLING, Dr., varieties of the dog, found in a cave, i. 19. + SCOTCH fir, local variation of, i. 363. + SCOTCH kail and cabbage, cross between, ii. 98. + SCOTT, John, irregularities in the sex of the flowers of Maize, i. 321; + bud-variation in _Imatophyllum miniatum_, i. 385; + crossing of species of _Verbascum_, ii. 106-107; + experiments on crossing _Primulæ_, ii. 109; + reproduction of orchids, ii. 133; + fertility of _Oncidium divaricatum_, ii. 164; + acclimatisation of the sweet pea in India, ii. 311; + number of seeds in _Acropera_ and _Gongora_, ii. 379. + SCOTT, Sir W., former range of wild cattle in Britain, i. 85. + SCROPE, on the Scotch deerhound, ii. 73, 121. + SEBRIGHT, Sir John, effects of close interbreeding in dogs, ii. 121; + care taken by, in selection of fowls, ii. 197. + _Secale cereale_, ii. 254. + SEDGWICK, W., effects of crossing on the female, i. 404; + on the "Porcupine-man," ii. 4; + on hereditary diseases, ii. 7; + hereditary affections of the eye, ii. 9, 78-79; + inheritance of polydactylism and anomalies of the extremities, ii. + 13-14; + morbid uniformity in the same family, ii. 17; + on deaf-mutes, ii. 22; + inheritance of injury to the eye, ii. 24; + atavism in diseases and anomalies of structure, ii. 34; + non-reversion to night-blindness, ii. 36; + sexual limitation of the transmission of peculiarities in man, ii. + 72-73; + on the effects of hard-drinking, ii. 289; + inherited baldness with deficiency of teeth, ii. 326-327; + occurrence of a molar tooth in place of an incisor, ii. 391; + diseases occurring in alternate generations, ii. 401. + SEDILLOT, on the removal of portions of bone, ii. 296. + SEEDS, early selection of, ii. 204; + rudimentary, in grapes, ii. 316; + relative position of, in the capsule, ii. 345. + SEEDS and buds, close analogies of, i. 411. + SEEMANN, B., crossing of the wolf and Esquimaux dog, i. 22. + SELBY, P. J., on the bud-destroying habits of the bullfinch, ii. 232. + SELECTION, ii. 192-249; + methodical, i. 214, ii. 194-210; + by the ancients and semi-civilised people, ii. 201-210; + of trifling characters, ii. 208-210; + unconscious, i. 214, 217, ii. 174, 210-217; + effects of, shown by differences in most valued parts, ii. 217-220; + produced by accumulation of variability, ii. 220-223; + natural, as affecting domestic productions, ii. 185-189, 224-233; + as the origin of species, genera and other groups, ii. 429-432; + circumstances favourable to, ii. 233-239; + tendency of towards extremes, ii. 239-242; + {477} + possible limit of, ii. 242; + influence of time on, ii. 243-244; + summary of subject, ii. 246-249; + effects of, in modifying breeds of cattle, i. 92, 93; + in preserving the purity of breeds of sheep, i. 99-100; + in producing varieties of pigeons, i. 213-218; + in breeding fowls, i. 232-233; + in the goose, i. 289; + in the canary, i. 295; + in the goldfish, i. 296; + in the silkworm, i. 300-301; + contrasted in cabbages and cereals, i. 323; + in the white mulberry, i. 334; + on gooseberries, i. 356; + applied to wheat, i. 317-318; + exemplified in carrots, &c., i. 326; + in the potato, i. 331; + in the melon, i. 360; + in flowering plants, i. 365; + in the hyacinth, i. 371; + applied to bud-varieties of plants, i. 411; + illustrations of, ii. 421-428. + SELECTION, sexual, ii. 75. + SELF-IMPOTENCE in plants, ii. 131-140; + in individual plants, ii. 136-138; + of hybrids, ii. 174. + SELWYN, Mr., on the Dingo, i. 26. + SELYS-LONGCHAMPS, on hybrid ducks, i. 190, ii. 46, 157; + hybrid of the hook-billed duck and Egyptian goose, i. 282. + SERINGE, on the St. Valery apple, i. 350. + SERPENT Melon, i. 360. + SERRES, Olivier de, wild poultry in Guiana, i. 237. + SESAMUM, white-seeded, antiquity of the, ii. 429. + _Setaria_, found in the Swiss lake-dwellings, i. 317. + SETTERS, degeneration of, in India, i. 38; + Youatt's remarks on, i. 41. + SEX, secondary characters of, latent, ii. 51-52; + of parents, influence of, on hybrids, ii. 267. + SEXUAL characters, sometimes lost in domestication, ii. 74. + SEXUAL limitation of characters, ii. 71-75. + SEXUAL peculiarities, induced by domestication in sheep, i. 95; + in fowls, i. 251-257; + transfer of, i. 255-257. + SEXUAL variability in pigeons, i. 161-162. + SEXUAL selection, ii. 75. + SHADDOCK, i. 335. + SHAILER, Mr., on the moss-rose, i. 379-380. + SHANGHAI fowls, i. 227. + SHANGHAI sheep, their fecundity, i. 97. + SHAN ponies, striped, i. 58. + SHEEP, disputed origin of, i. 94; + early domestication of, i. 94; + large-tailed, i. 94, 95, 98, ii. 279; + variations in horns, mammæ and other characters of, i. 95; + sexual characters of, induced by domestication, i. 95, 96; + adaptation of, to climate and pasture, i. 96, 97; + periods of gestation of, i. 97; + effect of heat on the fleece of, i. 98-99, ii. 278; + effect of selection on, i. 99-101; + "ancon" or "otter" breeds of, i. 17, 92, 100; + "Mauchamp-merino," i. 100-101; + cross of German and merino, ii. 85-89; + black, of the Tarentino, ii. 227; + Karakool, ii. 278; + Jaffna, with callosities on the knees, ii. 302; + Chinese, ii. 315; + Danish, of the bronze period, ii. 427; + polydactylism in, ii. 14; + occasional production of horns in hornless breeds of, ii. 30; + reversion of colour in, ii. 30; + influence of male, on offspring, ii. 68; + sexual differences in, ii. 73; + influence of crossing or segregation on, ii. 86, 95-96, 102-103; + interbreeding of, ii. 119-120; + effect of nourishment on the fertility of, ii. 111-112; + diminished fertility of, under certain conditions, ii. 161; + unconscious selection of, ii. 213; + natural selection in breeds of, ii. 224, 225, 227; + reduction of bones in, ii. 242; + individual differences of, ii. 251; + local changes in the fleece of, in England, ii. 278; + partial degeneration of, in Australia, ii. 278; + with numerous horns, ii. 291; + correlation of horns and fleece in, ii. 326; + feeding on flesh, ii. 303; + acclimatisation of, ii. 305-306; + mountain, resistance of, to severe weather, ii. 312; + white, poisoned by _Hypericum crispum_, ii. 337. + SHEEP dogs resembling wolves, i. 24. + SHELLS, sinistral and dextral, ii. 53. + SHERIFF, Mr. new varieties of wheat, i. 315, 317; + on crossing wheat, ii. 104-105; + continuous variation of wheat, ii. 241. + SIAM, cats of, i. 47; horses of, i. 53. + SHIRLEY, E. P., on the fallow-deer, ii. 103, 120. + SHORT, D., hybrids of the domestic cat and _Felis ornata_, i, 45. + SIBERIA, northern range of wild horses in, i. 52. + SICHEL, J., on the deafness of white cats with blue eyes, ii. 329. + SIDNEY, S., on the pedigrees of pigs, ii. 3; + on cross-reversion in pigs, ii. 35; + period of gestation in the pig, i. 74; + production of breeds of pigs by intercrossing, i. 78, 95; + fertility of the pig, ii. 112; + effects of interbreeding on pigs, ii. 121-122; + on the colours of pigs, ii. 210, 229. + SIEBOLD, on the sweet potato, ii. 309. + SIEBOLD, von Carl, on parthenogenesis, ii. 364. + _Silene_, contabescence in, ii. 166. + SILK-FOWLS, i. 230, ii. 67, 69. + {478} + SILK-MOTH, Arrindy, ii. 306, 312; + Tarroo, ii. 157. + SILK-MOTHS, i. 300-304; + domesticated species of, i. 300; + history of, _ibid._; + causes of modification in, i. 300-301; + differences presented by, i. 301-304; + crossing of, ii. 98; + disease in, ii. 228; + effects of disuse of parts in, ii. 298; + selection practised with, ii. 197, 199; + variation of, ii. 236; + parthenogenesis in, ii. 364. + SILKWORMS, variations of, i. 301-302; + yielding white cocoons, less liable to disease, ii. 336. + SILVER-GREY rabbit, i. 108, 111, 120. + SIMONDS, J. B., period of maturity in various breeds of cattle, i. 87; + differences in the periods of dentition in sheep, i. 96; + on the teeth in cattle, sheep, &c., ii. 322; + on the breeding of superior rams, ii. 196. + SIMON, on the raising of eggs of the silk-moth in China, ii. 197. + SIMPSON, Sir J., regenerative power of the human embryo, ii. 15. + _Siredon_, breeding in the branchiferous stage, ii. 384. + SISKIN, breeding in captivity, ii. 154. + _Sivatherium_, resemblance of the, to Niata cattle, i. 89. + SIZE, difference of, an obstacle to crossing, ii. 101. + SKIN, and its appendages, homologous, ii. 325; + hereditary affections of the, ii. 79. + SKIRVING, R. S., on pigeons settling on trees in Egypt, i. 181. + SKULL, characters of the, in breeds of dogs, i. 34; + in breeds of pigs, i. 71; + in rabbits, i. 116-120, 127; + in breeds of pigeons, i. 163-165; + in breeds of fowls, i. 260-266; + in ducks, i. 282-283. + SKULL and horns, correlation of the, ii. 333. + SKYLARK, ii. 154. + SLEEMAN, on the Cheetah, ii. 151. + SLOE, i. 345. + SMALL-POX, ii. 378. + SMITER (pigeon), i. 156. + SMITH, Sir A., on Caffrarian cattle, i. 88; + on the use of numerous plants as food in South Africa, i. 307. + SMITH, Colonel Hamilton, on the odour of the jackal, i. 30; + on the origin of the dog, i. 16; + wild dogs in St. Domingo, i. 28; + on the Thibet mastiff and the alco, i. 28-29; + development of the fifth toe in the hind feet of mastiffs, i. 35; + differences in the skull of dogs, i. 34; + history of the pointer, i. 42; + on the ears of the dog, ii. 301; + on the breeds of horses, i. 49; + origin of the horse, i. 51; + dappling of horses, i. 55; + striped horses in Spain, i. 58; + original colour of the horse, i. 60; + on horses scraping away snow, i. 52; + on _Asinus hemionus_, ii. 43; + feral pigs of Jamaica, i. 77-78. + SMITH, Sir J. E., production of nectarines and peaches by the same tree, + i. 340; + on _Viola amoena_, i. 368; + sterility of _Vinca minor_ in England, ii. 170. + SMITH, J., development of the ovary in _Bonatea speciosa_, by irritation + of the stigma, i. 403. + SMITH, N. H., influence of the bull "Favourite" on the breed of + Short-horn cattle, ii. 65. + SMITH, W., on the inter-crossing of strawberries, i. 352. + SNAKE-RAT, ii. 87, 88. + SNAKES, form of the viscera in, ii. 344. + SNAPDRAGON, bud-variation in, i. 381; + non-inheritance of colour in, ii. 21; + peloric, crossed with the normal form, ii. 70, 93; + asymmetrical variation of the, ii. 322. + SOIL, adaptation of plums to, i. 346; + influence of, on the zones of pelargoniums, i. 366; + on roses, i. 367; + on the variegation of leaves, i. 383; + advantages of change of, ii. 146-148. + SOIL and climate, effects of, on strawberries, i. 353. + _Solanum_, non-intercrossing of species of, ii. 91. + _Solanum tuberosum_, i. 330-331. + SOLID-HOOFED pigs, i. 75. + SOLOMON, his stud of horses, i. 55. + SOMERVILLE, Lord, on the fleece of Merino sheep, i. 99; + on crossing sheep, ii. 120; + on selection of sheep, ii. 195; + diminished fertility of Merino sheep brought from Spain, ii. 161. + SOOTY fowls, i. 230, 256. + SOTO, Ferdinand de, on the cultivation of native plants in Florida, i. + 312. + _Sorghum_, i. 371. + SPAIN, hawthorn monogynous in, i. 364. + SPALLANZANI, on feral rabbits in Lipari, i. 113; + experiments on salamanders, ii. 15, 293, 385; + experiments in feeding a pigeon with meat, ii. 304. + SPANIELS, in India, i. 38; + King Charles's, i. 41; + degeneration of, caused by interbreeding, ii. 121. + SPANISH fowls, i. 227, 250, 253; + figured, i. 226; + early development of sexual characters in, i. 250, 251; + furcula of, figured, i. 268. + SPECIES, difficulty of distinguishing from varieties, i. 4; + conversion of varieties into, i. 5; + origin of, by natural selection, ii. 414-415; + by mutual sterility of varieties, ii. 185-189. + {479} + SPENCER, Lord, on selection in breeding, ii. 195. + SPENCER, Herbert, on the "survival of the fittest," i. 6; + increase of fertility by domestication, ii. 111; + on life, ii. 148, 177; + changes produced by external conditions, ii. 281; + effects of use on organs, ii. 295, 296; + ascent of the sap in trees, ii. 296; + correlation exemplified in the Irish elk, ii. 333-334; + on "physiological units," ii. 375; + antagonism of growth and reproduction, ii. 384; + formation of ducts in plants, ii. 300. + SPERMATOPHORES of the cephalopoda, ii. 383. + SPERMATOZOIDS, ii. 363-364; + apparent independence of, in insects, ii. 384. + SPHINGIDÆ, sterility of, in captivity, ii. 157. + SPINOLA, on the injurious effect produced by flowering buckwheat on white + pigs, ii. 337. + SPITZ dog, i. 31. + SPOONER, W. C., cross-breeding of sheep, i. 100, ii. 95-96, 120; + on the effects of crossing, ii. 96-97; + on crossing cattle, ii. 118; + individual sterility, ii. 162. + SPORES, reproduction of abnormal forms by, i. 383. + SPORTS, i. 373; in pigeons, i. 213. + SPOT pigeon, i. 156, 207. + SPRENGEL, C. K., on dichogamous plants, ii. 90; + on the hollyhock, ii. 107; + on the functions of flowers, ii. 175. + SPROULE, Mr., inheritance of cleft-palate and hare-lip, ii. 24. + SPURS, of fowls, i. 255; + development of, in hens, ii. 318. + SQUASHES, i. 357. + SQUINTING, hereditary, ii. 9. + SQUIRRELS, generally sterile in captivity, ii. 152. + SQUIRRELS, flying, breeding in confinement, ii. 152. + "STAARHALSIGE Taube," i. 161. + STAG, one-horned, supposed heredity of character in, ii. 12; + degeneracy of, in the Highlands, ii. 208. + STAMENS, occurrence of rudimentary, ii. 316; + conversion of, into pistils, i. 365; + into petals, ii. 392. + _Staphylea_, ii. 168. + STEENSTRUP, Prof., on the dog of the Danish Middens, i. 18; + on the obliquity of flounders, ii. 53. + STEINAN, J., on hereditary diseases, ii. 7, 79. + STERILITY, in dogs, consequent on close confinement, i. 32; + comparative, of crosses, ii. 103, 104; + from changed conditions of life, ii. 148-165; + occurring in the descendants of wild animals bred in captivity, ii. + 160; + individual, ii. 162; + resulting from propagation by buds, cuttings, bulbs, &c., ii. 169; + in hybrids, ii. 178-180, 386, 410-411; + in specific hybrids of pigeons, i. 193; + as connected with natural selection, ii. 185-189. + STERNUM, characters of the, in rabbits, i. 123; + in pigeons, i. 167, 174-175; + in fowls, i. 268, 273; + effects of disuse on the, i. 174-175, 273. + STEPHENS, J. F., on the habits of the Bombycidæ, i. 303. + STEWART, H., on hereditary disease, ii. 79. + STIGMA, variation of the, in cultivated Cucurbitaceæ, i. 359; + satiation of the, i. 402-403. + STOCKS, bud-variation in, i. 381; + effect of crossing upon the colour of the seed of, i. 398-399; + true by seed, ii. 20; + crosses of, ii. 93; + varieties of, produced by selection, ii. 219; + reversion by the upper seeds in the pods of, ii. 347-348. + STOCKHOLM, fruit-trees of, ii. 307. + STOKES, Prof., calculation of the chance of transmission of abnormal + peculiarities in man, ii. 5. + STOLONS, variations in the production of, by strawberries, i. 353. + STOMACH, structure of the, affected by food, ii. 302. + STONE in the bladder, hereditary, ii. 8, 79. + STRAWBERRIES, i. 351-354; + remarkable varieties of, i. 352-353; + hautbois, dioecious, i. 353; + selection in, ii. 200; + mildew of, ii. 228; + probable further modification of, ii. 243; + variegated, effects of soil on, ii. 274. + STRICKLAND, A., on the domestication of _Anser ferus_, i. 287; + on the colour of the bill and legs in geese, i. 288. + _Strictoenas_, i. 183. + STRIPES on young of wild swine, i. 76; + of domestic pigs of Turkey, Westphalia, and the Zambesi, i. 76-77; + of feral swine of Jamaica and New Granada, i. 77; + of fruit and flowers, i. 400, ii. 37; + in horses, i. 56-60; + in the ass, i. 62-63; + production of, by crossing species of Equidæ, ii. 42-43. + _Strix grallaria_, ii. 302. + _Strix passerina_, ii. 154. + "STRUPP-TAUBE," i. 155. + STRUTHERS, Mr., osteology of the feet in solid-hoofed pigs, i. 75; + on polydactylism, ii. 13-14. + STURM, prepotency of transmission of characters in sheep and cattle, ii. + 66; + absorption of the minority in crossed races, ii. 88; + correlation of twisted horns and curled wool in sheep, ii. 326. + {480} + SUB-SPECIES, wild, of _Columba livia_ and other pigeons, i. 204. + SUCCESSION, geological, of organisms, i. 11. + SUCKERS, bud-variation by, i. 384. + SUGAR cane, sterility of, in various countries, ii. 169; + white, liability of, to disease, ii. 228, 336. + SUICIDE, hereditary tendency to, ii. 7, 78. + SULIVAN, Admiral, on the horses of the Falkland Islands, i. 53; + wild pigs of the Falkland Islands, i. 77; + feral cattle of the Falkland Islands, i. 86, 102; + feral rabbits of the Falkland Islands, i. 112. + SULTAN fowl, i. 228, 255. + _Sus indica_, i. 65, 67-70, ii. 110. + _Sus pliciceps_, i. 69 (figured). + _Sus scrofa_, i. 65, 66, ii. 110. + _Sus scrofa palustris_, i. 68. + _Sus vittatus_, i. 67. + SWALLOWS, a breed of pigeons, i. 156. + SWAYNE, Mr., on artificial crossing of varieties of the pea, i. 397. + SWEET Peas, ii. 91; + crosses of, ii. 93, 94; + varieties of, coming true by seed, ii. 20; + acclimatisation of, in India, ii. 311. + SWEET William, bud-variation in, i. 381. + SWINHOE, R., on Chinese pigeons, i. 28, 206; + on striped Chinese horses, i. 59. + SWITZERLAND, ancient dogs of, i. 19; + pigs of, in the Neolithic period, i. 67-68; + goats of, i. 101. + SYCAMORE, pale-leaved variety of the, ii. 330. + SYKES, Colonel, on a Pariah dog with crooked legs, i. 17; + on small Indian asses, i. 62; + on _Gallus Sonneratii_, i. 233; + on the voice of the Indian Kulm cock, i. 259; + fertility of the fowl in most climates, ii. 161. + SYMMETRY, hereditary departures from, ii. 12. + _Symphytum_, variegated, i. 384. + SYPHILIS, hereditary, ii. 332. + SYRIA, asses of, i. 62. + _Syringa persica_, _chinensis_, and _vulgaris_, ii. 164. + + TACITUS, on the care taken by the Celts in breeding animals, ii. 202. + _Tagetes signata_, dwarf variety of, ii. 20. + TAHITI, varieties of cultivated plants in, ii. 256. + TAIL, occasional development of, in man, ii. 57; + never curled in wild animals, ii. 301; + rudimentary in Chinese sheep, ii. 315. + TAIL-FEATHERS, numbers of, in breeds of pigeons, i. 158-159; + peculiarities of, in cocks, i. 254-255; + variability of, in fowls, i. 258; + curled, in _Anas boschas_, and tame drakes, i. 280. + TALENT, hereditary, ii. 7. + TANKERVILLE, Earl of, on Chillingham cattle, i. 84, ii. 119. + TANNER, Prof., effects of disuse of parts in cattle, ii. 299. + TAPIR, sterility of the, in captivity, ii. 150. + TARGIONI-TOZZETTI, on cultivated plants, i. 306; + on the vine, i. 332; + varieties of the peach, i. 342; + origin and varieties of the plum, i. 345; + origin of the cherry, i. 347; + origin of roses, i. 366. + TARSUS, variability of the, in fowls, i. 259; + reproduction of the, in a thrush, ii. 15. + TARTARS, their preference for spiral-horned sheep, ii. 209. + TAVERNIER, abundance of pigeons in Persia, i. 205. + _Taxus baccata_, ii. 18. + TEEBAY, Mr., reversion in fowls, ii. 38. + TEETH, number and position of, in dogs, i. 34; + deficiency of, in naked Turkish dogs, i. 35; + period of appearance of, in breeds of dogs, i. 35; + precocity of, in highly bred animals, ii. 322; + correlation of, with hair, ii. 326; + double row of, with redundant hair, in Julia Pastrana, ii. 328; + affected in form by hereditary syphilis and by pulmonary tubercle, ii. + 332; + fusion of, ii. 341; + developed on the palate, ii. 391. + TEGETMEIER, Mr., on a cat with monstrous teeth, i. 48; + on a swift-like pigeon, i. 157; + naked young of some pigeons, i. 170; + fertility of hybrid pigeons, i. 192; + on white pigeons, ii. 230; + reversion in crossed breeds of fowls, i. 239-244; + chicks of the white silk-fowl, i. 249; + development of the cranial protuberance in Polish fowls, i. 250; + on the skull in the Polish fowl, i. 257, 262; + on the intelligence of Polish fowls, i. 264; + correlation of the cranial protuberance and crest in Polish fowls, i. + 274; + development of the web in the feet of Polish fowls, i. 259; + early development of several peculiarities in Spanish cocks, i. 250; + on the comb in Spanish fowls, i. 253; + on the Spanish fowl, ii. 306; + varieties of game-fowls, i. 252; + pedigrees of game-fowls, ii. 3; + assumption of female plumage by a game cock, i. 253; + natural selection in the game cock, ii. 225; + pugnacity of game hens, i. 256; + length of the middle toe in Cochin fowls, i. 259; + origin of the Sebright bantam, ii. 54; + differences in the size of fowls, i. 257; + effect of crossing in fowls, i. 258, ii. 96; + effects of interbreeding in fowls, ii. 124-125; + incubation by mongrels of non-sitting races of fowls, ii. 44; + inverse correlation of crest and comb in fowls, i. 274; + {481} + occurrence of pencilled feathers in fowls, ii. 40; + on a variety of the goose from Sebastopol, i. 289; + on the fertility of the peahen, ii. 112; + on the intercrossing of bees, ii. 126. + TEMMINCK, origin of domestic cats, i. 43; + origin of domestic pigeons, i. 180; + on _Columba guinea_, i. 182; + on _Columba leucocephala_, i. 183; + asserted reluctance of some breeds of pigeons to cross, i. 192; + sterility of hybrid turtle-doves, i. 193; + variations of _Gallus bankiva_, i. 235; + on a buff-coloured breed of Turkeys, i. 293; + number of eggs laid by the peahen, ii. 112; + breeding of Guans in captivity, ii. 156; + behaviour of grouse in captivity, _ibid._; + sterility of the partridge in captivity, _ibid._ + TENDRILS in Cucurbitaceæ, i. 358, ii. 316. + TENNENT, Sir J. E., on the goose, i. 287; + on the growth of the apple in Ceylon, ii. 277; + on the Jaffna sheep, ii. 302. + _Teredo_, fertilisation in, ii. 363. + TERRIERS, wry-legged, ii. 245; + white, subject to distemper, ii. 336. + TESCHEMACHER, on a husked form of maize, i. 320. + TESSIER, on the period of gestation of the dog, i. 29; + of the pig, i. 74; + in cattle, i. 87; + experiments on change of soil, ii. 147. + _Tetrao_, breeding of species of, in captivity, ii. 156. + _Tetrapteryx paradisea_, ii. 156. + _Teucrium campanulatum_, pelorism in, ii. 345. + TEXAS, feral cattle in, i. 85. + THEOGNIS, his notice of the domestic fowl, i. 246. + THEOPHRASTUS, his notice of the peach, ii. 308. + _Thesium_, ii. 284. + THOMPSON, Mr., on the peach and nectarine, i. 342; + on the varieties of the apricot, i. 344; + classification of varieties of cherries, i. 347-348; + on the "Sister ribston-pippin," i. 350; + on the varieties of the gooseberry, i. 354, 355. + THOMPSON, William, on the pigeons of Islay, i. 184; + feral pigeons in Scotland, i. 190; + colour of the bill and legs in geese, i. 288; + breeding of _Tetrao scotius_ in captivity, ii. 156; + destruction of black-fowls by the osprey, ii. 230. + THOMPSON, Prof. W., on the obliquity of the flounder, ii. 53. + THORNS, reconversion of, into branches, in pear trees, ii. 318. + THORN, grafting of early and late, i. 363; + Glastonbury, i. 364. + THRUSH, asserted reproduction of the tarsus in a, ii. 15. + _Thuja pendula_ or _filiformis_, a variety of _T. orientalis_, i. 362. + THURET, on the division of the zoospores of an alga, ii. 378. + THWAITES, G. H., on the cats of Ceylon, i. 46; + on a twin seed of _Fuchsia coccinea_ and _fulgens_, i. 391. + TIBURTIUS, experiments in rearing wild ducks, i. 278. + TIGER, rarely fertile in captivity, ii. 150, 151. + _Tigridia conchiflora_, bud-variation in, i. 386. + TIME, importance of, in the production of races, ii. 243. + TINZMANN, self-impotence in the potato, ii. 137. + TISSUES, affinity of, for special organic substances, ii. 380. + TITMICE, destructive to thin-shelled walnuts, i. 356; + attacking nuts, i. 357; + attacking peas, ii. 231. + TOBACCO, crossing of varieties of, ii. 108; + cultivation of in Sweden, ii. 307. + TOBOLSK, red-coloured cats of, i. 47. + TOES, relative length of, in fowls, i. 259; + development of fifth in dogs, ii. 317. + TOLLET, Mr., his selection of cattle, ii. 199. + TOMATO, ii. 91. + TOMTITS. See _Titmice_. + TONGUE, relation of, to the beak in pigeons, i. 168. + TOOTH, occurrence of a molar, in place of an incisor, ii. 391. + "TORFSCHWEIN," i. 68. + TRAIL, R., on the union of half-tubers of different kinds of potatoes, i. + 395. + TREES, varieties of, suddenly produced, i. 361; + weeping or pendulous, i. 361; + fastigate or pyramidal, i. 361; + with variegated or changed foliage, i. 362; + early or late in leaf, i. 362-363; + forest, non-application of selection to, ii. 237. + "TREMBLEUR" (pigeons), i. 146. + TREMBLEY, on reproduction in Hydra, ii. 359. + "TREVOLTINI" silkworms, i. 301-302. + _Trichosanthes anguina_, i. 360. + TRICKS, inheritance of, ii. 6-7, 395. + _Trifolium minus_ and _repens_, ii. 164. + TRIMORPHIC plants, conditions of reproduction in, ii. 181-184. + TRISTRAM, H. B., selection of the dromedary, ii. 205-206. + _Triticum dicoccum_, i. 319. + _Triticum monococcum_, i. 319. + _Triticum spelta_, i. 319. + _Triticum turgidum_, i. 319. + _Triticum vulgare_, wild in Asia, i. 312. + {482} + TRITON, breeding in the branchiferous stage, ii. 384. + "TROMMEL-TAUBE," i. 154. + "TRONFO" pigeon, i. 144. + _Tropæolum_, ii. 38. + _Tropæolum minus_ and _majus_, reversion in hybrids of, i. 392. + TROUBETZKOY, Prince, experiments with pear-trees at Moscow, ii. 307. + TROUSSEAU, Prof., pathological resemblance of twins, ii. 252. + TRUMPETER pigeon, i. 154; + known in 1735, i. 207. + TSCHARNER, H. A. de, graft-hybrid produced by inosculation in the vine, + i. 395. + TSCHUDI, on the naked Peruvian dog, i. 23; + extinct varieties of maize from Peruvian tombs, i. 320, ii. 425. + TUBERS, bud-variation by, i. 384-385. + TUCKERMAN, Mr., sterility of _Carex rigida_, ii. 170. + TUFTED ducks, i. 281. + TULIPS, variability of, i. 370; + bud-variation in, i. 385-386; + influence of soil in "breaking," i. 385. + TUMBLER pigeon, i. 150-153; + short-faced, figured, i. 152; + skull figured, i. 163; + lower jaw figured, i. 165; + scapula and furcula figured, i. 167; + early known in India, i. 207; + history of, i. 209; + sub-breeds of, i. 220; + young unable to break the egg-shell, ii. 226; + probable further modification of, ii. 242. + "TÜMMLER" (pigeons), i. 150. + TUMOURS, ovarian, occurrence of hairs and teeth in, ii. 370; + polypoid, origin of, ii. 381. + "TÜRKISCHE TAUBE," i. 139. + TURBIT (pigeon), i. 148. + TURKEY, domestic, origin of, i. 292-293; + crossing of with North American wild Turkey, i. 292-293; + breeds of, i. 293; + crested white cock, i. 293; + wild, characters of, i. 293-294; + degeneration of, in India, i. 294, ii. 278; + failure of eggs of, in Delhi, ii. 161; + feral on the Parana, i. 190; + change produced in by domestication, ii. 262. + TURKEY, striped young pigs in, i. 76. + TURNER (pigeon), i. 156. + TURNER, W., on compensation in arteries and veins, ii. 300; + on cells, ii. 370. + TURNIPS, origin of, i. 325; + reversion in, ii. 31; + run wild, ii. 33; + crosses of, ii. 93, 96; + Swedish, preferred by hares, ii. 232; + acclimatisation of, in India, ii. 311. + TURNSPIT, on an Egyptian monument, i. 17; + crosses of the, ii. 92. + TURTLE-DOVE, white and coloured, crossing of, ii. 92. + _Turtur auritus_, hybrids of, with _T. cambayensis_ and _T. suratensis_, + i. 194. + _Turtur risorius_, crossing of, with the common pigeon, i. 193; + hybrid of, with _T. vulgaris_, _ibid._ + _Turtur suratensis_, sterile hybrids of, with _T. vulgaris_, i. 193; + hybrids of, with _T. auritus_, i. 194. + _Turtur vulgaris_, crossing of, with the common pigeon, i. 193; + hybrid of, with _T. risorius_, _ibid._; + sterile hybrids of, with _T. suratensis_ and _Ectopistes migratorius_, + _ibid._ + TUSKS of wild and domesticated pigs, i. 76, 77. + _Tussilago farfara_, variegated, i. 384. + TWIN-SEED _Fuchsia coccinea_ and _fulgens_, i. 391. + TYERMAN, B., on the pigs of the Pacific islands, i. 70, ii. 87; + on the dogs of the Pacific islands, ii. 87. + TYLOR, Mr., on the prohibition of consanguineous marriages, ii. 122-123. + + UDDERS, development of the, ii. 300. + _Ulex_, double-flowered, ii. 167. + _Ulmus campestris_ and _effusa_, hybrids of, ii. 130. + UNIFORMITY of character, maintained by crossing, ii. 85-90. + UNITS of the body, functional independence of the, ii. 368-371. + UNITY or plurality of origin of organisms, i. 13. + UPAS poison, ii. 380. + UREA, secretion of, ii. 380. + USE and disuse of parts, effects of, ii. 295-303, 352-353, 418-419; + in rabbits, i. 124-128; + in ducks, i. 284-286. + UTILITY, considerations of, leading to uniformity, ii. 241. + + VALENTIN, experimental production of double monsters by, ii. 340. + _Vallota_, ii. 139. + VAN BECK, Barbara, a hairy-faced woman, ii. 4. + VAN MONS on wild fruit-trees, i. 312, ii. 260; + production of varieties of the vine, i. 333; + correlated variability in fruit-trees, ii. 330; + production of almond-like fruit by peach-seedlings, i. 339. + _Vanessa_, species of, not copulating in captivity, ii. 157. + VARIABILITY, i. 4, ii. 371-373, 394-397, 406-420; + causes of, ii. 250-270; + correlated, ii. 319-338, 353-355, 419-420; + law of equable, ii. 351-352; + necessity of, for selection, ii. 192; + of selected characters, ii. 238-239; + of multiple homologous parts, ii. 342. + {483} + VARIATION, laws of, ii. 293-356; + continuity of, ii. 241; + possible limitation of, ii. 242, 416-417; + in domestic cats, i. 45-48; + origin of breeds of cattle by, i. 88; + in osteological characters of rabbits, i. 115-130; + of important organs, i. 359; + analogous or parallel, i. 348-352; + in horses, i. 55; + in the horse and ass, i. 64; + in fowls, i. 243-246; + in geese, i. 288; + exemplified in the production of fleshy stems in cabbages, &c., i. 326; + in the peach, nectarine, and apricot, i. 342, 344; + individual, in wheat, i. 314. + VARIEGATION of foliage, i. 383, ii. 167-168. + VARIETIES and species, resemblance of, i. 4, ii. 411-413; + conversion of, into species, i. 5; + abnormal, ii. 413; + domestic, gradually produced, ii. 414. + VARRO, on domestic ducks, i. 277; + on feral fowls, ii. 33; + crossing of the wild and domestic ass, ii. 206. + VASEY, Mr., on the number of sacral vertebræ in ordinary and humped + cattle, i. 79; + on Hungarian cattle, i. 80. + VAUCHER, sterility of _Ranunculus ficaria_ and _Acorus calamus_, ii. 170. + VEGETABLES, cultivated, reversion in, ii. 31-32; + European, culture of, in India, ii. 168-169. + VEITH, Mr., on breeds of horses, i. 49. + _Verbascum_, intercrossing of species of, i. 336, ii. 93, 105-107; + reversion in hybrids of, i. 392; + contabescent, wild plants of, ii. 165; + villosity in, ii. 277. + _Verbascum austriacum_, ii. 136. + _Verbascum blattaria_, ii. 105-106. + _Verbascum lychnitis_, ii. 105-106, 136. + _Verbascum nigrum_, ii. 136. + _Verbascum phoeniceum_, ii. 107, 137; + variable duration of, ii. 305. + _Verbascum thapsus_, ii. 106. + VERBENAS, origin of, i. 364; + white, liability of, to mildew, ii. 228, 336; + scorching of dark, ii. 229, 336; + effect of changed conditions of life on, ii. 273. + VERLOT, on the darkleaved Barberry, i. 362; + inheritance of peculiarities of foliage in trees, i. 362; + production of _Rosa cannabifolia_ by bud-variation from _R. alba_, i. + 381; + bud-variation in _Aralia trifoliata_, i. 382; + variegation of leaves, i. 383; + colours of tulips, i. 386; + uncertainty of inheritance, ii. 18; + persistency of white flowers, ii. 20; + peloric flowers of _Linaria_, ii. 58; + tendency of striped flowers to uniformity of colour, ii. 70; + non-intercrossing of certain allied plants, ii. 91; + sterility of _Primulæ_ with coloured calyces, ii. 166; + on fertile proliferous flowers, _ibid._; + on the Irish yew, ii. 241; + differences in the _Camellia_, ii. 251; + effect of soil on the variegated strawberry, ii. 274; + correlated variability in plants, ii. 330. + _Verruca_, ii. 53, 400. + VERTEBRÆ, characters of, in rabbits, i. 120-122; + in ducks, i. 283-284; + number and variations of, in pigeons, i. 165-166; + number and characters of, in fowls, i. 266-268; + variability of number of, in the pig, i. 74. + VERTUCH, see Putsche. + "VERUGAS," ii. 276. + VESPUCIUS, early cultivation in Brazil, i. 311. + VIBERT'S experiments on the cultivation of the vine from seed, i. 332. + _Viburnum opulus_, ii. 185, 316. + _Vicia sativa_, leaflet converted into a tendril in, ii. 392. + VICUNAS, selection of, ii. 207. + VILLOSITY of plants, influenced by dryness, ii. 277. + VILMORIN, cultivation of the wild carrot, i. 326, ii. 217; + colours of tulips, i. 386; + uncertainty of inheritance in balsams and roses, ii. 18; + experiments with dwarf varieties of _Saponaria calabrica_ and _Tagetes + signata_, ii. 20; + reversion of flowers by stripes and blotches, ii. 37; + on variability, ii. 262. + _Vinca minor_, sterility in, ii. 170. + VINE, i. 332-334; + parsley-leaved, reversion of, i. 382; + graft-hybrid produced by inosculation in the, i. 395; + disease of, influenced by colour of grapes, ii. 228; + influence of climate, &c., on varieties of the, ii. 278; + diminished extent of cultivation of the, ii. 308; + acclimatisation of the, in the West Indies, ii. 313. + _Viola_, species of, i. 368. + _Viola lutea_, different coloured flowers in, i. 408. + _Viola tricolor_, reversion in, ii. 31, 47. + VIRCHOW, Prof., blindness occurring in the offspring of consanguineous + marriages, ii. 143; + on the growth of bones, ii. 294, 381; + on cellular prolification, ii. 295; + independence of the elements of the body, ii. 369; + on the cell-theory, ii. 370; + presence of hairs and teeth in ovarian tumours, ii. 370; + of hairs in the brain, ii. 391; + special affinities of the tissues, ii. 380; + origin of polypoid excrescences and tumours, ii. 381. + VIRGIL on the selection of seed-corn, i. 318, ii. 203; + of cattle and sheep, ii. 202. + VIRGINIAN islands, ponies of, i. 52. + _Virgularia_, ii. 378. + VISION, hereditary peculiarities of, ii. 8-9; + {484} + in amphibious animals, ii. 223; + varieties of, ii. 300; + affections of organs of, correlated with other peculiarities, ii. 328. + _Vitis vinifera_, i. 332-334, 375. + _Viverra_, sterility of species of, in captivity, ii. 151. + VOGEL, varieties of the date palm, ii. 256. + VOGT, on the indications of stripes on black kittens, ii. 55. + VOICE, differences of, in fowls, i. 259; + peculiarities of, in ducks, i. 281; + inheritance of peculiarities of, ii. 6. + VOLZ, on the history of the dog, i. 16; + ancient history of the fowl, i. 246; + domestic ducks unknown to Aristotle, i. 277; + Indian cattle sent to Macedonia by Alexander, ii. 202; + mention of mules in the Bible, ii. 202; + history of the increase of breeds, ii. 244. + VON BERG on _Verbascum phoeniceum_, ii. 305. + VOORHELM, G., his knowledge of hyacinths, i. 371, ii. 251. + VROLIK, Prof., on polydactylism, ii. 12; + on double monsters, ii. 340; + influence of the shape of the mother's pelvis on her child's head, ii. + 344. + + WADERS, behaviour of, in confinement, ii. 156. + WAHLENBERG, on the propagation of Alpine plants by buds, runners, bulbs, + &c., ii. 169. + "WAHLVERWANDTSCHAFT" of Gärtner, ii. 180. + WALES, white cattle of, in the 10th century, i. 85. + WALKER, A., on intermarriage, i. 404; + on the inheritance of polydactylism, ii. 13. + WALKER, D., advantage of change of soil to wheat, ii. 146. + WALLACE, A. R., on a striped Javanese horse, i. 59; + on the conditions of life of feral animals, ii. 32; + artificial alteration of the plumage of birds, ii. 280; + on polymorphic butterflies, ii. 399-400; + on reversion, ii. 415; + on the limit of change, ii. 417. + WALLACE, Dr., on the sterility of Sphingidæ hatched in autumn, ii. 158. + WALLACHIAN sheep, sexual peculiarities in the horns of, i. 96. + WALLFLOWER, bud-variation in, i. 382. + WALLICH, Dr., on _Thuja pendula_ or _filiformis_, i. 362. + WALNUTS, i. 356-357; + thin-shelled, attacked by tomtits, ii. 231; + grafting of, ii. 259. + WALSH, B. D., on galls, ii. 282, 283; + his "Law of equable variability," ii. 351-352. + WALTHER, F. L., on the history of the dog, i. 16; + on the intercrossing of the zebu and ordinary cattle, i. 83. + WARING, Mr., on individual sterility, ii. 162. + WART hog, i. 76. + WATERER, Mr., spontaneous production of _Cytisus alpino-laburnum_, i. + 390. + WATER melon, i. 357. + WATERHOUSE, G. R., on the winter-colouring of _Lepus variabilis_, i. 111. + WATERTON, C., production of tailless foals, i. 53; + on taming wild ducks, i. 278; + on the wildness of half-bred wild ducks, ii. 45; + assumption of male characters by a hen, ii. 51. + WATSON, H. C., on British wild fruit-trees, i. 312; + on the non-variation of weeds, i. 317; + origin of the plum, i. 345; + variation in _Pyrus malus_, i. 348; + on _Viola amoena_ and _tricolor_, i. 368; + on reversion in Scotch kail, ii. 32; + fertility of _Draba sylvestris_ when cultivated, ii. 163; + on generally distributed British plants, ii. 285. + WATTLES, rudimentary, in some fowls, ii. 315. + WATTS, Miss, on Sultan fowls, i. 228. + WEBB, James, interbreeding of sheep, ii. 120. + WEBER, effect of the shape of the mother's pelvis on her child's head, + ii. 344. + WEEDS, supposed necessity for their modification, coincidently with + cultivated plants, i. 317. + WEEPING varieties of trees, i. 361. + WEEPING habit of trees, capricious inheritance of, ii. 18-19. + WEEVIL, injury done to stone-fruit by, in North America, ii. 231. + WELSH cattle, descended from _Bos longifrons_, i. 81. + WEST Indies, feral pigs of, i. 77; + effect of climate of, upon sheep, i. 98. + WESTERN, Lord, change effected by, in the sheep, ii. 198. + WESTPHALIA, striped young pigs in, i. 76. + WESTWOOD, J. O., on peloric flowers of _Calceolaria_, ii. 346. + WHATELY, Archbishop, on grafting early and late thorns, i. 363. + WHEAT, specific unity or diversity of, i. 312-313, 316-317; + Hasora, i. 313; + presence or absence of barbs in, i. 314; + Godron on variations in, _ibid._; + varieties of, i. 314-315; + effects of soil and climate on, i. 316; + deterioration of, _ibid._; + crossing of varieties of, _ibid._, ii. 96, 104-105, 130; + in the Swiss lake-dwellings, i. 317-319; + selection applied to, i. 318, ii. 200; + increased fertility of hybrids of, with _Ægilops_, ii. 110; + advantage of change of soil to, ii. 146; + {485} + differences of, in various parts of India, ii. 165; + continuous variation in, ii. 200; + red, hardiness of, ii. 229, 336; + Fenton, ii. 232; + natural selection in, ii. 233; + varieties of, found wild, ii. 260; + effects of change of climate on, ii. 307; + ancient variety of, ii. 429. + WHITBY, Mrs., on the markings of silkworms, i. 302; + on the silkmoth, i. 303. + WHITE, Mr., reproduction of supernumerary digits after amputation, ii. + 14; + time occupied in the blending of crossed races, ii. 87. + WHITE, Gilbert, vegetable diet of dogs, ii. 303. + WHITE and white-spotted animals, liability of, to disease, ii. 336-337. + WHITE flowers, most truly reproduced by seed, ii. 20. + WICHURA, Max, on hybrid willows, ii. 50, 131, 267; + analogy between the pollen of old-cultivated plants, and of hybrids, + ii. 268. + WICKING, Mr., inheritance of the primary characters of _Columba livia_ in + cross-bred pigeons, i. 201; + production of a white head in almond tumblers, ii. 199. + WICKSTED, Mr., on cases of individual sterility, ii. 162. + WIEGMANN, spontaneous crossing of blue and white peas, i. 397; + crossing of varieties of cabbage, ii. 130; + on contabescence, ii. 165. + WIGHT, Dr., sexual sterility of plants propagated by buds, &c., ii. 169. + WILDE, Sir W. R., occurrence of _Bos frontosus_ and _longifrons_ in Irish + crannoges, i. 81; + attention paid to breeds of animals by the ancient Irish, ii. 203. + WILDMAN, on the dahlia, ii. 216, 273. + WILDNESS of the progeny of crossed tame animals, ii. 44-46. + WILKES, Capt., on the taming of pigeons among the Polynesians, ii. 161. + WILKINSON, J., on crossed cattle, ii. 104. + WILLIAMS, Mr., change of plumage in a Hamburgh hen, i. 258. + WILLIAMS, Mr., intercrossing of strawberries, i. 352. + WILLIAMSON, Capt., degeneration of dogs in India, i. 37; + on small Indian asses, i. 62. + WILLIAMSON, Rev. W., doubling of _Anemone coronaria_ by selection, ii. + 200. + WILLOWS, weeping, i. 361; + reversion of spiral-leaved weeping, i. 383; + hybrids of, ii. 267; + galls of, ii. 282-283. + WILLOUGHBY, F., notice of spot pigeons, i. 156; + on a fantail pigeon, i. 208; + on tumbler pigeons, i. 209; + on the turbit, i. 209; + on the barb and carrier pigeons, i. 211; + on the hook-billed duck, i. 277. + WILMOT, Mr., on a crested white Turkey cock, i. 293; + reversion of sheep in colour, ii. 30. + WILSON, B. O., fertility of hybrids of humped and ordinary cattle in + Tasmania, i. 83. + WILSON, Dr., prepotency of the Manx over the common cat, ii. 66. + WILSON, James, origin of dogs, i. 16. + WILSON, Mr., on prepotency of transmission in sheep, ii. 69; + on the breeding of bulls, ii. 196. + WINGS, proportionate length of, in different breeds of pigeons, i. + 175-176; + of fowls, effects of disuse on, i. 270-272; + characters and variations of, in ducks, i. 284-286; + diminution of, in birds of small islands, i. 286-287. + WING-FEATHERS, number of, in pigeons, i. 159; + variability of, in fowls, i. 258. + WOLF, recent existence of, in Ireland, i. 16; + barking of young, i. 27; + hybrids of, with the dog, i. 32. + WOLF-DOG, black, of Florida, i. 22. + WOLVES, North American, their resemblance to dogs of the same region, i. + 21-22; + burrowing of, i. 27. + WOODBURY, Mr., crossing of the Ligurian and common hive bees, i. 299, ii. + 126; + variability of bees, i. 298. + WOODWARD, S. P., on Arctic Mollusca, ii. 256. + WOOD, Willoughby, on Mr. Bates' cattle, ii. 118. + WOOLER, W. A., on the young of the Himalayan rabbit, i. 109; + persistency of the coloured calyx in a crossed Polyanthus, i. 365. + WORRARA poison, ii. 380. + WOUNDS, healing of, ii. 294. + WRIGHT, J., production of crippled calves by shorthorned cattle, ii. 118; + on selection in cattle, ii. 194; + effect of close interbreeding on pigs, ii. 121-122; + deterioration of game cocks by close interbreeding, ii. 124. + WRIGHT, Strethill, on the development of the hydroida, ii. 368. + WYMAN, Dr., on Niata cattle, and on a similar malformation in the + codfish, i. 89; + on Virginian pigs, ii. 227. + + XENOPHON, on the colours of hunting dogs, ii. 209. + XIMENES, Cardinal, regulations for the selection of rams, ii. 204. + + "YAHOO," the name of the pigeon in Persia, i. 155. + YAKS, domestication of, i. 82; + selection of white-tailed, ii. 206, 209. + {486} + YAM, development of axillary bulbs in the, ii. 169. + YARRELL, Mr., deficiency of teeth in hairless dogs, i. 34, ii. 326; + on ducks, i. 279, ii. 262; + characters of domestic goose, resembling those of _Anser albifrons_, i. + 288; + whiteness of ganders, i. 288; + variations in goldfish, i. 296-297; + assumption of male plumage by the hen-pheasant, ii. 51; + effect of castration upon the cock, ii. 51-52; + breeding of the skylark in captivity, ii. 154; + plumage of the male linnet in confinement, ii. 158; + on the dingo, ii. 263. + YELLOW fever, in Mexico, ii. 276. + YEW, fastigate, ii. 241. + YEW, Irish, hardy in New York, ii. 309. + YEW, weeping, i. 361; + propagation of, by seed, ii. 18-19. + YOLK, variations of, in the eggs of ducks, i. 281. + YOUATT, Mr., history of the dog, i. 16-17; + variations of the pulse in breeds of dogs, i. 35; + liability to disease in dogs, i. 35, ii. 227; + inheritance of goître in dogs, ii. 10; + on the greyhound, i. 34, 41; + on King Charles' spaniels, i. 41; + on the setter, i. 41; + on breeds of horses, i. 49; + variation in the number of ribs in the horse, i. 50; + inheritance of diseases in the horse, ii. 10, 11; + introduction of Eastern blood into English horses, ii. 212-213; + on white Welsh cattle, i. 85, ii. 209; + improvement of British breeds of cattle, i. 93; + rudiments of horns in young hornless cattle, ii. 55, 315; + on crossed cattle, ii. 104, 119; + on Bakewell's long-horned cattle, ii. 118; + selection of qualities in cattle, ii. 196; + degeneration of cattle by neglect, ii. 239; + on the skull in hornless cattle, ii. 333; + disease of white parts of cattle, ii. 337; + displacement of long-horned by short-horned cattle, ii. 426; + on Angola sheep, i. 95; + on the fleece of sheep, i. 99; + correlation of horns and fleece in sheep, i. 95; + adaptation of breeds of sheep to climate and pasture, i. 96; + horns of Wallachian sheep, i. 96; + exotic sheep in the Zoological Gardens, i. 96-97, ii. 305; + occurrence of horns in hornless breeds of sheep, ii. 30; + on the colour of sheep, ii. 30; + on interbreeding sheep, ii. 120; + on Merino rams in Germany, ii. 196; + effect of unconscious selection on sheep, ii. 213; + reversion of Leicester sheep on the Lammermuir Hills, ii. 224; + on many-horned sheep, ii. 326; + reduction of bone in sheep, ii. 242; + persistency of character in breeds of animals in mountainous countries, + ii. 64; + on interbreeding, ii. 116; + on the power of selection, ii. 194-195; + slowness of production of breeds, ii. 244; + passages in the Bible relating to the breeding of animals, ii. 201-202. + YOUNG, J., on the Belgian rabbit, i. 106. + YULE, Capt., on a Burmese hairy family, ii. 77, 327. + + ZAMBESI, striped young pigs on the, i. 77. + ZAMBOS, character of the, ii. 47. + ZANO, J. G., introduction of rabbits into Porto Santo by, i. 112. + _Zea Mays_, i. 320. + ZEBU, i. 79; + domestication of the, i. 82; + fertile crossing of, with European cattle, i. 83, ii. 110. + ZEBRA, hybrids of, with the ass and mare, ii. 42. + _Zephyranthes candida_, ii. 164. + _Zinnia_, cultivation of, ii. 261. + ZOLLINGER on Malayan penguin ducks, i. 280. + ZOOSPORE, division of, in Algæ, ii. 378. + "ZOPF-TAUBE," i. 154. + +THE END. + +LONDON: PRINTED BY W. CLOWES AND SONS, DUKE STREET, STAMFORD STREET, AND +CHARING CROSS. + + * * * * * + + +NOTES + +[1] 'Medical Notes and Reflections,' 3rd edit., 1855, p. 267. + +[2] Mr. Buckle, in his grand work on 'Civilisation,' expresses doubts on +the subject owing to the want of statistics. _See_ also Mr. Bowen, +Professor of Moral Philosophy, in 'Proc. American Acad. of Sciences,' vol. +v. p. 102 + +[3] For greyhounds, _see_ Low's 'Domest. Animals of the British Islands,' +1845, p. 721. For game-fowls, _see_ 'The Poultry Book,' by Mr. Tegetmeier, +1866, p. 123. For pigs, _see_ Mr. Sidney's edit. of 'Youatt on the Pig,' +1860, pp. 11, 22. + +[4] 'The Stud Farm,' by Cecil, p. 39. + +[5] 'Philosophical Transactions,' 1755, p. 23. I have seen only second-hand +accounts of the two grandsons. Mr. Sedgwick, in a paper to which I shall +hereafter often refer, states that _four_ generations were affected, and in +each the males alone. + +[6] Barbara Van Beck, figured, as I am informed by the Rev. W. D. Fox, in +Woodburn's 'Gallery of Rare Portraits,' 1816, vol. ii. + +[7] 'Proc. Zoolog. Soc.,' 1833, p. 16 + +[8] Hofacker, 'Ueber die Eigenschaften,' &c., 1828, s. 34. Report by +Pariset in 'Comptes Rendus,' 1847, p. 592. + +[9] Hunter, as quoted in Harlan's 'Med. Researches,' p. 530. Sir A. +Carlisle, 'Phil. Transact.,' 1814, p. 94. + +[10] Girou de Buzareignues, 'De la Génération,' p. 282. + +[11] 'Macmillan's Magazine,' July and August, 1865. + +[12] The works which I have read and found most useful are Dr. Prosper +Lucas's great work, 'Traité de l'Hérédité Naturelle,' 1847. Mr. W. +Sedgwick, in 'British and Foreign Medico-Chirurg. Review,' April and July, +1861, and April and July, 1863: Dr. Garrod on Gout is quoted in these +articles. Sir Henry Holland, 'Medical Notes and Reflections,' 3rd edit., +1855. Piorry, 'De l'Hérédité dans les Maladies,' 1840. Adams, 'A +Philosophical Treatise on Hereditary Peculiarities,' 2nd edit., 1815. Essay +on 'Hereditary Diseases,' by Dr. J. Steinan, 1843. _See_ Paget, in 'Medical +Times,' 1857, p. 192, on the Inheritance of Cancer; Dr. Gould, in 'Proc. of +American Acad. of Sciences,' Nov. 8, 1853, gives a curious case of +hereditary bleeding in four generations. Harlan, 'Medical Researches,' p. +593. + +[13] Marshall, quoted by Youatt in his work on Cattle, p. 284. + +[14] 'Philosoph. Transact.,' 1814, p. 94. + +[15] 'Medical Notes and Reflections,' 3rd edit., p. 33. + +[16] This affection, as I hear from Mr. Bowman, has been ably described and +spoken of as hereditary by Dr. Dondera, of Utrecht, whose work was +published in English by the Sydenham Society in 1864. + +[17] Quoted by Mr. Herbert Spencer, 'Principles of Biology,' vol. i. p. +244. + +[18] 'British and Foreign Medico-Chirurg. Review, 'April, 1861, p. 482-6; +'l'Héréd. Nat.,' tom. i. pp. 391-408. + +[19] Dr. Osborne, Pres. of Royal College of Phys. in Ireland, published +this case in the 'Dublin Medical Journal' for 1835. + +[20] These various statements are taken from the following works and +papers:--Youatt on 'The Horse,' pp. 35, 220. Lawrence, 'The Horse,' p. 30. +Karkeek, in an excellent paper in 'Gard. Chronicle,' 1853, p. 92. Mr. +Burke, in 'Journal of R. Agricul. Soc. of England,' vol. v. p. 511. +'Encyclop. of Rural Sports,' p. 279. Girou de Buzareignues, 'Philosoph. +Phys.,' p. 215. _See_ following papers in 'The Veterinary:' Roberts, in +vol. ii. p. 144; M. Marrimpoey, vol. ii. p. 387; Mr. Karkeek, vol. iv. p. +5; Youatt on Goître in Dogs, vol. v. p. 483; Youatt, in vol. vi. pp. 66, +348, 412; M. Bernard, vol. xi. p. 539; Dr. Samesreuther, on Cattle, in vol. +xii. p. 181; Percivall, in vol. xiii. p. 47. With respect to blindness in +horses, _see_ also a whole row of authorities in Dr. P. Lucas's great work, +tom. i. p. 399. Mr. Baker, in 'The Veterinary,' vol. xiii. p. 721, gives a +strong case of hereditary imperfect vision and of jibbing. + +[21] Knight on 'The Culture of the Apple and Pear,' p. 31. Lindley's +'Horticulture,' p. 180. + +[22] These statements are taken from the following works in order:--Youatt +on 'The Horse,' p. 48; Mr. Darvill, in 'The Veterinary,' vol. viii. p. 50. +With respect to Robson, _see_ 'The Veterinary,' vol. iii. p. 580; Mr. +Lawrence on 'The Horse,' 1829, p. 9; 'The Stud Farm,' by Cecil, 1851; Baron +Cameronn, quoted in 'The Veterinary,' vol x. p. 500. + +[23] 'Recreations in Agriculture and Nat. Hist.,' vol. i. p. 68. + +[24] 'Ueber die Eigenschaften,' &c., 1828, s. 107. + +[25] Bronn's 'Geschichte der Natur,' band ii. s. 132. + +[26] Vrolik has discussed this point at full length in a work published in +Dutch, from which Mr. Paget has kindly translated for me passages. _See_, +also, Isidore Geoffroy St. Hilaire's 'Hist. des Anomalies,' 1832, tom. i. +p. 684. + +[27] 'Edinburgh New Phil. Journal,' July, 1863. + +[28] Some great anatomists, as Cuvier and Meckel, believe that the tubercle +one side of the hinder foot of the tailless Batrachians represents a sixth +digit. Certainly, when the hinder foot of a toad, as soon as it first +sprouts from the tadpole, is dissected, the partially ossified cartilage of +this tubercle resembles under the microscope, in a remarkable manner, a +digit. But the highest authority on such subjects, Gegenbaur (Untersuchung. +zur vergleich. anat. der Wirbelthiere: Carpus et Tarsus, 1864, s. 63), +concludes that this resemblance is not real, only superficial. + +[29] For these several statements, _see_ Dr. Struthers, in work cited, +especially on intermissions in the line of descent. Prof. Huxley, 'Lectures +on our Knowledge of Organic Nature,' 1863, p. 97. With respect to +inheritance, _see_ Dr. Prosper Lucas, 'L'Hérédité Nat.,' tom. i. p. 325. +Isid. Geoffroy, 'Anom.,' tom. i. p. 701. Sir A. Carlisle, in 'Phil. +Transact.,' 1814, p. 94. A. Walker, on 'Intermarriage,' 1838, p. 140, gives +a case of five generations; as does Mr. Sedgwick, in 'Brit. and Foreign +Medico-Chirurg. Review,' April, 1863, p. 462. On the inheritance of other +anomalies in the extremities, _see_ Dr. H. Dobell, in vol. xlvi. of +'Medico-Chirurg. Transactions,' 1863; also Mr. Sedgwick, in op. cit., +April, 1863, p. 460. With respect to additional digits in the negro, _see_ +Prichard, 'Physical History of Mankind.' Dr. Dieffenbach ('Journ. Royal +Geograph. Soc.,' 1841, p. 208) says this anomaly is not uncommon with the +Polynesians of the Chatham Islands. + +[30] 'The Poultry Chronicle,' 1854, p. 559. + +[31] The statements in this paragraph are taken from Isidore Geoffroy St. +Hilaire, 'Hist. des Anomalies,' tom. i. pp. 688-693. + +[32] As quoted by Carpenter, 'Princ. of Comp. Physiology,' 1854, p. 480. + +[33] Müller's 'Phys.,' Eng. translat., vol. i. 1838, p. 407. A thrush, +however, was exhibited before the British Association at Hull, in 1853, +which had lost its tarsus, and this member, it was asserted, had been +thrice reproduced: I presume it was lost each time by disease. + +[34] 'Monthly Journal of Medical Science,' Edinburgh, 1848, new series, +vol. ii. p. 890. + +[35] 'An Essay on Animal Reproduction,' trans. by Dr. Maty, 1769, p. 79. + +[36] Bonnet, 'Oeuvres d'Hist. Nat.,' tom. v., part i., 4to. edit., 1781, +pp. 343, 350, 353. + +[37] So with insects, the larvæ reproduce lost limbs, but, except in one +order, the mature insect has no such power. But the Myriapoda, which +apparently represent the larvæ of true insects, have, as Newport has shown, +this power until their last moult. _See_ an excellent discussion on this +whole subject by Dr. Carpenter in his 'Princ. Comp. Phys.,' 1854, p. 479. + +[38] Dr. Günther, in Owen's 'Anatomy of Vertebrates,' vol. i., 1866, p. +567. Spallanzani has made similar observations. + +[39] 'On the Anatomy of Vertebrates,' 1866, p. 170: with respect to the +pectoral fins of fishes, pp. 166-168. + +[40] 'Medical Notes and Reflections,' 1839, pp. 24, 34. _See_, also, Dr. P. +Lucas, 'l'Héréd. Nat.,' tom. ii. p. 33. + +[41] 'Du Danger des Mariages Consanguins,' 2nd edit., 1862, p. 103. + +[42] 'British and Foreign Medico-Chirurg. Review,' July, 1863, pp. 183, +189. + +[43] Verlot, 'La Production des Variétés,' 1865, p. 32. + +[44] Loudon's 'Gard. Mag.,' vol. xii., 1836, p. 368. + +[45] Verlot, 'La Product. des Variétés,' 1865, p. 94. + +[46] Bronn's 'Geschichte der Natur,' b. ii. s. 121. + +[47] Rev. W. A. Leighton, 'Flora of Shropshire,' p. 497; and Charlesworth's +'Mag. of Nat. Hist.,' vol. i, 1837, p. 30. + +[48] Verlot, op. cit., p. 93. + +[49] For these several statements, _see_ Loudon's 'Gard. Magazine,' vol. +x., 1834, pp. 408, 180; and vol. ix., 1833, p. 597. + +[50] These statements are taken from Alph. De Candolle, 'Bot. Géograph.,' +p. 1083. + +[51] Verlot, op. cit., p. 38. + +[52] Op. cit., p. 59. + +[53] Alph. De Candolle, 'Géograph. Bot.,' p. 1082. + +[54] _See_ 'Cottage Gardener,' April 10, 1860, p. 18, and Sept. 10, 1861, +p. 456; 'Gard. Chron.,' 1845, p. 102. + +[55] Darwin, in 'Journal of Proc. Linn. Soc. Bot.,' 1862, p. 94. + +[56] Hofacker, 'Ueber die Eigenschaften,' &c., s. 10. + +[57] Bechstein, 'Naturgesch. Deutschlands,' b. iv. s. 462. Mr. Brent, a +great breeder of canaries, informs me that he believes that these +statements are correct. + +[58] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 245. + +[59] 'British and Foreign Med.-Chirurg. Review,' July, 1861, pp. 200-204. +Mr. Sedgwick has given such full details on this subject, with ample +references, that I need refer to no other authorities. + +[60] 'De l'Espèce,' tom. ii., 1859, p. 299. + +[61] 'Philosoph. Magazine,' vol. iv., 1799, p. 5. + +[62] This last case is quoted by Mr. Sedgwick in 'British and Foreign +Medico-Chirurg. Review,' April, 1861, p. 484. For Blumenbach, _see_ +above-cited paper. _See_, also, Dr. P. Lucas, 'Traité de l'Héréd. Nat.,' +tom. ii. p. 492. Also 'Transact. Lin. Soc.,' vol. ix. p. 323. Some curious +cases are given by Mr. Baker in 'The Veterinary,' vol. xiii. p. 723. +Another curious case is given in the 'Annales des Scienc. Nat.,' 1st +series, tom. xi. p. 324. + +[63] 'Proc. Royal Soc.,' vol. x. p. 297. + +[64] Mr. Sproule, in 'British Medical Journal,' April 18, 1863. + +[65] Downing, 'Fruits of America,' p. 5; Sageret, 'Pom. Phys.,' pp. 43, 72. + +[66] Youatt on Sheep, pp. 20, 234. The same fact of loose horns +occasionally appearing in hornless breeds has been observed in Germany: +Bechstein, 'Naturgesch. Deutschlands,' b. i. s. 362. + +[67] Youatt on Cattle, pp. 155, 174. + +[68] Youatt on Sheep, 1838, pp. 17, 145. + +[69] I have been informed of this fact through the Rev. W. D. Fox, on the +excellent authority of Mr. Wilmot: _see_, also, remarks on this subject in +an original article in the 'Quarterly Review,' 1849, p. 395. + +[70] Youatt, pp. 19, 234. + +[71] 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 231. + +[72] Loudon's 'Gard. Mag.,' vol. x., 1834, p. 396: a nurseryman, with much +experience on this subject, has likewise assured me that this sometimes +occurs. + +[73] 'Gardener's Chron.,' 1855, p. 777. + +[74] Ibid., 1862, p. 721. + +[75] _See_ some excellent remarks on this subject by Mr. Wallace, 'Journal +Proc. Linn. Soc.,' 1858, vol. iii. p. 60. + +[76] Dureau de la Malle, in 'Comptes Rendus,' tom. xli., 1855, p. 807. From +the statements above given, the author concludes that the wild pigs of +Louisiana are not descended from the European _Sus scrofa_. + +[77] Capt. W. Allen, in his 'Expedition to the Niger,' states that fowls +have run wild on the island of Annobon, and have become modified in form +and voice. The account is so meagre and vague that it did not appear to me +worth copying; but I now find that Dureau de la Malle ('Comptes Rendus,' +tom. xli., 1855, p. 690) advances this as a good instance of reversion to +the primitive stock, and as confirmatory of a still more vague statement in +classical times by Varro. + +[78] 'Flora of Australia,' 1859, Introduct., p. ix. + +[79] 'De l'Espèce,' tom. ii. pp. 54, 58, 60. + +[80] Mr. Sedgwick gives many instances in the 'British and Foreign +Med.-Chirurg. Review,' April and July, 1863, pp. 448, 188. + +[81] In his edit. of 'Youatt on the Pig,' 1860, p. 27. + +[82] Dr. P. Lucas, 'Héréd. Nat.,' tom. ii. pp. 314, 892: _see_ a good +practical article on this subject in 'Gard. Chronicle,' 1856, p. 620. I +could add a vast number of references, but they would be superfluous. + +[83] Kölreuter gives cases in his 'Dritte Fortsetzung,' 1766, s. 53, 59; +and in his well-known 'Memoirs on Lavatera and Jalapa.' Gärtner, +'Bastarderzeugung,' s. 437, 441, &c. Naudin, in his 'Recherches sur +l'Hybridité, Nouvelles Archives du Muséum,' tom. i. p. 25. + +[84] Quoted by Mr. Sedgwick in 'Med.-Chirurg. Review,' April, 1861, p. 485. +Dr. H. Dobell, in 'Med.-Chirurg. Transactions,' vol. xlvi., gives an +analogous case, in which, in a large family, fingers with thickened joints +were transmitted to several members during five generations; but when the +blemish once disappeared it never reappeared. + +[85] Verlot, 'Des Variétés,' 1865, p. 63. + +[86] 'Nouvelles Archives du Muséum,' tom. i. p. 25. Alex. Braun (in his +'Rejuvenescence,' Ray Soc., 1853, p. 315) apparently holds a similar +opinion. + +[87] Mr. Teebay, in 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 72. + +[88] Quoted by Hofacker, 'Ueber die Eigenschaften,' &c., s. 98. + +[89] 'Essais Hist. Nat. du Paraguay,' tom. ii. 1801, p. 372. + +[90] These facts are given on the high authority of Mr. Hewitt, in 'The +Poultry Book,' by Mr. Tegetmeier, 1866, p. 248. + +[91] 'The Poultry Book,' by Tegetmeier, 1866, p. 97. + +[92] 'Gardener's Chron. and Agricultural Gazette,' 1866, p. 528. + +[93] Ibid., 1860, p. 343. + +[94] Sclater, in 'Proc. Zoolog. Soc.,' 1862, p. 163. + +[95] 'History of the Horse,' p. 212. + +[96] 'Mém. présentés par divers Savans à l'Acad. Royale,' tom. vi. 1835, p. +338. + +[97] 'Letters from Alabama,' 1859, p. 280. + +[98] 'Hist. Nat. des Mammifères,' 1820, tom. i. + +[99] 'Philosoph. Transact.,' 1821, p. 20. + +[100] Sclater, in 'Proc. Zoolog. Soc.,' 1862, p. 163: this species is the +Ghor-Khur of N.W. India, and has often been called the Hemionus of Pallas. +_See_, also, Mr. Blyth's excellent paper in 'Journ. of Asiatic Soc. of +Bengal,' vol. xxviii., 1860, p. 229. + +[101] Another species of wild ass, the true _A. hemionus_ or _Kiang_, which +ordinarily has no shoulder-stripes, is said occasionally to have them; and +these, as with the horse and ass, are sometimes double: _see_ Mr. Blyth, in +the paper just quoted, and in 'Indian Sporting Review,' 1856, p. 320; and +Col. Hamilton Smith, in 'Nat. Library, Horses,' p. 318; and 'Dict. Class. +d'Hist. Nat.,' tom. iii. p. 563. + +[102] Figured in the 'Gleanings from the Knowsley Menageries,' by Dr. J. E. +Gray. + +[103] Cases of both Spanish and Polish hens sitting are given in the +'Poultry Chronicle,' 1855, vol. iii. p. 477. + +[104] 'The Poultry Book,' by Mr. Tegetmeier, 1866, pp. 119, 163. The +author, who remarks on the two negatives ('Journ. of Hort.,' 1862, p. 325), +states that two broods were raised from a Spanish cock and Silver-pencilled +Hamburgh hen, neither of which are incubators, and no less than seven out +of eight hens in these two broods "showed a perfect obstinacy in sitting." +The Rev. E. S. Dixon ('Ornamental Poultry,' 1848, p. 200) says that +chickens reared from a cross between Golden and Black Polish fowls, are +"good and steady birds to sit." Mr. B. P. Brent informs me that he raised +some good sitting hens by crossing Pencilled Hamburgh and Polish breeds. A +cross-bred bird from a Spanish non-incubating cock and Cochin incubating +hen is mentioned in the 'Poultry Chronicle,' vol. iii. p. 13, as an +"exemplary mother." On the other hand, an exceptional case is given in the +'Cottage Gardener,' 1860, p. 388, of a hen raised from a Spanish cock and +black Polish hen which did not incubate. + +[105] 'The Poultry Book,' by Tegetmeier, 1866, pp. 165, 167. + +[106] 'Natural History Review,' 1863, April, p. 277. + +[107] 'Essays on Natural History,' p. 197. + +[108] As stated by Mr. Orton, in his 'Physiology of Breeding,' p. 12. + +[109] M. E. de Selys-Longchamps refers ('Bulletin Acad. Roy. de Bruxelles,' +tom. xii. No. 10) to more than seven of these hybrids shot in Switzerland +and France. M. Deby asserts ('Zoologist,' vol. v., 1845-46, p. 1254) that +several have been shot in various parts of Belgium and Northern France. +Audubon ('Ornitholog. Biography,' vol. iii. p. 168), speaking of these +hybrids, says that, in North America, they "now and then wander off and +become quite wild." + +[110] 'Journal of Researches,' 1845, p. 71. + +[111] 'Expedition to the Zambesi,' 1865, pp. 25, 150. + +[112] Dr. P. Broca, on 'Hybridity in the Genus Homo,' Eng. translat., 1864, +p. 39. + +[113] 'Nouvelles Archives du Muséum,' tom. i. p. 151. + +[114] 'Bastarderzeugung,' s. 582, 438, &c. + +[115] 'Die Bastardbefruchtung ... der Weiden,' 1865, s. 23. For Gärtner's +remarks on this head, _see_ 'Bastarderzeugung,' s. 474, 582. + +[116] Yarrell, 'Phil. Transact.,' 1827, p. 268; Dr. Hamilton, in 'Proc. +Zoolog. Soc.,' 1862, p. 23. + +[117] 'Archiv. Skand. Beiträge zur Naturgesch.,' viii. s. 397-413. + +[118] In his 'Essays on Nat. Hist.,' 1838. Mr. Hewitt gives analogous cases +with hen-pheasants in 'Journal of Horticulture,' July 12, 1864, p. 37. +Isidore Geoffroy Saint Hilaire, in his 'Essais de Zoolog. Gén.' (suites à +Buffon, 1842, pp. 496-513), has collected such cases in ten different kinds +of birds. It appears that Aristotle was well aware of the change in mental +disposition in old hens. The case of the female deer acquiring horns is +given at p. 513. + +[119] 'Cottage Gardener,' 1860, p. 379. + +[120] 'Art de faire Eclorre,' &c., 1749, tom. ii. p. 8. + +[121] Sir H. Holland, 'Medical Notes and Reflections,' 3rd edit., 1855, p. +31. + +[122] Prof. Thomson on Steenstrup's Views on the Obliquity of Flounders: +'Annals and Mag. of Nat. Hist.,' May, 1865, p. 361. + +[123] Dr. E. von Martens, in 'Annals and Mag. of Nat. Hist.,' March, 1866, +p. 209. + +[124] Darwin, 'Balanidæ,' Ray Soc., 1854, p. 499: _see_ also the appended +remarks on the apparently capricious development of the thoracic limbs on +the right and left sides in the higher crustaceans. + +[125] Mormodes ignea: Darwin, 'Fertilization of Orchids,' 1862, p. 251. + +[126] 'Journal of Horticulture,' July, 1864, p. 38. I have had the +opportunity of examining these remarkable feathers through the kindness of +Mr. Tegetmeier. + +[127] 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 241. + +[128] Carl Vogt, 'Lectures on Man,' Eng. translat., 1864, p. 411. + +[129] On Cattle, p. 174. + +[130] Isid. Geoffroy St. Hilaire, 'Des Anomalies,' tom. iii. p. 353. With +respect to the mammæ in women, _see_ tom. i. p. 710. + +[131] 'Natural Hist. Review,' April, 1863, p. 258. _See_ also his Lecture, +Royal Institution, March 16, 1860. On same subject, _see_ Moquin-Tandon, +'Eléments de Tératologie,' 1841, pp. 184, 352. + +[132] Verlot, 'Des Variétés,' 1865, p. 89; Naudin, 'Nouvelles Archives du +Muséum,' tom. i. p. 137. + +[133] In his discussion on some curious peloric calceolarias, quoted in +'Journal of Horticulture,' Feb. 24, 1863, p. 152. + +[134] For other cases of six divisions in peloric flowers of the Labiatæ +and Scrophulariaceæ, _see_ Moquin-Tandon, 'Tératologie,' p. 192. + +[135] Moquin-Tandon, 'Tératologie,' p. 186. + +[136] _See_ Youatt on Cattle, pp. 92, 69, 78, 88, 163: also Youatt on +Sheep, p. 325. Also Dr. Lucas, 'L'Héréd. Nat.,' tom. ii. p. 310. + +[137] 'Héréd. Nat.,' tom. ii. pp. 112-120. + +[138] Sir H. Holland, 'Chapters on Mental Physiology,' 1852, p. 234. + +[139] 'Gardener's Chronicle,' 1860, p. 270. + +[140] Mr. N. H. Smith, Observations on Breeding, quoted in 'Encyclop. of +Rural Sports,' p. 278. + +[141] Quoted by Bronn, 'Geschichte der Natur,' b. ii. s. 170. _See_ Sturm, +'Ueber Racen,' 1825, s. 104-107. For the niata cattle, _see_ my 'Journal of +Researches,' 1845, p. 146. + +[142] Lucas, 'l'Hérédité Nat.,' tom. ii. p. 112. + +[143] Mr. Orton, 'Physiology of Breeding,' 1855, p. 9. + +[144] Boitard and Corbié, 'Les Pigeons,' 1824, p. 224. + +[145] 'Les Pigeons, pp. 168, 198. + +[146] 'Das Ganze,' &c., 1837, s. 39. + +[147] 'The Pigeon Book,' p. 46. + +[148] 'Physiology of Breeding,' p.22; Mr. Hewitt, in 'The Poultry Book,' by +Tegetmeier, 1866, p. 224. + +[149] Boitard and Corbié, 'Les Pigeons,' 1824, p. 226. + +[150] 'Bastarderzeugung,' s. 256, 290, &c. Naudin ('Nouvelles Archives du +Muséum,' tom. i. p. 149) gives a striking instance of prepotency in _Datura +stramonium_ when crossed with two other species. + +[151] Flourens, 'Longévité Humaine,' p. 144, on crossed jackals. With +respect to the difference between the mule and the hinny, I am aware that +this has generally been attributed to the sire and dam transmitting their +characters differently; but Colin, who has given in his 'Traité Phys. +Comp.,' tom. ii. pp. 537-539, the fullest description which I have met with +of these reciprocal hybrids, is strongly of opinion that the ass +preponderates in both crosses, but in an unequal degree. This is likewise +the conclusion of Flourens, and of Bechstein in his 'Naturgeschichte +Deutschlands,' b. i. s. 294. The tail of the hinny is much more like that +of the horse than is the tail of the mule, and this is generally accounted +for by the males of both species transmitting with greater power this part +of their structure; but a compound hybrid which I saw in the Zoological +Gardens, from a mare by a hybrid ass-zebra, closely resembled its mother in +its tail. + +[152] Mr. Hewitt, who has had such great experience in raising these +hybrids, says ('Poultry Book,' by Mr. Tegetmeier, 1866, pp. 165-167) that +in all, the head was destitute of wattles, comb, and ear-lappets; and all +closely resembled the pheasant in the shape of the tail and general contour +of the body. These hybrids were raised from hens of several breeds by a +cock-pheasant; but another hybrid, described by Mr. Hewitt, was raised from +a hen-pheasant by a silver-laced Bantam cock, and this possessed a +rudimental comb and wattles. + +[153] 'L'Héréd. Nat.,' tom. ii. book ii. ch. i. + +[154] 'Bastarderzeugung,' s. 264-266. Naudin ('Nouvelles Archives du +Muséum,' tom. i. p. 148) has arrived at a similar conclusion. + +[155] 'Cottage Gardener,' 1856, pp. 101, 137. + +[156] _See_ some remarks on this head with respect to sheep by Mr. Wilson, +in 'Gardener's Chronicle,' 1863, p. 15. + +[157] Verlot, 'Des Variétés,' 1865, p. 66. + +[158] Moquin-Tandon, 'Tératologie,' p. 191. + +[159] 'Nouvelles Archives du Muséum,' tom. i. p. 137. + +[160] 'L'Héréd. Nat.,' tom. ii. pp. 137-165. _See_, also, Mr. Sedgwick's +four memoirs, immediately to be referred to. + +[161] On Sexual Limitation in Hereditary Diseases, 'Brit. and For. +Med.-Chirurg. Review,' April, 1861, p. 477; July, p. 198; April, 1863, p. +44; and July, p. 159. + +[162] W. Scrope, 'Art of Deer Stalking,' p. 354. + +[163] Boitard and Corbié, 'Les Pigeons,' p. 173; Dr. F. Chapuis, 'Le Pigeon +Voyageur Belge,' 1865, p. 87. + +[164] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 349. + +[165] 'Embassy to the Court of Ava,' vol. i. p. 320. The third generation +is described by Capt. Yule in his 'Narrative of the Mission to the Court of +Ava,' 1855, p. 94. + +[166] 'Das Ganze der Taubenzucht,' 1837, s. 21, tab. i., fig. 4; s. 24, +tab. iv., fig. 2. + +[167] Kidd's 'Treatise on the Canary,' p. 18. + +[168] Charlesworth, 'Mag. of Nat. Hist.,' vol. i., 1837, p. 167. + +[169] Dr. Prosper Lucas, 'Héréd. Nat.,' tom. ii. p. 713. + +[170] 'L'Héréd. dans les Maladies,' 1840, p. 135. For Hunter, _see_ +Harlan's 'Med. Researches,' p. 530. + +[171] 'L'Héréd. Nat.,' tom. ii. p. 850. + +[172] Sedgwick, 'Brit. and For. Med.-Chirurg. Review,' April 1861, p. 485. +I have seen three accounts, all taken from the same original authority +(which I have not been able to consult), and all differ in the details! but +as they agree in the main facts, I have ventured to quote this case. + +[173] Prosper Lucas, 'Héréd. Nat.,' tom. i. p. 400. + +[174] Sedgwick, idem, July, 1861, p. 202. + +[175] Piorry, p. 109; Prosper Lucas, tom. ii. p. 759. + +[176] Prosper Lucas, tom. ii. p. 748. + +[177] Prosper Lucas, tom. ii. pp. 678, 700, 702; Sedgwick, idem, April, +1863, p. 449, and July, 1863, p. 162; Dr. J. Steinan, 'Essay on Hereditary +Disease,' 1843, pp. 27, 34. + +[178] These cases are given by Mr. Sedgwick, on the authority of Dr. H. +Stewart, in 'Med.-Chirurg. Review,' April, 1863, pp. 449, 477. + +[179] 'Héréd. Nat.,' tom. ii. p. 852. + +[180] Communications to the Board of Agriculture, vol. i. p. 367. + +[181] 'Review of Reports, North of England,' 1808, p. 200. + +[182] 'Säugethiere von Paraguay,' 1830, s. 212. + +[183] Rengger, 'Säugethiere,' &c., s. 154. + +[184] White, 'Regular Gradation in Man,' p. 146. + +[185] Dr. W. F. Edwards, in his 'Charactères Physiolog. des Races +Humaines,' p. 23, first called attention to this subject, and ably +discussed it. + +[186] Rev. D. Tyerman, and Bennett, 'Journal of Voyages,' 1821-1829, vol. +i. p. 300. + +[187] Mr. S. J. Salter, 'Journal Linn. Soc.,' vol. vi., 1862, p. 71. + +[188] Sturm, 'Ueber Racen, &c.,' 1825, s. 107. Bronn, 'Geschichte der +Natur.,' b. ii. s. 170, gives a table of the proportions of blood after +successive crosses. Dr. P. Lucas, 'l'Hérédité Nat.,' tom. ii. p. 308. + +[189] 'Bastarderzeugung,' s. 463, 470. + +[190] 'Nova Acta Petrop.,' 1794, p. 393: _see_ also previous volume. + +[191] As quoted in the 'True Principles of Breeding,' by C. H. Macknight +and Dr. H. Madden, 1865, p. 11. + +[192] With respect to plants, an admirable essay on this subject (Die +Geschlechter-Vertheilung bei den Pflanzen: 1867) has lately been published +by Dr. Hildebrand, who arrives at the same general conclusions as I have +done. + +[193] 'Teoria della Riproduzione Vegetal,' 1816, p. 12. + +[194] Verlot, 'Des Variétés,' 1865, p. 72. + +[195] Duval-Jouve, 'Bull. Soc. Bot. de France,' tom. x., 1863, p. 194. + +[196] Extract of a letter from Sir R. Heron, 1838, given me by Mr. Yarrell. +With respect to mice, _see_ 'Annal. des Sc. Nat.,' tom. i. p. 180; and I +have heard of other similar cases. For turtle-doves, Boitard and Corbié, +'Les Pigeons,' &c., p. 238. For the Game fowl, 'The Poultry Book,' 1866, p. +128. For crosses of tailless fowls, _see_ Bechstein, 'Naturges. Deutsch.' +b. iii. s. 403. Bronn, 'Geschichte der Natur,' b. ii. s. 170, gives +analogous facts with horses. On the hairless condition of crossed South +American dogs, _see_ Rengger, 'Säugethiere von Paraguay,' s. 152: but I saw +in the Zoological Gardens mongrels, from a similar cross, which were +hairless, quite hairy, or hairy in patches, that is, piebald with hair. For +crosses of Dorking and other fowls, _see_ 'Poultry Chronicle,' vol. ii. p. +355. About the crossed pigs, extract of letter from Sir R. Heron to Mr. +Yarrell. For other cases, _see_ P. Lucas, 'Héréd. Nat.,' tom. i. p. 212. + +[197] 'Internat. Hort. and Bot. Congress of London,' 1866. + +[198] 'Bastarderzeugung,' s. 307. Kölreuter ('Dritte Fortsetszung,' s. 34, +39), however, obtained intermediate tints from similar crosses in the genus +Verbascum. With respect to the turnips, _see_ Herbert's 'Amaryllidaceæ,' +1837, p. 370. + +[199] 'Nouvelles Archives du Muséum,' tom. i. p. 100. + +[200] Richardson, 'Pigs,' 1847, pp. 37, 42; S. Sidney's edition of 'Youatt +on the Pig,' 1860, p. 3. + +[201] _See_ Mr. W. C. Spooner's excellent paper on Cross-Breeding, 'Journal +Royal Agricult. Soc.,' vol. xx., part ii.: _see_ also an equally good +article by Mr. Ch. Howard, in 'Gardener's Chronicle,' 1860, p. 320. + +[202] 'Gardener's Chronicle,' 1857, pp. 649, 652. + +[203] 'Bulletin de la Soc. d'Acclimat.,' 1862, tom. ix. p. 463. _See_ also, +for other cases, MM. Moll and Gayot, 'Du Boeuf,' 1860, p. xxxii. + +[204] 'Poultry Chronicle,' vol. ii., 1854, p. 36. + +[205] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 58. + +[206] 'Gardener's Chronicle,' 1852, p. 765. + +[207] Spooner, in 'Journal Royal Agricult. Soc.,' vol. xx., part ii. + +[208] _See_ Colin's 'Traité de Phys. Comp. des Animaux Domestiques,' tom. +ii. p. 536, where this subject is well treated. + +[209] 'Les Pigeons,' p. 37. + +[210] Vol. i., 1854, p. 101. + +[211] 'Cottage Gardener,' 1856, p. 110. + +[212] 'Bastarderzeugung,' s. 553. + +[213] Dr. Pigeaux, in 'Bull. Soc. d'Acclimat.,' tom. iii., July 1866, as +quoted in 'Annals and Mag. of Nat. Hist.,' 1867, vol. xx. p. 75. + +[214] 'Journal de Physiolog.,' tom. ii., 1859, p. 385. + +[215] Dec. 1863, p. 484. + +[216] On the Varieties of Wheat, p. 66. + +[217] Rengger, 'Säugethiere von Paraguay,' s. 336. + +[218] _See_ a memoir by MM. Lherbette and De Quatrefages, in 'Bull. Soc. +d'Acclimat.,' tom. viii., July, 1861, p. 312. + +[219] For the Norfolk sheep, _see_ Marshall's 'Rural Economy of Norfolk,' +vol. ii. p. 133. _See_ Rev. L. Landt's 'Description of Faroe,' p. 66. For +the ancon sheep, _see_ 'Phil. Transact.,' 1813, p. 90. + +[220] White's 'Nat. Hist. of Selbourne,' edited by Bennett, p. 39. With +respect to the origin of the dark-coloured deer, _see_ 'Some Account of +English Deer Parks,' by E. P. Shirley, Esq. + +[221] 'The Dovecote,' by the Rev. E. S. Dixon, p. 155; Bechstein, +'Naturgesch. Deutschlands,' Band iv., 1795, s. 17. + +[222] 'Cattle,' p. 202. + +[223] Mr. J. Wilkinson, in 'Remarks addressed to Sir J. Sebright,' 1820, p. +38. + +[224] 'Gardener's Chronicle,' 1858, p. 771. + +[225] 'Bastarderzeugung,' s. 87, 169. _See_ also the Table at the end of +volume. + +[226] 'Bastarderzeugung,' s. 87, 577. + +[227] 'Kenntniss der Befruchtung,' s. 137; 'Bastarderzeugung,' s. 92, 181. +On raising the two varieties from seed _see_ s. 307. + +[228] 'Bastarderzeugung,' s. 216. + +[229] The following facts, given by Kölreuter in his 'Dritte Fortsetzung,' +s. 34, 39, appear at first sight strongly to confirm Mr. Scott's and +Gärtner's statements; and to a certain limited extent they do so. Kölreuter +asserts, from innumerable observations, that insects incessantly carry +pollen from one species and variety of Verbascum to another; and I can +confirm this assertion; yet he found that the white and yellow varieties of +_Verbascum lychnitis_ often grew wild mingled together: moreover, he +cultivated these two varieties in considerable numbers during four years in +his garden, and they kept true by seed; but when he crossed them, they +produced flowers of an intermediate tint. Hence it might have thought that +both varieties must have a stronger elective affinity for the pollen of +their own variety than for that of the other; this elective affinity, I may +add, of each species for its own pollen (Kölreuter, 'Dritte Forts.,' s. 39, +and Gärtner, 'Bastarderz.,' _passim_) being a perfectly well-ascertained +power. But the force of the foregoing facts is much lessened by Gärtner's +numerous experiments, for, differently from Kölreuter, he never once got +('Bastarderz.,' s. 307) an intermediate tint when he crossed the yellow and +white flowered varieties of Verbascum. So that the fact of the white and +yellow varieties keeping true to their colour by seed does not prove that +they were not mutually fertilised by the pollen carried by insects from one +to the other. + +[230] 'Amaryllidaceæ,' 1837, p. 366. Gärtner has made a similar +observation. + +[231] Kölreuter first observed this fact. 'Mém. de l'Acad. St. Petersburg,' +vol. iii. p. 197. _See_ also C. K. Sprengel, 'Das Entdeckte Geheimniss,' s. +345. + +[232] Namely, Barbarines, Pastissons, Giraumous: 'Annal. des Sc. Nat.,' +tom. xxx., 1833, pp. 398 and 405. + +[233] 'Mémoire sur les Cucurbitaceæ,' 1826, pp. 46, 55. + +[234] 'Annales des Se. Nat.,' 4th series, tom. vi. M. Naudin considers +these forms as undoubtedly varieties of _Cucurbita pepo_. + +[235] 'Mém. Cucurb.,' p. 8. + +[236] 'Zweite Forts.,' s. 53, namely, Nicotiana major vulgaris; (2) +perennis; (3) Transylvanica; (4) a sub-var. of the last; (5) major latifol. +fl. alb. + +[237] Kölreuter was so much struck with this fact that he suspected that a +little pollen of _N. glutinosa_ in one of his experiments might have +accidentally got mingled with that of _var. perennis_, and thus aided its +fertilising power. But we now know conclusively from Gärtner +('Bastarderz.,' s. 34, 431) that two kinds of pollen never act _conjointly_ +on a third species; still less will the pollen of a distinct species, +mingled with a plant's own pollen, if the latter be present in sufficient +quantity, have any effect. The sole effect of mingling two kinds of pollen +is to produce in the same capsule seeds which yield plants, some taking +after the one and some after the other parent. + +[238] Mr. Scott has made some observations on the absolute sterility of a +purple and white primrose (_Primula vulgaris_) when fertilised by pollen +from the primrose ('Journal of Proc. of Linn. Soc.,' vol. viii., 1864, p. +98); but these observations require confirmation. I raised a number of +purple-flowered long-styled seedlings from seed kindly sent me by Mr. +Scott, and, though they were all some degree sterile, they were much more +fertile with pollen taken from the common primrose than with their own +pollen. Mr. Scott has likewise described a red equal-styled cowslip (_P. +veris_, idem, p. 106), which was found by him to be highly sterile when +crossed with the common cowslip; but this was not the case with several +equal-styled red seedlings raised by me from his plant. This variety of the +cowslip presents the remarkable peculiarity of combining male organs in +every respect like those of the short-styled form, with female organs +resembling in function and partly in structure those of the long-styled +form; so that we have the singular anomaly of the two forms combined in the +same flower. Hence it is not surprising that these flowers should be +spontaneously self-infertile in a high degree. + +[239] 'Act. Acad. St. Petersburg,' 1780, part ii., pp. 84, 100. + +[240] 'Annales des Sc. Nat.,' tom. xxi. (1st series), p. 61. + +[241] 'Bull. Bot. Soc. de France,' Dec. 27th, 1861, tom. viii. p. 612. + +[242] Quoted by Isid. Geoffroy St. Hilaire, 'Hist. Naturelle Générale,' +tom. iii. p. 476. Since this MS. has been sent to press a full discussion +on the present subject has appeared in Mr. Herbert Spencer's 'Principles of +Biology,' vol. ii. 1867, p. 457 _et seq._ + +[243] For cats and dogs, &c., _see_ Bellingeri, in 'Annal. des Sc. Nat.,' +2nd series, Zoolog., tom. xii. p. 155. For ferrets, Bechstein, +'Naturgeschichte Deutschlands,' Band i., 1801, s. 786, 795. For rabbits, +ditto, s. 1123, 1131; and Bronn's 'Geschichte der Natur,' B. ii. s. 99. For +mountain sheep, ditto, s. 102. For the fertility of the wild sow, _see_ +Bechstein's 'Naturgesch. Deutschlands,' B. i., 1801, s. 534; for the +domestic pig, Sidney's edit. of Youatt on the Pig, 1860, p. 62. With +respect to Lapland, _see_ Acerbi's 'Travels to the North Cape,' Eng. +translat., vol. ii. p. 222. About the Highland cows, _see_ Hogg on Sheep, +p. 263. + +[244] For the eggs of _Gallus bankiva_, _see_ Blyth, in 'Annals and Mag. of +Nat. Hist., 2nd series, vol. i., 1848, p. 456. For wild and tame ducks, +Macgillivray, 'British Birds,' vol. v. p. 37; and 'Die Enten,' s. 87. For +wild geese, L. Lloyd, 'Scandinavian Adventures,' vol. ii. 1854, p. 413; and +for tame geese, 'Ornamental Poultry,' by Rev. E. S. Dixon, p. 139. On the +breeding of pigeons, Pistor, 'Das Ganze der Taubenzucht,' 1831, s. 46; and +Boitard and Corbié, 'Les Pigeons,' p. 158. With respect to peacocks, +according to Temminck ('Hist. Nat. Gén. des Pigeons,' &c., 1813, tom. ii. +p. 41), the hen lays in India even as many as twenty eggs; but according to +Jerdon and another writer (quoted in Tegetmeier's 'Poultry Book,' 1866, pp. +280, 282), she there lays only from four to nine or ten eggs: in England +she is said, in the 'Poultry Book,' to lay five or six, but another writer +says from eight to twelve eggs. + +[245] 'The Art of Improving the Breed, &c.,' 1809, p. 16. + +[246] For Andrew Knight, _see_ A. Walker, on 'Intermarriage,' 1838, p. 227. +Sir J. Sebright's Treatise has just been quoted. + +[247] 'Cattle,' p. 199. + +[248] Nathusius, 'Ueber Shorthorn Rindvieh,' 1857, s. 71: _see_ also +'Gardener's Chronicle,' 1860, p. 270. Many analogous cases are given in a +pamphlet recently published by Mr. C. Macknight and Dr. H. Madden, 'On the +True Principles of Breeding;' Melbourne, Australia, 1865. + +[249] Mr. Willoughby Wood, in 'Gardener's Chronicle,' 1855, p. 411; and +1860, p. 270. _See_ the very clear tables and pedigrees given in Nathusius' +'Rindvieh,' s. 72-77. + +[250] Mr. Wright, 'Journal of Royal Agricult. Soc.,' vol. vii., 1846, p. +204. + +[251] Youatt on Cattle, p. 202. + +[252] Report British Assoc., Zoolog. Sect., 1838. + +[253] Azara, 'Quadrupèdes du Paraguay,' tom. ii. pp. 354, 368. + +[254] For the case of the Messrs. Brown, _see_ 'Gard. Chronicle,' 1855, p. +26. For the Foscote flock, 'Gard. Chron.,' 1860, p. 416. For the Naz flock, +'Bull. de la Soc. d'Acclimat.,' 1860, p. 477. + +[255] Nathusius, 'Rindvieh,' s. 65; Youatt on Sheep, p. 495. + +[256] 'Gard. Chronicle,' 1861, p. 631. + +[257] Lord Somerville, 'Facts on Sheep and Husbandry,' p. 6. Mr. Spooner, +in 'Journal of Royal Agricult. Soc. of England,' vol. xx., part ii. _See_ +also an excellent paper on the same subject in 'Gard. Chronicle,' 1860, p. +321, by Mr. Charles Howard. + +[258] 'Some Account of English Deer Parks,' by Evelyn P. Shirley, 1867. + +[259] 'The Art of Improving the Breed,' &c., p. 13. With respect to Scotch +deer-hounds, _see_ Scrope's 'Art of Deer Stalking,' pp. 350-353. + +[260] 'Cottage Gardener,' 1861, p. 327. + +[261] Sidney's edit. of Youatt on the Pig, 1860, p. 30; p. 33, quotation +from Mr. Druce; p. 29, on Lord Western's case. + +[262] 'Journal, Royal Agricult. Soc. of England,' 1846, vol. vii. p. 205. + +[263] 'Ueber Rindvieh,' &c., s. 78. + +[264] Sidney on the Pig, p. 36. _See_ also note, p. 34. Also Richardson on +the Pig, 1847, p. 26. + +[265] Dr. Dally has published an excellent article (translated in the +'Anthropolog. Review,' May, 1864, p. 65), criticising all writers who have +maintained that evil follows from consanguineous marriages. No doubt on +this side of the question many advocates have injured their cause by +inaccuracies: thus it has been stated (Devay, 'Du Danger des Mariages,' +&c., 1862, p. 141) that the marriages of cousins have been prohibited by +the legislature of Ohio; but I have been assured, in answer to inquiries +made in the United States, that this statement is a mere fable. + +[266] _See_ his most interesting work on the 'Early History of Man,' 1865, +chap. x. + +[267] On Consanguinity in Marriage, in the 'Fortnightly Review,' 1865, p. +710; Hofacker, 'Ueber die Eigenschaften,' &c. + +[268] Sir G. Grey's 'Journal of Expeditions into Australia,' vol. ii. p. +243; and Dobrizhoffer, 'On the Abipones of South America.' + +[269] 'The Art of Improving the Breed,' p. 13. + +[270] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 245. + +[271] 'Journal Royal Agricult. Soc.' 1846, vol. vii. p. 205; _see_ also +Ferguson on the Fowl, pp. 83, 317; _see_ also 'The Poultry Book,' by +Tegetmeier, 1866, p. 135, with respect to the extent to which cock-fighters +found that they could venture to breed in-and-in, viz., occasionally a hen +with her own son; "but they were cautious not to repeat the in-and-in +breeding." + +[272] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 79. + +[273] 'The Poultry Chronicle,' 1854, vol. i. p. 43. + +[274] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 79. + +[275] 'The Poultry Chronicle,' vol. i. p. 89. + +[276] 'The Poultry Book,' 1866, p. 210. + +[277] Ibid, 1866, p. 167; and 'Poultry Chronicle,' vol. iii., 1855, p. 15. + +[278] 'A Treatise on Fancy Pigeons,' by J. M. Eaton, p. 56. + +[279] 'The Pigeon Book,' p. 46. + +[280] 'Das Ganze der Taubenzucht,' 1837, s. 18. + +[281] 'Les Pigeons,' 1824, p. 35. + +[282] 'Proc. Entomolog. Soc.,' Aug. 6th, 1860, p. 126. + +[283] 'Journal of Horticulture,' 1861, pp. 39, 77, 158; and 1864, p. 206. + +[284] 'Beiträge zur Kenntniss der Befruchtung,' 1844, s. 366. + +[285] 'Amaryllidaceæ,' p. 371. + +[286] 'De la Fécondation,' 2nd edit., 1862, p. 79. + +[287] 'Mémoire sur les Cucurbitacées,' pp. 36, 28, 30. + +[288] Loudon's 'Gard. Mag.,' vol. viii., 1832, p. 52. + +[289] 'Transact. Hort. Soc.,' vol. i. p. 25. + +[290] 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. vi. p. 189. + +[291] 'Philosophical Transactions,' 1799, p. 200. + +[292] 'Ueber die Bastarderzeugung,' 1828, s. 32, 33. For Mr. Chaundy's +case, _see_ Loudon's 'Gard. Mag.,' vol. vii., 1831, p. 696. + +[293] 'Gardener's Chron.,' 1846, p. 601. + +[294] 'Philosoph. Transact.,' 1799, p. 201. + +[295] Quoted in 'Bull. Bot. Soc. France,' vol. ii., 1855, p. 327. + +[296] Gärtner, 'Bastarderzeugung,' s. 259, 518, 526 _et seq._ + +[297] 'Fortsetzung,' 1763, s. 29; 'Dritte Fortsetzung,' s. 44, 96; 'Act. +Acad. St. Petersburg,' 1782, part ii., p. 251; 'Nova Acta,' 1793, pp. 391, +394; 'Nova Acta,' 1795, pp. 316, 323. + +[298] 'Die Bastardbefruchtung,' &c., 1865, s. 31, 41, 42. + +[299] Max Wichura fully accepts this view ('Bastardbefruchtung,' s. 43), as +does the Rev. M. J. Berkeley, in 'Journal of Hort. Soc.,' Jan. 1866, p. 70. + +[300] 'Bastarderzeugung,' s. 394, 526, 528. + +[301] Kölreuter,' Nova Acta,' 1795, p. 316. + +[302] Gärtner, 'Bastarderzeugung,' s. 430. + +[303] 'Botanische Zeitung,' Jan. 1864, s. 3. + +[304] 'Monatsbericht Akad. Wissen,' Berlin, 1866, s. 372. + +[305] International Hort. Congress, London, 1866. + +[306] 'Proc. Bot. Soc. of Edinburgh,' May, 1863: these observations are +given in abstract, and others are added, in the 'Journal of Proc. of Linn. +Soc.,' vol. viii. Bot., 1864, p. 162. + +[307] Prof. Lecoq, 'De la Fécondation,' 2nd edit., 1862, p. 76. + +[308] 'Bastarderzeugung,' s. 64, 357. + +[309] Idem, s. 357. + +[310] 'Zweite Fortsetzung,' s. 10; 'Dritte Fort.,' s. 40. + +[311] Duvernoy, quoted by Gärtner, 'Bastarderzeugung,' s. 334. + +[312] 'Gardner's Chronicle,' 1846, p. 183. + +[313] 'Transact. Hort. Soc.,' vol. vii., 1830, p. 95. + +[314] Prof. Lecoq, 'De la Fécondation,' 1845, p. 70; Gärtner, +'Bastarderzeugung,' s. 64. + +[315] 'Gardener's Chron.' 1866, p. 1068. + +[316] 'Journal of Proc. of Linn. Soc.,' vol. viii., 1864, p. 168. + +[317] 'Amaryllidaceæ,' 1837, p. 371; 'Journal of Hort. Soc.,' vol. ii., +1847, p. 19. + +[318] Loudon's 'Gardener's Magazine,' vol. xi., 1835, p. 260. + +[319] 'Gardener's Chronicle,' 1850, p. 470. + +[320] 'Journal Hort. Soc., vol. v. p. 135. The seedlings thus raised were +given to the Hort. Soc.; but I find, on inquiry, that they unfortunately +died the following winter. + +[321] Mr. D. Beaton, in 'Journal of Hort.,' 1861, p. 453. Lecoq, however +('De la Fécond.,' 1862, p. 369), states that this hybrid is descended from +_G. psittacinus_ and _cardinalis_; but this is opposed to Herbert's +experience, who found that the former species could not be crossed. + +[322] This is the conclusion of Prof. Devay, 'Du Danger des Mariages +Consang.,' 1862, p. 97. Virchow quotes, in the 'Deutsche Jahrbücher,' 1863, +s. 354, some curious evidence on half the cases of a peculiar form of +blindness occurring in the offspring from near relations. + +[323] For England, _see_ below. For Germany, _see_ Metzger, +'Getreidearten,' 1841, s. 63. For France, Loiseleur-Deslongchamps ('Consid. +sur les Céreales,' 1843, p. 200) gives numerous references on this subject. +For Southern France, _see_ Godron, 'Florula Juvenalis,' 1854, p. 28. + +[324] 'A general Treatise of Husbandry,' vol. iii. p. 58. + +[325] 'Gardener's Chronicle and Agricult. Gazette,' 1858, p. 247; and for +the second statement, idem, 1850, p. 702. On this same subject, _see_ also +Rev. D. Walker's 'Prize Essay of Highland Agricult. Soc.,' vol. ii. p. 200. +Also Marshall's 'Minutes of Agriculture,' November, 1775. + +[326] Oberlin's 'Memoirs,' Eng. translat., p. 73. For Lancashire, _see_ +Marshall's 'Review of Reports,' 1808, p. 295. + +[327] 'Cottage Gardener,' 1856, p. 186. For Mr. Robson's subsequent +statements, _see_ 'Journal of Horticulture,' Feb. 18, 1866, p. 121. For Mr. +Abbey's remarks on grafting, &c., idem, July 18, 1865, p. 44. + +[328] 'Mém. de l'Acad. des Sciences,' 1790, p. 209. + +[329] 'On the Varieties of Wheat,' p. 52. + +[330] Mr. Spencer has fully and ably discussed this whole subject in his +'Principles of Biology,' 1864, vol. ii. ch. x. In the first edition of my +'Origin of Species,' 1859, p. 267, I spoke of the good effects from slight +changes in the conditions of life and from cross-breeding, and of the evil +effects from great changes in the conditions and from crossing widely +distinct forms, as a series of facts "connected together by some common but +unknown bond, which is essentially related to the principle of life." + +[331] 'Essais de Zoologie Générale,' 1841, p. 256. + +[332] Du Rut, 'Annales du Muséum,' 1807, tom. ix. p. 120. + +[333] 'Säugethiere von Paraguay,' 1830, s. 49, 106, 118, 124, 201, 208, +249, 265, 327. + +[334] 'The Naturalist on the Amazons,' 1863, vol. i. pp. 99, 193; vol. ii. +p. 113. + +[335] 'Embassy to the Court of Ava,' vol. i. p. 534. + +[336] 'Journal,' vol. i. p. 213. + +[337] 'Säugethiere,' s. 327. + +[338] On the Breeding of the larger Felidæ, 'Proc. Zoolog. Soc.,' 1861, p. +140. + +[339] Sleeman's 'Rambles in India,' vol. ii. p. 10. + +[340] Wiegmann's 'Archif für Naturgesch.,' 1837, s. 162. + +[341] Rengger, 'Säugethiere,' &c., s. 276. On the parentage of the +guinea-pig, _see_ also Isid. Geoffroy St. Hilaire, 'Hist. Nat. Gén.' + +[342] Although the existence of the _Leporides_, as described by Dr. Broca +('Journal de Phys.,' tom. ii. p. 370), is now positively denied, yet Dr. +Pigeaux ('Annals and Mag. of Nat. Hist.,' vol. xx., 1867, p. 75) affirms +that the hare and rabbit have produced hybrids. + +[343] 'Quadrupeds of North America,' by Audubon and Bachman, 1846, p. 268. + +[344] Loudon's 'Mag. of Nat. Hist.,' vol. ix., 1836, p. 571; Audubon and +Bachman's 'Quadrupeds of North America,' p. 221. + +[345] Flourens, 'De l'Instinct,' &c., 1845, p. 88. + +[346] _See_ 'Annual Reports Zoolog. Soc.,' 1855, 1858, 1863, 1864; 'Times' +newspaper, Aug. 10th, 1847; Flourens, 'De l'Instinct,' p. 85. + +[347] 'Säugethiere,' &c., s. 34, 49. + +[348] Art. Brazil, 'Penny Cyclop.,' p. 363. + +[349] 'The Naturalist on the River Amazon,' vol. i. p. 99. + +[350] 'Encyclop. of Rural Sports,' p. 691. + +[351] According to Sir A. Burnes ('Cabool,' &c., p. 51), eight species are +used for hawking in Scinde. + +[352] Loudon's 'Mag. of Nat. Hist.,' vol. vi., 1833, p. 110. + +[353] F. Cuvier, 'Annal. du Muséum,' tom. ix. p. 128. + +[354] 'The Zoologist,' vol. vii.-viii., 1849-50, p. 2648. + +[355] Knox, 'Ornithological Rambles in Sussex,' p. 91. + +[356] 'The Zoologist,' vol. vii.-viii., 1849-50, p. 2566; vol. ix.-x., +1851-2, p. 3207. + +[357] Bechstein, 'Naturgesch. der Stubenvögel,' 1840, s. 20. + +[358] 'Ornithological Biography,' vol. v. p. 517. + +[359] A case is recorded in 'The Zoologist,' vol. i.-ii., 1843-45, p. 453. +For the siskin breeding, vol. iii.-iv., 1845-46, p. 1075. Bechstein, +'Stubenvögel,' s. 139, speaks of bullfinches making nests, but rarely +producing young. + +[360] Yarrell's 'Hist. British Birds,' 1839, vol. i. p. 412. + +[361] Loudon's 'Mag. of Nat. History,' vol. ix., 1836, p. 347. + +[362] 'Mémoires du Muséum d'Hist. Nat.,' tom. x. p. 314: five cases of +parrots breeding in France are here recorded. _See_, also, 'Report Brit. +Assoc. Zoolog.,' 1843. + +[363] 'Stubenvögel,' s. 105, 83. + +[364] Dr. Hancock remarks ('Charlesworth's Mag. of Nat. Hist.,' vol. ii., +1838, p. 492), "it is singular that, amongst the numerous useful birds that +are indigenous to Guiana, none are found to propagate among the Indians; +yet the common fowl is reared in abundance throughout the country." + +[365] 'A Week at Port Royal,' 1855, p. 7. + +[366] Audubon, 'American Ornithology,' vol. v. pp. 552, 557. + +[367] Moubray on Poultry, 7th edit., p. 133. + +[368] Temminck, 'Hist. Nat. Gén. des Pigeons,' &c., 1813, tom. iii. pp. +288, 382; 'Annals and Mag. of Nat. Hist.,' vol. xii., 1843, p. 453. Other +species of partridge have occasionally bred; as the red-legged (_P. +rubra_), when kept in a large court in France (_see_ 'Journal de Physique,' +tom. xxv. p. 294), and in the Zoological Gardens in 1856. + +[369] Rev. E. S. Dixon, 'The Dovecote,' 1851, pp. 243-252. + +[370] Temminck, 'Hist. Nat. Gén. des Pigeons,' &c., tom. ii. pp. 456, 458; +tom. iii. pp. 2, 13, 47. + +[371] Bates, 'The Naturalist on the Amazons,' vol. i. p. 193; vol. ii. p. +112. + +[372] Temminck, 'Hist. Nat. Gén.,' &c., tom. iii. p. 125. For _Tetrao +urogallus_, _see_ L. Lloyd, 'Field Sports of North of Europe,' vol. i. pp. +287, 314; and 'Bull. de la Soc. d'Acclimat.,' tom. vii., 1860, p. 600. For +_T. Scoticus_, Thompson, 'Nat. Hist. of Ireland,' vol. ii., 1850, p. 49. +For _T. cupido_, 'Boston Journal of Nat. Hist.,' vol. iii. p. 199. + +[373] Marcel de Serres, 'Annales des Sci. Nat.,' 2nd series, Zoolog., tom. +xiii. p. 175. + +[374] Dr. Hancock, in 'Charlesworth's Mag. of Nat. Hist.' vol. ii., 1838, +p. 491; R. Hill, 'A Week at Port Royal,' p. 8; 'Guide to the Zoological +Gardens,' by P. L. Sclater, 1859, pp. 11, 12; 'The Knowsley Menagerie,' by +Dr. Gray, 1846, pl. xiv.; E. Blyth, 'Report Asiatic Soc. of Bengal,' May, +1855. + +[375] Prof. Newton, in 'Proc. Zoolog. Soc.,' 1860, p. 336. + +[376] 'The Dovecote and Aviary,' p. 428. + +[377] 'Ornithological Biography,' vol. iii. p. 9. + +[378] 'Geograph. Journal,' vol. xiii., 1844, p. 32. + +[379] Loudon's 'Mag. of Nat. Hist.,' vol. v., 1832, p. 153. + +[380] 'Zoologist,' vols. v.-vi., 1847-48, p. 1660. + +[381] 'Transact. Entomolog. Soc.,' vol. iv., 1845, p. 60. + +[382] 'Transact. Linn. Soc.,' vol. vii. p. 40. + +[383] _See_ an interesting paper by Mr. Newman, in the 'Zoologist,' 1857, +p. 5764; and Dr. Wallace, in 'Proc. Entomolog. Soc.,' June 4th, 1860, p. +119. + +[384] Yarrell's 'British Birds,' vol. i. p. 506; Bechstein, 'Stubenvögel,' +s. 185; 'Philosoph. Transact.,' 1772, p. 271. Bronn ('Geschichte der +Natur,' Band ii. s. 96) has collected a number of cases. For the case of +the deer, _see_ 'Penny Cyclop.,' vol. viii. p. 350. + +[385] 'Journal de Physiologie,' tom. ii. p. 347. + +[386] For additional evidence on this subject, _see_ F. Cuvier, in 'Annales +du Muséum,' tom. xii. p. 119. + +[387] Numerous instances could be given. Thus Livingstone ('Travels,' p. +217) states that the King of the Barotse, an inland tribe which never had +any communication with white men, was extremely fond of taming animals, and +every young antelope was brought to him. Mr. Galton informs me that the +Damaras are likewise fond of keeping pets. The Indians of South America +follow the same habit. Capt. Wilkes states that the Polynesians of the +Samoan Islands tamed pigeons; and the New Zealanders, as Mr. Mantell +informs me, kept various kinds of birds. + +[388] For analogous cases with the fowl, _see_ Réaumur, 'Art de faire +Eclorre,' &c., 1749, p. 243; and Col. Sykes, in 'Proc. Zoolog. Soc.,' 1832, +&c. With respect to the fowl not breeding in northern regions, _see_ +Latham's 'Hist. of Birds,' vol. viii., 1823, p. 169. + +[389] 'Mém. par divers Savans, Acad. des Sciences,' tom. vi., 1835, p. 347. + +[390] Youatt on Sheep, p. 181. + +[391] J. Mills, 'Treatise on Cattle,' 1776, p. 72. + +[392] Bechstein, 'Stubenvögel,' s. 242. + +[393] Crawfurd's 'Descriptive Dict. of the Indian Islands,' 1856, p. 145. + +[394] 'Bull. de la Soc. Acclimat., tom. ix., 1862, pp. 380, 384. + +[395] For pigeons, _see_ Dr. Chapuis, 'Le Pigeon Voyageur Belge,' 1865, p. +66. + +[396] 'Swedish Acts,' vol. i., 1739, p. 3. Pallas makes the same remark in +his Travels (Eng. translat.), vol. i. p. 292. + +[397] A. Kerner, 'Die Cultur der Alpenflanzen,' 1864, s. 139; Watson's +'Cybele Britannica,' vol. i. p. 131; Mr. D. Cameron, also, has written on +the culture of Alpine plants in 'Gard. Chronicle,' 1848, pp. 253, 268, and +mentions a few which seed. + +[398] 'Beiträge zur Kenntniss der Befruchtung,' 1844, s. 333. + +[399] 'Nova Acta Petrop.,' 1793, p. 391. + +[400] 'Cottage Gardener,' 1856, pp. 44, 109. + +[401] Dr. Herbert, 'Amaryllidaceæ,' p. 176. + +[402] Gärtner, 'Beiträge zur Kenntniss,' &c., s. 560, 564. + +[403] 'Gardener's Chronicle,' 1844, p. 215; 1850, p. 470. + +[404] 'Beiträge zur Kenntniss,' &c., s. 252, 333. + +[405] 'Journal of Hort. Soc.,' vol. ii. 1847, p. 83. + +[406] 'Beiträge zur Kenntniss,' &c., s. 117 _et seq._; Kölreuter, 'Zweite +Fortsetzung,' s. 10, 121; 'Dritte Fortsetzung,' s. 57. Herbert, +'Amaryllidaceæ,' p. 355. Wiegmann, 'Ueber die Bastarderzeugung,' s. 27. + +[407] 'Bastarderzeugung,' s. 356. + +[408] 'Teoria della Riproduzione,' 1816, p. 84; 'Traité du Citrus,' 1811, +p. 67. + +[409] Mr. C. W. Crocker, in 'Gard. Chronicle,' 1861, p. 1092. + +[410] Verlot, 'Des Variétés,' 1865, p. 80. + +[411] Verlot, idem, p. 88. + +[412] Prof. Allman, Brit. Assoc., quoted in the 'Phytologist,' vol. ii. p. +483. Prof. Harvey, on the authority of Mr. Andrews, who discovered the +plant, informed me that this monstrosity could be propagated by seed. With +respect to the poppy, _see_ Prof. Goeppert, as quoted in 'Journal of +Horticulture,' July 1st, 1863, p. 171. + +[413] 'Comptes Rendus,' Dec. 19th, 1864, p. 1039. + +[414] 'Gardener's Chronicle,' 1866, p. 681. + +[415] 'Theory of Horticulture,' p. 333. + +[416] Mr. Fairweather, in 'Transact. Hort. Soc.,' vol. iii. p. 406; Bosse, +quoted by Bronn, 'Geschichte der Natur,' B. ii. s. 77. On the effects of +the removal of the anthers, _see_ Mr. Leitner, in Silliman's 'North +American Journ. of Science,' vol. xxiii. p. 47; and Verlot, 'Des Variétés,' +1865, p. 84. + +[417] Lindley's 'Theory of Horticulture,' p. 333. + +[418] 'Gardener's Chronicle,' 1865, p. 626; 1866, pp. 290, 730; and Verlot, +'Des Variétés,' p. 75. + +[419] 'Gardener's Chronicle,' 1843, p. 628. In this article I suggested the +following theory on the doubleness of flowers. + +[420] Quoted by Gärtner, 'Bastarderzeugung,' s. 567. + +[421] 'Gardener's Chronicle,' 1866, p. 901. + +[422] Lindley, 'Theory of Horticulture,' p. 175-179; Godron, 'De l'Espèce,' +tom. i. p. 106: Pickering, 'Races of Man;' Gallesio, 'Teoria della +Riproduzione,' 1816, p. 101-110. Meyen ('Reise um Erde,' Th. ii. s. 214) +states that at Manilla one variety of the banana is full of seeds; and +Chamisso (Hooker's 'Bot. Misc.,' vol. i. p. 310) describes a variety of the +bread-fruit in the Mariana Islands with small fruit, containing seeds which +are frequently perfect. Burnes, in his 'Travels in Bokhara,' remarks on the +pomegranate seeding in Mazenderan, as a remarkable peculiarity. + +[423] Ingledew, in 'Transact. of Agricult. and Hort. Soc. of India,' vol. +ii. + +[424] 'De la Fécondation,' 1862, p. 308. + +[425] Hooker's 'Bot. Misc.,' vol. i. p. 99; Gallesio, 'Teoria della +Riproduzione,' p. 110. + +[426] 'Transact. Linn. Soc.,' vol. xvii. p. 563. + +[427] Godron, 'De l'Espèce,' tom. ii. p. 106; Herbert on Crocus, in +'Journal of Hort. Soc.,' vol. i., 1846, p. 254.--Dr. Wight, from what he +has seen in India, believes in this view; 'Madras Journal of Lit. and +Science,' vol. iv., 1836, p. 61. + +[428] Wahlenberg specifies eight species in this state on the Lapland Alps: +_see_ Appendix to Linnæus' 'Tour in Lapland,' translated by Sir J. E. +Smith, vol. ii. pp. 274-280. + +[429] 'Travels in North America,' Eng. translat., vol. iii. p. 175. + +[430] With respect to the ivy and Acorus, _see_ Dr. Bromfield in the +'Phytologist,' vol. iii. p. 376. _See_ also Lindley and Vaucher on the +Acorus. + +[431] 'Annal. des Sc. Nat.,' 3rd series, Zool., tom. iv. p. 280. Prof. +Decaisne refers also to analogous cases with mosses and lichens near Paris. + +[432] Mr. Tuckerman, in Silliman's 'American Journal of Science,' vol. xlv. +p. 41. + +[433] Sir J. E. Smith, 'English Flora,' vol. i. p. 339. + +[434] G. Planchon, 'Flora de Montpellier,' 1864, p. 20. + +[435] On the non-production of seeds in England _see_ Mr. Crocker, in +'Gardener's Weekly Magazine,' 1852, p. 70; Vaucher, 'Hist. Phys. Plantes +d'Europe,' tom. i. p. 33; Lecoq, 'Géograph. Bot. de l'Europe,' tom. iv. p. +466; Dr. D. Clos, in 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. xvii., +1852, p. 129: this latter author refers to other analogous cases. On the +non-production of pollen by this Ranunculus _see_ Chatin, in 'Comptes +Rendus,' June 11th, 1866. + +[436] 'Bastarderzeugung,' s. 565. Kölreuter ('Dritte Fortsetzung,' s. 73, +87, 119) also shows that when two species, one single and the other double, +are crossed, the hybrids are apt to be extremely double. + +[437] 'Teoria della Riproduzione Veg.,' 1816, p. 73. + +[438] 'Bastarderzeugung,' s. 573. + +[439] Ibid., s. 527. + +[440] 'Transactions Phil. Soc.,' 1799, p. 202. For Kölreuter, _see_ 'Mém. +de l'Acad. de St. Pétersbourg,' tom. iii., 1809 (published 1811), p. 197. +In reading C. K. Sprengel's remarkable work, 'Das entdeckte Geheimniss,' +&c., 1793, it is curious to observe how often this wonderfully acute +observer failed to understand the full meaning of the structure of the +flowers which he has so well described, from not always having before his +mind the key to the problem, namely, the good derived from the crossing of +distinct individual plants. + +[441] This abstract was published in the fourth edition (1866) of my +'Origin of Species;' but as this edition will be in the hands of but few +persons, and as my original observations on this point have not as yet been +published in detail, I have ventured here to reprint the abstract. + +[442] The term _unconscious selection_ has been objected to as a +contradiction: but _see_ some excellent observations on this head by Prof. +Huxley ('Nat. Hist. Review,' Oct. 1864, p. 578), who remarks that when the +wind heaps up sand-dunes it sifts and _unconsciously selects_ from the +gravel on the beach grains of sand of equal size. + +[443] Sheep, 1838, p. 60. + +[444] Mr. J. Wright on Shorthorn Cattle, in 'Journal of Royal Agricult. +Soc.,' vol. vii. pp. 208, 209. + +[445] H. D. Richardson on Pigs, 1817, p. 44. + +[446] 'Journal of R. Agricult. Soc.,' vol. i. p. 24. + +[447] Sheep, pp. 520, 319. + +[448] Loudon's 'Mag. of Nat. Hist.,' vol. viii., 1835, p. 618. + +[449] 'A Treatise on the Art of Breeding the Almond Tumbler,' 1851, p. 9. + +[450] 'Recreations in Agriculture,' vol. ii. p. 409. + +[451] Youatt on Cattle, pp. 191, 227. + +[452] Ferguson, 'Prize Poultry,' 1854, p. 208. + +[453] Wilson, in 'Transact. Highland Agricult. Soc.,' quoted in 'Gard. +Chronicle,' 1844, p. 29. + +[454] Simmonds, quoted in 'Gard. Chronicle,' 1855, p. 637. And for the +second quotation, _see_ Youatt on Sheep, p. 171. + +[455] Robinet, 'Vers à Soie,' 1848, p. 271. + +[456] Quatrefages, 'Les Maladies du Ver à Soie,' 1859, p. 101. + +[457] M. Simon, in 'Bull. de la Soc. d'Acclimat.,' tom. ix., 1862, p. 221. + +[458] 'The Poultry Chronicle,' vol. i., 1854, p. 607. + +[459] J. M. Eaton, 'A Treatise on Fancy Pigeons,' 1852, p. xiv., and 'A +Treatise on the Almond Tumbler,' 1851, p. 11. + +[460] 'Journal Royal Agricultural Soc.,' vol. vi. p. 22. + +[461] 'Poultry Chronicle,' vol. ii., 1855, p. 596. + +[462] Isid. Geoffroy St. Hilaire, 'Hist. Nat. Gén.,' tom. iii. p. 254. + +[463] 'Gardener's Chronicle,' 1850, p. 198. + +[464] 'Transact. Hort. Soc.,' vol. vi. p. 152. + +[465] 'Journal of Horticulture,' 1862, p. 369. + +[466] 'Transact. Hort. Soc.,' vol. iv. p. 381. + +[467] 'Transact. Hort. Soc.,' vol. iv. p. 285. + +[468] Rev. W. Bromehead, in 'Gard. Chronicle,' 1857, p. 550. + +[469] 'Gard. Chronicle,' 1862, p. 721. + +[470] Dr. Anderson, in 'The Bee,' vol. vi. p. 96; Mr. Barnes, in 'Gard. +Chronicle,' 1844, p. 476. + +[471] Godron, 'De l'Espèce,' 1859, tom. ii. p. 69; 'Gard. Chronicle,' 1854, +p. 258. + +[472] On Sheep, p. 18. + +[473] Volz, 'Beiträge zur Kulturgeschichte,' 1852, s. 47. + +[474] Mitford's 'History of Greece,' vol. i. p. 73. + +[475] Dr. Dally, translated in 'Anthropological Review,' May 1864, p. 101. + +[476] Volz, 'Beiträge,' &c., 1852, s. 80. + +[477] 'History of the World,' ch. 45. + +[478] 'Gardener's Chronicle,' 1848, p. 323. + +[479] Reynier, 'De l'Economie des Celtes,' 1818, pp. 487, 503. + +[480] Le Couteur on Wheat, p. 15. + +[481] Michel, 'Des Haras,' 1861, p. 84. + +[482] Sir W. Wilde, an 'Essay on Unmanufactured Animal Remains,' &c., 1860, +p. 11. + +[483] Col. Hamilton Smith, 'Nat. Library,' vol. xii., Horses, pp. 135, 140. + +[484] Michel, 'Des Haras,' p. 90. + +[485] Mr. Baker, 'History of the Horse,' Veterinary, vol. xiii. p. 423. + +[486] M. l'Abbé Carlier, in 'Journal de Physique,' vol. xxiv., 1784, p. +181: this memoir contains much information on the ancient selection of +sheep; and is my authority for rams not being killed young in England. + +[487] 'Gardener's Chronicle,' 1843, p. 389. + +[488] Communications to Board of Agriculture, quoted in Dr. Darwin's +'Phytologia,' 1800, p. 451. + +[489] 'Mémoire sur les Chinois,' 1786, tom. xi. p. 55; tom. v. p. 507. + +[490] 'Recherches sur l'Agriculture des Chinois,' par L. +D'Hervey-Saint-Denys, 1850, p. 229. With respect to Khang-hi, _see_ Huc's +'Chinese Empire,' p. 311. + +[491] Anderson, in 'Linn. Transact.,' vol. xii. p. 253. + +[492] 'Mém. de l'Acad.' (divers savans), tom. vi., 1835, p. 333. + +[493] 'Des Quadrupèdes du Paraguay,' 1801, tom. ii. p. 333, 371. + +[494] 'The Great Sahara,' by the Rev. H. B. Tristram, 1860, p. 238. + +[495] Pallas, 'Act. Acad. St. Petersburg,' 1777, p. 249; Moorcroft and +Trebeck, 'Travels in the Himalayan Provinces,' 1841. + +[496] Quoted from Raffles, in the 'Indian Field,' 1859, p. 196; for Varro, +_see_ Pallas, _ut supra_. + +[497] Erman's 'Travels in Siberia,' Eng. translat., vol. i. p. 453. + +[498] _See_ also 'Journal of R. Geograph. Soc.,' vol. xiii. part i. p. 65. + +[499] Livingstone's 'First Travels,' pp. 191, 439, 565; _see_ also +'Expedition to the Zambesi,' 1865, p. 465, for an analogous case respecting +a good breed of goats. + +[500] Andersson's 'Travels in South Africa,' pp. 232, 318, 319. + +[501] Dr. Vavasseur, in 'Bull. de la Soc. d'Acclimat.,' tom. viii., 1861, +p. 136. + +[502] 'The Natural History of Dee Side,' 1855, p. 476. + +[503] 'Bull. de la Soc. d'Acclimat.,' tom. vii., 1860, p. 457. + +[504] 'Cattle,' p. 48. + +[505] Livingstone's Travels, p. 576; Andersson, 'Lake Ngami,' 1856, p. 222. +With respect to the sale in Kaffraria, _see_ 'Quarterly Review,' 1860, p. +139. + +[506] 'Mémoire sur les Chinois' (by the Jesuits), 1786, tom. xi. p. 57. + +[507] F. Michel, 'Des Haras,' pp. 47, 50. + +[508] Col. Hamilton Smith, Dogs, in 'Nat. Lib.,' vol. x. p. 103. + +[509] Azara, 'Quadrupèdes du Paraguay,' tom. ii. p. 324. + +[510] Sidney's edit. of Youatt, 1860, pp. 24, 25. + +[511] 'Rural Economy of Yorkshire,' vol. ii. p. 182. + +[512] Moll et Gayot, 'Du Boeuf,' 1860, p. 547. + +[513] 'The India Sporting Review,' vol. ii. p. 181; 'The Stud Farm,' by +Cecil, p. 58. + +[514] 'The Horse,' p. 22. + +[515] 'History of England,' vol. i. p. 316. + +[516] 'Uber Beständigkeit der Arten.' + +[517] Youatt on Sheep, p. 315. + +[518] 'Ueber Shorthorn Rindvieh,' 1857, s. 51. + +[519] Low, 'Domesticated Animals,' 1845, p. 363. + +[520] 'Quarterly Review,' 1849, p. 392. + +[521] H. von Nathusius, 'Vorstudien ... Schweineschædel,' 1864, s. 140. + +[522] _See_ also Dr. Christ, in 'Rütimeyer's Pfahlbauten,' 1861, s. 226. + +[523] The passage is given 'Bull. Soc. d'Acclimat.,' 1858, p. 11. + +[524] 'Journal of Horticulture,' 1862, p. 394. + +[525] 'Gardener's Chronicle,' 1857, p. 85. + +[526] _See_ Mr. Wildman's address to the Floricult. Soc., in 'Gardener's +Chronicle,' 1843, p. 86. + +[527] 'Journal of Horticulture,' Oct. 24th, 1865, p. 239. + +[528] Prescott's 'Hist. of Mexico,' vol. ii. p. 61. + +[529] Sageret, 'Pomologie Physiologique,' 1830, p. 47; Gallesio, 'Teoria +della Riproduzione,' 1816, p. 88; Godron, 'De l'Espèce,' 1859, tom. ii. pp. +63, 67, 70. In my tenth and eleventh chapters I have given details on the +potato; and I can confirm similar remarks with respect to the onion. I have +also shown how far Naudin concurs in regard to the varieties of the melon. + +[530] Godron, 'De l'Espèce,' tom. ii. p. 27. + +[531] 'The Anthropological Treatises of Blumenbach,' 1865, p. 292. + +[532] Mr. J. J. Murphy in his opening address to the Belfast Nat. Hist. +Soc., as given in the Belfast Northern Whig, Nov. 19, 1866. Mr. Murphy here +follows the line of argument against my views previously and more +cautiously given by the Rev. C. Pritchard, Pres. Royal Astronomical Soc., +in his sermon (Appendix, p. 33) preached before the British Association at +Nottingham, 1866. + +[533] On the Vision of Fishes and Amphibia, translated in 'Annals and Mag. +of Nat. Hist.,' vol. xviii., 1866, p. 469. + +[534] Fourth edition, 1866, p. 215. + +[535] Quoted by Youatt on Sheep, p. 325. _See_ also Youatt on Cattle, pp. +62, 69. + +[536] MM. Lherbette and De Quatrefages, in 'Bull. Soc. Acclimat.,' tom. +viii., 1861, p. 311. + +[537] 'The Poultry Book,' 1866, p. 123. + +[538] Youatt on Sheep, p. 312. + +[539] 'Treatise on the Almond Tumbler,' 1851, p. 33. + +[540] Dr. Heusinger, 'Wochenschrift für die Heilkunde,' Berlin, 1846, s. +279. + +[541] Youatt on the Dog, p. 232. + +[542] 'The Fruit-trees of America,' 1845, p. 270: for peaches, p. 466. + +[543] 'Proc. Royal Soc. of Arts and Sciences of Mauritius,' 1852, p. cxxxv. + +[544] 'Gardener's Chronicle,' 1856, p. 379. + +[545] Quatrefages, 'Maladies Actuelles du Ver à Soie,' 1859, pp. 12, 214. + +[546] 'Gardener's Chronicle,' 1851, p. 595. + +[547] 'Journal of Horticulture,' 1862, p. 476. + +[548] 'Gardener's Chronicle,' 1852, pp. 435, 691. + +[549] Bechstein, 'Naturgesch. Deutschlands,' 1801, B. i. s. 310. + +[550] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 224. + +[551] G. Lewis's 'Journal of Residence in West Indies,' 'Home and Col. +Library,' p. 100. + +[552] Sidney's edit. of Youatt on the Pig, p.24. + +[553] 'Journal of Horticulture,' 1862, pp. 476, 498; 1865, p. 460. With +respect to the heartsease, 'Gardener's Chronicle,' 1863, p. 628. + +[554] 'Des Jacinthes, de leur Culture,' 1768, p. 53: on wheat, 'Gardener's +Chronicle,' 1846, p. 653. + +[555] W. B. Tegetmeier, 'The Field,' Feb. 25, 1865. With respect to black +fowls, _see_ a quotation in Thompson's 'Nat. Hist. of Ireland,' 1849, vol. +i. p. 22. + +[556] 'Bull. de la Soc. d'Acclimat.,' tom. vii. 1860, p. 359. + +[557] 'Transact. Hort. Soc.,' vol. i. 2nd series, 1835, p. 275. For +raspberries, _see_ 'Gard. Chronicle,' 1855, p. 154, and 1863, p. 245. + +[558] 'Gardener's Chronicle,' 1843, p. 806. + +[559] Ibid., 1850, p. 732. + +[560] Ibid., 1860, p. 956. + +[561] J. De Jonghe, in 'Gard. Chronicle,' 1860, p. 120. + +[562] Downing, 'Fruit-trees of North America,' pp. 266, 501: in regard to +the cherry, p. 198. + +[563] 'Gardener's Chronicle,' 1849, p. 755. + +[564] 'Journal of Horticulture,' Sept. 26th, 1865, p. 254; _see_ other +references given in chap. x. + +[565] Mr. Selby, in 'Mag. of Zoology and Botany,' Edinburgh, vol. ii., +1838, p. 393. + +[566] The Reine Claude de Bavay, 'Journal of Horticulture,' Dec. 27, 1864, +p. 511. + +[567] Mr. Pusey, in 'Journal of R. Agricult. Soc., vol. vi. p. 179. For +Swedish turnips, _see_ 'Gard. Chron.,' 1847, p. 91. + +[568] Godron, 'De l'Espèce,' tom. ii. p. 98. + +[569] 'Gardener's Chron.,' 1866, p. 732. + +[570] 'Gardener's Chronicle,' 1862, pp. 820, 821. + +[571] 'On the Varieties of Wheat,' p. 59. + +[572] Mr. Hewitt and others, in 'Journal of Hort.,' 1862, p. 773. + +[573] 'Encyclop. of Rural Sports,' p. 405. + +[574] Col. Le Couteur, 'Journal Roy. Agricult. Soc.,' vol. iv. p. 43. + +[575] 'Gardener's Chronicle,' 1845, p. 273. + +[576] 'Journal of Horticulture,' 1862, p. 157. + +[577] 'Cottage Gardener,' 1860, p. 368. + +[578] 'A Review of Reports,' 1808, p. 406. + +[579] 'Gardener's Chronicle,' 1853, p. 45. + +[580] Isidore Geoffroy St. Hilaire, 'Hist. Nat. Gén.,' tom. iii. p. 49. On +the Cochineal Insect, p. 46. + +[581] Capt. Marryat, quoted by Blyth in 'Journ. Asiatic Soc. of Bengal,' +vol. xxviii. p. 229. + +[582] Mr. Oxley, 'Journal of the Indian Archipelago,' vol. ii., 1848, p. +645. + +[583] Mr. Abbey, in 'Journal of Horticulture,' Dec. 1, 1863, p. 430. + +[584] 'On Naval Timber,' 1831, p. 107. + +[585] Mr. Baily, in 'The Poultry Chronicle,' vol. ii., 1854, p. 150. Also +vol. i. p. 342; vol. iii. p. 245. + +[586] 'Cottage Gardener,' 1855, December, p. 171; 1856, January, pp. 248, +323. + +[587] 'Ueber Shorthorn Rindvieh,' 1857, s. 51. + +[588] 'The Veterinary,' vol. xiii. p. 720. For the Glamorganshire cattle, +_see_ Youatt on Cattle, p. 51. + +[589] J. M. Eaton, 'A Treatise on Fancy Pigeons,' p. 82; Ferguson, on 'Rare +and Prize Poultry,' p. 162; Mr. Brent, in 'Cottage Gardener,' Oct. 1860. p. +13. + +[590] 'Die Racen des Schweines,' 1860, s. 48. + +[591] _See_ some good remarks on this head by M. de Quatrefages, 'Unité de +l'Espèce Humaine,' 1861, p. 119. + +[592] Verlot, 'Des Variétés,' 1865, p. 94. + +[593] Mr. Patrick Sheriff, in 'Gard. Chronicle,' 1858, p. 771. + +[594] 'Pomologie Physiolog.,' 1830, p. 106. + +[595] Youatt on Sheep, p. 521. + +[596] 'A Treatise on the Almond Tumbler,' p. i. + +[597] M. J. de Jonghe, in 'Gard. Chron.,' 1858, p. 173. + +[598] Max. Müller, 'Science of Language,' 1861, p. 223. + +[599] Youatt on Cattle, pp. 116, 128. + +[600] 'Domesticated Animals,' p. 188. + +[601] Volz, 'Beiträge zur Kulturgeschichte,' 1852, s. 99 _et passim_. + +[602] Blaine, 'Encyclop. of Rural Sports,' p. 213. + +[603] 'Des Jacinthes,' &c., Amsterdam, 1768, p. 43; Verlot, 'Des Variétés,' +&c., p. 86. On the reindeer, _see_ Linnæus, 'Tour in Lapland,' translated +by Sir J. E. Smith, vol. i. p. 314. The statement in regard to German +shepherds is given on the authority of Dr. Weinland. + +[604] Müller's 'Physiology,' Eng. translation, vol. ii. p. 1662. With +respect to the similarity of twins in constitution, Dr. William Ogle has +given me the following extract from Professor Trousseau's Lectures +('Clinique Médicale,' tom. i. p. 523), in which a curious case is +recorded:--"J'ai donné mes soins à deux frères jumeaux, tous deux si +extraordinairement ressemblants qu'il m'était impossible de les +reconnaître, à moins de les voir l'un à côté de l'autre. Cette ressemblance +physique s'étendait plus loin: ils avaient, permettez-moi l'expression, une +similitude pathologique plus remarquable encore. Ainsi l'un d'eux que je +voyais aux néothermes à Paris malade d'une ophthalmie rhumatismale me +disait, 'En ce moment mon frère doit avoir une ophthalmie comme la mienne;' +et comme je m'étais récrié, il me montrait quelques jours après une lettre +qu'il venait de recevoir de ce frère alors à Vienne, et qui lui écrivait en +effet--'J'ai mon ophthalmie, tu dois avoir la tienne.' Quelque singulier +que ceci puisse paraître, le fait non est pas moins exact: on ne me l'a pas +raconté, je l'ai vu, et j'en ai vu d'autres analogues dans ma pratique. Ces +deux jumeaux étaient aussi tous deux asthmatiques, et asthmatiques à un +effroyable degré. Originaires de Marseille, ils n'ont jamais pu demeurer +dans cette ville, où leurs intérêts les appelaient souvent, sans être pris +de leurs accès; jamais ils n'en éprouvaient à Paris. Bien mieux, il leur +suffisait de gagner Toulon pour être guéris de leurs attaques de +Marseilles. Voyageant sans cesse et dans tous pays pour leurs affaires, ils +avaient remarqué que certaines localités leur étaient funestes, que dans +d'autres ils étaient exempts de tout phénomène d'oppression." + +[605] Isid. Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. iii. p. 352; +Moquin Tandon, 'Tératologie Végétale,' 1841, p. 115. + +[606] Metzger, 'Die Getreidearten,' 1841, s. 39. + +[607] On the date-palm, _see_ Vogel, 'Annals and Mag. of Nat. Hist.,' 1854, +p. 460. On Indian varieties, Dr. F. Hamilton, 'Transact. Linn. Soc.,' vol. +xiv. p. 296. On the varieties cultivated in Tahiti, _see_ Dr. Bennett, in +Loudon's 'Mag. of N. Hist.,' vol. v., 1832, p. 484. Also Ellis, 'Polynesian +Researches,' vol. i. pp. 375, 370. On twenty varieties of the Pandanus and +other trees in the Marianne Island, _see_ 'Hooker's Miscellany,' vol. i. p. +308. On the bamboo in China, _see_ Huc's 'Chinese Empire,' vol. ii. p. 307. + +[608] 'Treatise on the Culture of the Apple,' &c., p. 3. + +[609] Gallesio, 'Teoria della Riproduzione Veg.,' p. 125. + +[610] _See_ Dr. Hooker's Memoir on Arctic Plants in 'Linn. Transact.,' vol. +xxiii, part ii. Mr. Woodward, and a higher authority cannot be quoted, +speaks of the Arctic mollusca (in his 'Rudimentary Treatise,' 1856, p. 355) +as remarkably subject to variation. + +[611] Bechstein, in his 'Naturgeschichte der Stubenvögel,' 1840, s. 238, +has some good remarks on this subject. He states that his canary-birds +varied in colour, though kept on uniform food. + +[612] 'The Plant,' by Schleiden, translated by Henfrey, 1848, p. 169. _See_ +also Alex. Braun, in 'Bot. Memoirs,' Ray. Soc., 1853, p. 313. + +[613] Messrs. Hardy and Son, of Maldon, in 'Gard. Chronicle,' 1856, p. 458. + +[614] 'Quadrupèdes du Paraguay,' 1801, tom. ii. p. 319. + +[615] McClelland on Indian Cyprinidæ, 'Asiatic Researches,' vol. xix. part +ii., 1839, pp. 266, 268, 313. + +[616] Quoted by Sageret, 'Pom. Phys.,' 1830, p. 43. + +[617] 'The Fruits of America,' 1845, p. 5. + +[618] M. Cardan, in 'Comptes Rendus,' Dec. 1848, quoted in 'Gard. +Chronicle,' 1849, p. 101. + +[619] M. Alexis Jordan mentions four excellent pears found in woods in +France, and alludes to others ('Mém. Acad. de Lyon,' tom. ii. 1852, p. +159). Poiteau's remark is quoted in 'Gardener's Mag.,' vol. iv., 1828, p. +385. _See_ 'Gard. Chronicle,' 1862, p. 335, for another case of a new +variety of the pear found in a hedge in France. Also for another case, +_see_ Loudon's 'Encyclop. of Gardening,' p. 901. Mr. Rivers has given me +similar information. + +[620] Duval, 'Hist. du Poirier,' 1849, p. 2. + +[621] I infer that this is the fact from Van Mons' statement ('Arbres +Fruitiers,' 1835, tom. i. p. 446) that he finds in the woods seedlings +resembling all the chief cultivated races of both the pear and apple. Van +Mons, however, looked at these wild varieties as aboriginal species. + +[622] Downing, 'Fruit-trees of North America,' p. 422; Foley, in 'Transact. +Hort. Soc.,' vol. vi. p. 412. + +[623] 'Gard. Chronicle,' 1847, p. 244. + +[624] 'Gardener's Chronicle,' 1841, p. 383; 1850, p. 700; 1854, p. 650. + +[625] 'Die Getreidearten,' 1843, s. 66, 116, 117. + +[626] Sabine, in 'Hort. Transact.,' vol. iii. p. 225; Bronn, 'Geschichte +der Natur,' b. ii. s. 119. + +[627] 'Journal of Horticulture,' 1861, p. 112; on Zinnia, 'Gardener's +Chronicle,' 1860, p. 852. + +[628] 'The Chrysanthemum, its History, &c.,' 1865, p. 3. + +[629] 'Gardener's Chron.,' 1855, p. 54; 'Journal of Horticulture,' May 9, +1865, p. 363. + +[630] Quoted by Verlot, 'Des Variétés,' &c., 1865, p. 28. + +[631] 'Examination of the Characteristics of Genera and Species:' +Charleston, 1855, p. 14. + +[632] Mr Hewitt, 'Journal of Hort.,' 1863, p. 39. + +[633] Devay, 'Mariages Consanguins,' pp. 97, 125. In conversation I have +found two or three naturalists of the same opinion. + +[634] Müller has conclusively argued against this belief, 'Elements of +Phys.,' Eng. translat., vol. ii., 1842, p. 1405. + +[635] 'Act. Acad. St. Petersburg,' 1780, part ii. p. 84, &c. + +[636] 'Bastarderzeugung,' s. 249, 255, 295. + +[637] 'Nova Acta, St. Petersburg,' 1794, p. 378; 1795, pp. 307, 313, 316; +1787, p. 407. + +[638] 'De la Fécondation,' 1862, p. 311. + +[639] 'Amaryllidaceæ,' 1837, p. 362. + +[640] Abstracted in 'Gard. Chronicle,' 1860, p. 1081. + +[641] This was the opinion of the elder De Candolle, as quoted in 'Dic. +Class. d'Hist. Nat.,' tom. viii. p. 405. Puvis, in his work, 'De la +Dégénération,' 1837, p. 37, has discussed this same point. + +[642] 'Comptes Rendus,' Novembre 21, 1864, p. 838. + +[643] 'Nova Acta, St. Petersburg,' 1794, p. 391. + +[644] 'Bastarderzeugung,' s. 507, 516, 572. + +[645] 'Die Bastardbefruchtung,' &c., 1865, s. 24. + +[646] 'Bastarderzeugung,' s. 452, 507. + +[647] 'Die Bastardbefruchtung,' s. 56. + +[648] 'Bastarderzeugung,' s. 423. + +[649] 'Dritte Fortsetzung,' &c., 1766, s. 85. + +[650] 'Die Bastardbefruchtung,' &c., 1865, s. 92; _see_ also the Rev. M. J. +Berkeley on the same subject, in 'Journal of Royal Hort. Soc.,' 1866, p. +80. + +[651] Dr. P. Lucas has given a history of opinion on this subject: 'Héréd. +Nat.,' 1847, tom. i. p. 175. + +[652] 'Hist. des Anomalies,' tom. iii. p. 499. + +[653] Idem., tom. iii. pp. 392, 502. + +[654] _See_ his interesting work, 'Métamorphoses de l'Homme,' &c., 1862, p. +129. + +[655] 'Dritte Fortsetzung,' &c., s. 123; 'Bastarderzeugung,' s. 249. + +[656] 'Gardener's Chronicle,' 1853, p. 183. + +[657] Mr. Wildman, 'Floricultural Soc.,' Feb. 7, 1843, reported in 'Gard. +Chron.,' 1843, p. 86. + +[658] Mr. Robson, in 'Journal of Horticulture,' Feb. 13th, 1866, p. 122. + +[659] 'Journal of Horticulture,' 1861, p. 24. + +[660] Ibid., 1862, p. 83. + +[661] 'Gard. Chron.,' 1845, p. 660. + +[662] Ibid., 1863, p. 628. + +[663] 'Journal of Hort.,' 1861, pp. 64, 309. + +[664] 'Des Variétés,' &c., p. 76. + +[665] Engel, 'Sur les Prop. Médicales des Plantes,' 1860, pp. 10, 25. On +changes in the odours of plants, _see_ Dalibert's Experiments, quoted by +Beckman, 'Inventions,' vol. ii. p. 344; and Nees, in Ferussac, 'Bull. des +Sc. Nat.,' 1824, tom. i. p. 60. With respect to the rhubarb, &c., _see_ +also 'Gardener's Chronicle,' 1849, p. 355; 1862, p. 1123. + +[666] Hooker, 'Flora Indica,' p. 32. + +[667] Naudin, 'Annales des Sc. Nat.,' 4th series, Bot., tom. xi., 1859, p. +81. 'Gardener's Chronicle,' 1859, p. 464. + +[668] Moorcroft's 'Travels,' &c., vol. ii. p. 143. + +[669] 'Gardener's Chronicle,' 1861, p. 1113. + +[670] Royle, 'Productive Resources of India,' p. 59. + +[671] 'Personal Narrative,' Eng. translat., vol. v. p. 101. This statement +has been confirmed by Karsten ('Beitrag zur Kenntniss der Rhynchoprion:' +Moscow, 1864. s. 39), and by others. + +[672] 'Organic Chemistry,' Eng. translat., 1st edit., p. 369. + +[673] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 155. + +[674] Darwin, 'Journal of Researches,' 1845, p. 434. + +[675] These statements on disease are taken from Dr. Boudin's 'Géographie +et de Statistique Médicales,' 1857, tom. i. p. xliv. and lii.; tom. ii. p. +315. + +[676] E. Desor, quoted in the 'Anthrop. Rev.,' 1863, p. 180. For much +confirmatory evidence, _see_ Quatrefages, 'Unité de l'Espèce Humaine,' +1861, p. 131. + +[677] 'Ceylon,' by Sir J. E. Tennent, vol. i., 1859, p. 89. + +[678] Godron, 'De l'Espèce,' tom. ii. p. 52. + +[679] 'Journal of Horticultural Soc.,' vol. vii., 1852, p. 117. + +[680] 'Journal of Hort. Soc.,' vol. i. p. 160. + +[681] _See_ Lecoq on the Villosity of Plants, 'Geograph. Bot.,' tom. iii. +pp. 287, 291; Gärtner, 'Bastarderz.,' s. 261; Mr. Musters, on the Opuntia, +in 'Gard. Chronicle,' 1846, p. 444. + +[682] 'Pom. Phys.,' p. 136. + +[683] 'Ampelographie,' 1849, p. 19. + +[684] Gärtner, 'Bastarderz.,' s. 606, has collected nearly all recorded +facts. Andrew Knight (in 'Transact. Hort. Soc.,' vol. ii. p. 160) goes so +far as to maintain that few varieties are absolutely permanent in character +when propagated by buds or grafts. + +[685] Mr. Blyth, in 'Annals and Mag. of Nat. Hist.,' vol. xx., 1847, p. +391. + +[686] 'Natural History Review,' 1862, p. 113. + +[687] 'Journal of Roy. Geographical Soc.,' vol. ix., 1839, p. 275. + +[688] 'Travels in Bokhara,' vol. iii. p. 151. + +[689] _See_ also, on the influence of marshy pastures on the wool, Godron, +'L'Espèce,' tom. ii. p. 22. + +[690] Isidore Geoffroy St. Hilaire, 'Hist. Nat. Gén.,' tom. iii. p. 438. + +[691] Azara has made some good remarks on this subject, 'Quadrupèdes du +Paraguay,' tom. ii. p. 337. _See_ an account of a family of naked mice +produced in England, 'Proc. Zoolog. Soc.,' 1856, p. 38. + +[692] 'Die Fauna der Pfahlbauten,' 1861, s. 15. + +[693] 'Schweinschædel,' 1864, s. 99. + +[694] 'Travels in Siberia,' Eng. translat., vol. i. p. 228. + +[695] A. R. Wallace, 'Travels on the Amazon and Rio Negro,' p. 294. + +[696] 'Naturgeschichte der Stubenvögel,' 1840, s. 262, 308. + +[697] 'Hist. Nat. Gén.,' tom. iii. p. 402. + +[698] 'Bull. de la Soc. Imp. d'Acclimat.,' tom. viii. p. 351. + +[699] _See_ an account of Mr. Gregson's experiments on the _Abraxus +grossulariata_, 'Proc. Entomolog. Soc.,' Jan. 6th, 1862: these experiments +have been confirmed by Mr. Greening, in 'Proc. of the Northern Entomolog. +Soc.,' July 28th, 1862. For the effects of food on caterpillars, see a +curious account by M. Michely, in 'Bull. de la Soc. Imp. d'Acclimat.,' tom. +viii. p. 563. For analogous facts from Dahlbom on Hymenoptera, _see_ +Westwood's 'Modern Class. of Insects,' vol. ii. p. 98. _See_ also Dr. L. +Möller, 'Die Abhängigkeit der Insecten,' 1867, s. 70. + +[700] 'The Principles of Biology,' vol. ii. 1866. The present chapters were +written before I had read Mr. Herbert Spencer's work, so that I have not +been able to make so much use of it as I should otherwise probably have +done. + +[701] 'Proc. Acad. Nat. Soc. of Philadelphia,' Jan. 28th, 1862. + +[702] _See_ Mr. B. D. Walsh's excellent papers in 'Proc. Entomolog. Soc. +Philadelphia,' Dec. 1866, p. 284. With respect to the willow, _see_ idem, +1864, p. 546. + +[703] _See_ his admirable Histoire des Galles, in 'Annal. des Sc. Nat. +Bot.,' 3rd series, tom. xix., 1853, p. 273. + +[704] Kirby and Spence's 'Entomology,' 1818, vol. i. p. 450; +Lucaze-Duthiers, idem, p. 284. + +[705] 'Proc. Entomolog. Soc. Philadelphia,' 1864, p. 558. + +[706] Mr. B. D. Walsh, idem, p. 633; and Dec. 1866, p. 275. + +[707] Mr. B. D. Walsh, idem, 1864, p. 545, 411, 495; and Dec. 1866, p. 278. +_See_ also Lucaze-Duthiers. + +[708] Lucaze-Duthiers, idem, pp. 325, 328. + +[709] 'Linnæa,' vol. xvii., 1843; quoted by Dr. M. T. Masters, Royal +Institution, March 16th, 1860. + +[710] Hewett C. Watson, 'Cybele Britannica,' vol. i., 1847, p. 11. + +[711] 'Gardener's Chronicle,' 1857, p. 629. + +[712] 'Mémoire sur la Production Artificielle des Monstrosités,' 1862, pp. +8-12; 'Recherches sur les Conditions, &c., chez les Monstres,' 1863, p. 6. +An abstract is given of Geoffroy's Experiments by his son, in his 'Vie, +Travaux, &c.,' 1847, p. 290. + +[713] Paget, 'Lectures on Surgical Pathology,' 1853, vol. i. p. 483. + +[714] 'Researches upon the Venom of the Rattle-snake,' Jan. 1861, by Dr. +Mitchell, p. 67. + +[715] Mr. Sedgwick, in 'British and Foreign Medico-Chirurg. Review,' July +1863, p. 175. + +[716] 'An Essay on Generation,' Eng. translat., p. 18; Paget, 'Lectures on +Surgical Pathology,' 1853, vol. i. p. 209. + +[717] 'An Essay on Animal Reproduction,' Eng. translat., 1769, p. 79. + +[718] Carpenter's 'Principles of Comp. Physiology,' 1854, p. 479. + +[719] Charlesworth's 'Mag. of Nat. Hist.,' vol. i., 1837, p. 145. + +[720] Paget, 'Lectures on Surgical Pathology,' vol. i. p. 239. + +[721] Quoted by Carpenter, 'Comp. Phys.,' p. 479. + +[722] Paget, 'Lectures,' &c., p. 257. + +[723] These cases are given by Blumenbach in his 'Essay on Generation,' pp. +52, 54. + +[724] 'Cellular Pathology,' trans. by Dr. Chance, 1860, pp. 27, 441. + +[725] Paget, 'Lectures on Pathology,' vol. i., 1853, p. 357. + +[726] Paget, idem, p. 150. + +[727] 'The Principles of Biology,' vol. ii., 1866, chap. 3-5. + +[728] 'Lectures on Pathology,' 1853, vol. i. p. 71. + +[729] 'Comptes Rendus,' Sept. 26th, 1864, p. 539. + +[730] 'The Principles of Biology,' vol. ii. p. 243. + +[731] Idem, vol. ii. p. 269. + +[732] Idem, vol. ii. p. 273. + +[733] Paget, 'Lectures on Pathology,' vol. ii. p. 209. + +[734] Müller's 'Phys.,' Eng. translat., pp. 54, 791. Prof. Reed has given +('Physiological and Anat. Researches,' p. 10) a curious account of the +atrophy of the limbs of rabbits after the destruction of the nerve. + +[735] Quoted by Lecoq, in 'Geograph. Bot.,' tom. i., 1854, p. 182. + +[736] 'Das Abändern der Vögel,' 1833, s. 74. + +[737] Nathusius, 'Die Racen des Schweines,' 1860, s. 53, 57; 'Vorstudien +... Schweineschædel,' 1864, s. 103, 130, 133. + +[738] 'Journal of Agriculture of Highland Soc.,' July, 1860, p. 321. + +[739] 'Principles of Biology,' vol. ii. p. 263. + +[740] 'Natural History Review,' vol. iv., Oct. 1864, p. 617. + +[741] 'Lectures on Surgical Pathology,' 1853, vol. i. p. 27. + +[742] Andersson, 'Travels in South Africa,' p. 318. For analogous cases in +South America, _see_ Aug. St. Hilaire, 'Voyage dans le Province de Goyaz,' +tom. i. p. 71. + +[743] Brickell's 'Nat. Hist. of North Carolina,' 1739, p. 53. + +[744] Livingstone, quoted by Youatt on Sheep, p. 142. Hodgson, in 'Journal +of Asiatic Soc. of Bengal,' vol. xvi., 1847, p. 1006, &c. &c. + +[745] 'Naturalist Library,' Dogs, vol. ii. 1840, p. 104. + +[746] 'De l'Espèce,' tom. i., 1859, p. 367. + +[747] 'Ceylon,' by Sir J. E. Tennent, 1859, vol. ii. p. 531. + +[748] For the foregoing statements, _see_ Hunter's 'Essays and +Observations,' 1861, vol. ii. p. 329; Dr. Edmondston, as quoted in +Macgillivray's 'British Birds,' vol. v. p. 550; Menetries, as quoted in +Bronn's 'Geschichte der Natur,' B. ii. s. 110. + +[749] These statements on the intestines are taken from Isidore Geoffroy +St. Hilaire, 'Hist. Nat. Gén.,' tom. iii. pp. 427, 441. + +[750] Gilbert White, 'Nat. Hist. Selbourne,' 1825, vol. ii. p. 121. + +[751] Burdach, 'Traité de Phys.,' tom. ii. p. 267, as quoted by Dr. P. +Lucas, 'L'Héréd. Nat.,' tom. i. p. 388. + +[752] This and several other cases are given by Colin, 'Physiologie Comp. +des Animaux Dom.,' 1854, tom. i. p. 426. + +[753] M. Michely de Cayenne, in 'Bull. Soc. d'Acclimat.,' tom. viii., 1861, +p. 563. + +[754] Quatrefages, 'Unité de l'Espèce Humaine,' 1861, p. 79. + +[755] 'Flora,' 1835, B. ii. p. 504. + +[756] Alph. De Candolle, 'Géograph. Bot.,' tom. ii. p. 1078. + +[757] Royle, 'Illustrations of the Botany of the Himalaya,' p. 19. + +[758] 'Gardener's Chronicle,' 1850, pp. 204, 219. + +[759] Rev. R. Everest, 'Journal As. Soc. of Bengal,' vol. iii. p. 19. + +[760] Youatt on Sheep, 1838, p. 491. + +[761] Royle, 'Prod. Resources of India,' p. 153. + +[762] Tegetmeier, 'Poultry Book,' 1866, p. 102. + +[763] Dr. R. Paterson, in a paper communicated to Bot. Soc. of Canada, +quoted in the 'Reader,' 1863. Nov. 13th. + +[764] _See_ remarks by Editor in 'Gard. Chronicle,' 1848, p. 5. + +[765] 'Gard. Chronicle,' 1860, p. 938. Remarks by Editor and quotation from +Decaisne. + +[766] J. de Jonghe, of Brussels, in 'Gard. Chronicle,' 1857, p. 612. + +[767] Ch. Martius, 'Voyage Bot. Côtes Sept. de la Norvège,' p. 26. + +[768] 'Journal de l'Acad. Hort. de Gand,' quoted in 'Gard. Chron.,' 1859, +p. 7. + +[769] 'Gard. Chronicle,' 1851, p. 396. + +[770] Idem., 1862, p. 235. + +[771] On the authority of Labat, quoted in 'Gard. Chron.,' 1862, p. 235. + +[772] MM. Edwards and Colin, 'Annal. des Sc. Nat.,' 2nd series, Bot., tom. +v. p. 22. + +[773] 'Géograph. Bot.,' p. 337. + +[774] 'Swedish Acts,' Eng. translat., 1739-40, vol. i. Kalm, in his +'Travels,' vol. ii. p. 166, gives an analogous case with cotton-plants +raised in New Jersey from Carolina seed. + +[775] De Candolle, 'Géograph. Bot.,' p. 339. + +[776] 'Gard. Chronicle,' 1862, p. 235. + +[777] Gallesio, 'Teoria della Riproduzione Veg.,' 1816, p. 125; and 'Traité +du Citrus,' 1811, p. 359. + +[778] 'Essai sur l'Hist. des Orangers,' 1813, p. 20, &c. + +[779] Alph. De Candolle, 'Géograph. Bot.,' p. 882. + +[780] 'Ch. Darwin's Lehre von der Entstehung,' &c., 1862, s. 87. + +[781] Decaisne, quoted in 'Gard. Chronicle,' 1865, p. 271. + +[782] For the magnolia, _see_ Loudon's 'Gard. Mag.,' vol. xiii., 1837, p. +21. For camellias and roses, _see_ 'Gard. Chron.,' 1860, p. 384. For the +yew, 'Journal of Hort.,' March 3rd, 1863, p. 174. For sweet potatoes, _see_ +Col. von Siebold, in 'Gard. Chron.,' 1855, p. 822. + +[783] The Editor, 'Gard. Chron.,' 1861, p. 239. + +[784] Loudon's 'Gard. Mag.,' vol. xii., 1836, p. 378. + +[785] 'Gardeners Chron.,' 1865, p. 699. + +[786] 'Arboretum et Fruticetum,' vol. iii. p. 1376. + +[787] Mr. Robson, in 'Journal of Horticulture,' 1861, p. 23. + +[788] Dr. Bonavia, 'Report of the Agri.-Hort. Soc. of Oudh,' 1866. + +[789] 'Cottage Gardener,' 1860, April, 24th, p. 57. + +[790] 'Gardener's Chronicle,' 1841, p. 291. + +[791] Mr. Beaton, in 'Cottage Gardener,' March 20th, 1860, p. 377. Queen +Mab will also stand stove heat, _see_ 'Gard. Chronicle,' 1845, p. 226. + +[792] 'Gardener's Chronicle,' 1841, p. 439. + +[793] Quoted by Asa Gray, in 'Am. Journ. of Sci.,' 2nd series, Jan. 1865, +p. 106. + +[794] For China, _see_ 'Mémoire sur les Chinois,' tom, xi., 1786, p. 60. +Columella is quoted by Carlier, in 'Journal de Physique,' tom. xxiv. 1784. + +[795] Messrs. Hardy and Son, in 'Gard. Chronicle,' 1856, p. 589. + +[796] Isid. Geoffroy St. Hilaire, 'Hist. Nat. des Anomalies,' 1836, tom. +ii. pp. 210, 223, 224, 395; 'Philosoph. Transact.,' 1775, p. 313. + +[797] Pallas, quoted by Youatt on Sheep, p. 25. + +[798] Youatt on Cattle, 1834, p. 174. + +[799] 'Encyclop. Méthod.,' 1820, p. 483: _see_ p. 500, on the Indian zebu +casting its horns. Similar cases in European cattle were given in the third +chapter. + +[800] Pallas, 'Travels,' Eng. translat., vol. i. p. 243. + +[801] Mr. Beaton, in 'Journal of Horticulture,' May 21, 1861, p. 133. + +[802] Lecoq, 'De la Fécondation,' 1862, p. 233. + +[803] 'Annales du Muséum,' tom. vi. p. 319. + +[804] 'Hist. des Anomalies,' tom. iii. p. 392. Prof. Huxley applies the +same principle in accounting for the remarkable, though normal, differences +in the arrangement of the nervous system in the Mollusca, in his great +paper on the Morphology of the Cephalous Mollusca, in 'Phil. Transact.,' +1853, p. 56. + +[805] 'Eléments de Tératologie Veg.,' 1841, p. 113. + +[806] Prof. J. B. Simonds, on the Age of the Ox, Sheep, &c., quoted in +'Gard. Chronicle,' 1854, p. 588. + +[807] 'Hist. des Anomalies,' tom. i. p. 674. + +[808] Quoted by Isid. Geoffroy, idem, tom. i. p. 635. + +[809] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 250. + +[810] A. Walker on Intermarriage, 1838, p. 160. + +[811] 'The Farrier and Naturalist,' vol. i., 1828, p. 456. + +[812] Godron, 'Sur l'Espèce,' tom. ii. p. 217. + +[813] 'Quadrupèdes du Paraguay,' tom. ii. p. 333. + +[814] On Sheep, p. 142. + +[815] 'Ueber Racen, Kreuzungen, &c.,' 1825, s. 24. + +[816] Quoted from Conolly, in 'The Indian Field,' Feb. 1859, vol. ii. p. +266. + +[817] 'Domesticated Animals of the British Islands,' pp. 307, 368. + +[818] 'Proceedings Zoolog. Soc.,' 1833, p. 113. + +[819] Sedgwick, 'Brit. and Foreign Medico-Chirurg. Review,' April 1863, p. +453. + +[820] 'Gard. Chronicle,' 1849, p. 205. + +[821] 'Embassy to the Court of Ava,' vol. i. p. 320. + +[822] 'Narrative of a Mission to the Court of Ava in 1855,' p. 94. + +[823] Those statements are taken from Mr. Sedgwick, in the 'Medico-Chirurg. +Review,' July 1861, p. 198; April 1863, pp. 455 and 458. Liebreich is +quoted by Professor Devay, in his 'Mariages Consanguins,' 1862, p. 116. + +[824] Loudon's 'Mag. of Nat. Hist.,' vol. i., 1829, pp. 66, 178. _See_ also +Dr. P. Lucas, 'L'Héréd. Nat.,' tom. i. p. 428, on the inheritance of +deafness in cats. + +[825] 'Annales des Sc. Nat.' Zoolog., 3rd series, 1847, tom. viii. p. 239. + +[826] 'Gardener's Chron.,' 1864, p. 1202. + +[827] Verlot gives several other instances, 'Des Variétés,' 1865, p. 72. + +[828] 'Arbres Fruitiers,' 1836, tom. ii. pp. 204, 226. + +[829] 'Annales du Muséum,' tom. xx. p. 188. + +[830] 'Gardener's Chron.,' 1843, p. 877. + +[831] Ibid., 1845, p. 102. + +[832] 'Hist. des Anomalies,' tom. iii. p. 402. _See_ also M. Camille +Dareste, 'Recherches sur les Conditions,' &c., 1863, pp. 16, 48. + +[833] Rev. E. S. Dixon, 'Ornamental Poultry,' 1848, p. 111; Isidore +Geoffroy, 'Hist. Anomalies,' tom. i. p. 211. + +[834] 'On the Breeding of Domestic Animals,' 1829, p. 6. + +[835] Youatt on Cattle, 1834, p. 283. + +[836] Mr. Herbert Spencer ('Principles of Biology,' 1864, vol. i. pp. 452, +468) takes a different view; and in one place remarks: "We have seen reason +to think that, as fast as essential faculties multiply, and as fast as the +number of organs that co-operate in any given function increases, indirect +equilibration through natural selection becomes less and less capable of +producing specific adaptations; and remains fully capable only of +maintaining the general fitness of constitution to conditions." This view +that natural selection can do little in modifying the higher animals +surprises me, seeing that man's selection has undoubtedly effected much +with our domesticated quadrupeds and birds. + +[837] Dr. Prosper Lucas apparently disbelieves in any such connexion, +'L'Héréd. Nat.,' tom. ii. pp. 88-94. + +[838] 'British Medical Journal,' 1862, p. 433. + +[839] Boudin, 'Geograph. Médicale,' tom. i. p. 406. + +[840] This fact and the following cases, when not stated to the contrary, +are taken from a very curious paper by Prof. Heusinger, in 'Wochenschrift +für Heilkunde,' May 1846, s. 277. + +[841] Mr. Mogford, in the 'Veterinarian,' quoted in 'The Field,' Jan. 22, +1861, p. 545. + +[842] 'Edinburgh Veterinary Journal,' Oct. 1860, p. 347. + +[843] 'Hist. des Anomalies,' 1832, tom. i. pp. 22, 537-556; tom. iii. p. +462. + +[844] 'Comptes Rendus,' 1855, pp. 855, 1029. + +[845] Carpenter's 'Comp. Phys.,' 1854, p. 480; _see_ also Camille Dareste, +'Comptes Rendus,' March 20th, 1865, p. 562. + +[846] 'Elements of Physiology,' Eng. translat, vol. i., 1838, p. 412. With +respect to Vrolik, _see_ Todd's 'Cyclop. of Anat. and Phys.,' vol. iv., +1849-52, p. 973. + +[847] 'Tératologie Vég.,' 1841, livre iii. + +[848] 'Hist. des Anomalies,' tom. iii. pp. 4, 5, 6. + +[849] 'Tératologie Vég.,' p. 156. _See_ also my paper on climbing plants in +'Journal of Linn. Soc. Bot.,' vol. ix., 1865, p. 114. + +[850] 'Mémoires du Muséum,' &c., tom. viii. p. 178. + +[851] Loudon's 'Encyclop. of Gardening,' p. 829. + +[852] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 324. + +[853] 'Annales des Sc. Nat.,' 1st series, tom. xix. p. 327. + +[854] 'Comptes Rendus,' Dec. 1864, p. 1039. + +[855] Ueber Fötale Rachites, 'Würzburger Medicin. Zeitschrift,' 1860, B. i. +s. 265. + +[856] 'Tératologie Vég.,' p. 192. Dr. M. Masters informs me that he doubts +the truth of this conclusion; but the facts to be given seem to be +sufficient to establish it. + +[857] 'Journal of Horticulture,' July 2nd, 1861, p. 253. + +[858] It would be worth trial to fertilise with the same pollen the central +and lateral flowers of the pelargonium, and of some other highly cultivated +plants, protecting them of course from insects: then to sow the seed +separately, and observe whether the one or the other lot of seedlings +varied the most. + +[859] Quoted in 'Journal of Horticulture,' Feb. 24, 1863, p. 152. + +[860] 'Gardener's Chronicle,' 1866, p. 612. For the Phalænopsis, _see_ +idem, 1867, p. 211. + +[861] Mémoires ... des Végétaux,' 1837, tom. ii. p. 170. + +[862] 'Journal of Horticulture,' July 23, 1861, p. 311. + +[863] 'Nouvelles Archives du Muséum,' tom. i. p. 137. + +[864] Hugo von Mohl, 'The Vegetable Cell,' Eng. tr., 1852, p. 76. + +[865] The Rev. H. H. Dombrain, in 'Journal of Horticulture,' 1861, June +4th, p. 174; and June 25th, p. 234; 1862, April 29th, p. 83. + +[866] 'Transact. Linn. Soc.,' vol. xxiii., 1861, p. 360. + +[867] 'Die Getreidearten,' 1843, s. 208, 209. + +[868] 'Gardener's Chronicle,' 1850, p. 198. + +[869] Quoted in 'Gardener's Chron.,' 1866, p. 74. + +[870] 'Ueber den Begriff der Pflanzenart,' 1834, s. 14. + +[871] 'Domesticated Animals,' 1845, p. 351. + +[872] Bechstein, 'Naturgeschichte Deutschlands,' Band iv., 1795, s. 31. + +[873] 'Proc. Entomolog. Soc. of Philadelphia,' Oct. 1863, p. 213. + +[874] Quoted by Paget, 'Lectures on Pathology,' 1853, p. 159. + +[875] Dr. Lachmann, also, observes ('Annals and Mag. of Nat. History,' 2nd +series, vol. xix., 1857, p. 231) with respect to infusoria, that "fissation +and gemmation pass into each other almost imperceptibly." Again, Mr. W. C. +Minor ('Annals and Mag. of Nat. Hist.,' 3rd series, vol. xi. p. 328) shows +that with Annelids the distinction that has been made between fission and +budding is not a fundamental one. _See_ Bonnet, 'Oeuvres d'Hist. Nat.,' +tom. v., 1781, p. 339, for remarks on the budding-out of the amputated +limbs of Salamanders. _See_, also, Professor Clark's work 'Mind in Nature,' +New York, 1865, pp. 62, 94. + +[876] Paget, 'Lectures on Pathology,' 1853, p. 158. + +[877] Idem, pp. 152, 164. + +[878] On the Asexual Reproduction of Cecydomyide Larvæ, translated in +'Annals and Mag. of Nat. Hist.,' March 1866, pp. 167, 171. + +[879] _See_ some excellent remarks on this head by Quatrefages, in 'Annales +des Sc. Nat.,' Zoolog., 3rd series, 1850, p. 138. + +[880] 'Annals and Mag. of Nat. Hist.,' 2nd series, vol. xx., 1857, pp. +153-455. + +[881] 'Annales des Sc. Nat.,' 3rd series, 1850, tom. xiii. + +[882] 'Transact. Phil. Soc.,' 1851, pp. 196, 208, 210; 1853, p. 245, 247. + +[883] 'Beitrage zur Kenntniss,' &c., 1844, s. 345. + +[884] 'Nouvelles Archives du Muséum,' tom. i. p. 27. + +[885] As quoted by Sir J. Lubbock in 'Nat. Hist. Review,' 1862, p. 345. + +[886] 'Transact. Linn. Soc.,' vol. xxiv., 1863, p. 62. + +[887] 'Parthenogenesis,' 1849, pp. 25-26. Prof. Huxley has some excellent +remarks ('Medical Times,' 1856, p. 637) on this subject, in reference to +the development of star-fishes, and shows how curiously metamorphosis +graduates into gemmation or zoid-formation, which is in fact the same as +metagenesis. + +[888] Prof. J. Reay Greene, in Günther's 'Record of Zoolog. Lit.,' 1865, p. +625. + +[889] Fritz Müller's 'Für Darwin,' 1864, s. 65, 71. The highest authority +on crustaceans, Prof. Milne Edwards, insists ('Annal. des Sci. Nat.,' 2nd +series, Zoolog., tom. iii. p. 322) on their metamorphoses differing even in +closely allied genera. + +[890] Prof. Allman, in 'Annals and Mag. of Nat. Hist.,' 3rd series, vol. +xiii., 1864, p. 348; Dr. S. Wright, idem, vol. viii., 1861, p. 127. _See_ +also p. 358 for analogous statements by Sars. + +[891] 'Tissus Vivants,' 1866, p. 22. + +[892] 'Cellular Pathology,' translat. by Dr. Chance, 1860, pp. 14, 18, 83, +460. + +[893] Paget, 'Surgical Pathology,' vol. i., 1853, pp. 12-14. + +[894] Idem, p. 19. + +[895] Mantegazza, quoted in 'Popular Science Review,' July 1865, p. 522. + +[896] 'De la Production Artificielle des Os,' p. 8. + +[897] Isidore Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. ii. pp. +549, 560, 562; Virchow, idem, p. 484. + +[898] For the most recent classification of cells, _see_ Ernst Häckel's +'Generelle Morpholog.,' Band ii., 1866, s. 275. + +[899] 'The Structure and Growth of Tissues,' 1865, p. 21, &c. + +[900] Dr. W. Turner, 'The present Aspect of Cellular Pathology,' 'Edinburgh +Medical Journal,' April, 1863. + +[901] This term is used by Dr. E. Montgomery ('On the Formation of +so-called Cells in Animal Bodies,' 1867, p. 42), who denies that cells are +derived from other cells by a process of growth, but believes that they +originate through certain chemical changes. + +[902] Prof. Huxley has called my attention to the views of Buffon and +Bonnet. The former ('Hist. Nat. Gén.,' edit. of 1749, tom. ii. pp. 54, 62, +329, 333, 420, 425) supposes that organic molecules exist in the food +consumed by every living creature; and that these molecules are analogous +in nature with the various organs by which they are absorbed. When the +organs thus become fully developed, the molecules being no longer required +collect and form buds or the sexual elements. If Buffon had assumed that +his organic molecules had been formed by each separate unit throughout the +body, his view and mine would have been closely similar. + +Bonnet ('Oeuvres d'Hist. Nat.,' tom. v., part i., 1781, 4to edit., p. 334) +speaks of the limbs having germs adapted for the reparation of all possible +losses; but whether these germs are supposed to be the same with those +within the buds and sexual organs is not clear. His famous but now exploded +theory of _emboîtement_ implies that perfect germs are included within +germs in endless succession, pre-formed and ready for all succeeding +generations. According to my view, the germs or gemmules of each separate +part were not originally pre-formed, but are continually produced at all +ages during each generation, with some handed down from preceding +generations. + +Prof. Owen remarks ('Parthenogenesis,' 1849, pp. 5-8), "Not all the progeny +of the primary impregnated germ-cell are required for the formation of the +body in all animals: certain of the derivative germ-cells may remain +unchanged and become included in that body which has been composed of their +metamorphosed and diversely combined or confluent brethren: so included, +any derivative germ-cell, or the nucleus of such, may commence and repeat +the same processes of growth by imbibition, and of propagation by +spontaneous fission, as those to which itself owed its origin;" &c. By the +agency of these germ-cells Prof. Owen accounts for parthenogenesis, for +propagation by self-division during successive generations, and for the +repairs of injuries. His view agrees with mine in the assumed transmission +and multiplication of his germ-cells, but differs fundamentally from mine +in the belief that the primary germ-cell was formed within the ovarium of +the female and was fertilised by the male. My gemmules are supposed to be +formed, quite independently of sexual concourse, by each separate cell or +unit throughout the body, and to be merely aggregated within the +reproductive organs. + +Lastly, Mr. Herbert Spencer ('Principles of Biology,' vol. i., 1863-4, +chaps. iv. and viii.) has discussed at considerable length what he +designates as physiological units. These agree with my gemmules in being +supposed to multiply and to be transmitted from parent to child; the sexual +elements are supposed to serve merely as their vehicles; they are the +efficient agents in all the forms of reproduction and in the repairs of +injuries; they account for inheritance, but they are not brought to bear on +reversion or atavism, and this is unintelligible to me; they are supposed +to possess polarity, or, as I call it, affinity; and apparently they are +believed to be derived from each separate part of the whole body. But +gemmules differ from Mr. Spencer's physiological units, inasmuch as a +certain number, or mass of them, are, as we shall see, requisite for the +development of each cell or part. Nevertheless I should have concluded that +Mr. Spencer's views were fundamentally the same with mine, had it not been +for several passages which, as far as I understand them, indicate something +quite different. I will quote some of these passages from pp. 254-256. "In +the fertilised germ we have two groups of physiological units, slightly +different in their structures."... "It is not obvious that change in the +form of the part, caused by changed action, involves such change in the +physiological units throughout the organism, that these, when groups of +them are thrown off in the shape of reproductive centres, will unfold into +organisms that have this part similarly changed in form. Indeed, when +treating of Adaptation, we saw that an organ modified by increase or +decrease of function can but slowly so react on the system at large as to +bring about those correlative changes required to produce a new +equilibrium; and yet only when such new equilibrium has been established, +can we expect it to be _fully_ expressed in the modified physiological +units of which the organism is built--only then can we count on a complete +transfer of the modification to descendants."... "That the change in the +offspring must, other things equal, be in the same direction as the change +in the parent, we may dimly see is implied by the fact, that the change +propagated throughout the parental system is a change towards a new state +of equilibrium--a change tending to bring the actions of all organs, +reproductive included, into harmony with these new actions." + +[903] M. Philipeaux ('Comptes Rendus,' Oct. 1, 1866, p. 576, and June, +1867) has lately shown that when the entire fore-limb, including the +scapula, is extirpated, the power of regrowth is lost. From this he +concludes that it is necessary for regrowth that a small portion of the +limb should be left. But as in the lower animals the whole body may be +bisected and both halves be reproduced, this belief does not seem probable. +May not the early closing of a deep wound, as in the case of the +extirpation of the scapula, prevent the formation or protrusion of the +nascent limb? + +[904] 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. xiv., 1850, p. 244. + +[905] _See_ some very interesting papers on this subject by Prof. Lionel +Beale, in 'Medical Times and Gazette,' Sept. 9th, 1865, pp. 273, 330. + +[906] Third Report of the R. Comm. on the Cattle Plague, as quoted in +'Gard. Chronicle,' 1866, p. 446. + +[907] In a cod-fish, weighing 20 lb., Mr. F. Buckland ('Land and Water,' +1867, p. 57) calculated the above number of eggs. In another instance, +Harmer ('Phil. Transact.,' 1767, p. 280) found 3,681,760 eggs. For the +Ascaris, _see_ Carpenter's 'Comp. Phys.,' 1854, p. 590. Mr. J. Scott, of +the Royal Botanic Garden of Edinburgh, calculated, in the same manner as I +have done for some British orchids ('Fertilisation of Orchids,' p. 344), +the number of seeds in a capsule of an Acropera, and found the number to be +371,250. Now this plant produces several flowers on a raceme and many +racemes during a season. In an allied genus, Gongora, Mr. Scott has seen +twenty capsules produced on a single raceme: ten such racemes on the +Acropera would yield above seventy-four millions of seed. I may add that +Fritz Müller informs me that he found in a capsule of a Maxillaria, in +South Brazil, that the seed weighed 42½ grains: he then arranged half a +grain of seed in a narrow line, and by counting a measured length found the +number in the half-grain to be 20,667, so that in the capsule there must +have been 1,756,440 seeds! The same plant sometimes produces half-a-dozen +capsules. + +[908] 'Annals and Mag. of Nat. Hist.,' 3rd series, vol. viii., 1861, p. +490. + +[909] Paget, 'Lectures on Pathology,' p. 27; Virchow, 'Cellular Pathology,' +translat. by Dr. Chance, pp. 123, 126, 294; Claude Bernard, 'Des Tissus +Vivants,' pp. 177, 210, 337; Müller's 'Physiology,' Eng. translat., p. 290. + +[910] Virchow, 'Cellular Pathology,' trans. by Dr. Chance, 1860, pp. 60, +162, 245, 441, 454. + +[911] Idem, pp. 412-426. + +[912] _See_ Rev. J. M. Berkeley, in 'Gard. Chron.,' April 28th, 1866, on a +bud developed on the petal of the Clarkia. _See_ also H. Schacht, 'Lehrbuch +der Anat.,' &c., 1859, Theile ii. s. 12, on adventitious buds. + +[913] Mr. Herbert Spencer ('Principles of Biology,' vol. ii. p. 430) has +fully discussed the antagonism between growth and reproduction. + +[914] The male salmon is known to breed at a very early age. The Triton and +Siredon, whilst retaining their larval branchiæ, according to Filippi and +Duméril ('Annals and Mag. of Nat. Hist.,' 3rd series, 1866, p. 157), are +capable of reproduction. Ernst Häckel has recently ('Monatsbericht Akad. +Wiss. Berlin,' Feb. 2nd, 1865) observed the surprising case of a medusa, +with its reproductive organs active, which produces by budding a widely +different form of medusa; and this latter also has the power of sexual +reproduction. Krohn has shown ('Annals and Mag. of Nat. Hist.,' 3rd series, +vol. xix., 1862, p. 6) that certain other medusæ, whilst sexually mature, +propagate by gemmæ. + +[915] _See_ his excellent discussion on this subject in 'Nouvelles Archives +du Muséum,' tom. i. p. 151. + +[916] Various physiologists have insisted on this distinction between +growth and development. Prof. Marshall ('Phil. Transact.,' 1864, p. 544) +gives a good instance in microcephalous idiots, in which the brain +continues to grow after having been arrested in its development. + +[917] 'Compte Rendu,' Nov. 14, 1864, p. 800. + +[918] As previously remarked by Quatrefages, in his 'Metamorphoses de +l'Homme,' &c., 1862, p. 129. + +[919] Günther's 'Zoological Record,' 1864, p. 279. + +[920] Sedgwick, in 'Medico-Chirurg. Review,' April 1863, p. 454. + +[921] Isid. Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. i., 1832, pp. +435, 657; and tom. ii. p. 560. + +[922] Virchow, 'Cellular Pathology,' 1860, p. 66. + +[923] Moquin-Tandon, 'Tératologie Veg.,' 1841, pp. 218, 220, 353. For the +case of the pea, _see_ 'Gardener's Chron.,' 1866, p. 897. + +[924] Müller's 'Physiology,' Eng. translat., vol. i. p. 407. + +[925] _See_ some remarks to this effect by Sir H. Holland in his 'Medical +Notes,' 1839, p. 32. + +[926] This is the view taken by Prof. Häckel, in his 'Generelle +Morphologie' (B. ii. s. 171), who says: "Lediglich die partielle Identität +der specifischconstituirten Materie im elterlichen und im kindlichen +Organismus, die Theilung dieser Materie bei der Fortpflanzung, ist die +Ursache der Erblichkeit." + +[927] In these remarks I, in fact, follow Naudin, who speaks of the +elements or essences of the two species which are crossed. See his +excellent memoir in the 'Nouvelles Archives du Muséum,' tom. i. p. 151. + +[928] Godron, 'De l'Espèce,' 1859, tom. ii. p. 44, &c. + +[929] Journal Proc. Linn. Soc., 1858, vol. iii. p. 60. + +[930] 'The Quarterly Journal of Science,' Oct. 1867, p. 486. + +[931] M. Rufz de Lavison, in 'Bull. Soc. Imp. d'Acclimat.,' Dec. 1862, p. +1009. + +[932] 'Races of Man,' 1850, p. 315. + +[933] 'Travels in Peru,' Eng. translat., p. 177. + +[934] Youatt on Cattle, 1834, p 200: on Pigs; _see_ 'Gard. Chronicle,' +1854, p. 410. + +[935] 'Die Pflanzen der Pfahlbauten,' 1865. + +[936] Morlot, 'Soc. Vaud. des Scien. Nat,' Mars 1860, p. 298. + +[937] Rütimeyer, 'Die Fauna der Pfahlbauten,' 1861, s. 30. + +[938] Godron, 'De l'Espèce,' tom. i., 1859, p. 368. + +[939] 'Géographie Botan.,' 1855, p. 989. + +[940] Pickering, 'Races of Man,' 1850, p. 318. + +[941] 'Journal of a Horticultural Tour,' by a Deputation of the Caledonian +Hist. Soc., 1823, p. 293. + + + + + + * * * * * + + + + + +Corrections made to printed original. + +p. iii. "APPEARANCE WITH ADVANCING AGE": 'ARPEARANCE' in original. + +p. vi. "SLIGHT CHANGES SUFFICIENT": 'SUFFICENT' in original. + +p. 61. "bearing in mind what has been said": 'bearnig' in original. + +p. 78. "not attached to any particular period": 'particuliar' in original. + +p. 243. "it permits innumerable individuals to be born": 'permitts' in +original. + +p. 294. "liable to complete absorption": 'absortion' in original. + +p. 297. "found that when the animal was compelled ...": 'found than ...' in +original. + +p. 318. "branches in a rudimentary condition": 'rudimentry' in original. + +p. 384. "force themselves into a minute orifice": 'into' was printed on +next line in original, after 'must'. + + + +***END OF THE PROJECT GUTENBERG EBOOK THE VARIATION OF ANIMALS AND PLANTS +UNDER DOMESTICATION, VOLUME II (OF 2)*** + + +******* This file should be named 28897-8.txt or 28897-8.zip ******* + + +This and all associated files of various formats will be found in: +http://www.gutenberg.org/dirs/2/8/8/9/28897 + + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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text-indent: 1em;} + .figure p.in, .figcenter p.in, .figright p.in, .figleft p.in {margin: 0; text-indent: 8em;} + .figcenter p.poem {margin-left: 1em; text-align: left; text-indent: 0;} + .figcenter {margin: auto;} + .figright {float: right;} + .figleft {float: left;} + img.middle { border: none; vertical-align: middle } + + hr.pg { width: 100%; + margin-top: 3em; + margin-bottom: 0em; + margin-left: auto; + margin-right: auto; + height: 4px; + border-width: 4px 0 0 0; /* remove all borders except the top one */ + border-style: solid; + border-color: #000000; + clear: both; } + </style> +</head> +<body> +<h1>The Project Gutenberg eBook, The Variation of Animals and Plants Under +Domestication, Volume II (of 2), by Charles Darwin</h1> +<pre> +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at <a href = "http://www.gutenberg.org">www.gutenberg.org</a></pre> +<p>Title: The Variation of Animals and Plants Under Domestication, Volume II (of 2)</p> +<p>Author: Charles Darwin</p> +<p>Release Date: May 20, 2009 [eBook #28897]</p> +<p>Language: English</p> +<p>Character set encoding: ISO-8859-1</p> +<p>***START OF THE PROJECT GUTENBERG EBOOK THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION, VOLUME II (OF 2)***</p> +<p> </p> +<h3>E-text prepared by Steven Gibbs, Keith Edkins,<br /> + and the Project Gutenberg Online Distributed Proofreading Team<br /> + (http://www.pgdp.net)</h3> +<p> </p> +<table border="0" cellpadding="10" style="background-color: #ccccff;"> +<tr> +<td style="width:25%; vertical-align:top"> +Transcriber's note: +</td> +<td> +A few typographical errors have been corrected. They +appear in the text <span class="correction" title="explanation will pop up">like this</span>, and the +explanation will appear when the mouse pointer is moved over the marked +passage. +</td> +</tr> +</table> +<p> </p> +<hr class="pg" /> +<p> </p> +<p> </p> +<p> </p> + +<h2>THE VARIATION</h2> + +<p class="cenhead">OF</p> + +<h1>ANIMALS AND PLANTS</h1> + +<h2>UNDER DOMESTICATION.</h2> + +<h3><span class="sc">By</span> CHARLES DARWIN, M.A., F.R.S., &c.</h3> + +<h3>IN TWO VOLUMES.—<span class="sc">Vol</span>. II.</h3> + +<h4>WITH ILLUSTRATIONS.</h4> +<p> </p> +<p> </p> + +<h3>LONDON:</h3> + +<h3>JOHN MURRAY, ALBEMARLE STREET.</h3> + +<h3>1868.</h3> + +<p class="cenhead"><i>The right of Translation is reserved.</i></p> + +<p class="cenhead"><span class="scac">LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET, AND CHARING CROSS.</span></p> + +<hr class="full" /> + +<p><!-- Page iii --><span class="pagenum"><a name="pageiii"></a>{iii}</span></p> + +<h2>CONTENTS OF VOLUME II.</h2> + +<h3>CHAPTER XII.</h3> + +<p class="cenhead">INHERITANCE.</p> + + <p><span class="scac">WONDERFUL NATURE OF INHERITANCE</span>—<span + class="scac">PEDIGREES OF OUR DOMESTICATED ANIMALS</span>—<span + class="scac">INHERITANCE NOT DUE TO CHANCE</span>—<span + class="scac">TRIFLING CHARACTERS INHERITED</span>—<span + class="scac">DISEASES INHERITED</span>—<span + class="scac">PECULIARITIES IN THE EYE INHERITED</span>—<span + class="scac">DISEASES IN THE HORSE</span>—<span + class="scac">LONGEVITY AND VIGOUR</span>—<span + class="scac">ASYMMETRICAL DEVIATIONS OF STRUCTURE</span>—<span + class="scac">POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY DIGITS AFTER + AMPUTATION</span>—<span class="scac">CASES OF SEVERAL CHILDREN + SIMILARLY AFFECTED FROM NON-AFFECTED PARENTS</span>—<span + class="scac">WEAK AND FLUCTUATING INHERITANCE: IN WEEPING TREES, IN + DWARFNESS, COLOUR OF FRUIT AND FLOWERS, COLOUR OF + HORSES</span>—<span class="scac">NON-INHERITANCE IN CERTAIN + CASES</span>—<span class="scac">INHERITANCE OF STRUCTURE AND HABITS + OVERBORNE BY HOSTILE CONDITIONS OF LIFE, BY INCESSANTLY RECURRING + VARIABILITY, AND BY REVERSION</span>—<span + class="scac">CONCLUSION</span> ... Page <a href="#page1">1</a></p> + +<h3>CHAPTER XIII.</h3> + +<p class="cenhead">INHERITANCE <i>continued</i>—REVERSION OR ATAVISM.</p> + + <p><span class="scac">DIFFERENT FORMS OF REVERSION</span>—<span + class="scac">IN PURE OR UNCROSSED BREEDS, AS IN PIGEONS, FOWLS, HORNLESS + CATTLE AND SHEEP, IN CULTIVATED PLANTS</span>—<span + class="scac">REVERSION IN FERAL ANIMALS AND PLANTS</span>—<span + class="scac">REVERSION IN CROSSED VARIETIES AND + SPECIES</span>—<span class="scac">REVERSION THROUGH + BUD-PROPAGATION, AND BY SEGMENTS IN THE SAME FLOWER OR + FRUIT</span>—<span class="scac">IN DIFFERENT PARTS OF THE BODY IN + THE SAME ANIMAL</span>—<span class="scac">THE ACT OF CROSSING A + DIRECT CAUSE OF REVERSION, VARIOUS CASES OF, WITH + INSTINCTS</span>—<span class="scac">OTHER PROXIMATE CAUSES OF + REVERSION</span>—<span class="scac">LATENT + CHARACTERS</span>—<span class="scac">SECONDARY SEXUAL + CHARACTERS</span>—<span class="scac">UNEQUAL DEVELOPMENT OF THE TWO + SIDES OF THE BODY</span>—<span class="scac"><span + class="correction" title="Original reads `ARPEARANCE'.">APPEARANCE</span> + WITH ADVANCING AGE OF CHARACTERS DERIVED FROM A CROSS</span>—<span + class="scac">THE GERM WITH ALL ITS LATENT CHARACTERS A WONDERFUL + OBJECT</span>—<span class="scac">MONSTROSITIES</span>—<span + class="scac">PELORIC FLOWERS DUE IN SOME CASES TO REVERSION</span> ... + Page <a href="#page28">28</a></p> + +<h3>CHAPTER XIV.</h3> + +<p class="cenhead">INHERITANCE <i>continued</i>—FIXEDNESS OF CHARACTER—PREPOTENCY—SEXUAL +LIMITATION—CORRESPONDENCE OF AGE.</p> + + <p><span class="scac">FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO + ANTIQUITY OF INHERITANCE</span>—<span class="scac">PREPOTENCY OF + TRANSMISSION IN INDIVIDUALS OF THE SAME FAMILY, IN CROSSED BREEDS AND + SPECIES; OFTEN STRONGER IN ONE SEX THAN THE OTHER; SOMETIMES DUE TO THE + SAME CHARACTER BEING PRESENT AND VISIBLE IN ONE BREED AND LATENT IN THE + OTHER</span>—<span class="scac">INHERITANCE AS LIMITED BY + SEX</span>—<span class="scac">NEWLY-ACQUIRED CHARACTERS IN OUR + DOMESTICATED ANIMALS OFTEN TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST + BY ONE SEX ALONE</span>—<span class="scac">INHERITANCE AT + CORRESPONDING PERIODS OF LIFE</span>—<span class="scac">THE + IMPORTANCE OF THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS EXHIBITED IN + DOMESTICATED ANIMALS; AS EXHIBITED IN THE APPEARANCE AND DISAPPEARANCE OF + INHERITED DISEASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN IN + THE PARENT</span>—<span class="scac">SUMMARY OF THE THREE PRECEDING + CHAPTERS</span> ... Page <a href="#page62">62</a></p> + +<p><!-- Page iv --><span class="pagenum"><a name="pageiv"></a>{iv}</span></p> + +<h3>CHAPTER XV.</h3> + +<p class="cenhead">ON CROSSING.</p> + + <p><span class="scac">FREE INTERCROSSING OBLITERATES THE DIFFERENCES + BETWEEN ALLIED BREEDS</span>—<span class="scac">WHEN THE NUMBERS OF + TWO COMMINGLING BREEDS ARE UNEQUAL, ONE ABSORBS THE + OTHER</span>—<span class="scac">THE RATE OF ABSORPTION DETERMINED + BY PREPOTENCY OF TRANSMISSION, BY THE CONDITIONS OF LIFE, AND BY NATURAL + SELECTION</span>—<span class="scac">ALL ORGANIC BEINGS OCCASIONALLY + INTERCROSS; APPARENT EXCEPTIONS</span>—<span class="scac">ON + CERTAIN CHARACTERS INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE + WHICH HAVE SUDDENLY APPEARED IN THE INDIVIDUAL</span>—<span + class="scac">ON THE MODIFICATION OF OLD RACES, AND THE FORMATION OF NEW + RACES, BY CROSSING</span>—<span class="scac">SOME CROSSED RACES + HAVE BRED TRUE FROM THEIR FIRST PRODUCTION</span>—<span + class="scac">ON THE CROSSING OF DISTINCT SPECIES IN RELATION TO THE + FORMATION OF DOMESTIC RACES</span> ... Page <a href="#page85">85</a></p> + +<h3>CHAPTER XVI.</h3> + +<p class="cenhead">CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF +VARIETIES—INFLUENCE OF DOMESTICATION ON FERTILITY.</p> + + <p><span class="scac">DIFFICULTIES IN JUDGING OF THE FERTILITY OF + VARIETIES WHEN CROSSED</span>—<span class="scac">VARIOUS CAUSES + WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING AND SEXUAL + PREFERENCE</span>—<span class="scac">VARIETIES OF WHEAT SAID TO BE + STERILE WHEN CROSSED</span>—<span class="scac">VARIETIES OF MAIZE, + VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND TOBACCO, RENDERED IN SOME + DEGREE MUTUALLY STERILE</span>—<span class="scac">DOMESTICATION + ELIMINATES THE TENDENCY TO STERILITY NATURAL TO SPECIES WHEN + CROSSED</span>—<span class="scac">ON THE INCREASED FERTILITY OF + UNCROSSED ANIMALS AND PLANTS FROM DOMESTICATION AND CULTIVATION</span> + ... Page <a href="#page100">100</a></p> + +<h3>CHAPTER XVII.</h3> + +<p class="cenhead">ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL +EFFECTS OF CLOSE INTERBREEDING.</p> + + <p><span class="scac">DEFINITION OF CLOSE + INTERBREEDING</span>—<span class="scac">AUGMENTATION OF MORBID + TENDENCIES</span>—<span class="scac">GENERAL EVIDENCE ON THE GOOD + EFFECTS DERIVED FROM CROSSING, AND ON THE EVIL EFFECTS FROM CLOSE + INTERBREEDING</span>—<span class="scac">CATTLE, CLOSELY INTERBRED; + HALF-WILD CATTLE LONG KEPT IN THE SAME PARKS</span>—<span + class="scac">SHEEP</span>—<span + class="scac">FALLOW-DEER</span>—<span + class="scac">DOGS</span>—<span + class="scac">RABBITS</span>—<span + class="scac">PIGS</span>—<span class="scac">MAN, ORIGIN OF HIS + ABHORRENCE OF INCESTUOUS MARRIAGES</span>—<span + class="scac">FOWLS</span>—<span + class="scac">PIGEONS</span>—<span + class="scac">HIVE-BEES</span>—<span class="scac">PLANTS, GENERAL + CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING</span>—<span + class="scac">MELONS, FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND + FOREST-TREES</span>—<span class="scac">ON THE INCREASED SIZE OF + HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY</span>—<span + class="scac">ON CERTAIN PLANTS WHICH EITHER NORMALLY OR ABNORMALLY ARE + SELF-IMPOTENT, BUT ARE FERTILE, BOTH ON THE MALE AND FEMALE SIDE, WHEN + CROSSED WITH DISTINCT INDIVIDUALS EITHER OF THE SAME OR ANOTHER + SPECIES</span>—<span class="scac">CONCLUSION</span> ... Page <a + href="#page114">114</a></p> + +<p><!-- Page v --><span class="pagenum"><a name="pagev"></a>{v}</span></p> + +<h3>CHAPTER XVIII.</h3> + +<p class="cenhead">ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED +CONDITIONS OF LIFE: STERILITY FROM VARIOUS CAUSES.</p> + + <p><span class="scac">ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE + CONDITIONS OF LIFE</span>—<span class="scac">STERILITY FROM CHANGED + CONDITIONS, IN ANIMALS, IN THEIR NATIVE COUNTRY AND IN + MENAGERIES</span>—<span class="scac">MAMMALS, BIRDS, AND + INSECTS</span>—<span class="scac">LOSS OF SECONDARY SEXUAL + CHARACTERS AND OF INSTINCTS</span>—<span class="scac">CAUSES OF + STERILITY</span>—<span class="scac">STERILITY OF DOMESTICATED + ANIMALS FROM CHANGED CONDITIONS</span>—<span class="scac">SEXUAL + INCOMPATIBILITY OF INDIVIDUAL ANIMALS</span>—<span + class="scac">STERILITY OF PLANTS FROM CHANGED CONDITIONS OF + LIFE</span>—<span class="scac">CONTABESCENCE OF THE + ANTHERS</span>—<span class="scac">MONSTROSITIES AS A CAUSE OF + STERILITY</span>—<span class="scac">DOUBLE + FLOWERS</span>—<span class="scac">SEEDLESS FRUIT</span>—<span + class="scac">STERILITY FROM THE EXCESSIVE DEVELOPMENT OF THE ORGANS OF + VEGETATION</span>—<span class="scac">FROM LONG-CONTINUED + PROPAGATION BY BUDS</span>—<span class="scac">INCIPIENT STERILITY + THE PRIMARY CAUSE OF DOUBLE FLOWERS AND SEEDLESS FRUIT</span> ... Page <a + href="#page145">145</a></p> + +<h3>CHAPTER XIX.</h3> + +<p class="cenhead">SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS +ON HYBRIDISM.</p> + + <p><span class="scac">ON THE EFFECTS OF CROSSING</span>—<span + class="scac">THE INFLUENCE OF DOMESTICATION ON + FERTILITY</span>—<span class="scac">CLOSE + INTERBREEDING</span>—<span class="scac">GOOD AND EVIL RESULTS FROM + CHANGED CONDITIONS OF LIFE</span>—<span class="scac">VARIETIES WHEN + CROSSED NOT INVARIABLY FERTILE</span>—<span class="scac">ON THE + DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND + VARIETIES</span>—<span class="scac">CONCLUSIONS WITH RESPECT TO + HYBRIDISM</span>—<span class="scac">LIGHT THROWN ON HYBRIDISM BY + THE ILLEGITIMATE PROGENY OF DIMORPHIC AND TRIMORPHIC + PLANTS</span>—<span class="scac">STERILITY OF CROSSED SPECIES DUE + TO DIFFERENCES CONFINED TO THE REPRODUCTIVE SYSTEM</span>—<span + class="scac">NOT ACCUMULATED THROUGH NATURAL SELECTION</span>—<span + class="scac">REASONS WHY DOMESTIC VARIETIES ARE NOT MUTUALLY + STERILE</span>—<span class="scac">TOO MUCH STRESS HAS BEEN LAID ON + THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND CROSSED + VARIETIES</span>—<span class="scac">CONCLUSION</span> ... Page <a + href="#page173">173</a></p> + +<h3>CHAPTER XX.</h3> + +<p class="cenhead">SELECTION BY MAN.</p> + + <p><span class="scac">SELECTION A DIFFICULT ART</span>—<span + class="scac">METHODICAL, UNCONSCIOUS, AND NATURAL + SELECTION</span>—<span class="scac">RESULTS OF METHODICAL + SELECTION</span>—<span class="scac">CARE TAKEN IN + SELECTION</span>—<span class="scac">SELECTION WITH + PLANTS</span>—<span class="scac">SELECTION CARRIED ON BY THE + ANCIENTS, AND BY SEMI-CIVILISED PEOPLE</span>—<span + class="scac">UNIMPORTANT CHARACTERS OFTEN ATTENDED TO</span>—<span + class="scac">UNCONSCIOUS SELECTION</span>—<span class="scac">AS + CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR DOMESTICATED ANIMALS CHANGED + THROUGH THE ACTION OF UNCONSCIOUS SELECTION</span>—<span + class="scac">INFLUENCE OF DIFFERENT BREEDERS ON THE SAME + SUB-VARIETY</span>—<span class="scac">PLANTS AS AFFECTED BY + UNCONSCIOUS SELECTION</span>—<span class="scac">EFFECTS OF + SELECTION AS SHOWN BY THE GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST + VALUED BY MAN</span> ... Page <a href="#page192">192</a></p> + +<p><!-- Page vi --><span class="pagenum"><a name="pagevi"></a>{vi}</span></p> + +<h3>CHAPTER XXI.</h3> + +<p class="cenhead">SELECTION—<i>continued.</i></p> + + <p><span class="scac">NATURAL SELECTION AS AFFECTING DOMESTIC + PRODUCTIONS</span>—<span class="scac">CHARACTERS WHICH APPEAR OF + TRIFLING VALUE OFTEN OF REAL IMPORTANCE</span>—<span + class="scac">CIRCUMSTANCES FAVOURABLE TO SELECTION BY + MAN</span>—<span class="scac">FACILITY IN PREVENTING CROSSES, AND + THE NATURE OF THE CONDITIONS</span>—<span class="scac">CLOSE + ATTENTION AND PERSEVERANCE INDISPENSABLE</span>—<span + class="scac">THE PRODUCTION OF A LARGE NUMBER OF INDIVIDUALS ESPECIALLY + FAVOURABLE</span>—<span class="scac">WHEN NO SELECTION IS APPLIED, + DISTINCT RACES ARE NOT FORMED</span>—<span class="scac">HIGHLY-BRED + ANIMALS LIABLE TO DEGENERATION</span>—<span class="scac">TENDENCY + IN MAN TO CARRY THE SELECTION OF EACH CHARACTER TO AN EXTREME POINT, + LEADING TO DIVERGENCE OF CHARACTER, RARELY TO + CONVERGENCE</span>—<span class="scac">CHARACTERS CONTINUING TO VARY + IN THE SAME DIRECTION IN WHICH THEY HAVE ALREADY + VARIED</span>—<span class="scac">DIVERGENCE OF CHARACTER, WITH THE + EXTINCTION OF INTERMEDIATE VARIETIES, LEADS TO DISTINCTNESS IN OUR + DOMESTIC RACES</span>—<span class="scac">LIMIT TO THE POWER OF + SELECTION</span>—<span class="scac">LAPSE OF TIME + IMPORTANT</span>—<span class="scac">MANNER IN WHICH DOMESTIC RACES + HAVE ORIGINATED</span>—<span class="scac">SUMMARY</span> ... Page + <a href="#page224">224</a></p> + +<h3>CHAPTER XXII.</h3> + +<p class="cenhead">CAUSES OF VARIABILITY.</p> + + <p><span class="scac">VARIABILITY DOES NOT NECESSARILY ACCOMPANY + REPRODUCTION</span>—<span class="scac">CAUSES ASSIGNED BY VARIOUS + AUTHORS</span>—<span class="scac">INDIVIDUAL + DIFFERENCES</span>—<span class="scac">VARIABILITY OF EVERY KIND DUE + TO CHANGED CONDITIONS OF LIFE</span>—<span class="scac">ON THE + NATURE OF SUCH CHANGES</span>—<span class="scac">CLIMATE, FOOD, + EXCESS OF NUTRIMENT</span>—<span class="scac">SLIGHT CHANGES <span + class="correction" title="Original reads `SUFFICENT'." + >SUFFICIENT</span></span>—<span class="scac">EFFECTS OF GRAFTING ON + THE VARIABILITY OF SEEDLING-TREES</span>—<span + class="scac">DOMESTIC PRODUCTIONS BECOME HABITUATED TO CHANGED + CONDITIONS</span>—<span class="scac">ON THE ACCUMULATIVE ACTION OF + CHANGED CONDITIONS</span>—<span class="scac">CLOSE INTERBREEDING + AND THE IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE + VARIABILITY</span>—<span class="scac">CROSSING AS A CAUSE OF THE + APPEARANCE OF NEW CHARACTERS</span>—<span class="scac">VARIABILITY + FROM THE COMMINGLING OF CHARACTERS AND FROM REVERSION</span>—<span + class="scac">ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH + EITHER DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE + VARIABILITY</span> ... Page <a href="#page250">250</a></p> + +<h3>CHAPTER XXIII.</h3> + +<p class="cenhead">DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS +OF LIFE.</p> + + <p><span class="scac">SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE + ACTION OF CHANGED CONDITIONS, IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND + IN THE STATE OF THE TISSUES</span>—<span class="scac">LOCAL + DISEASES</span>—<span class="scac">CONSPICUOUS MODIFICATIONS FROM + CHANGED CLIMATE OR FOOD, ETC.</span>—<span class="scac">PLUMAGE OF + BIRDS AFFECTED BY PECULIAR NUTRIMENT, AND BY THE INOCULATION OF + POISON</span>—<span class="scac">LAND-SHELLS</span>—<span + class="scac">MODIFICATIONS OF ORGANIC BEINGS IN A STATE OF NATURE THROUGH + THE DEFINITE ACTION OF EXTERNAL CONDITIONS</span>—<span + class="scac">COMPARISON OF AMERICAN AND EUROPEAN TREES</span>—<span + class="scac">GALLS</span>—<span class="scac">EFFECTS OF PARASITIC + FUNGI</span>—<span class="scac">CONSIDERATIONS OPPOSED TO THE + BELIEF IN THE POTENT INFLUENCE OF CHANGED EXTERNAL + CONDITIONS</span>—<span class="scac">PARALLEL SERIES OF + VARIETIES</span>—<span class="scac">AMOUNT OF VARIATION DOES NOT + CORRESPOND WITH THE DEGREE OF CHANGE IN THE CONDITIONS</span>—<span + class="scac">BUD-VARIATION</span>—<span class="scac">MONSTROSITIES + PRODUCED BY UNNATURAL TREATMENT</span>—<span + class="scac">SUMMARY</span> ... Page <a href="#page271">271</a></p> + +<p><!-- Page vii --><span class="pagenum"><a name="pagevii"></a>{vii}</span></p> + +<h3>CHAPTER XXIV.</h3> + +<p class="cenhead">LAWS OF VARIATION—USE AND DISUSE, ETC.</p> + + <p><span class="scac">NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE + ORGANISATION</span>—<span class="scac">ON THE EFFECTS OF THE + INCREASED USE AND DISUSE OF ORGANS</span>—<span + class="scac">CHANGED HABITS OF LIFE</span>—<span + class="scac">ACCLIMATISATION WITH ANIMALS AND PLANTS</span>—<span + class="scac">VARIOUS METHODS BY WHICH THIS CAN BE + EFFECTED</span>—<span class="scac">ARRESTS OF + DEVELOPMENT</span>—<span class="scac">RUDIMENTARY ORGANS</span> ... + Page <a href="#page293">293</a></p> + +<h3>CHAPTER XXV.</h3> + +<p class="cenhead">LAWS OF VARIATION, <i>continued</i>—CORRELATED VARIABILITY.</p> + + <p><span class="scac">EXPLANATION OF TERM</span>—<span + class="scac">CORRELATION AS CONNECTED WITH DEVELOPMENT</span>—<span + class="scac">MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED + SIZE OF PARTS</span>—<span class="scac">CORRELATED VARIATION OF + HOMOLOGOUS PARTS</span>—<span class="scac">FEATHERED FEET IN BIRDS + ASSUMING THE STRUCTURE OF THE WINGS</span>—<span + class="scac">CORRELATION BETWEEN THE HEAD AND THE + EXTREMITIES</span>—<span class="scac">BETWEEN THE SKIN AND DERMAL + APPENDAGES</span>—<span class="scac">BETWEEN THE ORGANS OF SIGHT + AND HEARING</span>—<span class="scac">CORRELATED MODIFICATIONS IN + THE ORGANS OF PLANTS</span>—<span class="scac">CORRELATED + MONSTROSITIES</span>—<span class="scac">CORRELATION BETWEEN THE + SKULL AND EARS</span>—<span class="scac">SKULL AND CREST OF + FEATHERS</span>—<span class="scac">SKULL AND + HORNS</span>—<span class="scac">CORRELATION OF GROWTH COMPLICATED + BY THE ACCUMULATED EFFECTS OF NATURAL SELECTION</span>—<span + class="scac">COLOUR AS CORRELATED WITH CONSTITUTIONAL + PECULIARITIES</span> ... Page <a href="#page319">319</a></p> + +<h3>CHAPTER XXVI.</h3> + +<p class="cenhead">LAWS OF VARIATION, <i>continued</i>—SUMMARY.</p> + + <p><span class="scac">ON THE AFFINITY AND COHESION OF HOMOLOGOUS + PARTS</span>—<span class="scac">ON THE VARIABILITY OF MULTIPLE AND + HOMOLOGOUS PARTS</span>—<span class="scac">COMPENSATION OF + GROWTH</span>—<span class="scac">MECHANICAL + PRESSURE</span>—<span class="scac">RELATIVE POSITION OF FLOWERS + WITH RESPECT TO THE AXIS OF THE PLANT, AND OF SEEDS IN THE CAPSULE, AS + INDUCING VARIATION</span>—<span class="scac">ANALOGOUS OR PARALLEL + VARIETIES</span>—<span class="scac">SUMMARY OF THE THREE LAST + CHAPTERS</span> ... Page <a href="#page339">339</a></p> + +<h3>CHAPTER XXVII.</h3> + +<p class="cenhead">PROVISIONAL HYPOTHESIS OF PANGENESIS.</p> + + <p><span class="scac">PRELIMINARY REMARKS</span>—<span + class="scac">FIRST PART:</span>—<span class="scac">THE FACTS TO BE + CONNECTED UNDER A SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF + REPRODUCTION</span>—<span class="scac">THE DIRECT ACTION OF THE + MALE ELEMENT ON THE FEMALE</span>—<span + class="scac">DEVELOPMENT</span>—<span class="scac">THE FUNCTIONAL + INDEPENDENCE OF THE ELEMENTS OR UNITS OF THE BODY</span>—<span + class="scac">VARIABILITY</span>—<span + class="scac">INHERITANCE</span>—<span + class="scac">REVERSION</span>.</p> + + <p><span class="scac">SECOND PART:</span>—<span + class="scac">STATEMENT OF THE HYPOTHESIS</span>—<span + class="scac">HOW FAR THE NECESSARY ASSUMPTIONS ARE + IMPROBABLE</span>—<span class="scac">EXPLANATION BY AID OF THE + HYPOTHESIS OF THE SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST + PART</span>—<span class="scac">CONCLUSION</span> ... Page <a + href="#page357">357</a></p> + +<p><!-- Page viii --><span class="pagenum"><a name="pageviii"></a>{viii}</span></p> + +<h3>CHAPTER XXVIII.</h3> + +<p class="cenhead">CONCLUDING REMARKS.</p> + + <p><span class="scac">DOMESTICATION</span>—<span + class="scac">NATURE AND CAUSES OF VARIABILITY</span>—<span + class="scac">SELECTION</span>—<span class="scac">DIVERGENCE AND + DISTINCTNESS OF CHARACTER</span>—<span class="scac">EXTINCTION OF + RACES</span>—<span class="scac">CIRCUMSTANCES FAVOURABLE TO + SELECTION BY MAN</span>—<span class="scac">ANTIQUITY OF CERTAIN + RACES</span>—<span class="scac">THE QUESTION WHETHER EACH + PARTICULAR VARIATION HAS BEEN SPECIALLY PREORDAINED</span> ... Page <a + href="#page405">405</a></p> + + <p><span class="sc">Index</span> ... Page <a href="#page433">433</a></p> + +<hr class="short" /> + +<p class="cenhead">ERRATA.</p> + + <div class="poem"> + <div class="stanza"> + <p>Vol. II., pp. 18, 232, 258, <i>for</i> Cratægus oxycantha, <i>read</i> oxyacantha.</p> + <p> ,, p. 98, 8 lines from top, <i>for</i> Dianthus armoria <i>read</i> armeria.</p> + <p> ,, ,, 156, 15 lines from bottom, <i>for</i> Casuarinus <i>read</i> Casuarius.</p> + <p> ,, ,, ,, 4 lines from bottom, <i>for</i> Grus cineria <i>read</i> cinerea.</p> + <p> ,, ,, 168, 11 lines from top, <i>for</i> Œsculus <i>read</i> Æsculus.</p> + <p> ,, ,, 300, 3 lines from top, <i>for</i> anastomising <i>read</i> anastomosing.</p> + <p> ,, ,, ,, foot-note, <i>for</i> Birckell <i>read</i> Brickell.</p> + </div> + </div> + +<hr class="full" /> + +<p><!-- Page 1 --><span class="pagenum"><a name="page1"></a>{1}</span></p> + +<p class="cenhead">THE</p> + +<h2>VARIATION OF ANIMALS AND PLANTS</h2> + +<h3>UNDER DOMESTICATION.</h3> + +<hr class="short" /> + +<h3>CHAPTER XII.</h3> + +<p class="cenhead">INHERITANCE.</p> + +<blockquote class="b1n"> + + <p><span class="scac">WONDERFUL NATURE OF INHERITANCE</span>—<span + class="scac">PEDIGREES OF OUR DOMESTICATED ANIMALS</span>—<span + class="scac">INHERITANCE NOT DUE TO CHANCE</span>—<span + class="scac">TRIFLING CHARACTERS INHERITED</span>—<span + class="scac">DISEASES INHERITED</span>—<span + class="scac">PECULIARITIES IN THE EYE INHERITED</span>—<span + class="scac">DISEASES IN THE HORSE</span>—<span + class="scac">LONGEVITY AND VIGOUR</span>—<span + class="scac">ASYMMETRICAL DEVIATIONS OF STRUCTURE</span>—<span + class="scac">POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY DIGITS AFTER + AMPUTATION</span>—<span class="scac">CASES OF SEVERAL CHILDREN + SIMILARLY AFFECTED FROM NON-AFFECTED PARENTS</span>—<span + class="scac">WEAK AND FLUCTUATING INHERITANCE: IN WEEPING TREES, IN + DWARFNESS, COLOUR OF FRUIT AND FLOWERS, COLOUR OF + HORSES</span>—<span class="scac">NON-INHERITANCE IN CERTAIN + CASES</span>—<span class="scac">INHERITANCE OF STRUCTURE AND HABITS + OVERBORNE BY HOSTILE CONDITIONS OF LIFE, BY INCESSANTLY RECURRING + VARIABILITY, AND BY REVERSION</span>—<span + class="scac">CONCLUSION.</span></p> + +</blockquote> + + <p>The subject of inheritance is an immense one, and has been treated by + many authors. One work alone, 'De l'Hérédité Naturelle,' by Dr. Prosper + Lucas, runs to the length of 1562 pages. We must confine ourselves to + certain points which have an important bearing on the general subject of + variation, both with domestic and natural productions. It is obvious that + a variation which is not inherited throws no light on the derivation of + species, nor is of any service to man, except in the case of perennial + plants, which can be propagated by buds.</p> + + <p>If animals and plants had never been domesticated, and wild ones alone + had been observed, we should probably never have heard the saying, that + "like begets like." The proposition would have been as self-evident, as + that all the buds on the same tree are alike, though neither proposition + is strictly true. For, as has often been remarked, probably no two + individuals are <!-- Page 2 --><span class="pagenum"><a + name="page2"></a>{2}</span>identically the same. All wild animals + recognise each other, which shows that there is some difference between + them; and when the eye is well practised, the shepherd knows each sheep, + and man can distinguish a fellow-man out of millions on millions of other + men. Some authors have gone so far as to maintain that the production of + slight differences is as much a necessary function of the powers of + generation, as the production of offspring like their parents. This view, + as we shall see in a future chapter, is not theoretically probable, + though practically it holds good. The saying that "like begets like" has + in fact arisen from the perfect confidence felt by breeders, that a + superior or inferior animal will generally reproduce its kind; but this + very superiority or inferiority shows that the individual in question has + departed slightly from its type.</p> + + <p>The whole subject of inheritance is wonderful. When a new character + arises, whatever its nature may be, it generally tends to be inherited, + at least in a temporary and sometimes in a most persistent manner. What + can be more wonderful than that some trifling peculiarity, not + primordially attached to the species, should be transmitted through the + male or female sexual cells, which are so minute as not to be visible to + the naked eye, and afterwards through the incessant changes of a long + course of development, undergone either in the womb or in the egg, and + ultimately appear in the offspring when mature, or even when quite old, + as in the case of certain diseases? Or again, what can be more wonderful + than the well-ascertained fact that the minute ovule of a good milking + cow will produce a male, from whom a cell, in union with an ovule, will + produce a female, and she, when mature, will have large mammary glands, + yielding an abundant supply of milk, and even milk of a particular + quality? Nevertheless, the real subject of surprise is, as Sir H. Holland + has well remarked,<a name="NtA_1" href="#Nt_1"><sup>[1]</sup></a> not + that a character should be inherited, but that any should ever fail to be + inherited. In a future chapter, devoted to an hypothesis which I have + termed pangenesis, an attempt will be made to show the means by which + characters of all kinds are transmitted from generation to + generation.</p> + +<p><!-- Page 3 --><span class="pagenum"><a name="page3"></a>{3}</span></p> + + <p>Some writers,<a name="NtA_2" href="#Nt_2"><sup>[2]</sup></a> who have + not attended to natural history, have attempted to show that the force of + inheritance has been much exaggerated. The breeders of animals would + smile at such simplicity; and if they condescended to make any answer, + might ask what would be the chance of winning a prize if two inferior + animals were paired together? They might ask whether the half-wild Arabs + were led by theoretical notions to keep pedigrees of their horses? Why + have pedigrees been scrupulously kept and published of the Shorthorn + cattle, and more recently of the Hereford breed? Is it an illusion that + these recently improved animals safely transmit their excellent qualities + even when crossed with other breeds? have the Shorthorns, without good + reason, been purchased at immense prices and exported to almost every + quarter of the globe, a thousand guineas having been given for a bull? + With greyhounds pedigrees have likewise been kept, and the names of such + dogs, as Snowball, Major, &c., are as well known to coursers as those + of Eclipse and Herod on the turf. Even with the Gamecock pedigrees of + famous strains were formerly kept, and extended back for a century. With + pigs, the Yorkshire and Cumberland breeders "preserve and print + pedigrees;" and to show how such highly-bred animals are valued, I may + mention that Mr. Brown, who won all the first prizes for small breeds at + Birmingham in 1850, sold a young sow and boar of his breed to Lord Ducie + for 43 guineas; the sow alone was afterwards sold to the Rev. F. Thursby + for 65 guineas; who writes, "she paid me very well, having sold her + produce for 300<i>l</i>., and having now four breeding sows from her."<a + name="NtA_3" href="#Nt_3"><sup>[3]</sup></a> Hard cash paid down, over + and over again, is an excellent test of inherited superiority. In fact, + the whole art of breeding, from which such great results have been + attained during the present century, depends on the inheritance of each + small <!-- Page 4 --><span class="pagenum"><a + name="page4"></a>{4}</span>detail of structure. But inheritance is not + certain; for if it were, the breeder's art<a name="NtA_4" + href="#Nt_4"><sup>[4]</sup></a> would be reduced to a certainty, and + there would be little scope left for all that skill and perseverance + shown by the men who have left an enduring monument of their success in + the present state of our domesticated animals.</p> + + <p>It is hardly possible, within a moderate compass, to impress on the + mind of those who have not attended to the subject, the full conviction + of the force of inheritance which is slowly acquired by rearing animals, + by studying the many treatises which have been published on the various + domestic animals, and by conversing with breeders. I will select a few + facts of the kind, which, as far as I can judge, have most influenced my + own mind. With man and the domestic animals, certain peculiarities have + appeared in an individual, at rare intervals, or only once or twice in + the history of the world, but have reappeared in several of the children + and grandchildren. Thus Lambert, "the porcupine-man," whose skin was + thickly covered with warty projections, which were periodically moulted, + had all his six children and two grandsons similarly affected.<a + name="NtA_5" href="#Nt_5"><sup>[5]</sup></a> The face and body being + covered with long hair, accompanied by deficient teeth (to which I shall + hereafter refer), occurred in three successive generations in a Siamese + family; but this case is not unique, as a woman<a name="NtA_6" + href="#Nt_6"><sup>[6]</sup></a> with a completely hairy face was + exhibited in London in 1663, and another instance has recently occurred. + Colonel Hallam<a name="NtA_7" href="#Nt_7"><sup>[7]</sup></a> has + described a race of two-legged pigs, "the hinder extremities being + entirely wanting;" and this deficiency was transmitted through three + generations. In fact, all races presenting any remarkable peculiarity, + such as solid-hoofed swine, Mauchamp sheep, niata cattle, &c., are + instances of the long-continued inheritance of rare deviations of + structure.</p> + + <p>When we reflect that certain extraordinary peculiarities have <!-- + Page 5 --><span class="pagenum"><a name="page5"></a>{5}</span>thus + appeared in a single individual out of many millions, all exposed in the + same country to the same general conditions of life, and, again, that the + same extraordinary peculiarity has sometimes appeared in individuals + living under widely different conditions of life, we are driven to + conclude that such peculiarities are not directly due to the action of + the surrounding conditions, but to unknown laws acting on the + organisation or constitution of the individual;—that their + production stands in hardly closer relation to the conditions than does + life itself. If this be so, and the occurrence of the same unusual + character in the child and parent cannot be attributed to both having + been exposed to the same unusual conditions, then the following problem + is worth consideration, as showing that the result cannot be due, as some + authors have supposed, to mere coincidence, but must be consequent on the + members of the same family inheriting something in common in their + constitution. Let it be assumed that, in a large population, a particular + affection occurs on an average in one out of a million, so that the <i>à + priori</i> chance that an individual taken at random will be so affected + is only one in a million. Let the population consist of sixty millions, + composed, we will assume, of ten million families, each containing six + members. On these data, Professor Stokes has calculated for me that the + odds will be no less than 8333 millions to 1 that in the ten million + families there will not be even a single family in which one parent and + two children will be affected by the peculiarity in question. But + numerous cases could be given, in which several children have been + affected by the same rare peculiarity with one of their parents; and in + this case, more especially if the grandchildren be included in the + calculation, the odds against mere coincidence become something + prodigious, almost beyond enumeration.</p> + + <p>In some respects the evidence of inheritance is more striking when we + consider the reappearance of trifling peculiarities. Dr. Hodgkin formerly + told me of an English family in which, for many generations, some members + had a single lock differently coloured from the rest of the hair. I knew + an Irish gentleman, who, on the right side of his head, had a small white + lock in the midst of his dark hair: he assured me that his grandmother + had <!-- Page 6 --><span class="pagenum"><a name="page6"></a>{6}</span>a + similar lock on the same side, and his mother on the opposite side. But + it is superfluous to give instances; every shade of expression, which may + often be seen alike in parents and children, tells the same story. On + what a curious combination of corporeal structure, mental character, and + training, must handwriting depend! yet every one must have noted the + occasional close similarity of the handwriting in father and son, + although the father had not taught his son. A great collector of franks + assured me that in his collection there were several franks of father and + son hardly distinguishable except by their dates. Hofacker, in Germany, + remarks on the inheritance of handwriting; and it has even been asserted + that English boys when taught to write in France naturally cling to their + English manner of writing.<a name="NtA_8" href="#Nt_8"><sup>[8]</sup></a> + Gait, gestures, voice, and general bearing are all inherited, as the + illustrious Hunter and Sir A. Carlisle have insisted.<a name="NtA_9" + href="#Nt_9"><sup>[9]</sup></a> My father communicated to me two or three + striking instances, in one of which a man died during the early infancy + of his son, and my father, who did not see this son until grown up and + out of health, declared that it seemed to him as if his old friend had + risen from the grave, with all his highly peculiar habits and manners. + Peculiar manners pass into tricks, and several instances could be given + of their inheritance; as in the case, often quoted, of the father who + generally slept on his back, with his right leg crossed over the left, + and whose daughter, whilst an infant in the cradle, followed exactly the + same habit, though an attempt was made to cure her.<a name="NtA_10" + href="#Nt_10"><sup>[10]</sup></a> I will give one instance which has + fallen under my own observation, and which is curious from being a trick + associated with a peculiar state of mind, namely, pleasurable emotion. A + boy had the singular habit, when pleased, of rapidly moving his fingers + parallel to each other, and, when much excited, of raising both hands, + with the fingers still moving, to the sides of his face on a level with + the eyes; this boy, when almost an old man, could still hardly resist + this trick when much pleased, but from its absurdity concealed it. He had + eight children. Of these, a girl, when <!-- Page 7 --><span + class="pagenum"><a name="page7"></a>{7}</span>pleased, at the age of four + and a half years, moved her fingers in exactly the same way, and what is + still odder, when much excited, the raised both her hands, with her + fingers still moving, to the sides of her face, in exactly the same + manner as her father had done, and sometimes even still continued to do + when alone. I never heard of any one excepting this one man and his + little daughter who had this strange habit; and certainly imitation was + in this instance out of the question.</p> + + <p>Some writers have doubted whether those complex mental attributes, on + which genius and talent depend, are inherited, even when both parents are + thus endowed. But he who will read Mr. Galton's able paper<a + name="NtA_11" href="#Nt_11"><sup>[11]</sup></a> on hereditary talent will + have his doubts allayed.</p> + + <p>Unfortunately it matters not, as far as inheritance is concerned, how + injurious a quality or structure may be if compatible with life. No one + can read the many treatises<a name="NtA_12" + href="#Nt_12"><sup>[12]</sup></a> on hereditary disease and doubt this. + The ancients were strongly of this opinion, or, as Ranchin expresses it, + <i>Omnes Græci, Arabes, et Latini in eo consentiunt</i>. A long catalogue + could be given of all sorts of inherited malformations and of + predisposition to various diseases. With gout, fifty per cent. of the + cases observed in hospital practice are, according to Dr. Garrod, + inherited, and a greater percentage in private practice. Every one knows + how often insanity runs in families, and some of the cases given by Mr. + Sedgwick are awful,—as of a surgeon, whose brother, father, and + four paternal uncles were all insane, the latter dying by suicide; of a + Jew, whose father, mother, and six brothers and sisters were all mad; and + in some other cases several members of the same family, during three or + four successive generations, have committed suicide. Striking instances + <!-- Page 8 --><span class="pagenum"><a name="page8"></a>{8}</span>have + been recorded of epilepsy, consumption, asthma, stone in the bladder, + cancer, profuse bleeding from the slightest injuries, of the mother not + giving milk, and of bad parturition being inherited. In this latter + respect I may mention an odd case given by a good observer,<a + name="NtA_13" href="#Nt_13"><sup>[13]</sup></a> in which the fault lay in + the offspring, and not in the mother: in a part of Yorkshire the farmers + continued to select cattle with large hind-quarters, until they made a + strain called "Dutch-buttocked," and "the monstrous size of the buttocks + of the calf was frequently fatal to the cow, and numbers of cows were + annually lost in calving."</p> + +<blockquote class="b1n"> + + <p>Instead of giving numerous details on various inherited malformations + and diseases, I will confine myself to one organ, that which is the most + complex, delicate, and probably best-known in the human frame, namely, + the eye, with its accessory parts. To begin with the latter: I have heard + of a family in which parents and children were affected by drooping + eyelids, in so peculiar a manner, that they could not see without + throwing their heads backwards; and Sir A. Carlisle<a name="NtA_14" + href="#Nt_14"><sup>[14]</sup></a> specifies a pendulous fold to the + eyelids as inherited. "In a family," says Sir H. Holland,<a name="NtA_15" + href="#Nt_15"><sup>[15]</sup></a> "where the father had a singular + elongation of the upper eyelid, seven or eight children were born with + the same deformity; two or three other children having it not." Many + persons, as I year from Mr. Paget, have two or three of the hairs in + their eyebrows (apparently corresponding with the vibrissæ of the lower + animals) much longer than the others; and even so trifling a peculiarity + as this certainly runs in families.</p> + + <p>With respect to the eye itself, the highest authority in England, Mr. + Bowman, has been so kind as to give me the following remarks on certain + inherited imperfections. First, hypermetropia, or morbidly long sight: in + this affection, the organ, instead of being spherical, is too flat from + front to back, and is often altogether too small, so that the retina is + brought too forward for the focus of the humours; consequently a convex + glass is required for clear vision of near objects, and frequently even + of distant ones. This state occurs congenitally, or at a very early age, + often in several children of the same family, where one of the parents + has presented it.<a name="NtA_16" href="#Nt_16"><sup>[16]</sup></a> + Secondly, myopia, or short-sight, in which the eye is egg-shaped, and too + long from front to back; the retina in this case lies behind the focus, + and is therefore fitted to see distinctly only very near objects. This + condition is not commonly congenital, but comes on in youth, the + liability to it being well known to be transmissible from parent to + child. The change from the spherical to the ovoidal shape seems the + immediate <!-- Page 9 --><span class="pagenum"><a + name="page9"></a>{9}</span>consequence of something like inflammation of + the coats, under which they yield, and there is ground for believing that + it may often originate in causes acting directly on the individual + affected, and may thenceforward become transmissible. When both parents + are myopic Mr. Bowman has observed the hereditary tendency in this + direction to be heightened, and some of the children to be myopic at an + earlier age or in a higher degree than their parents. Thirdly, squinting + is a familiar example of hereditary transmission: it is frequently a + result of such optical defects as have been above mentioned; but the more + primary and uncomplicated forms of it are also sometimes in a marked + degree transmitted in a family. Fourthly, <i>Cataract</i>, or opacity of + the crystalline lens, is commonly observed in persons whose parents have + been similarly affected, and often at an earlier age in the children than + in the parents. Occasionally more than one child in a family is thus + afflicted, one of whose parents or other relation presents the senile + form of the complaint. When cataract affects several members of a family + in the same generation, it is often seen to commence at about the same + age in each; <i>e.g.</i>, in one family several infants or young persons + may suffer from it; in another, several persons of middle age. Mr. Bowman + also informs me that he has occasionally seen, in several members of the + same family, various defects in either the right or left eye; and Mr. + White Cooper has often seen peculiarities of vision confined to one eye + reappearing in the same eye in the offspring.<a name="NtA_17" + href="#Nt_17"><sup>[17]</sup></a></p> + + <p>The following cases are taken from an able paper by Mr. W. Sedgwick, + and from Dr. Prosper Lucas.<a name="NtA_18" + href="#Nt_18"><sup>[18]</sup></a> Amaurosis, either congenital or coming + on late in life, and causing total blindness, is often inherited; it has + been observed in three successive generations. Congenital absence of the + iris has likewise been transmitted for three generations, a cleft-iris + for four generations, being limited in this latter case to the males of + the family. Opacity of the cornea and congenital smallness of the eyes + have been inherited. Portal records a curious case, in which a father and + two sons were rendered blind, whenever the head was bent downwards, + apparently owing to the crystalline lens, with its capsule, slipping + through an unusually large pupil into the anterior chamber of the eye. + Day-blindness, or imperfect vision under a bright light, is inherited, as + is night-blindness, or an incapacity to see except under a strong light: + a case has been recorded, by M. Cunier, of this latter defect having + affected eighty-five members of the same family during six generations. + The singular incapacity of distinguishing colours, which has been called + <i>Daltonism</i>, is notoriously hereditary, and has been traced through + five generations, in which it was confined to the female sex.</p> + + <p>With respect to the colour of the iris: deficiency of colouring matter + is well known to be hereditary in albinoes. The iris of one eye being of + a different colour from that of the other, and the iris being spotted, + are cases which have been inherited. Mr. Sedgwick gives, in addition, on + the <!-- Page 10 --><span class="pagenum"><a + name="page10"></a>{10}</span>authority of Dr. Osborne,<a name="NtA_19" + href="#Nt_19"><sup>[19]</sup></a> the following curious instance of + strong inheritance: a family of sixteen sons and five daughters all had + eyes "resembling in miniature the markings on the back of a tortoiseshell + cat." The mother of this large family had three sisters and a brother all + similarly marked, and they derived this peculiarity from their mother, + who belonged to a family notorious for transmitting it to their + posterity.</p> + + <p>Finally, Dr. Lucas emphatically remarks that there is not one single + faculty of the eye which is not subject to anomalies; and not one which + is not subjected to the principle of inheritance. Mr. Bowman agrees with + the general truth of this proposition; which of course does not imply + that all malformations are necessarily inherited; this would not even + follow if both parents were affected by an anomaly which in most cases + was transmissible.</p> + +</blockquote> + + <p>Even if no single fact had been known with respect to the inheritance + of disease and malformations by man, the evidence would have been ample + in the case of the horse. And this might have been expected, as horses + breed much quicker than man, are matched with care, and are highly + valued. I have consulted many works, and the unanimity of the belief by + veterinaries of all nations in the transmission of various morbid + tendencies is surprising. Authors, who have had wide experience, give in + detail many singular cases, and assert that contracted feet, with the + numerous contingent evils, of ring-bones, curbs, splints, spavin, founder + and weakness of the front legs, roaring or broken and thick wind, + melanosis, specific ophthalmia, and blindness (the great French + veterinary Hazard going so far as to say that a blind race could soon be + formed), crib-biting, jibbing, and ill-temper, are all plainly + hereditary. Youatt sums up by saying "there is scarcely a malady to which + the horse is subject which is not hereditary;" and M. Bernard adds that + the doctrine "that there is scarcely a disease which does not run in the + stock, is gaining new advocates every day."<a name="NtA_20" + href="#Nt_20"><sup>[20]</sup></a> So it <!-- Page 11 --><span + class="pagenum"><a name="page11"></a>{11}</span>is in regard to cattle, + with consumption, good and bad teeth, fine skin, &c. &c. But + enough, and more than enough, has been said on disease. Andrew Knight, + from his own experience, asserts that disease is hereditary with plants; + and this assertion is endorsed by Lindley.<a name="NtA_21" + href="#Nt_21"><sup>[21]</sup></a></p> + + <p>Seeing how hereditary evil qualities are, it is fortunate that good + health, vigour, and longevity are equally inherited. It was formerly a + well-known practice, when annuities were purchased to be received during + the lifetime of a nominee, to search out a person belonging to a family + of which many members had lived to extreme old age. As to the inheritance + of vigour and endurance, the English race-horse offers an excellent + instance. Eclipse begot 334, and King Herod 497 winners. A "cock-tail" is + a horse not purely bred, but with only one-eighth or one-sixteenth impure + blood in his veins, yet very few instances have ever occurred of such + horses having won a great race. They are sometimes as fleet for short + distances as thoroughbreds, but as Mr. Robson, the great trainer, + asserts, they are deficient in wind, and cannot keep up the pace. Mr. + Lawrence also remarks, "perhaps no instance has ever occurred of a + three-part-bred horse saving his '<i>distance</i>' in running two miles + with thoroughbred racers." It has been stated by Cecil, that when unknown + horses, whose parents were not celebrated, have unexpectedly won great + races, as in the case of Priam, they can always be proved to be descended + on both sides, through many generations, from first-rate ancestors. On + the Continent, Baron Cameronn challenges, in a German veterinary + periodical, the opponents of the English race-horse, to name one good + horse on the Continent which has not some English race-blood in his + veins.<a name="NtA_22" href="#Nt_22"><sup>[22]</sup></a></p> + + <p>With respect to the transmission of the many slight, but <!-- Page 12 + --><span class="pagenum"><a name="page12"></a>{12}</span>infinitely + diversified characters, by which the domestic races of animals and plants + are distinguished, nothing need be said; for the very existence of + persistent races proclaims the power of inheritance.</p> + + <p>A few special cases, however, deserve some consideration. It might + have been anticipated, that deviations from the law of symmetry would not + have been inherited. But Anderson<a name="NtA_23" + href="#Nt_23"><sup>[23]</sup></a> states that a rabbit produced in a + litter a young animal having only one ear; and from this animal a breed + was formed which steadily produced one-eared rabbits. He also mentions a + bitch, with a single leg deficient, and she produced several puppies with + the same deficiency. From Hofacker's account<a name="NtA_24" + href="#Nt_24"><sup>[24]</sup></a> it appears that a one-horned stag was + seen in 1781 in a forest in Germany, in 1788 two, and afterwards, from + year to year, many were observed with only one horn on the right side of + the head. A cow lost a horn by suppuration,<a name="NtA_25" + href="#Nt_25"><sup>[25]</sup></a> and she produced three calves which had + on the same side of the head, instead of a horn, a small bony lump + attached merely to the skin; but we here approach the doubtful subject of + inherited mutilations. A man who is left-handed, and a shell in which the + spire turns in the wrong direction, are departures from the normal though + a symmetrical condition, and they are well known to be inherited.</p> + +<blockquote class="b1n"> + + <p><i>Polydactylism.</i>—Supernumerary fingers and toes are + eminently liable, as various authors have insisted, to transmission, but + they are noticed here chiefly on account of their occasional regrowth + after amputation. Polydactylism graduates<a name="NtA_26" + href="#Nt_26"><sup>[26]</sup></a> by multifarious steps from a mere + cutaneous appendage, not including any bone, to a double hand. But an + additional digit, supported on a metacarpal bone, and furnished with all + the proper muscles, nerves, and vessels, is sometimes so perfect, that it + escapes detection, unless the fingers are actually counted. Occasionally + there are several supernumerary digits; but usually only one, making the + total number six. This one may represent either a thumb or finger, being + attached to the inner or outer margin of the hand. Generally, through the + law of correlation, both hands and feet are similarly affected. I have + tabulated the cases recorded in various works or privately communicated + <!-- Page 13 --><span class="pagenum"><a name="page13"></a>{13}</span>to + me, of forty-six persons with extra digits on one or both hands and feet; + if in each case all four extremities had been similarly affected, the + table would have shown a total of ninety-two hands and ninety-two feet + each with six digits. As it is, seventy-three hands and seventy-five feet + were thus affected. This proves, in contradiction to the result arrived + at by Dr. Struthers,<a name="NtA_27" href="#Nt_27"><sup>[27]</sup></a> + that the hands are not more frequently affected than the feet.</p> + + <p>The presence of more than five digits is a great anomaly, for this + number is not normally exceeded by any mammal, bird, or existing + reptile.<a name="NtA_28" href="#Nt_28"><sup>[28]</sup></a> Nevertheless, + supernumerary digits are strongly inherited; they have been transmitted + through five generations; and in some cases, after disappearing for one, + two, or even three generations, have reappeared through reversion. These + facts are rendered, as Professor Huxley has observed, more remarkable + from its being known in most cases that the affected person had not + married one similarly affected. In such cases the child of the fifth + generation would have only 1-32nd part of the blood of his first + sedigitated ancestor. Other cases are rendered remarkable by the + affection gathering force, as Dr. Struthers has shown, in each + generation, though in each the affected person had married one not + affected; moreover such additional digits are often amputated soon after + birth, and can seldom have been strengthened by use. Dr. Struthers gives + the following instance: in the first generation an additional digit + appeared on one hand; in the second, on both hands; in the third, three + brothers had both hands, and one of the brothers a foot affected; and in + the fourth generation all four limbs were affected. Yet we must not + over-estimate the force of inheritance. Dr. Struthers asserts that cases + of non-inheritance and of the first appearance of additional digits in + unaffected families are much more frequent than cases of inheritance. + Many other deviations of structure, of a nature almost as anomalous as + supernumerary digits, such as deficient phalanges, thickened joints, + crooked fingers, &c., are in like manner strongly inherited, and are + equally subject to intermission with reversion, though in such cases + there is no reason to suppose that both parents had been similarly + affected.<a name="NtA_29" href="#Nt_29"><sup>[29]</sup></a></p> + +<p><!-- Page 14 --><span class="pagenum"><a name="page14"></a>{14}</span></p> + + <p>Additional digits have been observed in negroes as well as in other + races of man, and in several of the lower animals. Six toes have been + described on the hind feet of the newt (<i>Salamandra cristata</i>), and, + as it is said, of the frog. It deserves notice from what follows, that + the six-toed newt, though adult, had preserved some of its larval + characters; for part of the hyoidal apparatus, which is properly absorbed + during the act of metamorphosis, was retained. In the dog, six toes on + the hinder feet have been transmitted through three generations; and I + have heard of a race of six-toed cats. In several breeds of the fowl the + hinder toe is double, and is generally transmitted truly, as is well + shown when Dorkings are crossed with common four-toed breeds.<a + name="NtA_30" href="#Nt_30"><sup>[30]</sup></a> With animals which have + properly less than five digits, the number is sometimes increased to + five, especially in the front legs, though rarely carried beyond that + number; but this is due to the development of a digit already existing in + a more or less rudimentary state. Thus the dog has properly four toes + behind, but in the larger breeds a fifth toe is commonly, though not + perfectly, developed. Horses, which properly have one toe alone fully + developed with rudiments of the others, have been described with each + foot bearing two or three small separate hoofs: analogous facts have been + noticed with sheep, goats, and pigs.<a name="NtA_31" + href="#Nt_31"><sup>[31]</sup></a></p> + + <p>The most interesting point with respect to supernumerary digits is + their occasional regrowth after amputation. Mr. White<a name="NtA_32" + href="#Nt_32"><sup>[32]</sup></a> describes a child, three years old, + with a thumb double from the first joint. He removed the lesser thumb, + which was furnished with a nail; but to his astonishment it grew again, + and reproduced a nail. The child was then taken to an eminent London + surgeon, and the newly-grown thumb was wholly removed by its + socket-joint, but again it grew and reproduced a nail. Dr. Struthers + mentions a case of partial regrowth of an additional thumb, amputated + when the child was three months old; and the late Dr. Falconer + communicated to me an analogous case which had fallen under his own + observation. A gentleman, who first called my attention to this subject, + has given me the following facts which occurred in his own family. He + himself, two brothers, and a sister were born with an extra digit to each + extremity. His parents were not affected, and there was no tradition in + the family, or in the village in which the family had long resided, of + any member having been thus affected. Whilst a child, both additional + toes, which were attached by bones, were rudely cut off; but the stump of + one grew again, and a second operation was performed in his thirty-third + year.</p> + +<p><!-- Page 15 --><span class="pagenum"><a name="page15"></a>{15}</span></p> + + <p>He has had fourteen children, of whom three have inherited additional + digits; and one of them, when about six weeks old, was operated on by an + eminent surgeon. The additional finger, which was attached by bone to the + outer side of the hand, was removed at the joint; the wound healed, but + immediately the digit began growing; and in about three months' time the + stump was removed for the second time by the root. But it has since grown + again, and is now fully a third of an inch in length, including a bone; + so that it will for the third time have to be operated on.</p> + + <p>Now the normal digits in adult man and other mammals, in birds, and, + as I believe, in true reptiles, have no power of regrowth. The nearest + approach to this power is exhibited by the occasional reappearance in man + of imperfect nails on the stumps of his fingers after amputation.<a + name="NtA_33" href="#Nt_33"><sup>[33]</sup></a> But man in his embryonic + condition has a considerable power of reproduction, for Sir J. Simpson<a + name="NtA_34" href="#Nt_34"><sup>[34]</sup></a> has several times + observed arms which had been cut off in the womb by bands of false + membrane, and which had grown again to a certain extent. In one instance, + the extremity was "divided into three minute nodules, on two of which + small points of nails could be detected;" so that these nodules clearly + represented fingers in process of regrowth. When, however, we descend to + the lower vertebrate classes, which are generally looked at as + representing the higher classes in their embryonic condition, we find + ample powers of regrowth. Spallanzani<a name="NtA_35" + href="#Nt_35"><sup>[35]</sup></a> cut off the legs and tail of a + salamander six times, and Bonnet eight times, successively, and they were + reproduced. An additional digit beyond the proper number was occasionally + formed after Bonnet had cut off or had divided longitudinally the hand or + foot, and in one instance three additional digits were thus formed.<a + name="NtA_36" href="#Nt_36"><sup>[36]</sup></a> These latter cases appear + at first sight quite distinct from the congenital production of + additional digits in the higher animals; but theoretically, as we shall + see in a future chapter, they probably present no real difference. The + larvæ or tadpoles of the tailless Batrachians, but not the adults,<a + name="NtA_37" href="#Nt_37"><sup>[37]</sup></a> are capable of + reproducing lost members.<a name="NtA_38" + href="#Nt_38"><sup>[38]</sup></a> Lastly, as I have been informed by Mr. + J. J. Briggs and Mr. F. Buckland, when portions of the pectoral and tail + fins of various <!-- Page 16 --><span class="pagenum"><a + name="page16"></a>{16}</span>fresh-water fish are cut off, they are + perfectly reproduced in about six weeks' time.</p> + +</blockquote> + + <p>From these several facts we may infer that supernumerary digits in man + retain to a certain extent an embryonic condition, and that they resemble + in this respect the normal digits and limbs in the lower vertebrate + classes. They also resemble the digits of some of the lower animals in + the number exceeding five; for no mammal, bird, existing reptile, or + amphibian (unless the tubercle on the hind feet of the toad and other + tailless Batrachians be viewed as a digit) has more than five; whilst + fishes sometimes have in their pectoral fins as many as twenty metacarpal + and phalangeal bones, which, together with the bony filaments, apparently + represent our digits with their nails. So, again, in certain extinct + reptiles, namely, the Ichthyopterygia, "the digits may be seven, eight, + or nine in number, a significant mark," says Professor Owen, "of piscine + affinity."<a name="NtA_39" href="#Nt_39"><sup>[39]</sup></a></p> + + <p>We encounter much difficulty in attempting to reduce these various + facts to any rule or law. The inconstant number of the additional + digits—their irregular attachment to either the inner or outer + margin of the hand—the gradation which can be traced from a mere + loose rudiment of a single digit to a completely double hand—the + occasional appearance of additional digits in the salamander after a limb + has been amputated—these various facts appear to indicate mere + fluctuating monstrosity; and this perhaps is all that can be safely said. + Nevertheless, as supernumerary digits in the higher animals, from their + power of regrowth and from the number thus acquired exceeding five, + partake of the nature of the digits in the lower vertebrate + animals;—as they occur by no means rarely, and are transmitted with + remarkable strength, though perhaps not more strongly than some other + anomalies;—and as with animals which have fewer than five digits, + when an additional one appears it is generally due to the development of + a visible rudiment;—we are led in all cases to suspect, that, + although no actual rudiment can be detected, yet that a latent tendency + to the formation of an additional digit exists in all mammals, including + man. On this view, as we shall more plainly see in the <!-- Page 17 + --><span class="pagenum"><a name="page17"></a>{17}</span>next chapter + when discussing latent tendencies, we should have to look at the whole + case as one of reversion to an enormously remote, lowly-organised, and + multidigitate progenitor.</p> + +<hr class="short" /> + + <p>I may here allude to a class of facts closely allied to, but somewhat + different from, ordinary cases of inheritance. Sir H. Holland<a + name="NtA_40" href="#Nt_40"><sup>[40]</sup></a> states that brothers and + sisters of the same family are frequently affected, often at about the + same age, by the same peculiar disease, not known to have previously + occurred in the family. He specifies the occurrence of diabetes in three + brothers under ten years old; he also remarks that children of the same + family often exhibit in common infantile diseases the same peculiar + symptoms. My father mentioned to me the case of four brothers who died + between the ages of sixty and seventy, in the same highly peculiar + comatose state. An instance has been already given of supernumerary + digits appearing in four children out of six in a previously unaffected + family. Dr. Devay states<a name="NtA_41" + href="#Nt_41"><sup>[41]</sup></a> that two brothers married two sisters, + their first-cousins, none of the four nor any relation being an albino; + but the seven children produced from this double marriage were all + perfect albinoes. Some of these cases, as Mr. Sedgwick<a name="NtA_42" + href="#Nt_42"><sup>[42]</sup></a> has shown, are probably the result of + reversion to a remote ancestor, of whom no record had been preserved; and + all these cases are so far directly connected with inheritance that no + doubt the children inherited a similar constitution from their parents, + and, from being exposed to nearly similar conditions of life, it is not + surprising that they should be affected in the same manner and at the + same period of life.</p> + +<hr class="short" /> + + <p>Most of the facts hitherto given have served to illustrate the force + of inheritance, but we must now consider cases, grouped as well as the + subject allows into classes, showing how feeble, capricious, or deficient + the power of inheritance sometimes is. When a new peculiarity first + appears, we can never predict whether it will be inherited. If both + parents from their birth present <!-- Page 18 --><span class="pagenum"><a + name="page18"></a>{18}</span>the same peculiarity, the probability is + strong that it will be transmitted to at least some of their offspring. + We have seen that variegation is transmitted much more feebly by seed + from a branch which had become variegated through bud-variation, than + from plants which were variegated as seedlings. With most plants the + power of transmission notoriously depends on some innate capacity in the + individual: thus Vilmorin<a name="NtA_43" + href="#Nt_43"><sup>[43]</sup></a> raised from a peculiarly coloured + balsam some seedlings, which all resembled their parent; but of these + seedlings some failed to transmit the new character, whilst others + transmitted it to all their descendants during several successive + generations. So again with a variety of the rose, two plants alone out of + six were found by Vilmorin to be capable of transmitting the desired + character.</p> + +<blockquote class="b1n"> + + <p>The weeping or pendulous growth of trees is strongly inherited in some + cases, and, without any assignable reason, feebly in other cases. I have + selected this character as an instance of capricious inheritance, because + it is certainly not proper to the parent-species, and because, both sexes + being borne on the same tree, both tend to transmit the same character. + Even supposing that there may have been in some instances crossing with + adjoining trees of the same species, it is not probable that all the + seedlings would have been thus affected. At Moccas Court there is a + famous weeping oak; many of its branches "are 30 feet long, and no + thicker in any part of this length than a common rope:" this tree + transmits its weeping character, in a greater or less degree, to all its + seedlings; some of the young oaks being so flexible that they have to be + supported by props; others not showing the weeping tendency till about + twenty years old.<a name="NtA_44" href="#Nt_44"><sup>[44]</sup></a> Mr. + Rivers fertilized, as he informs me, the flowers of a new Belgian weeping + thorn (<i>Cratægus <span class="correction" title="Original reads `oxycantha', corrected by errata, page viii." + >oxyacantha</span></i>) with pollen from a crimson not-weeping variety, + and three young trees, "now six or seven years old, show a decided + tendency to be pendulous, but as yet are not so much so as the + mother-plant." According to Mr. MacNab,<a name="NtA_45" + href="#Nt_45"><sup>[45]</sup></a> seedlings from a magnificent weeping + birch (<i>Betula alba</i>), in the Botanic Garden at Edinburgh, grew for + the first ten or fifteen years upright, but then all became weepers like + their parent. A peach with pendulous branches, like those of the weeping + willow, has been found capable of propagation by seed.<a name="NtA_46" + href="#Nt_46"><sup>[46]</sup></a> Lastly, a weeping and almost prostrate + yew (<i>Taxus baccata</i>) was found in a hedge in Shropshire; it was a + male, but one branch bore female flowers, and produced berries; these, + <!-- Page 19 --><span class="pagenum"><a + name="page19"></a>{19}</span>being sown, produced seventeen trees, all of + which had exactly the same peculiar habit with the parent-tree.<a + name="NtA_47" href="#Nt_47"><sup>[47]</sup></a></p> + + <p>These facts, it might have been thought, would have been sufficient to + render it probable that a pendulous habit would in all cases be strictly + inherited. But let us look to the other side. Mr. MacNab<a name="NtA_48" + href="#Nt_48"><sup>[48]</sup></a> sowed seeds of the weeping beech + (<i>Fagus sylvanica</i>), but succeeded in raising only common beeches. + Mr. Rivers, at my request, raised a number of seedlings from three + distinct varieties of weeping elm; and at least one of the parent-trees + was so situated that it could not have been crossed by any other elm; but + none of the young trees, now about a foot or two in height, show the + least signs of weeping. Mr. Rivers formerly sowed above twenty thousand + seeds of the weeping ash (<i>Fraxinus excelsior</i>), and not a single + seedling was in the least degree pendulous: in Germany, M. Borchmeyer + raised a thousand seedlings, with the same result. Nevertheless, Mr. + Anderson, of the Chelsea Botanic Garden, by sowing seed from a weeping + ash, which was found before the year 1780, in Cambridgeshire, raised + several pendulous trees.<a name="NtA_49" + href="#Nt_49"><sup>[49]</sup></a> Professor Henslow also informs me that + some seedlings from a female weeping ash in the Botanic Garden at + Cambridge were at first a little pendulous, but afterwards became quite + upright: it is probable that this latter tree, which transmits to a + certain extent its pendulous habit, was derived by a bud from the same + original Cambridgeshire stock; whilst other weeping ashes may have had a + distinct origin. But the crowning case, communicated to me by Mr. Rivers, + which shows how capricious is the inheritance of a pendulous habit, is + that a variety of another species of ash (<i>F. lentiscifolia</i>) which + was formerly pendulous, "now about twenty years old has long lost this + habit, every shoot being remarkably erect; but seedlings formerly raised + from it were perfectly prostrate, the stems not rising more than two + inches above the ground." Thus the weeping variety of the common ash, + which has been extensively propagated by buds during a long period, did + not, with Mr. Rivers, transmit its character to one seedling out of above + twenty thousand; whereas the weeping variety of a second species of ash, + which could not, whilst grown in the same garden, retain its own weeping + character, transmitted to its seedlings the pendulous habit in + excess!</p> + + <p>Many analogous facts could be given, showing how apparently capricious + is the principle of inheritance. All the seedlings from a variety of the + Barberry (<i>B. vulgaris</i>) with red leaves inherited the same + character; only about one-third of the seedlings of the copper Beech + (<i>Fagus sylvatica</i>) had purple leaves. Not one out of a hundred + seedlings of a variety of the <i>Cerasus padus</i>, with yellow fruit, + bore yellow fruit: one-twelfth of the seedlings of the variety of + <i>Cornus mascula</i>, with yellow fruit, came true:<a name="NtA_50" + href="#Nt_50"><sup>[50]</sup></a> and lastly, all the trees raised by my + father from a yellow-berried holly (<i>Ilex aquifolium</i>), <!-- Page 20 + --><span class="pagenum"><a name="page20"></a>{20}</span>found wild, + produced yellow berries. Vilmorin<a name="NtA_51" + href="#Nt_51"><sup>[51]</sup></a> observed in a bed of <i>Saponaria + calabrica</i> an extremely dwarf variety, and raised from it a large + number of seedlings; some of these partially resembled their parent, and + he selected their seed; but the grandchildren were not in the least + dwarfed: on the other hand, he observed a stunted and bushy variety of + <i>Tagetes signata</i> growing in the midst of the common varieties by + which it was probably crossed; for most of the seedlings raised from this + plant were intermediate in character, only two perfectly resembling their + parent; but seed saved from these two plants reproduced the new variety + so truly, that hardly any selection has since been necessary.</p> + + <p>Flowers transmit their colour truly, or most capriciously. Many + annuals come true: thus I purchased German seeds of thirty-four named + sub-varieties of one <i>race</i> of ten-week stocks (<i>Matthiola + annua</i>), and raised a hundred and forty plants, all of which, with the + exception of a single plant, came true. In saying this, however, it must + be understood that I could distinguish only twenty kinds out of the + thirty-four named sub-varieties; nor did the colour of the flower always + correspond with the name affixed to the packet; but I say that they came + true, because in each of the thirty-six short rows every plant was + absolutely alike, with the one single exception. Again, I procured + packets of German seed of twenty-five named varieties of common and + quilled asters, and raised a hundred and twenty-four plants; of these, + all except ten were true in the above limited sense; and I considered + even a wrong shade of colour as false.</p> + + <p>It is a singular circumstance that white varieties generally transmit + their colour much more truly than any other variety. This fact probably + stands in close relation with one observed by Verlot,<a name="NtA_52" + href="#Nt_52"><sup>[52]</sup></a> namely, that flowers which are normally + white rarely vary into any other colour. I have found that the white + varieties of <i>Delphinium consolida</i> and of the Stock are the truest. + It is, indeed, sufficient to look through a nurseryman's seed-list, to + see the large number of white varieties which can be propagated by seed. + The several coloured varieties of the sweet-pea (<i>Lathyrus + odoratus</i>) are very true; but I hear from Mr. Masters, of Canterbury, + who has particularly attended to this plant, that the white variety is + the truest. The hyacinth, when propagated by seed, is extremely + inconstant in colour, but "white hyacinths almost always give by seed + white-flowered plants;"<a name="NtA_53" href="#Nt_53"><sup>[53]</sup></a> + and Mr. Masters informs me that the yellow varieties also reproduce their + colour, but of different shades. On the other hand, pink and blue + varieties, the latter being the natural colour, are not nearly so true: + hence, as Mr. Masters has remarked to me, "we see that a garden variety + may acquire a more permanent habit than a natural species;" but it should + have been added, that this occurs under cultivation, and therefore under + changed conditions.</p> + + <p>With many flowers, especially perennials, nothing can be more + fluctuating than the colour of the seedlings, as is notoriously the case + with verbenas, carnations, dahlias, cinerarias, and others.<a + name="NtA_54" href="#Nt_54"><sup>[54]</sup></a> I sowed seed of twelve + <!-- Page 21 --><span class="pagenum"><a + name="page21"></a>{21}</span>named varieties of Snapdragon + (<i>Antirrhinum majus</i>), and utter confusion was the result. In most + cases the extremely fluctuating colour of seedling plants is probably in + chief part due to crosses between differently-coloured varieties during + previous generations. It is almost certain that this is the case with the + polyanthus and coloured primrose (<i>Primula veris</i> and + <i>vulgaris</i>), from their reciprocally dimorphic structure;<a + name="NtA_55" href="#Nt_55"><sup>[55]</sup></a> and these are plants + which florists speak of as never come true by seed: but if care be taken + to prevent crossing, neither species is by any means very inconstant in + colour; thus I raised twenty-three plants from a purple primrose, + fertilised by Mr. J. Scott with its own pollen, and eighteen came up + purple of different shades, and only five reverted to the ordinary yellow + colour: again, I raised twenty plants from a bright-red cowslip, + similarly treated by Mr. Scott, and every one perfectly resembled its + parent in colour, as likewise did, with the exception of a single plant, + 73 grandchildren. Even with the most variable flowers, it is probable + that each delicate shade of colour might be permanently fixed so as to be + transmitted by seed, by cultivation in the same soil, by long-continued + selection, and especially by the prevention of crosses. I infer this from + certain annual larkspurs (<i>Delphinium consolida</i> and <i>ajacis</i>), + of which common seedlings present a greater diversity of colour than any + other plant known to me; yet on procuring seed of five named German + varieties of <i>D. consolida</i>, only nine plants out of ninety-four + were false; and the seedlings of six varieties of <i>D. ajacis</i> were + true in the same manner and degree as with the stocks above described. A + distinguished botanist maintains that the annual species of Delphinium + are always self-fertilised; therefore I may mention that thirty-two + flowers on a branch of <i>D. consolida</i>, enclosed in a net, yielded + twenty-seven capsules, with an average of 17.2 seed in each; whilst five + flowers, under the same net, which were artificially fertilised, in the + same manner as must be effected by bees during their incessant visits, + yielded five capsules with an average of 35.2 fine seed; and this shows + that the agency of insects is necessary for the full fertility of this + plant. Analogous facts could be given with respect to the crossing of + many other flowers, such as carnations, &c., of which the varieties + fluctuate much in colour.</p> + + <p>As with flowers, so with our domesticated animals, no character is + more variable than colour, and probably in no animal more so than with + the horse. Yet with a little care in breeding, it appears that races of + any colour might soon be formed. Hofacker gives the result of matching + two hundred and sixteen mares of four different colours with + like-coloured stallions, without regard to the colour of their ancestors; + and of the two hundred and sixteen colts born, eleven alone failed to + inherit the colour of their parents: Autenrieth and Ammon assert that, + after two generations, colts of a uniform colour are produced with + certainty.<a name="NtA_56" href="#Nt_56"><sup>[56]</sup></a></p> + +</blockquote> + + <p>In a few rare cases peculiarities fail to be inherited, apparently + from the force of inheritance being too strong. I have been assured by + breeders of the canary-bird that to get a good <!-- Page 22 --><span + class="pagenum"><a name="page22"></a>{22}</span>jonquil-coloured bird it + does not answer to pair two jonquils, as the colour then comes out too + strong, or is even brown. So again, if two crested canaries are paired, + the young birds rarely inherit this character:<a name="NtA_57" + href="#Nt_57"><sup>[57]</sup></a> for in crested birds a narrow space of + bare skin is left on the back of the head, where the feathers are + up-turned to form the crest, and, when both parents are thus + characterised, the bareness becomes excessive, and the crest itself fails + to be developed. Mr. Hewitt, speaking of Laced Sebright Bantams, says<a + name="NtA_58" href="#Nt_58"><sup>[58]</sup></a> that, "why this should be + so, I know not, but I am confident that those that are best laced + frequently produce offspring very far from perfect in their markings, + whilst those exhibited by myself, which have so often proved successful, + were bred from the union of heavily-laced birds with those that were + scarcely sufficiently laced."</p> + + <p>It is a singular fact that, although several deaf-mutes often occur in + the same family, and though their cousins and other relations are often + in the same condition, yet their parents are very rarely deaf-mutes. To + give a single instance: not one scholar out of 148, who were at the same + time in the London Institution, was the child of parents similarly + afflicted. So again, when a male or a female deaf-mute marries a sound + person, their children are most rarely affected: in Ireland out of 203 + children thus produced one alone was mute. Even when both parents have + been deaf-mutes, as in the case of forty-one marriages in the United + States and of six in Ireland, only two deaf and dumb children were + produced. Mr. Sedgwick,<a name="NtA_59" href="#Nt_59"><sup>[59]</sup></a> + in commenting on this remarkable and fortunate failure in the power of + transmission in the direct line, remarks that it may possibly be owing to + "excess having reversed the action of some natural law in development." + But it is safer in the present state of our knowledge to look at the + whole case as simply unintelligible.</p> + +<hr class="short" /> + + <p>With respect to the inheritance of structures mutilated by injuries or + altered by disease it is difficult to come to any <!-- Page 23 --><span + class="pagenum"><a name="page23"></a>{23}</span>definite conclusion. In + some cases mutilations have been practised for a vast number of + generations without any inherited result. Godron has remarked<a + name="NtA_60" href="#Nt_60"><sup>[60]</sup></a> that different races of + man have from time immemorial knocked out their upper incisors, cut off + joints of their fingers, made holes of immense size through the lobes of + their ears or through their nostrils, made deep gashes in various parts + of their bodies, and there is no reason whatever to suppose that these + mutilations have ever been inherited. Adhesions due to inflammation and + pits from the small-pox (and formerly many consecutive generations must + have been thus pitted) are not inherited. With respect to Jews, I have + been assured by three medical men of the Jewish faith that circumcision, + which has been practised for so many ages, has produced no inherited + effect; Blumenbach, on the other hand, asserts<a name="NtA_61" + href="#Nt_61"><sup>[61]</sup></a> that in Germany Jews are often born in + a condition rendering circumcision difficult, so that a name is here + applied to them signifying "born circumcised." The oak and other trees + must have borne galls from primeval times, yet they do not produce + inherited excrescences; many other such facts could be adduced.</p> + + <p>On the other hand, various cases have been recorded of cats, dogs, and + horses, which have had their tails, legs, &c., amputated or injured, + producing offspring with the same parts ill-formed; but as it is not at + all rare for similar malformations to appear spontaneously, all such + cases may be due to mere coincidence. Nevertheless, Dr. Prosper Lucas has + given, on good authorities, such a long list of inherited injuries, that + it is difficult not to believe in them. Thus, a cow that had lost a horn + from an accident with consequent suppuration, produced three calves which + were hornless on the same side of the head. With the horse, there seems + hardly a doubt that bony exostoses on the legs, caused by too much + travelling on hard roads, are inherited. Blumenbach records the case of a + man who had his little finger on the right hand almost cut off, and which + in consequence grew crooked, and his sons had the same finger on the same + hand similarly crooked. A soldier, fifteen years before his marriage, + lost his left eye from purulent ophthalmia, and his <!-- Page 24 --><span + class="pagenum"><a name="page24"></a>{24}</span>two sons were + microphthalmic on the same side.<a name="NtA_62" + href="#Nt_62"><sup>[62]</sup></a> In all such cases, if truthfully + reported, in which the parent has had an organ injured on one side, and + more than one child has been born with the same organ affected on the + same side, the chances against mere coincidence are enormous. But perhaps + the most remarkable and trustworthy fact is that given by Dr. + Brown-Séquard,<a name="NtA_63" href="#Nt_63"><sup>[63]</sup></a> namely, + that many young guinea-pigs inherited an epileptic tendency from parents + which had been subjected to a particular operation, inducing in the + course of a few weeks a convulsive disease like epilepsy: and it should + be especially noted that this eminent physiologist bred a large number of + guinea-pigs from animals which had not been operated on, and not one of + these manifested the epileptic tendency. On the whole, we can hardly + avoid admitting, that injuries and mutilations, especially when followed + by disease, or perhaps exclusively when thus followed, are occasionally + inherited.</p> + + <p>Although many congenital monstrosities are inherited, of which + examples have already been given, and to which may be added the lately + recorded case of the transmission during a century of hare-lip with a + cleft-palate in the writer's own family,<a name="NtA_64" + href="#Nt_64"><sup>[64]</sup></a> yet other malformations are rarely or + never inherited. Of these later cases, many are probably due to injuries + in the womb or egg, and would come under the head of non-inherited + injuries or mutilations. With plants, a long catalogue of inherited + monstrosities of the most serious and diversified nature could easily be + given; and with plants, there is no reason to suppose that monstrosities + are caused by direct injuries to the seed or embryo.</p> + +<p class="cenhead"><i>Causes of Non-inheritance.</i></p> + + <p>A large number of cases of non-inheritance are intelligible on the + principle, that a strong tendency to inheritance does exist, but <!-- + Page 25 --><span class="pagenum"><a name="page25"></a>{25}</span>that it + is overborne by hostile or unfavourable conditions of life. No one would + expect that our improved pigs, if forced during several generations to + travel about and root in the ground for their own subsistence, would + transmit, as truly as they now do, their tendency to fatten, and their + short muzzles and legs. Dray-horses assuredly would not long transmit + their great size and massive limbs, if compelled to live on a cold, damp + mountainous region; we have indeed evidence of such deterioration in the + horses which have run wild on the Falkland Islands. European dogs in + India often fail to transmit their true character. Our sheep in tropical + countries lose their wool in a few generations. There seems also to be a + close relation between certain peculiar pastures and the inheritance of + an enlarged tail in fat-tailed sheep, which form one of the most ancient + breeds in the world. With plants, we have seen that the American + varieties of maize lose their proper character in the course of two or + three generations, when cultivated in Europe. Our cabbages, which here + come so true by seed, cannot form heads in hot countries. Under changed + circumstances, periodical habits of life soon fail to be transmitted, as + the period of maturity in summer and winter wheat, barley, and vetches. + So it is with animals; for instance, a person whose statement I can + trust, procured eggs of Aylesbury ducks from that town, where they are + kept in houses and are reared as early as possible for the London market; + the ducks bred from these eggs in a distant part of England, hatched + their first brood on January 24th, whilst common ducks, kept in the same + yard and treated in the same manner, did not hatch till the end of March; + and this shows that the period of hatching was inherited. But the + grandchildren of these Aylesbury ducks completely lost their early habit + of incubation, and hatched their eggs at the same time with the common + ducks of the same place.</p> + + <p>Many cases of non-inheritance apparently result from the conditions of + life continually inducing fresh variability. We have seen that when the + seeds of pears, plums, apples, &c., are sown, the seedlings generally + inherit some degree of family likeness from the parent-variety. Mingled + with these seedlings, a few, and sometimes many, worthless, wild-looking + plants commonly appear; and their appearance may be attributed to the + principle of reversion. But scarcely a single seedling will be found <!-- + Page 26 --><span class="pagenum"><a + name="page26"></a>{26}</span>perfectly to resemble the parent-form; and + this, I believe, may be accounted for by constantly recurring variability + induced by the conditions of life. I believe in this, because it has been + observed that certain fruit-trees truly propagate their kind whilst + growing on their own roots, but when grafted on other stocks, and by this + process their natural state is manifestly affected, they produce + seedlings which vary greatly, departing from the parental type in many + characters.<a name="NtA_65" href="#Nt_65"><sup>[65]</sup></a> Metzger, as + stated in the ninth chapter, found that certain kinds of wheat brought + from Spain and cultivated in Germany, failed during many years to + reproduce themselves truly; but that at last, when accustomed to their + new conditions, they ceased to be variable,—that is, they became + amenable to the power of inheritance. Nearly all the plants which cannot + be propagated with any approach to certainty by seed, are kinds which + have long been propagated by buds, cuttings, offsets, tubers, &c., + and have in consequence been frequently exposed during their individual + lives to widely diversified conditions of life. Plants thus propagated + become so variable, that they are subject, as we have seen in the last + chapter, even to bud-variation. Our domesticated animals, on the other + hand, are not exposed during their individual lives to such extremely + diversified conditions, and are not liable to such extreme variability; + therefore they do not lose the power of transmitting most of their + characteristic features. In the foregoing remarks on non-inheritance, + crossed breeds are of course excluded, as their diversity mainly depends + on the unequal development of characters derived from either parent, + modified by the principles of reversion and prepotency.</p> + +<p class="cenhead"><i>Conclusion.</i></p> + + <p>It has, I think, been shown in the early part of this chapter how + strongly new characters of the most diversified nature, whether normal or + abnormal, injurious or beneficial, whether affecting organs of the + highest or most trifling importance, are inherited. Contrary to the + common opinion, it is often sufficient for the inheritance of some + peculiar character, that one parent alone should possess it, as in most + cases in which the rarer <!-- Page 27 --><span class="pagenum"><a + name="page27"></a>{27}</span>anomalies have been transmitted. But the + power of transmission is extremely variable: in a number of individuals + descended from the same parents, and treated in the same manner, some + display this power in a perfect manner, and in some it is quite + deficient; and for this difference no reason can be assigned. In some + cases the effects of injuries or mutilations apparently are inherited; + and we shall see in a future chapter that the effects of the + long-continued use and disuse of parts are certainly inherited. Even + those characters which are considered the most fluctuating, such as + colour, are with rare exceptions transmitted much more forcibly than is + generally supposed. The wonder, indeed, in all cases is not that any + character should be transmitted, but that the power of inheritance should + ever fail. The checks to inheritance, as far as we know them, are, + firstly, circumstances hostile to the particular character in question; + secondly, conditions of life incessantly inducing fresh variability; and + lastly, the crossing of distinct varieties during some previous + generation, together with reversion or atavism—that is, the + tendency in the child to resemble its grand-parents or more remote + ancestors instead of its immediate parents. This latter subject will be + fully discussed in the following chapter.</p> + +<hr class="full" /> + +<p><!-- Page 28 --><span class="pagenum"><a name="page28"></a>{28}</span></p> + +<h3>CHAPTER XIII.</h3> + +<p class="cenhead">INHERITANCE <i>continued</i>—REVERSION OR ATAVISM.</p> + +<blockquote class="b1n"> + + <p><span class="scac">DIFFERENT FORMS OF REVERSION</span>—<span + class="scac">IN PURE OR UNCROSSED BREEDS, AS IN PIGEONS, FOWLS, HORNLESS + CATTLE AND SHEEP, IN CULTIVATED PLANTS</span>—<span + class="scac">REVERSION IN FERAL ANIMALS AND PLANTS</span>—<span + class="scac">REVERSION IN CROSSED VARIETIES AND + SPECIES</span>—<span class="scac">REVERSION THROUGH + BUD-PROPAGATION, AND BY SEGMENTS IN THE SAME FLOWER OR + FRUIT</span>—<span class="scac">IN DIFFERENT PARTS OF THE BODY IN + THE SAME ANIMAL</span>—<span class="scac">THE ACT OF CROSSING A + DIRECT CAUSE OF REVERSION, VARIOUS CASES OF, WITH + INSTINCTS</span>—<span class="scac">OTHER PROXIMATE CAUSES OF + REVERSION</span>—<span class="scac">LATENT + CHARACTERS</span>—<span class="scac">SECONDARY SEXUAL + CHARACTERS</span>—<span class="scac">UNEQUAL DEVELOPMENT OF THE TWO + SIDES OF THE BODY</span>—<span class="scac">APPEARANCE WITH + ADVANCING AGE OF CHARACTERS DERIVED FROM A CROSS</span>—<span + class="scac">THE GERM WITH ALL ITS LATENT CHARACTERS A WONDERFUL + OBJECT</span>—<span class="scac">MONSTROSITIES</span>—<span + class="scac">PELORIC FLOWERS DUE IN SOME CASES TO REVERSION.</span></p> + +</blockquote> + + <p>The great principle of inheritance to be discussed in this chapter has + been recognised by agriculturists and authors of various nations, as + shown by the scientific term <i>Atavism</i>, derived from atavus, an + ancestor; by the English terms of <i>Reversion</i>, or <i>Throwing + back</i>; by the French <i>Pas-en-arrière</i>; and by the German + <i>Rück-schlag</i>, or <i>Rück-schritt</i>. When the child resembles + either grandparent more closely than its immediate parents, our attention + is not much arrested, though in truth the fact is highly remarkable; but + when the child resembles some remote ancestor, or some distant member in + a collateral line,—and we must attribute the latter case to the + descent of all the members from a common progenitor,—we feel a just + degree of astonishment. When one parent alone displays some + newly-acquired and generally inheritable character, and the offspring do + not inherit it, the cause may lie in the other parent having the power of + prepotent transmission. But when both parents are similarly + characterised, and the child does not, whatever the cause may be, inherit + the character in question, but resembles its grandparents, we have one of + the simplest cases of reversion. We continually see another and even more + simple case of atavism, though not generally included under this head, + namely, when <!-- Page 29 --><span class="pagenum"><a + name="page29"></a>{29}</span>the son more closely resembles his maternal + than his paternal grandsire in some male attribute, as in any peculiarity + in the beard of man, the horns of the bull, the hackles or comb of the + cock, or, as in certain diseases necessarily confined to the male sex; + for the mother cannot possess or exhibit such male attributes, yet the + child has inherited them, through her blood, from his maternal + grandsire.</p> + + <p>The cases of reversion may be divided into two main classes, which, + however, in some instances, blend into each other; namely, first, those + occurring in a variety or race which has not been crossed, but has lost + by variation some character that it formerly possessed, and which + afterwards reappears. The second class includes all cases in which a + distinguishable individual, sub-variety, race, or species, has at some + former period been crossed with a distinct form, and a character derived + from this cross, after having disappeared during one or several + generations, suddenly reappears. A third class, differing only in the + manner of reproduction, might be formed to include all cases of reversion + effected by means of buds, and therefore independent of true or seminal + generation. Perhaps even a fourth class might be instituted, to include + reversions by segments in the same individual flower or fruit, and in + different parts of the body in the same individual animal as it grows + old. But the two first main classes will be sufficient for our + purpose.</p> + +<hr class="short" /> + + <p><i>Reversion to lost Characters by pure or uncrossed + forms.</i>—Striking instances of this first class of cases were + given in the sixth chapter, namely, of the occasional reappearance, in + variously-coloured pure breeds of the pigeon, of blue birds with all the + marks which characterise the wild <i>Columba livia</i>. Similar cases + were given in the case of the fowl. With the common ass, as we now know + that the legs of the wild progenitor are striped, we may feel assured + that the occasional appearance of such stripes in the domestic animal is + a case of simple reversion. But I shall be compelled to refer again to + these cases, and therefore will here pass them over.</p> + + <p>The aboriginal species from which our domesticated cattle and sheep + are descended, no doubt possessed horns; but several hornless breeds are + now well established. Yet in these—for instance, <!-- Page 30 + --><span class="pagenum"><a name="page30"></a>{30}</span>in Southdown + sheep—"it is not unusual to find among the male lambs some with + small horns." The horns, which thus occasionally reappear in other polled + breeds, either "grow to the full size, or are curiously attached to the + skin alone and hang loosely down, or drop off."<a name="NtA_66" + href="#Nt_66"><sup>[66]</sup></a> The Galloways and Suffolk cattle have + been hornless for the last 100 or 150 years, but a horned calf, with the + horn often loosely attached, is occasionally born.<a name="NtA_67" + href="#Nt_67"><sup>[67]</sup></a></p> + + <p>There is reason to believe that sheep in their early domesticated + condition were "brown or dingy black;" but even in the time of David + certain flocks were spoken of as white as snow. During the classical + period the sheep of Spain are described by several ancient authors as + being black, red, or tawny.<a name="NtA_68" + href="#Nt_68"><sup>[68]</sup></a> At the present day, notwithstanding the + great care which is taken to prevent it, particoloured lambs and some + entirely black are occasionally dropped by our most highly improved and + valued breeds, such as the Southdowns. Since the time of the famous + Bakewell, during the last century, the Leicester sheep have been bred + with the most scrupulous care; yet occasionally grey-faced, or + black-spotted, or wholly black lambs appear.<a name="NtA_69" + href="#Nt_69"><sup>[69]</sup></a> This occurs still more frequently with + the less improved breeds, such as the Norfolks.<a name="NtA_70" + href="#Nt_70"><sup>[70]</sup></a> As bearing on this tendency in sheep to + revert to dark colours, I may state (though in doing so I trench on the + reversion of crossed breeds, and likewise on the subject of prepotency) + that the Rev. W. D. Fox was informed that seven white Southdown ewes were + put to a so-called Spanish ram, which had two small black spots on his + sides, and they produced thirteen lambs, all perfectly black. Mr. Fox + believes that this ram belonged to a breed which he has himself kept, and + which is always spotted with black and white; and he finds that Leicester + sheep crossed by rams of this breed always produce black lambs: he has + gone on recrossing these crossed sheep with pure white Leicesters during + three successive <!-- Page 31 --><span class="pagenum"><a + name="page31"></a>{31}</span>generations, but always with the same + result. Mr. Fox was also told by the friend from whom the spotted breed + was procured, that he likewise had gone on for six or seven generations + crossing with white sheep, but still black lambs were invariably + produced.</p> + + <p>Similar facts could be given with respect to tailless breeds of + various animals. For instance, Mr. Hewitt<a name="NtA_71" + href="#Nt_71"><sup>[71]</sup></a> states that chickens bred from some + Rumpless fowls, which were reckoned so good that they won a prize at an + exhibition, "in a considerable number of instances were furnished with + fully developed tail-feathers." On inquiry, the original breeder of these + fowls stated that, from the time when he had first kept them, they had + often produced fowls furnished with tails; but that these latter would + again reproduce rumpless chickens.</p> + + <p>Analogous cases of reversion occur in the vegetable kingdom; thus + "from seeds gathered from the finest cultivated varieties of Heartsease + (<i>Viola tricolor</i>), plants perfectly wild both in their foliage and + their flowers are frequently produced;"<a name="NtA_72" + href="#Nt_72"><sup>[72]</sup></a> but the reversion in this instance is + not to a very ancient period, for the best existing varieties of the + heartsease are of comparatively modern origin. With most of our + cultivated vegetables there is some tendency to reversion to what is + known to be, or may be presumed to be, their aboriginal state; and this + would be more evident if gardeners did not generally look over their beds + of seedlings, and pull up the false plants or "rogues" as they are + called. It has already been remarked, that some few seedling apples and + pears generally resemble, but apparently are not identical with, the wild + trees from which they are descended. In our turnip<a name="NtA_73" + href="#Nt_73"><sup>[73]</sup></a> and carrot-beds a few plants often + "break"—that is, flower too soon; and their roots are generally + found to be hard and stringy, as in the parent-species. By the aid of a + little selection, carried on during a few generations, most of our + cultivated plants could probably be brought back, without any great + change in their conditions of life, to a wild or nearly wild condition: + Mr. Buckman has effected this with the parsnip;<a name="NtA_74" + href="#Nt_74"><sup>[74]</sup></a> <!-- Page 32 --><span + class="pagenum"><a name="page32"></a>{32}</span>and Mr. Hewett C. Watson, + as he informs me, selected, during three generations, "the most diverging + plants of Scotch kail, perhaps one of the least modified varieties of the + cabbage; and in the third generation some of the plants came very close + to the forms now established in England about old castle-walls, and + called indigenous."</p> + +<hr class="short" /> + + <p><i>Reversion in Animals and Plants which have run wild.</i>—In + the cases hitherto considered, the reverting animals and plants have not + been exposed to any great or abrupt change in their conditions of life + which could have induced this tendency; but it is very different with + animals and plants which have become feral or run wild. It has been + repeatedly asserted in the most positive manner by various authors, that + feral animals and plants invariably return to their primitive specific + type. It is curious on what little evidence this belief rests. Many of + our domesticated animals could not subsist in a wild state; thus, the + more highly improved breeds of the pigeon will not "field" or search for + their own food. Sheep have never become feral, and would be destroyed by + almost every beast of prey. In several cases we do not know the + aboriginal parent-species, and cannot possibly tell whether or not there + has been any close degree of reversion. It is not known in any instance + what variety was first turned out; several varieties have probably in + some cases run wild, and their crossing alone would tend to obliterate + their proper character. Our domesticated animals and plants, when they + run wild, must always be exposed to new conditions of life, for, as Mr. + Wallace<a name="NtA_75" href="#Nt_75"><sup>[75]</sup></a> has well + remarked, they have to obtain their own food, and are exposed to + competition with the native productions. Under these circumstances, if + our domesticated animals did not undergo change of some kind, the result + would be quite opposed to the conclusions arrived at in this work. + Nevertheless, I do not doubt that the simple fact of animals and plants + becoming feral, does cause some tendency to reversion to the primitive + state; though this tendency has been much exaggerated by some + authors.</p> + +<p><!-- Page 33 --><span class="pagenum"><a name="page33"></a>{33}</span></p> + +<blockquote class="b1n"> + + <p>I will briefly run through the recorded cases. With neither horses nor + cattle is the primitive stock known; and it has been shown in former + chapters that they have assumed different colours in different countries. + Thus the horses which have run wild in South America are generally + brownish-bay, and in the East dun-coloured; their heads have become + larger and coarser, and this may be due to reversion. No careful + description has been given of the feral goat. Dogs which have run wild in + various countries have hardly anywhere assumed a uniform character; but + they are probably descended from several domestic races, and aboriginally + from several distinct species. Feral cats, both in Europe and La Plata, + are regularly striped; in some cases they have grown to an unusually + large size, but do not differ from the domestic animal in any other + character. When variously-coloured tame rabbits are turned out in Europe, + they generally reacquire the colouring of the wild animal; there can be + no doubt that this does really occur, but we should remember that + oddly-coloured and conspicuous animals would suffer much from beasts of + prey and from being easily shot; this at least was the opinion of a + gentleman who tried to stock his woods with a nearly white variety; and + when thus destroyed, they would in truth be supplanted by, instead of + being transformed into, the common rabbit. We have seen that the feral + rabbits of Jamaica, and especially of Porto Santo, have assumed new + colours and other new characters. The best known case of reversion, and + that on which the widely-spread belief in its universality apparently + rests, is that of pigs. These animals have run wild in the West Indies, + South America, and the Falkland Islands, and have everywhere acquired the + dark colour, the thick bristles, and great tusks of the wild boar; and + the young have reacquired longitudinal stripes. But even in the case of + the pig, Roulin describes the half-wild animals in different parts of + South America as differing in several respects. In Louisiana the pig<a + name="NtA_76" href="#Nt_76"><sup>[76]</sup></a> has run wild, and is said + to differ a little in form, and much in colour, from the domestic animal, + yet does not closely resemble the wild boar of Europe. With pigeons and + fowls,<a name="NtA_77" href="#Nt_77"><sup>[77]</sup></a> it is not known + what variety was first turned out, nor what character the feral birds + have assumed. The guinea-fowl in the West Indies, when feral, seems to + vary more than in the domesticated state.</p> + + <p>With respect to plants run wild, Dr. Hooker<a name="NtA_78" + href="#Nt_78"><sup>[78]</sup></a> has strongly insisted on what slight + evidence the common belief in their power of reversion rests. Godron<a + name="NtA_79" href="#Nt_79"><sup>[79]</sup></a> describes wild turnips, + carrots, and celery; but these plants in their cultivated state hardly + differ from their wild prototypes, except in the <!-- Page 34 --><span + class="pagenum"><a name="page34"></a>{34}</span>succulency and + enlargement of certain parts,—characters which would be surely lost + by plants growing in a poor soil and struggling with other plants. No + cultivated plant has run wild on so enormous a scale as the cardoon + (<i>Cynara cardunculus</i>) in La Plata. Every botanist who has seen it + growing there, in vast beds, as high as a horse's back, has been struck + with its peculiar appearance; but whether it differs in any important + point from the cultivated Spanish form, which is said not to be prickly + like its American descendant, or whether it differs from he wild + Mediterranean species, which is said not to be social, I do not know.</p> + +</blockquote> + +<hr class="short" /> + + <p><i>Reversion to Characters derived from a Cross, in the case of + Sub-varieties, Races, and Species.</i>—When an individual having + some recognizable peculiarity unites with another of the same + sub-variety, not having the peculiarity in question, it often reappears + in the descendants after an interval of several generations. Every one + must have noticed, or heard from old people of children closely + resembling in appearance or mental disposition, or in so small and + complex a character as expression, one of their grandparents, or some + more distant collateral relation. Very many anomalies of structure and + diseases,<a name="NtA_80" href="#Nt_80"><sup>[80]</sup></a> of which + instances have been given in the last chapter, have come into a family + from one parent, and have reappeared in the progeny after passing over + two or three generations. The following case has been communicated to me + on good authority, and may, I believe, be fully trusted: a pointer-bitch + produced seven puppies; four were marked with blue and white, which is so + unusual a colour with pointers that she was thought to have played false + with one of the greyhounds, and the whole litter was condemned; but the + gamekeeper was permitted to save one as a curiosity. Two years afterwards + a friend of the owner saw the young dog, and declared that he was the + image of his old pointer-bitch Sappho, the only blue and white pointer of + pure descent which he had ever seen. This led to close inquiry, and it + was proved that he was the great-great-grandson of Sappho; so that, + according to the common expression, he had only 1-16th of her blood in + his veins. Here it can hardly be doubted that a character derived from a + cross with an individual of the same variety reappeared after passing + over three generations.</p> + +<p><!-- Page 35 --><span class="pagenum"><a name="page35"></a>{35}</span></p> + + <p>When two distinct races are crossed, it is notorious that the tendency + in the offspring to revert to one or both parent-forms is strong, and + endures for many generations. I have myself seen the clearest evidence of + this in crossed pigeons and with various plants. Mr. Sidney<a + name="NtA_81" href="#Nt_81"><sup>[81]</sup></a> states that, in a litter + of Essex pigs, two young ones appeared which were the image of the + Berkshire boar that had been used twenty-eight years before in giving + size and constitution to the breed. I observed in the farmyard at Betley + Hall some fowls showing a strong likeness to the Malay breed, and was + told by Mr. Tollet that he had forty years before crossed his birds with + Malays; and that, though he had at first attempted to get rid of this + strain, he had subsequently given up the attempt in despair, as the Malay + character would reappear.</p> + + <p>This strong tendency in crossed breeds to revert has given rise to + endless discussions in how many generations after a single cross, either + with a distinct breed or merely with an inferior animal, the breed may be + considered as pure, and free from all danger of reversion. No one + supposes that less than three generations suffices, and most breeders + think that six, seven, or eight are necessary, and some go to still + greater lengths.<a name="NtA_82" href="#Nt_82"><sup>[82]</sup></a> But + neither in the case of a breed which has been contaminated by a single + cross, nor when, in the attempt to form an intermediate breed, half-bred + animals have been matched together during many generations, can any rule + be laid down how soon the tendency to reversion will be obliterated. It + depends on the difference in the strength or prepotency of transmission + in the two parent-forms, on their actual amount of difference, and on the + nature of the conditions of life to which the crossed offspring are + exposed. But we must be careful not to confound these cases of reversion + to characters gained from a cross, with those given under the first + class, in which characters originally common to <i>both</i> parents, but + lost at some former period, reappear; for such characters may recur after + an almost indefinite number of generations.</p> + +<p><!-- Page 36 --><span class="pagenum"><a name="page36"></a>{36}</span></p> + + <p>The law of reversion is equally powerful with hybrids, when they are + sufficiently fertile to breed together, or when they are repeatedly + crossed with either pure parent-form, as with mongrels. It is not + necessary to give instances, for in the case of plants almost every one + who has worked on this subject from the time of Kölreuter to the present + day has insisted on this tendency. Gärtner has recorded some good + instances; but no one has given more striking cases than Naudin.<a + name="NtA_83" href="#Nt_83"><sup>[83]</sup></a> The tendency differs in + degree or strength in different groups, and partly depends, as we shall + presently see, on the fact of the parent-plants having been long + cultivated. Although the tendency to reversion is extremely general with + nearly all mongrels and hybrids, it cannot be considered as invariably + characteristic of them; there is, also, reason to believe that it may be + mastered by long-continued selection; but these subjects will more + properly be discussed in a future chapter on Crossing. From what we see + of the power and scope of reversion, both in pure races and when + varieties or species are crossed, we may infer that characters of almost + every kind are capable of reappearance after having been lost for a great + length of time. But it does not follow from this that in each particular + case certain characters will reappear: for instance, this will not occur + when a race is crossed with another endowed with prepotency of + transmission. In some few cases the power of reversion wholly fails, + without our being able to assign any cause for the failure: thus it has + been stated that in a French family in which 85 out of above 600 members, + during six generations, had been subject to night-blindness, "there has + not been a single example of this affection in the children of parents + who were themselves free from it."<a name="NtA_84" + href="#Nt_84"><sup>[84]</sup></a></p> + +<hr class="short" /> + + <p><i>Reversion through Bud-propagation—Partial Reversion, by + segments in the same flower or fruit, or in different parts of the <!-- + Page 37 --><span class="pagenum"><a name="page37"></a>{37}</span>body in + the same individual animal.</i>—In the eleventh chapter, many cases + of reversion by buds, independently of seminal generation, were + given—as when a leaf-bud on a variegated, curled, or laciniated + variety suddenly reassumes its proper character; or as when a + Provence-rose appears on a moss-rose, or a peach on a nectarine-tree. In + some of these cases only half the flower or fruit, or a smaller segment, + or mere stripes, reassumed their former character; and here we have with + buds reversion by segments. Vilmorin<a name="NtA_85" + href="#Nt_85"><sup>[85]</sup></a> has also recorded several cases with + plants derived from seed, of flowers reverting by stripes or blotches to + their primitive colours: he states that in all such cases a white or + pale-coloured variety must first be formed, and, when this is propagated + for a length of time by seed, striped seedlings occasionally make their + appearance; and these can afterwards by care be multiplied by seed.</p> + + <p>The stripes and segments just referred to are not due, as far as is + known, to reversion to characters derived from a cross, but to characters + lost by variation. These cases, however, as Naudin<a name="NtA_86" + href="#Nt_86"><sup>[86]</sup></a> insists in his discussion on + disjunction of character, are closely analogous with those given in the + eleventh chapter, in which crossed plants are known to have produced + half-and-half or striped flowers and fruit, or distinct kinds of flowers + on the same root resembling the two parent-forms. Many piebald animals + probably come under this same head. Such cases, as we shall see in the + chapter on Crossing, apparently result from certain characters not + readily blending together, and, as a consequence of this incapacity for + fusion, the offspring either perfectly resemble one of their two parents, + or resemble one parent in one part and the other parent in another part; + or whilst young are intermediate in character, but with advancing age + revert wholly or by segments to either parent-form, or to both. Thus + young trees of the <i>Cytisus adami</i> are intermediate in foliage and + flowers between the two parent-forms; but when older the buds continually + revert either partially or wholly to both forms. The cases given in the + eleventh chapter on the changes which occurred during growth <!-- Page 38 + --><span class="pagenum"><a name="page38"></a>{38}</span>in crossed + plants of Tropæolum, Cereus, Datura, and Lathyrus are all analogous. As + however these plants are hybrids of the first generation, and as their + buds after a time come to resemble their parents and not their + grandparents, these cases do not at first appear to come under the law of + reversion in the ordinary sense of the word; nevertheless, as the change + is effected through a succession of bud-generations on the same plant, + they may be thus included.</p> + + <p>Analogous facts have been observed in the animal kingdom, and are more + remarkable, as they occur strictly in the same individual, and not as + with plants through a succession of bud-generations. With animals the act + of reversion, if it can be so designated, does not pass over a true + generation, but merely over the early stages of growth in the same + individual. For instance, I crossed several white hens with a black cock, + and many of the chickens were during the first year perfectly white, but + acquired during the second year black feathers; on the other hand, some + of the chickens which were at first black became during the second year + piebald with white. A great breeder<a name="NtA_87" + href="#Nt_87"><sup>[87]</sup></a> says, that a Pencilled Brahma hen which + has any of the blood of the Light Brahma in her, will "occasionally + produce a pullet well pencilled during the first year, but she will most + likely moult brown on the shoulders and become quite unlike her original + colours in the second year." The same thing occurs with Light Brahmas if + of impure blood. I have observed exactly similar cases with the crossed + offspring from differently coloured pigeons. But here is a more + remarkable fact: I crossed a turbit, which has a frill formed by the + feathers being reversed on its breast, with a trumpeter; and one of the + young pigeons thus raised showed at first not a trace of the frill, but, + after moulting thrice, a small yet unmistakably distinct frill appeared + on its breast. According to Girou,<a name="NtA_88" + href="#Nt_88"><sup>[88]</sup></a> calves produced from a red cow by a + black bull, or from a black cow by a red bull, are not rarely born red, + and subsequently become black.</p> + + <p>In the foregoing cases, the characters which appear with advancing age + are the result of a cross in the previous or some <!-- Page 39 --><span + class="pagenum"><a name="page39"></a>{39}</span>former generation; but in + the following cases, the characters which thus reappear formerly + appertained to the species, and were lost at a more or less remote epoch. + Thus, according to Azara,<a name="NtA_89" + href="#Nt_89"><sup>[89]</sup></a> the calves of a hornless race of cattle + which originated in Corrientes, though at first quite hornless, as they + become adult sometimes acquire small, crooked, and loose horns; and these + in succeeding years occasionally become attached to the skull. White and + black bantams, both of which generally breed true, sometimes assume as + they grow old a saffron or red plumage. For instance, a first-rate black + bantam has been described, which during three seasons was perfectly + black, but then annually became more and more red; and it deserves notice + that this tendency to change, whenever it occurs in a bantam, "is almost + certain to prove hereditary."<a name="NtA_90" + href="#Nt_90"><sup>[90]</sup></a> The cuckoo or blue-mottled Dorking + cock, when old, is liable to acquire yellow or orange hackles in place of + his proper bluish-grey hackles.<a name="NtA_91" + href="#Nt_91"><sup>[91]</sup></a> Now, as <i>Gallus bankiva</i> is + coloured red and orange, and as Dorking fowls and both kinds of bantams + are descended from this species, we can hardly doubt that the change + which occasionally occurs in the plumage of these birds as their age + advances, results from a tendency in the individual to revert to the + primitive type.</p> + +<hr class="short" /> + + <p><i>Crossing as a direct cause of Reversion.</i>—It has long been + notorious that hybrids and mongrels often revert to both or to one of + their parent-forms, after an interval of from two to seven or eight, or + according to some authorities even a greater number of generations. But + that the act of crossing in itself gives an impulse towards reversion, as + shown by the reappearance of long-lost characters, has never, I believe, + been hitherto proved. The proof lies in certain peculiarities, which do + not characterise the immediate parents, and therefore cannot have been + derived from them, frequently appearing in the offspring of two breeds + when crossed, which peculiarities never appear, or appear with extreme + rarity, in these same breeds, as long as they are <!-- Page 40 --><span + class="pagenum"><a name="page40"></a>{40}</span>precluded from crossing. + As this conclusion seems to me highly curious and novel, I will give the + evidence in detail.</p> + +<blockquote class="b1n"> + + <p>My attention was first called to this subject, and I was led to make + numerous experiments, by MM. Boitard and Corbié having stated that, when + they crossed certain breeds, pigeons coloured like the wild <i>C. + livia</i>, or the common dovecot, namely, slaty-blue, with double black + wing-bars, sometimes chequered with black, white loins, the tail barred + with black, with the outer feathers edged with white, were almost + invariably produced. The breeds which I crossed, and the remarkable + results attained, have been fully described in the sixth chapter. I + selected pigeons, belonging to true and ancient breeds, which had not a + trace of blue or any of the above specified marks; but when crossed, and + their mongrels recrossed, young birds were continually produced, more or + less plainly coloured slaty-blue, with some or all of the proper + characteristic marks. I may recall to the reader's memory one case, + namely, that of a pigeon, hardly distinguishable from the wild Shetland + species, the grandchild of a red-spot, white fantail, and two black + barbs, from any of which, when purely-bred, the production of a pigeon + coloured like the wild <i>C. livia</i> would have been almost a + prodigy.</p> + + <p>I was thus led to make the experiments, recorded in the seventh + chapter, on fowls. I selected long-established, pure breeds, in which + there was not a trace of red, yet in several of the mongrels feathers of + this colour appeared; and one magnificent bird, the offspring of a black + Spanish cock and white Silk hen, was coloured almost exactly like the + wild <i>Gallus bankiva</i>. All who know anything of the breeding of + poultry will admit that tens of thousands of pure Spanish and of pure + white Silk fowls might have been reared without the appearance of a red + feather. The fact, given on the authority of Mr. Tegetmeier, of the + frequent appearance, in mongrel fowls, of pencilled or + transversely-barred feathers, like those common to many gallinaceous + birds, is likewise apparently a case of reversion to a character formerly + possessed by some ancient progenitor of the family. I owe to the kindness + of this same excellent observer the inspection of some neck-hackles and + tail-feathers from a hybrid between the common fowl and a very distinct + species, the <i>Gallus varius</i>; and these feathers are transversely + striped in a conspicuous manner with dark metallic blue and grey, a + character which could not have been derived from either immediate + parent.</p> + + <p>I have been informed by Mr. B. P. Brent, that he crossed a white + Aylesbury drake and a black so-called Labrador duck, both of which are + true breeds, and he obtained a young drake closely like the mallard + (<i>A. boschas</i>). Of the musk-duck (<i>A. moschata</i>, Linn.) there + are two sub-breeds, namely, white and slate-coloured; and these I am + informed breed true, or nearly true. But the Rev. W. D. Fox tells me + that, by putting a white drake to a slate-coloured duck, black birds, + pied with white, like the wild musk-duck, were always produced.</p> + + <p>We have seen in the fourth chapter, that the so-called Himalayan + rabbit, with its snow-white body, black ears, nose, tail, and feet, + breeds <!-- Page 41 --><span class="pagenum"><a + name="page41"></a>{41}</span>perfectly true. This race is known to have + been formed by the union of two varieties of silver-grey rabbits. Now, + when a Himalayan doe was crossed by a sandy-coloured buck, a silver-grey + rabbit was produced; and this is evidently a case of reversion to one of + the parent varieties. The young of the Himalayan rabbit are born + snow-white, and the dark marks do not appear until some time + subsequently; but occasionally young Himalayan rabbits are born of a + light silver-grey, which colour soon disappears; so that here we have a + trace of reversion, during an early period of life, to the + parent-varieties, independently of any recent cross.</p> + + <p>In the third chapter is was shown that at an ancient period some + breeds of cattle in the wilder parts of Britain were white with dark + ears, and that the cattle now kept half wild in certain parks, and those + which have run quite wild in two distant parts of the world, are likewise + thus coloured. Now, an experienced breeder, Mr. J. Beasley, of + Northamptonshire,<a name="NtA_92" href="#Nt_92"><sup>[92]</sup></a> + crossed some carefully selected West Highland cows with purely-bred + shorthorn bulls. The bulls were red, red and white, or dark roan; and the + Highland cows were all of a red colour, inclining to a light or yellow + shade. But a considerable number of the offspring—and Mr. Beasley + calls attention to this as a remarkable fact—were white, or white + with red ears. Bearing in mind that none of the parents were white, and + that they were purely-bred animals, it is highly probable that here the + offspring reverted, in consequence of the cross, to the colour either of + the aboriginal parent-species or of some ancient and half-wild + parent-breed. The following case, perhaps, comes under the same head: + cows in their natural state have their udders but little developed, and + do not yield nearly so much milk as our domesticated animals. Now there + is some reason to believe<a name="NtA_93" + href="#Nt_93"><sup>[93]</sup></a> that cross-bred animals between two + kinds, both of which are good milkers, such as Alderneys and Shorthorns, + often turn out worthless in this respect.</p> + + <p>In the chapter on the Horse reasons were assigned for believing that + the primitive stock was striped and dun-coloured; and details were given, + showing that in all parts of the world stripes of a dark colour + frequently appear along the spine, across the legs, and on the shoulders, + where they are occasionally double or treble, and even sometimes on the + face and body of horses of all breeds and of all colours. But the stripes + appear most frequently on the various kinds of duns. They may sometimes + plainly be seen on foals, and subsequently disappear. The dun-colour and + the stripes are strongly transmitted when a horse thus characterised is + crossed with any other; but I was not able to prove that striped duns are + generally produced from the crossing of two distinct breeds, neither of + which are duns, though this does sometimes occur.</p> + + <p>The legs of the ass are often striped, and this may be considered as a + reversion to the wild parent-form, the <i>Asinus tæniopus</i> of + Abyssinia,<a name="NtA_94" href="#Nt_94"><sup>[94]</sup></a> which is + thus striped. In the domestic animal the stripes on the shoulder are + occasionally double, or forked at the extremity, as in certain zebrine + <!-- Page 42 --><span class="pagenum"><a + name="page42"></a>{42}</span>species. There is reason to believe that the + foal is frequently more plainly striped on the legs than the adult + animal. As with the horse, I have not acquired any distinct evidence that + the crossing of differently-coloured varieties of the ass brings out the + stripes.</p> + + <p>But now let us turn to the result of crossing the horse and ass. + Although mules are not nearly so numerous in England as asses, I have + seen a much greater number with striped legs, and with the stripes far + more conspicuous than in either parent-form. Such mules are generally + light-coloured, and might be called fallow-duns. The shoulder-stripe in + one instance was deeply forked at the extremity, and in another instance + was double, though united in the middle. Mr. Martin gives a figure of a + Spanish mule with strong zebra-like marks on its legs,<a name="NtA_95" + href="#Nt_95"><sup>[95]</sup></a> and remarks, that mules are + particularly liable to be thus striped on their legs. In South America, + according to Roulin,<a name="NtA_96" href="#Nt_96"><sup>[96]</sup></a> + such stripes are more frequent and conspicuous in the mule than in the + ass. In the United States, Mr. Gosse,<a name="NtA_97" + href="#Nt_97"><sup>[97]</sup></a> speaking of these animals, says, "that + in a great number, perhaps in nine out of every ten, the legs are banded + with transverse dark stripes."</p> + + <p>Many years ago I saw in the Zoological Gardens a curious triple + hybrid, from a bay mare, by a hybrid from a male ass and female zebra. + This animal when old had hardly any stripes; but I was assured by the + superintendent, that when young it had shoulder-stripes, and faint + stripes on its flanks and legs. I mention this case more especially as an + instance of the stripes being much plainer during youth than in old + age.</p> + + <p>As the zebra has such conspicuously striped legs, it might have been + expected that the hybrids from this animal and the common ass would have + had their legs in some degree striped; but it appears from the figures + given in Dr. Gray's 'Knowsley Gleanings,' and still more plainly from + that given by Geoffroy and F. Cuvier,<a name="NtA_98" + href="#Nt_98"><sup>[98]</sup></a> that the legs are much more + conspicuously striped than the rest of the body; and this fact is + intelligible only on the belief that the ass aids in giving, through the + power of reversion, this character to its hybrid offspring.</p> + + <p>The quagga is banded over the whole front part of its body like a + zebra, but has no stripes on its legs, or mere traces of them. But in the + famous hybrid bred by Lord Morton,<a name="NtA_99" + href="#Nt_99"><sup>[99]</sup></a> from a chesnut, nearly purely-bred, + Arabian mare, by a male quagga, the stripes were "more strongly defined + and darker than those on the legs of the quagga." The mare was + subsequently put to a black Arabian horse, and bore two colts, both of + which, as formerly stated, were plainly striped on the legs, and one of + them likewise had stripes on the neck and body.</p> + + <p>The <i>Asinus Indicus</i><a name="NtA_100" + href="#Nt_100"><sup>[100]</sup></a> is characterised by a spinal stripe, + without shoulder <!-- Page 43 --><span class="pagenum"><a + name="page43"></a>{43}</span>or leg stripes; but traces of these latter + stripes may occasionally be seen even in the adult;<a name="NtA_101" + href="#Nt_101"><sup>[101]</sup></a> and Colonel S. Poole, who has had + ample opportunities for observation, informs me that in the foal, when + first born, the head and legs are often striped, but the shoulder-stripe + is not so distinct as in the domestic ass; all these stripes, excepting + that along the spine, soon disappear. Now a hybrid, raised at Knowsley<a + name="NtA_102" href="#Nt_102"><sup>[102]</sup></a> from a female of this + species by a male domestic ass, had all four legs transversely and + conspicuously striped, had three short stripes on each shoulder, and had + even some zebra-like stripes on its face! Dr. Gray informs me that he has + seen a second hybrid of the same parentage similarly striped.</p> + +</blockquote> + + <p>From these facts we see that the crossing of the several equine + species tends in a marked manner to cause stripes to appear on various + parts of the body, especially on the legs. As we do not know whether the + primordial parent of the genus was striped, the appearance of the stripes + can only hypothetically be attributed to reversion. But most persons, + after considering the many undoubted cases of variously coloured marks + reappearing by reversion in crossed pigeons, fowls, ducks, &c., will + come to the same conclusion with respect to the horse-genus; and in this + case we must admit that the progenitor of the group was striped on the + legs, shoulders, face, and probably over the whole body, like a zebra. If + we reject this view, the frequent and almost regular appearance of + stripes in the several foregoing hybrids is left without any + explanation.</p> + +<hr class="short" /> + + <p>It would appear that with crossed animals a similar tendency to the + recovery of lost characters holds good even with instincts. There are + some breeds of fowls which are called "everlasting layers," because they + have lost the instinct of incubation; and so rare is it for them to + incubate that I have seen notices published in works on poultry, when + hens of such breeds have taken to sit.<a name="NtA_103" + href="#Nt_103"><sup>[103]</sup></a> Yet the aboriginal species was of + course a good incubator; for with birds in a state of nature hardly any + <!-- Page 44 --><span class="pagenum"><a + name="page44"></a>{44}</span>instinct is so strong as this. Now, so many + cases have been recorded of the crossed offspring from two races, neither + of which are incubators, becoming first-rate sitters, that the + reappearance of this instinct must be attributed to reversion from + crossing. One author goes so far as to say, "that a cross between two + non-sitting varieties almost invariably produces a mongrel that becomes + broody, and sits with remarkable steadiness."<a name="NtA_104" + href="#Nt_104"><sup>[104]</sup></a> Another author, after giving a + striking example, remarks that the fact can be explained only on the + principle that "two negatives make a positive." It cannot, however, be + maintained that hens produced from a cross between two non-sitting breeds + invariably recover their lost instinct, any more than that crossed fowls + or pigeons invariably recover the red or blue plumage of their + prototypes. I raised several chickens from a Polish hen by a Spanish + cock,—breeds which do not incubate,—and none of the young + hens at first recovered their instinct, and this appeared to afford a + well-marked exception to the foregoing rule; but one of these hens, the + only one which was preserved, in the third year sat well on her eggs and + reared a brood of chickens. So that here we have the appearance with + advancing age of a primitive instinct, in the same manner as we have seen + that the red plumage of the <i>Gallus bankiva</i> is sometimes reacquired + by crossed and purely-bred fowls of various kinds as they grow old.</p> + + <p>The parents of all our domesticated animals were of course + aboriginally wild in disposition; and when a domesticated species is + crossed with a distinct species, whether this is a domesticated or only + tamed animal, the hybrids are often wild <!-- Page 45 --><span + class="pagenum"><a name="page45"></a>{45}</span>to such a degree, that + the fact is intelligible only on the principle that the cross has caused + a partial return to the primitive disposition.</p> + + <p>The Earl of Powis formerly imported some thoroughly domesticated + humped cattle from India, and crossed them with English breeds, which + belong to a distinct species; and his agent remarked to me, without any + question having been asked, how oddly wild the cross-bred animals were. + The European wild boar and the Chinese domesticated pig are almost + certainly specifically distinct: Sir F. Darwin crossed a sow of the + latter breed with a wild Alpine boar which had become extremely tame, but + the young, though having half-domesticated blood in their veins, were + "extremely wild in confinement, and would not eat swill like common + English pigs." Mr. Hewitt, who has had great experience in crossing tame + cock-pheasants with fowls belonging to five breeds, gives as the + character of all "extraordinary wildness;"<a name="NtA_105" + href="#Nt_105"><sup>[105]</sup></a> but I have myself seen one exception + to this rule. Mr. S. J. Salter,<a name="NtA_106" + href="#Nt_106"><sup>[106]</sup></a> who raised a large number of hybrids + from a bantam-hen by <i>Gallus Sonneratii</i>, states that "all were + exceedingly wild." Mr. Waterton<a name="NtA_107" + href="#Nt_107"><sup>[107]</sup></a> bred some wild ducks from eggs + hatched under a common duck, and the young were allowed to cross freely + both amongst themselves and with the tame ducks; they were "half wild and + half tame; they came to the windows to be fed, but still they had a + wariness about them quite remarkable."</p> + + <p>On the other hand, mules from the horse and ass are certainly not in + the least wild, yet they are notorious for obstinacy and vice. Mr. Brent, + who has crossed canary-birds with many kinds of finches, has not + observed, as he informs me, that the hybrids were in any way remarkably + wild. Hybrids are often raised between the common and musk duck, and I + have been assured by three persons, who have kept these crossed birds, + that they were not wild; but Mr. Garnett<a name="NtA_108" + href="#Nt_108"><sup>[108]</sup></a> observed that his female hybrids + exhibited "migratory propensities," of which there is not a vestige in + the common or musk duck. No case is <!-- Page 46 --><span + class="pagenum"><a name="page46"></a>{46}</span>known of this latter bird + having escaped and become wild in Europe or Asia, except, according to + Pallas, on the Caspian Sea; and the common domestic duck only + occasionally becomes wild in districts where large lakes and fens abound. + Nevertheless, a large number of cases have been recorded<a name="NtA_109" + href="#Nt_109"><sup>[109]</sup></a> of hybrids from these two ducks, + although so few are reared in comparison with purely-bred birds of either + species, having been shot in a completely wild state. It is improbable + that any of these hybrids could have acquired their wildness from the + musk-duck having paired with a truly wild duck; and this is known not to + be the case in North America; hence we must infer that they have + reacquired, through reversion, their wildness, as well as renewed powers + of flight.</p> + + <p>These latter facts remind us of the statements, so frequently made by + travellers in all parts of the world, on the degraded state and savage + disposition of crossed races of man. That many excellent and kind-hearted + mulattos have existed no one will dispute; and a more mild and gentle set + of men could hardly be found than the inhabitants of the island of + Chiloe, who consist of Indians commingled with Spaniards in various + proportions. On the other hand, many years ago, long before I had thought + of the present subject, I was struck with the fact that, in South + America, men of complicated descent between Negroes, Indians, and + Spaniards, seldom had, whatever the cause might be, a good expression.<a + name="NtA_110" href="#Nt_110"><sup>[110]</sup></a> Livingstone,—and + a more unimpeachable authority cannot be quoted,—after speaking of + a half-caste man on the Zambesi, described by the Portuguese as a rare + monster of inhumanity, remarks, "It is unaccountable why half-castes, + such as he, are so much more cruel than the Portuguese, but such is + undoubtedly the case." An inhabitant remarked to Livingstone, "God made + white men, and God made black men, but the Devil made half-castes."<a + name="NtA_111" href="#Nt_111"><sup>[111]</sup></a> When two races, both + <!-- Page 47 --><span class="pagenum"><a name="page47"></a>{47}</span>low + in the scale, are crossed, the progeny seems to be eminently bad. Thus + the noble-hearted Humboldt, who felt none of that prejudice against the + inferior races now so current in England, speaks in strong terms of the + bad and savage disposition of Zambos, or half-castes between Indians and + Negroes; and this conclusion has been arrived at by various observers.<a + name="NtA_112" href="#Nt_112"><sup>[112]</sup></a> From these facts we + may perhaps infer that the degraded state of so many half-castes is in + part due to reversion to a primitive and savage condition, induced by the + act of crossing, as well as to the unfavourable moral conditions under + which they generally exist.</p> + +<hr class="short" /> + + <p><i>Summary on the proximate causes leading to + Reversion.</i>—When purely-bred animals or plants reassume + long-lost characters,—when the common ass, for instance, is born + with striped legs, when a pure race of black or white pigeons throws a + slaty-blue bird, or when a cultivated heartsease with large and rounded + flowers produces a seedling with small and elongated flowers,—we + are quite unable to assign any proximate cause. When animals run wild, + the tendency to reversion, which, though it has been greatly exaggerated, + no doubt exists, is sometimes to a certain extent intelligible. Thus, + with feral pigs, exposure to the weather will probably favour the growth + of the bristles, as is known to be the case with the hair of other + domesticated animals, and through correlation the tusks will tend to be + redeveloped. But the reappearance of coloured longitudinal stripes on + young feral pigs cannot be attributed to the direct action of external + conditions. In this case, and in many others, we can only say that + changed habits of life apparently have favoured a tendency, inherent or + latent in the species, to return to the primitive state.</p> + + <p>It will be shown in a future chapter that the position of flowers on + the summit of the axis, and the position of seeds within the capsule, + sometimes determine a tendency towards reversion; and this apparently + depends on the amount of sap or nutriment which the flower-buds and seeds + receive. The position, also, of buds, either on branches or on roots, + sometimes determines, as was formerly shown, the transmission of the <!-- + Page 48 --><span class="pagenum"><a name="page48"></a>{48}</span>proper + character of the variety, or its reversion to a former state.</p> + + <p>We have seen in the last section that when two races or species are + crossed there is the strongest tendency to the reappearance in the + offspring of long-lost characters, possessed by neither parent nor + immediate progenitor. When two white, or red, or black pigeons, of + well-established breeds, are united, the offspring are almost sure to + inherit the same colours; but when differently-coloured birds are + crossed, the opposed forces of inheritance apparently counteract each + other, and the tendency which is inherent in both parents to produce + slaty-blue offspring becomes predominant. So it is in several other + cases. But when, for instance, the ass is crossed with <i>A. Indicus</i> + or with the horse,—animals which have not striped legs,—and + the hybrids have conspicuous stripes on their legs and even on their + faces, all that can be said is, that an inherent tendency to reversion is + evolved through some disturbance in the organisation caused by the act of + crossing.</p> + + <p>Another form of reversion is far commoner, indeed is almost universal + with the offspring from a cross, namely, to the characters proper to + either pure parent-form. As a general rule, crossed offspring in the + first generation are nearly intermediate between their parents, but the + grandchildren and succeeding generations continually revert, in a greater + or lesser degree, to one or both of their progenitors. Several authors + have maintained that hybrids and mongrels include all the characters of + both parents, not fused together, but merely mingled in different + proportions in different parts of the body; or, as Naudin<a + name="NtA_113" href="#Nt_113"><sup>[113]</sup></a> has expressed it, a + hybrid is a living mosaic-work, in which the eye cannot distinguish the + discordant elements, so completely are they intermingled. We can hardly + doubt that, in a certain sense, this is true, as when we behold in a + hybrid the elements of both species segregating themselves into segments + in the same flower or fruit, by a process of self-attraction or + self-affinity; this segregation taking place either by seminal or by + bud-propagation. Naudin further believes that the segregation of the two + specific elements or essences is eminently liable to occur in the male + and female reproductive matter; and he thus explains the almost <!-- Page + 49 --><span class="pagenum"><a name="page49"></a>{49}</span>universal + tendency to reversion in successive hybrid generations. For this would be + the natural result of the union of pollen and ovules, in both of which + the elements of the same species had been segregated by self-affinity. + If, on the other hand, pollen which included the elements of one species + happened to unite with ovules including the elements of the other + species, the intermediate or hybrid state would still be retained, and + there would be no reversion. But it would, as I suspect, be more correct + to say that the elements of both parent-species exist in every hybrid in + a double state, namely, blended together and completely separate. How + this is possible, and what the term specific essence or element may be + supposed to express, I shall attempt to show in the hypothetical chapter + on pangenesis.</p> + + <p>But Naudin's view, as propounded by him, is not applicable to the + reappearance of characters lost long ago by variation; and it is hardly + applicable to races or species which, after having been crossed at some + former period with a distinct form, and having since lost all traces of + the cross, nevertheless occasionally yield an individual which reverts + (as in the case of the great-great-grandchild of the pointer Sappho) to + the crossing form. The most simple case of reversion, namely, of a hybrid + or mongrel to its grandparents, is connected by an almost perfect series + with the extreme case of a purely-bred race recovering characters which + had been lost during many ages; and we are thus led to infer that all the + cases must be related by some common bond.</p> + + <p>Gärtner believed that only those hybrid plants which are highly + sterile exhibit any tendency to reversion to their parent-forms. It is + rash to doubt so good an observer, but this conclusion must I think be an + error; and it may perhaps be accounted for by the nature of the genera + observed by him, for he admits that the tendency differs in different + genera. The statement is also directly contradicted by Naudin's + observations, and by the notorious fact that perfectly fertile mongrels + exhibit the tendency in a high degree,—even in a higher degree, + according to Gärtner himself, than hybrids.<a name="NtA_114" + href="#Nt_114"><sup>[114]</sup></a></p> + + <p>Gärtner further states that reversions rarely occur with <!-- Page 50 + --><span class="pagenum"><a name="page50"></a>{50}</span>hybrid plants + raised from species which have not been cultivated, whilst, with those + which have been long cultivated, they are of frequent occurrence. This + conclusion explains a curious discrepancy: Max Wichura,<a name="NtA_115" + href="#Nt_115"><sup>[115]</sup></a> who worked exclusively on willows, + which had not been subjected to culture, never saw an instance of + reversion; and he goes so far as to suspect that the careful Gärtner had + not sufficiently protected his hybrids from the pollen of the + parent-species: Naudin, on the other hand, who chiefly experimented on + cucurbitaceous and other cultivated plants, insists more strenuously than + any other author on the tendency to reversion in all hybrids. The + conclusion that the condition of the parent-species, as affected by + culture, is one of the proximate causes leading to reversion, agrees + fairly well with the converse case of domesticated animals and cultivated + plants being liable to reversion when they become feral; for in both + cases the organisation or constitution must be disturbed, though in a + very different way.</p> + + <p>Finally, we have seen that characters often reappear in purely-bred + races without our being able to assign any proximate cause; but when they + become feral this is either indirectly or directly induced by the change + in their conditions of life. With crossed breeds, the act of crossing in + itself certainly leads to the recovery of long-lost characters, as well + as of those derived from either parent-form. Changed conditions, + consequent on cultivation, and the relative position of buds, flowers, + and seeds on the plant, all apparently aid in giving this same tendency. + Reversion may occur either through seminal or bud generation, generally + at birth, but sometimes only with an advance of age. Segments or portions + of the individual may alone be thus affected. That a being should be born + resembling in certain characters an ancestor removed by two or three, and + in some cases by hundreds or even thousands of generations, is assuredly + a wonderful fact. In these cases the child is commonly said to inherit + such characters directly from its grandparents or more remote ancestors. + But this view is hardly conceivable. If, however, we suppose that every + character is derived <!-- Page 51 --><span class="pagenum"><a + name="page51"></a>{51}</span>exclusively from the father or mother, but + that many characters lie latent in both parents during a long succession + of generations, the foregoing facts are intelligible. In what manner + characters may be conceived to lie latent, will be considered in a future + chapter to which I have lately alluded.</p> + +<hr class="short" /> + + <p><i>Latent Characters.</i>—But I must explain what is meant by + characters lying latent. The most obvious illustration is afforded by + secondary sexual characters. In every female all the secondary male + characters, and in every male all the secondary female characters, + apparently exist in a latent state, ready to be evolved under certain + conditions. It is well known that a large number of female birds, such as + fowls, various pheasants, partridges, peahens, ducks, &c., when old + or diseased, or when operated on, partly assume the secondary male + characters of their species. In the case of the hen-pheasant this has + been observed to occur far more frequently during certain seasons than + during others.<a name="NtA_116" href="#Nt_116"><sup>[116]</sup></a> A + duck ten years old has been known to assume both the perfect winter and + summer plumage of the drake.<a name="NtA_117" + href="#Nt_117"><sup>[117]</sup></a> Waterton<a name="NtA_118" + href="#Nt_118"><sup>[118]</sup></a> gives a curious case of a hen which + had ceased laying, and had assumed the plumage, voice, spurs, and warlike + disposition of the cock; when opposed to an enemy she would erect her + hackles and show fight. Thus every character, even to the instinct and + manner of fighting, must have lain dormant in this hen as long as her + ovaria continued to act. The females of two kinds of deer, when old, have + been known to acquire horns; and, as Hunter has remarked, we see + something of an analogous nature in the human species.</p> + + <p>On the other hand, with male animals, it is notorious that the + secondary sexual characters are more or less completely lost when they + are subjected to castration. Thus, if the operation be performed on a + young cock, he never, as Yarrell states, crows <!-- Page 52 --><span + class="pagenum"><a name="page52"></a>{52}</span>again; the comb, wattles, + and spurs do not grow to their full size, and the hackles assume an + intermediate appearance between true hackles and the feathers of the hen. + Cases are recorded of confinement alone causing analogous results. But + characters properly confined to the female are likewise acquired; the + capon takes to sitting on eggs, and will bring up chickens; and what is + more curious, the utterly sterile male hybrids from the pheasant and the + fowl act in the same manner, "their delight being to watch when the hens + leave their nests, and to take on themselves the office of a sitter."<a + name="NtA_119" href="#Nt_119"><sup>[119]</sup></a> That admirable + observer Réaumur<a name="NtA_120" href="#Nt_120"><sup>[120]</sup></a> + asserts that a cock, by being long confined in solitude and darkness, can + be taught to take charge of young chickens; he then utters a peculiar + cry, and retains during his whole life this newly acquired maternal + instinct. The many well-ascertained cases of various male mammals giving + milk, show that their rudimentary mammary glands retain this capacity in + a latent condition.</p> + + <p>We thus see that in many, probably in all cases, the secondary + characters of each sex lie dormant or latent in the opposite sex, ready + to be evolved under peculiar circumstances. We can thus understand how, + for instance, it is possible for a good milking cow to transmit her good + qualities through her male offspring to future generations; for we may + confidently believe that these qualities are present, though latent, in + the males of each generation. So it is with the game-cock, who can + transmit his superiority in courage and vigour through his female to his + male offspring; and with man it is known <a name="NtA_121" + href="#Nt_121"><sup>[121]</sup></a> that diseases, such as hydrocele, + necessarily confined to the male sex, can be transmitted through the + female to the grandson. Such cases as these offer, as was remarked at the + commencement of this chapter, the simplest possible examples of + reversion; and they are intelligible on the belief that characters common + to the grandparent and grandchild of the same sex are present, though + latent, in the intermediate parent of the opposite sex.</p> + + <p>The subject of latent characters is so important, as we shall see in a + future chapter, that I will give another illustration. <!-- Page 53 + --><span class="pagenum"><a name="page53"></a>{53}</span>Many animals + have the right and left sides of their body unequally developed: this is + well known to be the case with flat-fish, in which the one side differs + in thickness and colour, and in the shape of the fins, from the other; + and during the growth of the young fish one eye actually travels, as + shown by Steenstrup, from the lower to the upper surface.<a + name="NtA_122" href="#Nt_122"><sup>[122]</sup></a> In most flat-fishes + the left is the blind side, but in some it is the right; though in both + cases "wrong fishes," which are developed in a reversed manner to what is + usual, occasionally occur, and in <i>Platessa flesus</i> the right or + left side is indifferently developed, the one as often as the other. With + gasteropods or shell-fish, the right and left sides are extremely + unequal; the far greater number of species are dextral, with rare and + occasional reversals of development, and some few are normally sinistral; + but certain species of Bulimus, and, many Achatinellæ,<a name="NtA_123" + href="#Nt_123"><sup>[123]</sup></a> are as often sinistral as dextral. I + will give an analogous case in the great Articulate kingdom: the two + sides of Verruca<a name="NtA_124" href="#Nt_124"><sup>[124]</sup></a> are + so wonderfully unlike, that without careful dissection it is extremely + difficult to recognise the corresponding parts on the opposite sides of + the body; yet it is apparently a mere matter of chance whether it be the + right or the left side that undergoes so singular an amount of change. + One plant is known to me<a name="NtA_125" + href="#Nt_125"><sup>[125]</sup></a> in which the flower, according as it + stands on the one or other side of the spike, is unequally developed. In + all the foregoing cases the two sides of the animal are perfectly + symmetrical at an early period of growth. Now, whenever a species is as + liable to be unequally developed on the one as on the other side, we may + infer that the capacity for such development is present, though latent, + in the undeveloped side. And as a reversal of development occasionally + occurs in animals of many kinds, this latent capacity is probably very + common.</p> + + <p>The best yet simplest instances of characters lying dormant are, + perhaps, those previously given, in which chickens and <!-- Page 54 + --><span class="pagenum"><a name="page54"></a>{54}</span>young pigeons, + raised from a cross between differently coloured birds, are at first of + one colour, but in a year or two acquire feathers of the colour of the + other parent; for in this case the tendency to a change of plumage is + clearly latent in the young bird. So it is with hornless breeds of + cattle, some of which acquire, as they grow old, small horns. Purely bred + black and white bantams, and some other fowls, occasionally assume, with + advancing years, the red feathers of the parent-species. I will here add + a somewhat different case, as it connects in a striking manner latent + characters of two classes. Mr. Hewitt<a name="NtA_126" + href="#Nt_126"><sup>[126]</sup></a> possessed an excellent Sebright + gold-laced hen bantam, which, as she became old, grew diseased in her + ovaria, and assumed male characters. In this breed the males resemble the + females in all respects except in their combs, wattles, spurs, and + instincts; hence it might have been expected that the diseased hen would + have assumed only those masculine characters which are proper to the + breed, but she acquired, in addition, well-arched tail sickle-feathers + quite a foot in length, saddle-feathers on the loins, and hackles on the + neck,—ornaments which, as Mr. Hewitt remarks, "would be held as + abominable in this breed." The Sebright bantam is known<a name="NtA_127" + href="#Nt_127"><sup>[127]</sup></a> to have originated about the year + 1800 from a cross between a common bantam and a Polish fowl, recrossed by + a hen-tailed bantam, and carefully selected; hence there can hardly be a + doubt that the sickle-feathers and hackles which appeared in the old hen + were derived from the Polish fowl or common bantam; and we thus see that + not only certain masculine characters proper to the Sebright bantam, but + other masculine characters derived from the first progenitors of the + breed, removed by a period of above sixty years, were lying latent in + this hen-bird, ready to be evolved as soon as her ovaria became + diseased.</p> + + <p>From these several facts it must be admitted that certain characters, + capacities, and instincts may lie latent in an individual, and even in a + succession of individuals, without our being able to detect the least + signs of their presence. We have <!-- Page 55 --><span class="pagenum"><a + name="page55"></a>{55}</span>already seen that the transmission of a + character from the grandparent to the grandchild, with its apparent + omission in the intermediate parent of the opposite sex, becomes simple + on this view. When fowls, pigeons, or cattle of different colours are + crossed, and their offspring change colour as they grow old, or when the + crossed turbit acquired the characteristic frill after its third moult, + or when purely-bred bantams partially assume the red plumage of their + prototype, we cannot doubt that these qualities were from the first + present, though latent, in the individual animal, like the characters of + a moth in the caterpillar. Now, if these animals had produced offspring + before they had acquired with advancing age their new characters, nothing + is more probable than that they would have transmitted them to some of + their offspring, which in this case would in appearance have received + such characters from their grandparents or more distant progenitors. We + should then have had a case of reversion, that is, of the reappearance in + the child of an ancestral character, actually present, though during + youth completely latent, in the parent; and this we may safely conclude + is what occurs with reversions of all kinds to progenitors however + remote.</p> + + <p>This view of the latency in each generation of all the characters + which appear through reversion, is also supported by their actual + presence in some cases during early youth alone, or by their more + frequent appearance and greater distinctness at this age than during + maturity. We have seen that this is often the case with the stripes on + the legs and faces of the several species of the horse-genus. The + Himalayan rabbit, when crossed, sometimes produces offspring which revert + to the parent silver-grey breed, and we have seen that in purely bred + animals pale-grey fur occasionally reappears during early youth. Black + cats, we may feel assured, would occasionally produce by reversion + tabbies; and on young black kittens, with a pedigree<a name="NtA_128" + href="#Nt_128"><sup>[128]</sup></a> known to have been long pure, faint + traces of stripes may almost always be seen which afterwards disappear. + Hornless Suffolk cattle occasionally produce by reversion horned animals; + and Youatt<a name="NtA_129" href="#Nt_129"><sup>[129]</sup></a> asserts + that even in hornless individuals <!-- Page 56 --><span + class="pagenum"><a name="page56"></a>{56}</span>"the rudiment of a horn + may be often felt at an early age."</p> + + <p>No doubt it appears at first sight in the highest degree improbable + that in every horse of every generation there should be a latent capacity + and tendency to produce stripes, though these may not appear once in a + thousand generations; that in every white, black, or other coloured + pigeon, which may have transmitted its proper colour during centuries, + there should be a latent capacity in the plumage to become blue and to be + marked with certain characteristic bars; that in every child in a + six-fingered family there should be the capacity for the production of an + additional digit; and so in other cases. Nevertheless there is no more + inherent improbability in this being the case than in a useless and + rudimentary organ, or even in only a tendency to the production of a + rudimentary organ, being inherited during millions of generations, as is + well known to occur with a multitude of organic beings. There is no more + inherent improbability in each domestic pig, during a thousand + generations, retaining the capacity and tendency to develop great tusks + under fitting conditions, than in the young calf having retained for an + indefinite number of generations rudimentary incisor teeth, which never + protrude through the gums.</p> + + <p>I shall give at the end of the next chapter a summary of the three + preceding chapters; but as isolated and striking cases of reversion have + here been chiefly insisted on, I wish to guard the reader against + supposing that reversion is due to some rare or accidental combination of + circumstances. When a character, lost during hundreds of generations, + suddenly reappears, no doubt some such combination must occur; but + reversions may be constantly observed, at least to the immediately + preceding generations, in the offspring of most unions. This has been + universally recognised in the case of hybrids and mongrels, but it has + been recognised simply from the difference between the united forms + rendering the resemblance of the offspring to their grandparents or more + remote progenitors of easy detection. Reversion is likewise almost + invariably the rule, as Mr. Sedgwick has shown, with certain diseases. + Hence we must conclude that a tendency to this peculiar form of + transmission is an integral part of the general law of inheritance. <!-- + Page 57 --><span class="pagenum"><a name="page57"></a>{57}</span></p> + +<hr class="short" /> + + <p><i>Monstrosities.</i>—A large number of monstrous growths and of + lesser anomalies are admitted by every one to be due to an arrest of + development, that is to the persistence of an embryonic condition. If + every horse or ass had striped legs whilst young, the stripes which + occasionally appear on these animals when adult would have to be + considered as due to the anomalous retention of an early character, and + not as due to reversion. Now, the leg-stripes in the horse-genus, and + some other characters in analogous cases, are apt to occur during early + youth and then to disappear; thus the persistence of early characters and + reversion are brought into close connexion.</p> + + <p>But many monstrosities can hardly be considered as the result of an + arrest of development; for parts of which no trace can be detected in the + embryo, but which occur in other members of the same class of animals or + plants, occasionally appear, and these may probably with truth be + attributed to reversion. For instance: supernumerary mammæ, capable of + secreting milk, are not extremely rare in women; and as many as five have + been observed. When four are developed, they are generally arranged + symmetrically on each side of the chest; and in one instance a woman (the + daughter of another with supernumerary mammæ) had one mamma, which + yielded milk, developed in the inguinal region. This latter case, when we + remember the position of the mammæ in some of the lower animals on both + the chest and inguinal region, is highly remarkable, and leads to the + belief that in all cases the additional mammæ in woman are due to + reversion. The facts given in the last chapter on the tendency in + supernumerary digits to regrowth after amputation, indicate their + relation to the digits of the lower vertebrate animals, and lead to the + suspicion that their appearance may in some manner be connected with + reversion. But I shall have to recur, in the chapter on pangenesis, to + the abnormal multiplication of organs, and likewise to their occasional + transposition. The occasional development in man of the coccygeal + vertebræ into a short and free tail, though it thus becomes in one sense + more perfectly developed, may at the same time be considered as an arrest + of development, and as a case of reversion. The greater frequency of a + monstrous kind of proboscis in the pig than in any other mammal, + considering the position of the pig <!-- Page 58 --><span + class="pagenum"><a name="page58"></a>{58}</span>in the mammalian series, + has likewise been attributed, perhaps truly, to reversion.<a + name="NtA_130" href="#Nt_130"><sup>[130]</sup></a></p> + +<blockquote class="b1n"> + + <p>When flowers which are properly irregular in structure become regular + or peloric, the change is generally looked at by botanists as a return to + the primitive state. But Dr. Maxwell Masters,<a name="NtA_131" + href="#Nt_131"><sup>[131]</sup></a> who has ably discussed this subject, + remarks that when, for instance, all the sepals of a Tropæolum become + green and of the same shape, instead of being coloured with one alone + prolonged into a spur, or when all the petals of a Linaria become simple + and regular, such cases may be due merely to an arrest of development; + for in these flowers all the organs during their earliest condition are + symmetrical, and, if arrested at this stage of growth, they would not + become irregular. If, moreover, the arrest were to take place at a still + earlier period of development, the result would be a simple tuft of green + leaves; and no one probably would call this a case of reversion. Dr. + Masters designates the cases first alluded to as regular peloria; and + others, in which all the corresponding parts assume a similar form of + irregularity, as when all the petals in a Linaria become spurred, as + irregular peloria. We have no right to attribute these latter cases to + reversion, until it can be shown to be probable that the parent-form, for + instance, of the genus Linaria had had all its petals spurred; for a + change of this nature might result from the spreading of an anomalous + structure, in accordance with the law, to be discussed in a future + chapter, of homologous parts tending to vary in the same manner. But as + both forms of peloria frequently occur on the same individual plant of + the Linaria,<a name="NtA_132" href="#Nt_132"><sup>[132]</sup></a> they + probably stand in some close relation to each other. On the doctrine that + peloria is simply the result of an arrest of development, it is difficult + to understand how an organ arrested at a very early period of growth + should acquire its full functional perfection;—how a petal, + supposed to be thus arrested, should acquire its brilliant colours, and + serve as an envelope to the flower, or a stamen produce efficient pollen; + yet this occurs with many peloric flowers. That pelorism is not due to + mere chance variability, but either to an arrest of development or to + reversion, we may infer from an observation made by Ch. Morren,<a + name="NtA_133" href="#Nt_133"><sup>[133]</sup></a> namely, that families + which have irregular flowers often "return by these monstrous growths to + their regular form; whilst we never see a regular flower realise the + structure of an irregular one."</p> + + <p>Some flowers have almost certainly become more or less completely + peloric through reversion. <i>Corydalis tuberosa</i> properly has one of + its two nectaries colourless, destitute of nectar, only half the size of + the other, and <!-- Page 59 --><span class="pagenum"><a + name="page59"></a>{59}</span>therefore, to a certain extent, in a + rudimentary state; the pistil is curved towards the perfect nectary, and + the hood, formed of the inner petals, slips off the pistil and stamens in + one direction alone, so that, when a bee sucks the perfect nectary, the + stigma and stamens are exposed and rubbed against the insect's body. In + several closely allied genera, as in Dielytra, &c., there are two + perfect nectaries, the pistil is straight, and the hood slips off on + either side, according as the bee sucks either nectary. Now, I have + examined several flowers of <i>Corydalis tuberosa</i>, in which both + nectaries were equally developed and contained nectar; in this we see + only the redevelopment of a partially aborted organ; but with this + redevelopment the pistil becomes straight, and the hood slips off in + either direction; so that these flowers have acquired the perfect + structure, so well adapted for insect agency, of Dielytra and its allies. + We cannot attribute these coadapted modifications to chance, or to + correlated variability; we must attribute them to reversion to a + primordial condition of the species.</p> + + <p>The peloric flowers of Pelargonium have their five petals in all + respects alike, and there is no nectary; so that they resemble the + symmetrical flowers of the closely allied Geranium-genus; but the + alternate stamens are also sometimes destitute of anthers, the shortened + filaments being left as rudiments, and in this respect they resemble the + symmetrical flowers of the closely allied genus, Erodium. Hence we are + led to look at the peloric flowers of Pelargonium as having probably + reverted to the state of some primordial form, the progenitor of the + three closely related genera of Pelargonium, Geranium, and Erodium.</p> + + <p>In the peloric form of <i>Antirrhinum majus</i>, appropriately called + the "<i>Wonder</i>," the tubular and elongated flowers differ wonderfully + from those of the common snapdragon; the calyx and the mouth of the + corolla consist of six equal lobes, and include six equal instead of four + unequal stamens. One of the two additional stamens is manifestly formed + by the development of a microscopically minute papilla, which may be + found at the base of the upper lip of the flower in all common + snapdragons, at least in nineteen plants examined by me. That this + papilla is a rudiment of a stamen was well shown by its various degrees + of development in crossed plants between the common and peloric + Antirrhinum. Again, a peloric <i>Galeobdolon luteum</i>, growing in my + garden, had five equal petals, all striped like the ordinary lower lip, + and included five equal instead of four unequal stamens; but Mr. R. + Keeley, who sent me this plant, informs me that the flowers vary greatly, + having from four to six lobes to the corolla, and from three to six + stamens.<a name="NtA_134" href="#Nt_134"><sup>[134]</sup></a> Now, as the + members of the two great families to which the Antirrhinum and + Galeobdolon belong are properly pentamerous, with some of the parts + confluent and others suppressed, we ought not to look at the sixth stamen + and the sixth lobe to the corolla in either case as due to reversion, any + more than the additional petals in double flowers in these same two + families. But the case is different with the fifth stamen in the peloric + Antirrhinum, which <!-- Page 60 --><span class="pagenum"><a + name="page60"></a>{60}</span>is produced by the redevelopment of a + rudiment always present, and which probably reveals to us the state of + the flower, as far as the stamens are concerned, at some ancient epoch. + It is also difficult to believe that the other four stamens and the + petals, after an arrest of development at a very early embryonic age, + would have come to full perfection in colour, structure, and function, + unless these organs had at some former period normally passed through a + similar course of growth. Hence it appears to me probable that the + progenitor of the genus Antirrhinum must at some remote epoch have + included five stamens and borne flowers in some degree resembling those + now produced by the peloric form.</p> + + <p>Lastly, I may add that many instances have been recorded of flowers, + not generally ranked as peloric, in which certain organs, normally few in + number, have been abnormally augmented. As such an increase of parts + cannot be looked at as an arrest of development, nor as due to the + redevelopment of rudiments, for no rudiments are present, and as these + additional parts bring the plant into closer relationship with its + natural allies, they ought probably to be viewed as reversions to a + primordial condition.</p> + +</blockquote> + + <p>These several facts show us in an interesting manner how intimately + certain abnormal states are connected together; namely, arrests of + development causing parts to become rudimentary or to be wholly + suppressed,—the redevelopment of parts at present in a more or less + rudimentary condition,—the reappearance of organs of which not a + vestige can now be detected,—and to these may be added, in the case + of animals, the presence during youth, and subsequent disappearance, of + certain characters which occasionally are retained throughout life. Some + naturalists look at all such abnormal structures as a return to the ideal + state of the group to which the affected being belongs; but it is + difficult to conceive what is meant to be conveyed by this expression. + Other naturalists maintain, with greater probability and distinctness of + view, that the common bond of connection between the several foregoing + cases is an actual, though partial, return to the structure of the + ancient progenitor of the group. If this view be correct, we must believe + that a vast number of characters, capable of evolution, lie hidden in + every organic being. But it would be a mistake to suppose that the number + is equally great in all beings. We know, for instance, that plants of + many orders occasionally become peloric; but many more cases have been + observed in the Labiatæ and Scrophulariaceæ than in any other order; and + in one genus of the Scrophulariaceæ, namely Linaria, no less <!-- Page 61 + --><span class="pagenum"><a name="page61"></a>{61}</span>than thirteen + species have been described in a peloric condition.<a name="NtA_135" + href="#Nt_135"><sup>[135]</sup></a> On this view of the nature of peloric + flowers, and <span class="correction" title="Original reads `bearnig'." + >bearing</span> in mind what has been said with respect to certain + monstrosities in the animal kingdom, we must conclude that the + progenitors of most plants and animals, though widely different in + structure, have left an impression capable of redevelopment on the germs + of their descendants.</p> + + <p>The fertilised germ of one of the higher animals, subjected as it is + to so vast a series of changes from the germinal cell to old + age,—incessantly agitated by what Quatrefages well calls the + <i>tourbillon vital</i>,—is perhaps the most wonderful object in + nature. It is probable that hardly a change of any kind affects either + parent, without some mark being left on the germ. But on the doctrine of + reversion, as given in this chapter, the germ becomes a far more + marvellous object, for, besides the visible changes to which it is + subjected, we must believe that it is crowded with invisible characters, + proper to both sexes, to both the right and left side of the body, and to + a long line of male and female ancestors separated by hundreds or even + thousands of generations from the present time; and these characters, + like those written on paper with invisible ink, all lie ready to be + evolved under certain known or unknown conditions.</p> + +<hr class="full" /> + +<p><!-- Page 62 --><span class="pagenum"><a name="page62"></a>{62}</span></p> + +<h3>CHAPTER XIV.</h3> + +<p class="cenhead">INHERITANCE <i>continued</i>—FIXEDNESS OF CHARACTER—PREPOTENCY—SEXUAL +LIMITATION—CORRESPONDENCE OF AGE.</p> + +<blockquote class="b1n"> + + <p><span class="scac">FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO + ANTIQUITY OF INHERITANCE</span>—<span class="scac">PREPOTENCY OF + TRANSMISSION IN INDIVIDUALS OF THE SAME FAMILY, IN CROSSED BREEDS AND + SPECIES; OFTEN STRONGER IN ONE SEX THAN THE OTHER; SOMETIMES DUE TO THE + SAME CHARACTER BEING PRESENT AND VISIBLE IN ONE BREED AND LATENT IN THE + OTHER</span>—<span class="scac">INHERITANCE AS LIMITED BY + SEX</span>—<span class="scac">NEWLY-ACQUIRED CHARACTERS IN OUR + DOMESTICATED ANIMALS OFTEN TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST + BY ONE SEX ALONE</span>—<span class="scac">INHERITANCE AT + CORRESPONDING PERIODS OF LIFE</span>—<span class="scac">THE + IMPORTANCE OF THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS EXHIBITED IN + DOMESTICATED ANIMALS; AS EXHIBITED IN THE APPEARANCE AND DISAPPEARANCE OF + INHERITED DISEASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN IN + THE PARENT</span>—<span class="scac">SUMMARY OF THE THREE PRECEDING + CHAPTERS.</span></p> + +</blockquote> + + <p>In the two last chapters the nature and force of Inheritance, the + circumstances which interfere with its power, and the tendency to + Reversion, with its many remarkable contingencies, were discussed. In the + present chapter some other related phenomena will be treated of, as fully + as my materials permit.</p> + +<p class="cenhead"><i>Fixedness of Character.</i></p> + + <p>It is a general belief amongst breeders that the longer any character + has been transmitted by a breed, the more firmly it will continue to be + transmitted. I do not wish to dispute the truth of the proposition, that + inheritance gains strength simply through long continuance, but I doubt + whether it can be proved. In one sense the proposition is little better + than a truism; if any character has remained constant during many + generations, it will obviously be little likely, the conditions of life + remaining the same, to vary during the next generation. So, again, in + improving a breed, if care be taken for a length of time to exclude all + inferior individuals, the breed will obviously tend to become truer, as + it will not have been crossed during many generations by an inferior + animal. We have previously seen, <!-- Page 63 --><span class="pagenum"><a + name="page63"></a>{63}</span>but without being able to assign any cause, + that, when a new character appears, it is occasionally from the first + well fixed, or fluctuates much, or wholly fails to be transmitted. So it + is with the aggregate of slight differences which characterise a new + variety, for some propagate their kind from the first much truer than + others. Even with plants multiplied by bulbs, layers, &c., which may + in one sense be said to form parts of the same individual, it is well + known that certain varieties retain and transmit through successive + bud-generations their newly-acquired characters more truly than others. + In none of these, nor in the following cases, does there appear to be any + relation between the force with which a character is transmissible and + the length of time during which it has already been transmitted. Some + varieties, such as white and yellow hyacinths and white sweet-peas, + transmit their colours more faithfully than do the varieties which have + retained their natural colour. In the Irish family, mentioned in the + twelfth chapter, the peculiar tortoiseshell-like colouring of the eyes + was transmitted far more faithfully than any ordinary colour. Ancon and + Mauchamp sheep and niata cattle, which are all comparatively modern + breeds, exhibit remarkably strong powers of inheritance. Many similar + cases could be adduced.</p> + + <p>As all domesticated animals and cultivated plants have varied, and yet + are descended from aboriginally wild forms, which no doubt had retained + the same character from an immensely remote epoch, we see that scarcely + any degree of antiquity ensures a character being transmitted perfectly + true. In this case, however, it may be said that changed conditions of + life induce certain modifications, and not that the power of inheritance + fails; but in every case of failure, some cause, either internal or + external, must interfere. It will generally be found that the parts in + our domesticated productions which have varied, or which still continue + to vary,—that is, which fail to retain their primordial + state,—are the same with the parts which differ in the natural + species of the same genus. As, on the theory of descent with + modification, the species of the same genus have been modified since they + branched off from a common progenitor, it follows that the characters by + which they differ from each other have varied whilst other parts of the + organisation have remained unchanged; and it might be argued that <!-- + Page 64 --><span class="pagenum"><a name="page64"></a>{64}</span>these + same characters now vary under domestication, or fail to be inherited, + owing to their lesser antiquity. But we must believe structures, which + have already varied, would be more liable to go on varying, rather than + structures which during an immense lapse of time have remained unaltered; + and this variation is probably the result of certain relations between + the conditions of life and the organisation, quite independently of the + greater or less antiquity of each particular character.</p> + + <p>Fixedness of character, or the strength of inheritance, has often been + judged of by the preponderance of certain characters in the crossed + offspring between distinct races; but prepotency of transmission here + comes into play, and this, as we shall immediately see, is a very + different consideration from the strength or weakness of inheritance. It + has often been observed<a name="NtA_136" + href="#Nt_136"><sup>[136]</sup></a> that breeds of animals inhabiting + wild and mountainous countries cannot be permanently modified by our + improved breeds; and as these latter are of modern origin, it has been + thought that the greater antiquity of the wilder breeds has been the + cause of their resistance to improvement by crossing; but it is more + probably due to their structure and constitution being better adapted to + the surrounding conditions. When plants are first subjected to culture, + it has been found that, during several generations, they transmit their + characters truly, that is, do not vary, and this has been attributed to + ancient characters being strongly inherited; but it may with equal or + greater probability be consequent on changed conditions of life requiring + a long time for their accumulative action. Notwithstanding these + considerations, it would perhaps be rash to deny that characters become + more strongly fixed the longer they are transmitted; but I believe that + the proposition resolves itself into this,—that all characters of + all kinds, whether new or old, tend to be inherited, and that those which + have already withstood all counteracting influences and been truly + transmitted, will, as a general rule, continue to withstand them, and + consequently be faithfully inherited.</p> + +<p><!-- Page 65 --><span class="pagenum"><a name="page65"></a>{65}</span></p> + +<p class="cenhead"><i>Prepotency in the Transmission of Character.</i></p> + + <p>When individuals distinct enough to be recognised, but of the same + family, or when two well-marked races, or two species, are crossed, the + usual result, as stated in the previous chapter, is, that the offspring + in the first generation are intermediate between their parents, or + resemble one parent in one part and the other parent in another part. But + this is by no means the invariable rule; for in many cases it is found + that certain individuals, races, and species are prepotent in + transmitting their likeness. This subject has been ably discussed by + Prosper Lucas,<a name="NtA_137" href="#Nt_137"><sup>[137]</sup></a> but + is rendered extremely complicated by the prepotency sometimes running + equally in both sexes, and sometimes more strongly in one sex than in the + other; it is likewise complicated by the presence of secondary sexual + characters, which render the comparison of mongrels with their + parent-breeds difficult.</p> + + <p>It would appear that in certain families some one ancestor, and after + him others in the same family, must have had great power in transmitting + their likeness through the male line; for we cannot otherwise understand + how the same features should so often be transmitted after marriages with + various females, as has been the case with the Austrian Emperors, and as, + according to Niebuhr, formerly occurred in certain Roman families with + their mental qualities.<a name="NtA_138" + href="#Nt_138"><sup>[138]</sup></a> The famous bull Favourite is + believed<a name="NtA_139" href="#Nt_139"><sup>[139]</sup></a> to have had + a prepotent influence on the shorthorn race. It has also been observed<a + name="NtA_140" href="#Nt_140"><sup>[140]</sup></a> with English + race-horses that certain mares have generally transmitted their own + character, whilst other mares of equally pure blood have allowed the + character of the sire to prevail.</p> + +<blockquote class="b1n"> + + <p>The truth of the principle of prepotency comes out more clearly when + certain races are crossed. The improved Shorthorns, notwithstanding that + the breed is comparatively modern, are generally acknowledged to possess + great power in impressing their likeness on all other breeds; and it is + chiefly in consequence of this power that they are so highly valued <!-- + Page 66 --><span class="pagenum"><a name="page66"></a>{66}</span>for + exportation.<a name="NtA_141" href="#Nt_141"><sup>[141]</sup></a> Godine + has given a curious case of a ram of a goat-like breed of sheep from the + Cape of Good Hope, which produced offspring hardly to be distinguished + from himself, when crossed with ewes of twelve other breeds. But two of + these half-bred ewes, when put to a merino ram, produced lambs closely + resembling the merino breed. Girou de Buzareingues<a name="NtA_142" + href="#Nt_142"><sup>[142]</sup></a> found that of two races of French + sheep the ewes of one, when crossed during successive generations with + merino rams, yielded up their character far sooner than the ewes of the + other race. Sturm and Girou have given analogous cases with other breeds + of sheep and with cattle, the prepotency running in these cases through + the male side; but I was assured on good authority in South America, that + when niata cattle are crossed with common cattle, though the niata breed + is prepotent whether males or females are used, yet that the prepotency + is strongest through the female line. The Manx cat is tailless and has + long hind legs; Dr. Wilson crossed a male Manx with common cats, and, out + of twenty-three kittens, seventeen were destitute of tails; but when the + female Manx was crossed by common male cats all the kittens had tails, + though they were generally short and imperfect.<a name="NtA_143" + href="#Nt_143"><sup>[143]</sup></a></p> + + <p>In making reciprocal crosses between pouter and fantail pigeons, the + pouter-race seemed to be prepotent through both sexes over the fantail. + But this is probably due to weak power in the fantail rather than to any + unusually strong power in the pouter, for I have observed that barbs also + preponderated over fantails. This weakness of transmission in the + fantail, though the breed is an ancient one, is said<a name="NtA_144" + href="#Nt_144"><sup>[144]</sup></a> to be general; but I have observed + one exception to the rule, namely, in a cross between a fantail and + laugher. The most curious instance known to me of weak power in both + sexes is in the trumpeter pigeon. This breed has been well known for at + least 130 years: it breeds perfectly true, as I have been assured by + those who have long kept many birds: it is characterised by a peculiar + tuft of feathers over the beak, by a crest on the head, by a most + peculiar coo quite unlike that of any other breed, and by much-feathered + feet. I have crossed both sexes with turbits of two sub-breeds, with + almond tumblers, spots, and runts, and reared many mongrels and recrossed + them; and though the crest on the head and feathered feet were inherited + (as is generally the case with most breeds), I have never seen a vestige + of the tuft over the beak or heard the peculiar coo. Boitard and Corbié<a + name="NtA_145" href="#Nt_145"><sup>[145]</sup></a> assert that this is + the invariable result of crossing trumpeters with any other breed: + Neumeister,<a name="NtA_146" href="#Nt_146"><sup>[146]</sup></a> however, + states that in Germany mongrels have been obtained, though very rarely, + which were furnished with the tuft and would trumpet: but a pair of these + mongrels with a tuft, which I imported, never trumpeted. Mr. Brent + states<a name="NtA_147" href="#Nt_147"><sup>[147]</sup></a> that the + crossed offspring of a trumpeter were crossed <!-- Page 67 --><span + class="pagenum"><a name="page67"></a>{67}</span>with trumpeters for three + generations, by which time the mongrels had 7-8ths of this blood in their + veins, yet the tuft over the beak did not appear. At the fourth + generation the tuft appeared, but the birds, though now having 15-16ths + trumpeter's blood, still did not trumpet. This case well shows the wide + difference between inheritance and prepotency; for here we have a + well-established old race which transmits it characters faithfully, but + which, when crossed with any other race, has the feeblest power of + transmitting its two chief characteristic qualities.</p> + + <p>I will give one other instance with fowls and pigeons of weakness and + strength in the transmission of the same character to their crossed + offspring. The Silk-fowl breeds true, and there is reason to believe is a + very ancient race; but when I reared a large number of mongrels from a + Silk-hen by a Spanish cock, not one exhibited even a trace of the + so-called silkiness. Mr. Hewitt also asserts that in no instance are the + silky feathers transmitted by this breed when crossed with any other + variety. But three birds out of many raised by Mr. Orton from a cross + between a silk-cock and a bantam-hen, had silky feathers.<a + name="NtA_148" href="#Nt_148"><sup>[148]</sup></a> So that it is certain + that this breed very seldom has the power of transmitting its peculiar + plumage to its crossed progeny. On the other hand, there is a silk + sub-variety of the fantail pigeon, which has its feathers in nearly the + same state as in the Silk-fowl: now we have already seen that fantails, + when crossed, possess singularly weak power in transmitting their general + qualities; but the silk sub-variety when crossed with any other + small-sized race invariably transmits its silky feathers!<a + name="NtA_149" href="#Nt_149"><sup>[149]</sup></a></p> + + <p>The law of prepotency comes into action when species are crossed, as + with races and individuals. Gärtner has unequivocally shown<a + name="NtA_150" href="#Nt_150"><sup>[150]</sup></a> that this is the case + with plants. To give one instance: when <i>Nicotiana paniculata</i> and + <i>vincæflora</i> are crossed, the character of <i>N. paniculata</i> is + almost completely lost in the hybrid; but if <i>N. quadrivalvis</i> be + crossed with <i>N. vincæflora</i>, this later species, which was before + so prepotent, now in its turn almost disappears under the power of <i>N. + quadrivalvis</i>. It is remarkable that the prepotency of one species + over another in transmission is quite independent, as shown by Gärtner, + of the greater or less facility with which the one fertilises the + other.</p> + + <p>With animals, the jackal is prepotent over the dog, as is stated by + Flourens who made many crosses between these animals; and this was + likewise the case with a hybrid which I once saw between a jackal and + terrier. I cannot doubt, from the observations of Colin and others, that + the ass is prepotent over the horse; the prepotency in this instance + running more strongly through the male than through the female ass; so + that the mule resembles the ass more closely than does the hinny.<a + name="NtA_151" href="#Nt_151"><sup>[151]</sup></a> The <!-- Page 68 + --><span class="pagenum"><a name="page68"></a>{68}</span>male pheasant, + judging from Mr. Hewitt's descriptions,<a name="NtA_152" + href="#Nt_152"><sup>[152]</sup></a> and from the hybrids which I have + seen, preponderates over the domestic fowl; but the latter, as far as + colour is concerned, has considerable power of transmission, for hybrids + raised from five differently coloured hens differed greatly in plumage. I + formerly examined some curious hybrids in the Zoological Gardens, between + the Penguin variety of the common duck and the Egyptian goose (<i>Tadorna + Ægyptiaca</i>); and although I will not assert that the domesticated + variety preponderated over the natural species, yet it had strongly + impressed its unnatural upright figure on these hybrids.</p> + + <p>I am aware that such cases as the foregoing have been ascribed by + various authors, not to one species, race, or individual being prepotent + over the other in impressing it character on its crossed offspring, but + to such rules as that the father influences the external characters and + the mother the internal or vital organs. But the great diversity of the + rules given by various authors almost proves their falseness. Dr. Prosper + Lucas has fully discussed this point, and has shown<a name="NtA_153" + href="#Nt_153"><sup>[153]</sup></a> that none of the rules (and I could + add others to those quoted by him) apply to all animals. Similar rules + have been enounced for plants, and have been proved by Gärtner<a + name="NtA_154" href="#Nt_154"><sup>[154]</sup></a> to be all erroneous. + If we confine our view to the domesticated races of a single species, or + perhaps even to the species of the same genus, some such rules may hold + good; for instance, it seems that in reciprocally crossing various breeds + of fowls the male generally gives colour;<a name="NtA_155" + href="#Nt_155"><sup>[155]</sup></a> but conspicuous exceptions have + passed under my own eyes. In sheep it seems that the ram usually gives + its peculiar horns and fleece to its crossed offspring, and the bull the + presence or absence of horns.</p> + + <p>In the following chapter on Crossing I shall have occasion to show + that certain characters are rarely or never blended by crossing, but are + <!-- Page 69 --><span class="pagenum"><a + name="page69"></a>{69}</span>transmitted in an unmodified state from + either parent-form; I refer to this fact here because it is sometimes + accompanied on the one side by prepotency, which thus acquires the false + appearance of unusual strength. In the same chapter I shall show that the + rate at which a species or breed absorbs and obliterates another by + repeated crosses, depends in chief part on prepotency in + transmission.</p> + +</blockquote> + + <p>In conclusion, some of the cases above given,—for instance, that + of the trumpeter pigeon,—prove that there is a wide difference + between mere inheritance and prepotency. This latter power seems to us, + in our ignorance, to act in most cases quite capriciously. The very same + character, even though it be an abnormal or monstrous one, such as silky + feathers, may be transmitted by different species, when crossed, either + with prepotent force or singular feebleness. It is obvious, that a + purely-bred form of either sex, in all cases in which prepotency does not + run more strongly in one sex than the other, will transmit its character + with prepotent force over a mongrelized and already variable form.<a + name="NtA_156" href="#Nt_156"><sup>[156]</sup></a> From several of the + above-given cases we may conclude that mere antiquity of character does + not by any means necessarily make it prepotent. In some cases prepotency + apparently depends on the same character being present and visible in one + of the two breeds which are crossed, and latent or invisible in the other + breed; and in this case it is natural that the character which is + potentially present in both should be prepotent. Thus, we have reason to + believe that there is a latent tendency in all horses to be dun-coloured + and striped; and when a horse of this kind is crossed with one of any + other colour, it is said that the offspring are almost sure to be + striped. Sheep have a similar latent tendency to become dark-coloured, + and we have seen with what prepotent force a ram with a few black spots, + when crossed with sheep of various breeds, coloured its offspring. All + pigeons have a latent tendency to become slaty-blue, with certain + characteristic marks, and it is known that, when a bird thus coloured is + crossed with one of any other colour, it is most difficult afterwards to + eradicate the blue tint. A nearly parallel case is offered by those black + bantams which, as they grow <!-- Page 70 --><span class="pagenum"><a + name="page70"></a>{70}</span>old, develop a latent tendency to acquire + red feathers. But there are exceptions to the rule: hornless breeds of + cattle possess a latent capacity to reproduce horns, yet when crossed + with horned breeds they do not invariably produce offspring bearing + horns.</p> + + <p>We meet with analogous cases with plants. Striped flowers, though they + can be propagated truly by seed, have a latent tendency to become + uniformly coloured, but when once crossed by a uniformly coloured + variety, they ever afterwards fail to produce striped seedlings.<a + name="NtA_157" href="#Nt_157"><sup>[157]</sup></a> Another case is in + some respects more curious: plants bearing peloric or regular flowers + have so strong a latent tendency to reproduce their normally irregular + flowers, that this often occurs by buds when a plant is transplanted into + poorer or richer soil.<a name="NtA_158" + href="#Nt_158"><sup>[158]</sup></a> Now I crossed the peloric snapdragon + (<i>Antirrhinum majus</i>), described in the last chapter, with pollen of + the common form; and the latter, reciprocally, with peloric pollen. I + thus raised two great beds of seedlings, and not one was peloric. + Naudin<a name="NtA_159" href="#Nt_159"><sup>[159]</sup></a> obtained the + same result from crossing a peloric Linaria with the common form. I + carefully examined the flowers of ninety plants of the crossed + Antirrhinum in the two beds, and their structure had not been in the + least affected by the cross, except that in a few instances the minute + rudiment of the fifth stamen, which is always present, was more fully or + even completely developed. It must not be supposed that this entire + obliteration of the peloric structure in the crossed plants can be + accounted for by any incapacity of transmission; for I raised a large bed + of plants from the peloric Antirrhinum, artificially fertilised by its + own pollen, and sixteen plants, which alone survived the winter, were all + as perfectly peloric as the parent-plant. Here we have a good instance of + the wide difference between the inheritance of a character and the power + of transmitting it to crossed offspring. The crossed plants, which + perfectly resembled the common snapdragon, were allowed to sow + themselves, and, out of a hundred and twenty-seven seedlings, + eighty-eight proved to be common snapdragons, two were in an intermediate + condition between the peloric and normal state, <!-- Page 71 --><span + class="pagenum"><a name="page71"></a>{71}</span>and thirty-seven were + perfectly peloric, having reverted to the structure of their one + grandparent. This case seems at first sight to offer an exception to the + rule formerly given, namely, that a character which is present in one + form and latent in the other is generally transmitted with prepotent + force when the two forms are crossed. For in all the Scrophulariaceæ, and + especially in the genera Antirrhinum and Linaria, there is, as was shown + in the last chapter, a strong latent tendency to become peloric; and + there is also, as we have just seen, a still stronger tendency in all + peloric plants to reacquire their normal irregular structure. So that we + have two opposed latent tendencies in the same plants. Now, with the + crossed Antirrhinums the tendency to produce normal or irregular flowers, + like those of the common Snapdragon, prevailed in the first generation; + whilst the tendency to pelorism, appearing to gain strength by the + intermission of a generation, prevailed to a large extent in the second + set of seedlings. How it is possible for a character to gain strength by + the intermission of a generation, will be considered in the chapter on + pangenesis.</p> + + <p>On the whole, the subject of prepotency is extremely + intricate,—from its varying so much in strength, even in regard to + the same character, in different animals,—from its running either + equally in both sexes, or, as frequently is the case with animals, but + not with plants, much stronger in the one sex than the other,—from + the existence of secondary sexual characters,—from the transmission + of certain characters being limited, as we shall immediately see, by + sex,—from certain characters not blending together,—and, + perhaps, occasionally from the effects of a previous fertilisation on the + mother. It is therefore not surprising that every one hitherto has been + baffled in drawing up general rules on the subject of prepotency.</p> + +<p class="cenhead"><i>Inheritance as limited by Sex.</i></p> + + <p>New characters often appear in one sex, and are afterwards transmitted + to the same sex, either exclusively or in a much greater degree than to + the other. This subject is important, because with animals of many kinds + in a state of nature, both high and low in the scale, secondary sexual + characters, not in <!-- Page 72 --><span class="pagenum"><a + name="page72"></a>{72}</span>any way directly connected with the organs + of reproduction, are often conspicuously present. With our domesticated + animals, also, these same secondary characters are often found to differ + greatly from the state in which they exist in the parent-species. And the + principle of inheritance as limited by sex shows how such characters + might have been first acquired and subsequently modified.</p> + +<blockquote class="b1n"> + + <p>Dr. P. Lucas, who has collected many facts on this subject, shows<a + name="NtA_160" href="#Nt_160"><sup>[160]</sup></a> that when a + peculiarity, in no manner connected with the reproductive organs, appears + in either parent, it is often transmitted exclusively to the offspring of + the same sex, or to a much greater number of them than of the opposite + sex. Thus, in the family of Lambert, the horn-like projections on the + skin were transmitted from the father to his sons and grandsons alone; so + it has been with other cases of ichthyosis, with supernumerary digits, + with a deficiency of digits and phalanges, and in a lesser degree with + various diseases, especially with colour-blindness, and a hæmorrhagic + diathesis, that is, an extreme liability to profuse and uncontrollable + bleeding from trifling wounds. On the other hand, mothers have + transmitted, during several generations, to their daughters alone, + supernumerary and deficient digits, colour-blindness, and other + peculiarities. So that we see that the very same peculiarity may become + attached to either sex, and be long inherited by that sex alone; but the + attachment in certain cases is much more frequent to one than the other + sex. The same peculiarities also may be promiscuously transmitted to + either sex. Dr. Lucas gives other cases, showing that the male + occasionally transmits his peculiarities to his daughters alone, and the + mother to her sons alone; but even in this case we see that inheritance + is to a certain extent, though inversely, regulated by sex. Dr. Lucas, + after weighing the whole evidence, comes to the conclusion that every + peculiarity, according to the sex in which it first appears, tends to be + transmitted in a greater or lesser degree to that sex.</p> + + <p>A few details from the many cases collected by Mr. Sedgwick,<a + name="NtA_161" href="#Nt_161"><sup>[161]</sup></a> may be here given. + Colour-blindness, from some unknown cause, shows itself much oftener in + males than in females; in upwards of two hundred cases collected by Mr. + Sedgwick, nine-tenths related to men; but it is eminently liable to be + transmitted through women. In the case given by Dr. Earle, members of + eight related families were affected during five generations: these + families consisted of sixty-one individuals, namely, of thirty-two males, + of whom nine-sixteenths were incapable of distinguishing colour, and of + twenty-nine females, of whom only one-fifteenth were thus affected. <!-- + Page 73 --><span class="pagenum"><a name="page73"></a>{73}</span>Although + colour-blindness thus generally clings to the male sex, nevertheless, in + one instance in which it first appeared in a female, it was transmitted + during five generations to thirteen individuals, all of whom were + females. A hæmorrhagic diathesis, often accompanied by rheumatism, has + been known to affect the males alone during five generations, being + transmitted, however, through the females. It is said that deficient + phalanges in the fingers have been inherited by the females alone during + ten generations. In another case, a man thus deficient in both hands and + feet, transmitted the peculiarity to his two sons and one daughter; but + in the third generation, out of nineteen grandchildren, twelve sons had + the family defect, whilst the seven daughters were free. In ordinary + cases of sexual limitation, the sons or daughters inherit the + peculiarity, whatever it may be, from their father or mother, and + transmit it to their children of the same sex; but generally with the + hæmorrhagic diathesis, and often with colour-blindness, and in some other + cases, the sons never inherit the peculiarity directly from their + fathers, but the daughters, and the daughters alone, transmit the latent + tendency, so that the sons of the daughters alone exhibit it. Thus, the + father, grandson, and great-great-grandson will exhibit a + peculiarity,—the grandmother, daughter, and great-granddaughter + having transmitted it in a latent state. Hence we have, as Mr. Sedgwick + remarks, a double kind of atavism or reversion; each grandson apparently + receiving and developing the peculiarity from his grandfather, and each + daughter apparently receiving the latent tendency from her + grandmother.</p> + + <p>From the various facts recorded by Dr. Prosper Lucas, Mr. Sedgwick, + and others, there can be no doubt that peculiarities first appearing in + either sex, though not in any way necessarily or invariably connected + with that sex, strongly tend to be inherited by the offspring of the same + sex, but are often transmitted in a latent state through the opposite + sex.</p> + + <p>Turning now to domesticated animals, we find that certain characters + not proper to the parent-species are often confined to, and inherited by, + one sex alone; but we do not know the history of the first appearance of + such characters. In the chapter on Sheep, we have seen that the males of + certain races differ greatly from the females in the shape of their + horns, these being absent in the ewes of some breeds, in the development + of fat in the tail in certain fat-tailed breeds, and in the outline of + the forehead. These differences, judging from the character of the allied + wild species, cannot be accounted for by supposing that they have been + derived from distinct parent-forms. There is, also, a great difference + between the horns of the two sexes in one Indian breed of goats. The bull + zebu is said to have a larger hump than the cow. In the Scotch deer-hound + the two sexes differ in size more than in any other variety of the dog,<a + name="NtA_162" href="#Nt_162"><sup>[162]</sup></a> and, judging from + analogy, more than in the aboriginal parent-species. The peculiar colour + called tortoise-shell is very rarely seen in a male cat; the males of + this variety being of a rusty tint. A tendency to baldness in man before + the advent of old age is certainly inherited; and in the European, or at + least in the <!-- Page 74 --><span class="pagenum"><a + name="page74"></a>{74}</span>Englishman, is an attribute of the male sex, + and may almost be ranked as an incipient secondary sexual character.</p> + + <p>In various breeds of the fowl the males and females often differ + greatly; and these differences are far from being the same with those + which distinguish the two sexes in the parent-species, the <i>Gallus + bankiva</i>; and consequently have originated under domestication. In + certain sub-varieties of the Game race we have the unusual case of the + hens differing from each other more than the cocks. In an Indian breed of + a white colour stained with soot, the hens invariably have black skins, + and their bones are covered by a black periosteum, whilst the cocks are + never or most rarely thus characterised. Pigeons offer a more interesting + case; for the two sexes rarely differ throughout the whole great family, + and the males and females of the parent-form, the <i>C. livia</i>, are + undistinguishable; yet we have seen that with Pouters the male has the + characteristic quality of pouting more strongly developed than the + female; and in certain sub-varieties<a name="NtA_163" + href="#Nt_163"><sup>[163]</sup></a> the males alone are spotted or + striated with black. When male and female English carrier-pigeons are + exhibited in separate pens, the difference in the development of the + wattle over the beak and round the eyes is conspicuous. So that here we + have instances of the appearance of secondary sexual characters in the + domesticated races of a species in which such differences are naturally + quite absent.</p> + +</blockquote> + + <p>On the other hand, secondary sexual characters which properly belong + to the species are sometimes quite lost, or greatly diminished, under + domestication. We see this in the small size of the tusks in our improved + breeds of the pig, in comparison with those of the wild boar. There are + sub-breeds of fowls in which the males have lost the fine flowing + tail-feathers and hackles; and others in which there is no difference in + colour between the two sexes. In some cases the barred plumage, which in + gallinaceous birds is commonly the attribute of the hen, has been + transferred to the cock, as in the cuckoo sub-breeds. In other cases + masculine characters have been partly transferred to the female, as with + the splendid plumage of the golden-spangled Hamburgh hen, the enlarged + comb of the Spanish hen, the pugnacious disposition of the Game hen, and + as in the well-developed spurs which occasionally appear in the hens of + various breeds. In Polish fowls both sexes are ornamented with a topknot, + that of the male being formed of hackle-like feathers, and this is a new + male character in the genus Gallus. On the whole, as far as I can judge, + new characters are more apt <!-- Page 75 --><span class="pagenum"><a + name="page75"></a>{75}</span>to appear in the males of our domesticated + animals than in the females, and afterwards to be either exclusively or + more strongly inherited by the males. Finally, in accordance with the + principle of inheritance as limited by sex, the appearance of secondary + sexual characters in natural species offers no especial difficulty, and + their subsequent increase and modification, if of any service to the + species, would follow through that form of selection which in my 'Origin + of Species' I have called sexual selection.</p> + +<p class="cenhead"><i>Inheritance at corresponding periods of Life.</i></p> + + <p>This is an important subject. Since the publication of my 'Origin of + Species,' I have seen no reason to doubt the truth of the explanation + there given of perhaps the most remarkable of all the facts in biology, + namely, the difference between the embryo and the adult animal. The + explanation is, that variations do not necessarily or generally occur at + a very early period of embryonic growth, and that such variations are + inherited at a corresponding age. As a consequence of this the embryo, + even when the parent-form undergoes a great amount of modification, is + left only slightly modified; and the embryos of widely-different animals + which are descended from a common progenitor remain in many important + respects like each other and their common progenitor. We can thus + understand why embryology should throw a flood of light on the natural + system of classification, for this ought to be as far as possible + genealogical. When the embryo leads an independent life, that is, becomes + a larva, it has to be adapted to the surrounding conditions in its + structure and instincts, independently of those of its parents; and the + principle of inheritance at corresponding periods of life renders this + possible.</p> + + <p>This principle is, indeed, in one way so obvious that it escapes + attention. We possess a number of races of animals and plants, which, + when compared with each other and with their parent-forms, present + conspicuous differences, both in the immature and mature states. Look at + the seeds of the several kinds of peas, beans, maize, which can be + propagated truly, and see how they differ in size, colour, and shape, + whilst the <!-- Page 76 --><span class="pagenum"><a + name="page76"></a>{76}</span>full-grown plants differ but little. + Cabbages on the other hand differ greatly in foliage and manner of + growth, but hardly at all in their seeds; and generally it will be found + that the differences between cultivated plants at different periods of + growth are not necessarily closely connected together, for plants may + differ much in their seeds and little when full-grown, and conversely may + yield seeds hardly distinguishable, yet differ much when full-grown. In + the several breeds of poultry, descended from a single species, + differences in the eggs and chickens, in the plumage at the first and + subsequent moults, in the comb and wattles during maturity, are all + inherited. With man peculiarities in the milk and second teeth, of which + I have received the details, are inheritable, and with man longevity is + often transmitted. So again with our improved breeds of cattle and sheep, + early maturity, including the early development of the teeth, and with + certain breeds of fowl the early appearance of secondary sexual + characters, all come under the same head of inheritance at corresponding + periods.</p> + + <p>Numerous analogous facts could be given. The silk-moth, perhaps, + offers the best instance; for in the breeds which transmit their + characters truly, the eggs differ in size, colour, and shape;—the + caterpillars differ, in moulting three or four times, in colour, even in + having a dark-coloured mark like an eyebrow, and in the loss of certain + instincts;—the cocoons differ in size, shape, and in the colour and + quality of the silk; these several differences being followed by slight + or barely distinguishable differences in the mature moth.</p> + + <p>But it may be said that, if in the above cases a new peculiarity is + inherited, it must be at the corresponding stage of development; for an + egg or seed can resemble only an egg or seed, and the horn in a + full-grown ox can resemble only a horn. The following cases show + inheritance at corresponding periods more plainly, because they refer to + peculiarities which might have supervened, as far as we can see, earlier + or later in life, yet are inherited at the same period at which they + first appeared.</p> + +<blockquote class="b1n"> + + <p>In the Lambert family the porcupine-like excrescences appeared in the + father and sons at the same age, namely, about nine weeks after <!-- Page + 77 --><span class="pagenum"><a name="page77"></a>{77}</span>birth.<a + name="NtA_164" href="#Nt_164"><sup>[164]</sup></a> In the extraordinary + hairy family described by Mr. Crawfurd,<a name="NtA_165" + href="#Nt_165"><sup>[165]</sup></a> children were produced during three + generations with hairy ears; in the father the hair began to grow over + his body at six years old; in his daughter somewhat earlier, namely, at + one year; and in both generations the milk teeth appeared late in life, + the permanent teeth being afterwards singularly deficient. Greyness of + hair at an unusually early age has been transmitted in some families. + These cases border on diseases inherited at corresponding periods of + life, to which I shall immediately refer.</p> + + <p>It is a well-known peculiarity with almond-tumbler pigeons, that the + full beauty and peculiar character of the plumage does not appear until + the bird has moulted two or three times. Neumeister describes and figures + a breed of pigeons in which the whole body is white except the breast, + neck, and head; but before the first moult all the white feathers acquire + coloured edges. Another breed is more remarkable: its first plumage is + black, with rusty-red wing-bars and a crescent-shaped mark on the breast; + these marks then became white, and remain so during three or four moults; + but after this period the white spreads over the body, and the bird loses + its beauty.<a name="NtA_166" href="#Nt_166"><sup>[166]</sup></a> Prize + canary-birds have their wings and tail black: "this colour, however, is + only retained until the first moult, so that they must be exhibited ere + the change takes place. Once moulted, the peculiarity has ceased. Of + course all the birds emanating from this stock have black wings and tails + the first year."<a name="NtA_167" href="#Nt_167"><sup>[167]</sup></a> A + curious and somewhat analogous account has been given<a name="NtA_168" + href="#Nt_168"><sup>[168]</sup></a> of a family of wild pied rooks which + were first observed in 1798, near Chalfont, and which every year from + that date up to the period of the published notice, viz. 1837, "have + several of their brood particoloured, black and white. This variegation + of the plumage, however, disappears with the first moult; but among the + next young families there are always a few pied ones." These changes of + plumage, which appear and are inherited at various corresponding periods + of life in the pigeon, canary-bird, and rook, are remarkable, because the + parent-species undergo no such change.</p> + + <p>Inherited diseases afford evidence in some respects of less value than + the foregoing cases, because diseases are not necessarily connected with + any change in structure; but in other respects of more value, because the + periods have been more carefully observed. Certain diseases are + communicated to the child apparently by a process like inoculation, and + the child is from the first affected; such cases may be here passed over. + Large classes of diseases usually appear at certain ages, such as St. + Vitus's dance in youth, consumption in early mid-life, gout later, and + apoplexy still later; and these are naturally inherited at the same + period. But even in diseases of this class, instances have been recorded, + as with St. Vitus's <!-- Page 78 --><span class="pagenum"><a + name="page78"></a>{78}</span>dance, showing that an unusually early or + late tendency to the disease is inheritable.<a name="NtA_169" + href="#Nt_169"><sup>[169]</sup></a> In most cases the appearance of any + inherited disease is largely determined by certain critical periods in + each person's life, as well as by unfavourable conditions. There are many + other diseases, which are not attached to any <span class="correction" + title="Original reads `particuliar'.">particular</span> period, but which + certainly tend to appear in the child at about the same age at which the + parent was first attacked. An array of high authorities, ancient and + modern, could be given in support of this proposition. The illustrious + Hunter believed in it; and Piorry<a name="NtA_170" + href="#Nt_170"><sup>[170]</sup></a> cautions the physician to look + closely to the child at the period when any grave inheritable disease + attacked the parent. Dr. Prosper Lucas,<a name="NtA_171" + href="#Nt_171"><sup>[171]</sup></a> after collecting facts from every + source, asserts that affections of all kinds, though not related to any + particular period of life, tend to reappear in the offspring at whatever + period of life they first appeared in the progenitor.</p> + + <p>As the subject is important, it may be well to give a few instances, + simply as illustrations, not as proof; for proof, recourse must be had to + the authorities above quoted. Some of the following cases have been + selected for the sake of showing that, when a slight departure from the + rule occurs, the child is affected somewhat earlier in life than the + parent. In the family of Le Compte blindness was inherited during three + generations, and no less than thirty-seven children and grandchildren + were all affected at about the same age, namely seventeen or eighteen.<a + name="NtA_172" href="#Nt_172"><sup>[172]</sup></a> In another case a + father and his four children all became blind at twenty-one years old; in + another, a grandmother grew blind at thirty-five, her daughter at + nineteen, and three grandchildren at the ages of thirteen and eleven.<a + name="NtA_173" href="#Nt_173"><sup>[173]</sup></a> So with deafness, two + brothers, their father and paternal grandfather, all became deaf at the + age of forty.<a name="NtA_174" href="#Nt_174"><sup>[174]</sup></a></p> + + <p>Esquirol gives several striking instances of insanity coming on at the + same age, as that of a grandfather, father, and son, who all committed + suicide near their fiftieth year. Many other cases could be given, as of + a whole family who became insane at the age of forty.<a name="NtA_175" + href="#Nt_175"><sup>[175]</sup></a> Other cerebral affections sometimes + follow the same rule,—for instance, epilepsy and apoplexy. A woman + died of the latter disease when sixty-three years old; one of her + daughters at forty-three, and the other at sixty-seven: the latter had + twelve children, who all died from tubercular meningitis.<a + name="NtA_176" href="#Nt_176"><sup>[176]</sup></a> I mention this latter + case because it illustrates a frequent occurrence, namely, a change in + the precise nature of an inherited disease, though still affecting the + same organ.</p> + +<p><!-- Page 79 --><span class="pagenum"><a name="page79"></a>{79}</span></p> + + <p>Asthma has attacked several members of the same family when forty + years old, and other families during infancy. The most different + diseases, as angina pectoris, stone in the bladder, and various + affections of the skin, have appeared in successive generations at nearly + the same age. The little finger of a man began from some unknown cause to + grow inwards, and the same finger in his two sons began at the same age + to bend inwards in a similar manner. Strange and inexplicable neuralgic + affections have caused parents and children to suffer agonies at about + the same period of life.<a name="NtA_177" + href="#Nt_177"><sup>[177]</sup></a></p> + + <p>I will give only two other cases, which are interesting as + illustrating the disappearance as well as the appearance of disease at + the same age. Two brothers, their father, their paternal uncles, seven + cousins, and their paternal grandfather, were all similarly affected by a + skin-disease, called pityriasis versicolor; "the disease, strictly + limited to the males of the family (though transmitted through the + females), usually appeared at puberty, and disappeared at about the age + of forty or forty-five years." The second case is that of four brothers, + who when about twelve years old suffered almost every week from severe + headaches, which were relieved only by a recumbent position in a dark + room. Their father, paternal uncles, paternal grandfather, and paternal + granduncles all suffered in the same way from headaches, which ceased at + the age of fifty-four or fifty-five in all those who lived so long. None + of the females of the family were affected.<a name="NtA_178" + href="#Nt_178"><sup>[178]</sup></a></p> + +</blockquote> + + <p>It is impossible to read the foregoing accounts, and the many others + which have been recorded, of diseases coming on during three or even more + generations, at the same age in several members of the same family, + especially in the case of rare affections in which the coincidence cannot + be attributed to chance, and doubt that there is a strong tendency to + inheritance in disease at corresponding periods of life. When the rule + fails, the disease is apt to come on earlier in the child than in the + parent; the exceptions in the other direction being vey much rarer. Dr. + Lucas<a name="NtA_179" href="#Nt_179"><sup>[179]</sup></a> alludes to + several cases of inherited diseases coming on at an earlier period. I + have already given one striking instance with blindness during three + generations; and Mr. Bowman remarks that this frequently occurs with + cataract. With cancer there seems to be a peculiar liability to earlier + inheritance: Mr. Paget, who has particularly <!-- Page 80 --><span + class="pagenum"><a name="page80"></a>{80}</span>attended to this subject, + and tabulated a large number of cases, informs me that he believes that + in nine cases out of ten the later generation suffers from the disease at + an earlier period than the previous generation. He adds, "In the + instances in which the opposite relation holds, and the members of later + generations have cancer at a later age than their predecessors, I think + it will be found that the non-cancerous parents have lived to extreme old + ages." So that the longevity of a non-affected parent seems to have the + power of determining in the offspring the fatal period; and we thus + apparently get another element of complexity in inheritance.</p> + + <p>The facts, showing that with certain diseases the period of + inheritance occasionally or even frequently advances, are important with + respect to the general descent-theory, for they render it in some degree + probable that the same thing would occur with ordinary modifications of + structure. The final result of a long series of such advances would be + the gradual obliteration of characters proper to the embryo and larva, + which would thus come to resemble more and more closely the mature + parent-form. But any structure which was of service to the embryo or + larva would be preserved by the destruction at this stage of growth of + each individual which manifested any tendency to lose at too early an age + its own proper character.</p> + + <p>Finally, from the numerous races of cultivated plants and domestic + animals, in which the seed or eggs, the young or old, differ from each + other and from their parent-species;—from the cases in which new + characters have appeared at a particular period, and afterwards have been + inherited at the same period;—and from what we know with respect to + disease, we must believe in the truth of the great principle of + inheritance at corresponding periods of life.</p> + +<hr class="short" /> + + <p><i>Summary of the three preceding Chapters.</i>—Strong as is the + force of inheritance, it allows the incessant appearance of new + characters. These, whether beneficial or injurious, of the most trifling + importance, such as a shade of colour in a flower, a coloured lock of + hair, or a mere gesture; or of the highest importance, as when affecting + the brain or an organ so perfect <!-- Page 81 --><span class="pagenum"><a + name="page81"></a>{81}</span>and complex as the eye; or of so grave a + nature as to deserve to be called a monstrosity, or so peculiar as not to + occur normally in any member of the same natural class, are all sometimes + strongly inherited by man, the lower animals, and plants. In numberless + cases it suffices for the inheritance of a peculiarity that one parent + alone should be thus characterised. Inequalities in the two sides of the + body, though opposed to the law of symmetry, may be transmitted. There is + a considerable body of evidence showing that even mutilations, and the + effects of accidents, especially or perhaps exclusively when followed by + disease, are occasionally inherited. There can be no doubt that the evil + effects of long-continued exposure in the parent to injurious conditions + are sometimes transmitted to the offspring. So it is, as we shall see in + a future chapter, with the effects of the use and disuse of parts, and of + mental habits. Periodical habits are likewise transmitted, but generally, + as it would appear, with little force.</p> + + <p>Hence we are led to look at inheritance as the rule, and + non-inheritance as the anomaly. But this power often appears to us in our + ignorance to act capriciously, transmitting a character with inexplicable + strength or feebleness. The very same peculiarity, as the weeping habit + of trees, silky-feathers, &c., may be inherited either firmly or not + at all by different members of the same group, and even by different + individuals of the same species, though treated in the same manner. In + this latter case we see that the power of transmission is a quality which + is merely individual in its attachment. As with single characters, so it + is with the several concurrent slight differences which distinguish + sub-varieties or races; for of these, some can be propagated almost as + truly as species, whilst others cannot be relied on. The same rule holds + good with plants, when propagated by bulbs, offsets, &c., which in + one sense still form parts of the same individual, for some varieties + retain or inherit through successive bud-generations their character far + more truly than others.</p> + + <p>Some characters not proper to the parent-species have certainly been + inherited from an extremely remote epoch, and may therefore be considered + as firmly fixed. But it is doubtful whether length of inheritance in + itself gives fixedness of character; <!-- Page 82 --><span + class="pagenum"><a name="page82"></a>{82}</span>though the chances are + obviously in favour of any character which has long been transmitted true + or unaltered, still being transmitted true as long as the conditions of + life remain the same. We know that many species, after having retained + the same character for countless ages, whilst living under their natural + conditions, when domesticated have varied in the most diversified manner, + that is, have failed to transmit their original form; so that no + character appears to be absolutely fixed. We can sometimes account for + the failure of inheritance by the conditions of life being opposed to the + development of certain characters; and still oftener, as with plants + cultivated by grafts and buds, by the conditions causing new and slight + modifications incessantly to appear. In this latter case it is not that + inheritance wholly fails, but that new characters are continually + superadded. In some few cases, in which both parents are similarly + characterised, inheritance seems to gain so much force by the combined + action of the two parents, that it counteracts its own power, and a new + modification is the result.</p> + + <p>In many cases the failure of the parents to transmit their likeness is + due to the breed having been at some former period crossed; and the child + takes after his grandparent or more remote ancestor of foreign blood. In + other cases, in which the breed has not been crossed, but some ancient + character has been lost through variation, it occasionally reappears + through reversion, so that the parents apparently fail to transmit their + own likeness. In all cases, however, we may safely conclude that the + child inherits all its characters from its parents, in whom certain + characters are latent, like the secondary sexual characters of one sex in + the other. When, after a long succession of bud-generations, a flower or + fruit becomes separated into distinct segments, having the colours or + other attributes of both parent-forms, we cannot doubt that these + characters were latent in the earlier buds, though they could not then be + detected, or could be detected only in an intimately commingled state. So + it is with animals of crossed parentage, which with advancing years + occasionally exhibit characters derived from one of their two parents, of + which not a trace could at first be perceived. Certain monstrosities, + which resemble what naturalists call the typical form of the group in + question, <!-- Page 83 --><span class="pagenum"><a + name="page83"></a>{83}</span>apparently come under the same law of + reversion. It is assuredly an astonishing fact that the male and female + sexual elements, that buds, and even full-grown animals, should retain + characters, during several generations in the case of crossed breeds, and + during thousands of generations in the case of pure breeds, written as it + were in invisible ink, yet ready at any time to be evolved under the + requisite conditions.</p> + + <p>What these conditions are, we do not in many cases at all know. But + the act of crossing in itself, apparently from causing some disturbance + in the organisation, certainly gives a strong tendency to the + reappearance of long-lost characters, both corporeal and mental, + independently of those derived from the cross. A return of any species to + its natural conditions of life, as with feral animals and plants, favours + reversion; though it is certain that this tendency exists, we do not know + how far it prevails, and it has been much exaggerated. On the other hand, + the crossed offspring of plants which have had their organisation + disturbed by cultivation, are more liable to reversion than the crossed + offspring of species which have always lived under their natural + conditions.</p> + + <p>When distinguishable individuals of the same family, or races, or + species are crossed, we see that the one is often prepotent over the + other in transmitting its own character. A race may possess a strong + power of inheritance, and yet when crossed, as we have seen with + trumpeter-pigeons, yield to the prepotency of every other race. + Prepotentcy of transmission may be equal in the two sexes of the same + species, but often runs more strongly in one sex. It plays an important + part in determining the rate at which one race can be modified or wholly + absorbed by repeated crosses with another. We can seldom tell what makes + one race or species prepotent over another; but it sometimes depends on + the same character being present and visible in one parent, and latent or + potentially present in the other.</p> + + <p>Characters may first appear in either sex, but oftener in the male + than in the female, and afterwards be transmitted to the offspring of the + same sex. In this case we may feel confident that the peculiarity in + question is really present though latent in the opposite sex; hence the + father may transmit through his daughter any character to his grandson; + and the mother <!-- Page 84 --><span class="pagenum"><a + name="page84"></a>{84}</span>conversely to her granddaughter. We thus + learn, and the fact is an important one, that transmission and + development are distinct powers. Occasionally these two powers seem to be + antagonistic, or incapable of combination in the same individual; for + several cases have been recorded in which the son has not directly + inherited a character from his father, or directly transmitted it to his + son, but has received it by transmission through his non-affected mother, + and transmitted it through his non-affected daughter. Owing to + inheritance being limited by sex, we can see how secondary sexual + characters may first have arisen under nature; their preservation and + accumulation being dependent on their service to either sex.</p> + + <p>At whatever period of life a new character first appears, it generally + remains latent in the offspring until a corresponding age is attained, + and then it is developed. When this rule fails, the child generally + exhibits the character at an earlier period than the parent. On this + principle of inheritance at corresponding periods, we can understand how + it is that most animals display from the germ to maturity such a + marvellous succession of characters.</p> + + <p>Finally, though much remains obscure with respect to Inheritance, we + may look at the following laws as fairly well established. Firstly, a + tendency in every character, new and old, to be transmitted by seminal + and bud generation, though often counteracted by various known and + unknown causes. Secondly, reversion or atavism, which depends on + transmission and development being distinct powers: it acts in various + degrees and manners through both seminal and bud generation. Thirdly, + prepotency of transmission, which may be confined to one sex, or be + common to both sexes of the prepotent form. Fourthly, transmission, + limited by sex, generally to the same sex in which the inherited + character first appeared. Fifthly, inheritance at corresponding periods + of life, with some tendency to the earlier development of the inherited + character. In these laws of Inheritance, as displayed under + domestication, we see an ample provision for the production, through + variability and natural selection, of new specific forms.</p> + +<hr class="full" /> + +<p><!-- Page 85 --><span class="pagenum"><a name="page85"></a>{85}</span></p> + +<h3>CHAPTER XV.</h3> + +<p class="cenhead">ON CROSSING.</p> + +<blockquote class="b1n"> + + <p><span class="scac">FREE INTERCROSSING OBLITERATES THE DIFFERENCES + BETWEEN ALLIED BREEDS</span>—<span class="scac">WHEN THE NUMBERS OF + TWO COMMINGLING BREEDS ARE UNEQUAL, ONE ABSORBS THE + OTHER</span>—<span class="scac">THE RATE OF ABSORPTION DETERMINED + BY PREPOTENCY OF TRANSMISSION, BY THE CONDITIONS OF LIFE, AND BY NATURAL + SELECTION</span>—<span class="scac">ALL ORGANIC BEINGS OCCASIONALLY + INTERCROSS; APPARENT EXCEPTIONS</span>—<span class="scac">ON + CERTAIN CHARACTERS INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE + WHICH HAVE SUDDENLY APPEARED IN THE INDIVIDUAL</span>—<span + class="scac">ON THE MODIFICATION OF OLD RACES, AND THE FORMATION OF NEW + RACES, BY CROSSING</span>—<span class="scac">SOME CROSSED RACES + HAVE BRED TRUE FROM THEIR FIRST PRODUCTION</span>—<span + class="scac">ON THE CROSSING OF DISTINCT SPECIES IN RELATION TO THE + FORMATION OF DOMESTIC RACES.</span></p> + +</blockquote> + + <p>In the two previous chapters, when discussing reversion and + prepotency, I was necessarily led to give many facts on crossing. In the + present chapter I shall consider the part which crossing plays in two + opposed directions,—firstly, in obliterating characters, and + consequently in preventing the formation of new races; and secondly, in + the modification of old races, or in the formation of new and + intermediate races, by a combination of characters. I shall also show + that certain characters are incapable of fusion.</p> + + <p>The effects of free or uncontrolled breeding between the members of + the same variety or of closely allied varieties are important; but are so + obvious that they need not be discussed at much length. It is free + intercrossing which chiefly gives uniformity, both under nature and under + domestication, to the individuals of the same species or variety, when + they live mingled together and are not exposed to any cause inducing + excessive variability. The prevention of free crossing, and the + intentional matching of individual animals, are the corner-stones of the + breeder's art. No man in his senses would expect to improve or modify a + breed in any particular manner, or keep an old breed true and distinct, + unless he separated his animals. The killing of inferior animals in each + generation comes to the <!-- Page 86 --><span class="pagenum"><a + name="page86"></a>{86}</span>same thing as their separation. In savage + and semi-civilised countries, where the inhabitants have not the means of + separating their animals, more than a single breed of the same species + rarely or never exists. In former times, even in a country so civilised + as North America, there were no distinct races of sheep, for all had been + mingled together.<a name="NtA_180" href="#Nt_180"><sup>[180]</sup></a> + The celebrated agriculturist Marshall<a name="NtA_181" + href="#Nt_181"><sup>[181]</sup></a> remarks that "sheep that are kept + within fences, as well as shepherded flocks in open countries, have + generally a similarity, if not a uniformity, of character in the + individuals of each flock;" for they breed freely together, and are + prevented from crossing with other kinds; whereas in the unenclosed parts + of England the unshepherded sheep, even of the same flock, are far from + true or uniform, owing to various breeds having mingled and crossed. We + have seen that the half-wild cattle in the several British parks are + uniform in character in each; but in the different parks, from not having + mingled and crossed during many generations, they differ in a slight + degree.</p> + + <p>We cannot doubt that the extraordinary number of varieties and + sub-varieties of the pigeon, amounting to at least one hundred and fifty, + is partly due to their remaining, differently from other domesticated + birds, paired for life when once matched. On the other hand, breeds of + cats imported into this country soon disappear, for their nocturnal and + rambling habits render it hardly possible to prevent free crossing. + Rengger<a name="NtA_182" href="#Nt_182"><sup>[182]</sup></a> gives an + interesting case with respect to the cat in Paraguay: in all the distant + parts of the kingdom it has assumed, apparently from the effects of the + climate, a peculiar character, but near the capital this change has been + prevented, owing, as he asserts, to the native animal frequently crossing + with cats imported from Europe. In all cases like the foregoing, the + effects of an occasional cross will be augmented by the increased vigour + and fertility of the crossed offspring, of which fact evidence will + hereafter be given; for this will lead to the mongrels increasing more + rapidly than the pure parent-breeds.</p> + +<p><!-- Page 87 --><span class="pagenum"><a name="page87"></a>{87}</span></p> + + <p>When distinct breeds are allowed to cross freely, the result will be a + heterogenous body; for instance, the dogs in Paraguay are far from + uniform, and can no longer be affiliated to their parent-races.<a + name="NtA_183" href="#Nt_183"><sup>[183]</sup></a> The character which a + crossed body of animals will ultimately assume must depend on several + contingencies,—namely, on the relative numbers of the individuals + belonging to the two or more races which are allowed to mingle; on the + prepotency of one race over the other in the transmission of character; + and on the conditions of life to which they are exposed. When two + commingled breeds exist at first in nearly equal numbers, the whole will + sooner or later become intimately blended, but not so soon, both breeds + being equally favoured in all respects, as might have been expected. The + following calculation<a name="NtA_184" + href="#Nt_184"><sup>[184]</sup></a> shows that this is the case: if a + colony with an equal number of black and white men were founded, and we + assume that they marry indiscriminately, are equally prolific, and that + one in thirty annually dies and is born; then "in 65 years the number of + blacks, whites, and mulattoes would be equal. In 91 years the whites + would be 1-10th, the blacks 1-10th, and the mulattoes, or people of + intermediate degrees of colour, 8-10ths of the whole number. In three + centuries not 1-100th part of the whites would exist."</p> + + <p>When one of two mingled races exceeds the other greatly in number, the + latter will soon be wholly, or almost wholly, absorbed and lost.<a + name="NtA_185" href="#Nt_185"><sup>[185]</sup></a> Thus European pigs and + dogs have been largely introduced into the islands of the Pacific Ocean, + and the native races have been absorbed and lost in the course of about + fifty or sixty years;<a name="NtA_186" + href="#Nt_186"><sup>[186]</sup></a> but the imported races no doubt were + favoured. Rats may be considered as semi-domesticated animals. Some + snake-rats (<i>Mus alexandrinus</i>) escaped in the Zoological Gardens of + London, "and for a long time afterwards the keepers frequently caught + cross-bred rats, at first half-breds, afterwards with less and less of + the character of the snake-rat, till at length all traces of it + disappeared."<a name="NtA_187" href="#Nt_187"><sup>[187]</sup></a> On the + other hand, <!-- Page 88 --><span class="pagenum"><a + name="page88"></a>{88}</span>in some parts of London, especially near the + docks, where fresh rats are frequently imported, an endless variety of + intermediate forms may be found between the brown, black, and snake rat, + which are all three usually ranked as distinct species.</p> + + <p>How many generations are necessary for one species or race to absorb + another by repeated crosses has often been discussed;<a name="NtA_188" + href="#Nt_188"><sup>[188]</sup></a> and the requisite number has probably + been much exaggerated. Some writers have maintained that a dozen, or + score, or even more generations, are necessary; but this in itself is + improbable, for in the tenth generation there will be only 1-1024th part + of foreign blood in the offspring. Gärtner found,<a name="NtA_189" + href="#Nt_189"><sup>[189]</sup></a> that with plants one species could be + made to absorb another in from three to five generations, and he believes + that this could always be effected in from six to seventh generations. In + one instance, however, Kölreuter<a name="NtA_190" + href="#Nt_190"><sup>[190]</sup></a> speaks of the offspring of + <i>Mirabilis vulgaris</i>, crossed during eight successive generations by + <i>M. longiflora</i>, as resembling this latter species so closely, that + the most scrupulous observer could detect "vix aliquam notabilem + differentiam;"—he succeeded, as he says, "ad plenariam fere + transmutationem." But this expression shows that the act of absorption + was not even then absolutely complete, though these crossed plants + contained only the 1-256th part of <i>M. vulgaris</i>. The conclusions of + such accurate observers as Gärtner and Kölreuter are of far higher worth + than those made without scientific aim by breeders. The most remarkable + statement which I have met with of the persistent endurance of the + effects of a single cross is given by Fleischmann,<a name="NtA_191" + href="#Nt_191"><sup>[191]</sup></a> who, in reference to German sheep, + says "that the original coarse sheep have 5500 fibres of wool on a square + inch; grades of the third or fourth Merino cross produced about 8000, the + twentieth cross 27,000, the perfect pure Merino blood 40,000 to 48,000." + So that in this case common German sheep crossed twenty times + successively with Merinos have not by any means acquired wool as fine as + that of the pure breed. In all cases, the rate of absorption will <!-- + Page 89 --><span class="pagenum"><a name="page89"></a>{89}</span>depend + largely on the conditions of life being favourable to any particular + character; and we may suspect that there would be under the climate of + Germany a constant tendency to degeneration in the wool of Merinos, + unless prevented by careful selection; and thus perhaps the foregoing + remarkable case may be explained. The rate of absorption must also depend + on the amount of distinguishable difference between the two forms which + are crossed, and especially, as Gärtner insists, on prepotency of + transmission in the one form over the other. We have seen in the last + chapter that one of two French breeds of sheep yielded up its character, + when crossed with Merinos, very much slower than the other; and the + common German sheep referred to by Fleischmann may present an analogous + case. But in all cases there will be during many subsequent generations + more or less liability to reversion, and it is this fact which has + probably led authors to maintain that a score or more of generations are + requisite for one race to absorb another. In considering the final result + of the commingling of two or more breeds, we must not forget that the act + of crossing in itself tends to bring back long-lost characters not proper + to the immediate parent-forms.</p> + + <p>With respect to the influence of the conditions of life on any two + breeds which are allowed to cross freely, unless both are indigenous and + have long been accustomed to the country where they live, they will, in + all probability, be unequally affected by the conditions, and this will + modify the result. Even with indigenous breeds, it will rarely or never + occur that both are equally well adapted to the surrounding + circumstances; more especially when permitted to roam freely, and not + carefully tended, as will generally be the case with breeds allowed to + cross. As a consequence of this, natural selection will to a certain + extent come into action, and the best fitted will survive, and this will + aid in determining the ultimate character of the commingled body.</p> + + <p>How long a time it would require before such a crossed body of animals + would assume within a limited area a uniform character no one can say; + that they would ultimately become uniform from free intercrossing, and + from the survival of the fittest, we may feel assured; but the character + thus acquired would rarely or never, as we may infer from the several + previous <!-- Page 90 --><span class="pagenum"><a + name="page90"></a>{90}</span>considerations, be exactly intermediate + between that of the two parent-breeds. With respect to the very slight + differences by which the individuals of the same sub-variety, or even of + allied varieties, are characterised, it is obvious that free crossing + would soon obliterate such small distinctions. The formation of new + varieties, independently of selection, would also thus be prevented; + except when the same variation continually recurred from the action of + some strongly predisposing cause. Hence we may conclude that free + crossing has in all cases played an important part in giving to all the + members of the same domestic race, and of the same natural species, + uniformity of character, though largely modified by natural selection and + by the direct action of the surrounding conditions.</p> + + <p><i>On the possibility of all organic beings occasionally + intercrossing.</i>—But it may be asked, can free crossing occur + with hermaphrodite animals and plants? All the higher animals, and the + few insects which have been domesticated, have separated sexes, and must + inevitably unite for each birth. With respect to the crossing of + hermaphrodites, the subject is too large for the present volume, and will + be more properly treated in a succeeding work. In my 'Origin of Species,' + however, I have given a short abstract of the reasons which induce me to + believe that all organic beings occasionally cross, though perhaps in + some cases only at long intervals of time.<a name="NtA_192" + href="#Nt_192"><sup>[192]</sup></a> I will here just recall the fact that + many plants, though hermaphrodite in structure, are unisexual in + function;—such as those called by C. K. Sprengel + <i>dichogamous</i>, in which the pollen and stigma of the same flower are + matured at different periods; or those called by me <i>reciprocally + dimorphic</i>, in which the flower's own pollen is not fitted to + fertilise its own stigma; or again, the many kinds in which curious + mechanical contrivances exist, effectually preventing self-fertilisation. + There are, however, many hermaphrodite plants which are not in any way + specially constructed to favour intercrossing, but which nevertheless + commingle almost as freely as animals with separated sexes. This is the + case with cabbages, radishes, and onions, as I know from <!-- Page 91 + --><span class="pagenum"><a name="page91"></a>{91}</span>having + experimented on them: even the peasants of Liguria say that cabbages must + be prevented "from falling in love" with each other. In the orange tribe, + Gallesio<a name="NtA_193" href="#Nt_193"><sup>[193]</sup></a> remarks + that the amelioration of the various kinds is checked by their continual + and almost regular crossing. So it is with numerous other plants.</p> + + <p>Nevertheless some cultivated plants can be named which rarely + intercross, as the common pea, or which never intercross, as I have + reason to believe is the case with the sweet-pea (<i>Lathyrus + odoratus</i>); yet the structure of these flowers certainly favours an + occasional cross. The varieties of the tomato and aubergine + (<i>Solanum</i>) and pimenta (<i>Pimenta vulgaris?</i>) are said<a + name="NtA_194" href="#Nt_194"><sup>[194]</sup></a> never to cross, even + when growing alongside each other. But it should be observed that these + are all exotic plants, and we do not know how they would behave in their + native country when visited by the proper insects.</p> + + <p>It must also be admitted that some few natural species appear under + our present state of knowledge to be perpetually self-fertilised, as in + the case of the Bee Ophrys (<i>O. apifera</i>), though adapted in its + structure to be occasionally crossed. The <i>Leersia oryzoides</i> + produces minute enclosed flowers which cannot possibly be crossed, and + these alone, to the exclusion of the ordinary flowers, have as yet been + known to yield seed.<a name="NtA_195" href="#Nt_195"><sup>[195]</sup></a> + A few additional and analogous cases could be advanced. But these facts + do not make me doubt that it is a general law of nature that the + individuals of the same species occasionally intercross, and that some + great advantage is derived from this act. It is well known (and I shall + hereafter have to give instances) that some plants, both indigenous and + naturalised, rarely or never produce flowers; or, if they flower, never + produce seeds. But no one is thus led to doubt that it is a general law + of nature that phanerogamic plants should produce flowers, and that these + flowers should produce seed. When they fail, we believe that such plants + would perform their proper functions under different conditions, or that + they formerly did so and will do so again. On analogous grounds, I + believe that the few flowers <!-- Page 92 --><span class="pagenum"><a + name="page92"></a>{92}</span>which do not now intercross, either would do + so under different conditions, or that they formerly fertilised each + other at intervals—the means for effecting this being generally + still retained—and they will do so again at some future period, + unless indeed they become extinct. On this view alone, many points in the + structure and action of the reproductive organs in hermaphrodite plants + and animals are intelligible,—for instance, the male and female + organs never being so completely enclosed as to render access from + without impossible. Hence we may conclude that the most important of all + the means for giving uniformity to the individuals of the same species, + namely, the capacity of occasionally intercrossing, is present, or has + been formerly present, with all organic beings.</p> + +<blockquote class="b1n"> + + <p><i>On certain Characters not blending.</i>—When two breeds are + crossed their characters usually become intimately fused together; but + some characters refuse to blend, and are transmitted in an unmodified + state either from both parents or from one. When grey and white mice are + paired, the young are not piebald nor of an intermediate tint, but are + pure white or of the ordinary grey colour: so it is when white and common + collared turtle-doves are paired. In breeding Game fowls, a great + authority, Mr. J. Douglas, remarks, "I may here state a strange fact: if + you cross a black with a white game, you get birds of both breeds of the + clearest colour." Sir R. Heron crossed during many years white, black, + brown, and fawn-coloured Angora rabbits, and never once got these colours + mingled in the same animal, but often all four colours in the same + litter.<a name="NtA_196" href="#Nt_196"><sup>[196]</sup></a> Additional + cases could be given, but this form of inheritance is very far from + universal even with respect to the most distinct colours. When turnspit + dogs and ancon sheep, both of which have dwarfed limbs, are crossed with + common breeds, the offspring are not intermediate in structure, but take + after either parent. When tailless or hornless animals are crossed with + perfect animals, it frequently, but by no means invariably, happens that + the offspring are <!-- Page 93 --><span class="pagenum"><a + name="page93"></a>{93}</span>either perfectly furnished with these organs + or are quite destitute of them. According to Rengger, the hairless + condition of the Paraguay dog is either perfectly or not at all + transmitted to its mongrel offspring; but I have seen one partial + exception in a dog of this parentage which had part of its skin hairy, + and part naked; the parts being distinctly separated as in a piebald + animal. When Dorking fowls with five toes are crossed with other breeds, + the chickens often have five toes on one foot and four on the other. Some + crossed pigs raised by Sir R. Heron between the solid-hoofed and common + pig had not all four feet in an intermediate condition, but two feet were + furnished with properly divided, and two with united hoofs.</p> + + <p>Analogous facts have been observed with plants: Major Trevor Clarke + crossed the little, glabrous-leaved, annual stock (<i>Matthiola</i>), + with pollen of a large, red-flowered, rough-leaved, biennial stock, + called <i>cocardeau</i> by the French, and the result was that half the + seedlings had glabrous and the other half rough leaves, but none had + leaves in an intermediate state. That the glabrous seedlings were the + product of the rough-leaved variety, and not accidentally of the + mother-plant's own pollen, was shown by their tall and strong habit of + growth.<a name="NtA_197" href="#Nt_197"><sup>[197]</sup></a> In the + succeeding generations raised from the rough-leaved crossed seedlings, + some glabrous plants appeared, showing that the glabrous character, + though incapable of blending with and modifying the rough leaves, was all + the time latent in this family of plants. The numerous plants formerly + referred to, which I raised from reciprocal crosses between the peloric + and common Antirrhinum, offer a nearly parallel case; for in the first + generation all the plants resembled the common form, and in the next + generation, out of one hundred and thirty-seven plants, two alone were in + an intermediate condition, the others perfectly resembling either the + peloric or common form. Major Trevor Clarke also fertilised the + above-mentioned red-flowered stock with pollen from the purple Queen + stock, and about half the seedlings scarcely differed in habit, and not + at all in the red colour of the flower, from the mother-plant, the other + half bearing blossoms of a rich purple, closely like those of the + paternal plant. Gärtner crossed many white and yellow-flowered species + and varieties of Verbascum; and these colours were never blended, but the + offspring bore either pure white or pure yellow blossoms; the former in + the larger proportion.<a name="NtA_198" + href="#Nt_198"><sup>[198]</sup></a> Dr. Herbert raised many seedlings, as + he informed me, from Swedish turnips crossed by two other varieties, and + these never produced flowers of an intermediate tint, but always like one + of their parents. I fertilised the purple sweet-pea (<i>Lathyrus + odoratus</i>), which has a dark reddish-purple standard-petal and + violet-coloured wings and keel, with pollen of the painted-lady + sweet-pea, which has a pale cherry-coloured standard, and almost white + wings and keel; and from the same pod I twice raised plants perfectly + resembling both sorts; the greater number resembling the father. So + perfect was the resemblance, that I should have thought there had <!-- + Page 94 --><span class="pagenum"><a name="page94"></a>{94}</span>been + some mistake, if the plants which were at first identical with the + paternal variety, namely, the painted-lady, had not later in the season + produced, as mentioned in a former chapter, flowers blotched and streaked + with dark purple. I raised grandchildren and great-grandchildren from + these crossed plants, and they continued to resemble the painted-lady, + but during the later generations became rather more blotched with purple, + yet none reverted completely to the original mother-plant, the purple + sweet-pea. The following case is slightly different, but still shows the + same principle: Naudin<a name="NtA_199" + href="#Nt_199"><sup>[199]</sup></a> raised numerous hybrids between the + yellow <i>Linaria vulgaris</i> and the purple <i>L. purpurea</i>, and + during three successive generations the colours kept distinct in + different parts of the same flower.</p> + + <p>From such cases as the foregoing, in which the offspring of the first + generation perfectly resemble either parent, we come by a small step to + those cases in which differently coloured flowers borne on the same root + resemble both parents, and by another step to those in which the same + flower or fruit is striped or blotched with the two parental colours, or + bears a single stripe of the colour or other characteristic quality of + one of the parent-forms. With hybrids and mongrels it frequently or even + generally happens that one part of the body resembles more or less + closely one parent and another part the other parent; and here again some + resistance to fusion, or, what comes to the same thing, some mutual + affinity between the organic atoms of the same nature, apparently comes + into play, for otherwise all parts of the body would be equally + intermediate in character. So again, when the offspring of hybrids or + mongrels, which are themselves nearly intermediate in character, revert + either wholly or by segments to their ancestors, the principle of the + affinity of similar, or the repulsion of dissimilar atoms, must come into + action. To this principle, which seems to be extremely general, we shall + recur in the chapter on pangenesis.</p> + + <p>It is remarkable, as has been strongly insisted upon by Isidore + Geoffroy St. Hilaire in regard to animals, that the transmission of + characters without fusion occurs most rarely when species are crossed; I + know of one exception alone, namely, with the hybrids naturally produced + between the common and hooded crow (<i>Corvus corone</i> and + <i>cornix</i>), which, however, are closely allied species, differing in + nothing except colour. Nor have I met with any well-ascertained cases of + transmission of this kind, even when one form is strongly prepotent over + another, when two races are crossed which have been slowly formed by + man's selection, and therefore resemble to a certain extent natural + species. Such cases as puppies in the same litter closely resembling two + distinct breeds, are probably due to super-fœtation,—that is, + to the influence of two fathers. All the characters above enumerated, + which are transmitted in a perfect state to some of the offspring and not + to others,—such as distinct colours, nakedness of skin, smoothness + of leaves, absence of horns or tail, additional toes, pelorism, dwarfed + structure, &c.,—have all been known to appear suddenly in + individual animals and plants. From this fact, and from the several + slight, aggregated differences which distinguish domestic races and + species from <!-- Page 95 --><span class="pagenum"><a + name="page95"></a>{95}</span>each other, not being liable to this + peculiar form of transmission, we may conclude that it is in some way + connected with the sudden appearance of the characters in question.</p> + +</blockquote> + + <p><i>On the Modification of old Races and the Formation of new Races by + Crossing.</i>—We have hitherto chiefly considered the effects of + crossing in giving uniformity of character; we must now look to an + opposite result. There can be no doubt that crossing, with the aid of + rigorous selection during several generations, has been a potent means in + modifying old races, and in forming new ones. Lord Orford crossed his + famous stud of greyhounds once with the bulldog, which breed was chosen + from being deficient in scenting powers, and from having what was wanted, + courage and perseverance. In the course of six or seven generations all + traces of the external form of the bulldog were eliminated, but courage + and perseverance remained. Certain pointers have been crossed, as I hear + from the Rev. W. D. Fox, with the foxhound, to give them dash and speed. + Certain strains of Dorking fowls have had a slight infusion of Game + blood; and I have known a great fancier who on a single occasion crossed + his turbit-pigeons with barbs, for the sake of gaining greater breadth of + beak.</p> + + <p>In the foregoing cases breeds have been crossed once, for the sake of + modifying some particular character; but with most of the improved races + of the pig, which now breed true, there have been repeated + crosses,—for instance, the improved Essex owes its excellence to + repeated crosses with the Neapolitan, together probably with some + infusion of Chinese blood.<a name="NtA_200" + href="#Nt_200"><sup>[200]</sup></a> So with our British sheep: almost all + the races, except the Southdown, have been largely crossed; "this, in + fact, has been the history of our principal breeds."<a name="NtA_201" + href="#Nt_201"><sup>[201]</sup></a> To give an example, the "Oxfordshire + Downs" now rank as an established breed.<a name="NtA_202" + href="#Nt_202"><sup>[202]</sup></a> They were produced about the year + 1830 by crossing "Hampshire and in some instances Southdown ewes with + Cotswold rams:" now the Hampshire ram was itself produced by repeated + crosses between the native <!-- Page 96 --><span class="pagenum"><a + name="page96"></a>{96}</span>Hampshire sheep and Southdowns; and the + long-woolled Cotswold were improved by crosses with the Leicester, which + latter again is believed to have been a cross between several + long-woolled sheep. Mr. Spooner, after considering the various cases + which have been carefully recorded, concludes "that from a judicious + pairing of cross-bred animals it is practicable to establish a new + breed." On the Continent the history of several crossed races of cattle + and of other animals has been well ascertained. To give one instance: the + King of Wurtemberg, after twenty-five years' careful breeding, that is + after six or seven generations, made a new breed of cattle from a cross + between a Dutch and Swiss breed, combined with other breeds.<a + name="NtA_203" href="#Nt_203"><sup>[203]</sup></a> The Sebright bantam, + which breeds as true as any other kind of fowl, was formed about sixty + years ago by a complicated cross.<a name="NtA_204" + href="#Nt_204"><sup>[204]</sup></a> Dark Brahmas, which are believed by + some fanciers to constitute a distinct species, were undoubtedly formed<a + name="NtA_205" href="#Nt_205"><sup>[205]</sup></a> in the United States, + within a recent period, by a cross between Chittagongs and Cochins. With + plants I believe there is little doubt that some kinds of turnips, now + extensively cultivated, are crossed races; and the history of a variety + of wheat which was raised from two very distinct varieties, and which + after six years' culture presented an even sample, has been recorded on + good authority.<a name="NtA_206" href="#Nt_206"><sup>[206]</sup></a></p> + + <p>Until quite lately, cautious and experienced breeders, though not + averse to a single infusion of foreign blood, were almost universally + convinced that the attempt to establish a new race, intermediate between + two widely distinct races, was hopeless: "they clung with superstitious + tenacity to the doctrine of purity of blood, believing it to be the ark + in which alone true safety could be found."<a name="NtA_207" + href="#Nt_207"><sup>[207]</sup></a> Nor was this conviction unreasonable: + when two distinct races are crossed, the offspring of the first + generation are generally nearly uniform in character; but even this + sometimes fails to be the case, especially with crossed dogs and fowls, + the young of which from the first are sometimes much <!-- Page 97 + --><span class="pagenum"><a name="page97"></a>{97}</span>diversified. As + cross-bred animals are generally of large size and vigorous, they have + been raised in great numbers for immediate consumption. But for breeding + they are found to be utterly useless; for though they may be themselves + uniform in character, when paired together they yield during many + generations offspring astonishingly diversified. The breeder is driven to + despair, and concludes that he will never form an intermediate race. But + from the cases already given, and from others which have been recorded, + it appears that patience alone is necessary; as Mr. Spooner remarks, + "nature opposes no barrier to successful admixture; in the course of + time, by the aid of selection and careful weeding, it is practicable to + establish a new breed." After six or seven generations the hoped-for + result will in most cases be obtained; but even then an occasional + reversion, or failure to keep true, may be expected. The attempt, + however, will assuredly fail if the conditions of life be decidedly + unfavourable to the characters of either parent-breed.<a name="NtA_208" + href="#Nt_208"><sup>[208]</sup></a></p> + + <p>Although the grandchildren and succeeding generations of cross-bred + animals are generally variable in an extreme degree, some curious + exceptions to the rule have been observed, both with crossed races and + species. Thus Boitard and Corbié<a name="NtA_209" + href="#Nt_209"><sup>[209]</sup></a> assert that from a Pouter and a Runt + "a Cavalier will appear, which we have classed amongst pigeons of pure + race, because it transmits all its qualities to its posterity." The + editor of the 'Poultry Chronicle'<a name="NtA_210" + href="#Nt_210"><sup>[210]</sup></a> bred some bluish fowls from a black + Spanish cock and a Malay hen; and these remained true to colour + "generation after generation." The Himalayan breed of rabbits was + certainly formed by crossing two sub-varieties of the silver-grey rabbit; + although it suddenly assumed its present character, which differs much + from that of either parent-breed, yet it has ever since been easily and + truly propagated. I crossed some Labrador and Penguin ducks, and + recrossed the mongrels with Penguins; afterwards, most of the ducks + reared during three generations were nearly uniform in character, being + brown with a white crescentic mark on the lower part of the breast, <!-- + Page 98 --><span class="pagenum"><a name="page98"></a>{98}</span>and with + some white spots at the base of the beak; so that by the aid of a little + selection a new breed might easily have been formed. In regard to crossed + varieties of plants, Mr. Beaton remarks<a name="NtA_211" + href="#Nt_211"><sup>[211]</sup></a> that "Melville's extraordinary cross + between the Scotch kale and an early cabbage is as true and genuine as + any on record;" but in this case no doubt selection was practised. + Gärtner<a name="NtA_212" href="#Nt_212"><sup>[212]</sup></a> has given + five cases of hybrids, in which the progeny kept constant; and hybrids + between <i>Dianthus <span class="correction" title="Original reads `armoria', corrected by errata, page viii." + >armeria</span></i> and <i>deltoides</i> remained true and uniform to the + tenth generation. Dr. Herbert likewise showed me a hybrid from two + species of Loasa which from its first production had kept constant during + several generations.</p> + + <p>We have seen in the earlier chapters, that some of our domesticated + animals, such as dogs, cattle, pigs, &c., are almost certainly + descended from more than one species, or wild race, if any one prefers to + apply this latter term to forms which were enabled to keep distinct in a + state of nature. Hence the crossing of aboriginally distinct species + probably came into play at an early period in the formation of our + present races. From Rütimeyer's observations there can be little doubt + that this occurred with cattle; but in most cases some one of the forms + which were allowed to cross freely, will, it is probable, have absorbed + and obliterated the others. For it is not likely that semi-civilized men + would have taken the necessary pains to modify by selection their + commingled, crossed, and fluctuating stock. Nevertheless, those animals + which were best adapted to their conditions of life would have survived + through natural selection; and by this means crossing will often have + indirectly aided in the formation of primeval domesticated breeds.</p> + + <p>Within recent times, as far as animals are concerned, the crossing of + distinct species has done little or nothing in the formation or + modification of our races. It is not yet known whether the species of + silk-moth which have been recently crossed in France will yield permanent + races. In the fourth chapter I alluded with some hesitation to the + statement that a new breed, between the hare and rabbit, called + leporides, had been formed in France, and was found capable of + propagating <!-- Page 99 --><span class="pagenum"><a + name="page99"></a>{99}</span>itself; but it is now positively affirmed<a + name="NtA_213" href="#Nt_213"><sup>[213]</sup></a> that this is an error. + With plants which can be multiplied by buds and cuttings, hybridisation + has done wonders, as with many kinds of Roses, Rhododendrons, + Pelargoniums, Calceolarias, and Petunias. Nearly all these plants can be + propagated by seed; most of them freely; but extremely few or none come + true by seed.</p> + + <p>Some authors believe that crossing is the chief cause of + variability,—that is, of the appearance of absolutely new + characters. Some have gone so far as to look at it as the sole cause; but + this conclusion is disproved by some of the facts given in the chapter on + Bud-variation. The belief that characters not present in either parent or + in their ancestors frequently originate from crossing is doubtful; that + they occasionally thus arise is probable; but this subject will be more + conveniently discussed in a future chapter on the causes of + Variability.</p> + + <p>A condensed summary of this and of the three following chapters, + together with some remarks on Hybridism, will be given in the nineteenth + chapter.</p> + +<hr class="full" /> + +<p><!-- Page 100 --><span class="pagenum"><a name="page100"></a>{100}</span></p> + +<h3>CHAPTER XVI.</h3> + +<p class="cenhead">CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF +VARIETIES—INFLUENCE OF DOMESTICATION ON FERTILITY.</p> + +<blockquote class="b1n"> + + <p><span class="scac">DIFFICULTIES IN JUDGING OF THE FERTILITY OF + VARIETIES WHEN CROSSED</span>—<span class="scac">VARIOUS CAUSES + WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING AND SEXUAL + PREFERENCE</span>—<span class="scac">VARIETIES OF WHEAT SAID TO BE + STERILE WHEN CROSSED</span>—<span class="scac">VARIETIES OF MAIZE, + VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND TOBACCO, RENDERED IN SOME + DEGREE MUTUALLY STERILE</span>—<span class="scac">DOMESTICATION + ELIMINATES THE TENDENCY TO STERILITY NATURAL TO SPECIES WHEN + CROSSED</span>—<span class="scac">ON THE INCREASED FERTILITY OF + UNCROSSED ANIMALS AND PLANTS FROM DOMESTICATION AND + CULTIVATION.</span></p> + +</blockquote> + + <p>The domesticated races of both animals and plants, when crossed, are + with extremely few exceptions quite prolific,—in some cases even + more so than the purely bred parent-races. The offspring, also, raised + from such crosses are likewise, as we shall see in the following chapter, + generally more vigorous and fertile than their parents. On the other + hand, species when crossed, and their hybrid offspring, are almost + invariability in some degree sterile; and here there seems to exist a + broad and insuperable distinction between races and species. The + importance of this subject as bearing on the origin of species is + obvious; and we shall hereafter recur to it.</p> + + <p>It is unfortunate how few precise observations have been made on the + fertility of mongrel animals and plants during several successive + generations. Dr. Broca<a name="NtA_214" + href="#Nt_214"><sup>[214]</sup></a> has remarked that no one has observed + whether, for instance, mongrel dogs, bred <i>inter se</i>, are + indefinitely fertile; yet, if a shade of infertility be detected by + careful observation in the offspring of natural forms when crossed, it is + thought that their specific distinction is proved. But so many breeds of + sheep, cattle, pigs, dogs, and poultry, have been crossed and recrossed + in various ways, that any sterility, if it had existed, would from being + injurious <!-- Page 101 --><span class="pagenum"><a + name="page101"></a>{101}</span>almost certainly have been observed. In + investigating the fertility of crossed varieties many sources of doubt + occur. Whenever the least trace of sterility between two plants, however + closely allied, was observed by Kölreuter, and more especially by + Gärtner, who counted the exact number of seed in each capsule, the two + forms were at once ranked as distinct species; and if this rule be + followed, assuredly it will never be proved that varieties when crossed + are in any degree sterile. We have formerly seen that certain breeds of + dogs do not readily pair together; but no observations have been made + whether, when paired, they produce the full number of young, and whether + the latter are perfectly fertile <i>inter se</i>; but, supposing that + some degree of sterility were found to exist, naturalists would simply + infer that these breeds were descended from aboriginally distinct + species; and it would be scarcely possible to ascertain whether or not + this explanation was the true one.</p> + + <p>The Sebright Bantam is much less prolific than any other breed of + fowls, and is descended from a cross between two very distinct breeds, + recrossed by a third sub-variety. But it would be extremely rash to infer + that the loss of fertility was in any manner connected with its crossed + origin, for it may with more probability be attributed either to + long-continued close interbreeding, or to an innate tendency to sterility + correlated with the absence of hackles and sickle tail-feathers.</p> + + <p>Before giving the few recorded cases of forms, which must be ranked as + varieties, being in some degree sterile when crossed, I may remark that + other causes sometimes interfere with varieties freely intercrossing. + Thus they may differ too greatly in size, as with some kinds of dogs and + fowls: for instance, the editor of the 'Journal of Horticulture, + &c.,'<a name="NtA_215" href="#Nt_215"><sup>[215]</sup></a> says that + he can keep Bantams with the larger breeds without much danger of their + crossing, but not with the smaller breeds, such as Games, Hamburgs, + &c. With plants a difference in the period of flowering serves to + keep varieties distinct, as with the various kinds of maize and wheat: + thus Colonel Le Couteur<a name="NtA_216" + href="#Nt_216"><sup>[216]</sup></a> remarks, "the Talavera wheat, from + flowering much earlier than any other kind, is sure to continue pure." In + different parts of <!-- Page 102 --><span class="pagenum"><a + name="page102"></a>{102}</span>the Falkland Islands the cattle are + breaking up into herds of different colours; and those on the higher + ground, which are generally white, usually breed, as I am informed by + Admiral Sulivan, three months earlier than those on the lowlands; and + this would manifestly tend to keep the herds from blending.</p> + + <p>Certain domestic races seem to prefer breeding with their own kind; + and this is a fact of some importance, for it is a step towards that + instinctive feeling which helps to keep closely allied species in a state + of nature distinct. We have now abundant evidence that, if it were not + for this feeling, many more hybrids would be naturally produced than is + the case. We have seen in the first chapter that the alco dog of Mexico + dislikes dogs of other breeds; and the hairless dog of Paraguay mixes + less readily with the European races, than the latter do with each other. + In Germany the female Spitz-dog is said to receive the fox more readily + than will other dogs; a female Australian Dingo in England attracted the + wild male foxes. But these differences in the sexual instinct and + attractive power of the various breeds may be wholly due to their descent + from distinct species. In Paraguay the horses have much freedom, and an + excellent observer<a name="NtA_217" href="#Nt_217"><sup>[217]</sup></a> + believes that the native horses of the same colour and size prefer + associating with each other, and that the horses which have been imported + from Entre Rios and Banda Oriental into Paraguay likewise prefer + associating together. In Circassia six sub-races of the horse are known + and have received distinct names; and a native proprietor of rank<a + name="NtA_218" href="#Nt_218"><sup>[218]</sup></a> asserts that horses of + three of these races, whilst living a free life, almost always refuse to + mingle and cross, and will even attack each other.</p> + + <p>It has been observed, in a district stocked with heavy Lincolnshire + and light Norfolk sheep, that both kinds, though bred together, when + turned out, "in a short time separate to a sheep;" the Lincolnshires + drawing off to the rich soil, and the Norfolks to their own dry light + soil; and as long as there is plenty of grass, "the two breeds keep + themselves as distinct as rooks and pigeons." In this case different + habits of <!-- Page 103 --><span class="pagenum"><a + name="page103"></a>{103}</span>life tend to keep the races distinct. On + one of the Faroe islands, not more than half a mile in diameter, the + half-wild native black sheep are said not to have readily mixed with the + imported white sheep. It is a more curious fact that the semi-monstrous + ancon sheep of modern origin "have been observed to keep together, + separating themselves from the rest of the flock, when put into + enclosures with other sheep."<a name="NtA_219" + href="#Nt_219"><sup>[219]</sup></a> With respect to fallow deer, which + live in a semi-domesticated condition, Mr. Bennett<a name="NtA_220" + href="#Nt_220"><sup>[220]</sup></a> states that the dark and pale + coloured herds, which have long been kept together in the Forest of Dean, + in High Meadow Woods, and in the New Forest, have never been known to + mingle: the dark-coloured deer, it may be added, are believed to have + been first brought by James I. from Norway, on account of their greater + hardiness. I imported from the island of Porto Santo two of the feral + rabbits, which differ, as described in the fourth chapter, from common + rabbits; both proved to be males, and, though they lived during some + years in the Zoological Gardens, the superintendent, Mr. Bartlett, in + vain endeavoured to make them breed with various tame kinds; but whether + this refusal to breed was due to any change in instinct, or simply to + their extreme wildness; or whether confinement had rendered them sterile, + as often occurs, cannot be told.</p> + + <p>Whilst matching for the sake of experiment many of the most distinct + breeds of pigeons, it frequently appeared to me that the birds, though + faithful to their marriage vow, retained some desire after their own + kind. Accordingly I asked Mr. Wicking, who has kept a larger stock of + various breeds together than any man in England, whether he thought that + they would prefer pairing with their own kind, supposing that there were + males and females enough of each; and he without hesitation answered that + he was convinced that this was the case. It has often been noticed that + the dovecot pigeon seems to have an actual aversion towards the several + fancy breeds;<a name="NtA_221" href="#Nt_221"><sup>[221]</sup></a> yet + all have <!-- Page 104 --><span class="pagenum"><a + name="page104"></a>{104}</span>certainly sprung from a common progenitor. + The Rev. W. D. Fox informs me that his flocks of white and common Chinese + geese kept distinct.</p> + + <p>These facts and statements, though some of them are incapable of + proof, resting only on the opinion of experienced observers, show that + some domestic races are led by different habits of life to keep to a + certain extent separate, and that others prefer coupling with their own + kind, in the same manner as species in a state of nature, though in a + much less degree.</p> + +<blockquote class="b1n"> + + <p>With respect to sterility from the crossing of domestic races, I know + of no well-ascertained case with animals. This fact, seeing the great + difference in structure between some breeds of pigeons, fowls, pigs, + dogs, &c., is extraordinary, in contrast with the sterility of many + closely allied natural species when crossed; but we shall hereafter + attempt to show that it is not so extraordinary as it at first appears. + And it may be well here to recall to mind that the amount of external + difference between two species will not safely guide us in foretelling + whether or not they will breed together,—some closely allied + species when crossed being utterly sterile, and others which are + extremely unlike being moderately fertile. I have said that no case of + sterility in crossed races rests on satisfactory evidence; but here is + one which at first seems trustworthy. Mr. Youatt,<a name="NtA_222" + href="#Nt_222"><sup>[222]</sup></a> and a better authority cannot be + quoted, states, that formerly in Lancashire crosses were frequently made + between longhorn and shorthorn cattle; the first cross was excellent, but + the produce was uncertain; in the third or fourth generation the cows + were bad milkers; "in addition to which, there was much uncertainty + whether the cows would conceive; and full one-third of the cows among + some of these half-breds failed to be in calf." This at first seems a + good case; but Mr. Wilkinson states,<a name="NtA_223" + href="#Nt_223"><sup>[223]</sup></a> that a breed derived from this same + cross was actually established in another part of England; and if it had + failed in fertility, the fact would surely have been noticed. Moreover, + supposing that Mr. Youatt had proved his case, it might be argued that + the sterility was wholly due to the two parent-breeds being descended + from primordially distinct species.</p> + + <p>I will give a case with plants, to show how difficult it is to get + sufficient evidence. Mr. Sheriff, who has been so successful in the + formation of new races of wheat, fertilised the Hopetoun with the + Talavera; in the first and second generations the produce was + intermediate in character, but in the fourth generation "it was found to + consist of many varieties; nine-tenths of the florets proved barren, and + many of the seeds seemed shrivelled abortions, void of vitality, and the + whole race was evidently verging to extinction."<a name="NtA_224" + href="#Nt_224"><sup>[224]</sup></a> Now, considering how little these + <!-- Page 105 --><span class="pagenum"><a + name="page105"></a>{105}</span>varieties of wheat differ in any important + character, it seems to me very improbable that the sterility resulted, as + Mr. Sheriff thought, from the cross, but from some quite distinct cause. + Until such experiments are many times repeated, it would be rash to trust + them; but unfortunately they have been rarely tried even once with + sufficient care.</p> + + <p>Gärtner has recorded a more remarkable and trustworthy case: he + fertilised thirteen panicles (and subsequently nine others) on a dwarf + maize bearing yellow seed<a name="NtA_225" + href="#Nt_225"><sup>[225]</sup></a> with pollen of a tall maize having + red seed; and one head alone produced good seed, only five in number. + Though these plants are monœcious, and therefore do not require + castration, yet I should have suspected some accident in the manipulation + had not Gärtner expressly stated that he had during many years grown + these two varieties together, and they did not spontaneously cross; and + this, considering that the plants are monœcious and abound with + pollen, and are well known generally to cross freely, seems explicable + only on the belief that these two varieties are in some degree mutually + infertile. The hybrid plants raised from the above five seed were + intermediate in structure, extremely variable, and perfectly fertile.<a + name="NtA_226" href="#Nt_226"><sup>[226]</sup></a> No one, I believe, has + hitherto suspected that these varieties of maize are distinct species; + but had the hybrids been in the least sterile, no doubt Gärtner would at + once have so classed them. I may here remark, that with undoubted species + there is not necessarily any close relation between the sterility of a + first cross and that of the hybrid offspring. Some species can be crossed + with facility, but produce utterly sterile hybrids; others can be crossed + with extreme difficulty, but the hybrids when produced are moderately + fertile. I am not aware, however, of any instance quite like this of the + maize with natural species, namely, of a first cross made with + difficulty, but yielding perfectly fertile hybrids.</p> + + <p>The following case is much more remarkable, and evidently perplexed + Gärtner, whose strong wish it was to draw a broad line of distinction + between species and varieties. In the genus Verbascum, he made, during + eighteen years, a vast number of experiments, and crossed no less than + 1085 flowers and counted their seeds. Many of these experiments consisted + in crossing white and yellow varieties of both <i>V. lychnitis</i> and + <i>V. blattaria</i> with nine other species and their hybrids. That the + white and yellow flowered plants of these two species are really + varieties, no one has doubted; and Gärtner actually raised in the case of + both species one variety from the seed of the other. Now in two of his + works<a name="NtA_227" href="#Nt_227"><sup>[227]</sup></a> he distinctly + asserts that crosses between similarly-coloured flowers yield more seed + than between dissimilarly-coloured; so that the yellow-flowered variety + of either species (and conversely with the white-flowered variety), when + crossed with pollen of its own kind, yields more seed than when crossed + with that of the white variety; and so it is when differently coloured + species are crossed. The general results may be seen in the Table at the + <!-- Page 106 --><span class="pagenum"><a + name="page106"></a>{106}</span>end of his volume. In one instance he + gives<a name="NtA_228" href="#Nt_228"><sup>[228]</sup></a> the following + details; but I must premise that Gärtner, to avoid exaggerating the + degree of sterility in his crosses, always compares the <i>maximum</i> + number obtained from a cross with the <i>average</i> number naturally + given by the pure mother-plant. The white-variety of <i>V. lychnitis</i>, + naturally fertilised by its own pollen, gave from an <i>average</i> of + twelve capsules ninety-six good seeds in each; whilst twenty flowers + fertilised with pollen from the yellow variety of this same species, gave + as the <i>maximum</i> only eighty-nine good seed; so that we have the + proportion of 1000 to 908, according to Gärtner's usual scale. I should + have thought it possible that so small a difference in fertility might + have been accounted for by the evil effects of the necessary castration; + but Gärtner shows that the white variety of <i>V. lychnitis</i>, when + fertilised first by the white variety of <i>V. blattaria</i>, and then by + the yellow variety of this species, yielded seed in the proportion of 622 + to 438; and in both these cases castration was performed. Now the + sterility which results from the crossing of the differently coloured + varieties of the same species, is fully as great as that which occurs in + many cases when distinct species are crossed. Unfortunately Gärtner + compared the results of the first unions alone, and not the sterility of + the two sets of hybrids produced from the white variety of <i>V. + lychnitis</i> when fertilised by the white and yellow varieties of <i>V. + blattaria</i>, for it is probable that they would have differed in this + respect.</p> + + <p>Mr. J. Scott has given me the results of a series of experiments on + Verbascum, made by him in the Botanic Gardens of Edinburgh. He repeated + some of Gärtner's experiments on distinct species, but obtained only + fluctuating results; some confirmatory, but the greater number + contradictory; nevertheless these seem hardly sufficient to overthrow the + conclusions arrived at by Gärtner from experiments tried on a much larger + scale. In the second place Mr. Scott experimented on the relative + fertility of unions between similarly and dissimilarly-coloured varieties + of the same species. Thus he fertilised six flowers of the yellow variety + of <i>V. lychnitis</i> by its own pollen, and obtained six capsules, and + calling, for the sake of having a standard of comparison, the average + number of good seed in each one hundred, he found that this same yellow + variety, when fertilised by the white variety, yielded from seven + capsules an average of ninety-four seed. On the same principle, the white + variety of <i>V. lychnitis</i> by its own pollen (from six capsules), and + by the pollen of the yellow variety (eight capsules), yielded seed in the + proportion of 100 to 82. The yellow variety of <i>V. thapsus</i> by its + own pollen (eight capsules), and by that of the white variety (only two + capsules), yielded seed in the proportion of 100 to 94. Lastly, the white + variety of <i>V. blattaria</i> by its own pollen (eight capsules), and by + that of the yellow variety (five capsules), yielded seed in the + proportion of 100 to 79. So that in every case the unions of + dissimilarly-coloured varieties of the same species were less fertile + than the unions of similarly-coloured varieties; when all the cases are + grouped together, the difference of fertility is as 86 to 100. Some + additional trials were made, and altogether thirty-six similarly-coloured + unions yielded thirty-five good <!-- Page 107 --><span class="pagenum"><a + name="page107"></a>{107}</span>capsules; whilst thirty-five + dissimilarly-coloured unions yielded only twenty-six good capsules. + Besides the foregoing experiments, the purple <i>V. phœniceum</i> + was crossed by a rose-coloured and a white variety of the same species; + these two varieties were also crossed together, and these several unions + yielded less seed than <i>V. phœniceum</i> by its own pollen. Hence + it follows from Mr. Scott's experiments, that in the genus Verbascum the + similarly and dissimilarly-coloured varieties of the same species behave, + when crossed, like closely allied but distinct species.<a name="NtA_229" + href="#Nt_229"><sup>[229]</sup></a></p> + + <p>This remarkable fact of the sexual affinity of similarly-coloured + varieties, as observed by Gärtner and Mr. Scott, may not be of very rare + occurrence; for the subject has not been attended to by others. The + following case is worth giving, partly to show how difficult it is to + avoid error. Dr. Herbert<a name="NtA_230" + href="#Nt_230"><sup>[230]</sup></a> has remarked that variously-coloured + double varieties of the hollyhock (<i>Althæa rosea</i>) may be raised + with certainty by seed from plants growing close together. I have been + informed that nurserymen who raise seed for sale do not separate their + plants; accordingly I procured seed of eighteen named varieties; of + these, eleven varieties produced sixty-two plants all perfectly true to + their kind; and seven produced forty-nine plants, half of which were true + and half false. Mr. Masters of Canterbury has given me a more striking + case; he saved seed from a great bed of twenty-four named varieties + planted in closely adjoining rows, and each variety reproduced itself + truly with only sometimes a shade of difference in tint. Now in the + hollyhock the pollen, which is abundant, is matured and nearly all shed + before the stigma of the same flower is ready to receive it;<a + name="NtA_231" href="#Nt_231"><sup>[231]</sup></a> and as bees covered + with pollen incessantly fly from plant to plant, it would appear that + adjoining varieties could not escape being crossed. As, however, this + does not occur, it appeared to me probable that the pollen <!-- Page 108 + --><span class="pagenum"><a name="page108"></a>{108}</span>of each + variety was prepotent on its own stigma over that of all other varieties. + But Mr. C. Turner of Slough, well known for his success in the + cultivation of this plant, informs me that it is the doubleness of the + flowers which prevents the bees gaining access to the pollen and stigma; + and he finds that it is difficult even to cross them artificially. + Whether this explanation will fully account for varieties in close + proximity propagating themselves so truly by seed, I do not know.</p> + + <p>The following cases are worth giving, as they relate to + monœcious forms, which do not require, and consequently have not + been injured by, castration. Girou de Buzareingues crossed what he + designates three varieties of gourd,<a name="NtA_232" + href="#Nt_232"><sup>[232]</sup></a> and asserts that their mutual + fertilisation is less easy in proportion to the difference which they + present. I am aware how imperfectly the forms in this group were until + recently known; but Sageret,<a name="NtA_233" + href="#Nt_233"><sup>[233]</sup></a> who ranked them according to their + mutual fertility, considers the three forms above alluded to as + varieties, as does a far higher authority, namely, M. Naudin.<a + name="NtA_234" href="#Nt_234"><sup>[234]</sup></a> Sageret<a + name="NtA_235" href="#Nt_235"><sup>[235]</sup></a> has observed that + certain melons have a greater tendency, whatever the cause may be, to + keep true than others; and M. Naudin, who has had such immense experience + in this group, informs me that he believes that certain varieties + intercross more readily than others of the same species; but he has not + proved the truth of this conclusion; the frequent abortion of the pollen + near Paris being one great difficulty. Nevertheless, he has grown close + together, during seven years, certain forms of Citrullus, which, as they + could be artificially crossed with perfect facility and produced fertile + offspring, are ranked as varieties; but these forms when not artificially + crossed kept true. Many other varieties, on the other hand, in the same + group cross with such facility, as M. Naudin repeatedly insists, that + without being grown far apart they cannot be kept in the least true.</p> + + <p>Another case, though somewhat different, may be here given, as it is + highly remarkable, and is established on excellent evidence. Kölreuter + minutely describes five varieties of the common tobacco,<a name="NtA_236" + href="#Nt_236"><sup>[236]</sup></a> which were reciprocally crossed, and + the offspring were intermediate in character and as fertile as their + parents: from this fact Kölreuter inferred that they are really + varieties; and no one, as far as I can discover, seems to have doubted + that such is the case. He also crossed reciprocally these five varieties + with <i>N. glutinosa</i>, and they yielded very sterile hybrids; but + those raised from the <i>var. perennis</i>, whether used as the father or + mother plant, were not so sterile as the hybrids from the four other + varieties.<a name="NtA_237" href="#Nt_237"><sup>[237]</sup></a> So that + the sexual <!-- Page 109 --><span class="pagenum"><a + name="page109"></a>{109}</span>capacity of this one variety has certainly + been in some degree modified, so as to approach in nature that of <i>N. + glutinosa</i>.<a name="NtA_238" href="#Nt_238"><sup>[238]</sup></a></p> + +</blockquote> + + <p>These facts with respect to plants show that in some few cases certain + varieties have had their sexual powers so far modified, that they cross + together less readily and yield less seed than other varieties of the + same species. We shall presently see that the sexual functions of most + animals and plants are eminently liable to be affected by the conditions + of life to which they are exposed; and hereafter we shall briefly discuss + the conjoint bearing of this and other facts on the difference in + fertility between crossed varieties and crossed species.</p> + +<p class="cenhead"><i>Domestication eliminates the tendency to Sterility which is general +with Species when crossed.</i></p> + + <p>This hypothesis was first propounded by Pallas,<a name="NtA_239" + href="#Nt_239"><sup>[239]</sup></a> and has been adopted by several + authors. I can find hardly any direct facts in its support; but + unfortunately no one has compared, in the case of either animals or + plants, the fertility of anciently domesticated varieties, when crossed + with a distinct species, with that of the wild parent-species when + similarly crossed. No one has compared, for instance, the fertility of + <i>Gallus bankiva</i> and of the domesticated fowl, when crossed with a + distinct species of Gallus or Phasianus; and the <!-- Page 110 --><span + class="pagenum"><a name="page110"></a>{110}</span>experiment would in all + cases be surrounded by many difficulties. Dureau de la Malle, who has so + closely studied classical literature, states<a name="NtA_240" + href="#Nt_240"><sup>[240]</sup></a> that in the time of the Romans the + common mule was produced with more difficulty than at the present day; + but whether this statement may be trusted I know not. A much more + important, though somewhat different, case is given by M. Groenland,<a + name="NtA_241" href="#Nt_241"><sup>[241]</sup></a> namely, that plants, + known from their intermediate character and sterility to be hybrids + between Ægilops and wheat, have perpetuated themselves under culture + since 1857, <i>with a rapid but varying increase of fertility in each + generation</i>. In the fourth generation the plants, still retaining + their intermediate character, had become as fertile as common cultivated + wheat.</p> + + <p>The indirect evidence in favour of the Pallasian doctrine appears to + me to be extremely strong. In the earlier chapters I have attempted to + show that our various breeds of dogs are descended from several wild + species; and this probably is the case with sheep. There can no longer be + any doubt that the Zebu or humped Indian ox belongs to a distinct species + from European cattle: the latter, moreover, are descended from two or + three forms, which may be called either species or wild races, but which + co-existed in a state of nature and kept distinct. We have good evidence + that our domesticated pigs belong to at least two specific types, <i>S. + scrofa</i> and <i>Indica</i>, which probably lived together in a wild + state in South-eastern Europe. Now, a widely-extended analogy leads to + the belief that if these several allied species, in the wild state or + when first reclaimed, had been crossed, they would have exhibited, both + in their first unions and in their hybrid offspring, some degree of + sterility. Nevertheless the several domesticated races descended from + them are now all, as far as can be ascertained, perfectly fertile + together. If this reasoning be trustworthy, and it is apparently sound, + we must admit the Pallasian doctrine that long-continued domestication + tends to eliminate that sterility which is natural to species when + crossed in their aboriginal state.</p> + +<p><!-- Page 111 --><span class="pagenum"><a name="page111"></a>{111}</span></p> + +<p class="cenhead"><i>On increased Fertility from Domestication and Cultivation.</i></p> + + <p>Increased fertility from domestication, without any reference to + crossing, may be here briefly considered. This subject bears indirectly + on two or three points connected with the modification of organic beings. + As Buffon long ago remarked,<a name="NtA_242" + href="#Nt_242"><sup>[242]</sup></a> domestic animals breed oftener in the + year and produce more young at a birth than wild animals of the same + species; they, also, sometimes breed at an earlier age. The case would + hardly have deserved further notice, had not some authors lately + attempted to show that fertility increases and decreases in an inverse + ratio with the amount of food. This strange doctrine has apparently + arisen from individual animals when supplied with an inordinate quantity + of food, and from plants of many kinds when grown on excessively rich + soil, as on a dunghill, becoming sterile; but to this latter point I + shall have occasion presently to return. With hardly an exception, our + domesticated animals, which have long been habituated to a regular and + copious supply of food, without the labour of searching for it, are more + fertile than the corresponding wild animals. It is notorious how + frequently cats and dogs breed, and how many young they produce at a + birth. The wild rabbit is said generally to breed four times yearly, and + to produce from four to eight young; the tame rabbit breeds six or seven + times yearly, and produces from four to eleven young. The ferret, though + generally so closely confined, is more prolific than its supposed wild + prototype. The wild sow is remarkably prolific, for she often breeds + twice in the year, and produces from four to eight and sometimes even + twelve young at a birth; but the domestic sow regularly breeds twice a + year, and would breed oftener if permitted; and a sow that produces less + than eight at a birth "is worth little, and the sooner she is fattened + for the butcher the better." The amount of food affects the fertility + even of the same individual: thus sheep, which on mountains never produce + more than one lamb at a birth, when brought <!-- Page 112 --><span + class="pagenum"><a name="page112"></a>{112}</span>down to lowland + pastures frequently bear twins. This difference apparently is not due to + the cold of the higher land, for sheep and other domestic animals are + said to be extremely prolific in Lapland. Hard living, also, retards the + period at which animals conceive; for it has been found disadvantageous + in the northern islands of Scotland to allow cows to bear calves before + they are four years old.<a name="NtA_243" + href="#Nt_243"><sup>[243]</sup></a></p> + +<blockquote class="b1n"> + + <p>Birds offer still better evidence of increased fertility from + domestication: the hen of the wild <i>Gallus bankiva</i> lays from six to + ten eggs, a number which would be thought nothing of with the domestic + hen. The wild duck lays from five to ten eggs; the tame one in the course + of the year from eighty to one hundred. The wild grey-lag goose lays from + five to eight eggs; the tame from thirteen to eighteen, and she lays a + second time; as Mr. Dixon has remarked, "high-feeding, care, and moderate + warmth induce a habit of prolificacy which becomes in some measure + hereditary." Whether the semi-domesticated dovecot pigeon is more fertile + than the wild rock-pigeon <i>C. livia</i>, I know not; but the more + thoroughly domesticated breeds are nearly twice as fertile as dovecots: + the latter, however, when caged and highly fed, become equally fertile + with house pigeons. The peahen alone of domesticated birds is rather more + fertile, according to some accounts, when wild in its native Indian home, + than when domesticated in Europe and exposed to our much colder + climate.<a name="NtA_244" href="#Nt_244"><sup>[244]</sup></a></p> + + <p>With respect to plants, no one would expect wheat to tiller more, and + each ear to produce more grain, in poor than in rich soil; or to get in + poor soil a heavy crop of peas or beans. Seeds vary so much in number + <!-- Page 113 --><span class="pagenum"><a + name="page113"></a>{113}</span>that it is difficult to estimate them; but + on comparing beds of carrots saved for seed in a nursery garden with wild + plants, the former seemed to produce about twice as much seed. Cultivated + cabbages yielded thrice as many pods by measure as wild cabbages from the + rocks of South Wales. The excess of berries produced by the cultivated + Asparagus in comparison with the wild plant is enormous. No doubt many + highly cultivated plants, such as pears, pineapples, bananas, sugar-cane, + &c., are nearly or quite sterile; and I am inclined to attribute this + sterility to excess of food and to other unnatural conditions; but to + this subject I shall presently recur.</p> + +</blockquote> + + <p>In some cases, as with the pig, rabbit, &c., and with those plants + which are valued for their seed, the direct selection of the more fertile + individuals has probably much increased their fertility; and in all cases + this may have occurred indirectly, from the better chance of the more + numerous offspring produced by the more fertile individuals having + survived. But with cats, ferrets, and dogs, and with plants like carrots, + cabbages, and asparagus, which are not valued for their prolificacy, + selection can have played only a subordinate part; and their increased + fertility must be attributed to the more favourable conditions of life + under which they have long existed.</p> + +<hr class="full" /> + +<p><!-- Page 114 --><span class="pagenum"><a name="page114"></a>{114}</span></p> + +<h3>CHAPTER XVII.</h3> + +<p class="cenhead">ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL +EFFECTS OF CLOSE INTERBREEDING.</p> + +<blockquote class="b1n"> + + <p><span class="scac">DEFINITION OF CLOSE + INTERBREEDING</span>—<span class="scac">AUGMENTATION OF MORBID + TENDENCIES</span>—<span class="scac">GENERAL EVIDENCE ON THE GOOD + EFFECTS DERIVED FROM CROSSING, AND ON THE EVIL EFFECTS FROM CLOSE + INTERBREEDING</span>—<span class="scac">CATTLE, CLOSELY INTERBRED; + HALF-WILD CATTLE LONG KEPT IN THE SAME PARKS</span>—<span + class="scac">SHEEP</span>—<span + class="scac">FALLOW-DEER</span>—<span + class="scac">DOGS</span>—<span + class="scac">RABBITS</span>—<span + class="scac">PIGS</span>—<span class="scac">MAN, ORIGIN OF HIS + ABHORRENCE OF INCESTUOUS MARRIAGES</span>—<span + class="scac">FOWLS</span>—<span + class="scac">PIGEONS</span>—<span + class="scac">HIVE-BEES</span>—<span class="scac">PLANTS, GENERAL + CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING</span>—<span + class="scac">MELONS, FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND + FOREST-TREES</span>—<span class="scac">ON THE INCREASED SIZE OF + HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY</span>—<span + class="scac">ON CERTAIN PLANTS WHICH EITHER NORMALLY OR ABNORMALLY ARE + SELF-IMPOTENT, BUT ARE FERTILE, BOTH ON THE MALE AND FEMALE SIDE, WHEN + CROSSED WITH DISTINCT INDIVIDUALS EITHER OF THE SAME OR ANOTHER + SPECIES</span>—<span class="scac">CONCLUSION.</span></p> + +</blockquote> + + <p>The gain in constitutional vigour, derived from an occasional cross + between individuals of the same variety, but belonging to distinct + families, or between distinct varieties, has not been so largely or so + frequently discussed, as have the evil effects of too close + interbreeding. But the former point is the more important of the two, + inasmuch as the evidence is more decisive. The evil results from close + interbreeding are difficult to detect, for they accumulate slowly, and + differ much in degree with different species; whilst the good effects + which almost invariably follow a cross are from the first manifest. It + should, however, be clearly understood that the advantage of close + interbreeding, as far as the retention of character is concerned, is + indisputable, and often outweighs the evil of a slight loss of + constitutional vigour. In relation to the subject of domestication, the + whole question is of some importance, as too close interbreeding + interferes with the improvement of old races, and especially with the + formation of new ones. It is important as indirectly bearing on + Hybridism; and perhaps on the extinction of species, when any form has + become so rare that only a few individuals <!-- Page 115 --><span + class="pagenum"><a name="page115"></a>{115}</span>remain within a + confined area. It bears in an important manner on the influence of free + intercrossing, in obliterating individual differences, and thus giving + uniformity of character to the individuals of the same race or species; + for if additional vigour and fertility be thus gained, the crossed + offspring will multiply and prevail, and the ultimate result will be far + greater than otherwise would have occurred. Lastly, the question is of + high interest, as bearing on mankind. Hence I shall discuss this subject + at full length. As the facts which prove the evil effects of close + interbreeding are more copious, though less decisive, than those on the + good effects of crossing, I shall, under each group of beings, begin with + the former.</p> + + <p>There is no difficulty in defining what is meant by a cross; but this + is by no means easy in regard to "breeding in and in" or "too close + interbreeding," because, as we shall see, different species of animals + are differently affected by the same degree of interbreeding. The pairing + of a father and daughter, or mother and son, or brothers and sisters, if + carried on during several generations, is the closest possible form of + interbreeding. But some good judges, for instance Sir J. Sebright, + believe that the pairing of a brother and sister is closer than that of + parents and children; for when the father is matched with his daughter he + crosses, as is said, with only half his own blood. The consequences of + close interbreeding carried on for too long a time, are, as is generally + believed, loss of size, constitutional vigour, and fertility, sometimes + accompanied by a tendency to malformation. Manifest evil does not usually + follow from pairing the nearest relations for two, three, or even four + generations; but several causes interfere with our detecting the + evil—such as the deterioration being very gradual, and the + difficulty of distinguishing between such direct evil and the inevitable + augmentation of any morbid tendencies which may be latent or apparent in + the related parents. On the other hand, the benefit from a cross, even + when there has not been any very close interbreeding, is almost + invariably at once conspicuous. There is reason to believe, and this was + the opinion of that most experienced observer Sir J. Sebright,<a + name="NtA_245" href="#Nt_245"><sup>[245]</sup></a> that the evil effects + of close interbreeding may be checked by the related individuals <!-- + Page 116 --><span class="pagenum"><a name="page116"></a>{116}</span>being + separated during a few generations and exposed to different conditions of + life.</p> + + <p>That evil directly follows from any degree of close interbreeding has + been denied by many persons; but rarely by any practical breeder; and + never, as far as I know, by one who has largely bred animals which + propagate their kind quickly. Many physiologists attribute the evil + exclusively to the combination and consequent increase of morbid + tendencies common to both parents: that this is an active source of + mischief there can be no doubt. It is unfortunately too notorious that + men and various domestic animals endowed with a wretched constitution, + and with a strong hereditary disposition to disease, if not actually ill, + are fully capable of procreating their kind. Close interbreeding, on the + other hand, induces sterility; and this indicates something quite + distinct from the augmentation of morbid tendencies common to both + parents. The evidence immediately to be given convinces me that it is a + great law of nature, that all organic beings profit from an occasional + cross with individuals not closely related to them in blood; and that, on + the other hand, long-continued close interbreeding is injurious.</p> + + <p>Various general considerations have had much influence in leading me + to this conclusion; but the reader will probably rely more on special + facts and opinions. The authority of experienced observers, even when + they do not advance the grounds of their belief, is of some little value. + Now almost all men who have bred many kinds of animals and have written + on the subject, such as Sir J. Sebright, Andrew Knight, &c.,<a + name="NtA_246" href="#Nt_246"><sup>[246]</sup></a> have expressed the + strongest conviction on the impossibility of long-continued close + interbreeding. Those who have compiled works on agriculture, and have + associated much with breeders, such as the sagacious Youatt, Low, + &c., have strongly declared their opinion to the same effect. Prosper + Lucas, trusting largely to French authorities, has come to a similar + conclusion. The distinguished German agriculturist Hermann von Nathusius, + who has written the most able treatise on this subject which I have met + with, concurs; and as I shall have to quote from <!-- Page 117 --><span + class="pagenum"><a name="page117"></a>{117}</span>this treatise, I may + state that Nathusius is not only intimately acquainted with works on + agriculture in all languages, and knows the pedigrees of our British + breeds better than most Englishmen, but has imported many of our improved + animals, and is himself an experienced breeder.</p> + + <p>Evidence of the evil effects of close interbreeding can most readily + be acquired in the case of animals, such as fowls, pigeons, &c., + which propagate quickly, and, from being kept in the same place, are + exposed to the same conditions. Now I have inquired of very many breeders + of these birds, and I have hitherto not met with a single man who was not + thoroughly convinced that an occasional cross with another strain of the + same sub-variety was absolutely necessary. Most breeders of + highly-improved or fancy birds value their own strain, and are most + unwilling, at the risk, in their opinion, of deterioration, to make a + cross. The purchase of a first-rate bird of another strain is expensive, + and exchanges are troublesome; yet all breeders, as far as I can hear, + excepting those who keep large stocks at different places for the sake of + crossing, are driven after a time to take this step.</p> + + <p>Another general consideration which has had great influence on my mind + is, that with all hermaphrodite animals and plants, which it might have + been thought would have perpetually fertilised themselves, and thus have + been subjected for long ages to the closest interbreeding, there is no + single species, as far as I can discover, in which the structure ensures + self-fertilisation. On the contrary, there are in a multitude of cases, + as briefly stated in the fifteenth chapter, manifest adaptations which + favour or inevitably lead to an occasional cross between one + hermaphrodite and another of the same species; and these adaptive + structures are utterly purposeless, as far as we can see, for any other + end.</p> + +<blockquote class="b1n"> + + <p>With <i>Cattle</i> there can be no doubt that extremely close + interbreeding may be long carried on, advantageously with respect to + external characters and with no manifestly apparent evil as far as + constitution is concerned. The same remark is applicable to sheep. + Whether these animals have gradually been rendered less susceptible than + others to this evil, in order to permit them to live in herds,—a + habit which leads the old and vigorous males to expel all intruders, and + in consequence often to pair with their own daughters, I will not pretend + to decide. The case of Bakewell's Long-horns, which were closely + interbred for a long period, has often been <!-- Page 118 --><span + class="pagenum"><a name="page118"></a>{118}</span>quoted; yet Youatt + says<a name="NtA_247" href="#Nt_247"><sup>[247]</sup></a> the breed "had + acquired a delicacy of constitution inconsistent with common management," + and "the propagation of the species was not always certain." But the + Shorthorns offer the most striking case of close interbreeding; for + instance, the famous bull Favourite (who was himself the offspring of a + half-brother and sister from Foljambe) was matched with his own daughter, + granddaughter, and great-granddaughter; so that the produce of this last + union, or the great-great-granddaughter, had 15-16ths, or 93.75 per cent. + of the blood of Favourite in her veins. This cow was matched with the + bull Wellington, having 62.5 per cent. of Favourite blood in his veins, + and produced Clarissa; Clarissa was matched with the bull Lancaster, + having 68.75 of the same blood, and she yielded valuable offspring.<a + name="NtA_248" href="#Nt_248"><sup>[248]</sup></a> Nevertheless Collings, + who reared these animals, and was a strong advocate for close breeding, + once crossed his stock with a Galloway, and the cows from this cross + realised the highest prices. Bates's herd was esteemed the most + celebrated in the world. For thirteen years he bred most closely in and + in; but during the next seventeen years, though he had the most exalted + notion of the value of his own stock, he thrice infused fresh blood into + his herd: it is said that he did this, not to improve the form of his + animals, but on account of their lessened fertility. Mr. Bates's own + view, as given by a celebrated breeder,<a name="NtA_249" + href="#Nt_249"><sup>[249]</sup></a> was, that "to breed in and in from a + bad stock was ruin and devastation; yet that the practice may be safely + followed within certain limits when the parents so related are descended + from first-rate animals." We thus see that there has been extremely close + interbreeding with Shorthorns; but Nathusius, after the most careful + study of their pedigrees, says that he can find no instance of a breeder + who has strictly followed this practice during his whole life. From this + study and his own experience, he concludes that close interbreeding is + necessary to ennoble the stock; but that in effecting this the greatest + care is necessary, on account of the tendency to infertility and + weakness. It may be added, that another high authority<a name="NtA_250" + href="#Nt_250"><sup>[250]</sup></a> asserts that many more calves are + born cripples from Shorthorns than from other and less closely interbred + races of cattle.</p> + + <p>Although by carefully selecting the best animals (as Nature + effectually does by the law of battle) close interbreeding may be long + carried on with cattle, yet the good effects of a cross between almost + any two breeds is at once shown by the greater size and vigour of the + offspring; as Mr. Spooner writes to me, "crossing distinct breeds + certainly improves cattle for the butcher." Such crossed animals are of + course of no value to the breeder; but they have been raised during many + years in several <!-- Page 119 --><span class="pagenum"><a + name="page119"></a>{119}</span>parts of England to be slaughtered;<a + name="NtA_251" href="#Nt_251"><sup>[251]</sup></a> and their merit is now + so fully recognised, that at fat-cattle shows a separate class has been + formed for their reception. The best fat ox at the great show at + Islington in 1862 was a crossed animal.</p> + + <p>The half-wild cattle, which have been kept in British parks probably + for 400 or 500 years, or even for a longer period, have been advanced by + Culley and others as a case of long-continued interbreeding within the + limits of the same herd without any consequent injury. With respect to + the cattle at Chillingham, the late Lord Tankerville owned that they were + bad breeders.<a name="NtA_252" href="#Nt_252"><sup>[252]</sup></a> The + agent, Mr. Hardy, estimates (in a letter to me, dated May, 1861) that in + the herd of about fifty the average number annually slaughtered, killed + by fighting, and dying, is about ten, or one in five. As the herd is kept + up to nearly the same average number, the annual rate of increase must be + likewise about one in five. The bulls, I may add, engage in furious + battles, of which battles the present Lord Tankerville has given me a + graphic description, so that there will always be rigorous selection of + the most vigorous males. I procured in 1855 from Mr. D. Gardner, agent to + the Duke of Hamilton, the following account of the wild cattle kept in + the Duke's park in Lanarkshire, which is about 200 acres in extent. The + number of cattle varies from sixty-five to eighty; and the number + annually killed (I presume by all causes) is from eight to ten; so that + the annual rate of increase can hardly be more than one in six. Now in + South America, where the herds are half-wild, and therefore offer a + nearly fair standard of comparison, according to Azara the natural + increase of the cattle on an estancia is from one-third to one-fourth of + the total number, or one in between three and four; and this, no doubt, + applies exclusively to adult animals fit for consumption. Hence the + half-wild British cattle which have long interbred within the limits of + the same herd are relatively far less fertile. Although in an unenclosed + country like Paraguay there must be some crossing between the different + herds, yet even there the inhabitants believe that the occasional + introduction of animals from distant localities is necessary to prevent + "degeneration in size and diminution of fertility."<a name="NtA_253" + href="#Nt_253"><sup>[253]</sup></a> The decrease in size from ancient + times in the Chillingham and Hamilton cattle must have been prodigious, + for Professor Rütimeyer has shown that they are almost certainly the + descendants of the gigantic <i>Bos primigenius</i>. No doubt this + decrease in size may be largely attributed to less favourable conditions + of life; yet animals roaming over large parks, and fed during severe + winters, can hardly be considered as placed under very unfavourable + conditions.</p> + + <p>With <i>Sheep</i> there has often been long-continued interbreeding + within the limits of the same flock; but whether the nearest relations + have been matched so frequently as in the case of Shorthorn cattle, I do + not know. The Messrs. Brown during fifty years have never infused fresh + blood into their excellent flock of Leicesters. Since 1810 Mr. Barford + has acted on the same principle with the Foscote flock. He asserts that + half a century <!-- Page 120 --><span class="pagenum"><a + name="page120"></a>{120}</span>of experience has convinced him that when + two nearly related animals are quite sound in constitution, in-and-in + breeding does not induce degeneracy; but he adds that he "does not pride + himself on breeding from the nearest affinities." In France the Naz flock + has been bred for sixty years without the introduction of a single + strange ram.<a name="NtA_254" href="#Nt_254"><sup>[254]</sup></a> + Nevertheless, most great breeders of sheep have protested against close + interbreeding prolonged for too great a length of time.<a name="NtA_255" + href="#Nt_255"><sup>[255]</sup></a> The most celebrated of recent + breeders, Jonas Webb, kept five separate families to work on, thus + "retaining the requisite distance of relationship between the sexes."<a + name="NtA_256" href="#Nt_256"><sup>[256]</sup></a></p> + + <p>Although by the aid of careful selection the near interbreeding of + sheep may be long continued without any manifest evil, yet it has often + been the practice with farmers to cross distinct breeds to obtain animals + for the butcher, which plainly shows that good is derived from this + practice. Mr. Spooner sums up his excellent Essay on Crossing by + asserting that there is a direct pecuniary advantage in judicious + cross-breeding, especially when the male is larger than the female. A + former celebrated breeder, Lord Somerville, distinctly states that his + half-breeds from Ryelands and Spanish sheep were larger animals than + either the pure Ryelands or pure Spanish sheep.<a name="NtA_257" + href="#Nt_257"><sup>[257]</sup></a></p> + + <p>As some of our British parks are ancient, it occurred to me that there + must have been long-continued close interbreeding with the fallow deer + (<i>Cervus dama</i>) kept in them; but on inquiry I find that it is a + common practice to infuse new blood by procuring bucks from other parks. + Mr. Shirley,<a name="NtA_258" href="#Nt_258"><sup>[258]</sup></a> who has + carefully studied the management of deer, admits that in some parks there + has been no admixture of foreign blood from a time beyond the memory of + man. But he concludes "that in the end the constant breeding in-and-in is + sure to tell to the disadvantage of the whole herd, though it may take a + very long time to prove it; moreover, when we find, as is very constantly + the case, that the introduction of fresh blood has been of the very + greatest use to deer, both by improving their size and appearance, and + particularly by being of service in removing the taint of 'rickback,' if + not of other diseases, to which deer are sometimes subject when the blood + has not been changed, there can, I think, be no doubt but that a + judicious cross with a good stock is of the greatest consequence, and is + indeed essential, sooner or later, to the prosperity of every + well-ordered park."</p> + + <p>Mr. Meynell's famous foxhounds have been adduced, as showing that no + ill effects follow from close interbreeding; and Sir J. Sebright + ascertained from him that he frequently bred from father and daughter, + mother and <!-- Page 121 --><span class="pagenum"><a + name="page121"></a>{121}</span>son, and sometimes even from brothers and + sisters. Sir J. Sebright, however, declares,<a name="NtA_259" + href="#Nt_259"><sup>[259]</sup></a> that by breeding <i>in-and-in</i>, by + which he means matching brothers and sisters, he has actually seen strong + spaniels become weak and diminutive lapdogs. The Rev. W. D. Fox has + communicated to me the case of a small lot of bloodhounds, long kept in + the same family, which had become very bad breeders, and nearly all had a + bony enlargement in the tail. A single cross with a distinct strain of + bloodhounds restored their fertility, and drove away the tendency to + malformation in the tail. I have heard the particulars of another case + with bloodhounds, in which the female had to be held to the male. + Considering how rapid is the natural increase of the dog, it is difficult + to understand the high price of most highly improved breeds, which almost + implies long-continued close interbreeding, except on the belief that + this process lessens fertility and increases liability to distemper and + other diseases. A high authority, Mr. Scrope, attributes the rarity and + deterioration in size of the Scotch deerhound (the few individuals now + existing throughout the country being all related) in large part to close + interbreeding.</p> + + <p>With all highly-bred animals there is more or less difficulty in + getting them to procreate quickly, and all suffer much from delicacy of + constitution; but I do not pretend that these effects ought to be wholly + attributed to close interbreeding. A great judge of rabbits<a + name="NtA_260" href="#Nt_260"><sup>[260]</sup></a> says, "the long-eared + does are often too highly bred or forced in their youth to be of much + value as breeders, often turning out barren or bad mothers." Again: "Very + long-eared bucks will also sometimes prove barren." These highly-bred + rabbits often desert their young, so that it is necessary to have + nurse-rabbits.</p> + + <p>With <i>Pigs</i> there is more unanimity amongst breeders on the evil + effects of close interbreeding than, perhaps, with any other large + animal. Mr. Druce, a great and successful breeder of the Improved + Oxfordshires (a crossed race), writes, "without a change of boars of a + different tribe, but of the same breed, constitution cannot be + preserved." Mr. Fisher Hobbs, the raiser of the celebrated Improved Essex + breed, divided his stock into three separate families, by which means he + maintained the breed for more than twenty years, "by judicious selection + from the <i>three distinct families</i>."<a name="NtA_261" + href="#Nt_261"><sup>[261]</sup></a> Lord Western was the first importer + of a Neapolitan boar and sow. "From this pair he bred in-and-in, until + the breed was in danger of becoming extinct, a sure result (as Mr. Sidney + remarks) of in-and-in breeding." Lord Western then crossed his Neapolitan + pigs with the old Essex, and made the first great step towards the + Improved Essex breed. Here is a more interesting case. Mr. J. Wright, + well known as a breeder, crossed<a name="NtA_262" + href="#Nt_262"><sup>[262]</sup></a> the same boar with the daughter, + granddaughter, and great-granddaughter, and so on for seven generations. + The result was, that in many instances the offspring failed to breed; in + others they produced few that lived; and of the latter many were idiotic, + without sense <!-- Page 122 --><span class="pagenum"><a + name="page122"></a>{122}</span>even to suck, and when attempting to move + could not walk straight. Now it deserves especial notice, that the two + last sows produced by this long course of interbreeding were sent to + other boars, and they bore several litters of healthy pigs. The best sow + in external appearance produced during the whole seven generations was + one in the last stage of descent; but the litter consisted of this one + sow. She would not breed to her sire, yet bred at the first trial to a + stranger in blood. So that, in Mr. Wright's case, long-continued and + extremely close interbreeding did not affect the external form or merit + of the young; but with many of them the general constitution and mental + powers, and especially the reproductive functions, were seriously + affected.</p> + + <p>Nathusius gives<a name="NtA_263" href="#Nt_263"><sup>[263]</sup></a> + an analogous and even more striking case: he imported from England a + pregnant sow of the large Yorkshire breed, and bred the product closely + in-and-in for three generations: the result was unfavourable, as the + young were weak in constitution, with impaired fertility. One of the + latest sows, which he esteemed a good animal, produced, when paired with + her own uncle (who was known to be productive with sows of other breeds), + a litter of six, and a second time a litter of only five weak young pigs. + He then paired this sow with a boar of a small black breed, which he had + likewise imported from England, and which boar, when matched with sows of + his own breed, produced from seven to nine young: now, the sow of the + large breed, which was so unproductive when paired with her own uncle, + yielded to the small black boar, in the first litter twenty-one, and in + the second litter eighteen young pigs; so that in one year she produced + thirty-nine fine young animals!</p> + + <p>As in the case of several other animals already mentioned, even when + no injury is perceptible from moderately close interbreeding, yet, to + quote the words of Mr. Coate, a most successful breeder (who five times + won the annual gold medal of the Smithfield Club Show for the best pen of + pigs), "Crosses answer well for profit to the farmer, as you get more + constitution and quicker growth; but for me, who sell a great number of + pigs for breeding purposes, I find it will not do, as it requires many + years to get anything like purity of blood again."<a name="NtA_264" + href="#Nt_264"><sup>[264]</sup></a></p> + +</blockquote> + + <p>Before passing on to Birds, I ought to refer to man, though I am + unwilling to enter on this subject, as it is surrounded by natural + prejudices. It has moreover been discussed by various authors under many + points of view.<a name="NtA_265" href="#Nt_265"><sup>[265]</sup></a> Mr. + Tylor<a name="NtA_266" href="#Nt_266"><sup>[266]</sup></a> has shown <!-- + Page 123 --><span class="pagenum"><a name="page123"></a>{123}</span>that + with widely different races, in the most distant quarters of the world, + marriages between relations—even between distant + relations—have been strictly prohibited. A few exceptional cases + can be specified, especially with royal families; and these have been + enlarged on in a learned article<a name="NtA_267" + href="#Nt_267"><sup>[267]</sup></a> by Mr. W. Adam, and formerly in 1828 + by Hofacker. Mr. Tylor is inclined to believe that the almost universal + prohibition of closely-related marriages has arisen from their evil + effects having been observed, and he ingeniously explains some apparent + anomalies in the prohibition not extending equally to the relations on + both the male and female side. He admits, however, that other causes, + such as the extension of friendly alliances, may have come into play. Mr. + W. Adam, on the other hand, concludes that related marriages are + prohibited and viewed with repugnance from the confusion which would thus + arise in the descent of property, and from other still more recondite + reasons; but I cannot accept this view, seeing that the savages of + Australia and South America,<a name="NtA_268" + href="#Nt_268"><sup>[268]</sup></a> who have no property to bequeath or + fine moral feelings to confuse, hold the crime of incest in + abhorrence.</p> + + <p>It would be interesting to know, if it could be ascertained, as + throwing light on this question with respect to man, what occurs with the + higher anthropomorphous apes—whether the young males and females + soon wander away from their parents, or whether the old males become + jealous of their sons and expel them, or whether any inherited + instinctive feeling, from being beneficial, has been generated, leading + the young males and females of the same family to prefer pairing with + distinct families, and to dislike pairing with each other. A considerable + body of evidence has already been advanced, showing that the offspring + from parents which are not related are more vigorous and fertile than + those from parents which are closely related; hence any slight feeling, + arising from the sexual excitement of novelty or other cause, which led + to the former rather than to the latter unions, would be augmented + through natural selection, and thus might become instinctive; for those + individuals which had an innate preference of this kind would increase in + number. It seems more probable, that degraded savages should <!-- Page + 124 --><span class="pagenum"><a name="page124"></a>{124}</span>thus + unconsciously have acquired their dislike and even abhorrence of + incestuous marriages, rather than that they should have discovered by + reasoning and observation the evil results. The abhorrence occasionally + failing is no valid argument against the feeling being instinctive, for + any instinct may occasionally fail or become vitiated, as sometimes + occurs with parental love and the social sympathies. In the case of man, + the question whether evil follows from close interbreeding will probably + never be answered by direct evidence, as he propagates his kind so slowly + and cannot be subjected to experiment; but the almost universal practice + of all races at all times of avoiding closely-related marriages is an + argument of considerable weight; and whatever conclusion we arrive at in + regard to the higher animals may be safely extended to man.</p> + +<blockquote class="b1n"> + + <p>Turning now to Birds: in the case of the <i>Fowl</i> a whole array of + authorities could be given against too close interbreeding. Sir J. + Sebright positively asserts that he made many trials, and that his fowls, + when thus treated, became long in the legs, small in the body, and bad + breeders.<a name="NtA_269" href="#Nt_269"><sup>[269]</sup></a> He + produced the famous Sebright Bantams by complicated crosses, and by + breeding in-and-in; and since his time there has been much close + interbreeding with these Bantams; and they are now notoriously bad + breeders. I have seen Silver Bantams, directly descended from his stock, + which had become almost as barren as hybrids; for not a single chicken + had been that year hatched from two full nests of eggs. Mr. Hewitt says + that with these Bantams the sterility of the male stands, with rare + exceptions, in the closest relation with their loss of certain secondary + male characters: he adds, "I have noticed, as a general rule, that even + the slightest deviation from feminine character in the tail of the male + Sebright—say the elongation by only half an inch of the two + principal tail-feathers—brings with it improved probability of + increased fertility."<a name="NtA_270" + href="#Nt_270"><sup>[270]</sup></a></p> + + <p>Mr. Wright states<a name="NtA_271" href="#Nt_271"><sup>[271]</sup></a> + that Mr. Clark, "whose fighting-cocks were so notorious, continued to + breed from his own kind till they lost their disposition to fight, but + stood to be cut up without making any resistance, and were so reduced in + size as to be under those weights required for the best prizes; but on + obtaining a cross from Mr. Leighton, they again resumed their former + courage and weight." It should be borne in mind that game-cocks before + they fought were always weighed, so that nothing was left to the + imagination about any reduction or increase of <!-- Page 125 --><span + class="pagenum"><a name="page125"></a>{125}</span>weight. Mr. Clark does + not seem to have bred from brothers and sisters, which is the most + injurious kind of union; and he found, after repeated trials, that there + was a greater reduction in weight in the young from a father paired with + his daughter, than from a mother with her son. I may add that Mr. Eyton, + of Eyton, the well-known ornithologist, who is a large breeder of Grey + Dorkings, informs me that they certainly diminish in size, and become + less prolific, unless a cross with another strain is occasionally + obtained. So it is with Malays, according to Mr. Hewitt, as far as size + is concerned.<a name="NtA_272" href="#Nt_272"><sup>[272]</sup></a></p> + + <p>An experienced writer<a name="NtA_273" + href="#Nt_273"><sup>[273]</sup></a> remarks that the same amateur, as is + well known, seldom long maintains the superiority of his birds; and this, + he adds, undoubtedly is due to all his stock "being of the same blood;" + hence it is indispensable that he should occasionally procure a bird of + another strain. But this is not necessary with those who keep a stock of + fowls at different stations. Thus, Mr. Ballance, who has bred Malays for + thirty years, and has won more prizes with these birds than any other + fancier in England, says that breeding in-and-in does not necessarily + cause deterioration; "but all depends upon how this is managed." "My plan + has been to keep about five or six distinct runs, and to rear about two + hundred or three hundred chickens each year, and select the best birds + from each run for crossing. I thus secure sufficient crossing to prevent + deterioration."<a name="NtA_274" href="#Nt_274"><sup>[274]</sup></a></p> + + <p>We thus see that there is almost complete unanimity with + poultry-breeders that, when fowls are kept at the same place, evil + quickly follows from interbreeding carried on to an extent which would be + disregarded in the case of most quadrupeds. On the other hand, it is a + generally received opinion that cross-bred chickens are the hardiest and + most easily reared.<a name="NtA_275" href="#Nt_275"><sup>[275]</sup></a> + Mr. Tegetmeier, who has carefully attended to poultry of all breeds, + says<a name="NtA_276" href="#Nt_276"><sup>[276]</sup></a> that Dorking + hens, allowed to run with Houdan or Crevecœur cocks, "produce in + the early spring chickens that for size, hardihood, early maturity, and + fitness for the market, surpass those of any pure breed that we have ever + raised." Mr. Hewitt gives it as a general rule with fowls, that crossing + the breed increases their size. He makes this remark after stating that + hybrids from the pheasant and fowl are considerably larger than either + progenitor: so again, hybrids from the male golden pheasant and hen + common pheasant "are of far larger size than either parent-bird."<a + name="NtA_277" href="#Nt_277"><sup>[277]</sup></a> To this subject of the + increased size of hybrids I shall presently return.</p> + + <p>With <i>Pigeons</i>, breeders are unanimous, as previously stated, + that it is absolutely indispensable, notwithstanding the trouble and + expense thus caused, occasionally to cross their much-prized birds with + individuals of another strain, but belonging, of course, to the same + variety. It deserves <!-- Page 126 --><span class="pagenum"><a + name="page126"></a>{126}</span>notice that, when large size is one of the + desired characters, as with pouters,<a name="NtA_278" + href="#Nt_278"><sup>[278]</sup></a> the evil effects of close + interbreeding are much sooner perceived than when small birds, such as + short-faced tumblers, are valued. The extreme delicacy of the high fancy + breeds, such as these tumblers and improved English carriers, is + remarkable; they are liable to many diseases, and often die in the egg or + during the first moult; and their eggs have generally to be hatched under + foster-mothers. Although these highly-prized birds have invariably been + subjected to much close interbreeding, yet their extreme delicacy of + constitution cannot perhaps be thus fully explained. Mr. Yarrell informed + me that Sir J. Sebright continued closely interbreeding some owl-pigeons, + until from their extreme sterility he as nearly as possible lost the + whole family. Mr. Brent<a name="NtA_279" + href="#Nt_279"><sup>[279]</sup></a> tried to raise a breed of trumpeters, + by crossing a common pigeon, and recrossing the daughter, granddaughter, + great-granddaughter, and great-great-granddaughter, with the same male + trumpeter, until he obtained a bird with <sup>15</sup>/<sub>16</sub>ths + of trumpeter's blood; but then the experiment failed, for "breeding so + close stopped reproduction." The experienced Neumeister<a name="NtA_280" + href="#Nt_280"><sup>[280]</sup></a> also asserts that the offspring from + dovecotes and various other breeds are "generally very fertile and hardy + birds:" so again, MM. Boitard and Corbié,<a name="NtA_281" + href="#Nt_281"><sup>[281]</sup></a> after forty-five years' experience, + recommend persons to cross their breeds for amusement; for, if they fail + to make interesting birds, they will succeed under an economical point of + view, "as it is found that mongrels are more fertile than pigeons of pure + race."</p> + + <p>I will refer only to one other animal, namely, the Hive-bee, because a + distinguished entomologist has advanced this as a case of inevitable + close interbreeding. As the hive is tenanted by a single female, it might + have been thought that her male and female offspring would always have + bred together, more especially as bees of different hives are hostile to + each other; a strange worker being almost always attacked when trying to + enter another hive. But Mr. Tegetmeier has shown<a name="NtA_282" + href="#Nt_282"><sup>[282]</sup></a> that this instinct does not apply to + drones, which are permitted to enter any hive; so that there is no <i>à + priori</i> improbability of a queen receiving a foreign drone. The fact + of the union invariably and necessarily taking place on the wing, during + the queen's nuptial flight, seems to be a special provision against + continued interbreeding. However this may be, experience has shown, since + the introduction of the yellow-banded Ligurian race into Germany and + England, that bees freely cross: Mr. Woodbury, who introduced Ligurian + bees into Devonshire, found during a single season that three stocks, at + distances of from one to two miles from his hives, were crossed by his + drones. In one case the Ligurian drones must have flown over the city of + Exeter, and over several intermediate hives. On another occasion several + common black queens were crossed by Ligurian drones at a distance of from + one to three and a half miles.<a name="NtA_283" + href="#Nt_283"><sup>[283]</sup></a></p> + +</blockquote> + +<p><!-- Page 127 --><span class="pagenum"><a name="page127"></a>{127}</span></p> + +<p class="cenhead"><i>Plants.</i></p> + +<blockquote class="b1n"> + + <p>When a single plant of a new species is introduced into any country, + if propagated by seed, many individuals will soon be raised, so that if + the proper insects be present there will be crossing. With + newly-introduced trees or other plants not propagated by seed we are not + here concerned. With old-established plants it is an almost universal + practice occasionally to make exchanges of seed, by which means + individuals which have been exposed to different conditions of + life,—and this, as we have seen, diminishes the evil from close + interbreeding,—will occasionally be introduced into each + district.</p> + + <p>Experiments have not been tried on the effects of fertilising flowers + with their own pollen during <i>several</i> generations. But we shall + presently see that certain plants, either normally or abnormally, are + more or less sterile, even in the first generation, when fertilised by + their own pollen. Although nothing is directly known on the evil effects + of long-continued close interbreeding with plants, the converse + proposition that great good is derived from crossing is well + established.</p> + + <p>With respect to the crossing of individuals belonging to the same + sub-variety, Gärtner, whose accuracy and experience exceeded that of all + other hybridisers, states<a name="NtA_284" + href="#Nt_284"><sup>[284]</sup></a> that he has many times observed good + effects from this step, especially with exotic genera, of which the + fertility is somewhat impaired, such as Passiflora, Lobelia, and Fuchsia. + Herbert also says,<a name="NtA_285" href="#Nt_285"><sup>[285]</sup></a> + "I am inclined to think that I have derived advantage from impregnating + the flower from which I wished to obtain seed with pollen from another + individual of the same variety, or at least from another flower, rather + than with its own." Again, Professor Lecoq asserts that he has + ascertained that crossed offspring are more vigorous and robust than + their parents.<a name="NtA_286" href="#Nt_286"><sup>[286]</sup></a></p> + + <p>General statements of this kind, however, can seldom be fully trusted; + consequently I have begun a series of experiments, which, if they + continue to give the same results as hitherto, will for ever settle the + question of the good effects of crossing two distinct plants of the same + variety, and of the evil effects of self-fertilisation. A clear light + will thus also be thrown on the fact that flowers are invariably + constructed so as to permit, or favour, or necessitate the union of two + individuals. We shall clearly understand why monœcious and + diœcious,—why dimorphic and trimorphic plants exist, and many + other such cases. The plan which I have followed in my experiments is to + grow plants in the same pot, or in pots of the same size, or close + together in the open ground; to carefully exclude insects; and then to + fertilise some of the flowers with pollen from the same flower, and + others on the same plant with pollen from a distinct but adjoining plant. + In many, but not all, of these experiments, the crossed plants yielded + much more seed than the self-fertilised plants; and I have never seen the + <!-- Page 128 --><span class="pagenum"><a + name="page128"></a>{128}</span>reversed case. The self-fertilised and + crossed seeds thus obtained were allowed to germinate in the same glass + vessel on damp sand; and as the seeds successively germinated, they were + planted in pairs on opposite sides of the same pot, with a superficial + partition between them, and were placed so as to be equally exposed to + the light. In other cases the self-fertilised and crossed seeds were + simply sown on opposite sides of the same small pot. I have, in short, + followed different plans, but in every case have taken all the + precautions which I could think of, so that the two lots should be + equally favoured. Now, I have carefully observed the growth of plants + raised from crossed and self-fertilised seed, from their germination to + maturity, in species of the following genera, namely, Brassica, Lathyrus, + Lupinus, Lobelia, Lactuca, Dianthus, Myosotis, Petunia, Linaria, + Calceolaria, Mimulus, and Ipomœa, and the difference in their + powers of growth, and of withstanding in certain cases unfavourable + conditions, was most manifest and strongly marked. It is of importance + that the two lots of seed should be sown or planted on opposite sides of + the same pot, so that the seedlings may struggle against each other; for + if sown separately in ample and good soil, there is often but little + difference in their growth.</p> + + <p>I will briefly describe the two most striking cases as yet observed by + me. Six crossed and six self-fertilised seeds of <i>Ipomœa + purpurea</i>, from plants treated in the manner above described, were + planted as soon as they had germinated, in pairs on opposite sides of two + pots, and rods of equal thickness were given them to twine up. Five of + the crossed plants grew from the first more quickly than the opposed + self-fertilised plants; the sixth, however, was weakly and was for a time + beaten, but at last its sounder constitution prevailed and it shot ahead + of its antagonist. As soon as each crossed plant reached the top of its + seven-foot rod its fellow was measured, and the result was that, when the + crossed plants were seven feet high, the self-fertilised had attained the + average height of only five feet four and a half inches. The crossed + plants flowered a little before, and more profusely than the + self-fertilised plants. On opposite sides of another <i>small</i> pot a + large number of crossed and self-fertilised seeds were sown, so that they + had to struggle for bare existence; a single rod was given to each lot: + here again the crossed plants showed from the first their advantage; they + never quite reached the summit of the seven-foot rod, but relatively to + the self-fertilised plants their average height was as seven feet to five + feet two inches. The experiment was repeated in the two following + generations with plants raised from the self-fertilised and crossed + plants, treated in exactly the same manner, and with nearly the same + result. In the second generation, the crossed plants, which were again + crossed, produced 121 seed-capsules, whilst the self-fertilised plants, + again self-fertilised, produced only 84 capsules.</p> + + <p>Some flowers of the <i>Mimulus luteus</i> were fertilised with their + own pollen, and others were crossed with pollen from distinct plants + growing in the same pot. The seeds after germinating were thickly planted + on opposite sides of a pot. The seedlings were at first equal in height; + but when the young crossed plants were exactly half an inch, the <!-- + Page 129 --><span class="pagenum"><a + name="page129"></a>{129}</span>self-fertilised plants were only a quarter + of an inch high. But this inequality did not continue, for, when the + crossed plants were four and a half inches high, the self-fertilised were + three inches; and they retained the same relative difference till their + growth was complete. The crossed plants looked far more vigorous than the + uncrossed, and flowered before them; they produced also a far greater + number of flowers, which yielded capsules (judging, however, from only a + few) containing more seeds. As in the former case, the experiment was + repeated in the same manner during the next two generations, and with + exactly the same result. Had I not watched these plants of the Mimulus + and Ipomœa during their whole growth, I could not have believed it + possible, that a difference apparently so slight, as that of the pollen + being taken from the same flower, and from a distinct plant growing in + the same small pot, could have made so wonderful a difference in the + growth and vigour of the plants thus produced. This, under a + physiological point of view, is a most remarkable phenomenon.</p> + +<hr class="short" /> + + <p>With respect to the benefit derived from crossing distinct varieties, + plenty of evidence has been published. Sageret<a name="NtA_287" + href="#Nt_287"><sup>[287]</sup></a> repeatedly speaks in strong terms of + the vigour of melons raised by crossing different varieties, and adds + that they are more easily fertilised than common melons, and produce + numerous good seed. Here follows the evidence of an English gardener:<a + name="NtA_288" href="#Nt_288"><sup>[288]</sup></a> "I have this summer + met with better success in my cultivation of melons, in an unprotected + state, from the seeds of hybrids (<i>i.e.</i> mongrels) obtained by cross + impregnation, than with old varieties. The offspring of three different + hybridisations (one more especially, of which the parents were the two + most dissimilar varieties I could select) each yielded more ample and + finer produce than any one of between twenty and thirty established + varieties."</p> + + <p>Andrew Knight<a name="NtA_289" href="#Nt_289"><sup>[289]</sup></a> + believed that his seedlings from crossed varieties of the apple exhibited + increased vigour and luxuriance; and M. Chevreul<a name="NtA_290" + href="#Nt_290"><sup>[290]</sup></a> alludes to the extreme vigour of some + of the crossed fruit-trees raised by Sageret.</p> + + <p>By crossing reciprocally the tallest and shortest peas, Knight<a + name="NtA_291" href="#Nt_291"><sup>[291]</sup></a> says, "I had in this + experiment a striking instance of the stimulative effects of crossing the + breeds; for the smallest variety, whose height rarely exceeded two feet, + was increased to six feet; whilst the height of the large and luxuriant + kind was very little diminished." Mr. Laxton gave me seed-peas produced + from crosses between four distinct kinds; and the plants thus raised were + extraordinarily vigorous, being in each case from one to two or three + feet taller than the parent-forms growing close alongside them.</p> + +<p><!-- Page 130 --><span class="pagenum"><a name="page130"></a>{130}</span></p> + + <p>Wiegmann<a name="NtA_292" href="#Nt_292"><sup>[292]</sup></a> made + many crosses between several varieties of cabbage; and he speaks with + astonishment of the vigour and height of the mongrels, which excited the + amazement of all the gardeners who beheld them. Mr. Chaundy raised a + great number of mongrels by planting together six distinct varieties of + cabbage. These mongrels displayed an infinite diversity of character; + "But the most remarkable circumstance was, that, while all the other + cabbages and borecoles in the nursery were destroyed by a severe winter, + these hybrids were little injured, and supplied the kitchen when there + was no other cabbage to be had."</p> + + <p>Mr. Maund exhibited before the Royal Agricultural Society<a + name="NtA_293" href="#Nt_293"><sup>[293]</sup></a> specimens of crossed + wheat, together with their parent varieties; and the editor states that + they were intermediate in character, "united with that greater vigour of + growth, which it appears, in the vegetable as in the animal world, is the + result of a first cross." Knight also crossed several varieties of + wheat,<a name="NtA_294" href="#Nt_294"><sup>[294]</sup></a> and he says + "that in the years 1795 and 1796, when almost the whole crop of corn in + the island was blighted, the varieties thus obtained, and these only, + escaped in this neighbourhood, though sown in several different soils and + situations."</p> + + <p>Here is a remarkable case: M. Clotzsch<a name="NtA_295" + href="#Nt_295"><sup>[295]</sup></a> crossed <i>Pinus sylvestris</i> and + <i>nigricans</i>, <i>Quercus robur</i> and <i>pedunculata, Alnus + glutinosa</i> and <i>incana</i>, <i>Ulmus campestris</i> and + <i>effusa</i>; and the cross-fertilised seeds, as well as seeds of the + pure parent-trees, were all sown at the same time and in the same place. + The result was, that after an interval of eight years, the hybrids were + one-third taller than the pure trees!</p> + +<hr class="short" /> + + <p>The facts above given refer to undoubted varieties, excepting the + trees crossed by Clotzsch, which are ranked by various botanists as + strongly-marked races, sub-species, or species. That true hybrids raised + from entirely distinct species, though they lose in fertility, often gain + in size and constitutional vigour, is certain. It would be superfluous to + quote any facts; for all experimenters, Kölreuter, Gärtner, Herbert, + Sageret, Lecoq, and Naudin, have been struck with the wonderful vigour, + height, size, tenacity of life, precocity, and hardiness of their hybrid + productions. Gärtner<a name="NtA_296" href="#Nt_296"><sup>[296]</sup></a> + sums up his conviction on this head in the strongest terms. Kölreuter<a + name="NtA_297" href="#Nt_297"><sup>[297]</sup></a> gives numerous precise + measurements of the weight and height of his hybrids in comparison with + measurements of both parent-forms; and speaks with astonishment of their + "<i>statura portentosa</i>," their "<i>ambitus vastissimus ac altitudo + valde conspicua</i>." Some exceptions to the rule in the case of very + sterile hybrids have, however, been noticed by Gärtner and <!-- Page 131 + --><span class="pagenum"><a name="page131"></a>{131}</span>Herbert; but + the most striking exceptions are given by Max Wichura,<a name="NtA_298" + href="#Nt_298"><sup>[298]</sup></a> who found that hybrid willows were + generally tender in constitution, dwarf, and short-lived.</p> + + <p>Kölreuter explains the vast increase in the size of the roots, stems, + &c., of his hybrids, as the result of a sort of compensation due to + their sterility, in the same way as many emasculated animals are larger + than the perfect males. This view seems at first sight extremely + probable, and has been accepted by various authors;<a name="NtA_299" + href="#Nt_299"><sup>[299]</sup></a> but Gärtner<a name="NtA_300" + href="#Nt_300"><sup>[300]</sup></a> has well remarked that there is much + difficulty in fully admitting it; for with many hybrids there is no + parallelism between the degree of their sterility and their increased + size and vigour. The most striking instances of luxuriant growth have + been observed with hybrids which were not sterile in any extreme degree. + In the genus Mirabilis, certain hybrids are unusually fertile, and their + extraordinary luxuriance of growth, together with their enormous roots,<a + name="NtA_301" href="#Nt_301"><sup>[301]</sup></a> have been transmitted + to their progeny. The increased size of the hybrids produced between the + fowl and pheasant, and between the distinct species of pheasants, has + been already noticed. The result in all cases is probably in part due to + the saving of nutriment and vital force through the sexual organs not + acting, or acting imperfectly, but more especially to the general law of + good being derived from a cross. For it deserves especial attention that + mongrel animals and plants, which are so far from being sterile that + their fertility is often actually augmented, have, as previously shown, + their size, hardiness, and constitutional vigour generally increased. It + is not a little remarkable that an accession of vigour and size should + thus arise under the opposite contingencies of increased and diminished + fertility.</p> + + <p>It is a perfectly well ascertained fact<a name="NtA_302" + href="#Nt_302"><sup>[302]</sup></a> that hybrids will invariably breed + more readily with either pure parent, and not rarely with a distinct + species, than with each other. Herbert is inclined to explain even this + fact by the advantage derived from a cross; but Gärtner more justly + accounts for it by the pollen of the hybrid, and probably its ovules, + being in some degree vitiated, whereas the pollen and ovules of both pure + parents and of any third species are sound. Nevertheless there are some + well-ascertained and remarkable facts, which, as we shall immediately + see, show that the act of crossing in itself undoubtedly tends to + increase or re-establish the fertility of hybrids.</p> + +</blockquote> + +<p class="cenhead"><i>On certain Hermaphrodite Plants which, either normally or abnormally, +require to be fertilised by pollen from a distinct individual +or species.</i></p> + + <p>The facts now to be given differ from those hitherto detailed, as the + self-sterility does not here result from long-continued, <!-- Page 132 + --><span class="pagenum"><a name="page132"></a>{132}</span>close + interbreeding. These facts are, however, connected with our present + subject, because a cross with a distinct individual is shown to be either + necessary or advantageous. Dimorphic and trimorphic plants, though they + are hermaphrodites, must be reciprocally crossed, one set of forms by the + other, in order to be fully fertile, and in some cases to be fertile in + any degree. But I should not have noticed these plants, had it not been + for the following cases given by Dr. Hildebrand:<a name="NtA_303" + href="#Nt_303"><sup>[303]</sup></a>—</p> + +<blockquote class="b1n"> + + <p><i>Primula sinensis</i> is a reciprocally dimorphic species: Dr. + Hildebrand fertilised twenty-eight flowers of both forms, each by pollen + of the other form, and obtained the full number of capsules containing on + an average 42.7 seed per capsule; here we have complete and normal + fertility. He then fertilised forty-two flowers of both forms with pollen + of the same form, but taken from a distinct plant, and all produced + capsules containing on an average only 19.6 seed. Lastly, and here we + come to our more immediate point, he fertilised forty-eight flowers of + both forms with pollen of the same form, taken from the same flower, and + now he obtained only thirty-two capsules, and these contained on an + average 18.6 seed, or one less per capsule than in the former case. So + that, with these illegitimate unions, the act of impregnation is less + assured, and the fertility slightly less, when the pollen and ovules + belong to the same flower, than when belonging to two distinct + individuals of the same form. Dr. Hildebrand has recently made analogous + experiments on the long-styled form of <i>Oxalis rosea</i>, with the same + result.<a name="NtA_304" href="#Nt_304"><sup>[304]</sup></a></p> + +</blockquote> + + <p>It has recently been discovered that certain plants, whilst growing in + their native country under natural conditions, cannot be fertilised with + pollen from the same plant. They are sometimes so utterly self-impotent, + that, though they can readily be fertilised by the pollen of a distinct + species or even distinct genus, yet, wonderful as the fact is, they never + produce a single seed by their own pollen. In some cases, moreover, the + plant's own pollen and stigma mutually act on each other in a deleterious + manner. Most of the facts to be given relate to Orchids, but I will + commence with a plant belonging to a widely different family.</p> + +<blockquote class="b1n"> + + <p>Sixty-three flowers of <i>Corydalis cava</i>, borne on distinct + plants, were fertilised by Dr. Hildebrand<a name="NtA_305" + href="#Nt_305"><sup>[305]</sup></a> with pollen from other plants of the + same species; and fifty-eight capsules were obtained, including on an + average <!-- Page 133 --><span class="pagenum"><a + name="page133"></a>{133}</span>4.5 seed in each. He then fertilised + sixteen flowers produced by the same raceme, one with another, but + obtained only three capsules, one of which alone contained any good + seeds, namely, two in number. Lastly, he fertilised twenty-seven flowers, + each with its own pollen; he left also fifty-seven flowers to be + spontaneously fertilised, and this would certainly have ensued if it had + been possible, for the anthers not only touch the stigma, but the + pollen-tubes were seen by Dr. Hildebrand to penetrate it; nevertheless + these eighty-four flowers did not produce a single seed-capsule! This + whole case is highly instructive, as it shows how widely different the + action of the same pollen is, according as it is placed on the stigma of + the same flower, or on that of another flower on the same raceme, or on + that of a distinct plant.</p> + + <p>With exotic Orchids several analogous cases have been observed, + chiefly by Mr. John Scott.<a name="NtA_306" + href="#Nt_306"><sup>[306]</sup></a> <i>Oncidium sphacelatum</i> has + effective pollen, for with it Mr. Scott fertilised two distinct species; + its ovules are likewise capable of impregnation, for they were readily + fertilised by the pollen of <i>O. divaricatum</i>; nevertheless, between + one and two hundred flowers fertilised by their own pollen did not + produce a single capsule, though the stigmas were penetrated by the + pollen-tubes. Mr. Robinson Munro, of the Royal Botanic Gardens of + Edinburgh, also informs me (1864) that a hundred and twenty flowers of + this same species were fertilised by him with their own pollen, and did + not produce a capsule, but eight flowers fertilised by the pollen of + <i>O. divaricatum</i> produced four fine capsules: again, between two and + three hundred flowers of <i>O. divaricatum</i>, fertilised by their own + pollen, did not set a capsule, but twelve flowers fertilised by <i>O. + flexuosum</i> produced eight fine capsules: so that here we have three + utterly self-impotent species, with their male and female organs perfect, + as shown by their mutual fertilisation. In these cases fertilisation was + effected only by the aid of a distinct species. But, as we shall + presently see, distinct plants, raised from seed, of <i>Oncidium + flexuosum</i>, and probably of the other species, would have been + perfectly capable of fertilising each other, for this is the natural + process. Again, Mr. Scott found that the pollen of a plant of <i>O. + microchilum</i> was good, for with it he fertilised two distinct species; + he found its ovules good, for they could be fertilised by the pollen of + one of these species, and by the pollen of a distinct plant of <i>O. + microchilum</i>; but they could not be fertilised by pollen of the same + plant, though the pollen-tubes penetrated the stigma. An analogous case + has been recorded by M. Rivière,<a name="NtA_307" + href="#Nt_307"><sup>[307]</sup></a> with two plants of <i>O. + Cavendishianum</i>, which were both self-sterile, but reciprocally + fertilised each other. All these cases refer to the genus Oncidium, but + Mr. Scott found that <i>Maxillaria atro-rubens</i> was "totally + insusceptible of fertilisation with its own pollen," but fertilised, and + was fertilised by, a widely distinct species, viz. <i>M. + squalens</i>.</p> + + <p>As these orchids had grown under unnatural conditions, in <!-- Page + 134 --><span class="pagenum"><a + name="page134"></a>{134}</span>hot-houses, I concluded without hesitation + that their self-sterility was due to this cause. But Fritz Müller informs + me that at Desterro, in Brazil, he fertilised above one hundred flowers + of the above-mentioned <i>Oncidium flexuosum</i>, which is there endemic, + with its own pollen, and with that taken from distinct plants; all the + former were sterile, whilst those fertilised by pollen from any <i>other + plant</i> of the same species were fertile. During the first three days + there was no difference in the action of the two kinds of pollen: that + placed on the stigma of the same plant separated in the usual manner into + grains, and emitted tubes which penetrated the column, and the stigmatic + chamber shut itself; but the flowers alone which had been fertilised by + pollen taken from a distinct plant produced seed-capsules. On a + subsequent occasion these experiments were repeated on a large scale with + the same result. Fritz Müller found that four other endemic species of + Oncidium were in like manner utterly sterile with their own pollen, but + fertile with that from any other plant: some of them likewise produced + seed-capsules when impregnated with pollen of widely distinct genera, + such as Leptotes, Cyrtopodium, and Rodriguezia! <i>Oncidium crispum</i>, + however, differs from the foregoing species in varying much in its + self-sterility; some plants producing fine pods with their own pollen, + others failing to do so; in two or three instances, Fritz Müller observed + that the pods produced by pollen taken from a distinct flower on the same + plant, were larger than those produced by the flower's own pollen. In + <i>Epidendrum cinnabarinum</i>, an orchid belonging to another division + of the family, fine pods were produced by the plant's own pollen, but + they contained by weight only about half as much seed as the capsules + which had been fertilized by pollen from a distinct plant, and in one + instance from a distinct species; moreover, a very large proportion, and + in some cases nearly all the seed produced by the plant's own pollen, was + embryonless and worthless. Some self-fertilized capsules of a Maxillaria + were in a similar state.</p> + + <p>Another observation made by Fritz Müller is highly remarkable, namely, + that with various orchids the plant's own pollen not only fails to + impregnate the flower, but acts on the stigma, and is acted on, in an + injurious or poisonous manner. This is shown by the surface of the stigma + in contact with the pollen, and by the pollen itself, becoming in from + three to five days dark brown, and then decaying. The discolouration and + decay are not caused by parasitic cryptogams, which were observed by + Fritz Müller in only a single instance. These changes are well shown by + placing on the same stigma, at the same time, the plant's own pollen and + that from a distinct plant of the same species, or of another species, or + even of another and widely remote genus. Thus, on the stigma of + <i>Oncidium flexuosum</i>, the plant's own pollen and that from a + distinct plant were placed side by side, and in five days' time the + latter was perfectly fresh, whilst the plant's own pollen was brown. On + the other hand, when the pollen of a distinct plant of the <i>Oncidium + flexuosum</i>, and of the <i>Epidendrum zebra</i> (<i>nov. spec.?</i>), + were placed together on the same stigma, they behaved in exactly the same + manner, the grains separating, emitting tubes, and penetrating the + stigma, so that the two <!-- Page 135 --><span class="pagenum"><a + name="page135"></a>{135}</span>pollen-masses, after an interval of eleven + days, could not be distinguished except by the difference of their + caudicles, which, of course, undergo no change. Fritz Müller has, + moreover, made a large number of crosses between orchids belonging to + distinct species and genera, and he finds that in all cases when the + flowers are not fertilised their footstalks first begin to wither; and + the withering slowly spreads upwards until the germens fall off, after an + interval of one or two weeks, and in one instance of between six and + seven weeks; but even in this latter case, and in most other cases, the + pollen and stigma remained in appearance fresh. Occasionally, however, + the pollen becomes brownish, generally on the external surface, and not + in contact with the stigma, as is invariably the case when the plant's + own pollen is applied.</p> + + <p>Fritz Müller observed the poisonous action of the plant's own pollen + in the above-mentioned <i>Oncidium flexuosum</i>, <i>O. unicorne, + pubes</i> (<i>?</i>), and in two other unnamed species. Also in two + species of Rodriguezia, in two of Notylia, in one of Burlingtonia, and of + a fourth genus in the same group. In all these cases, except the last, it + was proved that the flowers were, as might have been expected, fertile + with pollen from a distinct plant of the same species. Numerous flowers + of one species of Notylia were fertilized with pollen from the same + raceme; in two days' time they all withered, the germens began to shrink, + the pollen-masses became dark brown, and not one pollen-grain emitted a + tube. So that in this orchid the injurious action of the plant's own + pollen is more rapid than with <i>Oncidium flexuosum</i>. Eight other + flowers on the same raceme were fertilized with pollen from a distinct + plant of the same species: two of these were dissected, and their stigmas + were found to be penetrated by numberless pollen-tubes; and the germens + of the other six flowers became well developed. On a subsequent occasion + many other flowers were fertilized with their own pollen, and all fell + off dead in a few days; whilst some flowers on the same raceme which had + been left simply unfertilised adhered and long remained fresh. We have + seen that in cross-unions between extremely distinct orchids the pollen + long remains undecayed; but Notylia behaved in this respect differently; + for when its pollen was placed on the stigma of <i>Oncidium + flexuosum</i>, both the stigma and pollen quickly became dark brown, in + the same manner as if the plant's own pollen had been applied.</p> + + <p>Fritz Müller suggests that, as in all these cases the plant's own + pollen is not only impotent (thus effectually preventing + self-fertilization), but likewise prevents, as was ascertained in the + case of the Notylia and <i>Oncidium flexuosum</i>, the action of + subsequently applied pollen from a distinct individual, it would be an + advantage to the plant to have its own pollen rendered more and more + deleterious; for the germens would thus quickly be killed, and, dropping + off, there would be no further waste in nourishing a part which + ultimately could be of no avail. Fritz Müller's discovery that a plant's + own pollen and stigma in some cases act on each other as if mutually + poisonous, is certainly most remarkable.</p> + +</blockquote> + + <p>We now come to cases closely analogous with those just <!-- Page 136 + --><span class="pagenum"><a name="page136"></a>{136}</span>given, but + different, inasmuch as individual plants alone of the species are + self-impotent. This self-impotence does not depend on the pollen or + ovules being in a state unfit for fertilisation, for both have been found + effective in union with other plants of the same or of a distinct + species. The fact of these plants having spontaneously acquired so + peculiar a constitution, that they can be fertilised more readily by the + pollen of a distinct species than by their own, is remarkable. These + abnormal cases, as well as the foregoing normal cases, in which certain + orchids, for instance, can be much more easily fertilised by the pollen + of a distinct species than by their own, are exactly the reverse of what + occurs with all ordinary species. For in these latter the two sexual + elements of the same individual plant are capable of freely acting on + each other; but are so constituted that they are more or less impotent + when brought into union with the sexual elements of a distinct species, + and produce more or less sterile hybrids. It would appear that the pollen + or ovules, or both, of the individual plants which are in this abnormal + state, have been affected in some strange manner by the conditions to + which they themselves or their parents have been exposed; but whilst thus + rendered self-sterile, they have retained the capacity common to most + species of partially fertilizing and being partially fertilized by allied + forms. However this may be, the subject, to a certain extent, is related + to our general conclusion that good is derived from the act of + crossing.</p> + +<blockquote class="b1n"> + + <p>Gärtner experimented on two plants of <i>Lobelia fulgens</i>, brought + from separate places, and found<a name="NtA_308" + href="#Nt_308"><sup>[308]</sup></a> that their pollen was good, for he + fertilised with it <i>L. cardinalis</i> and <i>syphilitica</i>; their + ovules were likewise good, for they were fertilised by the pollen of + these same two species; but these two plants of <i>L. fulgens</i> could + not be fertilised by their own pollen, as can generally be effected with + perfect ease with this species. Again, the pollen of a plant of + <i>Verbascum nigrum</i> grown in a pot was found by Gärtner<a + name="NtA_309" href="#Nt_309"><sup>[309]</sup></a> capable of fertilising + <i>V. lychnitis</i> and <i>V. Austriacum</i>; the ovules could be + fertilised by the pollen of <i>V. thapsus</i>; but the flowers could not + be fertilised by their own pollen. Kölreuter, also,<a name="NtA_310" + href="#Nt_310"><sup>[310]</sup></a> gives the case of three <!-- Page 137 + --><span class="pagenum"><a name="page137"></a>{137}</span>garden plants + of <i>Verbascum phœniceum</i>, which bore during two years many + flowers; these he successfully fertilised by the pollen of no less than + four distinct species, but they produced not a seed with their own + apparently good pollen; subsequently these same plants, and others raised + from seed, assumed a strangely fluctuating condition, being temporarily + sterile on the male or female side, or on both sides, and sometimes + fertile on both sides; but two of the plants were perfectly fertile + throughout the summer.</p> + + <p>It appears<a name="NtA_311" href="#Nt_311"><sup>[311]</sup></a> that + certain flowers on certain plants of <i>Lilium candidum</i> can be + fertilised more easily by pollen from a distinct individual than by their + own. So, again, with the varieties of the potato. Tinzmann,<a + name="NtA_312" href="#Nt_312"><sup>[312]</sup></a> who made many trials + with this plant, says that pollen from another variety sometimes "exerts + a powerful influence, and I have found sorts of potatoes which would not + bear seed from impregnation with the pollen of their own flowers, would + bear it when impregnated with other pollen." It does not, however, appear + to have been proved that the pollen which failed to act on the flower's + own stigma was in itself good.</p> + + <p>In the genus Passiflora it has long been known that several species do + not produce fruit, unless fertilised by pollen taken from distinct + species: thus, Mr. Mowbray<a name="NtA_313" + href="#Nt_313"><sup>[313]</sup></a> found that he could not get fruit + from <i>P. alata</i> and <i>racemosa</i> except by reciprocally + fertilising them with each other's pollen. Similar facts have been + observed in Germany and France;<a name="NtA_314" + href="#Nt_314"><sup>[314]</sup></a> and I have received two authentic + accounts of <i>P. quadrangularis</i>, which never produced fruit with its + own pollen, but would do so freely when fertilised in one case with the + pollen of <i>P. cœrulea</i>, and in another case with that of <i>P. + edulis</i>. So again, with respect to <i>P. laurifolia</i>, a cultivator + of much experience has recently remarked<a name="NtA_315" + href="#Nt_315"><sup>[315]</sup></a> that the flowers "must be fertilised + with the pollen of <i>P. cœrulea</i>, or of some other common kind, + as their own pollen will not fertilise them." But the fullest details on + this subject have been given by Mr. Scott:<a name="NtA_316" + href="#Nt_316"><sup>[316]</sup></a> plants of <i>Passiflora racemosa</i>, + <i>cœrulea</i>, and <i>alata</i> flowered profusely during many + years in the Botanic Gardens of Edinburgh, and, though repeatedly + fertilised by Mr. Scott and by others with their own pollen, never + produced any seed; yet this occurred at once with all three species when + they were crossed together in various ways. But in the case of <i>P. + cœrulea</i>, three plants, two of which grew in the Botanic + Gardens, were all rendered fertile, merely by impregnating the one with + pollen of the other. The same result was attained in the same manner with + <i>P. alata</i>, but only with one plant out of three. As so many + self-sterile species have been mentioned, it may be stated that in the + case of <i>P. gracilis</i>, which is an annual, the flowers are nearly as + fertile with their own pollen as with that from a distinct plant; thus + sixteen flowers <!-- Page 138 --><span class="pagenum"><a + name="page138"></a>{138}</span>spontaneously self-fertilised produced + fruit, each containing on an average 21.3 seed, whilst fruit from + fourteen crossed flowers contained 24.1 seed.</p> + + <p>Returning to <i>P. alata</i>, I have received (1866) some interesting + details from Mr. Robinson Munro. Three plants, including one in England, + have already been mentioned which were inveterately self-sterile, and Mr. + Munro informs me of several others which, after repeated trials during + many years, have been found in the same predicament. At some other + places, however, this species fruits readily when fertilised with its own + pollen. At Taymouth Castle there is a plant which was formerly grafted by + Mr. Donaldson on a distinct species, name unknown, and ever since the + operation it has produced fruit in abundance by its own pollen; so that + this small and unnatural change in the state of this plant has restored + its self-fertility! Some of the seedlings from the Taymouth Castle plant + were found to be not only sterile with their own pollen, but with each + other's pollen, and with the pollen of distinct species. Pollen from the + Taymouth plant failed to fertilise certain plants of the same species, + but was successful on one plant in the Edinburgh Botanic Gardens. + Seedlings were raised from this latter union, and some of their flowers + were fertilised by Mr. Munro with their own pollen; but they were found + to be as self-impotent as the mother-plant had always proved, except when + fertilised by the grafted Taymouth plant, and except, as we shall see, + when fertilised by her own seedlings. For Mr. Munro fertilised eighteen + flowers on the self-impotent mother-plant with pollen from these her own + self-impotent seedlings, and obtained, remarkable as the fact is, + eighteen fine capsules full of excellent seed! I have met with no case in + regard to plants which shows so well as this of <i>P. alata</i>, on what + small and mysterious causes complete fertility or complete sterility + depends.</p> + +</blockquote> + + <p>The facts hitherto given relate to the much-lessened or completely + destroyed fertility of pure species when impregnated with their own + pollen, in comparison with their fertility when impregnated by distinct + individuals or distinct species; but closely analogous facts have been + observed with hybrids.</p> + +<blockquote class="b1n"> + + <p>Herbert states<a name="NtA_317" href="#Nt_317"><sup>[317]</sup></a> + that having in flower at the same time nine hybrid Hippeastrums, of + complicated origin, descended from several species, he found that "almost + every flower touched with pollen from another cross produced seed + abundantly, and those which were touched with their own pollen either + failed entirely, or formed slowly a pod of inferior size, with fewer + seeds." In the 'Horticultural Journal' he adds that, "the admission of + the pollen of another cross-bred Hippeastrum (however complicated the + cross) to any <i>one</i> flower of the number, is almost sure to check + the fructification of the others." In a letter written to me in 1839, Dr. + Herbert says that he had already tried these experiments during five + consecutive years, and he subsequently repeated them, with the same + invariable result. <!-- Page 139 --><span class="pagenum"><a + name="page139"></a>{139}</span>He was thus led to make an analogous trial + on a pure species, namely, on the <i>Hippeastrum aulicum</i>, which he + had lately imported from Brazil: this bulb produced four flowers, three + of which were fertilised by their own pollen, and the fourth by the + pollen of a triple cross between <i>H. bulbulosum</i>, <i>reginæ</i>, and + <i>vittatum</i>; the result was, that "the ovaries of the three first + flowers soon ceased to grow, and after a few days perished entirely: + whereas the pod impregnated by the hybrid made vigorous and rapid + progress to maturity, and bore good seed, which vegetated freely." This + is, indeed, as Herbert remarks, "a strange truth," but not so strange as + it then appeared.</p> + + <p>As a confirmation of these statements, I may add that Mr. M. Mayes,<a + name="NtA_318" href="#Nt_318"><sup>[318]</sup></a> after much experience + in crossing the species of Amaryllis (Hippeastrum), says, "neither the + species nor the hybrids will, we are well aware, produce seed so + abundantly from their own pollen as from that of others." So, again, Mr. + Bidwell, in New South Wales,<a name="NtA_319" + href="#Nt_319"><sup>[319]</sup></a> asserts that <i>Amaryllis + belladonna</i> bears many more seeds when fertilised by the pollen of + <i>Brunswigia</i> (<i>Amaryllis</i> of some authors) <i>Josephinæ</i> or + of <i>B. multiflora</i>, than when fertilised by its own pollen. Mr. + Beaton dusted four flowers of a Cyrtanthus with their own pollen, and + four with the pollen of <i>Vallota</i> (<i>Amaryllis</i>) + <i>purpurea</i>; on the seventh day "those which received their own + pollen slackened their growth, and ultimately perished; those which were + crossed with the Vallota held on."<a name="NtA_320" + href="#Nt_320"><sup>[320]</sup></a> These latter cases, however, relate + to uncrossed species, like those before given with respect to Passiflora, + Orchids, &c., and are here referred to only because the plants belong + to the same group of Amaryllidaceæ.</p> + + <p>In the experiments on the hybrid Hippeastrums, if Herbert had found + that the pollen of two or three kinds alone had been more efficient on + certain kinds than their own pollen, it might have been argued that + these, from their mixed parentage, had a closer mutual affinity than the + others; but this explanation is inadmissible, for the trials were made + reciprocally backwards and forwards on nine different hybrids; and a + cross, whichever way taken, always proved highly beneficial. I can add a + striking and analogous case from experiments made by the Rev. A. Rawson, + of Bromley Common, with some complex hybrids of Gladiolus. This skilful + horticulturist possessed a number of French varieties, differing from + each other only in the colour and size of the flowers, all descended from + Gandavensis, a well-known old hybrid, said to be descended from <i>G. + Natalensis</i> by the pollen of <i>G. oppositiflorus</i>.<a + name="NtA_321" href="#Nt_321"><sup>[321]</sup></a> Mr. Rawson, after + repeated trials, found that none of the varieties would set seed with + their own pollen, although <!-- Page 140 --><span class="pagenum"><a + name="page140"></a>{140}</span>taken from distinct plants of the same + variety, which had, of course, been propagated by bulbs, but that they + all seeded freely with pollen from any other variety. To give two + examples: Ophir did not produce a capsule with its own pollen, but when + fertilised with that of Janire, Brenchleyensis, Vulcain, and Linné, it + produced ten fine capsules; but the pollen of Ophir was good, for when + Linné was fertilised by it seven capsules were produced. This later + variety, on the other hand, was utterly barren with its own pollen, which + we have seen was perfectly efficient on Ophir. Altogether, Mr. Rawson, in + the year 1861, fertilised twenty-six flowers borne by four varieties with + pollen taken from other varieties, and every single flower produced a + fine seed-capsule; whereas fifty-two flowers on the same plants, + fertilised at the same time with their own pollen, did not yield a single + seed-capsule. Mr. Rawson fertilised, in some cases, the alternate + flowers, and in other cases all those down one side of the spike, with + pollen of other varieties, and the remaining flowers with their own + pollen; I saw these plants when the capsules were nearly mature, and + their curious arrangement at once brought full conviction to the mind + that an immense advantage had been derived from crossing these + hybrids.</p> + + <p>Lastly, I have heard from Dr. E. Bornet, of Antibes, who has made + numerous experiments in crossing the species of Cistus, but as not yet + published the results, that, when any of these hybrids are fertile, they + may be said to be, in regard to function, diœcious; "for the + flowers are always sterile when the pistil is fertilised by pollen taken + from the same flower or from flowers on the same plant. But they are + often fertile if pollen be employed from a distinct individual of the + same hybrid nature, or from a hybrid made by a reciprocal cross."</p> + +</blockquote> + + <p><i>Conclusion.</i>—The facts just given, which show that certain + plants are self-sterile, although both sexual elements are in a fit state + for reproduction when united with distinct individuals of the same or + other species, appear at first sight opposed to all analogy. The sexual + elements of the same flower have become, as already remarked, + differentiated in relation to each other, almost like those of two + distinct species.</p> + + <p>With respect to the species which, whilst living under their natural + conditions, have their reproductive organs in this peculiar state, we may + conclude that it has been naturally acquired for the sake of effectually + preventing self-fertilisation. The case is closely analous with dimorphic + and trimorphic plants, which can be fully fertilised only by plants + belong to the opposite form, and not, as in the foregoing cases, in + differently by any other plant. Some of these dimorphic plants are + completely sterile with pollen taken from the same plant or from the same + <!-- Page 141 --><span class="pagenum"><a + name="page141"></a>{141}</span>form. It is interesting to observe the + graduated series from plants which, when fertilised by their own pollen, + yield the full number of seed, but with the seedlings a little dwarfed in + stature—to plants which when self-fertilised yield few + seeds—to those with yield none—and, lastly, to those in which + the plant's own pollen and stigma act on each other like poison. This + peculiar state of the reproductive organs, when occurring in certain + individuals alone, is evidently abnormal; and as it chiefly affects + exotic plants, or indigenous plants cultivated in pots, we may attribute + it to some change in the conditions of life, acting on the plants + themselves or on their parents. The self-impotent <i>Passiflora + alata</i>, which recovered its self-fertility after having been grafted + on a distinct stock, shows how small a change is sufficient to act + powerfully on the reproductive system. The possibility of a plant + becoming under culture self-impotent is interesting as throwing light on + the occurrence of this same condition in natural species. A cultivated + plant in this state generally remains so during its whole life; and from + this fact we may infer that the state is probably congenital.</p> + + <p>Kölreuter, however, has described some plants of Verbascum which + varied in this respect even during the same season. As in all the normal + cases, and in many, probably in most, of the abnormal cases, any two + self-impotent plants can reciprocally fertilize each other, we may infer + that a very slight difference in the nature of their sexual elements + suffices to give fertility; but in other instances, as with some + Passifloras and the hybrid Gladioli, a greater degree of differentiation + appears to be necessary, for with these plants fertility is gained only + by the union of distinct species, or of hybrids of distinct parentage. + These facts all point to the same general conclusion, namely, that good + is derived from a cross between individuals, which either innately, or + from exposure to dissimilar conditions, have come to differ in sexual + constitution.</p> + + <p>Exotic animals confined in menageries are sometimes in nearly the same + state as the above-described self-impotent plants; for, as we shall see + in the following chapter, certain monkeys, the larger carnivora, several + finches, geese, and pheasants, cross together, quite as freely as, or + even more freely than, the individuals of the same species breed + together. Cases will, <!-- Page 142 --><span class="pagenum"><a + name="page142"></a>{142}</span>also, be given of sexual incompatibility + between certain male and female domesticated animals, which, + nevertheless, are fertile when matched with any other individual of the + same kind.</p> + + <p>In the early part of this chapter it was shown that the crossing of + distinct forms, whether closely or distantly allied, gives increased size + and constitutional vigour, and, except in the case of crossed species, + increased fertility, to the offspring. The evidence rests on the + universal testimony of breeders (for it should be observed that I am not + here speaking of the evil results of close interbreeding), and is + practically exemplified in the higher value of cross-bred animals for + immediate consumption. The good results of crossing have also been + demonstrated, in the case of some animals and of numerous plants, by + actual weight and measurement. Although animals of pure blood will + obviously be deteriorated by crossing, as far as their characteristic + qualities are concerned, there seems to be no exception to the rule that + advantages of the kind just mentioned are thus gained, even when there + has not been any previous close interbreeding. The rule applies to all + animals, even to cattle and sheep, which can long resist breeding + in-and-in between the nearest blood-relations. It applies to individuals + of the same sub-variety but of distinct families, to varieties or races, + to sub-species, as well as to quite distinct species.</p> + + <p>In this latter case, however, whilst size, vigour, precocity, and + hardiness are, with rare exceptions, gained, fertility, in a greater or + less degree, is lost; but the gain cannot be exclusively attributed to + the principle of compensation; for there is no close parallelism between + the increased size and vigour of the offspring and their sterility. + Moreover it has been clearly proved that mongrels which are perfectly + fertile gain these same advantages as well as sterile hybrids.</p> + + <p>The evil consequences of long-continued close interbreeding are not so + easily recognised as the good effects from crossing, for the + deterioration is gradual. Nevertheless it is the general opinion of those + who have had most experience, especially with animals which propagate + quickly, that evil does inevitably follow sooner or later, but at + different rates with different animals. No doubt a false belief may + widely prevail like a superstition; yet it is difficult to suppose that + so many acute and original <!-- Page 143 --><span class="pagenum"><a + name="page143"></a>{143}</span>observers have all been deceived at the + expense of much cost and trouble. A male animal may sometimes be paired + with his daughter, granddaughter, and so on, even for seven generations, + without any manifest bad result; but the experiment has never been tried + of matching brothers and sisters, which is considered the closest form of + interbreeding, for an equal number of generations. There is good reason + to believe that by keeping the members of the same family in distinct + bodies, especially if exposed to somewhat different conditions of life, + and by occasionally crossing these families, the evil results may be much + diminished, or quite eliminated. These results are loss of constitutional + vigour, size, and fertility; but there is no necessary deterioration in + the general form of the body, or in other good qualities. We have seen + that with pigs first-rate animals have been produced after long-continued + close interbreeding, though they had become extremely infertile when + paired with their near relations. The loss of fertility, when it occurs, + seems never to be absolute, but only relative to animals of the same + blood; so that this sterility is to a certain extent analogous with that + of self-impotent plants which cannot be fertilised by their own pollen, + but are perfectly fertile with pollen of any other plant of the same + species. The fact of infertility of this peculiar nature being one of the + results of long-continued interbreeding, shows that interbreeding does + not act merely by combining and augmenting various morbid tendencies + common to both parents; for animals with such tendencies, if not at the + time actually ill, can generally propagate their kind. Although offspring + descended from the nearest blood-relations are not necessarily + deteriorated in structure, yet some authors<a name="NtA_322" + href="#Nt_322"><sup>[322]</sup></a> believe that they are eminently + liable to malformations; and this is not improbable, as everything which + lessens the vital powers acts in this manner. Instances of this kind have + been recorded in the case of pigs, bloodhounds, and some other + animals.</p> + + <p>Finally, when we consider the various facts now given which plainly + show that good follows from crossing, and less plainly <!-- Page 144 + --><span class="pagenum"><a name="page144"></a>{144}</span>that evil + follows from close interbreeding, and when we bear in mind that + throughout the whole organic world elaborate provision has been made for + the occasional union of distinct individuals, the existence of a great + law of nature is, if not proved, at least rendered in the highest degree + probable; namely, that the crossing of animals and plants which are not + closely related to beach other is highly beneficial or even necessary, + and that interbreeding prolonged during many generations is highly + injurious.</p> + +<hr class="full" /> + +<p><!-- Page 145 --><span class="pagenum"><a name="page145"></a>{145}</span></p> + +<h3>CHAPTER XVIII.</h3> + +<p class="cenhead">ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED +CONDITIONS OF LIFE: STERILITY FROM VARIOUS CAUSES.</p> + +<blockquote class="b1n"> + + <p><span class="scac">ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE + CONDITIONS OF LIFE</span>—<span class="scac">STERILITY FROM CHANGED + CONDITIONS, IN ANIMALS, IN THEIR NATIVE COUNTRY AND IN + MENAGERIES</span>—<span class="scac">MAMMALS, BIRDS, AND + INSECTS</span>—<span class="scac">LOSS OF SECONDARY SEXUAL + CHARACTERS AND OF INSTINCTS</span>—<span class="scac">CAUSES OF + STERILITY</span>—<span class="scac">STERILITY OF DOMESTICATED + ANIMALS FROM CHANGED CONDITIONS</span>—<span class="scac">SEXUAL + INCOMPATIBILITY OF INDIVIDUAL ANIMALS</span>—<span + class="scac">STERILITY OF PLANTS FROM CHANGED CONDITIONS OF + LIFE</span>—<span class="scac">CONTABESCENCE OF THE + ANTHERS</span>—<span class="scac">MONSTROSITIES AS A CAUSE OF + STERILITY</span>—<span class="scac">DOUBLE + FLOWERS</span>—<span class="scac">SEEDLESS FRUIT</span>—<span + class="scac">STERILITY FROM THE EXCESSIVE DEVELOPMENT OF THE ORGANS OF + VEGETATION</span>—<span class="scac">FROM LONG-CONTINUED + PROPAGATION BY BUDS</span>—<span class="scac">INCIPIENT STERILITY + THE PRIMARY CAUSE OF DOUBLE FLOWERS AND SEEDLESS FRUIT.</span></p> + +</blockquote> + + <p><i>On the Good derived from slight Changes in the Conditions of + Life.</i>—In considering whether any facts were known which might + throw light on the conclusion arrived at in the last chapter, namely, + that benefits ensue from crossing, and that it is a law of nature that + all organic beings should occasionally cross, it appeared to me probable + that the good derived from slight changes in the conditions of life, from + being an analogous phenomenon, might serve this purpose. No two + individuals, and still less no two varieties, are absolutely alike in + constitution and structure; and when the germ of one is fertilised by the + male element of another, we may believe that it is acted on in a somewhat + similar manner as an individual when exposed to slightly changed + conditions. Now, every one must have observed the remarkable influence on + convalescents of a change of residence, and no medical man doubts the + truth of this fact. Small farmers who hold but little land are convinced + that their cattle derive great benefit from a change of pasture. In the + case of plants, the evidence is strong that a great advantage is derived + from exchanging seeds, tubers, bulbs, and cuttings from one soil or place + to another as different as possible. <!-- Page 146 --><span + class="pagenum"><a name="page146"></a>{146}</span></p> + +<blockquote class="b1n"> + + <p>The belief that plants are thus benefited, whether or not well + founded, has been firmly maintained from the time of Columella, who wrote + shortly after the Christian era, to the present day; and it now prevails + in England, France, and Germany.<a name="NtA_323" + href="#Nt_323"><sup>[323]</sup></a> A sagacious observer, Bradley, + writing in 1724,<a name="NtA_324" href="#Nt_324"><sup>[324]</sup></a> + says, "When we once become Masters of a good Sort of Seed, we should at + least put it into Two or Three Hands, where the Soils and Situations are + as different as possible; and every Year the Parties should change with + one another; by which Means, I find the Goodness of the Seed will be + maintained for several Years. For Want of this Use many Farmers have + failed in their Crops and been great Losers." He then gives his own + practical experience on this head. A modern writer<a name="NtA_325" + href="#Nt_325"><sup>[325]</sup></a> asserts, "Nothing can be more clearly + established in agriculture than that the continual growth of any one + variety in the same district makes it liable to deterioration either in + quality or quantity." Another writer states that he sowed close together + in the same field two lots of wheat-seed, the product of the same + original stock, one of which had been grown on the same land, and the + other at a distance, and the difference in favour of the crop from the + latter seed was remarkable. A gentleman in Surrey who has long made it + his business to raise wheat to sell for seed, and who has constantly + realised in the market higher prices than others, assures me that he + finds it indispensable continually to change his seed; and that for this + purpose he keeps two farms differing much in soil and elevation.</p> + + <p>With respect to the tubers of the potato, I find that at the present + day the practice of exchanging sets is almost everywhere followed. The + great growers of potatoes in Lancashire formerly used to get tubers from + Scotland, but they found that "a change from the moss-lands, and <i>vice + versâ</i>, was generally sufficient." In former times in France the crop + of potatoes in the Vosges had become reduced in the course of fifty or + sixty years in the proportion from 120-150 to 30-40 bushels; and the + famous Oberlin attributed the surprising good which he effected in large + part to changing the sets.<a name="NtA_326" + href="#Nt_326"><sup>[326]</sup></a></p> + + <p>A well-known practical gardener, Mr. Robson<a name="NtA_327" + href="#Nt_327"><sup>[327]</sup></a> positively states that he has himself + witnessed decided advantage from obtaining bulbs of the onion, tubers of + the potato, and various seeds, all of the same kind, from different soils + and distant parts of England. He further states that with <!-- Page 147 + --><span class="pagenum"><a name="page147"></a>{147}</span>plants + propagated by cuttings, as with the Pelargonium, and especially the + Dahlia, manifest advantage is derived from getting plans of the same + variety, which have been cultivated in another place; or, "where the + extent of the place allows, to take cuttings from one description of soil + to plant on another, so as to afford the change that seems so necessary + to the well-being of the plants." He maintains that after a time an + exchange of this nature is "forced on the grower, whether he be prepared + for it or not." Similar remarks have been made by another excellent + gardener, Mr. Fish, namely, that cuttings of the same variety of + Calceolaria, which he obtained from a neighbour, "showed much greater + vigour than some of his own that were treated in exactly the same + manner," and he attributed this solely to his own plants having become + "to a certain extent worn out or tired of their quarters." Something of + this kind apparently occurs in grafting and budding fruit-trees; for, + according to Mr. Abbey, grafts or buds generally take on a distinct + variety or even species, or on a stock previously grafted, with greater + facility than on stocks raised from seeds of the variety which is to be + grafted; and he believes this cannot be altogether explained by the + stocks in question being better adapted to the soil and climate of the + place. It should, however, be added, that varieties grafted or budded on + very distinct kinds, though they may take more readily and grow at first + more vigorously than when grafted on closely allied stocks, afterwards + often become unhealthy.</p> + + <p>I have studied M. Tessier's careful and elaborate experiments,<a + name="NtA_328" href="#Nt_328"><sup>[328]</sup></a> made to disprove the + common belief that good is derived from a change of seed; and he + certainly shows that the same seed may with care be cultivated on the + same farm (it is not stated whether on exactly the same soil) for ten + consecutive years without loss. Another excellent observer, Colonel Le + Couteur,<a name="NtA_329" href="#Nt_329"><sup>[329]</sup></a> has come to + the same conclusion; but then he expressly adds, if the same seed be + used, "that which is grown on land manured from the mixen one year + becomes seed for land prepared with lime, and that again becomes seed for + land dressed with ashes, then for land dressed with mixed manure, and so + on." But this in effect is a systematic exchange of seed, within the + limits of the same farm.</p> + +</blockquote> + + <p>On the whole the belief, which has long been held by many skilful + cultivators, that good follows from exchanging seed, tubers, &c., + seems to be fairly well founded. Considering the small size of most + seeds, it seems hardly credible that the advantage thus derived can be + due to the seeds obtaining in one soil some chemical element deficient in + the other soil. As plants after once germinating naturally become fixed + to the same spot, it might have been anticipated that they would show the + good effects of a change more plainly than animals, which continually + wander about; and this apparently is the <!-- Page 148 --><span + class="pagenum"><a name="page148"></a>{148}</span>case. Life depending + on, or consisting in, an incessant play of the most complex forces, it + would appear that their action is in some way stimulated by slight + changes in the circumstances to which each organism is exposed. All + forces throughout nature, as Mr. Herbert Spencer<a name="NtA_330" + href="#Nt_330"><sup>[330]</sup></a> remarks, tend towards an equilibrium, + and for the life of each being it is necessary that this tendency should + be checked. If these views and the foregoing facts can be trusted, they + probably throw light, on the one hand, on the good effects of crossing + the breed, for the germ will be thus slightly modified or acted on by new + forces; and on the other hand, on the evil effects of close interbreeding + prolonged during many generations, during which the germ will be acted on + by a male having almost identically the same constitution.</p> + +<p class="cenhead"><i>Sterility from changed Conditions of Life.</i></p> + + <p>I will now attempt to show that animals and plants, when removed from + their natural conditions, are often rendered in some degree infertile or + completely barren; and this occurs even when the conditions have not been + greatly changed. This conclusion is not necessarily opposed to that at + which we have just arrived, namely, that lesser changes of other kinds + are advantageous to organic beings. Our present subject is of some + importance, from having an intimate connexion with the causes of + variability. Indirectly it perhaps bears on the sterility of species when + crossed: for as, on the one hand, slight changes in the conditions of + life are favourable to plants and animals, and the crossing of varieties + adds to the size, vigour, and fertility of their offspring; so, on the + other hand, certain other changes in the conditions of life cause + sterility; and as this likewise ensues from crossing much-modified forms + or species, we have a parallel and double series of facts, which + apparently stand in close relation to each other.</p> + + <p>It is notorious that many animals, though perfectly tamed, <!-- Page + 149 --><span class="pagenum"><a name="page149"></a>{149}</span>refuse to + breed in captivity. Isidore Geoffroy St. Hilaire<a name="NtA_331" + href="#Nt_331"><sup>[331]</sup></a> consequently has drawn a broad + distinction between tamed animals which will not breed under captivity, + and truly domesticated animals which breed freely—generally more + freely, as shown in the sixteenth chapter, than in a state of nature. It + is possible and generally easy to tame most animals; but experience has + shown that it is difficult to get them to breed regularly, or even at + all. I shall discuss this subject in detail; but will give only those + cases which seem most illustrative. My materials are derived from notices + scattered through various works, and especially from a Report, drawn up + for me by the kindness of the officers of the Zoological Society of + London, which has especial value, as it records all the cases, during + nine years from 1838-46, in which the animals were seen to couple but + produced no offspring, as well as the cases in which they never, as far + as known, coupled. This MS. Report I have corrected by the annual Reports + subsequently published. Many facts are given on the breeding of the + animals in that magnificent work, 'Gleanings from the Menageries of + Knowsley Hall,' by Dr. Gray. I made, also, particular inquiries from the + experienced keeper of the birds in the old Surrey Zoological Gardens. I + should premise that a slight change in the treatment of animals sometimes + makes a great difference in their fertility; and it is probable that the + results observed in different menageries would differ. Indeed some + animals in our Zoological Gardens have become more productive since the + year 1846. It is, also, manifest from F. Cuvier's account of the Jardin + des Plantes,<a name="NtA_332" href="#Nt_332"><sup>[332]</sup></a> that + the animals formerly bred much less freely there than with us; for + instance, in the Duck tribe, which is highly prolific, only one species + had at that period produced young.</p> + +<blockquote class="b1n"> + + <p>The most remarkable cases, however, are afforded by animals kept in + their native country, which, though perfectly tamed, quite healthy, and + allowed some freedom, are absolutely incapable of breeding. Rengger,<a + name="NtA_333" href="#Nt_333"><sup>[333]</sup></a> who in Paraguay + particularly attended to this subject, specifies six quadrupeds in this + condition; and he mentions two or three others which most rarely <!-- + Page 150 --><span class="pagenum"><a + name="page150"></a>{150}</span>breed. Mr. Bates, in his admirable work on + the Amazons, strongly insists on similar cases;<a name="NtA_334" + href="#Nt_334"><sup>[334]</sup></a> and he remarks, that the fact of + thoroughly tamed native mammals and birds not breeding when kept by the + Indians, cannot be wholly accounted for by their negligence or + indifference, for the turkey is valued by them, and the fowl has been + adopted by the remotest tribes. In almost every part of the + world—for instance, in the interior of Africa, and in several of + the Polynesian islands—the natives are extremely fond of taming the + indigenous quadrupeds and birds; but they rarely or never succeed in + getting them to breed.</p> + + <p>The most notorious case of an animal not breeding in captivity is that + of the elephant. Elephants are kept in large numbers in their native + Indian home, live to old age, and are vigorous enough for the severest + labour; yet, with one or two exceptions, they have never been known even + to couple, though both males and females have their proper periodical + seasons. If, however, we proceed a little eastward to Ava, we hear from + Mr. Crawfurd<a name="NtA_335" href="#Nt_335"><sup>[335]</sup></a> that + their "breeding in the domestic state, or at least in the half-domestic + state in which the female elephants are generally kept, is of every-day + occurrence;" and Mr. Crawfurd informs me that he believes that the + difference must be attributed solely to the females being allowed to roam + the forests with some degree of freedom. The captive rhinoceros, on the + other hand, seems from Bishop Heber's account<a name="NtA_336" + href="#Nt_336"><sup>[336]</sup></a> to breed in India far more readily + than the elephant. Four wild species of the horse genus have bred in + Europe, though here exposed to a great change in their natural habits of + life; but the species have generally been crossed one with another. Most + of the members of the pig family breed readily in our menageries: even + the Red River hog (<i>Potamochœrus penicillatus</i>), from the + sweltering plains of West Africa, has bred twice in the Zoological + Gardens. Here also the Peccary (<i>Dicotyles torquatus</i>) has bred + several times; but another species, the <i>D. labiatus</i>, though + rendered so tame as to be half-domesticated, breeds so rarely in its + native country of Paraguay, that according to Rengger<a name="NtA_337" + href="#Nt_337"><sup>[337]</sup></a> the fact requires confirmation. Mr. + Bates remarks that the tapir, though often kept tame in Amazonia by the + Indians, never breeds.</p> + + <p>Ruminants generally breed quite freely in England, though brought from + widely different climates, as may be seen in the Annual Reports of the + Zoological Gardens, and in the Gleanings from Lord Derby's menagerie.</p> + + <p>The Carnivora, with the exception of the Plantigrade division, + generally breed (though with capricious exceptions) almost as freely as + ruminants. Many species of Felidæ have bred in various menageries, + although imported from various climates and closely confined. Mr. + Bartlett, the present superintendent of the Zoological Gardens,<a + name="NtA_338" href="#Nt_338"><sup>[338]</sup></a> remarks that the lion + appears to breed more frequently and to bring forth more young at a birth + than any other species of the family. He adds that the tiger has rarely + bred; <!-- Page 151 --><span class="pagenum"><a + name="page151"></a>{151}</span>"but there are several well-authenticated + instances of the female tiger breeding with the lion." Strange as the + fact may appear, many animals under confinement unite with distinct + species and produce hybrids quite as freely as, or even more freely than, + with their own species. On inquiring from Dr. Falconer and others, it + appears that the tiger when confined in India does not breed, though it + has been known to couple. The cheetah (<i>Felis jubata</i>) has never + been known by Mr. Bartlett to breed in England, but it has bred at + Frankfort; nor does it breed in India, where it is kept in large numbers + for hunting; but no pains would be taken to make them breed, as only + those animals which have hunted for themselves in a state of nature are + serviceable and worth training.<a name="NtA_339" + href="#Nt_339"><sup>[339]</sup></a> According to Rengger, two species of + wild cats in Paraguay, though thoroughly tamed, have never bred. Although + so many of the Felidæ breed readily in the Zoological Gardens, yet + conception by no means always follows union: in the nine-year Report, + various species are specified which were observed to couple seventy-three + times, and no doubt this must have passed many times unnoticed; yet from + the seventy-three unions only fifteen births ensued. The Carnivora in the + Zoological Gardens were formerly less freely exposed to the air and cold + than at present, and this change of treatment, as I was assured by the + former superintendent, Mr. Miller, greatly increased their fertility. Mr. + Bartlett, and there cannot be a more capable judge, says, "it is + remarkable that lions breed more freely in travelling collections than in + the Zoological Gardens; probably the constant excitement and irritation + produced by moving from place to place, or change of air, may have + considerable influence in the matter."</p> + + <p>Many members of the Dog family breed readily when confined. The Dhole + is one of the most untameable animals in India, yet a pair kept there by + Dr. Falconer produced young. Foxes, on the other hand, rarely breed, and + I have never heard of such an occurrence with the European fox: the + silver fox of North America (<i>Canis argentatus</i>), however, has bred + several times in the Zoological Gardens. Even the otter has bred there. + Every one knows how readily the semi-domesticated ferret breeds, though + shut up in miserably small cages; but other species of Viverra and + Paradoxurus absolutely refuse to breed in the Zoological Gardens. The + Genetta has bred both here and in the Jardin des Plantes, and produced + hybrids. The <i>Herpestes fasciatus</i> has likewise bred; but I was + formerly assured that the <i>H. griseus</i>, though many were kept in the + Gardens, never bred.</p> + + <p>The Plantigrade Carnivora breed under confinement much less freely, + without our being able to assign any reason, than other members of the + group. In the nine-year Report it is stated that the bears had been seen + in the Zoological Gardens to couple freely, but previously to 1848 had + most rarely conceived. In the Reports published since this date three + species have produced young (hybrids in one case), and, wonderful to + relate, the white Polar bear has produced young. The badger (<i>Meles + taxus</i>) has bred several times in the Gardens; but I have not heard of + this <!-- Page 152 --><span class="pagenum"><a + name="page152"></a>{152}</span>occurring elsewhere in England, and the + event must be very rare, for an instance in Germany has been thought + worth recording.<a name="NtA_340" href="#Nt_340"><sup>[340]</sup></a> In + Paraguay the native Nasua, though kept in pairs during many years and + perfectly tamed, has never been known, according to Rengger, to breed or + show any sexual passion; nor, as I hear from Mr. Bates, does this animal, + or the Cercoleptes, breed in the region of the Amazons. Two other + plantigrade genera, Procyon and Gulo, though often kept tame in Paraguay, + never breed there. In the Zoological Gardens species of Nasua and Procyon + have been seen to couple; but they did not produce young.</p> + + <p>As domesticated rabbits, guinea-pigs, and white mice breed so + abundantly when closely confined under various climates, it might have + been thought that most other members of the Rodent order would have bred + in captivity, but this is not the case. It deserves notice, as showing + how the capacity to breed sometimes goes by affinity, that the one native + rodent of Paraguay, which there breeds <i>freely</i> and has yielded + successive generations, is the <i>Cavia aperea</i>; and this animal is so + closely allied to the guinea-pig, that it has been erroneously thought to + be the parent-form.<a name="NtA_341" href="#Nt_341"><sup>[341]</sup></a> + In the Zoological Gardens, some rodents have coupled, but have never + produced young; some have neither coupled nor bred; but a few have bred, + as the porcupine more than once, the Barbary mouse, lemming, chinchilla, + and the agouti (<i>Dasyprocta aguti</i>), several times. This latter + animal has also produced young in Paraguay, though they were born dead + and ill-formed; but in Amazonia, according to Mr. Bates, it never breeds, + though often kept tame about the houses. Nor does the paca + (<i>Cœlogenys paca</i>) breed there. The common hare when confined + has, I believe, never bred in Europe;<a name="NtA_342" + href="#Nt_342"><sup>[342]</sup></a> though, according to a recent + statement, it has crossed with the rabbit. I have never heard of the + dormouse breeding in confinement. But squirrels offer a more curious + case: with one exception, no species has ever bred in the Zoological + Gardens, yet as many as fourteen individuals of <i>S. palmarum</i> were + kept together during several years. The <i>S. cinerea</i> has been seen + to couple, but it did not produce young; nor has this species, when + rendered extremely tame in its native country, North America, been ever + known to breed.<a name="NtA_343" href="#Nt_343"><sup>[343]</sup></a> At + Lord Derby's menagerie squirrels of many kinds were kept in numbers, but + Mr. Thompson, the superintendent, told me that none had ever bred there, + or elsewhere as far as he knew. I have never heard of the English + squirrel breeding in confinement. But the species which has bred more + than once in the Zoological Gardens is the one which perhaps might have + been least expected, namely, the flying squirrel (<i>Sciuropterus + volucella</i>): it has, also, bred several times <!-- Page 153 --><span + class="pagenum"><a name="page153"></a>{153}</span>near Birmingham; but + the female never produced more than two young at a birth, whereas in its + native American home she bears from three to six young.<a name="NtA_344" + href="#Nt_344"><sup>[344]</sup></a></p> + + <p>Monkeys, in the nine-year Report from the Zoological Gardens, are + stated to unite most freely, but during this period, though many + individuals were kept, there were only seven births. I have heard of one + American monkey alone, the Ouistiti, breeding in Europe.<a name="NtA_345" + href="#Nt_345"><sup>[345]</sup></a> A Macacus, according to Flourens, + bred in Paris; and more than one species of this genus has produced young + in London, especially the <i>Macacus rhesus</i>, which everywhere shows a + special capacity to breed under confinement. Hybrids have been produced + both in Paris and London from this same genus. The Arabian baboon, or + <i>Cynocephalus hamadryas</i>,<a name="NtA_346" + href="#Nt_346"><sup>[346]</sup></a> and a Cercopithecus have bred in the + Zoological Gardens, and the latter species at the Duke of + Northumberland's. Several members of the family of Lemurs have produced + hybrids in the Zoological Gardens. It is much more remarkable that + monkeys very rarely breed when confined in their native country; thus the + Cay (<i>Cebus azaræ</i>) is frequently and completely tamed in Paraguay, + but Rengger<a name="NtA_347" href="#Nt_347"><sup>[347]</sup></a> says + that it breeds so rarely, that he never saw more than two females which + had produced young. A similar observation has been made with respect to + the monkeys which are frequently tamed by the aborigines in Brazil.<a + name="NtA_348" href="#Nt_348"><sup>[348]</sup></a> In the region of the + Amazons, these animals are so often kept in a tame state, that Mr. Bates + in walking through the streets of Parà counted thirteen species; but, as + he asserts, they have never been known to breed in captivity.<a + name="NtA_349" href="#Nt_349"><sup>[349]</sup></a></p> + +</blockquote> + +<p class="cenhead"><i>Birds.</i></p> + +<blockquote class="b1n"> + + <p>Birds offer in some respects better evidence than quadrupeds, from + their breeding more rapidly and being kept in greater numbers. We have + seen that carnivorous animals are more fertile under confinement than + most other mammals. The reverse holds good with carnivorous birds. It is + said<a name="NtA_350" href="#Nt_350"><sup>[350]</sup></a> that as many as + eighteen species have been used in Europe for hawking, and several others + in Persia and India;<a name="NtA_351" href="#Nt_351"><sup>[351]</sup></a> + they have been kept in their native country in the finest condition, and + have been flown during six, eight, or nine years;<a name="NtA_352" + href="#Nt_352"><sup>[352]</sup></a> yet there is no record of their + having ever produced young. As these birds were formerly caught whilst + young, at great expense, being imported from Iceland, Norway, and Sweden, + there can <!-- Page 154 --><span class="pagenum"><a + name="page154"></a>{154}</span>be little doubt that, if possible, they + would have been propagated. In the Jardin des Plantes, no bird of prey + has been known to couple.<a name="NtA_353" + href="#Nt_353"><sup>[353]</sup></a> No hawk, vulture, or owl has ever + produced fertile eggs in the Zoological Gardens, or in the old Surrey + Gardens, with the exception, in the former place on one occasion, of a + condor and a kite (<i>Milvus niger</i>). Yet several species, namely, the + <i>Aquila fusca</i>, <i>Haliætus leucocephalus</i>, <i>Falco + tinnunculus</i>, <i>F. subbuteo</i>, and <i>Buteo vulgaris</i>, have been + seen to couple in the Zoological Gardens. Mr. Morris<a name="NtA_354" + href="#Nt_354"><sup>[354]</sup></a> mentions as a unique fact that a + kestrel (<i>Falco tinnunculus</i>) bred in an aviary. The one kind of owl + which has been known to couple in the Zoological Gardens was the Eagle + Owl (<i>Bubo maximus</i>); and this species shows a special inclination + to breed in captivity; for a pair at Arundel Castle, kept more nearly in + a state of nature "than ever fell to the lot of an animal deprived of its + liberty,"<a name="NtA_355" href="#Nt_355"><sup>[355]</sup></a> actually + reared their young. Mr. Gurney has given another instance of this same + owl breeding in confinement; and he records the case of a second species + of owl, the <i>Strix passerina</i>, breeding in captivity.<a + name="NtA_356" href="#Nt_356"><sup>[356]</sup></a></p> + + <p>Of the smaller graminivorous birds, many kinds have been kept tame in + their native countries, and have lived long; yet, as the highest + authority on cage-birds<a name="NtA_357" + href="#Nt_357"><sup>[357]</sup></a> remarks, their propagation is + "uncommonly difficult." The canary-bird shows that there is no inherent + difficulty in these birds breeding freely in confinement; and Audubon + says<a name="NtA_358" href="#Nt_358"><sup>[358]</sup></a> that the + <i>Fringilla</i> (<i>Spiza</i>) <i>ciris</i> of North America breeds as + perfectly as the canary. The difficulty with the many finches which have + been kept in confinement is all the more remarkable as more than a dozen + species could be named which have yielded hybrids with the canary; but + hardly any of these, with the exception of the siskin (<i>Fringilla + spinus</i>), have reproduced their own kind. Even the bullfinch (<i>Loxia + pyrrhula</i>) has bred as frequently with the canary, though belonging to + a distinct genus, as with its own species.<a name="NtA_359" + href="#Nt_359"><sup>[359]</sup></a> With respect to the skylark + (<i>Alauda arvensis</i>), I have heard of birds living for seven years in + an aviary, which never produced young; and a great London bird-fancier + assured me that he had never known an instance of their breeding; + nevertheless one case has been recorded.<a name="NtA_360" + href="#Nt_360"><sup>[360]</sup></a> In the nine-year Report from the + Zoological Society, twenty-four incessorial species are enumerated which + had not bred, and of these only four were known to have coupled.</p> + + <p>Parrots are singularly long-lived birds; and Humboldt mentions the + curious fact of a parrot in South America, which spoke the language of + <!-- Page 155 --><span class="pagenum"><a + name="page155"></a>{155}</span>an extinct Indian tribe, so that this bird + preserved the sole relic of a lost language. Even in this country there + is reason to believe<a name="NtA_361" href="#Nt_361"><sup>[361]</sup></a> + that parrots have lived to the age of nearly one hundred years; yet, + though many have been kept in Europe, they breed so rarely that the event + has been thought worth recording in the gravest publications.<a + name="NtA_362" href="#Nt_362"><sup>[362]</sup></a> According to + Bechstein<a name="NtA_363" href="#Nt_363"><sup>[363]</sup></a> the + African <i>Psittacus erithacus</i> breeds oftener than any other species: + the <i>P. macoa</i> occasionally lays fertile eggs, but rarely succeeds + in hatching them; this bird, however, has the instinct of incubation + sometimes so strongly developed, that it will hatch the eggs of fowls or + pigeons. In the Zoological Gardens and in the old Surrey Gardens some few + species have coupled, but, with the exception of three species of + parrakeets, none have bred. It is a much more remarkable fact that in + Guiana parrots of two kinds, as I am informed by Sir E. Schomburgk, are + often taken from the nests by the Indians and reared in large numbers; + they are so tame that they fly freely about the houses, and come when + called to be fed, like pigeons; yet he has never heard of a single + instance of their breeding.<a name="NtA_364" + href="#Nt_364"><sup>[364]</sup></a> In Jamaica, a resident naturalist, + Mr. R. Hill,<a name="NtA_365" href="#Nt_365"><sup>[365]</sup></a> says, + "no birds more readily submit to human dependence than the parrot-tribe, + but no instance of a parrot breeding in this tame life has been known + yet." Mr. Hill specifies a number of other native birds kept tame in the + West Indies, which never breed in this state.</p> + + <p>The great pigeon family offers a striking contrast with parrots: in + the nine-year Report thirteen species are recorded as having bred, and, + what is more noticeable, only two were seen to couple without any result. + Since the above date every annual Report gives many cases of various + pigeons breeding. The two magnificent crowned pigeons (<i>Goura + coronata</i> and <i>Victoriæ</i>) produced hybrids; nevertheless, of the + former species more than a dozen birds were kept, as I am informed by Mr. + Crawfurd, in a park at Penang, under a perfectly well-adapted climate, + but never once bred. The <i>Columba migratoria</i> in its native country, + North America, invariably lays two eggs, but in Lord Derby's menagerie + never more than one. The same fact has been observed with the <i>C. + leucocephala</i>.<a name="NtA_366" + href="#Nt_366"><sup>[366]</sup></a></p> + + <p>Gallinaceous birds of many genera likewise show an eminent capacity + for breeding under captivity. This is particularly the case with + pheasants; yet our English species seldom lays more than ten eggs in + confinement; whilst from eighteen to twenty is the usual number in the + wild state.<a name="NtA_367" href="#Nt_367"><sup>[367]</sup></a> With the + Gallinaceæ, as with all other orders, there are marked and <!-- Page 156 + --><span class="pagenum"><a name="page156"></a>{156}</span>inexplicable + exceptions in regard to the fertility of certain species and genera under + confinement. Although many trials have been made with the common + partridge, it has rarely bred, even when reared in large aviaries; and + the hen will never hatch her own eggs.<a name="NtA_368" + href="#Nt_368"><sup>[368]</sup></a> The American tribe of Guans or + Cracidæ are tamed with remarkable ease, but are very shy breeders in this + country;<a name="NtA_369" href="#Nt_369"><sup>[369]</sup></a> but with + care various species were formerly made to breed rather freely in + Holland.<a name="NtA_370" href="#Nt_370"><sup>[370]</sup></a> Birds of + this tribe are often kept in a perfectly tamed condition in their native + country by the Indians, but they never breed.<a name="NtA_371" + href="#Nt_371"><sup>[371]</sup></a> It might have been expected that + grouse from their habits of life would not have bred in captivity, more + especially as they are said soon to languish and die.<a name="NtA_372" + href="#Nt_372"><sup>[372]</sup></a> But many cases are recorded of their + breeding: the capercailzie (<i>Tetrao urogallus</i>) has bred in the + Zoological Gardens; it breeds without much difficulty when confined in + Norway, and in Russia five successive generations have been reared: + <i>Tetrao tetrix</i> has likewise bred in Norway; <i>T. Scoticus</i> in + Ireland; <i>T. umbellus</i> at Lord Derby's; and <i>T. cupido</i> in + North America.</p> + + <p>It is scarcely possible to imagine a greater change in habits than + that which the members of the ostrich family must suffer, when cooped up + in small enclosures under a temperate climate, after freely roaming over + desert and tropical plains or entangled forests. Yet almost all the + kinds, even the mooruk (<i><span class="correction" title="Original reads `Casuarinus', corrected by errata, page viii." + >Casuarius</span> Bennettii</i>) from New Ireland, has frequently + produced young in the various European menageries. The African ostrich, + though perfectly healthy and living long in the South of France, never + lays more than from twelve to fifteen eggs, though in its native country + it lays from twenty-five to thirty.<a name="NtA_373" + href="#Nt_373"><sup>[373]</sup></a> Here we have another instance of + fertility impaired, but not lost, under confinement, as with the flying + squirrel, the hen-pheasant, and two species of American pigeons.</p> + + <p>Most Waders can be tamed, as the Rev. E. S. Dixon informs me, with + remarkable facility; but several of them are short-lived under + confinement, so that their sterility in this state is not surprising. The + cranes breed more readily than other genera: <i>Grus montigresia</i> has + bred several times in Paris and in the Zoological Gardens, as has <i>G. + <span class="correction" title="Original reads `cineria', corrected by errata, page viii." + >cinerea</span></i> at the latter place, and <i>G. antigone</i> at + Calcutta. Of other members of this great order, <i>Tetrapteryx + paradisea</i> has bred at Knowsley, a Porphyrio in Sicily, and the + <i>Gallinula chloropus</i> in the Zoological Gardens. On the other hand, + several <!-- Page 157 --><span class="pagenum"><a + name="page157"></a>{157}</span>birds belonging to this order will not + breed in their native country, Jamaica; and the Psophia, though often + kept by the Indians of Guiana about their houses, "is seldom or never + known to breed."<a name="NtA_374" href="#Nt_374"><sup>[374]</sup></a></p> + + <p>No birds breed with such complete facility under confinement as the + members of the great Duck family; yet, considering their aquatic and + wandering habits, and the nature of their food, this could not have been + anticipated. Even some time ago above two dozen species had bred in the + Zoological Gardens; and M. Selys-Longchamps has recorded the production + of hybrids from forty-four different members of the family; and to these + Professor Newton has added a few more cases.<a name="NtA_375" + href="#Nt_375"><sup>[375]</sup></a> "There is not," says Mr. Dixon,<a + name="NtA_376" href="#Nt_376"><sup>[376]</sup></a> "in the wide world, a + goose which is not in the strict sense of the word domesticable;" that + is, capable of breeding under confinement; but this statement is probably + too bold. The capacity to breed sometimes varies in individuals of the + same species; thus Audubon<a name="NtA_377" + href="#Nt_377"><sup>[377]</sup></a> kept for more than eight years some + wild geese (<i>Anser Canadensis</i>), but they would not mate; whilst + other individuals of the same species produced young during the second + year. I know of but one instance in the whole family of a species which + absolutely refuses to breed in captivity, namely, the <i>Dendrocygna + viduata</i>, although, according to Sir R. Schomburgk,<a name="NtA_378" + href="#Nt_378"><sup>[378]</sup></a> it is easily tamed, and is frequently + kept by the Indians of Guiana. Lastly, with respect to Gulls, though many + have been kept in the Zoological Gardens and in the old Surrey Gardens, + no instance was known before the year 1848 of their coupling or breeding; + but since that period the herring gull (<i>Larus argentatus</i>) has bred + many times in the Zoological Gardens and at Knowsley.</p> + + <p>There is reason to believe that insects are affected by confinement + like the higher animals. It is well known that the Sphingidæ rarely breed + when thus treated. An entomologist<a name="NtA_379" + href="#Nt_379"><sup>[379]</sup></a> in Paris kept twenty-five specimens + of <i>Saturnia pyri</i>, but did not succeed in getting a single fertile + egg. A number of females of <i>Orthosia munda</i> and of <i>Mamestra + suasa</i> reared in confinement were unattractive to the males.<a + name="NtA_380" href="#Nt_380"><sup>[380]</sup></a> Mr. Newport kept + nearly a hundred individuals of two species of Vanessa, but not one + paired; this, however, might have been due to their habit of coupling on + the wing.<a name="NtA_381" href="#Nt_381"><sup>[381]</sup></a> Mr. + Atkinson could never succeed in India in making the Tarroo silk-moth + breed in confinement.<a name="NtA_382" + href="#Nt_382"><sup>[382]</sup></a> It appears that a number of moths, + especially the Sphingidæ, when hatched in the autumn out of their proper + season, <!-- Page 158 --><span class="pagenum"><a + name="page158"></a>{158}</span>are completely barren; but this latter + case is still involved in some obscurity.<a name="NtA_383" + href="#Nt_383"><sup>[383]</sup></a></p> + +</blockquote> + + <p>Independently of the fact of many animals under confinement not + coupling, or, if they couple, not producing young, there is evidence of + another kind, that their sexual functions are thus disturbed. For many + cases have been recorded of the loss by male birds when confined of their + characteristic plumage. Thus the common linnet (<i>Linota cannabina</i>) + when caged does not acquire the fine crimson colour on its breast, and + one of the buntings (<i>Emberiza passerina</i>) loses the black on its + head. A Pyrrhula and an Oriolus have been observed to assume the quiet + plumage of the hen-bird; and the <i>Falco albidus</i> returned to the + dress of an earlier age.<a name="NtA_384" + href="#Nt_384"><sup>[384]</sup></a> Mr. Thomson, the superintendent of + the Knowsley menagerie, informed me that he had often observed analogous + facts. The horns of a male deer (<i>Cervus Canadensis</i>) during the + voyage from America were badly developed; but subsequently in Paris + perfect horns were produced.</p> + + <p>When conception takes place under confinement, the young are often + born dead, or die soon, or are ill-formed. This frequently occurs in the + Zoological Gardens, and, according to Rengger, with native animals + confined in Paraguay. The mother's milk often fails. We may also + attribute to the disturbance of the sexual functions the frequent + occurrence of that monstrous instinct which leads the mother to devour + her own offspring,—a mysterious case of perversion, as it at first + appears.</p> + + <p>Sufficient evidence has now been advanced to prove that animals when + first confined are eminently liable to suffer in their reproductive + systems. We feel at first naturally inclined to attribute the result to + loss of health, or at least to loss of vigour; but this view can hardly + be admitted when we reflect how healthy, long-lived, and vigorous many + animals are under <!-- Page 159 --><span class="pagenum"><a + name="page159"></a>{159}</span>captivity, such as parrots, and hawks when + used for hawking, chetahs when used for hunting, and elephants. The + reproductive organs themselves are not diseased; and the diseases, from + which animals in menageries usually perish, are not those which in any + way affect their fertility. No domestic animal is more subject too + disease than the sheep, yet it is remarkably prolific. The failure of + animals to breed under confinement has been sometimes attributed + exclusively to a failure in their sexual instincts: this may occasionally + come into play, but there is no obvious reason why this instinct should + be especially liable to be affected with perfectly tamed animals, except + indeed indirectly through the reproductive system itself being disturbed. + Moreover, numerous cases have been given of various animals which couple + freely under confinement, but never conceive; or, if they conceive and + produce young, these are fewer in number than is natural to the species. + In the vegetable kingdom instinct of course can play no part; and we + shall presently see that plants when removed from their natural + conditions are affected in nearly the same manner as animals. Change of + climate cannot be the cause of the loss of fertility, for, whilst many + animals imported into Europe from extremely different climates breed + freely, many others when confined in their native land are completely + sterile. Change of food cannot be the chief cause; for ostriches, ducks, + and many other animals, which must have undergone a great change in this + respect, breed freely. Carnivorous birds when confined are extremely + sterile; whilst most carnivorous mammals, except plantigrades, are + moderately fertile. Nor can the amount of food be the cause; for a + sufficient supply will certainly be given to valuable animals; and there + is no reason to suppose that much more food would be given to them, than + to our choice domestic productions which retain their full fertility. + Lastly, we may infer from the case of the elephant, chetah, various + hawks, and of many animals which are allowed to lead an almost free life + in their native land, that want of exercise is not the sole cause.</p> + + <p>It would appear that any change in the habits of life, whatever these + habits may be, if great enough, tends to affect in an inexplicable manner + the powers of reproduction. The result <!-- Page 160 --><span + class="pagenum"><a name="page160"></a>{160}</span>depends more on the + constitution of the species than on the nature of the change; for certain + whole groups are affected more than others; but exceptions always occur, + for some species in the most fertile groups refuse to breed, and some in + the most sterile groups breed freely. Those animals which usually breed + freely under confinement, rarely breed, as I was assured, in the + Zoological Gardens, within a year or two after their first importation. + When an animal which is generally sterile under confinement happens to + breed, the young apparently do not inherit this power; for had this been + the case, various quadrupeds and birds, which are valuable for + exhibition, would have become common. Dr. Broca even affirms<a + name="NtA_385" href="#Nt_385"><sup>[385]</sup></a> that many animals in + the Jardin des Plantes, after having produced young for three or four + successive generations, become sterile; but this may be the result of too + close interbreeding. It is a remarkable circumstance that many mammals + and birds have produced hybrids under confinement quite as readily as, or + even more readily than, they have procreated their own kind. Of this fact + many instances have been given;<a name="NtA_386" + href="#Nt_386"><sup>[386]</sup></a> and we are thus reminded of those + plants which when cultivated refuse to be fertilised by their own pollen, + but can easily be fertilised by that of a distinct species. Finally, we + must conclude, limited as the conclusion is, that changed conditions of + life have an especial power of acting injuriously on the reproductive + system. The whole case is quite peculiar, for these organs, though not + diseased, are thus rendered incapable of performing their proper + functions, or perform them imperfectly.</p> + +<blockquote class="b1n"> + + <p><i>Sterility of Domesticated Animals from changed + conditions.</i>—With respect to domesticated animals, as their + domestication mainly depends on the accident of their breeding freely + under captivity, we ought not to expect that their reproductive system + would be affected by any moderate degree of change. Those orders of + quadrupeds and birds, of which the wild species breed most readily in our + menageries, have afforded us the greatest number of domesticated + productions. Savages in most parts of the world are fond of taming + animals;<a name="NtA_387" href="#Nt_387"><sup>[387]</sup></a> and if any + of these regularly produced <!-- Page 161 --><span class="pagenum"><a + name="page161"></a>{161}</span>young, and were at the same time useful, + they would be at once domesticated. If, when their masters migrated into + other countries, they were in addition found capable of withstanding + various climates, they would be still more valuable; and it appears that + the animals which breed readily in captivity can generally withstand + different climates. Some few domesticated animals, such as the reindeer + and camel, offer an exception to this rule. Many of our domesticated + animals can bear with undiminished fertility the most unnatural + conditions; for instance, rabbits, guinea-pigs, and ferrets breed in + miserably confined hutches. Few European dogs of any kind withstand + without degeneration the climate of India; but as long as they survive, + they retain, as I hear from Mr. Falconer, their fertility; so it is, + according to Dr. Daniell, with English dogs taken to Sierra Leone. The + fowl, a native of the hot jungles of India, becomes more fertile than its + parent-stock in every quarter of the world, until we advance as far north + as Greenland and Northern Siberia, where this bird will not breed. Both + fowls and pigeons, which I received during the autumn direct from Sierra + Leone, were at once ready to couple.<a name="NtA_388" + href="#Nt_388"><sup>[388]</sup></a> I have, also, seen pigeons breeding + as freely as the common kinds within a year after their importation from + the Upper Nile. The guinea-fowl, an aboriginal of the hot and dry deserts + of Africa, whilst living under our damp and cool climate, produces a + large supply of eggs.</p> + + <p>Nevertheless, our domesticated animals under new conditions + occasionally show signs of lessened fertility. Roulin asserts that in the + hot valleys of the equatorial Cordillera sheep are not fully fecund;<a + name="NtA_389" href="#Nt_389"><sup>[389]</sup></a> and according to Lord + Somerville,<a name="NtA_390" href="#Nt_390"><sup>[390]</sup></a> the + merino-sheep which he imported from Spain were not at first perfectly + fertile. It is said<a name="NtA_391" href="#Nt_391"><sup>[391]</sup></a> + that mares brought up on dry food in the stable, and turned out to grass, + do not at first breed. The peahen, as we have seen, is said not to lay so + many eggs in England as in India. It was long before the canary-bird was + fully fertile, and even now first-rate breeding birds are not common.<a + name="NtA_392" href="#Nt_392"><sup>[392]</sup></a> In the hot and dry + province of Delhi, the eggs of the turkey, as I hear from Dr. Falconer, + though placed under a hen, are extremely liable to fail. According to + Roulin, geese taken within a recent period to the lofty plateau of + Bogota, at first laid seldom, and then only a few eggs; of these scarcely + a fourth were hatched, and half the young birds died: in the second + generation they were more fertile; and when Roulin wrote they were + becoming as <!-- Page 162 --><span class="pagenum"><a + name="page162"></a>{162}</span>fertile as our geese in Europe. In the + Philippine Archipelago the goose, it is asserted, will not breed or even + lay eggs.<a name="NtA_393" href="#Nt_393"><sup>[393]</sup></a> A more + curious case is that of the fowl, which, according to Roulin, when first + introduced would not breed at Cusco in Bolivia, but subsequently became + quite fertile; and the English Game fowl, lately introduced, had not as + yet arrived a its full fertility, for to raise two or three chickens from + a nest of eggs was thought fortunate. In Europe close confinement has a + marked effect on the fertility of the fowl: it has been found in France + that with fowls allowed considerable freedom only twenty per cent. of the + eggs failed; when allowed less freedom forty per cent. failed; and in + close confinement sixty out of the hundred were not hatched.<a + name="NtA_394" href="#Nt_394"><sup>[394]</sup></a> So we see that + unnatural and changed conditions of life produce some effect on the + fertility of our most thoroughly domesticated animals, in the same + manner, though in a far less degree, as with captive wild animals.</p> + + <p>It is by no means rare to find certain males and females which will + not breed together, though both are known to be perfectly fertile with + other males and females. We have no reason to suppose that this is caused + by these animals having been subjected to any change in their habits of + life; therefore such cases are hardly related to our present subject. The + cause apparently lies in an innate sexual incompatibility of the pair + which are matched. Several instances have been communicated to me by Mr. + W. C. Spooner (well known for his essay on Cross-breeding), by Mr. Eyton + of Eyton, by Mr. Wicksted and othe breeders, and especially by Mr. Waring + of Chelsfield, in relation to horses, cattle, pigs, foxhounds, other + dogs, and pigeons.<a name="NtA_395" href="#Nt_395"><sup>[395]</sup></a> + In these cases, females, which either previously or subsequently were + proved to be fertile, failed to breed with certain males, with whom it + was particularly desired to match them. A change in the constitution of + the female may sometimes have occurred before she was put to the second + male; but in other cases this explanation is hardly tenable, for a + female, known not to be barren, has been unsuccessfully paired seven or + eight times with the same male likewise known to be perfectly fertile. + With cart-mares, which sometimes will not breed with stallions of pure + blood, but subsequently have bred with cart-stallions, Mr. Spooner is + inclined to attribute the failure to the lesser sexual power of the + race-horse. But I have heard from the greatest breeder of race-horses at + the present day, through Mr. Waring, that "it frequently occurs with a + mare to be put several times during one or two seasons to a particular + stallion of acknowledged power, and yet prove barren; the mare afterwards + breeding at once with some other horse." These facts are worth recording, + as they show, like so many previous facts, on what slight constitutional + differences the fertility of an animal often depends.</p> + +</blockquote> + +<p><!-- Page 163 --><span class="pagenum"><a name="page163"></a>{163}</span></p> + +<p class="cenhead"><i>Sterility of Plants from changed Conditions of Life, and from +other causes.</i></p> + + <p>In the vegetable kingdom cases of sterility frequently occur, + analogous with those previously given in the animal kingdom. But the + subject is obscured by several circumstances, presently to be discussed, + namely, the contabescence of the anthers, as Gärtner has named a certain + affection—monstrosities—doubleness of the + flower—much-enlarged fruit—and long-continued or excessive + propagation by buds.</p> + +<blockquote class="b1n"> + + <p>It is notorious that many plants in our gardens and hot-houses, though + preserved in the most perfect health, rarely or never produce seed. I do + not allude to plants which run to leaves, from being kept too damp, or + too warm, or too much manured; for these do not produce the reproductive + individual or flower, and the case may be wholly different. Nor do I + allude to fruit not ripening from want of heat, or rotting from too much + moisture. But many exotic plants, with their ovules and pollen appearing + perfectly sound, will not set any seed. The sterility in many cases, as I + know from my own observation, is simply due to the absence of the proper + insects for carrying the pollen to the stigma. But after excluding the + several cases just specified, there are many plants in which the + reproductive system has been seriously affected by the altered conditions + of life to which they have been subjected.</p> + + <p>It would be tedious to enter on many details. Linnæus long ago + observed<a name="NtA_396" href="#Nt_396"><sup>[396]</sup></a> that Alpine + plants, although naturally laded with seed, produce either few or none + when cultivated in gardens. But exceptions often occur: the <i>Draba + sylvestris</i>, one of our most thoroughly Alpine plants, multiplies + itself by seed in Mr. H. C. Watson's garden, near London; and Kerner, who + has particularly attended to the cultivation of Alpine plants, found that + various kinds, when cultivated, spontaneously sowed themselves.<a + name="NtA_397" href="#Nt_397"><sup>[397]</sup></a> Many plants which + naturally grow in peat-earth are entirely sterile in our gardens. I have + noticed the same fact with several liliaceous plants, which nevertheless + grew vigorously.</p> + + <p>Too much manure renders some kinds utterly sterile, as I have myself + observed. The tendency to sterility from this cause runs in families; + thus, according to Gärtner,<a name="NtA_398" + href="#Nt_398"><sup>[398]</sup></a> it is hardly possible to give too + much manure to most Gramineæ, Cruciferæ, and Leguminosæ, whilst succulent + and bulbous-rooted plants are easily affected. Extreme poverty of soil is + less <!-- Page 164 --><span class="pagenum"><a + name="page164"></a>{164}</span>apt to induce sterility; but dwarfed + plants of <i>Trifolium minus</i> and <i>repens</i>, growing on a lawn + often mown and never manured, did not produce any seed. The temperature + of the soil, and the season at which plants are watered, often have a + marked effect on their fertility, as was observed by Kölreuter in the + case of Mirabilis.<a name="NtA_399" href="#Nt_399"><sup>[399]</sup></a> + Mr. Scott in the Botanic Gardens of Edinburgh observed that <i>Oncidium + divaricatum</i> would not set seed when grown in a basket in which it + throve, but was capable of fertilisation in a pot where it was a little + damper. <i>Pelargonium fulgidum</i>, for many years after its + introduction, seeded freely; it then became sterile; now it is fertile<a + name="NtA_400" href="#Nt_400"><sup>[400]</sup></a> if kept in a dry stove + during the winter. Other varieties of pelargonium are sterile and others + fertile without our being able to assign any cause. Very slight changes + in the position of a plant, whether planted on a bank or at its base, + sometimes make all the difference in its producing seed. Temperature + apparently has a much more powerful influence on the fertility of plants + than on that of animals. Nevertheless it is wonderful what changes some + few plants will withstand with undiminished fertility: thus the + <i>Zephyranthes candida</i>, a native of the moderately warm banks of the + Plata, sows itself in the hot dry country near Lima, and in Yorkshire + resists the severest frosts, and I have seen seeds gathered from pods + which had been covered with snow during three weeks.<a name="NtA_401" + href="#Nt_401"><sup>[401]</sup></a> <i>Berberis Wallichii</i>, from the + hot Khasia range in India, is uninjured by our sharpest frosts, and + ripens its fruit under our cool summers. Nevertheless I presume we must + attribute to change of climate the sterility of many foreign plants; thus + the Persian and Chinese lilacs (<i>Syringa Persica</i> and + <i>Chinensis</i>), though perfectly hardly, never here produce a seed; + the common lilac (<i>S. vulgaris</i>) seeds with us moderately well, but + in parts of Germany the capsules never contain seed.<a name="NtA_402" + href="#Nt_402"><sup>[402]</sup></a></p> + + <p>Some of the cases, given in the last chapter, of self-impotent plants, + which are fertile both on the male and female side when united with + distinct individuals or species, might have been here introduced; for as + this peculiar form of sterility generally occurs with exotic plants or + with endemic plants cultivated in pots, and as it disappeared in the + <i>Passiflora alata</i> when grafted, we may conclude that in these cases + it is the result of the treatment to which the plants or their parents + have been exposed.</p> + + <p>The liability of plants to be affected in their fertility by slightly + changed conditions is the more remarkable, as the pollen when once in + process of formation is not easily injured; a plant may be transplanted, + or a branch with flower-buds be cut off and placed in water, and the + pollen will be matured. Pollen, also, when once mature, may be kept for + weeks or even months.<a name="NtA_403" + href="#Nt_403"><sup>[403]</sup></a> The female organs are more sensitive, + for Gärtner<a name="NtA_404" href="#Nt_404"><sup>[404]</sup></a> found + that dicotyledonous plants, when carefully removed so that they did not + in the least flag, could seldom be fertilised; this occurred even with + potted <!-- Page 165 --><span class="pagenum"><a + name="page165"></a>{165}</span>plants if the roots had grown out of the + hole at the bottom. In some few cases, however, as with Digitalis, + transplantation did not prevent fertilisation; and according to the + testimony of Mawz, <i>Brassica rapa</i>, when pulled up by its roots and + placed in water, ripened its seed. Flower-stems of several + monocotyledonous plants when cut off and placed in water likewise produce + seed. But in these cases I presume that the flowers had been already + fertilised, for Herbert<a name="NtA_405" + href="#Nt_405"><sup>[405]</sup></a> found with the Crocus that the plants + might be removed or mutilated after the act of fertilisation, and would + still perfect their seeds; but that, if transplanted before being + fertilised, the application of pollen was powerless.</p> + + <p>Plants which have been long cultivated can generally endure with + undiminished fertility various and great changes; but not in most cases + so great a change of climate as domesticated animals. It is remarkable + that many plants under these circumstances are so much affected that the + proportions and the nature of their chemical ingredients are modified, + yet their fertility is unimpaired. Thus, as Dr. Falconer informs me, + there is a great difference in the character of the fibre in hemp, in the + quantity of oil in the seed of the Linum, in the proportion of narcotin + to morphine in the poppy, in gluten to starch in wheat, when these plants + are cultivated on the plains and on the mountains of India; nevertheless, + they all remain fully fertile.</p> + + <p><i>Contabescence.</i>—Gärtner has designated by this term a + peculiar condition of the anthers in certain plants, in which they are + shrivelled, or become brown and tough, and contain no good pollen. When + in this state they exactly resemble the anthers of the most sterile + hybrids. Gärtner,<a name="NtA_406" href="#Nt_406"><sup>[406]</sup></a> in + his discussion on this subject, has shown that plants of many orders are + occasionally thus affected; but the Caryophyllaceæ and Liliaceæ suffer + most, and to these orders, I think, the Ericaceæ may be added. + Contabescence varies in degree, but on the same plant all the flowers are + generally affected to nearly the same extent. The anthers are affected at + a very early period in the flower-bud, and remain in the same state (with + one recorded exception) during the life of the plant. The affection + cannot be cured by any change of treatment, and is propagated by layers, + cuttings, &c., and perhaps even by seed. In contabescent plants the + female organs are seldom affected, or merely become precocious in their + development. The cause of this affection is doubtful, and is different in + different cases. Until I read Gärtner's discussion I attributed it, as + apparently did Herbert, to the unnatural treatment of the plants; but its + permanence under changed conditions, and the female organs not being + affected, seem incompatible with this view. The fact of several endemic + plants becoming contabescent in our gardens seems, at first sight, + equally incompatible with this view; but Kölreuter believes that this is + the result of their transplantation. The contabescent plants of Dianthus + and Verbascum, found wild by Wiegmann, grew on a dry and sterile bank. + The fact that exotic <!-- Page 166 --><span class="pagenum"><a + name="page166"></a>{166}</span>plants are eminently liable to this + affection also seems to show that it is in some manner caused by their + unnatural treatment. In some instances, as with Silene, Gärtner's view + seems the most probable, namely, that it is caused by an inherent + tendency in the species to become diœcious. I can add another + cause, namely, the illegitimate unions of reciprocally dimorphic or + trimorphic plants, for I have observed seedlings of three species of + Primula and of <i>Lythrum salicaria</i>, which had been raised from + plants illegitimately fertilised by their own-form pollen, with some or + all their anthers in a contabescent state. There is perhaps an additional + cause, namely, self-fertilisation; for many plants of Dianthus and + Lobelia, which had been raised from self-fertilised seeds, had their + anthers in this state; but these instances are not conclusive, as both + genera are liable from other causes to this affection.</p> + + <p>Cases of an opposite nature likewise occur, namely, plants with the + female organs struck with sterility, whilst the male organs remain + perfect. <i>Dianthus Japonicus</i>, a Passiflora, and Nicotiana, have + been described by Gärtner<a name="NtA_407" + href="#Nt_407"><sup>[407]</sup></a> as being in this unusual + condition.</p> + + <p><i>Monstrosities as a cause of Sterility.</i>—Great deviations + of structure, even when the reproductive organs themselves are not + seriously affected, sometimes cause plants to become sterile. But in + other cases plants may become monstrous to an extreme degree and yet + retain their full fertility. Gallesio, who certainly had great + experience,<a name="NtA_408" href="#Nt_408"><sup>[408]</sup></a> often + attributes sterility to this cause; but it may be suspected that in some + of his cases sterility was the cause, and not the result, of the + monstrous growths. The curious St. Valery apple, although it bears fruit, + rarely produces seed. The wonderfully anomalous flowers of <i>Begonia + frigida</i>, formerly described, though they appear fit for + fructification, are sterile.<a name="NtA_409" + href="#Nt_409"><sup>[409]</sup></a> Species of Primulæ, in which the + calyx is brightly coloured, are said<a name="NtA_410" + href="#Nt_410"><sup>[410]</sup></a> to be often sterile, though I have + known them to be fertile. On the other hand, Verlot gives several cases + of proliferous flowers which can be propagated by seed. This was the case + with a poppy, which had become monopetalous by the union of its petals.<a + name="NtA_411" href="#Nt_411"><sup>[411]</sup></a> Another extraordinary + poppy, with the stamens replaced by numerous small supplementary + capsules, likewise reproduces itself by seed. This has also occurred with + a plant of <i>Saxifraga geum</i>, in which a series of adventitious + carpels, bearing ovules on their margins, had been developed between the + stamens and the normal carpels.<a name="NtA_412" + href="#Nt_412"><sup>[412]</sup></a> Lastly, with respect to peloric + flowers, which depart wonderfully from the natural structure,—those + of <i>Linaria vulgaris</i> seem generally to be more or less sterile, + whilst those before described of <i>Antirrhinum majus</i>, when + artificially fertilised with their own pollen, are perfectly <!-- Page + 167 --><span class="pagenum"><a name="page167"></a>{167}</span>fertile, + though sterile when left to themselves, for bees are unable to crawl into + the narrow tubular flower. The peloric flowers of <i>Corydalis + solida</i>, according to Godron,<a name="NtA_413" + href="#Nt_413"><sup>[413]</sup></a> are barren; whilst those of Gloxinia + are well known to yield plenty of seed. In our greenhouse Pelargoniums, + the central flower of the truss is often peloric, and Mr. Masters informs + me that he tried in vain during several years to get seed from these + flowers. I likewise made many vain attempts, but sometimes succeeded in + fertilising them with pollen from a normal flower of another variety; and + conversely I several times fertilised ordinary flowers with peloric + pollen. Only once I succeeded in raising a plant from a peloric flower + fertilised by pollen from a peloric flower borne by another variety; but + the plant, it may be added, presented nothing particular in its + structure. Hence we may conclude that no general rule can be laid down; + but any great deviation from the normal structure, even when the + reproductive organs themselves are not seriously affected, certainly + often leads to sexual impotence.</p> + + <p><i>Double Flowers.</i>—When the stamens are converted into + petals, the plant becomes on the male side sterile; when both stamens and + pistils are thus changed, the plant becomes completely barren. + Symmetrical flowers having numerous stamens and petals are the most + liable to become double, as perhaps follows from all multiple organs + being the most subject to variability. But flowers furnished with only a + few stamens, and others which are asymmetrical in structure, sometimes + become double, as we see with the double gorse or Ulex, Petunia, and + Antirrhinum. The Compositæ bear what are called double flowers by the + abnormal development of the corolla of their central florets. Doubleness + is sometimes connected with prolification,<a name="NtA_414" + href="#Nt_414"><sup>[414]</sup></a> or the continued growth of the axis + of the flower. Doubleness is strongly inherited. No one has produced, as + Lindley remarks,<a name="NtA_415" href="#Nt_415"><sup>[415]</sup></a> + double flowers by promoting the perfect health of the plant. On the + contrary, unnatural conditions of life favour their production. There is + some reason to believe that seeds kept during many years, and seeds + believed to be imperfectly fertilised, yield double flowers more freely + than fresh and perfectly fertilised seed.<a name="NtA_416" + href="#Nt_416"><sup>[416]</sup></a> Long-continued cultivation in rich + soil seems to be the commonest exciting cause. A double narcissus and a + double <i>Anthemis nobilis</i>, transplanted into very poor soil, have + been observed to become single;<a name="NtA_417" + href="#Nt_417"><sup>[417]</sup></a> and I have seen a completely double + white primrose rendered permanently single by being divided and + transplanted whilst in full flower. It has been observed by Professor + Morren that doubleness of the flowers and variegation of the leaves are + antagonistic states; but so many exceptions to the rule have lately been + recorded,<a name="NtA_418" href="#Nt_418"><sup>[418]</sup></a> that, + though general, it cannot be looked at as invariable. <!-- Page 168 + --><span class="pagenum"><a name="page168"></a>{168}</span>Variegation + seems generally to result from a feeble or atrophied condition of the + plant, and a large proportion of the seedlings raised from parents both + of which are variegated usually perish at an early age; hence we may + perhaps infer that doubleness, which is the antagonistic state, commonly + arises from a plethoric condition. On the other hand, extremely poor soil + sometimes, though rarely, appears to cause doubleness: I formerly + described<a name="NtA_419" href="#Nt_419"><sup>[419]</sup></a> some + completely double, bud-like, flowers produced in large numbers by stunted + wild plants of <i>Gentiana amarella</i> growing on a poor chalky bank. I + have also noticed a distinct tendency to doubleness in the flowers of a + Ranunculus, Horse-chesnut, and Bladder-nut (<i>Ranunculus repens</i>, + <i><span class="correction" title="Original reads `Œsculus', corrected by errata, page viii." + >Æsculus</span> pavia</i>, and <i>Staphylea</i>), growing under very + unfavourable conditions. Professor Lehman<a name="NtA_420" + href="#Nt_420"><sup>[420]</sup></a> found several wild plants growing + near a hot spring with double flowers. With respect to the cause of + doubleness, which arises, as we see, under widely different + circumstances, I shall presently attempt to show that the most probable + view is that unnatural conditions first give a tendency to sterility, and + that then, on the principle of compensation, as the reproductive organs + do not perform their proper functions, they either become developed into + petals, or additional petals are formed. This view has lately been + supported by Mr. Laxton,<a name="NtA_421" + href="#Nt_421"><sup>[421]</sup></a> who advances the case of some common + peas, which, after long-continued heavy rain, flowered a second time, and + produced double flowers.</p> + + <p><i>Seedless Fruit.</i>—Many of our most valuable fruits, + although consisting in a homological sense of widely different organs, + are either quite sterile, or produce extremely few seeds. This is + notoriously the case with our best pears, grapes, and figs, with the + pine-apple, banana, bread-fruit, pomegranate, azarole, date-palms, and + some members of the orange-tribe. Poorer varieties of these same fruits + either habitually or occasionally yield seed.<a name="NtA_422" + href="#Nt_422"><sup>[422]</sup></a> Most horticulturists look at the + great size and anomalous development of the fruit as the cause, and + sterility as the result; but the opposite view, as we shall presently + see, is more probable.</p> + + <p><i>Sterility from the excessive development of the Organs of Growth or + Vegetation.</i>—Plants which from any cause grow too luxuriantly, + and produce leaves, stems, runners, suckers, tubers, bulbs, &c., in + excess, sometimes do not flower, or if they flower do not yield seed. To + make European vegetables under the hot climate of India yield seed, it is + necessary to check their growth; and, when one-third grown, they are + taken up, and their stems and <!-- Page 169 --><span class="pagenum"><a + name="page169"></a>{169}</span>tap-roots are cut or mutilated.<a + name="NtA_423" href="#Nt_423"><sup>[423]</sup></a> So it is with hybrids; + for instance, Prof. Lecoq<a name="NtA_424" + href="#Nt_424"><sup>[424]</sup></a> had three plants of Mirabilis, which, + though they grew luxuriantly and flowered, were quite sterile; but after + beating one with a stick until a few branches alone were left, these at + once yielded good seed. The sugar-cane, which grows vigorously and + produces a large supply of succulent stems, never, according to various + observers, bears seed in the West Indies, Malaga, India, Cochin China, or + the Malay Archipelago.<a name="NtA_425" + href="#Nt_425"><sup>[425]</sup></a> Plants which produce a large number + of tubers are apt to be sterile, as occurs, to a certain extent, with the + common potato; and Mr. Fortune informs me that the sweet potato + (<i>Convolvulus batatas</i>) in China never, as far as he has seen, + yields seed. Dr. Royle remarks<a name="NtA_426" + href="#Nt_426"><sup>[426]</sup></a> that in India the <i>Agave + vivipara</i>, when grown in rich soil, invariably produces bulbs, but no + seeds; whilst a poor soil and dry climate leads to an opposite result. In + China, according to Mr. Fortune, an extraordinary number of little bulbs + are developed in the axils of the leaves of the yam, and this plant does + not bear seed. Whether in these cases, as in those of double flowers and + seedless fruit, sexual sterility from changed conditions of life is the + primary cause which leads to the excessive development of the organs of + vegetation, is doubtful; though some evidence might be advanced in favour + of this view. It is perhaps a more probable view that plants which + propagate themselves largely by one method, namely by buds, have not + sufficient vital power or organised matter for the other method of sexual + generation.</p> + + <p>Several distinguished botanists and good practical judges believe that + long-continued propagation by cuttings, runners, tubers, bulbs, &c., + independently of any excessive development of these parts, is the cause + of many plants failing to produce flowers and of others failing to + produce fertile flowers,—it is as if they had lost the habit of + sexual generation.<a name="NtA_427" href="#Nt_427"><sup>[427]</sup></a> + That many plants when thus propagated are sterile there can be no doubt, + but whether the long continuance of this form of propagation is the + actual cause of their sterility, I will not venture, from the want of + sufficient evidence, to express an opinion.</p> + + <p>That plants may be propagated for long periods by buds, without the + aid of sexual generation, we may safely infer from this being the case + with many plants which must have long survived in a state of nature. As I + have had occasion before to allude to this subject, I will here give such + cases as I have collected. Many alpine plants ascend mountains beyond the + height at which they can produce seed.<a name="NtA_428" + href="#Nt_428"><sup>[428]</sup></a> Certain species of <!-- Page 170 + --><span class="pagenum"><a name="page170"></a>{170}</span>Poa and + Festuca, when growing on mountain-pastures, propagate themselves, as I + hear from Mr. Bentham, almost exclusively by bulblets. Kalm gives a more + curious instance<a name="NtA_429" href="#Nt_429"><sup>[429]</sup></a> of + several American trees, which grow so plentifully in marshes or in thick + woods, that they are certainly well adapted for these stations, yet + scarcely ever produce seeds; but when accidentally growing on the outside + of the marsh or wood, are loaded with seed. The common ivy is found in + Northern Sweden and Russia, but flowers and fruits only in the southern + provinces. The <i>Acorus calamus</i> extends over a large portion of the + globe, but so rarely perfects its fruit that this has been seen but by + few botanists.<a name="NtA_430" href="#Nt_430"><sup>[430]</sup></a> The + <i>Hypericum calycinum</i>, which propagates itself so freely in our + shrubberies by rhizomas and is naturalised in Ireland, blossoms + profusely, but sets no seed; nor did it set any when fertilised in my + garden by pollen from plants growing at a distance. The <i>Lysimachia + nummularia</i>, which is furnished with long runners, so seldom produces + seed-capsules, that Prof. Decaisne,<a name="NtA_431" + href="#Nt_431"><sup>[431]</sup></a> who has especially attended to this + plant, has never seen it in fruit. The <i>Carex rigida</i> often fails to + perfect its seed in Scotland, Lapland, Greenland, Germany, and New + Hampshire in the United States.<a name="NtA_432" + href="#Nt_432"><sup>[432]</sup></a> The periwinkle (<i>Vinca minor</i>), + which spreads largely by runners, is said scarcely ever to produce fruit + in England;<a name="NtA_433" href="#Nt_433"><sup>[433]</sup></a> but this + plant requires insect-aid for its fertilisation, and the proper insects + may be absent or rare. The <i>Jussiæa grandiflora</i> has become + naturalised in Southern France, and has spread by its rhizomas so + extensively as to impede the navigation of the waters, but never produces + fertile seed.<a name="NtA_434" href="#Nt_434"><sup>[434]</sup></a> The + horse-radish (<i>Cochlearia armoracia</i>) spreads pertinaciously and is + naturalised in various parts of Europe; though it bears flowers, these + rarely produce capsules: Professor Caspary also informs me that he has + watched this plant since 1851, but has never seen its fruit; nor is this + surprising, as he finds scarcely a grain of good pollen. The common + little <i>Ranunculus ficaria</i> rarely, and some say never, bears seed + in England, France, or Switzerland; but in 1863 I observed seeds on + several plants growing near my house. According to M. Chatin, there are + two forms of this Ranunculus; and it is the bulbiferous form which does + not yield seed from producing no pollen.<a name="NtA_435" + href="#Nt_435"><sup>[435]</sup></a> Other cases <!-- Page 171 --><span + class="pagenum"><a name="page171"></a>{171}</span>analogous with the + foregoing could be given; for instance, some kinds of mosses and lichens + have never been seen to fructify in France.</p> + + <p>Some of these endemic and naturalised plants are probably rendered + sterile from excessive multiplication by buds, and their consequent + incapacity to produce and nourish seed. But the sterility of others more + probably depends on the peculiar conditions under which they live, as in + the case of the ivy in the northern parts of Europe, and of the trees in + the swamps of the United States; yet these plants must be in some + respects eminently well adapted for the stations which they occupy, for + they hold their places against a host of competitors.</p> + +</blockquote> + + <p>Finally, when we reflect on the sterility which accompanies the + doubling of flowers,—the excessive development of fruit,—and + a great increase in the organs of vegetation, we must bear in mind that + the whole effect has seldom been caused at once. An incipient tendency is + observed, and continued selection completes the work, as is known to be + the case with our double flowers and best fruits. The view which seems + the most probable, and which connects together all the foregoing facts + and brings them within our present subject, is, that changed and + unnatural conditions of life first give a tendency to sterility; and in + consequence of this, the organs of reproduction being no longer able + fully to perform their proper functions, a supply of organised matter, + not required for the development of the seed, flows either into these + same organs and renders them foliaceous, or into the fruit, stems, + tubers, &c., increasing their size and succulency. But I am far from + wishing to deny that there exists, independently of any incipient + sterility, an antagonism between the two forms of reproduction, namely, + by seed and by buds, when either is carried to an extreme degree. That + incipient sterility plays an important part in the doubling of flowers, + and in the other cases just specified, I infer chiefly from the following + facts. When fertility is lost from a wholly different cause, namely, from + hybridism, there is a strong tendency, as Gärtner<a name="NtA_436" + href="#Nt_436"><sup>[436]</sup></a> affirms, for flowers to become + double, and this tendency is inherited. Moreover it is notorious that + with hybrids the male organs become sterile before the female organs, and + with double flowers the stamens first become <!-- Page 172 --><span + class="pagenum"><a name="page172"></a>{172}</span>foliaceous. This latter + fact is well shown by the male flowers of diœcious plants, which, + according to Gallesio,<a name="NtA_437" + href="#Nt_437"><sup>[437]</sup></a> first become double. Again, Gärtner<a + name="NtA_438" href="#Nt_438"><sup>[438]</sup></a> often insists that the + flowers of even utterly sterile hybrids, which do not produce any seed, + generally yield perfect capsules or fruit,—a fact which has + likewise been repeatedly observed by Naudin with the Cucurbitaceæ; so + that the production of fruit by plants rendered sterile through any other + and distinct cause is intelligible. Kölreuter has also expressed his + unbounded astonishment at the size and development of the tubers in + certain hybrids; and all experimentalists<a name="NtA_439" + href="#Nt_439"><sup>[439]</sup></a> have remarked on the strong tendency + in hybrids to increase by roots, runners, and suckers. Seeing that hybrid + plants, which from their nature are more or less sterile, thus tend to + produce double flowers; that they have the parts including the seed, that + is the fruit, perfectly developed, even when containing no seed; that + they sometimes yield gigantic roots; that they almost invariably tend to + increase largely by suckers and other such means;—seeing this, and + knowing, from the many facts given in the earlier parts of this chapter, + that almost all organic beings when exposed to unnatural conditions tend + to become more or less sterile, it seems much the most probable view that + with cultivated plants sterility is the exciting cause, and double + flowers, rich seedless fruit, and in some cases largely-developed organs + of vegetation, &c., are the indirect results—these results + having been in most cases largely increased through continued selection + by man.</p> + +<hr class="full" /> + +<p><!-- Page 173 --><span class="pagenum"><a name="page173"></a>{173}</span></p> + +<h3>CHAPTER XIX.</h3> + +<p class="cenhead">SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS +ON HYBRIDISM.</p> + +<blockquote class="b1n"> + + <p><span class="scac">ON THE EFFECTS OF CROSSING</span>—<span + class="scac">THE INFLUENCE OF DOMESTICATION ON + FERTILITY</span>—<span class="scac">CLOSE + INTERBREEDING</span>—<span class="scac">GOOD AND EVIL RESULTS FROM + CHANGED CONDITIONS OF LIFE</span>—<span class="scac">VARIETIES WHEN + CROSSED NOT INVARIABLY FERTILE</span>—<span class="scac">ON THE + DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND + VARIETIES</span>—<span class="scac">CONCLUSIONS WITH RESPECT TO + HYBRIDISM</span>—<span class="scac">LIGHT THROWN ON HYBRIDISM BY + THE ILLEGITIMATE PROGENY OF DIMORPHIC AND TRIMORPHIC + PLANTS</span>—<span class="scac">STERILITY OF CROSSED SPECIES DUE + TO DIFFERENCES CONFINED TO THE REPRODUCTIVE SYSTEM</span>—<span + class="scac">NOT ACCUMULATED THROUGH NATURAL SELECTION</span>—<span + class="scac">REASONS WHY DOMESTIC VARIETIES ARE NOT MUTUALLY + STERILE</span>—<span class="scac">TOO MUCH STRESS HAS BEEN LAID ON + THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND CROSSED + VARIETIES</span>—<span class="scac">CONCLUSION.</span></p> + +</blockquote> + + <p>It was shown in the fifteenth chapter that when individuals of the + same variety, or even of a distinct variety, are allowed freely to + intercross, uniformity of character is ultimately acquired. Some few + characters, however, are incapable of fusion, but these are unimportant, + as they are almost always of a semi-monstrous nature, and have suddenly + appeared. Hence, to preserve our domesticated breeds true, or to improve + them by methodical selection, it is obviously necessary that they should + be kept separate. Nevertheless, through unconscious selection, a whole + body of individuals may be slowly modified, as we shall see in a future + chapter, without separating them into distinct lots. Domestic races have + often been intentionally modified by one or two crosses, made with some + allied race, and occasionally even by repeated crosses with very distinct + races; but in almost all such cases, long-continued and careful selection + has been absolutely necessary, owing to the excessive variability of the + crossed offspring, due to the principle of reversion. In a few instances, + however, mongrels have retained a uniform character from their first + production.</p> + + <p>When two varieties are allowed to cross freely, and one is <!-- Page + 174 --><span class="pagenum"><a name="page174"></a>{174}</span>much more + numerous than the other, the former will ultimately absorb the latter. + Should both varieties exist in nearly equal numbers, it is probable that + a considerable period would elapse before the acquirement of a uniform + character; and the character ultimately acquired would largely depend on + prepotency of transmission, and on the conditions of life; for the nature + of these conditions would generally favour one variety more than another, + so that a kind of natural selection would come into play. Unless the + crossed offspring were slaughtered by man without the least + discrimination, some degree of unmethodical selection would likewise come + into action. From these several considerations we may infer, that when + two or more closely allied species first came into the possession of the + same tribe, their crossing will not have influenced, in so great a degree + as has often been supposed, the character of the offspring in future + times; although in some cases it probably has had a considerable + effect.</p> + + <p>Domestication, as a general rule, increases the prolificness of + animals and plants. It eliminates the tendency to sterility which is + common to species when first taken from a state of nature and crossed. On + this latter head we have no direct evidence; but as our races of dogs, + cattle, pigs, &c., are almost certainly descended from aboriginally + distinct stocks, and as these races are now fully fertile together, or at + least incomparably more fertile than most species when crossed, we may + with much confidence accept this conclusion.</p> + + <p>Abundant evidence has been given that crossing adds to the size, + vigour, and fertility of the offspring. This holds good when there has + been no previous close interbreeding. It applies to the individuals of + the same variety but belonging to different families, to distinct + varieties, sub-species, and partially even to species. In the latter + case, though size is often gained, fertility is lost; but the increased + size, vigour, and hardiness of many hybrids cannot be accounted for + solely on the principle of compensation from the inaction of the + reproductive system. Certain plants, both of pure and hybrid origin, + though perfectly healthy, have become self-impotent, apparently from the + unnatural conditions to which they have been exposed; and such plants, as + well as others in their normal state, can be stimulated to <!-- Page 175 + --><span class="pagenum"><a name="page175"></a>{175}</span>fertility only + by crossing them with other individuals of the same species or even of a + distinct species.</p> + + <p>On the other hand, long-continued close interbreeding between the + nearest relations diminishes the constitutional vigour, size, and + fertility of the offspring; and occasionally leads to malformations, but + not necessarily to general deterioration of form or structure. This + failure of fertility shows that the evil results of interbreeding are + independent of the augmentation of morbid tendencies common to both + parents, though this augmentation no doubt is often highly injurious. Our + belief that evil follows from close interbreeding rests to a large extent + on the experience of practical breeders, especially of those who have + reared many animals of the kinds which can be propagated quickly; but it + likewise rests on several carefully recorded experiments. With some + animals close interbreeding may be carried on for a long period with + impunity by the selection of the most vigorous and healthy individuals; + but sooner or later evil follows. The evil, however, comes on so slowly + and gradually that it easily escapes observation, but can be recognised + by the almost instantaneous manner in which size, constitutional vigour, + and fertility are regained when animals that have long been interbred are + crossed with a distinct family.</p> + + <p>These two great classes of facts, namely, the good derived from + crossing, and the evil from close interbreeding, with the consideration + of the innumerable adaptations throughout nature for compelling, or + favouring, or at least permitting, the occasional union of distinct + individuals, taken together, lead to the conclusion that it is a law of + nature that organic beings shall not fertilise themselves for perpetuity. + This law was first plainly hinted at in 1799, with respect to plants, by + Andrew Knight,<a name="NtA_440" href="#Nt_440"><sup>[440]</sup></a> and, + not long afterwards, that sagacious observer Kölreuter, after showing how + well the Malvaceæ are adapted for <!-- Page 176 --><span + class="pagenum"><a name="page176"></a>{176}</span>crossing, asks, "an id + aliquid in recessu habeat, quod hujuscemodi flores nunquam proprio suo + pulvere, sed semper eo aliarum suæ speciei impregnentur, merito quæritur? + Certe natura nil facit frustra." Although we may demur to Kölreuter's + saying that nature does nothing in vain, seeing how many organic beings + retain rudimentary and useless organs, yet undoubtedly the argument from + the innumerable contrivances, which favour the crossing of distinct + individuals of the same species, is of the greatest weight. The most + important result of this law is that it leads to uniformity of character + in the individuals of the same species. In the case of certain + hermaphrodites, which probably intercross only at long intervals of time, + and with unisexual animals inhabiting somewhat separated localities, + which can only occasionally come into contact and pair, the greater + vigour and fertility of the crossed offspring will ultimately prevail in + giving uniformity of character to the individuals of the same species. + But when we go beyond the limits of the same species, free intercrossing + is barred by the law of sterility.</p> + + <p>In searching for facts which might throw light on the cause of the + good effects from crossing, and of the evil effects from close + interbreeding, we have seen that, on the one hand, it is a widely + prevalent and ancient belief that animals and plants profit from slight + changes in their condition of life; and it would appear that the germ, in + a somewhat analogous manner, is more effectually stimulated by the male + element, when taken from a distinct individual, and therefore slightly + modified in nature, than when taken from a male having the same identical + constitution. On the other hand, numerous facts have been given, showing + that when animals are first subjected to captivity, even in their native + land, and although allowed much liberty, their reproductive functions are + often greatly impaired or quite annulled. Some groups of animals are more + affected than others, but with apparently capricious exceptions in every + group. Some animals never or rarely couple: some couple freely, but never + or rarely conceive. The secondary male characters, the maternal functions + and instincts, are occasionally affected. With plants, when first + subjected to cultivation, analogous facts have been observed. We probably + owe our double flowers, rich seedless <!-- Page 177 --><span + class="pagenum"><a name="page177"></a>{177}</span>fruits, and in some + cases greatly developed tubers, &c., to incipient sterility of the + above nature combined with a copious supply of nutriment. Animals which + have long been domesticated, and plants which have long been cultivated, + can generally withstand with unimpaired fertility great changes in their + conditions of life; though both are sometimes slightly affected. With + animals the somewhat rare capacity of breeding freely under confinement + has mainly determined, together with their utility, the kinds which have + been domesticated.</p> + + <p>We can in no case precisely say what is the cause of the diminished + fertility of an animal when first captured, or of a plant when first + cultivated; we can only infer that it is caused by a change of some kind + in the natural conditions of life. The remarkable susceptibility of the + reproductive system to such changes,—a susceptibility not common to + any other organ,—apparently has an important bearing on + Variability, as we shall see in a future chapter.</p> + + <p>It is impossible not to be struck with the double parallelism between + the two classes of facts just alluded to. On the one hand, slight changes + in the conditions of life, and crosses between slightly modified forms or + varieties, are beneficial as far as prolificness and constitutional + vigour are concerned. On the other hand, changes in the conditions + greater in degree, or of a different nature, and crosses between forms + which have been slowly and greatly modified by natural means,—in + other words, between species,—are highly injurious, as far as the + reproductive system is concerned, and in some few instances as far as + constitutional vigour is concerned. Can this parallelism be accidental? + Does it not rather indicate some real bond of connection? As a fire goes + out unless it be stirred up, so the vital forces are always tending, + according to Mr. Herbert Spencer, to a state of equilibrium, unless + disturbed and renovated through the action of other forces.</p> + + <p>In some few cases varieties tend to keep distinct, by breeding at + different periods, by great differences in size, or by sexual + preference,—in this latter respect more especially resembling + species in a state of nature. But the actual crossing of varieties, far + from diminishing, generally adds to the fertility of both the first union + and the mongrel offspring. Whether all <!-- Page 178 --><span + class="pagenum"><a name="page178"></a>{178}</span>the most widely + distinct domestic varieties are invariably quite fertile when crossed, we + do not positively know; much time and trouble would be requisite for the + necessary experiments, and many difficulties occur, such as the descent + of the various races from aboriginally distinct species, and the doubts + whether certain forms ought to be ranked as species or varieties. + Nevertheless, the wide experience of practical breeders proves that the + great majority of varieties, even if some should hereafter prove not to + be indefinitely fertile <i>inter se</i>, are far more fertile when + crossed, than the vast majority of closely allied natural species. A few + remarkable cases have, however, been given on the authority of excellent + observers, showing that with plants certain forms, which undoubtedly must + be ranked as varieties, yield fewer seeds when crossed than is natural to + the parent-species. Other varieties have had their reproductive powers so + far modified that they are either more or less fertile than are their + parents, when crossed with a distinct species.</p> + + <p>Nevertheless, the fact remains indisputable that domesticated + varieties of animals and of plants, which differ greatly from each other + in structure, but which are certainly descended from the same aboriginal + species, such as the races of the fowl, pigeon, many vegetables, and a + host of other productions, are extremely fertile when crossed; and this + seems to make a broad and impassable barrier between domestic varieties + and natural species. But, as I will now attempt to show, the distinction + is not so great and overwhelmingly important as it at first appears.</p> + +<p class="cenhead"><i>On the Difference in Fertility between Varieties and Species when +crossed.</i></p> + + <p>This work is not the proper place for fully treating the subject of + hybridism, and I have already given in my 'Origin of Species' a + moderately full abstract. I will here merely enumerate the general + conclusions which may be relied on, and which bear on our present + point.</p> + + <p><i>Firstly</i>, the laws governing the production of hybrids are + identical, or nearly identical, in the animal and vegetable kingdoms.</p> + + <p><i>Secondly</i>, the sterility of distinct species when first united, + <!-- Page 179 --><span class="pagenum"><a + name="page179"></a>{179}</span>and that of their hybrid offspring, + graduates, by an almost infinite number of steps, from zero, when the + ovule is never impregnated and a seed-capsule is never formed, up to + complete fertility. We can only escape the conclusion that some species + are fully fertile when crossed, by determining to designate as varieties + all the forms which are quite fertile. This high degree of fertility is, + however, rare. Nevertheless plants, which have been exposed to unnatural + conditions, sometimes become modified in so peculiar a manner, that they + are much more fertile when crossed by a distinct species than when + fertilised by their own pollen. Success in effecting a first union + between two species, and the fertility of their hybrids, depends in an + eminent degree on the conditions of life being favourable. The innate + sterility of hybrids of the same parentage and raised from the same + seed-capsule often differs much in degree.</p> + + <p><i>Thirdly</i>, the degree of sterility of a first cross between two + species does not always run strictly parallel with that of their hybrid + offspring. Many cases are known of species which can be crossed with + ease, but yield hybrids excessively sterile; and conversely some which + can be crossed with great difficulty, but produce fairly fertile hybrids. + This is an inexplicable fact, on the view that species have been + specially endowed with mutual sterility in order to keep them + distinct.</p> + + <p><i>Fourthly</i>, the degree of sterility often differs greatly in two + species when reciprocally crossed; for the first will readily fertilise + the second; but the latter is incapable, after hundreds of trials, of + fertilising the former. Hybrids produced from reciprocal crosses between + the same two species, likewise sometimes differ in their degree of + sterility. These cases also are utterly inexplicable on the view of + sterility being a special endowment.</p> + + <p><i>Fifthly</i>, the degree of sterility of first crosses and of + hybrids runs, to a certain extent, parallel with the general or + systematic affinity of the forms which are united. For species belonging + to distinct genera can rarely, and those belonging to distinct families + can never, be crossed. The parallelism, however, is far from complete; + for a multitude of closely allied species will not unite, or unite with + extreme difficulty, whilst other species, widely different from each + other, can be crossed with perfect facility. Nor does the difficulty + depend on ordinary <!-- Page 180 --><span class="pagenum"><a + name="page180"></a>{180}</span>constitutional differences, for annual and + perennial plants, deciduous and evergreen trees, plants flowering at + different seasons, inhabiting different stations, and naturally living + under the most opposite climates, can often be crossed with ease. The + difficulty or facility apparently depends exclusively on the sexual + constitution of the species which are crossed; or on their sexual + elective affinity, <i>i. e.</i> <i>Wahlverwandtschaft</i> of Gärtner. As + species rarely or never become modified in one character, without being + at the same time modified in many, and as systematic affinity includes + all visible resemblances and dissimilarities, any difference in sexual + constitution between two species would naturally stand in more or less + close relation with their systematic position.</p> + + <p><i>Sixthly</i>, the sterility of species when first crossed, and that + of hybrids, may possibly depend to a certain extent on distinct causes. + With pure species the reproductive organs are in a perfect condition, + whilst with hybrids they are often plainly deteriorated. A hybrid embryo + which partakes of the constitution of its father and mother is exposed to + unnatural conditions, as long as it is nourished within the womb, or egg, + or seed of the mother-form; and as we know that unnatural conditions + often induce sterility, the reproductive organs of the hybrid might at + this early age be permanently affected. But this cause has no bearing on + the infertility of first unions. The diminished number of the offspring + from first unions may often result, as is certainly sometimes the case, + from the premature death of most of the hybrid embryos. But we shall + immediately see that a law of an unknown nature apparently exists, which + causes the offspring from unions, which are infertile, to be themselves + more or less infertile; and this at present is all that can be said.</p> + + <p><i>Seventhly</i>, hybrids and mongrels present, with the one great + exception of fertility, the most striking accordance in all other + respects; namely, in the laws of their resemblance to their two parents, + in their tendency to reversion, in their variability, and in being + absorbed through repeated crosses by either parent-form.</p> + + <p>Since arriving at the foregoing conclusions, condensed from my former + work, I have been led to investigate a subject which throws considerable + light on hybridism, namely, the fertility of <!-- Page 181 --><span + class="pagenum"><a name="page181"></a>{181}</span>reciprocally dimorphic + and trimorphic plants, when illegitimately united. I have had occasion + several times to allude to these plants, and I may here give a brief + abstract<a name="NtA_441" href="#Nt_441"><sup>[441]</sup></a> of my + observations. Several plants belonging to distinct orders present two + forms, which exist in about equal numbers, and which differ in no respect + except in their reproductive organs; one form having a long pistil with + short stamens, the other a short pistil with long stamens; both with + differently sized pollen-grains. With trimorphic plants there are three + forms likewise differing in the lengths of their pistils and stamens, in + the size and colour of the pollen-grains, and in some other respects; and + as in each of the three forms there are two sets of stamens, there are + altogether six sets of stamens and three kinds of pistils. These organs + are so proportioned in length to each other that, in any two of the + forms, half the stamens in each stand on a level with the stigma of the + third form. Now I have shown, and the result has been confirmed by other + observers, that, in order to obtain full fertility with these plants, it + is necessary that the stigma of the one form should be fertilised by + pollen taken from the stamens of corresponding height in the other form. + So that with dimorphic species two unions, which may be called + legitimate, are fully fertile, and two, which may be called illegitimate, + are more or less infertile. With trimorphic species six unions are + legitimate or fully fertile, and twelve are illegitimate or more or less + infertile.</p> + + <p>The infertility which may be observed in various dimorphic and + trimorphic plants, when they are illegitimately fertilised, that is, by + pollen taken from stamens not corresponding in height with the pistil, + differs much in degree, up to absolute and utter sterility; just in the + same manner as occurs in crossing distinct species. As the degree of + sterility in the latter case depends in an eminent degree on the + conditions of life being more or less favourable, so I have found it with + illegitimate unions. It is well known that if pollen of a distinct + species be placed on the stigma of a flower, and its own pollen be + afterwards, even <!-- Page 182 --><span class="pagenum"><a + name="page182"></a>{182}</span>after a considerable interval of time, + placed on the same stigma, its action is so strongly prepotent that it + generally annihilates the effect of the foreign pollen; so it is with the + pollen of the several forms of the same species, for legitimate pollen is + strongly prepotent over illegitimate pollen, when both are placed on the + same stigma. I ascertained this by fertilising several flowers, first + illegitimately, and twenty-four hours afterwards legitimately, with + pollen taken from a peculiarly coloured variety, and all the seedlings + were similarly coloured; this shows that the legitimate pollen, though + applied twenty-four hours subsequently, had wholly destroyed or prevented + the action of the previously applied illegitimate pollen. Again, as, in + making reciprocal crosses between the same two species, there is + occasionally a great difference in the result, so something analogous + occurs with dimorphic plants; for a short-styled cowslip (<i>P. + veris</i>) yields more seed when fertilised by the long-styled form, and + less seed when fertilised by its own form, compared with a long-styled + cowslip when fertilised in the two corresponding methods.</p> + + <p>In all these respects the forms of the same undoubted species, when + illegitimately united, behave in exactly the same manner as do two + distinct species when crossed. This led me carefully to observe during + four years many seedlings, raised from several illegitimate unions. The + chief result is that these illegitimate plants, as they may be called, + are not fully fertile. It is possible to raise from dimorphic species, + both long-styled and short-styled illegitimate plants, and from + trimorphic plants all three illegitimate forms. These can then be + properly united in a legitimate manner. When this is done, there is no + apparent reason why they should not yield as many seeds as did their + parents when legitimately fertilised. But such is not the case; they are + all infertile, but in various degrees; some being so utterly and + incurably sterile that they did not yield during four seasons a single + seed or even seed-capsule. These illegitimate plants, which are so + sterile, although united with each other in a legitimate manner, may be + strictly compared with hybrids when crossed <i>inter se</i>, and it is + well known how sterile these latter generally are. When, on the other + hand, a hybrid is crossed with either pure parent-species, the sterility + is usually much lessened: and so it is when an illegitimate plant is + fertilised by <!-- Page 183 --><span class="pagenum"><a + name="page183"></a>{183}</span>a legitimate plant. In the same manner as + the sterility of hybrids does not always run parallel with the difficulty + of making the first cross between the two parent species, so the + sterility of certain illegitimate plants was unusually great, whilst the + sterility of the union from which they were derived was by no means + great. With hybrids raised from the same seed-capsule the degree of + sterility is innately variable, so it is in a marked manner with + illegitimate plants. Lastly, many hybrids are profuse and persistent + flowerers, whilst other and more sterile hybrids produce few flowers, and + are weak, miserable dwarfs; exactly similar cases occur with the + illegitimate offspring of various dimorphic and trimorphic plants.</p> + + <p>Altogether there is the closest identity in character and behaviour + between illegitimate plants and hybrids. It is hardly an exaggeration to + maintain that the former are hybrids, but produced within the limits of + the same species by the improper union of certain forms, whilst ordinary + hybrids are produced from an improper union between so-called distinct + species. We have already seen that there is the closest similarity in all + respects between first illegitimate unions, and first crosses between + distinct species. This will perhaps be made more fully apparent by an + illustration: we may suppose that a botanist found two well-marked + varieties (and such occur) of the long-styled form of the trimorphic + <i>Lythrum salicaria</i>, and that he determined to try by crossing + whether they were specifically distinct. He would find that they yielded + only about one-fifth of the proper number of seed, and that they behaved + in all the other above-specified respects as if they had been two + distinct species. But to make the case sure, he would raise plants from + his supposed hybridised seed, and he would find that the seedlings were + miserably dwarfed and utterly sterile, and that they behaved in all other + respects like ordinary hybrids. He might then maintain that he had + actually proved, in accordance with the common view, that his two + varieties were as good and as distinct species as any in the world; but + he would be completely mistaken.</p> + + <p>The facts now given on dimorphic and trimorphic plants are important, + because they show us, firstly, that the physiological <!-- Page 184 + --><span class="pagenum"><a name="page184"></a>{184}</span>test of + lessened fertility, both in first crosses and in hybrids, is no safe + criterion of specific distinction; secondly, because we may conclude that + there must be some unknown law or bond connecting the infertility of + illegitimate unions with that of their illegitimate offspring, and we are + thus led to extend this view to first crosses and hybrids; thirdly, + because we find, and this seems to me of especial importance, that with + trimorphic plants three forms of the same species exist, which when + crossed in a particular manner are infertile, and yet these forms differ + in no respect from each other, except in their reproductive + organs,—as in the relative length of the stamens and pistils, in + the size, form, and colour of the pollen-grains, in the structure of the + stigma, and in, the number and size of the seeds. With these differences + and no others, either in organisation or constitution, we find that the + illegitimate unions and the illegitimate progeny of these three forms are + more or less sterile, and closely resemble in a whole series of relations + the first unions and hybrid offspring of distinct species. From this we + may infer that the sterility of species when crossed and of their hybrid + progeny is likewise in all probability exclusively due to differences + confined to the reproductive system. We have indeed been brought to a + similar conclusion by observing that the sterility of crossed species + does not strictly coincide with their systematic affinity, that is, with + the sum of their external resemblances; nor does it coincide with their + similarity in general constitution. But we are more especially led to + this same conclusion by considering reciprocal crosses, in which the male + of one species cannot be united, or can be united with extreme + difficulty, with the female of a second species, whilst the converse + cross can be effected with perfect facility; for this difference in the + facility of making reciprocal crosses, and in the fertility of their + offspring, must be attributed either to the male or female element in the + first species having been differentiated with reference to the sexual + element of the second species in a higher degree than in the converse + case. In so complex a subject as Hybridism it is of considerable + importance thus to arrive at a definitive conclusion, namely, that the + sterility which almost invariably follows the union of distinct <!-- Page + 185 --><span class="pagenum"><a name="page185"></a>{185}</span>species + depends exclusively on differences in their sexual constitution.</p> + +<hr class="short" /> + + <p>On the principle which makes it necessary for man, whilst he is + selecting and improving his domestic varieties, to keep them separate, it + would clearly be advantageous to varieties in a state of nature, that is + to incipient species, if they could be kept from blending, either through + sexual aversion, or by becoming mutually sterile. Hence it at one time + appeared to me probable, as it has to others, that this sterility might + have been acquired through natural selection. On this view we must + suppose that a shade of lessened fertility first spontaneously appeared, + like any other modification, in certain individuals of a species when + crossed with other individuals of the same species; and that successive + slight degrees of infertility, from being advantageous, were slowly + accumulated. This appears all the more probable, if we admit that the + structural differences between the forms of dimorphic and trimorphic + plants, as the length and curvature of the pistil, &c., have been + co-adapted through natural selection; for if this be admitted, we can + hardly avoid extending the same conclusion to their mutual infertility. + Sterility moreover has been acquired through natural selection for other + and widely different purposes, as with neuter insects in reference to + their social economy. In the case of plants, the flowers on the + circumference of the truss in the guelder-rose (<i>Viburnum opulus</i>) + and those on the summit of the spike in the feather-hyacinth (<i>Muscari + comosum</i>) have been rendered conspicuous, and apparently in + consequence sterile, in order that insects might easily discover and + visit the other flowers. But when we endeavour to apply the principle of + natural selection to the acquirement by distinct species of mutual + sterility, we meet with great difficulties. In the first place, it may be + remarked that separate regions are often inhabited by groups of species + or by single species, which when brought together and crossed are found + to be more or less sterile; now it could clearly have been of no + advantage to such separated species to have been rendered mutually + sterile, and consequently this could not have been effected through + natural selection; but it may perhaps be argued, that, if a species were + rendered sterile with <!-- Page 186 --><span class="pagenum"><a + name="page186"></a>{186}</span>some one compatriot, sterility with other + species would follow as a necessary consequence. In the second place, it + is as much opposed to the theory of natural selection, as to the theory + of special creation, that in reciprocal crosses the male element of one + form should have been rendered utterly impotent on a second form, whilst + at the same time the male element of this second form is enabled freely + to fertilise the first form; for this peculiar state of the reproductive + system could not possibly be advantageous to either species.</p> + + <p>In considering the probability of natural selection having come into + action in rendering species mutually sterile, one great difficulty will + be found to lie in the existence of many graduated steps from slightly + lessened fertility to absolute sterility. It may be admitted, on the + principle above explained, that it would profit an incipient species if + it were rendered in some slight degree sterile when crossed with its + parent-form or with some other variety; for thus fewer bastardised and + deteriorated offspring would be produced to commingle their blood with + the new species in process of formation. But he who will take the trouble + to reflect on the steps by which this first degree of sterility could be + increased through natural selection to that higher degree which is common + to so many species, and which is universal with species which have been + differentiated to a generic or family rank, will find the subject + extraordinarily complex. After mature reflection it seems to me that this + could not have been effected through natural selection; for it could have + been of no direct advantage to an individual animal to breed badly with + another individual of a different variety, and thus leave few offspring; + consequently such individuals could not have been preserved or selected. + Or take the case of two species which in their present state, when + crossed, produce few and sterile offspring; now, what is there which + could favour the survival of those individuals which happened to be + endowed in a slightly higher degree with mutual infertility and which + thus approached by one small step towards absolute sterility? yet an + advance of this kind, if the theory of natural selection be brought to + bear, must have incessantly occurred with many species, for a multitude + are mutually quite barren. With sterile neuter insects we have reason to + <!-- Page 187 --><span class="pagenum"><a + name="page187"></a>{187}</span>believe that modifications in their + structure have been slowly accumulated by natural selection, from an + advantage having been thus indirectly given to the community to which + they belonged over other communities of the same species; but an + individual animal, if rendered slightly sterile when crossed with some + other variety, would not thus in itself gain any advantage, or indirectly + give any advantage to its nearest relatives or to other individuals of + the same variety, leading to their preservation. I infer from these + considerations that, as far as animals are concerned, the various degrees + of lessened fertility which occur with species when crossed cannot have + been slowly accumulated by means of natural selection.</p> + + <p>With plants, it is possible that the case may be somewhat different. + With many kinds, insects constantly carry pollen from neighbouring plants + to the stigmas of each flower; and with some species this is effected by + the wind. Now, if the pollen of a variety, when deposited on the stigma + of the same variety, should become by spontaneous variation in ever so + slight a degree prepotent over the pollen of other varieties, this would + certainly be an advantage to the variety; for its own pollen would thus + obliterate the effects of the pollen of other varieties, and prevent + deterioration of character. And the more prepotent the variety's own + pollen could be rendered through natural selection, the greater the + advantage would be. We know from the researches of Gärtner that, with + species which are mutually sterile, the pollen of each is always + prepotent on its own stigma over that of the other species; but we do not + know whether this prepotency is a consequence of the mutual sterility, or + the sterility a consequence of the prepotency. If the latter view be + correct, as the prepotency became stronger through natural selection, + from being advantageous to a species in process of formation, so the + sterility consequent on prepotency would at the same time be augmented; + and the final result would be various degrees of sterility, such as + occurs with existing species. This view might be extended to animals, if + the female before each birth received several males, so that the sexual + element of the prepotent male of her own variety obliterated the effects + of the access of previous males belonging to other varieties; but we have + no reason to believe, at least <!-- Page 188 --><span class="pagenum"><a + name="page188"></a>{188}</span>with terrestrial animals, that this is the + ease; as most males and females pair for each birth, and some few for + life.</p> + + <p>On the whole we may conclude that with animals the sterility of + crossed species has not been slowly augmented through natural selection; + and as this sterility follows the same general laws in the vegetable as + in the animal kingdom, it is improbable, though apparently possible, that + with plants crossed species should have been rendered sterile by a + different process. From this consideration, and remembering that species + which have never co-existed in the same country, and which therefore + could not have received any advantage from having been rendered mutually + infertile, yet are generally sterile when crossed; and bearing in mind + that in reciprocal crosses between the same two species there is + sometimes the widest difference in their sterility, we must give up the + belief that natural selection has come into play.</p> + + <p>As species have not been rendered mutually infertile through the + accumulative action of natural selection, and as we may safely conclude, + from the previous as well as from other and more general considerations, + that they have not been endowed through an act of creation with this + quality, we must infer that it has arisen incidentally during their slow + formation in connection with other and unknown changes in their + organisation. By a quality arising incidentally, I refer to such cases as + different species of animals and plants being differently affected by + poisons to which they are not naturally exposed; and this difference in + susceptibility is clearly incidental on other and unknown differences in + their organisation. So again the capacity in different kinds of trees to + be grafted on each other, or on a third species, differs much, and is of + no advantage to these trees, but is incidental on structural or + functional differences in their woody tissues. We need not feel surprise + at sterility incidentally resulting from crosses between distinct + species,—the modified descendants of a common + progenitor,—when we bear in mind how easily the reproductive system + is affected by various causes—often by extremely slight changes in + the conditions of life, by too close interbreeding, and by other + agencies. It is well to bear in mind such cases, as that of the + <i>Passiflora alata</i>, which recovered its self-fertility from <!-- + Page 189 --><span class="pagenum"><a name="page189"></a>{189}</span>being + grafted on a distinct species—the cases of plants which normally or + abnormally are self-impotent, but can readily be fertilised by the pollen + of a distinct species—and lastly the cases of individual + domesticated animals which evince towards each other sexual + incompatibility.</p> + +<hr class="short" /> + + <p>We now at last come to the immediate point under discussion: how is it + that, with some few exceptions in the case of plants, domesticated + varieties, such as those of the dog, fowl, pigeon, several fruit-trees, + and culinary vegetables, which differ from each other in external + characters more than many species, are perfectly fertile when crossed, or + even fertile in excess, whilst closely allied species are almost + invariably in some degree sterile? We can, to a certain extent, give a + satisfactory answer to this question. Passing over the fact that the + amount of external difference between two species is no sure guide to + their degree of mutual sterility, so that similar differences in the case + of varieties would be no sure guide, we know that with species the cause + lies exclusively in differences in their sexual constitution. Now the + conditions to which domesticated animals and cultivated plants have been + subjected, have had so little tendency towards modifying the reproductive + system in a manner leading to mutual sterility, that we have good grounds + for admitting the directly opposite doctrine of Pallas, namely, that such + conditions generally eliminate this tendency; so that the domesticated + descendants of species, which in their natural state would have been in + some degree sterile when crossed, become perfectly fertile together. With + plants, so far is cultivation from giving a tendency towards mutual + sterility, that in several well-authenticated cases, already often + alluded to, certain species have been affected in a very different + manner, for they have become self-impotent, whilst still retaining the + capacity of fertilising, and being fertilised by, distinct species. If + the Pallasian doctrine of the elimination of sterility through + long-continued domestication be admitted, and it can hardly be rejected, + it becomes in the highest degree improbable that similar circumstances + should commonly both induce and eliminate the same tendency; though in + certain cases, with species having a peculiar constitution, sterility + might occasionally be thus <!-- Page 190 --><span class="pagenum"><a + name="page190"></a>{190}</span>induced. Thus, as I believe, we can + understand why with domesticated animals varieties have not been produced + which are mutually sterile; and why with plants only a few such cases + have been observed, namely, by Gärtner, with certain varieties of maize + and verbascum, by other experimentalists with varieties of the gourd and + melon, and by Kölreuter with one kind of tobacco.</p> + + <p>With respect to varieties which have originated in a state of nature, + it is almost hopeless to expect to prove by direct evidence that they + have been rendered mutually sterile; for if even a trace of sterility + could be detected, such varieties would at once be raised by almost every + naturalist to the rank of distinct species. If, for instance, Gärtner's + statement were fully confirmed, that the blue and red-flowered forms of + the pimpernel (<i>Anagallis arvensis</i>) are sterile when crossed, I + presume that all the botanists who now maintain on various grounds that + these two forms are merely fleeting varieties, would at once admit that + they were specifically distinct.</p> + + <p>The real difficulty in our present subject is not, as it appears to + me, why domestic varieties have not become mutually infertile when + crossed, but why this has so generally occurred with natural varieties as + soon as they have been modified in a sufficient and permanent degree to + take rank as species. We are far from precisely knowing the cause; nor is + this surprising, seeing how profoundly ignorant we are in regard to the + normal and abnormal action of the reproductive system. But we can see + that species, owing to their struggle for life with numerous competitors, + must have been exposed to more uniform conditions during long periods of + time, than have been domestic varieties; and this may well make a wide + difference in the result. For we know how commonly wild animals and + plants, when taken from their natural conditions and subjected to + captivity, are rendered sterile; and the reproductive functions of + organic beings which have always lived and been slowly modified under + natural conditions would probably in like manner be eminently sensitive + to the influence of an unnatural cross. Domesticated productions, on the + other hand, which, as shown by the mere fact of their domestication, were + not originally highly sensitive to changes in their conditions of life, + and which can now generally resist <!-- Page 191 --><span + class="pagenum"><a name="page191"></a>{191}</span>with undiminished + fertility repeated changes of conditions, might be expected to produce + varieties, which would be little liable to have their reproductive powers + injuriously affected by the act of crossing with other varieties which + had originated in a like manner.</p> + + <p>Certain naturalists have recently laid too great stress, as it appears + to me, on the difference in fertility between varieties and species when + crossed. Some allied species of trees cannot be grafted on each + other,—all varieties can be so grafted. Some allied animals are + affected in a very different manner by the same poison, but with + varieties no such case until recently was known, but now it has been + proved that immunity from certain poisons stands in some cases in + correlation with the colour of the hair. The period of gestation + generally differs much with distinct species, but with varieties until + lately no such difference had been observed. The time required for the + germination of seeds differs in an analogous manner, and I am not aware + that any difference in this respect has as yet been detected with + varieties. Here we have various physiological differences, and no doubt + others could be added, between one species and another of the same genus, + which do not occur, or occur with extreme rarity, in the case of + varieties; and these differences are apparently wholly or in chief part + incidental on other constitutional differences, just in the same manner + as the sterility of crossed species is incidental on differences confined + to the sexual system. Why, then, should these latter differences, however + serviceable they may indirectly be in keeping the inhabitants of the same + country distinct, be thought of such paramount importance, in comparison + with other incidental and functional differences? No sufficient answer to + this question can be given. Hence the fact that the most distinct + domestic varieties are, with rare exceptions, perfectly fertile when + crossed, and produce fertile offspring, whilst closely allied species + are, with rare exceptions, more or less sterile, is not nearly so + formidable an objection as it appears at first to the theory of the + common descent of allied species.</p> + +<hr class="full" /> + +<p><!-- Page 192 --><span class="pagenum"><a name="page192"></a>{192}</span></p> + +<h3>CHAPTER XX.</h3> + +<p class="cenhead">SELECTION BY MAN.</p> + +<blockquote class="b1n"> + + <p><span class="scac">SELECTION A DIFFICULT ART</span>—<span + class="scac">METHODICAL, UNCONSCIOUS, AND NATURAL + SELECTION</span>—<span class="scac">RESULTS OF METHODICAL + SELECTION</span>—<span class="scac">CARE TAKEN IN + SELECTION</span>—<span class="scac">SELECTION WITH + PLANTS</span>—<span class="scac">SELECTION CARRIED ON BY THE + ANCIENTS, AND BY SEMI-CIVILIZED PEOPLE</span>—<span + class="scac">UNIMPORTANT CHARACTERS OFTEN ATTENDED TO</span>—<span + class="scac">UNCONSCIOUS SELECTION</span>—<span class="scac">AS + CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR DOMESTICATED ANIMALS CHANGED + THROUGH THE ACTION OF UNCONSCIOUS SELECTION</span>—<span + class="scac">INFLUENCE OF DIFFERENT BREEDERS ON THE SAME + SUB-VARIETY</span>—<span class="scac">PLANTS AS AFFECTED BY + UNCONSCIOUS SELECTION</span>—<span class="scac">EFFECTS OF + SELECTION AS SHOWN BY THE GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST + VALUED BY MAN.</span></p> + +</blockquote> + + <p>The power of Selection, whether exercised by man, or brought into play + under nature through the struggle for existence and the consequent + survival of the fittest, absolutely depends on the variability of organic + beings. Without variability nothing can be effected; slight individual + differences, however, suffice for the work, and are probably the sole + differences which are effective in the production of new species. Hence + our discussion on the causes and laws of variability ought in strict + order to have preceded our present subject, as well as the previous + subjects of inheritance, crossing, &c.; but practically the present + arrangement has been found the most convenient. Man does not attempt to + cause variability; though he unintentionally effects this by exposing + organisms to new conditions of life, and by crossing breeds already + formed. But variability being granted, he works wonders. Unless some + degree of selection be exercised, the free commingling of the individuals + of the same variety soon obliterates, as we have previously seen, the + slight differences which may arise, and gives to the whole body of + individuals uniformity of character. In separated districts, + long-continued exposure to different conditions of life may perhaps + produce new races without the aid of selection; but to this difficult + subject <!-- Page 193 --><span class="pagenum"><a + name="page193"></a>{193}</span>of the direct action of the conditions of + life we shall in a future chapter recur.</p> + + <p>When animals or plants are born with some conspicuous and firmly + inherited new character, selection is reduced to the preservation of such + individuals, and to the subsequent prevention of crosses; so that nothing + more need be said on the subject. But in the great majority of cases a + new character, or some superiority in an old character, is at first + faintly pronounced, and is not strongly inherited; and then the full + difficulty of selection is experienced. Indomitable patience, the finest + powers of discrimination, and sound judgment must be exercised during + many years. A clearly predetermined object must be kept steadily in view. + Few men are endowed with all these qualities, especially with that of + discriminating very slight differences; judgment can be acquired only by + long experience; but if any of these qualities be wanting, the labour of + a life may be thrown away. I have been astonished when celebrated + breeders, whose skill and judgment have been proved by their success at + exhibitions, have shown me their animals, which appeared all alike, and + have assigned their reasons for matching this and that individual. The + importance of the great principle of Selection mainly lies in this power + of selecting scarcely appreciable differences, which nevertheless are + found to be transmissible, and which can be accumulated until the result + is made manifest to the eyes of every beholder.</p> + + <p>The principle of selection may be conveniently divided into three + kinds. <i>Methodical selection</i> is that which guides a man who + systematically endeavours to modify a breed according to some + predetermined standard. <i>Unconscious selection</i> is that which + follows from men naturally preserving the most valued and destroying the + less valued individuals, without any thought of altering the breed; and + undoubtedly this process slowly works great changes. Unconscious + selection graduates into methodical, and only extreme cases can be + distinctly separated; for he who preserves a useful or perfect animal + will generally breed from it with the hope of getting offspring of the + same character; but as long as he has not a predetermined purpose to + improve the breed, he may be said to be selecting <!-- Page 194 --><span + class="pagenum"><a name="page194"></a>{194}</span>unconsciously.<a + name="NtA_442" href="#Nt_442"><sup>[442]</sup></a> Lastly, we have + <i>Natural selection</i>, which implies that the individuals which are + best fitted for the complex, and in the course of ages changing + conditions to which they are exposed, generally survive and procreate + their kind. With domestic productions, with which alone we are here + strictly concerned, natural selection comes to a certain extent into + action, independently of, and even in opposition to, the will of man.</p> + +<hr class="short" /> + + <p><i>Methodical Selection.</i>—What man has effected within recent + times in England by methodical selection is clearly shown by our + exhibitions of improved quadrupeds and fancy birds. With respect to + cattle, sheep, and pigs, we owe their great improvement to a long series + of well-known names—Bakewell, Colling, Ellman, Bates, Jonas Webb, + Lords Leicester and Western, Fisher Hobbs, and others. Agricultural + writers are unanimous on the power of selection: any number of statements + to this effect could be quoted; a few will suffice. Youatt, a sagacious + and experienced observer, writes,<a name="NtA_443" + href="#Nt_443"><sup>[443]</sup></a> the principle of selection is "that + which enables the agriculturist, not only to modify the character of his + flock, but to change it altogether." A great breeder of shorthorns<a + name="NtA_444" href="#Nt_444"><sup>[444]</sup></a> says, "In the anatomy + of the shoulder modern breeders have made great improvements on the + Ketton shorthorns by correcting the defect in the knuckle or + shoulder-joint, and by laying the top of the shoulder more snugly into + the crop, and thereby filling up the hollow behind it.... The eye has its + fashion at different periods: at one time the eye high and outstanding + from the head, and at another time the sleepy eye sunk into the head; but + these extremes have merged into the medium of a full, clear, and + prominent eye with a placid look."</p> + + <p>Again, hear what an excellent judge of pigs<a name="NtA_445" + href="#Nt_445"><sup>[445]</sup></a> says: "The legs <!-- Page 195 + --><span class="pagenum"><a name="page195"></a>{195}</span>should be no + longer than just to prevent the animal's belly from trailing on the + ground. The leg is the least profitable portion of the hog, and we + therefore require no more of it than is absolutely necessary for the + support of the rest." Let any one compare the wild-boar with any improved + breed, and he will see how effectually the legs have been shortened.</p> + + <p>Few persons, except breeders, are aware of the systematic care taken + in selecting animals, and of the necessity of having a clear and almost + prophetic vision into futurity. Lord Spencer's skill and judgment were + well known; and he writes,<a name="NtA_446" + href="#Nt_446"><sup>[446]</sup></a> "It is therefore very desirable, + before any man commences to breed either cattle or sheep, that he should + make up his mind to the shape and qualities he wishes to obtain, and + steadily pursue this object." Lord Somerville, in speaking of the + marvellous improvement of the New Leicester sheep, effected by Bakewell + and his successors, says, "It would seem as if they had first drawn a + perfect form, and then given it life." Youatt<a name="NtA_447" + href="#Nt_447"><sup>[447]</sup></a> urges the necessity of annually + drafting each flock, as many animals will certainly degenerate "from the + standard of excellence, which the breeder has established in his own + mind." Even with a bird of such little importance as the canary, long ago + (1780-1790) rules were established, and a standard of perfection was + fixed, according to which the London fanciers tried to breed the several + sub-varieties.<a name="NtA_448" href="#Nt_448"><sup>[448]</sup></a> A + great winner of prizes at the Pigeon-shows,<a name="NtA_449" + href="#Nt_449"><sup>[449]</sup></a> in describing the Short-faced Almond + Tumbler, says, "There are many first-rate fanciers who are particularly + partial to what is called the goldfinch-beak, which is very beautiful; + others say, take a full-size round cherry, then take a barley-corn, and + judiciously placing and thrusting it into the cherry, form as it were + your beak; and that is not all, for it will form a good head and beak, + provided, as I said before, it is judiciously done; others take an oat; + but as I think the goldfinch-beak the handsomest, I would advise the + inexperienced fancier to get the head of a goldfinch, and keep it by him + for his observation." Wonderfully different as is the beak of the + rock-pigeon and goldfinch, undoubtedly, as far as <!-- Page 196 --><span + class="pagenum"><a name="page196"></a>{196}</span>external shape and + proportions are concerned, the end has been nearly gained.</p> + + <p>Not only should our animals be examined with the greatest care whilst + alive, but, as Anderson remarks,<a name="NtA_450" + href="#Nt_450"><sup>[450]</sup></a> their carcases should be scrutinised, + "so as to breed from the descendants of such only as, in the language of + the butcher, cut up well." The "grain of the meat" in cattle, and its + being well marbled with fat,<a name="NtA_451" + href="#Nt_451"><sup>[451]</sup></a> and the greater or less accumulation + of fat in the abdomen of our sheep, have been attended to with success. + So with poultry, a writer,<a name="NtA_452" + href="#Nt_452"><sup>[452]</sup></a> speaking of Cochin-China fowls, which + are said to differ much in the quality of their flesh, says, "the best + mode is to purchase two young brother-cocks, kill, dress, and serve up + one; if he be indifferent, similarly dispose of the other, and try again; + if, however, he be fine and well-flavoured, his brother will not be amiss + for breeding purposes for the table."</p> + + <p>The great principle of the division of labour has been brought to bear + on selection. In certain districts<a name="NtA_453" + href="#Nt_453"><sup>[453]</sup></a> "the breeding of bulls is confined to + a very limited number of persons, who by devoting their whole attention + to this department, are able from year to year to furnish a class of + bulls which are steadily improving the general breed of the district." + The rearing and letting of choice rams has long been, as is well known, a + chief source of profit to several eminent breeders. In parts of Germany + this principle is carried with merino sheep to an extreme point.<a + name="NtA_454" href="#Nt_454"><sup>[454]</sup></a> "So important is the + proper selection of breeding animals considered, that the best + flock-masters do not trust to their own judgment, or to that of their + shepherds, but employ persons called 'sheep-classifiers,' who make it + their special business to attend to this part of the management of + several flocks, and thus to preserve, or if possible to improve, the best + qualities of both parents in the lambs." In Saxony, "when the lambs are + weaned, each in his turn is placed upon a table that his wool and form + may be minutely observed. <!-- Page 197 --><span class="pagenum"><a + name="page197"></a>{197}</span>The finest are selected for breeding and + receive a first mark. When they are one year old, and prior to shearing + them, another close examination of those previously marked takes place: + those in which no defect can be found receive a second mark, and the rest + are condemned. A few months afterwards a third and last scrutiny is made; + the prime rams and ewes receive a third and final mark, but the slightest + blemish is sufficient to cause the rejection of the animal." These sheep + are bred and valued almost exclusively for the fineness of their wool; + and the result corresponds with the labour bestowed on their selection. + Instruments have been invented to measure accurately the thickness of the + fibres; and "an Austrian fleece has been produced of which twelve hairs + equalled in thickness one from a Leicester sheep."</p> + + <p>Throughout the world, wherever silk is produced, the greatest care is + bestowed on selecting the cocoons from which the moths for breeding are + to be reared. A careful cultivator<a name="NtA_455" + href="#Nt_455"><sup>[455]</sup></a> likewise examines the moths + themselves, and destroys those that are not perfect. But what more + immediately concerns us is that certain families in France devote + themselves to raising eggs for sale.<a name="NtA_456" + href="#Nt_456"><sup>[456]</sup></a> In China, near Shanghai, the + inhabitants of two small districts have the privilege of raising eggs for + the whole surrounding country, and that they may give up their whole time + to this business, they are interdicted by law from producing silk.<a + name="NtA_457" href="#Nt_457"><sup>[457]</sup></a></p> + + <p>The care which successful breeders take in matching their birds is + surprising. Sir John Sebright, whose fame is perpetuated by the "Sebright + Bantam," used to spend "two and three days in examining, consulting, and + disputing with a friend which were the best of five or six birds."<a + name="NtA_458" href="#Nt_458"><sup>[458]</sup></a> Mr. Bult, whose + pouter-pigeons won so many prizes and were exported to North America + under the charge of a man sent on purpose, told me that he always + deliberated for several days before he matched each pair. Hence we can + understand the advice of an eminent fancier, who writes,<a name="NtA_459" + href="#Nt_459"><sup>[459]</sup></a> "I would here particularly guard <!-- + Page 198 --><span class="pagenum"><a name="page198"></a>{198}</span>you + against having too great a variety of pigeons, otherwise you will know a + little of all, but nothing about one as it ought to be known." Apparently + it transcends the power of the human intellect to breed all kinds: "it is + possible that there may be a few fanciers that have a good general + knowledge of fancy pigeons; but there are many more who labour under the + delusion of supposing they know what they do not." The excellence of one + sub-variety, the Almond Tumbler, lies in the plumage, carriage, head, + beak, and eye; but it is too presumptuous in the beginner to try for all + these points. The great judge above quoted says, "there are some young + fanciers who are over-covetous, who go for all the above five properties + at once; they have their reward by getting nothing." We thus see that + breeding even fancy pigeons is no simple art: we may smile at the + solemnity of these precepts, but he who laughs will win no prizes.</p> + + <p>What methodical selection has effected for our animals is sufficiently + proved, as already remarked, by our Exhibitions. So greatly were the + sheep belonging to some of the earlier breeders, such as Bakewell and + Lord Western, changed, that many persons could not be persuaded that they + had not been crossed. Our pigs, as Mr. Corringham remarks,<a + name="NtA_460" href="#Nt_460"><sup>[460]</sup></a> during the last twenty + years have undergone, through rigorous selection together with crossing, + a complete metamorphosis. The first exhibition for poultry was held in + the Zoological Gardens in 1845; and the improvement effected since that + time has been great. As Mr. Baily, the great judge, remarked to me, it + was formerly ordered that the comb of the Spanish cock should be upright, + and in four or five years all good birds had upright combs; it was + ordered that the Polish cock should have no comb or wattles, and now a + bird thus furnished would be at once disqualified; beards were ordered, + and out of fifty-seven pens lately (1860) exhibited at the Crystal + Palace, all had beards. So it has been in many other cases. But in all + cases the judges order only what is occasionally produced and what can be + improved and rendered constant by selection. The steady increase of + weight during the last few years in our <!-- Page 199 --><span + class="pagenum"><a name="page199"></a>{199}</span>fowls, turkeys, ducks, + and geese is notorious; "six-pound ducks are now common, whereas four + pounds was formerly the average." As the actual time required to make a + change has not often been recorded, it may be worth mentioning that it + took Mr. Wicking thirteen years to put a clean white head on an almond + tumbler's body, "a triumph," says another fancier, "of which he may be + justly proud."<a name="NtA_461" href="#Nt_461"><sup>[461]</sup></a></p> + + <p>Mr. Tollet, of Betley Hall, selected cows, and especially bulls, + descended from good milkers, for the sole purpose of improving his cattle + for the production of cheese; he steadily tested the milk with the + lactometer, and in eight years he increased, as I was informed by him, + the product in the proportion of four to three. Here is a curious case<a + name="NtA_462" href="#Nt_462"><sup>[462]</sup></a> of steady but slow + progress, with the end not as yet fully attained: in 1784 a race of + silkworms was introduced into France, in which one hundred out of the + thousand failed to produce white cocoons; but now, after careful + selection during sixty-five generations, the proportion of yellow cocoons + has been reduced to thirty-five in the thousand.</p> + + <p>With plants selection has been followed with the same good results as + with animals. But the process is simpler, for plants in the great + majority of cases bear both sexes. Nevertheless, with most kinds it is + necessary to take as much care to prevent crosses as with animals or + unisexual plants; but with some plants, such as peas, this care does not + seem to be necessary. With all improved plants, excepting of course those + which are propagated by buds, cuttings, &c., it is almost + indispensable to examine the seedlings and destroy those which depart + from the proper type. This is called "roguing," and is, in fact, a form + of selection, like the rejection of inferior animals. Experienced + horticulturists and agriculturists incessantly urge every one to preserve + the finest plants for the production of seed.</p> + + <p>Although plants often present much more conspicuous variations than + animals, yet the closest attention is generally requisite to detect each + slight and favourable change. Mr. Masters relates<a name="NtA_463" + href="#Nt_463"><sup>[463]</sup></a> how "many a patient hour was + devoted," whilst he was <!-- Page 200 --><span class="pagenum"><a + name="page200"></a>{200}</span>young, to the detection of differences in + peas intended for seed. Mr. Barnet<a name="NtA_464" + href="#Nt_464"><sup>[464]</sup></a> remarks that the old scarlet American + strawberry was cultivated for more than a century without producing a + single variety; and another writer observes how singular it was that when + gardeners first began to attend to this fruit it began to vary; the truth + no doubt being that it had always varied, but that, until slight + varieties were selected and propagated by seed, no conspicuous result was + obtained. The finest shades of difference in wheat have been + discriminated and selected with almost as much care, as we see in Colonel + Le Couteur's works, as in the case of the higher animals; but with our + cereals the process of selection has seldom or never been long + continued.</p> + + <p>It may be worth while to give a few examples of methodical selection + with plants; but in fact the great improvement of all our anciently + cultivated plants may be attributed to selection long carried on, in part + methodically, and in part unconsciously. I have shown in a former chapter + how the weight of the gooseberry has been increased by systematic + selection and culture. The flowers of the Heartsease have been similarly + increased in size and regularity of outline. With the Cineraria, Mr. + Glenny<a name="NtA_465" href="#Nt_465"><sup>[465]</sup></a> "was bold + enough, when the flowers were ragged and starry and ill defined in + colour, to fix a standard which was then considered outrageously high and + impossible, and which, even if reached, it was said, we should be no + gainers by, as it would spoil the beauty of the flowers. He maintained + that he was right; and the event has proved it to be so." The doubling of + flowers has several times been effected by careful selection: the Rev. W. + Williamson,<a name="NtA_466" href="#Nt_466"><sup>[466]</sup></a> after + sowing during several years seed of <i>Anemone coronaria</i>, found a + plant with one additional petal; he sowed the seed of this, and by + perseverance in the same course obtained several varieties with six or + seven rows of petals. The single Scotch rose was doubled, and yielded + eight good varieties in nine or ten years.<a name="NtA_467" + href="#Nt_467"><sup>[467]</sup></a> The Canterbury bell (<i>Campanula + medium</i>) was doubled by careful selection in four generations.<a + name="NtA_468" href="#Nt_468"><sup>[468]</sup></a> In four years Mr. + Buckman,<a name="NtA_469" href="#Nt_469"><sup>[469]</sup></a> by culture + and <!-- Page 201 --><span class="pagenum"><a + name="page201"></a>{201}</span>careful selection, converted parsnips, + raised from wild seed, into a new and good variety. By selection during a + long course of years, the early maturity of peas has been hastened from + ten to twenty-one days.<a name="NtA_470" + href="#Nt_470"><sup>[470]</sup></a> A more curious case is offered by the + beet-plant, which, since its cultivation in France, has almost exactly + doubled its yield of sugar. This has been effected by the most careful + selection; the specific gravity of the roots being regularly tested, and + the best roots saved for the production of seed.<a name="NtA_471" + href="#Nt_471"><sup>[471]</sup></a></p> + +<p class="cenhead"><i>Selection by Ancient and Semi-civilised People.</i></p> + + <p>In attributing so much importance to the selection of animals and + plants, it may be objected that methodical selection would not have been + carried on during ancient times. A distinguished naturalist considers it + as absurd to suppose that semi-civilised people should have practised + selection of any kind. Undoubtedly the principle has been systematically + acknowledged and followed to a far greater extent within the last hundred + years than at any former period, and a corresponding result has been + gained; but it would be a great error to suppose, as we shall immediately + see, that its importance was not recognised and acted on during the most + ancient times, and by semi-civilised people. I should premise that many + facts now to be given only show that care was taken in breeding; but when + this is the case, selection is almost sure to be practised to a certain + extent. We shall hereafter be enabled better to judge how far selection, + when only occasionally carried on, by a few of the inhabitants of a + country, will slowly produce a great effect.</p> + + <p>In a well-known passage in the thirtieth chapter of Genesis, rules are + given for influencing, as was then thought possible, the colour of sheep; + and speckled and dark breeds are spoken of as being kept separate. By the + time of David the fleece was likened to snow. Youatt,<a name="NtA_472" + href="#Nt_472"><sup>[472]</sup></a> who has discussed all the passages in + relation to breeding in the Old Testament, concludes that <!-- Page 202 + --><span class="pagenum"><a name="page202"></a>{202}</span>at this early + period "some of the best principles of breeding must have been steadily + and long pursued." It was ordered, according to Moses, that "Thou shalt + not let thy cattle gender with a diverse kind;" but mules were + purchased,<a name="NtA_473" href="#Nt_473"><sup>[473]</sup></a> so that + at this early period other nations must have crossed the horse and ass. + It is said<a name="NtA_474" href="#Nt_474"><sup>[474]</sup></a> that + Erichthonius, some generations before the Trojan war, had many + brood-mares, "which by his care and judgment in the choice of stallions + produced a breed of horses superior to any in the surrounding countries." + Homer (Book v.) speaks of Æneas's horses as bred from mares which were + put to the steeds of Laomedon. Plato, in his 'Republic,' says to Glaucus, + "I see that you raise at your house a great many dogs for the chase. Do + you take care about breeding and pairing them? Among animals of good + blood, are there not always some which are superior to the rest?" To + which Glaucus answers in the affirmative.<a name="NtA_475" + href="#Nt_475"><sup>[475]</sup></a> Alexander the Great selected the + finest Indian cattle to send to Macedonia to improve the breed.<a + name="NtA_476" href="#Nt_476"><sup>[476]</sup></a> According to Pliny,<a + name="NtA_477" href="#Nt_477"><sup>[477]</sup></a> King Pyrrhus had an + especially valuable breed of oxen; and he did not suffer the bulls and + cows to come together till four years old, that the breed might not + degenerate. Virgil, in his Georgics (lib. iii.), gives as strong advice + as any modern agriculturist could do, carefully to select the breeding + stock; "to note the tribe, the lineage, and the sire; whom to reserve for + husband of the herd;"—to brand the progeny;—to select sheep + of the purest white, and to examine if their tongues are swarthy. We have + seen that the Romans kept pedigrees of their pigeons, and this would have + been a senseless proceeding had not great care been taken in breeding + them. Columella gives detailed instructions about breeding fowls: "Let + the breeding hens therefore be of a choice colour, a robust body, + square-built, full-breasted, with large heads, with upright and + bright-red combs. Those are believed to be the best bred which have five + toes."<a name="NtA_478" href="#Nt_478"><sup>[478]</sup></a> According to + Tacitus, the Celts attended to the races of their domestic animals; <!-- + Page 203 --><span class="pagenum"><a name="page203"></a>{203}</span>and + Cæsar states that they paid high prices to merchants for fine imported + horses.<a name="NtA_479" href="#Nt_479"><sup>[479]</sup></a> In regard to + plants, Virgil speaks of yearly culling the largest seeds; and Celsus + says, "where the corn and crop is but small, we must pick out the best + ears of corn, and of them lay up our seed separately by itself."<a + name="NtA_480" href="#Nt_480"><sup>[480]</sup></a></p> + + <p>Coming down the stream of time, we may be brief. At about the + beginning of the ninth century Charlemagne expressly ordered his officers + to take great care of his stallions; and if any proved bad or old, to + forewarn him in good time before they were put to the mares.<a + name="NtA_481" href="#Nt_481"><sup>[481]</sup></a> Even in a country so + little civilised as Ireland during the ninth century, it would appear + from some ancient verses,<a name="NtA_482" + href="#Nt_482"><sup>[482]</sup></a> describing a ransom demanded by + Cormac, that animals from particular places, or having a particular + character, were valued. Thus it is said,—</p> + + <div class="poem"> + <div class="stanza"> + <p>Two pigs of the pigs of Mac Lir,</p> + <p>A ram and ewe both round and red,</p> + <p>I brought with me from Aengus.</p> + <p>I brought with me a stallion and a mare</p> + <p>From the beautiful stud of Manannan,</p> + <p>A bull and a white cow from Druim Cain.</p> + </div> + </div> + + <p>Athelstan, in 930, received as a present from Germany, running-horses; + and he prohibited the exportation of English horses. King John imported + "one hundred chosen stallions from Flanders."<a name="NtA_483" + href="#Nt_483"><sup>[483]</sup></a> On June 16th, 1305, the Prince of + Wales wrote to the Archbishop of Canterbury, begging for the loan of any + choice stallion, and promising its return at the end of the season.<a + name="NtA_484" href="#Nt_484"><sup>[484]</sup></a> There are numerous + records at ancient periods in English history of the importation of + choice animals of various kinds, and of foolish laws against their + exportation. In the reigns of Henry VII. and VIII. it was ordered that + the magistrates, at Michaelmas, should scour the heaths and commons, and + destroy all mares beneath a certain size.<a name="NtA_485" + href="#Nt_485"><sup>[485]</sup></a> Some of our earlier kings passed laws + against the slaughtering rams of any good breed before they were seven + years old, so that they <!-- Page 204 --><span class="pagenum"><a + name="page204"></a>{204}</span>might have time to breed. In Spain + Cardinal Ximenes issued, in 1509, regulations on the <i>selection</i> of + good rams for breeding.<a name="NtA_486" + href="#Nt_486"><sup>[486]</sup></a></p> + + <p>The Emperor Akbar Khan before the year 1600 is said to have + "wonderfully improved" his pigeons by crossing the breeds; and this + necessarily implies careful selection. About the same period the Dutch + attended with the greatest care to the breeding of these birds. Belon in + 1555 says that good managers in France examined the colour of their + goslings in order to get geese of a white colour and better kinds. + Markham in 1631 tells the breeder "to elect the largest and goodliest + conies," and enters into minute details. Even with respect to seeds of + plants for the flower-garden, Sir J. Hanmer writing about the year 1660<a + name="NtA_487" href="#Nt_487"><sup>[487]</sup></a> says, in "choosing + seed, the best seed is the most weighty, and is had from the lustiest and + most vigorous stems;" and he then gives rules about leaving only a few + flowers on plants for seed; so that even such details were attended to in + our flower-gardens two hundred years ago. In order to show that selection + has been silently carried on in places where it would not have been + expected, I may add that in the middle of the last century, in a remote + part of North America, Mr. Cooper improved by careful selection all his + vegetables, "so that they were greatly superior to those of any other + person. When his radishes, for instance, are fit for use, he takes ten or + twelve that he most approves, and plants them at least 100 yards from + others that blossom at the same time. In the same manner he treats all + his other plants, varying the circumstances according to their nature."<a + name="NtA_488" href="#Nt_488"><sup>[488]</sup></a></p> + + <p>In the great work on China published in the last century by the + Jesuits, and which is chiefly compiled from ancient Chinese + encyclopædias, it is said that with sheep "improving the breed consists + in choosing with particular care the lambs which are destined for + propagation, in nourishing them well, and in keeping the flocks + separate." The same principles were applied by the Chinese to various + plants and fruit-trees.<a name="NtA_489" + href="#Nt_489"><sup>[489]</sup></a> An <!-- Page 205 --><span + class="pagenum"><a name="page205"></a>{205}</span>imperial edict + recommends the choice of seed of remarkable size; and selection was + practised even by imperial hands, for it is said that the Ya-mi, or + imperial rice, was noticed at an ancient period in a field by the Emperor + Khang-hi, was saved and cultivated in his garden, and has since become + valuable from being the only kind which will grow north of the Great + Wall.<a name="NtA_490" href="#Nt_490"><sup>[490]</sup></a> Even with + flowers, the tree pæony (<i>P. moutan</i>) has been cultivated, according + to Chinese traditions, for 1400 years; between 200 and 300 varieties have + been raised, which are cherished like tulips formerly were by the + Dutch.<a name="NtA_491" href="#Nt_491"><sup>[491]</sup></a></p> + + <p>Turning now to semi-civilised people and to savages: it occurred to + me, from what I had seen of several parts of South America, where fences + do not exist, and where the animals are of little value, that there would + be absolutely no care in breeding or selecting them; and this to a large + extent is true. Roulin,<a name="NtA_492" + href="#Nt_492"><sup>[492]</sup></a> however, describes in Colombia a + naked race of cattle, which are not allowed to increase, on account of + their delicate constitution. According to Azara<a name="NtA_493" + href="#Nt_493"><sup>[493]</sup></a> horses are often born in Paraguay + with curly hair; but, as the natives do not like them, they are + destroyed. On the other hand, Azara states that a hornless bull, born in + 1770, was preserved and propagated its race. I was informed of the + existence in Banda Oriental of a breed with reversed hair; and the + extraordinary niata cattle first appeared and have since been kept + distinct in La Plata. Hence certain conspicuous variations have been + preserved, and others have been habitually destroyed, in these countries, + which are so little favourable for careful selection. We have also seen + that the inhabitants sometimes introduce cattle on their estates to + prevent the evil effects of close interbreeding. On the other hand, I + have heard on reliable authority that the Gauchos of the Pampas never + take any pains in selecting the best bulls or stallions for breeding; and + this probably accounts for the cattle and horses being remarkably uniform + in character throughout the immense range of the Argentine republic.</p> + + <p>Looking to the Old World, in the Sahara Desert "The Touareg is as + careful in the selection of his breeding Mahari <!-- Page 206 --><span + class="pagenum"><a name="page206"></a>{206}</span>(a fine race of the + dromedary) as the Arab is in that of his horse. The pedigrees are handed + down, and many a dromedary can boast a genealogy far longer than the + descendants of the Darley Arabian."<a name="NtA_494" + href="#Nt_494"><sup>[494]</sup></a> According to Pallas the Mongolians + endeavour to breed the Yaks or horse-tailed buffaloes with white tails, + for these are sold to the Chinese mandarins as fly-flappers; and + Moorcroft, about seventy years after Pallas, found that white-tailed + animals were still selected for breeding.<a name="NtA_495" + href="#Nt_495"><sup>[495]</sup></a></p> + + <p>We have seen in the chapter on the Dog that savages in different parts + of North America and in Guiana cross their dogs with wild Canidæ, as did + the ancient Gauls, according to Pliny. This was done to give their dogs + strength and vigour, in the same way as the keepers in large warrens now + sometimes cross their ferrets (as I have been informed by Mr. Yarrell) + with the wild polecat, "to give them more devil." According to Varro, the + wild ass was formerly caught and crossed with the tame animal to improve + the breed, in the same manner as at the present day the natives of Java + sometimes drive their cattle into the forests to cross with the wild + Banteng (<i>Bos sondaicus</i>).<a name="NtA_496" + href="#Nt_496"><sup>[496]</sup></a> In Northern Siberia, among the + Ostyaks the dogs vary in markings in different districts, but in each + place they are spotted black and white in a remarkably uniform manner;<a + name="NtA_497" href="#Nt_497"><sup>[497]</sup></a> and from this fact + alone we may infer careful breeding, more especially as the dogs of one + locality are famed throughout the country for their superiority. I have + heard of certain tribes of Esquimaux who take pride in their teams of + dogs being uniformly coloured. In Guiana, as Sir R. Schomburgk informs + me,<a name="NtA_498" href="#Nt_498"><sup>[498]</sup></a> the dogs of the + Turuma Indians are highly valued and extensively bartered: the price of a + good one is the same as that given for a wife: they are kept in a sort of + cage, and the Indians "take great care when the female is in season to + prevent her uniting with a dog of an inferior description." The Indians + told Sir Robert that, if a dog proved bad or useless, <!-- Page 207 + --><span class="pagenum"><a name="page207"></a>{207}</span>he was not + killed, but was left to die from sheer neglect. Hardly any nation is more + barbarous than the Fuegians, but I hear from Mr. Bridges, the Catechist + to the Mission, that, "when these savages have a large, strong, and + active bitch, they take care to put her to a fine dog, and even take care + to feed her well, that her young may be strong and well favoured."</p> + + <p>In the interior of Africa, negroes, who have not associated with white + men, show great anxiety to improve their animals: they "always choose the + larger and stronger males for stock:" the Malakolo were much pleased at + Livingstone's promise to send them a bull, and some Bakalolo carried a + live cock all the way from Loanda into the interior.<a name="NtA_499" + href="#Nt_499"><sup>[499]</sup></a> Further south on the same continent, + Andersson states that he has known a Damara give two fine oxen for a dog + which struck his fancy. The Damaras take great delight in having whole + droves of cattle of the same colour, and they prize their oxen in + proportion to the size of their horns. "The Namaquas have a perfect mania + for a uniform team; and almost all the people of Southern Africa value + their cattle next to their women, and take a pride in possessing animals + that look high-bred." "They rarely or never make use of a handsome animal + as a beast of burden."<a name="NtA_500" + href="#Nt_500"><sup>[500]</sup></a> The power of discrimination which + these savages possess is wonderful, and they can recognise to which tribe + any cattle belong. Mr. Andersson further informs me that the natives + frequently match a particular bull with a particular cow.</p> + + <p>The most curious case of selection by semi-civilised people, or indeed + by any people, which I have found recorded, is that given by Garcilazo de + la Vega, a descendant of the Incas, as having been practised in Peru + before the country was subjugated by the Spaniards.<a name="NtA_501" + href="#Nt_501"><sup>[501]</sup></a> The Incas annually held great hunts, + when all the wild animals were driven from an immense circuit to a + central point. The beasts of prey were first destroyed as injurious. The + wild Guanacos and Vicunas were sheared; the old males and females killed, + and the others set at liberty. The various kinds of deer were examined; + the old males and females <!-- Page 208 --><span class="pagenum"><a + name="page208"></a>{208}</span>were likewise killed; "but the young + females, with a certain number of males, selected from the most beautiful + and strong," were given their freedom. Here, then, we have selection by + man aiding natural selection. So that the Incas followed exactly the + reverse system of that which our Scottish sportsmen are accused of + following, namely, of steadily killing the finest stags, thus causing the + whole race to degenerate.<a name="NtA_502" + href="#Nt_502"><sup>[502]</sup></a> In regard to the domesticated llamas + and alpacas, they were separated in the time of the Incas according to + colour; and if by chance one in a flock was born of the wrong colour, it + was eventually put into another flock.</p> + + <p>In the genus Auchenia there are four forms,—the Guanaco and + Vicuna, found wild and undoubtedly distinct species; the Llama and + Alpaca, known only in a domesticated condition. These four animals appear + so different, that most professed naturalists, especially those who have + studied these animals in their native country, maintain that they are + specifically distinct, notwithstanding that no one pretends to have seen + a wild llama or alpaca. Mr. Ledger, however, who has closely studied + these animals both in Peru and during their exportation to Australia, and + who has made many experiments on their propagation, adduces arguments<a + name="NtA_503" href="#Nt_503"><sup>[503]</sup></a> which seem to me + conclusive, that the llama is the domesticated descendant of the guanaco, + and the alpaca of the vicuna. And now that we know that these animals + many centuries ago were systematically bred and selected, there is + nothing surprising in the great amount of change which they have + undergone.</p> + + <p>It appeared to me at one time probable that, though ancient and + semi-civilised people might have attended to the improvement of their + more useful animals in essential points, yet that they would have + disregarded unimportant characters. But human nature is the same + throughout the world: fashion everywhere reigns supreme, and man is apt + to value whatever he may chance to possess. We have seen that in South + America the niata cattle, which certainly are not made useful by their + shortened faces and upturned nostrils, have been preserved. The Damaras + of South Africa value their cattle for uniformity <!-- Page 209 --><span + class="pagenum"><a name="page209"></a>{209}</span>of colour and + enormously long horns. The Mongolians value their yaks for their white + tails. And I shall now show that there is hardly any peculiarity in our + most useful animals which, from fashion, superstition, or some other + motive, has not been valued, and consequently preserved. With respect to + cattle, "an early record," according to Youatt,<a name="NtA_504" + href="#Nt_504"><sup>[504]</sup></a> "speaks of a hundred white cows with + red ears being demanded as a compensation by the princes of North and + South Wales. If the cattle were of a dark or black colour, 150 were to be + presented." So that colour was attended to in Wales before its + subjugation by England. In Central Africa, an ox that beats the ground + with its tail is killed; and in South Africa some of the Damaras will not + eat the flesh of a spotted ox. The Kaffirs value an animal with a musical + voice; and "at a sale in British Kaffraria the low of a heifer excited so + much admiration that a sharp competition sprung up for her possession, + and she realised a considerable price."<a name="NtA_505" + href="#Nt_505"><sup>[505]</sup></a> With respect to sheep, the Chinese + prefer rams without horns; the Tartars prefer them with spirally wound + horns, because the hornless are thought to lose courage.<a name="NtA_506" + href="#Nt_506"><sup>[506]</sup></a> Some of the Damaras will not eat the + flesh of hornless sheep. In regard to horses, at the end of the fifteenth + century animals of the colour described as <i>liart pommé</i> were most + valued in France. The Arabs have a proverb, "Never buy a horse with four + white feet, for he carries his shroud with him;"<a name="NtA_507" + href="#Nt_507"><sup>[507]</sup></a> the Arabs also, as we have seen, + despise dun-coloured horses. So with dogs, Xenophon and others at an + ancient period were prejudiced in favour of certain colours; and "white + or slate-coloured hunting dogs were not esteemed."<a name="NtA_508" + href="#Nt_508"><sup>[508]</sup></a></p> + + <p>Turning to poultry, the old Roman gourmands thought that the liver of + a white goose was the most savoury. In Paraguay black-skinned fowls are + kept because they are thought to be more productive, and their flesh the + most proper for invalids.<a name="NtA_509" + href="#Nt_509"><sup>[509]</sup></a> In Guiana, as I am informed by Sir R. + Schomburgk, the aborigines will not eat the flesh or eggs of the fowl, + but two <!-- Page 210 --><span class="pagenum"><a + name="page210"></a>{210}</span>races are kept distinct merely for + ornament. In the Philippines, no less than nine sub-varieties of the game + cock are kept and named, so that they must be separately bred.</p> + + <p>At the present time in Europe, the smallest peculiarities are + carefully attended to in our most useful animals, either from fashion, or + as a mark of purity of blood. Many examples could be given, two will + suffice. "In the Western counties of England the prejudice against a + white pig is nearly as strong as against a black one in Yorkshire." In + one of the Berkshire sub-breeds, it is said, "the white should be + confined to four white feet, a white spot between the eyes, and a few + white hairs behind each shoulder." Mr. Saddler possessed "three hundred + pigs, every one of which was marked in this manner."<a name="NtA_510" + href="#Nt_510"><sup>[510]</sup></a> Marshall, towards the close of the + last century, in speaking of a change in one of the Yorkshire breeds of + cattle, says the horns have been considerably modified, as "a clean, + small, sharp horn has been <i>fashionable</i> for the last twenty + years."<a name="NtA_511" href="#Nt_511"><sup>[511]</sup></a> In a part of + Germany the cattle of the Race de Gfoehl are valued for many good + qualities, but they must have horns of a particular curvature and tint, + so much so that mechanical means are applied if they take a wrong + direction; but the inhabitants "consider it of the highest importance + that the nostrils of the bull should be flesh-coloured, and the eyelashes + light; this is an indispensable condition. A calf with blue nostrils + would not be purchased, or purchased at a very low price."<a + name="NtA_512" href="#Nt_512"><sup>[512]</sup></a> Therefore let no man + say that any point or character is too trifling to be methodically + attended to and selected by breeders.</p> + +<hr class="short" /> + + <p><i>Unconscious Selection.</i>—By this term I mean, as already + more than once explained, the preservation by man of the most valued, and + the destruction of the least valued individuals, without any conscious + intention on his part of altering the breed. It is difficult to offer + direct proofs of the results which follow from this kind of selection; + but the indirect evidence is abundant. In fact, except that in the one + case man acts intentionally, and in the other unintentionally, there is + little difference between <!-- Page 211 --><span class="pagenum"><a + name="page211"></a>{211}</span>methodical and unconscious selection. In + both cases man preserves the animals which are most useful or pleasing to + him, and destroys or neglects the others. But no doubt a far more rapid + result follows from methodical than from unconscious selection. The + "roguing" of plants by gardeners, and the destruction by law in Henry + VIII.'s reign of all under-sized mares, are instances of a process the + reverse of selection in the ordinary sense of the word, but leading to + the same general result. The influence of the destruction of individuals + having a particular character is well shown by the necessity of killing + every lamb with a trace of black about it, in order to keep the flock + white; or again, by the effects on the average height of the men of + France of the destructive wars of Napoleon, by which many tall men were + killed, the short ones being left to be the fathers of families. This at + least is the conclusion of those who have closely studied the subject of + the conscription; and it is certain that since Napoleon's time the + standard for the army has been lowered two or three times.</p> + + <p>Unconscious selection so blends into methodical that it is scarcely + possible to separate them. When a fancier long ago first happened to + notice a pigeon with an unusually short beak, or one with the + tail-feathers unusually developed, although he bred from these birds with + the distinct intention of propagating the variety, yet he could not have + intended to make a short-faced tumbler or a fantail, and was far from + knowing that he had made the first step towards this end. If he could + have seen the final result, he would have been struck with astonishment, + but, from what we know of the habits of fanciers, probably not with + admiration. Our English carriers, barbs, and short-faced tumblers have + been greatly modified in the same manner, as we may infer both from the + historical evidence given in the chapters on the Pigeon, and from the + comparison of birds brought from distant countries.</p> + + <p>So it has been with dogs; our present fox-hounds differ from the old + English hound; our greyhounds have become lighter; the wolf-dog, which + belonged to the greyhound class, has become extinct; the Scotch + deer-hound has been modified, and is now rare. Our bulldogs differ from + those which were formerly used for baiting bulls. Our pointers and + Newfoundlands do not <!-- Page 212 --><span class="pagenum"><a + name="page212"></a>{212}</span>closely resemble any native dog now found + in the countries whence they were brought, These changes have been + effected partly by crosses; but in every case the result has been + governed by the strictest selection. Nevertheless there is no reason to + suppose that man intentionally and methodically made the breeds exactly + what they now are. As our horses became fleeter, and the country more + cultivated and smoother, fleeter fox-hounds were desired and produced, + but probably without any one distinctly foreseeing what they would + become. Our pointers and setters, the latter almost certainly descended + from large spaniels, have been greatly modified in accordance with + fashion and the desire for increased speed. Wolves have become extinct, + deer have become rarer, bulls are no longer baited, and the corresponding + breeds of the dog have answered to the change. But we may feel almost + sure that when, for instance, bulls were no longer baited, no man said to + himself, I will now breed my dogs of smaller size, and thus create the + present race. As circumstances changed, men unconsciously and slowly + modified their course of selection.</p> + + <p>With race-horses selection for swiftness has been followed + methodically, and our horses can now easily beat their progenitors. The + increased size and different appearance of the English race-horse led a + good observer in India to ask, "Could any one in this year of 1856, + looking at our race-horses, conceive that they were the result of the + union of the Arab horse and the African mare?"<a name="NtA_513" + href="#Nt_513"><sup>[513]</sup></a> This change has, it is probable, been + largely effected through unconscious selection, that is, by the general + wish to breed as fine horses as possible in each generation, combined + with training and high feeding, but without any intention to give to them + their present appearance. According to Youatt,<a name="NtA_514" + href="#Nt_514"><sup>[514]</sup></a> the introduction in Oliver Cromwell's + time of three celebrated Eastern stallions speedily affected the English + breed; "so that Lord Harleigh, one of the old school, complained that the + great horse was fast disappearing." This is an excellent proof how + carefully selection must have been attended to; for without such care, + all traces of so small an infusion of Eastern blood would soon have been + absorbed and <!-- Page 213 --><span class="pagenum"><a + name="page213"></a>{213}</span>lost. Notwithstanding that the climate of + England has never been esteemed particularly favourable to the horse, yet + long-continued selection, both methodical and unconscious, together with + that practised by the Arabs during a still longer and earlier period, has + ended in giving us the best breed of horses in the world. Macaulay<a + name="NtA_515" href="#Nt_515"><sup>[515]</sup></a> remarks, "Two men + whose authority on such subjects was held in great esteem, the Duke of + Newcastle and Sir John Fenwick, pronounced that the meanest hack ever + imported from Tangier would produce a finer progeny than could be + expected from the best sire of our native breed. They would not readily + have believed that a time would come when the princes and nobles of + neighbouring lands would be as eager to obtain horses from England as + ever the English had been to obtain horses from Barbary."</p> + + <p>The London dray-horse, which differs so much in appearance from any + natural species, and which from its size has so astonished many Eastern + princes, was probably formed by the heaviest and most powerful animals + having been selected during many generations in Flanders and England, but + without the least intention or expectation of creating a horse such as we + now see. If we go back to an early period of history, we behold in the + antique Greek statues, as Schaaffhausen has remarked,<a name="NtA_516" + href="#Nt_516"><sup>[516]</sup></a> a horse equally unlike a race or dray + horse, and differing from any existing breed.</p> + + <p>The results of unconscious selection, in an early stage, are well + shown in the difference between the flocks descended from the same stock, + but separately reared by careful breeders. Youatt gives an excellent + instance of this fact in the sheep belonging to Messrs. Buckley and + Burgess, which "have been purely bred from the original stock of Mr. + Bakewell for upwards of fifty years. There is not a suspicion existing in + the mind of any one at all acquainted with the subject that the owner of + either flock has deviated in any one instance from the pure blood of Mr. + Bakewell's flock; yet the difference between the sheep possessed by these + two gentlemen is so great, that they have the appearance of being quite + different varieties."<a name="NtA_517" + href="#Nt_517"><sup>[517]</sup></a> I have seen several analogous and + <!-- Page 214 --><span class="pagenum"><a + name="page214"></a>{214}</span>well-marked cases with pigeons: for + instance, I had a family of barbs, descended from those long bred by Sir + J. Sebright, and another family long bred by another fancier, and the two + families plainly differed from each other. Nathusius—and a more + competent witness could not be cited—observes that, though the + Shorthorns are remarkably uniform inn appearance (except in colouring), + yet that the individual character and wishes of each breeder become + impressed on his cattle, so that different herds differ slightly from + each other.<a name="NtA_518" href="#Nt_518"><sup>[518]</sup></a> The + Hereford cattle assumed their present well-marked character soon after + the year 1769, through careful selection by Mr. Tomkins,<a name="NtA_519" + href="#Nt_519"><sup>[519]</sup></a> and the breed has lately split into + two strains—one strain having a white face, and differing slightly, + it is said,<a name="NtA_520" href="#Nt_520"><sup>[520]</sup></a> in some + other points; but there is no reason to believe that this split, the + origin of which is unknown, was intentionally made; it may with much more + probability be attributed to different breeders having attended to + different points. So again, the Berkshire breed of swine in the year 1810 + had greatly changed from what it had been in 1780; and since 1810 at + least two distinct sub-breeds have borne this same name.<a name="NtA_521" + href="#Nt_521"><sup>[521]</sup></a> When we bear in mind how rapidly all + animals increase, and that some must be annually slaughtered and some + saved for breeding, then, if the same breeder during a long course of + years deliberately settles which shall be saved and which shall be + killed, it is almost inevitable that his individual frame of mind will + influence the character of his stock, without his having had any + intention to modify the breed or form a new strain.</p> + + <p>Unconscious selection in the strictest sense of the word, that is, the + saving of the more useful animals and the neglect or slaughter of the + less useful, without any thought of the future, must have gone on + occasionally from the remotest period and amongst the most barbarous + nations. Savages often suffer from famines, and are sometimes expelled by + war from their own homes. In such cases it can hardly be doubted that + they would save their most useful animals. When the Fuegians <!-- Page + 215 --><span class="pagenum"><a name="page215"></a>{215}</span>are hard + pressed by want, they kill their old women for food rather than their + dogs; for, as we were assured, "old women no use—dogs catch + otters." The same sound sense would surely lead them to preserve their + more useful dogs when still harder pressed by famine. Mr. Oldfield, who + has seen so much of the aborigines of Australia, informs me that "they + are all very glad to get a European kangaroo dog, and several instances + have been known of the father killing his own infant that the mother + might suckle the much-prized puppy." Different kinds of dogs would be + useful to the Australian for hunting opossums and kangaroos, and to the + Fuegian for catching fish and otters; and the occasional preservation in + the two countries of the most useful animals would ultimately lead to the + formation of two widely distinct breeds.</p> + +<hr class="short" /> + + <p>With plants, from the earliest dawn of civilisation, the best variety + which at each period was known would generally have been cultivated and + its seeds occasionally sown; so that there will have been some selection + from an extremely remote period, but without any prefixed standard of + excellence or thought of the future. We at the present day profit by a + course of selection occasionally and unconsciously carried on during + thousands of years. This is proved in an interesting manner by Oswald + Heer's researches on the lake-inhabitants of Switzerland, as given in a + former chapter; for he shows that the grain and seed of our present + varieties of wheat, barley, oats, peas, beans, lentils, and poppy, exceed + in size those which were cultivated in Switzerland during the Neolithic + and Bronze periods. These ancient people, during the Neolithic period, + possessed also a crab considerably larger than that now growing wild on + the Jura.<a name="NtA_522" href="#Nt_522"><sup>[522]</sup></a> The pears + described by Pliny were evidently extremely inferior in quality to our + present pears. We can realise the effects of long-continued selection and + cultivation in another way, for would any one in his senses expect to + raise a first-rate apple from the seed of a truly wild crab, or a + luscious melting pear from the wild pear? Alphonse De Candolle informs me + that he has lately seen on an ancient mosaic at Rome a representation of + <!-- Page 216 --><span class="pagenum"><a + name="page216"></a>{216}</span>the melon; and as the Romans, who were + such gourmands, are silent on this fruit, he infers that the melon has + been greatly ameliorated since the classical period.</p> + + <p>Coming to later times, Buffon,<a name="NtA_523" + href="#Nt_523"><sup>[523]</sup></a> on comparing the flowers, fruit, and + vegetables which were then cultivated, with some excellent drawings made + a hundred and fifty years previously, was struck with surprise at the + great improvement which had been effected; and remarks that these ancient + flowers and vegetables would now be rejected, not only by a florist but + by a village gardener. Since the time of Buffon the work of improvement + has steadily and rapidly gone on. Every florist who compares our present + flowers with those figured in books published not long since, is + astonished at the change. A well-known amateur,<a name="NtA_524" + href="#Nt_524"><sup>[524]</sup></a> in speaking of the varieties of + Pelargonium raised by Mr. Garth only twenty-two years before, remarks, + "what a rage they excited: surely we had attained perfection, it was + said; and now not one of the flowers of those days will be looked at. But + none the less is the debt of gratitude which we owe to those who saw what + was to be done, and did it." Mr. Paul, the well-known horticulturist, in + writing of the same flower,<a name="NtA_525" + href="#Nt_525"><sup>[525]</sup></a> says he remembers when young being + delighted with the portraits in Sweet's work; "but what are they in point + of beauty compared with the Pelargoniums of this day? Here again nature + did not advance by leaps; the improvement was gradual, and, if we had + neglected those very gradual advances, we must have foregone the present + grand results." How well this practical horticulturist appreciates and + illustrates the gradual and accumulative force of selection! The Dahlia + has advanced in beauty in a like manner; the line of improvement being + guided by fashion, and by the successive modifications which the flower + slowly underwent.<a name="NtA_526" href="#Nt_526"><sup>[526]</sup></a> A + steady and gradual change has been noticed in many other flowers: thus an + old florist,<a name="NtA_527" href="#Nt_527"><sup>[527]</sup></a> after + describing the leading varieties of the Pink which were grown in 1813, + adds, "the pinks of those days would now be scarcely grown as + border-flowers." The improvement of <!-- Page 217 --><span + class="pagenum"><a name="page217"></a>{217}</span>so many flowers and the + number of the varieties which have been raised is all the more striking + when we hear that the earliest known flower-garden in Europe, namely at + Padua, dates only from the year 1545.<a name="NtA_528" + href="#Nt_528"><sup>[528]</sup></a></p> + +<hr class="short" /> + + <p><i>Effects of Selection, as shown by the parts most valued by man + presenting the greatest amount of Difference.</i>—The power of + long-continued selection, whether methodical or unconscious, or both + combined, is well shown in a general way, namely, by the comparison of + the differences between the varieties of distinct species, which are + valued for different parts, such as for the leaves, or stems, or tubers, + the seed, or fruit, or flowers. Whatever part man values most, that part + will be found to present the greatest amount of difference. With trees + cultivated for their fruit, Sageret remarks that the fruit is larger than + in the parent-species, whilst with those cultivated for the seed, as with + nuts, walnuts, almonds, chesnuts, &c., it is the seed itself which is + larger; and he accounts for this fact by the fruit in the one case, and + by the seed in the other, having been carefully attended to and selected + during many ages. Gallesio has made the same observation. Godron insists + on the diversity of the tuber in the potato, of the bulb in the onion, + and of the fruit in the melon; and on the close similarity in these same + plants of the other parts.<a name="NtA_529" + href="#Nt_529"><sup>[529]</sup></a></p> + + <p>In order to judge how far my own impression on this subject was + correct, I cultivated numerous varieties of the same species close to + each other. The comparison of the amount of difference between widely + different organs is necessarily vague; I will therefore give the results + in only a few cases. We have previously seen in the ninth chapter how + greatly the varieties of the cabbage differ in their foliage and stems, + which are the selected parts, and how closely they resembled each other + in their flowers, capsules, and seeds. In seven varieties of the radish, + the roots differed greatly in colour and shape, but no difference <!-- + Page 218 --><span class="pagenum"><a + name="page218"></a>{218}</span>whatever could be detected in their + foliage, flowers, or seeds. Now what a contrast is presented, if we + compare the flowers of the varieties of these two plants with those of + any species cultivated in our flower-gardens for ornament; or if we + compare their seeds with those of the varieties of maize, peas, beans, + &c., which are valued and cultivated for their seeds. In the ninth + chapter it was shown that the varieties of the pea differ but little + except in the tallness of the plant, moderately in the shape of the pod, + and greatly in the pea itself, and these are all selected points. The + varieties, however, of the <i>Pois sans parchemin</i> differ much more in + their pods, and these are eaten and valued. I cultivated twelve varieties + of the common bean; one alone, the Dwarf Fan, differed considerably in + general appearance; two differed in the colour of their flowers, one + being an albino, and the other being wholly instead of partially purple; + several differed considerably in the shape and size of the pod, but far + more in the bean itself, and this is the valued and selected part. + Toker's bean, for instance, is twice-and-a-half as long and broad as the + horse-bean, and is much thinner and of a different shape.</p> + + <p>The varieties of the gooseberry, as formerly described, differ much in + their fruit, but hardly perceptibly in their flowers or organs of + vegetation. With the plum, the differences likewise appear to be greater + in the fruit than in the flowers or leaves. On the other hand, the seed + of the strawberry, which corresponds with the fruit of the plum, differs + hardly at all; whilst every one knows how greatly the fruit—that + is, the enlarged receptacle—differs in the several varieties. In + apples, pears, and peaches the flowers and leaves differ considerably, + but not, as far as I can judge, in proportion with the fruit. The Chinese + double-flowering peaches, on the other hand, show that varieties of this + tree have been formed, which differ more in the flower than in fruit. If, + as is highly probable, the peach is the modified descendant of the + almond, a surprising amount of change has been effected in the same + species, in the fleshy covering of the former and in the kernels of the + latter.</p> + + <p>When parts stand in such close relation to each other as the fleshy + covering of the fruit (whatever its homological nature may be) and the + seed, when one part is modified, so generally is the other, but by no + means necessarily in the same degree. With <!-- Page 219 --><span + class="pagenum"><a name="page219"></a>{219}</span>the plum-tree, for + instance, some varieties produce plums which are nearly alike, but + include stones extremely dissimilar in shape; whilst conversely other + varieties produce dissimilar fruit with barely distinguishable stones; + and generally the stones, though they have never been subjected to + selection, differ greatly in the several varieties of the plum. In other + cases organs which are not manifestly related, through some unknown bond + vary together, and are consequently liable, without any intention on + man's part, to be simultaneously acted on by selection. Thus the + varieties of the stock (Matthiola) have been selected solely for the + beauty of their flowers, but the seeds differ greatly in colour and + somewhat in size. Varieties of the lettuce have been selected solely on + account of their leaves, yet produce seeds which likewise differ in + colour. Generally, through the law of correlation, when a variety differs + greatly from its fellow-varieties in any one character, it differs to a + certain extent in several other characters. I observed this fact when I + cultivated together many varieties of the same species, for I used first + to make a list of the varieties which differed most from each other in + their foliage and manner of growth, afterwards of those that differed + most in their flowers, then in their seed-capsules, and lastly in their + mature seed; and I found that the same names generally occurred in two, + three, or four of the successive lists. Nevertheless the greatest amount + of difference between the varieties was always exhibited, as far as I + could judge, by that part or organ for which the plant was + cultivated.</p> + + <p>When we bear in mind that each plant was at first cultivated because + useful to man, and that its variation was a subsequent, often a long + subsequent, event, we cannot explain the greater amount of diversity in + the valuable parts by supposing that species endowed with an especial + tendency to vary in any particular manner, were originally chosen. We + must attribute the result to the variations in these parts having been + successively preserved, and thus continually augmented; whilst other + variations, excepting such as inevitably appeared through correlation, + were neglected and lost. Hence we may infer that most plants might be + made, through long-continued selection, to yield races as different from + each other in any character <!-- Page 220 --><span class="pagenum"><a + name="page220"></a>{220}</span>as they now are in those parts for which + they are valued and cultivated.</p> + + <p>With animals we see something of the same kind; but they have not been + domesticated in sufficient number or yielded sufficient varieties for a + fair comparison. Sheep are valued for their wool, and the wool differs + much more in the several races than the hair in cattle. Neither sheep, + goats, European cattle, nor pigs are valued for their fleetness or + strength; and we do not possess breeds differing in these respects like + the race-horse and dray-horse. But fleetness and strength are valued in + camels and dogs; and we have with the former the swift dromedary and + heavy camel; with the latter the greyhound and mastiff. But dogs are + valued even in a higher degree for their mental qualities and senses; and + every one knows how greatly the races differ in these respects. On the + other hand, where the dog is valued solely to serve for food, as in the + Polynesian islands and China, it is described as an extremely stupid + animal.<a name="NtA_530" href="#Nt_530"><sup>[530]</sup></a> Blumenbach + remarks that "many dogs, such as the badger-dog, have a build so marked + and so appropriate for particular purposes, that I should find it very + difficult to persuade myself that this astonishing figure was an + accidental consequence of degeneration."<a name="NtA_531" + href="#Nt_531"><sup>[531]</sup></a> But had Blumenbach reflected on the + great principle of selection, he would not have used the term + degeneration, and he would not have been astonished that dogs and other + animals should become excellently adapted for the service of man.</p> + + <p>On the whole we may conclude that whatever part or character is most + valued—whether the leaves, stems, tubers, bulbs, flowers, fruit, or + seed of plants, or the size, strength, fleetness, hairy covering, or + intellect of animals—that character will almost invariably be found + to present the greatest amount of difference both in kind and degree. And + this result may be safely attributed to man having preserved during a + long course of generations the variations which were useful to him, and + neglected the others.</p> + + <p>I will conclude this chapter by some remarks on an important subject. + With animals such as the giraffe, of which <!-- Page 221 --><span + class="pagenum"><a name="page221"></a>{221}</span>the whole structure is + admirably co-ordinated for certain purposes, it has been supposed that + all the parts must have been simultaneously modified; and it has been + argued that, on the principle of natural selection, this is scarcely + possible. But in thus arguing, it has been tacitly assumed that the + variations must have been abrupt and great. No doubt, if the neck of a + ruminant were suddenly to become greatly elongated, the fore limbs and + back would have to be simultaneously strengthened and modified; but it + cannot be denied that an animal might have its neck, or head, or tongue, + or fore-limbs elongated a very little without any corresponding + modification in other parts of the body; and animals thus slightly + modified would, during a dearth, have a slight advantage, and be enabled + to browse on higher twigs, and thus survive. A few mouthfuls more or less + every day would make all the difference between life and death. By the + repetition of the same process, and by the occasional intercrossing of + the survivors, there would be some progress, slow and fluctuating though + it would be, towards the admirably co-ordinated structure of the giraffe. + If the short-faced tumbler-pigeon, with its small conical beak, globular + head, rounded body, short wings, and small feet—characters which + appear all in harmony—had been a natural species, its whole + structure would have been viewed as well fitted for its life; but in this + case we know that inexperienced breeders are urged to attend to point + after point, and not to attempt improving the whole structure at the same + time. Look at the greyhound, that perfect image of grace, symmetry, and + vigour; no natural species can boast of a more admirably co-ordinated + structure, with its tapering head, slim body, deep chest, tucked-up + abdomen, rat-like tail, and long muscular limbs, all adapted for extreme + fleetness, and for running down weak prey. Now, from what we see of the + variability of animals, and from what we know of the method which + different men follow in improving their stock—some chiefly + attending to one point, others to another point, others again correcting + defects by crosses, and so forth—we may feel assured that if we + could see the long line of ancestors of a first-rate greyhound, up to its + wild wolf-like progenitor, we should behold an infinite number of the + finest gradations, sometimes in one character and sometimes in another, + but all leading towards our <!-- Page 222 --><span class="pagenum"><a + name="page222"></a>{222}</span>present perfect type. By small and + doubtful steps such as these, nature, as we may confidently believe, has + progressed on her grand march of improvement and development.</p> + + <p>A similar line of reasoning is as applicable to separate organs as to + the whole organisation. A writer<a name="NtA_532" + href="#Nt_532"><sup>[532]</sup></a> has recently maintained that "it is + probably no exaggeration to suppose that, in order to improve such an + organ as the eye at all, it must be improved in ten different ways at + once. And the improbability of any complex organ being produced and + brought to perfection in any such way is an improbability of the same + kind and degree as that of producing a poem or a mathematical + demonstration by throwing letters at random on a table." If the eye were + abruptly and greatly modified, no doubt many parts would have to be + simultaneously altered, in order that the organ should remain + serviceable.</p> + + <p>But is this the case with smaller changes? There are persons who can + see distinctly only in a dull light, and this condition depends, I + believe, on the abnormal sensitiveness of the retina, and is known to be + inherited. Now, if a bird, for instance, received some great advantage + from seeing well in the twilight, all the individuals with the most + sensitive retina would succeed best and be the most likely to survive; + and why should not all those which happened to have the eye itself a + little larger, or the pupil capable of greater dilatation, be likewise + preserved, whether or not these modifications were strictly simultaneous? + These individuals would subsequently intercross and blend their + respective advantages. By such slight successive changes, the eye of a + diurnal bird would be brought into the condition of that of an owl, which + has often been advanced as an excellent instance of adaptation. + Short-sight, which is often inherited, permits a person to see distinctly + a minute object at so near a distance that it would be indistinct to + ordinary eyes; and here we have a capacity which might be serviceable + under certain conditions, abruptly gained. The Fuegians on board the <!-- + Page 223 --><span class="pagenum"><a + name="page223"></a>{223}</span>Beagle could certainly see distant objects + more distinctly than our sailors with all their long practice; I do not + know whether this depends on nervous sensitiveness or on the power of + adjustment in the focus; but this capacity for distant vision might, it + is probable, be slightly augmented by successive modifications of either + kind. Amphibious animals, which are enabled to see both in the water and + in the air, require and possess, as M. Plateau has shown,<a + name="NtA_533" href="#Nt_533"><sup>[533]</sup></a> eyes constructed on + the following plan: "the cornea is always flat, or at least much + flattened in front of the crystalline and over a space equal to the + diameter of that lens, whilst the lateral portions may be much curved." + The crystalline is very nearly a sphere, and the humours have nearly the + same density as water. Now, as a terrestrial animal slowly became more + and more aquatic in its habits, very slight changes, first in the + curvature of the cornea or crystalline, and then in the density of the + humours, or conversely, might successively occur, and would be + advantageous to the animal whilst under water, without serious detriment + to its power of vision in the air. It is of course impossible to + conjecture by what steps the fundamental structure of the eye in the + Vertebrata was originally acquired, for we know absolutely nothing about + this organ in the first progenitors of the class. With respect to the + lowest animals in the scale, the transitional states through which the + eye at first probably passed, can by the aid of analogy be indicated, as + I have attempted to show in my 'Origin of Species.'<a name="NtA_534" + href="#Nt_534"><sup>[534]</sup></a></p> + +<hr class="full" /> + +<p><!-- Page 224 --><span class="pagenum"><a name="page224"></a>{224}</span></p> + +<h3>CHAPTER XXI.</h3> + +<p class="cenhead">SELECTION, <i>continued</i>.</p> + +<blockquote class="b1n"> + + <p><span class="scac">NATURAL SELECTION AS AFFECTING DOMESTIC + PRODUCTIONS</span>—<span class="scac">CHARACTERS WHICH APPEAR OF + TRIFLING VALUE OFTEN OF REAL IMPORTANCE</span>—<span + class="scac">CIRCUMSTANCES FAVOURABLE TO SELECTION BY + MAN</span>—<span class="scac">FACILITY IN PREVENTING CROSSES, AND + THE NATURE OF THE CONDITIONS</span>—<span class="scac">CLOSE + ATTENTION AND PERSEVERANCE INDISPENSABLE</span>—<span + class="scac">THE PRODUCTION OF A LARGE NUMBER OF INDIVIDUALS ESPECIALLY + FAVOURABLE</span>—<span class="scac">WHEN NO SELECTION IS APPLIED, + DISTINCT RACES ARE NOT FORMED</span>—<span class="scac">HIGHLY-BRED + ANIMALS LIABLE TO DEGENERATION</span>—<span class="scac">TENDENCY + IN MAN TO CARRY THE SELECTION OF EACH CHARACTER TO AN EXTREME POINT, + LEADING TO DIVERGENCE OF CHARACTER, RARELY TO + CONVERGENCE</span>—<span class="scac">CHARACTERS CONTINUING TO VARY + IN THE SAME DIRECTION IN WHICH THEY HAVE ALREADY + VARIED</span>—<span class="scac">DIVERGENCE OF CHARACTER, WITH THE + EXTINCTION OF INTERMEDIATE VARIETIES, LEADS TO DISTINCTNESS IN OUR + DOMESTIC RACES</span>—<span class="scac">LIMIT TO THE POWER OF + SELECTION</span>—<span class="scac">LAPSE OF TIME + IMPORTANT</span>—<span class="scac">MANNER IN WHICH DOMESTIC RACES + HAVE ORIGINATED</span>—<span class="scac">SUMMARY.</span></p> + +</blockquote> + + <p><i>Natural Selection, or the Survival of the Fittest, as affecting + domestic productions.</i>—We know little on this head. But as + animals kept by savages have to provide their own food, either entirely + or to a large extent, throughout the year, it can hardly be doubted that, + in different countries, varieties differing in constitution and in + various characters would succeed best, and so be naturally selected. + Hence perhaps it is that the few domesticated animals kept by savages + partake, as has been remarked by more than one writer, of the wild + appearance of their masters, and likewise resemble natural species. Even + in long-civilised countries, at least in the wilder parts, natural + selection must act on our domestic races. It is obvious that varieties, + having very different habits, constitution, and structure, would succeed + best on mountains and on rich lowland pastures. For example, the improved + Leicester sheep were formerly taken to the Lammermuir Hills; but an + intelligent sheep-master reported that "our coarse lean pastures were + unequal to the task of supporting such heavy-bodied sheep; and they + gradually dwindled away into less and less bulk: <!-- Page 225 --><span + class="pagenum"><a name="page225"></a>{225}</span>each generation was + inferior to the preceding one; and when the spring was severe, seldom + more than two-thirds of the lambs survived the ravages of the storms."<a + name="NtA_535" href="#Nt_535"><sup>[535]</sup></a> So with the mountain + cattle of North Wales and the Hebrides, it has been found that they could + not withstand being crossed with the larger and more delicate lowland + breeds. Two French naturalists, in describing the horses of Circassia, + remark that, subjected as they are to extreme vicissitudes of climate, + having to search for scanty pasture, and exposed to constant danger from + wolves, the strongest and most vigorous alone survive.<a name="NtA_536" + href="#Nt_536"><sup>[536]</sup></a></p> + + <p>Every one must have been struck with the surpassing grace, strength, + and vigour of the Game-cock, with its bold and confident air, its long, + yet firm neck, compact body, powerful and closely pressed wings, muscular + thighs, strong beak massive at the base, dense and sharp spurs set low on + the legs for delivering the fatal blow, and its compact, glossy, and + mail-like plumage serving as a defence. Now the English game-cock has not + only been improved during many years by man's careful selection, but in + addition, as Mr. Tegetmeier has remarked,<a name="NtA_537" + href="#Nt_537"><sup>[537]</sup></a> by a kind of natural selection, for + the strongest, most active and courageous birds have stricken down their + antagonists in the cockpit, generation after generation, and have + subsequently served as the progenitors of their kind.</p> + + <p>In Great Britain, in former times, almost every district had its own + breed of cattle and sheep; "they were indigenous to the soil, climate, + and pasturage of the locality on which they grazed: they seemed to have + been formed for it and by it."<a name="NtA_538" + href="#Nt_538"><sup>[538]</sup></a> But in this case we are quite unable + to disentangle the effects of the direct action of the conditions of + life,—of use or habit—of natural selection—and of that + kind of selection which we have seen is occasionally and unconsciously + followed by man even during the rudest periods of history.</p> + + <p>Let us now look to the action of natural selection on special + characters. Although nature is difficult to resist, yet man often strives + against her power, and sometimes, as we shall see, with <!-- Page 226 + --><span class="pagenum"><a name="page226"></a>{226}</span>success. From + the facts to be given, it will also be seen that natural selection would + powerfully affect many of our domestic productions if left unprotected. + This is a point of much interest, for we thus learn that differences + apparently of very slight importance would certainly determine the + survival of a form when forced to struggle for its own existence. It may + have occurred to some naturalists, as it formerly did to me, that, though + selection acting under natural conditions would determine the structure + of all important organs, yet that it could not affect characters which + are esteemed by us of little importance; but this is an error to which we + are eminently liable, from our ignorance of what characters are of real + value to each living creature.</p> + + <p>When man attempts to breed an animal with some serious defect in + structure, or in the mutual relation of parts, he will either partially + or completely fail, or encounter much difficulty; and this is in fact a + form of natural selection. We have seen that the attempt was once made in + Yorkshire to breed cattle with enormous buttocks, but the cows perished + so often in bringing forth their calves, that the attempt had to be given + up. In rearing short-faced tumblers, Mr. Eaton says,<a name="NtA_539" + href="#Nt_539"><sup>[539]</sup></a> "I am convinced that better head and + beak birds have perished in the shell than ever were hatched; the reason + being that the amazingly short-faced bird cannot reach and break the + shell with its beak, and so perishes." Here is a more curious case, in + which natural selection comes into play only at long intervals of time: + during ordinary seasons the Niata cattle can graze as well as others, but + occasionally, as from 1827 to 1830, the plains of La Plata suffer from + long-continued droughts and the pasture is burnt up; at such times common + cattle and horses perish by the thousand, but many survive by browsing on + twigs, reeds, &c.; this the Niata cattle cannot so well effect from + their upturned jaws and the shape of their lips; consequently, if not + attended to, they perish before the other cattle. In Colombia, according + to Roulin, there is a breed of nearly hairless cattle, called Pelones; + these succeed in their native hot district, but are found too tender for + the Cordillera; in this case, natural selection <!-- Page 227 --><span + class="pagenum"><a name="page227"></a>{227}</span>determines only the + range of the variety. It is obvious that a host of artificial races could + never survive in a state of nature;—such as Italian + greyhounds,—hairless and almost toothless Turkish + dogs,—fantail pigeons, which cannot fly well against a strong + wind,—barbs with their vision impeded by their + eye-wattle,—Polish fowls with their vision impeded by their great + topknots,—hornless bulls and rams which consequently cannot cope + with other males, and thus have a poor chance of leaving + offspring,—seedless plants, and many other such cases.</p> + + <p>Colour is generally esteemed by the systematic naturalist as + unimportant: let us, therefore, see how far it indirectly affects our + domestic productions, and how far it would affect them if they were left + exposed to the full force of natural selection. In a future chapter I + shall have to show that constitutional peculiarities of the strangest + kind, entailing liability to the action of certain poisons, are + correlated with the colour of the skin. I will here give a single case, + on the high authority of Professor Wyman; he informs me that, being + surprised at all the pigs in a part of Virginia being black, he made + inquiries, and ascertained that these animals feed on the roots of the + <i>Lachnanthes tinctoria</i>, which colours their bones pink, and, + excepting in the case of the black varieties, causes the hoofs to drop + off. Hence, as one of the squatters remarked, "we select the black + members of the litter for raising, as they alone have a good chance of + living." So that here we have artificial and natural selection working + hand in hand. I may add that in the Tarentino the inhabitants keep black + sheep alone, because the <i>Hypericum crispum</i> abounds there; and this + plant does not injure black sheep, but kills the white ones in about a + fortnight's time.<a name="NtA_540" + href="#Nt_540"><sup>[540]</sup></a></p> + + <p>Complexion, and liability to certain diseases, are believed to run + together in man and the lower animals. Thus white terriers suffer more + than terriers of any other colour from the fatal Distemper.<a + name="NtA_541" href="#Nt_541"><sup>[541]</sup></a> In North America + plum-trees are liable to a disease which Downing<a name="NtA_542" + href="#Nt_542"><sup>[542]</sup></a> believes is not caused by insects; + the kinds bearing purple fruit are most affected, "and we have never + known the green or yellow fruited varieties infected <!-- Page 228 + --><span class="pagenum"><a name="page228"></a>{228}</span>until the + other sorts had first become filled with the knots." On the other hand, + peaches in North America suffer much from a disease called the + <i>yellows</i>, which seems to be peculiar to that continent, and "more + than nine-tenths of the victims, when the disease first appeared, were + the yellow-fleshed peaches. The white-fleshed kinds are much more rarely + attacked; in some parts of the country never." In Mauritius, the white + sugar-canes have of late years been so severely attacked by a disease, + that many planters have been compelled to give up growing this variety + (although fresh plants were imported from China for trial), and cultivate + only red canes.<a name="NtA_543" href="#Nt_543"><sup>[543]</sup></a> Now, + if these plants had been forced to struggle with other competing plants + and enemies, there cannot be a doubt that the colour of the flesh or skin + of the fruit, unimportant as these characters are considered, would have + rigorously determined their existence.</p> + + <p>Liability to the attacks of parasites is also connected with colour. + It appears that white chickens are certainly more subject than + dark-coloured chickens to the <i>gapes</i>, which is caused by a + parasitic worm in the trachea.<a name="NtA_544" + href="#Nt_544"><sup>[544]</sup></a> On the other hand, experience has + shown that in France the caterpillars which produce white cocoons resist + the deadly fungus better than those producing yellow cocoons.<a + name="NtA_545" href="#Nt_545"><sup>[545]</sup></a> Analogous facts have + been observed with plants: a new and beautiful white onion, imported from + France, though planted close to other kinds, was alone attacked by a + parasitic fungus.<a name="NtA_546" href="#Nt_546"><sup>[546]</sup></a> + White verbenas are especially liable to mildew.<a name="NtA_547" + href="#Nt_547"><sup>[547]</sup></a> Near Malaga, during an early period + of the vine-disease, the green sorts suffered most; "and red and black + grapes, even when interwoven with the sick plants, suffered not at all." + In France whole groups of varieties were comparatively free, and others, + such as the Chasselas, did not afford a single fortunate exception; but I + do not know whether any correlation between colour and liability to + disease was here observed.<a name="NtA_548" + href="#Nt_548"><sup>[548]</sup></a> In a former chapter it was shown how + curiously liable one variety of the strawberry is to mildew.</p> + +<p><!-- Page 229 --><span class="pagenum"><a name="page229"></a>{229}</span></p> + + <p>It is certain that insects regulate in many cases the range and even + the existence of the higher animals, whilst living under their natural + conditions. Under domestication light-coloured animals suffer most: in + Thuringia<a name="NtA_549" href="#Nt_549"><sup>[549]</sup></a> the + inhabitants do not like grey, white, or pale cattle, because they are + much more troubled by various kinds of flies than the brown, red, or + black cattle. An Albino negro, it has been remarked,<a name="NtA_550" + href="#Nt_550"><sup>[550]</sup></a> was peculiarly sensitive to the bites + of insects. In the West Indies<a name="NtA_551" + href="#Nt_551"><sup>[551]</sup></a> it is said that "the only horned + cattle fit for work are those which have a good deal of black in them. + The white are terribly tormented by the insects; and they are weak and + sluggish in proportion to the white."</p> + + <p>In Devonshire there is a prejudice against white pigs, because it is + believed that the sun blisters them when turned out;<a name="NtA_552" + href="#Nt_552"><sup>[552]</sup></a> and I knew a man who would not keep + white pigs in Kent, for the same reason. The scorching of flowers by the + sun seems likewise to depend much on colour; thus, dark pelargoniums + suffer most; and from various accounts it is clear that the cloth-of-gold + variety will not withstand a degree of exposure to sunshine which other + varieties enjoy. Another amateur asserts that not only all dark-coloured + verbenas, but likewise scarlets, suffer from the sun; "the paler kinds + stand better, and pale blue is perhaps the best of all." So again with + the heartsease (<i>Viola tricolor</i>); hot weather suits the blotched + sorts, whilst it destroys the beautiful markings of some other kinds.<a + name="NtA_553" href="#Nt_553"><sup>[553]</sup></a> During one extremely + cold season in Holland all red-flowered hyacinths were observed to be + very inferior in quality. It is believed by many agriculturists that red + wheat is hardier in northern climates than white wheat.<a name="NtA_554" + href="#Nt_554"><sup>[554]</sup></a></p> + + <p>With animals, white varieties from being conspicuous are the most + liable to be attacked by beasts and birds of prey. In parts of France and + Germany where hawks abound, persons are advised not to keep white + pigeons; for, as Parmentier says, "it <!-- Page 230 --><span + class="pagenum"><a name="page230"></a>{230}</span>is certain that in a + flock the white always first fall victims to the kite." In Belgium, where + so many societies have been established for the flight of + carrier-pigeons, white is the one colour which for the same reason is + disliked.<a name="NtA_555" href="#Nt_555"><sup>[555]</sup></a> On the + other hand, it is said that the sea-eagle (<i>Falco ossifragus</i>, + Linn.) on the west coast of Ireland picks out the black fowls, so that + "the villagers avoid as much as possible rearing birds of that colour." + M. Daudin,<a name="NtA_556" href="#Nt_556"><sup>[556]</sup></a> speaking + of white rabbits kept in warrens in Russia, remarks that their colour is + a great disadvantage, as they are thus more exposed to attack, and can be + seen during bright nights from a distance. A gentleman in Kent, who + failed to stock his woods with a nearly white and hardy kind of rabbit, + accounted in the same manner for their early disappearance. Any one who + will watch a white cat prowling after her prey will soon perceive under + what a disadvantage she lies.</p> + + <p>The white Tartarian cherry, "owing either to its colour being so much + like that of the leaves, or to the fruit always appearing from a distance + unripe," is not so readily attacked by birds as other sorts. The + yellow-fruited raspberry, which generally comes nearly true by seed, "is + very little molested by birds, who evidently are not fond of it; so that + nets may be dispensed with in places where nothing else will protect the + red fruit."<a name="NtA_557" href="#Nt_557"><sup>[557]</sup></a> This + immunity, though a benefit to the gardener, would be a disadvantage in a + state of nature both to the cherry and raspberry, as their dissemination + depends on birds. I noticed during several winters that some trees of the + yellow-berried holly, which were raised from seed from a wild tree found + by my father, remained covered with fruit, whilst not a scarlet berry + could be seen on the adjoining trees of the common kind. A friend informs + me that a mountain-ash (<i>Pyrus aucuparia</i>) growing in his garden + bears berries which, though not differently coloured, are always devoured + by birds before those on the other trees. This variety of the + mountain-ash would thus be more freely disseminated, and the + yellow-berried variety of the holly less freely, than the common + varieties of these two trees.</p> + +<p><!-- Page 231 --><span class="pagenum"><a name="page231"></a>{231}</span></p> + + <p>Independently of colour, other trifling differences are sometimes + found to be of importance to plants under cultivation, and would be of + paramount importance if they had to fight their own battle and to + struggle with many competitors. The thin-shelled peas, called <i>pois + sans parchemin</i>, are attacked by birds<a name="NtA_558" + href="#Nt_558"><sup>[558]</sup></a> much more than common peas. On the + other hand, the purple-podded pea, which has a hard shell, escaped the + attacks of tomtits (<i>Parus major</i>) in my garden far better than any + other kind. The thin-shelled walnut likewise suffers greatly from the + tomtit.<a name="NtA_559" href="#Nt_559"><sup>[559]</sup></a> These same + birds have been observed to pass over and thus favour the filbert, + destroying only the other kinds of nuts which grew in the same orchard.<a + name="NtA_560" href="#Nt_560"><sup>[560]</sup></a></p> + + <p>Certain varieties of the pear have soft bark, and these suffer + severely from boring wood-beetles; whilst other varieties are known to + resist their attacks much better.<a name="NtA_561" + href="#Nt_561"><sup>[561]</sup></a> In North America the smoothness, or + absence of down on the fruit, makes a great difference in the attacks of + the weevil, "which is the uncompromising foe of all smooth stone-fruits;" + and the cultivator "has the frequent mortification of seeing nearly all, + or indeed often the whole crop, fall from the trees when half or + two-thirds grown." Hence the nectarine suffers more than the peach. A + particular variety of the Morello cherry, raised in North America, is + without any assignable cause more liable to be injured by this same + insect than other cherry-trees.<a name="NtA_562" + href="#Nt_562"><sup>[562]</sup></a> From some unknown cause, the Winter + Majetin apple enjoys the great advantage of not being infested by the + coccus. On the other hand, a particular case has been recorded in which + aphides confined themselves to the Winter Nelis pear, and touched no + other kind in an extensive orchard.<a name="NtA_563" + href="#Nt_563"><sup>[563]</sup></a> The existence of minute glands on the + leaves of peaches, nectarines, and apricots, would not be esteemed by + botanists as a character of the least importance, for they are present or + absent in closely related sub-varieties, descended from the same + parent-tree; yet there is good evidence<a name="NtA_564" + href="#Nt_564"><sup>[564]</sup></a> that the <!-- Page 232 --><span + class="pagenum"><a name="page232"></a>{232}</span>absence of glands leads + to mildew, which is highly injurious to these trees.</p> + + <p>A difference either in flavour or in the amount of nutriment in + certain varieties causes them to be more eagerly attacked by various + enemies than other varieties of the same species. Bullfinches + (<i>Pyrrhula vulgaris</i>) injure our fruit-trees by devouring the + flower-buds, and a pair of these birds have been seen "to denude a large + plum-tree in a couple of days of almost every bud;" but certain + varieties<a name="NtA_565" href="#Nt_565"><sup>[565]</sup></a> of the + apple and thorn (<i>Cratægus <span class="correction" title="Original reads `oxycantha', corrected by errata, page viii." + >oxyacantha</span></i>) are more especially liable to be attacked. A + striking instance of this was observed in Mr. Rivers's garden, in which + two rows of a particular variety of plum<a name="NtA_566" + href="#Nt_566"><sup>[566]</sup></a> had to be carefully protected, as + they were usually stripped of all their buds during the winter, whilst + other sorts growing near them escaped. The root (or enlarged stem) of + Laing's Swedish turnip is preferred by hares, and therefore suffers more + than other varieties. Hares and rabbits eat down common rye before St. + John's-day-rye, when both grow together.<a name="NtA_567" + href="#Nt_567"><sup>[567]</sup></a> In the South of France, when an + orchard of almond-trees is formed, the nuts of the bitter variety are + sown, "in order that they may not be devoured by field-mice;"<a + name="NtA_568" href="#Nt_568"><sup>[568]</sup></a> so we see the use of + the bitter principle in almonds.</p> + + <p>Other slight differences, which would be thought quite unimportant, + are no doubt sometimes of great service both to plants and animals. The + Whitesmith's gooseberry, as formerly stated, produces its leaves later + than other varieties, and, as the flowers are thus left unprotected, the + fruit often fails. In one variety of the cherry, according to Mr. + Rivers,<a name="NtA_569" href="#Nt_569"><sup>[569]</sup></a> the petals + are much curled backwards, and in consequence of this the stigmas were + observed to be killed by a severe frost; whilst at the same time, in + another variety with incurved petals, the stigmas were not in the least + injured. The straw of the Fenton wheat is remarkably unequal in height; + and a competent observer believes that this variety is highly productive, + partly because the ears, from being distributed at various heights above + the ground, <!-- Page 233 --><span class="pagenum"><a + name="page233"></a>{233}</span>are less crowded together. The same + observer maintains that in the upright varieties the divergent awns are + serviceable by breaking the shocks when the ears are dashed together by + the wind.<a name="NtA_570" href="#Nt_570"><sup>[570]</sup></a> If several + varieties of a plant are grown together, and the seed is indiscriminately + harvested, it is clear that the hardier and more productive kinds will, + by a sort of natural selection, gradually prevail over the others; this + takes place, as Colonel Le Couteur believes,<a name="NtA_571" + href="#Nt_571"><sup>[571]</sup></a> in our wheat-fields, for, as formerly + shown, no variety is quite uniform in character. The same thing, as I am + assured by nurserymen, would take place in our flower-gardens, if the + seed of the different varieties were not separately saved. When the eggs + of the wild and tame duck are hatched together, the young wild ducks + almost invariably perish, from being of smaller size and not getting + their fair share of food.<a name="NtA_572" + href="#Nt_572"><sup>[572]</sup></a></p> + + <p>Facts in sufficient number have now been given showing that natural + selection often checks, but occasionally favours, man's power of + selection. These facts teach us, in addition, a valuable lesson, namely, + that we ought to be extremely cautious in judging what characters are of + importance in a state of nature to animals and plants, which have to + struggle from the hour of their birth to that of their death for + existence,—their existence depending on conditions, about which we + are profoundly ignorant.</p> + +<p class="cenhead"><i>Circumstances favourable to Selection by Man.</i></p> + + <p>The possibility of selection rests on variability, and this, as we + shall see in the following chapters, mainly depends on changed conditions + of life, but is governed by infinitely complex, and, to a great extent, + unknown laws. Domestication, even when long continued, occasionally + causes but a small amount of variability, as in the case of the goose and + turkey. The slight differences, however, which characterise each + individual animal and plant would in most, probably in all cases, suffice + for the production of distinct races through careful and prolonged + selection. We see what selection, though acting on mere individual + differences, can effect when families of cattle, sheep, <!-- Page 234 + --><span class="pagenum"><a name="page234"></a>{234}</span>pigeons, + &c., of the same race, have been separately bred during a number of + years by different men without any wish on their part to modify the + breed. We see the same fact in the difference between hounds bred for + hunting in different districts,<a name="NtA_573" + href="#Nt_573"><sup>[573]</sup></a> and in many other such cases.</p> + + <p>In order that selection should produce any result, it is manifest that + the crossing of distinct races must be prevented; hence facility in + pairing, as with the pigeon, is highly favourable for the work; and + difficulty in pairing, as with cats, prevents the formation of distinct + breeds. On nearly the same principle the cattle of the small island of + Jersey have been improved in their milking qualities "with a rapidity + that could not have been obtained in a widely extended country like + France."<a name="NtA_574" href="#Nt_574"><sup>[574]</sup></a> Although + free crossing is a danger on the one side which every one can see, too + close interbreeding is a hidden danger on the other side. Unfavourable + conditions of life overrule the power of selection. Our improved heavy + breeds of cattle and sheep could not have been formed on mountainous + pastures; nor could dray-horses have been raised on a barren and + inhospitable land, such as the Falkland islands, where even the light + horses of La Plata rapidly decrease in size. Nor could the wool of sheep + have been much increased in length within the Tropics; yet selection has + kept Merino sheep nearly true under diversified and unfavourable + conditions of life. The power of selection is so great, that breeds of + the dog, sheep, and poultry, of the largest and least size, long and + short beaked pigeons, and other breeds with opposite characters, have had + their characteristic qualities augmented, though treated in every way + alike, being exposed to the same climate and fed on the same food. + Selection, however, is either checked or favoured by the effects of use + or habit. Our wonderfully-improved pigs could never have been formed if + they had been forced to search for their own food; the English racehorse + and greyhound could not have been improved up to their present high + standard of excellence without constant training.</p> + + <p>As conspicuous deviations of structure occur rarely, the improvement + of each breed is generally the result, as already <!-- Page 235 --><span + class="pagenum"><a name="page235"></a>{235}</span>remarked, of the + selection of slight individual differences. Hence the closest attention, + the sharpest powers of observation, and indomitable perseverance, are + indispensable. It is, also, highly important that many individuals of the + breed which is to be improved should be raised; for thus there will be a + better chance of the appearance of variations in the right direction, and + individuals varying in an unfavourable manner may be freely rejected or + destroyed. But that a large number of individuals should be raised, it is + necessary that the conditions of life should favour the propagation of + the species. Had the peacock been bred as easily as the fowl, we should + probably ere this have had many distinct races. We see the importance of + a large number of plants, from the fact of nursery gardeners almost + always beating amateurs in the exhibition of new varieties. In 1845 it + was estimated<a name="NtA_575" href="#Nt_575"><sup>[575]</sup></a> that + between 4000 and 5000 pelargoniums were annually raised from seed in + England, yet a decidedly improved variety is rarely obtained. At Messrs. + Carter's grounds, in Essex, where such flowers as the Lobelia, Nemophila, + Mignonette, &c., are grown by the acre for seed, "scarcely a season + passes without some new kinds being raised, or some improvement affected + on old kinds."<a name="NtA_576" href="#Nt_576"><sup>[576]</sup></a> At + Kew, as Mr. Beaton remarks, where many seedlings of common plants are + raised, "you see new forms of Laburnums, Spiræas, and other shrubs."<a + name="NtA_577" href="#Nt_577"><sup>[577]</sup></a> So with animals: + Marshall,<a name="NtA_578" href="#Nt_578"><sup>[578]</sup></a> in + speaking of the sheep in one part of Yorkshire, remarks, "as they belong + to poor people, and are mostly in small lots, they never can be + improved." Lord Rivers, when asked how he succeeded in always having + first-rate greyhounds, answered, "I breed many, and hang many." This, as + another man remarks, "was the secret of his success; and the same will be + found in exhibiting fowls,—successful competitors breed largely, + and keep the best."<a name="NtA_579" + href="#Nt_579"><sup>[579]</sup></a></p> + + <p>It follows from this that the capacity of breeding at an early age and + at short successive intervals, as with pigeons, rabbits, &c., + facilitates selection; for the result is thus soon made visible, and + perseverance in the work is encouraged. It can hardly be <!-- Page 236 + --><span class="pagenum"><a name="page236"></a>{236}</span>accidental + that the great majority of the culinary and agricultural plants which + have yielded numerous races are annuals or biennials, which therefore are + capable of rapid propagation and thus of improvement. Sea-kale, + asparagus, common and Jerusalem artichokes, potatoes, and onions, alone + are perennials. Onions are propagated like annuals, and of the other + plants just specified, none, with the exception of the potato, have + yielded more than one or two varieties. No doubt fruit-trees, which + cannot be propagated quickly by seed, have yielded a host of varieties, + though not permanent races; but these, judging from pre-historic remains, + were produced at a later and more civilised epoch than the races of + culinary and agricultural plants.</p> + + <p>A species may be highly variable, but distinct races will not be + formed, if from any cause selection be not applied. The carp is highly + variable, but it would be extremely difficult to select slight variations + in fishes whilst living in their natural state, and distinct races have + not been formed;<a name="NtA_580" href="#Nt_580"><sup>[580]</sup></a> on + the other hand, a closely allied species, the gold-fish, from being + reared in glass or open vessels, and from having been carefully attended + to by the Chinese, has yielded many races. Neither the bee, which has + been semi-domesticated from an extremely remote period, nor the cochineal + insect, which was cultivated by the aboriginal Mexicans, has yielded + races; and it would be impossible to match the queen-bee with any + particular drone, and most difficult to match cochineal insects. + Silk-moths, on the other hand, have been subjected to rigorous selection, + and have produced a host of races. Cats, which from their nocturnal + habits cannot be selected for breeding, do not, as formerly remarked, + yield distinct races in the same country. The ass in England varies much + in colour and size; but it is an animal of little value, bred by poor + people; consequently there has been no selection, and distinct races have + not been formed. We must not attribute the inferiority of our asses to + climate, for in India they are of even smaller size than in Europe. But + when selection is brought to bear on the ass, all is changed. Near + Cordova, as I am informed (Feb. 1860) by Mr. W. E. Webb, C.E., they are + carefully bred, as much as 200<i>l.</i> having been paid for a stallion + ass, <!-- Page 237 --><span class="pagenum"><a + name="page237"></a>{237}</span>and they have been immensely improved. In + Kentucky, asses have been imported (for breeding mules) from Spain, + Malta, and France; these "seldom averaged more than fourteen hands high; + but the Kentuckians, by great care, have raised them up to fifteen hands, + and sometimes even to sixteen. The prices paid for these splendid + animals, for such they really are, will prove how much they are in + request. One male, of great celebrity, was sold for upwards of one + thousand pounds sterling." These choice asses are sent to cattle-shows, + one day being given to their exhibition.<a name="NtA_581" + href="#Nt_581"><sup>[581]</sup></a></p> + + <p>Analogous facts have been observed with plants: the nutmeg-tree in the + Malay archipelago is highly variable, but there has been no selection, + and there are no distinct races.<a name="NtA_582" + href="#Nt_582"><sup>[582]</sup></a> The common mignonette (<i>Reseda + odorata</i>), from bearing inconspicuous flowers, valued solely for their + fragrance, "remains in the same unimproved condition as when first + introduced."<a name="NtA_583" href="#Nt_583"><sup>[583]</sup></a> Our + common forest-trees are very variable, as may be seen in every extensive + nursery-ground; but as they are not valued like fruit-trees, and as they + seed late in life, no selection has been applied to them; consequently, + as Mr. Patrick Matthews remarks,<a name="NtA_584" + href="#Nt_584"><sup>[584]</sup></a> they have not yielded distinct races, + leafing at different periods, growing to different sizes, and producing + timber fit for different purposes. We have gained only some fanciful and + semi-monstrous varieties, which no doubt appeared suddenly as we now see + them.</p> + + <p>Some botanists have argued that plants cannot have so strong a + tendency to vary as is generally supposed, because many species long + grown in botanic gardens, or unintentionally cultivated year after year + mingled with our corn crops, have not produced distinct races; but this + is accounted for by slight variations not having been selected and + propagated. Let a plant which is now grown in a botanic garden, or any + common weed, be cultivated on a large scale, and let a sharp-sighted + gardener look out for each slight variety and sow the seed, and then, if + distinct races are not produced, the argument will be valid.</p> + +<p><!-- Page 238 --><span class="pagenum"><a name="page238"></a>{238}</span></p> + + <p>The importance of selection is likewise shown by considering special + characters. For instance, with most breeds of fowls the form of the comb + and the colour of the plumage have been attended to, and are eminently + characteristic of each race; but in Dorkings, fashion has never demanded + uniformity of comb or colour; and the utmost diversity in these respects + prevails. Rose-combs, double-combs, cup-combs, &c., and colours of + all kinds, may be seen in purely-bred and closely related Dorking fowls, + whilst other points, such as the general form of body, and the presence + of an additional toe, have been attended to, and are invariably present. + It has also been ascertained that colour can be fixed in this breed, as + well as in any other.<a name="NtA_585" + href="#Nt_585"><sup>[585]</sup></a></p> + +<hr class="short" /> + + <p>During the formation or improvement of a breed, its members will + always be found to vary much in those characters to which especial + attention is directed, and of which each slight improvement is eagerly + sought and selected. Thus with short-faced tumbler-pigeons, the shortness + of the beak, shape of head and plumage,—with carriers, the length + of the beak and wattle,—with fantails, the tail and + carriage,—with Spanish fowls, the white face and comb,—with + long-eared rabbits, the length of ear, are all points which are eminently + variable. So it is in every case, and the large price paid for first-rate + animals proves the difficulty of breeding them up to the highest standard + of excellence. This subject has been discussed by fanciers,<a + name="NtA_586" href="#Nt_586"><sup>[586]</sup></a> and the greater prizes + given for highly improved breeds, in comparison with those given for old + breeds which are not now undergoing rapid improvement, has been fully + justified. Nathusius makes<a name="NtA_587" + href="#Nt_587"><sup>[587]</sup></a> a similar remark when discussing the + less uniform character of improved Shorthorn cattle and of the English + horse, in comparison, for example, with the unennobled cattle of Hungary, + or with the horses of the Asiatic steppes. This want of uniformity in the + parts which at the time are undergoing selection, chiefly depends on the + strength of the principle of reversion but it likewise depends to a + certain extent on the continued <!-- Page 239 --><span class="pagenum"><a + name="page239"></a>{239}</span>variability of the parts which have + recently varied. That the same parts do continue varying in the same + manner we must admit, for, if it were not so, there could be no + improvement beyond an early standard of excellence, and we know that such + improvement is not only possible, but is of general occurrence.</p> + + <p>As a consequence of continued variability, and more especially of + reversion, all highly improved races, if neglected or not subjected to + incessant selection, soon degenerate. Youatt gives a curious instance of + this in some cattle formerly kept in Glamorganshire; but in this case the + cattle were not fed with sufficient care. Mr. Baker, in his memoir on the + Horse, sums up: "It must have been observed in the preceding pages that, + whenever there has been neglect, the breed has proportionally + deteriorated."<a name="NtA_588" href="#Nt_588"><sup>[588]</sup></a> If a + considerable number of improved cattle, sheep, or other animals of the + same race, were allowed to breed freely together, with no selection, but + with no change in their condition of life, there can be no doubt that + after a score or hundred generations they would be very far from + excellent of their kind; but, from what we see of the many common races + of dogs, cattle, fowls, pigeons, &c., which without any particular + care have long retained nearly the same character, we have no grounds for + believing that they would altogether depart from their type.</p> + + <p>It is a general belief amongst breeders that characters of all kinds + become fixed by long-continued inheritance. But I have attempted to show + in the fourteenth chapter that this belief apparently resolves itself + into the following proposition, namely, that all characters whatever, + whether recently acquired or ancient, tend to be transmitted, but that + those which have already long withstood all counteracting influences, + will, as a general rule, continue to withstand them, and consequently be + faithfully transmitted.</p> + +<p class="cenhead"><i>Tendency in Man to carry the practice of Selection to an extreme +point.</i></p> + + <p>It is an important principle that in the process of selection man + almost invariably wishes to go to an extreme point. Thus, in useful + qualities, there is no limit to his desire to breed certain <!-- Page 240 + --><span class="pagenum"><a name="page240"></a>{240}</span>horses and + dogs as fleet as possible, and others as strong as possible; certain + kinds of sheep for extreme fineness, and others for extreme length of + wool; and he wishes to produce fruit, grain, tubers, and other useful + parts of plants, as large and excellent as possible. With animals bred + for amusement, the same principle is even more powerful; for fashion, as + we see even in our dress, always runs to extremes. This view has been + expressly admitted by fanciers. Instances were given in the chapters on + the pigeon, but here is another: Mr. Eaton, after describing a + comparatively new variety, namely, the Archangel, remarks, "What fanciers + intend doing with this bird I am at a loss to know, whether they intend + to breed it down to the tumbler's head and beak, or carry it out to the + carrier's head and beak; leaving it as they found it, is not + progressing." Ferguson, speaking of fowls, says, "their peculiarities, + whatever they may be, must necessarily be fully developed: a little + peculiarity forms nought but ugliness, seeing it violates the existing + laws of symmetry." So Mr. Brent, in discussing the merits of the + sub-varieties of the Belgian canary-bird, remarks, "Fanciers always go to + extremes; they do not admire indefinite properties."<a name="NtA_589" + href="#Nt_589"><sup>[589]</sup></a></p> + + <p>This principle, which necessarily leads to divergence of character, + explains the present state of various domestic races. We can thus see how + it is that race-horses and dray-horses, greyhounds and mastiffs, which + are opposed to each other in every character,—how varieties so + distinct as Cochin-China fowls and bantams, or carrier-pigeons with very + long beaks, and tumblers with excessively short beaks, have been derived + from the same stock. As each breed is slowly improved, the inferior + varieties are first neglected and finally lost. In a few cases, by the + aid of old records, or from intermediate varieties still existing in + countries where other fashions have prevailed, we are enabled partially + to trace the graduated changes through which certain breeds have passed. + Selection, whether methodical or unconscious, always tending towards an + extreme point, together with the neglect and slow extinction of the + intermediate and less-valued forms, is the key which unlocks the mystery + how man has produced such wonderful results.</p> + +<p><!-- Page 241 --><span class="pagenum"><a name="page241"></a>{241}</span></p> + + <p>In a few instances selection, guided by utility for a single purpose, + has led to convergence of character. All the improved and different races + of the pig, as Nathusius has well shown,<a name="NtA_590" + href="#Nt_590"><sup>[590]</sup></a> closely approach each other in + character, in their shortened legs and muzzles, their almost hairless, + large, rounded bodies, and small tusks. We see some degree of convergence + in the similar outline of the body in well-bred cattle belonging to + distinct races.<a name="NtA_591" href="#Nt_591"><sup>[591]</sup></a> I + know of no other such cases.</p> + + <p>Continued divergence of character depends on, and is indeed a clear + proof, as previously remarked, of the same parts continuing to vary in + the same direction. The tendency to mere general variability or + plasticity of organisation can certainly be inherited, even from one + parent, as has been shown by Gärtner and Kölreuter, in the production of + varying hybrids from two species, of which one alone was variable. It is + in itself probable that, when an organ has varied in any manner, it will + again vary in the same manner, if the conditions which first caused the + being to vary remain, as far as can be judged, the same. This is either + tacitly or expressly admitted by all horticulturists: if a gardener + observes one or two additional petals in a flower, he feels confident + that in a few generations he will be able to raise a double flower, + crowded with petals. Some of the seedlings from the weeping Moccas oak + were so prostrate that they only crawled along the ground. A seedling + from the fastigate or upright Irish yew is described as differing greatly + from the parent-form "by the exaggeration of the fastigate habit of its + branches."<a name="NtA_592" href="#Nt_592"><sup>[592]</sup></a> Mr. + Sheriff, who has been more successful than any other man in raising new + kinds of wheat, remarks, "A good variety may safely be regarded as the + forerunner of a better one."<a name="NtA_593" + href="#Nt_593"><sup>[593]</sup></a> A great rose-grower, Mr. Rivers, has + made the same remark with respect to roses. Sageret,<a name="NtA_594" + href="#Nt_594"><sup>[594]</sup></a> who had large experience, in speaking + of the future progress of fruit-trees, observes that the most important + principle is "that the more plants have departed from their original + type, the more they tend to depart from it." There is apparently much + truth in this <!-- Page 242 --><span class="pagenum"><a + name="page242"></a>{242}</span>remark; for we can in no other way + understand the surprising amount of difference between varieties in the + parts or qualities which are valued, whilst other parts retain nearly + their original character.</p> + + <p>The foregoing discussion naturally leads to the question, what is the + limit to the possible amount of variation in any part or quality, and, + consequently, is there any limit to what selection can effect? Will a + race-horse ever be reared fleeter than Eclipse? Can our prize-cattle and + sheep be still further improved? Will a gooseberry ever weigh more than + that produced by "London" in 1852? Will the beet-root in France yield a + greater percentage of sugar? Will future varieties of wheat and other + grain produce heavier crops than our present varieties? These questions + cannot be positively answered; but it is certain that we ought to be + cautious in answering by a negative. In some lines of variation the limit + has probably been reached. Youatt believes that the reduction of bone in + some of our sheep has already been carried so far that it entails great + delicacy of constitution.<a name="NtA_595" + href="#Nt_595"><sup>[595]</sup></a> But seeing the great improvement + within recent times in our cattle and sheep, and especially in our pigs; + seeing the wonderful increase in weight in our poultry of all kinds + during the last few years; he would be a bold man who would assert that + perfection has been reached. Eclipse perhaps may never be beaten until + all our race-horses have been rendered swifter, through the selection of + the best horses during many generations; and then the old Eclipse may + possibly be eclipsed; but, as Mr. Wallace has remarked, there must be an + ultimate limit to the fleetness of every animal, whether under nature or + domestication; and with the horse this limit has perhaps been reached. + Until our fields are better manured, it may be impossible for a new + variety of wheat to yield a heavier crop. But in many cases those who are + best qualified to judge do not believe that the extreme point has as yet + been reached even with respect to characters which have already been + carried to a high standard of perfection. For instance, the short-faced + tumbler-pigeon has been greatly modified; nevertheless, according to Mr. + Eaton,<a name="NtA_596" href="#Nt_596"><sup>[596]</sup></a> "the field is + still as open for fresh competitors as it was one hundred years ago." + Over and over again it has been said that <!-- Page 243 --><span + class="pagenum"><a name="page243"></a>{243}</span>perfection had been + attained with our flowers, but a higher standard has soon been reached. + Hardly any fruit has been more improved than the strawberry, yet a great + authority remarks,<a name="NtA_597" href="#Nt_597"><sup>[597]</sup></a> + "it must not be concealed that we are far from the extreme limits at + which we may arrive."</p> + + <p>Time is an important element in the formation of our domestic races, + as it <span class="correction" title="Original reads `permitts'." + >permits</span> innumerable individuals to be born, and these when + exposed to diversified conditions are rendered variable. Methodical + selection has been occasionally practised from an ancient period to the + present day, even by semi-civilised people, and during former times will + have produced some effect. Unconscious selection will have been still + more effective; for during a lengthened period the more valuable + individual animals will occasionally have been saved, and the less + valuable neglected. In the course, also, of time, different varieties, + especially in the less civilised countries, will have been more or less + modified through natural selection. It is generally believed, though on + this head we have little or no evidence, that new characters in time + become fixed; and after having long remained fixed it seems possible that + under new conditions they might again be rendered variable.</p> + + <p>How great the lapse of time has been since man first domesticated + animals and cultivated plants, we begin dimly to see. When the + lake-buildings of Switzerland were inhabited during the Neolithic period, + several animals were already domesticated and various plants cultivated. + If we may judge from what we now see of the habits of savages, it is + probable that the men of the earlier Stone period—when many great + quadrupeds were living which are now extinct, and when the face of the + country was widely different from what it now is—possessed at least + some few domesticated animals, although their remains have not as yet + been discovered. If the science of language can be trusted, the art of + ploughing and sowing the land was followed, and the chief animals had + been already domesticated, at an epoch so immensely remote, that the + Sanskrit, Greek, Latin, Gothic, Celtic, and Sclavonic languages had not + as yet diverged from their common parent-tongue.<a name="NtA_598" + href="#Nt_598"><sup>[598]</sup></a></p> + +<p><!-- Page 244 --><span class="pagenum"><a name="page244"></a>{244}</span></p> + + <p>It is scarcely possible to overrate the effects of selection + occasionally carried on in various ways and places during thousands of + generations. All that we know, and, in a still stronger degree, all that + we do not know,<a name="NtA_599" href="#Nt_599"><sup>[599]</sup></a> of + the history of the great majority of our breeds, even of our more modern + breeds, agrees with the view that their production, through the action of + unconscious and methodical selection, has been almost insensibly slow. + When a man attends rather more closely than is usual to the breeding of + his animals, he is almost sure to improve them to a slight extent. They + are in consequence valued in his immediate neighbourhood, and are bred by + others; and their characteristic features, whatever these may be, will + then slowly but steadily be increased, sometimes by methodical and almost + always by unconscious selection. At last a strain, deserving to be called + a sub-variety, becomes a little more widely known, receives a local name, + and spreads. The spreading will have been extremely slow during ancient + and less civilised times, but now is rapid. By the time that the new + breed had assumed a somewhat distinct character, its history, hardly + noticed at the time, will have been completely forgotten; for, as Low + remarks,<a name="NtA_600" href="#Nt_600"><sup>[600]</sup></a> "we know + how quickly the memory of such events is effaced."</p> + + <p>As soon as a new breed is thus formed, it is liable through the same + process to break up into new strains and sub-varieties. For different + varieties are suited for, and are valued under, different circumstances. + Fashion changes, but, should a fashion last for even a moderate length of + time, so strong is the principle of inheritance, that some effect will + probably be impressed on the breed. Thus varieties go on increasing in + number, and history shows us how wonderfully they have increased since + the earliest records.<a name="NtA_601" + href="#Nt_601"><sup>[601]</sup></a> As each new variety is produced, the + earlier, intermediate, and less valuable forms will be neglected, and + perish. When a breed, from not being valued, is kept in small numbers, + its extinction almost inevitably follows sooner or later, either from + accidental causes of destruction or from close interbreeding; and this is + an event which, in the case of well-marked breeds, excites attention. The + birth or production of a new domestic race is so slow a process that it + <!-- Page 245 --><span class="pagenum"><a + name="page245"></a>{245}</span>escapes notice; its death or destruction + is comparatively sudden, is often recorded, and when too late sometimes + regretted.</p> + + <p>Several authors have drawn a wide distinction between artificial and + natural races. The latter are more uniform in character, possessing in a + high degree the character of natural species, and are of ancient origin. + They are generally found in less civilised countries, and have probably + been largely modified by natural selection, and only to a small extent by + man's unconscious and methodical selection. They have, also, during a + long period, been directly acted on by the physical conditions of the + countries which they inhabit. The so-called artificial races, on the + other hand, are not so uniform in character; some have a semi-monstrous + character, such as "the wry-legged terriers so useful in + rabbit-shooting,"<a name="NtA_602" href="#Nt_602"><sup>[602]</sup></a> + turnspit dogs, ancon sheep, niata oxen, Polish fowls, fantail-pigeons, + &c.; their characteristic features have generally been acquired + suddenly, though subsequently increased in many cases by careful + selection. Other races, which certainly must be called artificial, for + they have been largely modified by methodical selection and by crossing, + as the English race-horse, terrier-dogs, the English game-cock, Antwerp + carrier-pigeons, &c., nevertheless cannot be said to have an + unnatural appearance; and no distinct line, as it seems to me, can be + drawn between natural and artificial races.</p> + + <p>It is not surprising that domestic races should generally present a + different aspect from natural species. Man selects and propagates + modifications solely for his own use or fancy, and not for the creature's + own good. His attention is struck by strongly marked modifications, which + have appeared suddenly, due to some great disturbing cause in the + organisation. He attends almost exclusively to external characters; and + when he succeeds in modifying internal organs,—when for instance he + reduces the bones and offal, or loads the viscera with fat, or gives + early maturity, &c.,—the chances are strong that he will at the + same time weaken the constitution. On the other hand, when an animal has + to struggle throughout its life with many competitors and enemies, under + circumstances inconceivably complex and liable to change, modifications + of the most varied nature—in the internal organs as well as in + external characters, in the <!-- Page 246 --><span class="pagenum"><a + name="page246"></a>{246}</span>functions and mutual relations of + parts—will be rigorously tested, preserved, or rejected. Natural + selection often checks man's comparatively feeble and capricious attempts + at improvement; and if this were not so, the result of his work, and of + nature's work, would be even still more different. Nevertheless, we must + not overrate the amount of difference between natural species and + domestic races; the most experienced naturalists have often disputed + whether the latter are descended from one or from several aboriginal + stocks, and this clearly shows that there is no palpable difference + between species and races.</p> + + <p>Domestic races propagate their kind far more truly, and endure for + much longer periods, than most naturalists are willing to admit. Breeders + feel no doubt on this head; ask a man who has long reared Shorthorn or + Hereford cattle, Leicester or Southdown sheep, Spanish or Game poultry, + tumbler or carrier-pigeons, whether these races may not have been derived + from common progenitors, and he will probably laugh you to scorn. The + breeder admits that he may hope to produce sheep with finer or longer + wool and with better carcases, or handsomer fowls, or carrier-pigeons + with beaks just perceptibly longer to the practised eye, and thus be + successful at an exhibition. Thus far he will go, but no farther. He does + not reflect on what follows from adding up during a long course of time + many, slight, successive modifications; nor does he reflect on the former + existence of numerous varieties, connecting the links in each divergent + line of descent. He concludes, as was shown in the earlier chapters, that + all the chief breeds to which he has long attended are aboriginal + productions. The systematic naturalist, on the other hand, who generally + knows nothing of the art of breeding, who does not pretend to know how + and when the several domestic races were formed, who cannot have seen the + intermediate gradations, for they do not now exist, nevertheless feels no + doubt that these races are sprung from a single source. But ask him + whether the closely allied natural species which he has studied may not + have descended from a common progenitor, and he in his turn will perhaps + reject the notion with scorn. Thus the naturalist and breeder may + mutually learn a useful lesson from each other.</p> + +<hr class="short" /> + + <p><i>Summary on Selection by Man.</i>—There can be no doubt that + <!-- Page 247 --><span class="pagenum"><a + name="page247"></a>{247}</span>methodical selection has effected and will + effect wonderful results. It was occasionally practised in ancient times, + and is still practised by semi-civilised people. Characters of the + highest importance, and others of trifling value, have been attended to, + and modified. I need not here repeat what has been so often said on the + part which unconscious selection has played: we see its power in the + difference between flocks which have been separately bred, and in the + slow changes, as circumstances have slowly changed, which many animals + have undergone in the same country, or when transported into a foreign + land. We see the combined effects of methodical and unconscious selection + in the great amount of difference between varieties in those parts or + qualities which are valued by man, in comparison with those which are not + valued, and consequently have not been attended to. Natural selection + often determines man's power of selection. We sometimes err in imagining + that characters, which are considered as unimportant by the systematic + naturalist, could not be affected by the struggle for existence, and + therefore be acted on by natural selection; but striking cases have been + given, showing how great an error this is.</p> + + <p>The possibility of selection coming into action rests on variability; + and this is mainly caused, as we shall hereafter see, by changes in the + conditions of life. Selection is sometimes rendered difficult, or even + impossible, by the conditions being opposed to the desired character or + quality. It is sometimes checked by the lessened fertility and weakened + constitution which follow from long-continued close interbreeding. That + methodical selection may be successful, the closest attention and + discernment, combined with unwearied patience, are absolutely necessary; + and these same qualities, though not indispensable, are highly + serviceable in the case of unconscious selection. It is almost necessary + that a large number of individuals should be reared; for thus there will + be a fair chance of variations of the desired nature arising, and every + individual with the slightest blemish or in any degree inferior may be + freely rejected. Hence length of time is an important element of success. + Thus, also, propagation at an early age and at short intervals favours + the work. Facility in pairing animals, or their inhabiting a confined + area, is advantageous as a check to free crossing. Whenever and <!-- Page + 248 --><span class="pagenum"><a name="page248"></a>{248}</span>wherever + selection is not practised, distinct races are not formed. When any one + part of the body or quality is not attended to, it remains either + unchanged or varies in a fluctuating manner, whilst at the same time + other parts and other qualities may become permanently and greatly + modified. But from the tendency to reversion and to continued + variability, those parts or organs which are now undergoing rapid + improvement through selection, are likewise found to vary much. + Consequently highly-bred animals, when neglected, soon degenerate; but we + have no reason to believe that the effects of long-continued selection + would, if the conditions of life remained the same, be soon and + completely lost.</p> + + <p>Man always tends to go to an extreme point in the selection, whether + methodical or unconscious, of all useful and pleasing qualities. This is + an important principle, as it leads to continued divergence, and in some + rare cases to convergence of character. The possibility of continued + divergence rests on the tendency in each part or organ to go on varying + in the same manner in which it has already varied; and that this occurs, + is proved by the steady and gradual improvement of many animals and + plants during lengthened periods. The principle of divergence of + character, combined with the neglect and final extinction of all + previous, less-valued, and intermediate varieties, explains the amount of + difference and the distinctness of our several races. Although we may + have reached the utmost limit to which certain characters can be + modified, yet we are far from having reached, as we have good reason to + believe, the limit in the majority of cases. Finally, from the difference + between selection as carried on by man and by nature, we can understand + how it is that domestic races often, though by no means always, differ in + general aspect from closely allied natural species.</p> + + <p>Throughout this chapter and elsewhere I have spoken of selection as + the paramount power, yet its action absolutely depends on what we in our + ignorance call spontaneous or accidental variability. Let an architect be + compelled to build an edifice with uncut stones, fallen from a precipice. + The shape of each fragment may be called accidental; yet the shape of + each has been determined by the force of gravity, the nature <!-- Page + 249 --><span class="pagenum"><a name="page249"></a>{249}</span>of the + rock, and the slope of the precipice,—events and circumstances, all + of which depend on natural laws; but there is no relation between these + laws and the purpose for which each fragment is used by the builder. In + the same manner the variations of each creature are determined by fixed + and immutable laws; but these bear no relation to the living structure + which is slowly built up through the power of selection, whether this be + natural or artificial selection.</p> + + <p>If our architect succeeded in rearing a noble edifice, using the rough + wedge-shaped fragments for the arches, the longer stones for the lintels, + and so forth, we should admire his skill even in a higher degree than if + he had used stones shaped for the purpose. So it is with selection, + whether applied by man or by nature; for though variability is + indispensably necessary, yet, when we look at some highly complex and + excellently adapted organism, variability sinks to a quite subordinate + position in importance in comparison with selection, in the same manner + as the shape of each fragment used by our supposed architect is + unimportant in comparison with his skill.</p> + +<hr class="full" /> + +<p><!-- Page 250 --><span class="pagenum"><a name="page250"></a>{250}</span></p> + +<h3>CHAPTER XXII.</h3> + +<p class="cenhead">CAUSES OF VARIABILITY.</p> + +<blockquote class="b1n"> + + <p><span class="scac">VARIABILITY DOES NOT NECESSARILY ACCOMPANY + REPRODUCTION</span>—<span class="scac">CAUSES ASSIGNED BY VARIOUS + AUTHORS</span>—<span class="scac">INDIVIDUAL + DIFFERENCES</span>—<span class="scac">VARIABILITY OF EVERY KIND DUE + TO CHANGED CONDITIONS OF LIFE</span>—<span class="scac">ON THE + NATURE OF SUCH CHANGES</span>—<span class="scac">CLIMATE, FOOD, + EXCESS OF NUTRIMENT</span>—<span class="scac">SLIGHT CHANGES + SUFFICIENT</span>—<span class="scac">EFFECTS OF GRAFTING ON THE + VARIABILITY OF SEEDLING-TREES</span>—<span class="scac">DOMESTIC + PRODUCTIONS BECOME HABITUATED TO CHANGED CONDITIONS</span>—<span + class="scac">ON THE ACCUMULATIVE ACTION OF CHANGED + CONDITIONS</span>—<span class="scac">CLOSE INTERBREEDING AND THE + IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE + VARIABILITY</span>—<span class="scac">CROSSING AS A CAUSE OF THE + APPEARANCE OF NEW CHARACTERS</span>—<span class="scac">VARIABILITY + FROM THE COMMINGLING OF CHARACTERS AND FROM REVERSION</span>—<span + class="scac">ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH + EITHER DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE + VARIABILITY.</span></p> + +</blockquote> + + <p>We will now consider, as far as we can, the causes of the almost + universal variability of our domesticated productions. The subject is an + obscure one; but it may be useful to probe our ignorance. Some authors, + for instance Dr. Prosper Lucas, look at variability as a necessary + contingent on reproduction, and as much an aboriginal law, as growth or + inheritance. Others have of late encouraged, perhaps unintentionally, + this view by speaking of inheritance and variability as equal and + antagonistic principles. Pallas maintained, and he has had some + followers, that variability depends exclusively on the crossing of + primordially distinct forms. Other authors attribute the tendency to + variability to an excess of food, and with animals to an excess + relatively to the amount of exercise taken, or again to the effects of a + more genial climate. That these causes are all effective is highly + probable. But we must, I think, take a broader view, and conclude that + organic beings, when subjected during several generations to any change + whatever in their conditions, tend to vary; the kind of variation which + ensues depending in a far higher degree on the nature or constitution of + the being, than on the nature of the changed conditions. <!-- Page 251 + --><span class="pagenum"><a name="page251"></a>{251}</span></p> + + <p>Those authors who believe that it is a law of nature that each + individual should differ in some slight degree from every other, may + maintain, apparently with truth, that this is the fact, not only with all + domesticated animals and cultivated plants, but likewise with all organic + beings in a state of nature. The Laplander by long practice knows and + gives a name to each reindeer, though, as Linnæus remarks, "to + distinguish one from another among such multitudes was beyond my + comprehension, for they were like ants on an ant-hill." In Germany + shepherds have won wagers by recognising each sheep in a flock of a + hundred, which they had never seen until the previous fortnight. This + power of discrimination, however, is as nothing compared to that which + some florists have acquired. Verlot mentions a gardener who could + distinguish 150 kinds of camellia, when not in flower; and it has been + positively asserted that the famous old Dutch florist Voorhelm, who kept + above 1200 varieties of the hyacinth, was hardly ever deceived in knowing + each variety by the bulb alone. Hence we must conclude that the bulbs of + the hyacinth and the branches and leaves of the camellia, though + appearing to an unpractised eye absolutely undistinguishable, yet really + differ.<a name="NtA_603" href="#Nt_603"><sup>[603]</sup></a></p> + + <p>As Linnæus has compared the reindeer in number to ants, I may add that + each ant knows its fellow of the same community. Several times I carried + ants of the same species (<i>Formica rufa</i>) from one ant-hill to + another, inhabited apparently by tens of thousands of ants; but the + strangers were instantly detected and killed. I then put some ants taken + from a very large nest into a bottle strongly perfumed with + assafœtida, and after an interval of twenty-four hours returned + them to their home; they were at first threatened by their fellows, but + were soon recognised and allowed to pass. Hence each ant certainly + recognises, independently of odour, its fellow; and if all the ants of + the same community have not some countersign or watchword, they must + present to each other's senses some distinguishable character.</p> + +<p><!-- Page 252 --><span class="pagenum"><a name="page252"></a>{252}</span></p> + + <p>The dissimilarity of brothers or sisters of the same family, and of + seedlings from the same capsule, may be in part accounted for by the + unequal blending of the characters of the two parents, and by the more or + less complete recovery through reversion of ancestral characters on + either side; but we thus only push the difficulty further back in time, + for what made the parents or their progenitors different? Hence the + belief<a name="NtA_604" href="#Nt_604"><sup>[604]</sup></a> that an + innate tendency to vary exists, independently of external conditions, + seems at first sight probable. But even the seeds nurtured in the same + capsule are not subjected to absolutely uniform conditions, as they draw + their nourishment from different points; and we shall see in a future + chapter that this difference sometimes suffices greatly to affect the + character of the future plant. The less close similarity of the + successive children of the same family in comparison with human twins, + which often resemble each other in external appearance, mental + disposition, and constitution, in so extraordinary a manner, apparently + proves that the state of the parents at the exact period of conception, + or the nature of the subsequent embryonic development, has a direct and + powerful influence on the character of the offspring. Nevertheless, when + we reflect on the <!-- Page 253 --><span class="pagenum"><a + name="page253"></a>{253}</span>individual differences between organic + beings in a state of nature, as shown by every wild animal knowing its + mate; and when we reflect on the infinite diversity of the many varieties + of our domesticated productions, we may well be inclined to exclaim, + though falsely as I believe, that Variability must be looked at as an + ultimate fact, necessarily contingent on reproduction.</p> + + <p>Those authors who adopt this latter view would probably deny that each + separate variation has its own proper exciting cause. Although we can + seldom trace the precise relation between cause and effect, yet the + considerations presently to be given lead to the conclusion that each + modification must have its own distinct cause. When we hear of an infant + born, for instance, with a crooked finger, a misplaced tooth, or other + slight deviation of structure, it is difficult to bring the conviction + home to the mind that such abnormal cases are the result of fixed laws, + and not of what we blindly call accident. Under this point of view the + following case, which has been carefully examined and communicated to me + by Dr. William Ogle, is highly instructive. Two girls, born as twins, and + in all respects extremely alike, had their little fingers on both hands + crooked; and in both children the second bicuspid tooth in the upper jaw, + of the second dentition, was misplaced; for these teeth, instead of + standing in a line with the others, grew from the roof of the mouth + behind the first bicuspids. Neither the parents nor any other member of + the family had exhibited any similar peculiarity. Now, as both these + children were affected in exactly the same manner by both deviations of + structure, the idea of accident is at once excluded; and we are compelled + to admit that there must have existed some precise and sufficient cause + which, if it had occurred a hundred times, would have affected a hundred + children.</p> + + <p>We will now consider the general arguments, which appear to me to have + great weight, in favour of the view that variations of all kinds and + degrees are directly or indirectly caused by the conditions of life to + which each being, and more especially its ancestors, have been + exposed.</p> + + <p>No one doubts that domesticated productions are more variable than + organic beings which have never been removed from their <!-- Page 254 + --><span class="pagenum"><a name="page254"></a>{254}</span>natural + conditions. Monstrosities graduate so insensibly into mere variations + that it is impossible to separate them; and all those who have studied + monstrosities believe that they are far commoner with domesticated than + with wild animals and plants;<a name="NtA_605" + href="#Nt_605"><sup>[605]</sup></a> and in the case of plants, + monstrosities would be equally noticeable in the natural as in the + cultivated state. Under nature, the individuals of the same species are + exposed to nearly uniform conditions, for they are rigorously kept to + their proper places by a host of competing animals and plants; they have, + also, long been habituated to their conditions of life; but it cannot be + said that they are subject to quite uniform conditions, and they are + liable to a certain amount of variation. The circumstances under which + our domestic productions are reared are widely different: they are + protected from competition; they have not only been removed from their + natural conditions and often from their native land, but they are + frequently carried from district to district, where they are treated + differently, so that they never remain during a considerable length of + time exposed to closely similar conditions. In conformity with this, all + our domesticated productions, with the rarest exceptions, vary far more + than natural species. The hive-bee, which feeds itself and follows in + most respects its natural habits of life, is the least variable of all + domesticated animals, and probably the goose is the next least variable; + but even the goose varies more than almost any wild bird, so that it + cannot be affiliated with perfect certainty to any natural species. + Hardly a single plant can be named, which has long been cultivated and + propagated by seed, that is not highly variable; common rye (<i>Secale + cereale</i>) has afforded fewer and less marked varieties than almost any + other cultivated plant;<a name="NtA_606" + href="#Nt_606"><sup>[606]</sup></a> but it may be doubted whether the + variations of this, the least valuable of all our cereals, have been + closely observed.</p> + + <p>Bud-variation, which was fully discussed in a former chapter, shows us + that variability may be quite independent of seminal reproduction, and + likewise of reversion to long-lost ancestral characters. No one will + maintain that the sudden appearance <!-- Page 255 --><span + class="pagenum"><a name="page255"></a>{255}</span>of a moss-rose on a + Provence-rose is a return to a former state, for mossiness of the calyx + has been observed in no natural species; the same argument is applicable + to variegated and laciniated leaves; nor can the appearance of nectarines + on peach-trees be accounted for with any probability on the principle of + reversion. But bud-variations more immediately concern us, as they occur + far more frequently on plants which have been highly cultivated during a + length of time, than on other and less highly cultivated plants; and very + few well-marked instances have been observed with plants growing under + strictly natural conditions. I have given one instance of an ash-tree + growing in a gentleman's pleasure-grounds; and occasionally there may be + seen, on beech and other trees, twigs leafing at a different period from + the other branches. But our forest trees in England can hardly be + considered as living under strictly natural conditions; the seedlings are + raised and protected in nursery-grounds, and must often be transplanted + into places where wild trees of the kind would not naturally grow. It + would be esteemed a prodigy if a dog-rose growing in a hedge produced by + bud-variation a moss-rose, or a wild bullace or wild cherry-tree yielded + a branch bearing fruit of a different shape and colour from the ordinary + fruit. The prodigy would be enhanced if these varying branches were found + capable of propagation, not only by grafts, but sometimes by seed; yet + analogous cases have occurred with many of our highly cultivated trees + and herbs.</p> + + <p>These several considerations alone render it probable that variability + of every kind is directly or indirectly caused by changed conditions of + life. Or, to put the case under another point of view, if it were + possible to expose all the individuals of a species during many + generations to absolutely uniform conditions of life, there would be no + variability.</p> + +<p class="cenhead"><i>On the Nature of the Changes in the Conditions of Life which +induce Variability.</i></p> + + <p>From a remote period to the present day, under climates and + circumstances as different as it is possible to conceive, organic beings + of all kinds, when domesticated or cultivated, have <!-- Page 256 + --><span class="pagenum"><a name="page256"></a>{256}</span>varied. We see + this with the many domestic races of quadrupeds and birds belonging to + different orders, with gold-fish and silkworms, with plants of many + kinds, raised in various quarters of the world. In the deserts of + northern Africa the date-palm has yielded thirty-eight varieties; in the + fertile plains of India it is notorious how many varieties of rice and of + a host of other plants exist; in a single Polynesian island, twenty-four + varieties of the bread-fruit, the same number of the banana, and + twenty-two varieties of the arum, are cultivated by the natives; the + mulberry-tree in India and Europe has yielded many varieties serving as + food for the silkworm; and in China sixty-three varieties of the bamboo + are used for various domestic purposes.<a name="NtA_607" + href="#Nt_607"><sup>[607]</sup></a> These facts alone, and innumerable + others could be added, indicate that a change of almost any kind in the + conditions of life suffices to cause variability—different changes + acting on different organisms.</p> + + <p>Andrew Knight<a name="NtA_608" href="#Nt_608"><sup>[608]</sup></a> + attributed the variation of both animals and plants to a more abundant + supply of nourishment, or to a more favourable climate, than that natural + to the species. A more genial climate, however, is far from necessary; + the kidney-bean, which is often injured by our spring frosts, and + peaches, which require the protection of a wall, have varied much in + England, as has the orange-tree in northern Italy, where it is barely + able to exist.<a name="NtA_609" href="#Nt_609"><sup>[609]</sup></a> Nor + can we overlook the fact, though not immediately connected with our + present subject, that the plants and shells of the arctic regions are + eminently variable.<a name="NtA_610" href="#Nt_610"><sup>[610]</sup></a> + Moreover, it does not appear that a change of climate, whether more or + less genial, is one of the most potent causes of variability; for in + regard to plants Alph. De Candolle, in his 'Géographie <!-- Page 257 + --><span class="pagenum"><a name="page257"></a>{257}</span>Botanique,' + repeatedly shows that the native country of a plant, where in most cases + it has been longest cultivated, is that where it has yielded the greatest + number of varieties.</p> + + <p>It is doubtful whether a change in the nature of the food is a potent + cause of variability. Scarcely any domesticated animal has varied more + than the pigeon or the fowl, but their food, especially that of + highly-bred pigeons, is generally the same. Nor can our cattle and sheep + have been subjected to any great change in this respect. But in all these + cases the food probably is much less varied in kind than that which was + consumed by the species in its natural state.<a name="NtA_611" + href="#Nt_611"><sup>[611]</sup></a></p> + + <p>Of all the causes which induce variability, excess of food, whether or + not changed in nature, is probably the most powerful. This view was held + with regard to plants by Andrew Knight, and is now held by Schleiden, + more especially in reference to the inorganic elements of the food.<a + name="NtA_612" href="#Nt_612"><sup>[612]</sup></a> In order to give a + plant more food it suffices in most cases to grow it separately, and thus + prevent other plants robbing its roots. It is surprising, as I have often + seen, how vigorously our common wild plants flourish when planted by + themselves, though not in highly manured land. Growing plants separately + is, in fact, the first step in cultivation. We see the converse of the + belief that excess of food induces variability in the following statement + by a great raiser of seeds of all kinds.<a name="NtA_613" + href="#Nt_613"><sup>[613]</sup></a> "It is a rule invariably with us, + when we desire to keep a true stock of any one kind of seed, to grow it + on poor land without dung; but when we grow for quantity, we act + contrary, and sometimes have dearly to repent of it."</p> + + <p>In the case of animals the want of a proper amount of exercise, as + Bechstein has remarked, has perhaps played, independently of the direct + effects of the disuse of any particular organ, an important part in + causing variability. We can see in a vague manner that, when the + organised and nutrient fluids of the body are not used during growth, or + by the wear and tear of the tissues, <!-- Page 258 --><span + class="pagenum"><a name="page258"></a>{258}</span>they will be in excess; + and as growth, nutrition, and reproduction are intimately allied + processes, this superfluity might disturb the due and proper action of + the reproductive organs, and consequently affect the character of the + future offspring. But it may be argued that neither an excess of food nor + a superfluity in the organised fluids of the body necessarily induces + variability. The goose and the turkey have been well fed for many + generations, yet have varied very little. Our fruit-trees and culinary + plants, which are so variable, have been cultivated from an ancient + period, and, though they probably still receive more nutriment than in + their natural state, yet they must have received during many generations + nearly the same amount; and it might be thought that they would have + become habituated to the excess. Nevertheless, on the whole, Knight's + view, that excess of food is one of the most potent causes of + variability, appears, as far as I can judge, probable.</p> + + <p>Whether or not our various cultivated plants have received nutriment + in excess, all have been exposed to changes of various kinds. Fruit-trees + are grafted on different stocks, and grown in various soils. The seeds of + culinary and agricultural plants are carried from place to place; and + during the last century the rotation of our crops and the manures used + have been greatly changed.</p> + + <p>Slight changes of treatment often suffice to induce variability. The + simple fact of almost all our cultivated plants and domesticated animals + having varied in all places and at all times, leads to this conclusion. + Seeds taken from common English forest-trees, grown under their native + climate, not highly manured or otherwise artificially treated, yield + seedlings which vary much, as may be seen in every extensive seed-bed. I + have shown in a former chapter what a number of well marked and singular + varieties the thorn (<i>Cratægus <span class="correction" title="Original reads `oxycantha', corrected by errata, page viii." + >oxyacantha</span></i>) has produced; yet this tree has been subjected to + hardly any cultivation. In Staffordshire I carefully examined a large + number of two British plants, namely, <i>Geranium phæum</i> and + <i>Pyrenaicum</i>, which have never been highly cultivated. These plants + had spread spontaneously by seed from a common garden into an open + plantation; and the seedlings varied in almost every single character, + both in their flowers and foliage, to a degree which <!-- Page 259 + --><span class="pagenum"><a name="page259"></a>{259}</span>I have never + seen exceeded; yet they could not have been exposed to any great change + in their conditions.</p> + + <p>With respect to animals, Azara has remarked with much surprise,<a + name="NtA_614" href="#Nt_614"><sup>[614]</sup></a> that, whilst the feral + horses on the Pampas are always of one of three colours, and the cattle + always of a uniform colour, yet these animals, when bred on the + unenclosed estancias, though kept in a state which can hardly be called + domesticated, and apparently exposed to almost identically the same + conditions as when they are feral, nevertheless display a great diversity + of colour. So again in India several species of fresh-water fish are only + so far treated artificially, that they are reared in great tanks; but + this small change is sufficient to induce much variability.<a + name="NtA_615" href="#Nt_615"><sup>[615]</sup></a></p> + + <p>Some facts on the effects of grafting, in regard to the variability of + trees, deserve attention. Cabanis asserts that when certain pears are + grafted on the quince, their seeds yield more varieties than do the seeds + of the same variety of pear when grafted on the wild pear.<a + name="NtA_616" href="#Nt_616"><sup>[616]</sup></a> But as the pear and + quince are distinct species, though so closely related that the one can + be readily grafted and succeeds admirably on the other, the fact of + variability being thus caused is not surprising; we are, however, here + enabled to see the cause, namely, the different nature of the stock with + its roots and the rest of the tree. Several North American varieties of + the plum and peach are well known to reproduce themselves truly by seed; + but Downing asserts,<a name="NtA_617" href="#Nt_617"><sup>[617]</sup></a> + "that when a graft is taken from one of these trees and placed upon + another stock, this grafted tree is found to lose its singular property + of producing the same variety by seed, and becomes like all other worked + trees;"—that is, its seedlings become highly variable. Another case + is worth giving: the Lalande variety of the walnut-tree leafs between + April 20th and May 15th, and its seedlings invariably inherit the same + habit; whilst several other varieties of the walnut leaf in June. Now, if + seedlings are raised from the May-leafing Lalande variety, grafted on + another May-leafing variety, though both stock and graft have the same + early habit of leafing, yet the seedlings leaf at various times, <!-- + Page 260 --><span class="pagenum"><a name="page260"></a>{260}</span>even + as late as the 5th of June.<a name="NtA_618" + href="#Nt_618"><sup>[618]</sup></a> Such facts as these are well fitted + to show, on what obscure and slight causes variability rests.</p> + +<blockquote class="b1n"> + + <p>I may here just allude to the appearance of new and valuable varieties + of fruit-trees and of wheat in woods and waste places, which at first + sight seems a most anomalous circumstance. In France a considerable + number of the best pears have been discovered in woods; and this has + occurred so frequently, that Poiteau asserts that "improved varieties of + our cultivated fruits rarely originate with nurserymen."<a name="NtA_619" + href="#Nt_619"><sup>[619]</sup></a> In England, on the other hand, no + instance of a good pear having been found wild has been recorded; and Mr. + Rivers informs me that he knows of only one instance with apples, namely, + the Bess Poole, which was discovered in a wood in Nottinghamshire. This + difference between the two countries may be in part accounted for by the + more favourable climate of France, but chiefly from the great number of + seedlings which spring up there in the woods. I infer that this is the + case from a remark made by a French gardener,<a name="NtA_620" + href="#Nt_620"><sup>[620]</sup></a> who regards it as a national calamity + that such a number of pear-trees are periodically cut down for firewood, + before they have borne fruit. The new varieties which thus spring up in + the woods, though they cannot have received any excess of nutriment, will + have been exposed to abruptly changed conditions, but whether this is the + cause of their production is very doubtful. These varieties, however, are + probably all descended<a name="NtA_621" + href="#Nt_621"><sup>[621]</sup></a> from old cultivated kinds growing in + adjoining orchards,—a circumstance which will account for their + variability; and out of a vast number of varying trees there will always + be a good chance of the appearance of a valuable kind. In North America, + where fruit-trees frequently spring up in waste places, the Washington + pear was found in a hedge, and the Emperor peach in a wood.<a + name="NtA_622" href="#Nt_622"><sup>[622]</sup></a></p> + + <p>With respect to wheat, some writers have spoken<a name="NtA_623" + href="#Nt_623"><sup>[623]</sup></a> as if it were an ordinary event for + new varieties to be found in waste places; the Fenton wheat was certainly + discovered growing on a pile of basaltic detritus in a quarry, but in + such a situation the plant would probably receive a sufficient amount + <!-- Page 261 --><span class="pagenum"><a + name="page261"></a>{261}</span>of nutriment. The Chidham wheat was raised + from an ear found <i>on</i> a hedge; and Hunter's wheat was discovered + <i>by</i> the roadside in Scotland, but it is not said that this latter + variety grew where it was found.<a name="NtA_624" + href="#Nt_624"><sup>[624]</sup></a></p> + +</blockquote> + + <p>Whether our domestic productions would ever become so completely + habituated to the conditions under which they now live, as to cease + varying, we have no sufficient means for judging. But, in fact, our + domestic productions are never exposed for a great length of time to + uniform conditions, and it is certain that our most anciently cultivated + plants, as well as animals, still go on varying, for all have recently + undergone marked improvement. In some few cases, however, plants have + become habituated to new conditions. Thus Metzger, who cultivated in + Germany during many years numerous varieties of wheat, brought from + different countries,<a name="NtA_625" href="#Nt_625"><sup>[625]</sup></a> + states that some kinds were at first extremely variable, but gradually, + in one instance after an interval of twenty-five years, became constant; + and it does not appear that this resulted from the selection of the more + constant forms.</p> + +<hr class="short" /> + + <p><i>On the Accumulative Action of changed Conditions of + Life.</i>—We have good grounds for believing that the influence of + changed conditions accumulates, so that no effect is produced on a + species until it has been exposed during several generations to continued + cultivation or domestication. Universal experience shows us that when new + flowers are first introduced into our gardens they do not vary; but + ultimately all, with the rarest exceptions, vary to a greater or less + extent. In a few cases the requisite number of generations, as well as + the successive steps in the progress of variation, have been recorded, as + in the often-quoted instance of the Dahlia.<a name="NtA_626" + href="#Nt_626"><sup>[626]</sup></a> After several years' culture the + Zinnia has only lately (1860) begun to vary in any great degree. "In the + first seven or eight years of high cultivation the Swan River daisy + (<i>Brachycome iberidifolia</i>) kept to its original colour; it then + varied into lilac and purple and other minor shades."<a name="NtA_627" + href="#Nt_627"><sup>[627]</sup></a> Analogous facts have been recorded + with the Scotch rose. In discussing the variability of plants several + experienced horticulturists have spoken to the <!-- Page 262 --><span + class="pagenum"><a name="page262"></a>{262}</span>same general effect. + Mr. Salter<a name="NtA_628" href="#Nt_628"><sup>[628]</sup></a> remarks, + "Every one knows that the chief difficulty is in breaking through the + original form and colour of the species, and every one will be on the + look-out for any natural sport, either from seed or branch; that being + once obtained, however trifling the change may be, the result depends + upon himself." M. de Jonghe, who has had so much success in raising new + varieties of pears and strawberries,<a name="NtA_629" + href="#Nt_629"><sup>[629]</sup></a> remarks with respect to the former, + "There is another principle, namely, that the more a type has entered + into a state of variation, the greater is its tendency to continue doing + so; and the more it has varied from the original type, the more it is + disposed to vary still farther." We have, indeed, already discussed this + latter point when treating of the power which man possesses, through + selection, of continually augmenting in the same direction each + modification; for this power depends on continued variability of the same + general kind. The most celebrated horticulturist in France, namely, + Vilmorin,<a name="NtA_630" href="#Nt_630"><sup>[630]</sup></a> even + maintains that, when any particular variation is desired, the first step + is to get the plant to vary in any manner whatever, and to go on + selecting the most variable individuals, even though they vary in the + wrong direction; for the fixed character of the species being once + broken, the desired variation will sooner or later appear.</p> + + <p>As nearly all our animals were domesticated at an extremely remote + epoch, we cannot, of course, say whether they varied quickly or slowly + when first subjected to new conditions. But Dr. Bachman<a name="NtA_631" + href="#Nt_631"><sup>[631]</sup></a> states that he has seen turkeys + raised from the eggs of the wild species lose their metallic tints and + become spotted with white in the third generation. Mr. Yarrell many years + ago informed me that the wild ducks bred on the ponds in St. James's + Park, which had never been crossed, as it is believed, with domestic + ducks, lost their true plumage after a few generations. An excellent + observer,<a name="NtA_632" href="#Nt_632"><sup>[632]</sup></a> who has + often reared birds from the eggs of the wild duck, and who took + precautions <!-- Page 263 --><span class="pagenum"><a + name="page263"></a>{263}</span>that there should be no crossing with + domestic breeds, has given, as previously stated, full details on the + changes which they gradually undergo. He found that he could not breed + these wild ducks true for more than five or six generations, "as they + then proved so much less beautiful. The white collar round the neck of + the mallard became much broader and more irregular, and white feathers + appeared in the ducklings' wings." They increased also in size of body; + their legs became less fine, and they lost their elegant carriage. Fresh + eggs were then procured from wild birds; but again the same result + followed. In these cases of the duck and turkey we see that animals, like + plants, do not depart from their primitive type until they have been + subjected during several generations to domestication. On the other hand, + Mr. Yarrell informed me that the Australian dingos, bred in the + Zoological Gardens, almost invariably produced in the first generation + puppies marked with white and other colours; but these introduced dingos + had probably been procured from the natives, who keep them in a + semi-domesticated state. It is certainly a remarkable fact that changed + conditions should at first produce, as far as we can see, absolutely no + effect; but that they should subsequently cause the character of the + species to change. In the chapter on pangenesis I shall attempt to throw + a little light on this fact.</p> + +<hr class="short" /> + + <p>Returning now to the causes which are supposed to induce variability. + Some authors<a name="NtA_633" href="#Nt_633"><sup>[633]</sup></a> believe + that close interbreeding gives this tendency, and leads to the production + of monstrosities. In the seventeenth chapter some few facts were + advanced, showing that monstrosities are, as it appears, occasionally + thus caused; and there can be no doubt that close interbreeding induces + lessened fertility and a weakened constitution; hence it may lead to + variability: but I have not sufficient evidence on this head. On the + other hand, close interbreeding, if not carried to an injurious extreme, + far from causing variability, tends to fix the character of each + breed.</p> + + <p>It was formerly a common belief, still held by some persons, that the + imagination of the mother affects the child in <!-- Page 264 --><span + class="pagenum"><a name="page264"></a>{264}</span>the womb.<a + name="NtA_634" href="#Nt_634"><sup>[634]</sup></a> This view is evidently + not applicable to the lower animals, which lay unimpregnated eggs, or to + plants. Dr. William Hunter, in the last century, told my father that + during many years every woman in a large London Lying-in Hospital was + asked before her confinement whether anything had specially affected her + mind, and the answer was written down; and it so happened that in no one + instance could a coincidence be detected between the woman's answer and + any abnormal structure; but when she knew the nature of the structure, + she frequently suggested some fresh cause. The belief in the power of the + mother's imagination may perhaps have arisen from the children of a + second marriage resembling the previous father, as certainly sometimes + occurs, in accordance with the facts given in the eleventh chapter.</p> + +<hr class="short" /> + + <p><i>Crossing as a Cause of Variability.</i>—In an early part of + this chapter it was stated that Pallas<a name="NtA_635" + href="#Nt_635"><sup>[635]</sup></a> and a few other naturalists maintain + that variability is wholly due to crossing. If this means that new + characters never spontaneously appear in our domestic races, but that + they are all directly derived from certain aboriginal species, the + doctrine is little less than absurd; for it implies that animals like + Italian greyhounds, pug-dogs, bull-dogs, pouter and fantail pigeons, + &c., were able to exist in a state of nature. But the doctrine may + mean something widely different, namely, that the crossing of distinct + species is the sole cause of the first appearance of new characters, and + that without this aid man could not have formed his various breeds. As, + however, new characters have appeared in certain cases by bud-variation, + we may conclude with certainty that crossing is not necessary for + variability. It is, moreover, almost certain that the breeds of various + animals, such as of the rabbit, pigeon, duck, &c., and the varieties + of several plants, are the modified descendants of a single wild species. + Nevertheless, it is probable that the crossing of two forms, when one or + both have long been domesticated or cultivated, adds to the variability + of the offspring, independently of the commingling of the characters + derived from the two parent-forms; and this implies <!-- Page 265 + --><span class="pagenum"><a name="page265"></a>{265}</span>that new + characters actually arise. But we must not forget the facts advanced in + the thirteenth chapter, which clearly prove that the act of crossing + often leads to the reappearance or reversion of long-lost characters; and + in most cases it would be impossible to distinguish between the + reappearance of ancient characters and the first appearance of new + characters. Practically, whether new or old, they would be new to the + breed in which they reappeared.</p> + +<blockquote class="b1n"> + + <p>Gärtner declares,<a name="NtA_636" href="#Nt_636"><sup>[636]</sup></a> + and his experience is of the highest value on such a point, that, when he + crossed native plants which had not been cultivated, he never once saw in + the offspring any new character; but that from the odd manner in which + the characters derived from the parents were combined, they sometimes + appeared as if new. When, on the other hand, he crossed cultivated + plants, he admits that new characters occasionally appeared, but he is + strongly inclined to attribute their appearance to ordinary variability, + not in any way to the cross. An opposite conclusion, however, appears to + me the more probable. According to Kölreuter, hybrids in the genus + Mirabilis vary almost infinitely, and he describes new and singular + characters in the form of the seeds, in the colour of the anthers, in the + cotyledons being of immense size, in new and highly peculiar odours, in + the flowers expanding early in the season, and in their closing at night. + With respect to one lot of these hybrids, he remarks that they presented + characters exactly the reverse of what might have been expected from + their parentage.<a name="NtA_637" href="#Nt_637"><sup>[637]</sup></a></p> + + <p>Prof. Lecoq<a name="NtA_638" href="#Nt_638"><sup>[638]</sup></a> + speaks strongly to the same effect in regard to this same genus, and + asserts that many of the hybrids from <i>Mirabilis jalapa</i> and + <i>multiflora</i> might easily be mistaken for distinct species, and adds + that they differed in a greater degree, than the other species of the + genus, from <i>M. jalapa</i>. Herbert, also, has described<a + name="NtA_639" href="#Nt_639"><sup>[639]</sup></a> the offspring from a + hybrid Rhododendron as being "as <i>unlike all others</i> in foliage, as + if they had been a separate species." The common experience of + floriculturists proves that the crossing and recrossing of distinct but + allied plants, such as the species of Petunia, Calceolaria, Fuchsia, + Verbena, &c., induces excessive variability; hence the appearance of + quite new characters is probable. M. Carrière<a name="NtA_640" + href="#Nt_640"><sup>[640]</sup></a> has lately discussed this subject: he + states that <i>Erythrina cristagalli</i> had been multiplied by seed for + many years, but had not yielded any varieties: it was then crossed with + the allied <i>E. herbacea</i>, and "the resistance was now overcome, and + varieties were produced with flowers of extremely different size, form, + and colour."</p> + + <p>From the general and apparently well-founded belief that the crossing + <!-- Page 266 --><span class="pagenum"><a + name="page266"></a>{266}</span>of distinct species, besides commingling + their characters, adds greatly to their variability, it has probably + arisen that some botanists have gone so far as to maintain<a + name="NtA_641" href="#Nt_641"><sup>[641]</sup></a> that, when a genus + includes only a single species, this when cultivated never varies. The + proposition made so broadly cannot be admitted; but it is probably true + that the variability of cultivated monotypic genera is much less than + that of genera including numerous species, and this quite independently + of the effects of crossing. I have stated in my 'Origin of Species,' and + in a future work shall more fully show, that the species belonging to + small genera generally yield a less number of varieties in a state of + nature than those belonging to large genera. Hence the species of small + genera would, it is probable, produce fewer varieties under cultivation + than the already variable species of larger genera.</p> + + <p>Although we have not at present sufficient evidence that the crossing + of species, which have never been cultivated, leads to the appearance of + new characters, this apparently does occur with species which have been + already rendered in some degree variable through cultivation. Hence + crossing, like any other change in the conditions of life, seems to be an + element, probably a potent one, in causing variability. But we seldom + have the means of distinguishing, as previously remarked, between the + appearance of really new characters and the reappearance of long-lost + characters, evoked through the act of crossing. I will give an instance + of the difficulty in distinguishing such cases. The species of Datura may + be divided into two sections, those having white flowers with green + stems, and those having purple flowers with brown stems: now Naudin<a + name="NtA_642" href="#Nt_642"><sup>[642]</sup></a> crossed <i>Datura + lævis</i> and <i>ferox</i>, both of which belong to the white section, + and raised from them 205 hybrids. Of these hybrids, every one had brown + stems and bore purple flowers; so that they resembled the species of the + other section of the genus, and not their own two parents. Naudin was so + much astonished at this fact, that he was led carefully to observe both + parent-species, and he discovered that the pure seedlings of <i>D. + ferox</i>, immediately after germination, had dark purple stems, + extending from the young roots up to the cotyledons, and that this tint + remained ever afterwards as a ring round the base of the stem of the + plant when old. Now I have shown in the thirteenth chapter that the + retention or exaggeration of an early character is so intimately related + to reversion, that it evidently comes under the same principle. Hence + probably we ought to look at the purple flowers and brown stems of these + hybrids, not as new characters due to variability, but as a return to the + former state of some ancient progenitor.</p> + + <p>Independently of the appearance of new characters from crossing, a few + words may be added to what has been said in former chapters on the + unequal combination and transmission of the characters proper to the two + parent-forms. When two species or races are crossed, the offspring of + <!-- Page 267 --><span class="pagenum"><a + name="page267"></a>{267}</span>the first generation are generally + uniform, but subsequently they display an almost infinite diversity of + character. He who wishes, says Kölreuter,<a name="NtA_643" + href="#Nt_643"><sup>[643]</sup></a> to obtain an endless number of + varieties from hybrids should cross and recross them. There is also much + variability when hybrids or mongrels are reduced or absorbed by repeated + crosses with either pure parent-form; and a still higher degree of + variability when three distinct species, and most of all when four + species, are blended together by successive crosses. Beyond this point + Gärtner,<a name="NtA_644" href="#Nt_644"><sup>[644]</sup></a> on whose + authority the foregoing statements are made, never succeeded in effecting + a union; but Max Wichura<a name="NtA_645" + href="#Nt_645"><sup>[645]</sup></a> united six distinct species of + willows into a single hybrid. The sex of the parent-species affects in an + inexplicable manner the degree of variability of hybrids; for Gärtner<a + name="NtA_646" href="#Nt_646"><sup>[646]</sup></a> repeatedly found that + when a hybrid was used as the father, and either one of the pure + parent-species, or a third species, was used as the mother, the offspring + were more variable than when the same hybrid was used as the mother, and + either pure parent or the same third species as the father: thus + seedlings from <i>Dianthus barbatus</i> crossed by the hybrid <i>D. + chinensi-barbatus</i> were more variable than those raised from this + latter hybrid fertilised by the pure <i>D. barbatus</i>. Max Wichura<a + name="NtA_647" href="#Nt_647"><sup>[647]</sup></a> insists strongly on an + analogous result with his hybrid willows. Again Gärtner<a name="NtA_648" + href="#Nt_648"><sup>[648]</sup></a> asserts that the degree of + variability sometimes differs in hybrids raised from reciprocal crosses + between the same two species; and here the sole difference is, that the + one species is first used as the father and then as the mother. On the + whole we see that, independently of the appearance of new characters, the + variability of successive crossed generations is extremely complex, + partly from the offspring partaking unequally of the characters of the + two parent-forms, and more especially from their unequal tendency to + revert to these same characters or to those of more ancient + progenitors.</p> + +</blockquote> + +<hr class="short" /> + + <p><i>On the Manner and on the Period of Action of the Causes which + induce Variability.</i>—This is an extremely obscure subject, and + we need here only briefly consider, firstly, whether inherited variations + are caused by the organisation being directly acted on, or indirectly + through the reproductive system; and secondly, at what period of life or + growth they are primarily caused. We shall see in the two following + chapters that various agencies, such as an abundant supply of food, + exposure to a different climate, increased use or disuse of parts, + &c., prolonged during several generations, certainly modify either + the whole organisation or certain organs. This direct action of changed + conditions perhaps comes into play much more frequently than can be + proved, and it is at least clear that in all cases of <!-- Page 268 + --><span class="pagenum"><a name="page268"></a>{268}</span>bud-variation + the action cannot have been through the reproductive system.</p> + +<blockquote class="b1n"> + + <p>With respect to the part which the reproductive system takes in + causing variability, we have seen in the eighteenth chapter that even + slight changes in the conditions of life have a remarkable power in + causing a greater or less degree of sterility. Hence it seems not + improbable that being generated though a system so easily affected should + themselves be affected, or should fail to inherit, or inherit in excess, + characters proper to their parents. We know that certain groups of + organic beings, but with exceptions in each group, have their + reproductive systems much more easily affected by changed conditions than + other groups; for instance, carnivorous birds more readily than + carnivorous mammals, and parrots more readily than pigeons; and this fact + harmonizes with the apparently capricious manner and degree in which + various groups of animals and plants vary under domestication.</p> + + <p>Kölreuter<a name="NtA_649" href="#Nt_649"><sup>[649]</sup></a> was + struck with the parallelism between the excessive variability of hybrids + when crossed and recrossed in various ways,—these hybrids having + their reproductive powers more or less affected,—and the + variability of anciently cultivated plants. Max Wichura<a name="NtA_650" + href="#Nt_650"><sup>[650]</sup></a> has gone one step farther, and shows + that with many of our highly cultivated plants, such as the hyacinth, + tulip, auricula, snapdragon, potato, cabbage, &c., which there is no + reason to believe have been hybridized, the anthers contain many + irregular pollen-grains, in the same state as in hybrids. He finds also + in certain wild forms, the same coincidence between the state of the + pollen and a high degree of variability, as in many species of Rubus; but + in <i>R. cæsius</i> and <i>idæus</i>, which are not highly variable + species, the pollen is sound. It is also notorious that many cultivated + plants, such as the banana, pine-apple, breadfruit, and others previously + mentioned, have their reproductive organs so seriously affected as to be + generally quite sterile; and when they do yield seed, the seedlings, + judging from the large number of cultivated races which exist, must be + variable in an extreme degree. These facts indicate that there is some + relation between the state of the reproductive organs and a tendency to + variability; but we must not conclude that the relation is strict. + Although many of our highly cultivated plants may have their pollen in a + deteriorated condition, yet, as we have previously seen, they yield more + seed, and our anciently domesticated animals are more prolific, than the + corresponding species in a state of nature. The peacock is almost the + only bird which is believed to be less fertile under domestication than + in its native state, and it has varied in a remarkably small degree. From + these considerations it would seem that changes in the conditions of life + lead either to sterility or to variability, or to both; and not that + sterility induces variability. On the whole it is probable that any cause + affecting the organs of reproduction would likewise affect their + product,—that is, the offspring thus generated.</p> + +<p><!-- Page 269 --><span class="pagenum"><a name="page269"></a>{269}</span></p> + + <p>The period of life at which the causes that induce variability act, is + another obscure subject, which has been discussed by various authors.<a + name="NtA_651" href="#Nt_651"><sup>[651]</sup></a> In some of the cases, + to be given in the following chapter, of modifications from the direct + action of changed conditions, which are inherited, there can be no doubt + that the causes have acted on the mature or nearly mature animal. On the + other hand, monstrosities, which cannot be distinctly separated from + lesser variations, are often caused by the embryo being injured whilst in + the mother's womb or in the egg. Thus I. Geoffroy St. Hilaire<a + name="NtA_652" href="#Nt_652"><sup>[652]</sup></a> asserts that poor + women who work hard during their pregnancy, and the mothers of + illegitimate children troubled in their minds and forced to conceal their + state, are far more liable to give birth to monsters than women in easy + circumstances. The eggs of the fowl when placed upright or otherwise + treated unnaturally frequently produce monstrous chickens. It would, + however, appear that complex monstrosities are induced more frequently + during a rather late than during a very early period of embryonic life; + but this may partly result from some one part, which has been injured + during an early period, affecting by its abnormal growth other parts + subsequently developed; and this would be less likely to occur with parts + injured at a later period.<a name="NtA_653" + href="#Nt_653"><sup>[653]</sup></a> When any part or organ becomes + monstrous through abortion, a rudiment is generally left, and this + likewise indicates that its development had already commenced.</p> + + <p>Insects sometimes have their antennæ or legs in a monstrous condition, + and yet the larvæ from which they are metamorphosed do not possess either + antennæ or legs; and in those cases, as Quatrefages<a name="NtA_654" + href="#Nt_654"><sup>[654]</sup></a> believes, we are enabled to see the + precise period at which the normal progress of development has been + troubled. But the nature of the food given to a caterpillar sometimes + affects the colours of the moth, without the caterpillar itself being + affected; therefore it seems possible that other characters in the mature + insect might be indirectly modified through the larvæ. There is no reason + to suppose that organs which have been rendered monstrous have always + been acted on during their development; the cause may have acted on the + organisation at a much earlier stage. It is even probable that either the + male or female sexual elements, or both, before their union, may be + affected in such a manner as to lead to modifications in organs developed + at a late period of life; in nearly the same manner as a child may + inherit from his father a disease which does not appear until old + age.</p> + + <p>In accordance with the facts above given, which prove that in many + cases a close relation exists between variability and the sterility + following from changed conditions, we may conclude that the exciting + cause often acts at the earliest possible period, namely, on the sexual + elements, before impregnation has taken place. That an affection of the + female sexual element may induce variability we may likewise infer as + probable from the occurrence of bud-variations; for a bud seems to be the + analogue of an ovule. But the male element is apparently much oftener + affected by changed <!-- Page 270 --><span class="pagenum"><a + name="page270"></a>{270}</span>conditions, at least in a visible manner, + than the female element or ovule; and we know from Gärtner's and + Wichura's statements that a hybrid used as the father and crossed with a + pure species gives a greater degree of variability to the offspring, than + does the same hybrid when used as the mother. Lastly, it is certain that + variability may be transmitted through either sexual element, whether or + not originally excited in them, for Kölreuter and Gärtner<a + name="NtA_655" href="#Nt_655"><sup>[655]</sup></a> found that when two + species were crossed, if either one was variable, the offspring were + rendered variable.</p> + +</blockquote> + +<hr class="short" /> + + <p><i>Summary.</i>—From the facts given in this chapter, we may + conclude that the variability of organic beings under domestication, + although so general, is not an inevitable contingent on growth and + reproduction, but results from the conditions to which the parents have + been exposed. Changes of any kind in the conditions of life, even + extremely slight changes, often suffice to cause variability. Excess of + nutriment is perhaps the most efficient single exciting cause. Animals + and plants continue to be variable for an immense period after their + first domestication; but the conditions to which they are exposed never + long remain quite constant. In the course of time they can be habituated + to certain changes, so as to become less variable; and it is possible + that when first domesticated they may have been even more variable than + at present. There is good evidence that the power of changed conditions + accumulates; so that two, three, or more generations must be exposed to + new conditions before any effect is visible. The crossing of distinct + forms, which have already become variable, increases in the offspring the + tendency to further variability, by the unequal commingling of the + characters of the two parents, by the reappearance of long-lost + characters, and by the appearance of absolutely new characters. Some + variations are induced by the direct action of the surrounding conditions + on the whole organisation, or on certain parts alone, and other + variations are induced indirectly through the reproductive system being + affected in the same manner as is so common with organic beings when + removed from their natural conditions. The causes which induce + variability act on the mature organism, on the embryo, and, as we have + good reason to believe, on both sexual elements before impregnation has + been effected.</p> + +<hr class="full" /> + +<p><!-- Page 271 --><span class="pagenum"><a name="page271"></a>{271}</span></p> + +<h3>CHAPTER XXIII.</h3> + +<p class="cenhead">DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS +OF LIFE.</p> + +<blockquote class="b1n"> + + <p><span class="scac">SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE + ACTION OF CHANGED CONDITIONS IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND IN + THE STATE OF THE TISSUES</span>—<span class="scac">LOCAL + DISEASES</span>—<span class="scac">CONSPICUOUS MODIFICATIONS FROM + CHANGED CLIMATE OR FOOD, ETC.</span>—<span class="scac">PLUMAGE OF + BIRDS AFFECTED BY PECULIAR NUTRIMENT, AND BY THE INOCULATION OF + POISON</span>—<span class="scac">LAND-SHELLS</span>—<span + class="scac">MODIFICATIONS OF ORGANIC BEINGS IN A STATE OF NATURE THROUGH + THE DEFINITE ACTION OF EXTERNAL CONDITIONS</span>—<span + class="scac">COMPARISON OF AMERICAN AND EUROPEAN TREES</span>—<span + class="scac">GALLS</span>—<span class="scac">EFFECTS OF PARASITIC + FUNGI</span>—<span class="scac">CONSIDERATIONS OPPOSED TO THE + BELIEF IN THE POTENT INFLUENCE OF CHANGED EXTERNAL + CONDITIONS</span>—<span class="scac">PARALLEL SERIES OF + VARIETIES</span>—<span class="scac">AMOUNT OF VARIATION DOES NOT + CORRESPOND WITH THE DEGREE OF CHANGE IN THE CONDITIONS</span>—<span + class="scac">BUD-VARIATION</span>—<span class="scac">MONSTROSITIES + PRODUCED BY UNNATURAL TREATMENT</span>—<span + class="scac">SUMMARY.</span></p> + +</blockquote> + + <p>If we ask ourselves why this or that character has been modified under + domestication, we are, in most cases lost in utter darkness. Many + naturalists, especially of the French school, attribute every + modification to the "monde ambiant," that is, to changed climate, with + all its diversities of heat and cold, dampness and dryness, light and + electricity, to the nature of the soil, and to varied kinds and amount of + food. By the term definite action, as used in this chapter, I mean an + action of such a nature that, when many individuals of the same variety + are exposed during several generations to any change in their physical + conditions of life, all, or nearly all the individuals, are modified in + the same manner. A new sub-variety would thus be produced without the aid + of selection.</p> + + <p>I do not include under the term of definite action the effects of + habit or of the increased use and disuse of various organs. Modifications + of this nature, no doubt, are definitely caused by the conditions to + which the beings are subjected; but they depend much less on the nature + of the conditions than on the laws of growth; hence they are included + under a distinct head in the <!-- Page 272 --><span class="pagenum"><a + name="page272"></a>{272}</span>following chapter. We know, however, far + too little of the causes and laws of variation to make a sound + classification. The direct action of the conditions of life, whether + leading to definite or indefinite results, is a totally distinct + consideration from the effects of natural selection; for natural + selection depends on the survival under various and complex circumstances + of the best-fitted individuals, but has no relation whatever to the + primary cause of any modification of structure.</p> + + <p>I will first give in detail all the facts which I have been able to + collect, rendering it probable that climate, food, &c., have acted so + definitely and powerfully on the organisation of our domesticated + productions, that they have sufficed to form new sub-varieties or races, + without the aid of selection by man or of natural selection. I will then + give the facts and considerations opposed to this conclusion, and finally + we will weigh, as fairly as we can, the evidence on both sides.</p> + + <p>When we reflect that distinct races of almost all our domesticated + animals exist in each kingdom of Europe, and formerly even in each + district of England, we are at first strongly inclined to attribute their + origin to the definite action of the physical conditions of each country; + and this has been the conclusion of many authors. But we should bear in + mind that man annually has to choose which animals shall be preserved for + breeding, and which shall be slaughtered. We have also seen that both + methodical and unconscious selection were formerly practised, and are now + occasionally practised by the most barbarous races, to a much greater + extent than might have been anticipated. Hence it is very difficult to + judge how far the difference in conditions between, for instance, the + several districts in England, could have sufficed without the aid of + selection to modify the breeds which have been reared in each. It may be + argued that, as numerous wild animals and plants have ranged during many + ages throughout Great Britain, and still retain the same character, the + difference in conditions between the several districts could not have + modified in so marked a manner the various native races of cattle, sheep, + pigs, and horses. The same difficulty of distinguishing between selection + and the definite effects of the conditions of life, is encountered in a + still higher degree when we compare closely allied natural <!-- Page 273 + --><span class="pagenum"><a name="page273"></a>{273}</span>forms, + inhabiting two countries, such as North America and Europe, which do not + differ greatly in climate, nature of soil, &c., for in this case + natural selection will inevitably and rigorously have acted during a long + succession of ages.</p> + +<blockquote class="b1n"> + + <p>From the importance of the difficulty just alluded to, it will be + advisable to give as large a body of facts as possible, showing that + extremely slight differences in treatment, either in different parts of + the same country, or during different seasons, certainly cause an + appreciable effect, at least on varieties which are already in an + unstable condition. Ornamental flowers are good for this purpose, as they + are highly variable, and are carefully observed. All floriculturists are + unanimous that certain varieties are affected by very slight differences + in the nature of the artificial compost in which they are grown, and by + the natural soil of the district, and by the season. Thus, a skilful + judge, in writing on Carnations and Picotees,<a name="NtA_656" + href="#Nt_656"><sup>[656]</sup></a> asks "where can Admiral Curzon be + seen possessing the colour, size, and strength which it has in + Derbyshire? Where can Flora's Garland be found equal to those at Slough? + Where do high-coloured flowers revel better than at Woolwich and + Birmingham? Yet in no two of these districts do the same varieties attain + an equal degree of excellence, although each may be receiving the + attention of the most skilful cultivators." The same writer then + recommends every cultivator to keep five different kinds of soil and + manure, "and to endeavour to suit the respective appetites of the plants + you are dealing with, for without such attention all hope of general + success will be vain." So it is with the Dahlia:<a name="NtA_657" + href="#Nt_657"><sup>[657]</sup></a> the Lady Cooper rarely succeeds near + London, but does admirably in other districts; the reverse holds good + with other varieties; and again, there are others which succeed equally + well in various situations. A skilful gardener<a name="NtA_658" + href="#Nt_658"><sup>[658]</sup></a> states that he procured cuttings of + an old and well-known variety (pulchella) of Verbena, which from having + been propagated in a different situation presented a slightly different + shade of colour; the two varieties were afterwards multiplied by + cuttings, being carefully kept distinct; but in the second year they + could hardly be distinguished, and in the third year no one could + distinguish them.</p> + + <p>The nature of the season has an especial influence on certain + varieties of the Dahlia: in 1841 two varieties were pre-eminently good, + and the next year these same two were pre-eminently bad. A famous + amateur<a name="NtA_659" href="#Nt_659"><sup>[659]</sup></a> asserts that + in 1861 many varieties of the Rose came so untrue in character, "that it + was hardly possible to recognise them, and the thought was not seldom + entertained that the grower had lost his tally." The same amateur<a + name="NtA_660" href="#Nt_660"><sup>[660]</sup></a> states that in 1862 + two-thirds of his Auriculas produced central trusses of flowers, and + these are remarkable from not keeping true; <!-- Page 274 --><span + class="pagenum"><a name="page274"></a>{274}</span>and he adds that in + some seasons certain varieties of this plant all prove good, and the next + season all prove bad; whilst exactly the reverse happens with other + varieties. In 1845 the editor of the 'Gardener's Chronicle'<a + name="NtA_661" href="#Nt_661"><sup>[661]</sup></a> remarked how singular + it was that this year many Calceolarias tended to assume a tubular form. + With Heartsease<a name="NtA_662" href="#Nt_662"><sup>[662]</sup></a> the + blotched sorts do not acquire their proper character until hot weather + sets in; whilst other varieties lose their beautiful marks as soon as + this occurs.</p> + + <p>Analogous facts have been observed with leaves: Mr. Beaton asserts<a + name="NtA_663" href="#Nt_663"><sup>[663]</sup></a> that he raised at + Shrubland, during six years, twenty thousand seedlings from the Punch + Pelargonium, and not one had variegated leaves; but at Surbiton, in + Surrey, one-third, or even a greater proportion, of the seedlings from + this same variety were more or less variegated. The soil of another + district in Surrey has a strong tendency to cause variegation, as appears + from information given me by Sir F. Pollock. Verlot<a name="NtA_664" + href="#Nt_664"><sup>[664]</sup></a> states that the variegated strawberry + retains its character as long as grown in a dryish soil, but soon loses + it when planted in fresh and humid soil. Mr. Salter, who is well known + for his success in cultivating variegated plants, informs me that rows of + strawberries were planted in his garden in 1859, in the usual way; and at + various distances in one row, several plants simultaneously became + variegated, and what made the case more extraordinary, all were + variegated in precisely the same manner. These plants were removed, but + during the three succeeding years other plants in the same row became + variegated, and in no instance were the plants in any adjoining row + affected.</p> + + <p>The chemical qualities, odours, and tissues of plants are often + modified by a change which seems to us slight. The Hemlock is said not to + yield conicine in Scotland. The root of the <i>Aconitum napellus</i> + becomes innocuous in frigid climates. The medicinal properties of the + Digitalis are easily affected by culture. The Rhubarb flourishes in + England, but does not produce the medicinal substance which makes the + plant so valuable in Chinese Tartary. As the <i>Pistacia lentiscus</i> + grows abundantly in the South of France, the climate must suit it, but it + yields no mastic. The <i>Laurus sassafras</i> in Europe loses the odour + proper to it in North America.<a name="NtA_665" + href="#Nt_665"><sup>[665]</sup></a> Many similar facts could be given, + and they are remarkable because it might have been thought that definite + chemical compounds would have been little liable to change either in + quality or quantity.</p> + + <p>The wood of the American Locust-tree (<i>Robinia</i>) when grown in + England is nearly worthless, as is that of the Oak-tree when grown at the + Cape of Good Hope.<a name="NtA_666" href="#Nt_666"><sup>[666]</sup></a> + Hemp and flax, as I hear from Dr. Falconer, flourish and yield plenty of + seed on the plains of India, but their fibres are brittle <!-- Page 275 + --><span class="pagenum"><a name="page275"></a>{275}</span>and useless. + Hemp, on the other hand, fails to produce in England that resinous matter + which is so largely used in India as an intoxicating drug.</p> + + <p>The fruit of the Melon is greatly influenced by slight differences in + culture and climate. Hence it is generally a better plan, according to + Naudin, to improve an old kind than to introduce a new one into any + locality. The seed of the Persian Melon produces near Paris fruit + inferior to the poorest market kinds, but at Bordeaux yields delicious + fruit.<a name="NtA_667" href="#Nt_667"><sup>[667]</sup></a> Seed is + annually brought from Thibet to Kashmir,<a name="NtA_668" + href="#Nt_668"><sup>[668]</sup></a> and produces fruit weighing from four + to ten pounds, but plants raised from seed saved in Kashmir next year + give fruit weighing only from two to three pounds. It is well known that + American varieties of the Apple produce in their native land magnificent + and brightly-coloured fruit, but in England of poor quality and a dull + colour. In Hungary there are many varieties of the Kidney-bean, + remarkable for the beauty of their seeds, but the Rev. M. J. Berkeley<a + name="NtA_669" href="#Nt_669"><sup>[669]</sup></a> found that their + beauty could hardly ever be preserved in England, and in some cases the + colour was greatly changed. We have seen in the ninth chapter, with + respect to wheat, what a remarkable effect transportal from the North to + the South of France, and reversely, produced on the weight of the + grain.</p> + +</blockquote> + + <p>When man can perceive no change in plants or animals which have been + exposed to a new climate or to different treatment, insects can sometimes + perceive a marked change. The same species of cactus has been carried to + India from Canton, Manilla, Mauritius, and from the hot-houses of Kew, + and there is likewise a so-called native kind, formerly introduced from + South America; all these plants are alike in appearance, but the + cochineal insect flourishes only on the native kind, on which it thrives + prodigiously.<a name="NtA_670" href="#Nt_670"><sup>[670]</sup></a> + Humboldt remarks<a name="NtA_671" href="#Nt_671"><sup>[671]</sup></a> + that white men "born in the torrid zone walk barefoot with impunity in + the same apartment where a European, recently landed, is exposed to the + attacks of the <i>Pulex penetrans</i>." This insect, the too well-known + chigoe, must therefore be able to distinguish what the most delicate + chemical analysis fails to distinguish, namely, a difference between the + blood or tissues of a European and those of a white man born in the + country. But the discernment of the chigoe is not so surprising as it at + first appears; for <!-- Page 276 --><span class="pagenum"><a + name="page276"></a>{276}</span>according to Liebig<a name="NtA_672" + href="#Nt_672"><sup>[672]</sup></a> the blood of men with different + complexions, though inhabiting the same country, emits a different + odour.</p> + +<blockquote class="b1n"> + + <p>Diseases peculiar to certain localities, heights, or climates, may be + here briefly noticed, as showing the influence of external circumstances + on the human body. Diseases confined to certain races of man do not + concern us, for the constitution of the race may play the more important + part, and this may have been determined by unknown causes. The Plica + Polonica stands, in this respect, in a nearly intermediate position; for + it rarely affects Germans, who inhabit the neighbourhood of the Vistula, + where so many Poles are grievously affected; and on the other hand, it + does not affect Russians, who are said to belong to the same original + stock with the Poles.<a name="NtA_673" + href="#Nt_673"><sup>[673]</sup></a> The elevation of a district often + governs the appearance of diseases; in Mexico the yellow fever does not + extend above 924 mètres; and in Peru, people are affected with the + <i>verugas</i> only between 600 and 1600 mètres above the sea; many other + such cases could be given. A peculiar cutaneous complaint, called the + <i>Bouton d'Alep</i>, affects in Aleppo and some neighbouring districts + almost every native infant, and some few strangers; and it seems fairly + well established that this singular complaint depends on drinking certain + waters. In the healthy little island of St. Helena the scarlet-fever is + dreaded like the Plague; analogous facts have been observed in Chili and + Mexico.<a name="NtA_674" href="#Nt_674"><sup>[674]</sup></a> Even in the + different departments of France it is found that the various infirmities + which render the conscript unfit for serving in the army, prevail with + remarkable inequality, revealing, as Boudin observes, that many of them + are endemic, which otherwise would never have been suspected.<a + name="NtA_675" href="#Nt_675"><sup>[675]</sup></a> Any one who will study + the distribution of disease will be struck with surprise at what slight + differences in the surrounding circumstances govern the nature and + severity of the complaints by which man is at least temporarily + affected.</p> + +</blockquote> + + <p>The modifications as yet referred to have been extremely slight, and + in most cases have been caused, as far as we can judge, by equally slight + changes in the conditions. But can it be safely maintained that such + changed conditions, if acting during a long series of generations, would + not produce a marked effect? It is commonly believed that the people of + the United States differ in appearance from the parent Anglo-Saxon race; + and selection cannot have come into action within so short a period. A + good observer<a name="NtA_676" href="#Nt_676"><sup>[676]</sup></a> states + that a general absence of fat, <!-- Page 277 --><span class="pagenum"><a + name="page277"></a>{277}</span>a thin and elongated neck, stiff and lank + hair, are the chief characteristics. The change in the nature of the hair + is supposed to be caused by the dryness of the atmosphere. If immigration + into the United States were now stopped, who can say that the character + of the whole people would not be greatly modified in the course of two or + three thousand years?</p> + +<blockquote class="b1n"> + + <p>The direct and definite action of changed conditions, in + contradistinction to the accumulation of indefinite variations, seems to + me so important that I will give a large additional body of miscellaneous + facts. With plants, a considerable change of climate sometimes produces a + conspicuous result. I have given in detail in the ninth chapter the most + remarkable case known to me, namely, that in Germany several varieties of + maize brought from the hotter parts of America were transformed in the + course of only two or three generations. Dr. Falconer informs me that he + has seen the English Ribston-pippin apple, a Himalayan oak, Prunus and + Pyrus, all assume in the hotter parts of India a fastigate or pyramidal + habit; and this fact is the more interesting, as a Chinese tropical + species of Pyrus naturally has this habit of growth. Although in these + cases the changed manner of growth seems to have been directly caused by + the great heat, we know that many fastigate trees have originated in + their temperate homes. In the Botanic Gardens of Ceylon the apple-tree<a + name="NtA_677" href="#Nt_677"><sup>[677]</sup></a> "sends out numerous + runners under ground, which continually rise into small stems, and form a + growth around the parent-tree." The varieties of the cabbage which + produce heads in Europe fail to do so in certain tropical countries.<a + name="NtA_678" href="#Nt_678"><sup>[678]</sup></a> The <i>Rhododendron + ciliatum</i> produced at Kew flowers so much larger and paler-coloured + than those which it bears on its native Himalayan mountain, that Dr. + Hooker<a name="NtA_679" href="#Nt_679"><sup>[679]</sup></a> would hardly + have recognised the species by the flowers alone. Many similar facts with + respect to the colour and size of flowers could be given.</p> + + <p>The experiments of Vilmorin and Buckman on carrots and parsnips prove + that abundant nutriment produces a definite and inheritable effect on the + so-called roots, with scarcely any change in other parts of the plant. + Alum directly influences the colour of the flowers of the Hydrangea.<a + name="NtA_680" href="#Nt_680"><sup>[680]</sup></a> Dryness seems + generally to favour the hairyness or villosity of plants. Gärtner found + that hybrid Verbascums became extremely woolly when grown in pots. Mr. + Masters, on the other hand, states that the <i>Opuntia leucotricha</i> + "is well clothed with beautiful white hairs when grown in a damp heat; + but in a dry heat exhibits none of this peculiarity."<a name="NtA_681" + href="#Nt_681"><sup>[681]</sup></a> Slight variations of many kinds, not + worth specifying in detail, are retained only as <!-- Page 278 --><span + class="pagenum"><a name="page278"></a>{278}</span>long as plants are + grown in certain soils, of which Sageret<a name="NtA_682" + href="#Nt_682"><sup>[682]</sup></a> gives from his own experience some + instances. Odart, who insists strongly on the permanence of the varieties + of the grape, admits<a name="NtA_683" href="#Nt_683"><sup>[683]</sup></a> + that some varieties, when grown under a different climate or treated + differently, vary in an extremely slight degree, as in the tint of the + fruit and in the period of ripening. Some authors have denied that + grafting causes even the slightest difference in the scion; but there is + sufficient evidence that the fruit is sometimes slightly affected in size + and flavour, the leaves in duration, and the flowers in appearance.<a + name="NtA_684" href="#Nt_684"><sup>[684]</sup></a></p> + + <p>With animals there can be no doubt, from the facts given in the first + chapter, that European dogs deteriorate in India, not only in their + instincts but in structure; but the changes which they undergo are of + such a nature, that they may be partly due to reversion to a primitive + form, as in the case of feral animals. In parts of India the turkey + becomes reduced in size, "with the pendulous appendage over the beak + enormously developed."<a name="NtA_685" + href="#Nt_685"><sup>[685]</sup></a> We have seen how soon the wild duck, + when domesticated, loses its true character, from the effects of abundant + or changed food, or from taking little exercise. From the direct action + of a humid climate and poor pasture the horse rapidly decreases in size + in the Falkland Islands. From information which I have received, this + seems likewise to be the case to a certain extent with sheep in + Australia.</p> + + <p>Climate definitely influences the hairy covering of animals; in the + West Indies a great change is produced in the fleece of sheep, in about + three generations. Dr. Falconer states<a name="NtA_686" + href="#Nt_686"><sup>[686]</sup></a> that the Thibet mastiff and goat, + when brought down from the Himalaya to Kashmir, lose their fine wool. At + Angora not only goats, but shepherd-dogs and cats, have fine fleecy hair, + and Mr. Ainsworth<a name="NtA_687" href="#Nt_687"><sup>[687]</sup></a> + attributes the thickness of the fleece to the severe winters, and its + silky lustre to the hot summers. Burnes states positively<a + name="NtA_688" href="#Nt_688"><sup>[688]</sup></a> that the Karakool + sheep lose their peculiar black curled fleeces when removed into any + other country. Even within the limits of England, I have been assured + that with two breeds of sheep the wool was slightly changed by the flocks + being pastured in different localities.<a name="NtA_689" + href="#Nt_689"><sup>[689]</sup></a> It has been asserted on good + authority<a name="NtA_690" href="#Nt_690"><sup>[690]</sup></a> that + horses kept during several years in the deep coal-mines of Belgium become + covered with velvety hair, almost like that on the mole. These cases + probably stand in close relation to the natural change of coat in winter + and summer. Naked varieties of several domestic animals have occasionally + appeared; but there is no reason to <!-- Page 279 --><span + class="pagenum"><a name="page279"></a>{279}</span>believe that this is in + any way related to the nature of the climate to which they have been + exposed.<a name="NtA_691" href="#Nt_691"><sup>[691]</sup></a></p> + + <p>It appears at first sight probable that the increased size, the + tendency to fatten, the early maturity and altered forms of our improved + cattle, sheep, and pigs, have directly resulted from their abundant + supply of food. This is the opinion of many competent judges, and + probably is to a great extent true. But as far as form is concerned, we + must not overlook the equal or more potent influence of lessened use on + the limbs and lungs. We see, moreover, as far as size is concerned, that + selection is apparently a more powerful agent than a large supply of + food, for we can thus only account for the existence, as remarked to me + by Mr. Blyth, of the largest and smallest breeds of sheep in the same + country, of Cochin-China fowls and Bantams, of small Tumbler and large + Runt pigeons, all kept together and supplied with abundant nourishment. + Nevertheless there can be little doubt that our domesticated animals have + been modified, independently of the increased or lessened use of parts, + by the conditions to which they have been subjected, without the aid of + selection. For instance, Prof. Rütimeyer<a name="NtA_692" + href="#Nt_692"><sup>[692]</sup></a> shows that the bones of all + domesticated quadrupeds can be distinguished from those of wild animals + by the state of their surface and general appearance. It is scarcely + possible to read Nathusius's excellent 'Vorstudien,'<a name="NtA_693" + href="#Nt_693"><sup>[693]</sup></a> and doubt that, with the highly + improved races of the pig, abundant food has produced a conspicuous + effect on the general form of the body, on the breadth of the head and + face, and even on the teeth. Nathusius rests much on the case of a purely + bred Berkshire pig, which when two months old became diseased in its + digestive organs, and was preserved for observation until nineteen months + old; at this age it had lost several characteristic features of the + breed, and had acquired a long, narrow head, of large size relatively to + its small body, and elongated legs. But in this case and in some others + we ought not to assume that, because certain characters are lost, perhaps + through reversion, under one course of treatment, therefore that they had + been at first directly produced by an opposite course.</p> + + <p>In the case of the rabbit, which has become feral on the island of + Porto Santo, we are at first strongly tempted to attribute the whole + change—the greatly reduced size, the altered tints of the fur, and + the loss of certain characteristic marks—to the definite action of + the new conditions to which it has been exposed. But in all such cases we + have to consider in addition the tendency to reversion to progenitors + more or less remote, and the natural selection of the finest shades of + difference.</p> + + <p>The nature of the food sometimes either definitely induces certain + peculiarities, or stands in some close relation with them. Pallas long + ago asserted that the fat-tailed sheep of Siberia degenerated and lost + their enormous tails when removed from certain saline pastures; and + recently <!-- Page 280 --><span class="pagenum"><a + name="page280"></a>{280}</span>Erman<a name="NtA_694" + href="#Nt_694"><sup>[694]</sup></a> states that this occurs with the + Kirgisian sheep when brought to Orenburgh.</p> + + <p>It is well known that hemp-seed causes bullfinches and certain other + birds to become black. Mr. Wallace has communicated to me some much more + remarkable facts of the same nature. The natives of the Amazonian region + feed the common green parrot (<i>Chrysotis festiva</i>, Linn.) with the + fat of large Siluroid fishes, and the birds thus treated become + beautifully variegated with red and yellow feathers. In the Malayan + archipelago, the natives of Gilolo alter in an analogous manner the + colours of another parrot, namely, the <i>Lorius garrulus</i>, Linn., and + thus produce the <i>Lori rajah</i> or King-Lory. These parrots in the + Malay Islands and South America, when fed by the natives on natural + vegetable food, such as rice and plantains, retain their proper colours. + Mr. Wallace has, also, recorded<a name="NtA_695" + href="#Nt_695"><sup>[695]</sup></a> a still more singular fact. "The + Indians (of S. America) have a curious art by which they change the + colours of the feathers of many birds. They pluck out those from the part + they wish to paint, and inoculate the fresh wound with the milky + secretion from the skin of a small toad. The feathers grow of a brilliant + yellow colour, and on being plucked out, it is said, grow again of the + same colour without any fresh operation."</p> + + <p>Bechstein<a name="NtA_696" href="#Nt_696"><sup>[696]</sup></a> does + not entertain any doubt that seclusion from light affects, at least + temporarily, the colours of cage-birds.</p> + + <p>It is well known that the shells of land-mollusca are affected by the + abundance of lime in different districts. Isidore Geoffroy St. Hilaire<a + name="NtA_697" href="#Nt_697"><sup>[697]</sup></a> gives the case of + <i>Helix lactea</i>, which has recently been carried from Spain to the + South of France and to the Rio Plata, and in both these countries now + presents a distinct appearance, but whether this has resulted from food + or climate is not known. With respect to the common oyster, Mr. F. + Buckland informs me that he can generally distinguish the shells from + different districts; young oysters brought from Wales and laid down in + beds where "<i>natives</i>" are indigenous, in the short space of two + months begin to assume the "native" character. M. Costa<a name="NtA_698" + href="#Nt_698"><sup>[698]</sup></a> has recorded a much more remarkable + case of the same nature, namely, that young shells taken from the shores + of England and placed in the Mediterranean, at once altered their manner + of growth and formed prominent diverging rays, like those on the shells + of the proper Mediterranean oyster. The same individual shell, showing + both forms of growth, was exhibited before a society in Paris. Lastly, it + is well known that caterpillars fed on different food sometimes either + themselves acquire a different colour or produce moths different in + colour.<a name="NtA_699" href="#Nt_699"><sup>[699]</sup></a></p> + +<p><!-- Page 281 --><span class="pagenum"><a name="page281"></a>{281}</span></p> + + <p>It would be travelling beyond my proper limits here to discuss how far + organic beings in a state of nature are definitely modified by changed + conditions. In my 'Origin of Species' I have given a brief abstract of + the facts bearing on this point, and have shown the influence of light on + the colours of birds, and of residence near the sea on the lurid tints of + insects, and on the succulency of plants. Mr. Herbert Spencer<a + name="NtA_700" href="#Nt_700"><sup>[700]</sup></a> has recently discussed + with much ability this whole subject on broad and general grounds. He + argues, for instance, that with all animals the external and internal + tissues are differently acted on by the surrounding conditions, and they + invariably differ in intimate structure. So again the upper and lower + surfaces of true leaves, as well as of stems and petioles, when these + assume the function and occupy the position of leaves, are differently + circumstanced with respect to light, &c., and apparently in + consequence differ in structure. But, as Mr. Herbert Spencer admits, it + is most difficult in all such cases to distinguish between the effects of + the definite action of physical conditions and the accumulation through + natural selection of inherited variations which are serviceable to the + organism, and which have arisen independently of the definite action of + these conditions.</p> + +</blockquote> + + <p>Although we are not here concerned with organic beings in a state of + nature, yet I may call attention to one case. Mr. Meehan,<a + name="NtA_701" href="#Nt_701"><sup>[701]</sup></a> in a remarkable paper, + compares twenty-nine kinds of American trees, belonging to various + orders, with their nearest European allies, all grown in close proximity + in the same garden and under as nearly as possible the same conditions. + In the American species Mr. Meehan finds, with the rarest exceptions, + that the leaves fall earlier in the season, and assume before falling a + brighter tint; that they are less deeply toothed or serrated; that the + buds are smaller; that the trees are more diffuse in growth and have + fewer branchlets; and, lastly, that the seeds are smaller—all in + comparison with the corresponding European species. Now, considering that + these trees belong to distinct orders, it is out of the question that the + peculiarities just specified should have been inherited in the one + continent from one progenitor, and in the other from another progenitor; + and considering that the trees inhabit widely different stations, these + peculiarities can hardly be supposed to be of any special <!-- Page 282 + --><span class="pagenum"><a name="page282"></a>{282}</span>service to the + two series in the Old and New Worlds; therefore these peculiarities + cannot have been naturally selected. Hence we are led to infer that they + have been definitely caused by the long-continued action of the different + climate of the two continents on the trees.</p> + + <p><i>Galls.</i>—Another class of facts, not relating to cultivated + plants, deserves attention. I allude to the production of galls. Every + one knows the curious, bright-red, hairy productions on the wild + rose-tree, and the various different galls produced by the oak. Some of + the latter resemble fruit, with one face as rosy as the rosiest apple. + These bright colours can be of no service either to the gall-forming + insect or to the tree, and probably are the direct result of the action + of the light, in the same manner as the apples of Nova Scotia or Canada + are brighter coloured than English apples. The strongest upholder of the + doctrine that organic beings are created beautiful to please mankind + would not, I presume, extend this view to galls. According to Osten + Sacken's latest revision, no less than fifty-eight kinds of galls are + produced on the several species of oak, by Cynips with its sub-genera; + and Mr. B. D. Walsh<a name="NtA_702" href="#Nt_702"><sup>[702]</sup></a> + states that he can add many others to the list. One American species of + willow, the <i>Salix humilis</i>, bears ten distinct kinds of galls. The + leaves which spring from the galls of various English willows differ + completely in shape from the natural leaves. The young shoots of junipers + and firs, when punctured by certain insects, yield monstrous growths like + flowers and cones; and the flowers of some plants become from the same + cause wholly changed in appearance. Galls are produced in every quarter + of the world; of several sent to me by Mr. Thwaites from Ceylon, some + were as symmetrical as a composite flower when in bud, others smooth and + spherical like a berry; some protected by long spines, others clothed + with yellow wool formed of long cellular hairs, others with regularly + tufted hairs. In some galls the internal structure is simple, but in + others it is highly complex; thus M. Lucaze-Duthiers<a name="NtA_703" + href="#Nt_703"><sup>[703]</sup></a> has figured in the common ink-gall no + less than seven concentric layers, composed of distinct tissue, <!-- Page + 283 --><span class="pagenum"><a name="page283"></a>{283}</span>namely, + the epidermic, sub-epidermic, spongy, intermediate, and the hard + protective layer formed of curiously thickened woody cells, and, lastly, + the central mass abounding with starch-granules on which the larvæ + feed.</p> + + <p>Galls are produced by insects of various orders, but the greater + number by species of Cynips. It is impossible to read M. Lucaze-Duthier's + discussion and doubt that the poisonous secretion of the insect causes + the growth of the gall, and every one knows how virulent is the poison + secreted by wasps and bees, which belong to the same order with Cynips. + Galls grow with extraordinary rapidity, and it is said that they attain + their full size in a few days;<a name="NtA_704" + href="#Nt_704"><sup>[704]</sup></a> it is certain that they are almost + completely developed before the larvæ are hatched. Considering that many + gall-insects are extremely small, the drop of secreted poison must be + excessively minute; it probably acts on one or two cells alone, which, + being abnormally stimulated, rapidly increase by a process of + self-division. Galls, as Mr. Walsh<a name="NtA_705" + href="#Nt_705"><sup>[705]</sup></a> remarks, afford good, constant, and + definite characters, each kind keeping as true to form as does any + independent organic being. This fact becomes still more remarkable when + we hear that, for instance, seven out of the ten different kinds of galls + produced on <i>Salix humilis</i> are formed by gall-gnats + (<i>Cecidomyidæ</i>) which, "though essentially distinct species, yet + resemble one another so closely that in almost all cases it is difficult, + and in some cases impossible, to distinguish the full-grown insects one + from the other."<a name="NtA_706" href="#Nt_706"><sup>[706]</sup></a> For + in accordance with a wide-spread analogy we may safely infer that the + poison secreted by insects so closely allied would not differ much in + nature; yet this slight difference is sufficient to induce widely + different results. In some few cases the same species of gall-gnat + produces on distinct species of willows galls which cannot be + distinguished; the <i>Cynips fecundatrix</i>, also, has been known to + produce on the Turkish oak, to which it is not properly attached, exactly + the same kind of gall as on the European oak.<a name="NtA_707" + href="#Nt_707"><sup>[707]</sup></a> These latter facts apparently prove + that the nature of the poison is a much more powerful <!-- Page 284 + --><span class="pagenum"><a name="page284"></a>{284}</span>agent in + determining the form of the gall than the specific character of the tree + which is acted on.</p> + + <p>As the poisonous secretion of insects belonging to various orders has + the special power of affecting the growth of various plants;—as a + slight difference in the nature of the poison suffices to produce widely + different results;—and lastly, as we know that the chemical + compounds secreted by plants are eminently liable to be modified by + changed conditions of life, we may believe it possible that various parts + of a plant might be modified through the agency of its own altered + secretions. Compare, for instance, the mossy and viscid calyx of a + moss-rose, which suddenly appears through bud-variation on a + Provence-rose, with the gall of red moss growing from the inoculated leaf + of a wild rose, with each filament symmetrically branched like a + microscopical spruce-fir, bearing a glandular tip and secreting + odoriferous gummy matter.<a name="NtA_708" + href="#Nt_708"><sup>[708]</sup></a> Or compare, on the one hand, the + fruit of the peach, with its hairy skin, fleshy covering, hard shell and + kernel, and on the other hand one of the more complex galls with its + epidermic, spongy, and woody layers, surrounding tissue loaded with + starch granules. These normal and abnormal structures manifestly present + a certain degree of resemblance. Or, again, reflect on the cases above + given of parrots which have had their plumage brightly decorated through + some change in their blood, caused by having been fed on certain fishes, + or locally inoculated with the poison of a toad. I am far from wishing to + maintain that the moss-rose or the hard shell of the peach-stone or the + bright colours of birds are actually due to any chemical change in the + sap or blood; but these cases of galls and of parrots are excellently + adapted to show us how powerfully and singularly external agencies may + affect structure. With such facts before us, we need feel no surprise at + the appearance of any modification in any organic being.</p> + +<blockquote class="b1n"> + + <p>I may, also, here allude to the remarkable effects which parasitic + fungi sometimes produce on plants. Reissek<a name="NtA_709" + href="#Nt_709"><sup>[709]</sup></a> has described a Thesium, affected by + an Œcidium, which was greatly modified, and assumed some of the + <!-- Page 285 --><span class="pagenum"><a + name="page285"></a>{285}</span>characteristic features of certain allied + species, or even genera. Suppose, says Reissek, "the condition originally + caused by the fungus to become constant in the course of time, the plant + would, if found growing wild, be considered as a distinct species or even + as belonging to a new genus." I quote this remark to show how profoundly, + yet in how natural a manner, this plant must have been modified by the + parasitic fungus.</p> + +</blockquote> + +<p class="cenhead"><i>Facts and Considerations opposed to the belief that the Conditions +of Life act in a potent manner in causing definite Modifications +of Structure.</i></p> + + <p>I have alluded to the slight differences in species when naturally + living in distinct countries under different conditions; and such + differences we feel at first inclined, probably to a limited extent with + justice, to attribute to the definite action of the surrounding + conditions. But it must be borne in mind that there are a far greater + number of animals and plants which range widely and have been exposed to + great diversities of conditions, yet remain nearly uniform in character. + Some authors, as previously remarked, account for the varieties of our + culinary and agricultural plants by the definite action of the conditions + to which they have been exposed in the different parts of Great Britain; + but there are about 200 plants<a name="NtA_710" + href="#Nt_710"><sup>[710]</sup></a> which are found in every single + English county; these plants must have been exposed for an immense period + to considerable differences of climate and soil, yet do not differ. So, + again, some birds, insects, other animals, and plants range over large + portions of the world, yet retain the same character.</p> + +<blockquote class="b1n"> + + <p>Notwithstanding the facts previously given on the occurrence of highly + peculiar local diseases and on the strange modifications of structure in + plants caused by the inoculated poison of insects, and other analogous + cases; still there are a multitude of variations—such as the + modified skull of the niata ox and bulldog, the long horns of Caffre + cattle, the conjoined toes of the solid-hoofed swine, the immense crest + and protuberant skull of Polish fowls, the crop of the pouter-pigeon, and + a host of other such cases—which we can hardly attribute to the + definite action, in the sense before specified, of the external + conditions of life. No doubt in every case there must have been some + exciting cause; but as we see innumerable individuals exposed to nearly + the same conditions, and one alone is affected, we may conclude that the + constitution of the individual is of far higher <!-- Page 286 --><span + class="pagenum"><a name="page286"></a>{286}</span>importance than the + conditions to which it has been exposed. It seems, indeed, to be a + general rule that conspicuous variations occur rarely, and in one + individual alone out of many thousands, though all may have been exposed, + as far as we can judge, to nearly the same conditions. As the most + strongly marked variations graduate insensibly into the most trifling, we + are led by the same train of thought to attribute each slight variation + much more to innate differences of constitution, however caused, than to + the definite action of the surrounding conditions.</p> + + <p>We are led to the same conclusion by considering the cases, formerly + alluded to, of fowls and pigeons, which have varied and will no doubt go + on varying in directly opposite ways, though kept during many generations + under nearly the same conditions. Some, for instance, are born with their + beaks, wings, tails, legs, &c., a little longer, and others with + these same parts a little shorter. By the long-continued selection of + such slight individual differences, which occur in birds kept in the same + aviary, widely different races could certainly be formed; and + long-continued selection, important as is the result, does nothing but + preserve the variations which appear to us to arise spontaneously.</p> + + <p>In these cases we see that domesticated animals vary in an indefinite + number of particulars, though treated as uniformly as is possible. On the + other hand, there are instances of animals and plants, which, though + exposed to very different conditions, both under nature and + domestication, have varied in nearly the same manner. Mr. Layard informs + me that he has observed amongst the Caffres of South Africa a dog + singularly like an arctic Esquimaux dog. Pigeons in India present nearly + the same wide diversities of colour as in Europe; and I have seen + chequered and simply barred pigeons, and pigeons with blue and white + loins, from Sierra Leone, Madeira, England, and India. New varieties of + flowers are continually raised in different parts of Great Britain, but + many of these are found by the judges at our exhibitions to be almost + identical with old varieties. A vast number of new fruit-trees and + culinary vegetables have been produced in North America: these differ + from European varieties in the same general manner as the several + varieties raised in Europe differ from each other; and no one has ever + pretended that the climate of America has given to the many American + varieties any general character by which they can be recognised. + Nevertheless, from the facts previously advanced on the authority of Mr. + Meehan with respect to American and European forest-trees, it would be + rash to affirm that varieties raised in the two countries would not in + the course of ages assume a distinctive character. Mr. Masters has + recorded a striking fact<a name="NtA_711" + href="#Nt_711"><sup>[711]</sup></a> bearing on this subject: he raised + numerous plants of <i>Hybiscus Syriacus</i> from seed collected in South + Carolina and the Holy Land, where the parent-plants must have been + exposed to considerably different conditions; yet the seedlings from both + localities broke into two similar strains, one with obtuse leaves and + purple or crimson flowers, and the other with elongated leaves and more + or less pink flowers.</p> + +<p><!-- Page 287 --><span class="pagenum"><a name="page287"></a>{287}</span></p> + + <p>We may, also, infer the prepotent influence of the constitution of the + organism over the definite action of the conditions of life, from the + several cases given in the earlier chapters of parallel series of + varieties,—an important subject, hereafter to be more fully + discussed. Sub-varieties of the several kinds of wheat, gourds, peaches, + and other plants, and to a certain limited extent sub-varieties of the + fowl, pigeon, and dog, have been shown either to resemble or to differ + from each other in a closely corresponding and parallel manner. In other + cases, a variety of one species resembles a distinct species; or the + varieties of two distinct species resemble each other. Although these + parallel resemblances no doubt often result from reversion to the former + characters of a common progenitor; yet in other cases, when new + characters first appear, the resemblance must be attributed to the + inheritance of a similar constitution, and consequently to a tendency to + vary in the same manner. We see something of a similar kind in the same + monstrosity appearing and reappearing many times in the same animal, and, + as Dr. Maxwell Masters has remarked to me, in the same plant.</p> + +</blockquote> + + <p>We may at least conclude thus far, that the amount of modification + which animals and plants have undergone under domestication, does not + correspond with the degree to which they have been subjected to changed + circumstances. As we know the parentage of domesticated birds far better + than of most quadrupeds, we will glance through the list. The pigeon has + varied in Europe more than almost any other bird; yet it is a native + species, and has not been exposed to any extraordinary change of + conditions. The fowl has varied equally, or almost equally, with the + pigeon, and is a native of the hot jungles of India. Neither the peacock, + a native of the same country, nor the guinea-fowl, an inhabitant of the + dry deserts of Africa, has varied at all, or only in colour. The turkey, + from Mexico, has varied but little. The duck, on the other hand, a native + of Europe, has yielded some well-marked races; and as this is an aquatic + bird, it must have been subjected to a far more serious change in its + habits than the pigeon or even the fowl, which nevertheless have varied + in a much higher degree. The goose, a native of Europe and aquatic like + the duck, has varied less than any other domesticated bird, except the + peacock.</p> + + <p>Bud-variation is, also, important under our present point of view. In + some few cases, as when all the eyes or buds on the same tuber of the + potato, or all the fruit on the same plum-tree, or all the flowers on the + same plant, have suddenly varied in the same manner, it might be argued + that the <!-- Page 288 --><span class="pagenum"><a + name="page288"></a>{288}</span>variation had been definitely caused by + some change in the conditions to which the plants had been exposed; yet, + in other cases, such an admission is extremely difficult. As new + characters sometimes appear by bud-variation, which do not occur in the + parent-species or in any allied species, we may reject, at least in these + cases, the idea that they are due to reversion. Now it is well worth + while to reflect maturely on some striking case of bud-variation, for + instance that of the peach. This tree has been cultivated by the million + in various parts of the world, has been treated differently, grown on its + own roots and grafted on various stocks, planted as a standard, against a + wall, and under glass; yet each bud of each sub-variety keeps true to its + kind. But occasionally, at long intervals of time, a tree in England, or + under the widely-different climate of Virginia, produces a single bud, + and this yields a branch which ever afterwards bears nectarines. + Nectarines differ, as every one knows, from peaches in their smoothness, + size, and flavour; and the difference is so great, that some botanists + have maintained that they are specifically distinct. So permanent are the + characters thus suddenly acquired, that a nectarine produced by + bud-variation has propagated itself by seed. To guard against the + supposition that there is some fundamental distinction between bud and + seminal variation, it is well to bear in mind that nectarines have + likewise been produced from the stone of the peach; and, reversely, + peaches from the stone of the nectarine. Now is it possible to conceive + external conditions more closely alike than those to which the buds on + the same tree are exposed? Yet one bud alone, out of the many thousands + borne by the same tree, has suddenly without any apparent cause produced + a nectarine. But the case is even stronger than this, for the same + flower-bud has yielded a fruit, one-half or one-quarter a nectarine, and + the other half or three-quarters a peach. Again, seven or eight varieties + of the peach have yielded by bud-variation nectarines: the nectarines + thus produced, no doubt, differ a little from each other; but still they + are nectarines. Of course there must be some cause, internal or external, + to excite the peach-bud to change its nature; but I cannot imagine a + class of facts better adapted to force on our minds the conviction that + what we call the external conditions of life are quite insignificant in + <!-- Page 289 --><span class="pagenum"><a + name="page289"></a>{289}</span>relation to any particular variation, in + comparison with the organisation or constitution of the being which + varies.</p> + + <p>It is known from the labours of Geoffroy St. Hilaire, and recently + from those of Dareste and others, that eggs of the fowl, if shaken, + placed upright, perforated, covered in part with varnish, &c., + produce monstrous chickens. Now these monstrosities may be said to be + directly caused by such unnatural conditions, but the modifications thus + induced are not of a definite nature. An excellent observer, M. Camille + Dareste,<a name="NtA_712" href="#Nt_712"><sup>[712]</sup></a> remarks + "that the various species of monstrosities are not determined by specific + causes; the external agencies which modify the development of the embryo + act solely in causing a perturbation—a perversion in the normal + course of development." He compares the result to what we see in illness: + a sudden chill, for instance, affects one individual alone out of many, + causing either a cold, or sore-throat, rheumatism, or inflammation of the + lungs or pleura. Contagious matter acts in an analogous manner.<a + name="NtA_713" href="#Nt_713"><sup>[713]</sup></a> We may take a still + more specific instance: seven pigeons were struck by rattle-snakes;<a + name="NtA_714" href="#Nt_714"><sup>[714]</sup></a> some suffered from + convulsions; some had their blood coagulated, in others it was perfectly + fluid; some showed ecchymosed spots on the heart, others on the + intestines, &c.; others again showed no visible lesion in any organ. + It is well known that excess in drinking causes different diseases in + different men; but men living under a cold and tropical climate are + differently affected:<a name="NtA_715" + href="#Nt_715"><sup>[715]</sup></a> and in this case we see the definite + influence of opposite conditions. The foregoing facts apparently give us + as good an idea as we are likely for a long time to obtain, how in many + cases external conditions act directly, though not definitely, in causing + modifications of structure.</p> + +<hr class="short" /> + + <p><i>Summary.</i>—There can be no doubt, from the facts given in + the early part of this chapter, that extremely slight changes in <!-- + Page 290 --><span class="pagenum"><a name="page290"></a>{290}</span>the + conditions of life sometimes act in a definite manner on our already + variable domesticated productions; and, as the action of changed + conditions in causing general or indefinite variability is accumulative, + so it may be with their definite action. Hence it is possible that great + and definite modifications of structure may result from altered + conditions acting during a long series of generations. In some few + instances a marked effect has been produced quickly on all, or nearly + all, the individuals which have been exposed to some considerable change + of climate, food, or other circumstance. This has occurred, and is now + occurring, with European men in the United States, with European dogs in + India, with horses in the Falkland Islands, apparently with various + animals at Angora, with foreign oysters in the Mediterranean, and with + maize grown in Europe from tropical seed. We have seen that the chemical + compounds secreted by plants and the state of their tissues are readily + affected by changed conditions. In some cases a relation apparently + exists between certain characters and certain conditions, so that if the + latter be changed the character is lost—as with cultivated flowers, + with some few culinary plants, with the fruit of the melon, with + fat-tailed sheep, and other sheep having peculiar fleeces.</p> + + <p>The production of galls, and the change of plumage in parrots when fed + on peculiar food or when inoculated by the poison of a toad, prove to us + what great and mysterious changes in structure and colour may be the + definite result of chemical changes in the nutrient fluids or + tissues.</p> + + <p>We have also reason to believe that organic beings in a state of + nature may be modified in various definite ways by the conditions to + which they have been long exposed, as in the case of American trees in + comparison with their representatives in Europe. But in all such cases it + is most difficult to distinguish between the definite results of changed + conditions, and the accumulation through natural selection of serviceable + variations which have arisen independently of the nature of the + conditions. If, for instance, a plant had to be modified so as to become + fitted to inhabit a humid instead of an arid station, we have no reason + to believe that variations of the right kind would occur more frequently + if the parent-plant inhabited a station a little more <!-- Page 291 + --><span class="pagenum"><a name="page291"></a>{291}</span>humid than + usual. Whether the station was unusually dry or humid, variations + adapting the plant in a slight degree for directly opposite habits of + life would occasionally arise, as we have reason to believe from what we + know in other cases.</p> + + <p>In most, perhaps in all cases, the organisation or constitution of the + being which is acted on, is a much more important element than the nature + of the changed conditions, in determining the nature of the variation. We + have evidence of this in the appearance of nearly similar modifications + under different conditions, and of different modifications under + apparently nearly the same conditions. We have still better evidence of + this in closely parallel varieties being frequently produced from + distinct races, or even distinct species, and in the frequent recurrence + of the same monstrosity in the same species. We have also seen that the + degree to which domesticated birds have varied, does not stand in any + close relation with the amount of change to which they have been + subjected.</p> + + <p>To recur once again to bud-variations. When we reflect on the millions + of buds which many trees have produced, before some one bud has varied, + we are lost in wonder what the precise cause of each variation can be. + Let us recall the case given by Andrew Knight of the forty-year-old tree + of the yellow magnum bonum plum, an old variety which has been propagated + by grafts on various stocks for a very long period throughout Europe and + North America, and on which a single bud suddenly produced the red magnum + bonum. We should also bear in mind that distinct varieties, and even + distinct species,—as in the case of peaches, nectarines, and + apricots,—of certain roses and camellias,—although separated + by a vast number of generations from any progenitor in common, and + although cultivated under diversified conditions, have yielded by + bud-variation closely analogous varieties. When we reflect on these facts + we become deeply impressed with the conviction that in such cases the + nature of the variation depends but little on the conditions to which the + plant has been exposed, and not in any especial manner on its individual + character, but much more on the general nature or constitution, inherited + from some remote progenitor, of the whole group of allied beings to which + the plant belongs. We are thus driven to conclude that in most <!-- Page + 292 --><span class="pagenum"><a name="page292"></a>{292}</span>cases the + conditions of life play a subordinate part in causing any particular + modification; like that which a spark plays, when a mass of combustibles + bursts into flame—the nature of the flame depending on the + combustible matter, and not on the spark.</p> + + <p>No doubt each slight variation must have its efficient cause; but it + is as hopeless an attempt to discover the cause of each as to say why a + chill or a poison affects one man differently from another. Even with + modifications resulting from the definite action of the conditions of + life, when all or nearly all the individuals, which have been similarly + exposed, are similarly affected, we can rarely see the precise relation + between cause and effect. In the next chapter it will be shown that the + increased use or disuse of various organs, produces an inherited effect. + It will further be seen that certain variations are bound together by + correlation and other laws. Beyond this we cannot at present explain + either the causes or manner of action of Variation.</p> + + <p>Finally, as indefinite and almost illimitable variability is the usual + result of domestication and cultivation, with the same part or organ + varying in different individuals in different or even in directly + opposite ways; and as the same variation, if strongly pronounced, usually + recurs only after long intervals of time, any particular variation would + generally be lost by crossing, reversion, and the accidental destruction + of the varying individuals, unless carefully preserved by man. Hence, + although it must be admitted that new conditions of life do sometimes + definitely affect organic beings, it may be doubted whether well-marked + races have often been produced by the direct action of changed conditions + without the aid of selection either by man or nature.</p> + +<hr class="full" /> + +<p><!-- Page 293 --><span class="pagenum"><a name="page293"></a>{293}</span></p> + +<h3>CHAPTER XXIV.</h3> + +<p class="cenhead">LAWS OF VARIATION—USE AND DISUSE, ETC.</p> + +<blockquote class="b1n"> + + <p><span class="scac">NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE + ORGANISATION</span>—<span class="scac">ON THE EFFECTS OF THE + INCREASED USE AND DISUSE OF ORGANS</span>—<span + class="scac">CHANGED HABITS OF LIFE</span>—<span + class="scac">ACCLIMATISATION WITH ANIMALS AND PLANTS</span>—<span + class="scac">VARIOUS METHODS BY WHICH THIS CAN BE + EFFECTED</span>—<span class="scac">ARRESTS OF + DEVELOPMENT</span>—<span class="scac">RUDIMENTARY + ORGANS.</span></p> + +</blockquote> + + <p>In this and the two following chapters I shall discuss, as well as the + difficulty of the subject permits, the several laws which govern + Variability. These may be grouped under the effects of use and disuse, + including changed habits and acclimatisation—arrests of + development—correlated variation—the cohesion of homologous + parts—the variability of multiple parts—compensation of + growth—the position of buds with respect to the axis of the + plant—and lastly, analogous variation. These several subjects so + graduate into each other that their distinction is often arbitrary.</p> + + <p>It may be convenient first briefly to discuss that co-ordinating and + reparative power which is common, in a higher or lower degree, to all + organic beings, and which was formerly designated by physiologists as the + <i>nisus formativus</i>.</p> + +<blockquote class="b1n"> + + <p>Blumenbach and others<a name="NtA_716" + href="#Nt_716"><sup>[716]</sup></a> have insisted that the principle + which permits a Hydra, when cut into fragments, to develop itself into + two or more perfect animals, is the same with that which causes a wound + in the higher animals to heal by a cicatrice. Such cases as that of the + Hydra are evidently analogous with the spontaneous division or + fissiparous generation of the lowest animals, and likewise with the + budding of plants. Between these extreme cases and that of a mere + cicatrice we have every gradation. Spallanzani,<a name="NtA_717" + href="#Nt_717"><sup>[717]</sup></a> by cutting off the legs and tail of a + Salamander, got in the course of three months six crops of these members; + so that 687 perfect bones were reproduced by one animal during one + season. At whatever <!-- Page 294 --><span class="pagenum"><a + name="page294"></a>{294}</span>point the limb was cut off, the deficient + part, and no more, was exactly reproduced. Even with man, as we have seen + in the twelfth chapter, when treating of polydactylism, the entire limb + whilst in an embryonic state, and supernumerary digits, are occasionally, + though imperfectly, reproduced after amputation. When a diseased bone has + been removed, a new one sometimes "gradually assumes the regular form, + and all the attachments of muscles, ligaments, &c., become as + complete as before."<a name="NtA_718" + href="#Nt_718"><sup>[718]</sup></a></p> + + <p>This power of regrowth does not, however, always act perfectly: the + reproduced tail of a lizard differs in the forms of the scales from the + normal tail: with certain Orthopterous insects the large hind legs are + reproduced of smaller size:<a name="NtA_719" + href="#Nt_719"><sup>[719]</sup></a> the white cicatrice which in the + higher animals unites the edges of a deep wound is not formed of perfect + skin, for elastic tissue is not produced till long afterwards.<a + name="NtA_720" href="#Nt_720"><sup>[720]</sup></a> "The activity of the + <i>nisus formativus</i>," says Blumenbach, "is in an inverse ratio to the + age of the organised body." To this may be added that its power is + greater in animals the lower they are in the scale of organisation; and + animals low in the scale correspond with the embryos of higher animals + belonging to the same class. Newport's observations<a name="NtA_721" + href="#Nt_721"><sup>[721]</sup></a> afford a good illustration of this + fact, for he found that "myriapods, whose highest development scarcely + carries them beyond the larvæ of perfect insects, can regenerate limbs + and antennæ up to the time of their last moult;" and so can the larvæ of + true insects, but not the mature insect. Salamanders correspond in + development with the tadpoles or larvæ of the tailless Batrachians, and + both possess to a large extent the power of regrowth; but not so the + mature tailless Batrachians.</p> + + <p>Absorption often plays an important part in the repairs of injuries. + When a bone is broken, and does not unite, the ends are absorbed and + rounded, so that a false joint is formed; or if the ends unite, but + overlap, the projecting parts are removed.<a name="NtA_722" + href="#Nt_722"><sup>[722]</sup></a> But absorption comes into action, as + Virchow remarks, during the normal growth of bones; parts which are solid + during youth become hollowed out for the medullary tissue as the bone + increases in size. In trying to understand the many well-adapted cases of + regrowth when aided by absorption, we should remember that most parts of + the organisation, even whilst retaining the same form, undergo constant + renewal; so that a part which was not renewed would naturally be liable + to complete <span class="correction" title="Original reads `absortion'." + >absorption</span>.</p> + + <p>Some cases, usually classed under the so-called <i>nisus + formativus</i>, at first appear to come under a distinct head; for not + only are old structures reproduced, but structures which appear new are + formed. Thus, after inflammation "false membranes," furnished with + blood-vessels, lymphatics, and nerves, are developed; or a fœtus + escapes from the Fallopian tubes, and falls into the abdomen, "nature + pours out a quantity of plastic lymph, which forms itself into organised + membrane, richly supplied with blood-vessels," and the fœtus is + nourished for a time. In certain cases of <!-- Page 295 --><span + class="pagenum"><a name="page295"></a>{295}</span>hydrocephalus the open + and dangerous spaces in the skull are filled up with new bones, which + interlock by perfect serrated sutures.<a name="NtA_723" + href="#Nt_723"><sup>[723]</sup></a> But most physiologists, especially on + the Continent, have now given up the belief in plastic lymph or blastema, + and Virchow<a name="NtA_724" href="#Nt_724"><sup>[724]</sup></a> + maintains that every structure, new or old, is formed by the + proliferation of pre-existing cells. On this view false membranes, like + cancerous or other tumours, are merely abnormal developments of normal + growths; and we can thus understand how it is that they resemble + adjoining structures; for instance, that "false membrane in the serous + cavities acquires a covering of epithelium exactly like that which covers + the original serous membrane; adhesions of the iris may become black + apparently from the production of pigment-cells like those of the + uvea."<a name="NtA_725" href="#Nt_725"><sup>[725]</sup></a></p> + + <p>No doubt the power of reparation, though not always quite perfect, is + an admirable provision, ready for various emergencies, even for those + which occur only at long intervals of time.<a name="NtA_726" + href="#Nt_726"><sup>[726]</sup></a> Yet this power is not more wonderful + than the growth and development of every single creature, more especially + of those which are propagated by fissiparous generation. This subject has + been here noticed, because we may infer that, when any part or organ is + either greatly increased in size or wholly suppressed through variation + and continued selection, the co-ordinating power of the organisation will + continually tend to bring all the parts again into harmony with each + other.</p> + +</blockquote> + +<p class="cenhead"><i>On the Effects of the Increased Use and Disuse of Organs.</i></p> + + <p>It is notorious, and we shall immediately adduce proofs, that + increased use or action strengthens muscles, glands, sense-organs, + &c.; and that disuse, on the other hand, weakens them. I have not met + with any clear explanation of this fact in works on Physiology. Mr. + Herbert Spencer<a name="NtA_727" href="#Nt_727"><sup>[727]</sup></a> + maintains that when muscles are much used, or when intermittent pressure + is applied to the epidermis, an excess of nutritive matter exudes from + the vessels, and that this gives additional development to the adjoining + parts. That an increased flow of blood towards an organ leads to its + greater development is probable, if not certain. Mr. Paget<a + name="NtA_728" href="#Nt_728"><sup>[728]</sup></a> thus accounts for the + long, thick, and dark-coloured hair which occasionally grows, even in + young children, near old-standing inflamed surfaces or fractured bones. + When Hunter <!-- Page 296 --><span class="pagenum"><a + name="page296"></a>{296}</span>inserted the spur of a cock into the comb, + which is well supplied with blood-vessels, it grew in one case in a + spiral direction to a length of six inches, and in another case forward, + like a horn, so that the bird could not touch the ground with its beak. + But whether Mr. Herbert Spencer's view of the exudation of nutritive + matter due to increased movement and pressure, will fully account for the + augmented size of bones, ligaments, and especially of internal glands and + nerves, seems doubtful. According to the interesting observations of M. + Sedillot,<a name="NtA_729" href="#Nt_729"><sup>[729]</sup></a> when a + portion of one bone of the leg or fore-arm of an animal is removed and is + not replaced by growth, the associated bone enlarges till it attains a + bulk equal to that of the two bones, of which it has to perform the + functions. This is best exhibited in dogs in which the tibia has been + removed; the companion bone, which is naturally almost filiform and not + one-fifth the size of the other, soon acquires a size equal to or greater + than the tibia. Now, it is at first difficult to believe that increased + weight acting on a straight bone could, by alternately increased and + diminished pressure, cause nutritive matter to exude from the vessels + which permeate the periosteum. Nevertheless, the observations adduced by + Mr. Spencer,<a name="NtA_730" href="#Nt_730"><sup>[730]</sup></a> on the + strengthening of the bowed bones of rickety children, along their concave + sides, leads to the belief that this is possible.</p> + + <p>Mr. H. Spencer has also shown that the ascent of the sap in trees is + aided by the rocking movement caused by the wind; and the sap strengthens + the trunk "in proportion to the stress to be borne; since the more severe + and the more repeated the strains, the greater must be the exudation from + the vessels into the surrounding tissue, and the greater the thickening + of this tissue by secondary deposits."<a name="NtA_731" + href="#Nt_731"><sup>[731]</sup></a> But woody trunks may be formed of + hard tissue without their having been subjected to any movement, as we + see with ivy closely attached to old walls. In all these cases, it is + very difficult to disentangle the effects of long-continued selection + from those consequent on the increased action or movement of the part. + Mr. H. Spencer<a name="NtA_732" href="#Nt_732"><sup>[732]</sup></a> + acknowledges this difficulty, and gives as an instance the spines <!-- + Page 297 --><span class="pagenum"><a name="page297"></a>{297}</span>or + thorns of trees, and the shells of nuts. Here we have extremely hard + woody tissue without the possibility of any movement to cause exudation, + and without, as far as we can see, any other directly exciting cause; and + as the hardness of these parts is of manifest service to the plant, we + may look at the result as probably due to the selection of so-called + spontaneous variations. Every one knows that hard work thickens the + epidermis on the hands; and when we hear that with infants long before + their birth the epidermis is thicker on the palms and soles of the feet + than on any other part of the body, as was observed with admiration by + Albinus,<a name="NtA_733" href="#Nt_733"><sup>[733]</sup></a> we are + naturally inclined to attribute this to the inherited effects of + long-continued use or pressure. We are tempted to extend the same view + even to the hoofs of quadrupeds; but who will pretend to determine how + far natural selection may have aided in the formation of structures of + such obvious importance to the animal?</p> + +<blockquote class="b1n"> + + <p>That use strengthens the muscles may be seen in the limbs of artisans + who follow different trades; and when a muscle is strengthened, the + tendons, and the crests of bone to which they are attached, become + enlarged; and this must likewise be the case with the blood-vessels and + nerves. On the other hand, when a limb is not used, as by Eastern + fanatics, or when the nerve supplying it with nervous power is + effectually destroyed, the muscles wither. So again, when the eye is + destroyed the optic nerve becomes atrophied, sometimes even in the course + of a few months.<a name="NtA_734" href="#Nt_734"><sup>[734]</sup></a> The + Proteus is furnished with branchiæ as well as with lungs: and + Schreibers<a name="NtA_735" href="#Nt_735"><sup>[735]</sup></a> found + <span class="correction" title="Original reads `than'.">that</span> when + the animal was compelled to live in deep water the branchiæ were + developed to thrice their ordinary size, and the lungs were partially + atrophied. When, on the other hand, the animal was compelled to live in + shallow water, the lungs became larger and more vascular, whilst the + branchiæ disappeared in a more or less complete degree. Such + modifications as these are, however, of comparatively little value for + us, as we do not actually know that they tend to be inherited.</p> + + <p>In many cases there is reason to believe that the lessened use of + various organs has affected the corresponding parts in the offspring. But + there is no good evidence that this ever follows in the course of a + single generation. It appears, as in the case of general or indefinite + variability, that several generations must be subjected to changed habits + for any appreciable result. Our domestic fowls, ducks, and geese have + almost lost, not <!-- Page 298 --><span class="pagenum"><a + name="page298"></a>{298}</span>only in the individual but in the race, + their power of flight; for we do not see a chicken, when frightened, take + flight like a young pheasant. Hence I was led carefully to compare the + limb-bones of fowls, ducks, pigeons, and rabbits, with the same bones in + the wild parent-species. As the measurements and weights were fully given + in the earlier chapters, I need here only recapitulate the results. With + domestic pigeons, the length of the sternum, the prominence of its crest, + the length of the scapulæ and furcula, the length of the wings as + measured from tip to tip of the radius, are all reduced relatively to the + same parts in the wild pigeon. The wing and tail feathers, however, are + increased in length, but this may have as little connection with the use + of the wings or tail, as the lengthened hair on a dog with the amount of + exercise which the breed has habitually taken. The feet of pigeons, + except in the long-beaked races, are reduced in size. With fowls the + crest of the sternum is less prominent, and is often distorted or + monstrous; the wing-bones have become lighter relatively to the + leg-bones, and are apparently a little shorter in comparison with those + of the parent-form, the <i>Gallus bankiva</i>. With ducks, the crest of + the sternum is affected in the same manner as in the foregoing cases: the + furcula, coracoids, and scapulæ are all reduced in weight relatively to + the whole skeleton: the bones of the wings are shorter and lighter, and + the bones of the legs longer and heavier, relatively to each other, and + relatively to the whole skeleton, in comparison with the same bones in + the wild-duck. The decreased weight and size of the bones, in the + foregoing cases, is probably the indirect result of the reaction of the + weakened muscles on the bones. I failed to compare the feathers of the + wings of the tame and wild duck; but Gloger<a name="NtA_736" + href="#Nt_736"><sup>[736]</sup></a> asserts that in the wild duck the + tips of the wing-feathers reach almost to the end of the tail, whilst in + the domestic duck they often hardly reach to its base. He remarks, also, + on the greater thickness of the legs, and says that the swimming membrane + between the toes is reduced; but I was not able to detect this latter + difference.</p> + + <p>With the domesticated rabbit the body, together with the whole + skeleton, is generally larger and heavier than in the wild animal, and + the leg-bones are heavier in due proportion; but whatever standard of + comparison be taken, neither the leg-bones nor the scapulæ have increased + in length proportionally with the increased dimensions of the rest of the + skeleton. The skull has become in a marked manner narrower, and, from the + measurements of its capacity formerly given, we may conclude, that this + narrowness results from the decreased size of the brain, consequent on + the mentally inactive life led by these closely-confined animals.</p> + + <p>We have seen in the eighth chapter that silk-moths, which have been + kept during many centuries closely confined, emerge from their cocoons + with their wings distorted, incapable of flight, often greatly reduced in + size, or even, according to Quatrefages, quite rudimentary. This + condition of the wings may be largely owing to the same kind of + monstrosity which often affects wild Lepidoptera when artificially reared + from the cocoon; or it may <!-- Page 299 --><span class="pagenum"><a + name="page299"></a>{299}</span>be in part due to an inherent tendency, + which is common to the females of many Bombycidæ, to have their wings in + a more or less rudimentary state; but part of the effect may probably be + attributed to long-continued disuse.</p> + +</blockquote> + + <p>From the foregoing facts there can be no doubt that certain parts of + the skeleton in our anciently domesticated animals, have been modified in + length and weight by the effects of decreased or increased use; but they + have not been modified, as shown in the earlier chapters, in shape or + structure. We must, however, be cautious in extending this latter + conclusion to animals living a free life; for these will occasionally be + exposed during successive generations to the severest competition. With + wild animals it would be an advantage in the struggle for life that every + superfluous and useless detail of structure should be removed or + absorbed; and thus the reduced bones might ultimately become changed in + structure. With highly-fed domesticated animals, on the other hand, there + is no economy of growth; nor any tendency to the elimination of trifling + and superfluous details of structure.</p> + + <p>Turning now to more general observations, Nathusius has shown that, + with the improved races of the pig, the shortened legs and snout, the + form of the articular condyles of the occiput, and the position of the + jaws with the upper canine teeth projecting in a most anomalous manner in + front of the lower canines, may be attributed to these parts not having + been fully exercised. For the highly-cultivated races do not travel in + search of food, nor root up the ground with their ringed muzzles. These + modifications of structure, which are all strictly inherited, + characterise several improved breeds, so that they cannot have been + derived from any single domestic or wild stock.<a name="NtA_737" + href="#Nt_737"><sup>[737]</sup></a> With respect to cattle, Professor + Tanner has remarked that the lungs and liver in the improved breeds "are + found to be considerably reduced in size when compared with those + possessed by animals having perfect liberty;"<a name="NtA_738" + href="#Nt_738"><sup>[738]</sup></a> and the reduction of these organs + affects the general shape of the body. The cause of the reduced lungs in + highly-bred animals which take little exercise is <!-- Page 300 --><span + class="pagenum"><a name="page300"></a>{300}</span>obvious; and perhaps + the liver may be affected by the nutritious and artificial food on which + they largely subsist.</p> + +<blockquote class="b1n"> + + <p>It is well known that, when an artery is tied, the <span + class="correction" title="Original reads `anastomising', corrected by errata, page viii." + >anastomosing</span> branches, from being forced to transmit more blood, + increase in diameter; and this increase cannot be accounted for by mere + extension, as their coats gain in strength. Mr. Herbert Spencer<a + name="NtA_739" href="#Nt_739"><sup>[739]</sup></a> has argued that with + plants the flow of sap from the point of supply to the growing part first + elongates the cells in this line; and that the cells then become + confluent, thus forming the ducts; so that, on this view, the vessels in + plants are formed by the mutual reaction of the flowing sap and cellular + tissue. Dr. W. Turner has remarked,<a name="NtA_740" + href="#Nt_740"><sup>[740]</sup></a> with respect to the branches of + arteries, and likewise to a certain extent with nerves, that the great + principle of compensation frequently comes into play; for "when two + nerves pass to adjacent cutaneous areas, an inverse relation as regards + size may subsist between them; a deficiency in one may be supplied by an + increase in the other, and thus the area of the former may be trespassed + on by the latter nerve." But how far in these cases the difference in + size in the nerves and arteries is due to original variation, and how far + to increased use or action, is not clear.</p> + + <p>In reference to glands, Mr. Paget observes that "when one kidney is + destroyed the other often becomes much larger, and does double work."<a + name="NtA_741" href="#Nt_741"><sup>[741]</sup></a> If we compare the size + of the udders and their power of secretion in cows which have been long + domesticated, and in certain goats in which the udders nearly touch the + ground, with the size and power of secretion of these organs in wild or + half-domesticated animals, the difference is great. A good cow with us + daily yields more than five gallons, or forty pints of milk, whilst a + first-rate animal, kept, for instance, by the Damaras of South Africa,<a + name="NtA_742" href="#Nt_742"><sup>[742]</sup></a> "rarely gives more + than two or three pints of milk daily, and, should her calf be taken from + her, she absolutely refuses to give any." We may attribute the excellence + of our cows, and of certain goats, partly to the continued selection of + the best milking animals, and partly to the inherited effects of the + increased action, through man's art, of the secreting glands.</p> + + <p>It is notorious, as was remarked in the twelfth chapter, that + short-sight is inherited; and if we compare watchmakers or engravers + with, for instance, sailors, we can hardly doubt that vision continually + directed towards a near object permanently affects the structure of the + eye.</p> + + <p>Veterinarians are unanimous that horses become affected with spavins, + splints, ringbones, &c., from being shod, and from travelling on hard + roads, and they are almost equally unanimous that these injuries are + transmitted. Formerly horses were not shod in North Carolina, and it has + been asserted that they did not then suffer from these diseases of the + legs and feet.<a name="NtA_743" href="#Nt_743"><sup>[743]</sup></a></p> + +</blockquote> + +<p><!-- Page 301 --><span class="pagenum"><a name="page301"></a>{301}</span></p> + + <p>Our domesticated quadrupeds are all descended, as far as is known, + from species having erect ears; yet few kinds can be named, of which at + least one race has not drooping ears. Cats in China, horses in parts of + Russia, sheep in Italy and elsewhere, the guinea-pig in Germany, goats + and cattle in India, rabbits, pigs, and dogs in all long-civilised + countries, have dependent ears. With wild animals, which constantly use + their ears like funnels to catch every passing sound, and especially to + ascertain the direction whence it comes, there is not, as Mr. Blyth has + remarked, any species with drooping ears except the elephant. Hence the + incapacity to erect the ears is certainly in some manner the result of + domestication; and this incapacity has been attributed by various + authors<a name="NtA_744" href="#Nt_744"><sup>[744]</sup></a> to disuse, + for animals protected by man are not compelled habitually to use their + ears. Col. Hamilton Smith<a name="NtA_745" + href="#Nt_745"><sup>[745]</sup></a> states that in ancient effigies of + the dog, "with the exception of one Egyptian instance, no sculpture of + the earlier Grecian era produces representations of hounds with + completely drooping ears; those with them half pendulous are missing in + the most ancient; and this character increases, by degrees, in the works + of the Roman period." Godron also has remarked that "the pigs of the + ancient Egyptians had not their ears enlarged and pendent."<a + name="NtA_746" href="#Nt_746"><sup>[746]</sup></a> But it is remarkable + that the drooping of the ears, though probably the effect of disuse, is + not accompanied by any decrease in size; on the contrary, when we + remember that animals so different as fancy rabbits, certain Indian + breeds of the goat, our petted spaniels, bloodhounds, and other dogs, + have enormously elongated ears, it would appear as if disuse actually + caused an increase in length. With rabbits, the drooping of the much + elongated ears has affected even the structure of the skull.</p> + + <p>The tail of no wild animal, as remarked to me by Mr. Blyth, is curled; + whereas pigs and some races of dogs have their tails much curled. This + deformity, therefore, appears to be the result of domestication, but + whether in any way connected with the lessened use of the tail is + doubtful.</p> + +<p><!-- Page 302 --><span class="pagenum"><a name="page302"></a>{302}</span></p> + + <p>The epidermis on our hands is easily thickened, as every one knows, by + hard work. In a district of Ceylon the sheep have "horny callosities that + defend their knees, and which arise from their habit of kneeling down to + crop the short herbage, and this distinguishes the Jaffna flocks from + those of other portions of the island;" but it is not stated whether this + peculiarity is inherited.<a name="NtA_747" + href="#Nt_747"><sup>[747]</sup></a></p> + + <p>The mucous membrane which lines the stomach is continuous with the + external skin of the body; therefore it is not surprising that its + texture should be affected by the nature of the food consumed, but other + and more interesting changes likewise follow. Hunter long ago observed + that the muscular coat of the stomach of a gull (<i>Larus + tridactylus</i>) which had been fed for a year chiefly on grain was + thickened; and, according to Dr. Edmondston, a similar change + periodically occurs in the Shetland Islands in the stomach of the + <i>Larus argentatus</i>, which in the spring frequents the corn-fields + and feeds on the seed. The same careful observer has noticed a great + change in the stomach of a raven which had been long fed on vegetable + food. In the case of an owl (<i>Strix grallaria</i>) similarly treated, + Menetries states that the form of the stomach was changed, the inner coat + became leathery, and the liver increased in size. Whether these + modifications in the digestive organs would in the course of generations + become inherited is not known.<a name="NtA_748" + href="#Nt_748"><sup>[748]</sup></a></p> + + <p>The increased or diminished length of the intestines, which apparently + results from changed diet, is a more remarkable case, because it is + characteristic of certain animals in their domesticated condition, and + therefore must be inherited. The complex absorbent system, the + blood-vessels, nerves, and muscles, are necessarily all modified together + with the intestines. According to Daubenton, the intestines of the + domestic cat are one-third longer than those of the wild cat of Europe; + and although this species is not the parent-stock of the domestic animal, + yet, as Isidore Geoffroy has remarked, the several species <!-- Page 303 + --><span class="pagenum"><a name="page303"></a>{303}</span>of cats are so + closely allied that the comparison is probably a fair one. The increased + length appears to be due to the domestic cat being less strictly + carnivorous in its diet than any wild feline species; I have seen a + French kitten eating vegetables as readily as meat. According to Cuvier, + the intestines of the domesticated pig exceed greatly in proportionate + length those of the wild boar. In the tame and wild rabbit the change is + of an opposite nature, and probably results from the nutritious food + given to the tame rabbit.<a name="NtA_749" + href="#Nt_749"><sup>[749]</sup></a></p> + +<hr class="short" /> + + <p><i>Changed Habits of Life, independently of the Use or Disuse of + particular Organs.</i>—This subject, as far as the mental powers of + animals are concerned, so blends into instinct, on which I shall treat in + a future work, that I will here only remind the reader of the many cases + which occur under domestication, and which are familiar to every + one—for instance the tameness of our animals—the pointing or + retrieving of dogs—their not attacking the smaller animals kept by + man—and so forth. How much of these changes ought to be attributed + to inherited habit, and how much to the selection of individuals which + have varied in the desired manner, irrespectively of the special + circumstances under which they have been kept, can seldom be told. We + have already seen that animals may be habituated to a changed diet; but a + few additional instances may here be given.</p> + + <p>In the Polynesian Islands and in China the dog is fed exclusively on + vegetable matter, and the taste for this kind of food is to a certain + extent inherited.<a name="NtA_750" href="#Nt_750"><sup>[750]</sup></a> + Our sporting dogs will not touch the bones of game birds, whilst other + dogs devour them with greediness. In some parts of the world sheep have + been largely fed on fish. The domestic hog is fond of barley, the wild + boar is said to disdain it; and the disdain is partially inherited, for + some young wild pigs bred in captivity showed an aversion for this grain, + whilst others of the same brood relished it.<a name="NtA_751" + href="#Nt_751"><sup>[751]</sup></a> One of my relations bred some young + pigs from <!-- Page 304 --><span class="pagenum"><a + name="page304"></a>{304}</span>a Chinese sow by a wild Alpine boar; they + lived free in the park, and were so tame that they came to the house to + be fed; but they would not touch swill, which was devoured by the other + pigs. An animal when once accustomed to an unnatural diet, which can + generally be effected only during youth, dislikes its proper food, as + Spallanzani found to be the case with a pigeon which had been long fed on + meat. Individuals of the same species take to new food with different + degrees of readiness; one horse, it is stated, soon learned to eat meat, + whilst another would have perished from hunger rather than have partaken + of it.<a name="NtA_752" href="#Nt_752"><sup>[752]</sup></a></p> + + <p>The caterpillars of the <i>Bombyx hesperus</i> feed in a state of + nature on the leaves of the <i>Café diable</i>, but, after having been + reared on the Ailanthus, they would not touch the <i>Café diable</i>, and + actually died of hunger.<a name="NtA_753" + href="#Nt_753"><sup>[753]</sup></a></p> + + <p>It has been found possible to accustom marine fish to live in fresh + water; but as such changes in fish, and other marine animals, have been + chiefly observed in a state of nature, they do not properly belong to our + present subject. The period of gestation and of maturity, as shown in the + earlier chapters,—the season and the frequency of the act of + breeding,—have all been greatly modified under domestication. With + the Egyptian goose the rate of change in the season has been recorded.<a + name="NtA_754" href="#Nt_754"><sup>[754]</sup></a> The wild drake pairs + with one female, the domestic drake is polygamous. Certain breeds of + fowls have lost the habit of incubation. The paces of the horse, and the + manner of flight in certain breeds of the pigeon, have been modified, and + are inherited. The voice differs much in certain fowls and pigeons. Some + breeds are clamorous and others silent, as in the Call and common duck, + or in the Spitz and pointer dog. Every one knows how dogs differ from + each other in their manner of hunting, and in their ardour after + different kinds of game or vermin.</p> + + <p>With plants the period of vegetation is easily changed and is + inherited, as in the case of summer and winter wheat, barley, <!-- Page + 305 --><span class="pagenum"><a name="page305"></a>{305}</span>and + vetches; but to this subject we shall immediately return under + acclimatisation. Annual plants sometimes become perennial under a new + climate, as I hear from Dr. Hooker is the case with the stock and + mignonette in Tasmania. On the other hand, perennials sometimes become + annuals, as with the Ricinus in England, and as, according to Captain + Mangles, with many varieties of the heartsease. Von Berg<a name="NtA_755" + href="#Nt_755"><sup>[755]</sup></a> raised from seed of <i>Verbascum + phœnicium</i>, which is usually a biennial, both annual and + perennial varieties. Some deciduous bushes become evergreen in hot + countries.<a name="NtA_756" href="#Nt_756"><sup>[756]</sup></a> Rice + requires much water, but there is one variety in India which can be grown + without irrigation.<a name="NtA_757" href="#Nt_757"><sup>[757]</sup></a> + Certain varieties of the oat and of our other cereals are best fitted for + certain soils.<a name="NtA_758" href="#Nt_758"><sup>[758]</sup></a> + Endless similar facts could be given in the animal and vegetable + kingdoms. They are noticed here because they illustrate analogous + differences in closely allied natural species, and because such changed + habits of life, whether due to use and disuse, or to the direct action of + external conditions, or to so-called spontaneous variation, would be apt + to lead to modifications of structure.</p> + +<hr class="short" /> + + <p><i>Acclimatisation.</i>—From the previous remarks we are + naturally led to the much disputed subject of acclimatisation. There are + two distinct questions: Do varieties descended from the same species + differ in their power of living under different climates? And secondly, + if they so differ, how have they become thus adapted? We have seen that + European dogs do not succeed well in India, and it is asserted,<a + name="NtA_759" href="#Nt_759"><sup>[759]</sup></a> that no one has + succeeded in there keeping the Newfoundland long alive; but then it may + be argued, probably with truth, that these northern breeds are + specifically distinct from the native dogs which flourish in India. The + same remark may be made with respect to different breeds of sheep, of + which, according to Youatt,<a name="NtA_760" + href="#Nt_760"><sup>[760]</sup></a> not one brought "from a torrid + climate lasts out the second year," in the Zoological Gardens. But sheep + are capable of some degree of acclimatisation, for Merino sheep bred at + the Cape of Good Hope have been found <!-- Page 306 --><span + class="pagenum"><a name="page306"></a>{306}</span>far better adapted for + India than those imported from England.<a name="NtA_761" + href="#Nt_761"><sup>[761]</sup></a> It is almost certain that the breeds + of the fowl are descended from the same species; but the Spanish breed, + which there is good reason to believe originated near the + Mediterranean,<a name="NtA_762" href="#Nt_762"><sup>[762]</sup></a> + though so fine and vigorous in England, suffers more from frost than any + other breed. The Arrindy silk-moth introduced from Bengal, and the + Ailanthus moth from the temperate province of Shan Tung, in China, belong + to the same species, as we may infer from their identity in the + caterpillar, cocoon, and mature states;<a name="NtA_763" + href="#Nt_763"><sup>[763]</sup></a> yet they differ much in constitution: + the Indian form "will flourish only in warm latitudes," the other is + quite hardy and withstands cold and rain.</p> + +<blockquote class="b1n"> + + <p>Plants are more strictly adapted to climate than are animals. The + latter when domesticated withstand such great diversities of climate, + that we find nearly the same species in tropical and temperate countries; + whilst the cultivated plants are widely dissimilar. Hence a larger field + is open for inquiry in regard to the acclimatisation of plants than of + animals. It is no exaggeration to say that with almost every plant which + has long been cultivated varieties exist, which are endowed with + constitutions fitted for very different climates; I will select only a + few of the more striking cases, as it would be tedious to give all. In + North America numerous fruit-trees have been raised, and in horticultural + publications,—for instance, in Downing,—lists are given of + the varieties which are best able to withstand the severe climate of the + northern States and Canada. Many American varieties of the pear, plum, + and peach are excellent in their own country, but until recently hardly + one was known that succeeded in England; and with apples,<a + name="NtA_764" href="#Nt_764"><sup>[764]</sup></a> not one succeeds. + Though the American varieties can withstand a severer winter than ours, + the summer here is not hot enough. Fruit-trees have originated in Europe + as in America with different constitutions, but they are not here much + noticed, as the same nurserymen do not supply a wide area. The Forelle + pear flowers early, and when the flowers have just set, and this is the + critical period, they have been observed, both in France and England, to + withstand with complete impunity a frost of 18° and even 14° Fahr., which + killed the flowers, whether fully expanded or in bud, of all other kinds + of pears.<a name="NtA_765" href="#Nt_765"><sup>[765]</sup></a> This power + in the flower of resisting cold and afterwards producing fruit does not + invariably depend, as we know on good authority,<a name="NtA_766" + href="#Nt_766"><sup>[766]</sup></a> on general constitutional vigour.</p> + +<p><!-- Page 307 --><span class="pagenum"><a name="page307"></a>{307}</span></p> + + <p>In proceeding northward, the number of varieties which are enabled to + resist the climate rapidly decreases, as may be seen in the list of the + varieties of the cherry, apple, and pear, which can be cultivated in the + neighbourhood of Stockholm.<a name="NtA_767" + href="#Nt_767"><sup>[767]</sup></a> Near Moscow, Prince Troubetzkoy + planted for experiment in the open ground several varieties of the pear, + but one alone, the <i>Poire sans Pepins</i>, withstood the cold of + winter.<a name="NtA_768" href="#Nt_768"><sup>[768]</sup></a> We thus see + that our fruit-trees, like distinct species of the same genus, certainly + differ from each other in their constitutional adaptation to different + climates.</p> + + <p>With the varieties of many plants, the adaptation to climate is often + very close. Thus it has been proved by repeated trials "that few if any + of the English varieties of wheat are adapted for cultivation in + Scotland;"<a name="NtA_769" href="#Nt_769"><sup>[769]</sup></a> but the + failure in this case is at first only in the quantity, though ultimately + in the quality, of the grain produced. The Rev. J. M. Berkeley sowed + wheat-seed from India, and got "the most meagre ears," on land which + would certainly have yielded a good crop from English wheat.<a + name="NtA_770" href="#Nt_770"><sup>[770]</sup></a> In these cases + varieties have been carried from a warmer to a cooler climate; in the + reverse case, as "when wheat was imported directly from France into the + West Indian Islands, it produced either wholly barren spikes or furnished + with only two or three miserable seeds, while West Indian seed by its + side yielded an enormous harvest."<a name="NtA_771" + href="#Nt_771"><sup>[771]</sup></a> Here is another case of close + adaptation to a slightly cooler climate; a kind of wheat which in England + may be used indifferently either as a winter or summer variety, when sown + under the warmer climate of Grignan, in France, behaved exactly as if it + had been a true winter wheat.<a name="NtA_772" + href="#Nt_772"><sup>[772]</sup></a></p> + + <p>Botanists believe that all the varieties of maize belong to the same + species; and we have seen that in North America, in proceeding northward, + the varieties cultivated in each zone produce their flowers and ripen + their seed within shorter and shorter periods. So that the tall, slowly + maturing southern varieties do not succeed in New England, and the New + English varieties do not succeed in Canada. I have not met with any + statement that the southern varieties are actually injured or killed by a + degree of cold which the northern varieties withstand with impunity, + though this is probable; but the production of early flowering and early + seeding varieties deserves to be considered as one form of + acclimatisation. Hence it has been found possible, according to Kalm, to + cultivate maize further and further northwards in America. In Europe, + also, as we learn from the evidence given by Alph. De Candolle, the + culture of maize has extended since the end of the last century thirty + leagues north of its former boundary.<a name="NtA_773" + href="#Nt_773"><sup>[773]</sup></a> On the authority of the great + Linnæus,<a name="NtA_774" href="#Nt_774"><sup>[774]</sup></a> I may quote + an <!-- Page 308 --><span class="pagenum"><a + name="page308"></a>{308}</span>analogous case, namely, that in Sweden + tobacco raised from home-grown seed ripens its seed a month sooner and is + less liable to miscarry than plants raised from foreign seed.</p> + + <p>With the Vine, differently from the maize, the line of practical + culture has retreated a little southward since the middle ages;<a + name="NtA_775" href="#Nt_775"><sup>[775]</sup></a> but this seems due to + commerce, including that of wine, being now freer or more easy. + Nevertheless the fact of the vine not having spread northward shows that + acclimatisation has made no progress during several centuries. There is, + however, a marked difference in the constitution of the several + varieties,—some being hardy, whilst others, like the muscat of + Alexandria, require a very high temperature to come to perfection. + According to Labat,<a name="NtA_776" href="#Nt_776"><sup>[776]</sup></a> + vines taken from France to the West Indies succeed with extreme + difficulty, whilst those imported from Madeira, or the Canary Islands, + thrive admirably.</p> + + <p>Gallesio gives a curious account of the naturalisation of the Orange + in Italy. Daring many centuries the sweet orange was propagated + exclusively by grafts, and so often suffered from frosts that it required + protection. After the severe frost of 1709, and more especially after + that of 1763, so many trees were destroyed that seedlings from the sweet + orange were raised, and, to the surprise of the inhabitants, their fruit + was found to be sweet. The trees thus raised were larger, more + productive, and hardier than the former kinds; and seedlings are now + continually raised. Hence Gallesio concludes that much more was effected + for the naturalisation of the orange in Italy by the accidental + production of new kinds during a period of about sixty years, than had + been effected by grafting old varieties during many ages.<a + name="NtA_777" href="#Nt_777"><sup>[777]</sup></a> I may add that Risso<a + name="NtA_778" href="#Nt_778"><sup>[778]</sup></a> describes some + Portuguese varieties of the orange as extremely sensitive to cold, and as + much tenderer than certain other varieties.</p> + + <p>The peach was known to Theophrastus, 322 <span + class="scac">B.C.</span><a name="NtA_779" + href="#Nt_779"><sup>[779]</sup></a> According to the authorities quoted + by Dr. F. Rolle,<a name="NtA_780" href="#Nt_780"><sup>[780]</sup></a> it + was tender when first introduced into Greece, and even in the island of + Rhodes only occasionally bore fruit. If this be correct, the peach, in + spreading during the last two thousand years over the middle parts of + Europe, must have become much hardier. At the present day different + varieties differ much in hardiness: some French varieties will not + succeed in England; and near Paris, the <i>Pavie de Bonneuil</i> does not + ripen its fruit till very late, even when grown on a wall; "it is, + therefore, only fit for a very hot southern climate."<a name="NtA_781" + href="#Nt_781"><sup>[781]</sup></a></p> + + <p>I will briefly give a few other cases. A variety of <i>Magnolia + grandiflora</i>, raised by M. Roy, withstands cold several degrees lower + than that which any other variety can resist. With camellias there is + much difference in hardiness. One particular variety of Noisette rose + withstood the severe frost of 1860 "untouched and hale amidst a universal + destruction of other <!-- Page 309 --><span class="pagenum"><a + name="page309"></a>{309}</span>Noisettes." In New York the "Irish yew is + quite hardy, but the common yew is liable to be cut down." I may add that + there are varieties of the sweet potato (<i>Convolvulus batatas</i>) + which are suited for warmer, as well as for colder, climates.<a + name="NtA_782" href="#Nt_782"><sup>[782]</sup></a></p> + +</blockquote> + + <p>The plants as yet mentioned have been found capable of resisting an + unusual degree of cold or heat, when fully grown. The following cases + refer to plants whilst young. In a large bed of young Araucarias of the + same age, growing close together and equally exposed, it was observed,<a + name="NtA_783" href="#Nt_783"><sup>[783]</sup></a> after the unusually + severe winter of 1860-61, that, "in the midst of the dying, numerous + individuals remained on which the frost had absolutely made no kind of + impression." Dr. Lindley, after alluding to this and other similar cases, + remarks, "Among the lessons which the late formidable winter has taught + us, is that, even in their power of resisting cold, individuals of the + same species of plants are remarkably different." Near Salisbury, there + was a sharp frost on the night of May 24th, 1836, and all the French + beans (<i>Phaseolus vulgaris</i>) in a bed were killed except about one + in thirty, which completely escaped.<a name="NtA_784" + href="#Nt_784"><sup>[784]</sup></a> On the same day of the month, but in + the year 1864, there was a severe frost in Kent, and two rows of + scarlet-runners (<i>P. multiflorus</i>) in my garden, containing 390 + plants of the same age and equally exposed, were all blackened and killed + except about a dozen plants. In an adjoining row of "Fulmer's dwarf bean" + (<i>P. vulgaris</i>), one single plant escaped. A still more severe frost + occurred four days afterwards, and of the dozen plants which had + previously escaped only three survived; these were not taller or more + vigorous than the other young plants, but they escaped completely, with + not even the tips of their leaves browned. It was impossible to behold + these three plants, with their blackened, withered, and dead brethren all + round them, and not see at a glance that they differed widely in + constitutional power of resisting frost.</p> + + <p>This work is not the proper place to show that wild plants <!-- Page + 310 --><span class="pagenum"><a name="page310"></a>{310}</span>of the + same species, naturally growing at different altitudes or under different + latitudes, become to a certain extent acclimatised, as is proved by the + different behaviour of their seedlings when raised in England. In my + 'Origin of Species' I have alluded to some cases, and I could add others. + One instance must suffice: Mr. Grigor, of Forres,<a name="NtA_785" + href="#Nt_785"><sup>[785]</sup></a> states that seedlings of the Scotch + fir (<i>Pinus sylvestris</i>), raised from seed from the Continent and + from the forests of Scotland, differ much. "The difference is perceptible + in one-year-old, and more so in two-year-old seedlings; but the effects + of the winter on the second year's growth almost uniformly makes those + from the Continent quite brown, and so damaged, that by the month of + March they are quite unsaleable, while the plants from the native Scotch + pine, under the same treatment, and standing alongside, although + considerably shorter, are rather stouter and quite green, so that the + beds of the one can be known from the other when seen from the distance + of a mile." Closely similar facts have been observed with seedling + larches.</p> + +<blockquote class="b1n"> + + <p>Hardy varieties would alone be valued or noticed in Europe; whilst + tender varieties, requiring more warmth, would generally be neglected; + but such occasionally arise. Thus Loudon<a name="NtA_786" + href="#Nt_786"><sup>[786]</sup></a> describes a Cornish variety of the + elm which is almost an evergreen, and of which the shoots are often + killed by the autumnal frosts, so that its timber is of little value. + Horticulturists know that some varieties are much more tender than + others: thus all the varieties of the broccoli are more tender than + cabbages; but there is much difference in this respect in the + sub-varieties of the broccoli; the pink and purple kinds are a little + hardier than the white Cape broccoli, "but they are not to be depended on + after the thermometer falls below 24° Fahr.:" the Walcheren broccoli is + less tender than the Cape, and there are several varieties which will + stand much severer cold than the Walcheren.<a name="NtA_787" + href="#Nt_787"><sup>[787]</sup></a> Cauliflowers seed more freely in + India than cabbages.<a name="NtA_788" href="#Nt_788"><sup>[788]</sup></a> + To give one instance with flowers: eleven plants raised from a hollyhock, + called the <i>Queen of the Whites</i>,<a name="NtA_789" + href="#Nt_789"><sup>[789]</sup></a> were found to be much more tender + than various other seedlings. It may be presumed that all tender + varieties would succeed better under a climate warmer than ours. With + fruit-trees, it is well known that certain varieties, for instance of the + peach, stand forcing in a hot-house better than others; and this shows + <!-- Page 311 --><span class="pagenum"><a + name="page311"></a>{311}</span>either pliability of organisation or some + constitutional difference. The same individual cherry-tree, when forced, + has been observed during successive years gradually to change its period + of vegetation.<a name="NtA_790" href="#Nt_790"><sup>[790]</sup></a> Few + pelargoniums can resist the heat of a stove, but <i>Alba multiflora</i> + will, as a most skilful gardener asserts, "stand pine-apple top and + bottom heat the whole winter, without looking any more drawn than if it + had stood in a common greenhouse; and <i>Blanche Fleur</i> seems as if it + had been made on purpose for growing in winter, like many bulbs, and to + rest all summer."<a name="NtA_791" href="#Nt_791"><sup>[791]</sup></a> + There can hardly be a doubt that the <i>Alba multiflora</i> pelargonium + must have a widely different constitution from that of most other + varieties of this plant; it would probably withstand even an equatorial + climate.</p> + + <p>We have seen that according to Labat the vine and wheat require + acclimatisation in order to succeed in the West Indies. Similar facts + have been observed at Madras: "two parcels of mignonette-seed, one direct + from Europe, the other saved at Bangalore (of which the mean temperature + is much below that of Madras) were sown at the same time: they both + vegetated equally favourably, but the former all died off a few days + after they appeared above ground; the latter still survive, and are + vigorous healthy plants." So again, "turnip and carrot seed saved at + Hyderabad are found to answer better at Madras than seed from Europe or + from the Cape of Good Hope."<a name="NtA_792" + href="#Nt_792"><sup>[792]</sup></a> Mr. J. Scott, of the Calcutta Botanic + Gardens, informs me that seeds of the sweet-pea (<i>Lathyrus + odoratus</i>) imported from England produce plants, with thick, rigid + stems and small leaves, which rarely blossom and never yield seed; plants + raised from French seed blossom sparingly, but all the flowers are + sterile; on the other hand, plants raised from sweet-peas grown near + Darjeeling in Upper India, but originally derived from England, can be + successfully cultivated on the plains of India; for they flower and seed + profusely, and their stems are lax and scandent. In some of the foregoing + cases, as Dr. Hooker has remarked to me, the greater success may perhaps + be attributed to the seeds having been more fully ripened under a more + favourable climate; but this view can hardly be extended to so many + cases, including plants, which, from being cultivated under a climate + hotter than their native one, become fitted for a still hotter climate. + We may therefore safely conclude that plants can to a certain extent + become accustomed to a climate either hotter or colder than their own; + although these latter cases have been more frequently observed.</p> + +</blockquote> + + <p>We will now consider the means by which acclimatisation may be + effected, namely, through the spontaneous appearance of varieties having + a different constitution, and through the effects of use or habit. In + regard to the first process, there is no evidence that a change in the + constitution of the <!-- Page 312 --><span class="pagenum"><a + name="page312"></a>{312}</span>offspring necessarily stands in any direct + relation with the nature of the climate inhabited by the parents. On the + contrary, it is certain that hardy and tender varieties of the same + species appear in the same country. New varieties thus spontaneously + arising become fitted to slightly different climates in two different + ways; firstly, they may have the power, either as seedlings or when + full-grown, of resisting intense cold, as with the Moscow pear, or of + resisting intense heat, as with some kinds of Pelargonium, or the flowers + may withstand severe frost, as with the Forelle pear. Secondly, plants + may become adapted to climates widely different from their own, from + flowering and fruiting either earlier or later in the season. In both + these cases the power of acclimatisation by man consists simply in the + selection and preservation of new varieties. But without any direct + intention on his part of securing a hardier variety, acclimatisation may + be unconsciously effected by merely raising tender plants from seed, and + by occasionally attempting their cultivation further and further + northwards, as in the case of maize, the orange, and the peach.</p> + + <p>How much influence ought to be attributed to inherited habit or custom + in the acclimatisation of animals and plants is a much more difficult + question. In many cases natural selection can hardly have failed to have + come into play and complicated the result. It is notorious that mountain + sheep resist severe weather and storms of snow which would destroy + lowland breeds; but then mountain sheep have been thus exposed from time + immemorial, and all delicate individuals will have been destroyed, and + the hardiest preserved. So with the Arrindy silk-moths of China and + India; who can tell how far natural selection may have taken a share in + the formation of the two races, which are now fitted for such widely + different climates? It seems at first probable that the many fruit-trees, + which are so well fitted for the hot summers and cold winters of North + America, in contrast with their poor success under our climate, have + become adapted through habit; but when we reflect on the multitude of + seedlings annually raised in that country, and that none would succeed + unless born with a fitting constitution, it is possible that mere habit + may have done nothing towards their acclimatisation. On the other hand, + when we <!-- Page 313 --><span class="pagenum"><a + name="page313"></a>{313}</span>hear that Merino sheep, bred during no + great number of generations at the Cape of Good Hope—that some + European plants raised during only a few generations in the cooler parts + of India, withstand the hotter parts of that country much better than the + sheep or seeds imported directly from England, we must attribute some + influence to habit. We are led to the same conclusion when we hear from + Naudin<a name="NtA_793" href="#Nt_793"><sup>[793]</sup></a> that the + races of melons, squashes, and gourds, which have long been cultivated in + Northern Europe, are comparatively more precocious, and need much less + heat for maturing their fruit, than the varieties of the same species + recently brought from tropical regions. In the reciprocal conversion of + summer and winter wheat, barley, and vetches into each other, habit + produces a marked effect in the course of a very few generations. The + same thing apparently occurs with the varieties of maize, which, when + carried from the Southern to the Northern States of America, or into + Germany, soon become accustomed to their new homes. With vine-plants + taken to the West Indies from Madeira, which are said to succeed better + than plants brought directly from France, we have some degree of + acclimatisation in the individual, independently of the production of new + varieties by seed.</p> + + <p>The common experience of agriculturists is of some value, and they + often advise persons to be cautious in trying in one country the + productions of another. The ancient agricultural writers of China + recommend the preservation and cultivation of the varieties peculiar to + each country. During the classical period, Columella wrote, "Vernaculum + pecus peregrino longe præstantius est."<a name="NtA_794" + href="#Nt_794"><sup>[794]</sup></a></p> + + <p>I am aware that the attempt to acclimatise either animals or plants + has been called a vain chimæra. No doubt the attempt in most cases + deserves to be thus called, if made independently of the production of + new varieties endowed with a different constitution. Habit, however much + prolonged, rarely produces any effect on a plant propagated by buds; it + apparently acts only through successive seminal generations. <!-- Page + 314 --><span class="pagenum"><a name="page314"></a>{314}</span>The + laurel, bay, laurestinus, &c., and the Jerusalem artichoke, which are + propagated by cuttings or tubers, are probably now as tender in England + as when first introduced; and this appears to be the case with the + potato, which until recently was seldom multiplied by seed. With plants + propagated by seed, and with animals, there will be little or no + acclimatisation unless the hardier individuals are either intentionally + or unconsciously preserved. The kidney-bean has often been advanced as an + instance of a plant which has not become hardier since its first + introduction into Britain. We hear, however, on excellent authority,<a + name="NtA_795" href="#Nt_795"><sup>[795]</sup></a> that some very fine + seed, imported from abroad, produced plants "which blossomed most + profusely, but were nearly all but abortive, whilst plants grown + alongside from English seed podded abundantly;" and this apparently shows + some degree of acclimatisation in our English plants. We have also seen + that seedlings of the kidney-bean occasionally appear with a marked power + of resisting frost; but no one, as far as I can hear, has ever separated + such hardy seedlings, so as to prevent accidental crossing, and then + gathered their seed, and repeated the process year after year. It may, + however, be objected with truth that natural selection ought to have had + a decided effect on the hardiness of our kidney-beans; for the tenderest + individuals must have been killed during every severe spring, and the + hardier preserved. But it should be borne in mind that the result of + increased hardiness would simply be that gardeners, who are always + anxious for as early a crop as possible, would sow their seed a few days + earlier than formerly. Now, as the period of sowing depends much on the + soil and elevation of each district, and varies with the season; and as + new varieties have often been imported from abroad, can we feel sure that + our kidney-beans are not somewhat hardier? I have not been able, by + searching old horticultural works, to answer this question + satisfactorily.</p> + + <p>On the whole the facts now given show that, though habit does + something towards acclimatisation, yet that the spontaneous appearance of + constitutionally different individuals is a far more effective agent. As + no single instance has been recorded, either with animals or plants, of + hardier individuals <!-- Page 315 --><span class="pagenum"><a + name="page315"></a>{315}</span>having been long and steadily selected, + though such selection is admitted to be indispensable for the improvement + of any other character, it is not surprising that man has done little in + the acclimatisation of domesticated animals and cultivated plants. We + need not, however, doubt that under nature new races and new species + would become adapted to widely different climates, by spontaneous + variation, aided by habit, and regulated by natural selection.</p> + +<p class="cenhead"><i>Arrests of Development: Rudimentary and Aborted Organs.</i></p> + +<blockquote class="b1n"> + + <p>These subjects are here introduced because there is reason to believe + that rudimentary organs are in many cases the result of disuse. + Modifications of structure from arrested development, so great or so + serious as to deserve to be called monstrosities, are of common + occurrence, but, as they differ much from any normal structure, they + require here only a passing notice. When a part or organ is arrested + during its embryonic growth, a rudiment is generally left. Thus the whole + head may be represented by a soft nipple-like projection, and the limbs + by mere papillæ. These rudiments of limbs are sometimes inherited, as has + been observed in a dog.<a name="NtA_796" + href="#Nt_796"><sup>[796]</sup></a></p> + + <p>Many lesser anomalies in our domesticated animals appear to be due to + arrested development. What the cause of the arrest may be, we seldom + know, except in the case of direct injury to the embryo within the egg or + womb. That the cause does not generally act at a very early embryonic + period we may infer from the affected organ seldom being wholly + aborted,—a rudiment being generally preserved. The external ears + are represented by mere vestiges in a Chinese breed of sheep; and in + another breed, the tail is reduced "to a little button, suffocated, in a + manner, by fat."<a name="NtA_797" href="#Nt_797"><sup>[797]</sup></a> In + tailless dogs and cats a stump is left; but I do not know whether it + includes at an early embryonic age rudiments of all the caudal vertebræ. + In certain breeds of fowls the comb and wattles are reduced to rudiments; + in the Cochin-China breed scarcely more than rudiments of spurs exist. + With polled Suffolk cattle, "rudiments of horns can often be felt at an + early age;"<a name="NtA_798" href="#Nt_798"><sup>[798]</sup></a> and with + species in a state of nature, the relatively greater development of + rudimentary organs at an early period of life is highly characteristic of + such organs. With hornless breeds of cattle and sheep; another and + singular kind of rudiment has been observed, namely, minute dangling + horns attached to the skin alone, and which are often shed and grow + again. With hornless goats, according to Desmarest,<a name="NtA_799" + href="#Nt_799"><sup>[799]</sup></a> <!-- Page 316 --><span + class="pagenum"><a name="page316"></a>{316}</span>the bony protuberances + which properly support the horns exist as mere rudiments.</p> + + <p>With cultivated plants it is far from rare to find the petals, + stamens, and pistils represented by rudiments, like those observed in + natural species. So it is with the whole seed in many fruits; thus near + Astrakhan there is a grape with mere traces of seeds, "so small and lying + so near the stalk that they are not perceived in eating the grape."<a + name="NtA_800" href="#Nt_800"><sup>[800]</sup></a> In certain varieties + of the gourd, the tendrils, according to Naudin, are represented by + rudiments or by various monstrous growths. In the broccoli and + cauliflower the greater number of the flowers are incapable of expansion, + and include rudimentary organs. In the Feather hyacinth (<i>Muscari + comosum</i>) the upper and central flowers are brightly coloured but + rudimentary; under cultivation the tendency to abortion travels downwards + and outwards, and all the flowers become rudimentary; but the abortive + stamens and pistils are not so small in the lower as in the upper + flowers. In the <i>Viburnum opulus</i>, on the other hand, the outer + flowers naturally have their organs of fructification in a rudimentary + state, and the corolla is of large size; under cultivation, the change + spreads to the centre, and all the flowers become affected; thus the + well-known Snow-ball bush is produced. In the Compositæ, the so-called + doubling of the flowers consists in the greater development of the + corolla of the central florets, generally accompanied with some degree of + sterility; and it has been observed<a name="NtA_801" + href="#Nt_801"><sup>[801]</sup></a> that the progressive doubling + invariably spreads from the circumference to the centre,—that is, + from the ray florets, which so often include rudimentary organs, to those + of the disc. I may add, as bearing on this subject, that, with Asters, + seeds taken from the florets of the circumference have been found to + yield the greatest number of double flowers.<a name="NtA_802" + href="#Nt_802"><sup>[802]</sup></a> In these several cases we have a + natural tendency in certain parts to become rudimentary, and this under + culture spreads either to, or from, the axis of the plant. It deserves + notice, as showing how the same laws govern the changes which natural + species and artificial varieties undergo, that in a series of species in + the genus Carthamus, one of the Compositæ, a tendency in the seeds to the + abortion of the pappus may be traced extending from the circumference to + the centre of the disc: thus, according to A. de Jussieu,<a + name="NtA_803" href="#Nt_803"><sup>[803]</sup></a> the abortion is only + partial in <i>Carthamus creticus</i>, but more extended in <i>C. + lanatus</i>; for in this species two or three alone of the central seeds + are furnished with a pappus, the surrounding seeds being either quite + naked or furnished with a few hairs; and lastly, in <i>C. tinctorius</i>, + even the central seeds are destitute of pappus, and the abortion is + complete.</p> + + <p>With animals and plants under domestication, when an organ disappears, + leaving only a rudiment, the loss has generally been sudden, as with + hornless and tailless breeds; and such cases may be ranked as inherited + monstrosities. But in some few cases the loss has been gradual, and <!-- + Page 317 --><span class="pagenum"><a name="page317"></a>{317}</span>has + been partly effected by selection, as with the rudimentary combs and + wattles of certain fowls. We have also seen that the wings of some + domesticated birds have been slightly reduced by disuse, and the great + reduction of the wings in certain silk-moths, with mere rudiments left, + has probably been aided by disuse.</p> + + <p>With species in a state of nature, rudimentary organs are so extremely + common that scarcely one can be named which is wholly free from a blemish + of this nature. Such organs are generally variable, as several + naturalists have observed; for, being useless, they are not regulated by + natural selection, and they are more or less liable to reversion. The + same rule certainly holds good with parts which have become rudimentary + under domestication. We do not know through what steps under nature + rudimentary organs have passed in being reduced to their present + condition; but we so incessantly see in species of the same group the + finest gradations between an organ in a rudimentary and perfect state, + that we are led to believe that the passage must have been extremely + gradual. It may be doubted whether a change of structure so abrupt as the + sudden loss of an organ would ever be of service to a species in a state + of nature; for the conditions to which all organisms are closely adapted + usually change very slowly. Even if an organ did suddenly disappear in + some one individual by an arrest of development, intercrossing with the + other individuals of the same species would cause it to reappear in a + more or less perfect manner, so that its final reduction could only be + effected by the slow process of continued disuse or natural selection. It + is much more probable that, from changed habits of life, organs first + become of less and less use, and ultimately superfluous; or their place + may be supplied by some other organ; and then disuse, acting on the + offspring through inheritance at corresponding periods of life, would go + on reducing the organ; but as most organs could be of no use at an early + embryonic period, they would not be affected by disuse; consequently they + would be preserved at this stage of growth, and would remain as + rudiments. In addition to the effects of disuse, the principle of economy + of growth, already alluded to in this chapter, would lead to the still + further reduction of all superfluous parts. With respect to the final and + total suppression or abortion of any organ, another and distinct + principle, which will be discussed in the chapter on pangenesis, probably + takes a share in the work.</p> + + <p>With animals and plants reared by man there is no severe or recurrent + struggle for existence, and the principle of economy will not come into + action. So far, indeed, is this from being the case, that in some + instances organs, which are naturally rudimentary in the parent-species, + become partially redeveloped in the domesticated descendants. Thus cows, + like most other ruminants, properly have four active and two rudimentary + mammæ; but in our domesticated animals, the latter occasionally become + considerably developed and yield milk. The atrophied mammæ, which, in + male domesticated animals, including man, have in some rare cases grown + to full size and secreted milk, perhaps offer an analogous case. The hind + feet of dogs include rudiments of a fifth toe, and in certain large + breeds these toes, though still rudimentary, become considerably + developed <!-- Page 318 --><span class="pagenum"><a + name="page318"></a>{318}</span>and are furnished with claws. In the + common Hen, the spurs and comb are rudimentary, but in certain breeds + these become, independently of age or disease of the ovaria, well + developed. The stallion has canine teeth, but the mare has only traces of + the alveoli, which, as I am informed by the eminent veterinary Mr. G. T. + Brown, frequently contain minute irregular nodules of bone. These + nodules, however, sometimes become developed into imperfect teeth, + protruding through the gums and coated with enamel; and occasionally they + grow to a third or even a fourth of the length of the canines in the + stallion. With plants I do not know whether the redevelopment of + rudimentary organs occurs more frequently under culture than under + nature. Perhaps the pear-tree may be a case in point, for when wild it + bears thorns, which though useful as a protection are formed of branches + in a <span class="correction" title="Original reads `rudimentry'." + >rudimentary</span> condition, but, when the tree is cultivated, the + thorns are reconverted into branches.</p> + +</blockquote> + + <p>Finally, though organs which must be classed as rudimentary frequently + occur in our domesticated animals and cultivated plants, these have + generally been formed suddenly, through an arrest of development. They + usually differ in appearance from the rudiments which so frequently + characterise natural species. In the latter, rudimentary organs have been + slowly formed through continued disuse, acting by inheritance at a + corresponding age, aided by the principle of the economy of growth, all + under the control of natural selection. With domesticated animals, on the + other hand, the principle of economy is far from coming into action, and + their organs, although often slightly reduced by disuse, are not thus + almost obliterated with mere rudiments left.</p> + +<hr class="full" /> + +<p><!-- Page 319 --><span class="pagenum"><a name="page319"></a>{319}</span></p> + +<h3>CHAPTER XXV.</h3> + +<p class="cenhead">LAWS OF VARIATION, <i>continued</i>—CORRELATED VARIABILITY.</p> + +<blockquote class="b1n"> + + <p><span class="scac">EXPLANATION OF TERM</span>—<span + class="scac">CORRELATION AS CONNECTED WITH DEVELOPMENT</span>—<span + class="scac">MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED + SIZE OF PARTS</span>—<span class="scac">CORRELATED VARIATION OF + HOMOLOGOUS PARTS</span>—<span class="scac">FEATHERED FEET IN BIRDS + ASSUMING THE STRUCTURE OF THE WINGS</span>—<span + class="scac">CORRELATION BETWEEN THE HEAD AND THE + EXTREMITIES</span>—<span class="scac">BETWEEN THE SKIN AND DERMAL + APPENDAGES</span>—<span class="scac">BETWEEN THE ORGANS OF SIGHT + AND HEARING</span>—<span class="scac">CORRELATED MODIFICATIONS IN + THE ORGANS OF PLANTS</span>—<span class="scac">CORRELATED + MONSTROSITIES</span>—<span class="scac">CORRELATION BETWEEN THE + SKULL AND EARS</span>—<span class="scac">SKULL AND CREST OF + FEATHERS</span>—<span class="scac">SKULL AND + HORNS</span>—<span class="scac">CORRELATION OF GROWTH COMPLICATED + BY THE ACCUMULATED EFFECTS OF NATURAL SELECTION</span>—<span + class="scac">COLOUR AS CORRELATED WITH CONSTITUTIONAL + PECULIARITIES.</span></p> + +</blockquote> + + <p>All the parts of the organisation are to a certain extent connected or + correlated together; but the connexion may be so slight that it hardly + exists, as with compound animals or the buds on the same tree. Even in + the higher animals various parts are not at all closely related; for one + part may be wholly suppressed or rendered monstrous without any other + part of the body being affected. But in some cases, when one part varies, + certain other parts always, or nearly always, simultaneously vary; they + are then subject to the law of correlated variation. Formerly I used the + somewhat vague expression of correlation of growth, which may be applied + to many large classes of facts. Thus, all the parts of the body are + admirably coordinated for the peculiar habits of life of each organic + being, and they may be said, as the Duke of Argyll insists in his 'Reign + of Law,' to be correlated for this purpose. Again, in large groups of + animals certain structures always co-exist; for instance, a peculiar form + of stomach with teeth of peculiar form, and such structures may in one + sense be said to be correlated. But these cases have no necessary + connexion with the law to be discussed in the present chapter; for we do + not know that <!-- Page 320 --><span class="pagenum"><a + name="page320"></a>{320}</span>the initial or primary variations of the + several parts were in any way related; slight modifications or individual + differences may have been preserved, first in one and then in another + part, until the final and perfectly co-adapted structure was acquired; + but to this subject I shall presently recur. Again, in many groups of + animals the males alone are furnished with weapons, or are ornamented + with gay colours; and these characters manifestly stand in some sort of + correlation with the male reproductive organs, for when the latter are + destroyed these characters disappear. But it was shown in the twelfth + chapter that the very same peculiarity may become attached at any age to + either sex, and afterwards be exclusively transmitted by the same sex at + a corresponding age. In these cases we have inheritance limited by, or + correlated with, both sex and age; but we have no reason for supposing + that the original cause of the variation was necessarily connected with + the reproductive organs, or with the age of the affected being.</p> + + <p>In cases of true correlated variation, we are sometimes able to see + the nature of the connexion; but in most cases the bond is hidden from + us, and certainly differs in different cases. We can seldom say which of + two correlated parts first varies, and induces a change in the other; or + whether the two are simultaneously produced by some distinct cause. + Correlated variation is an important subject for us; for when one part is + modified through continued selection, either by man or under nature, + other parts of the organisation will be unavoidably modified. From this + correlation it apparently follows that, with our domesticated animals and + plants, varieties rarely or never differ from each other by some single + character alone.</p> + + <p>One of the simplest cases of correlation is that a modification which + arises during an early stage of growth tends to influence the subsequent + development of the same part, as well as of other and intimately + connected parts. Isidore Geoffroy St. Hilaire states<a name="NtA_804" + href="#Nt_804"><sup>[804]</sup></a> that this may constantly be observed + with monstrosities <!-- Page 321 --><span class="pagenum"><a + name="page321"></a>{321}</span>in the animal kingdom; and Moquin-Tandon<a + name="NtA_805" href="#Nt_805"><sup>[805]</sup></a> remarks, that, as with + plants the axis cannot become monstrous without in some way affecting the + organs subsequently produced from it, so axial anomalies are almost + always accompanied by deviations of structure in the appended parts. We + shall presently see that with short-muzzled races of the dog certain + histological changes in the basal elements of the bones arrest their + development and shorten them, and this affects the position of the + subsequently developed molar teeth. It is probable that certain + modifications in the larvæ of insects would affect the structure of the + mature insects. But we must be very careful not to extend this view too + far, for, during the normal course of development, certain members in the + same group of animals are known to pass through an extraordinary course + of change, whilst other and closely allied members arrive at maturity + with little change of structure.</p> + + <p>Another simple case of correlation is that with the increased or + decreased dimensions of the whole body, or of any particular part, + certain organs are increased or diminished in number, or are otherwise + modified. Thus pigeon-fanciers have gone on selecting pouters for length + of body, and we have seen that their vertebræ are generally increased in + number, and their ribs in breadth. Tumblers have been selected for their + small bodies, and their ribs and primary wing-feathers are generally + lessened in number. Fantails have been selected for their large, + widely-expanded tails, with numerous tail-feathers, and the caudal + vertebræ are increased in size and number. Carriers have been selected + for length of beak, and their tongues have become longer, but not in + strict accordance with the length of beak. In this latter breed and in + others having large feet, the number of the scutellæ on the toes is + greater than in the breeds with small feet. Many similar cases could be + given. In Germany it has been observed that the period of gestation is + longer in large-sized than in small-sized breeds of cattle. With our + highly-improved animals of all kinds the period of maturity has advanced, + both with respect to the full growth of the body and the period of + reproduction; and, in correspondence with this, the teeth are now + developed earlier than formerly, so that, <!-- Page 322 --><span + class="pagenum"><a name="page322"></a>{322}</span>to the surprise of + agriculturists, the ancient rules for judging the age of an animal by the + state of its teeth are no longer trustworthy.<a name="NtA_806" + href="#Nt_806"><sup>[806]</sup></a></p> + + <p><i>Correlated Variation of Homologous Parts.</i>—Parts which are + homologous tend to vary in the same manner; and this is what might have + been expected, for such parts are identical in form and structure during + an early period of embryonic development, and are exposed in the egg or + womb to similar conditions. The symmetry, in most kinds of animals, of + the corresponding or homologous organs on the right and left sides of the + body, is the simplest case in point; but this symmetry sometimes fails, + as with rabbits having only one ear, or stags with one horn, or with + many-horned sheep which sometimes carry an additional horn on one side of + their heads. With flowers which have regular corollas, the petals + generally vary in the same manner, as we see in the same complicated and + elegant pattern, on the flowers of the Chinese pink; but with irregular + flowers, though the petals are of course homologous, this symmetry often + fails, as with the varieties of the <i>Antirrhinum</i> or snapdragon, or + that variety of the kidney-bean (<i>Phaseolus multiflorus</i>) which has + a white standard-petal.</p> + + <p>In the vertebrata the front and hind limbs are homologous, and they + tend to vary in the same manner, as we see in long and short-legged, or + in thick and thin-legged races of the horse and dog. Isidore Geoffroy<a + name="NtA_807" href="#Nt_807"><sup>[807]</sup></a> has remarked on the + tendency of supernumerary digits in man to appear, not only on the right + and left sides, but on the upper and lower extremities. Meckel has + insisted<a name="NtA_808" href="#Nt_808"><sup>[808]</sup></a> that, when + the muscles of the arm depart in number or arrangement from their proper + type, they almost always imitate those of the leg; and so conversely the + varying muscles of the leg imitate the normal muscles of the arm.</p> + + <p>In several distinct breeds of the pigeon and fowl, the legs and the + two outer toes are heavily feathered, so that in the trumpeter pigeon + they appear like little wings. In the feather-legged bantam the "boots" + or feathers, which grow from the outside of the leg and generally from + the two outer toes, have, <!-- Page 323 --><span class="pagenum"><a + name="page323"></a>{323}</span>according to the excellent authority of + Mr. Hewitt,<a name="NtA_809" href="#Nt_809"><sup>[809]</sup></a> been + seen to exceed the wing-feathers in length, and in one case were actually + nine and a half inches in length! As Mr. Blyth has remarked to me, these + leg-feathers resemble the primary wing-feathers, and are totally unlike + the fine down which naturally grows on the legs of some birds, such as + grouse and owls. Hence it may be suspected that excess of food has first + given redundancy to the plumage, and then that the law of homologous + variation has led to the development of feathers on the legs, in a + position corresponding with those on the wing, namely, on the outside of + the tarsi and toes. I am strengthened in this belief by the following + curious case of correlation, which for a long time seemed to me utterly + inexplicable, namely, that in pigeons of any breed, if the legs are + feathered, the two outer toes are partially connected by skin. These two + outer toes correspond with our third and fourth toes. Now, in the wing of + the pigeon or any other bird, the first and fifth digits are wholly + aborted; the second is rudimentary and carries the so-called + "bastard-wing;" whilst the third and fourth digits are completely united + and enclosed by skin, together forming the extremity of the wing. So that + in feather-footed pigeons, not only does the exterior surface support a + row of long feathers, like wing-feathers, but the very same digits which + in the wing are completely united by skin become partially united by skin + in the feet; and thus by the law of the correlated variation of + homologous parts we can understand the curious connection of feathered + legs and membrane between the two outer toes.</p> + + <p>Andrew Knight<a name="NtA_810" href="#Nt_810"><sup>[810]</sup></a> has + remarked that the face or head and the limbs vary together in general + proportions. Compare, for instance, the head and limbs of a dray and + race-horse, or of a greyhound and mastiff. What a monster a greyhound + would appear with the head of a mastiff! The <i>modern</i> bulldog, + however, has fine limbs, but this is a recently-selected character. From + the measurements given in the sixth chapter, we clearly see that in all + the breeds of the pigeon the length of the beak and the size of the feet + are correlated. The view which, as before explained, seems the most + probable is, that disuse in all cases tends <!-- Page 324 --><span + class="pagenum"><a name="page324"></a>{324}</span>to diminish the feet, + the beak becoming at the same time through correlation shorter; but that + in those few breeds in which length of beak has been a selected point, + the feet, notwithstanding disuse, have through correlation increased in + size.</p> + + <p>With the increased length of the beak in pigeons, not only the tongue + increases in length, but likewise the orifice of the nostrils. But the + increased length of the orifice of the nostrils perhaps stands in closer + correlation with the development of the corrugated skin or wattle at the + base of the beak; for when there is much wattle round the eyes, the + eyelids are greatly increased or even doubled in length.</p> + + <p>There is apparently some correlation even in colour between the head + and the extremities. Thus with horses a large white star or blaze on the + forehead is generally accompanied by white feet.<a name="NtA_811" + href="#Nt_811"><sup>[811]</sup></a> With white rabbits and cattle, dark + marks often co-exist on the tips of the ears and on the feet. In black + and tan dogs of different breeds, tan-coloured spots over the eyes and + tan-coloured feet almost invariably go together. These latter cases of + connected colouring may be due either to reversion or to analogous + variation,—subjects to which we shall hereafter return,—but + this does not necessarily determine the question of their original + correlation. If those naturalists are correct who maintain that the + jaw-bones are homologous with the limb-bones, then we can understand why + the head and limbs tend to vary together in shape and even in colour; but + several highly competent judges dispute the correctness of this view.</p> + + <p>The lopping forwards and downwards of the immense ears of fancy + rabbits is in part due to the disuse of the muscles, and in part to the + weight and length of the ears, which have been increased by selection + during many generations. Now, with the increased size and changed + direction of the ears, not only has the bony auditory meatus become + changed in outline, direction, and greatly in size, but the whole skull + has been slightly modified. This could be clearly seen in + "half-lops"—that is, in rabbits with one ear alone lopping + forward—for the opposite sides of their skulls were not strictly + symmetrical. This seems to me a curious instance of correlation, between + hard <!-- Page 325 --><span class="pagenum"><a + name="page325"></a>{325}</span>bones and organs so soft and flexible, as + well as so unimportant under a physiological point of view, as the + external ears. The result no doubt is largely due to mere mechanical + action, that is, to the weight of the ears, on the same principle that + the skull of a human infant is easily modified by pressure.</p> + + <p>The skin and the appendages of hair, feathers, hoofs, horns, and + teeth, are homologous over the whole body. Every one knows that the + colour of the skin and that of the hair usually vary together; so that + Virgil advises the shepherd to look whether the mouth and tongue of the + ram are black, lest the lambs should not be purely white. With poultry + and certain ducks we have seen that the colour of the plumage stands in + some connexion with the colour of the shell of the egg,—that is, + with the mucous membrane which secretes the shell. The colour of the skin + and hair, and the odour emitted by the glands of the skin, are said<a + name="NtA_812" href="#Nt_812"><sup>[812]</sup></a> to be connected, even + in the same race of men. Generally the hair varies in the same way all + over the body in length, fineness, and curliness. The same rule holds + good with feathers, as we see with the laced and frizzled breeds both of + fowls and pigeons. In the common cock the feathers on the neck and loins + are always of a particular shape, called hackles: now in the Polish + breed, both sexes are characterised by a tuft of feathers on the head; + but through correlation these feathers in the male always assume the form + of hackles. The wing and tail-feathers, though arising from parts not + homologous, vary in length together; so that long or short winged pigeons + generally have long or short tails. The case of the Jacobin-pigeon is + more curious, for the wing and tail feathers are remarkably long; and + this apparently has arisen in correlation with the elongated and reversed + feathers on the back of the neck, which form the hood.</p> + + <p>The hoofs and hair are homologous appendages; and a careful observer, + namely Azara,<a name="NtA_813" href="#Nt_813"><sup>[813]</sup></a> states + that in Paraguay horses of various colours are often born with their hair + curled and twisted like that on the head of a negro. This peculiarity is + strongly inherited. But what is remarkable is that the hoofs of these + horses "are absolutely like those of a mule." The hair also of the mane + and tail is invariably much shorter than usual, being only from four <!-- + Page 326 --><span class="pagenum"><a name="page326"></a>{326}</span>to + twelve inches in length; so that curliness and shortness of the hair are + here, as with the negro, apparently correlated.</p> + + <p>With respect to the horns of sheep, Youatt<a name="NtA_814" + href="#Nt_814"><sup>[814]</sup></a> remarks that "multiplicity of horns + is not found in any breed of much value: it is generally accompanied by + great length and coarseness of the fleece." Several tropical breeds of + sheep, which are clothed with hair instead of wool, have horns almost + like those of a goat. Sturm<a name="NtA_815" + href="#Nt_815"><sup>[815]</sup></a> expressly declares that in different + races the more the wool is curled the more the horns are spirally + twisted. We have seen in the third chapter, where other analogous facts + have been given, that the parent of the Mauchamp breed, so famous for its + fleece, had peculiarly shaped horns. The inhabitants of Angora assert<a + name="NtA_816" href="#Nt_816"><sup>[816]</sup></a> that "only the white + goats which have horns wear the fleece in the long curly locks that are + so much admired; those which are not horned having a comparatively close + coat." From these cases we may conclude that the hair or wool and the + horns vary in a correlated manner. Those who have tried hydropathy are + aware that the frequent application of cold water stimulates the skin; + and whatever stimulates the skin tends to increase the growth of the + hair, as is well shown in the abnormal growth of hair near old inflamed + surfaces. Now, Professor Low<a name="NtA_817" + href="#Nt_817"><sup>[817]</sup></a> is convinced that with the different + races of British cattle thick skin and long hair depend on the humidity + of the climate which they inhabit. We can thus see how a humid climate + might act on the horns—in the first place directly on the skin and + hair, and secondly by correlation on the horns. The presence or absence + of horns, moreover, both in the case of sheep and cattle, acts, as will + presently be shown, by some sort of correlation on the skull.</p> + + <p>With respect to hair and teeth, Mr. Yarrell<a name="NtA_818" + href="#Nt_818"><sup>[818]</sup></a> found many of the teeth deficient in + three hairless "<i>Ægyptian</i>" dogs, and in a hairless terrier. The + incisors, canines, and premolars suffered most, but in one case all the + teeth, except the large tubercular molar on each side, were deficient. + With man several striking cases have been recorded<a name="NtA_819" + href="#Nt_819"><sup>[819]</sup></a> of inherited baldness with <!-- Page + 327 --><span class="pagenum"><a name="page327"></a>{327}</span>inherited + deficiency, either complete or partial, of the teeth. We see the same + connexion in those rare cases in which the hair has been renewed in old + age, for this has "usually been accompanied by a renewal of the teeth." I + have remarked in a former part of this volume that the great reduction in + the size of the tusks in domestic boars probably stands in close relation + with their diminished bristles, due to a certain amount of protection; + and that the reappearance of the tusks in boars, which have become feral + and are fully exposed to the weather, probably depends on the + reappearance of the bristles. I may add, though not strictly connected + with our present point, that an agriculturist<a name="NtA_820" + href="#Nt_820"><sup>[820]</sup></a> asserts that "pigs with little hair + on their bodies are most liable to lose their tails, showing a weakness + of the tegumental structure. It may be prevented by crossing with a more + hairy breed."</p> + + <p>In the previous cases deficient hair, and teeth deficient in number or + size, are apparently connected. In the following cases abnormally + redundant hair, and teeth either deficient or redundant, are likewise + connected. Mr. Crawfurd<a name="NtA_821" + href="#Nt_821"><sup>[821]</sup></a> saw at the Burmese Court a man, + thirty years old, with his whole body, except the hands and feet, covered + with straight silky hair, which on the shoulders and spine was five + inches in length. At birth the ears alone were covered. He did not arrive + at puberty, or shed his milk teeth, until twenty years old; and at this + period he acquired five teeth in the upper jaw, namely four incisors and + one canine, and four incisor teeth in the lower jaw; all the teeth were + small. This man had a daughter, who was born with hair within her ears; + and the hair soon extended over her body. When Captain Yule<a + name="NtA_822" href="#Nt_822"><sup>[822]</sup></a> visited the Court, he + found this girl grown up; and she presented a strange appearance with + even her nose densely covered with soft hair. Like her father, she was + furnished with incisor teeth alone. The King had with difficulty bribed a + man to marry her, and of her two children, one, a boy fourteen months + old, had hair growing out of his ears, with a beard and moustache. This + strange peculiarity had, therefore, been inherited for three generations, + with the molar teeth deficient in the grandfather and mother; whether + <!-- Page 328 --><span class="pagenum"><a + name="page328"></a>{328}</span>these teeth would likewise fail in the + infant could not be told. Here is another case communicated to me by Mr. + Wallace on the authority of Dr. Purland, a dentist: Julia Pastrana, a + Spanish dancer, was a remarkably fine woman, but she had a thick + masculine beard and a hairy forehead; she was photographed, and her + stuffed skin was exhibited as a show; but what concerns us is, that she + had in both the upper and lower jaw an irregular double set of teeth, one + row being placed within the other, of which Dr. Purland took a cast. From + the redundancy of the teeth her mouth projected, and her face had a + gorilla-like appearance. These cases and those of the hairless dogs + forcibly call to mind the fact, that the two orders of + mammals—namely, the Edentata and Cetacea—which are the most + abnormal in their dermal covering, are likewise the most abnormal either + by deficiency or redundancy of teeth.</p> + + <p>The organs of sight and hearing are generally admitted to be + homologous, both with each other and with the various dermal appendages; + hence these parts are liable to be abnormally affected in conjunction. + Mr. White Cowper says "that in all cases of double microphthalmia brought + under his notice he has at the same time met with defective development + of the dental system." Certain forms of blindness seem to be associated + with the colour of the hair; a man with black hair and a woman with + light-coloured hair, both of sound constitution, married and had nine + children, all of whom were born blind; of these children, five "with dark + hair and brown iris were afflicted with amaurosis; the four others, with + light-coloured hair and blue iris, had amaurosis and cataract conjoined." + Several cases could be given, showing that some relation exists between + various affections of the eyes and ears; thus Liebreich states that out + of 241 deaf-mutes in Berlin, no less than fourteen suffered from the rare + disease called pigmentary retinitis. Mr. White Cowper and Dr. Earle have + remarked that inability to distinguish different colours, or + colour-blindness, "is often associated with a corresponding inability to + distinguish musical sounds."<a name="NtA_823" + href="#Nt_823"><sup>[823]</sup></a></p> + +<p><!-- Page 329 --><span class="pagenum"><a name="page329"></a>{329}</span></p> + + <p>Here is a more curious case: white cats, if they have blue eyes, are + almost always deaf. I formerly thought that the rule was invariable, but + I have heard of a few authentic exceptions. The first two notices were + published in 1829, and relate to English and Persian cats: of the latter, + the Rev. W. T. Bree possessed a female, and he states "that of the + offspring produced at one and the same birth, such as, like the mother, + were entirely white (with blue eyes) were, like her, invariably deaf; + while those that had the least speck of colour on their fur, as + invariably possessed the usual faculty of hearing."<a name="NtA_824" + href="#Nt_824"><sup>[824]</sup></a> The Rev. W. Darwin Fox informs me + that he has seen more than a dozen instances of this correlation in + English, Persian, and Danish cats; but he adds "that, if one eye, as I + have several times observed, be not blue, the cat hears. On the other + hand, I have never seen a white cat with eyes of the common colour that + was deaf." In France Dr. Sichel<a name="NtA_825" + href="#Nt_825"><sup>[825]</sup></a> has observed during twenty years + similar facts; he adds the remarkable case of the iris beginning, at the + end of four months, to grow dark-coloured, and then the cat first began + to hear.</p> + + <p>This case of correlation in cats has struck many persons as + marvellous. There is nothing unusual in the relation between blue eyes + and white fur; and we have already seen that the organs of sight and + hearing are often simultaneously affected. In the present instance the + cause probably lies in a slight arrest of development in the nervous + system in connection with the sense-organs. Kittens during the first nine + days, whilst their eyes are closed, appear to be completely deaf; I have + made a great clanging noise with a poker and shovel close to their heads, + both when they were asleep and awake, without producing any effect. The + trial must not be made by shouting close to their ears, for they are, + even when asleep, extremely sensitive to a breath of air. Now, as long as + the eyes continue closed, the iris is no doubt blue, for in all the + kittens which I have seen this colour remains for some time after the + eyelids open. Hence, if we suppose the development of the organs of sight + and hearing to be arrested at the stage of the closed eyelids, the eyes + would <!-- Page 330 --><span class="pagenum"><a + name="page330"></a>{330}</span>remain permanently blue and the ears would + be incapable of perceiving sound; and we should thus understand this + curious case. As, however, the colour of the fur is determined long + before birth, and as the blueness of the eyes and the whiteness of the + fur are obviously connected, we must believe that some primary cause acts + at an early period.</p> + + <p>The instances of correlated variability hitherto given have been + chiefly drawn from the animal kingdom, and we will now turn to plants. + Leaves, sepals, petals, stamens, and pistils are all homologous. In + double flowers we see that the stamens and pistils vary in the same + manner, and assume the form and colour of the petals. In the double + columbine (<i>Aquilegia vulgaris</i>), the successive whorls of stamens + are converted into cornucopias, which are enclosed within each other and + resemble the petals. In hose-and-hose flowers the sepals mock the petals. + In some cases the flowers and leaves vary together in tint: in all the + varieties of the common pea, which have purple flowers, a purple mark may + be seen on the stipules. In other cases the leaves and fruit and seeds + vary together in colour, as in a curious pale-leaved variety of the + sycamore, which has recently been described in France,<a name="NtA_826" + href="#Nt_826"><sup>[826]</sup></a> and as in the purple-leaved hazel, in + which the leaves, the husk of the nut, and the pellicle round the kernel + are all coloured purple.<a name="NtA_827" + href="#Nt_827"><sup>[827]</sup></a> Pomologists can predict to a certain + extent, from the size and appearance of the leaves of their seedlings, + the probable nature of the fruit; for, as Van Mons remarks,<a + name="NtA_828" href="#Nt_828"><sup>[828]</sup></a> variations in the + leaves are generally accompanied by some modification in the flower, and + consequently in the fruit. In the Serpent melon, which has a narrow + tortuous fruit above a yard in length, the stem of the plant, the + peduncle of the female flower, and the middle lobe of the leaf, are all + elongated in a remarkable manner. On the other hand, several varieties of + Cucurbita, which have dwarfed stems, all produce, as Naudin remarks with + surprise, leaves of the same peculiar shape. Mr. G. Maw informs me that + all the varieties of the scarlet Pelargoniums which have contracted or + imperfect leaves have contracted flowers: the difference between <!-- + Page 331 --><span class="pagenum"><a + name="page331"></a>{331}</span>"Brilliant" and its parent "Tom Thumb" is + a good instance of this. It may be suspected that the curious case + described by Risso,<a name="NtA_829" href="#Nt_829"><sup>[829]</sup></a> + of a variety of the Orange which produces on the young shoots rounded + leaves with winged petioles, and afterwards elongated leaves on long but + wingless petioles, is connected with the remarkable change in form and + nature which the fruit undergoes during its development.</p> + + <p>In the following instance we have the colour and form of the petals + apparently correlated, and both dependent on the nature of the season. An + observer, skilled in the subject, writes,<a name="NtA_830" + href="#Nt_830"><sup>[830]</sup></a> "I noticed, during the year 1842, + that every Dahlia, of which the colour had any tendency to scarlet, was + deeply notched—indeed to so great an extent as to give the petals + the appearance of a saw; the indentures were, in some instances, more + than a quarter of an inch deep." Again, Dahlias which have their petals + tipped with a different colour from the rest are very inconstant, and + during certain years some, or even all the flowers, become uniformly + coloured; and it has been observed with several varieties,<a + name="NtA_831" href="#Nt_831"><sup>[831]</sup></a> that when this happens + the petals grow much elongated and lose their proper shape. This, + however, may be due to reversion, both in colour and form, to the + aboriginal species.</p> + +<hr class="short" /> + + <p>In this discussion on correlation, we have hitherto treated of cases + in which we can partly understand the bond of connexion; but I will now + give cases in which we cannot even conjecture, or can only very obscurely + see, what is the nature of the bond. Isidore Geoffroy St. Hilaire, in his + work on Monstrosities, insists,<a name="NtA_832" + href="#Nt_832"><sup>[832]</sup></a> "que certaines anomalies coexistent + rarement entr'elles, d'autres fréquemment, d'autres enfin presque + constamment, malgré la différence très-grande de leur nature, et + quoiqu'elles puissent paraître <i>complètement indépendantes</i> les unes + des autres." We see something analogous in certain diseases: thus I hear + from Mr. Paget that in a rare affection of the <!-- Page 332 --><span + class="pagenum"><a name="page332"></a>{332}</span>renal capsules (of + which the functions are unknown), the skin becomes bronzed; and in + hereditary syphilis, both the milk and the second teeth assume a peculiar + and characteristic form. Professor Rolleston, also, informs me that the + incisor teeth are sometimes furnished with a vascular rim in correlation + with intra-pulmonary deposition of tubercles. In other cases of phthisis + and of cyanosis the nails and finger-ends become clubbed like acorns. I + believe that no explanation has been offered of these and of many other + cases of correlated disease.</p> + + <p>What can be more curious and less intelligible than the fact + previously given, on the authority of Mr. Tegetmeier, that young pigeons + of all breeds, which when mature have white, yellow, silver-blue, or + dun-coloured plumage, come out of the egg almost naked; whereas pigeons + of other colours when first born are clothed with plenty of down? White + Pea-fowls, as has been observed both in England and France,<a + name="NtA_833" href="#Nt_833"><sup>[833]</sup></a> and as I have myself + seen, are inferior in size to the common coloured kind; and this cannot + be accounted for by the belief that albinism is always accompanied by + constitutional weakness; for white or albino moles are generally larger + than the common kind.</p> + + <p>To turn to more important characters: the niata cattle of the Pampas + are remarkable from their short foreheads, upturned muzzles, and curved + lower jaws. In the skull the nasal and premaxillary bones are much + shortened, the maxillaries are excluded from any junction with the + nasals, and all the bones are slightly modified, even to the plane of the + occiput. From the analogical case of the dog, hereafter to be given, it + is probable that the shortening of the nasal and adjoining bones is the + proximate cause of the other modifications in the skull, including the + upward curvature of the lower jaw, though we cannot follow out the steps + by which these changes have been effected.</p> + + <p>Polish fowls have a large tuft of feathers on their heads; and their + skulls are perforated by numerous holes, so that a pin can be driven into + the brain without touching any bone. That this deficiency of bone is in + some way connected with the tuft of feathers is clear from tufted ducks + and geese likewise having <!-- Page 333 --><span class="pagenum"><a + name="page333"></a>{333}</span>perforated skulls. The case would probably + be considered by some authors as one of balancement or compensation. In + the chapter on Fowls, I have shown that with Polish fowls the tuft of + feathers was probably at first small; by continued selection it became + larger, and then rested on a fleshy or fibrous mass; and finally, as it + became still larger, the skull itself became more and more protuberant + until it acquired its present extraordinary structure. Through + correlation with the protuberance of the skull, the shape and even the + relative connexion of the premaxillary and nasal bones, the shape of the + orifice of the nostrils, the breadth of the frontal bone, the shape of + the post-lateral processes of the frontal and squamosal bones, and the + direction of the bony cavity of the ear, have all been modified. The + internal configuration of the skull and the whole shape of the brain have + likewise been altered in a truly marvellous manner.</p> + + <p>After this case of the Polish fowl it would be superfluous to do more + than refer to the details previously given on the manner in which the + changed form of the comb, in various breeds of the fowl, has affected the + skull, causing by correlation crests, protuberances, and depressions on + its surface.</p> + + <p>With our cattle and sheep the horns stand in close connexion with the + size of the skull, and with the shape of the frontal bones; thus Cline<a + name="NtA_834" href="#Nt_834"><sup>[834]</sup></a> found that the skull + of a horned ram weighed five times as much as that of a hornless ram of + the same age. When cattle become hornless, the frontal bones are + "materially diminished in breadth towards the poll;" and the cavities + between the bony plates "are not so deep, nor do they extend beyond the + frontals."<a name="NtA_835" href="#Nt_835"><sup>[835]</sup></a></p> + +<hr class="short" /> + + <p>It may be well here to pause and observe how the effects of correlated + variability, of the increased use of parts, and of the accumulation + through natural selection of so-called spontaneous variations, are in + many cases inextricably commingled. We may borrow an illustration from + Mr. Herbert Spencer, who remarks that, when the Irish elk acquired its + gigantic horns, weighing above one hundred pounds, numerous co-ordinated + <!-- Page 334 --><span class="pagenum"><a + name="page334"></a>{334}</span>changes of structure would have been + indispensable,—namely, a thickened skull to carry the horns; + strengthened cervical vertebræ, with strengthened ligaments; enlarged + dorsal vertebræ to support the neck, with powerful fore-legs and feet; + all these parts being supplied with proper muscles, blood-vessels, and + nerves. How then could these admirably co-ordinated modifications of + structure have been acquired? According to the doctrine which I maintain, + the horns of the male elk were slowly gained through sexual + selection,—that is, by the best-armed males conquering the + worse-armed, and leaving a greater number of descendants. But it is not + at all necessary that the several parts of the body should have + simultaneously varied. Each stag presents individual differences, and in + the same district those which had slightly heavier horns, or stronger + necks, or stronger bodies, or were the most courageous, would secure the + greater number of does, and consequently leave a greater number of + offspring. The offspring would inherit, in a greater or less degree, + these same qualities, would occasionally intercross with each other, or + with other individuals varying in some favourable manner; and of their + offspring, those which were the best endowed in any respect would + continue multiplying; and so onwards, always progressing, sometimes in + one direction, and sometimes in another, towards the present excellently + co-ordinated structure of the male elk. To make this clear, let us + reflect on the probable steps, as shown in the twentieth chapter, by + which our race and dray-horses have arrived at their present state of + excellence; if we could view the whole series of intermediate forms + between one of these animals and an early unimproved progenitor, we + should behold a vast number of animals, not equally improved in each + generation throughout their entire structure, but sometimes a little more + in one point, and sometimes in another, yet on the whole gradually + approaching in character to our present race or dray-horses, which are so + admirably fitted in the one case for fleetness and in the other for + draught.</p> + + <p>Although natural selection would thus<a name="NtA_836" + href="#Nt_836"><sup>[836]</sup></a> tend to give to the <!-- Page 335 + --><span class="pagenum"><a name="page335"></a>{335}</span>male elk its + present structure, yet it is probable that the inherited influence of use + has played an equal or more important part. As the horns gradually + increased in weight, the muscles of the neck, with the bones to which + they are attached, would increase in size and strength; and these parts + would react on the body and legs. Nor must we overlook the fact that + certain parts of the skull and the extremities would, judging by analogy, + tend from the first to vary in a correlated manner. The increased weight + of the horns would also act directly on the skull, in the same manner as, + when one bone is removed in the leg of a dog, the other bone, which has + to carry the whole weight of the body, increases in thickness. But from + the facts given with respect to horned and hornless cattle, it is + probable that the horns and skull would immediately act on each other + through the principle of correlation. Lastly, the growth and subsequent + wear and tear of the augmented muscles and bones would require an + increased supply of blood, and consequently an increased supply of food; + and this again would require increased powers of mastication, digestion, + respiration, and excretion.</p> + +<p class="cenhead"><i>Colour as Correlated with Constitutional Peculiarities.</i></p> + + <p>It is an old belief that with man there is a connexion between + complexion and constitution; and I find that some of the best authorities + believe in this to the present day.<a name="NtA_837" + href="#Nt_837"><sup>[837]</sup></a> Thus Dr. Beddoe by his tables shows<a + name="NtA_838" href="#Nt_838"><sup>[838]</sup></a> that a relation exists + between liability to consumption and the colour of the hair, eyes, and + skin. It has been affirmed<a name="NtA_839" + href="#Nt_839"><sup>[839]</sup></a> that, in the French army which + invaded Russia, soldiers having a dark complexion, from the <!-- Page 336 + --><span class="pagenum"><a name="page336"></a>{336}</span>southern parts + of Europe, withstood the intense cold better than those with lighter + complexions from the north; but no doubt such statements are liable to + error.</p> + + <p>In the second chapter on Selection I have given several cases proving + that with animals and plants differences in colour are correlated with + constitutional differences, as shown by greater or less immunity from + certain diseases, from the attacks of parasitic plants and animals, from + burning by the sun, and from the action of certain poisons. When all the + individuals of any one variety possess an immunity of this nature, we + cannot feel sure that it stands in any sort of correlation with their + colour; but when several varieties of the same species, which are + similarly coloured, are thus characterised, whilst other coloured + varieties are not thus favoured, we must believe in the existence of a + correlation of this kind. Thus in the United States purple-fruited plums + of many kinds are far more affected by a certain disease than green or + yellow-fruited varieties. On the other hand, yellow-fleshed peaches of + various kinds suffer from another disease much more than the + white-fleshed varieties. In the Mauritius red sugar-canes are much less + affected by a particular disease than the white canes. White onions and + verbenas are the most liable to mildew; and in Spain the green-fruited + grapes suffered from the vine-disease more than other coloured varieties. + Dark-coloured pelargoniums and verbenas are more scorched by the sun than + varieties of other colours. Red wheats are believed to be hardier than + white; whilst red-flowered hyacinths were more injured during one + particular winter in Holland than other coloured varieties. With animals, + white terriers suffer most from the distemper, white chickens from a + parasitic worm in their tracheæ, white pigs from scorching by the sun, + and white cattle from flies; but the caterpillars of the silk-moth which + yield white cocoons suffered in France less from the deadly parasitic + fungus than those producing yellow silk.</p> + + <p>The cases of immunity from the action of certain vegetable poisons, in + connexion with colour, are more interesting, and are at present wholly + inexplicable. I have already given a remarkable instance, on the + authority of Professor Wyman, of all the hogs, excepting those of a black + colour, suffering severely in Virginia from eating the root of the + <i>Lachnanthes tinctoria</i>. <!-- Page 337 --><span class="pagenum"><a + name="page337"></a>{337}</span>According to Spinola and others,<a + name="NtA_840" href="#Nt_840"><sup>[840]</sup></a> buckwheat + (<i>Polygonum fagopyrum</i>), when in flower, is highly injurious to + white or white-spotted pigs, if they are exposed to the heat of the sun, + but is quite innocuous to black pigs. By two accounts, the <i>Hypericum + crispum</i> in Sicily is poisonous to white sheep alone; their heads + swell, their wool falls off, and they often die; but this plant, + according to Lecce, is poisonous only when it grows in swamps; nor is + this improbable, as we know how readily the poisonous principle in plants + is influenced by the conditions under which they grow.</p> + + <p>Three accounts have been published in Eastern Prussia, of white and + white-spotted horses being greatly injured by eating mildewed and + honeydewed vetches; every spot of skin bearing white hairs becoming + inflamed and gangrenous. The Rev. J. Rodwell informs me that his father + turned out about fifteen cart-horses into a field of tares which in parts + swarmed with black aphides, and which no doubt were honeydewed, and + probably mildewed; the horses, with two exceptions, were chesnuts and + bays with white marks on their faces and pasterns, and the white parts + alone swelled and became angry scabs. The two bay horses with no white + marks entirely escaped all injury. In Guernsey, when horses eat fools' + parsley (<i>Æthusa cynapium</i>) they are sometimes violently purged; and + this plant "has a peculiar effect on the nose and lips, causing deep + cracks and ulcers, particularly on horses with white muzzles."<a + name="NtA_841" href="#Nt_841"><sup>[841]</sup></a> With cattle, + independently of the action of any poison, cases have been published by + Youatt and Erdt of cutaneous diseases with much constitutional + disturbance (in one instance after exposure to a hot sun) affecting every + single point which bore a white hair, but completely passing over other + parts of the body. Similar cases have been observed with horses.<a + name="NtA_842" href="#Nt_842"><sup>[842]</sup></a></p> + + <p>We thus see that not only do those parts of the skin which bear white + hair differ in a remarkable manner from those bearing <!-- Page 338 + --><span class="pagenum"><a name="page338"></a>{338}</span>hair of any + other colour, but that in addition some great, constitutional difference + must stand in correlation with the colour of the hair; for in the + above-mentioned cases, vegetable poisons caused fever, swelling of the + head, as well as other symptoms, and even death, to all the white or + white-spotted animals.</p> + +<hr class="full" /> + +<p><!-- Page 339 --><span class="pagenum"><a name="page339"></a>{339}</span></p> + +<h3>CHAPTER XXVI.</h3> + +<p class="cenhead">LAWS OF VARIATION, <i>continued</i>—SUMMARY.</p> + +<blockquote class="b1n"> + + <p><span class="scac">ON THE AFFINITY AND COHESION OF HOMOLOGOUS + PARTS</span>—<span class="scac">ON THE VARIABILITY OF MULTIPLE AND + HOMOLOGOUS PARTS</span>—<span class="scac">COMPENSATION OF + GROWTH</span>—<span class="scac">MECHANICAL + PRESSURE</span>—<span class="scac">RELATIVE POSITION OF FLOWERS + WITH RESPECT TO THE AXIS OF THE PLANT, AND OF SEEDS IN THE CAPSULE, AS + INDUCING VARIATION</span>—<span class="scac">ANALOGOUS OR PARALLEL + VARIETIES</span>—<span class="scac">SUMMARY OF THE THREE LAST + CHAPTERS.</span></p> + +</blockquote> + + <p><i>On the Affinity of Homologous Parts.</i>—This law was first + generalised by Geoffroy Saint Hilaire, under the expression of <i>La loi + de l'affinité de soi pour soi</i>. It has been fully discussed and + illustrated by his son, Isidore Geoffroy, with respect to monsters in the + animal kingdom,<a name="NtA_843" href="#Nt_843"><sup>[843]</sup></a> and + by Moquin-Tandon, with respect to monstrous plants. When similar or + homologous parts, whether belonging to the same embryo or to two distinct + embryos, are brought during an early stage of development into contact, + they often blend into a single part or organ; and this complete fusion + indicates some mutual affinity between the parts, otherwise they would + simply cohere. Whether any power exists which tends to bring homologous + parts into contact seems more doubtful. The tendency to complete fusion + is not a rare or exceptional fact. It is exhibited in the most striking + manner by double monsters. Nothing can be more extraordinary than the + manner, as shown in various published plates, in which the corresponding + parts of two embryos become intimately fused together. This is perhaps + best seen in monsters with two heads, which are united, summit to summit, + or face to face, or, Janus-like, back to back, or obliquely side to side. + In one instance of two heads united almost face to face, but a little + obliquely, four ears were developed, and on one side a perfect face, + which was manifestly formed by the union of two <!-- Page 340 --><span + class="pagenum"><a name="page340"></a>{340}</span>half-faces. Whenever + two bodies or two heads are united, each bone, muscle, vessel, and nerve + on the line of junction seems to seek out its fellow, and becomes + completely fused with it. Lereboullet,<a name="NtA_844" + href="#Nt_844"><sup>[844]</sup></a> who carefully studied the development + of double monsters in fishes, observed in fifteen instances the steps by + which two heads gradually became fused into one. In this and other such + cases, no one, I presume, supposes that the two already formed heads + actually blend together, but that the corresponding parts of each head + grow into one during the further progress of development, accompanied as + it always is with incessant absorption and renovation. Double monsters + were formerly thought to be formed by the union of two originally + distinct embryos developed upon distinct vitelli; but now it is admitted + that "their production is due to the spontaneous divarication of the + embryonic mass into two halves;"<a name="NtA_845" + href="#Nt_845"><sup>[845]</sup></a> this, however, is effected by + different methods. But the belief that double monsters originate from the + division of one germ, does not necessarily affect the question of + subsequent fusion, or render less true the law of the affinity of + homologous parts.</p> + + <p>The cautious and sagacious J. Müller,<a name="NtA_846" + href="#Nt_846"><sup>[846]</sup></a> when speaking of Janus-like monsters, + says, that "without the supposition that some kind of affinity or + attraction is exerted between corresponding parts, unions of this kind + are inexplicable." On the other hand, Vrolik, and he is followed by + others, disputes this conclusion, and argues from the existence of a + whole series of monstrosities, graduating from a perfectly double monster + to a mere rudiment of an additional digit, that "an excess of formative + power" is the cause and origin of every monstrous duplicity. That there + are two distinct classes of cases, and that parts may be doubled + independently of the existence of two embryos, is certain; for a single + embryo, or even a single adult animal, may produce doubled organs. Thus + Valentin, as quoted by Vrolik, injured the caudal extremity of an embryo, + and three days afterwards it produced rudiments of a double pelvis and of + double hind limbs. <!-- Page 341 --><span class="pagenum"><a + name="page341"></a>{341}</span>Hunter and others have observed lizards + with their tails reproduced and doubled. When Bonnet divided + longitudinally the foot of the salamander, several additional digits were + occasionally formed. But neither these cases, nor the perfect series from + a double monster to an additional digit, seem to me opposed to the belief + that corresponding parts have a mutual affinity, and consequently tend to + fuse together. A part may be doubled and remain in this state, or the two + parts thus formed may afterwards through the law of affinity become + blended; or two homologous parts in two separate embryos may, through the + same principle, unite and form a single part.</p> + + <p>The law of the affinity and fusion of similar parts applies to the + homologous organs of the same individual animal, as well as to double + monsters. Isidore Geoffroy gives a number of instances of two or more + digits, of two whole legs, of two kidneys, and of several teeth becoming + symmetrically fused together in a more or less perfect manner. Even the + two eyes have been known to unite into a single eye, forming a cyclopean + monster, as have the two ears, though naturally standing so far apart. As + Geoffroy remarks, these facts illustrate in an admirable manner the + normal fusion of various organs which during an early embryonic period + are double, but which afterwards always unite into a single median organ. + Organs of this nature are generally found in a permanently double + condition in other members of the same class. These cases of normal + fusion appear to me to afford the strongest support in favour of the + present law. Adjoining parts which are not homologous sometimes cohere; + but this cohesion appears to result from mere juxtaposition, and not from + mutual affinity.</p> + + <p>In the vegetable kingdom Moquin-Tandon<a name="NtA_847" + href="#Nt_847"><sup>[847]</sup></a> gives a long list of cases, showing + how frequently homologous parts, such as leaves, petals, stamens, and + pistils, as well as aggregates of homologous parts, such as buds, + flowers, and fruit, become blended into each other with perfect symmetry. + It is interesting to examine a compound flower of this nature, formed of + exactly double the proper number of sepals, petals, stamens, and pistils, + with each whorl of organs circular, and with no trace left of the <!-- + Page 342 --><span class="pagenum"><a + name="page342"></a>{342}</span>process of fusion. The tendency in + homologous parts to unite during their early development, Moquin-Tandon + considers as one of the most striking laws governing the production of + monsters. It apparently explains a multitude of cases, both in the animal + and vegetable kingdoms; it throws a clear light on many normal structures + which have evidently been formed by the union of originally distinct + parts, and it possesses, as we shall see in a future chapter, much + theoretical interest.</p> + +<hr class="short" /> + + <p><i>On the Variability of Multiple and Homologous + Parts.</i>—Isidore Geoffroy<a name="NtA_848" + href="#Nt_848"><sup>[848]</sup></a> insists that, when any part or organ + is repeated many times in the same animal, it is particularly liable to + vary both in number and structure. With respect to number, the + proposition may, I think, be considered as fully established; but the + evidence is chiefly derived from organic beings living under their + natural conditions, with which we are not here concerned. When the + vertebræ, or teeth, or rays in the fins of fishes, or feathers in the + tails of birds, or petals, stamens, pistils, and seeds in plants, are + very numerous, the number is generally variable. The explanation of this + simple fact is by no means obvious. With respect to the variability in + structure of multiple parts, the evidence is not so decisive; but the + fact, as far as it may be trusted, probably depends on multiple parts + being of less physiological importance than single parts; consequently + their perfect standard of structure has been less rigorously enforced by + natural selection.</p> + +<hr class="short" /> + + <p><i>Compensation of Growth, or Balancement.</i>—This law, as + applied to natural species, was propounded by Goethe and Geoffroy St. + Hilaire at nearly the same time. It implies that, when much organised + matter is used in building up some one part, other parts are starved and + become reduced. Several authors, especially botanists, believe in this + law; others reject it. As far as I can judge, it occasionally holds good; + but its importance has probably been exaggerated. It is scarcely possible + to distinguish between the supposed effects of such compensation of + growth, and the effects of long-continued selection, which <!-- Page 343 + --><span class="pagenum"><a name="page343"></a>{343}</span>may at the + same time lead to the augmentation of one part and the diminution of + another. There can be no doubt that an organ may be greatly increased + without any corresponding diminution in the adjoining parts. To recur to + our former illustration of the Irish elk, it may be asked what part has + suffered in consequence of the immense development of the horns?</p> + + <p>It has already been observed that the struggle for existence does not + bear hard on our domesticated productions; consequently the principle of + economy of growth will seldom affect them, and we ought not to expect to + find frequent evidence of compensation. We have, however, some such + cases. Moquin-Tandon describes a monstrous bean,<a name="NtA_849" + href="#Nt_849"><sup>[849]</sup></a> in which the stipules were enormously + developed, and the leaflets apparently in consequence completely aborted; + this case is interesting, as it represents the natural condition of + <i>Lathyrus aphaca</i>, with its stipules of great size, and its leaves + reduced to mere threads, which act as tendrils. De Candolle<a + name="NtA_850" href="#Nt_850"><sup>[850]</sup></a> has remarked that the + varieties of <i>Raphanus sativus</i> which have small roots yield + numerous seed, valuable from containing oil, whilst those with large + roots are not productive in this latter respect; and so it is with + <i>Brassica asperifolia</i>. The varieties of the potato which produce + tubers very early in the season rarely bear flowers; but Andrew Knight,<a + name="NtA_851" href="#Nt_851"><sup>[851]</sup></a> by checking the growth + of the tubers, forced the plants to flower. The varieties of <i>Cucurbita + pepo</i> which produce large fruit yield, according to Naudin, few in + number; whilst those producing small fruit yield a vast number. Lastly, I + have endeavoured to show in the eighteenth chapter that with many + cultivated plants unnatural treatment checks the full and proper action + of the reproductive organs, and they are thus rendered more or less + sterile; consequently, in the way of compensation, the fruit becomes + greatly enlarged, and, in double flowers, the petals are greatly + increased in number.</p> + + <p>With animals, it has been found difficult to produce cows which should + first yield much milk, and afterwards be capable of <!-- Page 344 + --><span class="pagenum"><a name="page344"></a>{344}</span>fattening + well. With fowls which have large topknots and beards the comb and + wattles are generally much reduced in size. Perhaps the entire absence of + the oil-gland in fantail pigeons may be connected with the great + development of their tails.</p> + +<hr class="short" /> + + <p><i>Mechanical Pressure as a Cause of Modifications.</i>—In some + few cases there is reason to believe that mere mechanical pressure has + affected certain structures. Every one knows that savages alter the shape + of their infants' skulls by pressure at an early age; but there is no + reason to believe that the result is ever inherited. Nevertheless Vrolik + and Weber<a name="NtA_852" href="#Nt_852"><sup>[852]</sup></a> maintain + that the shape of the human head is influenced by the shape of the + mother's pelvis. The kidneys in different birds differ much in form, and + St. Ange<a name="NtA_853" href="#Nt_853"><sup>[853]</sup></a> believes + that this is determined by the form of the pelvis, which again, no doubt, + stands in close relation with their various habits of locomotion. In + snakes, the viscera are curiously displaced, in comparison with their + position in other vertebrates; and this has been attributed by some + authors to the elongation of their bodies; but here, as in so many + previous cases, it is impossible to disentangle any direct result of this + kind from that consequent on natural selection. Godron has argued<a + name="NtA_854" href="#Nt_854"><sup>[854]</sup></a> that the normal + abortion of the spur on the inner side of the flower in Corydalis, is + caused by the buds being closely pressed at a very early period of + growth, whilst under ground, against each other and against the stem. + Some botanists believe that the singular difference in the shape both of + the seed and corolla, in the interior and exterior florets in certain + compositous and umbelliferous plants, is due to the pressure to which the + inner florets are subjected; but this conclusion is doubtful.</p> + + <p>The facts just given do not relate to domesticated productions, and + therefore do not strictly concern us. But here is a more appropriate + case: H. Müller<a name="NtA_855" href="#Nt_855"><sup>[855]</sup></a> has + shown that in <!-- Page 345 --><span class="pagenum"><a + name="page345"></a>{345}</span>short-faced races of the dog some of the + molar teeth are placed in a slightly different position from that which + they occupy in other dogs, especially in those having elongated muzzles; + and as he remarks, any inherited change in the arrangement of the teeth + deserves notice, considering their classificatory importance. This + difference in position is due to the shortening of certain facial bones, + and the consequent want of space; and the shortening results from a + peculiar and abnormal state of the basal cartilages of the bones.</p> + +<p class="cenhead"><i>Relative Position of Flowers with respect to the Axis, and of Seeds +in the Capsule, as inducing Variation.</i></p> + +<blockquote class="b1n"> + + <p>In the thirteenth chapter various peloric flowers were described, and + their production was shown to be due either to arrested development, or + to reversion to a primordial condition. Moquin-Tandon has remarked that + the flowers which stand on the summit of the main stem or of a lateral + branch are more liable to become peloric than those on the sides;<a + name="NtA_856" href="#Nt_856"><sup>[856]</sup></a> and he adduces, + amongst other instances, that of <i>Teucrium campanulatum</i>. In another + Labiate plant grown by me, viz. the <i>Galeobdolon luteum</i>, the + peloric flowers were always produced on the summit of the stem, where + flowers are not usually borne. In Pelargonium, a <i>single</i> flower in + the truss is frequently peloric, and when this occurs I have during + several years invariably observed it to be the central flower. This is of + such frequent occurrence that one observer<a name="NtA_857" + href="#Nt_857"><sup>[857]</sup></a> gives the names of ten varieties + flowering at the same time, in every one of which the central flower was + peloric. Occasionally more than one flower in the truss is peloric, and + then of course the additional ones must be lateral. These flowers are + interesting as showing how the whole structure is correlated. In the + common Pelargonium the upper sepal is produced into a nectary which + coheres with the flower-peduncle; the two upper petals differ a little in + shape from the three lower ones, and are marked with dark shades of + colour; the stamens are graduated in length and upturned. In the peloric + flowers, the nectary aborts; all the petals become alike both in shape + and colour; the stamens are generally reduced in number and become + straight, so that the whole flower resembles that of the allied genus + Erodium. The correlation between these changes is well shown when one of + the two upper petals alone loses its dark mark, for in this case the + nectary does not entirely abort, but is usually much reduced in length.<a + name="NtA_858" href="#Nt_858"><sup>[858]</sup></a></p> + +<p><!-- Page 346 --><span class="pagenum"><a name="page346"></a>{346}</span></p> + + <p>Morren has described<a name="NtA_859" + href="#Nt_859"><sup>[859]</sup></a> a marvellous flask-shaped flower of + the Calceolaria, nearly four inches in length, which was almost + completely peloric; it grew on the summit of the plant, with a normal + flower on each side; Prof. Westwood also has described<a name="NtA_860" + href="#Nt_860"><sup>[860]</sup></a> three similar peloric flowers, which + all occupied a central position on the flower-branches. In the Orchideous + genus, Phalænopsis, the terminal flower has been seen to become + peloric.</p> + + <p>In a Laburnum-tree I observed that about a fourth part of the racemes + produced terminal flowers which had lost their papilionaceous structure. + These were produced after almost all the other flowers on the same + racemes had withered. The most perfectly pelorised examples had six + petals, each marked with black striæ like those on the standard-petal. + The keel seemed to resist the change more than the other petals. + Dutrochet has described<a name="NtA_861" + href="#Nt_861"><sup>[861]</sup></a> an exactly similar case in France, + and I believe these are the only two instances of pelorism in the + laburnum which have been recorded. Dutrochet remarks that the racemes on + this tree do not properly produce a terminal flower, so that, as in the + case of the Galeobdolon, their position as well as their structure are + both anomalies, which no doubt are in some manner related. Dr. Masters + has briefly described another leguminous plant,<a name="NtA_862" + href="#Nt_862"><sup>[862]</sup></a> namely, a species of clover, in which + the uppermost and central flowers were regular or had lost their + papilionaceous structure. In some of these plants the flower-heads were + also proliferous.</p> + + <p>Lastly, Linaria produces two kinds of peloric flowers, one having + simple petals, and the other having them all spurred. The two forms, as + Naudin remarks,<a name="NtA_863" href="#Nt_863"><sup>[863]</sup></a> not + rarely occur on the same plant, but in this case the spurred form almost + invariably stands on the summit of the spike.</p> + + <p>The tendency in the terminal or central flower to become peloric more + frequently than other flowers, probably results from "the bud which + stands on the end of a shoot receiving the most sap; it grows out into a + stronger shoot than those situated lower down."<a name="NtA_864" + href="#Nt_864"><sup>[864]</sup></a> I have discussed the connection + between pelorism and a central position, partly because some few plants + are known normally to produce a terminal flower different in structure + from the lateral ones; but chiefly on account of the following case, in + which we see a tendency to variability or to reversion connected with the + same position. A great judge of Auriculas<a name="NtA_865" + href="#Nt_865"><sup>[865]</sup></a> states that when an Auricula throws + up a side bloom it is pretty sure to keep its character; but that if it + grows from the centre or heart of the plant, whatever the colour of the + edging ought to be, "it is just as likely to come in any other class as + in the one to which it properly belongs." This is so notorious a <!-- + Page 347 --><span class="pagenum"><a name="page347"></a>{347}</span>fact, + that some florists regularly pinch off the central trusses of flowers. + Whether in the highly improved varieties the departure of the central + trusses from their proper type is due to reversion, I do not know. Mr. + Dombrain insists that, whatever may be the commonest kind of imperfection + in each variety, this is generally exaggerated in the central truss. Thus + one variety "sometimes has the fault of producing a little green floret + in the centre of the flower," and in central blooms these become + excessive in size. In some central blooms, sent to me by Mr. Dombrain, + all the organs of the flower were rudimentary in structure, of minute + size, and of a green colour, so that by a little further change all would + have been converted into small leaves. In this case we clearly see a + tendency to prolification—a term which, I may explain to those who + have never attended to botany, means the production of a branch or + flower, or head of flowers, out of another flower. Now Dr. Masters<a + name="NtA_866" href="#Nt_866"><sup>[866]</sup></a> states that the + central or uppermost flower on a plant is generally the most liable to + prolification. Thus, in the varieties of the Auricula, the loss of their + proper character and a tendency to prolification, and in other plants a + tendency to prolification and pelorism, are all connected together, and + are due either to arrested development, or to reversion to a former + condition.</p> + + <p>The following is a more interesting case; Metzger<a name="NtA_867" + href="#Nt_867"><sup>[867]</sup></a> cultivated in Germany several kinds + of maize brought from the hotter parts of America, and he found, as has + been previously described, that in two or three generations the grains + became greatly changed in form, size, and colour; and with respect to two + races he expressly states that in the first generation, whilst the lower + grains on each head retained their proper character, the uppermost grains + already began to assume that character which in the third generation all + the grains acquired. As we do not know the aboriginal parent of the + maize, we cannot tell whether these changes are in any way connected with + reversion.</p> + + <p>In the two following cases, reversion, as influenced by the position + of the seed in the capsule, evidently acts. The Blue Imperial pea is the + offspring of the Blue Prussian, and has larger seed and broader pods than + its parent. Now Mr. Masters, of Canterbury, a careful observer and a + raiser of new varieties of the pea, states<a name="NtA_868" + href="#Nt_868"><sup>[868]</sup></a> that the Blue Imperial always has a + strong tendency to revert to its parent-stock, and the reversion "occurs + in this manner: the last (or uppermost) pea in the pod is frequently much + smaller than the rest; and if these small peas are carefully collected + and sown separately, very many more, in proportion, will revert to their + origin, than those taken from the other parts of the pod." Again M. + Chaté<a name="NtA_869" href="#Nt_869"><sup>[869]</sup></a> says that in + raising seedling stocks he succeeds in getting eighty per cent. to bear + double flowers, by leaving only a few of the secondary branches to seed; + but in addition to this, "at the time of extracting the seeds, the upper + portion of the pod is separated and <!-- Page 348 --><span + class="pagenum"><a name="page348"></a>{348}</span>placed aside, because + it has been ascertained that the plants coming from the seeds situated in + this portion of the pod, give eighty per cent. of single flowers." Now + the production of single-flowering plants from the seed of + double-flowering plants is clearly a case of reversion. These latter + facts, as well as the connection between a central position and pelorism + and prolification, show in an interesting manner how small a + difference—namely a little greater freedom in the flow of sap + towards one part of the same plant—determines important changes of + structure.</p> + +</blockquote> + +<hr class="short" /> + + <p><i>Analogous or Parallel Variation.</i>—By this term I wish to + express that similar characters occasionally make their appearance in the + several varieties or races descended from the same species, and more + rarely in the offspring of widely distinct species. We are here + concerned, not as hitherto with the causes of variation, but with the + results; but this discussion could not have been more conveniently + introduced elsewhere. The cases of analogous variation, as far as their + origin is concerned, may be grouped, disregarding minor subdivisions, + under two main heads; firstly, those due to unknown causes having acted + on organic beings with nearly the same constitution, and which + consequently vary in an analogous manner; and secondly, those due to the + reappearance of characters which were possessed by a more or less remote + progenitor. But these two main divisions can often be only conjecturally + separated, and graduate, as we shall presently see, into each other.</p> + +<blockquote class="b1n"> + + <p>Under the first head of analogous variations, not due to reversion, we + have the many cases of trees belonging to quite different orders which + have produced pendulous and fastigate varieties. The beech, hazel, and + barberry have given rise to purple-leaved varieties; and as Bernhardi has + remarked,<a name="NtA_870" href="#Nt_870"><sup>[870]</sup></a> a + multitude of plants, as distinct as possible, have yielded varieties with + deeply-cut or laciniated leaves. Varieties descended from three distinct + species of Brassica have their stems, or so-called roots, enlarged into + globular masses. The nectarine is the offspring of the peach; and the + varieties of both these trees offer a remarkable parallelism in the fruit + being white, red, or yellow fleshed—in being clingstones or + freestones—in the flowers being large or small—in the leaves + being serrated or crenated, furnished with globose or reniform glands, or + quite destitute of glands. It should be remarked that each variety of the + nectarine has not derived its character from a corresponding variety of + the peach. The several varieties also of a closely allied genus, namely + the apricot, differ from each other in nearly the same parallel manner. + There is no reason <!-- Page 349 --><span class="pagenum"><a + name="page349"></a>{349}</span>to believe that in any of these cases + long-lost characters have reappeared, and in most of them this certainly + has not occurred.</p> + + <p>Three species of Cucurbita have yielded a multitude of races, which + correspond so closely in character that, as Naudin insists, they may be + arranged in an almost strictly parallel series. Several varieties of the + melon are interesting from resembling in important characters other + species, either of the same genus or of allied genera; thus, one variety + has fruit so like, both externally and internally, the fruit of a + perfectly distinct species, namely, the cucumber, as hardly to be + distinguished from it; another has long cylindrical fruit twisting about + like a serpent; in another the seeds adhere to portions of the pulp; in + another the fruit, when ripe, suddenly cracks and falls into pieces; and + all these highly remarkable peculiarities are characteristic of species + belonging to allied genera. We can hardly account for the appearance of + so many unusual characters by reversion to a single ancient form; but we + must believe that all the members of the family have inherited a nearly + similar constitution from an early progenitor. Our cereal and many other + plants offer similar cases.</p> + + <p>With animals we have fewer cases of analogous variation, independently + of direct reversion. We see something of the kind in the resemblance + between the short-muzzled races of the dog, such as the pug and bulldog; + in feather-footed races of the fowl, pigeon, and canary-bird; in horses + of the most different races presenting the same range of colour; in all + black-and-tan dogs having tan-coloured eye-spots and feet, but in this + latter case reversion may possibly have played a part. Low has remarked<a + name="NtA_871" href="#Nt_871"><sup>[871]</sup></a> that several breeds of + cattle are "sheeted,"—that is, have a broad band of white passing + round their bodies like a sheet; this character is strongly inherited and + sometimes originates from a cross; it may be the first step in reversion + to an original or early type, for, as was shown in the third chapter, + white cattle with dark ears, feet, and tip of tail formerly existed, and + now exist in a feral or semi-feral condition in several quarters of the + world.</p> + + <p>Under our second main division, namely, of analogous variations due to + reversion, the best cases are afforded by animals, and by none better + than by pigeons. In all the most distinct breeds sub-varieties + occasionally appear coloured exactly like the parent rock-pigeon, with + black wing-bars, white loins, banded tail, &c.; and no one can doubt + that these characters are simply due to reversion. So with minor details; + turbits properly have white tails, but occasionally a bird is born with a + dark-coloured and banded tail; pouters properly have white primary + wing-feathers, but not rarely a "sword-flighted" bird, that is, one with + the few first primaries dark-coloured, appears; and in these cases we + have characters proper to the rock-pigeon, but new to the breed, + evidently appearing from reversion. In some domestic varieties the + wing-bars, instead of being simply black, as in the rock-pigeon, are + beautifully edged with different zones of colour, and they then present a + striking analogy with the wing-bars in certain natural species of the + same family, such as <i>Phaps chalcoptera</i>; and this may probably be + accounted for by <!-- Page 350 --><span class="pagenum"><a + name="page350"></a>{350}</span>all the forms descended from the same + remote progenitor having a tendency to vary in the same manner. Thus also + we can perhaps understand the fact of some Laugher-pigeons cooing almost + like turtle-doves, and of several races having peculiarities in their + flight, for certain natural species (viz. <i>C. torquatrix</i> and + <i>palumbus</i>) display singular vagaries in this respect. In other + cases a race, instead of imitating in character a distinct species, + resembles some other race; thus certain runts tremble and slightly + elevate their tails, like fantails; and turbits inflate the upper part of + their œsophagus, like pouter-pigeons.</p> + + <p>It is a common circumstance to find certain coloured marks + persistently characterising all the species of a genus, but differing + much in tint; and the same thing occurs with the varieties of the pigeon: + thus, instead of the general plumage being blue with the wing-bars black, + there are snow-white varieties with red bars, and black varieties with + white bars; in other varieties the wing-bars, as we have seen, are + elegantly zoned with different tints. The Spot pigeon is characterised by + the whole plumage being white, excepting the tail and a spot on the + forehead; but these parts may be red, yellow, or black. In the + rock-pigeon and in many varieties the tail is blue, with the outer edges + of the outer feathers white; but in one sub-variety of the monk-pigeon we + have a reversed variation, for the tail is white, except the outer edges + of the outer feathers, which are black.<a name="NtA_872" + href="#Nt_872"><sup>[872]</sup></a></p> + + <p>With some species of birds, for instance with gulls, certain coloured + parts appear as if almost washed out, and I have observed exactly the + same appearance in the terminal dark tail-bar in certain pigeons, and in + the whole plumage of certain varieties of the duck. Analogous facts in + the vegetable kingdom could be given.</p> + + <p>Many sub-varieties of the pigeon have reversed and somewhat lengthened + feathers on the back part of their heads, and this is certainly not due + to reversion to the parent-species, which shows no trace of such + structure; but when we remember that sub-varieties of the fowl, turkey, + canary-bird, duck, and goose, all have topknots or reversed feathers on + their heads; and when we remember that scarcely a single large natural + group of birds can be named, in which some members have not a tuft of + feathers on their heads, we may suspect that reversion to some extremely + remote form has come into action.</p> + + <p>Several breeds of the fowl have either spangled or pencilled feathers; + and these cannot be derived from the parent-species, the <i>Gallus + bankiva</i>; though of course it is possible that an early progenitor of + this species may have been spangled, and a still earlier or a later + progenitor may have been pencilled. But as many gallinaceous birds are + spangled or pencilled, it is a more probable view that the several + domestic breeds of the fowl have acquired this kind of plumage from all + the members of the family inheriting a tendency to vary in a like manner. + The same principle may account for the ewes in certain breeds of sheep + being hornless, like the females of some other hollow-horned ruminants; + it may account for certain domestic cats having slightly-tufted ears, + like those of the lynx; and for the skulls of domestic rabbits often + differing from each <!-- Page 351 --><span class="pagenum"><a + name="page351"></a>{351}</span>other in the same characters by which the + skulls of the various species of the genus Lepus differ.</p> + + <p>I will only allude to one other case, already discussed. Now that we + know that the wild parent of the ass has striped legs, we may feel + confident that the occasional appearance of stripes on the legs of the + domestic ass is due to direct reversion; but this will not account for + the lower end of the shoulder-stripe being sometimes angularly bent or + slightly forked. So, again, when we see dun and other coloured horses + with stripes on the spine, shoulders, and legs, we are led, from reasons + formerly given, to believe that they reappear from direct reversion to + the wild parent-horse. But when horses have two or three shoulder-stripes + with one of them occasionally forked at the lower end, or when they have + stripes on their faces, or as foals are faintly striped over nearly their + whole bodies, with the stripes angularly bent one under the other on the + forehead, or irregularly branched in other parts, it would be rash to + attribute such diversified characters to the reappearance of those proper + to the aboriginal wild horse. As three African species of the genus are + much striped, and as we have seen that the crossing of the unstriped + species often leads to the hybrid offspring being conspicuously + striped—bearing also in mind that the act of crossing certainly + causes the reappearance of long-lost characters—it is a more + probable view that the above-specified stripes are due to reversion, not + to the immediate wild parent-horse, but to the striped progenitor of the + whole genus.</p> + +</blockquote> + + <p>I have discussed this subject of analogous variation at considerable + length, because, in a future work on natural species, it will be shown + that the varieties of one species frequently mock distinct + species—a fact in perfect harmony with the foregoing cases, and + explicable only on the theory of descent. Secondly, because these facts + are important from showing, as remarked in a former chapter, that each + trifling variation is governed by law, and is determined in a much higher + degree by the nature of the organisation, than by the nature of the + conditions to which the varying being has been exposed. Thirdly, because + these facts are to a certain extent related to a more general law, + namely, that which Mr. B. D. Walsh<a name="NtA_873" + href="#Nt_873"><sup>[873]</sup></a> has called the "Law of <i>Equable + Variability</i>," or, as he explains it, "if any given character is very + variable in one species of a group, it will tend to be variable in allied + species; and if any given character is perfectly constant in one species + of a group, it will tend to be constant in allied species."</p> + + <p>This leads me to recall a discussion in the chapter on Selection, in + which it was shown that with domestic races, which are <!-- Page 352 + --><span class="pagenum"><a name="page352"></a>{352}</span>now undergoing + rapid improvement, those parts or characters which are the most valued + vary the most. This naturally follows from recently selected characters + continually tending to revert to their former less improved standard, and + from their being still acted on by the same agencies, whatever these may + be, which first caused the characters in question to vary. The same + principle is applicable to natural species, for, as stated in my 'Origin + of Species,' generic characters are less variable than specific + characters; and the latter are those which have been modified by + variation and natural selection, since the period when all the species + belonging to the same genus branched off from a common progenitor, whilst + generic characters are those which have remained unaltered from a much + more remote epoch, and accordingly are now less variable. This statement + makes a near approach to Mr. Walsh's law of Equable Variability. + Secondary sexual characters, it may be added, rarely serve to + characterise distinct genera, for they usually differ much in the species + of the same genus, and are highly variable in the individuals of the same + species; we have also seen in the earlier chapters of this work how + variable secondary sexual characters become under domestication.</p> + +<p class="cenhead"><i>Summary of the three previous Chapters, on the Laws of Variation.</i></p> + + <p>In the twenty-third chapter we have seen that changed conditions + occasionally act in a definite manner on the organisation, so that all, + or nearly all, the individuals thus exposed become modified in the same + manner. But a far more frequent result of changed conditions, whether + acting directly on the organisation or indirectly through the + reproductive system being affected is indefinite and fluctuating + variability. In the three latter chapters we have endeavoured to trace + some of the laws by which such variability is regulated.</p> + + <p>Increased use adds the size of a muscle, together with the + blood-vessels, nerves, ligaments, the crests of bone to which these are + attached, the whole bone and other connected bones. So it is with various + glands. Increased functional activity strengthens the sense-organs. + Increased and intermittent pressure thickens the epidermis; and a change + in the nature of the food sometimes modifies the coats of the stomach, + and increases or <!-- Page 353 --><span class="pagenum"><a + name="page353"></a>{353}</span>decreases the length of the intestines. + Continued disuse, on the other hand, weakens and diminishes all parts of + the organisation. Animals which during many generations have taken but + little exercise, have their lungs reduced in size, and as a consequence + the bony fabric of the chest, and the whole form of the body, become + modified. With our anciently domesticated birds, the wings have been + little used, and they are slightly reduced; with their decrease, the + crest of the sternum, the scapulæ, coracoids, and furcula, have all been + reduced.</p> + + <p>With domesticated animals, the reduction of a part from disuse is + never carried so far that a mere rudiment is left, but we have good + reason to believe that this has often occurred under nature. The cause of + this difference probably is that with domestic animals not only + sufficient time has not been granted for so profound a change, but that, + from not being exposed to a severe struggle for life, the principle of + the economy of organisation does not come into action. On the contrary, + we sometimes see that structures which are rudimentary in the + parent-species become partially redeveloped in their domesticated + progeny. When rudiments are formed or left under domestication, they are + the result of a sudden arrest of development, and not of long-continued + disuse with the absorption of all superfluous parts; nevertheless they + are of interest, as showing that rudiments are the relics of organs once + perfectly developed.</p> + + <p>Corporeal, periodical, and mental habits, though the latter have been + almost passed over in this work, become changed under domestication, and + the changes are often inherited. Such changed habits in any organic + being, especially when living a free life, would often lead to the + augmented or diminished use of various organs, and consequently to their + modification. From long-continued habit, and more especially from the + occasional birth of individuals with a slightly different constitution, + domestic animals and cultivated plants become to a certain extent + acclimatised, or adapted to a climate different from that proper to the + parent-species.</p> + + <p>Through the principle of correlated variability, when one part varies + other parts vary,—either simultaneously, or one after the other. + Thus an organ modified during an early embryonic period affects other + parts subsequently developed. When an <!-- Page 354 --><span + class="pagenum"><a name="page354"></a>{354}</span>organ, such as the + beak, increases or decreases in length, adjoining or correlated parts, as + the tongue and the orifice of the nostrils, tend to vary in the same + manner. When the whole body increases or decreases in size, various parts + become modified; thus with pigeons the ribs increase or decrease in + number and breadth. Homologous parts, which are identical during their + early development and are exposed to similar conditions, tend to vary in + the same or in some connected manner,—as in the case of the right + and left sides of the body, of the front and hind limbs, and even of the + head and limbs. So it is with the organs of sight and hearing; for + instance, white cats with blue eyes are almost always deaf. There is a + manifest relation throughout the body between the skin and its various + appendages of hair, feathers, hoofs, horns, and teeth. In Paraguay, + horses with curly hair have hoofs like those of a mule; the wool and the + horns of sheep vary together; hairless dogs are deficient in their teeth; + men with redundant hair have abnormal teeth, either deficient or in + excess. Birds with long wing-feathers usually have long tail-feathers. + When long feathers grow from the outside of the legs and toes of pigeons, + the two outer toes are connected by membrane; for the whole leg tends to + assume the structure of the wing. There is a manifest relation between a + crest of feathers on the head and a marvellous amount of change in the + skull of various fowls; and in a lesser degree, between the greatly + elongated, lopping ears of rabbits and the structure of their skulls. + With plants, the leaves, various parts of the flower, and the fruit, + often vary together in a correlated manner.</p> + + <p>In some cases we find correlation without being able even to + conjecture what is the nature of the connexion, as with various + correlated monstrosities and diseases. This is likewise the case with the + colour of the adult pigeon, in connexion with the presence of down on the + young bird. Numerous curious instances have been given of peculiarities + of constitution, in correlation with colour, as shown by the immunity of + individuals of some one colour from certain diseases, from the attacks of + parasites, and from the action of certain vegetable poisons.</p> + + <p>Correlation is an important subject; for with species, and in a lesser + degree with domestic races, we continually find that <!-- Page 355 + --><span class="pagenum"><a name="page355"></a>{355}</span>certain parts + have been greatly modified to serve some useful purpose; but we almost + invariably find that other parts have likewise been more or less + modified, without our being able to discover any advantage in the change. + No doubt great caution is necessary in coming to this conclusion, for it + is difficult to overrate our ignorance on the use of various parts of the + organisation; but from what we have now seen, we may believe that many + modifications are of no direct service, having arisen in correlation with + other and useful changes.</p> + + <p>Homologous parts during their early development evince an affinity for + each other,—that is, they tend to cohere and fuse together much + more readily than other parts. This tendency to fusion explains a + multitude of normal structures. Multiple and homologous organs are + especially liable to vary in number and probably in form. As the supply + of organised matter is not unlimited, the principle of compensation + sometimes comes into action; so that, when one part is greatly developed, + adjoining parts or functions are apt to be reduced; but this principle is + probably of much less importance than the more general one of the economy + of growth. Through mere mechanical pressure hard parts occasionally + affect soft adjoining parts. With plants the position of the flowers on + the axis, and of the seeds in the capsule, sometimes leads, through a + freer flow of sap, to changes of structure; but these changes are often + due to reversion. Modifications, in whatever manner caused, will be to a + certain extent regulated by that co-ordinating power or <i>nisus + formativus</i>, which is in fact a remnant of one of the forms of + reproduction, displayed by many lowly organised beings in their power of + fissiparous generation and budding. Finally, the effects of the laws, + which directly or indirectly govern variability, may be largely + influenced by man's selection, and will so far be determined by natural + selection that changes advantageous to any race will be favoured and + disadvantageous changes checked.</p> + + <p>Domestic races descended from the same species, or from two or more + allied species, are liable to revert to characters derived from their + common progenitor, and, as they have much in common in their + constitutions, they are also liable under changed conditions to vary in + the same manner; from these <!-- Page 356 --><span class="pagenum"><a + name="page356"></a>{356}</span>two causes analogous varieties often + arise. When we reflect on the several foregoing laws, imperfectly as we + understand them, and when we bear in mind how much remains to be + discovered, we need not be surprised at the extremely intricate manner in + which our domestic productions have varied, and still go on varying.</p> + +<hr class="full" /> + +<p><!-- Page 357 --><span class="pagenum"><a name="page357"></a>{357}</span></p> + +<h3>CHAPTER XXVII.</h3> + +<p class="cenhead">PROVISIONAL HYPOTHESIS OF PANGENESIS.</p> + +<blockquote class="b1n"> + + <p><span class="scac">PRELIMINARY REMARKS.</span>—<span + class="scac">FIRST PART:</span>—<span class="scac">THE FACTS TO BE + CONNECTED UNDER A SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF + REPRODUCTION</span>—<span class="scac">THE DIRECT ACTION OF THE + MALE ELEMENT ON THE FEMALE</span>—<span + class="scac">DEVELOPMENT</span>—<span class="scac">THE FUNCTIONAL + INDEPENDENCE OF THE ELEMENTS OR UNITS OF THE BODY</span>—<span + class="scac">VARIABILITY</span>—<span + class="scac">INHERITANCE</span>—<span + class="scac">REVERSION.</span></p> + + <p><span class="scac">SECOND PART:</span>—<span + class="scac">STATEMENT OF THE HYPOTHESIS</span>—<span + class="scac">HOW FAR THE NECESSARY ASSUMPTIONS ARE + IMPROBABLE</span>—<span class="scac">EXPLANATION BY AID OF THE + HYPOTHESIS OF THE SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST + PART</span>—<span class="scac">CONCLUSION.</span></p> + +</blockquote> + + <p>In the previous chapters large classes of facts, such as those bearing + on bud-variation, the various forms of inheritance, the causes and laws + of variation, have been discussed; and it is obvious that these subjects, + as well as the several modes of reproduction, stand in some sort of + relation to each other. I have been led, or rather forced, to form a view + which to a certain extent connects these facts by a tangible method. + Every one would wish to explain to himself, even in an imperfect manner, + how it is possible for a character possessed by some remote ancestor + suddenly to reappear in the offspring; how the effects of increased or + decreased use of a limb can be transmitted to the child; how the male + sexual element can act not solely on the ovule, but occasionally on the + mother-form; how a limb can be reproduced on the exact line of + amputation, with neither too much nor too little added; how the various + modes of reproduction are connected, and so forth. I am aware that my + view is merely a provisional hypothesis or speculation; but until a + better one be advanced, it may be serviceable by bringing together a + multitude of facts which are at present left disconnected by any + efficient cause. As Whewell, the historian of the inductive sciences, + remarks:—"Hypotheses may often be of service to science, when they + involve a certain portion of incompleteness, and even of error." Under + this point of view I venture to advance the hypothesis of Pangenesis, + which <!-- Page 358 --><span class="pagenum"><a + name="page358"></a>{358}</span>implies that the whole organisation, in + the sense of every separate atom or unit, reproduces itself. Hence ovules + and pollen-grains,—the fertilised seed or egg, as well as + buds,—include and consist of a multitude of germs thrown off from + each separate atom of the organism.</p> + + <p>In the First Part I will enumerate as briefly as I can the groups of + facts which seem to demand connection; but certain subjects, not hitherto + discussed, must be treated at disproportionate length. In the Second Part + the hypothesis will be given; and we shall see, after considering how far + the necessary assumptions are in themselves improbable, whether it serves + to bring under a single point of view the various facts.</p> + +<p class="cenhead"><span class="sc">Part I.</span></p> + + <p>Reproduction may be divided into two main classes, namely, sexual and + asexual. The latter is effected in many ways—by gemmation, that is + by the formation of buds of various kinds, and by fissiparous generation, + that is by spontaneous or artificial division. It is notorious that some + of the lower animals, when cut into many pieces, reproduce so many + perfect individuals: Lyonnet cut a Nais or freshwater worm into nearly + forty pieces, and these all reproduced perfect animals.<a name="NtA_874" + href="#Nt_874"><sup>[874]</sup></a> It is probable that segmentation + could be carried much further in some of the protozoa, and with some of + the lowest plants each cell will reproduce the parent-form. Johannes + Müller thought that there was an important distinction between gemmation + and fission; for in the latter case the divided portion, however small, + is more perfectly organised; but most physiologists are now convinced + that the two processes are essentially alike.<a name="NtA_875" + href="#Nt_875"><sup>[875]</sup></a> Prof. Huxley remarks, "fission is + little more than a peculiar <!-- Page 359 --><span class="pagenum"><a + name="page359"></a>{359}</span>mode of budding," and Prof. H. J. Clark, + who has especially attended to this subject, shows in detail that there + is sometimes "a compromise between self-division and budding." When a + limb is amputated, or when the whole body is bisected, the cut + extremities are said to bud forth; and as the papilla, which is first + formed, consists of undeveloped cellular tissue like that forming an + ordinary bud, the expression is apparently correct. We see the connection + of the two processes in another way; for Trembley observed that with the + hydra the reproduction of the head after amputation was checked as soon + as the animal began to bud.<a name="NtA_876" + href="#Nt_876"><sup>[876]</sup></a></p> + + <p>Between the production, by fissiparous generation, of two or more + complete individuals, and the repair of even a very slight injury, we + have, as remarked in a former chapter, so perfect and insensible a + gradation, that it is impossible to doubt that they are connected + processes. Between the power which repairs a trifling injury in any part, + and the power which previously "was occupied in its maintenance by the + continued mutation of its particles," there cannot be any great + difference; and we may follow Mr. Paget in believing them to be the + selfsame power. As at each stage of growth an amputated part is replaced + by one in the same state of development, we must likewise follow Mr. + Paget in admitting "that the powers of development from the embryo are + identical with those exercised for the restoration from injuries: in + other words, that the powers are the same by which perfection is first + achieved, and by which, when lost, it is recovered."<a name="NtA_877" + href="#Nt_877"><sup>[877]</sup></a> Finally, we may conclude that the + several forms of gemmation, and of fissiparous generation, the repair of + injuries, the maintenance of each part in its proper state, and the + growth or progressive development of the whole structure of the embryo, + are all essentially the results of one and the same great power.</p> + + <p><i>Sexual Generation.</i>—The union of the two sexual elements + seems to make a broad distinction between sexual and asexual + reproduction. But the well-ascertained cases of Parthenogenesis prove + that the distinction is not really so great as it at first appears; for + ovules occasionally, and even in some cases <!-- Page 360 --><span + class="pagenum"><a name="page360"></a>{360}</span>frequently, become + developed into perfect beings, without the concourse of the male element. + J. Müller and others admit that ovules and buds have the same essential + nature. Certain bodies, which during their early development cannot be + distinguished by any external character from true ovules, nevertheless + must be classed as buds, for though formed within the ovarium they are + incapable of fertilisation. This is the case with the germ-balls of the + Cecidomyide larvæ, as described by Leuckart.<a name="NtA_878" + href="#Nt_878"><sup>[878]</sup></a> Ovules and the male element, before + they become united, have, like buds, an independent existence.<a + name="NtA_879" href="#Nt_879"><sup>[879]</sup></a> Both have the power of + transmitting every single character possessed by the parent-form. We see + this clearly when hybrids are paired <i>inter se</i>, for the characters + of either grandparent often reappear, either perfectly or by segments, in + the progeny. It is an error to suppose that the male transmits certain + characters and the female other characters; though no doubt, from unknown + causes, one sex sometimes has a stronger power of transmission than the + other.</p> + + <p>It has been maintained by some authors that a bud differs essentially + from a fertilised germ, by always reproducing the perfect character of + the parent-stock; whilst fertilised germs become developed into beings + which differ, in a greater or less degree, from each other and from their + parents. But there is no such broad distinction as this. In the eleventh + chapter, numerous cases were given showing that buds occasionally grow + into plants having new and strongly marked characters; and varieties thus + produced can be propagated for a length of time by buds, and occasionally + by seed. Nevertheless, it must be admitted that beings produced sexually + are much more liable to vary than those produced asexually; and of this + fact a partial explanation will hereafter be attempted. The variability + in both cases is determined by the same general causes, and is governed + by the same laws. Hence new varieties arising from buds cannot be + distinguished from those arising from seed. Although bud-varieties + usually retain their character during <!-- Page 361 --><span + class="pagenum"><a name="page361"></a>{361}</span>successive + bud-generations, yet they occasionally revert, even after a long series + of bud-generations, to their former character. This tendency to reversion + in buds is one of the most remarkable of the several points of agreement + between the offspring from bud and seminal reproduction.</p> + + <p>There is, however, one difference between beings produced sexually and + asexually, which is very general. The former usually pass in the course + of their development from a lower to a higher grade, as we see in the + metamorphoses of insects and in the concealed metamorphoses of the + vertebrata; but this passage from a lower to a higher grade cannot be + considered as a necessary accompaniment of sexual reproduction, for + hardly anything of the kind occurs in the development of Aphis amongst + insects, or with certain crustaceans, cephalopods, or with any of the + higher vascular plants. Animals propagated asexually by buds or fission + are on the other hand never known to undergo a retrogressive + metamorphosis; that is, they do not first sink to a lower, before passing + on to their higher and final stage of development. But during the act of + asexual production or subsequently to it, they often advance in + organisation, as we see in the many cases of "alternate generation." In + thus speaking of alternate generation, I follow those naturalists who + look at the process as essentially one of internal budding or of + fissiparous generation. Some of the lower plants, however, such as mosses + and certain algæ, according to Dr. L. Radlkofer,<a name="NtA_880" + href="#Nt_880"><sup>[880]</sup></a> when propagated asexually, do undergo + a retrogressive metamorphosis. We can to a certain extent understand, as + far as the final cause is concerned, why beings propagated by buds should + so rarely retrogress during development; for with each organism the + structure acquired at each stage of development must be adapted to its + peculiar habits. Now, with beings produced by gemmation,—and this, + differently from sexual reproduction, may occur at any period of + growth,—if there were places for the support of many individuals at + some one stage of development, the simplest plan would be that they + should be multiplied by gemmation at that stage, and not that they should + first retrograde in their development to an earlier or simpler structure, + which might not be fitted for the surrounding conditions.</p> + +<p><!-- Page 362 --><span class="pagenum"><a name="page362"></a>{362}</span></p> + + <p>From the several foregoing considerations we may conclude that the + difference between sexual and asexual generation is not nearly so great + as it at first appears; and we have already seen that there is the + closest agreement between gemmation, fissiparous generation, the repair + of injuries, and ordinary growth or development. The capacity of + fertilisation by the male element seems to be the chief distinction + between an ovule and a bud; and this capacity is not invariably brought + into action, as in the cases of parthenogenetic reproduction. We are here + naturally led to inquire what the final cause can be of the necessity in + ordinary generation for the concourse of the two sexual elements.</p> + + <p>Seeds and ova are often highly serviceable as the means of + disseminating plants and animals, and of preserving them during one or + more seasons in a dormant state; but unimpregnated seeds or ova, and + detached buds, would be equally serviceable for both purposes. We can, + however, indicate two important advantages gained by the concourse of the + two sexes, or rather of two individuals belonging to opposite sexes; for, + as I have shown in a former chapter, the structure of every organism + appears to be especially adapted for the concurrence, at least + occasionally, of two individuals. In nearly the same manner as it is + admitted by naturalists that hybridism, from inducing sterility, is of + service in keeping the forms of life distinct and fitted for their proper + places; so, when species are rendered highly variable by changed + conditions of life, the free intercrossing of the varying individuals + will tend to keep each form fitted for its proper place in nature; and + crossing can be effected only by sexual generation, but whether the end + thus gained is of sufficient importance to account for the first origin + of sexual intercourse is very doubtful. Secondly, I have shown, from the + consideration of a large body of facts, that, as a slight change in the + conditions of life is beneficial to each creature, so, in an analogous + manner, is the change effected in the germ by sexual union with a + distinct individual; and I have been led, from observing the many + widely-extended provisions throughout nature for this purpose, and from + the greater vigour of crossed organisms of all kinds, as proved by direct + experiments, as well as from the evil effects of close interbreeding when + long <!-- Page 363 --><span class="pagenum"><a + name="page363"></a>{363}</span>continued, to believe that the advantage + thus gained is very great. Besides these two important ends, there may, + of course, be others, as yet unknown to us, gained by the concourse of + the two sexes.</p> + + <p>Why the germ, which before impregnation undergoes a certain amount of + development, ceases to progress and perishes, unless it be acted on by + the male element; and why conversely the male element, which is enabled + to keep alive for even four or five years within the spermatheca of a + female insect, likewise perishes, unless it acts on or unites with the + germ, are questions which cannot be answered with any certainty. It is, + however, possible that both sexual elements perish, unless brought into + union, simply from including too little formative matter for independent + existence and development; for certainly they do not in ordinary cases + differ in their power of giving character to the embryo. This view of the + importance of the quantity of formative matter seems probable from the + following considerations. There is no reason to suspect that the + spermatozoa or pollen-grains of the same individual animal or plant + differ from each other; yet Quatrefages has shown in the case of the + Teredo,<a name="NtA_881" href="#Nt_881"><sup>[881]</sup></a> as did + formerly Prevost and Dumas with other animals, that more than one + spermatozoon is requisite to fertilise an ovule. This has likewise been + clearly proved by Newport,<a name="NtA_882" + href="#Nt_882"><sup>[882]</sup></a> who adds the important fact, + established by numerous experiments, that, when a very small number of + spermatozoa are applied to the ova of Batrachians, they are only + partially impregnated and the embryo is never fully developed: the first + step, however, towards development, namely, the partial segmentation of + the yelk, does occur to a greater or less extent, but is never completed + up to granulation. The rate of the segmentation is likewise determined by + the number of the spermatozoa. With respect to plants, nearly the same + results were obtained by Kölreuter and Gärtner. This last careful + observer found,<a name="NtA_883" href="#Nt_883"><sup>[883]</sup></a> + after making successive trials on a Malva with more and more + pollen-grains, that even thirty grains did not fertilise a single seed; + but when forty grains were applied to the <!-- Page 364 --><span + class="pagenum"><a name="page364"></a>{364}</span>stigma, a few seeds of + small size were formed. The pollen-grains of Mirabilis are + extraordinarily large, and the ovarium contains only a single ovule; and + these circumstances led Naudin<a name="NtA_884" + href="#Nt_884"><sup>[884]</sup></a> to make the following interesting + experiments: a flower was fertilised by three grains and succeeded + perfectly; twelve flowers were fertilised by two grains, and seventeen + flowers by a single grain, and of these one flower alone in each lot + perfected its seed; and it deserves especial notice that the plants + produced by these two seeds never attained their proper dimensions, and + bore flowers of remarkably small size. From these facts we clearly see + that the quantity of the peculiar formative matter which is contained + within the spermatozoa and pollen-grains is an all-important element in + the act of fertilisation, not only in the full development of the seed, + but in the vigour of the plant produced from such seed. We see something + of the same kind in certain cases of parthenogenesis, that is, when the + male element is wholly excluded; for M. Jourdan<a name="NtA_885" + href="#Nt_885"><sup>[885]</sup></a> found that, out of about 58,000 eggs + laid by unimpregnated silk-moths, many passed through their early + embryonic stages, showing that they were capable of self-development, but + only twenty-nine out of the whole number produced caterpillars. Therefore + it is not an improbable view that deficient bulk or quantity in the + formative matter, contained within the sexual elements, is the main cause + of their not having the capacity of prolonged separate existence and + development. The belief that it is the function of the spermatozoa to + communicate life to the ovule seems a strange one, seeing that the + unimpregnated ovule is already alive and continues for a considerable + time alive. We shall hereafter see that it is probable that the sexual + elements, or possibly only the female element, include certain primordial + cells, that is, such as have undergone no differentiation, and which are + not present in an active state in buds.</p> + + <p><i>Graft-hybrids.</i>—When discussing in the eleventh chapter + the curious case of the <i>Cytisus adami</i>, facts were given which + render it to a certain degree probable, in accordance with the belief of + some distinguished botanists, that, when the tissues of two plants <!-- + Page 365 --><span class="pagenum"><a + name="page365"></a>{365}</span>belonging to distinct species or varieties + are intimately united, buds are afterwards occasionally produced which, + like hybrids, combine the characters of the two united forms. It is + certain that when trees with variegated leaves are grafted or budded on a + common stock, the latter sometimes produces buds bearing variegated + leaves; but this may perhaps be looked at as a case of inoculated + disease. Should it ever be proved that hybridised buds can be formed by + the union of two distinct vegetative tissues, the essential identity of + sexual and asexual reproduction would be shown in the most interesting + manner; for the power of combining in the offspring the characters of + both parents, is the most striking of all the functions of sexual + generation.</p> + + <p><i>Direct Action of the Male Element on the Female.</i>—In the + chapter just referred to, I have given abundant proofs that foreign + pollen occasionally affects the mother-plant in a direct manner. Thus, + when Gallesio fertilised an orange-flower with pollen from the lemon, the + fruit bore stripes of perfectly characterised lemon-peel: with peas, + several observers have seen the colour of the seed-coats and even of the + pod directly affected by the pollen of a distinct variety; so it has been + with the fruit of the apple, which consists of the modified calyx and + upper part of the flower-stalk. These parts in ordinary cases are wholly + formed by the mother-plant. We here see the male element affecting and + hybridising not that part which it is properly adapted to affect, namely + the ovule, but the partially developed tissues of a distinct individual. + We are thus brought half-way towards a graft-hybrid, in which the + cellular tissue of one form, instead of its pollen, is believed to + hybridise the tissues of a distinct form. I formerly assigned reasons for + rejecting the belief that the mother-plant is affected through the + intervention of the hybridised embryo; but even if this view were + admitted, the case would become one of graft-hybridism, for the + fertilised embryo and the mother-plant must be looked at as distinct + individuals.</p> + + <p>With animals which do not breed until nearly mature, and of which all + the parts are then fully developed, it is hardly possible that the male + element should directly affect the female. But we have the analogous and + perfectly well-ascertained case of the male element of a distinct form, + as with the <!-- Page 366 --><span class="pagenum"><a + name="page366"></a>{366}</span>quagga and Lord Morton's mare, affecting + the ovarium of the female, so that the ovules and offspring subsequently + produced by her when impregnated by other males are plainly affected and + hybridised by the first male.</p> + + <p><i>Development.</i>—The fertilised germ reaches maturity by a + vast number of changes: these are either slight and slowly effected, as + when the child grows into the man, or are great and sudden, as with the + metamorphoses of most insects. Between these extremes we have, even + within the same class, every gradation: thus, as Sir J. Lubbock has + shown,<a name="NtA_886" href="#Nt_886"><sup>[886]</sup></a> there is an + Ephemerous insect which moults above twenty times, undergoing each time a + slight but decided change of structure; and these changes, as he further + remarks, probably reveal to us the normal stages of development which are + concealed and hurried through, or suppressed, in most other insects. In + ordinary metamorphoses, the parts and organs appear to become changed + into the corresponding parts in the next stage of development; but there + is another form of development, which has been called by Professor Owen + metagenesis. In this case "the new parts are not moulded upon the inner + surface of the old ones. The plastic force has changed its course of + operation. The outer case, and all that gave form and character to the + precedent individual, perish and are cast off; they are not changed into + the corresponding parts of the new individual. These are due to a new and + distinct developmental process," &c.<a name="NtA_887" + href="#Nt_887"><sup>[887]</sup></a> Metamorphosis, however, graduates so + insensibly into metagenesis, that the two processes cannot be distinctly + separated. For instance, in the last change which Cirripedes undergo, the + alimentary canal and some other organs are moulded on pre-existing parts; + but the eyes of the old and the young animal are developed in entirely + different parts of the body; the tips of the mature limbs are formed + within the larval limbs, and may be said to be metamorphosed from them; + but their basal portions and the whole thorax are developed in a plane + actually at right angles to the limbs and thorax of the larva; and this + <!-- Page 367 --><span class="pagenum"><a + name="page367"></a>{367}</span>may be called metagenesis. The metagenetic + process is carried to an extreme degree in the development of some + Echinoderms, for the animal in the second stage of development is formed + almost like a bud within the animal of the first stage, the latter being + then cast off like an old vestment, yet sometimes still maintaining for a + short period an independent vitality.<a name="NtA_888" + href="#Nt_888"><sup>[888]</sup></a></p> + + <p>If, instead of a single individual, several were to be thus developed + metagenetically within a pre-existing form, the process would be called + one of alternate generation. The young thus developed may either closely + resemble the encasing parent-form, as with the larvæ of Cecidomyia, or + may differ to an astonishing degree, as with many parasitic worms and + with jelly-fishes; but this does not make any essential difference in the + process, any more than the greatness or abruptness of the change in the + metamorphoses of insects.</p> + + <p>The whole question of development is of great importance for our + present subject. When an organ, the eye for instance, is metagenetically + formed in a part of the body where during the previous stage of + development no eye existed, we must look at it as a new and independent + growth. The absolute independence of new and old structures, which + correspond in structure and function, is still more obvious when several + individuals are formed within a previous encasing form, as in the cases + of alternate generation. The same important principle probably comes + largely into play even in the case of continuous growth, as we shall see + when we consider the inheritance of modifications at corresponding + ages.</p> + + <p>We are led to the same conclusion, namely, the independence of parts + successively developed, by another and quite distinct group of facts. It + is well known that many animals belonging to the same class, and + therefore not differing widely from each other, pass through an extremely + different course of development. Thus certain beetles, not in any way + remarkably different from others of the same order, undergo what has been + called a hyper-metamorphosis—that is, they pass through an early + stage wholly different from the ordinary grub-like larva. In the same + sub-order of crabs, namely, the Macroura, as Fritz <!-- Page 368 --><span + class="pagenum"><a name="page368"></a>{368}</span>Müller remarks, the + river cray-fish is hatched under the same form which it ever afterwards + retains; the young lobster has divided legs, like a Mysis; the Palæmon + appears under the form of a Zoea, and Peneus under the Nauplius-form; and + how wonderfully these larval forms differ from each other, is known to + every naturalist.<a name="NtA_889" href="#Nt_889"><sup>[889]</sup></a> + Some other crustaceans, as the same author observes, start from the same + point and arrive at nearly the same end, but in the middle of their + development are widely different from each other. Still more striking + cases could be given with respect to the Echinodermata. With the Medusæ + or jelly-fishes Professor Allman observes, "the classification of the + Hydroida would be a comparatively simple task if, as has been erroneously + asserted, generically-identical medusoids always arose from + generically-identical polypoids; and on the other hand, that + generically-identical polypoids always gave origin to + generically-identical medusoids." So, again, Dr. Strethill Wright + remarks, "in the life-history of the Hydroidæ any phase, planuloid, + polypoid, or medusoid, may be absent."<a name="NtA_890" + href="#Nt_890"><sup>[890]</sup></a></p> + + <p>According to the belief now generally accepted by our best + naturalists, all the members of the same order or class, the Macrourous + crustaceans for instance, are descended from a common progenitor. During + their descent they have diverged much in structure, but have retained + much in common; and this divergence and retention of character has been + effected, though they have passed and still pass through marvellously + different metamorphoses. This fact well illustrates how independent each + structure must be from that which precedes and follows it in the course + of development.</p> + + <p><i>The Functional Independence of the Elements or Units of the + Body.</i>—Physiologists agree that the whole organism consists of a + multitude of elemental parts, which are to a great extent independent of + each other. Each organ, says Claude Bernard,<a name="NtA_891" + href="#Nt_891"><sup>[891]</sup></a> <!-- Page 369 --><span + class="pagenum"><a name="page369"></a>{369}</span>has its proper life, + its autonomy; it can develop and reproduce itself independently of the + adjoining tissues. The great German authority, Virchow,<a name="NtA_892" + href="#Nt_892"><sup>[892]</sup></a> asserts still more emphatically that + each system, as the nervous or osseous system, or the blood, consists of + an "enormous mass of minute centres of action.... Every element has its + own special action, and even though it derive its stimulus to activity + from other parts, yet alone effects the actual performance of its + duties.... Every single epithelial and muscular fibre-cell leads a sort + of parasitical existence in relation to the rest of the body.... Every + single bone-corpuscle really possesses conditions of nutrition peculiar + to itself." Each element, as Mr. Paget remarks, lives its appointed time, + and then dies, and, after being cast off or absorbed, is replaced.<a + name="NtA_893" href="#Nt_893"><sup>[893]</sup></a> I presume that no + physiologist doubts that, for instance, each bone-corpuscle of the finger + differs from the corresponding corpuscle in the corresponding joint of + the toe; and there can hardly be a doubt that even those on the + corresponding sides of the body differ, though almost identical in + nature. This near approach to identity is curiously shown in many + diseases in which the same exact points on the right and left sides of + the body are similarly affected; thus Mr. Paget<a name="NtA_894" + href="#Nt_894"><sup>[894]</sup></a> gives a drawing of a diseased pelvis, + in which the bone has grown into a most complicated pattern, but "there + is not one spot or line on one side which is not represented, as exactly + as it would be in a mirror, on the other."</p> + + <p>Many facts support this view of the independent life of each minute + element of the body. Virchow insists that a single bone-corpuscle or a + single cell in the skin may become diseased. The spur of a cock, after + being inserted into the eye of an ox, lived for eight years, and acquired + a weight of 306 grammes, or nearly fourteen ounces.<a name="NtA_895" + href="#Nt_895"><sup>[895]</sup></a> The tail of a pig has been grafted + into the middle of its back, and reacquired sensibility. Dr. Ollier<a + name="NtA_896" href="#Nt_896"><sup>[896]</sup></a> inserted a piece of + periosteum from the bone of a young dog under the skin of a rabbit, and + true bone was developed. A multitude of similar facts could be given. The + <!-- Page 370 --><span class="pagenum"><a + name="page370"></a>{370}</span>frequent presence of hairs and of + perfectly developed teeth, even teeth of the second dentition, in ovarian + tumours,<a name="NtA_897" href="#Nt_897"><sup>[897]</sup></a> are facts + leading to the same conclusion.</p> + + <p>Whether each of the innumerable autonomous elements of the body is a + cell or the modified product of a cell, is a more doubtful question, even + if so wide a definition be given to the term, as to include cell-like + bodies without walls and without nuclei.<a name="NtA_898" + href="#Nt_898"><sup>[898]</sup></a> Professor Lionel Beale uses the term + "germinal matter" for the contents of cells, taken in this wide + acceptation, and he draws a broad distinction between germinal matter and + "formed material" or the various products of cells.<a name="NtA_899" + href="#Nt_899"><sup>[899]</sup></a> But the doctrine of <i>omnis cellula + e cellulâ</i> is admitted for plants, and is a widely prevalent belief + with respect to animals.<a name="NtA_900" + href="#Nt_900"><sup>[900]</sup></a> Thus Virchow, the great supporter of + the cellular theory, whilst allowing that difficulties exist, maintains + that every atom of tissue is derived from cells, and these from + pre-existing cells, and these primarily from the egg, which he regards as + a great cell. That cells, still retaining the same nature, increase by + self-division or proliferation, is admitted by almost every one. But when + an organism undergoes a great change of structure during development, the + cells, which at each stage are supposed to be directly derived from + previously-existing cells, must likewise be greatly changed in nature; + this change is apparently attributed by the supporters of the cellular + doctrine to some inherent power which the cells possess, and not to any + external agency.</p> + + <p>Another school maintains that cells and tissues of all kinds may be + formed, independently of pre-existing cells, from plastic lymph or + blastema; and this it is thought is well exhibited in the repair of + wounds. As I have not especially attended to histology, it would be + presumptuous in me to express an opinion on the two opposed doctrines. + But every one appears to admit that the body consists of a multitude of + "organic units,"<a name="NtA_901" href="#Nt_901"><sup>[901]</sup></a> + <!-- Page 371 --><span class="pagenum"><a + name="page371"></a>{371}</span>each of which possesses its own proper + attributes, and is to a certain extent independent of all others. Hence + it will be convenient to use indifferently the terms cells or organic + units or simply units.</p> + + <p><i>Variability and Inheritance.</i>—We have seen in the + twenty-second chapter that variability is not a principle co-ordinate + with life or reproduction, but results from special causes, generally + from changed conditions acting during successive generations. Part of the + fluctuating variability thus induced is apparently due to the sexual + system being easily affected by changed conditions, so that it is often + rendered impotent; and when not so seriously affected, it often fails in + its proper function of transmitting truly the characters of the parents + to the offspring. But variability is not necessarily connected with the + sexual system, as we see from the cases of bud-variation; and although we + may not be able to trace the nature of the connexion, it is probable that + many deviations of structure which appear in sexual offspring result from + changed conditions acting directly on the organisation, independently of + the reproductive organs. In some instances we may feel sure of this, when + all, or nearly all the individuals which have been similarly exposed are + similarly and definitely affected—as in the dwarfed and otherwise + changed maize brought from hot countries when cultivated in Germany; in + the change of the fleece in sheep within the tropics; to a certain extent + in the increased size and early maturity of our highly-improved + domesticated animals; in inherited gout from intemperance; and in many + other such cases. Now, as such changed conditions do not especially + affect the reproductive organs, it seems mysterious on any ordinary view + why their product, the new organic being, should be similarly + affected.</p> + + <p>How, again, can we explain to ourselves the inherited effects of the + use or disuse of particular organs? The domesticated duck flies less and + walks more than the wild duck, and its limb-bones have become in a + corresponding manner diminished and increased in comparison with those of + the wild duck. A horse is trained to certain paces, and the colt inherits + similar consensual movements. The domesticated rabbit becomes tame from + close confinement; the dog intelligent from associating with man; the + retriever is taught to fetch and carry: and these <!-- Page 372 --><span + class="pagenum"><a name="page372"></a>{372}</span>mental endowments and + bodily powers are all inherited. Nothing in the whole circuit of + physiology is more wonderful. How can the use or disuse of a particular + limb or of the brain affect a small aggregate of reproductive cells, + seated in a distant part of the body, in such a manner that the being + developed from these cells inherits the characters of either one or both + parents? Even an imperfect answer to this question would be + satisfactory.</p> + + <p>Sexual reproduction does not essentially differ, as we have seen, from + budding or self-division, and these processes graduate through the repair + of injuries into ordinary development and growth; it might therefore be + expected that every character would be as regularly transmitted by all + the methods of reproduction as by continued growth. In the chapters + devoted to inheritance it was shown that a multitude of newly-acquired + characters, whether injurious or beneficial, whether of the lowest or + highest vital importance, are often faithfully + transmitted—frequently even when one parent alone possesses some + new peculiarity. It deserves especial attention that characters appearing + at any age tend to reappear at a corresponding age. We may on the whole + conclude that in all cases inheritance is the rule, and non-inheritance + the anomaly. In some instances a character is not inherited, from the + conditions of life being directly opposed to its development; in many + instances, from the conditions incessantly inducing fresh variability, as + with grafted fruit-trees and highly cultivated flowers. In the remaining + cases the failure may be attributed to reversion, by which the child + resembles its grandparents or more remote progenitors, instead of its + parents.</p> + + <p>This principle of Reversion is the most wonderful of all the + attributes of Inheritance. It proves to us that the transmission of a + character and its development, which ordinarily go together and thus + escape discrimination, are distinct powers; and these powers in some + cases are even antagonistic, for each acts alternately in successive + generations. Reversion is not a rare event, depending on some unusual or + favourable combination of circumstances, but occurs so regularly with + crossed animals and plants, and so frequently with uncrossed breeds, that + it is evidently an essential part of the principle of inheritance. We + know that <!-- Page 373 --><span class="pagenum"><a + name="page373"></a>{373}</span>changed conditions have the power of + evoking long-lost characters, as in the case of some feral animals. The + act of crossing in itself possesses this power in a high degree. What can + be more wonderful than that characters, which have disappeared during + scores, or hundreds, or even thousands of generations, should suddenly + reappear perfectly developed, as in the case of pigeons and fowls when + purely bred, and especially when crossed; or as with the zebrine stripes + on dun-coloured horses, and other such cases? Many monstrosities come + under this same head, as when rudimentary organs are redeveloped, or when + an organ which we must believe was possessed by an early progenitor, but + of which not even a rudiment is left, suddenly reappears, as with the + fifth stamen in some Scrophulariaceæ. We have already seen that reversion + acts in bud-reproduction; and we know that it occasionally acts during + the growth of the same individual animal, especially, but not + exclusively, when of crossed parentage,—as in the rare cases + described of individual fowls, pigeons, cattle, and rabbits, which have + reverted as they advanced in years to the colours of one of their parents + or ancestors.</p> + + <p>We are led to believe, as formerly explained, that every character + which occasionally reappears is present in a latent form in each + generation, in nearly the same manner as in male and female animals + secondary characters of the opposite sex lie latent, ready to be evolved + when the reproductive organs are injured. This comparison of the + secondary sexual characters which are latent in both sexes, with other + latent characters, is the more appropriate from the case recorded of the + Hen, which assumed some of the masculine characters, not of her own race, + but of an early progenitor; she thus exhibited at the same time the + redevelopment of latent characters of both kinds and connected both + classes. In every living creature we may feel assured that a host of lost + characters lie ready to be evolved under proper conditions. How can we + make intelligible, and connect with other facts, this wonderful and + common capacity of reversion,—this power of calling back to life + long-lost characters? <!-- Page 374 --><span class="pagenum"><a + name="page374"></a>{374}</span></p> + +<p class="cenhead"><span class="sc">Part II.</span></p> + + <p>I have now enumerated the chief facts which every one would desire to + connect by some intelligible bond. This can be done, as it seems to me, + if we make the following assumptions; if the first and chief one be not + rejected, the others, from being supported by various physiological + considerations, will not appear very improbable. It is almost universally + admitted that cells, or the units of the body, propagate themselves by + self-division or proliferation, retaining the same nature, and ultimately + becoming converted into the various tissues and substances of the body. + But besides this means of increase I assume that cells, before their + conversion into completely passive or "formed material," throw off minute + granules or atoms, which circulate freely throughout the system, and when + supplied with proper nutriment multiply by self-division, subsequently + becoming developed into cells like those from which they were derived. + These granules for the sake of distinctness may be called cell-gemmules, + or, as the cellular theory is not fully established, simply gemmules. + They are supposed to be transmitted from the parents to the offspring, + and are generally developed in the generation which immediately succeeds, + but are often transmitted in a dormant state during many generations and + are then developed. Their development is supposed to depend on their + union with other partially developed cells or gemmules which precede them + in the regular course of growth. Why I use the term union, will be seen + when we discuss the direct action of pollen on the tissues of the + mother-plant. Gemmules are supposed to be thrown off by every cell or + unit, not only during the adult state, but during all the stages of + development. Lastly, I assume that the gemmules in their dormant state + have a mutual affinity for each other, leading to their aggregation + either into buds or into the sexual elements. Hence, speaking strictly, + it is not the reproductive elements, nor the buds, which generate new + organisms, but the cells themselves throughout the body. These + assumptions constitute the provisional hypothesis which I have called + Pangenesis. Nearly <!-- Page 375 --><span class="pagenum"><a + name="page375"></a>{375}</span>similar views have been propounded, as I + find, by other authors, more especially by Mr. Herbert Spencer;<a + name="NtA_902" href="#Nt_902"><sup>[902]</sup></a> but they are here + modified and amplified.</p> + +<p><!-- Page 376 --><span class="pagenum"><a name="page376"></a>{376}</span></p> + + <p>Before proceeding to show, firstly, how far these assumptions are in + themselves probable, and secondly, how far they connect and explain the + various groups of facts with which we are concerned, it may be useful to + give an illustration of the hypothesis. If one of the simplest Protozoa + be formed, as appears under the microscope, of a small mass of + homogeneous gelatinous matter, a minute atom thrown off from any part and + nourished under favourable circumstances would naturally reproduce the + whole; but if the upper and lower surfaces were to differ in texture from + the central portion, then all three parts would have to throw off atoms + or gemmules, which when aggregated by mutual affinity would form either + buds or the sexual elements. Precisely the same view may be extended to + one of the higher animals; although in this case many thousand gemmules + must be thrown off from the various parts of the body. Now, when the leg, + for instance, of a salamander is cut off, a slight crust forms over the + wound, and beneath this crust the uninjured cells or units of bone, + muscle, nerves, &c., are supposed to unite with the diffused gemmules + of those cells which in the perfect leg come next in order; and these as + they become slightly developed unite with others, and so on until a + papilla of soft cellular tissue, the "budding leg," is formed, and in + time a perfect leg.<a name="NtA_903" href="#Nt_903"><sup>[903]</sup></a> + Thus, that portion of the leg which had <!-- Page 377 --><span + class="pagenum"><a name="page377"></a>{377}</span>been cut off, neither + more nor less, would be reproduced. If the tail or leg of a young animal + had been cut off, a young tail or leg would have been reproduced, as + actually occurs with the amputated tail of the tadpole; for gemmules of + all the units which compose the tail are diffused throughout the body at + all ages. But during the adult state the gemmules of the larval tail + would remain dormant, for they would not meet with pre-existing cells in + a proper state of development with which to unite. If from changed + conditions or any other cause any part of the body should become + permanently modified, the gemmules, which are merely minute portions of + the contents of the cells forming the part, would naturally reproduce the + same modification. But gemmules previously derived from the same part + before it had undergone any change, would still be diffused throughout + the organisation, and would be transmitted from generation to generation, + so that under favourable circumstances they might be redeveloped, and + then the new modification would be for a time or for ever lost. The + aggregation of gemmules derived from every part of the body, through + their mutual affinity, would form buds, and their aggregation in some + special manner, apparently in small quantity, together probably with the + presence of gemmules of certain primordial cells, would constitute the + sexual elements. By means of these illustrations the hypothesis of + pangenesis has, I hope, been rendered intelligible.</p> + +<hr class="short" /> + + <p>Physiologists maintain, as we have seen, that each cell, though to a + large extent dependent on others, is likewise, to a certain extent, + independent or autonomous. I go one small step further, and assume that + each cell casts off a free gemmule, which is capable of reproducing a + similar cell. There is some analogy between this view and what we see in + compound animals and in the flower-buds on the same tree; for these are + distinct individuals capable of true or seminal reproduction, yet have + parts in common and are dependent on each other; thus <!-- Page 378 + --><span class="pagenum"><a name="page378"></a>{378}</span>the tree has + its bark and trunk, and certain corals, as the Virgularia, have not only + parts, but movements in common.</p> + + <p>The existence of free gemmules is a gratuitous assumption, yet can + hardly be considered as very improbable, seeing that cells have the power + of multiplication through the self-division of their contents. Gemmules + differ from true ovules or buds inasmuch as they are supposed to be + capable of multiplication in their undeveloped state. No one probably + will object to this capacity as improbable. The blastema within the egg + has been known to divide and give birth to two embryos; and Thuret<a + name="NtA_904" href="#Nt_904"><sup>[904]</sup></a> has seen the zoospore + of an alga divide itself, and both halves germinate. An atom of small-pox + matter, so minute as to be borne by the wind, must multiply itself many + thousand-fold in a person thus inoculated.<a name="NtA_905" + href="#Nt_905"><sup>[905]</sup></a> It has recently been ascertained<a + name="NtA_906" href="#Nt_906"><sup>[906]</sup></a> that a minute portion + of the mucous discharge from an animal affected with rinderpest, if + placed in the blood of a healthy ox, increases so fast that in a short + space of time "the whole mass of blood, weighing many pounds, is + infected, and every small particle of that blood contains enough poison + to give, within less than forty-eight hours, the disease to another + animal."</p> + + <p>The retention of free and undeveloped gemmules in the same body from + early youth to old age may appear improbable, but we should remember how + long seeds lie dormant in the earth and buds in the bark of a tree. Their + transmission from generation to generation may appear still more + improbable; but here again we should remember that many rudimentary and + useless organs are transmitted and have been transmitted during an + indefinite number of generations. We shall presently see how well the + long-continued transmission of undeveloped gemmules explains many + facts.</p> + + <p>As each unit, or group of similar units throughout the body, casts off + its gemmules, and as all are contained within the smallest egg or seed, + and within each spermatozoon or pollen-grain, their number and minuteness + must be something <!-- Page 379 --><span class="pagenum"><a + name="page379"></a>{379}</span>inconceivable. I shall hereafter recur to + this objection, which at first appears so formidable; but it may here be + remarked that a cod-fish has been found to produce 4,872,000 eggs, a + single Ascaris about 64,000,000 eggs, and a single Orchidaceous plant + probably as many million seeds.<a name="NtA_907" + href="#Nt_907"><sup>[907]</sup></a> In these several cases, the + spermatozoa and pollen-grains must exist in considerably larger numbers. + Now, when we have to deal with numbers such as these, which the human + intellect cannot grasp, there is no good reason for rejecting our present + hypothesis on account of the assumed existence of cell-gemmules a few + thousand times more numerous.</p> + + <p>The gemmules in each organism must be thoroughly diffused; nor does + this seem improbable considering their minuteness, and the steady + circulation of fluids throughout the body. So it must be with the + gemmules of plants, for with certain kinds even a minute fragment of a + leaf will reproduce the whole. But a difficulty here occurs; it would + appear that with plants, and probably with compound animals, such as + corals, the gemmules do not spread from bud to bud, but only through the + tissues developed from each separate bud. We are led to this conclusion + from the stock being rarely affected by the insertion of a bud or graft + from a distinct variety. This non-diffusion of the gemmules is still more + plainly shown in the case of ferns; for Mr. Bridgman<a name="NtA_908" + href="#Nt_908"><sup>[908]</sup></a> has proved that, when spores (which + it should be remembered are of the nature of buds) are taken from a + monstrous part of a frond, and others from an ordinary part, <!-- Page + 380 --><span class="pagenum"><a name="page380"></a>{380}</span>each + reproduces the form of the part whence derived. But this non-diffusion of + the gemmules from bud to bud may be only apparent, depending, as we shall + hereafter see, on the nature of the first-formed cells in the buds.</p> + + <p>The assumed elective affinity of each gemmule for that particular cell + which precedes it in the order of development is supported by many + analogies. In all ordinary cases of sexual reproduction the male and + female elements have a mutual affinity for each other: thus, it is + believed that about ten thousand species of Compositæ exist, and there + can be no doubt that if the pollen of all these species could be, + simultaneously or successively, placed on the stigma of any one species, + this one would elect with unerring certainty its own pollen. This + elective capacity is all the more wonderful, as it must have been + acquired since the many species of this great group of plants branched + off from a common progenitor. On any view of the nature of sexual + reproduction, the protoplasm contained within the ovules and within the + sperm-cells (or the "spermatic force" of the latter, if so vague a term + be preferred) must act on each other by some law of special affinity, + either during or subsequently to impregnation, so that corresponding + parts alone affect each other; thus, a calf produced from a short-horned + cow by a long-horned bull has its horns and not its horny hoofs affected + by the union of the two forms, and the offspring from two birds with + differently coloured tails have their tails and not their whole plumage + affected.</p> + + <p>The various tissues of the body plainly show, as many physiologists + have insisted,<a name="NtA_909" href="#Nt_909"><sup>[909]</sup></a> an + affinity for special organic substances, whether natural or foreign to + the body. We see this in the cells of the kidneys attracting urea from + the blood; in the worrara poison affecting the nerves; upas and digitalis + the muscles; the Lytta vesicatoria the kidneys; and in the poisonous + matter of many diseases, as small-pox, scarlet-fever, hooping-cough, + glanders, cancer, and hydrophobia, affecting certain definite parts of + the body or certain tissues or glands.</p> + + <p>The affinity of various parts of the body for each other during <!-- + Page 381 --><span class="pagenum"><a name="page381"></a>{381}</span>their + early development was shown in the last chapter, when discussing the + tendency to fusion in homologous parts. This affinity displays itself in + the normal fusion of organs which are separate at an early embryonic age, + and still more plainly in those marvellous cases of double monsters in + which each bone, muscle, vessel, and nerve in the one embryo, blends with + the corresponding part in the other. The affinity between homologous + organs may come into action with single parts, or with the entire + individual, as in the case of flowers or fruits which are symmetrically + blended together with all their parts doubled, but without any other + trace of fusion.</p> + + <p>It has also been assumed that the development of each gemmule depends + on its union with another cell or unit which has just commenced its + development, and which, from preceding it in order of growth, is of a + somewhat different nature. Nor is it a very improbable assumption that + the development of a gemmule is determined by its union with a cell + slightly different in nature, for abundant evidence was given in the + seventeenth chapter, showing that a slight degree of differentiation in + the male and female sexual elements favours in a marked manner their + union and subsequent development. But what determines the development of + the gemmules of the first-formed or primordial cell in the unimpregnated + ovule, is beyond conjecture.</p> + + <p>It must also be admitted that analogy fails to guide us towards any + determination on several other points: for instance, whether cells, + derived from the same parent-cell, may, in the regular course of growth, + become developed into different structures, from absorbing peculiar kinds + of nutriment, independently of their union with distinct gemmules. We + shall appreciate this difficulty if we call to mind, what complex yet + symmetrical growths the cells of plants yield when they are inoculated by + the poison of a gall-insect. With animals various polypoid excrescences + and tumours are now generally admitted<a name="NtA_910" + href="#Nt_910"><sup>[910]</sup></a> to be the direct product, through + proliferation, of normal cells which have become abnormal. In the regular + growth and repair of bones, the tissues undergo, as Virchow remarks,<a + name="NtA_911" href="#Nt_911"><sup>[911]</sup></a> a whole series of + permutations and substitutions. "The cartilage-cells may be <!-- Page 382 + --><span class="pagenum"><a name="page382"></a>{382}</span>converted by a + direct transformation into marrow-cells, and continue as such; or they + may first be converted into osseous and then into medullary tissue; or + lastly, they may first be converted into marrow and then into bone. So + variable are the permutations of these tissues, in themselves so nearly + allied, and yet in their external appearance so completely distinct." But + as these tissues thus change their nature at any age, without any obvious + change in their nutrition, we must suppose in accordance with our + hypothesis that gemmules derived from one kind of tissue combine with the + cells of another kind, and cause the successive modifications.</p> + + <p>It is useless to speculate at what period of development each organic + unit casts off its gemmules; for the whole subject of the development of + the various elemental tissues is as yet involved in much doubt. Some + physiologists, for instance, maintain that muscle or nerve-fibres are + developed from cells, which are afterwards nourished by their own proper + powers of absorption; whilst other physiologists deny their cellular + origin; and Beale maintains that such fibres are renovated exclusively by + the conversion of fresh germinal matter (that is the so-called nuclei) + into "formed material." However this may be, it appears probable that all + external agencies, such as changed nutrition, increased use or disuse, + &c., which induced any permanent modification in a structure, would + at the same time or previously act on the cells, nuclei, germinal or + formative matter, from which the structures in question were developed, + and consequently would act on the gemmules or cast-off atoms.</p> + + <p>There is another point on which it is useless to speculate, namely, + whether all gemmules are free and separate, or whether some are from the + first united into small aggregates. A feather, for instance, is a complex + structure, and, as each separate part is liable to inherited variations, + I conclude that each feather certainly generates a large number of + gemmules; but it is possible that these may be aggregated into a compound + gemmule. The same remark applies to the petals of a flower, which in some + cases are highly complex, with each ridge and hollow contrived for + special purposes, so that each part must have been separately modified, + and the modifications transmitted; consequently, separate gemmules, + according to our hypothesis, <!-- Page 383 --><span class="pagenum"><a + name="page383"></a>{383}</span>must have been thrown off from each cell + or part. But, as we sometimes see half an anther or a small portion of a + filament becoming petaliform, or parts or mere stripes of the calyx + assuming the colour and texture of the corolla, it is probable that with + petals the gemmules of each cell are not aggregated together into a + compound gemmule, but are freely and separately diffused.</p> + +<hr class="short" /> + + <p>Having now endeavoured to show that the several foregoing assumptions + are to a certain extent supported by analogous facts, and having + discussed some of the most doubtful points, we will consider how far the + hypothesis brings under a single point of view the various cases + enumerated in the First Part. All the forms of reproduction graduate into + each other and agree in their product; for it is impossible to + distinguish between organisms produced from buds, from self-division, or + from fertilised germs; such organisms are liable to variations of the + same nature and to reversion of character; and as we now see that all the + forms of reproduction depend on the aggregation of gemmules derived from + the whole body, we can understand this general agreement. It is + satisfactory to find that sexual and asexual generation, by both of which + widely different processes the same living creature is habitually + produced, are fundamentally the same. Parthenogenesis is no longer + wonderful; in fact, the wonder is that it should not oftener occur. We + see that the reproductive organs do not actually create the sexual + elements; they merely determine or permit the aggregation of the gemmules + in a special manner. These organs, together with their accessory parts, + have, however, high functions to perform; they give to both elements a + special affinity for each other, independently of the contents of the + male and female cells, as is shown in the case of plants by the mutual + reaction of the stigma and pollen-grains; they adapt one or both elements + for independent temporary existence, and for mutual union. The + contrivances for these purposes are sometimes wonderfully complex, as + with the spermatophores of the Cephalopoda. The male element sometimes + possesses attributes which, if observed in an independent animal, would + be put down to instinct guided by sense-organs, as when the <!-- Page 384 + --><span class="pagenum"><a name="page384"></a>{384}</span>spermatozoon + of an insect finds its way into the minute micropyle of the egg, or as + when the antherozoids of certain algæ swim by the aid of their ciliæ to + the female plant, and force themselves <span class="correction" + title="Originally printed on following line, after `must'.">into</span> a + minute orifice. In these latter cases, however, we must believe that the + male element has acquired its powers, on the same principle with the + larvæ of animals, namely by successive modifications developed at + corresponding periods of life: we can hardly avoid in these cases looking + at the male element as a sort of premature larva, which unites, or, like + one of the lower algæ, conjugates, with the female element. What + determines the aggregation of the gemmules within the sexual organs we do + not in the least know; nor do we know why buds are formed in certain + definite places, leading to the symmetrical growth of trees and corals, + nor why adventitious buds may be formed almost anywhere, even on a petal, + and frequently upon healed wounds.<a name="NtA_912" + href="#Nt_912"><sup>[912]</sup></a> As soon as the gemmules have + aggregated themselves, development apparently commences, but in the case + of buds is often afterwards suspended, and in the case of the sexual + elements soon ceases, unless the elements of the opposite sexes combine; + even after this has occurred, the fertilised germ, as with seeds buried + in the ground, may remain during a lengthened period in a dormant + state.</p> + + <p>The antagonism which has long been observed,<a name="NtA_913" + href="#Nt_913"><sup>[913]</sup></a> though exceptions occur,<a + name="NtA_914" href="#Nt_914"><sup>[914]</sup></a> between active growth + and the power of sexual reproduction—between the repair of injuries + and gemmation—and with plants, between rapid increase by buds, + rhizomes, &c., and the production of seed, is partly explained by the + gemmules not existing in sufficient numbers for both processes. <!-- Page + 385 --><span class="pagenum"><a name="page385"></a>{385}</span>But this + explanation hardly applies to those plants which naturally produce a + multitude of seeds, but which, through a comparatively small increase in + the number of the buds on their rhizomes or offsets, yield few or no + seed. As, however, we shall presently see that buds probably include + tissue which has already been to a certain extent developed or + differentiated, some additional organised matter will thus have been + expended.</p> + + <p>From one of the forms of Reproduction, namely, spontaneous + self-division, we are led by insensible steps to the repair of the + slightest injury; and the existence of gemmules, derived from every cell + or unit throughout the body and everywhere diffused, explains all such + cases,—even the wonderful fact that, when the limbs of the + salamander were cut off many times successively by Spallanzani and + Bonnet, they were exactly and completely reproduced. I have heard this + process compared with the recrystallisation which occurs when the angles + of a broken crystal are repaired; and the two processes have this much in + common, that in the one case the polarity of the molecules is the + efficient cause, and in the other the affinity of the gemmules for + particular nascent cells.</p> + + <p>Pangenesis does not throw much light on Hybridism, but agrees well + with most of the ascertained facts. We may conclude from the fact of a + single spermatozoon or pollen-grain being insufficient for impregnation, + that a certain number of gemmules derived from each cell or unit are + required for the development of each part. From the occurrence of + parthenogenesis, more especially in the case of the silk-moth, in which + the embryo is often partially formed, we may also infer that the female + element includes nearly sufficient gemmules of all kinds for independent + development, so that when united with the male element the gemmules must + be superabundant. Now, as a general rule, when two species or races are + crossed reciprocally, the offspring do not differ, and this shows that + both sexual elements agree in power, in accordance with the view that + they include the same gemmules. Hybrids and mongrels are generally + intermediate in character between the two parent-forms, yet occasionally + they closely resemble one parent in one part and the other parent in + another part, or even in their whole structure: nor is this difficult to + understand on <!-- Page 386 --><span class="pagenum"><a + name="page386"></a>{386}</span>the admission that the gemmules in the + fertilised germ are superabundant in number, and that those derived from + one parent have some advantage in number, affinity, or vigour over those + derived from the other parent. Crossed forms sometimes exhibit the colour + or other characters of either parent in stripes or blotches; and this may + occur in the first generation, or through reversion in succeeding bud and + seminal generations, as in the several instances given in the eleventh + chapter. In these cases we must follow Naudin,<a name="NtA_915" + href="#Nt_915"><sup>[915]</sup></a> and admit that the "essence" or + "element" of the two species, which terms I should translate into the + gemmules, have an affinity for their own kind, and thus separate + themselves into distinct stripes or blotches; and reasons were given, + when discussing in the fifteenth chapter the incompatibility of certain + characters to unite, for believing in such mutual affinity. When two + forms are crossed, one is not rarely found to be prepotent in the + transmission of character over the other; and this we can explain only by + again assuming that the one form has some advantage in the number, + vigour, or affinity of its gemmules, except in those cases, where certain + characters are present in the one form and latent in the other. For + instance, there is a latent tendency in all pigeons to become blue, and, + when a blue pigeon is crossed with one of any other colour, the blue tint + is generally prepotent. When we consider latent characters, the + explanation of this form of prepotency will be obvious.</p> + + <p>When one species is crossed with another it is notorious that they do + not yield the full or proper number of offspring; and we can only say on + this head that, as the development of each organism depends on such + nicely-balanced affinities between a host of gemmules and developing + cells or units, we need not feel at all surprised that the commixture of + gemmules derived from two distinct species should lead to a partial or + complete failure of development. With respect to the sterility of hybrids + produced from the union of two distinct species, it was shown in the + nineteenth chapter that this depends exclusively on the reproductive + organs being specially affected; but why these organs should be thus + affected we do not know, any more than <!-- Page 387 --><span + class="pagenum"><a name="page387"></a>{387}</span>why unnatural + conditions of life, though compatible with health, should cause + sterility; or why continued close interbreeding, or the illegitimate + unions of dimorphic and trimorphic plants, induce the same result. The + conclusion that the reproductive organs alone are affected, and not the + whole organisation, agrees perfectly with the unimpaired or even + increased capacity in hybrid plants for propagation by buds; for this + implies, according to our hypothesis, that the cells of the hybrids throw + off hybridised cell-gemmules, which become aggregated into buds, but fail + to become aggregated within the reproductive organs, so as to form the + sexual elements. In a similar manner many plants, when placed under + unnatural conditions, fail to produce seed, but can readily be propagated + by buds. We shall presently see that pangenesis agrees well with the + strong tendency to reversion exhibited by all crossed animals and + plants.</p> + + <p>It was shown in the discussion on graft-hybrids that there is some + reason to believe that portions of cellular tissue taken from distinct + plants become so intimately united, as afterwards occasionally to produce + crossed or hybridised buds. If this fact were fully established, it + would, by the aid of our hypothesis, connect gemmation and sexual + reproduction in the closest manner.</p> + + <p>Abundant evidence has been advanced proving that pollen taken from one + species or variety and applied to the stigma of another sometimes + directly affects the tissues of the mother-plant. It is probable that + this occurs with many plants during fertilisation, but can only be + detected when distinct forms are crossed. On any ordinary theory of + reproduction this is a most anomalous circumstance, for the pollen-grains + are manifestly adapted to act on the ovule, but in these cases they act + on the colour, texture, and form of the coats of the seeds, on the + ovarium itself, which is a modified leaf, and even on the calyx and upper + part of the flower-peduncle. In accordance with the hypothesis of + pangenesis pollen includes gemmules, derived from every part of the + organisation, which diffuse themselves and multiply by self-division; + hence it is not surprising that gemmules within the pollen, which are + derived from the parts near the reproductive organs, should sometimes be + able to affect the same parts, whilst still undergoing development, in + the mother-plant. <!-- Page 388 --><span class="pagenum"><a + name="page388"></a>{388}</span></p> + + <p>As, during all the stages of development, the tissues of plants + consist of cells, and as new cells are not known to be formed between, or + independently of, pre-existing cells, we must conclude that the gemmules + derived from the foreign pollen do not become developed merely in contact + with pre-existing cells, but actually penetrate the nascent cells of the + mother-plant. This process may be compared with the ordinary act of + fertilisation, during which the contents of the pollen-tubes penetrate + the closed embryonic sack within the ovule, and determine the development + of the embryo. According to this view, the cells of the mother-plant may + almost literally be said to be fertilised by the gemmules derived from + the foreign pollen. With all organisms, as we shall presently see, the + cells or organic units of the embryo during the successive stages of + development may in like manner be said to be fertilised by the gemmules + of the cells, which come next in the order of formation.</p> + + <p>Animals, when capable of sexual reproduction, are fully developed, and + it is scarcely possible that the male element should affect the tissues + of the mother in the same direct manner as with plants; nevertheless it + is certain that her ovaria are sometimes affected by a previous + impregnation, so that the ovules subsequently fertilised by a distinct + male are plainly influenced in character; and this, as in the case of + foreign pollen, is intelligible through the diffusion, retention, and + action of the gemmules included within the spermatozoa of the previous + male.</p> + + <p>Each organism reaches maturity through a longer or shorter course of + development. The changes may be small and insensibly slow, as when a + child grows into a man, or many, abrupt, and slight, as in the + metamorphoses of certain ephemerous insects, or again few and strongly + marked, as with most other insects. Each part may be moulded within a + previously existing and corresponding part, and in this case it will + appear, falsely as I believe, to be formed from the old part; or it may + be developed within a wholly distinct part of the body, as in the extreme + cases of metagenesis. An eye, for instance, may be developed at a spot + where no eye previously existed. We have also seen that allied organic + beings in the course of their metamorphoses sometimes attain nearly the + same structure after passing <!-- Page 389 --><span class="pagenum"><a + name="page389"></a>{389}</span>through widely different forms; or + conversely, after passing through nearly the same early forms, arrive at + a widely different termination. In these cases it is very difficult to + believe that the early cells or units possess the inherent power, + independently of any external agent, of producing new structures wholly + different in form, position, and function. But these cases become plain + on the hypothesis of pangenesis. The organic units, during each stage of + development, throw off gemmules, which, multiplying, are transmitted to + the offspring. In the offspring, as soon as any particular cell or unit + in the proper order of development becomes partially developed, it unites + with (or to speak metaphorically is fertilised by) the gemmule of the + next succeeding cell, and so onwards. Now, supposing that at any stage of + development, certain cells or aggregates of cells had been slightly + modified by the action of some disturbing cause, the cast-off gemmules or + atoms of the cell-contents could hardly fail to be similarly affected, + and consequently would reproduce the same modification. This process + might be repeated until the structure of the part at this particular + stage of development became greatly changed, but this would not + necessarily affect other parts whether previously or subsequently + developed. In this manner we can understand the remarkable independence + of structure in the successive metamorphoses, and especially in the + successive metageneses of many animals.</p> + + <p>The term growth ought strictly to be confined to mere increase of + size, and development to change of structure.<a name="NtA_916" + href="#Nt_916"><sup>[916]</sup></a> Now, a child is said to grow into a + man, and a foal into a horse, but, as in these cases there is much change + of structure, the process properly belongs to the order of development. + We have indirect evidence of this in many variations and diseases + supervening during so-called growth at a particular period, and being + inherited at a corresponding period. In the case, however, of diseases + which supervene during old age, subsequently to the ordinary period of + procreation, and which nevertheless are sometimes inherited, as occurs + with brain and heart complaints, we <!-- Page 390 --><span + class="pagenum"><a name="page390"></a>{390}</span>must suppose that the + organs were in fact affected at an earlier age and threw off at this + period affected gemmules; but that the affection became visible or + injurious only after the prolonged growth of the part in the strict sense + of the word. In all the changes of structure which regularly supervene + during old age, we see the effects of deteriorated growth, and not of + true development.</p> + + <p>In the so-called process of <i>alternate generation</i> many + individuals are generated asexually during very early or later stages of + development. These individuals may closely resemble the preceding larval + form, but generally are wonderfully dissimilar. To understand this + process we must suppose that at a certain stage of development the + gemmules are multiplied at an unusual rate, and become aggregated by + mutual affinity at many centres of attraction, or buds. These buds, it + may be remarked, must include gemmules not only of all the succeeding but + likewise of all the preceding stages of development; for when mature they + have the power of transmitting by sexual generation gemmules of all the + stages, however numerous these may be. It was shown in the First Part, at + least in regard to animals, that the new beings which are thus at any + period asexually generated do not retrograde in development—that + is, they do not pass through those earlier stages, through which the + fertilised germ of the same animal has to pass; and an explanation of + this fact was attempted as far as the final or teleological cause is + concerned. We can likewise understand the proximate cause, if we assume, + and the assumption is far from improbable, that buds, like chopped-up + fragments of a hydra, are formed of tissue which has already passed + through several of the earlier stages of development; for in this case + their component cells or units would not unite with the gemmules derived + from the earlier-formed cells, but only with those which came next in the + order of development. On the other hand, we must believe that, in the + sexual elements, or probably in the female alone, gemmules of certain + primordial cells are present; and these, as soon as their development + commences, unite in due succession with the gemmules of every part of the + body, from the first to the last period of life.</p> + + <p>The principle of the independent formation of each part, in <!-- Page + 391 --><span class="pagenum"><a name="page391"></a>{391}</span>so far as + its development depends on the union of the proper gemmules with certain + nascent cells, together with the superabundance of the gemmules derived + from both parents and self-multiplied, throws light on a widely different + group of facts, which on any ordinary view of development appears very + strange. I allude to organs which are abnormally multiplied or + transposed. Thus gold-fish often have supernumerary fins placed on + various parts of their bodies. We have seen that, when the tail of a + lizard is broken off, a double tail is sometimes reproduced, and when the + foot of the salamander is divided longitudinally, additional digits are + occasionally formed. When frogs, toads, &c., are born with their + limbs doubled, as sometimes occurs, the doubling, as Gervais remarks,<a + name="NtA_917" href="#Nt_917"><sup>[917]</sup></a> cannot be due to the + complete fusion of two embryos, with the exception of the limbs, for the + larvæ are limbless. The same argument is applicable<a name="NtA_918" + href="#Nt_918"><sup>[918]</sup></a> to certain insects produced with + multiple legs or antennæ, for these are metamorphosed from apodal or + antennæless larvæ. Alphonse Milne-Edwards<a name="NtA_919" + href="#Nt_919"><sup>[919]</sup></a> has described the curious case of a + crustacean in which one eye-peduncle supported, instead of a complete + eye, only an imperfect cornea, out of the centre of which a portion of an + antenna was developed. A case has been recorded<a name="NtA_920" + href="#Nt_920"><sup>[920]</sup></a> of a man who had during both + dentitions a double tooth in place of the left second incisor, and he + inherited this peculiarity from his paternal grandfather. Several cases + are known<a name="NtA_921" href="#Nt_921"><sup>[921]</sup></a> of + additional teeth having been developed in the palate, more especially + with horses, and in the orbit of the eye. Certain breeds of sheep bear a + whole crowd of horns on their foreheads. Hairs occasionally appear in + strange situations, as within the ears of the Siamese hairy family; and + hairs "quite natural in structure" have been observed "within the + substance of the brain."<a name="NtA_922" + href="#Nt_922"><sup>[922]</sup></a> As many as five spurs have been seen + on both legs in certain Game-fowls. In the Polish fowl the male is + ornamented with a topknot of hackles <!-- Page 392 --><span + class="pagenum"><a name="page392"></a>{392}</span>like those on his neck, + whilst the female has one of common feathers. In feather-footed pigeons + and fowls, feathers like those on the wing arise from the outer side of + the legs and toes. Even the elemental parts of the same feather may be + transposed; for in the Sebastopol goose, barbules are developed on the + divided filaments of the shaft.</p> + + <p>Analogous cases are of such frequent occurrence with plants that they + do not strike us with sufficient surprise. Supernumerary petals, stamens, + and pistils, are often produced. I have seen a leaflet low down in the + compound leaf of <i>Vicia sativa</i> converted into a tendril, and a + tendril possesses many peculiar properties, such as spontaneous movement + and irritability. The calyx sometimes assumes, either wholly or by + stripes, the colour and texture of the corolla. Stamens are so frequently + converted, more or less completely, into petals, that such cases are + passed over as not deserving notice; but as petals have special functions + to perform, namely, to protect the included organs, to attract insects, + and in not a few cases to guide their entrance by well-adapted + contrivances, we can hardly account for the conversion of stamens into + petals merely by unnatural or superfluous nourishment. Again, the edge of + a petal may occasionally be found including one of the highest products + of the plant, namely the pollen; for instance, I have seen in an Ophrys a + pollen-mass with its curious structure of little packets, united together + and to the caudicle by elastic threads, formed between the edges of an + upper petal. The segments of the calyx of the common pea have been + observed partially converted into carpels, including ovules, and with + their tips converted into stigmas. Numerous analogous facts could be + given.<a name="NtA_923" href="#Nt_923"><sup>[923]</sup></a></p> + + <p>I do not know how physiologists look at such facts as the foregoing. + According to the doctrine of pangenesis, the free and superabundant + gemmules of the transposed organs are developed in the wrong place, from + uniting with wrong cells or aggregates of cells during their nascent + state; and this would follow from a slight modification in the elective + affinity of such cells, or possibly of certain gemmules. Nor ought we to + feel much surprise at the affinities of cells and gemmules varying <!-- + Page 393 --><span class="pagenum"><a name="page393"></a>{393}</span>under + domestication, when we remember the many curious cases given, in the + seventeenth chapter, of cultivated plants which absolutely refuse to be + fertilised by their own pollen or by that of the same species, but are + abundantly fertile with pollen of a distinct species; for this implies + that their sexual elective affinities—and this is the term used by + Gärtner—have been modified. As the cells of adjoining or homologous + parts will have nearly the same nature, they will be liable to acquire by + variation each other's elective affinities; and we can thus to a certain + extent understand such cases as a crowd of horns on the heads in certain + sheep, of several spurs on the leg, and of hackles on the head of the + fowl, and with the pigeon the occurrence of wing-feathers on their legs + and of membrane between their toes; for the leg is the homologue of the + wing. As all the organs of plants are homologous and spring from a common + axis, it is natural that they should be eminently liable to + transposition. It ought to be observed that when any compound part, such + as an additional limb or an antenna, springs from a false position, it is + only necessary that the few first gemmules should be wrongly attached; + for these whilst developing would attract others in due succession, as in + the regrowth of an amputated limb. When parts which are homologous and + similar in structure, as the vertebræ in snakes or the stamens in + polyandrous flowers, &c., are repeated many times in the same + organism, closely allied gemmules must be extremely numerous, as well as + the points to which they ought to become united; and, in accordance with + the foregoing views, we can to a certain extent understand Isid. Geoffroy + St. Hilaire's law, namely, that parts, which are already multiple, are + extremely liable to vary in number.</p> + + <p>The same general principles apply to the fusion of homologous parts; + and with respect to mere cohesion there is probably always some degree of + fusion, at least near the surface. When two embryos during their early + development come into close contact, as both include corresponding + gemmules, which must be in all respects almost identical in nature, it is + not surprising that some derived from one embryo and some from the other + should unite at the point of contact with a single nascent cell or + aggregate of cells, and thus give rise to a single part or organ. For + instance, two embryos might thus come to have on their <!-- Page 394 + --><span class="pagenum"><a name="page394"></a>{394}</span>adjoining + sides a single symmetrical arm, which in one sense will have been formed + by the fusion of the bones, muscles, &c., belonging to the arms of + both embryos. In the case of the fish described by Lereboullet, in which + a double head was seen gradually to fuse into a single one, the same + process must have taken place, together with the absorption of all the + parts which had been already formed. These cases are exactly the reverse + of those in which a part is doubled either spontaneously or after an + injury; for in the case of doubling, the superabundant gemmules of the + same part are separately developed in union with adjoining points; whilst + in the case of fusion the gemmules derived from two homologous parts + become mingled and form a single part; or it may be that the gemmules + from one of two adjoining embryos alone become developed.</p> + +<hr class="short" /> + + <p>Variability often depends, as I have attempted to show, on the + reproductive organs being injuriously affected by changed conditions; and + in this case the gemmules derived from the various parts of the body are + probably aggregated in an irregular manner, some superfluous and others + deficient. Whether a superabundance of gemmules, together with fusion + during development, would lead to the increased size of any part cannot + be told; but we can see that their partial deficiency, without + necessarily leading to the entire abortion of the part, might cause + considerable modifications; for in the same manner as a plant, if its own + pollen be excluded, is easily hybridised, so, in the case of a cell, if + the properly succeeding gemmules were absent, it would probably combine + easily with other and allied gemmules. We see this in the case of + imperfect nails growing on the stumps of amputated fingers,<a + name="NtA_924" href="#Nt_924"><sup>[924]</sup></a> for the gemmules of + the nails have manifestly been developed at the nearest point.</p> + + <p>In variations caused by the direct action of changed conditions, + whether of a definite or indefinite nature, as with the fleeces of sheep + in hot countries, with maize grown in cold countries, with inherited + gout, &c., the tissues of the body, according to the doctrine of + pangenesis, are directly affected by the new conditions, and consequently + throw off modified gemmules, which are transmitted with their newly + acquired peculiarities to the offspring. On any ordinary view it is + unintelligible how changed <!-- Page 395 --><span class="pagenum"><a + name="page395"></a>{395}</span>conditions, whether acting on the embryo, + the young or adult animal, can cause inherited modifications. It is + equally or even more unintelligible on any ordinary view, how the effects + of the long-continued use or disuse of any part, or of changed habits of + body or mind, can be inherited. A more perplexing problem can hardly be + proposed; but on our view we have only to suppose that certain cells + become at last not only functionally but structurally modified; and that + these throw off similarly modified gemmules. This may occur at any period + of development, and the modification will be inherited at a corresponding + period; for the modified gemmules will unite in all ordinary cases with + the proper preceding cells, and they will consequently be developed at + the same period at which the modification first arose. With respect to + mental habits or instincts, we are so profoundly ignorant on the relation + between the brain and the power of thought that we do not know whether an + inveterate habit or trick induces any change in the nervous system; but + when any habit or other mental attribute, or insanity, is inherited, we + must believe that some actual modification is transmitted;<a + name="NtA_925" href="#Nt_925"><sup>[925]</sup></a> and this implies, + according to our hypothesis, that gemmules derived from modified + nerve-cells are transmitted to the offspring.</p> + + <p>It is generally, perhaps always, necessary that an organism should be + exposed during several generations to changed conditions or habits, in + order that any modification in the structure of the offspring should + ensue. This may be partly due to the changes not being at first marked + enough to catch the attention, but this explanation is insufficient; and + I can account for the fact, only by the assumption, which we shall see + under the head of reversion is strongly supported, that gemmules derived + from each cell before it had undergone the least modification are + transmitted in large numbers to successive generations, but that the + gemmules derived from the same cells after modification, naturally go on + increasing under the same favouring conditions, until at last they become + sufficiently numerous to overpower and supplant the old gemmules.</p> + + <p>Another difficulty may be here noticed; we have seen that <!-- Page + 396 --><span class="pagenum"><a name="page396"></a>{396}</span>there is + an important difference in the frequency, though not in the nature, of + the variations in plants propagated by sexual and asexual generation. As + far as variability depends on the imperfect action of the reproductive + organs under changed conditions, we can at once see why seedlings should + be far more variable than plants propagated by buds. We know that + extremely slight causes,—for instance, whether a tree has been + grafted or grows on its own stock, the position of the seeds within the + capsule, and of the flowers on the spike,—sometimes suffice to + determine the variation of a plant, when raised from seed. Now, it is + probable, as explained when discussing alternate generation, that a bud + is formed of a portion of already differentiated tissue; consequently an + organism thus formed does not pass through the earlier phases of + development, and cannot be so freely exposed, at the age when its + structure would be most readily modified, to the various causes inducing + variability; but it is very doubtful whether this is a sufficient + explanation of the difficulty.</p> + + <p>With respect to the tendency to reversion, there is a similar + difference between plants propagated from buds and seed. Many varieties, + whether originally produced from seed or buds, can be securely propagated + by buds, but generally or invariably revert by seed. So, also, hybridised + plants can be multiplied to any extent by buds, but are continually + liable to reversion by seed,—that is, to the loss of their hybrid + or intermediate character. I can offer no satisfactory explanation of + this fact. Here is a still more perplexing case: certain plants with + variegated leaves, phloxes with striped flowers, barberries with seedless + fruit, can all be securely propagated by the buds on cuttings; but the + buds developed from the roots of these cuttings almost invariably lose + their character and revert to their former condition.</p> + + <p>Finally, we can see on the hypothesis of pangenesis that variability + depends on at least two distinct groups of causes. Firstly, on the + deficiency, superabundance, fusion, and transposition of gemmules, and on + the redevelopment of those which have long been dormant. In these cases + the gemmules themselves have undergone no modification; but the mutations + in the above respects will amply account for much fluctuating <!-- Page + 397 --><span class="pagenum"><a + name="page397"></a>{397}</span>variability. Secondly, in the cases in + which the organisation has been modified by changed conditions, the + increased use or disuse of parts, or any other cause, the gemmules cast + off from the modified units of the body will be themselves modified, and, + when sufficiently multiplied, will be developed into new and changed + structures.</p> + +<hr class="short" /> + + <p>Turning now to Inheritance: if we suppose a homogeneous gelatinous + protozoon to vary and assume a reddish colour, a minute separated atom we + aid naturally, as it grew to full size, retain the same colour; and we + should have the simplest form of inheritance.<a name="NtA_926" + href="#Nt_926"><sup>[926]</sup></a> Precisely the same view may be + extended to the infinitely numerous and diversified units of which the + whole body in one of the higher animals is composed; and the separated + atoms are our gemmules. We have already sufficiently discussed the + inheritance of the direct effects of changed conditions, and of increased + use or disuse of parts, and, by implication, the important principle of + inheritance at corresponding ages. These groups of facts are to a large + extent intelligible on the hypothesis of pangenesis, and on no other + hypothesis as yet advanced.</p> + + <p>A few words must be added on the complete abortion or suppression of + organs. When a part becomes diminished by disuse prolonged during many + generations, the principle of economy of growth, as previously explained, + will tend to reduce it still further; but this will not account for the + complete or almost complete obliteration of, for instance, a minute + papilla of cellular tissue representing a pistil, or of a microscopically + minute nodule of bone representing a tooth. In certain cases of + suppression not yet completed, in which a rudiment occasionally reappears + through reversion, diffused gemmules derived from this part must, + according to our view, still exist; hence we must suppose that the cells, + in union with which the rudiment was formerly developed, in these cases + fail in their affinity for such gemmules. But in the cases of complete + and final abortion the gemmules themselves no doubt have perished; nor is + this <!-- Page 398 --><span class="pagenum"><a + name="page398"></a>{398}</span>in any way improbable, for, though a vast + number of active and long-dormant gemmules are diffused and nourished in + each living creature, yet there must be some limit to their number; and + it appears natural that gemmules derived from an enfeebled and useless + rudiment would be more liable to perish than those derived from other + parts which are still in full functional activity.</p> + + <p>With respect to mutilations, it is certain that a part may be removed + or injured during many generations, and no inherited result follow; and + this is an apparent objection to the hypothesis which will occur to every + one. But, in the first place, a being can hardly be intentionally + mutilated during its early stages of growth whilst in the womb or egg; + and such mutilations, when naturally caused, would appear like congenital + deficiencies, which are occasionally inherited. In the second place, + according to our hypothesis, gemmules multiply by self-division and are + transmitted from generation to generation; so that during a long period + they would be present and ready to reproduce a part which was repeatedly + amputated. Nevertheless it appears, from the facts given in the twelfth + chapter, that in some rare cases mutilations have been inherited, but in + most of these the mutilated surface became diseased. In this case it may + be conjectured that the gemmules of the lost part were gradually all + attracted by the partially diseased surface, and thus perished. Although + this would occur in the injured individual alone, and therefore in only + one parent, yet this might suffice for the inheritance of a mutilation, + on the same principle that a hornless animal of either sex, when crossed + with a perfect animal of the opposite sex, often transmits its + deficiency.</p> + + <p>The last subject that need here be discussed, namely Reversion, rests + on the principle that transmission and development, though generally + acting in conjunction, are distinct powers; and the transmission of + gemmules and their subsequent development show us how the existence of + these two distinct powers is possible. We plainly see this distinction in + the many cases in which a grandfather transmits to his grandson, through + his daughter, characters which she does not, or cannot, possess. Why the + development of certain characters, not necessarily in any way connected + with the reproductive organs, should be confined to one sex + alone—that is, why certain cells in one sex <!-- Page 399 --><span + class="pagenum"><a name="page399"></a>{399}</span>should unite with and + cause the development of certain gemmules—we do not in the least + know; but it is the common attribute of most organic beings in which the + sexes are separate.</p> + + <p>The distinction between transmission and development is likewise seen + in all ordinary cases of Reversion; but before discussing this subject it + may be advisable to say a few words on those characters which I have + called latent, and which would not be classed under Reversion in its + usual sense. Most, or perhaps all, the secondary characters, which + appertain to one sex, lie dormant in the other sex; that is, gemmules + capable of development into the secondary male sexual characters are + included within the female; and conversely female characters in the male. + Why in the female, when her ovaria become diseased or fail to act, + certain masculine gemmules become developed, we do not clearly know, any + more than why when a young bull is castrated his horns continue growing + until they almost resemble those of a cow; or why, when a stag is + castrated, the gemmules derived from the antlers of his progenitors quite + fail to be developed. But in many cases, with variable organic beings, + the mutual affinities of the cells and gemmules become modified, so that + parts are transposed or multiplied; and it would appear that a slight + change in the constitution of an animal, in connection with the state of + the reproductive organs, leads to changed affinities in the tissues of + various parts of the body. Thus, when male animals first arrive at + puberty, and subsequently during each recurrent season, certain cells or + parts acquire an affinity for certain gemmules, which become developed + into the secondary masculine characters; but if the reproductive organs + be destroyed, or even temporarily disturbed by changed conditions, these + affinities are not excited. Nevertheless, the male, before he arrives at + puberty, and during the season when the species does not breed, must + include the proper gemmules in a latent state. The curious case formerly + given of a Hen which assumed the masculine characters, not of her own + breed but of a remote progenitor, illustrates the connexion between + latent sexual characters and ordinary reversion. With those animals and + plants which habitually produce several forms, as with certain + butterflies described by Mr. Wallace, in which three female forms and + <!-- Page 400 --><span class="pagenum"><a + name="page400"></a>{400}</span>the male exist, or as with the trimorphic + species of Lythrum and Oxalis, gemmules capable of reproducing several + widely-different forms must be latent in each individual.</p> + + <p>The same principle of the latency of certain characters, combined with + the transposition of organs, may be applied to those singular cases of + butterflies and other insects, in which exactly one half or one quarter + of the body resembles the male, and the other half or three quarters the + female; and when this occurs the opposite sides of the body, separated + from each other by a distinct line, sometimes differ in the most + conspicuous manner. Again, these same principles apply to the cases given + in the thirteenth chapter, in which the right and left sides of the body + differ to an extraordinary degree, as in the spiral winding of certain + shells, and as in the genus Verruca among cirripedes; for in these cases + it is known that either side indifferently may undergo the same + remarkable change of development.</p> + + <p>Reversion, in the ordinary sense of the word, comes into action so + incessantly, that it evidently forms an essential part of the general law + of inheritance. It occurs with beings, however propagated, whether by + buds or seminal generation, and sometimes may even be observed in the + same individual as it advances in age. The tendency to reversion is often + induced by a change of conditions, and in the plainest manner by the act + of crossing. Crossed forms are generally at first nearly intermediate in + character between their two parents; but in the next generation the + offspring generally revert to one or both of their grandparents, and + occasionally to more remote ancestors. How can we account for these + facts? Each organic unit in a hybrid must throw off, according to the + doctrine of pangenesis, an abundance of hybridised gemmules, for crossed + plants can be readily and largely propagated by buds; but by the same + hypothesis there will likewise be present dormant gemmules derived from + both pure parent-forms; and as these latter retain their normal + condition, they would, it is probable, be enabled to multiply largely + during the lifetime of each hybrid. Consequently the sexual elements of a + hybrid will include both pure and hybridised gemmules; and when two + hybrids pair, the combination of pure gemmules derived from the one + hybrid with the pure gemmules of the same parts derived from the other + would <!-- Page 401 --><span class="pagenum"><a + name="page401"></a>{401}</span>necessarily lead to complete reversion of + character; and it is, perhaps, not too bold a supposition that unmodified + and undeteriorated gemmules of the same nature would be especially apt to + combine. Pure gemmules in combination with hybridised gemmules would lead + to partial reversion. And lastly, hybridised gemmules derived from both + parent-hybrids would simply reproduce the original hybrid form.<a + name="NtA_927" href="#Nt_927"><sup>[927]</sup></a> All these cases and + degrees of reversion incessantly occur.</p> + + <p>It was shown in the fifteenth chapter that certain characters are + antagonistic to each other or do not readily blend together; hence, when + two animals with antagonistic characters are crossed, it might well + happen that a sufficiency of gemmules in the male alone for the + reproduction of his peculiar characters, and in the female alone for the + reproduction of her peculiar characters, would not be present; and in + this case dormant gemmules derived from some remote progenitor might + easily gain the ascendency, and cause the reappearance of long-lost + characters. For instance, when black and white pigeons, or black and + white fowls, are crossed,—colours which do not readily + blend,—blue plumage in the one case, evidently derived from the + rock-pigeon, and red plumage in the other case, derived from the wild + jungle-cock, occasionally reappear. With uncrossed breeds the same result + would follow, under conditions which favoured the multiplication and + development of certain dormant gemmules, as when animals become feral and + revert to their pristine character. A certain number of gemmules being + requisite for the development of each character, as is known to be the + case from several spermatozoa or pollen-grains being necessary for + fertilisation, and time favouring their multiplication, will together + account for the curious cases, insisted on by Mr. Sedgwick, of certain + diseases regularly appearing in alternate generations. This likewise + holds good, more or less strictly, with other weakly inherited + modifications. Hence, as I have heard it remarked, certain diseases + appear actually to gain strength by the intermission of a generation. The + transmission of dormant gemmules during many successive generations is + hardly in itself more improbable, as <!-- Page 402 --><span + class="pagenum"><a name="page402"></a>{402}</span>previously remarked, + than the retention during many ages of rudimentary organs, or even only + of a tendency to the production of a rudiment; but there is no reason to + suppose that all dormant gemmules would be transmitted and propagated for + ever. Excessively minute and numerous as they are believed to be, an + infinite number derived, during a long course of modification and + descent, from each cell of each progenitor, could not be supported or + nourished by the organism. On the other hand, it does not seem improbable + that certain gemmules, under favourable conditions, should be retained + and go on multiplying for a longer period than others. Finally, on the + views here given, we certainly gain some clear insight into the wonderful + fact that the child may depart from the type of both its parents, and + resemble its grandparents, or ancestors removed by many generations.</p> + +<p class="cenhead"><i>Conclusion.</i></p> + + <p>The hypothesis of Pangenesis, as applied to the several great classes + of facts just discussed, no doubt is extremely complex; but so assuredly + are the facts. The assumptions, however, on which the hypothesis rests + cannot be considered as complex in any extreme degree—namely, that + all organic units, besides having the power, as is generally admitted, of + growing by self-division, throw off free and minute atoms of their + contents, that is gemmules. These multiply and aggregate themselves into + buds and the sexual elements; their development depends on their union + with other nascent cells or units; and they are capable of transmission + in a dormant state to successive generations.</p> + + <p>In a highly organised and complex animal, the gemmules thrown off from + each different cell or unit throughout the body must be inconceivably + numerous and minute. Each unit of each part, as it changes during + development, and we know that some insects undergo at least twenty + metamorphoses, must throw off its gemmules. All organic beings, moreover, + include many dormant gemmules derived from their grandparents and more + remote progenitors, but not from all their progenitors. These almost + infinitely numerous and minute gemmules must be included in each bud, + ovule, spermatozoon, and pollen-grain. Such an admission will be declared + impossible; but, as previously <!-- Page 403 --><span class="pagenum"><a + name="page403"></a>{403}</span>remarked, number and size are only + relative difficulties, and the eggs or seeds produced by certain animals + or plants are so numerous that they cannot be grasped by the + intellect.</p> + + <p>The organic particles with which the wind is tainted over miles of + space by certain offensive animals must be infinitely minute and + numerous; yet they strongly affect the olfactory nerves. An analogy more + appropriate is afforded by the contagious particles of certain diseases, + which are so minute that they float in the atmosphere and adhere to + smooth paper; yet we know how largely they increase within the human + body, and how powerfully they act. Independent organisms exist which are + barely visible under the highest powers of our recently-improved + microscopes, and which probably are fully as large as the cells or units + in one of the higher animals; yet these organisms no doubt reproduce + themselves by germs of extreme minuteness, relatively to their own minute + size. Hence the difficulty, which at first appears insurmountable, of + believing in the existence of gemmules so numerous and so small as they + must be according to our hypothesis, has really little weight.</p> + + <p>The cells or units of the body are generally admitted by physiologists + to be autonomous, like the buds on a tree, but in a less degree. I go one + step further and assume that they throw off reproductive gemmules. Thus + an animal does not, as a whole, generate its kind through the sole agency + of the reproductive system, but each separate cell generates its kind. It + has often been said by naturalists that each cell of a plant has the + actual or potential capacity of reproducing the whole plant; but it has + this power only in virtue of containing gemmules derived from every part. + If our hypothesis be provisionally accepted, we must look at all the + forms of asexual reproduction, whether occurring at maturity or as in the + case of alternate generation during youth, as fundamentally the same, and + dependent on the mutual aggregation and multiplication of the gemmules. + The regrowth of an amputated limb or the healing of a wound is the same + process partially carried out. Sexual generation differs in some + important respects, chiefly, as it would appear, in an insufficient + number of gemmules being aggregated within the separate sexual elements, + and probably in the presence of certain primordial cells. The development + of each being, including all the <!-- Page 404 --><span + class="pagenum"><a name="page404"></a>{404}</span>forms of metamorphosis + and metagenesis, as well as the so-called growth of the higher animals, + in which structure changes though not in a striking manner, depends on + the presence of gemmules thrown off at each period of life, and on their + development, at a corresponding period, in union with preceding cells. + Such cells may be said to be fertilised by the gemmules which come next + in the order of development. Thus the ordinary act of impregnation and + the development of each being are closely analogous processes. The child, + strictly speaking, does not grow into the man, but includes germs which + slowly and successively become developed and form the man. In the child, + as well as in the adult, each part generates the same part for the next + generation. Inheritance must be looked at as merely a form of growth, + like the self-division of a lowly-organised unicellular plant. Reversion + depends on the transmission from the forefather to his descendants of + dormant gemmules, which occasionally become developed under certain known + or unknown conditions. Each animal and plant may be compared to a bed of + mould full of seeds, most of which soon germinate, some lie for a period + dormant, whilst others perish. When we hear it said that a man carries in + his constitution the seeds of an inherited disease, there is much literal + truth in the expression. Finally, the power of propagation possessed by + each separate cell, using the term in its largest sense, determines the + reproduction, the variability, the development and renovation of each + living organism. No other attempt, as far as I am aware, has been made, + imperfect as this confessedly is, to connect under one point of view + these several grand classes of facts. We cannot fathom the marvellous + complexity of an organic being; but on the hypothesis here advanced this + complexity is much increased. Each living creature must be looked at as a + microcosm—a little universe, formed of a host of self-propagating + organisms, inconceivably minute and as numerous as the stars in + heaven.</p> + +<hr class="full" /> + +<p><!-- Page 405 --><span class="pagenum"><a name="page405"></a>{405}</span></p> + +<h3>CHAPTER XXVIII.</h3> + +<p class="cenhead">CONCLUDING REMARKS.</p> + +<blockquote class="b1n"> + + <p><span class="scac">DOMESTICATION</span>—<span + class="scac">NATURE AND CAUSES OF VARIABILITY</span>—<span + class="scac">SELECTION</span>—<span class="scac">DIVERGENCE AND + DISTINCTNESS OF CHARACTER</span>—<span class="scac">EXTINCTION OF + RACES</span>—<span class="scac">CIRCUMSTANCES FAVOURABLE TO + SELECTION BY MAN</span>—<span class="scac">ANTIQUITY OF CERTAIN + RACES</span>—<span class="scac">THE QUESTION WHETHER EACH + PARTICULAR VARIATION HAS BEEN SPECIALLY PREORDAINED.</span></p> + +</blockquote> + + <p>As summaries have been added to nearly all the chapters, and as, in + the chapter on pangenesis, various subjects, such as the forms of + reproduction, inheritance, reversion, the causes and laws of variability, + &c., have been recently discussed, I will here only make a few + general remarks on the more important conclusions which may be deduced + from the multifarious details given throughout this work.</p> + + <p>Savages in all parts of the world easily succeed in taming wild + animals; and those inhabiting any country or island, when first invaded + by man, would probably have been still more easily tamed. Complete + subjugation generally depends on an animal being social in its habits, + and on receiving man as the chief of the herd or family. Domestication + implies almost complete fertility under new and changed conditions of + life, and this is far from being invariably the case. An animal would not + have been worth the labour of domestication, at least during early times, + unless of service to man. From these circumstances the number of + domesticated animals has never been large. With respect to plants, I have + shown in the ninth chapter how their varied uses were probably first + discovered, and the early steps in their cultivation. Man could not have + known, when he first domesticated an animal or plant, whether it would + flourish and multiply when transported to other countries, therefore he + could not have been thus influenced in his choice. We see that the close + adaptation of the reindeer and camel to extremely cold and hot countries + has not prevented their domestication. Still less <!-- Page 406 --><span + class="pagenum"><a name="page406"></a>{406}</span>could man have foreseen + whether his animals and plants would vary in succeeding generations and + thus give birth to new races; and the small capacity of variability in + the goose and ass has not prevented their domestication from the remotest + epoch.</p> + + <p>With extremely few exceptions, all animals and plants which have been + long domesticated, have varied greatly. It matters not under what + climate, or for what purpose, they are kept, whether as food for man or + beast, for draught or hunting, for clothing or mere pleasure,—under + all these circumstances domesticated animals and plants have varied to a + much greater extent than the forms which in a state of nature are ranked + as one species. Why certain animals and plants have varied more under + domestication than others we do not know, any more than why some are + rendered more sterile than others under changed conditions of life. But + we frequently judge of the amount of variation by the production of + numerous and diversified races, and we can clearly see why in many cases + this has not occurred, namely, because slight successive variations have + not been steadily accumulated; and such variations will never be + accumulated when an animal or plant is not closely observed, or much + valued, or kept in large numbers.</p> + + <p>The fluctuating, and, as far as we can judge, never-ending variability + of our domesticated productions,—the plasticity of their whole + organisation,—is one of the most important facts which we learn + from the numerous details given in the earlier chapters of this work. Yet + domesticated animals and plants can hardly have been exposed to greater + changes in their conditions than have many natural species during the + incessant geological, geographical, and climatal changes of the whole + world. The former will, however, commonly have been exposed to more + sudden changes and to less continuously uniform conditions. As man has + domesticated so many animals and plants belonging to widely different + classes, and as he certainly did not with prophetic instinct choose those + species which would vary most, we may infer that all natural species, if + subjected to analogous conditions, would, on an average, vary to the same + degree. Few men at the present day will maintain that animals and plants + were created with a tendency to vary, which long remained dormant, in + order that fanciers in after ages might <!-- Page 407 --><span + class="pagenum"><a name="page407"></a>{407}</span>rear, for instance, + curious breeds of the fowl, pigeon, or canary-bird.</p> + + <p>From several causes it is difficult to judge of the amount of + modification which our domestic productions have undergone. In some cases + the primitive parent-stock has become extinct, or cannot be recognised + with certainty owing to its supposed descendants having been so much + modified. In other cases two or more closely allied forms, after being + domesticated, have crossed; and then it is difficult to estimate how much + of the change ought to be attributed to variation. But the degree to + which our domestic breeds have been modified by the crossing of distinct + natural forms has probably been exaggerated by some authors. A few + individuals of one form would seldom permanently affect another form + existing in much greater numbers; for, without careful selection, the + stain of the foreign blood would soon be obliterated, and during early + and barbarous times, when our animals were first domesticated, such care + would seldom have been taken.</p> + + <p>There is good reason to believe that several of the breeds of the dog, + ox, pig, and of some other animals, are respectively descended from + distinct wild prototypes; nevertheless the belief in the multiple origin + of our domesticated animals has been extended by some few naturalists and + by many breeders to an unauthorised extent. Breeders refuse to look at + the whole subject under a single point of view; I have heard one, who + maintained that our fowls were the descendants of at least half-a-dozen + aboriginal species, protest that he was in no way concerned with the + origin of pigeons, ducks, rabbits, horses, or any other animal. They + overlook the improbability of many species having been domesticated at an + early and barbarous period. They do not consider the improbability of + species having existed in a state of nature which, if like our present + domestic breeds, would have been highly abnormal in comparison with all + their congeners. They maintain that certain species, which formerly + existed, have become extinct or unknown, although the world is now so + much better known. The assumption of so much recent extinction is no + difficulty in their eyes; for they do not judge of its probability by the + facility or difficulty of the extinction of other closely allied wild + forms. Lastly, <!-- Page 408 --><span class="pagenum"><a + name="page408"></a>{408}</span>they often ignore the whole subject of + geographical distribution as completely as if its laws were the result of + chance.</p> + + <p>Although from the reasons just assigned it is often difficult to judge + accurately of the amount of change which our domesticated productions + have undergone, yet this can be ascertained in the cases in which we know + that all the breeds are descended from a single species, as with the + pigeon, duck, rabbit, and almost certainly with the fowl; and by the aid + of analogy this is to a certain extent possible in the case of animals + descended from several wild stocks. It is impossible to read the details + given in the earlier chapters, and in many published works, or to visit + our various exhibitions, without being deeply impressed with the extreme + variability of our domesticated animals and cultivated plants. I have in + many instances purposely given details on new and strange peculiarities + which have arisen. No part of the organisation escapes the tendency to + vary. The variations generally affect parts of small vital or + physiological importance, but so it is with the differences which exist + between closely allied species. In these unimportant characters there is + often a greater difference between the breeds of the same species than + between the natural species of the same genus, as Isidore Geoffroy has + shown to be the case with size, and as is often the case with the colour, + texture, form, &c., of the hair, feathers, horns, and other dermal + appendages.</p> + + <p>It has often been asserted that important parts never vary under + domestication, but this is a complete error. Look at the skull of the pig + in any one of the highly improved breeds, with the occipital condyles and + other parts greatly modified; or look at that of the niata ox. Or again, + in the several breeds of the rabbit, observe the elongated skull, with + the differently shaped occipital foramen, atlas, and other cervical + vertebræ. The whole shape of the brain, together with the skull, has been + modified in Polish fowls; in other breeds of the fowl the number of the + vertebræ and the forms of the cervical vertebræ have been changed. In + certain pigeons the shape of the lower jaw, the relative length of the + tongue, the size of the nostrils and eyelids, the number and shape of the + ribs, the form and size of the œsophagus, have all varied. In + certain quadrupeds the length of the intestines has been much increased + or <!-- Page 409 --><span class="pagenum"><a + name="page409"></a>{409}</span>diminished. With plants we see wonderful + differences in the stones of various fruits. In the Cucurbitaceæ several + highly important characters have varied, such as the sessile position of + the stigmas on the ovarium, the position of the carpels within the + ovarium, and its projection out of the receptacle. But it would be + useless to run through the many facts given in the earlier chapters.</p> + + <p>It is notorious how greatly the mental disposition, tastes, habits, + consensual movements, loquacity or silence, and the tone of voice have + varied and been inherited with our domesticated animals. The dog offers + the most striking instance of changed mental attributes, and these + differences cannot be accounted for by descent from distinct wild types. + New mental characters have certainly often been acquired, and natural + ones lost, under domestication.</p> + + <p>New characters may appear and disappear at any stage of growth, and be + inherited at a corresponding period. We see this in the difference + between the eggs of various breeds of the fowl, and in the down on + chickens; and still more plainly in the differences between the + caterpillars and cocoons of various breeds of the silk-moth. These facts, + simple as they appear, throw light on the characters which distinguish + the larval and adult states of natural species, and on the whole great + subject of embryology. New characters are liable to become attached + exclusively to that sex in which they first appeared, or they may be + developed in a much higher degree in the one than the other sex; or + again, after having become attached to one sex, they may be partially + transferred to the opposite sex. These facts, and more especially the + circumstance that new characters seem to be particularly liable, from + some unknown cause, to become attached to the male sex, have an important + bearing on the acquirement by animals in a state of nature of secondary + sexual characters.</p> + + <p>It has sometimes been said that our domestic productions do not differ + in constitutional peculiarities, but this cannot be maintained. In our + improved cattle, pigs, &c., the period of maturity, including that of + the second dentition, has been much hastened. The period of gestation + varies much, but has been modified in a fixed manner in only one or two + cases. In <!-- Page 410 --><span class="pagenum"><a + name="page410"></a>{410}</span>our poultry and pigeons the acquirement of + down and of the first plumage by the young, and of the secondary sexual + characters by the males, differ. The number of moults through which the + larvæ of silk-moths pass, varies. The tendency to fatten, to yield much + milk, to produce many young or eggs at a birth or during life, differs in + different breeds. We find different degrees of adaptation to climate, and + different tendencies to certain diseases, to the attacks of parasites, + and to the action of certain vegetable poisons. With plants, adaptation + to certain soils, as with some kinds of plums, the power of resisting + frost, the period of flowering and fruiting, the duration of life, the + period of shedding the leaves and of retaining them throughout the + winter, the proportion and nature of certain chemical compounds in the + tissues or seeds, all vary.</p> + + <p>There is, however, one important constitutional difference between + domestic races and species; I refer to the sterility which almost + invariably follows, in a greater or less degree, when species are + crossed, and to the perfect fertility of the most distinct domestic + races, with the exception of a very few plants, when similarly crossed. + It certainly appears a remarkable fact that many closely allied species + which in appearance differ extremely little should yield when united only + a few, more or less sterile offspring, or none at all; whilst domestic + races which differ conspicuously from each other, are when united + remarkably fertile, and yield perfectly fertile offspring. But this fact + is not in reality so inexplicable as it at first appears. In the first + place, it was clearly shown in the nineteenth chapter that the sterility + of crossed species does not closely depend on differences in their + external structure or general constitution, but results exclusively from + differences in the reproductive system, analogous with those which cause + the lessened fertility of the illegitimate unions and illegitimate + offspring of dimorphic and trimorphic plants. In the second place, the + Pallasian doctrine, that species after having been long domesticated lose + their natural tendency to sterility when crossed, has been shown to be + highly probable; we can scarcely avoid this conclusion when we reflect on + the parentage and present fertility of the several breeds of the dog, of + Indian and European cattle, sheep, and pigs. Hence it would be + unreasonable to expect that races formed under domestication <!-- Page + 411 --><span class="pagenum"><a name="page411"></a>{411}</span>should + acquire sterility when crossed, whilst at the same time we admit that + domestication eliminates the normal sterility of crossed species. Why + with closely allied species their reproductive systems should almost + invariably have been modified in so peculiar a manner as to be mutually + incapable of acting on each other—though in unequal degrees in the + two sexes, as shown by the difference in fertility between reciprocal + crosses in the same species—we do not know, but may with much + probability infer the cause to be as follows. Most natural species have + been habituated to nearly uniform conditions of life for an incomparably + longer period of time than have domestic races; and we positively know + that changed conditions exert an especial and powerful influence on the + reproductive system. Hence this difference in habituation may well + account for the different action of the reproductive organs when domestic + races and when species are crossed. It is a nearly analogous fact, that + most domestic races may be suddenly transported from one climate to + another, or be placed under widely different conditions, and yet retain + their fertility unimpaired; whilst a multitude of species subjected to + lesser changes are rendered incapable of breeding.</p> + + <p>With the exception of fertility, domestic varieties resemble species + when crossed in transmitting their characters in the same unequal manner + to their offspring, in being subject to the prepotency of one form over + the other, and in their liability to reversion. By repeated crosses a + variety or a species may be made completely to absorb another. Varieties, + as we shall see when we treat of their antiquity, sometimes inherit their + new characters almost, or even quite, as firmly as species. With both, + the conditions leading to variability and the laws governing its nature + appear to be the same. Domestic varieties can be classed in groups under + groups, like species under genera, and these under families and orders; + and the classification may be either artificial,—that is, founded + on any arbitrary character,—or natural. With varieties a natural + classification is certainly founded, and with species is apparently + founded, on community of descent, together with the amount of + modification which the forms have undergone. The characters by which + domestic varieties differ from each other are more <!-- Page 412 --><span + class="pagenum"><a name="page412"></a>{412}</span>variable than those + distinguishing species, though hardly more so than with certain protean + species; but this greater degree of variability is not surprising, as + varieties have generally been exposed within recent times to fluctuating + conditions of life, are much more liable to have been crossed, and are + still in many cases undergoing, or have recently undergone, modification + by man's methodical or unconscious selection.</p> + + <p>Domestic varieties as a general rule certainly differ from each other + in less important parts of their organisation than do species; and when + important differences occur, they are seldom firmly fixed; but this fact + is intelligible if we consider man's method of selection. In the living + animal or plant he cannot observe internal modifications in the more + important organs; nor does he regard them as long as they are compatible + with health and life. What does the breeder care about any slight change + in the molar teeth of his pigs, or for an additional molar tooth in the + dog; or for any change in the intestinal canal or other internal organ? + The breeder cares for the flesh of his cattle being well marbled with + fat, and for an accumulation of fat within the abdomen of his sheep, and + this he has effected. What would the floriculturist care for any change + in the structure of the ovarium or of the ovules? As important internal + organs are certainly liable to numerous slight variations, and as these + would probably be inherited, for many strange monstrosities are + transmitted, man could undoubtedly effect a certain amount of change in + these organs. When he has produced any modification in an important part, + it has generally been unintentionally in correlation with some other + conspicuous part, as when he has given ridges and protuberances to the + skulls of fowls, by attending to the form of the comb, and in the case of + the Polish fowl to the plume of feathers on the head. By attending to the + external form of the pouter-pigeon, he has enormously increased the size + of the œsophagus, and has added to the number of the ribs, and + given them greater breadth. With the carrier-pigeon, by increasing, + through steady selection, the wattles on the upper mandible, he has + greatly modified the form of the lower mandible; and so in many other + cases. Natural species, on the other hand, have been modified exclusively + for their own good, to fit them for infinitely <!-- Page 413 --><span + class="pagenum"><a name="page413"></a>{413}</span>diversified conditions + of life, to avoid enemies of all kinds, and to struggle against a host of + competitors. Hence, under such complex conditions, it would often happen + that modifications of the most varied kinds, in important as well as in + unimportant parts, would be advantageous or even necessary; and they + would slowly but surely be acquired through the survival of the fittest. + Various indirect modifications would likewise arise through the law of + correlated variation.</p> + + <p>Domestic breeds often have an abnormal or semi-monstrous character, as + the Italian greyhound, bulldog, Blenheim spaniel, and bloodhound amongst + dogs,—some breeds of cattle and pigs, several breeds of the fowl, + and the chief breeds of the pigeon. The differences between such abnormal + breeds occur in parts which in closely-allied natural species differ but + slightly or not at all. This may be accounted for by man's often + selecting, especially at first, conspicuous and semi-monstrous deviations + of structure. We should, however, be cautious in deciding what deviations + ought to be called monstrous: there can hardly be a doubt that, if the + brush of horse-like hair on the breast of the turkey-cock had first + appeared on the domesticated bird, it would have been considered a + monstrosity; the great plume of feathers on the head of the Polish cock + has been thus designated, though plumes are common with many kinds of + birds; we might call the wattle or corrugated skin round the base of the + beak of the English carrier-pigeon a monstrosity, but we do not thus + speak of the globular fleshy excrescence at the base of the beak of the + male <i>Carpophaga oceanica</i>.</p> + + <p>Some authors have drawn a wide distinction between artificial and + natural breeds; although in extreme cases the distinction is plain, in + many other cases an arbitrary line has to be drawn. The difference + depends chiefly on the kind of selection which has been applied. + Artificial breeds are those which have been intentionally improved by + man; they frequently have an unnatural appearance, and are especially + liable to loss of excellence through reversion and continued variability. + The so-called natural breeds, on the other hand, are those which are now + found in semi-civilised countries, and which formerly inhabited separate + districts in nearly all the European kingdoms. They have been rarely + acted on by man's <!-- Page 414 --><span class="pagenum"><a + name="page414"></a>{414}</span>intentional selection; more frequently, it + is probable, by unconscious selection, and partly by natural selection, + for animals kept in semi-civilised countries have to provide largely for + their own wants. Such natural breeds will also, it may be presumed, have + been directly acted on to some extent by the differences, though slight, + in the surrounding physical conditions.</p> + + <p>It is a much more important distinction that some breeds have been + from their first origin modified in so slow and insensible a manner, that + if we could see their early progenitors we should hardly be able to say + when or how the breed first arose; whilst other breeds have originated + from a strongly-marked or semi-monstrous deviation of structure, which, + however, may subsequently have been augmented by selection. From what we + know of the history of the racehorse, greyhound, gamecock, &c., and + from their general appearance, we may feel nearly confident that they + were formed by a slow process of improvement: and with the + carrier-pigeon, as well as with some other pigeons, we know that this has + been the case. On the other hand, it is certain that the ancon and + mauchamp breeds of sheep, and almost certain that the niata cattle, + turnspit and pug-dogs, jumper and frizzled fowls, short-faced tumbler + pigeons, hook-billed ducks, &c., and with plants a multitude of + varieties, suddenly appeared in nearly the same state as we now see them. + The frequency of these cases is likely to lead to the false belief that + natural species have often originated in the same abrupt manner. But we + have no evidence of the appearance, or at least of the continued + procreation, under nature, of abrupt modifications of structure; and + various general reasons could be assigned against such a belief: for + instance, without separation a single monstrous variation would almost + certainly be soon obliterated by crossing.</p> + + <p>On the other hand, we have abundant evidence of the constant + occurrence under nature of slight individual differences of the most + diversified kinds; and thus we are led to conclude that species have + generally originated by the natural selection, not of abrupt + modifications, but of extremely slight differences. This process may be + strictly compared with the slow and gradual improvement of the racehorse, + greyhound, and gamecock. As every detail of structure in each species is + closely adapted to its general <!-- Page 415 --><span class="pagenum"><a + name="page415"></a>{415}</span>habits of life, it will rarely happen that + one part alone will be modified; but the co-adapted modifications, as + formerly shown, need not be absolutely simultaneous. Many variations, + however, are from the first connected by the law of correlation. Hence it + follows that even closely-allied species rarely or never differ from each + other by some one character alone; and this same remark applies to a + certain extent to domestic races; for these, if they differ much, + generally differ in many respects.</p> + + <p>Some naturalists boldly insist<a name="NtA_928" + href="#Nt_928"><sup>[928]</sup></a> that species are absolutely distinct + productions, never passing by intermediate links into each other; whilst + they maintain that domestic varieties can always be connected either with + each other or with their parent-forms. But if we could always find the + links between the several breeds of the dog, horse, cattle, sheep, pigs, + &c., the incessant doubts whether they are descended from one or + several species would not have arisen. The greyhound genus, if such a + term may be used, cannot be closely connected with any other breed, + unless, perhaps, we go back to the ancient Egyptian monuments. Our + English bulldog also forms a very distinct breed. In all these cases + crossed breeds must of course be excluded, for the most distinct natural + species can thus be connected. By what links can the Cochin fowl be + closely united with others? By searching for breeds still preserved in + distant lands, and by going back to historical records, tumbler-pigeons, + carriers, and barbs can be closely connected with the parent rock-pigeon; + but we cannot thus connect the turbit or the pouter. The degree of + distinctness between the various domestic breeds depends on the amount of + modification which they have undergone, and especially on the neglect and + final extinction of the linking, intermediate, and less valued forms.</p> + + <p>It has often been argued that no light is thrown, from the admitted + changes of domestic races, on the changes which natural species are + believed to undergo, as the former are said to be mere temporary + productions, always reverting, as soon as they become feral, to their + pristine form. This argument has been well combated by Mr. Wallace;<a + name="NtA_929" href="#Nt_929"><sup>[929]</sup></a> and full details were + given in the thirteenth chapter, showing that the tendency to reversion + in feral <!-- Page 416 --><span class="pagenum"><a + name="page416"></a>{416}</span>animals and plants has been greatly + exaggerated, though no doubt to a certain extent it exists. It would be + opposed to all the principles inculcated in this work, if domestic + animals, when exposed to new conditions and compelled to struggle for + their own wants against a host of foreign competitors, were not in the + course of time in some manner modified. It should also be remembered that + many characters lie latent in all organic beings ready to be evolved + under fitting conditions; and in breeds modified within recent times the + tendency to reversion is particularly strong. But the antiquity of + various breeds clearly proves that they remain nearly constant as long as + their conditions of life remain the same.</p> + + <p>It has been boldly maintained by some authors that the amount of + variation to which our domestic productions are liable is strictly + limited; but this is an assertion resting on little evidence. Whether or + not the amount in any particular direction is fixed, the tendency to + general variability seems unlimited. Cattle, sheep, and pigs have been + domesticated and have varied from the remotest period, as shown by the + researches of Rütimeyer and others, yet these animals have, within quite + recent times, been improved in an unparalleled degree; and this implies + continued variability of structure. Wheat, as we know from the remains + found in the Swiss lake-habitations, is one of the most anciently + cultivated plants, yet at the present day new and better varieties + occasionally arise. It may be that an ox will never be produced of larger + size or finer proportions than our present animals, or a race-horse + fleeter than Eclipse, or a gooseberry larger than the London variety; but + he would be a bold man who would assert that the extreme limit in these + respects has been finally attained. With flowers and fruit it has + repeatedly been asserted that perfection has been reached, but the + standard has soon been excelled. A breed of pigeons may never be produced + with a beak shorter than that of the present short-faced tumbler, or with + one longer than that of the English carrier, for these birds have weak + constitutions and are bad breeders; but the shortness and length of the + beak are the points which have been steadily improved during at least the + last 150 years; and some of the best judges deny that the goal has yet + been reached. We may, also, reasonably suspect, from what <!-- Page 417 + --><span class="pagenum"><a name="page417"></a>{417}</span>we see in + natural species of the variability of extremely modified parts, that any + structure, after remaining constant during a long series of generations, + would, under new and changed conditions of life, recommence its course of + variability, and might again be acted on by selection. Nevertheless, as + Mr. Wallace<a name="NtA_930" href="#Nt_930"><sup>[930]</sup></a> has + recently remarked with much force and truth, there must be both with + natural and domestic productions a limit to change in certain directions; + for instance, there must be a limit to the fleetness of any terrestrial + animal, as this will be determined by the friction to be overcome, the + weight to be carried, and the power of contraction in the muscular + fibres. The English racehorse may have reached this limit; but it already + surpasses in fleetness its own wild progenitor, and all other equine + species.</p> + + <p>It is not surprising, seeing the great difference between many + domestic breeds, that some few naturalists have concluded that all are + descended from distinct aboriginal stocks, more especially as the + principle of selection has been ignored, and the high antiquity of man, + as a breeder of animals, has only recently become known. Most + naturalists, however, freely admit that various extremely dissimilar + breeds are descended from a single stock, although they do not know much + about the art of breeding, cannot show the connecting links, nor say + where and when the breeds arose. Yet these same naturalists will declare, + with an air of philosophical caution, that they can never admit that one + natural species has given birth to another until they behold all the + transitional steps. But fanciers have used exactly the same language with + respect to domestic breeds; thus an author of an excellent treatise says + he will never allow that carrier and fantail pigeons are the descendants + of the wild rock-pigeon, until the transitions have "actually been + observed, and can be repeated whenever man chooses to set about the + task." No doubt it is difficult to realise that slight changes added up + during long centuries can produce such results; but he who wishes to + understand the origin of domestic breeds or natural species must overcome + this difficulty.</p> + + <p>The causes inducing and the laws governing variability have been so + lately discussed, that I need here only enumerate the leading points. As + domesticated organisms are much more <!-- Page 418 --><span + class="pagenum"><a name="page418"></a>{418}</span>liable to slight + deviations of structure and to monstrosities, than species living under + their natural conditions, and as widely-ranging species vary more than + those which inhabit restricted areas, we may infer that variability + mainly depends on changed conditions of life. We must not overlook the + effects of the unequal combination of the characters derived from both + parents, nor reversion to former progenitors. Changed conditions have an + especial tendency to render the reproductive organs more or less + impotent, as shown in the chapter devoted to this subject; and these + organs consequently often fail to transmit faithfully the parental + characters. Changed conditions also act directly and definitely on the + organisation, so that all or nearly all the individuals of the same + species thus exposed become modified in the same manner; but why this or + that part is especially affected we can seldom or never say. In most + cases, however, of the direct action of changed conditions, independently + of the indirect variability caused by the reproductive organs being + affected, indefinite modifications are the result; in nearly the same + manner as exposure to cold or the absorption of the same poison affects + different individuals in various ways. We have reason to suspect that an + habitual excess of highly nutritious food, or an excess relatively to the + wear and tear of the organisation from exercise, is a powerful exciting + cause of variability. When we see the symmetrical and complex outgrowths, + caused by a minute atom of the poison of a gall-insect, we may believe + that slight changes in the chemical nature of the sap or blood would lead + to extraordinary modifications of structure.</p> + + <p>The increased use of a muscle with its various attached parts, and the + increased activity of a gland or other organ, lead to their increased + development. Disuse has a contrary effect. With domesticated productions + organs sometimes become rudimentary through abortion; but we have no + reason to suppose that this has ever followed from mere disuse. With + natural species, on the contrary, many organs appear to have been + rendered rudimentary through disuse, aided by the principle of the + economy of growth, and by the hypothetical principle discussed in the + last chapter, namely, the final destruction of the germs or gemmules of + such useless parts. This difference may be partly <!-- Page 419 --><span + class="pagenum"><a name="page419"></a>{419}</span>accounted for by disuse + having acted on domestic forms for an insufficient length of time, and + partly from their exemption from any severe struggle for existence, + entailing rigid economy in the development of each part, to which all + species under nature are subjected. Nevertheless the law of compensation + or balancement apparently affects, to a certain extent, our domesticated + productions.</p> + + <p>We must not exaggerate the importance of the definite action of + changed conditions in modifying all the individuals of the same species + in the same manner, or of use and disuse. As every part of the + organisation is highly variable, and as variations are so easily + selected, both consciously and unconsciously, it is very difficult to + distinguish between the effects of the selection of indefinite + variations, and the direct action of the conditions of life. For + instance, it is possible that the feet of our water-dogs, and of the + American dogs which have to travel much over the snow, may have become + partially webbed from the stimulus of widely extending their toes; but it + is far more probable that the webbing, like the membrane between the toes + of certain pigeons, spontaneously appeared and was afterwards increased + by the best swimmers and the best snow-travellers being preserved during + many generations. A fancier who wished to decrease the size of his + bantams or tumbler-pigeons would never think of starving them, but would + select the smallest individuals which spontaneously appeared. Quadrupeds + are sometimes born destitute of hair, and hairless breeds have been + formed, but there is no reason to believe that this is caused by a hot + climate. Within the tropics heat often causes sheep to lose their + fleeces, and on the other hand wet and cold act as a direct stimulus to + the growth of hair; it is, however, possible that these changes may + merely be an exaggeration of the regular yearly change of coat; and who + will pretend to decide how far this yearly change, or the thick fur of + arctic animals, or as I may add their white colour, is due to the direct + action of a severe climate, and how far to the preservation of the best + protected individuals during a long succession of generations?</p> + + <p>Of all the laws governing variability, that of correlation is the most + important. In many cases of slight deviations of structure as well as of + grave monstrosities, we cannot even <!-- Page 420 --><span + class="pagenum"><a name="page420"></a>{420}</span>conjecture what is the + nature of the bond of connexion. But between homologous + parts—between the fore and hind limbs—between the hair, + hoofs, horns, and teeth—we can see that parts which are closely + similar during their early development, and which are exposed to similar + conditions, would be liable to be modified in the same manner. Homologous + parts, from having the same nature, are apt to blend together and, when + many exist, to vary in number.</p> + + <p>Although every variation is either directly or indirectly caused by + some change in the surrounding conditions, we must never forget that the + nature of the organisation which is acted on essentially governs the + result. Distinct organisms, when placed under similar conditions, vary in + different manners, whilst closely-allied organisms under dissimilar + conditions often vary in nearly the same manner. We see this in the same + modification frequently reappearing at long intervals of time in the same + variety, and likewise in the several striking cases given of analogous or + parallel varieties. Although some of these latter cases are simply due to + reversion, others cannot thus be accounted for.</p> + + <p>From the indirect action of changed conditions on the organisation, + through the impaired state of the reproductive organs—from the + direct action of such conditions (and this will cause the individuals of + the same species either to vary in the same manner, or differently in + accordance with slight differences in their constitution)—from the + effects of the increased or decreased use of parts,—and from + correlation,—the variability of our domesticated productions is + complicated in an extreme degree. The whole organisation becomes slightly + plastic. Although each modification must have its proper exciting cause, + and though each is subjected to law, yet we can so rarely trace the + precise relation between cause and effect, that we are tempted to speak + of variations as if they spontaneously arose. We may even call them + accidental, but this must be only in the sense in which we say that a + fragment of rock dropped from a height owes its shape to accident.</p> + +<hr class="short" /> + + <p>It may be worth while briefly to consider the results of the exposure + to unnatural conditions of a large number of animals of the same species, + allowed to cross freely, with no selection of any <!-- Page 421 --><span + class="pagenum"><a name="page421"></a>{421}</span>kind; and afterwards to + consider the results when selection is brought into play. Let us suppose + that 500 wild rock-pigeons were confined in their native land in an + aviary, and fed in the same manner as pigeons usually are; and that they + were not allowed to increase in number. As pigeons propagate so rapidly, + I suppose that a thousand or fifteen hundred birds would have to be + annually killed by mere chance. After several generations had been thus + reared, we may feel sure that some of the young birds would vary, and the + variations would tend to be inherited; for at the present day slight + deviations of structure often occur, but, as most breeds are already well + established, these modifications are rejected as blemishes. It would be + tedious even to enumerate the multitude of points which still go on + varying or have recently varied. Many variations would occur in + correlation, as the length of the wing and tail feathers—the number + of the primary wing-feathers, as well as the number and breadth of the + ribs, in correlation with the size and form of the body—the number + of the scutellæ, with the size of the feet—the length of the + tongue, with the length of the beak—the size of the nostrils and + eyelids and the form of lower jaw in correlation with the development of + wattle—the nakedness of the young with the future colour of the + plumage—the size of the feet and beak, and other such points. + Lastly, as our birds are supposed to be confined in an aviary, they would + use their wings and legs but little, and certain parts of the skeleton, + such as the sternum and scapulæ and the feet, would in consequence become + slightly reduced in size.</p> + + <p>As in our assumed case many birds have to be indiscriminately killed + every year, the chances are against any new variety surviving long enough + to breed. And as the variations which arise are of an extremely + diversified nature, the chances are very great against two birds pairing + which have varied in the same manner; nevertheless, a varying bird even + when not thus paired would occasionally transmit its character to its + young; and these would not only be exposed to the same conditions which + first caused the variation in question to appear, but would in addition + inherit from their one modified parent a tendency again to vary in the + same manner. So that, if the conditions decidedly tended to induce some + particular variation, all the birds might <!-- Page 422 --><span + class="pagenum"><a name="page422"></a>{422}</span>in the course of time + become similarly modified. But a far commoner result would be, that one + bird would vary in one way and another bird in another way; one would be + born with a little longer beak, and another with a shorter beak; one + would gain some black feathers, another some white or red feathers. And + as these birds would be continually intercrossing, the final result would + be a body of individuals differing from each other slightly in many ways, + yet far more than did the original rock-pigeons. But there would not be + the least tendency to the formation of distinct breeds.</p> + + <p>If two separate lots of pigeons were to be treated in the manner just + described, one in England and the other in a tropical country, the two + lots being supplied with different food, would they, after many + generations had passed, differ? When we reflect on the cases given in the + twenty-third chapter, and on such facts as the difference in former times + between the breeds of cattle, sheep, &c., in almost every district of + Europe, we are strongly inclined to admit that the two lots would be + differently modified through the influence of climate and food. But the + evidence on the definite action of changed conditions is in most cases + insufficient; and, with respect to pigeons, I have had the opportunity of + examining a large collection of domesticated birds, sent to me by Sir W. + Elliot from India, and they varied in a remarkably similar manner with + our European birds.</p> + + <p>If two distinct breeds were to be confined together in equal numbers, + there is reason to suspect that they would to a certain extent prefer + pairing with their own kind; but they would likewise intercross. From the + greater vigour and fertility of the crossed offspring, the whole body + would by this means become interblended sooner than would otherwise have + occurred. From certain breeds being prepotent over others, it does not + follow that the interblended progeny would be strictly intermediate in + character. I have, also, proved that the act of crossing in itself gives + a strong tendency to reversion, so that the crossed offspring would tend + to revert to the state of the aboriginal rock-pigeon. In the course of + time they would probably be not much more heterogeneous in character than + in our first case, when birds of the same breed were confined together. + <!-- Page 423 --><span class="pagenum"><a + name="page423"></a>{423}</span></p> + + <p>I have just said that the crossed offspring would gain in vigour and + fertility. From the facts given in the seventeenth chapter there can be + no doubt of this; and there can be little doubt, though the evidence on + this head is not so easily acquired, that long-continued close + interbreeding leads to evil results. With hermaphrodites of all kinds, if + the sexual elements of the same individual habitually acted on each + other, the closest possible interbreeding would be perpetual. Therefore + we should bear in mind that with all hermaphrodite animals, as far as I + can learn, their structure permits and frequently necessitates a cross + with a distinct individual. With hermaphrodite plants we incessantly meet + with elaborate and perfect contrivances for this same end. It is no + exaggeration to assert that, if the use of the talons and tusks of a + carnivorous animal, or the use of the viscid threads of a spider's web, + or of the plumes and hooks on a seed may be safely inferred from their + structure, we may with equal safety infer that many flowers are + constructed for the express purpose of ensuring a cross with a distinct + plant. From these various considerations, the conclusion arrived at in + the chapter just referred to—namely, that great good of some kind + is derived from the sexual concourse of distinct individuals—must + be admitted.</p> + + <p>To return to our illustration: we have hitherto assumed that the birds + were kept down to the same number by indiscriminate slaughter; but if the + least choice be permitted in their preservation and slaughter, the whole + result will be changed. Should the owner observe any slight variation in + one of his birds, and wish to obtain a breed thus characterised, he would + succeed in a surprisingly short time by carefully selecting and pairing + the young. As any part which has once varied generally goes on varying in + the same direction, it is easy, by continually preserving the most + strongly marked individuals, to increase the amount of difference up to a + high, predetermined standard of excellence. This is methodical + selection.</p> + + <p>If the owner of the aviary, without any thought of making a new breed, + simply admired, for instance, short-beaked more than long-beaked birds, + he would, when he had to reduce the number, generally kill the latter; + and there can be no doubt that he would thus in the course of time + sensibly modify his <!-- Page 424 --><span class="pagenum"><a + name="page424"></a>{424}</span>stock. It is improbable, if two men were + to keep pigeons and act in this manner, that they would prefer exactly + the same characters; they would, as we know, often prefer directly + opposite characters, and the two lots would ultimately come to differ. + This has actually occurred with strains or families of cattle, sheep, and + pigeons, which have been long kept and carefully attended to by different + breeders without any wish on their part to form new and distinct + sub-breeds. This unconscious kind of selection will more especially come + into action with animals which are highly serviceable to man; for every + one tries to get the best dog, horse, cow, or sheep, and these animals + will transmit more or less surely their good qualities to their + offspring. Hardly any one is so careless as to breed from his worst + animals. Even savages, when compelled from extreme want to kill some of + their animals, would destroy the worst and preserve the best. With + animals kept for use and not for mere amusement, different fashions + prevail in different districts, leading to the preservation, and + consequently to the transmission, of all sorts of trifling peculiarities + of character. The same process will have been pursued with our + fruit-trees and vegetables, for the best will always have been the most + largely cultivated, and will occasionally have yielded seedlings better + than their parents.</p> + + <p>The different strains, just alluded to, which have been raised by + different breeders without any wish for such a result, and the + unintentional modification of foreign breeds in their new homes, both + afford excellent evidence of the power of unconscious selection. This + form of selection has probably led to far more important results than + methodical selection, and is likewise more important under a theoretical + point of view from closely resembling natural selection. For during this + process the best or most valued individuals are not separated and + prevented crossing with others of the same breed, but are simply + preferred and preserved; but this inevitably leads during a long + succession of generations to their increase in number and to their + gradual improvement; so that finally they prevail to the exclusion of the + old parent-form.</p> + + <p>With our domesticated animals natural selection checks the production + of races with any injurious deviation of <!-- Page 425 --><span + class="pagenum"><a name="page425"></a>{425}</span>structure. In the case + of animals kept by savages and semi-civilised people, which have to + provide largely for their own wants under different circumstances, + natural selection will probably play a more important part. Hence such + animals often closely resemble natural species.</p> + + <p>As there is no limit to man's desire to possess animals and plants + more and more useful in any respect, and as the fancier always wishes, + from fashion running into extremes, to produce each character more and + more strongly pronounced, there is a constant tendency in every breed, + through the prolonged action of methodical and unconscious selection, to + become more and more different from its parent-stock; and when several + breeds have been produced and are valued for different qualities, to + differ more and more from each other. This leads to Divergence of + Character. As improved sub-varieties and races are slowly formed, the + older and less improved breeds are neglected and decrease in number. When + few individuals of any breed exist within the same locality, close + interbreeding, by lessening their vigour and fertility, aids in their + final extinction. Thus the intermediate links are lost, and breeds which + have already diverged gain Distinctness of Character.</p> + + <p>In the chapters on the Pigeon, it was proved by historical details and + by the existence of connecting sub-varieties in distant lands that + several breeds have steadily diverged in character, and that many old and + intermediate sub-breeds have become extinct. Other cases could be adduced + of the extinction of domestic breeds, as of the Irish wolf-dog, the old + English hound, and of two breeds in France, one of which was formerly + highly valued.<a name="NtA_931" href="#Nt_931"><sup>[931]</sup></a> Mr. + Pickering remarks<a name="NtA_932" href="#Nt_932"><sup>[932]</sup></a> + that "the sheep figured on the most ancient Egyptian monuments is unknown + at the present day; and at least one variety of the bullock, formerly + known in Egypt, has in like manner become extinct." So it has been with + some animals, and with several plants cultivated by the ancient + inhabitants of Europe during the neolithic period. In Peru, Von Tschudi<a + name="NtA_933" href="#Nt_933"><sup>[933]</sup></a> found in certain + tombs, apparently prior to the dynasty of the Incas, two kinds of maize + not now known in the country. With our flowers and culinary vegetables, + <!-- Page 426 --><span class="pagenum"><a + name="page426"></a>{426}</span>the production of new varieties and their + extinction has incessantly recurred. At the present time improved breeds + sometimes displace at an extraordinarily rapid rate older breeds; as has + recently occurred throughout England with pigs. The Long-horn cattle in + their native home were "suddenly swept away as if by some murderous + pestilence," by the introduction of Short-horns.<a name="NtA_934" + href="#Nt_934"><sup>[934]</sup></a></p> + + <p>What grand results have followed from the long-continued action of + methodical and unconscious selection, checked and regulated to a certain + extent by natural selection, is seen on every side of us. Compare the + many animals and plants which are displayed at our exhibitions with their + parent-forms when these are known, or consult old historical records with + respect to their former state. Almost all our domesticated animals have + given rise to numerous and distinct races, excepting those which cannot + be easily subjected to selection—such as cats, the cochineal + insect, and the hive-bee,—and excepting those animals which are not + much valued. In accordance with what we know of the process of selection, + the formation of our many races has been slow and gradual. The man who + first observed and preserved a pigeon with its œsophagus a little + enlarged, its beak a little longer, or its tail a little more expanded + than usual, never dreamed that he had made the first step in the creation + of the pouter, carrier, and fantail-pigeon. Man can create not only + anomalous breeds, but others with their whole structure admirably + co-ordinated for certain purposes, such as the race-horse and dray-horse, + or the greyhound. It is by no means necessary that each small change of + structure throughout the body, leading towards excellence, should + simultaneously arise and be selected. Although man seldom attends to + differences in organs which are important under a physiological point of + view, yet he has so profoundly modified some breeds, that assuredly, if + found wild, they would be ranked under distinct genera.</p> + + <p>The best proof of what selection has effected is perhaps afforded by + the fact that whatever part or quality in any animal, and more especially + in any plant, is most valued by man, that part or quality differs most in + the several races. This result is well seen by comparing the amount of + difference <!-- Page 427 --><span class="pagenum"><a + name="page427"></a>{427}</span>between the fruits produced by the + varieties of the same fruit-tree, between the flowers of the varieties in + our flower-garden, between the seeds, roots, or leaves of our culinary + and agricultural plants, in comparison with the other and not valued + parts of the same plants. Striking evidence of a different kind is + afforded by the fact ascertained by Oswald Heer,<a name="NtA_935" + href="#Nt_935"><sup>[935]</sup></a> namely, that the seeds of a large + number of plants,—wheat, barley, oats, peas, beans, lentils, + poppies,—cultivated for their seed by the ancient Lake-inhabitants + of Switzerland, were all smaller than the seeds of our existing + varieties. Rütimeyer has shown that the sheep and cattle which were kept + by the earlier Lake-inhabitants were likewise smaller than our present + breeds. In the middens of Denmark, the earliest dog of which the remains + have been found was the weakest; this was succeeded during the Bronze age + by a stronger kind, and this again during the Iron age by one still + stronger. The sheep of Denmark during the Bronze period had + extraordinarily slender limbs, and the horse was smaller than our present + animal.<a name="NtA_936" href="#Nt_936"><sup>[936]</sup></a> No doubt in + these cases the new and larger breeds were generally introduced from + foreign lands by the immigration of new hordes of men. But it is not + probable that each larger breed, which in the course of time supplanted a + previous and smaller breed, was the descendant of a distinct and larger + species; it is far more probable that the domestic races of our various + animals were gradually improved in different parts of the great + Europæo-Asiatic continent, and thence spread to other countries. This + fact of the gradual increase in size of our domestic animals is all the + more striking as certain wild or half-wild animals, such as red-deer, + aurochs, park-cattle, and boars,<a name="NtA_937" + href="#Nt_937"><sup>[937]</sup></a> have within nearly the same period + decreased in size.</p> + + <p>The conditions favourable to selection by man are,—the closest + attention being paid to every character,—long-continued + perseverance,—facility in matching or separating animals,—and + especially a large number being kept, so that the inferior individuals + may be freely rejected or destroyed, and the better ones preserved. When + many are kept there will also be a <!-- Page 428 --><span + class="pagenum"><a name="page428"></a>{428}</span>greater chance of the + occurrence of well-marked deviations of structure. Length of time is + all-important; for as each character, in order to become strongly + pronounced, has to be augmented by the selection of successive variations + of the same nature, this can only be effected during a long series of + generations. Length of time will, also, allow any new feature to become + fixed by the continued rejection of those individuals which revert or + vary, and the preservation of those which inherit the new character. + Hence, although some few animals have varied rapidly in certain respects + under new conditions of life, as dogs in India and sheep in the West + Indies, yet all the animals and plants which have produced strongly + marked races were domesticated at an extremely remote epoch, often before + the dawn of history. As a consequence of this, no record has been + preserved of the origin of our chief domestic breeds. Even at the present + day new strains or sub-breeds are formed so slowly that their first + appearance passes unnoticed. A man attends to some particular character, + or merely matches his animals with unusual care, and after a time a + slight difference is perceived by his neighbours;—the difference + goes on being augmented by unconscious and methodical selection, until at + last a new sub-breed is formed, receives a local name, and spreads; but, + by this time, its history is almost forgotten. When the new breed has + spread widely, it gives rise to new strains and sub-breeds, and the best + of these succeed and spread, supplanting other and older breeds; and so + always onwards in the march of improvement.</p> + + <p>When a well-marked breed has once been established, if not supplanted + by still improving sub-breeds, and if not exposed to greatly changed + conditions of life, inducing further variability or reversion to + long-lost characters, it may apparently last for an enormous period. We + may infer that this is the case from the high antiquity of certain races; + but some caution is necessary on this head, for the same variation may + appear independently after long intervals of time, or in distant places. + We may safely assume that this has occurred with the turnspit-dog which + is figured on the ancient Egyptian monuments, with the solid-hoofed + swine<a name="NtA_938" href="#Nt_938"><sup>[938]</sup></a> mentioned by + Aristotle, with five-toed fowls <!-- Page 429 --><span class="pagenum"><a + name="page429"></a>{429}</span>described by Columella, and certainly with + the nectarine. The dogs represented on the Egyptian monuments, about 2000 + <span class="scac">B.C.</span>, show us that some of the chief breeds + then existed, but it is extremely doubtful whether any are identically + the same with our present breeds. A great mastiff sculptured on an + Assyrian tomb, 640 <span class="scac">B.C.</span>, is said to be the same + with the dog still imported into the same region from Thibet. The true + greyhound existed during the Roman classical period. Coming down to a + later period, we have seen that, though most of the chief breeds of the + pigeon existed between two and three centuries ago, they have not all + retained to the present day exactly the same character; but this has + occurred in certain cases in which improvement was not desired, for + instance in the case of the Spot or the Indian ground-tumbler.</p> + + <p>De Candolle<a name="NtA_939" href="#Nt_939"><sup>[939]</sup></a> has + fully discussed the antiquity of various races of plants; he states that + the black-seeded poppy was known in the time of Homer, the white-seeded + sesamum by the ancient Egyptians, and almonds with sweet and bitter + kernels by the Hebrews; but it does not seem improbable that some of + these varieties may have been lost and reappeared. One variety of barley + and apparently one of wheat, both of which were cultivated at an + immensely remote period by the Lake-inhabitants of Switzerland, still + exist. It is said<a name="NtA_940" href="#Nt_940"><sup>[940]</sup></a> + that "specimens of a small variety of gourd which is still common in the + market of Lima were exhumed from an ancient cemetery in Peru." De + Candolle remarks that, in the books and drawings of the sixteenth + century, the principal races of the cabbage, turnip, and gourd can be + recognised; this might have been expected at so late a period, but + whether any of these plants are absolutely identical with our present + sub-varieties is not certain. It is, however, said that the Brussels + sprout, a variety which in some places is liable to degeneration, has + remained genuine for more than four centuries in the district where it is + believed to have originated.<a name="NtA_941" + href="#Nt_941"><sup>[941]</sup></a></p> + +<hr class="short" /> + + <p>In accordance with the views maintained by me in this work and + elsewhere, not only the various domestic races, but the <!-- Page 430 + --><span class="pagenum"><a name="page430"></a>{430}</span>most distinct + genera and orders within the same great class,—for instance, + whales, mice, birds, and fishes—are all the descendants of one + common progenitor, and we must admit that the whole vast amount of + difference between these forms of life has primarily arisen from simple + variability. To consider the subject under this point of view is enough + to strike one dumb with amazement. But our amazement ought to be lessened + when we reflect that beings, almost infinite in number, during an almost + infinite lapse of time, have often had their whole organisation rendered + in some degree plastic, and that each slight modification of structure + which was in any way beneficial under excessively complex conditions of + life, will have been preserved, whilst each which was in any way + injurious will have been rigorously destroyed. And the long-continued + accumulation of beneficial variations will infallibly lead to structures + as diversified, as beautifully adapted for various purposes, and as + excellently co-ordinated, as we see in the animals and plants all around + us. Hence I have spoken of selection as the paramount power, whether + applied by man to the formation of domestic breeds, or by nature to the + production of species. I may recur to the metaphor given in a former + chapter: if an architect were to rear a noble and commodious edifice, + without the use of cut stone, by selecting from the fragments at the base + of a precipice wedge-formed stones for his arches, elongated stones for + his lintels, and flat stones for his roof, we should admire his skill and + regard him as the paramount power. Now, the fragments of stone, though + indispensable to the architect, bear to the edifice built by him the same + relation which the fluctuating variations of each organic being bear to + the varied and admirable structures ultimately acquired by its modified + descendants.</p> + + <p>Some authors have declared that natural selection explains nothing, + unless the precise cause of each slight individual difference be made + clear. Now, if it were explained to a savage utterly ignorant of the art + of building, how the edifice had been raised stone upon stone, and why + wedge-formed fragments were used for the arches, flat stones for the + roof, &c.; and if the use of each part and of the whole building were + pointed out, it would be unreasonable if he declared that nothing had + been <!-- Page 431 --><span class="pagenum"><a + name="page431"></a>{431}</span>made clear to him, because the precise + cause of the shape of each fragment could not be given. But this is a + nearly parallel case with the objection that selection explains nothing, + because we know not the cause of each individual difference in the + structure of each being.</p> + + <p>The shape of the fragments of stone at the base of our precipice may + be called accidental, but this is not strictly correct; for the shape of + each depends on a long sequence of events, all obeying natural laws; on + the nature of the rock, on the lines of deposition or cleavage, on the + form of the mountain which depends on its upheaval and subsequent + denudation, and lastly on the storm or earthquake which threw down the + fragments. But in regard to the use to which the fragments may be put, + their shape may be strictly said to be accidental. And here we are led to + face a great difficulty, in alluding to which I am aware that I am + travelling beyond my proper province. An omniscient Creator must have + foreseen every consequence which results from the laws imposed by Him. + But can it be reasonably maintained that the Creator intentionally + ordered, if we use the words in any ordinary sense, that certain + fragments of rock should assume certain shapes so that the builder might + erect his edifice? If the various laws which have determined the shape of + each fragment were not predetermined for the builder's sake, can it with + any greater probability be maintained that He specially ordained for the + sake of the breeder each of the innumerable variations in our domestic + animals and plants;—many of these variations being of no service to + man, and not beneficial, far more often injurious, to the creatures + themselves? Did He ordain that the crop and tail-feathers of the pigeon + should vary in order that the fancier might make his grotesque pouter and + fantail breeds? Did He cause the frame and mental qualities of the dog to + vary in order that a breed might be formed of indomitable ferocity, with + jaws fitted to pin down the bull for man's brutal sport? But if we give + up the principle in one case,—if we do not admit that the + variations of the primeval dog were intentionally guided in order that + the greyhound, for instance, that perfect image of symmetry and vigour, + might be formed,—no shadow of reason can be assigned for the belief + that variations, alike in nature and the result <!-- Page 432 --><span + class="pagenum"><a name="page432"></a>{432}</span>of the same general + laws, which have been the groundwork through natural selection of the + formation of the most perfectly adapted animals in the world, man + included, were intentionally and specially guided. However much we may + wish it, we can hardly follow Professor Asa Gray in his belief "that + variation has been led along certain beneficial lines," like a stream + "along definite and useful lines of irrigation." If we assume that each + particular variation was from the beginning of all time preordained, the + plasticity of organisation, which leads to many injurious deviations of + structure, as well as that redundant power of reproduction which + inevitably leads to a struggle for existence, and, as a consequence, to + the natural selection or survival of the fittest, must appear to us + superfluous laws of nature. On the other hand, an omnipotent and + omniscient Creator ordains everything and foresees everything. Thus we + are brought face to face with a difficulty as insoluble as is that of + free will and predestination.</p> + +<hr class="full" /> + +<p><!-- Page 433 --><span class="pagenum"><a name="page433"></a>{433}</span></p> + + <div class="poem"> + <div class="stanza"> + <p class="i16">INDEX.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Abbas</span> Pacha, a fancier of fantailed pigeons, i. 206.</p> + <p><span class="sc">Abbey</span>, Mr., on grafting, ii. <a href="#page147">147</a>;</p> + <p class="i2">on mignonette, ii. <a href="#page237">237</a>.</p> + <p><span class="sc">Abbott</span>, Mr. Keith, on the Persian tumbler pigeon, i. 150.</p> + <p><span class="sc">Abbreviation</span> of the facial bones, i. 73.</p> + <p><span class="sc">Abortion</span> of organs, ii. <a href="#page315">315</a>-<a href="#page318">318</a>, <a href="#page397">397</a>.</p> + <p><span class="sc">Absorption</span> of minority in crossed races, ii. <a href="#page87">87</a>-<a href="#page89">89</a>, <a href="#page174">174</a>.</p> + <p><span class="sc">Acclimatisation</span>, ii. <a href="#page305">305</a>-<a href="#page315">315</a>;</p> + <p class="i2">of maize, i. 322.</p> + <p><span class="sc">Acerbi</span>, on the fertility of domestic animals in Lapland, ii. <a href="#page112">112</a>.</p> + <p><i>Achatinella</i>, ii. <a href="#page53">53</a>.</p> + <p><i>Achillea millefolium</i>, bud variation in, i. 408.</p> + <p><i>Aconitum napellus</i>, roots of, innocuous in cold climates, ii. <a href="#page274">274</a>.</p> + <p><i>Acorus calamus</i>, sterility of, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Acosta</span>, on fowls in South America at its discovery, i. 237.</p> + <p><i>Acropera</i>, number of seeds in, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Adam</span>, Mr., origin of <i>Cytisus Adami</i>, i. 390.</p> + <p><span class="sc">Adam</span>, W., on consanguineous marriages, ii. <a href="#page123">123</a>.</p> + <p><span class="sc">Adams</span>, Mr., on hereditary diseases, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Advancement</span> in scale of organisation, i. 8.</p> + <p><i>Ægilops triticoides</i>, observations of Fabre and Godron on, i. 313;</p> + <p class="i2">increasing fertility of hybrids of, with wheat, ii. <a href="#page110">110</a>.</p> + <p><i>Æsculus flava</i> and <i>rubicunda</i>, i. 392.</p> + <p><i>Æsculus pavia</i>, tendency of, to become double, ii. <a href="#page168">168</a>.</p> + <p><i>Æthusa cynapium</i>, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Affinity</span>, sexual elective, ii. <a href="#page180">180</a>.</p> + <p><span class="sc">Africa</span>, white bull from, i. 91;</p> + <p class="i2">feral cattle in, i. 85;</p> + <p class="i2">food-plants of savages of, i. 307-309;</p> + <p class="i2">South, diversity of breeds of cattle in, i. 80;</p> + <p class="i2">West, change in fleece of sheep in, i. 98.</p> + <p><i>Agave vivipara</i>, seeding of, in poor soil, ii. <a href="#page169">169</a>.</p> + <p><span class="sc">Age</span>, changes in trees, dependent on, i. 387.</p> + <p><span class="sc">Agouti</span>, fertility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Agriculture</span>, antiquity of, ii. <a href="#page243">243</a>.</p> + <p><i>Agrostis</i>, seeds of, used as food, i. 309.</p> + <p><span class="sc">Aguara</span>, i. 26.</p> + <p><span class="sc">Ainsworth</span>, Mr., on the change in the hair of animals at Angora, ii. <a href="#page278">278</a>.</p> + <p><span class="sc">Akbar</span> Khan, his fondness for pigeons, i. 205; ii. <a href="#page204">204</a>.</p> + <p><i>Alauda arvensis</i>, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Albin</span>, on "Golden Hamburgh" fowls, i. 247;</p> + <p class="i2">figure of the hook-billed duck, i. 277.</p> + <p><span class="sc">Albinism</span>, i. 111, ii. <a href="#page17">17</a>.</p> + <p><span class="sc">Albino</span>, negro, attacked by insects, ii. <a href="#page229">229</a>.</p> + <p><span class="sc">Albinoes</span>, heredity of, ii. <a href="#page9">9</a>.</p> + <p><span class="sc">Albinus</span>, thickness of the epidermis on the palms of the hands in man, ii. <a href="#page297">297</a>.</p> + <p><span class="sc">Alco</span>, i. 31, ii. <a href="#page102">102</a>.</p> + <p><span class="sc">Aldrovandi</span>, on rabbits, i. 104;</p> + <p class="i2">description of the nun pigeon, i. 156;</p> + <p class="i2">on the fondness of the Dutch for pigeons in the seventeenth century, i. 205;</p> + <p class="i2">notice of several varieties of pigeons, i. 207-210;</p> + <p class="i2">on the breeds of fowls, i. 247;</p> + <p class="i2">on the origin of the domestic duck, i. 278.</p> + <p><span class="sc">Alefield</span>, Dr., on the varieties of peas and their specific unity, i. 326;</p> + <p class="i2">on the varieties of beans, i. 330.</p> + <p><span class="sc">Alexander</span> the Great, his selection of Indian cattle, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Algæ</span>, retrogressive metamorphosis in, ii. <a href="#page361">361</a>;</p> + <p class="i2">division of zoospores of, ii. <a href="#page378">378</a>.</p> + <p><span class="sc">Allen</span>, W., on feral fowls, i. 237; ii. <a href="#page33">33</a>.</p> + <p><span class="sc">Allman</span>, Professor, on a monstrous <i>Saxifraga geum</i>, ii. <a href="#page166">166</a>;</p> + <p class="i2">on the development of the Hydroida, ii. <a href="#page368">368</a>.</p> + <p><span class="sc">Almond</span>, i. 337;</p> + <p class="i2">antiquity of, ii. <a href="#page429">429</a>;</p> + <p class="i2">bitter, not eaten by mice, ii. <a href="#page232">232</a>.</p> + <p><i>Alnus glutinosa</i> and <i>incana</i>, hybrids of, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Alpaca</span>, selection of, ii. <a href="#page208">208</a>.</p> + <p><i>Althæa rosea</i>, i. 378, ii. <a href="#page107">107</a>.</p> + <p><i>Amaryllis</i>, ii. <a href="#page139">139</a>.</p> + <p><i>Amaryllis vittata</i>, effect of foreign pollen on, i. 400.</p> + <p><span class="sc">Amaurosis</span>, hereditary, ii. <a href="#page9">9</a>.</p> + <p><span class="sc">America</span>, limits within which no useful plants have been furnished by, i. 310;</p> + <p class="i2">colours of feral horses in, i. 60-61;</p> + <p class="i2">North, native cultivated plants of, i. 312;</p> + <p class="i2">skin of feral pig from, i. 77;</p> + <p class="i2">South, variations in cattle of, i. 88, 92.</p> + <p><i>Amygdalus persica</i>, i. 336-344, 374.</p> +<!-- Page 434 --><span class="pagenum"><a name="page434"></a>{434}</span> + <p><span class="sc">Ammon</span>, on the persistency of colour in horses, ii. <a href="#page21">21</a>.</p> + <p><i>Anagallis arvensis</i>, ii. <a href="#page190">190</a>.</p> + <p><span class="sc">Analogous</span> variation, i. 409, ii. <a href="#page348">348</a>-<a href="#page352">352</a>;</p> + <p class="i2">in horses, i. 55;</p> + <p class="i2">in the horse and ass, i. 64;</p> + <p class="i2">in fowls, i. 243-246.</p> + <p><i>Anas boschas</i>, i. 277, ii. <a href="#page40">40</a>;</p> + <p class="i2">skull of, figured, i. 282.</p> + <p><i>Anas moschata</i>, ii. <a href="#page40">40</a>.</p> + <p>"<span class="sc">Ancon</span>" sheep of Massachusetts, i. 100, ii. <a href="#page103">103</a>.</p> + <p><span class="sc">Andalusian</span> fowls, i. 227.</p> + <p><span class="sc">Andalusian</span> rabbits, i. 105.</p> + <p><span class="sc">Anderson, J.</span>, on the origin of British sheep, i. 94;</p> + <p class="i2">on the selection of qualities in cattle, ii. <a href="#page196">196</a>;</p> + <p class="i2">on a one-eared breed of rabbits, i. 108;</p> + <p class="i2">on the inheritance of characters from a one-eared rabbit and three-legged bitch, ii. <a href="#page12">12</a>;</p> + <p class="i2">on the persistency of varieties of peas, i. 329;</p> + <p class="i2">on the production of early peas by selection, ii. <a href="#page201">201</a>;</p> + <p class="i2">on the varieties of the potato, i. 330-331;</p> + <p class="i2">on crossing varieties of the melon, i. 399;</p> + <p class="i2">on reversion in the barberry, i. 384.</p> + <p><span class="sc">Anderson</span>, Mr., on the reproduction of the weeping ash by seed, ii. <a href="#page19">19</a>;</p> + <p class="i2">on the cultivation of the tree pæony in China, ii. <a href="#page205">205</a>.</p> + <p><span class="sc">Andersson</span>, Mr., on the Damara, Bechuana, and Namaqua cattle, i. 88;</p> + <p class="i2">on the cows of the Damaras, ii. <a href="#page300">300</a>;</p> + <p class="i2">selection practised by the Damaras and Namaquas, ii. <a href="#page207">207</a>;</p> + <p class="i2">on the use of grass-seeds and the roots of reeds as food in South Africa, i. 309.</p> + <p><i>Anemone coronaria</i>, doubled by selection, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Angina</span> pectoris, hereditary, occurring at a certain age, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">Anglesea</span>, cattle of, i. 80.</p> + <p><span class="sc">Angola</span> sheep, i. 95.</p> + <p><span class="sc">Angora</span>, change in hair of animals at, ii. <a href="#page278">278</a>;</p> + <p class="i2">cats of, i. 45, 47;</p> + <p class="i2">rabbits of, i. 106, 120.</p> + <p><span class="sc">Animals</span>, domestication of, facilitated by fearlessness of man, i. 20;</p> + <p class="i2">refusal of wild, to breed in captivity, ii. <a href="#page149">149</a>;</p> + <p class="i2">compound, individual peculiarities of, reproduced by budding, i. 374;</p> + <p class="i2">variation by selection in useful qualities of, ii. <a href="#page220">220</a>.</p> + <p><span class="sc">Annual</span> plants, rarity of bud-variation in, i. 408.</p> + <p><span class="sc">Anomalies</span> in the osteology of the horse, i. 50.</p> + <p><span class="sc">Anomalous</span> breeds of pigs, i. 75;</p> + <p class="i2">of cattle, i. 89.</p> + <p><i>Anser albifrons</i>, characters of, reproduced in domestic geese, i. 288.</p> + <p><i>Anser ægyptiacus</i>, i. 282; ii. <a href="#page68">68</a>.</p> + <p><i>Anser canadensis</i>, ii. <a href="#page157">157</a>.</p> + <p><i>Anser cygnoides</i>, i. 237.</p> + <p><i>Anser ferus</i>, the original of the domestic goose, i. 287;</p> + <p class="i2">fertility of cross of, with domestic goose, i. 288.</p> + <p><span class="sc">Anson</span>, on feral fowls in the Ladrones, i. 238.</p> + <p><span class="sc">Antagonism</span> between growth and reproduction, ii. <a href="#page384">384</a>.</p> + <p><i>Anthemis nobilis</i>, bud-variation in flowers of, i. 379;</p> + <p class="i2">becomes single in poor soil, ii. <a href="#page167">167</a>.</p> + <p><span class="sc">Antherozoids</span>, apparent independence of, in algæ, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Anthers</span>, contabescence of, ii. <a href="#page165">165</a>-<a href="#page166">166</a>.</p> + <p><span class="sc">Antigua</span>, cats of, i. 46;</p> + <p class="i2">changed fleece of sheep in, i. 98.</p> + <p><i>Antirrhinum majus</i>, peloric, i. 365; ii. <a href="#page59">59</a>, <a href="#page70">70</a>, <a href="#page166">166</a>;</p> + <p class="i2">double-flowered, ii. <a href="#page167">167</a>;</p> + <p class="i2">bud-variation in, i. 381.</p> + <p><span class="sc">Ants</span>, individual recognition of, ii. <a href="#page251">251</a>.</p> + <p><span class="sc">Apes</span>, anthropomorphous, ii. <a href="#page123">123</a>.</p> + <p><span class="sc">Aphides</span>, attacking pear-trees, ii. <a href="#page231">231</a>;</p> + <p class="i2">development of, ii. <a href="#page361">361</a>-<a href="#page362">362</a>.</p> + <p><span class="sc">Apoplexy</span>, hereditary, occurring at a certain age, ii. <a href="#page78">78</a>.</p> + <p><span class="sc">Apple</span>, i. 348-350;</p> + <p class="i2">fruit of, in Swiss lake-dwellings, i. 317;</p> + <p class="i2">rendered fastigate by heat in India, i. 361;</p> + <p class="i2">bud-variation in the, i. 376;</p> + <p class="i2">with dimidiate fruit, i. 392-393;</p> + <p class="i2">with two kinds of fruit on the same branch, i. 392;</p> + <p class="i2">artificial fecundation of, i. 401;</p> + <p class="i2">St. Valéry, i. 401; ii. <a href="#page166">166</a>;</p> + <p class="i2">reversion in seedlings of, ii. <a href="#page31">31</a>;</p> + <p class="i2">crossing of varieties of, ii. <a href="#page129">129</a>;</p> + <p class="i2">growth of the, in Ceylon, ii. <a href="#page277">277</a>;</p> + <p class="i2">Winter Majetin, not attacked by <i>coccus</i>, ii. <a href="#page231">231</a>;</p> + <p class="i2">flower-buds of, attacked by bullfinches, ii. <a href="#page232">232</a>;</p> + <p class="i2">American, change of when grown in England, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Apricot</span>, i. 344-345;</p> + <p class="i2">glands on the leaves of, ii. <a href="#page231">231</a>;</p> + <p class="i2">analogous variation in the, ii. <a href="#page348">348</a>.</p> + <p><i>Aquila fusca</i>, copulating in captivity, ii. <a href="#page154">154</a>.</p> + <p><i>Aquilegia vulgaris</i>, i. 365; ii. <a href="#page330">330</a>.</p> + <p><span class="sc">Arab</span> boarhound, described by Harcourt, i. 17.</p> + <p><i>Arabis blepharophylla</i> and <i>A. Soyeri,</i> effects of crossing, i. 400.</p> + <p><i>Aralia trifoliata</i>, bud-variation in leaves of, i. 382.</p> + <p><span class="sc">Araucarias</span>, young, variable resistance of, to frost, ii. <a href="#page309">309</a>.</p> + <p><span class="sc">Archangel</span> pigeon, ii. <a href="#page240">240</a>.</p> + <p><span class="sc">Arctic</span> regions, variability of plants and shells of, ii. <a href="#page256">256</a>.</p> + <p><i>Aria vestita</i>, grafted on thorns, i. 387.</p> + <p><span class="sc">Aristophanes</span>, fowls mentioned by, i. 246.</p> + <p><span class="sc">Aristotle</span>, on solid-hoofed pigs, i. 75;</p> + <p class="i2">domestic duck unknown to, i. 277;</p> + <p class="i2">on the assumption of male characters by old hens, ii. <a href="#page51">51</a>.</p> +<!-- Page 435 --><span class="pagenum"><a name="page435"></a>{435}</span> + <p><span class="sc">Arni</span>, domestication of the, i. 82.</p> + <p><span class="sc">Arrest</span> of development, ii. <a href="#page315">315</a>-<a href="#page318">318</a>.</p> + <p><span class="sc">Arteries</span>, increase of anastomosing branches of, when tied, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Aru</span> islands, wild pig of, i. 67.</p> + <p><span class="sc">Arum</span>, Polynesian varieties of, ii. <a href="#page256">256</a>.</p> + <p><i>Ascaris</i>, number of eggs of, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Ash</span>, varieties of the, i. 360;</p> + <p class="i2">weeping, i. 361;</p> + <p class="i2">simple-leaved, i. 362;</p> + <p class="i2">bud-variation in, i. 382;</p> + <p class="i2">effects of graft upon the stock in the, i. 394;</p> + <p class="i2">production of the blotched Breadalbane, <i>ibid.</i>;</p> + <p class="i2">weeping, capricious reproduction of, by seed, ii. <a href="#page19">19</a>.</p> + <p><i>Asinus Burchellii</i>, i. 64.</p> + <p><i>Asinus hemionus</i>, ii. <a href="#page43">43</a>.</p> + <p><i>Asinus indicus</i>, ii. <a href="#page42">42</a>-<a href="#page43">43</a>, <a href="#page48">48</a>.</p> + <p><i>Asinus quagga</i>, i. 64.</p> + <p><i>Asinus tæniopus</i>, ii. <a href="#page41">41</a>;</p> + <p class="i2">the original of the domestic ass, i. 62.</p> + <p><span class="sc">Asparagus</span>, increased fertility of cultivated, ii. <a href="#page113">113</a>.</p> + <p><span class="sc">Ass</span>, early domestication of the, i. 62;</p> + <p class="i2">breeds of, <i>ibid.</i>;</p> + <p class="i2">small size of, in India, <i>ibid.</i>;</p> + <p class="i2">stripes of, i. 62-63; ii. <a href="#page351">351</a>;</p> + <p class="i2">dislike of to cross water, i. 181;</p> + <p class="i2">reversion in, ii. <a href="#page41">41</a>-<a href="#page43">43</a>, <a href="#page47">47</a>;</p> + <p class="i2">hybrid of the, with mare and zebra, ii. <a href="#page42">42</a>;</p> + <p class="i2">prepotency of the, over the horse, ii. <a href="#page67">67</a>-<a href="#page68">68</a>;</p> + <p class="i2">crossed with wild ass, ii. <a href="#page206">206</a>;</p> + <p class="i2">variation and selection of the, ii. <a href="#page236">236</a>.</p> + <p><span class="sc">Assyrian</span> sculpture of a mastiff, i. 17.</p> + <p><span class="sc">Asters</span>, ii. <a href="#page20">20</a>, <a href="#page316">316</a>.</p> + <p><span class="sc">Asthma</span>, hereditary, ii. <a href="#page8">8</a>, <a href="#page79">79</a>.</p> + <p><span class="sc">Atavism</span>. <i>See</i> Reversion.</p> + <p><span class="sc">Athelstan</span>, his care of horses, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Atkinson</span>, Mr., on the sterility of the Tarroo silk-moth in confinement, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Aubergine</span>, ii. <a href="#page91">91</a>.</p> + <p><span class="sc">Audubon</span>, on feral hybrid ducks, i. 190; ii. <a href="#page46">46</a>;</p> + <p class="i2">on the domestication of wild ducks on the Mississippi, i. 278;</p> + <p class="i2">on the wild cock turkey visiting domestic hens, i. 292;</p> + <p class="i2">fertility of <i>Fringilla ciris</i> in captivity, ii. <a href="#page154">154</a>;</p> + <p class="i2">fertility of <i>Columba migratoria</i> and <i>leucocephala</i> in captivity, ii. <a href="#page155">155</a>;</p> + <p class="i2">breeding of <i>Anser canadensis</i> in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Audubon</span> and Bachman, on the change of coat in <i>Ovis montana</i>, i. 99;</p> + <p class="i2">sterility of <i>Sciurus cinerea</i> in confinement, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Auricula</span>, effect of seasonal conditions on the, ii. <a href="#page273">273</a>;</p> + <p class="i2">blooming of, ii. <a href="#page346">346</a>.</p> + <p><span class="sc">Australia</span>, no generally useful plants derived from, i. 310;</p> + <p class="i2">useful plants of, enumerated by Hooker, i. 311.</p> + <p><span class="sc">Austria</span>, heredity of character in emperors of, ii. <a href="#page65">65</a>.</p> + <p><span class="sc">Autenrieth</span>, on persistency of colour in horses, ii. <a href="#page21">21</a>.</p> + <p><span class="sc">Ava</span>, horses of, i. 53.</p> + <p><i>Avena fatua</i>, cultivability of, i. 313.</p> + <p><span class="sc">Ayeen</span> Akbery, pigeons mentioned in the, i. 150, 155, 185, 205, 207, 208.</p> + <p><span class="sc">Ayres, W. P.</span>, on bud-variation in pelargoniums, i. 378.</p> + <p><i>Azalea indica</i>, bud-variation in, i. 377.</p> + <p><span class="sc">Azara</span>, on the feral dogs of La Plata, i. 27;</p> + <p class="i2">on the crossing of domestic with wild cats in Paraguay, i. 45;</p> + <p class="i2">on hornlike processes in horses, i. 50;</p> + <p class="i2">on curled hair in horses, i. 54; ii. <a href="#page205">205</a>, <a href="#page325">325</a>;</p> + <p class="i2">on the colours of feral horses, i. 60, 61; ii. <a href="#page259">259</a>;</p> + <p class="i2">on the cattle of Paraguay and La Plata, i. 82, 86, 89; ii. <a href="#page250">250</a>;</p> + <p class="i2">on a hornless bull, ii. <a href="#page205">205</a>;</p> + <p class="i2">on the increase of cattle in South America, ii. <a href="#page119">119</a>;</p> + <p class="i2">on the growth of horns in the hornless cattle of Corrientes, ii. <a href="#page39">39</a>;</p> + <p class="i2">on the "Niata" cattle, i. 90;</p> + <p class="i2">on naked quadrupeds, ii. <a href="#page279">279</a>;</p> + <p class="i2">on a race of black-skinned fowls in South America, i. 258; ii. <a href="#page209">209</a>;</p> + <p class="i2">on a variety of maize, i. 321.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Babington, C. C.</span>, on the origin of the plum, i. 345;</p> + <p class="i2">British species of the genus <i>Rosa</i>, i. 366;</p> + <p class="i2">distinctness of <i>Viola lutea</i> and <i>tricolor</i>, i. 368.</p> + <p><span class="sc">Bachmann</span>, Mr., on the turkey, ii. <a href="#page262">262</a>.</p> + <p class="i2"><i>See also</i> Audubon.</p> + <p><span class="sc">Badger</span>, breeding in confinement, ii. <a href="#page151">151</a>.</p> + <p>"<span class="sc">Bagadotten-Taube</span>," i. 141.</p> + <p><span class="sc">Baily</span>, Mr., on the effect of selection on fowls, ii. <a href="#page198">198</a>;</p> + <p class="i2">on Dorking fowls, ii. <a href="#page238">238</a>.</p> + <p><span class="sc">Baird, S.</span>, on the origin of the turkey, i. 292.</p> + <p><span class="sc">Baker</span>, Mr., on heredity in the horse, ii. <a href="#page11">11</a>;</p> + <p class="i2">on the degeneration of the horse by neglect, ii. <a href="#page239">239</a>;</p> + <p class="i2">orders of Henrys VII. and VIII. for the destruction of undersized mares, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Bakewell</span>, change in the sheep effected by, ii. <a href="#page198">198</a>.</p> + <p><span class="sc">Balancement</span>, ii. <a href="#page342">342</a>-<a href="#page344">344</a>;</p> + <p class="i2">of growth, law of, i. 274.</p> + <p><span class="sc">Baldhead</span>, pigeon, i. 151.</p> + <p><span class="sc">Baldness</span>, in man, inherited, ii. <a href="#page73">73</a>-<a href="#page74">74</a>;</p> + <p class="i2">with deficiency in teeth, ii. <a href="#page326">326</a>-<a href="#page327">327</a>.</p> + <p><span class="sc">Ballance</span>, Mr., on the effects of interbreeding on fowls, ii. <a href="#page125">125</a>;</p> + <p class="i2">on variation in the eggs of fowls, i. 248.</p> + <p><i>Ballota nigra</i>, transmission of variegated leaves in, i. 383.</p> + <p><span class="sc">Bamboo</span>, varieties of the, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Banana</span>, variation of the, i. 372; ii. <a href="#page256">256</a>, <a href="#page258">258</a>;</p> + <p class="i2">bud-variation in the, i. 377;</p> + <p class="i2">sterility of the, ii. <a href="#page268">268</a>.</p> + <p><span class="sc">Bantam</span> fowls, i. 230;</p> + <p class="i2">Sebright, origin of, ii. <a href="#page96">96</a>;</p> + <p class="i2">sterility of, ii. <a href="#page101">101</a>.</p> + <p><span class="sc">Barb</span> (Pigeon), i. 144-146, 210; ii. <a href="#page227">227</a>;</p> +<!-- Page 436 --><span class="pagenum"><a name="page436"></a>{436}</span> + <p class="i2">figure of, i. 145;</p> + <p class="i2">figure of lower jaw of, i. 164.</p> + <p><span class="sc">Barbs</span>, of wheat, i. 314.</p> + <p><span class="sc">Barberry</span>, dark or red-leaved variety, i. 362; ii. <a href="#page19">19</a>;</p> + <p class="i2">reversion in suckers of seedless variety, i. 384.</p> + <p><span class="sc">Barbut, J.</span>, on the dogs of Guinea, i. 25;</p> + <p class="i2">on the domestic pigeons in Guinea, i. 186;</p> + <p class="i2">fowls not native in Guinea, i. 237.</p> + <p><span class="sc">Barking</span>, acquisition of the habit of, by various dogs, i. 27.</p> + <p><span class="sc">Barley</span>, wild, i. 313;</p> + <p class="i2">of the lake-dwellings, i. 317-318;</p> + <p class="i2">ancient variety of, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Barnes</span>, Mr., production of early peas by selection, ii. <a href="#page201">201</a>.</p> + <p><span class="sc">Barnet</span>, Mr., on the intercrossing of strawberries, i. 351;</p> + <p class="i2">diœciousness of the Hautbois strawberry, i. 353;</p> + <p class="i2">on the scarlet American strawberry, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Barth</span>, Dr., use of grass-seeds as food in Central Africa, i. 308.</p> + <p><span class="sc">Bartlett, A. D.</span>, on the origin of "Himalayan" rabbits by intercrossing, i. 109;</p> + <p class="i2">on the feral rabbits of Porto Santo, i. 114;</p> + <p class="i2">on geese with reversed feathers on the head and neck, i. 288;</p> + <p class="i2">on the young of the black-shouldered peacock, i. 290;</p> + <p class="i2">on the breeding of the Felidæ in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Bartram</span>, on the black wolf-dog of Florida, i. 22.</p> + <p><span class="sc">Bates, H. W.</span>, refusal of wild animals to breed in captivity, ii. <a href="#page150">150</a>, <a href="#page152">152</a>;</p> + <p class="i2">sterility of American monkeys in captivity, ii. <a href="#page153">153</a>;</p> + <p class="i2">sterility of tamed guans, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Batrachia</span>, regeneration of lost parts in, ii. <a href="#page15">15</a>.</p> + <p><span class="sc">Beach</span>, raised, in Peru, containing heads of maize, i. 320.</p> + <p><span class="sc">Beak</span>, variability of, in fowls, i. 258;</p> + <p class="i2">individual differences of, in pigeons, i. 160;</p> + <p class="i2">correlation of, with the feet in pigeons, i. 171-174.</p> + <p><span class="sc">Beale</span>, Lionel, on the contents of cells, ii. <a href="#page370">370</a>;</p> + <p class="i2">on the multiplication of infectious atoms, ii. <a href="#page378">378</a>;</p> + <p class="i2">on the origin of fibres, ii. <a href="#page382">382</a>.</p> + <p><span class="sc">Beans</span>, i. 330;</p> + <p class="i2">of Swiss lake-dwellings, i. 319;</p> + <p class="i2">varieties of, produced by selection, ii. <a href="#page218">218</a>;</p> + <p class="i2">French and scarlet, variable resistance of to frost, ii. <a href="#page309">309</a>, <a href="#page314">314</a>;</p> + <p class="i2">superiority of native seed of, ii. <a href="#page314">314</a>;</p> + <p class="i2">a symmetrical variation of scarlet, ii. <a href="#page322">322</a>;</p> + <p class="i2">experiments on kidney, i. 330;</p> + <p class="i2">with monstrous stipules and abortive leaflets, ii. <a href="#page343">343</a>.</p> + <p><span class="sc">Beard</span>, pigeon, i. 151.</p> + <p><span class="sc">Bears</span>, breeding in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Beasley, J.</span>, reversion in crossed cattle, ii. <a href="#page41">41</a>.</p> + <p><span class="sc">Beaton, D.</span>, effect of soil upon strawberries, i. 353;</p> + <p class="i2">on varieties of pelargonium, i. 364, ii. <a href="#page274">274</a>, <a href="#page311">311</a>;</p> + <p class="i2">bud-variation in <i>Gladiolus colvillii</i>, i. 382;</p> + <p class="i2">cross between Scotch kail and cabbage, ii. <a href="#page98">98</a>;</p> + <p class="i2">hybrid gladiolus, ii. <a href="#page139">139</a>;</p> + <p class="i2">constant occurrence of new forms among seedlings, ii. <a href="#page235">235</a>;</p> + <p class="i2">on the doubling of the compositæ, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Bechuana</span> cattle, i. 88.</p> + <p><span class="sc">Beck</span>, Mr., constitutional differences in pelargoniums, i. 364.</p> + <p><span class="sc">Beckmann</span>, on changes in the odours of plants, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Beckstein</span>, on the burrowing of wolves, i. 27;</p> + <p class="i2">"Spitz" dog, i. 31;</p> + <p class="i2">origin of the Newfoundland dog, i. 42;</p> + <p class="i2">crossing of domestic and wild swine, i. 66;</p> + <p class="i2">on the Jacobin pigeon, i. 154, 209;</p> + <p class="i2">notice of swallow-pigeons, i. 156;</p> + <p class="i2">on a fork-tailed pigeon, i. 157;</p> + <p class="i2">variations in the colour of the croup in pigeons, i. 184;</p> + <p class="i2">on the German dove-cot pigeon, i. 185;</p> + <p class="i2">fertility of mongrel pigeons, i. 192;</p> + <p class="i2">on hybrid turtle-doves, i. 193;</p> + <p class="i2">on crossing the pigeon with <i>Columba œnas</i>, <i>C. palumbus</i>, <i>Turtur risoria</i>, and <i>T. vulgaris</i>, i. 193;</p> + <p class="i2">development of spurs in the silk-hen, i. 256;</p> + <p class="i2">on Polish fowls, i. 257, 264;</p> + <p class="i2">on crested birds, i. 257;</p> + <p class="i2">on the Canary-bird, i. 295, ii. <a href="#page22">22</a>, <a href="#page161">161</a>;</p> + <p class="i2">German superstition about the turkey, i. 293;</p> + <p class="i2">occurrence of horns in hornless breeds of sheep, ii. <a href="#page30">30</a>;</p> + <p class="i2">hybrids of the horse and ass, ii. <a href="#page68">68</a>;</p> + <p class="i2">crosses of tailless fowls, ii. <a href="#page92">92</a>;</p> + <p class="i2">difficulty of pairing dove-cot and fancy pigeons, ii. <a href="#page103">103</a>;</p> + <p class="i2">fertility of tame ferrets and rabbits, ii. <a href="#page112">112</a>;</p> + <p class="i2">fertility of wild sow, <i>ibid.</i>;</p> + <p class="i2">difficulty of breeding caged birds, ii. <a href="#page154">154</a>;</p> + <p class="i2">comparative fertility of <i>Psittacus erithacus</i> in captivity, ii. <a href="#page155">155</a>;</p> + <p class="i2">on changes of plumage in captivity, ii. <a href="#page158">158</a>;</p> + <p class="i2">liability of light-coloured cattle to the attacks of flies, ii. <a href="#page229">229</a>;</p> + <p class="i2">want of exercise a cause of variability, ii. <a href="#page257">257</a>;</p> + <p class="i2">effect of privation of light upon the plumage of birds, ii. <a href="#page280">280</a>;</p> + <p class="i2">on a sub-variety of the monk-pigeon, ii. <a href="#page350">350</a>.</p> + <p><span class="sc">Beddoe</span>, Dr., correlation of complexion with consumption, ii. <a href="#page335">335</a>.</p> + <p><span class="sc">Bedeguar</span> gall, ii. <a href="#page284">284</a>.</p> + <p><span class="sc">Bee</span>, persistency of character of, ii. <a href="#page236">236</a>, <a href="#page254">254</a>;</p> + <p class="i2">intercrossing, ii. <a href="#page126">126</a>;</p> + <p class="i2">conveyance, of pollen of peas by, i. 329.</p> + <p><span class="sc">Bee-Ophrys</span>, self-fertilisation of, ii. <a href="#page91">91</a>.</p> + <p><span class="sc">Beech</span>, dark-leaved, i. 362, ii. <a href="#page19">19</a>;</p> + <p class="i2">fern-leaved, reversion of, i. 382;</p> + <p class="i2">weeping, non-production of by seed, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Beechey</span>, horses of Loochoo Islands, i. 53.</p> + <p><span class="sc">Beet</span>, i. 326;</p> + <p class="i2">increase of sugar in, by selection, ii. <a href="#page201">201</a>.</p> +<!-- Page 437 --><span class="pagenum"><a name="page437"></a>{437}</span> + <p><i>Begonia frigida</i>, singular variety of, i. 365;</p> + <p class="i2">sterility of, ii. <a href="#page166">166</a>.</p> + <p><span class="sc">Belgian</span> rabbit, i. 106.</p> + <p><span class="sc">Bell, T.</span>, statement that white cattle have coloured ears, i. 85.</p> + <p><span class="sc">Bell, W.</span>, bud-variation in <i>Cistus tricuspis</i>, i. 377.</p> + <p><span class="sc">Bellingeri</span>, observations on gestation in the dog, i. 30;</p> + <p class="i2">on the fertility of dogs and cats, ii. <a href="#page112">112</a>.</p> + <p><span class="sc">Belon</span>, on high-flying pigeons in Paphlagonia, i. 209;</p> + <p class="i2">varieties of the goose, i. 289.</p> + <p><span class="sc">Benguela</span>, cattle of, i. 88.</p> + <p><span class="sc">Bennett</span>, Dr. G., pigs of the Pacific islands, i. 70, 87;</p> + <p class="i2">dogs of the Pacific islands, i. 87;</p> + <p class="i2">varieties of cultivated plants in Tahiti, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Bennett</span>, Mr., on the fallow deer, ii. <a href="#page103">103</a>.</p> + <p><span class="sc">Bentham, G.</span>, number and origin of cultivated plants, i. 306;</p> + <p class="i2">cereals all cultivated varieties, i. 312;</p> + <p class="i2">species of the orange group, i. 334-335;</p> + <p class="i2">distinctions of almond and peach, i. 338;</p> + <p class="i2">British species of <i>Rosa</i>, i. 366;</p> + <p class="i2">identity of <i>Viola lutea</i> and <i>tricolor</i>, i. 368.</p> + <p><i>Berberis vulgaris</i>, i. 384, ii. <a href="#page19">19</a>.</p> + <p><i>Berberis Wallichii</i>, indifference of, to climate, ii. <a href="#page164">164</a>.</p> + <p><span class="sc">Berjean</span>, on the history of the dog, i. 16, 18.</p> + <p><span class="sc">Berkeley, G. F.</span>, production of hen-cocks in a strain of game-fowls, i. 253.</p> + <p><span class="sc">Berkeley, M. J.</span>, crossing of varieties of the pea, i. 397;</p> + <p class="i2">effect of foreign pollen on grapes, i. 400;</p> + <p class="i2">on hybrid plants, ii. <a href="#page131">131</a>;</p> + <p class="i2">analogy between pollen of highly-cultivated plants and hybrids, ii. <a href="#page268">268</a>;</p> + <p class="i2">on Hungarian kidney-beans, ii. <a href="#page275">275</a>;</p> + <p class="i2">failure of Indian wheat in England, ii. <a href="#page307">307</a>;</p> + <p class="i2">bud developed on the petal of a <i>Clarkia</i>, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Bernard</span>, inheritance of disease in the horse, ii. <a href="#page10">10</a>.</p> + <p><span class="sc">Bernard, C.</span>, independence of the organs of the body, ii. <a href="#page368">368</a>-<a href="#page369">369</a>;</p> + <p class="i2">special affinities of the tissues, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Bernhardi</span>, varieties of plants with laciniated leaves, ii. <a href="#page348">348</a>.</p> + <p><i>Bernicla antarctica</i>, i. 288.</p> + <p><span class="sc">Bertero</span>, on feral pigeons in Juan Fernandez, i. 190.</p> + <p><i>Betula alba</i>, ii. <a href="#page18">18</a>.</p> + <p><span class="sc">Bewick</span>, on the British wild cattle, i. 84.</p> + <p><span class="sc">Bible</span>, reference to breeding studs of horses in, i. 54;</p> + <p class="i2">references to domestic pigeons in the, i. 205;</p> + <p class="i2">indications of selection of sheep in the, ii. <a href="#page201">201</a>;</p> + <p class="i2">notice of mules in the, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Bidwell</span>, Mr., on self-impotence in <i>Amaryllis</i>, ii. <a href="#page139">139</a>.</p> + <p><span class="sc">Birch</span>, weeping, i. 387, ii. <a href="#page18">18</a>.</p> + <p><span class="sc">Birch</span>, Dr. S., on the ancient domestication of the pigeon in Egypt, i. 205;</p> + <p class="i2">notice of bantam fowls in a Japanese encyclopædia, i. 230, 247.</p> + <p><span class="sc">Birch</span>, Wyrley, on silver-grey rabbits, i. 109-110.</p> + <p><span class="sc">Birds</span>, sterility caused in, by change of conditions, ii. <a href="#page153">153</a>-<a href="#page157">157</a>.</p> + <p><span class="sc">Bladder-nut</span>, tendency of the, to become double, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Blaine</span>, Mr., on wry-legged terriers, ii. <a href="#page245">245</a>.</p> + <p><span class="sc">Blainville</span>, origin and history of the dog, i. 15-16;</p> + <p class="i2">variations in the number of teeth in dogs, i. 34;</p> + <p class="i2">variations in the number of toes in dogs, i. 35;</p> + <p class="i2">on mummies of cats, i. 43;</p> + <p class="i2">on the osteology of solid-hoofed pigs, i. 75;</p> + <p class="i2">on feral Patagonian and N. American pigs, i. 77.</p> + <p>"<span class="sc">Blass-Taube</span>," i. 156.</p> + <p><span class="sc">Bleeding</span>, hereditary, ii. <a href="#page7">7</a>, <a href="#page8">8</a>;</p> + <p class="i2">sexual limitation of excessive, ii. <a href="#page73">73</a>.</p> + <p><span class="sc">Blending</span> of crossed races, time occupied by the, ii. <a href="#page87">87</a>.</p> + <p><span class="sc">Blindness</span>, hereditary, ii. <a href="#page9">9</a>;</p> + <p class="i2">at a certain age, ii. <a href="#page78">78</a>;</p> + <p class="i2">associated with colour of hair, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Bloodhounds</span>, degeneration of, caused by interbreeding, ii. <a href="#page121">121</a>.</p> + <p><span class="sc">Blumenbach</span>, on the protuberance of the skull in Polish fowls, i. 257;</p> + <p class="i2">on the effect of circumcision, ii. <a href="#page23">23</a>;</p> + <p class="i2">inheritance of a crooked finger, ii. <a href="#page23">23</a>;</p> + <p class="i2">on badger-dogs and other varieties of the dog, ii. <a href="#page220">220</a>;</p> + <p class="i2">on <i>Hydra</i>, ii. <a href="#page293">293</a>;</p> + <p class="i2">on the "nisus formativus," ii. <a href="#page294">294</a>.</p> + <p><span class="sc">Blyth, E.</span>, on the Pariah dog, i. 24;</p> + <p class="i2">hybrids of dog and jackal, i. 32;</p> + <p class="i2">early domestication of cats in India, i. 43;</p> + <p class="i2">origin of domestic cat, <i>ib.</i>;</p> + <p class="i2">crossing of domestic and wild cats, i. 44;</p> + <p class="i2">on Indian cats resembling <i>Felis chaus</i>, i. 45;</p> + <p class="i2">on striped Burmese ponies, i. 58;</p> + <p class="i2">on the stripes of the ass, i. 63;</p> + <p class="i2">on Indian wild pigs, i. 66;</p> + <p class="i2">on humped cattle, i. 79, 80;</p> + <p class="i2">occurrence of <i>Bos frontosus</i> in Irish crannoges, i. 81;</p> + <p class="i2">fertile crossing of zebus and common cattle, i. 83;</p> + <p class="i2">on the species of sheep, i. 94;</p> + <p class="i2">on the fat-tailed Indian sheep, i. 96;</p> + <p class="i2">origin of the goat, i. 101;</p> + <p class="i2">on rabbits breeding in India, i. 112;</p> + <p class="i2">number of tail-feathers in fantails, i. 146;</p> + <p class="i2">Lotan tumbler pigeons, i. 150;</p> + <p class="i2">number of tail-feathers in <i>Ectopistes</i>, i. 159;</p> + <p class="i2">on <i>Columba affinis</i>, i. 183;</p> + <p class="i2">pigeons roosting in trees, i. 181;</p> + <p class="i2">on <i>Columba leuconota</i>, i. 182;</p> + <p class="i2">on <i>Columba intermedia</i> of Strickland, i. 184;</p> + <p class="i2">variation in colour of croup in pigeons, i. 184-185, 197;</p> + <p class="i2">voluntary domestication of rock-pigeons in India, i. 185;</p> + <p class="i2">feral pigeons on the Hudson, i. 190;</p> +<!-- Page 438 --><span class="pagenum"><a name="page438"></a>{438}</span> + <p class="i2">occurrence of sub-species of pigeons, i. 204;</p> + <p class="i2">notice of pigeon-fanciers in Delhi, &c., i. 206;</p> + <p class="i2">hybrids of <i>Gallus Sonneratii</i> and the domestic hen, i. 234;</p> + <p class="i2">supposed hybridity of <i>Gallus Temminckii</i>, i. 235;</p> + <p class="i2">variations and domestication of <i>Gallus bankiva</i>, i. 235-236, 237;</p> + <p class="i2">crossing of wild and tame fowls in Burmah, i. 236;</p> + <p class="i2">restricted range of the larger gallinaceous birds, i. 237;</p> + <p class="i2">feral fowls in the Nicobar islands, i. 238;</p> + <p class="i2">black-skinned fowls occurring near Calcutta, i. 256;</p> + <p class="i2">weight of <i>Gallus bankiva</i>, i. 272;</p> + <p class="i2">degeneration of the turkey in India, i. 294, ii. <a href="#page278">278</a>;</p> + <p class="i2">on the colour of gold-fish, i. 296;</p> + <p class="i2">on the Ghor-Khur (<i>Asinus indicus</i>), ii. <a href="#page42">42</a>;</p> + <p class="i2">on <i>Asinus hemionus</i>, ii. <a href="#page43">43</a>;</p> + <p class="i2">number of eggs of <i>Gallus bankiva</i>, ii. <a href="#page112">112</a>;</p> + <p class="i2">on the breeding of birds in captivity, ii. <a href="#page157">157</a>;</p> + <p class="i2">co-existence of large and small breeds in the same country, ii. <a href="#page279">279</a>;</p> + <p class="i2">on the drooping ears of the elephant, ii. <a href="#page301">301</a>;</p> + <p class="i2">homology of leg and wing feathers, ii. <a href="#page323">323</a>.</p> + <p><span class="sc">Boethius</span> on Scotch wild cattle, i. 85.</p> + <p><span class="sc">Boitard</span> and Corbié, on the breeds of pigeons, i. 132;</p> + <p class="i2">Lille pouter pigeon, i. 138;</p> + <p class="i2">notice of a gliding pigeon, i. 156;</p> + <p class="i2">variety of the pouter pigeon, i. 162;</p> + <p class="i2">dove-cot pigeon, i. 185;</p> + <p class="i2">crossing pigeons, i. 192-193, ii. <a href="#page97">97</a>, <a href="#page126">126</a>;</p> + <p class="i2">sterility of hybrids of turtle-doves, i. 193;</p> + <p class="i2">reversion of crossed pigeons, i. 197, ii. <a href="#page40">40</a>;</p> + <p class="i2">on the fantail, i. 208, ii. <a href="#page66">66</a>;</p> + <p class="i2">on the trumpeter, ii. <a href="#page66">66</a>;</p> + <p class="i2">prepotency of transmission in silky fantail, ii. <a href="#page67">67</a>, <a href="#page69">69</a>;</p> + <p class="i2">secondary sexual characters in pigeons, ii. <a href="#page74">74</a>;</p> + <p class="i2">crossing of white and coloured turtle-doves, ii. <a href="#page92">92</a>;</p> + <p class="i2">fertility of pigeons, ii. <a href="#page112">112</a>.</p> + <p><span class="sc">Bombycidæ</span>, wingless females of, ii. <a href="#page299">299</a>.</p> + <p><i>Bombyx hesperus</i>, ii. <a href="#page304">304</a>.</p> + <p><i>Bombyx Huttoni</i>, i. 302.</p> + <p><i>Bombyx mori</i>, i. 300-304.</p> + <p><span class="sc">Bonafous</span>, on maize, i. 320, 321.</p> + <p><span class="sc">Bonaparte</span>, number of species of Columbidæ, i. 133;</p> + <p class="i2">number of tail-feathers in pigeons, i. 158;</p> + <p class="i2">size of the feet in Columbidæ, i. 174;</p> + <p class="i2">on <i>Columba guinea</i>, i. 182;</p> + <p class="i2"><i>Columba turricola</i>, <i>rupestris</i>, and <i>Schimperi</i>, i. 184.</p> + <p><i>Bonatea speciosa</i>, development of ovary of, i. 403.</p> + <p><span class="sc">Bonavia</span>, Dr., growth of cauliflowers in India, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Bones</span>, removal of portions of, ii. <a href="#page296">296</a>;</p> + <p class="i2">regeneration of, ii. <a href="#page294">294</a>;</p> + <p class="i2">growth and repair of, ii. <a href="#page381">381</a>-<a href="#page382">382</a>.</p> + <p><span class="sc">Bonnet</span>, on the salamander, ii. <a href="#page15">15</a>, <a href="#page341">341</a>, <a href="#page358">358</a>, <a href="#page385">385</a>;</p> + <p class="i2">theory of reproduction, ii. <a href="#page385">385</a>.</p> + <p><span class="sc">Borchmeyer</span>, experiments with the seeds of the weeping ash, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Borecole</span>, i. 323.</p> + <p><span class="sc">Borelli</span>, on Polish fowls, i. 247.</p> + <p><span class="sc">Borneo</span>, fowls of, with tail-bands, i. 235.</p> + <p><span class="sc">Bornet, E.</span>, condition of the ovary in hybrid <i>Cisti</i>, i. 389;</p> + <p class="i2">self-impotence of hybrid <i>Cisti</i>, ii. <a href="#page140">140</a>.</p> + <p><span class="sc">Borrow, G.</span>, on pointers, i. 42.</p> + <p><span class="sc">Bory</span> de Saint-Vincent, on gold-fish, i. 297.</p> + <p><i>Bos</i>, probable origin of European domestic cattle from three species of, i. 83.</p> + <p><i>Bos frontosus</i>, i. 79, 81-82.</p> + <p><i>Bos indicus</i>, i. 79.</p> + <p><i>Bos longifrons</i>, i. 79, 81.</p> + <p><i>Bos primigenius</i>, i. 79-81, 119.</p> + <p><i>Bos sondaicus</i>, ii. <a href="#page206">206</a>.</p> + <p><i>Bos taurus</i>, i. 79.</p> + <p><i>Bos trochoceros</i>, i. 81.</p> + <p><span class="sc">Bosc</span>, heredity in foliage-varieties of the elm, i. 362.</p> + <p><span class="sc">Bosse</span>, production of double flowers from old seed, ii. <a href="#page167">167</a>.</p> + <p><span class="sc">Bossi</span>, on breeding dark-coloured silkworms, i. 302.</p> + <p><span class="sc">Bouchardat</span>, on the vine disease, i. 334.</p> + <p><span class="sc">Boudin</span>, on local diseases, ii. <a href="#page276">276</a>;</p> + <p class="i2">resistance to cold of dark-complexioned men, ii. <a href="#page335">335</a>.</p> + <p>"<span class="sc">Boulans</span>," i. 137.</p> + <p>"<span class="sc">Bouton</span> d'Alep," ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Bowen</span>, Prof., doubts as to the importance of inheritance, ii. <a href="#page3">3</a>.</p> + <p><span class="sc">Bowman</span>, Mr., hereditary peculiarities in the human eye, ii. <a href="#page8">8</a>-<a href="#page10">10</a>;</p> + <p class="i2">hereditary cataract, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">Brace</span>, Mr., on Hungarian cattle, i. 80.</p> + <p><i>Brachycome iberidifolia</i>, ii. <a href="#page261">261</a>.</p> + <p><span class="sc">Bracts</span>, unusual development of, in gooseberries, i. 355.</p> + <p><span class="sc">Bradley</span>, Mr., effect of grafts upon the stock in the ash, i. 394;</p> + <p class="i2">effect of foreign pollen upon apples, i. 401;</p> + <p class="i2">on change of soil, ii. <a href="#page146">146</a>.</p> + <p>"<span class="sc">Brahma</span> Pootras," a new breed of fowls, i. 245.</p> + <p><span class="sc">Brain</span>, proportion of, in hares and rabbits, i. 126-129.</p> + <p><span class="sc">Brandt</span>, origin of the goat, i. 101.</p> + <p><i>Brassica</i>, varieties of, with enlarged stems, ii. <a href="#page348">348</a>.</p> + <p><i>Brassica asperifolia</i>, ii. <a href="#page343">343</a>.</p> + <p><i>Brassica napus</i>, i. 325.</p> + <p><i>Brassica oleracea</i>, i. 323.</p> + <p><i>Brassica rapa</i>, i. 325, ii. <a href="#page165">165</a>.</p> + <p><span class="sc">Braun, A.</span>, bud-variation in the vine, i. 375;</p> + <p class="i2">in the currant, i. 376;</p> + <p class="i2">in <i>Mirabilis jalapa</i>, i. 382;</p> + <p class="i2">in <i>Cytisus adami</i>, i. 388;</p> + <p class="i2">on reversion in the foliage of trees, i. 382;</p> + <p class="i2">spontaneous production of <i>Cytisus purpureo-elongatus</i>, i. 390;</p> + <p class="i2">reversion of flowers by stripes and blotches, ii. <a href="#page37">37</a>;</p> + <p class="i2">excess of nourishment a source of variability, ii. <a href="#page257">257</a>.</p> +<!-- Page 439 --><span class="pagenum"><a name="page439"></a>{439}</span> + <p><span class="sc">Brazil</span>, cattle of, i. 88.</p> + <p><span class="sc">Bread-fruit</span>, varieties of, ii. <a href="#page256">256</a>;</p> + <p class="i2">sterility and variability of, ii. <a href="#page262">262</a>.</p> + <p><span class="sc">Bree, W. T.</span>, bud-variation in <i>Geranium pratense</i> and <i>Centaurea cyanus</i>, i. 379;</p> + <p class="i2">by tubers in the dahlia, i. 385;</p> + <p class="i2">on the deafness of white cats with blue eyes, ii. <a href="#page329">329</a>.</p> + <p><span class="sc">Breeding</span>, high, dependent on inheritance, ii. <a href="#page3">3</a>-<a href="#page4">4</a>.</p> + <p><span class="sc">Breeds</span>, domestic, persistency of, ii. <a href="#page246">246</a>, <a href="#page428">428</a>-<a href="#page429">429</a>;</p> + <p class="i2">artificial and natural, ii. <a href="#page413">413</a>-<a href="#page414">414</a>;</p> + <p class="i2">extinction of, ii. <a href="#page425">425</a>;</p> + <p class="i2">of domestic cats, i. 45-47;</p> + <p class="i2">of pigs produced by crossing, i. 78;</p> + <p class="i2">of cattle, i. 86-87, 91-93;</p> + <p class="i2">of goats, i. 101.</p> + <p><span class="sc">Brehm</span>, on <i>Columba amaliæ</i>, i. 183.</p> + <p><span class="sc">Brent, B. P.</span>, number of mammæ in rabbits, i. 106;</p> + <p class="i2">habits of the tumbler pigeon, i. 151;</p> + <p class="i2">Laugher pigeon, i. 155;</p> + <p class="i2">colouring of the kite tumbler, i. 160;</p> + <p class="i2">crossing of the pigeon with <i>Columba œnas</i>, i. 193;</p> + <p class="i2">mongrels of the trumpeter pigeon, ii. <a href="#page66">66</a>;</p> + <p class="i2">close interbreeding of pigeons, ii. <a href="#page126">126</a>;</p> + <p class="i2">opinion on Aldrovandi's fowls, i. 247;</p> + <p class="i2">on stripes in chickens, i. 249-250;</p> + <p class="i2">on the combs of fowls, i. 253;</p> + <p class="i2">double-spurred Dorking fowls, i. 255;</p> + <p class="i2">effect of crossing on colour of plumage in fowls, i. 258;</p> + <p class="i2">incubatory instinct of mongrels between non-sitting varieties of fowls, ii. <a href="#page44">44</a>;</p> + <p class="i2">origin of the domestic duck, i. 277;</p> + <p class="i2">fertility of the hook-billed duck, <i>ibid.</i>;</p> + <p class="i2">occurrence of the plumage of the wild duck in domestic breeds, i. 280;</p> + <p class="i2">voice of ducks, i. 281;</p> + <p class="i2">occurrence of a short upper mandible in crosses of hook-billed and common ducks, i. 281;</p> + <p class="i2">reversion in ducks produced by crossing, ii. <a href="#page40">40</a>;</p> + <p class="i2">variation of the canary-bird, i. 295;</p> + <p class="i2">fashion in the canary, ii. <a href="#page240">240</a>;</p> + <p class="i2">hybrids of canary and finches, ii. <a href="#page45">45</a>.</p> + <p><span class="sc">Brickell</span>, on raising nectarines from seed, i. 340;</p> + <p class="i2">on the horses of North Carolina, ii. <a href="#page300">300</a>.</p> + <p><span class="sc">Bridges</span>, Mr., on the dogs of Tierra del Fuego, i. 39;</p> + <p class="i2">on the selection of dogs by the Fuegians, ii. <a href="#page207">207</a>.</p> + <p><span class="sc">Bridgman, W. K.</span>, reproduction of abnormal ferns, i. 383, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Briggs, J. J.</span>, regeneration of portions of the fins of fishes, ii. <a href="#page15">15</a>.</p> + <p><span class="sc">Broca, P.</span>, on the intercrossing of dogs, i. 31-32;</p> + <p class="i2">on hybrids of hare and rabbit, i. 105;</p> + <p class="i2">on the rumpless fowl, i. 259;</p> + <p class="i2">on the character of half-castes, ii. <a href="#page47">47</a>;</p> + <p class="i2">degree of fertility of mongrels, ii. <a href="#page100">100</a>;</p> + <p class="i2">sterility of descendants of wild animals bred in captivity, ii. <a href="#page160">160</a>.</p> + <p><span class="sc">Broccoli</span>, i. 323;</p> + <p class="i2">rudimentary flowers in, ii. <a href="#page316">316</a>;</p> + <p class="i2">tenderness of, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Bromehead, W.</span>, doubling of the Canterbury bell by selection, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Bromfield</span>, Dr., sterility of the ivy and <i>Acorus calamus</i>, ii. <a href="#page170">170</a>.</p> + <p><i>Bromus secalinus</i>, i. 314.</p> + <p><span class="sc">Bronn, H. G.</span>, bud-variation in <i>Anthemis</i>, i. 379;</p> + <p class="i2">effects of cross-breeding on the female, i. 404;</p> + <p class="i2">on heredity in a one-horned cow, ii. <a href="#page12">12</a>, <a href="#page13">13</a>;</p> + <p class="i2">propagation of a pendulous peach by seed, ii. <a href="#page18">18</a>;</p> + <p class="i2">absorption of the minority in crossed races, ii. <a href="#page88">88</a>;</p> + <p class="i2">on the crossing of horses, ii. <a href="#page92">92</a>;</p> + <p class="i2">fertility of tame rabbits and sheep, ii. <a href="#page112">112</a>;</p> + <p class="i2">changes of plumage in captivity, ii. <a href="#page158">158</a>;</p> + <p class="i2">on the dahlia, ii. <a href="#page261">261</a>.</p> + <p><span class="sc">Bronze</span> period, dog of, i. 18.</p> + <p><span class="sc">Brown, G.</span>, variations in the dentition of the horse, i. 50.</p> + <p><span class="sc">Brown-Séquard</span>, Dr., inheritance of artificially-produced epilepsy in the guinea-pig, ii. <a href="#page24">24</a>.</p> + <p><i>Brunswigia</i>, ii. <a href="#page139">139</a>.</p> + <p><span class="sc">Brussels</span> Sprouts, i. 323, ii. <a href="#page429">429</a>.</p> + <p><i>Bubo maximus</i>, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Buckland, F.</span>, on oysters, ii. <a href="#page280">280</a>;</p> + <p class="i2">number of eggs in a codfish, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Buckle</span>, Mr., doubts as to the importance of inheritance, ii. <a href="#page3">3</a>.</p> + <p><span class="sc">Buckley</span>, Miss, carrier-pigeons roosting in trees, i. 181.</p> + <p><span class="sc">Buckman</span>, Prof., cultivation of <i>Avena fatua</i>, i. 313;</p> + <p class="i2">cultivation of the wild parsnip, i. 326, ii. <a href="#page201">201</a>, <a href="#page277">277</a>;</p> + <p class="i2">reversion in the parsnip, ii. <a href="#page31">31</a>.</p> + <p><span class="sc">Buckwheat</span>, injurious to white pigs, when in flower, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Bud</span> and seed, close analogy of, i. 411.</p> + <p><span class="sc">Bud-reversion</span>, ii. <a href="#page37">37</a>.</p> + <p><span class="sc">Buds</span>, adventitious, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Bud-variation</span>, i. 373-411, ii. <a href="#page254">254</a>, <a href="#page287">287</a>-<a href="#page288">288</a>, <a href="#page291">291</a>;</p> + <p class="i2">contrasted with seminal reproduction, i. 373;</p> + <p class="i2">peculiar to plants, i. 374;</p> + <p class="i2">in the peach, i. 340, 374;</p> + <p class="i2">in plums, i. 375;</p> + <p class="i2">in the cherry, <i>ibid.</i>;</p> + <p class="i2">in grapes, <i>ibid.</i>;</p> + <p class="i2">in the gooseberry, currant, pear, and apple, i. 376;</p> + <p class="i2">in the banana, camellia, hawthorn, <i>Azalea indica</i>, and <i>Cistus tricuspis</i>, i. 377;</p> + <p class="i2">in the hollyhock and pelargonium, i. 378;</p> + <p class="i2">in <i>Geranium pratense</i> and the chrysanthemum, i. 379;</p> + <p class="i2">in roses, i. 367, 379-381;</p> + <p class="i2">in sweet williams, carnations, pinks, stocks, and snapdragons, i. 381;</p> + <p class="i2">in wall-flowers, cyclamen, <i>Œnothera biennis</i>, <i>Gladiolus colvillii</i>, fuchsias, and <i>Mirabilis jalapa</i>, i. 382;</p> + <p class="i2">in foliage of various trees, i. 382-384;</p> + <p class="i2">in cryptogamic plants, i. 383;</p> + <p class="i2">by suckers in <i>Phlox</i> and barberry, i. 384;</p> + <p class="i2">by tubers in the potato, <i>ibid.</i>;</p> + <p class="i2">in the dahlia, i. 385;</p> + <p class="i2">by bulbs in hyacinths, <i>Imatophyllum miniatum</i>, and tulips, i. 385;</p> + <p class="i2">in <i>Tigridia conchiflora</i>, i. 386;</p> +<!-- Page 440 --><span class="pagenum"><a name="page440"></a>{440}</span> + <p class="i2">in <i>Hemerocallis</i>, <i>ibid.</i>;</p> + <p class="i2">doubtful cases, i. 386-387;</p> + <p class="i2">in <i>Cytisus Adami</i>, i. 387-394;</p> + <p class="i2">probable in <i>Æsculus rubicunda</i>, i. 392;</p> + <p class="i2">summary of observations on, 406.</p> + <p><span class="sc">Buffon</span>, on crossing the wolf and dog, i. 32;</p> + <p class="i2">increase of fertility by domestication, ii. <a href="#page111">111</a>;</p> + <p class="i2">improvement of plants by unconscious selection, ii. <a href="#page216">216</a>;</p> + <p class="i2">theory of reproduction, ii. <a href="#page375">375</a>.</p> + <p><i>Bulimus</i>, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Bull</span>, apparent influence of, on offspring, ii. <a href="#page68">68</a>.</p> + <p><span class="sc">Bullace</span>, i. 345.</p> + <p><span class="sc">Bulldog</span>, recent modifications of, i. 42.</p> + <p><span class="sc">Bullfinch</span>, breeding in captivity, ii. <a href="#page154">154</a>;</p> + <p class="i2">attacking flower-buds, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Bult</span>, Mr., selection of pouter pigeons, ii. <a href="#page197">197</a>.</p> + <p>"<span class="sc">Bündtnerschwein</span>," i. 67.</p> + <p><span class="sc">Bunting</span>, reed, in captivity, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Burdach</span>, crossing of domestic and wild animals, i. 66;</p> + <p class="i2">aversion of the wild boar to barley, ii. <a href="#page303">303</a>.</p> + <p><span class="sc">Burke</span>, Mr., inheritance in the horse, ii. <a href="#page10">10</a>.</p> + <p><i>Burlingtonia</i>, ii. <a href="#page135">135</a>.</p> + <p><span class="sc">Burmah</span>, cats of, i. 47.</p> + <p><span class="sc">Burmese</span> ponies, striped, i. 58, 59.</p> + <p><span class="sc">Burnes</span>, Sir A., on the Karakool sheep, i. 98, ii. <a href="#page278">278</a>;</p> + <p class="i2">varieties of the vine in Cabool, i. 333;</p> + <p class="i2">hawks, trained in Scinde, ii. <a href="#page153">153</a>;</p> + <p class="i2">pomegranates producing seed, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Burton</span> Constable, wild cattle at, i. 84.</p> + <p>"<span class="sc">Burzel-Tauben</span>," i. 150.</p> + <p><span class="sc">Bussorah</span> carrier, i. 141.</p> + <p><i>Buteo vulgaris</i>, copulation of, in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Butterflies</span>, polymorphic, ii. <a href="#page399">399</a>-<a href="#page400">400</a>.</p> + <p><span class="sc">Buzareingues</span>, Girou de, inheritance of tricks, ii. <a href="#page6">6</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Cabanis</span>, pears grafted on the quince, ii. <a href="#page239">239</a>.</p> + <p><span class="sc">Cabbage</span>, i. 323-326;</p> + <p class="i2">varieties of, i. 323;</p> + <p class="i2">unity of character in flowers and seeds of, i. 323-324;</p> + <p class="i2">cultivated by ancient Celts, i. 324;</p> + <p class="i2">classification of varieties of, <i>ibid.</i>;</p> + <p class="i2">ready crossing of, <i>ibid.</i>, ii. <a href="#page90">90</a>, <a href="#page91">91</a>, <a href="#page98">98</a>, <a href="#page130">130</a>;</p> + <p class="i2">origin of, i. 325;</p> + <p class="i2">increased fertility of, when cultivated, ii. <a href="#page113">113</a>;</p> + <p class="i2">growth of, in tropical countries, ii. <a href="#page277">277</a>.</p> + <p><span class="sc">Cabool</span>, vines of, i. 333.</p> + <p><span class="sc">Cabral</span>, on early cultivation in Brazil, i. 311.</p> + <p><span class="sc">Cactus</span>, growth of cochineal on, in India, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Cæsar</span>, <i>Bos primigenius</i> wild in Europe in the time of, i. 81;</p> + <p class="i2">notice of fowls in Britain, i. 246;</p> + <p class="i2">notice of the importation of horses by the Celts, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Caffre</span> fowls, i. 230.</p> + <p><span class="sc">Caffres</span>, different kinds of cattle possessed by the, i. 88.</p> + <p>"<span class="sc">Cágias</span>," a breed of sheep, i. 95.</p> + <p><span class="sc">Calceolarias</span>, i. 364; ii. <a href="#page147">147</a>;</p> + <p class="i2">effects of seasonal conditions on, ii. <a href="#page274">274</a>;</p> + <p class="i2">peloric flowers in, ii. <a href="#page346">346</a>.</p> + <p>"<span class="sc">Calongos</span>," a Columbian breed of cattle, i. 88.</p> + <p><span class="sc">Calver</span>, Mr., on a seedling peach producing both peaches and nectarines, i. 341.</p> + <p><span class="sc">Calyx</span>, segments of the, converted into carpels, ii. <a href="#page392">392</a>.</p> + <p><span class="sc">Camel</span>, its dislike to crossing water, i. 181.</p> + <p><i>Camellia</i>, bud-variations in, i. 377;</p> + <p class="i2">recognition of varieties of, ii. <a href="#page251">251</a>;</p> + <p class="i2">variety in, hardiness of, ii. <a href="#page308">308</a>.</p> + <p><span class="sc">Cameron, D.</span>, on the cultivation of Alpine plants, ii. <a href="#page163">163</a>.</p> + <p><span class="sc">Cameronn</span>, Baron, value of English blood in race-horses, ii. <a href="#page11">11</a>.</p> + <p><i>Campanula medium</i>, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Canary-bird</span>, i. 295;</p> + <p class="i2">conditions of inheritance in, ii. <a href="#page22">22</a>;</p> + <p class="i2">hybrids of, ii. <a href="#page45">45</a>;</p> + <p class="i2">period of perfect plumage in, ii. <a href="#page77">77</a>;</p> + <p class="i2">diminished fertility of, ii. <a href="#page161">161</a>;</p> + <p class="i2">standard of perfection in, ii. <a href="#page195">195</a>;</p> + <p class="i2">analogous variation in, ii. <a href="#page349">349</a>.</p> + <p><span class="sc">Cancer</span>, heredity of, ii. <a href="#page7">7</a>, <a href="#page8">8</a>, <a href="#page79">79</a>.</p> + <p><span class="sc">Canine</span> teeth, development of the, in mares, ii. <a href="#page318">318</a>.</p> + <p><i>Canis alopex</i>, i. 29.</p> + <p><i>Canis antarcticus</i>, i. 20.</p> + <p><i>Canis argentatus</i>, ii. <a href="#page151">151</a>.</p> + <p><i>Canis aureus</i>, i. 29.</p> + <p><i>Canis cancrivorus</i>, domesticated and crossed in Guiana, i. 23.</p> + <p><i>Canis cinereo-variegatus</i>, i. 29.</p> + <p><i>Canis fulvus</i>, i. 29.</p> + <p><i>Canis Ingæ</i>, the naked Peruvian dog, i. 23.</p> + <p><i>Canis latrans</i>, resemblance of, to the Hare Indian dog, i. 22;</p> + <p class="i2">one of the original stocks, i. 26.</p> + <p><i>Canis lupaster</i>, i. 25.</p> + <p><i>Canis lupus</i>, var. <i>occidentalis</i>, resemblance of, to North American dogs, i. 21;</p> + <p class="i2">crossed with dogs, i. 22;</p> + <p class="i2">one of the original stocks, i. 26.</p> + <p><i>Canis mesomelas</i>, i. 25, 29.</p> + <p><i>Canis primævus</i>, tamed by Mr. Hodgson, i. 26.</p> + <p><i>Canis sabbar</i>, i. 25.</p> + <p><i>Canis simensis</i>, possible original of greyhounds, i. 33.</p> + <p><i>Canis thaleb</i>, i. 29.</p> + <p><i>Canis variegatus</i>, i. 29.</p> + <p><span class="sc">Canterbury</span> Bell, doubled by selection, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Cape</span> of Good Hope, different kinds of cattle at the, i. 88;</p> +<!-- Page 441 --><span class="pagenum"><a name="page441"></a>{441}</span> + <p class="i2">no useful plants derived from the, i. 310.</p> + <p><span class="sc">Capercailzie</span>, breeding in captivity, ii. <a href="#page156">156</a>.</p> + <p><i>Capra ægagrus</i> and <i>C. Falconeri</i>, probable parents of domestic goat, i. 101.</p> + <p><span class="sc">Capsicum</span>, i. 371.</p> + <p><span class="sc">Cardan</span>, on a variety of the walnut, i. 356;</p> + <p class="i2">on grafted walnuts, ii. <a href="#page259">259</a>-<a href="#page260">260</a>.</p> + <p><span class="sc">Cardoon</span>, ii. <a href="#page34">34</a>.</p> + <p><i>Carex rigida</i>, local sterility of the, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Carlier</span>, early selection of sheep, ii. <a href="#page204">204</a>.</p> + <p><span class="sc">Carlisle</span>, Sir A., inheritance of peculiarities, ii. <a href="#page6">6</a>, <a href="#page8">8</a>;</p> + <p class="i2">of polydactylism, ii. <a href="#page13">13</a>.</p> + <p>"<span class="sc">Carme</span>" pigeon, i. 156.</p> + <p><span class="sc">Carnation</span>, bud-variation in, i. 381;</p> + <p class="i2">variability of, i. 370;</p> + <p class="i2">striped, produced by crossing red and white, i. 393;</p> + <p class="i2">effect of conditions of life on the, ii. <a href="#page273">273</a>.</p> + <p><span class="sc">Carnivora</span>, general fertility of, in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Caroline</span> Archipelago, cats of, i. 47.</p> + <p><span class="sc">Carp</span>, ii. <a href="#page236">236</a>.</p> + <p><span class="sc">Carpels</span>, variation of, in cultivated cucurbitaceæ, i. 359.</p> + <p><span class="sc">Carpenter, W. B.</span>, regeneration of bone, ii. <a href="#page294">294</a>;</p> + <p class="i2">production of double monsters, ii. <a href="#page340">340</a>;</p> + <p class="i2">number of eggs in an <i>Ascaris</i>, ii. <a href="#page379">379</a>.</p> + <p><i>Carpinus betulus</i>, i. 362.</p> + <p><i>Carpophaga littoralis</i> and <i>luctuosa</i>, i. 182.</p> + <p><span class="sc">Carrier</span> pigeon, i. 139-142;</p> + <p class="i2">English, i. 139-141;</p> + <p class="i2">figured, i. 140;</p> + <p class="i2">skull figured, i. 163;</p> + <p class="i2">history of the, i. 211;</p> + <p class="i2">Persian, i. 141;</p> + <p class="i2">Bussorah, <i>ibid.</i>;</p> + <p class="i2">Bagadotten, skull figured, i. 163;</p> + <p class="i2">lower jaw figured, i. 165.</p> + <p><span class="sc">Carrière</span>, cultivation of the wild carrot, i. 326;</p> + <p class="i2">intermediate form between the almond and the peach, i. 338;</p> + <p class="i2">glands of peach-leaves, i. 343;</p> + <p class="i2">bud-variation in the vine, i. 375;</p> + <p class="i2">grafts of <i>Aria vestita</i> upon thorns, i. 387;</p> + <p class="i2">variability of hybrids of <i>Erythrina</i>, ii. <a href="#page265">265</a>.</p> + <p><span class="sc">Carrot</span>, wild, effects of cultivation on the, i. 326;</p> + <p class="i2">reversion in the, ii. <a href="#page31">31</a>;</p> + <p class="i2">run wild, ii. <a href="#page33">33</a>;</p> + <p class="i2">increased fertility of cultivated, ii. <a href="#page113">113</a>;</p> + <p class="i2">experiments on the, ii. <a href="#page277">277</a>;</p> + <p class="i2">acclimatisation of the, in India, ii. <a href="#page311">311</a>.</p> + <p><i>Carthamus</i>, abortion of the pappus in, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Cartier</span>, cultivation of native plants in Canada, i. 312.</p> + <p><span class="sc">Caryophyllaceæ</span>, frequency of contabescence in the, ii. <a href="#page165">165</a>.</p> + <p><span class="sc">Caspary</span>, bud-variation in the moss-rose, i. 380;</p> + <p class="i2">on the ovules and pollen of <i>Cytisus</i>, i. 388-389;</p> + <p class="i2">crossing of <i>Cytisus purpureus</i> and <i>C. laburnum</i>, i. 389;</p> + <p class="i2">trifacial orange, i. 391;</p> + <p class="i2">differently-coloured flowers in the wild <i>Viola lutea,</i> i. 408;</p> + <p class="i2">sterility of the horse-radish, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Castelnau</span>, on Brazilian cattle, i. 88.</p> + <p><span class="sc">Castration</span>, assumption of female characters caused by, ii. <a href="#page51">51</a>-<a href="#page52">52</a>.</p> + <p><i>Casuarius bennettii</i>, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Cat</span>, domestic, i. 43-48;</p> + <p class="i2">early domestication and probable origin of the, i. 43-44;</p> + <p class="i2">intercrossing of with wild species, i. 44-45;</p> + <p class="i2">variations of, i. 45-48;</p> + <p class="i2">feral, i. 47, ii. <a href="#page33">33</a>;</p> + <p class="i2">anomalous, i. 48;</p> + <p class="i2">polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">black, indications of stripes in young, ii. <a href="#page55">55</a>;</p> + <p class="i2">tortoiseshell, ii. <a href="#page73">73</a>;</p> + <p class="i2">effects of crossing in, ii. <a href="#page86">86</a>;</p> + <p class="i2">fertility of, ii. <a href="#page111">111</a>;</p> + <p class="i2">difficulty of selection in, ii. <a href="#page234">234</a>, <a href="#page236">236</a>;</p> + <p class="i2">length of intestines in, ii. <a href="#page302">302</a>;</p> + <p class="i2">white with blue eyes, deafness of, ii. <a href="#page329">329</a>;</p> + <p class="i2">with tufted ears, ii. <a href="#page350">350</a>.</p> + <p><span class="sc">Cataract</span>, hereditary, ii. <a href="#page9">9</a>, <a href="#page79">79</a>.</p> + <p><span class="sc">Caterpillars</span>, effect of changed food on, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Catlin, G.</span>, colour of feral horses in North America, i. 61.</p> + <p><span class="sc">Cattle</span>, European, their probable origin from three original species, i. 79-82;</p> + <p class="i2">humped, or Zebus, i. 79-80;</p> + <p class="i2">intercrossing of, i. 83, 91-93;</p> + <p class="i2">wild, of Chillingham, Hamilton, Chartley, Burton Constable, and Gisburne, i. 84, ii. <a href="#page119">119</a>;</p> + <p class="i2">colour of feral, i. 84-85, ii. <a href="#page102">102</a>;</p> + <p class="i2">British breeds of, i. 86-87;</p> + <p class="i2">South African breeds of, i. 88;</p> + <p class="i2">South American breeds of, i. 89, ii. <a href="#page205">205</a>;</p> + <p class="i2">Niata, i. 89-91, ii. <a href="#page205">205</a>, <a href="#page208">208</a>, <a href="#page332">332</a>;</p> + <p class="i2">effects of food and climate on, i. 91-92;</p> + <p class="i2">effects of selection on, i. 92-93;</p> + <p class="i2">Dutch-buttocked, ii. <a href="#page8">8</a>;</p> + <p class="i2">hornless, production of horns in, ii. <a href="#page29">29</a>-<a href="#page30">30</a>, <a href="#page39">39</a>;</p> + <p class="i2">reversion in, when crossed, ii. <a href="#page41">41</a>;</p> + <p class="i2">wildness of hybrid, ii. <a href="#page45">45</a>;</p> + <p class="i2">short-horned, prepotency of, ii. <a href="#page65">65</a>;</p> + <p class="i2">wild, influence of crossing and segregation on, ii. <a href="#page86">86</a>;</p> + <p class="i2">crosses of, ii. <a href="#page96">96</a>, <a href="#page104">104</a>, <a href="#page118">118</a>;</p> + <p class="i2">of Falkland islands, ii. <a href="#page102">102</a>;</p> + <p class="i2">mutual fertility of all varieties of, ii. <a href="#page110">110</a>;</p> + <p class="i2">effects of interbreeding on, ii. <a href="#page117">117</a>-<a href="#page119">119</a>;</p> + <p class="i2">effects of careful selection on, ii. <a href="#page194">194</a>, <a href="#page199">199</a>;</p> + <p class="i2">naked, of Columbia, ii. <a href="#page205">205</a>;</p> + <p class="i2">crossed with wild banteng in Java, ii. <a href="#page206">206</a>;</p> + <p class="i2">with reversed hair in Banda Oriental, ii. <a href="#page205">205</a>;</p> + <p class="i2">selection of trifling characters in, ii. <a href="#page209">209</a>;</p> + <p class="i2">fashion in, ii. <a href="#page210">210</a>;</p> + <p class="i2">similarity of best races of, ii. <a href="#page241">241</a>;</p> + <p class="i2">unconscious selection in, ii. <a href="#page214">214</a>;</p> + <p class="i2">effects of natural selection on anomalous breeds of, ii. <a href="#page226">226</a>-<a href="#page227">227</a>;</p> + <p class="i2">light-coloured, attacked by flies, ii. <a href="#page229">229</a>, <a href="#page336">336</a>;</p> + <p class="i2">Jersey, rapid improvement of, ii. <a href="#page234">234</a>;</p> + <p class="i2">effects of disuse of parts in, ii. <a href="#page299">299</a>;</p> + <p class="i2">rudimentary horns in, ii. <a href="#page315">315</a>;</p> + <p class="i2">supposed influence of humidity on the hair of, ii. <a href="#page326">326</a>;</p> +<!-- Page 442 --><span class="pagenum"><a name="page442"></a>{442}</span> + <p class="i2">white spots of, liable to disease, ii. <a href="#page337">337</a>;</p> + <p class="i2">supposed analogous variation in, ii. <a href="#page349">349</a>;</p> + <p class="i2">displacement of long-horned by short-horned, ii. <a href="#page426">426</a>.</p> + <p><span class="sc">Cauliflower</span>, i. 323;</p> + <p class="i2">free-seeding of, in India, ii. <a href="#page310">310</a>;</p> + <p class="i2">rudimentary flowers in, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Cavalier</span> pigeon, ii. <a href="#page97">97</a>.</p> + <p><i>Cavia aperea</i>, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Cay</span> (<i>Cebus azaræ</i>), sterility of, in confinement, ii. <a href="#page153">153</a>.</p> + <p><i>Cebus azaræ</i>, ii. <a href="#page153">153</a>.</p> + <p><i>Cecidomyia</i>, larval development of, ii. <a href="#page283">283</a>, <a href="#page360">360</a>, <a href="#page367">367</a>;</p> + <p class="i2">and <i>Misocampus</i>, i. 5.</p> + <p><span class="sc">Cedars</span> of Lebanon and Atlas, i. 364.</p> + <p><span class="sc">Celery</span>, turnip-rooted, i. 336;</p> + <p class="i2">run wild, ii. <a href="#page33">33</a>.</p> + <p><span class="sc">Cell-theory</span>, ii. <a href="#page370">370</a>.</p> + <p><i>Celosia cristata</i>, i. 365.</p> + <p><span class="sc">Celsus</span>, on the selection of seed-corn, i. 318, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Celts</span>, early cultivation of the cabbage by the, i. 324;</p> + <p class="i2">selection of cattle and horses by the, ii. <a href="#page202">202</a>-<a href="#page203">203</a>.</p> + <p><i>Cenchrus</i>, seeds of a, used as food, i. 309.</p> + <p><i>Centaurea cyanus</i>, bud-variation in, i. 379.</p> + <p><span class="sc">Cephalopoda</span>, spermatophores of, ii. <a href="#page383">383</a>.</p> + <p><i>Cerasus padus</i>, yellow-fruited, ii. <a href="#page19">19</a>.</p> + <p><i>Cercoleptes</i>, sterility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><i>Cercopithecus</i>, breeding of a species of, in captivity, ii. <a href="#page153">153</a>.</p> + <p><span class="sc">Cereals</span>, i. 312-313;</p> + <p class="i2">of the Neolithic period in Switzerland, i. 317;</p> + <p class="i2">adaptation of, to soils, ii. <a href="#page305">305</a>.</p> + <p><i>Cereus</i>, ii. <a href="#page38">38</a>.</p> + <p><i>Cereus speciosissimus</i> and <i>phyllanthus</i>, reversion in hybrids of, i. 392.</p> + <p><i>Cervus canadensis</i>, ii. <a href="#page158">158</a>.</p> + <p><i>Cervus dama</i>, ii. <a href="#page120">120</a>.</p> + <p><span class="sc">Cetacea</span>, correlation of dermal system and teeth in the, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Ceylon</span>, cats of, i. 46;</p> + <p class="i2">pigeon-fancying in, i. 206.</p> + <p><i>Chamærops humilis</i>, crossed with date palm, i. 399.</p> + <p><span class="sc">Chamisso</span>, on seeding bread-fruit, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Channel</span> islands, breeds of cattle in, i. 80.</p> + <p><span class="sc">Chapman</span>, Professor, peach-trees producing nectarines, i. 341.</p> + <p><span class="sc">Chapuis, F.</span>, sexual peculiarities in pigeons, i. 162, ii. <a href="#page74">74</a>;</p> + <p class="i2">effect produced by first male upon the subsequent progeny of the female, i. 405;</p> + <p class="i2">sterility of the union of some pigeons, ii. <a href="#page162">162</a>.</p> + <p><span class="sc">Characters</span>, fixity of, ii. <a href="#page239">239</a>;</p> + <p class="i2">latent, ii. <a href="#page51">51</a>-<a href="#page56">56</a>, <a href="#page399">399</a>-<a href="#page400">400</a>;</p> + <p class="i2">continued divergence of, ii. <a href="#page241">241</a>;</p> + <p class="i2">antagonistic, ii. <a href="#page401">401</a>.</p> + <p><span class="sc">Chardin</span>, abundance of pigeons in Persia, i. 205.</p> + <p><span class="sc">Charlemagne</span>, orders as to the selection of stallions, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Chartley</span>, wild cattle of, i. 84.</p> + <p><span class="sc">Chaté</span>, reversion of the upper seeds in the pods of stocks, ii. <a href="#page347">347</a>-<a href="#page348">348</a>.</p> + <p><span class="sc">Chatin</span>, on <i>Ranunculus ficaria</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Chaundy</span>, Mr., crossed varieties of cabbage, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Cheetah</span>, general sterility of, in captivity, ii. <a href="#page151">151</a>.</p> + <p><i>Cheiranthus cheiri</i>, i. 382.</p> + <p><span class="sc">Cherries</span>, i. 347-348;</p> + <p class="i2">bud-variation in, i. 375;</p> + <p class="i2">white Tartarian, ii. <a href="#page230">230</a>;</p> + <p class="i2">variety of, with curled petals, ii. <a href="#page232">232</a>;</p> + <p class="i2">period of vegetation of, changed by forcing, ii. <a href="#page311">311</a>.</p> + <p><span class="sc">Chevreul</span>, on crossing fruit-trees, ii. <a href="#page129">129</a>.</p> + <p><span class="sc">Chickens</span>, differences in characters of, i. 249-250;</p> + <p class="i2">white, liable to gapes, ii. <a href="#page228">228</a>, <a href="#page336">336</a>.</p> + <p><span class="sc">Chigoe</span>, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Chile</span>, sheep of, i. 95.</p> + <p><span class="sc">Chillingham</span> cattle, identical with <i>Bos primigenius</i>, i. 81;</p> + <p class="i2">characters of, i. 83-84.</p> + <p><span class="sc">Chiloe</span>, half-castes of, ii. <a href="#page46">46</a>.</p> + <p><span class="sc">China</span>, cats of, with drooping ears, i. 47;</p> + <p class="i2">horses of, i. 53;</p> + <p class="i2">striped ponies of, i. 59;</p> + <p class="i2">asses of, i. 62;</p> + <p class="i2">notice of rabbits in, by Confucius, i. 103;</p> + <p class="i2">breeds of pigeons reared in, i. 206;</p> + <p class="i2">breeds of fowls of, in fifteenth century, i. 232, 247;</p> + <p class="i2">goose of, i. 237.</p> + <p><span class="sc">Chinchilla</span>, fertility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Chinese</span>, selection practised by the, ii. <a href="#page204">204</a>-<a href="#page205">205</a>;</p> + <p class="i2">preference of the, for hornless rams, ii. <a href="#page209">209</a>;</p> + <p class="i2">recognition of the value of native breeds by the, ii. <a href="#page313">313</a>.</p> + <p><span class="sc">Chinese</span>, or Himalayan rabbit, i. 108.</p> + <p>"<span class="sc">Chivos</span>," a breed of cattle in Paraguay, i. 89.</p> + <p><span class="sc">Choux-raves</span>, i. 323.</p> + <p><span class="sc">Christ, H.</span>, on the plants of the Swiss Lake-dwellings, i. 309, 318;</p> + <p class="i2">intermediate forms between <i>Pinus sylvestris</i> and <i>montana</i>, i. 363.</p> + <p><span class="sc">Chrysanthemum</span>, i. 379.</p> + <p><i>Chrysotis festiva</i>, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Cineraria</span>, effects of selection on the, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Circassia</span>, horses of, ii. <a href="#page102">102</a>.</p> + <p><span class="sc">Circumcision</span>, ii. <a href="#page23">23</a>.</p> + <p><span class="sc">Cirripedes</span>, metagenesis in, ii. <a href="#page366">366</a>.</p> + <p><i>Cistus</i>, intercrossing and hybrids of, i. 336, 389, ii. <a href="#page140">140</a>.</p> + <p><i>Cistus tricuspis</i>, bud-variation in, i. 377.</p> + <p><span class="sc">Citrons</span>, i. 334-335.</p> + <p>"<i>Citrus aurantium fructu variabili</i>," i. 336.</p> + <p><i>Citrus decumana</i>, i. 335.</p> + <p><i>Citrus lemonum</i>, i. 336.</p> +<!-- Page 443 --><span class="pagenum"><a name="page443"></a>{443}</span> + <p><i>Citrus medica</i>, i. 335-336.</p> + <p><span class="sc">Cleft</span> palate, inheritance of, ii. <a href="#page24">24</a>.</p> + <p><span class="sc">Clemente</span>, on wild vines in Spain, i. 332.</p> + <p><span class="sc">Clermont-Tonnerre</span>, on the St. Valery apple, i. 401.</p> + <p><span class="sc">Clapham, A.</span>, bud-variation in the hawthorn, i. 377.</p> + <p>"<span class="sc">Claquant</span>," i. 138.</p> + <p>"<span class="sc">Claquers</span>" (pigeons), i. 156.</p> + <p><span class="sc">Clark, G.</span>, on the wild dogs of Juan de Nova, i. 27;</p> + <p class="i2">on striped Burmese and Javanese ponies, i. 59;</p> + <p class="i2">breeds of goats imported into the Mauritius, i. 101;</p> + <p class="i2">variations in the mammæ of goats, i. 102;</p> + <p class="i2">bilobed scrotum of Muscat goat, <i>ibid.</i></p> + <p><span class="sc">Clark, H. J.</span>, on fission and gemmation, ii. <a href="#page359">359</a>.</p> + <p><span class="sc">Clarke, R. T.</span>, intercrossing of strawberries, i. 352.</p> + <p><span class="sc">Clarke, T.</span>, hybridisation of stocks, i. 399, ii. <a href="#page93">93</a>.</p> + <p><span class="sc">Clarkson</span>, Mr., prize-cultivation of the gooseberry, i. 355.</p> + <p><span class="sc">Classification</span>, explained by the theory of natural selection, i. 11.</p> + <p><span class="sc">Climate</span>, effect of, upon breeds of dogs, i. 37;</p> + <p class="i2">on horses, i. 52, 53;</p> + <p class="i2">on cattle, i. 91, 92;</p> + <p class="i2">on the fleece of sheep, i. 98, 99;</p> + <p class="i2">on seeds of wheat, i. 316;</p> + <p class="i2">on cultivated cabbages, i. 325;</p> + <p class="i2">adaptation of maize to, i. 322.</p> + <p><span class="sc">Climate</span> and pasture, adaptation of breeds of sheep to, i. 96-97.</p> + <p><span class="sc">Climate</span> and soil, effects of, upon strawberries, i. 353.</p> + <p><span class="sc">Cline</span>, Mr., on the skull in horned and hornless rams, ii. <a href="#page333">333</a>.</p> + <p><span class="sc">Clos</span>, on sterility in <i>Ranunculus ficaria</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Clotzsch</span>, hybrids of various trees, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Clover</span>, pelorism in, ii. <a href="#page340">340</a>.</p> + <p><span class="sc">Coate</span>, Mr., on interbreeding pigs, ii. <a href="#page122">122</a>.</p> + <p><span class="sc">Coccus</span> of apple trees, ii. <a href="#page231">231</a>.</p> + <p><span class="sc">Cochin</span> fowls, i. 227, 250, 252, 260-261;</p> + <p class="i2">occipital foramen of, figured, i. 261;</p> + <p class="i2">section of skull of, figured, i. 263;</p> + <p class="i2">cervical vertebra of, figured, i. 267.</p> + <p><span class="sc">Cochineal</span>, persistence of, ii. <a href="#page236">236</a>;</p> + <p class="i2">preference of, for a particular cactus, ii. <a href="#page275">275</a>.</p> + <p><i>Cochlearia armoracia</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Cock</span>, game, natural selection in, ii. <a href="#page225">225</a>;</p> + <p class="i2">spur of, grafted on the comb, ii. <a href="#page296">296</a>;</p> + <p class="i2">spur of, inserted into the eye of an ox, ii. <a href="#page369">369</a>;</p> + <p class="i2">effect of castration upon the, ii. <a href="#page51">51</a>-<a href="#page52">52</a>.</p> + <p><span class="sc">Cock's-comb</span>, varieties of the, i. 365.</p> + <p><span class="sc">Cocoons</span>, of silkworms, variations in, i. 302-303.</p> + <p><span class="sc">Codfish</span>, bulldog, i. 89;</p> + <p class="i2">number of eggs in the, ii. <a href="#page379">379</a>.</p> + <p><i>Cœlogenys paca</i>, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Colin</span>, prepotency of the ass over the horse, ii. <a href="#page67">67</a>-<a href="#page68">68</a>;</p> + <p class="i2">on cross-breeding, ii. <a href="#page97">97</a>;</p> + <p class="i2">on change of diet, ii. <a href="#page304">304</a>.</p> + <p><span class="sc">Collinson</span>, Peter, peach-tree producing a nectarine, i. 340.</p> + <p><span class="sc">Coloration</span>, in pigeons, an evidence of unity of descent, i. 195-197.</p> + <p><span class="sc">Colour</span>, correlation of, in dogs, i. 28-29;</p> + <p class="i2">persistence of, in horses, i. 50;</p> + <p class="i2">inheritance and diversity of, in horses, i. 55;</p> + <p class="i2">variations of, in the ass, i. 62-63;</p> + <p class="i2">of wild or feral cattle, i. 85;</p> + <p class="i2">transmission of, in rabbits, i. 107;</p> + <p class="i2">peculiarities of, in Himalayan rabbits, i. 111;</p> + <p class="i2">influence of, ii. <a href="#page227">227</a>-<a href="#page230">230</a>;</p> + <p class="i2">correlation of, in head and limbs, ii. <a href="#page324">324</a>;</p> + <p class="i2">correlated with constitutional peculiarities, ii. <a href="#page335">335</a>-<a href="#page338">338</a>.</p> + <p><span class="sc">Colour</span> and odour, correlation of, ii. <a href="#page325">325</a>.</p> + <p><span class="sc">Colour-blindness</span>, hereditary, ii. <a href="#page9">9</a>;</p> + <p class="i2">more common in men than in women, ii. <a href="#page72">72</a>-<a href="#page73">73</a>;</p> + <p class="i2">associated with inability to distinguish musical sounds, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Colours</span>, sometimes not blended by crossing, ii. <a href="#page92">92</a>.</p> + <p><i>Columba affinis</i>, Blyth, a variety of <i>C. livia</i>, i. 183.</p> + <p><i>Columba amaliæ</i>, Brehm, a variety of <i>C. livia</i>, i. 183.</p> + <p><i>Columba guinea</i>, i. 182.</p> + <p><i>Columba gymnocyclus</i>, Gray, a form of <i>C. livia</i>, i. 184.</p> + <p><i>Columba gymnophthalmos</i>, hybrids of, with <i>C. œnas</i>, i. 193;</p> + <p class="i2">with <i>C. maculosa</i>, i. 194.</p> + <p><i>Columba intermedia</i>, Strickland, a variety of <i>C. livia</i>, i. 184.</p> + <p><i>Columba leucocephala</i>, ii. <a href="#page155">155</a>.</p> + <p><i>Columba leuconota</i>, i. 182, 195.</p> + <p><i>Columba littoralis</i>, i. 182.</p> + <p><i>Columba livia</i>, ii. <a href="#page29">29</a>, <a href="#page40">40</a>;</p> + <p class="i2">the parent of domestic breeds of pigeons, i. 183;</p> + <p class="i2">measurements of, i. 134;</p> + <p class="i2">figured, i. 135;</p> + <p class="i2">skull figured, i. 163;</p> + <p class="i2">lower jaw figured, i. 164, 168;</p> + <p class="i2">scapula figured, i. 167.</p> + <p><i>Columba luctuosa</i>, i. 182.</p> + <p><i>Columba migratoria</i> and <i>leucocephala</i>, diminished fertility of, in captivity, ii. <a href="#page155">155</a>.</p> + <p><i>Columba œnas</i>, i. 183;</p> + <p class="i2">crossed with common pigeon and <i>C. gymnophthalmos</i>, i. 193.</p> + <p><i>Columba palumbus</i>, i. 193, ii. <a href="#page350">350</a>.</p> + <p><i>Columba rupestris</i>, i. 182, 184, 195.</p> + <p><i>Columba Schimperi</i>, i. 184.</p> + <p><i>Columba torquatrix</i>, ii. <a href="#page350">350</a>.</p> + <p><i>Columba turricola</i>, i. 184.</p> + <p><span class="sc">Columbia</span>, cattle of, i. 88.</p> + <p><span class="sc">Columbine</span>, double, i. 365, ii. <a href="#page330">330</a>.</p> +<!-- Page 444 --><span class="pagenum"><a name="page444"></a>{444}</span> + <p><span class="sc">Columbus</span>, on West Indian dogs, i. 23.</p> + <p><span class="sc">Columella</span>, on Italian shepherd's dogs, i. 23;</p> + <p class="i2">on domestic fowls, i. 231, 247, ii. <a href="#page202">202</a>, <a href="#page429">429</a>;</p> + <p class="i2">on the keeping of ducks, i. 277;</p> + <p class="i2">on the selection of seed-corn, i. 318;</p> + <p class="i2">on the benefits of change of soil to plants, ii. <a href="#page146">146</a>;</p> + <p class="i2">on the value of native breeds, ii. <a href="#page313">313</a>.</p> + <p><span class="sc">Colza</span>, i. 325.</p> + <p><span class="sc">Comb</span>, in fowls, variations of, i. 253-254;</p> + <p class="i2">sometimes rudimentary, ii. <a href="#page315">315</a>.</p> + <p><span class="sc">Compensation</span>, law of, i. 274.</p> + <p><span class="sc">Compensation</span> of growth, ii. <a href="#page342">342</a>-<a href="#page344">344</a>.</p> + <p><span class="sc">Complexion</span>, connexion of, with constitution, ii. <a href="#page335">335</a>.</p> + <p><span class="sc">Compositæ</span>, double flowers of, i. 365, ii. <a href="#page167">167</a>, <a href="#page316">316</a>.</p> + <p><span class="sc">Conception</span>, earlier in Alderney and Zetland cows than in other breeds, i. 87.</p> + <p><span class="sc">Conditions</span> of life, changed, effect of, ii. <a href="#page418">418</a>-<a href="#page419">419</a>;</p> + <p class="i2">on horses, i. 52;</p> + <p class="i2">upon variation in pigeons, i. 212-213;</p> + <p class="i2">upon wheat, i. 315-316;</p> + <p class="i2">upon trees, i. 361;</p> + <p class="i2">in producing bud-variation, i. 408;</p> + <p class="i2">advantages of, ii. <a href="#page145">145</a>-<a href="#page148">148</a>, <a href="#page176">176</a>-<a href="#page177">177</a>;</p> + <p class="i2">sterility caused by, ii. <a href="#page148">148</a>-<a href="#page165">165</a>;</p> + <p class="i2">conducive to variability, ii. <a href="#page255">255</a>-<a href="#page261">261</a>, <a href="#page394">394</a>;</p> + <p class="i2">accumulative action of, ii. <a href="#page261">261</a>-<a href="#page263">263</a>;</p> + <p class="i2">direct action of, ii. <a href="#page271">271</a>-<a href="#page292">292</a>.</p> + <p><span class="sc">Condor</span>, breeding in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Confinement</span>, effect of, upon the cock, ii. <a href="#page52">52</a>.</p> + <p><span class="sc">Confucius</span>, on the breeding of rabbits in China, i. 103.</p> + <p><span class="sc">Conolly</span>, Mr., on Angora goats, ii. <a href="#page326">326</a>.</p> + <p><span class="sc">Constitutional</span> differences in sheep, i. 96-97;</p> + <p class="i2">in varieties of apples, i. 349-350;</p> + <p class="i2">in pelargoniums, i. 364;</p> + <p class="i2">in dahlias, i. 370.</p> + <p><span class="sc">Constitutional</span> peculiarities in strawberries, i. 353;</p> + <p class="i2">in roses, i. 367.</p> + <p><span class="sc">Consumption</span>, hereditary, ii. <a href="#page8">8</a>;</p> + <p class="i2">period of appearance of, ii. <a href="#page77">77</a>;</p> + <p class="i2">correlated with complexion, ii. <a href="#page335">335</a>.</p> + <p><span class="sc">Contabescence</span>, ii. <a href="#page165">165</a>-<a href="#page166">166</a>.</p> + <p><i>Convolvulus batatas</i>, ii. <a href="#page169">169</a>, <a href="#page309">309</a>.</p> + <p><i>Convolvulus tricolor</i>, bud-variation in, i. 408.</p> + <p><span class="sc">Cooper</span>, Mr., improvement of vegetables by selection, ii. <a href="#page204">204</a>.</p> + <p><span class="sc">Cooper</span>, White, hereditary peculiarities of vision, ii. <a href="#page9">9</a>;</p> + <p class="i2">association of affections of the eyes with those of other systems, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Corals</span>, bud-variation in, i. 374;</p> + <p class="i2">non-diffusion of cell-gemmules in, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Corbié</span>. <i>See</i> Boitard.</p> + <p><span class="sc">Cornea</span>, opacity of, inherited, ii. <a href="#page9">9</a>.</p> + <p><i>Cornus mascula</i>, yellow-fruited, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Correlation</span>, ii. <a href="#page319">319</a>;</p> + <p class="i2">of neighbouring parts, ii. <a href="#page320">320</a>;</p> + <p class="i2">of change in the whole body and in some of its parts, ii. <a href="#page321">321</a>;</p> + <p class="i2">of homologous parts, ii. <a href="#page322">322</a>-<a href="#page331">331</a>;</p> + <p class="i2">inexplicable, ii. <a href="#page331">331</a>-<a href="#page333">333</a>;</p> + <p class="i2">commingling of, with the effects of other agencies, ii. <a href="#page333">333</a>-<a href="#page335">335</a>.</p> + <p><span class="sc">Correlation</span> of skull and limbs in swine, i. 73;</p> + <p class="i2">of tusks and bristles in swine, i. 76;</p> + <p class="i2">of multiplicity of horns and coarseness of wool in sheep, i. 95;</p> + <p class="i2">of beak and feet in pigeons, i. 172-173;</p> + <p class="i2">between nestling down and colour of plumage in pigeons, i. 194;</p> + <p class="i2">of changes in silkworms, i. 304;</p> + <p class="i2">in plants, ii. <a href="#page219">219</a>;</p> + <p class="i2">in maize, i. 323;</p> + <p class="i2">in pigeons, i. 167-171, 218;</p> + <p class="i2">in fowls, i. 274-275.</p> + <p><span class="sc">Corresponding</span> periods, inheritance at, ii. <a href="#page75">75</a>-<a href="#page80">80</a>.</p> + <p><span class="sc">Corrientes</span>, dwarf cattle of, i. 89.</p> + <p><span class="sc">Corringham</span>, Mr., influence of selection on pigs, ii. <a href="#page198">198</a>.</p> + <p><span class="sc">Corsica</span>, ponies of, i. 52.</p> + <p>"<span class="sc">Cortbeck</span>" (pigeon) of Aldrovandi, i. 209.</p> + <p><i>Corvus corone</i> and <i>C. cornix</i>, hybrids of, ii. <a href="#page94">94</a>.</p> + <p><i>Corydalis</i>, flower of, ii. <a href="#page304">304</a>.</p> + <p><i>Corydalis cava</i>, ii. <a href="#page132">132</a>-<a href="#page133">133</a>.</p> + <p><i>Corydalis solida</i>, sterile when peloric, ii. <a href="#page167">167</a>.</p> + <p><i>Corydalis tuberosa</i>, peloric by reversion, ii. <a href="#page58">58</a>-<a href="#page59">59</a>.</p> + <p><i>Corylus avellana</i>, i. 357.</p> + <p><span class="sc">Costa, A.</span>, on shells transferred from England to the Mediterranean, ii. <a href="#page280">280</a>.</p> + <p>"<span class="sc">Couve Tronchuda</span>," i. 323.</p> + <p><span class="sc">Cow</span>, inheritance of loss of one horn in the, ii. <a href="#page12">12</a>, <a href="#page23">23</a>;</p> + <p class="i2">amount of milk furnished by the, ii. <a href="#page300">300</a>;</p> + <p class="i2">development of six mammæ in, ii. <a href="#page317">317</a>.</p> + <p><span class="sc">Cowslip</span>, ii. <a href="#page21">21</a>, <a href="#page182">182</a>.</p> + <p><span class="sc">Cracidæ</span>, sterility of the, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Cranes</span>, fertility of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><i>Cratægus oxyacantha</i>, i. 363, ii. <a href="#page18">18</a>, <a href="#page232">232</a>, <a href="#page258">258</a>, <a href="#page377">377</a>.</p> + <p><i>Cratægus monogyna</i>, i. 364.</p> + <p><i>Cratægus sibirica</i>, i. 364.</p> + <p><span class="sc">Crawfurd, J.</span>, Malasian cats, i. 47;</p> + <p class="i2">horses of the Malay Archipelago, i. 49;</p> + <p class="i2">horses of Japan, i. 53;</p> + <p class="i2">occurrence of stripes in young wild pigs of Malacca, i. 76;</p> + <p class="i2">on a Burmese hairy family with deficient teeth, ii. <a href="#page77">77</a>, <a href="#page327">327</a>;</p> + <p class="i2">Japanese origin of the bantam, i. 230;</p> + <p class="i2">game fowls of the Philippine islands, i. 232;</p> + <p class="i2">hybrids of <i>Gallus varius</i> and domestic fowl, i. 234;</p> + <p class="i2">domestication of <i>Gallus bankiva</i>, i. 236;</p> + <p class="i2">feral fowls in the Pellew islands, i. 238;</p> + <p class="i2">history of the fowl, i. 246;</p> + <p class="i2">history of the domestic duck, i. 277;</p> + <p class="i2">domestication of the goose, i. 287;</p> + <p class="i2">cultivated plants of New Zealand, i. 312;</p> +<!-- Page 445 --><span class="pagenum"><a name="page445"></a>{445}</span> + <p class="i2">breeding of tame elephants in Ava, ii. <a href="#page150">150</a>;</p> + <p class="i2">sterility of <i>Goura coronata</i> in confinement, ii. <a href="#page155">155</a>;</p> + <p class="i2">geese of the Philippine islands, ii. <a href="#page162">162</a>.</p> + <p><span class="sc">Creepers</span>, a breed of fowls, i. 230.</p> + <p><span class="sc">Crested</span> fowl, i. 227;</p> + <p class="i2">figured, i. 229.</p> + <p>"<span class="sc">Crève-cœur</span>," a French sub-breed of fowls, i. 229.</p> + <p><span class="sc">Crisp</span>, Dr., on the brains of the hare and rabbit, i. 126.</p> + <p><span class="sc">Crocker, C. W.</span>, singular form of <i>Begonia frigida</i>, i. 365-366, ii. <a href="#page166">166</a>;</p> + <p class="i2">sterility in <i>Ranunculus ficaria</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Crocus</span>, ii. <a href="#page165">165</a>.</p> + <p><span class="sc">Cross-breeding</span>, permanent effect of, on the female, i. 404.</p> + <p><span class="sc">Crossing</span>, ii. <a href="#page85">85</a>-<a href="#page144">144</a>, <a href="#page173">173</a>-<a href="#page192">192</a>;</p> + <p class="i2">a cause of uniformity, ii. <a href="#page85">85</a>-<a href="#page90">90</a>, <a href="#page173">173</a>;</p> + <p class="i2">occurs in all organised beings, ii. <a href="#page90">90</a>-<a href="#page92">92</a>;</p> + <p class="i2">some characters not blended by, ii. <a href="#page92">92</a>-<a href="#page95">95</a>, <a href="#page173">173</a>;</p> + <p class="i2">modifications and new races produced by, ii. <a href="#page95">95</a>-<a href="#page99">99</a>;</p> + <p class="i2">causes which check, ii. <a href="#page100">100</a>-<a href="#page109">109</a>;</p> + <p class="i2">domestication and cultivation favourable to, ii. <a href="#page109">109</a>-<a href="#page113">113</a>, <a href="#page189">189</a>;</p> + <p class="i2">beneficial effects of, ii. <a href="#page114">114</a>-<a href="#page131">131</a>, <a href="#page174">174</a>-<a href="#page176">176</a>;</p> + <p class="i2">necessary in some plants, ii. <a href="#page131">131</a>-<a href="#page140">140</a>, <a href="#page175">175</a>-<a href="#page176">176</a>, <a href="#page423">423</a>;</p> + <p class="i2">summary of subject of, ii. <a href="#page140">140</a>-<a href="#page144">144</a>;</p> + <p class="i2">of dogs with wolves in North America, i. 21-22;</p> + <p class="i2">with <i>Canis cancrivorus</i> in Guiana, i. 23;</p> + <p class="i2">of dog with wolf, described by Pliny and others, i. 24;</p> + <p class="i2">characters furnished by, brought out by reversion in the progeny, ii. <a href="#page34">34</a>-<a href="#page36">36</a>;</p> + <p class="i2">a direct cause of reversion, ii. <a href="#page39">39</a>-<a href="#page47">47</a>, <a href="#page48">48</a>;</p> + <p class="i2">a cause of variability, ii. <a href="#page264">264</a>-<a href="#page267">267</a>.</p> + <p><span class="sc">Crustacea</span>, macrourous, differences in the development of the, ii. <a href="#page368">368</a>.</p> + <p><span class="sc">Crustacean</span> with an antenna-like development of the eye-peduncle, ii. <a href="#page391">391</a>.</p> + <p><span class="sc">Cryptogamic</span> plants, bud-variation in, i. 383.</p> + <p><span class="sc">Cuba</span>, wild dogs of, i. 27.</p> + <p>"<span class="sc">Cuckoo</span>," sub-breeds of fowls, i. 244.</p> + <p><span class="sc">Cucumber</span>, variation in number of carpels of, i. 359;</p> + <p class="i2">supposed crossing of varieties of the, i. 400.</p> + <p><i>Cucumis momordica</i>, i. 360.</p> + <p><i>Cucumis sativa</i>, i. 359.</p> + <p><i>Cucurbita</i>, dwarf, correlation of leaves in, ii. <a href="#page330">330</a>.</p> + <p><i>Cucurbita maxima</i>, i. 357, 359.</p> + <p><i>Cucurbita moschata</i>, i. 357, 359.</p> + <p><i>Cucurbita pepo</i>, i. 357, ii. <a href="#page108">108</a>;</p> + <p class="i2">varieties of, i. 358;</p> + <p class="i2">relation in size and number of fruit of, ii. <a href="#page343">343</a>.</p> + <p><span class="sc">Cucurbitaceæ</span>, i. 357-360;</p> + <p class="i2">supposed crossing of, i. 399;</p> + <p class="i2">Naudin's observations on hybrids of, ii. <a href="#page172">172</a>;</p> + <p class="i2">acclimatisation of, ii. <a href="#page313">313</a>.</p> + <p>"<span class="sc">Culbutants</span>" (pigeons), i. 150.</p> + <p><span class="sc">Cultivation</span> of plants, origin of, among savages, i. 309-310;</p> + <p class="i2">fertility increased by, ii. <a href="#page111">111</a>-<a href="#page113">113</a>.</p> + <p><span class="sc">Cunier</span>, on hereditary night-blindness, ii. <a href="#page9">9</a>.</p> + <p><span class="sc">Currants</span>, of Tierra del Fuego, i. 309;</p> + <p class="i2">bud-variation in, i. 376.</p> + <p><span class="sc">Curtis</span>, Mr., bud-variation in the rose, i. 381.</p> + <p><span class="sc">Cuvier</span>, on the gestation of the wolf, i. 29;</p> + <p class="i2">the odour of the jackal, an obstacle to domestication, i. 30;</p> + <p class="i2">differences of the skull in dogs, i. 34;</p> + <p class="i2">external characters of dogs, i. 35;</p> + <p class="i2">elongation of the intestines in domestic pigs, i. 73, ii. <a href="#page303">303</a>;</p> + <p class="i2">fertility of the hook-billed duck, i. 277;</p> + <p class="i2">number of digits, ii. <a href="#page13">13</a>;</p> + <p class="i2">hybrid of ass and zebra, ii. <a href="#page42">42</a>;</p> + <p class="i2">breeding of animals in the Jardin des Plantes, ii. <a href="#page149">149</a>;</p> + <p class="i2">sterility of predaceous birds in captivity, ii. <a href="#page154">154</a>;</p> + <p class="i2">facility of hybridisation in confinement, ii. <a href="#page160">160</a>.</p> + <p><span class="sc">Cyanosis</span>, affection of fingers in, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Cyclamen</span>, bud-variation in, i. 382.</p> + <p><i>Cynara cardunculus</i>, ii. <a href="#page34">34</a>.</p> + <p><i>Cynips fecundatrix</i>, ii. <a href="#page283">283</a>.</p> + <p><i>Cynocephalus hamadryas</i>, ii. <a href="#page153">153</a>.</p> + <p><i>Cyprinus auratus</i>, i. 296-297.</p> + <p><i>Cyrtanthus</i>, ii. <a href="#page139">139</a>.</p> + <p><i>Cyrtopodium</i>, ii. <a href="#page134">134</a>.</p> + <p><i>Cytisus Adami</i>, ii. <a href="#page364">364</a>;</p> + <p class="i2">its bud-variation, i. 387-389, 406, ii. <a href="#page37">37</a>;</p> + <p class="i2">seedlings from, i. 388;</p> + <p class="i2">different views of its origin, i. 389-390;</p> + <p class="i2">experiments in crossing <i>C. purpureus</i> and <i>laburnum</i> to produce, i. 389;</p> + <p class="i2">its production by M. Adam, i. 390;</p> + <p class="i2">discussion of origin of, i. 396.</p> + <p><i>Cytisus alpino-laburnum</i>, ovules and pollen of, i. 389;</p> + <p class="i2">origin of, i. 390.</p> + <p><i>Cytisus alpinus</i>, i. 388.</p> + <p><i>Cytisus laburnum</i>, i. 387, 389, 390, 396.</p> + <p><i>Cytisus purpureo-elongatus</i>, ovules and pollen of, i. 389;</p> + <p class="i2">production of, i. 390.</p> + <p><i>Cytisus purpureus</i>, i. 387, 388, 389, 390, 396.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Dahlbom</span>, effects of food on hymenoptera, ii. <a href="#page281">281</a>.</p> + <p><span class="sc">Dahlia</span>, i. 369-370, ii. <a href="#page147">147</a>;</p> + <p class="i2">bud-variation by tubers in the, i. 385;</p> + <p class="i2">improvement of, by selection, ii. <a href="#page216">216</a>;</p> + <p class="i2">steps in cultivation of, ii. <a href="#page261">261</a>;</p> + <p class="i2">effect of conditions of life on, ii. <a href="#page273">273</a>;</p> + <p class="i2">correlation of form and colour in, ii. <a href="#page331">331</a>.</p> + <p><span class="sc">Daisy</span>, hen and chicken, i. 365;</p> + <p class="i2">Swan River, ii. <a href="#page261">261</a>.</p> + <p><span class="sc">Dalbret</span>, varieties of wheat, i. 314.</p> + <p><span class="sc">Dalibert</span>, changes in the odours of plants, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Dally</span>, Dr., on consanguineous marriages, ii. <a href="#page122">122</a>.</p> + <p><span class="sc">Daltonism</span>, hereditary, ii. <a href="#page9">9</a>.</p> + <p><span class="sc">Damaras</span>, cattle of, i. 88, ii. <a href="#page207">207</a>-<a href="#page208">208</a>.</p> +<!-- Page 446 --><span class="pagenum"><a name="page446"></a>{446}</span> + <p><span class="sc">Damson</span>, i. 347.</p> + <p><span class="sc">Dandolo</span>, Count, on silkworms, i. 301.</p> + <p><span class="sc">Daniell</span>, fertility of English dogs in Sierra Leone, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Danish</span> Middens, remains of dogs in, i. 18.</p> + <p><span class="sc">Dappling</span> in horses, asses, and hybrids, i. 55.</p> + <p><span class="sc">Dareste. C.</span>, on the skull of the Polish fowl, i. 262;</p> + <p class="i2">on the production of monstrous chickens, ii. <a href="#page289">289</a>;</p> + <p class="i2">co-existence of anomalies, ii. <a href="#page331">331</a>;</p> + <p class="i2">production of double monsters, ii. <a href="#page340">340</a>.</p> + <p><span class="sc">Darvill</span>, Mr., heredity of good qualities in horses, ii. <a href="#page11">11</a>.</p> + <p><span class="sc">Darwin, C.</span>, on <i>Lepus magellanicus</i>, i. 112;</p> + <p class="i2">on the wild potato, i. 330;</p> + <p class="i2">dimorphism in the polyanthus and primrose, ii. <a href="#page21">21</a>.</p> + <p><span class="sc">Darwin</span>, Dr., improvement of vegetables by selection, ii. <a href="#page204">204</a>.</p> + <p><span class="sc">Darwin</span>, Sir F., wildness of crossed pigs, ii. <a href="#page45">45</a>.</p> + <p><span class="sc">D'Asso</span>, monogynous condition of the hawthorn in Spain, i. 364.</p> + <p><i>Dasyprocta aguti</i>, ii. <a href="#page152">152</a>.</p> + <p>Date-palm, varieties of the, ii. <a href="#page256">256</a>;</p> + <p class="i2">effect of pollen of, upon the fruit of <i>Chamærops</i>, i. 299.</p> + <p><i>Datura</i>, ii. <a href="#page38">38</a>;</p> + <p class="i2">variability in, ii. <a href="#page266">266</a>.</p> + <p><i>Datura lævis</i> and <i>stramonium</i>, reversion in hybrids of, i. 392.</p> + <p><i>Datura stramonium</i>, ii. <a href="#page67">67</a>.</p> + <p><span class="sc">Daubenton</span>, variations in the number of mammæ in dogs, i. 35;</p> + <p class="i2">proportions of intestines in wild and domestic cats, i. 48, ii. <a href="#page302">302</a>.</p> + <p><span class="sc">Daudin</span>, on white rabbits, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Davy</span>, Dr., on sheep in the West Indies, i. 98.</p> + <p><span class="sc">Dawkins</span> and Sandford, early domestication of <i>Bos longifrons</i> in Britain, i. 81.</p> + <p><span class="sc">Deaf-mutes</span>, non-heredity of, ii. <a href="#page22">22</a>.</p> + <p><span class="sc">Deafness</span>, inheritance of, ii. <a href="#page78">78</a>.</p> + <p><span class="sc">Deby</span>, wild hybrids of common and musk ducks, ii. <a href="#page46">46</a>.</p> + <p><span class="sc">De Candolle</span>, Alph., number and origin of cultivated plants, i. 306-307, 371;</p> + <p class="i2">regions which have furnished no useful plants, i. 310;</p> + <p class="i2">wild wheat, i. 312-313;</p> + <p class="i2">wild rye and oats, i. 313;</p> + <p class="i2">antiquity of varieties of wheat, i. 316;</p> + <p class="i2">apparent inefficacy of selection in wheat, i. 318;</p> + <p class="i2">origin and cultivation of maize, i. 320, ii. <a href="#page307">307</a>;</p> + <p class="i2">colours of seeds of maize, i. 321;</p> + <p class="i2">varieties and origin of the cabbage, i. 324-325;</p> + <p class="i2">origin of the garden-pea, i. 326;</p> + <p class="i2">on the vine, i. 332, ii. <a href="#page308">308</a>;</p> + <p class="i2">cultivated species of the orange group, i. 335;</p> + <p class="i2">probable Chinese origin of the peach, i. 337;</p> + <p class="i2">on the peach and nectarine, i. 340, 342;</p> + <p class="i2">varieties of the peach, i. 342;</p> + <p class="i2">origin of the apricot, i. 344;</p> + <p class="i2">origin and varieties of the plum, i. 345;</p> + <p class="i2">origin of the cherry, i. 347;</p> + <p class="i2">varieties of the gooseberry, i. 354;</p> + <p class="i2">selection practised with forest-trees, i. 361;</p> + <p class="i2">wild fastigate oak, i. 361;</p> + <p class="i2">dark-leaved varieties of trees, i. 362;</p> + <p class="i2">conversion of stamens into pistils in the poppy, i. 365;</p> + <p class="i2">variegated foliage, i. 366;</p> + <p class="i2">heredity of white hyacinths, i. 371, ii. <a href="#page20">20</a>;</p> + <p class="i2">changes in oaks dependent on age, i. 387;</p> + <p class="i2">inheritance of anomalous characters, ii. <a href="#page19">19</a>;</p> + <p class="i2">variation of plants in their native countries, ii. <a href="#page256">256</a>;</p> + <p class="i2">deciduous bushes becoming evergreen in hot climates, ii. <a href="#page305">305</a>;</p> + <p class="i2">antiquity of races of plants, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">De Candolle, P.</span>, non-variability of monotypic genera, ii. <a href="#page266">266</a>;</p> + <p class="i2">relative development of root and seed in <i>Raphanus sativus</i>, ii. <a href="#page343">343</a>.</p> + <p><span class="sc">Decaisne</span>, on the cultivation of the wild carrot, i. 326;</p> + <p class="i2">varieties of the pear, i. 350;</p> + <p class="i2">inter-crossing of strawberries, i. 351;</p> + <p class="i2">fruit of the apple, i. 401;</p> + <p class="i2">sterility of <i>Lysimachia nummularia</i>, ii. <a href="#page170">170</a>;</p> + <p class="i2">tender variety of the peach, ii. <a href="#page308">308</a>.</p> + <p><span class="sc">Deer</span>, assumption of horns by female, ii. <a href="#page51">51</a>;</p> + <p class="i2">imperfect development of horns in a, on a voyage, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Deer</span>, fallow, ii. <a href="#page103">103</a>.</p> + <p><span class="sc">Deerhound</span>. Scotch, difference in size of the sexes of, ii. <a href="#page73">73</a>;</p> + <p class="i2">deterioration of, ii. <a href="#page121">121</a>.</p> + <p><span class="sc">Degeneration</span> of high-bred races, under neglect, ii. <a href="#page239">239</a>.</p> + <p><span class="sc">De Jonghe, J.</span>, on strawberries, i. 352, ii. <a href="#page243">243</a>;</p> + <p class="i2">soft-barked pears, ii. <a href="#page231">231</a>;</p> + <p class="i2">on accumulative variation, ii. <a href="#page262">262</a>;</p> + <p class="i2">resistance of blossoms to frost, ii. <a href="#page306">306</a>.</p> + <p><span class="sc">Delamer, E. S.</span>, on rabbits, i. 107, 112.</p> + <p><i>Delphinium ajacis</i>, ii. <a href="#page21">21</a>.</p> + <p><i>Delphinium consolida</i>, ii. <a href="#page20">20</a>-<a href="#page21">21</a>.</p> + <p><i>Dendrocygna viduata</i>, i. 182, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Dentition</span>, variations of, in the horse, i. 50.</p> + <p><span class="sc">Deodar</span>, i. 364.</p> + <p><span class="sc">Desmarest</span>, distribution of white on dogs, i. 29;</p> + <p class="i2">cat from the Cape of Good Hope, i. 47;</p> + <p class="i2">cats of Madagascar, i. 47;</p> + <p class="i2">occurrence of striped young in Turkish pigs, i. 76;</p> + <p class="i2">French breeds of cattle, i. 80;</p> + <p class="i2">horns of goats, i. 102;</p> + <p class="i2">on hornless goats, ii. <a href="#page315">315</a>.</p> + <p><span class="sc">Desor, E.</span>, on the Anglo-Saxon race in America, ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Desportes</span>, number of varieties of roses, i. 367.</p> + <p><span class="sc">Devay</span>, Dr., singular case of albinism, ii. <a href="#page17">17</a>;</p> + <p class="i2">on the marriage of cousins, ii. <a href="#page122">122</a>;</p> + <p class="i2">on the effects of close interbreeding, ii. <a href="#page143">143</a>, <a href="#page263">263</a>.</p> + <p><span class="sc">Development</span> and metamorphosis, ii. <a href="#page388">388</a>-<a href="#page389">389</a>.</p> + <p><span class="sc">Development</span>, arrests of, ii. <a href="#page315">315</a>-<a href="#page318">318</a>.</p> + <p><span class="sc">Development</span>, embryonic, ii. <a href="#page366">366</a>-<a href="#page368">368</a>.</p> +<!-- Page 447 --><span class="pagenum"><a name="page447"></a>{447}</span> + <p><span class="sc">D'Hervey</span>-Saint-Denys, L., on the ya-mi, or imperial rice of the Chinese, ii. <a href="#page205">205</a>.</p> + <p><span class="sc">Dhole</span>, fertility of the, in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Diabetes</span>, occurrence of, in three brothers, ii. <a href="#page17">17</a>.</p> + <p><i>Dianthus</i>, contabescent plants of, ii. <a href="#page165">165</a>-<a href="#page166">166</a>;</p> + <p class="i2">hybrid varieties of, ii. <a href="#page267">267</a>.</p> + <p><i>Dianthus armeria</i> and <i>deltoides</i>, hybrids of, ii. <a href="#page98">98</a>.</p> + <p><i>Dianthus barbatus</i>, i. 381.</p> + <p><i>Dianthus caryophyllus</i>, i. 381.</p> + <p><i>Dianthus japonicus</i>, contabescence of female organs in, ii. <a href="#page166">166</a>.</p> + <p><span class="sc">Dichogamous</span> plants, ii. <a href="#page90">90</a>.</p> + <p><span class="sc">Dickson</span>, Mr., on "running" in carnations, i. 381;</p> + <p class="i2">on the colours of tulips, i. 386.</p> + <p><i>Dicotyles torquatus</i> and <i>labiatus</i>, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Dieffenbach</span>, dog of New Zealand, i. 26;</p> + <p class="i2">feral cats in New Zealand, i. 47;</p> + <p class="i2">polydactylism in Polynesia, ii. <a href="#page14">14</a>.</p> + <p><i>Dielytra</i>, ii. <a href="#page59">59</a>.</p> + <p><span class="sc">Diet</span>, change of, ii. <a href="#page303">303</a>-<a href="#page304">304</a>.</p> + <p><i>Digitalis</i>, properties of, affected by culture, ii. <a href="#page274">274</a>;</p> + <p class="i2">poison of, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Digits</span>, supernumerary, ii. <a href="#page57">57</a>;</p> + <p class="i2">analogy of, with embryonic conditions, ii. <a href="#page16">16</a>;</p> + <p class="i2">fusion of, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Dimorphic</span> plants, ii. <a href="#page166">166</a>;</p> + <p class="i2">conditions of reproduction in, ii. <a href="#page181">181</a>-<a href="#page184">184</a>.</p> + <p><span class="sc">Dimorphism</span>, reciprocal, ii. <a href="#page90">90</a>.</p> + <p><span class="sc">Dingo</span>, i. 25;</p> + <p class="i2">variation of, in colour, i. 28;</p> + <p class="i2">half-bred, attempting to burrow, i. 28;</p> + <p class="i2">attraction of foxes by a female, i. 31;</p> + <p class="i2">variations of, in confinement, ii. <a href="#page263">263</a>.</p> + <p><span class="sc">Diœciousness</span> of strawberries, i. 353.</p> + <p><span class="sc">Diseases</span>, inheritance of, ii. <a href="#page7">7</a>-<a href="#page8">8</a>;</p> + <p class="i2">family uniformity of, ii. <a href="#page57">57</a>;</p> + <p class="i2">inherited at corresponding periods of life, ii. <a href="#page77">77</a>-<a href="#page80">80</a>;</p> + <p class="i2">peculiar to localities and climates, ii. <a href="#page276">276</a>;</p> + <p class="i2">obscure correlations in, ii. <a href="#page331">331</a>-<a href="#page332">332</a>;</p> + <p class="i2">affecting certain parts of the body, ii. <a href="#page380">380</a>;</p> + <p class="i2">occurring in alternate generations, ii. <a href="#page401">401</a>.</p> + <p><span class="sc">Distemper</span>, fatal to white terriers, ii. <a href="#page227">227</a>.</p> + <p><span class="sc">Disuse</span> and use of parts, effects of, ii. <a href="#page295">295</a>-<a href="#page303">303</a>, <a href="#page352">352</a>-<a href="#page353">353</a>, <a href="#page418">418</a>-<a href="#page419">419</a>;</p> + <p class="i2">in the skeleton of rabbits, i. 124-128;</p> + <p class="i2">in pigeons, i. 171-177;</p> + <p class="i2">in fowls, i. 270-274;</p> + <p class="i2">in ducks, i. 284-286;</p> + <p class="i2">in the silk-moth, i. 300-304.</p> + <p><span class="sc">Divergence</span>, influence of, in producing breeds of pigeons, i. 220.</p> + <p><span class="sc">Dixon, E. S.</span>, on the musk duck, i. 182;</p> + <p class="i2">on feral ducks, i. 190;</p> + <p class="i2">on feral pigeons in Norfolk Island, i. 190;</p> + <p class="i2">crossing of pigeons, i. 192;</p> + <p class="i2">origin of domestic fowls, i. 230;</p> + <p class="i2">crossing of <i>Gallus Sonneratii</i> and common fowl, i. 234;</p> + <p class="i2">occurrence of white in the young chicks of black fowls, i. 244;</p> + <p class="i2">Paduan fowl of Aldrovandi, i. 247;</p> + <p class="i2">peculiarities of the eggs of fowls, i. 248;</p> + <p class="i2">chickens, i. 249-250;</p> + <p class="i2">late development of the tail in Cochin cocks, i. 250;</p> + <p class="i2">comb of lark-crested fowls, i. 256;</p> + <p class="i2">development of webs in Polish fowls, i. 259;</p> + <p class="i2">on the voice of fowls, i. 259;</p> + <p class="i2">origin of the duck, i. 277;</p> + <p class="i2">ducks kept by the Romans, i. 278;</p> + <p class="i2">domestication of the goose, i. 287;</p> + <p class="i2">gander frequently white, i. 288;</p> + <p class="i2">breeds of turkeys, i. 293;</p> + <p class="i2">incubatory instinct of mongrels of non-sitting races of fowls, ii. <a href="#page44">44</a>;</p> + <p class="i2">aversion of the dove-cot pigeon to pair with fancy birds, ii. <a href="#page103">103</a>;</p> + <p class="i2">fertility of the goose, ii. <a href="#page112">112</a>;</p> + <p class="i2">general sterility of the guans in captivity, ii. <a href="#page156">156</a>;</p> + <p class="i2">fertility of geese in captivity, ii. <a href="#page157">157</a>;</p> + <p class="i2">white peafowl, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Dobell, H.</span>, inheritance of anomalies of the extremities, ii. <a href="#page14">14</a>;</p> + <p class="i2">non-reversion to a malformation, ii. <a href="#page36">36</a>.</p> + <p><span class="sc">Dobrizhoffer</span>, abhorrence of incest by the Abipones, ii. <a href="#page123">123</a>.</p> + <p><span class="sc">Dogs</span>, origin of, i. 15;</p> + <p class="i2">ancient breeds of, i. 17, ii. <a href="#page429">429</a>;</p> + <p class="i2">of neolithic, bronze and iron periods in Europe, i. 18-19, ii. <a href="#page427">427</a>;</p> + <p class="i2">resemblance of to various species of canidæ, i. 21;</p> + <p class="i2">of North America compared with wolves, i. 21-22;</p> + <p class="i2">of the West Indies, South America, and Mexico, i. 23, 31;</p> + <p class="i2">of Guiana, i. 23;</p> + <p class="i2">naked dogs of Paraguay and Peru, <i>ibid.</i> and 31;</p> + <p class="i2">dumb, on Juan Fernandez, i. 27;</p> + <p class="i2">of Juan de Nova, i. 27;</p> + <p class="i2">of La Plata, i. 27;</p> + <p class="i2">of Cuba, i. 27;</p> + <p class="i2">of St. Domingo, i. 28;</p> + <p class="i2">correlation of colour in, i. 28-29;</p> + <p class="i2">gestation of, i. 29-30;</p> + <p class="i2">hairless Turkish, i. 30, ii. <a href="#page227">227</a>;</p> + <p class="i2">inter-crossing of different breeds of, i. 31;</p> + <p class="i2">characters of different breeds of, discussed, i. 34-37;</p> + <p class="i2">degeneration of European, in warm climates, i. 36, 38; ii. <a href="#page278">278</a>, <a href="#page305">305</a>;</p> + <p class="i2">liability to certain diseases in different breeds of, i. 36 and <i>note</i>;</p> + <p class="i2">causes of differences of breeds discussed, i. 37-43;</p> + <p class="i2">catching fish and crabs in New Guinea and Tierra del Fuego, i. 39;</p> + <p class="i2">webbing of the feet in, i. 39;</p> + <p class="i2">influence of selection in producing different breeds of, i. 39, 43;</p> + <p class="i2">retention of original habits by, i. 182;</p> + <p class="i2">inheritance of polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">feral, ii. <a href="#page33">33</a>;</p> + <p class="i2">reversion in fourth generation of, ii. <a href="#page34">34</a>;</p> + <p class="i2">of the Pacific Islands, ii. <a href="#page87">87</a>, <a href="#page220">220</a>, <a href="#page303">303</a>;</p> + <p class="i2">mongrel, ii. <a href="#page92">92</a>-<a href="#page93">93</a>;</p> + <p class="i2">comparative facility of crossing different breeds of, ii. <a href="#page102">102</a>;</p> + <p class="i2">fertility of, ii. <a href="#page111">111</a>, <a href="#page151">151</a>;</p> + <p class="i2">inter-breeding of, ii. <a href="#page120">120</a>-<a href="#page121">121</a>;</p> + <p class="i2">selection of, among the Greeks, ii. <a href="#page202">202</a>, <a href="#page209">209</a>;</p> + <p class="i2">among savages, ii. <a href="#page206">206</a>-<a href="#page207">207</a>;</p> + <p class="i2">unconscious selection of, ii. <a href="#page211">211</a>-<a href="#page212">212</a>;</p> + <p class="i2">valued by the Fuegians, ii. <a href="#page215">215</a>;</p> + <p class="i2">climatal changes in hair of, ii. <a href="#page278">278</a>;</p> + <p class="i2">production of drooping ears in, ii. <a href="#page301">301</a>;</p> +<!-- Page 448 --><span class="pagenum"><a name="page448"></a>{448}</span> + <p class="i2">rejection of bones of game by, ii. <a href="#page303">303</a>;</p> + <p class="i2">inheritance of rudiments of limbs in, ii. <a href="#page315">315</a>;</p> + <p class="i2">development of fifth toe in, ii. <a href="#page317">317</a>;</p> + <p class="i2">hairless, deficiency of teeth in, ii. <a href="#page326">326</a>;</p> + <p class="i2">short-faced, teeth of, ii. <a href="#page345">345</a>;</p> + <p class="i2">probable analogous variation in, ii. <a href="#page349">349</a>;</p> + <p class="i2">extinction of breeds of, ii. <a href="#page425">425</a>.</p> + <p><span class="sc">Dombrain, H. H.</span>, on the auricula, ii. <a href="#page346">346</a>-<a href="#page347">347</a>.</p> + <p><span class="sc">Domestication</span>, essential points in, ii. <a href="#page405">405</a>-<a href="#page406">406</a>;</p> + <p class="i2">favourable to crossing, ii. <a href="#page109">109</a>-<a href="#page110">110</a>;</p> + <p class="i2">fertility increased by, ii. <a href="#page111">111</a>-<a href="#page113">113</a>, <a href="#page174">174</a>.</p> + <p><span class="sc">Domesticated</span> animals, origin of, ii. <a href="#page160">160</a>-<a href="#page161">161</a>;</p> + <p class="i2">occasional sterility of, under changed conditions, ii. <a href="#page161">161</a>-<a href="#page162">162</a>.</p> + <p><span class="sc">Donders</span>, Dr., hereditary hypermetropia, ii. <a href="#page8">8</a>.</p> + <p><span class="sc">Dorking</span> fowl, i. 227, 261;</p> + <p class="i2">furcula of, figured, i. 268.</p> + <p><span class="sc">Dormouse</span>, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Double flowers</span>, ii. <a href="#page167">167</a>-<a href="#page168">168</a>, <a href="#page171">171</a>-<a href="#page172">172</a>;</p> + <p class="i2">produced by selection, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Doubleday, H.</span>, cultivation of the filbert pine strawberry, i. 354.</p> + <p><span class="sc">Douglas, J.</span>, crossing of white and black game-fowls, ii. <a href="#page92">92</a>.</p> + <p><span class="sc">Downing</span>, Mr., wild varieties of the hickory, i. 310;</p> + <p class="i2">peaches and nectarines from seed, i. 339-340;</p> + <p class="i2">origin of the Boston nectarine, i. 340;</p> + <p class="i2">American varieties of the peach, i. 343;</p> + <p class="i2">North American apricot, i. 344;</p> + <p class="i2">varieties of the plum, i. 346;</p> + <p class="i2">origin and varieties of the cherry, i. 347-348;</p> + <p class="i2">"twin cluster pippins," i. 349;</p> + <p class="i2">varieties of the apple, i. 350;</p> + <p class="i2">on strawberries, i. 351, 353;</p> + <p class="i2">fruit of the wild gooseberry, i. 355;</p> + <p class="i2">effects of grafting upon the seed, ii. <a href="#page26">26</a>;</p> + <p class="i2">diseases of plum and peach trees, ii. <a href="#page227">227</a>-<a href="#page228">228</a>;</p> + <p class="i2">injury done to stone fruit in America by the "weevil," ii. <a href="#page231">231</a>;</p> + <p class="i2">grafts of the plum and peach, ii. <a href="#page259">259</a>;</p> + <p class="i2">wild varieties of pears, ii. <a href="#page260">260</a>;</p> + <p class="i2">varieties of fruit-trees suitable to different climates, ii. <a href="#page306">306</a>.</p> + <p><i>Draba sylvestris</i>, ii. <a href="#page163">163</a>.</p> + <p><span class="sc">Dragon</span>, pigeon, i. 139, 141.</p> + <p>"<span class="sc">Draijer</span>" (pigeon), i. 156.</p> + <p><span class="sc">Drinking</span>, effects of, in different climates, ii. <a href="#page289">289</a>.</p> + <p><span class="sc">Dromedary</span>, selection of, ii. <a href="#page205">205</a>-<a href="#page206">206</a>.</p> + <p><span class="sc">Druce</span>, Mr., inter-breeding of pigs, ii. <a href="#page121">121</a>.</p> + <p><span class="sc">Du Chaillu</span>, fruit-trees in West Africa, i. 309.</p> + <p><span class="sc">Duchesne</span> on <i>Fragaria vesca</i>, i. 351, 352, 353.</p> + <p><span class="sc">Dufour</span>, Léon, on <i>Cecidomyia</i> and <i>Misocampus</i>, i. 5.</p> + <p><span class="sc">Duck</span>, musk, retention of perching habit by the, i. 182;</p> + <p class="i2">feral hybrid of, i. 190.</p> + <p><span class="sc">Duck</span>, penguin, hybrid of, with Egyptian goose, ii. <a href="#page68">68</a>.</p> + <p><span class="sc">Duck</span>, wild, difficulty of rearing, ii. <a href="#page233">233</a>;</p> + <p class="i2">effects of domestication on, ii. <a href="#page278">278</a>.</p> + <p><span class="sc">Ducks</span>, breeds of, i. 276-277;</p> + <p class="i2">origin of, i. 277;</p> + <p class="i2">history of, <i>ibid.</i>;</p> + <p class="i2">wild, easily tamed, i. 278-279;</p> + <p class="i2">fertility of breeds of, when crossed, i. 279;</p> + <p class="i2">with the plumage of <i>Anas boschas</i>, i. 280;</p> + <p class="i2">Malayan penguin, identical in plumage with English, i. 280;</p> + <p class="i2">characters of the breeds of, i. 281-284;</p> + <p class="i2">eggs of, i. 281;</p> + <p class="i2">effects of use and disuse in, i. 284-286, ii. <a href="#page298">298</a>;</p> + <p class="i2">feral, in Norfolk, i. 190;</p> + <p class="i2">Aylesbury, inheritance of early hatching by, ii. <a href="#page25">25</a>;</p> + <p class="i2">reversion in, produced by crossing, ii. <a href="#page40">40</a>;</p> + <p class="i2">wildness of half-bred wild, ii. <a href="#page45">45</a>;</p> + <p class="i2">hybrids of, with the musk duck, ii. <a href="#page45">45</a>-<a href="#page46">46</a>;</p> + <p class="i2">assumption of male plumage by, ii. <a href="#page51">51</a>;</p> + <p class="i2">crossing of Labrador and penguin, ii. <a href="#page97">97</a>;</p> + <p class="i2">increased fertility of, by domestication, ii. <a href="#page112">112</a>;</p> + <p class="i2">general fertility of, in confinement, ii. <a href="#page157">157</a>;</p> + <p class="i2">increase of size of, by care in breeding, ii. <a href="#page199">199</a>;</p> + <p class="i2">change produced by domestication in, ii. <a href="#page262">262</a>.</p> + <p><span class="sc">Duméril</span>, Aug., breeding of <i>Siredon</i> in the branchiferous stage, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Dun</span>-coloured horses, origin of, i. 59.</p> + <p><span class="sc">Dureau</span> de la Malle, feral pigs in Louisiana, ii. <a href="#page33">33</a>;</p> + <p class="i2">feral fowls in Africa, <i>ibid.</i>;</p> + <p class="i2">bud-variation in the pear, i. 376;</p> + <p class="i2">production of mules among the Romans, ii. <a href="#page110">110</a>.</p> + <p><i>Dusicyon sylvestris</i>, i. 23.</p> + <p><span class="sc">Dutch</span> rabbit, i. 107.</p> + <p><span class="sc">Dutch</span> roller pigeon, i. 151.</p> + <p><span class="sc">Dutrochet</span>, pelorism in the laburnum, ii. <a href="#page346">346</a>.</p> + <p><span class="sc">Duval</span>, growth of pears in woods in France, ii. <a href="#page260">260</a>.</p> + <p><span class="sc">Duval</span>-Jouve, on <i>Leersia oryzoides</i>, ii. <a href="#page91">91</a>.</p> + <p><span class="sc">Duvernoy</span>, self-impotence in <i>Lilium candidum</i>, ii. <a href="#page137">137</a>.</p> + <p><span class="sc">Dzierzon</span>, variability in the characters and habits of bees, i. 298.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Earle</span>, Dr., on colour-blindness, ii. <a href="#page72">72</a>, <a href="#page328">328</a>.</p> + <p><span class="sc">Ears</span>, of fancy rabbits, i. 106;</p> + <p class="i2">deficiency of, in breeds of rabbits, i. 108;</p> + <p class="i2">rudimentary, in Chinese sheep, ii. <a href="#page315">315</a>;</p> + <p class="i2">drooping, ii. <a href="#page301">301</a>;</p> + <p class="i2">fusion of, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Eaton, J. M.</span>, on fancy pigeons, i. 148, 153;</p> + <p class="i2">variability of characters in breeds of pigeons, i. 161;</p> + <p class="i2">reversion of crossed pigeons to coloration of <i>Columba livia</i>, i. 198;</p> + <p class="i2">on pigeon-fancying, i. 206, 215-216;</p> + <p class="i2">on tumbler-pigeons, i. 209, ii. <a href="#page242">242</a>;</p> + <p class="i2">carrier-pigeon, i. 211;</p> + <p class="i2">effects of interbreeding on pigeons, ii. <a href="#page126">126</a>;</p> + <p class="i2">properties of pigeons, ii. <a href="#page197">197</a>-<a href="#page198">198</a>;</p> + <p class="i2">death of short-faced tumblers in the egg, ii. <a href="#page226">226</a>;</p> +<!-- Page 449 --><span class="pagenum"><a name="page449"></a>{449}</span> + <p class="i2">Archangel pigeon, ii. <a href="#page240">240</a>.</p> + <p><span class="sc">Echinodermata</span>, metagenesis in, ii. <a href="#page367">367</a>.</p> + <p><i>Ectopistes</i>, specific difference in number of tail-feathers in, i. 159.</p> + <p><i>Ectopistes migratorius</i>, sterile hybrids of, with <i>Turtur vulgaris</i>, i. 193.</p> + <p><span class="sc">Edentata</span>, correlation of dermal system and teeth in the, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Edgeworth</span>, Mr., use of grass-seeds as food in the Punjab, i. 309.</p> + <p><span class="sc">Edmonston</span>, Dr., on the stomach in <i>Larus argentatus</i> and the raven, ii. <a href="#page302">302</a>.</p> + <p><span class="sc">Edwards</span> and <span class="sc">Colin</span>, on English wheat in France, ii. <a href="#page307">307</a>.</p> + <p><span class="sc">Edwards</span>, W. F., absorption of the minority in crossed races, ii. <a href="#page87">87</a>.</p> + <p><span class="sc">Edwards</span>, W. W., occurrence of stripes in a nearly thoroughbred horse, i. 57;</p> + <p class="i2">in foals of racehorses, i. 59.</p> + <p><span class="sc">Eggs</span>, of fowls, characters of, i. 248;</p> + <p class="i2">variations of, in ducks, i. 281;</p> + <p class="i2">of the silkmoth, i. 301.</p> + <p><span class="sc">Egypt</span>, ancient dogs of, i. 17-18;</p> + <p class="i2">ancient domestication of the pigeon in, i. 204;</p> + <p class="i2">absence of the fowl in ancient, i. 246.</p> + <p><span class="sc">Egyptian</span> goose, hybrids of, with penguin duck, i. 282.</p> + <p><span class="sc">Ehrenberg</span>, Prof., multiple origin of the dog, i. 16;</p> + <p class="i2">dogs of Lower Egypt, i. 25;</p> + <p class="i2">mummies of <i>Felis maniculata</i>, i. 43.</p> + <p><span class="sc">Element</span>, male, compared to a premature larva, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Elements</span> of the body, functional independence of the, ii. <a href="#page368">368</a>-<a href="#page371">371</a>.</p> + <p><span class="sc">Elephant</span>, its sterility in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Elk</span>, Irish, correlations in the, ii. <a href="#page333">333</a>-<a href="#page334">334</a>.</p> + <p><span class="sc">Elliot</span>, Sir Walter, on striped horses, i. 58;</p> + <p class="i2">Indian domestic and wild swine, i. 66;</p> + <p class="i2">pigeons from Cairo and Constantinople, i. 132;</p> + <p class="i2">fantail pigeons, i. 146;</p> + <p class="i2">Lotan tumbler pigeons, i. 150;</p> + <p class="i2">a pigeon uttering the sound <i>Yahu</i>, i. 155;</p> + <p class="i2"><i>Gallus bankiva</i> in Pegu, i. 236.</p> + <p><span class="sc">Ellis</span>, Mr., varieties of cultivated plants in Tahiti, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Elm</span>, nearly evergreen Cornish variety of the, i. 363, ii. <a href="#page310">310</a>;</p> + <p class="i2">foliage-varieties of the, i. 362.</p> + <p><span class="sc">Elm</span>, weeping, i. 361;</p> + <p class="i2">not reproduced by seed, ii. <a href="#page19">19</a>.</p> + <p><i>Emberiza passerina</i>, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Embryos</span>, similarity of, i. 12;</p> + <p class="i2">fusion of, ii. <a href="#page339">339</a>.</p> + <p><span class="sc">Engel</span>, on <i>Laurus sassafras</i>, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">England</span>, domestication of <i>Bos longifrons</i> in, i. 81;</p> + <p class="i2">selection of horses in, in mediæval times, ii. <a href="#page203">203</a>;</p> + <p class="i2">laws against the early slaughter of rams in, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Ephemeridæ</span>, development of the, ii. <a href="#page366">366</a>.</p> + <p><i>Epidendrum cinnabarinum</i> and <i>E. zebra</i>, ii. <a href="#page134">134</a>.</p> + <p><span class="sc">Epilepsy</span>, hereditary, ii. <a href="#page8">8</a>, <a href="#page78">78</a>.</p> + <p><span class="sc">Erdt</span>, disease of the white parts of cattle, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Ericaceæ</span>, frequency of contabescence in the, ii. <a href="#page165">165</a>.</p> + <p><span class="sc">Erichthonius</span>, an improver of horses by selection, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Erman</span>, on the fat-tailed Kirghisian sheep, i. 98, ii. <a href="#page280">280</a>;</p> + <p class="i2">on the dogs of the Ostyaks, ii. <a href="#page206">206</a>.</p> + <p><i>Erodium</i>, ii. <a href="#page59">59</a>.</p> + <p><i>Erythrina Crista-galli</i> and <i>E. herbacea</i>, hybrids of, ii. <a href="#page265">265</a>.</p> + <p><span class="sc">Esquilant</span>, Mr., on the naked young of dun-coloured pigeons, i. 170.</p> + <p><span class="sc">Esquimaux</span> dogs, their resemblance to wolves, i. 21;</p> + <p class="i2">selection of, ii. <a href="#page206">206</a>.</p> + <p><span class="sc">Eudes-Deslongchamps</span>, on appendages under the jaw of pigs, i. 75-76.</p> + <p><i>Euonymus Japonicus</i>, i. 383.</p> + <p><span class="sc">European</span> cultivated plants, still wild in Europe, i. 307.</p> + <p><span class="sc">Evans</span>, Mr., on the Lotan tumbler pigeon, i. 150.</p> + <p><span class="sc">Evelyn</span>, pansies grown in his garden, i. 368.</p> + <p><span class="sc">Everest, R.</span>, on the Newfoundland dog in India, i. 36, ii. <a href="#page305">305</a>;</p> + <p class="i2">degeneration of setters in India, i. 38;</p> + <p class="i2">Indian wild boars, i. 66.</p> + <p><span class="sc">Ewes</span>, hornless, ii. <a href="#page350">350</a>.</p> + <p><span class="sc">Extinction</span> of domestic races, i. 221.</p> + <p><span class="sc">Eyes</span>, hereditary peculiarities of the, ii. <a href="#page8">8</a>-<a href="#page10">10</a>;</p> + <p class="i2">loss of, causing microphthalmia in children, ii. <a href="#page24">24</a>;</p> + <p class="i2">modification of the structure of, by natural selection, ii. <a href="#page222">222</a>-<a href="#page223">223</a>;</p> + <p class="i2">fusion of, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Eyebrows</span>, hereditary elongation of hairs in, ii. <a href="#page8">8</a>.</p> + <p><span class="sc">Eyelids</span>, inherited peculiarities of the, ii. <a href="#page8">8</a>.</p> + <p><span class="sc">Eyton</span>, Mr., on gestation in the dog, i. 30;</p> + <p class="i2">variability in number of vertebræ in the pig, i. 74;</p> + <p class="i2">individual sterility, ii. <a href="#page162">162</a>.</p> + </div> + + <div class="stanza"> + <p><i>Faba vulgaris</i>, i. 330.</p> + <p><span class="sc">Fabre</span>, observations on <i>Ægilops triticoides,</i> i. 313.</p> + <p><i>Fagus sylvatica</i>, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Fairweather</span>, Mr., production of double flowers from old seed, ii. <a href="#page167">167</a>.</p> + <p><i>Falco albidus</i>, resumption of young plumage by, in captivity, ii. <a href="#page158">158</a>.</p> + <p><i>Falco ossifragus</i>, ii. <a href="#page230">230</a>.</p> + <p><i>Falco subbuteo</i>, copulating in captivity, ii. <a href="#page154">154</a>.</p> + <p><i>Falco tinnunculus</i>, breeding in captivity, ii. <a href="#page154">154</a>.</p> +<!-- Page 450 --><span class="pagenum"><a name="page450"></a>{450}</span> + <p><span class="sc">Falconer</span>, Dr., sterility of English bulldogs in India, i, 38;</p> + <p class="i2">resemblance between <i>Sivatherium</i> and Niata cattle, i. 89;</p> + <p class="i2">selection of the silkworm in India, i. 301;</p> + <p class="i2">fastigate apple-trees in Calcutta, i. 361;</p> + <p class="i2">reproduction of a supernumerary thumb after amputation, ii. <a href="#page14">14</a>;</p> + <p class="i2">fertility of the dhole in captivity, ii. <a href="#page151">151</a>;</p> + <p class="i2">fertility of English dogs in India, ii. <a href="#page161">161</a>;</p> + <p class="i2">sterility of the tiger in captivity, ii. <a href="#page151">151</a>;</p> + <p class="i2">turkeys at Delhi, ii. <a href="#page161">161</a>;</p> + <p class="i2">on Indian cultivated plants, ii. <a href="#page165">165</a>;</p> + <p class="i2">Thibet mastiff and goat, ii. <a href="#page278">278</a>.</p> + <p><span class="sc">Falcons</span>, sterility of, in captivity, ii. <a href="#page153">153</a>.</p> + <p><span class="sc">Falkland</span> Islands, horses of the, i. 52-53, 61;</p> + <p class="i2">feral pigs of the, i. 77;</p> + <p class="i2">feral cattle of the, i. 82, 86;</p> + <p class="i2">feral rabbits of the, i. 112.</p> + <p><span class="sc">Fallow</span> deer, ii. <a href="#page103">103</a>, <a href="#page120">120</a>.</p> + <p><span class="sc">Fantail</span> pigeons, i. 146-148, ii. <a href="#page227">227</a>;</p> + <p class="i2">figured, i. 147;</p> + <p class="i2">furcula of, figured, i. 167;</p> + <p class="i2">history of, i. 208;</p> + <p class="i2">absence of oil-gland in, ii. <a href="#page344">344</a>.</p> + <p><span class="sc">Faroe</span> Islands, pigeons of the, i. 183.</p> + <p><span class="sc">Fashion</span>, influence of, in breeding, ii. <a href="#page240">240</a>.</p> + <p><span class="sc">Fastigate</span> trees, ii. <a href="#page277">277</a>, <a href="#page348">348</a>.</p> + <p><span class="sc">Faunas</span>, geographical differences, of, i. 10.</p> + <p>"<span class="sc">Favourite</span>" bull, ii. <a href="#page65">65</a>, <a href="#page118">118</a>.</p> + <p><span class="sc">Feathers</span>, homologous variation in, ii. <a href="#page325">325</a>.</p> + <p><span class="sc">Feet</span>, of pigeons, individual differences of, i. 160;</p> + <p class="i2">correlations of external characters in, i. 170-171.</p> + <p><span class="sc">Feet</span> and beak, correlation of, in pigeons, i. 171-174.</p> + <p><span class="sc">Felidæ</span>, fertility of, in captivity, ii. <a href="#page150">150</a>.</p> + <p><i>Felis bubastes</i>, i. 43.</p> + <p><i>Felis caffra</i>, i. 44.</p> + <p><i>Felis caligulata</i>, i. 43.</p> + <p><i>Felis chaus</i>, i. 43-44.</p> + <p><i>Felis jubata</i>, ii. <a href="#page151">151</a>.</p> + <p><i>Felis lybica</i>, i. 44.</p> + <p><i>Felis maniculata</i>, i. 43.</p> + <p><i>Felis manul</i>, i. 45.</p> + <p><i>Felis ornata</i>, i. 45.</p> + <p><i>Felis sylvestris</i>, i. 44.</p> + <p><i>Felis torquata</i>, i. 45.</p> + <p><span class="sc">Female</span>, affected by male element, ii. <a href="#page365">365</a>, <a href="#page387">387</a>-<a href="#page388">388</a>.</p> + <p><span class="sc">Female</span> flowers, in male panicle of maize, i. 321.</p> + <p><span class="sc">Fennel</span>, Italian variety of, i. 326.</p> + <p><span class="sc">Feral</span> cats, i. 47;</p> + <p class="i2">cattle, i. 86;</p> + <p class="i2">rabbits, i. 111-115;</p> + <p class="i2">Guinea fowl, i. 294;</p> + <p class="i2">animals and plants, reversion in, ii. <a href="#page32">32</a>-<a href="#page34">34</a>, <a href="#page47">47</a>.</p> + <p><span class="sc">Ferguson</span>, Mr., supposed plurality of origin of domestic fowls, i. 231;</p> + <p class="i2">chickens of black game-fowls, i. 244;</p> + <p class="i2">relative size of eggs of fowls, i. 248;</p> + <p class="i2">yolk of eggs of game-fowls, i. 249;</p> + <p class="i2">early pugnacity of game-cocks, i. 250;</p> + <p class="i2">voice of the Malay fowl, i. 259;</p> + <p class="i2">effects of interbreeding on fowls, ii. <a href="#page124">124</a>;</p> + <p class="i2">selection in Cochin China fowls, ii. <a href="#page196">196</a>;</p> + <p class="i2">on fashion in poultry, ii. <a href="#page240">240</a>.</p> + <p><span class="sc">Fernandez</span>, on Mexican dogs, i. 23.</p> + <p><span class="sc">Ferns</span>, reproduction of abnormal forms of, by spores, i. 383;</p> + <p class="i2">non-diffusion of cell-gemmules in, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Ferrets</span>, ii. <a href="#page111">111</a>, <a href="#page151">151</a>, <a href="#page206">206</a>.</p> + <p><span class="sc">Fertilisation</span>, artificial, of the St. Valery apple, i. 350.</p> + <p><span class="sc">Fertility</span>, various degrees of, in sheep, i. 97;</p> + <p class="i2">unlimited mutual, of breeds of pigeons, i. 192-194;</p> + <p class="i2">comparative of mongrels and hybrids, ii. <a href="#page100">100</a>-<a href="#page101">101</a>, <a href="#page178">178</a>-<a href="#page180">180</a>;</p> + <p class="i2">influence of nourishment on, ii. <a href="#page111">111</a>;</p> + <p class="i2">diminished by close interbreeding, ii. <a href="#page118">118</a>, <a href="#page175">175</a>;</p> + <p class="i2">reduced, of Chillingham wild cattle, ii. <a href="#page119">119</a>;</p> + <p class="i2">of domesticated varieties when crossed, ii. <a href="#page189">189</a>.</p> + <p><i>Festuca</i>, species of, propagated by bulblets, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Filberts</span>, spared by tomtits, ii. <a href="#page231">231</a>.</p> + <p><span class="sc">Filippi</span>, on the breeding of branchiferous tritons, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Finches</span>, general sterility of, in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Finnikin</span> (pigeon), i. 156.</p> + <p><span class="sc">Finnochio</span>, i. 326.</p> + <p><span class="sc">Fir</span>, Scotch, acclimatisation of, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Fish</span>, Mr., advantage of change of soil to plants, ii. <a href="#page147">147</a>.</p> + <p><span class="sc">Fishes</span>, regeneration of portions of fins of, ii. <a href="#page15">15</a>;</p> + <p class="i2">variability of, when kept in tanks, ii. <a href="#page259">259</a>;</p> + <p class="i2">marine, living in fresh water, ii. <a href="#page304">304</a>;</p> + <p class="i2">double monsters of, ii. <a href="#page340">340</a>.</p> + <p><span class="sc">Fission</span> and gemmation, ii. <a href="#page358">358</a>.</p> + <p><span class="sc">Fitch</span>, Mr., persistency of a variety of the pea, i. 329.</p> + <p><span class="sc">Fittest</span>, survival of the, i. 6.</p> + <p><span class="sc">Fitzinger</span>, origin of sheep, i. 94;</p> + <p class="i2">African maned sheep, i. 96.</p> + <p><span class="sc">Fixedness</span> of character, conditions of, discussed, ii. <a href="#page62">62</a>-<a href="#page64">64</a>.</p> + <p><span class="sc">Flax</span>, found in the Swiss lake-dwellings, i. 317;</p> + <p class="i2">climatal difference in products of, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Fleece</span>, fineness of, in Austrian merinos, ii. <a href="#page197">197</a>.</p> + <p><span class="sc">Fleischmann</span>, on German sheep crossed with merinos, ii. <a href="#page88">88</a>-<a href="#page89">89</a>.</p> + <p>"<span class="sc">Florentiner-Taube</span>," i. 142-143.</p> + <p><span class="sc">Flounder</span>, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Flourens</span>, crossing of wolf and dog, i. 32;</p> + <p class="i2">prepotency of the jackal over the dog, ii. <a href="#page67">67</a>;</p> + <p class="i2">hybrids of the horse and ass, ii. <a href="#page68">68</a>;</p> + <p class="i2">breeding of monkeys in Europe, ii. <a href="#page153">153</a>.</p> +<!-- Page 451 --><span class="pagenum"><a name="page451"></a>{451}</span> + <p><span class="sc">Flower-garden</span>, earliest known, in Europe, ii. <a href="#page217">217</a>.</p> + <p><span class="sc">Flowers</span>, capricious transmission of colour-varieties in, ii. <a href="#page20">20</a>-<a href="#page21">21</a>;</p> + <p class="i2">tendency to uniformity in striped, ii. <a href="#page70">70</a>;</p> + <p class="i2">scorching of, dependent on colour, ii. <a href="#page229">229</a>;</p> + <p class="i2">change in, caused by conditions of life, ii. <a href="#page273">273</a>;</p> + <p class="i2">rudimentary, ii. <a href="#page316">316</a>;</p> + <p class="i2">relative position of, to the axis, ii. <a href="#page345">345</a>.</p> + <p><span class="sc">Fœtation</span>, abdominal, ii. <a href="#page294">294</a>.</p> + <p><span class="sc">Foley</span>, Mr., wild varieties of pears, ii. <a href="#page260">260</a>.</p> + <p><span class="sc">Foliage</span>, inherited peculiarities of, i. 362;</p> + <p class="i2">variegation, of, i. 366;</p> + <p class="i2">bud-variation in, i. 382-384.</p> + <p><span class="sc">Food</span>, influence of, on the pig, i. 72;</p> + <p class="i2">on cattle, i. 91;</p> + <p class="i2">excess of, a cause of variability, ii. <a href="#page257">257</a>.</p> + <p><span class="sc">Forbes, D.</span>, on Chilian sheep, i. 95;</p> + <p class="i2">on the horses of Spain, Chili, and the Pampas, i. 52.</p> + <p><i>Formica rufa</i>, ii. <a href="#page251">251</a>.</p> + <p><span class="sc">Fortune, R.</span>, sterility of the sweet potato in China, ii. <a href="#page169">169</a>;</p> + <p class="i2">development of axillary bulbs in the yam, <i>ibid.</i></p> + <p><span class="sc">Fowl</span>, common, breeds of, i. 225-230;</p> + <p class="i2">supposed plurality of origin, i. 230;</p> + <p class="i2">early history of, i. 231-233;</p> + <p class="i2">causes of production of breeds of, i. 233;</p> + <p class="i2">origin of from <i>Gallus bankiva</i>, i. 236-239, 245;</p> + <p class="i2">feral, notices of, i. 237-238;</p> + <p class="i2">reversion and analogous variation in, i. 239-246, ii. <a href="#page35">35</a>, <a href="#page38">38</a>, <a href="#page39">39</a>, <a href="#page40">40</a>, <a href="#page349">349</a>, <a href="#page350">350</a>;</p> + <p class="i2">"cuckoo" sub-breeds of, i. 244;</p> + <p class="i2">history of, i. 246-247;</p> + <p class="i2">structural characters of, i. 247-250;</p> + <p class="i2">sexual peculiarities of, i. 251-257, ii. <a href="#page74">74</a>;</p> + <p class="i2">external differences of, i. 257-260;</p> + <p class="i2">differences of breeds of, from <i>G. bankiva</i>, i. 260;</p> + <p class="i2">osteological characters of, i. 260-270;</p> + <p class="i2">effects of disuse of parts in, i. 270-274, ii. <a href="#page298">298</a>;</p> + <p class="i2">feral, i. 190, ii. <a href="#page33">33</a>;</p> + <p class="i2">polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">fertility of, increased by domestication, ii. <a href="#page112">112</a>, <a href="#page167">167</a>;</p> + <p class="i2">sterility of, under certain conditions, ii. <a href="#page162">162</a>;</p> + <p class="i2">influence of selection on, ii. <a href="#page196">196</a>, <a href="#page198">198</a>, <a href="#page209">209</a>, <a href="#page210">210</a>;</p> + <p class="i2">evils of close interbreeding of, ii. <a href="#page124">124</a>-<a href="#page125">125</a>;</p> + <p class="i2">crossing of, ii. <a href="#page95">95</a>, <a href="#page96">96</a>, <a href="#page97">97</a>;</p> + <p class="i2">prepotency of transmission in, ii. <a href="#page67">67</a>;</p> + <p class="i2">rudimentary organs in, ii. <a href="#page315">315</a>;</p> + <p class="i2">crossing of non-sitting varieties of, ii. <a href="#page43">43</a>-<a href="#page44">44</a>;</p> + <p class="i2">homology of wing and leg feathers in, ii. <a href="#page323">323</a>;</p> + <p class="i2">hybrids of, with pheasants and <i>Gallus Sonneratii</i>, ii. <a href="#page45">45</a>;</p> + <p class="i2">black-skinned, ii. <a href="#page209">209</a>-<a href="#page210">210</a>;</p> + <p class="i2">black, preyed upon by the osprey in Iceland, ii. <a href="#page230">230</a>;</p> + <p class="i2">five-toed, mentioned by Columella, ii. <a href="#page429">429</a>;</p> + <p class="i2">rumpless, tailed chickens produced by, ii. <a href="#page31">31</a>;</p> + <p class="i2">Dorking, crosses of, ii. <a href="#page93">93</a>;</p> + <p class="i2">form of comb and colour of plumage in, ii. <a href="#page238">238</a>;</p> + <p class="i2">game, crossing of white and black, ii. <a href="#page92">92</a>;</p> + <p class="i2">five-spurred, ii. <a href="#page391">391</a>;</p> + <p class="i2">Spanish, liable to suffer from frost, ii. <a href="#page306">306</a>;</p> + <p class="i2">Polish, peculiarities of skull of, ii. <a href="#page332">332</a>-<a href="#page333">333</a>.</p> + <p><span class="sc">Fox</span>, sterility of, in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Fox</span>, S. Bevan, races of bees, i. 298.</p> + <p><span class="sc">Fox</span>, W. Darwin, gestation of the dog, i. 30;</p> + <p class="i2">"Negro" cat, i. 46;</p> + <p class="i2">reversion of sheep in colour, ii. <a href="#page30">30</a>;</p> + <p class="i2">period of gestation in the pig, i. 74;</p> + <p class="i2">young of the Himalayan rabbit, i. 109;</p> + <p class="i2">crossing of wild and domestic turkeys, i. 292;</p> + <p class="i2">reversion in crossed musk ducks, ii. <a href="#page40">40</a>;</p> + <p class="i2">spontaneous segregation of varieties of geese, ii. <a href="#page104">104</a>;</p> + <p class="i2">effects of close interbreeding upon bloodhounds, ii. <a href="#page121">121</a>;</p> + <p class="i2">deafness of white cats with blue eyes, ii. <a href="#page329">329</a>.</p> + <p><span class="sc">Foxhounds</span>, i. 40, ii. <a href="#page120">120</a>.</p> + <p><i>Fragaria chiloensis</i>, i. 351.</p> + <p><i>Fragaria collina</i>, i. 351.</p> + <p><i>Fragaria dioica</i> of Duchesne, i. 353.</p> + <p><i>Fragaria elatior</i>, i. 351.</p> + <p><i>Fragaria grandiflora</i>, i. 351.</p> + <p><i>Fragaria vesca</i>, i. 351.</p> + <p><i>Fragaria virginiana</i>, i. 351.</p> + <p><i>Fraxinus excelsior</i>, i. 360, 362, ii. <a href="#page19">19</a>.</p> + <p><i>Fraxinus lentiscifolia</i>, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Friesland</span> cattle, probably descended from <i>Bos primigenius</i>, i. 81.</p> + <p><span class="sc">Frillback</span> (pigeon), i. 155;</p> + <p class="i2">Indian, i. 153.</p> + <p><i>Fringilla ciris</i>, ii. <a href="#page154">154</a>.</p> + <p><i>Fringilla spinus</i>, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Frizzled</span> fowls, i. 230;</p> + <p class="i2">horses, i. 54.</p> + <p><span class="sc">Frog</span>, polydactylism in the, ii. <a href="#page14">14</a>.</p> + <p><span class="sc">Fruit</span>, seedless, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Fruit-trees</span>, varieties of, occurring wild, i. 310.</p> + <p><span class="sc">Fry</span>, Mr., on fertile hybrid cats, i. 44;</p> + <p class="i2">on feral fowls in Ascension, i. 238.</p> + <p><span class="sc">Fuchsias</span>, origin of, i. 364;</p> + <p class="i2">bud-variation in, i. 382.</p> + <p><i>Fuchsia coccinea</i> and <i>fulgens</i>, twin seed produced by crossing, i. 391.</p> + <p><span class="sc">Fuegians</span>, their superstition about killing young water-fowl, i. 310;</p> + <p class="i2">selection of dogs by the, ii. <a href="#page207">207</a>;</p> + <p class="i2">their comparative estimation of dogs and old women, ii. <a href="#page215">215</a>;</p> + <p class="i2">their power of distant vision, ii. <a href="#page223">223</a>.</p> + <p><span class="sc">Fungi</span>, parasitic, ii. <a href="#page284">284</a>-<a href="#page285">285</a>.</p> + <p><span class="sc">Furcula</span>, characters and variations of the, in pigeons, i. 167;</p> + <p class="i2">alteration of, by disuse, in pigeons, i. 175;</p> + <p class="i2">characters of, in fowls, i. 268.</p> + <p><span class="sc">Fusion</span> of homologous parts, ii. <a href="#page393">393</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Gait</span>, inheritance of peculiarities of, ii. <a href="#page6">6</a>.</p> + <p><span class="sc">Galapagos</span> Archipelago, its peculiar fauna and flora, i. 9.</p> + <p><i>Galeobdolon luteum</i>, pelorism in, ii. <a href="#page59">59</a>, <a href="#page345">345</a>.</p> +<!-- Page 452 --><span class="pagenum"><a name="page452"></a>{452}</span> + <p><span class="sc">Galls</span>, ii. <a href="#page282">282</a>-<a href="#page284">284</a>.</p> + <p><span class="sc">Gall-gnats</span>, ii. <a href="#page283">283</a>.</p> + <p><span class="sc">Gall-like</span> excrescences not inherited, ii. <a href="#page23">23</a>.</p> + <p><span class="sc">Gallinaceous</span> birds, restricted range of large, i. 237;</p> + <p class="i2">general fertility of in captivity, ii. <a href="#page155">155</a>.</p> + <p><i>Gallinula chloropus</i>, ii. <a href="#page156">156</a>.</p> + <p><i>Gallinula nesiotis</i>, i. 287.</p> + <p><span class="sc">Galton</span>, Mr., fondness of savages for taming animals, i. 20, ii. <a href="#page160">160</a>;</p> + <p class="i2">cattle of Benguela, i. 88;</p> + <p class="i2">on hereditary talent, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Gallesio</span>, species of oranges, i. 334, 335, 336;</p> + <p class="i2">hybridisation of oranges, i. 336;</p> + <p class="i2">persistency of races in the peach, i. 339;</p> + <p class="i2">supposed specific distinctions of peach and nectarine, i. 340;</p> + <p class="i2">Bizzaria orange, i. 391;</p> + <p class="i2">crossing of red and white carnations, i. 393;</p> + <p class="i2">crossing of the orange and lemon, i. 399, ii. <a href="#page365">365</a>;</p> + <p class="i2">effect of foreign pollen on maize, i. 400;</p> + <p class="i2">spontaneous crossing of oranges, ii. <a href="#page91">91</a>;</p> + <p class="i2">monstrosities a cause of sterility in plants, ii. <a href="#page166">166</a>;</p> + <p class="i2">seeding of ordinarily seedless fruits, ii. <a href="#page168">168</a>;</p> + <p class="i2">sterility of the sugar cane, ii. <a href="#page169">169</a>;</p> + <p class="i2">tendency of male flowers to become double, ii. <a href="#page171">171</a>;</p> + <p class="i2">effects of selection in enlarging fruit, &c., ii. <a href="#page217">217</a>;</p> + <p class="i2">variation of the orange tree in North Italy, ii. <a href="#page256">256</a>;</p> + <p class="i2">naturalisation of the orange in Italy, ii. <a href="#page309">309</a>.</p> + <p><i>Gallus æneus</i>, a hybrid of <i>G. varius</i> and the domestic fowl, i. 235.</p> + <p><i>Gallus bankiva</i>, probable original of domestic fowls, i. 233, 236-239, 245;</p> + <p class="i2">game-fowl, nearest to, i. 226;</p> + <p class="i2">crossed with <i>G. Sonneratii</i>, i. 234;</p> + <p class="i2">its character and habits, i. 235-236, ii. <a href="#page109">109</a>;</p> + <p class="i2">differences of various breeds of fowls from, i. 260;</p> + <p class="i2">occipital foramen of, figured, i. 261;</p> + <p class="i2">skull of, figured, i. 262;</p> + <p class="i2">cervical vertebra of, figured, i. 267;</p> + <p class="i2">furcula of, figured, i. 268;</p> + <p class="i2">reversion to, in crossed fowls, ii. <a href="#page39">39</a>-<a href="#page40">40</a>;</p> + <p class="i2">hybrid of, with <i>G. varius</i>, i. 235, ii. <a href="#page40">40</a>;</p> + <p class="i2">number of eggs of, ii. <a href="#page112">112</a>.</p> + <p><i>Gallus ferrugineus</i>, i. 226.</p> + <p><i>Gallus furcatus</i>, i. 234.</p> + <p><i>Gallus giganteus</i>, i. 235.</p> + <p><i>Gallus Sonneratii</i>, characters and habits of, i. 233;</p> + <p class="i2">hybrids of, i. 234, ii. <a href="#page45">45</a>.</p> + <p><i>Gallus Stanleyi</i>, hybrids of, i. 234.</p> + <p><i>Gallus Temminckii</i>, probably a hybrid, i. 235.</p> + <p><i>Gallus varius</i>, character and habits of, i. 234;</p> + <p class="i2">hybrids and probable hybrids of, i. 234-235.</p> + <p><span class="sc">Gambier</span>, Lord, his early cultivation of the pansy, i. 368.</p> + <p><span class="sc">Game-fowl</span>, i. 226, 250, 251, 252.</p> + <p><span class="sc">Gapes</span>, ii. <a href="#page228">228</a>.</p> + <p><span class="sc">Garcilazo</span> de la Vega, annual hunts of the Peruvian Incas, ii. <a href="#page207">207</a>.</p> + <p><span class="sc">Garnett</span>, Mr., migratory propensities of hybrid ducks, ii. <a href="#page45">45</a>.</p> + <p><span class="sc">Garrod</span>, Dr., on hereditary gout, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Gasparini</span>, a genus of pumpkins, founded on stigmatic characters, i. 359.</p> + <p><span class="sc">Gaudichaud</span>, bud-variation in the pear, i. 376;</p> + <p class="i2">apple tree with two kinds of fruit on branch, i. 392.</p> + <p><span class="sc">Gaudry</span>, anomalous structure in the feet of horses, i. 50.</p> + <p><span class="sc">Gay</span>, on <i>Fragaria grandiflora</i>, i. 351;</p> + <p class="i2">on <i>Viola lutea</i> and <i>tricolor</i>, i. 368;</p> + <p class="i2">on the nectary of <i>Viola grandiflora</i>, i. 369.</p> + <p><span class="sc">Gayal</span>, domestication of the, i. 82.</p> + <p><span class="sc">Gayot</span>, <i>see</i> Moll.</p> + <p><span class="sc">Gärtner</span>, on the sterility of hybrids, i. 192, ii. <a href="#page101">101</a>;</p> + <p class="i2">acquired sterility of varieties of plants when crossed, i. 358;</p> + <p class="i2">sterility in transplanted plants, and in the lilac in Germany, ii. <a href="#page164">164</a>;</p> + <p class="i2">mutual sterility of blue and red flowers of the pimpernel, ii. <a href="#page190">190</a>;</p> + <p class="i2">supposed rules of transmission in crossing plants, ii. <a href="#page68">68</a>;</p> + <p class="i2">on crossing plants, ii. <a href="#page98">98</a>, <a href="#page127">127</a>, <a href="#page130">130</a>, <a href="#page131">131</a>;</p> + <p class="i2">on repeated crossing, ii. <a href="#page267">267</a>;</p> + <p class="i2">absorption of one species by another, when crossed, ii. <a href="#page88">88</a>;</p> + <p class="i2">crossing of varieties of the pea, i. 397;</p> + <p class="i2">crossing maize, ii. <a href="#page105">105</a>;</p> + <p class="i2">crossing of species of <i>Verbascum</i>, ii. <a href="#page93">93</a>, <a href="#page105">105</a>;</p> + <p class="i2">reversion in hybrids, ii. <a href="#page36">36</a>, <a href="#page49">49</a>, <a href="#page50">50</a>;</p> + <p class="i2">of <i>Cereus</i>, i. 392;</p> + <p class="i2">of <i>Tropæolum majus</i> and <i>minus</i>, i. 392;</p> + <p class="i2">variability of hybrids, ii. <a href="#page265">265</a>;</p> + <p class="i2">variable hybrids from one variable parent, ii. <a href="#page270">270</a>;</p> + <p class="i2">graft hybrid produced by inosculation in the vine, i. 395;</p> + <p class="i2">effect produced by grafts on the stock, i. 394, ii. <a href="#page278">278</a>;</p> + <p class="i2">tendency of hybrid plants to produce double flowers, ii. <a href="#page171">171</a>;</p> + <p class="i2">production of perfect fruit by sterile hybrids, ii. <a href="#page172">172</a>;</p> + <p class="i2">sexual elective affinity, ii. <a href="#page180">180</a>;</p> + <p class="i2">self-impotence in <i>Lobelia</i>, <i>Verbascum</i>, <i>Lilium</i>, and <i>Passiflora</i>, ii. <a href="#page136">136</a>-<a href="#page137">137</a>;</p> + <p class="i2">on the action of pollen, ii. <a href="#page108">108</a>;</p> + <p class="i2">fertilisation of <i>Malva</i>, i. 402-403, ii. <a href="#page363">363</a>;</p> + <p class="i2">prepotency of pollen, ii. <a href="#page187">187</a>;</p> + <p class="i2">prepotency of transmission in species of <i>Nicotiana</i>, ii. <a href="#page67">67</a>;</p> + <p class="i2">bud-variation in <i>Pelargonium zonale</i>, i. 375;</p> + <p class="i2">in <i>Œnothera biennis</i>, i. 382;</p> + <p class="i2">in <i>Achillæa millefolium</i>, i. 408;</p> + <p class="i2">effect of manure on the fertility of plants, ii. <a href="#page163">163</a>;</p> + <p class="i2">on contabescence, ii. <a href="#page165">165</a>-<a href="#page166">166</a>;</p> + <p class="i2">inheritance of plasticity, ii. <a href="#page241">241</a>;</p> + <p class="i2">villosity of plants, ii. <a href="#page277">277</a>.</p> + <p><span class="sc">Geese</span> (<i>anseres</i>) general fertility of, in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Gegenbaur</span>, on the number of digits, ii. <a href="#page13">13</a>.</p> + <p><span class="sc">Gemmation</span> and fission, ii. <a href="#page358">358</a>.</p> +<!-- Page 453 --><span class="pagenum"><a name="page453"></a>{453}</span> + <p><span class="sc">Gemmules</span>, or cell-gemmules, ii. <a href="#page374">374</a>, <a href="#page378">378</a>-<a href="#page381">381</a>, <a href="#page384">384</a>.</p> + <p><span class="sc">Genet</span>, fertility of the, in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Generation</span>, alternate, ii. <a href="#page361">361</a>, <a href="#page367">367</a>, <a href="#page390">390</a>.</p> + <p><span class="sc">Generation</span>, sexual, ii. <a href="#page359">359</a>-<a href="#page364">364</a>.</p> + <p><span class="sc">Genius</span>, inheritance of, ii. <a href="#page7">7</a>.</p> + <p><i>Gentiana amarella</i>, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Geoffroy</span> Saint-Hilaire, production of monstrous chickens, ii. <a href="#page289">289</a>;</p> + <p class="i2">"<i>Loi de l'affinité de soi pour soi</i>," ii. <a href="#page339">339</a>;</p> + <p class="i2">compensation of growth, ii. <a href="#page342">342</a>.</p> + <p><span class="sc">Geoffroy</span> Saint-Hilaire, Isid., origin of the dog, i. 66;</p> + <p class="i2">barking of a jackal, i. 27;</p> + <p class="i2">period of gestation and odour of the jackal, i. 30;</p> + <p class="i2">anomalies in the teeth of dogs, i. 34;</p> + <p class="i2">variations in the proportions of dogs, i. 35;</p> + <p class="i2">webbed feet of Newfoundland dogs, i. 39;</p> + <p class="i2">crossing of domestic and wild cats, i. 44;</p> + <p class="i2">domestication of the arni, i. 82;</p> + <p class="i2">supposed introduction of cattle into Europe from the East, <i>ibid.</i>;</p> + <p class="i2">absence of interdigital pits in sheep, i. 95;</p> + <p class="i2">origin of the goat, i. 101;</p> + <p class="i2">feral geese, i. 190;</p> + <p class="i2">ancient history of the fowl, i. 246;</p> + <p class="i2">skull of the Polish fowl, i. 262;</p> + <p class="i2">preference of the Romans for the liver of white geese, i. 289;</p> + <p class="i2">polydactylism, ii. <a href="#page12">12</a>;</p> + <p class="i2">assumption of male characters by female birds, ii. <a href="#page51">51</a>;</p> + <p class="i2">supernumerary mammæ in women, ii. <a href="#page58">58</a>;</p> + <p class="i2">development of a proboscis in the pig, <i>ibid.</i>;</p> + <p class="i2">transmission and blending of characters in hybrids, ii. <a href="#page94">94</a>;</p> + <p class="i2">refusal of animals to breed in captivity, ii. <a href="#page149">149</a>;</p> + <p class="i2">on the Guinea pig, ii. <a href="#page152">152</a>;</p> + <p class="i2">silkworms producing white cocoons, ii. <a href="#page199">199</a>;</p> + <p class="i2">on the carp, ii. <a href="#page236">236</a>;</p> + <p class="i2">on <i>Helix lactea</i>, ii. <a href="#page280">280</a>;</p> + <p class="i2">on monstrosities, ii. <a href="#page254">254</a>;</p> + <p class="i2">injury to the embryo a cause of monstrosity, ii. <a href="#page269">269</a>;</p> + <p class="i2">alteration in the coat of horses in coal mines, ii. <a href="#page278">278</a>;</p> + <p class="i2">length of the intestines in wild and tame animals, ii. <a href="#page302">302</a>-<a href="#page303">303</a>;</p> + <p class="i2">inheritance of rudimentary limbs in the dog, ii. <a href="#page315">315</a>;</p> + <p class="i2">correlation in monstrosities, ii. <a href="#page320">320</a>;</p> + <p class="i2">supernumerary digits in man, ii. <a href="#page322">322</a>;</p> + <p class="i2">co-existence of anomalies, ii. <a href="#page331">331</a>;</p> + <p class="i2">fusion of homologous parts, ii. <a href="#page341">341</a>-<a href="#page342">342</a>;</p> + <p class="i2">presence of hairs and teeth in ovarian tumours, ii. <a href="#page370">370</a>;</p> + <p class="i2">development of teeth on the palate in the horse, ii. <a href="#page391">391</a>.</p> + <p><span class="sc">Geographical</span> differences of faunas, i. 10.</p> + <p><span class="sc">Geological</span> succession of organisms, i. 11.</p> + <p><i>Geranium</i>, ii. <a href="#page59">59</a>.</p> + <p><i>Geranium phæum</i> and <i>pyrenaicum</i>, ii. <a href="#page258">258</a>.</p> + <p><i>Geranium pratense</i>, i. 379.</p> + <p><span class="sc">Gerard</span>, asserted climatal change in Burgundian bees, i. 297.</p> + <p><span class="sc">Gerarde</span>, on varieties of the hyacinth, i. 370.</p> + <p><span class="sc">Gerstäcker</span>, on hive-bees, i. 299.</p> + <p><span class="sc">Gervais</span>, Prof., origin of the dog, i. 16;</p> + <p class="i2">resemblance of dogs and jackals, i. 24;</p> + <p class="i2">taming of the jackal, i. 26;</p> + <p class="i2">number of teeth in dogs, i. 34;</p> + <p class="i2">breeds of dogs, i. 36;</p> + <p class="i2">on tertiary horses, i. 51;</p> + <p class="i2">biblical notices of horses, i. 55;</p> + <p class="i2">species of <i>Ovis</i>, i. 94;</p> + <p class="i2">wild and domestic rabbits, i. 103;</p> + <p class="i2">rabbits from Mount Sinai and Algeria, i. 105;</p> + <p class="i2">earless rabbits, i. 108;</p> + <p class="i2">batrachia with doubled limbs, ii. <a href="#page391">391</a>.</p> + <p><span class="sc">Gestation</span>, period of, in the dog, wolf, &c, i. 29-30;</p> + <p class="i2">in the pig, i. 74;</p> + <p class="i2">in cattle, i. 87, ii. <a href="#page321">321</a>;</p> + <p class="i2">in sheep, i. 97.</p> + <p><span class="sc">Gestures</span>, inheritance of peculiarities in, ii. <a href="#page6">6</a>.</p> + <p>"<span class="sc">Ghoondooks</span>" a sub-breed of fowls, i. 229.</p> + <p><span class="sc">Ghor-Khur</span>, ii. <a href="#page42">42</a>.</p> + <p><span class="sc">Giles</span>, Mr., effect of cross-breeding in the pig, i. 404.</p> + <p><span class="sc">Giraffe</span>, co-ordination of structure of, ii. <a href="#page221">221</a>.</p> + <p><span class="sc">Girard</span>, period of appearance of permanent teeth in dogs, i. 35.</p> + <p><span class="sc">Girou</span> de Buzareingues, inheritance in the horse, ii. <a href="#page10">10</a>;</p> + <p class="i2">reversion by age in cattle, ii. <a href="#page38">38</a>;</p> + <p class="i2">prepotency of transmission of character in sheep and cattle, ii. <a href="#page66">66</a>;</p> + <p class="i2">on crossing gourds, ii. <a href="#page108">108</a>.</p> + <p><span class="sc">Gisburne</span>, wild cattle at, i. 84.</p> + <p><i>Gladiolus</i>, i. 364;</p> + <p class="i2">self-impotence of hybrids of, ii. <a href="#page139">139</a>.</p> + <p><i>Gladiolus colvillii</i>, bud-variation in, i. 382.</p> + <p><span class="sc">Glands</span>, compensatory development of, ii. <a href="#page300">300</a>.</p> + <p><span class="sc">Glastonbury</span> thorn, i. 364.</p> + <p><span class="sc">Glenny</span>, Mr., on the <i>Cineraria</i>, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Gloede</span>, F., on strawberries, i. 353.</p> + <p><span class="sc">Gloger</span>, on the wings of ducks, ii. <a href="#page298">298</a>.</p> + <p>"<span class="sc">Glouglou</span>" (pigeon), i. 154.</p> + <p><i>Gloxiniæ</i>, peloric, i. 365, ii. <a href="#page167">167</a>.</p> + <p><span class="sc">Gmelin</span>, on red cats, at Tobolsk, i. 47.</p> + <p><span class="sc">Goat</span>, i. 101-102, ii. <a href="#page33">33</a>;</p> + <p class="i2">polydactylism in the, ii. <a href="#page14">14</a>;</p> + <p class="i2">sexual differences in horns of, ii. <a href="#page73">73</a>;</p> + <p class="i2">valued by South Africans, ii. <a href="#page207">207</a>;</p> + <p class="i2">Thibet, ii. <a href="#page278">278</a>;</p> + <p class="i2">amount of milk and development of udders in the, ii. <a href="#page300">300</a>;</p> + <p class="i2">hornless, rudimentary bony cores in, ii. <a href="#page316">316</a>;</p> + <p class="i2">Angora, ii. <a href="#page326">326</a>.</p> + <p><span class="sc">Godron</span>, odour of the hairless Turkish dog, i. 30;</p> + <p class="i2">differences in the skull of dogs, i. 34;</p> + <p class="i2">increase of breeds of horses, i. 51;</p> + <p class="i2">crossing of domestic and wild swine, i. 66;</p> + <p class="i2">on goats, i. 101-102;</p> + <p class="i2">colour of the skin in fowls, i. 258;</p> + <p class="i2">bees of north and south of France, i. 297;</p> + <p class="i2">introduction of the silkworm into Europe, i. 300;</p> + <p class="i2">variability in the silkworm, i. 304;</p> + <p class="i2">supposed species of wheat, i. 312-314;</p> + <p class="i2">on <i>Ægilops triticoides</i>, i. 313;</p> + <p class="i2">variable presence of barbs in grasses, i. 314;</p> +<!-- Page 454 --><span class="pagenum"><a name="page454"></a>{454}</span> + <p class="i2">colours of the seeds of maize, i. 321;</p> + <p class="i2">unity of character in cabbages, i. 323;</p> + <p class="i2">correlation of colour and odour, i. 325;</p> + <p class="i2">effect of heat and moisture on the cabbage, i. 325;</p> + <p class="i2">on the cultivated species of <i>Brassica</i>, i. 325;</p> + <p class="i2">on the Rouncival and sugar peas, i. 327;</p> + <p class="i2">variation in the numbers of peas in the same pod, i. 328;</p> + <p class="i2">wild vines in Spain, i. 332;</p> + <p class="i2">on raising peaches from seed, i. 339;</p> + <p class="i2">supposed specific distinctness of peach and nectarine, i. 340;</p> + <p class="i2">nectarine producing peaches, i. 341;</p> + <p class="i2">on the flower of <i>Corydalis</i>, i. 344;</p> + <p class="i2">origin and variations of the plum, i. 345;</p> + <p class="i2">origin of the cherry, i. 347;</p> + <p class="i2">reversion of single-leaved strawberries, i. 353;</p> + <p class="i2">five-leaved variety of <i>Fragaria collina</i>, i. 353;</p> + <p class="i2">supposed immutability of specific characters, i. 358-359;</p> + <p class="i2">varieties of <i>Robinia</i>, i. 361;</p> + <p class="i2">permanency of the simple-leaved ash, i. 362;</p> + <p class="i2">non-inheritance of certain mutilations, ii. <a href="#page23">23</a>;</p> + <p class="i2">wild turnips, carrots, and celery, ii. <a href="#page33">33</a>;</p> + <p class="i2">pre-potency of a goat-like ram, ii. <a href="#page66">66</a>;</p> + <p class="i2">benefit of change of soil to plants, ii. <a href="#page146">146</a>;</p> + <p class="i2">fertility of peloric flowers of <i>Corydalis solida</i>, ii. <a href="#page167">167</a>;</p> + <p class="i2">seeding of ordinarily seedless fruit, ii. <a href="#page168">168</a>;</p> + <p class="i2">sexual sterility of plants propagated by buds, &c., ii. <a href="#page169">169</a>;</p> + <p class="i2">increase of sugar in beet-root, ii. <a href="#page201">201</a>;</p> + <p class="i2">effects of selection in enlarging particular parts of plants, ii. <a href="#page217">217</a>;</p> + <p class="i2">growth of the cabbage in the tropics, ii. <a href="#page277">277</a>;</p> + <p class="i2">rejection of bitter almonds by mice, ii. <a href="#page232">232</a>;</p> + <p class="i2">influence of marshy pasture on the fleece of sheep, ii. <a href="#page278">278</a>;</p> + <p class="i2">on the ears of ancient Egyptian pigs, ii. <a href="#page301">301</a>;</p> + <p class="i2">primitive distinctness of species, ii. <a href="#page415">415</a>;</p> + <p class="i2">solid hoofed swine, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Goethe</span>, on compensation of growth, ii. <a href="#page342">342</a>.</p> + <p><span class="sc">Goldfish</span>, i. 296-297, ii. <a href="#page236">236</a>.</p> + <p><span class="sc">Gomara</span>, on South American cats, i. 46.</p> + <p><span class="sc">Gongora</span>, number of seeds in the, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Goose</span>, ancient domestication of, i. 287;</p> + <p class="i2">sacred to Juno in Rome, <i>ibid.</i>;</p> + <p class="i2">inflexibility of organisation of, i. 288;</p> + <p class="i2">skull perforated in tufted, i. 288;</p> + <p class="i2">characters of breeds and sub-breeds of, i. 288-289;</p> + <p class="i2">variety of, from Sebastopol, i. 289, ii. <a href="#page392">392</a>;</p> + <p class="i2">feral in La Plata, i. 190;</p> + <p class="i2">Egyptian, hybrid of, with penguin duck, ii. <a href="#page68">68</a>;</p> + <p class="i2">spontaneous segregation of varieties of, ii. <a href="#page104">104</a>;</p> + <p class="i2">fertility of, increased by domestication, ii. <a href="#page112">112</a>;</p> + <p class="i2">decreased fertility of, in Bogota, ii. <a href="#page161">161</a>;</p> + <p class="i2">sterility of, in the Philippine Islands, ii. <a href="#page162">162</a>;</p> + <p class="i2">selection of, ii. <a href="#page204">204</a>;</p> + <p class="i2">white, preference of the Romans for the liver of, ii. <a href="#page209">209</a>;</p> + <p class="i2">persistency of character in, ii. <a href="#page254">254</a>;</p> + <p class="i2">Egyptian, change in breeding season of, ii. <a href="#page304">304</a>.</p> + <p><span class="sc">Gooseberry</span>, i. 354-356;</p> + <p class="i2">bud-variation in the, i. 376;</p> + <p class="i2">Whitesmith's, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Göppert</span>, on monstrous poppies, ii. <a href="#page166">166</a>.</p> + <p><span class="sc">Gosse</span>, P. H., feral dogs in Jamaica, i. 28;</p> + <p class="i2">feral pigs of Jamaica, i. 77-78;</p> + <p class="i2">feral rabbits of Jamaica, i. 112;</p> + <p class="i2">on <i>Columba leucocephala</i>, i. 183;</p> + <p class="i2">feral Guinea fowl in Jamaica, i. 190;</p> + <p class="i2">reproduction of individual peculiarities by gemmation in a coral, i. 374;</p> + <p class="i2">frequency of striped legs in mules, ii. <a href="#page42">42</a>.</p> + <p><span class="sc">Gould</span>, Dr., on hereditary hæmorrhage, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Gould</span>, John, origin of the turkey, i. 292.</p> + <p><i>Goura coronata</i> and <i>Victoriæ</i>, hybrids of, i. 194, ii. <a href="#page155">155</a>.</p> + <p><span class="sc">Gourds</span>, i. 357;</p> + <p class="i2">crossing of varieties of, ii. <a href="#page108">108</a>;</p> + <p class="i2">ancient Peruvian variety of, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Gout</span>, inheritance of, ii. <a href="#page7">7</a>;</p> + <p class="i2">period of appearance of, ii. <a href="#page77">77</a>.</p> + <p><span class="sc">Graba</span>, on the pigeon of the Faroe islands, i. 183.</p> + <p><span class="sc">Grafting</span>, ii. <a href="#page147">147</a>;</p> + <p class="i2">effects of, ii. <a href="#page259">259</a>, <a href="#page278">278</a>;</p> + <p class="i2">upon the stock, i. 394-395;</p> + <p class="i2">upon the variability of trees, ii. <a href="#page259">259</a>;</p> + <p class="i2">changes analogous to bud-variation produced by, i. 387, 389.</p> + <p><span class="sc">Graft-hybrids</span>, i. 390-391, 394-397, ii. <a href="#page364">364</a>-<a href="#page365">365</a>.</p> + <p><span class="sc">Grapes</span>, bud-variation in, i. 375;</p> + <p class="i2">cross of white and purple, i. 393;</p> + <p class="i2">green, liable to disease, ii. <a href="#page336">336</a>;</p> + <p class="i2">effect of foreign pollen on, i. 400.</p> + <p><span class="sc">Grasses</span>, seeds of, used as food by savages, i. 307-309.</p> + <p><span class="sc">Gray</span>, Asa, superior wild varieties of fruit-trees, i. 310;</p> + <p class="i2">cultivated native plants of North America, i. 312, 357;</p> + <p class="i2">non-variation of weeds, i. 317;</p> + <p class="i2">supposed spontaneous crossing of pumpkins, i. 399;</p> + <p class="i2">pre-ordination of variation, ii. <a href="#page432">432</a>;</p> + <p class="i2">progeny of husked form of maize, i. 320;</p> + <p class="i2">wild intermediate forms of strawberries, i. 352.</p> + <p><span class="sc">Gray</span>, G. R., on <i>Columba gymnocyclus</i>, i. 184.</p> + <p><span class="sc">Gray</span>, J. E., on <i>Sus pliciceps</i>, i. 70;</p> + <p class="i2">on a variety of the gold-fish, i. 297;</p> + <p class="i2">hybrids of the ass and zebra, ii. <a href="#page42">42</a>-<a href="#page43">43</a>;</p> + <p class="i2">on the breeding of animals at Knowsley, ii. <a href="#page149">149</a>;</p> + <p class="i2">on the breeding of birds in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Greene</span>, J. Reay, on the development of the echinodermata, ii. <a href="#page367">367</a>.</p> + <p><span class="sc">Greenhow</span>, Mr., on a Canadian web-footed dog, i. 39.</p> + <p><span class="sc">Greening</span>, Mr., experiments on <i>Abraxas grossulariata</i>, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Gregson</span>, Mr., experiments on <i>Abraxas grossulariata</i>, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Grey</span>, Sir George, preservation of seed-bearing plants by the Australian savages, i. 310;</p> +<!-- Page 455 --><span class="pagenum"><a name="page455"></a>{455}</span> + <p class="i2">detestation of incest by Australian savages, ii. <a href="#page123">123</a>.</p> + <p><span class="sc">Greyhounds</span>, sculptured on Egyptian monuments, and in the Villa of Antoninus, i. 17;</p> + <p class="i2">modern breed of, i. 41;</p> + <p class="i2">crossed with the bulldog, by Lord Orford, ii. <a href="#page95">95</a>;</p> + <p class="i2">co-ordination of structure of, due to selection, ii. <a href="#page221">221</a>-<a href="#page222">222</a>;</p> + <p class="i2">Italian, ii. <a href="#page227">227</a>.</p> + <p><span class="sc">Greyness</span>, inherited at corresponding periods of life, ii. <a href="#page77">77</a>.</p> + <p><span class="sc">Grieve</span>, Mr., on early-flowering dahlias, i. 370.</p> + <p><span class="sc">Grigor</span>, Mr., acclimatisation of the Scotch fir, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Groom-Napier</span>, C. O., on the webbed feet of the otter-hound, i. 40.</p> + <p>"<span class="sc">Grosses-gorges</span>" (pigeons), i. 137.</p> + <p><span class="sc">Ground-tumbler</span>, Indian, i. 150.</p> + <p><span class="sc">Grouse</span>, fertility of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Grönland</span>, hybrids of <i>Ægilops</i> and wheat, ii. <a href="#page110">110</a>.</p> + <p><i>Grus montigresia</i>, <i>cinerea</i>, and <i>Antigone</i>, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Guanacos</span>, selection of, ii. <a href="#page207">207</a>.</p> + <p><span class="sc">Guans</span>, general fertility of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Guelder-rose</span>, ii. <a href="#page185">185</a>.</p> + <p><span class="sc">Guelderland</span> fowls, i. 230.</p> + <p><span class="sc">Guiana</span>, selection of dogs by the Indians of, ii. <a href="#page206">206</a>.</p> + <p><span class="sc">Guinea fowl</span>, i. 294;</p> + <p class="i2">feral in Ascension, and Jamaica, i. 190, ii. <a href="#page33">33</a>;</p> + <p class="i2">indifference of to change of climate, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Guinea</span> pig, ii. <a href="#page24">24</a>, <a href="#page152">152</a>.</p> + <p><span class="sc">Güldenstadt</span>, on the jackal, i. 25.</p> + <p><span class="sc">Gull</span>, herring, breeding in confinement, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Gulls</span>, general sterility of, in captivity, ii. <a href="#page157">157</a>.</p> + <p><i>Gulo</i>, sterility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Günther</span>, A., on tufted ducks and geese, i. 274;</p> + <p class="i2">on the regeneration of lost parts in batrachia, ii. <a href="#page15">15</a>.</p> + <p><span class="sc">Gurney</span>, Mr., owls breeding in captivity, ii. <a href="#page154">154</a>;</p> + <p class="i2">appearance of "black-shouldered" among ordinary peacocks, i. 291.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Habit</span>, influence of, in acclimatisation, ii. <a href="#page312">312</a>-<a href="#page315">315</a>.</p> + <p><span class="sc">Habits</span>, inheritance of, ii. <a href="#page395">395</a>.</p> + <p><span class="sc">Häckel</span>, on cells, ii. <a href="#page370">370</a>;</p> + <p class="i2">on the double reproduction of medusæ, ii. <a href="#page384">384</a>;</p> + <p class="i2">on inheritance, ii. <a href="#page397">397</a>.</p> + <p><span class="sc">Hackles</span>, peculiarities of, in fowls, i. 254.</p> + <p><span class="sc">Hair</span>, on the face, inheritance of, in man, ii. <a href="#page4">4</a>;</p> + <p class="i2">peculiar lock of, inherited, ii. <a href="#page5">5</a>;</p> + <p class="i2">growth of, under stimulation of skin, ii. <a href="#page326">326</a>;</p> + <p class="i2">homologous variation of, ii. <a href="#page325">325</a>;</p> + <p class="i2">development of, within the ears and in the brain, ii. <a href="#page391">391</a>.</p> + <p><span class="sc">Hair</span> and teeth, correlation of, ii. <a href="#page326">326</a>-<a href="#page328">328</a>.</p> + <p><span class="sc">Hairy</span> family, corresponding period of inheritance in, ii. <a href="#page77">77</a>.</p> + <p><span class="sc">Half-castes</span>, character of, ii. <a href="#page46">46</a>.</p> + <p><span class="sc">Half-lop</span> rabbits, figured and described, i. 107-108;</p> + <p class="i2">skull of, i. 119.</p> + <p><i>Haliætus leucocephalus</i>, copulating in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Hallam</span>, Col., on a two-legged race of pigs, ii. <a href="#page4">4</a>.</p> + <p><span class="sc">Hamburgh</span> fowl, i. 227, 261;</p> + <p class="i2">figured, i. 228.</p> + <p><span class="sc">Hamilton</span>, wild cattle of, i. 84.</p> + <p><span class="sc">Hamilton</span>, Dr., on the assumption of male plumage by the hen pheasant, ii. <a href="#page51">51</a>.</p> + <p><span class="sc">Hamilton</span>, F. Buchanan, on the shaddock, i. 335;</p> + <p class="i2">varieties of Indian cultivated plants, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Hancock</span>, Mr., sterility of tamed birds, ii. <a href="#page155">155</a>-<a href="#page157">157</a>.</p> + <p><span class="sc">Handwriting</span>, inheritance of peculiarities in, ii. <a href="#page6">6</a>.</p> + <p><span class="sc">Hanmer</span>, Sir J., on selection of flower seeds, ii. <a href="#page204">204</a>.</p> + <p><span class="sc">Hansell</span>, Mr., inheritance of dark yolks in duck's eggs, i. 281.</p> + <p><span class="sc">Harcourt</span>, E. V., on the Arab boar-hound, i. 17;</p> + <p class="i2">aversion of the Arabs to dun-coloured horses, i. 55.</p> + <p><span class="sc">Hardy</span>, Mr., effect of excess of nourishment on plants, ii. <a href="#page257">257</a>.</p> + <p><span class="sc">Hare</span>, hybrids of, with rabbit, i. 105;</p> + <p class="i2">sterility of the, in confinement, ii. <a href="#page152">152</a>;</p> + <p class="i2">preference of, for particular plants, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Hare-lip</span>, inheritance of, ii. <a href="#page24">24</a>.</p> + <p><span class="sc">Harlan</span>, Dr., on hereditary diseases, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Harmer</span>, Mr., on the number of eggs in a codfish, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Harvey</span>, Mr., monstrous red and white African bull, i. 91.</p> + <p><span class="sc">Harvey</span>, Prof., singular form of <i>Begonia frigida</i>, i. 365-366;</p> + <p class="i2">effects of cross-breeding on the female, i. 404;</p> + <p class="i2">monstrous saxifrage, ii. <a href="#page166">166</a>.</p> + <p><span class="sc">Hasora</span> wheat, i. 313.</p> + <p><span class="sc">Hautbois</span> strawberry, i. 353.</p> + <p><span class="sc">Hawker</span>, Col., on call or decoy ducks, i. 281.</p> + <p><span class="sc">Hawthorn</span>, varieties of, i. 360-364;</p> + <p class="i2">pyramidal, i. 361;</p> + <p class="i2">pendulous hybridised, ii. <a href="#page18">18</a>;</p> + <p class="i2">changes of, by age, i. 364, 387;</p> + <p class="i2">bud-variation in the, i. 377;</p> + <p class="i2">flower buds of, attacked by bullfinches, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Hayes</span>, Dr., character of Esquimaux dogs, i. 21-22.</p> + <p><span class="sc">Haywood</span>, W., on the feral rabbits of Porto Santo, i. 114.</p> + <p><span class="sc">Hazel</span>, purple-leaved, i. 362, 395, ii. <a href="#page330">330</a>.</p> + <p><span class="sc">Head</span> of wild boar and Yorkshire pig, figured, i. 72.</p> +<!-- Page 456 --><span class="pagenum"><a name="page456"></a>{456}</span> + <p><span class="sc">Head</span> and limbs, correlated variability of, ii. <a href="#page323">323</a>.</p> + <p><span class="sc">Headache</span>, inheritance of, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">Heartsease</span>, i. 368-369;</p> + <p class="i2">change produced in the, by transplantation, i. 386;</p> + <p class="i2">reversion in, ii. <a href="#page31">31</a>, <a href="#page47">47</a>;</p> + <p class="i2">effects of selection on, ii. <a href="#page200">200</a>;</p> + <p class="i2">scorching of, ii. <a href="#page229">229</a>;</p> + <p class="i2">effects of seasonal conditions on the, ii. <a href="#page274">274</a>;</p> + <p class="i2">annual varieties of the, ii. <a href="#page305">305</a>.</p> + <p><span class="sc">Heat</span>, effect of, upon the fleece of sheep, i. 98.</p> + <p><span class="sc">Heber</span>, Bishop, on the breeding of the rhinoceros in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Hebrides</span>, cattle of the, i. 80;</p> + <p class="i2">pigeons of the, i. 183.</p> + <p><span class="sc">Heer</span>, O., on the plants of the Swiss lake-dwellings, i. 309, ii. <a href="#page215">215</a>, <a href="#page427">427</a>;</p> + <p class="i2">on the cereals, i. 317-319;</p> + <p class="i2">on the peas, i. 326;</p> + <p class="i2">on the vine growing in Italy in the bronze age, i. 332.</p> + <p><i>Helix lactea</i>, ii. <a href="#page280">280</a>.</p> + <p><i>Hemerocallis fulva</i> and <i>flava</i>, interchanging by bud-variation, i. 386.</p> + <p><span class="sc">Hemlock</span> yields no conicine in Scotland, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Hemp</span>, differences of, in various parts of India, ii. <a href="#page165">165</a>;</p> + <p class="i2">climatal difference in products of, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Hempseed</span>, effect of, upon the colour of birds, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Hermaphrodite</span> flowers, occurrence of, in Maize, i. 321.</p> + <p><span class="sc">Hen</span>, assumption of male characters by the, ii. <a href="#page51">51</a>, <a href="#page54">54</a>;</p> + <p class="i2">development of spurs in the, ii. <a href="#page318">318</a>.</p> + <p>"<span class="sc">Hennies</span>," or hen-like male fowls, i. 252.</p> + <p><span class="sc">Henry</span>, T. A., a variety of the ash produced by grafting, i. 394;</p> + <p class="i2">crossing of species of <i>Rhododendron</i> and <i>Arabis</i>, i. 400.</p> + <p><span class="sc">Henslow</span>, Prof., individual variation in wheat, i. 314;</p> + <p class="i2">bud-variation in the Austrian bramble rose, i. 381;</p> + <p class="i2">partial reproduction of the weeping ash by seed, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Hepatica</span>, changed by transplantation, i. 386.</p> + <p><span class="sc">Herbert</span>, Dr., variations of <i>Viola grandiflora</i>, i. 368;</p> + <p class="i2">bud-variation in camellias, i. 377;</p> + <p class="i2">seedlings from reverted <i>Cytisus Adami</i>, i. 388;</p> + <p class="i2">crosses of Swedish and other turnips, ii. <a href="#page93">93</a>;</p> + <p class="i2">on hollyhocks, ii. <a href="#page107">107</a>;</p> + <p class="i2">breeding of hybrids, ii. <a href="#page131">131</a>;</p> + <p class="i2">self-impotence in hybrid hippeastrums, ii. <a href="#page138">138</a>-<a href="#page139">139</a>;</p> + <p class="i2">hybrid <i>Gladiolus</i>, ii. <a href="#page139">139</a>;</p> + <p class="i2">on <i>Zephyranthes candida</i>, ii. <a href="#page164">164</a>;</p> + <p class="i2">fertility of the crocus, ii. <a href="#page165">165</a>;</p> + <p class="i2">on contabescence, ii. <a href="#page165">165</a>;</p> + <p class="i2">hybrid <i>Rhododendron</i>, ii. <a href="#page265">265</a>.</p> + <p><span class="sc">Herculaneum</span>, figure of a pig found in, i. 67.</p> + <p><span class="sc">Heron</span>, Sir R., appearance of "black-shouldered" among ordinary peacocks, i. 290-291;</p> + <p class="i2">non-inheritance of monstrous characters by goldfish, i. 296;</p> + <p class="i2">crossing of white and coloured Angora rabbits, ii. <a href="#page92">92</a>;</p> + <p class="i2">crosses of solid-hoofed pigs, ii. <a href="#page93">93</a>.</p> + <p><i>Herpestes fasciatus</i> and <i>griseus</i>, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Heusinger</span>, on the sheep of the Tarentino, ii. <a href="#page227">227</a>;</p> + <p class="i2">on correlated constitutional peculiarities, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Hewitt</span>, Mr., reversion in bantam cocks, i. 240;</p> + <p class="i2">degeneration of silk fowls, i. 243;</p> + <p class="i2">partial sterility of hen-like male fowls, i. 252;</p> + <p class="i2">production of tailed chickens by rumpless fowls, i. 259;</p> + <p class="i2">on taming and rearing wild ducks, i. 278-279, ii. <a href="#page233">233</a>, <a href="#page262">262</a>-<a href="#page263">263</a>;</p> + <p class="i2">conditions of inheritance in laced Sebright bantams, ii. <a href="#page22">22</a>;</p> + <p class="i2">reversion in rumpless fowls, ii. <a href="#page31">31</a>;</p> + <p class="i2">reversion in fowls by age, ii. <a href="#page39">39</a>;</p> + <p class="i2">hybrids of pheasant and fowl, ii. <a href="#page45">45</a>, <a href="#page68">68</a>;</p> + <p class="i2">assumption of male characters by female pheasants, ii. <a href="#page51">51</a>;</p> + <p class="i2">development of latent characters in a barren bantam hen, ii. <a href="#page54">54</a>;</p> + <p class="i2">mongrels from the silk-fowl, ii. <a href="#page67">67</a>;</p> + <p class="i2">effects of close interbreeding on fowls, ii. <a href="#page124">124</a>-<a href="#page125">125</a>;</p> + <p class="i2">on feathered-legged bantams, ii. <a href="#page323">323</a>.</p> + <p><span class="sc">Hibbert</span>, Mr., on the pigs of the Shetland Islands, i. 70.</p> + <p><span class="sc">Highland</span> cattle, descended from <i>Bos longifrons</i>, i. 81.</p> + <p><span class="sc">Hildebrand</span>, Dr., on the fertilisation of <i>Orchideæ</i>, i. 402-403;</p> + <p class="i2">occasional necessary crossing of plants, ii. <a href="#page90">90</a>;</p> + <p class="i2">on <i>Primula sinensis</i> and <i>Oxalis rosea</i>, ii. <a href="#page132">132</a>;</p> + <p class="i2">on <i>Corydalis cava</i>, ii. <a href="#page132">132</a>-<a href="#page133">133</a>.</p> + <p><span class="sc">Hill</span>, R., on the Alco, i. 31;</p> + <p class="i2">feral rabbits in Jamaica, i. 112;</p> + <p class="i2">feral peacocks in Jamaica, i. 190;</p> + <p class="i2">variation of the Guinea fowl in Jamaica, i. 294;</p> + <p class="i2">sterility of tamed birds in Jamaica, ii. <a href="#page155">155</a>, <a href="#page157">157</a>.</p> + <p><span class="sc">Himalaya</span>, range of gallinaceous birds in the, i. 237.</p> + <p><span class="sc">Himalayan</span> rabbit, i. 107, 108-111;</p> + <p class="i2">skull of, i. 120.</p> + <p><span class="sc">Himalayan</span> sheep, i. 95.</p> + <p><span class="sc">Hindmarsh</span>, Mr., on Chillingham cattle, i. 84.</p> + <p>"<span class="sc">Hinkel-Taube</span>," i. 142-143.</p> + <p><span class="sc">Hinny</span> and mule, difference of, ii. <a href="#page67">67</a>-<a href="#page68">68</a>.</p> + <p><i>Hipparion</i>, anomalous resemblance to in horses, i. 50.</p> + <p><i>Hippeastrum</i>, hybrids of, ii. <a href="#page138">138</a>-<a href="#page139">139</a>.</p> + <p><span class="sc">Hive-bees</span>, ancient domestication of, i. 297;</p> + <p class="i2">breeds of, i. 298;</p> + <p class="i2">smaller when produced in old combs, i. 297;</p> + <p class="i2">variability in, i. 298;</p> + <p class="i2">crossing of Ligurian and common, i. 299.</p> + <p>"<span class="sc">Hocker-Taube</span>," i. 141.</p> + <p><span class="sc">Hobbs</span>, Fisher, on interbreeding pigs, ii. <a href="#page121">121</a>.</p> + <p><span class="sc">Hodgkin</span>, Dr., on the attraction of foxes by a female Dingo, i. 31;</p> +<!-- Page 457 --><span class="pagenum"><a name="page457"></a>{457}</span> + <p class="i2">origin of the Newfoundland dog, i. 42;</p> + <p class="i2">transmission of a peculiar lock of hair, ii. <a href="#page5">5</a>.</p> + <p><span class="sc">Hodgson</span>, Mr., domestication of <i>Canis primævus</i>, i. 26;</p> + <p class="i2">development of a fifth digit in Thibet mastiffs, i. 35;</p> + <p class="i2">number of ribs in humped cattle, i. 79;</p> + <p class="i2">on the sheep of the Himalaya, i. 95;</p> + <p class="i2">presence of four mammæ in sheep, <i>ibid.</i>;</p> + <p class="i2">arched nose in sheep, i. 96;</p> + <p class="i2">measurements of the intestines of goats, i. 102;</p> + <p class="i2">presence of interdigital pits in goats, <i>ibid.</i>;</p> + <p class="i2">disuse a cause of drooping ears, ii. <a href="#page301">301</a>.</p> + <p><span class="sc">Hofacker</span>, persistency of colour in horses, i. 51, ii. <a href="#page21">21</a>;</p> + <p class="i2">production of dun horses from parents of different colours, i. 59;</p> + <p class="i2">inheritance of peculiarities in handwriting, ii. <a href="#page6">6</a>;</p> + <p class="i2">heredity in a one-horned stag, ii. <a href="#page12">12</a>;</p> + <p class="i2">on consanguineous marriages, ii. <a href="#page123">123</a>.</p> + <p><span class="sc">Hog</span>, Red River, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Hogg</span>, Mr., retardation of breeding in cows by hard living, ii. <a href="#page112">112</a>.</p> + <p><span class="sc">Holland</span>, Sir H., necessity of inheritance, ii. <a href="#page2">2</a>;</p> + <p class="i2">on hereditary diseases, ii. <a href="#page7">7</a>;</p> + <p class="i2">hereditary peculiarity in the eyelid, ii. <a href="#page8">8</a>;</p> + <p class="i2">morbid uniformity in the same family, ii. <a href="#page17">17</a>;</p> + <p class="i2">transmission of hydrocele through the female, ii. <a href="#page52">52</a>;</p> + <p class="i2">inheritance of habits and tricks, ii. <a href="#page395">395</a>.</p> + <p><span class="sc">Holly</span>, varieties of the, i. 360, 362;</p> + <p class="i2">bud-reversion in, i. 384;</p> + <p class="i2">yellow-berried, ii. <a href="#page19">19</a>, <a href="#page230">230</a>.</p> + <p><span class="sc">Hollyhock</span>, bud-variation in, i. 378;</p> + <p class="i2">non-crossing of double varieties of, ii. <a href="#page107">107</a>;</p> + <p class="i2">tender variety of the, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Homer</span>, notice of Geese, i. 287;</p> + <p class="i2">breeding of the horses of Æneas, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Homologous</span> parts, correlated variability of, ii. <a href="#page322">322</a>-<a href="#page331">331</a>, <a href="#page354">354</a>-<a href="#page355">355</a>;</p> + <p class="i2">fusion of, ii. <a href="#page393">393</a>;</p> + <p class="i2">affinity of, ii. <a href="#page339">339</a>-<a href="#page342">342</a>.</p> + <p><span class="sc">Hoofs</span>, correlated with hair in variation, ii. <a href="#page325">325</a>.</p> + <p><span class="sc">Hook-billed duck</span>, skull figured, i. 282.</p> + <p><span class="sc">Hooker</span>, Dr. J. D., forked shoulder-stripe in Syrian asses, i. 63;</p> + <p class="i2">voice of the cock in Sikkim, i. 259;</p> + <p class="i2">use of Arum-roots as food, i. 307;</p> + <p class="i2">native useful plants of Australia, i. 311;</p> + <p class="i2">wild walnut of the Himalayas, i. 356;</p> + <p class="i2">variety of the plane tree, i. 362;</p> + <p class="i2">production of <i>Thuja orientalis</i> from seeds of <i>T. pendula</i>, i. 362;</p> + <p class="i2">singular form of <i>Begonia frigida</i>, i. 365;</p> + <p class="i2">reversion in plants run wild, ii. <a href="#page33">33</a>;</p> + <p class="i2">on the sugar-cane, ii. <a href="#page169">169</a>;</p> + <p class="i2">on Arctic plants, ii. <a href="#page256">256</a>;</p> + <p class="i2">on the oak grown at the Cape of Good Hope, ii. <a href="#page274">274</a>;</p> + <p class="i2">on <i>Rhododendron ciliatum</i>, ii. <a href="#page277">277</a>;</p> + <p class="i2">stock and mignonette, perennial in Tasmania, ii. <a href="#page305">305</a>.</p> + <p><span class="sc">Hopkirk</span>, Mr., bud-variation in the rose, i. 381;</p> + <p class="i2">in <i>Mirabilis jalapa</i>, i. 382;</p> + <p class="i2">in <i>Convolvulus tricolor</i>, i. 408.</p> + <p><span class="sc">Hornbeam</span>, heterophyllous, i. 362.</p> + <p><span class="sc">Horned</span> fowl, i. 229;</p> + <p class="i2">skull figured, i. 265.</p> + <p><span class="sc">Hornless</span> cattle in Paraguay, i. 89.</p> + <p><span class="sc">Horns</span> of sheep, i. 95;</p> + <p class="i2">correlation of, with fleece in sheep, ii. <a href="#page326">326</a>;</p> + <p class="i2">correlation of, with the skull, ii. <a href="#page333">333</a>;</p> + <p class="i2">rudimentary in young polled cattle, ii. <a href="#page315">315</a>;</p> + <p class="i2">of goats, i. 102.</p> + <p><span class="sc">Horses</span>, in Swiss lake-dwellings, i. 49;</p> + <p class="i2">different breeds of, in Malay Archipelago, i. 49;</p> + <p class="i2">anomalies in osteology and dentition of, i. 50;</p> + <p class="i2">mutual fertility of different breeds, i. 51;</p> + <p class="i2">feral, i. 51;</p> + <p class="i2">habit of scraping away snow, i. 53;</p> + <p class="i2">mode of production of breeds of, i. 54;</p> + <p class="i2">inheritance and diversity of colour in, i. 55;</p> + <p class="i2">dark stripes in, i. 56-61, ii. <a href="#page351">351</a>;</p> + <p class="i2">dun-coloured, origin of, i. 59;</p> + <p class="i2">colours of feral, i. 60-61;</p> + <p class="i2">effect of fecundation by a Quagga on the subsequent progeny of, i. 403-404;</p> + <p class="i2">inheritance of peculiarities in, ii. <a href="#page10">10</a>-<a href="#page11">11</a>;</p> + <p class="i2">polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">inheritance of colour in, ii. <a href="#page21">21</a>;</p> + <p class="i2">inheritance of exostoses in legs of, ii. <a href="#page23">23</a>;</p> + <p class="i2">reversion in, ii. <a href="#page33">33</a>, <a href="#page41">41</a>;</p> + <p class="i2">hybrids of, with ass and zebra, ii. <a href="#page42">42</a>;</p> + <p class="i2">prepotency of transmission in the sexes of, ii. <a href="#page65">65</a>;</p> + <p class="i2">segregation of, in Paraguay, ii. <a href="#page102">102</a>;</p> + <p class="i2">wild species of, breeding in captivity, ii. <a href="#page150">150</a>;</p> + <p class="i2">curly, in Paraguay, ii. <a href="#page205">205</a>, <a href="#page325">325</a>;</p> + <p class="i2">selection of, for trifling characters, ii. <a href="#page209">209</a>;</p> + <p class="i2">unconscious selection of, ii. <a href="#page212">212</a>-<a href="#page213">213</a>;</p> + <p class="i2">natural selection in Circassia, ii. <a href="#page225">225</a>;</p> + <p class="i2">alteration of coat of, in coal-mines, ii. <a href="#page278">278</a>;</p> + <p class="i2">degeneration of, in the Falkland Islands, ii. <a href="#page278">278</a>;</p> + <p class="i2">diseases of, caused by shoeing, ii. <a href="#page300">300</a>;</p> + <p class="i2">feeding on meat, ii. <a href="#page305">305</a>;</p> + <p class="i2">white and white-spotted, poisoned by mildewed vetches, ii. <a href="#page337">337</a>;</p> + <p class="i2">analogous variations in the colour of, ii. <a href="#page349">349</a>;</p> + <p class="i2">teeth developed on palate of, ii. <a href="#page391">391</a>;</p> + <p class="i2">of bronze period in Denmark, ii. <a href="#page427">427</a>.</p> + <p><span class="sc">Horse-chesnut</span>, early, at the Tuileries, i. 362;</p> + <p class="i2">tendency to doubleness in, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Horse-radish</span>, general sterility of the, ii. <a href="#page170">170</a>.</p> + <p>"<span class="sc">Houdan</span>," a French sub-breed of fowls, i. 229.</p> + <p><span class="sc">Howard</span>, C., on an Egyptian monument, i. 17;</p> + <p class="i2">on crossing sheep, ii. <a href="#page95">95</a>, <a href="#page120">120</a>.</p> + <p><span class="sc">Huc</span>, on the Emperor Khang-hi, ii. <a href="#page205">205</a>;</p> + <p class="i2">Chinese varieties of the bamboo, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Humboldt</span>, A., character of the Zambos, ii. <a href="#page47">47</a>;</p> + <p class="i2">parrot speaking the language of an extinct tribe, ii. <a href="#page154">154</a>;</p> + <p class="i2">on <i>Pulex penetrans</i>, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Humidity</span>, injurious effect of, upon horses, i. 53.</p> + <p><span class="sc">Humphreys</span>, Col., on Ancon sheep, i. 100.</p> + <p><span class="sc">Hungarian</span> cattle, i. 80.</p> +<!-- Page 458 --><span class="pagenum"><a name="page458"></a>{458}</span> + <p><span class="sc">Hunter</span>, John, period of gestation in the dog, i. 29;</p> + <p class="i2">on secondary sexual characters, i. 179;</p> + <p class="i2">fertile crossing of <i>Anser ferus</i> and the domestic goose, i. 288;</p> + <p class="i2">inheritance of peculiarities in gestures, voice, &c., ii. <a href="#page6">6</a>;</p> + <p class="i2">assumption of male characters by the human female, ii. <a href="#page51">51</a>;</p> + <p class="i2">period of appearance of hereditary diseases, ii. <a href="#page78">78</a>;</p> + <p class="i2">graft of the spur of a cock upon its comb, ii. <a href="#page296">296</a>;</p> + <p class="i2">on the stomach of <i>Larus tridentatus</i>, ii. <a href="#page302">302</a>;</p> + <p class="i2">double-tailed lizards, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Hunter</span>, W., evidence against the influence of imagination upon the offspring, ii. <a href="#page264">264</a>.</p> + <p><span class="sc">Hutton</span>, Capt., on the variability of the silk moth, i. 303;</p> + <p class="i2">on the number of species of silkworms, i. 300;</p> + <p class="i2">markings of silkworms, i. 302;</p> + <p class="i2">domestication of the rock-pigeon in India, i. 185;</p> + <p class="i2">domestication and crossing of <i>Gallus bankiva</i>, i. 236.</p> + <p><span class="sc">Hutchinson</span>, Col., liability of dogs to distemper, i. 35.</p> + <p><span class="sc">Huxley</span>, Prof., on the transmission of polydactylism, ii. <a href="#page13">13</a>;</p> + <p class="i2">on unconscious selection, ii. <a href="#page194">194</a>;</p> + <p class="i2">on correlation in the mollusca, ii. <a href="#page320">320</a>;</p> + <p class="i2">on gemmation and fission, ii. <a href="#page359">359</a>;</p> + <p class="i2">development of star-fishes, ii. <a href="#page366">366</a>.</p> + <p><span class="sc">Hyacinths</span>, i. 370-371;</p> + <p class="i2">bud-variation in, i. 385;</p> + <p class="i2">graft-hybrid by union of half bulbs of, i. 395;</p> + <p class="i2">white, reproduced by seed, ii. <a href="#page20">20</a>;</p> + <p class="i2">red, ii. <a href="#page229">229</a>, <a href="#page336">336</a>;</p> + <p class="i2">varieties of, recognisable by the bulb, ii. <a href="#page251">251</a>.</p> + <p><span class="sc">Hyacinth</span>, feather, ii. <a href="#page185">185</a>, <a href="#page316">316</a>.</p> + <p><i>Hyacinthus orientalis</i>, i. 370.</p> + <p><i>Hybiscus syriacus</i>, ii. <a href="#page286">286</a>.</p> + <p><span class="sc">Hybrids</span>, of hare and rabbit, i. 105;</p> + <p class="i2">of various species of <i>Gallus</i>, i. 234-236;</p> + <p class="i2">of almond, peach, and nectarine, i. 339;</p> + <p class="i2">naturally produced, of species of <i>Cytisus</i>, i. 390;</p> + <p class="i2">from twin-seed of <i>Fuchsia coccinea</i> and <i>fulgens</i>, i. 391;</p> + <p class="i2">reversion of, i. 392-394, ii. <a href="#page36">36</a>, <a href="#page48">48</a>-<a href="#page50">50</a>;</p> + <p class="i2">from mare, ass, and zebra, ii. <a href="#page42">42</a>;</p> + <p class="i2">of tame animals, wildness of, ii. <a href="#page44">44</a>-<a href="#page46">46</a>;</p> + <p class="i2">female instincts of sterile male, ii. <a href="#page52">52</a>;</p> + <p class="i2">transmission and blending of characters in, ii. <a href="#page92">92</a>-<a href="#page95">95</a>;</p> + <p class="i2">breed better with parent species than with each other, ii. <a href="#page131">131</a>;</p> + <p class="i2">self-impotence in, ii. <a href="#page138">138</a>-<a href="#page140">140</a>;</p> + <p class="i2">readily produced in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Hybridisation</span>, singular effects of, in oranges, i. 336;</p> + <p class="i2">of cherries, i. 347;</p> + <p class="i2">difficulty of, in <i>Cucurbitæ</i>, i. 358;</p> + <p class="i2">of roses, i. 366.</p> + <p><span class="sc">Hybridism</span>, ii. <a href="#page178">178</a>-<a href="#page191">191</a>;</p> + <p class="i2">the cause of a tendency to double flowers, ii. <a href="#page171">171</a>;</p> + <p class="i2">in relation to pangenesis, ii. <a href="#page385">385</a>.</p> + <p><span class="sc">Hybridity</span> in cats, i. 44-45;</p> + <p class="i2">supposed of peach and nectarine, i. 342.</p> + <p><i>Hydra</i>, i. 374, ii. <a href="#page293">293</a>, <a href="#page359">359</a>.</p> + <p><span class="sc">Hydrangea</span>, colour of flowers of, influenced by alum, ii. <a href="#page277">277</a>.</p> + <p><span class="sc">Hydrocele</span>, ii. <a href="#page52">52</a>.</p> + <p><span class="sc">Hydrocephalus</span>, ii. <a href="#page295">295</a>.</p> + <p><i>Hypericum calycinum</i>, ii. <a href="#page170">170</a>.</p> + <p><i>Hypericum crispum</i>, ii. <a href="#page227">227</a>, <a href="#page337">337</a>.</p> + <p><span class="sc">Hypermetamorphosis</span>, ii. <a href="#page367">367</a>.</p> + <p><span class="sc">Hypermetropia</span>, hereditary, ii. <a href="#page8">8</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Ichthyopterygia</span>, number of digits in the, ii. <a href="#page16">16</a>.</p> + <p><i>Ilex aquifolium</i>, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Imagination</span>, supposed effect of, on offspring, ii. <a href="#page263">263</a>.</p> + <p><i>Imatophyllum miniatum</i>, bud-variation in, i. 385.</p> + <p><span class="sc">Incest</span>, abhorred by savages, ii. <a href="#page123">123</a>-<a href="#page124">124</a>.</p> + <p><span class="sc">Incubation</span>, by crossed fowls of non-sitting varieties, ii. <a href="#page43">43</a>-<a href="#page44">44</a>.</p> + <p><span class="sc">India</span>, striped horses of, i. 58;</p> + <p class="i2">pigs of, i. 66, 67, 76;</p> + <p class="i2">breeding of rabbits in, i. 112;</p> + <p class="i2">cultivation of pigeons in, i. 205-206.</p> + <p><span class="sc">Individual</span> variability in pigeons, i. 158-160.</p> + <p><span class="sc">Ingledew</span>, Mr., cultivation of European vegetables in India, ii. <a href="#page169">169</a>.</p> + <p>"<span class="sc">Indische</span> Taube," ii. <a href="#page144">144</a>.</p> + <p><span class="sc">Inheritance</span>, ii. <a href="#page1">1</a>-<a href="#page84">84</a>, <a href="#page371">371</a>-<a href="#page373">373</a>, <a href="#page395">395</a>, <a href="#page397">397</a>-<a href="#page402">402</a>;</p> + <p class="i2">doubts entertained of by some writers, ii. <a href="#page3">3</a>;</p> + <p class="i2">importance of to breeders, <a href="#page3">3</a>-<a href="#page4">4</a>;</p> + <p class="i2">evidence of, derived from statistics of chances, <a href="#page5">5</a>;</p> + <p class="i2">of peculiarities in man, <a href="#page5">5</a>-<a href="#page7">7</a>, <a href="#page12">12</a>-<a href="#page16">16</a>;</p> + <p class="i2">of disease, <a href="#page7">7</a>-<a href="#page8">8</a>, <a href="#page17">17</a>;</p> + <p class="i2">of peculiarities in the eye, <a href="#page8">8</a>-<a href="#page10">10</a>;</p> + <p class="i2">of deviations from symmetry, <a href="#page12">12</a>;</p> + <p class="i2">of polydactylism, <a href="#page12">12</a>-<a href="#page16">16</a>;</p> + <p class="i2">capriciousness of, <a href="#page17">17</a>-<a href="#page22">22</a>, <a href="#page27">27</a>;</p> + <p class="i2">of mutilations, <a href="#page22">22</a>-<a href="#page24">24</a>;</p> + <p class="i2">of congenital monstrosities, <a href="#page24">24</a>;</p> + <p class="i2">causes of absence of, <a href="#page24">24</a>-<a href="#page26">26</a>;</p> + <p class="i2">by reversion or atavism, <a href="#page28">28</a>-<a href="#page61">61</a>;</p> + <p class="i2">its connexion with fixedness of character, <a href="#page62">62</a>-<a href="#page64">64</a>;</p> + <p class="i2">affected by prepotency of transmission of character, <a href="#page65">65</a>-<a href="#page71">71</a>;</p> + <p class="i2">limited by sex, <a href="#page71">71</a>-<a href="#page75">75</a>;</p> + <p class="i2">at corresponding periods of life, <a href="#page75">75</a>-<a href="#page80">80</a>;</p> + <p class="i2">summary of the subject of, <a href="#page80">80</a>-<a href="#page84">84</a>;</p> + <p class="i2">laws of, the same in seminal and bud varieties, i. 409;</p> + <p class="i2">of characters in the horse, i. 10-11;</p> + <p class="i2">in cattle, i. 87;</p> + <p class="i2">in rabbits, i. 107;</p> + <p class="i2">in the peach, i. 339;</p> + <p class="i2">in the nectarine, i. 340;</p> + <p class="i2">in plums, i. 347;</p> + <p class="i2">in apples, i. 350;</p> + <p class="i2">in pears, i. 351;</p> + <p class="i2">in the pansy, i. 369;</p> + <p class="i2">of primary characters of <i>Columba livia</i> in crossed pigeons, i. 201;</p> + <p class="i2">of peculiarities of plumage in pigeons, i. 160-161;</p> + <p class="i2">of peculiarities of foliage in trees, i. 362;</p> + <p class="i2">effects of, in varieties of the cabbage, i. 325.</p> + <p><span class="sc">Insanity</span>, inheritance of, ii. <a href="#page7">7</a>, <a href="#page78">78</a>.</p> + <p><span class="sc">Insects</span>, regeneration of lost parts in, ii. <a href="#page15">15</a>, <a href="#page294">294</a>;</p> + <p class="i2">agency of, in fecundation of larkspurs, ii. <a href="#page21">21</a>;</p> + <p class="i2">effect of changed conditions upon, ii. <a href="#page157">157</a>;</p> + <p class="i2">sterile neuter, ii. <a href="#page186">186</a>-<a href="#page187">187</a>;</p> +<!-- Page 459 --><span class="pagenum"><a name="page459"></a>{459}</span> + <p class="i2">monstrosities in, ii. <a href="#page269">269</a>, <a href="#page391">391</a>.</p> + <p><span class="sc">Instincts</span>, defective, of silkworms, i. 304.</p> + <p><span class="sc">Interbreeding</span>, close, ill effects of, ii. <a href="#page114">114</a>-<a href="#page131">131</a>, <a href="#page175">175</a>.</p> + <p><span class="sc">Intercrossing</span>, of species, as a cause of variation, i. 188;</p> + <p class="i2">natural, of plants, i. 336;</p> + <p class="i2">of species of Canidæ and breeds of dogs, i. 31-33;</p> + <p class="i2">of domestic and wild cats, i. 44-45;</p> + <p class="i2">of breeds of pigs, i. 71, 78;</p> + <p class="i2">of cattle, i. 83;</p> + <p class="i2">of varieties of cabbage, i. 324;</p> + <p class="i2">of peas, i. 326, 329-330;</p> + <p class="i2">of varieties of orange, i. 336;</p> + <p class="i2">of species of strawberries, i. 351-352;</p> + <p class="i2">of <i>Cucurbitæ</i>, i. 357-358;</p> + <p class="i2">of flowering plants, i. 364;</p> + <p class="i2">of pansies, i. 368.</p> + <p><span class="sc">Interdigital</span> pits, in goats, i. 102.</p> + <p><span class="sc">Intermarriages</span>, close, ii. <a href="#page122">122</a>-<a href="#page123">123</a>.</p> + <p><span class="sc">Intestines</span>, elongation of, in pigs, i. 73;</p> + <p class="i2">relative measurements of parts of, in goats, i. 102;</p> + <p class="i2">effects of changed diet on, ii. <a href="#page302">302</a>.</p> + <p><i>Ipomœa purpurea</i>, ii. <a href="#page128">128</a>.</p> + <p><span class="sc">Ireland</span>, remains of <i>Bos frontosus</i> and <i>longifrons</i> found in, i. 81.</p> + <p><span class="sc">Iris</span>, hereditary absence of the, ii. <a href="#page9">9</a>;</p> + <p class="i2">hereditary peculiarities of colour of the, ii. <a href="#page9">9</a>-<a href="#page10">10</a>.</p> + <p><span class="sc">Irish</span>, ancient, selection practised by the, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Iron</span> period, in Europe, dog of, i. 18.</p> + <p><span class="sc">Islands</span>, oceanic, scarcity of useful plants on, i. 311.</p> + <p><span class="sc">Islay</span>, pigeons of, i. 183.</p> + <p><span class="sc">Isolation</span>, effect of, in favour of selection, ii. <a href="#page233">233</a>-<a href="#page234">234</a>.</p> + <p><span class="sc">Italy</span>, vine growing in, during the bronze period, i. 332.</p> + <p><span class="sc">Ivy</span>, sterility of, in the north of Europe, ii. <a href="#page170">170</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Jack</span>, Mr., effect of foreign pollen on grapes, i. 400.</p> + <p><span class="sc">Jackal</span>, i. 24, 27, 30;</p> + <p class="i2">hybrids of, with the dog, i. 32;</p> + <p class="i2">prepotency of, over the dog, ii. <a href="#page67">67</a>.</p> + <p><span class="sc">Jacobin</span> pigeon, i. 154, 208.</p> + <p><span class="sc">Jacquemet-Bonnefort</span>, on the mulberry, i. 334.</p> + <p><span class="sc">Jaguar</span>, with crooked legs, i. 17.</p> + <p><span class="sc">Jamaica</span>, feral dogs of, i. 28;</p> + <p class="i2">feral pigs of, i. 77;</p> + <p class="i2">feral rabbits of, i. 112.</p> + <p><span class="sc">Japan</span>, horses of, i. 53.</p> + <p><span class="sc">Japanese</span> pig (figured), i. 69.</p> + <p><span class="sc">Jardine</span>, Sir W., crossing of domestic and wild cats, i. 44.</p> + <p><span class="sc">Jarves</span>, J., silkworm in the Sandwich islands, i. 301.</p> + <p><span class="sc">Java</span>, Fantail pigeon in, i. 148.</p> + <p><span class="sc">Javanese</span> ponies, i. 53, 59.</p> + <p><span class="sc">Jemmy Button</span>, i. 309.</p> + <p><span class="sc">Jenyns</span>, L., whiteness of ganders, i. 288;</p> + <p class="i2">sunfish-like variety of the goldfish, i. 297.</p> + <p><span class="sc">Jerdon</span>, J. C., number of eggs laid by the pea-hen, ii. <a href="#page112">112</a>;</p> + <p class="i2">origin of domestic fowl, i. 237.</p> + <p><span class="sc">Jersey</span>, arborescent cabbages of, i. 323.</p> + <p><span class="sc">Jessamine</span>, i. 394.</p> + <p><span class="sc">Jeitteles</span>, Hungarian sheep-dogs, i. 24;</p> + <p class="i2">crossing of domestic and wild cats, i. 44.</p> + <p><span class="sc">John</span>, King, importation of stallions from Flanders by, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Johnson</span>, D., occurrence of stripes on young wild pigs in India, i. 76.</p> + <p><span class="sc">Jordan</span>, A., on Vibert's experiments on the vine, i. 332;</p> + <p class="i2">origin of varieties of the apple, i. 350;</p> + <p class="i2">varieties of pears found wild in woods, ii. <a href="#page260">260</a>.</p> + <p><span class="sc">Jourdan</span>, parthenogenesis in the silk moth, ii. <a href="#page364">364</a>.</p> + <p><span class="sc">Juan de Nova</span>, wild dogs on, i. 27.</p> + <p><span class="sc">Juan Fernandez</span>, dumb dogs on, i. 27.</p> + <p><i>Juglans regia</i>, i. 356-357.</p> + <p><span class="sc">Jukes</span>, Prof., origin of the Newfoundland dog, i. 42.</p> + <p><span class="sc">Julien</span>, Stanislas, early domestication of pigs in China, i. 68;</p> + <p class="i2">antiquity of the domestication of the silk-worm in China, i. 300.</p> + <p><span class="sc">Jumpers</span>, a breed of fowls, i. 230.</p> + <p><span class="sc">Juniper</span>, variations of the, i. 361, 364.</p> + <p><i>Juniperus suecica</i>, i. 361.</p> + <p><i>Jussiæa grandiflora</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Jussieu</span>, A. de, structure of the pappus in <i>Carthamus</i>, ii. <a href="#page316">316</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Kail</span>, Scotch, reversion in, ii. <a href="#page32">32</a>.</p> + <p>"<span class="sc">Kala-par</span>" pigeon, i. 142.</p> + <p><span class="sc">Kales</span>, i. 323.</p> + <p><span class="sc">Kalm</span>, P., on maize, i. 322, ii. <a href="#page307">307</a>;</p> + <p class="i2">introduction of wheat into Canada, i. 315;</p> + <p class="i2">sterility of trees growing in marshes and dense woods, ii. <a href="#page170">170</a>.</p> + <p>"<span class="sc">Kalmi</span> Lotan," tumbler pigeon, i. 151.</p> + <p><span class="sc">Kane</span>, Dr., on Esquimaux dogs, i. 21.</p> + <p><span class="sc">Karakool</span> sheep, i. 98.</p> + <p><span class="sc">Karkeek</span>, on inheritance in the horse, ii. <a href="#page10">10</a>.</p> + <p>"<span class="sc">Karmeliten</span> Taube," i. 156.</p> + <p><span class="sc">Karsten</span> on <i>Pulex penetrans</i>, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Kattywar</span> horses, i. 58.</p> + <p><span class="sc">Keeley</span>, R., pelorism in <i>Galeobdolon luteum</i>, ii. <a href="#page59">59</a>.</p> + <p><span class="sc">Kerner</span> on the culture of Alpine plants, ii. <a href="#page163">163</a>.</p> + <p><span class="sc">Kestrel</span>, breeding in captivity, ii. <a href="#page154">154</a>.</p> + <p>"<span class="sc">Khandési</span>," i. 141.</p> + <p><span class="sc">Khang-hi</span>, selection of a variety of rice by, ii. <a href="#page205">205</a>.</p> + <p><span class="sc">Kiang</span>, ii. <a href="#page43">43</a>.</p> + <p><span class="sc">Kidd</span>, on the canary bird, i. 77, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Kidney</span> Bean, i. 371;</p> + <p class="i2">varieties of, ii. <a href="#page256">256</a>, <a href="#page275">275</a>.</p> +<!-- Page 460 --><span class="pagenum"><a name="page460"></a>{460}</span> + <p><span class="sc">Kidneys</span>, compensatory development of the, ii. <a href="#page300">300</a>;</p> + <p class="i2">fusion of the, ii. <a href="#page341">341</a>;</p> + <p class="i2">shape of, in birds, influenced by the form of the pelvis, ii. <a href="#page344">344</a>.</p> + <p><span class="sc">King</span>, Col., domestication of rock doves from the Orkneys, i. 184, 185.</p> + <p><span class="sc">King</span>, P. S., on the Dingo, i. 21, 28.</p> + <p><span class="sc">Kirby</span> and Spence, on the growth of galls, ii. <a href="#page283">283</a>.</p> + <p><span class="sc">Kirghisian</span> sheep, i. 98.</p> + <p><span class="sc">Kite</span>, breeding in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Kleine</span>, variability of bees, i. 298.</p> + <p><span class="sc">Knight</span>, Andrew, on crossing horses of different breeds, i. 51;</p> + <p class="i2">crossing varieties of peas, i. 326, ii. <a href="#page129">129</a>;</p> + <p class="i2">persistency of varieties of peas, i. 329;</p> + <p class="i2">origin of the peach, i. 338;</p> + <p class="i2">hybridisation of the morello by the Elton cherry, i. 347;</p> + <p class="i2">on seedling cherries, <i>ibid.</i>;</p> + <p class="i2">variety of the apple not attacked by coccus, i. 349;</p> + <p class="i2">intercrossing of strawberries, i, 351, 352;</p> + <p class="i2">broad variety of the cock's comb, i. 365;</p> + <p class="i2">bud variation in the cherry and plum, i. 375;</p> + <p class="i2">crossing of white and purple grapes, i. 393;</p> + <p class="i2">experiments in crossing apples, i. 402, ii. <a href="#page129">129</a>;</p> + <p class="i2">hereditary disease in plants, ii. <a href="#page11">11</a>;</p> + <p class="i2">on interbreeding, ii. <a href="#page116">116</a>;</p> + <p class="i2">crossed varieties of wheat, ii. <a href="#page130">130</a>;</p> + <p class="i2">necessity of intercrossing in plants, ii. <a href="#page175">175</a>;</p> + <p class="i2">on variation, ii. <a href="#page256">256</a>, <a href="#page257">257</a>;</p> + <p class="i2">effects of grafting, i. 387, ii. <a href="#page278">278</a>;</p> + <p class="i2">bud-variation in a plum, ii. <a href="#page289">289</a>;</p> + <p class="i2">compulsory flowering of early potatoes, ii. <a href="#page343">343</a>;</p> + <p class="i2">correlated variation of head and limbs, ii. <a href="#page323">323</a>.</p> + <p><span class="sc">Knox</span>, Mr., breeding of the eagle owl in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Koch</span>, degeneracy in the turnip, i. 325.</p> + <p><span class="sc">Kohlrabi</span>, i. 323.</p> + <p><span class="sc">Kölreuter</span>, reversion in hybrids, i. 392, ii. <a href="#page36">36</a>;</p> + <p class="i2">acquired sterility of crossed varieties of plants, i. 358, ii. <a href="#page101">101</a>;</p> + <p class="i2">absorption of <i>Mirabilis vulgaris</i> by <i>M. longiflora</i>, ii. <a href="#page88">88</a>;</p> + <p class="i2">crosses of species of <i>Verbascum</i>, ii. <a href="#page93">93</a>, <a href="#page107">107</a>;</p> + <p class="i2">on the hollyhock, ii. <a href="#page107">107</a>;</p> + <p class="i2">crossing varieties of tobacco, ii. <a href="#page108">108</a>;</p> + <p class="i2">benefits of crossing plants, ii. <a href="#page130">130</a>, <a href="#page131">131</a>, <a href="#page175">175</a>-<a href="#page176">176</a>;</p> + <p class="i2">self-impotence in <i>Verbascum</i>, ii. <a href="#page136">136</a>, <a href="#page141">141</a>;</p> + <p class="i2">effects of conditions of growth upon fertility in <i>Mirabilis</i>, ii. <a href="#page164">164</a>;</p> + <p class="i2">great development of tubers in hybrid plants, ii. <a href="#page172">172</a>;</p> + <p class="i2">inheritance of plasticity, ii. <a href="#page241">241</a>;</p> + <p class="i2">variability of hybrids of <i>Mirabilis</i>, ii. <a href="#page265">265</a>;</p> + <p class="i2">repeated crossing a cause of variation, ii. <a href="#page267">267</a>-<a href="#page268">268</a>;</p> + <p class="i2">number of pollen-grains necessary for fertilization, ii. <a href="#page363">363</a>.</p> + <p>"<span class="sc">Krauseschwein</span>," i. 67.</p> + <p><span class="sc">Krohn</span>, on the double reproduction of Medusæ, ii. <a href="#page384">384</a>.</p> + <p>"<span class="sc">Kropf-Tauben</span>," i. 137.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Labat</span>, on the tusks of feral bears in the West Indies, i. 77;</p> + <p class="i2">on French wheat grown in the West Indies, ii. <a href="#page307">307</a>;</p> + <p class="i2">on the culture of the vine in the West Indies, ii. <a href="#page308">308</a>.</p> + <p><span class="sc">Laburnum</span>, Adam's, see <i>Cytisus Adami</i>;</p> + <p class="i2">oak-leaved, reversion of, i. 382;</p> + <p class="i2">pelorism in the, ii. <a href="#page346">346</a>;</p> + <p class="i2">Waterer's, i. 390.</p> + <p><span class="sc">Lachmann</span>, on gemmation and fission, ii. <a href="#page358">358</a>.</p> + <p><i>Lachnanthes tinctoria</i>, ii. <a href="#page227">227</a>, <a href="#page336">336</a>.</p> + <p><span class="sc">Lactation</span>, imperfect, hereditary, ii. <a href="#page8">8</a>;</p> + <p class="i2">deficient, of wild animals in captivity, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Ladrone</span> islands, cattle of, i. 86.</p> + <p><span class="sc">Laing</span>, Mr., resemblance of Norwegian and Devonshire cattle, i. 82.</p> + <p><span class="sc">Lake-dwellings</span>, sheep of, i. 94, ii. <a href="#page427">427</a>;</p> + <p class="i2">cattle of, ii. <a href="#page427">427</a>;</p> + <p class="i2">absence of the fowl in, i. 246;</p> + <p class="i2">cultivated plants of, i. 309, ii. <a href="#page427">427</a>, <a href="#page429">429</a>;</p> + <p class="i2">cereals of, i. 317-319;</p> + <p class="i2">peas found in, i. 326;</p> + <p class="i2">beans found in, i. 330.</p> + <p><span class="sc">Lamare-Piquot</span>, observations on half-bred North American wolves, i. 22.</p> + <p><span class="sc">Lambert</span>, A. B., on <i>Thuja pendula</i> or <i>filiformis</i>, i. 362.</p> + <p><span class="sc">Lambert</span> family, ii. <a href="#page4">4</a>, <a href="#page76">76</a>.</p> + <p><span class="sc">Lambertye</span> on strawberries, i. 351, 352;</p> + <p class="i2">five-leaved variety of <i>Fragaria collina</i>, i. 353.</p> + <p><span class="sc">Landt</span>, L., on sheep in the Faroe islands, ii. <a href="#page103">103</a>.</p> + <p><span class="sc">La Plata</span>, wild dogs of, i. 27;</p> + <p class="i2">feral cat from, i. 47.</p> + <p><span class="sc">Larch</span>, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Larkspurs</span>, insect agency necessary for the full fecundation of, ii. <a href="#page21">21</a>.</p> + <p><i>Larus argentatus</i>, ii. <a href="#page157">157</a>.</p> + <p><i>Larus tridactylus</i>, ii. <a href="#page302">302</a>.</p> + <p><span class="sc">Lasterye</span>, merino sheep in different countries, i. 99.</p> + <p><span class="sc">Latent</span> characters, ii. <a href="#page51">51</a>-<a href="#page56">56</a>.</p> + <p><span class="sc">Latham</span>, on the fowl not breeding in the extreme north, ii. <a href="#page161">161</a>.</p> + <p><i>Lathyrus</i>, ii. <a href="#page38">38</a>.</p> + <p><i>Lathyrus aphaca</i>, ii. <a href="#page343">343</a>.</p> + <p><i>Lathyrus odoratus</i>, ii. <a href="#page20">20</a>, <a href="#page91">91</a>, <a href="#page93">93</a>, <a href="#page311">311</a>, <a href="#page393">393</a>.</p> + <p><span class="sc">La Touche</span>, J. D., on a Canadian apple with dimidiate fruit, i. 392-393.</p> + <p>"<span class="sc">Latz-Taube</span>," i. 154.</p> + <p><span class="sc">Laugher</span> pigeon, i. 155, 207.</p> + <p><i>Laurus sassafras</i>, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Lawrence</span>, J., production of a new breed of fox-hounds, i. 40;</p> + <p class="i2">occurrence of canines in mares, i. 50;</p> + <p class="i2">on three-parts-bred horses, i. 54;</p> + <p class="i2">on inheritance in the horse, ii. <a href="#page10">10</a>-<a href="#page11">11</a>.</p> + <p><span class="sc">Lawson</span>, Mr., varieties of the potato, i. 330.</p> + <p><span class="sc">Laxton</span>, Mr., bud-variation in the gooseberry, i. 376;</p> + <p class="i2">crossing of varieties of the pea, i. 397-398;</p> +<!-- Page 461 --><span class="pagenum"><a name="page461"></a>{461}</span> + <p class="i2">double-flowered peas, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Layard</span>, E. L., resemblance of a Caffre dog to the Esquimaux breed, i. 25, ii. <a href="#page286">286</a>;</p> + <p class="i2">crossing of the domestic cat with <i>Felis Caffra</i>, i. 44;</p> + <p class="i2">feral pigeons in Ascension, i. 190;</p> + <p class="i2">domestic pigeons of Ceylon, i. 206;</p> + <p class="i2">on <i>Gallus Stanleyi</i>, i. 234;</p> + <p class="i2">on black-skinned Ceylonese fowls, i. 256.</p> + <p><span class="sc">Le Compte</span> family, blindness inherited in, ii. <a href="#page78">78</a>.</p> + <p><span class="sc">Lecoq</span>, bud-variation in <i>Mirabilis jalapa</i>, i. 382;</p> + <p class="i2">hybrids of <i>Mirabilis</i>, i. 393, ii. <a href="#page169">169</a>, <a href="#page265">265</a>;</p> + <p class="i2">crossing in plants, ii. <a href="#page127">127</a>;</p> + <p class="i2">fecundation of <i>Passiflora</i>, ii. <a href="#page137">137</a>;</p> + <p class="i2">hybrid <i>Gladiolus</i>, ii. <a href="#page139">139</a>;</p> + <p class="i2">sterility of <i>Ranunculus ficaria</i>, ii. <a href="#page170">170</a>;</p> + <p class="i2">villosity in plants, ii. <a href="#page277">277</a>;</p> + <p class="i2">double asters, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Le Couteur</span>, J., varieties of wheat, i. 313-315;</p> + <p class="i2">acclimatisation of exotic wheat in Europe, i. 315;</p> + <p class="i2">adaptation of wheat to soil and climate, i. 316;</p> + <p class="i2">selection of seed-corn, i. 318;</p> + <p class="i2">on change of soil, ii. <a href="#page147">147</a>;</p> + <p class="i2">selection of wheat, ii. <a href="#page200">200</a>;</p> + <p class="i2">natural selection in wheat, ii. <a href="#page233">233</a>;</p> + <p class="i2">cattle of Jersey, ii. <a href="#page234">234</a>.</p> + <p><span class="sc">Ledger</span>, Mr., on the Llama and Alpaca, ii. <a href="#page208">208</a>.</p> + <p><span class="sc">Lee</span>, Mr., his early culture of the pansy, i. 368.</p> + <p><i>Leersia oryzoides</i>, ii. <a href="#page91">91</a>.</p> + <p><span class="sc">Lefour</span>, period of gestation in cattle, i. 87.</p> + <p><span class="sc">Legs</span>, of fowls, effects of disuse on, i. 270-272;</p> + <p class="i2">characters and variations of, in ducks, i. 284-288;</p> + <p class="i2">fusion of, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Leguat</span>, cattle of the Cape of Good Hope, i. 88.</p> + <p><span class="sc">Lehmann</span>, occurrence of wild double-flowered plants near a hot spring, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Leighton</span>, W. A., propagation of a weeping yew by seed, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Leitner</span>, effects of the removal of anthers, ii. <a href="#page167">167</a>.</p> + <p><span class="sc">Lemming</span>, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Lemoine</span>, variegated <i>Symphytum</i> and <i>Phlox</i>, i. 384.</p> + <p><span class="sc">Lemon</span>, i. 334, 335;</p> + <p class="i2">orange fecundated by pollen of the, i. 399.</p> + <p><span class="sc">Lemurs</span>, hybrid, ii. <a href="#page153">153</a>.</p> + <p><span class="sc">Leporides</span>, ii. <a href="#page98">98</a>-<a href="#page99">99</a>, <a href="#page152">152</a>.</p> + <p><span class="sc">Lepsius</span>, figures of ancient Egyptian dogs, i. 17;</p> + <p class="i2">domestication of pigeons in ancient Egypt, i. 204.</p> + <p><i>Leptotes</i>, ii. <a href="#page134">134</a>.</p> + <p><i>Lepus glacialis</i>, i. 111.</p> + <p><i>Lepus magellanicus</i>, i. 112.</p> + <p><i>Lepus nigripes</i>, i. 108.</p> + <p><i>Lepus tibetanus</i>, i. 111.</p> + <p><i>Lepus variabilis</i>, i. 111.</p> + <p><span class="sc">Lereboullet</span>, double monsters of fishes, ii. <a href="#page340">340</a>.</p> + <p><span class="sc">Leslie</span>, on Scotch wild cattle, i. 85.</p> + <p><span class="sc">Lesson</span>, on <i>Lepus magellanicus</i>, i. 112.</p> + <p><span class="sc">Leuckart</span> on the larva of Cecidomyidæ, ii. <a href="#page360">360</a>.</p> + <p><span class="sc">Lewis</span>, G., cattle of the West Indies, ii. <a href="#page229">229</a>.</p> + <p><span class="sc">Lherbette</span> and Quatrefages, on the horses of Circassia, ii. <a href="#page102">102</a>, <a href="#page225">225</a>.</p> + <p><span class="sc">Liebig</span>, differences in human blood, according to complexion, ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Liebreich</span>, occurrence of pigmentary retinitis in deaf-mutes, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Lichens</span>, sterility in, ii. <a href="#page171">171</a>.</p> + <p><span class="sc">Lichtenstein</span>, resemblance of Bosjesman's dogs to <i>Canis mesomelas</i>, i. 25;</p> + <p class="i2">Newfoundland dog at the Cape of Good Hope, i. 36.</p> + <p><span class="sc">Lilacs</span>, ii. <a href="#page164">164</a>.</p> + <p><span class="sc">Liliaceæ</span>, contabescence in, ii. <a href="#page165">165</a>.</p> + <p><i>Lilium candidum</i>, ii. <a href="#page137">137</a>.</p> + <p><span class="sc">Limbs</span>, regeneration of, ii. <a href="#page376">376</a>-<a href="#page377">377</a>.</p> + <p><span class="sc">Limbs</span> and head, correlated variation of, ii. <a href="#page323">323</a>.</p> + <p><span class="sc">Lime</span>, effect of, upon shells of the mollusca, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Lime</span> tree, changes of by age, i. 364, 387.</p> + <p><span class="sc">Limitation</span>, sexual, ii. <a href="#page71">71</a>-<a href="#page75">75</a>.</p> + <p><span class="sc">Limitation</span>, supposed, of variation, ii. <a href="#page416">416</a>.</p> + <p><i>Linaria</i>, pelorism in, ii. <a href="#page58">58</a>, <a href="#page61">61</a>, <a href="#page346">346</a>;</p> + <p class="i2">peloric, crossed with the normal form, ii. <a href="#page70">70</a>;</p> + <p class="i2">sterility of, ii. <a href="#page166">166</a>.</p> + <p><i>Linaria vulgaris</i> and <i>purpurea</i>, hybrids of, ii. <a href="#page94">94</a>.</p> + <p><span class="sc">Lindley</span>, John, classification of varieties of cabbages, i. 324;</p> + <p class="i2">origin of the peach, i. 338;</p> + <p class="i2">influence of soil on peaches and nectarines, i. 340;</p> + <p class="i2">varieties of the peach and nectarine, i. 343;</p> + <p class="i2">on the New Town pippin, i. 349;</p> + <p class="i2">freedom of the Winter Majetin apple from coccus, i. 349;</p> + <p class="i2">production of monœcious Hautbois strawberries by bud-selection, i. 353;</p> + <p class="i2">origin of the large tawny nectarine, i. 375;</p> + <p class="i2">bud-variation in the gooseberry, i. 376;</p> + <p class="i2">hereditary disease in plants, ii. <a href="#page11">11</a>;</p> + <p class="i2">on double flowers, ii. <a href="#page167">167</a>;</p> + <p class="i2">seeding of ordinarily seedless fruits, ii. <a href="#page168">168</a>;</p> + <p class="i2">sterility of <i>Acorus calamus</i>, ii. <a href="#page170">170</a>;</p> + <p class="i2">resistance of individual plants to cold, ii. <a href="#page309">309</a>.</p> + <p><span class="sc">Linnæus</span>, summer and winter wheat regarded as distinct species by, i. 315;</p> + <p class="i2">on the single-leaved strawberry, i. 353;</p> + <p class="i2">sterility of Alpine plants in gardens, ii. <a href="#page163">163</a>;</p> + <p class="i2">recognition of individual reindeer by the Laplanders, ii. <a href="#page251">251</a>;</p> + <p class="i2">growth of tobacco in Sweden, ii. <a href="#page307">307</a>.</p> + <p><span class="sc">Linnet</span>, ii. <a href="#page158">158</a>.</p> + <p><i>Linota cannabina</i>, ii. <a href="#page158">158</a>.</p> +<!-- Page 462 --><span class="pagenum"><a name="page462"></a>{462}</span> + <p><span class="sc">Linum</span>, ii. <a href="#page165">165</a>.</p> + <p><span class="sc">Lion</span>, fertility of, in captivity, ii. <a href="#page150">150</a>, <a href="#page151">151</a>.</p> + <p><span class="sc">Lipari</span>, feral rabbits of, i. 113.</p> + <p><span class="sc">Livingstone</span>, Dr., striped young pigs on the Zambesi, i. 77;</p> + <p class="i2">domestic rabbits at Loanda, i. 112;</p> + <p class="i2">use of grass-seeds as food in Africa, i. 308;</p> + <p class="i2">planting of fruit-trees by the Batokas, i. 309;</p> + <p class="i2">character of half-castes, ii. <a href="#page46">46</a>;</p> + <p class="i2">taming of animals among the Barotse, ii. <a href="#page160">160</a>;</p> + <p class="i2">selection practised in South Africa, ii. <a href="#page207">207</a>, <a href="#page209">209</a>.</p> + <p><span class="sc">Livingstone</span>, Mr., disuse a cause of drooping ears, ii. <a href="#page301">301</a>.</p> + <p><span class="sc">Lizards</span>, reproduction of tail in, ii. <a href="#page294">294</a>;</p> + <p class="i2">with a double tail, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Llama</span>, selection of, ii. <a href="#page208">208</a>.</p> + <p><span class="sc">Lloyd</span>, Mr., taming of the wolf, i. 26;</p> + <p class="i2">English dogs in northern Europe, i. 36;</p> + <p class="i2">fertility of the goose increased by domestication, i. 288;</p> + <p class="i2">number of eggs laid by the wild goose, ii. <a href="#page112">112</a>;</p> + <p class="i2">breeding of the capercailzie in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Loanda</span>, domestic rabbits at, i. 112.</p> + <p><i>Loasa</i>, hybrid of two species of, ii. <a href="#page98">98</a>.</p> + <p><i>Lobelia</i>, reversion in hybrids of, ii. <a href="#page392">392</a>;</p> + <p class="i2">contabescence in, ii. <a href="#page166">166</a>.</p> + <p><i>Lobelia fulgens</i>, <i>cardinalis</i>, and <i>syphilitica</i>, ii. <a href="#page136">136</a>.</p> + <p><span class="sc">Lockhart</span>, Dr., on Chinese pigeons, i. 206.</p> + <p><span class="sc">Locust-tree</span>, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Loiseleur-Deslongchamps</span>, originals of cultivated plants, i. 307;</p> + <p class="i2">Mongolian varieties of wheat, i. 313;</p> + <p class="i2">characters of the ear in wheat, i. 314;</p> + <p class="i2">acclimatisation of exotic wheat in Europe, i. 315;</p> + <p class="i2">effect of change of climate on wheat, i. 316;</p> + <p class="i2">on the supposed necessity of the coincident variation of weeds and cultivated plants, i. 317;</p> + <p class="i2">advantage of change of soil to plants, ii. <a href="#page146">146</a>.</p> + <p><i>Lolium temulentum</i>, variable presence of barbs in, i. 314.</p> + <p><span class="sc">Long-tailed</span> sheep, i. 94, 95.</p> + <p><span class="sc">Loochoo</span> islands, horses of, i. 53.</p> + <p><span class="sc">Lord</span>, J. K., on Canis latrans, i. 22.</p> + <p>"<span class="sc">Lori rajah</span>," how produced, ii. <a href="#page280">280</a>.</p> + <p><i>Lorius garrulus</i>, ii. <a href="#page280">280</a>.</p> + <p>"<span class="sc">Lotan</span>," tumbler pigeon, i. 150.</p> + <p><span class="sc">Loudon</span>, J. W., varieties of the carrot, i. 326;</p> + <p class="i2">short duration of varieties of peas, i. 329;</p> + <p class="i2">on the glands of peach-leaves, i. 343;</p> + <p class="i2">presence of bloom on Russian apples, i. 349;</p> + <p class="i2">origin of varieties of the apple, i. 350;</p> + <p class="i2">varieties of the gooseberry, i. 354;</p> + <p class="i2">on the nut tree, i. 357;</p> + <p class="i2">varieties of the ash, i. 360;</p> + <p class="i2">fastigate juniper (<i>J. suecica</i>), i. 361;</p> + <p class="i2">on <i>Ilex aquifolium ferox</i>, i. 362;</p> + <p class="i2">varieties of the Scotch fir, i. 363;</p> + <p class="i2">varieties of the hawthorn, <i>ibid.</i>;</p> + <p class="i2">variation in the persistency of leaves on the elm and Turkish oak, i. 363;</p> + <p class="i2">importance of cultivated varieties, <i>ibid.</i>;</p> + <p class="i2">varieties of <i>Rosa spinosissima</i>, i. 367;</p> + <p class="i2">variation of dahlias from the same seed, i. 370;</p> + <p class="i2">production of Provence roses from seeds of the moss rose, i. 380;</p> + <p class="i2">effect of grafting the purple-leaved upon the common hazel, i. 395;</p> + <p class="i2">nearly evergreen Cornish variety of the elm, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Low</span>, G., on the pigs of the Orkney islands, i. 70.</p> + <p><span class="sc">Low</span>, Prof., pedigrees of greyhounds, ii. <a href="#page3">3</a>;</p> + <p class="i2">origin of the dog, i. 10;</p> + <p class="i2">burrowing instinct of a half-bred Dingo, i. 28;</p> + <p class="i2">inheritance of qualities in horses, i. 51;</p> + <p class="i2">comparative powers of English race-horses, Arabs, &c., i. 54;</p> + <p class="i2">British breeds of cattle, i. 80;</p> + <p class="i2">wild cattle of Chartley, i. 84;</p> + <p class="i2">effect of abundance of food on the size of cattle, i. 91;</p> + <p class="i2">effects of climate on the skin of cattle, i. 92, ii. <a href="#page326">326</a>;</p> + <p class="i2">on interbreeding, ii. <a href="#page116">116</a>;</p> + <p class="i2">selection in Hereford cattle, ii. <a href="#page214">214</a>;</p> + <p class="i2">formation of new breeds, ii. <a href="#page244">244</a>;</p> + <p class="i2">on "sheeted" cattle, ii. <a href="#page349">349</a>.</p> + <p><span class="sc">Lowe</span>, Mr., on hive bees, i. 299.</p> + <p><span class="sc">Lowe, Rev</span>. Mr., on the range of <i>Pyrus malus</i> and <i>P. acerba</i>, i. 348.</p> + <p>"<span class="sc">Lowtan</span>" tumbler pigeon, i. 150.</p> + <p><i>Loxia pyrrhula</i>, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Lubbock</span>, Sir J., developments of the Ephemeridæ, ii. <a href="#page366">366</a>.</p> + <p><span class="sc">Lucas</span>, P., effects of cross-breeding on the female, i. 404;</p> + <p class="i2">hereditary diseases, ii. <a href="#page7">7</a>, <a href="#page78">78</a>-<a href="#page79">79</a>;</p> + <p class="i2">hereditary affections of the eye, ii. <a href="#page9">9</a>-<a href="#page10">10</a>;</p> + <p class="i2">inheritance of anomalies in the human eye and in that of the horse, ii. <a href="#page10">10</a>, <a href="#page11">11</a>;</p> + <p class="i2">inheritance of polydactylism, ii. <a href="#page13">13</a>;</p> + <p class="i2">morbid uniformity in the same family, ii. <a href="#page17">17</a>;</p> + <p class="i2">inheritance of mutilations, ii. <a href="#page23">23</a>;</p> + <p class="i2">persistency of cross-reversion, ii. <a href="#page35">35</a>;</p> + <p class="i2">persistency of character in breeds of animals in wild countries, ii. <a href="#page64">64</a>;</p> + <p class="i2">prepotency of transmission, ii. <a href="#page65">65</a>, <a href="#page68">68</a>;</p> + <p class="i2">supposed rules of transmission in crossing animals, ii. <a href="#page68">68</a>;</p> + <p class="i2">sexual limitations of transmission of peculiarities, ii. <a href="#page72">72</a>-<a href="#page73">73</a>;</p> + <p class="i2">absorption of the minority in crossed races, ii. <a href="#page88">88</a>;</p> + <p class="i2">crosses without blending of certain characters, ii. <a href="#page92">92</a>;</p> + <p class="i2">on interbreeding, ii. <a href="#page116">116</a>;</p> + <p class="i2">variability dependent on reproduction, ii. <a href="#page250">250</a>;</p> + <p class="i2">period of action of variability, ii. <a href="#page260">260</a>;</p> + <p class="i2">inheritance of deafness in cats, ii. <a href="#page329">329</a>;</p> + <p class="i2">complexion and constitution, ii. <a href="#page335">335</a>.</p> + <p><span class="sc">Lucaze-Duthiers</span>, structure and growth of galls, ii. <a href="#page282">282</a>-<a href="#page284">284</a>.</p> + <p><span class="sc">Luizet</span>, grafting of a peach-almond on a peach, i. 338.</p> +<!-- Page 463 --><span class="pagenum"><a name="page463"></a>{463}</span> + <p><span class="sc">Lütke</span>, cats of the Caroline Archipelago, i. 47.</p> + <p><span class="sc">Luxuriance</span>, of vegetative organs, a cause of sterility in plants, ii. <a href="#page168">168</a>-<a href="#page171">171</a>.</p> + <p><span class="sc">Lyonnet</span>, on the scission of <i>Nais</i>, ii. <a href="#page358">358</a>.</p> + <p><i>Lysimachia nummularia</i>, sterility of, ii. <a href="#page170">170</a>.</p> + <p><i>Lythrum</i>, trimorphic species of, ii. <a href="#page400">400</a>.</p> + <p><i>Lythrum salicaria</i>, ii. <a href="#page183">183</a>;</p> + <p class="i2">contabescence in, ii. <a href="#page166">166</a>.</p> + <p><i>Lytta vesicatoria</i>, affecting the kidneys, ii. <a href="#page380">380</a>.</p> + </div> + + <div class="stanza"> + <p><i>Macacus</i>, species of, bred in captivity, ii. <a href="#page153">153</a>.</p> + <p><span class="sc">Macaulay</span>, Lord, improvement of the English horse, ii. <a href="#page213">213</a>.</p> + <p><span class="sc">M<sup>c</sup>Clelland</span>, Dr., variability of fresh-water fishes in India, ii. <a href="#page259">259</a>.</p> + <p><span class="sc">M<sup>c</sup>Coy</span>, Prof., on the dingo, i. 26.</p> + <p><span class="sc">Macfayden</span>, influence of soil in producing sweet or bitter oranges from the same seed, i. 335.</p> + <p><span class="sc">Macgillivray</span>, domestication of the rock-dove, i. 185;</p> + <p class="i2">feral pigeons in Scotland, i. 190;</p> + <p class="i2">number of vertebræ in birds, i. 266;</p> + <p class="i2">on wild geese, i. 287;</p> + <p class="i2">number of eggs of wild and tame ducks, ii. <a href="#page112">112</a>.</p> + <p><span class="sc">Mackenzie</span>, Sir G., peculiar variety of the potato, i. 330.</p> + <p><span class="sc">Mackenzie</span>, P., bud-variation in the currant, i. 376.</p> + <p><span class="sc">Mackinnon</span>, Mr., horses of the Falkland islands, i. 52;</p> + <p class="i2">feral cattle of the Falkland islands, i. 86.</p> + <p><span class="sc">MacKnight</span>, C., on interbreeding cattle, ii. <a href="#page118">118</a>.</p> + <p><span class="sc">MacNab</span>, Mr., on seedling weeping birches, ii. <a href="#page18">18</a>;</p> + <p class="i2">non-production of the weeping beech by seed, ii. <a href="#page19">19</a>.</p> + <p><span class="sc">Madagascar</span>, cats of, i. 47.</p> + <p><span class="sc">Madden</span>, H., on interbreeding cattle, ii. <a href="#page118">118</a>.</p> + <p><span class="sc">Madeira</span>, rock pigeon of, i. 184.</p> + <p><i>Magnolia grandiflora</i>, ii. <a href="#page308">308</a>.</p> + <p><span class="sc">Maize</span>, its unity of origin, i. 320;</p> + <p class="i2">antiquity of, <i>ibid.</i>;</p> + <p class="i2">with husked grains said to grow wild, <i>ibid.</i>;</p> + <p class="i2">variation of, i. 321;</p> + <p class="i2">irregularities in the flowers of, i. 321;</p> + <p class="i2">persistence of varieties, <i>ibid.</i>;</p> + <p class="i2">adaptation of to climate, i. 322, ii. <a href="#page307">307</a>;</p> + <p class="i2">acclimatisation of, ii. <a href="#page313">313</a>, <a href="#page347">347</a>;</p> + <p class="i2">crossing of, i. 400, ii. <a href="#page104">104</a>-<a href="#page105">105</a>;</p> + <p class="i2">extinct Peruvian varieties of, ii. <a href="#page425">425</a>.</p> + <p><span class="sc">Malay</span> fowl, i. 227.</p> + <p><span class="sc">Malay</span> Archipelago, horses of, i. 53;</p> + <p class="i2">short-tailed cats of, i. 47;</p> + <p class="i2">striped young wild pigs of, i. 76;</p> + <p class="i2">ducks of, i. 280.</p> + <p><span class="sc">Male</span>, influence of, on the fecundated female, i. 397-406;</p> + <p class="i2">supposed influence of, on offspring, ii. <a href="#page68">68</a>.</p> + <p><span class="sc">Male</span> flowers, appearance of, among female flowers in maize, i. 321.</p> + <p><span class="sc">Malformations</span>, hereditary, ii. <a href="#page79">79</a>.</p> + <p><i>Malva</i>, fertilisation of, i. 402, ii. <a href="#page363">363</a>.</p> + <p><i>Mamestra suasa</i>, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Mammæ</span>, variable in number in the pig, i. 74;</p> + <p class="i2">rudimentary, occasional full development of, in cows, i. 87, ii. <a href="#page317">317</a>;</p> + <p class="i2">four present in some sheep, i. 95;</p> + <p class="i2">variable in number in rabbits, i. 106;</p> + <p class="i2">latent functions of, in male animals, ii. <a href="#page52">52</a>, <a href="#page317">317</a>;</p> + <p class="i2">supernumerary and inguinal, in women, ii. <a href="#page57">57</a>.</p> + <p><span class="sc">Mangles</span>, Mr., annual varieties of the heartsease, ii. <a href="#page305">305</a>.</p> + <p><span class="sc">Mantell</span>, Mr., taming of birds by the New Zealanders, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Manu</span>, domestic fowl noticed in the Institutes of, i. 246.</p> + <p><span class="sc">Manure</span>, effect of, on the fertility of plants, ii. <a href="#page163">163</a>.</p> + <p><span class="sc">Manx</span> cats, i. 46, ii. <a href="#page66">66</a>.</p> + <p><span class="sc">Marcel</span> de Serres, fertility of the ostrich, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Marianne</span> islands, varieties of <i>Pandanus</i> in, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Markham</span>, Gervase, on rabbits, i. 104, ii. <a href="#page204">204</a>.</p> + <p><span class="sc">Markhor</span>, probably one of the parents of the goat, i. 101.</p> + <p><span class="sc">Marquand</span>, cattle of the channel islands, i. 80.</p> + <p><span class="sc">Marrimpoey</span>, inheritance in the horse, ii. <a href="#page10">10</a>.</p> + <p><span class="sc">Marrow</span>, vegetable, i. 357.</p> + <p><span class="sc">Marryatt</span>, Capt., breeding of asses in Kentucky, ii. <a href="#page237">237</a>.</p> + <p><span class="sc">Marsden</span>, notice of <i>Gallus giganteus</i>, i. 235.</p> + <p><span class="sc">Marshall</span>, Mr., voluntary selection of pasture by sheep, i. 96;</p> + <p class="i2">adaptation of wheats to soil and climate, i. 316;</p> + <p class="i2">"Dutch-buttocked" cattle, ii. <a href="#page8">8</a>;</p> + <p class="i2">segregation of herds of sheep, ii. <a href="#page103">103</a>;</p> + <p class="i2">advantage of change of soil to wheat and potatoes, ii. <a href="#page146">146</a>;</p> + <p class="i2">fashionable change in the horns of cattle, ii. <a href="#page210">210</a>;</p> + <p class="i2">sheep in Yorkshire, ii. <a href="#page235">235</a>.</p> + <p><span class="sc">Marshall</span>, Prof., growth of the brain in microcephalous idiots, ii. <a href="#page389">389</a>.</p> + <p><span class="sc">Martens</span>, E. Von, on <i>Achatinella</i>, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Martin</span>, W. C. L., origin of the dog, i. 16;</p> + <p class="i2">Egyptian dogs, i. 18;</p> + <p class="i2">barking of a Mackenzie River dog, i. 27;</p> + <p class="i2">African hounds in the Tower menagerie, i. 32;</p> + <p class="i2">on dun horses and dappled asses, i. 55;</p> + <p class="i2">breeds of the horse, i. 49;</p> + <p class="i2">wild horses, i. 51;</p> + <p class="i2">Syrian breeds of asses, i. 62;</p> + <p class="i2">asses without stripes, i. 63;</p> + <p class="i2">effects of cross-breeding on the female in dogs, i. 404;</p> + <p class="i2">striped legs of mules, ii. <a href="#page42">42</a>.</p> + <p><span class="sc">Martins</span>, defective instincts of silkworms, i. 304.</p> + <p><span class="sc">Martins</span>, C., fruit trees of Stockholm, ii. <a href="#page307">307</a>.</p> +<!-- Page 464 --><span class="pagenum"><a name="page464"></a>{464}</span> + <p><span class="sc">Mason</span>, W., bud-variation in the ash, i. 382.</p> + <p><span class="sc">Masters</span>, Dr., reversion in the spiral-leaved weeping willow, i. 383;</p> + <p class="i2">on peloric flowers, ii. <a href="#page58">58</a>;</p> + <p class="i2">pelorism in a clover, ii. <a href="#page346">346</a>;</p> + <p class="i2">position as a cause of pelorism, ii. <a href="#page345">345</a>, <a href="#page347">347</a>.</p> + <p><span class="sc">Masters</span>, Mr., persistence of varieties of peas, i. 329;</p> + <p class="i2">reproduction of colour in hyacinths, ii. <a href="#page20">20</a>;</p> + <p class="i2">on hollyhocks, ii. <a href="#page107">107</a>;</p> + <p class="i2">selection of peas for seed, ii. <a href="#page199">199</a>-<a href="#page200">200</a>;</p> + <p class="i2">on <i>Opuntia leucotricha</i>, ii. <a href="#page286">286</a>;</p> + <p class="i2">reversion by the terminal pea in the pod, ii. <a href="#page347">347</a>.</p> + <p><span class="sc">Mastiff</span>, sculptured on an Assyrian monument, i. 17, ii. <a href="#page429">429</a>;</p> + <p class="i2">Tibetan, i. 35-36, ii. <a href="#page278">278</a>.</p> + <p><span class="sc">Matthews</span>, Patrick, on forest trees, ii. <a href="#page237">237</a>.</p> + <p><i>Matthiola annua</i>, i. 399, ii. <a href="#page20">20</a>.</p> + <p><i>Matthiola incana</i>, i. 381, 399.</p> + <p><span class="sc">Mauchamp</span>, merino sheep, i. 100.</p> + <p><span class="sc">Mauduyt</span>, crossing of wolves and dogs in the Pyrenees, i. 24.</p> + <p><span class="sc">Maund</span>, Mr. crossed varieties of wheat, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Maupertuis</span>, axiom of "least action," i. 12.</p> + <p><span class="sc">Mauritius</span>, importation of goats into, i. 101.</p> + <p><span class="sc">Maw</span>, G., correlation of contracted leaves and flowers in pelargoniums, ii. <a href="#page330">330</a>, <a href="#page331">331</a>.</p> + <p><span class="sc">Mawz</span>, fertility of <i>Brassica rapa</i>, ii. <a href="#page165">165</a>.</p> + <p><i>Maxillaria</i>, self-fertilised capsules of, ii. <a href="#page134">134</a>;</p> + <p class="i2">number of seeds in, ii. <a href="#page379">379</a>.</p> + <p><i>Maxillaria atro-rubens</i>, fertilisation of, by <i>M. squalens</i>, ii. <a href="#page133">133</a>.</p> + <p><span class="sc">Mayes</span>, M., self-impotence in <i>Amaryllis</i>, ii. <a href="#page139">139</a>.</p> + <p><span class="sc">Meckel</span>, on the number of digits, ii. <a href="#page13">13</a>;</p> + <p class="i2">correlation of abnormal muscles in the leg and arm, ii. <a href="#page322">322</a>.</p> + <p><span class="sc">Medusæ</span>, development of, ii. <a href="#page368">368</a>, <a href="#page384">384</a>.</p> + <p><span class="sc">Meehan</span>, Mr., comparison of European and American trees, ii. <a href="#page281">281</a>.</p> + <p><i>Meleagris mexicana</i>, i. 292.</p> + <p><i>Meles taxus</i>, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Melons</span>, i. 359-360;</p> + <p class="i2">mongrel, supposed to be produced from a twin-seed, i. 391;</p> + <p class="i2">crossing of varieties of, i. 399, ii. <a href="#page108">108</a>, <a href="#page129">129</a>;</p> + <p class="i2">inferiority of, in Roman times, ii. <a href="#page216">216</a>;</p> + <p class="i2">changes in, by culture and climate, ii. <a href="#page275">275</a>;</p> + <p class="i2">serpent, correlation of variations in, ii. <a href="#page330">330</a>;</p> + <p class="i2">analogous variations in, ii. <a href="#page349">349</a>.</p> + <p><span class="sc">Membranes</span>, false, ii. <a href="#page294">294</a>-<a href="#page295">295</a>.</p> + <p><span class="sc">Ménétries</span>, on the stomach of <i>Strix grallaria</i>, ii. <a href="#page302">302</a>.</p> + <p><span class="sc">Meningitis</span>, tubercular, inherited, ii. <a href="#page78">78</a>.</p> + <p><span class="sc">Metagenesis</span>, ii. <a href="#page366">366</a>.</p> + <p><span class="sc">Metamorphosis</span>, ii. <a href="#page366">366</a>.</p> + <p><span class="sc">Metamorphosis</span> and development, ii. <a href="#page388">388</a>, <a href="#page389">389</a>.</p> + <p><span class="sc">Metzger</span>, on the supposed species of wheat, i. 312-313;</p> + <p class="i2">tendency of wheat to vary, i. 315;</p> + <p class="i2">variation of maize, i. 321-322;</p> + <p class="i2">cultivation of American maize in Europe, i. 322, ii. <a href="#page347">347</a>;</p> + <p class="i2">on cabbages, i. 323-325;</p> + <p class="i2">acclimatisation of Spanish wheat in Germany, ii. <a href="#page26">26</a>;</p> + <p class="i2">advantage of change of soil to plants, ii. <a href="#page146">146</a>;</p> + <p class="i2">on rye, ii. <a href="#page254">254</a>;</p> + <p class="i2">cultivation of different kinds of wheat, ii. <a href="#page261">261</a>.</p> + <p><span class="sc">Mexico</span>, dog from, with tan spots on the eyes, i. 29;</p> + <p class="i2">colours of feral horses in, i. 61.</p> + <p><span class="sc">Meyen</span>, on sending of bananas, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Mice</span>, grey and white, colours of, not blended by crossing, ii. <a href="#page92">92</a>;</p> + <p class="i2">rejection of bitter almonds by, ii. <a href="#page232">232</a>;</p> + <p class="i2">naked, ii. <a href="#page279">279</a>.</p> + <p><span class="sc">Michaux</span>, F., roan-coloured feral horses of Mexico, i. 61;</p> + <p class="i2">origin of domestic turkey, i. 292;</p> + <p class="i2">on raising peaches from seed, i. 339.</p> + <p><span class="sc">Michel</span>, F., selection of horses in mediæval times, ii. <a href="#page203">203</a>;</p> + <p class="i2">horses preferred on account of slight characters, ii. <a href="#page209">209</a>.</p> + <p><span class="sc">Michely</span>, effects of food on caterpillars, ii. <a href="#page280">280</a>;</p> + <p class="i2">on <i>Bombyx hesperus</i>, ii. <a href="#page304">304</a>.</p> + <p><span class="sc">Microphthalmia</span>, associated with defective teeth, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Middens</span>, Danish, remains of dogs in, i. 18, ii. <a href="#page427">427</a>.</p> + <p><span class="sc">Mignonette</span>, ii. <a href="#page237">237</a>, <a href="#page311">311</a>.</p> + <p><span class="sc">Millet</span>, i. 371.</p> + <p><span class="sc">Mills</span>, J., diminished fertility of mares when first turned out to grass, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Milne-Edwards</span>, on the development of the crustacea, ii. <a href="#page368">368</a>.</p> + <p><span class="sc">Milne-Edwards</span>, A., on a crustacean with a monstrous eye-peduncle, ii. <a href="#page391">391</a>.</p> + <p><i>Milvus niger</i>, ii. <a href="#page154">154</a>.</p> + <p><i>Mimulus luteus</i>, ii. <a href="#page128">128</a>.</p> + <p><span class="sc">Minor</span>, W. C., gemmation and fission in the Annelida, ii. <a href="#page358">358</a>.</p> + <p><i>Mirabilis</i>, fertilisation of, ii. <a href="#page363">363</a>;</p> + <p class="i2">hybrids of, ii. <a href="#page131">131</a>, <a href="#page169">169</a>, <a href="#page265">265</a>.</p> + <p><i>Mirabilis jalapa</i>, i. 382, 393.</p> + <p><i>Mirabilis longiflora</i>, ii. <a href="#page88">88</a>.</p> + <p><i>Mirabilis vulgaris</i>, ii. <a href="#page88">88</a>.</p> + <p><i>Misocampus</i> and <i>Cecidomyia</i>, i. 5.</p> + <p><span class="sc">Mitchell</span>, Dr., effects of the poison of the rattlesnake, ii. <a href="#page289">289</a>.</p> + <p><span class="sc">Mitford</span>, Mr., notice of the breeding of horses by Erichthonius, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Moccas</span> Court, weeping oak at, ii. <a href="#page18">18</a>.</p> + <p><span class="sc">Mogford</span>, horses poisoned by fool's parsley, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Möller</span>, L., effects of food on insects, ii. <a href="#page281">281</a>.</p> + <p><span class="sc">Moquin-Tandon</span>, original form of maize, i. 320;</p> + <p class="i2">variety of the double columbine, i. 365;</p> +<!-- Page 465 --><span class="pagenum"><a name="page465"></a>{465}</span> + <p class="i2">peloric flowers, ii. <a href="#page58">58</a>-<a href="#page59">59</a>, <a href="#page61">61</a>;</p> + <p class="i2">position as a cause of pelorism in flowers, ii. <a href="#page345">345</a>;</p> + <p class="i2">tendency of peloric flowers to become irregular, ii. <a href="#page70">70</a>;</p> + <p class="i2">on monstrosities, ii. <a href="#page254">254</a>;</p> + <p class="i2">correlation in the axis and appendages of plants, ii. <a href="#page321">321</a>;</p> + <p class="i2">fusion of homologous parts in plants, ii. <a href="#page339">339</a>, <a href="#page341">341</a>-<a href="#page342">342</a>;</p> + <p class="i2">on a bean with monstrous stipules and abortive leaflets, ii. <a href="#page343">343</a>;</p> + <p class="i2">conversion of parts of flowers, ii. <a href="#page392">392</a>.</p> + <p><span class="sc">Mole</span>, white, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Moll</span> and Gayot, on cattle, i. 80, ii. <a href="#page96">96</a>, <a href="#page210">210</a>.</p> + <p><span class="sc">Mollusca</span>, change in shells of, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Monke</span>, Lady, culture of the pansy by, i. 368.</p> + <p><span class="sc">Monkeys</span>, rarely fertile in captivity, ii. <a href="#page153">153</a>.</p> + <p><span class="sc">Monnier</span>, identity of summer and winter wheat, i. 315.</p> + <p><span class="sc">Monster</span>, cyclopean, ii. <a href="#page341">341</a>.</p> + <p><span class="sc">Monsters</span>, double, ii. <a href="#page339">339</a>-<a href="#page340">340</a>.</p> + <p><span class="sc">Monstrosities</span>, occurrence of, in domesticated animals and cultivated plants, i. 366, ii. <a href="#page254">254</a>;</p> + <p class="i2">due to persistence of embryonic conditions, ii. <a href="#page57">57</a>;</p> + <p class="i2">occurring by reversion, ii. <a href="#page57">57</a>-<a href="#page60">60</a>;</p> + <p class="i2">a cause of sterility, ii. <a href="#page166">166</a>-<a href="#page167">167</a>;</p> + <p class="i2">caused by injury to the embryo, ii. <a href="#page269">269</a>.</p> + <p><span class="sc">Montegazza</span>, growth of a cock's-spur inserted into the eye of an ox, ii. <a href="#page369">369</a>.</p> + <p><span class="sc">Montgomery</span>, E., formation of cells, ii. <a href="#page370">370</a>.</p> + <p><span class="sc">Moor</span>, J. H., deterioration of the horse in Malasia, i. 53.</p> + <p><span class="sc">Moorcroft</span>, Mr., on Hasora wheat, i. 313;</p> + <p class="i2">selection of white-tailed yaks, ii. <a href="#page206">206</a>;</p> + <p class="i2">melon of Kaschmir, ii. <a href="#page275">275</a>;</p> + <p class="i2">varieties of the apricot cultivated in Ladakh, i. 345;</p> + <p class="i2">varieties of the walnut cultivated in Kaschmir, i. 356.</p> + <p><span class="sc">Moore</span>, Mr., on breeds of pigeons, i. 148, 156, 208, 209, 211.</p> + <p><span class="sc">Mooruk</span>, fertility of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Morlot</span>, dogs of the Danish Middens, i. 18;</p> + <p class="i2">sheep and horse of the bronze period, ii. <a href="#page427">427</a>.</p> + <p><i>Mormodes ignea</i>, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Morocco</span>, estimation of pigeons in, i. 205.</p> + <p><span class="sc">Morren</span>, C., on pelorism, ii. <a href="#page58">58</a>;</p> + <p class="i2">in <i>Calceolaria</i>, ii. <a href="#page346">346</a>;</p> + <p class="i2">non-coincidence of double flowers and variegated leaves, ii. <a href="#page167">167</a>.</p> + <p><span class="sc">Morris</span>, Mr., breeding of the Kestrel in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Morton</span>, Lord, effect of fecundation by a quagga on an Arab mare, i. 403-404.</p> + <p><span class="sc">Morton</span>, Dr., origin of the dog, i. 16;</p> + <p class="i2">hybrid of zebra and mare, ii. <a href="#page42">42</a>.</p> + <p><i>Morus alba</i>, i. 334.</p> + <p><span class="sc">Moscow</span>, rabbits of, i. 106, 120;</p> + <p class="i2">effects of cold on pear-trees at, ii. <a href="#page307">307</a>.</p> + <p><span class="sc">Mosses</span>, sterility in, ii. <a href="#page171">171</a>;</p> + <p class="i2">retrogressive metamorphosis in, ii. <a href="#page361">361</a>.</p> + <p><span class="sc">Moss-rose</span>, probable origin of, from <i>Rosa centifolia</i>, i. 379;</p> + <p class="i2">Provence roses produced from seeds of, i. 380.</p> + <p><span class="sc">Mosto</span>, Cada, on the introduction of rabbits into Porto Santo, i. 113.</p> + <p><span class="sc">Mottling</span> of fruits and flowers, i. 400.</p> + <p><span class="sc">Moufflon</span>, i. 94.</p> + <p><span class="sc">Mountain-ash</span>, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Mouse</span>, Barbary, ii. <a href="#page152">152</a>.</p> + <p>"<span class="sc">Möven-taube</span>," i. 148.</p> + <p><span class="sc">Mowbray</span>, Mr., on the eggs of game fowls, i. 248;</p> + <p class="i2">early pugnacity of game cocks, i. 251;</p> + <p class="i2">diminished fecundity of the pheasant in captivity, ii. <a href="#page155">155</a>.</p> + <p><span class="sc">Mowbray</span>, Mr., reciprocal fecundation of <i>Passiflora alata</i> and <i>racemosa</i>, ii. <a href="#page137">137</a>.</p> + <p><span class="sc">Mulattos</span>, character of, ii. <a href="#page46">46</a>.</p> + <p><span class="sc">Mulberry</span>, i. 334, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Mule</span> and hinny, differences in the, ii. <a href="#page67">67</a>-<a href="#page68">68</a>.</p> + <p><span class="sc">Mules</span><span class="scac"></span>, striped colouring of, ii. <a href="#page42">42</a>;</p> + <p class="i2">obstinacy of, ii. <a href="#page45">45</a>;</p> + <p class="i2">production of, among the Romans, ii. <a href="#page110">110</a>;</p> + <p class="i2">noticed in the Bible, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Müller</span>, Fritz, reproduction of orchids, ii. <a href="#page134">134</a>-<a href="#page135">135</a>;</p> + <p class="i2">development of crustacea, ii. <a href="#page368">368</a>;</p> + <p class="i2">number of seeds in a <i>maxillaria</i>, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Müller</span>, H., on the face and teeth in dogs, i. 34, 73, ii. <a href="#page345">345</a>.</p> + <p><span class="sc">Müller</span>, J., production of imperfect nails after partial amputation of the fingers, ii. <a href="#page15">15</a>;</p> + <p class="i2">tendency to variation, ii. <a href="#page252">252</a>;</p> + <p class="i2">atrophy of the optic nerve consequent on destruction of the eye, ii. <a href="#page297">297</a>;</p> + <p class="i2">on Janus-like monsters, ii. <a href="#page340">340</a>;</p> + <p class="i2">on gemmation and fission, ii. <a href="#page358">358</a>;</p> + <p class="i2">identity of ovules and buds, ii. <a href="#page360">360</a>;</p> + <p class="i2">special affinities of the tissues, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Müller</span>, Max, antiquity of agriculture, ii. <a href="#page243">243</a>.</p> + <p><span class="sc">Multiplicity</span> of origin of pigeons, hypotheses of, discussed, i. 188-194.</p> + <p><span class="sc">Muniz</span>, F., on Niata cattle, i. 90.</p> + <p><span class="sc">Munro</span>, R., on the fertilisation of orchids, ii. <a href="#page133">133</a>;</p> + <p class="i2">reproduction of <i>Passiflora alata</i>, ii. <a href="#page138">138</a>.</p> + <p>"<span class="sc">Murassa</span>" pigeon, i. 144.</p> + <p><span class="sc">Murphy</span>, J. J., the structure of the eye not producible by selection, ii. <a href="#page222">222</a>.</p> + <p><i>Mus alexandrinus</i>, ii. <a href="#page87">87</a>-<a href="#page88">88</a>.</p> + <p><i>Musa sapientum</i>, <i>Chinensis</i> and <i>Cavendishii</i>, i. 377.</p> + <p><i>Muscari comosum</i>, ii. <a href="#page185">185</a>, <a href="#page316">316</a>.</p> + <p><span class="sc">Muscles</span>, effects of use on, ii. <a href="#page297">297</a>.</p> + <p><span class="sc">Musk</span> duck, feral hybrid of, with the common duck, i. 190.</p> +<!-- Page 466 --><span class="pagenum"><a name="page466"></a>{466}</span> + <p><span class="sc">Musmon</span>, female, sometimes hornless, i. 95.</p> + <p><span class="sc">Mutilations</span>, inheritance or non-inheritance of, ii. <a href="#page22">22</a>-<a href="#page24">24</a>, <a href="#page397">397</a>.</p> + <p><span class="sc">Myatt</span>, on a five-leaved variety of the strawberry, i. 353.</p> + <p><span class="sc">Myopia</span>, hereditary, ii. <a href="#page8">8</a>.</p> + <p><span class="sc">Myriapoda</span>, regeneration of lost parts in, ii. <a href="#page15">15</a>, <a href="#page294">294</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Nails</span>, growing on stumps of fingers, ii. <a href="#page394">394</a>.</p> + <p><span class="sc">Nais</span>, scission of, ii. <a href="#page358">358</a>.</p> + <p><span class="sc">Namaquas</span>, cattle of the, i. 88, ii. <a href="#page207">207</a>.</p> + <p><span class="sc">Narcissus</span>, double, becoming single in poor soil, ii. <a href="#page167">167</a>.</p> + <p><span class="sc">Narvaez</span>, on the cultivation of native plants in Florida, i. 312.</p> + <p><i>Nasua</i>, sterility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p>"<span class="sc">Natas</span>," or Niatas, a South American breed of cattle, i. 89-91.</p> + <p><span class="sc">Nathusius</span>, H. von, on the pigs of the Swiss lake-dwellings, i. 68;</p> + <p class="i2">on the races of pigs, i. 65-68;</p> + <p class="i2">convergence of character in highly-bred pigs, i. 73, ii. <a href="#page241">241</a>;</p> + <p class="i2">causes of changes in the form of the pig's skull, i. 72-73;</p> + <p class="i2">changes in breeds of pigs by crossing, i. 78;</p> + <p class="i2">change of form in the pig, ii. <a href="#page279">279</a>;</p> + <p class="i2">effects of disuse of parts in the pig, ii. <a href="#page299">299</a>;</p> + <p class="i2">period of gestation in the pig, i. 74;</p> + <p class="i2">appendages to the jaw in pigs, i. 76;</p> + <p class="i2">on <i>Sus pliciceps</i>, i. 70;</p> + <p class="i2">period of gestation in sheep, i. 97;</p> + <p class="i2">on Niata cattle, i. 89;</p> + <p class="i2">on short-horn cattle, ii. <a href="#page118">118</a>;</p> + <p class="i2">on interbreeding, ii. <a href="#page116">116</a>;</p> + <p class="i2">in the sheep, ii. <a href="#page120">120</a>;</p> + <p class="i2">in pigs, ii. <a href="#page122">122</a>;</p> + <p class="i2">unconscious selection in cattle and pigs, ii. <a href="#page214">214</a>;</p> + <p class="i2">variability of highly selected races, ii. <a href="#page238">238</a>.</p> + <p><span class="sc">Nato</span>, P., on the Bizzaria orange, i. 391.</p> + <p><span class="sc">Natural</span> selection, its general principles, i. 2-14.</p> + <p><span class="sc">Nature</span>, sense in which the term is employed, i. 6.</p> + <p><span class="sc">Naudin</span>, supposed rules of transmission in crossing plants, ii. <a href="#page68">68</a>;</p> + <p class="i2">on the nature of hybrids, ii. <a href="#page48">48</a>-<a href="#page49">49</a>;</p> + <p class="i2">essences of the species in hybrids, ii. <a href="#page386">386</a>, <a href="#page401">401</a>;</p> + <p class="i2">reversion of hybrids, ii. <a href="#page36">36</a>, <a href="#page49">49</a>-<a href="#page50">50</a>;</p> + <p class="i2">reversion in flowers by stripes and blotches, ii. <a href="#page37">37</a>;</p> + <p class="i2">hybrids of <i>Linaria vulgaris</i> and <i>purpurea</i>, ii. <a href="#page94">94</a>;</p> + <p class="i2">pelorism in <i>Linaria</i>, ii. <a href="#page58">58</a>, <a href="#page346">346</a>;</p> + <p class="i2">crossing of peloric <i>Linaria</i> with the normal form, ii. <a href="#page70">70</a>;</p> + <p class="i2">variability in <i>Datura</i>, ii. <a href="#page266">266</a>;</p> + <p class="i2">hybrids of <i>Datura lævis</i> and <i>stramonium</i>, i. 392;</p> + <p class="i2">prepotency of transmission of <i>Datura stramonium</i> when crossed, ii. <a href="#page67">67</a>;</p> + <p class="i2">on the pollen of <i>Mirabilis</i> and of hybrids, i. 389;</p> + <p class="i2">fertilisation of <i>Mirabilis</i>, ii. <a href="#page363">363</a>;</p> + <p class="i2">crossing of <i>Chamærops humilis</i> and the date palm, i. 399;</p> + <p class="i2">cultivated Cucurbitaceæ, i. 357-360, ii. <a href="#page108">108</a>;</p> + <p class="i2">rudimentary tendrils in gourds, ii. <a href="#page316">316</a>;</p> + <p class="i2">dwarf <i>Cucurbitæ</i>, ii. <a href="#page330">330</a>;</p> + <p class="i2">relation between the size and number of the fruit in <i>Cucurbita pepo</i>, ii. <a href="#page343">343</a>;</p> + <p class="i2">analogous variation in <i>Cucurbitæ</i>, ii. <a href="#page349">349</a>;</p> + <p class="i2">acclimatisation of Cucurbitaceæ, ii. <a href="#page313">313</a>;</p> + <p class="i2">production of fruit by sterile hybrid Cucurbitaceæ, ii. <a href="#page172">172</a>;</p> + <p class="i2">on the melon, i. 360, ii. <a href="#page108">108</a>, <a href="#page275">275</a>;</p> + <p class="i2">incapacity of the cucumber to cross with other species, i. 359.</p> + <p><span class="sc">Nectarine</span>, i. 336-344;</p> + <p class="i2">derived from the peach, i. 337, 339-342;</p> + <p class="i2">hybrids of, i. 339;</p> + <p class="i2">persistency of characters in seedling, i. 340;</p> + <p class="i2">origin of, <i>ibid.</i>;</p> + <p class="i2">produced on peach trees, i. 340-341;</p> + <p class="i2">producing peaches, i. 341;</p> + <p class="i2">variation in, i. 342-343;</p> + <p class="i2">bud-variation in, i. 374;</p> + <p class="i2">glands in the leaves of the, ii. <a href="#page231">231</a>;</p> + <p class="i2">analogous variation in, ii. <a href="#page348">348</a>.</p> + <p><span class="sc">Nectary</span>, variations of, in pansies, i. 369.</p> + <p><span class="sc">Nees</span>, on changes in the odour of plants, ii. <a href="#page274">274</a>.</p> + <p>"<span class="sc">Negro</span>" cat, i. 46.</p> + <p><span class="sc">Negroes</span>, polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">selection of cattle practised by, ii. <a href="#page207">207</a>.</p> + <p><span class="sc">Neolithic</span> period, domestication of <i>Bos longifrons</i> and <i>primigenius</i> in the, i. 81;</p> + <p class="i2">cattle of the, distinct from the original species, i. 87;</p> + <p class="i2">domestic goat in the, i. 101;</p> + <p class="i2">cereals of the, i. 317.</p> + <p><span class="sc">Nerve</span>, optic, atrophy of the, ii. <a href="#page297">297</a>.</p> + <p><span class="sc">Neumeister</span>, on the Dutch and German pouter pigeons, i. 138;</p> + <p class="i2">on the Jacobin pigeon, i. 154;</p> + <p class="i2">duplication of the middle flight feather in pigeons, i. 159;</p> + <p class="i2">on a peculiarly coloured breed of pigeons, "Staarhalsige Taube," i. 161;</p> + <p class="i2">fertility of hybrid pigeons, i. 192;</p> + <p class="i2">mongrels of the trumpeter pigeon, ii. <a href="#page66">66</a>;</p> + <p class="i2">period of perfect plumage in pigeons, ii. <a href="#page77">77</a>;</p> + <p class="i2">advantage of crossing pigeons, ii. <a href="#page126">126</a>.</p> + <p><span class="sc">Neuralgia</span>, hereditary, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">New Zealand</span>, feral cats of, i. 47;</p> + <p class="i2">cultivated plants of, i. 311.</p> + <p><span class="sc">Newfoundland</span> dog, modification of, in England, i. 42.</p> + <p><span class="sc">Newman</span>, E., sterility of Sphingidæ under certain conditions, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Newport</span>, G., non-copulation of <i>Vanessæ</i> in confinement, ii. <a href="#page157">157</a>;</p> + <p class="i2">regeneration of limbs in myriapoda, ii. <a href="#page294">294</a>;</p> + <p class="i2">fertilisation of the ovule in batrachia, ii. <a href="#page363">363</a>.</p> + <p><span class="sc">Newt</span>, polydactylism in the, ii. <a href="#page14">14</a>.</p> + <p><span class="sc">Newton</span>, A., absence of sexual distinctions in the Columbidæ, i. 162;</p> + <p class="i2">production of a "black-shouldered" pea-hen among the ordinary kind, i. 291;</p> + <p class="i2">on hybrid ducks, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Ngami</span>, Lake, cattle of, i. 88.</p> + <p>"<span class="sc">Niata</span>" cattle, i. 89-91;</p> + <p class="i2">resemblance of to <i>Sivatherium</i>, i. 89;</p> +<!-- Page 467 --><span class="pagenum"><a name="page467"></a>{467}</span> + <p class="i2">prepotency of transmission of character by, ii. <a href="#page66">66</a>.</p> + <p>"<span class="sc">Nicard</span>" rabbit, i. 107.</p> + <p><span class="sc">Nicholson</span>, Dr., on the cats of Antigua, i. 46;</p> + <p class="i2">on the sheep of Antigua, i. 98.</p> + <p><i>Nicotiana</i>, crossing of varieties and species of, ii. <a href="#page108">108</a>;</p> + <p class="i2">prepotency of transmission of characters in species of, ii. <a href="#page67">67</a>;</p> + <p class="i2">contabescence of female organs in, ii. <a href="#page166">166</a>.</p> + <p><i>Nicotiana glutinosa</i>, ii. <a href="#page108">108</a>.</p> + <p><span class="sc">Niebuhr</span>, on the heredity of mental characteristics in some Roman families, ii. <a href="#page65">65</a>.</p> + <p><span class="sc">Night-blindness</span>, non-reversion to, ii. <a href="#page36">36</a>.</p> + <p><span class="sc">Nilsson</span>, Prof., on the barking of a young wolf, i. 27;</p> + <p class="i2">parentage of European breeds of cattle, i. 80, 81;</p> + <p class="i2">on <i>Bos frontosus</i> in Scania, i. 81.</p> + <p><span class="sc">Nind</span>, Mr., on the dingo, i. 39.</p> + <p>"<span class="sc">Nisus</span> formativus," i. 293, 294, 355.</p> + <p><span class="sc">Nitzsch</span>, on the absence of the oil-gland in certain Columbæ, i. 147.</p> + <p><span class="sc">Non-inheritance</span>, causes of, ii. <a href="#page24">24</a>-<a href="#page26">26</a>.</p> + <p>"<span class="sc">Nonnain</span>" pigeon, i. 154.</p> + <p><span class="sc">Nordmann</span>, dogs of Awhasie, i. 25.</p> + <p><span class="sc">Normandy</span>, pigs of, with appendages under the jaw, i. 75.</p> + <p><span class="sc">Norway</span>, striped ponies of, i. 58.</p> + <p><span class="sc">Nott</span> and Gliddon, on the origin of the dog, i. 16;</p> + <p class="i2">mastiff represented on an Assyrian tomb, i. 17;</p> + <p class="i2">on Egyptian dogs, i. 18;</p> + <p class="i2">on the Hare-Indian dog, i. 22.</p> + <p><i>Notylia</i>, ii. <a href="#page135">135</a>.</p> + <p><span class="sc">Nourishment</span>, excess of, a cause of variability, ii. <a href="#page257">257</a>.</p> + <p><span class="sc">Number</span>, importance of, in selection, ii. <a href="#page235">235</a>.</p> + <p><i>Numida ptilorhyncha</i>, the original of the Guinea-fowl, i. 294.</p> + <p><span class="sc">Nun</span> pigeon, i. 155;</p> + <p class="i2">known to Aldrovandi, i. 207.</p> + <p><span class="sc">Nutmeg</span> tree, ii. <a href="#page237">237</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Oak</span>, weeping, i. 361, ii. <a href="#page18">18</a>, <a href="#page241">241</a>;</p> + <p class="i2">pyramidal, i. 361;</p> + <p class="i2">Hessian, i. 361;</p> + <p class="i2">late-leaved, i. 363;</p> + <p class="i2">variation in persistency of leaves of, i. 363;</p> + <p class="i2">valueless as timber at the Cape of Good Hope, ii. <a href="#page274">274</a>;</p> + <p class="i2">changes in, dependent on age, i. 387;</p> + <p class="i2">galls of the, ii. <a href="#page282">282</a>.</p> + <p><span class="sc">Oats</span>, wild, i. 313;</p> + <p class="i2">in the Swiss lake-dwellings, i. 319.</p> + <p><span class="sc">Oberlin</span>, change of soil beneficial to the potato, ii. <a href="#page146">146</a>.</p> + <p><span class="sc">Odart</span>, Count, varieties of the vine, i. 333, ii. <a href="#page278">278</a>;</p> + <p class="i2">bud-variation in the vine, i. 375.</p> + <p><span class="sc">Odour</span> and colour, correlation of, ii. <a href="#page325">325</a>.</p> + <p><i>Œcidium</i>, ii. <a href="#page284">284</a>.</p> + <p><i>Œnothera biennis</i>, bud-variation in, i. 382.</p> + <p><span class="sc">Ogle</span>, W., resemblance of twins, ii. <a href="#page252">252</a>.</p> + <p><span class="sc">Oil-gland</span>, absence of, in fantail pigeons, i. 147, 160.</p> + <p><span class="sc">Oldfield</span>, Mr., estimation of European dogs among the natives of Australia, ii. <a href="#page215">215</a>.</p> + <p><span class="sc">Oleander</span>, stock affected by grafting in the, i. 394.</p> + <p><span class="sc">Ollier</span>, Dr., insertion of the periosteum of a dog beneath the skin of a rabbit, ii. <a href="#page369">369</a>.</p> + <p><i>Oncidium</i>, reproduction of, ii. <a href="#page133">133</a>-<a href="#page135">135</a>, <a href="#page164">164</a>.</p> + <p><span class="sc">Onions</span>, crossing of, ii. <a href="#page90">90</a>;</p> + <p class="i2">white, liable to the attacks of fungi and disease, ii. <a href="#page228">228</a>, <a href="#page336">336</a>.</p> + <p><i>Ophrys apifera</i>, self-fertilisation of, ii. <a href="#page91">91</a>;</p> + <p class="i2">formation of pollen by a petal in, ii. <a href="#page392">392</a>.</p> + <p><i>Opuntia leucotricha</i>, ii. <a href="#page277">277</a>.</p> + <p><span class="sc">Orange</span>, i. 334-336;</p> + <p class="i2">crossing of, ii. <a href="#page91">91</a>;</p> + <p class="i2">with the lemon, i. 399, ii. <a href="#page365">365</a>;</p> + <p class="i2">naturalisation of, in Italy, ii. <a href="#page308">308</a>;</p> + <p class="i2">variation of, in North Italy, ii. <a href="#page256">256</a>;</p> + <p class="i2">peculiar variety of, ii. <a href="#page331">331</a>;</p> + <p class="i2">Bizzaria, i. 391;</p> + <p class="i2">trifacial, <i>ibid.</i></p> + <p><span class="sc">Orchids</span>, reproduction of, i. 402, 403; ii. <a href="#page133">133</a>-<a href="#page135">135</a>.</p> + <p><span class="sc">Orford</span>, Lord, crossing greyhounds with the bulldog, i. 41.</p> + <p><span class="sc">Organisms</span>, origin of, i. 13.</p> + <p><span class="sc">Organisation</span>, advancement in, i. 8.</p> + <p><span class="sc">Organs</span>, rudimentary and aborted, ii. <a href="#page315">315</a>-<a href="#page318">318</a>;</p> + <p class="i2">multiplication of abnormal, ii. <a href="#page391">391</a>.</p> + <p><span class="sc">Oriole</span>, assumption of hen-plumage by a male in confinement, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Orkney</span> islands, pigs of, i. 70;</p> + <p class="i2">pigeons of, i. 184.</p> + <p><span class="sc">Orthoptera</span>, regeneration of hind legs in the, ii. <a href="#page294">294</a>.</p> + <p><i>Orthosia munda</i>, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Orton</span>, R., on the effects of cross-breeding on the female, i. 404;</p> + <p class="i2">on the Manx cat, ii. <a href="#page66">66</a>;</p> + <p class="i2">on mongrels from the silk-fowl, ii. <a href="#page67">67</a>.</p> + <p><span class="sc">Osborne</span>, Dr., inherited mottling of the iris, ii. <a href="#page10">10</a>.</p> + <p><span class="sc">Osprey</span>, preying on Black-fowls, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Osten-Sacken</span>, Baron, on American oak galls, ii. <a href="#page282">282</a>.</p> + <p><span class="sc">Osteological</span> characters of pigs, i. 66, 67, 71-74;</p> + <p class="i2">of rabbits, i. 115-130;</p> + <p class="i2">of pigeons, i. 162-167;</p> + <p class="i2">of ducks, i. 282-284.</p> + <p><span class="sc">Ostrich</span>, diminished fertility of the, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Ostyaks</span>, selection of dogs by the, ii. <a href="#page206">206</a>.</p> + <p><span class="sc">Otter</span>, ii. <a href="#page151">151</a>.</p> + <p>"<span class="sc">Otter</span>" sheep of Massachusetts, i. 100.</p> + <p><span class="sc">Oude</span>, feral humped cattle in, i. 79.</p> + <p><span class="sc">Ouistiti</span>, breed in Europe, ii. <a href="#page153">153</a>.</p> +<!-- Page 468 --><span class="pagenum"><a name="page468"></a>{468}</span> + <p><span class="sc">Ovary</span>, variation of, in <i>Cucurbita moschata</i>, i. 359;</p> + <p class="i2">development of, independently of pollen, i. 403.</p> + <p><i>Ovis montana</i>, i. 99.</p> + <p><span class="sc">Ovules</span> and buds, identity of nature of, ii. <a href="#page360">360</a>.</p> + <p><span class="sc">Owen</span>, Capt., on stiff-haired cats at Mombas, i. 46.</p> + <p><span class="sc">Owen</span>, Prof. R., palæontological evidence as to the origin of dogs, i. 15;</p> + <p class="i2">on <i>Bos longifrons</i>, i. 81;</p> + <p class="i2">on the skull of the "Niata" cattle, i. 89, 90;</p> + <p class="i2">on fossil remains of rabbits, i. 104;</p> + <p class="i2">on the significance of the brain, i. 124;</p> + <p class="i2">on the number of digits in the Ichthyopterygia, ii. <a href="#page16">16</a>;</p> + <p class="i2">on metagenesis, ii. <a href="#page366">366</a>;</p> + <p class="i2">theory of reproduction and parthenogenesis, ii. <a href="#page375">375</a>.</p> + <p><span class="sc">Owl</span>, eagle, breeding in captivity, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Owl</span> pigeon, i. 148;</p> + <p class="i2">African, figured, i. 149;</p> + <p class="i2">known in 1735, i. 209.</p> + <p><i>Oxalis</i>, trimorphic species of, ii. <a href="#page400">400</a>.</p> + <p><i>Oxalis rosea</i>, ii. <a href="#page132">132</a>.</p> + <p><span class="sc">Oxley</span>, Mr., on the nutmeg tree, ii. <a href="#page237">237</a>.</p> + <p><span class="sc">Oysters</span>, differences in the shells of, ii. <a href="#page280">280</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Paca</span>, sterility of the, in confinement, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Pacific</span> islands, pigs of the, i. 70.</p> + <p><span class="sc">Padua</span>, earliest known flower garden at, ii. <a href="#page217">217</a>.</p> + <p><span class="sc">Paduan</span> fowl of Aldrovandi, i. 247.</p> + <p><i>Pæonia moutan</i>, ii. <a href="#page205">205</a>.</p> + <p><span class="sc">Pæony</span>, tree, ancient cultivation of, in China, ii. <a href="#page205">205</a>.</p> + <p><span class="sc">Pampas</span>, feral cattle on the, i. 85.</p> + <p><i>Pandanus</i>, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Pangenesis</span>, hypothesis of, ii. <a href="#page357">357</a>-<a href="#page404">404</a>.</p> + <p><i>Panicum</i>, seeds of, used as food, i. 309;</p> + <p class="i2">found in the Swiss lake-dwellings, i. 317.</p> + <p><span class="sc">Pansy</span>, i. 368-370.</p> + <p><span class="sc">Pappus</span>, abortion of the, in <i>Carthamus</i>, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Paget</span>, on the Hungarian sheep dog, i. 24.</p> + <p><span class="sc">Paget</span>, inheritance of cancer, ii. <a href="#page7">7</a>;</p> + <p class="i2">hereditary elongation of hairs in the eyebrow, ii. <a href="#page8">8</a>;</p> + <p class="i2">period of inheritance of cancer, ii. <a href="#page79">79</a>-<a href="#page80">80</a>;</p> + <p class="i2">on <i>Hydra</i>, ii. <a href="#page293">293</a>;</p> + <p class="i2">on the healing of wounds, ii. <a href="#page294">294</a>;</p> + <p class="i2">on the reparation of bones, <i>ibid.</i>;</p> + <p class="i2">growth of hair near inflamed surfaces or fractures, ii. <a href="#page295">295</a>;</p> + <p class="i2">on false membranes, <i>ibid.</i>;</p> + <p class="i2">compensatory development of the kidney, ii. <a href="#page300">300</a>;</p> + <p class="i2">bronzed skin in disease of supra-renal capsules, ii. <a href="#page331">331</a>;</p> + <p class="i2">unity of growth and gemmation, ii. <a href="#page359">359</a>;</p> + <p class="i2">independence of the elements of the body, ii. <a href="#page369">369</a>;</p> + <p class="i2">affinity of the tissues for special organic substances, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Pallas</span>, on the influence of domestication upon the sterility of intercrossed species, i. 31, 83, 193, ii. <a href="#page109">109</a>;</p> + <p class="i2">hypothesis that variability is wholly due to crossing, i. 188, 374, ii. <a href="#page250">250</a>, <a href="#page264">264</a>;</p> + <p class="i2">on the origin of the dog, i. 16;</p> + <p class="i2">variation in dogs, i. 33;</p> + <p class="i2">crossing of dog and jackal, i. 25;</p> + <p class="i2">origin of domestic cats, i. 43;</p> + <p class="i2">origin of Angora cat, i. 45;</p> + <p class="i2">on wild horses, i. 52, 60;</p> + <p class="i2">on Persian sheep, i. 94;</p> + <p class="i2">on Siberian fat-tailed sheep, ii. <a href="#page279">279</a>;</p> + <p class="i2">on Chinese sheep, ii. <a href="#page315">315</a>;</p> + <p class="i2">on Crimean varieties of the vine, i. 333;</p> + <p class="i2">on a grape with rudimentary seeds, ii. <a href="#page316">316</a>;</p> + <p class="i2">on feral musk-ducks, ii. <a href="#page46">46</a>;</p> + <p class="i2">sterility of Alpine plants in gardens, ii. <a href="#page163">163</a>;</p> + <p class="i2">selection of white-tailed yaks, ii. <a href="#page206">206</a>.</p> + <p><i>Paradoxurus</i>, sterility of species of, in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Paraguay</span>, cats of, i. 46;</p> + <p class="i2">cattle of, i. 89;</p> + <p class="i2">horses of, ii. <a href="#page102">102</a>;</p> + <p class="i2">dogs of, ii. <a href="#page102">102</a>;</p> + <p class="i2">black-skinned domestic fowl of, i. 232.</p> + <p><span class="sc">Parallel</span> variation, ii. <a href="#page348">348</a>-<a href="#page352">352</a>.</p> + <p><span class="sc">Paramos</span>, woolly pigs of, i. 78.</p> + <p><span class="sc">Parasites</span>, liability to attacks of, dependent on colour, ii. <a href="#page228">228</a>.</p> + <p><span class="sc">Pariah</span> dog, with crooked legs, i. 17;</p> + <p class="i2">resembling the Indian wolf, i. 24.</p> + <p><span class="sc">Pariset</span>, inheritance of handwriting, ii. <a href="#page6">6</a>.</p> + <p><span class="sc">Parker</span>, W. K., number of vertebræ in fowls, i. 266.</p> + <p><span class="sc">Parkinson</span>, Mr., varieties of the hyacinth, i. 370.</p> + <p><span class="sc">Parkyns</span>, Mansfield, on <i>Columba guinea</i>, i. 183.</p> + <p><span class="sc">Parmentier</span>, differences in the nidification of pigeons, i. 178;</p> + <p class="i2">on white pigeons, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Parrots</span>, general sterility of, in confinement, ii. <a href="#page155">155</a>;</p> + <p class="i2">alteration of plumage of, ii. <a href="#page280">280</a>.</p> + <p><span class="sc">Parsnip</span>, reversion in, ii. <a href="#page31">31</a>;</p> + <p class="i2">influence of selection on, ii. <a href="#page201">201</a>;</p> + <p class="i2">experiments on, ii. <a href="#page277">277</a>;</p> + <p class="i2">wild, enlargement of roots of, by cultivation, i. 326.</p> + <p><span class="sc">Parthenogenesis</span>, ii. <a href="#page359">359</a>, <a href="#page364">364</a>.</p> + <p><span class="sc">Partridge</span>, sterility of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Parturition</span>, difficult, hereditary, ii. <a href="#page8">8</a>.</p> + <p><i>Parus major</i>, ii. <a href="#page231">231</a>.</p> + <p><i>Passiflora</i>, self-impotence in species of, ii. <a href="#page137">137</a>-<a href="#page138">138</a>;</p> + <p class="i2">contabescence of female organs in, ii. <a href="#page166">166</a>.</p> + <p><i>Passiflora alata</i>, fertility of, when grafted, ii. <a href="#page188">188</a>.</p> + <p><span class="sc">Pasture</span> and climate, adaptation of breeds of sheep to, i. 96, 97.</p> + <p><span class="sc">Pastrana</span>, Julia, peculiarities in the hair and teeth of, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Patagonia</span>, crania of pigs from, i. 77.</p> + <p><span class="sc">Patagonian</span> rabbit, i. 105.</p> +<!-- Page 469 --><span class="pagenum"><a name="page469"></a>{469}</span> + <p><span class="sc">Paterson</span>, R., on the Arrindy silk moth, ii. <a href="#page306">306</a>.</p> + <p><span class="sc">Paul</span>, W., on the hyacinth, i. 370;</p> + <p class="i2">varieties of pelargoniums, i. 378;</p> + <p class="i2">improvement of pelargoniums, ii. <a href="#page216">216</a>.</p> + <p><i>Pavo cristatus</i> and <i>muticus</i>, hybrids of, i. 290.</p> + <p><i>Pavo nigripennis</i>, i. 290-291.</p> + <p>"<span class="sc">Pavodotten-Taube</span>," i. 141.</p> + <p><span class="sc">Peach</span>, i. 336-344;</p> + <p class="i2">derived from the almond, i. 337;</p> + <p class="i2">stones of, figured, <i>ibid.</i>;</p> + <p class="i2">contrasted with almonds, i. 338;</p> + <p class="i2">double-flowering, i. 338-339, 343;</p> + <p class="i2">hybrids of, i. 339;</p> + <p class="i2">persistency of races of, <i>ibid.</i>;</p> + <p class="i2">trees producing nectarines, i. 340-341;</p> + <p class="i2">variation in, i. 342-343, ii. <a href="#page256">256</a>;</p> + <p class="i2">bud-variation in, i. 374;</p> + <p class="i2">pendulous, ii. <a href="#page18">18</a>;</p> + <p class="i2">variation by selection in, ii. <a href="#page218">218</a>;</p> + <p class="i2">peculiar disease of the, ii. <a href="#page228">228</a>;</p> + <p class="i2">glands on the leaves of the, ii. <a href="#page231">231</a>;</p> + <p class="i2">antiquity of the, ii. <a href="#page308">308</a>;</p> + <p class="i2">increased hardiness of the, <i>ibid.</i>;</p> + <p class="i2">varieties of, adapted for forcing, ii. <a href="#page310">310</a>;</p> + <p class="i2">yellow-fleshed, liable to certain diseases, ii. <a href="#page336">336</a>.</p> + <p><span class="sc">Peach-almond</span>, i. 338.</p> + <p><span class="sc">Peafowl</span>, origin of, i. 290;</p> + <p class="i2">japanned or black-shouldered, i. 290-291;</p> + <p class="i2">feral, in Jamaica, i. 190;</p> + <p class="i2">comparative fertility of, in wild and tame states, ii. <a href="#page112">112</a>, <a href="#page268">268</a>;</p> + <p class="i2">white, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Pears</span>, i. 350;</p> + <p class="i2">bud-variation in, i. 376;</p> + <p class="i2">reversion in seedling, ii. <a href="#page31">31</a>;</p> + <p class="i2">inferiority of, in Pliny's time, ii. <a href="#page215">215</a>;</p> + <p class="i2">winter nelis, attacked by aphides, ii. <a href="#page231">231</a>;</p> + <p class="i2">soft-barked varieties of, attacked by wood-boring beetles, ii. <a href="#page231">231</a>;</p> + <p class="i2">origination of good varieties of, in woods, ii. <a href="#page260">260</a>;</p> + <p class="i2">Forelle, resistance of, to frost, ii. <a href="#page306">306</a>.</p> + <p><span class="sc">Peas</span>, i. 326-330;</p> + <p class="i2">origin of, 326;</p> + <p class="i2">varieties of, 326-329;</p> + <p class="i2">found in Swiss lake-dwellings, i. 317, 319, 326-329;</p> + <p class="i2">fruit and seeds figured, i. 328;</p> + <p class="i2">persistency of varieties, i. 329;</p> + <p class="i2">intercrossing of varieties, i. 330, 397, ii. <a href="#page129">129</a>;</p> + <p class="i2">effect of crossing on the female organs in, i. 398;</p> + <p class="i2">double-flowered, ii. <a href="#page168">168</a>;</p> + <p class="i2">maturity of, accelerated by selection, ii. <a href="#page201">201</a>;</p> + <p class="i2">varieties of, produced by selection, ii. <a href="#page218">218</a>;</p> + <p class="i2">thin-shelled, liable to the attacks of birds, ii. <a href="#page231">231</a>;</p> + <p class="i2">reversion of, by the terminal seed in the pod, ii. <a href="#page347">347</a>.</p> + <p><span class="sc">Peccary</span>, breeding of the, in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Pedigrees</span> of horses, cattle, greyhounds, game-cocks, and pigs, ii. <a href="#page3">3</a>.</p> + <p><span class="sc">Pegu</span>, cats of, i. 47;</p> + <p class="i2">horses of, i. 53.</p> + <p><span class="sc">Pelargoniums</span>, multiple origin of, i. 364;</p> + <p class="i2">zones of, i. 366;</p> + <p class="i2">bud-variation in, i. 378;</p> + <p class="i2">variegation in, accompanied by dwarfing, i. 384;</p> + <p class="i2">pelorism in, ii. <a href="#page167">167</a>, <a href="#page345">345</a>;</p> + <p class="i2">by reversion, ii. <a href="#page59">59</a>;</p> + <p class="i2">advantage of change of soil to, ii. <a href="#page147">147</a>;</p> + <p class="i2">improvement of, by selection, ii. <a href="#page216">216</a>;</p> + <p class="i2">scorching of, ii. <a href="#page229">229</a>;</p> + <p class="i2">numbers of, raised from seed, ii. <a href="#page235">235</a>;</p> + <p class="i2">effects of conditions of life on, ii. <a href="#page274">274</a>;</p> + <p class="i2">stove-variety of, ii. <a href="#page311">311</a>;</p> + <p class="i2">correlation of contracted leaves and flowers in, ii. <a href="#page330">330</a>-<a href="#page331">331</a>.</p> + <p><i>Pelargonium fulgidum</i>, conditions of fertility in, ii. <a href="#page164">164</a>.</p> + <p>"<span class="sc">Pelones</span>," a Columbian breed of cattle, i. 88.</p> + <p><span class="sc">Peloric</span> flowers, tendency of, to acquire the normal form, ii. <a href="#page70">70</a>;</p> + <p class="i2">fertility or sterility of, ii. <a href="#page166">166</a>-<a href="#page167">167</a>.</p> + <p><span class="sc">Peloric</span> races of <i>Gloxinia speciosa</i> and <i>Antirrhinum majus</i>, i. 365.</p> + <p><span class="sc">Pelorism</span>, ii. <a href="#page58">58</a>-<a href="#page60">60</a>, <a href="#page345">345</a>-<a href="#page346">346</a>.</p> + <p><span class="sc">Pelvis</span>, characters of, in rabbits, i. 122-123;</p> + <p class="i2">in pigeons, i. 166;</p> + <p class="i2">in fowls, i. 268;</p> + <p class="i2">in ducks, i. 284.</p> + <p><span class="sc">Pembroke</span> cattle, i. 81.</p> + <p><span class="sc">Pendulous</span> trees, i. 361, ii. <a href="#page348">348</a>;</p> + <p class="i2">uncertainty of transmission of, ii. <a href="#page18">18</a>-<a href="#page19">19</a>.</p> + <p><span class="sc">Penguin</span> ducks, i. 280, 282;</p> + <p class="i2">hybrid of the, with the Egyptian goose, i. 282.</p> + <p><span class="sc">Pennant</span>, production of wolf-like curs at Fochabers, i. 37;</p> + <p class="i2">on the Duke of Queensberry's wild cattle, i. 84.</p> + <p><i>Pennisetum</i>, seeds of, used as food in the Punjab, i. 309.</p> + <p><i>Pennisetum distichum</i>, seeds of, used as food in Central Africa, i. 308.</p> + <p><span class="sc">Percival</span>, Mr., on inheritance in horses, ii. <a href="#page10">10</a>;</p> + <p class="i2">on horn-like processes in horses, i. 50.</p> + <p><i>Perdix rubra</i>, occasional fertility of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Period</span> of action of causes of variability, ii. <a href="#page269">269</a>.</p> + <p><span class="sc">Periosteum</span> of a dog, producing bone in a rabbit, ii. <a href="#page369">369</a>.</p> + <p><span class="sc">Periwinkle</span>, sterility of, in England, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Persia</span>, estimation of pigeons in, i. 205;</p> + <p class="i2">carrier pigeon of, i. 141;</p> + <p class="i2">tumbler pigeon of, i. 150;</p> + <p class="i2">cats of, i. 45-47;</p> + <p class="i2">sheep of, i. 94.</p> + <p><i>Persica intermedia</i>, i. 338.</p> + <p><span class="sc">Persistence</span> of colour in horses, i. 50;</p> + <p class="i2">of generic peculiarities, i. 111.</p> + <p><span class="sc">Peru</span>, antiquity of maize in, i. 320;</p> + <p class="i2">peculiar potato from, i. 331;</p> + <p class="i2">selection of wild animals practised by the Incas of, ii. <a href="#page207">207</a>-<a href="#page208">208</a>.</p> + <p>"<span class="sc">Perücken-Taube</span>," i. 154.</p> + <p><span class="sc">Petals</span>, rudimentary, in cultivated plants, ii. <a href="#page316">316</a>;</p> + <p class="i2">producing pollen, ii. <a href="#page392">392</a>.</p> + <p><span class="sc">Petunias</span>, multiple origin of, i. 364;</p> + <p class="i2">double-flowered, ii. <a href="#page167">167</a>.</p> + <p>"<span class="sc">Pfauen-Taube</span>," i. 146.</p> + <p><i>Phacochœrus Africanus</i>, i. 76.</p> + <p><i>Phalænopsis</i>, pelorism in, ii. <a href="#page346">346</a>.</p> + <p><span class="sc">Phalanges</span>, deficiency of, ii. <a href="#page73">73</a>.</p> +<!-- Page 470 --><span class="pagenum"><a name="page470"></a>{470}</span> + <p><i>Phaps chalcoptera</i>, ii. <a href="#page349">349</a>.</p> + <p><i>Phaseolus multiflorus</i>, ii. <a href="#page309">309</a>, <a href="#page322">322</a>.</p> + <p><i>Phaseolus vulgaris</i>, ii. <a href="#page309">309</a>.</p> + <p><i>Phasianus pictus</i>, i. 275.</p> + <p><i>Phasianus Amherstiæ</i>, i. 275.</p> + <p><span class="sc">Pheasant</span>, assumption of male plumage by the hen, ii. <a href="#page51">51</a>;</p> + <p class="i2">wildness of hybrids of, with the common fowl, ii. <a href="#page45">45</a>;</p> + <p class="i2">prepotency of the, over the fowl, ii. <a href="#page68">68</a>;</p> + <p class="i2">diminished fecundity of the, in captivity, ii. <a href="#page155">155</a>.</p> + <p><span class="sc">Pheasants</span>, golden and Lady Amherst's, i. 275.</p> + <p><span class="sc">Pheasant-fowls</span>, i. 244.</p> + <p><span class="sc">Philipeaux</span>, regeneration of limbs in the salamander, ii. <a href="#page376">376</a>.</p> + <p><span class="sc">Philippar</span>, on the varieties of wheat, i. 314.</p> + <p><span class="sc">Philippine</span> Islands, named breeds of game fowl in the, i. 232.</p> + <p><span class="sc">Phillips</span>, Mr., on bud-variation in the potato, i. 385.</p> + <p><i>Phlox</i>, bud-variation by suckers in, i. 384.</p> + <p><span class="sc">Phthisis</span>, affection of the fingers in, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Pickering</span>, Mr., on the grunting voice of humped cattle, i. 79;</p> + <p class="i2">occurrence of the head of a fowl in an ancient Egyptian procession, i. 246;</p> + <p class="i2">seeding of ordinarily seedless fruits, ii. <a href="#page168">168</a>;</p> + <p class="i2">extinction of ancient Egyptian breeds of sheep and oxen, ii. <a href="#page425">425</a>;</p> + <p class="i2">on an ancient Peruvian gourd, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Picotees</span>, effect of conditions of life on, ii. <a href="#page273">273</a>.</p> + <p><span class="sc">Pictet</span>, A., oriental names of the pigeon, i. 205.</p> + <p><span class="sc">Pictet</span>, Prof., origin of the dog, i. 15;</p> + <p class="i2">on fossil oxen, i. 81.</p> + <p><span class="sc">Piebalds</span>, probably due to reversion, ii. <a href="#page37">37</a>.</p> + <p><span class="sc">Pigeaux</span>, hybrids of the hare and rabbit, ii. <a href="#page99">99</a>, <a href="#page152">152</a>.</p> + <p><span class="sc">Pigeon</span> à cravate, i. 148.</p> + <p><span class="sc">Pigeon</span> Bagadais, i. 142, 143.</p> + <p><span class="sc">Pigeon</span> coquille, i. 155.</p> + <p><span class="sc">Pigeon</span> cygne, i. 143.</p> + <p><span class="sc">Pigeon</span> heurté, i. 156.</p> + <p><span class="sc">Pigeon</span> Patu plongeur, i. 156.</p> + <p><span class="sc">Pigeon</span> Polonais, i. 144.</p> + <p><span class="sc">Pigeon</span> Romain, i. 142, 144.</p> + <p><span class="sc">Pigeon</span> tambour, i. 154.</p> + <p><span class="sc">Pigeon</span> Turc, i. 139.</p> + <p><span class="sc">Pigeons</span>, origin of, i. 131-134, 180-204;</p> + <p class="i2">classified table of breeds of, i. 136;</p> + <p class="i2">pouter, i. 137-139;</p> + <p class="i2">carrier, i. 139-142;</p> + <p class="i2">runt, i. 142-144;</p> + <p class="i2">barbs, i. 144-146;</p> + <p class="i2">fantail, i. 146-148;</p> + <p class="i2">turbit and owl, i. 148-149;</p> + <p class="i2">tumbler, i. 150-153;</p> + <p class="i2">Indian frill-back, i. 153;</p> + <p class="i2">Jacobin, i. 154;</p> + <p class="i2">trumpeter, i. 154;</p> + <p class="i2">other breeds of, i. 155-157;</p> + <p class="i2">differences of, equal to generic, i. 157-158;</p> + <p class="i2">individual variations of, i. 158-160;</p> + <p class="i2">variability of peculiarities characteristic of breeds in, i. 161;</p> + <p class="i2">sexual variability in, i. 161-162;</p> + <p class="i2">osteology of, i. 162-167;</p> + <p class="i2">correlation of growth in, i. 167-171, ii. <a href="#page321">321</a>;</p> + <p class="i2">young of some varieties naked when hatched, i. 170, ii. <a href="#page332">332</a>;</p> + <p class="i2">effects of disuse in, i. 172-177;</p> + <p class="i2">settling and roosting in trees, i. 181;</p> + <p class="i2">floating in the Nile to drink, i. 181;</p> + <p class="i2">Dovecot, i. 185-186;</p> + <p class="i2">arguments for unity of origin of, i. 188-204;</p> + <p class="i2">feral in various places, i. 190, ii. <a href="#page33">33</a>;</p> + <p class="i2">unity of coloration in, i. 195-197;</p> + <p class="i2">reversion of mongrel, to coloration of, <i>C. livia</i>, i. 197-202;</p> + <p class="i2">history of the cultivation of, i. 205-207;</p> + <p class="i2">history of the principal races of, i. 207-212;</p> + <p class="i2">mode of production of races of, i. 212-224;</p> + <p class="i2">reversion in, ii. <a href="#page29">29</a>, <a href="#page47">47</a>;</p> + <p class="i2">by age, ii. <a href="#page38">38</a>;</p> + <p class="i2">produced by crossing in, ii. <a href="#page40">40</a>, <a href="#page48">48</a>;</p> + <p class="i2">prepotency of transmission of character in breeds of, ii. <a href="#page66">66</a>-<a href="#page67">67</a>;</p> + <p class="i2">sexual differences in some varieties of, ii. <a href="#page74">74</a>;</p> + <p class="i2">period of perfect plumage in, ii. <a href="#page77">77</a>;</p> + <p class="i2">effect of segregation on, ii. <a href="#page86">86</a>;</p> + <p class="i2">preferent pairing of, within the same breed, ii. <a href="#page103">103</a>;</p> + <p class="i2">fertility of, increased by domestication, ii. <a href="#page112">112</a>, <a href="#page155">155</a>;</p> + <p class="i2">effects of interbreeding and necessity of crossing, ii. <a href="#page125">125</a>-126;</p> + <p class="i2">indifference of, to change of climate, ii. <a href="#page161">161</a>;</p> + <p class="i2">selection of, ii. <a href="#page195">195</a>, <a href="#page199">199</a>, <a href="#page204">204</a>;</p> + <p class="i2">among the Romans, ii. <a href="#page202">202</a>;</p> + <p class="i2">unconscious selection of, ii. <a href="#page211">211</a>, <a href="#page214">214</a>;</p> + <p class="i2">facility of selection of, ii. <a href="#page234">234</a>;</p> + <p class="i2">white, liable to the attacks of hawks, ii. <a href="#page230">230</a>;</p> + <p class="i2">effects of disuse of parts in, ii. <a href="#page298">298</a>;</p> + <p class="i2">fed upon meat, ii. <a href="#page304">304</a>;</p> + <p class="i2">effect of first male upon the subsequent progeny of the female, i. 405;</p> + <p class="i2">homology of the leg and wing feathers in, ii. <a href="#page323">323</a>;</p> + <p class="i2">union of two outer toes in feather-legged, <i>ibid.</i>;</p> + <p class="i2">correlation of beak, limbs, tongue, and nostrils in, ii. <a href="#page324">324</a>;</p> + <p class="i2">analogous variation in, ii. <a href="#page349">349</a>-<a href="#page350">350</a>;</p> + <p class="i2">permanence of breeds of, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Pigs</span>, of Swiss lake-dwellings, i. 67-68;</p> + <p class="i2">types of, derived from <i>Sus scrofa</i> and <i>Sus indica</i>, i. 66-67;</p> + <p class="i2">Japanese (<i>Sus pliciceps</i>, Gray), figured, i. 69;</p> + <p class="i2">of Pacific islands, i. 70, ii. <a href="#page87">87</a>;</p> + <p class="i2">modifications, of skull in, i. 71-73;</p> + <p class="i2">length of intestines in, i. 73, ii. <a href="#page303">303</a>;</p> + <p class="i2">period of gestation of, i. 74;</p> + <p class="i2">number of vertebræ and ribs in, i. 74;</p> + <p class="i2">anomalous forms, i. 75-76;</p> + <p class="i2">development of tusks and bristles in, i. 76;</p> + <p class="i2">striped young of, i. 76-77;</p> + <p class="i2">reversion of feral, to wild type, i. 77-78, ii. <a href="#page33">33</a>, <a href="#page47">47</a>;</p> + <p class="i2">production and changes of breeds of, by intercrossing, i. 78;</p> + <p class="i2">effects produced by the first male upon the subsequent progeny of the female, i. 404;</p> + <p class="i2">two-legged race of, ii. <a href="#page4">4</a>;</p> +<!-- Page 471 --><span class="pagenum"><a name="page471"></a>{471}</span> + <p class="i2">polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">cross-reversion in, ii. <a href="#page35">35</a>;</p> + <p class="i2">hybrid, wildness of, ii. <a href="#page45">45</a>;</p> + <p class="i2">monstrous development of a proboscis in, ii. <a href="#page57">57</a>;</p> + <p class="i2">disappearance of tusks in male under domestication, ii, 74;</p> + <p class="i2">solid hoofed, ii. <a href="#page429">429</a>;</p> + <p class="i2">crosses of, ii. <a href="#page93">93</a>, <a href="#page95">95</a>;</p> + <p class="i2">mutual fertility of all varieties of, ii. <a href="#page110">110</a>;</p> + <p class="i2">increased fertility by domestication, ii. <a href="#page111">111</a>;</p> + <p class="i2">ill effects of close interbreeding in, ii. <a href="#page121">121</a>-<a href="#page122">122</a>;</p> + <p class="i2">influence of selection on, ii. <a href="#page198">198</a>;</p> + <p class="i2">prejudice against certain colours in, ii. <a href="#page210">210</a>, <a href="#page229">229</a>, <a href="#page336">336</a>;</p> + <p class="i2">unconscious selection of, ii. <a href="#page214">214</a>;</p> + <p class="i2">black Virginian, ii. <a href="#page227">227</a>, <a href="#page336">336</a>;</p> + <p class="i2">similarity of the best breeds of, ii. <a href="#page241">241</a>;</p> + <p class="i2">change of form in, ii. <a href="#page279">279</a>;</p> + <p class="i2">effects of disuse of parts in, ii. <a href="#page299">299</a>;</p> + <p class="i2">ears of, ii. <a href="#page301">301</a>;</p> + <p class="i2">correlations in, ii. <a href="#page327">327</a>;</p> + <p class="i2">white, buck-wheat injurious to, ii. <a href="#page337">337</a>;</p> + <p class="i2">tail of, grafted upon the back, ii. <a href="#page369">369</a>;</p> + <p class="i2">extinction of the older races of, ii. <a href="#page426">426</a>.</p> + <p><span class="sc">Pimenta</span>, ii. <a href="#page91">91</a>.</p> + <p><span class="sc">Pimpernel</span>, ii. <a href="#page190">190</a>.</p> + <p><span class="sc">Pine-apple</span>, sterility and variability of the, ii. <a href="#page262">262</a>.</p> + <p><span class="sc">Pink</span>, Chinese. 322.</p> + <p><span class="sc">Pinks</span>, bud-variation in, i. 381;</p> + <p class="i2">improvement of, ii. <a href="#page216">216</a>.</p> + <p><i>Pinus pumilio</i>, <i>Mughus</i>, and <i>nana</i>, varieties of <i>P. sylvestris</i>, i. 363.</p> + <p><i>Pinus sylvestris</i>, i. 363, ii. <a href="#page310">310</a>;</p> + <p class="i2">hybrids of, with <i>P. nigricans</i>, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Piorry</span>, on hereditary disease, ii. <a href="#page7">7</a>, <a href="#page78">78</a>.</p> + <p><i>Pistacia lentiscus</i>, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Pistils</span>, rudimentary, in cultivated plants, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Pistor</span>, sterility of some mongrel pigeons, i. 192;</p> + <p class="i2">fertility of pigeons, ii. <a href="#page112">112</a>.</p> + <p><i>Pisum arvense</i> and <i>sativum</i>, i. 326.</p> + <p><span class="sc">Pityriasis</span> versicolor, inheritance of, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">Planchon</span>, G., on a fossil vine, i. 332;</p> + <p class="i2">sterility of <i>Jussiæa grandifiora</i> in France, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Plane</span> tree, variety of the, i. 362.</p> + <p><span class="sc">Plantigrade</span> carnivora, general sterility of the, in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Plants</span>, progress of cultivation of, i. 305-312;</p> + <p class="i2">cultivated, their geographical derivation, i. 311;</p> + <p class="i2">crossing of, ii. <a href="#page98">98</a>, <a href="#page99">99</a>, <a href="#page127">127</a>;</p> + <p class="i2">comparative fertility of wild and cultivated, ii. <a href="#page112">112</a>-<a href="#page113">113</a>;</p> + <p class="i2">self-impotent, ii. <a href="#page131">131</a>-<a href="#page140">140</a>;</p> + <p class="i2">dimorphic and trimorphic, ii. <a href="#page132">132</a>, <a href="#page140">140</a>;</p> + <p class="i2">sterility of, from changed conditions, ii. <a href="#page163">163</a>-<a href="#page165">165</a>;</p> + <p class="i2">from contabescence of anthers, ii. <a href="#page165">165</a>-<a href="#page166">166</a>;</p> + <p class="i2">from monstrosities, ii. <a href="#page166">166</a>-<a href="#page167">167</a>;</p> + <p class="i2">from doubling of the flowers, ii. <a href="#page167">167</a>-<a href="#page168">168</a>;</p> + <p class="i2">from seedless fruit, ii. <a href="#page168">168</a>;</p> + <p class="i2">from excessive development of vegetative organs, ii. <a href="#page168">168</a>-<a href="#page171">171</a>;</p> + <p class="i2">influence of selection on, ii. <a href="#page199">199</a>-<a href="#page201">201</a>;</p> + <p class="i2">variation by selection, in useful parts of, ii. <a href="#page217">217</a>-<a href="#page219">219</a>;</p> + <p class="i2">variability of, ii. <a href="#page237">237</a>;</p> + <p class="i2">variability of, induced by crossing, ii. <a href="#page265">265</a>;</p> + <p class="i2">direct action of change of climate on, ii. <a href="#page277">277</a>;</p> + <p class="i2">change of period of vegetation in, ii. <a href="#page304">304</a>-<a href="#page305">305</a>;</p> + <p class="i2">varieties of, suitable to different climates, ii. <a href="#page306">306</a>;</p> + <p class="i2">correlated variability of, ii. <a href="#page330">330</a>-<a href="#page331">331</a>;</p> + <p class="i2">antiquity of races of, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Plasticity</span>, inheritance of, ii. <a href="#page241">241</a>.</p> + <p><span class="sc">Plateau</span>, F., on the vision of amphibious animals, ii. <a href="#page223">223</a>.</p> + <p><i>Platessa flesus</i>, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Plato</span>, notice of selection in breeding dogs by, ii. <a href="#page212">212</a>.</p> + <p><span class="sc">Plica</span> polonica, ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Pliny</span>, on the crossing of shepherd's dogs with the wolf, i. 24;</p> + <p class="i2">on Pyrrhus' breed of cattle, ii. <a href="#page202">202</a>;</p> + <p class="i2">on the estimation of pigeons among the Romans, i. 205;</p> + <p class="i2">pears described by, ii. <a href="#page215">215</a>.</p> + <p><span class="sc">Plum</span>, i. 345-347;</p> + <p class="i2">stones figured, i. 345;</p> + <p class="i2">varieties of the, i. 345-346, ii. <a href="#page219">219</a>;</p> + <p class="i2">bud-variation in the, i. 375;</p> + <p class="i2">peculiar disease of the, ii. <a href="#page227">227</a>;</p> + <p class="i2">flower-buds of, destroyed by bullfinches, ii. <a href="#page232">232</a>;</p> + <p class="i2">purple-fruited, liable to certain diseases, ii. <a href="#page336">336</a>.</p> + <p><span class="sc">Plumage</span>, inherited peculiarities of, in pigeons, i. 160-161;</p> + <p class="i2">sexual peculiarities of, in fowls, i. 251-255.</p> + <p><span class="sc">Plurality</span> of races, Pouchet's views on, i. 2.</p> + <p><i>Poa</i>, seeds of, used as food, i. 308;</p> + <p class="i2">species of, propagated by bulblets, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Podolian</span> cattle, i. 80.</p> + <p><span class="sc">Pointers</span>, modification of, i. 42;</p> + <p class="i2">crossed with the foxhound, ii. <a href="#page95">95</a>.</p> + <p><span class="sc">Pois</span> sans parchemin, ii. <a href="#page231">231</a>.</p> + <p><span class="sc">Poiteau</span>, origin of <i>Cytisus Adami</i>, i. 390;</p> + <p class="i2">origin of cultivated varieties of fruit-trees, ii. <a href="#page260">260</a>.</p> + <p><span class="sc">Polish</span> fowl, i. 227, 250, 254, 256-257, 262;</p> + <p class="i2">skull figured, i. 262;</p> + <p class="i2">section of skull figured, i. 263;</p> + <p class="i2">development of protuberance of skull, i. 250;</p> + <p class="i2">furcula figured, i. 268.</p> + <p><span class="sc">Polish</span>, or Himalayan rabbit, i. 108.</p> + <p><span class="sc">Pollen</span>, ii. <a href="#page363">363</a>-<a href="#page364">364</a>;</p> + <p class="i2">action of, ii. <a href="#page108">108</a>;</p> + <p class="i2">injurious action of, in some orchids, ii. <a href="#page134">134</a>-<a href="#page135">135</a>;</p> + <p class="i2">resistance of, to injurious treatment, ii. <a href="#page164">164</a>;</p> + <p class="i2">prepotency of, ii. <a href="#page187">187</a>.</p> + <p><span class="sc">Pollock</span>, Sir F., transmission of variegated leaves in <i>Ballota nigra</i>, i. 383;</p> + <p class="i2">on local tendency to variegation, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Polyanthus</span>, ii. <a href="#page21">21</a>.</p> + <p><span class="sc">Polydactylism</span>, inheritance of, ii. <a href="#page12">12</a>-<a href="#page16">16</a>;</p> + <p class="i2">significance of, ii. <a href="#page16">16</a>-<a href="#page17">17</a>.</p> + <p><i>Polyplectron</i>, i. 255.</p> + <p><span class="sc">Ponies</span>, most frequent on islands and mountains, i. 52;</p> + <p class="i2">Javanese, i. 53.</p> + <p><span class="sc">Poole</span>, Col., on striped Indian horses, i. 58, 59;</p> +<!-- Page 472 --><span class="pagenum"><a name="page472"></a>{472}</span> + <p class="i2">on the young of <i>Asinus indicus</i>, ii. <a href="#page43">43</a>.</p> + <p><span class="sc">Poplar</span>, Lombardy, i. 361.</p> + <p><span class="sc">Pöppig</span>, on Cuban wild dogs, i. 27.</p> + <p><span class="sc">Poppy</span>, found in the Swiss lake-dwellings, i. 317, 319;</p> + <p class="i2">with the stamens converted into pistils, i. 365;</p> + <p class="i2">differences of the, in different parts of India, ii. <a href="#page165">165</a>;</p> + <p class="i2">monstrous, fertility of, ii. <a href="#page166">166</a>;</p> + <p class="i2">black-seeded, antiquity of, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Porcupine</span>, breeding of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Porcupine</span> family, ii. <a href="#page4">4</a>, <a href="#page76">76</a>.</p> + <p><i>Porphyrio</i>, breeding of a species of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Portal</span>, on a peculiar hereditary affection of the eye, ii. <a href="#page9">9</a>.</p> + <p><span class="sc">Porto</span> Santo, feral rabbits of, i. 112.</p> + <p><i>Potamochœrus penicillatus</i>, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Potato</span>, i. 330-331;</p> + <p class="i2">bud-variation by tubers in the, i. 384-385;</p> + <p class="i2">graft-hybrid of, by union of half-tubers, i. 395;</p> + <p class="i2">individual self-impotence in the, ii. <a href="#page137">137</a>;</p> + <p class="i2">sterility of, ii. <a href="#page169">169</a>;</p> + <p class="i2">advantage of change of soil to the, ii. <a href="#page146">146</a>;</p> + <p class="i2">relation of tubers and flowers in the, ii. <a href="#page343">343</a>.</p> + <p><span class="sc">Potato</span>, sweet, sterility of the, in China, ii. <a href="#page169">169</a>;</p> + <p class="i2">varieties of the, suited to different climates, ii. <a href="#page309">309</a>.</p> + <p><span class="sc">Pouchet</span>, M., his views on plurality of races, i. 2.</p> + <p><span class="sc">Pouter</span> pigeons, i. 137-139;</p> + <p class="i2">furcula figured, i. 167;</p> + <p class="i2">history of, i. 207.</p> + <p><span class="sc">Powis</span>, Lord, experiments in crossing humped and English cattle, i. 83, ii. <a href="#page45">45</a>.</p> + <p><span class="sc">Poynter</span>, Mr., on a graft-hybrid rose, i. 396.</p> + <p><span class="sc">Prairie</span> wolf, i. 22.</p> + <p><span class="sc">Precocity</span> of highly-improved breeds, ii. <a href="#page321">321</a>.</p> + <p><span class="sc">Prepotency</span> of pollen, ii. <a href="#page187">187</a>.</p> + <p><span class="sc">Prepotency</span> of transmission of character, ii. <a href="#page65">65</a>, <a href="#page174">174</a>;</p> + <p class="i2">in the Austrian emperors and some Roman families, ii. <a href="#page65">65</a>;</p> + <p class="i2">in cattle, ii. <a href="#page65">65</a>-<a href="#page66">66</a>;</p> + <p class="i2">in sheep, ii. <a href="#page66">66</a>;</p> + <p class="i2">in cats, <i>ibid.</i>;</p> + <p class="i2">in pigeons, ii. <a href="#page66">66</a>-<a href="#page67">67</a>;</p> + <p class="i2">in fowls, ii. <a href="#page67">67</a>;</p> + <p class="i2">in plants, <i>ibid.</i>;</p> + <p class="i2">in a variety of the pumpkin, i. 358;</p> + <p class="i2">in the jackal over the dog, ii. <a href="#page67">67</a>;</p> + <p class="i2">in the ass over the horse, <i>ibid.</i>;</p> + <p class="i2">in the pheasant over the fowl, ii. <a href="#page68">68</a>;</p> + <p class="i2">in the penguin duck over the Egyptian goose, <i>ibid.</i>;</p> + <p class="i2">discussion of the phenomena of, ii. <a href="#page69">69</a>-<a href="#page71">71</a>.</p> + <p><span class="sc">Prescott</span>, Mr., on the earliest known European flower-garden, ii. <a href="#page217">217</a>.</p> + <p><span class="sc">Pressure</span>, mechanical, a cause of modification, ii. <a href="#page344">344</a>-<a href="#page345">345</a>.</p> + <p><span class="sc">Prevost</span> and Dumas, on the employment of several spermatozoids to fertilise one ovule, ii. <a href="#page363">363</a>.</p> + <p><span class="sc">Price</span>, Mr., variations in the structure of the feet in horses, i. 50.</p> + <p><span class="sc">Prichard</span>, Dr., on polydactylism in the negro, ii. <a href="#page14">14</a>;</p> + <p class="i2">on the Lambert family, ii. <a href="#page77">77</a>;</p> + <p class="i2">on an albino negro, ii. <a href="#page229">229</a>;</p> + <p class="i2">on Plica polonica, ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Primrose</span>, ii. <a href="#page21">21</a>;</p> + <p class="i2">double, rendered single by transplantation, ii. <a href="#page167">167</a>.</p> + <p><i>Primula</i>, intercrossing of species of, i. 336;</p> + <p class="i2">contabescence in, ii. <a href="#page166">166</a>;</p> + <p class="i2">hose and hose, i. 365;</p> + <p class="i2">with coloured calyces, sterility of, ii. <a href="#page166">166</a>.</p> + <p><i>Primula sinensis</i>, reciprocally dimorphic, ii. <a href="#page132">132</a>.</p> + <p><i>Primula veris</i>, ii. <a href="#page21">21</a>, <a href="#page109">109</a>, <a href="#page182">182</a>.</p> + <p><i>Primula vulgaris</i>, ii. <a href="#page21">21</a>, <a href="#page109">109</a>.</p> + <p><span class="sc">Prince</span>, Mr., on the intercrossing of strawberries, i. 352.</p> + <p><i>Procyon</i>, sterility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Prolificacy</span>, increased by domestication, ii. <a href="#page174">174</a>.</p> + <p><span class="sc">Propagation</span>, rapidity of, favourable to selection, ii. <a href="#page297">297</a>.</p> + <p><span class="sc">Protozoa</span>, reproduction of the, ii. <a href="#page376">376</a>.</p> + <p><i>Prunus armeniaca</i>, i. 344-345.</p> + <p><i>Prunus avium</i>, i. 347.</p> + <p><i>Prunus cerasus</i>, i. 347, 375.</p> + <p><i>Prunus domestica</i>, i. 345.</p> + <p><i>Prunus insititia</i>, i. 345-347.</p> + <p><i>Prunus spinosa</i>, i. 345.</p> + <p><span class="sc">Prussia</span>, wild horses in, i. 60.</p> + <p><i>Psittacus erithacus</i>, ii. <a href="#page155">155</a>.</p> + <p><i>Psittacus macoa</i>, ii. <a href="#page155">155</a>.</p> + <p><i>Psophia</i>, general sterility of, in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Ptarmigan</span> fowls, i. 228.</p> + <p><i>Pulex penetrans</i>, ii. <a href="#page275">275</a>.</p> + <p><span class="sc">Pumpkins</span>, i. 357.</p> + <p><span class="sc">Puno</span> ponies of the Cordillera, i. 52.</p> + <p><span class="sc">Purser</span>, Mr. on <i>Cytisus Adami</i>, i. 389.</p> + <p><span class="sc">Pusey</span>, Mr., preference of hares and rabbits for common rye, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Putsche</span> and Vertuch, varieties of the potato, i. 330.</p> + <p><span class="sc">Puvis</span>, effects of foreign pollen on apples, i. 401;</p> + <p class="i2">supposed non-variability of monotypic genera, ii. <a href="#page266">266</a>.</p> + <p><i>Pyrrhula vulgaris</i>, ii. <a href="#page232">232</a>;</p> + <p class="i2">assumption of the hen-plumage by the male, in confinement, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Pyrrhus</span>, his breed of cattle, ii. <a href="#page202">202</a>.</p> + <p><i>Pyrus</i>, fastigate Chinese species of, ii. <a href="#page277">277</a>.</p> + <p><i>Pyrus acerba</i>, i. 348.</p> + <p><i>Pyrus aucuparia</i>, ii. <a href="#page230">230</a>.</p> + <p><i>Pyrus communis</i>, i. 350, 376.</p> + <p><i>Pyrus malus</i>, i. 348, 376.</p> + <p><i>Pyrus paradisiaca</i>, i. 348.</p> + <p><i>Pyrus præcox</i>, i. 348.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Quagga</span>, effect of fecundation by, on the subsequent progeny of a mare, i. 403-404.</p> + <p><span class="sc">Quatrefages</span>, A. de, on the burrowing of a bitch to litter, i. 77;</p> +<!-- Page 473 --><span class="pagenum"><a name="page473"></a>{473}</span> + <p class="i2">selection in the silkworm, i. 301;</p> + <p class="i2">development of the wings in the silkmoth, i. 303, ii. <a href="#page298">298</a>;</p> + <p class="i2">on varieties of the mulberry, i. 334;</p> + <p class="i2">special raising of eggs of the silkmoth, ii. <a href="#page197">197</a>;</p> + <p class="i2">on disease of the silkworm, ii. <a href="#page228">228</a>;</p> + <p class="i2">on monstrosities in insects, ii. <a href="#page269">269</a>, <a href="#page391">391</a>;</p> + <p class="i2">on the Anglo-Saxon race in America, ii. <a href="#page276">276</a>;</p> + <p class="i2">on a change in the breeding season of the Egyptian goose, ii. <a href="#page304">304</a>;</p> + <p class="i2">fertilisation of the <i>Teredo</i>, ii. <a href="#page363">363</a>;</p> + <p class="i2">tendency to similarity in the best races, ii. <a href="#page241">241</a>;</p> + <p class="i2">on his "<i>tourbillon vital</i>," ii. <a href="#page61">61</a>;</p> + <p class="i2">on the independent existence of the sexual elements, ii. <a href="#page360">360</a>.</p> + <p><i>Quercus cerris</i>, i. 363.</p> + <p><i>Quercus robur</i> and <i>pedunculata</i>, hybrids of, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Quince</span>, pears grafted on the, ii. <a href="#page259">259</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Rabbits</span>, domestic, their origin, i. 103-105;</p> + <p class="i2">of Mount Sinai and Algeria, i. 105;</p> + <p class="i2">breeds of, i. 105-111;</p> + <p class="i2">Himalayan, Chinese, Polish, or Russian, i. 108-111, ii. <a href="#page97">97</a>;</p> + <p class="i2">feral, i. 111-115;</p> + <p class="i2">of Jamaica, i. 112;</p> + <p class="i2">of the Falkland islands, i. 112;</p> + <p class="i2">of Porto Santo, i. 112-115, ii. <a href="#page103">103</a>, <a href="#page279">279</a>;</p> + <p class="i2">osteological characters of, i. 115-129;</p> + <p class="i2">discussion of modifications in, i. 129-130;</p> + <p class="i2">one-eared, transmission of peculiarity of, ii. <a href="#page12">12</a>;</p> + <p class="i2">reversion in feral, ii. <a href="#page33">33</a>;</p> + <p class="i2">in the Himalayan, ii. <a href="#page41">41</a>;</p> + <p class="i2">crossing of white and coloured Angora, ii. <a href="#page92">92</a>;</p> + <p class="i2">comparative fertility of wild and tame, ii. <a href="#page111">111</a>;</p> + <p class="i2">high-bred, often bad breeders, ii. <a href="#page121">121</a>;</p> + <p class="i2">selection of, ii. <a href="#page204">204</a>;</p> + <p class="i2">white, liable to destruction, ii. <a href="#page230">230</a>;</p> + <p class="i2">effects of disuse of parts in, ii. <a href="#page298">298</a>;</p> + <p class="i2">skull of, affected by drooping ears, ii. <a href="#page301">301</a>;</p> + <p class="i2">length of intestines in, ii. <a href="#page303">303</a>;</p> + <p class="i2">correlation of ears and skull in, ii. <a href="#page324">324</a>-<a href="#page325">325</a>;</p> + <p class="i2">variations in skull of, ii. <a href="#page350">350</a>;</p> + <p class="i2">periosteum of a dog producing bone in, ii. <a href="#page369">369</a>.</p> + <p><span class="sc">Race-horse</span>, origin of, i. 54.</p> + <p><span class="sc">Races</span>, modification and formation of, by crossing, ii. <a href="#page95">95</a>-<a href="#page99">99</a>;</p> + <p class="i2">natural and artificial, ii. <a href="#page245">245</a>;</p> + <p class="i2">Pouchet's views on plurality of, i. 2;</p> + <p class="i2">of pigeons, i. 207-212.</p> + <p><span class="sc">Radishes</span>, i. 326; crossing of, ii. <a href="#page90">90</a>;</p> + <p class="i2">varieties of, ii. <a href="#page217">217</a>-<a href="#page218">218</a>.</p> + <p><span class="sc">Radclyffe</span>, W. F., effect of climate and soil on strawberries, i. 354;</p> + <p class="i2">constitutional differences in roses, i. 367.</p> + <p><span class="sc">Radlkofer</span>, retrogressive metamorphosis in mosses and algæ, ii. <a href="#page361">361</a>.</p> + <p><span class="sc">Raffles</span>, Sir Stamford, on the crossing of Javanese cattle with <i>Bos sondaicus</i>, ii. <a href="#page206">206</a>.</p> + <p><span class="sc">Ram</span>, goat-like, from the Cape of Good Hope, ii. <a href="#page66">66</a>.</p> + <p><span class="sc">Ranchin</span>, heredity of diseases, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Range</span> of gallinaceous birds on the Himalaya, i. 237.</p> + <p><i>Ranunculus ficaria</i>, ii. <a href="#page170">170</a>.</p> + <p><i>Ranunculus repens</i>, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Rape</span>, i. 325.</p> + <p><i>Raphanus sativus</i>, ii. <a href="#page343">343</a>.</p> + <p><span class="sc">Raspberry</span>, yellow-fruited, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Rattlesnake</span>, experiments with poison of the, ii. <a href="#page289">289</a>.</p> + <p><span class="sc">Raven</span>, stomach of, affected by vegetable diet, ii. <a href="#page302">302</a>.</p> + <p><span class="sc">Rawson</span>, A., self-impotence in hybrids of <i>Gladiolus</i>, ii. <a href="#page139">139</a>-<a href="#page140">140</a>.</p> + <p><span class="sc">Ré</span>, Le Compte, on the assumption of a yellow colour by all varieties of maize, i. 321.</p> + <p><span class="sc">Réaumur</span>, effect of confinement upon the cock, ii. <a href="#page52">52</a>;</p> + <p class="i2">fertility of fowls in most climates, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Reed</span>, Mr., atrophy of the limbs of rabbits, consequent on the destruction of their nerves, ii. <a href="#page297">297</a>.</p> + <p><span class="sc">Regeneration</span> of amputated parts in man, ii. <a href="#page14">14</a>;</p> + <p class="i2">in the human embryo, ii. <a href="#page15">15</a>;</p> + <p class="i2">in the lower vertebrata, insects, and myriapoda, <i>ibid.</i></p> + <p><span class="sc">Reindeer</span>, individuals recognised by the Laplanders, ii. <a href="#page251">251</a>.</p> + <p><span class="sc">Regnier</span>, early cultivation of the cabbage by the Celts, i. 324.</p> + <p><span class="sc">Reissek</span>, experiments in crossing <i>Cytisus purpureus</i> and <i>laburnum</i>, i. 389;</p> + <p class="i2">modification of a <i>Thesium</i> by <i>Œcidium</i>, ii. <a href="#page284">284</a>.</p> + <p><span class="sc">Relations</span>, characters of, reproduced in children, ii. <a href="#page34">34</a>.</p> + <p><span class="sc">Rengger</span>, occurrence of jaguars with crooked legs in Paraguay, i. 17;</p> + <p class="i2">naked dogs of Paraguay, i. 23, 31, ii. <a href="#page93">93</a>, <a href="#page102">102</a>;</p> + <p class="i2">feral dogs of La Plata, i. 27;</p> + <p class="i2">on the aguara, i. 26;</p> + <p class="i2">cats of Paraguay, i. 46, ii. <a href="#page86">86</a>, <a href="#page151">151</a>;</p> + <p class="i2">dogs of Paraguay, ii. <a href="#page87">87</a>;</p> + <p class="i2">feral pigs of Buenos Ayres, i. 77;</p> + <p class="i2">on the refusal of wild animals to breed in captivity, ii. <a href="#page149">149</a>;</p> + <p class="i2">on <i>Dicotyles labiatus</i>, ii. <a href="#page150">150</a>;</p> + <p class="i2">sterility of plantigrade carnivora in captivity, ii. <a href="#page152">152</a>;</p> + <p class="i2">on <i>Cavia aperea</i>, ii. <a href="#page152">152</a>;</p> + <p class="i2">sterility of <i>Cebus azaræ</i> in captivity, ii. <a href="#page153">153</a>;</p> + <p class="i2">abortions produced by wild animals in captivity, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Reproduction</span>, sexual and asexual, contrasted, ii. <a href="#page361">361</a>;</p> + <p class="i2">unity of forms of, ii. <a href="#page383">383</a>;</p> + <p class="i2">antagonism of, to growth, ii. <a href="#page384">384</a>.</p> + <p><i>Reseda odorata</i>, ii. <a href="#page237">237</a>.</p> + <p><span class="sc">Retinitis</span>, pigmentary, in deaf-mutes, ii. <a href="#page328">328</a>.</p> + <p><span class="sc">Reversion</span>, ii. <a href="#page28">28</a>-<a href="#page29">29</a>, <a href="#page372">372</a>-<a href="#page373">373</a>, <a href="#page396">396</a>, <a href="#page398">398</a>-<a href="#page402">402</a>;</p> + <p class="i2">in pigeons, ii. <a href="#page29">29</a>;</p> + <p class="i2">in cattle, ii. <a href="#page29">29</a>-<a href="#page30">30</a>;</p> + <p class="i2">in sheep, ii. <a href="#page30">30</a>;</p> + <p class="i2">in fowls, ii. <a href="#page31">31</a>;</p> + <p class="i2">in the heartsease, <i>ibid.</i>;</p> + <p class="i2">in vegetables, <i>ibid.</i>;</p> + <p class="i2">in feral animals and plants, ii. <a href="#page32">32</a>-<a href="#page34">34</a>;</p> + <p class="i2">to characters derived from a previous cross in man, dogs, pigeons, pigs, and fowls, ii. <a href="#page34">34</a>-<a href="#page35">35</a>;</p> +<!-- Page 474 --><span class="pagenum"><a name="page474"></a>{474}</span> + <p class="i2">in hybrids, ii. <a href="#page36">36</a>;</p> + <p class="i2">by bud-propagation in plants, ii. <a href="#page36">36</a>-<a href="#page38">38</a>;</p> + <p class="i2">by age in fowls, cattle, &c., ii. <a href="#page38">38</a>-<a href="#page39">39</a>;</p> + <p class="i2">caused by crossing, ii. <a href="#page39">39</a>-<a href="#page51">51</a>;</p> + <p class="i2">explained by latent characters, ii. <a href="#page51">51</a>-<a href="#page56">56</a>;</p> + <p class="i2">producing monstrosities, ii. <a href="#page57">57</a>;</p> + <p class="i2">producing peloric flowers, ii. <a href="#page58">58</a>-<a href="#page60">60</a>;</p> + <p class="i2">of feral pigs to the wild type, i. 77-78;</p> + <p class="i2">of supposed feral rabbits to the wild type, i. 104, 111, 115;</p> + <p class="i2">of pigeons, in coloration, when crossed, i. 197-202;</p> + <p class="i2">in fowls, i. 239-246;</p> + <p class="i2">in the silkworm, i. 302;</p> + <p class="i2">in the pansy, i. 369;</p> + <p class="i2">in a pelargonium, i. 378;</p> + <p class="i2">in Chrysanthemums, i. 379;</p> + <p class="i2">of varieties of the China rose in St. Domingo, i. 380;</p> + <p class="i2">by buds in pinks and carnations, i. 381;</p> + <p class="i2">of laciniated varieties of trees to the normal form, i. 382;</p> + <p class="i2">in variegated leaves of plants, i. 383-384;</p> + <p class="i2">in tulips, i. 386;</p> + <p class="i2">of suckers of the seedless barberry to the common form, i. 384;</p> + <p class="i2">by buds in hybrids of <i>Tropæolum</i>, i. 392;</p> + <p class="i2">in plants, i. 409;</p> + <p class="i2">of crossed peloric snapdragons, ii. <a href="#page71">71</a>;</p> + <p class="i2">analogous variations due to, ii. <a href="#page349">349</a>-<a href="#page351">351</a>.</p> + <p><span class="sc">Reynier</span>, selection practised by the Celts, ii. <a href="#page202">202</a>-<a href="#page203">203</a>.</p> + <p><span class="sc">Rhinoceros</span>, breeding in captivity in India, ii. <a href="#page150">150</a>.</p> + <p><i>Rhododendron</i>, hybrid, ii. <a href="#page265">265</a>.</p> + <p><i>Rhododendron ciliatum</i>, ii. <a href="#page277">277</a>.</p> + <p><i>Rhododendron Dalhousiæ</i>, effect of pollen of <i>R. Nuttallii</i> upon, i. 400.</p> + <p><span class="sc">Rhubarb</span>, not medicinal when grown in England, ii. <a href="#page274">274</a>.</p> + <p><i>Ribes grossularia</i>, i. 354-356, 376.</p> + <p><i>Ribes rubrum</i>, i. 376.</p> + <p><span class="sc">Ribs</span>, number and characters of, in fowls, i. 267;</p> + <p class="i2">characters of, in ducks, i. 283-284.</p> + <p><span class="sc">Rice</span>, Imperial, of China, ii. <a href="#page205">205</a>;</p> + <p class="i2">Indian varieties of, ii. <a href="#page256">256</a>;</p> + <p class="i2">variety of, not requiring water, ii. <a href="#page305">305</a>.</p> + <p><span class="sc">Richardson</span>, H. D., on jaw-appendages in Irish pigs, i. 76;</p> + <p class="i2">management of pigs in China, i. 68;</p> + <p class="i2">occurrence of striped young in Westphalian pigs, i. 76;</p> + <p class="i2">on crossing pigs, ii. <a href="#page95">95</a>;</p> + <p class="i2">on interbreeding pigs, ii. <a href="#page122">122</a>;</p> + <p class="i2">on selection in pigs, ii. <a href="#page194">194</a>.</p> + <p><span class="sc">Richardson</span>, Sir John, observations on the resemblance between North American dogs and wolves, i. 21-22;</p> + <p class="i2">on the burrowing of wolves, i. 27;</p> + <p class="i2">on the broad feet of dogs, wolves, and foxes in North America, i. 40;</p> + <p class="i2">on North American horses scraping away the snow, i. 53.</p> + <p><i>Ricinus</i>, annual in England, ii. <a href="#page305">305</a>.</p> + <p><span class="sc">Riedel</span>, on the "Bagadotte" pigeon, i. 141;</p> + <p class="i2">on the Jacobin pigeon, i. 154;</p> + <p class="i2">fertility of hybrid pigeons, i. 192.</p> + <p><span class="sc">Rinderpest</span>, ii. <a href="#page378">378</a>.</p> + <p><span class="sc">Risso</span>, on varieties of the orange, i. 336, ii. <a href="#page308">308</a>, <a href="#page331">331</a>.</p> + <p><span class="sc">Rivers</span>, Lord, on the selection of greyhounds, ii. <a href="#page235">235</a>.</p> + <p><span class="sc">Rivers</span>, Mr., persistency of characters in seedling potatoes, i. 331;</p> + <p class="i2">on the peach, i. 338, 339;</p> + <p class="i2">persistency of races in the peach and nectarine, i. 339, 340;</p> + <p class="i2">connexion between the peach and the nectarine, i. 340;</p> + <p class="i2">persistency of character in seedling apricots, i. 344;</p> + <p class="i2">origin of the plum, i. 345;</p> + <p class="i2">seedling varieties of the plum, i. 346;</p> + <p class="i2">persistency of character in seedling plums, i. 347;</p> + <p class="i2">bud-variation in the plum, i. 375;</p> + <p class="i2">plum, attacked by bullfinches, ii. <a href="#page232">232</a>;</p> + <p class="i2">seedling apples with surface-roots, i. 349;</p> + <p class="i2">variety of the apple found in a wood, ii. <a href="#page260">260</a>;</p> + <p class="i2">on roses, i. 366-367;</p> + <p class="i2">bud-variation in roses, i. 379-381;</p> + <p class="i2">production of Provence roses from seeds of the moss-rose, i. 380;</p> + <p class="i2">effect produced by grafting on the stock in jessamine, i. 394;</p> + <p class="i2">in the ash, i. 394;</p> + <p class="i2">on grafted hazels, i. 395;</p> + <p class="i2">hybridisation of a weeping thorn, ii. <a href="#page18">18</a>;</p> + <p class="i2">experiments with the seed of the weeping elm and ash, ii. <a href="#page19">19</a>;</p> + <p class="i2">variety of the cherry with curled petals, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Rivière</span>, reproduction of <i>Oncidium Cavendishianum</i>, ii. <a href="#page133">133</a>.</p> + <p><span class="sc">Roberts</span>, Mr., on inheritance in the horse, ii. <a href="#page10">10</a>.</p> + <p><span class="sc">Robertson</span>, Mr., on glandular-leaved peaches, i. 343.</p> + <p><span class="sc">Robinet</span>, on the silkworm, i. 301-304, ii. <a href="#page197">197</a>.</p> + <p><i>Robinia</i>, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Robson</span>, Mr., deficiencies of half-bred horses, ii. <a href="#page11">11</a>.</p> + <p><span class="sc">Robson</span>, Mr., on the advantage of change of soil to plants, ii. <a href="#page146">146</a>-<a href="#page147">147</a>;</p> + <p class="i2">on the growth of the verbena, ii. <a href="#page273">273</a>;</p> + <p class="i2">on broccoli, ii. <a href="#page310">310</a>.</p> + <p><span class="sc">Rock</span> pigeon, measurements of the, i. 134;</p> + <p class="i2">figured, i. 135.</p> + <p><span class="sc">Rodents</span>, sterility of, in captivity, ii. <a href="#page152">152</a>.</p> + <p><i>Rodriguezia</i>, ii. <a href="#page134">134</a>, <a href="#page135">135</a>.</p> + <p><span class="sc">Rodwell</span>, J., poisoning of horses by mildewed tares, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Rohilcund</span>, feral humped cattle in, i. 79.</p> + <p><span class="sc">Rolle</span>, F., on the history of the peach, ii. <a href="#page308">308</a>.</p> + <p><span class="sc">Roller-pigeons</span>, Dutch, i. 151.</p> + <p><span class="sc">Rolleston</span>, Prof., incisor teeth affected in form in cases of pulmonary tubercle, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Romans</span>, estimation of pigeons by, i. 205;</p> + <p class="i2">breeds of fowls possessed by, i. 231, 247.</p> +<!-- Page 475 --><span class="pagenum"><a name="page475"></a>{475}</span> + <p><span class="sc">Rooks</span>, pied, ii. <a href="#page77">77</a>.</p> + <p><i>Rosa</i>, cultivated species of, i. 366.</p> + <p><i>Rosa devoniensis</i>, graft-hybrid produced by, on the white Banksian rose, i. 396.</p> + <p><i>Rosa indica</i> and <i>centifolia</i>, fertile hybrids of, i. 366.</p> + <p><i>Rosa spinosissima</i>, history of the culture of, i. 367.</p> + <p><span class="sc">Rosellini</span>, on Egyptian dogs, i. 17.</p> + <p><span class="sc">Roses</span>, i. 366-367;</p> + <p class="i2">origin of, i. 364;</p> + <p class="i2">bud-variation in, i. 379-381;</p> + <p class="i2">Scotch, doubled by selection, ii. <a href="#page200">200</a>;</p> + <p class="i2">continuous variation of, ii. <a href="#page241">241</a>;</p> + <p class="i2">effect of seasonal conditions on, ii. <a href="#page273">273</a>;</p> + <p class="i2">noisette, ii. <a href="#page308">308</a>;</p> + <p class="i2">galls of, ii. <a href="#page284">284</a>.</p> + <p><span class="sc">Rouennais</span> rabbit, i. 105.</p> + <p><span class="sc">Roulin</span>, on the dogs of Juan Fernandez, i. 27;</p> + <p class="i2">on South American cats, i. 46;</p> + <p class="i2">striped young pigs, i. 77;</p> + <p class="i2">feral pigs in South America, i. 78, ii. <a href="#page33">33</a>;</p> + <p class="i2">on Columbian cattle, i. 88, ii. <a href="#page205">205</a>, <a href="#page226">226</a>;</p> + <p class="i2">effects of heat on the hides of cattle in South America, i. 92;</p> + <p class="i2">fleece of sheep in the hot valleys of the Cordilleras, i. 98;</p> + <p class="i2">diminished fertility of these sheep, ii. <a href="#page161">161</a>;</p> + <p class="i2">on black-boned South American fowls, i. 258;</p> + <p class="i2">variation of the guinea-fowl in tropical America, i. 294;</p> + <p class="i2">frequency of striped legs in mules, ii. <a href="#page42">42</a>;</p> + <p class="i2">geese in Bogota, ii. <a href="#page161">161</a>;</p> + <p class="i2">sterility of fowls introduced into Bolivia, ii. <a href="#page162">162</a>.</p> + <p><span class="sc">Roy</span>, M., on a variety of <i>Magnolia grandiflora</i>, ii. <a href="#page308">308</a>.</p> + <p><span class="sc">Royle</span>, Dr., Indian varieties of the mulberry, i. 334;</p> + <p class="i2">on <i>Agave vivipara</i>, ii. <a href="#page169">169</a>;</p> + <p class="i2">variety of rice not requiring irrigation, ii. <a href="#page305">305</a>;</p> + <p class="i2">sheep from the Cape in India, ii. <a href="#page306">306</a>.</p> + <p><i>Rubus</i>, pollen of, ii. <a href="#page268">268</a>.</p> + <p><span class="sc">Rudimentary</span> organs, i. 12, ii. <a href="#page315">315</a>-<a href="#page318">318</a>.</p> + <p><span class="sc">Rufz</span> de Lavison, extinction of breeds of dogs in France, ii. <a href="#page425">425</a>.</p> + <p><span class="sc">Ruminants</span>, general fertility of, in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Rumpless</span> fowls, i. 230.</p> + <p><span class="sc">Runts</span>, i. 142-144;</p> + <p class="i2">history of, i. 210;</p> + <p class="i2">lower jaws and skull figured, i. 164-165.</p> + <p><span class="sc">Russian</span> or Himalayan rabbit, i. 108.</p> + <p><span class="sc">Rütimeyer</span>, Prof., dogs of the Neolithic period, i. 19;</p> + <p class="i2">horses of Swiss lake-dwellings, i. 49;</p> + <p class="i2">diversity of early domesticated horses i. 51;</p> + <p class="i2">pigs of the Swiss lake-dwellings, i. 65, 67-68;</p> + <p class="i2">on humped cattle, i. 80;</p> + <p class="i2">parentage of European breeds of cattle, i. 80, 81, ii. <a href="#page427">427</a>;</p> + <p class="i2">on "Niata" cattle, i. 89;</p> + <p class="i2">sheep of the Swiss lake-dwellings, i. 94, ii. <a href="#page427">427</a>;</p> + <p class="i2">goats of the Swiss lake-dwellings, i. 101;</p> + <p class="i2">absence of fowls in the Swiss lake-dwellings, i. 246;</p> + <p class="i2">on crossing cattle, ii. <a href="#page98">98</a>;</p> + <p class="i2">differences in the bones of wild and domesticated animals, ii. <a href="#page279">279</a>;</p> + <p class="i2">decrease in size of wild European animals, ii. <a href="#page427">427</a>.</p> + <p><span class="sc">Rye</span>, wild, De Candolle's observations on, i. 313;</p> + <p class="i2">found in the Swiss lake-dwellings, i. 319;</p> + <p class="i2">common, preferred by hares and rabbits, ii. <a href="#page232">232</a>;</p> + <p class="i2">less variable than other cultivated plants, ii. <a href="#page254">254</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Sabine</span>, Mr., on the cultivation of <i>Rosa spinosissima</i>, i. 367;</p> + <p class="i2">on the cultivation of the dahlia, i. 369-370, ii. <a href="#page261">261</a>;</p> + <p class="i2">effect of foreign pollen on the seed-vessel in <i>Amaryllis vittata</i>, i. 400.</p> + <p><span class="sc">St. Ange</span>, influence of the pelvis on the shape of the kidneys in birds, ii. <a href="#page344">344</a>.</p> + <p><span class="sc">St. Domingo</span>, wild dogs of, i. 28;</p> + <p class="i2">bud-variation of dahlias in, i. 385.</p> + <p><span class="sc">St. Hilaire</span>, Aug., milk furnished by cows in South America, ii. <a href="#page300">300</a>;</p> + <p class="i2">husked form of maize, i. 320.</p> + <p><span class="sc">St. John</span>, C., feral cats in Scotland, i. 47;</p> + <p class="i2">taming of wild ducks, i. 278.</p> + <p><span class="sc">St. Valery</span> apple, singular structure of the, i. 350;</p> + <p class="i2">artificial fecundation of the, i. 401.</p> + <p><span class="sc">St. Vitus'</span> Dance, period of appearance of, ii. <a href="#page77">77</a>.</p> + <p><span class="sc">Sageret</span>, origin and varieties of the cherry, i. 347-348;</p> + <p class="i2">origin of varieties of the apple, i. 350;</p> + <p class="i2">incapacity of the cucumber for crossing with other species, i. 359;</p> + <p class="i2">varieties of the melon, i. 360;</p> + <p class="i2">supposed twin-mongrel melon, i. 391;</p> + <p class="i2">crossing melons, ii. <a href="#page108">108</a>, <a href="#page129">129</a>;</p> + <p class="i2">on gourds, ii. <a href="#page108">108</a>;</p> + <p class="i2">effects of selection in enlarging fruit, ii. <a href="#page217">217</a>;</p> + <p class="i2">on the tendency to depart from type, ii. <a href="#page241">241</a>;</p> + <p class="i2">variation of plants in particular soils, ii. <a href="#page278">278</a>.</p> + <p><span class="sc">Salamander</span>, experiments on the, ii. <a href="#page293">293</a>, <a href="#page341">341</a>;</p> + <p class="i2">regeneration of lost parts in the, ii. <a href="#page15">15</a>, <a href="#page376">376</a>, <a href="#page385">385</a>.</p> + <p><i>Salamandra cristata</i>, polydactylism in, ii. <a href="#page14">14</a>.</p> + <p><span class="sc">Salisbury</span>, Mr., on the production of nectarines by peach-trees, i. 341;</p> + <p class="i2">on the dahlia, i. 369-370.</p> + <p><i>Salix</i>, intercrossing of species of, i. 336.</p> + <p><i>Salix humilis</i>, galls of, ii. <a href="#page282">282</a>, <a href="#page283">283</a>.</p> + <p><span class="sc">Sallé</span>, feral guinea-fowl in St. Domingo, i. 294.</p> + <p><span class="sc">Salmon</span>, early breeding of male, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Salter</span>, Mr., on bud-variation in pelargoniums, i. 378;</p> + <p class="i2">in the Chrysanthemum, i. 379;</p> + <p class="i2">transmission of variegated leaves by seed, i. 383;</p> + <p class="i2">bud-variation by suckers in <i>Phlox</i>, i. 384;</p> + <p class="i2">application of selection to bud-varieties of plants, i. 411;</p> + <p class="i2">accumulative effect of changed conditions of life, ii. <a href="#page262">262</a>;</p> + <p class="i2">on the variegation of strawberry leaves, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Salter</span>, S. J., hybrids of <i>Gallus Sonneratii</i> and the common fowl, i. 234, ii. <a href="#page45">45</a>;</p> +<!-- Page 476 --><span class="pagenum"><a name="page476"></a>{476}</span> + <p class="i2">crossing of races or species of rats, ii. <a href="#page87">87</a>-<a href="#page88">88</a>.</p> + <p><span class="sc">Samesreuther</span>, on inheritance in cattle, ii. <a href="#page10">10</a>.</p> + <p><span class="sc">Sandford</span>. <i>See</i> <span class="sc">Dawkins</span>.</p> + <p><span class="sc">Sap</span>, ascent of the, ii. <a href="#page296">296</a>.</p> + <p><i>Saponaria calabrica</i>, ii. <a href="#page20">20</a>.</p> + <p><span class="sc">Sardinia</span>, ponies of, i. 52.</p> + <p><span class="sc">Sars</span>, on the development of the hydroida, ii. <a href="#page368">368</a>.</p> + <p><span class="sc">Satiation</span> of the stigma, i. 402-403.</p> + <p><i>Saturnia pyri</i>, sterility of, in confinement, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Saul</span>, on the management of prize gooseberries, i. 356.</p> + <p><span class="sc">Sauvigny</span>, varieties of the goldfish, i. 296.</p> + <p><span class="sc">Savages</span>, their indiscriminate use of plants as food, i. 307-310;</p> + <p class="i2">fondness of, for taming animals, ii. <a href="#page160">160</a>.</p> + <p><span class="sc">Savi</span>, effect of foreign pollen on maize, i. 400.</p> + <p><i>Saxifraga geum</i>, ii. <a href="#page166">166</a>.</p> + <p><span class="sc">Sayzid Mohammed Musari</span>, on carrier-pigeons, i. 141;</p> + <p class="i2">on a pigeon which utters the sound "Yahu," i. 155.</p> + <p><span class="sc">Scanderoons</span> (pigeons), i. 142, 143.</p> + <p><span class="sc">Scania</span>, remains of <i>Bos frontosus</i> found in, i. 81.</p> + <p><span class="sc">Scapula</span>, characters of, in rabbits, i. 123;</p> + <p class="i2">in fowls, i. 268;</p> + <p class="i2">in pigeons, i. 167;</p> + <p class="i2">alteration of, by disuse, in pigeons, i. 175.</p> + <p><span class="sc">Scarlet</span> fever, ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Schaaffhausen</span>, on the horses represented in Greek statues, ii. <a href="#page213">213</a>.</p> + <p><span class="sc">Schacht</span>, H., on adventitious buds, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Schleiden</span>, excess of nourishment a cause of variability, ii. <a href="#page257">257</a>.</p> + <p><span class="sc">Schomburgk</span>, Sir R., on the dogs of the Indians of Guiana, i. 19, 23, ii. <a href="#page206">206</a>;</p> + <p class="i2">on the musk duck, i. 182;</p> + <p class="i2">bud-variation in the Banana, i. 377;</p> + <p class="i2">reversion of varieties of the China rose in St. Domingo, i. 380;</p> + <p class="i2">sterility of tame parrots in Guiana, ii. <a href="#page155">155</a>;</p> + <p class="i2">on <i>Dendrocygna viduata</i>, ii. <a href="#page157">157</a>;</p> + <p class="i2">selection of fowls in Guiana, ii. <a href="#page209">209</a>.</p> + <p><span class="sc">Schreibers</span>, on <i>Proteus</i>, ii. <a href="#page297">297</a>.</p> + <p><i>Sciuropterus volucella</i>, ii. <a href="#page152">152</a>.</p> + <p><i>Sciurus palmarum</i> and <i>cinerea</i>, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Sclater</span>, P. L., on <i>Asinus tæniopus</i>, i. 62, ii. <a href="#page41">41</a>;</p> + <p class="i2">on <i>Asinus indicus</i>, ii. <a href="#page42">42</a>;</p> + <p class="i2">striped character of young wild pigs, i. 70;</p> + <p class="i2">osteology of <i>Gallinula nesiotis</i>, i. 287;</p> + <p class="i2">on the black-shouldered peacock, i. 290;</p> + <p class="i2">on the breeding of birds in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Schmerling</span>, Dr., varieties of the dog, found in a cave, i. 19.</p> + <p><span class="sc">Scotch</span> fir, local variation of, i. 363.</p> + <p><span class="sc">Scotch</span> kail and cabbage, cross between, ii. <a href="#page98">98</a>.</p> + <p><span class="sc">Scott</span>, John, irregularities in the sex of the flowers of Maize, i. 321;</p> + <p class="i2">bud-variation in <i>Imatophyllum miniatum</i>, i. 385;</p> + <p class="i2">crossing of species of <i>Verbascum</i>, ii. <a href="#page106">106</a>-<a href="#page107">107</a>;</p> + <p class="i2">experiments on crossing <i>Primulæ</i>, ii. <a href="#page109">109</a>;</p> + <p class="i2">reproduction of orchids, ii. <a href="#page133">133</a>;</p> + <p class="i2">fertility of <i>Oncidium divaricatum</i>, ii. <a href="#page164">164</a>;</p> + <p class="i2">acclimatisation of the sweet pea in India, ii. <a href="#page311">311</a>;</p> + <p class="i2">number of seeds in <i>Acropera</i> and <i>Gongora</i>, ii. <a href="#page379">379</a>.</p> + <p><span class="sc">Scott</span>, Sir W., former range of wild cattle in Britain, i. 85.</p> + <p><span class="sc">Scrope</span>, on the Scotch deerhound, ii. <a href="#page73">73</a>, <a href="#page121">121</a>.</p> + <p><span class="sc">Sebright</span>, Sir John, effects of close interbreeding in dogs, ii. <a href="#page121">121</a>;</p> + <p class="i2">care taken by, in selection of fowls, ii. <a href="#page197">197</a>.</p> + <p><i>Secale cereale</i>, ii. <a href="#page254">254</a>.</p> + <p><span class="sc">Sedgwick, W.</span>, effects of crossing on the female, i. 404;</p> + <p class="i2">on the "Porcupine-man," ii. <a href="#page4">4</a>;</p> + <p class="i2">on hereditary diseases, ii. <a href="#page7">7</a>;</p> + <p class="i2">hereditary affections of the eye, ii. <a href="#page9">9</a>, <a href="#page78">78</a>-<a href="#page79">79</a>;</p> + <p class="i2">inheritance of polydactylism and anomalies of the extremities, ii. <a href="#page13">13</a>-<a href="#page14">14</a>;</p> + <p class="i2">morbid uniformity in the same family, ii. <a href="#page17">17</a>;</p> + <p class="i2">on deaf-mutes, ii. <a href="#page22">22</a>;</p> + <p class="i2">inheritance of injury to the eye, ii. <a href="#page24">24</a>;</p> + <p class="i2">atavism in diseases and anomalies of structure, ii. <a href="#page34">34</a>;</p> + <p class="i2">non-reversion to night-blindness, ii. <a href="#page36">36</a>;</p> + <p class="i2">sexual limitation of the transmission of peculiarities in man, ii. <a href="#page72">72</a>-<a href="#page73">73</a>;</p> + <p class="i2">on the effects of hard-drinking, ii. <a href="#page289">289</a>;</p> + <p class="i2">inherited baldness with deficiency of teeth, ii. <a href="#page326">326</a>-<a href="#page327">327</a>;</p> + <p class="i2">occurrence of a molar tooth in place of an incisor, ii. <a href="#page391">391</a>;</p> + <p class="i2">diseases occurring in alternate generations, ii. <a href="#page401">401</a>.</p> + <p><span class="sc">Sedillot</span>, on the removal of portions of bone, ii. <a href="#page296">296</a>.</p> + <p><span class="sc">Seeds</span>, early selection of, ii. <a href="#page204">204</a>;</p> + <p class="i2">rudimentary, in grapes, ii. <a href="#page316">316</a>;</p> + <p class="i2">relative position of, in the capsule, ii. <a href="#page345">345</a>.</p> + <p><span class="sc">Seeds</span> and buds, close analogies of, i. 411.</p> + <p><span class="sc">Seemann, B.</span>, crossing of the wolf and Esquimaux dog, i. 22.</p> + <p><span class="sc">Selby, P. J.</span>, on the bud-destroying habits of the bullfinch, ii. <a href="#page232">232</a>.</p> + <p><span class="sc">Selection</span>, ii. <a href="#page192">192</a>-<a href="#page249">249</a>;</p> + <p class="i2">methodical, i. 214, ii. <a href="#page194">194</a>-<a href="#page210">210</a>;</p> + <p class="i2">by the ancients and semi-civilised people, ii. <a href="#page201">201</a>-<a href="#page210">210</a>;</p> + <p class="i2">of trifling characters, ii. <a href="#page208">208</a>-<a href="#page210">210</a>;</p> + <p class="i2">unconscious, i. 214, 217, ii. <a href="#page174">174</a>, <a href="#page210">210</a>-<a href="#page217">217</a>;</p> + <p class="i2">effects of, shown by differences in most valued parts, ii. <a href="#page217">217</a>-<a href="#page220">220</a>;</p> + <p class="i2">produced by accumulation of variability, ii. <a href="#page220">220</a>-<a href="#page223">223</a>;</p> + <p class="i2">natural, as affecting domestic productions, ii. <a href="#page185">185</a>-<a href="#page189">189</a>, <a href="#page224">224</a>-<a href="#page233">233</a>;</p> + <p class="i2">as the origin of species, genera and other groups, ii. <a href="#page429">429</a>-<a href="#page432">432</a>;</p> + <p class="i2">circumstances favourable to, ii. <a href="#page233">233</a>-<a href="#page239">239</a>;</p> + <p class="i2">tendency of towards extremes, ii. <a href="#page239">239</a>-<a href="#page242">242</a>;</p> +<!-- Page 477 --><span class="pagenum"><a name="page477"></a>{477}</span> + <p class="i2">possible limit of, ii. <a href="#page242">242</a>;</p> + <p class="i2">influence of time on, ii. <a href="#page243">243</a>-<a href="#page244">244</a>;</p> + <p class="i2">summary of subject, ii. <a href="#page246">246</a>-<a href="#page249">249</a>;</p> + <p class="i2">effects of, in modifying breeds of cattle, i. 92, 93;</p> + <p class="i2">in preserving the purity of breeds of sheep, i. 99-100;</p> + <p class="i2">in producing varieties of pigeons, i. 213-218;</p> + <p class="i2">in breeding fowls, i. 232-233;</p> + <p class="i2">in the goose, i. 289;</p> + <p class="i2">in the canary, i. 295;</p> + <p class="i2">in the goldfish, i. 296;</p> + <p class="i2">in the silkworm, i. 300-301;</p> + <p class="i2">contrasted in cabbages and cereals, i. 323;</p> + <p class="i2">in the white mulberry, i. 334;</p> + <p class="i2">on gooseberries, i. 356;</p> + <p class="i2">applied to wheat, i. 317-318;</p> + <p class="i2">exemplified in carrots, &c., i. 326;</p> + <p class="i2">in the potato, i. 331;</p> + <p class="i2">in the melon, i. 360;</p> + <p class="i2">in flowering plants, i. 365;</p> + <p class="i2">in the hyacinth, i. 371;</p> + <p class="i2">applied to bud-varieties of plants, i. 411;</p> + <p class="i2">illustrations of, ii. <a href="#page421">421</a>-<a href="#page428">428</a>.</p> + <p><span class="sc">Selection</span>, sexual, ii. <a href="#page75">75</a>.</p> + <p><span class="sc">Self-impotence</span> in plants, ii. <a href="#page131">131</a>-<a href="#page140">140</a>;</p> + <p class="i2">in individual plants, ii. <a href="#page136">136</a>-<a href="#page138">138</a>;</p> + <p class="i2">of hybrids, ii. <a href="#page174">174</a>.</p> + <p><span class="sc">Selwyn</span>, Mr., on the Dingo, i. 26.</p> + <p><span class="sc">Selys-Longchamps</span>, on hybrid ducks, i. 190, ii. <a href="#page46">46</a>, <a href="#page157">157</a>;</p> + <p class="i2">hybrid of the hook-billed duck and Egyptian goose, i. 282.</p> + <p><span class="sc">Seringe</span>, on the St. Valery apple, i. 350.</p> + <p><span class="sc">Serpent</span> Melon, i. 360.</p> + <p><span class="sc">Serres</span>, Olivier de, wild poultry in Guiana, i. 237.</p> + <p><span class="sc">Sesamum</span>, white-seeded, antiquity of the, ii. <a href="#page429">429</a>.</p> + <p><i>Setaria</i>, found in the Swiss lake-dwellings, i. 317.</p> + <p><span class="sc">Setters</span>, degeneration of, in India, i. 38;</p> + <p class="i2">Youatt's remarks on, i. 41.</p> + <p><span class="sc">Sex</span>, secondary characters of, latent, ii. <a href="#page51">51</a>-<a href="#page52">52</a>;</p> + <p class="i2">of parents, influence of, on hybrids, ii. <a href="#page267">267</a>.</p> + <p><span class="sc">Sexual</span> characters, sometimes lost in domestication, ii. <a href="#page74">74</a>.</p> + <p><span class="sc">Sexual</span> limitation of characters, ii. <a href="#page71">71</a>-<a href="#page75">75</a>.</p> + <p><span class="sc">Sexual</span> peculiarities, induced by domestication in sheep, i. 95;</p> + <p class="i2">in fowls, i. 251-257;</p> + <p class="i2">transfer of, i. 255-257.</p> + <p><span class="sc">Sexual</span> variability in pigeons, i. 161-162.</p> + <p><span class="sc">Sexual</span> selection, ii. <a href="#page75">75</a>.</p> + <p><span class="sc">Shaddock</span>, i. 335.</p> + <p><span class="sc">Shailer</span>, Mr., on the moss-rose, i. 379-380.</p> + <p><span class="sc">Shanghai</span> fowls, i. 227.</p> + <p><span class="sc">Shanghai</span> sheep, their fecundity, i. 97.</p> + <p><span class="sc">Shan</span> ponies, striped, i. 58.</p> + <p><span class="sc">Sheep</span>, disputed origin of, i. 94;</p> + <p class="i2">early domestication of, i. 94;</p> + <p class="i2">large-tailed, i. 94, 95, 98, ii. <a href="#page279">279</a>;</p> + <p class="i2">variations in horns, mammæ and other characters of, i. 95;</p> + <p class="i2">sexual characters of, induced by domestication, i. 95, 96;</p> + <p class="i2">adaptation of, to climate and pasture, i. 96, 97;</p> + <p class="i2">periods of gestation of, i. 97;</p> + <p class="i2">effect of heat on the fleece of, i. 98-99, ii. <a href="#page278">278</a>;</p> + <p class="i2">effect of selection on, i. 99-101;</p> + <p class="i2">"ancon" or "otter" breeds of, i. 17, 92, 100;</p> + <p class="i2">"Mauchamp-merino," i. 100-101;</p> + <p class="i2">cross of German and merino, ii. <a href="#page85">85</a>-<a href="#page89">89</a>;</p> + <p class="i2">black, of the Tarentino, ii. <a href="#page227">227</a>;</p> + <p class="i2">Karakool, ii. <a href="#page278">278</a>;</p> + <p class="i2">Jaffna, with callosities on the knees, ii. <a href="#page302">302</a>;</p> + <p class="i2">Chinese, ii. <a href="#page315">315</a>;</p> + <p class="i2">Danish, of the bronze period, ii. <a href="#page427">427</a>;</p> + <p class="i2">polydactylism in, ii. <a href="#page14">14</a>;</p> + <p class="i2">occasional production of horns in hornless breeds of, ii. <a href="#page30">30</a>;</p> + <p class="i2">reversion of colour in, ii. <a href="#page30">30</a>;</p> + <p class="i2">influence of male, on offspring, ii. <a href="#page68">68</a>;</p> + <p class="i2">sexual differences in, ii. <a href="#page73">73</a>;</p> + <p class="i2">influence of crossing or segregation on, ii. <a href="#page86">86</a>, <a href="#page95">95</a>-<a href="#page96">96</a>, <a href="#page102">102</a>-<a href="#page103">103</a>;</p> + <p class="i2">interbreeding of, ii. <a href="#page119">119</a>-<a href="#page120">120</a>;</p> + <p class="i2">effect of nourishment on the fertility of, ii. <a href="#page111">111</a>-<a href="#page112">112</a>;</p> + <p class="i2">diminished fertility of, under certain conditions, ii. <a href="#page161">161</a>;</p> + <p class="i2">unconscious selection of, ii. <a href="#page213">213</a>;</p> + <p class="i2">natural selection in breeds of, ii. <a href="#page224">224</a>, <a href="#page225">225</a>, <a href="#page227">227</a>;</p> + <p class="i2">reduction of bones in, ii. <a href="#page242">242</a>;</p> + <p class="i2">individual differences of, ii. <a href="#page251">251</a>;</p> + <p class="i2">local changes in the fleece of, in England, ii. <a href="#page278">278</a>;</p> + <p class="i2">partial degeneration of, in Australia, ii. <a href="#page278">278</a>;</p> + <p class="i2">with numerous horns, ii. <a href="#page291">291</a>;</p> + <p class="i2">correlation of horns and fleece in, ii. <a href="#page326">326</a>;</p> + <p class="i2">feeding on flesh, ii. <a href="#page303">303</a>;</p> + <p class="i2">acclimatisation of, ii. <a href="#page305">305</a>-<a href="#page306">306</a>;</p> + <p class="i2">mountain, resistance of, to severe weather, ii. <a href="#page312">312</a>;</p> + <p class="i2">white, poisoned by <i>Hypericum crispum</i>, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Sheep</span> dogs resembling wolves, i. 24.</p> + <p><span class="sc">Shells</span>, sinistral and dextral, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Sheriff</span>, Mr. new varieties of wheat, i. 315, 317;</p> + <p class="i2">on crossing wheat, ii. <a href="#page104">104</a>-<a href="#page105">105</a>;</p> + <p class="i2">continuous variation of wheat, ii. <a href="#page241">241</a>.</p> + <p><span class="sc">Siam</span>, cats of, i. 47; horses of, i. 53.</p> + <p><span class="sc">Shirley</span>, E. P., on the fallow-deer, ii. <a href="#page103">103</a>, <a href="#page120">120</a>.</p> + <p><span class="sc">Short</span>, D., hybrids of the domestic cat and <i>Felis ornata</i>, i, 45.</p> + <p><span class="sc">Siberia</span>, northern range of wild horses in, i. 52.</p> + <p><span class="sc">Sichel</span>, J., on the deafness of white cats with blue eyes, ii. <a href="#page329">329</a>.</p> + <p><span class="sc">Sidney</span>, S., on the pedigrees of pigs, ii. <a href="#page3">3</a>;</p> + <p class="i2">on cross-reversion in pigs, ii. <a href="#page35">35</a>;</p> + <p class="i2">period of gestation in the pig, i. 74;</p> + <p class="i2">production of breeds of pigs by intercrossing, i. 78, 95;</p> + <p class="i2">fertility of the pig, ii. <a href="#page112">112</a>;</p> + <p class="i2">effects of interbreeding on pigs, ii. <a href="#page121">121</a>-<a href="#page122">122</a>;</p> + <p class="i2">on the colours of pigs, ii. <a href="#page210">210</a>, <a href="#page229">229</a>.</p> + <p><span class="sc">Siebold</span>, on the sweet potato, ii. <a href="#page309">309</a>.</p> + <p><span class="sc">Siebold</span>, von Carl, on parthenogenesis, ii. <a href="#page364">364</a>.</p> + <p><i>Silene</i>, contabescence in, ii. <a href="#page166">166</a>.</p> + <p><span class="sc">Silk-fowls</span>, i. 230, ii. <a href="#page67">67</a>, <a href="#page69">69</a>.</p> +<!-- Page 478 --><span class="pagenum"><a name="page478"></a>{478}</span> + <p><span class="sc">Silk-moth</span>, Arrindy, ii. <a href="#page306">306</a>, <a href="#page312">312</a>;</p> + <p class="i2">Tarroo, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Silk-moths</span>, i. 300-304;</p> + <p class="i2">domesticated species of, i. 300;</p> + <p class="i2">history of, <i>ibid.</i>;</p> + <p class="i2">causes of modification in, i. 300-301;</p> + <p class="i2">differences presented by, i. 301-304;</p> + <p class="i2">crossing of, ii. <a href="#page98">98</a>;</p> + <p class="i2">disease in, ii. <a href="#page228">228</a>;</p> + <p class="i2">effects of disuse of parts in, ii. <a href="#page298">298</a>;</p> + <p class="i2">selection practised with, ii. <a href="#page197">197</a>, <a href="#page199">199</a>;</p> + <p class="i2">variation of, ii. <a href="#page236">236</a>;</p> + <p class="i2">parthenogenesis in, ii. <a href="#page364">364</a>.</p> + <p><span class="sc">Silkworms</span>, variations of, i. 301-302;</p> + <p class="i2">yielding white cocoons, less liable to disease, ii. <a href="#page336">336</a>.</p> + <p><span class="sc">Silver-Grey</span> rabbit, i. 108, 111, 120.</p> + <p><span class="sc">Simonds</span>, J. B., period of maturity in various breeds of cattle, i. 87;</p> + <p class="i2">differences in the periods of dentition in sheep, i. 96;</p> + <p class="i2">on the teeth in cattle, sheep, &c., ii. <a href="#page322">322</a>;</p> + <p class="i2">on the breeding of superior rams, ii. <a href="#page196">196</a>.</p> + <p><span class="sc">Simon</span>, on the raising of eggs of the silk-moth in China, ii. <a href="#page197">197</a>.</p> + <p><span class="sc">Simpson</span>, Sir J., regenerative power of the human embryo, ii. <a href="#page15">15</a>.</p> + <p><i>Siredon</i>, breeding in the branchiferous stage, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Siskin</span>, breeding in captivity, ii. <a href="#page154">154</a>.</p> + <p><i>Sivatherium</i>, resemblance of the, to Niata cattle, i. 89.</p> + <p><span class="sc">Size</span>, difference of, an obstacle to crossing, ii. <a href="#page101">101</a>.</p> + <p><span class="sc">Skin</span>, and its appendages, homologous, ii. <a href="#page325">325</a>;</p> + <p class="i2">hereditary affections of the, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">Skirving</span>, R. S., on pigeons settling on trees in Egypt, i. 181.</p> + <p><span class="sc">Skull</span>, characters of the, in breeds of dogs, i. 34;</p> + <p class="i2">in breeds of pigs, i. 71;</p> + <p class="i2">in rabbits, i. 116-120, 127;</p> + <p class="i2">in breeds of pigeons, i. 163-165;</p> + <p class="i2">in breeds of fowls, i. 260-266;</p> + <p class="i2">in ducks, i. 282-283.</p> + <p><span class="sc">Skull</span> and horns, correlation of the, ii. <a href="#page333">333</a>.</p> + <p><span class="sc">Skylark</span>, ii. <a href="#page154">154</a>.</p> + <p><span class="sc">Sleeman</span>, on the Cheetah, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Sloe</span>, i. 345.</p> + <p><span class="sc">Small-pox</span>, ii. <a href="#page378">378</a>.</p> + <p><span class="sc">Smiter</span> (pigeon), i. 156.</p> + <p><span class="sc">Smith</span>, Sir A., on Caffrarian cattle, i. 88;</p> + <p class="i2">on the use of numerous plants as food in South Africa, i. 307.</p> + <p><span class="sc">Smith</span>, Colonel Hamilton, on the odour of the jackal, i. 30;</p> + <p class="i2">on the origin of the dog, i. 16;</p> + <p class="i2">wild dogs in St. Domingo, i. 28;</p> + <p class="i2">on the Thibet mastiff and the alco, i. 28-29;</p> + <p class="i2">development of the fifth toe in the hind feet of mastiffs, i. 35;</p> + <p class="i2">differences in the skull of dogs, i. 34;</p> + <p class="i2">history of the pointer, i. 42;</p> + <p class="i2">on the ears of the dog, ii. <a href="#page301">301</a>;</p> + <p class="i2">on the breeds of horses, i. 49;</p> + <p class="i2">origin of the horse, i. 51;</p> + <p class="i2">dappling of horses, i. 55;</p> + <p class="i2">striped horses in Spain, i. 58;</p> + <p class="i2">original colour of the horse, i. 60;</p> + <p class="i2">on horses scraping away snow, i. 52;</p> + <p class="i2">on <i>Asinus hemionus</i>, ii. <a href="#page43">43</a>;</p> + <p class="i2">feral pigs of Jamaica, i. 77-78.</p> + <p><span class="sc">Smith</span>, Sir J. E., production of nectarines and peaches by the same tree, i. 340;</p> + <p class="i2">on <i>Viola amœna</i>, i. 368;</p> + <p class="i2">sterility of <i>Vinca minor</i> in England, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Smith</span>, J., development of the ovary in <i>Bonatea speciosa</i>, by irritation of the stigma, i. 403.</p> + <p><span class="sc">Smith</span>, N. H., influence of the bull "Favourite" on the breed of Short-horn cattle, ii. <a href="#page65">65</a>.</p> + <p><span class="sc">Smith</span>, W., on the inter-crossing of strawberries, i. 352.</p> + <p><span class="sc">Snake-rat</span>, ii. <a href="#page87">87</a>, <a href="#page88">88</a>.</p> + <p><span class="sc">Snakes</span>, form of the viscera in, ii. <a href="#page344">344</a>.</p> + <p><span class="sc">Snapdragon</span>, bud-variation in, i. 381;</p> + <p class="i2">non-inheritance of colour in, ii. <a href="#page21">21</a>;</p> + <p class="i2">peloric, crossed with the normal form, ii. <a href="#page70">70</a>, <a href="#page93">93</a>;</p> + <p class="i2">asymmetrical variation of the, ii. <a href="#page322">322</a>.</p> + <p><span class="sc">Soil</span>, adaptation of plums to, i. 346;</p> + <p class="i2">influence of, on the zones of pelargoniums, i. 366;</p> + <p class="i2">on roses, i. 367;</p> + <p class="i2">on the variegation of leaves, i. 383;</p> + <p class="i2">advantages of change of, ii. <a href="#page146">146</a>-<a href="#page148">148</a>.</p> + <p><span class="sc">Soil</span> and climate, effects of, on strawberries, i. 353.</p> + <p><i>Solanum</i>, non-intercrossing of species of, ii. <a href="#page91">91</a>.</p> + <p><i>Solanum tuberosum</i>, i. 330-331.</p> + <p><span class="sc">Solid-hoofed</span> pigs, i. 75.</p> + <p><span class="sc">Solomon</span>, his stud of horses, i. 55.</p> + <p><span class="sc">Somerville</span>, Lord, on the fleece of Merino sheep, i. 99;</p> + <p class="i2">on crossing sheep, ii. <a href="#page120">120</a>;</p> + <p class="i2">on selection of sheep, ii. <a href="#page195">195</a>;</p> + <p class="i2">diminished fertility of Merino sheep brought from Spain, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Sooty</span> fowls, i. 230, 256.</p> + <p><span class="sc">Soto</span>, Ferdinand de, on the cultivation of native plants in Florida, i. 312.</p> + <p><i>Sorghum</i>, i. 371.</p> + <p><span class="sc">Spain</span>, hawthorn monogynous in, i. 364.</p> + <p><span class="sc">Spallanzani</span>, on feral rabbits in Lipari, i. 113;</p> + <p class="i2">experiments on salamanders, ii. <a href="#page15">15</a>, <a href="#page293">293</a>, <a href="#page385">385</a>;</p> + <p class="i2">experiments in feeding a pigeon with meat, ii. <a href="#page304">304</a>.</p> + <p><span class="sc">Spaniels</span>, in India, i. 38;</p> + <p class="i2">King Charles's, i. 41;</p> + <p class="i2">degeneration of, caused by interbreeding, ii. <a href="#page121">121</a>.</p> + <p><span class="sc">Spanish</span> fowls, i. 227, 250, 253;</p> + <p class="i2">figured, i. 226;</p> + <p class="i2">early development of sexual characters in, i. 250, 251;</p> + <p class="i2">furcula of, figured, i. 268.</p> + <p><span class="sc">Species</span>, difficulty of distinguishing from varieties, i. 4;</p> + <p class="i2">conversion of varieties into, i. 5;</p> + <p class="i2">origin of, by natural selection, ii. <a href="#page414">414</a>-<a href="#page415">415</a>;</p> + <p class="i2">by mutual sterility of varieties, ii. <a href="#page185">185</a>-<a href="#page189">189</a>.</p> +<!-- Page 479 --><span class="pagenum"><a name="page479"></a>{479}</span> + <p><span class="sc">Spencer</span>, Lord, on selection in breeding, ii. <a href="#page195">195</a>.</p> + <p><span class="sc">Spencer</span>, Herbert, on the "survival of the fittest," i. 6;</p> + <p class="i2">increase of fertility by domestication, ii. <a href="#page111">111</a>;</p> + <p class="i2">on life, ii. <a href="#page148">148</a>, <a href="#page177">177</a>;</p> + <p class="i2">changes produced by external conditions, ii. <a href="#page281">281</a>;</p> + <p class="i2">effects of use on organs, ii. <a href="#page295">295</a>, <a href="#page296">296</a>;</p> + <p class="i2">ascent of the sap in trees, ii. <a href="#page296">296</a>;</p> + <p class="i2">correlation exemplified in the Irish elk, ii. <a href="#page333">333</a>-<a href="#page334">334</a>;</p> + <p class="i2">on "physiological units," ii. <a href="#page375">375</a>;</p> + <p class="i2">antagonism of growth and reproduction, ii. <a href="#page384">384</a>;</p> + <p class="i2">formation of ducts in plants, ii. <a href="#page300">300</a>.</p> + <p><span class="sc">Spermatophores</span> of the cephalopoda, ii. <a href="#page383">383</a>.</p> + <p><span class="sc">Spermatozoids</span>, ii. <a href="#page363">363</a>-<a href="#page364">364</a>;</p> + <p class="i2">apparent independence of, in insects, ii. <a href="#page384">384</a>.</p> + <p><span class="sc">Sphingidæ</span>, sterility of, in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Spinola</span>, on the injurious effect produced by flowering buckwheat on white pigs, ii. <a href="#page337">337</a>.</p> + <p><span class="sc">Spitz</span> dog, i. 31.</p> + <p><span class="sc">Spooner</span>, W. C., cross-breeding of sheep, i. 100, ii. <a href="#page95">95</a>-<a href="#page96">96</a>, <a href="#page120">120</a>;</p> + <p class="i2">on the effects of crossing, ii. <a href="#page96">96</a>-<a href="#page97">97</a>;</p> + <p class="i2">on crossing cattle, ii. <a href="#page118">118</a>;</p> + <p class="i2">individual sterility, ii. <a href="#page162">162</a>.</p> + <p><span class="sc">Spores</span>, reproduction of abnormal forms by, i. 383.</p> + <p><span class="sc">Sports</span>, i. 373; in pigeons, i. 213.</p> + <p><span class="sc">Spot</span> pigeon, i. 156, 207.</p> + <p><span class="sc">Sprengel</span>, C. K., on dichogamous plants, ii. <a href="#page90">90</a>;</p> + <p class="i2">on the hollyhock, ii. <a href="#page107">107</a>;</p> + <p class="i2">on the functions of flowers, ii. <a href="#page175">175</a>.</p> + <p><span class="sc">Sproule</span>, Mr., inheritance of cleft-palate and hare-lip, ii. <a href="#page24">24</a>.</p> + <p><span class="sc">Spurs</span>, of fowls, i. 255;</p> + <p class="i2">development of, in hens, ii. <a href="#page318">318</a>.</p> + <p><span class="sc">Squashes</span>, i. 357.</p> + <p><span class="sc">Squinting</span>, hereditary, ii. <a href="#page9">9</a>.</p> + <p><span class="sc">Squirrels</span>, generally sterile in captivity, ii. <a href="#page152">152</a>.</p> + <p><span class="sc">Squirrels</span>, flying, breeding in confinement, ii. <a href="#page152">152</a>.</p> + <p>"<span class="sc">Staarhalsige</span> Taube," i. 161.</p> + <p><span class="sc">Stag</span>, one-horned, supposed heredity of character in, ii. <a href="#page12">12</a>;</p> + <p class="i2">degeneracy of, in the Highlands, ii. <a href="#page208">208</a>.</p> + <p><span class="sc">Stamens</span>, occurrence of rudimentary, ii. <a href="#page316">316</a>;</p> + <p class="i2">conversion of, into pistils, i. 365;</p> + <p class="i2">into petals, ii. <a href="#page392">392</a>.</p> + <p><i>Staphylea</i>, ii. <a href="#page168">168</a>.</p> + <p><span class="sc">Steenstrup</span>, Prof., on the dog of the Danish Middens, i. 18;</p> + <p class="i2">on the obliquity of flounders, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Steinan</span>, J., on hereditary diseases, ii. <a href="#page7">7</a>, <a href="#page79">79</a>.</p> + <p><span class="sc">Sterility</span>, in dogs, consequent on close confinement, i. 32;</p> + <p class="i2">comparative, of crosses, ii. <a href="#page103">103</a>, <a href="#page104">104</a>;</p> + <p class="i2">from changed conditions of life, ii. <a href="#page148">148</a>-<a href="#page165">165</a>;</p> + <p class="i2">occurring in the descendants of wild animals bred in captivity, ii. <a href="#page160">160</a>;</p> + <p class="i2">individual, ii. <a href="#page162">162</a>;</p> + <p class="i2">resulting from propagation by buds, cuttings, bulbs, &c., ii. <a href="#page169">169</a>;</p> + <p class="i2">in hybrids, ii. <a href="#page178">178</a>-<a href="#page180">180</a>, <a href="#page386">386</a>, <a href="#page410">410</a>-<a href="#page411">411</a>;</p> + <p class="i2">in specific hybrids of pigeons, i. 193;</p> + <p class="i2">as connected with natural selection, ii. <a href="#page185">185</a>-<a href="#page189">189</a>.</p> + <p><span class="sc">Sternum</span>, characters of the, in rabbits, i. 123;</p> + <p class="i2">in pigeons, i. 167, 174-175;</p> + <p class="i2">in fowls, i. 268, 273;</p> + <p class="i2">effects of disuse on the, i. 174-175, 273.</p> + <p><span class="sc">Stephens</span>, J. F., on the habits of the Bombycidæ, i. 303.</p> + <p><span class="sc">Stewart</span>, H., on hereditary disease, ii. <a href="#page79">79</a>.</p> + <p><span class="sc">Stigma</span>, variation of the, in cultivated Cucurbitaceæ, i. 359;</p> + <p class="i2">satiation of the, i. 402-403.</p> + <p><span class="sc">Stocks</span>, bud-variation in, i. 381;</p> + <p class="i2">effect of crossing upon the colour of the seed of, i. 398-399;</p> + <p class="i2">true by seed, ii. <a href="#page20">20</a>;</p> + <p class="i2">crosses of, ii. <a href="#page93">93</a>;</p> + <p class="i2">varieties of, produced by selection, ii. <a href="#page219">219</a>;</p> + <p class="i2">reversion by the upper seeds in the pods of, ii. <a href="#page347">347</a>-<a href="#page348">348</a>.</p> + <p><span class="sc">Stockholm</span>, fruit-trees of, ii. <a href="#page307">307</a>.</p> + <p><span class="sc">Stokes</span>, Prof., calculation of the chance of transmission of abnormal peculiarities in man, ii. <a href="#page5">5</a>.</p> + <p><span class="sc">Stolons</span>, variations in the production of, by strawberries, i. 353.</p> + <p><span class="sc">Stomach</span>, structure of the, affected by food, ii. <a href="#page302">302</a>.</p> + <p><span class="sc">Stone</span> in the bladder, hereditary, ii. <a href="#page8">8</a>, <a href="#page79">79</a>.</p> + <p><span class="sc">Strawberries</span>, i. 351-354;</p> + <p class="i2">remarkable varieties of, i. 352-353;</p> + <p class="i2">hautbois, diœcious, i. 353;</p> + <p class="i2">selection in, ii. <a href="#page200">200</a>;</p> + <p class="i2">mildew of, ii. <a href="#page228">228</a>;</p> + <p class="i2">probable further modification of, ii. <a href="#page243">243</a>;</p> + <p class="i2">variegated, effects of soil on, ii. <a href="#page274">274</a>.</p> + <p><span class="sc">Strickland</span>, A., on the domestication of <i>Anser ferus</i>, i. 287;</p> + <p class="i2">on the colour of the bill and legs in geese, i. 288.</p> + <p><i>Strictœnas</i>, i. 183.</p> + <p><span class="sc">Stripes</span> on young of wild swine, i. 76;</p> + <p class="i2">of domestic pigs of Turkey, Westphalia, and the Zambesi, i. 76-77;</p> + <p class="i2">of feral swine of Jamaica and New Granada, i. 77;</p> + <p class="i2">of fruit and flowers, i. 400, ii. <a href="#page37">37</a>;</p> + <p class="i2">in horses, i. 56-60;</p> + <p class="i2">in the ass, i. 62-63;</p> + <p class="i2">production of, by crossing species of Equidæ, ii. <a href="#page42">42</a>-<a href="#page43">43</a>.</p> + <p><i>Strix grallaria</i>, ii. <a href="#page302">302</a>.</p> + <p><i>Strix passerina</i>, ii. <a href="#page154">154</a>.</p> + <p>"<span class="sc">Strupp-Taube</span>," i. 155.</p> + <p><span class="sc">Struthers</span>, Mr., osteology of the feet in solid-hoofed pigs, i. 75;</p> + <p class="i2">on polydactylism, ii. <a href="#page13">13</a>-<a href="#page14">14</a>.</p> + <p><span class="sc">Sturm</span>, prepotency of transmission of characters in sheep and cattle, ii. <a href="#page66">66</a>;</p> + <p class="i2">absorption of the minority in crossed races, ii. <a href="#page88">88</a>;</p> + <p class="i2">correlation of twisted horns and curled wool in sheep, ii. <a href="#page326">326</a>.</p> +<!-- Page 480 --><span class="pagenum"><a name="page480"></a>{480}</span> + <p><span class="sc">Sub-species</span>, wild, of <i>Columba livia</i> and other pigeons, i. 204.</p> + <p><span class="sc">Succession</span>, geological, of organisms, i. 11.</p> + <p><span class="sc">Suckers</span>, bud-variation by, i. 384.</p> + <p><span class="sc">Sugar</span> cane, sterility of, in various countries, ii. <a href="#page169">169</a>;</p> + <p class="i2">white, liability of, to disease, ii. <a href="#page228">228</a>, <a href="#page336">336</a>.</p> + <p><span class="sc">Suicide</span>, hereditary tendency to, ii. <a href="#page7">7</a>, <a href="#page78">78</a>.</p> + <p><span class="sc">Sulivan</span>, Admiral, on the horses of the Falkland Islands, i. 53;</p> + <p class="i2">wild pigs of the Falkland Islands, i. 77;</p> + <p class="i2">feral cattle of the Falkland Islands, i. 86, 102;</p> + <p class="i2">feral rabbits of the Falkland Islands, i. 112.</p> + <p><span class="sc">Sultan</span> fowl, i. 228, 255.</p> + <p><i>Sus indica</i>, i. 65, 67-70, ii. <a href="#page110">110</a>.</p> + <p><i>Sus pliciceps</i>, i. 69 (figured).</p> + <p><i>Sus scrofa</i>, i. 65, 66, ii. <a href="#page110">110</a>.</p> + <p><i>Sus scrofa palustris</i>, i. 68.</p> + <p><i>Sus vittatus</i>, i. 67.</p> + <p><span class="sc">Swallows</span>, a breed of pigeons, i. 156.</p> + <p><span class="sc">Swayne</span>, Mr., on artificial crossing of varieties of the pea, i. 397.</p> + <p><span class="sc">Sweet</span> Peas, ii. <a href="#page91">91</a>;</p> + <p class="i2">crosses of, ii. <a href="#page93">93</a>, <a href="#page94">94</a>;</p> + <p class="i2">varieties of, coming true by seed, ii. <a href="#page20">20</a>;</p> + <p class="i2">acclimatisation of, in India, ii. <a href="#page311">311</a>.</p> + <p><span class="sc">Sweet</span> William, bud-variation in, i. 381.</p> + <p><span class="sc">Swinhoe</span>, R., on Chinese pigeons, i. 28, 206;</p> + <p class="i2">on striped Chinese horses, i. 59.</p> + <p><span class="sc">Switzerland</span>, ancient dogs of, i. 19;</p> + <p class="i2">pigs of, in the Neolithic period, i. 67-68;</p> + <p class="i2">goats of, i. 101.</p> + <p><span class="sc">Sycamore</span>, pale-leaved variety of the, ii. <a href="#page330">330</a>.</p> + <p><span class="sc">Sykes</span>, Colonel, on a Pariah dog with crooked legs, i. 17;</p> + <p class="i2">on small Indian asses, i. 62;</p> + <p class="i2">on <i>Gallus Sonneratii</i>, i. 233;</p> + <p class="i2">on the voice of the Indian Kulm cock, i. 259;</p> + <p class="i2">fertility of the fowl in most climates, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Symmetry</span>, hereditary departures from, ii. <a href="#page12">12</a>.</p> + <p><i>Symphytum</i>, variegated, i. 384.</p> + <p><span class="sc">Syphilis</span>, hereditary, ii. <a href="#page332">332</a>.</p> + <p><span class="sc">Syria</span>, asses of, i. 62.</p> + <p><i>Syringa persica</i>, <i>chinensis</i>, and <i>vulgaris</i>, ii. <a href="#page164">164</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Tacitus</span>, on the care taken by the Celts in breeding animals, ii. <a href="#page202">202</a>.</p> + <p><i>Tagetes signata</i>, dwarf variety of, ii. <a href="#page20">20</a>.</p> + <p><span class="sc">Tahiti</span>, varieties of cultivated plants in, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Tail</span>, occasional development of, in man, ii. <a href="#page57">57</a>;</p> + <p class="i2">never curled in wild animals, ii. <a href="#page301">301</a>;</p> + <p class="i2">rudimentary in Chinese sheep, ii. <a href="#page315">315</a>.</p> + <p><span class="sc">Tail-feathers</span>, numbers of, in breeds of pigeons, i. 158-159;</p> + <p class="i2">peculiarities of, in cocks, i. 254-255;</p> + <p class="i2">variability of, in fowls, i. 258;</p> + <p class="i2">curled, in <i>Anas boschas</i>, and tame drakes, i. 280.</p> + <p><span class="sc">Talent</span>, hereditary, ii. <a href="#page7">7</a>.</p> + <p><span class="sc">Tankerville</span>, Earl of, on Chillingham cattle, i. 84, ii. <a href="#page119">119</a>.</p> + <p><span class="sc">Tanner</span>, Prof., effects of disuse of parts in cattle, ii. <a href="#page299">299</a>.</p> + <p><span class="sc">Tapir</span>, sterility of the, in captivity, ii. <a href="#page150">150</a>.</p> + <p><span class="sc">Targioni-Tozzetti</span>, on cultivated plants, i. 306;</p> + <p class="i2">on the vine, i. 332;</p> + <p class="i2">varieties of the peach, i. 342;</p> + <p class="i2">origin and varieties of the plum, i. 345;</p> + <p class="i2">origin of the cherry, i. 347;</p> + <p class="i2">origin of roses, i. 366.</p> + <p><span class="sc">Tarsus</span>, variability of the, in fowls, i. 259;</p> + <p class="i2">reproduction of the, in a thrush, ii. <a href="#page15">15</a>.</p> + <p><span class="sc">Tartars</span>, their preference for spiral-horned sheep, ii. <a href="#page209">209</a>.</p> + <p><span class="sc">Tavernier</span>, abundance of pigeons in Persia, i. 205.</p> + <p><i>Taxus baccata</i>, ii. <a href="#page18">18</a>.</p> + <p><span class="sc">Teebay</span>, Mr., reversion in fowls, ii. <a href="#page38">38</a>.</p> + <p><span class="sc">Teeth</span>, number and position of, in dogs, i. 34;</p> + <p class="i2">deficiency of, in naked Turkish dogs, i. 35;</p> + <p class="i2">period of appearance of, in breeds of dogs, i. 35;</p> + <p class="i2">precocity of, in highly bred animals, ii. <a href="#page322">322</a>;</p> + <p class="i2">correlation of, with hair, ii. <a href="#page326">326</a>;</p> + <p class="i2">double row of, with redundant hair, in Julia Pastrana, ii. <a href="#page328">328</a>;</p> + <p class="i2">affected in form by hereditary syphilis and by pulmonary tubercle, ii. <a href="#page332">332</a>;</p> + <p class="i2">fusion of, ii. <a href="#page341">341</a>;</p> + <p class="i2">developed on the palate, ii. <a href="#page391">391</a>.</p> + <p><span class="sc">Tegetmeier</span>, Mr., on a cat with monstrous teeth, i. 48;</p> + <p class="i2">on a swift-like pigeon, i. 157;</p> + <p class="i2">naked young of some pigeons, i. 170;</p> + <p class="i2">fertility of hybrid pigeons, i. 192;</p> + <p class="i2">on white pigeons, ii. <a href="#page230">230</a>;</p> + <p class="i2">reversion in crossed breeds of fowls, i. 239-244;</p> + <p class="i2">chicks of the white silk-fowl, i. 249;</p> + <p class="i2">development of the cranial protuberance in Polish fowls, i. 250;</p> + <p class="i2">on the skull in the Polish fowl, i. 257, 262;</p> + <p class="i2">on the intelligence of Polish fowls, i. 264;</p> + <p class="i2">correlation of the cranial protuberance and crest in Polish fowls, i. 274;</p> + <p class="i2">development of the web in the feet of Polish fowls, i. 259;</p> + <p class="i2">early development of several peculiarities in Spanish cocks, i. 250;</p> + <p class="i2">on the comb in Spanish fowls, i. 253;</p> + <p class="i2">on the Spanish fowl, ii. <a href="#page306">306</a>;</p> + <p class="i2">varieties of game-fowls, i. 252;</p> + <p class="i2">pedigrees of game-fowls, ii. <a href="#page3">3</a>;</p> + <p class="i2">assumption of female plumage by a game cock, i. 253;</p> + <p class="i2">natural selection in the game cock, ii. <a href="#page225">225</a>;</p> + <p class="i2">pugnacity of game hens, i. 256;</p> + <p class="i2">length of the middle toe in Cochin fowls, i. 259;</p> + <p class="i2">origin of the Sebright bantam, ii. <a href="#page54">54</a>;</p> + <p class="i2">differences in the size of fowls, i. 257;</p> + <p class="i2">effect of crossing in fowls, i. 258, ii. <a href="#page96">96</a>;</p> + <p class="i2">effects of interbreeding in fowls, ii. <a href="#page124">124</a>-<a href="#page125">125</a>;</p> + <p class="i2">incubation by mongrels of non-sitting races of fowls, ii. <a href="#page44">44</a>;</p> + <p class="i2">inverse correlation of crest and comb in fowls, i. 274;</p> +<!-- Page 481 --><span class="pagenum"><a name="page481"></a>{481}</span> + <p class="i2">occurrence of pencilled feathers in fowls, ii. <a href="#page40">40</a>;</p> + <p class="i2">on a variety of the goose from Sebastopol, i. 289;</p> + <p class="i2">on the fertility of the peahen, ii. <a href="#page112">112</a>;</p> + <p class="i2">on the intercrossing of bees, ii. <a href="#page126">126</a>.</p> + <p><span class="sc">Temminck</span>, origin of domestic cats, i. 43;</p> + <p class="i2">origin of domestic pigeons, i. 180;</p> + <p class="i2">on <i>Columba guinea</i>, i. 182;</p> + <p class="i2">on <i>Columba leucocephala</i>, i. 183;</p> + <p class="i2">asserted reluctance of some breeds of pigeons to cross, i. 192;</p> + <p class="i2">sterility of hybrid turtle-doves, i. 193;</p> + <p class="i2">variations of <i>Gallus bankiva</i>, i. 235;</p> + <p class="i2">on a buff-coloured breed of Turkeys, i. 293;</p> + <p class="i2">number of eggs laid by the peahen, ii. <a href="#page112">112</a>;</p> + <p class="i2">breeding of Guans in captivity, ii. <a href="#page156">156</a>;</p> + <p class="i2">behaviour of grouse in captivity, <i>ibid.</i>;</p> + <p class="i2">sterility of the partridge in captivity, <i>ibid.</i></p> + <p><span class="sc">Tendrils</span> in Cucurbitaceæ, i. 358, ii. <a href="#page316">316</a>.</p> + <p><span class="sc">Tennent</span>, Sir J. E., on the goose, i. 287;</p> + <p class="i2">on the growth of the apple in Ceylon, ii. <a href="#page277">277</a>;</p> + <p class="i2">on the Jaffna sheep, ii. <a href="#page302">302</a>.</p> + <p><i>Teredo</i>, fertilisation in, ii. <a href="#page363">363</a>.</p> + <p><span class="sc">Terriers</span>, wry-legged, ii. <a href="#page245">245</a>;</p> + <p class="i2">white, subject to distemper, ii. <a href="#page336">336</a>.</p> + <p><span class="sc">Teschemacher</span>, on a husked form of maize, i. 320.</p> + <p><span class="sc">Tessier</span>, on the period of gestation of the dog, i. 29;</p> + <p class="i2">of the pig, i. 74;</p> + <p class="i2">in cattle, i. 87;</p> + <p class="i2">experiments on change of soil, ii. <a href="#page147">147</a>.</p> + <p><i>Tetrao</i>, breeding of species of, in captivity, ii. <a href="#page156">156</a>.</p> + <p><i>Tetrapteryx paradisea</i>, ii. <a href="#page156">156</a>.</p> + <p><i>Teucrium campanulatum</i>, pelorism in, ii. <a href="#page345">345</a>.</p> + <p><span class="sc">Texas</span>, feral cattle in, i. 85.</p> + <p><span class="sc">Theognis</span>, his notice of the domestic fowl, i. 246.</p> + <p><span class="sc">Theophrastus</span>, his notice of the peach, ii. <a href="#page308">308</a>.</p> + <p><i>Thesium</i>, ii. <a href="#page284">284</a>.</p> + <p><span class="sc">Thompson</span>, Mr., on the peach and nectarine, i. 342;</p> + <p class="i2">on the varieties of the apricot, i. 344;</p> + <p class="i2">classification of varieties of cherries, i. 347-348;</p> + <p class="i2">on the "Sister ribston-pippin," i. 350;</p> + <p class="i2">on the varieties of the gooseberry, i. 354, 355.</p> + <p><span class="sc">Thompson</span>, William, on the pigeons of Islay, i. 184;</p> + <p class="i2">feral pigeons in Scotland, i. 190;</p> + <p class="i2">colour of the bill and legs in geese, i. 288;</p> + <p class="i2">breeding of <i>Tetrao scotius</i> in captivity, ii. <a href="#page156">156</a>;</p> + <p class="i2">destruction of black-fowls by the osprey, ii. <a href="#page230">230</a>.</p> + <p><span class="sc">Thompson</span>, Prof. W., on the obliquity of the flounder, ii. <a href="#page53">53</a>.</p> + <p><span class="sc">Thorns</span>, reconversion of, into branches, in pear trees, ii. <a href="#page318">318</a>.</p> + <p><span class="sc">Thorn</span>, grafting of early and late, i. 363;</p> + <p class="i2">Glastonbury, i. 364.</p> + <p><span class="sc">Thrush</span>, asserted reproduction of the tarsus in a, ii. <a href="#page15">15</a>.</p> + <p><i>Thuja pendula</i> or <i>filiformis</i>, a variety of <i>T. orientalis</i>, i. 362.</p> + <p><span class="sc">Thuret</span>, on the division of the zoospores of an alga, ii. <a href="#page378">378</a>.</p> + <p><span class="sc">Thwaites</span>, G. H., on the cats of Ceylon, i. 46;</p> + <p class="i2">on a twin seed of <i>Fuchsia coccinea</i> and <i>fulgens</i>, i. 391.</p> + <p><span class="sc">Tiburtius</span>, experiments in rearing wild ducks, i. 278.</p> + <p><span class="sc">Tiger</span>, rarely fertile in captivity, ii. <a href="#page150">150</a>, <a href="#page151">151</a>.</p> + <p><i>Tigridia conchiflora</i>, bud-variation in, i. 386.</p> + <p><span class="sc">Time</span>, importance of, in the production of races, ii. <a href="#page243">243</a>.</p> + <p><span class="sc">Tinzmann</span>, self-impotence in the potato, ii. <a href="#page137">137</a>.</p> + <p><span class="sc">Tissues</span>, affinity of, for special organic substances, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Titmice</span>, destructive to thin-shelled walnuts, i. 356;</p> + <p class="i2">attacking nuts, i. 357;</p> + <p class="i2">attacking peas, ii. <a href="#page231">231</a>.</p> + <p><span class="sc">Tobacco</span>, crossing of varieties of, ii. <a href="#page108">108</a>;</p> + <p class="i2">cultivation of in Sweden, ii. <a href="#page307">307</a>.</p> + <p><span class="sc">Tobolsk</span>, red-coloured cats of, i. 47.</p> + <p><span class="sc">Toes</span>, relative length of, in fowls, i. 259;</p> + <p class="i2">development of fifth in dogs, ii. <a href="#page317">317</a>.</p> + <p><span class="sc">Tollet</span>, Mr., his selection of cattle, ii. <a href="#page199">199</a>.</p> + <p><span class="sc">Tomato</span>, ii. <a href="#page91">91</a>.</p> + <p><span class="sc">Tomtits</span>. See <i>Titmice</i>.</p> + <p><span class="sc">Tongue</span>, relation of, to the beak in pigeons, i. 168.</p> + <p><span class="sc">Tooth</span>, occurrence of a molar, in place of an incisor, ii. <a href="#page391">391</a>.</p> + <p>"<span class="sc">Torfschwein</span>," i. 68.</p> + <p><span class="sc">Trail</span>, R., on the union of half-tubers of different kinds of potatoes, i. 395.</p> + <p><span class="sc">Trees</span>, varieties of, suddenly produced, i. 361;</p> + <p class="i2">weeping or pendulous, i. 361;</p> + <p class="i2">fastigate or pyramidal, i. 361;</p> + <p class="i2">with variegated or changed foliage, i. 362;</p> + <p class="i2">early or late in leaf, i. 362-363;</p> + <p class="i2">forest, non-application of selection to, ii. <a href="#page237">237</a>.</p> + <p>"<span class="sc">Trembleur</span>" (pigeons), i. 146.</p> + <p><span class="sc">Trembley</span>, on reproduction in Hydra, ii. <a href="#page359">359</a>.</p> + <p>"<span class="sc">Trevoltini</span>" silkworms, i. 301-302.</p> + <p><i>Trichosanthes anguina</i>, i. 360.</p> + <p><span class="sc">Tricks</span>, inheritance of, ii. <a href="#page6">6</a>-<a href="#page7">7</a>, <a href="#page395">395</a>.</p> + <p><i>Trifolium minus</i> and <i>repens</i>, ii. <a href="#page164">164</a>.</p> + <p><span class="sc">Trimorphic</span> plants, conditions of reproduction in, ii. <a href="#page181">181</a>-<a href="#page184">184</a>.</p> + <p><span class="sc">Tristram</span>, H. B., selection of the dromedary, ii. <a href="#page205">205</a>-<a href="#page206">206</a>.</p> + <p><i>Triticum dicoccum</i>, i. 319.</p> + <p><i>Triticum monococcum</i>, i. 319.</p> + <p><i>Triticum spelta</i>, i. 319.</p> + <p><i>Triticum turgidum</i>, i. 319.</p> + <p><i>Triticum vulgare</i>, wild in Asia, i. 312.</p> +<!-- Page 482 --><span class="pagenum"><a name="page482"></a>{482}</span> + <p><span class="sc">Triton</span>, breeding in the branchiferous stage, ii. <a href="#page384">384</a>.</p> + <p>"<span class="sc">Trommel-Taube</span>," i. 154.</p> + <p>"<span class="sc">Tronfo</span>" pigeon, i. 144.</p> + <p><i>Tropæolum</i>, ii. <a href="#page38">38</a>.</p> + <p><i>Tropæolum minus</i> and <i>majus</i>, reversion in hybrids of, i. 392.</p> + <p><span class="sc">Troubetzkoy</span>, Prince, experiments with pear-trees at Moscow, ii. <a href="#page307">307</a>.</p> + <p><span class="sc">Trousseau</span>, Prof., pathological resemblance of twins, ii. <a href="#page252">252</a>.</p> + <p><span class="sc">Trumpeter</span> pigeon, i. 154;</p> + <p class="i2">known in 1735, i. 207.</p> + <p><span class="sc">Tscharner</span>, H. A. de, graft-hybrid produced by inosculation in the vine, i. 395.</p> + <p><span class="sc">Tschudi</span>, on the naked Peruvian dog, i. 23;</p> + <p class="i2">extinct varieties of maize from Peruvian tombs, i. 320, ii. <a href="#page425">425</a>.</p> + <p><span class="sc">Tubers</span>, bud-variation by, i. 384-385.</p> + <p><span class="sc">Tuckerman</span>, Mr., sterility of <i>Carex rigida</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Tufted</span> ducks, i. 281.</p> + <p><span class="sc">Tulips</span>, variability of, i. 370;</p> + <p class="i2">bud-variation in, i. 385-386;</p> + <p class="i2">influence of soil in "breaking," i. 385.</p> + <p><span class="sc">Tumbler</span> pigeon, i. 150-153;</p> + <p class="i2">short-faced, figured, i. 152;</p> + <p class="i2">skull figured, i. 163;</p> + <p class="i2">lower jaw figured, i. 165;</p> + <p class="i2">scapula and furcula figured, i. 167;</p> + <p class="i2">early known in India, i. 207;</p> + <p class="i2">history of, i. 209;</p> + <p class="i2">sub-breeds of, i. 220;</p> + <p class="i2">young unable to break the egg-shell, ii. <a href="#page226">226</a>;</p> + <p class="i2">probable further modification of, ii. <a href="#page242">242</a>.</p> + <p>"<span class="sc">Tümmler</span>" (pigeons), i. 150.</p> + <p><span class="sc">Tumours</span>, ovarian, occurrence of hairs and teeth in, ii. <a href="#page370">370</a>;</p> + <p class="i2">polypoid, origin of, ii. <a href="#page381">381</a>.</p> + <p>"<span class="sc">Türkische Taube</span>," i. 139.</p> + <p><span class="sc">Turbit</span> (pigeon), i. 148.</p> + <p><span class="sc">Turkey</span>, domestic, origin of, i. 292-293;</p> + <p class="i2">crossing of with North American wild Turkey, i. 292-293;</p> + <p class="i2">breeds of, i. 293;</p> + <p class="i2">crested white cock, i. 293;</p> + <p class="i2">wild, characters of, i. 293-294;</p> + <p class="i2">degeneration of, in India, i. 294, ii. <a href="#page278">278</a>;</p> + <p class="i2">failure of eggs of, in Delhi, ii. <a href="#page161">161</a>;</p> + <p class="i2">feral on the Parana, i. 190;</p> + <p class="i2">change produced in by domestication, ii. <a href="#page262">262</a>.</p> + <p><span class="sc">Turkey</span>, striped young pigs in, i. 76.</p> + <p><span class="sc">Turner</span> (pigeon), i. 156.</p> + <p><span class="sc">Turner</span>, W., on compensation in arteries and veins, ii. <a href="#page300">300</a>;</p> + <p class="i2">on cells, ii. <a href="#page370">370</a>.</p> + <p><span class="sc">Turnips</span>, origin of, i. 325;</p> + <p class="i2">reversion in, ii. <a href="#page31">31</a>;</p> + <p class="i2">run wild, ii. <a href="#page33">33</a>;</p> + <p class="i2">crosses of, ii. <a href="#page93">93</a>, <a href="#page96">96</a>;</p> + <p class="i2">Swedish, preferred by hares, ii. <a href="#page232">232</a>;</p> + <p class="i2">acclimatisation of, in India, ii. <a href="#page311">311</a>.</p> + <p><span class="sc">Turnspit</span>, on an Egyptian monument, i. 17;</p> + <p class="i2">crosses of the, ii. <a href="#page92">92</a>.</p> + <p><span class="sc">Turtle-dove</span>, white and coloured, crossing of, ii. <a href="#page92">92</a>.</p> + <p><i>Turtur auritus</i>, hybrids of, with <i>T. cambayensis</i> and <i>T. suratensis</i>, i. 194.</p> + <p><i>Turtur risorius</i>, crossing of, with the common pigeon, i. 193;</p> + <p class="i2">hybrid of, with <i>T. vulgaris</i>, <i>ibid.</i></p> + <p><i>Turtur suratensis</i>, sterile hybrids of, with <i>T. vulgaris</i>, i. 193;</p> + <p class="i2">hybrids of, with <i>T. auritus</i>, i. 194.</p> + <p><i>Turtur vulgaris</i>, crossing of, with the common pigeon, i. 193;</p> + <p class="i2">hybrid of, with <i>T. risorius</i>, <i>ibid.</i>;</p> + <p class="i2">sterile hybrids of, with <i>T. suratensis</i> and <i>Ectopistes migratorius</i>, <i>ibid.</i></p> + <p><span class="sc">Tusks</span> of wild and domesticated pigs, i. 76, 77.</p> + <p><i>Tussilago farfara</i>, variegated, i. 384.</p> + <p><span class="sc">Twin-seed</span> <i>Fuchsia coccinea</i> and <i>fulgens</i>, i. 391.</p> + <p><span class="sc">Tyerman</span>, B., on the pigs of the Pacific islands, i. 70, ii. <a href="#page87">87</a>;</p> + <p class="i2">on the dogs of the Pacific islands, ii. <a href="#page87">87</a>.</p> + <p><span class="sc">Tylor</span>, Mr., on the prohibition of consanguineous marriages, ii. <a href="#page122">122</a>-<a href="#page123">123</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Udders</span>, development of the, ii. <a href="#page300">300</a>.</p> + <p><i>Ulex</i>, double-flowered, ii. <a href="#page167">167</a>.</p> + <p><i>Ulmus campestris</i> and <i>effusa</i>, hybrids of, ii. <a href="#page130">130</a>.</p> + <p><span class="sc">Uniformity</span> of character, maintained by crossing, ii. <a href="#page85">85</a>-<a href="#page90">90</a>.</p> + <p><span class="sc">Units</span> of the body, functional independence of the, ii. <a href="#page368">368</a>-<a href="#page371">371</a>.</p> + <p><span class="sc">Unity</span> or plurality of origin of organisms, i. 13.</p> + <p><span class="sc">Upas</span> poison, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Urea</span>, secretion of, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Use</span> and disuse of parts, effects of, ii. <a href="#page295">295</a>-<a href="#page303">303</a>, <a href="#page352">352</a>-<a href="#page353">353</a>, <a href="#page418">418</a>-<a href="#page419">419</a>;</p> + <p class="i2">in rabbits, i. 124-128;</p> + <p class="i2">in ducks, i. 284-286.</p> + <p><span class="sc">Utility</span>, considerations of, leading to uniformity, ii. <a href="#page241">241</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Valentin</span>, experimental production of double monsters by, ii. <a href="#page340">340</a>.</p> + <p><i>Vallota</i>, ii. <a href="#page139">139</a>.</p> + <p><span class="sc">Van Beck</span>, Barbara, a hairy-faced woman, ii. <a href="#page4">4</a>.</p> + <p><span class="sc">Van Mons</span> on wild fruit-trees, i. 312, ii. <a href="#page260">260</a>;</p> + <p class="i2">production of varieties of the vine, i. 333;</p> + <p class="i2">correlated variability in fruit-trees, ii. <a href="#page330">330</a>;</p> + <p class="i2">production of almond-like fruit by peach-seedlings, i. 339.</p> + <p><i>Vanessa</i>, species of, not copulating in captivity, ii. <a href="#page157">157</a>.</p> + <p><span class="sc">Variability</span>, i. 4, ii. <a href="#page371">371</a>-<a href="#page373">373</a>, <a href="#page394">394</a>-<a href="#page397">397</a>, <a href="#page406">406</a>-<a href="#page420">420</a>;</p> + <p class="i2">causes of, ii. <a href="#page250">250</a>-<a href="#page270">270</a>;</p> + <p class="i2">correlated, ii. <a href="#page319">319</a>-<a href="#page338">338</a>, <a href="#page353">353</a>-<a href="#page355">355</a>, <a href="#page419">419</a>-<a href="#page420">420</a>;</p> + <p class="i2">law of equable, ii. <a href="#page351">351</a>-<a href="#page352">352</a>;</p> + <p class="i2">necessity of, for selection, ii. <a href="#page192">192</a>;</p> + <p class="i2">of selected characters, ii. <a href="#page238">238</a>-<a href="#page239">239</a>;</p> + <p class="i2">of multiple homologous parts, ii. <a href="#page342">342</a>.</p> +<!-- Page 483 --><span class="pagenum"><a name="page483"></a>{483}</span> + <p><span class="sc">Variation</span>, laws of, ii. <a href="#page293">293</a>-<a href="#page356">356</a>;</p> + <p class="i2">continuity of, ii. <a href="#page241">241</a>;</p> + <p class="i2">possible limitation of, ii. <a href="#page242">242</a>, <a href="#page416">416</a>-<a href="#page417">417</a>;</p> + <p class="i2">in domestic cats, i. 45-48;</p> + <p class="i2">origin of breeds of cattle by, i. 88;</p> + <p class="i2">in osteological characters of rabbits, i. 115-130;</p> + <p class="i2">of important organs, i. 359;</p> + <p class="i2">analogous or parallel, i. 348-352;</p> + <p class="i2">in horses, i. 55;</p> + <p class="i2">in the horse and ass, i. 64;</p> + <p class="i2">in fowls, i. 243-246;</p> + <p class="i2">in geese, i. 288;</p> + <p class="i2">exemplified in the production of fleshy stems in cabbages, &c., i. 326;</p> + <p class="i2">in the peach, nectarine, and apricot, i. 342, 344;</p> + <p class="i2">individual, in wheat, i. 314.</p> + <p><span class="sc">Variegation</span> of foliage, i. 383, ii. <a href="#page167">167</a>-<a href="#page168">168</a>.</p> + <p><span class="sc">Varieties</span> and species, resemblance of, i. 4, ii. <a href="#page411">411</a>-<a href="#page413">413</a>;</p> + <p class="i2">conversion of, into species, i. 5;</p> + <p class="i2">abnormal, ii. <a href="#page413">413</a>;</p> + <p class="i2">domestic, gradually produced, ii. <a href="#page414">414</a>.</p> + <p><span class="sc">Varro</span>, on domestic ducks, i. 277;</p> + <p class="i2">on feral fowls, ii. <a href="#page33">33</a>;</p> + <p class="i2">crossing of the wild and domestic ass, ii. <a href="#page206">206</a>.</p> + <p><span class="sc">Vasey</span>, Mr., on the number of sacral vertebræ in ordinary and humped cattle, i. 79;</p> + <p class="i2">on Hungarian cattle, i. 80.</p> + <p><span class="sc">Vaucher</span>, sterility of <i>Ranunculus ficaria</i> and <i>Acorus calamus</i>, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Vegetables</span>, cultivated, reversion in, ii. <a href="#page31">31</a>-<a href="#page32">32</a>;</p> + <p class="i2">European, culture of, in India, ii. <a href="#page168">168</a>-<a href="#page169">169</a>.</p> + <p><span class="sc">Veith</span>, Mr., on breeds of horses, i. 49.</p> + <p><i>Verbascum</i>, intercrossing of species of, i. 336, ii. <a href="#page93">93</a>, <a href="#page105">105</a>-<a href="#page107">107</a>;</p> + <p class="i2">reversion in hybrids of, i. 392;</p> + <p class="i2">contabescent, wild plants of, ii. <a href="#page165">165</a>;</p> + <p class="i2">villosity in, ii. <a href="#page277">277</a>.</p> + <p><i>Verbascum austriacum</i>, ii. <a href="#page136">136</a>.</p> + <p><i>Verbascum blattaria</i>, ii. <a href="#page105">105</a>-<a href="#page106">106</a>.</p> + <p><i>Verbascum lychnitis</i>, ii. <a href="#page105">105</a>-<a href="#page106">106</a>, <a href="#page136">136</a>.</p> + <p><i>Verbascum nigrum</i>, ii. <a href="#page136">136</a>.</p> + <p><i>Verbascum phœniceum</i>, ii. <a href="#page107">107</a>, <a href="#page137">137</a>;</p> + <p class="i2">variable duration of, ii. <a href="#page305">305</a>.</p> + <p><i>Verbascum thapsus</i>, ii. <a href="#page106">106</a>.</p> + <p><span class="sc">Verbenas</span>, origin of, i. 364;</p> + <p class="i2">white, liability of, to mildew, ii. <a href="#page228">228</a>, <a href="#page336">336</a>;</p> + <p class="i2">scorching of dark, ii. <a href="#page229">229</a>, <a href="#page336">336</a>;</p> + <p class="i2">effect of changed conditions of life on, ii. <a href="#page273">273</a>.</p> + <p><span class="sc">Verlot</span>, on the darkleaved Barberry, i. 362;</p> + <p class="i2">inheritance of peculiarities of foliage in trees, i. 362;</p> + <p class="i2">production of <i>Rosa cannabifolia</i> by bud-variation from <i>R. alba</i>, i. 381;</p> + <p class="i2">bud-variation in <i>Aralia trifoliata</i>, i. 382;</p> + <p class="i2">variegation of leaves, i. 383;</p> + <p class="i2">colours of tulips, i. 386;</p> + <p class="i2">uncertainty of inheritance, ii. <a href="#page18">18</a>;</p> + <p class="i2">persistency of white flowers, ii. <a href="#page20">20</a>;</p> + <p class="i2">peloric flowers of <i>Linaria</i>, ii. <a href="#page58">58</a>;</p> + <p class="i2">tendency of striped flowers to uniformity of colour, ii. <a href="#page70">70</a>;</p> + <p class="i2">non-intercrossing of certain allied plants, ii. <a href="#page91">91</a>;</p> + <p class="i2">sterility of <i>Primulæ</i> with coloured calyces, ii. <a href="#page166">166</a>;</p> + <p class="i2">on fertile proliferous flowers, <i>ibid.</i>;</p> + <p class="i2">on the Irish yew, ii. <a href="#page241">241</a>;</p> + <p class="i2">differences in the <i>Camellia</i>, ii. <a href="#page251">251</a>;</p> + <p class="i2">effect of soil on the variegated strawberry, ii. <a href="#page274">274</a>;</p> + <p class="i2">correlated variability in plants, ii. <a href="#page330">330</a>.</p> + <p><i>Verruca</i>, ii. <a href="#page53">53</a>, <a href="#page400">400</a>.</p> + <p><span class="sc">Vertebræ</span>, characters of, in rabbits, i. 120-122;</p> + <p class="i2">in ducks, i. 283-284;</p> + <p class="i2">number and variations of, in pigeons, i. 165-166;</p> + <p class="i2">number and characters of, in fowls, i. 266-268;</p> + <p class="i2">variability of number of, in the pig, i. 74.</p> + <p><span class="sc">Vertuch</span>, see Putsche.</p> + <p>"<span class="sc">Verugas</span>," ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Vespucius</span>, early cultivation in Brazil, i. 311.</p> + <p><span class="sc">Vibert's</span> experiments on the cultivation of the vine from seed, i. 332.</p> + <p><i>Viburnum opulus</i>, ii. <a href="#page185">185</a>, <a href="#page316">316</a>.</p> + <p><i>Vicia sativa</i>, leaflet converted into a tendril in, ii. <a href="#page392">392</a>.</p> + <p><span class="sc">Vicunas</span>, selection of, ii. <a href="#page207">207</a>.</p> + <p><span class="sc">Villosity</span> of plants, influenced by dryness, ii. <a href="#page277">277</a>.</p> + <p><span class="sc">Vilmorin</span>, cultivation of the wild carrot, i. 326, ii. <a href="#page217">217</a>;</p> + <p class="i2">colours of tulips, i. 386;</p> + <p class="i2">uncertainty of inheritance in balsams and roses, ii. <a href="#page18">18</a>;</p> + <p class="i2">experiments with dwarf varieties of <i>Saponaria calabrica</i> and <i>Tagetes signata</i>, ii. <a href="#page20">20</a>;</p> + <p class="i2">reversion of flowers by stripes and blotches, ii. <a href="#page37">37</a>;</p> + <p class="i2">on variability, ii. <a href="#page262">262</a>.</p> + <p><i>Vinca minor</i>, sterility in, ii. <a href="#page170">170</a>.</p> + <p><span class="sc">Vine</span>, i. 332-334;</p> + <p class="i2">parsley-leaved, reversion of, i. 382;</p> + <p class="i2">graft-hybrid produced by inosculation in the, i. 395;</p> + <p class="i2">disease of, influenced by colour of grapes, ii. <a href="#page228">228</a>;</p> + <p class="i2">influence of climate, &c., on varieties of the, ii. <a href="#page278">278</a>;</p> + <p class="i2">diminished extent of cultivation of the, ii. <a href="#page308">308</a>;</p> + <p class="i2">acclimatisation of the, in the West Indies, ii. <a href="#page313">313</a>.</p> + <p><i>Viola</i>, species of, i. 368.</p> + <p><i>Viola lutea</i>, different coloured flowers in, i. 408.</p> + <p><i>Viola tricolor</i>, reversion in, ii. <a href="#page31">31</a>, <a href="#page47">47</a>.</p> + <p><span class="sc">Virchow</span>, Prof., blindness occurring in the offspring of consanguineous marriages, ii. <a href="#page143">143</a>;</p> + <p class="i2">on the growth of bones, ii. <a href="#page294">294</a>, <a href="#page381">381</a>;</p> + <p class="i2">on cellular prolification, ii. <a href="#page295">295</a>;</p> + <p class="i2">independence of the elements of the body, ii. <a href="#page369">369</a>;</p> + <p class="i2">on the cell-theory, ii. <a href="#page370">370</a>;</p> + <p class="i2">presence of hairs and teeth in ovarian tumours, ii. <a href="#page370">370</a>;</p> + <p class="i2">of hairs in the brain, ii. <a href="#page391">391</a>;</p> + <p class="i2">special affinities of the tissues, ii. <a href="#page380">380</a>;</p> + <p class="i2">origin of polypoid excrescences and tumours, ii. <a href="#page381">381</a>.</p> + <p><span class="sc">Virgil</span> on the selection of seed-corn, i. 318, ii. <a href="#page203">203</a>;</p> + <p class="i2">of cattle and sheep, ii. <a href="#page202">202</a>.</p> + <p><span class="sc">Virginian</span> islands, ponies of, i. 52.</p> + <p><i>Virgularia</i>, ii. <a href="#page378">378</a>.</p> + <p><span class="sc">Vision</span>, hereditary peculiarities of, ii. <a href="#page8">8</a>-<a href="#page9">9</a>;</p> +<!-- Page 484 --><span class="pagenum"><a name="page484"></a>{484}</span> + <p class="i2">in amphibious animals, ii. <a href="#page223">223</a>;</p> + <p class="i2">varieties of, ii. <a href="#page300">300</a>;</p> + <p class="i2">affections of organs of, correlated with other peculiarities, ii. <a href="#page328">328</a>.</p> + <p><i>Vitis vinifera</i>, i. 332-334, 375.</p> + <p><i>Viverra</i>, sterility of species of, in captivity, ii. <a href="#page151">151</a>.</p> + <p><span class="sc">Vogel</span>, varieties of the date palm, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Vogt</span>, on the indications of stripes on black kittens, ii. <a href="#page55">55</a>.</p> + <p><span class="sc">Voice</span>, differences of, in fowls, i. 259;</p> + <p class="i2">peculiarities of, in ducks, i. 281;</p> + <p class="i2">inheritance of peculiarities of, ii. <a href="#page6">6</a>.</p> + <p><span class="sc">Volz</span>, on the history of the dog, i. 16;</p> + <p class="i2">ancient history of the fowl, i. 246;</p> + <p class="i2">domestic ducks unknown to Aristotle, i. 277;</p> + <p class="i2">Indian cattle sent to Macedonia by Alexander, ii. <a href="#page202">202</a>;</p> + <p class="i2">mention of mules in the Bible, ii. <a href="#page202">202</a>;</p> + <p class="i2">history of the increase of breeds, ii. <a href="#page244">244</a>.</p> + <p><span class="sc">Von Berg</span> on <i>Verbascum phœniceum</i>, ii. <a href="#page305">305</a>.</p> + <p><span class="sc">Voorhelm</span>, G., his knowledge of hyacinths, i. 371, ii. <a href="#page251">251</a>.</p> + <p><span class="sc">Vrolik</span>, Prof., on polydactylism, ii. <a href="#page12">12</a>;</p> + <p class="i2">on double monsters, ii. <a href="#page340">340</a>;</p> + <p class="i2">influence of the shape of the mother's pelvis on her child's head, ii. <a href="#page344">344</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Waders</span>, behaviour of, in confinement, ii. <a href="#page156">156</a>.</p> + <p><span class="sc">Wahlenberg</span>, on the propagation of Alpine plants by buds, runners, bulbs, &c., ii. <a href="#page169">169</a>.</p> + <p>"<span class="sc">Wahlverwandtschaft</span>" of Gärtner, ii. <a href="#page180">180</a>.</p> + <p><span class="sc">Wales</span>, white cattle of, in the 10th century, i. 85.</p> + <p><span class="sc">Walker</span>, A., on intermarriage, i. 404;</p> + <p class="i2">on the inheritance of polydactylism, ii. <a href="#page13">13</a>.</p> + <p><span class="sc">Walker</span>, D., advantage of change of soil to wheat, ii. <a href="#page146">146</a>.</p> + <p><span class="sc">Wallace</span>, A. R., on a striped Javanese horse, i. 59;</p> + <p class="i2">on the conditions of life of feral animals, ii. <a href="#page32">32</a>;</p> + <p class="i2">artificial alteration of the plumage of birds, ii. <a href="#page280">280</a>;</p> + <p class="i2">on polymorphic butterflies, ii. <a href="#page399">399</a>-<a href="#page400">400</a>;</p> + <p class="i2">on reversion, ii. <a href="#page415">415</a>;</p> + <p class="i2">on the limit of change, ii. <a href="#page417">417</a>.</p> + <p><span class="sc">Wallace</span>, Dr., on the sterility of Sphingidæ hatched in autumn, ii. <a href="#page158">158</a>.</p> + <p><span class="sc">Wallachian</span> sheep, sexual peculiarities in the horns of, i. 96.</p> + <p><span class="sc">Wallflower</span>, bud-variation in, i. 382.</p> + <p><span class="sc">Wallich</span>, Dr., on <i>Thuja pendula</i> or <i>filiformis</i>, i. 362.</p> + <p><span class="sc">Walnuts</span>, i. 356-357;</p> + <p class="i2">thin-shelled, attacked by tomtits, ii. <a href="#page231">231</a>;</p> + <p class="i2">grafting of, ii. <a href="#page259">259</a>.</p> + <p><span class="sc">Walsh</span>, B. D., on galls, ii. <a href="#page282">282</a>, <a href="#page283">283</a>;</p> + <p class="i2">his "Law of equable variability," ii. <a href="#page351">351</a>-<a href="#page352">352</a>.</p> + <p><span class="sc">Walther</span>, F. L., on the history of the dog, i. 16;</p> + <p class="i2">on the intercrossing of the zebu and ordinary cattle, i. 83.</p> + <p><span class="sc">Waring</span>, Mr., on individual sterility, ii. <a href="#page162">162</a>.</p> + <p><span class="sc">Wart</span> hog, i. 76.</p> + <p><span class="sc">Waterer</span>, Mr., spontaneous production of <i>Cytisus alpino-laburnum</i>, i. 390.</p> + <p><span class="sc">Water</span> melon, i. 357.</p> + <p><span class="sc">Waterhouse</span>, G. R., on the winter-colouring of <i>Lepus variabilis</i>, i. 111.</p> + <p><span class="sc">Waterton</span>, C., production of tailless foals, i. 53;</p> + <p class="i2">on taming wild ducks, i. 278;</p> + <p class="i2">on the wildness of half-bred wild ducks, ii. <a href="#page45">45</a>;</p> + <p class="i2">assumption of male characters by a hen, ii. <a href="#page51">51</a>.</p> + <p><span class="sc">Watson</span>, H. C., on British wild fruit-trees, i. 312;</p> + <p class="i2">on the non-variation of weeds, i. 317;</p> + <p class="i2">origin of the plum, i. 345;</p> + <p class="i2">variation in <i>Pyrus malus</i>, i. 348;</p> + <p class="i2">on <i>Viola amœna</i> and <i>tricolor</i>, i. 368;</p> + <p class="i2">on reversion in Scotch kail, ii. <a href="#page32">32</a>;</p> + <p class="i2">fertility of <i>Draba sylvestris</i> when cultivated, ii. <a href="#page163">163</a>;</p> + <p class="i2">on generally distributed British plants, ii. <a href="#page285">285</a>.</p> + <p><span class="sc">Wattles</span>, rudimentary, in some fowls, ii. <a href="#page315">315</a>.</p> + <p><span class="sc">Watts</span>, Miss, on Sultan fowls, i. 228.</p> + <p><span class="sc">Webb</span>, James, interbreeding of sheep, ii. <a href="#page120">120</a>.</p> + <p><span class="sc">Weber</span>, effect of the shape of the mother's pelvis on her child's head, ii. <a href="#page344">344</a>.</p> + <p><span class="sc">Weeds</span>, supposed necessity for their modification, coincidently with cultivated plants, i. 317.</p> + <p><span class="sc">Weeping</span> varieties of trees, i. 361.</p> + <p><span class="sc">Weeping</span> habit of trees, capricious inheritance of, ii. <a href="#page18">18</a>-<a href="#page19">19</a>.</p> + <p><span class="sc">Weevil</span>, injury done to stone-fruit by, in North America, ii. <a href="#page231">231</a>.</p> + <p><span class="sc">Welsh</span> cattle, descended from <i>Bos longifrons</i>, i. 81.</p> + <p><span class="sc">West</span> Indies, feral pigs of, i. 77;</p> + <p class="i2">effect of climate of, upon sheep, i. 98.</p> + <p><span class="sc">Western</span>, Lord, change effected by, in the sheep, ii. <a href="#page198">198</a>.</p> + <p><span class="sc">Westphalia</span>, striped young pigs in, i. 76.</p> + <p><span class="sc">Westwood</span>, J. O., on peloric flowers of <i>Calceolaria</i>, ii. <a href="#page346">346</a>.</p> + <p><span class="sc">Whately</span>, Archbishop, on grafting early and late thorns, i. 363.</p> + <p><span class="sc">Wheat</span>, specific unity or diversity of, i. 312-313, 316-317;</p> + <p class="i2">Hasora, i. 313;</p> + <p class="i2">presence or absence of barbs in, i. 314;</p> + <p class="i2">Godron on variations in, <i>ibid.</i>;</p> + <p class="i2">varieties of, i. 314-315;</p> + <p class="i2">effects of soil and climate on, i. 316;</p> + <p class="i2">deterioration of, <i>ibid.</i>;</p> + <p class="i2">crossing of varieties of, <i>ibid.</i>, ii. <a href="#page96">96</a>, <a href="#page104">104</a>-<a href="#page105">105</a>, <a href="#page130">130</a>;</p> + <p class="i2">in the Swiss lake-dwellings, i. 317-319;</p> + <p class="i2">selection applied to, i. 318, ii. <a href="#page200">200</a>;</p> + <p class="i2">increased fertility of hybrids of, with <i>Ægilops</i>, ii. <a href="#page110">110</a>;</p> + <p class="i2">advantage of change of soil to, ii. <a href="#page146">146</a>;</p> +<!-- Page 485 --><span class="pagenum"><a name="page485"></a>{485}</span> + <p class="i2">differences of, in various parts of India, ii. <a href="#page165">165</a>;</p> + <p class="i2">continuous variation in, ii. <a href="#page200">200</a>;</p> + <p class="i2">red, hardiness of, ii. <a href="#page229">229</a>, <a href="#page336">336</a>;</p> + <p class="i2">Fenton, ii. <a href="#page232">232</a>;</p> + <p class="i2">natural selection in, ii. <a href="#page233">233</a>;</p> + <p class="i2">varieties of, found wild, ii. <a href="#page260">260</a>;</p> + <p class="i2">effects of change of climate on, ii. <a href="#page307">307</a>;</p> + <p class="i2">ancient variety of, ii. <a href="#page429">429</a>.</p> + <p><span class="sc">Whitby</span>, Mrs., on the markings of silkworms, i. 302;</p> + <p class="i2">on the silkmoth, i. 303.</p> + <p><span class="sc">White</span>, Mr., reproduction of supernumerary digits after amputation, ii. <a href="#page14">14</a>;</p> + <p class="i2">time occupied in the blending of crossed races, ii. <a href="#page87">87</a>.</p> + <p><span class="sc">White</span>, Gilbert, vegetable diet of dogs, ii. <a href="#page303">303</a>.</p> + <p><span class="sc">White</span> and white-spotted animals, liability of, to disease, ii. <a href="#page336">336</a>-<a href="#page337">337</a>.</p> + <p><span class="sc">White</span> flowers, most truly reproduced by seed, ii. <a href="#page20">20</a>.</p> + <p><span class="sc">Wichura</span>, Max, on hybrid willows, ii. <a href="#page50">50</a>, <a href="#page131">131</a>, <a href="#page267">267</a>;</p> + <p class="i2">analogy between the pollen of old-cultivated plants, and of hybrids, ii. <a href="#page268">268</a>.</p> + <p><span class="sc">Wicking</span>, Mr., inheritance of the primary characters of <i>Columba livia</i> in cross-bred pigeons, i. 201;</p> + <p class="i2">production of a white head in almond tumblers, ii. <a href="#page199">199</a>.</p> + <p><span class="sc">Wicksted</span>, Mr., on cases of individual sterility, ii. <a href="#page162">162</a>.</p> + <p><span class="sc">Wiegmann</span>, spontaneous crossing of blue and white peas, i. 397;</p> + <p class="i2">crossing of varieties of cabbage, ii. <a href="#page130">130</a>;</p> + <p class="i2">on contabescence, ii. <a href="#page165">165</a>.</p> + <p><span class="sc">Wight</span>, Dr., sexual sterility of plants propagated by buds, &c., ii. <a href="#page169">169</a>.</p> + <p><span class="sc">Wilde</span>, Sir W. R., occurrence of <i>Bos frontosus</i> and <i>longifrons</i> in Irish crannoges, i. 81;</p> + <p class="i2">attention paid to breeds of animals by the ancient Irish, ii. <a href="#page203">203</a>.</p> + <p><span class="sc">Wildman</span>, on the dahlia, ii. <a href="#page216">216</a>, <a href="#page273">273</a>.</p> + <p><span class="sc">Wildness</span> of the progeny of crossed tame animals, ii. <a href="#page44">44</a>-<a href="#page46">46</a>.</p> + <p><span class="sc">Wilkes</span>, Capt., on the taming of pigeons among the Polynesians, ii. <a href="#page161">161</a>.</p> + <p><span class="sc">Wilkinson</span>, J., on crossed cattle, ii. <a href="#page104">104</a>.</p> + <p><span class="sc">Williams</span>, Mr., change of plumage in a Hamburgh hen, i. 258.</p> + <p><span class="sc">Williams</span>, Mr., intercrossing of strawberries, i. 352.</p> + <p><span class="sc">Williamson</span>, Capt., degeneration of dogs in India, i. 37;</p> + <p class="i2">on small Indian asses, i. 62.</p> + <p><span class="sc">Williamson</span>, Rev. W., doubling of <i>Anemone coronaria</i> by selection, ii. <a href="#page200">200</a>.</p> + <p><span class="sc">Willows</span>, weeping, i. 361;</p> + <p class="i2">reversion of spiral-leaved weeping, i. 383;</p> + <p class="i2">hybrids of, ii. <a href="#page267">267</a>;</p> + <p class="i2">galls of, ii. <a href="#page282">282</a>-<a href="#page283">283</a>.</p> + <p><span class="sc">Willoughby</span>, F., notice of spot pigeons, i. 156;</p> + <p class="i2">on a fantail pigeon, i. 208;</p> + <p class="i2">on tumbler pigeons, i. 209;</p> + <p class="i2">on the turbit, i. 209;</p> + <p class="i2">on the barb and carrier pigeons, i. 211;</p> + <p class="i2">on the hook-billed duck, i. 277.</p> + <p><span class="sc">Wilmot</span>, Mr., on a crested white Turkey cock, i. 293;</p> + <p class="i2">reversion of sheep in colour, ii. <a href="#page30">30</a>.</p> + <p><span class="sc">Wilson</span>, B. O., fertility of hybrids of humped and ordinary cattle in Tasmania, i. 83.</p> + <p><span class="sc">Wilson</span>, Dr., prepotency of the Manx over the common cat, ii. <a href="#page66">66</a>.</p> + <p><span class="sc">Wilson</span>, James, origin of dogs, i. 16.</p> + <p><span class="sc">Wilson</span>, Mr., on prepotency of transmission in sheep, ii. <a href="#page69">69</a>;</p> + <p class="i2">on the breeding of bulls, ii. <a href="#page196">196</a>.</p> + <p><span class="sc">Wings</span>, proportionate length of, in different breeds of pigeons, i. 175-176;</p> + <p class="i2">of fowls, effects of disuse on, i. 270-272;</p> + <p class="i2">characters and variations of, in ducks, i. 284-286;</p> + <p class="i2">diminution of, in birds of small islands, i. 286-287.</p> + <p><span class="sc">Wing-feathers</span>, number of, in pigeons, i. 159;</p> + <p class="i2">variability of, in fowls, i. 258.</p> + <p><span class="sc">Wolf</span>, recent existence of, in Ireland, i. 16;</p> + <p class="i2">barking of young, i. 27;</p> + <p class="i2">hybrids of, with the dog, i. 32.</p> + <p><span class="sc">Wolf-dog</span>, black, of Florida, i. 22.</p> + <p><span class="sc">Wolves</span>, North American, their resemblance to dogs of the same region, i. 21-22;</p> + <p class="i2">burrowing of, i. 27.</p> + <p><span class="sc">Woodbury</span>, Mr., crossing of the Ligurian and common hive bees, i. 299, ii. <a href="#page126">126</a>;</p> + <p class="i2">variability of bees, i. 298.</p> + <p><span class="sc">Woodward</span>, S. P., on Arctic Mollusca, ii. <a href="#page256">256</a>.</p> + <p><span class="sc">Wood</span>, Willoughby, on Mr. Bates' cattle, ii. <a href="#page118">118</a>.</p> + <p><span class="sc">Wooler</span>, W. A., on the young of the Himalayan rabbit, i. 109;</p> + <p class="i2">persistency of the coloured calyx in a crossed Polyanthus, i. 365.</p> + <p><span class="sc">Worrara</span> poison, ii. <a href="#page380">380</a>.</p> + <p><span class="sc">Wounds</span>, healing of, ii. <a href="#page294">294</a>.</p> + <p><span class="sc">Wright</span>, J., production of crippled calves by shorthorned cattle, ii. <a href="#page118">118</a>;</p> + <p class="i2">on selection in cattle, ii. <a href="#page194">194</a>;</p> + <p class="i2">effect of close interbreeding on pigs, ii. <a href="#page121">121</a>-<a href="#page122">122</a>;</p> + <p class="i2">deterioration of game cocks by close interbreeding, ii. <a href="#page124">124</a>.</p> + <p><span class="sc">Wright</span>, Strethill, on the development of the hydroida, ii. <a href="#page368">368</a>.</p> + <p><span class="sc">Wyman</span>, Dr., on Niata cattle, and on a similar malformation in the codfish, i. 89;</p> + <p class="i2">on Virginian pigs, ii. <a href="#page227">227</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Xenophon</span>, on the colours of hunting dogs, ii. <a href="#page209">209</a>.</p> + <p><span class="sc">Ximenes</span>, Cardinal, regulations for the selection of rams, ii. <a href="#page204">204</a>.</p> + </div> + + <div class="stanza"> + <p>"<span class="sc">Yahoo</span>," the name of the pigeon in Persia, i. 155.</p> + <p><span class="sc">Yaks</span>, domestication of, i. 82;</p> + <p class="i2">selection of white-tailed, ii. <a href="#page206">206</a>, <a href="#page209">209</a>.</p> +<!-- Page 486 --><span class="pagenum"><a name="page486"></a>{486}</span> + <p><span class="sc">Yam</span>, development of axillary bulbs in the, ii. <a href="#page169">169</a>.</p> + <p><span class="sc">Yarrell</span>, Mr., deficiency of teeth in hairless dogs, i. 34, ii. <a href="#page326">326</a>;</p> + <p class="i2">on ducks, i. 279, ii. <a href="#page262">262</a>;</p> + <p class="i2">characters of domestic goose, resembling those of <i>Anser albifrons</i>, i. 288;</p> + <p class="i2">whiteness of ganders, i. 288;</p> + <p class="i2">variations in goldfish, i. 296-297;</p> + <p class="i2">assumption of male plumage by the hen-pheasant, ii. <a href="#page51">51</a>;</p> + <p class="i2">effect of castration upon the cock, ii. <a href="#page51">51</a>-<a href="#page52">52</a>;</p> + <p class="i2">breeding of the skylark in captivity, ii. <a href="#page154">154</a>;</p> + <p class="i2">plumage of the male linnet in confinement, ii. <a href="#page158">158</a>;</p> + <p class="i2">on the dingo, ii. <a href="#page263">263</a>.</p> + <p><span class="sc">Yellow</span> fever, in Mexico, ii. <a href="#page276">276</a>.</p> + <p><span class="sc">Yew</span>, fastigate, ii. <a href="#page241">241</a>.</p> + <p><span class="sc">Yew</span>, Irish, hardy in New York, ii. <a href="#page309">309</a>.</p> + <p><span class="sc">Yew</span>, weeping, i. 361;</p> + <p class="i2">propagation of, by seed, ii. <a href="#page18">18</a>-<a href="#page19">19</a>.</p> + <p><span class="sc">Yolk</span>, variations of, in the eggs of ducks, i. 281.</p> + <p><span class="sc">Youatt</span>, Mr., history of the dog, i. 16-17;</p> + <p class="i2">variations of the pulse in breeds of dogs, i. 35;</p> + <p class="i2">liability to disease in dogs, i. 35, ii. <a href="#page227">227</a>;</p> + <p class="i2">inheritance of goître in dogs, ii. <a href="#page10">10</a>;</p> + <p class="i2">on the greyhound, i. 34, 41;</p> + <p class="i2">on King Charles' spaniels, i. 41;</p> + <p class="i2">on the setter, i. 41;</p> + <p class="i2">on breeds of horses, i. 49;</p> + <p class="i2">variation in the number of ribs in the horse, i. 50;</p> + <p class="i2">inheritance of diseases in the horse, ii. <a href="#page10">10</a>, <a href="#page11">11</a>;</p> + <p class="i2">introduction of Eastern blood into English horses, ii. <a href="#page212">212</a>-<a href="#page213">213</a>;</p> + <p class="i2">on white Welsh cattle, i. 85, ii. <a href="#page209">209</a>;</p> + <p class="i2">improvement of British breeds of cattle, i. 93;</p> + <p class="i2">rudiments of horns in young hornless cattle, ii. <a href="#page55">55</a>, <a href="#page315">315</a>;</p> + <p class="i2">on crossed cattle, ii. <a href="#page104">104</a>, <a href="#page119">119</a>;</p> + <p class="i2">on Bakewell's long-horned cattle, ii. <a href="#page118">118</a>;</p> + <p class="i2">selection of qualities in cattle, ii. <a href="#page196">196</a>;</p> + <p class="i2">degeneration of cattle by neglect, ii. <a href="#page239">239</a>;</p> + <p class="i2">on the skull in hornless cattle, ii. <a href="#page333">333</a>;</p> + <p class="i2">disease of white parts of cattle, ii. <a href="#page337">337</a>;</p> + <p class="i2">displacement of long-horned by short-horned cattle, ii. <a href="#page426">426</a>;</p> + <p class="i2">on Angola sheep, i. 95;</p> + <p class="i2">on the fleece of sheep, i. 99;</p> + <p class="i2">correlation of horns and fleece in sheep, i. 95;</p> + <p class="i2">adaptation of breeds of sheep to climate and pasture, i. 96;</p> + <p class="i2">horns of Wallachian sheep, i. 96;</p> + <p class="i2">exotic sheep in the Zoological Gardens, i. 96-97, ii. <a href="#page305">305</a>;</p> + <p class="i2">occurrence of horns in hornless breeds of sheep, ii. <a href="#page30">30</a>;</p> + <p class="i2">on the colour of sheep, ii. <a href="#page30">30</a>;</p> + <p class="i2">on interbreeding sheep, ii. <a href="#page120">120</a>;</p> + <p class="i2">on Merino rams in Germany, ii. <a href="#page196">196</a>;</p> + <p class="i2">effect of unconscious selection on sheep, ii. <a href="#page213">213</a>;</p> + <p class="i2">reversion of Leicester sheep on the Lammermuir Hills, ii. <a href="#page224">224</a>;</p> + <p class="i2">on many-horned sheep, ii. <a href="#page326">326</a>;</p> + <p class="i2">reduction of bone in sheep, ii. <a href="#page242">242</a>;</p> + <p class="i2">persistency of character in breeds of animals in mountainous countries, ii. <a href="#page64">64</a>;</p> + <p class="i2">on interbreeding, ii. <a href="#page116">116</a>;</p> + <p class="i2">on the power of selection, ii. <a href="#page194">194</a>-<a href="#page195">195</a>;</p> + <p class="i2">slowness of production of breeds, ii. <a href="#page244">244</a>;</p> + <p class="i2">passages in the Bible relating to the breeding of animals, ii. <a href="#page201">201</a>-<a href="#page202">202</a>.</p> + <p><span class="sc">Young</span>, J., on the Belgian rabbit, i. 106.</p> + <p><span class="sc">Yule</span>, Capt., on a Burmese hairy family, ii. <a href="#page77">77</a>, <a href="#page327">327</a>.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Zambesi</span>, striped young pigs on the, i. 77.</p> + <p><span class="sc">Zambos</span>, character of the, ii. <a href="#page47">47</a>.</p> + <p><span class="sc">Zano</span>, J. G., introduction of rabbits into Porto Santo by, i. 112.</p> + <p><i>Zea Mays</i>, i. 320.</p> + <p><span class="sc">Zebu</span>, i. 79;</p> + <p class="i2">domestication of the, i. 82;</p> + <p class="i2">fertile crossing of, with European cattle, i. 83, ii. <a href="#page110">110</a>.</p> + <p><span class="sc">Zebra</span>, hybrids of, with the ass and mare, ii. <a href="#page42">42</a>.</p> + <p><i>Zephyranthes candida</i>, ii. <a href="#page164">164</a>.</p> + <p><i>Zinnia</i>, cultivation of, ii. <a href="#page261">261</a>.</p> + <p><span class="sc">Zollinger</span> on Malayan penguin ducks, i. 280.</p> + <p><span class="sc">Zoospore</span>, division of, in Algæ, ii. <a href="#page378">378</a>.</p> + <p>"<span class="sc">Zopf-Taube</span>," i. 154.</p> + </div> + </div> + +<p class="cenhead">THE END.</p> + +<p class="cenhead"><span class="scac">LONDON: PRINTED BY W. CLOWES AND SONS, DUKE STREET, STAMFORD STREET, AND CHARING CROSS.</span></p> + +<hr class="full" /> + +<h2>NOTES</h2> + +<div class="note"> + <p><a name="Nt_1" href="#NtA_1">[1]</a> 'Medical Notes and Reflections,' + 3rd edit., 1855, p. 267.</p> + + <p><a name="Nt_2" href="#NtA_2">[2]</a> Mr. Buckle, in his grand work on + 'Civilisation,' expresses doubts on the subject owing to the want of + statistics. <i>See</i> also Mr. Bowen, Professor of Moral Philosophy, in + 'Proc. American Acad. of Sciences,' vol. v. p. 102</p> + + <p><a name="Nt_3" href="#NtA_3">[3]</a> For greyhounds, <i>see</i> Low's + 'Domest. Animals of the British Islands,' 1845, p. 721. For game-fowls, + <i>see</i> 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 123. For pigs, + <i>see</i> Mr. Sidney's edit. of 'Youatt on the Pig,' 1860, pp. 11, + 22.</p> + + <p><a name="Nt_4" href="#NtA_4">[4]</a> 'The Stud Farm,' by Cecil, p. + 39.</p> + + <p><a name="Nt_5" href="#NtA_5">[5]</a> 'Philosophical Transactions,' + 1755, p. 23. I have seen only second-hand accounts of the two grandsons. + Mr. Sedgwick, in a paper to which I shall hereafter often refer, states + that <i>four</i> generations were affected, and in each the males + alone.</p> + + <p><a name="Nt_6" href="#NtA_6">[6]</a> Barbara Van Beck, figured, as I + am informed by the Rev. W. D. Fox, in Woodburn's 'Gallery of Rare + Portraits,' 1816, vol. ii.</p> + + <p><a name="Nt_7" href="#NtA_7">[7]</a> 'Proc. Zoolog. Soc.,' 1833, p. + 16</p> + + <p><a name="Nt_8" href="#NtA_8">[8]</a> Hofacker, 'Ueber die + Eigenschaften,' &c., 1828, s. 34. Report by Pariset in 'Comptes + Rendus,' 1847, p. 592.</p> + + <p><a name="Nt_9" href="#NtA_9">[9]</a> Hunter, as quoted in Harlan's + 'Med. Researches,' p. 530. Sir A. Carlisle, 'Phil. Transact.,' 1814, p. + 94.</p> + + <p><a name="Nt_10" href="#NtA_10">[10]</a> Girou de Buzareignues, 'De la + Génération,' p. 282.</p> + + <p><a name="Nt_11" href="#NtA_11">[11]</a> 'Macmillan's Magazine,' July + and August, 1865.</p> + + <p><a name="Nt_12" href="#NtA_12">[12]</a> The works which I have read + and found most useful are Dr. Prosper Lucas's great work, 'Traité de + l'Hérédité Naturelle,' 1847. Mr. W. Sedgwick, in 'British and Foreign + Medico-Chirurg. Review,' April and July, 1861, and April and July, 1863: + Dr. Garrod on Gout is quoted in these articles. Sir Henry Holland, + 'Medical Notes and Reflections,' 3rd edit., 1855. Piorry, 'De l'Hérédité + dans les Maladies,' 1840. Adams, 'A Philosophical Treatise on Hereditary + Peculiarities,' 2nd edit., 1815. Essay on 'Hereditary Diseases,' by Dr. + J. Steinan, 1843. <i>See</i> Paget, in 'Medical Times,' 1857, p. 192, on + the Inheritance of Cancer; Dr. Gould, in 'Proc. of American Acad. of + Sciences,' Nov. 8, 1853, gives a curious case of hereditary bleeding in + four generations. Harlan, 'Medical Researches,' p. 593.</p> + + <p><a name="Nt_13" href="#NtA_13">[13]</a> Marshall, quoted by Youatt in + his work on Cattle, p. 284.</p> + + <p><a name="Nt_14" href="#NtA_14">[14]</a> 'Philosoph. Transact.,' 1814, + p. 94.</p> + + <p><a name="Nt_15" href="#NtA_15">[15]</a> 'Medical Notes and + Reflections,' 3rd edit., p. 33.</p> + + <p><a name="Nt_16" href="#NtA_16">[16]</a> This affection, as I hear from + Mr. Bowman, has been ably described and spoken of as hereditary by Dr. + Dondera, of Utrecht, whose work was published in English by the Sydenham + Society in 1864.</p> + + <p><a name="Nt_17" href="#NtA_17">[17]</a> Quoted by Mr. Herbert Spencer, + 'Principles of Biology,' vol. i. p. 244.</p> + + <p><a name="Nt_18" href="#NtA_18">[18]</a> 'British and Foreign + Medico-Chirurg. Review, 'April, 1861, p. 482-6; 'l'Héréd. Nat.,' tom. i. + pp. 391-408.</p> + + <p><a name="Nt_19" href="#NtA_19">[19]</a> Dr. Osborne, Pres. of Royal + College of Phys. in Ireland, published this case in the 'Dublin Medical + Journal' for 1835.</p> + + <p><a name="Nt_20" href="#NtA_20">[20]</a> These various statements are + taken from the following works and papers:—Youatt on 'The Horse,' + pp. 35, 220. Lawrence, 'The Horse,' p. 30. Karkeek, in an excellent paper + in 'Gard. Chronicle,' 1853, p. 92. Mr. Burke, in 'Journal of R. Agricul. + Soc. of England,' vol. v. p. 511. 'Encyclop. of Rural Sports,' p. 279. + Girou de Buzareignues, 'Philosoph. Phys.,' p. 215. <i>See</i> following + papers in 'The Veterinary:' Roberts, in vol. ii. p. 144; M. Marrimpoey, + vol. ii. p. 387; Mr. Karkeek, vol. iv. p. 5; Youatt on Goître in Dogs, + vol. v. p. 483; Youatt, in vol. vi. pp. 66, 348, 412; M. Bernard, vol. + xi. p. 539; Dr. Samesreuther, on Cattle, in vol. xii. p. 181; Percivall, + in vol. xiii. p. 47. With respect to blindness in horses, <i>see</i> also + a whole row of authorities in Dr. P. Lucas's great work, tom. i. p. 399. + Mr. Baker, in 'The Veterinary,' vol. xiii. p. 721, gives a strong case of + hereditary imperfect vision and of jibbing.</p> + + <p><a name="Nt_21" href="#NtA_21">[21]</a> Knight on 'The Culture of the + Apple and Pear,' p. 31. Lindley's 'Horticulture,' p. 180.</p> + + <p><a name="Nt_22" href="#NtA_22">[22]</a> These statements are taken + from the following works in order:—Youatt on 'The Horse,' p. 48; + Mr. Darvill, in 'The Veterinary,' vol. viii. p. 50. With respect to + Robson, <i>see</i> 'The Veterinary,' vol. iii. p. 580; Mr. Lawrence on + 'The Horse,' 1829, p. 9; 'The Stud Farm,' by Cecil, 1851; Baron Cameronn, + quoted in 'The Veterinary,' vol x. p. 500.</p> + + <p><a name="Nt_23" href="#NtA_23">[23]</a> 'Recreations in Agriculture + and Nat. Hist.,' vol. i. p. 68.</p> + + <p><a name="Nt_24" href="#NtA_24">[24]</a> 'Ueber die Eigenschaften,' + &c., 1828, s. 107.</p> + + <p><a name="Nt_25" href="#NtA_25">[25]</a> Bronn's 'Geschichte der + Natur,' band ii. s. 132.</p> + + <p><a name="Nt_26" href="#NtA_26">[26]</a> Vrolik has discussed this + point at full length in a work published in Dutch, from which Mr. Paget + has kindly translated for me passages. <i>See</i>, also, Isidore Geoffroy + St. Hilaire's 'Hist. des Anomalies,' 1832, tom. i. p. 684.</p> + + <p><a name="Nt_27" href="#NtA_27">[27]</a> 'Edinburgh New Phil. Journal,' + July, 1863.</p> + + <p><a name="Nt_28" href="#NtA_28">[28]</a> Some great anatomists, as + Cuvier and Meckel, believe that the tubercle one side of the hinder foot + of the tailless Batrachians represents a sixth digit. Certainly, when the + hinder foot of a toad, as soon as it first sprouts from the tadpole, is + dissected, the partially ossified cartilage of this tubercle resembles + under the microscope, in a remarkable manner, a digit. But the highest + authority on such subjects, Gegenbaur (Untersuchung. zur vergleich. anat. + der Wirbelthiere: Carpus et Tarsus, 1864, s. 63), concludes that this + resemblance is not real, only superficial.</p> + + <p><a name="Nt_29" href="#NtA_29">[29]</a> For these several statements, + <i>see</i> Dr. Struthers, in work cited, especially on intermissions in + the line of descent. Prof. Huxley, 'Lectures on our Knowledge of Organic + Nature,' 1863, p. 97. With respect to inheritance, <i>see</i> Dr. Prosper + Lucas, 'L'Hérédité Nat.,' tom. i. p. 325. Isid. Geoffroy, 'Anom.,' tom. + i. p. 701. Sir A. Carlisle, in 'Phil. Transact.,' 1814, p. 94. A. Walker, + on 'Intermarriage,' 1838, p. 140, gives a case of five generations; as + does Mr. Sedgwick, in 'Brit. and Foreign Medico-Chirurg. Review,' April, + 1863, p. 462. On the inheritance of other anomalies in the extremities, + <i>see</i> Dr. H. Dobell, in vol. xlvi. of 'Medico-Chirurg. + Transactions,' 1863; also Mr. Sedgwick, in op. cit., April, 1863, p. 460. + With respect to additional digits in the negro, <i>see</i> Prichard, + 'Physical History of Mankind.' Dr. Dieffenbach ('Journ. Royal Geograph. + Soc.,' 1841, p. 208) says this anomaly is not uncommon with the + Polynesians of the Chatham Islands.</p> + + <p><a name="Nt_30" href="#NtA_30">[30]</a> 'The Poultry Chronicle,' 1854, + p. 559.</p> + + <p><a name="Nt_31" href="#NtA_31">[31]</a> The statements in this + paragraph are taken from Isidore Geoffroy St. Hilaire, 'Hist. des + Anomalies,' tom. i. pp. 688-693.</p> + + <p><a name="Nt_32" href="#NtA_32">[32]</a> As quoted by Carpenter, + 'Princ. of Comp. Physiology,' 1854, p. 480.</p> + + <p><a name="Nt_33" href="#NtA_33">[33]</a> Müller's 'Phys.,' Eng. + translat., vol. i. 1838, p. 407. A thrush, however, was exhibited before + the British Association at Hull, in 1853, which had lost its tarsus, and + this member, it was asserted, had been thrice reproduced: I presume it + was lost each time by disease.</p> + + <p><a name="Nt_34" href="#NtA_34">[34]</a> 'Monthly Journal of Medical + Science,' Edinburgh, 1848, new series, vol. ii. p. 890.</p> + + <p><a name="Nt_35" href="#NtA_35">[35]</a> 'An Essay on Animal + Reproduction,' trans. by Dr. Maty, 1769, p. 79.</p> + + <p><a name="Nt_36" href="#NtA_36">[36]</a> Bonnet, 'Œuvres d'Hist. + Nat.,' tom. v., part i., 4to. edit., 1781, pp. 343, 350, 353.</p> + + <p><a name="Nt_37" href="#NtA_37">[37]</a> So with insects, the larvæ + reproduce lost limbs, but, except in one order, the mature insect has no + such power. But the Myriapoda, which apparently represent the larvæ of + true insects, have, as Newport has shown, this power until their last + moult. <i>See</i> an excellent discussion on this whole subject by Dr. + Carpenter in his 'Princ. Comp. Phys.,' 1854, p. 479.</p> + + <p><a name="Nt_38" href="#NtA_38">[38]</a> Dr. Günther, in Owen's + 'Anatomy of Vertebrates,' vol. i., 1866, p. 567. Spallanzani has made + similar observations.</p> + + <p><a name="Nt_39" href="#NtA_39">[39]</a> 'On the Anatomy of + Vertebrates,' 1866, p. 170: with respect to the pectoral fins of fishes, + pp. 166-168.</p> + + <p><a name="Nt_40" href="#NtA_40">[40]</a> 'Medical Notes and + Reflections,' 1839, pp. 24, 34. <i>See</i>, also, Dr. P. Lucas, 'l'Héréd. + Nat.,' tom. ii. p. 33.</p> + + <p><a name="Nt_41" href="#NtA_41">[41]</a> 'Du Danger des Mariages + Consanguins,' 2nd edit., 1862, p. 103.</p> + + <p><a name="Nt_42" href="#NtA_42">[42]</a> 'British and Foreign + Medico-Chirurg. Review,' July, 1863, pp. 183, 189.</p> + + <p><a name="Nt_43" href="#NtA_43">[43]</a> Verlot, 'La Production des + Variétés,' 1865, p. 32.</p> + + <p><a name="Nt_44" href="#NtA_44">[44]</a> Loudon's 'Gard. Mag.,' vol. + xii., 1836, p. 368.</p> + + <p><a name="Nt_45" href="#NtA_45">[45]</a> Verlot, 'La Product. des + Variétés,' 1865, p. 94.</p> + + <p><a name="Nt_46" href="#NtA_46">[46]</a> Bronn's 'Geschichte der + Natur,' b. ii. s. 121.</p> + + <p><a name="Nt_47" href="#NtA_47">[47]</a> Rev. W. A. Leighton, 'Flora of + Shropshire,' p. 497; and Charlesworth's 'Mag. of Nat. Hist.,' vol. i, + 1837, p. 30.</p> + + <p><a name="Nt_48" href="#NtA_48">[48]</a> Verlot, op. cit., p. 93.</p> + + <p><a name="Nt_49" href="#NtA_49">[49]</a> For these several statements, + <i>see</i> Loudon's 'Gard. Magazine,' vol. x., 1834, pp. 408, 180; and + vol. ix., 1833, p. 597.</p> + + <p><a name="Nt_50" href="#NtA_50">[50]</a> These statements are taken + from Alph. De Candolle, 'Bot. Géograph.,' p. 1083.</p> + + <p><a name="Nt_51" href="#NtA_51">[51]</a> Verlot, op. cit., p. 38.</p> + + <p><a name="Nt_52" href="#NtA_52">[52]</a> Op. cit., p. 59.</p> + + <p><a name="Nt_53" href="#NtA_53">[53]</a> Alph. De Candolle, 'Géograph. + Bot.,' p. 1082.</p> + + <p><a name="Nt_54" href="#NtA_54">[54]</a> <i>See</i> 'Cottage Gardener,' + April 10, 1860, p. 18, and Sept. 10, 1861, p. 456; 'Gard. Chron.,' 1845, + p. 102.</p> + + <p><a name="Nt_55" href="#NtA_55">[55]</a> Darwin, in 'Journal of Proc. + Linn. Soc. Bot.,' 1862, p. 94.</p> + + <p><a name="Nt_56" href="#NtA_56">[56]</a> Hofacker, 'Ueber die + Eigenschaften,' &c., s. 10.</p> + + <p><a name="Nt_57" href="#NtA_57">[57]</a> Bechstein, 'Naturgesch. + Deutschlands,' b. iv. s. 462. Mr. Brent, a great breeder of canaries, + informs me that he believes that these statements are correct.</p> + + <p><a name="Nt_58" href="#NtA_58">[58]</a> 'The Poultry Book,' by W. B. + Tegetmeier, 1866, p. 245.</p> + + <p><a name="Nt_59" href="#NtA_59">[59]</a> 'British and Foreign + Med.-Chirurg. Review,' July, 1861, pp. 200-204. Mr. Sedgwick has given + such full details on this subject, with ample references, that I need + refer to no other authorities.</p> + + <p><a name="Nt_60" href="#NtA_60">[60]</a> 'De l'Espèce,' tom. ii., 1859, + p. 299.</p> + + <p><a name="Nt_61" href="#NtA_61">[61]</a> 'Philosoph. Magazine,' vol. + iv., 1799, p. 5.</p> + + <p><a name="Nt_62" href="#NtA_62">[62]</a> This last case is quoted by + Mr. Sedgwick in 'British and Foreign Medico-Chirurg. Review,' April, + 1861, p. 484. For Blumenbach, <i>see</i> above-cited paper. <i>See</i>, + also, Dr. P. Lucas, 'Traité de l'Héréd. Nat.,' tom. ii. p. 492. Also + 'Transact. Lin. Soc.,' vol. ix. p. 323. Some curious cases are given by + Mr. Baker in 'The Veterinary,' vol. xiii. p. 723. Another curious case is + given in the 'Annales des Scienc. Nat.,' 1st series, tom. xi. p. 324.</p> + + <p><a name="Nt_63" href="#NtA_63">[63]</a> 'Proc. Royal Soc.,' vol. x. p. + 297.</p> + + <p><a name="Nt_64" href="#NtA_64">[64]</a> Mr. Sproule, in 'British + Medical Journal,' April 18, 1863.</p> + + <p><a name="Nt_65" href="#NtA_65">[65]</a> Downing, 'Fruits of America,' + p. 5; Sageret, 'Pom. Phys.,' pp. 43, 72.</p> + + <p><a name="Nt_66" href="#NtA_66">[66]</a> Youatt on Sheep, pp. 20, 234. + The same fact of loose horns occasionally appearing in hornless breeds + has been observed in Germany: Bechstein, 'Naturgesch. Deutschlands,' b. + i. s. 362.</p> + + <p><a name="Nt_67" href="#NtA_67">[67]</a> Youatt on Cattle, pp. 155, + 174.</p> + + <p><a name="Nt_68" href="#NtA_68">[68]</a> Youatt on Sheep, 1838, pp. 17, + 145.</p> + + <p><a name="Nt_69" href="#NtA_69">[69]</a> I have been informed of this + fact through the Rev. W. D. Fox, on the excellent authority of Mr. + Wilmot: <i>see</i>, also, remarks on this subject in an original article + in the 'Quarterly Review,' 1849, p. 395.</p> + + <p><a name="Nt_70" href="#NtA_70">[70]</a> Youatt, pp. 19, 234.</p> + + <p><a name="Nt_71" href="#NtA_71">[71]</a> 'The Poultry Book,' by Mr. + Tegetmeier, 1866, p. 231.</p> + + <p><a name="Nt_72" href="#NtA_72">[72]</a> Loudon's 'Gard. Mag.,' vol. + x., 1834, p. 396: a nurseryman, with much experience on this subject, has + likewise assured me that this sometimes occurs.</p> + + <p><a name="Nt_73" href="#NtA_73">[73]</a> 'Gardener's Chron.,' 1855, p. + 777.</p> + + <p><a name="Nt_74" href="#NtA_74">[74]</a> Ibid., 1862, p. 721.</p> + + <p><a name="Nt_75" href="#NtA_75">[75]</a> <i>See</i> some excellent + remarks on this subject by Mr. Wallace, 'Journal Proc. Linn. Soc.,' 1858, + vol. iii. p. 60.</p> + + <p><a name="Nt_76" href="#NtA_76">[76]</a> Dureau de la Malle, in + 'Comptes Rendus,' tom. xli., 1855, p. 807. From the statements above + given, the author concludes that the wild pigs of Louisiana are not + descended from the European <i>Sus scrofa</i>.</p> + + <p><a name="Nt_77" href="#NtA_77">[77]</a> Capt. W. Allen, in his + 'Expedition to the Niger,' states that fowls have run wild on the island + of Annobon, and have become modified in form and voice. The account is so + meagre and vague that it did not appear to me worth copying; but I now + find that Dureau de la Malle ('Comptes Rendus,' tom. xli., 1855, p. 690) + advances this as a good instance of reversion to the primitive stock, and + as confirmatory of a still more vague statement in classical times by + Varro.</p> + + <p><a name="Nt_78" href="#NtA_78">[78]</a> 'Flora of Australia,' 1859, + Introduct., p. ix.</p> + + <p><a name="Nt_79" href="#NtA_79">[79]</a> 'De l'Espèce,' tom. ii. pp. + 54, 58, 60.</p> + + <p><a name="Nt_80" href="#NtA_80">[80]</a> Mr. Sedgwick gives many + instances in the 'British and Foreign Med.-Chirurg. Review,' April and + July, 1863, pp. 448, 188.</p> + + <p><a name="Nt_81" href="#NtA_81">[81]</a> In his edit. of 'Youatt on the + Pig,' 1860, p. 27.</p> + + <p><a name="Nt_82" href="#NtA_82">[82]</a> Dr. P. Lucas, 'Héréd. Nat.,' + tom. ii. pp. 314, 892: <i>see</i> a good practical article on this + subject in 'Gard. Chronicle,' 1856, p. 620. I could add a vast number of + references, but they would be superfluous.</p> + + <p><a name="Nt_83" href="#NtA_83">[83]</a> Kölreuter gives cases in his + 'Dritte Fortsetzung,' 1766, s. 53, 59; and in his well-known 'Memoirs on + Lavatera and Jalapa.' Gärtner, 'Bastarderzeugung,' s. 437, 441, &c. + Naudin, in his 'Recherches sur l'Hybridité, Nouvelles Archives du + Muséum,' tom. i. p. 25.</p> + + <p><a name="Nt_84" href="#NtA_84">[84]</a> Quoted by Mr. Sedgwick in + 'Med.-Chirurg. Review,' April, 1861, p. 485. Dr. H. Dobell, in + 'Med.-Chirurg. Transactions,' vol. xlvi., gives an analogous case, in + which, in a large family, fingers with thickened joints were transmitted + to several members during five generations; but when the blemish once + disappeared it never reappeared.</p> + + <p><a name="Nt_85" href="#NtA_85">[85]</a> Verlot, 'Des Variétés,' 1865, + p. 63.</p> + + <p><a name="Nt_86" href="#NtA_86">[86]</a> 'Nouvelles Archives du + Muséum,' tom. i. p. 25. Alex. Braun (in his 'Rejuvenescence,' Ray Soc., + 1853, p. 315) apparently holds a similar opinion.</p> + + <p><a name="Nt_87" href="#NtA_87">[87]</a> Mr. Teebay, in 'The Poultry + Book,' by Mr. Tegetmeier, 1866, p. 72.</p> + + <p><a name="Nt_88" href="#NtA_88">[88]</a> Quoted by Hofacker, 'Ueber die + Eigenschaften,' &c., s. 98.</p> + + <p><a name="Nt_89" href="#NtA_89">[89]</a> 'Essais Hist. Nat. du + Paraguay,' tom. ii. 1801, p. 372.</p> + + <p><a name="Nt_90" href="#NtA_90">[90]</a> These facts are given on the + high authority of Mr. Hewitt, in 'The Poultry Book,' by Mr. Tegetmeier, + 1866, p. 248.</p> + + <p><a name="Nt_91" href="#NtA_91">[91]</a> 'The Poultry Book,' by + Tegetmeier, 1866, p. 97.</p> + + <p><a name="Nt_92" href="#NtA_92">[92]</a> 'Gardener's Chron. and + Agricultural Gazette,' 1866, p. 528.</p> + + <p><a name="Nt_93" href="#NtA_93">[93]</a> Ibid., 1860, p. 343.</p> + + <p><a name="Nt_94" href="#NtA_94">[94]</a> Sclater, in 'Proc. Zoolog. + Soc.,' 1862, p. 163.</p> + + <p><a name="Nt_95" href="#NtA_95">[95]</a> 'History of the Horse,' p. + 212.</p> + + <p><a name="Nt_96" href="#NtA_96">[96]</a> 'Mém. présentés par divers + Savans à l'Acad. Royale,' tom. vi. 1835, p. 338.</p> + + <p><a name="Nt_97" href="#NtA_97">[97]</a> 'Letters from Alabama,' 1859, + p. 280.</p> + + <p><a name="Nt_98" href="#NtA_98">[98]</a> 'Hist. Nat. des Mammifères,' + 1820, tom. i.</p> + + <p><a name="Nt_99" href="#NtA_99">[99]</a> 'Philosoph. Transact.,' 1821, + p. 20.</p> + + <p><a name="Nt_100" href="#NtA_100">[100]</a> Sclater, in 'Proc. Zoolog. + Soc.,' 1862, p. 163: this species is the Ghor-Khur of N.W. India, and has + often been called the Hemionus of Pallas. <i>See</i>, also, Mr. Blyth's + excellent paper in 'Journ. of Asiatic Soc. of Bengal,' vol. xxviii., + 1860, p. 229.</p> + + <p><a name="Nt_101" href="#NtA_101">[101]</a> Another species of wild + ass, the true <i>A. hemionus</i> or <i>Kiang</i>, which ordinarily has no + shoulder-stripes, is said occasionally to have them; and these, as with + the horse and ass, are sometimes double: <i>see</i> Mr. Blyth, in the + paper just quoted, and in 'Indian Sporting Review,' 1856, p. 320; and + Col. Hamilton Smith, in 'Nat. Library, Horses,' p. 318; and 'Dict. Class. + d'Hist. Nat.,' tom. iii. p. 563.</p> + + <p><a name="Nt_102" href="#NtA_102">[102]</a> Figured in the 'Gleanings + from the Knowsley Menageries,' by Dr. J. E. Gray.</p> + + <p><a name="Nt_103" href="#NtA_103">[103]</a> Cases of both Spanish and + Polish hens sitting are given in the 'Poultry Chronicle,' 1855, vol. iii. + p. 477.</p> + + <p><a name="Nt_104" href="#NtA_104">[104]</a> 'The Poultry Book,' by Mr. + Tegetmeier, 1866, pp. 119, 163. The author, who remarks on the two + negatives ('Journ. of Hort.,' 1862, p. 325), states that two broods were + raised from a Spanish cock and Silver-pencilled Hamburgh hen, neither of + which are incubators, and no less than seven out of eight hens in these + two broods "showed a perfect obstinacy in sitting." The Rev. E. S. Dixon + ('Ornamental Poultry,' 1848, p. 200) says that chickens reared from a + cross between Golden and Black Polish fowls, are "good and steady birds + to sit." Mr. B. P. Brent informs me that he raised some good sitting hens + by crossing Pencilled Hamburgh and Polish breeds. A cross-bred bird from + a Spanish non-incubating cock and Cochin incubating hen is mentioned in + the 'Poultry Chronicle,' vol. iii. p. 13, as an "exemplary mother." On + the other hand, an exceptional case is given in the 'Cottage Gardener,' + 1860, p. 388, of a hen raised from a Spanish cock and black Polish hen + which did not incubate.</p> + + <p><a name="Nt_105" href="#NtA_105">[105]</a> 'The Poultry Book,' by + Tegetmeier, 1866, pp. 165, 167.</p> + + <p><a name="Nt_106" href="#NtA_106">[106]</a> 'Natural History Review,' + 1863, April, p. 277.</p> + + <p><a name="Nt_107" href="#NtA_107">[107]</a> 'Essays on Natural + History,' p. 197.</p> + + <p><a name="Nt_108" href="#NtA_108">[108]</a> As stated by Mr. Orton, in + his 'Physiology of Breeding,' p. 12.</p> + + <p><a name="Nt_109" href="#NtA_109">[109]</a> M. E. de Selys-Longchamps + refers ('Bulletin Acad. Roy. de Bruxelles,' tom. xii. No. 10) to more + than seven of these hybrids shot in Switzerland and France. M. Deby + asserts ('Zoologist,' vol. v., 1845-46, p. 1254) that several have been + shot in various parts of Belgium and Northern France. Audubon + ('Ornitholog. Biography,' vol. iii. p. 168), speaking of these hybrids, + says that, in North America, they "now and then wander off and become + quite wild."</p> + + <p><a name="Nt_110" href="#NtA_110">[110]</a> 'Journal of Researches,' + 1845, p. 71.</p> + + <p><a name="Nt_111" href="#NtA_111">[111]</a> 'Expedition to the + Zambesi,' 1865, pp. 25, 150.</p> + + <p><a name="Nt_112" href="#NtA_112">[112]</a> Dr. P. Broca, on 'Hybridity + in the Genus Homo,' Eng. translat., 1864, p. 39.</p> + + <p><a name="Nt_113" href="#NtA_113">[113]</a> 'Nouvelles Archives du + Muséum,' tom. i. p. 151.</p> + + <p><a name="Nt_114" href="#NtA_114">[114]</a> 'Bastarderzeugung,' s. 582, + 438, &c.</p> + + <p><a name="Nt_115" href="#NtA_115">[115]</a> 'Die Bastardbefruchtung ... + der Weiden,' 1865, s. 23. For Gärtner's remarks on this head, <i>see</i> + 'Bastarderzeugung,' s. 474, 582.</p> + + <p><a name="Nt_116" href="#NtA_116">[116]</a> Yarrell, 'Phil. Transact.,' + 1827, p. 268; Dr. Hamilton, in 'Proc. Zoolog. Soc.,' 1862, p. 23.</p> + + <p><a name="Nt_117" href="#NtA_117">[117]</a> 'Archiv. Skand. Beiträge + zur Naturgesch.,' viii. s. 397-413.</p> + + <p><a name="Nt_118" href="#NtA_118">[118]</a> In his 'Essays on Nat. + Hist.,' 1838. Mr. Hewitt gives analogous cases with hen-pheasants in + 'Journal of Horticulture,' July 12, 1864, p. 37. Isidore Geoffroy Saint + Hilaire, in his 'Essais de Zoolog. Gén.' (suites à Buffon, 1842, pp. + 496-513), has collected such cases in ten different kinds of birds. It + appears that Aristotle was well aware of the change in mental disposition + in old hens. The case of the female deer acquiring horns is given at p. + 513.</p> + + <p><a name="Nt_119" href="#NtA_119">[119]</a> 'Cottage Gardener,' 1860, + p. 379.</p> + + <p><a name="Nt_120" href="#NtA_120">[120]</a> 'Art de faire Eclorre,' + &c., 1749, tom. ii. p. 8.</p> + + <p><a name="Nt_121" href="#NtA_121">[121]</a> Sir H. Holland, 'Medical + Notes and Reflections,' 3rd edit., 1855, p. 31.</p> + + <p><a name="Nt_122" href="#NtA_122">[122]</a> Prof. Thomson on + Steenstrup's Views on the Obliquity of Flounders: 'Annals and Mag. of + Nat. Hist.,' May, 1865, p. 361.</p> + + <p><a name="Nt_123" href="#NtA_123">[123]</a> Dr. E. von Martens, in + 'Annals and Mag. of Nat. Hist.,' March, 1866, p. 209.</p> + + <p><a name="Nt_124" href="#NtA_124">[124]</a> Darwin, 'Balanidæ,' Ray + Soc., 1854, p. 499: <i>see</i> also the appended remarks on the + apparently capricious development of the thoracic limbs on the right and + left sides in the higher crustaceans.</p> + + <p><a name="Nt_125" href="#NtA_125">[125]</a> Mormodes ignea: Darwin, + 'Fertilization of Orchids,' 1862, p. 251.</p> + + <p><a name="Nt_126" href="#NtA_126">[126]</a> 'Journal of Horticulture,' + July, 1864, p. 38. I have had the opportunity of examining these + remarkable feathers through the kindness of Mr. Tegetmeier.</p> + + <p><a name="Nt_127" href="#NtA_127">[127]</a> 'The Poultry Book,' by Mr. + Tegetmeier, 1866, p. 241.</p> + + <p><a name="Nt_128" href="#NtA_128">[128]</a> Carl Vogt, 'Lectures on + Man,' Eng. translat., 1864, p. 411.</p> + + <p><a name="Nt_129" href="#NtA_129">[129]</a> On Cattle, p. 174.</p> + + <p><a name="Nt_130" href="#NtA_130">[130]</a> Isid. Geoffroy St. Hilaire, + 'Des Anomalies,' tom. iii. p. 353. With respect to the mammæ in women, + <i>see</i> tom. i. p. 710.</p> + + <p><a name="Nt_131" href="#NtA_131">[131]</a> 'Natural Hist. Review,' + April, 1863, p. 258. <i>See</i> also his Lecture, Royal Institution, + March 16, 1860. On same subject, <i>see</i> Moquin-Tandon, 'Eléments de + Tératologie,' 1841, pp. 184, 352.</p> + + <p><a name="Nt_132" href="#NtA_132">[132]</a> Verlot, 'Des Variétés,' + 1865, p. 89; Naudin, 'Nouvelles Archives du Muséum,' tom. i. p. 137.</p> + + <p><a name="Nt_133" href="#NtA_133">[133]</a> In his discussion on some + curious peloric calceolarias, quoted in 'Journal of Horticulture,' Feb. + 24, 1863, p. 152.</p> + + <p><a name="Nt_134" href="#NtA_134">[134]</a> For other cases of six + divisions in peloric flowers of the Labiatæ and Scrophulariaceæ, + <i>see</i> Moquin-Tandon, 'Tératologie,' p. 192.</p> + + <p><a name="Nt_135" href="#NtA_135">[135]</a> Moquin-Tandon, + 'Tératologie,' p. 186.</p> + + <p><a name="Nt_136" href="#NtA_136">[136]</a> <i>See</i> Youatt on + Cattle, pp. 92, 69, 78, 88, 163: also Youatt on Sheep, p. 325. Also Dr. + Lucas, 'L'Héréd. Nat.,' tom. ii. p. 310.</p> + + <p><a name="Nt_137" href="#NtA_137">[137]</a> 'Héréd. Nat.,' tom. ii. pp. + 112-120.</p> + + <p><a name="Nt_138" href="#NtA_138">[138]</a> Sir H. Holland, 'Chapters + on Mental Physiology,' 1852, p. 234.</p> + + <p><a name="Nt_139" href="#NtA_139">[139]</a> 'Gardener's Chronicle,' + 1860, p. 270.</p> + + <p><a name="Nt_140" href="#NtA_140">[140]</a> Mr. N. H. Smith, + Observations on Breeding, quoted in 'Encyclop. of Rural Sports,' p. + 278.</p> + + <p><a name="Nt_141" href="#NtA_141">[141]</a> Quoted by Bronn, + 'Geschichte der Natur,' b. ii. s. 170. <i>See</i> Sturm, 'Ueber Racen,' + 1825, s. 104-107. For the niata cattle, <i>see</i> my 'Journal of + Researches,' 1845, p. 146.</p> + + <p><a name="Nt_142" href="#NtA_142">[142]</a> Lucas, 'l'Hérédité Nat.,' + tom. ii. p. 112.</p> + + <p><a name="Nt_143" href="#NtA_143">[143]</a> Mr. Orton, 'Physiology of + Breeding,' 1855, p. 9.</p> + + <p><a name="Nt_144" href="#NtA_144">[144]</a> Boitard and Corbié, 'Les + Pigeons,' 1824, p. 224.</p> + + <p><a name="Nt_145" href="#NtA_145">[145]</a> 'Les Pigeons, pp. 168, + 198.</p> + + <p><a name="Nt_146" href="#NtA_146">[146]</a> 'Das Ganze,' &c., 1837, + s. 39.</p> + + <p><a name="Nt_147" href="#NtA_147">[147]</a> 'The Pigeon Book,' p. + 46.</p> + + <p><a name="Nt_148" href="#NtA_148">[148]</a> 'Physiology of Breeding,' + p.22; Mr. Hewitt, in 'The Poultry Book,' by Tegetmeier, 1866, p. 224.</p> + + <p><a name="Nt_149" href="#NtA_149">[149]</a> Boitard and Corbié, 'Les + Pigeons,' 1824, p. 226.</p> + + <p><a name="Nt_150" href="#NtA_150">[150]</a> 'Bastarderzeugung,' s. 256, + 290, &c. Naudin ('Nouvelles Archives du Muséum,' tom. i. p. 149) + gives a striking instance of prepotency in <i>Datura stramonium</i> when + crossed with two other species.</p> + + <p><a name="Nt_151" href="#NtA_151">[151]</a> Flourens, 'Longévité + Humaine,' p. 144, on crossed jackals. With respect to the difference + between the mule and the hinny, I am aware that this has generally been + attributed to the sire and dam transmitting their characters differently; + but Colin, who has given in his 'Traité Phys. Comp.,' tom. ii. pp. + 537-539, the fullest description which I have met with of these + reciprocal hybrids, is strongly of opinion that the ass preponderates in + both crosses, but in an unequal degree. This is likewise the conclusion + of Flourens, and of Bechstein in his 'Naturgeschichte Deutschlands,' b. + i. s. 294. The tail of the hinny is much more like that of the horse than + is the tail of the mule, and this is generally accounted for by the males + of both species transmitting with greater power this part of their + structure; but a compound hybrid which I saw in the Zoological Gardens, + from a mare by a hybrid ass-zebra, closely resembled its mother in its + tail.</p> + + <p><a name="Nt_152" href="#NtA_152">[152]</a> Mr. Hewitt, who has had + such great experience in raising these hybrids, says ('Poultry Book,' by + Mr. Tegetmeier, 1866, pp. 165-167) that in all, the head was destitute of + wattles, comb, and ear-lappets; and all closely resembled the pheasant in + the shape of the tail and general contour of the body. These hybrids were + raised from hens of several breeds by a cock-pheasant; but another + hybrid, described by Mr. Hewitt, was raised from a hen-pheasant by a + silver-laced Bantam cock, and this possessed a rudimental comb and + wattles.</p> + + <p><a name="Nt_153" href="#NtA_153">[153]</a> 'L'Héréd. Nat.,' tom. ii. + book ii. ch. i.</p> + + <p><a name="Nt_154" href="#NtA_154">[154]</a> 'Bastarderzeugung,' s. + 264-266. Naudin ('Nouvelles Archives du Muséum,' tom. i. p. 148) has + arrived at a similar conclusion.</p> + + <p><a name="Nt_155" href="#NtA_155">[155]</a> 'Cottage Gardener,' 1856, + pp. 101, 137.</p> + + <p><a name="Nt_156" href="#NtA_156">[156]</a> <i>See</i> some remarks on + this head with respect to sheep by Mr. Wilson, in 'Gardener's Chronicle,' + 1863, p. 15.</p> + + <p><a name="Nt_157" href="#NtA_157">[157]</a> Verlot, 'Des Variétés,' + 1865, p. 66.</p> + + <p><a name="Nt_158" href="#NtA_158">[158]</a> Moquin-Tandon, + 'Tératologie,' p. 191.</p> + + <p><a name="Nt_159" href="#NtA_159">[159]</a> 'Nouvelles Archives du + Muséum,' tom. i. p. 137.</p> + + <p><a name="Nt_160" href="#NtA_160">[160]</a> 'L'Héréd. Nat.,' tom. ii. + pp. 137-165. <i>See</i>, also, Mr. Sedgwick's four memoirs, immediately + to be referred to.</p> + + <p><a name="Nt_161" href="#NtA_161">[161]</a> On Sexual Limitation in + Hereditary Diseases, 'Brit. and For. Med.-Chirurg. Review,' April, 1861, + p. 477; July, p. 198; April, 1863, p. 44; and July, p. 159.</p> + + <p><a name="Nt_162" href="#NtA_162">[162]</a> W. Scrope, 'Art of Deer + Stalking,' p. 354.</p> + + <p><a name="Nt_163" href="#NtA_163">[163]</a> Boitard and Corbié, 'Les + Pigeons,' p. 173; Dr. F. Chapuis, 'Le Pigeon Voyageur Belge,' 1865, p. + 87.</p> + + <p><a name="Nt_164" href="#NtA_164">[164]</a> Prichard, 'Phys. Hist. of + Mankind,' 1851, vol. i. p. 349.</p> + + <p><a name="Nt_165" href="#NtA_165">[165]</a> 'Embassy to the Court of + Ava,' vol. i. p. 320. The third generation is described by Capt. Yule in + his 'Narrative of the Mission to the Court of Ava,' 1855, p. 94.</p> + + <p><a name="Nt_166" href="#NtA_166">[166]</a> 'Das Ganze der + Taubenzucht,' 1837, s. 21, tab. i., fig. 4; s. 24, tab. iv., fig. 2.</p> + + <p><a name="Nt_167" href="#NtA_167">[167]</a> Kidd's 'Treatise on the + Canary,' p. 18.</p> + + <p><a name="Nt_168" href="#NtA_168">[168]</a> Charlesworth, 'Mag. of Nat. + Hist.,' vol. i., 1837, p. 167.</p> + + <p><a name="Nt_169" href="#NtA_169">[169]</a> Dr. Prosper Lucas, 'Héréd. + Nat.,' tom. ii. p. 713.</p> + + <p><a name="Nt_170" href="#NtA_170">[170]</a> 'L'Héréd. dans les + Maladies,' 1840, p. 135. For Hunter, <i>see</i> Harlan's 'Med. + Researches,' p. 530.</p> + + <p><a name="Nt_171" href="#NtA_171">[171]</a> 'L'Héréd. Nat.,' tom. ii. + p. 850.</p> + + <p><a name="Nt_172" href="#NtA_172">[172]</a> Sedgwick, 'Brit. and For. + Med.-Chirurg. Review,' April 1861, p. 485. I have seen three accounts, + all taken from the same original authority (which I have not been able to + consult), and all differ in the details! but as they agree in the main + facts, I have ventured to quote this case.</p> + + <p><a name="Nt_173" href="#NtA_173">[173]</a> Prosper Lucas, 'Héréd. + Nat.,' tom. i. p. 400.</p> + + <p><a name="Nt_174" href="#NtA_174">[174]</a> Sedgwick, idem, July, 1861, + p. 202.</p> + + <p><a name="Nt_175" href="#NtA_175">[175]</a> Piorry, p. 109; Prosper + Lucas, tom. ii. p. 759.</p> + + <p><a name="Nt_176" href="#NtA_176">[176]</a> Prosper Lucas, tom. ii. p. + 748.</p> + + <p><a name="Nt_177" href="#NtA_177">[177]</a> Prosper Lucas, tom. ii. pp. + 678, 700, 702; Sedgwick, idem, April, 1863, p. 449, and July, 1863, p. + 162; Dr. J. Steinan, 'Essay on Hereditary Disease,' 1843, pp. 27, 34.</p> + + <p><a name="Nt_178" href="#NtA_178">[178]</a> These cases are given by + Mr. Sedgwick, on the authority of Dr. H. Stewart, in 'Med.-Chirurg. + Review,' April, 1863, pp. 449, 477.</p> + + <p><a name="Nt_179" href="#NtA_179">[179]</a> 'Héréd. Nat.,' tom. ii. p. + 852.</p> + + <p><a name="Nt_180" href="#NtA_180">[180]</a> Communications to the Board + of Agriculture, vol. i. p. 367.</p> + + <p><a name="Nt_181" href="#NtA_181">[181]</a> 'Review of Reports, North + of England,' 1808, p. 200.</p> + + <p><a name="Nt_182" href="#NtA_182">[182]</a> 'Säugethiere von Paraguay,' + 1830, s. 212.</p> + + <p><a name="Nt_183" href="#NtA_183">[183]</a> Rengger, 'Säugethiere,' + &c., s. 154.</p> + + <p><a name="Nt_184" href="#NtA_184">[184]</a> White, 'Regular Gradation + in Man,' p. 146.</p> + + <p><a name="Nt_185" href="#NtA_185">[185]</a> Dr. W. F. Edwards, in his + 'Charactères Physiolog. des Races Humaines,' p. 23, first called + attention to this subject, and ably discussed it.</p> + + <p><a name="Nt_186" href="#NtA_186">[186]</a> Rev. D. Tyerman, and + Bennett, 'Journal of Voyages,' 1821-1829, vol. i. p. 300.</p> + + <p><a name="Nt_187" href="#NtA_187">[187]</a> Mr. S. J. Salter, 'Journal + Linn. Soc.,' vol. vi., 1862, p. 71.</p> + + <p><a name="Nt_188" href="#NtA_188">[188]</a> Sturm, 'Ueber Racen, + &c.,' 1825, s. 107. Bronn, 'Geschichte der Natur.,' b. ii. s. 170, + gives a table of the proportions of blood after successive crosses. Dr. + P. Lucas, 'l'Hérédité Nat.,' tom. ii. p. 308.</p> + + <p><a name="Nt_189" href="#NtA_189">[189]</a> 'Bastarderzeugung,' s. 463, + 470.</p> + + <p><a name="Nt_190" href="#NtA_190">[190]</a> 'Nova Acta Petrop.,' 1794, + p. 393: <i>see</i> also previous volume.</p> + + <p><a name="Nt_191" href="#NtA_191">[191]</a> As quoted in the 'True + Principles of Breeding,' by C. H. Macknight and Dr. H. Madden, 1865, p. + 11.</p> + + <p><a name="Nt_192" href="#NtA_192">[192]</a> With respect to plants, an + admirable essay on this subject (Die Geschlechter-Vertheilung bei den + Pflanzen: 1867) has lately been published by Dr. Hildebrand, who arrives + at the same general conclusions as I have done.</p> + + <p><a name="Nt_193" href="#NtA_193">[193]</a> 'Teoria della Riproduzione + Vegetal,' 1816, p. 12.</p> + + <p><a name="Nt_194" href="#NtA_194">[194]</a> Verlot, 'Des Variétés,' + 1865, p. 72.</p> + + <p><a name="Nt_195" href="#NtA_195">[195]</a> Duval-Jouve, 'Bull. Soc. + Bot. de France,' tom. x., 1863, p. 194.</p> + + <p><a name="Nt_196" href="#NtA_196">[196]</a> Extract of a letter from + Sir R. Heron, 1838, given me by Mr. Yarrell. With respect to mice, + <i>see</i> 'Annal. des Sc. Nat.,' tom. i. p. 180; and I have heard of + other similar cases. For turtle-doves, Boitard and Corbié, 'Les Pigeons,' + &c., p. 238. For the Game fowl, 'The Poultry Book,' 1866, p. 128. For + crosses of tailless fowls, <i>see</i> Bechstein, 'Naturges. Deutsch.' b. + iii. s. 403. Bronn, 'Geschichte der Natur,' b. ii. s. 170, gives + analogous facts with horses. On the hairless condition of crossed South + American dogs, <i>see</i> Rengger, 'Säugethiere von Paraguay,' s. 152: + but I saw in the Zoological Gardens mongrels, from a similar cross, which + were hairless, quite hairy, or hairy in patches, that is, piebald with + hair. For crosses of Dorking and other fowls, <i>see</i> 'Poultry + Chronicle,' vol. ii. p. 355. About the crossed pigs, extract of letter + from Sir R. Heron to Mr. Yarrell. For other cases, <i>see</i> P. Lucas, + 'Héréd. Nat.,' tom. i. p. 212.</p> + + <p><a name="Nt_197" href="#NtA_197">[197]</a> 'Internat. Hort. and Bot. + Congress of London,' 1866.</p> + + <p><a name="Nt_198" href="#NtA_198">[198]</a> 'Bastarderzeugung,' s. 307. + Kölreuter ('Dritte Fortsetszung,' s. 34, 39), however, obtained + intermediate tints from similar crosses in the genus Verbascum. With + respect to the turnips, <i>see</i> Herbert's 'Amaryllidaceæ,' 1837, p. + 370.</p> + + <p><a name="Nt_199" href="#NtA_199">[199]</a> 'Nouvelles Archives du + Muséum,' tom. i. p. 100.</p> + + <p><a name="Nt_200" href="#NtA_200">[200]</a> Richardson, 'Pigs,' 1847, + pp. 37, 42; S. Sidney's edition of 'Youatt on the Pig,' 1860, p. 3.</p> + + <p><a name="Nt_201" href="#NtA_201">[201]</a> <i>See</i> Mr. W. C. + Spooner's excellent paper on Cross-Breeding, 'Journal Royal Agricult. + Soc.,' vol. xx., part ii.: <i>see</i> also an equally good article by Mr. + Ch. Howard, in 'Gardener's Chronicle,' 1860, p. 320.</p> + + <p><a name="Nt_202" href="#NtA_202">[202]</a> 'Gardener's Chronicle,' + 1857, pp. 649, 652.</p> + + <p><a name="Nt_203" href="#NtA_203">[203]</a> 'Bulletin de la Soc. + d'Acclimat.,' 1862, tom. ix. p. 463. <i>See</i> also, for other cases, + MM. Moll and Gayot, 'Du Bœuf,' 1860, p. xxxii.</p> + + <p><a name="Nt_204" href="#NtA_204">[204]</a> 'Poultry Chronicle,' vol. + ii., 1854, p. 36.</p> + + <p><a name="Nt_205" href="#NtA_205">[205]</a> 'The Poultry Book,' by W. + B. Tegetmeier, 1866, p. 58.</p> + + <p><a name="Nt_206" href="#NtA_206">[206]</a> 'Gardener's Chronicle,' + 1852, p. 765.</p> + + <p><a name="Nt_207" href="#NtA_207">[207]</a> Spooner, in 'Journal Royal + Agricult. Soc.,' vol. xx., part ii.</p> + + <p><a name="Nt_208" href="#NtA_208">[208]</a> <i>See</i> Colin's 'Traité + de Phys. Comp. des Animaux Domestiques,' tom. ii. p. 536, where this + subject is well treated.</p> + + <p><a name="Nt_209" href="#NtA_209">[209]</a> 'Les Pigeons,' p. 37.</p> + + <p><a name="Nt_210" href="#NtA_210">[210]</a> Vol. i., 1854, p. 101.</p> + + <p><a name="Nt_211" href="#NtA_211">[211]</a> 'Cottage Gardener,' 1856, + p. 110.</p> + + <p><a name="Nt_212" href="#NtA_212">[212]</a> 'Bastarderzeugung,' s. + 553.</p> + + <p><a name="Nt_213" href="#NtA_213">[213]</a> Dr. Pigeaux, in 'Bull. Soc. + d'Acclimat.,' tom. iii., July 1866, as quoted in 'Annals and Mag. of Nat. + Hist.,' 1867, vol. xx. p. 75.</p> + + <p><a name="Nt_214" href="#NtA_214">[214]</a> 'Journal de Physiolog.,' + tom. ii., 1859, p. 385.</p> + + <p><a name="Nt_215" href="#NtA_215">[215]</a> Dec. 1863, p. 484.</p> + + <p><a name="Nt_216" href="#NtA_216">[216]</a> On the Varieties of Wheat, + p. 66.</p> + + <p><a name="Nt_217" href="#NtA_217">[217]</a> Rengger, 'Säugethiere von + Paraguay,' s. 336.</p> + + <p><a name="Nt_218" href="#NtA_218">[218]</a> <i>See</i> a memoir by MM. + Lherbette and De Quatrefages, in 'Bull. Soc. d'Acclimat.,' tom. viii., + July, 1861, p. 312.</p> + + <p><a name="Nt_219" href="#NtA_219">[219]</a> For the Norfolk sheep, + <i>see</i> Marshall's 'Rural Economy of Norfolk,' vol. ii. p. 133. + <i>See</i> Rev. L. Landt's 'Description of Faroe,' p. 66. For the ancon + sheep, <i>see</i> 'Phil. Transact.,' 1813, p. 90.</p> + + <p><a name="Nt_220" href="#NtA_220">[220]</a> White's 'Nat. Hist. of + Selbourne,' edited by Bennett, p. 39. With respect to the origin of the + dark-coloured deer, <i>see</i> 'Some Account of English Deer Parks,' by + E. P. Shirley, Esq.</p> + + <p><a name="Nt_221" href="#NtA_221">[221]</a> 'The Dovecote,' by the Rev. + E. S. Dixon, p. 155; Bechstein, 'Naturgesch. Deutschlands,' Band iv., + 1795, s. 17.</p> + + <p><a name="Nt_222" href="#NtA_222">[222]</a> 'Cattle,' p. 202.</p> + + <p><a name="Nt_223" href="#NtA_223">[223]</a> Mr. J. Wilkinson, in + 'Remarks addressed to Sir J. Sebright,' 1820, p. 38.</p> + + <p><a name="Nt_224" href="#NtA_224">[224]</a> 'Gardener's Chronicle,' + 1858, p. 771.</p> + + <p><a name="Nt_225" href="#NtA_225">[225]</a> 'Bastarderzeugung,' s. 87, + 169. <i>See</i> also the Table at the end of volume.</p> + + <p><a name="Nt_226" href="#NtA_226">[226]</a> 'Bastarderzeugung,' s. 87, + 577.</p> + + <p><a name="Nt_227" href="#NtA_227">[227]</a> 'Kenntniss der + Befruchtung,' s. 137; 'Bastarderzeugung,' s. 92, 181. On raising the two + varieties from seed <i>see</i> s. 307.</p> + + <p><a name="Nt_228" href="#NtA_228">[228]</a> 'Bastarderzeugung,' s. + 216.</p> + + <p><a name="Nt_229" href="#NtA_229">[229]</a> The following facts, given + by Kölreuter in his 'Dritte Fortsetzung,' s. 34, 39, appear at first + sight strongly to confirm Mr. Scott's and Gärtner's statements; and to a + certain limited extent they do so. Kölreuter asserts, from innumerable + observations, that insects incessantly carry pollen from one species and + variety of Verbascum to another; and I can confirm this assertion; yet he + found that the white and yellow varieties of <i>Verbascum lychnitis</i> + often grew wild mingled together: moreover, he cultivated these two + varieties in considerable numbers during four years in his garden, and + they kept true by seed; but when he crossed them, they produced flowers + of an intermediate tint. Hence it might have thought that both varieties + must have a stronger elective affinity for the pollen of their own + variety than for that of the other; this elective affinity, I may add, of + each species for its own pollen (Kölreuter, 'Dritte Forts.,' s. 39, and + Gärtner, 'Bastarderz.,' <i>passim</i>) being a perfectly well-ascertained + power. But the force of the foregoing facts is much lessened by Gärtner's + numerous experiments, for, differently from Kölreuter, he never once got + ('Bastarderz.,' s. 307) an intermediate tint when he crossed the yellow + and white flowered varieties of Verbascum. So that the fact of the white + and yellow varieties keeping true to their colour by seed does not prove + that they were not mutually fertilised by the pollen carried by insects + from one to the other.</p> + + <p><a name="Nt_230" href="#NtA_230">[230]</a> 'Amaryllidaceæ,' 1837, p. + 366. Gärtner has made a similar observation.</p> + + <p><a name="Nt_231" href="#NtA_231">[231]</a> Kölreuter first observed + this fact. 'Mém. de l'Acad. St. Petersburg,' vol. iii. p. 197. <i>See</i> + also C. K. Sprengel, 'Das Entdeckte Geheimniss,' s. 345.</p> + + <p><a name="Nt_232" href="#NtA_232">[232]</a> Namely, Barbarines, + Pastissons, Giraumous: 'Annal. des Sc. Nat.,' tom. xxx., 1833, pp. 398 + and 405.</p> + + <p><a name="Nt_233" href="#NtA_233">[233]</a> 'Mémoire sur les + Cucurbitaceæ,' 1826, pp. 46, 55.</p> + + <p><a name="Nt_234" href="#NtA_234">[234]</a> 'Annales des Se. Nat.,' 4th + series, tom. vi. M. Naudin considers these forms as undoubtedly varieties + of <i>Cucurbita pepo</i>.</p> + + <p><a name="Nt_235" href="#NtA_235">[235]</a> 'Mém. Cucurb.,' p. 8.</p> + + <p><a name="Nt_236" href="#NtA_236">[236]</a> 'Zweite Forts.,' s. 53, + namely, Nicotiana major vulgaris; (2) perennis; (3) Transylvanica; (4) a + sub-var. of the last; (5) major latifol. fl. alb.</p> + + <p><a name="Nt_237" href="#NtA_237">[237]</a> Kölreuter was so much + struck with this fact that he suspected that a little pollen of <i>N. + glutinosa</i> in one of his experiments might have accidentally got + mingled with that of <i>var. perennis</i>, and thus aided its fertilising + power. But we now know conclusively from Gärtner ('Bastarderz.,' s. 34, + 431) that two kinds of pollen never act <i>conjointly</i> on a third + species; still less will the pollen of a distinct species, mingled with a + plant's own pollen, if the latter be present in sufficient quantity, have + any effect. The sole effect of mingling two kinds of pollen is to produce + in the same capsule seeds which yield plants, some taking after the one + and some after the other parent.</p> + + <p><a name="Nt_238" href="#NtA_238">[238]</a> Mr. Scott has made some + observations on the absolute sterility of a purple and white primrose + (<i>Primula vulgaris</i>) when fertilised by pollen from the primrose + ('Journal of Proc. of Linn. Soc.,' vol. viii., 1864, p. 98); but these + observations require confirmation. I raised a number of purple-flowered + long-styled seedlings from seed kindly sent me by Mr. Scott, and, though + they were all some degree sterile, they were much more fertile with + pollen taken from the common primrose than with their own pollen. Mr. + Scott has likewise described a red equal-styled cowslip (<i>P. veris</i>, + idem, p. 106), which was found by him to be highly sterile when crossed + with the common cowslip; but this was not the case with several + equal-styled red seedlings raised by me from his plant. This variety of + the cowslip presents the remarkable peculiarity of combining male organs + in every respect like those of the short-styled form, with female organs + resembling in function and partly in structure those of the long-styled + form; so that we have the singular anomaly of the two forms combined in + the same flower. Hence it is not surprising that these flowers should be + spontaneously self-infertile in a high degree.</p> + + <p><a name="Nt_239" href="#NtA_239">[239]</a> 'Act. Acad. St. + Petersburg,' 1780, part ii., pp. 84, 100.</p> + + <p><a name="Nt_240" href="#NtA_240">[240]</a> 'Annales des Sc. Nat.,' + tom. xxi. (1st series), p. 61.</p> + + <p><a name="Nt_241" href="#NtA_241">[241]</a> 'Bull. Bot. Soc. de + France,' Dec. 27th, 1861, tom. viii. p. 612.</p> + + <p><a name="Nt_242" href="#NtA_242">[242]</a> Quoted by Isid. Geoffroy + St. Hilaire, 'Hist. Naturelle Générale,' tom. iii. p. 476. Since this MS. + has been sent to press a full discussion on the present subject has + appeared in Mr. Herbert Spencer's 'Principles of Biology,' vol. ii. 1867, + p. 457 <i>et seq.</i></p> + + <p><a name="Nt_243" href="#NtA_243">[243]</a> For cats and dogs, &c., + <i>see</i> Bellingeri, in 'Annal. des Sc. Nat.,' 2nd series, Zoolog., + tom. xii. p. 155. For ferrets, Bechstein, 'Naturgeschichte Deutschlands,' + Band i., 1801, s. 786, 795. For rabbits, ditto, s. 1123, 1131; and + Bronn's 'Geschichte der Natur,' B. ii. s. 99. For mountain sheep, ditto, + s. 102. For the fertility of the wild sow, <i>see</i> Bechstein's + 'Naturgesch. Deutschlands,' B. i., 1801, s. 534; for the domestic pig, + Sidney's edit. of Youatt on the Pig, 1860, p. 62. With respect to + Lapland, <i>see</i> Acerbi's 'Travels to the North Cape,' Eng. translat., + vol. ii. p. 222. About the Highland cows, <i>see</i> Hogg on Sheep, p. + 263.</p> + + <p><a name="Nt_244" href="#NtA_244">[244]</a> For the eggs of <i>Gallus + bankiva</i>, <i>see</i> Blyth, in 'Annals and Mag. of Nat. Hist., 2nd + series, vol. i., 1848, p. 456. For wild and tame ducks, Macgillivray, + 'British Birds,' vol. v. p. 37; and 'Die Enten,' s. 87. For wild geese, + L. Lloyd, 'Scandinavian Adventures,' vol. ii. 1854, p. 413; and for tame + geese, 'Ornamental Poultry,' by Rev. E. S. Dixon, p. 139. On the breeding + of pigeons, Pistor, 'Das Ganze der Taubenzucht,' 1831, s. 46; and Boitard + and Corbié, 'Les Pigeons,' p. 158. With respect to peacocks, according to + Temminck ('Hist. Nat. Gén. des Pigeons,' &c., 1813, tom. ii. p. 41), + the hen lays in India even as many as twenty eggs; but according to + Jerdon and another writer (quoted in Tegetmeier's 'Poultry Book,' 1866, + pp. 280, 282), she there lays only from four to nine or ten eggs: in + England she is said, in the 'Poultry Book,' to lay five or six, but + another writer says from eight to twelve eggs.</p> + + <p><a name="Nt_245" href="#NtA_245">[245]</a> 'The Art of Improving the + Breed, &c.,' 1809, p. 16.</p> + + <p><a name="Nt_246" href="#NtA_246">[246]</a> For Andrew Knight, + <i>see</i> A. Walker, on 'Intermarriage,' 1838, p. 227. Sir J. Sebright's + Treatise has just been quoted.</p> + + <p><a name="Nt_247" href="#NtA_247">[247]</a> 'Cattle,' p. 199.</p> + + <p><a name="Nt_248" href="#NtA_248">[248]</a> Nathusius, 'Ueber Shorthorn + Rindvieh,' 1857, s. 71: <i>see</i> also 'Gardener's Chronicle,' 1860, p. + 270. Many analogous cases are given in a pamphlet recently published by + Mr. C. Macknight and Dr. H. Madden, 'On the True Principles of Breeding;' + Melbourne, Australia, 1865.</p> + + <p><a name="Nt_249" href="#NtA_249">[249]</a> Mr. Willoughby Wood, in + 'Gardener's Chronicle,' 1855, p. 411; and 1860, p. 270. <i>See</i> the + very clear tables and pedigrees given in Nathusius' 'Rindvieh,' s. + 72-77.</p> + + <p><a name="Nt_250" href="#NtA_250">[250]</a> Mr. Wright, 'Journal of + Royal Agricult. Soc.,' vol. vii., 1846, p. 204.</p> + + <p><a name="Nt_251" href="#NtA_251">[251]</a> Youatt on Cattle, p. + 202.</p> + + <p><a name="Nt_252" href="#NtA_252">[252]</a> Report British Assoc., + Zoolog. Sect., 1838.</p> + + <p><a name="Nt_253" href="#NtA_253">[253]</a> Azara, 'Quadrupèdes du + Paraguay,' tom. ii. pp. 354, 368.</p> + + <p><a name="Nt_254" href="#NtA_254">[254]</a> For the case of the Messrs. + Brown, <i>see</i> 'Gard. Chronicle,' 1855, p. 26. For the Foscote flock, + 'Gard. Chron.,' 1860, p. 416. For the Naz flock, 'Bull. de la Soc. + d'Acclimat.,' 1860, p. 477.</p> + + <p><a name="Nt_255" href="#NtA_255">[255]</a> Nathusius, 'Rindvieh,' s. + 65; Youatt on Sheep, p. 495.</p> + + <p><a name="Nt_256" href="#NtA_256">[256]</a> 'Gard. Chronicle,' 1861, p. + 631.</p> + + <p><a name="Nt_257" href="#NtA_257">[257]</a> Lord Somerville, 'Facts on + Sheep and Husbandry,' p. 6. Mr. Spooner, in 'Journal of Royal Agricult. + Soc. of England,' vol. xx., part ii. <i>See</i> also an excellent paper + on the same subject in 'Gard. Chronicle,' 1860, p. 321, by Mr. Charles + Howard.</p> + + <p><a name="Nt_258" href="#NtA_258">[258]</a> 'Some Account of English + Deer Parks,' by Evelyn P. Shirley, 1867.</p> + + <p><a name="Nt_259" href="#NtA_259">[259]</a> 'The Art of Improving the + Breed,' &c., p. 13. With respect to Scotch deer-hounds, <i>see</i> + Scrope's 'Art of Deer Stalking,' pp. 350-353.</p> + + <p><a name="Nt_260" href="#NtA_260">[260]</a> 'Cottage Gardener,' 1861, + p. 327.</p> + + <p><a name="Nt_261" href="#NtA_261">[261]</a> Sidney's edit. of Youatt on + the Pig, 1860, p. 30; p. 33, quotation from Mr. Druce; p. 29, on Lord + Western's case.</p> + + <p><a name="Nt_262" href="#NtA_262">[262]</a> 'Journal, Royal Agricult. + Soc. of England,' 1846, vol. vii. p. 205.</p> + + <p><a name="Nt_263" href="#NtA_263">[263]</a> 'Ueber Rindvieh,' &c., + s. 78.</p> + + <p><a name="Nt_264" href="#NtA_264">[264]</a> Sidney on the Pig, p. 36. + <i>See</i> also note, p. 34. Also Richardson on the Pig, 1847, p. 26.</p> + + <p><a name="Nt_265" href="#NtA_265">[265]</a> Dr. Dally has published an + excellent article (translated in the 'Anthropolog. Review,' May, 1864, p. + 65), criticising all writers who have maintained that evil follows from + consanguineous marriages. No doubt on this side of the question many + advocates have injured their cause by inaccuracies: thus it has been + stated (Devay, 'Du Danger des Mariages,' &c., 1862, p. 141) that the + marriages of cousins have been prohibited by the legislature of Ohio; but + I have been assured, in answer to inquiries made in the United States, + that this statement is a mere fable.</p> + + <p><a name="Nt_266" href="#NtA_266">[266]</a> <i>See</i> his most + interesting work on the 'Early History of Man,' 1865, chap. x.</p> + + <p><a name="Nt_267" href="#NtA_267">[267]</a> On Consanguinity in + Marriage, in the 'Fortnightly Review,' 1865, p. 710; Hofacker, 'Ueber die + Eigenschaften,' &c.</p> + + <p><a name="Nt_268" href="#NtA_268">[268]</a> Sir G. Grey's 'Journal of + Expeditions into Australia,' vol. ii. p. 243; and Dobrizhoffer, 'On the + Abipones of South America.'</p> + + <p><a name="Nt_269" href="#NtA_269">[269]</a> 'The Art of Improving the + Breed,' p. 13.</p> + + <p><a name="Nt_270" href="#NtA_270">[270]</a> 'The Poultry Book,' by W. + B. Tegetmeier, 1866, p. 245.</p> + + <p><a name="Nt_271" href="#NtA_271">[271]</a> 'Journal Royal Agricult. + Soc.' 1846, vol. vii. p. 205; <i>see</i> also Ferguson on the Fowl, pp. + 83, 317; <i>see</i> also 'The Poultry Book,' by Tegetmeier, 1866, p. 135, + with respect to the extent to which cock-fighters found that they could + venture to breed in-and-in, viz., occasionally a hen with her own son; + "but they were cautious not to repeat the in-and-in breeding."</p> + + <p><a name="Nt_272" href="#NtA_272">[272]</a> 'The Poultry Book,' by W. + B. Tegetmeier, 1866, p. 79.</p> + + <p><a name="Nt_273" href="#NtA_273">[273]</a> 'The Poultry Chronicle,' + 1854, vol. i. p. 43.</p> + + <p><a name="Nt_274" href="#NtA_274">[274]</a> 'The Poultry Book,' by W. + B. Tegetmeier, 1866, p. 79.</p> + + <p><a name="Nt_275" href="#NtA_275">[275]</a> 'The Poultry Chronicle,' + vol. i. p. 89.</p> + + <p><a name="Nt_276" href="#NtA_276">[276]</a> 'The Poultry Book,' 1866, + p. 210.</p> + + <p><a name="Nt_277" href="#NtA_277">[277]</a> Ibid, 1866, p. 167; and + 'Poultry Chronicle,' vol. iii., 1855, p. 15.</p> + + <p><a name="Nt_278" href="#NtA_278">[278]</a> 'A Treatise on Fancy + Pigeons,' by J. M. Eaton, p. 56.</p> + + <p><a name="Nt_279" href="#NtA_279">[279]</a> 'The Pigeon Book,' p. + 46.</p> + + <p><a name="Nt_280" href="#NtA_280">[280]</a> 'Das Ganze der + Taubenzucht,' 1837, s. 18.</p> + + <p><a name="Nt_281" href="#NtA_281">[281]</a> 'Les Pigeons,' 1824, p. + 35.</p> + + <p><a name="Nt_282" href="#NtA_282">[282]</a> 'Proc. Entomolog. Soc.,' + Aug. 6th, 1860, p. 126.</p> + + <p><a name="Nt_283" href="#NtA_283">[283]</a> 'Journal of Horticulture,' + 1861, pp. 39, 77, 158; and 1864, p. 206.</p> + + <p><a name="Nt_284" href="#NtA_284">[284]</a> 'Beiträge zur Kenntniss der + Befruchtung,' 1844, s. 366.</p> + + <p><a name="Nt_285" href="#NtA_285">[285]</a> 'Amaryllidaceæ,' p. + 371.</p> + + <p><a name="Nt_286" href="#NtA_286">[286]</a> 'De la Fécondation,' 2nd + edit., 1862, p. 79.</p> + + <p><a name="Nt_287" href="#NtA_287">[287]</a> 'Mémoire sur les + Cucurbitacées,' pp. 36, 28, 30.</p> + + <p><a name="Nt_288" href="#NtA_288">[288]</a> Loudon's 'Gard. Mag.,' vol. + viii., 1832, p. 52.</p> + + <p><a name="Nt_289" href="#NtA_289">[289]</a> 'Transact. Hort. Soc.,' + vol. i. p. 25.</p> + + <p><a name="Nt_290" href="#NtA_290">[290]</a> 'Annal. des Sc. Nat.,' 3rd + series, Bot., tom. vi. p. 189.</p> + + <p><a name="Nt_291" href="#NtA_291">[291]</a> 'Philosophical + Transactions,' 1799, p. 200.</p> + + <p><a name="Nt_292" href="#NtA_292">[292]</a> 'Ueber die + Bastarderzeugung,' 1828, s. 32, 33. For Mr. Chaundy's case, <i>see</i> + Loudon's 'Gard. Mag.,' vol. vii., 1831, p. 696.</p> + + <p><a name="Nt_293" href="#NtA_293">[293]</a> 'Gardener's Chron.,' 1846, + p. 601.</p> + + <p><a name="Nt_294" href="#NtA_294">[294]</a> 'Philosoph. Transact.,' + 1799, p. 201.</p> + + <p><a name="Nt_295" href="#NtA_295">[295]</a> Quoted in 'Bull. Bot. Soc. + France,' vol. ii., 1855, p. 327.</p> + + <p><a name="Nt_296" href="#NtA_296">[296]</a> Gärtner, + 'Bastarderzeugung,' s. 259, 518, 526 <i>et seq.</i></p> + + <p><a name="Nt_297" href="#NtA_297">[297]</a> 'Fortsetzung,' 1763, s. 29; + 'Dritte Fortsetzung,' s. 44, 96; 'Act. Acad. St. Petersburg,' 1782, part + ii., p. 251; 'Nova Acta,' 1793, pp. 391, 394; 'Nova Acta,' 1795, pp. 316, + 323.</p> + + <p><a name="Nt_298" href="#NtA_298">[298]</a> 'Die Bastardbefruchtung,' + &c., 1865, s. 31, 41, 42.</p> + + <p><a name="Nt_299" href="#NtA_299">[299]</a> Max Wichura fully accepts + this view ('Bastardbefruchtung,' s. 43), as does the Rev. M. J. Berkeley, + in 'Journal of Hort. Soc.,' Jan. 1866, p. 70.</p> + + <p><a name="Nt_300" href="#NtA_300">[300]</a> 'Bastarderzeugung,' s. 394, + 526, 528.</p> + + <p><a name="Nt_301" href="#NtA_301">[301]</a> Kölreuter,' Nova Acta,' + 1795, p. 316.</p> + + <p><a name="Nt_302" href="#NtA_302">[302]</a> Gärtner, + 'Bastarderzeugung,' s. 430.</p> + + <p><a name="Nt_303" href="#NtA_303">[303]</a> 'Botanische Zeitung,' Jan. + 1864, s. 3.</p> + + <p><a name="Nt_304" href="#NtA_304">[304]</a> 'Monatsbericht Akad. + Wissen,' Berlin, 1866, s. 372.</p> + + <p><a name="Nt_305" href="#NtA_305">[305]</a> International Hort. + Congress, London, 1866.</p> + + <p><a name="Nt_306" href="#NtA_306">[306]</a> 'Proc. Bot. Soc. of + Edinburgh,' May, 1863: these observations are given in abstract, and + others are added, in the 'Journal of Proc. of Linn. Soc.,' vol. viii. + Bot., 1864, p. 162.</p> + + <p><a name="Nt_307" href="#NtA_307">[307]</a> Prof. Lecoq, 'De la + Fécondation,' 2nd edit., 1862, p. 76.</p> + + <p><a name="Nt_308" href="#NtA_308">[308]</a> 'Bastarderzeugung,' s. 64, + 357.</p> + + <p><a name="Nt_309" href="#NtA_309">[309]</a> Idem, s. 357.</p> + + <p><a name="Nt_310" href="#NtA_310">[310]</a> 'Zweite Fortsetzung,' s. + 10; 'Dritte Fort.,' s. 40.</p> + + <p><a name="Nt_311" href="#NtA_311">[311]</a> Duvernoy, quoted by + Gärtner, 'Bastarderzeugung,' s. 334.</p> + + <p><a name="Nt_312" href="#NtA_312">[312]</a> 'Gardner's Chronicle,' + 1846, p. 183.</p> + + <p><a name="Nt_313" href="#NtA_313">[313]</a> 'Transact. Hort. Soc.,' + vol. vii., 1830, p. 95.</p> + + <p><a name="Nt_314" href="#NtA_314">[314]</a> Prof. Lecoq, 'De la + Fécondation,' 1845, p. 70; Gärtner, 'Bastarderzeugung,' s. 64.</p> + + <p><a name="Nt_315" href="#NtA_315">[315]</a> 'Gardener's Chron.' 1866, + p. 1068.</p> + + <p><a name="Nt_316" href="#NtA_316">[316]</a> 'Journal of Proc. of Linn. + Soc.,' vol. viii., 1864, p. 168.</p> + + <p><a name="Nt_317" href="#NtA_317">[317]</a> 'Amaryllidaceæ,' 1837, p. + 371; 'Journal of Hort. Soc.,' vol. ii., 1847, p. 19.</p> + + <p><a name="Nt_318" href="#NtA_318">[318]</a> Loudon's 'Gardener's + Magazine,' vol. xi., 1835, p. 260.</p> + + <p><a name="Nt_319" href="#NtA_319">[319]</a> 'Gardener's Chronicle,' + 1850, p. 470.</p> + + <p><a name="Nt_320" href="#NtA_320">[320]</a> 'Journal Hort. Soc., vol. + v. p. 135. The seedlings thus raised were given to the Hort. Soc.; but I + find, on inquiry, that they unfortunately died the following winter.</p> + + <p><a name="Nt_321" href="#NtA_321">[321]</a> Mr. D. Beaton, in 'Journal + of Hort.,' 1861, p. 453. Lecoq, however ('De la Fécond.,' 1862, p. 369), + states that this hybrid is descended from <i>G. psittacinus</i> and + <i>cardinalis</i>; but this is opposed to Herbert's experience, who found + that the former species could not be crossed.</p> + + <p><a name="Nt_322" href="#NtA_322">[322]</a> This is the conclusion of + Prof. Devay, 'Du Danger des Mariages Consang.,' 1862, p. 97. Virchow + quotes, in the 'Deutsche Jahrbücher,' 1863, s. 354, some curious evidence + on half the cases of a peculiar form of blindness occurring in the + offspring from near relations.</p> + + <p><a name="Nt_323" href="#NtA_323">[323]</a> For England, <i>see</i> + below. For Germany, <i>see</i> Metzger, 'Getreidearten,' 1841, s. 63. For + France, Loiseleur-Deslongchamps ('Consid. sur les Céreales,' 1843, p. + 200) gives numerous references on this subject. For Southern France, + <i>see</i> Godron, 'Florula Juvenalis,' 1854, p. 28.</p> + + <p><a name="Nt_324" href="#NtA_324">[324]</a> 'A general Treatise of + Husbandry,' vol. iii. p. 58.</p> + + <p><a name="Nt_325" href="#NtA_325">[325]</a> 'Gardener's Chronicle and + Agricult. Gazette,' 1858, p. 247; and for the second statement, idem, + 1850, p. 702. On this same subject, <i>see</i> also Rev. D. Walker's + 'Prize Essay of Highland Agricult. Soc.,' vol. ii. p. 200. Also + Marshall's 'Minutes of Agriculture,' November, 1775.</p> + + <p><a name="Nt_326" href="#NtA_326">[326]</a> Oberlin's 'Memoirs,' Eng. + translat., p. 73. For Lancashire, <i>see</i> Marshall's 'Review of + Reports,' 1808, p. 295.</p> + + <p><a name="Nt_327" href="#NtA_327">[327]</a> 'Cottage Gardener,' 1856, + p. 186. For Mr. Robson's subsequent statements, <i>see</i> 'Journal of + Horticulture,' Feb. 18, 1866, p. 121. For Mr. Abbey's remarks on + grafting, &c., idem, July 18, 1865, p. 44.</p> + + <p><a name="Nt_328" href="#NtA_328">[328]</a> 'Mém. de l'Acad. des + Sciences,' 1790, p. 209.</p> + + <p><a name="Nt_329" href="#NtA_329">[329]</a> 'On the Varieties of + Wheat,' p. 52.</p> + + <p><a name="Nt_330" href="#NtA_330">[330]</a> Mr. Spencer has fully and + ably discussed this whole subject in his 'Principles of Biology,' 1864, + vol. ii. ch. x. In the first edition of my 'Origin of Species,' 1859, p. + 267, I spoke of the good effects from slight changes in the conditions of + life and from cross-breeding, and of the evil effects from great changes + in the conditions and from crossing widely distinct forms, as a series of + facts "connected together by some common but unknown bond, which is + essentially related to the principle of life."</p> + + <p><a name="Nt_331" href="#NtA_331">[331]</a> 'Essais de Zoologie + Générale,' 1841, p. 256.</p> + + <p><a name="Nt_332" href="#NtA_332">[332]</a> Du Rut, 'Annales du + Muséum,' 1807, tom. ix. p. 120.</p> + + <p><a name="Nt_333" href="#NtA_333">[333]</a> 'Säugethiere von Paraguay,' + 1830, s. 49, 106, 118, 124, 201, 208, 249, 265, 327.</p> + + <p><a name="Nt_334" href="#NtA_334">[334]</a> 'The Naturalist on the + Amazons,' 1863, vol. i. pp. 99, 193; vol. ii. p. 113.</p> + + <p><a name="Nt_335" href="#NtA_335">[335]</a> 'Embassy to the Court of + Ava,' vol. i. p. 534.</p> + + <p><a name="Nt_336" href="#NtA_336">[336]</a> 'Journal,' vol. i. p. + 213.</p> + + <p><a name="Nt_337" href="#NtA_337">[337]</a> 'Säugethiere,' s. 327.</p> + + <p><a name="Nt_338" href="#NtA_338">[338]</a> On the Breeding of the + larger Felidæ, 'Proc. Zoolog. Soc.,' 1861, p. 140.</p> + + <p><a name="Nt_339" href="#NtA_339">[339]</a> Sleeman's 'Rambles in + India,' vol. ii. p. 10.</p> + + <p><a name="Nt_340" href="#NtA_340">[340]</a> Wiegmann's 'Archif für + Naturgesch.,' 1837, s. 162.</p> + + <p><a name="Nt_341" href="#NtA_341">[341]</a> Rengger, 'Säugethiere,' + &c., s. 276. On the parentage of the guinea-pig, <i>see</i> also + Isid. Geoffroy St. Hilaire, 'Hist. Nat. Gén.'</p> + + <p><a name="Nt_342" href="#NtA_342">[342]</a> Although the existence of + the <i>Leporides</i>, as described by Dr. Broca ('Journal de Phys.,' tom. + ii. p. 370), is now positively denied, yet Dr. Pigeaux ('Annals and Mag. + of Nat. Hist.,' vol. xx., 1867, p. 75) affirms that the hare and rabbit + have produced hybrids.</p> + + <p><a name="Nt_343" href="#NtA_343">[343]</a> 'Quadrupeds of North + America,' by Audubon and Bachman, 1846, p. 268.</p> + + <p><a name="Nt_344" href="#NtA_344">[344]</a> Loudon's 'Mag. of Nat. + Hist.,' vol. ix., 1836, p. 571; Audubon and Bachman's 'Quadrupeds of + North America,' p. 221.</p> + + <p><a name="Nt_345" href="#NtA_345">[345]</a> Flourens, 'De l'Instinct,' + &c., 1845, p. 88.</p> + + <p><a name="Nt_346" href="#NtA_346">[346]</a> <i>See</i> 'Annual Reports + Zoolog. Soc.,' 1855, 1858, 1863, 1864; 'Times' newspaper, Aug. 10th, + 1847; Flourens, 'De l'Instinct,' p. 85.</p> + + <p><a name="Nt_347" href="#NtA_347">[347]</a> 'Säugethiere,' &c., s. + 34, 49.</p> + + <p><a name="Nt_348" href="#NtA_348">[348]</a> Art. Brazil, 'Penny + Cyclop.,' p. 363.</p> + + <p><a name="Nt_349" href="#NtA_349">[349]</a> 'The Naturalist on the + River Amazon,' vol. i. p. 99.</p> + + <p><a name="Nt_350" href="#NtA_350">[350]</a> 'Encyclop. of Rural + Sports,' p. 691.</p> + + <p><a name="Nt_351" href="#NtA_351">[351]</a> According to Sir A. Burnes + ('Cabool,' &c., p. 51), eight species are used for hawking in + Scinde.</p> + + <p><a name="Nt_352" href="#NtA_352">[352]</a> Loudon's 'Mag. of Nat. + Hist.,' vol. vi., 1833, p. 110.</p> + + <p><a name="Nt_353" href="#NtA_353">[353]</a> F. Cuvier, 'Annal. du + Muséum,' tom. ix. p. 128.</p> + + <p><a name="Nt_354" href="#NtA_354">[354]</a> 'The Zoologist,' vol. + vii.-viii., 1849-50, p. 2648.</p> + + <p><a name="Nt_355" href="#NtA_355">[355]</a> Knox, 'Ornithological + Rambles in Sussex,' p. 91.</p> + + <p><a name="Nt_356" href="#NtA_356">[356]</a> 'The Zoologist,' vol. + vii.-viii., 1849-50, p. 2566; vol. ix.-x., 1851-2, p. 3207.</p> + + <p><a name="Nt_357" href="#NtA_357">[357]</a> Bechstein, 'Naturgesch. der + Stubenvögel,' 1840, s. 20.</p> + + <p><a name="Nt_358" href="#NtA_358">[358]</a> 'Ornithological Biography,' + vol. v. p. 517.</p> + + <p><a name="Nt_359" href="#NtA_359">[359]</a> A case is recorded in 'The + Zoologist,' vol. i.-ii., 1843-45, p. 453. For the siskin breeding, vol. + iii.-iv., 1845-46, p. 1075. Bechstein, 'Stubenvögel,' s. 139, speaks of + bullfinches making nests, but rarely producing young.</p> + + <p><a name="Nt_360" href="#NtA_360">[360]</a> Yarrell's 'Hist. British + Birds,' 1839, vol. i. p. 412.</p> + + <p><a name="Nt_361" href="#NtA_361">[361]</a> Loudon's 'Mag. of Nat. + History,' vol. ix., 1836, p. 347.</p> + + <p><a name="Nt_362" href="#NtA_362">[362]</a> 'Mémoires du Muséum d'Hist. + Nat.,' tom. x. p. 314: five cases of parrots breeding in France are here + recorded. <i>See</i>, also, 'Report Brit. Assoc. Zoolog.,' 1843.</p> + + <p><a name="Nt_363" href="#NtA_363">[363]</a> 'Stubenvögel,' s. 105, + 83.</p> + + <p><a name="Nt_364" href="#NtA_364">[364]</a> Dr. Hancock remarks + ('Charlesworth's Mag. of Nat. Hist.,' vol. ii., 1838, p. 492), "it is + singular that, amongst the numerous useful birds that are indigenous to + Guiana, none are found to propagate among the Indians; yet the common + fowl is reared in abundance throughout the country."</p> + + <p><a name="Nt_365" href="#NtA_365">[365]</a> 'A Week at Port Royal,' + 1855, p. 7.</p> + + <p><a name="Nt_366" href="#NtA_366">[366]</a> Audubon, 'American + Ornithology,' vol. v. pp. 552, 557.</p> + + <p><a name="Nt_367" href="#NtA_367">[367]</a> Moubray on Poultry, 7th + edit., p. 133.</p> + + <p><a name="Nt_368" href="#NtA_368">[368]</a> Temminck, 'Hist. Nat. Gén. + des Pigeons,' &c., 1813, tom. iii. pp. 288, 382; 'Annals and Mag. of + Nat. Hist.,' vol. xii., 1843, p. 453. Other species of partridge have + occasionally bred; as the red-legged (<i>P. rubra</i>), when kept in a + large court in France (<i>see</i> 'Journal de Physique,' tom. xxv. p. + 294), and in the Zoological Gardens in 1856.</p> + + <p><a name="Nt_369" href="#NtA_369">[369]</a> Rev. E. S. Dixon, 'The + Dovecote,' 1851, pp. 243-252.</p> + + <p><a name="Nt_370" href="#NtA_370">[370]</a> Temminck, 'Hist. Nat. Gén. + des Pigeons,' &c., tom. ii. pp. 456, 458; tom. iii. pp. 2, 13, + 47.</p> + + <p><a name="Nt_371" href="#NtA_371">[371]</a> Bates, 'The Naturalist on + the Amazons,' vol. i. p. 193; vol. ii. p. 112.</p> + + <p><a name="Nt_372" href="#NtA_372">[372]</a> Temminck, 'Hist. Nat. + Gén.,' &c., tom. iii. p. 125. For <i>Tetrao urogallus</i>, <i>see</i> + L. Lloyd, 'Field Sports of North of Europe,' vol. i. pp. 287, 314; and + 'Bull. de la Soc. d'Acclimat.,' tom. vii., 1860, p. 600. For <i>T. + Scoticus</i>, Thompson, 'Nat. Hist. of Ireland,' vol. ii., 1850, p. 49. + For <i>T. cupido</i>, 'Boston Journal of Nat. Hist.,' vol. iii. p. + 199.</p> + + <p><a name="Nt_373" href="#NtA_373">[373]</a> Marcel de Serres, 'Annales + des Sci. Nat.,' 2nd series, Zoolog., tom. xiii. p. 175.</p> + + <p><a name="Nt_374" href="#NtA_374">[374]</a> Dr. Hancock, in + 'Charlesworth's Mag. of Nat. Hist.' vol. ii., 1838, p. 491; R. Hill, 'A + Week at Port Royal,' p. 8; 'Guide to the Zoological Gardens,' by P. L. + Sclater, 1859, pp. 11, 12; 'The Knowsley Menagerie,' by Dr. Gray, 1846, + pl. xiv.; E. Blyth, 'Report Asiatic Soc. of Bengal,' May, 1855.</p> + + <p><a name="Nt_375" href="#NtA_375">[375]</a> Prof. Newton, in 'Proc. + Zoolog. Soc.,' 1860, p. 336.</p> + + <p><a name="Nt_376" href="#NtA_376">[376]</a> 'The Dovecote and Aviary,' + p. 428.</p> + + <p><a name="Nt_377" href="#NtA_377">[377]</a> 'Ornithological Biography,' + vol. iii. p. 9.</p> + + <p><a name="Nt_378" href="#NtA_378">[378]</a> 'Geograph. Journal,' vol. + xiii., 1844, p. 32.</p> + + <p><a name="Nt_379" href="#NtA_379">[379]</a> Loudon's 'Mag. of Nat. + Hist.,' vol. v., 1832, p. 153.</p> + + <p><a name="Nt_380" href="#NtA_380">[380]</a> 'Zoologist,' vols. v.-vi., + 1847-48, p. 1660.</p> + + <p><a name="Nt_381" href="#NtA_381">[381]</a> 'Transact. Entomolog. + Soc.,' vol. iv., 1845, p. 60.</p> + + <p><a name="Nt_382" href="#NtA_382">[382]</a> 'Transact. Linn. Soc.,' + vol. vii. p. 40.</p> + + <p><a name="Nt_383" href="#NtA_383">[383]</a> <i>See</i> an interesting + paper by Mr. Newman, in the 'Zoologist,' 1857, p. 5764; and Dr. Wallace, + in 'Proc. Entomolog. Soc.,' June 4th, 1860, p. 119.</p> + + <p><a name="Nt_384" href="#NtA_384">[384]</a> Yarrell's 'British Birds,' + vol. i. p. 506; Bechstein, 'Stubenvögel,' s. 185; 'Philosoph. Transact.,' + 1772, p. 271. Bronn ('Geschichte der Natur,' Band ii. s. 96) has + collected a number of cases. For the case of the deer, <i>see</i> 'Penny + Cyclop.,' vol. viii. p. 350.</p> + + <p><a name="Nt_385" href="#NtA_385">[385]</a> 'Journal de Physiologie,' + tom. ii. p. 347.</p> + + <p><a name="Nt_386" href="#NtA_386">[386]</a> For additional evidence on + this subject, <i>see</i> F. Cuvier, in 'Annales du Muséum,' tom. xii. p. + 119.</p> + + <p><a name="Nt_387" href="#NtA_387">[387]</a> Numerous instances could be + given. Thus Livingstone ('Travels,' p. 217) states that the King of the + Barotse, an inland tribe which never had any communication with white + men, was extremely fond of taming animals, and every young antelope was + brought to him. Mr. Galton informs me that the Damaras are likewise fond + of keeping pets. The Indians of South America follow the same habit. + Capt. Wilkes states that the Polynesians of the Samoan Islands tamed + pigeons; and the New Zealanders, as Mr. Mantell informs me, kept various + kinds of birds.</p> + + <p><a name="Nt_388" href="#NtA_388">[388]</a> For analogous cases with + the fowl, <i>see</i> Réaumur, 'Art de faire Eclorre,' &c., 1749, p. + 243; and Col. Sykes, in 'Proc. Zoolog. Soc.,' 1832, &c. With respect + to the fowl not breeding in northern regions, <i>see</i> Latham's 'Hist. + of Birds,' vol. viii., 1823, p. 169.</p> + + <p><a name="Nt_389" href="#NtA_389">[389]</a> 'Mém. par divers Savans, + Acad. des Sciences,' tom. vi., 1835, p. 347.</p> + + <p><a name="Nt_390" href="#NtA_390">[390]</a> Youatt on Sheep, p. + 181.</p> + + <p><a name="Nt_391" href="#NtA_391">[391]</a> J. Mills, 'Treatise on + Cattle,' 1776, p. 72.</p> + + <p><a name="Nt_392" href="#NtA_392">[392]</a> Bechstein, 'Stubenvögel,' + s. 242.</p> + + <p><a name="Nt_393" href="#NtA_393">[393]</a> Crawfurd's 'Descriptive + Dict. of the Indian Islands,' 1856, p. 145.</p> + + <p><a name="Nt_394" href="#NtA_394">[394]</a> 'Bull. de la Soc. + Acclimat., tom. ix., 1862, pp. 380, 384.</p> + + <p><a name="Nt_395" href="#NtA_395">[395]</a> For pigeons, <i>see</i> Dr. + Chapuis, 'Le Pigeon Voyageur Belge,' 1865, p. 66.</p> + + <p><a name="Nt_396" href="#NtA_396">[396]</a> 'Swedish Acts,' vol. i., + 1739, p. 3. Pallas makes the same remark in his Travels (Eng. translat.), + vol. i. p. 292.</p> + + <p><a name="Nt_397" href="#NtA_397">[397]</a> A. Kerner, 'Die Cultur der + Alpenflanzen,' 1864, s. 139; Watson's 'Cybele Britannica,' vol. i. p. + 131; Mr. D. Cameron, also, has written on the culture of Alpine plants in + 'Gard. Chronicle,' 1848, pp. 253, 268, and mentions a few which seed.</p> + + <p><a name="Nt_398" href="#NtA_398">[398]</a> 'Beiträge zur Kenntniss der + Befruchtung,' 1844, s. 333.</p> + + <p><a name="Nt_399" href="#NtA_399">[399]</a> 'Nova Acta Petrop.,' 1793, + p. 391.</p> + + <p><a name="Nt_400" href="#NtA_400">[400]</a> 'Cottage Gardener,' 1856, + pp. 44, 109.</p> + + <p><a name="Nt_401" href="#NtA_401">[401]</a> Dr. Herbert, + 'Amaryllidaceæ,' p. 176.</p> + + <p><a name="Nt_402" href="#NtA_402">[402]</a> Gärtner, 'Beiträge zur + Kenntniss,' &c., s. 560, 564.</p> + + <p><a name="Nt_403" href="#NtA_403">[403]</a> 'Gardener's Chronicle,' + 1844, p. 215; 1850, p. 470.</p> + + <p><a name="Nt_404" href="#NtA_404">[404]</a> 'Beiträge zur Kenntniss,' + &c., s. 252, 333.</p> + + <p><a name="Nt_405" href="#NtA_405">[405]</a> 'Journal of Hort. Soc.,' + vol. ii. 1847, p. 83.</p> + + <p><a name="Nt_406" href="#NtA_406">[406]</a> 'Beiträge zur Kenntniss,' + &c., s. 117 <i>et seq.</i>; Kölreuter, 'Zweite Fortsetzung,' s. 10, + 121; 'Dritte Fortsetzung,' s. 57. Herbert, 'Amaryllidaceæ,' p. 355. + Wiegmann, 'Ueber die Bastarderzeugung,' s. 27.</p> + + <p><a name="Nt_407" href="#NtA_407">[407]</a> 'Bastarderzeugung,' s. + 356.</p> + + <p><a name="Nt_408" href="#NtA_408">[408]</a> 'Teoria della + Riproduzione,' 1816, p. 84; 'Traité du Citrus,' 1811, p. 67.</p> + + <p><a name="Nt_409" href="#NtA_409">[409]</a> Mr. C. W. Crocker, in + 'Gard. Chronicle,' 1861, p. 1092.</p> + + <p><a name="Nt_410" href="#NtA_410">[410]</a> Verlot, 'Des Variétés,' + 1865, p. 80.</p> + + <p><a name="Nt_411" href="#NtA_411">[411]</a> Verlot, idem, p. 88.</p> + + <p><a name="Nt_412" href="#NtA_412">[412]</a> Prof. Allman, Brit. Assoc., + quoted in the 'Phytologist,' vol. ii. p. 483. Prof. Harvey, on the + authority of Mr. Andrews, who discovered the plant, informed me that this + monstrosity could be propagated by seed. With respect to the poppy, + <i>see</i> Prof. Goeppert, as quoted in 'Journal of Horticulture,' July + 1st, 1863, p. 171.</p> + + <p><a name="Nt_413" href="#NtA_413">[413]</a> 'Comptes Rendus,' Dec. + 19th, 1864, p. 1039.</p> + + <p><a name="Nt_414" href="#NtA_414">[414]</a> 'Gardener's Chronicle,' + 1866, p. 681.</p> + + <p><a name="Nt_415" href="#NtA_415">[415]</a> 'Theory of Horticulture,' + p. 333.</p> + + <p><a name="Nt_416" href="#NtA_416">[416]</a> Mr. Fairweather, in + 'Transact. Hort. Soc.,' vol. iii. p. 406; Bosse, quoted by Bronn, + 'Geschichte der Natur,' B. ii. s. 77. On the effects of the removal of + the anthers, <i>see</i> Mr. Leitner, in Silliman's 'North American Journ. + of Science,' vol. xxiii. p. 47; and Verlot, 'Des Variétés,' 1865, p. + 84.</p> + + <p><a name="Nt_417" href="#NtA_417">[417]</a> Lindley's 'Theory of + Horticulture,' p. 333.</p> + + <p><a name="Nt_418" href="#NtA_418">[418]</a> 'Gardener's Chronicle,' + 1865, p. 626; 1866, pp. 290, 730; and Verlot, 'Des Variétés,' p. 75.</p> + + <p><a name="Nt_419" href="#NtA_419">[419]</a> 'Gardener's Chronicle,' + 1843, p. 628. In this article I suggested the following theory on the + doubleness of flowers.</p> + + <p><a name="Nt_420" href="#NtA_420">[420]</a> Quoted by Gärtner, + 'Bastarderzeugung,' s. 567.</p> + + <p><a name="Nt_421" href="#NtA_421">[421]</a> 'Gardener's Chronicle,' + 1866, p. 901.</p> + + <p><a name="Nt_422" href="#NtA_422">[422]</a> Lindley, 'Theory of + Horticulture,' p. 175-179; Godron, 'De l'Espèce,' tom. i. p. 106: + Pickering, 'Races of Man;' Gallesio, 'Teoria della Riproduzione,' 1816, + p. 101-110. Meyen ('Reise um Erde,' Th. ii. s. 214) states that at + Manilla one variety of the banana is full of seeds; and Chamisso + (Hooker's 'Bot. Misc.,' vol. i. p. 310) describes a variety of the + bread-fruit in the Mariana Islands with small fruit, containing seeds + which are frequently perfect. Burnes, in his 'Travels in Bokhara,' + remarks on the pomegranate seeding in Mazenderan, as a remarkable + peculiarity.</p> + + <p><a name="Nt_423" href="#NtA_423">[423]</a> Ingledew, in 'Transact. of + Agricult. and Hort. Soc. of India,' vol. ii.</p> + + <p><a name="Nt_424" href="#NtA_424">[424]</a> 'De la Fécondation,' 1862, + p. 308.</p> + + <p><a name="Nt_425" href="#NtA_425">[425]</a> Hooker's 'Bot. Misc.,' vol. + i. p. 99; Gallesio, 'Teoria della Riproduzione,' p. 110.</p> + + <p><a name="Nt_426" href="#NtA_426">[426]</a> 'Transact. Linn. Soc.,' + vol. xvii. p. 563.</p> + + <p><a name="Nt_427" href="#NtA_427">[427]</a> Godron, 'De l'Espèce,' tom. + ii. p. 106; Herbert on Crocus, in 'Journal of Hort. Soc.,' vol. i., 1846, + p. 254.—Dr. Wight, from what he has seen in India, believes in this + view; 'Madras Journal of Lit. and Science,' vol. iv., 1836, p. 61.</p> + + <p><a name="Nt_428" href="#NtA_428">[428]</a> Wahlenberg specifies eight + species in this state on the Lapland Alps: <i>see</i> Appendix to + Linnæus' 'Tour in Lapland,' translated by Sir J. E. Smith, vol. ii. pp. + 274-280.</p> + + <p><a name="Nt_429" href="#NtA_429">[429]</a> 'Travels in North America,' + Eng. translat., vol. iii. p. 175.</p> + + <p><a name="Nt_430" href="#NtA_430">[430]</a> With respect to the ivy and + Acorus, <i>see</i> Dr. Bromfield in the 'Phytologist,' vol. iii. p. 376. + <i>See</i> also Lindley and Vaucher on the Acorus.</p> + + <p><a name="Nt_431" href="#NtA_431">[431]</a> 'Annal. des Sc. Nat.,' 3rd + series, Zool., tom. iv. p. 280. Prof. Decaisne refers also to analogous + cases with mosses and lichens near Paris.</p> + + <p><a name="Nt_432" href="#NtA_432">[432]</a> Mr. Tuckerman, in + Silliman's 'American Journal of Science,' vol. xlv. p. 41.</p> + + <p><a name="Nt_433" href="#NtA_433">[433]</a> Sir J. E. Smith, 'English + Flora,' vol. i. p. 339.</p> + + <p><a name="Nt_434" href="#NtA_434">[434]</a> G. Planchon, 'Flora de + Montpellier,' 1864, p. 20.</p> + + <p><a name="Nt_435" href="#NtA_435">[435]</a> On the non-production of + seeds in England <i>see</i> Mr. Crocker, in 'Gardener's Weekly Magazine,' + 1852, p. 70; Vaucher, 'Hist. Phys. Plantes d'Europe,' tom. i. p. 33; + Lecoq, 'Géograph. Bot. de l'Europe,' tom. iv. p. 466; Dr. D. Clos, in + 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. xvii., 1852, p. 129: this + latter author refers to other analogous cases. On the non-production of + pollen by this Ranunculus <i>see</i> Chatin, in 'Comptes Rendus,' June + 11th, 1866.</p> + + <p><a name="Nt_436" href="#NtA_436">[436]</a> 'Bastarderzeugung,' s. 565. + Kölreuter ('Dritte Fortsetzung,' s. 73, 87, 119) also shows that when two + species, one single and the other double, are crossed, the hybrids are + apt to be extremely double.</p> + + <p><a name="Nt_437" href="#NtA_437">[437]</a> 'Teoria della Riproduzione + Veg.,' 1816, p. 73.</p> + + <p><a name="Nt_438" href="#NtA_438">[438]</a> 'Bastarderzeugung,' s. + 573.</p> + + <p><a name="Nt_439" href="#NtA_439">[439]</a> Ibid., s. 527.</p> + + <p><a name="Nt_440" href="#NtA_440">[440]</a> 'Transactions Phil. Soc.,' + 1799, p. 202. For Kölreuter, <i>see</i> 'Mém. de l'Acad. de St. + Pétersbourg,' tom. iii., 1809 (published 1811), p. 197. In reading C. K. + Sprengel's remarkable work, 'Das entdeckte Geheimniss,' &c., 1793, it + is curious to observe how often this wonderfully acute observer failed to + understand the full meaning of the structure of the flowers which he has + so well described, from not always having before his mind the key to the + problem, namely, the good derived from the crossing of distinct + individual plants.</p> + + <p><a name="Nt_441" href="#NtA_441">[441]</a> This abstract was published + in the fourth edition (1866) of my 'Origin of Species;' but as this + edition will be in the hands of but few persons, and as my original + observations on this point have not as yet been published in detail, I + have ventured here to reprint the abstract.</p> + + <p><a name="Nt_442" href="#NtA_442">[442]</a> The term <i>unconscious + selection</i> has been objected to as a contradiction: but <i>see</i> + some excellent observations on this head by Prof. Huxley ('Nat. Hist. + Review,' Oct. 1864, p. 578), who remarks that when the wind heaps up + sand-dunes it sifts and <i>unconsciously selects</i> from the gravel on + the beach grains of sand of equal size.</p> + + <p><a name="Nt_443" href="#NtA_443">[443]</a> Sheep, 1838, p. 60.</p> + + <p><a name="Nt_444" href="#NtA_444">[444]</a> Mr. J. Wright on Shorthorn + Cattle, in 'Journal of Royal Agricult. Soc.,' vol. vii. pp. 208, 209.</p> + + <p><a name="Nt_445" href="#NtA_445">[445]</a> H. D. Richardson on Pigs, + 1817, p. 44.</p> + + <p><a name="Nt_446" href="#NtA_446">[446]</a> 'Journal of R. Agricult. + Soc.,' vol. i. p. 24.</p> + + <p><a name="Nt_447" href="#NtA_447">[447]</a> Sheep, pp. 520, 319.</p> + + <p><a name="Nt_448" href="#NtA_448">[448]</a> Loudon's 'Mag. of Nat. + Hist.,' vol. viii., 1835, p. 618.</p> + + <p><a name="Nt_449" href="#NtA_449">[449]</a> 'A Treatise on the Art of + Breeding the Almond Tumbler,' 1851, p. 9.</p> + + <p><a name="Nt_450" href="#NtA_450">[450]</a> 'Recreations in + Agriculture,' vol. ii. p. 409.</p> + + <p><a name="Nt_451" href="#NtA_451">[451]</a> Youatt on Cattle, pp. 191, + 227.</p> + + <p><a name="Nt_452" href="#NtA_452">[452]</a> Ferguson, 'Prize Poultry,' + 1854, p. 208.</p> + + <p><a name="Nt_453" href="#NtA_453">[453]</a> Wilson, in 'Transact. + Highland Agricult. Soc.,' quoted in 'Gard. Chronicle,' 1844, p. 29.</p> + + <p><a name="Nt_454" href="#NtA_454">[454]</a> Simmonds, quoted in 'Gard. + Chronicle,' 1855, p. 637. And for the second quotation, <i>see</i> Youatt + on Sheep, p. 171.</p> + + <p><a name="Nt_455" href="#NtA_455">[455]</a> Robinet, 'Vers à Soie,' + 1848, p. 271.</p> + + <p><a name="Nt_456" href="#NtA_456">[456]</a> Quatrefages, 'Les Maladies + du Ver à Soie,' 1859, p. 101.</p> + + <p><a name="Nt_457" href="#NtA_457">[457]</a> M. Simon, in 'Bull. de la + Soc. d'Acclimat.,' tom. ix., 1862, p. 221.</p> + + <p><a name="Nt_458" href="#NtA_458">[458]</a> 'The Poultry Chronicle,' + vol. i., 1854, p. 607.</p> + + <p><a name="Nt_459" href="#NtA_459">[459]</a> J. M. Eaton, 'A Treatise on + Fancy Pigeons,' 1852, p. xiv., and 'A Treatise on the Almond Tumbler,' + 1851, p. 11.</p> + + <p><a name="Nt_460" href="#NtA_460">[460]</a> 'Journal Royal Agricultural + Soc.,' vol. vi. p. 22.</p> + + <p><a name="Nt_461" href="#NtA_461">[461]</a> 'Poultry Chronicle,' vol. + ii., 1855, p. 596.</p> + + <p><a name="Nt_462" href="#NtA_462">[462]</a> Isid. Geoffroy St. Hilaire, + 'Hist. Nat. Gén.,' tom. iii. p. 254.</p> + + <p><a name="Nt_463" href="#NtA_463">[463]</a> 'Gardener's Chronicle,' + 1850, p. 198.</p> + + <p><a name="Nt_464" href="#NtA_464">[464]</a> 'Transact. Hort. Soc.,' + vol. vi. p. 152.</p> + + <p><a name="Nt_465" href="#NtA_465">[465]</a> 'Journal of Horticulture,' + 1862, p. 369.</p> + + <p><a name="Nt_466" href="#NtA_466">[466]</a> 'Transact. Hort. Soc.,' + vol. iv. p. 381.</p> + + <p><a name="Nt_467" href="#NtA_467">[467]</a> 'Transact. Hort. Soc.,' + vol. iv. p. 285.</p> + + <p><a name="Nt_468" href="#NtA_468">[468]</a> Rev. W. Bromehead, in + 'Gard. Chronicle,' 1857, p. 550.</p> + + <p><a name="Nt_469" href="#NtA_469">[469]</a> 'Gard. Chronicle,' 1862, p. + 721.</p> + + <p><a name="Nt_470" href="#NtA_470">[470]</a> Dr. Anderson, in 'The Bee,' + vol. vi. p. 96; Mr. Barnes, in 'Gard. Chronicle,' 1844, p. 476.</p> + + <p><a name="Nt_471" href="#NtA_471">[471]</a> Godron, 'De l'Espèce,' + 1859, tom. ii. p. 69; 'Gard. Chronicle,' 1854, p. 258.</p> + + <p><a name="Nt_472" href="#NtA_472">[472]</a> On Sheep, p. 18.</p> + + <p><a name="Nt_473" href="#NtA_473">[473]</a> Volz, 'Beiträge zur + Kulturgeschichte,' 1852, s. 47.</p> + + <p><a name="Nt_474" href="#NtA_474">[474]</a> Mitford's 'History of + Greece,' vol. i. p. 73.</p> + + <p><a name="Nt_475" href="#NtA_475">[475]</a> Dr. Dally, translated in + 'Anthropological Review,' May 1864, p. 101.</p> + + <p><a name="Nt_476" href="#NtA_476">[476]</a> Volz, 'Beiträge,' &c., + 1852, s. 80.</p> + + <p><a name="Nt_477" href="#NtA_477">[477]</a> 'History of the World,' ch. + 45.</p> + + <p><a name="Nt_478" href="#NtA_478">[478]</a> 'Gardener's Chronicle,' + 1848, p. 323.</p> + + <p><a name="Nt_479" href="#NtA_479">[479]</a> Reynier, 'De l'Economie des + Celtes,' 1818, pp. 487, 503.</p> + + <p><a name="Nt_480" href="#NtA_480">[480]</a> Le Couteur on Wheat, p. + 15.</p> + + <p><a name="Nt_481" href="#NtA_481">[481]</a> Michel, 'Des Haras,' 1861, + p. 84.</p> + + <p><a name="Nt_482" href="#NtA_482">[482]</a> Sir W. Wilde, an 'Essay on + Unmanufactured Animal Remains,' &c., 1860, p. 11.</p> + + <p><a name="Nt_483" href="#NtA_483">[483]</a> Col. Hamilton Smith, 'Nat. + Library,' vol. xii., Horses, pp. 135, 140.</p> + + <p><a name="Nt_484" href="#NtA_484">[484]</a> Michel, 'Des Haras,' p. + 90.</p> + + <p><a name="Nt_485" href="#NtA_485">[485]</a> Mr. Baker, 'History of the + Horse,' Veterinary, vol. xiii. p. 423.</p> + + <p><a name="Nt_486" href="#NtA_486">[486]</a> M. l'Abbé Carlier, in + 'Journal de Physique,' vol. xxiv., 1784, p. 181: this memoir contains + much information on the ancient selection of sheep; and is my authority + for rams not being killed young in England.</p> + + <p><a name="Nt_487" href="#NtA_487">[487]</a> 'Gardener's Chronicle,' + 1843, p. 389.</p> + + <p><a name="Nt_488" href="#NtA_488">[488]</a> Communications to Board of + Agriculture, quoted in Dr. Darwin's 'Phytologia,' 1800, p. 451.</p> + + <p><a name="Nt_489" href="#NtA_489">[489]</a> 'Mémoire sur les Chinois,' + 1786, tom. xi. p. 55; tom. v. p. 507.</p> + + <p><a name="Nt_490" href="#NtA_490">[490]</a> 'Recherches sur + l'Agriculture des Chinois,' par L. D'Hervey-Saint-Denys, 1850, p. 229. + With respect to Khang-hi, <i>see</i> Huc's 'Chinese Empire,' p. 311.</p> + + <p><a name="Nt_491" href="#NtA_491">[491]</a> Anderson, in 'Linn. + Transact.,' vol. xii. p. 253.</p> + + <p><a name="Nt_492" href="#NtA_492">[492]</a> 'Mém. de l'Acad.' (divers + savans), tom. vi., 1835, p. 333.</p> + + <p><a name="Nt_493" href="#NtA_493">[493]</a> 'Des Quadrupèdes du + Paraguay,' 1801, tom. ii. p. 333, 371.</p> + + <p><a name="Nt_494" href="#NtA_494">[494]</a> 'The Great Sahara,' by the + Rev. H. B. Tristram, 1860, p. 238.</p> + + <p><a name="Nt_495" href="#NtA_495">[495]</a> Pallas, 'Act. Acad. St. + Petersburg,' 1777, p. 249; Moorcroft and Trebeck, 'Travels in the + Himalayan Provinces,' 1841.</p> + + <p><a name="Nt_496" href="#NtA_496">[496]</a> Quoted from Raffles, in the + 'Indian Field,' 1859, p. 196; for Varro, <i>see</i> Pallas, <i>ut + supra</i>.</p> + + <p><a name="Nt_497" href="#NtA_497">[497]</a> Erman's 'Travels in + Siberia,' Eng. translat., vol. i. p. 453.</p> + + <p><a name="Nt_498" href="#NtA_498">[498]</a> <i>See</i> also 'Journal of + R. Geograph. Soc.,' vol. xiii. part i. p. 65.</p> + + <p><a name="Nt_499" href="#NtA_499">[499]</a> Livingstone's 'First + Travels,' pp. 191, 439, 565; <i>see</i> also 'Expedition to the Zambesi,' + 1865, p. 465, for an analogous case respecting a good breed of goats.</p> + + <p><a name="Nt_500" href="#NtA_500">[500]</a> Andersson's 'Travels in + South Africa,' pp. 232, 318, 319.</p> + + <p><a name="Nt_501" href="#NtA_501">[501]</a> Dr. Vavasseur, in 'Bull. de + la Soc. d'Acclimat.,' tom. viii., 1861, p. 136.</p> + + <p><a name="Nt_502" href="#NtA_502">[502]</a> 'The Natural History of Dee + Side,' 1855, p. 476.</p> + + <p><a name="Nt_503" href="#NtA_503">[503]</a> 'Bull. de la Soc. + d'Acclimat.,' tom. vii., 1860, p. 457.</p> + + <p><a name="Nt_504" href="#NtA_504">[504]</a> 'Cattle,' p. 48.</p> + + <p><a name="Nt_505" href="#NtA_505">[505]</a> Livingstone's Travels, p. + 576; Andersson, 'Lake Ngami,' 1856, p. 222. With respect to the sale in + Kaffraria, <i>see</i> 'Quarterly Review,' 1860, p. 139.</p> + + <p><a name="Nt_506" href="#NtA_506">[506]</a> 'Mémoire sur les Chinois' + (by the Jesuits), 1786, tom. xi. p. 57.</p> + + <p><a name="Nt_507" href="#NtA_507">[507]</a> F. Michel, 'Des Haras,' pp. + 47, 50.</p> + + <p><a name="Nt_508" href="#NtA_508">[508]</a> Col. Hamilton Smith, Dogs, + in 'Nat. Lib.,' vol. x. p. 103.</p> + + <p><a name="Nt_509" href="#NtA_509">[509]</a> Azara, 'Quadrupèdes du + Paraguay,' tom. ii. p. 324.</p> + + <p><a name="Nt_510" href="#NtA_510">[510]</a> Sidney's edit. of Youatt, + 1860, pp. 24, 25.</p> + + <p><a name="Nt_511" href="#NtA_511">[511]</a> 'Rural Economy of + Yorkshire,' vol. ii. p. 182.</p> + + <p><a name="Nt_512" href="#NtA_512">[512]</a> Moll et Gayot, 'Du + Bœuf,' 1860, p. 547.</p> + + <p><a name="Nt_513" href="#NtA_513">[513]</a> 'The India Sporting + Review,' vol. ii. p. 181; 'The Stud Farm,' by Cecil, p. 58.</p> + + <p><a name="Nt_514" href="#NtA_514">[514]</a> 'The Horse,' p. 22.</p> + + <p><a name="Nt_515" href="#NtA_515">[515]</a> 'History of England,' vol. + i. p. 316.</p> + + <p><a name="Nt_516" href="#NtA_516">[516]</a> 'Uber Beständigkeit der + Arten.'</p> + + <p><a name="Nt_517" href="#NtA_517">[517]</a> Youatt on Sheep, p. + 315.</p> + + <p><a name="Nt_518" href="#NtA_518">[518]</a> 'Ueber Shorthorn Rindvieh,' + 1857, s. 51.</p> + + <p><a name="Nt_519" href="#NtA_519">[519]</a> Low, 'Domesticated + Animals,' 1845, p. 363.</p> + + <p><a name="Nt_520" href="#NtA_520">[520]</a> 'Quarterly Review,' 1849, + p. 392.</p> + + <p><a name="Nt_521" href="#NtA_521">[521]</a> H. von Nathusius, + 'Vorstudien ... Schweineschædel,' 1864, s. 140.</p> + + <p><a name="Nt_522" href="#NtA_522">[522]</a> <i>See</i> also Dr. Christ, + in 'Rütimeyer's Pfahlbauten,' 1861, s. 226.</p> + + <p><a name="Nt_523" href="#NtA_523">[523]</a> The passage is given 'Bull. + Soc. d'Acclimat.,' 1858, p. 11.</p> + + <p><a name="Nt_524" href="#NtA_524">[524]</a> 'Journal of Horticulture,' + 1862, p. 394.</p> + + <p><a name="Nt_525" href="#NtA_525">[525]</a> 'Gardener's Chronicle,' + 1857, p. 85.</p> + + <p><a name="Nt_526" href="#NtA_526">[526]</a> <i>See</i> Mr. Wildman's + address to the Floricult. Soc., in 'Gardener's Chronicle,' 1843, p. + 86.</p> + + <p><a name="Nt_527" href="#NtA_527">[527]</a> 'Journal of Horticulture,' + Oct. 24th, 1865, p. 239.</p> + + <p><a name="Nt_528" href="#NtA_528">[528]</a> Prescott's 'Hist. of + Mexico,' vol. ii. p. 61.</p> + + <p><a name="Nt_529" href="#NtA_529">[529]</a> Sageret, 'Pomologie + Physiologique,' 1830, p. 47; Gallesio, 'Teoria della Riproduzione,' 1816, + p. 88; Godron, 'De l'Espèce,' 1859, tom. ii. pp. 63, 67, 70. In my tenth + and eleventh chapters I have given details on the potato; and I can + confirm similar remarks with respect to the onion. I have also shown how + far Naudin concurs in regard to the varieties of the melon.</p> + + <p><a name="Nt_530" href="#NtA_530">[530]</a> Godron, 'De l'Espèce,' tom. + ii. p. 27.</p> + + <p><a name="Nt_531" href="#NtA_531">[531]</a> 'The Anthropological + Treatises of Blumenbach,' 1865, p. 292.</p> + + <p><a name="Nt_532" href="#NtA_532">[532]</a> Mr. J. J. Murphy in his + opening address to the Belfast Nat. Hist. Soc., as given in the Belfast + Northern Whig, Nov. 19, 1866. Mr. Murphy here follows the line of + argument against my views previously and more cautiously given by the + Rev. C. Pritchard, Pres. Royal Astronomical Soc., in his sermon + (Appendix, p. 33) preached before the British Association at Nottingham, + 1866.</p> + + <p><a name="Nt_533" href="#NtA_533">[533]</a> On the Vision of Fishes and + Amphibia, translated in 'Annals and Mag. of Nat. Hist.,' vol. xviii., + 1866, p. 469.</p> + + <p><a name="Nt_534" href="#NtA_534">[534]</a> Fourth edition, 1866, p. + 215.</p> + + <p><a name="Nt_535" href="#NtA_535">[535]</a> Quoted by Youatt on Sheep, + p. 325. <i>See</i> also Youatt on Cattle, pp. 62, 69.</p> + + <p><a name="Nt_536" href="#NtA_536">[536]</a> MM. Lherbette and De + Quatrefages, in 'Bull. Soc. Acclimat.,' tom. viii., 1861, p. 311.</p> + + <p><a name="Nt_537" href="#NtA_537">[537]</a> 'The Poultry Book,' 1866, + p. 123.</p> + + <p><a name="Nt_538" href="#NtA_538">[538]</a> Youatt on Sheep, p. + 312.</p> + + <p><a name="Nt_539" href="#NtA_539">[539]</a> 'Treatise on the Almond + Tumbler,' 1851, p. 33.</p> + + <p><a name="Nt_540" href="#NtA_540">[540]</a> Dr. Heusinger, + 'Wochenschrift für die Heilkunde,' Berlin, 1846, s. 279.</p> + + <p><a name="Nt_541" href="#NtA_541">[541]</a> Youatt on the Dog, p. + 232.</p> + + <p><a name="Nt_542" href="#NtA_542">[542]</a> 'The Fruit-trees of + America,' 1845, p. 270: for peaches, p. 466.</p> + + <p><a name="Nt_543" href="#NtA_543">[543]</a> 'Proc. Royal Soc. of Arts + and Sciences of Mauritius,' 1852, p. cxxxv.</p> + + <p><a name="Nt_544" href="#NtA_544">[544]</a> 'Gardener's Chronicle,' + 1856, p. 379.</p> + + <p><a name="Nt_545" href="#NtA_545">[545]</a> Quatrefages, 'Maladies + Actuelles du Ver à Soie,' 1859, pp. 12, 214.</p> + + <p><a name="Nt_546" href="#NtA_546">[546]</a> 'Gardener's Chronicle,' + 1851, p. 595.</p> + + <p><a name="Nt_547" href="#NtA_547">[547]</a> 'Journal of Horticulture,' + 1862, p. 476.</p> + + <p><a name="Nt_548" href="#NtA_548">[548]</a> 'Gardener's Chronicle,' + 1852, pp. 435, 691.</p> + + <p><a name="Nt_549" href="#NtA_549">[549]</a> Bechstein, 'Naturgesch. + Deutschlands,' 1801, B. i. s. 310.</p> + + <p><a name="Nt_550" href="#NtA_550">[550]</a> Prichard, 'Phys. Hist. of + Mankind,' 1851, vol. i. p. 224.</p> + + <p><a name="Nt_551" href="#NtA_551">[551]</a> G. Lewis's 'Journal of + Residence in West Indies,' 'Home and Col. Library,' p. 100.</p> + + <p><a name="Nt_552" href="#NtA_552">[552]</a> Sidney's edit. of Youatt on + the Pig, p.24.</p> + + <p><a name="Nt_553" href="#NtA_553">[553]</a> 'Journal of Horticulture,' + 1862, pp. 476, 498; 1865, p. 460. With respect to the heartsease, + 'Gardener's Chronicle,' 1863, p. 628.</p> + + <p><a name="Nt_554" href="#NtA_554">[554]</a> 'Des Jacinthes, de leur + Culture,' 1768, p. 53: on wheat, 'Gardener's Chronicle,' 1846, p. + 653.</p> + + <p><a name="Nt_555" href="#NtA_555">[555]</a> W. B. Tegetmeier, 'The + Field,' Feb. 25, 1865. With respect to black fowls, <i>see</i> a + quotation in Thompson's 'Nat. Hist. of Ireland,' 1849, vol. i. p. 22.</p> + + <p><a name="Nt_556" href="#NtA_556">[556]</a> 'Bull. de la Soc. + d'Acclimat.,' tom. vii. 1860, p. 359.</p> + + <p><a name="Nt_557" href="#NtA_557">[557]</a> 'Transact. Hort. Soc.,' + vol. i. 2nd series, 1835, p. 275. For raspberries, <i>see</i> 'Gard. + Chronicle,' 1855, p. 154, and 1863, p. 245.</p> + + <p><a name="Nt_558" href="#NtA_558">[558]</a> 'Gardener's Chronicle,' + 1843, p. 806.</p> + + <p><a name="Nt_559" href="#NtA_559">[559]</a> Ibid., 1850, p. 732.</p> + + <p><a name="Nt_560" href="#NtA_560">[560]</a> Ibid., 1860, p. 956.</p> + + <p><a name="Nt_561" href="#NtA_561">[561]</a> J. De Jonghe, in 'Gard. + Chronicle,' 1860, p. 120.</p> + + <p><a name="Nt_562" href="#NtA_562">[562]</a> Downing, 'Fruit-trees of + North America,' pp. 266, 501: in regard to the cherry, p. 198.</p> + + <p><a name="Nt_563" href="#NtA_563">[563]</a> 'Gardener's Chronicle,' + 1849, p. 755.</p> + + <p><a name="Nt_564" href="#NtA_564">[564]</a> 'Journal of Horticulture,' + Sept. 26th, 1865, p. 254; <i>see</i> other references given in chap. + x.</p> + + <p><a name="Nt_565" href="#NtA_565">[565]</a> Mr. Selby, in 'Mag. of + Zoology and Botany,' Edinburgh, vol. ii., 1838, p. 393.</p> + + <p><a name="Nt_566" href="#NtA_566">[566]</a> The Reine Claude de Bavay, + 'Journal of Horticulture,' Dec. 27, 1864, p. 511.</p> + + <p><a name="Nt_567" href="#NtA_567">[567]</a> Mr. Pusey, in 'Journal of + R. Agricult. Soc., vol. vi. p. 179. For Swedish turnips, <i>see</i> + 'Gard. Chron.,' 1847, p. 91.</p> + + <p><a name="Nt_568" href="#NtA_568">[568]</a> Godron, 'De l'Espèce,' tom. + ii. p. 98.</p> + + <p><a name="Nt_569" href="#NtA_569">[569]</a> 'Gardener's Chron.,' 1866, + p. 732.</p> + + <p><a name="Nt_570" href="#NtA_570">[570]</a> 'Gardener's Chronicle,' + 1862, pp. 820, 821.</p> + + <p><a name="Nt_571" href="#NtA_571">[571]</a> 'On the Varieties of + Wheat,' p. 59.</p> + + <p><a name="Nt_572" href="#NtA_572">[572]</a> Mr. Hewitt and others, in + 'Journal of Hort.,' 1862, p. 773.</p> + + <p><a name="Nt_573" href="#NtA_573">[573]</a> 'Encyclop. of Rural + Sports,' p. 405.</p> + + <p><a name="Nt_574" href="#NtA_574">[574]</a> Col. Le Couteur, 'Journal + Roy. Agricult. Soc.,' vol. iv. p. 43.</p> + + <p><a name="Nt_575" href="#NtA_575">[575]</a> 'Gardener's Chronicle,' + 1845, p. 273.</p> + + <p><a name="Nt_576" href="#NtA_576">[576]</a> 'Journal of Horticulture,' + 1862, p. 157.</p> + + <p><a name="Nt_577" href="#NtA_577">[577]</a> 'Cottage Gardener,' 1860, + p. 368.</p> + + <p><a name="Nt_578" href="#NtA_578">[578]</a> 'A Review of Reports,' + 1808, p. 406.</p> + + <p><a name="Nt_579" href="#NtA_579">[579]</a> 'Gardener's Chronicle,' + 1853, p. 45.</p> + + <p><a name="Nt_580" href="#NtA_580">[580]</a> Isidore Geoffroy St. + Hilaire, 'Hist. Nat. Gén.,' tom. iii. p. 49. On the Cochineal Insect, p. + 46.</p> + + <p><a name="Nt_581" href="#NtA_581">[581]</a> Capt. Marryat, quoted by + Blyth in 'Journ. Asiatic Soc. of Bengal,' vol. xxviii. p. 229.</p> + + <p><a name="Nt_582" href="#NtA_582">[582]</a> Mr. Oxley, 'Journal of the + Indian Archipelago,' vol. ii., 1848, p. 645.</p> + + <p><a name="Nt_583" href="#NtA_583">[583]</a> Mr. Abbey, in 'Journal of + Horticulture,' Dec. 1, 1863, p. 430.</p> + + <p><a name="Nt_584" href="#NtA_584">[584]</a> 'On Naval Timber,' 1831, p. + 107.</p> + + <p><a name="Nt_585" href="#NtA_585">[585]</a> Mr. Baily, in 'The Poultry + Chronicle,' vol. ii., 1854, p. 150. Also vol. i. p. 342; vol. iii. p. + 245.</p> + + <p><a name="Nt_586" href="#NtA_586">[586]</a> 'Cottage Gardener,' 1855, + December, p. 171; 1856, January, pp. 248, 323.</p> + + <p><a name="Nt_587" href="#NtA_587">[587]</a> 'Ueber Shorthorn Rindvieh,' + 1857, s. 51.</p> + + <p><a name="Nt_588" href="#NtA_588">[588]</a> 'The Veterinary,' vol. + xiii. p. 720. For the Glamorganshire cattle, <i>see</i> Youatt on Cattle, + p. 51.</p> + + <p><a name="Nt_589" href="#NtA_589">[589]</a> J. M. Eaton, 'A Treatise on + Fancy Pigeons,' p. 82; Ferguson, on 'Rare and Prize Poultry,' p. 162; Mr. + Brent, in 'Cottage Gardener,' Oct. 1860. p. 13.</p> + + <p><a name="Nt_590" href="#NtA_590">[590]</a> 'Die Racen des Schweines,' + 1860, s. 48.</p> + + <p><a name="Nt_591" href="#NtA_591">[591]</a> <i>See</i> some good + remarks on this head by M. de Quatrefages, 'Unité de l'Espèce Humaine,' + 1861, p. 119.</p> + + <p><a name="Nt_592" href="#NtA_592">[592]</a> Verlot, 'Des Variétés,' + 1865, p. 94.</p> + + <p><a name="Nt_593" href="#NtA_593">[593]</a> Mr. Patrick Sheriff, in + 'Gard. Chronicle,' 1858, p. 771.</p> + + <p><a name="Nt_594" href="#NtA_594">[594]</a> 'Pomologie Physiolog.,' + 1830, p. 106.</p> + + <p><a name="Nt_595" href="#NtA_595">[595]</a> Youatt on Sheep, p. + 521.</p> + + <p><a name="Nt_596" href="#NtA_596">[596]</a> 'A Treatise on the Almond + Tumbler,' p. i.</p> + + <p><a name="Nt_597" href="#NtA_597">[597]</a> M. J. de Jonghe, in 'Gard. + Chron.,' 1858, p. 173.</p> + + <p><a name="Nt_598" href="#NtA_598">[598]</a> Max. Müller, 'Science of + Language,' 1861, p. 223.</p> + + <p><a name="Nt_599" href="#NtA_599">[599]</a> Youatt on Cattle, pp. 116, + 128.</p> + + <p><a name="Nt_600" href="#NtA_600">[600]</a> 'Domesticated Animals,' p. + 188.</p> + + <p><a name="Nt_601" href="#NtA_601">[601]</a> Volz, 'Beiträge zur + Kulturgeschichte,' 1852, s. 99 <i>et passim</i>.</p> + + <p><a name="Nt_602" href="#NtA_602">[602]</a> Blaine, 'Encyclop. of Rural + Sports,' p. 213.</p> + + <p><a name="Nt_603" href="#NtA_603">[603]</a> 'Des Jacinthes,' &c., + Amsterdam, 1768, p. 43; Verlot, 'Des Variétés,' &c., p. 86. On the + reindeer, <i>see</i> Linnæus, 'Tour in Lapland,' translated by Sir J. E. + Smith, vol. i. p. 314. The statement in regard to German shepherds is + given on the authority of Dr. Weinland.</p> + + <p><a name="Nt_604" href="#NtA_604">[604]</a> Müller's 'Physiology,' Eng. + translation, vol. ii. p. 1662. With respect to the similarity of twins in + constitution, Dr. William Ogle has given me the following extract from + Professor Trousseau's Lectures ('Clinique Médicale,' tom. i. p. 523), in + which a curious case is recorded:—"J'ai donné mes soins à deux + frères jumeaux, tous deux si extraordinairement ressemblants qu'il + m'était impossible de les reconnaître, à moins de les voir l'un à côté de + l'autre. Cette ressemblance physique s'étendait plus loin: ils avaient, + permettez-moi l'expression, une similitude pathologique plus remarquable + encore. Ainsi l'un d'eux que je voyais aux néothermes à Paris malade + d'une ophthalmie rhumatismale me disait, 'En ce moment mon frère doit + avoir une ophthalmie comme la mienne;' et comme je m'étais récrié, il me + montrait quelques jours après une lettre qu'il venait de recevoir de ce + frère alors à Vienne, et qui lui écrivait en effet—'J'ai mon + ophthalmie, tu dois avoir la tienne.' Quelque singulier que ceci puisse + paraître, le fait non est pas moins exact: on ne me l'a pas raconté, je + l'ai vu, et j'en ai vu d'autres analogues dans ma pratique. Ces deux + jumeaux étaient aussi tous deux asthmatiques, et asthmatiques à un + effroyable degré. Originaires de Marseille, ils n'ont jamais pu demeurer + dans cette ville, où leurs intérêts les appelaient souvent, sans être + pris de leurs accès; jamais ils n'en éprouvaient à Paris. Bien mieux, il + leur suffisait de gagner Toulon pour être guéris de leurs attaques de + Marseilles. Voyageant sans cesse et dans tous pays pour leurs affaires, + ils avaient remarqué que certaines localités leur étaient funestes, que + dans d'autres ils étaient exempts de tout phénomène d'oppression."</p> + + <p><a name="Nt_605" href="#NtA_605">[605]</a> Isid. Geoffroy St. Hilaire, + 'Hist. des Anomalies,' tom. iii. p. 352; Moquin Tandon, 'Tératologie + Végétale,' 1841, p. 115.</p> + + <p><a name="Nt_606" href="#NtA_606">[606]</a> Metzger, 'Die + Getreidearten,' 1841, s. 39.</p> + + <p><a name="Nt_607" href="#NtA_607">[607]</a> On the date-palm, + <i>see</i> Vogel, 'Annals and Mag. of Nat. Hist.,' 1854, p. 460. On + Indian varieties, Dr. F. Hamilton, 'Transact. Linn. Soc.,' vol. xiv. p. + 296. On the varieties cultivated in Tahiti, <i>see</i> Dr. Bennett, in + Loudon's 'Mag. of N. Hist.,' vol. v., 1832, p. 484. Also Ellis, + 'Polynesian Researches,' vol. i. pp. 375, 370. On twenty varieties of the + Pandanus and other trees in the Marianne Island, <i>see</i> 'Hooker's + Miscellany,' vol. i. p. 308. On the bamboo in China, <i>see</i> Huc's + 'Chinese Empire,' vol. ii. p. 307.</p> + + <p><a name="Nt_608" href="#NtA_608">[608]</a> 'Treatise on the Culture of + the Apple,' &c., p. 3.</p> + + <p><a name="Nt_609" href="#NtA_609">[609]</a> Gallesio, 'Teoria della + Riproduzione Veg.,' p. 125.</p> + + <p><a name="Nt_610" href="#NtA_610">[610]</a> <i>See</i> Dr. Hooker's + Memoir on Arctic Plants in 'Linn. Transact.,' vol. xxiii, part ii. Mr. + Woodward, and a higher authority cannot be quoted, speaks of the Arctic + mollusca (in his 'Rudimentary Treatise,' 1856, p. 355) as remarkably + subject to variation.</p> + + <p><a name="Nt_611" href="#NtA_611">[611]</a> Bechstein, in his + 'Naturgeschichte der Stubenvögel,' 1840, s. 238, has some good remarks on + this subject. He states that his canary-birds varied in colour, though + kept on uniform food.</p> + + <p><a name="Nt_612" href="#NtA_612">[612]</a> 'The Plant,' by Schleiden, + translated by Henfrey, 1848, p. 169. <i>See</i> also Alex. Braun, in + 'Bot. Memoirs,' Ray. Soc., 1853, p. 313.</p> + + <p><a name="Nt_613" href="#NtA_613">[613]</a> Messrs. Hardy and Son, of + Maldon, in 'Gard. Chronicle,' 1856, p. 458.</p> + + <p><a name="Nt_614" href="#NtA_614">[614]</a> 'Quadrupèdes du Paraguay,' + 1801, tom. ii. p. 319.</p> + + <p><a name="Nt_615" href="#NtA_615">[615]</a> M<sup>c</sup>Clelland on + Indian Cyprinidæ, 'Asiatic Researches,' vol. xix. part ii., 1839, pp. + 266, 268, 313.</p> + + <p><a name="Nt_616" href="#NtA_616">[616]</a> Quoted by Sageret, 'Pom. + Phys.,' 1830, p. 43.</p> + + <p><a name="Nt_617" href="#NtA_617">[617]</a> 'The Fruits of America,' + 1845, p. 5.</p> + + <p><a name="Nt_618" href="#NtA_618">[618]</a> M. Cardan, in 'Comptes + Rendus,' Dec. 1848, quoted in 'Gard. Chronicle,' 1849, p. 101.</p> + + <p><a name="Nt_619" href="#NtA_619">[619]</a> M. Alexis Jordan mentions + four excellent pears found in woods in France, and alludes to others + ('Mém. Acad. de Lyon,' tom. ii. 1852, p. 159). Poiteau's remark is quoted + in 'Gardener's Mag.,' vol. iv., 1828, p. 385. <i>See</i> 'Gard. + Chronicle,' 1862, p. 335, for another case of a new variety of the pear + found in a hedge in France. Also for another case, <i>see</i> Loudon's + 'Encyclop. of Gardening,' p. 901. Mr. Rivers has given me similar + information.</p> + + <p><a name="Nt_620" href="#NtA_620">[620]</a> Duval, 'Hist. du Poirier,' + 1849, p. 2.</p> + + <p><a name="Nt_621" href="#NtA_621">[621]</a> I infer that this is the + fact from Van Mons' statement ('Arbres Fruitiers,' 1835, tom. i. p. 446) + that he finds in the woods seedlings resembling all the chief cultivated + races of both the pear and apple. Van Mons, however, looked at these wild + varieties as aboriginal species.</p> + + <p><a name="Nt_622" href="#NtA_622">[622]</a> Downing, 'Fruit-trees of + North America,' p. 422; Foley, in 'Transact. Hort. Soc.,' vol. vi. p. + 412.</p> + + <p><a name="Nt_623" href="#NtA_623">[623]</a> 'Gard. Chronicle,' 1847, p. + 244.</p> + + <p><a name="Nt_624" href="#NtA_624">[624]</a> 'Gardener's Chronicle,' + 1841, p. 383; 1850, p. 700; 1854, p. 650.</p> + + <p><a name="Nt_625" href="#NtA_625">[625]</a> 'Die Getreidearten,' 1843, + s. 66, 116, 117.</p> + + <p><a name="Nt_626" href="#NtA_626">[626]</a> Sabine, in 'Hort. + Transact.,' vol. iii. p. 225; Bronn, 'Geschichte der Natur,' b. ii. s. + 119.</p> + + <p><a name="Nt_627" href="#NtA_627">[627]</a> 'Journal of Horticulture,' + 1861, p. 112; on Zinnia, 'Gardener's Chronicle,' 1860, p. 852.</p> + + <p><a name="Nt_628" href="#NtA_628">[628]</a> 'The Chrysanthemum, its + History, &c.,' 1865, p. 3.</p> + + <p><a name="Nt_629" href="#NtA_629">[629]</a> 'Gardener's Chron.,' 1855, + p. 54; 'Journal of Horticulture,' May 9, 1865, p. 363.</p> + + <p><a name="Nt_630" href="#NtA_630">[630]</a> Quoted by Verlot, 'Des + Variétés,' &c., 1865, p. 28.</p> + + <p><a name="Nt_631" href="#NtA_631">[631]</a> 'Examination of the + Characteristics of Genera and Species:' Charleston, 1855, p. 14.</p> + + <p><a name="Nt_632" href="#NtA_632">[632]</a> Mr Hewitt, 'Journal of + Hort.,' 1863, p. 39.</p> + + <p><a name="Nt_633" href="#NtA_633">[633]</a> Devay, 'Mariages + Consanguins,' pp. 97, 125. In conversation I have found two or three + naturalists of the same opinion.</p> + + <p><a name="Nt_634" href="#NtA_634">[634]</a> Müller has conclusively + argued against this belief, 'Elements of Phys.,' Eng. translat., vol. + ii., 1842, p. 1405.</p> + + <p><a name="Nt_635" href="#NtA_635">[635]</a> 'Act. Acad. St. + Petersburg,' 1780, part ii. p. 84, &c.</p> + + <p><a name="Nt_636" href="#NtA_636">[636]</a> 'Bastarderzeugung,' s. 249, + 255, 295.</p> + + <p><a name="Nt_637" href="#NtA_637">[637]</a> 'Nova Acta, St. + Petersburg,' 1794, p. 378; 1795, pp. 307, 313, 316; 1787, p. 407.</p> + + <p><a name="Nt_638" href="#NtA_638">[638]</a> 'De la Fécondation,' 1862, + p. 311.</p> + + <p><a name="Nt_639" href="#NtA_639">[639]</a> 'Amaryllidaceæ,' 1837, p. + 362.</p> + + <p><a name="Nt_640" href="#NtA_640">[640]</a> Abstracted in 'Gard. + Chronicle,' 1860, p. 1081.</p> + + <p><a name="Nt_641" href="#NtA_641">[641]</a> This was the opinion of the + elder De Candolle, as quoted in 'Dic. Class. d'Hist. Nat.,' tom. viii. p. + 405. Puvis, in his work, 'De la Dégénération,' 1837, p. 37, has discussed + this same point.</p> + + <p><a name="Nt_642" href="#NtA_642">[642]</a> 'Comptes Rendus,' Novembre + 21, 1864, p. 838.</p> + + <p><a name="Nt_643" href="#NtA_643">[643]</a> 'Nova Acta, St. + Petersburg,' 1794, p. 391.</p> + + <p><a name="Nt_644" href="#NtA_644">[644]</a> 'Bastarderzeugung,' s. 507, + 516, 572.</p> + + <p><a name="Nt_645" href="#NtA_645">[645]</a> 'Die Bastardbefruchtung,' + &c., 1865, s. 24.</p> + + <p><a name="Nt_646" href="#NtA_646">[646]</a> 'Bastarderzeugung,' s. 452, + 507.</p> + + <p><a name="Nt_647" href="#NtA_647">[647]</a> 'Die Bastardbefruchtung,' + s. 56.</p> + + <p><a name="Nt_648" href="#NtA_648">[648]</a> 'Bastarderzeugung,' s. + 423.</p> + + <p><a name="Nt_649" href="#NtA_649">[649]</a> 'Dritte Fortsetzung,' + &c., 1766, s. 85.</p> + + <p><a name="Nt_650" href="#NtA_650">[650]</a> 'Die Bastardbefruchtung,' + &c., 1865, s. 92; <i>see</i> also the Rev. M. J. Berkeley on the same + subject, in 'Journal of Royal Hort. Soc.,' 1866, p. 80.</p> + + <p><a name="Nt_651" href="#NtA_651">[651]</a> Dr. P. Lucas has given a + history of opinion on this subject: 'Héréd. Nat.,' 1847, tom. i. p. + 175.</p> + + <p><a name="Nt_652" href="#NtA_652">[652]</a> 'Hist. des Anomalies,' tom. + iii. p. 499.</p> + + <p><a name="Nt_653" href="#NtA_653">[653]</a> Idem., tom. iii. pp. 392, + 502.</p> + + <p><a name="Nt_654" href="#NtA_654">[654]</a> <i>See</i> his interesting + work, 'Métamorphoses de l'Homme,' &c., 1862, p. 129.</p> + + <p><a name="Nt_655" href="#NtA_655">[655]</a> 'Dritte Fortsetzung,' + &c., s. 123; 'Bastarderzeugung,' s. 249.</p> + + <p><a name="Nt_656" href="#NtA_656">[656]</a> 'Gardener's Chronicle,' + 1853, p. 183.</p> + + <p><a name="Nt_657" href="#NtA_657">[657]</a> Mr. Wildman, 'Floricultural + Soc.,' Feb. 7, 1843, reported in 'Gard. Chron.,' 1843, p. 86.</p> + + <p><a name="Nt_658" href="#NtA_658">[658]</a> Mr. Robson, in 'Journal of + Horticulture,' Feb. 13th, 1866, p. 122.</p> + + <p><a name="Nt_659" href="#NtA_659">[659]</a> 'Journal of Horticulture,' + 1861, p. 24.</p> + + <p><a name="Nt_660" href="#NtA_660">[660]</a> Ibid., 1862, p. 83.</p> + + <p><a name="Nt_661" href="#NtA_661">[661]</a> 'Gard. Chron.,' 1845, p. + 660.</p> + + <p><a name="Nt_662" href="#NtA_662">[662]</a> Ibid., 1863, p. 628.</p> + + <p><a name="Nt_663" href="#NtA_663">[663]</a> 'Journal of Hort.,' 1861, + pp. 64, 309.</p> + + <p><a name="Nt_664" href="#NtA_664">[664]</a> 'Des Variétés,' &c., p. + 76.</p> + + <p><a name="Nt_665" href="#NtA_665">[665]</a> Engel, 'Sur les Prop. + Médicales des Plantes,' 1860, pp. 10, 25. On changes in the odours of + plants, <i>see</i> Dalibert's Experiments, quoted by Beckman, + 'Inventions,' vol. ii. p. 344; and Nees, in Ferussac, 'Bull. des Sc. + Nat.,' 1824, tom. i. p. 60. With respect to the rhubarb, &c., + <i>see</i> also 'Gardener's Chronicle,' 1849, p. 355; 1862, p. 1123.</p> + + <p><a name="Nt_666" href="#NtA_666">[666]</a> Hooker, 'Flora Indica,' p. + 32.</p> + + <p><a name="Nt_667" href="#NtA_667">[667]</a> Naudin, 'Annales des Sc. + Nat.,' 4th series, Bot., tom. xi., 1859, p. 81. 'Gardener's Chronicle,' + 1859, p. 464.</p> + + <p><a name="Nt_668" href="#NtA_668">[668]</a> Moorcroft's 'Travels,' + &c., vol. ii. p. 143.</p> + + <p><a name="Nt_669" href="#NtA_669">[669]</a> 'Gardener's Chronicle,' + 1861, p. 1113.</p> + + <p><a name="Nt_670" href="#NtA_670">[670]</a> Royle, 'Productive + Resources of India,' p. 59.</p> + + <p><a name="Nt_671" href="#NtA_671">[671]</a> 'Personal Narrative,' Eng. + translat., vol. v. p. 101. This statement has been confirmed by Karsten + ('Beitrag zur Kenntniss der Rhynchoprion:' Moscow, 1864. s. 39), and by + others.</p> + + <p><a name="Nt_672" href="#NtA_672">[672]</a> 'Organic Chemistry,' Eng. + translat., 1st edit., p. 369.</p> + + <p><a name="Nt_673" href="#NtA_673">[673]</a> Prichard, 'Phys. Hist. of + Mankind,' 1851, vol. i. p. 155.</p> + + <p><a name="Nt_674" href="#NtA_674">[674]</a> Darwin, 'Journal of + Researches,' 1845, p. 434.</p> + + <p><a name="Nt_675" href="#NtA_675">[675]</a> These statements on disease + are taken from Dr. Boudin's 'Géographie et de Statistique Médicales,' + 1857, tom. i. p. xliv. and lii.; tom. ii. p. 315.</p> + + <p><a name="Nt_676" href="#NtA_676">[676]</a> E. Desor, quoted in the + 'Anthrop. Rev.,' 1863, p. 180. For much confirmatory evidence, <i>see</i> + Quatrefages, 'Unité de l'Espèce Humaine,' 1861, p. 131.</p> + + <p><a name="Nt_677" href="#NtA_677">[677]</a> 'Ceylon,' by Sir J. E. + Tennent, vol. i., 1859, p. 89.</p> + + <p><a name="Nt_678" href="#NtA_678">[678]</a> Godron, 'De l'Espèce,' tom. + ii. p. 52.</p> + + <p><a name="Nt_679" href="#NtA_679">[679]</a> 'Journal of Horticultural + Soc.,' vol. vii., 1852, p. 117.</p> + + <p><a name="Nt_680" href="#NtA_680">[680]</a> 'Journal of Hort. Soc.,' + vol. i. p. 160.</p> + + <p><a name="Nt_681" href="#NtA_681">[681]</a> <i>See</i> Lecoq on the + Villosity of Plants, 'Geograph. Bot.,' tom. iii. pp. 287, 291; Gärtner, + 'Bastarderz.,' s. 261; Mr. Musters, on the Opuntia, in 'Gard. Chronicle,' + 1846, p. 444.</p> + + <p><a name="Nt_682" href="#NtA_682">[682]</a> 'Pom. Phys.,' p. 136.</p> + + <p><a name="Nt_683" href="#NtA_683">[683]</a> 'Ampelographie,' 1849, p. + 19.</p> + + <p><a name="Nt_684" href="#NtA_684">[684]</a> Gärtner, 'Bastarderz.,' s. + 606, has collected nearly all recorded facts. Andrew Knight (in + 'Transact. Hort. Soc.,' vol. ii. p. 160) goes so far as to maintain that + few varieties are absolutely permanent in character when propagated by + buds or grafts.</p> + + <p><a name="Nt_685" href="#NtA_685">[685]</a> Mr. Blyth, in 'Annals and + Mag. of Nat. Hist.,' vol. xx., 1847, p. 391.</p> + + <p><a name="Nt_686" href="#NtA_686">[686]</a> 'Natural History Review,' + 1862, p. 113.</p> + + <p><a name="Nt_687" href="#NtA_687">[687]</a> 'Journal of Roy. + Geographical Soc.,' vol. ix., 1839, p. 275.</p> + + <p><a name="Nt_688" href="#NtA_688">[688]</a> 'Travels in Bokhara,' vol. + iii. p. 151.</p> + + <p><a name="Nt_689" href="#NtA_689">[689]</a> <i>See</i> also, on the + influence of marshy pastures on the wool, Godron, 'L'Espèce,' tom. ii. p. + 22.</p> + + <p><a name="Nt_690" href="#NtA_690">[690]</a> Isidore Geoffroy St. + Hilaire, 'Hist. Nat. Gén.,' tom. iii. p. 438.</p> + + <p><a name="Nt_691" href="#NtA_691">[691]</a> Azara has made some good + remarks on this subject, 'Quadrupèdes du Paraguay,' tom. ii. p. 337. + <i>See</i> an account of a family of naked mice produced in England, + 'Proc. Zoolog. Soc.,' 1856, p. 38.</p> + + <p><a name="Nt_692" href="#NtA_692">[692]</a> 'Die Fauna der + Pfahlbauten,' 1861, s. 15.</p> + + <p><a name="Nt_693" href="#NtA_693">[693]</a> 'Schweinschædel,' 1864, s. + 99.</p> + + <p><a name="Nt_694" href="#NtA_694">[694]</a> 'Travels in Siberia,' Eng. + translat., vol. i. p. 228.</p> + + <p><a name="Nt_695" href="#NtA_695">[695]</a> A. R. Wallace, 'Travels on + the Amazon and Rio Negro,' p. 294.</p> + + <p><a name="Nt_696" href="#NtA_696">[696]</a> 'Naturgeschichte der + Stubenvögel,' 1840, s. 262, 308.</p> + + <p><a name="Nt_697" href="#NtA_697">[697]</a> 'Hist. Nat. Gén.,' tom. + iii. p. 402.</p> + + <p><a name="Nt_698" href="#NtA_698">[698]</a> 'Bull. de la Soc. Imp. + d'Acclimat.,' tom. viii. p. 351.</p> + + <p><a name="Nt_699" href="#NtA_699">[699]</a> <i>See</i> an account of + Mr. Gregson's experiments on the <i>Abraxus grossulariata</i>, 'Proc. + Entomolog. Soc.,' Jan. 6th, 1862: these experiments have been confirmed + by Mr. Greening, in 'Proc. of the Northern Entomolog. Soc.,' July 28th, + 1862. For the effects of food on caterpillars, see a curious account by + M. Michely, in 'Bull. de la Soc. Imp. d'Acclimat.,' tom. viii. p. 563. + For analogous facts from Dahlbom on Hymenoptera, <i>see</i> Westwood's + 'Modern Class. of Insects,' vol. ii. p. 98. <i>See</i> also Dr. L. + Möller, 'Die Abhängigkeit der Insecten,' 1867, s. 70.</p> + + <p><a name="Nt_700" href="#NtA_700">[700]</a> 'The Principles of + Biology,' vol. ii. 1866. The present chapters were written before I had + read Mr. Herbert Spencer's work, so that I have not been able to make so + much use of it as I should otherwise probably have done.</p> + + <p><a name="Nt_701" href="#NtA_701">[701]</a> 'Proc. Acad. Nat. Soc. of + Philadelphia,' Jan. 28th, 1862.</p> + + <p><a name="Nt_702" href="#NtA_702">[702]</a> <i>See</i> Mr. B. D. + Walsh's excellent papers in 'Proc. Entomolog. Soc. Philadelphia,' Dec. + 1866, p. 284. With respect to the willow, <i>see</i> idem, 1864, p. + 546.</p> + + <p><a name="Nt_703" href="#NtA_703">[703]</a> <i>See</i> his admirable + Histoire des Galles, in 'Annal. des Sc. Nat. Bot.,' 3rd series, tom. + xix., 1853, p. 273.</p> + + <p><a name="Nt_704" href="#NtA_704">[704]</a> Kirby and Spence's + 'Entomology,' 1818, vol. i. p. 450; Lucaze-Duthiers, idem, p. 284.</p> + + <p><a name="Nt_705" href="#NtA_705">[705]</a> 'Proc. Entomolog. Soc. + Philadelphia,' 1864, p. 558.</p> + + <p><a name="Nt_706" href="#NtA_706">[706]</a> Mr. B. D. Walsh, idem, p. + 633; and Dec. 1866, p. 275.</p> + + <p><a name="Nt_707" href="#NtA_707">[707]</a> Mr. B. D. Walsh, idem, + 1864, p. 545, 411, 495; and Dec. 1866, p. 278. <i>See</i> also + Lucaze-Duthiers.</p> + + <p><a name="Nt_708" href="#NtA_708">[708]</a> Lucaze-Duthiers, idem, pp. + 325, 328.</p> + + <p><a name="Nt_709" href="#NtA_709">[709]</a> 'Linnæa,' vol. xvii., 1843; + quoted by Dr. M. T. Masters, Royal Institution, March 16th, 1860.</p> + + <p><a name="Nt_710" href="#NtA_710">[710]</a> Hewett C. Watson, 'Cybele + Britannica,' vol. i., 1847, p. 11.</p> + + <p><a name="Nt_711" href="#NtA_711">[711]</a> 'Gardener's Chronicle,' + 1857, p. 629.</p> + + <p><a name="Nt_712" href="#NtA_712">[712]</a> 'Mémoire sur la Production + Artificielle des Monstrosités,' 1862, pp. 8-12; 'Recherches sur les + Conditions, &c., chez les Monstres,' 1863, p. 6. An abstract is given + of Geoffroy's Experiments by his son, in his 'Vie, Travaux, &c.,' + 1847, p. 290.</p> + + <p><a name="Nt_713" href="#NtA_713">[713]</a> Paget, 'Lectures on + Surgical Pathology,' 1853, vol. i. p. 483.</p> + + <p><a name="Nt_714" href="#NtA_714">[714]</a> 'Researches upon the Venom + of the Rattle-snake,' Jan. 1861, by Dr. Mitchell, p. 67.</p> + + <p><a name="Nt_715" href="#NtA_715">[715]</a> Mr. Sedgwick, in 'British + and Foreign Medico-Chirurg. Review,' July 1863, p. 175.</p> + + <p><a name="Nt_716" href="#NtA_716">[716]</a> 'An Essay on Generation,' + Eng. translat., p. 18; Paget, 'Lectures on Surgical Pathology,' 1853, + vol. i. p. 209.</p> + + <p><a name="Nt_717" href="#NtA_717">[717]</a> 'An Essay on Animal + Reproduction,' Eng. translat., 1769, p. 79.</p> + + <p><a name="Nt_718" href="#NtA_718">[718]</a> Carpenter's 'Principles of + Comp. Physiology,' 1854, p. 479.</p> + + <p><a name="Nt_719" href="#NtA_719">[719]</a> Charlesworth's 'Mag. of + Nat. Hist.,' vol. i., 1837, p. 145.</p> + + <p><a name="Nt_720" href="#NtA_720">[720]</a> Paget, 'Lectures on + Surgical Pathology,' vol. i. p. 239.</p> + + <p><a name="Nt_721" href="#NtA_721">[721]</a> Quoted by Carpenter, 'Comp. + Phys.,' p. 479.</p> + + <p><a name="Nt_722" href="#NtA_722">[722]</a> Paget, 'Lectures,' &c., + p. 257.</p> + + <p><a name="Nt_723" href="#NtA_723">[723]</a> These cases are given by + Blumenbach in his 'Essay on Generation,' pp. 52, 54.</p> + + <p><a name="Nt_724" href="#NtA_724">[724]</a> 'Cellular Pathology,' + trans. by Dr. Chance, 1860, pp. 27, 441.</p> + + <p><a name="Nt_725" href="#NtA_725">[725]</a> Paget, 'Lectures on + Pathology,' vol. i., 1853, p. 357.</p> + + <p><a name="Nt_726" href="#NtA_726">[726]</a> Paget, idem, p. 150.</p> + + <p><a name="Nt_727" href="#NtA_727">[727]</a> 'The Principles of + Biology,' vol. ii., 1866, chap. 3-5.</p> + + <p><a name="Nt_728" href="#NtA_728">[728]</a> 'Lectures on Pathology,' + 1853, vol. i. p. 71.</p> + + <p><a name="Nt_729" href="#NtA_729">[729]</a> 'Comptes Rendus,' Sept. + 26th, 1864, p. 539.</p> + + <p><a name="Nt_730" href="#NtA_730">[730]</a> 'The Principles of + Biology,' vol. ii. p. 243.</p> + + <p><a name="Nt_731" href="#NtA_731">[731]</a> Idem, vol. ii. p. 269.</p> + + <p><a name="Nt_732" href="#NtA_732">[732]</a> Idem, vol. ii. p. 273.</p> + + <p><a name="Nt_733" href="#NtA_733">[733]</a> Paget, 'Lectures on + Pathology,' vol. ii. p. 209.</p> + + <p><a name="Nt_734" href="#NtA_734">[734]</a> Müller's 'Phys.,' Eng. + translat., pp. 54, 791. Prof. Reed has given ('Physiological and Anat. + Researches,' p. 10) a curious account of the atrophy of the limbs of + rabbits after the destruction of the nerve.</p> + + <p><a name="Nt_735" href="#NtA_735">[735]</a> Quoted by Lecoq, in + 'Geograph. Bot.,' tom. i., 1854, p. 182.</p> + + <p><a name="Nt_736" href="#NtA_736">[736]</a> 'Das Abändern der Vögel,' + 1833, s. 74.</p> + + <p><a name="Nt_737" href="#NtA_737">[737]</a> Nathusius, 'Die Racen des + Schweines,' 1860, s. 53, 57; 'Vorstudien ... Schweineschædel,' 1864, s. + 103, 130, 133.</p> + + <p><a name="Nt_738" href="#NtA_738">[738]</a> 'Journal of Agriculture of + Highland Soc.,' July, 1860, p. 321.</p> + + <p><a name="Nt_739" href="#NtA_739">[739]</a> 'Principles of Biology,' + vol. ii. p. 263.</p> + + <p><a name="Nt_740" href="#NtA_740">[740]</a> 'Natural History Review,' + vol. iv., Oct. 1864, p. 617.</p> + + <p><a name="Nt_741" href="#NtA_741">[741]</a> 'Lectures on Surgical + Pathology,' 1853, vol. i. p. 27.</p> + + <p><a name="Nt_742" href="#NtA_742">[742]</a> Andersson, 'Travels in + South Africa,' p. 318. For analogous cases in South America, <i>see</i> + Aug. St. Hilaire, 'Voyage dans le Province de Goyaz,' tom. i. p. 71.</p> + + <p><a name="Nt_743" href="#NtA_743">[743]</a> <span class="correction" + title="Original reads `Birckell', corrected by errata, page viii." + >Brickell</span>'s 'Nat. Hist. of North Carolina,' 1739, p. 53.</p> + + <p><a name="Nt_744" href="#NtA_744">[744]</a> Livingstone, quoted by + Youatt on Sheep, p. 142. Hodgson, in 'Journal of Asiatic Soc. of Bengal,' + vol. xvi., 1847, p. 1006, &c. &c.</p> + + <p><a name="Nt_745" href="#NtA_745">[745]</a> 'Naturalist Library,' Dogs, + vol. ii. 1840, p. 104.</p> + + <p><a name="Nt_746" href="#NtA_746">[746]</a> 'De l'Espèce,' tom. i., + 1859, p. 367.</p> + + <p><a name="Nt_747" href="#NtA_747">[747]</a> 'Ceylon,' by Sir J. E. + Tennent, 1859, vol. ii. p. 531.</p> + + <p><a name="Nt_748" href="#NtA_748">[748]</a> For the foregoing + statements, <i>see</i> Hunter's 'Essays and Observations,' 1861, vol. ii. + p. 329; Dr. Edmondston, as quoted in Macgillivray's 'British Birds,' vol. + v. p. 550; Menetries, as quoted in Bronn's 'Geschichte der Natur,' B. ii. + s. 110.</p> + + <p><a name="Nt_749" href="#NtA_749">[749]</a> These statements on the + intestines are taken from Isidore Geoffroy St. Hilaire, 'Hist. Nat. + Gén.,' tom. iii. pp. 427, 441.</p> + + <p><a name="Nt_750" href="#NtA_750">[750]</a> Gilbert White, 'Nat. Hist. + Selbourne,' 1825, vol. ii. p. 121.</p> + + <p><a name="Nt_751" href="#NtA_751">[751]</a> Burdach, 'Traité de Phys.,' + tom. ii. p. 267, as quoted by Dr. P. Lucas, 'L'Héréd. Nat.,' tom. i. p. + 388.</p> + + <p><a name="Nt_752" href="#NtA_752">[752]</a> This and several other + cases are given by Colin, 'Physiologie Comp. des Animaux Dom.,' 1854, + tom. i. p. 426.</p> + + <p><a name="Nt_753" href="#NtA_753">[753]</a> M. Michely de Cayenne, in + 'Bull. Soc. d'Acclimat.,' tom. viii., 1861, p. 563.</p> + + <p><a name="Nt_754" href="#NtA_754">[754]</a> Quatrefages, 'Unité de + l'Espèce Humaine,' 1861, p. 79.</p> + + <p><a name="Nt_755" href="#NtA_755">[755]</a> 'Flora,' 1835, B. ii. p. + 504.</p> + + <p><a name="Nt_756" href="#NtA_756">[756]</a> Alph. De Candolle, + 'Géograph. Bot.,' tom. ii. p. 1078.</p> + + <p><a name="Nt_757" href="#NtA_757">[757]</a> Royle, 'Illustrations of + the Botany of the Himalaya,' p. 19.</p> + + <p><a name="Nt_758" href="#NtA_758">[758]</a> 'Gardener's Chronicle,' + 1850, pp. 204, 219.</p> + + <p><a name="Nt_759" href="#NtA_759">[759]</a> Rev. R. Everest, 'Journal + As. Soc. of Bengal,' vol. iii. p. 19.</p> + + <p><a name="Nt_760" href="#NtA_760">[760]</a> Youatt on Sheep, 1838, p. + 491.</p> + + <p><a name="Nt_761" href="#NtA_761">[761]</a> Royle, 'Prod. Resources of + India,' p. 153.</p> + + <p><a name="Nt_762" href="#NtA_762">[762]</a> Tegetmeier, 'Poultry Book,' + 1866, p. 102.</p> + + <p><a name="Nt_763" href="#NtA_763">[763]</a> Dr. R. Paterson, in a paper + communicated to Bot. Soc. of Canada, quoted in the 'Reader,' 1863. Nov. + 13th.</p> + + <p><a name="Nt_764" href="#NtA_764">[764]</a> <i>See</i> remarks by + Editor in 'Gard. Chronicle,' 1848, p. 5.</p> + + <p><a name="Nt_765" href="#NtA_765">[765]</a> 'Gard. Chronicle,' 1860, p. + 938. Remarks by Editor and quotation from Decaisne.</p> + + <p><a name="Nt_766" href="#NtA_766">[766]</a> J. de Jonghe, of Brussels, + in 'Gard. Chronicle,' 1857, p. 612.</p> + + <p><a name="Nt_767" href="#NtA_767">[767]</a> Ch. Martius, 'Voyage Bot. + Côtes Sept. de la Norvège,' p. 26.</p> + + <p><a name="Nt_768" href="#NtA_768">[768]</a> 'Journal de l'Acad. Hort. + de Gand,' quoted in 'Gard. Chron.,' 1859, p. 7.</p> + + <p><a name="Nt_769" href="#NtA_769">[769]</a> 'Gard. Chronicle,' 1851, p. + 396.</p> + + <p><a name="Nt_770" href="#NtA_770">[770]</a> Idem., 1862, p. 235.</p> + + <p><a name="Nt_771" href="#NtA_771">[771]</a> On the authority of Labat, + quoted in 'Gard. Chron.,' 1862, p. 235.</p> + + <p><a name="Nt_772" href="#NtA_772">[772]</a> MM. Edwards and Colin, + 'Annal. des Sc. Nat.,' 2nd series, Bot., tom. v. p. 22.</p> + + <p><a name="Nt_773" href="#NtA_773">[773]</a> 'Géograph. Bot.,' p. + 337.</p> + + <p><a name="Nt_774" href="#NtA_774">[774]</a> 'Swedish Acts,' Eng. + translat., 1739-40, vol. i. Kalm, in his 'Travels,' vol. ii. p. 166, + gives an analogous case with cotton-plants raised in New Jersey from + Carolina seed.</p> + + <p><a name="Nt_775" href="#NtA_775">[775]</a> De Candolle, 'Géograph. + Bot.,' p. 339.</p> + + <p><a name="Nt_776" href="#NtA_776">[776]</a> 'Gard. Chronicle,' 1862, p. + 235.</p> + + <p><a name="Nt_777" href="#NtA_777">[777]</a> Gallesio, 'Teoria della + Riproduzione Veg.,' 1816, p. 125; and 'Traité du Citrus,' 1811, p. + 359.</p> + + <p><a name="Nt_778" href="#NtA_778">[778]</a> 'Essai sur l'Hist. des + Orangers,' 1813, p. 20, &c.</p> + + <p><a name="Nt_779" href="#NtA_779">[779]</a> Alph. De Candolle, + 'Géograph. Bot.,' p. 882.</p> + + <p><a name="Nt_780" href="#NtA_780">[780]</a> 'Ch. Darwin's Lehre von der + Entstehung,' &c., 1862, s. 87.</p> + + <p><a name="Nt_781" href="#NtA_781">[781]</a> Decaisne, quoted in 'Gard. + Chronicle,' 1865, p. 271.</p> + + <p><a name="Nt_782" href="#NtA_782">[782]</a> For the magnolia, + <i>see</i> Loudon's 'Gard. Mag.,' vol. xiii., 1837, p. 21. For camellias + and roses, <i>see</i> 'Gard. Chron.,' 1860, p. 384. For the yew, 'Journal + of Hort.,' March 3rd, 1863, p. 174. For sweet potatoes, <i>see</i> Col. + von Siebold, in 'Gard. Chron.,' 1855, p. 822.</p> + + <p><a name="Nt_783" href="#NtA_783">[783]</a> The Editor, 'Gard. Chron.,' + 1861, p. 239.</p> + + <p><a name="Nt_784" href="#NtA_784">[784]</a> Loudon's 'Gard. Mag.,' vol. + xii., 1836, p. 378.</p> + + <p><a name="Nt_785" href="#NtA_785">[785]</a> 'Gardeners Chron.,' 1865, + p. 699.</p> + + <p><a name="Nt_786" href="#NtA_786">[786]</a> 'Arboretum et Fruticetum,' + vol. iii. p. 1376.</p> + + <p><a name="Nt_787" href="#NtA_787">[787]</a> Mr. Robson, in 'Journal of + Horticulture,' 1861, p. 23.</p> + + <p><a name="Nt_788" href="#NtA_788">[788]</a> Dr. Bonavia, 'Report of the + Agri.-Hort. Soc. of Oudh,' 1866.</p> + + <p><a name="Nt_789" href="#NtA_789">[789]</a> 'Cottage Gardener,' 1860, + April, 24th, p. 57.</p> + + <p><a name="Nt_790" href="#NtA_790">[790]</a> 'Gardener's Chronicle,' + 1841, p. 291.</p> + + <p><a name="Nt_791" href="#NtA_791">[791]</a> Mr. Beaton, in 'Cottage + Gardener,' March 20th, 1860, p. 377. Queen Mab will also stand stove + heat, <i>see</i> 'Gard. Chronicle,' 1845, p. 226.</p> + + <p><a name="Nt_792" href="#NtA_792">[792]</a> 'Gardener's Chronicle,' + 1841, p. 439.</p> + + <p><a name="Nt_793" href="#NtA_793">[793]</a> Quoted by Asa Gray, in 'Am. + Journ. of Sci.,' 2nd series, Jan. 1865, p. 106.</p> + + <p><a name="Nt_794" href="#NtA_794">[794]</a> For China, <i>see</i> + 'Mémoire sur les Chinois,' tom, xi., 1786, p. 60. Columella is quoted by + Carlier, in 'Journal de Physique,' tom. xxiv. 1784.</p> + + <p><a name="Nt_795" href="#NtA_795">[795]</a> Messrs. Hardy and Son, in + 'Gard. Chronicle,' 1856, p. 589.</p> + + <p><a name="Nt_796" href="#NtA_796">[796]</a> Isid. Geoffroy St. Hilaire, + 'Hist. Nat. des Anomalies,' 1836, tom. ii. pp. 210, 223, 224, 395; + 'Philosoph. Transact.,' 1775, p. 313.</p> + + <p><a name="Nt_797" href="#NtA_797">[797]</a> Pallas, quoted by Youatt on + Sheep, p. 25.</p> + + <p><a name="Nt_798" href="#NtA_798">[798]</a> Youatt on Cattle, 1834, p. + 174.</p> + + <p><a name="Nt_799" href="#NtA_799">[799]</a> 'Encyclop. Méthod.,' 1820, + p. 483: <i>see</i> p. 500, on the Indian zebu casting its horns. Similar + cases in European cattle were given in the third chapter.</p> + + <p><a name="Nt_800" href="#NtA_800">[800]</a> Pallas, 'Travels,' Eng. + translat., vol. i. p. 243.</p> + + <p><a name="Nt_801" href="#NtA_801">[801]</a> Mr. Beaton, in 'Journal of + Horticulture,' May 21, 1861, p. 133.</p> + + <p><a name="Nt_802" href="#NtA_802">[802]</a> Lecoq, 'De la Fécondation,' + 1862, p. 233.</p> + + <p><a name="Nt_803" href="#NtA_803">[803]</a> 'Annales du Muséum,' tom. + vi. p. 319.</p> + + <p><a name="Nt_804" href="#NtA_804">[804]</a> 'Hist. des Anomalies,' tom. + iii. p. 392. Prof. Huxley applies the same principle in accounting for + the remarkable, though normal, differences in the arrangement of the + nervous system in the Mollusca, in his great paper on the Morphology of + the Cephalous Mollusca, in 'Phil. Transact.,' 1853, p. 56.</p> + + <p><a name="Nt_805" href="#NtA_805">[805]</a> 'Eléments de Tératologie + Veg.,' 1841, p. 113.</p> + + <p><a name="Nt_806" href="#NtA_806">[806]</a> Prof. J. B. Simonds, on the + Age of the Ox, Sheep, &c., quoted in 'Gard. Chronicle,' 1854, p. + 588.</p> + + <p><a name="Nt_807" href="#NtA_807">[807]</a> 'Hist. des Anomalies,' tom. + i. p. 674.</p> + + <p><a name="Nt_808" href="#NtA_808">[808]</a> Quoted by Isid. Geoffroy, + idem, tom. i. p. 635.</p> + + <p><a name="Nt_809" href="#NtA_809">[809]</a> 'The Poultry Book,' by W. + B. Tegetmeier, 1866, p. 250.</p> + + <p><a name="Nt_810" href="#NtA_810">[810]</a> A. Walker on Intermarriage, + 1838, p. 160.</p> + + <p><a name="Nt_811" href="#NtA_811">[811]</a> 'The Farrier and + Naturalist,' vol. i., 1828, p. 456.</p> + + <p><a name="Nt_812" href="#NtA_812">[812]</a> Godron, 'Sur l'Espèce,' + tom. ii. p. 217.</p> + + <p><a name="Nt_813" href="#NtA_813">[813]</a> 'Quadrupèdes du Paraguay,' + tom. ii. p. 333.</p> + + <p><a name="Nt_814" href="#NtA_814">[814]</a> On Sheep, p. 142.</p> + + <p><a name="Nt_815" href="#NtA_815">[815]</a> 'Ueber Racen, Kreuzungen, + &c.,' 1825, s. 24.</p> + + <p><a name="Nt_816" href="#NtA_816">[816]</a> Quoted from Conolly, in + 'The Indian Field,' Feb. 1859, vol. ii. p. 266.</p> + + <p><a name="Nt_817" href="#NtA_817">[817]</a> 'Domesticated Animals of + the British Islands,' pp. 307, 368.</p> + + <p><a name="Nt_818" href="#NtA_818">[818]</a> 'Proceedings Zoolog. Soc.,' + 1833, p. 113.</p> + + <p><a name="Nt_819" href="#NtA_819">[819]</a> Sedgwick, 'Brit. and + Foreign Medico-Chirurg. Review,' April 1863, p. 453.</p> + + <p><a name="Nt_820" href="#NtA_820">[820]</a> 'Gard. Chronicle,' 1849, p. + 205.</p> + + <p><a name="Nt_821" href="#NtA_821">[821]</a> 'Embassy to the Court of + Ava,' vol. i. p. 320.</p> + + <p><a name="Nt_822" href="#NtA_822">[822]</a> 'Narrative of a Mission to + the Court of Ava in 1855,' p. 94.</p> + + <p><a name="Nt_823" href="#NtA_823">[823]</a> Those statements are taken + from Mr. Sedgwick, in the 'Medico-Chirurg. Review,' July 1861, p. 198; + April 1863, pp. 455 and 458. Liebreich is quoted by Professor Devay, in + his 'Mariages Consanguins,' 1862, p. 116.</p> + + <p><a name="Nt_824" href="#NtA_824">[824]</a> Loudon's 'Mag. of Nat. + Hist.,' vol. i., 1829, pp. 66, 178. <i>See</i> also Dr. P. Lucas, + 'L'Héréd. Nat.,' tom. i. p. 428, on the inheritance of deafness in + cats.</p> + + <p><a name="Nt_825" href="#NtA_825">[825]</a> 'Annales des Sc. Nat.' + Zoolog., 3rd series, 1847, tom. viii. p. 239.</p> + + <p><a name="Nt_826" href="#NtA_826">[826]</a> 'Gardener's Chron.,' 1864, + p. 1202.</p> + + <p><a name="Nt_827" href="#NtA_827">[827]</a> Verlot gives several other + instances, 'Des Variétés,' 1865, p. 72.</p> + + <p><a name="Nt_828" href="#NtA_828">[828]</a> 'Arbres Fruitiers,' 1836, + tom. ii. pp. 204, 226.</p> + + <p><a name="Nt_829" href="#NtA_829">[829]</a> 'Annales du Muséum,' tom. + xx. p. 188.</p> + + <p><a name="Nt_830" href="#NtA_830">[830]</a> 'Gardener's Chron.,' 1843, + p. 877.</p> + + <p><a name="Nt_831" href="#NtA_831">[831]</a> Ibid., 1845, p. 102.</p> + + <p><a name="Nt_832" href="#NtA_832">[832]</a> 'Hist. des Anomalies,' tom. + iii. p. 402. <i>See</i> also M. Camille Dareste, 'Recherches sur les + Conditions,' &c., 1863, pp. 16, 48.</p> + + <p><a name="Nt_833" href="#NtA_833">[833]</a> Rev. E. S. Dixon, + 'Ornamental Poultry,' 1848, p. 111; Isidore Geoffroy, 'Hist. Anomalies,' + tom. i. p. 211.</p> + + <p><a name="Nt_834" href="#NtA_834">[834]</a> 'On the Breeding of + Domestic Animals,' 1829, p. 6.</p> + + <p><a name="Nt_835" href="#NtA_835">[835]</a> Youatt on Cattle, 1834, p. + 283.</p> + + <p><a name="Nt_836" href="#NtA_836">[836]</a> Mr. Herbert Spencer + ('Principles of Biology,' 1864, vol. i. pp. 452, 468) takes a different + view; and in one place remarks: "We have seen reason to think that, as + fast as essential faculties multiply, and as fast as the number of organs + that co-operate in any given function increases, indirect equilibration + through natural selection becomes less and less capable of producing + specific adaptations; and remains fully capable only of maintaining the + general fitness of constitution to conditions." This view that natural + selection can do little in modifying the higher animals surprises me, + seeing that man's selection has undoubtedly effected much with our + domesticated quadrupeds and birds.</p> + + <p><a name="Nt_837" href="#NtA_837">[837]</a> Dr. Prosper Lucas + apparently disbelieves in any such connexion, 'L'Héréd. Nat.,' tom. ii. + pp. 88-94.</p> + + <p><a name="Nt_838" href="#NtA_838">[838]</a> 'British Medical Journal,' + 1862, p. 433.</p> + + <p><a name="Nt_839" href="#NtA_839">[839]</a> Boudin, 'Geograph. + Médicale,' tom. i. p. 406.</p> + + <p><a name="Nt_840" href="#NtA_840">[840]</a> This fact and the following + cases, when not stated to the contrary, are taken from a very curious + paper by Prof. Heusinger, in 'Wochenschrift für Heilkunde,' May 1846, s. + 277.</p> + + <p><a name="Nt_841" href="#NtA_841">[841]</a> Mr. Mogford, in the + 'Veterinarian,' quoted in 'The Field,' Jan. 22, 1861, p. 545.</p> + + <p><a name="Nt_842" href="#NtA_842">[842]</a> 'Edinburgh Veterinary + Journal,' Oct. 1860, p. 347.</p> + + <p><a name="Nt_843" href="#NtA_843">[843]</a> 'Hist. des Anomalies,' + 1832, tom. i. pp. 22, 537-556; tom. iii. p. 462.</p> + + <p><a name="Nt_844" href="#NtA_844">[844]</a> 'Comptes Rendus,' 1855, pp. + 855, 1029.</p> + + <p><a name="Nt_845" href="#NtA_845">[845]</a> Carpenter's 'Comp. Phys.,' + 1854, p. 480; <i>see</i> also Camille Dareste, 'Comptes Rendus,' March + 20th, 1865, p. 562.</p> + + <p><a name="Nt_846" href="#NtA_846">[846]</a> 'Elements of Physiology,' + Eng. translat, vol. i., 1838, p. 412. With respect to Vrolik, <i>see</i> + Todd's 'Cyclop. of Anat. and Phys.,' vol. iv., 1849-52, p. 973.</p> + + <p><a name="Nt_847" href="#NtA_847">[847]</a> 'Tératologie Vég.,' 1841, + livre iii.</p> + + <p><a name="Nt_848" href="#NtA_848">[848]</a> 'Hist. des Anomalies,' tom. + iii. pp. 4, 5, 6.</p> + + <p><a name="Nt_849" href="#NtA_849">[849]</a> 'Tératologie Vég.,' p. 156. + <i>See</i> also my paper on climbing plants in 'Journal of Linn. Soc. + Bot.,' vol. ix., 1865, p. 114.</p> + + <p><a name="Nt_850" href="#NtA_850">[850]</a> 'Mémoires du Muséum,' + &c., tom. viii. p. 178.</p> + + <p><a name="Nt_851" href="#NtA_851">[851]</a> Loudon's 'Encyclop. of + Gardening,' p. 829.</p> + + <p><a name="Nt_852" href="#NtA_852">[852]</a> Prichard, 'Phys. Hist. of + Mankind,' 1851, vol. i. p. 324.</p> + + <p><a name="Nt_853" href="#NtA_853">[853]</a> 'Annales des Sc. Nat.,' 1st + series, tom. xix. p. 327.</p> + + <p><a name="Nt_854" href="#NtA_854">[854]</a> 'Comptes Rendus,' Dec. + 1864, p. 1039.</p> + + <p><a name="Nt_855" href="#NtA_855">[855]</a> Ueber Fötale Rachites, + 'Würzburger Medicin. Zeitschrift,' 1860, B. i. s. 265.</p> + + <p><a name="Nt_856" href="#NtA_856">[856]</a> 'Tératologie Vég.,' p. 192. + Dr. M. Masters informs me that he doubts the truth of this conclusion; + but the facts to be given seem to be sufficient to establish it.</p> + + <p><a name="Nt_857" href="#NtA_857">[857]</a> 'Journal of Horticulture,' + July 2nd, 1861, p. 253.</p> + + <p><a name="Nt_858" href="#NtA_858">[858]</a> It would be worth trial to + fertilise with the same pollen the central and lateral flowers of the + pelargonium, and of some other highly cultivated plants, protecting them + of course from insects: then to sow the seed separately, and observe + whether the one or the other lot of seedlings varied the most.</p> + + <p><a name="Nt_859" href="#NtA_859">[859]</a> Quoted in 'Journal of + Horticulture,' Feb. 24, 1863, p. 152.</p> + + <p><a name="Nt_860" href="#NtA_860">[860]</a> 'Gardener's Chronicle,' + 1866, p. 612. For the Phalænopsis, <i>see</i> idem, 1867, p. 211.</p> + + <p><a name="Nt_861" href="#NtA_861">[861]</a> Mémoires ... des Végétaux,' + 1837, tom. ii. p. 170.</p> + + <p><a name="Nt_862" href="#NtA_862">[862]</a> 'Journal of Horticulture,' + July 23, 1861, p. 311.</p> + + <p><a name="Nt_863" href="#NtA_863">[863]</a> 'Nouvelles Archives du + Muséum,' tom. i. p. 137.</p> + + <p><a name="Nt_864" href="#NtA_864">[864]</a> Hugo von Mohl, 'The + Vegetable Cell,' Eng. tr., 1852, p. 76.</p> + + <p><a name="Nt_865" href="#NtA_865">[865]</a> The Rev. H. H. Dombrain, in + 'Journal of Horticulture,' 1861, June 4th, p. 174; and June 25th, p. 234; + 1862, April 29th, p. 83.</p> + + <p><a name="Nt_866" href="#NtA_866">[866]</a> 'Transact. Linn. Soc.,' + vol. xxiii., 1861, p. 360.</p> + + <p><a name="Nt_867" href="#NtA_867">[867]</a> 'Die Getreidearten,' 1843, + s. 208, 209.</p> + + <p><a name="Nt_868" href="#NtA_868">[868]</a> 'Gardener's Chronicle,' + 1850, p. 198.</p> + + <p><a name="Nt_869" href="#NtA_869">[869]</a> Quoted in 'Gardener's + Chron.,' 1866, p. 74.</p> + + <p><a name="Nt_870" href="#NtA_870">[870]</a> 'Ueber den Begriff der + Pflanzenart,' 1834, s. 14.</p> + + <p><a name="Nt_871" href="#NtA_871">[871]</a> 'Domesticated Animals,' + 1845, p. 351.</p> + + <p><a name="Nt_872" href="#NtA_872">[872]</a> Bechstein, 'Naturgeschichte + Deutschlands,' Band iv., 1795, s. 31.</p> + + <p><a name="Nt_873" href="#NtA_873">[873]</a> 'Proc. Entomolog. Soc. of + Philadelphia,' Oct. 1863, p. 213.</p> + + <p><a name="Nt_874" href="#NtA_874">[874]</a> Quoted by Paget, 'Lectures + on Pathology,' 1853, p. 159.</p> + + <p><a name="Nt_875" href="#NtA_875">[875]</a> Dr. Lachmann, also, + observes ('Annals and Mag. of Nat. History,' 2nd series, vol. xix., 1857, + p. 231) with respect to infusoria, that "fissation and gemmation pass + into each other almost imperceptibly." Again, Mr. W. C. Minor ('Annals + and Mag. of Nat. Hist.,' 3rd series, vol. xi. p. 328) shows that with + Annelids the distinction that has been made between fission and budding + is not a fundamental one. <i>See</i> Bonnet, 'Œuvres d'Hist. Nat.,' + tom. v., 1781, p. 339, for remarks on the budding-out of the amputated + limbs of Salamanders. <i>See</i>, also, Professor Clark's work 'Mind in + Nature,' New York, 1865, pp. 62, 94.</p> + + <p><a name="Nt_876" href="#NtA_876">[876]</a> Paget, 'Lectures on + Pathology,' 1853, p. 158.</p> + + <p><a name="Nt_877" href="#NtA_877">[877]</a> Idem, pp. 152, 164.</p> + + <p><a name="Nt_878" href="#NtA_878">[878]</a> On the Asexual Reproduction + of Cecydomyide Larvæ, translated in 'Annals and Mag. of Nat. Hist.,' + March 1866, pp. 167, 171.</p> + + <p><a name="Nt_879" href="#NtA_879">[879]</a> <i>See</i> some excellent + remarks on this head by Quatrefages, in 'Annales des Sc. Nat.,' Zoolog., + 3rd series, 1850, p. 138.</p> + + <p><a name="Nt_880" href="#NtA_880">[880]</a> 'Annals and Mag. of Nat. + Hist.,' 2nd series, vol. xx., 1857, pp. 153-455.</p> + + <p><a name="Nt_881" href="#NtA_881">[881]</a> 'Annales des Sc. Nat.,' 3rd + series, 1850, tom. xiii.</p> + + <p><a name="Nt_882" href="#NtA_882">[882]</a> 'Transact. Phil. Soc.,' + 1851, pp. 196, 208, 210; 1853, p. 245, 247.</p> + + <p><a name="Nt_883" href="#NtA_883">[883]</a> 'Beitrage zur Kenntniss,' + &c., 1844, s. 345.</p> + + <p><a name="Nt_884" href="#NtA_884">[884]</a> 'Nouvelles Archives du + Muséum,' tom. i. p. 27.</p> + + <p><a name="Nt_885" href="#NtA_885">[885]</a> As quoted by Sir J. Lubbock + in 'Nat. Hist. Review,' 1862, p. 345.</p> + + <p><a name="Nt_886" href="#NtA_886">[886]</a> 'Transact. Linn. Soc.,' + vol. xxiv., 1863, p. 62.</p> + + <p><a name="Nt_887" href="#NtA_887">[887]</a> 'Parthenogenesis,' 1849, + pp. 25-26. Prof. Huxley has some excellent remarks ('Medical Times,' + 1856, p. 637) on this subject, in reference to the development of + star-fishes, and shows how curiously metamorphosis graduates into + gemmation or zoid-formation, which is in fact the same as + metagenesis.</p> + + <p><a name="Nt_888" href="#NtA_888">[888]</a> Prof. J. Reay Greene, in + Günther's 'Record of Zoolog. Lit.,' 1865, p. 625.</p> + + <p><a name="Nt_889" href="#NtA_889">[889]</a> Fritz Müller's 'Für + Darwin,' 1864, s. 65, 71. The highest authority on crustaceans, Prof. + Milne Edwards, insists ('Annal. des Sci. Nat.,' 2nd series, Zoolog., tom. + iii. p. 322) on their metamorphoses differing even in closely allied + genera.</p> + + <p><a name="Nt_890" href="#NtA_890">[890]</a> Prof. Allman, in 'Annals + and Mag. of Nat. Hist.,' 3rd series, vol. xiii., 1864, p. 348; Dr. S. + Wright, idem, vol. viii., 1861, p. 127. <i>See</i> also p. 358 for + analogous statements by Sars.</p> + + <p><a name="Nt_891" href="#NtA_891">[891]</a> 'Tissus Vivants,' 1866, p. + 22.</p> + + <p><a name="Nt_892" href="#NtA_892">[892]</a> 'Cellular Pathology,' + translat. by Dr. Chance, 1860, pp. 14, 18, 83, 460.</p> + + <p><a name="Nt_893" href="#NtA_893">[893]</a> Paget, 'Surgical + Pathology,' vol. i., 1853, pp. 12-14.</p> + + <p><a name="Nt_894" href="#NtA_894">[894]</a> Idem, p. 19.</p> + + <p><a name="Nt_895" href="#NtA_895">[895]</a> Mantegazza, quoted in + 'Popular Science Review,' July 1865, p. 522.</p> + + <p><a name="Nt_896" href="#NtA_896">[896]</a> 'De la Production + Artificielle des Os,' p. 8.</p> + + <p><a name="Nt_897" href="#NtA_897">[897]</a> Isidore Geoffroy St. + Hilaire, 'Hist. des Anomalies,' tom. ii. pp. 549, 560, 562; Virchow, + idem, p. 484.</p> + + <p><a name="Nt_898" href="#NtA_898">[898]</a> For the most recent + classification of cells, <i>see</i> Ernst Häckel's 'Generelle + Morpholog.,' Band ii., 1866, s. 275.</p> + + <p><a name="Nt_899" href="#NtA_899">[899]</a> 'The Structure and Growth + of Tissues,' 1865, p. 21, &c.</p> + + <p><a name="Nt_900" href="#NtA_900">[900]</a> Dr. W. Turner, 'The present + Aspect of Cellular Pathology,' 'Edinburgh Medical Journal,' April, + 1863.</p> + + <p><a name="Nt_901" href="#NtA_901">[901]</a> This term is used by Dr. E. + Montgomery ('On the Formation of so-called Cells in Animal Bodies,' 1867, + p. 42), who denies that cells are derived from other cells by a process + of growth, but believes that they originate through certain chemical + changes.</p> + + <p><a name="Nt_902" href="#NtA_902">[902]</a> Prof. Huxley has called my + attention to the views of Buffon and Bonnet. The former ('Hist. Nat. + Gén.,' edit. of 1749, tom. ii. pp. 54, 62, 329, 333, 420, 425) supposes + that organic molecules exist in the food consumed by every living + creature; and that these molecules are analogous in nature with the + various organs by which they are absorbed. When the organs thus become + fully developed, the molecules being no longer required collect and form + buds or the sexual elements. If Buffon had assumed that his organic + molecules had been formed by each separate unit throughout the body, his + view and mine would have been closely similar.</p> + + <p>Bonnet ('Œuvres d'Hist. Nat.,' tom. v., part i., 1781, 4to + edit., p. 334) speaks of the limbs having germs adapted for the + reparation of all possible losses; but whether these germs are supposed + to be the same with those within the buds and sexual organs is not clear. + His famous but now exploded theory of <i>emboîtement</i> implies that + perfect germs are included within germs in endless succession, pre-formed + and ready for all succeeding generations. According to my view, the germs + or gemmules of each separate part were not originally pre-formed, but are + continually produced at all ages during each generation, with some handed + down from preceding generations.</p> + + <p>Prof. Owen remarks ('Parthenogenesis,' 1849, pp. 5-8), "Not all the + progeny of the primary impregnated germ-cell are required for the + formation of the body in all animals: certain of the derivative + germ-cells may remain unchanged and become included in that body which + has been composed of their metamorphosed and diversely combined or + confluent brethren: so included, any derivative germ-cell, or the nucleus + of such, may commence and repeat the same processes of growth by + imbibition, and of propagation by spontaneous fission, as those to which + itself owed its origin;" &c. By the agency of these germ-cells Prof. + Owen accounts for parthenogenesis, for propagation by self-division + during successive generations, and for the repairs of injuries. His view + agrees with mine in the assumed transmission and multiplication of his + germ-cells, but differs fundamentally from mine in the belief that the + primary germ-cell was formed within the ovarium of the female and was + fertilised by the male. My gemmules are supposed to be formed, quite + independently of sexual concourse, by each separate cell or unit + throughout the body, and to be merely aggregated within the reproductive + organs.</p> + + <p>Lastly, Mr. Herbert Spencer ('Principles of Biology,' vol. i., 1863-4, + chaps. iv. and viii.) has discussed at considerable length what he + designates as physiological units. These agree with my gemmules in being + supposed to multiply and to be transmitted from parent to child; the + sexual elements are supposed to serve merely as their vehicles; they are + the efficient agents in all the forms of reproduction and in the repairs + of injuries; they account for inheritance, but they are not brought to + bear on reversion or atavism, and this is unintelligible to me; they are + supposed to possess polarity, or, as I call it, affinity; and apparently + they are believed to be derived from each separate part of the whole + body. But gemmules differ from Mr. Spencer's physiological units, + inasmuch as a certain number, or mass of them, are, as we shall see, + requisite for the development of each cell or part. Nevertheless I should + have concluded that Mr. Spencer's views were fundamentally the same with + mine, had it not been for several passages which, as far as I understand + them, indicate something quite different. I will quote some of these + passages from pp. 254-256. "In the fertilised germ we have two groups of + physiological units, slightly different in their structures."... "It is + not obvious that change in the form of the part, caused by changed + action, involves such change in the physiological units throughout the + organism, that these, when groups of them are thrown off in the shape of + reproductive centres, will unfold into organisms that have this part + similarly changed in form. Indeed, when treating of Adaptation, we saw + that an organ modified by increase or decrease of function can but slowly + so react on the system at large as to bring about those correlative + changes required to produce a new equilibrium; and yet only when such new + equilibrium has been established, can we expect it to be <i>fully</i> + expressed in the modified physiological units of which the organism is + built—only then can we count on a complete transfer of the + modification to descendants."... "That the change in the offspring must, + other things equal, be in the same direction as the change in the parent, + we may dimly see is implied by the fact, that the change propagated + throughout the parental system is a change towards a new state of + equilibrium—a change tending to bring the actions of all organs, + reproductive included, into harmony with these new actions."</p> + + <p><a name="Nt_903" href="#NtA_903">[903]</a> M. Philipeaux ('Comptes + Rendus,' Oct. 1, 1866, p. 576, and June, 1867) has lately shown that when + the entire fore-limb, including the scapula, is extirpated, the power of + regrowth is lost. From this he concludes that it is necessary for + regrowth that a small portion of the limb should be left. But as in the + lower animals the whole body may be bisected and both halves be + reproduced, this belief does not seem probable. May not the early closing + of a deep wound, as in the case of the extirpation of the scapula, + prevent the formation or protrusion of the nascent limb?</p> + + <p><a name="Nt_904" href="#NtA_904">[904]</a> 'Annal. des Sc. Nat.,' 3rd + series, Bot., tom. xiv., 1850, p. 244.</p> + + <p><a name="Nt_905" href="#NtA_905">[905]</a> <i>See</i> some very + interesting papers on this subject by Prof. Lionel Beale, in 'Medical + Times and Gazette,' Sept. 9th, 1865, pp. 273, 330.</p> + + <p><a name="Nt_906" href="#NtA_906">[906]</a> Third Report of the R. + Comm. on the Cattle Plague, as quoted in 'Gard. Chronicle,' 1866, p. + 446.</p> + + <p><a name="Nt_907" href="#NtA_907">[907]</a> In a cod-fish, weighing 20 + lb., Mr. F. Buckland ('Land and Water,' 1867, p. 57) calculated the above + number of eggs. In another instance, Harmer ('Phil. Transact.,' 1767, p. + 280) found 3,681,760 eggs. For the Ascaris, <i>see</i> Carpenter's 'Comp. + Phys.,' 1854, p. 590. Mr. J. Scott, of the Royal Botanic Garden of + Edinburgh, calculated, in the same manner as I have done for some British + orchids ('Fertilisation of Orchids,' p. 344), the number of seeds in a + capsule of an Acropera, and found the number to be 371,250. Now this + plant produces several flowers on a raceme and many racemes during a + season. In an allied genus, Gongora, Mr. Scott has seen twenty capsules + produced on a single raceme: ten such racemes on the Acropera would yield + above seventy-four millions of seed. I may add that Fritz Müller informs + me that he found in a capsule of a Maxillaria, in South Brazil, that the + seed weighed 42½ grains: he then arranged half a grain of seed in a + narrow line, and by counting a measured length found the number in the + half-grain to be 20,667, so that in the capsule there must have been + 1,756,440 seeds! The same plant sometimes produces half-a-dozen + capsules.</p> + + <p><a name="Nt_908" href="#NtA_908">[908]</a> 'Annals and Mag. of Nat. + Hist.,' 3rd series, vol. viii., 1861, p. 490.</p> + + <p><a name="Nt_909" href="#NtA_909">[909]</a> Paget, 'Lectures on + Pathology,' p. 27; Virchow, 'Cellular Pathology,' translat. by Dr. + Chance, pp. 123, 126, 294; Claude Bernard, 'Des Tissus Vivants,' pp. 177, + 210, 337; Müller's 'Physiology,' Eng. translat., p. 290.</p> + + <p><a name="Nt_910" href="#NtA_910">[910]</a> Virchow, 'Cellular + Pathology,' trans. by Dr. Chance, 1860, pp. 60, 162, 245, 441, 454.</p> + + <p><a name="Nt_911" href="#NtA_911">[911]</a> Idem, pp. 412-426.</p> + + <p><a name="Nt_912" href="#NtA_912">[912]</a> <i>See</i> Rev. J. M. + Berkeley, in 'Gard. Chron.,' April 28th, 1866, on a bud developed on the + petal of the Clarkia. <i>See</i> also H. Schacht, 'Lehrbuch der Anat.,' + &c., 1859, Theile ii. s. 12, on adventitious buds.</p> + + <p><a name="Nt_913" href="#NtA_913">[913]</a> Mr. Herbert Spencer + ('Principles of Biology,' vol. ii. p. 430) has fully discussed the + antagonism between growth and reproduction.</p> + + <p><a name="Nt_914" href="#NtA_914">[914]</a> The male salmon is known to + breed at a very early age. The Triton and Siredon, whilst retaining their + larval branchiæ, according to Filippi and Duméril ('Annals and Mag. of + Nat. Hist.,' 3rd series, 1866, p. 157), are capable of reproduction. + Ernst Häckel has recently ('Monatsbericht Akad. Wiss. Berlin,' Feb. 2nd, + 1865) observed the surprising case of a medusa, with its reproductive + organs active, which produces by budding a widely different form of + medusa; and this latter also has the power of sexual reproduction. Krohn + has shown ('Annals and Mag. of Nat. Hist.,' 3rd series, vol. xix., 1862, + p. 6) that certain other medusæ, whilst sexually mature, propagate by + gemmæ.</p> + + <p><a name="Nt_915" href="#NtA_915">[915]</a> <i>See</i> his excellent + discussion on this subject in 'Nouvelles Archives du Muséum,' tom. i. p. + 151.</p> + + <p><a name="Nt_916" href="#NtA_916">[916]</a> Various physiologists have + insisted on this distinction between growth and development. Prof. + Marshall ('Phil. Transact.,' 1864, p. 544) gives a good instance in + microcephalous idiots, in which the brain continues to grow after having + been arrested in its development.</p> + + <p><a name="Nt_917" href="#NtA_917">[917]</a> 'Compte Rendu,' Nov. 14, + 1864, p. 800.</p> + + <p><a name="Nt_918" href="#NtA_918">[918]</a> As previously remarked by + Quatrefages, in his 'Metamorphoses de l'Homme,' &c., 1862, p. + 129.</p> + + <p><a name="Nt_919" href="#NtA_919">[919]</a> Günther's 'Zoological + Record,' 1864, p. 279.</p> + + <p><a name="Nt_920" href="#NtA_920">[920]</a> Sedgwick, in + 'Medico-Chirurg. Review,' April 1863, p. 454.</p> + + <p><a name="Nt_921" href="#NtA_921">[921]</a> Isid. Geoffroy St. Hilaire, + 'Hist. des Anomalies,' tom. i., 1832, pp. 435, 657; and tom. ii. p. + 560.</p> + + <p><a name="Nt_922" href="#NtA_922">[922]</a> Virchow, 'Cellular + Pathology,' 1860, p. 66.</p> + + <p><a name="Nt_923" href="#NtA_923">[923]</a> Moquin-Tandon, 'Tératologie + Veg.,' 1841, pp. 218, 220, 353. For the case of the pea, <i>see</i> + 'Gardener's Chron.,' 1866, p. 897.</p> + + <p><a name="Nt_924" href="#NtA_924">[924]</a> Müller's 'Physiology,' Eng. + translat., vol. i. p. 407.</p> + + <p><a name="Nt_925" href="#NtA_925">[925]</a> <i>See</i> some remarks to + this effect by Sir H. Holland in his 'Medical Notes,' 1839, p. 32.</p> + + <p><a name="Nt_926" href="#NtA_926">[926]</a> This is the view taken by + Prof. Häckel, in his 'Generelle Morphologie' (B. ii. s. 171), who says: + "Lediglich die partielle Identität der specifischconstituirten Materie im + elterlichen und im kindlichen Organismus, die Theilung dieser Materie bei + der Fortpflanzung, ist die Ursache der Erblichkeit."</p> + + <p><a name="Nt_927" href="#NtA_927">[927]</a> In these remarks I, in + fact, follow Naudin, who speaks of the elements or essences of the two + species which are crossed. See his excellent memoir in the 'Nouvelles + Archives du Muséum,' tom. i. p. 151.</p> + + <p><a name="Nt_928" href="#NtA_928">[928]</a> Godron, 'De l'Espèce,' + 1859, tom. ii. p. 44, &c.</p> + + <p><a name="Nt_929" href="#NtA_929">[929]</a> Journal Proc. Linn. Soc., + 1858, vol. iii. p. 60.</p> + + <p><a name="Nt_930" href="#NtA_930">[930]</a> 'The Quarterly Journal of + Science,' Oct. 1867, p. 486.</p> + + <p><a name="Nt_931" href="#NtA_931">[931]</a> M. Rufz de Lavison, in + 'Bull. Soc. Imp. d'Acclimat.,' Dec. 1862, p. 1009.</p> + + <p><a name="Nt_932" href="#NtA_932">[932]</a> 'Races of Man,' 1850, p. + 315.</p> + + <p><a name="Nt_933" href="#NtA_933">[933]</a> 'Travels in Peru,' Eng. + translat., p. 177.</p> + + <p><a name="Nt_934" href="#NtA_934">[934]</a> Youatt on Cattle, 1834, p + 200: on Pigs; <i>see</i> 'Gard. Chronicle,' 1854, p. 410.</p> + + <p><a name="Nt_935" href="#NtA_935">[935]</a> 'Die Pflanzen der + Pfahlbauten,' 1865.</p> + + <p><a name="Nt_936" href="#NtA_936">[936]</a> Morlot, 'Soc. Vaud. des + Scien. Nat,' Mars 1860, p. 298.</p> + + <p><a name="Nt_937" href="#NtA_937">[937]</a> Rütimeyer, 'Die Fauna der + Pfahlbauten,' 1861, s. 30.</p> + + <p><a name="Nt_938" href="#NtA_938">[938]</a> Godron, 'De l'Espèce,' tom. + i., 1859, p. 368.</p> + + <p><a name="Nt_939" href="#NtA_939">[939]</a> 'Géographie Botan.,' 1855, + p. 989.</p> + + <p><a name="Nt_940" href="#NtA_940">[940]</a> Pickering, 'Races of Man,' + 1850, p. 318.</p> + + <p><a name="Nt_941" href="#NtA_941">[941]</a> 'Journal of a Horticultural + Tour,' by a Deputation of the Caledonian Hist. Soc., 1823, p. 293.</p> + +<p> </p> +<p> </p> +<hr class="pg" /> +</div> +<p>***END OF THE PROJECT GUTENBERG EBOOK THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION, VOLUME II (OF 2)***</p> +<p>******* This file should be named 28897-h.txt or 28897-h.zip *******</p> +<p>This and all associated files of various formats will be found in:<br /> +<a href="http://www.gutenberg.org/dirs/2/8/8/9/28897">http://www.gutenberg.org/2/8/8/9/28897</a></p> +<p>Updated editions will replace the previous one--the old editions +will be renamed.</p> + +<p>Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: The Variation of Animals and Plants Under Domestication, Volume II (of 2) + + +Author: Charles Darwin + + + +Release Date: May 20, 2009 [eBook #28897] + +Language: English + +Character set encoding: ISO-646-US (US-ASCII) + + +***START OF THE PROJECT GUTENBERG EBOOK THE VARIATION OF ANIMALS AND +PLANTS UNDER DOMESTICATION, VOLUME II (OF 2)*** + + +E-text prepared by Steven Gibbs, Keith Edkins, and the Project Gutenberg +Online Distributed Proofreading Team (http://www.pgdp.net) + + + +Transcriber's note: + + A few typographical errors have been corrected: they are listed + at the end of the text. The Errata on page viii, which were in + the original book, have been applied to this e-text. + + Page numbers within curly brackets (such as {iii} and {27} + have been included so that the reader might use the index. + + + + + +THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION. + +by + +CHARLES DARWIN, M.A., F.R.S., &c. + +IN TWO VOLUMES.--VOL. II. + +With Illustrations. + + + + + + + +LONDON: +John Murray, Albemarle Street. +1868. + +The right of Translation is reserved. + +London: Printed by William Clowes and Sons, Stamford Street, and Charing +Cross. + + + + +{iii} + +CONTENTS OF VOLUME II. + +CHAPTER XII. + +INHERITANCE. + +WONDERFUL NATURE OF INHERITANCE--PEDIGREES OF OUR DOMESTICATED +ANIMALS--INHERITANCE NOT DUE TO CHANCE--TRIFLING CHARACTERS +INHERITED--DISEASES INHERITED--PECULIARITIES IN THE EYE INHERITED--DISEASES +IN THE HORSE--LONGEVITY AND VIGOUR--ASYMMETRICAL DEVIATIONS OF +STRUCTURE--POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY DIGITS AFTER +AMPUTATION--CASES OF SEVERAL CHILDREN SIMILARLY AFFECTED FROM NON-AFFECTED +PARENTS--WEAK AND FLUCTUATING INHERITANCE: IN WEEPING TREES, IN DWARFNESS, +COLOUR OF FRUIT AND FLOWERS, COLOUR OF HORSES--NON-INHERITANCE IN CERTAIN +CASES--INHERITANCE OF STRUCTURE AND HABITS OVERBORNE BY HOSTILE CONDITIONS +OF LIFE, BY INCESSANTLY RECURRING VARIABILITY, AND BY REVERSION--CONCLUSION +... Page 1 + +CHAPTER XIII. + +INHERITANCE _continued_--REVERSION OR ATAVISM. + +DIFFERENT FORMS OF REVERSION--IN PURE OR UNCROSSED BREEDS, AS IN PIGEONS, +FOWLS, HORNLESS CATTLE AND SHEEP, IN CULTIVATED PLANTS--REVERSION IN FERAL +ANIMALS AND PLANTS--REVERSION IN CROSSED VARIETIES AND SPECIES--REVERSION +THROUGH BUD-PROPAGATION, AND BY SEGMENTS IN THE SAME FLOWER OR FRUIT--IN +DIFFERENT PARTS OF THE BODY IN THE SAME ANIMAL--THE ACT OF CROSSING A +DIRECT CAUSE OF REVERSION, VARIOUS CASES OF, WITH INSTINCTS--OTHER +PROXIMATE CAUSES OF REVERSION--LATENT CHARACTERS--SECONDARY SEXUAL +CHARACTERS--UNEQUAL DEVELOPMENT OF THE TWO SIDES OF THE BODY--APPEARANCE +WITH ADVANCING AGE OF CHARACTERS DERIVED FROM A CROSS--THE GERM WITH ALL +ITS LATENT CHARACTERS A WONDERFUL OBJECT--MONSTROSITIES--PELORIC FLOWERS +DUE IN SOME CASES TO REVERSION ... Page 28 + +CHAPTER XIV. + +INHERITANCE _continued_--FIXEDNESS OF CHARACTER--PREPOTENCY--SEXUAL +LIMITATION--CORRESPONDENCE OF AGE. + +FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO ANTIQUITY OF +INHERITANCE--PREPOTENCY OF TRANSMISSION IN INDIVIDUALS OF THE SAME FAMILY, +IN CROSSED BREEDS AND SPECIES; OFTEN STRONGER IN ONE SEX THAN THE OTHER; +SOMETIMES DUE TO THE SAME CHARACTER BEING PRESENT AND VISIBLE IN ONE BREED +AND LATENT IN THE OTHER--INHERITANCE AS LIMITED BY SEX--NEWLY-ACQUIRED +CHARACTERS IN OUR DOMESTICATED ANIMALS OFTEN TRANSMITTED BY ONE SEX ALONE, +SOMETIMES LOST BY ONE SEX ALONE--INHERITANCE AT CORRESPONDING PERIODS OF +LIFE--THE IMPORTANCE OF THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS +EXHIBITED IN DOMESTICATED ANIMALS; AS EXHIBITED IN THE APPEARANCE AND +DISAPPEARANCE OF INHERITED DISEASES; SOMETIMES SUPERVENING EARLIER IN THE +CHILD THAN IN THE PARENT--SUMMARY OF THE THREE PRECEDING CHAPTERS ... Page +62 + +{iv} + +CHAPTER XV. + +ON CROSSING. + +FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED BREEDS--WHEN +THE NUMBERS OF TWO COMMINGLING BREEDS ARE UNEQUAL, ONE ABSORBS THE +OTHER--THE RATE OF ABSORPTION DETERMINED BY PREPOTENCY OF TRANSMISSION, BY +THE CONDITIONS OF LIFE, AND BY NATURAL SELECTION--ALL ORGANIC BEINGS +OCCASIONALLY INTERCROSS; APPARENT EXCEPTIONS--ON CERTAIN CHARACTERS +INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE WHICH HAVE SUDDENLY +APPEARED IN THE INDIVIDUAL--ON THE MODIFICATION OF OLD RACES, AND THE +FORMATION OF NEW RACES, BY CROSSING--SOME CROSSED RACES HAVE BRED TRUE FROM +THEIR FIRST PRODUCTION--ON THE CROSSING OF DISTINCT SPECIES IN RELATION TO +THE FORMATION OF DOMESTIC RACES ... Page 85 + +CHAPTER XVI. + +CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES--INFLUENCE OF +DOMESTICATION ON FERTILITY. + +DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN CROSSED--VARIOUS +CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING AND SEXUAL +PREFERENCE--VARIETIES OF WHEAT SAID TO BE STERILE WHEN CROSSED--VARIETIES +OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND TOBACCO, RENDERED IN +SOME DEGREE MUTUALLY STERILE--DOMESTICATION ELIMINATES THE TENDENCY TO +STERILITY NATURAL TO SPECIES WHEN CROSSED--ON THE INCREASED FERTILITY OF +UNCROSSED ANIMALS AND PLANTS FROM DOMESTICATION AND CULTIVATION ... Page +100 + +CHAPTER XVII. + +ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL EFFECTS OF CLOSE +INTERBREEDING. + +DEFINITION OF CLOSE INTERBREEDING--AUGMENTATION OF MORBID +TENDENCIES--GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, AND +ON THE EVIL EFFECTS FROM CLOSE INTERBREEDING--CATTLE, CLOSELY INTERBRED; +HALF-WILD CATTLE LONG KEPT IN THE SAME +PARKS--SHEEP--FALLOW-DEER--DOGS--RABBITS--PIGS--MAN, ORIGIN OF HIS +ABHORRENCE OF INCESTUOUS MARRIAGES--FOWLS--PIGEONS--HIVE-BEES--PLANTS, +GENERAL CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING--MELONS, +FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND FOREST-TREES--ON THE INCREASED SIZE +OF HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY--ON CERTAIN PLANTS +WHICH EITHER NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, BUT ARE FERTILE, +BOTH ON THE MALE AND FEMALE SIDE, WHEN CROSSED WITH DISTINCT INDIVIDUALS +EITHER OF THE SAME OR ANOTHER SPECIES--CONCLUSION ... Page 114 + +{v} + +CHAPTER XVIII. + +ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED CONDITIONS OF LIFE: +STERILITY FROM VARIOUS CAUSES. + +ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE CONDITIONS OF +LIFE--STERILITY FROM CHANGED CONDITIONS, IN ANIMALS, IN THEIR NATIVE +COUNTRY AND IN MENAGERIES--MAMMALS, BIRDS, AND INSECTS--LOSS OF SECONDARY +SEXUAL CHARACTERS AND OF INSTINCTS--CAUSES OF STERILITY--STERILITY OF +DOMESTICATED ANIMALS FROM CHANGED CONDITIONS--SEXUAL INCOMPATIBILITY OF +INDIVIDUAL ANIMALS--STERILITY OF PLANTS FROM CHANGED CONDITIONS OF +LIFE--CONTABESCENCE OF THE ANTHERS--MONSTROSITIES AS A CAUSE OF +STERILITY--DOUBLE FLOWERS--SEEDLESS FRUIT--STERILITY FROM THE EXCESSIVE +DEVELOPMENT OF THE ORGANS OF VEGETATION--FROM LONG-CONTINUED PROPAGATION BY +BUDS--INCIPIENT STERILITY THE PRIMARY CAUSE OF DOUBLE FLOWERS AND SEEDLESS +FRUIT ... Page 145 + +CHAPTER XIX. + +SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS ON HYBRIDISM. + +ON THE EFFECTS OF CROSSING--THE INFLUENCE OF DOMESTICATION ON +FERTILITY--CLOSE INTERBREEDING--GOOD AND EVIL RESULTS FROM CHANGED +CONDITIONS OF LIFE--VARIETIES WHEN CROSSED NOT INVARIABLY FERTILE--ON THE +DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND VARIETIES--CONCLUSIONS +WITH RESPECT TO HYBRIDISM--LIGHT THROWN ON HYBRIDISM BY THE ILLEGITIMATE +PROGENY OF DIMORPHIC AND TRIMORPHIC PLANTS--STERILITY OF CROSSED SPECIES +DUE TO DIFFERENCES CONFINED TO THE REPRODUCTIVE SYSTEM--NOT ACCUMULATED +THROUGH NATURAL SELECTION--REASONS WHY DOMESTIC VARIETIES ARE NOT MUTUALLY +STERILE--TOO MUCH STRESS HAS BEEN LAID ON THE DIFFERENCE IN FERTILITY +BETWEEN CROSSED SPECIES AND CROSSED VARIETIES--CONCLUSION ... Page 173 + +CHAPTER XX. + +SELECTION BY MAN. + +SELECTION A DIFFICULT ART--METHODICAL, UNCONSCIOUS, AND NATURAL +SELECTION--RESULTS OF METHODICAL SELECTION--CARE TAKEN IN +SELECTION--SELECTION WITH PLANTS--SELECTION CARRIED ON BY THE ANCIENTS, AND +BY SEMI-CIVILISED PEOPLE--UNIMPORTANT CHARACTERS OFTEN ATTENDED +TO--UNCONSCIOUS SELECTION--AS CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR +DOMESTICATED ANIMALS CHANGED THROUGH THE ACTION OF UNCONSCIOUS +SELECTION--INFLUENCE OF DIFFERENT BREEDERS ON THE SAME SUB-VARIETY--PLANTS +AS AFFECTED BY UNCONSCIOUS SELECTION--EFFECTS OF SELECTION AS SHOWN BY THE +GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST VALUED BY MAN ... Page 192 + +{vi} + +CHAPTER XXI. + +SELECTION--_continued._ + +NATURAL SELECTION AS AFFECTING DOMESTIC PRODUCTIONS--CHARACTERS WHICH +APPEAR OF TRIFLING VALUE OFTEN OF REAL IMPORTANCE--CIRCUMSTANCES FAVOURABLE +TO SELECTION BY MAN--FACILITY IN PREVENTING CROSSES, AND THE NATURE OF THE +CONDITIONS--CLOSE ATTENTION AND PERSEVERANCE INDISPENSABLE--THE PRODUCTION +OF A LARGE NUMBER OF INDIVIDUALS ESPECIALLY FAVOURABLE--WHEN NO SELECTION +IS APPLIED, DISTINCT RACES ARE NOT FORMED--HIGHLY-BRED ANIMALS LIABLE TO +DEGENERATION--TENDENCY IN MAN TO CARRY THE SELECTION OF EACH CHARACTER TO +AN EXTREME POINT, LEADING TO DIVERGENCE OF CHARACTER, RARELY TO +CONVERGENCE--CHARACTERS CONTINUING TO VARY IN THE SAME DIRECTION IN WHICH +THEY HAVE ALREADY VARIED--DIVERGENCE OF CHARACTER, WITH THE EXTINCTION OF +INTERMEDIATE VARIETIES, LEADS TO DISTINCTNESS IN OUR DOMESTIC RACES--LIMIT +TO THE POWER OF SELECTION--LAPSE OF TIME IMPORTANT--MANNER IN WHICH +DOMESTIC RACES HAVE ORIGINATED--SUMMARY ... Page 224 + +CHAPTER XXII. + +CAUSES OF VARIABILITY. + +VARIABILITY DOES NOT NECESSARILY ACCOMPANY REPRODUCTION--CAUSES ASSIGNED BY +VARIOUS AUTHORS--INDIVIDUAL DIFFERENCES--VARIABILITY OF EVERY KIND DUE TO +CHANGED CONDITIONS OF LIFE--ON THE NATURE OF SUCH CHANGES--CLIMATE, FOOD, +EXCESS OF NUTRIMENT--SLIGHT CHANGES SUFFICIENT--EFFECTS OF GRAFTING ON THE +VARIABILITY OF SEEDLING-TREES--DOMESTIC PRODUCTIONS BECOME HABITUATED TO +CHANGED CONDITIONS--ON THE ACCUMULATIVE ACTION OF CHANGED CONDITIONS--CLOSE +INTERBREEDING AND THE IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE +VARIABILITY--CROSSING AS A CAUSE OF THE APPEARANCE OF NEW +CHARACTERS--VARIABILITY FROM THE COMMINGLING OF CHARACTERS AND FROM +REVERSION--ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH EITHER +DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE VARIABILITY +... Page 250 + +CHAPTER XXIII. + +DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS OF LIFE. + +SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE ACTION OF CHANGED +CONDITIONS, IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND IN THE STATE OF THE +TISSUES--LOCAL DISEASES--CONSPICUOUS MODIFICATIONS FROM CHANGED CLIMATE OR +FOOD, ETC.--PLUMAGE OF BIRDS AFFECTED BY PECULIAR NUTRIMENT, AND BY THE +INOCULATION OF POISON--LAND-SHELLS--MODIFICATIONS OF ORGANIC BEINGS IN A +STATE OF NATURE THROUGH THE DEFINITE ACTION OF EXTERNAL +CONDITIONS--COMPARISON OF AMERICAN AND EUROPEAN TREES--GALLS--EFFECTS OF +PARASITIC FUNGI--CONSIDERATIONS OPPOSED TO THE BELIEF IN THE POTENT +INFLUENCE OF CHANGED EXTERNAL CONDITIONS--PARALLEL SERIES OF +VARIETIES--AMOUNT OF VARIATION DOES NOT CORRESPOND WITH THE DEGREE OF +CHANGE IN THE CONDITIONS--BUD-VARIATION--MONSTROSITIES PRODUCED BY +UNNATURAL TREATMENT--SUMMARY ... Page 271 + +{vii} + +CHAPTER XXIV. + +LAWS OF VARIATION--USE AND DISUSE, ETC. + +NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE ORGANISATION--ON THE +EFFECTS OF THE INCREASED USE AND DISUSE OF ORGANS--CHANGED HABITS OF +LIFE--ACCLIMATISATION WITH ANIMALS AND PLANTS--VARIOUS METHODS BY WHICH +THIS CAN BE EFFECTED--ARRESTS OF DEVELOPMENT--RUDIMENTARY ORGANS ... Page +293 + +CHAPTER XXV. + +LAWS OF VARIATION, _continued_--CORRELATED VARIABILITY. + +EXPLANATION OF TERM--CORRELATION AS CONNECTED WITH +DEVELOPMENT--MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED SIZE +OF PARTS--CORRELATED VARIATION OF HOMOLOGOUS PARTS--FEATHERED FEET IN BIRDS +ASSUMING THE STRUCTURE OF THE WINGS--CORRELATION BETWEEN THE HEAD AND THE +EXTREMITIES--BETWEEN THE SKIN AND DERMAL APPENDAGES--BETWEEN THE ORGANS OF +SIGHT AND HEARING--CORRELATED MODIFICATIONS IN THE ORGANS OF +PLANTS--CORRELATED MONSTROSITIES--CORRELATION BETWEEN THE SKULL AND +EARS--SKULL AND CREST OF FEATHERS--SKULL AND HORNS--CORRELATION OF GROWTH +COMPLICATED BY THE ACCUMULATED EFFECTS OF NATURAL SELECTION--COLOUR AS +CORRELATED WITH CONSTITUTIONAL PECULIARITIES ... Page 319 + +CHAPTER XXVI. + +LAWS OF VARIATION, _continued_--SUMMARY. + +ON THE AFFINITY AND COHESION OF HOMOLOGOUS PARTS--ON THE VARIABILITY OF +MULTIPLE AND HOMOLOGOUS PARTS--COMPENSATION OF GROWTH--MECHANICAL +PRESSURE--RELATIVE POSITION OF FLOWERS WITH RESPECT TO THE AXIS OF THE +PLANT, AND OF SEEDS IN THE CAPSULE, AS INDUCING VARIATION--ANALOGOUS OR +PARALLEL VARIETIES--SUMMARY OF THE THREE LAST CHAPTERS ... Page 339 + +CHAPTER XXVII. + +PROVISIONAL HYPOTHESIS OF PANGENESIS. + +PRELIMINARY REMARKS--FIRST PART:--THE FACTS TO BE CONNECTED UNDER A SINGLE +POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION--THE DIRECT ACTION +OF THE MALE ELEMENT ON THE FEMALE--DEVELOPMENT--THE FUNCTIONAL INDEPENDENCE +OF THE ELEMENTS OR UNITS OF THE BODY--VARIABILITY--INHERITANCE--REVERSION. + +SECOND PART:--STATEMENT OF THE HYPOTHESIS--HOW FAR THE NECESSARY +ASSUMPTIONS ARE IMPROBABLE--EXPLANATION BY AID OF THE HYPOTHESIS OF THE +SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST PART--CONCLUSION ... Page +357 + +{viii} + +CHAPTER XXVIII. + +CONCLUDING REMARKS. + +DOMESTICATION--NATURE AND CAUSES OF VARIABILITY--SELECTION--DIVERGENCE AND +DISTINCTNESS OF CHARACTER--EXTINCTION OF RACES--CIRCUMSTANCES FAVOURABLE TO +SELECTION BY MAN--ANTIQUITY OF CERTAIN RACES--THE QUESTION WHETHER EACH +PARTICULAR VARIATION HAS BEEN SPECIALLY PREORDAINED ... Page 405 + +INDEX ... Page 433 + + * * * * * + +ERRATA. + + Vol. II., pp. 18, 232, 258, for Crataegus oxycantha, read oxyacantha. + ,, p. 98, 8 lines from top, for Dianthus armoria read armeria. + ,, ,, 156, 15 lines from bottom, for Casuarinus read Casuarius. + ,, ,, ,, 4 lines from bottom, for Grus cineria read cinerea. + ,, ,, 168, 11 lines from top, for Oesculus read Aesculus. + ,, ,, 300, 3 lines from top, for anastomising read anastomosing. + ,, ,, ,, foot-note, for Birckell read Brickell. + + * * * * * + + +{1} THE + +VARIATION OF ANIMALS AND PLANTS + +UNDER DOMESTICATION. + + * * * * * + +CHAPTER XII. + +INHERITANCE. + + WONDERFUL NATURE OF INHERITANCE--PEDIGREES OF OUR DOMESTICATED + ANIMALS--INHERITANCE NOT DUE TO CHANCE--TRIFLING CHARACTERS + INHERITED--DISEASES INHERITED--PECULIARITIES IN THE EYE + INHERITED--DISEASES IN THE HORSE--LONGEVITY AND VIGOUR--ASYMMETRICAL + DEVIATIONS OF STRUCTURE--POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY + DIGITS AFTER AMPUTATION--CASES OF SEVERAL CHILDREN SIMILARLY AFFECTED + FROM NON-AFFECTED PARENTS--WEAK AND FLUCTUATING INHERITANCE: IN WEEPING + TREES, IN DWARFNESS, COLOUR OF FRUIT AND FLOWERS, COLOUR OF + HORSES--NON-INHERITANCE IN CERTAIN CASES--INHERITANCE OF STRUCTURE AND + HABITS OVERBORNE BY HOSTILE CONDITIONS OF LIFE, BY INCESSANTLY + RECURRING VARIABILITY, AND BY REVERSION--CONCLUSION. + +The subject of inheritance is an immense one, and has been treated by many +authors. One work alone, 'De l'Heredite Naturelle,' by Dr. Prosper Lucas, +runs to the length of 1562 pages. We must confine ourselves to certain +points which have an important bearing on the general subject of variation, +both with domestic and natural productions. It is obvious that a variation +which is not inherited throws no light on the derivation of species, nor is +of any service to man, except in the case of perennial plants, which can be +propagated by buds. + +If animals and plants had never been domesticated, and wild ones alone had +been observed, we should probably never have heard the saying, that "like +begets like." The proposition would have been as self-evident, as that all +the buds on the same tree are alike, though neither proposition is strictly +true. For, as has often been remarked, probably no two individuals are {2} +identically the same. All wild animals recognise each other, which shows +that there is some difference between them; and when the eye is well +practised, the shepherd knows each sheep, and man can distinguish a +fellow-man out of millions on millions of other men. Some authors have gone +so far as to maintain that the production of slight differences is as much +a necessary function of the powers of generation, as the production of +offspring like their parents. This view, as we shall see in a future +chapter, is not theoretically probable, though practically it holds good. +The saying that "like begets like" has in fact arisen from the perfect +confidence felt by breeders, that a superior or inferior animal will +generally reproduce its kind; but this very superiority or inferiority +shows that the individual in question has departed slightly from its type. + +The whole subject of inheritance is wonderful. When a new character arises, +whatever its nature may be, it generally tends to be inherited, at least in +a temporary and sometimes in a most persistent manner. What can be more +wonderful than that some trifling peculiarity, not primordially attached to +the species, should be transmitted through the male or female sexual cells, +which are so minute as not to be visible to the naked eye, and afterwards +through the incessant changes of a long course of development, undergone +either in the womb or in the egg, and ultimately appear in the offspring +when mature, or even when quite old, as in the case of certain diseases? Or +again, what can be more wonderful than the well-ascertained fact that the +minute ovule of a good milking cow will produce a male, from whom a cell, +in union with an ovule, will produce a female, and she, when mature, will +have large mammary glands, yielding an abundant supply of milk, and even +milk of a particular quality? Nevertheless, the real subject of surprise +is, as Sir H. Holland has well remarked,[1] not that a character should be +inherited, but that any should ever fail to be inherited. In a future +chapter, devoted to an hypothesis which I have termed pangenesis, an +attempt will be made to show the means by which characters of all kinds are +transmitted from generation to generation. + +{3} + +Some writers,[2] who have not attended to natural history, have attempted +to show that the force of inheritance has been much exaggerated. The +breeders of animals would smile at such simplicity; and if they +condescended to make any answer, might ask what would be the chance of +winning a prize if two inferior animals were paired together? They might +ask whether the half-wild Arabs were led by theoretical notions to keep +pedigrees of their horses? Why have pedigrees been scrupulously kept and +published of the Shorthorn cattle, and more recently of the Hereford breed? +Is it an illusion that these recently improved animals safely transmit +their excellent qualities even when crossed with other breeds? have the +Shorthorns, without good reason, been purchased at immense prices and +exported to almost every quarter of the globe, a thousand guineas having +been given for a bull? With greyhounds pedigrees have likewise been kept, +and the names of such dogs, as Snowball, Major, &c., are as well known to +coursers as those of Eclipse and Herod on the turf. Even with the Gamecock +pedigrees of famous strains were formerly kept, and extended back for a +century. With pigs, the Yorkshire and Cumberland breeders "preserve and +print pedigrees;" and to show how such highly-bred animals are valued, I +may mention that Mr. Brown, who won all the first prizes for small breeds +at Birmingham in 1850, sold a young sow and boar of his breed to Lord Ducie +for 43 guineas; the sow alone was afterwards sold to the Rev. F. Thursby +for 65 guineas; who writes, "she paid me very well, having sold her produce +for 300_l_., and having now four breeding sows from her."[3] Hard cash paid +down, over and over again, is an excellent test of inherited superiority. +In fact, the whole art of breeding, from which such great results have been +attained during the present century, depends on the inheritance of each +small {4} detail of structure. But inheritance is not certain; for if it +were, the breeder's art[4] would be reduced to a certainty, and there would +be little scope left for all that skill and perseverance shown by the men +who have left an enduring monument of their success in the present state of +our domesticated animals. + +It is hardly possible, within a moderate compass, to impress on the mind of +those who have not attended to the subject, the full conviction of the +force of inheritance which is slowly acquired by rearing animals, by +studying the many treatises which have been published on the various +domestic animals, and by conversing with breeders. I will select a few +facts of the kind, which, as far as I can judge, have most influenced my +own mind. With man and the domestic animals, certain peculiarities have +appeared in an individual, at rare intervals, or only once or twice in the +history of the world, but have reappeared in several of the children and +grandchildren. Thus Lambert, "the porcupine-man," whose skin was thickly +covered with warty projections, which were periodically moulted, had all +his six children and two grandsons similarly affected.[5] The face and body +being covered with long hair, accompanied by deficient teeth (to which I +shall hereafter refer), occurred in three successive generations in a +Siamese family; but this case is not unique, as a woman[6] with a +completely hairy face was exhibited in London in 1663, and another instance +has recently occurred. Colonel Hallam[7] has described a race of two-legged +pigs, "the hinder extremities being entirely wanting;" and this deficiency +was transmitted through three generations. In fact, all races presenting +any remarkable peculiarity, such as solid-hoofed swine, Mauchamp sheep, +niata cattle, &c., are instances of the long-continued inheritance of rare +deviations of structure. + +When we reflect that certain extraordinary peculiarities have {5} thus +appeared in a single individual out of many millions, all exposed in the +same country to the same general conditions of life, and, again, that the +same extraordinary peculiarity has sometimes appeared in individuals living +under widely different conditions of life, we are driven to conclude that +such peculiarities are not directly due to the action of the surrounding +conditions, but to unknown laws acting on the organisation or constitution +of the individual;--that their production stands in hardly closer relation +to the conditions than does life itself. If this be so, and the occurrence +of the same unusual character in the child and parent cannot be attributed +to both having been exposed to the same unusual conditions, then the +following problem is worth consideration, as showing that the result cannot +be due, as some authors have supposed, to mere coincidence, but must be +consequent on the members of the same family inheriting something in common +in their constitution. Let it be assumed that, in a large population, a +particular affection occurs on an average in one out of a million, so that +the _a priori_ chance that an individual taken at random will be so +affected is only one in a million. Let the population consist of sixty +millions, composed, we will assume, of ten million families, each +containing six members. On these data, Professor Stokes has calculated for +me that the odds will be no less than 8333 millions to 1 that in the ten +million families there will not be even a single family in which one parent +and two children will be affected by the peculiarity in question. But +numerous cases could be given, in which several children have been affected +by the same rare peculiarity with one of their parents; and in this case, +more especially if the grandchildren be included in the calculation, the +odds against mere coincidence become something prodigious, almost beyond +enumeration. + +In some respects the evidence of inheritance is more striking when we +consider the reappearance of trifling peculiarities. Dr. Hodgkin formerly +told me of an English family in which, for many generations, some members +had a single lock differently coloured from the rest of the hair. I knew an +Irish gentleman, who, on the right side of his head, had a small white lock +in the midst of his dark hair: he assured me that his grandmother had {6} a +similar lock on the same side, and his mother on the opposite side. But it +is superfluous to give instances; every shade of expression, which may +often be seen alike in parents and children, tells the same story. On what +a curious combination of corporeal structure, mental character, and +training, must handwriting depend! yet every one must have noted the +occasional close similarity of the handwriting in father and son, although +the father had not taught his son. A great collector of franks assured me +that in his collection there were several franks of father and son hardly +distinguishable except by their dates. Hofacker, in Germany, remarks on the +inheritance of handwriting; and it has even been asserted that English boys +when taught to write in France naturally cling to their English manner of +writing.[8] Gait, gestures, voice, and general bearing are all inherited, +as the illustrious Hunter and Sir A. Carlisle have insisted.[9] My father +communicated to me two or three striking instances, in one of which a man +died during the early infancy of his son, and my father, who did not see +this son until grown up and out of health, declared that it seemed to him +as if his old friend had risen from the grave, with all his highly peculiar +habits and manners. Peculiar manners pass into tricks, and several +instances could be given of their inheritance; as in the case, often +quoted, of the father who generally slept on his back, with his right leg +crossed over the left, and whose daughter, whilst an infant in the cradle, +followed exactly the same habit, though an attempt was made to cure +her.[10] I will give one instance which has fallen under my own +observation, and which is curious from being a trick associated with a +peculiar state of mind, namely, pleasurable emotion. A boy had the singular +habit, when pleased, of rapidly moving his fingers parallel to each other, +and, when much excited, of raising both hands, with the fingers still +moving, to the sides of his face on a level with the eyes; this boy, when +almost an old man, could still hardly resist this trick when much pleased, +but from its absurdity concealed it. He had eight children. Of these, a +girl, when {7} pleased, at the age of four and a half years, moved her +fingers in exactly the same way, and what is still odder, when much +excited, the raised both her hands, with her fingers still moving, to the +sides of her face, in exactly the same manner as her father had done, and +sometimes even still continued to do when alone. I never heard of any one +excepting this one man and his little daughter who had this strange habit; +and certainly imitation was in this instance out of the question. + +Some writers have doubted whether those complex mental attributes, on which +genius and talent depend, are inherited, even when both parents are thus +endowed. But he who will read Mr. Galton's able paper[11] on hereditary +talent will have his doubts allayed. + +Unfortunately it matters not, as far as inheritance is concerned, how +injurious a quality or structure may be if compatible with life. No one can +read the many treatises[12] on hereditary disease and doubt this. The +ancients were strongly of this opinion, or, as Ranchin expresses it, _Omnes +Graeci, Arabes, et Latini in eo consentiunt_. A long catalogue could be +given of all sorts of inherited malformations and of predisposition to +various diseases. With gout, fifty per cent. of the cases observed in +hospital practice are, according to Dr. Garrod, inherited, and a greater +percentage in private practice. Every one knows how often insanity runs in +families, and some of the cases given by Mr. Sedgwick are awful,--as of a +surgeon, whose brother, father, and four paternal uncles were all insane, +the latter dying by suicide; of a Jew, whose father, mother, and six +brothers and sisters were all mad; and in some other cases several members +of the same family, during three or four successive generations, have +committed suicide. Striking instances {8} have been recorded of epilepsy, +consumption, asthma, stone in the bladder, cancer, profuse bleeding from +the slightest injuries, of the mother not giving milk, and of bad +parturition being inherited. In this latter respect I may mention an odd +case given by a good observer,[13] in which the fault lay in the offspring, +and not in the mother: in a part of Yorkshire the farmers continued to +select cattle with large hind-quarters, until they made a strain called +"Dutch-buttocked," and "the monstrous size of the buttocks of the calf was +frequently fatal to the cow, and numbers of cows were annually lost in +calving." + + Instead of giving numerous details on various inherited malformations + and diseases, I will confine myself to one organ, that which is the + most complex, delicate, and probably best-known in the human frame, + namely, the eye, with its accessory parts. To begin with the latter: I + have heard of a family in which parents and children were affected by + drooping eyelids, in so peculiar a manner, that they could not see + without throwing their heads backwards; and Sir A. Carlisle[14] + specifies a pendulous fold to the eyelids as inherited. "In a family," + says Sir H. Holland,[15] "where the father had a singular elongation of + the upper eyelid, seven or eight children were born with the same + deformity; two or three other children having it not." Many persons, as + I year from Mr. Paget, have two or three of the hairs in their eyebrows + (apparently corresponding with the vibrissae of the lower animals) much + longer than the others; and even so trifling a peculiarity as this + certainly runs in families. + + With respect to the eye itself, the highest authority in England, Mr. + Bowman, has been so kind as to give me the following remarks on certain + inherited imperfections. First, hypermetropia, or morbidly long sight: + in this affection, the organ, instead of being spherical, is too flat + from front to back, and is often altogether too small, so that the + retina is brought too forward for the focus of the humours; + consequently a convex glass is required for clear vision of near + objects, and frequently even of distant ones. This state occurs + congenitally, or at a very early age, often in several children of the + same family, where one of the parents has presented it.[16] Secondly, + myopia, or short-sight, in which the eye is egg-shaped, and too long + from front to back; the retina in this case lies behind the focus, and + is therefore fitted to see distinctly only very near objects. This + condition is not commonly congenital, but comes on in youth, the + liability to it being well known to be transmissible from parent to + child. The change from the spherical to the ovoidal shape seems the + immediate {9} consequence of something like inflammation of the coats, + under which they yield, and there is ground for believing that it may + often originate in causes acting directly on the individual affected, + and may thenceforward become transmissible. When both parents are + myopic Mr. Bowman has observed the hereditary tendency in this + direction to be heightened, and some of the children to be myopic at an + earlier age or in a higher degree than their parents. Thirdly, + squinting is a familiar example of hereditary transmission: it is + frequently a result of such optical defects as have been above + mentioned; but the more primary and uncomplicated forms of it are also + sometimes in a marked degree transmitted in a family. Fourthly, + _Cataract_, or opacity of the crystalline lens, is commonly observed in + persons whose parents have been similarly affected, and often at an + earlier age in the children than in the parents. Occasionally more than + one child in a family is thus afflicted, one of whose parents or other + relation presents the senile form of the complaint. When cataract + affects several members of a family in the same generation, it is often + seen to commence at about the same age in each; _e.g._, in one family + several infants or young persons may suffer from it; in another, + several persons of middle age. Mr. Bowman also informs me that he has + occasionally seen, in several members of the same family, various + defects in either the right or left eye; and Mr. White Cooper has often + seen peculiarities of vision confined to one eye reappearing in the + same eye in the offspring.[17] + + The following cases are taken from an able paper by Mr. W. Sedgwick, + and from Dr. Prosper Lucas.[18] Amaurosis, either congenital or coming + on late in life, and causing total blindness, is often inherited; it + has been observed in three successive generations. Congenital absence + of the iris has likewise been transmitted for three generations, a + cleft-iris for four generations, being limited in this latter case to + the males of the family. Opacity of the cornea and congenital smallness + of the eyes have been inherited. Portal records a curious case, in + which a father and two sons were rendered blind, whenever the head was + bent downwards, apparently owing to the crystalline lens, with its + capsule, slipping through an unusually large pupil into the anterior + chamber of the eye. Day-blindness, or imperfect vision under a bright + light, is inherited, as is night-blindness, or an incapacity to see + except under a strong light: a case has been recorded, by M. Cunier, of + this latter defect having affected eighty-five members of the same + family during six generations. The singular incapacity of + distinguishing colours, which has been called _Daltonism_, is + notoriously hereditary, and has been traced through five generations, + in which it was confined to the female sex. + + With respect to the colour of the iris: deficiency of colouring matter + is well known to be hereditary in albinoes. The iris of one eye being + of a different colour from that of the other, and the iris being + spotted, are cases which have been inherited. Mr. Sedgwick gives, in + addition, on the {10} authority of Dr. Osborne,[19] the following + curious instance of strong inheritance: a family of sixteen sons and + five daughters all had eyes "resembling in miniature the markings on + the back of a tortoiseshell cat." The mother of this large family had + three sisters and a brother all similarly marked, and they derived this + peculiarity from their mother, who belonged to a family notorious for + transmitting it to their posterity. + + Finally, Dr. Lucas emphatically remarks that there is not one single + faculty of the eye which is not subject to anomalies; and not one which + is not subjected to the principle of inheritance. Mr. Bowman agrees + with the general truth of this proposition; which of course does not + imply that all malformations are necessarily inherited; this would not + even follow if both parents were affected by an anomaly which in most + cases was transmissible. + +Even if no single fact had been known with respect to the inheritance of +disease and malformations by man, the evidence would have been ample in the +case of the horse. And this might have been expected, as horses breed much +quicker than man, are matched with care, and are highly valued. I have +consulted many works, and the unanimity of the belief by veterinaries of +all nations in the transmission of various morbid tendencies is surprising. +Authors, who have had wide experience, give in detail many singular cases, +and assert that contracted feet, with the numerous contingent evils, of +ring-bones, curbs, splints, spavin, founder and weakness of the front legs, +roaring or broken and thick wind, melanosis, specific ophthalmia, and +blindness (the great French veterinary Hazard going so far as to say that a +blind race could soon be formed), crib-biting, jibbing, and ill-temper, are +all plainly hereditary. Youatt sums up by saying "there is scarcely a +malady to which the horse is subject which is not hereditary;" and M. +Bernard adds that the doctrine "that there is scarcely a disease which does +not run in the stock, is gaining new advocates every day."[20] So it {11} +is in regard to cattle, with consumption, good and bad teeth, fine skin, +&c. &c. But enough, and more than enough, has been said on disease. Andrew +Knight, from his own experience, asserts that disease is hereditary with +plants; and this assertion is endorsed by Lindley.[21] + +Seeing how hereditary evil qualities are, it is fortunate that good health, +vigour, and longevity are equally inherited. It was formerly a well-known +practice, when annuities were purchased to be received during the lifetime +of a nominee, to search out a person belonging to a family of which many +members had lived to extreme old age. As to the inheritance of vigour and +endurance, the English race-horse offers an excellent instance. Eclipse +begot 334, and King Herod 497 winners. A "cock-tail" is a horse not purely +bred, but with only one-eighth or one-sixteenth impure blood in his veins, +yet very few instances have ever occurred of such horses having won a great +race. They are sometimes as fleet for short distances as thoroughbreds, but +as Mr. Robson, the great trainer, asserts, they are deficient in wind, and +cannot keep up the pace. Mr. Lawrence also remarks, "perhaps no instance +has ever occurred of a three-part-bred horse saving his '_distance_' in +running two miles with thoroughbred racers." It has been stated by Cecil, +that when unknown horses, whose parents were not celebrated, have +unexpectedly won great races, as in the case of Priam, they can always be +proved to be descended on both sides, through many generations, from +first-rate ancestors. On the Continent, Baron Cameronn challenges, in a +German veterinary periodical, the opponents of the English race-horse, to +name one good horse on the Continent which has not some English race-blood +in his veins.[22] + +With respect to the transmission of the many slight, but {12} infinitely +diversified characters, by which the domestic races of animals and plants +are distinguished, nothing need be said; for the very existence of +persistent races proclaims the power of inheritance. + +A few special cases, however, deserve some consideration. It might have +been anticipated, that deviations from the law of symmetry would not have +been inherited. But Anderson[23] states that a rabbit produced in a litter +a young animal having only one ear; and from this animal a breed was formed +which steadily produced one-eared rabbits. He also mentions a bitch, with a +single leg deficient, and she produced several puppies with the same +deficiency. From Hofacker's account[24] it appears that a one-horned stag +was seen in 1781 in a forest in Germany, in 1788 two, and afterwards, from +year to year, many were observed with only one horn on the right side of +the head. A cow lost a horn by suppuration,[25] and she produced three +calves which had on the same side of the head, instead of a horn, a small +bony lump attached merely to the skin; but we here approach the doubtful +subject of inherited mutilations. A man who is left-handed, and a shell in +which the spire turns in the wrong direction, are departures from the +normal though a symmetrical condition, and they are well known to be +inherited. + + _Polydactylism._--Supernumerary fingers and toes are eminently liable, + as various authors have insisted, to transmission, but they are noticed + here chiefly on account of their occasional regrowth after amputation. + Polydactylism graduates[26] by multifarious steps from a mere cutaneous + appendage, not including any bone, to a double hand. But an additional + digit, supported on a metacarpal bone, and furnished with all the + proper muscles, nerves, and vessels, is sometimes so perfect, that it + escapes detection, unless the fingers are actually counted. + Occasionally there are several supernumerary digits; but usually only + one, making the total number six. This one may represent either a thumb + or finger, being attached to the inner or outer margin of the hand. + Generally, through the law of correlation, both hands and feet are + similarly affected. I have tabulated the cases recorded in various + works or privately communicated {13} to me, of forty-six persons with + extra digits on one or both hands and feet; if in each case all four + extremities had been similarly affected, the table would have shown a + total of ninety-two hands and ninety-two feet each with six digits. As + it is, seventy-three hands and seventy-five feet were thus affected. + This proves, in contradiction to the result arrived at by Dr. + Struthers,[27] that the hands are not more frequently affected than the + feet. + + The presence of more than five digits is a great anomaly, for this + number is not normally exceeded by any mammal, bird, or existing + reptile.[28] Nevertheless, supernumerary digits are strongly inherited; + they have been transmitted through five generations; and in some cases, + after disappearing for one, two, or even three generations, have + reappeared through reversion. These facts are rendered, as Professor + Huxley has observed, more remarkable from its being known in most cases + that the affected person had not married one similarly affected. In + such cases the child of the fifth generation would have only 1-32nd + part of the blood of his first sedigitated ancestor. Other cases are + rendered remarkable by the affection gathering force, as Dr. Struthers + has shown, in each generation, though in each the affected person had + married one not affected; moreover such additional digits are often + amputated soon after birth, and can seldom have been strengthened by + use. Dr. Struthers gives the following instance: in the first + generation an additional digit appeared on one hand; in the second, on + both hands; in the third, three brothers had both hands, and one of the + brothers a foot affected; and in the fourth generation all four limbs + were affected. Yet we must not over-estimate the force of inheritance. + Dr. Struthers asserts that cases of non-inheritance and of the first + appearance of additional digits in unaffected families are much more + frequent than cases of inheritance. Many other deviations of structure, + of a nature almost as anomalous as supernumerary digits, such as + deficient phalanges, thickened joints, crooked fingers, &c., are in + like manner strongly inherited, and are equally subject to intermission + with reversion, though in such cases there is no reason to suppose that + both parents had been similarly affected.[29] + + {14} + + Additional digits have been observed in negroes as well as in other + races of man, and in several of the lower animals. Six toes have been + described on the hind feet of the newt (_Salamandra cristata_), and, as + it is said, of the frog. It deserves notice from what follows, that the + six-toed newt, though adult, had preserved some of its larval + characters; for part of the hyoidal apparatus, which is properly + absorbed during the act of metamorphosis, was retained. In the dog, six + toes on the hinder feet have been transmitted through three + generations; and I have heard of a race of six-toed cats. In several + breeds of the fowl the hinder toe is double, and is generally + transmitted truly, as is well shown when Dorkings are crossed with + common four-toed breeds.[30] With animals which have properly less than + five digits, the number is sometimes increased to five, especially in + the front legs, though rarely carried beyond that number; but this is + due to the development of a digit already existing in a more or less + rudimentary state. Thus the dog has properly four toes behind, but in + the larger breeds a fifth toe is commonly, though not perfectly, + developed. Horses, which properly have one toe alone fully developed + with rudiments of the others, have been described with each foot + bearing two or three small separate hoofs: analogous facts have been + noticed with sheep, goats, and pigs.[31] + + The most interesting point with respect to supernumerary digits is + their occasional regrowth after amputation. Mr. White[32] describes a + child, three years old, with a thumb double from the first joint. He + removed the lesser thumb, which was furnished with a nail; but to his + astonishment it grew again, and reproduced a nail. The child was then + taken to an eminent London surgeon, and the newly-grown thumb was + wholly removed by its socket-joint, but again it grew and reproduced a + nail. Dr. Struthers mentions a case of partial regrowth of an + additional thumb, amputated when the child was three months old; and + the late Dr. Falconer communicated to me an analogous case which had + fallen under his own observation. A gentleman, who first called my + attention to this subject, has given me the following facts which + occurred in his own family. He himself, two brothers, and a sister were + born with an extra digit to each extremity. His parents were not + affected, and there was no tradition in the family, or in the village + in which the family had long resided, of any member having been thus + affected. Whilst a child, both additional toes, which were attached by + bones, were rudely cut off; but the stump of one grew again, and a + second operation was performed in his thirty-third year. + + {15} + + He has had fourteen children, of whom three have inherited additional + digits; and one of them, when about six weeks old, was operated on by + an eminent surgeon. The additional finger, which was attached by bone + to the outer side of the hand, was removed at the joint; the wound + healed, but immediately the digit began growing; and in about three + months' time the stump was removed for the second time by the root. But + it has since grown again, and is now fully a third of an inch in + length, including a bone; so that it will for the third time have to be + operated on. + + Now the normal digits in adult man and other mammals, in birds, and, as + I believe, in true reptiles, have no power of regrowth. The nearest + approach to this power is exhibited by the occasional reappearance in + man of imperfect nails on the stumps of his fingers after + amputation.[33] But man in his embryonic condition has a considerable + power of reproduction, for Sir J. Simpson[34] has several times + observed arms which had been cut off in the womb by bands of false + membrane, and which had grown again to a certain extent. In one + instance, the extremity was "divided into three minute nodules, on two + of which small points of nails could be detected;" so that these + nodules clearly represented fingers in process of regrowth. When, + however, we descend to the lower vertebrate classes, which are + generally looked at as representing the higher classes in their + embryonic condition, we find ample powers of regrowth. Spallanzani[35] + cut off the legs and tail of a salamander six times, and Bonnet eight + times, successively, and they were reproduced. An additional digit + beyond the proper number was occasionally formed after Bonnet had cut + off or had divided longitudinally the hand or foot, and in one instance + three additional digits were thus formed.[36] These latter cases appear + at first sight quite distinct from the congenital production of + additional digits in the higher animals; but theoretically, as we shall + see in a future chapter, they probably present no real difference. The + larvae or tadpoles of the tailless Batrachians, but not the adults,[37] + are capable of reproducing lost members.[38] Lastly, as I have been + informed by Mr. J. J. Briggs and Mr. F. Buckland, when portions of the + pectoral and tail fins of various {16} fresh-water fish are cut off, + they are perfectly reproduced in about six weeks' time. + +From these several facts we may infer that supernumerary digits in man +retain to a certain extent an embryonic condition, and that they resemble +in this respect the normal digits and limbs in the lower vertebrate +classes. They also resemble the digits of some of the lower animals in the +number exceeding five; for no mammal, bird, existing reptile, or amphibian +(unless the tubercle on the hind feet of the toad and other tailless +Batrachians be viewed as a digit) has more than five; whilst fishes +sometimes have in their pectoral fins as many as twenty metacarpal and +phalangeal bones, which, together with the bony filaments, apparently +represent our digits with their nails. So, again, in certain extinct +reptiles, namely, the Ichthyopterygia, "the digits may be seven, eight, or +nine in number, a significant mark," says Professor Owen, "of piscine +affinity."[39] + +We encounter much difficulty in attempting to reduce these various facts to +any rule or law. The inconstant number of the additional digits--their +irregular attachment to either the inner or outer margin of the hand--the +gradation which can be traced from a mere loose rudiment of a single digit +to a completely double hand--the occasional appearance of additional digits +in the salamander after a limb has been amputated--these various facts +appear to indicate mere fluctuating monstrosity; and this perhaps is all +that can be safely said. Nevertheless, as supernumerary digits in the +higher animals, from their power of regrowth and from the number thus +acquired exceeding five, partake of the nature of the digits in the lower +vertebrate animals;--as they occur by no means rarely, and are transmitted +with remarkable strength, though perhaps not more strongly than some other +anomalies;--and as with animals which have fewer than five digits, when an +additional one appears it is generally due to the development of a visible +rudiment;--we are led in all cases to suspect, that, although no actual +rudiment can be detected, yet that a latent tendency to the formation of an +additional digit exists in all mammals, including man. On this view, as we +shall more plainly see in the {17} next chapter when discussing latent +tendencies, we should have to look at the whole case as one of reversion to +an enormously remote, lowly-organised, and multidigitate progenitor. + + * * * * * + +I may here allude to a class of facts closely allied to, but somewhat +different from, ordinary cases of inheritance. Sir H. Holland[40] states +that brothers and sisters of the same family are frequently affected, often +at about the same age, by the same peculiar disease, not known to have +previously occurred in the family. He specifies the occurrence of diabetes +in three brothers under ten years old; he also remarks that children of the +same family often exhibit in common infantile diseases the same peculiar +symptoms. My father mentioned to me the case of four brothers who died +between the ages of sixty and seventy, in the same highly peculiar comatose +state. An instance has been already given of supernumerary digits appearing +in four children out of six in a previously unaffected family. Dr. Devay +states[41] that two brothers married two sisters, their first-cousins, none +of the four nor any relation being an albino; but the seven children +produced from this double marriage were all perfect albinoes. Some of these +cases, as Mr. Sedgwick[42] has shown, are probably the result of reversion +to a remote ancestor, of whom no record had been preserved; and all these +cases are so far directly connected with inheritance that no doubt the +children inherited a similar constitution from their parents, and, from +being exposed to nearly similar conditions of life, it is not surprising +that they should be affected in the same manner and at the same period of +life. + + * * * * * + +Most of the facts hitherto given have served to illustrate the force of +inheritance, but we must now consider cases, grouped as well as the subject +allows into classes, showing how feeble, capricious, or deficient the power +of inheritance sometimes is. When a new peculiarity first appears, we can +never predict whether it will be inherited. If both parents from their +birth present {18} the same peculiarity, the probability is strong that it +will be transmitted to at least some of their offspring. We have seen that +variegation is transmitted much more feebly by seed from a branch which had +become variegated through bud-variation, than from plants which were +variegated as seedlings. With most plants the power of transmission +notoriously depends on some innate capacity in the individual: thus +Vilmorin[43] raised from a peculiarly coloured balsam some seedlings, which +all resembled their parent; but of these seedlings some failed to transmit +the new character, whilst others transmitted it to all their descendants +during several successive generations. So again with a variety of the rose, +two plants alone out of six were found by Vilmorin to be capable of +transmitting the desired character. + + The weeping or pendulous growth of trees is strongly inherited in some + cases, and, without any assignable reason, feebly in other cases. I + have selected this character as an instance of capricious inheritance, + because it is certainly not proper to the parent-species, and because, + both sexes being borne on the same tree, both tend to transmit the same + character. Even supposing that there may have been in some instances + crossing with adjoining trees of the same species, it is not probable + that all the seedlings would have been thus affected. At Moccas Court + there is a famous weeping oak; many of its branches "are 30 feet long, + and no thicker in any part of this length than a common rope:" this + tree transmits its weeping character, in a greater or less degree, to + all its seedlings; some of the young oaks being so flexible that they + have to be supported by props; others not showing the weeping tendency + till about twenty years old.[44] Mr. Rivers fertilized, as he informs + me, the flowers of a new Belgian weeping thorn (_Crataegus oxyacantha_) + with pollen from a crimson not-weeping variety, and three young trees, + "now six or seven years old, show a decided tendency to be pendulous, + but as yet are not so much so as the mother-plant." According to Mr. + MacNab,[45] seedlings from a magnificent weeping birch (_Betula alba_), + in the Botanic Garden at Edinburgh, grew for the first ten or fifteen + years upright, but then all became weepers like their parent. A peach + with pendulous branches, like those of the weeping willow, has been + found capable of propagation by seed.[46] Lastly, a weeping and almost + prostrate yew (_Taxus baccata_) was found in a hedge in Shropshire; it + was a male, but one branch bore female flowers, and produced berries; + these, {19} being sown, produced seventeen trees, all of which had + exactly the same peculiar habit with the parent-tree.[47] + + These facts, it might have been thought, would have been sufficient to + render it probable that a pendulous habit would in all cases be + strictly inherited. But let us look to the other side. Mr. MacNab[48] + sowed seeds of the weeping beech (_Fagus sylvanica_), but succeeded in + raising only common beeches. Mr. Rivers, at my request, raised a number + of seedlings from three distinct varieties of weeping elm; and at least + one of the parent-trees was so situated that it could not have been + crossed by any other elm; but none of the young trees, now about a foot + or two in height, show the least signs of weeping. Mr. Rivers formerly + sowed above twenty thousand seeds of the weeping ash (_Fraxinus + excelsior_), and not a single seedling was in the least degree + pendulous: in Germany, M. Borchmeyer raised a thousand seedlings, with + the same result. Nevertheless, Mr. Anderson, of the Chelsea Botanic + Garden, by sowing seed from a weeping ash, which was found before the + year 1780, in Cambridgeshire, raised several pendulous trees.[49] + Professor Henslow also informs me that some seedlings from a female + weeping ash in the Botanic Garden at Cambridge were at first a little + pendulous, but afterwards became quite upright: it is probable that + this latter tree, which transmits to a certain extent its pendulous + habit, was derived by a bud from the same original Cambridgeshire + stock; whilst other weeping ashes may have had a distinct origin. But + the crowning case, communicated to me by Mr. Rivers, which shows how + capricious is the inheritance of a pendulous habit, is that a variety + of another species of ash (_F. lentiscifolia_) which was formerly + pendulous, "now about twenty years old has long lost this habit, every + shoot being remarkably erect; but seedlings formerly raised from it + were perfectly prostrate, the stems not rising more than two inches + above the ground." Thus the weeping variety of the common ash, which + has been extensively propagated by buds during a long period, did not, + with Mr. Rivers, transmit its character to one seedling out of above + twenty thousand; whereas the weeping variety of a second species of + ash, which could not, whilst grown in the same garden, retain its own + weeping character, transmitted to its seedlings the pendulous habit in + excess! + + Many analogous facts could be given, showing how apparently capricious + is the principle of inheritance. All the seedlings from a variety of + the Barberry (_B. vulgaris_) with red leaves inherited the same + character; only about one-third of the seedlings of the copper Beech + (_Fagus sylvatica_) had purple leaves. Not one out of a hundred + seedlings of a variety of the _Cerasus padus_, with yellow fruit, bore + yellow fruit: one-twelfth of the seedlings of the variety of _Cornus + mascula_, with yellow fruit, came true:[50] and lastly, all the trees + raised by my father from a yellow-berried holly (_Ilex aquifolium_), + {20} found wild, produced yellow berries. Vilmorin[51] observed in a + bed of _Saponaria calabrica_ an extremely dwarf variety, and raised + from it a large number of seedlings; some of these partially resembled + their parent, and he selected their seed; but the grandchildren were + not in the least dwarfed: on the other hand, he observed a stunted and + bushy variety of _Tagetes signata_ growing in the midst of the common + varieties by which it was probably crossed; for most of the seedlings + raised from this plant were intermediate in character, only two + perfectly resembling their parent; but seed saved from these two plants + reproduced the new variety so truly, that hardly any selection has + since been necessary. + + Flowers transmit their colour truly, or most capriciously. Many annuals + come true: thus I purchased German seeds of thirty-four named + sub-varieties of one _race_ of ten-week stocks (_Matthiola annua_), and + raised a hundred and forty plants, all of which, with the exception of + a single plant, came true. In saying this, however, it must be + understood that I could distinguish only twenty kinds out of the + thirty-four named sub-varieties; nor did the colour of the flower + always correspond with the name affixed to the packet; but I say that + they came true, because in each of the thirty-six short rows every + plant was absolutely alike, with the one single exception. Again, I + procured packets of German seed of twenty-five named varieties of + common and quilled asters, and raised a hundred and twenty-four plants; + of these, all except ten were true in the above limited sense; and I + considered even a wrong shade of colour as false. + + It is a singular circumstance that white varieties generally transmit + their colour much more truly than any other variety. This fact probably + stands in close relation with one observed by Verlot,[52] namely, that + flowers which are normally white rarely vary into any other colour. I + have found that the white varieties of _Delphinium consolida_ and of + the Stock are the truest. It is, indeed, sufficient to look through a + nurseryman's seed-list, to see the large number of white varieties + which can be propagated by seed. The several coloured varieties of the + sweet-pea (_Lathyrus odoratus_) are very true; but I hear from Mr. + Masters, of Canterbury, who has particularly attended to this plant, + that the white variety is the truest. The hyacinth, when propagated by + seed, is extremely inconstant in colour, but "white hyacinths almost + always give by seed white-flowered plants;"[53] and Mr. Masters informs + me that the yellow varieties also reproduce their colour, but of + different shades. On the other hand, pink and blue varieties, the + latter being the natural colour, are not nearly so true: hence, as Mr. + Masters has remarked to me, "we see that a garden variety may acquire a + more permanent habit than a natural species;" but it should have been + added, that this occurs under cultivation, and therefore under changed + conditions. + + With many flowers, especially perennials, nothing can be more + fluctuating than the colour of the seedlings, as is notoriously the + case with verbenas, carnations, dahlias, cinerarias, and others.[54] I + sowed seed of twelve {21} named varieties of Snapdragon (_Antirrhinum + majus_), and utter confusion was the result. In most cases the + extremely fluctuating colour of seedling plants is probably in chief + part due to crosses between differently-coloured varieties during + previous generations. It is almost certain that this is the case with + the polyanthus and coloured primrose (_Primula veris_ and _vulgaris_), + from their reciprocally dimorphic structure;[55] and these are plants + which florists speak of as never come true by seed: but if care be + taken to prevent crossing, neither species is by any means very + inconstant in colour; thus I raised twenty-three plants from a purple + primrose, fertilised by Mr. J. Scott with its own pollen, and eighteen + came up purple of different shades, and only five reverted to the + ordinary yellow colour: again, I raised twenty plants from a bright-red + cowslip, similarly treated by Mr. Scott, and every one perfectly + resembled its parent in colour, as likewise did, with the exception of + a single plant, 73 grandchildren. Even with the most variable flowers, + it is probable that each delicate shade of colour might be permanently + fixed so as to be transmitted by seed, by cultivation in the same soil, + by long-continued selection, and especially by the prevention of + crosses. I infer this from certain annual larkspurs (_Delphinium + consolida_ and _ajacis_), of which common seedlings present a greater + diversity of colour than any other plant known to me; yet on procuring + seed of five named German varieties of _D. consolida_, only nine plants + out of ninety-four were false; and the seedlings of six varieties of + _D. ajacis_ were true in the same manner and degree as with the stocks + above described. A distinguished botanist maintains that the annual + species of Delphinium are always self-fertilised; therefore I may + mention that thirty-two flowers on a branch of _D. consolida_, enclosed + in a net, yielded twenty-seven capsules, with an average of 17.2 seed + in each; whilst five flowers, under the same net, which were + artificially fertilised, in the same manner as must be effected by bees + during their incessant visits, yielded five capsules with an average of + 35.2 fine seed; and this shows that the agency of insects is necessary + for the full fertility of this plant. Analogous facts could be given + with respect to the crossing of many other flowers, such as carnations, + &c., of which the varieties fluctuate much in colour. + + As with flowers, so with our domesticated animals, no character is more + variable than colour, and probably in no animal more so than with the + horse. Yet with a little care in breeding, it appears that races of any + colour might soon be formed. Hofacker gives the result of matching two + hundred and sixteen mares of four different colours with like-coloured + stallions, without regard to the colour of their ancestors; and of the + two hundred and sixteen colts born, eleven alone failed to inherit the + colour of their parents: Autenrieth and Ammon assert that, after two + generations, colts of a uniform colour are produced with certainty.[56] + +In a few rare cases peculiarities fail to be inherited, apparently from the +force of inheritance being too strong. I have been assured by breeders of +the canary-bird that to get a good {22} jonquil-coloured bird it does not +answer to pair two jonquils, as the colour then comes out too strong, or is +even brown. So again, if two crested canaries are paired, the young birds +rarely inherit this character:[57] for in crested birds a narrow space of +bare skin is left on the back of the head, where the feathers are up-turned +to form the crest, and, when both parents are thus characterised, the +bareness becomes excessive, and the crest itself fails to be developed. Mr. +Hewitt, speaking of Laced Sebright Bantams, says[58] that, "why this should +be so, I know not, but I am confident that those that are best laced +frequently produce offspring very far from perfect in their markings, +whilst those exhibited by myself, which have so often proved successful, +were bred from the union of heavily-laced birds with those that were +scarcely sufficiently laced." + +It is a singular fact that, although several deaf-mutes often occur in the +same family, and though their cousins and other relations are often in the +same condition, yet their parents are very rarely deaf-mutes. To give a +single instance: not one scholar out of 148, who were at the same time in +the London Institution, was the child of parents similarly afflicted. So +again, when a male or a female deaf-mute marries a sound person, their +children are most rarely affected: in Ireland out of 203 children thus +produced one alone was mute. Even when both parents have been deaf-mutes, +as in the case of forty-one marriages in the United States and of six in +Ireland, only two deaf and dumb children were produced. Mr. Sedgwick,[59] +in commenting on this remarkable and fortunate failure in the power of +transmission in the direct line, remarks that it may possibly be owing to +"excess having reversed the action of some natural law in development." But +it is safer in the present state of our knowledge to look at the whole case +as simply unintelligible. + + * * * * * + +With respect to the inheritance of structures mutilated by injuries or +altered by disease it is difficult to come to any {23} definite conclusion. +In some cases mutilations have been practised for a vast number of +generations without any inherited result. Godron has remarked[60] that +different races of man have from time immemorial knocked out their upper +incisors, cut off joints of their fingers, made holes of immense size +through the lobes of their ears or through their nostrils, made deep gashes +in various parts of their bodies, and there is no reason whatever to +suppose that these mutilations have ever been inherited. Adhesions due to +inflammation and pits from the small-pox (and formerly many consecutive +generations must have been thus pitted) are not inherited. With respect to +Jews, I have been assured by three medical men of the Jewish faith that +circumcision, which has been practised for so many ages, has produced no +inherited effect; Blumenbach, on the other hand, asserts[61] that in +Germany Jews are often born in a condition rendering circumcision +difficult, so that a name is here applied to them signifying "born +circumcised." The oak and other trees must have borne galls from primeval +times, yet they do not produce inherited excrescences; many other such +facts could be adduced. + +On the other hand, various cases have been recorded of cats, dogs, and +horses, which have had their tails, legs, &c., amputated or injured, +producing offspring with the same parts ill-formed; but as it is not at all +rare for similar malformations to appear spontaneously, all such cases may +be due to mere coincidence. Nevertheless, Dr. Prosper Lucas has given, on +good authorities, such a long list of inherited injuries, that it is +difficult not to believe in them. Thus, a cow that had lost a horn from an +accident with consequent suppuration, produced three calves which were +hornless on the same side of the head. With the horse, there seems hardly a +doubt that bony exostoses on the legs, caused by too much travelling on +hard roads, are inherited. Blumenbach records the case of a man who had his +little finger on the right hand almost cut off, and which in consequence +grew crooked, and his sons had the same finger on the same hand similarly +crooked. A soldier, fifteen years before his marriage, lost his left eye +from purulent ophthalmia, and his {24} two sons were microphthalmic on the +same side.[62] In all such cases, if truthfully reported, in which the +parent has had an organ injured on one side, and more than one child has +been born with the same organ affected on the same side, the chances +against mere coincidence are enormous. But perhaps the most remarkable and +trustworthy fact is that given by Dr. Brown-Sequard,[63] namely, that many +young guinea-pigs inherited an epileptic tendency from parents which had +been subjected to a particular operation, inducing in the course of a few +weeks a convulsive disease like epilepsy: and it should be especially noted +that this eminent physiologist bred a large number of guinea-pigs from +animals which had not been operated on, and not one of these manifested the +epileptic tendency. On the whole, we can hardly avoid admitting, that +injuries and mutilations, especially when followed by disease, or perhaps +exclusively when thus followed, are occasionally inherited. + +Although many congenital monstrosities are inherited, of which examples +have already been given, and to which may be added the lately recorded case +of the transmission during a century of hare-lip with a cleft-palate in the +writer's own family,[64] yet other malformations are rarely or never +inherited. Of these later cases, many are probably due to injuries in the +womb or egg, and would come under the head of non-inherited injuries or +mutilations. With plants, a long catalogue of inherited monstrosities of +the most serious and diversified nature could easily be given; and with +plants, there is no reason to suppose that monstrosities are caused by +direct injuries to the seed or embryo. + +_Causes of Non-inheritance._ + +A large number of cases of non-inheritance are intelligible on the +principle, that a strong tendency to inheritance does exist, but {25} that +it is overborne by hostile or unfavourable conditions of life. No one would +expect that our improved pigs, if forced during several generations to +travel about and root in the ground for their own subsistence, would +transmit, as truly as they now do, their tendency to fatten, and their +short muzzles and legs. Dray-horses assuredly would not long transmit their +great size and massive limbs, if compelled to live on a cold, damp +mountainous region; we have indeed evidence of such deterioration in the +horses which have run wild on the Falkland Islands. European dogs in India +often fail to transmit their true character. Our sheep in tropical +countries lose their wool in a few generations. There seems also to be a +close relation between certain peculiar pastures and the inheritance of an +enlarged tail in fat-tailed sheep, which form one of the most ancient +breeds in the world. With plants, we have seen that the American varieties +of maize lose their proper character in the course of two or three +generations, when cultivated in Europe. Our cabbages, which here come so +true by seed, cannot form heads in hot countries. Under changed +circumstances, periodical habits of life soon fail to be transmitted, as +the period of maturity in summer and winter wheat, barley, and vetches. So +it is with animals; for instance, a person whose statement I can trust, +procured eggs of Aylesbury ducks from that town, where they are kept in +houses and are reared as early as possible for the London market; the ducks +bred from these eggs in a distant part of England, hatched their first +brood on January 24th, whilst common ducks, kept in the same yard and +treated in the same manner, did not hatch till the end of March; and this +shows that the period of hatching was inherited. But the grandchildren of +these Aylesbury ducks completely lost their early habit of incubation, and +hatched their eggs at the same time with the common ducks of the same +place. + +Many cases of non-inheritance apparently result from the conditions of life +continually inducing fresh variability. We have seen that when the seeds of +pears, plums, apples, &c., are sown, the seedlings generally inherit some +degree of family likeness from the parent-variety. Mingled with these +seedlings, a few, and sometimes many, worthless, wild-looking plants +commonly appear; and their appearance may be attributed to the principle of +reversion. But scarcely a single seedling will be found {26} perfectly to +resemble the parent-form; and this, I believe, may be accounted for by +constantly recurring variability induced by the conditions of life. I +believe in this, because it has been observed that certain fruit-trees +truly propagate their kind whilst growing on their own roots, but when +grafted on other stocks, and by this process their natural state is +manifestly affected, they produce seedlings which vary greatly, departing +from the parental type in many characters.[65] Metzger, as stated in the +ninth chapter, found that certain kinds of wheat brought from Spain and +cultivated in Germany, failed during many years to reproduce themselves +truly; but that at last, when accustomed to their new conditions, they +ceased to be variable,--that is, they became amenable to the power of +inheritance. Nearly all the plants which cannot be propagated with any +approach to certainty by seed, are kinds which have long been propagated by +buds, cuttings, offsets, tubers, &c., and have in consequence been +frequently exposed during their individual lives to widely diversified +conditions of life. Plants thus propagated become so variable, that they +are subject, as we have seen in the last chapter, even to bud-variation. +Our domesticated animals, on the other hand, are not exposed during their +individual lives to such extremely diversified conditions, and are not +liable to such extreme variability; therefore they do not lose the power of +transmitting most of their characteristic features. In the foregoing +remarks on non-inheritance, crossed breeds are of course excluded, as their +diversity mainly depends on the unequal development of characters derived +from either parent, modified by the principles of reversion and prepotency. + +_Conclusion._ + +It has, I think, been shown in the early part of this chapter how strongly +new characters of the most diversified nature, whether normal or abnormal, +injurious or beneficial, whether affecting organs of the highest or most +trifling importance, are inherited. Contrary to the common opinion, it is +often sufficient for the inheritance of some peculiar character, that one +parent alone should possess it, as in most cases in which the rarer {27} +anomalies have been transmitted. But the power of transmission is extremely +variable: in a number of individuals descended from the same parents, and +treated in the same manner, some display this power in a perfect manner, +and in some it is quite deficient; and for this difference no reason can be +assigned. In some cases the effects of injuries or mutilations apparently +are inherited; and we shall see in a future chapter that the effects of the +long-continued use and disuse of parts are certainly inherited. Even those +characters which are considered the most fluctuating, such as colour, are +with rare exceptions transmitted much more forcibly than is generally +supposed. The wonder, indeed, in all cases is not that any character should +be transmitted, but that the power of inheritance should ever fail. The +checks to inheritance, as far as we know them, are, firstly, circumstances +hostile to the particular character in question; secondly, conditions of +life incessantly inducing fresh variability; and lastly, the crossing of +distinct varieties during some previous generation, together with reversion +or atavism--that is, the tendency in the child to resemble its +grand-parents or more remote ancestors instead of its immediate parents. +This latter subject will be fully discussed in the following chapter. + + * * * * * + + +{28} + +CHAPTER XIII. + +INHERITANCE _continued_--REVERSION OR ATAVISM. + + DIFFERENT FORMS OF REVERSION--IN PURE OR UNCROSSED BREEDS, AS IN + PIGEONS, FOWLS, HORNLESS CATTLE AND SHEEP, IN CULTIVATED + PLANTS--REVERSION IN FERAL ANIMALS AND PLANTS--REVERSION IN CROSSED + VARIETIES AND SPECIES--REVERSION THROUGH BUD-PROPAGATION, AND BY + SEGMENTS IN THE SAME FLOWER OR FRUIT--IN DIFFERENT PARTS OF THE BODY IN + THE SAME ANIMAL--THE ACT OF CROSSING A DIRECT CAUSE OF REVERSION, + VARIOUS CASES OF, WITH INSTINCTS--OTHER PROXIMATE CAUSES OF + REVERSION--LATENT CHARACTERS--SECONDARY SEXUAL CHARACTERS--UNEQUAL + DEVELOPMENT OF THE TWO SIDES OF THE BODY--APPEARANCE WITH ADVANCING AGE + OF CHARACTERS DERIVED FROM A CROSS--THE GERM WITH ALL ITS LATENT + CHARACTERS A WONDERFUL OBJECT--MONSTROSITIES--PELORIC FLOWERS DUE IN + SOME CASES TO REVERSION. + +The great principle of inheritance to be discussed in this chapter has been +recognised by agriculturists and authors of various nations, as shown by +the scientific term _Atavism_, derived from atavus, an ancestor; by the +English terms of _Reversion_, or _Throwing back_; by the French +_Pas-en-arriere_; and by the German _Rueck-schlag_, or _Rueck-schritt_. +When the child resembles either grandparent more closely than its immediate +parents, our attention is not much arrested, though in truth the fact is +highly remarkable; but when the child resembles some remote ancestor, or +some distant member in a collateral line,--and we must attribute the latter +case to the descent of all the members from a common progenitor,--we feel a +just degree of astonishment. When one parent alone displays some +newly-acquired and generally inheritable character, and the offspring do +not inherit it, the cause may lie in the other parent having the power of +prepotent transmission. But when both parents are similarly characterised, +and the child does not, whatever the cause may be, inherit the character in +question, but resembles its grandparents, we have one of the simplest cases +of reversion. We continually see another and even more simple case of +atavism, though not generally included under this head, namely, when {29} +the son more closely resembles his maternal than his paternal grandsire in +some male attribute, as in any peculiarity in the beard of man, the horns +of the bull, the hackles or comb of the cock, or, as in certain diseases +necessarily confined to the male sex; for the mother cannot possess or +exhibit such male attributes, yet the child has inherited them, through her +blood, from his maternal grandsire. + +The cases of reversion may be divided into two main classes, which, +however, in some instances, blend into each other; namely, first, those +occurring in a variety or race which has not been crossed, but has lost by +variation some character that it formerly possessed, and which afterwards +reappears. The second class includes all cases in which a distinguishable +individual, sub-variety, race, or species, has at some former period been +crossed with a distinct form, and a character derived from this cross, +after having disappeared during one or several generations, suddenly +reappears. A third class, differing only in the manner of reproduction, +might be formed to include all cases of reversion effected by means of +buds, and therefore independent of true or seminal generation. Perhaps even +a fourth class might be instituted, to include reversions by segments in +the same individual flower or fruit, and in different parts of the body in +the same individual animal as it grows old. But the two first main classes +will be sufficient for our purpose. + + * * * * * + +_Reversion to lost Characters by pure or uncrossed forms._--Striking +instances of this first class of cases were given in the sixth chapter, +namely, of the occasional reappearance, in variously-coloured pure breeds +of the pigeon, of blue birds with all the marks which characterise the wild +_Columba livia_. Similar cases were given in the case of the fowl. With the +common ass, as we now know that the legs of the wild progenitor are +striped, we may feel assured that the occasional appearance of such stripes +in the domestic animal is a case of simple reversion. But I shall be +compelled to refer again to these cases, and therefore will here pass them +over. + +The aboriginal species from which our domesticated cattle and sheep are +descended, no doubt possessed horns; but several hornless breeds are now +well established. Yet in these--for instance, {30} in Southdown sheep--"it +is not unusual to find among the male lambs some with small horns." The +horns, which thus occasionally reappear in other polled breeds, either +"grow to the full size, or are curiously attached to the skin alone and +hang loosely down, or drop off."[66] The Galloways and Suffolk cattle have +been hornless for the last 100 or 150 years, but a horned calf, with the +horn often loosely attached, is occasionally born.[67] + +There is reason to believe that sheep in their early domesticated condition +were "brown or dingy black;" but even in the time of David certain flocks +were spoken of as white as snow. During the classical period the sheep of +Spain are described by several ancient authors as being black, red, or +tawny.[68] At the present day, notwithstanding the great care which is +taken to prevent it, particoloured lambs and some entirely black are +occasionally dropped by our most highly improved and valued breeds, such as +the Southdowns. Since the time of the famous Bakewell, during the last +century, the Leicester sheep have been bred with the most scrupulous care; +yet occasionally grey-faced, or black-spotted, or wholly black lambs +appear.[69] This occurs still more frequently with the less improved +breeds, such as the Norfolks.[70] As bearing on this tendency in sheep to +revert to dark colours, I may state (though in doing so I trench on the +reversion of crossed breeds, and likewise on the subject of prepotency) +that the Rev. W. D. Fox was informed that seven white Southdown ewes were +put to a so-called Spanish ram, which had two small black spots on his +sides, and they produced thirteen lambs, all perfectly black. Mr. Fox +believes that this ram belonged to a breed which he has himself kept, and +which is always spotted with black and white; and he finds that Leicester +sheep crossed by rams of this breed always produce black lambs: he has gone +on recrossing these crossed sheep with pure white Leicesters during three +successive {31} generations, but always with the same result. Mr. Fox was +also told by the friend from whom the spotted breed was procured, that he +likewise had gone on for six or seven generations crossing with white +sheep, but still black lambs were invariably produced. + +Similar facts could be given with respect to tailless breeds of various +animals. For instance, Mr. Hewitt[71] states that chickens bred from some +Rumpless fowls, which were reckoned so good that they won a prize at an +exhibition, "in a considerable number of instances were furnished with +fully developed tail-feathers." On inquiry, the original breeder of these +fowls stated that, from the time when he had first kept them, they had +often produced fowls furnished with tails; but that these latter would +again reproduce rumpless chickens. + +Analogous cases of reversion occur in the vegetable kingdom; thus "from +seeds gathered from the finest cultivated varieties of Heartsease (_Viola +tricolor_), plants perfectly wild both in their foliage and their flowers +are frequently produced;"[72] but the reversion in this instance is not to +a very ancient period, for the best existing varieties of the heartsease +are of comparatively modern origin. With most of our cultivated vegetables +there is some tendency to reversion to what is known to be, or may be +presumed to be, their aboriginal state; and this would be more evident if +gardeners did not generally look over their beds of seedlings, and pull up +the false plants or "rogues" as they are called. It has already been +remarked, that some few seedling apples and pears generally resemble, but +apparently are not identical with, the wild trees from which they are +descended. In our turnip[73] and carrot-beds a few plants often +"break"--that is, flower too soon; and their roots are generally found to +be hard and stringy, as in the parent-species. By the aid of a little +selection, carried on during a few generations, most of our cultivated +plants could probably be brought back, without any great change in their +conditions of life, to a wild or nearly wild condition: Mr. Buckman has +effected this with the parsnip;[74] {32} and Mr. Hewett C. Watson, as he +informs me, selected, during three generations, "the most diverging plants +of Scotch kail, perhaps one of the least modified varieties of the cabbage; +and in the third generation some of the plants came very close to the forms +now established in England about old castle-walls, and called indigenous." + + * * * * * + +_Reversion in Animals and Plants which have run wild._--In the cases +hitherto considered, the reverting animals and plants have not been exposed +to any great or abrupt change in their conditions of life which could have +induced this tendency; but it is very different with animals and plants +which have become feral or run wild. It has been repeatedly asserted in the +most positive manner by various authors, that feral animals and plants +invariably return to their primitive specific type. It is curious on what +little evidence this belief rests. Many of our domesticated animals could +not subsist in a wild state; thus, the more highly improved breeds of the +pigeon will not "field" or search for their own food. Sheep have never +become feral, and would be destroyed by almost every beast of prey. In +several cases we do not know the aboriginal parent-species, and cannot +possibly tell whether or not there has been any close degree of reversion. +It is not known in any instance what variety was first turned out; several +varieties have probably in some cases run wild, and their crossing alone +would tend to obliterate their proper character. Our domesticated animals +and plants, when they run wild, must always be exposed to new conditions of +life, for, as Mr. Wallace[75] has well remarked, they have to obtain their +own food, and are exposed to competition with the native productions. Under +these circumstances, if our domesticated animals did not undergo change of +some kind, the result would be quite opposed to the conclusions arrived at +in this work. Nevertheless, I do not doubt that the simple fact of animals +and plants becoming feral, does cause some tendency to reversion to the +primitive state; though this tendency has been much exaggerated by some +authors. + +{33} + + I will briefly run through the recorded cases. With neither horses nor + cattle is the primitive stock known; and it has been shown in former + chapters that they have assumed different colours in different + countries. Thus the horses which have run wild in South America are + generally brownish-bay, and in the East dun-coloured; their heads have + become larger and coarser, and this may be due to reversion. No careful + description has been given of the feral goat. Dogs which have run wild + in various countries have hardly anywhere assumed a uniform character; + but they are probably descended from several domestic races, and + aboriginally from several distinct species. Feral cats, both in Europe + and La Plata, are regularly striped; in some cases they have grown to + an unusually large size, but do not differ from the domestic animal in + any other character. When variously-coloured tame rabbits are turned + out in Europe, they generally reacquire the colouring of the wild + animal; there can be no doubt that this does really occur, but we + should remember that oddly-coloured and conspicuous animals would + suffer much from beasts of prey and from being easily shot; this at + least was the opinion of a gentleman who tried to stock his woods with + a nearly white variety; and when thus destroyed, they would in truth be + supplanted by, instead of being transformed into, the common rabbit. We + have seen that the feral rabbits of Jamaica, and especially of Porto + Santo, have assumed new colours and other new characters. The best + known case of reversion, and that on which the widely-spread belief in + its universality apparently rests, is that of pigs. These animals have + run wild in the West Indies, South America, and the Falkland Islands, + and have everywhere acquired the dark colour, the thick bristles, and + great tusks of the wild boar; and the young have reacquired + longitudinal stripes. But even in the case of the pig, Roulin describes + the half-wild animals in different parts of South America as differing + in several respects. In Louisiana the pig[76] has run wild, and is said + to differ a little in form, and much in colour, from the domestic + animal, yet does not closely resemble the wild boar of Europe. With + pigeons and fowls,[77] it is not known what variety was first turned + out, nor what character the feral birds have assumed. The guinea-fowl + in the West Indies, when feral, seems to vary more than in the + domesticated state. + + With respect to plants run wild, Dr. Hooker[78] has strongly insisted + on what slight evidence the common belief in their power of reversion + rests. Godron[79] describes wild turnips, carrots, and celery; but + these plants in their cultivated state hardly differ from their wild + prototypes, except in the {34} succulency and enlargement of certain + parts,--characters which would be surely lost by plants growing in a + poor soil and struggling with other plants. No cultivated plant has run + wild on so enormous a scale as the cardoon (_Cynara cardunculus_) in La + Plata. Every botanist who has seen it growing there, in vast beds, as + high as a horse's back, has been struck with its peculiar appearance; + but whether it differs in any important point from the cultivated + Spanish form, which is said not to be prickly like its American + descendant, or whether it differs from he wild Mediterranean species, + which is said not to be social, I do not know. + + * * * * * + +_Reversion to Characters derived from a Cross, in the case of +Sub-varieties, Races, and Species._--When an individual having some +recognizable peculiarity unites with another of the same sub-variety, not +having the peculiarity in question, it often reappears in the descendants +after an interval of several generations. Every one must have noticed, or +heard from old people of children closely resembling in appearance or +mental disposition, or in so small and complex a character as expression, +one of their grandparents, or some more distant collateral relation. Very +many anomalies of structure and diseases,[80] of which instances have been +given in the last chapter, have come into a family from one parent, and +have reappeared in the progeny after passing over two or three generations. +The following case has been communicated to me on good authority, and may, +I believe, be fully trusted: a pointer-bitch produced seven puppies; four +were marked with blue and white, which is so unusual a colour with pointers +that she was thought to have played false with one of the greyhounds, and +the whole litter was condemned; but the gamekeeper was permitted to save +one as a curiosity. Two years afterwards a friend of the owner saw the +young dog, and declared that he was the image of his old pointer-bitch +Sappho, the only blue and white pointer of pure descent which he had ever +seen. This led to close inquiry, and it was proved that he was the +great-great-grandson of Sappho; so that, according to the common +expression, he had only 1-16th of her blood in his veins. Here it can +hardly be doubted that a character derived from a cross with an individual +of the same variety reappeared after passing over three generations. + +{35} + +When two distinct races are crossed, it is notorious that the tendency in +the offspring to revert to one or both parent-forms is strong, and endures +for many generations. I have myself seen the clearest evidence of this in +crossed pigeons and with various plants. Mr. Sidney[81] states that, in a +litter of Essex pigs, two young ones appeared which were the image of the +Berkshire boar that had been used twenty-eight years before in giving size +and constitution to the breed. I observed in the farmyard at Betley Hall +some fowls showing a strong likeness to the Malay breed, and was told by +Mr. Tollet that he had forty years before crossed his birds with Malays; +and that, though he had at first attempted to get rid of this strain, he +had subsequently given up the attempt in despair, as the Malay character +would reappear. + +This strong tendency in crossed breeds to revert has given rise to endless +discussions in how many generations after a single cross, either with a +distinct breed or merely with an inferior animal, the breed may be +considered as pure, and free from all danger of reversion. No one supposes +that less than three generations suffices, and most breeders think that +six, seven, or eight are necessary, and some go to still greater +lengths.[82] But neither in the case of a breed which has been contaminated +by a single cross, nor when, in the attempt to form an intermediate breed, +half-bred animals have been matched together during many generations, can +any rule be laid down how soon the tendency to reversion will be +obliterated. It depends on the difference in the strength or prepotency of +transmission in the two parent-forms, on their actual amount of difference, +and on the nature of the conditions of life to which the crossed offspring +are exposed. But we must be careful not to confound these cases of +reversion to characters gained from a cross, with those given under the +first class, in which characters originally common to _both_ parents, but +lost at some former period, reappear; for such characters may recur after +an almost indefinite number of generations. + +{36} + +The law of reversion is equally powerful with hybrids, when they are +sufficiently fertile to breed together, or when they are repeatedly crossed +with either pure parent-form, as with mongrels. It is not necessary to give +instances, for in the case of plants almost every one who has worked on +this subject from the time of Koelreuter to the present day has insisted on +this tendency. Gaertner has recorded some good instances; but no one has +given more striking cases than Naudin.[83] The tendency differs in degree +or strength in different groups, and partly depends, as we shall presently +see, on the fact of the parent-plants having been long cultivated. Although +the tendency to reversion is extremely general with nearly all mongrels and +hybrids, it cannot be considered as invariably characteristic of them; +there is, also, reason to believe that it may be mastered by long-continued +selection; but these subjects will more properly be discussed in a future +chapter on Crossing. From what we see of the power and scope of reversion, +both in pure races and when varieties or species are crossed, we may infer +that characters of almost every kind are capable of reappearance after +having been lost for a great length of time. But it does not follow from +this that in each particular case certain characters will reappear: for +instance, this will not occur when a race is crossed with another endowed +with prepotency of transmission. In some few cases the power of reversion +wholly fails, without our being able to assign any cause for the failure: +thus it has been stated that in a French family in which 85 out of above +600 members, during six generations, had been subject to night-blindness, +"there has not been a single example of this affection in the children of +parents who were themselves free from it."[84] + + * * * * * + +_Reversion through Bud-propagation--Partial Reversion, by segments in the +same flower or fruit, or in different parts of the {37} body in the same +individual animal._--In the eleventh chapter, many cases of reversion by +buds, independently of seminal generation, were given--as when a leaf-bud +on a variegated, curled, or laciniated variety suddenly reassumes its +proper character; or as when a Provence-rose appears on a moss-rose, or a +peach on a nectarine-tree. In some of these cases only half the flower or +fruit, or a smaller segment, or mere stripes, reassumed their former +character; and here we have with buds reversion by segments. Vilmorin[85] +has also recorded several cases with plants derived from seed, of flowers +reverting by stripes or blotches to their primitive colours: he states that +in all such cases a white or pale-coloured variety must first be formed, +and, when this is propagated for a length of time by seed, striped +seedlings occasionally make their appearance; and these can afterwards by +care be multiplied by seed. + +The stripes and segments just referred to are not due, as far as is known, +to reversion to characters derived from a cross, but to characters lost by +variation. These cases, however, as Naudin[86] insists in his discussion on +disjunction of character, are closely analogous with those given in the +eleventh chapter, in which crossed plants are known to have produced +half-and-half or striped flowers and fruit, or distinct kinds of flowers on +the same root resembling the two parent-forms. Many piebald animals +probably come under this same head. Such cases, as we shall see in the +chapter on Crossing, apparently result from certain characters not readily +blending together, and, as a consequence of this incapacity for fusion, the +offspring either perfectly resemble one of their two parents, or resemble +one parent in one part and the other parent in another part; or whilst +young are intermediate in character, but with advancing age revert wholly +or by segments to either parent-form, or to both. Thus young trees of the +_Cytisus adami_ are intermediate in foliage and flowers between the two +parent-forms; but when older the buds continually revert either partially +or wholly to both forms. The cases given in the eleventh chapter on the +changes which occurred during growth {38} in crossed plants of Tropaeolum, +Cereus, Datura, and Lathyrus are all analogous. As however these plants are +hybrids of the first generation, and as their buds after a time come to +resemble their parents and not their grandparents, these cases do not at +first appear to come under the law of reversion in the ordinary sense of +the word; nevertheless, as the change is effected through a succession of +bud-generations on the same plant, they may be thus included. + +Analogous facts have been observed in the animal kingdom, and are more +remarkable, as they occur strictly in the same individual, and not as with +plants through a succession of bud-generations. With animals the act of +reversion, if it can be so designated, does not pass over a true +generation, but merely over the early stages of growth in the same +individual. For instance, I crossed several white hens with a black cock, +and many of the chickens were during the first year perfectly white, but +acquired during the second year black feathers; on the other hand, some of +the chickens which were at first black became during the second year +piebald with white. A great breeder[87] says, that a Pencilled Brahma hen +which has any of the blood of the Light Brahma in her, will "occasionally +produce a pullet well pencilled during the first year, but she will most +likely moult brown on the shoulders and become quite unlike her original +colours in the second year." The same thing occurs with Light Brahmas if of +impure blood. I have observed exactly similar cases with the crossed +offspring from differently coloured pigeons. But here is a more remarkable +fact: I crossed a turbit, which has a frill formed by the feathers being +reversed on its breast, with a trumpeter; and one of the young pigeons thus +raised showed at first not a trace of the frill, but, after moulting +thrice, a small yet unmistakably distinct frill appeared on its breast. +According to Girou,[88] calves produced from a red cow by a black bull, or +from a black cow by a red bull, are not rarely born red, and subsequently +become black. + +In the foregoing cases, the characters which appear with advancing age are +the result of a cross in the previous or some {39} former generation; but +in the following cases, the characters which thus reappear formerly +appertained to the species, and were lost at a more or less remote epoch. +Thus, according to Azara,[89] the calves of a hornless race of cattle which +originated in Corrientes, though at first quite hornless, as they become +adult sometimes acquire small, crooked, and loose horns; and these in +succeeding years occasionally become attached to the skull. White and black +bantams, both of which generally breed true, sometimes assume as they grow +old a saffron or red plumage. For instance, a first-rate black bantam has +been described, which during three seasons was perfectly black, but then +annually became more and more red; and it deserves notice that this +tendency to change, whenever it occurs in a bantam, "is almost certain to +prove hereditary."[90] The cuckoo or blue-mottled Dorking cock, when old, +is liable to acquire yellow or orange hackles in place of his proper +bluish-grey hackles.[91] Now, as _Gallus bankiva_ is coloured red and +orange, and as Dorking fowls and both kinds of bantams are descended from +this species, we can hardly doubt that the change which occasionally occurs +in the plumage of these birds as their age advances, results from a +tendency in the individual to revert to the primitive type. + + * * * * * + +_Crossing as a direct cause of Reversion._--It has long been notorious that +hybrids and mongrels often revert to both or to one of their parent-forms, +after an interval of from two to seven or eight, or according to some +authorities even a greater number of generations. But that the act of +crossing in itself gives an impulse towards reversion, as shown by the +reappearance of long-lost characters, has never, I believe, been hitherto +proved. The proof lies in certain peculiarities, which do not characterise +the immediate parents, and therefore cannot have been derived from them, +frequently appearing in the offspring of two breeds when crossed, which +peculiarities never appear, or appear with extreme rarity, in these same +breeds, as long as they are {40} precluded from crossing. As this +conclusion seems to me highly curious and novel, I will give the evidence +in detail. + + My attention was first called to this subject, and I was led to make + numerous experiments, by MM. Boitard and Corbie having stated that, + when they crossed certain breeds, pigeons coloured like the wild _C. + livia_, or the common dovecot, namely, slaty-blue, with double black + wing-bars, sometimes chequered with black, white loins, the tail barred + with black, with the outer feathers edged with white, were almost + invariably produced. The breeds which I crossed, and the remarkable + results attained, have been fully described in the sixth chapter. I + selected pigeons, belonging to true and ancient breeds, which had not a + trace of blue or any of the above specified marks; but when crossed, + and their mongrels recrossed, young birds were continually produced, + more or less plainly coloured slaty-blue, with some or all of the + proper characteristic marks. I may recall to the reader's memory one + case, namely, that of a pigeon, hardly distinguishable from the wild + Shetland species, the grandchild of a red-spot, white fantail, and two + black barbs, from any of which, when purely-bred, the production of a + pigeon coloured like the wild _C. livia_ would have been almost a + prodigy. + + I was thus led to make the experiments, recorded in the seventh + chapter, on fowls. I selected long-established, pure breeds, in which + there was not a trace of red, yet in several of the mongrels feathers + of this colour appeared; and one magnificent bird, the offspring of a + black Spanish cock and white Silk hen, was coloured almost exactly like + the wild _Gallus bankiva_. All who know anything of the breeding of + poultry will admit that tens of thousands of pure Spanish and of pure + white Silk fowls might have been reared without the appearance of a red + feather. The fact, given on the authority of Mr. Tegetmeier, of the + frequent appearance, in mongrel fowls, of pencilled or + transversely-barred feathers, like those common to many gallinaceous + birds, is likewise apparently a case of reversion to a character + formerly possessed by some ancient progenitor of the family. I owe to + the kindness of this same excellent observer the inspection of some + neck-hackles and tail-feathers from a hybrid between the common fowl + and a very distinct species, the _Gallus varius_; and these feathers + are transversely striped in a conspicuous manner with dark metallic + blue and grey, a character which could not have been derived from + either immediate parent. + + I have been informed by Mr. B. P. Brent, that he crossed a white + Aylesbury drake and a black so-called Labrador duck, both of which are + true breeds, and he obtained a young drake closely like the mallard + (_A. boschas_). Of the musk-duck (_A. moschata_, Linn.) there are two + sub-breeds, namely, white and slate-coloured; and these I am informed + breed true, or nearly true. But the Rev. W. D. Fox tells me that, by + putting a white drake to a slate-coloured duck, black birds, pied with + white, like the wild musk-duck, were always produced. + + We have seen in the fourth chapter, that the so-called Himalayan + rabbit, with its snow-white body, black ears, nose, tail, and feet, + breeds {41} perfectly true. This race is known to have been formed by + the union of two varieties of silver-grey rabbits. Now, when a + Himalayan doe was crossed by a sandy-coloured buck, a silver-grey + rabbit was produced; and this is evidently a case of reversion to one + of the parent varieties. The young of the Himalayan rabbit are born + snow-white, and the dark marks do not appear until some time + subsequently; but occasionally young Himalayan rabbits are born of a + light silver-grey, which colour soon disappears; so that here we have a + trace of reversion, during an early period of life, to the + parent-varieties, independently of any recent cross. + + In the third chapter is was shown that at an ancient period some breeds + of cattle in the wilder parts of Britain were white with dark ears, and + that the cattle now kept half wild in certain parks, and those which + have run quite wild in two distant parts of the world, are likewise + thus coloured. Now, an experienced breeder, Mr. J. Beasley, of + Northamptonshire,[92] crossed some carefully selected West Highland + cows with purely-bred shorthorn bulls. The bulls were red, red and + white, or dark roan; and the Highland cows were all of a red colour, + inclining to a light or yellow shade. But a considerable number of the + offspring--and Mr. Beasley calls attention to this as a remarkable + fact--were white, or white with red ears. Bearing in mind that none of + the parents were white, and that they were purely-bred animals, it is + highly probable that here the offspring reverted, in consequence of the + cross, to the colour either of the aboriginal parent-species or of some + ancient and half-wild parent-breed. The following case, perhaps, comes + under the same head: cows in their natural state have their udders but + little developed, and do not yield nearly so much milk as our + domesticated animals. Now there is some reason to believe[93] that + cross-bred animals between two kinds, both of which are good milkers, + such as Alderneys and Shorthorns, often turn out worthless in this + respect. + + In the chapter on the Horse reasons were assigned for believing that + the primitive stock was striped and dun-coloured; and details were + given, showing that in all parts of the world stripes of a dark colour + frequently appear along the spine, across the legs, and on the + shoulders, where they are occasionally double or treble, and even + sometimes on the face and body of horses of all breeds and of all + colours. But the stripes appear most frequently on the various kinds of + duns. They may sometimes plainly be seen on foals, and subsequently + disappear. The dun-colour and the stripes are strongly transmitted when + a horse thus characterised is crossed with any other; but I was not + able to prove that striped duns are generally produced from the + crossing of two distinct breeds, neither of which are duns, though this + does sometimes occur. + + The legs of the ass are often striped, and this may be considered as a + reversion to the wild parent-form, the _Asinus taeniopus_ of + Abyssinia,[94] which is thus striped. In the domestic animal the + stripes on the shoulder are occasionally double, or forked at the + extremity, as in certain zebrine {42} species. There is reason to + believe that the foal is frequently more plainly striped on the legs + than the adult animal. As with the horse, I have not acquired any + distinct evidence that the crossing of differently-coloured varieties + of the ass brings out the stripes. + + But now let us turn to the result of crossing the horse and ass. + Although mules are not nearly so numerous in England as asses, I have + seen a much greater number with striped legs, and with the stripes far + more conspicuous than in either parent-form. Such mules are generally + light-coloured, and might be called fallow-duns. The shoulder-stripe in + one instance was deeply forked at the extremity, and in another + instance was double, though united in the middle. Mr. Martin gives a + figure of a Spanish mule with strong zebra-like marks on its legs,[95] + and remarks, that mules are particularly liable to be thus striped on + their legs. In South America, according to Roulin,[96] such stripes are + more frequent and conspicuous in the mule than in the ass. In the + United States, Mr. Gosse,[97] speaking of these animals, says, "that in + a great number, perhaps in nine out of every ten, the legs are banded + with transverse dark stripes." + + Many years ago I saw in the Zoological Gardens a curious triple hybrid, + from a bay mare, by a hybrid from a male ass and female zebra. This + animal when old had hardly any stripes; but I was assured by the + superintendent, that when young it had shoulder-stripes, and faint + stripes on its flanks and legs. I mention this case more especially as + an instance of the stripes being much plainer during youth than in old + age. + + As the zebra has such conspicuously striped legs, it might have been + expected that the hybrids from this animal and the common ass would + have had their legs in some degree striped; but it appears from the + figures given in Dr. Gray's 'Knowsley Gleanings,' and still more + plainly from that given by Geoffroy and F. Cuvier,[98] that the legs + are much more conspicuously striped than the rest of the body; and this + fact is intelligible only on the belief that the ass aids in giving, + through the power of reversion, this character to its hybrid offspring. + + The quagga is banded over the whole front part of its body like a + zebra, but has no stripes on its legs, or mere traces of them. But in + the famous hybrid bred by Lord Morton,[99] from a chesnut, nearly + purely-bred, Arabian mare, by a male quagga, the stripes were "more + strongly defined and darker than those on the legs of the quagga." The + mare was subsequently put to a black Arabian horse, and bore two colts, + both of which, as formerly stated, were plainly striped on the legs, + and one of them likewise had stripes on the neck and body. + + The _Asinus Indicus_[100] is characterised by a spinal stripe, without + shoulder {43} or leg stripes; but traces of these latter stripes may + occasionally be seen even in the adult;[101] and Colonel S. Poole, who + has had ample opportunities for observation, informs me that in the + foal, when first born, the head and legs are often striped, but the + shoulder-stripe is not so distinct as in the domestic ass; all these + stripes, excepting that along the spine, soon disappear. Now a hybrid, + raised at Knowsley[102] from a female of this species by a male + domestic ass, had all four legs transversely and conspicuously striped, + had three short stripes on each shoulder, and had even some zebra-like + stripes on its face! Dr. Gray informs me that he has seen a second + hybrid of the same parentage similarly striped. + +From these facts we see that the crossing of the several equine species +tends in a marked manner to cause stripes to appear on various parts of the +body, especially on the legs. As we do not know whether the primordial +parent of the genus was striped, the appearance of the stripes can only +hypothetically be attributed to reversion. But most persons, after +considering the many undoubted cases of variously coloured marks +reappearing by reversion in crossed pigeons, fowls, ducks, &c., will come +to the same conclusion with respect to the horse-genus; and in this case we +must admit that the progenitor of the group was striped on the legs, +shoulders, face, and probably over the whole body, like a zebra. If we +reject this view, the frequent and almost regular appearance of stripes in +the several foregoing hybrids is left without any explanation. + + * * * * * + +It would appear that with crossed animals a similar tendency to the +recovery of lost characters holds good even with instincts. There are some +breeds of fowls which are called "everlasting layers," because they have +lost the instinct of incubation; and so rare is it for them to incubate +that I have seen notices published in works on poultry, when hens of such +breeds have taken to sit.[103] Yet the aboriginal species was of course a +good incubator; for with birds in a state of nature hardly any {44} +instinct is so strong as this. Now, so many cases have been recorded of the +crossed offspring from two races, neither of which are incubators, becoming +first-rate sitters, that the reappearance of this instinct must be +attributed to reversion from crossing. One author goes so far as to say, +"that a cross between two non-sitting varieties almost invariably produces +a mongrel that becomes broody, and sits with remarkable steadiness."[104] +Another author, after giving a striking example, remarks that the fact can +be explained only on the principle that "two negatives make a positive." It +cannot, however, be maintained that hens produced from a cross between two +non-sitting breeds invariably recover their lost instinct, any more than +that crossed fowls or pigeons invariably recover the red or blue plumage of +their prototypes. I raised several chickens from a Polish hen by a Spanish +cock,--breeds which do not incubate,--and none of the young hens at first +recovered their instinct, and this appeared to afford a well-marked +exception to the foregoing rule; but one of these hens, the only one which +was preserved, in the third year sat well on her eggs and reared a brood of +chickens. So that here we have the appearance with advancing age of a +primitive instinct, in the same manner as we have seen that the red plumage +of the _Gallus bankiva_ is sometimes reacquired by crossed and purely-bred +fowls of various kinds as they grow old. + +The parents of all our domesticated animals were of course aboriginally +wild in disposition; and when a domesticated species is crossed with a +distinct species, whether this is a domesticated or only tamed animal, the +hybrids are often wild {45} to such a degree, that the fact is intelligible +only on the principle that the cross has caused a partial return to the +primitive disposition. + +The Earl of Powis formerly imported some thoroughly domesticated humped +cattle from India, and crossed them with English breeds, which belong to a +distinct species; and his agent remarked to me, without any question having +been asked, how oddly wild the cross-bred animals were. The European wild +boar and the Chinese domesticated pig are almost certainly specifically +distinct: Sir F. Darwin crossed a sow of the latter breed with a wild +Alpine boar which had become extremely tame, but the young, though having +half-domesticated blood in their veins, were "extremely wild in +confinement, and would not eat swill like common English pigs." Mr. Hewitt, +who has had great experience in crossing tame cock-pheasants with fowls +belonging to five breeds, gives as the character of all "extraordinary +wildness;"[105] but I have myself seen one exception to this rule. Mr. +S. J. Salter,[106] who raised a large number of hybrids from a bantam-hen +by _Gallus Sonneratii_, states that "all were exceedingly wild." Mr. +Waterton[107] bred some wild ducks from eggs hatched under a common duck, +and the young were allowed to cross freely both amongst themselves and with +the tame ducks; they were "half wild and half tame; they came to the +windows to be fed, but still they had a wariness about them quite +remarkable." + +On the other hand, mules from the horse and ass are certainly not in the +least wild, yet they are notorious for obstinacy and vice. Mr. Brent, who +has crossed canary-birds with many kinds of finches, has not observed, as +he informs me, that the hybrids were in any way remarkably wild. Hybrids +are often raised between the common and musk duck, and I have been assured +by three persons, who have kept these crossed birds, that they were not +wild; but Mr. Garnett[108] observed that his female hybrids exhibited +"migratory propensities," of which there is not a vestige in the common or +musk duck. No case is {46} known of this latter bird having escaped and +become wild in Europe or Asia, except, according to Pallas, on the Caspian +Sea; and the common domestic duck only occasionally becomes wild in +districts where large lakes and fens abound. Nevertheless, a large number +of cases have been recorded[109] of hybrids from these two ducks, although +so few are reared in comparison with purely-bred birds of either species, +having been shot in a completely wild state. It is improbable that any of +these hybrids could have acquired their wildness from the musk-duck having +paired with a truly wild duck; and this is known not to be the case in +North America; hence we must infer that they have reacquired, through +reversion, their wildness, as well as renewed powers of flight. + +These latter facts remind us of the statements, so frequently made by +travellers in all parts of the world, on the degraded state and savage +disposition of crossed races of man. That many excellent and kind-hearted +mulattos have existed no one will dispute; and a more mild and gentle set +of men could hardly be found than the inhabitants of the island of Chiloe, +who consist of Indians commingled with Spaniards in various proportions. On +the other hand, many years ago, long before I had thought of the present +subject, I was struck with the fact that, in South America, men of +complicated descent between Negroes, Indians, and Spaniards, seldom had, +whatever the cause might be, a good expression.[110] Livingstone,--and a +more unimpeachable authority cannot be quoted,--after speaking of a +half-caste man on the Zambesi, described by the Portuguese as a rare +monster of inhumanity, remarks, "It is unaccountable why half-castes, such +as he, are so much more cruel than the Portuguese, but such is undoubtedly +the case." An inhabitant remarked to Livingstone, "God made white men, and +God made black men, but the Devil made half-castes."[111] When two races, +both {47} low in the scale, are crossed, the progeny seems to be eminently +bad. Thus the noble-hearted Humboldt, who felt none of that prejudice +against the inferior races now so current in England, speaks in strong +terms of the bad and savage disposition of Zambos, or half-castes between +Indians and Negroes; and this conclusion has been arrived at by various +observers.[112] From these facts we may perhaps infer that the degraded +state of so many half-castes is in part due to reversion to a primitive and +savage condition, induced by the act of crossing, as well as to the +unfavourable moral conditions under which they generally exist. + + * * * * * + +_Summary on the proximate causes leading to Reversion._--When purely-bred +animals or plants reassume long-lost characters,--when the common ass, for +instance, is born with striped legs, when a pure race of black or white +pigeons throws a slaty-blue bird, or when a cultivated heartsease with +large and rounded flowers produces a seedling with small and elongated +flowers,--we are quite unable to assign any proximate cause. When animals +run wild, the tendency to reversion, which, though it has been greatly +exaggerated, no doubt exists, is sometimes to a certain extent +intelligible. Thus, with feral pigs, exposure to the weather will probably +favour the growth of the bristles, as is known to be the case with the hair +of other domesticated animals, and through correlation the tusks will tend +to be redeveloped. But the reappearance of coloured longitudinal stripes on +young feral pigs cannot be attributed to the direct action of external +conditions. In this case, and in many others, we can only say that changed +habits of life apparently have favoured a tendency, inherent or latent in +the species, to return to the primitive state. + +It will be shown in a future chapter that the position of flowers on the +summit of the axis, and the position of seeds within the capsule, sometimes +determine a tendency towards reversion; and this apparently depends on the +amount of sap or nutriment which the flower-buds and seeds receive. The +position, also, of buds, either on branches or on roots, sometimes +determines, as was formerly shown, the transmission of the {48} proper +character of the variety, or its reversion to a former state. + +We have seen in the last section that when two races or species are crossed +there is the strongest tendency to the reappearance in the offspring of +long-lost characters, possessed by neither parent nor immediate progenitor. +When two white, or red, or black pigeons, of well-established breeds, are +united, the offspring are almost sure to inherit the same colours; but when +differently-coloured birds are crossed, the opposed forces of inheritance +apparently counteract each other, and the tendency which is inherent in +both parents to produce slaty-blue offspring becomes predominant. So it is +in several other cases. But when, for instance, the ass is crossed with _A. +Indicus_ or with the horse,--animals which have not striped legs,--and the +hybrids have conspicuous stripes on their legs and even on their faces, all +that can be said is, that an inherent tendency to reversion is evolved +through some disturbance in the organisation caused by the act of crossing. + +Another form of reversion is far commoner, indeed is almost universal with +the offspring from a cross, namely, to the characters proper to either pure +parent-form. As a general rule, crossed offspring in the first generation +are nearly intermediate between their parents, but the grandchildren and +succeeding generations continually revert, in a greater or lesser degree, +to one or both of their progenitors. Several authors have maintained that +hybrids and mongrels include all the characters of both parents, not fused +together, but merely mingled in different proportions in different parts of +the body; or, as Naudin[113] has expressed it, a hybrid is a living +mosaic-work, in which the eye cannot distinguish the discordant elements, +so completely are they intermingled. We can hardly doubt that, in a certain +sense, this is true, as when we behold in a hybrid the elements of both +species segregating themselves into segments in the same flower or fruit, +by a process of self-attraction or self-affinity; this segregation taking +place either by seminal or by bud-propagation. Naudin further believes that +the segregation of the two specific elements or essences is eminently +liable to occur in the male and female reproductive matter; and he thus +explains the almost {49} universal tendency to reversion in successive +hybrid generations. For this would be the natural result of the union of +pollen and ovules, in both of which the elements of the same species had +been segregated by self-affinity. If, on the other hand, pollen which +included the elements of one species happened to unite with ovules +including the elements of the other species, the intermediate or hybrid +state would still be retained, and there would be no reversion. But it +would, as I suspect, be more correct to say that the elements of both +parent-species exist in every hybrid in a double state, namely, blended +together and completely separate. How this is possible, and what the term +specific essence or element may be supposed to express, I shall attempt to +show in the hypothetical chapter on pangenesis. + +But Naudin's view, as propounded by him, is not applicable to the +reappearance of characters lost long ago by variation; and it is hardly +applicable to races or species which, after having been crossed at some +former period with a distinct form, and having since lost all traces of the +cross, nevertheless occasionally yield an individual which reverts (as in +the case of the great-great-grandchild of the pointer Sappho) to the +crossing form. The most simple case of reversion, namely, of a hybrid or +mongrel to its grandparents, is connected by an almost perfect series with +the extreme case of a purely-bred race recovering characters which had been +lost during many ages; and we are thus led to infer that all the cases must +be related by some common bond. + +Gaertner believed that only those hybrid plants which are highly sterile +exhibit any tendency to reversion to their parent-forms. It is rash to +doubt so good an observer, but this conclusion must I think be an error; +and it may perhaps be accounted for by the nature of the genera observed by +him, for he admits that the tendency differs in different genera. The +statement is also directly contradicted by Naudin's observations, and by +the notorious fact that perfectly fertile mongrels exhibit the tendency in +a high degree,--even in a higher degree, according to Gaertner himself, +than hybrids.[114] + +Gaertner further states that reversions rarely occur with {50} hybrid +plants raised from species which have not been cultivated, whilst, with +those which have been long cultivated, they are of frequent occurrence. +This conclusion explains a curious discrepancy: Max Wichura,[115] who +worked exclusively on willows, which had not been subjected to culture, +never saw an instance of reversion; and he goes so far as to suspect that +the careful Gaertner had not sufficiently protected his hybrids from the +pollen of the parent-species: Naudin, on the other hand, who chiefly +experimented on cucurbitaceous and other cultivated plants, insists more +strenuously than any other author on the tendency to reversion in all +hybrids. The conclusion that the condition of the parent-species, as +affected by culture, is one of the proximate causes leading to reversion, +agrees fairly well with the converse case of domesticated animals and +cultivated plants being liable to reversion when they become feral; for in +both cases the organisation or constitution must be disturbed, though in a +very different way. + +Finally, we have seen that characters often reappear in purely-bred races +without our being able to assign any proximate cause; but when they become +feral this is either indirectly or directly induced by the change in their +conditions of life. With crossed breeds, the act of crossing in itself +certainly leads to the recovery of long-lost characters, as well as of +those derived from either parent-form. Changed conditions, consequent on +cultivation, and the relative position of buds, flowers, and seeds on the +plant, all apparently aid in giving this same tendency. Reversion may occur +either through seminal or bud generation, generally at birth, but sometimes +only with an advance of age. Segments or portions of the individual may +alone be thus affected. That a being should be born resembling in certain +characters an ancestor removed by two or three, and in some cases by +hundreds or even thousands of generations, is assuredly a wonderful fact. +In these cases the child is commonly said to inherit such characters +directly from its grandparents or more remote ancestors. But this view is +hardly conceivable. If, however, we suppose that every character is derived +{51} exclusively from the father or mother, but that many characters lie +latent in both parents during a long succession of generations, the +foregoing facts are intelligible. In what manner characters may be +conceived to lie latent, will be considered in a future chapter to which I +have lately alluded. + + * * * * * + +_Latent Characters._--But I must explain what is meant by characters lying +latent. The most obvious illustration is afforded by secondary sexual +characters. In every female all the secondary male characters, and in every +male all the secondary female characters, apparently exist in a latent +state, ready to be evolved under certain conditions. It is well known that +a large number of female birds, such as fowls, various pheasants, +partridges, peahens, ducks, &c., when old or diseased, or when operated on, +partly assume the secondary male characters of their species. In the case +of the hen-pheasant this has been observed to occur far more frequently +during certain seasons than during others.[116] A duck ten years old has +been known to assume both the perfect winter and summer plumage of the +drake.[117] Waterton[118] gives a curious case of a hen which had ceased +laying, and had assumed the plumage, voice, spurs, and warlike disposition +of the cock; when opposed to an enemy she would erect her hackles and show +fight. Thus every character, even to the instinct and manner of fighting, +must have lain dormant in this hen as long as her ovaria continued to act. +The females of two kinds of deer, when old, have been known to acquire +horns; and, as Hunter has remarked, we see something of an analogous nature +in the human species. + +On the other hand, with male animals, it is notorious that the secondary +sexual characters are more or less completely lost when they are subjected +to castration. Thus, if the operation be performed on a young cock, he +never, as Yarrell states, crows {52} again; the comb, wattles, and spurs do +not grow to their full size, and the hackles assume an intermediate +appearance between true hackles and the feathers of the hen. Cases are +recorded of confinement alone causing analogous results. But characters +properly confined to the female are likewise acquired; the capon takes to +sitting on eggs, and will bring up chickens; and what is more curious, the +utterly sterile male hybrids from the pheasant and the fowl act in the same +manner, "their delight being to watch when the hens leave their nests, and +to take on themselves the office of a sitter."[119] That admirable observer +Reaumur[120] asserts that a cock, by being long confined in solitude and +darkness, can be taught to take charge of young chickens; he then utters a +peculiar cry, and retains during his whole life this newly acquired +maternal instinct. The many well-ascertained cases of various male mammals +giving milk, show that their rudimentary mammary glands retain this +capacity in a latent condition. + +We thus see that in many, probably in all cases, the secondary characters +of each sex lie dormant or latent in the opposite sex, ready to be evolved +under peculiar circumstances. We can thus understand how, for instance, it +is possible for a good milking cow to transmit her good qualities through +her male offspring to future generations; for we may confidently believe +that these qualities are present, though latent, in the males of each +generation. So it is with the game-cock, who can transmit his superiority +in courage and vigour through his female to his male offspring; and with +man it is known [121] that diseases, such as hydrocele, necessarily +confined to the male sex, can be transmitted through the female to the +grandson. Such cases as these offer, as was remarked at the commencement of +this chapter, the simplest possible examples of reversion; and they are +intelligible on the belief that characters common to the grandparent and +grandchild of the same sex are present, though latent, in the intermediate +parent of the opposite sex. + +The subject of latent characters is so important, as we shall see in a +future chapter, that I will give another illustration. {53} Many animals +have the right and left sides of their body unequally developed: this is +well known to be the case with flat-fish, in which the one side differs in +thickness and colour, and in the shape of the fins, from the other; and +during the growth of the young fish one eye actually travels, as shown by +Steenstrup, from the lower to the upper surface.[122] In most flat-fishes +the left is the blind side, but in some it is the right; though in both +cases "wrong fishes," which are developed in a reversed manner to what is +usual, occasionally occur, and in _Platessa flesus_ the right or left side +is indifferently developed, the one as often as the other. With gasteropods +or shell-fish, the right and left sides are extremely unequal; the far +greater number of species are dextral, with rare and occasional reversals +of development, and some few are normally sinistral; but certain species of +Bulimus, and, many Achatinellae,[123] are as often sinistral as dextral. I +will give an analogous case in the great Articulate kingdom: the two sides +of Verruca[124] are so wonderfully unlike, that without careful dissection +it is extremely difficult to recognise the corresponding parts on the +opposite sides of the body; yet it is apparently a mere matter of chance +whether it be the right or the left side that undergoes so singular an +amount of change. One plant is known to me[125] in which the flower, +according as it stands on the one or other side of the spike, is unequally +developed. In all the foregoing cases the two sides of the animal are +perfectly symmetrical at an early period of growth. Now, whenever a species +is as liable to be unequally developed on the one as on the other side, we +may infer that the capacity for such development is present, though latent, +in the undeveloped side. And as a reversal of development occasionally +occurs in animals of many kinds, this latent capacity is probably very +common. + +The best yet simplest instances of characters lying dormant are, perhaps, +those previously given, in which chickens and {54} young pigeons, raised +from a cross between differently coloured birds, are at first of one +colour, but in a year or two acquire feathers of the colour of the other +parent; for in this case the tendency to a change of plumage is clearly +latent in the young bird. So it is with hornless breeds of cattle, some of +which acquire, as they grow old, small horns. Purely bred black and white +bantams, and some other fowls, occasionally assume, with advancing years, +the red feathers of the parent-species. I will here add a somewhat +different case, as it connects in a striking manner latent characters of +two classes. Mr. Hewitt[126] possessed an excellent Sebright gold-laced hen +bantam, which, as she became old, grew diseased in her ovaria, and assumed +male characters. In this breed the males resemble the females in all +respects except in their combs, wattles, spurs, and instincts; hence it +might have been expected that the diseased hen would have assumed only +those masculine characters which are proper to the breed, but she acquired, +in addition, well-arched tail sickle-feathers quite a foot in length, +saddle-feathers on the loins, and hackles on the neck,--ornaments which, as +Mr. Hewitt remarks, "would be held as abominable in this breed." The +Sebright bantam is known[127] to have originated about the year 1800 from a +cross between a common bantam and a Polish fowl, recrossed by a hen-tailed +bantam, and carefully selected; hence there can hardly be a doubt that the +sickle-feathers and hackles which appeared in the old hen were derived from +the Polish fowl or common bantam; and we thus see that not only certain +masculine characters proper to the Sebright bantam, but other masculine +characters derived from the first progenitors of the breed, removed by a +period of above sixty years, were lying latent in this hen-bird, ready to +be evolved as soon as her ovaria became diseased. + +From these several facts it must be admitted that certain characters, +capacities, and instincts may lie latent in an individual, and even in a +succession of individuals, without our being able to detect the least signs +of their presence. We have {55} already seen that the transmission of a +character from the grandparent to the grandchild, with its apparent +omission in the intermediate parent of the opposite sex, becomes simple on +this view. When fowls, pigeons, or cattle of different colours are crossed, +and their offspring change colour as they grow old, or when the crossed +turbit acquired the characteristic frill after its third moult, or when +purely-bred bantams partially assume the red plumage of their prototype, we +cannot doubt that these qualities were from the first present, though +latent, in the individual animal, like the characters of a moth in the +caterpillar. Now, if these animals had produced offspring before they had +acquired with advancing age their new characters, nothing is more probable +than that they would have transmitted them to some of their offspring, +which in this case would in appearance have received such characters from +their grandparents or more distant progenitors. We should then have had a +case of reversion, that is, of the reappearance in the child of an +ancestral character, actually present, though during youth completely +latent, in the parent; and this we may safely conclude is what occurs with +reversions of all kinds to progenitors however remote. + +This view of the latency in each generation of all the characters which +appear through reversion, is also supported by their actual presence in +some cases during early youth alone, or by their more frequent appearance +and greater distinctness at this age than during maturity. We have seen +that this is often the case with the stripes on the legs and faces of the +several species of the horse-genus. The Himalayan rabbit, when crossed, +sometimes produces offspring which revert to the parent silver-grey breed, +and we have seen that in purely bred animals pale-grey fur occasionally +reappears during early youth. Black cats, we may feel assured, would +occasionally produce by reversion tabbies; and on young black kittens, with +a pedigree[128] known to have been long pure, faint traces of stripes may +almost always be seen which afterwards disappear. Hornless Suffolk cattle +occasionally produce by reversion horned animals; and Youatt[129] asserts +that even in hornless individuals {56} "the rudiment of a horn may be often +felt at an early age." + +No doubt it appears at first sight in the highest degree improbable that in +every horse of every generation there should be a latent capacity and +tendency to produce stripes, though these may not appear once in a thousand +generations; that in every white, black, or other coloured pigeon, which +may have transmitted its proper colour during centuries, there should be a +latent capacity in the plumage to become blue and to be marked with certain +characteristic bars; that in every child in a six-fingered family there +should be the capacity for the production of an additional digit; and so in +other cases. Nevertheless there is no more inherent improbability in this +being the case than in a useless and rudimentary organ, or even in only a +tendency to the production of a rudimentary organ, being inherited during +millions of generations, as is well known to occur with a multitude of +organic beings. There is no more inherent improbability in each domestic +pig, during a thousand generations, retaining the capacity and tendency to +develop great tusks under fitting conditions, than in the young calf having +retained for an indefinite number of generations rudimentary incisor teeth, +which never protrude through the gums. + +I shall give at the end of the next chapter a summary of the three +preceding chapters; but as isolated and striking cases of reversion have +here been chiefly insisted on, I wish to guard the reader against supposing +that reversion is due to some rare or accidental combination of +circumstances. When a character, lost during hundreds of generations, +suddenly reappears, no doubt some such combination must occur; but +reversions may be constantly observed, at least to the immediately +preceding generations, in the offspring of most unions. This has been +universally recognised in the case of hybrids and mongrels, but it has been +recognised simply from the difference between the united forms rendering +the resemblance of the offspring to their grandparents or more remote +progenitors of easy detection. Reversion is likewise almost invariably the +rule, as Mr. Sedgwick has shown, with certain diseases. Hence we must +conclude that a tendency to this peculiar form of transmission is an +integral part of the general law of inheritance. {57} + + * * * * * + +_Monstrosities._--A large number of monstrous growths and of lesser +anomalies are admitted by every one to be due to an arrest of development, +that is to the persistence of an embryonic condition. If every horse or ass +had striped legs whilst young, the stripes which occasionally appear on +these animals when adult would have to be considered as due to the +anomalous retention of an early character, and not as due to reversion. +Now, the leg-stripes in the horse-genus, and some other characters in +analogous cases, are apt to occur during early youth and then to disappear; +thus the persistence of early characters and reversion are brought into +close connexion. + +But many monstrosities can hardly be considered as the result of an arrest +of development; for parts of which no trace can be detected in the embryo, +but which occur in other members of the same class of animals or plants, +occasionally appear, and these may probably with truth be attributed to +reversion. For instance: supernumerary mammae, capable of secreting milk, +are not extremely rare in women; and as many as five have been observed. +When four are developed, they are generally arranged symmetrically on each +side of the chest; and in one instance a woman (the daughter of another +with supernumerary mammae) had one mamma, which yielded milk, developed in +the inguinal region. This latter case, when we remember the position of the +mammae in some of the lower animals on both the chest and inguinal region, +is highly remarkable, and leads to the belief that in all cases the +additional mammae in woman are due to reversion. The facts given in the +last chapter on the tendency in supernumerary digits to regrowth after +amputation, indicate their relation to the digits of the lower vertebrate +animals, and lead to the suspicion that their appearance may in some manner +be connected with reversion. But I shall have to recur, in the chapter on +pangenesis, to the abnormal multiplication of organs, and likewise to their +occasional transposition. The occasional development in man of the +coccygeal vertebrae into a short and free tail, though it thus becomes in +one sense more perfectly developed, may at the same time be considered as +an arrest of development, and as a case of reversion. The greater frequency +of a monstrous kind of proboscis in the pig than in any other mammal, +considering the position of the pig {58} in the mammalian series, has +likewise been attributed, perhaps truly, to reversion.[130] + + When flowers which are properly irregular in structure become regular + or peloric, the change is generally looked at by botanists as a return + to the primitive state. But Dr. Maxwell Masters,[131] who has ably + discussed this subject, remarks that when, for instance, all the sepals + of a Tropaeolum become green and of the same shape, instead of being + coloured with one alone prolonged into a spur, or when all the petals + of a Linaria become simple and regular, such cases may be due merely to + an arrest of development; for in these flowers all the organs during + their earliest condition are symmetrical, and, if arrested at this + stage of growth, they would not become irregular. If, moreover, the + arrest were to take place at a still earlier period of development, the + result would be a simple tuft of green leaves; and no one probably + would call this a case of reversion. Dr. Masters designates the cases + first alluded to as regular peloria; and others, in which all the + corresponding parts assume a similar form of irregularity, as when all + the petals in a Linaria become spurred, as irregular peloria. We have + no right to attribute these latter cases to reversion, until it can be + shown to be probable that the parent-form, for instance, of the genus + Linaria had had all its petals spurred; for a change of this nature + might result from the spreading of an anomalous structure, in + accordance with the law, to be discussed in a future chapter, of + homologous parts tending to vary in the same manner. But as both forms + of peloria frequently occur on the same individual plant of the + Linaria,[132] they probably stand in some close relation to each other. + On the doctrine that peloria is simply the result of an arrest of + development, it is difficult to understand how an organ arrested at a + very early period of growth should acquire its full functional + perfection;--how a petal, supposed to be thus arrested, should acquire + its brilliant colours, and serve as an envelope to the flower, or a + stamen produce efficient pollen; yet this occurs with many peloric + flowers. That pelorism is not due to mere chance variability, but + either to an arrest of development or to reversion, we may infer from + an observation made by Ch. Morren,[133] namely, that families which + have irregular flowers often "return by these monstrous growths to + their regular form; whilst we never see a regular flower realise the + structure of an irregular one." + + Some flowers have almost certainly become more or less completely + peloric through reversion. _Corydalis tuberosa_ properly has one of its + two nectaries colourless, destitute of nectar, only half the size of + the other, and {59} therefore, to a certain extent, in a rudimentary + state; the pistil is curved towards the perfect nectary, and the hood, + formed of the inner petals, slips off the pistil and stamens in one + direction alone, so that, when a bee sucks the perfect nectary, the + stigma and stamens are exposed and rubbed against the insect's body. In + several closely allied genera, as in Dielytra, &c., there are two + perfect nectaries, the pistil is straight, and the hood slips off on + either side, according as the bee sucks either nectary. Now, I have + examined several flowers of _Corydalis tuberosa_, in which both + nectaries were equally developed and contained nectar; in this we see + only the redevelopment of a partially aborted organ; but with this + redevelopment the pistil becomes straight, and the hood slips off in + either direction; so that these flowers have acquired the perfect + structure, so well adapted for insect agency, of Dielytra and its + allies. We cannot attribute these coadapted modifications to chance, or + to correlated variability; we must attribute them to reversion to a + primordial condition of the species. + + The peloric flowers of Pelargonium have their five petals in all + respects alike, and there is no nectary; so that they resemble the + symmetrical flowers of the closely allied Geranium-genus; but the + alternate stamens are also sometimes destitute of anthers, the + shortened filaments being left as rudiments, and in this respect they + resemble the symmetrical flowers of the closely allied genus, Erodium. + Hence we are led to look at the peloric flowers of Pelargonium as + having probably reverted to the state of some primordial form, the + progenitor of the three closely related genera of Pelargonium, + Geranium, and Erodium. + + In the peloric form of _Antirrhinum majus_, appropriately called the + "_Wonder_," the tubular and elongated flowers differ wonderfully from + those of the common snapdragon; the calyx and the mouth of the corolla + consist of six equal lobes, and include six equal instead of four + unequal stamens. One of the two additional stamens is manifestly formed + by the development of a microscopically minute papilla, which may be + found at the base of the upper lip of the flower in all common + snapdragons, at least in nineteen plants examined by me. That this + papilla is a rudiment of a stamen was well shown by its various degrees + of development in crossed plants between the common and peloric + Antirrhinum. Again, a peloric _Galeobdolon luteum_, growing in my + garden, had five equal petals, all striped like the ordinary lower lip, + and included five equal instead of four unequal stamens; but Mr. R. + Keeley, who sent me this plant, informs me that the flowers vary + greatly, having from four to six lobes to the corolla, and from three + to six stamens.[134] Now, as the members of the two great families to + which the Antirrhinum and Galeobdolon belong are properly pentamerous, + with some of the parts confluent and others suppressed, we ought not to + look at the sixth stamen and the sixth lobe to the corolla in either + case as due to reversion, any more than the additional petals in double + flowers in these same two families. But the case is different with the + fifth stamen in the peloric Antirrhinum, which {60} is produced by the + redevelopment of a rudiment always present, and which probably reveals + to us the state of the flower, as far as the stamens are concerned, at + some ancient epoch. It is also difficult to believe that the other four + stamens and the petals, after an arrest of development at a very early + embryonic age, would have come to full perfection in colour, structure, + and function, unless these organs had at some former period normally + passed through a similar course of growth. Hence it appears to me + probable that the progenitor of the genus Antirrhinum must at some + remote epoch have included five stamens and borne flowers in some + degree resembling those now produced by the peloric form. + + Lastly, I may add that many instances have been recorded of flowers, + not generally ranked as peloric, in which certain organs, normally few + in number, have been abnormally augmented. As such an increase of parts + cannot be looked at as an arrest of development, nor as due to the + redevelopment of rudiments, for no rudiments are present, and as these + additional parts bring the plant into closer relationship with its + natural allies, they ought probably to be viewed as reversions to a + primordial condition. + +These several facts show us in an interesting manner how intimately certain +abnormal states are connected together; namely, arrests of development +causing parts to become rudimentary or to be wholly suppressed,--the +redevelopment of parts at present in a more or less rudimentary +condition,--the reappearance of organs of which not a vestige can now be +detected,--and to these may be added, in the case of animals, the presence +during youth, and subsequent disappearance, of certain characters which +occasionally are retained throughout life. Some naturalists look at all +such abnormal structures as a return to the ideal state of the group to +which the affected being belongs; but it is difficult to conceive what is +meant to be conveyed by this expression. Other naturalists maintain, with +greater probability and distinctness of view, that the common bond of +connection between the several foregoing cases is an actual, though +partial, return to the structure of the ancient progenitor of the group. If +this view be correct, we must believe that a vast number of characters, +capable of evolution, lie hidden in every organic being. But it would be a +mistake to suppose that the number is equally great in all beings. We know, +for instance, that plants of many orders occasionally become peloric; but +many more cases have been observed in the Labiatae and Scrophulariaceae +than in any other order; and in one genus of the Scrophulariaceae, namely +Linaria, no less {61} than thirteen species have been described in a +peloric condition.[135] On this view of the nature of peloric flowers, and +bearing in mind what has been said with respect to certain monstrosities in +the animal kingdom, we must conclude that the progenitors of most plants +and animals, though widely different in structure, have left an impression +capable of redevelopment on the germs of their descendants. + +The fertilised germ of one of the higher animals, subjected as it is to so +vast a series of changes from the germinal cell to old age,--incessantly +agitated by what Quatrefages well calls the _tourbillon vital_,--is perhaps +the most wonderful object in nature. It is probable that hardly a change of +any kind affects either parent, without some mark being left on the germ. +But on the doctrine of reversion, as given in this chapter, the germ +becomes a far more marvellous object, for, besides the visible changes to +which it is subjected, we must believe that it is crowded with invisible +characters, proper to both sexes, to both the right and left side of the +body, and to a long line of male and female ancestors separated by hundreds +or even thousands of generations from the present time; and these +characters, like those written on paper with invisible ink, all lie ready +to be evolved under certain known or unknown conditions. + + * * * * * + + +{62} + +CHAPTER XIV. + +INHERITANCE _continued_--FIXEDNESS OF CHARACTER--PREPOTENCY--SEXUAL +LIMITATION--CORRESPONDENCE OF AGE. + + FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO ANTIQUITY OF + INHERITANCE--PREPOTENCY OF TRANSMISSION IN INDIVIDUALS OF THE SAME + FAMILY, IN CROSSED BREEDS AND SPECIES; OFTEN STRONGER IN ONE SEX THAN + THE OTHER; SOMETIMES DUE TO THE SAME CHARACTER BEING PRESENT AND + VISIBLE IN ONE BREED AND LATENT IN THE OTHER--INHERITANCE AS LIMITED BY + SEX--NEWLY-ACQUIRED CHARACTERS IN OUR DOMESTICATED ANIMALS OFTEN + TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST BY ONE SEX + ALONE--INHERITANCE AT CORRESPONDING PERIODS OF LIFE--THE IMPORTANCE OF + THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS EXHIBITED IN DOMESTICATED + ANIMALS; AS EXHIBITED IN THE APPEARANCE AND DISAPPEARANCE OF INHERITED + DISEASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN IN THE + PARENT--SUMMARY OF THE THREE PRECEDING CHAPTERS. + +In the two last chapters the nature and force of Inheritance, the +circumstances which interfere with its power, and the tendency to +Reversion, with its many remarkable contingencies, were discussed. In the +present chapter some other related phenomena will be treated of, as fully +as my materials permit. + +_Fixedness of Character._ + +It is a general belief amongst breeders that the longer any character has +been transmitted by a breed, the more firmly it will continue to be +transmitted. I do not wish to dispute the truth of the proposition, that +inheritance gains strength simply through long continuance, but I doubt +whether it can be proved. In one sense the proposition is little better +than a truism; if any character has remained constant during many +generations, it will obviously be little likely, the conditions of life +remaining the same, to vary during the next generation. So, again, in +improving a breed, if care be taken for a length of time to exclude all +inferior individuals, the breed will obviously tend to become truer, as it +will not have been crossed during many generations by an inferior animal. +We have previously seen, {63} but without being able to assign any cause, +that, when a new character appears, it is occasionally from the first well +fixed, or fluctuates much, or wholly fails to be transmitted. So it is with +the aggregate of slight differences which characterise a new variety, for +some propagate their kind from the first much truer than others. Even with +plants multiplied by bulbs, layers, &c., which may in one sense be said to +form parts of the same individual, it is well known that certain varieties +retain and transmit through successive bud-generations their newly-acquired +characters more truly than others. In none of these, nor in the following +cases, does there appear to be any relation between the force with which a +character is transmissible and the length of time during which it has +already been transmitted. Some varieties, such as white and yellow +hyacinths and white sweet-peas, transmit their colours more faithfully than +do the varieties which have retained their natural colour. In the Irish +family, mentioned in the twelfth chapter, the peculiar tortoiseshell-like +colouring of the eyes was transmitted far more faithfully than any ordinary +colour. Ancon and Mauchamp sheep and niata cattle, which are all +comparatively modern breeds, exhibit remarkably strong powers of +inheritance. Many similar cases could be adduced. + +As all domesticated animals and cultivated plants have varied, and yet are +descended from aboriginally wild forms, which no doubt had retained the +same character from an immensely remote epoch, we see that scarcely any +degree of antiquity ensures a character being transmitted perfectly true. +In this case, however, it may be said that changed conditions of life +induce certain modifications, and not that the power of inheritance fails; +but in every case of failure, some cause, either internal or external, must +interfere. It will generally be found that the parts in our domesticated +productions which have varied, or which still continue to vary,--that is, +which fail to retain their primordial state,--are the same with the parts +which differ in the natural species of the same genus. As, on the theory of +descent with modification, the species of the same genus have been modified +since they branched off from a common progenitor, it follows that the +characters by which they differ from each other have varied whilst other +parts of the organisation have remained unchanged; and it might be argued +that {64} these same characters now vary under domestication, or fail to be +inherited, owing to their lesser antiquity. But we must believe structures, +which have already varied, would be more liable to go on varying, rather +than structures which during an immense lapse of time have remained +unaltered; and this variation is probably the result of certain relations +between the conditions of life and the organisation, quite independently of +the greater or less antiquity of each particular character. + +Fixedness of character, or the strength of inheritance, has often been +judged of by the preponderance of certain characters in the crossed +offspring between distinct races; but prepotency of transmission here comes +into play, and this, as we shall immediately see, is a very different +consideration from the strength or weakness of inheritance. It has often +been observed[136] that breeds of animals inhabiting wild and mountainous +countries cannot be permanently modified by our improved breeds; and as +these latter are of modern origin, it has been thought that the greater +antiquity of the wilder breeds has been the cause of their resistance to +improvement by crossing; but it is more probably due to their structure and +constitution being better adapted to the surrounding conditions. When +plants are first subjected to culture, it has been found that, during +several generations, they transmit their characters truly, that is, do not +vary, and this has been attributed to ancient characters being strongly +inherited; but it may with equal or greater probability be consequent on +changed conditions of life requiring a long time for their accumulative +action. Notwithstanding these considerations, it would perhaps be rash to +deny that characters become more strongly fixed the longer they are +transmitted; but I believe that the proposition resolves itself into +this,--that all characters of all kinds, whether new or old, tend to be +inherited, and that those which have already withstood all counteracting +influences and been truly transmitted, will, as a general rule, continue to +withstand them, and consequently be faithfully inherited. + +{65} + +_Prepotency in the Transmission of Character._ + +When individuals distinct enough to be recognised, but of the same family, +or when two well-marked races, or two species, are crossed, the usual +result, as stated in the previous chapter, is, that the offspring in the +first generation are intermediate between their parents, or resemble one +parent in one part and the other parent in another part. But this is by no +means the invariable rule; for in many cases it is found that certain +individuals, races, and species are prepotent in transmitting their +likeness. This subject has been ably discussed by Prosper Lucas,[137] but +is rendered extremely complicated by the prepotency sometimes running +equally in both sexes, and sometimes more strongly in one sex than in the +other; it is likewise complicated by the presence of secondary sexual +characters, which render the comparison of mongrels with their +parent-breeds difficult. + +It would appear that in certain families some one ancestor, and after him +others in the same family, must have had great power in transmitting their +likeness through the male line; for we cannot otherwise understand how the +same features should so often be transmitted after marriages with various +females, as has been the case with the Austrian Emperors, and as, according +to Niebuhr, formerly occurred in certain Roman families with their mental +qualities.[138] The famous bull Favourite is believed[139] to have had a +prepotent influence on the shorthorn race. It has also been observed[140] +with English race-horses that certain mares have generally transmitted +their own character, whilst other mares of equally pure blood have allowed +the character of the sire to prevail. + + The truth of the principle of prepotency comes out more clearly when + certain races are crossed. The improved Shorthorns, notwithstanding + that the breed is comparatively modern, are generally acknowledged to + possess great power in impressing their likeness on all other breeds; + and it is chiefly in consequence of this power that they are so highly + valued {66} for exportation.[141] Godine has given a curious case of a + ram of a goat-like breed of sheep from the Cape of Good Hope, which + produced offspring hardly to be distinguished from himself, when + crossed with ewes of twelve other breeds. But two of these half-bred + ewes, when put to a merino ram, produced lambs closely resembling the + merino breed. Girou de Buzareingues[142] found that of two races of + French sheep the ewes of one, when crossed during successive + generations with merino rams, yielded up their character far sooner + than the ewes of the other race. Sturm and Girou have given analogous + cases with other breeds of sheep and with cattle, the prepotency + running in these cases through the male side; but I was assured on good + authority in South America, that when niata cattle are crossed with + common cattle, though the niata breed is prepotent whether males or + females are used, yet that the prepotency is strongest through the + female line. The Manx cat is tailless and has long hind legs; Dr. + Wilson crossed a male Manx with common cats, and, out of twenty-three + kittens, seventeen were destitute of tails; but when the female Manx + was crossed by common male cats all the kittens had tails, though they + were generally short and imperfect.[143] + + In making reciprocal crosses between pouter and fantail pigeons, the + pouter-race seemed to be prepotent through both sexes over the fantail. + But this is probably due to weak power in the fantail rather than to + any unusually strong power in the pouter, for I have observed that + barbs also preponderated over fantails. This weakness of transmission + in the fantail, though the breed is an ancient one, is said[144] to be + general; but I have observed one exception to the rule, namely, in a + cross between a fantail and laugher. The most curious instance known to + me of weak power in both sexes is in the trumpeter pigeon. This breed + has been well known for at least 130 years: it breeds perfectly true, + as I have been assured by those who have long kept many birds: it is + characterised by a peculiar tuft of feathers over the beak, by a crest + on the head, by a most peculiar coo quite unlike that of any other + breed, and by much-feathered feet. I have crossed both sexes with + turbits of two sub-breeds, with almond tumblers, spots, and runts, and + reared many mongrels and recrossed them; and though the crest on the + head and feathered feet were inherited (as is generally the case with + most breeds), I have never seen a vestige of the tuft over the beak or + heard the peculiar coo. Boitard and Corbie[145] assert that this is the + invariable result of crossing trumpeters with any other breed: + Neumeister,[146] however, states that in Germany mongrels have been + obtained, though very rarely, which were furnished with the tuft and + would trumpet: but a pair of these mongrels with a tuft, which I + imported, never trumpeted. Mr. Brent states[147] that the crossed + offspring of a trumpeter were crossed {67} with trumpeters for three + generations, by which time the mongrels had 7-8ths of this blood in + their veins, yet the tuft over the beak did not appear. At the fourth + generation the tuft appeared, but the birds, though now having 15-16ths + trumpeter's blood, still did not trumpet. This case well shows the wide + difference between inheritance and prepotency; for here we have a + well-established old race which transmits it characters faithfully, but + which, when crossed with any other race, has the feeblest power of + transmitting its two chief characteristic qualities. + + I will give one other instance with fowls and pigeons of weakness and + strength in the transmission of the same character to their crossed + offspring. The Silk-fowl breeds true, and there is reason to believe is + a very ancient race; but when I reared a large number of mongrels from + a Silk-hen by a Spanish cock, not one exhibited even a trace of the + so-called silkiness. Mr. Hewitt also asserts that in no instance are + the silky feathers transmitted by this breed when crossed with any + other variety. But three birds out of many raised by Mr. Orton from a + cross between a silk-cock and a bantam-hen, had silky feathers.[148] So + that it is certain that this breed very seldom has the power of + transmitting its peculiar plumage to its crossed progeny. On the other + hand, there is a silk sub-variety of the fantail pigeon, which has its + feathers in nearly the same state as in the Silk-fowl: now we have + already seen that fantails, when crossed, possess singularly weak power + in transmitting their general qualities; but the silk sub-variety when + crossed with any other small-sized race invariably transmits its silky + feathers![149] + + The law of prepotency comes into action when species are crossed, as + with races and individuals. Gaertner has unequivocally shown[150] that + this is the case with plants. To give one instance: when _Nicotiana + paniculata_ and _vincaeflora_ are crossed, the character of _N. + paniculata_ is almost completely lost in the hybrid; but if _N. + quadrivalvis_ be crossed with _N. vincaeflora_, this later species, + which was before so prepotent, now in its turn almost disappears under + the power of _N. quadrivalvis_. It is remarkable that the prepotency of + one species over another in transmission is quite independent, as shown + by Gaertner, of the greater or less facility with which the one + fertilises the other. + + With animals, the jackal is prepotent over the dog, as is stated by + Flourens who made many crosses between these animals; and this was + likewise the case with a hybrid which I once saw between a jackal and + terrier. I cannot doubt, from the observations of Colin and others, + that the ass is prepotent over the horse; the prepotency in this + instance running more strongly through the male than through the female + ass; so that the mule resembles the ass more closely than does the + hinny.[151] The {68} male pheasant, judging from Mr. Hewitt's + descriptions,[152] and from the hybrids which I have seen, + preponderates over the domestic fowl; but the latter, as far as colour + is concerned, has considerable power of transmission, for hybrids + raised from five differently coloured hens differed greatly in plumage. + I formerly examined some curious hybrids in the Zoological Gardens, + between the Penguin variety of the common duck and the Egyptian goose + (_Tadorna Aegyptiaca_); and although I will not assert that the + domesticated variety preponderated over the natural species, yet it had + strongly impressed its unnatural upright figure on these hybrids. + + I am aware that such cases as the foregoing have been ascribed by + various authors, not to one species, race, or individual being + prepotent over the other in impressing it character on its crossed + offspring, but to such rules as that the father influences the external + characters and the mother the internal or vital organs. But the great + diversity of the rules given by various authors almost proves their + falseness. Dr. Prosper Lucas has fully discussed this point, and has + shown[153] that none of the rules (and I could add others to those + quoted by him) apply to all animals. Similar rules have been enounced + for plants, and have been proved by Gaertner[154] to be all erroneous. + If we confine our view to the domesticated races of a single species, + or perhaps even to the species of the same genus, some such rules may + hold good; for instance, it seems that in reciprocally crossing various + breeds of fowls the male generally gives colour;[155] but conspicuous + exceptions have passed under my own eyes. In sheep it seems that the + ram usually gives its peculiar horns and fleece to its crossed + offspring, and the bull the presence or absence of horns. + + In the following chapter on Crossing I shall have occasion to show that + certain characters are rarely or never blended by crossing, but are + {69} transmitted in an unmodified state from either parent-form; I + refer to this fact here because it is sometimes accompanied on the one + side by prepotency, which thus acquires the false appearance of unusual + strength. In the same chapter I shall show that the rate at which a + species or breed absorbs and obliterates another by repeated crosses, + depends in chief part on prepotency in transmission. + +In conclusion, some of the cases above given,--for instance, that of the +trumpeter pigeon,--prove that there is a wide difference between mere +inheritance and prepotency. This latter power seems to us, in our +ignorance, to act in most cases quite capriciously. The very same +character, even though it be an abnormal or monstrous one, such as silky +feathers, may be transmitted by different species, when crossed, either +with prepotent force or singular feebleness. It is obvious, that a +purely-bred form of either sex, in all cases in which prepotency does not +run more strongly in one sex than the other, will transmit its character +with prepotent force over a mongrelized and already variable form.[156] +From several of the above-given cases we may conclude that mere antiquity +of character does not by any means necessarily make it prepotent. In some +cases prepotency apparently depends on the same character being present and +visible in one of the two breeds which are crossed, and latent or invisible +in the other breed; and in this case it is natural that the character which +is potentially present in both should be prepotent. Thus, we have reason to +believe that there is a latent tendency in all horses to be dun-coloured +and striped; and when a horse of this kind is crossed with one of any other +colour, it is said that the offspring are almost sure to be striped. Sheep +have a similar latent tendency to become dark-coloured, and we have seen +with what prepotent force a ram with a few black spots, when crossed with +sheep of various breeds, coloured its offspring. All pigeons have a latent +tendency to become slaty-blue, with certain characteristic marks, and it is +known that, when a bird thus coloured is crossed with one of any other +colour, it is most difficult afterwards to eradicate the blue tint. A +nearly parallel case is offered by those black bantams which, as they grow +{70} old, develop a latent tendency to acquire red feathers. But there are +exceptions to the rule: hornless breeds of cattle possess a latent capacity +to reproduce horns, yet when crossed with horned breeds they do not +invariably produce offspring bearing horns. + +We meet with analogous cases with plants. Striped flowers, though they can +be propagated truly by seed, have a latent tendency to become uniformly +coloured, but when once crossed by a uniformly coloured variety, they ever +afterwards fail to produce striped seedlings.[157] Another case is in some +respects more curious: plants bearing peloric or regular flowers have so +strong a latent tendency to reproduce their normally irregular flowers, +that this often occurs by buds when a plant is transplanted into poorer or +richer soil.[158] Now I crossed the peloric snapdragon (_Antirrhinum +majus_), described in the last chapter, with pollen of the common form; and +the latter, reciprocally, with peloric pollen. I thus raised two great beds +of seedlings, and not one was peloric. Naudin[159] obtained the same result +from crossing a peloric Linaria with the common form. I carefully examined +the flowers of ninety plants of the crossed Antirrhinum in the two beds, +and their structure had not been in the least affected by the cross, except +that in a few instances the minute rudiment of the fifth stamen, which is +always present, was more fully or even completely developed. It must not be +supposed that this entire obliteration of the peloric structure in the +crossed plants can be accounted for by any incapacity of transmission; for +I raised a large bed of plants from the peloric Antirrhinum, artificially +fertilised by its own pollen, and sixteen plants, which alone survived the +winter, were all as perfectly peloric as the parent-plant. Here we have a +good instance of the wide difference between the inheritance of a character +and the power of transmitting it to crossed offspring. The crossed plants, +which perfectly resembled the common snapdragon, were allowed to sow +themselves, and, out of a hundred and twenty-seven seedlings, eighty-eight +proved to be common snapdragons, two were in an intermediate condition +between the peloric and normal state, {71} and thirty-seven were perfectly +peloric, having reverted to the structure of their one grandparent. This +case seems at first sight to offer an exception to the rule formerly given, +namely, that a character which is present in one form and latent in the +other is generally transmitted with prepotent force when the two forms are +crossed. For in all the Scrophulariaceae, and especially in the genera +Antirrhinum and Linaria, there is, as was shown in the last chapter, a +strong latent tendency to become peloric; and there is also, as we have +just seen, a still stronger tendency in all peloric plants to reacquire +their normal irregular structure. So that we have two opposed latent +tendencies in the same plants. Now, with the crossed Antirrhinums the +tendency to produce normal or irregular flowers, like those of the common +Snapdragon, prevailed in the first generation; whilst the tendency to +pelorism, appearing to gain strength by the intermission of a generation, +prevailed to a large extent in the second set of seedlings. How it is +possible for a character to gain strength by the intermission of a +generation, will be considered in the chapter on pangenesis. + +On the whole, the subject of prepotency is extremely intricate,--from its +varying so much in strength, even in regard to the same character, in +different animals,--from its running either equally in both sexes, or, as +frequently is the case with animals, but not with plants, much stronger in +the one sex than the other,--from the existence of secondary sexual +characters,--from the transmission of certain characters being limited, as +we shall immediately see, by sex,--from certain characters not blending +together,--and, perhaps, occasionally from the effects of a previous +fertilisation on the mother. It is therefore not surprising that every one +hitherto has been baffled in drawing up general rules on the subject of +prepotency. + +_Inheritance as limited by Sex._ + +New characters often appear in one sex, and are afterwards transmitted to +the same sex, either exclusively or in a much greater degree than to the +other. This subject is important, because with animals of many kinds in a +state of nature, both high and low in the scale, secondary sexual +characters, not in {72} any way directly connected with the organs of +reproduction, are often conspicuously present. With our domesticated +animals, also, these same secondary characters are often found to differ +greatly from the state in which they exist in the parent-species. And the +principle of inheritance as limited by sex shows how such characters might +have been first acquired and subsequently modified. + + Dr. P. Lucas, who has collected many facts on this subject, shows[160] + that when a peculiarity, in no manner connected with the reproductive + organs, appears in either parent, it is often transmitted exclusively + to the offspring of the same sex, or to a much greater number of them + than of the opposite sex. Thus, in the family of Lambert, the horn-like + projections on the skin were transmitted from the father to his sons + and grandsons alone; so it has been with other cases of ichthyosis, + with supernumerary digits, with a deficiency of digits and phalanges, + and in a lesser degree with various diseases, especially with + colour-blindness, and a haemorrhagic diathesis, that is, an extreme + liability to profuse and uncontrollable bleeding from trifling wounds. + On the other hand, mothers have transmitted, during several + generations, to their daughters alone, supernumerary and deficient + digits, colour-blindness, and other peculiarities. So that we see that + the very same peculiarity may become attached to either sex, and be + long inherited by that sex alone; but the attachment in certain cases + is much more frequent to one than the other sex. The same peculiarities + also may be promiscuously transmitted to either sex. Dr. Lucas gives + other cases, showing that the male occasionally transmits his + peculiarities to his daughters alone, and the mother to her sons alone; + but even in this case we see that inheritance is to a certain extent, + though inversely, regulated by sex. Dr. Lucas, after weighing the whole + evidence, comes to the conclusion that every peculiarity, according to + the sex in which it first appears, tends to be transmitted in a greater + or lesser degree to that sex. + + A few details from the many cases collected by Mr. Sedgwick,[161] may + be here given. Colour-blindness, from some unknown cause, shows itself + much oftener in males than in females; in upwards of two hundred cases + collected by Mr. Sedgwick, nine-tenths related to men; but it is + eminently liable to be transmitted through women. In the case given by + Dr. Earle, members of eight related families were affected during five + generations: these families consisted of sixty-one individuals, namely, + of thirty-two males, of whom nine-sixteenths were incapable of + distinguishing colour, and of twenty-nine females, of whom only + one-fifteenth were thus affected. {73} Although colour-blindness thus + generally clings to the male sex, nevertheless, in one instance in + which it first appeared in a female, it was transmitted during five + generations to thirteen individuals, all of whom were females. A + haemorrhagic diathesis, often accompanied by rheumatism, has been known + to affect the males alone during five generations, being transmitted, + however, through the females. It is said that deficient phalanges in + the fingers have been inherited by the females alone during ten + generations. In another case, a man thus deficient in both hands and + feet, transmitted the peculiarity to his two sons and one daughter; but + in the third generation, out of nineteen grandchildren, twelve sons had + the family defect, whilst the seven daughters were free. In ordinary + cases of sexual limitation, the sons or daughters inherit the + peculiarity, whatever it may be, from their father or mother, and + transmit it to their children of the same sex; but generally with the + haemorrhagic diathesis, and often with colour-blindness, and in some + other cases, the sons never inherit the peculiarity directly from their + fathers, but the daughters, and the daughters alone, transmit the + latent tendency, so that the sons of the daughters alone exhibit it. + Thus, the father, grandson, and great-great-grandson will exhibit a + peculiarity,--the grandmother, daughter, and great-granddaughter having + transmitted it in a latent state. Hence we have, as Mr. Sedgwick + remarks, a double kind of atavism or reversion; each grandson + apparently receiving and developing the peculiarity from his + grandfather, and each daughter apparently receiving the latent tendency + from her grandmother. + + From the various facts recorded by Dr. Prosper Lucas, Mr. Sedgwick, and + others, there can be no doubt that peculiarities first appearing in + either sex, though not in any way necessarily or invariably connected + with that sex, strongly tend to be inherited by the offspring of the + same sex, but are often transmitted in a latent state through the + opposite sex. + + Turning now to domesticated animals, we find that certain characters + not proper to the parent-species are often confined to, and inherited + by, one sex alone; but we do not know the history of the first + appearance of such characters. In the chapter on Sheep, we have seen + that the males of certain races differ greatly from the females in the + shape of their horns, these being absent in the ewes of some breeds, in + the development of fat in the tail in certain fat-tailed breeds, and in + the outline of the forehead. These differences, judging from the + character of the allied wild species, cannot be accounted for by + supposing that they have been derived from distinct parent-forms. There + is, also, a great difference between the horns of the two sexes in one + Indian breed of goats. The bull zebu is said to have a larger hump than + the cow. In the Scotch deer-hound the two sexes differ in size more + than in any other variety of the dog,[162] and, judging from analogy, + more than in the aboriginal parent-species. The peculiar colour called + tortoise-shell is very rarely seen in a male cat; the males of this + variety being of a rusty tint. A tendency to baldness in man before the + advent of old age is certainly inherited; and in the European, or at + least in the {74} Englishman, is an attribute of the male sex, and may + almost be ranked as an incipient secondary sexual character. + + In various breeds of the fowl the males and females often differ + greatly; and these differences are far from being the same with those + which distinguish the two sexes in the parent-species, the _Gallus + bankiva_; and consequently have originated under domestication. In + certain sub-varieties of the Game race we have the unusual case of the + hens differing from each other more than the cocks. In an Indian breed + of a white colour stained with soot, the hens invariably have black + skins, and their bones are covered by a black periosteum, whilst the + cocks are never or most rarely thus characterised. Pigeons offer a more + interesting case; for the two sexes rarely differ throughout the whole + great family, and the males and females of the parent-form, the _C. + livia_, are undistinguishable; yet we have seen that with Pouters the + male has the characteristic quality of pouting more strongly developed + than the female; and in certain sub-varieties[163] the males alone are + spotted or striated with black. When male and female English + carrier-pigeons are exhibited in separate pens, the difference in the + development of the wattle over the beak and round the eyes is + conspicuous. So that here we have instances of the appearance of + secondary sexual characters in the domesticated races of a species in + which such differences are naturally quite absent. + +On the other hand, secondary sexual characters which properly belong to the +species are sometimes quite lost, or greatly diminished, under +domestication. We see this in the small size of the tusks in our improved +breeds of the pig, in comparison with those of the wild boar. There are +sub-breeds of fowls in which the males have lost the fine flowing +tail-feathers and hackles; and others in which there is no difference in +colour between the two sexes. In some cases the barred plumage, which in +gallinaceous birds is commonly the attribute of the hen, has been +transferred to the cock, as in the cuckoo sub-breeds. In other cases +masculine characters have been partly transferred to the female, as with +the splendid plumage of the golden-spangled Hamburgh hen, the enlarged comb +of the Spanish hen, the pugnacious disposition of the Game hen, and as in +the well-developed spurs which occasionally appear in the hens of various +breeds. In Polish fowls both sexes are ornamented with a topknot, that of +the male being formed of hackle-like feathers, and this is a new male +character in the genus Gallus. On the whole, as far as I can judge, new +characters are more apt {75} to appear in the males of our domesticated +animals than in the females, and afterwards to be either exclusively or +more strongly inherited by the males. Finally, in accordance with the +principle of inheritance as limited by sex, the appearance of secondary +sexual characters in natural species offers no especial difficulty, and +their subsequent increase and modification, if of any service to the +species, would follow through that form of selection which in my 'Origin of +Species' I have called sexual selection. + +_Inheritance at corresponding periods of Life._ + +This is an important subject. Since the publication of my 'Origin of +Species,' I have seen no reason to doubt the truth of the explanation there +given of perhaps the most remarkable of all the facts in biology, namely, +the difference between the embryo and the adult animal. The explanation is, +that variations do not necessarily or generally occur at a very early +period of embryonic growth, and that such variations are inherited at a +corresponding age. As a consequence of this the embryo, even when the +parent-form undergoes a great amount of modification, is left only slightly +modified; and the embryos of widely-different animals which are descended +from a common progenitor remain in many important respects like each other +and their common progenitor. We can thus understand why embryology should +throw a flood of light on the natural system of classification, for this +ought to be as far as possible genealogical. When the embryo leads an +independent life, that is, becomes a larva, it has to be adapted to the +surrounding conditions in its structure and instincts, independently of +those of its parents; and the principle of inheritance at corresponding +periods of life renders this possible. + +This principle is, indeed, in one way so obvious that it escapes attention. +We possess a number of races of animals and plants, which, when compared +with each other and with their parent-forms, present conspicuous +differences, both in the immature and mature states. Look at the seeds of +the several kinds of peas, beans, maize, which can be propagated truly, and +see how they differ in size, colour, and shape, whilst the {76} full-grown +plants differ but little. Cabbages on the other hand differ greatly in +foliage and manner of growth, but hardly at all in their seeds; and +generally it will be found that the differences between cultivated plants +at different periods of growth are not necessarily closely connected +together, for plants may differ much in their seeds and little when +full-grown, and conversely may yield seeds hardly distinguishable, yet +differ much when full-grown. In the several breeds of poultry, descended +from a single species, differences in the eggs and chickens, in the plumage +at the first and subsequent moults, in the comb and wattles during +maturity, are all inherited. With man peculiarities in the milk and second +teeth, of which I have received the details, are inheritable, and with man +longevity is often transmitted. So again with our improved breeds of cattle +and sheep, early maturity, including the early development of the teeth, +and with certain breeds of fowl the early appearance of secondary sexual +characters, all come under the same head of inheritance at corresponding +periods. + +Numerous analogous facts could be given. The silk-moth, perhaps, offers the +best instance; for in the breeds which transmit their characters truly, the +eggs differ in size, colour, and shape;--the caterpillars differ, in +moulting three or four times, in colour, even in having a dark-coloured +mark like an eyebrow, and in the loss of certain instincts;--the cocoons +differ in size, shape, and in the colour and quality of the silk; these +several differences being followed by slight or barely distinguishable +differences in the mature moth. + +But it may be said that, if in the above cases a new peculiarity is +inherited, it must be at the corresponding stage of development; for an egg +or seed can resemble only an egg or seed, and the horn in a full-grown ox +can resemble only a horn. The following cases show inheritance at +corresponding periods more plainly, because they refer to peculiarities +which might have supervened, as far as we can see, earlier or later in +life, yet are inherited at the same period at which they first appeared. + + In the Lambert family the porcupine-like excrescences appeared in the + father and sons at the same age, namely, about nine weeks after {77} + birth.[164] In the extraordinary hairy family described by Mr. + Crawfurd,[165] children were produced during three generations with + hairy ears; in the father the hair began to grow over his body at six + years old; in his daughter somewhat earlier, namely, at one year; and + in both generations the milk teeth appeared late in life, the permanent + teeth being afterwards singularly deficient. Greyness of hair at an + unusually early age has been transmitted in some families. These cases + border on diseases inherited at corresponding periods of life, to which + I shall immediately refer. + + It is a well-known peculiarity with almond-tumbler pigeons, that the + full beauty and peculiar character of the plumage does not appear until + the bird has moulted two or three times. Neumeister describes and + figures a breed of pigeons in which the whole body is white except the + breast, neck, and head; but before the first moult all the white + feathers acquire coloured edges. Another breed is more remarkable: its + first plumage is black, with rusty-red wing-bars and a crescent-shaped + mark on the breast; these marks then became white, and remain so during + three or four moults; but after this period the white spreads over the + body, and the bird loses its beauty.[166] Prize canary-birds have their + wings and tail black: "this colour, however, is only retained until the + first moult, so that they must be exhibited ere the change takes place. + Once moulted, the peculiarity has ceased. Of course all the birds + emanating from this stock have black wings and tails the first + year."[167] A curious and somewhat analogous account has been + given[168] of a family of wild pied rooks which were first observed in + 1798, near Chalfont, and which every year from that date up to the + period of the published notice, viz. 1837, "have several of their brood + particoloured, black and white. This variegation of the plumage, + however, disappears with the first moult; but among the next young + families there are always a few pied ones." These changes of plumage, + which appear and are inherited at various corresponding periods of life + in the pigeon, canary-bird, and rook, are remarkable, because the + parent-species undergo no such change. + + Inherited diseases afford evidence in some respects of less value than + the foregoing cases, because diseases are not necessarily connected + with any change in structure; but in other respects of more value, + because the periods have been more carefully observed. Certain diseases + are communicated to the child apparently by a process like inoculation, + and the child is from the first affected; such cases may be here passed + over. Large classes of diseases usually appear at certain ages, such as + St. Vitus's dance in youth, consumption in early mid-life, gout later, + and apoplexy still later; and these are naturally inherited at the same + period. But even in diseases of this class, instances have been + recorded, as with St. Vitus's {78} dance, showing that an unusually + early or late tendency to the disease is inheritable.[169] In most + cases the appearance of any inherited disease is largely determined by + certain critical periods in each person's life, as well as by + unfavourable conditions. There are many other diseases, which are not + attached to any particular period, but which certainly tend to appear + in the child at about the same age at which the parent was first + attacked. An array of high authorities, ancient and modern, could be + given in support of this proposition. The illustrious Hunter believed + in it; and Piorry[170] cautions the physician to look closely to the + child at the period when any grave inheritable disease attacked the + parent. Dr. Prosper Lucas,[171] after collecting facts from every + source, asserts that affections of all kinds, though not related to any + particular period of life, tend to reappear in the offspring at + whatever period of life they first appeared in the progenitor. + + As the subject is important, it may be well to give a few instances, + simply as illustrations, not as proof; for proof, recourse must be had + to the authorities above quoted. Some of the following cases have been + selected for the sake of showing that, when a slight departure from the + rule occurs, the child is affected somewhat earlier in life than the + parent. In the family of Le Compte blindness was inherited during three + generations, and no less than thirty-seven children and grandchildren + were all affected at about the same age, namely seventeen or + eighteen.[172] In another case a father and his four children all + became blind at twenty-one years old; in another, a grandmother grew + blind at thirty-five, her daughter at nineteen, and three grandchildren + at the ages of thirteen and eleven.[173] So with deafness, two + brothers, their father and paternal grandfather, all became deaf at the + age of forty.[174] + + Esquirol gives several striking instances of insanity coming on at the + same age, as that of a grandfather, father, and son, who all committed + suicide near their fiftieth year. Many other cases could be given, as + of a whole family who became insane at the age of forty.[175] Other + cerebral affections sometimes follow the same rule,--for instance, + epilepsy and apoplexy. A woman died of the latter disease when + sixty-three years old; one of her daughters at forty-three, and the + other at sixty-seven: the latter had twelve children, who all died from + tubercular meningitis.[176] I mention this latter case because it + illustrates a frequent occurrence, namely, a change in the precise + nature of an inherited disease, though still affecting the same organ. + + {79} + + Asthma has attacked several members of the same family when forty years + old, and other families during infancy. The most different diseases, as + angina pectoris, stone in the bladder, and various affections of the + skin, have appeared in successive generations at nearly the same age. + The little finger of a man began from some unknown cause to grow + inwards, and the same finger in his two sons began at the same age to + bend inwards in a similar manner. Strange and inexplicable neuralgic + affections have caused parents and children to suffer agonies at about + the same period of life.[177] + + I will give only two other cases, which are interesting as illustrating + the disappearance as well as the appearance of disease at the same age. + Two brothers, their father, their paternal uncles, seven cousins, and + their paternal grandfather, were all similarly affected by a + skin-disease, called pityriasis versicolor; "the disease, strictly + limited to the males of the family (though transmitted through the + females), usually appeared at puberty, and disappeared at about the age + of forty or forty-five years." The second case is that of four + brothers, who when about twelve years old suffered almost every week + from severe headaches, which were relieved only by a recumbent position + in a dark room. Their father, paternal uncles, paternal grandfather, + and paternal granduncles all suffered in the same way from headaches, + which ceased at the age of fifty-four or fifty-five in all those who + lived so long. None of the females of the family were affected.[178] + +It is impossible to read the foregoing accounts, and the many others which +have been recorded, of diseases coming on during three or even more +generations, at the same age in several members of the same family, +especially in the case of rare affections in which the coincidence cannot +be attributed to chance, and doubt that there is a strong tendency to +inheritance in disease at corresponding periods of life. When the rule +fails, the disease is apt to come on earlier in the child than in the +parent; the exceptions in the other direction being vey much rarer. Dr. +Lucas[179] alludes to several cases of inherited diseases coming on at an +earlier period. I have already given one striking instance with blindness +during three generations; and Mr. Bowman remarks that this frequently +occurs with cataract. With cancer there seems to be a peculiar liability to +earlier inheritance: Mr. Paget, who has particularly {80} attended to this +subject, and tabulated a large number of cases, informs me that he believes +that in nine cases out of ten the later generation suffers from the disease +at an earlier period than the previous generation. He adds, "In the +instances in which the opposite relation holds, and the members of later +generations have cancer at a later age than their predecessors, I think it +will be found that the non-cancerous parents have lived to extreme old +ages." So that the longevity of a non-affected parent seems to have the +power of determining in the offspring the fatal period; and we thus +apparently get another element of complexity in inheritance. + +The facts, showing that with certain diseases the period of inheritance +occasionally or even frequently advances, are important with respect to the +general descent-theory, for they render it in some degree probable that the +same thing would occur with ordinary modifications of structure. The final +result of a long series of such advances would be the gradual obliteration +of characters proper to the embryo and larva, which would thus come to +resemble more and more closely the mature parent-form. But any structure +which was of service to the embryo or larva would be preserved by the +destruction at this stage of growth of each individual which manifested any +tendency to lose at too early an age its own proper character. + +Finally, from the numerous races of cultivated plants and domestic animals, +in which the seed or eggs, the young or old, differ from each other and +from their parent-species;--from the cases in which new characters have +appeared at a particular period, and afterwards have been inherited at the +same period;--and from what we know with respect to disease, we must +believe in the truth of the great principle of inheritance at corresponding +periods of life. + + * * * * * + +_Summary of the three preceding Chapters._--Strong as is the force of +inheritance, it allows the incessant appearance of new characters. These, +whether beneficial or injurious, of the most trifling importance, such as a +shade of colour in a flower, a coloured lock of hair, or a mere gesture; or +of the highest importance, as when affecting the brain or an organ so +perfect {81} and complex as the eye; or of so grave a nature as to deserve +to be called a monstrosity, or so peculiar as not to occur normally in any +member of the same natural class, are all sometimes strongly inherited by +man, the lower animals, and plants. In numberless cases it suffices for the +inheritance of a peculiarity that one parent alone should be thus +characterised. Inequalities in the two sides of the body, though opposed to +the law of symmetry, may be transmitted. There is a considerable body of +evidence showing that even mutilations, and the effects of accidents, +especially or perhaps exclusively when followed by disease, are +occasionally inherited. There can be no doubt that the evil effects of +long-continued exposure in the parent to injurious conditions are sometimes +transmitted to the offspring. So it is, as we shall see in a future +chapter, with the effects of the use and disuse of parts, and of mental +habits. Periodical habits are likewise transmitted, but generally, as it +would appear, with little force. + +Hence we are led to look at inheritance as the rule, and non-inheritance as +the anomaly. But this power often appears to us in our ignorance to act +capriciously, transmitting a character with inexplicable strength or +feebleness. The very same peculiarity, as the weeping habit of trees, +silky-feathers, &c., may be inherited either firmly or not at all by +different members of the same group, and even by different individuals of +the same species, though treated in the same manner. In this latter case we +see that the power of transmission is a quality which is merely individual +in its attachment. As with single characters, so it is with the several +concurrent slight differences which distinguish sub-varieties or races; for +of these, some can be propagated almost as truly as species, whilst others +cannot be relied on. The same rule holds good with plants, when propagated +by bulbs, offsets, &c., which in one sense still form parts of the same +individual, for some varieties retain or inherit through successive +bud-generations their character far more truly than others. + +Some characters not proper to the parent-species have certainly been +inherited from an extremely remote epoch, and may therefore be considered +as firmly fixed. But it is doubtful whether length of inheritance in itself +gives fixedness of character; {82} though the chances are obviously in +favour of any character which has long been transmitted true or unaltered, +still being transmitted true as long as the conditions of life remain the +same. We know that many species, after having retained the same character +for countless ages, whilst living under their natural conditions, when +domesticated have varied in the most diversified manner, that is, have +failed to transmit their original form; so that no character appears to be +absolutely fixed. We can sometimes account for the failure of inheritance +by the conditions of life being opposed to the development of certain +characters; and still oftener, as with plants cultivated by grafts and +buds, by the conditions causing new and slight modifications incessantly to +appear. In this latter case it is not that inheritance wholly fails, but +that new characters are continually superadded. In some few cases, in which +both parents are similarly characterised, inheritance seems to gain so much +force by the combined action of the two parents, that it counteracts its +own power, and a new modification is the result. + +In many cases the failure of the parents to transmit their likeness is due +to the breed having been at some former period crossed; and the child takes +after his grandparent or more remote ancestor of foreign blood. In other +cases, in which the breed has not been crossed, but some ancient character +has been lost through variation, it occasionally reappears through +reversion, so that the parents apparently fail to transmit their own +likeness. In all cases, however, we may safely conclude that the child +inherits all its characters from its parents, in whom certain characters +are latent, like the secondary sexual characters of one sex in the other. +When, after a long succession of bud-generations, a flower or fruit becomes +separated into distinct segments, having the colours or other attributes of +both parent-forms, we cannot doubt that these characters were latent in the +earlier buds, though they could not then be detected, or could be detected +only in an intimately commingled state. So it is with animals of crossed +parentage, which with advancing years occasionally exhibit characters +derived from one of their two parents, of which not a trace could at first +be perceived. Certain monstrosities, which resemble what naturalists call +the typical form of the group in question, {83} apparently come under the +same law of reversion. It is assuredly an astonishing fact that the male +and female sexual elements, that buds, and even full-grown animals, should +retain characters, during several generations in the case of crossed +breeds, and during thousands of generations in the case of pure breeds, +written as it were in invisible ink, yet ready at any time to be evolved +under the requisite conditions. + +What these conditions are, we do not in many cases at all know. But the act +of crossing in itself, apparently from causing some disturbance in the +organisation, certainly gives a strong tendency to the reappearance of +long-lost characters, both corporeal and mental, independently of those +derived from the cross. A return of any species to its natural conditions +of life, as with feral animals and plants, favours reversion; though it is +certain that this tendency exists, we do not know how far it prevails, and +it has been much exaggerated. On the other hand, the crossed offspring of +plants which have had their organisation disturbed by cultivation, are more +liable to reversion than the crossed offspring of species which have always +lived under their natural conditions. + +When distinguishable individuals of the same family, or races, or species +are crossed, we see that the one is often prepotent over the other in +transmitting its own character. A race may possess a strong power of +inheritance, and yet when crossed, as we have seen with trumpeter-pigeons, +yield to the prepotency of every other race. Prepotentcy of transmission +may be equal in the two sexes of the same species, but often runs more +strongly in one sex. It plays an important part in determining the rate at +which one race can be modified or wholly absorbed by repeated crosses with +another. We can seldom tell what makes one race or species prepotent over +another; but it sometimes depends on the same character being present and +visible in one parent, and latent or potentially present in the other. + +Characters may first appear in either sex, but oftener in the male than in +the female, and afterwards be transmitted to the offspring of the same sex. +In this case we may feel confident that the peculiarity in question is +really present though latent in the opposite sex; hence the father may +transmit through his daughter any character to his grandson; and the mother +{84} conversely to her granddaughter. We thus learn, and the fact is an +important one, that transmission and development are distinct powers. +Occasionally these two powers seem to be antagonistic, or incapable of +combination in the same individual; for several cases have been recorded in +which the son has not directly inherited a character from his father, or +directly transmitted it to his son, but has received it by transmission +through his non-affected mother, and transmitted it through his +non-affected daughter. Owing to inheritance being limited by sex, we can +see how secondary sexual characters may first have arisen under nature; +their preservation and accumulation being dependent on their service to +either sex. + +At whatever period of life a new character first appears, it generally +remains latent in the offspring until a corresponding age is attained, and +then it is developed. When this rule fails, the child generally exhibits +the character at an earlier period than the parent. On this principle of +inheritance at corresponding periods, we can understand how it is that most +animals display from the germ to maturity such a marvellous succession of +characters. + +Finally, though much remains obscure with respect to Inheritance, we may +look at the following laws as fairly well established. Firstly, a tendency +in every character, new and old, to be transmitted by seminal and bud +generation, though often counteracted by various known and unknown causes. +Secondly, reversion or atavism, which depends on transmission and +development being distinct powers: it acts in various degrees and manners +through both seminal and bud generation. Thirdly, prepotency of +transmission, which may be confined to one sex, or be common to both sexes +of the prepotent form. Fourthly, transmission, limited by sex, generally to +the same sex in which the inherited character first appeared. Fifthly, +inheritance at corresponding periods of life, with some tendency to the +earlier development of the inherited character. In these laws of +Inheritance, as displayed under domestication, we see an ample provision +for the production, through variability and natural selection, of new +specific forms. + + * * * * * + + +{85} + +CHAPTER XV. + +ON CROSSING. + + FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED + BREEDS--WHEN THE NUMBERS OF TWO COMMINGLING BREEDS ARE UNEQUAL, ONE + ABSORBS THE OTHER--THE RATE OF ABSORPTION DETERMINED BY PREPOTENCY OF + TRANSMISSION, BY THE CONDITIONS OF LIFE, AND BY NATURAL SELECTION--ALL + ORGANIC BEINGS OCCASIONALLY INTERCROSS; APPARENT EXCEPTIONS--ON CERTAIN + CHARACTERS INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE WHICH HAVE + SUDDENLY APPEARED IN THE INDIVIDUAL--ON THE MODIFICATION OF OLD RACES, + AND THE FORMATION OF NEW RACES, BY CROSSING--SOME CROSSED RACES HAVE + BRED TRUE FROM THEIR FIRST PRODUCTION--ON THE CROSSING OF DISTINCT + SPECIES IN RELATION TO THE FORMATION OF DOMESTIC RACES. + +In the two previous chapters, when discussing reversion and prepotency, I +was necessarily led to give many facts on crossing. In the present chapter +I shall consider the part which crossing plays in two opposed +directions,--firstly, in obliterating characters, and consequently in +preventing the formation of new races; and secondly, in the modification of +old races, or in the formation of new and intermediate races, by a +combination of characters. I shall also show that certain characters are +incapable of fusion. + +The effects of free or uncontrolled breeding between the members of the +same variety or of closely allied varieties are important; but are so +obvious that they need not be discussed at much length. It is free +intercrossing which chiefly gives uniformity, both under nature and under +domestication, to the individuals of the same species or variety, when they +live mingled together and are not exposed to any cause inducing excessive +variability. The prevention of free crossing, and the intentional matching +of individual animals, are the corner-stones of the breeder's art. No man +in his senses would expect to improve or modify a breed in any particular +manner, or keep an old breed true and distinct, unless he separated his +animals. The killing of inferior animals in each generation comes to the +{86} same thing as their separation. In savage and semi-civilised +countries, where the inhabitants have not the means of separating their +animals, more than a single breed of the same species rarely or never +exists. In former times, even in a country so civilised as North America, +there were no distinct races of sheep, for all had been mingled +together.[180] The celebrated agriculturist Marshall[181] remarks that +"sheep that are kept within fences, as well as shepherded flocks in open +countries, have generally a similarity, if not a uniformity, of character +in the individuals of each flock;" for they breed freely together, and are +prevented from crossing with other kinds; whereas in the unenclosed parts +of England the unshepherded sheep, even of the same flock, are far from +true or uniform, owing to various breeds having mingled and crossed. We +have seen that the half-wild cattle in the several British parks are +uniform in character in each; but in the different parks, from not having +mingled and crossed during many generations, they differ in a slight +degree. + +We cannot doubt that the extraordinary number of varieties and +sub-varieties of the pigeon, amounting to at least one hundred and fifty, +is partly due to their remaining, differently from other domesticated +birds, paired for life when once matched. On the other hand, breeds of cats +imported into this country soon disappear, for their nocturnal and rambling +habits render it hardly possible to prevent free crossing. Rengger[182] +gives an interesting case with respect to the cat in Paraguay: in all the +distant parts of the kingdom it has assumed, apparently from the effects of +the climate, a peculiar character, but near the capital this change has +been prevented, owing, as he asserts, to the native animal frequently +crossing with cats imported from Europe. In all cases like the foregoing, +the effects of an occasional cross will be augmented by the increased +vigour and fertility of the crossed offspring, of which fact evidence will +hereafter be given; for this will lead to the mongrels increasing more +rapidly than the pure parent-breeds. + +{87} + +When distinct breeds are allowed to cross freely, the result will be a +heterogenous body; for instance, the dogs in Paraguay are far from uniform, +and can no longer be affiliated to their parent-races.[183] The character +which a crossed body of animals will ultimately assume must depend on +several contingencies,--namely, on the relative numbers of the individuals +belonging to the two or more races which are allowed to mingle; on the +prepotency of one race over the other in the transmission of character; and +on the conditions of life to which they are exposed. When two commingled +breeds exist at first in nearly equal numbers, the whole will sooner or +later become intimately blended, but not so soon, both breeds being equally +favoured in all respects, as might have been expected. The following +calculation[184] shows that this is the case: if a colony with an equal +number of black and white men were founded, and we assume that they marry +indiscriminately, are equally prolific, and that one in thirty annually +dies and is born; then "in 65 years the number of blacks, whites, and +mulattoes would be equal. In 91 years the whites would be 1-10th, the +blacks 1-10th, and the mulattoes, or people of intermediate degrees of +colour, 8-10ths of the whole number. In three centuries not 1-100th part of +the whites would exist." + +When one of two mingled races exceeds the other greatly in number, the +latter will soon be wholly, or almost wholly, absorbed and lost.[185] Thus +European pigs and dogs have been largely introduced into the islands of the +Pacific Ocean, and the native races have been absorbed and lost in the +course of about fifty or sixty years;[186] but the imported races no doubt +were favoured. Rats may be considered as semi-domesticated animals. Some +snake-rats (_Mus alexandrinus_) escaped in the Zoological Gardens of +London, "and for a long time afterwards the keepers frequently caught +cross-bred rats, at first half-breds, afterwards with less and less of the +character of the snake-rat, till at length all traces of it +disappeared."[187] On the other hand, {88} in some parts of London, +especially near the docks, where fresh rats are frequently imported, an +endless variety of intermediate forms may be found between the brown, +black, and snake rat, which are all three usually ranked as distinct +species. + +How many generations are necessary for one species or race to absorb +another by repeated crosses has often been discussed;[188] and the +requisite number has probably been much exaggerated. Some writers have +maintained that a dozen, or score, or even more generations, are necessary; +but this in itself is improbable, for in the tenth generation there will be +only 1-1024th part of foreign blood in the offspring. Gaertner found,[189] +that with plants one species could be made to absorb another in from three +to five generations, and he believes that this could always be effected in +from six to seventh generations. In one instance, however, Koelreuter[190] +speaks of the offspring of _Mirabilis vulgaris_, crossed during eight +successive generations by _M. longiflora_, as resembling this latter +species so closely, that the most scrupulous observer could detect "vix +aliquam notabilem differentiam;"--he succeeded, as he says, "ad plenariam +fere transmutationem." But this expression shows that the act of absorption +was not even then absolutely complete, though these crossed plants +contained only the 1-256th part of _M. vulgaris_. The conclusions of such +accurate observers as Gaertner and Koelreuter are of far higher worth than +those made without scientific aim by breeders. The most remarkable +statement which I have met with of the persistent endurance of the effects +of a single cross is given by Fleischmann,[191] who, in reference to German +sheep, says "that the original coarse sheep have 5500 fibres of wool on a +square inch; grades of the third or fourth Merino cross produced about +8000, the twentieth cross 27,000, the perfect pure Merino blood 40,000 to +48,000." So that in this case common German sheep crossed twenty times +successively with Merinos have not by any means acquired wool as fine as +that of the pure breed. In all cases, the rate of absorption will {89} +depend largely on the conditions of life being favourable to any particular +character; and we may suspect that there would be under the climate of +Germany a constant tendency to degeneration in the wool of Merinos, unless +prevented by careful selection; and thus perhaps the foregoing remarkable +case may be explained. The rate of absorption must also depend on the +amount of distinguishable difference between the two forms which are +crossed, and especially, as Gaertner insists, on prepotency of transmission +in the one form over the other. We have seen in the last chapter that one +of two French breeds of sheep yielded up its character, when crossed with +Merinos, very much slower than the other; and the common German sheep +referred to by Fleischmann may present an analogous case. But in all cases +there will be during many subsequent generations more or less liability to +reversion, and it is this fact which has probably led authors to maintain +that a score or more of generations are requisite for one race to absorb +another. In considering the final result of the commingling of two or more +breeds, we must not forget that the act of crossing in itself tends to +bring back long-lost characters not proper to the immediate parent-forms. + +With respect to the influence of the conditions of life on any two breeds +which are allowed to cross freely, unless both are indigenous and have long +been accustomed to the country where they live, they will, in all +probability, be unequally affected by the conditions, and this will modify +the result. Even with indigenous breeds, it will rarely or never occur that +both are equally well adapted to the surrounding circumstances; more +especially when permitted to roam freely, and not carefully tended, as will +generally be the case with breeds allowed to cross. As a consequence of +this, natural selection will to a certain extent come into action, and the +best fitted will survive, and this will aid in determining the ultimate +character of the commingled body. + +How long a time it would require before such a crossed body of animals +would assume within a limited area a uniform character no one can say; that +they would ultimately become uniform from free intercrossing, and from the +survival of the fittest, we may feel assured; but the character thus +acquired would rarely or never, as we may infer from the several previous +{90} considerations, be exactly intermediate between that of the two +parent-breeds. With respect to the very slight differences by which the +individuals of the same sub-variety, or even of allied varieties, are +characterised, it is obvious that free crossing would soon obliterate such +small distinctions. The formation of new varieties, independently of +selection, would also thus be prevented; except when the same variation +continually recurred from the action of some strongly predisposing cause. +Hence we may conclude that free crossing has in all cases played an +important part in giving to all the members of the same domestic race, and +of the same natural species, uniformity of character, though largely +modified by natural selection and by the direct action of the surrounding +conditions. + +_On the possibility of all organic beings occasionally intercrossing._--But +it may be asked, can free crossing occur with hermaphrodite animals and +plants? All the higher animals, and the few insects which have been +domesticated, have separated sexes, and must inevitably unite for each +birth. With respect to the crossing of hermaphrodites, the subject is too +large for the present volume, and will be more properly treated in a +succeeding work. In my 'Origin of Species,' however, I have given a short +abstract of the reasons which induce me to believe that all organic beings +occasionally cross, though perhaps in some cases only at long intervals of +time.[192] I will here just recall the fact that many plants, though +hermaphrodite in structure, are unisexual in function;--such as those +called by C. K. Sprengel _dichogamous_, in which the pollen and stigma of +the same flower are matured at different periods; or those called by me +_reciprocally dimorphic_, in which the flower's own pollen is not fitted to +fertilise its own stigma; or again, the many kinds in which curious +mechanical contrivances exist, effectually preventing self-fertilisation. +There are, however, many hermaphrodite plants which are not in any way +specially constructed to favour intercrossing, but which nevertheless +commingle almost as freely as animals with separated sexes. This is the +case with cabbages, radishes, and onions, as I know from {91} having +experimented on them: even the peasants of Liguria say that cabbages must +be prevented "from falling in love" with each other. In the orange tribe, +Gallesio[193] remarks that the amelioration of the various kinds is checked +by their continual and almost regular crossing. So it is with numerous +other plants. + +Nevertheless some cultivated plants can be named which rarely intercross, +as the common pea, or which never intercross, as I have reason to believe +is the case with the sweet-pea (_Lathyrus odoratus_); yet the structure of +these flowers certainly favours an occasional cross. The varieties of the +tomato and aubergine (_Solanum_) and pimenta (_Pimenta vulgaris?_) are +said[194] never to cross, even when growing alongside each other. But it +should be observed that these are all exotic plants, and we do not know how +they would behave in their native country when visited by the proper +insects. + +It must also be admitted that some few natural species appear under our +present state of knowledge to be perpetually self-fertilised, as in the +case of the Bee Ophrys (_O. apifera_), though adapted in its structure to +be occasionally crossed. The _Leersia oryzoides_ produces minute enclosed +flowers which cannot possibly be crossed, and these alone, to the exclusion +of the ordinary flowers, have as yet been known to yield seed.[195] A few +additional and analogous cases could be advanced. But these facts do not +make me doubt that it is a general law of nature that the individuals of +the same species occasionally intercross, and that some great advantage is +derived from this act. It is well known (and I shall hereafter have to give +instances) that some plants, both indigenous and naturalised, rarely or +never produce flowers; or, if they flower, never produce seeds. But no one +is thus led to doubt that it is a general law of nature that phanerogamic +plants should produce flowers, and that these flowers should produce seed. +When they fail, we believe that such plants would perform their proper +functions under different conditions, or that they formerly did so and will +do so again. On analogous grounds, I believe that the few flowers {92} +which do not now intercross, either would do so under different conditions, +or that they formerly fertilised each other at intervals--the means for +effecting this being generally still retained--and they will do so again at +some future period, unless indeed they become extinct. On this view alone, +many points in the structure and action of the reproductive organs in +hermaphrodite plants and animals are intelligible,--for instance, the male +and female organs never being so completely enclosed as to render access +from without impossible. Hence we may conclude that the most important of +all the means for giving uniformity to the individuals of the same species, +namely, the capacity of occasionally intercrossing, is present, or has been +formerly present, with all organic beings. + + _On certain Characters not blending._--When two breeds are crossed + their characters usually become intimately fused together; but some + characters refuse to blend, and are transmitted in an unmodified state + either from both parents or from one. When grey and white mice are + paired, the young are not piebald nor of an intermediate tint, but are + pure white or of the ordinary grey colour: so it is when white and + common collared turtle-doves are paired. In breeding Game fowls, a + great authority, Mr. J. Douglas, remarks, "I may here state a strange + fact: if you cross a black with a white game, you get birds of both + breeds of the clearest colour." Sir R. Heron crossed during many years + white, black, brown, and fawn-coloured Angora rabbits, and never once + got these colours mingled in the same animal, but often all four + colours in the same litter.[196] Additional cases could be given, but + this form of inheritance is very far from universal even with respect + to the most distinct colours. When turnspit dogs and ancon sheep, both + of which have dwarfed limbs, are crossed with common breeds, the + offspring are not intermediate in structure, but take after either + parent. When tailless or hornless animals are crossed with perfect + animals, it frequently, but by no means invariably, happens that the + offspring are {93} either perfectly furnished with these organs or are + quite destitute of them. According to Rengger, the hairless condition + of the Paraguay dog is either perfectly or not at all transmitted to + its mongrel offspring; but I have seen one partial exception in a dog + of this parentage which had part of its skin hairy, and part naked; the + parts being distinctly separated as in a piebald animal. When Dorking + fowls with five toes are crossed with other breeds, the chickens often + have five toes on one foot and four on the other. Some crossed pigs + raised by Sir R. Heron between the solid-hoofed and common pig had not + all four feet in an intermediate condition, but two feet were furnished + with properly divided, and two with united hoofs. + + Analogous facts have been observed with plants: Major Trevor Clarke + crossed the little, glabrous-leaved, annual stock (_Matthiola_), with + pollen of a large, red-flowered, rough-leaved, biennial stock, called + _cocardeau_ by the French, and the result was that half the seedlings + had glabrous and the other half rough leaves, but none had leaves in an + intermediate state. That the glabrous seedlings were the product of the + rough-leaved variety, and not accidentally of the mother-plant's own + pollen, was shown by their tall and strong habit of growth.[197] In the + succeeding generations raised from the rough-leaved crossed seedlings, + some glabrous plants appeared, showing that the glabrous character, + though incapable of blending with and modifying the rough leaves, was + all the time latent in this family of plants. The numerous plants + formerly referred to, which I raised from reciprocal crosses between + the peloric and common Antirrhinum, offer a nearly parallel case; for + in the first generation all the plants resembled the common form, and + in the next generation, out of one hundred and thirty-seven plants, two + alone were in an intermediate condition, the others perfectly + resembling either the peloric or common form. Major Trevor Clarke also + fertilised the above-mentioned red-flowered stock with pollen from the + purple Queen stock, and about half the seedlings scarcely differed in + habit, and not at all in the red colour of the flower, from the + mother-plant, the other half bearing blossoms of a rich purple, closely + like those of the paternal plant. Gaertner crossed many white and + yellow-flowered species and varieties of Verbascum; and these colours + were never blended, but the offspring bore either pure white or pure + yellow blossoms; the former in the larger proportion.[198] Dr. Herbert + raised many seedlings, as he informed me, from Swedish turnips crossed + by two other varieties, and these never produced flowers of an + intermediate tint, but always like one of their parents. I fertilised + the purple sweet-pea (_Lathyrus odoratus_), which has a dark + reddish-purple standard-petal and violet-coloured wings and keel, with + pollen of the painted-lady sweet-pea, which has a pale cherry-coloured + standard, and almost white wings and keel; and from the same pod I + twice raised plants perfectly resembling both sorts; the greater number + resembling the father. So perfect was the resemblance, that I should + have thought there had {94} been some mistake, if the plants which were + at first identical with the paternal variety, namely, the painted-lady, + had not later in the season produced, as mentioned in a former chapter, + flowers blotched and streaked with dark purple. I raised grandchildren + and great-grandchildren from these crossed plants, and they continued + to resemble the painted-lady, but during the later generations became + rather more blotched with purple, yet none reverted completely to the + original mother-plant, the purple sweet-pea. The following case is + slightly different, but still shows the same principle: Naudin[199] + raised numerous hybrids between the yellow _Linaria vulgaris_ and the + purple _L. purpurea_, and during three successive generations the + colours kept distinct in different parts of the same flower. + + From such cases as the foregoing, in which the offspring of the first + generation perfectly resemble either parent, we come by a small step to + those cases in which differently coloured flowers borne on the same + root resemble both parents, and by another step to those in which the + same flower or fruit is striped or blotched with the two parental + colours, or bears a single stripe of the colour or other characteristic + quality of one of the parent-forms. With hybrids and mongrels it + frequently or even generally happens that one part of the body + resembles more or less closely one parent and another part the other + parent; and here again some resistance to fusion, or, what comes to the + same thing, some mutual affinity between the organic atoms of the same + nature, apparently comes into play, for otherwise all parts of the body + would be equally intermediate in character. So again, when the + offspring of hybrids or mongrels, which are themselves nearly + intermediate in character, revert either wholly or by segments to their + ancestors, the principle of the affinity of similar, or the repulsion + of dissimilar atoms, must come into action. To this principle, which + seems to be extremely general, we shall recur in the chapter on + pangenesis. + + It is remarkable, as has been strongly insisted upon by Isidore + Geoffroy St. Hilaire in regard to animals, that the transmission of + characters without fusion occurs most rarely when species are crossed; + I know of one exception alone, namely, with the hybrids naturally + produced between the common and hooded crow (_Corvus corone_ and + _cornix_), which, however, are closely allied species, differing in + nothing except colour. Nor have I met with any well-ascertained cases + of transmission of this kind, even when one form is strongly prepotent + over another, when two races are crossed which have been slowly formed + by man's selection, and therefore resemble to a certain extent natural + species. Such cases as puppies in the same litter closely resembling + two distinct breeds, are probably due to super-foetation,--that is, to + the influence of two fathers. All the characters above enumerated, + which are transmitted in a perfect state to some of the offspring and + not to others,--such as distinct colours, nakedness of skin, smoothness + of leaves, absence of horns or tail, additional toes, pelorism, dwarfed + structure, &c.,--have all been known to appear suddenly in individual + animals and plants. From this fact, and from the several slight, + aggregated differences which distinguish domestic races and species + from {95} each other, not being liable to this peculiar form of + transmission, we may conclude that it is in some way connected with the + sudden appearance of the characters in question. + +_On the Modification of old Races and the Formation of new Races by +Crossing._--We have hitherto chiefly considered the effects of crossing in +giving uniformity of character; we must now look to an opposite result. +There can be no doubt that crossing, with the aid of rigorous selection +during several generations, has been a potent means in modifying old races, +and in forming new ones. Lord Orford crossed his famous stud of greyhounds +once with the bulldog, which breed was chosen from being deficient in +scenting powers, and from having what was wanted, courage and perseverance. +In the course of six or seven generations all traces of the external form +of the bulldog were eliminated, but courage and perseverance remained. +Certain pointers have been crossed, as I hear from the Rev. W. D. Fox, with +the foxhound, to give them dash and speed. Certain strains of Dorking fowls +have had a slight infusion of Game blood; and I have known a great fancier +who on a single occasion crossed his turbit-pigeons with barbs, for the +sake of gaining greater breadth of beak. + +In the foregoing cases breeds have been crossed once, for the sake of +modifying some particular character; but with most of the improved races of +the pig, which now breed true, there have been repeated crosses,--for +instance, the improved Essex owes its excellence to repeated crosses with +the Neapolitan, together probably with some infusion of Chinese blood.[200] +So with our British sheep: almost all the races, except the Southdown, have +been largely crossed; "this, in fact, has been the history of our principal +breeds."[201] To give an example, the "Oxfordshire Downs" now rank as an +established breed.[202] They were produced about the year 1830 by crossing +"Hampshire and in some instances Southdown ewes with Cotswold rams:" now +the Hampshire ram was itself produced by repeated crosses between the +native {96} Hampshire sheep and Southdowns; and the long-woolled Cotswold +were improved by crosses with the Leicester, which latter again is believed +to have been a cross between several long-woolled sheep. Mr. Spooner, after +considering the various cases which have been carefully recorded, concludes +"that from a judicious pairing of cross-bred animals it is practicable to +establish a new breed." On the Continent the history of several crossed +races of cattle and of other animals has been well ascertained. To give one +instance: the King of Wurtemberg, after twenty-five years' careful +breeding, that is after six or seven generations, made a new breed of +cattle from a cross between a Dutch and Swiss breed, combined with other +breeds.[203] The Sebright bantam, which breeds as true as any other kind of +fowl, was formed about sixty years ago by a complicated cross.[204] Dark +Brahmas, which are believed by some fanciers to constitute a distinct +species, were undoubtedly formed[205] in the United States, within a recent +period, by a cross between Chittagongs and Cochins. With plants I believe +there is little doubt that some kinds of turnips, now extensively +cultivated, are crossed races; and the history of a variety of wheat which +was raised from two very distinct varieties, and which after six years' +culture presented an even sample, has been recorded on good authority.[206] + +Until quite lately, cautious and experienced breeders, though not averse to +a single infusion of foreign blood, were almost universally convinced that +the attempt to establish a new race, intermediate between two widely +distinct races, was hopeless: "they clung with superstitious tenacity to +the doctrine of purity of blood, believing it to be the ark in which alone +true safety could be found."[207] Nor was this conviction unreasonable: +when two distinct races are crossed, the offspring of the first generation +are generally nearly uniform in character; but even this sometimes fails to +be the case, especially with crossed dogs and fowls, the young of which +from the first are sometimes much {97} diversified. As cross-bred animals +are generally of large size and vigorous, they have been raised in great +numbers for immediate consumption. But for breeding they are found to be +utterly useless; for though they may be themselves uniform in character, +when paired together they yield during many generations offspring +astonishingly diversified. The breeder is driven to despair, and concludes +that he will never form an intermediate race. But from the cases already +given, and from others which have been recorded, it appears that patience +alone is necessary; as Mr. Spooner remarks, "nature opposes no barrier to +successful admixture; in the course of time, by the aid of selection and +careful weeding, it is practicable to establish a new breed." After six or +seven generations the hoped-for result will in most cases be obtained; but +even then an occasional reversion, or failure to keep true, may be +expected. The attempt, however, will assuredly fail if the conditions of +life be decidedly unfavourable to the characters of either +parent-breed.[208] + +Although the grandchildren and succeeding generations of cross-bred animals +are generally variable in an extreme degree, some curious exceptions to the +rule have been observed, both with crossed races and species. Thus Boitard +and Corbie[209] assert that from a Pouter and a Runt "a Cavalier will +appear, which we have classed amongst pigeons of pure race, because it +transmits all its qualities to its posterity." The editor of the 'Poultry +Chronicle'[210] bred some bluish fowls from a black Spanish cock and a +Malay hen; and these remained true to colour "generation after generation." +The Himalayan breed of rabbits was certainly formed by crossing two +sub-varieties of the silver-grey rabbit; although it suddenly assumed its +present character, which differs much from that of either parent-breed, yet +it has ever since been easily and truly propagated. I crossed some Labrador +and Penguin ducks, and recrossed the mongrels with Penguins; afterwards, +most of the ducks reared during three generations were nearly uniform in +character, being brown with a white crescentic mark on the lower part of +the breast, {98} and with some white spots at the base of the beak; so that +by the aid of a little selection a new breed might easily have been formed. +In regard to crossed varieties of plants, Mr. Beaton remarks[211] that +"Melville's extraordinary cross between the Scotch kale and an early +cabbage is as true and genuine as any on record;" but in this case no doubt +selection was practised. Gaertner[212] has given five cases of hybrids, in +which the progeny kept constant; and hybrids between _Dianthus armeria_ and +_deltoides_ remained true and uniform to the tenth generation. Dr. Herbert +likewise showed me a hybrid from two species of Loasa which from its first +production had kept constant during several generations. + +We have seen in the earlier chapters, that some of our domesticated +animals, such as dogs, cattle, pigs, &c., are almost certainly descended +from more than one species, or wild race, if any one prefers to apply this +latter term to forms which were enabled to keep distinct in a state of +nature. Hence the crossing of aboriginally distinct species probably came +into play at an early period in the formation of our present races. From +Ruetimeyer's observations there can be little doubt that this occurred with +cattle; but in most cases some one of the forms which were allowed to cross +freely, will, it is probable, have absorbed and obliterated the others. For +it is not likely that semi-civilized men would have taken the necessary +pains to modify by selection their commingled, crossed, and fluctuating +stock. Nevertheless, those animals which were best adapted to their +conditions of life would have survived through natural selection; and by +this means crossing will often have indirectly aided in the formation of +primeval domesticated breeds. + +Within recent times, as far as animals are concerned, the crossing of +distinct species has done little or nothing in the formation or +modification of our races. It is not yet known whether the species of +silk-moth which have been recently crossed in France will yield permanent +races. In the fourth chapter I alluded with some hesitation to the +statement that a new breed, between the hare and rabbit, called leporides, +had been formed in France, and was found capable of propagating {99} +itself; but it is now positively affirmed[213] that this is an error. With +plants which can be multiplied by buds and cuttings, hybridisation has done +wonders, as with many kinds of Roses, Rhododendrons, Pelargoniums, +Calceolarias, and Petunias. Nearly all these plants can be propagated by +seed; most of them freely; but extremely few or none come true by seed. + +Some authors believe that crossing is the chief cause of variability,--that +is, of the appearance of absolutely new characters. Some have gone so far +as to look at it as the sole cause; but this conclusion is disproved by +some of the facts given in the chapter on Bud-variation. The belief that +characters not present in either parent or in their ancestors frequently +originate from crossing is doubtful; that they occasionally thus arise is +probable; but this subject will be more conveniently discussed in a future +chapter on the causes of Variability. + +A condensed summary of this and of the three following chapters, together +with some remarks on Hybridism, will be given in the nineteenth chapter. + + * * * * * + + +{100} + +CHAPTER XVI. + +CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES--INFLUENCE OF +DOMESTICATION ON FERTILITY. + + DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN + CROSSED--VARIOUS CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF + BREEDING AND SEXUAL PREFERENCE--VARIETIES OF WHEAT SAID TO BE STERILE + WHEN CROSSED--VARIETIES OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, + AND TOBACCO, RENDERED IN SOME DEGREE MUTUALLY STERILE--DOMESTICATION + ELIMINATES THE TENDENCY TO STERILITY NATURAL TO SPECIES WHEN + CROSSED--ON THE INCREASED FERTILITY OF UNCROSSED ANIMALS AND PLANTS + FROM DOMESTICATION AND CULTIVATION. + +The domesticated races of both animals and plants, when crossed, are with +extremely few exceptions quite prolific,--in some cases even more so than +the purely bred parent-races. The offspring, also, raised from such crosses +are likewise, as we shall see in the following chapter, generally more +vigorous and fertile than their parents. On the other hand, species when +crossed, and their hybrid offspring, are almost invariability in some +degree sterile; and here there seems to exist a broad and insuperable +distinction between races and species. The importance of this subject as +bearing on the origin of species is obvious; and we shall hereafter recur +to it. + +It is unfortunate how few precise observations have been made on the +fertility of mongrel animals and plants during several successive +generations. Dr. Broca[214] has remarked that no one has observed whether, +for instance, mongrel dogs, bred _inter se_, are indefinitely fertile; yet, +if a shade of infertility be detected by careful observation in the +offspring of natural forms when crossed, it is thought that their specific +distinction is proved. But so many breeds of sheep, cattle, pigs, dogs, and +poultry, have been crossed and recrossed in various ways, that any +sterility, if it had existed, would from being injurious {101} almost +certainly have been observed. In investigating the fertility of crossed +varieties many sources of doubt occur. Whenever the least trace of +sterility between two plants, however closely allied, was observed by +Koelreuter, and more especially by Gaertner, who counted the exact number +of seed in each capsule, the two forms were at once ranked as distinct +species; and if this rule be followed, assuredly it will never be proved +that varieties when crossed are in any degree sterile. We have formerly +seen that certain breeds of dogs do not readily pair together; but no +observations have been made whether, when paired, they produce the full +number of young, and whether the latter are perfectly fertile _inter se_; +but, supposing that some degree of sterility were found to exist, +naturalists would simply infer that these breeds were descended from +aboriginally distinct species; and it would be scarcely possible to +ascertain whether or not this explanation was the true one. + +The Sebright Bantam is much less prolific than any other breed of fowls, +and is descended from a cross between two very distinct breeds, recrossed +by a third sub-variety. But it would be extremely rash to infer that the +loss of fertility was in any manner connected with its crossed origin, for +it may with more probability be attributed either to long-continued close +interbreeding, or to an innate tendency to sterility correlated with the +absence of hackles and sickle tail-feathers. + +Before giving the few recorded cases of forms, which must be ranked as +varieties, being in some degree sterile when crossed, I may remark that +other causes sometimes interfere with varieties freely intercrossing. Thus +they may differ too greatly in size, as with some kinds of dogs and fowls: +for instance, the editor of the 'Journal of Horticulture, &c.,'[215] says +that he can keep Bantams with the larger breeds without much danger of +their crossing, but not with the smaller breeds, such as Games, Hamburgs, +&c. With plants a difference in the period of flowering serves to keep +varieties distinct, as with the various kinds of maize and wheat: thus +Colonel Le Couteur[216] remarks, "the Talavera wheat, from flowering much +earlier than any other kind, is sure to continue pure." In different parts +of {102} the Falkland Islands the cattle are breaking up into herds of +different colours; and those on the higher ground, which are generally +white, usually breed, as I am informed by Admiral Sulivan, three months +earlier than those on the lowlands; and this would manifestly tend to keep +the herds from blending. + +Certain domestic races seem to prefer breeding with their own kind; and +this is a fact of some importance, for it is a step towards that +instinctive feeling which helps to keep closely allied species in a state +of nature distinct. We have now abundant evidence that, if it were not for +this feeling, many more hybrids would be naturally produced than is the +case. We have seen in the first chapter that the alco dog of Mexico +dislikes dogs of other breeds; and the hairless dog of Paraguay mixes less +readily with the European races, than the latter do with each other. In +Germany the female Spitz-dog is said to receive the fox more readily than +will other dogs; a female Australian Dingo in England attracted the wild +male foxes. But these differences in the sexual instinct and attractive +power of the various breeds may be wholly due to their descent from +distinct species. In Paraguay the horses have much freedom, and an +excellent observer[217] believes that the native horses of the same colour +and size prefer associating with each other, and that the horses which have +been imported from Entre Rios and Banda Oriental into Paraguay likewise +prefer associating together. In Circassia six sub-races of the horse are +known and have received distinct names; and a native proprietor of +rank[218] asserts that horses of three of these races, whilst living a free +life, almost always refuse to mingle and cross, and will even attack each +other. + +It has been observed, in a district stocked with heavy Lincolnshire and +light Norfolk sheep, that both kinds, though bred together, when turned +out, "in a short time separate to a sheep;" the Lincolnshires drawing off +to the rich soil, and the Norfolks to their own dry light soil; and as long +as there is plenty of grass, "the two breeds keep themselves as distinct as +rooks and pigeons." In this case different habits of {103} life tend to +keep the races distinct. On one of the Faroe islands, not more than half a +mile in diameter, the half-wild native black sheep are said not to have +readily mixed with the imported white sheep. It is a more curious fact that +the semi-monstrous ancon sheep of modern origin "have been observed to keep +together, separating themselves from the rest of the flock, when put into +enclosures with other sheep."[219] With respect to fallow deer, which live +in a semi-domesticated condition, Mr. Bennett[220] states that the dark and +pale coloured herds, which have long been kept together in the Forest of +Dean, in High Meadow Woods, and in the New Forest, have never been known to +mingle: the dark-coloured deer, it may be added, are believed to have been +first brought by James I. from Norway, on account of their greater +hardiness. I imported from the island of Porto Santo two of the feral +rabbits, which differ, as described in the fourth chapter, from common +rabbits; both proved to be males, and, though they lived during some years +in the Zoological Gardens, the superintendent, Mr. Bartlett, in vain +endeavoured to make them breed with various tame kinds; but whether this +refusal to breed was due to any change in instinct, or simply to their +extreme wildness; or whether confinement had rendered them sterile, as +often occurs, cannot be told. + +Whilst matching for the sake of experiment many of the most distinct breeds +of pigeons, it frequently appeared to me that the birds, though faithful to +their marriage vow, retained some desire after their own kind. Accordingly +I asked Mr. Wicking, who has kept a larger stock of various breeds together +than any man in England, whether he thought that they would prefer pairing +with their own kind, supposing that there were males and females enough of +each; and he without hesitation answered that he was convinced that this +was the case. It has often been noticed that the dovecot pigeon seems to +have an actual aversion towards the several fancy breeds;[221] yet all have +{104} certainly sprung from a common progenitor. The Rev. W. D. Fox informs +me that his flocks of white and common Chinese geese kept distinct. + +These facts and statements, though some of them are incapable of proof, +resting only on the opinion of experienced observers, show that some +domestic races are led by different habits of life to keep to a certain +extent separate, and that others prefer coupling with their own kind, in +the same manner as species in a state of nature, though in a much less +degree. + + With respect to sterility from the crossing of domestic races, I know + of no well-ascertained case with animals. This fact, seeing the great + difference in structure between some breeds of pigeons, fowls, pigs, + dogs, &c., is extraordinary, in contrast with the sterility of many + closely allied natural species when crossed; but we shall hereafter + attempt to show that it is not so extraordinary as it at first appears. + And it may be well here to recall to mind that the amount of external + difference between two species will not safely guide us in foretelling + whether or not they will breed together,--some closely allied species + when crossed being utterly sterile, and others which are extremely + unlike being moderately fertile. I have said that no case of sterility + in crossed races rests on satisfactory evidence; but here is one which + at first seems trustworthy. Mr. Youatt,[222] and a better authority + cannot be quoted, states, that formerly in Lancashire crosses were + frequently made between longhorn and shorthorn cattle; the first cross + was excellent, but the produce was uncertain; in the third or fourth + generation the cows were bad milkers; "in addition to which, there was + much uncertainty whether the cows would conceive; and full one-third of + the cows among some of these half-breds failed to be in calf." This at + first seems a good case; but Mr. Wilkinson states,[223] that a breed + derived from this same cross was actually established in another part + of England; and if it had failed in fertility, the fact would surely + have been noticed. Moreover, supposing that Mr. Youatt had proved his + case, it might be argued that the sterility was wholly due to the two + parent-breeds being descended from primordially distinct species. + + I will give a case with plants, to show how difficult it is to get + sufficient evidence. Mr. Sheriff, who has been so successful in the + formation of new races of wheat, fertilised the Hopetoun with the + Talavera; in the first and second generations the produce was + intermediate in character, but in the fourth generation "it was found + to consist of many varieties; nine-tenths of the florets proved barren, + and many of the seeds seemed shrivelled abortions, void of vitality, + and the whole race was evidently verging to extinction."[224] Now, + considering how little these {105} varieties of wheat differ in any + important character, it seems to me very improbable that the sterility + resulted, as Mr. Sheriff thought, from the cross, but from some quite + distinct cause. Until such experiments are many times repeated, it + would be rash to trust them; but unfortunately they have been rarely + tried even once with sufficient care. + + Gaertner has recorded a more remarkable and trustworthy case: he + fertilised thirteen panicles (and subsequently nine others) on a dwarf + maize bearing yellow seed[225] with pollen of a tall maize having red + seed; and one head alone produced good seed, only five in number. + Though these plants are monoecious, and therefore do not require + castration, yet I should have suspected some accident in the + manipulation had not Gaertner expressly stated that he had during many + years grown these two varieties together, and they did not + spontaneously cross; and this, considering that the plants are + monoecious and abound with pollen, and are well known generally to + cross freely, seems explicable only on the belief that these two + varieties are in some degree mutually infertile. The hybrid plants + raised from the above five seed were intermediate in structure, + extremely variable, and perfectly fertile.[226] No one, I believe, has + hitherto suspected that these varieties of maize are distinct species; + but had the hybrids been in the least sterile, no doubt Gaertner would + at once have so classed them. I may here remark, that with undoubted + species there is not necessarily any close relation between the + sterility of a first cross and that of the hybrid offspring. Some + species can be crossed with facility, but produce utterly sterile + hybrids; others can be crossed with extreme difficulty, but the hybrids + when produced are moderately fertile. I am not aware, however, of any + instance quite like this of the maize with natural species, namely, of + a first cross made with difficulty, but yielding perfectly fertile + hybrids. + + The following case is much more remarkable, and evidently perplexed + Gaertner, whose strong wish it was to draw a broad line of distinction + between species and varieties. In the genus Verbascum, he made, during + eighteen years, a vast number of experiments, and crossed no less than + 1085 flowers and counted their seeds. Many of these experiments + consisted in crossing white and yellow varieties of both _V. lychnitis_ + and _V. blattaria_ with nine other species and their hybrids. That the + white and yellow flowered plants of these two species are really + varieties, no one has doubted; and Gaertner actually raised in the case + of both species one variety from the seed of the other. Now in two of + his works[227] he distinctly asserts that crosses between + similarly-coloured flowers yield more seed than between + dissimilarly-coloured; so that the yellow-flowered variety of either + species (and conversely with the white-flowered variety), when crossed + with pollen of its own kind, yields more seed than when crossed with + that of the white variety; and so it is when differently coloured + species are crossed. The general results may be seen in the Table at + the {106} end of his volume. In one instance he gives[228] the + following details; but I must premise that Gaertner, to avoid + exaggerating the degree of sterility in his crosses, always compares + the _maximum_ number obtained from a cross with the _average_ number + naturally given by the pure mother-plant. The white-variety of _V. + lychnitis_, naturally fertilised by its own pollen, gave from an + _average_ of twelve capsules ninety-six good seeds in each; whilst + twenty flowers fertilised with pollen from the yellow variety of this + same species, gave as the _maximum_ only eighty-nine good seed; so that + we have the proportion of 1000 to 908, according to Gaertner's usual + scale. I should have thought it possible that so small a difference in + fertility might have been accounted for by the evil effects of the + necessary castration; but Gaertner shows that the white variety of _V. + lychnitis_, when fertilised first by the white variety of _V. + blattaria_, and then by the yellow variety of this species, yielded + seed in the proportion of 622 to 438; and in both these cases + castration was performed. Now the sterility which results from the + crossing of the differently coloured varieties of the same species, is + fully as great as that which occurs in many cases when distinct species + are crossed. Unfortunately Gaertner compared the results of the first + unions alone, and not the sterility of the two sets of hybrids produced + from the white variety of _V. lychnitis_ when fertilised by the white + and yellow varieties of _V. blattaria_, for it is probable that they + would have differed in this respect. + + Mr. J. Scott has given me the results of a series of experiments on + Verbascum, made by him in the Botanic Gardens of Edinburgh. He repeated + some of Gaertner's experiments on distinct species, but obtained only + fluctuating results; some confirmatory, but the greater number + contradictory; nevertheless these seem hardly sufficient to overthrow + the conclusions arrived at by Gaertner from experiments tried on a much + larger scale. In the second place Mr. Scott experimented on the + relative fertility of unions between similarly and + dissimilarly-coloured varieties of the same species. Thus he fertilised + six flowers of the yellow variety of _V. lychnitis_ by its own pollen, + and obtained six capsules, and calling, for the sake of having a + standard of comparison, the average number of good seed in each one + hundred, he found that this same yellow variety, when fertilised by the + white variety, yielded from seven capsules an average of ninety-four + seed. On the same principle, the white variety of _V. lychnitis_ by its + own pollen (from six capsules), and by the pollen of the yellow variety + (eight capsules), yielded seed in the proportion of 100 to 82. The + yellow variety of _V. thapsus_ by its own pollen (eight capsules), and + by that of the white variety (only two capsules), yielded seed in the + proportion of 100 to 94. Lastly, the white variety of _V. blattaria_ by + its own pollen (eight capsules), and by that of the yellow variety + (five capsules), yielded seed in the proportion of 100 to 79. So that + in every case the unions of dissimilarly-coloured varieties of the same + species were less fertile than the unions of similarly-coloured + varieties; when all the cases are grouped together, the difference of + fertility is as 86 to 100. Some additional trials were made, and + altogether thirty-six similarly-coloured unions yielded thirty-five + good {107} capsules; whilst thirty-five dissimilarly-coloured unions + yielded only twenty-six good capsules. Besides the foregoing + experiments, the purple _V. phoeniceum_ was crossed by a rose-coloured + and a white variety of the same species; these two varieties were also + crossed together, and these several unions yielded less seed than _V. + phoeniceum_ by its own pollen. Hence it follows from Mr. Scott's + experiments, that in the genus Verbascum the similarly and + dissimilarly-coloured varieties of the same species behave, when + crossed, like closely allied but distinct species.[229] + + This remarkable fact of the sexual affinity of similarly-coloured + varieties, as observed by Gaertner and Mr. Scott, may not be of very + rare occurrence; for the subject has not been attended to by others. + The following case is worth giving, partly to show how difficult it is + to avoid error. Dr. Herbert[230] has remarked that variously-coloured + double varieties of the hollyhock (_Althaea rosea_) may be raised with + certainty by seed from plants growing close together. I have been + informed that nurserymen who raise seed for sale do not separate their + plants; accordingly I procured seed of eighteen named varieties; of + these, eleven varieties produced sixty-two plants all perfectly true to + their kind; and seven produced forty-nine plants, half of which were + true and half false. Mr. Masters of Canterbury has given me a more + striking case; he saved seed from a great bed of twenty-four named + varieties planted in closely adjoining rows, and each variety + reproduced itself truly with only sometimes a shade of difference in + tint. Now in the hollyhock the pollen, which is abundant, is matured + and nearly all shed before the stigma of the same flower is ready to + receive it;[231] and as bees covered with pollen incessantly fly from + plant to plant, it would appear that adjoining varieties could not + escape being crossed. As, however, this does not occur, it appeared to + me probable that the pollen {108} of each variety was prepotent on its + own stigma over that of all other varieties. But Mr. C. Turner of + Slough, well known for his success in the cultivation of this plant, + informs me that it is the doubleness of the flowers which prevents the + bees gaining access to the pollen and stigma; and he finds that it is + difficult even to cross them artificially. Whether this explanation + will fully account for varieties in close proximity propagating + themselves so truly by seed, I do not know. + + The following cases are worth giving, as they relate to monoecious + forms, which do not require, and consequently have not been injured by, + castration. Girou de Buzareingues crossed what he designates three + varieties of gourd,[232] and asserts that their mutual fertilisation is + less easy in proportion to the difference which they present. I am + aware how imperfectly the forms in this group were until recently + known; but Sageret,[233] who ranked them according to their mutual + fertility, considers the three forms above alluded to as varieties, as + does a far higher authority, namely, M. Naudin.[234] Sageret[235] has + observed that certain melons have a greater tendency, whatever the + cause may be, to keep true than others; and M. Naudin, who has had such + immense experience in this group, informs me that he believes that + certain varieties intercross more readily than others of the same + species; but he has not proved the truth of this conclusion; the + frequent abortion of the pollen near Paris being one great difficulty. + Nevertheless, he has grown close together, during seven years, certain + forms of Citrullus, which, as they could be artificially crossed with + perfect facility and produced fertile offspring, are ranked as + varieties; but these forms when not artificially crossed kept true. + Many other varieties, on the other hand, in the same group cross with + such facility, as M. Naudin repeatedly insists, that without being + grown far apart they cannot be kept in the least true. + + Another case, though somewhat different, may be here given, as it is + highly remarkable, and is established on excellent evidence. Koelreuter + minutely describes five varieties of the common tobacco,[236] which + were reciprocally crossed, and the offspring were intermediate in + character and as fertile as their parents: from this fact Koelreuter + inferred that they are really varieties; and no one, as far as I can + discover, seems to have doubted that such is the case. He also crossed + reciprocally these five varieties with _N. glutinosa_, and they yielded + very sterile hybrids; but those raised from the _var. perennis_, + whether used as the father or mother plant, were not so sterile as the + hybrids from the four other varieties.[237] So that the sexual {109} + capacity of this one variety has certainly been in some degree + modified, so as to approach in nature that of _N. glutinosa_.[238] + +These facts with respect to plants show that in some few cases certain +varieties have had their sexual powers so far modified, that they cross +together less readily and yield less seed than other varieties of the same +species. We shall presently see that the sexual functions of most animals +and plants are eminently liable to be affected by the conditions of life to +which they are exposed; and hereafter we shall briefly discuss the conjoint +bearing of this and other facts on the difference in fertility between +crossed varieties and crossed species. + +_Domestication eliminates the tendency to Sterility which is general with +Species when crossed._ + +This hypothesis was first propounded by Pallas,[239] and has been adopted +by several authors. I can find hardly any direct facts in its support; but +unfortunately no one has compared, in the case of either animals or plants, +the fertility of anciently domesticated varieties, when crossed with a +distinct species, with that of the wild parent-species when similarly +crossed. No one has compared, for instance, the fertility of _Gallus +bankiva_ and of the domesticated fowl, when crossed with a distinct species +of Gallus or Phasianus; and the {110} experiment would in all cases be +surrounded by many difficulties. Dureau de la Malle, who has so closely +studied classical literature, states[240] that in the time of the Romans +the common mule was produced with more difficulty than at the present day; +but whether this statement may be trusted I know not. A much more +important, though somewhat different, case is given by M. Groenland,[241] +namely, that plants, known from their intermediate character and sterility +to be hybrids between Aegilops and wheat, have perpetuated themselves under +culture since 1857, _with a rapid but varying increase of fertility in each +generation_. In the fourth generation the plants, still retaining their +intermediate character, had become as fertile as common cultivated wheat. + +The indirect evidence in favour of the Pallasian doctrine appears to me to +be extremely strong. In the earlier chapters I have attempted to show that +our various breeds of dogs are descended from several wild species; and +this probably is the case with sheep. There can no longer be any doubt that +the Zebu or humped Indian ox belongs to a distinct species from European +cattle: the latter, moreover, are descended from two or three forms, which +may be called either species or wild races, but which co-existed in a state +of nature and kept distinct. We have good evidence that our domesticated +pigs belong to at least two specific types, _S. scrofa_ and _Indica_, which +probably lived together in a wild state in South-eastern Europe. Now, a +widely-extended analogy leads to the belief that if these several allied +species, in the wild state or when first reclaimed, had been crossed, they +would have exhibited, both in their first unions and in their hybrid +offspring, some degree of sterility. Nevertheless the several domesticated +races descended from them are now all, as far as can be ascertained, +perfectly fertile together. If this reasoning be trustworthy, and it is +apparently sound, we must admit the Pallasian doctrine that long-continued +domestication tends to eliminate that sterility which is natural to species +when crossed in their aboriginal state. + +{111} + +_On increased Fertility from Domestication and Cultivation._ + +Increased fertility from domestication, without any reference to crossing, +may be here briefly considered. This subject bears indirectly on two or +three points connected with the modification of organic beings. As Buffon +long ago remarked,[242] domestic animals breed oftener in the year and +produce more young at a birth than wild animals of the same species; they, +also, sometimes breed at an earlier age. The case would hardly have +deserved further notice, had not some authors lately attempted to show that +fertility increases and decreases in an inverse ratio with the amount of +food. This strange doctrine has apparently arisen from individual animals +when supplied with an inordinate quantity of food, and from plants of many +kinds when grown on excessively rich soil, as on a dunghill, becoming +sterile; but to this latter point I shall have occasion presently to +return. With hardly an exception, our domesticated animals, which have long +been habituated to a regular and copious supply of food, without the labour +of searching for it, are more fertile than the corresponding wild animals. +It is notorious how frequently cats and dogs breed, and how many young they +produce at a birth. The wild rabbit is said generally to breed four times +yearly, and to produce from four to eight young; the tame rabbit breeds six +or seven times yearly, and produces from four to eleven young. The ferret, +though generally so closely confined, is more prolific than its supposed +wild prototype. The wild sow is remarkably prolific, for she often breeds +twice in the year, and produces from four to eight and sometimes even +twelve young at a birth; but the domestic sow regularly breeds twice a +year, and would breed oftener if permitted; and a sow that produces less +than eight at a birth "is worth little, and the sooner she is fattened for +the butcher the better." The amount of food affects the fertility even of +the same individual: thus sheep, which on mountains never produce more than +one lamb at a birth, when brought {112} down to lowland pastures frequently +bear twins. This difference apparently is not due to the cold of the higher +land, for sheep and other domestic animals are said to be extremely +prolific in Lapland. Hard living, also, retards the period at which animals +conceive; for it has been found disadvantageous in the northern islands of +Scotland to allow cows to bear calves before they are four years old.[243] + + Birds offer still better evidence of increased fertility from + domestication: the hen of the wild _Gallus bankiva_ lays from six to + ten eggs, a number which would be thought nothing of with the domestic + hen. The wild duck lays from five to ten eggs; the tame one in the + course of the year from eighty to one hundred. The wild grey-lag goose + lays from five to eight eggs; the tame from thirteen to eighteen, and + she lays a second time; as Mr. Dixon has remarked, "high-feeding, care, + and moderate warmth induce a habit of prolificacy which becomes in some + measure hereditary." Whether the semi-domesticated dovecot pigeon is + more fertile than the wild rock-pigeon _C. livia_, I know not; but the + more thoroughly domesticated breeds are nearly twice as fertile as + dovecots: the latter, however, when caged and highly fed, become + equally fertile with house pigeons. The peahen alone of domesticated + birds is rather more fertile, according to some accounts, when wild in + its native Indian home, than when domesticated in Europe and exposed to + our much colder climate.[244] + + With respect to plants, no one would expect wheat to tiller more, and + each ear to produce more grain, in poor than in rich soil; or to get in + poor soil a heavy crop of peas or beans. Seeds vary so much in number + {113} that it is difficult to estimate them; but on comparing beds of + carrots saved for seed in a nursery garden with wild plants, the former + seemed to produce about twice as much seed. Cultivated cabbages yielded + thrice as many pods by measure as wild cabbages from the rocks of South + Wales. The excess of berries produced by the cultivated Asparagus in + comparison with the wild plant is enormous. No doubt many highly + cultivated plants, such as pears, pineapples, bananas, sugar-cane, &c., + are nearly or quite sterile; and I am inclined to attribute this + sterility to excess of food and to other unnatural conditions; but to + this subject I shall presently recur. + +In some cases, as with the pig, rabbit, &c., and with those plants which +are valued for their seed, the direct selection of the more fertile +individuals has probably much increased their fertility; and in all cases +this may have occurred indirectly, from the better chance of the more +numerous offspring produced by the more fertile individuals having +survived. But with cats, ferrets, and dogs, and with plants like carrots, +cabbages, and asparagus, which are not valued for their prolificacy, +selection can have played only a subordinate part; and their increased +fertility must be attributed to the more favourable conditions of life +under which they have long existed. + + * * * * * + + +{114} + +CHAPTER XVII. + +ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL EFFECTS OF CLOSE +INTERBREEDING. + + DEFINITION OF CLOSE INTERBREEDING--AUGMENTATION OF MORBID + TENDENCIES--GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, + AND ON THE EVIL EFFECTS FROM CLOSE INTERBREEDING--CATTLE, CLOSELY + INTERBRED; HALF-WILD CATTLE LONG KEPT IN THE SAME + PARKS--SHEEP--FALLOW-DEER--DOGS--RABBITS--PIGS--MAN, ORIGIN OF HIS + ABHORRENCE OF INCESTUOUS MARRIAGES--FOWLS--PIGEONS--HIVE-BEES--PLANTS, + GENERAL CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING--MELONS, + FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND FOREST-TREES--ON THE INCREASED + SIZE OF HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY--ON + CERTAIN PLANTS WHICH EITHER NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, + BUT ARE FERTILE, BOTH ON THE MALE AND FEMALE SIDE, WHEN CROSSED WITH + DISTINCT INDIVIDUALS EITHER OF THE SAME OR ANOTHER SPECIES--CONCLUSION. + +The gain in constitutional vigour, derived from an occasional cross between +individuals of the same variety, but belonging to distinct families, or +between distinct varieties, has not been so largely or so frequently +discussed, as have the evil effects of too close interbreeding. But the +former point is the more important of the two, inasmuch as the evidence is +more decisive. The evil results from close interbreeding are difficult to +detect, for they accumulate slowly, and differ much in degree with +different species; whilst the good effects which almost invariably follow a +cross are from the first manifest. It should, however, be clearly +understood that the advantage of close interbreeding, as far as the +retention of character is concerned, is indisputable, and often outweighs +the evil of a slight loss of constitutional vigour. In relation to the +subject of domestication, the whole question is of some importance, as too +close interbreeding interferes with the improvement of old races, and +especially with the formation of new ones. It is important as indirectly +bearing on Hybridism; and perhaps on the extinction of species, when any +form has become so rare that only a few individuals {115} remain within a +confined area. It bears in an important manner on the influence of free +intercrossing, in obliterating individual differences, and thus giving +uniformity of character to the individuals of the same race or species; for +if additional vigour and fertility be thus gained, the crossed offspring +will multiply and prevail, and the ultimate result will be far greater than +otherwise would have occurred. Lastly, the question is of high interest, as +bearing on mankind. Hence I shall discuss this subject at full length. As +the facts which prove the evil effects of close interbreeding are more +copious, though less decisive, than those on the good effects of crossing, +I shall, under each group of beings, begin with the former. + +There is no difficulty in defining what is meant by a cross; but this is by +no means easy in regard to "breeding in and in" or "too close +interbreeding," because, as we shall see, different species of animals are +differently affected by the same degree of interbreeding. The pairing of a +father and daughter, or mother and son, or brothers and sisters, if carried +on during several generations, is the closest possible form of +interbreeding. But some good judges, for instance Sir J. Sebright, believe +that the pairing of a brother and sister is closer than that of parents and +children; for when the father is matched with his daughter he crosses, as +is said, with only half his own blood. The consequences of close +interbreeding carried on for too long a time, are, as is generally +believed, loss of size, constitutional vigour, and fertility, sometimes +accompanied by a tendency to malformation. Manifest evil does not usually +follow from pairing the nearest relations for two, three, or even four +generations; but several causes interfere with our detecting the evil--such +as the deterioration being very gradual, and the difficulty of +distinguishing between such direct evil and the inevitable augmentation of +any morbid tendencies which may be latent or apparent in the related +parents. On the other hand, the benefit from a cross, even when there has +not been any very close interbreeding, is almost invariably at once +conspicuous. There is reason to believe, and this was the opinion of that +most experienced observer Sir J. Sebright,[245] that the evil effects of +close interbreeding may be checked by the related individuals {116} being +separated during a few generations and exposed to different conditions of +life. + +That evil directly follows from any degree of close interbreeding has been +denied by many persons; but rarely by any practical breeder; and never, as +far as I know, by one who has largely bred animals which propagate their +kind quickly. Many physiologists attribute the evil exclusively to the +combination and consequent increase of morbid tendencies common to both +parents: that this is an active source of mischief there can be no doubt. +It is unfortunately too notorious that men and various domestic animals +endowed with a wretched constitution, and with a strong hereditary +disposition to disease, if not actually ill, are fully capable of +procreating their kind. Close interbreeding, on the other hand, induces +sterility; and this indicates something quite distinct from the +augmentation of morbid tendencies common to both parents. The evidence +immediately to be given convinces me that it is a great law of nature, that +all organic beings profit from an occasional cross with individuals not +closely related to them in blood; and that, on the other hand, +long-continued close interbreeding is injurious. + +Various general considerations have had much influence in leading me to +this conclusion; but the reader will probably rely more on special facts +and opinions. The authority of experienced observers, even when they do not +advance the grounds of their belief, is of some little value. Now almost +all men who have bred many kinds of animals and have written on the +subject, such as Sir J. Sebright, Andrew Knight, &c.,[246] have expressed +the strongest conviction on the impossibility of long-continued close +interbreeding. Those who have compiled works on agriculture, and have +associated much with breeders, such as the sagacious Youatt, Low, &c., have +strongly declared their opinion to the same effect. Prosper Lucas, trusting +largely to French authorities, has come to a similar conclusion. The +distinguished German agriculturist Hermann von Nathusius, who has written +the most able treatise on this subject which I have met with, concurs; and +as I shall have to quote from {117} this treatise, I may state that +Nathusius is not only intimately acquainted with works on agriculture in +all languages, and knows the pedigrees of our British breeds better than +most Englishmen, but has imported many of our improved animals, and is +himself an experienced breeder. + +Evidence of the evil effects of close interbreeding can most readily be +acquired in the case of animals, such as fowls, pigeons, &c., which +propagate quickly, and, from being kept in the same place, are exposed to +the same conditions. Now I have inquired of very many breeders of these +birds, and I have hitherto not met with a single man who was not thoroughly +convinced that an occasional cross with another strain of the same +sub-variety was absolutely necessary. Most breeders of highly-improved or +fancy birds value their own strain, and are most unwilling, at the risk, in +their opinion, of deterioration, to make a cross. The purchase of a +first-rate bird of another strain is expensive, and exchanges are +troublesome; yet all breeders, as far as I can hear, excepting those who +keep large stocks at different places for the sake of crossing, are driven +after a time to take this step. + +Another general consideration which has had great influence on my mind is, +that with all hermaphrodite animals and plants, which it might have been +thought would have perpetually fertilised themselves, and thus have been +subjected for long ages to the closest interbreeding, there is no single +species, as far as I can discover, in which the structure ensures +self-fertilisation. On the contrary, there are in a multitude of cases, as +briefly stated in the fifteenth chapter, manifest adaptations which favour +or inevitably lead to an occasional cross between one hermaphrodite and +another of the same species; and these adaptive structures are utterly +purposeless, as far as we can see, for any other end. + + With _Cattle_ there can be no doubt that extremely close interbreeding + may be long carried on, advantageously with respect to external + characters and with no manifestly apparent evil as far as constitution + is concerned. The same remark is applicable to sheep. Whether these + animals have gradually been rendered less susceptible than others to + this evil, in order to permit them to live in herds,--a habit which + leads the old and vigorous males to expel all intruders, and in + consequence often to pair with their own daughters, I will not pretend + to decide. The case of Bakewell's Long-horns, which were closely + interbred for a long period, has often been {118} quoted; yet Youatt + says[247] the breed "had acquired a delicacy of constitution + inconsistent with common management," and "the propagation of the + species was not always certain." But the Shorthorns offer the most + striking case of close interbreeding; for instance, the famous bull + Favourite (who was himself the offspring of a half-brother and sister + from Foljambe) was matched with his own daughter, granddaughter, and + great-granddaughter; so that the produce of this last union, or the + great-great-granddaughter, had 15-16ths, or 93.75 per cent. of the + blood of Favourite in her veins. This cow was matched with the bull + Wellington, having 62.5 per cent. of Favourite blood in his veins, and + produced Clarissa; Clarissa was matched with the bull Lancaster, having + 68.75 of the same blood, and she yielded valuable offspring.[248] + Nevertheless Collings, who reared these animals, and was a strong + advocate for close breeding, once crossed his stock with a Galloway, + and the cows from this cross realised the highest prices. Bates's herd + was esteemed the most celebrated in the world. For thirteen years he + bred most closely in and in; but during the next seventeen years, + though he had the most exalted notion of the value of his own stock, he + thrice infused fresh blood into his herd: it is said that he did this, + not to improve the form of his animals, but on account of their + lessened fertility. Mr. Bates's own view, as given by a celebrated + breeder,[249] was, that "to breed in and in from a bad stock was ruin + and devastation; yet that the practice may be safely followed within + certain limits when the parents so related are descended from + first-rate animals." We thus see that there has been extremely close + interbreeding with Shorthorns; but Nathusius, after the most careful + study of their pedigrees, says that he can find no instance of a + breeder who has strictly followed this practice during his whole life. + From this study and his own experience, he concludes that close + interbreeding is necessary to ennoble the stock; but that in effecting + this the greatest care is necessary, on account of the tendency to + infertility and weakness. It may be added, that another high + authority[250] asserts that many more calves are born cripples from + Shorthorns than from other and less closely interbred races of cattle. + + Although by carefully selecting the best animals (as Nature effectually + does by the law of battle) close interbreeding may be long carried on + with cattle, yet the good effects of a cross between almost any two + breeds is at once shown by the greater size and vigour of the + offspring; as Mr. Spooner writes to me, "crossing distinct breeds + certainly improves cattle for the butcher." Such crossed animals are of + course of no value to the breeder; but they have been raised during + many years in several {119} parts of England to be slaughtered;[251] + and their merit is now so fully recognised, that at fat-cattle shows a + separate class has been formed for their reception. The best fat ox at + the great show at Islington in 1862 was a crossed animal. + + The half-wild cattle, which have been kept in British parks probably + for 400 or 500 years, or even for a longer period, have been advanced + by Culley and others as a case of long-continued interbreeding within + the limits of the same herd without any consequent injury. With respect + to the cattle at Chillingham, the late Lord Tankerville owned that they + were bad breeders.[252] The agent, Mr. Hardy, estimates (in a letter to + me, dated May, 1861) that in the herd of about fifty the average number + annually slaughtered, killed by fighting, and dying, is about ten, or + one in five. As the herd is kept up to nearly the same average number, + the annual rate of increase must be likewise about one in five. The + bulls, I may add, engage in furious battles, of which battles the + present Lord Tankerville has given me a graphic description, so that + there will always be rigorous selection of the most vigorous males. I + procured in 1855 from Mr. D. Gardner, agent to the Duke of Hamilton, + the following account of the wild cattle kept in the Duke's park in + Lanarkshire, which is about 200 acres in extent. The number of cattle + varies from sixty-five to eighty; and the number annually killed (I + presume by all causes) is from eight to ten; so that the annual rate of + increase can hardly be more than one in six. Now in South America, + where the herds are half-wild, and therefore offer a nearly fair + standard of comparison, according to Azara the natural increase of the + cattle on an estancia is from one-third to one-fourth of the total + number, or one in between three and four; and this, no doubt, applies + exclusively to adult animals fit for consumption. Hence the half-wild + British cattle which have long interbred within the limits of the same + herd are relatively far less fertile. Although in an unenclosed country + like Paraguay there must be some crossing between the different herds, + yet even there the inhabitants believe that the occasional introduction + of animals from distant localities is necessary to prevent + "degeneration in size and diminution of fertility."[253] The decrease + in size from ancient times in the Chillingham and Hamilton cattle must + have been prodigious, for Professor Ruetimeyer has shown that they are + almost certainly the descendants of the gigantic _Bos primigenius_. No + doubt this decrease in size may be largely attributed to less + favourable conditions of life; yet animals roaming over large parks, + and fed during severe winters, can hardly be considered as placed under + very unfavourable conditions. + + With _Sheep_ there has often been long-continued interbreeding within + the limits of the same flock; but whether the nearest relations have + been matched so frequently as in the case of Shorthorn cattle, I do not + know. The Messrs. Brown during fifty years have never infused fresh + blood into their excellent flock of Leicesters. Since 1810 Mr. Barford + has acted on the same principle with the Foscote flock. He asserts that + half a century {120} of experience has convinced him that when two + nearly related animals are quite sound in constitution, in-and-in + breeding does not induce degeneracy; but he adds that he "does not + pride himself on breeding from the nearest affinities." In France the + Naz flock has been bred for sixty years without the introduction of a + single strange ram.[254] Nevertheless, most great breeders of sheep + have protested against close interbreeding prolonged for too great a + length of time.[255] The most celebrated of recent breeders, Jonas + Webb, kept five separate families to work on, thus "retaining the + requisite distance of relationship between the sexes."[256] + + Although by the aid of careful selection the near interbreeding of + sheep may be long continued without any manifest evil, yet it has often + been the practice with farmers to cross distinct breeds to obtain + animals for the butcher, which plainly shows that good is derived from + this practice. Mr. Spooner sums up his excellent Essay on Crossing by + asserting that there is a direct pecuniary advantage in judicious + cross-breeding, especially when the male is larger than the female. A + former celebrated breeder, Lord Somerville, distinctly states that his + half-breeds from Ryelands and Spanish sheep were larger animals than + either the pure Ryelands or pure Spanish sheep.[257] + + As some of our British parks are ancient, it occurred to me that there + must have been long-continued close interbreeding with the fallow deer + (_Cervus dama_) kept in them; but on inquiry I find that it is a common + practice to infuse new blood by procuring bucks from other parks. Mr. + Shirley,[258] who has carefully studied the management of deer, admits + that in some parks there has been no admixture of foreign blood from a + time beyond the memory of man. But he concludes "that in the end the + constant breeding in-and-in is sure to tell to the disadvantage of the + whole herd, though it may take a very long time to prove it; moreover, + when we find, as is very constantly the case, that the introduction of + fresh blood has been of the very greatest use to deer, both by + improving their size and appearance, and particularly by being of + service in removing the taint of 'rickback,' if not of other diseases, + to which deer are sometimes subject when the blood has not been + changed, there can, I think, be no doubt but that a judicious cross + with a good stock is of the greatest consequence, and is indeed + essential, sooner or later, to the prosperity of every well-ordered + park." + + Mr. Meynell's famous foxhounds have been adduced, as showing that no + ill effects follow from close interbreeding; and Sir J. Sebright + ascertained from him that he frequently bred from father and daughter, + mother and {121} son, and sometimes even from brothers and sisters. Sir + J. Sebright, however, declares,[259] that by breeding _in-and-in_, by + which he means matching brothers and sisters, he has actually seen + strong spaniels become weak and diminutive lapdogs. The Rev. W. D. Fox + has communicated to me the case of a small lot of bloodhounds, long + kept in the same family, which had become very bad breeders, and nearly + all had a bony enlargement in the tail. A single cross with a distinct + strain of bloodhounds restored their fertility, and drove away the + tendency to malformation in the tail. I have heard the particulars of + another case with bloodhounds, in which the female had to be held to + the male. Considering how rapid is the natural increase of the dog, it + is difficult to understand the high price of most highly improved + breeds, which almost implies long-continued close interbreeding, except + on the belief that this process lessens fertility and increases + liability to distemper and other diseases. A high authority, Mr. + Scrope, attributes the rarity and deterioration in size of the Scotch + deerhound (the few individuals now existing throughout the country + being all related) in large part to close interbreeding. + + With all highly-bred animals there is more or less difficulty in + getting them to procreate quickly, and all suffer much from delicacy of + constitution; but I do not pretend that these effects ought to be + wholly attributed to close interbreeding. A great judge of rabbits[260] + says, "the long-eared does are often too highly bred or forced in their + youth to be of much value as breeders, often turning out barren or bad + mothers." Again: "Very long-eared bucks will also sometimes prove + barren." These highly-bred rabbits often desert their young, so that it + is necessary to have nurse-rabbits. + + With _Pigs_ there is more unanimity amongst breeders on the evil + effects of close interbreeding than, perhaps, with any other large + animal. Mr. Druce, a great and successful breeder of the Improved + Oxfordshires (a crossed race), writes, "without a change of boars of a + different tribe, but of the same breed, constitution cannot be + preserved." Mr. Fisher Hobbs, the raiser of the celebrated Improved + Essex breed, divided his stock into three separate families, by which + means he maintained the breed for more than twenty years, "by judicious + selection from the _three distinct families_."[261] Lord Western was + the first importer of a Neapolitan boar and sow. "From this pair he + bred in-and-in, until the breed was in danger of becoming extinct, a + sure result (as Mr. Sidney remarks) of in-and-in breeding." Lord + Western then crossed his Neapolitan pigs with the old Essex, and made + the first great step towards the Improved Essex breed. Here is a more + interesting case. Mr. J. Wright, well known as a breeder, crossed[262] + the same boar with the daughter, granddaughter, and + great-granddaughter, and so on for seven generations. The result was, + that in many instances the offspring failed to breed; in others they + produced few that lived; and of the latter many were idiotic, without + sense {122} even to suck, and when attempting to move could not walk + straight. Now it deserves especial notice, that the two last sows + produced by this long course of interbreeding were sent to other boars, + and they bore several litters of healthy pigs. The best sow in external + appearance produced during the whole seven generations was one in the + last stage of descent; but the litter consisted of this one sow. She + would not breed to her sire, yet bred at the first trial to a stranger + in blood. So that, in Mr. Wright's case, long-continued and extremely + close interbreeding did not affect the external form or merit of the + young; but with many of them the general constitution and mental + powers, and especially the reproductive functions, were seriously + affected. + + Nathusius gives[263] an analogous and even more striking case: he + imported from England a pregnant sow of the large Yorkshire breed, and + bred the product closely in-and-in for three generations: the result + was unfavourable, as the young were weak in constitution, with impaired + fertility. One of the latest sows, which he esteemed a good animal, + produced, when paired with her own uncle (who was known to be + productive with sows of other breeds), a litter of six, and a second + time a litter of only five weak young pigs. He then paired this sow + with a boar of a small black breed, which he had likewise imported from + England, and which boar, when matched with sows of his own breed, + produced from seven to nine young: now, the sow of the large breed, + which was so unproductive when paired with her own uncle, yielded to + the small black boar, in the first litter twenty-one, and in the second + litter eighteen young pigs; so that in one year she produced + thirty-nine fine young animals! + + As in the case of several other animals already mentioned, even when no + injury is perceptible from moderately close interbreeding, yet, to + quote the words of Mr. Coate, a most successful breeder (who five times + won the annual gold medal of the Smithfield Club Show for the best pen + of pigs), "Crosses answer well for profit to the farmer, as you get + more constitution and quicker growth; but for me, who sell a great + number of pigs for breeding purposes, I find it will not do, as it + requires many years to get anything like purity of blood again."[264] + +Before passing on to Birds, I ought to refer to man, though I am unwilling +to enter on this subject, as it is surrounded by natural prejudices. It has +moreover been discussed by various authors under many points of view.[265] +Mr. Tylor[266] has shown {123} that with widely different races, in the +most distant quarters of the world, marriages between relations--even +between distant relations--have been strictly prohibited. A few exceptional +cases can be specified, especially with royal families; and these have been +enlarged on in a learned article[267] by Mr. W. Adam, and formerly in 1828 +by Hofacker. Mr. Tylor is inclined to believe that the almost universal +prohibition of closely-related marriages has arisen from their evil effects +having been observed, and he ingeniously explains some apparent anomalies +in the prohibition not extending equally to the relations on both the male +and female side. He admits, however, that other causes, such as the +extension of friendly alliances, may have come into play. Mr. W. Adam, on +the other hand, concludes that related marriages are prohibited and viewed +with repugnance from the confusion which would thus arise in the descent of +property, and from other still more recondite reasons; but I cannot accept +this view, seeing that the savages of Australia and South America,[268] who +have no property to bequeath or fine moral feelings to confuse, hold the +crime of incest in abhorrence. + +It would be interesting to know, if it could be ascertained, as throwing +light on this question with respect to man, what occurs with the higher +anthropomorphous apes--whether the young males and females soon wander away +from their parents, or whether the old males become jealous of their sons +and expel them, or whether any inherited instinctive feeling, from being +beneficial, has been generated, leading the young males and females of the +same family to prefer pairing with distinct families, and to dislike +pairing with each other. A considerable body of evidence has already been +advanced, showing that the offspring from parents which are not related are +more vigorous and fertile than those from parents which are closely +related; hence any slight feeling, arising from the sexual excitement of +novelty or other cause, which led to the former rather than to the latter +unions, would be augmented through natural selection, and thus might become +instinctive; for those individuals which had an innate preference of this +kind would increase in number. It seems more probable, that degraded +savages should {124} thus unconsciously have acquired their dislike and +even abhorrence of incestuous marriages, rather than that they should have +discovered by reasoning and observation the evil results. The abhorrence +occasionally failing is no valid argument against the feeling being +instinctive, for any instinct may occasionally fail or become vitiated, as +sometimes occurs with parental love and the social sympathies. In the case +of man, the question whether evil follows from close interbreeding will +probably never be answered by direct evidence, as he propagates his kind so +slowly and cannot be subjected to experiment; but the almost universal +practice of all races at all times of avoiding closely-related marriages is +an argument of considerable weight; and whatever conclusion we arrive at in +regard to the higher animals may be safely extended to man. + + Turning now to Birds: in the case of the _Fowl_ a whole array of + authorities could be given against too close interbreeding. Sir J. + Sebright positively asserts that he made many trials, and that his + fowls, when thus treated, became long in the legs, small in the body, + and bad breeders.[269] He produced the famous Sebright Bantams by + complicated crosses, and by breeding in-and-in; and since his time + there has been much close interbreeding with these Bantams; and they + are now notoriously bad breeders. I have seen Silver Bantams, directly + descended from his stock, which had become almost as barren as hybrids; + for not a single chicken had been that year hatched from two full nests + of eggs. Mr. Hewitt says that with these Bantams the sterility of the + male stands, with rare exceptions, in the closest relation with their + loss of certain secondary male characters: he adds, "I have noticed, as + a general rule, that even the slightest deviation from feminine + character in the tail of the male Sebright--say the elongation by only + half an inch of the two principal tail-feathers--brings with it + improved probability of increased fertility."[270] + + Mr. Wright states[271] that Mr. Clark, "whose fighting-cocks were so + notorious, continued to breed from his own kind till they lost their + disposition to fight, but stood to be cut up without making any + resistance, and were so reduced in size as to be under those weights + required for the best prizes; but on obtaining a cross from Mr. + Leighton, they again resumed their former courage and weight." It + should be borne in mind that game-cocks before they fought were always + weighed, so that nothing was left to the imagination about any + reduction or increase of {125} weight. Mr. Clark does not seem to have + bred from brothers and sisters, which is the most injurious kind of + union; and he found, after repeated trials, that there was a greater + reduction in weight in the young from a father paired with his + daughter, than from a mother with her son. I may add that Mr. Eyton, of + Eyton, the well-known ornithologist, who is a large breeder of Grey + Dorkings, informs me that they certainly diminish in size, and become + less prolific, unless a cross with another strain is occasionally + obtained. So it is with Malays, according to Mr. Hewitt, as far as size + is concerned.[272] + + An experienced writer[273] remarks that the same amateur, as is well + known, seldom long maintains the superiority of his birds; and this, he + adds, undoubtedly is due to all his stock "being of the same blood;" + hence it is indispensable that he should occasionally procure a bird of + another strain. But this is not necessary with those who keep a stock + of fowls at different stations. Thus, Mr. Ballance, who has bred Malays + for thirty years, and has won more prizes with these birds than any + other fancier in England, says that breeding in-and-in does not + necessarily cause deterioration; "but all depends upon how this is + managed." "My plan has been to keep about five or six distinct runs, + and to rear about two hundred or three hundred chickens each year, and + select the best birds from each run for crossing. I thus secure + sufficient crossing to prevent deterioration."[274] + + We thus see that there is almost complete unanimity with + poultry-breeders that, when fowls are kept at the same place, evil + quickly follows from interbreeding carried on to an extent which would + be disregarded in the case of most quadrupeds. On the other hand, it is + a generally received opinion that cross-bred chickens are the hardiest + and most easily reared.[275] Mr. Tegetmeier, who has carefully attended + to poultry of all breeds, says[276] that Dorking hens, allowed to run + with Houdan or Crevecoeur cocks, "produce in the early spring chickens + that for size, hardihood, early maturity, and fitness for the market, + surpass those of any pure breed that we have ever raised." Mr. Hewitt + gives it as a general rule with fowls, that crossing the breed + increases their size. He makes this remark after stating that hybrids + from the pheasant and fowl are considerably larger than either + progenitor: so again, hybrids from the male golden pheasant and hen + common pheasant "are of far larger size than either parent-bird."[277] + To this subject of the increased size of hybrids I shall presently + return. + + With _Pigeons_, breeders are unanimous, as previously stated, that it + is absolutely indispensable, notwithstanding the trouble and expense + thus caused, occasionally to cross their much-prized birds with + individuals of another strain, but belonging, of course, to the same + variety. It deserves {126} notice that, when large size is one of the + desired characters, as with pouters,[278] the evil effects of close + interbreeding are much sooner perceived than when small birds, such as + short-faced tumblers, are valued. The extreme delicacy of the high + fancy breeds, such as these tumblers and improved English carriers, is + remarkable; they are liable to many diseases, and often die in the egg + or during the first moult; and their eggs have generally to be hatched + under foster-mothers. Although these highly-prized birds have + invariably been subjected to much close interbreeding, yet their + extreme delicacy of constitution cannot perhaps be thus fully + explained. Mr. Yarrell informed me that Sir J. Sebright continued + closely interbreeding some owl-pigeons, until from their extreme + sterility he as nearly as possible lost the whole family. Mr. + Brent[279] tried to raise a breed of trumpeters, by crossing a common + pigeon, and recrossing the daughter, granddaughter, + great-granddaughter, and great-great-granddaughter, with the same male + trumpeter, until he obtained a bird with 15/16ths of trumpeter's blood; + but then the experiment failed, for "breeding so close stopped + reproduction." The experienced Neumeister[280] also asserts that the + offspring from dovecotes and various other breeds are "generally very + fertile and hardy birds:" so again, MM. Boitard and Corbie,[281] after + forty-five years' experience, recommend persons to cross their breeds + for amusement; for, if they fail to make interesting birds, they will + succeed under an economical point of view, "as it is found that + mongrels are more fertile than pigeons of pure race." + + I will refer only to one other animal, namely, the Hive-bee, because a + distinguished entomologist has advanced this as a case of inevitable + close interbreeding. As the hive is tenanted by a single female, it + might have been thought that her male and female offspring would always + have bred together, more especially as bees of different hives are + hostile to each other; a strange worker being almost always attacked + when trying to enter another hive. But Mr. Tegetmeier has shown[282] + that this instinct does not apply to drones, which are permitted to + enter any hive; so that there is no _a priori_ improbability of a queen + receiving a foreign drone. The fact of the union invariably and + necessarily taking place on the wing, during the queen's nuptial + flight, seems to be a special provision against continued + interbreeding. However this may be, experience has shown, since the + introduction of the yellow-banded Ligurian race into Germany and + England, that bees freely cross: Mr. Woodbury, who introduced Ligurian + bees into Devonshire, found during a single season that three stocks, + at distances of from one to two miles from his hives, were crossed by + his drones. In one case the Ligurian drones must have flown over the + city of Exeter, and over several intermediate hives. On another + occasion several common black queens were crossed by Ligurian drones at + a distance of from one to three and a half miles.[283] + +{127} + +_Plants._ + + When a single plant of a new species is introduced into any country, if + propagated by seed, many individuals will soon be raised, so that if + the proper insects be present there will be crossing. With + newly-introduced trees or other plants not propagated by seed we are + not here concerned. With old-established plants it is an almost + universal practice occasionally to make exchanges of seed, by which + means individuals which have been exposed to different conditions of + life,--and this, as we have seen, diminishes the evil from close + interbreeding,--will occasionally be introduced into each district. + + Experiments have not been tried on the effects of fertilising flowers + with their own pollen during _several_ generations. But we shall + presently see that certain plants, either normally or abnormally, are + more or less sterile, even in the first generation, when fertilised by + their own pollen. Although nothing is directly known on the evil + effects of long-continued close interbreeding with plants, the converse + proposition that great good is derived from crossing is well + established. + + With respect to the crossing of individuals belonging to the same + sub-variety, Gaertner, whose accuracy and experience exceeded that of + all other hybridisers, states[284] that he has many times observed good + effects from this step, especially with exotic genera, of which the + fertility is somewhat impaired, such as Passiflora, Lobelia, and + Fuchsia. Herbert also says,[285] "I am inclined to think that I have + derived advantage from impregnating the flower from which I wished to + obtain seed with pollen from another individual of the same variety, or + at least from another flower, rather than with its own." Again, + Professor Lecoq asserts that he has ascertained that crossed offspring + are more vigorous and robust than their parents.[286] + + General statements of this kind, however, can seldom be fully trusted; + consequently I have begun a series of experiments, which, if they + continue to give the same results as hitherto, will for ever settle the + question of the good effects of crossing two distinct plants of the + same variety, and of the evil effects of self-fertilisation. A clear + light will thus also be thrown on the fact that flowers are invariably + constructed so as to permit, or favour, or necessitate the union of two + individuals. We shall clearly understand why monoecious and + dioecious,--why dimorphic and trimorphic plants exist, and many other + such cases. The plan which I have followed in my experiments is to grow + plants in the same pot, or in pots of the same size, or close together + in the open ground; to carefully exclude insects; and then to fertilise + some of the flowers with pollen from the same flower, and others on the + same plant with pollen from a distinct but adjoining plant. In many, + but not all, of these experiments, the crossed plants yielded much more + seed than the self-fertilised plants; and I have never seen the {128} + reversed case. The self-fertilised and crossed seeds thus obtained were + allowed to germinate in the same glass vessel on damp sand; and as the + seeds successively germinated, they were planted in pairs on opposite + sides of the same pot, with a superficial partition between them, and + were placed so as to be equally exposed to the light. In other cases + the self-fertilised and crossed seeds were simply sown on opposite + sides of the same small pot. I have, in short, followed different + plans, but in every case have taken all the precautions which I could + think of, so that the two lots should be equally favoured. Now, I have + carefully observed the growth of plants raised from crossed and + self-fertilised seed, from their germination to maturity, in species of + the following genera, namely, Brassica, Lathyrus, Lupinus, Lobelia, + Lactuca, Dianthus, Myosotis, Petunia, Linaria, Calceolaria, Mimulus, + and Ipomoea, and the difference in their powers of growth, and of + withstanding in certain cases unfavourable conditions, was most + manifest and strongly marked. It is of importance that the two lots of + seed should be sown or planted on opposite sides of the same pot, so + that the seedlings may struggle against each other; for if sown + separately in ample and good soil, there is often but little difference + in their growth. + + I will briefly describe the two most striking cases as yet observed by + me. Six crossed and six self-fertilised seeds of _Ipomoea purpurea_, + from plants treated in the manner above described, were planted as soon + as they had germinated, in pairs on opposite sides of two pots, and + rods of equal thickness were given them to twine up. Five of the + crossed plants grew from the first more quickly than the opposed + self-fertilised plants; the sixth, however, was weakly and was for a + time beaten, but at last its sounder constitution prevailed and it shot + ahead of its antagonist. As soon as each crossed plant reached the top + of its seven-foot rod its fellow was measured, and the result was that, + when the crossed plants were seven feet high, the self-fertilised had + attained the average height of only five feet four and a half inches. + The crossed plants flowered a little before, and more profusely than + the self-fertilised plants. On opposite sides of another _small_ pot a + large number of crossed and self-fertilised seeds were sown, so that + they had to struggle for bare existence; a single rod was given to each + lot: here again the crossed plants showed from the first their + advantage; they never quite reached the summit of the seven-foot rod, + but relatively to the self-fertilised plants their average height was + as seven feet to five feet two inches. The experiment was repeated in + the two following generations with plants raised from the + self-fertilised and crossed plants, treated in exactly the same manner, + and with nearly the same result. In the second generation, the crossed + plants, which were again crossed, produced 121 seed-capsules, whilst + the self-fertilised plants, again self-fertilised, produced only 84 + capsules. + + Some flowers of the _Mimulus luteus_ were fertilised with their own + pollen, and others were crossed with pollen from distinct plants + growing in the same pot. The seeds after germinating were thickly + planted on opposite sides of a pot. The seedlings were at first equal + in height; but when the young crossed plants were exactly half an inch, + the {129} self-fertilised plants were only a quarter of an inch high. + But this inequality did not continue, for, when the crossed plants were + four and a half inches high, the self-fertilised were three inches; and + they retained the same relative difference till their growth was + complete. The crossed plants looked far more vigorous than the + uncrossed, and flowered before them; they produced also a far greater + number of flowers, which yielded capsules (judging, however, from only + a few) containing more seeds. As in the former case, the experiment was + repeated in the same manner during the next two generations, and with + exactly the same result. Had I not watched these plants of the Mimulus + and Ipomoea during their whole growth, I could not have believed it + possible, that a difference apparently so slight, as that of the pollen + being taken from the same flower, and from a distinct plant growing in + the same small pot, could have made so wonderful a difference in the + growth and vigour of the plants thus produced. This, under a + physiological point of view, is a most remarkable phenomenon. + + * * * * * + + With respect to the benefit derived from crossing distinct varieties, + plenty of evidence has been published. Sageret[287] repeatedly speaks + in strong terms of the vigour of melons raised by crossing different + varieties, and adds that they are more easily fertilised than common + melons, and produce numerous good seed. Here follows the evidence of an + English gardener:[288] "I have this summer met with better success in + my cultivation of melons, in an unprotected state, from the seeds of + hybrids (_i.e._ mongrels) obtained by cross impregnation, than with old + varieties. The offspring of three different hybridisations (one more + especially, of which the parents were the two most dissimilar varieties + I could select) each yielded more ample and finer produce than any one + of between twenty and thirty established varieties." + + Andrew Knight[289] believed that his seedlings from crossed varieties + of the apple exhibited increased vigour and luxuriance; and M. + Chevreul[290] alludes to the extreme vigour of some of the crossed + fruit-trees raised by Sageret. + + By crossing reciprocally the tallest and shortest peas, Knight[291] + says, "I had in this experiment a striking instance of the stimulative + effects of crossing the breeds; for the smallest variety, whose height + rarely exceeded two feet, was increased to six feet; whilst the height + of the large and luxuriant kind was very little diminished." Mr. Laxton + gave me seed-peas produced from crosses between four distinct kinds; + and the plants thus raised were extraordinarily vigorous, being in each + case from one to two or three feet taller than the parent-forms growing + close alongside them. + + {130} + + Wiegmann[292] made many crosses between several varieties of cabbage; + and he speaks with astonishment of the vigour and height of the + mongrels, which excited the amazement of all the gardeners who beheld + them. Mr. Chaundy raised a great number of mongrels by planting + together six distinct varieties of cabbage. These mongrels displayed an + infinite diversity of character; "But the most remarkable circumstance + was, that, while all the other cabbages and borecoles in the nursery + were destroyed by a severe winter, these hybrids were little injured, + and supplied the kitchen when there was no other cabbage to be had." + + Mr. Maund exhibited before the Royal Agricultural Society[293] + specimens of crossed wheat, together with their parent varieties; and + the editor states that they were intermediate in character, "united + with that greater vigour of growth, which it appears, in the vegetable + as in the animal world, is the result of a first cross." Knight also + crossed several varieties of wheat,[294] and he says "that in the years + 1795 and 1796, when almost the whole crop of corn in the island was + blighted, the varieties thus obtained, and these only, escaped in this + neighbourhood, though sown in several different soils and situations." + + Here is a remarkable case: M. Clotzsch[295] crossed _Pinus sylvestris_ + and _nigricans_, _Quercus robur_ and _pedunculata, Alnus glutinosa_ and + _incana_, _Ulmus campestris_ and _effusa_; and the cross-fertilised + seeds, as well as seeds of the pure parent-trees, were all sown at the + same time and in the same place. The result was, that after an interval + of eight years, the hybrids were one-third taller than the pure trees! + + * * * * * + + The facts above given refer to undoubted varieties, excepting the trees + crossed by Clotzsch, which are ranked by various botanists as + strongly-marked races, sub-species, or species. That true hybrids + raised from entirely distinct species, though they lose in fertility, + often gain in size and constitutional vigour, is certain. It would be + superfluous to quote any facts; for all experimenters, Koelreuter, + Gaertner, Herbert, Sageret, Lecoq, and Naudin, have been struck with + the wonderful vigour, height, size, tenacity of life, precocity, and + hardiness of their hybrid productions. Gaertner[296] sums up his + conviction on this head in the strongest terms. Koelreuter[297] gives + numerous precise measurements of the weight and height of his hybrids + in comparison with measurements of both parent-forms; and speaks with + astonishment of their "_statura portentosa_," their "_ambitus + vastissimus ac altitudo valde conspicua_." Some exceptions to the rule + in the case of very sterile hybrids have, however, been noticed by + Gaertner and {131} Herbert; but the most striking exceptions are given + by Max Wichura,[298] who found that hybrid willows were generally + tender in constitution, dwarf, and short-lived. + + Koelreuter explains the vast increase in the size of the roots, stems, + &c., of his hybrids, as the result of a sort of compensation due to + their sterility, in the same way as many emasculated animals are larger + than the perfect males. This view seems at first sight extremely + probable, and has been accepted by various authors;[299] but + Gaertner[300] has well remarked that there is much difficulty in fully + admitting it; for with many hybrids there is no parallelism between the + degree of their sterility and their increased size and vigour. The most + striking instances of luxuriant growth have been observed with hybrids + which were not sterile in any extreme degree. In the genus Mirabilis, + certain hybrids are unusually fertile, and their extraordinary + luxuriance of growth, together with their enormous roots,[301] have + been transmitted to their progeny. The increased size of the hybrids + produced between the fowl and pheasant, and between the distinct + species of pheasants, has been already noticed. The result in all cases + is probably in part due to the saving of nutriment and vital force + through the sexual organs not acting, or acting imperfectly, but more + especially to the general law of good being derived from a cross. For + it deserves especial attention that mongrel animals and plants, which + are so far from being sterile that their fertility is often actually + augmented, have, as previously shown, their size, hardiness, and + constitutional vigour generally increased. It is not a little + remarkable that an accession of vigour and size should thus arise under + the opposite contingencies of increased and diminished fertility. + + It is a perfectly well ascertained fact[302] that hybrids will + invariably breed more readily with either pure parent, and not rarely + with a distinct species, than with each other. Herbert is inclined to + explain even this fact by the advantage derived from a cross; but + Gaertner more justly accounts for it by the pollen of the hybrid, and + probably its ovules, being in some degree vitiated, whereas the pollen + and ovules of both pure parents and of any third species are sound. + Nevertheless there are some well-ascertained and remarkable facts, + which, as we shall immediately see, show that the act of crossing in + itself undoubtedly tends to increase or re-establish the fertility of + hybrids. + +_On certain Hermaphrodite Plants which, either normally or abnormally, +require to be fertilised by pollen from a distinct individual or species._ + +The facts now to be given differ from those hitherto detailed, as the +self-sterility does not here result from long-continued, {132} close +interbreeding. These facts are, however, connected with our present +subject, because a cross with a distinct individual is shown to be either +necessary or advantageous. Dimorphic and trimorphic plants, though they are +hermaphrodites, must be reciprocally crossed, one set of forms by the +other, in order to be fully fertile, and in some cases to be fertile in any +degree. But I should not have noticed these plants, had it not been for the +following cases given by Dr. Hildebrand:[303]-- + + _Primula sinensis_ is a reciprocally dimorphic species: Dr. Hildebrand + fertilised twenty-eight flowers of both forms, each by pollen of the + other form, and obtained the full number of capsules containing on an + average 42.7 seed per capsule; here we have complete and normal + fertility. He then fertilised forty-two flowers of both forms with + pollen of the same form, but taken from a distinct plant, and all + produced capsules containing on an average only 19.6 seed. Lastly, and + here we come to our more immediate point, he fertilised forty-eight + flowers of both forms with pollen of the same form, taken from the same + flower, and now he obtained only thirty-two capsules, and these + contained on an average 18.6 seed, or one less per capsule than in the + former case. So that, with these illegitimate unions, the act of + impregnation is less assured, and the fertility slightly less, when the + pollen and ovules belong to the same flower, than when belonging to two + distinct individuals of the same form. Dr. Hildebrand has recently made + analogous experiments on the long-styled form of _Oxalis rosea_, with + the same result.[304] + +It has recently been discovered that certain plants, whilst growing in +their native country under natural conditions, cannot be fertilised with +pollen from the same plant. They are sometimes so utterly self-impotent, +that, though they can readily be fertilised by the pollen of a distinct +species or even distinct genus, yet, wonderful as the fact is, they never +produce a single seed by their own pollen. In some cases, moreover, the +plant's own pollen and stigma mutually act on each other in a deleterious +manner. Most of the facts to be given relate to Orchids, but I will +commence with a plant belonging to a widely different family. + + Sixty-three flowers of _Corydalis cava_, borne on distinct plants, were + fertilised by Dr. Hildebrand[305] with pollen from other plants of the + same species; and fifty-eight capsules were obtained, including on an + average {133} 4.5 seed in each. He then fertilised sixteen flowers + produced by the same raceme, one with another, but obtained only three + capsules, one of which alone contained any good seeds, namely, two in + number. Lastly, he fertilised twenty-seven flowers, each with its own + pollen; he left also fifty-seven flowers to be spontaneously + fertilised, and this would certainly have ensued if it had been + possible, for the anthers not only touch the stigma, but the + pollen-tubes were seen by Dr. Hildebrand to penetrate it; nevertheless + these eighty-four flowers did not produce a single seed-capsule! This + whole case is highly instructive, as it shows how widely different the + action of the same pollen is, according as it is placed on the stigma + of the same flower, or on that of another flower on the same raceme, or + on that of a distinct plant. + + With exotic Orchids several analogous cases have been observed, chiefly + by Mr. John Scott.[306] _Oncidium sphacelatum_ has effective pollen, + for with it Mr. Scott fertilised two distinct species; its ovules are + likewise capable of impregnation, for they were readily fertilised by + the pollen of _O. divaricatum_; nevertheless, between one and two + hundred flowers fertilised by their own pollen did not produce a single + capsule, though the stigmas were penetrated by the pollen-tubes. Mr. + Robinson Munro, of the Royal Botanic Gardens of Edinburgh, also informs + me (1864) that a hundred and twenty flowers of this same species were + fertilised by him with their own pollen, and did not produce a capsule, + but eight flowers fertilised by the pollen of _O. divaricatum_ produced + four fine capsules: again, between two and three hundred flowers of _O. + divaricatum_, fertilised by their own pollen, did not set a capsule, + but twelve flowers fertilised by _O. flexuosum_ produced eight fine + capsules: so that here we have three utterly self-impotent species, + with their male and female organs perfect, as shown by their mutual + fertilisation. In these cases fertilisation was effected only by the + aid of a distinct species. But, as we shall presently see, distinct + plants, raised from seed, of _Oncidium flexuosum_, and probably of the + other species, would have been perfectly capable of fertilising each + other, for this is the natural process. Again, Mr. Scott found that the + pollen of a plant of _O. microchilum_ was good, for with it he + fertilised two distinct species; he found its ovules good, for they + could be fertilised by the pollen of one of these species, and by the + pollen of a distinct plant of _O. microchilum_; but they could not be + fertilised by pollen of the same plant, though the pollen-tubes + penetrated the stigma. An analogous case has been recorded by M. + Riviere,[307] with two plants of _O. Cavendishianum_, which were both + self-sterile, but reciprocally fertilised each other. All these cases + refer to the genus Oncidium, but Mr. Scott found that _Maxillaria + atro-rubens_ was "totally insusceptible of fertilisation with its own + pollen," but fertilised, and was fertilised by, a widely distinct + species, viz. _M. squalens_. + + As these orchids had grown under unnatural conditions, in {134} + hot-houses, I concluded without hesitation that their self-sterility + was due to this cause. But Fritz Mueller informs me that at Desterro, + in Brazil, he fertilised above one hundred flowers of the + above-mentioned _Oncidium flexuosum_, which is there endemic, with its + own pollen, and with that taken from distinct plants; all the former + were sterile, whilst those fertilised by pollen from any _other plant_ + of the same species were fertile. During the first three days there was + no difference in the action of the two kinds of pollen: that placed on + the stigma of the same plant separated in the usual manner into grains, + and emitted tubes which penetrated the column, and the stigmatic + chamber shut itself; but the flowers alone which had been fertilised by + pollen taken from a distinct plant produced seed-capsules. On a + subsequent occasion these experiments were repeated on a large scale + with the same result. Fritz Mueller found that four other endemic + species of Oncidium were in like manner utterly sterile with their own + pollen, but fertile with that from any other plant: some of them + likewise produced seed-capsules when impregnated with pollen of widely + distinct genera, such as Leptotes, Cyrtopodium, and Rodriguezia! + _Oncidium crispum_, however, differs from the foregoing species in + varying much in its self-sterility; some plants producing fine pods + with their own pollen, others failing to do so; in two or three + instances, Fritz Mueller observed that the pods produced by pollen + taken from a distinct flower on the same plant, were larger than those + produced by the flower's own pollen. In _Epidendrum cinnabarinum_, an + orchid belonging to another division of the family, fine pods were + produced by the plant's own pollen, but they contained by weight only + about half as much seed as the capsules which had been fertilized by + pollen from a distinct plant, and in one instance from a distinct + species; moreover, a very large proportion, and in some cases nearly + all the seed produced by the plant's own pollen, was embryonless and + worthless. Some self-fertilized capsules of a Maxillaria were in a + similar state. + + Another observation made by Fritz Mueller is highly remarkable, namely, + that with various orchids the plant's own pollen not only fails to + impregnate the flower, but acts on the stigma, and is acted on, in an + injurious or poisonous manner. This is shown by the surface of the + stigma in contact with the pollen, and by the pollen itself, becoming + in from three to five days dark brown, and then decaying. The + discolouration and decay are not caused by parasitic cryptogams, which + were observed by Fritz Mueller in only a single instance. These changes + are well shown by placing on the same stigma, at the same time, the + plant's own pollen and that from a distinct plant of the same species, + or of another species, or even of another and widely remote genus. + Thus, on the stigma of _Oncidium flexuosum_, the plant's own pollen and + that from a distinct plant were placed side by side, and in five days' + time the latter was perfectly fresh, whilst the plant's own pollen was + brown. On the other hand, when the pollen of a distinct plant of the + _Oncidium flexuosum_, and of the _Epidendrum zebra_ (_nov. spec.?_), + were placed together on the same stigma, they behaved in exactly the + same manner, the grains separating, emitting tubes, and penetrating the + stigma, so that the two {135} pollen-masses, after an interval of + eleven days, could not be distinguished except by the difference of + their caudicles, which, of course, undergo no change. Fritz Mueller + has, moreover, made a large number of crosses between orchids belonging + to distinct species and genera, and he finds that in all cases when the + flowers are not fertilised their footstalks first begin to wither; and + the withering slowly spreads upwards until the germens fall off, after + an interval of one or two weeks, and in one instance of between six and + seven weeks; but even in this latter case, and in most other cases, the + pollen and stigma remained in appearance fresh. Occasionally, however, + the pollen becomes brownish, generally on the external surface, and not + in contact with the stigma, as is invariably the case when the plant's + own pollen is applied. + + Fritz Mueller observed the poisonous action of the plant's own pollen + in the above-mentioned _Oncidium flexuosum_, _O. unicorne, pubes_ + (_?_), and in two other unnamed species. Also in two species of + Rodriguezia, in two of Notylia, in one of Burlingtonia, and of a fourth + genus in the same group. In all these cases, except the last, it was + proved that the flowers were, as might have been expected, fertile with + pollen from a distinct plant of the same species. Numerous flowers of + one species of Notylia were fertilized with pollen from the same + raceme; in two days' time they all withered, the germens began to + shrink, the pollen-masses became dark brown, and not one pollen-grain + emitted a tube. So that in this orchid the injurious action of the + plant's own pollen is more rapid than with _Oncidium flexuosum_. Eight + other flowers on the same raceme were fertilized with pollen from a + distinct plant of the same species: two of these were dissected, and + their stigmas were found to be penetrated by numberless pollen-tubes; + and the germens of the other six flowers became well developed. On a + subsequent occasion many other flowers were fertilized with their own + pollen, and all fell off dead in a few days; whilst some flowers on the + same raceme which had been left simply unfertilised adhered and long + remained fresh. We have seen that in cross-unions between extremely + distinct orchids the pollen long remains undecayed; but Notylia behaved + in this respect differently; for when its pollen was placed on the + stigma of _Oncidium flexuosum_, both the stigma and pollen quickly + became dark brown, in the same manner as if the plant's own pollen had + been applied. + + Fritz Mueller suggests that, as in all these cases the plant's own + pollen is not only impotent (thus effectually preventing + self-fertilization), but likewise prevents, as was ascertained in the + case of the Notylia and _Oncidium flexuosum_, the action of + subsequently applied pollen from a distinct individual, it would be an + advantage to the plant to have its own pollen rendered more and more + deleterious; for the germens would thus quickly be killed, and, + dropping off, there would be no further waste in nourishing a part + which ultimately could be of no avail. Fritz Mueller's discovery that a + plant's own pollen and stigma in some cases act on each other as if + mutually poisonous, is certainly most remarkable. + +We now come to cases closely analogous with those just {136} given, but +different, inasmuch as individual plants alone of the species are +self-impotent. This self-impotence does not depend on the pollen or ovules +being in a state unfit for fertilisation, for both have been found +effective in union with other plants of the same or of a distinct species. +The fact of these plants having spontaneously acquired so peculiar a +constitution, that they can be fertilised more readily by the pollen of a +distinct species than by their own, is remarkable. These abnormal cases, as +well as the foregoing normal cases, in which certain orchids, for instance, +can be much more easily fertilised by the pollen of a distinct species than +by their own, are exactly the reverse of what occurs with all ordinary +species. For in these latter the two sexual elements of the same individual +plant are capable of freely acting on each other; but are so constituted +that they are more or less impotent when brought into union with the sexual +elements of a distinct species, and produce more or less sterile hybrids. +It would appear that the pollen or ovules, or both, of the individual +plants which are in this abnormal state, have been affected in some strange +manner by the conditions to which they themselves or their parents have +been exposed; but whilst thus rendered self-sterile, they have retained the +capacity common to most species of partially fertilizing and being +partially fertilized by allied forms. However this may be, the subject, to +a certain extent, is related to our general conclusion that good is derived +from the act of crossing. + + Gaertner experimented on two plants of _Lobelia fulgens_, brought from + separate places, and found[308] that their pollen was good, for he + fertilised with it _L. cardinalis_ and _syphilitica_; their ovules were + likewise good, for they were fertilised by the pollen of these same two + species; but these two plants of _L. fulgens_ could not be fertilised + by their own pollen, as can generally be effected with perfect ease + with this species. Again, the pollen of a plant of _Verbascum nigrum_ + grown in a pot was found by Gaertner[309] capable of fertilising _V. + lychnitis_ and _V. Austriacum_; the ovules could be fertilised by the + pollen of _V. thapsus_; but the flowers could not be fertilised by + their own pollen. Koelreuter, also,[310] gives the case of three {137} + garden plants of _Verbascum phoeniceum_, which bore during two years + many flowers; these he successfully fertilised by the pollen of no less + than four distinct species, but they produced not a seed with their own + apparently good pollen; subsequently these same plants, and others + raised from seed, assumed a strangely fluctuating condition, being + temporarily sterile on the male or female side, or on both sides, and + sometimes fertile on both sides; but two of the plants were perfectly + fertile throughout the summer. + + It appears[311] that certain flowers on certain plants of _Lilium + candidum_ can be fertilised more easily by pollen from a distinct + individual than by their own. So, again, with the varieties of the + potato. Tinzmann,[312] who made many trials with this plant, says that + pollen from another variety sometimes "exerts a powerful influence, and + I have found sorts of potatoes which would not bear seed from + impregnation with the pollen of their own flowers, would bear it when + impregnated with other pollen." It does not, however, appear to have + been proved that the pollen which failed to act on the flower's own + stigma was in itself good. + + In the genus Passiflora it has long been known that several species do + not produce fruit, unless fertilised by pollen taken from distinct + species: thus, Mr. Mowbray[313] found that he could not get fruit from + _P. alata_ and _racemosa_ except by reciprocally fertilising them with + each other's pollen. Similar facts have been observed in Germany and + France;[314] and I have received two authentic accounts of _P. + quadrangularis_, which never produced fruit with its own pollen, but + would do so freely when fertilised in one case with the pollen of _P. + coerulea_, and in another case with that of _P. edulis_. So again, with + respect to _P. laurifolia_, a cultivator of much experience has + recently remarked[315] that the flowers "must be fertilised with the + pollen of _P. coerulea_, or of some other common kind, as their own + pollen will not fertilise them." But the fullest details on this + subject have been given by Mr. Scott:[316] plants of _Passiflora + racemosa_, _coerulea_, and _alata_ flowered profusely during many years + in the Botanic Gardens of Edinburgh, and, though repeatedly fertilised + by Mr. Scott and by others with their own pollen, never produced any + seed; yet this occurred at once with all three species when they were + crossed together in various ways. But in the case of _P. coerulea_, + three plants, two of which grew in the Botanic Gardens, were all + rendered fertile, merely by impregnating the one with pollen of the + other. The same result was attained in the same manner with _P. alata_, + but only with one plant out of three. As so many self-sterile species + have been mentioned, it may be stated that in the case of _P. + gracilis_, which is an annual, the flowers are nearly as fertile with + their own pollen as with that from a distinct plant; thus sixteen + flowers {138} spontaneously self-fertilised produced fruit, each + containing on an average 21.3 seed, whilst fruit from fourteen crossed + flowers contained 24.1 seed. + + Returning to _P. alata_, I have received (1866) some interesting + details from Mr. Robinson Munro. Three plants, including one in + England, have already been mentioned which were inveterately + self-sterile, and Mr. Munro informs me of several others which, after + repeated trials during many years, have been found in the same + predicament. At some other places, however, this species fruits readily + when fertilised with its own pollen. At Taymouth Castle there is a + plant which was formerly grafted by Mr. Donaldson on a distinct + species, name unknown, and ever since the operation it has produced + fruit in abundance by its own pollen; so that this small and unnatural + change in the state of this plant has restored its self-fertility! Some + of the seedlings from the Taymouth Castle plant were found to be not + only sterile with their own pollen, but with each other's pollen, and + with the pollen of distinct species. Pollen from the Taymouth plant + failed to fertilise certain plants of the same species, but was + successful on one plant in the Edinburgh Botanic Gardens. Seedlings + were raised from this latter union, and some of their flowers were + fertilised by Mr. Munro with their own pollen; but they were found to + be as self-impotent as the mother-plant had always proved, except when + fertilised by the grafted Taymouth plant, and except, as we shall see, + when fertilised by her own seedlings. For Mr. Munro fertilised eighteen + flowers on the self-impotent mother-plant with pollen from these her + own self-impotent seedlings, and obtained, remarkable as the fact is, + eighteen fine capsules full of excellent seed! I have met with no case + in regard to plants which shows so well as this of _P. alata_, on what + small and mysterious causes complete fertility or complete sterility + depends. + +The facts hitherto given relate to the much-lessened or completely +destroyed fertility of pure species when impregnated with their own pollen, +in comparison with their fertility when impregnated by distinct individuals +or distinct species; but closely analogous facts have been observed with +hybrids. + + Herbert states[317] that having in flower at the same time nine hybrid + Hippeastrums, of complicated origin, descended from several species, he + found that "almost every flower touched with pollen from another cross + produced seed abundantly, and those which were touched with their own + pollen either failed entirely, or formed slowly a pod of inferior size, + with fewer seeds." In the 'Horticultural Journal' he adds that, "the + admission of the pollen of another cross-bred Hippeastrum (however + complicated the cross) to any _one_ flower of the number, is almost + sure to check the fructification of the others." In a letter written to + me in 1839, Dr. Herbert says that he had already tried these + experiments during five consecutive years, and he subsequently repeated + them, with the same invariable result. {139} He was thus led to make an + analogous trial on a pure species, namely, on the _Hippeastrum + aulicum_, which he had lately imported from Brazil: this bulb produced + four flowers, three of which were fertilised by their own pollen, and + the fourth by the pollen of a triple cross between _H. bulbulosum_, + _reginae_, and _vittatum_; the result was, that "the ovaries of the + three first flowers soon ceased to grow, and after a few days perished + entirely: whereas the pod impregnated by the hybrid made vigorous and + rapid progress to maturity, and bore good seed, which vegetated + freely." This is, indeed, as Herbert remarks, "a strange truth," but + not so strange as it then appeared. + + As a confirmation of these statements, I may add that Mr. M. + Mayes,[318] after much experience in crossing the species of Amaryllis + (Hippeastrum), says, "neither the species nor the hybrids will, we are + well aware, produce seed so abundantly from their own pollen as from + that of others." So, again, Mr. Bidwell, in New South Wales,[319] + asserts that _Amaryllis belladonna_ bears many more seeds when + fertilised by the pollen of _Brunswigia_ (_Amaryllis_ of some authors) + _Josephinae_ or of _B. multiflora_, than when fertilised by its own + pollen. Mr. Beaton dusted four flowers of a Cyrtanthus with their own + pollen, and four with the pollen of _Vallota_ (_Amaryllis_) _purpurea_; + on the seventh day "those which received their own pollen slackened + their growth, and ultimately perished; those which were crossed with + the Vallota held on."[320] These latter cases, however, relate to + uncrossed species, like those before given with respect to Passiflora, + Orchids, &c., and are here referred to only because the plants belong + to the same group of Amaryllidaceae. + + In the experiments on the hybrid Hippeastrums, if Herbert had found + that the pollen of two or three kinds alone had been more efficient on + certain kinds than their own pollen, it might have been argued that + these, from their mixed parentage, had a closer mutual affinity than + the others; but this explanation is inadmissible, for the trials were + made reciprocally backwards and forwards on nine different hybrids; and + a cross, whichever way taken, always proved highly beneficial. I can + add a striking and analogous case from experiments made by the Rev. A. + Rawson, of Bromley Common, with some complex hybrids of Gladiolus. This + skilful horticulturist possessed a number of French varieties, + differing from each other only in the colour and size of the flowers, + all descended from Gandavensis, a well-known old hybrid, said to be + descended from _G. Natalensis_ by the pollen of _G. + oppositiflorus_.[321] Mr. Rawson, after repeated trials, found that + none of the varieties would set seed with their own pollen, although + {140} taken from distinct plants of the same variety, which had, of + course, been propagated by bulbs, but that they all seeded freely with + pollen from any other variety. To give two examples: Ophir did not + produce a capsule with its own pollen, but when fertilised with that of + Janire, Brenchleyensis, Vulcain, and Linne, it produced ten fine + capsules; but the pollen of Ophir was good, for when Linne was + fertilised by it seven capsules were produced. This later variety, on + the other hand, was utterly barren with its own pollen, which we have + seen was perfectly efficient on Ophir. Altogether, Mr. Rawson, in the + year 1861, fertilised twenty-six flowers borne by four varieties with + pollen taken from other varieties, and every single flower produced a + fine seed-capsule; whereas fifty-two flowers on the same plants, + fertilised at the same time with their own pollen, did not yield a + single seed-capsule. Mr. Rawson fertilised, in some cases, the + alternate flowers, and in other cases all those down one side of the + spike, with pollen of other varieties, and the remaining flowers with + their own pollen; I saw these plants when the capsules were nearly + mature, and their curious arrangement at once brought full conviction + to the mind that an immense advantage had been derived from crossing + these hybrids. + + Lastly, I have heard from Dr. E. Bornet, of Antibes, who has made + numerous experiments in crossing the species of Cistus, but as not yet + published the results, that, when any of these hybrids are fertile, + they may be said to be, in regard to function, dioecious; "for the + flowers are always sterile when the pistil is fertilised by pollen + taken from the same flower or from flowers on the same plant. But they + are often fertile if pollen be employed from a distinct individual of + the same hybrid nature, or from a hybrid made by a reciprocal cross." + +_Conclusion._--The facts just given, which show that certain plants are +self-sterile, although both sexual elements are in a fit state for +reproduction when united with distinct individuals of the same or other +species, appear at first sight opposed to all analogy. The sexual elements +of the same flower have become, as already remarked, differentiated in +relation to each other, almost like those of two distinct species. + +With respect to the species which, whilst living under their natural +conditions, have their reproductive organs in this peculiar state, we may +conclude that it has been naturally acquired for the sake of effectually +preventing self-fertilisation. The case is closely analous with dimorphic +and trimorphic plants, which can be fully fertilised only by plants belong +to the opposite form, and not, as in the foregoing cases, in differently by +any other plant. Some of these dimorphic plants are completely sterile with +pollen taken from the same plant or from the same {141} form. It is +interesting to observe the graduated series from plants which, when +fertilised by their own pollen, yield the full number of seed, but with the +seedlings a little dwarfed in stature--to plants which when self-fertilised +yield few seeds--to those with yield none--and, lastly, to those in which +the plant's own pollen and stigma act on each other like poison. This +peculiar state of the reproductive organs, when occurring in certain +individuals alone, is evidently abnormal; and as it chiefly affects exotic +plants, or indigenous plants cultivated in pots, we may attribute it to +some change in the conditions of life, acting on the plants themselves or +on their parents. The self-impotent _Passiflora alata_, which recovered its +self-fertility after having been grafted on a distinct stock, shows how +small a change is sufficient to act powerfully on the reproductive system. +The possibility of a plant becoming under culture self-impotent is +interesting as throwing light on the occurrence of this same condition in +natural species. A cultivated plant in this state generally remains so +during its whole life; and from this fact we may infer that the state is +probably congenital. + +Koelreuter, however, has described some plants of Verbascum which varied in +this respect even during the same season. As in all the normal cases, and +in many, probably in most, of the abnormal cases, any two self-impotent +plants can reciprocally fertilize each other, we may infer that a very +slight difference in the nature of their sexual elements suffices to give +fertility; but in other instances, as with some Passifloras and the hybrid +Gladioli, a greater degree of differentiation appears to be necessary, for +with these plants fertility is gained only by the union of distinct +species, or of hybrids of distinct parentage. These facts all point to the +same general conclusion, namely, that good is derived from a cross between +individuals, which either innately, or from exposure to dissimilar +conditions, have come to differ in sexual constitution. + +Exotic animals confined in menageries are sometimes in nearly the same +state as the above-described self-impotent plants; for, as we shall see in +the following chapter, certain monkeys, the larger carnivora, several +finches, geese, and pheasants, cross together, quite as freely as, or even +more freely than, the individuals of the same species breed together. Cases +will, {142} also, be given of sexual incompatibility between certain male +and female domesticated animals, which, nevertheless, are fertile when +matched with any other individual of the same kind. + +In the early part of this chapter it was shown that the crossing of +distinct forms, whether closely or distantly allied, gives increased size +and constitutional vigour, and, except in the case of crossed species, +increased fertility, to the offspring. The evidence rests on the universal +testimony of breeders (for it should be observed that I am not here +speaking of the evil results of close interbreeding), and is practically +exemplified in the higher value of cross-bred animals for immediate +consumption. The good results of crossing have also been demonstrated, in +the case of some animals and of numerous plants, by actual weight and +measurement. Although animals of pure blood will obviously be deteriorated +by crossing, as far as their characteristic qualities are concerned, there +seems to be no exception to the rule that advantages of the kind just +mentioned are thus gained, even when there has not been any previous close +interbreeding. The rule applies to all animals, even to cattle and sheep, +which can long resist breeding in-and-in between the nearest +blood-relations. It applies to individuals of the same sub-variety but of +distinct families, to varieties or races, to sub-species, as well as to +quite distinct species. + +In this latter case, however, whilst size, vigour, precocity, and hardiness +are, with rare exceptions, gained, fertility, in a greater or less degree, +is lost; but the gain cannot be exclusively attributed to the principle of +compensation; for there is no close parallelism between the increased size +and vigour of the offspring and their sterility. Moreover it has been +clearly proved that mongrels which are perfectly fertile gain these same +advantages as well as sterile hybrids. + +The evil consequences of long-continued close interbreeding are not so +easily recognised as the good effects from crossing, for the deterioration +is gradual. Nevertheless it is the general opinion of those who have had +most experience, especially with animals which propagate quickly, that evil +does inevitably follow sooner or later, but at different rates with +different animals. No doubt a false belief may widely prevail like a +superstition; yet it is difficult to suppose that so many acute and +original {143} observers have all been deceived at the expense of much cost +and trouble. A male animal may sometimes be paired with his daughter, +granddaughter, and so on, even for seven generations, without any manifest +bad result; but the experiment has never been tried of matching brothers +and sisters, which is considered the closest form of interbreeding, for an +equal number of generations. There is good reason to believe that by +keeping the members of the same family in distinct bodies, especially if +exposed to somewhat different conditions of life, and by occasionally +crossing these families, the evil results may be much diminished, or quite +eliminated. These results are loss of constitutional vigour, size, and +fertility; but there is no necessary deterioration in the general form of +the body, or in other good qualities. We have seen that with pigs +first-rate animals have been produced after long-continued close +interbreeding, though they had become extremely infertile when paired with +their near relations. The loss of fertility, when it occurs, seems never to +be absolute, but only relative to animals of the same blood; so that this +sterility is to a certain extent analogous with that of self-impotent +plants which cannot be fertilised by their own pollen, but are perfectly +fertile with pollen of any other plant of the same species. The fact of +infertility of this peculiar nature being one of the results of +long-continued interbreeding, shows that interbreeding does not act merely +by combining and augmenting various morbid tendencies common to both +parents; for animals with such tendencies, if not at the time actually ill, +can generally propagate their kind. Although offspring descended from the +nearest blood-relations are not necessarily deteriorated in structure, yet +some authors[322] believe that they are eminently liable to malformations; +and this is not improbable, as everything which lessens the vital powers +acts in this manner. Instances of this kind have been recorded in the case +of pigs, bloodhounds, and some other animals. + +Finally, when we consider the various facts now given which plainly show +that good follows from crossing, and less plainly {144} that evil follows +from close interbreeding, and when we bear in mind that throughout the +whole organic world elaborate provision has been made for the occasional +union of distinct individuals, the existence of a great law of nature is, +if not proved, at least rendered in the highest degree probable; namely, +that the crossing of animals and plants which are not closely related to +beach other is highly beneficial or even necessary, and that interbreeding +prolonged during many generations is highly injurious. + + * * * * * + + +{145} + +CHAPTER XVIII. + +ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED CONDITIONS OF LIFE: +STERILITY FROM VARIOUS CAUSES. + + ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE CONDITIONS OF + LIFE--STERILITY FROM CHANGED CONDITIONS, IN ANIMALS, IN THEIR NATIVE + COUNTRY AND IN MENAGERIES--MAMMALS, BIRDS, AND INSECTS--LOSS OF + SECONDARY SEXUAL CHARACTERS AND OF INSTINCTS--CAUSES OF + STERILITY--STERILITY OF DOMESTICATED ANIMALS FROM CHANGED + CONDITIONS--SEXUAL INCOMPATIBILITY OF INDIVIDUAL ANIMALS--STERILITY OF + PLANTS FROM CHANGED CONDITIONS OF LIFE--CONTABESCENCE OF THE + ANTHERS--MONSTROSITIES AS A CAUSE OF STERILITY--DOUBLE + FLOWERS--SEEDLESS FRUIT--STERILITY FROM THE EXCESSIVE DEVELOPMENT OF + THE ORGANS OF VEGETATION--FROM LONG-CONTINUED PROPAGATION BY + BUDS--INCIPIENT STERILITY THE PRIMARY CAUSE OF DOUBLE FLOWERS AND + SEEDLESS FRUIT. + +_On the Good derived from slight Changes in the Conditions of Life._--In +considering whether any facts were known which might throw light on the +conclusion arrived at in the last chapter, namely, that benefits ensue from +crossing, and that it is a law of nature that all organic beings should +occasionally cross, it appeared to me probable that the good derived from +slight changes in the conditions of life, from being an analogous +phenomenon, might serve this purpose. No two individuals, and still less no +two varieties, are absolutely alike in constitution and structure; and when +the germ of one is fertilised by the male element of another, we may +believe that it is acted on in a somewhat similar manner as an individual +when exposed to slightly changed conditions. Now, every one must have +observed the remarkable influence on convalescents of a change of +residence, and no medical man doubts the truth of this fact. Small farmers +who hold but little land are convinced that their cattle derive great +benefit from a change of pasture. In the case of plants, the evidence is +strong that a great advantage is derived from exchanging seeds, tubers, +bulbs, and cuttings from one soil or place to another as different as +possible. {146} + + The belief that plants are thus benefited, whether or not well founded, + has been firmly maintained from the time of Columella, who wrote + shortly after the Christian era, to the present day; and it now + prevails in England, France, and Germany.[323] A sagacious observer, + Bradley, writing in 1724,[324] says, "When we once become Masters of a + good Sort of Seed, we should at least put it into Two or Three Hands, + where the Soils and Situations are as different as possible; and every + Year the Parties should change with one another; by which Means, I find + the Goodness of the Seed will be maintained for several Years. For Want + of this Use many Farmers have failed in their Crops and been great + Losers." He then gives his own practical experience on this head. A + modern writer[325] asserts, "Nothing can be more clearly established in + agriculture than that the continual growth of any one variety in the + same district makes it liable to deterioration either in quality or + quantity." Another writer states that he sowed close together in the + same field two lots of wheat-seed, the product of the same original + stock, one of which had been grown on the same land, and the other at a + distance, and the difference in favour of the crop from the latter seed + was remarkable. A gentleman in Surrey who has long made it his business + to raise wheat to sell for seed, and who has constantly realised in the + market higher prices than others, assures me that he finds it + indispensable continually to change his seed; and that for this purpose + he keeps two farms differing much in soil and elevation. + + With respect to the tubers of the potato, I find that at the present + day the practice of exchanging sets is almost everywhere followed. The + great growers of potatoes in Lancashire formerly used to get tubers + from Scotland, but they found that "a change from the moss-lands, and + _vice versa_, was generally sufficient." In former times in France the + crop of potatoes in the Vosges had become reduced in the course of + fifty or sixty years in the proportion from 120-150 to 30-40 bushels; + and the famous Oberlin attributed the surprising good which he effected + in large part to changing the sets.[326] + + A well-known practical gardener, Mr. Robson[327] positively states that + he has himself witnessed decided advantage from obtaining bulbs of the + onion, tubers of the potato, and various seeds, all of the same kind, + from different soils and distant parts of England. He further states + that with {147} plants propagated by cuttings, as with the Pelargonium, + and especially the Dahlia, manifest advantage is derived from getting + plans of the same variety, which have been cultivated in another place; + or, "where the extent of the place allows, to take cuttings from one + description of soil to plant on another, so as to afford the change + that seems so necessary to the well-being of the plants." He maintains + that after a time an exchange of this nature is "forced on the grower, + whether he be prepared for it or not." Similar remarks have been made + by another excellent gardener, Mr. Fish, namely, that cuttings of the + same variety of Calceolaria, which he obtained from a neighbour, + "showed much greater vigour than some of his own that were treated in + exactly the same manner," and he attributed this solely to his own + plants having become "to a certain extent worn out or tired of their + quarters." Something of this kind apparently occurs in grafting and + budding fruit-trees; for, according to Mr. Abbey, grafts or buds + generally take on a distinct variety or even species, or on a stock + previously grafted, with greater facility than on stocks raised from + seeds of the variety which is to be grafted; and he believes this + cannot be altogether explained by the stocks in question being better + adapted to the soil and climate of the place. It should, however, be + added, that varieties grafted or budded on very distinct kinds, though + they may take more readily and grow at first more vigorously than when + grafted on closely allied stocks, afterwards often become unhealthy. + + I have studied M. Tessier's careful and elaborate experiments,[328] + made to disprove the common belief that good is derived from a change + of seed; and he certainly shows that the same seed may with care be + cultivated on the same farm (it is not stated whether on exactly the + same soil) for ten consecutive years without loss. Another excellent + observer, Colonel Le Couteur,[329] has come to the same conclusion; but + then he expressly adds, if the same seed be used, "that which is grown + on land manured from the mixen one year becomes seed for land prepared + with lime, and that again becomes seed for land dressed with ashes, + then for land dressed with mixed manure, and so on." But this in effect + is a systematic exchange of seed, within the limits of the same farm. + +On the whole the belief, which has long been held by many skilful +cultivators, that good follows from exchanging seed, tubers, &c., seems to +be fairly well founded. Considering the small size of most seeds, it seems +hardly credible that the advantage thus derived can be due to the seeds +obtaining in one soil some chemical element deficient in the other soil. As +plants after once germinating naturally become fixed to the same spot, it +might have been anticipated that they would show the good effects of a +change more plainly than animals, which continually wander about; and this +apparently is the {148} case. Life depending on, or consisting in, an +incessant play of the most complex forces, it would appear that their +action is in some way stimulated by slight changes in the circumstances to +which each organism is exposed. All forces throughout nature, as Mr. +Herbert Spencer[330] remarks, tend towards an equilibrium, and for the life +of each being it is necessary that this tendency should be checked. If +these views and the foregoing facts can be trusted, they probably throw +light, on the one hand, on the good effects of crossing the breed, for the +germ will be thus slightly modified or acted on by new forces; and on the +other hand, on the evil effects of close interbreeding prolonged during +many generations, during which the germ will be acted on by a male having +almost identically the same constitution. + +_Sterility from changed Conditions of Life._ + +I will now attempt to show that animals and plants, when removed from their +natural conditions, are often rendered in some degree infertile or +completely barren; and this occurs even when the conditions have not been +greatly changed. This conclusion is not necessarily opposed to that at +which we have just arrived, namely, that lesser changes of other kinds are +advantageous to organic beings. Our present subject is of some importance, +from having an intimate connexion with the causes of variability. +Indirectly it perhaps bears on the sterility of species when crossed: for +as, on the one hand, slight changes in the conditions of life are +favourable to plants and animals, and the crossing of varieties adds to the +size, vigour, and fertility of their offspring; so, on the other hand, +certain other changes in the conditions of life cause sterility; and as +this likewise ensues from crossing much-modified forms or species, we have +a parallel and double series of facts, which apparently stand in close +relation to each other. + +It is notorious that many animals, though perfectly tamed, {149} refuse to +breed in captivity. Isidore Geoffroy St. Hilaire[331] consequently has +drawn a broad distinction between tamed animals which will not breed under +captivity, and truly domesticated animals which breed freely--generally +more freely, as shown in the sixteenth chapter, than in a state of nature. +It is possible and generally easy to tame most animals; but experience has +shown that it is difficult to get them to breed regularly, or even at all. +I shall discuss this subject in detail; but will give only those cases +which seem most illustrative. My materials are derived from notices +scattered through various works, and especially from a Report, drawn up for +me by the kindness of the officers of the Zoological Society of London, +which has especial value, as it records all the cases, during nine years +from 1838-46, in which the animals were seen to couple but produced no +offspring, as well as the cases in which they never, as far as known, +coupled. This MS. Report I have corrected by the annual Reports +subsequently published. Many facts are given on the breeding of the animals +in that magnificent work, 'Gleanings from the Menageries of Knowsley Hall,' +by Dr. Gray. I made, also, particular inquiries from the experienced keeper +of the birds in the old Surrey Zoological Gardens. I should premise that a +slight change in the treatment of animals sometimes makes a great +difference in their fertility; and it is probable that the results observed +in different menageries would differ. Indeed some animals in our Zoological +Gardens have become more productive since the year 1846. It is, also, +manifest from F. Cuvier's account of the Jardin des Plantes,[332] that the +animals formerly bred much less freely there than with us; for instance, in +the Duck tribe, which is highly prolific, only one species had at that +period produced young. + + The most remarkable cases, however, are afforded by animals kept in + their native country, which, though perfectly tamed, quite healthy, and + allowed some freedom, are absolutely incapable of breeding. + Rengger,[333] who in Paraguay particularly attended to this subject, + specifies six quadrupeds in this condition; and he mentions two or + three others which most rarely {150} breed. Mr. Bates, in his admirable + work on the Amazons, strongly insists on similar cases;[334] and he + remarks, that the fact of thoroughly tamed native mammals and birds not + breeding when kept by the Indians, cannot be wholly accounted for by + their negligence or indifference, for the turkey is valued by them, and + the fowl has been adopted by the remotest tribes. In almost every part + of the world--for instance, in the interior of Africa, and in several + of the Polynesian islands--the natives are extremely fond of taming the + indigenous quadrupeds and birds; but they rarely or never succeed in + getting them to breed. + + The most notorious case of an animal not breeding in captivity is that + of the elephant. Elephants are kept in large numbers in their native + Indian home, live to old age, and are vigorous enough for the severest + labour; yet, with one or two exceptions, they have never been known + even to couple, though both males and females have their proper + periodical seasons. If, however, we proceed a little eastward to Ava, + we hear from Mr. Crawfurd[335] that their "breeding in the domestic + state, or at least in the half-domestic state in which the female + elephants are generally kept, is of every-day occurrence;" and Mr. + Crawfurd informs me that he believes that the difference must be + attributed solely to the females being allowed to roam the forests with + some degree of freedom. The captive rhinoceros, on the other hand, + seems from Bishop Heber's account[336] to breed in India far more + readily than the elephant. Four wild species of the horse genus have + bred in Europe, though here exposed to a great change in their natural + habits of life; but the species have generally been crossed one with + another. Most of the members of the pig family breed readily in our + menageries: even the Red River hog (_Potamochoerus penicillatus_), from + the sweltering plains of West Africa, has bred twice in the Zoological + Gardens. Here also the Peccary (_Dicotyles torquatus_) has bred several + times; but another species, the _D. labiatus_, though rendered so tame + as to be half-domesticated, breeds so rarely in its native country of + Paraguay, that according to Rengger[337] the fact requires + confirmation. Mr. Bates remarks that the tapir, though often kept tame + in Amazonia by the Indians, never breeds. + + Ruminants generally breed quite freely in England, though brought from + widely different climates, as may be seen in the Annual Reports of the + Zoological Gardens, and in the Gleanings from Lord Derby's menagerie. + + The Carnivora, with the exception of the Plantigrade division, + generally breed (though with capricious exceptions) almost as freely as + ruminants. Many species of Felidae have bred in various menageries, + although imported from various climates and closely confined. Mr. + Bartlett, the present superintendent of the Zoological Gardens,[338] + remarks that the lion appears to breed more frequently and to bring + forth more young at a birth than any other species of the family. He + adds that the tiger has rarely bred; {151} "but there are several + well-authenticated instances of the female tiger breeding with the + lion." Strange as the fact may appear, many animals under confinement + unite with distinct species and produce hybrids quite as freely as, or + even more freely than, with their own species. On inquiring from Dr. + Falconer and others, it appears that the tiger when confined in India + does not breed, though it has been known to couple. The cheetah (_Felis + jubata_) has never been known by Mr. Bartlett to breed in England, but + it has bred at Frankfort; nor does it breed in India, where it is kept + in large numbers for hunting; but no pains would be taken to make them + breed, as only those animals which have hunted for themselves in a + state of nature are serviceable and worth training.[339] According to + Rengger, two species of wild cats in Paraguay, though thoroughly tamed, + have never bred. Although so many of the Felidae breed readily in the + Zoological Gardens, yet conception by no means always follows union: in + the nine-year Report, various species are specified which were observed + to couple seventy-three times, and no doubt this must have passed many + times unnoticed; yet from the seventy-three unions only fifteen births + ensued. The Carnivora in the Zoological Gardens were formerly less + freely exposed to the air and cold than at present, and this change of + treatment, as I was assured by the former superintendent, Mr. Miller, + greatly increased their fertility. Mr. Bartlett, and there cannot be a + more capable judge, says, "it is remarkable that lions breed more + freely in travelling collections than in the Zoological Gardens; + probably the constant excitement and irritation produced by moving from + place to place, or change of air, may have considerable influence in + the matter." + + Many members of the Dog family breed readily when confined. The Dhole + is one of the most untameable animals in India, yet a pair kept there + by Dr. Falconer produced young. Foxes, on the other hand, rarely breed, + and I have never heard of such an occurrence with the European fox: the + silver fox of North America (_Canis argentatus_), however, has bred + several times in the Zoological Gardens. Even the otter has bred there. + Every one knows how readily the semi-domesticated ferret breeds, though + shut up in miserably small cages; but other species of Viverra and + Paradoxurus absolutely refuse to breed in the Zoological Gardens. The + Genetta has bred both here and in the Jardin des Plantes, and produced + hybrids. The _Herpestes fasciatus_ has likewise bred; but I was + formerly assured that the _H. griseus_, though many were kept in the + Gardens, never bred. + + The Plantigrade Carnivora breed under confinement much less freely, + without our being able to assign any reason, than other members of the + group. In the nine-year Report it is stated that the bears had been + seen in the Zoological Gardens to couple freely, but previously to 1848 + had most rarely conceived. In the Reports published since this date + three species have produced young (hybrids in one case), and, wonderful + to relate, the white Polar bear has produced young. The badger (_Meles + taxus_) has bred several times in the Gardens; but I have not heard of + this {152} occurring elsewhere in England, and the event must be very + rare, for an instance in Germany has been thought worth recording.[340] + In Paraguay the native Nasua, though kept in pairs during many years + and perfectly tamed, has never been known, according to Rengger, to + breed or show any sexual passion; nor, as I hear from Mr. Bates, does + this animal, or the Cercoleptes, breed in the region of the Amazons. + Two other plantigrade genera, Procyon and Gulo, though often kept tame + in Paraguay, never breed there. In the Zoological Gardens species of + Nasua and Procyon have been seen to couple; but they did not produce + young. + + As domesticated rabbits, guinea-pigs, and white mice breed so + abundantly when closely confined under various climates, it might have + been thought that most other members of the Rodent order would have + bred in captivity, but this is not the case. It deserves notice, as + showing how the capacity to breed sometimes goes by affinity, that the + one native rodent of Paraguay, which there breeds _freely_ and has + yielded successive generations, is the _Cavia aperea_; and this animal + is so closely allied to the guinea-pig, that it has been erroneously + thought to be the parent-form.[341] In the Zoological Gardens, some + rodents have coupled, but have never produced young; some have neither + coupled nor bred; but a few have bred, as the porcupine more than once, + the Barbary mouse, lemming, chinchilla, and the agouti (_Dasyprocta + aguti_), several times. This latter animal has also produced young in + Paraguay, though they were born dead and ill-formed; but in Amazonia, + according to Mr. Bates, it never breeds, though often kept tame about + the houses. Nor does the paca (_Coelogenys paca_) breed there. The + common hare when confined has, I believe, never bred in Europe;[342] + though, according to a recent statement, it has crossed with the + rabbit. I have never heard of the dormouse breeding in confinement. But + squirrels offer a more curious case: with one exception, no species has + ever bred in the Zoological Gardens, yet as many as fourteen + individuals of _S. palmarum_ were kept together during several years. + The _S. cinerea_ has been seen to couple, but it did not produce young; + nor has this species, when rendered extremely tame in its native + country, North America, been ever known to breed.[343] At Lord Derby's + menagerie squirrels of many kinds were kept in numbers, but Mr. + Thompson, the superintendent, told me that none had ever bred there, or + elsewhere as far as he knew. I have never heard of the English squirrel + breeding in confinement. But the species which has bred more than once + in the Zoological Gardens is the one which perhaps might have been + least expected, namely, the flying squirrel (_Sciuropterus volucella_): + it has, also, bred several times {153} near Birmingham; but the female + never produced more than two young at a birth, whereas in its native + American home she bears from three to six young.[344] + + Monkeys, in the nine-year Report from the Zoological Gardens, are + stated to unite most freely, but during this period, though many + individuals were kept, there were only seven births. I have heard of + one American monkey alone, the Ouistiti, breeding in Europe.[345] A + Macacus, according to Flourens, bred in Paris; and more than one + species of this genus has produced young in London, especially the + _Macacus rhesus_, which everywhere shows a special capacity to breed + under confinement. Hybrids have been produced both in Paris and London + from this same genus. The Arabian baboon, or _Cynocephalus + hamadryas_,[346] and a Cercopithecus have bred in the Zoological + Gardens, and the latter species at the Duke of Northumberland's. + Several members of the family of Lemurs have produced hybrids in the + Zoological Gardens. It is much more remarkable that monkeys very rarely + breed when confined in their native country; thus the Cay (_Cebus + azarae_) is frequently and completely tamed in Paraguay, but + Rengger[347] says that it breeds so rarely, that he never saw more than + two females which had produced young. A similar observation has been + made with respect to the monkeys which are frequently tamed by the + aborigines in Brazil.[348] In the region of the Amazons, these animals + are so often kept in a tame state, that Mr. Bates in walking through + the streets of Para counted thirteen species; but, as he asserts, they + have never been known to breed in captivity.[349] + +_Birds._ + + Birds offer in some respects better evidence than quadrupeds, from + their breeding more rapidly and being kept in greater numbers. We have + seen that carnivorous animals are more fertile under confinement than + most other mammals. The reverse holds good with carnivorous birds. It + is said[350] that as many as eighteen species have been used in Europe + for hawking, and several others in Persia and India;[351] they have + been kept in their native country in the finest condition, and have + been flown during six, eight, or nine years;[352] yet there is no + record of their having ever produced young. As these birds were + formerly caught whilst young, at great expense, being imported from + Iceland, Norway, and Sweden, there can {154} be little doubt that, if + possible, they would have been propagated. In the Jardin des Plantes, + no bird of prey has been known to couple.[353] No hawk, vulture, or owl + has ever produced fertile eggs in the Zoological Gardens, or in the old + Surrey Gardens, with the exception, in the former place on one + occasion, of a condor and a kite (_Milvus niger_). Yet several species, + namely, the _Aquila fusca_, _Haliaetus leucocephalus_, _Falco + tinnunculus_, _F. subbuteo_, and _Buteo vulgaris_, have been seen to + couple in the Zoological Gardens. Mr. Morris[354] mentions as a unique + fact that a kestrel (_Falco tinnunculus_) bred in an aviary. The one + kind of owl which has been known to couple in the Zoological Gardens + was the Eagle Owl (_Bubo maximus_); and this species shows a special + inclination to breed in captivity; for a pair at Arundel Castle, kept + more nearly in a state of nature "than ever fell to the lot of an + animal deprived of its liberty,"[355] actually reared their young. Mr. + Gurney has given another instance of this same owl breeding in + confinement; and he records the case of a second species of owl, the + _Strix passerina_, breeding in captivity.[356] + + Of the smaller graminivorous birds, many kinds have been kept tame in + their native countries, and have lived long; yet, as the highest + authority on cage-birds[357] remarks, their propagation is "uncommonly + difficult." The canary-bird shows that there is no inherent difficulty + in these birds breeding freely in confinement; and Audubon says[358] + that the _Fringilla_ (_Spiza_) _ciris_ of North America breeds as + perfectly as the canary. The difficulty with the many finches which + have been kept in confinement is all the more remarkable as more than a + dozen species could be named which have yielded hybrids with the + canary; but hardly any of these, with the exception of the siskin + (_Fringilla spinus_), have reproduced their own kind. Even the + bullfinch (_Loxia pyrrhula_) has bred as frequently with the canary, + though belonging to a distinct genus, as with its own species.[359] + With respect to the skylark (_Alauda arvensis_), I have heard of birds + living for seven years in an aviary, which never produced young; and a + great London bird-fancier assured me that he had never known an + instance of their breeding; nevertheless one case has been + recorded.[360] In the nine-year Report from the Zoological Society, + twenty-four incessorial species are enumerated which had not bred, and + of these only four were known to have coupled. + + Parrots are singularly long-lived birds; and Humboldt mentions the + curious fact of a parrot in South America, which spoke the language of + {155} an extinct Indian tribe, so that this bird preserved the sole + relic of a lost language. Even in this country there is reason to + believe[361] that parrots have lived to the age of nearly one hundred + years; yet, though many have been kept in Europe, they breed so rarely + that the event has been thought worth recording in the gravest + publications.[362] According to Bechstein[363] the African _Psittacus + erithacus_ breeds oftener than any other species: the _P. macoa_ + occasionally lays fertile eggs, but rarely succeeds in hatching them; + this bird, however, has the instinct of incubation sometimes so + strongly developed, that it will hatch the eggs of fowls or pigeons. In + the Zoological Gardens and in the old Surrey Gardens some few species + have coupled, but, with the exception of three species of parrakeets, + none have bred. It is a much more remarkable fact that in Guiana + parrots of two kinds, as I am informed by Sir E. Schomburgk, are often + taken from the nests by the Indians and reared in large numbers; they + are so tame that they fly freely about the houses, and come when called + to be fed, like pigeons; yet he has never heard of a single instance of + their breeding.[364] In Jamaica, a resident naturalist, Mr. R. + Hill,[365] says, "no birds more readily submit to human dependence than + the parrot-tribe, but no instance of a parrot breeding in this tame + life has been known yet." Mr. Hill specifies a number of other native + birds kept tame in the West Indies, which never breed in this state. + + The great pigeon family offers a striking contrast with parrots: in the + nine-year Report thirteen species are recorded as having bred, and, + what is more noticeable, only two were seen to couple without any + result. Since the above date every annual Report gives many cases of + various pigeons breeding. The two magnificent crowned pigeons (_Goura + coronata_ and _Victoriae_) produced hybrids; nevertheless, of the + former species more than a dozen birds were kept, as I am informed by + Mr. Crawfurd, in a park at Penang, under a perfectly well-adapted + climate, but never once bred. The _Columba migratoria_ in its native + country, North America, invariably lays two eggs, but in Lord Derby's + menagerie never more than one. The same fact has been observed with the + _C. leucocephala_.[366] + + Gallinaceous birds of many genera likewise show an eminent capacity for + breeding under captivity. This is particularly the case with pheasants; + yet our English species seldom lays more than ten eggs in confinement; + whilst from eighteen to twenty is the usual number in the wild + state.[367] With the Gallinaceae, as with all other orders, there are + marked and {156} inexplicable exceptions in regard to the fertility of + certain species and genera under confinement. Although many trials have + been made with the common partridge, it has rarely bred, even when + reared in large aviaries; and the hen will never hatch her own + eggs.[368] The American tribe of Guans or Cracidae are tamed with + remarkable ease, but are very shy breeders in this country;[369] but + with care various species were formerly made to breed rather freely in + Holland.[370] Birds of this tribe are often kept in a perfectly tamed + condition in their native country by the Indians, but they never + breed.[371] It might have been expected that grouse from their habits + of life would not have bred in captivity, more especially as they are + said soon to languish and die.[372] But many cases are recorded of + their breeding: the capercailzie (_Tetrao urogallus_) has bred in the + Zoological Gardens; it breeds without much difficulty when confined in + Norway, and in Russia five successive generations have been reared: + _Tetrao tetrix_ has likewise bred in Norway; _T. Scoticus_ in Ireland; + _T. umbellus_ at Lord Derby's; and _T. cupido_ in North America. + + It is scarcely possible to imagine a greater change in habits than that + which the members of the ostrich family must suffer, when cooped up in + small enclosures under a temperate climate, after freely roaming over + desert and tropical plains or entangled forests. Yet almost all the + kinds, even the mooruk (_Casuarius Bennettii_) from New Ireland, has + frequently produced young in the various European menageries. The + African ostrich, though perfectly healthy and living long in the South + of France, never lays more than from twelve to fifteen eggs, though in + its native country it lays from twenty-five to thirty.[373] Here we + have another instance of fertility impaired, but not lost, under + confinement, as with the flying squirrel, the hen-pheasant, and two + species of American pigeons. + + Most Waders can be tamed, as the Rev. E. S. Dixon informs me, with + remarkable facility; but several of them are short-lived under + confinement, so that their sterility in this state is not surprising. + The cranes breed more readily than other genera: _Grus montigresia_ has + bred several times in Paris and in the Zoological Gardens, as has _G. + cinerea_ at the latter place, and _G. antigone_ at Calcutta. Of other + members of this great order, _Tetrapteryx paradisea_ has bred at + Knowsley, a Porphyrio in Sicily, and the _Gallinula chloropus_ in the + Zoological Gardens. On the other hand, several {157} birds belonging to + this order will not breed in their native country, Jamaica; and the + Psophia, though often kept by the Indians of Guiana about their houses, + "is seldom or never known to breed."[374] + + No birds breed with such complete facility under confinement as the + members of the great Duck family; yet, considering their aquatic and + wandering habits, and the nature of their food, this could not have + been anticipated. Even some time ago above two dozen species had bred + in the Zoological Gardens; and M. Selys-Longchamps has recorded the + production of hybrids from forty-four different members of the family; + and to these Professor Newton has added a few more cases.[375] "There + is not," says Mr. Dixon,[376] "in the wide world, a goose which is not + in the strict sense of the word domesticable;" that is, capable of + breeding under confinement; but this statement is probably too bold. + The capacity to breed sometimes varies in individuals of the same + species; thus Audubon[377] kept for more than eight years some wild + geese (_Anser Canadensis_), but they would not mate; whilst other + individuals of the same species produced young during the second year. + I know of but one instance in the whole family of a species which + absolutely refuses to breed in captivity, namely, the _Dendrocygna + viduata_, although, according to Sir R. Schomburgk,[378] it is easily + tamed, and is frequently kept by the Indians of Guiana. Lastly, with + respect to Gulls, though many have been kept in the Zoological Gardens + and in the old Surrey Gardens, no instance was known before the year + 1848 of their coupling or breeding; but since that period the herring + gull (_Larus argentatus_) has bred many times in the Zoological Gardens + and at Knowsley. + + There is reason to believe that insects are affected by confinement + like the higher animals. It is well known that the Sphingidae rarely + breed when thus treated. An entomologist[379] in Paris kept twenty-five + specimens of _Saturnia pyri_, but did not succeed in getting a single + fertile egg. A number of females of _Orthosia munda_ and of _Mamestra + suasa_ reared in confinement were unattractive to the males.[380] Mr. + Newport kept nearly a hundred individuals of two species of Vanessa, + but not one paired; this, however, might have been due to their habit + of coupling on the wing.[381] Mr. Atkinson could never succeed in India + in making the Tarroo silk-moth breed in confinement.[382] It appears + that a number of moths, especially the Sphingidae, when hatched in the + autumn out of their proper season, {158} are completely barren; but + this latter case is still involved in some obscurity.[383] + +Independently of the fact of many animals under confinement not coupling, +or, if they couple, not producing young, there is evidence of another kind, +that their sexual functions are thus disturbed. For many cases have been +recorded of the loss by male birds when confined of their characteristic +plumage. Thus the common linnet (_Linota cannabina_) when caged does not +acquire the fine crimson colour on its breast, and one of the buntings +(_Emberiza passerina_) loses the black on its head. A Pyrrhula and an +Oriolus have been observed to assume the quiet plumage of the hen-bird; and +the _Falco albidus_ returned to the dress of an earlier age.[384] Mr. +Thomson, the superintendent of the Knowsley menagerie, informed me that he +had often observed analogous facts. The horns of a male deer (_Cervus +Canadensis_) during the voyage from America were badly developed; but +subsequently in Paris perfect horns were produced. + +When conception takes place under confinement, the young are often born +dead, or die soon, or are ill-formed. This frequently occurs in the +Zoological Gardens, and, according to Rengger, with native animals confined +in Paraguay. The mother's milk often fails. We may also attribute to the +disturbance of the sexual functions the frequent occurrence of that +monstrous instinct which leads the mother to devour her own offspring,--a +mysterious case of perversion, as it at first appears. + +Sufficient evidence has now been advanced to prove that animals when first +confined are eminently liable to suffer in their reproductive systems. We +feel at first naturally inclined to attribute the result to loss of health, +or at least to loss of vigour; but this view can hardly be admitted when we +reflect how healthy, long-lived, and vigorous many animals are under {159} +captivity, such as parrots, and hawks when used for hawking, chetahs when +used for hunting, and elephants. The reproductive organs themselves are not +diseased; and the diseases, from which animals in menageries usually +perish, are not those which in any way affect their fertility. No domestic +animal is more subject too disease than the sheep, yet it is remarkably +prolific. The failure of animals to breed under confinement has been +sometimes attributed exclusively to a failure in their sexual instincts: +this may occasionally come into play, but there is no obvious reason why +this instinct should be especially liable to be affected with perfectly +tamed animals, except indeed indirectly through the reproductive system +itself being disturbed. Moreover, numerous cases have been given of various +animals which couple freely under confinement, but never conceive; or, if +they conceive and produce young, these are fewer in number than is natural +to the species. In the vegetable kingdom instinct of course can play no +part; and we shall presently see that plants when removed from their +natural conditions are affected in nearly the same manner as animals. +Change of climate cannot be the cause of the loss of fertility, for, whilst +many animals imported into Europe from extremely different climates breed +freely, many others when confined in their native land are completely +sterile. Change of food cannot be the chief cause; for ostriches, ducks, +and many other animals, which must have undergone a great change in this +respect, breed freely. Carnivorous birds when confined are extremely +sterile; whilst most carnivorous mammals, except plantigrades, are +moderately fertile. Nor can the amount of food be the cause; for a +sufficient supply will certainly be given to valuable animals; and there is +no reason to suppose that much more food would be given to them, than to +our choice domestic productions which retain their full fertility. Lastly, +we may infer from the case of the elephant, chetah, various hawks, and of +many animals which are allowed to lead an almost free life in their native +land, that want of exercise is not the sole cause. + +It would appear that any change in the habits of life, whatever these +habits may be, if great enough, tends to affect in an inexplicable manner +the powers of reproduction. The result {160} depends more on the +constitution of the species than on the nature of the change; for certain +whole groups are affected more than others; but exceptions always occur, +for some species in the most fertile groups refuse to breed, and some in +the most sterile groups breed freely. Those animals which usually breed +freely under confinement, rarely breed, as I was assured, in the Zoological +Gardens, within a year or two after their first importation. When an animal +which is generally sterile under confinement happens to breed, the young +apparently do not inherit this power; for had this been the case, various +quadrupeds and birds, which are valuable for exhibition, would have become +common. Dr. Broca even affirms[385] that many animals in the Jardin des +Plantes, after having produced young for three or four successive +generations, become sterile; but this may be the result of too close +interbreeding. It is a remarkable circumstance that many mammals and birds +have produced hybrids under confinement quite as readily as, or even more +readily than, they have procreated their own kind. Of this fact many +instances have been given;[386] and we are thus reminded of those plants +which when cultivated refuse to be fertilised by their own pollen, but can +easily be fertilised by that of a distinct species. Finally, we must +conclude, limited as the conclusion is, that changed conditions of life +have an especial power of acting injuriously on the reproductive system. +The whole case is quite peculiar, for these organs, though not diseased, +are thus rendered incapable of performing their proper functions, or +perform them imperfectly. + + _Sterility of Domesticated Animals from changed conditions._--With + respect to domesticated animals, as their domestication mainly depends + on the accident of their breeding freely under captivity, we ought not + to expect that their reproductive system would be affected by any + moderate degree of change. Those orders of quadrupeds and birds, of + which the wild species breed most readily in our menageries, have + afforded us the greatest number of domesticated productions. Savages in + most parts of the world are fond of taming animals;[387] and if any of + these regularly produced {161} young, and were at the same time useful, + they would be at once domesticated. If, when their masters migrated + into other countries, they were in addition found capable of + withstanding various climates, they would be still more valuable; and + it appears that the animals which breed readily in captivity can + generally withstand different climates. Some few domesticated animals, + such as the reindeer and camel, offer an exception to this rule. Many + of our domesticated animals can bear with undiminished fertility the + most unnatural conditions; for instance, rabbits, guinea-pigs, and + ferrets breed in miserably confined hutches. Few European dogs of any + kind withstand without degeneration the climate of India; but as long + as they survive, they retain, as I hear from Mr. Falconer, their + fertility; so it is, according to Dr. Daniell, with English dogs taken + to Sierra Leone. The fowl, a native of the hot jungles of India, + becomes more fertile than its parent-stock in every quarter of the + world, until we advance as far north as Greenland and Northern Siberia, + where this bird will not breed. Both fowls and pigeons, which I + received during the autumn direct from Sierra Leone, were at once ready + to couple.[388] I have, also, seen pigeons breeding as freely as the + common kinds within a year after their importation from the Upper Nile. + The guinea-fowl, an aboriginal of the hot and dry deserts of Africa, + whilst living under our damp and cool climate, produces a large supply + of eggs. + + Nevertheless, our domesticated animals under new conditions + occasionally show signs of lessened fertility. Roulin asserts that in + the hot valleys of the equatorial Cordillera sheep are not fully + fecund;[389] and according to Lord Somerville,[390] the merino-sheep + which he imported from Spain were not at first perfectly fertile. It is + said[391] that mares brought up on dry food in the stable, and turned + out to grass, do not at first breed. The peahen, as we have seen, is + said not to lay so many eggs in England as in India. It was long before + the canary-bird was fully fertile, and even now first-rate breeding + birds are not common.[392] In the hot and dry province of Delhi, the + eggs of the turkey, as I hear from Dr. Falconer, though placed under a + hen, are extremely liable to fail. According to Roulin, geese taken + within a recent period to the lofty plateau of Bogota, at first laid + seldom, and then only a few eggs; of these scarcely a fourth were + hatched, and half the young birds died: in the second generation they + were more fertile; and when Roulin wrote they were becoming as {162} + fertile as our geese in Europe. In the Philippine Archipelago the + goose, it is asserted, will not breed or even lay eggs.[393] A more + curious case is that of the fowl, which, according to Roulin, when + first introduced would not breed at Cusco in Bolivia, but subsequently + became quite fertile; and the English Game fowl, lately introduced, had + not as yet arrived a its full fertility, for to raise two or three + chickens from a nest of eggs was thought fortunate. In Europe close + confinement has a marked effect on the fertility of the fowl: it has + been found in France that with fowls allowed considerable freedom only + twenty per cent. of the eggs failed; when allowed less freedom forty + per cent. failed; and in close confinement sixty out of the hundred + were not hatched.[394] So we see that unnatural and changed conditions + of life produce some effect on the fertility of our most thoroughly + domesticated animals, in the same manner, though in a far less degree, + as with captive wild animals. + + It is by no means rare to find certain males and females which will not + breed together, though both are known to be perfectly fertile with + other males and females. We have no reason to suppose that this is + caused by these animals having been subjected to any change in their + habits of life; therefore such cases are hardly related to our present + subject. The cause apparently lies in an innate sexual incompatibility + of the pair which are matched. Several instances have been communicated + to me by Mr. W. C. Spooner (well known for his essay on + Cross-breeding), by Mr. Eyton of Eyton, by Mr. Wicksted and othe + breeders, and especially by Mr. Waring of Chelsfield, in relation to + horses, cattle, pigs, foxhounds, other dogs, and pigeons.[395] In these + cases, females, which either previously or subsequently were proved to + be fertile, failed to breed with certain males, with whom it was + particularly desired to match them. A change in the constitution of the + female may sometimes have occurred before she was put to the second + male; but in other cases this explanation is hardly tenable, for a + female, known not to be barren, has been unsuccessfully paired seven or + eight times with the same male likewise known to be perfectly fertile. + With cart-mares, which sometimes will not breed with stallions of pure + blood, but subsequently have bred with cart-stallions, Mr. Spooner is + inclined to attribute the failure to the lesser sexual power of the + race-horse. But I have heard from the greatest breeder of race-horses + at the present day, through Mr. Waring, that "it frequently occurs with + a mare to be put several times during one or two seasons to a + particular stallion of acknowledged power, and yet prove barren; the + mare afterwards breeding at once with some other horse." These facts + are worth recording, as they show, like so many previous facts, on what + slight constitutional differences the fertility of an animal often + depends. + +{163} + +_Sterility of Plants from changed Conditions of Life, and from other +causes._ + +In the vegetable kingdom cases of sterility frequently occur, analogous +with those previously given in the animal kingdom. But the subject is +obscured by several circumstances, presently to be discussed, namely, the +contabescence of the anthers, as Gaertner has named a certain +affection--monstrosities--doubleness of the flower--much-enlarged +fruit--and long-continued or excessive propagation by buds. + + It is notorious that many plants in our gardens and hot-houses, though + preserved in the most perfect health, rarely or never produce seed. I + do not allude to plants which run to leaves, from being kept too damp, + or too warm, or too much manured; for these do not produce the + reproductive individual or flower, and the case may be wholly + different. Nor do I allude to fruit not ripening from want of heat, or + rotting from too much moisture. But many exotic plants, with their + ovules and pollen appearing perfectly sound, will not set any seed. The + sterility in many cases, as I know from my own observation, is simply + due to the absence of the proper insects for carrying the pollen to the + stigma. But after excluding the several cases just specified, there are + many plants in which the reproductive system has been seriously + affected by the altered conditions of life to which they have been + subjected. + + It would be tedious to enter on many details. Linnaeus long ago + observed[396] that Alpine plants, although naturally laded with seed, + produce either few or none when cultivated in gardens. But exceptions + often occur: the _Draba sylvestris_, one of our most thoroughly Alpine + plants, multiplies itself by seed in Mr. H. C. Watson's garden, near + London; and Kerner, who has particularly attended to the cultivation of + Alpine plants, found that various kinds, when cultivated, spontaneously + sowed themselves.[397] Many plants which naturally grow in peat-earth + are entirely sterile in our gardens. I have noticed the same fact with + several liliaceous plants, which nevertheless grew vigorously. + + Too much manure renders some kinds utterly sterile, as I have myself + observed. The tendency to sterility from this cause runs in families; + thus, according to Gaertner,[398] it is hardly possible to give too + much manure to most Gramineae, Cruciferae, and Leguminosae, whilst + succulent and bulbous-rooted plants are easily affected. Extreme + poverty of soil is less {164} apt to induce sterility; but dwarfed + plants of _Trifolium minus_ and _repens_, growing on a lawn often mown + and never manured, did not produce any seed. The temperature of the + soil, and the season at which plants are watered, often have a marked + effect on their fertility, as was observed by Koelreuter in the case of + Mirabilis.[399] Mr. Scott in the Botanic Gardens of Edinburgh observed + that _Oncidium divaricatum_ would not set seed when grown in a basket + in which it throve, but was capable of fertilisation in a pot where it + was a little damper. _Pelargonium fulgidum_, for many years after its + introduction, seeded freely; it then became sterile; now it is + fertile[400] if kept in a dry stove during the winter. Other varieties + of pelargonium are sterile and others fertile without our being able to + assign any cause. Very slight changes in the position of a plant, + whether planted on a bank or at its base, sometimes make all the + difference in its producing seed. Temperature apparently has a much + more powerful influence on the fertility of plants than on that of + animals. Nevertheless it is wonderful what changes some few plants will + withstand with undiminished fertility: thus the _Zephyranthes candida_, + a native of the moderately warm banks of the Plata, sows itself in the + hot dry country near Lima, and in Yorkshire resists the severest + frosts, and I have seen seeds gathered from pods which had been covered + with snow during three weeks.[401] _Berberis Wallichii_, from the hot + Khasia range in India, is uninjured by our sharpest frosts, and ripens + its fruit under our cool summers. Nevertheless I presume we must + attribute to change of climate the sterility of many foreign plants; + thus the Persian and Chinese lilacs (_Syringa Persica_ and + _Chinensis_), though perfectly hardly, never here produce a seed; the + common lilac (_S. vulgaris_) seeds with us moderately well, but in + parts of Germany the capsules never contain seed.[402] + + Some of the cases, given in the last chapter, of self-impotent plants, + which are fertile both on the male and female side when united with + distinct individuals or species, might have been here introduced; for + as this peculiar form of sterility generally occurs with exotic plants + or with endemic plants cultivated in pots, and as it disappeared in the + _Passiflora alata_ when grafted, we may conclude that in these cases it + is the result of the treatment to which the plants or their parents + have been exposed. + + The liability of plants to be affected in their fertility by slightly + changed conditions is the more remarkable, as the pollen when once in + process of formation is not easily injured; a plant may be + transplanted, or a branch with flower-buds be cut off and placed in + water, and the pollen will be matured. Pollen, also, when once mature, + may be kept for weeks or even months.[403] The female organs are more + sensitive, for Gaertner[404] found that dicotyledonous plants, when + carefully removed so that they did not in the least flag, could seldom + be fertilised; this occurred even with potted {165} plants if the roots + had grown out of the hole at the bottom. In some few cases, however, as + with Digitalis, transplantation did not prevent fertilisation; and + according to the testimony of Mawz, _Brassica rapa_, when pulled up by + its roots and placed in water, ripened its seed. Flower-stems of + several monocotyledonous plants when cut off and placed in water + likewise produce seed. But in these cases I presume that the flowers + had been already fertilised, for Herbert[405] found with the Crocus + that the plants might be removed or mutilated after the act of + fertilisation, and would still perfect their seeds; but that, if + transplanted before being fertilised, the application of pollen was + powerless. + + Plants which have been long cultivated can generally endure with + undiminished fertility various and great changes; but not in most cases + so great a change of climate as domesticated animals. It is remarkable + that many plants under these circumstances are so much affected that + the proportions and the nature of their chemical ingredients are + modified, yet their fertility is unimpaired. Thus, as Dr. Falconer + informs me, there is a great difference in the character of the fibre + in hemp, in the quantity of oil in the seed of the Linum, in the + proportion of narcotin to morphine in the poppy, in gluten to starch in + wheat, when these plants are cultivated on the plains and on the + mountains of India; nevertheless, they all remain fully fertile. + + _Contabescence._--Gaertner has designated by this term a peculiar + condition of the anthers in certain plants, in which they are + shrivelled, or become brown and tough, and contain no good pollen. When + in this state they exactly resemble the anthers of the most sterile + hybrids. Gaertner,[406] in his discussion on this subject, has shown + that plants of many orders are occasionally thus affected; but the + Caryophyllaceae and Liliaceae suffer most, and to these orders, I + think, the Ericaceae may be added. Contabescence varies in degree, but + on the same plant all the flowers are generally affected to nearly the + same extent. The anthers are affected at a very early period in the + flower-bud, and remain in the same state (with one recorded exception) + during the life of the plant. The affection cannot be cured by any + change of treatment, and is propagated by layers, cuttings, &c., and + perhaps even by seed. In contabescent plants the female organs are + seldom affected, or merely become precocious in their development. The + cause of this affection is doubtful, and is different in different + cases. Until I read Gaertner's discussion I attributed it, as + apparently did Herbert, to the unnatural treatment of the plants; but + its permanence under changed conditions, and the female organs not + being affected, seem incompatible with this view. The fact of several + endemic plants becoming contabescent in our gardens seems, at first + sight, equally incompatible with this view; but Koelreuter believes + that this is the result of their transplantation. The contabescent + plants of Dianthus and Verbascum, found wild by Wiegmann, grew on a dry + and sterile bank. The fact that exotic {166} plants are eminently + liable to this affection also seems to show that it is in some manner + caused by their unnatural treatment. In some instances, as with Silene, + Gaertner's view seems the most probable, namely, that it is caused by + an inherent tendency in the species to become dioecious. I can add + another cause, namely, the illegitimate unions of reciprocally + dimorphic or trimorphic plants, for I have observed seedlings of three + species of Primula and of _Lythrum salicaria_, which had been raised + from plants illegitimately fertilised by their own-form pollen, with + some or all their anthers in a contabescent state. There is perhaps an + additional cause, namely, self-fertilisation; for many plants of + Dianthus and Lobelia, which had been raised from self-fertilised seeds, + had their anthers in this state; but these instances are not + conclusive, as both genera are liable from other causes to this + affection. + + Cases of an opposite nature likewise occur, namely, plants with the + female organs struck with sterility, whilst the male organs remain + perfect. _Dianthus Japonicus_, a Passiflora, and Nicotiana, have been + described by Gaertner[407] as being in this unusual condition. + + _Monstrosities as a cause of Sterility._--Great deviations of + structure, even when the reproductive organs themselves are not + seriously affected, sometimes cause plants to become sterile. But in + other cases plants may become monstrous to an extreme degree and yet + retain their full fertility. Gallesio, who certainly had great + experience,[408] often attributes sterility to this cause; but it may + be suspected that in some of his cases sterility was the cause, and not + the result, of the monstrous growths. The curious St. Valery apple, + although it bears fruit, rarely produces seed. The wonderfully + anomalous flowers of _Begonia frigida_, formerly described, though they + appear fit for fructification, are sterile.[409] Species of Primulae, + in which the calyx is brightly coloured, are said[410] to be often + sterile, though I have known them to be fertile. On the other hand, + Verlot gives several cases of proliferous flowers which can be + propagated by seed. This was the case with a poppy, which had become + monopetalous by the union of its petals.[411] Another extraordinary + poppy, with the stamens replaced by numerous small supplementary + capsules, likewise reproduces itself by seed. This has also occurred + with a plant of _Saxifraga geum_, in which a series of adventitious + carpels, bearing ovules on their margins, had been developed between + the stamens and the normal carpels.[412] Lastly, with respect to + peloric flowers, which depart wonderfully from the natural + structure,--those of _Linaria vulgaris_ seem generally to be more or + less sterile, whilst those before described of _Antirrhinum majus_, + when artificially fertilised with their own pollen, are perfectly {167} + fertile, though sterile when left to themselves, for bees are unable to + crawl into the narrow tubular flower. The peloric flowers of _Corydalis + solida_, according to Godron,[413] are barren; whilst those of Gloxinia + are well known to yield plenty of seed. In our greenhouse Pelargoniums, + the central flower of the truss is often peloric, and Mr. Masters + informs me that he tried in vain during several years to get seed from + these flowers. I likewise made many vain attempts, but sometimes + succeeded in fertilising them with pollen from a normal flower of + another variety; and conversely I several times fertilised ordinary + flowers with peloric pollen. Only once I succeeded in raising a plant + from a peloric flower fertilised by pollen from a peloric flower borne + by another variety; but the plant, it may be added, presented nothing + particular in its structure. Hence we may conclude that no general rule + can be laid down; but any great deviation from the normal structure, + even when the reproductive organs themselves are not seriously + affected, certainly often leads to sexual impotence. + + _Double Flowers._--When the stamens are converted into petals, the + plant becomes on the male side sterile; when both stamens and pistils + are thus changed, the plant becomes completely barren. Symmetrical + flowers having numerous stamens and petals are the most liable to + become double, as perhaps follows from all multiple organs being the + most subject to variability. But flowers furnished with only a few + stamens, and others which are asymmetrical in structure, sometimes + become double, as we see with the double gorse or Ulex, Petunia, and + Antirrhinum. The Compositae bear what are called double flowers by the + abnormal development of the corolla of their central florets. + Doubleness is sometimes connected with prolification,[414] or the + continued growth of the axis of the flower. Doubleness is strongly + inherited. No one has produced, as Lindley remarks,[415] double flowers + by promoting the perfect health of the plant. On the contrary, + unnatural conditions of life favour their production. There is some + reason to believe that seeds kept during many years, and seeds believed + to be imperfectly fertilised, yield double flowers more freely than + fresh and perfectly fertilised seed.[416] Long-continued cultivation in + rich soil seems to be the commonest exciting cause. A double narcissus + and a double _Anthemis nobilis_, transplanted into very poor soil, have + been observed to become single;[417] and I have seen a completely + double white primrose rendered permanently single by being divided and + transplanted whilst in full flower. It has been observed by Professor + Morren that doubleness of the flowers and variegation of the leaves are + antagonistic states; but so many exceptions to the rule have lately + been recorded,[418] that, though general, it cannot be looked at as + invariable. {168} Variegation seems generally to result from a feeble + or atrophied condition of the plant, and a large proportion of the + seedlings raised from parents both of which are variegated usually + perish at an early age; hence we may perhaps infer that doubleness, + which is the antagonistic state, commonly arises from a plethoric + condition. On the other hand, extremely poor soil sometimes, though + rarely, appears to cause doubleness: I formerly described[419] some + completely double, bud-like, flowers produced in large numbers by + stunted wild plants of _Gentiana amarella_ growing on a poor chalky + bank. I have also noticed a distinct tendency to doubleness in the + flowers of a Ranunculus, Horse-chesnut, and Bladder-nut (_Ranunculus + repens_, _Aesculus pavia_, and _Staphylea_), growing under very + unfavourable conditions. Professor Lehman[420] found several wild + plants growing near a hot spring with double flowers. With respect to + the cause of doubleness, which arises, as we see, under widely + different circumstances, I shall presently attempt to show that the + most probable view is that unnatural conditions first give a tendency + to sterility, and that then, on the principle of compensation, as the + reproductive organs do not perform their proper functions, they either + become developed into petals, or additional petals are formed. This + view has lately been supported by Mr. Laxton,[421] who advances the + case of some common peas, which, after long-continued heavy rain, + flowered a second time, and produced double flowers. + + _Seedless Fruit._--Many of our most valuable fruits, although + consisting in a homological sense of widely different organs, are + either quite sterile, or produce extremely few seeds. This is + notoriously the case with our best pears, grapes, and figs, with the + pine-apple, banana, bread-fruit, pomegranate, azarole, date-palms, and + some members of the orange-tribe. Poorer varieties of these same fruits + either habitually or occasionally yield seed.[422] Most horticulturists + look at the great size and anomalous development of the fruit as the + cause, and sterility as the result; but the opposite view, as we shall + presently see, is more probable. + + _Sterility from the excessive development of the Organs of Growth or + Vegetation._--Plants which from any cause grow too luxuriantly, and + produce leaves, stems, runners, suckers, tubers, bulbs, &c., in excess, + sometimes do not flower, or if they flower do not yield seed. To make + European vegetables under the hot climate of India yield seed, it is + necessary to check their growth; and, when one-third grown, they are + taken up, and their stems and {169} tap-roots are cut or + mutilated.[423] So it is with hybrids; for instance, Prof. Lecoq[424] + had three plants of Mirabilis, which, though they grew luxuriantly and + flowered, were quite sterile; but after beating one with a stick until + a few branches alone were left, these at once yielded good seed. The + sugar-cane, which grows vigorously and produces a large supply of + succulent stems, never, according to various observers, bears seed in + the West Indies, Malaga, India, Cochin China, or the Malay + Archipelago.[425] Plants which produce a large number of tubers are apt + to be sterile, as occurs, to a certain extent, with the common potato; + and Mr. Fortune informs me that the sweet potato (_Convolvulus + batatas_) in China never, as far as he has seen, yields seed. Dr. Royle + remarks[426] that in India the _Agave vivipara_, when grown in rich + soil, invariably produces bulbs, but no seeds; whilst a poor soil and + dry climate leads to an opposite result. In China, according to Mr. + Fortune, an extraordinary number of little bulbs are developed in the + axils of the leaves of the yam, and this plant does not bear seed. + Whether in these cases, as in those of double flowers and seedless + fruit, sexual sterility from changed conditions of life is the primary + cause which leads to the excessive development of the organs of + vegetation, is doubtful; though some evidence might be advanced in + favour of this view. It is perhaps a more probable view that plants + which propagate themselves largely by one method, namely by buds, have + not sufficient vital power or organised matter for the other method of + sexual generation. + + Several distinguished botanists and good practical judges believe that + long-continued propagation by cuttings, runners, tubers, bulbs, &c., + independently of any excessive development of these parts, is the cause + of many plants failing to produce flowers and of others failing to + produce fertile flowers,--it is as if they had lost the habit of sexual + generation.[427] That many plants when thus propagated are sterile + there can be no doubt, but whether the long continuance of this form of + propagation is the actual cause of their sterility, I will not venture, + from the want of sufficient evidence, to express an opinion. + + That plants may be propagated for long periods by buds, without the aid + of sexual generation, we may safely infer from this being the case with + many plants which must have long survived in a state of nature. As I + have had occasion before to allude to this subject, I will here give + such cases as I have collected. Many alpine plants ascend mountains + beyond the height at which they can produce seed.[428] Certain species + of {170} Poa and Festuca, when growing on mountain-pastures, propagate + themselves, as I hear from Mr. Bentham, almost exclusively by bulblets. + Kalm gives a more curious instance[429] of several American trees, + which grow so plentifully in marshes or in thick woods, that they are + certainly well adapted for these stations, yet scarcely ever produce + seeds; but when accidentally growing on the outside of the marsh or + wood, are loaded with seed. The common ivy is found in Northern Sweden + and Russia, but flowers and fruits only in the southern provinces. The + _Acorus calamus_ extends over a large portion of the globe, but so + rarely perfects its fruit that this has been seen but by few + botanists.[430] The _Hypericum calycinum_, which propagates itself so + freely in our shrubberies by rhizomas and is naturalised in Ireland, + blossoms profusely, but sets no seed; nor did it set any when + fertilised in my garden by pollen from plants growing at a distance. + The _Lysimachia nummularia_, which is furnished with long runners, so + seldom produces seed-capsules, that Prof. Decaisne,[431] who has + especially attended to this plant, has never seen it in fruit. The + _Carex rigida_ often fails to perfect its seed in Scotland, Lapland, + Greenland, Germany, and New Hampshire in the United States.[432] The + periwinkle (_Vinca minor_), which spreads largely by runners, is said + scarcely ever to produce fruit in England;[433] but this plant requires + insect-aid for its fertilisation, and the proper insects may be absent + or rare. The _Jussiaea grandiflora_ has become naturalised in Southern + France, and has spread by its rhizomas so extensively as to impede the + navigation of the waters, but never produces fertile seed.[434] The + horse-radish (_Cochlearia armoracia_) spreads pertinaciously and is + naturalised in various parts of Europe; though it bears flowers, these + rarely produce capsules: Professor Caspary also informs me that he has + watched this plant since 1851, but has never seen its fruit; nor is + this surprising, as he finds scarcely a grain of good pollen. The + common little _Ranunculus ficaria_ rarely, and some say never, bears + seed in England, France, or Switzerland; but in 1863 I observed seeds + on several plants growing near my house. According to M. Chatin, there + are two forms of this Ranunculus; and it is the bulbiferous form which + does not yield seed from producing no pollen.[435] Other cases {171} + analogous with the foregoing could be given; for instance, some kinds + of mosses and lichens have never been seen to fructify in France. + + Some of these endemic and naturalised plants are probably rendered + sterile from excessive multiplication by buds, and their consequent + incapacity to produce and nourish seed. But the sterility of others + more probably depends on the peculiar conditions under which they live, + as in the case of the ivy in the northern parts of Europe, and of the + trees in the swamps of the United States; yet these plants must be in + some respects eminently well adapted for the stations which they + occupy, for they hold their places against a host of competitors. + +Finally, when we reflect on the sterility which accompanies the doubling of +flowers,--the excessive development of fruit,--and a great increase in the +organs of vegetation, we must bear in mind that the whole effect has seldom +been caused at once. An incipient tendency is observed, and continued +selection completes the work, as is known to be the case with our double +flowers and best fruits. The view which seems the most probable, and which +connects together all the foregoing facts and brings them within our +present subject, is, that changed and unnatural conditions of life first +give a tendency to sterility; and in consequence of this, the organs of +reproduction being no longer able fully to perform their proper functions, +a supply of organised matter, not required for the development of the seed, +flows either into these same organs and renders them foliaceous, or into +the fruit, stems, tubers, &c., increasing their size and succulency. But I +am far from wishing to deny that there exists, independently of any +incipient sterility, an antagonism between the two forms of reproduction, +namely, by seed and by buds, when either is carried to an extreme degree. +That incipient sterility plays an important part in the doubling of +flowers, and in the other cases just specified, I infer chiefly from the +following facts. When fertility is lost from a wholly different cause, +namely, from hybridism, there is a strong tendency, as Gaertner[436] +affirms, for flowers to become double, and this tendency is inherited. +Moreover it is notorious that with hybrids the male organs become sterile +before the female organs, and with double flowers the stamens first become +{172} foliaceous. This latter fact is well shown by the male flowers of +dioecious plants, which, according to Gallesio,[437] first become double. +Again, Gaertner[438] often insists that the flowers of even utterly sterile +hybrids, which do not produce any seed, generally yield perfect capsules or +fruit,--a fact which has likewise been repeatedly observed by Naudin with +the Cucurbitaceae; so that the production of fruit by plants rendered +sterile through any other and distinct cause is intelligible. Koelreuter +has also expressed his unbounded astonishment at the size and development +of the tubers in certain hybrids; and all experimentalists[439] have +remarked on the strong tendency in hybrids to increase by roots, runners, +and suckers. Seeing that hybrid plants, which from their nature are more or +less sterile, thus tend to produce double flowers; that they have the parts +including the seed, that is the fruit, perfectly developed, even when +containing no seed; that they sometimes yield gigantic roots; that they +almost invariably tend to increase largely by suckers and other such +means;--seeing this, and knowing, from the many facts given in the earlier +parts of this chapter, that almost all organic beings when exposed to +unnatural conditions tend to become more or less sterile, it seems much the +most probable view that with cultivated plants sterility is the exciting +cause, and double flowers, rich seedless fruit, and in some cases +largely-developed organs of vegetation, &c., are the indirect +results--these results having been in most cases largely increased through +continued selection by man. + + * * * * * + + +{173} + +CHAPTER XIX. + +SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS ON HYBRIDISM. + + ON THE EFFECTS OF CROSSING--THE INFLUENCE OF DOMESTICATION ON + FERTILITY--CLOSE INTERBREEDING--GOOD AND EVIL RESULTS FROM CHANGED + CONDITIONS OF LIFE--VARIETIES WHEN CROSSED NOT INVARIABLY FERTILE--ON + THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND + VARIETIES--CONCLUSIONS WITH RESPECT TO HYBRIDISM--LIGHT THROWN ON + HYBRIDISM BY THE ILLEGITIMATE PROGENY OF DIMORPHIC AND TRIMORPHIC + PLANTS--STERILITY OF CROSSED SPECIES DUE TO DIFFERENCES CONFINED TO THE + REPRODUCTIVE SYSTEM--NOT ACCUMULATED THROUGH NATURAL SELECTION--REASONS + WHY DOMESTIC VARIETIES ARE NOT MUTUALLY STERILE--TOO MUCH STRESS HAS + BEEN LAID ON THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND + CROSSED VARIETIES--CONCLUSION. + +It was shown in the fifteenth chapter that when individuals of the same +variety, or even of a distinct variety, are allowed freely to intercross, +uniformity of character is ultimately acquired. Some few characters, +however, are incapable of fusion, but these are unimportant, as they are +almost always of a semi-monstrous nature, and have suddenly appeared. +Hence, to preserve our domesticated breeds true, or to improve them by +methodical selection, it is obviously necessary that they should be kept +separate. Nevertheless, through unconscious selection, a whole body of +individuals may be slowly modified, as we shall see in a future chapter, +without separating them into distinct lots. Domestic races have often been +intentionally modified by one or two crosses, made with some allied race, +and occasionally even by repeated crosses with very distinct races; but in +almost all such cases, long-continued and careful selection has been +absolutely necessary, owing to the excessive variability of the crossed +offspring, due to the principle of reversion. In a few instances, however, +mongrels have retained a uniform character from their first production. + +When two varieties are allowed to cross freely, and one is {174} much more +numerous than the other, the former will ultimately absorb the latter. +Should both varieties exist in nearly equal numbers, it is probable that a +considerable period would elapse before the acquirement of a uniform +character; and the character ultimately acquired would largely depend on +prepotency of transmission, and on the conditions of life; for the nature +of these conditions would generally favour one variety more than another, +so that a kind of natural selection would come into play. Unless the +crossed offspring were slaughtered by man without the least discrimination, +some degree of unmethodical selection would likewise come into action. From +these several considerations we may infer, that when two or more closely +allied species first came into the possession of the same tribe, their +crossing will not have influenced, in so great a degree as has often been +supposed, the character of the offspring in future times; although in some +cases it probably has had a considerable effect. + +Domestication, as a general rule, increases the prolificness of animals and +plants. It eliminates the tendency to sterility which is common to species +when first taken from a state of nature and crossed. On this latter head we +have no direct evidence; but as our races of dogs, cattle, pigs, &c., are +almost certainly descended from aboriginally distinct stocks, and as these +races are now fully fertile together, or at least incomparably more fertile +than most species when crossed, we may with much confidence accept this +conclusion. + +Abundant evidence has been given that crossing adds to the size, vigour, +and fertility of the offspring. This holds good when there has been no +previous close interbreeding. It applies to the individuals of the same +variety but belonging to different families, to distinct varieties, +sub-species, and partially even to species. In the latter case, though size +is often gained, fertility is lost; but the increased size, vigour, and +hardiness of many hybrids cannot be accounted for solely on the principle +of compensation from the inaction of the reproductive system. Certain +plants, both of pure and hybrid origin, though perfectly healthy, have +become self-impotent, apparently from the unnatural conditions to which +they have been exposed; and such plants, as well as others in their normal +state, can be stimulated to {175} fertility only by crossing them with +other individuals of the same species or even of a distinct species. + +On the other hand, long-continued close interbreeding between the nearest +relations diminishes the constitutional vigour, size, and fertility of the +offspring; and occasionally leads to malformations, but not necessarily to +general deterioration of form or structure. This failure of fertility shows +that the evil results of interbreeding are independent of the augmentation +of morbid tendencies common to both parents, though this augmentation no +doubt is often highly injurious. Our belief that evil follows from close +interbreeding rests to a large extent on the experience of practical +breeders, especially of those who have reared many animals of the kinds +which can be propagated quickly; but it likewise rests on several carefully +recorded experiments. With some animals close interbreeding may be carried +on for a long period with impunity by the selection of the most vigorous +and healthy individuals; but sooner or later evil follows. The evil, +however, comes on so slowly and gradually that it easily escapes +observation, but can be recognised by the almost instantaneous manner in +which size, constitutional vigour, and fertility are regained when animals +that have long been interbred are crossed with a distinct family. + +These two great classes of facts, namely, the good derived from crossing, +and the evil from close interbreeding, with the consideration of the +innumerable adaptations throughout nature for compelling, or favouring, or +at least permitting, the occasional union of distinct individuals, taken +together, lead to the conclusion that it is a law of nature that organic +beings shall not fertilise themselves for perpetuity. This law was first +plainly hinted at in 1799, with respect to plants, by Andrew Knight,[440] +and, not long afterwards, that sagacious observer Koelreuter, after showing +how well the Malvaceae are adapted for {176} crossing, asks, "an id aliquid +in recessu habeat, quod hujuscemodi flores nunquam proprio suo pulvere, sed +semper eo aliarum suae speciei impregnentur, merito quaeritur? Certe natura +nil facit frustra." Although we may demur to Koelreuter's saying that +nature does nothing in vain, seeing how many organic beings retain +rudimentary and useless organs, yet undoubtedly the argument from the +innumerable contrivances, which favour the crossing of distinct individuals +of the same species, is of the greatest weight. The most important result +of this law is that it leads to uniformity of character in the individuals +of the same species. In the case of certain hermaphrodites, which probably +intercross only at long intervals of time, and with unisexual animals +inhabiting somewhat separated localities, which can only occasionally come +into contact and pair, the greater vigour and fertility of the crossed +offspring will ultimately prevail in giving uniformity of character to the +individuals of the same species. But when we go beyond the limits of the +same species, free intercrossing is barred by the law of sterility. + +In searching for facts which might throw light on the cause of the good +effects from crossing, and of the evil effects from close interbreeding, we +have seen that, on the one hand, it is a widely prevalent and ancient +belief that animals and plants profit from slight changes in their +condition of life; and it would appear that the germ, in a somewhat +analogous manner, is more effectually stimulated by the male element, when +taken from a distinct individual, and therefore slightly modified in +nature, than when taken from a male having the same identical constitution. +On the other hand, numerous facts have been given, showing that when +animals are first subjected to captivity, even in their native land, and +although allowed much liberty, their reproductive functions are often +greatly impaired or quite annulled. Some groups of animals are more +affected than others, but with apparently capricious exceptions in every +group. Some animals never or rarely couple: some couple freely, but never +or rarely conceive. The secondary male characters, the maternal functions +and instincts, are occasionally affected. With plants, when first subjected +to cultivation, analogous facts have been observed. We probably owe our +double flowers, rich seedless {177} fruits, and in some cases greatly +developed tubers, &c., to incipient sterility of the above nature combined +with a copious supply of nutriment. Animals which have long been +domesticated, and plants which have long been cultivated, can generally +withstand with unimpaired fertility great changes in their conditions of +life; though both are sometimes slightly affected. With animals the +somewhat rare capacity of breeding freely under confinement has mainly +determined, together with their utility, the kinds which have been +domesticated. + +We can in no case precisely say what is the cause of the diminished +fertility of an animal when first captured, or of a plant when first +cultivated; we can only infer that it is caused by a change of some kind in +the natural conditions of life. The remarkable susceptibility of the +reproductive system to such changes,--a susceptibility not common to any +other organ,--apparently has an important bearing on Variability, as we +shall see in a future chapter. + +It is impossible not to be struck with the double parallelism between the +two classes of facts just alluded to. On the one hand, slight changes in +the conditions of life, and crosses between slightly modified forms or +varieties, are beneficial as far as prolificness and constitutional vigour +are concerned. On the other hand, changes in the conditions greater in +degree, or of a different nature, and crosses between forms which have been +slowly and greatly modified by natural means,--in other words, between +species,--are highly injurious, as far as the reproductive system is +concerned, and in some few instances as far as constitutional vigour is +concerned. Can this parallelism be accidental? Does it not rather indicate +some real bond of connection? As a fire goes out unless it be stirred up, +so the vital forces are always tending, according to Mr. Herbert Spencer, +to a state of equilibrium, unless disturbed and renovated through the +action of other forces. + +In some few cases varieties tend to keep distinct, by breeding at different +periods, by great differences in size, or by sexual preference,--in this +latter respect more especially resembling species in a state of nature. But +the actual crossing of varieties, far from diminishing, generally adds to +the fertility of both the first union and the mongrel offspring. Whether +all {178} the most widely distinct domestic varieties are invariably quite +fertile when crossed, we do not positively know; much time and trouble +would be requisite for the necessary experiments, and many difficulties +occur, such as the descent of the various races from aboriginally distinct +species, and the doubts whether certain forms ought to be ranked as species +or varieties. Nevertheless, the wide experience of practical breeders +proves that the great majority of varieties, even if some should hereafter +prove not to be indefinitely fertile _inter se_, are far more fertile when +crossed, than the vast majority of closely allied natural species. A few +remarkable cases have, however, been given on the authority of excellent +observers, showing that with plants certain forms, which undoubtedly must +be ranked as varieties, yield fewer seeds when crossed than is natural to +the parent-species. Other varieties have had their reproductive powers so +far modified that they are either more or less fertile than are their +parents, when crossed with a distinct species. + +Nevertheless, the fact remains indisputable that domesticated varieties of +animals and of plants, which differ greatly from each other in structure, +but which are certainly descended from the same aboriginal species, such as +the races of the fowl, pigeon, many vegetables, and a host of other +productions, are extremely fertile when crossed; and this seems to make a +broad and impassable barrier between domestic varieties and natural +species. But, as I will now attempt to show, the distinction is not so +great and overwhelmingly important as it at first appears. + +_On the Difference in Fertility between Varieties and Species when +crossed._ + +This work is not the proper place for fully treating the subject of +hybridism, and I have already given in my 'Origin of Species' a moderately +full abstract. I will here merely enumerate the general conclusions which +may be relied on, and which bear on our present point. + +_Firstly_, the laws governing the production of hybrids are identical, or +nearly identical, in the animal and vegetable kingdoms. + +_Secondly_, the sterility of distinct species when first united, {179} and +that of their hybrid offspring, graduates, by an almost infinite number of +steps, from zero, when the ovule is never impregnated and a seed-capsule is +never formed, up to complete fertility. We can only escape the conclusion +that some species are fully fertile when crossed, by determining to +designate as varieties all the forms which are quite fertile. This high +degree of fertility is, however, rare. Nevertheless plants, which have been +exposed to unnatural conditions, sometimes become modified in so peculiar a +manner, that they are much more fertile when crossed by a distinct species +than when fertilised by their own pollen. Success in effecting a first +union between two species, and the fertility of their hybrids, depends in +an eminent degree on the conditions of life being favourable. The innate +sterility of hybrids of the same parentage and raised from the same +seed-capsule often differs much in degree. + +_Thirdly_, the degree of sterility of a first cross between two species +does not always run strictly parallel with that of their hybrid offspring. +Many cases are known of species which can be crossed with ease, but yield +hybrids excessively sterile; and conversely some which can be crossed with +great difficulty, but produce fairly fertile hybrids. This is an +inexplicable fact, on the view that species have been specially endowed +with mutual sterility in order to keep them distinct. + +_Fourthly_, the degree of sterility often differs greatly in two species +when reciprocally crossed; for the first will readily fertilise the second; +but the latter is incapable, after hundreds of trials, of fertilising the +former. Hybrids produced from reciprocal crosses between the same two +species, likewise sometimes differ in their degree of sterility. These +cases also are utterly inexplicable on the view of sterility being a +special endowment. + +_Fifthly_, the degree of sterility of first crosses and of hybrids runs, to +a certain extent, parallel with the general or systematic affinity of the +forms which are united. For species belonging to distinct genera can +rarely, and those belonging to distinct families can never, be crossed. The +parallelism, however, is far from complete; for a multitude of closely +allied species will not unite, or unite with extreme difficulty, whilst +other species, widely different from each other, can be crossed with +perfect facility. Nor does the difficulty depend on ordinary {180} +constitutional differences, for annual and perennial plants, deciduous and +evergreen trees, plants flowering at different seasons, inhabiting +different stations, and naturally living under the most opposite climates, +can often be crossed with ease. The difficulty or facility apparently +depends exclusively on the sexual constitution of the species which are +crossed; or on their sexual elective affinity, _i. e._ _Wahlverwandtschaft_ +of Gaertner. As species rarely or never become modified in one character, +without being at the same time modified in many, and as systematic affinity +includes all visible resemblances and dissimilarities, any difference in +sexual constitution between two species would naturally stand in more or +less close relation with their systematic position. + +_Sixthly_, the sterility of species when first crossed, and that of +hybrids, may possibly depend to a certain extent on distinct causes. With +pure species the reproductive organs are in a perfect condition, whilst +with hybrids they are often plainly deteriorated. A hybrid embryo which +partakes of the constitution of its father and mother is exposed to +unnatural conditions, as long as it is nourished within the womb, or egg, +or seed of the mother-form; and as we know that unnatural conditions often +induce sterility, the reproductive organs of the hybrid might at this early +age be permanently affected. But this cause has no bearing on the +infertility of first unions. The diminished number of the offspring from +first unions may often result, as is certainly sometimes the case, from the +premature death of most of the hybrid embryos. But we shall immediately see +that a law of an unknown nature apparently exists, which causes the +offspring from unions, which are infertile, to be themselves more or less +infertile; and this at present is all that can be said. + +_Seventhly_, hybrids and mongrels present, with the one great exception of +fertility, the most striking accordance in all other respects; namely, in +the laws of their resemblance to their two parents, in their tendency to +reversion, in their variability, and in being absorbed through repeated +crosses by either parent-form. + +Since arriving at the foregoing conclusions, condensed from my former work, +I have been led to investigate a subject which throws considerable light on +hybridism, namely, the fertility of {181} reciprocally dimorphic and +trimorphic plants, when illegitimately united. I have had occasion several +times to allude to these plants, and I may here give a brief abstract[441] +of my observations. Several plants belonging to distinct orders present two +forms, which exist in about equal numbers, and which differ in no respect +except in their reproductive organs; one form having a long pistil with +short stamens, the other a short pistil with long stamens; both with +differently sized pollen-grains. With trimorphic plants there are three +forms likewise differing in the lengths of their pistils and stamens, in +the size and colour of the pollen-grains, and in some other respects; and +as in each of the three forms there are two sets of stamens, there are +altogether six sets of stamens and three kinds of pistils. These organs are +so proportioned in length to each other that, in any two of the forms, half +the stamens in each stand on a level with the stigma of the third form. Now +I have shown, and the result has been confirmed by other observers, that, +in order to obtain full fertility with these plants, it is necessary that +the stigma of the one form should be fertilised by pollen taken from the +stamens of corresponding height in the other form. So that with dimorphic +species two unions, which may be called legitimate, are fully fertile, and +two, which may be called illegitimate, are more or less infertile. With +trimorphic species six unions are legitimate or fully fertile, and twelve +are illegitimate or more or less infertile. + +The infertility which may be observed in various dimorphic and trimorphic +plants, when they are illegitimately fertilised, that is, by pollen taken +from stamens not corresponding in height with the pistil, differs much in +degree, up to absolute and utter sterility; just in the same manner as +occurs in crossing distinct species. As the degree of sterility in the +latter case depends in an eminent degree on the conditions of life being +more or less favourable, so I have found it with illegitimate unions. It is +well known that if pollen of a distinct species be placed on the stigma of +a flower, and its own pollen be afterwards, even {182} after a considerable +interval of time, placed on the same stigma, its action is so strongly +prepotent that it generally annihilates the effect of the foreign pollen; +so it is with the pollen of the several forms of the same species, for +legitimate pollen is strongly prepotent over illegitimate pollen, when both +are placed on the same stigma. I ascertained this by fertilising several +flowers, first illegitimately, and twenty-four hours afterwards +legitimately, with pollen taken from a peculiarly coloured variety, and all +the seedlings were similarly coloured; this shows that the legitimate +pollen, though applied twenty-four hours subsequently, had wholly destroyed +or prevented the action of the previously applied illegitimate pollen. +Again, as, in making reciprocal crosses between the same two species, there +is occasionally a great difference in the result, so something analogous +occurs with dimorphic plants; for a short-styled cowslip (_P. veris_) +yields more seed when fertilised by the long-styled form, and less seed +when fertilised by its own form, compared with a long-styled cowslip when +fertilised in the two corresponding methods. + +In all these respects the forms of the same undoubted species, when +illegitimately united, behave in exactly the same manner as do two distinct +species when crossed. This led me carefully to observe during four years +many seedlings, raised from several illegitimate unions. The chief result +is that these illegitimate plants, as they may be called, are not fully +fertile. It is possible to raise from dimorphic species, both long-styled +and short-styled illegitimate plants, and from trimorphic plants all three +illegitimate forms. These can then be properly united in a legitimate +manner. When this is done, there is no apparent reason why they should not +yield as many seeds as did their parents when legitimately fertilised. But +such is not the case; they are all infertile, but in various degrees; some +being so utterly and incurably sterile that they did not yield during four +seasons a single seed or even seed-capsule. These illegitimate plants, +which are so sterile, although united with each other in a legitimate +manner, may be strictly compared with hybrids when crossed _inter se_, and +it is well known how sterile these latter generally are. When, on the other +hand, a hybrid is crossed with either pure parent-species, the sterility is +usually much lessened: and so it is when an illegitimate plant is +fertilised by {183} a legitimate plant. In the same manner as the sterility +of hybrids does not always run parallel with the difficulty of making the +first cross between the two parent species, so the sterility of certain +illegitimate plants was unusually great, whilst the sterility of the union +from which they were derived was by no means great. With hybrids raised +from the same seed-capsule the degree of sterility is innately variable, so +it is in a marked manner with illegitimate plants. Lastly, many hybrids are +profuse and persistent flowerers, whilst other and more sterile hybrids +produce few flowers, and are weak, miserable dwarfs; exactly similar cases +occur with the illegitimate offspring of various dimorphic and trimorphic +plants. + +Altogether there is the closest identity in character and behaviour between +illegitimate plants and hybrids. It is hardly an exaggeration to maintain +that the former are hybrids, but produced within the limits of the same +species by the improper union of certain forms, whilst ordinary hybrids are +produced from an improper union between so-called distinct species. We have +already seen that there is the closest similarity in all respects between +first illegitimate unions, and first crosses between distinct species. This +will perhaps be made more fully apparent by an illustration: we may suppose +that a botanist found two well-marked varieties (and such occur) of the +long-styled form of the trimorphic _Lythrum salicaria_, and that he +determined to try by crossing whether they were specifically distinct. He +would find that they yielded only about one-fifth of the proper number of +seed, and that they behaved in all the other above-specified respects as if +they had been two distinct species. But to make the case sure, he would +raise plants from his supposed hybridised seed, and he would find that the +seedlings were miserably dwarfed and utterly sterile, and that they behaved +in all other respects like ordinary hybrids. He might then maintain that he +had actually proved, in accordance with the common view, that his two +varieties were as good and as distinct species as any in the world; but he +would be completely mistaken. + +The facts now given on dimorphic and trimorphic plants are important, +because they show us, firstly, that the physiological {184} test of +lessened fertility, both in first crosses and in hybrids, is no safe +criterion of specific distinction; secondly, because we may conclude that +there must be some unknown law or bond connecting the infertility of +illegitimate unions with that of their illegitimate offspring, and we are +thus led to extend this view to first crosses and hybrids; thirdly, because +we find, and this seems to me of especial importance, that with trimorphic +plants three forms of the same species exist, which when crossed in a +particular manner are infertile, and yet these forms differ in no respect +from each other, except in their reproductive organs,--as in the relative +length of the stamens and pistils, in the size, form, and colour of the +pollen-grains, in the structure of the stigma, and in, the number and size +of the seeds. With these differences and no others, either in organisation +or constitution, we find that the illegitimate unions and the illegitimate +progeny of these three forms are more or less sterile, and closely resemble +in a whole series of relations the first unions and hybrid offspring of +distinct species. From this we may infer that the sterility of species when +crossed and of their hybrid progeny is likewise in all probability +exclusively due to differences confined to the reproductive system. We have +indeed been brought to a similar conclusion by observing that the sterility +of crossed species does not strictly coincide with their systematic +affinity, that is, with the sum of their external resemblances; nor does it +coincide with their similarity in general constitution. But we are more +especially led to this same conclusion by considering reciprocal crosses, +in which the male of one species cannot be united, or can be united with +extreme difficulty, with the female of a second species, whilst the +converse cross can be effected with perfect facility; for this difference +in the facility of making reciprocal crosses, and in the fertility of their +offspring, must be attributed either to the male or female element in the +first species having been differentiated with reference to the sexual +element of the second species in a higher degree than in the converse case. +In so complex a subject as Hybridism it is of considerable importance thus +to arrive at a definitive conclusion, namely, that the sterility which +almost invariably follows the union of distinct {185} species depends +exclusively on differences in their sexual constitution. + + * * * * * + +On the principle which makes it necessary for man, whilst he is selecting +and improving his domestic varieties, to keep them separate, it would +clearly be advantageous to varieties in a state of nature, that is to +incipient species, if they could be kept from blending, either through +sexual aversion, or by becoming mutually sterile. Hence it at one time +appeared to me probable, as it has to others, that this sterility might +have been acquired through natural selection. On this view we must suppose +that a shade of lessened fertility first spontaneously appeared, like any +other modification, in certain individuals of a species when crossed with +other individuals of the same species; and that successive slight degrees +of infertility, from being advantageous, were slowly accumulated. This +appears all the more probable, if we admit that the structural differences +between the forms of dimorphic and trimorphic plants, as the length and +curvature of the pistil, &c., have been co-adapted through natural +selection; for if this be admitted, we can hardly avoid extending the same +conclusion to their mutual infertility. Sterility moreover has been +acquired through natural selection for other and widely different purposes, +as with neuter insects in reference to their social economy. In the case of +plants, the flowers on the circumference of the truss in the guelder-rose +(_Viburnum opulus_) and those on the summit of the spike in the +feather-hyacinth (_Muscari comosum_) have been rendered conspicuous, and +apparently in consequence sterile, in order that insects might easily +discover and visit the other flowers. But when we endeavour to apply the +principle of natural selection to the acquirement by distinct species of +mutual sterility, we meet with great difficulties. In the first place, it +may be remarked that separate regions are often inhabited by groups of +species or by single species, which when brought together and crossed are +found to be more or less sterile; now it could clearly have been of no +advantage to such separated species to have been rendered mutually sterile, +and consequently this could not have been effected through natural +selection; but it may perhaps be argued, that, if a species were rendered +sterile with {186} some one compatriot, sterility with other species would +follow as a necessary consequence. In the second place, it is as much +opposed to the theory of natural selection, as to the theory of special +creation, that in reciprocal crosses the male element of one form should +have been rendered utterly impotent on a second form, whilst at the same +time the male element of this second form is enabled freely to fertilise +the first form; for this peculiar state of the reproductive system could +not possibly be advantageous to either species. + +In considering the probability of natural selection having come into action +in rendering species mutually sterile, one great difficulty will be found +to lie in the existence of many graduated steps from slightly lessened +fertility to absolute sterility. It may be admitted, on the principle above +explained, that it would profit an incipient species if it were rendered in +some slight degree sterile when crossed with its parent-form or with some +other variety; for thus fewer bastardised and deteriorated offspring would +be produced to commingle their blood with the new species in process of +formation. But he who will take the trouble to reflect on the steps by +which this first degree of sterility could be increased through natural +selection to that higher degree which is common to so many species, and +which is universal with species which have been differentiated to a generic +or family rank, will find the subject extraordinarily complex. After mature +reflection it seems to me that this could not have been effected through +natural selection; for it could have been of no direct advantage to an +individual animal to breed badly with another individual of a different +variety, and thus leave few offspring; consequently such individuals could +not have been preserved or selected. Or take the case of two species which +in their present state, when crossed, produce few and sterile offspring; +now, what is there which could favour the survival of those individuals +which happened to be endowed in a slightly higher degree with mutual +infertility and which thus approached by one small step towards absolute +sterility? yet an advance of this kind, if the theory of natural selection +be brought to bear, must have incessantly occurred with many species, for a +multitude are mutually quite barren. With sterile neuter insects we have +reason to {187} believe that modifications in their structure have been +slowly accumulated by natural selection, from an advantage having been thus +indirectly given to the community to which they belonged over other +communities of the same species; but an individual animal, if rendered +slightly sterile when crossed with some other variety, would not thus in +itself gain any advantage, or indirectly give any advantage to its nearest +relatives or to other individuals of the same variety, leading to their +preservation. I infer from these considerations that, as far as animals are +concerned, the various degrees of lessened fertility which occur with +species when crossed cannot have been slowly accumulated by means of +natural selection. + +With plants, it is possible that the case may be somewhat different. With +many kinds, insects constantly carry pollen from neighbouring plants to the +stigmas of each flower; and with some species this is effected by the wind. +Now, if the pollen of a variety, when deposited on the stigma of the same +variety, should become by spontaneous variation in ever so slight a degree +prepotent over the pollen of other varieties, this would certainly be an +advantage to the variety; for its own pollen would thus obliterate the +effects of the pollen of other varieties, and prevent deterioration of +character. And the more prepotent the variety's own pollen could be +rendered through natural selection, the greater the advantage would be. We +know from the researches of Gaertner that, with species which are mutually +sterile, the pollen of each is always prepotent on its own stigma over that +of the other species; but we do not know whether this prepotency is a +consequence of the mutual sterility, or the sterility a consequence of the +prepotency. If the latter view be correct, as the prepotency became +stronger through natural selection, from being advantageous to a species in +process of formation, so the sterility consequent on prepotency would at +the same time be augmented; and the final result would be various degrees +of sterility, such as occurs with existing species. This view might be +extended to animals, if the female before each birth received several +males, so that the sexual element of the prepotent male of her own variety +obliterated the effects of the access of previous males belonging to other +varieties; but we have no reason to believe, at least {188} with +terrestrial animals, that this is the ease; as most males and females pair +for each birth, and some few for life. + +On the whole we may conclude that with animals the sterility of crossed +species has not been slowly augmented through natural selection; and as +this sterility follows the same general laws in the vegetable as in the +animal kingdom, it is improbable, though apparently possible, that with +plants crossed species should have been rendered sterile by a different +process. From this consideration, and remembering that species which have +never co-existed in the same country, and which therefore could not have +received any advantage from having been rendered mutually infertile, yet +are generally sterile when crossed; and bearing in mind that in reciprocal +crosses between the same two species there is sometimes the widest +difference in their sterility, we must give up the belief that natural +selection has come into play. + +As species have not been rendered mutually infertile through the +accumulative action of natural selection, and as we may safely conclude, +from the previous as well as from other and more general considerations, +that they have not been endowed through an act of creation with this +quality, we must infer that it has arisen incidentally during their slow +formation in connection with other and unknown changes in their +organisation. By a quality arising incidentally, I refer to such cases as +different species of animals and plants being differently affected by +poisons to which they are not naturally exposed; and this difference in +susceptibility is clearly incidental on other and unknown differences in +their organisation. So again the capacity in different kinds of trees to be +grafted on each other, or on a third species, differs much, and is of no +advantage to these trees, but is incidental on structural or functional +differences in their woody tissues. We need not feel surprise at sterility +incidentally resulting from crosses between distinct species,--the modified +descendants of a common progenitor,--when we bear in mind how easily the +reproductive system is affected by various causes--often by extremely +slight changes in the conditions of life, by too close interbreeding, and +by other agencies. It is well to bear in mind such cases, as that of the +_Passiflora alata_, which recovered its self-fertility from {189} being +grafted on a distinct species--the cases of plants which normally or +abnormally are self-impotent, but can readily be fertilised by the pollen +of a distinct species--and lastly the cases of individual domesticated +animals which evince towards each other sexual incompatibility. + + * * * * * + +We now at last come to the immediate point under discussion: how is it +that, with some few exceptions in the case of plants, domesticated +varieties, such as those of the dog, fowl, pigeon, several fruit-trees, and +culinary vegetables, which differ from each other in external characters +more than many species, are perfectly fertile when crossed, or even fertile +in excess, whilst closely allied species are almost invariably in some +degree sterile? We can, to a certain extent, give a satisfactory answer to +this question. Passing over the fact that the amount of external difference +between two species is no sure guide to their degree of mutual sterility, +so that similar differences in the case of varieties would be no sure +guide, we know that with species the cause lies exclusively in differences +in their sexual constitution. Now the conditions to which domesticated +animals and cultivated plants have been subjected, have had so little +tendency towards modifying the reproductive system in a manner leading to +mutual sterility, that we have good grounds for admitting the directly +opposite doctrine of Pallas, namely, that such conditions generally +eliminate this tendency; so that the domesticated descendants of species, +which in their natural state would have been in some degree sterile when +crossed, become perfectly fertile together. With plants, so far is +cultivation from giving a tendency towards mutual sterility, that in +several well-authenticated cases, already often alluded to, certain species +have been affected in a very different manner, for they have become +self-impotent, whilst still retaining the capacity of fertilising, and +being fertilised by, distinct species. If the Pallasian doctrine of the +elimination of sterility through long-continued domestication be admitted, +and it can hardly be rejected, it becomes in the highest degree improbable +that similar circumstances should commonly both induce and eliminate the +same tendency; though in certain cases, with species having a peculiar +constitution, sterility might occasionally be thus {190} induced. Thus, as +I believe, we can understand why with domesticated animals varieties have +not been produced which are mutually sterile; and why with plants only a +few such cases have been observed, namely, by Gaertner, with certain +varieties of maize and verbascum, by other experimentalists with varieties +of the gourd and melon, and by Koelreuter with one kind of tobacco. + +With respect to varieties which have originated in a state of nature, it is +almost hopeless to expect to prove by direct evidence that they have been +rendered mutually sterile; for if even a trace of sterility could be +detected, such varieties would at once be raised by almost every naturalist +to the rank of distinct species. If, for instance, Gaertner's statement +were fully confirmed, that the blue and red-flowered forms of the pimpernel +(_Anagallis arvensis_) are sterile when crossed, I presume that all the +botanists who now maintain on various grounds that these two forms are +merely fleeting varieties, would at once admit that they were specifically +distinct. + +The real difficulty in our present subject is not, as it appears to me, why +domestic varieties have not become mutually infertile when crossed, but why +this has so generally occurred with natural varieties as soon as they have +been modified in a sufficient and permanent degree to take rank as species. +We are far from precisely knowing the cause; nor is this surprising, seeing +how profoundly ignorant we are in regard to the normal and abnormal action +of the reproductive system. But we can see that species, owing to their +struggle for life with numerous competitors, must have been exposed to more +uniform conditions during long periods of time, than have been domestic +varieties; and this may well make a wide difference in the result. For we +know how commonly wild animals and plants, when taken from their natural +conditions and subjected to captivity, are rendered sterile; and the +reproductive functions of organic beings which have always lived and been +slowly modified under natural conditions would probably in like manner be +eminently sensitive to the influence of an unnatural cross. Domesticated +productions, on the other hand, which, as shown by the mere fact of their +domestication, were not originally highly sensitive to changes in their +conditions of life, and which can now generally resist {191} with +undiminished fertility repeated changes of conditions, might be expected to +produce varieties, which would be little liable to have their reproductive +powers injuriously affected by the act of crossing with other varieties +which had originated in a like manner. + +Certain naturalists have recently laid too great stress, as it appears to +me, on the difference in fertility between varieties and species when +crossed. Some allied species of trees cannot be grafted on each other,--all +varieties can be so grafted. Some allied animals are affected in a very +different manner by the same poison, but with varieties no such case until +recently was known, but now it has been proved that immunity from certain +poisons stands in some cases in correlation with the colour of the hair. +The period of gestation generally differs much with distinct species, but +with varieties until lately no such difference had been observed. The time +required for the germination of seeds differs in an analogous manner, and I +am not aware that any difference in this respect has as yet been detected +with varieties. Here we have various physiological differences, and no +doubt others could be added, between one species and another of the same +genus, which do not occur, or occur with extreme rarity, in the case of +varieties; and these differences are apparently wholly or in chief part +incidental on other constitutional differences, just in the same manner as +the sterility of crossed species is incidental on differences confined to +the sexual system. Why, then, should these latter differences, however +serviceable they may indirectly be in keeping the inhabitants of the same +country distinct, be thought of such paramount importance, in comparison +with other incidental and functional differences? No sufficient answer to +this question can be given. Hence the fact that the most distinct domestic +varieties are, with rare exceptions, perfectly fertile when crossed, and +produce fertile offspring, whilst closely allied species are, with rare +exceptions, more or less sterile, is not nearly so formidable an objection +as it appears at first to the theory of the common descent of allied +species. + + * * * * * + + +{192} + +CHAPTER XX. + +SELECTION BY MAN. + + SELECTION A DIFFICULT ART--METHODICAL, UNCONSCIOUS, AND NATURAL + SELECTION--RESULTS OF METHODICAL SELECTION--CARE TAKEN IN + SELECTION--SELECTION WITH PLANTS--SELECTION CARRIED ON BY THE ANCIENTS, + AND BY SEMI-CIVILIZED PEOPLE--UNIMPORTANT CHARACTERS OFTEN ATTENDED + TO--UNCONSCIOUS SELECTION--AS CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR + DOMESTICATED ANIMALS CHANGED THROUGH THE ACTION OF UNCONSCIOUS + SELECTION--INFLUENCE OF DIFFERENT BREEDERS ON THE SAME + SUB-VARIETY--PLANTS AS AFFECTED BY UNCONSCIOUS SELECTION--EFFECTS OF + SELECTION AS SHOWN BY THE GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST + VALUED BY MAN. + +The power of Selection, whether exercised by man, or brought into play +under nature through the struggle for existence and the consequent survival +of the fittest, absolutely depends on the variability of organic beings. +Without variability nothing can be effected; slight individual differences, +however, suffice for the work, and are probably the sole differences which +are effective in the production of new species. Hence our discussion on the +causes and laws of variability ought in strict order to have preceded our +present subject, as well as the previous subjects of inheritance, crossing, +&c.; but practically the present arrangement has been found the most +convenient. Man does not attempt to cause variability; though he +unintentionally effects this by exposing organisms to new conditions of +life, and by crossing breeds already formed. But variability being granted, +he works wonders. Unless some degree of selection be exercised, the free +commingling of the individuals of the same variety soon obliterates, as we +have previously seen, the slight differences which may arise, and gives to +the whole body of individuals uniformity of character. In separated +districts, long-continued exposure to different conditions of life may +perhaps produce new races without the aid of selection; but to this +difficult subject {193} of the direct action of the conditions of life we +shall in a future chapter recur. + +When animals or plants are born with some conspicuous and firmly inherited +new character, selection is reduced to the preservation of such +individuals, and to the subsequent prevention of crosses; so that nothing +more need be said on the subject. But in the great majority of cases a new +character, or some superiority in an old character, is at first faintly +pronounced, and is not strongly inherited; and then the full difficulty of +selection is experienced. Indomitable patience, the finest powers of +discrimination, and sound judgment must be exercised during many years. A +clearly predetermined object must be kept steadily in view. Few men are +endowed with all these qualities, especially with that of discriminating +very slight differences; judgment can be acquired only by long experience; +but if any of these qualities be wanting, the labour of a life may be +thrown away. I have been astonished when celebrated breeders, whose skill +and judgment have been proved by their success at exhibitions, have shown +me their animals, which appeared all alike, and have assigned their reasons +for matching this and that individual. The importance of the great +principle of Selection mainly lies in this power of selecting scarcely +appreciable differences, which nevertheless are found to be transmissible, +and which can be accumulated until the result is made manifest to the eyes +of every beholder. + +The principle of selection may be conveniently divided into three kinds. +_Methodical selection_ is that which guides a man who systematically +endeavours to modify a breed according to some predetermined standard. +_Unconscious selection_ is that which follows from men naturally preserving +the most valued and destroying the less valued individuals, without any +thought of altering the breed; and undoubtedly this process slowly works +great changes. Unconscious selection graduates into methodical, and only +extreme cases can be distinctly separated; for he who preserves a useful or +perfect animal will generally breed from it with the hope of getting +offspring of the same character; but as long as he has not a predetermined +purpose to improve the breed, he may be said to be selecting {194} +unconsciously.[442] Lastly, we have _Natural selection_, which implies that +the individuals which are best fitted for the complex, and in the course of +ages changing conditions to which they are exposed, generally survive and +procreate their kind. With domestic productions, with which alone we are +here strictly concerned, natural selection comes to a certain extent into +action, independently of, and even in opposition to, the will of man. + + * * * * * + +_Methodical Selection._--What man has effected within recent times in +England by methodical selection is clearly shown by our exhibitions of +improved quadrupeds and fancy birds. With respect to cattle, sheep, and +pigs, we owe their great improvement to a long series of well-known +names--Bakewell, Colling, Ellman, Bates, Jonas Webb, Lords Leicester and +Western, Fisher Hobbs, and others. Agricultural writers are unanimous on +the power of selection: any number of statements to this effect could be +quoted; a few will suffice. Youatt, a sagacious and experienced observer, +writes,[443] the principle of selection is "that which enables the +agriculturist, not only to modify the character of his flock, but to change +it altogether." A great breeder of shorthorns[444] says, "In the anatomy of +the shoulder modern breeders have made great improvements on the Ketton +shorthorns by correcting the defect in the knuckle or shoulder-joint, and +by laying the top of the shoulder more snugly into the crop, and thereby +filling up the hollow behind it.... The eye has its fashion at different +periods: at one time the eye high and outstanding from the head, and at +another time the sleepy eye sunk into the head; but these extremes have +merged into the medium of a full, clear, and prominent eye with a placid +look." + +Again, hear what an excellent judge of pigs[445] says: "The legs {195} +should be no longer than just to prevent the animal's belly from trailing +on the ground. The leg is the least profitable portion of the hog, and we +therefore require no more of it than is absolutely necessary for the +support of the rest." Let any one compare the wild-boar with any improved +breed, and he will see how effectually the legs have been shortened. + +Few persons, except breeders, are aware of the systematic care taken in +selecting animals, and of the necessity of having a clear and almost +prophetic vision into futurity. Lord Spencer's skill and judgment were well +known; and he writes,[446] "It is therefore very desirable, before any man +commences to breed either cattle or sheep, that he should make up his mind +to the shape and qualities he wishes to obtain, and steadily pursue this +object." Lord Somerville, in speaking of the marvellous improvement of the +New Leicester sheep, effected by Bakewell and his successors, says, "It +would seem as if they had first drawn a perfect form, and then given it +life." Youatt[447] urges the necessity of annually drafting each flock, as +many animals will certainly degenerate "from the standard of excellence, +which the breeder has established in his own mind." Even with a bird of +such little importance as the canary, long ago (1780-1790) rules were +established, and a standard of perfection was fixed, according to which the +London fanciers tried to breed the several sub-varieties.[448] A great +winner of prizes at the Pigeon-shows,[449] in describing the Short-faced +Almond Tumbler, says, "There are many first-rate fanciers who are +particularly partial to what is called the goldfinch-beak, which is very +beautiful; others say, take a full-size round cherry, then take a +barley-corn, and judiciously placing and thrusting it into the cherry, form +as it were your beak; and that is not all, for it will form a good head and +beak, provided, as I said before, it is judiciously done; others take an +oat; but as I think the goldfinch-beak the handsomest, I would advise the +inexperienced fancier to get the head of a goldfinch, and keep it by him +for his observation." Wonderfully different as is the beak of the +rock-pigeon and goldfinch, undoubtedly, as far as {196} external shape and +proportions are concerned, the end has been nearly gained. + +Not only should our animals be examined with the greatest care whilst +alive, but, as Anderson remarks,[450] their carcases should be scrutinised, +"so as to breed from the descendants of such only as, in the language of +the butcher, cut up well." The "grain of the meat" in cattle, and its being +well marbled with fat,[451] and the greater or less accumulation of fat in +the abdomen of our sheep, have been attended to with success. So with +poultry, a writer,[452] speaking of Cochin-China fowls, which are said to +differ much in the quality of their flesh, says, "the best mode is to +purchase two young brother-cocks, kill, dress, and serve up one; if he be +indifferent, similarly dispose of the other, and try again; if, however, he +be fine and well-flavoured, his brother will not be amiss for breeding +purposes for the table." + +The great principle of the division of labour has been brought to bear on +selection. In certain districts[453] "the breeding of bulls is confined to +a very limited number of persons, who by devoting their whole attention to +this department, are able from year to year to furnish a class of bulls +which are steadily improving the general breed of the district." The +rearing and letting of choice rams has long been, as is well known, a chief +source of profit to several eminent breeders. In parts of Germany this +principle is carried with merino sheep to an extreme point.[454] "So +important is the proper selection of breeding animals considered, that the +best flock-masters do not trust to their own judgment, or to that of their +shepherds, but employ persons called 'sheep-classifiers,' who make it their +special business to attend to this part of the management of several +flocks, and thus to preserve, or if possible to improve, the best qualities +of both parents in the lambs." In Saxony, "when the lambs are weaned, each +in his turn is placed upon a table that his wool and form may be minutely +observed. {197} The finest are selected for breeding and receive a first +mark. When they are one year old, and prior to shearing them, another close +examination of those previously marked takes place: those in which no +defect can be found receive a second mark, and the rest are condemned. A +few months afterwards a third and last scrutiny is made; the prime rams and +ewes receive a third and final mark, but the slightest blemish is +sufficient to cause the rejection of the animal." These sheep are bred and +valued almost exclusively for the fineness of their wool; and the result +corresponds with the labour bestowed on their selection. Instruments have +been invented to measure accurately the thickness of the fibres; and "an +Austrian fleece has been produced of which twelve hairs equalled in +thickness one from a Leicester sheep." + +Throughout the world, wherever silk is produced, the greatest care is +bestowed on selecting the cocoons from which the moths for breeding are to +be reared. A careful cultivator[455] likewise examines the moths +themselves, and destroys those that are not perfect. But what more +immediately concerns us is that certain families in France devote +themselves to raising eggs for sale.[456] In China, near Shanghai, the +inhabitants of two small districts have the privilege of raising eggs for +the whole surrounding country, and that they may give up their whole time +to this business, they are interdicted by law from producing silk.[457] + +The care which successful breeders take in matching their birds is +surprising. Sir John Sebright, whose fame is perpetuated by the "Sebright +Bantam," used to spend "two and three days in examining, consulting, and +disputing with a friend which were the best of five or six birds."[458] Mr. +Bult, whose pouter-pigeons won so many prizes and were exported to North +America under the charge of a man sent on purpose, told me that he always +deliberated for several days before he matched each pair. Hence we can +understand the advice of an eminent fancier, who writes,[459] "I would here +particularly guard {198} you against having too great a variety of pigeons, +otherwise you will know a little of all, but nothing about one as it ought +to be known." Apparently it transcends the power of the human intellect to +breed all kinds: "it is possible that there may be a few fanciers that have +a good general knowledge of fancy pigeons; but there are many more who +labour under the delusion of supposing they know what they do not." The +excellence of one sub-variety, the Almond Tumbler, lies in the plumage, +carriage, head, beak, and eye; but it is too presumptuous in the beginner +to try for all these points. The great judge above quoted says, "there are +some young fanciers who are over-covetous, who go for all the above five +properties at once; they have their reward by getting nothing." We thus see +that breeding even fancy pigeons is no simple art: we may smile at the +solemnity of these precepts, but he who laughs will win no prizes. + +What methodical selection has effected for our animals is sufficiently +proved, as already remarked, by our Exhibitions. So greatly were the sheep +belonging to some of the earlier breeders, such as Bakewell and Lord +Western, changed, that many persons could not be persuaded that they had +not been crossed. Our pigs, as Mr. Corringham remarks,[460] during the last +twenty years have undergone, through rigorous selection together with +crossing, a complete metamorphosis. The first exhibition for poultry was +held in the Zoological Gardens in 1845; and the improvement effected since +that time has been great. As Mr. Baily, the great judge, remarked to me, it +was formerly ordered that the comb of the Spanish cock should be upright, +and in four or five years all good birds had upright combs; it was ordered +that the Polish cock should have no comb or wattles, and now a bird thus +furnished would be at once disqualified; beards were ordered, and out of +fifty-seven pens lately (1860) exhibited at the Crystal Palace, all had +beards. So it has been in many other cases. But in all cases the judges +order only what is occasionally produced and what can be improved and +rendered constant by selection. The steady increase of weight during the +last few years in our {199} fowls, turkeys, ducks, and geese is notorious; +"six-pound ducks are now common, whereas four pounds was formerly the +average." As the actual time required to make a change has not often been +recorded, it may be worth mentioning that it took Mr. Wicking thirteen +years to put a clean white head on an almond tumbler's body, "a triumph," +says another fancier, "of which he may be justly proud."[461] + +Mr. Tollet, of Betley Hall, selected cows, and especially bulls, descended +from good milkers, for the sole purpose of improving his cattle for the +production of cheese; he steadily tested the milk with the lactometer, and +in eight years he increased, as I was informed by him, the product in the +proportion of four to three. Here is a curious case[462] of steady but slow +progress, with the end not as yet fully attained: in 1784 a race of +silkworms was introduced into France, in which one hundred out of the +thousand failed to produce white cocoons; but now, after careful selection +during sixty-five generations, the proportion of yellow cocoons has been +reduced to thirty-five in the thousand. + +With plants selection has been followed with the same good results as with +animals. But the process is simpler, for plants in the great majority of +cases bear both sexes. Nevertheless, with most kinds it is necessary to +take as much care to prevent crosses as with animals or unisexual plants; +but with some plants, such as peas, this care does not seem to be +necessary. With all improved plants, excepting of course those which are +propagated by buds, cuttings, &c., it is almost indispensable to examine +the seedlings and destroy those which depart from the proper type. This is +called "roguing," and is, in fact, a form of selection, like the rejection +of inferior animals. Experienced horticulturists and agriculturists +incessantly urge every one to preserve the finest plants for the production +of seed. + +Although plants often present much more conspicuous variations than +animals, yet the closest attention is generally requisite to detect each +slight and favourable change. Mr. Masters relates[463] how "many a patient +hour was devoted," whilst he was {200} young, to the detection of +differences in peas intended for seed. Mr. Barnet[464] remarks that the old +scarlet American strawberry was cultivated for more than a century without +producing a single variety; and another writer observes how singular it was +that when gardeners first began to attend to this fruit it began to vary; +the truth no doubt being that it had always varied, but that, until slight +varieties were selected and propagated by seed, no conspicuous result was +obtained. The finest shades of difference in wheat have been discriminated +and selected with almost as much care, as we see in Colonel Le Couteur's +works, as in the case of the higher animals; but with our cereals the +process of selection has seldom or never been long continued. + +It may be worth while to give a few examples of methodical selection with +plants; but in fact the great improvement of all our anciently cultivated +plants may be attributed to selection long carried on, in part +methodically, and in part unconsciously. I have shown in a former chapter +how the weight of the gooseberry has been increased by systematic selection +and culture. The flowers of the Heartsease have been similarly increased in +size and regularity of outline. With the Cineraria, Mr. Glenny[465] "was +bold enough, when the flowers were ragged and starry and ill defined in +colour, to fix a standard which was then considered outrageously high and +impossible, and which, even if reached, it was said, we should be no +gainers by, as it would spoil the beauty of the flowers. He maintained that +he was right; and the event has proved it to be so." The doubling of +flowers has several times been effected by careful selection: the Rev. W. +Williamson,[466] after sowing during several years seed of _Anemone +coronaria_, found a plant with one additional petal; he sowed the seed of +this, and by perseverance in the same course obtained several varieties +with six or seven rows of petals. The single Scotch rose was doubled, and +yielded eight good varieties in nine or ten years.[467] The Canterbury bell +(_Campanula medium_) was doubled by careful selection in four +generations.[468] In four years Mr. Buckman,[469] by culture and {201} +careful selection, converted parsnips, raised from wild seed, into a new +and good variety. By selection during a long course of years, the early +maturity of peas has been hastened from ten to twenty-one days.[470] A more +curious case is offered by the beet-plant, which, since its cultivation in +France, has almost exactly doubled its yield of sugar. This has been +effected by the most careful selection; the specific gravity of the roots +being regularly tested, and the best roots saved for the production of +seed.[471] + +_Selection by Ancient and Semi-civilised People._ + +In attributing so much importance to the selection of animals and plants, +it may be objected that methodical selection would not have been carried on +during ancient times. A distinguished naturalist considers it as absurd to +suppose that semi-civilised people should have practised selection of any +kind. Undoubtedly the principle has been systematically acknowledged and +followed to a far greater extent within the last hundred years than at any +former period, and a corresponding result has been gained; but it would be +a great error to suppose, as we shall immediately see, that its importance +was not recognised and acted on during the most ancient times, and by +semi-civilised people. I should premise that many facts now to be given +only show that care was taken in breeding; but when this is the case, +selection is almost sure to be practised to a certain extent. We shall +hereafter be enabled better to judge how far selection, when only +occasionally carried on, by a few of the inhabitants of a country, will +slowly produce a great effect. + +In a well-known passage in the thirtieth chapter of Genesis, rules are +given for influencing, as was then thought possible, the colour of sheep; +and speckled and dark breeds are spoken of as being kept separate. By the +time of David the fleece was likened to snow. Youatt,[472] who has +discussed all the passages in relation to breeding in the Old Testament, +concludes that {202} at this early period "some of the best principles of +breeding must have been steadily and long pursued." It was ordered, +according to Moses, that "Thou shalt not let thy cattle gender with a +diverse kind;" but mules were purchased,[473] so that at this early period +other nations must have crossed the horse and ass. It is said[474] that +Erichthonius, some generations before the Trojan war, had many brood-mares, +"which by his care and judgment in the choice of stallions produced a breed +of horses superior to any in the surrounding countries." Homer (Book v.) +speaks of Aeneas's horses as bred from mares which were put to the steeds +of Laomedon. Plato, in his 'Republic,' says to Glaucus, "I see that you +raise at your house a great many dogs for the chase. Do you take care about +breeding and pairing them? Among animals of good blood, are there not +always some which are superior to the rest?" To which Glaucus answers in +the affirmative.[475] Alexander the Great selected the finest Indian cattle +to send to Macedonia to improve the breed.[476] According to Pliny,[477] +King Pyrrhus had an especially valuable breed of oxen; and he did not +suffer the bulls and cows to come together till four years old, that the +breed might not degenerate. Virgil, in his Georgics (lib. iii.), gives as +strong advice as any modern agriculturist could do, carefully to select the +breeding stock; "to note the tribe, the lineage, and the sire; whom to +reserve for husband of the herd;"--to brand the progeny;--to select sheep +of the purest white, and to examine if their tongues are swarthy. We have +seen that the Romans kept pedigrees of their pigeons, and this would have +been a senseless proceeding had not great care been taken in breeding them. +Columella gives detailed instructions about breeding fowls: "Let the +breeding hens therefore be of a choice colour, a robust body, square-built, +full-breasted, with large heads, with upright and bright-red combs. Those +are believed to be the best bred which have five toes."[478] According to +Tacitus, the Celts attended to the races of their domestic animals; {203} +and Caesar states that they paid high prices to merchants for fine imported +horses.[479] In regard to plants, Virgil speaks of yearly culling the +largest seeds; and Celsus says, "where the corn and crop is but small, we +must pick out the best ears of corn, and of them lay up our seed separately +by itself."[480] + +Coming down the stream of time, we may be brief. At about the beginning of +the ninth century Charlemagne expressly ordered his officers to take great +care of his stallions; and if any proved bad or old, to forewarn him in +good time before they were put to the mares.[481] Even in a country so +little civilised as Ireland during the ninth century, it would appear from +some ancient verses,[482] describing a ransom demanded by Cormac, that +animals from particular places, or having a particular character, were +valued. Thus it is said,-- + + Two pigs of the pigs of Mac Lir, + A ram and ewe both round and red, + I brought with me from Aengus. + I brought with me a stallion and a mare + From the beautiful stud of Manannan, + A bull and a white cow from Druim Cain. + +Athelstan, in 930, received as a present from Germany, running-horses; and +he prohibited the exportation of English horses. King John imported "one +hundred chosen stallions from Flanders."[483] On June 16th, 1305, the +Prince of Wales wrote to the Archbishop of Canterbury, begging for the loan +of any choice stallion, and promising its return at the end of the +season.[484] There are numerous records at ancient periods in English +history of the importation of choice animals of various kinds, and of +foolish laws against their exportation. In the reigns of Henry VII. and +VIII. it was ordered that the magistrates, at Michaelmas, should scour the +heaths and commons, and destroy all mares beneath a certain size.[485] Some +of our earlier kings passed laws against the slaughtering rams of any good +breed before they were seven years old, so that they {204} might have time +to breed. In Spain Cardinal Ximenes issued, in 1509, regulations on the +_selection_ of good rams for breeding.[486] + +The Emperor Akbar Khan before the year 1600 is said to have "wonderfully +improved" his pigeons by crossing the breeds; and this necessarily implies +careful selection. About the same period the Dutch attended with the +greatest care to the breeding of these birds. Belon in 1555 says that good +managers in France examined the colour of their goslings in order to get +geese of a white colour and better kinds. Markham in 1631 tells the breeder +"to elect the largest and goodliest conies," and enters into minute +details. Even with respect to seeds of plants for the flower-garden, Sir J. +Hanmer writing about the year 1660[487] says, in "choosing seed, the best +seed is the most weighty, and is had from the lustiest and most vigorous +stems;" and he then gives rules about leaving only a few flowers on plants +for seed; so that even such details were attended to in our flower-gardens +two hundred years ago. In order to show that selection has been silently +carried on in places where it would not have been expected, I may add that +in the middle of the last century, in a remote part of North America, Mr. +Cooper improved by careful selection all his vegetables, "so that they were +greatly superior to those of any other person. When his radishes, for +instance, are fit for use, he takes ten or twelve that he most approves, +and plants them at least 100 yards from others that blossom at the same +time. In the same manner he treats all his other plants, varying the +circumstances according to their nature."[488] + +In the great work on China published in the last century by the Jesuits, +and which is chiefly compiled from ancient Chinese encyclopaedias, it is +said that with sheep "improving the breed consists in choosing with +particular care the lambs which are destined for propagation, in nourishing +them well, and in keeping the flocks separate." The same principles were +applied by the Chinese to various plants and fruit-trees.[489] An {205} +imperial edict recommends the choice of seed of remarkable size; and +selection was practised even by imperial hands, for it is said that the +Ya-mi, or imperial rice, was noticed at an ancient period in a field by the +Emperor Khang-hi, was saved and cultivated in his garden, and has since +become valuable from being the only kind which will grow north of the Great +Wall.[490] Even with flowers, the tree paeony (_P. moutan_) has been +cultivated, according to Chinese traditions, for 1400 years; between 200 +and 300 varieties have been raised, which are cherished like tulips +formerly were by the Dutch.[491] + +Turning now to semi-civilised people and to savages: it occurred to me, +from what I had seen of several parts of South America, where fences do not +exist, and where the animals are of little value, that there would be +absolutely no care in breeding or selecting them; and this to a large +extent is true. Roulin,[492] however, describes in Colombia a naked race of +cattle, which are not allowed to increase, on account of their delicate +constitution. According to Azara[493] horses are often born in Paraguay +with curly hair; but, as the natives do not like them, they are destroyed. +On the other hand, Azara states that a hornless bull, born in 1770, was +preserved and propagated its race. I was informed of the existence in Banda +Oriental of a breed with reversed hair; and the extraordinary niata cattle +first appeared and have since been kept distinct in La Plata. Hence certain +conspicuous variations have been preserved, and others have been habitually +destroyed, in these countries, which are so little favourable for careful +selection. We have also seen that the inhabitants sometimes introduce +cattle on their estates to prevent the evil effects of close interbreeding. +On the other hand, I have heard on reliable authority that the Gauchos of +the Pampas never take any pains in selecting the best bulls or stallions +for breeding; and this probably accounts for the cattle and horses being +remarkably uniform in character throughout the immense range of the +Argentine republic. + +Looking to the Old World, in the Sahara Desert "The Touareg is as careful +in the selection of his breeding Mahari {206} (a fine race of the +dromedary) as the Arab is in that of his horse. The pedigrees are handed +down, and many a dromedary can boast a genealogy far longer than the +descendants of the Darley Arabian."[494] According to Pallas the Mongolians +endeavour to breed the Yaks or horse-tailed buffaloes with white tails, for +these are sold to the Chinese mandarins as fly-flappers; and Moorcroft, +about seventy years after Pallas, found that white-tailed animals were +still selected for breeding.[495] + +We have seen in the chapter on the Dog that savages in different parts of +North America and in Guiana cross their dogs with wild Canidae, as did the +ancient Gauls, according to Pliny. This was done to give their dogs +strength and vigour, in the same way as the keepers in large warrens now +sometimes cross their ferrets (as I have been informed by Mr. Yarrell) with +the wild polecat, "to give them more devil." According to Varro, the wild +ass was formerly caught and crossed with the tame animal to improve the +breed, in the same manner as at the present day the natives of Java +sometimes drive their cattle into the forests to cross with the wild +Banteng (_Bos sondaicus_).[496] In Northern Siberia, among the Ostyaks the +dogs vary in markings in different districts, but in each place they are +spotted black and white in a remarkably uniform manner;[497] and from this +fact alone we may infer careful breeding, more especially as the dogs of +one locality are famed throughout the country for their superiority. I have +heard of certain tribes of Esquimaux who take pride in their teams of dogs +being uniformly coloured. In Guiana, as Sir R. Schomburgk informs me,[498] +the dogs of the Turuma Indians are highly valued and extensively bartered: +the price of a good one is the same as that given for a wife: they are kept +in a sort of cage, and the Indians "take great care when the female is in +season to prevent her uniting with a dog of an inferior description." The +Indians told Sir Robert that, if a dog proved bad or useless, {207} he was +not killed, but was left to die from sheer neglect. Hardly any nation is +more barbarous than the Fuegians, but I hear from Mr. Bridges, the +Catechist to the Mission, that, "when these savages have a large, strong, +and active bitch, they take care to put her to a fine dog, and even take +care to feed her well, that her young may be strong and well favoured." + +In the interior of Africa, negroes, who have not associated with white men, +show great anxiety to improve their animals: they "always choose the larger +and stronger males for stock:" the Malakolo were much pleased at +Livingstone's promise to send them a bull, and some Bakalolo carried a live +cock all the way from Loanda into the interior.[499] Further south on the +same continent, Andersson states that he has known a Damara give two fine +oxen for a dog which struck his fancy. The Damaras take great delight in +having whole droves of cattle of the same colour, and they prize their oxen +in proportion to the size of their horns. "The Namaquas have a perfect +mania for a uniform team; and almost all the people of Southern Africa +value their cattle next to their women, and take a pride in possessing +animals that look high-bred." "They rarely or never make use of a handsome +animal as a beast of burden."[500] The power of discrimination which these +savages possess is wonderful, and they can recognise to which tribe any +cattle belong. Mr. Andersson further informs me that the natives frequently +match a particular bull with a particular cow. + +The most curious case of selection by semi-civilised people, or indeed by +any people, which I have found recorded, is that given by Garcilazo de la +Vega, a descendant of the Incas, as having been practised in Peru before +the country was subjugated by the Spaniards.[501] The Incas annually held +great hunts, when all the wild animals were driven from an immense circuit +to a central point. The beasts of prey were first destroyed as injurious. +The wild Guanacos and Vicunas were sheared; the old males and females +killed, and the others set at liberty. The various kinds of deer were +examined; the old males and females {208} were likewise killed; "but the +young females, with a certain number of males, selected from the most +beautiful and strong," were given their freedom. Here, then, we have +selection by man aiding natural selection. So that the Incas followed +exactly the reverse system of that which our Scottish sportsmen are accused +of following, namely, of steadily killing the finest stags, thus causing +the whole race to degenerate.[502] In regard to the domesticated llamas and +alpacas, they were separated in the time of the Incas according to colour; +and if by chance one in a flock was born of the wrong colour, it was +eventually put into another flock. + +In the genus Auchenia there are four forms,--the Guanaco and Vicuna, found +wild and undoubtedly distinct species; the Llama and Alpaca, known only in +a domesticated condition. These four animals appear so different, that most +professed naturalists, especially those who have studied these animals in +their native country, maintain that they are specifically distinct, +notwithstanding that no one pretends to have seen a wild llama or alpaca. +Mr. Ledger, however, who has closely studied these animals both in Peru and +during their exportation to Australia, and who has made many experiments on +their propagation, adduces arguments[503] which seem to me conclusive, that +the llama is the domesticated descendant of the guanaco, and the alpaca of +the vicuna. And now that we know that these animals many centuries ago were +systematically bred and selected, there is nothing surprising in the great +amount of change which they have undergone. + +It appeared to me at one time probable that, though ancient and +semi-civilised people might have attended to the improvement of their more +useful animals in essential points, yet that they would have disregarded +unimportant characters. But human nature is the same throughout the world: +fashion everywhere reigns supreme, and man is apt to value whatever he may +chance to possess. We have seen that in South America the niata cattle, +which certainly are not made useful by their shortened faces and upturned +nostrils, have been preserved. The Damaras of South Africa value their +cattle for uniformity {209} of colour and enormously long horns. The +Mongolians value their yaks for their white tails. And I shall now show +that there is hardly any peculiarity in our most useful animals which, from +fashion, superstition, or some other motive, has not been valued, and +consequently preserved. With respect to cattle, "an early record," +according to Youatt,[504] "speaks of a hundred white cows with red ears +being demanded as a compensation by the princes of North and South Wales. +If the cattle were of a dark or black colour, 150 were to be presented." So +that colour was attended to in Wales before its subjugation by England. In +Central Africa, an ox that beats the ground with its tail is killed; and in +South Africa some of the Damaras will not eat the flesh of a spotted ox. +The Kaffirs value an animal with a musical voice; and "at a sale in British +Kaffraria the low of a heifer excited so much admiration that a sharp +competition sprung up for her possession, and she realised a considerable +price."[505] With respect to sheep, the Chinese prefer rams without horns; +the Tartars prefer them with spirally wound horns, because the hornless are +thought to lose courage.[506] Some of the Damaras will not eat the flesh of +hornless sheep. In regard to horses, at the end of the fifteenth century +animals of the colour described as _liart pomme_ were most valued in +France. The Arabs have a proverb, "Never buy a horse with four white feet, +for he carries his shroud with him;"[507] the Arabs also, as we have seen, +despise dun-coloured horses. So with dogs, Xenophon and others at an +ancient period were prejudiced in favour of certain colours; and "white or +slate-coloured hunting dogs were not esteemed."[508] + +Turning to poultry, the old Roman gourmands thought that the liver of a +white goose was the most savoury. In Paraguay black-skinned fowls are kept +because they are thought to be more productive, and their flesh the most +proper for invalids.[509] In Guiana, as I am informed by Sir R. Schomburgk, +the aborigines will not eat the flesh or eggs of the fowl, but two {210} +races are kept distinct merely for ornament. In the Philippines, no less +than nine sub-varieties of the game cock are kept and named, so that they +must be separately bred. + +At the present time in Europe, the smallest peculiarities are carefully +attended to in our most useful animals, either from fashion, or as a mark +of purity of blood. Many examples could be given, two will suffice. "In the +Western counties of England the prejudice against a white pig is nearly as +strong as against a black one in Yorkshire." In one of the Berkshire +sub-breeds, it is said, "the white should be confined to four white feet, a +white spot between the eyes, and a few white hairs behind each shoulder." +Mr. Saddler possessed "three hundred pigs, every one of which was marked in +this manner."[510] Marshall, towards the close of the last century, in +speaking of a change in one of the Yorkshire breeds of cattle, says the +horns have been considerably modified, as "a clean, small, sharp horn has +been _fashionable_ for the last twenty years."[511] In a part of Germany +the cattle of the Race de Gfoehl are valued for many good qualities, but +they must have horns of a particular curvature and tint, so much so that +mechanical means are applied if they take a wrong direction; but the +inhabitants "consider it of the highest importance that the nostrils of the +bull should be flesh-coloured, and the eyelashes light; this is an +indispensable condition. A calf with blue nostrils would not be purchased, +or purchased at a very low price."[512] Therefore let no man say that any +point or character is too trifling to be methodically attended to and +selected by breeders. + + * * * * * + +_Unconscious Selection._--By this term I mean, as already more than once +explained, the preservation by man of the most valued, and the destruction +of the least valued individuals, without any conscious intention on his +part of altering the breed. It is difficult to offer direct proofs of the +results which follow from this kind of selection; but the indirect evidence +is abundant. In fact, except that in the one case man acts intentionally, +and in the other unintentionally, there is little difference between {211} +methodical and unconscious selection. In both cases man preserves the +animals which are most useful or pleasing to him, and destroys or neglects +the others. But no doubt a far more rapid result follows from methodical +than from unconscious selection. The "roguing" of plants by gardeners, and +the destruction by law in Henry VIII.'s reign of all under-sized mares, are +instances of a process the reverse of selection in the ordinary sense of +the word, but leading to the same general result. The influence of the +destruction of individuals having a particular character is well shown by +the necessity of killing every lamb with a trace of black about it, in +order to keep the flock white; or again, by the effects on the average +height of the men of France of the destructive wars of Napoleon, by which +many tall men were killed, the short ones being left to be the fathers of +families. This at least is the conclusion of those who have closely studied +the subject of the conscription; and it is certain that since Napoleon's +time the standard for the army has been lowered two or three times. + +Unconscious selection so blends into methodical that it is scarcely +possible to separate them. When a fancier long ago first happened to notice +a pigeon with an unusually short beak, or one with the tail-feathers +unusually developed, although he bred from these birds with the distinct +intention of propagating the variety, yet he could not have intended to +make a short-faced tumbler or a fantail, and was far from knowing that he +had made the first step towards this end. If he could have seen the final +result, he would have been struck with astonishment, but, from what we know +of the habits of fanciers, probably not with admiration. Our English +carriers, barbs, and short-faced tumblers have been greatly modified in the +same manner, as we may infer both from the historical evidence given in the +chapters on the Pigeon, and from the comparison of birds brought from +distant countries. + +So it has been with dogs; our present fox-hounds differ from the old +English hound; our greyhounds have become lighter; the wolf-dog, which +belonged to the greyhound class, has become extinct; the Scotch deer-hound +has been modified, and is now rare. Our bulldogs differ from those which +were formerly used for baiting bulls. Our pointers and Newfoundlands do not +{212} closely resemble any native dog now found in the countries whence +they were brought, These changes have been effected partly by crosses; but +in every case the result has been governed by the strictest selection. +Nevertheless there is no reason to suppose that man intentionally and +methodically made the breeds exactly what they now are. As our horses +became fleeter, and the country more cultivated and smoother, fleeter +fox-hounds were desired and produced, but probably without any one +distinctly foreseeing what they would become. Our pointers and setters, the +latter almost certainly descended from large spaniels, have been greatly +modified in accordance with fashion and the desire for increased speed. +Wolves have become extinct, deer have become rarer, bulls are no longer +baited, and the corresponding breeds of the dog have answered to the +change. But we may feel almost sure that when, for instance, bulls were no +longer baited, no man said to himself, I will now breed my dogs of smaller +size, and thus create the present race. As circumstances changed, men +unconsciously and slowly modified their course of selection. + +With race-horses selection for swiftness has been followed methodically, +and our horses can now easily beat their progenitors. The increased size +and different appearance of the English race-horse led a good observer in +India to ask, "Could any one in this year of 1856, looking at our +race-horses, conceive that they were the result of the union of the Arab +horse and the African mare?"[513] This change has, it is probable, been +largely effected through unconscious selection, that is, by the general +wish to breed as fine horses as possible in each generation, combined with +training and high feeding, but without any intention to give to them their +present appearance. According to Youatt,[514] the introduction in Oliver +Cromwell's time of three celebrated Eastern stallions speedily affected the +English breed; "so that Lord Harleigh, one of the old school, complained +that the great horse was fast disappearing." This is an excellent proof how +carefully selection must have been attended to; for without such care, all +traces of so small an infusion of Eastern blood would soon have been +absorbed and {213} lost. Notwithstanding that the climate of England has +never been esteemed particularly favourable to the horse, yet +long-continued selection, both methodical and unconscious, together with +that practised by the Arabs during a still longer and earlier period, has +ended in giving us the best breed of horses in the world. Macaulay[515] +remarks, "Two men whose authority on such subjects was held in great +esteem, the Duke of Newcastle and Sir John Fenwick, pronounced that the +meanest hack ever imported from Tangier would produce a finer progeny than +could be expected from the best sire of our native breed. They would not +readily have believed that a time would come when the princes and nobles of +neighbouring lands would be as eager to obtain horses from England as ever +the English had been to obtain horses from Barbary." + +The London dray-horse, which differs so much in appearance from any natural +species, and which from its size has so astonished many Eastern princes, +was probably formed by the heaviest and most powerful animals having been +selected during many generations in Flanders and England, but without the +least intention or expectation of creating a horse such as we now see. If +we go back to an early period of history, we behold in the antique Greek +statues, as Schaaffhausen has remarked,[516] a horse equally unlike a race +or dray horse, and differing from any existing breed. + +The results of unconscious selection, in an early stage, are well shown in +the difference between the flocks descended from the same stock, but +separately reared by careful breeders. Youatt gives an excellent instance +of this fact in the sheep belonging to Messrs. Buckley and Burgess, which +"have been purely bred from the original stock of Mr. Bakewell for upwards +of fifty years. There is not a suspicion existing in the mind of any one at +all acquainted with the subject that the owner of either flock has deviated +in any one instance from the pure blood of Mr. Bakewell's flock; yet the +difference between the sheep possessed by these two gentlemen is so great, +that they have the appearance of being quite different varieties."[517] I +have seen several analogous and {214} well-marked cases with pigeons: for +instance, I had a family of barbs, descended from those long bred by Sir J. +Sebright, and another family long bred by another fancier, and the two +families plainly differed from each other. Nathusius--and a more competent +witness could not be cited--observes that, though the Shorthorns are +remarkably uniform inn appearance (except in colouring), yet that the +individual character and wishes of each breeder become impressed on his +cattle, so that different herds differ slightly from each other.[518] The +Hereford cattle assumed their present well-marked character soon after the +year 1769, through careful selection by Mr. Tomkins,[519] and the breed has +lately split into two strains--one strain having a white face, and +differing slightly, it is said,[520] in some other points; but there is no +reason to believe that this split, the origin of which is unknown, was +intentionally made; it may with much more probability be attributed to +different breeders having attended to different points. So again, the +Berkshire breed of swine in the year 1810 had greatly changed from what it +had been in 1780; and since 1810 at least two distinct sub-breeds have +borne this same name.[521] When we bear in mind how rapidly all animals +increase, and that some must be annually slaughtered and some saved for +breeding, then, if the same breeder during a long course of years +deliberately settles which shall be saved and which shall be killed, it is +almost inevitable that his individual frame of mind will influence the +character of his stock, without his having had any intention to modify the +breed or form a new strain. + +Unconscious selection in the strictest sense of the word, that is, the +saving of the more useful animals and the neglect or slaughter of the less +useful, without any thought of the future, must have gone on occasionally +from the remotest period and amongst the most barbarous nations. Savages +often suffer from famines, and are sometimes expelled by war from their own +homes. In such cases it can hardly be doubted that they would save their +most useful animals. When the Fuegians {215} are hard pressed by want, they +kill their old women for food rather than their dogs; for, as we were +assured, "old women no use--dogs catch otters." The same sound sense would +surely lead them to preserve their more useful dogs when still harder +pressed by famine. Mr. Oldfield, who has seen so much of the aborigines of +Australia, informs me that "they are all very glad to get a European +kangaroo dog, and several instances have been known of the father killing +his own infant that the mother might suckle the much-prized puppy." +Different kinds of dogs would be useful to the Australian for hunting +opossums and kangaroos, and to the Fuegian for catching fish and otters; +and the occasional preservation in the two countries of the most useful +animals would ultimately lead to the formation of two widely distinct +breeds. + + * * * * * + +With plants, from the earliest dawn of civilisation, the best variety which +at each period was known would generally have been cultivated and its seeds +occasionally sown; so that there will have been some selection from an +extremely remote period, but without any prefixed standard of excellence or +thought of the future. We at the present day profit by a course of +selection occasionally and unconsciously carried on during thousands of +years. This is proved in an interesting manner by Oswald Heer's researches +on the lake-inhabitants of Switzerland, as given in a former chapter; for +he shows that the grain and seed of our present varieties of wheat, barley, +oats, peas, beans, lentils, and poppy, exceed in size those which were +cultivated in Switzerland during the Neolithic and Bronze periods. These +ancient people, during the Neolithic period, possessed also a crab +considerably larger than that now growing wild on the Jura.[522] The pears +described by Pliny were evidently extremely inferior in quality to our +present pears. We can realise the effects of long-continued selection and +cultivation in another way, for would any one in his senses expect to raise +a first-rate apple from the seed of a truly wild crab, or a luscious +melting pear from the wild pear? Alphonse De Candolle informs me that he +has lately seen on an ancient mosaic at Rome a representation of {216} the +melon; and as the Romans, who were such gourmands, are silent on this +fruit, he infers that the melon has been greatly ameliorated since the +classical period. + +Coming to later times, Buffon,[523] on comparing the flowers, fruit, and +vegetables which were then cultivated, with some excellent drawings made a +hundred and fifty years previously, was struck with surprise at the great +improvement which had been effected; and remarks that these ancient flowers +and vegetables would now be rejected, not only by a florist but by a +village gardener. Since the time of Buffon the work of improvement has +steadily and rapidly gone on. Every florist who compares our present +flowers with those figured in books published not long since, is astonished +at the change. A well-known amateur,[524] in speaking of the varieties of +Pelargonium raised by Mr. Garth only twenty-two years before, remarks, +"what a rage they excited: surely we had attained perfection, it was said; +and now not one of the flowers of those days will be looked at. But none +the less is the debt of gratitude which we owe to those who saw what was to +be done, and did it." Mr. Paul, the well-known horticulturist, in writing +of the same flower,[525] says he remembers when young being delighted with +the portraits in Sweet's work; "but what are they in point of beauty +compared with the Pelargoniums of this day? Here again nature did not +advance by leaps; the improvement was gradual, and, if we had neglected +those very gradual advances, we must have foregone the present grand +results." How well this practical horticulturist appreciates and +illustrates the gradual and accumulative force of selection! The Dahlia has +advanced in beauty in a like manner; the line of improvement being guided +by fashion, and by the successive modifications which the flower slowly +underwent.[526] A steady and gradual change has been noticed in many other +flowers: thus an old florist,[527] after describing the leading varieties +of the Pink which were grown in 1813, adds, "the pinks of those days would +now be scarcely grown as border-flowers." The improvement of {217} so many +flowers and the number of the varieties which have been raised is all the +more striking when we hear that the earliest known flower-garden in Europe, +namely at Padua, dates only from the year 1545.[528] + + * * * * * + +_Effects of Selection, as shown by the parts most valued by man presenting +the greatest amount of Difference._--The power of long-continued selection, +whether methodical or unconscious, or both combined, is well shown in a +general way, namely, by the comparison of the differences between the +varieties of distinct species, which are valued for different parts, such +as for the leaves, or stems, or tubers, the seed, or fruit, or flowers. +Whatever part man values most, that part will be found to present the +greatest amount of difference. With trees cultivated for their fruit, +Sageret remarks that the fruit is larger than in the parent-species, whilst +with those cultivated for the seed, as with nuts, walnuts, almonds, +chesnuts, &c., it is the seed itself which is larger; and he accounts for +this fact by the fruit in the one case, and by the seed in the other, +having been carefully attended to and selected during many ages. Gallesio +has made the same observation. Godron insists on the diversity of the tuber +in the potato, of the bulb in the onion, and of the fruit in the melon; and +on the close similarity in these same plants of the other parts.[529] + +In order to judge how far my own impression on this subject was correct, I +cultivated numerous varieties of the same species close to each other. The +comparison of the amount of difference between widely different organs is +necessarily vague; I will therefore give the results in only a few cases. +We have previously seen in the ninth chapter how greatly the varieties of +the cabbage differ in their foliage and stems, which are the selected +parts, and how closely they resembled each other in their flowers, +capsules, and seeds. In seven varieties of the radish, the roots differed +greatly in colour and shape, but no difference {218} whatever could be +detected in their foliage, flowers, or seeds. Now what a contrast is +presented, if we compare the flowers of the varieties of these two plants +with those of any species cultivated in our flower-gardens for ornament; or +if we compare their seeds with those of the varieties of maize, peas, +beans, &c., which are valued and cultivated for their seeds. In the ninth +chapter it was shown that the varieties of the pea differ but little except +in the tallness of the plant, moderately in the shape of the pod, and +greatly in the pea itself, and these are all selected points. The +varieties, however, of the _Pois sans parchemin_ differ much more in their +pods, and these are eaten and valued. I cultivated twelve varieties of the +common bean; one alone, the Dwarf Fan, differed considerably in general +appearance; two differed in the colour of their flowers, one being an +albino, and the other being wholly instead of partially purple; several +differed considerably in the shape and size of the pod, but far more in the +bean itself, and this is the valued and selected part. Toker's bean, for +instance, is twice-and-a-half as long and broad as the horse-bean, and is +much thinner and of a different shape. + +The varieties of the gooseberry, as formerly described, differ much in +their fruit, but hardly perceptibly in their flowers or organs of +vegetation. With the plum, the differences likewise appear to be greater in +the fruit than in the flowers or leaves. On the other hand, the seed of the +strawberry, which corresponds with the fruit of the plum, differs hardly at +all; whilst every one knows how greatly the fruit--that is, the enlarged +receptacle--differs in the several varieties. In apples, pears, and peaches +the flowers and leaves differ considerably, but not, as far as I can judge, +in proportion with the fruit. The Chinese double-flowering peaches, on the +other hand, show that varieties of this tree have been formed, which differ +more in the flower than in fruit. If, as is highly probable, the peach is +the modified descendant of the almond, a surprising amount of change has +been effected in the same species, in the fleshy covering of the former and +in the kernels of the latter. + +When parts stand in such close relation to each other as the fleshy +covering of the fruit (whatever its homological nature may be) and the +seed, when one part is modified, so generally is the other, but by no means +necessarily in the same degree. With {219} the plum-tree, for instance, +some varieties produce plums which are nearly alike, but include stones +extremely dissimilar in shape; whilst conversely other varieties produce +dissimilar fruit with barely distinguishable stones; and generally the +stones, though they have never been subjected to selection, differ greatly +in the several varieties of the plum. In other cases organs which are not +manifestly related, through some unknown bond vary together, and are +consequently liable, without any intention on man's part, to be +simultaneously acted on by selection. Thus the varieties of the stock +(Matthiola) have been selected solely for the beauty of their flowers, but +the seeds differ greatly in colour and somewhat in size. Varieties of the +lettuce have been selected solely on account of their leaves, yet produce +seeds which likewise differ in colour. Generally, through the law of +correlation, when a variety differs greatly from its fellow-varieties in +any one character, it differs to a certain extent in several other +characters. I observed this fact when I cultivated together many varieties +of the same species, for I used first to make a list of the varieties which +differed most from each other in their foliage and manner of growth, +afterwards of those that differed most in their flowers, then in their +seed-capsules, and lastly in their mature seed; and I found that the same +names generally occurred in two, three, or four of the successive lists. +Nevertheless the greatest amount of difference between the varieties was +always exhibited, as far as I could judge, by that part or organ for which +the plant was cultivated. + +When we bear in mind that each plant was at first cultivated because useful +to man, and that its variation was a subsequent, often a long subsequent, +event, we cannot explain the greater amount of diversity in the valuable +parts by supposing that species endowed with an especial tendency to vary +in any particular manner, were originally chosen. We must attribute the +result to the variations in these parts having been successively preserved, +and thus continually augmented; whilst other variations, excepting such as +inevitably appeared through correlation, were neglected and lost. Hence we +may infer that most plants might be made, through long-continued selection, +to yield races as different from each other in any character {220} as they +now are in those parts for which they are valued and cultivated. + +With animals we see something of the same kind; but they have not been +domesticated in sufficient number or yielded sufficient varieties for a +fair comparison. Sheep are valued for their wool, and the wool differs much +more in the several races than the hair in cattle. Neither sheep, goats, +European cattle, nor pigs are valued for their fleetness or strength; and +we do not possess breeds differing in these respects like the race-horse +and dray-horse. But fleetness and strength are valued in camels and dogs; +and we have with the former the swift dromedary and heavy camel; with the +latter the greyhound and mastiff. But dogs are valued even in a higher +degree for their mental qualities and senses; and every one knows how +greatly the races differ in these respects. On the other hand, where the +dog is valued solely to serve for food, as in the Polynesian islands and +China, it is described as an extremely stupid animal.[530] Blumenbach +remarks that "many dogs, such as the badger-dog, have a build so marked and +so appropriate for particular purposes, that I should find it very +difficult to persuade myself that this astonishing figure was an accidental +consequence of degeneration."[531] But had Blumenbach reflected on the +great principle of selection, he would not have used the term degeneration, +and he would not have been astonished that dogs and other animals should +become excellently adapted for the service of man. + +On the whole we may conclude that whatever part or character is most +valued--whether the leaves, stems, tubers, bulbs, flowers, fruit, or seed +of plants, or the size, strength, fleetness, hairy covering, or intellect +of animals--that character will almost invariably be found to present the +greatest amount of difference both in kind and degree. And this result may +be safely attributed to man having preserved during a long course of +generations the variations which were useful to him, and neglected the +others. + +I will conclude this chapter by some remarks on an important subject. With +animals such as the giraffe, of which {221} the whole structure is +admirably co-ordinated for certain purposes, it has been supposed that all +the parts must have been simultaneously modified; and it has been argued +that, on the principle of natural selection, this is scarcely possible. But +in thus arguing, it has been tacitly assumed that the variations must have +been abrupt and great. No doubt, if the neck of a ruminant were suddenly to +become greatly elongated, the fore limbs and back would have to be +simultaneously strengthened and modified; but it cannot be denied that an +animal might have its neck, or head, or tongue, or fore-limbs elongated a +very little without any corresponding modification in other parts of the +body; and animals thus slightly modified would, during a dearth, have a +slight advantage, and be enabled to browse on higher twigs, and thus +survive. A few mouthfuls more or less every day would make all the +difference between life and death. By the repetition of the same process, +and by the occasional intercrossing of the survivors, there would be some +progress, slow and fluctuating though it would be, towards the admirably +co-ordinated structure of the giraffe. If the short-faced tumbler-pigeon, +with its small conical beak, globular head, rounded body, short wings, and +small feet--characters which appear all in harmony--had been a natural +species, its whole structure would have been viewed as well fitted for its +life; but in this case we know that inexperienced breeders are urged to +attend to point after point, and not to attempt improving the whole +structure at the same time. Look at the greyhound, that perfect image of +grace, symmetry, and vigour; no natural species can boast of a more +admirably co-ordinated structure, with its tapering head, slim body, deep +chest, tucked-up abdomen, rat-like tail, and long muscular limbs, all +adapted for extreme fleetness, and for running down weak prey. Now, from +what we see of the variability of animals, and from what we know of the +method which different men follow in improving their stock--some chiefly +attending to one point, others to another point, others again correcting +defects by crosses, and so forth--we may feel assured that if we could see +the long line of ancestors of a first-rate greyhound, up to its wild +wolf-like progenitor, we should behold an infinite number of the finest +gradations, sometimes in one character and sometimes in another, but all +leading towards our {222} present perfect type. By small and doubtful steps +such as these, nature, as we may confidently believe, has progressed on her +grand march of improvement and development. + +A similar line of reasoning is as applicable to separate organs as to the +whole organisation. A writer[532] has recently maintained that "it is +probably no exaggeration to suppose that, in order to improve such an organ +as the eye at all, it must be improved in ten different ways at once. And +the improbability of any complex organ being produced and brought to +perfection in any such way is an improbability of the same kind and degree +as that of producing a poem or a mathematical demonstration by throwing +letters at random on a table." If the eye were abruptly and greatly +modified, no doubt many parts would have to be simultaneously altered, in +order that the organ should remain serviceable. + +But is this the case with smaller changes? There are persons who can see +distinctly only in a dull light, and this condition depends, I believe, on +the abnormal sensitiveness of the retina, and is known to be inherited. +Now, if a bird, for instance, received some great advantage from seeing +well in the twilight, all the individuals with the most sensitive retina +would succeed best and be the most likely to survive; and why should not +all those which happened to have the eye itself a little larger, or the +pupil capable of greater dilatation, be likewise preserved, whether or not +these modifications were strictly simultaneous? These individuals would +subsequently intercross and blend their respective advantages. By such +slight successive changes, the eye of a diurnal bird would be brought into +the condition of that of an owl, which has often been advanced as an +excellent instance of adaptation. Short-sight, which is often inherited, +permits a person to see distinctly a minute object at so near a distance +that it would be indistinct to ordinary eyes; and here we have a capacity +which might be serviceable under certain conditions, abruptly gained. The +Fuegians on board the {223} Beagle could certainly see distant objects more +distinctly than our sailors with all their long practice; I do not know +whether this depends on nervous sensitiveness or on the power of adjustment +in the focus; but this capacity for distant vision might, it is probable, +be slightly augmented by successive modifications of either kind. +Amphibious animals, which are enabled to see both in the water and in the +air, require and possess, as M. Plateau has shown,[533] eyes constructed on +the following plan: "the cornea is always flat, or at least much flattened +in front of the crystalline and over a space equal to the diameter of that +lens, whilst the lateral portions may be much curved." The crystalline is +very nearly a sphere, and the humours have nearly the same density as +water. Now, as a terrestrial animal slowly became more and more aquatic in +its habits, very slight changes, first in the curvature of the cornea or +crystalline, and then in the density of the humours, or conversely, might +successively occur, and would be advantageous to the animal whilst under +water, without serious detriment to its power of vision in the air. It is +of course impossible to conjecture by what steps the fundamental structure +of the eye in the Vertebrata was originally acquired, for we know +absolutely nothing about this organ in the first progenitors of the class. +With respect to the lowest animals in the scale, the transitional states +through which the eye at first probably passed, can by the aid of analogy +be indicated, as I have attempted to show in my 'Origin of Species.'[534] + + * * * * * + + +{224} + +CHAPTER XXI. + +SELECTION, _continued_. + + NATURAL SELECTION AS AFFECTING DOMESTIC PRODUCTIONS--CHARACTERS WHICH + APPEAR OF TRIFLING VALUE OFTEN OF REAL IMPORTANCE--CIRCUMSTANCES + FAVOURABLE TO SELECTION BY MAN--FACILITY IN PREVENTING CROSSES, AND THE + NATURE OF THE CONDITIONS--CLOSE ATTENTION AND PERSEVERANCE + INDISPENSABLE--THE PRODUCTION OF A LARGE NUMBER OF INDIVIDUALS + ESPECIALLY FAVOURABLE--WHEN NO SELECTION IS APPLIED, DISTINCT RACES ARE + NOT FORMED--HIGHLY-BRED ANIMALS LIABLE TO DEGENERATION--TENDENCY IN MAN + TO CARRY THE SELECTION OF EACH CHARACTER TO AN EXTREME POINT, LEADING + TO DIVERGENCE OF CHARACTER, RARELY TO CONVERGENCE--CHARACTERS + CONTINUING TO VARY IN THE SAME DIRECTION IN WHICH THEY HAVE ALREADY + VARIED--DIVERGENCE OF CHARACTER, WITH THE EXTINCTION OF INTERMEDIATE + VARIETIES, LEADS TO DISTINCTNESS IN OUR DOMESTIC RACES--LIMIT TO THE + POWER OF SELECTION--LAPSE OF TIME IMPORTANT--MANNER IN WHICH DOMESTIC + RACES HAVE ORIGINATED--SUMMARY. + +_Natural Selection, or the Survival of the Fittest, as affecting domestic +productions._--We know little on this head. But as animals kept by savages +have to provide their own food, either entirely or to a large extent, +throughout the year, it can hardly be doubted that, in different countries, +varieties differing in constitution and in various characters would succeed +best, and so be naturally selected. Hence perhaps it is that the few +domesticated animals kept by savages partake, as has been remarked by more +than one writer, of the wild appearance of their masters, and likewise +resemble natural species. Even in long-civilised countries, at least in the +wilder parts, natural selection must act on our domestic races. It is +obvious that varieties, having very different habits, constitution, and +structure, would succeed best on mountains and on rich lowland pastures. +For example, the improved Leicester sheep were formerly taken to the +Lammermuir Hills; but an intelligent sheep-master reported that "our coarse +lean pastures were unequal to the task of supporting such heavy-bodied +sheep; and they gradually dwindled away into less and less bulk: {225} each +generation was inferior to the preceding one; and when the spring was +severe, seldom more than two-thirds of the lambs survived the ravages of +the storms."[535] So with the mountain cattle of North Wales and the +Hebrides, it has been found that they could not withstand being crossed +with the larger and more delicate lowland breeds. Two French naturalists, +in describing the horses of Circassia, remark that, subjected as they are +to extreme vicissitudes of climate, having to search for scanty pasture, +and exposed to constant danger from wolves, the strongest and most vigorous +alone survive.[536] + +Every one must have been struck with the surpassing grace, strength, and +vigour of the Game-cock, with its bold and confident air, its long, yet +firm neck, compact body, powerful and closely pressed wings, muscular +thighs, strong beak massive at the base, dense and sharp spurs set low on +the legs for delivering the fatal blow, and its compact, glossy, and +mail-like plumage serving as a defence. Now the English game-cock has not +only been improved during many years by man's careful selection, but in +addition, as Mr. Tegetmeier has remarked,[537] by a kind of natural +selection, for the strongest, most active and courageous birds have +stricken down their antagonists in the cockpit, generation after +generation, and have subsequently served as the progenitors of their kind. + +In Great Britain, in former times, almost every district had its own breed +of cattle and sheep; "they were indigenous to the soil, climate, and +pasturage of the locality on which they grazed: they seemed to have been +formed for it and by it."[538] But in this case we are quite unable to +disentangle the effects of the direct action of the conditions of life,--of +use or habit--of natural selection--and of that kind of selection which we +have seen is occasionally and unconsciously followed by man even during the +rudest periods of history. + +Let us now look to the action of natural selection on special characters. +Although nature is difficult to resist, yet man often strives against her +power, and sometimes, as we shall see, with {226} success. From the facts +to be given, it will also be seen that natural selection would powerfully +affect many of our domestic productions if left unprotected. This is a +point of much interest, for we thus learn that differences apparently of +very slight importance would certainly determine the survival of a form +when forced to struggle for its own existence. It may have occurred to some +naturalists, as it formerly did to me, that, though selection acting under +natural conditions would determine the structure of all important organs, +yet that it could not affect characters which are esteemed by us of little +importance; but this is an error to which we are eminently liable, from our +ignorance of what characters are of real value to each living creature. + +When man attempts to breed an animal with some serious defect in structure, +or in the mutual relation of parts, he will either partially or completely +fail, or encounter much difficulty; and this is in fact a form of natural +selection. We have seen that the attempt was once made in Yorkshire to +breed cattle with enormous buttocks, but the cows perished so often in +bringing forth their calves, that the attempt had to be given up. In +rearing short-faced tumblers, Mr. Eaton says,[539] "I am convinced that +better head and beak birds have perished in the shell than ever were +hatched; the reason being that the amazingly short-faced bird cannot reach +and break the shell with its beak, and so perishes." Here is a more curious +case, in which natural selection comes into play only at long intervals of +time: during ordinary seasons the Niata cattle can graze as well as others, +but occasionally, as from 1827 to 1830, the plains of La Plata suffer from +long-continued droughts and the pasture is burnt up; at such times common +cattle and horses perish by the thousand, but many survive by browsing on +twigs, reeds, &c.; this the Niata cattle cannot so well effect from their +upturned jaws and the shape of their lips; consequently, if not attended +to, they perish before the other cattle. In Colombia, according to Roulin, +there is a breed of nearly hairless cattle, called Pelones; these succeed +in their native hot district, but are found too tender for the Cordillera; +in this case, natural selection {227} determines only the range of the +variety. It is obvious that a host of artificial races could never survive +in a state of nature;--such as Italian greyhounds,--hairless and almost +toothless Turkish dogs,--fantail pigeons, which cannot fly well against a +strong wind,--barbs with their vision impeded by their eye-wattle,--Polish +fowls with their vision impeded by their great topknots,--hornless bulls +and rams which consequently cannot cope with other males, and thus have a +poor chance of leaving offspring,--seedless plants, and many other such +cases. + +Colour is generally esteemed by the systematic naturalist as unimportant: +let us, therefore, see how far it indirectly affects our domestic +productions, and how far it would affect them if they were left exposed to +the full force of natural selection. In a future chapter I shall have to +show that constitutional peculiarities of the strangest kind, entailing +liability to the action of certain poisons, are correlated with the colour +of the skin. I will here give a single case, on the high authority of +Professor Wyman; he informs me that, being surprised at all the pigs in a +part of Virginia being black, he made inquiries, and ascertained that these +animals feed on the roots of the _Lachnanthes tinctoria_, which colours +their bones pink, and, excepting in the case of the black varieties, causes +the hoofs to drop off. Hence, as one of the squatters remarked, "we select +the black members of the litter for raising, as they alone have a good +chance of living." So that here we have artificial and natural selection +working hand in hand. I may add that in the Tarentino the inhabitants keep +black sheep alone, because the _Hypericum crispum_ abounds there; and this +plant does not injure black sheep, but kills the white ones in about a +fortnight's time.[540] + +Complexion, and liability to certain diseases, are believed to run together +in man and the lower animals. Thus white terriers suffer more than terriers +of any other colour from the fatal Distemper.[541] In North America +plum-trees are liable to a disease which Downing[542] believes is not +caused by insects; the kinds bearing purple fruit are most affected, "and +we have never known the green or yellow fruited varieties infected {228} +until the other sorts had first become filled with the knots." On the other +hand, peaches in North America suffer much from a disease called the +_yellows_, which seems to be peculiar to that continent, and "more than +nine-tenths of the victims, when the disease first appeared, were the +yellow-fleshed peaches. The white-fleshed kinds are much more rarely +attacked; in some parts of the country never." In Mauritius, the white +sugar-canes have of late years been so severely attacked by a disease, that +many planters have been compelled to give up growing this variety (although +fresh plants were imported from China for trial), and cultivate only red +canes.[543] Now, if these plants had been forced to struggle with other +competing plants and enemies, there cannot be a doubt that the colour of +the flesh or skin of the fruit, unimportant as these characters are +considered, would have rigorously determined their existence. + +Liability to the attacks of parasites is also connected with colour. It +appears that white chickens are certainly more subject than dark-coloured +chickens to the _gapes_, which is caused by a parasitic worm in the +trachea.[544] On the other hand, experience has shown that in France the +caterpillars which produce white cocoons resist the deadly fungus better +than those producing yellow cocoons.[545] Analogous facts have been +observed with plants: a new and beautiful white onion, imported from +France, though planted close to other kinds, was alone attacked by a +parasitic fungus.[546] White verbenas are especially liable to mildew.[547] +Near Malaga, during an early period of the vine-disease, the green sorts +suffered most; "and red and black grapes, even when interwoven with the +sick plants, suffered not at all." In France whole groups of varieties were +comparatively free, and others, such as the Chasselas, did not afford a +single fortunate exception; but I do not know whether any correlation +between colour and liability to disease was here observed.[548] In a former +chapter it was shown how curiously liable one variety of the strawberry is +to mildew. + +{229} + +It is certain that insects regulate in many cases the range and even the +existence of the higher animals, whilst living under their natural +conditions. Under domestication light-coloured animals suffer most: in +Thuringia[549] the inhabitants do not like grey, white, or pale cattle, +because they are much more troubled by various kinds of flies than the +brown, red, or black cattle. An Albino negro, it has been remarked,[550] +was peculiarly sensitive to the bites of insects. In the West Indies[551] +it is said that "the only horned cattle fit for work are those which have a +good deal of black in them. The white are terribly tormented by the +insects; and they are weak and sluggish in proportion to the white." + +In Devonshire there is a prejudice against white pigs, because it is +believed that the sun blisters them when turned out;[552] and I knew a man +who would not keep white pigs in Kent, for the same reason. The scorching +of flowers by the sun seems likewise to depend much on colour; thus, dark +pelargoniums suffer most; and from various accounts it is clear that the +cloth-of-gold variety will not withstand a degree of exposure to sunshine +which other varieties enjoy. Another amateur asserts that not only all +dark-coloured verbenas, but likewise scarlets, suffer from the sun; "the +paler kinds stand better, and pale blue is perhaps the best of all." So +again with the heartsease (_Viola tricolor_); hot weather suits the +blotched sorts, whilst it destroys the beautiful markings of some other +kinds.[553] During one extremely cold season in Holland all red-flowered +hyacinths were observed to be very inferior in quality. It is believed by +many agriculturists that red wheat is hardier in northern climates than +white wheat.[554] + +With animals, white varieties from being conspicuous are the most liable to +be attacked by beasts and birds of prey. In parts of France and Germany +where hawks abound, persons are advised not to keep white pigeons; for, as +Parmentier says, "it {230} is certain that in a flock the white always +first fall victims to the kite." In Belgium, where so many societies have +been established for the flight of carrier-pigeons, white is the one colour +which for the same reason is disliked.[555] On the other hand, it is said +that the sea-eagle (_Falco ossifragus_, Linn.) on the west coast of Ireland +picks out the black fowls, so that "the villagers avoid as much as possible +rearing birds of that colour." M. Daudin,[556] speaking of white rabbits +kept in warrens in Russia, remarks that their colour is a great +disadvantage, as they are thus more exposed to attack, and can be seen +during bright nights from a distance. A gentleman in Kent, who failed to +stock his woods with a nearly white and hardy kind of rabbit, accounted in +the same manner for their early disappearance. Any one who will watch a +white cat prowling after her prey will soon perceive under what a +disadvantage she lies. + +The white Tartarian cherry, "owing either to its colour being so much like +that of the leaves, or to the fruit always appearing from a distance +unripe," is not so readily attacked by birds as other sorts. The +yellow-fruited raspberry, which generally comes nearly true by seed, "is +very little molested by birds, who evidently are not fond of it; so that +nets may be dispensed with in places where nothing else will protect the +red fruit."[557] This immunity, though a benefit to the gardener, would be +a disadvantage in a state of nature both to the cherry and raspberry, as +their dissemination depends on birds. I noticed during several winters that +some trees of the yellow-berried holly, which were raised from seed from a +wild tree found by my father, remained covered with fruit, whilst not a +scarlet berry could be seen on the adjoining trees of the common kind. A +friend informs me that a mountain-ash (_Pyrus aucuparia_) growing in his +garden bears berries which, though not differently coloured, are always +devoured by birds before those on the other trees. This variety of the +mountain-ash would thus be more freely disseminated, and the yellow-berried +variety of the holly less freely, than the common varieties of these two +trees. + +{231} + +Independently of colour, other trifling differences are sometimes found to +be of importance to plants under cultivation, and would be of paramount +importance if they had to fight their own battle and to struggle with many +competitors. The thin-shelled peas, called _pois sans parchemin_, are +attacked by birds[558] much more than common peas. On the other hand, the +purple-podded pea, which has a hard shell, escaped the attacks of tomtits +(_Parus major_) in my garden far better than any other kind. The +thin-shelled walnut likewise suffers greatly from the tomtit.[559] These +same birds have been observed to pass over and thus favour the filbert, +destroying only the other kinds of nuts which grew in the same +orchard.[560] + +Certain varieties of the pear have soft bark, and these suffer severely +from boring wood-beetles; whilst other varieties are known to resist their +attacks much better.[561] In North America the smoothness, or absence of +down on the fruit, makes a great difference in the attacks of the weevil, +"which is the uncompromising foe of all smooth stone-fruits;" and the +cultivator "has the frequent mortification of seeing nearly all, or indeed +often the whole crop, fall from the trees when half or two-thirds grown." +Hence the nectarine suffers more than the peach. A particular variety of +the Morello cherry, raised in North America, is without any assignable +cause more liable to be injured by this same insect than other +cherry-trees.[562] From some unknown cause, the Winter Majetin apple enjoys +the great advantage of not being infested by the coccus. On the other hand, +a particular case has been recorded in which aphides confined themselves to +the Winter Nelis pear, and touched no other kind in an extensive +orchard.[563] The existence of minute glands on the leaves of peaches, +nectarines, and apricots, would not be esteemed by botanists as a character +of the least importance, for they are present or absent in closely related +sub-varieties, descended from the same parent-tree; yet there is good +evidence[564] that the {232} absence of glands leads to mildew, which is +highly injurious to these trees. + +A difference either in flavour or in the amount of nutriment in certain +varieties causes them to be more eagerly attacked by various enemies than +other varieties of the same species. Bullfinches (_Pyrrhula vulgaris_) +injure our fruit-trees by devouring the flower-buds, and a pair of these +birds have been seen "to denude a large plum-tree in a couple of days of +almost every bud;" but certain varieties[565] of the apple and thorn +(_Crataegus oxyacantha_) are more especially liable to be attacked. A +striking instance of this was observed in Mr. Rivers's garden, in which two +rows of a particular variety of plum[566] had to be carefully protected, as +they were usually stripped of all their buds during the winter, whilst +other sorts growing near them escaped. The root (or enlarged stem) of +Laing's Swedish turnip is preferred by hares, and therefore suffers more +than other varieties. Hares and rabbits eat down common rye before St. +John's-day-rye, when both grow together.[567] In the South of France, when +an orchard of almond-trees is formed, the nuts of the bitter variety are +sown, "in order that they may not be devoured by field-mice;"[568] so we +see the use of the bitter principle in almonds. + +Other slight differences, which would be thought quite unimportant, are no +doubt sometimes of great service both to plants and animals. The +Whitesmith's gooseberry, as formerly stated, produces its leaves later than +other varieties, and, as the flowers are thus left unprotected, the fruit +often fails. In one variety of the cherry, according to Mr. Rivers,[569] +the petals are much curled backwards, and in consequence of this the +stigmas were observed to be killed by a severe frost; whilst at the same +time, in another variety with incurved petals, the stigmas were not in the +least injured. The straw of the Fenton wheat is remarkably unequal in +height; and a competent observer believes that this variety is highly +productive, partly because the ears, from being distributed at various +heights above the ground, {233} are less crowded together. The same +observer maintains that in the upright varieties the divergent awns are +serviceable by breaking the shocks when the ears are dashed together by the +wind.[570] If several varieties of a plant are grown together, and the seed +is indiscriminately harvested, it is clear that the hardier and more +productive kinds will, by a sort of natural selection, gradually prevail +over the others; this takes place, as Colonel Le Couteur believes,[571] in +our wheat-fields, for, as formerly shown, no variety is quite uniform in +character. The same thing, as I am assured by nurserymen, would take place +in our flower-gardens, if the seed of the different varieties were not +separately saved. When the eggs of the wild and tame duck are hatched +together, the young wild ducks almost invariably perish, from being of +smaller size and not getting their fair share of food.[572] + +Facts in sufficient number have now been given showing that natural +selection often checks, but occasionally favours, man's power of selection. +These facts teach us, in addition, a valuable lesson, namely, that we ought +to be extremely cautious in judging what characters are of importance in a +state of nature to animals and plants, which have to struggle from the hour +of their birth to that of their death for existence,--their existence +depending on conditions, about which we are profoundly ignorant. + +_Circumstances favourable to Selection by Man._ + +The possibility of selection rests on variability, and this, as we shall +see in the following chapters, mainly depends on changed conditions of +life, but is governed by infinitely complex, and, to a great extent, +unknown laws. Domestication, even when long continued, occasionally causes +but a small amount of variability, as in the case of the goose and turkey. +The slight differences, however, which characterise each individual animal +and plant would in most, probably in all cases, suffice for the production +of distinct races through careful and prolonged selection. We see what +selection, though acting on mere individual differences, can effect when +families of cattle, sheep, {234} pigeons, &c., of the same race, have been +separately bred during a number of years by different men without any wish +on their part to modify the breed. We see the same fact in the difference +between hounds bred for hunting in different districts,[573] and in many +other such cases. + +In order that selection should produce any result, it is manifest that the +crossing of distinct races must be prevented; hence facility in pairing, as +with the pigeon, is highly favourable for the work; and difficulty in +pairing, as with cats, prevents the formation of distinct breeds. On nearly +the same principle the cattle of the small island of Jersey have been +improved in their milking qualities "with a rapidity that could not have +been obtained in a widely extended country like France."[574] Although free +crossing is a danger on the one side which every one can see, too close +interbreeding is a hidden danger on the other side. Unfavourable conditions +of life overrule the power of selection. Our improved heavy breeds of +cattle and sheep could not have been formed on mountainous pastures; nor +could dray-horses have been raised on a barren and inhospitable land, such +as the Falkland islands, where even the light horses of La Plata rapidly +decrease in size. Nor could the wool of sheep have been much increased in +length within the Tropics; yet selection has kept Merino sheep nearly true +under diversified and unfavourable conditions of life. The power of +selection is so great, that breeds of the dog, sheep, and poultry, of the +largest and least size, long and short beaked pigeons, and other breeds +with opposite characters, have had their characteristic qualities +augmented, though treated in every way alike, being exposed to the same +climate and fed on the same food. Selection, however, is either checked or +favoured by the effects of use or habit. Our wonderfully-improved pigs +could never have been formed if they had been forced to search for their +own food; the English racehorse and greyhound could not have been improved +up to their present high standard of excellence without constant training. + +As conspicuous deviations of structure occur rarely, the improvement of +each breed is generally the result, as already {235} remarked, of the +selection of slight individual differences. Hence the closest attention, +the sharpest powers of observation, and indomitable perseverance, are +indispensable. It is, also, highly important that many individuals of the +breed which is to be improved should be raised; for thus there will be a +better chance of the appearance of variations in the right direction, and +individuals varying in an unfavourable manner may be freely rejected or +destroyed. But that a large number of individuals should be raised, it is +necessary that the conditions of life should favour the propagation of the +species. Had the peacock been bred as easily as the fowl, we should +probably ere this have had many distinct races. We see the importance of a +large number of plants, from the fact of nursery gardeners almost always +beating amateurs in the exhibition of new varieties. In 1845 it was +estimated[575] that between 4000 and 5000 pelargoniums were annually raised +from seed in England, yet a decidedly improved variety is rarely obtained. +At Messrs. Carter's grounds, in Essex, where such flowers as the Lobelia, +Nemophila, Mignonette, &c., are grown by the acre for seed, "scarcely a +season passes without some new kinds being raised, or some improvement +affected on old kinds."[576] At Kew, as Mr. Beaton remarks, where many +seedlings of common plants are raised, "you see new forms of Laburnums, +Spiraeas, and other shrubs."[577] So with animals: Marshall,[578] in +speaking of the sheep in one part of Yorkshire, remarks, "as they belong to +poor people, and are mostly in small lots, they never can be improved." +Lord Rivers, when asked how he succeeded in always having first-rate +greyhounds, answered, "I breed many, and hang many." This, as another man +remarks, "was the secret of his success; and the same will be found in +exhibiting fowls,--successful competitors breed largely, and keep the +best."[579] + +It follows from this that the capacity of breeding at an early age and at +short successive intervals, as with pigeons, rabbits, &c., facilitates +selection; for the result is thus soon made visible, and perseverance in +the work is encouraged. It can hardly be {236} accidental that the great +majority of the culinary and agricultural plants which have yielded +numerous races are annuals or biennials, which therefore are capable of +rapid propagation and thus of improvement. Sea-kale, asparagus, common and +Jerusalem artichokes, potatoes, and onions, alone are perennials. Onions +are propagated like annuals, and of the other plants just specified, none, +with the exception of the potato, have yielded more than one or two +varieties. No doubt fruit-trees, which cannot be propagated quickly by +seed, have yielded a host of varieties, though not permanent races; but +these, judging from pre-historic remains, were produced at a later and more +civilised epoch than the races of culinary and agricultural plants. + +A species may be highly variable, but distinct races will not be formed, if +from any cause selection be not applied. The carp is highly variable, but +it would be extremely difficult to select slight variations in fishes +whilst living in their natural state, and distinct races have not been +formed;[580] on the other hand, a closely allied species, the gold-fish, +from being reared in glass or open vessels, and from having been carefully +attended to by the Chinese, has yielded many races. Neither the bee, which +has been semi-domesticated from an extremely remote period, nor the +cochineal insect, which was cultivated by the aboriginal Mexicans, has +yielded races; and it would be impossible to match the queen-bee with any +particular drone, and most difficult to match cochineal insects. +Silk-moths, on the other hand, have been subjected to rigorous selection, +and have produced a host of races. Cats, which from their nocturnal habits +cannot be selected for breeding, do not, as formerly remarked, yield +distinct races in the same country. The ass in England varies much in +colour and size; but it is an animal of little value, bred by poor people; +consequently there has been no selection, and distinct races have not been +formed. We must not attribute the inferiority of our asses to climate, for +in India they are of even smaller size than in Europe. But when selection +is brought to bear on the ass, all is changed. Near Cordova, as I am +informed (Feb. 1860) by Mr. W. E. Webb, C.E., they are carefully bred, as +much as 200l. having been paid for a stallion ass, {237} and they have been +immensely improved. In Kentucky, asses have been imported (for breeding +mules) from Spain, Malta, and France; these "seldom averaged more than +fourteen hands high; but the Kentuckians, by great care, have raised them +up to fifteen hands, and sometimes even to sixteen. The prices paid for +these splendid animals, for such they really are, will prove how much they +are in request. One male, of great celebrity, was sold for upwards of one +thousand pounds sterling." These choice asses are sent to cattle-shows, one +day being given to their exhibition.[581] + +Analogous facts have been observed with plants: the nutmeg-tree in the +Malay archipelago is highly variable, but there has been no selection, and +there are no distinct races.[582] The common mignonette (_Reseda odorata_), +from bearing inconspicuous flowers, valued solely for their fragrance, +"remains in the same unimproved condition as when first introduced."[583] +Our common forest-trees are very variable, as may be seen in every +extensive nursery-ground; but as they are not valued like fruit-trees, and +as they seed late in life, no selection has been applied to them; +consequently, as Mr. Patrick Matthews remarks,[584] they have not yielded +distinct races, leafing at different periods, growing to different sizes, +and producing timber fit for different purposes. We have gained only some +fanciful and semi-monstrous varieties, which no doubt appeared suddenly as +we now see them. + +Some botanists have argued that plants cannot have so strong a tendency to +vary as is generally supposed, because many species long grown in botanic +gardens, or unintentionally cultivated year after year mingled with our +corn crops, have not produced distinct races; but this is accounted for by +slight variations not having been selected and propagated. Let a plant +which is now grown in a botanic garden, or any common weed, be cultivated +on a large scale, and let a sharp-sighted gardener look out for each slight +variety and sow the seed, and then, if distinct races are not produced, the +argument will be valid. + +{238} + +The importance of selection is likewise shown by considering special +characters. For instance, with most breeds of fowls the form of the comb +and the colour of the plumage have been attended to, and are eminently +characteristic of each race; but in Dorkings, fashion has never demanded +uniformity of comb or colour; and the utmost diversity in these respects +prevails. Rose-combs, double-combs, cup-combs, &c., and colours of all +kinds, may be seen in purely-bred and closely related Dorking fowls, whilst +other points, such as the general form of body, and the presence of an +additional toe, have been attended to, and are invariably present. It has +also been ascertained that colour can be fixed in this breed, as well as in +any other.[585] + + * * * * * + +During the formation or improvement of a breed, its members will always be +found to vary much in those characters to which especial attention is +directed, and of which each slight improvement is eagerly sought and +selected. Thus with short-faced tumbler-pigeons, the shortness of the beak, +shape of head and plumage,--with carriers, the length of the beak and +wattle,--with fantails, the tail and carriage,--with Spanish fowls, the +white face and comb,--with long-eared rabbits, the length of ear, are all +points which are eminently variable. So it is in every case, and the large +price paid for first-rate animals proves the difficulty of breeding them up +to the highest standard of excellence. This subject has been discussed by +fanciers,[586] and the greater prizes given for highly improved breeds, in +comparison with those given for old breeds which are not now undergoing +rapid improvement, has been fully justified. Nathusius makes[587] a similar +remark when discussing the less uniform character of improved Shorthorn +cattle and of the English horse, in comparison, for example, with the +unennobled cattle of Hungary, or with the horses of the Asiatic steppes. +This want of uniformity in the parts which at the time are undergoing +selection, chiefly depends on the strength of the principle of reversion +but it likewise depends to a certain extent on the continued {239} +variability of the parts which have recently varied. That the same parts do +continue varying in the same manner we must admit, for, if it were not so, +there could be no improvement beyond an early standard of excellence, and +we know that such improvement is not only possible, but is of general +occurrence. + +As a consequence of continued variability, and more especially of +reversion, all highly improved races, if neglected or not subjected to +incessant selection, soon degenerate. Youatt gives a curious instance of +this in some cattle formerly kept in Glamorganshire; but in this case the +cattle were not fed with sufficient care. Mr. Baker, in his memoir on the +Horse, sums up: "It must have been observed in the preceding pages that, +whenever there has been neglect, the breed has proportionally +deteriorated."[588] If a considerable number of improved cattle, sheep, or +other animals of the same race, were allowed to breed freely together, with +no selection, but with no change in their condition of life, there can be +no doubt that after a score or hundred generations they would be very far +from excellent of their kind; but, from what we see of the many common +races of dogs, cattle, fowls, pigeons, &c., which without any particular +care have long retained nearly the same character, we have no grounds for +believing that they would altogether depart from their type. + +It is a general belief amongst breeders that characters of all kinds become +fixed by long-continued inheritance. But I have attempted to show in the +fourteenth chapter that this belief apparently resolves itself into the +following proposition, namely, that all characters whatever, whether +recently acquired or ancient, tend to be transmitted, but that those which +have already long withstood all counteracting influences, will, as a +general rule, continue to withstand them, and consequently be faithfully +transmitted. + +_Tendency in Man to carry the practice of Selection to an extreme point._ + +It is an important principle that in the process of selection man almost +invariably wishes to go to an extreme point. Thus, in useful qualities, +there is no limit to his desire to breed certain {240} horses and dogs as +fleet as possible, and others as strong as possible; certain kinds of sheep +for extreme fineness, and others for extreme length of wool; and he wishes +to produce fruit, grain, tubers, and other useful parts of plants, as large +and excellent as possible. With animals bred for amusement, the same +principle is even more powerful; for fashion, as we see even in our dress, +always runs to extremes. This view has been expressly admitted by fanciers. +Instances were given in the chapters on the pigeon, but here is another: +Mr. Eaton, after describing a comparatively new variety, namely, the +Archangel, remarks, "What fanciers intend doing with this bird I am at a +loss to know, whether they intend to breed it down to the tumbler's head +and beak, or carry it out to the carrier's head and beak; leaving it as +they found it, is not progressing." Ferguson, speaking of fowls, says, +"their peculiarities, whatever they may be, must necessarily be fully +developed: a little peculiarity forms nought but ugliness, seeing it +violates the existing laws of symmetry." So Mr. Brent, in discussing the +merits of the sub-varieties of the Belgian canary-bird, remarks, "Fanciers +always go to extremes; they do not admire indefinite properties."[589] + +This principle, which necessarily leads to divergence of character, +explains the present state of various domestic races. We can thus see how +it is that race-horses and dray-horses, greyhounds and mastiffs, which are +opposed to each other in every character,--how varieties so distinct as +Cochin-China fowls and bantams, or carrier-pigeons with very long beaks, +and tumblers with excessively short beaks, have been derived from the same +stock. As each breed is slowly improved, the inferior varieties are first +neglected and finally lost. In a few cases, by the aid of old records, or +from intermediate varieties still existing in countries where other +fashions have prevailed, we are enabled partially to trace the graduated +changes through which certain breeds have passed. Selection, whether +methodical or unconscious, always tending towards an extreme point, +together with the neglect and slow extinction of the intermediate and +less-valued forms, is the key which unlocks the mystery how man has +produced such wonderful results. + +{241} + +In a few instances selection, guided by utility for a single purpose, has +led to convergence of character. All the improved and different races of +the pig, as Nathusius has well shown,[590] closely approach each other in +character, in their shortened legs and muzzles, their almost hairless, +large, rounded bodies, and small tusks. We see some degree of convergence +in the similar outline of the body in well-bred cattle belonging to +distinct races.[591] I know of no other such cases. + +Continued divergence of character depends on, and is indeed a clear proof, +as previously remarked, of the same parts continuing to vary in the same +direction. The tendency to mere general variability or plasticity of +organisation can certainly be inherited, even from one parent, as has been +shown by Gaertner and Koelreuter, in the production of varying hybrids from +two species, of which one alone was variable. It is in itself probable +that, when an organ has varied in any manner, it will again vary in the +same manner, if the conditions which first caused the being to vary remain, +as far as can be judged, the same. This is either tacitly or expressly +admitted by all horticulturists: if a gardener observes one or two +additional petals in a flower, he feels confident that in a few generations +he will be able to raise a double flower, crowded with petals. Some of the +seedlings from the weeping Moccas oak were so prostrate that they only +crawled along the ground. A seedling from the fastigate or upright Irish +yew is described as differing greatly from the parent-form "by the +exaggeration of the fastigate habit of its branches."[592] Mr. Sheriff, who +has been more successful than any other man in raising new kinds of wheat, +remarks, "A good variety may safely be regarded as the forerunner of a +better one."[593] A great rose-grower, Mr. Rivers, has made the same remark +with respect to roses. Sageret,[594] who had large experience, in speaking +of the future progress of fruit-trees, observes that the most important +principle is "that the more plants have departed from their original type, +the more they tend to depart from it." There is apparently much truth in +this {242} remark; for we can in no other way understand the surprising +amount of difference between varieties in the parts or qualities which are +valued, whilst other parts retain nearly their original character. + +The foregoing discussion naturally leads to the question, what is the limit +to the possible amount of variation in any part or quality, and, +consequently, is there any limit to what selection can effect? Will a +race-horse ever be reared fleeter than Eclipse? Can our prize-cattle and +sheep be still further improved? Will a gooseberry ever weigh more than +that produced by "London" in 1852? Will the beet-root in France yield a +greater percentage of sugar? Will future varieties of wheat and other grain +produce heavier crops than our present varieties? These questions cannot be +positively answered; but it is certain that we ought to be cautious in +answering by a negative. In some lines of variation the limit has probably +been reached. Youatt believes that the reduction of bone in some of our +sheep has already been carried so far that it entails great delicacy of +constitution.[595] But seeing the great improvement within recent times in +our cattle and sheep, and especially in our pigs; seeing the wonderful +increase in weight in our poultry of all kinds during the last few years; +he would be a bold man who would assert that perfection has been reached. +Eclipse perhaps may never be beaten until all our race-horses have been +rendered swifter, through the selection of the best horses during many +generations; and then the old Eclipse may possibly be eclipsed; but, as Mr. +Wallace has remarked, there must be an ultimate limit to the fleetness of +every animal, whether under nature or domestication; and with the horse +this limit has perhaps been reached. Until our fields are better manured, +it may be impossible for a new variety of wheat to yield a heavier crop. +But in many cases those who are best qualified to judge do not believe that +the extreme point has as yet been reached even with respect to characters +which have already been carried to a high standard of perfection. For +instance, the short-faced tumbler-pigeon has been greatly modified; +nevertheless, according to Mr. Eaton,[596] "the field is still as open for +fresh competitors as it was one hundred years ago." Over and over again it +has been said that {243} perfection had been attained with our flowers, but +a higher standard has soon been reached. Hardly any fruit has been more +improved than the strawberry, yet a great authority remarks,[597] "it must +not be concealed that we are far from the extreme limits at which we may +arrive." + +Time is an important element in the formation of our domestic races, as it +permits innumerable individuals to be born, and these when exposed to +diversified conditions are rendered variable. Methodical selection has been +occasionally practised from an ancient period to the present day, even by +semi-civilised people, and during former times will have produced some +effect. Unconscious selection will have been still more effective; for +during a lengthened period the more valuable individual animals will +occasionally have been saved, and the less valuable neglected. In the +course, also, of time, different varieties, especially in the less +civilised countries, will have been more or less modified through natural +selection. It is generally believed, though on this head we have little or +no evidence, that new characters in time become fixed; and after having +long remained fixed it seems possible that under new conditions they might +again be rendered variable. + +How great the lapse of time has been since man first domesticated animals +and cultivated plants, we begin dimly to see. When the lake-buildings of +Switzerland were inhabited during the Neolithic period, several animals +were already domesticated and various plants cultivated. If we may judge +from what we now see of the habits of savages, it is probable that the men +of the earlier Stone period--when many great quadrupeds were living which +are now extinct, and when the face of the country was widely different from +what it now is--possessed at least some few domesticated animals, although +their remains have not as yet been discovered. If the science of language +can be trusted, the art of ploughing and sowing the land was followed, and +the chief animals had been already domesticated, at an epoch so immensely +remote, that the Sanskrit, Greek, Latin, Gothic, Celtic, and Sclavonic +languages had not as yet diverged from their common parent-tongue.[598] + +{244} + +It is scarcely possible to overrate the effects of selection occasionally +carried on in various ways and places during thousands of generations. All +that we know, and, in a still stronger degree, all that we do not +know,[599] of the history of the great majority of our breeds, even of our +more modern breeds, agrees with the view that their production, through the +action of unconscious and methodical selection, has been almost insensibly +slow. When a man attends rather more closely than is usual to the breeding +of his animals, he is almost sure to improve them to a slight extent. They +are in consequence valued in his immediate neighbourhood, and are bred by +others; and their characteristic features, whatever these may be, will then +slowly but steadily be increased, sometimes by methodical and almost always +by unconscious selection. At last a strain, deserving to be called a +sub-variety, becomes a little more widely known, receives a local name, and +spreads. The spreading will have been extremely slow during ancient and +less civilised times, but now is rapid. By the time that the new breed had +assumed a somewhat distinct character, its history, hardly noticed at the +time, will have been completely forgotten; for, as Low remarks,[600] "we +know how quickly the memory of such events is effaced." + +As soon as a new breed is thus formed, it is liable through the same +process to break up into new strains and sub-varieties. For different +varieties are suited for, and are valued under, different circumstances. +Fashion changes, but, should a fashion last for even a moderate length of +time, so strong is the principle of inheritance, that some effect will +probably be impressed on the breed. Thus varieties go on increasing in +number, and history shows us how wonderfully they have increased since the +earliest records.[601] As each new variety is produced, the earlier, +intermediate, and less valuable forms will be neglected, and perish. When a +breed, from not being valued, is kept in small numbers, its extinction +almost inevitably follows sooner or later, either from accidental causes of +destruction or from close interbreeding; and this is an event which, in the +case of well-marked breeds, excites attention. The birth or production of a +new domestic race is so slow a process that it {245} escapes notice; its +death or destruction is comparatively sudden, is often recorded, and when +too late sometimes regretted. + +Several authors have drawn a wide distinction between artificial and +natural races. The latter are more uniform in character, possessing in a +high degree the character of natural species, and are of ancient origin. +They are generally found in less civilised countries, and have probably +been largely modified by natural selection, and only to a small extent by +man's unconscious and methodical selection. They have, also, during a long +period, been directly acted on by the physical conditions of the countries +which they inhabit. The so-called artificial races, on the other hand, are +not so uniform in character; some have a semi-monstrous character, such as +"the wry-legged terriers so useful in rabbit-shooting,"[602] turnspit dogs, +ancon sheep, niata oxen, Polish fowls, fantail-pigeons, &c.; their +characteristic features have generally been acquired suddenly, though +subsequently increased in many cases by careful selection. Other races, +which certainly must be called artificial, for they have been largely +modified by methodical selection and by crossing, as the English +race-horse, terrier-dogs, the English game-cock, Antwerp carrier-pigeons, +&c., nevertheless cannot be said to have an unnatural appearance; and no +distinct line, as it seems to me, can be drawn between natural and +artificial races. + +It is not surprising that domestic races should generally present a +different aspect from natural species. Man selects and propagates +modifications solely for his own use or fancy, and not for the creature's +own good. His attention is struck by strongly marked modifications, which +have appeared suddenly, due to some great disturbing cause in the +organisation. He attends almost exclusively to external characters; and +when he succeeds in modifying internal organs,--when for instance he +reduces the bones and offal, or loads the viscera with fat, or gives early +maturity, &c.,--the chances are strong that he will at the same time weaken +the constitution. On the other hand, when an animal has to struggle +throughout its life with many competitors and enemies, under circumstances +inconceivably complex and liable to change, modifications of the most +varied nature--in the internal organs as well as in external characters, in +the {246} functions and mutual relations of parts--will be rigorously +tested, preserved, or rejected. Natural selection often checks man's +comparatively feeble and capricious attempts at improvement; and if this +were not so, the result of his work, and of nature's work, would be even +still more different. Nevertheless, we must not overrate the amount of +difference between natural species and domestic races; the most experienced +naturalists have often disputed whether the latter are descended from one +or from several aboriginal stocks, and this clearly shows that there is no +palpable difference between species and races. + +Domestic races propagate their kind far more truly, and endure for much +longer periods, than most naturalists are willing to admit. Breeders feel +no doubt on this head; ask a man who has long reared Shorthorn or Hereford +cattle, Leicester or Southdown sheep, Spanish or Game poultry, tumbler or +carrier-pigeons, whether these races may not have been derived from common +progenitors, and he will probably laugh you to scorn. The breeder admits +that he may hope to produce sheep with finer or longer wool and with better +carcases, or handsomer fowls, or carrier-pigeons with beaks just +perceptibly longer to the practised eye, and thus be successful at an +exhibition. Thus far he will go, but no farther. He does not reflect on +what follows from adding up during a long course of time many, slight, +successive modifications; nor does he reflect on the former existence of +numerous varieties, connecting the links in each divergent line of descent. +He concludes, as was shown in the earlier chapters, that all the chief +breeds to which he has long attended are aboriginal productions. The +systematic naturalist, on the other hand, who generally knows nothing of +the art of breeding, who does not pretend to know how and when the several +domestic races were formed, who cannot have seen the intermediate +gradations, for they do not now exist, nevertheless feels no doubt that +these races are sprung from a single source. But ask him whether the +closely allied natural species which he has studied may not have descended +from a common progenitor, and he in his turn will perhaps reject the notion +with scorn. Thus the naturalist and breeder may mutually learn a useful +lesson from each other. + + * * * * * + +_Summary on Selection by Man._--There can be no doubt that {247} methodical +selection has effected and will effect wonderful results. It was +occasionally practised in ancient times, and is still practised by +semi-civilised people. Characters of the highest importance, and others of +trifling value, have been attended to, and modified. I need not here repeat +what has been so often said on the part which unconscious selection has +played: we see its power in the difference between flocks which have been +separately bred, and in the slow changes, as circumstances have slowly +changed, which many animals have undergone in the same country, or when +transported into a foreign land. We see the combined effects of methodical +and unconscious selection in the great amount of difference between +varieties in those parts or qualities which are valued by man, in +comparison with those which are not valued, and consequently have not been +attended to. Natural selection often determines man's power of selection. +We sometimes err in imagining that characters, which are considered as +unimportant by the systematic naturalist, could not be affected by the +struggle for existence, and therefore be acted on by natural selection; but +striking cases have been given, showing how great an error this is. + +The possibility of selection coming into action rests on variability; and +this is mainly caused, as we shall hereafter see, by changes in the +conditions of life. Selection is sometimes rendered difficult, or even +impossible, by the conditions being opposed to the desired character or +quality. It is sometimes checked by the lessened fertility and weakened +constitution which follow from long-continued close interbreeding. That +methodical selection may be successful, the closest attention and +discernment, combined with unwearied patience, are absolutely necessary; +and these same qualities, though not indispensable, are highly serviceable +in the case of unconscious selection. It is almost necessary that a large +number of individuals should be reared; for thus there will be a fair +chance of variations of the desired nature arising, and every individual +with the slightest blemish or in any degree inferior may be freely +rejected. Hence length of time is an important element of success. Thus, +also, propagation at an early age and at short intervals favours the work. +Facility in pairing animals, or their inhabiting a confined area, is +advantageous as a check to free crossing. Whenever and {248} wherever +selection is not practised, distinct races are not formed. When any one +part of the body or quality is not attended to, it remains either unchanged +or varies in a fluctuating manner, whilst at the same time other parts and +other qualities may become permanently and greatly modified. But from the +tendency to reversion and to continued variability, those parts or organs +which are now undergoing rapid improvement through selection, are likewise +found to vary much. Consequently highly-bred animals, when neglected, soon +degenerate; but we have no reason to believe that the effects of +long-continued selection would, if the conditions of life remained the +same, be soon and completely lost. + +Man always tends to go to an extreme point in the selection, whether +methodical or unconscious, of all useful and pleasing qualities. This is an +important principle, as it leads to continued divergence, and in some rare +cases to convergence of character. The possibility of continued divergence +rests on the tendency in each part or organ to go on varying in the same +manner in which it has already varied; and that this occurs, is proved by +the steady and gradual improvement of many animals and plants during +lengthened periods. The principle of divergence of character, combined with +the neglect and final extinction of all previous, less-valued, and +intermediate varieties, explains the amount of difference and the +distinctness of our several races. Although we may have reached the utmost +limit to which certain characters can be modified, yet we are far from +having reached, as we have good reason to believe, the limit in the +majority of cases. Finally, from the difference between selection as +carried on by man and by nature, we can understand how it is that domestic +races often, though by no means always, differ in general aspect from +closely allied natural species. + +Throughout this chapter and elsewhere I have spoken of selection as the +paramount power, yet its action absolutely depends on what we in our +ignorance call spontaneous or accidental variability. Let an architect be +compelled to build an edifice with uncut stones, fallen from a precipice. +The shape of each fragment may be called accidental; yet the shape of each +has been determined by the force of gravity, the nature {249} of the rock, +and the slope of the precipice,--events and circumstances, all of which +depend on natural laws; but there is no relation between these laws and the +purpose for which each fragment is used by the builder. In the same manner +the variations of each creature are determined by fixed and immutable laws; +but these bear no relation to the living structure which is slowly built up +through the power of selection, whether this be natural or artificial +selection. + +If our architect succeeded in rearing a noble edifice, using the rough +wedge-shaped fragments for the arches, the longer stones for the lintels, +and so forth, we should admire his skill even in a higher degree than if he +had used stones shaped for the purpose. So it is with selection, whether +applied by man or by nature; for though variability is indispensably +necessary, yet, when we look at some highly complex and excellently adapted +organism, variability sinks to a quite subordinate position in importance +in comparison with selection, in the same manner as the shape of each +fragment used by our supposed architect is unimportant in comparison with +his skill. + + * * * * * + + +{250} + +CHAPTER XXII. + +CAUSES OF VARIABILITY. + + VARIABILITY DOES NOT NECESSARILY ACCOMPANY REPRODUCTION--CAUSES + ASSIGNED BY VARIOUS AUTHORS--INDIVIDUAL DIFFERENCES--VARIABILITY OF + EVERY KIND DUE TO CHANGED CONDITIONS OF LIFE--ON THE NATURE OF SUCH + CHANGES--CLIMATE, FOOD, EXCESS OF NUTRIMENT--SLIGHT CHANGES + SUFFICIENT--EFFECTS OF GRAFTING ON THE VARIABILITY OF + SEEDLING-TREES--DOMESTIC PRODUCTIONS BECOME HABITUATED TO CHANGED + CONDITIONS--ON THE ACCUMULATIVE ACTION OF CHANGED CONDITIONS--CLOSE + INTERBREEDING AND THE IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE + VARIABILITY--CROSSING AS A CAUSE OF THE APPEARANCE OF NEW + CHARACTERS--VARIABILITY FROM THE COMMINGLING OF CHARACTERS AND FROM + REVERSION--ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH + EITHER DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE + VARIABILITY. + +We will now consider, as far as we can, the causes of the almost universal +variability of our domesticated productions. The subject is an obscure one; +but it may be useful to probe our ignorance. Some authors, for instance Dr. +Prosper Lucas, look at variability as a necessary contingent on +reproduction, and as much an aboriginal law, as growth or inheritance. +Others have of late encouraged, perhaps unintentionally, this view by +speaking of inheritance and variability as equal and antagonistic +principles. Pallas maintained, and he has had some followers, that +variability depends exclusively on the crossing of primordially distinct +forms. Other authors attribute the tendency to variability to an excess of +food, and with animals to an excess relatively to the amount of exercise +taken, or again to the effects of a more genial climate. That these causes +are all effective is highly probable. But we must, I think, take a broader +view, and conclude that organic beings, when subjected during several +generations to any change whatever in their conditions, tend to vary; the +kind of variation which ensues depending in a far higher degree on the +nature or constitution of the being, than on the nature of the changed +conditions. {251} + +Those authors who believe that it is a law of nature that each individual +should differ in some slight degree from every other, may maintain, +apparently with truth, that this is the fact, not only with all +domesticated animals and cultivated plants, but likewise with all organic +beings in a state of nature. The Laplander by long practice knows and gives +a name to each reindeer, though, as Linnaeus remarks, "to distinguish one +from another among such multitudes was beyond my comprehension, for they +were like ants on an ant-hill." In Germany shepherds have won wagers by +recognising each sheep in a flock of a hundred, which they had never seen +until the previous fortnight. This power of discrimination, however, is as +nothing compared to that which some florists have acquired. Verlot mentions +a gardener who could distinguish 150 kinds of camellia, when not in flower; +and it has been positively asserted that the famous old Dutch florist +Voorhelm, who kept above 1200 varieties of the hyacinth, was hardly ever +deceived in knowing each variety by the bulb alone. Hence we must conclude +that the bulbs of the hyacinth and the branches and leaves of the camellia, +though appearing to an unpractised eye absolutely undistinguishable, yet +really differ.[603] + +As Linnaeus has compared the reindeer in number to ants, I may add that +each ant knows its fellow of the same community. Several times I carried +ants of the same species (_Formica rufa_) from one ant-hill to another, +inhabited apparently by tens of thousands of ants; but the strangers were +instantly detected and killed. I then put some ants taken from a very large +nest into a bottle strongly perfumed with assafoetida, and after an +interval of twenty-four hours returned them to their home; they were at +first threatened by their fellows, but were soon recognised and allowed to +pass. Hence each ant certainly recognises, independently of odour, its +fellow; and if all the ants of the same community have not some countersign +or watchword, they must present to each other's senses some distinguishable +character. + +{252} + +The dissimilarity of brothers or sisters of the same family, and of +seedlings from the same capsule, may be in part accounted for by the +unequal blending of the characters of the two parents, and by the more or +less complete recovery through reversion of ancestral characters on either +side; but we thus only push the difficulty further back in time, for what +made the parents or their progenitors different? Hence the belief[604] that +an innate tendency to vary exists, independently of external conditions, +seems at first sight probable. But even the seeds nurtured in the same +capsule are not subjected to absolutely uniform conditions, as they draw +their nourishment from different points; and we shall see in a future +chapter that this difference sometimes suffices greatly to affect the +character of the future plant. The less close similarity of the successive +children of the same family in comparison with human twins, which often +resemble each other in external appearance, mental disposition, and +constitution, in so extraordinary a manner, apparently proves that the +state of the parents at the exact period of conception, or the nature of +the subsequent embryonic development, has a direct and powerful influence +on the character of the offspring. Nevertheless, when we reflect on the +{253} individual differences between organic beings in a state of nature, +as shown by every wild animal knowing its mate; and when we reflect on the +infinite diversity of the many varieties of our domesticated productions, +we may well be inclined to exclaim, though falsely as I believe, that +Variability must be looked at as an ultimate fact, necessarily contingent +on reproduction. + +Those authors who adopt this latter view would probably deny that each +separate variation has its own proper exciting cause. Although we can +seldom trace the precise relation between cause and effect, yet the +considerations presently to be given lead to the conclusion that each +modification must have its own distinct cause. When we hear of an infant +born, for instance, with a crooked finger, a misplaced tooth, or other +slight deviation of structure, it is difficult to bring the conviction home +to the mind that such abnormal cases are the result of fixed laws, and not +of what we blindly call accident. Under this point of view the following +case, which has been carefully examined and communicated to me by Dr. +William Ogle, is highly instructive. Two girls, born as twins, and in all +respects extremely alike, had their little fingers on both hands crooked; +and in both children the second bicuspid tooth in the upper jaw, of the +second dentition, was misplaced; for these teeth, instead of standing in a +line with the others, grew from the roof of the mouth behind the first +bicuspids. Neither the parents nor any other member of the family had +exhibited any similar peculiarity. Now, as both these children were +affected in exactly the same manner by both deviations of structure, the +idea of accident is at once excluded; and we are compelled to admit that +there must have existed some precise and sufficient cause which, if it had +occurred a hundred times, would have affected a hundred children. + +We will now consider the general arguments, which appear to me to have +great weight, in favour of the view that variations of all kinds and +degrees are directly or indirectly caused by the conditions of life to +which each being, and more especially its ancestors, have been exposed. + +No one doubts that domesticated productions are more variable than organic +beings which have never been removed from their {254} natural conditions. +Monstrosities graduate so insensibly into mere variations that it is +impossible to separate them; and all those who have studied monstrosities +believe that they are far commoner with domesticated than with wild animals +and plants;[605] and in the case of plants, monstrosities would be equally +noticeable in the natural as in the cultivated state. Under nature, the +individuals of the same species are exposed to nearly uniform conditions, +for they are rigorously kept to their proper places by a host of competing +animals and plants; they have, also, long been habituated to their +conditions of life; but it cannot be said that they are subject to quite +uniform conditions, and they are liable to a certain amount of variation. +The circumstances under which our domestic productions are reared are +widely different: they are protected from competition; they have not only +been removed from their natural conditions and often from their native +land, but they are frequently carried from district to district, where they +are treated differently, so that they never remain during a considerable +length of time exposed to closely similar conditions. In conformity with +this, all our domesticated productions, with the rarest exceptions, vary +far more than natural species. The hive-bee, which feeds itself and follows +in most respects its natural habits of life, is the least variable of all +domesticated animals, and probably the goose is the next least variable; +but even the goose varies more than almost any wild bird, so that it cannot +be affiliated with perfect certainty to any natural species. Hardly a +single plant can be named, which has long been cultivated and propagated by +seed, that is not highly variable; common rye (_Secale cereale_) has +afforded fewer and less marked varieties than almost any other cultivated +plant;[606] but it may be doubted whether the variations of this, the least +valuable of all our cereals, have been closely observed. + +Bud-variation, which was fully discussed in a former chapter, shows us that +variability may be quite independent of seminal reproduction, and likewise +of reversion to long-lost ancestral characters. No one will maintain that +the sudden appearance {255} of a moss-rose on a Provence-rose is a return +to a former state, for mossiness of the calyx has been observed in no +natural species; the same argument is applicable to variegated and +laciniated leaves; nor can the appearance of nectarines on peach-trees be +accounted for with any probability on the principle of reversion. But +bud-variations more immediately concern us, as they occur far more +frequently on plants which have been highly cultivated during a length of +time, than on other and less highly cultivated plants; and very few +well-marked instances have been observed with plants growing under strictly +natural conditions. I have given one instance of an ash-tree growing in a +gentleman's pleasure-grounds; and occasionally there may be seen, on beech +and other trees, twigs leafing at a different period from the other +branches. But our forest trees in England can hardly be considered as +living under strictly natural conditions; the seedlings are raised and +protected in nursery-grounds, and must often be transplanted into places +where wild trees of the kind would not naturally grow. It would be esteemed +a prodigy if a dog-rose growing in a hedge produced by bud-variation a +moss-rose, or a wild bullace or wild cherry-tree yielded a branch bearing +fruit of a different shape and colour from the ordinary fruit. The prodigy +would be enhanced if these varying branches were found capable of +propagation, not only by grafts, but sometimes by seed; yet analogous cases +have occurred with many of our highly cultivated trees and herbs. + +These several considerations alone render it probable that variability of +every kind is directly or indirectly caused by changed conditions of life. +Or, to put the case under another point of view, if it were possible to +expose all the individuals of a species during many generations to +absolutely uniform conditions of life, there would be no variability. + +_On the Nature of the Changes in the Conditions of Life which induce +Variability._ + +From a remote period to the present day, under climates and circumstances +as different as it is possible to conceive, organic beings of all kinds, +when domesticated or cultivated, have {256} varied. We see this with the +many domestic races of quadrupeds and birds belonging to different orders, +with gold-fish and silkworms, with plants of many kinds, raised in various +quarters of the world. In the deserts of northern Africa the date-palm has +yielded thirty-eight varieties; in the fertile plains of India it is +notorious how many varieties of rice and of a host of other plants exist; +in a single Polynesian island, twenty-four varieties of the bread-fruit, +the same number of the banana, and twenty-two varieties of the arum, are +cultivated by the natives; the mulberry-tree in India and Europe has +yielded many varieties serving as food for the silkworm; and in China +sixty-three varieties of the bamboo are used for various domestic +purposes.[607] These facts alone, and innumerable others could be added, +indicate that a change of almost any kind in the conditions of life +suffices to cause variability--different changes acting on different +organisms. + +Andrew Knight[608] attributed the variation of both animals and plants to a +more abundant supply of nourishment, or to a more favourable climate, than +that natural to the species. A more genial climate, however, is far from +necessary; the kidney-bean, which is often injured by our spring frosts, +and peaches, which require the protection of a wall, have varied much in +England, as has the orange-tree in northern Italy, where it is barely able +to exist.[609] Nor can we overlook the fact, though not immediately +connected with our present subject, that the plants and shells of the +arctic regions are eminently variable.[610] Moreover, it does not appear +that a change of climate, whether more or less genial, is one of the most +potent causes of variability; for in regard to plants Alph. De Candolle, in +his 'Geographie {257} Botanique,' repeatedly shows that the native country +of a plant, where in most cases it has been longest cultivated, is that +where it has yielded the greatest number of varieties. + +It is doubtful whether a change in the nature of the food is a potent cause +of variability. Scarcely any domesticated animal has varied more than the +pigeon or the fowl, but their food, especially that of highly-bred pigeons, +is generally the same. Nor can our cattle and sheep have been subjected to +any great change in this respect. But in all these cases the food probably +is much less varied in kind than that which was consumed by the species in +its natural state.[611] + +Of all the causes which induce variability, excess of food, whether or not +changed in nature, is probably the most powerful. This view was held with +regard to plants by Andrew Knight, and is now held by Schleiden, more +especially in reference to the inorganic elements of the food.[612] In +order to give a plant more food it suffices in most cases to grow it +separately, and thus prevent other plants robbing its roots. It is +surprising, as I have often seen, how vigorously our common wild plants +flourish when planted by themselves, though not in highly manured land. +Growing plants separately is, in fact, the first step in cultivation. We +see the converse of the belief that excess of food induces variability in +the following statement by a great raiser of seeds of all kinds.[613] "It +is a rule invariably with us, when we desire to keep a true stock of any +one kind of seed, to grow it on poor land without dung; but when we grow +for quantity, we act contrary, and sometimes have dearly to repent of it." + +In the case of animals the want of a proper amount of exercise, as +Bechstein has remarked, has perhaps played, independently of the direct +effects of the disuse of any particular organ, an important part in causing +variability. We can see in a vague manner that, when the organised and +nutrient fluids of the body are not used during growth, or by the wear and +tear of the tissues, {258} they will be in excess; and as growth, +nutrition, and reproduction are intimately allied processes, this +superfluity might disturb the due and proper action of the reproductive +organs, and consequently affect the character of the future offspring. But +it may be argued that neither an excess of food nor a superfluity in the +organised fluids of the body necessarily induces variability. The goose and +the turkey have been well fed for many generations, yet have varied very +little. Our fruit-trees and culinary plants, which are so variable, have +been cultivated from an ancient period, and, though they probably still +receive more nutriment than in their natural state, yet they must have +received during many generations nearly the same amount; and it might be +thought that they would have become habituated to the excess. Nevertheless, +on the whole, Knight's view, that excess of food is one of the most potent +causes of variability, appears, as far as I can judge, probable. + +Whether or not our various cultivated plants have received nutriment in +excess, all have been exposed to changes of various kinds. Fruit-trees are +grafted on different stocks, and grown in various soils. The seeds of +culinary and agricultural plants are carried from place to place; and +during the last century the rotation of our crops and the manures used have +been greatly changed. + +Slight changes of treatment often suffice to induce variability. The simple +fact of almost all our cultivated plants and domesticated animals having +varied in all places and at all times, leads to this conclusion. Seeds +taken from common English forest-trees, grown under their native climate, +not highly manured or otherwise artificially treated, yield seedlings which +vary much, as may be seen in every extensive seed-bed. I have shown in a +former chapter what a number of well marked and singular varieties the +thorn (_Crataegus oxyacantha_) has produced; yet this tree has been +subjected to hardly any cultivation. In Staffordshire I carefully examined +a large number of two British plants, namely, _Geranium phaeum_ and +_Pyrenaicum_, which have never been highly cultivated. These plants had +spread spontaneously by seed from a common garden into an open plantation; +and the seedlings varied in almost every single character, both in their +flowers and foliage, to a degree which {259} I have never seen exceeded; +yet they could not have been exposed to any great change in their +conditions. + +With respect to animals, Azara has remarked with much surprise,[614] that, +whilst the feral horses on the Pampas are always of one of three colours, +and the cattle always of a uniform colour, yet these animals, when bred on +the unenclosed estancias, though kept in a state which can hardly be called +domesticated, and apparently exposed to almost identically the same +conditions as when they are feral, nevertheless display a great diversity +of colour. So again in India several species of fresh-water fish are only +so far treated artificially, that they are reared in great tanks; but this +small change is sufficient to induce much variability.[615] + +Some facts on the effects of grafting, in regard to the variability of +trees, deserve attention. Cabanis asserts that when certain pears are +grafted on the quince, their seeds yield more varieties than do the seeds +of the same variety of pear when grafted on the wild pear.[616] But as the +pear and quince are distinct species, though so closely related that the +one can be readily grafted and succeeds admirably on the other, the fact of +variability being thus caused is not surprising; we are, however, here +enabled to see the cause, namely, the different nature of the stock with +its roots and the rest of the tree. Several North American varieties of the +plum and peach are well known to reproduce themselves truly by seed; but +Downing asserts,[617] "that when a graft is taken from one of these trees +and placed upon another stock, this grafted tree is found to lose its +singular property of producing the same variety by seed, and becomes like +all other worked trees;"--that is, its seedlings become highly variable. +Another case is worth giving: the Lalande variety of the walnut-tree leafs +between April 20th and May 15th, and its seedlings invariably inherit the +same habit; whilst several other varieties of the walnut leaf in June. Now, +if seedlings are raised from the May-leafing Lalande variety, grafted on +another May-leafing variety, though both stock and graft have the same +early habit of leafing, yet the seedlings leaf at various times, {260} even +as late as the 5th of June.[618] Such facts as these are well fitted to +show, on what obscure and slight causes variability rests. + + I may here just allude to the appearance of new and valuable varieties + of fruit-trees and of wheat in woods and waste places, which at first + sight seems a most anomalous circumstance. In France a considerable + number of the best pears have been discovered in woods; and this has + occurred so frequently, that Poiteau asserts that "improved varieties + of our cultivated fruits rarely originate with nurserymen."[619] In + England, on the other hand, no instance of a good pear having been + found wild has been recorded; and Mr. Rivers informs me that he knows + of only one instance with apples, namely, the Bess Poole, which was + discovered in a wood in Nottinghamshire. This difference between the + two countries may be in part accounted for by the more favourable + climate of France, but chiefly from the great number of seedlings which + spring up there in the woods. I infer that this is the case from a + remark made by a French gardener,[620] who regards it as a national + calamity that such a number of pear-trees are periodically cut down for + firewood, before they have borne fruit. The new varieties which thus + spring up in the woods, though they cannot have received any excess of + nutriment, will have been exposed to abruptly changed conditions, but + whether this is the cause of their production is very doubtful. These + varieties, however, are probably all descended[621] from old cultivated + kinds growing in adjoining orchards,--a circumstance which will account + for their variability; and out of a vast number of varying trees there + will always be a good chance of the appearance of a valuable kind. In + North America, where fruit-trees frequently spring up in waste places, + the Washington pear was found in a hedge, and the Emperor peach in a + wood.[622] + + With respect to wheat, some writers have spoken[623] as if it were an + ordinary event for new varieties to be found in waste places; the + Fenton wheat was certainly discovered growing on a pile of basaltic + detritus in a quarry, but in such a situation the plant would probably + receive a sufficient amount {261} of nutriment. The Chidham wheat was + raised from an ear found _on_ a hedge; and Hunter's wheat was + discovered _by_ the roadside in Scotland, but it is not said that this + latter variety grew where it was found.[624] + +Whether our domestic productions would ever become so completely habituated +to the conditions under which they now live, as to cease varying, we have +no sufficient means for judging. But, in fact, our domestic productions are +never exposed for a great length of time to uniform conditions, and it is +certain that our most anciently cultivated plants, as well as animals, +still go on varying, for all have recently undergone marked improvement. In +some few cases, however, plants have become habituated to new conditions. +Thus Metzger, who cultivated in Germany during many years numerous +varieties of wheat, brought from different countries,[625] states that some +kinds were at first extremely variable, but gradually, in one instance +after an interval of twenty-five years, became constant; and it does not +appear that this resulted from the selection of the more constant forms. + + * * * * * + +_On the Accumulative Action of changed Conditions of Life._--We have good +grounds for believing that the influence of changed conditions accumulates, +so that no effect is produced on a species until it has been exposed during +several generations to continued cultivation or domestication. Universal +experience shows us that when new flowers are first introduced into our +gardens they do not vary; but ultimately all, with the rarest exceptions, +vary to a greater or less extent. In a few cases the requisite number of +generations, as well as the successive steps in the progress of variation, +have been recorded, as in the often-quoted instance of the Dahlia.[626] +After several years' culture the Zinnia has only lately (1860) begun to +vary in any great degree. "In the first seven or eight years of high +cultivation the Swan River daisy (_Brachycome iberidifolia_) kept to its +original colour; it then varied into lilac and purple and other minor +shades."[627] Analogous facts have been recorded with the Scotch rose. In +discussing the variability of plants several experienced horticulturists +have spoken to the {262} same general effect. Mr. Salter[628] remarks, +"Every one knows that the chief difficulty is in breaking through the +original form and colour of the species, and every one will be on the +look-out for any natural sport, either from seed or branch; that being once +obtained, however trifling the change may be, the result depends upon +himself." M. de Jonghe, who has had so much success in raising new +varieties of pears and strawberries,[629] remarks with respect to the +former, "There is another principle, namely, that the more a type has +entered into a state of variation, the greater is its tendency to continue +doing so; and the more it has varied from the original type, the more it is +disposed to vary still farther." We have, indeed, already discussed this +latter point when treating of the power which man possesses, through +selection, of continually augmenting in the same direction each +modification; for this power depends on continued variability of the same +general kind. The most celebrated horticulturist in France, namely, +Vilmorin,[630] even maintains that, when any particular variation is +desired, the first step is to get the plant to vary in any manner whatever, +and to go on selecting the most variable individuals, even though they vary +in the wrong direction; for the fixed character of the species being once +broken, the desired variation will sooner or later appear. + +As nearly all our animals were domesticated at an extremely remote epoch, +we cannot, of course, say whether they varied quickly or slowly when first +subjected to new conditions. But Dr. Bachman[631] states that he has seen +turkeys raised from the eggs of the wild species lose their metallic tints +and become spotted with white in the third generation. Mr. Yarrell many +years ago informed me that the wild ducks bred on the ponds in St. James's +Park, which had never been crossed, as it is believed, with domestic ducks, +lost their true plumage after a few generations. An excellent +observer,[632] who has often reared birds from the eggs of the wild duck, +and who took precautions {263} that there should be no crossing with +domestic breeds, has given, as previously stated, full details on the +changes which they gradually undergo. He found that he could not breed +these wild ducks true for more than five or six generations, "as they then +proved so much less beautiful. The white collar round the neck of the +mallard became much broader and more irregular, and white feathers appeared +in the ducklings' wings." They increased also in size of body; their legs +became less fine, and they lost their elegant carriage. Fresh eggs were +then procured from wild birds; but again the same result followed. In these +cases of the duck and turkey we see that animals, like plants, do not +depart from their primitive type until they have been subjected during +several generations to domestication. On the other hand, Mr. Yarrell +informed me that the Australian dingos, bred in the Zoological Gardens, +almost invariably produced in the first generation puppies marked with +white and other colours; but these introduced dingos had probably been +procured from the natives, who keep them in a semi-domesticated state. It +is certainly a remarkable fact that changed conditions should at first +produce, as far as we can see, absolutely no effect; but that they should +subsequently cause the character of the species to change. In the chapter +on pangenesis I shall attempt to throw a little light on this fact. + + * * * * * + +Returning now to the causes which are supposed to induce variability. Some +authors[633] believe that close interbreeding gives this tendency, and +leads to the production of monstrosities. In the seventeenth chapter some +few facts were advanced, showing that monstrosities are, as it appears, +occasionally thus caused; and there can be no doubt that close +interbreeding induces lessened fertility and a weakened constitution; hence +it may lead to variability: but I have not sufficient evidence on this +head. On the other hand, close interbreeding, if not carried to an +injurious extreme, far from causing variability, tends to fix the character +of each breed. + +It was formerly a common belief, still held by some persons, that the +imagination of the mother affects the child in {264} the womb.[634] This +view is evidently not applicable to the lower animals, which lay +unimpregnated eggs, or to plants. Dr. William Hunter, in the last century, +told my father that during many years every woman in a large London +Lying-in Hospital was asked before her confinement whether anything had +specially affected her mind, and the answer was written down; and it so +happened that in no one instance could a coincidence be detected between +the woman's answer and any abnormal structure; but when she knew the nature +of the structure, she frequently suggested some fresh cause. The belief in +the power of the mother's imagination may perhaps have arisen from the +children of a second marriage resembling the previous father, as certainly +sometimes occurs, in accordance with the facts given in the eleventh +chapter. + + * * * * * + +_Crossing as a Cause of Variability._--In an early part of this chapter it +was stated that Pallas[635] and a few other naturalists maintain that +variability is wholly due to crossing. If this means that new characters +never spontaneously appear in our domestic races, but that they are all +directly derived from certain aboriginal species, the doctrine is little +less than absurd; for it implies that animals like Italian greyhounds, +pug-dogs, bull-dogs, pouter and fantail pigeons, &c., were able to exist in +a state of nature. But the doctrine may mean something widely different, +namely, that the crossing of distinct species is the sole cause of the +first appearance of new characters, and that without this aid man could not +have formed his various breeds. As, however, new characters have appeared +in certain cases by bud-variation, we may conclude with certainty that +crossing is not necessary for variability. It is, moreover, almost certain +that the breeds of various animals, such as of the rabbit, pigeon, duck, +&c., and the varieties of several plants, are the modified descendants of a +single wild species. Nevertheless, it is probable that the crossing of two +forms, when one or both have long been domesticated or cultivated, adds to +the variability of the offspring, independently of the commingling of the +characters derived from the two parent-forms; and this implies {265} that +new characters actually arise. But we must not forget the facts advanced in +the thirteenth chapter, which clearly prove that the act of crossing often +leads to the reappearance or reversion of long-lost characters; and in most +cases it would be impossible to distinguish between the reappearance of +ancient characters and the first appearance of new characters. Practically, +whether new or old, they would be new to the breed in which they +reappeared. + + Gaertner declares,[636] and his experience is of the highest value on + such a point, that, when he crossed native plants which had not been + cultivated, he never once saw in the offspring any new character; but + that from the odd manner in which the characters derived from the + parents were combined, they sometimes appeared as if new. When, on the + other hand, he crossed cultivated plants, he admits that new characters + occasionally appeared, but he is strongly inclined to attribute their + appearance to ordinary variability, not in any way to the cross. An + opposite conclusion, however, appears to me the more probable. + According to Koelreuter, hybrids in the genus Mirabilis vary almost + infinitely, and he describes new and singular characters in the form of + the seeds, in the colour of the anthers, in the cotyledons being of + immense size, in new and highly peculiar odours, in the flowers + expanding early in the season, and in their closing at night. With + respect to one lot of these hybrids, he remarks that they presented + characters exactly the reverse of what might have been expected from + their parentage.[637] + + Prof. Lecoq[638] speaks strongly to the same effect in regard to this + same genus, and asserts that many of the hybrids from _Mirabilis + jalapa_ and _multiflora_ might easily be mistaken for distinct species, + and adds that they differed in a greater degree, than the other species + of the genus, from _M. jalapa_. Herbert, also, has described[639] the + offspring from a hybrid Rhododendron as being "as _unlike all others_ + in foliage, as if they had been a separate species." The common + experience of floriculturists proves that the crossing and recrossing + of distinct but allied plants, such as the species of Petunia, + Calceolaria, Fuchsia, Verbena, &c., induces excessive variability; + hence the appearance of quite new characters is probable. M. + Carriere[640] has lately discussed this subject: he states that + _Erythrina cristagalli_ had been multiplied by seed for many years, but + had not yielded any varieties: it was then crossed with the allied _E. + herbacea_, and "the resistance was now overcome, and varieties were + produced with flowers of extremely different size, form, and colour." + + From the general and apparently well-founded belief that the crossing + {266} of distinct species, besides commingling their characters, adds + greatly to their variability, it has probably arisen that some + botanists have gone so far as to maintain[641] that, when a genus + includes only a single species, this when cultivated never varies. The + proposition made so broadly cannot be admitted; but it is probably true + that the variability of cultivated monotypic genera is much less than + that of genera including numerous species, and this quite independently + of the effects of crossing. I have stated in my 'Origin of Species,' + and in a future work shall more fully show, that the species belonging + to small genera generally yield a less number of varieties in a state + of nature than those belonging to large genera. Hence the species of + small genera would, it is probable, produce fewer varieties under + cultivation than the already variable species of larger genera. + + Although we have not at present sufficient evidence that the crossing + of species, which have never been cultivated, leads to the appearance + of new characters, this apparently does occur with species which have + been already rendered in some degree variable through cultivation. + Hence crossing, like any other change in the conditions of life, seems + to be an element, probably a potent one, in causing variability. But we + seldom have the means of distinguishing, as previously remarked, + between the appearance of really new characters and the reappearance of + long-lost characters, evoked through the act of crossing. I will give + an instance of the difficulty in distinguishing such cases. The species + of Datura may be divided into two sections, those having white flowers + with green stems, and those having purple flowers with brown stems: now + Naudin[642] crossed _Datura laevis_ and _ferox_, both of which belong + to the white section, and raised from them 205 hybrids. Of these + hybrids, every one had brown stems and bore purple flowers; so that + they resembled the species of the other section of the genus, and not + their own two parents. Naudin was so much astonished at this fact, that + he was led carefully to observe both parent-species, and he discovered + that the pure seedlings of _D. ferox_, immediately after germination, + had dark purple stems, extending from the young roots up to the + cotyledons, and that this tint remained ever afterwards as a ring round + the base of the stem of the plant when old. Now I have shown in the + thirteenth chapter that the retention or exaggeration of an early + character is so intimately related to reversion, that it evidently + comes under the same principle. Hence probably we ought to look at the + purple flowers and brown stems of these hybrids, not as new characters + due to variability, but as a return to the former state of some ancient + progenitor. + + Independently of the appearance of new characters from crossing, a few + words may be added to what has been said in former chapters on the + unequal combination and transmission of the characters proper to the + two parent-forms. When two species or races are crossed, the offspring + of {267} the first generation are generally uniform, but subsequently + they display an almost infinite diversity of character. He who wishes, + says Koelreuter,[643] to obtain an endless number of varieties from + hybrids should cross and recross them. There is also much variability + when hybrids or mongrels are reduced or absorbed by repeated crosses + with either pure parent-form; and a still higher degree of variability + when three distinct species, and most of all when four species, are + blended together by successive crosses. Beyond this point + Gaertner,[644] on whose authority the foregoing statements are made, + never succeeded in effecting a union; but Max Wichura[645] united six + distinct species of willows into a single hybrid. The sex of the + parent-species affects in an inexplicable manner the degree of + variability of hybrids; for Gaertner[646] repeatedly found that when a + hybrid was used as the father, and either one of the pure + parent-species, or a third species, was used as the mother, the + offspring were more variable than when the same hybrid was used as the + mother, and either pure parent or the same third species as the father: + thus seedlings from _Dianthus barbatus_ crossed by the hybrid _D. + chinensi-barbatus_ were more variable than those raised from this + latter hybrid fertilised by the pure _D. barbatus_. Max Wichura[647] + insists strongly on an analogous result with his hybrid willows. Again + Gaertner[648] asserts that the degree of variability sometimes differs + in hybrids raised from reciprocal crosses between the same two species; + and here the sole difference is, that the one species is first used as + the father and then as the mother. On the whole we see that, + independently of the appearance of new characters, the variability of + successive crossed generations is extremely complex, partly from the + offspring partaking unequally of the characters of the two + parent-forms, and more especially from their unequal tendency to revert + to these same characters or to those of more ancient progenitors. + + * * * * * + +_On the Manner and on the Period of Action of the Causes which induce +Variability._--This is an extremely obscure subject, and we need here only +briefly consider, firstly, whether inherited variations are caused by the +organisation being directly acted on, or indirectly through the +reproductive system; and secondly, at what period of life or growth they +are primarily caused. We shall see in the two following chapters that +various agencies, such as an abundant supply of food, exposure to a +different climate, increased use or disuse of parts, &c., prolonged during +several generations, certainly modify either the whole organisation or +certain organs. This direct action of changed conditions perhaps comes into +play much more frequently than can be proved, and it is at least clear that +in all cases of {268} bud-variation the action cannot have been through the +reproductive system. + + With respect to the part which the reproductive system takes in causing + variability, we have seen in the eighteenth chapter that even slight + changes in the conditions of life have a remarkable power in causing a + greater or less degree of sterility. Hence it seems not improbable that + being generated though a system so easily affected should themselves be + affected, or should fail to inherit, or inherit in excess, characters + proper to their parents. We know that certain groups of organic beings, + but with exceptions in each group, have their reproductive systems much + more easily affected by changed conditions than other groups; for + instance, carnivorous birds more readily than carnivorous mammals, and + parrots more readily than pigeons; and this fact harmonizes with the + apparently capricious manner and degree in which various groups of + animals and plants vary under domestication. + + Koelreuter[649] was struck with the parallelism between the excessive + variability of hybrids when crossed and recrossed in various + ways,--these hybrids having their reproductive powers more or less + affected,--and the variability of anciently cultivated plants. Max + Wichura[650] has gone one step farther, and shows that with many of our + highly cultivated plants, such as the hyacinth, tulip, auricula, + snapdragon, potato, cabbage, &c., which there is no reason to believe + have been hybridized, the anthers contain many irregular pollen-grains, + in the same state as in hybrids. He finds also in certain wild forms, + the same coincidence between the state of the pollen and a high degree + of variability, as in many species of Rubus; but in _R. caesius_ and + _idaeus_, which are not highly variable species, the pollen is sound. + It is also notorious that many cultivated plants, such as the banana, + pine-apple, breadfruit, and others previously mentioned, have their + reproductive organs so seriously affected as to be generally quite + sterile; and when they do yield seed, the seedlings, judging from the + large number of cultivated races which exist, must be variable in an + extreme degree. These facts indicate that there is some relation + between the state of the reproductive organs and a tendency to + variability; but we must not conclude that the relation is strict. + Although many of our highly cultivated plants may have their pollen in + a deteriorated condition, yet, as we have previously seen, they yield + more seed, and our anciently domesticated animals are more prolific, + than the corresponding species in a state of nature. The peacock is + almost the only bird which is believed to be less fertile under + domestication than in its native state, and it has varied in a + remarkably small degree. From these considerations it would seem that + changes in the conditions of life lead either to sterility or to + variability, or to both; and not that sterility induces variability. On + the whole it is probable that any cause affecting the organs of + reproduction would likewise affect their product,--that is, the + offspring thus generated. + + {269} + + The period of life at which the causes that induce variability act, is + another obscure subject, which has been discussed by various + authors.[651] In some of the cases, to be given in the following + chapter, of modifications from the direct action of changed conditions, + which are inherited, there can be no doubt that the causes have acted + on the mature or nearly mature animal. On the other hand, + monstrosities, which cannot be distinctly separated from lesser + variations, are often caused by the embryo being injured whilst in the + mother's womb or in the egg. Thus I. Geoffroy St. Hilaire[652] asserts + that poor women who work hard during their pregnancy, and the mothers + of illegitimate children troubled in their minds and forced to conceal + their state, are far more liable to give birth to monsters than women + in easy circumstances. The eggs of the fowl when placed upright or + otherwise treated unnaturally frequently produce monstrous chickens. It + would, however, appear that complex monstrosities are induced more + frequently during a rather late than during a very early period of + embryonic life; but this may partly result from some one part, which + has been injured during an early period, affecting by its abnormal + growth other parts subsequently developed; and this would be less + likely to occur with parts injured at a later period.[653] When any + part or organ becomes monstrous through abortion, a rudiment is + generally left, and this likewise indicates that its development had + already commenced. + + Insects sometimes have their antennae or legs in a monstrous condition, + and yet the larvae from which they are metamorphosed do not possess + either antennae or legs; and in those cases, as Quatrefages[654] + believes, we are enabled to see the precise period at which the normal + progress of development has been troubled. But the nature of the food + given to a caterpillar sometimes affects the colours of the moth, + without the caterpillar itself being affected; therefore it seems + possible that other characters in the mature insect might be indirectly + modified through the larvae. There is no reason to suppose that organs + which have been rendered monstrous have always been acted on during + their development; the cause may have acted on the organisation at a + much earlier stage. It is even probable that either the male or female + sexual elements, or both, before their union, may be affected in such a + manner as to lead to modifications in organs developed at a late period + of life; in nearly the same manner as a child may inherit from his + father a disease which does not appear until old age. + + In accordance with the facts above given, which prove that in many + cases a close relation exists between variability and the sterility + following from changed conditions, we may conclude that the exciting + cause often acts at the earliest possible period, namely, on the sexual + elements, before impregnation has taken place. That an affection of the + female sexual element may induce variability we may likewise infer as + probable from the occurrence of bud-variations; for a bud seems to be + the analogue of an ovule. But the male element is apparently much + oftener affected by changed {270} conditions, at least in a visible + manner, than the female element or ovule; and we know from Gaertner's + and Wichura's statements that a hybrid used as the father and crossed + with a pure species gives a greater degree of variability to the + offspring, than does the same hybrid when used as the mother. Lastly, + it is certain that variability may be transmitted through either sexual + element, whether or not originally excited in them, for Koelreuter and + Gaertner[655] found that when two species were crossed, if either one + was variable, the offspring were rendered variable. + + * * * * * + +_Summary._--From the facts given in this chapter, we may conclude that the +variability of organic beings under domestication, although so general, is +not an inevitable contingent on growth and reproduction, but results from +the conditions to which the parents have been exposed. Changes of any kind +in the conditions of life, even extremely slight changes, often suffice to +cause variability. Excess of nutriment is perhaps the most efficient single +exciting cause. Animals and plants continue to be variable for an immense +period after their first domestication; but the conditions to which they +are exposed never long remain quite constant. In the course of time they +can be habituated to certain changes, so as to become less variable; and it +is possible that when first domesticated they may have been even more +variable than at present. There is good evidence that the power of changed +conditions accumulates; so that two, three, or more generations must be +exposed to new conditions before any effect is visible. The crossing of +distinct forms, which have already become variable, increases in the +offspring the tendency to further variability, by the unequal commingling +of the characters of the two parents, by the reappearance of long-lost +characters, and by the appearance of absolutely new characters. Some +variations are induced by the direct action of the surrounding conditions +on the whole organisation, or on certain parts alone, and other variations +are induced indirectly through the reproductive system being affected in +the same manner as is so common with organic beings when removed from their +natural conditions. The causes which induce variability act on the mature +organism, on the embryo, and, as we have good reason to believe, on both +sexual elements before impregnation has been effected. + + * * * * * + + +{271} + +CHAPTER XXIII. + +DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS OF LIFE. + + SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE ACTION OF CHANGED + CONDITIONS IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND IN THE STATE OF + THE TISSUES--LOCAL DISEASES--CONSPICUOUS MODIFICATIONS FROM CHANGED + CLIMATE OR FOOD, ETC.--PLUMAGE OF BIRDS AFFECTED BY PECULIAR NUTRIMENT, + AND BY THE INOCULATION OF POISON--LAND-SHELLS--MODIFICATIONS OF ORGANIC + BEINGS IN A STATE OF NATURE THROUGH THE DEFINITE ACTION OF EXTERNAL + CONDITIONS--COMPARISON OF AMERICAN AND EUROPEAN TREES--GALLS--EFFECTS + OF PARASITIC FUNGI--CONSIDERATIONS OPPOSED TO THE BELIEF IN THE POTENT + INFLUENCE OF CHANGED EXTERNAL CONDITIONS--PARALLEL SERIES OF + VARIETIES--AMOUNT OF VARIATION DOES NOT CORRESPOND WITH THE DEGREE OF + CHANGE IN THE CONDITIONS--BUD-VARIATION--MONSTROSITIES PRODUCED BY + UNNATURAL TREATMENT--SUMMARY. + +If we ask ourselves why this or that character has been modified under +domestication, we are, in most cases lost in utter darkness. Many +naturalists, especially of the French school, attribute every modification +to the "monde ambiant," that is, to changed climate, with all its +diversities of heat and cold, dampness and dryness, light and electricity, +to the nature of the soil, and to varied kinds and amount of food. By the +term definite action, as used in this chapter, I mean an action of such a +nature that, when many individuals of the same variety are exposed during +several generations to any change in their physical conditions of life, +all, or nearly all the individuals, are modified in the same manner. A new +sub-variety would thus be produced without the aid of selection. + +I do not include under the term of definite action the effects of habit or +of the increased use and disuse of various organs. Modifications of this +nature, no doubt, are definitely caused by the conditions to which the +beings are subjected; but they depend much less on the nature of the +conditions than on the laws of growth; hence they are included under a +distinct head in the {272} following chapter. We know, however, far too +little of the causes and laws of variation to make a sound classification. +The direct action of the conditions of life, whether leading to definite or +indefinite results, is a totally distinct consideration from the effects of +natural selection; for natural selection depends on the survival under +various and complex circumstances of the best-fitted individuals, but has +no relation whatever to the primary cause of any modification of structure. + +I will first give in detail all the facts which I have been able to +collect, rendering it probable that climate, food, &c., have acted so +definitely and powerfully on the organisation of our domesticated +productions, that they have sufficed to form new sub-varieties or races, +without the aid of selection by man or of natural selection. I will then +give the facts and considerations opposed to this conclusion, and finally +we will weigh, as fairly as we can, the evidence on both sides. + +When we reflect that distinct races of almost all our domesticated animals +exist in each kingdom of Europe, and formerly even in each district of +England, we are at first strongly inclined to attribute their origin to the +definite action of the physical conditions of each country; and this has +been the conclusion of many authors. But we should bear in mind that man +annually has to choose which animals shall be preserved for breeding, and +which shall be slaughtered. We have also seen that both methodical and +unconscious selection were formerly practised, and are now occasionally +practised by the most barbarous races, to a much greater extent than might +have been anticipated. Hence it is very difficult to judge how far the +difference in conditions between, for instance, the several districts in +England, could have sufficed without the aid of selection to modify the +breeds which have been reared in each. It may be argued that, as numerous +wild animals and plants have ranged during many ages throughout Great +Britain, and still retain the same character, the difference in conditions +between the several districts could not have modified in so marked a manner +the various native races of cattle, sheep, pigs, and horses. The same +difficulty of distinguishing between selection and the definite effects of +the conditions of life, is encountered in a still higher degree when we +compare closely allied natural {273} forms, inhabiting two countries, such +as North America and Europe, which do not differ greatly in climate, nature +of soil, &c., for in this case natural selection will inevitably and +rigorously have acted during a long succession of ages. + + From the importance of the difficulty just alluded to, it will be + advisable to give as large a body of facts as possible, showing that + extremely slight differences in treatment, either in different parts of + the same country, or during different seasons, certainly cause an + appreciable effect, at least on varieties which are already in an + unstable condition. Ornamental flowers are good for this purpose, as + they are highly variable, and are carefully observed. All + floriculturists are unanimous that certain varieties are affected by + very slight differences in the nature of the artificial compost in + which they are grown, and by the natural soil of the district, and by + the season. Thus, a skilful judge, in writing on Carnations and + Picotees,[656] asks "where can Admiral Curzon be seen possessing the + colour, size, and strength which it has in Derbyshire? Where can + Flora's Garland be found equal to those at Slough? Where do + high-coloured flowers revel better than at Woolwich and Birmingham? Yet + in no two of these districts do the same varieties attain an equal + degree of excellence, although each may be receiving the attention of + the most skilful cultivators." The same writer then recommends every + cultivator to keep five different kinds of soil and manure, "and to + endeavour to suit the respective appetites of the plants you are + dealing with, for without such attention all hope of general success + will be vain." So it is with the Dahlia:[657] the Lady Cooper rarely + succeeds near London, but does admirably in other districts; the + reverse holds good with other varieties; and again, there are others + which succeed equally well in various situations. A skilful + gardener[658] states that he procured cuttings of an old and well-known + variety (pulchella) of Verbena, which from having been propagated in a + different situation presented a slightly different shade of colour; the + two varieties were afterwards multiplied by cuttings, being carefully + kept distinct; but in the second year they could hardly be + distinguished, and in the third year no one could distinguish them. + + The nature of the season has an especial influence on certain varieties + of the Dahlia: in 1841 two varieties were pre-eminently good, and the + next year these same two were pre-eminently bad. A famous amateur[659] + asserts that in 1861 many varieties of the Rose came so untrue in + character, "that it was hardly possible to recognise them, and the + thought was not seldom entertained that the grower had lost his tally." + The same amateur[660] states that in 1862 two-thirds of his Auriculas + produced central trusses of flowers, and these are remarkable from not + keeping true; {274} and he adds that in some seasons certain varieties + of this plant all prove good, and the next season all prove bad; whilst + exactly the reverse happens with other varieties. In 1845 the editor of + the 'Gardener's Chronicle'[661] remarked how singular it was that this + year many Calceolarias tended to assume a tubular form. With + Heartsease[662] the blotched sorts do not acquire their proper + character until hot weather sets in; whilst other varieties lose their + beautiful marks as soon as this occurs. + + Analogous facts have been observed with leaves: Mr. Beaton asserts[663] + that he raised at Shrubland, during six years, twenty thousand + seedlings from the Punch Pelargonium, and not one had variegated + leaves; but at Surbiton, in Surrey, one-third, or even a greater + proportion, of the seedlings from this same variety were more or less + variegated. The soil of another district in Surrey has a strong + tendency to cause variegation, as appears from information given me by + Sir F. Pollock. Verlot[664] states that the variegated strawberry + retains its character as long as grown in a dryish soil, but soon loses + it when planted in fresh and humid soil. Mr. Salter, who is well known + for his success in cultivating variegated plants, informs me that rows + of strawberries were planted in his garden in 1859, in the usual way; + and at various distances in one row, several plants simultaneously + became variegated, and what made the case more extraordinary, all were + variegated in precisely the same manner. These plants were removed, but + during the three succeeding years other plants in the same row became + variegated, and in no instance were the plants in any adjoining row + affected. + + The chemical qualities, odours, and tissues of plants are often + modified by a change which seems to us slight. The Hemlock is said not + to yield conicine in Scotland. The root of the _Aconitum napellus_ + becomes innocuous in frigid climates. The medicinal properties of the + Digitalis are easily affected by culture. The Rhubarb flourishes in + England, but does not produce the medicinal substance which makes the + plant so valuable in Chinese Tartary. As the _Pistacia lentiscus_ grows + abundantly in the South of France, the climate must suit it, but it + yields no mastic. The _Laurus sassafras_ in Europe loses the odour + proper to it in North America.[665] Many similar facts could be given, + and they are remarkable because it might have been thought that + definite chemical compounds would have been little liable to change + either in quality or quantity. + + The wood of the American Locust-tree (_Robinia_) when grown in England + is nearly worthless, as is that of the Oak-tree when grown at the Cape + of Good Hope.[666] Hemp and flax, as I hear from Dr. Falconer, flourish + and yield plenty of seed on the plains of India, but their fibres are + brittle {275} and useless. Hemp, on the other hand, fails to produce in + England that resinous matter which is so largely used in India as an + intoxicating drug. + + The fruit of the Melon is greatly influenced by slight differences in + culture and climate. Hence it is generally a better plan, according to + Naudin, to improve an old kind than to introduce a new one into any + locality. The seed of the Persian Melon produces near Paris fruit + inferior to the poorest market kinds, but at Bordeaux yields delicious + fruit.[667] Seed is annually brought from Thibet to Kashmir,[668] and + produces fruit weighing from four to ten pounds, but plants raised from + seed saved in Kashmir next year give fruit weighing only from two to + three pounds. It is well known that American varieties of the Apple + produce in their native land magnificent and brightly-coloured fruit, + but in England of poor quality and a dull colour. In Hungary there are + many varieties of the Kidney-bean, remarkable for the beauty of their + seeds, but the Rev. M. J. Berkeley[669] found that their beauty could + hardly ever be preserved in England, and in some cases the colour was + greatly changed. We have seen in the ninth chapter, with respect to + wheat, what a remarkable effect transportal from the North to the South + of France, and reversely, produced on the weight of the grain. + +When man can perceive no change in plants or animals which have been +exposed to a new climate or to different treatment, insects can sometimes +perceive a marked change. The same species of cactus has been carried to +India from Canton, Manilla, Mauritius, and from the hot-houses of Kew, and +there is likewise a so-called native kind, formerly introduced from South +America; all these plants are alike in appearance, but the cochineal insect +flourishes only on the native kind, on which it thrives prodigiously.[670] +Humboldt remarks[671] that white men "born in the torrid zone walk barefoot +with impunity in the same apartment where a European, recently landed, is +exposed to the attacks of the _Pulex penetrans_." This insect, the too +well-known chigoe, must therefore be able to distinguish what the most +delicate chemical analysis fails to distinguish, namely, a difference +between the blood or tissues of a European and those of a white man born in +the country. But the discernment of the chigoe is not so surprising as it +at first appears; for {276} according to Liebig[672] the blood of men with +different complexions, though inhabiting the same country, emits a +different odour. + + Diseases peculiar to certain localities, heights, or climates, may be + here briefly noticed, as showing the influence of external + circumstances on the human body. Diseases confined to certain races of + man do not concern us, for the constitution of the race may play the + more important part, and this may have been determined by unknown + causes. The Plica Polonica stands, in this respect, in a nearly + intermediate position; for it rarely affects Germans, who inhabit the + neighbourhood of the Vistula, where so many Poles are grievously + affected; and on the other hand, it does not affect Russians, who are + said to belong to the same original stock with the Poles.[673] The + elevation of a district often governs the appearance of diseases; in + Mexico the yellow fever does not extend above 924 metres; and in Peru, + people are affected with the _verugas_ only between 600 and 1600 metres + above the sea; many other such cases could be given. A peculiar + cutaneous complaint, called the _Bouton d'Alep_, affects in Aleppo and + some neighbouring districts almost every native infant, and some few + strangers; and it seems fairly well established that this singular + complaint depends on drinking certain waters. In the healthy little + island of St. Helena the scarlet-fever is dreaded like the Plague; + analogous facts have been observed in Chili and Mexico.[674] Even in + the different departments of France it is found that the various + infirmities which render the conscript unfit for serving in the army, + prevail with remarkable inequality, revealing, as Boudin observes, that + many of them are endemic, which otherwise would never have been + suspected.[675] Any one who will study the distribution of disease will + be struck with surprise at what slight differences in the surrounding + circumstances govern the nature and severity of the complaints by which + man is at least temporarily affected. + +The modifications as yet referred to have been extremely slight, and in +most cases have been caused, as far as we can judge, by equally slight +changes in the conditions. But can it be safely maintained that such +changed conditions, if acting during a long series of generations, would +not produce a marked effect? It is commonly believed that the people of the +United States differ in appearance from the parent Anglo-Saxon race; and +selection cannot have come into action within so short a period. A good +observer[676] states that a general absence of fat, {277} a thin and +elongated neck, stiff and lank hair, are the chief characteristics. The +change in the nature of the hair is supposed to be caused by the dryness of +the atmosphere. If immigration into the United States were now stopped, who +can say that the character of the whole people would not be greatly +modified in the course of two or three thousand years? + + The direct and definite action of changed conditions, in + contradistinction to the accumulation of indefinite variations, seems + to me so important that I will give a large additional body of + miscellaneous facts. With plants, a considerable change of climate + sometimes produces a conspicuous result. I have given in detail in the + ninth chapter the most remarkable case known to me, namely, that in + Germany several varieties of maize brought from the hotter parts of + America were transformed in the course of only two or three + generations. Dr. Falconer informs me that he has seen the English + Ribston-pippin apple, a Himalayan oak, Prunus and Pyrus, all assume in + the hotter parts of India a fastigate or pyramidal habit; and this fact + is the more interesting, as a Chinese tropical species of Pyrus + naturally has this habit of growth. Although in these cases the changed + manner of growth seems to have been directly caused by the great heat, + we know that many fastigate trees have originated in their temperate + homes. In the Botanic Gardens of Ceylon the apple-tree[677] "sends out + numerous runners under ground, which continually rise into small stems, + and form a growth around the parent-tree." The varieties of the cabbage + which produce heads in Europe fail to do so in certain tropical + countries.[678] The _Rhododendron ciliatum_ produced at Kew flowers so + much larger and paler-coloured than those which it bears on its native + Himalayan mountain, that Dr. Hooker[679] would hardly have recognised + the species by the flowers alone. Many similar facts with respect to + the colour and size of flowers could be given. + + The experiments of Vilmorin and Buckman on carrots and parsnips prove + that abundant nutriment produces a definite and inheritable effect on + the so-called roots, with scarcely any change in other parts of the + plant. Alum directly influences the colour of the flowers of the + Hydrangea.[680] Dryness seems generally to favour the hairyness or + villosity of plants. Gaertner found that hybrid Verbascums became + extremely woolly when grown in pots. Mr. Masters, on the other hand, + states that the _Opuntia leucotricha_ "is well clothed with beautiful + white hairs when grown in a damp heat; but in a dry heat exhibits none + of this peculiarity."[681] Slight variations of many kinds, not worth + specifying in detail, are retained only as {278} long as plants are + grown in certain soils, of which Sageret[682] gives from his own + experience some instances. Odart, who insists strongly on the + permanence of the varieties of the grape, admits[683] that some + varieties, when grown under a different climate or treated differently, + vary in an extremely slight degree, as in the tint of the fruit and in + the period of ripening. Some authors have denied that grafting causes + even the slightest difference in the scion; but there is sufficient + evidence that the fruit is sometimes slightly affected in size and + flavour, the leaves in duration, and the flowers in appearance.[684] + + With animals there can be no doubt, from the facts given in the first + chapter, that European dogs deteriorate in India, not only in their + instincts but in structure; but the changes which they undergo are of + such a nature, that they may be partly due to reversion to a primitive + form, as in the case of feral animals. In parts of India the turkey + becomes reduced in size, "with the pendulous appendage over the beak + enormously developed."[685] We have seen how soon the wild duck, when + domesticated, loses its true character, from the effects of abundant or + changed food, or from taking little exercise. From the direct action of + a humid climate and poor pasture the horse rapidly decreases in size in + the Falkland Islands. From information which I have received, this + seems likewise to be the case to a certain extent with sheep in + Australia. + + Climate definitely influences the hairy covering of animals; in the + West Indies a great change is produced in the fleece of sheep, in about + three generations. Dr. Falconer states[686] that the Thibet mastiff and + goat, when brought down from the Himalaya to Kashmir, lose their fine + wool. At Angora not only goats, but shepherd-dogs and cats, have fine + fleecy hair, and Mr. Ainsworth[687] attributes the thickness of the + fleece to the severe winters, and its silky lustre to the hot summers. + Burnes states positively[688] that the Karakool sheep lose their + peculiar black curled fleeces when removed into any other country. Even + within the limits of England, I have been assured that with two breeds + of sheep the wool was slightly changed by the flocks being pastured in + different localities.[689] It has been asserted on good authority[690] + that horses kept during several years in the deep coal-mines of Belgium + become covered with velvety hair, almost like that on the mole. These + cases probably stand in close relation to the natural change of coat in + winter and summer. Naked varieties of several domestic animals have + occasionally appeared; but there is no reason to {279} believe that + this is in any way related to the nature of the climate to which they + have been exposed.[691] + + It appears at first sight probable that the increased size, the + tendency to fatten, the early maturity and altered forms of our + improved cattle, sheep, and pigs, have directly resulted from their + abundant supply of food. This is the opinion of many competent judges, + and probably is to a great extent true. But as far as form is + concerned, we must not overlook the equal or more potent influence of + lessened use on the limbs and lungs. We see, moreover, as far as size + is concerned, that selection is apparently a more powerful agent than a + large supply of food, for we can thus only account for the existence, + as remarked to me by Mr. Blyth, of the largest and smallest breeds of + sheep in the same country, of Cochin-China fowls and Bantams, of small + Tumbler and large Runt pigeons, all kept together and supplied with + abundant nourishment. Nevertheless there can be little doubt that our + domesticated animals have been modified, independently of the increased + or lessened use of parts, by the conditions to which they have been + subjected, without the aid of selection. For instance, Prof. + Ruetimeyer[692] shows that the bones of all domesticated quadrupeds can + be distinguished from those of wild animals by the state of their + surface and general appearance. It is scarcely possible to read + Nathusius's excellent 'Vorstudien,'[693] and doubt that, with the + highly improved races of the pig, abundant food has produced a + conspicuous effect on the general form of the body, on the breadth of + the head and face, and even on the teeth. Nathusius rests much on the + case of a purely bred Berkshire pig, which when two months old became + diseased in its digestive organs, and was preserved for observation + until nineteen months old; at this age it had lost several + characteristic features of the breed, and had acquired a long, narrow + head, of large size relatively to its small body, and elongated legs. + But in this case and in some others we ought not to assume that, + because certain characters are lost, perhaps through reversion, under + one course of treatment, therefore that they had been at first directly + produced by an opposite course. + + In the case of the rabbit, which has become feral on the island of + Porto Santo, we are at first strongly tempted to attribute the whole + change--the greatly reduced size, the altered tints of the fur, and the + loss of certain characteristic marks--to the definite action of the new + conditions to which it has been exposed. But in all such cases we have + to consider in addition the tendency to reversion to progenitors more + or less remote, and the natural selection of the finest shades of + difference. + + The nature of the food sometimes either definitely induces certain + peculiarities, or stands in some close relation with them. Pallas long + ago asserted that the fat-tailed sheep of Siberia degenerated and lost + their enormous tails when removed from certain saline pastures; and + recently {280} Erman[694] states that this occurs with the Kirgisian + sheep when brought to Orenburgh. + + It is well known that hemp-seed causes bullfinches and certain other + birds to become black. Mr. Wallace has communicated to me some much + more remarkable facts of the same nature. The natives of the Amazonian + region feed the common green parrot (_Chrysotis festiva_, Linn.) with + the fat of large Siluroid fishes, and the birds thus treated become + beautifully variegated with red and yellow feathers. In the Malayan + archipelago, the natives of Gilolo alter in an analogous manner the + colours of another parrot, namely, the _Lorius garrulus_, Linn., and + thus produce the _Lori rajah_ or King-Lory. These parrots in the Malay + Islands and South America, when fed by the natives on natural vegetable + food, such as rice and plantains, retain their proper colours. Mr. + Wallace has, also, recorded[695] a still more singular fact. "The + Indians (of S. America) have a curious art by which they change the + colours of the feathers of many birds. They pluck out those from the + part they wish to paint, and inoculate the fresh wound with the milky + secretion from the skin of a small toad. The feathers grow of a + brilliant yellow colour, and on being plucked out, it is said, grow + again of the same colour without any fresh operation." + + Bechstein[696] does not entertain any doubt that seclusion from light + affects, at least temporarily, the colours of cage-birds. + + It is well known that the shells of land-mollusca are affected by the + abundance of lime in different districts. Isidore Geoffroy St. + Hilaire[697] gives the case of _Helix lactea_, which has recently been + carried from Spain to the South of France and to the Rio Plata, and in + both these countries now presents a distinct appearance, but whether + this has resulted from food or climate is not known. With respect to + the common oyster, Mr. F. Buckland informs me that he can generally + distinguish the shells from different districts; young oysters brought + from Wales and laid down in beds where "_natives_" are indigenous, in + the short space of two months begin to assume the "native" character. + M. Costa[698] has recorded a much more remarkable case of the same + nature, namely, that young shells taken from the shores of England and + placed in the Mediterranean, at once altered their manner of growth and + formed prominent diverging rays, like those on the shells of the proper + Mediterranean oyster. The same individual shell, showing both forms of + growth, was exhibited before a society in Paris. Lastly, it is well + known that caterpillars fed on different food sometimes either + themselves acquire a different colour or produce moths different in + colour.[699] + + {281} + + It would be travelling beyond my proper limits here to discuss how far + organic beings in a state of nature are definitely modified by changed + conditions. In my 'Origin of Species' I have given a brief abstract of + the facts bearing on this point, and have shown the influence of light + on the colours of birds, and of residence near the sea on the lurid + tints of insects, and on the succulency of plants. Mr. Herbert + Spencer[700] has recently discussed with much ability this whole + subject on broad and general grounds. He argues, for instance, that + with all animals the external and internal tissues are differently + acted on by the surrounding conditions, and they invariably differ in + intimate structure. So again the upper and lower surfaces of true + leaves, as well as of stems and petioles, when these assume the + function and occupy the position of leaves, are differently + circumstanced with respect to light, &c., and apparently in consequence + differ in structure. But, as Mr. Herbert Spencer admits, it is most + difficult in all such cases to distinguish between the effects of the + definite action of physical conditions and the accumulation through + natural selection of inherited variations which are serviceable to the + organism, and which have arisen independently of the definite action of + these conditions. + +Although we are not here concerned with organic beings in a state of +nature, yet I may call attention to one case. Mr. Meehan,[701] in a +remarkable paper, compares twenty-nine kinds of American trees, belonging +to various orders, with their nearest European allies, all grown in close +proximity in the same garden and under as nearly as possible the same +conditions. In the American species Mr. Meehan finds, with the rarest +exceptions, that the leaves fall earlier in the season, and assume before +falling a brighter tint; that they are less deeply toothed or serrated; +that the buds are smaller; that the trees are more diffuse in growth and +have fewer branchlets; and, lastly, that the seeds are smaller--all in +comparison with the corresponding European species. Now, considering that +these trees belong to distinct orders, it is out of the question that the +peculiarities just specified should have been inherited in the one +continent from one progenitor, and in the other from another progenitor; +and considering that the trees inhabit widely different stations, these +peculiarities can hardly be supposed to be of any special {282} service to +the two series in the Old and New Worlds; therefore these peculiarities +cannot have been naturally selected. Hence we are led to infer that they +have been definitely caused by the long-continued action of the different +climate of the two continents on the trees. + +_Galls._--Another class of facts, not relating to cultivated plants, +deserves attention. I allude to the production of galls. Every one knows +the curious, bright-red, hairy productions on the wild rose-tree, and the +various different galls produced by the oak. Some of the latter resemble +fruit, with one face as rosy as the rosiest apple. These bright colours can +be of no service either to the gall-forming insect or to the tree, and +probably are the direct result of the action of the light, in the same +manner as the apples of Nova Scotia or Canada are brighter coloured than +English apples. The strongest upholder of the doctrine that organic beings +are created beautiful to please mankind would not, I presume, extend this +view to galls. According to Osten Sacken's latest revision, no less than +fifty-eight kinds of galls are produced on the several species of oak, by +Cynips with its sub-genera; and Mr. B. D. Walsh[702] states that he can add +many others to the list. One American species of willow, the _Salix +humilis_, bears ten distinct kinds of galls. The leaves which spring from +the galls of various English willows differ completely in shape from the +natural leaves. The young shoots of junipers and firs, when punctured by +certain insects, yield monstrous growths like flowers and cones; and the +flowers of some plants become from the same cause wholly changed in +appearance. Galls are produced in every quarter of the world; of several +sent to me by Mr. Thwaites from Ceylon, some were as symmetrical as a +composite flower when in bud, others smooth and spherical like a berry; +some protected by long spines, others clothed with yellow wool formed of +long cellular hairs, others with regularly tufted hairs. In some galls the +internal structure is simple, but in others it is highly complex; thus M. +Lucaze-Duthiers[703] has figured in the common ink-gall no less than seven +concentric layers, composed of distinct tissue, {283} namely, the +epidermic, sub-epidermic, spongy, intermediate, and the hard protective +layer formed of curiously thickened woody cells, and, lastly, the central +mass abounding with starch-granules on which the larvae feed. + +Galls are produced by insects of various orders, but the greater number by +species of Cynips. It is impossible to read M. Lucaze-Duthier's discussion +and doubt that the poisonous secretion of the insect causes the growth of +the gall, and every one knows how virulent is the poison secreted by wasps +and bees, which belong to the same order with Cynips. Galls grow with +extraordinary rapidity, and it is said that they attain their full size in +a few days;[704] it is certain that they are almost completely developed +before the larvae are hatched. Considering that many gall-insects are +extremely small, the drop of secreted poison must be excessively minute; it +probably acts on one or two cells alone, which, being abnormally +stimulated, rapidly increase by a process of self-division. Galls, as Mr. +Walsh[705] remarks, afford good, constant, and definite characters, each +kind keeping as true to form as does any independent organic being. This +fact becomes still more remarkable when we hear that, for instance, seven +out of the ten different kinds of galls produced on _Salix humilis_ are +formed by gall-gnats (_Cecidomyidae_) which, "though essentially distinct +species, yet resemble one another so closely that in almost all cases it is +difficult, and in some cases impossible, to distinguish the full-grown +insects one from the other."[706] For in accordance with a wide-spread +analogy we may safely infer that the poison secreted by insects so closely +allied would not differ much in nature; yet this slight difference is +sufficient to induce widely different results. In some few cases the same +species of gall-gnat produces on distinct species of willows galls which +cannot be distinguished; the _Cynips fecundatrix_, also, has been known to +produce on the Turkish oak, to which it is not properly attached, exactly +the same kind of gall as on the European oak.[707] These latter facts +apparently prove that the nature of the poison is a much more powerful +{284} agent in determining the form of the gall than the specific character +of the tree which is acted on. + +As the poisonous secretion of insects belonging to various orders has the +special power of affecting the growth of various plants;--as a slight +difference in the nature of the poison suffices to produce widely different +results;--and lastly, as we know that the chemical compounds secreted by +plants are eminently liable to be modified by changed conditions of life, +we may believe it possible that various parts of a plant might be modified +through the agency of its own altered secretions. Compare, for instance, +the mossy and viscid calyx of a moss-rose, which suddenly appears through +bud-variation on a Provence-rose, with the gall of red moss growing from +the inoculated leaf of a wild rose, with each filament symmetrically +branched like a microscopical spruce-fir, bearing a glandular tip and +secreting odoriferous gummy matter.[708] Or compare, on the one hand, the +fruit of the peach, with its hairy skin, fleshy covering, hard shell and +kernel, and on the other hand one of the more complex galls with its +epidermic, spongy, and woody layers, surrounding tissue loaded with starch +granules. These normal and abnormal structures manifestly present a certain +degree of resemblance. Or, again, reflect on the cases above given of +parrots which have had their plumage brightly decorated through some change +in their blood, caused by having been fed on certain fishes, or locally +inoculated with the poison of a toad. I am far from wishing to maintain +that the moss-rose or the hard shell of the peach-stone or the bright +colours of birds are actually due to any chemical change in the sap or +blood; but these cases of galls and of parrots are excellently adapted to +show us how powerfully and singularly external agencies may affect +structure. With such facts before us, we need feel no surprise at the +appearance of any modification in any organic being. + + I may, also, here allude to the remarkable effects which parasitic + fungi sometimes produce on plants. Reissek[709] has described a + Thesium, affected by an Oecidium, which was greatly modified, and + assumed some of the {285} characteristic features of certain allied + species, or even genera. Suppose, says Reissek, "the condition + originally caused by the fungus to become constant in the course of + time, the plant would, if found growing wild, be considered as a + distinct species or even as belonging to a new genus." I quote this + remark to show how profoundly, yet in how natural a manner, this plant + must have been modified by the parasitic fungus. + +_Facts and Considerations opposed to the belief that the Conditions of Life +act in a potent manner in causing definite Modifications of Structure._ + +I have alluded to the slight differences in species when naturally living +in distinct countries under different conditions; and such differences we +feel at first inclined, probably to a limited extent with justice, to +attribute to the definite action of the surrounding conditions. But it must +be borne in mind that there are a far greater number of animals and plants +which range widely and have been exposed to great diversities of +conditions, yet remain nearly uniform in character. Some authors, as +previously remarked, account for the varieties of our culinary and +agricultural plants by the definite action of the conditions to which they +have been exposed in the different parts of Great Britain; but there are +about 200 plants[710] which are found in every single English county; these +plants must have been exposed for an immense period to considerable +differences of climate and soil, yet do not differ. So, again, some birds, +insects, other animals, and plants range over large portions of the world, +yet retain the same character. + + Notwithstanding the facts previously given on the occurrence of highly + peculiar local diseases and on the strange modifications of structure + in plants caused by the inoculated poison of insects, and other + analogous cases; still there are a multitude of variations--such as the + modified skull of the niata ox and bulldog, the long horns of Caffre + cattle, the conjoined toes of the solid-hoofed swine, the immense crest + and protuberant skull of Polish fowls, the crop of the pouter-pigeon, + and a host of other such cases--which we can hardly attribute to the + definite action, in the sense before specified, of the external + conditions of life. No doubt in every case there must have been some + exciting cause; but as we see innumerable individuals exposed to nearly + the same conditions, and one alone is affected, we may conclude that + the constitution of the individual is of far higher {286} importance + than the conditions to which it has been exposed. It seems, indeed, to + be a general rule that conspicuous variations occur rarely, and in one + individual alone out of many thousands, though all may have been + exposed, as far as we can judge, to nearly the same conditions. As the + most strongly marked variations graduate insensibly into the most + trifling, we are led by the same train of thought to attribute each + slight variation much more to innate differences of constitution, + however caused, than to the definite action of the surrounding + conditions. + + We are led to the same conclusion by considering the cases, formerly + alluded to, of fowls and pigeons, which have varied and will no doubt + go on varying in directly opposite ways, though kept during many + generations under nearly the same conditions. Some, for instance, are + born with their beaks, wings, tails, legs, &c., a little longer, and + others with these same parts a little shorter. By the long-continued + selection of such slight individual differences, which occur in birds + kept in the same aviary, widely different races could certainly be + formed; and long-continued selection, important as is the result, does + nothing but preserve the variations which appear to us to arise + spontaneously. + + In these cases we see that domesticated animals vary in an indefinite + number of particulars, though treated as uniformly as is possible. On + the other hand, there are instances of animals and plants, which, + though exposed to very different conditions, both under nature and + domestication, have varied in nearly the same manner. Mr. Layard + informs me that he has observed amongst the Caffres of South Africa a + dog singularly like an arctic Esquimaux dog. Pigeons in India present + nearly the same wide diversities of colour as in Europe; and I have + seen chequered and simply barred pigeons, and pigeons with blue and + white loins, from Sierra Leone, Madeira, England, and India. New + varieties of flowers are continually raised in different parts of Great + Britain, but many of these are found by the judges at our exhibitions + to be almost identical with old varieties. A vast number of new + fruit-trees and culinary vegetables have been produced in North + America: these differ from European varieties in the same general + manner as the several varieties raised in Europe differ from each + other; and no one has ever pretended that the climate of America has + given to the many American varieties any general character by which + they can be recognised. Nevertheless, from the facts previously + advanced on the authority of Mr. Meehan with respect to American and + European forest-trees, it would be rash to affirm that varieties raised + in the two countries would not in the course of ages assume a + distinctive character. Mr. Masters has recorded a striking fact[711] + bearing on this subject: he raised numerous plants of _Hybiscus + Syriacus_ from seed collected in South Carolina and the Holy Land, + where the parent-plants must have been exposed to considerably + different conditions; yet the seedlings from both localities broke into + two similar strains, one with obtuse leaves and purple or crimson + flowers, and the other with elongated leaves and more or less pink + flowers. + + {287} + + We may, also, infer the prepotent influence of the constitution of the + organism over the definite action of the conditions of life, from the + several cases given in the earlier chapters of parallel series of + varieties,--an important subject, hereafter to be more fully discussed. + Sub-varieties of the several kinds of wheat, gourds, peaches, and other + plants, and to a certain limited extent sub-varieties of the fowl, + pigeon, and dog, have been shown either to resemble or to differ from + each other in a closely corresponding and parallel manner. In other + cases, a variety of one species resembles a distinct species; or the + varieties of two distinct species resemble each other. Although these + parallel resemblances no doubt often result from reversion to the + former characters of a common progenitor; yet in other cases, when new + characters first appear, the resemblance must be attributed to the + inheritance of a similar constitution, and consequently to a tendency + to vary in the same manner. We see something of a similar kind in the + same monstrosity appearing and reappearing many times in the same + animal, and, as Dr. Maxwell Masters has remarked to me, in the same + plant. + +We may at least conclude thus far, that the amount of modification which +animals and plants have undergone under domestication, does not correspond +with the degree to which they have been subjected to changed circumstances. +As we know the parentage of domesticated birds far better than of most +quadrupeds, we will glance through the list. The pigeon has varied in +Europe more than almost any other bird; yet it is a native species, and has +not been exposed to any extraordinary change of conditions. The fowl has +varied equally, or almost equally, with the pigeon, and is a native of the +hot jungles of India. Neither the peacock, a native of the same country, +nor the guinea-fowl, an inhabitant of the dry deserts of Africa, has varied +at all, or only in colour. The turkey, from Mexico, has varied but little. +The duck, on the other hand, a native of Europe, has yielded some +well-marked races; and as this is an aquatic bird, it must have been +subjected to a far more serious change in its habits than the pigeon or +even the fowl, which nevertheless have varied in a much higher degree. The +goose, a native of Europe and aquatic like the duck, has varied less than +any other domesticated bird, except the peacock. + +Bud-variation is, also, important under our present point of view. In some +few cases, as when all the eyes or buds on the same tuber of the potato, or +all the fruit on the same plum-tree, or all the flowers on the same plant, +have suddenly varied in the same manner, it might be argued that the {288} +variation had been definitely caused by some change in the conditions to +which the plants had been exposed; yet, in other cases, such an admission +is extremely difficult. As new characters sometimes appear by +bud-variation, which do not occur in the parent-species or in any allied +species, we may reject, at least in these cases, the idea that they are due +to reversion. Now it is well worth while to reflect maturely on some +striking case of bud-variation, for instance that of the peach. This tree +has been cultivated by the million in various parts of the world, has been +treated differently, grown on its own roots and grafted on various stocks, +planted as a standard, against a wall, and under glass; yet each bud of +each sub-variety keeps true to its kind. But occasionally, at long +intervals of time, a tree in England, or under the widely-different climate +of Virginia, produces a single bud, and this yields a branch which ever +afterwards bears nectarines. Nectarines differ, as every one knows, from +peaches in their smoothness, size, and flavour; and the difference is so +great, that some botanists have maintained that they are specifically +distinct. So permanent are the characters thus suddenly acquired, that a +nectarine produced by bud-variation has propagated itself by seed. To guard +against the supposition that there is some fundamental distinction between +bud and seminal variation, it is well to bear in mind that nectarines have +likewise been produced from the stone of the peach; and, reversely, peaches +from the stone of the nectarine. Now is it possible to conceive external +conditions more closely alike than those to which the buds on the same tree +are exposed? Yet one bud alone, out of the many thousands borne by the same +tree, has suddenly without any apparent cause produced a nectarine. But the +case is even stronger than this, for the same flower-bud has yielded a +fruit, one-half or one-quarter a nectarine, and the other half or +three-quarters a peach. Again, seven or eight varieties of the peach have +yielded by bud-variation nectarines: the nectarines thus produced, no +doubt, differ a little from each other; but still they are nectarines. Of +course there must be some cause, internal or external, to excite the +peach-bud to change its nature; but I cannot imagine a class of facts +better adapted to force on our minds the conviction that what we call the +external conditions of life are quite insignificant in {289} relation to +any particular variation, in comparison with the organisation or +constitution of the being which varies. + +It is known from the labours of Geoffroy St. Hilaire, and recently from +those of Dareste and others, that eggs of the fowl, if shaken, placed +upright, perforated, covered in part with varnish, &c., produce monstrous +chickens. Now these monstrosities may be said to be directly caused by such +unnatural conditions, but the modifications thus induced are not of a +definite nature. An excellent observer, M. Camille Dareste,[712] remarks +"that the various species of monstrosities are not determined by specific +causes; the external agencies which modify the development of the embryo +act solely in causing a perturbation--a perversion in the normal course of +development." He compares the result to what we see in illness: a sudden +chill, for instance, affects one individual alone out of many, causing +either a cold, or sore-throat, rheumatism, or inflammation of the lungs or +pleura. Contagious matter acts in an analogous manner.[713] We may take a +still more specific instance: seven pigeons were struck by +rattle-snakes;[714] some suffered from convulsions; some had their blood +coagulated, in others it was perfectly fluid; some showed ecchymosed spots +on the heart, others on the intestines, &c.; others again showed no visible +lesion in any organ. It is well known that excess in drinking causes +different diseases in different men; but men living under a cold and +tropical climate are differently affected:[715] and in this case we see the +definite influence of opposite conditions. The foregoing facts apparently +give us as good an idea as we are likely for a long time to obtain, how in +many cases external conditions act directly, though not definitely, in +causing modifications of structure. + + * * * * * + +_Summary._--There can be no doubt, from the facts given in the early part +of this chapter, that extremely slight changes in {290} the conditions of +life sometimes act in a definite manner on our already variable +domesticated productions; and, as the action of changed conditions in +causing general or indefinite variability is accumulative, so it may be +with their definite action. Hence it is possible that great and definite +modifications of structure may result from altered conditions acting during +a long series of generations. In some few instances a marked effect has +been produced quickly on all, or nearly all, the individuals which have +been exposed to some considerable change of climate, food, or other +circumstance. This has occurred, and is now occurring, with European men in +the United States, with European dogs in India, with horses in the Falkland +Islands, apparently with various animals at Angora, with foreign oysters in +the Mediterranean, and with maize grown in Europe from tropical seed. We +have seen that the chemical compounds secreted by plants and the state of +their tissues are readily affected by changed conditions. In some cases a +relation apparently exists between certain characters and certain +conditions, so that if the latter be changed the character is lost--as with +cultivated flowers, with some few culinary plants, with the fruit of the +melon, with fat-tailed sheep, and other sheep having peculiar fleeces. + +The production of galls, and the change of plumage in parrots when fed on +peculiar food or when inoculated by the poison of a toad, prove to us what +great and mysterious changes in structure and colour may be the definite +result of chemical changes in the nutrient fluids or tissues. + +We have also reason to believe that organic beings in a state of nature may +be modified in various definite ways by the conditions to which they have +been long exposed, as in the case of American trees in comparison with +their representatives in Europe. But in all such cases it is most difficult +to distinguish between the definite results of changed conditions, and the +accumulation through natural selection of serviceable variations which have +arisen independently of the nature of the conditions. If, for instance, a +plant had to be modified so as to become fitted to inhabit a humid instead +of an arid station, we have no reason to believe that variations of the +right kind would occur more frequently if the parent-plant inhabited a +station a little more {291} humid than usual. Whether the station was +unusually dry or humid, variations adapting the plant in a slight degree +for directly opposite habits of life would occasionally arise, as we have +reason to believe from what we know in other cases. + +In most, perhaps in all cases, the organisation or constitution of the +being which is acted on, is a much more important element than the nature +of the changed conditions, in determining the nature of the variation. We +have evidence of this in the appearance of nearly similar modifications +under different conditions, and of different modifications under apparently +nearly the same conditions. We have still better evidence of this in +closely parallel varieties being frequently produced from distinct races, +or even distinct species, and in the frequent recurrence of the same +monstrosity in the same species. We have also seen that the degree to which +domesticated birds have varied, does not stand in any close relation with +the amount of change to which they have been subjected. + +To recur once again to bud-variations. When we reflect on the millions of +buds which many trees have produced, before some one bud has varied, we are +lost in wonder what the precise cause of each variation can be. Let us +recall the case given by Andrew Knight of the forty-year-old tree of the +yellow magnum bonum plum, an old variety which has been propagated by +grafts on various stocks for a very long period throughout Europe and North +America, and on which a single bud suddenly produced the red magnum bonum. +We should also bear in mind that distinct varieties, and even distinct +species,--as in the case of peaches, nectarines, and apricots,--of certain +roses and camellias,--although separated by a vast number of generations +from any progenitor in common, and although cultivated under diversified +conditions, have yielded by bud-variation closely analogous varieties. When +we reflect on these facts we become deeply impressed with the conviction +that in such cases the nature of the variation depends but little on the +conditions to which the plant has been exposed, and not in any especial +manner on its individual character, but much more on the general nature or +constitution, inherited from some remote progenitor, of the whole group of +allied beings to which the plant belongs. We are thus driven to conclude +that in most {292} cases the conditions of life play a subordinate part in +causing any particular modification; like that which a spark plays, when a +mass of combustibles bursts into flame--the nature of the flame depending +on the combustible matter, and not on the spark. + +No doubt each slight variation must have its efficient cause; but it is as +hopeless an attempt to discover the cause of each as to say why a chill or +a poison affects one man differently from another. Even with modifications +resulting from the definite action of the conditions of life, when all or +nearly all the individuals, which have been similarly exposed, are +similarly affected, we can rarely see the precise relation between cause +and effect. In the next chapter it will be shown that the increased use or +disuse of various organs, produces an inherited effect. It will further be +seen that certain variations are bound together by correlation and other +laws. Beyond this we cannot at present explain either the causes or manner +of action of Variation. + +Finally, as indefinite and almost illimitable variability is the usual +result of domestication and cultivation, with the same part or organ +varying in different individuals in different or even in directly opposite +ways; and as the same variation, if strongly pronounced, usually recurs +only after long intervals of time, any particular variation would generally +be lost by crossing, reversion, and the accidental destruction of the +varying individuals, unless carefully preserved by man. Hence, although it +must be admitted that new conditions of life do sometimes definitely affect +organic beings, it may be doubted whether well-marked races have often been +produced by the direct action of changed conditions without the aid of +selection either by man or nature. + + * * * * * + + +{293} + +CHAPTER XXIV. + +LAWS OF VARIATION--USE AND DISUSE, ETC. + + NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE ORGANISATION--ON + THE EFFECTS OF THE INCREASED USE AND DISUSE OF ORGANS--CHANGED HABITS + OF LIFE--ACCLIMATISATION WITH ANIMALS AND PLANTS--VARIOUS METHODS BY + WHICH THIS CAN BE EFFECTED--ARRESTS OF DEVELOPMENT--RUDIMENTARY ORGANS. + +In this and the two following chapters I shall discuss, as well as the +difficulty of the subject permits, the several laws which govern +Variability. These may be grouped under the effects of use and disuse, +including changed habits and acclimatisation--arrests of +development--correlated variation--the cohesion of homologous parts--the +variability of multiple parts--compensation of growth--the position of buds +with respect to the axis of the plant--and lastly, analogous variation. +These several subjects so graduate into each other that their distinction +is often arbitrary. + +It may be convenient first briefly to discuss that co-ordinating and +reparative power which is common, in a higher or lower degree, to all +organic beings, and which was formerly designated by physiologists as the +_nisus formativus_. + + Blumenbach and others[716] have insisted that the principle which + permits a Hydra, when cut into fragments, to develop itself into two or + more perfect animals, is the same with that which causes a wound in the + higher animals to heal by a cicatrice. Such cases as that of the Hydra + are evidently analogous with the spontaneous division or fissiparous + generation of the lowest animals, and likewise with the budding of + plants. Between these extreme cases and that of a mere cicatrice we + have every gradation. Spallanzani,[717] by cutting off the legs and + tail of a Salamander, got in the course of three months six crops of + these members; so that 687 perfect bones were reproduced by one animal + during one season. At whatever {294} point the limb was cut off, the + deficient part, and no more, was exactly reproduced. Even with man, as + we have seen in the twelfth chapter, when treating of polydactylism, + the entire limb whilst in an embryonic state, and supernumerary digits, + are occasionally, though imperfectly, reproduced after amputation. When + a diseased bone has been removed, a new one sometimes "gradually + assumes the regular form, and all the attachments of muscles, + ligaments, &c., become as complete as before."[718] + + This power of regrowth does not, however, always act perfectly: the + reproduced tail of a lizard differs in the forms of the scales from the + normal tail: with certain Orthopterous insects the large hind legs are + reproduced of smaller size:[719] the white cicatrice which in the + higher animals unites the edges of a deep wound is not formed of + perfect skin, for elastic tissue is not produced till long + afterwards.[720] "The activity of the _nisus formativus_," says + Blumenbach, "is in an inverse ratio to the age of the organised body." + To this may be added that its power is greater in animals the lower + they are in the scale of organisation; and animals low in the scale + correspond with the embryos of higher animals belonging to the same + class. Newport's observations[721] afford a good illustration of this + fact, for he found that "myriapods, whose highest development scarcely + carries them beyond the larvae of perfect insects, can regenerate limbs + and antennae up to the time of their last moult;" and so can the larvae + of true insects, but not the mature insect. Salamanders correspond in + development with the tadpoles or larvae of the tailless Batrachians, + and both possess to a large extent the power of regrowth; but not so + the mature tailless Batrachians. + + Absorption often plays an important part in the repairs of injuries. + When a bone is broken, and does not unite, the ends are absorbed and + rounded, so that a false joint is formed; or if the ends unite, but + overlap, the projecting parts are removed.[722] But absorption comes + into action, as Virchow remarks, during the normal growth of bones; + parts which are solid during youth become hollowed out for the + medullary tissue as the bone increases in size. In trying to understand + the many well-adapted cases of regrowth when aided by absorption, we + should remember that most parts of the organisation, even whilst + retaining the same form, undergo constant renewal; so that a part which + was not renewed would naturally be liable to complete absorption. + + Some cases, usually classed under the so-called _nisus formativus_, at + first appear to come under a distinct head; for not only are old + structures reproduced, but structures which appear new are formed. + Thus, after inflammation "false membranes," furnished with + blood-vessels, lymphatics, and nerves, are developed; or a foetus + escapes from the Fallopian tubes, and falls into the abdomen, "nature + pours out a quantity of plastic lymph, which forms itself into + organised membrane, richly supplied with blood-vessels," and the foetus + is nourished for a time. In certain cases of {295} hydrocephalus the + open and dangerous spaces in the skull are filled up with new bones, + which interlock by perfect serrated sutures.[723] But most + physiologists, especially on the Continent, have now given up the + belief in plastic lymph or blastema, and Virchow[724] maintains that + every structure, new or old, is formed by the proliferation of + pre-existing cells. On this view false membranes, like cancerous or + other tumours, are merely abnormal developments of normal growths; and + we can thus understand how it is that they resemble adjoining + structures; for instance, that "false membrane in the serous cavities + acquires a covering of epithelium exactly like that which covers the + original serous membrane; adhesions of the iris may become black + apparently from the production of pigment-cells like those of the + uvea."[725] + + No doubt the power of reparation, though not always quite perfect, is + an admirable provision, ready for various emergencies, even for those + which occur only at long intervals of time.[726] Yet this power is not + more wonderful than the growth and development of every single + creature, more especially of those which are propagated by fissiparous + generation. This subject has been here noticed, because we may infer + that, when any part or organ is either greatly increased in size or + wholly suppressed through variation and continued selection, the + co-ordinating power of the organisation will continually tend to bring + all the parts again into harmony with each other. + +_On the Effects of the Increased Use and Disuse of Organs._ + +It is notorious, and we shall immediately adduce proofs, that increased use +or action strengthens muscles, glands, sense-organs, &c.; and that disuse, +on the other hand, weakens them. I have not met with any clear explanation +of this fact in works on Physiology. Mr. Herbert Spencer[727] maintains +that when muscles are much used, or when intermittent pressure is applied +to the epidermis, an excess of nutritive matter exudes from the vessels, +and that this gives additional development to the adjoining parts. That an +increased flow of blood towards an organ leads to its greater development +is probable, if not certain. Mr. Paget[728] thus accounts for the long, +thick, and dark-coloured hair which occasionally grows, even in young +children, near old-standing inflamed surfaces or fractured bones. When +Hunter {296} inserted the spur of a cock into the comb, which is well +supplied with blood-vessels, it grew in one case in a spiral direction to a +length of six inches, and in another case forward, like a horn, so that the +bird could not touch the ground with its beak. But whether Mr. Herbert +Spencer's view of the exudation of nutritive matter due to increased +movement and pressure, will fully account for the augmented size of bones, +ligaments, and especially of internal glands and nerves, seems doubtful. +According to the interesting observations of M. Sedillot,[729] when a +portion of one bone of the leg or fore-arm of an animal is removed and is +not replaced by growth, the associated bone enlarges till it attains a bulk +equal to that of the two bones, of which it has to perform the functions. +This is best exhibited in dogs in which the tibia has been removed; the +companion bone, which is naturally almost filiform and not one-fifth the +size of the other, soon acquires a size equal to or greater than the tibia. +Now, it is at first difficult to believe that increased weight acting on a +straight bone could, by alternately increased and diminished pressure, +cause nutritive matter to exude from the vessels which permeate the +periosteum. Nevertheless, the observations adduced by Mr. Spencer,[730] on +the strengthening of the bowed bones of rickety children, along their +concave sides, leads to the belief that this is possible. + +Mr. H. Spencer has also shown that the ascent of the sap in trees is aided +by the rocking movement caused by the wind; and the sap strengthens the +trunk "in proportion to the stress to be borne; since the more severe and +the more repeated the strains, the greater must be the exudation from the +vessels into the surrounding tissue, and the greater the thickening of this +tissue by secondary deposits."[731] But woody trunks may be formed of hard +tissue without their having been subjected to any movement, as we see with +ivy closely attached to old walls. In all these cases, it is very difficult +to disentangle the effects of long-continued selection from those +consequent on the increased action or movement of the part. Mr. H. +Spencer[732] acknowledges this difficulty, and gives as an instance the +spines {297} or thorns of trees, and the shells of nuts. Here we have +extremely hard woody tissue without the possibility of any movement to +cause exudation, and without, as far as we can see, any other directly +exciting cause; and as the hardness of these parts is of manifest service +to the plant, we may look at the result as probably due to the selection of +so-called spontaneous variations. Every one knows that hard work thickens +the epidermis on the hands; and when we hear that with infants long before +their birth the epidermis is thicker on the palms and soles of the feet +than on any other part of the body, as was observed with admiration by +Albinus,[733] we are naturally inclined to attribute this to the inherited +effects of long-continued use or pressure. We are tempted to extend the +same view even to the hoofs of quadrupeds; but who will pretend to +determine how far natural selection may have aided in the formation of +structures of such obvious importance to the animal? + + That use strengthens the muscles may be seen in the limbs of artisans + who follow different trades; and when a muscle is strengthened, the + tendons, and the crests of bone to which they are attached, become + enlarged; and this must likewise be the case with the blood-vessels and + nerves. On the other hand, when a limb is not used, as by Eastern + fanatics, or when the nerve supplying it with nervous power is + effectually destroyed, the muscles wither. So again, when the eye is + destroyed the optic nerve becomes atrophied, sometimes even in the + course of a few months.[734] The Proteus is furnished with branchiae as + well as with lungs: and Schreibers[735] found that when the animal was + compelled to live in deep water the branchiae were developed to thrice + their ordinary size, and the lungs were partially atrophied. When, on + the other hand, the animal was compelled to live in shallow water, the + lungs became larger and more vascular, whilst the branchiae disappeared + in a more or less complete degree. Such modifications as these are, + however, of comparatively little value for us, as we do not actually + know that they tend to be inherited. + + In many cases there is reason to believe that the lessened use of + various organs has affected the corresponding parts in the offspring. + But there is no good evidence that this ever follows in the course of a + single generation. It appears, as in the case of general or indefinite + variability, that several generations must be subjected to changed + habits for any appreciable result. Our domestic fowls, ducks, and geese + have almost lost, not {298} only in the individual but in the race, + their power of flight; for we do not see a chicken, when frightened, + take flight like a young pheasant. Hence I was led carefully to compare + the limb-bones of fowls, ducks, pigeons, and rabbits, with the same + bones in the wild parent-species. As the measurements and weights were + fully given in the earlier chapters, I need here only recapitulate the + results. With domestic pigeons, the length of the sternum, the + prominence of its crest, the length of the scapulae and furcula, the + length of the wings as measured from tip to tip of the radius, are all + reduced relatively to the same parts in the wild pigeon. The wing and + tail feathers, however, are increased in length, but this may have as + little connection with the use of the wings or tail, as the lengthened + hair on a dog with the amount of exercise which the breed has + habitually taken. The feet of pigeons, except in the long-beaked races, + are reduced in size. With fowls the crest of the sternum is less + prominent, and is often distorted or monstrous; the wing-bones have + become lighter relatively to the leg-bones, and are apparently a little + shorter in comparison with those of the parent-form, the _Gallus + bankiva_. With ducks, the crest of the sternum is affected in the same + manner as in the foregoing cases: the furcula, coracoids, and scapulae + are all reduced in weight relatively to the whole skeleton: the bones + of the wings are shorter and lighter, and the bones of the legs longer + and heavier, relatively to each other, and relatively to the whole + skeleton, in comparison with the same bones in the wild-duck. The + decreased weight and size of the bones, in the foregoing cases, is + probably the indirect result of the reaction of the weakened muscles on + the bones. I failed to compare the feathers of the wings of the tame + and wild duck; but Gloger[736] asserts that in the wild duck the tips + of the wing-feathers reach almost to the end of the tail, whilst in the + domestic duck they often hardly reach to its base. He remarks, also, on + the greater thickness of the legs, and says that the swimming membrane + between the toes is reduced; but I was not able to detect this latter + difference. + + With the domesticated rabbit the body, together with the whole + skeleton, is generally larger and heavier than in the wild animal, and + the leg-bones are heavier in due proportion; but whatever standard of + comparison be taken, neither the leg-bones nor the scapulae have + increased in length proportionally with the increased dimensions of the + rest of the skeleton. The skull has become in a marked manner narrower, + and, from the measurements of its capacity formerly given, we may + conclude, that this narrowness results from the decreased size of the + brain, consequent on the mentally inactive life led by these + closely-confined animals. + + We have seen in the eighth chapter that silk-moths, which have been + kept during many centuries closely confined, emerge from their cocoons + with their wings distorted, incapable of flight, often greatly reduced + in size, or even, according to Quatrefages, quite rudimentary. This + condition of the wings may be largely owing to the same kind of + monstrosity which often affects wild Lepidoptera when artificially + reared from the cocoon; or it may {299} be in part due to an inherent + tendency, which is common to the females of many Bombycidae, to have + their wings in a more or less rudimentary state; but part of the effect + may probably be attributed to long-continued disuse. + +From the foregoing facts there can be no doubt that certain parts of the +skeleton in our anciently domesticated animals, have been modified in +length and weight by the effects of decreased or increased use; but they +have not been modified, as shown in the earlier chapters, in shape or +structure. We must, however, be cautious in extending this latter +conclusion to animals living a free life; for these will occasionally be +exposed during successive generations to the severest competition. With +wild animals it would be an advantage in the struggle for life that every +superfluous and useless detail of structure should be removed or absorbed; +and thus the reduced bones might ultimately become changed in structure. +With highly-fed domesticated animals, on the other hand, there is no +economy of growth; nor any tendency to the elimination of trifling and +superfluous details of structure. + +Turning now to more general observations, Nathusius has shown that, with +the improved races of the pig, the shortened legs and snout, the form of +the articular condyles of the occiput, and the position of the jaws with +the upper canine teeth projecting in a most anomalous manner in front of +the lower canines, may be attributed to these parts not having been fully +exercised. For the highly-cultivated races do not travel in search of food, +nor root up the ground with their ringed muzzles. These modifications of +structure, which are all strictly inherited, characterise several improved +breeds, so that they cannot have been derived from any single domestic or +wild stock.[737] With respect to cattle, Professor Tanner has remarked that +the lungs and liver in the improved breeds "are found to be considerably +reduced in size when compared with those possessed by animals having +perfect liberty;"[738] and the reduction of these organs affects the +general shape of the body. The cause of the reduced lungs in highly-bred +animals which take little exercise is {300} obvious; and perhaps the liver +may be affected by the nutritious and artificial food on which they largely +subsist. + + It is well known that, when an artery is tied, the anastomosing + branches, from being forced to transmit more blood, increase in + diameter; and this increase cannot be accounted for by mere extension, + as their coats gain in strength. Mr. Herbert Spencer[739] has argued + that with plants the flow of sap from the point of supply to the + growing part first elongates the cells in this line; and that the cells + then become confluent, thus forming the ducts; so that, on this view, + the vessels in plants are formed by the mutual reaction of the flowing + sap and cellular tissue. Dr. W. Turner has remarked,[740] with respect + to the branches of arteries, and likewise to a certain extent with + nerves, that the great principle of compensation frequently comes into + play; for "when two nerves pass to adjacent cutaneous areas, an inverse + relation as regards size may subsist between them; a deficiency in one + may be supplied by an increase in the other, and thus the area of the + former may be trespassed on by the latter nerve." But how far in these + cases the difference in size in the nerves and arteries is due to + original variation, and how far to increased use or action, is not + clear. + + In reference to glands, Mr. Paget observes that "when one kidney is + destroyed the other often becomes much larger, and does double + work."[741] If we compare the size of the udders and their power of + secretion in cows which have been long domesticated, and in certain + goats in which the udders nearly touch the ground, with the size and + power of secretion of these organs in wild or half-domesticated + animals, the difference is great. A good cow with us daily yields more + than five gallons, or forty pints of milk, whilst a first-rate animal, + kept, for instance, by the Damaras of South Africa,[742] "rarely gives + more than two or three pints of milk daily, and, should her calf be + taken from her, she absolutely refuses to give any." We may attribute + the excellence of our cows, and of certain goats, partly to the + continued selection of the best milking animals, and partly to the + inherited effects of the increased action, through man's art, of the + secreting glands. + + It is notorious, as was remarked in the twelfth chapter, that + short-sight is inherited; and if we compare watchmakers or engravers + with, for instance, sailors, we can hardly doubt that vision + continually directed towards a near object permanently affects the + structure of the eye. + + Veterinarians are unanimous that horses become affected with spavins, + splints, ringbones, &c., from being shod, and from travelling on hard + roads, and they are almost equally unanimous that these injuries are + transmitted. Formerly horses were not shod in North Carolina, and it + has been asserted that they did not then suffer from these diseases of + the legs and feet.[743] + +{301} + +Our domesticated quadrupeds are all descended, as far as is known, from +species having erect ears; yet few kinds can be named, of which at least +one race has not drooping ears. Cats in China, horses in parts of Russia, +sheep in Italy and elsewhere, the guinea-pig in Germany, goats and cattle +in India, rabbits, pigs, and dogs in all long-civilised countries, have +dependent ears. With wild animals, which constantly use their ears like +funnels to catch every passing sound, and especially to ascertain the +direction whence it comes, there is not, as Mr. Blyth has remarked, any +species with drooping ears except the elephant. Hence the incapacity to +erect the ears is certainly in some manner the result of domestication; and +this incapacity has been attributed by various authors[744] to disuse, for +animals protected by man are not compelled habitually to use their ears. +Col. Hamilton Smith[745] states that in ancient effigies of the dog, "with +the exception of one Egyptian instance, no sculpture of the earlier Grecian +era produces representations of hounds with completely drooping ears; those +with them half pendulous are missing in the most ancient; and this +character increases, by degrees, in the works of the Roman period." Godron +also has remarked that "the pigs of the ancient Egyptians had not their +ears enlarged and pendent."[746] But it is remarkable that the drooping of +the ears, though probably the effect of disuse, is not accompanied by any +decrease in size; on the contrary, when we remember that animals so +different as fancy rabbits, certain Indian breeds of the goat, our petted +spaniels, bloodhounds, and other dogs, have enormously elongated ears, it +would appear as if disuse actually caused an increase in length. With +rabbits, the drooping of the much elongated ears has affected even the +structure of the skull. + +The tail of no wild animal, as remarked to me by Mr. Blyth, is curled; +whereas pigs and some races of dogs have their tails much curled. This +deformity, therefore, appears to be the result of domestication, but +whether in any way connected with the lessened use of the tail is doubtful. + +{302} + +The epidermis on our hands is easily thickened, as every one knows, by hard +work. In a district of Ceylon the sheep have "horny callosities that defend +their knees, and which arise from their habit of kneeling down to crop the +short herbage, and this distinguishes the Jaffna flocks from those of other +portions of the island;" but it is not stated whether this peculiarity is +inherited.[747] + +The mucous membrane which lines the stomach is continuous with the external +skin of the body; therefore it is not surprising that its texture should be +affected by the nature of the food consumed, but other and more interesting +changes likewise follow. Hunter long ago observed that the muscular coat of +the stomach of a gull (_Larus tridactylus_) which had been fed for a year +chiefly on grain was thickened; and, according to Dr. Edmondston, a similar +change periodically occurs in the Shetland Islands in the stomach of the +_Larus argentatus_, which in the spring frequents the corn-fields and feeds +on the seed. The same careful observer has noticed a great change in the +stomach of a raven which had been long fed on vegetable food. In the case +of an owl (_Strix grallaria_) similarly treated, Menetries states that the +form of the stomach was changed, the inner coat became leathery, and the +liver increased in size. Whether these modifications in the digestive +organs would in the course of generations become inherited is not +known.[748] + +The increased or diminished length of the intestines, which apparently +results from changed diet, is a more remarkable case, because it is +characteristic of certain animals in their domesticated condition, and +therefore must be inherited. The complex absorbent system, the +blood-vessels, nerves, and muscles, are necessarily all modified together +with the intestines. According to Daubenton, the intestines of the domestic +cat are one-third longer than those of the wild cat of Europe; and although +this species is not the parent-stock of the domestic animal, yet, as +Isidore Geoffroy has remarked, the several species {303} of cats are so +closely allied that the comparison is probably a fair one. The increased +length appears to be due to the domestic cat being less strictly +carnivorous in its diet than any wild feline species; I have seen a French +kitten eating vegetables as readily as meat. According to Cuvier, the +intestines of the domesticated pig exceed greatly in proportionate length +those of the wild boar. In the tame and wild rabbit the change is of an +opposite nature, and probably results from the nutritious food given to the +tame rabbit.[749] + + * * * * * + +_Changed Habits of Life, independently of the Use or Disuse of particular +Organs._--This subject, as far as the mental powers of animals are +concerned, so blends into instinct, on which I shall treat in a future +work, that I will here only remind the reader of the many cases which occur +under domestication, and which are familiar to every one--for instance the +tameness of our animals--the pointing or retrieving of dogs--their not +attacking the smaller animals kept by man--and so forth. How much of these +changes ought to be attributed to inherited habit, and how much to the +selection of individuals which have varied in the desired manner, +irrespectively of the special circumstances under which they have been +kept, can seldom be told. We have already seen that animals may be +habituated to a changed diet; but a few additional instances may here be +given. + +In the Polynesian Islands and in China the dog is fed exclusively on +vegetable matter, and the taste for this kind of food is to a certain +extent inherited.[750] Our sporting dogs will not touch the bones of game +birds, whilst other dogs devour them with greediness. In some parts of the +world sheep have been largely fed on fish. The domestic hog is fond of +barley, the wild boar is said to disdain it; and the disdain is partially +inherited, for some young wild pigs bred in captivity showed an aversion +for this grain, whilst others of the same brood relished it.[751] One of my +relations bred some young pigs from {304} a Chinese sow by a wild Alpine +boar; they lived free in the park, and were so tame that they came to the +house to be fed; but they would not touch swill, which was devoured by the +other pigs. An animal when once accustomed to an unnatural diet, which can +generally be effected only during youth, dislikes its proper food, as +Spallanzani found to be the case with a pigeon which had been long fed on +meat. Individuals of the same species take to new food with different +degrees of readiness; one horse, it is stated, soon learned to eat meat, +whilst another would have perished from hunger rather than have partaken of +it.[752] + +The caterpillars of the _Bombyx hesperus_ feed in a state of nature on the +leaves of the _Cafe diable_, but, after having been reared on the +Ailanthus, they would not touch the _Cafe diable_, and actually died of +hunger.[753] + +It has been found possible to accustom marine fish to live in fresh water; +but as such changes in fish, and other marine animals, have been chiefly +observed in a state of nature, they do not properly belong to our present +subject. The period of gestation and of maturity, as shown in the earlier +chapters,--the season and the frequency of the act of breeding,--have all +been greatly modified under domestication. With the Egyptian goose the rate +of change in the season has been recorded.[754] The wild drake pairs with +one female, the domestic drake is polygamous. Certain breeds of fowls have +lost the habit of incubation. The paces of the horse, and the manner of +flight in certain breeds of the pigeon, have been modified, and are +inherited. The voice differs much in certain fowls and pigeons. Some breeds +are clamorous and others silent, as in the Call and common duck, or in the +Spitz and pointer dog. Every one knows how dogs differ from each other in +their manner of hunting, and in their ardour after different kinds of game +or vermin. + +With plants the period of vegetation is easily changed and is inherited, as +in the case of summer and winter wheat, barley, {305} and vetches; but to +this subject we shall immediately return under acclimatisation. Annual +plants sometimes become perennial under a new climate, as I hear from Dr. +Hooker is the case with the stock and mignonette in Tasmania. On the other +hand, perennials sometimes become annuals, as with the Ricinus in England, +and as, according to Captain Mangles, with many varieties of the +heartsease. Von Berg[755] raised from seed of _Verbascum phoenicium_, which +is usually a biennial, both annual and perennial varieties. Some deciduous +bushes become evergreen in hot countries.[756] Rice requires much water, +but there is one variety in India which can be grown without +irrigation.[757] Certain varieties of the oat and of our other cereals are +best fitted for certain soils.[758] Endless similar facts could be given in +the animal and vegetable kingdoms. They are noticed here because they +illustrate analogous differences in closely allied natural species, and +because such changed habits of life, whether due to use and disuse, or to +the direct action of external conditions, or to so-called spontaneous +variation, would be apt to lead to modifications of structure. + + * * * * * + +_Acclimatisation._--From the previous remarks we are naturally led to the +much disputed subject of acclimatisation. There are two distinct questions: +Do varieties descended from the same species differ in their power of +living under different climates? And secondly, if they so differ, how have +they become thus adapted? We have seen that European dogs do not succeed +well in India, and it is asserted,[759] that no one has succeeded in there +keeping the Newfoundland long alive; but then it may be argued, probably +with truth, that these northern breeds are specifically distinct from the +native dogs which flourish in India. The same remark may be made with +respect to different breeds of sheep, of which, according to Youatt,[760] +not one brought "from a torrid climate lasts out the second year," in the +Zoological Gardens. But sheep are capable of some degree of +acclimatisation, for Merino sheep bred at the Cape of Good Hope have been +found {306} far better adapted for India than those imported from +England.[761] It is almost certain that the breeds of the fowl are +descended from the same species; but the Spanish breed, which there is good +reason to believe originated near the Mediterranean,[762] though so fine +and vigorous in England, suffers more from frost than any other breed. The +Arrindy silk-moth introduced from Bengal, and the Ailanthus moth from the +temperate province of Shan Tung, in China, belong to the same species, as +we may infer from their identity in the caterpillar, cocoon, and mature +states;[763] yet they differ much in constitution: the Indian form "will +flourish only in warm latitudes," the other is quite hardy and withstands +cold and rain. + + Plants are more strictly adapted to climate than are animals. The + latter when domesticated withstand such great diversities of climate, + that we find nearly the same species in tropical and temperate + countries; whilst the cultivated plants are widely dissimilar. Hence a + larger field is open for inquiry in regard to the acclimatisation of + plants than of animals. It is no exaggeration to say that with almost + every plant which has long been cultivated varieties exist, which are + endowed with constitutions fitted for very different climates; I will + select only a few of the more striking cases, as it would be tedious to + give all. In North America numerous fruit-trees have been raised, and + in horticultural publications,--for instance, in Downing,--lists are + given of the varieties which are best able to withstand the severe + climate of the northern States and Canada. Many American varieties of + the pear, plum, and peach are excellent in their own country, but until + recently hardly one was known that succeeded in England; and with + apples,[764] not one succeeds. Though the American varieties can + withstand a severer winter than ours, the summer here is not hot + enough. Fruit-trees have originated in Europe as in America with + different constitutions, but they are not here much noticed, as the + same nurserymen do not supply a wide area. The Forelle pear flowers + early, and when the flowers have just set, and this is the critical + period, they have been observed, both in France and England, to + withstand with complete impunity a frost of 18deg and even 14deg Fahr., + which killed the flowers, whether fully expanded or in bud, of all + other kinds of pears.[765] This power in the flower of resisting cold + and afterwards producing fruit does not invariably depend, as we know + on good authority,[766] on general constitutional vigour. + + {307} + + In proceeding northward, the number of varieties which are enabled to + resist the climate rapidly decreases, as may be seen in the list of the + varieties of the cherry, apple, and pear, which can be cultivated in + the neighbourhood of Stockholm.[767] Near Moscow, Prince Troubetzkoy + planted for experiment in the open ground several varieties of the + pear, but one alone, the _Poire sans Pepins_, withstood the cold of + winter.[768] We thus see that our fruit-trees, like distinct species of + the same genus, certainly differ from each other in their + constitutional adaptation to different climates. + + With the varieties of many plants, the adaptation to climate is often + very close. Thus it has been proved by repeated trials "that few if any + of the English varieties of wheat are adapted for cultivation in + Scotland;"[769] but the failure in this case is at first only in the + quantity, though ultimately in the quality, of the grain produced. The + Rev. J. M. Berkeley sowed wheat-seed from India, and got "the most + meagre ears," on land which would certainly have yielded a good crop + from English wheat.[770] In these cases varieties have been carried + from a warmer to a cooler climate; in the reverse case, as "when wheat + was imported directly from France into the West Indian Islands, it + produced either wholly barren spikes or furnished with only two or + three miserable seeds, while West Indian seed by its side yielded an + enormous harvest."[771] Here is another case of close adaptation to a + slightly cooler climate; a kind of wheat which in England may be used + indifferently either as a winter or summer variety, when sown under the + warmer climate of Grignan, in France, behaved exactly as if it had been + a true winter wheat.[772] + + Botanists believe that all the varieties of maize belong to the same + species; and we have seen that in North America, in proceeding + northward, the varieties cultivated in each zone produce their flowers + and ripen their seed within shorter and shorter periods. So that the + tall, slowly maturing southern varieties do not succeed in New England, + and the New English varieties do not succeed in Canada. I have not met + with any statement that the southern varieties are actually injured or + killed by a degree of cold which the northern varieties withstand with + impunity, though this is probable; but the production of early + flowering and early seeding varieties deserves to be considered as one + form of acclimatisation. Hence it has been found possible, according to + Kalm, to cultivate maize further and further northwards in America. In + Europe, also, as we learn from the evidence given by Alph. De Candolle, + the culture of maize has extended since the end of the last century + thirty leagues north of its former boundary.[773] On the authority of + the great Linnaeus,[774] I may quote an {308} analogous case, namely, + that in Sweden tobacco raised from home-grown seed ripens its seed a + month sooner and is less liable to miscarry than plants raised from + foreign seed. + + With the Vine, differently from the maize, the line of practical + culture has retreated a little southward since the middle ages;[775] + but this seems due to commerce, including that of wine, being now freer + or more easy. Nevertheless the fact of the vine not having spread + northward shows that acclimatisation has made no progress during + several centuries. There is, however, a marked difference in the + constitution of the several varieties,--some being hardy, whilst + others, like the muscat of Alexandria, require a very high temperature + to come to perfection. According to Labat,[776] vines taken from France + to the West Indies succeed with extreme difficulty, whilst those + imported from Madeira, or the Canary Islands, thrive admirably. + + Gallesio gives a curious account of the naturalisation of the Orange in + Italy. Daring many centuries the sweet orange was propagated + exclusively by grafts, and so often suffered from frosts that it + required protection. After the severe frost of 1709, and more + especially after that of 1763, so many trees were destroyed that + seedlings from the sweet orange were raised, and, to the surprise of + the inhabitants, their fruit was found to be sweet. The trees thus + raised were larger, more productive, and hardier than the former kinds; + and seedlings are now continually raised. Hence Gallesio concludes that + much more was effected for the naturalisation of the orange in Italy by + the accidental production of new kinds during a period of about sixty + years, than had been effected by grafting old varieties during many + ages.[777] I may add that Risso[778] describes some Portuguese + varieties of the orange as extremely sensitive to cold, and as much + tenderer than certain other varieties. + + The peach was known to Theophrastus, 322 B.C.[779] According to the + authorities quoted by Dr. F. Rolle,[780] it was tender when first + introduced into Greece, and even in the island of Rhodes only + occasionally bore fruit. If this be correct, the peach, in spreading + during the last two thousand years over the middle parts of Europe, + must have become much hardier. At the present day different varieties + differ much in hardiness: some French varieties will not succeed in + England; and near Paris, the _Pavie de Bonneuil_ does not ripen its + fruit till very late, even when grown on a wall; "it is, therefore, + only fit for a very hot southern climate."[781] + + I will briefly give a few other cases. A variety of _Magnolia + grandiflora_, raised by M. Roy, withstands cold several degrees lower + than that which any other variety can resist. With camellias there is + much difference in hardiness. One particular variety of Noisette rose + withstood the severe frost of 1860 "untouched and hale amidst a + universal destruction of other {309} Noisettes." In New York the "Irish + yew is quite hardy, but the common yew is liable to be cut down." I may + add that there are varieties of the sweet potato (_Convolvulus + batatas_) which are suited for warmer, as well as for colder, + climates.[782] + +The plants as yet mentioned have been found capable of resisting an unusual +degree of cold or heat, when fully grown. The following cases refer to +plants whilst young. In a large bed of young Araucarias of the same age, +growing close together and equally exposed, it was observed,[783] after the +unusually severe winter of 1860-61, that, "in the midst of the dying, +numerous individuals remained on which the frost had absolutely made no +kind of impression." Dr. Lindley, after alluding to this and other similar +cases, remarks, "Among the lessons which the late formidable winter has +taught us, is that, even in their power of resisting cold, individuals of +the same species of plants are remarkably different." Near Salisbury, there +was a sharp frost on the night of May 24th, 1836, and all the French beans +(_Phaseolus vulgaris_) in a bed were killed except about one in thirty, +which completely escaped.[784] On the same day of the month, but in the +year 1864, there was a severe frost in Kent, and two rows of +scarlet-runners (_P. multiflorus_) in my garden, containing 390 plants of +the same age and equally exposed, were all blackened and killed except +about a dozen plants. In an adjoining row of "Fulmer's dwarf bean" (_P. +vulgaris_), one single plant escaped. A still more severe frost occurred +four days afterwards, and of the dozen plants which had previously escaped +only three survived; these were not taller or more vigorous than the other +young plants, but they escaped completely, with not even the tips of their +leaves browned. It was impossible to behold these three plants, with their +blackened, withered, and dead brethren all round them, and not see at a +glance that they differed widely in constitutional power of resisting +frost. + +This work is not the proper place to show that wild plants {310} of the +same species, naturally growing at different altitudes or under different +latitudes, become to a certain extent acclimatised, as is proved by the +different behaviour of their seedlings when raised in England. In my +'Origin of Species' I have alluded to some cases, and I could add others. +One instance must suffice: Mr. Grigor, of Forres,[785] states that +seedlings of the Scotch fir (_Pinus sylvestris_), raised from seed from the +Continent and from the forests of Scotland, differ much. "The difference is +perceptible in one-year-old, and more so in two-year-old seedlings; but the +effects of the winter on the second year's growth almost uniformly makes +those from the Continent quite brown, and so damaged, that by the month of +March they are quite unsaleable, while the plants from the native Scotch +pine, under the same treatment, and standing alongside, although +considerably shorter, are rather stouter and quite green, so that the beds +of the one can be known from the other when seen from the distance of a +mile." Closely similar facts have been observed with seedling larches. + + Hardy varieties would alone be valued or noticed in Europe; whilst + tender varieties, requiring more warmth, would generally be neglected; + but such occasionally arise. Thus Loudon[786] describes a Cornish + variety of the elm which is almost an evergreen, and of which the + shoots are often killed by the autumnal frosts, so that its timber is + of little value. Horticulturists know that some varieties are much more + tender than others: thus all the varieties of the broccoli are more + tender than cabbages; but there is much difference in this respect in + the sub-varieties of the broccoli; the pink and purple kinds are a + little hardier than the white Cape broccoli, "but they are not to be + depended on after the thermometer falls below 24deg Fahr.:" the + Walcheren broccoli is less tender than the Cape, and there are several + varieties which will stand much severer cold than the Walcheren.[787] + Cauliflowers seed more freely in India than cabbages.[788] To give one + instance with flowers: eleven plants raised from a hollyhock, called + the _Queen of the Whites_,[789] were found to be much more tender than + various other seedlings. It may be presumed that all tender varieties + would succeed better under a climate warmer than ours. With + fruit-trees, it is well known that certain varieties, for instance of + the peach, stand forcing in a hot-house better than others; and this + shows {311} either pliability of organisation or some constitutional + difference. The same individual cherry-tree, when forced, has been + observed during successive years gradually to change its period of + vegetation.[790] Few pelargoniums can resist the heat of a stove, but + _Alba multiflora_ will, as a most skilful gardener asserts, "stand + pine-apple top and bottom heat the whole winter, without looking any + more drawn than if it had stood in a common greenhouse; and _Blanche + Fleur_ seems as if it had been made on purpose for growing in winter, + like many bulbs, and to rest all summer."[791] There can hardly be a + doubt that the _Alba multiflora_ pelargonium must have a widely + different constitution from that of most other varieties of this plant; + it would probably withstand even an equatorial climate. + + We have seen that according to Labat the vine and wheat require + acclimatisation in order to succeed in the West Indies. Similar facts + have been observed at Madras: "two parcels of mignonette-seed, one + direct from Europe, the other saved at Bangalore (of which the mean + temperature is much below that of Madras) were sown at the same time: + they both vegetated equally favourably, but the former all died off a + few days after they appeared above ground; the latter still survive, + and are vigorous healthy plants." So again, "turnip and carrot seed + saved at Hyderabad are found to answer better at Madras than seed from + Europe or from the Cape of Good Hope."[792] Mr. J. Scott, of the + Calcutta Botanic Gardens, informs me that seeds of the sweet-pea + (_Lathyrus odoratus_) imported from England produce plants, with thick, + rigid stems and small leaves, which rarely blossom and never yield + seed; plants raised from French seed blossom sparingly, but all the + flowers are sterile; on the other hand, plants raised from sweet-peas + grown near Darjeeling in Upper India, but originally derived from + England, can be successfully cultivated on the plains of India; for + they flower and seed profusely, and their stems are lax and scandent. + In some of the foregoing cases, as Dr. Hooker has remarked to me, the + greater success may perhaps be attributed to the seeds having been more + fully ripened under a more favourable climate; but this view can hardly + be extended to so many cases, including plants, which, from being + cultivated under a climate hotter than their native one, become fitted + for a still hotter climate. We may therefore safely conclude that + plants can to a certain extent become accustomed to a climate either + hotter or colder than their own; although these latter cases have been + more frequently observed. + +We will now consider the means by which acclimatisation may be effected, +namely, through the spontaneous appearance of varieties having a different +constitution, and through the effects of use or habit. In regard to the +first process, there is no evidence that a change in the constitution of +the {312} offspring necessarily stands in any direct relation with the +nature of the climate inhabited by the parents. On the contrary, it is +certain that hardy and tender varieties of the same species appear in the +same country. New varieties thus spontaneously arising become fitted to +slightly different climates in two different ways; firstly, they may have +the power, either as seedlings or when full-grown, of resisting intense +cold, as with the Moscow pear, or of resisting intense heat, as with some +kinds of Pelargonium, or the flowers may withstand severe frost, as with +the Forelle pear. Secondly, plants may become adapted to climates widely +different from their own, from flowering and fruiting either earlier or +later in the season. In both these cases the power of acclimatisation by +man consists simply in the selection and preservation of new varieties. But +without any direct intention on his part of securing a hardier variety, +acclimatisation may be unconsciously effected by merely raising tender +plants from seed, and by occasionally attempting their cultivation further +and further northwards, as in the case of maize, the orange, and the peach. + +How much influence ought to be attributed to inherited habit or custom in +the acclimatisation of animals and plants is a much more difficult +question. In many cases natural selection can hardly have failed to have +come into play and complicated the result. It is notorious that mountain +sheep resist severe weather and storms of snow which would destroy lowland +breeds; but then mountain sheep have been thus exposed from time +immemorial, and all delicate individuals will have been destroyed, and the +hardiest preserved. So with the Arrindy silk-moths of China and India; who +can tell how far natural selection may have taken a share in the formation +of the two races, which are now fitted for such widely different climates? +It seems at first probable that the many fruit-trees, which are so well +fitted for the hot summers and cold winters of North America, in contrast +with their poor success under our climate, have become adapted through +habit; but when we reflect on the multitude of seedlings annually raised in +that country, and that none would succeed unless born with a fitting +constitution, it is possible that mere habit may have done nothing towards +their acclimatisation. On the other hand, when we {313} hear that Merino +sheep, bred during no great number of generations at the Cape of Good +Hope--that some European plants raised during only a few generations in the +cooler parts of India, withstand the hotter parts of that country much +better than the sheep or seeds imported directly from England, we must +attribute some influence to habit. We are led to the same conclusion when +we hear from Naudin[793] that the races of melons, squashes, and gourds, +which have long been cultivated in Northern Europe, are comparatively more +precocious, and need much less heat for maturing their fruit, than the +varieties of the same species recently brought from tropical regions. In +the reciprocal conversion of summer and winter wheat, barley, and vetches +into each other, habit produces a marked effect in the course of a very few +generations. The same thing apparently occurs with the varieties of maize, +which, when carried from the Southern to the Northern States of America, or +into Germany, soon become accustomed to their new homes. With vine-plants +taken to the West Indies from Madeira, which are said to succeed better +than plants brought directly from France, we have some degree of +acclimatisation in the individual, independently of the production of new +varieties by seed. + +The common experience of agriculturists is of some value, and they often +advise persons to be cautious in trying in one country the productions of +another. The ancient agricultural writers of China recommend the +preservation and cultivation of the varieties peculiar to each country. +During the classical period, Columella wrote, "Vernaculum pecus peregrino +longe praestantius est."[794] + +I am aware that the attempt to acclimatise either animals or plants has +been called a vain chimaera. No doubt the attempt in most cases deserves to +be thus called, if made independently of the production of new varieties +endowed with a different constitution. Habit, however much prolonged, +rarely produces any effect on a plant propagated by buds; it apparently +acts only through successive seminal generations. {314} The laurel, bay, +laurestinus, &c., and the Jerusalem artichoke, which are propagated by +cuttings or tubers, are probably now as tender in England as when first +introduced; and this appears to be the case with the potato, which until +recently was seldom multiplied by seed. With plants propagated by seed, and +with animals, there will be little or no acclimatisation unless the hardier +individuals are either intentionally or unconsciously preserved. The +kidney-bean has often been advanced as an instance of a plant which has not +become hardier since its first introduction into Britain. We hear, however, +on excellent authority,[795] that some very fine seed, imported from +abroad, produced plants "which blossomed most profusely, but were nearly +all but abortive, whilst plants grown alongside from English seed podded +abundantly;" and this apparently shows some degree of acclimatisation in +our English plants. We have also seen that seedlings of the kidney-bean +occasionally appear with a marked power of resisting frost; but no one, as +far as I can hear, has ever separated such hardy seedlings, so as to +prevent accidental crossing, and then gathered their seed, and repeated the +process year after year. It may, however, be objected with truth that +natural selection ought to have had a decided effect on the hardiness of +our kidney-beans; for the tenderest individuals must have been killed +during every severe spring, and the hardier preserved. But it should be +borne in mind that the result of increased hardiness would simply be that +gardeners, who are always anxious for as early a crop as possible, would +sow their seed a few days earlier than formerly. Now, as the period of +sowing depends much on the soil and elevation of each district, and varies +with the season; and as new varieties have often been imported from abroad, +can we feel sure that our kidney-beans are not somewhat hardier? I have not +been able, by searching old horticultural works, to answer this question +satisfactorily. + +On the whole the facts now given show that, though habit does something +towards acclimatisation, yet that the spontaneous appearance of +constitutionally different individuals is a far more effective agent. As no +single instance has been recorded, either with animals or plants, of +hardier individuals {315} having been long and steadily selected, though +such selection is admitted to be indispensable for the improvement of any +other character, it is not surprising that man has done little in the +acclimatisation of domesticated animals and cultivated plants. We need not, +however, doubt that under nature new races and new species would become +adapted to widely different climates, by spontaneous variation, aided by +habit, and regulated by natural selection. + +_Arrests of Development: Rudimentary and Aborted Organs._ + + These subjects are here introduced because there is reason to believe + that rudimentary organs are in many cases the result of disuse. + Modifications of structure from arrested development, so great or so + serious as to deserve to be called monstrosities, are of common + occurrence, but, as they differ much from any normal structure, they + require here only a passing notice. When a part or organ is arrested + during its embryonic growth, a rudiment is generally left. Thus the + whole head may be represented by a soft nipple-like projection, and the + limbs by mere papillae. These rudiments of limbs are sometimes + inherited, as has been observed in a dog.[796] + + Many lesser anomalies in our domesticated animals appear to be due to + arrested development. What the cause of the arrest may be, we seldom + know, except in the case of direct injury to the embryo within the egg + or womb. That the cause does not generally act at a very early + embryonic period we may infer from the affected organ seldom being + wholly aborted,--a rudiment being generally preserved. The external + ears are represented by mere vestiges in a Chinese breed of sheep; and + in another breed, the tail is reduced "to a little button, suffocated, + in a manner, by fat."[797] In tailless dogs and cats a stump is left; + but I do not know whether it includes at an early embryonic age + rudiments of all the caudal vertebrae. In certain breeds of fowls the + comb and wattles are reduced to rudiments; in the Cochin-China breed + scarcely more than rudiments of spurs exist. With polled Suffolk + cattle, "rudiments of horns can often be felt at an early age;"[798] + and with species in a state of nature, the relatively greater + development of rudimentary organs at an early period of life is highly + characteristic of such organs. With hornless breeds of cattle and + sheep; another and singular kind of rudiment has been observed, namely, + minute dangling horns attached to the skin alone, and which are often + shed and grow again. With hornless goats, according to Desmarest,[799] + {316} the bony protuberances which properly support the horns exist as + mere rudiments. + + With cultivated plants it is far from rare to find the petals, stamens, + and pistils represented by rudiments, like those observed in natural + species. So it is with the whole seed in many fruits; thus near + Astrakhan there is a grape with mere traces of seeds, "so small and + lying so near the stalk that they are not perceived in eating the + grape."[800] In certain varieties of the gourd, the tendrils, according + to Naudin, are represented by rudiments or by various monstrous + growths. In the broccoli and cauliflower the greater number of the + flowers are incapable of expansion, and include rudimentary organs. In + the Feather hyacinth (_Muscari comosum_) the upper and central flowers + are brightly coloured but rudimentary; under cultivation the tendency + to abortion travels downwards and outwards, and all the flowers become + rudimentary; but the abortive stamens and pistils are not so small in + the lower as in the upper flowers. In the _Viburnum opulus_, on the + other hand, the outer flowers naturally have their organs of + fructification in a rudimentary state, and the corolla is of large + size; under cultivation, the change spreads to the centre, and all the + flowers become affected; thus the well-known Snow-ball bush is + produced. In the Compositae, the so-called doubling of the flowers + consists in the greater development of the corolla of the central + florets, generally accompanied with some degree of sterility; and it + has been observed[801] that the progressive doubling invariably spreads + from the circumference to the centre,--that is, from the ray florets, + which so often include rudimentary organs, to those of the disc. I may + add, as bearing on this subject, that, with Asters, seeds taken from + the florets of the circumference have been found to yield the greatest + number of double flowers.[802] In these several cases we have a natural + tendency in certain parts to become rudimentary, and this under culture + spreads either to, or from, the axis of the plant. It deserves notice, + as showing how the same laws govern the changes which natural species + and artificial varieties undergo, that in a series of species in the + genus Carthamus, one of the Compositae, a tendency in the seeds to the + abortion of the pappus may be traced extending from the circumference + to the centre of the disc: thus, according to A. de Jussieu,[803] the + abortion is only partial in _Carthamus creticus_, but more extended in + _C. lanatus_; for in this species two or three alone of the central + seeds are furnished with a pappus, the surrounding seeds being either + quite naked or furnished with a few hairs; and lastly, in _C. + tinctorius_, even the central seeds are destitute of pappus, and the + abortion is complete. + + With animals and plants under domestication, when an organ disappears, + leaving only a rudiment, the loss has generally been sudden, as with + hornless and tailless breeds; and such cases may be ranked as inherited + monstrosities. But in some few cases the loss has been gradual, and + {317} has been partly effected by selection, as with the rudimentary + combs and wattles of certain fowls. We have also seen that the wings of + some domesticated birds have been slightly reduced by disuse, and the + great reduction of the wings in certain silk-moths, with mere rudiments + left, has probably been aided by disuse. + + With species in a state of nature, rudimentary organs are so extremely + common that scarcely one can be named which is wholly free from a + blemish of this nature. Such organs are generally variable, as several + naturalists have observed; for, being useless, they are not regulated + by natural selection, and they are more or less liable to reversion. + The same rule certainly holds good with parts which have become + rudimentary under domestication. We do not know through what steps + under nature rudimentary organs have passed in being reduced to their + present condition; but we so incessantly see in species of the same + group the finest gradations between an organ in a rudimentary and + perfect state, that we are led to believe that the passage must have + been extremely gradual. It may be doubted whether a change of structure + so abrupt as the sudden loss of an organ would ever be of service to a + species in a state of nature; for the conditions to which all organisms + are closely adapted usually change very slowly. Even if an organ did + suddenly disappear in some one individual by an arrest of development, + intercrossing with the other individuals of the same species would + cause it to reappear in a more or less perfect manner, so that its + final reduction could only be effected by the slow process of continued + disuse or natural selection. It is much more probable that, from + changed habits of life, organs first become of less and less use, and + ultimately superfluous; or their place may be supplied by some other + organ; and then disuse, acting on the offspring through inheritance at + corresponding periods of life, would go on reducing the organ; but as + most organs could be of no use at an early embryonic period, they would + not be affected by disuse; consequently they would be preserved at this + stage of growth, and would remain as rudiments. In addition to the + effects of disuse, the principle of economy of growth, already alluded + to in this chapter, would lead to the still further reduction of all + superfluous parts. With respect to the final and total suppression or + abortion of any organ, another and distinct principle, which will be + discussed in the chapter on pangenesis, probably takes a share in the + work. + + With animals and plants reared by man there is no severe or recurrent + struggle for existence, and the principle of economy will not come into + action. So far, indeed, is this from being the case, that in some + instances organs, which are naturally rudimentary in the + parent-species, become partially redeveloped in the domesticated + descendants. Thus cows, like most other ruminants, properly have four + active and two rudimentary mammae; but in our domesticated animals, the + latter occasionally become considerably developed and yield milk. The + atrophied mammae, which, in male domesticated animals, including man, + have in some rare cases grown to full size and secreted milk, perhaps + offer an analogous case. The hind feet of dogs include rudiments of a + fifth toe, and in certain large breeds these toes, though still + rudimentary, become considerably developed {318} and are furnished with + claws. In the common Hen, the spurs and comb are rudimentary, but in + certain breeds these become, independently of age or disease of the + ovaria, well developed. The stallion has canine teeth, but the mare has + only traces of the alveoli, which, as I am informed by the eminent + veterinary Mr. G. T. Brown, frequently contain minute irregular nodules + of bone. These nodules, however, sometimes become developed into + imperfect teeth, protruding through the gums and coated with enamel; + and occasionally they grow to a third or even a fourth of the length of + the canines in the stallion. With plants I do not know whether the + redevelopment of rudimentary organs occurs more frequently under + culture than under nature. Perhaps the pear-tree may be a case in + point, for when wild it bears thorns, which though useful as a + protection are formed of branches in a rudimentary condition, but, when + the tree is cultivated, the thorns are reconverted into branches. + +Finally, though organs which must be classed as rudimentary frequently +occur in our domesticated animals and cultivated plants, these have +generally been formed suddenly, through an arrest of development. They +usually differ in appearance from the rudiments which so frequently +characterise natural species. In the latter, rudimentary organs have been +slowly formed through continued disuse, acting by inheritance at a +corresponding age, aided by the principle of the economy of growth, all +under the control of natural selection. With domesticated animals, on the +other hand, the principle of economy is far from coming into action, and +their organs, although often slightly reduced by disuse, are not thus +almost obliterated with mere rudiments left. + + * * * * * + + +{319} + +CHAPTER XXV. + +LAWS OF VARIATION, _continued_--CORRELATED VARIABILITY. + + EXPLANATION OF TERM--CORRELATION AS CONNECTED WITH + DEVELOPMENT--MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED + SIZE OF PARTS--CORRELATED VARIATION OF HOMOLOGOUS PARTS--FEATHERED FEET + IN BIRDS ASSUMING THE STRUCTURE OF THE WINGS--CORRELATION BETWEEN THE + HEAD AND THE EXTREMITIES--BETWEEN THE SKIN AND DERMAL + APPENDAGES--BETWEEN THE ORGANS OF SIGHT AND HEARING--CORRELATED + MODIFICATIONS IN THE ORGANS OF PLANTS--CORRELATED + MONSTROSITIES--CORRELATION BETWEEN THE SKULL AND EARS--SKULL AND CREST + OF FEATHERS--SKULL AND HORNS--CORRELATION OF GROWTH COMPLICATED BY THE + ACCUMULATED EFFECTS OF NATURAL SELECTION--COLOUR AS CORRELATED WITH + CONSTITUTIONAL PECULIARITIES. + +All the parts of the organisation are to a certain extent connected or +correlated together; but the connexion may be so slight that it hardly +exists, as with compound animals or the buds on the same tree. Even in the +higher animals various parts are not at all closely related; for one part +may be wholly suppressed or rendered monstrous without any other part of +the body being affected. But in some cases, when one part varies, certain +other parts always, or nearly always, simultaneously vary; they are then +subject to the law of correlated variation. Formerly I used the somewhat +vague expression of correlation of growth, which may be applied to many +large classes of facts. Thus, all the parts of the body are admirably +coordinated for the peculiar habits of life of each organic being, and they +may be said, as the Duke of Argyll insists in his 'Reign of Law,' to be +correlated for this purpose. Again, in large groups of animals certain +structures always co-exist; for instance, a peculiar form of stomach with +teeth of peculiar form, and such structures may in one sense be said to be +correlated. But these cases have no necessary connexion with the law to be +discussed in the present chapter; for we do not know that {320} the initial +or primary variations of the several parts were in any way related; slight +modifications or individual differences may have been preserved, first in +one and then in another part, until the final and perfectly co-adapted +structure was acquired; but to this subject I shall presently recur. Again, +in many groups of animals the males alone are furnished with weapons, or +are ornamented with gay colours; and these characters manifestly stand in +some sort of correlation with the male reproductive organs, for when the +latter are destroyed these characters disappear. But it was shown in the +twelfth chapter that the very same peculiarity may become attached at any +age to either sex, and afterwards be exclusively transmitted by the same +sex at a corresponding age. In these cases we have inheritance limited by, +or correlated with, both sex and age; but we have no reason for supposing +that the original cause of the variation was necessarily connected with the +reproductive organs, or with the age of the affected being. + +In cases of true correlated variation, we are sometimes able to see the +nature of the connexion; but in most cases the bond is hidden from us, and +certainly differs in different cases. We can seldom say which of two +correlated parts first varies, and induces a change in the other; or +whether the two are simultaneously produced by some distinct cause. +Correlated variation is an important subject for us; for when one part is +modified through continued selection, either by man or under nature, other +parts of the organisation will be unavoidably modified. From this +correlation it apparently follows that, with our domesticated animals and +plants, varieties rarely or never differ from each other by some single +character alone. + +One of the simplest cases of correlation is that a modification which +arises during an early stage of growth tends to influence the subsequent +development of the same part, as well as of other and intimately connected +parts. Isidore Geoffroy St. Hilaire states[804] that this may constantly be +observed with monstrosities {321} in the animal kingdom; and +Moquin-Tandon[805] remarks, that, as with plants the axis cannot become +monstrous without in some way affecting the organs subsequently produced +from it, so axial anomalies are almost always accompanied by deviations of +structure in the appended parts. We shall presently see that with +short-muzzled races of the dog certain histological changes in the basal +elements of the bones arrest their development and shorten them, and this +affects the position of the subsequently developed molar teeth. It is +probable that certain modifications in the larvae of insects would affect +the structure of the mature insects. But we must be very careful not to +extend this view too far, for, during the normal course of development, +certain members in the same group of animals are known to pass through an +extraordinary course of change, whilst other and closely allied members +arrive at maturity with little change of structure. + +Another simple case of correlation is that with the increased or decreased +dimensions of the whole body, or of any particular part, certain organs are +increased or diminished in number, or are otherwise modified. Thus +pigeon-fanciers have gone on selecting pouters for length of body, and we +have seen that their vertebrae are generally increased in number, and their +ribs in breadth. Tumblers have been selected for their small bodies, and +their ribs and primary wing-feathers are generally lessened in number. +Fantails have been selected for their large, widely-expanded tails, with +numerous tail-feathers, and the caudal vertebrae are increased in size and +number. Carriers have been selected for length of beak, and their tongues +have become longer, but not in strict accordance with the length of beak. +In this latter breed and in others having large feet, the number of the +scutellae on the toes is greater than in the breeds with small feet. Many +similar cases could be given. In Germany it has been observed that the +period of gestation is longer in large-sized than in small-sized breeds of +cattle. With our highly-improved animals of all kinds the period of +maturity has advanced, both with respect to the full growth of the body and +the period of reproduction; and, in correspondence with this, the teeth are +now developed earlier than formerly, so that, {322} to the surprise of +agriculturists, the ancient rules for judging the age of an animal by the +state of its teeth are no longer trustworthy.[806] + +_Correlated Variation of Homologous Parts._--Parts which are homologous +tend to vary in the same manner; and this is what might have been expected, +for such parts are identical in form and structure during an early period +of embryonic development, and are exposed in the egg or womb to similar +conditions. The symmetry, in most kinds of animals, of the corresponding or +homologous organs on the right and left sides of the body, is the simplest +case in point; but this symmetry sometimes fails, as with rabbits having +only one ear, or stags with one horn, or with many-horned sheep which +sometimes carry an additional horn on one side of their heads. With flowers +which have regular corollas, the petals generally vary in the same manner, +as we see in the same complicated and elegant pattern, on the flowers of +the Chinese pink; but with irregular flowers, though the petals are of +course homologous, this symmetry often fails, as with the varieties of the +_Antirrhinum_ or snapdragon, or that variety of the kidney-bean (_Phaseolus +multiflorus_) which has a white standard-petal. + +In the vertebrata the front and hind limbs are homologous, and they tend to +vary in the same manner, as we see in long and short-legged, or in thick +and thin-legged races of the horse and dog. Isidore Geoffroy[807] has +remarked on the tendency of supernumerary digits in man to appear, not only +on the right and left sides, but on the upper and lower extremities. Meckel +has insisted[808] that, when the muscles of the arm depart in number or +arrangement from their proper type, they almost always imitate those of the +leg; and so conversely the varying muscles of the leg imitate the normal +muscles of the arm. + +In several distinct breeds of the pigeon and fowl, the legs and the two +outer toes are heavily feathered, so that in the trumpeter pigeon they +appear like little wings. In the feather-legged bantam the "boots" or +feathers, which grow from the outside of the leg and generally from the two +outer toes, have, {323} according to the excellent authority of Mr. +Hewitt,[809] been seen to exceed the wing-feathers in length, and in one +case were actually nine and a half inches in length! As Mr. Blyth has +remarked to me, these leg-feathers resemble the primary wing-feathers, and +are totally unlike the fine down which naturally grows on the legs of some +birds, such as grouse and owls. Hence it may be suspected that excess of +food has first given redundancy to the plumage, and then that the law of +homologous variation has led to the development of feathers on the legs, in +a position corresponding with those on the wing, namely, on the outside of +the tarsi and toes. I am strengthened in this belief by the following +curious case of correlation, which for a long time seemed to me utterly +inexplicable, namely, that in pigeons of any breed, if the legs are +feathered, the two outer toes are partially connected by skin. These two +outer toes correspond with our third and fourth toes. Now, in the wing of +the pigeon or any other bird, the first and fifth digits are wholly +aborted; the second is rudimentary and carries the so-called +"bastard-wing;" whilst the third and fourth digits are completely united +and enclosed by skin, together forming the extremity of the wing. So that +in feather-footed pigeons, not only does the exterior surface support a row +of long feathers, like wing-feathers, but the very same digits which in the +wing are completely united by skin become partially united by skin in the +feet; and thus by the law of the correlated variation of homologous parts +we can understand the curious connection of feathered legs and membrane +between the two outer toes. + +Andrew Knight[810] has remarked that the face or head and the limbs vary +together in general proportions. Compare, for instance, the head and limbs +of a dray and race-horse, or of a greyhound and mastiff. What a monster a +greyhound would appear with the head of a mastiff! The _modern_ bulldog, +however, has fine limbs, but this is a recently-selected character. From +the measurements given in the sixth chapter, we clearly see that in all the +breeds of the pigeon the length of the beak and the size of the feet are +correlated. The view which, as before explained, seems the most probable +is, that disuse in all cases tends {324} to diminish the feet, the beak +becoming at the same time through correlation shorter; but that in those +few breeds in which length of beak has been a selected point, the feet, +notwithstanding disuse, have through correlation increased in size. + +With the increased length of the beak in pigeons, not only the tongue +increases in length, but likewise the orifice of the nostrils. But the +increased length of the orifice of the nostrils perhaps stands in closer +correlation with the development of the corrugated skin or wattle at the +base of the beak; for when there is much wattle round the eyes, the eyelids +are greatly increased or even doubled in length. + +There is apparently some correlation even in colour between the head and +the extremities. Thus with horses a large white star or blaze on the +forehead is generally accompanied by white feet.[811] With white rabbits +and cattle, dark marks often co-exist on the tips of the ears and on the +feet. In black and tan dogs of different breeds, tan-coloured spots over +the eyes and tan-coloured feet almost invariably go together. These latter +cases of connected colouring may be due either to reversion or to analogous +variation,--subjects to which we shall hereafter return,--but this does not +necessarily determine the question of their original correlation. If those +naturalists are correct who maintain that the jaw-bones are homologous with +the limb-bones, then we can understand why the head and limbs tend to vary +together in shape and even in colour; but several highly competent judges +dispute the correctness of this view. + +The lopping forwards and downwards of the immense ears of fancy rabbits is +in part due to the disuse of the muscles, and in part to the weight and +length of the ears, which have been increased by selection during many +generations. Now, with the increased size and changed direction of the +ears, not only has the bony auditory meatus become changed in outline, +direction, and greatly in size, but the whole skull has been slightly +modified. This could be clearly seen in "half-lops"--that is, in rabbits +with one ear alone lopping forward--for the opposite sides of their skulls +were not strictly symmetrical. This seems to me a curious instance of +correlation, between hard {325} bones and organs so soft and flexible, as +well as so unimportant under a physiological point of view, as the external +ears. The result no doubt is largely due to mere mechanical action, that +is, to the weight of the ears, on the same principle that the skull of a +human infant is easily modified by pressure. + +The skin and the appendages of hair, feathers, hoofs, horns, and teeth, are +homologous over the whole body. Every one knows that the colour of the skin +and that of the hair usually vary together; so that Virgil advises the +shepherd to look whether the mouth and tongue of the ram are black, lest +the lambs should not be purely white. With poultry and certain ducks we +have seen that the colour of the plumage stands in some connexion with the +colour of the shell of the egg,--that is, with the mucous membrane which +secretes the shell. The colour of the skin and hair, and the odour emitted +by the glands of the skin, are said[812] to be connected, even in the same +race of men. Generally the hair varies in the same way all over the body in +length, fineness, and curliness. The same rule holds good with feathers, as +we see with the laced and frizzled breeds both of fowls and pigeons. In the +common cock the feathers on the neck and loins are always of a particular +shape, called hackles: now in the Polish breed, both sexes are +characterised by a tuft of feathers on the head; but through correlation +these feathers in the male always assume the form of hackles. The wing and +tail-feathers, though arising from parts not homologous, vary in length +together; so that long or short winged pigeons generally have long or short +tails. The case of the Jacobin-pigeon is more curious, for the wing and +tail feathers are remarkably long; and this apparently has arisen in +correlation with the elongated and reversed feathers on the back of the +neck, which form the hood. + +The hoofs and hair are homologous appendages; and a careful observer, +namely Azara,[813] states that in Paraguay horses of various colours are +often born with their hair curled and twisted like that on the head of a +negro. This peculiarity is strongly inherited. But what is remarkable is +that the hoofs of these horses "are absolutely like those of a mule." The +hair also of the mane and tail is invariably much shorter than usual, being +only from four {326} to twelve inches in length; so that curliness and +shortness of the hair are here, as with the negro, apparently correlated. + +With respect to the horns of sheep, Youatt[814] remarks that "multiplicity +of horns is not found in any breed of much value: it is generally +accompanied by great length and coarseness of the fleece." Several tropical +breeds of sheep, which are clothed with hair instead of wool, have horns +almost like those of a goat. Sturm[815] expressly declares that in +different races the more the wool is curled the more the horns are spirally +twisted. We have seen in the third chapter, where other analogous facts +have been given, that the parent of the Mauchamp breed, so famous for its +fleece, had peculiarly shaped horns. The inhabitants of Angora assert[816] +that "only the white goats which have horns wear the fleece in the long +curly locks that are so much admired; those which are not horned having a +comparatively close coat." From these cases we may conclude that the hair +or wool and the horns vary in a correlated manner. Those who have tried +hydropathy are aware that the frequent application of cold water stimulates +the skin; and whatever stimulates the skin tends to increase the growth of +the hair, as is well shown in the abnormal growth of hair near old inflamed +surfaces. Now, Professor Low[817] is convinced that with the different +races of British cattle thick skin and long hair depend on the humidity of +the climate which they inhabit. We can thus see how a humid climate might +act on the horns--in the first place directly on the skin and hair, and +secondly by correlation on the horns. The presence or absence of horns, +moreover, both in the case of sheep and cattle, acts, as will presently be +shown, by some sort of correlation on the skull. + +With respect to hair and teeth, Mr. Yarrell[818] found many of the teeth +deficient in three hairless "_Aegyptian_" dogs, and in a hairless terrier. +The incisors, canines, and premolars suffered most, but in one case all the +teeth, except the large tubercular molar on each side, were deficient. With +man several striking cases have been recorded[819] of inherited baldness +with {327} inherited deficiency, either complete or partial, of the teeth. +We see the same connexion in those rare cases in which the hair has been +renewed in old age, for this has "usually been accompanied by a renewal of +the teeth." I have remarked in a former part of this volume that the great +reduction in the size of the tusks in domestic boars probably stands in +close relation with their diminished bristles, due to a certain amount of +protection; and that the reappearance of the tusks in boars, which have +become feral and are fully exposed to the weather, probably depends on the +reappearance of the bristles. I may add, though not strictly connected with +our present point, that an agriculturist[820] asserts that "pigs with +little hair on their bodies are most liable to lose their tails, showing a +weakness of the tegumental structure. It may be prevented by crossing with +a more hairy breed." + +In the previous cases deficient hair, and teeth deficient in number or +size, are apparently connected. In the following cases abnormally redundant +hair, and teeth either deficient or redundant, are likewise connected. Mr. +Crawfurd[821] saw at the Burmese Court a man, thirty years old, with his +whole body, except the hands and feet, covered with straight silky hair, +which on the shoulders and spine was five inches in length. At birth the +ears alone were covered. He did not arrive at puberty, or shed his milk +teeth, until twenty years old; and at this period he acquired five teeth in +the upper jaw, namely four incisors and one canine, and four incisor teeth +in the lower jaw; all the teeth were small. This man had a daughter, who +was born with hair within her ears; and the hair soon extended over her +body. When Captain Yule[822] visited the Court, he found this girl grown +up; and she presented a strange appearance with even her nose densely +covered with soft hair. Like her father, she was furnished with incisor +teeth alone. The King had with difficulty bribed a man to marry her, and of +her two children, one, a boy fourteen months old, had hair growing out of +his ears, with a beard and moustache. This strange peculiarity had, +therefore, been inherited for three generations, with the molar teeth +deficient in the grandfather and mother; whether {328} these teeth would +likewise fail in the infant could not be told. Here is another case +communicated to me by Mr. Wallace on the authority of Dr. Purland, a +dentist: Julia Pastrana, a Spanish dancer, was a remarkably fine woman, but +she had a thick masculine beard and a hairy forehead; she was photographed, +and her stuffed skin was exhibited as a show; but what concerns us is, that +she had in both the upper and lower jaw an irregular double set of teeth, +one row being placed within the other, of which Dr. Purland took a cast. +From the redundancy of the teeth her mouth projected, and her face had a +gorilla-like appearance. These cases and those of the hairless dogs +forcibly call to mind the fact, that the two orders of mammals--namely, the +Edentata and Cetacea--which are the most abnormal in their dermal covering, +are likewise the most abnormal either by deficiency or redundancy of teeth. + +The organs of sight and hearing are generally admitted to be homologous, +both with each other and with the various dermal appendages; hence these +parts are liable to be abnormally affected in conjunction. Mr. White Cowper +says "that in all cases of double microphthalmia brought under his notice +he has at the same time met with defective development of the dental +system." Certain forms of blindness seem to be associated with the colour +of the hair; a man with black hair and a woman with light-coloured hair, +both of sound constitution, married and had nine children, all of whom were +born blind; of these children, five "with dark hair and brown iris were +afflicted with amaurosis; the four others, with light-coloured hair and +blue iris, had amaurosis and cataract conjoined." Several cases could be +given, showing that some relation exists between various affections of the +eyes and ears; thus Liebreich states that out of 241 deaf-mutes in Berlin, +no less than fourteen suffered from the rare disease called pigmentary +retinitis. Mr. White Cowper and Dr. Earle have remarked that inability to +distinguish different colours, or colour-blindness, "is often associated +with a corresponding inability to distinguish musical sounds."[823] + +{329} + +Here is a more curious case: white cats, if they have blue eyes, are almost +always deaf. I formerly thought that the rule was invariable, but I have +heard of a few authentic exceptions. The first two notices were published +in 1829, and relate to English and Persian cats: of the latter, the Rev. +W. T. Bree possessed a female, and he states "that of the offspring +produced at one and the same birth, such as, like the mother, were entirely +white (with blue eyes) were, like her, invariably deaf; while those that +had the least speck of colour on their fur, as invariably possessed the +usual faculty of hearing."[824] The Rev. W. Darwin Fox informs me that he +has seen more than a dozen instances of this correlation in English, +Persian, and Danish cats; but he adds "that, if one eye, as I have several +times observed, be not blue, the cat hears. On the other hand, I have never +seen a white cat with eyes of the common colour that was deaf." In France +Dr. Sichel[825] has observed during twenty years similar facts; he adds the +remarkable case of the iris beginning, at the end of four months, to grow +dark-coloured, and then the cat first began to hear. + +This case of correlation in cats has struck many persons as marvellous. +There is nothing unusual in the relation between blue eyes and white fur; +and we have already seen that the organs of sight and hearing are often +simultaneously affected. In the present instance the cause probably lies in +a slight arrest of development in the nervous system in connection with the +sense-organs. Kittens during the first nine days, whilst their eyes are +closed, appear to be completely deaf; I have made a great clanging noise +with a poker and shovel close to their heads, both when they were asleep +and awake, without producing any effect. The trial must not be made by +shouting close to their ears, for they are, even when asleep, extremely +sensitive to a breath of air. Now, as long as the eyes continue closed, the +iris is no doubt blue, for in all the kittens which I have seen this colour +remains for some time after the eyelids open. Hence, if we suppose the +development of the organs of sight and hearing to be arrested at the stage +of the closed eyelids, the eyes would {330} remain permanently blue and the +ears would be incapable of perceiving sound; and we should thus understand +this curious case. As, however, the colour of the fur is determined long +before birth, and as the blueness of the eyes and the whiteness of the fur +are obviously connected, we must believe that some primary cause acts at an +early period. + +The instances of correlated variability hitherto given have been chiefly +drawn from the animal kingdom, and we will now turn to plants. Leaves, +sepals, petals, stamens, and pistils are all homologous. In double flowers +we see that the stamens and pistils vary in the same manner, and assume the +form and colour of the petals. In the double columbine (_Aquilegia +vulgaris_), the successive whorls of stamens are converted into +cornucopias, which are enclosed within each other and resemble the petals. +In hose-and-hose flowers the sepals mock the petals. In some cases the +flowers and leaves vary together in tint: in all the varieties of the +common pea, which have purple flowers, a purple mark may be seen on the +stipules. In other cases the leaves and fruit and seeds vary together in +colour, as in a curious pale-leaved variety of the sycamore, which has +recently been described in France,[826] and as in the purple-leaved hazel, +in which the leaves, the husk of the nut, and the pellicle round the kernel +are all coloured purple.[827] Pomologists can predict to a certain extent, +from the size and appearance of the leaves of their seedlings, the probable +nature of the fruit; for, as Van Mons remarks,[828] variations in the +leaves are generally accompanied by some modification in the flower, and +consequently in the fruit. In the Serpent melon, which has a narrow +tortuous fruit above a yard in length, the stem of the plant, the peduncle +of the female flower, and the middle lobe of the leaf, are all elongated in +a remarkable manner. On the other hand, several varieties of Cucurbita, +which have dwarfed stems, all produce, as Naudin remarks with surprise, +leaves of the same peculiar shape. Mr. G. Maw informs me that all the +varieties of the scarlet Pelargoniums which have contracted or imperfect +leaves have contracted flowers: the difference between {331} "Brilliant" +and its parent "Tom Thumb" is a good instance of this. It may be suspected +that the curious case described by Risso,[829] of a variety of the Orange +which produces on the young shoots rounded leaves with winged petioles, and +afterwards elongated leaves on long but wingless petioles, is connected +with the remarkable change in form and nature which the fruit undergoes +during its development. + +In the following instance we have the colour and form of the petals +apparently correlated, and both dependent on the nature of the season. An +observer, skilled in the subject, writes,[830] "I noticed, during the year +1842, that every Dahlia, of which the colour had any tendency to scarlet, +was deeply notched--indeed to so great an extent as to give the petals the +appearance of a saw; the indentures were, in some instances, more than a +quarter of an inch deep." Again, Dahlias which have their petals tipped +with a different colour from the rest are very inconstant, and during +certain years some, or even all the flowers, become uniformly coloured; and +it has been observed with several varieties,[831] that when this happens +the petals grow much elongated and lose their proper shape. This, however, +may be due to reversion, both in colour and form, to the aboriginal +species. + + * * * * * + +In this discussion on correlation, we have hitherto treated of cases in +which we can partly understand the bond of connexion; but I will now give +cases in which we cannot even conjecture, or can only very obscurely see, +what is the nature of the bond. Isidore Geoffroy St. Hilaire, in his work +on Monstrosities, insists,[832] "que certaines anomalies coexistent +rarement entr'elles, d'autres frequemment, d'autres enfin presque +constamment, malgre la difference tres-grande de leur nature, et +quoiqu'elles puissent paraitre _completement independantes_ les unes des +autres." We see something analogous in certain diseases: thus I hear from +Mr. Paget that in a rare affection of the {332} renal capsules (of which +the functions are unknown), the skin becomes bronzed; and in hereditary +syphilis, both the milk and the second teeth assume a peculiar and +characteristic form. Professor Rolleston, also, informs me that the incisor +teeth are sometimes furnished with a vascular rim in correlation with +intra-pulmonary deposition of tubercles. In other cases of phthisis and of +cyanosis the nails and finger-ends become clubbed like acorns. I believe +that no explanation has been offered of these and of many other cases of +correlated disease. + +What can be more curious and less intelligible than the fact previously +given, on the authority of Mr. Tegetmeier, that young pigeons of all +breeds, which when mature have white, yellow, silver-blue, or dun-coloured +plumage, come out of the egg almost naked; whereas pigeons of other colours +when first born are clothed with plenty of down? White Pea-fowls, as has +been observed both in England and France,[833] and as I have myself seen, +are inferior in size to the common coloured kind; and this cannot be +accounted for by the belief that albinism is always accompanied by +constitutional weakness; for white or albino moles are generally larger +than the common kind. + +To turn to more important characters: the niata cattle of the Pampas are +remarkable from their short foreheads, upturned muzzles, and curved lower +jaws. In the skull the nasal and premaxillary bones are much shortened, the +maxillaries are excluded from any junction with the nasals, and all the +bones are slightly modified, even to the plane of the occiput. From the +analogical case of the dog, hereafter to be given, it is probable that the +shortening of the nasal and adjoining bones is the proximate cause of the +other modifications in the skull, including the upward curvature of the +lower jaw, though we cannot follow out the steps by which these changes +have been effected. + +Polish fowls have a large tuft of feathers on their heads; and their skulls +are perforated by numerous holes, so that a pin can be driven into the +brain without touching any bone. That this deficiency of bone is in some +way connected with the tuft of feathers is clear from tufted ducks and +geese likewise having {333} perforated skulls. The case would probably be +considered by some authors as one of balancement or compensation. In the +chapter on Fowls, I have shown that with Polish fowls the tuft of feathers +was probably at first small; by continued selection it became larger, and +then rested on a fleshy or fibrous mass; and finally, as it became still +larger, the skull itself became more and more protuberant until it acquired +its present extraordinary structure. Through correlation with the +protuberance of the skull, the shape and even the relative connexion of the +premaxillary and nasal bones, the shape of the orifice of the nostrils, the +breadth of the frontal bone, the shape of the post-lateral processes of the +frontal and squamosal bones, and the direction of the bony cavity of the +ear, have all been modified. The internal configuration of the skull and +the whole shape of the brain have likewise been altered in a truly +marvellous manner. + +After this case of the Polish fowl it would be superfluous to do more than +refer to the details previously given on the manner in which the changed +form of the comb, in various breeds of the fowl, has affected the skull, +causing by correlation crests, protuberances, and depressions on its +surface. + +With our cattle and sheep the horns stand in close connexion with the size +of the skull, and with the shape of the frontal bones; thus Cline[834] +found that the skull of a horned ram weighed five times as much as that of +a hornless ram of the same age. When cattle become hornless, the frontal +bones are "materially diminished in breadth towards the poll;" and the +cavities between the bony plates "are not so deep, nor do they extend +beyond the frontals."[835] + + * * * * * + +It may be well here to pause and observe how the effects of correlated +variability, of the increased use of parts, and of the accumulation through +natural selection of so-called spontaneous variations, are in many cases +inextricably commingled. We may borrow an illustration from Mr. Herbert +Spencer, who remarks that, when the Irish elk acquired its gigantic horns, +weighing above one hundred pounds, numerous co-ordinated {334} changes of +structure would have been indispensable,--namely, a thickened skull to +carry the horns; strengthened cervical vertebrae, with strengthened +ligaments; enlarged dorsal vertebrae to support the neck, with powerful +fore-legs and feet; all these parts being supplied with proper muscles, +blood-vessels, and nerves. How then could these admirably co-ordinated +modifications of structure have been acquired? According to the doctrine +which I maintain, the horns of the male elk were slowly gained through +sexual selection,--that is, by the best-armed males conquering the +worse-armed, and leaving a greater number of descendants. But it is not at +all necessary that the several parts of the body should have simultaneously +varied. Each stag presents individual differences, and in the same district +those which had slightly heavier horns, or stronger necks, or stronger +bodies, or were the most courageous, would secure the greater number of +does, and consequently leave a greater number of offspring. The offspring +would inherit, in a greater or less degree, these same qualities, would +occasionally intercross with each other, or with other individuals varying +in some favourable manner; and of their offspring, those which were the +best endowed in any respect would continue multiplying; and so onwards, +always progressing, sometimes in one direction, and sometimes in another, +towards the present excellently co-ordinated structure of the male elk. To +make this clear, let us reflect on the probable steps, as shown in the +twentieth chapter, by which our race and dray-horses have arrived at their +present state of excellence; if we could view the whole series of +intermediate forms between one of these animals and an early unimproved +progenitor, we should behold a vast number of animals, not equally improved +in each generation throughout their entire structure, but sometimes a +little more in one point, and sometimes in another, yet on the whole +gradually approaching in character to our present race or dray-horses, +which are so admirably fitted in the one case for fleetness and in the +other for draught. + +Although natural selection would thus[836] tend to give to the {335} male +elk its present structure, yet it is probable that the inherited influence +of use has played an equal or more important part. As the horns gradually +increased in weight, the muscles of the neck, with the bones to which they +are attached, would increase in size and strength; and these parts would +react on the body and legs. Nor must we overlook the fact that certain +parts of the skull and the extremities would, judging by analogy, tend from +the first to vary in a correlated manner. The increased weight of the horns +would also act directly on the skull, in the same manner as, when one bone +is removed in the leg of a dog, the other bone, which has to carry the +whole weight of the body, increases in thickness. But from the facts given +with respect to horned and hornless cattle, it is probable that the horns +and skull would immediately act on each other through the principle of +correlation. Lastly, the growth and subsequent wear and tear of the +augmented muscles and bones would require an increased supply of blood, and +consequently an increased supply of food; and this again would require +increased powers of mastication, digestion, respiration, and excretion. + +_Colour as Correlated with Constitutional Peculiarities._ + +It is an old belief that with man there is a connexion between complexion +and constitution; and I find that some of the best authorities believe in +this to the present day.[837] Thus Dr. Beddoe by his tables shows[838] that +a relation exists between liability to consumption and the colour of the +hair, eyes, and skin. It has been affirmed[839] that, in the French army +which invaded Russia, soldiers having a dark complexion, from the {336} +southern parts of Europe, withstood the intense cold better than those with +lighter complexions from the north; but no doubt such statements are liable +to error. + +In the second chapter on Selection I have given several cases proving that +with animals and plants differences in colour are correlated with +constitutional differences, as shown by greater or less immunity from +certain diseases, from the attacks of parasitic plants and animals, from +burning by the sun, and from the action of certain poisons. When all the +individuals of any one variety possess an immunity of this nature, we +cannot feel sure that it stands in any sort of correlation with their +colour; but when several varieties of the same species, which are similarly +coloured, are thus characterised, whilst other coloured varieties are not +thus favoured, we must believe in the existence of a correlation of this +kind. Thus in the United States purple-fruited plums of many kinds are far +more affected by a certain disease than green or yellow-fruited varieties. +On the other hand, yellow-fleshed peaches of various kinds suffer from +another disease much more than the white-fleshed varieties. In the +Mauritius red sugar-canes are much less affected by a particular disease +than the white canes. White onions and verbenas are the most liable to +mildew; and in Spain the green-fruited grapes suffered from the +vine-disease more than other coloured varieties. Dark-coloured pelargoniums +and verbenas are more scorched by the sun than varieties of other colours. +Red wheats are believed to be hardier than white; whilst red-flowered +hyacinths were more injured during one particular winter in Holland than +other coloured varieties. With animals, white terriers suffer most from the +distemper, white chickens from a parasitic worm in their tracheae, white +pigs from scorching by the sun, and white cattle from flies; but the +caterpillars of the silk-moth which yield white cocoons suffered in France +less from the deadly parasitic fungus than those producing yellow silk. + +The cases of immunity from the action of certain vegetable poisons, in +connexion with colour, are more interesting, and are at present wholly +inexplicable. I have already given a remarkable instance, on the authority +of Professor Wyman, of all the hogs, excepting those of a black colour, +suffering severely in Virginia from eating the root of the _Lachnanthes +tinctoria_. {337} According to Spinola and others,[840] buckwheat +(_Polygonum fagopyrum_), when in flower, is highly injurious to white or +white-spotted pigs, if they are exposed to the heat of the sun, but is +quite innocuous to black pigs. By two accounts, the _Hypericum crispum_ in +Sicily is poisonous to white sheep alone; their heads swell, their wool +falls off, and they often die; but this plant, according to Lecce, is +poisonous only when it grows in swamps; nor is this improbable, as we know +how readily the poisonous principle in plants is influenced by the +conditions under which they grow. + +Three accounts have been published in Eastern Prussia, of white and +white-spotted horses being greatly injured by eating mildewed and +honeydewed vetches; every spot of skin bearing white hairs becoming +inflamed and gangrenous. The Rev. J. Rodwell informs me that his father +turned out about fifteen cart-horses into a field of tares which in parts +swarmed with black aphides, and which no doubt were honeydewed, and +probably mildewed; the horses, with two exceptions, were chesnuts and bays +with white marks on their faces and pasterns, and the white parts alone +swelled and became angry scabs. The two bay horses with no white marks +entirely escaped all injury. In Guernsey, when horses eat fools' parsley +(_Aethusa cynapium_) they are sometimes violently purged; and this plant +"has a peculiar effect on the nose and lips, causing deep cracks and +ulcers, particularly on horses with white muzzles."[841] With cattle, +independently of the action of any poison, cases have been published by +Youatt and Erdt of cutaneous diseases with much constitutional disturbance +(in one instance after exposure to a hot sun) affecting every single point +which bore a white hair, but completely passing over other parts of the +body. Similar cases have been observed with horses.[842] + +We thus see that not only do those parts of the skin which bear white hair +differ in a remarkable manner from those bearing {338} hair of any other +colour, but that in addition some great, constitutional difference must +stand in correlation with the colour of the hair; for in the +above-mentioned cases, vegetable poisons caused fever, swelling of the +head, as well as other symptoms, and even death, to all the white or +white-spotted animals. + + * * * * * + + +{339} + +CHAPTER XXVI. + +LAWS OF VARIATION, _continued_--SUMMARY. + + ON THE AFFINITY AND COHESION OF HOMOLOGOUS PARTS--ON THE VARIABILITY OF + MULTIPLE AND HOMOLOGOUS PARTS--COMPENSATION OF GROWTH--MECHANICAL + PRESSURE--RELATIVE POSITION OF FLOWERS WITH RESPECT TO THE AXIS OF THE + PLANT, AND OF SEEDS IN THE CAPSULE, AS INDUCING VARIATION--ANALOGOUS OR + PARALLEL VARIETIES--SUMMARY OF THE THREE LAST CHAPTERS. + +_On the Affinity of Homologous Parts._--This law was first generalised by +Geoffroy Saint Hilaire, under the expression of _La loi de l'affinite de +soi pour soi_. It has been fully discussed and illustrated by his son, +Isidore Geoffroy, with respect to monsters in the animal kingdom,[843] and +by Moquin-Tandon, with respect to monstrous plants. When similar or +homologous parts, whether belonging to the same embryo or to two distinct +embryos, are brought during an early stage of development into contact, +they often blend into a single part or organ; and this complete fusion +indicates some mutual affinity between the parts, otherwise they would +simply cohere. Whether any power exists which tends to bring homologous +parts into contact seems more doubtful. The tendency to complete fusion is +not a rare or exceptional fact. It is exhibited in the most striking manner +by double monsters. Nothing can be more extraordinary than the manner, as +shown in various published plates, in which the corresponding parts of two +embryos become intimately fused together. This is perhaps best seen in +monsters with two heads, which are united, summit to summit, or face to +face, or, Janus-like, back to back, or obliquely side to side. In one +instance of two heads united almost face to face, but a little obliquely, +four ears were developed, and on one side a perfect face, which was +manifestly formed by the union of two {340} half-faces. Whenever two bodies +or two heads are united, each bone, muscle, vessel, and nerve on the line +of junction seems to seek out its fellow, and becomes completely fused with +it. Lereboullet,[844] who carefully studied the development of double +monsters in fishes, observed in fifteen instances the steps by which two +heads gradually became fused into one. In this and other such cases, no +one, I presume, supposes that the two already formed heads actually blend +together, but that the corresponding parts of each head grow into one +during the further progress of development, accompanied as it always is +with incessant absorption and renovation. Double monsters were formerly +thought to be formed by the union of two originally distinct embryos +developed upon distinct vitelli; but now it is admitted that "their +production is due to the spontaneous divarication of the embryonic mass +into two halves;"[845] this, however, is effected by different methods. But +the belief that double monsters originate from the division of one germ, +does not necessarily affect the question of subsequent fusion, or render +less true the law of the affinity of homologous parts. + +The cautious and sagacious J. Mueller,[846] when speaking of Janus-like +monsters, says, that "without the supposition that some kind of affinity or +attraction is exerted between corresponding parts, unions of this kind are +inexplicable." On the other hand, Vrolik, and he is followed by others, +disputes this conclusion, and argues from the existence of a whole series +of monstrosities, graduating from a perfectly double monster to a mere +rudiment of an additional digit, that "an excess of formative power" is the +cause and origin of every monstrous duplicity. That there are two distinct +classes of cases, and that parts may be doubled independently of the +existence of two embryos, is certain; for a single embryo, or even a single +adult animal, may produce doubled organs. Thus Valentin, as quoted by +Vrolik, injured the caudal extremity of an embryo, and three days +afterwards it produced rudiments of a double pelvis and of double hind +limbs. {341} Hunter and others have observed lizards with their tails +reproduced and doubled. When Bonnet divided longitudinally the foot of the +salamander, several additional digits were occasionally formed. But neither +these cases, nor the perfect series from a double monster to an additional +digit, seem to me opposed to the belief that corresponding parts have a +mutual affinity, and consequently tend to fuse together. A part may be +doubled and remain in this state, or the two parts thus formed may +afterwards through the law of affinity become blended; or two homologous +parts in two separate embryos may, through the same principle, unite and +form a single part. + +The law of the affinity and fusion of similar parts applies to the +homologous organs of the same individual animal, as well as to double +monsters. Isidore Geoffroy gives a number of instances of two or more +digits, of two whole legs, of two kidneys, and of several teeth becoming +symmetrically fused together in a more or less perfect manner. Even the two +eyes have been known to unite into a single eye, forming a cyclopean +monster, as have the two ears, though naturally standing so far apart. As +Geoffroy remarks, these facts illustrate in an admirable manner the normal +fusion of various organs which during an early embryonic period are double, +but which afterwards always unite into a single median organ. Organs of +this nature are generally found in a permanently double condition in other +members of the same class. These cases of normal fusion appear to me to +afford the strongest support in favour of the present law. Adjoining parts +which are not homologous sometimes cohere; but this cohesion appears to +result from mere juxtaposition, and not from mutual affinity. + +In the vegetable kingdom Moquin-Tandon[847] gives a long list of cases, +showing how frequently homologous parts, such as leaves, petals, stamens, +and pistils, as well as aggregates of homologous parts, such as buds, +flowers, and fruit, become blended into each other with perfect symmetry. +It is interesting to examine a compound flower of this nature, formed of +exactly double the proper number of sepals, petals, stamens, and pistils, +with each whorl of organs circular, and with no trace left of the {342} +process of fusion. The tendency in homologous parts to unite during their +early development, Moquin-Tandon considers as one of the most striking laws +governing the production of monsters. It apparently explains a multitude of +cases, both in the animal and vegetable kingdoms; it throws a clear light +on many normal structures which have evidently been formed by the union of +originally distinct parts, and it possesses, as we shall see in a future +chapter, much theoretical interest. + + * * * * * + +_On the Variability of Multiple and Homologous Parts._--Isidore +Geoffroy[848] insists that, when any part or organ is repeated many times +in the same animal, it is particularly liable to vary both in number and +structure. With respect to number, the proposition may, I think, be +considered as fully established; but the evidence is chiefly derived from +organic beings living under their natural conditions, with which we are not +here concerned. When the vertebrae, or teeth, or rays in the fins of +fishes, or feathers in the tails of birds, or petals, stamens, pistils, and +seeds in plants, are very numerous, the number is generally variable. The +explanation of this simple fact is by no means obvious. With respect to the +variability in structure of multiple parts, the evidence is not so +decisive; but the fact, as far as it may be trusted, probably depends on +multiple parts being of less physiological importance than single parts; +consequently their perfect standard of structure has been less rigorously +enforced by natural selection. + + * * * * * + +_Compensation of Growth, or Balancement._--This law, as applied to natural +species, was propounded by Goethe and Geoffroy St. Hilaire at nearly the +same time. It implies that, when much organised matter is used in building +up some one part, other parts are starved and become reduced. Several +authors, especially botanists, believe in this law; others reject it. As +far as I can judge, it occasionally holds good; but its importance has +probably been exaggerated. It is scarcely possible to distinguish between +the supposed effects of such compensation of growth, and the effects of +long-continued selection, which {343} may at the same time lead to the +augmentation of one part and the diminution of another. There can be no +doubt that an organ may be greatly increased without any corresponding +diminution in the adjoining parts. To recur to our former illustration of +the Irish elk, it may be asked what part has suffered in consequence of the +immense development of the horns? + +It has already been observed that the struggle for existence does not bear +hard on our domesticated productions; consequently the principle of economy +of growth will seldom affect them, and we ought not to expect to find +frequent evidence of compensation. We have, however, some such cases. +Moquin-Tandon describes a monstrous bean,[849] in which the stipules were +enormously developed, and the leaflets apparently in consequence completely +aborted; this case is interesting, as it represents the natural condition +of _Lathyrus aphaca_, with its stipules of great size, and its leaves +reduced to mere threads, which act as tendrils. De Candolle[850] has +remarked that the varieties of _Raphanus sativus_ which have small roots +yield numerous seed, valuable from containing oil, whilst those with large +roots are not productive in this latter respect; and so it is with +_Brassica asperifolia_. The varieties of the potato which produce tubers +very early in the season rarely bear flowers; but Andrew Knight,[851] by +checking the growth of the tubers, forced the plants to flower. The +varieties of _Cucurbita pepo_ which produce large fruit yield, according to +Naudin, few in number; whilst those producing small fruit yield a vast +number. Lastly, I have endeavoured to show in the eighteenth chapter that +with many cultivated plants unnatural treatment checks the full and proper +action of the reproductive organs, and they are thus rendered more or less +sterile; consequently, in the way of compensation, the fruit becomes +greatly enlarged, and, in double flowers, the petals are greatly increased +in number. + +With animals, it has been found difficult to produce cows which should +first yield much milk, and afterwards be capable of {344} fattening well. +With fowls which have large topknots and beards the comb and wattles are +generally much reduced in size. Perhaps the entire absence of the oil-gland +in fantail pigeons may be connected with the great development of their +tails. + + * * * * * + +_Mechanical Pressure as a Cause of Modifications._--In some few cases there +is reason to believe that mere mechanical pressure has affected certain +structures. Every one knows that savages alter the shape of their infants' +skulls by pressure at an early age; but there is no reason to believe that +the result is ever inherited. Nevertheless Vrolik and Weber[852] maintain +that the shape of the human head is influenced by the shape of the mother's +pelvis. The kidneys in different birds differ much in form, and St. +Ange[853] believes that this is determined by the form of the pelvis, which +again, no doubt, stands in close relation with their various habits of +locomotion. In snakes, the viscera are curiously displaced, in comparison +with their position in other vertebrates; and this has been attributed by +some authors to the elongation of their bodies; but here, as in so many +previous cases, it is impossible to disentangle any direct result of this +kind from that consequent on natural selection. Godron has argued[854] that +the normal abortion of the spur on the inner side of the flower in +Corydalis, is caused by the buds being closely pressed at a very early +period of growth, whilst under ground, against each other and against the +stem. Some botanists believe that the singular difference in the shape both +of the seed and corolla, in the interior and exterior florets in certain +compositous and umbelliferous plants, is due to the pressure to which the +inner florets are subjected; but this conclusion is doubtful. + +The facts just given do not relate to domesticated productions, and +therefore do not strictly concern us. But here is a more appropriate case: +H. Mueller[855] has shown that in {345} short-faced races of the dog some +of the molar teeth are placed in a slightly different position from that +which they occupy in other dogs, especially in those having elongated +muzzles; and as he remarks, any inherited change in the arrangement of the +teeth deserves notice, considering their classificatory importance. This +difference in position is due to the shortening of certain facial bones, +and the consequent want of space; and the shortening results from a +peculiar and abnormal state of the basal cartilages of the bones. + +_Relative Position of Flowers with respect to the Axis, and of Seeds in the +Capsule, as inducing Variation._ + + In the thirteenth chapter various peloric flowers were described, and + their production was shown to be due either to arrested development, or + to reversion to a primordial condition. Moquin-Tandon has remarked that + the flowers which stand on the summit of the main stem or of a lateral + branch are more liable to become peloric than those on the sides;[856] + and he adduces, amongst other instances, that of _Teucrium + campanulatum_. In another Labiate plant grown by me, viz. the + _Galeobdolon luteum_, the peloric flowers were always produced on the + summit of the stem, where flowers are not usually borne. In + Pelargonium, a _single_ flower in the truss is frequently peloric, and + when this occurs I have during several years invariably observed it to + be the central flower. This is of such frequent occurrence that one + observer[857] gives the names of ten varieties flowering at the same + time, in every one of which the central flower was peloric. + Occasionally more than one flower in the truss is peloric, and then of + course the additional ones must be lateral. These flowers are + interesting as showing how the whole structure is correlated. In the + common Pelargonium the upper sepal is produced into a nectary which + coheres with the flower-peduncle; the two upper petals differ a little + in shape from the three lower ones, and are marked with dark shades of + colour; the stamens are graduated in length and upturned. In the + peloric flowers, the nectary aborts; all the petals become alike both + in shape and colour; the stamens are generally reduced in number and + become straight, so that the whole flower resembles that of the allied + genus Erodium. The correlation between these changes is well shown when + one of the two upper petals alone loses its dark mark, for in this case + the nectary does not entirely abort, but is usually much reduced in + length.[858] + + {346} + + Morren has described[859] a marvellous flask-shaped flower of the + Calceolaria, nearly four inches in length, which was almost completely + peloric; it grew on the summit of the plant, with a normal flower on + each side; Prof. Westwood also has described[860] three similar peloric + flowers, which all occupied a central position on the flower-branches. + In the Orchideous genus, Phalaenopsis, the terminal flower has been + seen to become peloric. + + In a Laburnum-tree I observed that about a fourth part of the racemes + produced terminal flowers which had lost their papilionaceous + structure. These were produced after almost all the other flowers on + the same racemes had withered. The most perfectly pelorised examples + had six petals, each marked with black striae like those on the + standard-petal. The keel seemed to resist the change more than the + other petals. Dutrochet has described[861] an exactly similar case in + France, and I believe these are the only two instances of pelorism in + the laburnum which have been recorded. Dutrochet remarks that the + racemes on this tree do not properly produce a terminal flower, so + that, as in the case of the Galeobdolon, their position as well as + their structure are both anomalies, which no doubt are in some manner + related. Dr. Masters has briefly described another leguminous + plant,[862] namely, a species of clover, in which the uppermost and + central flowers were regular or had lost their papilionaceous + structure. In some of these plants the flower-heads were also + proliferous. + + Lastly, Linaria produces two kinds of peloric flowers, one having + simple petals, and the other having them all spurred. The two forms, as + Naudin remarks,[863] not rarely occur on the same plant, but in this + case the spurred form almost invariably stands on the summit of the + spike. + + The tendency in the terminal or central flower to become peloric more + frequently than other flowers, probably results from "the bud which + stands on the end of a shoot receiving the most sap; it grows out into + a stronger shoot than those situated lower down."[864] I have discussed + the connection between pelorism and a central position, partly because + some few plants are known normally to produce a terminal flower + different in structure from the lateral ones; but chiefly on account of + the following case, in which we see a tendency to variability or to + reversion connected with the same position. A great judge of + Auriculas[865] states that when an Auricula throws up a side bloom it + is pretty sure to keep its character; but that if it grows from the + centre or heart of the plant, whatever the colour of the edging ought + to be, "it is just as likely to come in any other class as in the one + to which it properly belongs." This is so notorious a {347} fact, that + some florists regularly pinch off the central trusses of flowers. + Whether in the highly improved varieties the departure of the central + trusses from their proper type is due to reversion, I do not know. Mr. + Dombrain insists that, whatever may be the commonest kind of + imperfection in each variety, this is generally exaggerated in the + central truss. Thus one variety "sometimes has the fault of producing a + little green floret in the centre of the flower," and in central blooms + these become excessive in size. In some central blooms, sent to me by + Mr. Dombrain, all the organs of the flower were rudimentary in + structure, of minute size, and of a green colour, so that by a little + further change all would have been converted into small leaves. In this + case we clearly see a tendency to prolification--a term which, I may + explain to those who have never attended to botany, means the + production of a branch or flower, or head of flowers, out of another + flower. Now Dr. Masters[866] states that the central or uppermost + flower on a plant is generally the most liable to prolification. Thus, + in the varieties of the Auricula, the loss of their proper character + and a tendency to prolification, and in other plants a tendency to + prolification and pelorism, are all connected together, and are due + either to arrested development, or to reversion to a former condition. + + The following is a more interesting case; Metzger[867] cultivated in + Germany several kinds of maize brought from the hotter parts of + America, and he found, as has been previously described, that in two or + three generations the grains became greatly changed in form, size, and + colour; and with respect to two races he expressly states that in the + first generation, whilst the lower grains on each head retained their + proper character, the uppermost grains already began to assume that + character which in the third generation all the grains acquired. As we + do not know the aboriginal parent of the maize, we cannot tell whether + these changes are in any way connected with reversion. + + In the two following cases, reversion, as influenced by the position of + the seed in the capsule, evidently acts. The Blue Imperial pea is the + offspring of the Blue Prussian, and has larger seed and broader pods + than its parent. Now Mr. Masters, of Canterbury, a careful observer and + a raiser of new varieties of the pea, states[868] that the Blue + Imperial always has a strong tendency to revert to its parent-stock, + and the reversion "occurs in this manner: the last (or uppermost) pea + in the pod is frequently much smaller than the rest; and if these small + peas are carefully collected and sown separately, very many more, in + proportion, will revert to their origin, than those taken from the + other parts of the pod." Again M. Chate[869] says that in raising + seedling stocks he succeeds in getting eighty per cent. to bear double + flowers, by leaving only a few of the secondary branches to seed; but + in addition to this, "at the time of extracting the seeds, the upper + portion of the pod is separated and {348} placed aside, because it has + been ascertained that the plants coming from the seeds situated in this + portion of the pod, give eighty per cent. of single flowers." Now the + production of single-flowering plants from the seed of double-flowering + plants is clearly a case of reversion. These latter facts, as well as + the connection between a central position and pelorism and + prolification, show in an interesting manner how small a + difference--namely a little greater freedom in the flow of sap towards + one part of the same plant--determines important changes of structure. + + * * * * * + +_Analogous or Parallel Variation._--By this term I wish to express that +similar characters occasionally make their appearance in the several +varieties or races descended from the same species, and more rarely in the +offspring of widely distinct species. We are here concerned, not as +hitherto with the causes of variation, but with the results; but this +discussion could not have been more conveniently introduced elsewhere. The +cases of analogous variation, as far as their origin is concerned, may be +grouped, disregarding minor subdivisions, under two main heads; firstly, +those due to unknown causes having acted on organic beings with nearly the +same constitution, and which consequently vary in an analogous manner; and +secondly, those due to the reappearance of characters which were possessed +by a more or less remote progenitor. But these two main divisions can often +be only conjecturally separated, and graduate, as we shall presently see, +into each other. + + Under the first head of analogous variations, not due to reversion, we + have the many cases of trees belonging to quite different orders which + have produced pendulous and fastigate varieties. The beech, hazel, and + barberry have given rise to purple-leaved varieties; and as Bernhardi + has remarked,[870] a multitude of plants, as distinct as possible, have + yielded varieties with deeply-cut or laciniated leaves. Varieties + descended from three distinct species of Brassica have their stems, or + so-called roots, enlarged into globular masses. The nectarine is the + offspring of the peach; and the varieties of both these trees offer a + remarkable parallelism in the fruit being white, red, or yellow + fleshed--in being clingstones or freestones--in the flowers being large + or small--in the leaves being serrated or crenated, furnished with + globose or reniform glands, or quite destitute of glands. It should be + remarked that each variety of the nectarine has not derived its + character from a corresponding variety of the peach. The several + varieties also of a closely allied genus, namely the apricot, differ + from each other in nearly the same parallel manner. There is no reason + {349} to believe that in any of these cases long-lost characters have + reappeared, and in most of them this certainly has not occurred. + + Three species of Cucurbita have yielded a multitude of races, which + correspond so closely in character that, as Naudin insists, they may be + arranged in an almost strictly parallel series. Several varieties of + the melon are interesting from resembling in important characters other + species, either of the same genus or of allied genera; thus, one + variety has fruit so like, both externally and internally, the fruit of + a perfectly distinct species, namely, the cucumber, as hardly to be + distinguished from it; another has long cylindrical fruit twisting + about like a serpent; in another the seeds adhere to portions of the + pulp; in another the fruit, when ripe, suddenly cracks and falls into + pieces; and all these highly remarkable peculiarities are + characteristic of species belonging to allied genera. We can hardly + account for the appearance of so many unusual characters by reversion + to a single ancient form; but we must believe that all the members of + the family have inherited a nearly similar constitution from an early + progenitor. Our cereal and many other plants offer similar cases. + + With animals we have fewer cases of analogous variation, independently + of direct reversion. We see something of the kind in the resemblance + between the short-muzzled races of the dog, such as the pug and + bulldog; in feather-footed races of the fowl, pigeon, and canary-bird; + in horses of the most different races presenting the same range of + colour; in all black-and-tan dogs having tan-coloured eye-spots and + feet, but in this latter case reversion may possibly have played a + part. Low has remarked[871] that several breeds of cattle are + "sheeted,"--that is, have a broad band of white passing round their + bodies like a sheet; this character is strongly inherited and sometimes + originates from a cross; it may be the first step in reversion to an + original or early type, for, as was shown in the third chapter, white + cattle with dark ears, feet, and tip of tail formerly existed, and now + exist in a feral or semi-feral condition in several quarters of the + world. + + Under our second main division, namely, of analogous variations due to + reversion, the best cases are afforded by animals, and by none better + than by pigeons. In all the most distinct breeds sub-varieties + occasionally appear coloured exactly like the parent rock-pigeon, with + black wing-bars, white loins, banded tail, &c.; and no one can doubt + that these characters are simply due to reversion. So with minor + details; turbits properly have white tails, but occasionally a bird is + born with a dark-coloured and banded tail; pouters properly have white + primary wing-feathers, but not rarely a "sword-flighted" bird, that is, + one with the few first primaries dark-coloured, appears; and in these + cases we have characters proper to the rock-pigeon, but new to the + breed, evidently appearing from reversion. In some domestic varieties + the wing-bars, instead of being simply black, as in the rock-pigeon, + are beautifully edged with different zones of colour, and they then + present a striking analogy with the wing-bars in certain natural + species of the same family, such as _Phaps chalcoptera_; and this may + probably be accounted for by {350} all the forms descended from the + same remote progenitor having a tendency to vary in the same manner. + Thus also we can perhaps understand the fact of some Laugher-pigeons + cooing almost like turtle-doves, and of several races having + peculiarities in their flight, for certain natural species (viz. _C. + torquatrix_ and _palumbus_) display singular vagaries in this respect. + In other cases a race, instead of imitating in character a distinct + species, resembles some other race; thus certain runts tremble and + slightly elevate their tails, like fantails; and turbits inflate the + upper part of their oesophagus, like pouter-pigeons. + + It is a common circumstance to find certain coloured marks persistently + characterising all the species of a genus, but differing much in tint; + and the same thing occurs with the varieties of the pigeon: thus, + instead of the general plumage being blue with the wing-bars black, + there are snow-white varieties with red bars, and black varieties with + white bars; in other varieties the wing-bars, as we have seen, are + elegantly zoned with different tints. The Spot pigeon is characterised + by the whole plumage being white, excepting the tail and a spot on the + forehead; but these parts may be red, yellow, or black. In the + rock-pigeon and in many varieties the tail is blue, with the outer + edges of the outer feathers white; but in one sub-variety of the + monk-pigeon we have a reversed variation, for the tail is white, except + the outer edges of the outer feathers, which are black.[872] + + With some species of birds, for instance with gulls, certain coloured + parts appear as if almost washed out, and I have observed exactly the + same appearance in the terminal dark tail-bar in certain pigeons, and + in the whole plumage of certain varieties of the duck. Analogous facts + in the vegetable kingdom could be given. + + Many sub-varieties of the pigeon have reversed and somewhat lengthened + feathers on the back part of their heads, and this is certainly not due + to reversion to the parent-species, which shows no trace of such + structure; but when we remember that sub-varieties of the fowl, turkey, + canary-bird, duck, and goose, all have topknots or reversed feathers on + their heads; and when we remember that scarcely a single large natural + group of birds can be named, in which some members have not a tuft of + feathers on their heads, we may suspect that reversion to some + extremely remote form has come into action. + + Several breeds of the fowl have either spangled or pencilled feathers; + and these cannot be derived from the parent-species, the _Gallus + bankiva_; though of course it is possible that an early progenitor of + this species may have been spangled, and a still earlier or a later + progenitor may have been pencilled. But as many gallinaceous birds are + spangled or pencilled, it is a more probable view that the several + domestic breeds of the fowl have acquired this kind of plumage from all + the members of the family inheriting a tendency to vary in a like + manner. The same principle may account for the ewes in certain breeds + of sheep being hornless, like the females of some other hollow-horned + ruminants; it may account for certain domestic cats having + slightly-tufted ears, like those of the lynx; and for the skulls of + domestic rabbits often differing from each {351} other in the same + characters by which the skulls of the various species of the genus + Lepus differ. + + I will only allude to one other case, already discussed. Now that we + know that the wild parent of the ass has striped legs, we may feel + confident that the occasional appearance of stripes on the legs of the + domestic ass is due to direct reversion; but this will not account for + the lower end of the shoulder-stripe being sometimes angularly bent or + slightly forked. So, again, when we see dun and other coloured horses + with stripes on the spine, shoulders, and legs, we are led, from + reasons formerly given, to believe that they reappear from direct + reversion to the wild parent-horse. But when horses have two or three + shoulder-stripes with one of them occasionally forked at the lower end, + or when they have stripes on their faces, or as foals are faintly + striped over nearly their whole bodies, with the stripes angularly bent + one under the other on the forehead, or irregularly branched in other + parts, it would be rash to attribute such diversified characters to the + reappearance of those proper to the aboriginal wild horse. As three + African species of the genus are much striped, and as we have seen that + the crossing of the unstriped species often leads to the hybrid + offspring being conspicuously striped--bearing also in mind that the + act of crossing certainly causes the reappearance of long-lost + characters--it is a more probable view that the above-specified stripes + are due to reversion, not to the immediate wild parent-horse, but to + the striped progenitor of the whole genus. + +I have discussed this subject of analogous variation at considerable +length, because, in a future work on natural species, it will be shown that +the varieties of one species frequently mock distinct species--a fact in +perfect harmony with the foregoing cases, and explicable only on the theory +of descent. Secondly, because these facts are important from showing, as +remarked in a former chapter, that each trifling variation is governed by +law, and is determined in a much higher degree by the nature of the +organisation, than by the nature of the conditions to which the varying +being has been exposed. Thirdly, because these facts are to a certain +extent related to a more general law, namely, that which Mr. B. D. +Walsh[873] has called the "Law of _Equable Variability_," or, as he +explains it, "if any given character is very variable in one species of a +group, it will tend to be variable in allied species; and if any given +character is perfectly constant in one species of a group, it will tend to +be constant in allied species." + +This leads me to recall a discussion in the chapter on Selection, in which +it was shown that with domestic races, which are {352} now undergoing rapid +improvement, those parts or characters which are the most valued vary the +most. This naturally follows from recently selected characters continually +tending to revert to their former less improved standard, and from their +being still acted on by the same agencies, whatever these may be, which +first caused the characters in question to vary. The same principle is +applicable to natural species, for, as stated in my 'Origin of Species,' +generic characters are less variable than specific characters; and the +latter are those which have been modified by variation and natural +selection, since the period when all the species belonging to the same +genus branched off from a common progenitor, whilst generic characters are +those which have remained unaltered from a much more remote epoch, and +accordingly are now less variable. This statement makes a near approach to +Mr. Walsh's law of Equable Variability. Secondary sexual characters, it may +be added, rarely serve to characterise distinct genera, for they usually +differ much in the species of the same genus, and are highly variable in +the individuals of the same species; we have also seen in the earlier +chapters of this work how variable secondary sexual characters become under +domestication. + +_Summary of the three previous Chapters, on the Laws of Variation._ + +In the twenty-third chapter we have seen that changed conditions +occasionally act in a definite manner on the organisation, so that all, or +nearly all, the individuals thus exposed become modified in the same +manner. But a far more frequent result of changed conditions, whether +acting directly on the organisation or indirectly through the reproductive +system being affected is indefinite and fluctuating variability. In the +three latter chapters we have endeavoured to trace some of the laws by +which such variability is regulated. + +Increased use adds the size of a muscle, together with the blood-vessels, +nerves, ligaments, the crests of bone to which these are attached, the +whole bone and other connected bones. So it is with various glands. +Increased functional activity strengthens the sense-organs. Increased and +intermittent pressure thickens the epidermis; and a change in the nature of +the food sometimes modifies the coats of the stomach, and increases or +{353} decreases the length of the intestines. Continued disuse, on the +other hand, weakens and diminishes all parts of the organisation. Animals +which during many generations have taken but little exercise, have their +lungs reduced in size, and as a consequence the bony fabric of the chest, +and the whole form of the body, become modified. With our anciently +domesticated birds, the wings have been little used, and they are slightly +reduced; with their decrease, the crest of the sternum, the scapulae, +coracoids, and furcula, have all been reduced. + +With domesticated animals, the reduction of a part from disuse is never +carried so far that a mere rudiment is left, but we have good reason to +believe that this has often occurred under nature. The cause of this +difference probably is that with domestic animals not only sufficient time +has not been granted for so profound a change, but that, from not being +exposed to a severe struggle for life, the principle of the economy of +organisation does not come into action. On the contrary, we sometimes see +that structures which are rudimentary in the parent-species become +partially redeveloped in their domesticated progeny. When rudiments are +formed or left under domestication, they are the result of a sudden arrest +of development, and not of long-continued disuse with the absorption of all +superfluous parts; nevertheless they are of interest, as showing that +rudiments are the relics of organs once perfectly developed. + +Corporeal, periodical, and mental habits, though the latter have been +almost passed over in this work, become changed under domestication, and +the changes are often inherited. Such changed habits in any organic being, +especially when living a free life, would often lead to the augmented or +diminished use of various organs, and consequently to their modification. +From long-continued habit, and more especially from the occasional birth of +individuals with a slightly different constitution, domestic animals and +cultivated plants become to a certain extent acclimatised, or adapted to a +climate different from that proper to the parent-species. + +Through the principle of correlated variability, when one part varies other +parts vary,--either simultaneously, or one after the other. Thus an organ +modified during an early embryonic period affects other parts subsequently +developed. When an {354} organ, such as the beak, increases or decreases in +length, adjoining or correlated parts, as the tongue and the orifice of the +nostrils, tend to vary in the same manner. When the whole body increases or +decreases in size, various parts become modified; thus with pigeons the +ribs increase or decrease in number and breadth. Homologous parts, which +are identical during their early development and are exposed to similar +conditions, tend to vary in the same or in some connected manner,--as in +the case of the right and left sides of the body, of the front and hind +limbs, and even of the head and limbs. So it is with the organs of sight +and hearing; for instance, white cats with blue eyes are almost always +deaf. There is a manifest relation throughout the body between the skin and +its various appendages of hair, feathers, hoofs, horns, and teeth. In +Paraguay, horses with curly hair have hoofs like those of a mule; the wool +and the horns of sheep vary together; hairless dogs are deficient in their +teeth; men with redundant hair have abnormal teeth, either deficient or in +excess. Birds with long wing-feathers usually have long tail-feathers. When +long feathers grow from the outside of the legs and toes of pigeons, the +two outer toes are connected by membrane; for the whole leg tends to assume +the structure of the wing. There is a manifest relation between a crest of +feathers on the head and a marvellous amount of change in the skull of +various fowls; and in a lesser degree, between the greatly elongated, +lopping ears of rabbits and the structure of their skulls. With plants, the +leaves, various parts of the flower, and the fruit, often vary together in +a correlated manner. + +In some cases we find correlation without being able even to conjecture +what is the nature of the connexion, as with various correlated +monstrosities and diseases. This is likewise the case with the colour of +the adult pigeon, in connexion with the presence of down on the young bird. +Numerous curious instances have been given of peculiarities of +constitution, in correlation with colour, as shown by the immunity of +individuals of some one colour from certain diseases, from the attacks of +parasites, and from the action of certain vegetable poisons. + +Correlation is an important subject; for with species, and in a lesser +degree with domestic races, we continually find that {355} certain parts +have been greatly modified to serve some useful purpose; but we almost +invariably find that other parts have likewise been more or less modified, +without our being able to discover any advantage in the change. No doubt +great caution is necessary in coming to this conclusion, for it is +difficult to overrate our ignorance on the use of various parts of the +organisation; but from what we have now seen, we may believe that many +modifications are of no direct service, having arisen in correlation with +other and useful changes. + +Homologous parts during their early development evince an affinity for each +other,--that is, they tend to cohere and fuse together much more readily +than other parts. This tendency to fusion explains a multitude of normal +structures. Multiple and homologous organs are especially liable to vary in +number and probably in form. As the supply of organised matter is not +unlimited, the principle of compensation sometimes comes into action; so +that, when one part is greatly developed, adjoining parts or functions are +apt to be reduced; but this principle is probably of much less importance +than the more general one of the economy of growth. Through mere mechanical +pressure hard parts occasionally affect soft adjoining parts. With plants +the position of the flowers on the axis, and of the seeds in the capsule, +sometimes leads, through a freer flow of sap, to changes of structure; but +these changes are often due to reversion. Modifications, in whatever manner +caused, will be to a certain extent regulated by that co-ordinating power +or _nisus formativus_, which is in fact a remnant of one of the forms of +reproduction, displayed by many lowly organised beings in their power of +fissiparous generation and budding. Finally, the effects of the laws, which +directly or indirectly govern variability, may be largely influenced by +man's selection, and will so far be determined by natural selection that +changes advantageous to any race will be favoured and disadvantageous +changes checked. + +Domestic races descended from the same species, or from two or more allied +species, are liable to revert to characters derived from their common +progenitor, and, as they have much in common in their constitutions, they +are also liable under changed conditions to vary in the same manner; from +these {356} two causes analogous varieties often arise. When we reflect on +the several foregoing laws, imperfectly as we understand them, and when we +bear in mind how much remains to be discovered, we need not be surprised at +the extremely intricate manner in which our domestic productions have +varied, and still go on varying. + + * * * * * + + +{357} + +CHAPTER XXVII. + +PROVISIONAL HYPOTHESIS OF PANGENESIS. + + PRELIMINARY REMARKS.--FIRST PART:--THE FACTS TO BE CONNECTED UNDER A + SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION--THE + DIRECT ACTION OF THE MALE ELEMENT ON THE FEMALE--DEVELOPMENT--THE + FUNCTIONAL INDEPENDENCE OF THE ELEMENTS OR UNITS OF THE + BODY--VARIABILITY--INHERITANCE--REVERSION. + + SECOND PART:--STATEMENT OF THE HYPOTHESIS--HOW FAR THE NECESSARY + ASSUMPTIONS ARE IMPROBABLE--EXPLANATION BY AID OF THE HYPOTHESIS OF THE + SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST PART--CONCLUSION. + +In the previous chapters large classes of facts, such as those bearing on +bud-variation, the various forms of inheritance, the causes and laws of +variation, have been discussed; and it is obvious that these subjects, as +well as the several modes of reproduction, stand in some sort of relation +to each other. I have been led, or rather forced, to form a view which to a +certain extent connects these facts by a tangible method. Every one would +wish to explain to himself, even in an imperfect manner, how it is possible +for a character possessed by some remote ancestor suddenly to reappear in +the offspring; how the effects of increased or decreased use of a limb can +be transmitted to the child; how the male sexual element can act not solely +on the ovule, but occasionally on the mother-form; how a limb can be +reproduced on the exact line of amputation, with neither too much nor too +little added; how the various modes of reproduction are connected, and so +forth. I am aware that my view is merely a provisional hypothesis or +speculation; but until a better one be advanced, it may be serviceable by +bringing together a multitude of facts which are at present left +disconnected by any efficient cause. As Whewell, the historian of the +inductive sciences, remarks:--"Hypotheses may often be of service to +science, when they involve a certain portion of incompleteness, and even of +error." Under this point of view I venture to advance the hypothesis of +Pangenesis, which {358} implies that the whole organisation, in the sense +of every separate atom or unit, reproduces itself. Hence ovules and +pollen-grains,--the fertilised seed or egg, as well as buds,--include and +consist of a multitude of germs thrown off from each separate atom of the +organism. + +In the First Part I will enumerate as briefly as I can the groups of facts +which seem to demand connection; but certain subjects, not hitherto +discussed, must be treated at disproportionate length. In the Second Part +the hypothesis will be given; and we shall see, after considering how far +the necessary assumptions are in themselves improbable, whether it serves +to bring under a single point of view the various facts. + +PART I. + +Reproduction may be divided into two main classes, namely, sexual and +asexual. The latter is effected in many ways--by gemmation, that is by the +formation of buds of various kinds, and by fissiparous generation, that is +by spontaneous or artificial division. It is notorious that some of the +lower animals, when cut into many pieces, reproduce so many perfect +individuals: Lyonnet cut a Nais or freshwater worm into nearly forty +pieces, and these all reproduced perfect animals.[874] It is probable that +segmentation could be carried much further in some of the protozoa, and +with some of the lowest plants each cell will reproduce the parent-form. +Johannes Mueller thought that there was an important distinction between +gemmation and fission; for in the latter case the divided portion, however +small, is more perfectly organised; but most physiologists are now +convinced that the two processes are essentially alike.[875] Prof. Huxley +remarks, "fission is little more than a peculiar {359} mode of budding," +and Prof. H. J. Clark, who has especially attended to this subject, shows +in detail that there is sometimes "a compromise between self-division and +budding." When a limb is amputated, or when the whole body is bisected, the +cut extremities are said to bud forth; and as the papilla, which is first +formed, consists of undeveloped cellular tissue like that forming an +ordinary bud, the expression is apparently correct. We see the connection +of the two processes in another way; for Trembley observed that with the +hydra the reproduction of the head after amputation was checked as soon as +the animal began to bud.[876] + +Between the production, by fissiparous generation, of two or more complete +individuals, and the repair of even a very slight injury, we have, as +remarked in a former chapter, so perfect and insensible a gradation, that +it is impossible to doubt that they are connected processes. Between the +power which repairs a trifling injury in any part, and the power which +previously "was occupied in its maintenance by the continued mutation of +its particles," there cannot be any great difference; and we may follow Mr. +Paget in believing them to be the selfsame power. As at each stage of +growth an amputated part is replaced by one in the same state of +development, we must likewise follow Mr. Paget in admitting "that the +powers of development from the embryo are identical with those exercised +for the restoration from injuries: in other words, that the powers are the +same by which perfection is first achieved, and by which, when lost, it is +recovered."[877] Finally, we may conclude that the several forms of +gemmation, and of fissiparous generation, the repair of injuries, the +maintenance of each part in its proper state, and the growth or progressive +development of the whole structure of the embryo, are all essentially the +results of one and the same great power. + +_Sexual Generation._--The union of the two sexual elements seems to make a +broad distinction between sexual and asexual reproduction. But the +well-ascertained cases of Parthenogenesis prove that the distinction is not +really so great as it at first appears; for ovules occasionally, and even +in some cases {360} frequently, become developed into perfect beings, +without the concourse of the male element. J. Mueller and others admit that +ovules and buds have the same essential nature. Certain bodies, which +during their early development cannot be distinguished by any external +character from true ovules, nevertheless must be classed as buds, for +though formed within the ovarium they are incapable of fertilisation. This +is the case with the germ-balls of the Cecidomyide larvae, as described by +Leuckart.[878] Ovules and the male element, before they become united, +have, like buds, an independent existence.[879] Both have the power of +transmitting every single character possessed by the parent-form. We see +this clearly when hybrids are paired _inter se_, for the characters of +either grandparent often reappear, either perfectly or by segments, in the +progeny. It is an error to suppose that the male transmits certain +characters and the female other characters; though no doubt, from unknown +causes, one sex sometimes has a stronger power of transmission than the +other. + +It has been maintained by some authors that a bud differs essentially from +a fertilised germ, by always reproducing the perfect character of the +parent-stock; whilst fertilised germs become developed into beings which +differ, in a greater or less degree, from each other and from their +parents. But there is no such broad distinction as this. In the eleventh +chapter, numerous cases were given showing that buds occasionally grow into +plants having new and strongly marked characters; and varieties thus +produced can be propagated for a length of time by buds, and occasionally +by seed. Nevertheless, it must be admitted that beings produced sexually +are much more liable to vary than those produced asexually; and of this +fact a partial explanation will hereafter be attempted. The variability in +both cases is determined by the same general causes, and is governed by the +same laws. Hence new varieties arising from buds cannot be distinguished +from those arising from seed. Although bud-varieties usually retain their +character during {361} successive bud-generations, yet they occasionally +revert, even after a long series of bud-generations, to their former +character. This tendency to reversion in buds is one of the most remarkable +of the several points of agreement between the offspring from bud and +seminal reproduction. + +There is, however, one difference between beings produced sexually and +asexually, which is very general. The former usually pass in the course of +their development from a lower to a higher grade, as we see in the +metamorphoses of insects and in the concealed metamorphoses of the +vertebrata; but this passage from a lower to a higher grade cannot be +considered as a necessary accompaniment of sexual reproduction, for hardly +anything of the kind occurs in the development of Aphis amongst insects, or +with certain crustaceans, cephalopods, or with any of the higher vascular +plants. Animals propagated asexually by buds or fission are on the other +hand never known to undergo a retrogressive metamorphosis; that is, they do +not first sink to a lower, before passing on to their higher and final +stage of development. But during the act of asexual production or +subsequently to it, they often advance in organisation, as we see in the +many cases of "alternate generation." In thus speaking of alternate +generation, I follow those naturalists who look at the process as +essentially one of internal budding or of fissiparous generation. Some of +the lower plants, however, such as mosses and certain algae, according to +Dr. L. Radlkofer,[880] when propagated asexually, do undergo a +retrogressive metamorphosis. We can to a certain extent understand, as far +as the final cause is concerned, why beings propagated by buds should so +rarely retrogress during development; for with each organism the structure +acquired at each stage of development must be adapted to its peculiar +habits. Now, with beings produced by gemmation,--and this, differently from +sexual reproduction, may occur at any period of growth,--if there were +places for the support of many individuals at some one stage of +development, the simplest plan would be that they should be multiplied by +gemmation at that stage, and not that they should first retrograde in their +development to an earlier or simpler structure, which might not be fitted +for the surrounding conditions. + +{362} + +From the several foregoing considerations we may conclude that the +difference between sexual and asexual generation is not nearly so great as +it at first appears; and we have already seen that there is the closest +agreement between gemmation, fissiparous generation, the repair of +injuries, and ordinary growth or development. The capacity of fertilisation +by the male element seems to be the chief distinction between an ovule and +a bud; and this capacity is not invariably brought into action, as in the +cases of parthenogenetic reproduction. We are here naturally led to inquire +what the final cause can be of the necessity in ordinary generation for the +concourse of the two sexual elements. + +Seeds and ova are often highly serviceable as the means of disseminating +plants and animals, and of preserving them during one or more seasons in a +dormant state; but unimpregnated seeds or ova, and detached buds, would be +equally serviceable for both purposes. We can, however, indicate two +important advantages gained by the concourse of the two sexes, or rather of +two individuals belonging to opposite sexes; for, as I have shown in a +former chapter, the structure of every organism appears to be especially +adapted for the concurrence, at least occasionally, of two individuals. In +nearly the same manner as it is admitted by naturalists that hybridism, +from inducing sterility, is of service in keeping the forms of life +distinct and fitted for their proper places; so, when species are rendered +highly variable by changed conditions of life, the free intercrossing of +the varying individuals will tend to keep each form fitted for its proper +place in nature; and crossing can be effected only by sexual generation, +but whether the end thus gained is of sufficient importance to account for +the first origin of sexual intercourse is very doubtful. Secondly, I have +shown, from the consideration of a large body of facts, that, as a slight +change in the conditions of life is beneficial to each creature, so, in an +analogous manner, is the change effected in the germ by sexual union with a +distinct individual; and I have been led, from observing the many +widely-extended provisions throughout nature for this purpose, and from the +greater vigour of crossed organisms of all kinds, as proved by direct +experiments, as well as from the evil effects of close interbreeding when +long {363} continued, to believe that the advantage thus gained is very +great. Besides these two important ends, there may, of course, be others, +as yet unknown to us, gained by the concourse of the two sexes. + +Why the germ, which before impregnation undergoes a certain amount of +development, ceases to progress and perishes, unless it be acted on by the +male element; and why conversely the male element, which is enabled to keep +alive for even four or five years within the spermatheca of a female +insect, likewise perishes, unless it acts on or unites with the germ, are +questions which cannot be answered with any certainty. It is, however, +possible that both sexual elements perish, unless brought into union, +simply from including too little formative matter for independent existence +and development; for certainly they do not in ordinary cases differ in +their power of giving character to the embryo. This view of the importance +of the quantity of formative matter seems probable from the following +considerations. There is no reason to suspect that the spermatozoa or +pollen-grains of the same individual animal or plant differ from each +other; yet Quatrefages has shown in the case of the Teredo,[881] as did +formerly Prevost and Dumas with other animals, that more than one +spermatozoon is requisite to fertilise an ovule. This has likewise been +clearly proved by Newport,[882] who adds the important fact, established by +numerous experiments, that, when a very small number of spermatozoa are +applied to the ova of Batrachians, they are only partially impregnated and +the embryo is never fully developed: the first step, however, towards +development, namely, the partial segmentation of the yelk, does occur to a +greater or less extent, but is never completed up to granulation. The rate +of the segmentation is likewise determined by the number of the +spermatozoa. With respect to plants, nearly the same results were obtained +by Koelreuter and Gaertner. This last careful observer found,[883] after +making successive trials on a Malva with more and more pollen-grains, that +even thirty grains did not fertilise a single seed; but when forty grains +were applied to the {364} stigma, a few seeds of small size were formed. +The pollen-grains of Mirabilis are extraordinarily large, and the ovarium +contains only a single ovule; and these circumstances led Naudin[884] to +make the following interesting experiments: a flower was fertilised by +three grains and succeeded perfectly; twelve flowers were fertilised by two +grains, and seventeen flowers by a single grain, and of these one flower +alone in each lot perfected its seed; and it deserves especial notice that +the plants produced by these two seeds never attained their proper +dimensions, and bore flowers of remarkably small size. From these facts we +clearly see that the quantity of the peculiar formative matter which is +contained within the spermatozoa and pollen-grains is an all-important +element in the act of fertilisation, not only in the full development of +the seed, but in the vigour of the plant produced from such seed. We see +something of the same kind in certain cases of parthenogenesis, that is, +when the male element is wholly excluded; for M. Jourdan[885] found that, +out of about 58,000 eggs laid by unimpregnated silk-moths, many passed +through their early embryonic stages, showing that they were capable of +self-development, but only twenty-nine out of the whole number produced +caterpillars. Therefore it is not an improbable view that deficient bulk or +quantity in the formative matter, contained within the sexual elements, is +the main cause of their not having the capacity of prolonged separate +existence and development. The belief that it is the function of the +spermatozoa to communicate life to the ovule seems a strange one, seeing +that the unimpregnated ovule is already alive and continues for a +considerable time alive. We shall hereafter see that it is probable that +the sexual elements, or possibly only the female element, include certain +primordial cells, that is, such as have undergone no differentiation, and +which are not present in an active state in buds. + +_Graft-hybrids._--When discussing in the eleventh chapter the curious case +of the _Cytisus adami_, facts were given which render it to a certain +degree probable, in accordance with the belief of some distinguished +botanists, that, when the tissues of two plants {365} belonging to distinct +species or varieties are intimately united, buds are afterwards +occasionally produced which, like hybrids, combine the characters of the +two united forms. It is certain that when trees with variegated leaves are +grafted or budded on a common stock, the latter sometimes produces buds +bearing variegated leaves; but this may perhaps be looked at as a case of +inoculated disease. Should it ever be proved that hybridised buds can be +formed by the union of two distinct vegetative tissues, the essential +identity of sexual and asexual reproduction would be shown in the most +interesting manner; for the power of combining in the offspring the +characters of both parents, is the most striking of all the functions of +sexual generation. + +_Direct Action of the Male Element on the Female._--In the chapter just +referred to, I have given abundant proofs that foreign pollen occasionally +affects the mother-plant in a direct manner. Thus, when Gallesio fertilised +an orange-flower with pollen from the lemon, the fruit bore stripes of +perfectly characterised lemon-peel: with peas, several observers have seen +the colour of the seed-coats and even of the pod directly affected by the +pollen of a distinct variety; so it has been with the fruit of the apple, +which consists of the modified calyx and upper part of the flower-stalk. +These parts in ordinary cases are wholly formed by the mother-plant. We +here see the male element affecting and hybridising not that part which it +is properly adapted to affect, namely the ovule, but the partially +developed tissues of a distinct individual. We are thus brought half-way +towards a graft-hybrid, in which the cellular tissue of one form, instead +of its pollen, is believed to hybridise the tissues of a distinct form. I +formerly assigned reasons for rejecting the belief that the mother-plant is +affected through the intervention of the hybridised embryo; but even if +this view were admitted, the case would become one of graft-hybridism, for +the fertilised embryo and the mother-plant must be looked at as distinct +individuals. + +With animals which do not breed until nearly mature, and of which all the +parts are then fully developed, it is hardly possible that the male element +should directly affect the female. But we have the analogous and perfectly +well-ascertained case of the male element of a distinct form, as with the +{366} quagga and Lord Morton's mare, affecting the ovarium of the female, +so that the ovules and offspring subsequently produced by her when +impregnated by other males are plainly affected and hybridised by the first +male. + +_Development._--The fertilised germ reaches maturity by a vast number of +changes: these are either slight and slowly effected, as when the child +grows into the man, or are great and sudden, as with the metamorphoses of +most insects. Between these extremes we have, even within the same class, +every gradation: thus, as Sir J. Lubbock has shown,[886] there is an +Ephemerous insect which moults above twenty times, undergoing each time a +slight but decided change of structure; and these changes, as he further +remarks, probably reveal to us the normal stages of development which are +concealed and hurried through, or suppressed, in most other insects. In +ordinary metamorphoses, the parts and organs appear to become changed into +the corresponding parts in the next stage of development; but there is +another form of development, which has been called by Professor Owen +metagenesis. In this case "the new parts are not moulded upon the inner +surface of the old ones. The plastic force has changed its course of +operation. The outer case, and all that gave form and character to the +precedent individual, perish and are cast off; they are not changed into +the corresponding parts of the new individual. These are due to a new and +distinct developmental process," &c.[887] Metamorphosis, however, graduates +so insensibly into metagenesis, that the two processes cannot be distinctly +separated. For instance, in the last change which Cirripedes undergo, the +alimentary canal and some other organs are moulded on pre-existing parts; +but the eyes of the old and the young animal are developed in entirely +different parts of the body; the tips of the mature limbs are formed within +the larval limbs, and may be said to be metamorphosed from them; but their +basal portions and the whole thorax are developed in a plane actually at +right angles to the limbs and thorax of the larva; and this {367} may be +called metagenesis. The metagenetic process is carried to an extreme degree +in the development of some Echinoderms, for the animal in the second stage +of development is formed almost like a bud within the animal of the first +stage, the latter being then cast off like an old vestment, yet sometimes +still maintaining for a short period an independent vitality.[888] + +If, instead of a single individual, several were to be thus developed +metagenetically within a pre-existing form, the process would be called one +of alternate generation. The young thus developed may either closely +resemble the encasing parent-form, as with the larvae of Cecidomyia, or may +differ to an astonishing degree, as with many parasitic worms and with +jelly-fishes; but this does not make any essential difference in the +process, any more than the greatness or abruptness of the change in the +metamorphoses of insects. + +The whole question of development is of great importance for our present +subject. When an organ, the eye for instance, is metagenetically formed in +a part of the body where during the previous stage of development no eye +existed, we must look at it as a new and independent growth. The absolute +independence of new and old structures, which correspond in structure and +function, is still more obvious when several individuals are formed within +a previous encasing form, as in the cases of alternate generation. The same +important principle probably comes largely into play even in the case of +continuous growth, as we shall see when we consider the inheritance of +modifications at corresponding ages. + +We are led to the same conclusion, namely, the independence of parts +successively developed, by another and quite distinct group of facts. It is +well known that many animals belonging to the same class, and therefore not +differing widely from each other, pass through an extremely different +course of development. Thus certain beetles, not in any way remarkably +different from others of the same order, undergo what has been called a +hyper-metamorphosis--that is, they pass through an early stage wholly +different from the ordinary grub-like larva. In the same sub-order of +crabs, namely, the Macroura, as Fritz {368} Mueller remarks, the river +cray-fish is hatched under the same form which it ever afterwards retains; +the young lobster has divided legs, like a Mysis; the Palaemon appears +under the form of a Zoea, and Peneus under the Nauplius-form; and how +wonderfully these larval forms differ from each other, is known to every +naturalist.[889] Some other crustaceans, as the same author observes, start +from the same point and arrive at nearly the same end, but in the middle of +their development are widely different from each other. Still more striking +cases could be given with respect to the Echinodermata. With the Medusae or +jelly-fishes Professor Allman observes, "the classification of the Hydroida +would be a comparatively simple task if, as has been erroneously asserted, +generically-identical medusoids always arose from generically-identical +polypoids; and on the other hand, that generically-identical polypoids +always gave origin to generically-identical medusoids." So, again, Dr. +Strethill Wright remarks, "in the life-history of the Hydroidae any phase, +planuloid, polypoid, or medusoid, may be absent."[890] + +According to the belief now generally accepted by our best naturalists, all +the members of the same order or class, the Macrourous crustaceans for +instance, are descended from a common progenitor. During their descent they +have diverged much in structure, but have retained much in common; and this +divergence and retention of character has been effected, though they have +passed and still pass through marvellously different metamorphoses. This +fact well illustrates how independent each structure must be from that +which precedes and follows it in the course of development. + +_The Functional Independence of the Elements or Units of the +Body._--Physiologists agree that the whole organism consists of a multitude +of elemental parts, which are to a great extent independent of each other. +Each organ, says Claude Bernard,[891] {369} has its proper life, its +autonomy; it can develop and reproduce itself independently of the +adjoining tissues. The great German authority, Virchow,[892] asserts still +more emphatically that each system, as the nervous or osseous system, or +the blood, consists of an "enormous mass of minute centres of action.... +Every element has its own special action, and even though it derive its +stimulus to activity from other parts, yet alone effects the actual +performance of its duties.... Every single epithelial and muscular +fibre-cell leads a sort of parasitical existence in relation to the rest of +the body.... Every single bone-corpuscle really possesses conditions of +nutrition peculiar to itself." Each element, as Mr. Paget remarks, lives +its appointed time, and then dies, and, after being cast off or absorbed, +is replaced.[893] I presume that no physiologist doubts that, for instance, +each bone-corpuscle of the finger differs from the corresponding corpuscle +in the corresponding joint of the toe; and there can hardly be a doubt that +even those on the corresponding sides of the body differ, though almost +identical in nature. This near approach to identity is curiously shown in +many diseases in which the same exact points on the right and left sides of +the body are similarly affected; thus Mr. Paget[894] gives a drawing of a +diseased pelvis, in which the bone has grown into a most complicated +pattern, but "there is not one spot or line on one side which is not +represented, as exactly as it would be in a mirror, on the other." + +Many facts support this view of the independent life of each minute element +of the body. Virchow insists that a single bone-corpuscle or a single cell +in the skin may become diseased. The spur of a cock, after being inserted +into the eye of an ox, lived for eight years, and acquired a weight of 306 +grammes, or nearly fourteen ounces.[895] The tail of a pig has been grafted +into the middle of its back, and reacquired sensibility. Dr. Ollier[896] +inserted a piece of periosteum from the bone of a young dog under the skin +of a rabbit, and true bone was developed. A multitude of similar facts +could be given. The {370} frequent presence of hairs and of perfectly +developed teeth, even teeth of the second dentition, in ovarian +tumours,[897] are facts leading to the same conclusion. + +Whether each of the innumerable autonomous elements of the body is a cell +or the modified product of a cell, is a more doubtful question, even if so +wide a definition be given to the term, as to include cell-like bodies +without walls and without nuclei.[898] Professor Lionel Beale uses the term +"germinal matter" for the contents of cells, taken in this wide +acceptation, and he draws a broad distinction between germinal matter and +"formed material" or the various products of cells.[899] But the doctrine +of _omnis cellula e cellula_ is admitted for plants, and is a widely +prevalent belief with respect to animals.[900] Thus Virchow, the great +supporter of the cellular theory, whilst allowing that difficulties exist, +maintains that every atom of tissue is derived from cells, and these from +pre-existing cells, and these primarily from the egg, which he regards as a +great cell. That cells, still retaining the same nature, increase by +self-division or proliferation, is admitted by almost every one. But when +an organism undergoes a great change of structure during development, the +cells, which at each stage are supposed to be directly derived from +previously-existing cells, must likewise be greatly changed in nature; this +change is apparently attributed by the supporters of the cellular doctrine +to some inherent power which the cells possess, and not to any external +agency. + +Another school maintains that cells and tissues of all kinds may be formed, +independently of pre-existing cells, from plastic lymph or blastema; and +this it is thought is well exhibited in the repair of wounds. As I have not +especially attended to histology, it would be presumptuous in me to express +an opinion on the two opposed doctrines. But every one appears to admit +that the body consists of a multitude of "organic units,"[901] {371} each +of which possesses its own proper attributes, and is to a certain extent +independent of all others. Hence it will be convenient to use indifferently +the terms cells or organic units or simply units. + +_Variability and Inheritance._--We have seen in the twenty-second chapter +that variability is not a principle co-ordinate with life or reproduction, +but results from special causes, generally from changed conditions acting +during successive generations. Part of the fluctuating variability thus +induced is apparently due to the sexual system being easily affected by +changed conditions, so that it is often rendered impotent; and when not so +seriously affected, it often fails in its proper function of transmitting +truly the characters of the parents to the offspring. But variability is +not necessarily connected with the sexual system, as we see from the cases +of bud-variation; and although we may not be able to trace the nature of +the connexion, it is probable that many deviations of structure which +appear in sexual offspring result from changed conditions acting directly +on the organisation, independently of the reproductive organs. In some +instances we may feel sure of this, when all, or nearly all the individuals +which have been similarly exposed are similarly and definitely affected--as +in the dwarfed and otherwise changed maize brought from hot countries when +cultivated in Germany; in the change of the fleece in sheep within the +tropics; to a certain extent in the increased size and early maturity of +our highly-improved domesticated animals; in inherited gout from +intemperance; and in many other such cases. Now, as such changed conditions +do not especially affect the reproductive organs, it seems mysterious on +any ordinary view why their product, the new organic being, should be +similarly affected. + +How, again, can we explain to ourselves the inherited effects of the use or +disuse of particular organs? The domesticated duck flies less and walks +more than the wild duck, and its limb-bones have become in a corresponding +manner diminished and increased in comparison with those of the wild duck. +A horse is trained to certain paces, and the colt inherits similar +consensual movements. The domesticated rabbit becomes tame from close +confinement; the dog intelligent from associating with man; the retriever +is taught to fetch and carry: and these {372} mental endowments and bodily +powers are all inherited. Nothing in the whole circuit of physiology is +more wonderful. How can the use or disuse of a particular limb or of the +brain affect a small aggregate of reproductive cells, seated in a distant +part of the body, in such a manner that the being developed from these +cells inherits the characters of either one or both parents? Even an +imperfect answer to this question would be satisfactory. + +Sexual reproduction does not essentially differ, as we have seen, from +budding or self-division, and these processes graduate through the repair +of injuries into ordinary development and growth; it might therefore be +expected that every character would be as regularly transmitted by all the +methods of reproduction as by continued growth. In the chapters devoted to +inheritance it was shown that a multitude of newly-acquired characters, +whether injurious or beneficial, whether of the lowest or highest vital +importance, are often faithfully transmitted--frequently even when one +parent alone possesses some new peculiarity. It deserves especial attention +that characters appearing at any age tend to reappear at a corresponding +age. We may on the whole conclude that in all cases inheritance is the +rule, and non-inheritance the anomaly. In some instances a character is not +inherited, from the conditions of life being directly opposed to its +development; in many instances, from the conditions incessantly inducing +fresh variability, as with grafted fruit-trees and highly cultivated +flowers. In the remaining cases the failure may be attributed to reversion, +by which the child resembles its grandparents or more remote progenitors, +instead of its parents. + +This principle of Reversion is the most wonderful of all the attributes of +Inheritance. It proves to us that the transmission of a character and its +development, which ordinarily go together and thus escape discrimination, +are distinct powers; and these powers in some cases are even antagonistic, +for each acts alternately in successive generations. Reversion is not a +rare event, depending on some unusual or favourable combination of +circumstances, but occurs so regularly with crossed animals and plants, and +so frequently with uncrossed breeds, that it is evidently an essential part +of the principle of inheritance. We know that {373} changed conditions have +the power of evoking long-lost characters, as in the case of some feral +animals. The act of crossing in itself possesses this power in a high +degree. What can be more wonderful than that characters, which have +disappeared during scores, or hundreds, or even thousands of generations, +should suddenly reappear perfectly developed, as in the case of pigeons and +fowls when purely bred, and especially when crossed; or as with the zebrine +stripes on dun-coloured horses, and other such cases? Many monstrosities +come under this same head, as when rudimentary organs are redeveloped, or +when an organ which we must believe was possessed by an early progenitor, +but of which not even a rudiment is left, suddenly reappears, as with the +fifth stamen in some Scrophulariaceae. We have already seen that reversion +acts in bud-reproduction; and we know that it occasionally acts during the +growth of the same individual animal, especially, but not exclusively, when +of crossed parentage,--as in the rare cases described of individual fowls, +pigeons, cattle, and rabbits, which have reverted as they advanced in years +to the colours of one of their parents or ancestors. + +We are led to believe, as formerly explained, that every character which +occasionally reappears is present in a latent form in each generation, in +nearly the same manner as in male and female animals secondary characters +of the opposite sex lie latent, ready to be evolved when the reproductive +organs are injured. This comparison of the secondary sexual characters +which are latent in both sexes, with other latent characters, is the more +appropriate from the case recorded of the Hen, which assumed some of the +masculine characters, not of her own race, but of an early progenitor; she +thus exhibited at the same time the redevelopment of latent characters of +both kinds and connected both classes. In every living creature we may feel +assured that a host of lost characters lie ready to be evolved under proper +conditions. How can we make intelligible, and connect with other facts, +this wonderful and common capacity of reversion,--this power of calling +back to life long-lost characters? {374} + +PART II. + +I have now enumerated the chief facts which every one would desire to +connect by some intelligible bond. This can be done, as it seems to me, if +we make the following assumptions; if the first and chief one be not +rejected, the others, from being supported by various physiological +considerations, will not appear very improbable. It is almost universally +admitted that cells, or the units of the body, propagate themselves by +self-division or proliferation, retaining the same nature, and ultimately +becoming converted into the various tissues and substances of the body. But +besides this means of increase I assume that cells, before their conversion +into completely passive or "formed material," throw off minute granules or +atoms, which circulate freely throughout the system, and when supplied with +proper nutriment multiply by self-division, subsequently becoming developed +into cells like those from which they were derived. These granules for the +sake of distinctness may be called cell-gemmules, or, as the cellular +theory is not fully established, simply gemmules. They are supposed to be +transmitted from the parents to the offspring, and are generally developed +in the generation which immediately succeeds, but are often transmitted in +a dormant state during many generations and are then developed. Their +development is supposed to depend on their union with other partially +developed cells or gemmules which precede them in the regular course of +growth. Why I use the term union, will be seen when we discuss the direct +action of pollen on the tissues of the mother-plant. Gemmules are supposed +to be thrown off by every cell or unit, not only during the adult state, +but during all the stages of development. Lastly, I assume that the +gemmules in their dormant state have a mutual affinity for each other, +leading to their aggregation either into buds or into the sexual elements. +Hence, speaking strictly, it is not the reproductive elements, nor the +buds, which generate new organisms, but the cells themselves throughout the +body. These assumptions constitute the provisional hypothesis which I have +called Pangenesis. Nearly {375} similar views have been propounded, as I +find, by other authors, more especially by Mr. Herbert Spencer;[902] but +they are here modified and amplified. + +{376} + +Before proceeding to show, firstly, how far these assumptions are in +themselves probable, and secondly, how far they connect and explain the +various groups of facts with which we are concerned, it may be useful to +give an illustration of the hypothesis. If one of the simplest Protozoa be +formed, as appears under the microscope, of a small mass of homogeneous +gelatinous matter, a minute atom thrown off from any part and nourished +under favourable circumstances would naturally reproduce the whole; but if +the upper and lower surfaces were to differ in texture from the central +portion, then all three parts would have to throw off atoms or gemmules, +which when aggregated by mutual affinity would form either buds or the +sexual elements. Precisely the same view may be extended to one of the +higher animals; although in this case many thousand gemmules must be thrown +off from the various parts of the body. Now, when the leg, for instance, of +a salamander is cut off, a slight crust forms over the wound, and beneath +this crust the uninjured cells or units of bone, muscle, nerves, &c., are +supposed to unite with the diffused gemmules of those cells which in the +perfect leg come next in order; and these as they become slightly developed +unite with others, and so on until a papilla of soft cellular tissue, the +"budding leg," is formed, and in time a perfect leg.[903] Thus, that +portion of the leg which had {377} been cut off, neither more nor less, +would be reproduced. If the tail or leg of a young animal had been cut off, +a young tail or leg would have been reproduced, as actually occurs with the +amputated tail of the tadpole; for gemmules of all the units which compose +the tail are diffused throughout the body at all ages. But during the adult +state the gemmules of the larval tail would remain dormant, for they would +not meet with pre-existing cells in a proper state of development with +which to unite. If from changed conditions or any other cause any part of +the body should become permanently modified, the gemmules, which are merely +minute portions of the contents of the cells forming the part, would +naturally reproduce the same modification. But gemmules previously derived +from the same part before it had undergone any change, would still be +diffused throughout the organisation, and would be transmitted from +generation to generation, so that under favourable circumstances they might +be redeveloped, and then the new modification would be for a time or for +ever lost. The aggregation of gemmules derived from every part of the body, +through their mutual affinity, would form buds, and their aggregation in +some special manner, apparently in small quantity, together probably with +the presence of gemmules of certain primordial cells, would constitute the +sexual elements. By means of these illustrations the hypothesis of +pangenesis has, I hope, been rendered intelligible. + + * * * * * + +Physiologists maintain, as we have seen, that each cell, though to a large +extent dependent on others, is likewise, to a certain extent, independent +or autonomous. I go one small step further, and assume that each cell casts +off a free gemmule, which is capable of reproducing a similar cell. There +is some analogy between this view and what we see in compound animals and +in the flower-buds on the same tree; for these are distinct individuals +capable of true or seminal reproduction, yet have parts in common and are +dependent on each other; thus {378} the tree has its bark and trunk, and +certain corals, as the Virgularia, have not only parts, but movements in +common. + +The existence of free gemmules is a gratuitous assumption, yet can hardly +be considered as very improbable, seeing that cells have the power of +multiplication through the self-division of their contents. Gemmules differ +from true ovules or buds inasmuch as they are supposed to be capable of +multiplication in their undeveloped state. No one probably will object to +this capacity as improbable. The blastema within the egg has been known to +divide and give birth to two embryos; and Thuret[904] has seen the zoospore +of an alga divide itself, and both halves germinate. An atom of small-pox +matter, so minute as to be borne by the wind, must multiply itself many +thousand-fold in a person thus inoculated.[905] It has recently been +ascertained[906] that a minute portion of the mucous discharge from an +animal affected with rinderpest, if placed in the blood of a healthy ox, +increases so fast that in a short space of time "the whole mass of blood, +weighing many pounds, is infected, and every small particle of that blood +contains enough poison to give, within less than forty-eight hours, the +disease to another animal." + +The retention of free and undeveloped gemmules in the same body from early +youth to old age may appear improbable, but we should remember how long +seeds lie dormant in the earth and buds in the bark of a tree. Their +transmission from generation to generation may appear still more +improbable; but here again we should remember that many rudimentary and +useless organs are transmitted and have been transmitted during an +indefinite number of generations. We shall presently see how well the +long-continued transmission of undeveloped gemmules explains many facts. + +As each unit, or group of similar units throughout the body, casts off its +gemmules, and as all are contained within the smallest egg or seed, and +within each spermatozoon or pollen-grain, their number and minuteness must +be something {379} inconceivable. I shall hereafter recur to this +objection, which at first appears so formidable; but it may here be +remarked that a cod-fish has been found to produce 4,872,000 eggs, a single +Ascaris about 64,000,000 eggs, and a single Orchidaceous plant probably as +many million seeds.[907] In these several cases, the spermatozoa and +pollen-grains must exist in considerably larger numbers. Now, when we have +to deal with numbers such as these, which the human intellect cannot grasp, +there is no good reason for rejecting our present hypothesis on account of +the assumed existence of cell-gemmules a few thousand times more numerous. + +The gemmules in each organism must be thoroughly diffused; nor does this +seem improbable considering their minuteness, and the steady circulation of +fluids throughout the body. So it must be with the gemmules of plants, for +with certain kinds even a minute fragment of a leaf will reproduce the +whole. But a difficulty here occurs; it would appear that with plants, and +probably with compound animals, such as corals, the gemmules do not spread +from bud to bud, but only through the tissues developed from each separate +bud. We are led to this conclusion from the stock being rarely affected by +the insertion of a bud or graft from a distinct variety. This non-diffusion +of the gemmules is still more plainly shown in the case of ferns; for Mr. +Bridgman[908] has proved that, when spores (which it should be remembered +are of the nature of buds) are taken from a monstrous part of a frond, and +others from an ordinary part, {380} each reproduces the form of the part +whence derived. But this non-diffusion of the gemmules from bud to bud may +be only apparent, depending, as we shall hereafter see, on the nature of +the first-formed cells in the buds. + +The assumed elective affinity of each gemmule for that particular cell +which precedes it in the order of development is supported by many +analogies. In all ordinary cases of sexual reproduction the male and female +elements have a mutual affinity for each other: thus, it is believed that +about ten thousand species of Compositae exist, and there can be no doubt +that if the pollen of all these species could be, simultaneously or +successively, placed on the stigma of any one species, this one would elect +with unerring certainty its own pollen. This elective capacity is all the +more wonderful, as it must have been acquired since the many species of +this great group of plants branched off from a common progenitor. On any +view of the nature of sexual reproduction, the protoplasm contained within +the ovules and within the sperm-cells (or the "spermatic force" of the +latter, if so vague a term be preferred) must act on each other by some law +of special affinity, either during or subsequently to impregnation, so that +corresponding parts alone affect each other; thus, a calf produced from a +short-horned cow by a long-horned bull has its horns and not its horny +hoofs affected by the union of the two forms, and the offspring from two +birds with differently coloured tails have their tails and not their whole +plumage affected. + +The various tissues of the body plainly show, as many physiologists have +insisted,[909] an affinity for special organic substances, whether natural +or foreign to the body. We see this in the cells of the kidneys attracting +urea from the blood; in the worrara poison affecting the nerves; upas and +digitalis the muscles; the Lytta vesicatoria the kidneys; and in the +poisonous matter of many diseases, as small-pox, scarlet-fever, +hooping-cough, glanders, cancer, and hydrophobia, affecting certain +definite parts of the body or certain tissues or glands. + +The affinity of various parts of the body for each other during {381} their +early development was shown in the last chapter, when discussing the +tendency to fusion in homologous parts. This affinity displays itself in +the normal fusion of organs which are separate at an early embryonic age, +and still more plainly in those marvellous cases of double monsters in +which each bone, muscle, vessel, and nerve in the one embryo, blends with +the corresponding part in the other. The affinity between homologous organs +may come into action with single parts, or with the entire individual, as +in the case of flowers or fruits which are symmetrically blended together +with all their parts doubled, but without any other trace of fusion. + +It has also been assumed that the development of each gemmule depends on +its union with another cell or unit which has just commenced its +development, and which, from preceding it in order of growth, is of a +somewhat different nature. Nor is it a very improbable assumption that the +development of a gemmule is determined by its union with a cell slightly +different in nature, for abundant evidence was given in the seventeenth +chapter, showing that a slight degree of differentiation in the male and +female sexual elements favours in a marked manner their union and +subsequent development. But what determines the development of the gemmules +of the first-formed or primordial cell in the unimpregnated ovule, is +beyond conjecture. + +It must also be admitted that analogy fails to guide us towards any +determination on several other points: for instance, whether cells, derived +from the same parent-cell, may, in the regular course of growth, become +developed into different structures, from absorbing peculiar kinds of +nutriment, independently of their union with distinct gemmules. We shall +appreciate this difficulty if we call to mind, what complex yet symmetrical +growths the cells of plants yield when they are inoculated by the poison of +a gall-insect. With animals various polypoid excrescences and tumours are +now generally admitted[910] to be the direct product, through +proliferation, of normal cells which have become abnormal. In the regular +growth and repair of bones, the tissues undergo, as Virchow remarks,[911] a +whole series of permutations and substitutions. "The cartilage-cells may be +{382} converted by a direct transformation into marrow-cells, and continue +as such; or they may first be converted into osseous and then into +medullary tissue; or lastly, they may first be converted into marrow and +then into bone. So variable are the permutations of these tissues, in +themselves so nearly allied, and yet in their external appearance so +completely distinct." But as these tissues thus change their nature at any +age, without any obvious change in their nutrition, we must suppose in +accordance with our hypothesis that gemmules derived from one kind of +tissue combine with the cells of another kind, and cause the successive +modifications. + +It is useless to speculate at what period of development each organic unit +casts off its gemmules; for the whole subject of the development of the +various elemental tissues is as yet involved in much doubt. Some +physiologists, for instance, maintain that muscle or nerve-fibres are +developed from cells, which are afterwards nourished by their own proper +powers of absorption; whilst other physiologists deny their cellular +origin; and Beale maintains that such fibres are renovated exclusively by +the conversion of fresh germinal matter (that is the so-called nuclei) into +"formed material." However this may be, it appears probable that all +external agencies, such as changed nutrition, increased use or disuse, &c., +which induced any permanent modification in a structure, would at the same +time or previously act on the cells, nuclei, germinal or formative matter, +from which the structures in question were developed, and consequently +would act on the gemmules or cast-off atoms. + +There is another point on which it is useless to speculate, namely, whether +all gemmules are free and separate, or whether some are from the first +united into small aggregates. A feather, for instance, is a complex +structure, and, as each separate part is liable to inherited variations, I +conclude that each feather certainly generates a large number of gemmules; +but it is possible that these may be aggregated into a compound gemmule. +The same remark applies to the petals of a flower, which in some cases are +highly complex, with each ridge and hollow contrived for special purposes, +so that each part must have been separately modified, and the modifications +transmitted; consequently, separate gemmules, according to our hypothesis, +{383} must have been thrown off from each cell or part. But, as we +sometimes see half an anther or a small portion of a filament becoming +petaliform, or parts or mere stripes of the calyx assuming the colour and +texture of the corolla, it is probable that with petals the gemmules of +each cell are not aggregated together into a compound gemmule, but are +freely and separately diffused. + + * * * * * + +Having now endeavoured to show that the several foregoing assumptions are +to a certain extent supported by analogous facts, and having discussed some +of the most doubtful points, we will consider how far the hypothesis brings +under a single point of view the various cases enumerated in the First +Part. All the forms of reproduction graduate into each other and agree in +their product; for it is impossible to distinguish between organisms +produced from buds, from self-division, or from fertilised germs; such +organisms are liable to variations of the same nature and to reversion of +character; and as we now see that all the forms of reproduction depend on +the aggregation of gemmules derived from the whole body, we can understand +this general agreement. It is satisfactory to find that sexual and asexual +generation, by both of which widely different processes the same living +creature is habitually produced, are fundamentally the same. +Parthenogenesis is no longer wonderful; in fact, the wonder is that it +should not oftener occur. We see that the reproductive organs do not +actually create the sexual elements; they merely determine or permit the +aggregation of the gemmules in a special manner. These organs, together +with their accessory parts, have, however, high functions to perform; they +give to both elements a special affinity for each other, independently of +the contents of the male and female cells, as is shown in the case of +plants by the mutual reaction of the stigma and pollen-grains; they adapt +one or both elements for independent temporary existence, and for mutual +union. The contrivances for these purposes are sometimes wonderfully +complex, as with the spermatophores of the Cephalopoda. The male element +sometimes possesses attributes which, if observed in an independent animal, +would be put down to instinct guided by sense-organs, as when the {384} +spermatozoon of an insect finds its way into the minute micropyle of the +egg, or as when the antherozoids of certain algae swim by the aid of their +ciliae to the female plant, and force themselves into a minute orifice. In +these latter cases, however, we must believe that the male element has +acquired its powers, on the same principle with the larvae of animals, +namely by successive modifications developed at corresponding periods of +life: we can hardly avoid in these cases looking at the male element as a +sort of premature larva, which unites, or, like one of the lower algae, +conjugates, with the female element. What determines the aggregation of the +gemmules within the sexual organs we do not in the least know; nor do we +know why buds are formed in certain definite places, leading to the +symmetrical growth of trees and corals, nor why adventitious buds may be +formed almost anywhere, even on a petal, and frequently upon healed +wounds.[912] As soon as the gemmules have aggregated themselves, +development apparently commences, but in the case of buds is often +afterwards suspended, and in the case of the sexual elements soon ceases, +unless the elements of the opposite sexes combine; even after this has +occurred, the fertilised germ, as with seeds buried in the ground, may +remain during a lengthened period in a dormant state. + +The antagonism which has long been observed,[913] though exceptions +occur,[914] between active growth and the power of sexual +reproduction--between the repair of injuries and gemmation--and with +plants, between rapid increase by buds, rhizomes, &c., and the production +of seed, is partly explained by the gemmules not existing in sufficient +numbers for both processes. {385} But this explanation hardly applies to +those plants which naturally produce a multitude of seeds, but which, +through a comparatively small increase in the number of the buds on their +rhizomes or offsets, yield few or no seed. As, however, we shall presently +see that buds probably include tissue which has already been to a certain +extent developed or differentiated, some additional organised matter will +thus have been expended. + +From one of the forms of Reproduction, namely, spontaneous self-division, +we are led by insensible steps to the repair of the slightest injury; and +the existence of gemmules, derived from every cell or unit throughout the +body and everywhere diffused, explains all such cases,--even the wonderful +fact that, when the limbs of the salamander were cut off many times +successively by Spallanzani and Bonnet, they were exactly and completely +reproduced. I have heard this process compared with the recrystallisation +which occurs when the angles of a broken crystal are repaired; and the two +processes have this much in common, that in the one case the polarity of +the molecules is the efficient cause, and in the other the affinity of the +gemmules for particular nascent cells. + +Pangenesis does not throw much light on Hybridism, but agrees well with +most of the ascertained facts. We may conclude from the fact of a single +spermatozoon or pollen-grain being insufficient for impregnation, that a +certain number of gemmules derived from each cell or unit are required for +the development of each part. From the occurrence of parthenogenesis, more +especially in the case of the silk-moth, in which the embryo is often +partially formed, we may also infer that the female element includes nearly +sufficient gemmules of all kinds for independent development, so that when +united with the male element the gemmules must be superabundant. Now, as a +general rule, when two species or races are crossed reciprocally, the +offspring do not differ, and this shows that both sexual elements agree in +power, in accordance with the view that they include the same gemmules. +Hybrids and mongrels are generally intermediate in character between the +two parent-forms, yet occasionally they closely resemble one parent in one +part and the other parent in another part, or even in their whole +structure: nor is this difficult to understand on {386} the admission that +the gemmules in the fertilised germ are superabundant in number, and that +those derived from one parent have some advantage in number, affinity, or +vigour over those derived from the other parent. Crossed forms sometimes +exhibit the colour or other characters of either parent in stripes or +blotches; and this may occur in the first generation, or through reversion +in succeeding bud and seminal generations, as in the several instances +given in the eleventh chapter. In these cases we must follow Naudin,[915] +and admit that the "essence" or "element" of the two species, which terms I +should translate into the gemmules, have an affinity for their own kind, +and thus separate themselves into distinct stripes or blotches; and reasons +were given, when discussing in the fifteenth chapter the incompatibility of +certain characters to unite, for believing in such mutual affinity. When +two forms are crossed, one is not rarely found to be prepotent in the +transmission of character over the other; and this we can explain only by +again assuming that the one form has some advantage in the number, vigour, +or affinity of its gemmules, except in those cases, where certain +characters are present in the one form and latent in the other. For +instance, there is a latent tendency in all pigeons to become blue, and, +when a blue pigeon is crossed with one of any other colour, the blue tint +is generally prepotent. When we consider latent characters, the explanation +of this form of prepotency will be obvious. + +When one species is crossed with another it is notorious that they do not +yield the full or proper number of offspring; and we can only say on this +head that, as the development of each organism depends on such +nicely-balanced affinities between a host of gemmules and developing cells +or units, we need not feel at all surprised that the commixture of gemmules +derived from two distinct species should lead to a partial or complete +failure of development. With respect to the sterility of hybrids produced +from the union of two distinct species, it was shown in the nineteenth +chapter that this depends exclusively on the reproductive organs being +specially affected; but why these organs should be thus affected we do not +know, any more than {387} why unnatural conditions of life, though +compatible with health, should cause sterility; or why continued close +interbreeding, or the illegitimate unions of dimorphic and trimorphic +plants, induce the same result. The conclusion that the reproductive organs +alone are affected, and not the whole organisation, agrees perfectly with +the unimpaired or even increased capacity in hybrid plants for propagation +by buds; for this implies, according to our hypothesis, that the cells of +the hybrids throw off hybridised cell-gemmules, which become aggregated +into buds, but fail to become aggregated within the reproductive organs, so +as to form the sexual elements. In a similar manner many plants, when +placed under unnatural conditions, fail to produce seed, but can readily be +propagated by buds. We shall presently see that pangenesis agrees well with +the strong tendency to reversion exhibited by all crossed animals and +plants. + +It was shown in the discussion on graft-hybrids that there is some reason +to believe that portions of cellular tissue taken from distinct plants +become so intimately united, as afterwards occasionally to produce crossed +or hybridised buds. If this fact were fully established, it would, by the +aid of our hypothesis, connect gemmation and sexual reproduction in the +closest manner. + +Abundant evidence has been advanced proving that pollen taken from one +species or variety and applied to the stigma of another sometimes directly +affects the tissues of the mother-plant. It is probable that this occurs +with many plants during fertilisation, but can only be detected when +distinct forms are crossed. On any ordinary theory of reproduction this is +a most anomalous circumstance, for the pollen-grains are manifestly adapted +to act on the ovule, but in these cases they act on the colour, texture, +and form of the coats of the seeds, on the ovarium itself, which is a +modified leaf, and even on the calyx and upper part of the flower-peduncle. +In accordance with the hypothesis of pangenesis pollen includes gemmules, +derived from every part of the organisation, which diffuse themselves and +multiply by self-division; hence it is not surprising that gemmules within +the pollen, which are derived from the parts near the reproductive organs, +should sometimes be able to affect the same parts, whilst still undergoing +development, in the mother-plant. {388} + +As, during all the stages of development, the tissues of plants consist of +cells, and as new cells are not known to be formed between, or +independently of, pre-existing cells, we must conclude that the gemmules +derived from the foreign pollen do not become developed merely in contact +with pre-existing cells, but actually penetrate the nascent cells of the +mother-plant. This process may be compared with the ordinary act of +fertilisation, during which the contents of the pollen-tubes penetrate the +closed embryonic sack within the ovule, and determine the development of +the embryo. According to this view, the cells of the mother-plant may +almost literally be said to be fertilised by the gemmules derived from the +foreign pollen. With all organisms, as we shall presently see, the cells or +organic units of the embryo during the successive stages of development may +in like manner be said to be fertilised by the gemmules of the cells, which +come next in the order of formation. + +Animals, when capable of sexual reproduction, are fully developed, and it +is scarcely possible that the male element should affect the tissues of the +mother in the same direct manner as with plants; nevertheless it is certain +that her ovaria are sometimes affected by a previous impregnation, so that +the ovules subsequently fertilised by a distinct male are plainly +influenced in character; and this, as in the case of foreign pollen, is +intelligible through the diffusion, retention, and action of the gemmules +included within the spermatozoa of the previous male. + +Each organism reaches maturity through a longer or shorter course of +development. The changes may be small and insensibly slow, as when a child +grows into a man, or many, abrupt, and slight, as in the metamorphoses of +certain ephemerous insects, or again few and strongly marked, as with most +other insects. Each part may be moulded within a previously existing and +corresponding part, and in this case it will appear, falsely as I believe, +to be formed from the old part; or it may be developed within a wholly +distinct part of the body, as in the extreme cases of metagenesis. An eye, +for instance, may be developed at a spot where no eye previously existed. +We have also seen that allied organic beings in the course of their +metamorphoses sometimes attain nearly the same structure after passing +{389} through widely different forms; or conversely, after passing through +nearly the same early forms, arrive at a widely different termination. In +these cases it is very difficult to believe that the early cells or units +possess the inherent power, independently of any external agent, of +producing new structures wholly different in form, position, and function. +But these cases become plain on the hypothesis of pangenesis. The organic +units, during each stage of development, throw off gemmules, which, +multiplying, are transmitted to the offspring. In the offspring, as soon as +any particular cell or unit in the proper order of development becomes +partially developed, it unites with (or to speak metaphorically is +fertilised by) the gemmule of the next succeeding cell, and so onwards. +Now, supposing that at any stage of development, certain cells or +aggregates of cells had been slightly modified by the action of some +disturbing cause, the cast-off gemmules or atoms of the cell-contents could +hardly fail to be similarly affected, and consequently would reproduce the +same modification. This process might be repeated until the structure of +the part at this particular stage of development became greatly changed, +but this would not necessarily affect other parts whether previously or +subsequently developed. In this manner we can understand the remarkable +independence of structure in the successive metamorphoses, and especially +in the successive metageneses of many animals. + +The term growth ought strictly to be confined to mere increase of size, and +development to change of structure.[916] Now, a child is said to grow into +a man, and a foal into a horse, but, as in these cases there is much change +of structure, the process properly belongs to the order of development. We +have indirect evidence of this in many variations and diseases supervening +during so-called growth at a particular period, and being inherited at a +corresponding period. In the case, however, of diseases which supervene +during old age, subsequently to the ordinary period of procreation, and +which nevertheless are sometimes inherited, as occurs with brain and heart +complaints, we {390} must suppose that the organs were in fact affected at +an earlier age and threw off at this period affected gemmules; but that the +affection became visible or injurious only after the prolonged growth of +the part in the strict sense of the word. In all the changes of structure +which regularly supervene during old age, we see the effects of +deteriorated growth, and not of true development. + +In the so-called process of _alternate generation_ many individuals are +generated asexually during very early or later stages of development. These +individuals may closely resemble the preceding larval form, but generally +are wonderfully dissimilar. To understand this process we must suppose that +at a certain stage of development the gemmules are multiplied at an unusual +rate, and become aggregated by mutual affinity at many centres of +attraction, or buds. These buds, it may be remarked, must include gemmules +not only of all the succeeding but likewise of all the preceding stages of +development; for when mature they have the power of transmitting by sexual +generation gemmules of all the stages, however numerous these may be. It +was shown in the First Part, at least in regard to animals, that the new +beings which are thus at any period asexually generated do not retrograde +in development--that is, they do not pass through those earlier stages, +through which the fertilised germ of the same animal has to pass; and an +explanation of this fact was attempted as far as the final or teleological +cause is concerned. We can likewise understand the proximate cause, if we +assume, and the assumption is far from improbable, that buds, like +chopped-up fragments of a hydra, are formed of tissue which has already +passed through several of the earlier stages of development; for in this +case their component cells or units would not unite with the gemmules +derived from the earlier-formed cells, but only with those which came next +in the order of development. On the other hand, we must believe that, in +the sexual elements, or probably in the female alone, gemmules of certain +primordial cells are present; and these, as soon as their development +commences, unite in due succession with the gemmules of every part of the +body, from the first to the last period of life. + +The principle of the independent formation of each part, in {391} so far as +its development depends on the union of the proper gemmules with certain +nascent cells, together with the superabundance of the gemmules derived +from both parents and self-multiplied, throws light on a widely different +group of facts, which on any ordinary view of development appears very +strange. I allude to organs which are abnormally multiplied or transposed. +Thus gold-fish often have supernumerary fins placed on various parts of +their bodies. We have seen that, when the tail of a lizard is broken off, a +double tail is sometimes reproduced, and when the foot of the salamander is +divided longitudinally, additional digits are occasionally formed. When +frogs, toads, &c., are born with their limbs doubled, as sometimes occurs, +the doubling, as Gervais remarks,[917] cannot be due to the complete fusion +of two embryos, with the exception of the limbs, for the larvae are +limbless. The same argument is applicable[918] to certain insects produced +with multiple legs or antennae, for these are metamorphosed from apodal or +antennaeless larvae. Alphonse Milne-Edwards[919] has described the curious +case of a crustacean in which one eye-peduncle supported, instead of a +complete eye, only an imperfect cornea, out of the centre of which a +portion of an antenna was developed. A case has been recorded[920] of a man +who had during both dentitions a double tooth in place of the left second +incisor, and he inherited this peculiarity from his paternal grandfather. +Several cases are known[921] of additional teeth having been developed in +the palate, more especially with horses, and in the orbit of the eye. +Certain breeds of sheep bear a whole crowd of horns on their foreheads. +Hairs occasionally appear in strange situations, as within the ears of the +Siamese hairy family; and hairs "quite natural in structure" have been +observed "within the substance of the brain."[922] As many as five spurs +have been seen on both legs in certain Game-fowls. In the Polish fowl the +male is ornamented with a topknot of hackles {392} like those on his neck, +whilst the female has one of common feathers. In feather-footed pigeons and +fowls, feathers like those on the wing arise from the outer side of the +legs and toes. Even the elemental parts of the same feather may be +transposed; for in the Sebastopol goose, barbules are developed on the +divided filaments of the shaft. + +Analogous cases are of such frequent occurrence with plants that they do +not strike us with sufficient surprise. Supernumerary petals, stamens, and +pistils, are often produced. I have seen a leaflet low down in the compound +leaf of _Vicia sativa_ converted into a tendril, and a tendril possesses +many peculiar properties, such as spontaneous movement and irritability. +The calyx sometimes assumes, either wholly or by stripes, the colour and +texture of the corolla. Stamens are so frequently converted, more or less +completely, into petals, that such cases are passed over as not deserving +notice; but as petals have special functions to perform, namely, to protect +the included organs, to attract insects, and in not a few cases to guide +their entrance by well-adapted contrivances, we can hardly account for the +conversion of stamens into petals merely by unnatural or superfluous +nourishment. Again, the edge of a petal may occasionally be found including +one of the highest products of the plant, namely the pollen; for instance, +I have seen in an Ophrys a pollen-mass with its curious structure of little +packets, united together and to the caudicle by elastic threads, formed +between the edges of an upper petal. The segments of the calyx of the +common pea have been observed partially converted into carpels, including +ovules, and with their tips converted into stigmas. Numerous analogous +facts could be given.[923] + +I do not know how physiologists look at such facts as the foregoing. +According to the doctrine of pangenesis, the free and superabundant +gemmules of the transposed organs are developed in the wrong place, from +uniting with wrong cells or aggregates of cells during their nascent state; +and this would follow from a slight modification in the elective affinity +of such cells, or possibly of certain gemmules. Nor ought we to feel much +surprise at the affinities of cells and gemmules varying {393} under +domestication, when we remember the many curious cases given, in the +seventeenth chapter, of cultivated plants which absolutely refuse to be +fertilised by their own pollen or by that of the same species, but are +abundantly fertile with pollen of a distinct species; for this implies that +their sexual elective affinities--and this is the term used by +Gaertner--have been modified. As the cells of adjoining or homologous parts +will have nearly the same nature, they will be liable to acquire by +variation each other's elective affinities; and we can thus to a certain +extent understand such cases as a crowd of horns on the heads in certain +sheep, of several spurs on the leg, and of hackles on the head of the fowl, +and with the pigeon the occurrence of wing-feathers on their legs and of +membrane between their toes; for the leg is the homologue of the wing. As +all the organs of plants are homologous and spring from a common axis, it +is natural that they should be eminently liable to transposition. It ought +to be observed that when any compound part, such as an additional limb or +an antenna, springs from a false position, it is only necessary that the +few first gemmules should be wrongly attached; for these whilst developing +would attract others in due succession, as in the regrowth of an amputated +limb. When parts which are homologous and similar in structure, as the +vertebrae in snakes or the stamens in polyandrous flowers, &c., are +repeated many times in the same organism, closely allied gemmules must be +extremely numerous, as well as the points to which they ought to become +united; and, in accordance with the foregoing views, we can to a certain +extent understand Isid. Geoffroy St. Hilaire's law, namely, that parts, +which are already multiple, are extremely liable to vary in number. + +The same general principles apply to the fusion of homologous parts; and +with respect to mere cohesion there is probably always some degree of +fusion, at least near the surface. When two embryos during their early +development come into close contact, as both include corresponding +gemmules, which must be in all respects almost identical in nature, it is +not surprising that some derived from one embryo and some from the other +should unite at the point of contact with a single nascent cell or +aggregate of cells, and thus give rise to a single part or organ. For +instance, two embryos might thus come to have on their {394} adjoining +sides a single symmetrical arm, which in one sense will have been formed by +the fusion of the bones, muscles, &c., belonging to the arms of both +embryos. In the case of the fish described by Lereboullet, in which a +double head was seen gradually to fuse into a single one, the same process +must have taken place, together with the absorption of all the parts which +had been already formed. These cases are exactly the reverse of those in +which a part is doubled either spontaneously or after an injury; for in the +case of doubling, the superabundant gemmules of the same part are +separately developed in union with adjoining points; whilst in the case of +fusion the gemmules derived from two homologous parts become mingled and +form a single part; or it may be that the gemmules from one of two +adjoining embryos alone become developed. + + * * * * * + +Variability often depends, as I have attempted to show, on the reproductive +organs being injuriously affected by changed conditions; and in this case +the gemmules derived from the various parts of the body are probably +aggregated in an irregular manner, some superfluous and others deficient. +Whether a superabundance of gemmules, together with fusion during +development, would lead to the increased size of any part cannot be told; +but we can see that their partial deficiency, without necessarily leading +to the entire abortion of the part, might cause considerable modifications; +for in the same manner as a plant, if its own pollen be excluded, is easily +hybridised, so, in the case of a cell, if the properly succeeding gemmules +were absent, it would probably combine easily with other and allied +gemmules. We see this in the case of imperfect nails growing on the stumps +of amputated fingers,[924] for the gemmules of the nails have manifestly +been developed at the nearest point. + +In variations caused by the direct action of changed conditions, whether of +a definite or indefinite nature, as with the fleeces of sheep in hot +countries, with maize grown in cold countries, with inherited gout, &c., +the tissues of the body, according to the doctrine of pangenesis, are +directly affected by the new conditions, and consequently throw off +modified gemmules, which are transmitted with their newly acquired +peculiarities to the offspring. On any ordinary view it is unintelligible +how changed {395} conditions, whether acting on the embryo, the young or +adult animal, can cause inherited modifications. It is equally or even more +unintelligible on any ordinary view, how the effects of the long-continued +use or disuse of any part, or of changed habits of body or mind, can be +inherited. A more perplexing problem can hardly be proposed; but on our +view we have only to suppose that certain cells become at last not only +functionally but structurally modified; and that these throw off similarly +modified gemmules. This may occur at any period of development, and the +modification will be inherited at a corresponding period; for the modified +gemmules will unite in all ordinary cases with the proper preceding cells, +and they will consequently be developed at the same period at which the +modification first arose. With respect to mental habits or instincts, we +are so profoundly ignorant on the relation between the brain and the power +of thought that we do not know whether an inveterate habit or trick induces +any change in the nervous system; but when any habit or other mental +attribute, or insanity, is inherited, we must believe that some actual +modification is transmitted;[925] and this implies, according to our +hypothesis, that gemmules derived from modified nerve-cells are transmitted +to the offspring. + +It is generally, perhaps always, necessary that an organism should be +exposed during several generations to changed conditions or habits, in +order that any modification in the structure of the offspring should ensue. +This may be partly due to the changes not being at first marked enough to +catch the attention, but this explanation is insufficient; and I can +account for the fact, only by the assumption, which we shall see under the +head of reversion is strongly supported, that gemmules derived from each +cell before it had undergone the least modification are transmitted in +large numbers to successive generations, but that the gemmules derived from +the same cells after modification, naturally go on increasing under the +same favouring conditions, until at last they become sufficiently numerous +to overpower and supplant the old gemmules. + +Another difficulty may be here noticed; we have seen that {396} there is an +important difference in the frequency, though not in the nature, of the +variations in plants propagated by sexual and asexual generation. As far as +variability depends on the imperfect action of the reproductive organs +under changed conditions, we can at once see why seedlings should be far +more variable than plants propagated by buds. We know that extremely slight +causes,--for instance, whether a tree has been grafted or grows on its own +stock, the position of the seeds within the capsule, and of the flowers on +the spike,--sometimes suffice to determine the variation of a plant, when +raised from seed. Now, it is probable, as explained when discussing +alternate generation, that a bud is formed of a portion of already +differentiated tissue; consequently an organism thus formed does not pass +through the earlier phases of development, and cannot be so freely exposed, +at the age when its structure would be most readily modified, to the +various causes inducing variability; but it is very doubtful whether this +is a sufficient explanation of the difficulty. + +With respect to the tendency to reversion, there is a similar difference +between plants propagated from buds and seed. Many varieties, whether +originally produced from seed or buds, can be securely propagated by buds, +but generally or invariably revert by seed. So, also, hybridised plants can +be multiplied to any extent by buds, but are continually liable to +reversion by seed,--that is, to the loss of their hybrid or intermediate +character. I can offer no satisfactory explanation of this fact. Here is a +still more perplexing case: certain plants with variegated leaves, phloxes +with striped flowers, barberries with seedless fruit, can all be securely +propagated by the buds on cuttings; but the buds developed from the roots +of these cuttings almost invariably lose their character and revert to +their former condition. + +Finally, we can see on the hypothesis of pangenesis that variability +depends on at least two distinct groups of causes. Firstly, on the +deficiency, superabundance, fusion, and transposition of gemmules, and on +the redevelopment of those which have long been dormant. In these cases the +gemmules themselves have undergone no modification; but the mutations in +the above respects will amply account for much fluctuating {397} +variability. Secondly, in the cases in which the organisation has been +modified by changed conditions, the increased use or disuse of parts, or +any other cause, the gemmules cast off from the modified units of the body +will be themselves modified, and, when sufficiently multiplied, will be +developed into new and changed structures. + + * * * * * + +Turning now to Inheritance: if we suppose a homogeneous gelatinous +protozoon to vary and assume a reddish colour, a minute separated atom we +aid naturally, as it grew to full size, retain the same colour; and we +should have the simplest form of inheritance.[926] Precisely the same view +may be extended to the infinitely numerous and diversified units of which +the whole body in one of the higher animals is composed; and the separated +atoms are our gemmules. We have already sufficiently discussed the +inheritance of the direct effects of changed conditions, and of increased +use or disuse of parts, and, by implication, the important principle of +inheritance at corresponding ages. These groups of facts are to a large +extent intelligible on the hypothesis of pangenesis, and on no other +hypothesis as yet advanced. + +A few words must be added on the complete abortion or suppression of +organs. When a part becomes diminished by disuse prolonged during many +generations, the principle of economy of growth, as previously explained, +will tend to reduce it still further; but this will not account for the +complete or almost complete obliteration of, for instance, a minute papilla +of cellular tissue representing a pistil, or of a microscopically minute +nodule of bone representing a tooth. In certain cases of suppression not +yet completed, in which a rudiment occasionally reappears through +reversion, diffused gemmules derived from this part must, according to our +view, still exist; hence we must suppose that the cells, in union with +which the rudiment was formerly developed, in these cases fail in their +affinity for such gemmules. But in the cases of complete and final abortion +the gemmules themselves no doubt have perished; nor is this {398} in any +way improbable, for, though a vast number of active and long-dormant +gemmules are diffused and nourished in each living creature, yet there must +be some limit to their number; and it appears natural that gemmules derived +from an enfeebled and useless rudiment would be more liable to perish than +those derived from other parts which are still in full functional activity. + +With respect to mutilations, it is certain that a part may be removed or +injured during many generations, and no inherited result follow; and this +is an apparent objection to the hypothesis which will occur to every one. +But, in the first place, a being can hardly be intentionally mutilated +during its early stages of growth whilst in the womb or egg; and such +mutilations, when naturally caused, would appear like congenital +deficiencies, which are occasionally inherited. In the second place, +according to our hypothesis, gemmules multiply by self-division and are +transmitted from generation to generation; so that during a long period +they would be present and ready to reproduce a part which was repeatedly +amputated. Nevertheless it appears, from the facts given in the twelfth +chapter, that in some rare cases mutilations have been inherited, but in +most of these the mutilated surface became diseased. In this case it may be +conjectured that the gemmules of the lost part were gradually all attracted +by the partially diseased surface, and thus perished. Although this would +occur in the injured individual alone, and therefore in only one parent, +yet this might suffice for the inheritance of a mutilation, on the same +principle that a hornless animal of either sex, when crossed with a perfect +animal of the opposite sex, often transmits its deficiency. + +The last subject that need here be discussed, namely Reversion, rests on +the principle that transmission and development, though generally acting in +conjunction, are distinct powers; and the transmission of gemmules and +their subsequent development show us how the existence of these two +distinct powers is possible. We plainly see this distinction in the many +cases in which a grandfather transmits to his grandson, through his +daughter, characters which she does not, or cannot, possess. Why the +development of certain characters, not necessarily in any way connected +with the reproductive organs, should be confined to one sex alone--that is, +why certain cells in one sex {399} should unite with and cause the +development of certain gemmules--we do not in the least know; but it is the +common attribute of most organic beings in which the sexes are separate. + +The distinction between transmission and development is likewise seen in +all ordinary cases of Reversion; but before discussing this subject it may +be advisable to say a few words on those characters which I have called +latent, and which would not be classed under Reversion in its usual sense. +Most, or perhaps all, the secondary characters, which appertain to one sex, +lie dormant in the other sex; that is, gemmules capable of development into +the secondary male sexual characters are included within the female; and +conversely female characters in the male. Why in the female, when her +ovaria become diseased or fail to act, certain masculine gemmules become +developed, we do not clearly know, any more than why when a young bull is +castrated his horns continue growing until they almost resemble those of a +cow; or why, when a stag is castrated, the gemmules derived from the +antlers of his progenitors quite fail to be developed. But in many cases, +with variable organic beings, the mutual affinities of the cells and +gemmules become modified, so that parts are transposed or multiplied; and +it would appear that a slight change in the constitution of an animal, in +connection with the state of the reproductive organs, leads to changed +affinities in the tissues of various parts of the body. Thus, when male +animals first arrive at puberty, and subsequently during each recurrent +season, certain cells or parts acquire an affinity for certain gemmules, +which become developed into the secondary masculine characters; but if the +reproductive organs be destroyed, or even temporarily disturbed by changed +conditions, these affinities are not excited. Nevertheless, the male, +before he arrives at puberty, and during the season when the species does +not breed, must include the proper gemmules in a latent state. The curious +case formerly given of a Hen which assumed the masculine characters, not of +her own breed but of a remote progenitor, illustrates the connexion between +latent sexual characters and ordinary reversion. With those animals and +plants which habitually produce several forms, as with certain butterflies +described by Mr. Wallace, in which three female forms and {400} the male +exist, or as with the trimorphic species of Lythrum and Oxalis, gemmules +capable of reproducing several widely-different forms must be latent in +each individual. + +The same principle of the latency of certain characters, combined with the +transposition of organs, may be applied to those singular cases of +butterflies and other insects, in which exactly one half or one quarter of +the body resembles the male, and the other half or three quarters the +female; and when this occurs the opposite sides of the body, separated from +each other by a distinct line, sometimes differ in the most conspicuous +manner. Again, these same principles apply to the cases given in the +thirteenth chapter, in which the right and left sides of the body differ to +an extraordinary degree, as in the spiral winding of certain shells, and as +in the genus Verruca among cirripedes; for in these cases it is known that +either side indifferently may undergo the same remarkable change of +development. + +Reversion, in the ordinary sense of the word, comes into action so +incessantly, that it evidently forms an essential part of the general law +of inheritance. It occurs with beings, however propagated, whether by buds +or seminal generation, and sometimes may even be observed in the same +individual as it advances in age. The tendency to reversion is often +induced by a change of conditions, and in the plainest manner by the act of +crossing. Crossed forms are generally at first nearly intermediate in +character between their two parents; but in the next generation the +offspring generally revert to one or both of their grandparents, and +occasionally to more remote ancestors. How can we account for these facts? +Each organic unit in a hybrid must throw off, according to the doctrine of +pangenesis, an abundance of hybridised gemmules, for crossed plants can be +readily and largely propagated by buds; but by the same hypothesis there +will likewise be present dormant gemmules derived from both pure +parent-forms; and as these latter retain their normal condition, they +would, it is probable, be enabled to multiply largely during the lifetime +of each hybrid. Consequently the sexual elements of a hybrid will include +both pure and hybridised gemmules; and when two hybrids pair, the +combination of pure gemmules derived from the one hybrid with the pure +gemmules of the same parts derived from the other would {401} necessarily +lead to complete reversion of character; and it is, perhaps, not too bold a +supposition that unmodified and undeteriorated gemmules of the same nature +would be especially apt to combine. Pure gemmules in combination with +hybridised gemmules would lead to partial reversion. And lastly, hybridised +gemmules derived from both parent-hybrids would simply reproduce the +original hybrid form.[927] All these cases and degrees of reversion +incessantly occur. + +It was shown in the fifteenth chapter that certain characters are +antagonistic to each other or do not readily blend together; hence, when +two animals with antagonistic characters are crossed, it might well happen +that a sufficiency of gemmules in the male alone for the reproduction of +his peculiar characters, and in the female alone for the reproduction of +her peculiar characters, would not be present; and in this case dormant +gemmules derived from some remote progenitor might easily gain the +ascendency, and cause the reappearance of long-lost characters. For +instance, when black and white pigeons, or black and white fowls, are +crossed,--colours which do not readily blend,--blue plumage in the one +case, evidently derived from the rock-pigeon, and red plumage in the other +case, derived from the wild jungle-cock, occasionally reappear. With +uncrossed breeds the same result would follow, under conditions which +favoured the multiplication and development of certain dormant gemmules, as +when animals become feral and revert to their pristine character. A certain +number of gemmules being requisite for the development of each character, +as is known to be the case from several spermatozoa or pollen-grains being +necessary for fertilisation, and time favouring their multiplication, will +together account for the curious cases, insisted on by Mr. Sedgwick, of +certain diseases regularly appearing in alternate generations. This +likewise holds good, more or less strictly, with other weakly inherited +modifications. Hence, as I have heard it remarked, certain diseases appear +actually to gain strength by the intermission of a generation. The +transmission of dormant gemmules during many successive generations is +hardly in itself more improbable, as {402} previously remarked, than the +retention during many ages of rudimentary organs, or even only of a +tendency to the production of a rudiment; but there is no reason to suppose +that all dormant gemmules would be transmitted and propagated for ever. +Excessively minute and numerous as they are believed to be, an infinite +number derived, during a long course of modification and descent, from each +cell of each progenitor, could not be supported or nourished by the +organism. On the other hand, it does not seem improbable that certain +gemmules, under favourable conditions, should be retained and go on +multiplying for a longer period than others. Finally, on the views here +given, we certainly gain some clear insight into the wonderful fact that +the child may depart from the type of both its parents, and resemble its +grandparents, or ancestors removed by many generations. + +_Conclusion._ + +The hypothesis of Pangenesis, as applied to the several great classes of +facts just discussed, no doubt is extremely complex; but so assuredly are +the facts. The assumptions, however, on which the hypothesis rests cannot +be considered as complex in any extreme degree--namely, that all organic +units, besides having the power, as is generally admitted, of growing by +self-division, throw off free and minute atoms of their contents, that is +gemmules. These multiply and aggregate themselves into buds and the sexual +elements; their development depends on their union with other nascent cells +or units; and they are capable of transmission in a dormant state to +successive generations. + +In a highly organised and complex animal, the gemmules thrown off from each +different cell or unit throughout the body must be inconceivably numerous +and minute. Each unit of each part, as it changes during development, and +we know that some insects undergo at least twenty metamorphoses, must throw +off its gemmules. All organic beings, moreover, include many dormant +gemmules derived from their grandparents and more remote progenitors, but +not from all their progenitors. These almost infinitely numerous and minute +gemmules must be included in each bud, ovule, spermatozoon, and +pollen-grain. Such an admission will be declared impossible; but, as +previously {403} remarked, number and size are only relative difficulties, +and the eggs or seeds produced by certain animals or plants are so numerous +that they cannot be grasped by the intellect. + +The organic particles with which the wind is tainted over miles of space by +certain offensive animals must be infinitely minute and numerous; yet they +strongly affect the olfactory nerves. An analogy more appropriate is +afforded by the contagious particles of certain diseases, which are so +minute that they float in the atmosphere and adhere to smooth paper; yet we +know how largely they increase within the human body, and how powerfully +they act. Independent organisms exist which are barely visible under the +highest powers of our recently-improved microscopes, and which probably are +fully as large as the cells or units in one of the higher animals; yet +these organisms no doubt reproduce themselves by germs of extreme +minuteness, relatively to their own minute size. Hence the difficulty, +which at first appears insurmountable, of believing in the existence of +gemmules so numerous and so small as they must be according to our +hypothesis, has really little weight. + +The cells or units of the body are generally admitted by physiologists to +be autonomous, like the buds on a tree, but in a less degree. I go one step +further and assume that they throw off reproductive gemmules. Thus an +animal does not, as a whole, generate its kind through the sole agency of +the reproductive system, but each separate cell generates its kind. It has +often been said by naturalists that each cell of a plant has the actual or +potential capacity of reproducing the whole plant; but it has this power +only in virtue of containing gemmules derived from every part. If our +hypothesis be provisionally accepted, we must look at all the forms of +asexual reproduction, whether occurring at maturity or as in the case of +alternate generation during youth, as fundamentally the same, and dependent +on the mutual aggregation and multiplication of the gemmules. The regrowth +of an amputated limb or the healing of a wound is the same process +partially carried out. Sexual generation differs in some important +respects, chiefly, as it would appear, in an insufficient number of +gemmules being aggregated within the separate sexual elements, and probably +in the presence of certain primordial cells. The development of each being, +including all the {404} forms of metamorphosis and metagenesis, as well as +the so-called growth of the higher animals, in which structure changes +though not in a striking manner, depends on the presence of gemmules thrown +off at each period of life, and on their development, at a corresponding +period, in union with preceding cells. Such cells may be said to be +fertilised by the gemmules which come next in the order of development. +Thus the ordinary act of impregnation and the development of each being are +closely analogous processes. The child, strictly speaking, does not grow +into the man, but includes germs which slowly and successively become +developed and form the man. In the child, as well as in the adult, each +part generates the same part for the next generation. Inheritance must be +looked at as merely a form of growth, like the self-division of a +lowly-organised unicellular plant. Reversion depends on the transmission +from the forefather to his descendants of dormant gemmules, which +occasionally become developed under certain known or unknown conditions. +Each animal and plant may be compared to a bed of mould full of seeds, most +of which soon germinate, some lie for a period dormant, whilst others +perish. When we hear it said that a man carries in his constitution the +seeds of an inherited disease, there is much literal truth in the +expression. Finally, the power of propagation possessed by each separate +cell, using the term in its largest sense, determines the reproduction, the +variability, the development and renovation of each living organism. No +other attempt, as far as I am aware, has been made, imperfect as this +confessedly is, to connect under one point of view these several grand +classes of facts. We cannot fathom the marvellous complexity of an organic +being; but on the hypothesis here advanced this complexity is much +increased. Each living creature must be looked at as a microcosm--a little +universe, formed of a host of self-propagating organisms, inconceivably +minute and as numerous as the stars in heaven. + + * * * * * + + +{405} + +CHAPTER XXVIII. + +CONCLUDING REMARKS. + + DOMESTICATION--NATURE AND CAUSES OF VARIABILITY--SELECTION--DIVERGENCE + AND DISTINCTNESS OF CHARACTER--EXTINCTION OF RACES--CIRCUMSTANCES + FAVOURABLE TO SELECTION BY MAN--ANTIQUITY OF CERTAIN RACES--THE + QUESTION WHETHER EACH PARTICULAR VARIATION HAS BEEN SPECIALLY + PREORDAINED. + +As summaries have been added to nearly all the chapters, and as, in the +chapter on pangenesis, various subjects, such as the forms of reproduction, +inheritance, reversion, the causes and laws of variability, &c., have been +recently discussed, I will here only make a few general remarks on the more +important conclusions which may be deduced from the multifarious details +given throughout this work. + +Savages in all parts of the world easily succeed in taming wild animals; +and those inhabiting any country or island, when first invaded by man, +would probably have been still more easily tamed. Complete subjugation +generally depends on an animal being social in its habits, and on receiving +man as the chief of the herd or family. Domestication implies almost +complete fertility under new and changed conditions of life, and this is +far from being invariably the case. An animal would not have been worth the +labour of domestication, at least during early times, unless of service to +man. From these circumstances the number of domesticated animals has never +been large. With respect to plants, I have shown in the ninth chapter how +their varied uses were probably first discovered, and the early steps in +their cultivation. Man could not have known, when he first domesticated an +animal or plant, whether it would flourish and multiply when transported to +other countries, therefore he could not have been thus influenced in his +choice. We see that the close adaptation of the reindeer and camel to +extremely cold and hot countries has not prevented their domestication. +Still less {406} could man have foreseen whether his animals and plants +would vary in succeeding generations and thus give birth to new races; and +the small capacity of variability in the goose and ass has not prevented +their domestication from the remotest epoch. + +With extremely few exceptions, all animals and plants which have been long +domesticated, have varied greatly. It matters not under what climate, or +for what purpose, they are kept, whether as food for man or beast, for +draught or hunting, for clothing or mere pleasure,--under all these +circumstances domesticated animals and plants have varied to a much greater +extent than the forms which in a state of nature are ranked as one species. +Why certain animals and plants have varied more under domestication than +others we do not know, any more than why some are rendered more sterile +than others under changed conditions of life. But we frequently judge of +the amount of variation by the production of numerous and diversified +races, and we can clearly see why in many cases this has not occurred, +namely, because slight successive variations have not been steadily +accumulated; and such variations will never be accumulated when an animal +or plant is not closely observed, or much valued, or kept in large numbers. + +The fluctuating, and, as far as we can judge, never-ending variability of +our domesticated productions,--the plasticity of their whole +organisation,--is one of the most important facts which we learn from the +numerous details given in the earlier chapters of this work. Yet +domesticated animals and plants can hardly have been exposed to greater +changes in their conditions than have many natural species during the +incessant geological, geographical, and climatal changes of the whole +world. The former will, however, commonly have been exposed to more sudden +changes and to less continuously uniform conditions. As man has +domesticated so many animals and plants belonging to widely different +classes, and as he certainly did not with prophetic instinct choose those +species which would vary most, we may infer that all natural species, if +subjected to analogous conditions, would, on an average, vary to the same +degree. Few men at the present day will maintain that animals and plants +were created with a tendency to vary, which long remained dormant, in order +that fanciers in after ages might {407} rear, for instance, curious breeds +of the fowl, pigeon, or canary-bird. + +From several causes it is difficult to judge of the amount of modification +which our domestic productions have undergone. In some cases the primitive +parent-stock has become extinct, or cannot be recognised with certainty +owing to its supposed descendants having been so much modified. In other +cases two or more closely allied forms, after being domesticated, have +crossed; and then it is difficult to estimate how much of the change ought +to be attributed to variation. But the degree to which our domestic breeds +have been modified by the crossing of distinct natural forms has probably +been exaggerated by some authors. A few individuals of one form would +seldom permanently affect another form existing in much greater numbers; +for, without careful selection, the stain of the foreign blood would soon +be obliterated, and during early and barbarous times, when our animals were +first domesticated, such care would seldom have been taken. + +There is good reason to believe that several of the breeds of the dog, ox, +pig, and of some other animals, are respectively descended from distinct +wild prototypes; nevertheless the belief in the multiple origin of our +domesticated animals has been extended by some few naturalists and by many +breeders to an unauthorised extent. Breeders refuse to look at the whole +subject under a single point of view; I have heard one, who maintained that +our fowls were the descendants of at least half-a-dozen aboriginal species, +protest that he was in no way concerned with the origin of pigeons, ducks, +rabbits, horses, or any other animal. They overlook the improbability of +many species having been domesticated at an early and barbarous period. +They do not consider the improbability of species having existed in a state +of nature which, if like our present domestic breeds, would have been +highly abnormal in comparison with all their congeners. They maintain that +certain species, which formerly existed, have become extinct or unknown, +although the world is now so much better known. The assumption of so much +recent extinction is no difficulty in their eyes; for they do not judge of +its probability by the facility or difficulty of the extinction of other +closely allied wild forms. Lastly, {408} they often ignore the whole +subject of geographical distribution as completely as if its laws were the +result of chance. + +Although from the reasons just assigned it is often difficult to judge +accurately of the amount of change which our domesticated productions have +undergone, yet this can be ascertained in the cases in which we know that +all the breeds are descended from a single species, as with the pigeon, +duck, rabbit, and almost certainly with the fowl; and by the aid of analogy +this is to a certain extent possible in the case of animals descended from +several wild stocks. It is impossible to read the details given in the +earlier chapters, and in many published works, or to visit our various +exhibitions, without being deeply impressed with the extreme variability of +our domesticated animals and cultivated plants. I have in many instances +purposely given details on new and strange peculiarities which have arisen. +No part of the organisation escapes the tendency to vary. The variations +generally affect parts of small vital or physiological importance, but so +it is with the differences which exist between closely allied species. In +these unimportant characters there is often a greater difference between +the breeds of the same species than between the natural species of the same +genus, as Isidore Geoffroy has shown to be the case with size, and as is +often the case with the colour, texture, form, &c., of the hair, feathers, +horns, and other dermal appendages. + +It has often been asserted that important parts never vary under +domestication, but this is a complete error. Look at the skull of the pig +in any one of the highly improved breeds, with the occipital condyles and +other parts greatly modified; or look at that of the niata ox. Or again, in +the several breeds of the rabbit, observe the elongated skull, with the +differently shaped occipital foramen, atlas, and other cervical vertebrae. +The whole shape of the brain, together with the skull, has been modified in +Polish fowls; in other breeds of the fowl the number of the vertebrae and +the forms of the cervical vertebrae have been changed. In certain pigeons +the shape of the lower jaw, the relative length of the tongue, the size of +the nostrils and eyelids, the number and shape of the ribs, the form and +size of the oesophagus, have all varied. In certain quadrupeds the length +of the intestines has been much increased or {409} diminished. With plants +we see wonderful differences in the stones of various fruits. In the +Cucurbitaceae several highly important characters have varied, such as the +sessile position of the stigmas on the ovarium, the position of the carpels +within the ovarium, and its projection out of the receptacle. But it would +be useless to run through the many facts given in the earlier chapters. + +It is notorious how greatly the mental disposition, tastes, habits, +consensual movements, loquacity or silence, and the tone of voice have +varied and been inherited with our domesticated animals. The dog offers the +most striking instance of changed mental attributes, and these differences +cannot be accounted for by descent from distinct wild types. New mental +characters have certainly often been acquired, and natural ones lost, under +domestication. + +New characters may appear and disappear at any stage of growth, and be +inherited at a corresponding period. We see this in the difference between +the eggs of various breeds of the fowl, and in the down on chickens; and +still more plainly in the differences between the caterpillars and cocoons +of various breeds of the silk-moth. These facts, simple as they appear, +throw light on the characters which distinguish the larval and adult states +of natural species, and on the whole great subject of embryology. New +characters are liable to become attached exclusively to that sex in which +they first appeared, or they may be developed in a much higher degree in +the one than the other sex; or again, after having become attached to one +sex, they may be partially transferred to the opposite sex. These facts, +and more especially the circumstance that new characters seem to be +particularly liable, from some unknown cause, to become attached to the +male sex, have an important bearing on the acquirement by animals in a +state of nature of secondary sexual characters. + +It has sometimes been said that our domestic productions do not differ in +constitutional peculiarities, but this cannot be maintained. In our +improved cattle, pigs, &c., the period of maturity, including that of the +second dentition, has been much hastened. The period of gestation varies +much, but has been modified in a fixed manner in only one or two cases. In +{410} our poultry and pigeons the acquirement of down and of the first +plumage by the young, and of the secondary sexual characters by the males, +differ. The number of moults through which the larvae of silk-moths pass, +varies. The tendency to fatten, to yield much milk, to produce many young +or eggs at a birth or during life, differs in different breeds. We find +different degrees of adaptation to climate, and different tendencies to +certain diseases, to the attacks of parasites, and to the action of certain +vegetable poisons. With plants, adaptation to certain soils, as with some +kinds of plums, the power of resisting frost, the period of flowering and +fruiting, the duration of life, the period of shedding the leaves and of +retaining them throughout the winter, the proportion and nature of certain +chemical compounds in the tissues or seeds, all vary. + +There is, however, one important constitutional difference between domestic +races and species; I refer to the sterility which almost invariably +follows, in a greater or less degree, when species are crossed, and to the +perfect fertility of the most distinct domestic races, with the exception +of a very few plants, when similarly crossed. It certainly appears a +remarkable fact that many closely allied species which in appearance differ +extremely little should yield when united only a few, more or less sterile +offspring, or none at all; whilst domestic races which differ conspicuously +from each other, are when united remarkably fertile, and yield perfectly +fertile offspring. But this fact is not in reality so inexplicable as it at +first appears. In the first place, it was clearly shown in the nineteenth +chapter that the sterility of crossed species does not closely depend on +differences in their external structure or general constitution, but +results exclusively from differences in the reproductive system, analogous +with those which cause the lessened fertility of the illegitimate unions +and illegitimate offspring of dimorphic and trimorphic plants. In the +second place, the Pallasian doctrine, that species after having been long +domesticated lose their natural tendency to sterility when crossed, has +been shown to be highly probable; we can scarcely avoid this conclusion +when we reflect on the parentage and present fertility of the several +breeds of the dog, of Indian and European cattle, sheep, and pigs. Hence it +would be unreasonable to expect that races formed under domestication {411} +should acquire sterility when crossed, whilst at the same time we admit +that domestication eliminates the normal sterility of crossed species. Why +with closely allied species their reproductive systems should almost +invariably have been modified in so peculiar a manner as to be mutually +incapable of acting on each other--though in unequal degrees in the two +sexes, as shown by the difference in fertility between reciprocal crosses +in the same species--we do not know, but may with much probability infer +the cause to be as follows. Most natural species have been habituated to +nearly uniform conditions of life for an incomparably longer period of time +than have domestic races; and we positively know that changed conditions +exert an especial and powerful influence on the reproductive system. Hence +this difference in habituation may well account for the different action of +the reproductive organs when domestic races and when species are crossed. +It is a nearly analogous fact, that most domestic races may be suddenly +transported from one climate to another, or be placed under widely +different conditions, and yet retain their fertility unimpaired; whilst a +multitude of species subjected to lesser changes are rendered incapable of +breeding. + +With the exception of fertility, domestic varieties resemble species when +crossed in transmitting their characters in the same unequal manner to +their offspring, in being subject to the prepotency of one form over the +other, and in their liability to reversion. By repeated crosses a variety +or a species may be made completely to absorb another. Varieties, as we +shall see when we treat of their antiquity, sometimes inherit their new +characters almost, or even quite, as firmly as species. With both, the +conditions leading to variability and the laws governing its nature appear +to be the same. Domestic varieties can be classed in groups under groups, +like species under genera, and these under families and orders; and the +classification may be either artificial,--that is, founded on any arbitrary +character,--or natural. With varieties a natural classification is +certainly founded, and with species is apparently founded, on community of +descent, together with the amount of modification which the forms have +undergone. The characters by which domestic varieties differ from each +other are more {412} variable than those distinguishing species, though +hardly more so than with certain protean species; but this greater degree +of variability is not surprising, as varieties have generally been exposed +within recent times to fluctuating conditions of life, are much more liable +to have been crossed, and are still in many cases undergoing, or have +recently undergone, modification by man's methodical or unconscious +selection. + +Domestic varieties as a general rule certainly differ from each other in +less important parts of their organisation than do species; and when +important differences occur, they are seldom firmly fixed; but this fact is +intelligible if we consider man's method of selection. In the living animal +or plant he cannot observe internal modifications in the more important +organs; nor does he regard them as long as they are compatible with health +and life. What does the breeder care about any slight change in the molar +teeth of his pigs, or for an additional molar tooth in the dog; or for any +change in the intestinal canal or other internal organ? The breeder cares +for the flesh of his cattle being well marbled with fat, and for an +accumulation of fat within the abdomen of his sheep, and this he has +effected. What would the floriculturist care for any change in the +structure of the ovarium or of the ovules? As important internal organs are +certainly liable to numerous slight variations, and as these would probably +be inherited, for many strange monstrosities are transmitted, man could +undoubtedly effect a certain amount of change in these organs. When he has +produced any modification in an important part, it has generally been +unintentionally in correlation with some other conspicuous part, as when he +has given ridges and protuberances to the skulls of fowls, by attending to +the form of the comb, and in the case of the Polish fowl to the plume of +feathers on the head. By attending to the external form of the +pouter-pigeon, he has enormously increased the size of the oesophagus, and +has added to the number of the ribs, and given them greater breadth. With +the carrier-pigeon, by increasing, through steady selection, the wattles on +the upper mandible, he has greatly modified the form of the lower mandible; +and so in many other cases. Natural species, on the other hand, have been +modified exclusively for their own good, to fit them for infinitely {413} +diversified conditions of life, to avoid enemies of all kinds, and to +struggle against a host of competitors. Hence, under such complex +conditions, it would often happen that modifications of the most varied +kinds, in important as well as in unimportant parts, would be advantageous +or even necessary; and they would slowly but surely be acquired through the +survival of the fittest. Various indirect modifications would likewise +arise through the law of correlated variation. + +Domestic breeds often have an abnormal or semi-monstrous character, as the +Italian greyhound, bulldog, Blenheim spaniel, and bloodhound amongst +dogs,--some breeds of cattle and pigs, several breeds of the fowl, and the +chief breeds of the pigeon. The differences between such abnormal breeds +occur in parts which in closely-allied natural species differ but slightly +or not at all. This may be accounted for by man's often selecting, +especially at first, conspicuous and semi-monstrous deviations of +structure. We should, however, be cautious in deciding what deviations +ought to be called monstrous: there can hardly be a doubt that, if the +brush of horse-like hair on the breast of the turkey-cock had first +appeared on the domesticated bird, it would have been considered a +monstrosity; the great plume of feathers on the head of the Polish cock has +been thus designated, though plumes are common with many kinds of birds; we +might call the wattle or corrugated skin round the base of the beak of the +English carrier-pigeon a monstrosity, but we do not thus speak of the +globular fleshy excrescence at the base of the beak of the male _Carpophaga +oceanica_. + +Some authors have drawn a wide distinction between artificial and natural +breeds; although in extreme cases the distinction is plain, in many other +cases an arbitrary line has to be drawn. The difference depends chiefly on +the kind of selection which has been applied. Artificial breeds are those +which have been intentionally improved by man; they frequently have an +unnatural appearance, and are especially liable to loss of excellence +through reversion and continued variability. The so-called natural breeds, +on the other hand, are those which are now found in semi-civilised +countries, and which formerly inhabited separate districts in nearly all +the European kingdoms. They have been rarely acted on by man's {414} +intentional selection; more frequently, it is probable, by unconscious +selection, and partly by natural selection, for animals kept in +semi-civilised countries have to provide largely for their own wants. Such +natural breeds will also, it may be presumed, have been directly acted on +to some extent by the differences, though slight, in the surrounding +physical conditions. + +It is a much more important distinction that some breeds have been from +their first origin modified in so slow and insensible a manner, that if we +could see their early progenitors we should hardly be able to say when or +how the breed first arose; whilst other breeds have originated from a +strongly-marked or semi-monstrous deviation of structure, which, however, +may subsequently have been augmented by selection. From what we know of the +history of the racehorse, greyhound, gamecock, &c., and from their general +appearance, we may feel nearly confident that they were formed by a slow +process of improvement: and with the carrier-pigeon, as well as with some +other pigeons, we know that this has been the case. On the other hand, it +is certain that the ancon and mauchamp breeds of sheep, and almost certain +that the niata cattle, turnspit and pug-dogs, jumper and frizzled fowls, +short-faced tumbler pigeons, hook-billed ducks, &c., and with plants a +multitude of varieties, suddenly appeared in nearly the same state as we +now see them. The frequency of these cases is likely to lead to the false +belief that natural species have often originated in the same abrupt +manner. But we have no evidence of the appearance, or at least of the +continued procreation, under nature, of abrupt modifications of structure; +and various general reasons could be assigned against such a belief: for +instance, without separation a single monstrous variation would almost +certainly be soon obliterated by crossing. + +On the other hand, we have abundant evidence of the constant occurrence +under nature of slight individual differences of the most diversified +kinds; and thus we are led to conclude that species have generally +originated by the natural selection, not of abrupt modifications, but of +extremely slight differences. This process may be strictly compared with +the slow and gradual improvement of the racehorse, greyhound, and gamecock. +As every detail of structure in each species is closely adapted to its +general {415} habits of life, it will rarely happen that one part alone +will be modified; but the co-adapted modifications, as formerly shown, need +not be absolutely simultaneous. Many variations, however, are from the +first connected by the law of correlation. Hence it follows that even +closely-allied species rarely or never differ from each other by some one +character alone; and this same remark applies to a certain extent to +domestic races; for these, if they differ much, generally differ in many +respects. + +Some naturalists boldly insist[928] that species are absolutely distinct +productions, never passing by intermediate links into each other; whilst +they maintain that domestic varieties can always be connected either with +each other or with their parent-forms. But if we could always find the +links between the several breeds of the dog, horse, cattle, sheep, pigs, +&c., the incessant doubts whether they are descended from one or several +species would not have arisen. The greyhound genus, if such a term may be +used, cannot be closely connected with any other breed, unless, perhaps, we +go back to the ancient Egyptian monuments. Our English bulldog also forms a +very distinct breed. In all these cases crossed breeds must of course be +excluded, for the most distinct natural species can thus be connected. By +what links can the Cochin fowl be closely united with others? By searching +for breeds still preserved in distant lands, and by going back to +historical records, tumbler-pigeons, carriers, and barbs can be closely +connected with the parent rock-pigeon; but we cannot thus connect the +turbit or the pouter. The degree of distinctness between the various +domestic breeds depends on the amount of modification which they have +undergone, and especially on the neglect and final extinction of the +linking, intermediate, and less valued forms. + +It has often been argued that no light is thrown, from the admitted changes +of domestic races, on the changes which natural species are believed to +undergo, as the former are said to be mere temporary productions, always +reverting, as soon as they become feral, to their pristine form. This +argument has been well combated by Mr. Wallace;[929] and full details were +given in the thirteenth chapter, showing that the tendency to reversion in +feral {416} animals and plants has been greatly exaggerated, though no +doubt to a certain extent it exists. It would be opposed to all the +principles inculcated in this work, if domestic animals, when exposed to +new conditions and compelled to struggle for their own wants against a host +of foreign competitors, were not in the course of time in some manner +modified. It should also be remembered that many characters lie latent in +all organic beings ready to be evolved under fitting conditions; and in +breeds modified within recent times the tendency to reversion is +particularly strong. But the antiquity of various breeds clearly proves +that they remain nearly constant as long as their conditions of life remain +the same. + +It has been boldly maintained by some authors that the amount of variation +to which our domestic productions are liable is strictly limited; but this +is an assertion resting on little evidence. Whether or not the amount in +any particular direction is fixed, the tendency to general variability +seems unlimited. Cattle, sheep, and pigs have been domesticated and have +varied from the remotest period, as shown by the researches of Ruetimeyer +and others, yet these animals have, within quite recent times, been +improved in an unparalleled degree; and this implies continued variability +of structure. Wheat, as we know from the remains found in the Swiss +lake-habitations, is one of the most anciently cultivated plants, yet at +the present day new and better varieties occasionally arise. It may be that +an ox will never be produced of larger size or finer proportions than our +present animals, or a race-horse fleeter than Eclipse, or a gooseberry +larger than the London variety; but he would be a bold man who would assert +that the extreme limit in these respects has been finally attained. With +flowers and fruit it has repeatedly been asserted that perfection has been +reached, but the standard has soon been excelled. A breed of pigeons may +never be produced with a beak shorter than that of the present short-faced +tumbler, or with one longer than that of the English carrier, for these +birds have weak constitutions and are bad breeders; but the shortness and +length of the beak are the points which have been steadily improved during +at least the last 150 years; and some of the best judges deny that the goal +has yet been reached. We may, also, reasonably suspect, from what {417} we +see in natural species of the variability of extremely modified parts, that +any structure, after remaining constant during a long series of +generations, would, under new and changed conditions of life, recommence +its course of variability, and might again be acted on by selection. +Nevertheless, as Mr. Wallace[930] has recently remarked with much force and +truth, there must be both with natural and domestic productions a limit to +change in certain directions; for instance, there must be a limit to the +fleetness of any terrestrial animal, as this will be determined by the +friction to be overcome, the weight to be carried, and the power of +contraction in the muscular fibres. The English racehorse may have reached +this limit; but it already surpasses in fleetness its own wild progenitor, +and all other equine species. + +It is not surprising, seeing the great difference between many domestic +breeds, that some few naturalists have concluded that all are descended +from distinct aboriginal stocks, more especially as the principle of +selection has been ignored, and the high antiquity of man, as a breeder of +animals, has only recently become known. Most naturalists, however, freely +admit that various extremely dissimilar breeds are descended from a single +stock, although they do not know much about the art of breeding, cannot +show the connecting links, nor say where and when the breeds arose. Yet +these same naturalists will declare, with an air of philosophical caution, +that they can never admit that one natural species has given birth to +another until they behold all the transitional steps. But fanciers have +used exactly the same language with respect to domestic breeds; thus an +author of an excellent treatise says he will never allow that carrier and +fantail pigeons are the descendants of the wild rock-pigeon, until the +transitions have "actually been observed, and can be repeated whenever man +chooses to set about the task." No doubt it is difficult to realise that +slight changes added up during long centuries can produce such results; but +he who wishes to understand the origin of domestic breeds or natural +species must overcome this difficulty. + +The causes inducing and the laws governing variability have been so lately +discussed, that I need here only enumerate the leading points. As +domesticated organisms are much more {418} liable to slight deviations of +structure and to monstrosities, than species living under their natural +conditions, and as widely-ranging species vary more than those which +inhabit restricted areas, we may infer that variability mainly depends on +changed conditions of life. We must not overlook the effects of the unequal +combination of the characters derived from both parents, nor reversion to +former progenitors. Changed conditions have an especial tendency to render +the reproductive organs more or less impotent, as shown in the chapter +devoted to this subject; and these organs consequently often fail to +transmit faithfully the parental characters. Changed conditions also act +directly and definitely on the organisation, so that all or nearly all the +individuals of the same species thus exposed become modified in the same +manner; but why this or that part is especially affected we can seldom or +never say. In most cases, however, of the direct action of changed +conditions, independently of the indirect variability caused by the +reproductive organs being affected, indefinite modifications are the +result; in nearly the same manner as exposure to cold or the absorption of +the same poison affects different individuals in various ways. We have +reason to suspect that an habitual excess of highly nutritious food, or an +excess relatively to the wear and tear of the organisation from exercise, +is a powerful exciting cause of variability. When we see the symmetrical +and complex outgrowths, caused by a minute atom of the poison of a +gall-insect, we may believe that slight changes in the chemical nature of +the sap or blood would lead to extraordinary modifications of structure. + +The increased use of a muscle with its various attached parts, and the +increased activity of a gland or other organ, lead to their increased +development. Disuse has a contrary effect. With domesticated productions +organs sometimes become rudimentary through abortion; but we have no reason +to suppose that this has ever followed from mere disuse. With natural +species, on the contrary, many organs appear to have been rendered +rudimentary through disuse, aided by the principle of the economy of +growth, and by the hypothetical principle discussed in the last chapter, +namely, the final destruction of the germs or gemmules of such useless +parts. This difference may be partly {419} accounted for by disuse having +acted on domestic forms for an insufficient length of time, and partly from +their exemption from any severe struggle for existence, entailing rigid +economy in the development of each part, to which all species under nature +are subjected. Nevertheless the law of compensation or balancement +apparently affects, to a certain extent, our domesticated productions. + +We must not exaggerate the importance of the definite action of changed +conditions in modifying all the individuals of the same species in the same +manner, or of use and disuse. As every part of the organisation is highly +variable, and as variations are so easily selected, both consciously and +unconsciously, it is very difficult to distinguish between the effects of +the selection of indefinite variations, and the direct action of the +conditions of life. For instance, it is possible that the feet of our +water-dogs, and of the American dogs which have to travel much over the +snow, may have become partially webbed from the stimulus of widely +extending their toes; but it is far more probable that the webbing, like +the membrane between the toes of certain pigeons, spontaneously appeared +and was afterwards increased by the best swimmers and the best +snow-travellers being preserved during many generations. A fancier who +wished to decrease the size of his bantams or tumbler-pigeons would never +think of starving them, but would select the smallest individuals which +spontaneously appeared. Quadrupeds are sometimes born destitute of hair, +and hairless breeds have been formed, but there is no reason to believe +that this is caused by a hot climate. Within the tropics heat often causes +sheep to lose their fleeces, and on the other hand wet and cold act as a +direct stimulus to the growth of hair; it is, however, possible that these +changes may merely be an exaggeration of the regular yearly change of coat; +and who will pretend to decide how far this yearly change, or the thick fur +of arctic animals, or as I may add their white colour, is due to the direct +action of a severe climate, and how far to the preservation of the best +protected individuals during a long succession of generations? + +Of all the laws governing variability, that of correlation is the most +important. In many cases of slight deviations of structure as well as of +grave monstrosities, we cannot even {420} conjecture what is the nature of +the bond of connexion. But between homologous parts--between the fore and +hind limbs--between the hair, hoofs, horns, and teeth--we can see that +parts which are closely similar during their early development, and which +are exposed to similar conditions, would be liable to be modified in the +same manner. Homologous parts, from having the same nature, are apt to +blend together and, when many exist, to vary in number. + +Although every variation is either directly or indirectly caused by some +change in the surrounding conditions, we must never forget that the nature +of the organisation which is acted on essentially governs the result. +Distinct organisms, when placed under similar conditions, vary in different +manners, whilst closely-allied organisms under dissimilar conditions often +vary in nearly the same manner. We see this in the same modification +frequently reappearing at long intervals of time in the same variety, and +likewise in the several striking cases given of analogous or parallel +varieties. Although some of these latter cases are simply due to reversion, +others cannot thus be accounted for. + +From the indirect action of changed conditions on the organisation, through +the impaired state of the reproductive organs--from the direct action of +such conditions (and this will cause the individuals of the same species +either to vary in the same manner, or differently in accordance with slight +differences in their constitution)--from the effects of the increased or +decreased use of parts,--and from correlation,--the variability of our +domesticated productions is complicated in an extreme degree. The whole +organisation becomes slightly plastic. Although each modification must have +its proper exciting cause, and though each is subjected to law, yet we can +so rarely trace the precise relation between cause and effect, that we are +tempted to speak of variations as if they spontaneously arose. We may even +call them accidental, but this must be only in the sense in which we say +that a fragment of rock dropped from a height owes its shape to accident. + + * * * * * + +It may be worth while briefly to consider the results of the exposure to +unnatural conditions of a large number of animals of the same species, +allowed to cross freely, with no selection of any {421} kind; and +afterwards to consider the results when selection is brought into play. Let +us suppose that 500 wild rock-pigeons were confined in their native land in +an aviary, and fed in the same manner as pigeons usually are; and that they +were not allowed to increase in number. As pigeons propagate so rapidly, I +suppose that a thousand or fifteen hundred birds would have to be annually +killed by mere chance. After several generations had been thus reared, we +may feel sure that some of the young birds would vary, and the variations +would tend to be inherited; for at the present day slight deviations of +structure often occur, but, as most breeds are already well established, +these modifications are rejected as blemishes. It would be tedious even to +enumerate the multitude of points which still go on varying or have +recently varied. Many variations would occur in correlation, as the length +of the wing and tail feathers--the number of the primary wing-feathers, as +well as the number and breadth of the ribs, in correlation with the size +and form of the body--the number of the scutellae, with the size of the +feet--the length of the tongue, with the length of the beak--the size of +the nostrils and eyelids and the form of lower jaw in correlation with the +development of wattle--the nakedness of the young with the future colour of +the plumage--the size of the feet and beak, and other such points. Lastly, +as our birds are supposed to be confined in an aviary, they would use their +wings and legs but little, and certain parts of the skeleton, such as the +sternum and scapulae and the feet, would in consequence become slightly +reduced in size. + +As in our assumed case many birds have to be indiscriminately killed every +year, the chances are against any new variety surviving long enough to +breed. And as the variations which arise are of an extremely diversified +nature, the chances are very great against two birds pairing which have +varied in the same manner; nevertheless, a varying bird even when not thus +paired would occasionally transmit its character to its young; and these +would not only be exposed to the same conditions which first caused the +variation in question to appear, but would in addition inherit from their +one modified parent a tendency again to vary in the same manner. So that, +if the conditions decidedly tended to induce some particular variation, all +the birds might {422} in the course of time become similarly modified. But +a far commoner result would be, that one bird would vary in one way and +another bird in another way; one would be born with a little longer beak, +and another with a shorter beak; one would gain some black feathers, +another some white or red feathers. And as these birds would be continually +intercrossing, the final result would be a body of individuals differing +from each other slightly in many ways, yet far more than did the original +rock-pigeons. But there would not be the least tendency to the formation of +distinct breeds. + +If two separate lots of pigeons were to be treated in the manner just +described, one in England and the other in a tropical country, the two lots +being supplied with different food, would they, after many generations had +passed, differ? When we reflect on the cases given in the twenty-third +chapter, and on such facts as the difference in former times between the +breeds of cattle, sheep, &c., in almost every district of Europe, we are +strongly inclined to admit that the two lots would be differently modified +through the influence of climate and food. But the evidence on the definite +action of changed conditions is in most cases insufficient; and, with +respect to pigeons, I have had the opportunity of examining a large +collection of domesticated birds, sent to me by Sir W. Elliot from India, +and they varied in a remarkably similar manner with our European birds. + +If two distinct breeds were to be confined together in equal numbers, there +is reason to suspect that they would to a certain extent prefer pairing +with their own kind; but they would likewise intercross. From the greater +vigour and fertility of the crossed offspring, the whole body would by this +means become interblended sooner than would otherwise have occurred. From +certain breeds being prepotent over others, it does not follow that the +interblended progeny would be strictly intermediate in character. I have, +also, proved that the act of crossing in itself gives a strong tendency to +reversion, so that the crossed offspring would tend to revert to the state +of the aboriginal rock-pigeon. In the course of time they would probably be +not much more heterogeneous in character than in our first case, when birds +of the same breed were confined together. {423} + +I have just said that the crossed offspring would gain in vigour and +fertility. From the facts given in the seventeenth chapter there can be no +doubt of this; and there can be little doubt, though the evidence on this +head is not so easily acquired, that long-continued close interbreeding +leads to evil results. With hermaphrodites of all kinds, if the sexual +elements of the same individual habitually acted on each other, the closest +possible interbreeding would be perpetual. Therefore we should bear in mind +that with all hermaphrodite animals, as far as I can learn, their structure +permits and frequently necessitates a cross with a distinct individual. +With hermaphrodite plants we incessantly meet with elaborate and perfect +contrivances for this same end. It is no exaggeration to assert that, if +the use of the talons and tusks of a carnivorous animal, or the use of the +viscid threads of a spider's web, or of the plumes and hooks on a seed may +be safely inferred from their structure, we may with equal safety infer +that many flowers are constructed for the express purpose of ensuring a +cross with a distinct plant. From these various considerations, the +conclusion arrived at in the chapter just referred to--namely, that great +good of some kind is derived from the sexual concourse of distinct +individuals--must be admitted. + +To return to our illustration: we have hitherto assumed that the birds were +kept down to the same number by indiscriminate slaughter; but if the least +choice be permitted in their preservation and slaughter, the whole result +will be changed. Should the owner observe any slight variation in one of +his birds, and wish to obtain a breed thus characterised, he would succeed +in a surprisingly short time by carefully selecting and pairing the young. +As any part which has once varied generally goes on varying in the same +direction, it is easy, by continually preserving the most strongly marked +individuals, to increase the amount of difference up to a high, +predetermined standard of excellence. This is methodical selection. + +If the owner of the aviary, without any thought of making a new breed, +simply admired, for instance, short-beaked more than long-beaked birds, he +would, when he had to reduce the number, generally kill the latter; and +there can be no doubt that he would thus in the course of time sensibly +modify his {424} stock. It is improbable, if two men were to keep pigeons +and act in this manner, that they would prefer exactly the same characters; +they would, as we know, often prefer directly opposite characters, and the +two lots would ultimately come to differ. This has actually occurred with +strains or families of cattle, sheep, and pigeons, which have been long +kept and carefully attended to by different breeders without any wish on +their part to form new and distinct sub-breeds. This unconscious kind of +selection will more especially come into action with animals which are +highly serviceable to man; for every one tries to get the best dog, horse, +cow, or sheep, and these animals will transmit more or less surely their +good qualities to their offspring. Hardly any one is so careless as to +breed from his worst animals. Even savages, when compelled from extreme +want to kill some of their animals, would destroy the worst and preserve +the best. With animals kept for use and not for mere amusement, different +fashions prevail in different districts, leading to the preservation, and +consequently to the transmission, of all sorts of trifling peculiarities of +character. The same process will have been pursued with our fruit-trees and +vegetables, for the best will always have been the most largely cultivated, +and will occasionally have yielded seedlings better than their parents. + +The different strains, just alluded to, which have been raised by different +breeders without any wish for such a result, and the unintentional +modification of foreign breeds in their new homes, both afford excellent +evidence of the power of unconscious selection. This form of selection has +probably led to far more important results than methodical selection, and +is likewise more important under a theoretical point of view from closely +resembling natural selection. For during this process the best or most +valued individuals are not separated and prevented crossing with others of +the same breed, but are simply preferred and preserved; but this inevitably +leads during a long succession of generations to their increase in number +and to their gradual improvement; so that finally they prevail to the +exclusion of the old parent-form. + +With our domesticated animals natural selection checks the production of +races with any injurious deviation of {425} structure. In the case of +animals kept by savages and semi-civilised people, which have to provide +largely for their own wants under different circumstances, natural +selection will probably play a more important part. Hence such animals +often closely resemble natural species. + +As there is no limit to man's desire to possess animals and plants more and +more useful in any respect, and as the fancier always wishes, from fashion +running into extremes, to produce each character more and more strongly +pronounced, there is a constant tendency in every breed, through the +prolonged action of methodical and unconscious selection, to become more +and more different from its parent-stock; and when several breeds have been +produced and are valued for different qualities, to differ more and more +from each other. This leads to Divergence of Character. As improved +sub-varieties and races are slowly formed, the older and less improved +breeds are neglected and decrease in number. When few individuals of any +breed exist within the same locality, close interbreeding, by lessening +their vigour and fertility, aids in their final extinction. Thus the +intermediate links are lost, and breeds which have already diverged gain +Distinctness of Character. + +In the chapters on the Pigeon, it was proved by historical details and by +the existence of connecting sub-varieties in distant lands that several +breeds have steadily diverged in character, and that many old and +intermediate sub-breeds have become extinct. Other cases could be adduced +of the extinction of domestic breeds, as of the Irish wolf-dog, the old +English hound, and of two breeds in France, one of which was formerly +highly valued.[931] Mr. Pickering remarks[932] that "the sheep figured on +the most ancient Egyptian monuments is unknown at the present day; and at +least one variety of the bullock, formerly known in Egypt, has in like +manner become extinct." So it has been with some animals, and with several +plants cultivated by the ancient inhabitants of Europe during the neolithic +period. In Peru, Von Tschudi[933] found in certain tombs, apparently prior +to the dynasty of the Incas, two kinds of maize not now known in the +country. With our flowers and culinary vegetables, {426} the production of +new varieties and their extinction has incessantly recurred. At the present +time improved breeds sometimes displace at an extraordinarily rapid rate +older breeds; as has recently occurred throughout England with pigs. The +Long-horn cattle in their native home were "suddenly swept away as if by +some murderous pestilence," by the introduction of Short-horns.[934] + +What grand results have followed from the long-continued action of +methodical and unconscious selection, checked and regulated to a certain +extent by natural selection, is seen on every side of us. Compare the many +animals and plants which are displayed at our exhibitions with their +parent-forms when these are known, or consult old historical records with +respect to their former state. Almost all our domesticated animals have +given rise to numerous and distinct races, excepting those which cannot be +easily subjected to selection--such as cats, the cochineal insect, and the +hive-bee,--and excepting those animals which are not much valued. In +accordance with what we know of the process of selection, the formation of +our many races has been slow and gradual. The man who first observed and +preserved a pigeon with its oesophagus a little enlarged, its beak a little +longer, or its tail a little more expanded than usual, never dreamed that +he had made the first step in the creation of the pouter, carrier, and +fantail-pigeon. Man can create not only anomalous breeds, but others with +their whole structure admirably co-ordinated for certain purposes, such as +the race-horse and dray-horse, or the greyhound. It is by no means +necessary that each small change of structure throughout the body, leading +towards excellence, should simultaneously arise and be selected. Although +man seldom attends to differences in organs which are important under a +physiological point of view, yet he has so profoundly modified some breeds, +that assuredly, if found wild, they would be ranked under distinct genera. + +The best proof of what selection has effected is perhaps afforded by the +fact that whatever part or quality in any animal, and more especially in +any plant, is most valued by man, that part or quality differs most in the +several races. This result is well seen by comparing the amount of +difference {427} between the fruits produced by the varieties of the same +fruit-tree, between the flowers of the varieties in our flower-garden, +between the seeds, roots, or leaves of our culinary and agricultural +plants, in comparison with the other and not valued parts of the same +plants. Striking evidence of a different kind is afforded by the fact +ascertained by Oswald Heer,[935] namely, that the seeds of a large number +of plants,--wheat, barley, oats, peas, beans, lentils, poppies,--cultivated +for their seed by the ancient Lake-inhabitants of Switzerland, were all +smaller than the seeds of our existing varieties. Ruetimeyer has shown that +the sheep and cattle which were kept by the earlier Lake-inhabitants were +likewise smaller than our present breeds. In the middens of Denmark, the +earliest dog of which the remains have been found was the weakest; this was +succeeded during the Bronze age by a stronger kind, and this again during +the Iron age by one still stronger. The sheep of Denmark during the Bronze +period had extraordinarily slender limbs, and the horse was smaller than +our present animal.[936] No doubt in these cases the new and larger breeds +were generally introduced from foreign lands by the immigration of new +hordes of men. But it is not probable that each larger breed, which in the +course of time supplanted a previous and smaller breed, was the descendant +of a distinct and larger species; it is far more probable that the domestic +races of our various animals were gradually improved in different parts of +the great Europaeo-Asiatic continent, and thence spread to other countries. +This fact of the gradual increase in size of our domestic animals is all +the more striking as certain wild or half-wild animals, such as red-deer, +aurochs, park-cattle, and boars,[937] have within nearly the same period +decreased in size. + +The conditions favourable to selection by man are,--the closest attention +being paid to every character,--long-continued perseverance,--facility in +matching or separating animals,--and especially a large number being kept, +so that the inferior individuals may be freely rejected or destroyed, and +the better ones preserved. When many are kept there will also be a {428} +greater chance of the occurrence of well-marked deviations of structure. +Length of time is all-important; for as each character, in order to become +strongly pronounced, has to be augmented by the selection of successive +variations of the same nature, this can only be effected during a long +series of generations. Length of time will, also, allow any new feature to +become fixed by the continued rejection of those individuals which revert +or vary, and the preservation of those which inherit the new character. +Hence, although some few animals have varied rapidly in certain respects +under new conditions of life, as dogs in India and sheep in the West +Indies, yet all the animals and plants which have produced strongly marked +races were domesticated at an extremely remote epoch, often before the dawn +of history. As a consequence of this, no record has been preserved of the +origin of our chief domestic breeds. Even at the present day new strains or +sub-breeds are formed so slowly that their first appearance passes +unnoticed. A man attends to some particular character, or merely matches +his animals with unusual care, and after a time a slight difference is +perceived by his neighbours;--the difference goes on being augmented by +unconscious and methodical selection, until at last a new sub-breed is +formed, receives a local name, and spreads; but, by this time, its history +is almost forgotten. When the new breed has spread widely, it gives rise to +new strains and sub-breeds, and the best of these succeed and spread, +supplanting other and older breeds; and so always onwards in the march of +improvement. + +When a well-marked breed has once been established, if not supplanted by +still improving sub-breeds, and if not exposed to greatly changed +conditions of life, inducing further variability or reversion to long-lost +characters, it may apparently last for an enormous period. We may infer +that this is the case from the high antiquity of certain races; but some +caution is necessary on this head, for the same variation may appear +independently after long intervals of time, or in distant places. We may +safely assume that this has occurred with the turnspit-dog which is figured +on the ancient Egyptian monuments, with the solid-hoofed swine[938] +mentioned by Aristotle, with five-toed fowls {429} described by Columella, +and certainly with the nectarine. The dogs represented on the Egyptian +monuments, about 2000 B.C., show us that some of the chief breeds then +existed, but it is extremely doubtful whether any are identically the same +with our present breeds. A great mastiff sculptured on an Assyrian tomb, +640 B.C., is said to be the same with the dog still imported into the same +region from Thibet. The true greyhound existed during the Roman classical +period. Coming down to a later period, we have seen that, though most of +the chief breeds of the pigeon existed between two and three centuries ago, +they have not all retained to the present day exactly the same character; +but this has occurred in certain cases in which improvement was not +desired, for instance in the case of the Spot or the Indian ground-tumbler. + +De Candolle[939] has fully discussed the antiquity of various races of +plants; he states that the black-seeded poppy was known in the time of +Homer, the white-seeded sesamum by the ancient Egyptians, and almonds with +sweet and bitter kernels by the Hebrews; but it does not seem improbable +that some of these varieties may have been lost and reappeared. One variety +of barley and apparently one of wheat, both of which were cultivated at an +immensely remote period by the Lake-inhabitants of Switzerland, still +exist. It is said[940] that "specimens of a small variety of gourd which is +still common in the market of Lima were exhumed from an ancient cemetery in +Peru." De Candolle remarks that, in the books and drawings of the sixteenth +century, the principal races of the cabbage, turnip, and gourd can be +recognised; this might have been expected at so late a period, but whether +any of these plants are absolutely identical with our present sub-varieties +is not certain. It is, however, said that the Brussels sprout, a variety +which in some places is liable to degeneration, has remained genuine for +more than four centuries in the district where it is believed to have +originated.[941] + + * * * * * + +In accordance with the views maintained by me in this work and elsewhere, +not only the various domestic races, but the {430} most distinct genera and +orders within the same great class,--for instance, whales, mice, birds, and +fishes--are all the descendants of one common progenitor, and we must admit +that the whole vast amount of difference between these forms of life has +primarily arisen from simple variability. To consider the subject under +this point of view is enough to strike one dumb with amazement. But our +amazement ought to be lessened when we reflect that beings, almost infinite +in number, during an almost infinite lapse of time, have often had their +whole organisation rendered in some degree plastic, and that each slight +modification of structure which was in any way beneficial under excessively +complex conditions of life, will have been preserved, whilst each which was +in any way injurious will have been rigorously destroyed. And the +long-continued accumulation of beneficial variations will infallibly lead +to structures as diversified, as beautifully adapted for various purposes, +and as excellently co-ordinated, as we see in the animals and plants all +around us. Hence I have spoken of selection as the paramount power, whether +applied by man to the formation of domestic breeds, or by nature to the +production of species. I may recur to the metaphor given in a former +chapter: if an architect were to rear a noble and commodious edifice, +without the use of cut stone, by selecting from the fragments at the base +of a precipice wedge-formed stones for his arches, elongated stones for his +lintels, and flat stones for his roof, we should admire his skill and +regard him as the paramount power. Now, the fragments of stone, though +indispensable to the architect, bear to the edifice built by him the same +relation which the fluctuating variations of each organic being bear to the +varied and admirable structures ultimately acquired by its modified +descendants. + +Some authors have declared that natural selection explains nothing, unless +the precise cause of each slight individual difference be made clear. Now, +if it were explained to a savage utterly ignorant of the art of building, +how the edifice had been raised stone upon stone, and why wedge-formed +fragments were used for the arches, flat stones for the roof, &c.; and if +the use of each part and of the whole building were pointed out, it would +be unreasonable if he declared that nothing had been {431} made clear to +him, because the precise cause of the shape of each fragment could not be +given. But this is a nearly parallel case with the objection that selection +explains nothing, because we know not the cause of each individual +difference in the structure of each being. + +The shape of the fragments of stone at the base of our precipice may be +called accidental, but this is not strictly correct; for the shape of each +depends on a long sequence of events, all obeying natural laws; on the +nature of the rock, on the lines of deposition or cleavage, on the form of +the mountain which depends on its upheaval and subsequent denudation, and +lastly on the storm or earthquake which threw down the fragments. But in +regard to the use to which the fragments may be put, their shape may be +strictly said to be accidental. And here we are led to face a great +difficulty, in alluding to which I am aware that I am travelling beyond my +proper province. An omniscient Creator must have foreseen every consequence +which results from the laws imposed by Him. But can it be reasonably +maintained that the Creator intentionally ordered, if we use the words in +any ordinary sense, that certain fragments of rock should assume certain +shapes so that the builder might erect his edifice? If the various laws +which have determined the shape of each fragment were not predetermined for +the builder's sake, can it with any greater probability be maintained that +He specially ordained for the sake of the breeder each of the innumerable +variations in our domestic animals and plants;--many of these variations +being of no service to man, and not beneficial, far more often injurious, +to the creatures themselves? Did He ordain that the crop and tail-feathers +of the pigeon should vary in order that the fancier might make his +grotesque pouter and fantail breeds? Did He cause the frame and mental +qualities of the dog to vary in order that a breed might be formed of +indomitable ferocity, with jaws fitted to pin down the bull for man's +brutal sport? But if we give up the principle in one case,--if we do not +admit that the variations of the primeval dog were intentionally guided in +order that the greyhound, for instance, that perfect image of symmetry and +vigour, might be formed,--no shadow of reason can be assigned for the +belief that variations, alike in nature and the result {432} of the same +general laws, which have been the groundwork through natural selection of +the formation of the most perfectly adapted animals in the world, man +included, were intentionally and specially guided. However much we may wish +it, we can hardly follow Professor Asa Gray in his belief "that variation +has been led along certain beneficial lines," like a stream "along definite +and useful lines of irrigation." If we assume that each particular +variation was from the beginning of all time preordained, the plasticity of +organisation, which leads to many injurious deviations of structure, as +well as that redundant power of reproduction which inevitably leads to a +struggle for existence, and, as a consequence, to the natural selection or +survival of the fittest, must appear to us superfluous laws of nature. On +the other hand, an omnipotent and omniscient Creator ordains everything and +foresees everything. Thus we are brought face to face with a difficulty as +insoluble as is that of free will and predestination. + + * * * * * + + +{433} + + INDEX. + + ABBAS Pacha, a fancier of fantailed pigeons, i. 206. + ABBEY, Mr., on grafting, ii. 147; + on mignonette, ii. 237. + ABBOTT, Mr. Keith, on the Persian tumbler pigeon, i. 150. + ABBREVIATION of the facial bones, i. 73. + ABORTION of organs, ii. 315-318, 397. + ABSORPTION of minority in crossed races, ii. 87-89, 174. + ACCLIMATISATION, ii. 305-315; + of maize, i. 322. + ACERBI, on the fertility of domestic animals in Lapland, ii. 112. + _Achatinella_, ii. 53. + _Achillea millefolium_, bud variation in, i. 408. + _Aconitum napellus_, roots of, innocuous in cold climates, ii. 274. + _Acorus calamus_, sterility of, ii. 170. + ACOSTA, on fowls in South America at its discovery, i. 237. + _Acropera_, number of seeds in, ii. 379. + ADAM, Mr., origin of _Cytisus Adami_, i. 390. + ADAM, W., on consanguineous marriages, ii. 123. + ADAMS, Mr., on hereditary diseases, ii. 7. + ADVANCEMENT in scale of organisation, i. 8. + _Aegilops triticoides_, observations of Fabre and Godron on, i. 313; + increasing fertility of hybrids of, with wheat, ii. 110. + _Aesculus flava_ and _rubicunda_, i. 392. + _Aesculus pavia_, tendency of, to become double, ii. 168. + _Aethusa cynapium_, ii. 337. + AFFINITY, sexual elective, ii. 180. + AFRICA, white bull from, i. 91; + feral cattle in, i. 85; + food-plants of savages of, i. 307-309; + South, diversity of breeds of cattle in, i. 80; + West, change in fleece of sheep in, i. 98. + _Agave vivipara_, seeding of, in poor soil, ii. 169. + AGE, changes in trees, dependent on, i. 387. + AGOUTI, fertility of, in captivity, ii. 152. + AGRICULTURE, antiquity of, ii. 243. + _Agrostis_, seeds of, used as food, i. 309. + AGUARA, i. 26. + AINSWORTH, Mr., on the change in the hair of animals at Angora, ii. 278. + AKBAR Khan, his fondness for pigeons, i. 205; ii. 204. + _Alauda arvensis_, ii. 154. + ALBIN, on "Golden Hamburgh" fowls, i. 247; + figure of the hook-billed duck, i. 277. + ALBINISM, i. 111, ii. 17. + ALBINO, negro, attacked by insects, ii. 229. + ALBINOES, heredity of, ii. 9. + ALBINUS, thickness of the epidermis on the palms of the hands in man, ii. + 297. + ALCO, i. 31, ii. 102. + ALDROVANDI, on rabbits, i. 104; + description of the nun pigeon, i. 156; + on the fondness of the Dutch for pigeons in the seventeenth century, i. + 205; + notice of several varieties of pigeons, i. 207-210; + on the breeds of fowls, i. 247; + on the origin of the domestic duck, i. 278. + ALEFIELD, Dr., on the varieties of peas and their specific unity, i. 326; + on the varieties of beans, i. 330. + ALEXANDER the Great, his selection of Indian cattle, ii. 202. + ALGAE, retrogressive metamorphosis in, ii. 361; + division of zoospores of, ii. 378. + ALLEN, W., on feral fowls, i. 237; ii. 33. + ALLMAN, Professor, on a monstrous _Saxifraga geum_, ii. 166; + on the development of the Hydroida, ii. 368. + ALMOND, i. 337; + antiquity of, ii. 429; + bitter, not eaten by mice, ii. 232. + _Alnus glutinosa_ and _incana_, hybrids of, ii. 130. + ALPACA, selection of, ii. 208. + _Althaea rosea_, i. 378, ii. 107. + _Amaryllis_, ii. 139. + _Amaryllis vittata_, effect of foreign pollen on, i. 400. + AMAUROSIS, hereditary, ii. 9. + AMERICA, limits within which no useful plants have been furnished by, i. + 310; + colours of feral horses in, i. 60-61; + North, native cultivated plants of, i. 312; + skin of feral pig from, i. 77; + South, variations in cattle of, i. 88, 92. + _Amygdalus persica_, i. 336-344, 374. + {434} + AMMON, on the persistency of colour in horses, ii. 21. + _Anagallis arvensis_, ii. 190. + ANALOGOUS variation, i. 409, ii. 348-352; + in horses, i. 55; + in the horse and ass, i. 64; + in fowls, i. 243-246. + _Anas boschas_, i. 277, ii. 40; + skull of, figured, i. 282. + _Anas moschata_, ii. 40. + "ANCON" sheep of Massachusetts, i. 100, ii. 103. + ANDALUSIAN fowls, i. 227. + ANDALUSIAN rabbits, i. 105. + ANDERSON, J., on the origin of British sheep, i. 94; + on the selection of qualities in cattle, ii. 196; + on a one-eared breed of rabbits, i. 108; + on the inheritance of characters from a one-eared rabbit and + three-legged bitch, ii. 12; + on the persistency of varieties of peas, i. 329; + on the production of early peas by selection, ii. 201; + on the varieties of the potato, i. 330-331; + on crossing varieties of the melon, i. 399; + on reversion in the barberry, i. 384. + ANDERSON, Mr., on the reproduction of the weeping ash by seed, ii. 19; + on the cultivation of the tree paeony in China, ii. 205. + ANDERSSON, Mr., on the Damara, Bechuana, and Namaqua cattle, i. 88; + on the cows of the Damaras, ii. 300; + selection practised by the Damaras and Namaquas, ii. 207; + on the use of grass-seeds and the roots of reeds as food in South + Africa, i. 309. + _Anemone coronaria_, doubled by selection, ii. 200. + ANGINA pectoris, hereditary, occurring at a certain age, ii. 79. + ANGLESEA, cattle of, i. 80. + ANGOLA sheep, i. 95. + ANGORA, change in hair of animals at, ii. 278; + cats of, i. 45, 47; + rabbits of, i. 106, 120. + ANIMALS, domestication of, facilitated by fearlessness of man, i. 20; + refusal of wild, to breed in captivity, ii. 149; + compound, individual peculiarities of, reproduced by budding, i. 374; + variation by selection in useful qualities of, ii. 220. + ANNUAL plants, rarity of bud-variation in, i. 408. + ANOMALIES in the osteology of the horse, i. 50. + ANOMALOUS breeds of pigs, i. 75; + of cattle, i. 89. + _Anser albifrons_, characters of, reproduced in domestic geese, i. 288. + _Anser aegyptiacus_, i. 282; ii. 68. + _Anser canadensis_, ii. 157. + _Anser cygnoides_, i. 237. + _Anser ferus_, the original of the domestic goose, i. 287; + fertility of cross of, with domestic goose, i. 288. + ANSON, on feral fowls in the Ladrones, i. 238. + ANTAGONISM between growth and reproduction, ii. 384. + _Anthemis nobilis_, bud-variation in flowers of, i. 379; + becomes single in poor soil, ii. 167. + ANTHEROZOIDS, apparent independence of, in algae, ii. 384. + ANTHERS, contabescence of, ii. 165-166. + ANTIGUA, cats of, i. 46; + changed fleece of sheep in, i. 98. + _Antirrhinum majus_, peloric, i. 365; ii. 59, 70, 166; + double-flowered, ii. 167; + bud-variation in, i. 381. + ANTS, individual recognition of, ii. 251. + APES, anthropomorphous, ii. 123. + APHIDES, attacking pear-trees, ii. 231; + development of, ii. 361-362. + APOPLEXY, hereditary, occurring at a certain age, ii. 78. + APPLE, i. 348-350; + fruit of, in Swiss lake-dwellings, i. 317; + rendered fastigate by heat in India, i. 361; + bud-variation in the, i. 376; + with dimidiate fruit, i. 392-393; + with two kinds of fruit on the same branch, i. 392; + artificial fecundation of, i. 401; + St. Valery, i. 401; ii. 166; + reversion in seedlings of, ii. 31; + crossing of varieties of, ii. 129; + growth of the, in Ceylon, ii. 277; + Winter Majetin, not attacked by _coccus_, ii. 231; + flower-buds of, attacked by bullfinches, ii. 232; + American, change of when grown in England, ii. 275. + APRICOT, i. 344-345; + glands on the leaves of, ii. 231; + analogous variation in the, ii. 348. + _Aquila fusca_, copulating in captivity, ii. 154. + _Aquilegia vulgaris_, i. 365; ii. 330. + ARAB boarhound, described by Harcourt, i. 17. + _Arabis blepharophylla_ and _A. Soyeri,_ effects of crossing, i. 400. + _Aralia trifoliata_, bud-variation in leaves of, i. 382. + ARAUCARIAS, young, variable resistance of, to frost, ii. 309. + ARCHANGEL pigeon, ii. 240. + ARCTIC regions, variability of plants and shells of, ii. 256. + _Aria vestita_, grafted on thorns, i. 387. + ARISTOPHANES, fowls mentioned by, i. 246. + ARISTOTLE, on solid-hoofed pigs, i. 75; + domestic duck unknown to, i. 277; + on the assumption of male characters by old hens, ii. 51. + {435} + ARNI, domestication of the, i. 82. + ARREST of development, ii. 315-318. + ARTERIES, increase of anastomosing branches of, when tied, ii. 230. + ARU islands, wild pig of, i. 67. + ARUM, Polynesian varieties of, ii. 256. + _Ascaris_, number of eggs of, ii. 379. + ASH, varieties of the, i. 360; + weeping, i. 361; + simple-leaved, i. 362; + bud-variation in, i. 382; + effects of graft upon the stock in the, i. 394; + production of the blotched Breadalbane, _ibid._; + weeping, capricious reproduction of, by seed, ii. 19. + _Asinus Burchellii_, i. 64. + _Asinus hemionus_, ii. 43. + _Asinus indicus_, ii. 42-43, 48. + _Asinus quagga_, i. 64. + _Asinus taeniopus_, ii. 41; + the original of the domestic ass, i. 62. + ASPARAGUS, increased fertility of cultivated, ii. 113. + ASS, early domestication of the, i. 62; + breeds of, _ibid._; + small size of, in India, _ibid._; + stripes of, i. 62-63; ii. 351; + dislike of to cross water, i. 181; + reversion in, ii. 41-43, 47; + hybrid of the, with mare and zebra, ii. 42; + prepotency of the, over the horse, ii. 67-68; + crossed with wild ass, ii. 206; + variation and selection of the, ii. 236. + ASSYRIAN sculpture of a mastiff, i. 17. + ASTERS, ii. 20, 316. + ASTHMA, hereditary, ii. 8, 79. + ATAVISM. _See_ Reversion. + ATHELSTAN, his care of horses, ii. 203. + ATKINSON, Mr., on the sterility of the Tarroo silk-moth in confinement, + ii. 157. + AUBERGINE, ii. 91. + AUDUBON, on feral hybrid ducks, i. 190; ii. 46; + on the domestication of wild ducks on the Mississippi, i. 278; + on the wild cock turkey visiting domestic hens, i. 292; + fertility of _Fringilla ciris_ in captivity, ii. 154; + fertility of _Columba migratoria_ and _leucocephala_ in captivity, ii. + 155; + breeding of _Anser canadensis_ in captivity, ii. 157. + AUDUBON and Bachman, on the change of coat in _Ovis montana_, i. 99; + sterility of _Sciurus cinerea_ in confinement, ii. 152. + AURICULA, effect of seasonal conditions on the, ii. 273; + blooming of, ii. 346. + AUSTRALIA, no generally useful plants derived from, i. 310; + useful plants of, enumerated by Hooker, i. 311. + AUSTRIA, heredity of character in emperors of, ii. 65. + AUTENRIETH, on persistency of colour in horses, ii. 21. + AVA, horses of, i. 53. + _Avena fatua_, cultivability of, i. 313. + AYEEN Akbery, pigeons mentioned in the, i. 150, 155, 185, 205, 207, 208. + AYRES, W. P., on bud-variation in pelargoniums, i. 378. + _Azalea indica_, bud-variation in, i. 377. + AZARA, on the feral dogs of La Plata, i. 27; + on the crossing of domestic with wild cats in Paraguay, i. 45; + on hornlike processes in horses, i. 50; + on curled hair in horses, i. 54; ii. 205, 325; + on the colours of feral horses, i. 60, 61; ii. 259; + on the cattle of Paraguay and La Plata, i. 82, 86, 89; ii. 250; + on a hornless bull, ii. 205; + on the increase of cattle in South America, ii. 119; + on the growth of horns in the hornless cattle of Corrientes, ii. 39; + on the "Niata" cattle, i. 90; + on naked quadrupeds, ii. 279; + on a race of black-skinned fowls in South America, i. 258; ii. 209; + on a variety of maize, i. 321. + + BABINGTON, C. C., on the origin of the plum, i. 345; + British species of the genus _Rosa_, i. 366; + distinctness of _Viola lutea_ and _tricolor_, i. 368. + BACHMANN, Mr., on the turkey, ii. 262. + _See also_ Audubon. + BADGER, breeding in confinement, ii. 151. + "BAGADOTTEN-TAUBE," i. 141. + BAILY, Mr., on the effect of selection on fowls, ii. 198; + on Dorking fowls, ii. 238. + BAIRD, S., on the origin of the turkey, i. 292. + BAKER, Mr., on heredity in the horse, ii. 11; + on the degeneration of the horse by neglect, ii. 239; + orders of Henrys VII. and VIII. for the destruction of undersized + mares, ii. 203. + BAKEWELL, change in the sheep effected by, ii. 198. + BALANCEMENT, ii. 342-344; + of growth, law of, i. 274. + BALDHEAD, pigeon, i. 151. + BALDNESS, in man, inherited, ii. 73-74; + with deficiency in teeth, ii. 326-327. + BALLANCE, Mr., on the effects of interbreeding on fowls, ii. 125; + on variation in the eggs of fowls, i. 248. + _Ballota nigra_, transmission of variegated leaves in, i. 383. + BAMBOO, varieties of the, ii. 256. + BANANA, variation of the, i. 372; ii. 256, 258; + bud-variation in the, i. 377; + sterility of the, ii. 268. + BANTAM fowls, i. 230; + Sebright, origin of, ii. 96; + sterility of, ii. 101. + BARB (Pigeon), i. 144-146, 210; ii. 227; + {436} + figure of, i. 145; + figure of lower jaw of, i. 164. + BARBS, of wheat, i. 314. + BARBERRY, dark or red-leaved variety, i. 362; ii. 19; + reversion in suckers of seedless variety, i. 384. + BARBUT, J., on the dogs of Guinea, i. 25; + on the domestic pigeons in Guinea, i. 186; + fowls not native in Guinea, i. 237. + BARKING, acquisition of the habit of, by various dogs, i. 27. + BARLEY, wild, i. 313; + of the lake-dwellings, i. 317-318; + ancient variety of, ii. 429. + BARNES, Mr., production of early peas by selection, ii. 201. + BARNET, Mr., on the intercrossing of strawberries, i. 351; + dioeciousness of the Hautbois strawberry, i. 353; + on the scarlet American strawberry, ii. 200. + BARTH, Dr., use of grass-seeds as food in Central Africa, i. 308. + BARTLETT, A. D., on the origin of "Himalayan" rabbits by intercrossing, + i. 109; + on the feral rabbits of Porto Santo, i. 114; + on geese with reversed feathers on the head and neck, i. 288; + on the young of the black-shouldered peacock, i. 290; + on the breeding of the Felidae in captivity, ii. 150. + BARTRAM, on the black wolf-dog of Florida, i. 22. + BATES, H. W., refusal of wild animals to breed in captivity, ii. 150, + 152; + sterility of American monkeys in captivity, ii. 153; + sterility of tamed guans, ii. 156. + BATRACHIA, regeneration of lost parts in, ii. 15. + BEACH, raised, in Peru, containing heads of maize, i. 320. + BEAK, variability of, in fowls, i. 258; + individual differences of, in pigeons, i. 160; + correlation of, with the feet in pigeons, i. 171-174. + BEALE, Lionel, on the contents of cells, ii. 370; + on the multiplication of infectious atoms, ii. 378; + on the origin of fibres, ii. 382. + BEANS, i. 330; + of Swiss lake-dwellings, i. 319; + varieties of, produced by selection, ii. 218; + French and scarlet, variable resistance of to frost, ii. 309, 314; + superiority of native seed of, ii. 314; + a symmetrical variation of scarlet, ii. 322; + experiments on kidney, i. 330; + with monstrous stipules and abortive leaflets, ii. 343. + BEARD, pigeon, i. 151. + BEARS, breeding in captivity, ii. 151. + BEASLEY, J., reversion in crossed cattle, ii. 41. + BEATON, D., effect of soil upon strawberries, i. 353; + on varieties of pelargonium, i. 364, ii. 274, 311; + bud-variation in _Gladiolus colvillii_, i. 382; + cross between Scotch kail and cabbage, ii. 98; + hybrid gladiolus, ii. 139; + constant occurrence of new forms among seedlings, ii. 235; + on the doubling of the compositae, ii. 316. + BECHUANA cattle, i. 88. + BECK, Mr., constitutional differences in pelargoniums, i. 364. + BECKMANN, on changes in the odours of plants, ii. 274. + BECKSTEIN, on the burrowing of wolves, i. 27; + "Spitz" dog, i. 31; + origin of the Newfoundland dog, i. 42; + crossing of domestic and wild swine, i. 66; + on the Jacobin pigeon, i. 154, 209; + notice of swallow-pigeons, i. 156; + on a fork-tailed pigeon, i. 157; + variations in the colour of the croup in pigeons, i. 184; + on the German dove-cot pigeon, i. 185; + fertility of mongrel pigeons, i. 192; + on hybrid turtle-doves, i. 193; + on crossing the pigeon with _Columba oenas_, _C. palumbus_, _Turtur + risoria_, and _T. vulgaris_, i. 193; + development of spurs in the silk-hen, i. 256; + on Polish fowls, i. 257, 264; + on crested birds, i. 257; + on the Canary-bird, i. 295, ii. 22, 161; + German superstition about the turkey, i. 293; + occurrence of horns in hornless breeds of sheep, ii. 30; + hybrids of the horse and ass, ii. 68; + crosses of tailless fowls, ii. 92; + difficulty of pairing dove-cot and fancy pigeons, ii. 103; + fertility of tame ferrets and rabbits, ii. 112; + fertility of wild sow, _ibid._; + difficulty of breeding caged birds, ii. 154; + comparative fertility of _Psittacus erithacus_ in captivity, ii. 155; + on changes of plumage in captivity, ii. 158; + liability of light-coloured cattle to the attacks of flies, ii. 229; + want of exercise a cause of variability, ii. 257; + effect of privation of light upon the plumage of birds, ii. 280; + on a sub-variety of the monk-pigeon, ii. 350. + BEDDOE, Dr., correlation of complexion with consumption, ii. 335. + BEDEGUAR gall, ii. 284. + BEE, persistency of character of, ii. 236, 254; + intercrossing, ii. 126; + conveyance, of pollen of peas by, i. 329. + BEE-OPHRYS, self-fertilisation of, ii. 91. + BEECH, dark-leaved, i. 362, ii. 19; + fern-leaved, reversion of, i. 382; + weeping, non-production of by seed, ii. 19. + BEECHEY, horses of Loochoo Islands, i. 53. + BEET, i. 326; + increase of sugar in, by selection, ii. 201. + {437} + _Begonia frigida_, singular variety of, i. 365; + sterility of, ii. 166. + BELGIAN rabbit, i. 106. + BELL, T., statement that white cattle have coloured ears, i. 85. + BELL, W., bud-variation in _Cistus tricuspis_, i. 377. + BELLINGERI, observations on gestation in the dog, i. 30; + on the fertility of dogs and cats, ii. 112. + BELON, on high-flying pigeons in Paphlagonia, i. 209; + varieties of the goose, i. 289. + BENGUELA, cattle of, i. 88. + BENNETT, Dr. G., pigs of the Pacific islands, i. 70, 87; + dogs of the Pacific islands, i. 87; + varieties of cultivated plants in Tahiti, ii. 256. + BENNETT, Mr., on the fallow deer, ii. 103. + BENTHAM, G., number and origin of cultivated plants, i. 306; + cereals all cultivated varieties, i. 312; + species of the orange group, i. 334-335; + distinctions of almond and peach, i. 338; + British species of _Rosa_, i. 366; + identity of _Viola lutea_ and _tricolor_, i. 368. + _Berberis vulgaris_, i. 384, ii. 19. + _Berberis Wallichii_, indifference of, to climate, ii. 164. + BERJEAN, on the history of the dog, i. 16, 18. + BERKELEY, G. F., production of hen-cocks in a strain of game-fowls, i. + 253. + BERKELEY, M. J., crossing of varieties of the pea, i. 397; + effect of foreign pollen on grapes, i. 400; + on hybrid plants, ii. 131; + analogy between pollen of highly-cultivated plants and hybrids, ii. + 268; + on Hungarian kidney-beans, ii. 275; + failure of Indian wheat in England, ii. 307; + bud developed on the petal of a _Clarkia_, ii. 384. + BERNARD, inheritance of disease in the horse, ii. 10. + BERNARD, C., independence of the organs of the body, ii. 368-369; + special affinities of the tissues, ii. 380. + BERNHARDI, varieties of plants with laciniated leaves, ii. 348. + _Bernicla antarctica_, i. 288. + BERTERO, on feral pigeons in Juan Fernandez, i. 190. + _Betula alba_, ii. 18. + BEWICK, on the British wild cattle, i. 84. + BIBLE, reference to breeding studs of horses in, i. 54; + references to domestic pigeons in the, i. 205; + indications of selection of sheep in the, ii. 201; + notice of mules in the, ii. 202. + BIDWELL, Mr., on self-impotence in _Amaryllis_, ii. 139. + BIRCH, weeping, i. 387, ii. 18. + BIRCH, Dr. S., on the ancient domestication of the pigeon in Egypt, i. + 205; + notice of bantam fowls in a Japanese encyclopaedia, i. 230, 247. + BIRCH, Wyrley, on silver-grey rabbits, i. 109-110. + BIRDS, sterility caused in, by change of conditions, ii. 153-157. + BLADDER-NUT, tendency of the, to become double, ii. 168. + BLAINE, Mr., on wry-legged terriers, ii. 245. + BLAINVILLE, origin and history of the dog, i. 15-16; + variations in the number of teeth in dogs, i. 34; + variations in the number of toes in dogs, i. 35; + on mummies of cats, i. 43; + on the osteology of solid-hoofed pigs, i. 75; + on feral Patagonian and N. American pigs, i. 77. + "BLASS-TAUBE," i. 156. + BLEEDING, hereditary, ii. 7, 8; + sexual limitation of excessive, ii. 73. + BLENDING of crossed races, time occupied by the, ii. 87. + BLINDNESS, hereditary, ii. 9; + at a certain age, ii. 78; + associated with colour of hair, ii. 328. + BLOODHOUNDS, degeneration of, caused by interbreeding, ii. 121. + BLUMENBACH, on the protuberance of the skull in Polish fowls, i. 257; + on the effect of circumcision, ii. 23; + inheritance of a crooked finger, ii. 23; + on badger-dogs and other varieties of the dog, ii. 220; + on _Hydra_, ii. 293; + on the "nisus formativus," ii. 294. + BLYTH, E., on the Pariah dog, i. 24; + hybrids of dog and jackal, i. 32; + early domestication of cats in India, i. 43; + origin of domestic cat, _ib._; + crossing of domestic and wild cats, i. 44; + on Indian cats resembling _Felis chaus_, i. 45; + on striped Burmese ponies, i. 58; + on the stripes of the ass, i. 63; + on Indian wild pigs, i. 66; + on humped cattle, i. 79, 80; + occurrence of _Bos frontosus_ in Irish crannoges, i. 81; + fertile crossing of zebus and common cattle, i. 83; + on the species of sheep, i. 94; + on the fat-tailed Indian sheep, i. 96; + origin of the goat, i. 101; + on rabbits breeding in India, i. 112; + number of tail-feathers in fantails, i. 146; + Lotan tumbler pigeons, i. 150; + number of tail-feathers in _Ectopistes_, i. 159; + on _Columba affinis_, i. 183; + pigeons roosting in trees, i. 181; + on _Columba leuconota_, i. 182; + on _Columba intermedia_ of Strickland, i. 184; + variation in colour of croup in pigeons, i. 184-185, 197; + voluntary domestication of rock-pigeons in India, i. 185; + feral pigeons on the Hudson, i. 190; + {438} + occurrence of sub-species of pigeons, i. 204; + notice of pigeon-fanciers in Delhi, &c., i. 206; + hybrids of _Gallus Sonneratii_ and the domestic hen, i. 234; + supposed hybridity of _Gallus Temminckii_, i. 235; + variations and domestication of _Gallus bankiva_, i. 235-236, 237; + crossing of wild and tame fowls in Burmah, i. 236; + restricted range of the larger gallinaceous birds, i. 237; + feral fowls in the Nicobar islands, i. 238; + black-skinned fowls occurring near Calcutta, i. 256; + weight of _Gallus bankiva_, i. 272; + degeneration of the turkey in India, i. 294, ii. 278; + on the colour of gold-fish, i. 296; + on the Ghor-Khur (_Asinus indicus_), ii. 42; + on _Asinus hemionus_, ii. 43; + number of eggs of _Gallus bankiva_, ii. 112; + on the breeding of birds in captivity, ii. 157; + co-existence of large and small breeds in the same country, ii. 279; + on the drooping ears of the elephant, ii. 301; + homology of leg and wing feathers, ii. 323. + BOETHIUS on Scotch wild cattle, i. 85. + BOITARD and Corbie, on the breeds of pigeons, i. 132; + Lille pouter pigeon, i. 138; + notice of a gliding pigeon, i. 156; + variety of the pouter pigeon, i. 162; + dove-cot pigeon, i. 185; + crossing pigeons, i. 192-193, ii. 97, 126; + sterility of hybrids of turtle-doves, i. 193; + reversion of crossed pigeons, i. 197, ii. 40; + on the fantail, i. 208, ii. 66; + on the trumpeter, ii. 66; + prepotency of transmission in silky fantail, ii. 67, 69; + secondary sexual characters in pigeons, ii. 74; + crossing of white and coloured turtle-doves, ii. 92; + fertility of pigeons, ii. 112. + BOMBYCIDAE, wingless females of, ii. 299. + _Bombyx hesperus_, ii. 304. + _Bombyx Huttoni_, i. 302. + _Bombyx mori_, i. 300-304. + BONAFOUS, on maize, i. 320, 321. + BONAPARTE, number of species of Columbidae, i. 133; + number of tail-feathers in pigeons, i. 158; + size of the feet in Columbidae, i. 174; + on _Columba guinea_, i. 182; + _Columba turricola_, _rupestris_, and _Schimperi_, i. 184. + _Bonatea speciosa_, development of ovary of, i. 403. + BONAVIA, Dr., growth of cauliflowers in India, ii. 310. + BONES, removal of portions of, ii. 296; + regeneration of, ii. 294; + growth and repair of, ii. 381-382. + BONNET, on the salamander, ii. 15, 341, 358, 385; + theory of reproduction, ii. 385. + BORCHMEYER, experiments with the seeds of the weeping ash, ii. 19. + BORECOLE, i. 323. + BORELLI, on Polish fowls, i. 247. + BORNEO, fowls of, with tail-bands, i. 235. + BORNET, E., condition of the ovary in hybrid _Cisti_, i. 389; + self-impotence of hybrid _Cisti_, ii. 140. + BORROW, G., on pointers, i. 42. + BORY de Saint-Vincent, on gold-fish, i. 297. + _Bos_, probable origin of European domestic cattle from three species of, + i. 83. + _Bos frontosus_, i. 79, 81-82. + _Bos indicus_, i. 79. + _Bos longifrons_, i. 79, 81. + _Bos primigenius_, i. 79-81, 119. + _Bos sondaicus_, ii. 206. + _Bos taurus_, i. 79. + _Bos trochoceros_, i. 81. + BOSC, heredity in foliage-varieties of the elm, i. 362. + BOSSE, production of double flowers from old seed, ii. 167. + BOSSI, on breeding dark-coloured silkworms, i. 302. + BOUCHARDAT, on the vine disease, i. 334. + BOUDIN, on local diseases, ii. 276; + resistance to cold of dark-complexioned men, ii. 335. + "BOULANS," i. 137. + "BOUTON d'Alep," ii. 276. + BOWEN, Prof., doubts as to the importance of inheritance, ii. 3. + BOWMAN, Mr., hereditary peculiarities in the human eye, ii. 8-10; + hereditary cataract, ii. 79. + BRACE, Mr., on Hungarian cattle, i. 80. + _Brachycome iberidifolia_, ii. 261. + BRACTS, unusual development of, in gooseberries, i. 355. + BRADLEY, Mr., effect of grafts upon the stock in the ash, i. 394; + effect of foreign pollen upon apples, i. 401; + on change of soil, ii. 146. + "BRAHMA Pootras," a new breed of fowls, i. 245. + BRAIN, proportion of, in hares and rabbits, i. 126-129. + BRANDT, origin of the goat, i. 101. + _Brassica_, varieties of, with enlarged stems, ii. 348. + _Brassica asperifolia_, ii. 343. + _Brassica napus_, i. 325. + _Brassica oleracea_, i. 323. + _Brassica rapa_, i. 325, ii. 165. + BRAUN, A., bud-variation in the vine, i. 375; + in the currant, i. 376; + in _Mirabilis jalapa_, i. 382; + in _Cytisus adami_, i. 388; + on reversion in the foliage of trees, i. 382; + spontaneous production of _Cytisus purpureo-elongatus_, i. 390; + reversion of flowers by stripes and blotches, ii. 37; + excess of nourishment a source of variability, ii. 257. + {439} + BRAZIL, cattle of, i. 88. + BREAD-FRUIT, varieties of, ii. 256; + sterility and variability of, ii. 262. + BREE, W. T., bud-variation in _Geranium pratense_ and _Centaurea cyanus_, + i. 379; + by tubers in the dahlia, i. 385; + on the deafness of white cats with blue eyes, ii. 329. + BREEDING, high, dependent on inheritance, ii. 3-4. + BREEDS, domestic, persistency of, ii. 246, 428-429; + artificial and natural, ii. 413-414; + extinction of, ii. 425; + of domestic cats, i. 45-47; + of pigs produced by crossing, i. 78; + of cattle, i. 86-87, 91-93; + of goats, i. 101. + BREHM, on _Columba amaliae_, i. 183. + BRENT, B. P., number of mammae in rabbits, i. 106; + habits of the tumbler pigeon, i. 151; + Laugher pigeon, i. 155; + colouring of the kite tumbler, i. 160; + crossing of the pigeon with _Columba oenas_, i. 193; + mongrels of the trumpeter pigeon, ii. 66; + close interbreeding of pigeons, ii. 126; + opinion on Aldrovandi's fowls, i. 247; + on stripes in chickens, i. 249-250; + on the combs of fowls, i. 253; + double-spurred Dorking fowls, i. 255; + effect of crossing on colour of plumage in fowls, i. 258; + incubatory instinct of mongrels between non-sitting varieties of fowls, + ii. 44; + origin of the domestic duck, i. 277; + fertility of the hook-billed duck, _ibid._; + occurrence of the plumage of the wild duck in domestic breeds, i. 280; + voice of ducks, i. 281; + occurrence of a short upper mandible in crosses of hook-billed and + common ducks, i. 281; + reversion in ducks produced by crossing, ii. 40; + variation of the canary-bird, i. 295; + fashion in the canary, ii. 240; + hybrids of canary and finches, ii. 45. + BRICKELL, on raising nectarines from seed, i. 340; + on the horses of North Carolina, ii. 300. + BRIDGES, Mr., on the dogs of Tierra del Fuego, i. 39; + on the selection of dogs by the Fuegians, ii. 207. + BRIDGMAN, W. K., reproduction of abnormal ferns, i. 383, ii. 379. + BRIGGS, J. J., regeneration of portions of the fins of fishes, ii. 15. + BROCA, P., on the intercrossing of dogs, i. 31-32; + on hybrids of hare and rabbit, i. 105; + on the rumpless fowl, i. 259; + on the character of half-castes, ii. 47; + degree of fertility of mongrels, ii. 100; + sterility of descendants of wild animals bred in captivity, ii. 160. + BROCCOLI, i. 323; + rudimentary flowers in, ii. 316; + tenderness of, ii. 310. + BROMEHEAD, W., doubling of the Canterbury bell by selection, ii. 200. + BROMFIELD, Dr., sterility of the ivy and _Acorus calamus_, ii. 170. + _Bromus secalinus_, i. 314. + BRONN, H. G., bud-variation in _Anthemis_, i. 379; + effects of cross-breeding on the female, i. 404; + on heredity in a one-horned cow, ii. 12, 13; + propagation of a pendulous peach by seed, ii. 18; + absorption of the minority in crossed races, ii. 88; + on the crossing of horses, ii. 92; + fertility of tame rabbits and sheep, ii. 112; + changes of plumage in captivity, ii. 158; + on the dahlia, ii. 261. + BRONZE period, dog of, i. 18. + BROWN, G., variations in the dentition of the horse, i. 50. + BROWN-SEQUARD, Dr., inheritance of artificially-produced epilepsy in the + guinea-pig, ii. 24. + _Brunswigia_, ii. 139. + BRUSSELS Sprouts, i. 323, ii. 429. + _Bubo maximus_, ii. 154. + BUCKLAND, F., on oysters, ii. 280; + number of eggs in a codfish, ii. 379. + BUCKLE, Mr., doubts as to the importance of inheritance, ii. 3. + BUCKLEY, Miss, carrier-pigeons roosting in trees, i. 181. + BUCKMAN, Prof., cultivation of _Avena fatua_, i. 313; + cultivation of the wild parsnip, i. 326, ii. 201, 277; + reversion in the parsnip, ii. 31. + BUCKWHEAT, injurious to white pigs, when in flower, ii. 337. + BUD and seed, close analogy of, i. 411. + BUD-REVERSION, ii. 37. + BUDS, adventitious, ii. 384. + BUD-VARIATION, i. 373-411, ii. 254, 287-288, 291; + contrasted with seminal reproduction, i. 373; + peculiar to plants, i. 374; + in the peach, i. 340, 374; + in plums, i. 375; + in the cherry, _ibid._; + in grapes, _ibid._; + in the gooseberry, currant, pear, and apple, i. 376; + in the banana, camellia, hawthorn, _Azalea indica_, and _Cistus + tricuspis_, i. 377; + in the hollyhock and pelargonium, i. 378; + in _Geranium pratense_ and the chrysanthemum, i. 379; + in roses, i. 367, 379-381; + in sweet williams, carnations, pinks, stocks, and snapdragons, i. 381; + in wall-flowers, cyclamen, _Oenothera biennis_, _Gladiolus colvillii_, + fuchsias, and _Mirabilis jalapa_, i. 382; + in foliage of various trees, i. 382-384; + in cryptogamic plants, i. 383; + by suckers in _Phlox_ and barberry, i. 384; + by tubers in the potato, _ibid._; + in the dahlia, i. 385; + by bulbs in hyacinths, _Imatophyllum miniatum_, and tulips, i. 385; + in _Tigridia conchiflora_, i. 386; + {440} + in _Hemerocallis_, _ibid._; + doubtful cases, i. 386-387; + in _Cytisus Adami_, i. 387-394; + probable in _Aesculus rubicunda_, i. 392; + summary of observations on, 406. + BUFFON, on crossing the wolf and dog, i. 32; + increase of fertility by domestication, ii. 111; + improvement of plants by unconscious selection, ii. 216; + theory of reproduction, ii. 375. + _Bulimus_, ii. 53. + BULL, apparent influence of, on offspring, ii. 68. + BULLACE, i. 345. + BULLDOG, recent modifications of, i. 42. + BULLFINCH, breeding in captivity, ii. 154; + attacking flower-buds, ii. 232. + BULT, Mr., selection of pouter pigeons, ii. 197. + "BUENDTNERSCHWEIN," i. 67. + BUNTING, reed, in captivity, ii. 158. + BURDACH, crossing of domestic and wild animals, i. 66; + aversion of the wild boar to barley, ii. 303. + BURKE, Mr., inheritance in the horse, ii. 10. + _Burlingtonia_, ii. 135. + BURMAH, cats of, i. 47. + BURMESE ponies, striped, i. 58, 59. + BURNES, Sir A., on the Karakool sheep, i. 98, ii. 278; + varieties of the vine in Cabool, i. 333; + hawks, trained in Scinde, ii. 153; + pomegranates producing seed, ii. 168. + BURTON Constable, wild cattle at, i. 84. + "BURZEL-TAUBEN," i. 150. + BUSSORAH carrier, i. 141. + _Buteo vulgaris_, copulation of, in captivity, ii. 154. + BUTTERFLIES, polymorphic, ii. 399-400. + BUZAREINGUES, Girou de, inheritance of tricks, ii. 6. + + CABANIS, pears grafted on the quince, ii. 239. + CABBAGE, i. 323-326; + varieties of, i. 323; + unity of character in flowers and seeds of, i. 323-324; + cultivated by ancient Celts, i. 324; + classification of varieties of, _ibid._; + ready crossing of, _ibid._, ii. 90, 91, 98, 130; + origin of, i. 325; + increased fertility of, when cultivated, ii. 113; + growth of, in tropical countries, ii. 277. + CABOOL, vines of, i. 333. + CABRAL, on early cultivation in Brazil, i. 311. + CACTUS, growth of cochineal on, in India, ii. 275. + CAESAR, _Bos primigenius_ wild in Europe in the time of, i. 81; + notice of fowls in Britain, i. 246; + notice of the importation of horses by the Celts, ii. 203. + CAFFRE fowls, i. 230. + CAFFRES, different kinds of cattle possessed by the, i. 88. + "CAGIAS," a breed of sheep, i. 95. + CALCEOLARIAS, i. 364; ii. 147; + effects of seasonal conditions on, ii. 274; + peloric flowers in, ii. 346. + "CALONGOS," a Columbian breed of cattle, i. 88. + CALVER, Mr., on a seedling peach producing both peaches and nectarines, + i. 341. + CALYX, segments of the, converted into carpels, ii. 392. + CAMEL, its dislike to crossing water, i. 181. + _Camellia_, bud-variations in, i. 377; + recognition of varieties of, ii. 251; + variety in, hardiness of, ii. 308. + CAMERON, D., on the cultivation of Alpine plants, ii. 163. + CAMERONN, Baron, value of English blood in race-horses, ii. 11. + _Campanula medium_, ii. 200. + CANARY-BIRD, i. 295; + conditions of inheritance in, ii. 22; + hybrids of, ii. 45; + period of perfect plumage in, ii. 77; + diminished fertility of, ii. 161; + standard of perfection in, ii. 195; + analogous variation in, ii. 349. + CANCER, heredity of, ii. 7, 8, 79. + CANINE teeth, development of the, in mares, ii. 318. + _Canis alopex_, i. 29. + _Canis antarcticus_, i. 20. + _Canis argentatus_, ii. 151. + _Canis aureus_, i. 29. + _Canis cancrivorus_, domesticated and crossed in Guiana, i. 23. + _Canis cinereo-variegatus_, i. 29. + _Canis fulvus_, i. 29. + _Canis Ingae_, the naked Peruvian dog, i. 23. + _Canis latrans_, resemblance of, to the Hare Indian dog, i. 22; + one of the original stocks, i. 26. + _Canis lupaster_, i. 25. + _Canis lupus_, var. _occidentalis_, resemblance of, to North American + dogs, i. 21; + crossed with dogs, i. 22; + one of the original stocks, i. 26. + _Canis mesomelas_, i. 25, 29. + _Canis primaevus_, tamed by Mr. Hodgson, i. 26. + _Canis sabbar_, i. 25. + _Canis simensis_, possible original of greyhounds, i. 33. + _Canis thaleb_, i. 29. + _Canis variegatus_, i. 29. + CANTERBURY Bell, doubled by selection, ii. 200. + CAPE of Good Hope, different kinds of cattle at the, i. 88; + {441} + no useful plants derived from the, i. 310. + CAPERCAILZIE, breeding in captivity, ii. 156. + _Capra aegagrus_ and _C. Falconeri_, probable parents of domestic goat, + i. 101. + CAPSICUM, i. 371. + CARDAN, on a variety of the walnut, i. 356; + on grafted walnuts, ii. 259-260. + CARDOON, ii. 34. + _Carex rigida_, local sterility of the, ii. 170. + CARLIER, early selection of sheep, ii. 204. + CARLISLE, Sir A., inheritance of peculiarities, ii. 6, 8; + of polydactylism, ii. 13. + "CARME" pigeon, i. 156. + CARNATION, bud-variation in, i. 381; + variability of, i. 370; + striped, produced by crossing red and white, i. 393; + effect of conditions of life on the, ii. 273. + CARNIVORA, general fertility of, in captivity, ii. 150. + CAROLINE Archipelago, cats of, i. 47. + CARP, ii. 236. + CARPELS, variation of, in cultivated cucurbitaceae, i. 359. + CARPENTER, W. B., regeneration of bone, ii. 294; + production of double monsters, ii. 340; + number of eggs in an _Ascaris_, ii. 379. + _Carpinus betulus_, i. 362. + _Carpophaga littoralis_ and _luctuosa_, i. 182. + CARRIER pigeon, i. 139-142; + English, i. 139-141; + figured, i. 140; + skull figured, i. 163; + history of the, i. 211; + Persian, i. 141; + Bussorah, _ibid._; + Bagadotten, skull figured, i. 163; + lower jaw figured, i. 165. + CARRIERE, cultivation of the wild carrot, i. 326; + intermediate form between the almond and the peach, i. 338; + glands of peach-leaves, i. 343; + bud-variation in the vine, i. 375; + grafts of _Aria vestita_ upon thorns, i. 387; + variability of hybrids of _Erythrina_, ii. 265. + CARROT, wild, effects of cultivation on the, i. 326; + reversion in the, ii. 31; + run wild, ii. 33; + increased fertility of cultivated, ii. 113; + experiments on the, ii. 277; + acclimatisation of the, in India, ii. 311. + _Carthamus_, abortion of the pappus in, ii. 316. + CARTIER, cultivation of native plants in Canada, i. 312. + CARYOPHYLLACEAE, frequency of contabescence in the, ii. 165. + CASPARY, bud-variation in the moss-rose, i. 380; + on the ovules and pollen of _Cytisus_, i. 388-389; + crossing of _Cytisus purpureus_ and _C. laburnum_, i. 389; + trifacial orange, i. 391; + differently-coloured flowers in the wild _Viola lutea,_ i. 408; + sterility of the horse-radish, ii. 170. + CASTELNAU, on Brazilian cattle, i. 88. + CASTRATION, assumption of female characters caused by, ii. 51-52. + _Casuarius bennettii_, ii. 156. + CAT, domestic, i. 43-48; + early domestication and probable origin of the, i. 43-44; + intercrossing of with wild species, i. 44-45; + variations of, i. 45-48; + feral, i. 47, ii. 33; + anomalous, i. 48; + polydactylism in, ii. 14; + black, indications of stripes in young, ii. 55; + tortoiseshell, ii. 73; + effects of crossing in, ii. 86; + fertility of, ii. 111; + difficulty of selection in, ii. 234, 236; + length of intestines in, ii. 302; + white with blue eyes, deafness of, ii. 329; + with tufted ears, ii. 350. + CATARACT, hereditary, ii. 9, 79. + CATERPILLARS, effect of changed food on, ii. 280. + CATLIN, G., colour of feral horses in North America, i. 61. + CATTLE, European, their probable origin from three original species, i. + 79-82; + humped, or Zebus, i. 79-80; + intercrossing of, i. 83, 91-93; + wild, of Chillingham, Hamilton, Chartley, Burton Constable, and + Gisburne, i. 84, ii. 119; + colour of feral, i. 84-85, ii. 102; + British breeds of, i. 86-87; + South African breeds of, i. 88; + South American breeds of, i. 89, ii. 205; + Niata, i. 89-91, ii. 205, 208, 332; + effects of food and climate on, i. 91-92; + effects of selection on, i. 92-93; + Dutch-buttocked, ii. 8; + hornless, production of horns in, ii. 29-30, 39; + reversion in, when crossed, ii. 41; + wildness of hybrid, ii. 45; + short-horned, prepotency of, ii. 65; + wild, influence of crossing and segregation on, ii. 86; + crosses of, ii. 96, 104, 118; + of Falkland islands, ii. 102; + mutual fertility of all varieties of, ii. 110; + effects of interbreeding on, ii. 117-119; + effects of careful selection on, ii. 194, 199; + naked, of Columbia, ii. 205; + crossed with wild banteng in Java, ii. 206; + with reversed hair in Banda Oriental, ii. 205; + selection of trifling characters in, ii. 209; + fashion in, ii. 210; + similarity of best races of, ii. 241; + unconscious selection in, ii. 214; + effects of natural selection on anomalous breeds of, ii. 226-227; + light-coloured, attacked by flies, ii. 229, 336; + Jersey, rapid improvement of, ii. 234; + effects of disuse of parts in, ii. 299; + rudimentary horns in, ii. 315; + supposed influence of humidity on the hair of, ii. 326; + {442} + white spots of, liable to disease, ii. 337; + supposed analogous variation in, ii. 349; + displacement of long-horned by short-horned, ii. 426. + CAULIFLOWER, i. 323; + free-seeding of, in India, ii. 310; + rudimentary flowers in, ii. 316. + CAVALIER pigeon, ii. 97. + _Cavia aperea_, ii. 152. + CAY (_Cebus azarae_), sterility of, in confinement, ii. 153. + _Cebus azarae_, ii. 153. + _Cecidomyia_, larval development of, ii. 283, 360, 367; + and _Misocampus_, i. 5. + CEDARS of Lebanon and Atlas, i. 364. + CELERY, turnip-rooted, i. 336; + run wild, ii. 33. + CELL-THEORY, ii. 370. + _Celosia cristata_, i. 365. + CELSUS, on the selection of seed-corn, i. 318, ii. 203. + CELTS, early cultivation of the cabbage by the, i. 324; + selection of cattle and horses by the, ii. 202-203. + _Cenchrus_, seeds of a, used as food, i. 309. + _Centaurea cyanus_, bud-variation in, i. 379. + CEPHALOPODA, spermatophores of, ii. 383. + _Cerasus padus_, yellow-fruited, ii. 19. + _Cercoleptes_, sterility of, in captivity, ii. 152. + _Cercopithecus_, breeding of a species of, in captivity, ii. 153. + CEREALS, i. 312-313; + of the Neolithic period in Switzerland, i. 317; + adaptation of, to soils, ii. 305. + _Cereus_, ii. 38. + _Cereus speciosissimus_ and _phyllanthus_, reversion in hybrids of, i. + 392. + _Cervus canadensis_, ii. 158. + _Cervus dama_, ii. 120. + CETACEA, correlation of dermal system and teeth in the, ii. 328. + CEYLON, cats of, i. 46; + pigeon-fancying in, i. 206. + _Chamaerops humilis_, crossed with date palm, i. 399. + CHAMISSO, on seeding bread-fruit, ii. 168. + CHANNEL islands, breeds of cattle in, i. 80. + CHAPMAN, Professor, peach-trees producing nectarines, i. 341. + CHAPUIS, F., sexual peculiarities in pigeons, i. 162, ii. 74; + effect produced by first male upon the subsequent progeny of the + female, i. 405; + sterility of the union of some pigeons, ii. 162. + CHARACTERS, fixity of, ii. 239; + latent, ii. 51-56, 399-400; + continued divergence of, ii. 241; + antagonistic, ii. 401. + CHARDIN, abundance of pigeons in Persia, i. 205. + CHARLEMAGNE, orders as to the selection of stallions, ii. 203. + CHARTLEY, wild cattle of, i. 84. + CHATE, reversion of the upper seeds in the pods of stocks, ii. 347-348. + CHATIN, on _Ranunculus ficaria_, ii. 170. + CHAUNDY, Mr., crossed varieties of cabbage, ii. 130. + CHEETAH, general sterility of, in captivity, ii. 151. + _Cheiranthus cheiri_, i. 382. + CHERRIES, i. 347-348; + bud-variation in, i. 375; + white Tartarian, ii. 230; + variety of, with curled petals, ii. 232; + period of vegetation of, changed by forcing, ii. 311. + CHEVREUL, on crossing fruit-trees, ii. 129. + CHICKENS, differences in characters of, i. 249-250; + white, liable to gapes, ii. 228, 336. + CHIGOE, ii. 275. + CHILE, sheep of, i. 95. + CHILLINGHAM cattle, identical with _Bos primigenius_, i. 81; + characters of, i. 83-84. + CHILOE, half-castes of, ii. 46. + CHINA, cats of, with drooping ears, i. 47; + horses of, i. 53; + striped ponies of, i. 59; + asses of, i. 62; + notice of rabbits in, by Confucius, i. 103; + breeds of pigeons reared in, i. 206; + breeds of fowls of, in fifteenth century, i. 232, 247; + goose of, i. 237. + CHINCHILLA, fertility of, in captivity, ii. 152. + CHINESE, selection practised by the, ii. 204-205; + preference of the, for hornless rams, ii. 209; + recognition of the value of native breeds by the, ii. 313. + CHINESE, or Himalayan rabbit, i. 108. + "CHIVOS," a breed of cattle in Paraguay, i. 89. + CHOUX-RAVES, i. 323. + CHRIST, H., on the plants of the Swiss Lake-dwellings, i. 309, 318; + intermediate forms between _Pinus sylvestris_ and _montana_, i. 363. + CHRYSANTHEMUM, i. 379. + _Chrysotis festiva_, ii. 280. + CINERARIA, effects of selection on the, ii. 200. + CIRCASSIA, horses of, ii. 102. + CIRCUMCISION, ii. 23. + CIRRIPEDES, metagenesis in, ii. 366. + _Cistus_, intercrossing and hybrids of, i. 336, 389, ii. 140. + _Cistus tricuspis_, bud-variation in, i. 377. + CITRONS, i. 334-335. + "_Citrus aurantium fructu variabili_," i. 336. + _Citrus decumana_, i. 335. + _Citrus lemonum_, i. 336. + {443} + _Citrus medica_, i. 335-336. + CLEFT palate, inheritance of, ii. 24. + CLEMENTE, on wild vines in Spain, i. 332. + CLERMONT-TONNERRE, on the St. Valery apple, i. 401. + CLAPHAM, A., bud-variation in the hawthorn, i. 377. + "CLAQUANT," i. 138. + "CLAQUERS" (pigeons), i. 156. + CLARK, G., on the wild dogs of Juan de Nova, i. 27; + on striped Burmese and Javanese ponies, i. 59; + breeds of goats imported into the Mauritius, i. 101; + variations in the mammae of goats, i. 102; + bilobed scrotum of Muscat goat, _ibid._ + CLARK, H. J., on fission and gemmation, ii. 359. + CLARKE, R. T., intercrossing of strawberries, i. 352. + CLARKE, T., hybridisation of stocks, i. 399, ii. 93. + CLARKSON, Mr., prize-cultivation of the gooseberry, i. 355. + CLASSIFICATION, explained by the theory of natural selection, i. 11. + CLIMATE, effect of, upon breeds of dogs, i. 37; + on horses, i. 52, 53; + on cattle, i. 91, 92; + on the fleece of sheep, i. 98, 99; + on seeds of wheat, i. 316; + on cultivated cabbages, i. 325; + adaptation of maize to, i. 322. + CLIMATE and pasture, adaptation of breeds of sheep to, i. 96-97. + CLIMATE and soil, effects of, upon strawberries, i. 353. + CLINE, Mr., on the skull in horned and hornless rams, ii. 333. + CLOS, on sterility in _Ranunculus ficaria_, ii. 170. + CLOTZSCH, hybrids of various trees, ii. 130. + CLOVER, pelorism in, ii. 340. + COATE, Mr., on interbreeding pigs, ii. 122. + COCCUS of apple trees, ii. 231. + COCHIN fowls, i. 227, 250, 252, 260-261; + occipital foramen of, figured, i. 261; + section of skull of, figured, i. 263; + cervical vertebra of, figured, i. 267. + COCHINEAL, persistence of, ii. 236; + preference of, for a particular cactus, ii. 275. + _Cochlearia armoracia_, ii. 170. + COCK, game, natural selection in, ii. 225; + spur of, grafted on the comb, ii. 296; + spur of, inserted into the eye of an ox, ii. 369; + effect of castration upon the, ii. 51-52. + COCK'S-COMB, varieties of the, i. 365. + COCOONS, of silkworms, variations in, i. 302-303. + CODFISH, bulldog, i. 89; + number of eggs in the, ii. 379. + _Coelogenys paca_, ii. 152. + COLIN, prepotency of the ass over the horse, ii. 67-68; + on cross-breeding, ii. 97; + on change of diet, ii. 304. + COLLINSON, Peter, peach-tree producing a nectarine, i. 340. + COLORATION, in pigeons, an evidence of unity of descent, i. 195-197. + COLOUR, correlation of, in dogs, i. 28-29; + persistence of, in horses, i. 50; + inheritance and diversity of, in horses, i. 55; + variations of, in the ass, i. 62-63; + of wild or feral cattle, i. 85; + transmission of, in rabbits, i. 107; + peculiarities of, in Himalayan rabbits, i. 111; + influence of, ii. 227-230; + correlation of, in head and limbs, ii. 324; + correlated with constitutional peculiarities, ii. 335-338. + COLOUR and odour, correlation of, ii. 325. + COLOUR-BLINDNESS, hereditary, ii. 9; + more common in men than in women, ii. 72-73; + associated with inability to distinguish musical sounds, ii. 328. + COLOURS, sometimes not blended by crossing, ii. 92. + _Columba affinis_, Blyth, a variety of _C. livia_, i. 183. + _Columba amaliae_, Brehm, a variety of _C. livia_, i. 183. + _Columba guinea_, i. 182. + _Columba gymnocyclus_, Gray, a form of _C. livia_, i. 184. + _Columba gymnophthalmos_, hybrids of, with _C. oenas_, i. 193; + with _C. maculosa_, i. 194. + _Columba intermedia_, Strickland, a variety of _C. livia_, i. 184. + _Columba leucocephala_, ii. 155. + _Columba leuconota_, i. 182, 195. + _Columba littoralis_, i. 182. + _Columba livia_, ii. 29, 40; + the parent of domestic breeds of pigeons, i. 183; + measurements of, i. 134; + figured, i. 135; + skull figured, i. 163; + lower jaw figured, i. 164, 168; + scapula figured, i. 167. + _Columba luctuosa_, i. 182. + _Columba migratoria_ and _leucocephala_, diminished fertility of, in + captivity, ii. 155. + _Columba oenas_, i. 183; + crossed with common pigeon and _C. gymnophthalmos_, i. 193. + _Columba palumbus_, i. 193, ii. 350. + _Columba rupestris_, i. 182, 184, 195. + _Columba Schimperi_, i. 184. + _Columba torquatrix_, ii. 350. + _Columba turricola_, i. 184. + COLUMBIA, cattle of, i. 88. + COLUMBINE, double, i. 365, ii. 330. + {444} + COLUMBUS, on West Indian dogs, i. 23. + COLUMELLA, on Italian shepherd's dogs, i. 23; + on domestic fowls, i. 231, 247, ii. 202, 429; + on the keeping of ducks, i. 277; + on the selection of seed-corn, i. 318; + on the benefits of change of soil to plants, ii. 146; + on the value of native breeds, ii. 313. + COLZA, i. 325. + COMB, in fowls, variations of, i. 253-254; + sometimes rudimentary, ii. 315. + COMPENSATION, law of, i. 274. + COMPENSATION of growth, ii. 342-344. + COMPLEXION, connexion of, with constitution, ii. 335. + COMPOSITAE, double flowers of, i. 365, ii. 167, 316. + CONCEPTION, earlier in Alderney and Zetland cows than in other breeds, i. + 87. + CONDITIONS of life, changed, effect of, ii. 418-419; + on horses, i. 52; + upon variation in pigeons, i. 212-213; + upon wheat, i. 315-316; + upon trees, i. 361; + in producing bud-variation, i. 408; + advantages of, ii. 145-148, 176-177; + sterility caused by, ii. 148-165; + conducive to variability, ii. 255-261, 394; + accumulative action of, ii. 261-263; + direct action of, ii. 271-292. + CONDOR, breeding in captivity, ii. 154. + CONFINEMENT, effect of, upon the cock, ii. 52. + CONFUCIUS, on the breeding of rabbits in China, i. 103. + CONOLLY, Mr., on Angora goats, ii. 326. + CONSTITUTIONAL differences in sheep, i. 96-97; + in varieties of apples, i. 349-350; + in pelargoniums, i. 364; + in dahlias, i. 370. + CONSTITUTIONAL peculiarities in strawberries, i. 353; + in roses, i. 367. + CONSUMPTION, hereditary, ii. 8; + period of appearance of, ii. 77; + correlated with complexion, ii. 335. + CONTABESCENCE, ii. 165-166. + _Convolvulus batatas_, ii. 169, 309. + _Convolvulus tricolor_, bud-variation in, i. 408. + COOPER, Mr., improvement of vegetables by selection, ii. 204. + COOPER, White, hereditary peculiarities of vision, ii. 9; + association of affections of the eyes with those of other systems, ii. + 328. + CORALS, bud-variation in, i. 374; + non-diffusion of cell-gemmules in, ii. 379. + CORBIE. _See_ Boitard. + CORNEA, opacity of, inherited, ii. 9. + _Cornus mascula_, yellow-fruited, ii. 19. + CORRELATION, ii. 319; + of neighbouring parts, ii. 320; + of change in the whole body and in some of its parts, ii. 321; + of homologous parts, ii. 322-331; + inexplicable, ii. 331-333; + commingling of, with the effects of other agencies, ii. 333-335. + CORRELATION of skull and limbs in swine, i. 73; + of tusks and bristles in swine, i. 76; + of multiplicity of horns and coarseness of wool in sheep, i. 95; + of beak and feet in pigeons, i. 172-173; + between nestling down and colour of plumage in pigeons, i. 194; + of changes in silkworms, i. 304; + in plants, ii. 219; + in maize, i. 323; + in pigeons, i. 167-171, 218; + in fowls, i. 274-275. + CORRESPONDING periods, inheritance at, ii. 75-80. + CORRIENTES, dwarf cattle of, i. 89. + CORRINGHAM, Mr., influence of selection on pigs, ii. 198. + CORSICA, ponies of, i. 52. + "CORTBECK" (pigeon) of Aldrovandi, i. 209. + _Corvus corone_ and _C. cornix_, hybrids of, ii. 94. + _Corydalis_, flower of, ii. 304. + _Corydalis cava_, ii. 132-133. + _Corydalis solida_, sterile when peloric, ii. 167. + _Corydalis tuberosa_, peloric by reversion, ii. 58-59. + _Corylus avellana_, i. 357. + COSTA, A., on shells transferred from England to the Mediterranean, ii. + 280. + "COUVE TRONCHUDA," i. 323. + COW, inheritance of loss of one horn in the, ii. 12, 23; + amount of milk furnished by the, ii. 300; + development of six mammae in, ii. 317. + COWSLIP, ii. 21, 182. + CRACIDAE, sterility of the, in captivity, ii. 156. + CRANES, fertility of, in captivity, ii. 156. + _Crataegus oxyacantha_, i. 363, ii. 18, 232, 258, 377. + _Crataegus monogyna_, i. 364. + _Crataegus sibirica_, i. 364. + CRAWFURD, J., Malasian cats, i. 47; + horses of the Malay Archipelago, i. 49; + horses of Japan, i. 53; + occurrence of stripes in young wild pigs of Malacca, i. 76; + on a Burmese hairy family with deficient teeth, ii. 77, 327; + Japanese origin of the bantam, i. 230; + game fowls of the Philippine islands, i. 232; + hybrids of _Gallus varius_ and domestic fowl, i. 234; + domestication of _Gallus bankiva_, i. 236; + feral fowls in the Pellew islands, i. 238; + history of the fowl, i. 246; + history of the domestic duck, i. 277; + domestication of the goose, i. 287; + cultivated plants of New Zealand, i. 312; + {445} + breeding of tame elephants in Ava, ii. 150; + sterility of _Goura coronata_ in confinement, ii. 155; + geese of the Philippine islands, ii. 162. + CREEPERS, a breed of fowls, i. 230. + CRESTED fowl, i. 227; + figured, i. 229. + "CREVE-COEUR," a French sub-breed of fowls, i. 229. + CRISP, Dr., on the brains of the hare and rabbit, i. 126. + CROCKER, C. W., singular form of _Begonia frigida_, i. 365-366, ii. 166; + sterility in _Ranunculus ficaria_, ii. 170. + CROCUS, ii. 165. + CROSS-BREEDING, permanent effect of, on the female, i. 404. + CROSSING, ii. 85-144, 173-192; + a cause of uniformity, ii. 85-90, 173; + occurs in all organised beings, ii. 90-92; + some characters not blended by, ii. 92-95, 173; + modifications and new races produced by, ii. 95-99; + causes which check, ii. 100-109; + domestication and cultivation favourable to, ii. 109-113, 189; + beneficial effects of, ii. 114-131, 174-176; + necessary in some plants, ii. 131-140, 175-176, 423; + summary of subject of, ii. 140-144; + of dogs with wolves in North America, i. 21-22; + with _Canis cancrivorus_ in Guiana, i. 23; + of dog with wolf, described by Pliny and others, i. 24; + characters furnished by, brought out by reversion in the progeny, ii. + 34-36; + a direct cause of reversion, ii. 39-47, 48; + a cause of variability, ii. 264-267. + CRUSTACEA, macrourous, differences in the development of the, ii. 368. + CRUSTACEAN with an antenna-like development of the eye-peduncle, ii. 391. + CRYPTOGAMIC plants, bud-variation in, i. 383. + CUBA, wild dogs of, i. 27. + "CUCKOO," sub-breeds of fowls, i. 244. + CUCUMBER, variation in number of carpels of, i. 359; + supposed crossing of varieties of the, i. 400. + _Cucumis momordica_, i. 360. + _Cucumis sativa_, i. 359. + _Cucurbita_, dwarf, correlation of leaves in, ii. 330. + _Cucurbita maxima_, i. 357, 359. + _Cucurbita moschata_, i. 357, 359. + _Cucurbita pepo_, i. 357, ii. 108; + varieties of, i. 358; + relation in size and number of fruit of, ii. 343. + CUCURBITACEAE, i. 357-360; + supposed crossing of, i. 399; + Naudin's observations on hybrids of, ii. 172; + acclimatisation of, ii. 313. + "CULBUTANTS" (pigeons), i. 150. + CULTIVATION of plants, origin of, among savages, i. 309-310; + fertility increased by, ii. 111-113. + CUNIER, on hereditary night-blindness, ii. 9. + CURRANTS, of Tierra del Fuego, i. 309; + bud-variation in, i. 376. + CURTIS, Mr., bud-variation in the rose, i. 381. + CUVIER, on the gestation of the wolf, i. 29; + the odour of the jackal, an obstacle to domestication, i. 30; + differences of the skull in dogs, i. 34; + external characters of dogs, i. 35; + elongation of the intestines in domestic pigs, i. 73, ii. 303; + fertility of the hook-billed duck, i. 277; + number of digits, ii. 13; + hybrid of ass and zebra, ii. 42; + breeding of animals in the Jardin des Plantes, ii. 149; + sterility of predaceous birds in captivity, ii. 154; + facility of hybridisation in confinement, ii. 160. + CYANOSIS, affection of fingers in, ii. 332. + CYCLAMEN, bud-variation in, i. 382. + _Cynara cardunculus_, ii. 34. + _Cynips fecundatrix_, ii. 283. + _Cynocephalus hamadryas_, ii. 153. + _Cyprinus auratus_, i. 296-297. + _Cyrtanthus_, ii. 139. + _Cyrtopodium_, ii. 134. + _Cytisus Adami_, ii. 364; + its bud-variation, i. 387-389, 406, ii. 37; + seedlings from, i. 388; + different views of its origin, i. 389-390; + experiments in crossing _C. purpureus_ and _laburnum_ to produce, i. + 389; + its production by M. Adam, i. 390; + discussion of origin of, i. 396. + _Cytisus alpino-laburnum_, ovules and pollen of, i. 389; + origin of, i. 390. + _Cytisus alpinus_, i. 388. + _Cytisus laburnum_, i. 387, 389, 390, 396. + _Cytisus purpureo-elongatus_, ovules and pollen of, i. 389; + production of, i. 390. + _Cytisus purpureus_, i. 387, 388, 389, 390, 396. + + DAHLBOM, effects of food on hymenoptera, ii. 281. + DAHLIA, i. 369-370, ii. 147; + bud-variation by tubers in the, i. 385; + improvement of, by selection, ii. 216; + steps in cultivation of, ii. 261; + effect of conditions of life on, ii. 273; + correlation of form and colour in, ii. 331. + DAISY, hen and chicken, i. 365; + Swan River, ii. 261. + DALBRET, varieties of wheat, i. 314. + DALIBERT, changes in the odours of plants, ii. 274. + DALLY, Dr., on consanguineous marriages, ii. 122. + DALTONISM, hereditary, ii. 9. + DAMARAS, cattle of, i. 88, ii. 207-208. + {446} + DAMSON, i. 347. + DANDOLO, Count, on silkworms, i. 301. + DANIELL, fertility of English dogs in Sierra Leone, ii. 161. + DANISH Middens, remains of dogs in, i. 18. + DAPPLING in horses, asses, and hybrids, i. 55. + DARESTE. C., on the skull of the Polish fowl, i. 262; + on the production of monstrous chickens, ii. 289; + co-existence of anomalies, ii. 331; + production of double monsters, ii. 340. + DARVILL, Mr., heredity of good qualities in horses, ii. 11. + DARWIN, C., on _Lepus magellanicus_, i. 112; + on the wild potato, i. 330; + dimorphism in the polyanthus and primrose, ii. 21. + DARWIN, Dr., improvement of vegetables by selection, ii. 204. + DARWIN, Sir F., wildness of crossed pigs, ii. 45. + D'ASSO, monogynous condition of the hawthorn in Spain, i. 364. + _Dasyprocta aguti_, ii. 152. + Date-palm, varieties of the, ii. 256; + effect of pollen of, upon the fruit of _Chamaerops_, i. 299. + _Datura_, ii. 38; + variability in, ii. 266. + _Datura laevis_ and _stramonium_, reversion in hybrids of, i. 392. + _Datura stramonium_, ii. 67. + DAUBENTON, variations in the number of mammae in dogs, i. 35; + proportions of intestines in wild and domestic cats, i. 48, ii. 302. + DAUDIN, on white rabbits, ii. 230. + DAVY, Dr., on sheep in the West Indies, i. 98. + DAWKINS and Sandford, early domestication of _Bos longifrons_ in Britain, + i. 81. + DEAF-MUTES, non-heredity of, ii. 22. + DEAFNESS, inheritance of, ii. 78. + DEBY, wild hybrids of common and musk ducks, ii. 46. + DE CANDOLLE, Alph., number and origin of cultivated plants, i. 306-307, + 371; + regions which have furnished no useful plants, i. 310; + wild wheat, i. 312-313; + wild rye and oats, i. 313; + antiquity of varieties of wheat, i. 316; + apparent inefficacy of selection in wheat, i. 318; + origin and cultivation of maize, i. 320, ii. 307; + colours of seeds of maize, i. 321; + varieties and origin of the cabbage, i. 324-325; + origin of the garden-pea, i. 326; + on the vine, i. 332, ii. 308; + cultivated species of the orange group, i. 335; + probable Chinese origin of the peach, i. 337; + on the peach and nectarine, i. 340, 342; + varieties of the peach, i. 342; + origin of the apricot, i. 344; + origin and varieties of the plum, i. 345; + origin of the cherry, i. 347; + varieties of the gooseberry, i. 354; + selection practised with forest-trees, i. 361; + wild fastigate oak, i. 361; + dark-leaved varieties of trees, i. 362; + conversion of stamens into pistils in the poppy, i. 365; + variegated foliage, i. 366; + heredity of white hyacinths, i. 371, ii. 20; + changes in oaks dependent on age, i. 387; + inheritance of anomalous characters, ii. 19; + variation of plants in their native countries, ii. 256; + deciduous bushes becoming evergreen in hot climates, ii. 305; + antiquity of races of plants, ii. 429. + DE CANDOLLE, P., non-variability of monotypic genera, ii. 266; + relative development of root and seed in _Raphanus sativus_, ii. 343. + DECAISNE, on the cultivation of the wild carrot, i. 326; + varieties of the pear, i. 350; + inter-crossing of strawberries, i. 351; + fruit of the apple, i. 401; + sterility of _Lysimachia nummularia_, ii. 170; + tender variety of the peach, ii. 308. + DEER, assumption of horns by female, ii. 51; + imperfect development of horns in a, on a voyage, ii. 158. + DEER, fallow, ii. 103. + DEERHOUND. Scotch, difference in size of the sexes of, ii. 73; + deterioration of, ii. 121. + DEGENERATION of high-bred races, under neglect, ii. 239. + DE JONGHE, J., on strawberries, i. 352, ii. 243; + soft-barked pears, ii. 231; + on accumulative variation, ii. 262; + resistance of blossoms to frost, ii. 306. + DELAMER, E. S., on rabbits, i. 107, 112. + _Delphinium ajacis_, ii. 21. + _Delphinium consolida_, ii. 20-21. + _Dendrocygna viduata_, i. 182, ii. 157. + DENTITION, variations of, in the horse, i. 50. + DEODAR, i. 364. + DESMAREST, distribution of white on dogs, i. 29; + cat from the Cape of Good Hope, i. 47; + cats of Madagascar, i. 47; + occurrence of striped young in Turkish pigs, i. 76; + French breeds of cattle, i. 80; + horns of goats, i. 102; + on hornless goats, ii. 315. + DESOR, E., on the Anglo-Saxon race in America, ii. 276. + DESPORTES, number of varieties of roses, i. 367. + DEVAY, Dr., singular case of albinism, ii. 17; + on the marriage of cousins, ii. 122; + on the effects of close interbreeding, ii. 143, 263. + DEVELOPMENT and metamorphosis, ii. 388-389. + DEVELOPMENT, arrests of, ii. 315-318. + DEVELOPMENT, embryonic, ii. 366-368. + {447} + D'HERVEY-Saint-Denys, L., on the ya-mi, or imperial rice of the Chinese, + ii. 205. + DHOLE, fertility of the, in captivity, ii. 151. + DIABETES, occurrence of, in three brothers, ii. 17. + _Dianthus_, contabescent plants of, ii. 165-166; + hybrid varieties of, ii. 267. + _Dianthus armeria_ and _deltoides_, hybrids of, ii. 98. + _Dianthus barbatus_, i. 381. + _Dianthus caryophyllus_, i. 381. + _Dianthus japonicus_, contabescence of female organs in, ii. 166. + DICHOGAMOUS plants, ii. 90. + DICKSON, Mr., on "running" in carnations, i. 381; + on the colours of tulips, i. 386. + _Dicotyles torquatus_ and _labiatus_, ii. 150. + DIEFFENBACH, dog of New Zealand, i. 26; + feral cats in New Zealand, i. 47; + polydactylism in Polynesia, ii. 14. + _Dielytra_, ii. 59. + DIET, change of, ii. 303-304. + _Digitalis_, properties of, affected by culture, ii. 274; + poison of, ii. 380. + DIGITS, supernumerary, ii. 57; + analogy of, with embryonic conditions, ii. 16; + fusion of, ii. 341. + DIMORPHIC plants, ii. 166; + conditions of reproduction in, ii. 181-184. + DIMORPHISM, reciprocal, ii. 90. + DINGO, i. 25; + variation of, in colour, i. 28; + half-bred, attempting to burrow, i. 28; + attraction of foxes by a female, i. 31; + variations of, in confinement, ii. 263. + DIOECIOUSNESS of strawberries, i. 353. + DISEASES, inheritance of, ii. 7-8; + family uniformity of, ii. 57; + inherited at corresponding periods of life, ii. 77-80; + peculiar to localities and climates, ii. 276; + obscure correlations in, ii. 331-332; + affecting certain parts of the body, ii. 380; + occurring in alternate generations, ii. 401. + DISTEMPER, fatal to white terriers, ii. 227. + DISUSE and use of parts, effects of, ii. 295-303, 352-353, 418-419; + in the skeleton of rabbits, i. 124-128; + in pigeons, i. 171-177; + in fowls, i. 270-274; + in ducks, i. 284-286; + in the silk-moth, i. 300-304. + DIVERGENCE, influence of, in producing breeds of pigeons, i. 220. + DIXON, E. S., on the musk duck, i. 182; + on feral ducks, i. 190; + on feral pigeons in Norfolk Island, i. 190; + crossing of pigeons, i. 192; + origin of domestic fowls, i. 230; + crossing of _Gallus Sonneratii_ and common fowl, i. 234; + occurrence of white in the young chicks of black fowls, i. 244; + Paduan fowl of Aldrovandi, i. 247; + peculiarities of the eggs of fowls, i. 248; + chickens, i. 249-250; + late development of the tail in Cochin cocks, i. 250; + comb of lark-crested fowls, i. 256; + development of webs in Polish fowls, i. 259; + on the voice of fowls, i. 259; + origin of the duck, i. 277; + ducks kept by the Romans, i. 278; + domestication of the goose, i. 287; + gander frequently white, i. 288; + breeds of turkeys, i. 293; + incubatory instinct of mongrels of non-sitting races of fowls, ii. 44; + aversion of the dove-cot pigeon to pair with fancy birds, ii. 103; + fertility of the goose, ii. 112; + general sterility of the guans in captivity, ii. 156; + fertility of geese in captivity, ii. 157; + white peafowl, ii. 332. + DOBELL, H., inheritance of anomalies of the extremities, ii. 14; + non-reversion to a malformation, ii. 36. + DOBRIZHOFFER, abhorrence of incest by the Abipones, ii. 123. + DOGS, origin of, i. 15; + ancient breeds of, i. 17, ii. 429; + of neolithic, bronze and iron periods in Europe, i. 18-19, ii. 427; + resemblance of to various species of canidae, i. 21; + of North America compared with wolves, i. 21-22; + of the West Indies, South America, and Mexico, i. 23, 31; + of Guiana, i. 23; + naked dogs of Paraguay and Peru, _ibid._ and 31; + dumb, on Juan Fernandez, i. 27; + of Juan de Nova, i. 27; + of La Plata, i. 27; + of Cuba, i. 27; + of St. Domingo, i. 28; + correlation of colour in, i. 28-29; + gestation of, i. 29-30; + hairless Turkish, i. 30, ii. 227; + inter-crossing of different breeds of, i. 31; + characters of different breeds of, discussed, i. 34-37; + degeneration of European, in warm climates, i. 36, 38; ii. 278, 305; + liability to certain diseases in different breeds of, i. 36 and _note_; + causes of differences of breeds discussed, i. 37-43; + catching fish and crabs in New Guinea and Tierra del Fuego, i. 39; + webbing of the feet in, i. 39; + influence of selection in producing different breeds of, i. 39, 43; + retention of original habits by, i. 182; + inheritance of polydactylism in, ii. 14; + feral, ii. 33; + reversion in fourth generation of, ii. 34; + of the Pacific Islands, ii. 87, 220, 303; + mongrel, ii. 92-93; + comparative facility of crossing different breeds of, ii. 102; + fertility of, ii. 111, 151; + inter-breeding of, ii. 120-121; + selection of, among the Greeks, ii. 202, 209; + among savages, ii. 206-207; + unconscious selection of, ii. 211-212; + valued by the Fuegians, ii. 215; + climatal changes in hair of, ii. 278; + production of drooping ears in, ii. 301; + {448} + rejection of bones of game by, ii. 303; + inheritance of rudiments of limbs in, ii. 315; + development of fifth toe in, ii. 317; + hairless, deficiency of teeth in, ii. 326; + short-faced, teeth of, ii. 345; + probable analogous variation in, ii. 349; + extinction of breeds of, ii. 425. + DOMBRAIN, H. H., on the auricula, ii. 346-347. + DOMESTICATION, essential points in, ii. 405-406; + favourable to crossing, ii. 109-110; + fertility increased by, ii. 111-113, 174. + DOMESTICATED animals, origin of, ii. 160-161; + occasional sterility of, under changed conditions, ii. 161-162. + DONDERS, Dr., hereditary hypermetropia, ii. 8. + DORKING fowl, i. 227, 261; + furcula of, figured, i. 268. + DORMOUSE, ii. 152. + DOUBLE FLOWERS, ii. 167-168, 171-172; + produced by selection, ii. 200. + DOUBLEDAY, H., cultivation of the filbert pine strawberry, i. 354. + DOUGLAS, J., crossing of white and black game-fowls, ii. 92. + DOWNING, Mr., wild varieties of the hickory, i. 310; + peaches and nectarines from seed, i. 339-340; + origin of the Boston nectarine, i. 340; + American varieties of the peach, i. 343; + North American apricot, i. 344; + varieties of the plum, i. 346; + origin and varieties of the cherry, i. 347-348; + "twin cluster pippins," i. 349; + varieties of the apple, i. 350; + on strawberries, i. 351, 353; + fruit of the wild gooseberry, i. 355; + effects of grafting upon the seed, ii. 26; + diseases of plum and peach trees, ii. 227-228; + injury done to stone fruit in America by the "weevil," ii. 231; + grafts of the plum and peach, ii. 259; + wild varieties of pears, ii. 260; + varieties of fruit-trees suitable to different climates, ii. 306. + _Draba sylvestris_, ii. 163. + DRAGON, pigeon, i. 139, 141. + "DRAIJER" (pigeon), i. 156. + DRINKING, effects of, in different climates, ii. 289. + DROMEDARY, selection of, ii. 205-206. + DRUCE, Mr., inter-breeding of pigs, ii. 121. + DU CHAILLU, fruit-trees in West Africa, i. 309. + DUCHESNE on _Fragaria vesca_, i. 351, 352, 353. + DUFOUR, Leon, on _Cecidomyia_ and _Misocampus_, i. 5. + DUCK, musk, retention of perching habit by the, i. 182; + feral hybrid of, i. 190. + DUCK, penguin, hybrid of, with Egyptian goose, ii. 68. + DUCK, wild, difficulty of rearing, ii. 233; + effects of domestication on, ii. 278. + DUCKS, breeds of, i. 276-277; + origin of, i. 277; + history of, _ibid._; + wild, easily tamed, i. 278-279; + fertility of breeds of, when crossed, i. 279; + with the plumage of _Anas boschas_, i. 280; + Malayan penguin, identical in plumage with English, i. 280; + characters of the breeds of, i. 281-284; + eggs of, i. 281; + effects of use and disuse in, i. 284-286, ii. 298; + feral, in Norfolk, i. 190; + Aylesbury, inheritance of early hatching by, ii. 25; + reversion in, produced by crossing, ii. 40; + wildness of half-bred wild, ii. 45; + hybrids of, with the musk duck, ii. 45-46; + assumption of male plumage by, ii. 51; + crossing of Labrador and penguin, ii. 97; + increased fertility of, by domestication, ii. 112; + general fertility of, in confinement, ii. 157; + increase of size of, by care in breeding, ii. 199; + change produced by domestication in, ii. 262. + DUMERIL, Aug., breeding of _Siredon_ in the branchiferous stage, ii. 384. + DUN-coloured horses, origin of, i. 59. + DUREAU de la Malle, feral pigs in Louisiana, ii. 33; + feral fowls in Africa, _ibid._; + bud-variation in the pear, i. 376; + production of mules among the Romans, ii. 110. + _Dusicyon sylvestris_, i. 23. + DUTCH rabbit, i. 107. + DUTCH roller pigeon, i. 151. + DUTROCHET, pelorism in the laburnum, ii. 346. + DUVAL, growth of pears in woods in France, ii. 260. + DUVAL-Jouve, on _Leersia oryzoides_, ii. 91. + DUVERNOY, self-impotence in _Lilium candidum_, ii. 137. + DZIERZON, variability in the characters and habits of bees, i. 298. + + EARLE, Dr., on colour-blindness, ii. 72, 328. + EARS, of fancy rabbits, i. 106; + deficiency of, in breeds of rabbits, i. 108; + rudimentary, in Chinese sheep, ii. 315; + drooping, ii. 301; + fusion of, ii. 341. + EATON, J. M., on fancy pigeons, i. 148, 153; + variability of characters in breeds of pigeons, i. 161; + reversion of crossed pigeons to coloration of _Columba livia_, i. 198; + on pigeon-fancying, i. 206, 215-216; + on tumbler-pigeons, i. 209, ii. 242; + carrier-pigeon, i. 211; + effects of interbreeding on pigeons, ii. 126; + properties of pigeons, ii. 197-198; + death of short-faced tumblers in the egg, ii. 226; + {449} + Archangel pigeon, ii. 240. + ECHINODERMATA, metagenesis in, ii. 367. + _Ectopistes_, specific difference in number of tail-feathers in, i. 159. + _Ectopistes migratorius_, sterile hybrids of, with _Turtur vulgaris_, i. + 193. + EDENTATA, correlation of dermal system and teeth in the, ii. 328. + EDGEWORTH, Mr., use of grass-seeds as food in the Punjab, i. 309. + EDMONSTON, Dr., on the stomach in _Larus argentatus_ and the raven, ii. + 302. + EDWARDS and COLIN, on English wheat in France, ii. 307. + EDWARDS, W. F., absorption of the minority in crossed races, ii. 87. + EDWARDS, W. W., occurrence of stripes in a nearly thoroughbred horse, i. + 57; + in foals of racehorses, i. 59. + EGGS, of fowls, characters of, i. 248; + variations of, in ducks, i. 281; + of the silkmoth, i. 301. + EGYPT, ancient dogs of, i. 17-18; + ancient domestication of the pigeon in, i. 204; + absence of the fowl in ancient, i. 246. + EGYPTIAN goose, hybrids of, with penguin duck, i. 282. + EHRENBERG, Prof., multiple origin of the dog, i. 16; + dogs of Lower Egypt, i. 25; + mummies of _Felis maniculata_, i. 43. + ELEMENT, male, compared to a premature larva, ii. 384. + ELEMENTS of the body, functional independence of the, ii. 368-371. + ELEPHANT, its sterility in captivity, ii. 150. + ELK, Irish, correlations in the, ii. 333-334. + ELLIOT, Sir Walter, on striped horses, i. 58; + Indian domestic and wild swine, i. 66; + pigeons from Cairo and Constantinople, i. 132; + fantail pigeons, i. 146; + Lotan tumbler pigeons, i. 150; + a pigeon uttering the sound _Yahu_, i. 155; + _Gallus bankiva_ in Pegu, i. 236. + ELLIS, Mr., varieties of cultivated plants in Tahiti, ii. 256. + ELM, nearly evergreen Cornish variety of the, i. 363, ii. 310; + foliage-varieties of the, i. 362. + ELM, weeping, i. 361; + not reproduced by seed, ii. 19. + _Emberiza passerina_, ii. 158. + EMBRYOS, similarity of, i. 12; + fusion of, ii. 339. + ENGEL, on _Laurus sassafras_, ii. 274. + ENGLAND, domestication of _Bos longifrons_ in, i. 81; + selection of horses in, in mediaeval times, ii. 203; + laws against the early slaughter of rams in, ii. 203. + EPHEMERIDAE, development of the, ii. 366. + _Epidendrum cinnabarinum_ and _E. zebra_, ii. 134. + EPILEPSY, hereditary, ii. 8, 78. + ERDT, disease of the white parts of cattle, ii. 337. + ERICACEAE, frequency of contabescence in the, ii. 165. + ERICHTHONIUS, an improver of horses by selection, ii. 202. + ERMAN, on the fat-tailed Kirghisian sheep, i. 98, ii. 280; + on the dogs of the Ostyaks, ii. 206. + _Erodium_, ii. 59. + _Erythrina Crista-galli_ and _E. herbacea_, hybrids of, ii. 265. + ESQUILANT, Mr., on the naked young of dun-coloured pigeons, i. 170. + ESQUIMAUX dogs, their resemblance to wolves, i. 21; + selection of, ii. 206. + EUDES-DESLONGCHAMPS, on appendages under the jaw of pigs, i. 75-76. + _Euonymus Japonicus_, i. 383. + EUROPEAN cultivated plants, still wild in Europe, i. 307. + EVANS, Mr., on the Lotan tumbler pigeon, i. 150. + EVELYN, pansies grown in his garden, i. 368. + EVEREST, R., on the Newfoundland dog in India, i. 36, ii. 305; + degeneration of setters in India, i. 38; + Indian wild boars, i. 66. + EWES, hornless, ii. 350. + EXTINCTION of domestic races, i. 221. + EYES, hereditary peculiarities of the, ii. 8-10; + loss of, causing microphthalmia in children, ii. 24; + modification of the structure of, by natural selection, ii. 222-223; + fusion of, ii. 341. + EYEBROWS, hereditary elongation of hairs in, ii. 8. + EYELIDS, inherited peculiarities of the, ii. 8. + EYTON, Mr., on gestation in the dog, i. 30; + variability in number of vertebrae in the pig, i. 74; + individual sterility, ii. 162. + + _Faba vulgaris_, i. 330. + FABRE, observations on _Aegilops triticoides,_ i. 313. + _Fagus sylvatica_, ii. 19. + FAIRWEATHER, Mr., production of double flowers from old seed, ii. 167. + _Falco albidus_, resumption of young plumage by, in captivity, ii. 158. + _Falco ossifragus_, ii. 230. + _Falco subbuteo_, copulating in captivity, ii. 154. + _Falco tinnunculus_, breeding in captivity, ii. 154. + {450} + FALCONER, Dr., sterility of English bulldogs in India, i, 38; + resemblance between _Sivatherium_ and Niata cattle, i. 89; + selection of the silkworm in India, i. 301; + fastigate apple-trees in Calcutta, i. 361; + reproduction of a supernumerary thumb after amputation, ii. 14; + fertility of the dhole in captivity, ii. 151; + fertility of English dogs in India, ii. 161; + sterility of the tiger in captivity, ii. 151; + turkeys at Delhi, ii. 161; + on Indian cultivated plants, ii. 165; + Thibet mastiff and goat, ii. 278. + FALCONS, sterility of, in captivity, ii. 153. + FALKLAND Islands, horses of the, i. 52-53, 61; + feral pigs of the, i. 77; + feral cattle of the, i. 82, 86; + feral rabbits of the, i. 112. + FALLOW deer, ii. 103, 120. + FANTAIL pigeons, i. 146-148, ii. 227; + figured, i. 147; + furcula of, figured, i. 167; + history of, i. 208; + absence of oil-gland in, ii. 344. + FAROE Islands, pigeons of the, i. 183. + FASHION, influence of, in breeding, ii. 240. + FASTIGATE trees, ii. 277, 348. + FAUNAS, geographical differences, of, i. 10. + "FAVOURITE" bull, ii. 65, 118. + FEATHERS, homologous variation in, ii. 325. + FEET, of pigeons, individual differences of, i. 160; + correlations of external characters in, i. 170-171. + FEET and beak, correlation of, in pigeons, i. 171-174. + FELIDAE, fertility of, in captivity, ii. 150. + _Felis bubastes_, i. 43. + _Felis caffra_, i. 44. + _Felis caligulata_, i. 43. + _Felis chaus_, i. 43-44. + _Felis jubata_, ii. 151. + _Felis lybica_, i. 44. + _Felis maniculata_, i. 43. + _Felis manul_, i. 45. + _Felis ornata_, i. 45. + _Felis sylvestris_, i. 44. + _Felis torquata_, i. 45. + FEMALE, affected by male element, ii. 365, 387-388. + FEMALE flowers, in male panicle of maize, i. 321. + FENNEL, Italian variety of, i. 326. + FERAL cats, i. 47; + cattle, i. 86; + rabbits, i. 111-115; + Guinea fowl, i. 294; + animals and plants, reversion in, ii. 32-34, 47. + FERGUSON, Mr., supposed plurality of origin of domestic fowls, i. 231; + chickens of black game-fowls, i. 244; + relative size of eggs of fowls, i. 248; + yolk of eggs of game-fowls, i. 249; + early pugnacity of game-cocks, i. 250; + voice of the Malay fowl, i. 259; + effects of interbreeding on fowls, ii. 124; + selection in Cochin China fowls, ii. 196; + on fashion in poultry, ii. 240. + FERNANDEZ, on Mexican dogs, i. 23. + FERNS, reproduction of abnormal forms of, by spores, i. 383; + non-diffusion of cell-gemmules in, ii. 379. + FERRETS, ii. 111, 151, 206. + FERTILISATION, artificial, of the St. Valery apple, i. 350. + FERTILITY, various degrees of, in sheep, i. 97; + unlimited mutual, of breeds of pigeons, i. 192-194; + comparative of mongrels and hybrids, ii. 100-101, 178-180; + influence of nourishment on, ii. 111; + diminished by close interbreeding, ii. 118, 175; + reduced, of Chillingham wild cattle, ii. 119; + of domesticated varieties when crossed, ii. 189. + _Festuca_, species of, propagated by bulblets, ii. 170. + FILBERTS, spared by tomtits, ii. 231. + FILIPPI, on the breeding of branchiferous tritons, ii. 384. + FINCHES, general sterility of, in captivity, ii. 154. + FINNIKIN (pigeon), i. 156. + FINNOCHIO, i. 326. + FIR, Scotch, acclimatisation of, ii. 310. + FISH, Mr., advantage of change of soil to plants, ii. 147. + FISHES, regeneration of portions of fins of, ii. 15; + variability of, when kept in tanks, ii. 259; + marine, living in fresh water, ii. 304; + double monsters of, ii. 340. + FISSION and gemmation, ii. 358. + FITCH, Mr., persistency of a variety of the pea, i. 329. + FITTEST, survival of the, i. 6. + FITZINGER, origin of sheep, i. 94; + African maned sheep, i. 96. + FIXEDNESS of character, conditions of, discussed, ii. 62-64. + FLAX, found in the Swiss lake-dwellings, i. 317; + climatal difference in products of, ii. 274. + FLEECE, fineness of, in Austrian merinos, ii. 197. + FLEISCHMANN, on German sheep crossed with merinos, ii. 88-89. + "FLORENTINER-TAUBE," i. 142-143. + FLOUNDER, ii. 53. + FLOURENS, crossing of wolf and dog, i. 32; + prepotency of the jackal over the dog, ii. 67; + hybrids of the horse and ass, ii. 68; + breeding of monkeys in Europe, ii. 153. + {451} + FLOWER-GARDEN, earliest known, in Europe, ii. 217. + FLOWERS, capricious transmission of colour-varieties in, ii. 20-21; + tendency to uniformity in striped, ii. 70; + scorching of, dependent on colour, ii. 229; + change in, caused by conditions of life, ii. 273; + rudimentary, ii. 316; + relative position of, to the axis, ii. 345. + FOETATION, abdominal, ii. 294. + FOLEY, Mr., wild varieties of pears, ii. 260. + FOLIAGE, inherited peculiarities of, i. 362; + variegation, of, i. 366; + bud-variation in, i. 382-384. + FOOD, influence of, on the pig, i. 72; + on cattle, i. 91; + excess of, a cause of variability, ii. 257. + FORBES, D., on Chilian sheep, i. 95; + on the horses of Spain, Chili, and the Pampas, i. 52. + _Formica rufa_, ii. 251. + FORTUNE, R., sterility of the sweet potato in China, ii. 169; + development of axillary bulbs in the yam, _ibid._ + FOWL, common, breeds of, i. 225-230; + supposed plurality of origin, i. 230; + early history of, i. 231-233; + causes of production of breeds of, i. 233; + origin of from _Gallus bankiva_, i. 236-239, 245; + feral, notices of, i. 237-238; + reversion and analogous variation in, i. 239-246, ii. 35, 38, 39, 40, + 349, 350; + "cuckoo" sub-breeds of, i. 244; + history of, i. 246-247; + structural characters of, i. 247-250; + sexual peculiarities of, i. 251-257, ii. 74; + external differences of, i. 257-260; + differences of breeds of, from _G. bankiva_, i. 260; + osteological characters of, i. 260-270; + effects of disuse of parts in, i. 270-274, ii. 298; + feral, i. 190, ii. 33; + polydactylism in, ii. 14; + fertility of, increased by domestication, ii. 112, 167; + sterility of, under certain conditions, ii. 162; + influence of selection on, ii. 196, 198, 209, 210; + evils of close interbreeding of, ii. 124-125; + crossing of, ii. 95, 96, 97; + prepotency of transmission in, ii. 67; + rudimentary organs in, ii. 315; + crossing of non-sitting varieties of, ii. 43-44; + homology of wing and leg feathers in, ii. 323; + hybrids of, with pheasants and _Gallus Sonneratii_, ii. 45; + black-skinned, ii. 209-210; + black, preyed upon by the osprey in Iceland, ii. 230; + five-toed, mentioned by Columella, ii. 429; + rumpless, tailed chickens produced by, ii. 31; + Dorking, crosses of, ii. 93; + form of comb and colour of plumage in, ii. 238; + game, crossing of white and black, ii. 92; + five-spurred, ii. 391; + Spanish, liable to suffer from frost, ii. 306; + Polish, peculiarities of skull of, ii. 332-333. + FOX, sterility of, in captivity, ii. 151. + FOX, S. Bevan, races of bees, i. 298. + FOX, W. Darwin, gestation of the dog, i. 30; + "Negro" cat, i. 46; + reversion of sheep in colour, ii. 30; + period of gestation in the pig, i. 74; + young of the Himalayan rabbit, i. 109; + crossing of wild and domestic turkeys, i. 292; + reversion in crossed musk ducks, ii. 40; + spontaneous segregation of varieties of geese, ii. 104; + effects of close interbreeding upon bloodhounds, ii. 121; + deafness of white cats with blue eyes, ii. 329. + FOXHOUNDS, i. 40, ii. 120. + _Fragaria chiloensis_, i. 351. + _Fragaria collina_, i. 351. + _Fragaria dioica_ of Duchesne, i. 353. + _Fragaria elatior_, i. 351. + _Fragaria grandiflora_, i. 351. + _Fragaria vesca_, i. 351. + _Fragaria virginiana_, i. 351. + _Fraxinus excelsior_, i. 360, 362, ii. 19. + _Fraxinus lentiscifolia_, ii. 19. + FRIESLAND cattle, probably descended from _Bos primigenius_, i. 81. + FRILLBACK (pigeon), i. 155; + Indian, i. 153. + _Fringilla ciris_, ii. 154. + _Fringilla spinus_, ii. 154. + FRIZZLED fowls, i. 230; + horses, i. 54. + FROG, polydactylism in the, ii. 14. + FRUIT, seedless, ii. 168. + FRUIT-TREES, varieties of, occurring wild, i. 310. + FRY, Mr., on fertile hybrid cats, i. 44; + on feral fowls in Ascension, i. 238. + FUCHSIAS, origin of, i. 364; + bud-variation in, i. 382. + _Fuchsia coccinea_ and _fulgens_, twin seed produced by crossing, i. 391. + FUEGIANS, their superstition about killing young water-fowl, i. 310; + selection of dogs by the, ii. 207; + their comparative estimation of dogs and old women, ii. 215; + their power of distant vision, ii. 223. + FUNGI, parasitic, ii. 284-285. + FURCULA, characters and variations of the, in pigeons, i. 167; + alteration of, by disuse, in pigeons, i. 175; + characters of, in fowls, i. 268. + FUSION of homologous parts, ii. 393. + + GAIT, inheritance of peculiarities of, ii. 6. + GALAPAGOS Archipelago, its peculiar fauna and flora, i. 9. + _Galeobdolon luteum_, pelorism in, ii. 59, 345. + {452} + GALLS, ii. 282-284. + GALL-GNATS, ii. 283. + GALL-LIKE excrescences not inherited, ii. 23. + GALLINACEOUS birds, restricted range of large, i. 237; + general fertility of in captivity, ii. 155. + _Gallinula chloropus_, ii. 156. + _Gallinula nesiotis_, i. 287. + GALTON, Mr., fondness of savages for taming animals, i. 20, ii. 160; + cattle of Benguela, i. 88; + on hereditary talent, ii. 7. + GALLESIO, species of oranges, i. 334, 335, 336; + hybridisation of oranges, i. 336; + persistency of races in the peach, i. 339; + supposed specific distinctions of peach and nectarine, i. 340; + Bizzaria orange, i. 391; + crossing of red and white carnations, i. 393; + crossing of the orange and lemon, i. 399, ii. 365; + effect of foreign pollen on maize, i. 400; + spontaneous crossing of oranges, ii. 91; + monstrosities a cause of sterility in plants, ii. 166; + seeding of ordinarily seedless fruits, ii. 168; + sterility of the sugar cane, ii. 169; + tendency of male flowers to become double, ii. 171; + effects of selection in enlarging fruit, &c., ii. 217; + variation of the orange tree in North Italy, ii. 256; + naturalisation of the orange in Italy, ii. 309. + _Gallus aeneus_, a hybrid of _G. varius_ and the domestic fowl, i. 235. + _Gallus bankiva_, probable original of domestic fowls, i. 233, 236-239, + 245; + game-fowl, nearest to, i. 226; + crossed with _G. Sonneratii_, i. 234; + its character and habits, i. 235-236, ii. 109; + differences of various breeds of fowls from, i. 260; + occipital foramen of, figured, i. 261; + skull of, figured, i. 262; + cervical vertebra of, figured, i. 267; + furcula of, figured, i. 268; + reversion to, in crossed fowls, ii. 39-40; + hybrid of, with _G. varius_, i. 235, ii. 40; + number of eggs of, ii. 112. + _Gallus ferrugineus_, i. 226. + _Gallus furcatus_, i. 234. + _Gallus giganteus_, i. 235. + _Gallus Sonneratii_, characters and habits of, i. 233; + hybrids of, i. 234, ii. 45. + _Gallus Stanleyi_, hybrids of, i. 234. + _Gallus Temminckii_, probably a hybrid, i. 235. + _Gallus varius_, character and habits of, i. 234; + hybrids and probable hybrids of, i. 234-235. + GAMBIER, Lord, his early cultivation of the pansy, i. 368. + GAME-FOWL, i. 226, 250, 251, 252. + GAPES, ii. 228. + GARCILAZO de la Vega, annual hunts of the Peruvian Incas, ii. 207. + GARNETT, Mr., migratory propensities of hybrid ducks, ii. 45. + GARROD, Dr., on hereditary gout, ii. 7. + GASPARINI, a genus of pumpkins, founded on stigmatic characters, i. 359. + GAUDICHAUD, bud-variation in the pear, i. 376; + apple tree with two kinds of fruit on branch, i. 392. + GAUDRY, anomalous structure in the feet of horses, i. 50. + GAY, on _Fragaria grandiflora_, i. 351; + on _Viola lutea_ and _tricolor_, i. 368; + on the nectary of _Viola grandiflora_, i. 369. + GAYAL, domestication of the, i. 82. + GAYOT, _see_ Moll. + GAERTNER, on the sterility of hybrids, i. 192, ii. 101; + acquired sterility of varieties of plants when crossed, i. 358; + sterility in transplanted plants, and in the lilac in Germany, ii. 164; + mutual sterility of blue and red flowers of the pimpernel, ii. 190; + supposed rules of transmission in crossing plants, ii. 68; + on crossing plants, ii. 98, 127, 130, 131; + on repeated crossing, ii. 267; + absorption of one species by another, when crossed, ii. 88; + crossing of varieties of the pea, i. 397; + crossing maize, ii. 105; + crossing of species of _Verbascum_, ii. 93, 105; + reversion in hybrids, ii. 36, 49, 50; + of _Cereus_, i. 392; + of _Tropaeolum majus_ and _minus_, i. 392; + variability of hybrids, ii. 265; + variable hybrids from one variable parent, ii. 270; + graft hybrid produced by inosculation in the vine, i. 395; + effect produced by grafts on the stock, i. 394, ii. 278; + tendency of hybrid plants to produce double flowers, ii. 171; + production of perfect fruit by sterile hybrids, ii. 172; + sexual elective affinity, ii. 180; + self-impotence in _Lobelia_, _Verbascum_, _Lilium_, and _Passiflora_, + ii. 136-137; + on the action of pollen, ii. 108; + fertilisation of _Malva_, i. 402-403, ii. 363; + prepotency of pollen, ii. 187; + prepotency of transmission in species of _Nicotiana_, ii. 67; + bud-variation in _Pelargonium zonale_, i. 375; + in _Oenothera biennis_, i. 382; + in _Achillaea millefolium_, i. 408; + effect of manure on the fertility of plants, ii. 163; + on contabescence, ii. 165-166; + inheritance of plasticity, ii. 241; + villosity of plants, ii. 277. + GEESE (_anseres_) general fertility of, in captivity, ii. 157. + GEGENBAUR, on the number of digits, ii. 13. + GEMMATION and fission, ii. 358. + {453} + GEMMULES, or cell-gemmules, ii. 374, 378-381, 384. + GENET, fertility of the, in captivity, ii. 151. + GENERATION, alternate, ii. 361, 367, 390. + GENERATION, sexual, ii. 359-364. + GENIUS, inheritance of, ii. 7. + _Gentiana amarella_, ii. 168. + GEOFFROY Saint-Hilaire, production of monstrous chickens, ii. 289; + "_Loi de l'affinite de soi pour soi_," ii. 339; + compensation of growth, ii. 342. + GEOFFROY Saint-Hilaire, Isid., origin of the dog, i. 66; + barking of a jackal, i. 27; + period of gestation and odour of the jackal, i. 30; + anomalies in the teeth of dogs, i. 34; + variations in the proportions of dogs, i. 35; + webbed feet of Newfoundland dogs, i. 39; + crossing of domestic and wild cats, i. 44; + domestication of the arni, i. 82; + supposed introduction of cattle into Europe from the East, _ibid._; + absence of interdigital pits in sheep, i. 95; + origin of the goat, i. 101; + feral geese, i. 190; + ancient history of the fowl, i. 246; + skull of the Polish fowl, i. 262; + preference of the Romans for the liver of white geese, i. 289; + polydactylism, ii. 12; + assumption of male characters by female birds, ii. 51; + supernumerary mammae in women, ii. 58; + development of a proboscis in the pig, _ibid._; + transmission and blending of characters in hybrids, ii. 94; + refusal of animals to breed in captivity, ii. 149; + on the Guinea pig, ii. 152; + silkworms producing white cocoons, ii. 199; + on the carp, ii. 236; + on _Helix lactea_, ii. 280; + on monstrosities, ii. 254; + injury to the embryo a cause of monstrosity, ii. 269; + alteration in the coat of horses in coal mines, ii. 278; + length of the intestines in wild and tame animals, ii. 302-303; + inheritance of rudimentary limbs in the dog, ii. 315; + correlation in monstrosities, ii. 320; + supernumerary digits in man, ii. 322; + co-existence of anomalies, ii. 331; + fusion of homologous parts, ii. 341-342; + presence of hairs and teeth in ovarian tumours, ii. 370; + development of teeth on the palate in the horse, ii. 391. + GEOGRAPHICAL differences of faunas, i. 10. + GEOLOGICAL succession of organisms, i. 11. + _Geranium_, ii. 59. + _Geranium phaeum_ and _pyrenaicum_, ii. 258. + _Geranium pratense_, i. 379. + GERARD, asserted climatal change in Burgundian bees, i. 297. + GERARDE, on varieties of the hyacinth, i. 370. + GERSTAECKER, on hive-bees, i. 299. + GERVAIS, Prof., origin of the dog, i. 16; + resemblance of dogs and jackals, i. 24; + taming of the jackal, i. 26; + number of teeth in dogs, i. 34; + breeds of dogs, i. 36; + on tertiary horses, i. 51; + biblical notices of horses, i. 55; + species of _Ovis_, i. 94; + wild and domestic rabbits, i. 103; + rabbits from Mount Sinai and Algeria, i. 105; + earless rabbits, i. 108; + batrachia with doubled limbs, ii. 391. + GESTATION, period of, in the dog, wolf, &c, i. 29-30; + in the pig, i. 74; + in cattle, i. 87, ii. 321; + in sheep, i. 97. + GESTURES, inheritance of peculiarities in, ii. 6. + "GHOONDOOKS" a sub-breed of fowls, i. 229. + GHOR-KHUR, ii. 42. + GILES, Mr., effect of cross-breeding in the pig, i. 404. + GIRAFFE, co-ordination of structure of, ii. 221. + GIRARD, period of appearance of permanent teeth in dogs, i. 35. + GIROU de Buzareingues, inheritance in the horse, ii. 10; + reversion by age in cattle, ii. 38; + prepotency of transmission of character in sheep and cattle, ii. 66; + on crossing gourds, ii. 108. + GISBURNE, wild cattle at, i. 84. + _Gladiolus_, i. 364; + self-impotence of hybrids of, ii. 139. + _Gladiolus colvillii_, bud-variation in, i. 382. + GLANDS, compensatory development of, ii. 300. + GLASTONBURY thorn, i. 364. + GLENNY, Mr., on the _Cineraria_, ii. 200. + GLOEDE, F., on strawberries, i. 353. + GLOGER, on the wings of ducks, ii. 298. + "GLOUGLOU" (pigeon), i. 154. + _Gloxiniae_, peloric, i. 365, ii. 167. + GMELIN, on red cats, at Tobolsk, i. 47. + GOAT, i. 101-102, ii. 33; + polydactylism in the, ii. 14; + sexual differences in horns of, ii. 73; + valued by South Africans, ii. 207; + Thibet, ii. 278; + amount of milk and development of udders in the, ii. 300; + hornless, rudimentary bony cores in, ii. 316; + Angora, ii. 326. + GODRON, odour of the hairless Turkish dog, i. 30; + differences in the skull of dogs, i. 34; + increase of breeds of horses, i. 51; + crossing of domestic and wild swine, i. 66; + on goats, i. 101-102; + colour of the skin in fowls, i. 258; + bees of north and south of France, i. 297; + introduction of the silkworm into Europe, i. 300; + variability in the silkworm, i. 304; + supposed species of wheat, i. 312-314; + on _Aegilops triticoides_, i. 313; + variable presence of barbs in grasses, i. 314; + {454} + colours of the seeds of maize, i. 321; + unity of character in cabbages, i. 323; + correlation of colour and odour, i. 325; + effect of heat and moisture on the cabbage, i. 325; + on the cultivated species of _Brassica_, i. 325; + on the Rouncival and sugar peas, i. 327; + variation in the numbers of peas in the same pod, i. 328; + wild vines in Spain, i. 332; + on raising peaches from seed, i. 339; + supposed specific distinctness of peach and nectarine, i. 340; + nectarine producing peaches, i. 341; + on the flower of _Corydalis_, i. 344; + origin and variations of the plum, i. 345; + origin of the cherry, i. 347; + reversion of single-leaved strawberries, i. 353; + five-leaved variety of _Fragaria collina_, i. 353; + supposed immutability of specific characters, i. 358-359; + varieties of _Robinia_, i. 361; + permanency of the simple-leaved ash, i. 362; + non-inheritance of certain mutilations, ii. 23; + wild turnips, carrots, and celery, ii. 33; + pre-potency of a goat-like ram, ii. 66; + benefit of change of soil to plants, ii. 146; + fertility of peloric flowers of _Corydalis solida_, ii. 167; + seeding of ordinarily seedless fruit, ii. 168; + sexual sterility of plants propagated by buds, &c., ii. 169; + increase of sugar in beet-root, ii. 201; + effects of selection in enlarging particular parts of plants, ii. 217; + growth of the cabbage in the tropics, ii. 277; + rejection of bitter almonds by mice, ii. 232; + influence of marshy pasture on the fleece of sheep, ii. 278; + on the ears of ancient Egyptian pigs, ii. 301; + primitive distinctness of species, ii. 415; + solid hoofed swine, ii. 429. + GOETHE, on compensation of growth, ii. 342. + GOLDFISH, i. 296-297, ii. 236. + GOMARA, on South American cats, i. 46. + GONGORA, number of seeds in the, ii. 379. + GOOSE, ancient domestication of, i. 287; + sacred to Juno in Rome, _ibid._; + inflexibility of organisation of, i. 288; + skull perforated in tufted, i. 288; + characters of breeds and sub-breeds of, i. 288-289; + variety of, from Sebastopol, i. 289, ii. 392; + feral in La Plata, i. 190; + Egyptian, hybrid of, with penguin duck, ii. 68; + spontaneous segregation of varieties of, ii. 104; + fertility of, increased by domestication, ii. 112; + decreased fertility of, in Bogota, ii. 161; + sterility of, in the Philippine Islands, ii. 162; + selection of, ii. 204; + white, preference of the Romans for the liver of, ii. 209; + persistency of character in, ii. 254; + Egyptian, change in breeding season of, ii. 304. + GOOSEBERRY, i. 354-356; + bud-variation in the, i. 376; + Whitesmith's, ii. 232. + GOEPPERT, on monstrous poppies, ii. 166. + GOSSE, P. H., feral dogs in Jamaica, i. 28; + feral pigs of Jamaica, i. 77-78; + feral rabbits of Jamaica, i. 112; + on _Columba leucocephala_, i. 183; + feral Guinea fowl in Jamaica, i. 190; + reproduction of individual peculiarities by gemmation in a coral, i. + 374; + frequency of striped legs in mules, ii. 42. + GOULD, Dr., on hereditary haemorrhage, ii. 7. + GOULD, John, origin of the turkey, i. 292. + _Goura coronata_ and _Victoriae_, hybrids of, i. 194, ii. 155. + GOURDS, i. 357; + crossing of varieties of, ii. 108; + ancient Peruvian variety of, ii. 429. + GOUT, inheritance of, ii. 7; + period of appearance of, ii. 77. + GRABA, on the pigeon of the Faroe islands, i. 183. + GRAFTING, ii. 147; + effects of, ii. 259, 278; + upon the stock, i. 394-395; + upon the variability of trees, ii. 259; + changes analogous to bud-variation produced by, i. 387, 389. + GRAFT-HYBRIDS, i. 390-391, 394-397, ii. 364-365. + GRAPES, bud-variation in, i. 375; + cross of white and purple, i. 393; + green, liable to disease, ii. 336; + effect of foreign pollen on, i. 400. + GRASSES, seeds of, used as food by savages, i. 307-309. + GRAY, Asa, superior wild varieties of fruit-trees, i. 310; + cultivated native plants of North America, i. 312, 357; + non-variation of weeds, i. 317; + supposed spontaneous crossing of pumpkins, i. 399; + pre-ordination of variation, ii. 432; + progeny of husked form of maize, i. 320; + wild intermediate forms of strawberries, i. 352. + GRAY, G. R., on _Columba gymnocyclus_, i. 184. + GRAY, J. E., on _Sus pliciceps_, i. 70; + on a variety of the gold-fish, i. 297; + hybrids of the ass and zebra, ii. 42-43; + on the breeding of animals at Knowsley, ii. 149; + on the breeding of birds in captivity, ii. 157. + GREENE, J. Reay, on the development of the echinodermata, ii. 367. + GREENHOW, Mr., on a Canadian web-footed dog, i. 39. + GREENING, Mr., experiments on _Abraxas grossulariata_, ii. 280. + GREGSON, Mr., experiments on _Abraxas grossulariata_, ii. 280. + GREY, Sir George, preservation of seed-bearing plants by the Australian + savages, i. 310; + {455} + detestation of incest by Australian savages, ii. 123. + GREYHOUNDS, sculptured on Egyptian monuments, and in the Villa of + Antoninus, i. 17; + modern breed of, i. 41; + crossed with the bulldog, by Lord Orford, ii. 95; + co-ordination of structure of, due to selection, ii. 221-222; + Italian, ii. 227. + GREYNESS, inherited at corresponding periods of life, ii. 77. + GRIEVE, Mr., on early-flowering dahlias, i. 370. + GRIGOR, Mr., acclimatisation of the Scotch fir, ii. 310. + GROOM-NAPIER, C. O., on the webbed feet of the otter-hound, i. 40. + "GROSSES-GORGES" (pigeons), i. 137. + GROUND-TUMBLER, Indian, i. 150. + GROUSE, fertility of, in captivity, ii. 156. + GROENLAND, hybrids of _Aegilops_ and wheat, ii. 110. + _Grus montigresia_, _cinerea_, and _Antigone_, ii. 156. + GUANACOS, selection of, ii. 207. + GUANS, general fertility of, in captivity, ii. 156. + GUELDER-ROSE, ii. 185. + GUELDERLAND fowls, i. 230. + GUIANA, selection of dogs by the Indians of, ii. 206. + GUINEA FOWL, i. 294; + feral in Ascension, and Jamaica, i. 190, ii. 33; + indifference of to change of climate, ii. 161. + GUINEA pig, ii. 24, 152. + GUELDENSTADT, on the jackal, i. 25. + GULL, herring, breeding in confinement, ii. 157. + GULLS, general sterility of, in captivity, ii. 157. + _Gulo_, sterility of, in captivity, ii. 152. + GUENTHER, A., on tufted ducks and geese, i. 274; + on the regeneration of lost parts in batrachia, ii. 15. + GURNEY, Mr., owls breeding in captivity, ii. 154; + appearance of "black-shouldered" among ordinary peacocks, i. 291. + + HABIT, influence of, in acclimatisation, ii. 312-315. + HABITS, inheritance of, ii. 395. + HAECKEL, on cells, ii. 370; + on the double reproduction of medusae, ii. 384; + on inheritance, ii. 397. + HACKLES, peculiarities of, in fowls, i. 254. + HAIR, on the face, inheritance of, in man, ii. 4; + peculiar lock of, inherited, ii. 5; + growth of, under stimulation of skin, ii. 326; + homologous variation of, ii. 325; + development of, within the ears and in the brain, ii. 391. + HAIR and teeth, correlation of, ii. 326-328. + HAIRY family, corresponding period of inheritance in, ii. 77. + HALF-CASTES, character of, ii. 46. + HALF-LOP rabbits, figured and described, i. 107-108; + skull of, i. 119. + _Haliaetus leucocephalus_, copulating in captivity, ii. 154. + HALLAM, Col., on a two-legged race of pigs, ii. 4. + HAMBURGH fowl, i. 227, 261; + figured, i. 228. + HAMILTON, wild cattle of, i. 84. + HAMILTON, Dr., on the assumption of male plumage by the hen pheasant, ii. + 51. + HAMILTON, F. Buchanan, on the shaddock, i. 335; + varieties of Indian cultivated plants, ii. 256. + HANCOCK, Mr., sterility of tamed birds, ii. 155-157. + HANDWRITING, inheritance of peculiarities in, ii. 6. + HANMER, Sir J., on selection of flower seeds, ii. 204. + HANSELL, Mr., inheritance of dark yolks in duck's eggs, i. 281. + HARCOURT, E. V., on the Arab boar-hound, i. 17; + aversion of the Arabs to dun-coloured horses, i. 55. + HARDY, Mr., effect of excess of nourishment on plants, ii. 257. + HARE, hybrids of, with rabbit, i. 105; + sterility of the, in confinement, ii. 152; + preference of, for particular plants, ii. 232. + HARE-LIP, inheritance of, ii. 24. + HARLAN, Dr., on hereditary diseases, ii. 7. + HARMER, Mr., on the number of eggs in a codfish, ii. 379. + HARVEY, Mr., monstrous red and white African bull, i. 91. + HARVEY, Prof., singular form of _Begonia frigida_, i. 365-366; + effects of cross-breeding on the female, i. 404; + monstrous saxifrage, ii. 166. + HASORA wheat, i. 313. + HAUTBOIS strawberry, i. 353. + HAWKER, Col., on call or decoy ducks, i. 281. + HAWTHORN, varieties of, i. 360-364; + pyramidal, i. 361; + pendulous hybridised, ii. 18; + changes of, by age, i. 364, 387; + bud-variation in the, i. 377; + flower buds of, attacked by bullfinches, ii. 232. + HAYES, Dr., character of Esquimaux dogs, i. 21-22. + HAYWOOD, W., on the feral rabbits of Porto Santo, i. 114. + HAZEL, purple-leaved, i. 362, 395, ii. 330. + HEAD of wild boar and Yorkshire pig, figured, i. 72. + {456} + HEAD and limbs, correlated variability of, ii. 323. + HEADACHE, inheritance of, ii. 79. + HEARTSEASE, i. 368-369; + change produced in the, by transplantation, i. 386; + reversion in, ii. 31, 47; + effects of selection on, ii. 200; + scorching of, ii. 229; + effects of seasonal conditions on the, ii. 274; + annual varieties of the, ii. 305. + HEAT, effect of, upon the fleece of sheep, i. 98. + HEBER, Bishop, on the breeding of the rhinoceros in captivity, ii. 150. + HEBRIDES, cattle of the, i. 80; + pigeons of the, i. 183. + HEER, O., on the plants of the Swiss lake-dwellings, i. 309, ii. 215, + 427; + on the cereals, i. 317-319; + on the peas, i. 326; + on the vine growing in Italy in the bronze age, i. 332. + _Helix lactea_, ii. 280. + _Hemerocallis fulva_ and _flava_, interchanging by bud-variation, i. 386. + HEMLOCK yields no conicine in Scotland, ii. 274. + HEMP, differences of, in various parts of India, ii. 165; + climatal difference in products of, ii. 274. + HEMPSEED, effect of, upon the colour of birds, ii. 280. + HERMAPHRODITE flowers, occurrence of, in Maize, i. 321. + HEN, assumption of male characters by the, ii. 51, 54; + development of spurs in the, ii. 318. + "HENNIES," or hen-like male fowls, i. 252. + HENRY, T. A., a variety of the ash produced by grafting, i. 394; + crossing of species of _Rhododendron_ and _Arabis_, i. 400. + HENSLOW, Prof., individual variation in wheat, i. 314; + bud-variation in the Austrian bramble rose, i. 381; + partial reproduction of the weeping ash by seed, ii. 19. + HEPATICA, changed by transplantation, i. 386. + HERBERT, Dr., variations of _Viola grandiflora_, i. 368; + bud-variation in camellias, i. 377; + seedlings from reverted _Cytisus Adami_, i. 388; + crosses of Swedish and other turnips, ii. 93; + on hollyhocks, ii. 107; + breeding of hybrids, ii. 131; + self-impotence in hybrid hippeastrums, ii. 138-139; + hybrid _Gladiolus_, ii. 139; + on _Zephyranthes candida_, ii. 164; + fertility of the crocus, ii. 165; + on contabescence, ii. 165; + hybrid _Rhododendron_, ii. 265. + HERCULANEUM, figure of a pig found in, i. 67. + HERON, Sir R., appearance of "black-shouldered" among ordinary peacocks, + i. 290-291; + non-inheritance of monstrous characters by goldfish, i. 296; + crossing of white and coloured Angora rabbits, ii. 92; + crosses of solid-hoofed pigs, ii. 93. + _Herpestes fasciatus_ and _griseus_, ii. 151. + HEUSINGER, on the sheep of the Tarentino, ii. 227; + on correlated constitutional peculiarities, ii. 337. + HEWITT, Mr., reversion in bantam cocks, i. 240; + degeneration of silk fowls, i. 243; + partial sterility of hen-like male fowls, i. 252; + production of tailed chickens by rumpless fowls, i. 259; + on taming and rearing wild ducks, i. 278-279, ii. 233, 262-263; + conditions of inheritance in laced Sebright bantams, ii. 22; + reversion in rumpless fowls, ii. 31; + reversion in fowls by age, ii. 39; + hybrids of pheasant and fowl, ii. 45, 68; + assumption of male characters by female pheasants, ii. 51; + development of latent characters in a barren bantam hen, ii. 54; + mongrels from the silk-fowl, ii. 67; + effects of close interbreeding on fowls, ii. 124-125; + on feathered-legged bantams, ii. 323. + HIBBERT, Mr., on the pigs of the Shetland Islands, i. 70. + HIGHLAND cattle, descended from _Bos longifrons_, i. 81. + HILDEBRAND, Dr., on the fertilisation of _Orchideae_, i. 402-403; + occasional necessary crossing of plants, ii. 90; + on _Primula sinensis_ and _Oxalis rosea_, ii. 132; + on _Corydalis cava_, ii. 132-133. + HILL, R., on the Alco, i. 31; + feral rabbits in Jamaica, i. 112; + feral peacocks in Jamaica, i. 190; + variation of the Guinea fowl in Jamaica, i. 294; + sterility of tamed birds in Jamaica, ii. 155, 157. + HIMALAYA, range of gallinaceous birds in the, i. 237. + HIMALAYAN rabbit, i. 107, 108-111; + skull of, i. 120. + HIMALAYAN sheep, i. 95. + HINDMARSH, Mr., on Chillingham cattle, i. 84. + "HINKEL-TAUBE," i. 142-143. + HINNY and mule, difference of, ii. 67-68. + _Hipparion_, anomalous resemblance to in horses, i. 50. + _Hippeastrum_, hybrids of, ii. 138-139. + HIVE-BEES, ancient domestication of, i. 297; + breeds of, i. 298; + smaller when produced in old combs, i. 297; + variability in, i. 298; + crossing of Ligurian and common, i. 299. + "HOCKER-TAUBE," i. 141. + HOBBS, Fisher, on interbreeding pigs, ii. 121. + HODGKIN, Dr., on the attraction of foxes by a female Dingo, i. 31; + {457} + origin of the Newfoundland dog, i. 42; + transmission of a peculiar lock of hair, ii. 5. + HODGSON, Mr., domestication of _Canis primaevus_, i. 26; + development of a fifth digit in Thibet mastiffs, i. 35; + number of ribs in humped cattle, i. 79; + on the sheep of the Himalaya, i. 95; + presence of four mammae in sheep, _ibid._; + arched nose in sheep, i. 96; + measurements of the intestines of goats, i. 102; + presence of interdigital pits in goats, _ibid._; + disuse a cause of drooping ears, ii. 301. + HOFACKER, persistency of colour in horses, i. 51, ii. 21; + production of dun horses from parents of different colours, i. 59; + inheritance of peculiarities in handwriting, ii. 6; + heredity in a one-horned stag, ii. 12; + on consanguineous marriages, ii. 123. + HOG, Red River, ii. 150. + HOGG, Mr., retardation of breeding in cows by hard living, ii. 112. + HOLLAND, Sir H., necessity of inheritance, ii. 2; + on hereditary diseases, ii. 7; + hereditary peculiarity in the eyelid, ii. 8; + morbid uniformity in the same family, ii. 17; + transmission of hydrocele through the female, ii. 52; + inheritance of habits and tricks, ii. 395. + HOLLY, varieties of the, i. 360, 362; + bud-reversion in, i. 384; + yellow-berried, ii. 19, 230. + HOLLYHOCK, bud-variation in, i. 378; + non-crossing of double varieties of, ii. 107; + tender variety of the, ii. 310. + HOMER, notice of Geese, i. 287; + breeding of the horses of Aeneas, ii. 202. + HOMOLOGOUS parts, correlated variability of, ii. 322-331, 354-355; + fusion of, ii. 393; + affinity of, ii. 339-342. + HOOFS, correlated with hair in variation, ii. 325. + HOOK-BILLED DUCK, skull figured, i. 282. + HOOKER, Dr. J. D., forked shoulder-stripe in Syrian asses, i. 63; + voice of the cock in Sikkim, i. 259; + use of Arum-roots as food, i. 307; + native useful plants of Australia, i. 311; + wild walnut of the Himalayas, i. 356; + variety of the plane tree, i. 362; + production of _Thuja orientalis_ from seeds of _T. pendula_, i. 362; + singular form of _Begonia frigida_, i. 365; + reversion in plants run wild, ii. 33; + on the sugar-cane, ii. 169; + on Arctic plants, ii. 256; + on the oak grown at the Cape of Good Hope, ii. 274; + on _Rhododendron ciliatum_, ii. 277; + stock and mignonette, perennial in Tasmania, ii. 305. + HOPKIRK, Mr., bud-variation in the rose, i. 381; + in _Mirabilis jalapa_, i. 382; + in _Convolvulus tricolor_, i. 408. + HORNBEAM, heterophyllous, i. 362. + HORNED fowl, i. 229; + skull figured, i. 265. + HORNLESS cattle in Paraguay, i. 89. + HORNS of sheep, i. 95; + correlation of, with fleece in sheep, ii. 326; + correlation of, with the skull, ii. 333; + rudimentary in young polled cattle, ii. 315; + of goats, i. 102. + HORSES, in Swiss lake-dwellings, i. 49; + different breeds of, in Malay Archipelago, i. 49; + anomalies in osteology and dentition of, i. 50; + mutual fertility of different breeds, i. 51; + feral, i. 51; + habit of scraping away snow, i. 53; + mode of production of breeds of, i. 54; + inheritance and diversity of colour in, i. 55; + dark stripes in, i. 56-61, ii. 351; + dun-coloured, origin of, i. 59; + colours of feral, i. 60-61; + effect of fecundation by a Quagga on the subsequent progeny of, i. + 403-404; + inheritance of peculiarities in, ii. 10-11; + polydactylism in, ii. 14; + inheritance of colour in, ii. 21; + inheritance of exostoses in legs of, ii. 23; + reversion in, ii. 33, 41; + hybrids of, with ass and zebra, ii. 42; + prepotency of transmission in the sexes of, ii. 65; + segregation of, in Paraguay, ii. 102; + wild species of, breeding in captivity, ii. 150; + curly, in Paraguay, ii. 205, 325; + selection of, for trifling characters, ii. 209; + unconscious selection of, ii. 212-213; + natural selection in Circassia, ii. 225; + alteration of coat of, in coal-mines, ii. 278; + degeneration of, in the Falkland Islands, ii. 278; + diseases of, caused by shoeing, ii. 300; + feeding on meat, ii. 305; + white and white-spotted, poisoned by mildewed vetches, ii. 337; + analogous variations in the colour of, ii. 349; + teeth developed on palate of, ii. 391; + of bronze period in Denmark, ii. 427. + HORSE-CHESNUT, early, at the Tuileries, i. 362; + tendency to doubleness in, ii. 168. + HORSE-RADISH, general sterility of the, ii. 170. + "HOUDAN," a French sub-breed of fowls, i. 229. + HOWARD, C., on an Egyptian monument, i. 17; + on crossing sheep, ii. 95, 120. + HUC, on the Emperor Khang-hi, ii. 205; + Chinese varieties of the bamboo, ii. 256. + HUMBOLDT, A., character of the Zambos, ii. 47; + parrot speaking the language of an extinct tribe, ii. 154; + on _Pulex penetrans_, ii. 275. + HUMIDITY, injurious effect of, upon horses, i. 53. + HUMPHREYS, Col., on Ancon sheep, i. 100. + HUNGARIAN cattle, i. 80. + {458} + HUNTER, John, period of gestation in the dog, i. 29; + on secondary sexual characters, i. 179; + fertile crossing of _Anser ferus_ and the domestic goose, i. 288; + inheritance of peculiarities in gestures, voice, &c., ii. 6; + assumption of male characters by the human female, ii. 51; + period of appearance of hereditary diseases, ii. 78; + graft of the spur of a cock upon its comb, ii. 296; + on the stomach of _Larus tridentatus_, ii. 302; + double-tailed lizards, ii. 341. + HUNTER, W., evidence against the influence of imagination upon the + offspring, ii. 264. + HUTTON, Capt., on the variability of the silk moth, i. 303; + on the number of species of silkworms, i. 300; + markings of silkworms, i. 302; + domestication of the rock-pigeon in India, i. 185; + domestication and crossing of _Gallus bankiva_, i. 236. + HUTCHINSON, Col., liability of dogs to distemper, i. 35. + HUXLEY, Prof., on the transmission of polydactylism, ii. 13; + on unconscious selection, ii. 194; + on correlation in the mollusca, ii. 320; + on gemmation and fission, ii. 359; + development of star-fishes, ii. 366. + HYACINTHS, i. 370-371; + bud-variation in, i. 385; + graft-hybrid by union of half bulbs of, i. 395; + white, reproduced by seed, ii. 20; + red, ii. 229, 336; + varieties of, recognisable by the bulb, ii. 251. + HYACINTH, feather, ii. 185, 316. + _Hyacinthus orientalis_, i. 370. + _Hybiscus syriacus_, ii. 286. + HYBRIDS, of hare and rabbit, i. 105; + of various species of _Gallus_, i. 234-236; + of almond, peach, and nectarine, i. 339; + naturally produced, of species of _Cytisus_, i. 390; + from twin-seed of _Fuchsia coccinea_ and _fulgens_, i. 391; + reversion of, i. 392-394, ii. 36, 48-50; + from mare, ass, and zebra, ii. 42; + of tame animals, wildness of, ii. 44-46; + female instincts of sterile male, ii. 52; + transmission and blending of characters in, ii. 92-95; + breed better with parent species than with each other, ii. 131; + self-impotence in, ii. 138-140; + readily produced in captivity, ii. 151. + HYBRIDISATION, singular effects of, in oranges, i. 336; + of cherries, i. 347; + difficulty of, in _Cucurbitae_, i. 358; + of roses, i. 366. + HYBRIDISM, ii. 178-191; + the cause of a tendency to double flowers, ii. 171; + in relation to pangenesis, ii. 385. + HYBRIDITY in cats, i. 44-45; + supposed of peach and nectarine, i. 342. + _Hydra_, i. 374, ii. 293, 359. + HYDRANGEA, colour of flowers of, influenced by alum, ii. 277. + HYDROCELE, ii. 52. + HYDROCEPHALUS, ii. 295. + _Hypericum calycinum_, ii. 170. + _Hypericum crispum_, ii. 227, 337. + HYPERMETAMORPHOSIS, ii. 367. + HYPERMETROPIA, hereditary, ii. 8. + + ICHTHYOPTERYGIA, number of digits in the, ii. 16. + _Ilex aquifolium_, ii. 19. + IMAGINATION, supposed effect of, on offspring, ii. 263. + _Imatophyllum miniatum_, bud-variation in, i. 385. + INCEST, abhorred by savages, ii. 123-124. + INCUBATION, by crossed fowls of non-sitting varieties, ii. 43-44. + INDIA, striped horses of, i. 58; + pigs of, i. 66, 67, 76; + breeding of rabbits in, i. 112; + cultivation of pigeons in, i. 205-206. + INDIVIDUAL variability in pigeons, i. 158-160. + INGLEDEW, Mr., cultivation of European vegetables in India, ii. 169. + "INDISCHE Taube," ii. 144. + INHERITANCE, ii. 1-84, 371-373, 395, 397-402; + doubts entertained of by some writers, ii. 3; + importance of to breeders, 3-4; + evidence of, derived from statistics of chances, 5; + of peculiarities in man, 5-7, 12-16; + of disease, 7-8, 17; + of peculiarities in the eye, 8-10; + of deviations from symmetry, 12; + of polydactylism, 12-16; + capriciousness of, 17-22, 27; + of mutilations, 22-24; + of congenital monstrosities, 24; + causes of absence of, 24-26; + by reversion or atavism, 28-61; + its connexion with fixedness of character, 62-64; + affected by prepotency of transmission of character, 65-71; + limited by sex, 71-75; + at corresponding periods of life, 75-80; + summary of the subject of, 80-84; + laws of, the same in seminal and bud varieties, i. 409; + of characters in the horse, i. 10-11; + in cattle, i. 87; + in rabbits, i. 107; + in the peach, i. 339; + in the nectarine, i. 340; + in plums, i. 347; + in apples, i. 350; + in pears, i. 351; + in the pansy, i. 369; + of primary characters of _Columba livia_ in crossed pigeons, i. 201; + of peculiarities of plumage in pigeons, i. 160-161; + of peculiarities of foliage in trees, i. 362; + effects of, in varieties of the cabbage, i. 325. + INSANITY, inheritance of, ii. 7, 78. + INSECTS, regeneration of lost parts in, ii. 15, 294; + agency of, in fecundation of larkspurs, ii. 21; + effect of changed conditions upon, ii. 157; + sterile neuter, ii. 186-187; + {459} + monstrosities in, ii. 269, 391. + INSTINCTS, defective, of silkworms, i. 304. + INTERBREEDING, close, ill effects of, ii. 114-131, 175. + INTERCROSSING, of species, as a cause of variation, i. 188; + natural, of plants, i. 336; + of species of Canidae and breeds of dogs, i. 31-33; + of domestic and wild cats, i. 44-45; + of breeds of pigs, i. 71, 78; + of cattle, i. 83; + of varieties of cabbage, i. 324; + of peas, i. 326, 329-330; + of varieties of orange, i. 336; + of species of strawberries, i. 351-352; + of _Cucurbitae_, i. 357-358; + of flowering plants, i. 364; + of pansies, i. 368. + INTERDIGITAL pits, in goats, i. 102. + INTERMARRIAGES, close, ii. 122-123. + INTESTINES, elongation of, in pigs, i. 73; + relative measurements of parts of, in goats, i. 102; + effects of changed diet on, ii. 302. + _Ipomoea purpurea_, ii. 128. + IRELAND, remains of _Bos frontosus_ and _longifrons_ found in, i. 81. + IRIS, hereditary absence of the, ii. 9; + hereditary peculiarities of colour of the, ii. 9-10. + IRISH, ancient, selection practised by the, ii. 203. + IRON period, in Europe, dog of, i. 18. + ISLANDS, oceanic, scarcity of useful plants on, i. 311. + ISLAY, pigeons of, i. 183. + ISOLATION, effect of, in favour of selection, ii. 233-234. + ITALY, vine growing in, during the bronze period, i. 332. + IVY, sterility of, in the north of Europe, ii. 170. + + JACK, Mr., effect of foreign pollen on grapes, i. 400. + JACKAL, i. 24, 27, 30; + hybrids of, with the dog, i. 32; + prepotency of, over the dog, ii. 67. + JACOBIN pigeon, i. 154, 208. + JACQUEMET-BONNEFORT, on the mulberry, i. 334. + JAGUAR, with crooked legs, i. 17. + JAMAICA, feral dogs of, i. 28; + feral pigs of, i. 77; + feral rabbits of, i. 112. + JAPAN, horses of, i. 53. + JAPANESE pig (figured), i. 69. + JARDINE, Sir W., crossing of domestic and wild cats, i. 44. + JARVES, J., silkworm in the Sandwich islands, i. 301. + JAVA, Fantail pigeon in, i. 148. + JAVANESE ponies, i. 53, 59. + JEMMY BUTTON, i. 309. + JENYNS, L., whiteness of ganders, i. 288; + sunfish-like variety of the goldfish, i. 297. + JERDON, J. C., number of eggs laid by the pea-hen, ii. 112; + origin of domestic fowl, i. 237. + JERSEY, arborescent cabbages of, i. 323. + JESSAMINE, i. 394. + JEITTELES, Hungarian sheep-dogs, i. 24; + crossing of domestic and wild cats, i. 44. + JOHN, King, importation of stallions from Flanders by, ii. 203. + JOHNSON, D., occurrence of stripes on young wild pigs in India, i. 76. + JORDAN, A., on Vibert's experiments on the vine, i. 332; + origin of varieties of the apple, i. 350; + varieties of pears found wild in woods, ii. 260. + JOURDAN, parthenogenesis in the silk moth, ii. 364. + JUAN DE NOVA, wild dogs on, i. 27. + JUAN FERNANDEZ, dumb dogs on, i. 27. + _Juglans regia_, i. 356-357. + JUKES, Prof., origin of the Newfoundland dog, i. 42. + JULIEN, Stanislas, early domestication of pigs in China, i. 68; + antiquity of the domestication of the silk-worm in China, i. 300. + JUMPERS, a breed of fowls, i. 230. + JUNIPER, variations of the, i. 361, 364. + _Juniperus suecica_, i. 361. + _Jussiaea grandiflora_, ii. 170. + JUSSIEU, A. de, structure of the pappus in _Carthamus_, ii. 316. + + KAIL, Scotch, reversion in, ii. 32. + "KALA-PAR" pigeon, i. 142. + KALES, i. 323. + KALM, P., on maize, i. 322, ii. 307; + introduction of wheat into Canada, i. 315; + sterility of trees growing in marshes and dense woods, ii. 170. + "KALMI Lotan," tumbler pigeon, i. 151. + KANE, Dr., on Esquimaux dogs, i. 21. + KARAKOOL sheep, i. 98. + KARKEEK, on inheritance in the horse, ii. 10. + "KARMELITEN Taube," i. 156. + KARSTEN on _Pulex penetrans_, ii. 275. + KATTYWAR horses, i. 58. + KEELEY, R., pelorism in _Galeobdolon luteum_, ii. 59. + KERNER on the culture of Alpine plants, ii. 163. + KESTREL, breeding in captivity, ii. 154. + "KHANDESI," i. 141. + KHANG-HI, selection of a variety of rice by, ii. 205. + KIANG, ii. 43. + KIDD, on the canary bird, i. 77, ii. 275. + KIDNEY Bean, i. 371; + varieties of, ii. 256, 275. + {460} + KIDNEYS, compensatory development of the, ii. 300; + fusion of the, ii. 341; + shape of, in birds, influenced by the form of the pelvis, ii. 344. + KING, Col., domestication of rock doves from the Orkneys, i. 184, 185. + KING, P. S., on the Dingo, i. 21, 28. + KIRBY and Spence, on the growth of galls, ii. 283. + KIRGHISIAN sheep, i. 98. + KITE, breeding in captivity, ii. 154. + KLEINE, variability of bees, i. 298. + KNIGHT, Andrew, on crossing horses of different breeds, i. 51; + crossing varieties of peas, i. 326, ii. 129; + persistency of varieties of peas, i. 329; + origin of the peach, i. 338; + hybridisation of the morello by the Elton cherry, i. 347; + on seedling cherries, _ibid._; + variety of the apple not attacked by coccus, i. 349; + intercrossing of strawberries, i, 351, 352; + broad variety of the cock's comb, i. 365; + bud variation in the cherry and plum, i. 375; + crossing of white and purple grapes, i. 393; + experiments in crossing apples, i. 402, ii. 129; + hereditary disease in plants, ii. 11; + on interbreeding, ii. 116; + crossed varieties of wheat, ii. 130; + necessity of intercrossing in plants, ii. 175; + on variation, ii. 256, 257; + effects of grafting, i. 387, ii. 278; + bud-variation in a plum, ii. 289; + compulsory flowering of early potatoes, ii. 343; + correlated variation of head and limbs, ii. 323. + KNOX, Mr., breeding of the eagle owl in captivity, ii. 154. + KOCH, degeneracy in the turnip, i. 325. + KOHLRABI, i. 323. + KOELREUTER, reversion in hybrids, i. 392, ii. 36; + acquired sterility of crossed varieties of plants, i. 358, ii. 101; + absorption of _Mirabilis vulgaris_ by _M. longiflora_, ii. 88; + crosses of species of _Verbascum_, ii. 93, 107; + on the hollyhock, ii. 107; + crossing varieties of tobacco, ii. 108; + benefits of crossing plants, ii. 130, 131, 175-176; + self-impotence in _Verbascum_, ii. 136, 141; + effects of conditions of growth upon fertility in _Mirabilis_, ii. 164; + great development of tubers in hybrid plants, ii. 172; + inheritance of plasticity, ii. 241; + variability of hybrids of _Mirabilis_, ii. 265; + repeated crossing a cause of variation, ii. 267-268; + number of pollen-grains necessary for fertilization, ii. 363. + "KRAUSESCHWEIN," i. 67. + KROHN, on the double reproduction of Medusae, ii. 384. + "KROPF-TAUBEN," i. 137. + + LABAT, on the tusks of feral bears in the West Indies, i. 77; + on French wheat grown in the West Indies, ii. 307; + on the culture of the vine in the West Indies, ii. 308. + LABURNUM, Adam's, see _Cytisus Adami_; + oak-leaved, reversion of, i. 382; + pelorism in the, ii. 346; + Waterer's, i. 390. + LACHMANN, on gemmation and fission, ii. 358. + _Lachnanthes tinctoria_, ii. 227, 336. + LACTATION, imperfect, hereditary, ii. 8; + deficient, of wild animals in captivity, ii. 158. + LADRONE islands, cattle of, i. 86. + LAING, Mr., resemblance of Norwegian and Devonshire cattle, i. 82. + LAKE-DWELLINGS, sheep of, i. 94, ii. 427; + cattle of, ii. 427; + absence of the fowl in, i. 246; + cultivated plants of, i. 309, ii. 427, 429; + cereals of, i. 317-319; + peas found in, i. 326; + beans found in, i. 330. + LAMARE-PIQUOT, observations on half-bred North American wolves, i. 22. + LAMBERT, A. B., on _Thuja pendula_ or _filiformis_, i. 362. + LAMBERT family, ii. 4, 76. + LAMBERTYE on strawberries, i. 351, 352; + five-leaved variety of _Fragaria collina_, i. 353. + LANDT, L., on sheep in the Faroe islands, ii. 103. + LA PLATA, wild dogs of, i. 27; + feral cat from, i. 47. + LARCH, ii. 310. + LARKSPURS, insect agency necessary for the full fecundation of, ii. 21. + _Larus argentatus_, ii. 157. + _Larus tridactylus_, ii. 302. + LASTERYE, merino sheep in different countries, i. 99. + LATENT characters, ii. 51-56. + LATHAM, on the fowl not breeding in the extreme north, ii. 161. + _Lathyrus_, ii. 38. + _Lathyrus aphaca_, ii. 343. + _Lathyrus odoratus_, ii. 20, 91, 93, 311, 393. + LA TOUCHE, J. D., on a Canadian apple with dimidiate fruit, i. 392-393. + "LATZ-TAUBE," i. 154. + LAUGHER pigeon, i. 155, 207. + _Laurus sassafras_, ii. 274. + LAWRENCE, J., production of a new breed of fox-hounds, i. 40; + occurrence of canines in mares, i. 50; + on three-parts-bred horses, i. 54; + on inheritance in the horse, ii. 10-11. + LAWSON, Mr., varieties of the potato, i. 330. + LAXTON, Mr., bud-variation in the gooseberry, i. 376; + crossing of varieties of the pea, i. 397-398; + {461} + double-flowered peas, ii. 168. + LAYARD, E. L., resemblance of a Caffre dog to the Esquimaux breed, i. 25, + ii. 286; + crossing of the domestic cat with _Felis Caffra_, i. 44; + feral pigeons in Ascension, i. 190; + domestic pigeons of Ceylon, i. 206; + on _Gallus Stanleyi_, i. 234; + on black-skinned Ceylonese fowls, i. 256. + LE COMPTE family, blindness inherited in, ii. 78. + LECOQ, bud-variation in _Mirabilis jalapa_, i. 382; + hybrids of _Mirabilis_, i. 393, ii. 169, 265; + crossing in plants, ii. 127; + fecundation of _Passiflora_, ii. 137; + hybrid _Gladiolus_, ii. 139; + sterility of _Ranunculus ficaria_, ii. 170; + villosity in plants, ii. 277; + double asters, ii. 316. + LE COUTEUR, J., varieties of wheat, i. 313-315; + acclimatisation of exotic wheat in Europe, i. 315; + adaptation of wheat to soil and climate, i. 316; + selection of seed-corn, i. 318; + on change of soil, ii. 147; + selection of wheat, ii. 200; + natural selection in wheat, ii. 233; + cattle of Jersey, ii. 234. + LEDGER, Mr., on the Llama and Alpaca, ii. 208. + LEE, Mr., his early culture of the pansy, i. 368. + _Leersia oryzoides_, ii. 91. + LEFOUR, period of gestation in cattle, i. 87. + LEGS, of fowls, effects of disuse on, i. 270-272; + characters and variations of, in ducks, i. 284-288; + fusion of, ii. 341. + LEGUAT, cattle of the Cape of Good Hope, i. 88. + LEHMANN, occurrence of wild double-flowered plants near a hot spring, ii. + 168. + LEIGHTON, W. A., propagation of a weeping yew by seed, ii. 19. + LEITNER, effects of the removal of anthers, ii. 167. + LEMMING, ii. 152. + LEMOINE, variegated _Symphytum_ and _Phlox_, i. 384. + LEMON, i. 334, 335; + orange fecundated by pollen of the, i. 399. + LEMURS, hybrid, ii. 153. + LEPORIDES, ii. 98-99, 152. + LEPSIUS, figures of ancient Egyptian dogs, i. 17; + domestication of pigeons in ancient Egypt, i. 204. + _Leptotes_, ii. 134. + _Lepus glacialis_, i. 111. + _Lepus magellanicus_, i. 112. + _Lepus nigripes_, i. 108. + _Lepus tibetanus_, i. 111. + _Lepus variabilis_, i. 111. + LEREBOULLET, double monsters of fishes, ii. 340. + LESLIE, on Scotch wild cattle, i. 85. + LESSON, on _Lepus magellanicus_, i. 112. + LEUCKART on the larva of Cecidomyidae, ii. 360. + LEWIS, G., cattle of the West Indies, ii. 229. + LHERBETTE and Quatrefages, on the horses of Circassia, ii. 102, 225. + LIEBIG, differences in human blood, according to complexion, ii. 276. + LIEBREICH, occurrence of pigmentary retinitis in deaf-mutes, ii. 328. + LICHENS, sterility in, ii. 171. + LICHTENSTEIN, resemblance of Bosjesman's dogs to _Canis mesomelas_, i. + 25; + Newfoundland dog at the Cape of Good Hope, i. 36. + LILACS, ii. 164. + LILIACEAE, contabescence in, ii. 165. + _Lilium candidum_, ii. 137. + LIMBS, regeneration of, ii. 376-377. + LIMBS and head, correlated variation of, ii. 323. + LIME, effect of, upon shells of the mollusca, ii. 280. + LIME tree, changes of by age, i. 364, 387. + LIMITATION, sexual, ii. 71-75. + LIMITATION, supposed, of variation, ii. 416. + _Linaria_, pelorism in, ii. 58, 61, 346; + peloric, crossed with the normal form, ii. 70; + sterility of, ii. 166. + _Linaria vulgaris_ and _purpurea_, hybrids of, ii. 94. + LINDLEY, John, classification of varieties of cabbages, i. 324; + origin of the peach, i. 338; + influence of soil on peaches and nectarines, i. 340; + varieties of the peach and nectarine, i. 343; + on the New Town pippin, i. 349; + freedom of the Winter Majetin apple from coccus, i. 349; + production of monoecious Hautbois strawberries by bud-selection, i. + 353; + origin of the large tawny nectarine, i. 375; + bud-variation in the gooseberry, i. 376; + hereditary disease in plants, ii. 11; + on double flowers, ii. 167; + seeding of ordinarily seedless fruits, ii. 168; + sterility of _Acorus calamus_, ii. 170; + resistance of individual plants to cold, ii. 309. + LINNAEUS, summer and winter wheat regarded as distinct species by, i. + 315; + on the single-leaved strawberry, i. 353; + sterility of Alpine plants in gardens, ii. 163; + recognition of individual reindeer by the Laplanders, ii. 251; + growth of tobacco in Sweden, ii. 307. + LINNET, ii. 158. + _Linota cannabina_, ii. 158. + {462} + LINUM, ii. 165. + LION, fertility of, in captivity, ii. 150, 151. + LIPARI, feral rabbits of, i. 113. + LIVINGSTONE, Dr., striped young pigs on the Zambesi, i. 77; + domestic rabbits at Loanda, i. 112; + use of grass-seeds as food in Africa, i. 308; + planting of fruit-trees by the Batokas, i. 309; + character of half-castes, ii. 46; + taming of animals among the Barotse, ii. 160; + selection practised in South Africa, ii. 207, 209. + LIVINGSTONE, Mr., disuse a cause of drooping ears, ii. 301. + LIZARDS, reproduction of tail in, ii. 294; + with a double tail, ii. 341. + LLAMA, selection of, ii. 208. + LLOYD, Mr., taming of the wolf, i. 26; + English dogs in northern Europe, i. 36; + fertility of the goose increased by domestication, i. 288; + number of eggs laid by the wild goose, ii. 112; + breeding of the capercailzie in captivity, ii. 156. + LOANDA, domestic rabbits at, i. 112. + _Loasa_, hybrid of two species of, ii. 98. + _Lobelia_, reversion in hybrids of, ii. 392; + contabescence in, ii. 166. + _Lobelia fulgens_, _cardinalis_, and _syphilitica_, ii. 136. + LOCKHART, Dr., on Chinese pigeons, i. 206. + LOCUST-TREE, ii. 274. + LOISELEUR-DESLONGCHAMPS, originals of cultivated plants, i. 307; + Mongolian varieties of wheat, i. 313; + characters of the ear in wheat, i. 314; + acclimatisation of exotic wheat in Europe, i. 315; + effect of change of climate on wheat, i. 316; + on the supposed necessity of the coincident variation of weeds and + cultivated plants, i. 317; + advantage of change of soil to plants, ii. 146. + _Lolium temulentum_, variable presence of barbs in, i. 314. + LONG-TAILED sheep, i. 94, 95. + LOOCHOO islands, horses of, i. 53. + LORD, J. K., on Canis latrans, i. 22. + "LORI RAJAH," how produced, ii. 280. + _Lorius garrulus_, ii. 280. + "LOTAN," tumbler pigeon, i. 150. + LOUDON, J. W., varieties of the carrot, i. 326; + short duration of varieties of peas, i. 329; + on the glands of peach-leaves, i. 343; + presence of bloom on Russian apples, i. 349; + origin of varieties of the apple, i. 350; + varieties of the gooseberry, i. 354; + on the nut tree, i. 357; + varieties of the ash, i. 360; + fastigate juniper (_J. suecica_), i. 361; + on _Ilex aquifolium ferox_, i. 362; + varieties of the Scotch fir, i. 363; + varieties of the hawthorn, _ibid._; + variation in the persistency of leaves on the elm and Turkish oak, i. + 363; + importance of cultivated varieties, _ibid._; + varieties of _Rosa spinosissima_, i. 367; + variation of dahlias from the same seed, i. 370; + production of Provence roses from seeds of the moss rose, i. 380; + effect of grafting the purple-leaved upon the common hazel, i. 395; + nearly evergreen Cornish variety of the elm, ii. 310. + LOW, G., on the pigs of the Orkney islands, i. 70. + LOW, Prof., pedigrees of greyhounds, ii. 3; + origin of the dog, i. 10; + burrowing instinct of a half-bred Dingo, i. 28; + inheritance of qualities in horses, i. 51; + comparative powers of English race-horses, Arabs, &c., i. 54; + British breeds of cattle, i. 80; + wild cattle of Chartley, i. 84; + effect of abundance of food on the size of cattle, i. 91; + effects of climate on the skin of cattle, i. 92, ii. 326; + on interbreeding, ii. 116; + selection in Hereford cattle, ii. 214; + formation of new breeds, ii. 244; + on "sheeted" cattle, ii. 349. + LOWE, Mr., on hive bees, i. 299. + LOWE, REV. Mr., on the range of _Pyrus malus_ and _P. acerba_, i. 348. + "LOWTAN" tumbler pigeon, i. 150. + _Loxia pyrrhula_, ii. 154. + LUBBOCK, Sir J., developments of the Ephemeridae, ii. 366. + LUCAS, P., effects of cross-breeding on the female, i. 404; + hereditary diseases, ii. 7, 78-79; + hereditary affections of the eye, ii. 9-10; + inheritance of anomalies in the human eye and in that of the horse, ii. + 10, 11; + inheritance of polydactylism, ii. 13; + morbid uniformity in the same family, ii. 17; + inheritance of mutilations, ii. 23; + persistency of cross-reversion, ii. 35; + persistency of character in breeds of animals in wild countries, ii. + 64; + prepotency of transmission, ii. 65, 68; + supposed rules of transmission in crossing animals, ii. 68; + sexual limitations of transmission of peculiarities, ii. 72-73; + absorption of the minority in crossed races, ii. 88; + crosses without blending of certain characters, ii. 92; + on interbreeding, ii. 116; + variability dependent on reproduction, ii. 250; + period of action of variability, ii. 260; + inheritance of deafness in cats, ii. 329; + complexion and constitution, ii. 335. + LUCAZE-DUTHIERS, structure and growth of galls, ii. 282-284. + LUIZET, grafting of a peach-almond on a peach, i. 338. + {463} + LUETKE, cats of the Caroline Archipelago, i. 47. + LUXURIANCE, of vegetative organs, a cause of sterility in plants, ii. + 168-171. + LYONNET, on the scission of _Nais_, ii. 358. + _Lysimachia nummularia_, sterility of, ii. 170. + _Lythrum_, trimorphic species of, ii. 400. + _Lythrum salicaria_, ii. 183; + contabescence in, ii. 166. + _Lytta vesicatoria_, affecting the kidneys, ii. 380. + + _Macacus_, species of, bred in captivity, ii. 153. + MACAULAY, Lord, improvement of the English horse, ii. 213. + MCCLELLAND, Dr., variability of fresh-water fishes in India, ii. 259. + MCCOY, Prof., on the dingo, i. 26. + MACFAYDEN, influence of soil in producing sweet or bitter oranges from + the same seed, i. 335. + MACGILLIVRAY, domestication of the rock-dove, i. 185; + feral pigeons in Scotland, i. 190; + number of vertebrae in birds, i. 266; + on wild geese, i. 287; + number of eggs of wild and tame ducks, ii. 112. + MACKENZIE, Sir G., peculiar variety of the potato, i. 330. + MACKENZIE, P., bud-variation in the currant, i. 376. + MACKINNON, Mr., horses of the Falkland islands, i. 52; + feral cattle of the Falkland islands, i. 86. + MACKNIGHT, C., on interbreeding cattle, ii. 118. + MACNAB, Mr., on seedling weeping birches, ii. 18; + non-production of the weeping beech by seed, ii. 19. + MADAGASCAR, cats of, i. 47. + MADDEN, H., on interbreeding cattle, ii. 118. + MADEIRA, rock pigeon of, i. 184. + _Magnolia grandiflora_, ii. 308. + MAIZE, its unity of origin, i. 320; + antiquity of, _ibid._; + with husked grains said to grow wild, _ibid._; + variation of, i. 321; + irregularities in the flowers of, i. 321; + persistence of varieties, _ibid._; + adaptation of to climate, i. 322, ii. 307; + acclimatisation of, ii. 313, 347; + crossing of, i. 400, ii. 104-105; + extinct Peruvian varieties of, ii. 425. + MALAY fowl, i. 227. + MALAY Archipelago, horses of, i. 53; + short-tailed cats of, i. 47; + striped young wild pigs of, i. 76; + ducks of, i. 280. + MALE, influence of, on the fecundated female, i. 397-406; + supposed influence of, on offspring, ii. 68. + MALE flowers, appearance of, among female flowers in maize, i. 321. + MALFORMATIONS, hereditary, ii. 79. + _Malva_, fertilisation of, i. 402, ii. 363. + _Mamestra suasa_, ii. 157. + MAMMAE, variable in number in the pig, i. 74; + rudimentary, occasional full development of, in cows, i. 87, ii. 317; + four present in some sheep, i. 95; + variable in number in rabbits, i. 106; + latent functions of, in male animals, ii. 52, 317; + supernumerary and inguinal, in women, ii. 57. + MANGLES, Mr., annual varieties of the heartsease, ii. 305. + MANTELL, Mr., taming of birds by the New Zealanders, ii. 161. + MANU, domestic fowl noticed in the Institutes of, i. 246. + MANURE, effect of, on the fertility of plants, ii. 163. + MANX cats, i. 46, ii. 66. + MARCEL de Serres, fertility of the ostrich, ii. 156. + MARIANNE islands, varieties of _Pandanus_ in, ii. 256. + MARKHAM, Gervase, on rabbits, i. 104, ii. 204. + MARKHOR, probably one of the parents of the goat, i. 101. + MARQUAND, cattle of the channel islands, i. 80. + MARRIMPOEY, inheritance in the horse, ii. 10. + MARROW, vegetable, i. 357. + MARRYATT, Capt., breeding of asses in Kentucky, ii. 237. + MARSDEN, notice of _Gallus giganteus_, i. 235. + MARSHALL, Mr., voluntary selection of pasture by sheep, i. 96; + adaptation of wheats to soil and climate, i. 316; + "Dutch-buttocked" cattle, ii. 8; + segregation of herds of sheep, ii. 103; + advantage of change of soil to wheat and potatoes, ii. 146; + fashionable change in the horns of cattle, ii. 210; + sheep in Yorkshire, ii. 235. + MARSHALL, Prof., growth of the brain in microcephalous idiots, ii. 389. + MARTENS, E. Von, on _Achatinella_, ii. 53. + MARTIN, W. C. L., origin of the dog, i. 16; + Egyptian dogs, i. 18; + barking of a Mackenzie River dog, i. 27; + African hounds in the Tower menagerie, i. 32; + on dun horses and dappled asses, i. 55; + breeds of the horse, i. 49; + wild horses, i. 51; + Syrian breeds of asses, i. 62; + asses without stripes, i. 63; + effects of cross-breeding on the female in dogs, i. 404; + striped legs of mules, ii. 42. + MARTINS, defective instincts of silkworms, i. 304. + MARTINS, C., fruit trees of Stockholm, ii. 307. + {464} + MASON, W., bud-variation in the ash, i. 382. + MASTERS, Dr., reversion in the spiral-leaved weeping willow, i. 383; + on peloric flowers, ii. 58; + pelorism in a clover, ii. 346; + position as a cause of pelorism, ii. 345, 347. + MASTERS, Mr., persistence of varieties of peas, i. 329; + reproduction of colour in hyacinths, ii. 20; + on hollyhocks, ii. 107; + selection of peas for seed, ii. 199-200; + on _Opuntia leucotricha_, ii. 286; + reversion by the terminal pea in the pod, ii. 347. + MASTIFF, sculptured on an Assyrian monument, i. 17, ii. 429; + Tibetan, i. 35-36, ii. 278. + MATTHEWS, Patrick, on forest trees, ii. 237. + _Matthiola annua_, i. 399, ii. 20. + _Matthiola incana_, i. 381, 399. + MAUCHAMP, merino sheep, i. 100. + MAUDUYT, crossing of wolves and dogs in the Pyrenees, i. 24. + MAUND, Mr. crossed varieties of wheat, ii. 130. + MAUPERTUIS, axiom of "least action," i. 12. + MAURITIUS, importation of goats into, i. 101. + MAW, G., correlation of contracted leaves and flowers in pelargoniums, + ii. 330, 331. + MAWZ, fertility of _Brassica rapa_, ii. 165. + _Maxillaria_, self-fertilised capsules of, ii. 134; + number of seeds in, ii. 379. + _Maxillaria atro-rubens_, fertilisation of, by _M. squalens_, ii. 133. + MAYES, M., self-impotence in _Amaryllis_, ii. 139. + MECKEL, on the number of digits, ii. 13; + correlation of abnormal muscles in the leg and arm, ii. 322. + MEDUSAE, development of, ii. 368, 384. + MEEHAN, Mr., comparison of European and American trees, ii. 281. + _Meleagris mexicana_, i. 292. + _Meles taxus_, ii. 151. + MELONS, i. 359-360; + mongrel, supposed to be produced from a twin-seed, i. 391; + crossing of varieties of, i. 399, ii. 108, 129; + inferiority of, in Roman times, ii. 216; + changes in, by culture and climate, ii. 275; + serpent, correlation of variations in, ii. 330; + analogous variations in, ii. 349. + MEMBRANES, false, ii. 294-295. + MENETRIES, on the stomach of _Strix grallaria_, ii. 302. + MENINGITIS, tubercular, inherited, ii. 78. + METAGENESIS, ii. 366. + METAMORPHOSIS, ii. 366. + METAMORPHOSIS and development, ii. 388, 389. + METZGER, on the supposed species of wheat, i. 312-313; + tendency of wheat to vary, i. 315; + variation of maize, i. 321-322; + cultivation of American maize in Europe, i. 322, ii. 347; + on cabbages, i. 323-325; + acclimatisation of Spanish wheat in Germany, ii. 26; + advantage of change of soil to plants, ii. 146; + on rye, ii. 254; + cultivation of different kinds of wheat, ii. 261. + MEXICO, dog from, with tan spots on the eyes, i. 29; + colours of feral horses in, i. 61. + MEYEN, on sending of bananas, ii. 168. + MICE, grey and white, colours of, not blended by crossing, ii. 92; + rejection of bitter almonds by, ii. 232; + naked, ii. 279. + MICHAUX, F., roan-coloured feral horses of Mexico, i. 61; + origin of domestic turkey, i. 292; + on raising peaches from seed, i. 339. + MICHEL, F., selection of horses in mediaeval times, ii. 203; + horses preferred on account of slight characters, ii. 209. + MICHELY, effects of food on caterpillars, ii. 280; + on _Bombyx hesperus_, ii. 304. + MICROPHTHALMIA, associated with defective teeth, ii. 328. + MIDDENS, Danish, remains of dogs in, i. 18, ii. 427. + MIGNONETTE, ii. 237, 311. + MILLET, i. 371. + MILLS, J., diminished fertility of mares when first turned out to grass, + ii. 161. + MILNE-EDWARDS, on the development of the crustacea, ii. 368. + MILNE-EDWARDS, A., on a crustacean with a monstrous eye-peduncle, ii. + 391. + _Milvus niger_, ii. 154. + _Mimulus luteus_, ii. 128. + MINOR, W. C., gemmation and fission in the Annelida, ii. 358. + _Mirabilis_, fertilisation of, ii. 363; + hybrids of, ii. 131, 169, 265. + _Mirabilis jalapa_, i. 382, 393. + _Mirabilis longiflora_, ii. 88. + _Mirabilis vulgaris_, ii. 88. + _Misocampus_ and _Cecidomyia_, i. 5. + MITCHELL, Dr., effects of the poison of the rattlesnake, ii. 289. + MITFORD, Mr., notice of the breeding of horses by Erichthonius, ii. 202. + MOCCAS Court, weeping oak at, ii. 18. + MOGFORD, horses poisoned by fool's parsley, ii. 337. + MOELLER, L., effects of food on insects, ii. 281. + MOQUIN-TANDON, original form of maize, i. 320; + variety of the double columbine, i. 365; + {465} + peloric flowers, ii. 58-59, 61; + position as a cause of pelorism in flowers, ii. 345; + tendency of peloric flowers to become irregular, ii. 70; + on monstrosities, ii. 254; + correlation in the axis and appendages of plants, ii. 321; + fusion of homologous parts in plants, ii. 339, 341-342; + on a bean with monstrous stipules and abortive leaflets, ii. 343; + conversion of parts of flowers, ii. 392. + MOLE, white, ii. 332. + MOLL and Gayot, on cattle, i. 80, ii. 96, 210. + MOLLUSCA, change in shells of, ii. 280. + MONKE, Lady, culture of the pansy by, i. 368. + MONKEYS, rarely fertile in captivity, ii. 153. + MONNIER, identity of summer and winter wheat, i. 315. + MONSTER, cyclopean, ii. 341. + MONSTERS, double, ii. 339-340. + MONSTROSITIES, occurrence of, in domesticated animals and cultivated + plants, i. 366, ii. 254; + due to persistence of embryonic conditions, ii. 57; + occurring by reversion, ii. 57-60; + a cause of sterility, ii. 166-167; + caused by injury to the embryo, ii. 269. + MONTEGAZZA, growth of a cock's-spur inserted into the eye of an ox, ii. + 369. + MONTGOMERY, E., formation of cells, ii. 370. + MOOR, J. H., deterioration of the horse in Malasia, i. 53. + MOORCROFT, Mr., on Hasora wheat, i. 313; + selection of white-tailed yaks, ii. 206; + melon of Kaschmir, ii. 275; + varieties of the apricot cultivated in Ladakh, i. 345; + varieties of the walnut cultivated in Kaschmir, i. 356. + MOORE, Mr., on breeds of pigeons, i. 148, 156, 208, 209, 211. + MOORUK, fertility of, in captivity, ii. 156. + MORLOT, dogs of the Danish Middens, i. 18; + sheep and horse of the bronze period, ii. 427. + _Mormodes ignea_, ii. 53. + MOROCCO, estimation of pigeons in, i. 205. + MORREN, C., on pelorism, ii. 58; + in _Calceolaria_, ii. 346; + non-coincidence of double flowers and variegated leaves, ii. 167. + MORRIS, Mr., breeding of the Kestrel in captivity, ii. 154. + MORTON, Lord, effect of fecundation by a quagga on an Arab mare, i. + 403-404. + MORTON, Dr., origin of the dog, i. 16; + hybrid of zebra and mare, ii. 42. + _Morus alba_, i. 334. + MOSCOW, rabbits of, i. 106, 120; + effects of cold on pear-trees at, ii. 307. + MOSSES, sterility in, ii. 171; + retrogressive metamorphosis in, ii. 361. + MOSS-ROSE, probable origin of, from _Rosa centifolia_, i. 379; + Provence roses produced from seeds of, i. 380. + MOSTO, Cada, on the introduction of rabbits into Porto Santo, i. 113. + MOTTLING of fruits and flowers, i. 400. + MOUFFLON, i. 94. + MOUNTAIN-ASH, ii. 230. + MOUSE, Barbary, ii. 152. + "MOEVEN-TAUBE," i. 148. + MOWBRAY, Mr., on the eggs of game fowls, i. 248; + early pugnacity of game cocks, i. 251; + diminished fecundity of the pheasant in captivity, ii. 155. + MOWBRAY, Mr., reciprocal fecundation of _Passiflora alata_ and + _racemosa_, ii. 137. + MULATTOS, character of, ii. 46. + MULBERRY, i. 334, ii. 256. + MULE and hinny, differences in the, ii. 67-68. + MULES, striped colouring of, ii. 42; + obstinacy of, ii. 45; + production of, among the Romans, ii. 110; + noticed in the Bible, ii. 202. + MUELLER, Fritz, reproduction of orchids, ii. 134-135; + development of crustacea, ii. 368; + number of seeds in a _maxillaria_, ii. 379. + MUELLER, H., on the face and teeth in dogs, i. 34, 73, ii. 345. + MUELLER, J., production of imperfect nails after partial amputation of + the fingers, ii. 15; + tendency to variation, ii. 252; + atrophy of the optic nerve consequent on destruction of the eye, ii. + 297; + on Janus-like monsters, ii. 340; + on gemmation and fission, ii. 358; + identity of ovules and buds, ii. 360; + special affinities of the tissues, ii. 380. + MUELLER, Max, antiquity of agriculture, ii. 243. + MULTIPLICITY of origin of pigeons, hypotheses of, discussed, i. 188-194. + MUNIZ, F., on Niata cattle, i. 90. + MUNRO, R., on the fertilisation of orchids, ii. 133; + reproduction of _Passiflora alata_, ii. 138. + "MURASSA" pigeon, i. 144. + MURPHY, J. J., the structure of the eye not producible by selection, ii. + 222. + _Mus alexandrinus_, ii. 87-88. + _Musa sapientum_, _Chinensis_ and _Cavendishii_, i. 377. + _Muscari comosum_, ii. 185, 316. + MUSCLES, effects of use on, ii. 297. + MUSK duck, feral hybrid of, with the common duck, i. 190. + {466} + MUSMON, female, sometimes hornless, i. 95. + MUTILATIONS, inheritance or non-inheritance of, ii. 22-24, 397. + MYATT, on a five-leaved variety of the strawberry, i. 353. + MYOPIA, hereditary, ii. 8. + MYRIAPODA, regeneration of lost parts in, ii. 15, 294. + + NAILS, growing on stumps of fingers, ii. 394. + NAIS, scission of, ii. 358. + NAMAQUAS, cattle of the, i. 88, ii. 207. + NARCISSUS, double, becoming single in poor soil, ii. 167. + NARVAEZ, on the cultivation of native plants in Florida, i. 312. + _Nasua_, sterility of, in captivity, ii. 152. + "NATAS," or Niatas, a South American breed of cattle, i. 89-91. + NATHUSIUS, H. von, on the pigs of the Swiss lake-dwellings, i. 68; + on the races of pigs, i. 65-68; + convergence of character in highly-bred pigs, i. 73, ii. 241; + causes of changes in the form of the pig's skull, i. 72-73; + changes in breeds of pigs by crossing, i. 78; + change of form in the pig, ii. 279; + effects of disuse of parts in the pig, ii. 299; + period of gestation in the pig, i. 74; + appendages to the jaw in pigs, i. 76; + on _Sus pliciceps_, i. 70; + period of gestation in sheep, i. 97; + on Niata cattle, i. 89; + on short-horn cattle, ii. 118; + on interbreeding, ii. 116; + in the sheep, ii. 120; + in pigs, ii. 122; + unconscious selection in cattle and pigs, ii. 214; + variability of highly selected races, ii. 238. + NATO, P., on the Bizzaria orange, i. 391. + NATURAL selection, its general principles, i. 2-14. + NATURE, sense in which the term is employed, i. 6. + NAUDIN, supposed rules of transmission in crossing plants, ii. 68; + on the nature of hybrids, ii. 48-49; + essences of the species in hybrids, ii. 386, 401; + reversion of hybrids, ii. 36, 49-50; + reversion in flowers by stripes and blotches, ii. 37; + hybrids of _Linaria vulgaris_ and _purpurea_, ii. 94; + pelorism in _Linaria_, ii. 58, 346; + crossing of peloric _Linaria_ with the normal form, ii. 70; + variability in _Datura_, ii. 266; + hybrids of _Datura laevis_ and _stramonium_, i. 392; + prepotency of transmission of _Datura stramonium_ when crossed, ii. 67; + on the pollen of _Mirabilis_ and of hybrids, i. 389; + fertilisation of _Mirabilis_, ii. 363; + crossing of _Chamaerops humilis_ and the date palm, i. 399; + cultivated Cucurbitaceae, i. 357-360, ii. 108; + rudimentary tendrils in gourds, ii. 316; + dwarf _Cucurbitae_, ii. 330; + relation between the size and number of the fruit in _Cucurbita pepo_, + ii. 343; + analogous variation in _Cucurbitae_, ii. 349; + acclimatisation of Cucurbitaceae, ii. 313; + production of fruit by sterile hybrid Cucurbitaceae, ii. 172; + on the melon, i. 360, ii. 108, 275; + incapacity of the cucumber to cross with other species, i. 359. + NECTARINE, i. 336-344; + derived from the peach, i. 337, 339-342; + hybrids of, i. 339; + persistency of characters in seedling, i. 340; + origin of, _ibid._; + produced on peach trees, i. 340-341; + producing peaches, i. 341; + variation in, i. 342-343; + bud-variation in, i. 374; + glands in the leaves of the, ii. 231; + analogous variation in, ii. 348. + NECTARY, variations of, in pansies, i. 369. + NEES, on changes in the odour of plants, ii. 274. + "NEGRO" cat, i. 46. + NEGROES, polydactylism in, ii. 14; + selection of cattle practised by, ii. 207. + NEOLITHIC period, domestication of _Bos longifrons_ and _primigenius_ in + the, i. 81; + cattle of the, distinct from the original species, i. 87; + domestic goat in the, i. 101; + cereals of the, i. 317. + NERVE, optic, atrophy of the, ii. 297. + NEUMEISTER, on the Dutch and German pouter pigeons, i. 138; + on the Jacobin pigeon, i. 154; + duplication of the middle flight feather in pigeons, i. 159; + on a peculiarly coloured breed of pigeons, "Staarhalsige Taube," i. + 161; + fertility of hybrid pigeons, i. 192; + mongrels of the trumpeter pigeon, ii. 66; + period of perfect plumage in pigeons, ii. 77; + advantage of crossing pigeons, ii. 126. + NEURALGIA, hereditary, ii. 79. + NEW ZEALAND, feral cats of, i. 47; + cultivated plants of, i. 311. + NEWFOUNDLAND dog, modification of, in England, i. 42. + NEWMAN, E., sterility of Sphingidae under certain conditions, ii. 158. + NEWPORT, G., non-copulation of _Vanessae_ in confinement, ii. 157; + regeneration of limbs in myriapoda, ii. 294; + fertilisation of the ovule in batrachia, ii. 363. + NEWT, polydactylism in the, ii. 14. + NEWTON, A., absence of sexual distinctions in the Columbidae, i. 162; + production of a "black-shouldered" pea-hen among the ordinary kind, i. + 291; + on hybrid ducks, ii. 157. + NGAMI, Lake, cattle of, i. 88. + "NIATA" cattle, i. 89-91; + resemblance of to _Sivatherium_, i. 89; + {467} + prepotency of transmission of character by, ii. 66. + "NICARD" rabbit, i. 107. + NICHOLSON, Dr., on the cats of Antigua, i. 46; + on the sheep of Antigua, i. 98. + _Nicotiana_, crossing of varieties and species of, ii. 108; + prepotency of transmission of characters in species of, ii. 67; + contabescence of female organs in, ii. 166. + _Nicotiana glutinosa_, ii. 108. + NIEBUHR, on the heredity of mental characteristics in some Roman + families, ii. 65. + NIGHT-BLINDNESS, non-reversion to, ii. 36. + NILSSON, Prof., on the barking of a young wolf, i. 27; + parentage of European breeds of cattle, i. 80, 81; + on _Bos frontosus_ in Scania, i. 81. + NIND, Mr., on the dingo, i. 39. + "NISUS formativus," i. 293, 294, 355. + NITZSCH, on the absence of the oil-gland in certain Columbae, i. 147. + NON-INHERITANCE, causes of, ii. 24-26. + "NONNAIN" pigeon, i. 154. + NORDMANN, dogs of Awhasie, i. 25. + NORMANDY, pigs of, with appendages under the jaw, i. 75. + NORWAY, striped ponies of, i. 58. + NOTT and Gliddon, on the origin of the dog, i. 16; + mastiff represented on an Assyrian tomb, i. 17; + on Egyptian dogs, i. 18; + on the Hare-Indian dog, i. 22. + _Notylia_, ii. 135. + NOURISHMENT, excess of, a cause of variability, ii. 257. + NUMBER, importance of, in selection, ii. 235. + _Numida ptilorhyncha_, the original of the Guinea-fowl, i. 294. + NUN pigeon, i. 155; + known to Aldrovandi, i. 207. + NUTMEG tree, ii. 237. + + OAK, weeping, i. 361, ii. 18, 241; + pyramidal, i. 361; + Hessian, i. 361; + late-leaved, i. 363; + variation in persistency of leaves of, i. 363; + valueless as timber at the Cape of Good Hope, ii. 274; + changes in, dependent on age, i. 387; + galls of the, ii. 282. + OATS, wild, i. 313; + in the Swiss lake-dwellings, i. 319. + OBERLIN, change of soil beneficial to the potato, ii. 146. + ODART, Count, varieties of the vine, i. 333, ii. 278; + bud-variation in the vine, i. 375. + ODOUR and colour, correlation of, ii. 325. + _Oecidium_, ii. 284. + _Oenothera biennis_, bud-variation in, i. 382. + OGLE, W., resemblance of twins, ii. 252. + OIL-GLAND, absence of, in fantail pigeons, i. 147, 160. + OLDFIELD, Mr., estimation of European dogs among the natives of + Australia, ii. 215. + OLEANDER, stock affected by grafting in the, i. 394. + OLLIER, Dr., insertion of the periosteum of a dog beneath the skin of a + rabbit, ii. 369. + _Oncidium_, reproduction of, ii. 133-135, 164. + ONIONS, crossing of, ii. 90; + white, liable to the attacks of fungi and disease, ii. 228, 336. + _Ophrys apifera_, self-fertilisation of, ii. 91; + formation of pollen by a petal in, ii. 392. + _Opuntia leucotricha_, ii. 277. + ORANGE, i. 334-336; + crossing of, ii. 91; + with the lemon, i. 399, ii. 365; + naturalisation of, in Italy, ii. 308; + variation of, in North Italy, ii. 256; + peculiar variety of, ii. 331; + Bizzaria, i. 391; + trifacial, _ibid._ + ORCHIDS, reproduction of, i. 402, 403; ii. 133-135. + ORFORD, Lord, crossing greyhounds with the bulldog, i. 41. + ORGANISMS, origin of, i. 13. + ORGANISATION, advancement in, i. 8. + ORGANS, rudimentary and aborted, ii. 315-318; + multiplication of abnormal, ii. 391. + ORIOLE, assumption of hen-plumage by a male in confinement, ii. 158. + ORKNEY islands, pigs of, i. 70; + pigeons of, i. 184. + ORTHOPTERA, regeneration of hind legs in the, ii. 294. + _Orthosia munda_, ii. 157. + ORTON, R., on the effects of cross-breeding on the female, i. 404; + on the Manx cat, ii. 66; + on mongrels from the silk-fowl, ii. 67. + OSBORNE, Dr., inherited mottling of the iris, ii. 10. + OSPREY, preying on Black-fowls, ii. 230. + OSTEN-SACKEN, Baron, on American oak galls, ii. 282. + OSTEOLOGICAL characters of pigs, i. 66, 67, 71-74; + of rabbits, i. 115-130; + of pigeons, i. 162-167; + of ducks, i. 282-284. + OSTRICH, diminished fertility of the, in captivity, ii. 156. + OSTYAKS, selection of dogs by the, ii. 206. + OTTER, ii. 151. + "OTTER" sheep of Massachusetts, i. 100. + OUDE, feral humped cattle in, i. 79. + OUISTITI, breed in Europe, ii. 153. + {468} + OVARY, variation of, in _Cucurbita moschata_, i. 359; + development of, independently of pollen, i. 403. + _Ovis montana_, i. 99. + OVULES and buds, identity of nature of, ii. 360. + OWEN, Capt., on stiff-haired cats at Mombas, i. 46. + OWEN, Prof. R., palaeontological evidence as to the origin of dogs, i. + 15; + on _Bos longifrons_, i. 81; + on the skull of the "Niata" cattle, i. 89, 90; + on fossil remains of rabbits, i. 104; + on the significance of the brain, i. 124; + on the number of digits in the Ichthyopterygia, ii. 16; + on metagenesis, ii. 366; + theory of reproduction and parthenogenesis, ii. 375. + OWL, eagle, breeding in captivity, ii. 154. + OWL pigeon, i. 148; + African, figured, i. 149; + known in 1735, i. 209. + _Oxalis_, trimorphic species of, ii. 400. + _Oxalis rosea_, ii. 132. + OXLEY, Mr., on the nutmeg tree, ii. 237. + OYSTERS, differences in the shells of, ii. 280. + + PACA, sterility of the, in confinement, ii. 152. + PACIFIC islands, pigs of the, i. 70. + PADUA, earliest known flower garden at, ii. 217. + PADUAN fowl of Aldrovandi, i. 247. + _Paeonia moutan_, ii. 205. + PAEONY, tree, ancient cultivation of, in China, ii. 205. + PAMPAS, feral cattle on the, i. 85. + _Pandanus_, ii. 256. + PANGENESIS, hypothesis of, ii. 357-404. + _Panicum_, seeds of, used as food, i. 309; + found in the Swiss lake-dwellings, i. 317. + PANSY, i. 368-370. + PAPPUS, abortion of the, in _Carthamus_, ii. 316. + PAGET, on the Hungarian sheep dog, i. 24. + PAGET, inheritance of cancer, ii. 7; + hereditary elongation of hairs in the eyebrow, ii. 8; + period of inheritance of cancer, ii. 79-80; + on _Hydra_, ii. 293; + on the healing of wounds, ii. 294; + on the reparation of bones, _ibid._; + growth of hair near inflamed surfaces or fractures, ii. 295; + on false membranes, _ibid._; + compensatory development of the kidney, ii. 300; + bronzed skin in disease of supra-renal capsules, ii. 331; + unity of growth and gemmation, ii. 359; + independence of the elements of the body, ii. 369; + affinity of the tissues for special organic substances, ii. 380. + PALLAS, on the influence of domestication upon the sterility of + intercrossed species, i. 31, 83, 193, ii. 109; + hypothesis that variability is wholly due to crossing, i. 188, 374, ii. + 250, 264; + on the origin of the dog, i. 16; + variation in dogs, i. 33; + crossing of dog and jackal, i. 25; + origin of domestic cats, i. 43; + origin of Angora cat, i. 45; + on wild horses, i. 52, 60; + on Persian sheep, i. 94; + on Siberian fat-tailed sheep, ii. 279; + on Chinese sheep, ii. 315; + on Crimean varieties of the vine, i. 333; + on a grape with rudimentary seeds, ii. 316; + on feral musk-ducks, ii. 46; + sterility of Alpine plants in gardens, ii. 163; + selection of white-tailed yaks, ii. 206. + _Paradoxurus_, sterility of species of, in captivity, ii. 151. + PARAGUAY, cats of, i. 46; + cattle of, i. 89; + horses of, ii. 102; + dogs of, ii. 102; + black-skinned domestic fowl of, i. 232. + PARALLEL variation, ii. 348-352. + PARAMOS, woolly pigs of, i. 78. + PARASITES, liability to attacks of, dependent on colour, ii. 228. + PARIAH dog, with crooked legs, i. 17; + resembling the Indian wolf, i. 24. + PARISET, inheritance of handwriting, ii. 6. + PARKER, W. K., number of vertebrae in fowls, i. 266. + PARKINSON, Mr., varieties of the hyacinth, i. 370. + PARKYNS, Mansfield, on _Columba guinea_, i. 183. + PARMENTIER, differences in the nidification of pigeons, i. 178; + on white pigeons, ii. 230. + PARROTS, general sterility of, in confinement, ii. 155; + alteration of plumage of, ii. 280. + PARSNIP, reversion in, ii. 31; + influence of selection on, ii. 201; + experiments on, ii. 277; + wild, enlargement of roots of, by cultivation, i. 326. + PARTHENOGENESIS, ii. 359, 364. + PARTRIDGE, sterility of, in captivity, ii. 156. + PARTURITION, difficult, hereditary, ii. 8. + _Parus major_, ii. 231. + _Passiflora_, self-impotence in species of, ii. 137-138; + contabescence of female organs in, ii. 166. + _Passiflora alata_, fertility of, when grafted, ii. 188. + PASTURE and climate, adaptation of breeds of sheep to, i. 96, 97. + PASTRANA, Julia, peculiarities in the hair and teeth of, ii. 328. + PATAGONIA, crania of pigs from, i. 77. + PATAGONIAN rabbit, i. 105. + {469} + PATERSON, R., on the Arrindy silk moth, ii. 306. + PAUL, W., on the hyacinth, i. 370; + varieties of pelargoniums, i. 378; + improvement of pelargoniums, ii. 216. + _Pavo cristatus_ and _muticus_, hybrids of, i. 290. + _Pavo nigripennis_, i. 290-291. + "PAVODOTTEN-TAUBE," i. 141. + PEACH, i. 336-344; + derived from the almond, i. 337; + stones of, figured, _ibid._; + contrasted with almonds, i. 338; + double-flowering, i. 338-339, 343; + hybrids of, i. 339; + persistency of races of, _ibid._; + trees producing nectarines, i. 340-341; + variation in, i. 342-343, ii. 256; + bud-variation in, i. 374; + pendulous, ii. 18; + variation by selection in, ii. 218; + peculiar disease of the, ii. 228; + glands on the leaves of the, ii. 231; + antiquity of the, ii. 308; + increased hardiness of the, _ibid._; + varieties of, adapted for forcing, ii. 310; + yellow-fleshed, liable to certain diseases, ii. 336. + PEACH-ALMOND, i. 338. + PEAFOWL, origin of, i. 290; + japanned or black-shouldered, i. 290-291; + feral, in Jamaica, i. 190; + comparative fertility of, in wild and tame states, ii. 112, 268; + white, ii. 332. + PEARS, i. 350; + bud-variation in, i. 376; + reversion in seedling, ii. 31; + inferiority of, in Pliny's time, ii. 215; + winter nelis, attacked by aphides, ii. 231; + soft-barked varieties of, attacked by wood-boring beetles, ii. 231; + origination of good varieties of, in woods, ii. 260; + Forelle, resistance of, to frost, ii. 306. + PEAS, i. 326-330; + origin of, 326; + varieties of, 326-329; + found in Swiss lake-dwellings, i. 317, 319, 326-329; + fruit and seeds figured, i. 328; + persistency of varieties, i. 329; + intercrossing of varieties, i. 330, 397, ii. 129; + effect of crossing on the female organs in, i. 398; + double-flowered, ii. 168; + maturity of, accelerated by selection, ii. 201; + varieties of, produced by selection, ii. 218; + thin-shelled, liable to the attacks of birds, ii. 231; + reversion of, by the terminal seed in the pod, ii. 347. + PECCARY, breeding of the, in captivity, ii. 150. + PEDIGREES of horses, cattle, greyhounds, game-cocks, and pigs, ii. 3. + PEGU, cats of, i. 47; + horses of, i. 53. + PELARGONIUMS, multiple origin of, i. 364; + zones of, i. 366; + bud-variation in, i. 378; + variegation in, accompanied by dwarfing, i. 384; + pelorism in, ii. 167, 345; + by reversion, ii. 59; + advantage of change of soil to, ii. 147; + improvement of, by selection, ii. 216; + scorching of, ii. 229; + numbers of, raised from seed, ii. 235; + effects of conditions of life on, ii. 274; + stove-variety of, ii. 311; + correlation of contracted leaves and flowers in, ii. 330-331. + _Pelargonium fulgidum_, conditions of fertility in, ii. 164. + "PELONES," a Columbian breed of cattle, i. 88. + PELORIC flowers, tendency of, to acquire the normal form, ii. 70; + fertility or sterility of, ii. 166-167. + PELORIC races of _Gloxinia speciosa_ and _Antirrhinum majus_, i. 365. + PELORISM, ii. 58-60, 345-346. + PELVIS, characters of, in rabbits, i. 122-123; + in pigeons, i. 166; + in fowls, i. 268; + in ducks, i. 284. + PEMBROKE cattle, i. 81. + PENDULOUS trees, i. 361, ii. 348; + uncertainty of transmission of, ii. 18-19. + PENGUIN ducks, i. 280, 282; + hybrid of the, with the Egyptian goose, i. 282. + PENNANT, production of wolf-like curs at Fochabers, i. 37; + on the Duke of Queensberry's wild cattle, i. 84. + _Pennisetum_, seeds of, used as food in the Punjab, i. 309. + _Pennisetum distichum_, seeds of, used as food in Central Africa, i. 308. + PERCIVAL, Mr., on inheritance in horses, ii. 10; + on horn-like processes in horses, i. 50. + _Perdix rubra_, occasional fertility of, in captivity, ii. 156. + PERIOD of action of causes of variability, ii. 269. + PERIOSTEUM of a dog, producing bone in a rabbit, ii. 369. + PERIWINKLE, sterility of, in England, ii. 170. + PERSIA, estimation of pigeons in, i. 205; + carrier pigeon of, i. 141; + tumbler pigeon of, i. 150; + cats of, i. 45-47; + sheep of, i. 94. + _Persica intermedia_, i. 338. + PERSISTENCE of colour in horses, i. 50; + of generic peculiarities, i. 111. + PERU, antiquity of maize in, i. 320; + peculiar potato from, i. 331; + selection of wild animals practised by the Incas of, ii. 207-208. + "PERUECKEN-TAUBE," i. 154. + PETALS, rudimentary, in cultivated plants, ii. 316; + producing pollen, ii. 392. + PETUNIAS, multiple origin of, i. 364; + double-flowered, ii. 167. + "PFAUEN-TAUBE," i. 146. + _Phacochoerus Africanus_, i. 76. + _Phalaenopsis_, pelorism in, ii. 346. + PHALANGES, deficiency of, ii. 73. + {470} + _Phaps chalcoptera_, ii. 349. + _Phaseolus multiflorus_, ii. 309, 322. + _Phaseolus vulgaris_, ii. 309. + _Phasianus pictus_, i. 275. + _Phasianus Amherstiae_, i. 275. + PHEASANT, assumption of male plumage by the hen, ii. 51; + wildness of hybrids of, with the common fowl, ii. 45; + prepotency of the, over the fowl, ii. 68; + diminished fecundity of the, in captivity, ii. 155. + PHEASANTS, golden and Lady Amherst's, i. 275. + PHEASANT-FOWLS, i. 244. + PHILIPEAUX, regeneration of limbs in the salamander, ii. 376. + PHILIPPAR, on the varieties of wheat, i. 314. + PHILIPPINE Islands, named breeds of game fowl in the, i. 232. + PHILLIPS, Mr., on bud-variation in the potato, i. 385. + _Phlox_, bud-variation by suckers in, i. 384. + PHTHISIS, affection of the fingers in, ii. 332. + PICKERING, Mr., on the grunting voice of humped cattle, i. 79; + occurrence of the head of a fowl in an ancient Egyptian procession, i. + 246; + seeding of ordinarily seedless fruits, ii. 168; + extinction of ancient Egyptian breeds of sheep and oxen, ii. 425; + on an ancient Peruvian gourd, ii. 429. + PICOTEES, effect of conditions of life on, ii. 273. + PICTET, A., oriental names of the pigeon, i. 205. + PICTET, Prof., origin of the dog, i. 15; + on fossil oxen, i. 81. + PIEBALDS, probably due to reversion, ii. 37. + PIGEAUX, hybrids of the hare and rabbit, ii. 99, 152. + PIGEON a cravate, i. 148. + PIGEON Bagadais, i. 142, 143. + PIGEON coquille, i. 155. + PIGEON cygne, i. 143. + PIGEON heurte, i. 156. + PIGEON Patu plongeur, i. 156. + PIGEON Polonais, i. 144. + PIGEON Romain, i. 142, 144. + PIGEON tambour, i. 154. + PIGEON Turc, i. 139. + PIGEONS, origin of, i. 131-134, 180-204; + classified table of breeds of, i. 136; + pouter, i. 137-139; + carrier, i. 139-142; + runt, i. 142-144; + barbs, i. 144-146; + fantail, i. 146-148; + turbit and owl, i. 148-149; + tumbler, i. 150-153; + Indian frill-back, i. 153; + Jacobin, i. 154; + trumpeter, i. 154; + other breeds of, i. 155-157; + differences of, equal to generic, i. 157-158; + individual variations of, i. 158-160; + variability of peculiarities characteristic of breeds in, i. 161; + sexual variability in, i. 161-162; + osteology of, i. 162-167; + correlation of growth in, i. 167-171, ii. 321; + young of some varieties naked when hatched, i. 170, ii. 332; + effects of disuse in, i. 172-177; + settling and roosting in trees, i. 181; + floating in the Nile to drink, i. 181; + Dovecot, i. 185-186; + arguments for unity of origin of, i. 188-204; + feral in various places, i. 190, ii. 33; + unity of coloration in, i. 195-197; + reversion of mongrel, to coloration of, _C. livia_, i. 197-202; + history of the cultivation of, i. 205-207; + history of the principal races of, i. 207-212; + mode of production of races of, i. 212-224; + reversion in, ii. 29, 47; + by age, ii. 38; + produced by crossing in, ii. 40, 48; + prepotency of transmission of character in breeds of, ii. 66-67; + sexual differences in some varieties of, ii. 74; + period of perfect plumage in, ii. 77; + effect of segregation on, ii. 86; + preferent pairing of, within the same breed, ii. 103; + fertility of, increased by domestication, ii. 112, 155; + effects of interbreeding and necessity of crossing, ii. 125-126; + indifference of, to change of climate, ii. 161; + selection of, ii. 195, 199, 204; + among the Romans, ii. 202; + unconscious selection of, ii. 211, 214; + facility of selection of, ii. 234; + white, liable to the attacks of hawks, ii. 230; + effects of disuse of parts in, ii. 298; + fed upon meat, ii. 304; + effect of first male upon the subsequent progeny of the female, i. 405; + homology of the leg and wing feathers in, ii. 323; + union of two outer toes in feather-legged, _ibid._; + correlation of beak, limbs, tongue, and nostrils in, ii. 324; + analogous variation in, ii. 349-350; + permanence of breeds of, ii. 429. + PIGS, of Swiss lake-dwellings, i. 67-68; + types of, derived from _Sus scrofa_ and _Sus indica_, i. 66-67; + Japanese (_Sus pliciceps_, Gray), figured, i. 69; + of Pacific islands, i. 70, ii. 87; + modifications, of skull in, i. 71-73; + length of intestines in, i. 73, ii. 303; + period of gestation of, i. 74; + number of vertebrae and ribs in, i. 74; + anomalous forms, i. 75-76; + development of tusks and bristles in, i. 76; + striped young of, i. 76-77; + reversion of feral, to wild type, i. 77-78, ii. 33, 47; + production and changes of breeds of, by intercrossing, i. 78; + effects produced by the first male upon the subsequent progeny of the + female, i. 404; + two-legged race of, ii. 4; + {471} + polydactylism in, ii. 14; + cross-reversion in, ii. 35; + hybrid, wildness of, ii. 45; + monstrous development of a proboscis in, ii. 57; + disappearance of tusks in male under domestication, ii, 74; + solid hoofed, ii. 429; + crosses of, ii. 93, 95; + mutual fertility of all varieties of, ii. 110; + increased fertility by domestication, ii. 111; + ill effects of close interbreeding in, ii. 121-122; + influence of selection on, ii. 198; + prejudice against certain colours in, ii. 210, 229, 336; + unconscious selection of, ii. 214; + black Virginian, ii. 227, 336; + similarity of the best breeds of, ii. 241; + change of form in, ii. 279; + effects of disuse of parts in, ii. 299; + ears of, ii. 301; + correlations in, ii. 327; + white, buck-wheat injurious to, ii. 337; + tail of, grafted upon the back, ii. 369; + extinction of the older races of, ii. 426. + PIMENTA, ii. 91. + PIMPERNEL, ii. 190. + PINE-APPLE, sterility and variability of the, ii. 262. + PINK, Chinese. 322. + PINKS, bud-variation in, i. 381; + improvement of, ii. 216. + _Pinus pumilio_, _Mughus_, and _nana_, varieties of _P. sylvestris_, i. + 363. + _Pinus sylvestris_, i. 363, ii. 310; + hybrids of, with _P. nigricans_, ii. 130. + PIORRY, on hereditary disease, ii. 7, 78. + _Pistacia lentiscus_, ii. 274. + PISTILS, rudimentary, in cultivated plants, ii. 316. + PISTOR, sterility of some mongrel pigeons, i. 192; + fertility of pigeons, ii. 112. + _Pisum arvense_ and _sativum_, i. 326. + PITYRIASIS versicolor, inheritance of, ii. 79. + PLANCHON, G., on a fossil vine, i. 332; + sterility of _Jussiaea grandifiora_ in France, ii. 170. + PLANE tree, variety of the, i. 362. + PLANTIGRADE carnivora, general sterility of the, in captivity, ii. 151. + PLANTS, progress of cultivation of, i. 305-312; + cultivated, their geographical derivation, i. 311; + crossing of, ii. 98, 99, 127; + comparative fertility of wild and cultivated, ii. 112-113; + self-impotent, ii. 131-140; + dimorphic and trimorphic, ii. 132, 140; + sterility of, from changed conditions, ii. 163-165; + from contabescence of anthers, ii. 165-166; + from monstrosities, ii. 166-167; + from doubling of the flowers, ii. 167-168; + from seedless fruit, ii. 168; + from excessive development of vegetative organs, ii. 168-171; + influence of selection on, ii. 199-201; + variation by selection, in useful parts of, ii. 217-219; + variability of, ii. 237; + variability of, induced by crossing, ii. 265; + direct action of change of climate on, ii. 277; + change of period of vegetation in, ii. 304-305; + varieties of, suitable to different climates, ii. 306; + correlated variability of, ii. 330-331; + antiquity of races of, ii. 429. + PLASTICITY, inheritance of, ii. 241. + PLATEAU, F., on the vision of amphibious animals, ii. 223. + _Platessa flesus_, ii. 53. + PLATO, notice of selection in breeding dogs by, ii. 212. + PLICA polonica, ii. 276. + PLINY, on the crossing of shepherd's dogs with the wolf, i. 24; + on Pyrrhus' breed of cattle, ii. 202; + on the estimation of pigeons among the Romans, i. 205; + pears described by, ii. 215. + PLUM, i. 345-347; + stones figured, i. 345; + varieties of the, i. 345-346, ii. 219; + bud-variation in the, i. 375; + peculiar disease of the, ii. 227; + flower-buds of, destroyed by bullfinches, ii. 232; + purple-fruited, liable to certain diseases, ii. 336. + PLUMAGE, inherited peculiarities of, in pigeons, i. 160-161; + sexual peculiarities of, in fowls, i. 251-255. + PLURALITY of races, Pouchet's views on, i. 2. + _Poa_, seeds of, used as food, i. 308; + species of, propagated by bulblets, ii. 170. + PODOLIAN cattle, i. 80. + POINTERS, modification of, i. 42; + crossed with the foxhound, ii. 95. + POIS sans parchemin, ii. 231. + POITEAU, origin of _Cytisus Adami_, i. 390; + origin of cultivated varieties of fruit-trees, ii. 260. + POLISH fowl, i. 227, 250, 254, 256-257, 262; + skull figured, i. 262; + section of skull figured, i. 263; + development of protuberance of skull, i. 250; + furcula figured, i. 268. + POLISH, or Himalayan rabbit, i. 108. + POLLEN, ii. 363-364; + action of, ii. 108; + injurious action of, in some orchids, ii. 134-135; + resistance of, to injurious treatment, ii. 164; + prepotency of, ii. 187. + POLLOCK, Sir F., transmission of variegated leaves in _Ballota nigra_, i. + 383; + on local tendency to variegation, ii. 274. + POLYANTHUS, ii. 21. + POLYDACTYLISM, inheritance of, ii. 12-16; + significance of, ii. 16-17. + _Polyplectron_, i. 255. + PONIES, most frequent on islands and mountains, i. 52; + Javanese, i. 53. + POOLE, Col., on striped Indian horses, i. 58, 59; + {472} + on the young of _Asinus indicus_, ii. 43. + POPLAR, Lombardy, i. 361. + POEPPIG, on Cuban wild dogs, i. 27. + POPPY, found in the Swiss lake-dwellings, i. 317, 319; + with the stamens converted into pistils, i. 365; + differences of the, in different parts of India, ii. 165; + monstrous, fertility of, ii. 166; + black-seeded, antiquity of, ii. 429. + PORCUPINE, breeding of, in captivity, ii. 152. + PORCUPINE family, ii. 4, 76. + _Porphyrio_, breeding of a species of, in captivity, ii. 156. + PORTAL, on a peculiar hereditary affection of the eye, ii. 9. + PORTO Santo, feral rabbits of, i. 112. + _Potamochoerus penicillatus_, ii. 150. + POTATO, i. 330-331; + bud-variation by tubers in the, i. 384-385; + graft-hybrid of, by union of half-tubers, i. 395; + individual self-impotence in the, ii. 137; + sterility of, ii. 169; + advantage of change of soil to the, ii. 146; + relation of tubers and flowers in the, ii. 343. + POTATO, sweet, sterility of the, in China, ii. 169; + varieties of the, suited to different climates, ii. 309. + POUCHET, M., his views on plurality of races, i. 2. + POUTER pigeons, i. 137-139; + furcula figured, i. 167; + history of, i. 207. + POWIS, Lord, experiments in crossing humped and English cattle, i. 83, + ii. 45. + POYNTER, Mr., on a graft-hybrid rose, i. 396. + PRAIRIE wolf, i. 22. + PRECOCITY of highly-improved breeds, ii. 321. + PREPOTENCY of pollen, ii. 187. + PREPOTENCY of transmission of character, ii. 65, 174; + in the Austrian emperors and some Roman families, ii. 65; + in cattle, ii. 65-66; + in sheep, ii. 66; + in cats, _ibid._; + in pigeons, ii. 66-67; + in fowls, ii. 67; + in plants, _ibid._; + in a variety of the pumpkin, i. 358; + in the jackal over the dog, ii. 67; + in the ass over the horse, _ibid._; + in the pheasant over the fowl, ii. 68; + in the penguin duck over the Egyptian goose, _ibid._; + discussion of the phenomena of, ii. 69-71. + PRESCOTT, Mr., on the earliest known European flower-garden, ii. 217. + PRESSURE, mechanical, a cause of modification, ii. 344-345. + PREVOST and Dumas, on the employment of several spermatozoids to + fertilise one ovule, ii. 363. + PRICE, Mr., variations in the structure of the feet in horses, i. 50. + PRICHARD, Dr., on polydactylism in the negro, ii. 14; + on the Lambert family, ii. 77; + on an albino negro, ii. 229; + on Plica polonica, ii. 276. + PRIMROSE, ii. 21; + double, rendered single by transplantation, ii. 167. + _Primula_, intercrossing of species of, i. 336; + contabescence in, ii. 166; + hose and hose, i. 365; + with coloured calyces, sterility of, ii. 166. + _Primula sinensis_, reciprocally dimorphic, ii. 132. + _Primula veris_, ii. 21, 109, 182. + _Primula vulgaris_, ii. 21, 109. + PRINCE, Mr., on the intercrossing of strawberries, i. 352. + _Procyon_, sterility of, in captivity, ii. 152. + PROLIFICACY, increased by domestication, ii. 174. + PROPAGATION, rapidity of, favourable to selection, ii. 297. + PROTOZOA, reproduction of the, ii. 376. + _Prunus armeniaca_, i. 344-345. + _Prunus avium_, i. 347. + _Prunus cerasus_, i. 347, 375. + _Prunus domestica_, i. 345. + _Prunus insititia_, i. 345-347. + _Prunus spinosa_, i. 345. + PRUSSIA, wild horses in, i. 60. + _Psittacus erithacus_, ii. 155. + _Psittacus macoa_, ii. 155. + _Psophia_, general sterility of, in captivity, ii. 157. + PTARMIGAN fowls, i. 228. + _Pulex penetrans_, ii. 275. + PUMPKINS, i. 357. + PUNO ponies of the Cordillera, i. 52. + PURSER, Mr. on _Cytisus Adami_, i. 389. + PUSEY, Mr., preference of hares and rabbits for common rye, ii. 232. + PUTSCHE and Vertuch, varieties of the potato, i. 330. + PUVIS, effects of foreign pollen on apples, i. 401; + supposed non-variability of monotypic genera, ii. 266. + _Pyrrhula vulgaris_, ii. 232; + assumption of the hen-plumage by the male, in confinement, ii. 158. + PYRRHUS, his breed of cattle, ii. 202. + _Pyrus_, fastigate Chinese species of, ii. 277. + _Pyrus acerba_, i. 348. + _Pyrus aucuparia_, ii. 230. + _Pyrus communis_, i. 350, 376. + _Pyrus malus_, i. 348, 376. + _Pyrus paradisiaca_, i. 348. + _Pyrus praecox_, i. 348. + + QUAGGA, effect of fecundation by, on the subsequent progeny of a mare, i. + 403-404. + QUATREFAGES, A. de, on the burrowing of a bitch to litter, i. 77; + {473} + selection in the silkworm, i. 301; + development of the wings in the silkmoth, i. 303, ii. 298; + on varieties of the mulberry, i. 334; + special raising of eggs of the silkmoth, ii. 197; + on disease of the silkworm, ii. 228; + on monstrosities in insects, ii. 269, 391; + on the Anglo-Saxon race in America, ii. 276; + on a change in the breeding season of the Egyptian goose, ii. 304; + fertilisation of the _Teredo_, ii. 363; + tendency to similarity in the best races, ii. 241; + on his "_tourbillon vital_," ii. 61; + on the independent existence of the sexual elements, ii. 360. + _Quercus cerris_, i. 363. + _Quercus robur_ and _pedunculata_, hybrids of, ii. 130. + QUINCE, pears grafted on the, ii. 259. + + RABBITS, domestic, their origin, i. 103-105; + of Mount Sinai and Algeria, i. 105; + breeds of, i. 105-111; + Himalayan, Chinese, Polish, or Russian, i. 108-111, ii. 97; + feral, i. 111-115; + of Jamaica, i. 112; + of the Falkland islands, i. 112; + of Porto Santo, i. 112-115, ii. 103, 279; + osteological characters of, i. 115-129; + discussion of modifications in, i. 129-130; + one-eared, transmission of peculiarity of, ii. 12; + reversion in feral, ii. 33; + in the Himalayan, ii. 41; + crossing of white and coloured Angora, ii. 92; + comparative fertility of wild and tame, ii. 111; + high-bred, often bad breeders, ii. 121; + selection of, ii. 204; + white, liable to destruction, ii. 230; + effects of disuse of parts in, ii. 298; + skull of, affected by drooping ears, ii. 301; + length of intestines in, ii. 303; + correlation of ears and skull in, ii. 324-325; + variations in skull of, ii. 350; + periosteum of a dog producing bone in, ii. 369. + RACE-HORSE, origin of, i. 54. + RACES, modification and formation of, by crossing, ii. 95-99; + natural and artificial, ii. 245; + Pouchet's views on plurality of, i. 2; + of pigeons, i. 207-212. + RADISHES, i. 326; crossing of, ii. 90; + varieties of, ii. 217-218. + RADCLYFFE, W. F., effect of climate and soil on strawberries, i. 354; + constitutional differences in roses, i. 367. + RADLKOFER, retrogressive metamorphosis in mosses and algae, ii. 361. + RAFFLES, Sir Stamford, on the crossing of Javanese cattle with _Bos + sondaicus_, ii. 206. + RAM, goat-like, from the Cape of Good Hope, ii. 66. + RANCHIN, heredity of diseases, ii. 7. + RANGE of gallinaceous birds on the Himalaya, i. 237. + _Ranunculus ficaria_, ii. 170. + _Ranunculus repens_, ii. 168. + RAPE, i. 325. + _Raphanus sativus_, ii. 343. + RASPBERRY, yellow-fruited, ii. 230. + RATTLESNAKE, experiments with poison of the, ii. 289. + RAVEN, stomach of, affected by vegetable diet, ii. 302. + RAWSON, A., self-impotence in hybrids of _Gladiolus_, ii. 139-140. + RE, Le Compte, on the assumption of a yellow colour by all varieties of + maize, i. 321. + REAUMUR, effect of confinement upon the cock, ii. 52; + fertility of fowls in most climates, ii. 161. + REED, Mr., atrophy of the limbs of rabbits, consequent on the destruction + of their nerves, ii. 297. + REGENERATION of amputated parts in man, ii. 14; + in the human embryo, ii. 15; + in the lower vertebrata, insects, and myriapoda, _ibid._ + REINDEER, individuals recognised by the Laplanders, ii. 251. + REGNIER, early cultivation of the cabbage by the Celts, i. 324. + REISSEK, experiments in crossing _Cytisus purpureus_ and _laburnum_, i. + 389; + modification of a _Thesium_ by _Oecidium_, ii. 284. + RELATIONS, characters of, reproduced in children, ii. 34. + RENGGER, occurrence of jaguars with crooked legs in Paraguay, i. 17; + naked dogs of Paraguay, i. 23, 31, ii. 93, 102; + feral dogs of La Plata, i. 27; + on the aguara, i. 26; + cats of Paraguay, i. 46, ii. 86, 151; + dogs of Paraguay, ii. 87; + feral pigs of Buenos Ayres, i. 77; + on the refusal of wild animals to breed in captivity, ii. 149; + on _Dicotyles labiatus_, ii. 150; + sterility of plantigrade carnivora in captivity, ii. 152; + on _Cavia aperea_, ii. 152; + sterility of _Cebus azarae_ in captivity, ii. 153; + abortions produced by wild animals in captivity, ii. 158. + REPRODUCTION, sexual and asexual, contrasted, ii. 361; + unity of forms of, ii. 383; + antagonism of, to growth, ii. 384. + _Reseda odorata_, ii. 237. + RETINITIS, pigmentary, in deaf-mutes, ii. 328. + REVERSION, ii. 28-29, 372-373, 396, 398-402; + in pigeons, ii. 29; + in cattle, ii. 29-30; + in sheep, ii. 30; + in fowls, ii. 31; + in the heartsease, _ibid._; + in vegetables, _ibid._; + in feral animals and plants, ii. 32-34; + to characters derived from a previous cross in man, dogs, pigeons, + pigs, and fowls, ii. 34-35; + {474} + in hybrids, ii. 36; + by bud-propagation in plants, ii. 36-38; + by age in fowls, cattle, &c., ii. 38-39; + caused by crossing, ii. 39-51; + explained by latent characters, ii. 51-56; + producing monstrosities, ii. 57; + producing peloric flowers, ii. 58-60; + of feral pigs to the wild type, i. 77-78; + of supposed feral rabbits to the wild type, i. 104, 111, 115; + of pigeons, in coloration, when crossed, i. 197-202; + in fowls, i. 239-246; + in the silkworm, i. 302; + in the pansy, i. 369; + in a pelargonium, i. 378; + in Chrysanthemums, i. 379; + of varieties of the China rose in St. Domingo, i. 380; + by buds in pinks and carnations, i. 381; + of laciniated varieties of trees to the normal form, i. 382; + in variegated leaves of plants, i. 383-384; + in tulips, i. 386; + of suckers of the seedless barberry to the common form, i. 384; + by buds in hybrids of _Tropaeolum_, i. 392; + in plants, i. 409; + of crossed peloric snapdragons, ii. 71; + analogous variations due to, ii. 349-351. + REYNIER, selection practised by the Celts, ii. 202-203. + RHINOCEROS, breeding in captivity in India, ii. 150. + _Rhododendron_, hybrid, ii. 265. + _Rhododendron ciliatum_, ii. 277. + _Rhododendron Dalhousiae_, effect of pollen of _R. Nuttallii_ upon, i. + 400. + RHUBARB, not medicinal when grown in England, ii. 274. + _Ribes grossularia_, i. 354-356, 376. + _Ribes rubrum_, i. 376. + RIBS, number and characters of, in fowls, i. 267; + characters of, in ducks, i. 283-284. + RICE, Imperial, of China, ii. 205; + Indian varieties of, ii. 256; + variety of, not requiring water, ii. 305. + RICHARDSON, H. D., on jaw-appendages in Irish pigs, i. 76; + management of pigs in China, i. 68; + occurrence of striped young in Westphalian pigs, i. 76; + on crossing pigs, ii. 95; + on interbreeding pigs, ii. 122; + on selection in pigs, ii. 194. + RICHARDSON, Sir John, observations on the resemblance between North + American dogs and wolves, i. 21-22; + on the burrowing of wolves, i. 27; + on the broad feet of dogs, wolves, and foxes in North America, i. 40; + on North American horses scraping away the snow, i. 53. + _Ricinus_, annual in England, ii. 305. + RIEDEL, on the "Bagadotte" pigeon, i. 141; + on the Jacobin pigeon, i. 154; + fertility of hybrid pigeons, i. 192. + RINDERPEST, ii. 378. + RISSO, on varieties of the orange, i. 336, ii. 308, 331. + RIVERS, Lord, on the selection of greyhounds, ii. 235. + RIVERS, Mr., persistency of characters in seedling potatoes, i. 331; + on the peach, i. 338, 339; + persistency of races in the peach and nectarine, i. 339, 340; + connexion between the peach and the nectarine, i. 340; + persistency of character in seedling apricots, i. 344; + origin of the plum, i. 345; + seedling varieties of the plum, i. 346; + persistency of character in seedling plums, i. 347; + bud-variation in the plum, i. 375; + plum, attacked by bullfinches, ii. 232; + seedling apples with surface-roots, i. 349; + variety of the apple found in a wood, ii. 260; + on roses, i. 366-367; + bud-variation in roses, i. 379-381; + production of Provence roses from seeds of the moss-rose, i. 380; + effect produced by grafting on the stock in jessamine, i. 394; + in the ash, i. 394; + on grafted hazels, i. 395; + hybridisation of a weeping thorn, ii. 18; + experiments with the seed of the weeping elm and ash, ii. 19; + variety of the cherry with curled petals, ii. 232. + RIVIERE, reproduction of _Oncidium Cavendishianum_, ii. 133. + ROBERTS, Mr., on inheritance in the horse, ii. 10. + ROBERTSON, Mr., on glandular-leaved peaches, i. 343. + ROBINET, on the silkworm, i. 301-304, ii. 197. + _Robinia_, ii. 274. + ROBSON, Mr., deficiencies of half-bred horses, ii. 11. + ROBSON, Mr., on the advantage of change of soil to plants, ii. 146-147; + on the growth of the verbena, ii. 273; + on broccoli, ii. 310. + ROCK pigeon, measurements of the, i. 134; + figured, i. 135. + RODENTS, sterility of, in captivity, ii. 152. + _Rodriguezia_, ii. 134, 135. + RODWELL, J., poisoning of horses by mildewed tares, ii. 337. + ROHILCUND, feral humped cattle in, i. 79. + ROLLE, F., on the history of the peach, ii. 308. + ROLLER-PIGEONS, Dutch, i. 151. + ROLLESTON, Prof., incisor teeth affected in form in cases of pulmonary + tubercle, ii. 332. + ROMANS, estimation of pigeons by, i. 205; + breeds of fowls possessed by, i. 231, 247. + {475} + ROOKS, pied, ii. 77. + _Rosa_, cultivated species of, i. 366. + _Rosa devoniensis_, graft-hybrid produced by, on the white Banksian rose, + i. 396. + _Rosa indica_ and _centifolia_, fertile hybrids of, i. 366. + _Rosa spinosissima_, history of the culture of, i. 367. + ROSELLINI, on Egyptian dogs, i. 17. + ROSES, i. 366-367; + origin of, i. 364; + bud-variation in, i. 379-381; + Scotch, doubled by selection, ii. 200; + continuous variation of, ii. 241; + effect of seasonal conditions on, ii. 273; + noisette, ii. 308; + galls of, ii. 284. + ROUENNAIS rabbit, i. 105. + ROULIN, on the dogs of Juan Fernandez, i. 27; + on South American cats, i. 46; + striped young pigs, i. 77; + feral pigs in South America, i. 78, ii. 33; + on Columbian cattle, i. 88, ii. 205, 226; + effects of heat on the hides of cattle in South America, i. 92; + fleece of sheep in the hot valleys of the Cordilleras, i. 98; + diminished fertility of these sheep, ii. 161; + on black-boned South American fowls, i. 258; + variation of the guinea-fowl in tropical America, i. 294; + frequency of striped legs in mules, ii. 42; + geese in Bogota, ii. 161; + sterility of fowls introduced into Bolivia, ii. 162. + ROY, M., on a variety of _Magnolia grandiflora_, ii. 308. + ROYLE, Dr., Indian varieties of the mulberry, i. 334; + on _Agave vivipara_, ii. 169; + variety of rice not requiring irrigation, ii. 305; + sheep from the Cape in India, ii. 306. + _Rubus_, pollen of, ii. 268. + RUDIMENTARY organs, i. 12, ii. 315-318. + RUFZ de Lavison, extinction of breeds of dogs in France, ii. 425. + RUMINANTS, general fertility of, in captivity, ii. 150. + RUMPLESS fowls, i. 230. + RUNTS, i. 142-144; + history of, i. 210; + lower jaws and skull figured, i. 164-165. + RUSSIAN or Himalayan rabbit, i. 108. + RUETIMEYER, Prof., dogs of the Neolithic period, i. 19; + horses of Swiss lake-dwellings, i. 49; + diversity of early domesticated horses i. 51; + pigs of the Swiss lake-dwellings, i. 65, 67-68; + on humped cattle, i. 80; + parentage of European breeds of cattle, i. 80, 81, ii. 427; + on "Niata" cattle, i. 89; + sheep of the Swiss lake-dwellings, i. 94, ii. 427; + goats of the Swiss lake-dwellings, i. 101; + absence of fowls in the Swiss lake-dwellings, i. 246; + on crossing cattle, ii. 98; + differences in the bones of wild and domesticated animals, ii. 279; + decrease in size of wild European animals, ii. 427. + RYE, wild, De Candolle's observations on, i. 313; + found in the Swiss lake-dwellings, i. 319; + common, preferred by hares and rabbits, ii. 232; + less variable than other cultivated plants, ii. 254. + + SABINE, Mr., on the cultivation of _Rosa spinosissima_, i. 367; + on the cultivation of the dahlia, i. 369-370, ii. 261; + effect of foreign pollen on the seed-vessel in _Amaryllis vittata_, i. + 400. + ST. ANGE, influence of the pelvis on the shape of the kidneys in birds, + ii. 344. + ST. DOMINGO, wild dogs of, i. 28; + bud-variation of dahlias in, i. 385. + ST. HILAIRE, Aug., milk furnished by cows in South America, ii. 300; + husked form of maize, i. 320. + ST. JOHN, C., feral cats in Scotland, i. 47; + taming of wild ducks, i. 278. + ST. VALERY apple, singular structure of the, i. 350; + artificial fecundation of the, i. 401. + ST. VITUS' Dance, period of appearance of, ii. 77. + SAGERET, origin and varieties of the cherry, i. 347-348; + origin of varieties of the apple, i. 350; + incapacity of the cucumber for crossing with other species, i. 359; + varieties of the melon, i. 360; + supposed twin-mongrel melon, i. 391; + crossing melons, ii. 108, 129; + on gourds, ii. 108; + effects of selection in enlarging fruit, ii. 217; + on the tendency to depart from type, ii. 241; + variation of plants in particular soils, ii. 278. + SALAMANDER, experiments on the, ii. 293, 341; + regeneration of lost parts in the, ii. 15, 376, 385. + _Salamandra cristata_, polydactylism in, ii. 14. + SALISBURY, Mr., on the production of nectarines by peach-trees, i. 341; + on the dahlia, i. 369-370. + _Salix_, intercrossing of species of, i. 336. + _Salix humilis_, galls of, ii. 282, 283. + SALLE, feral guinea-fowl in St. Domingo, i. 294. + SALMON, early breeding of male, ii. 384. + SALTER, Mr., on bud-variation in pelargoniums, i. 378; + in the Chrysanthemum, i. 379; + transmission of variegated leaves by seed, i. 383; + bud-variation by suckers in _Phlox_, i. 384; + application of selection to bud-varieties of plants, i. 411; + accumulative effect of changed conditions of life, ii. 262; + on the variegation of strawberry leaves, ii. 274. + SALTER, S. J., hybrids of _Gallus Sonneratii_ and the common fowl, i. + 234, ii. 45; + {476} + crossing of races or species of rats, ii. 87-88. + SAMESREUTHER, on inheritance in cattle, ii. 10. + SANDFORD. _See_ DAWKINS. + SAP, ascent of the, ii. 296. + _Saponaria calabrica_, ii. 20. + SARDINIA, ponies of, i. 52. + SARS, on the development of the hydroida, ii. 368. + SATIATION of the stigma, i. 402-403. + _Saturnia pyri_, sterility of, in confinement, ii. 157. + SAUL, on the management of prize gooseberries, i. 356. + SAUVIGNY, varieties of the goldfish, i. 296. + SAVAGES, their indiscriminate use of plants as food, i. 307-310; + fondness of, for taming animals, ii. 160. + SAVI, effect of foreign pollen on maize, i. 400. + _Saxifraga geum_, ii. 166. + SAYZID MOHAMMED MUSARI, on carrier-pigeons, i. 141; + on a pigeon which utters the sound "Yahu," i. 155. + SCANDEROONS (pigeons), i. 142, 143. + SCANIA, remains of _Bos frontosus_ found in, i. 81. + SCAPULA, characters of, in rabbits, i. 123; + in fowls, i. 268; + in pigeons, i. 167; + alteration of, by disuse, in pigeons, i. 175. + SCARLET fever, ii. 276. + SCHAAFFHAUSEN, on the horses represented in Greek statues, ii. 213. + SCHACHT, H., on adventitious buds, ii. 384. + SCHLEIDEN, excess of nourishment a cause of variability, ii. 257. + SCHOMBURGK, Sir R., on the dogs of the Indians of Guiana, i. 19, 23, ii. + 206; + on the musk duck, i. 182; + bud-variation in the Banana, i. 377; + reversion of varieties of the China rose in St. Domingo, i. 380; + sterility of tame parrots in Guiana, ii. 155; + on _Dendrocygna viduata_, ii. 157; + selection of fowls in Guiana, ii. 209. + SCHREIBERS, on _Proteus_, ii. 297. + _Sciuropterus volucella_, ii. 152. + _Sciurus palmarum_ and _cinerea_, ii. 152. + SCLATER, P. L., on _Asinus taeniopus_, i. 62, ii. 41; + on _Asinus indicus_, ii. 42; + striped character of young wild pigs, i. 70; + osteology of _Gallinula nesiotis_, i. 287; + on the black-shouldered peacock, i. 290; + on the breeding of birds in captivity, ii. 157. + SCHMERLING, Dr., varieties of the dog, found in a cave, i. 19. + SCOTCH fir, local variation of, i. 363. + SCOTCH kail and cabbage, cross between, ii. 98. + SCOTT, John, irregularities in the sex of the flowers of Maize, i. 321; + bud-variation in _Imatophyllum miniatum_, i. 385; + crossing of species of _Verbascum_, ii. 106-107; + experiments on crossing _Primulae_, ii. 109; + reproduction of orchids, ii. 133; + fertility of _Oncidium divaricatum_, ii. 164; + acclimatisation of the sweet pea in India, ii. 311; + number of seeds in _Acropera_ and _Gongora_, ii. 379. + SCOTT, Sir W., former range of wild cattle in Britain, i. 85. + SCROPE, on the Scotch deerhound, ii. 73, 121. + SEBRIGHT, Sir John, effects of close interbreeding in dogs, ii. 121; + care taken by, in selection of fowls, ii. 197. + _Secale cereale_, ii. 254. + SEDGWICK, W., effects of crossing on the female, i. 404; + on the "Porcupine-man," ii. 4; + on hereditary diseases, ii. 7; + hereditary affections of the eye, ii. 9, 78-79; + inheritance of polydactylism and anomalies of the extremities, ii. + 13-14; + morbid uniformity in the same family, ii. 17; + on deaf-mutes, ii. 22; + inheritance of injury to the eye, ii. 24; + atavism in diseases and anomalies of structure, ii. 34; + non-reversion to night-blindness, ii. 36; + sexual limitation of the transmission of peculiarities in man, ii. + 72-73; + on the effects of hard-drinking, ii. 289; + inherited baldness with deficiency of teeth, ii. 326-327; + occurrence of a molar tooth in place of an incisor, ii. 391; + diseases occurring in alternate generations, ii. 401. + SEDILLOT, on the removal of portions of bone, ii. 296. + SEEDS, early selection of, ii. 204; + rudimentary, in grapes, ii. 316; + relative position of, in the capsule, ii. 345. + SEEDS and buds, close analogies of, i. 411. + SEEMANN, B., crossing of the wolf and Esquimaux dog, i. 22. + SELBY, P. J., on the bud-destroying habits of the bullfinch, ii. 232. + SELECTION, ii. 192-249; + methodical, i. 214, ii. 194-210; + by the ancients and semi-civilised people, ii. 201-210; + of trifling characters, ii. 208-210; + unconscious, i. 214, 217, ii. 174, 210-217; + effects of, shown by differences in most valued parts, ii. 217-220; + produced by accumulation of variability, ii. 220-223; + natural, as affecting domestic productions, ii. 185-189, 224-233; + as the origin of species, genera and other groups, ii. 429-432; + circumstances favourable to, ii. 233-239; + tendency of towards extremes, ii. 239-242; + {477} + possible limit of, ii. 242; + influence of time on, ii. 243-244; + summary of subject, ii. 246-249; + effects of, in modifying breeds of cattle, i. 92, 93; + in preserving the purity of breeds of sheep, i. 99-100; + in producing varieties of pigeons, i. 213-218; + in breeding fowls, i. 232-233; + in the goose, i. 289; + in the canary, i. 295; + in the goldfish, i. 296; + in the silkworm, i. 300-301; + contrasted in cabbages and cereals, i. 323; + in the white mulberry, i. 334; + on gooseberries, i. 356; + applied to wheat, i. 317-318; + exemplified in carrots, &c., i. 326; + in the potato, i. 331; + in the melon, i. 360; + in flowering plants, i. 365; + in the hyacinth, i. 371; + applied to bud-varieties of plants, i. 411; + illustrations of, ii. 421-428. + SELECTION, sexual, ii. 75. + SELF-IMPOTENCE in plants, ii. 131-140; + in individual plants, ii. 136-138; + of hybrids, ii. 174. + SELWYN, Mr., on the Dingo, i. 26. + SELYS-LONGCHAMPS, on hybrid ducks, i. 190, ii. 46, 157; + hybrid of the hook-billed duck and Egyptian goose, i. 282. + SERINGE, on the St. Valery apple, i. 350. + SERPENT Melon, i. 360. + SERRES, Olivier de, wild poultry in Guiana, i. 237. + SESAMUM, white-seeded, antiquity of the, ii. 429. + _Setaria_, found in the Swiss lake-dwellings, i. 317. + SETTERS, degeneration of, in India, i. 38; + Youatt's remarks on, i. 41. + SEX, secondary characters of, latent, ii. 51-52; + of parents, influence of, on hybrids, ii. 267. + SEXUAL characters, sometimes lost in domestication, ii. 74. + SEXUAL limitation of characters, ii. 71-75. + SEXUAL peculiarities, induced by domestication in sheep, i. 95; + in fowls, i. 251-257; + transfer of, i. 255-257. + SEXUAL variability in pigeons, i. 161-162. + SEXUAL selection, ii. 75. + SHADDOCK, i. 335. + SHAILER, Mr., on the moss-rose, i. 379-380. + SHANGHAI fowls, i. 227. + SHANGHAI sheep, their fecundity, i. 97. + SHAN ponies, striped, i. 58. + SHEEP, disputed origin of, i. 94; + early domestication of, i. 94; + large-tailed, i. 94, 95, 98, ii. 279; + variations in horns, mammae and other characters of, i. 95; + sexual characters of, induced by domestication, i. 95, 96; + adaptation of, to climate and pasture, i. 96, 97; + periods of gestation of, i. 97; + effect of heat on the fleece of, i. 98-99, ii. 278; + effect of selection on, i. 99-101; + "ancon" or "otter" breeds of, i. 17, 92, 100; + "Mauchamp-merino," i. 100-101; + cross of German and merino, ii. 85-89; + black, of the Tarentino, ii. 227; + Karakool, ii. 278; + Jaffna, with callosities on the knees, ii. 302; + Chinese, ii. 315; + Danish, of the bronze period, ii. 427; + polydactylism in, ii. 14; + occasional production of horns in hornless breeds of, ii. 30; + reversion of colour in, ii. 30; + influence of male, on offspring, ii. 68; + sexual differences in, ii. 73; + influence of crossing or segregation on, ii. 86, 95-96, 102-103; + interbreeding of, ii. 119-120; + effect of nourishment on the fertility of, ii. 111-112; + diminished fertility of, under certain conditions, ii. 161; + unconscious selection of, ii. 213; + natural selection in breeds of, ii. 224, 225, 227; + reduction of bones in, ii. 242; + individual differences of, ii. 251; + local changes in the fleece of, in England, ii. 278; + partial degeneration of, in Australia, ii. 278; + with numerous horns, ii. 291; + correlation of horns and fleece in, ii. 326; + feeding on flesh, ii. 303; + acclimatisation of, ii. 305-306; + mountain, resistance of, to severe weather, ii. 312; + white, poisoned by _Hypericum crispum_, ii. 337. + SHEEP dogs resembling wolves, i. 24. + SHELLS, sinistral and dextral, ii. 53. + SHERIFF, Mr. new varieties of wheat, i. 315, 317; + on crossing wheat, ii. 104-105; + continuous variation of wheat, ii. 241. + SIAM, cats of, i. 47; horses of, i. 53. + SHIRLEY, E. P., on the fallow-deer, ii. 103, 120. + SHORT, D., hybrids of the domestic cat and _Felis ornata_, i, 45. + SIBERIA, northern range of wild horses in, i. 52. + SICHEL, J., on the deafness of white cats with blue eyes, ii. 329. + SIDNEY, S., on the pedigrees of pigs, ii. 3; + on cross-reversion in pigs, ii. 35; + period of gestation in the pig, i. 74; + production of breeds of pigs by intercrossing, i. 78, 95; + fertility of the pig, ii. 112; + effects of interbreeding on pigs, ii. 121-122; + on the colours of pigs, ii. 210, 229. + SIEBOLD, on the sweet potato, ii. 309. + SIEBOLD, von Carl, on parthenogenesis, ii. 364. + _Silene_, contabescence in, ii. 166. + SILK-FOWLS, i. 230, ii. 67, 69. + {478} + SILK-MOTH, Arrindy, ii. 306, 312; + Tarroo, ii. 157. + SILK-MOTHS, i. 300-304; + domesticated species of, i. 300; + history of, _ibid._; + causes of modification in, i. 300-301; + differences presented by, i. 301-304; + crossing of, ii. 98; + disease in, ii. 228; + effects of disuse of parts in, ii. 298; + selection practised with, ii. 197, 199; + variation of, ii. 236; + parthenogenesis in, ii. 364. + SILKWORMS, variations of, i. 301-302; + yielding white cocoons, less liable to disease, ii. 336. + SILVER-GREY rabbit, i. 108, 111, 120. + SIMONDS, J. B., period of maturity in various breeds of cattle, i. 87; + differences in the periods of dentition in sheep, i. 96; + on the teeth in cattle, sheep, &c., ii. 322; + on the breeding of superior rams, ii. 196. + SIMON, on the raising of eggs of the silk-moth in China, ii. 197. + SIMPSON, Sir J., regenerative power of the human embryo, ii. 15. + _Siredon_, breeding in the branchiferous stage, ii. 384. + SISKIN, breeding in captivity, ii. 154. + _Sivatherium_, resemblance of the, to Niata cattle, i. 89. + SIZE, difference of, an obstacle to crossing, ii. 101. + SKIN, and its appendages, homologous, ii. 325; + hereditary affections of the, ii. 79. + SKIRVING, R. S., on pigeons settling on trees in Egypt, i. 181. + SKULL, characters of the, in breeds of dogs, i. 34; + in breeds of pigs, i. 71; + in rabbits, i. 116-120, 127; + in breeds of pigeons, i. 163-165; + in breeds of fowls, i. 260-266; + in ducks, i. 282-283. + SKULL and horns, correlation of the, ii. 333. + SKYLARK, ii. 154. + SLEEMAN, on the Cheetah, ii. 151. + SLOE, i. 345. + SMALL-POX, ii. 378. + SMITER (pigeon), i. 156. + SMITH, Sir A., on Caffrarian cattle, i. 88; + on the use of numerous plants as food in South Africa, i. 307. + SMITH, Colonel Hamilton, on the odour of the jackal, i. 30; + on the origin of the dog, i. 16; + wild dogs in St. Domingo, i. 28; + on the Thibet mastiff and the alco, i. 28-29; + development of the fifth toe in the hind feet of mastiffs, i. 35; + differences in the skull of dogs, i. 34; + history of the pointer, i. 42; + on the ears of the dog, ii. 301; + on the breeds of horses, i. 49; + origin of the horse, i. 51; + dappling of horses, i. 55; + striped horses in Spain, i. 58; + original colour of the horse, i. 60; + on horses scraping away snow, i. 52; + on _Asinus hemionus_, ii. 43; + feral pigs of Jamaica, i. 77-78. + SMITH, Sir J. E., production of nectarines and peaches by the same tree, + i. 340; + on _Viola amoena_, i. 368; + sterility of _Vinca minor_ in England, ii. 170. + SMITH, J., development of the ovary in _Bonatea speciosa_, by irritation + of the stigma, i. 403. + SMITH, N. H., influence of the bull "Favourite" on the breed of + Short-horn cattle, ii. 65. + SMITH, W., on the inter-crossing of strawberries, i. 352. + SNAKE-RAT, ii. 87, 88. + SNAKES, form of the viscera in, ii. 344. + SNAPDRAGON, bud-variation in, i. 381; + non-inheritance of colour in, ii. 21; + peloric, crossed with the normal form, ii. 70, 93; + asymmetrical variation of the, ii. 322. + SOIL, adaptation of plums to, i. 346; + influence of, on the zones of pelargoniums, i. 366; + on roses, i. 367; + on the variegation of leaves, i. 383; + advantages of change of, ii. 146-148. + SOIL and climate, effects of, on strawberries, i. 353. + _Solanum_, non-intercrossing of species of, ii. 91. + _Solanum tuberosum_, i. 330-331. + SOLID-HOOFED pigs, i. 75. + SOLOMON, his stud of horses, i. 55. + SOMERVILLE, Lord, on the fleece of Merino sheep, i. 99; + on crossing sheep, ii. 120; + on selection of sheep, ii. 195; + diminished fertility of Merino sheep brought from Spain, ii. 161. + SOOTY fowls, i. 230, 256. + SOTO, Ferdinand de, on the cultivation of native plants in Florida, i. + 312. + _Sorghum_, i. 371. + SPAIN, hawthorn monogynous in, i. 364. + SPALLANZANI, on feral rabbits in Lipari, i. 113; + experiments on salamanders, ii. 15, 293, 385; + experiments in feeding a pigeon with meat, ii. 304. + SPANIELS, in India, i. 38; + King Charles's, i. 41; + degeneration of, caused by interbreeding, ii. 121. + SPANISH fowls, i. 227, 250, 253; + figured, i. 226; + early development of sexual characters in, i. 250, 251; + furcula of, figured, i. 268. + SPECIES, difficulty of distinguishing from varieties, i. 4; + conversion of varieties into, i. 5; + origin of, by natural selection, ii. 414-415; + by mutual sterility of varieties, ii. 185-189. + {479} + SPENCER, Lord, on selection in breeding, ii. 195. + SPENCER, Herbert, on the "survival of the fittest," i. 6; + increase of fertility by domestication, ii. 111; + on life, ii. 148, 177; + changes produced by external conditions, ii. 281; + effects of use on organs, ii. 295, 296; + ascent of the sap in trees, ii. 296; + correlation exemplified in the Irish elk, ii. 333-334; + on "physiological units," ii. 375; + antagonism of growth and reproduction, ii. 384; + formation of ducts in plants, ii. 300. + SPERMATOPHORES of the cephalopoda, ii. 383. + SPERMATOZOIDS, ii. 363-364; + apparent independence of, in insects, ii. 384. + SPHINGIDAE, sterility of, in captivity, ii. 157. + SPINOLA, on the injurious effect produced by flowering buckwheat on white + pigs, ii. 337. + SPITZ dog, i. 31. + SPOONER, W. C., cross-breeding of sheep, i. 100, ii. 95-96, 120; + on the effects of crossing, ii. 96-97; + on crossing cattle, ii. 118; + individual sterility, ii. 162. + SPORES, reproduction of abnormal forms by, i. 383. + SPORTS, i. 373; in pigeons, i. 213. + SPOT pigeon, i. 156, 207. + SPRENGEL, C. K., on dichogamous plants, ii. 90; + on the hollyhock, ii. 107; + on the functions of flowers, ii. 175. + SPROULE, Mr., inheritance of cleft-palate and hare-lip, ii. 24. + SPURS, of fowls, i. 255; + development of, in hens, ii. 318. + SQUASHES, i. 357. + SQUINTING, hereditary, ii. 9. + SQUIRRELS, generally sterile in captivity, ii. 152. + SQUIRRELS, flying, breeding in confinement, ii. 152. + "STAARHALSIGE Taube," i. 161. + STAG, one-horned, supposed heredity of character in, ii. 12; + degeneracy of, in the Highlands, ii. 208. + STAMENS, occurrence of rudimentary, ii. 316; + conversion of, into pistils, i. 365; + into petals, ii. 392. + _Staphylea_, ii. 168. + STEENSTRUP, Prof., on the dog of the Danish Middens, i. 18; + on the obliquity of flounders, ii. 53. + STEINAN, J., on hereditary diseases, ii. 7, 79. + STERILITY, in dogs, consequent on close confinement, i. 32; + comparative, of crosses, ii. 103, 104; + from changed conditions of life, ii. 148-165; + occurring in the descendants of wild animals bred in captivity, ii. + 160; + individual, ii. 162; + resulting from propagation by buds, cuttings, bulbs, &c., ii. 169; + in hybrids, ii. 178-180, 386, 410-411; + in specific hybrids of pigeons, i. 193; + as connected with natural selection, ii. 185-189. + STERNUM, characters of the, in rabbits, i. 123; + in pigeons, i. 167, 174-175; + in fowls, i. 268, 273; + effects of disuse on the, i. 174-175, 273. + STEPHENS, J. F., on the habits of the Bombycidae, i. 303. + STEWART, H., on hereditary disease, ii. 79. + STIGMA, variation of the, in cultivated Cucurbitaceae, i. 359; + satiation of the, i. 402-403. + STOCKS, bud-variation in, i. 381; + effect of crossing upon the colour of the seed of, i. 398-399; + true by seed, ii. 20; + crosses of, ii. 93; + varieties of, produced by selection, ii. 219; + reversion by the upper seeds in the pods of, ii. 347-348. + STOCKHOLM, fruit-trees of, ii. 307. + STOKES, Prof., calculation of the chance of transmission of abnormal + peculiarities in man, ii. 5. + STOLONS, variations in the production of, by strawberries, i. 353. + STOMACH, structure of the, affected by food, ii. 302. + STONE in the bladder, hereditary, ii. 8, 79. + STRAWBERRIES, i. 351-354; + remarkable varieties of, i. 352-353; + hautbois, dioecious, i. 353; + selection in, ii. 200; + mildew of, ii. 228; + probable further modification of, ii. 243; + variegated, effects of soil on, ii. 274. + STRICKLAND, A., on the domestication of _Anser ferus_, i. 287; + on the colour of the bill and legs in geese, i. 288. + _Strictoenas_, i. 183. + STRIPES on young of wild swine, i. 76; + of domestic pigs of Turkey, Westphalia, and the Zambesi, i. 76-77; + of feral swine of Jamaica and New Granada, i. 77; + of fruit and flowers, i. 400, ii. 37; + in horses, i. 56-60; + in the ass, i. 62-63; + production of, by crossing species of Equidae, ii. 42-43. + _Strix grallaria_, ii. 302. + _Strix passerina_, ii. 154. + "STRUPP-TAUBE," i. 155. + STRUTHERS, Mr., osteology of the feet in solid-hoofed pigs, i. 75; + on polydactylism, ii. 13-14. + STURM, prepotency of transmission of characters in sheep and cattle, ii. + 66; + absorption of the minority in crossed races, ii. 88; + correlation of twisted horns and curled wool in sheep, ii. 326. + {480} + SUB-SPECIES, wild, of _Columba livia_ and other pigeons, i. 204. + SUCCESSION, geological, of organisms, i. 11. + SUCKERS, bud-variation by, i. 384. + SUGAR cane, sterility of, in various countries, ii. 169; + white, liability of, to disease, ii. 228, 336. + SUICIDE, hereditary tendency to, ii. 7, 78. + SULIVAN, Admiral, on the horses of the Falkland Islands, i. 53; + wild pigs of the Falkland Islands, i. 77; + feral cattle of the Falkland Islands, i. 86, 102; + feral rabbits of the Falkland Islands, i. 112. + SULTAN fowl, i. 228, 255. + _Sus indica_, i. 65, 67-70, ii. 110. + _Sus pliciceps_, i. 69 (figured). + _Sus scrofa_, i. 65, 66, ii. 110. + _Sus scrofa palustris_, i. 68. + _Sus vittatus_, i. 67. + SWALLOWS, a breed of pigeons, i. 156. + SWAYNE, Mr., on artificial crossing of varieties of the pea, i. 397. + SWEET Peas, ii. 91; + crosses of, ii. 93, 94; + varieties of, coming true by seed, ii. 20; + acclimatisation of, in India, ii. 311. + SWEET William, bud-variation in, i. 381. + SWINHOE, R., on Chinese pigeons, i. 28, 206; + on striped Chinese horses, i. 59. + SWITZERLAND, ancient dogs of, i. 19; + pigs of, in the Neolithic period, i. 67-68; + goats of, i. 101. + SYCAMORE, pale-leaved variety of the, ii. 330. + SYKES, Colonel, on a Pariah dog with crooked legs, i. 17; + on small Indian asses, i. 62; + on _Gallus Sonneratii_, i. 233; + on the voice of the Indian Kulm cock, i. 259; + fertility of the fowl in most climates, ii. 161. + SYMMETRY, hereditary departures from, ii. 12. + _Symphytum_, variegated, i. 384. + SYPHILIS, hereditary, ii. 332. + SYRIA, asses of, i. 62. + _Syringa persica_, _chinensis_, and _vulgaris_, ii. 164. + + TACITUS, on the care taken by the Celts in breeding animals, ii. 202. + _Tagetes signata_, dwarf variety of, ii. 20. + TAHITI, varieties of cultivated plants in, ii. 256. + TAIL, occasional development of, in man, ii. 57; + never curled in wild animals, ii. 301; + rudimentary in Chinese sheep, ii. 315. + TAIL-FEATHERS, numbers of, in breeds of pigeons, i. 158-159; + peculiarities of, in cocks, i. 254-255; + variability of, in fowls, i. 258; + curled, in _Anas boschas_, and tame drakes, i. 280. + TALENT, hereditary, ii. 7. + TANKERVILLE, Earl of, on Chillingham cattle, i. 84, ii. 119. + TANNER, Prof., effects of disuse of parts in cattle, ii. 299. + TAPIR, sterility of the, in captivity, ii. 150. + TARGIONI-TOZZETTI, on cultivated plants, i. 306; + on the vine, i. 332; + varieties of the peach, i. 342; + origin and varieties of the plum, i. 345; + origin of the cherry, i. 347; + origin of roses, i. 366. + TARSUS, variability of the, in fowls, i. 259; + reproduction of the, in a thrush, ii. 15. + TARTARS, their preference for spiral-horned sheep, ii. 209. + TAVERNIER, abundance of pigeons in Persia, i. 205. + _Taxus baccata_, ii. 18. + TEEBAY, Mr., reversion in fowls, ii. 38. + TEETH, number and position of, in dogs, i. 34; + deficiency of, in naked Turkish dogs, i. 35; + period of appearance of, in breeds of dogs, i. 35; + precocity of, in highly bred animals, ii. 322; + correlation of, with hair, ii. 326; + double row of, with redundant hair, in Julia Pastrana, ii. 328; + affected in form by hereditary syphilis and by pulmonary tubercle, ii. + 332; + fusion of, ii. 341; + developed on the palate, ii. 391. + TEGETMEIER, Mr., on a cat with monstrous teeth, i. 48; + on a swift-like pigeon, i. 157; + naked young of some pigeons, i. 170; + fertility of hybrid pigeons, i. 192; + on white pigeons, ii. 230; + reversion in crossed breeds of fowls, i. 239-244; + chicks of the white silk-fowl, i. 249; + development of the cranial protuberance in Polish fowls, i. 250; + on the skull in the Polish fowl, i. 257, 262; + on the intelligence of Polish fowls, i. 264; + correlation of the cranial protuberance and crest in Polish fowls, i. + 274; + development of the web in the feet of Polish fowls, i. 259; + early development of several peculiarities in Spanish cocks, i. 250; + on the comb in Spanish fowls, i. 253; + on the Spanish fowl, ii. 306; + varieties of game-fowls, i. 252; + pedigrees of game-fowls, ii. 3; + assumption of female plumage by a game cock, i. 253; + natural selection in the game cock, ii. 225; + pugnacity of game hens, i. 256; + length of the middle toe in Cochin fowls, i. 259; + origin of the Sebright bantam, ii. 54; + differences in the size of fowls, i. 257; + effect of crossing in fowls, i. 258, ii. 96; + effects of interbreeding in fowls, ii. 124-125; + incubation by mongrels of non-sitting races of fowls, ii. 44; + inverse correlation of crest and comb in fowls, i. 274; + {481} + occurrence of pencilled feathers in fowls, ii. 40; + on a variety of the goose from Sebastopol, i. 289; + on the fertility of the peahen, ii. 112; + on the intercrossing of bees, ii. 126. + TEMMINCK, origin of domestic cats, i. 43; + origin of domestic pigeons, i. 180; + on _Columba guinea_, i. 182; + on _Columba leucocephala_, i. 183; + asserted reluctance of some breeds of pigeons to cross, i. 192; + sterility of hybrid turtle-doves, i. 193; + variations of _Gallus bankiva_, i. 235; + on a buff-coloured breed of Turkeys, i. 293; + number of eggs laid by the peahen, ii. 112; + breeding of Guans in captivity, ii. 156; + behaviour of grouse in captivity, _ibid._; + sterility of the partridge in captivity, _ibid._ + TENDRILS in Cucurbitaceae, i. 358, ii. 316. + TENNENT, Sir J. E., on the goose, i. 287; + on the growth of the apple in Ceylon, ii. 277; + on the Jaffna sheep, ii. 302. + _Teredo_, fertilisation in, ii. 363. + TERRIERS, wry-legged, ii. 245; + white, subject to distemper, ii. 336. + TESCHEMACHER, on a husked form of maize, i. 320. + TESSIER, on the period of gestation of the dog, i. 29; + of the pig, i. 74; + in cattle, i. 87; + experiments on change of soil, ii. 147. + _Tetrao_, breeding of species of, in captivity, ii. 156. + _Tetrapteryx paradisea_, ii. 156. + _Teucrium campanulatum_, pelorism in, ii. 345. + TEXAS, feral cattle in, i. 85. + THEOGNIS, his notice of the domestic fowl, i. 246. + THEOPHRASTUS, his notice of the peach, ii. 308. + _Thesium_, ii. 284. + THOMPSON, Mr., on the peach and nectarine, i. 342; + on the varieties of the apricot, i. 344; + classification of varieties of cherries, i. 347-348; + on the "Sister ribston-pippin," i. 350; + on the varieties of the gooseberry, i. 354, 355. + THOMPSON, William, on the pigeons of Islay, i. 184; + feral pigeons in Scotland, i. 190; + colour of the bill and legs in geese, i. 288; + breeding of _Tetrao scotius_ in captivity, ii. 156; + destruction of black-fowls by the osprey, ii. 230. + THOMPSON, Prof. W., on the obliquity of the flounder, ii. 53. + THORNS, reconversion of, into branches, in pear trees, ii. 318. + THORN, grafting of early and late, i. 363; + Glastonbury, i. 364. + THRUSH, asserted reproduction of the tarsus in a, ii. 15. + _Thuja pendula_ or _filiformis_, a variety of _T. orientalis_, i. 362. + THURET, on the division of the zoospores of an alga, ii. 378. + THWAITES, G. H., on the cats of Ceylon, i. 46; + on a twin seed of _Fuchsia coccinea_ and _fulgens_, i. 391. + TIBURTIUS, experiments in rearing wild ducks, i. 278. + TIGER, rarely fertile in captivity, ii. 150, 151. + _Tigridia conchiflora_, bud-variation in, i. 386. + TIME, importance of, in the production of races, ii. 243. + TINZMANN, self-impotence in the potato, ii. 137. + TISSUES, affinity of, for special organic substances, ii. 380. + TITMICE, destructive to thin-shelled walnuts, i. 356; + attacking nuts, i. 357; + attacking peas, ii. 231. + TOBACCO, crossing of varieties of, ii. 108; + cultivation of in Sweden, ii. 307. + TOBOLSK, red-coloured cats of, i. 47. + TOES, relative length of, in fowls, i. 259; + development of fifth in dogs, ii. 317. + TOLLET, Mr., his selection of cattle, ii. 199. + TOMATO, ii. 91. + TOMTITS. See _Titmice_. + TONGUE, relation of, to the beak in pigeons, i. 168. + TOOTH, occurrence of a molar, in place of an incisor, ii. 391. + "TORFSCHWEIN," i. 68. + TRAIL, R., on the union of half-tubers of different kinds of potatoes, i. + 395. + TREES, varieties of, suddenly produced, i. 361; + weeping or pendulous, i. 361; + fastigate or pyramidal, i. 361; + with variegated or changed foliage, i. 362; + early or late in leaf, i. 362-363; + forest, non-application of selection to, ii. 237. + "TREMBLEUR" (pigeons), i. 146. + TREMBLEY, on reproduction in Hydra, ii. 359. + "TREVOLTINI" silkworms, i. 301-302. + _Trichosanthes anguina_, i. 360. + TRICKS, inheritance of, ii. 6-7, 395. + _Trifolium minus_ and _repens_, ii. 164. + TRIMORPHIC plants, conditions of reproduction in, ii. 181-184. + TRISTRAM, H. B., selection of the dromedary, ii. 205-206. + _Triticum dicoccum_, i. 319. + _Triticum monococcum_, i. 319. + _Triticum spelta_, i. 319. + _Triticum turgidum_, i. 319. + _Triticum vulgare_, wild in Asia, i. 312. + {482} + TRITON, breeding in the branchiferous stage, ii. 384. + "TROMMEL-TAUBE," i. 154. + "TRONFO" pigeon, i. 144. + _Tropaeolum_, ii. 38. + _Tropaeolum minus_ and _majus_, reversion in hybrids of, i. 392. + TROUBETZKOY, Prince, experiments with pear-trees at Moscow, ii. 307. + TROUSSEAU, Prof., pathological resemblance of twins, ii. 252. + TRUMPETER pigeon, i. 154; + known in 1735, i. 207. + TSCHARNER, H. A. de, graft-hybrid produced by inosculation in the vine, + i. 395. + TSCHUDI, on the naked Peruvian dog, i. 23; + extinct varieties of maize from Peruvian tombs, i. 320, ii. 425. + TUBERS, bud-variation by, i. 384-385. + TUCKERMAN, Mr., sterility of _Carex rigida_, ii. 170. + TUFTED ducks, i. 281. + TULIPS, variability of, i. 370; + bud-variation in, i. 385-386; + influence of soil in "breaking," i. 385. + TUMBLER pigeon, i. 150-153; + short-faced, figured, i. 152; + skull figured, i. 163; + lower jaw figured, i. 165; + scapula and furcula figured, i. 167; + early known in India, i. 207; + history of, i. 209; + sub-breeds of, i. 220; + young unable to break the egg-shell, ii. 226; + probable further modification of, ii. 242. + "TUEMMLER" (pigeons), i. 150. + TUMOURS, ovarian, occurrence of hairs and teeth in, ii. 370; + polypoid, origin of, ii. 381. + "TUERKISCHE TAUBE," i. 139. + TURBIT (pigeon), i. 148. + TURKEY, domestic, origin of, i. 292-293; + crossing of with North American wild Turkey, i. 292-293; + breeds of, i. 293; + crested white cock, i. 293; + wild, characters of, i. 293-294; + degeneration of, in India, i. 294, ii. 278; + failure of eggs of, in Delhi, ii. 161; + feral on the Parana, i. 190; + change produced in by domestication, ii. 262. + TURKEY, striped young pigs in, i. 76. + TURNER (pigeon), i. 156. + TURNER, W., on compensation in arteries and veins, ii. 300; + on cells, ii. 370. + TURNIPS, origin of, i. 325; + reversion in, ii. 31; + run wild, ii. 33; + crosses of, ii. 93, 96; + Swedish, preferred by hares, ii. 232; + acclimatisation of, in India, ii. 311. + TURNSPIT, on an Egyptian monument, i. 17; + crosses of the, ii. 92. + TURTLE-DOVE, white and coloured, crossing of, ii. 92. + _Turtur auritus_, hybrids of, with _T. cambayensis_ and _T. suratensis_, + i. 194. + _Turtur risorius_, crossing of, with the common pigeon, i. 193; + hybrid of, with _T. vulgaris_, _ibid._ + _Turtur suratensis_, sterile hybrids of, with _T. vulgaris_, i. 193; + hybrids of, with _T. auritus_, i. 194. + _Turtur vulgaris_, crossing of, with the common pigeon, i. 193; + hybrid of, with _T. risorius_, _ibid._; + sterile hybrids of, with _T. suratensis_ and _Ectopistes migratorius_, + _ibid._ + TUSKS of wild and domesticated pigs, i. 76, 77. + _Tussilago farfara_, variegated, i. 384. + TWIN-SEED _Fuchsia coccinea_ and _fulgens_, i. 391. + TYERMAN, B., on the pigs of the Pacific islands, i. 70, ii. 87; + on the dogs of the Pacific islands, ii. 87. + TYLOR, Mr., on the prohibition of consanguineous marriages, ii. 122-123. + + UDDERS, development of the, ii. 300. + _Ulex_, double-flowered, ii. 167. + _Ulmus campestris_ and _effusa_, hybrids of, ii. 130. + UNIFORMITY of character, maintained by crossing, ii. 85-90. + UNITS of the body, functional independence of the, ii. 368-371. + UNITY or plurality of origin of organisms, i. 13. + UPAS poison, ii. 380. + UREA, secretion of, ii. 380. + USE and disuse of parts, effects of, ii. 295-303, 352-353, 418-419; + in rabbits, i. 124-128; + in ducks, i. 284-286. + UTILITY, considerations of, leading to uniformity, ii. 241. + + VALENTIN, experimental production of double monsters by, ii. 340. + _Vallota_, ii. 139. + VAN BECK, Barbara, a hairy-faced woman, ii. 4. + VAN MONS on wild fruit-trees, i. 312, ii. 260; + production of varieties of the vine, i. 333; + correlated variability in fruit-trees, ii. 330; + production of almond-like fruit by peach-seedlings, i. 339. + _Vanessa_, species of, not copulating in captivity, ii. 157. + VARIABILITY, i. 4, ii. 371-373, 394-397, 406-420; + causes of, ii. 250-270; + correlated, ii. 319-338, 353-355, 419-420; + law of equable, ii. 351-352; + necessity of, for selection, ii. 192; + of selected characters, ii. 238-239; + of multiple homologous parts, ii. 342. + {483} + VARIATION, laws of, ii. 293-356; + continuity of, ii. 241; + possible limitation of, ii. 242, 416-417; + in domestic cats, i. 45-48; + origin of breeds of cattle by, i. 88; + in osteological characters of rabbits, i. 115-130; + of important organs, i. 359; + analogous or parallel, i. 348-352; + in horses, i. 55; + in the horse and ass, i. 64; + in fowls, i. 243-246; + in geese, i. 288; + exemplified in the production of fleshy stems in cabbages, &c., i. 326; + in the peach, nectarine, and apricot, i. 342, 344; + individual, in wheat, i. 314. + VARIEGATION of foliage, i. 383, ii. 167-168. + VARIETIES and species, resemblance of, i. 4, ii. 411-413; + conversion of, into species, i. 5; + abnormal, ii. 413; + domestic, gradually produced, ii. 414. + VARRO, on domestic ducks, i. 277; + on feral fowls, ii. 33; + crossing of the wild and domestic ass, ii. 206. + VASEY, Mr., on the number of sacral vertebrae in ordinary and humped + cattle, i. 79; + on Hungarian cattle, i. 80. + VAUCHER, sterility of _Ranunculus ficaria_ and _Acorus calamus_, ii. 170. + VEGETABLES, cultivated, reversion in, ii. 31-32; + European, culture of, in India, ii. 168-169. + VEITH, Mr., on breeds of horses, i. 49. + _Verbascum_, intercrossing of species of, i. 336, ii. 93, 105-107; + reversion in hybrids of, i. 392; + contabescent, wild plants of, ii. 165; + villosity in, ii. 277. + _Verbascum austriacum_, ii. 136. + _Verbascum blattaria_, ii. 105-106. + _Verbascum lychnitis_, ii. 105-106, 136. + _Verbascum nigrum_, ii. 136. + _Verbascum phoeniceum_, ii. 107, 137; + variable duration of, ii. 305. + _Verbascum thapsus_, ii. 106. + VERBENAS, origin of, i. 364; + white, liability of, to mildew, ii. 228, 336; + scorching of dark, ii. 229, 336; + effect of changed conditions of life on, ii. 273. + VERLOT, on the darkleaved Barberry, i. 362; + inheritance of peculiarities of foliage in trees, i. 362; + production of _Rosa cannabifolia_ by bud-variation from _R. alba_, i. + 381; + bud-variation in _Aralia trifoliata_, i. 382; + variegation of leaves, i. 383; + colours of tulips, i. 386; + uncertainty of inheritance, ii. 18; + persistency of white flowers, ii. 20; + peloric flowers of _Linaria_, ii. 58; + tendency of striped flowers to uniformity of colour, ii. 70; + non-intercrossing of certain allied plants, ii. 91; + sterility of _Primulae_ with coloured calyces, ii. 166; + on fertile proliferous flowers, _ibid._; + on the Irish yew, ii. 241; + differences in the _Camellia_, ii. 251; + effect of soil on the variegated strawberry, ii. 274; + correlated variability in plants, ii. 330. + _Verruca_, ii. 53, 400. + VERTEBRAE, characters of, in rabbits, i. 120-122; + in ducks, i. 283-284; + number and variations of, in pigeons, i. 165-166; + number and characters of, in fowls, i. 266-268; + variability of number of, in the pig, i. 74. + VERTUCH, see Putsche. + "VERUGAS," ii. 276. + VESPUCIUS, early cultivation in Brazil, i. 311. + VIBERT'S experiments on the cultivation of the vine from seed, i. 332. + _Viburnum opulus_, ii. 185, 316. + _Vicia sativa_, leaflet converted into a tendril in, ii. 392. + VICUNAS, selection of, ii. 207. + VILLOSITY of plants, influenced by dryness, ii. 277. + VILMORIN, cultivation of the wild carrot, i. 326, ii. 217; + colours of tulips, i. 386; + uncertainty of inheritance in balsams and roses, ii. 18; + experiments with dwarf varieties of _Saponaria calabrica_ and _Tagetes + signata_, ii. 20; + reversion of flowers by stripes and blotches, ii. 37; + on variability, ii. 262. + _Vinca minor_, sterility in, ii. 170. + VINE, i. 332-334; + parsley-leaved, reversion of, i. 382; + graft-hybrid produced by inosculation in the, i. 395; + disease of, influenced by colour of grapes, ii. 228; + influence of climate, &c., on varieties of the, ii. 278; + diminished extent of cultivation of the, ii. 308; + acclimatisation of the, in the West Indies, ii. 313. + _Viola_, species of, i. 368. + _Viola lutea_, different coloured flowers in, i. 408. + _Viola tricolor_, reversion in, ii. 31, 47. + VIRCHOW, Prof., blindness occurring in the offspring of consanguineous + marriages, ii. 143; + on the growth of bones, ii. 294, 381; + on cellular prolification, ii. 295; + independence of the elements of the body, ii. 369; + on the cell-theory, ii. 370; + presence of hairs and teeth in ovarian tumours, ii. 370; + of hairs in the brain, ii. 391; + special affinities of the tissues, ii. 380; + origin of polypoid excrescences and tumours, ii. 381. + VIRGIL on the selection of seed-corn, i. 318, ii. 203; + of cattle and sheep, ii. 202. + VIRGINIAN islands, ponies of, i. 52. + _Virgularia_, ii. 378. + VISION, hereditary peculiarities of, ii. 8-9; + {484} + in amphibious animals, ii. 223; + varieties of, ii. 300; + affections of organs of, correlated with other peculiarities, ii. 328. + _Vitis vinifera_, i. 332-334, 375. + _Viverra_, sterility of species of, in captivity, ii. 151. + VOGEL, varieties of the date palm, ii. 256. + VOGT, on the indications of stripes on black kittens, ii. 55. + VOICE, differences of, in fowls, i. 259; + peculiarities of, in ducks, i. 281; + inheritance of peculiarities of, ii. 6. + VOLZ, on the history of the dog, i. 16; + ancient history of the fowl, i. 246; + domestic ducks unknown to Aristotle, i. 277; + Indian cattle sent to Macedonia by Alexander, ii. 202; + mention of mules in the Bible, ii. 202; + history of the increase of breeds, ii. 244. + VON BERG on _Verbascum phoeniceum_, ii. 305. + VOORHELM, G., his knowledge of hyacinths, i. 371, ii. 251. + VROLIK, Prof., on polydactylism, ii. 12; + on double monsters, ii. 340; + influence of the shape of the mother's pelvis on her child's head, ii. + 344. + + WADERS, behaviour of, in confinement, ii. 156. + WAHLENBERG, on the propagation of Alpine plants by buds, runners, bulbs, + &c., ii. 169. + "WAHLVERWANDTSCHAFT" of Gaertner, ii. 180. + WALES, white cattle of, in the 10th century, i. 85. + WALKER, A., on intermarriage, i. 404; + on the inheritance of polydactylism, ii. 13. + WALKER, D., advantage of change of soil to wheat, ii. 146. + WALLACE, A. R., on a striped Javanese horse, i. 59; + on the conditions of life of feral animals, ii. 32; + artificial alteration of the plumage of birds, ii. 280; + on polymorphic butterflies, ii. 399-400; + on reversion, ii. 415; + on the limit of change, ii. 417. + WALLACE, Dr., on the sterility of Sphingidae hatched in autumn, ii. 158. + WALLACHIAN sheep, sexual peculiarities in the horns of, i. 96. + WALLFLOWER, bud-variation in, i. 382. + WALLICH, Dr., on _Thuja pendula_ or _filiformis_, i. 362. + WALNUTS, i. 356-357; + thin-shelled, attacked by tomtits, ii. 231; + grafting of, ii. 259. + WALSH, B. D., on galls, ii. 282, 283; + his "Law of equable variability," ii. 351-352. + WALTHER, F. L., on the history of the dog, i. 16; + on the intercrossing of the zebu and ordinary cattle, i. 83. + WARING, Mr., on individual sterility, ii. 162. + WART hog, i. 76. + WATERER, Mr., spontaneous production of _Cytisus alpino-laburnum_, i. + 390. + WATER melon, i. 357. + WATERHOUSE, G. R., on the winter-colouring of _Lepus variabilis_, i. 111. + WATERTON, C., production of tailless foals, i. 53; + on taming wild ducks, i. 278; + on the wildness of half-bred wild ducks, ii. 45; + assumption of male characters by a hen, ii. 51. + WATSON, H. C., on British wild fruit-trees, i. 312; + on the non-variation of weeds, i. 317; + origin of the plum, i. 345; + variation in _Pyrus malus_, i. 348; + on _Viola amoena_ and _tricolor_, i. 368; + on reversion in Scotch kail, ii. 32; + fertility of _Draba sylvestris_ when cultivated, ii. 163; + on generally distributed British plants, ii. 285. + WATTLES, rudimentary, in some fowls, ii. 315. + WATTS, Miss, on Sultan fowls, i. 228. + WEBB, James, interbreeding of sheep, ii. 120. + WEBER, effect of the shape of the mother's pelvis on her child's head, + ii. 344. + WEEDS, supposed necessity for their modification, coincidently with + cultivated plants, i. 317. + WEEPING varieties of trees, i. 361. + WEEPING habit of trees, capricious inheritance of, ii. 18-19. + WEEVIL, injury done to stone-fruit by, in North America, ii. 231. + WELSH cattle, descended from _Bos longifrons_, i. 81. + WEST Indies, feral pigs of, i. 77; + effect of climate of, upon sheep, i. 98. + WESTERN, Lord, change effected by, in the sheep, ii. 198. + WESTPHALIA, striped young pigs in, i. 76. + WESTWOOD, J. O., on peloric flowers of _Calceolaria_, ii. 346. + WHATELY, Archbishop, on grafting early and late thorns, i. 363. + WHEAT, specific unity or diversity of, i. 312-313, 316-317; + Hasora, i. 313; + presence or absence of barbs in, i. 314; + Godron on variations in, _ibid._; + varieties of, i. 314-315; + effects of soil and climate on, i. 316; + deterioration of, _ibid._; + crossing of varieties of, _ibid._, ii. 96, 104-105, 130; + in the Swiss lake-dwellings, i. 317-319; + selection applied to, i. 318, ii. 200; + increased fertility of hybrids of, with _Aegilops_, ii. 110; + advantage of change of soil to, ii. 146; + {485} + differences of, in various parts of India, ii. 165; + continuous variation in, ii. 200; + red, hardiness of, ii. 229, 336; + Fenton, ii. 232; + natural selection in, ii. 233; + varieties of, found wild, ii. 260; + effects of change of climate on, ii. 307; + ancient variety of, ii. 429. + WHITBY, Mrs., on the markings of silkworms, i. 302; + on the silkmoth, i. 303. + WHITE, Mr., reproduction of supernumerary digits after amputation, ii. + 14; + time occupied in the blending of crossed races, ii. 87. + WHITE, Gilbert, vegetable diet of dogs, ii. 303. + WHITE and white-spotted animals, liability of, to disease, ii. 336-337. + WHITE flowers, most truly reproduced by seed, ii. 20. + WICHURA, Max, on hybrid willows, ii. 50, 131, 267; + analogy between the pollen of old-cultivated plants, and of hybrids, + ii. 268. + WICKING, Mr., inheritance of the primary characters of _Columba livia_ in + cross-bred pigeons, i. 201; + production of a white head in almond tumblers, ii. 199. + WICKSTED, Mr., on cases of individual sterility, ii. 162. + WIEGMANN, spontaneous crossing of blue and white peas, i. 397; + crossing of varieties of cabbage, ii. 130; + on contabescence, ii. 165. + WIGHT, Dr., sexual sterility of plants propagated by buds, &c., ii. 169. + WILDE, Sir W. R., occurrence of _Bos frontosus_ and _longifrons_ in Irish + crannoges, i. 81; + attention paid to breeds of animals by the ancient Irish, ii. 203. + WILDMAN, on the dahlia, ii. 216, 273. + WILDNESS of the progeny of crossed tame animals, ii. 44-46. + WILKES, Capt., on the taming of pigeons among the Polynesians, ii. 161. + WILKINSON, J., on crossed cattle, ii. 104. + WILLIAMS, Mr., change of plumage in a Hamburgh hen, i. 258. + WILLIAMS, Mr., intercrossing of strawberries, i. 352. + WILLIAMSON, Capt., degeneration of dogs in India, i. 37; + on small Indian asses, i. 62. + WILLIAMSON, Rev. W., doubling of _Anemone coronaria_ by selection, ii. + 200. + WILLOWS, weeping, i. 361; + reversion of spiral-leaved weeping, i. 383; + hybrids of, ii. 267; + galls of, ii. 282-283. + WILLOUGHBY, F., notice of spot pigeons, i. 156; + on a fantail pigeon, i. 208; + on tumbler pigeons, i. 209; + on the turbit, i. 209; + on the barb and carrier pigeons, i. 211; + on the hook-billed duck, i. 277. + WILMOT, Mr., on a crested white Turkey cock, i. 293; + reversion of sheep in colour, ii. 30. + WILSON, B. O., fertility of hybrids of humped and ordinary cattle in + Tasmania, i. 83. + WILSON, Dr., prepotency of the Manx over the common cat, ii. 66. + WILSON, James, origin of dogs, i. 16. + WILSON, Mr., on prepotency of transmission in sheep, ii. 69; + on the breeding of bulls, ii. 196. + WINGS, proportionate length of, in different breeds of pigeons, i. + 175-176; + of fowls, effects of disuse on, i. 270-272; + characters and variations of, in ducks, i. 284-286; + diminution of, in birds of small islands, i. 286-287. + WING-FEATHERS, number of, in pigeons, i. 159; + variability of, in fowls, i. 258. + WOLF, recent existence of, in Ireland, i. 16; + barking of young, i. 27; + hybrids of, with the dog, i. 32. + WOLF-DOG, black, of Florida, i. 22. + WOLVES, North American, their resemblance to dogs of the same region, i. + 21-22; + burrowing of, i. 27. + WOODBURY, Mr., crossing of the Ligurian and common hive bees, i. 299, ii. + 126; + variability of bees, i. 298. + WOODWARD, S. P., on Arctic Mollusca, ii. 256. + WOOD, Willoughby, on Mr. Bates' cattle, ii. 118. + WOOLER, W. A., on the young of the Himalayan rabbit, i. 109; + persistency of the coloured calyx in a crossed Polyanthus, i. 365. + WORRARA poison, ii. 380. + WOUNDS, healing of, ii. 294. + WRIGHT, J., production of crippled calves by shorthorned cattle, ii. 118; + on selection in cattle, ii. 194; + effect of close interbreeding on pigs, ii. 121-122; + deterioration of game cocks by close interbreeding, ii. 124. + WRIGHT, Strethill, on the development of the hydroida, ii. 368. + WYMAN, Dr., on Niata cattle, and on a similar malformation in the + codfish, i. 89; + on Virginian pigs, ii. 227. + + XENOPHON, on the colours of hunting dogs, ii. 209. + XIMENES, Cardinal, regulations for the selection of rams, ii. 204. + + "YAHOO," the name of the pigeon in Persia, i. 155. + YAKS, domestication of, i. 82; + selection of white-tailed, ii. 206, 209. + {486} + YAM, development of axillary bulbs in the, ii. 169. + YARRELL, Mr., deficiency of teeth in hairless dogs, i. 34, ii. 326; + on ducks, i. 279, ii. 262; + characters of domestic goose, resembling those of _Anser albifrons_, i. + 288; + whiteness of ganders, i. 288; + variations in goldfish, i. 296-297; + assumption of male plumage by the hen-pheasant, ii. 51; + effect of castration upon the cock, ii. 51-52; + breeding of the skylark in captivity, ii. 154; + plumage of the male linnet in confinement, ii. 158; + on the dingo, ii. 263. + YELLOW fever, in Mexico, ii. 276. + YEW, fastigate, ii. 241. + YEW, Irish, hardy in New York, ii. 309. + YEW, weeping, i. 361; + propagation of, by seed, ii. 18-19. + YOLK, variations of, in the eggs of ducks, i. 281. + YOUATT, Mr., history of the dog, i. 16-17; + variations of the pulse in breeds of dogs, i. 35; + liability to disease in dogs, i. 35, ii. 227; + inheritance of goitre in dogs, ii. 10; + on the greyhound, i. 34, 41; + on King Charles' spaniels, i. 41; + on the setter, i. 41; + on breeds of horses, i. 49; + variation in the number of ribs in the horse, i. 50; + inheritance of diseases in the horse, ii. 10, 11; + introduction of Eastern blood into English horses, ii. 212-213; + on white Welsh cattle, i. 85, ii. 209; + improvement of British breeds of cattle, i. 93; + rudiments of horns in young hornless cattle, ii. 55, 315; + on crossed cattle, ii. 104, 119; + on Bakewell's long-horned cattle, ii. 118; + selection of qualities in cattle, ii. 196; + degeneration of cattle by neglect, ii. 239; + on the skull in hornless cattle, ii. 333; + disease of white parts of cattle, ii. 337; + displacement of long-horned by short-horned cattle, ii. 426; + on Angola sheep, i. 95; + on the fleece of sheep, i. 99; + correlation of horns and fleece in sheep, i. 95; + adaptation of breeds of sheep to climate and pasture, i. 96; + horns of Wallachian sheep, i. 96; + exotic sheep in the Zoological Gardens, i. 96-97, ii. 305; + occurrence of horns in hornless breeds of sheep, ii. 30; + on the colour of sheep, ii. 30; + on interbreeding sheep, ii. 120; + on Merino rams in Germany, ii. 196; + effect of unconscious selection on sheep, ii. 213; + reversion of Leicester sheep on the Lammermuir Hills, ii. 224; + on many-horned sheep, ii. 326; + reduction of bone in sheep, ii. 242; + persistency of character in breeds of animals in mountainous countries, + ii. 64; + on interbreeding, ii. 116; + on the power of selection, ii. 194-195; + slowness of production of breeds, ii. 244; + passages in the Bible relating to the breeding of animals, ii. 201-202. + YOUNG, J., on the Belgian rabbit, i. 106. + YULE, Capt., on a Burmese hairy family, ii. 77, 327. + + ZAMBESI, striped young pigs on the, i. 77. + ZAMBOS, character of the, ii. 47. + ZANO, J. G., introduction of rabbits into Porto Santo by, i. 112. + _Zea Mays_, i. 320. + ZEBU, i. 79; + domestication of the, i. 82; + fertile crossing of, with European cattle, i. 83, ii. 110. + ZEBRA, hybrids of, with the ass and mare, ii. 42. + _Zephyranthes candida_, ii. 164. + _Zinnia_, cultivation of, ii. 261. + ZOLLINGER on Malayan penguin ducks, i. 280. + ZOOSPORE, division of, in Algae, ii. 378. + "ZOPF-TAUBE," i. 154. + +THE END. + +LONDON: PRINTED BY W. CLOWES AND SONS, DUKE STREET, STAMFORD STREET, AND +CHARING CROSS. + + * * * * * + + +NOTES + +[1] 'Medical Notes and Reflections,' 3rd edit., 1855, p. 267. + +[2] Mr. Buckle, in his grand work on 'Civilisation,' expresses doubts on +the subject owing to the want of statistics. _See_ also Mr. Bowen, +Professor of Moral Philosophy, in 'Proc. American Acad. of Sciences,' vol. +v. p. 102 + +[3] For greyhounds, _see_ Low's 'Domest. Animals of the British Islands,' +1845, p. 721. For game-fowls, _see_ 'The Poultry Book,' by Mr. Tegetmeier, +1866, p. 123. For pigs, _see_ Mr. Sidney's edit. of 'Youatt on the Pig,' +1860, pp. 11, 22. + +[4] 'The Stud Farm,' by Cecil, p. 39. + +[5] 'Philosophical Transactions,' 1755, p. 23. I have seen only second-hand +accounts of the two grandsons. Mr. Sedgwick, in a paper to which I shall +hereafter often refer, states that _four_ generations were affected, and in +each the males alone. + +[6] Barbara Van Beck, figured, as I am informed by the Rev. W. D. Fox, in +Woodburn's 'Gallery of Rare Portraits,' 1816, vol. ii. + +[7] 'Proc. Zoolog. Soc.,' 1833, p. 16 + +[8] Hofacker, 'Ueber die Eigenschaften,' &c., 1828, s. 34. Report by +Pariset in 'Comptes Rendus,' 1847, p. 592. + +[9] Hunter, as quoted in Harlan's 'Med. Researches,' p. 530. Sir A. +Carlisle, 'Phil. Transact.,' 1814, p. 94. + +[10] Girou de Buzareignues, 'De la Generation,' p. 282. + +[11] 'Macmillan's Magazine,' July and August, 1865. + +[12] The works which I have read and found most useful are Dr. Prosper +Lucas's great work, 'Traite de l'Heredite Naturelle,' 1847. Mr. W. +Sedgwick, in 'British and Foreign Medico-Chirurg. Review,' April and July, +1861, and April and July, 1863: Dr. Garrod on Gout is quoted in these +articles. Sir Henry Holland, 'Medical Notes and Reflections,' 3rd edit., +1855. Piorry, 'De l'Heredite dans les Maladies,' 1840. Adams, 'A +Philosophical Treatise on Hereditary Peculiarities,' 2nd edit., 1815. Essay +on 'Hereditary Diseases,' by Dr. J. Steinan, 1843. _See_ Paget, in 'Medical +Times,' 1857, p. 192, on the Inheritance of Cancer; Dr. Gould, in 'Proc. of +American Acad. of Sciences,' Nov. 8, 1853, gives a curious case of +hereditary bleeding in four generations. Harlan, 'Medical Researches,' p. +593. + +[13] Marshall, quoted by Youatt in his work on Cattle, p. 284. + +[14] 'Philosoph. Transact.,' 1814, p. 94. + +[15] 'Medical Notes and Reflections,' 3rd edit., p. 33. + +[16] This affection, as I hear from Mr. Bowman, has been ably described and +spoken of as hereditary by Dr. Dondera, of Utrecht, whose work was +published in English by the Sydenham Society in 1864. + +[17] Quoted by Mr. Herbert Spencer, 'Principles of Biology,' vol. i. p. +244. + +[18] 'British and Foreign Medico-Chirurg. Review, 'April, 1861, p. 482-6; +'l'Hered. Nat.,' tom. i. pp. 391-408. + +[19] Dr. Osborne, Pres. of Royal College of Phys. in Ireland, published +this case in the 'Dublin Medical Journal' for 1835. + +[20] These various statements are taken from the following works and +papers:--Youatt on 'The Horse,' pp. 35, 220. Lawrence, 'The Horse,' p. 30. +Karkeek, in an excellent paper in 'Gard. Chronicle,' 1853, p. 92. Mr. +Burke, in 'Journal of R. Agricul. Soc. of England,' vol. v. p. 511. +'Encyclop. of Rural Sports,' p. 279. Girou de Buzareignues, 'Philosoph. +Phys.,' p. 215. _See_ following papers in 'The Veterinary:' Roberts, in +vol. ii. p. 144; M. Marrimpoey, vol. ii. p. 387; Mr. Karkeek, vol. iv. p. +5; Youatt on Goitre in Dogs, vol. v. p. 483; Youatt, in vol. vi. pp. 66, +348, 412; M. Bernard, vol. xi. p. 539; Dr. Samesreuther, on Cattle, in vol. +xii. p. 181; Percivall, in vol. xiii. p. 47. With respect to blindness in +horses, _see_ also a whole row of authorities in Dr. P. Lucas's great work, +tom. i. p. 399. Mr. Baker, in 'The Veterinary,' vol. xiii. p. 721, gives a +strong case of hereditary imperfect vision and of jibbing. + +[21] Knight on 'The Culture of the Apple and Pear,' p. 31. Lindley's +'Horticulture,' p. 180. + +[22] These statements are taken from the following works in order:--Youatt +on 'The Horse,' p. 48; Mr. Darvill, in 'The Veterinary,' vol. viii. p. 50. +With respect to Robson, _see_ 'The Veterinary,' vol. iii. p. 580; Mr. +Lawrence on 'The Horse,' 1829, p. 9; 'The Stud Farm,' by Cecil, 1851; Baron +Cameronn, quoted in 'The Veterinary,' vol x. p. 500. + +[23] 'Recreations in Agriculture and Nat. Hist.,' vol. i. p. 68. + +[24] 'Ueber die Eigenschaften,' &c., 1828, s. 107. + +[25] Bronn's 'Geschichte der Natur,' band ii. s. 132. + +[26] Vrolik has discussed this point at full length in a work published in +Dutch, from which Mr. Paget has kindly translated for me passages. _See_, +also, Isidore Geoffroy St. Hilaire's 'Hist. des Anomalies,' 1832, tom. i. +p. 684. + +[27] 'Edinburgh New Phil. Journal,' July, 1863. + +[28] Some great anatomists, as Cuvier and Meckel, believe that the tubercle +one side of the hinder foot of the tailless Batrachians represents a sixth +digit. Certainly, when the hinder foot of a toad, as soon as it first +sprouts from the tadpole, is dissected, the partially ossified cartilage of +this tubercle resembles under the microscope, in a remarkable manner, a +digit. But the highest authority on such subjects, Gegenbaur (Untersuchung. +zur vergleich. anat. der Wirbelthiere: Carpus et Tarsus, 1864, s. 63), +concludes that this resemblance is not real, only superficial. + +[29] For these several statements, _see_ Dr. Struthers, in work cited, +especially on intermissions in the line of descent. Prof. Huxley, 'Lectures +on our Knowledge of Organic Nature,' 1863, p. 97. With respect to +inheritance, _see_ Dr. Prosper Lucas, 'L'Heredite Nat.,' tom. i. p. 325. +Isid. Geoffroy, 'Anom.,' tom. i. p. 701. Sir A. Carlisle, in 'Phil. +Transact.,' 1814, p. 94. A. Walker, on 'Intermarriage,' 1838, p. 140, gives +a case of five generations; as does Mr. Sedgwick, in 'Brit. and Foreign +Medico-Chirurg. Review,' April, 1863, p. 462. On the inheritance of other +anomalies in the extremities, _see_ Dr. H. Dobell, in vol. xlvi. of +'Medico-Chirurg. Transactions,' 1863; also Mr. Sedgwick, in op. cit., +April, 1863, p. 460. With respect to additional digits in the negro, _see_ +Prichard, 'Physical History of Mankind.' Dr. Dieffenbach ('Journ. Royal +Geograph. Soc.,' 1841, p. 208) says this anomaly is not uncommon with the +Polynesians of the Chatham Islands. + +[30] 'The Poultry Chronicle,' 1854, p. 559. + +[31] The statements in this paragraph are taken from Isidore Geoffroy St. +Hilaire, 'Hist. des Anomalies,' tom. i. pp. 688-693. + +[32] As quoted by Carpenter, 'Princ. of Comp. Physiology,' 1854, p. 480. + +[33] Mueller's 'Phys.,' Eng. translat., vol. i. 1838, p. 407. A thrush, +however, was exhibited before the British Association at Hull, in 1853, +which had lost its tarsus, and this member, it was asserted, had been +thrice reproduced: I presume it was lost each time by disease. + +[34] 'Monthly Journal of Medical Science,' Edinburgh, 1848, new series, +vol. ii. p. 890. + +[35] 'An Essay on Animal Reproduction,' trans. by Dr. Maty, 1769, p. 79. + +[36] Bonnet, 'Oeuvres d'Hist. Nat.,' tom. v., part i., 4to. edit., 1781, +pp. 343, 350, 353. + +[37] So with insects, the larvae reproduce lost limbs, but, except in one +order, the mature insect has no such power. But the Myriapoda, which +apparently represent the larvae of true insects, have, as Newport has +shown, this power until their last moult. _See_ an excellent discussion on +this whole subject by Dr. Carpenter in his 'Princ. Comp. Phys.,' 1854, p. +479. + +[38] Dr. Guenther, in Owen's 'Anatomy of Vertebrates,' vol. i., 1866, p. +567. Spallanzani has made similar observations. + +[39] 'On the Anatomy of Vertebrates,' 1866, p. 170: with respect to the +pectoral fins of fishes, pp. 166-168. + +[40] 'Medical Notes and Reflections,' 1839, pp. 24, 34. _See_, also, Dr. P. +Lucas, 'l'Hered. Nat.,' tom. ii. p. 33. + +[41] 'Du Danger des Mariages Consanguins,' 2nd edit., 1862, p. 103. + +[42] 'British and Foreign Medico-Chirurg. Review,' July, 1863, pp. 183, +189. + +[43] Verlot, 'La Production des Varietes,' 1865, p. 32. + +[44] Loudon's 'Gard. Mag.,' vol. xii., 1836, p. 368. + +[45] Verlot, 'La Product. des Varietes,' 1865, p. 94. + +[46] Bronn's 'Geschichte der Natur,' b. ii. s. 121. + +[47] Rev. W. A. Leighton, 'Flora of Shropshire,' p. 497; and Charlesworth's +'Mag. of Nat. Hist.,' vol. i, 1837, p. 30. + +[48] Verlot, op. cit., p. 93. + +[49] For these several statements, _see_ Loudon's 'Gard. Magazine,' vol. +x., 1834, pp. 408, 180; and vol. ix., 1833, p. 597. + +[50] These statements are taken from Alph. De Candolle, 'Bot. Geograph.,' +p. 1083. + +[51] Verlot, op. cit., p. 38. + +[52] Op. cit., p. 59. + +[53] Alph. De Candolle, 'Geograph. Bot.,' p. 1082. + +[54] _See_ 'Cottage Gardener,' April 10, 1860, p. 18, and Sept. 10, 1861, +p. 456; 'Gard. Chron.,' 1845, p. 102. + +[55] Darwin, in 'Journal of Proc. Linn. Soc. Bot.,' 1862, p. 94. + +[56] Hofacker, 'Ueber die Eigenschaften,' &c., s. 10. + +[57] Bechstein, 'Naturgesch. Deutschlands,' b. iv. s. 462. Mr. Brent, a +great breeder of canaries, informs me that he believes that these +statements are correct. + +[58] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 245. + +[59] 'British and Foreign Med.-Chirurg. Review,' July, 1861, pp. 200-204. +Mr. Sedgwick has given such full details on this subject, with ample +references, that I need refer to no other authorities. + +[60] 'De l'Espece,' tom. ii., 1859, p. 299. + +[61] 'Philosoph. Magazine,' vol. iv., 1799, p. 5. + +[62] This last case is quoted by Mr. Sedgwick in 'British and Foreign +Medico-Chirurg. Review,' April, 1861, p. 484. For Blumenbach, _see_ +above-cited paper. _See_, also, Dr. P. Lucas, 'Traite de l'Hered. Nat.,' +tom. ii. p. 492. Also 'Transact. Lin. Soc.,' vol. ix. p. 323. Some curious +cases are given by Mr. Baker in 'The Veterinary,' vol. xiii. p. 723. +Another curious case is given in the 'Annales des Scienc. Nat.,' 1st +series, tom. xi. p. 324. + +[63] 'Proc. Royal Soc.,' vol. x. p. 297. + +[64] Mr. Sproule, in 'British Medical Journal,' April 18, 1863. + +[65] Downing, 'Fruits of America,' p. 5; Sageret, 'Pom. Phys.,' pp. 43, 72. + +[66] Youatt on Sheep, pp. 20, 234. The same fact of loose horns +occasionally appearing in hornless breeds has been observed in Germany: +Bechstein, 'Naturgesch. Deutschlands,' b. i. s. 362. + +[67] Youatt on Cattle, pp. 155, 174. + +[68] Youatt on Sheep, 1838, pp. 17, 145. + +[69] I have been informed of this fact through the Rev. W. D. Fox, on the +excellent authority of Mr. Wilmot: _see_, also, remarks on this subject in +an original article in the 'Quarterly Review,' 1849, p. 395. + +[70] Youatt, pp. 19, 234. + +[71] 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 231. + +[72] Loudon's 'Gard. Mag.,' vol. x., 1834, p. 396: a nurseryman, with much +experience on this subject, has likewise assured me that this sometimes +occurs. + +[73] 'Gardener's Chron.,' 1855, p. 777. + +[74] Ibid., 1862, p. 721. + +[75] _See_ some excellent remarks on this subject by Mr. Wallace, 'Journal +Proc. Linn. Soc.,' 1858, vol. iii. p. 60. + +[76] Dureau de la Malle, in 'Comptes Rendus,' tom. xli., 1855, p. 807. From +the statements above given, the author concludes that the wild pigs of +Louisiana are not descended from the European _Sus scrofa_. + +[77] Capt. W. Allen, in his 'Expedition to the Niger,' states that fowls +have run wild on the island of Annobon, and have become modified in form +and voice. The account is so meagre and vague that it did not appear to me +worth copying; but I now find that Dureau de la Malle ('Comptes Rendus,' +tom. xli., 1855, p. 690) advances this as a good instance of reversion to +the primitive stock, and as confirmatory of a still more vague statement in +classical times by Varro. + +[78] 'Flora of Australia,' 1859, Introduct., p. ix. + +[79] 'De l'Espece,' tom. ii. pp. 54, 58, 60. + +[80] Mr. Sedgwick gives many instances in the 'British and Foreign +Med.-Chirurg. Review,' April and July, 1863, pp. 448, 188. + +[81] In his edit. of 'Youatt on the Pig,' 1860, p. 27. + +[82] Dr. P. Lucas, 'Hered. Nat.,' tom. ii. pp. 314, 892: _see_ a good +practical article on this subject in 'Gard. Chronicle,' 1856, p. 620. I +could add a vast number of references, but they would be superfluous. + +[83] Koelreuter gives cases in his 'Dritte Fortsetzung,' 1766, s. 53, 59; +and in his well-known 'Memoirs on Lavatera and Jalapa.' Gaertner, +'Bastarderzeugung,' s. 437, 441, &c. Naudin, in his 'Recherches sur +l'Hybridite, Nouvelles Archives du Museum,' tom. i. p. 25. + +[84] Quoted by Mr. Sedgwick in 'Med.-Chirurg. Review,' April, 1861, p. 485. +Dr. H. Dobell, in 'Med.-Chirurg. Transactions,' vol. xlvi., gives an +analogous case, in which, in a large family, fingers with thickened joints +were transmitted to several members during five generations; but when the +blemish once disappeared it never reappeared. + +[85] Verlot, 'Des Varietes,' 1865, p. 63. + +[86] 'Nouvelles Archives du Museum,' tom. i. p. 25. Alex. Braun (in his +'Rejuvenescence,' Ray Soc., 1853, p. 315) apparently holds a similar +opinion. + +[87] Mr. Teebay, in 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 72. + +[88] Quoted by Hofacker, 'Ueber die Eigenschaften,' &c., s. 98. + +[89] 'Essais Hist. Nat. du Paraguay,' tom. ii. 1801, p. 372. + +[90] These facts are given on the high authority of Mr. Hewitt, in 'The +Poultry Book,' by Mr. Tegetmeier, 1866, p. 248. + +[91] 'The Poultry Book,' by Tegetmeier, 1866, p. 97. + +[92] 'Gardener's Chron. and Agricultural Gazette,' 1866, p. 528. + +[93] Ibid., 1860, p. 343. + +[94] Sclater, in 'Proc. Zoolog. Soc.,' 1862, p. 163. + +[95] 'History of the Horse,' p. 212. + +[96] 'Mem. presentes par divers Savans a l'Acad. Royale,' tom. vi. 1835, p. +338. + +[97] 'Letters from Alabama,' 1859, p. 280. + +[98] 'Hist. Nat. des Mammiferes,' 1820, tom. i. + +[99] 'Philosoph. Transact.,' 1821, p. 20. + +[100] Sclater, in 'Proc. Zoolog. Soc.,' 1862, p. 163: this species is the +Ghor-Khur of N.W. India, and has often been called the Hemionus of Pallas. +_See_, also, Mr. Blyth's excellent paper in 'Journ. of Asiatic Soc. of +Bengal,' vol. xxviii., 1860, p. 229. + +[101] Another species of wild ass, the true _A. hemionus_ or _Kiang_, which +ordinarily has no shoulder-stripes, is said occasionally to have them; and +these, as with the horse and ass, are sometimes double: _see_ Mr. Blyth, in +the paper just quoted, and in 'Indian Sporting Review,' 1856, p. 320; and +Col. Hamilton Smith, in 'Nat. Library, Horses,' p. 318; and 'Dict. Class. +d'Hist. Nat.,' tom. iii. p. 563. + +[102] Figured in the 'Gleanings from the Knowsley Menageries,' by Dr. J. E. +Gray. + +[103] Cases of both Spanish and Polish hens sitting are given in the +'Poultry Chronicle,' 1855, vol. iii. p. 477. + +[104] 'The Poultry Book,' by Mr. Tegetmeier, 1866, pp. 119, 163. The +author, who remarks on the two negatives ('Journ. of Hort.,' 1862, p. 325), +states that two broods were raised from a Spanish cock and Silver-pencilled +Hamburgh hen, neither of which are incubators, and no less than seven out +of eight hens in these two broods "showed a perfect obstinacy in sitting." +The Rev. E. S. Dixon ('Ornamental Poultry,' 1848, p. 200) says that +chickens reared from a cross between Golden and Black Polish fowls, are +"good and steady birds to sit." Mr. B. P. Brent informs me that he raised +some good sitting hens by crossing Pencilled Hamburgh and Polish breeds. A +cross-bred bird from a Spanish non-incubating cock and Cochin incubating +hen is mentioned in the 'Poultry Chronicle,' vol. iii. p. 13, as an +"exemplary mother." On the other hand, an exceptional case is given in the +'Cottage Gardener,' 1860, p. 388, of a hen raised from a Spanish cock and +black Polish hen which did not incubate. + +[105] 'The Poultry Book,' by Tegetmeier, 1866, pp. 165, 167. + +[106] 'Natural History Review,' 1863, April, p. 277. + +[107] 'Essays on Natural History,' p. 197. + +[108] As stated by Mr. Orton, in his 'Physiology of Breeding,' p. 12. + +[109] M. E. de Selys-Longchamps refers ('Bulletin Acad. Roy. de Bruxelles,' +tom. xii. No. 10) to more than seven of these hybrids shot in Switzerland +and France. M. Deby asserts ('Zoologist,' vol. v., 1845-46, p. 1254) that +several have been shot in various parts of Belgium and Northern France. +Audubon ('Ornitholog. Biography,' vol. iii. p. 168), speaking of these +hybrids, says that, in North America, they "now and then wander off and +become quite wild." + +[110] 'Journal of Researches,' 1845, p. 71. + +[111] 'Expedition to the Zambesi,' 1865, pp. 25, 150. + +[112] Dr. P. Broca, on 'Hybridity in the Genus Homo,' Eng. translat., 1864, +p. 39. + +[113] 'Nouvelles Archives du Museum,' tom. i. p. 151. + +[114] 'Bastarderzeugung,' s. 582, 438, &c. + +[115] 'Die Bastardbefruchtung ... der Weiden,' 1865, s. 23. For Gaertner's +remarks on this head, _see_ 'Bastarderzeugung,' s. 474, 582. + +[116] Yarrell, 'Phil. Transact.,' 1827, p. 268; Dr. Hamilton, in 'Proc. +Zoolog. Soc.,' 1862, p. 23. + +[117] 'Archiv. Skand. Beitraege zur Naturgesch.,' viii. s. 397-413. + +[118] In his 'Essays on Nat. Hist.,' 1838. Mr. Hewitt gives analogous cases +with hen-pheasants in 'Journal of Horticulture,' July 12, 1864, p. 37. +Isidore Geoffroy Saint Hilaire, in his 'Essais de Zoolog. Gen.' (suites a +Buffon, 1842, pp. 496-513), has collected such cases in ten different kinds +of birds. It appears that Aristotle was well aware of the change in mental +disposition in old hens. The case of the female deer acquiring horns is +given at p. 513. + +[119] 'Cottage Gardener,' 1860, p. 379. + +[120] 'Art de faire Eclorre,' &c., 1749, tom. ii. p. 8. + +[121] Sir H. Holland, 'Medical Notes and Reflections,' 3rd edit., 1855, p. +31. + +[122] Prof. Thomson on Steenstrup's Views on the Obliquity of Flounders: +'Annals and Mag. of Nat. Hist.,' May, 1865, p. 361. + +[123] Dr. E. von Martens, in 'Annals and Mag. of Nat. Hist.,' March, 1866, +p. 209. + +[124] Darwin, 'Balanidae,' Ray Soc., 1854, p. 499: _see_ also the appended +remarks on the apparently capricious development of the thoracic limbs on +the right and left sides in the higher crustaceans. + +[125] Mormodes ignea: Darwin, 'Fertilization of Orchids,' 1862, p. 251. + +[126] 'Journal of Horticulture,' July, 1864, p. 38. I have had the +opportunity of examining these remarkable feathers through the kindness of +Mr. Tegetmeier. + +[127] 'The Poultry Book,' by Mr. Tegetmeier, 1866, p. 241. + +[128] Carl Vogt, 'Lectures on Man,' Eng. translat., 1864, p. 411. + +[129] On Cattle, p. 174. + +[130] Isid. Geoffroy St. Hilaire, 'Des Anomalies,' tom. iii. p. 353. With +respect to the mammae in women, _see_ tom. i. p. 710. + +[131] 'Natural Hist. Review,' April, 1863, p. 258. _See_ also his Lecture, +Royal Institution, March 16, 1860. On same subject, _see_ Moquin-Tandon, +'Elements de Teratologie,' 1841, pp. 184, 352. + +[132] Verlot, 'Des Varietes,' 1865, p. 89; Naudin, 'Nouvelles Archives du +Museum,' tom. i. p. 137. + +[133] In his discussion on some curious peloric calceolarias, quoted in +'Journal of Horticulture,' Feb. 24, 1863, p. 152. + +[134] For other cases of six divisions in peloric flowers of the Labiatae +and Scrophulariaceae, _see_ Moquin-Tandon, 'Teratologie,' p. 192. + +[135] Moquin-Tandon, 'Teratologie,' p. 186. + +[136] _See_ Youatt on Cattle, pp. 92, 69, 78, 88, 163: also Youatt on +Sheep, p. 325. Also Dr. Lucas, 'L'Hered. Nat.,' tom. ii. p. 310. + +[137] 'Hered. Nat.,' tom. ii. pp. 112-120. + +[138] Sir H. Holland, 'Chapters on Mental Physiology,' 1852, p. 234. + +[139] 'Gardener's Chronicle,' 1860, p. 270. + +[140] Mr. N. H. Smith, Observations on Breeding, quoted in 'Encyclop. of +Rural Sports,' p. 278. + +[141] Quoted by Bronn, 'Geschichte der Natur,' b. ii. s. 170. _See_ Sturm, +'Ueber Racen,' 1825, s. 104-107. For the niata cattle, _see_ my 'Journal of +Researches,' 1845, p. 146. + +[142] Lucas, 'l'Heredite Nat.,' tom. ii. p. 112. + +[143] Mr. Orton, 'Physiology of Breeding,' 1855, p. 9. + +[144] Boitard and Corbie, 'Les Pigeons,' 1824, p. 224. + +[145] 'Les Pigeons, pp. 168, 198. + +[146] 'Das Ganze,' &c., 1837, s. 39. + +[147] 'The Pigeon Book,' p. 46. + +[148] 'Physiology of Breeding,' p.22; Mr. Hewitt, in 'The Poultry Book,' by +Tegetmeier, 1866, p. 224. + +[149] Boitard and Corbie, 'Les Pigeons,' 1824, p. 226. + +[150] 'Bastarderzeugung,' s. 256, 290, &c. Naudin ('Nouvelles Archives du +Museum,' tom. i. p. 149) gives a striking instance of prepotency in _Datura +stramonium_ when crossed with two other species. + +[151] Flourens, 'Longevite Humaine,' p. 144, on crossed jackals. With +respect to the difference between the mule and the hinny, I am aware that +this has generally been attributed to the sire and dam transmitting their +characters differently; but Colin, who has given in his 'Traite Phys. +Comp.,' tom. ii. pp. 537-539, the fullest description which I have met with +of these reciprocal hybrids, is strongly of opinion that the ass +preponderates in both crosses, but in an unequal degree. This is likewise +the conclusion of Flourens, and of Bechstein in his 'Naturgeschichte +Deutschlands,' b. i. s. 294. The tail of the hinny is much more like that +of the horse than is the tail of the mule, and this is generally accounted +for by the males of both species transmitting with greater power this part +of their structure; but a compound hybrid which I saw in the Zoological +Gardens, from a mare by a hybrid ass-zebra, closely resembled its mother in +its tail. + +[152] Mr. Hewitt, who has had such great experience in raising these +hybrids, says ('Poultry Book,' by Mr. Tegetmeier, 1866, pp. 165-167) that +in all, the head was destitute of wattles, comb, and ear-lappets; and all +closely resembled the pheasant in the shape of the tail and general contour +of the body. These hybrids were raised from hens of several breeds by a +cock-pheasant; but another hybrid, described by Mr. Hewitt, was raised from +a hen-pheasant by a silver-laced Bantam cock, and this possessed a +rudimental comb and wattles. + +[153] 'L'Hered. Nat.,' tom. ii. book ii. ch. i. + +[154] 'Bastarderzeugung,' s. 264-266. Naudin ('Nouvelles Archives du +Museum,' tom. i. p. 148) has arrived at a similar conclusion. + +[155] 'Cottage Gardener,' 1856, pp. 101, 137. + +[156] _See_ some remarks on this head with respect to sheep by Mr. Wilson, +in 'Gardener's Chronicle,' 1863, p. 15. + +[157] Verlot, 'Des Varietes,' 1865, p. 66. + +[158] Moquin-Tandon, 'Teratologie,' p. 191. + +[159] 'Nouvelles Archives du Museum,' tom. i. p. 137. + +[160] 'L'Hered. Nat.,' tom. ii. pp. 137-165. _See_, also, Mr. Sedgwick's +four memoirs, immediately to be referred to. + +[161] On Sexual Limitation in Hereditary Diseases, 'Brit. and For. +Med.-Chirurg. Review,' April, 1861, p. 477; July, p. 198; April, 1863, p. +44; and July, p. 159. + +[162] W. Scrope, 'Art of Deer Stalking,' p. 354. + +[163] Boitard and Corbie, 'Les Pigeons,' p. 173; Dr. F. Chapuis, 'Le Pigeon +Voyageur Belge,' 1865, p. 87. + +[164] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 349. + +[165] 'Embassy to the Court of Ava,' vol. i. p. 320. The third generation +is described by Capt. Yule in his 'Narrative of the Mission to the Court of +Ava,' 1855, p. 94. + +[166] 'Das Ganze der Taubenzucht,' 1837, s. 21, tab. i., fig. 4; s. 24, +tab. iv., fig. 2. + +[167] Kidd's 'Treatise on the Canary,' p. 18. + +[168] Charlesworth, 'Mag. of Nat. Hist.,' vol. i., 1837, p. 167. + +[169] Dr. Prosper Lucas, 'Hered. Nat.,' tom. ii. p. 713. + +[170] 'L'Hered. dans les Maladies,' 1840, p. 135. For Hunter, _see_ +Harlan's 'Med. Researches,' p. 530. + +[171] 'L'Hered. Nat.,' tom. ii. p. 850. + +[172] Sedgwick, 'Brit. and For. Med.-Chirurg. Review,' April 1861, p. 485. +I have seen three accounts, all taken from the same original authority +(which I have not been able to consult), and all differ in the details! but +as they agree in the main facts, I have ventured to quote this case. + +[173] Prosper Lucas, 'Hered. Nat.,' tom. i. p. 400. + +[174] Sedgwick, idem, July, 1861, p. 202. + +[175] Piorry, p. 109; Prosper Lucas, tom. ii. p. 759. + +[176] Prosper Lucas, tom. ii. p. 748. + +[177] Prosper Lucas, tom. ii. pp. 678, 700, 702; Sedgwick, idem, April, +1863, p. 449, and July, 1863, p. 162; Dr. J. Steinan, 'Essay on Hereditary +Disease,' 1843, pp. 27, 34. + +[178] These cases are given by Mr. Sedgwick, on the authority of Dr. H. +Stewart, in 'Med.-Chirurg. Review,' April, 1863, pp. 449, 477. + +[179] 'Hered. Nat.,' tom. ii. p. 852. + +[180] Communications to the Board of Agriculture, vol. i. p. 367. + +[181] 'Review of Reports, North of England,' 1808, p. 200. + +[182] 'Saeugethiere von Paraguay,' 1830, s. 212. + +[183] Rengger, 'Saeugethiere,' &c., s. 154. + +[184] White, 'Regular Gradation in Man,' p. 146. + +[185] Dr. W. F. Edwards, in his 'Characteres Physiolog. des Races +Humaines,' p. 23, first called attention to this subject, and ably +discussed it. + +[186] Rev. D. Tyerman, and Bennett, 'Journal of Voyages,' 1821-1829, vol. +i. p. 300. + +[187] Mr. S. J. Salter, 'Journal Linn. Soc.,' vol. vi., 1862, p. 71. + +[188] Sturm, 'Ueber Racen, &c.,' 1825, s. 107. Bronn, 'Geschichte der +Natur.,' b. ii. s. 170, gives a table of the proportions of blood after +successive crosses. Dr. P. Lucas, 'l'Heredite Nat.,' tom. ii. p. 308. + +[189] 'Bastarderzeugung,' s. 463, 470. + +[190] 'Nova Acta Petrop.,' 1794, p. 393: _see_ also previous volume. + +[191] As quoted in the 'True Principles of Breeding,' by C. H. Macknight +and Dr. H. Madden, 1865, p. 11. + +[192] With respect to plants, an admirable essay on this subject (Die +Geschlechter-Vertheilung bei den Pflanzen: 1867) has lately been published +by Dr. Hildebrand, who arrives at the same general conclusions as I have +done. + +[193] 'Teoria della Riproduzione Vegetal,' 1816, p. 12. + +[194] Verlot, 'Des Varietes,' 1865, p. 72. + +[195] Duval-Jouve, 'Bull. Soc. Bot. de France,' tom. x., 1863, p. 194. + +[196] Extract of a letter from Sir R. Heron, 1838, given me by Mr. Yarrell. +With respect to mice, _see_ 'Annal. des Sc. Nat.,' tom. i. p. 180; and I +have heard of other similar cases. For turtle-doves, Boitard and Corbie, +'Les Pigeons,' &c., p. 238. For the Game fowl, 'The Poultry Book,' 1866, p. +128. For crosses of tailless fowls, _see_ Bechstein, 'Naturges. Deutsch.' +b. iii. s. 403. Bronn, 'Geschichte der Natur,' b. ii. s. 170, gives +analogous facts with horses. On the hairless condition of crossed South +American dogs, _see_ Rengger, 'Saeugethiere von Paraguay,' s. 152: but I +saw in the Zoological Gardens mongrels, from a similar cross, which were +hairless, quite hairy, or hairy in patches, that is, piebald with hair. For +crosses of Dorking and other fowls, _see_ 'Poultry Chronicle,' vol. ii. p. +355. About the crossed pigs, extract of letter from Sir R. Heron to Mr. +Yarrell. For other cases, _see_ P. Lucas, 'Hered. Nat.,' tom. i. p. 212. + +[197] 'Internat. Hort. and Bot. Congress of London,' 1866. + +[198] 'Bastarderzeugung,' s. 307. Koelreuter ('Dritte Fortsetszung,' s. 34, +39), however, obtained intermediate tints from similar crosses in the genus +Verbascum. With respect to the turnips, _see_ Herbert's 'Amaryllidaceae,' +1837, p. 370. + +[199] 'Nouvelles Archives du Museum,' tom. i. p. 100. + +[200] Richardson, 'Pigs,' 1847, pp. 37, 42; S. Sidney's edition of 'Youatt +on the Pig,' 1860, p. 3. + +[201] _See_ Mr. W. C. Spooner's excellent paper on Cross-Breeding, 'Journal +Royal Agricult. Soc.,' vol. xx., part ii.: _see_ also an equally good +article by Mr. Ch. Howard, in 'Gardener's Chronicle,' 1860, p. 320. + +[202] 'Gardener's Chronicle,' 1857, pp. 649, 652. + +[203] 'Bulletin de la Soc. d'Acclimat.,' 1862, tom. ix. p. 463. _See_ also, +for other cases, MM. Moll and Gayot, 'Du Boeuf,' 1860, p. xxxii. + +[204] 'Poultry Chronicle,' vol. ii., 1854, p. 36. + +[205] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 58. + +[206] 'Gardener's Chronicle,' 1852, p. 765. + +[207] Spooner, in 'Journal Royal Agricult. Soc.,' vol. xx., part ii. + +[208] _See_ Colin's 'Traite de Phys. Comp. des Animaux Domestiques,' tom. +ii. p. 536, where this subject is well treated. + +[209] 'Les Pigeons,' p. 37. + +[210] Vol. i., 1854, p. 101. + +[211] 'Cottage Gardener,' 1856, p. 110. + +[212] 'Bastarderzeugung,' s. 553. + +[213] Dr. Pigeaux, in 'Bull. Soc. d'Acclimat.,' tom. iii., July 1866, as +quoted in 'Annals and Mag. of Nat. Hist.,' 1867, vol. xx. p. 75. + +[214] 'Journal de Physiolog.,' tom. ii., 1859, p. 385. + +[215] Dec. 1863, p. 484. + +[216] On the Varieties of Wheat, p. 66. + +[217] Rengger, 'Saeugethiere von Paraguay,' s. 336. + +[218] _See_ a memoir by MM. Lherbette and De Quatrefages, in 'Bull. Soc. +d'Acclimat.,' tom. viii., July, 1861, p. 312. + +[219] For the Norfolk sheep, _see_ Marshall's 'Rural Economy of Norfolk,' +vol. ii. p. 133. _See_ Rev. L. Landt's 'Description of Faroe,' p. 66. For +the ancon sheep, _see_ 'Phil. Transact.,' 1813, p. 90. + +[220] White's 'Nat. Hist. of Selbourne,' edited by Bennett, p. 39. With +respect to the origin of the dark-coloured deer, _see_ 'Some Account of +English Deer Parks,' by E. P. Shirley, Esq. + +[221] 'The Dovecote,' by the Rev. E. S. Dixon, p. 155; Bechstein, +'Naturgesch. Deutschlands,' Band iv., 1795, s. 17. + +[222] 'Cattle,' p. 202. + +[223] Mr. J. Wilkinson, in 'Remarks addressed to Sir J. Sebright,' 1820, p. +38. + +[224] 'Gardener's Chronicle,' 1858, p. 771. + +[225] 'Bastarderzeugung,' s. 87, 169. _See_ also the Table at the end of +volume. + +[226] 'Bastarderzeugung,' s. 87, 577. + +[227] 'Kenntniss der Befruchtung,' s. 137; 'Bastarderzeugung,' s. 92, 181. +On raising the two varieties from seed _see_ s. 307. + +[228] 'Bastarderzeugung,' s. 216. + +[229] The following facts, given by Koelreuter in his 'Dritte Fortsetzung,' +s. 34, 39, appear at first sight strongly to confirm Mr. Scott's and +Gaertner's statements; and to a certain limited extent they do so. +Koelreuter asserts, from innumerable observations, that insects incessantly +carry pollen from one species and variety of Verbascum to another; and I +can confirm this assertion; yet he found that the white and yellow +varieties of _Verbascum lychnitis_ often grew wild mingled together: +moreover, he cultivated these two varieties in considerable numbers during +four years in his garden, and they kept true by seed; but when he crossed +them, they produced flowers of an intermediate tint. Hence it might have +thought that both varieties must have a stronger elective affinity for the +pollen of their own variety than for that of the other; this elective +affinity, I may add, of each species for its own pollen (Koelreuter, +'Dritte Forts.,' s. 39, and Gaertner, 'Bastarderz.,' _passim_) being a +perfectly well-ascertained power. But the force of the foregoing facts is +much lessened by Gaertner's numerous experiments, for, differently from +Koelreuter, he never once got ('Bastarderz.,' s. 307) an intermediate tint +when he crossed the yellow and white flowered varieties of Verbascum. So +that the fact of the white and yellow varieties keeping true to their +colour by seed does not prove that they were not mutually fertilised by the +pollen carried by insects from one to the other. + +[230] 'Amaryllidaceae,' 1837, p. 366. Gaertner has made a similar +observation. + +[231] Koelreuter first observed this fact. 'Mem. de l'Acad. St. +Petersburg,' vol. iii. p. 197. _See_ also C. K. Sprengel, 'Das Entdeckte +Geheimniss,' s. 345. + +[232] Namely, Barbarines, Pastissons, Giraumous: 'Annal. des Sc. Nat.,' +tom. xxx., 1833, pp. 398 and 405. + +[233] 'Memoire sur les Cucurbitaceae,' 1826, pp. 46, 55. + +[234] 'Annales des Se. Nat.,' 4th series, tom. vi. M. Naudin considers +these forms as undoubtedly varieties of _Cucurbita pepo_. + +[235] 'Mem. Cucurb.,' p. 8. + +[236] 'Zweite Forts.,' s. 53, namely, Nicotiana major vulgaris; (2) +perennis; (3) Transylvanica; (4) a sub-var. of the last; (5) major latifol. +fl. alb. + +[237] Koelreuter was so much struck with this fact that he suspected that a +little pollen of _N. glutinosa_ in one of his experiments might have +accidentally got mingled with that of _var. perennis_, and thus aided its +fertilising power. But we now know conclusively from Gaertner +('Bastarderz.,' s. 34, 431) that two kinds of pollen never act _conjointly_ +on a third species; still less will the pollen of a distinct species, +mingled with a plant's own pollen, if the latter be present in sufficient +quantity, have any effect. The sole effect of mingling two kinds of pollen +is to produce in the same capsule seeds which yield plants, some taking +after the one and some after the other parent. + +[238] Mr. Scott has made some observations on the absolute sterility of a +purple and white primrose (_Primula vulgaris_) when fertilised by pollen +from the primrose ('Journal of Proc. of Linn. Soc.,' vol. viii., 1864, p. +98); but these observations require confirmation. I raised a number of +purple-flowered long-styled seedlings from seed kindly sent me by Mr. +Scott, and, though they were all some degree sterile, they were much more +fertile with pollen taken from the common primrose than with their own +pollen. Mr. Scott has likewise described a red equal-styled cowslip (_P. +veris_, idem, p. 106), which was found by him to be highly sterile when +crossed with the common cowslip; but this was not the case with several +equal-styled red seedlings raised by me from his plant. This variety of the +cowslip presents the remarkable peculiarity of combining male organs in +every respect like those of the short-styled form, with female organs +resembling in function and partly in structure those of the long-styled +form; so that we have the singular anomaly of the two forms combined in the +same flower. Hence it is not surprising that these flowers should be +spontaneously self-infertile in a high degree. + +[239] 'Act. Acad. St. Petersburg,' 1780, part ii., pp. 84, 100. + +[240] 'Annales des Sc. Nat.,' tom. xxi. (1st series), p. 61. + +[241] 'Bull. Bot. Soc. de France,' Dec. 27th, 1861, tom. viii. p. 612. + +[242] Quoted by Isid. Geoffroy St. Hilaire, 'Hist. Naturelle Generale,' +tom. iii. p. 476. Since this MS. has been sent to press a full discussion +on the present subject has appeared in Mr. Herbert Spencer's 'Principles of +Biology,' vol. ii. 1867, p. 457 _et seq._ + +[243] For cats and dogs, &c., _see_ Bellingeri, in 'Annal. des Sc. Nat.,' +2nd series, Zoolog., tom. xii. p. 155. For ferrets, Bechstein, +'Naturgeschichte Deutschlands,' Band i., 1801, s. 786, 795. For rabbits, +ditto, s. 1123, 1131; and Bronn's 'Geschichte der Natur,' B. ii. s. 99. For +mountain sheep, ditto, s. 102. For the fertility of the wild sow, _see_ +Bechstein's 'Naturgesch. Deutschlands,' B. i., 1801, s. 534; for the +domestic pig, Sidney's edit. of Youatt on the Pig, 1860, p. 62. With +respect to Lapland, _see_ Acerbi's 'Travels to the North Cape,' Eng. +translat., vol. ii. p. 222. About the Highland cows, _see_ Hogg on Sheep, +p. 263. + +[244] For the eggs of _Gallus bankiva_, _see_ Blyth, in 'Annals and Mag. of +Nat. Hist., 2nd series, vol. i., 1848, p. 456. For wild and tame ducks, +Macgillivray, 'British Birds,' vol. v. p. 37; and 'Die Enten,' s. 87. For +wild geese, L. Lloyd, 'Scandinavian Adventures,' vol. ii. 1854, p. 413; and +for tame geese, 'Ornamental Poultry,' by Rev. E. S. Dixon, p. 139. On the +breeding of pigeons, Pistor, 'Das Ganze der Taubenzucht,' 1831, s. 46; and +Boitard and Corbie, 'Les Pigeons,' p. 158. With respect to peacocks, +according to Temminck ('Hist. Nat. Gen. des Pigeons,' &c., 1813, tom. ii. +p. 41), the hen lays in India even as many as twenty eggs; but according to +Jerdon and another writer (quoted in Tegetmeier's 'Poultry Book,' 1866, pp. +280, 282), she there lays only from four to nine or ten eggs: in England +she is said, in the 'Poultry Book,' to lay five or six, but another writer +says from eight to twelve eggs. + +[245] 'The Art of Improving the Breed, &c.,' 1809, p. 16. + +[246] For Andrew Knight, _see_ A. Walker, on 'Intermarriage,' 1838, p. 227. +Sir J. Sebright's Treatise has just been quoted. + +[247] 'Cattle,' p. 199. + +[248] Nathusius, 'Ueber Shorthorn Rindvieh,' 1857, s. 71: _see_ also +'Gardener's Chronicle,' 1860, p. 270. Many analogous cases are given in a +pamphlet recently published by Mr. C. Macknight and Dr. H. Madden, 'On the +True Principles of Breeding;' Melbourne, Australia, 1865. + +[249] Mr. Willoughby Wood, in 'Gardener's Chronicle,' 1855, p. 411; and +1860, p. 270. _See_ the very clear tables and pedigrees given in Nathusius' +'Rindvieh,' s. 72-77. + +[250] Mr. Wright, 'Journal of Royal Agricult. Soc.,' vol. vii., 1846, p. +204. + +[251] Youatt on Cattle, p. 202. + +[252] Report British Assoc., Zoolog. Sect., 1838. + +[253] Azara, 'Quadrupedes du Paraguay,' tom. ii. pp. 354, 368. + +[254] For the case of the Messrs. Brown, _see_ 'Gard. Chronicle,' 1855, p. +26. For the Foscote flock, 'Gard. Chron.,' 1860, p. 416. For the Naz flock, +'Bull. de la Soc. d'Acclimat.,' 1860, p. 477. + +[255] Nathusius, 'Rindvieh,' s. 65; Youatt on Sheep, p. 495. + +[256] 'Gard. Chronicle,' 1861, p. 631. + +[257] Lord Somerville, 'Facts on Sheep and Husbandry,' p. 6. Mr. Spooner, +in 'Journal of Royal Agricult. Soc. of England,' vol. xx., part ii. _See_ +also an excellent paper on the same subject in 'Gard. Chronicle,' 1860, p. +321, by Mr. Charles Howard. + +[258] 'Some Account of English Deer Parks,' by Evelyn P. Shirley, 1867. + +[259] 'The Art of Improving the Breed,' &c., p. 13. With respect to Scotch +deer-hounds, _see_ Scrope's 'Art of Deer Stalking,' pp. 350-353. + +[260] 'Cottage Gardener,' 1861, p. 327. + +[261] Sidney's edit. of Youatt on the Pig, 1860, p. 30; p. 33, quotation +from Mr. Druce; p. 29, on Lord Western's case. + +[262] 'Journal, Royal Agricult. Soc. of England,' 1846, vol. vii. p. 205. + +[263] 'Ueber Rindvieh,' &c., s. 78. + +[264] Sidney on the Pig, p. 36. _See_ also note, p. 34. Also Richardson on +the Pig, 1847, p. 26. + +[265] Dr. Dally has published an excellent article (translated in the +'Anthropolog. Review,' May, 1864, p. 65), criticising all writers who have +maintained that evil follows from consanguineous marriages. No doubt on +this side of the question many advocates have injured their cause by +inaccuracies: thus it has been stated (Devay, 'Du Danger des Mariages,' +&c., 1862, p. 141) that the marriages of cousins have been prohibited by +the legislature of Ohio; but I have been assured, in answer to inquiries +made in the United States, that this statement is a mere fable. + +[266] _See_ his most interesting work on the 'Early History of Man,' 1865, +chap. x. + +[267] On Consanguinity in Marriage, in the 'Fortnightly Review,' 1865, p. +710; Hofacker, 'Ueber die Eigenschaften,' &c. + +[268] Sir G. Grey's 'Journal of Expeditions into Australia,' vol. ii. p. +243; and Dobrizhoffer, 'On the Abipones of South America.' + +[269] 'The Art of Improving the Breed,' p. 13. + +[270] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 245. + +[271] 'Journal Royal Agricult. Soc.' 1846, vol. vii. p. 205; _see_ also +Ferguson on the Fowl, pp. 83, 317; _see_ also 'The Poultry Book,' by +Tegetmeier, 1866, p. 135, with respect to the extent to which cock-fighters +found that they could venture to breed in-and-in, viz., occasionally a hen +with her own son; "but they were cautious not to repeat the in-and-in +breeding." + +[272] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 79. + +[273] 'The Poultry Chronicle,' 1854, vol. i. p. 43. + +[274] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 79. + +[275] 'The Poultry Chronicle,' vol. i. p. 89. + +[276] 'The Poultry Book,' 1866, p. 210. + +[277] Ibid, 1866, p. 167; and 'Poultry Chronicle,' vol. iii., 1855, p. 15. + +[278] 'A Treatise on Fancy Pigeons,' by J. M. Eaton, p. 56. + +[279] 'The Pigeon Book,' p. 46. + +[280] 'Das Ganze der Taubenzucht,' 1837, s. 18. + +[281] 'Les Pigeons,' 1824, p. 35. + +[282] 'Proc. Entomolog. Soc.,' Aug. 6th, 1860, p. 126. + +[283] 'Journal of Horticulture,' 1861, pp. 39, 77, 158; and 1864, p. 206. + +[284] 'Beitraege zur Kenntniss der Befruchtung,' 1844, s. 366. + +[285] 'Amaryllidaceae,' p. 371. + +[286] 'De la Fecondation,' 2nd edit., 1862, p. 79. + +[287] 'Memoire sur les Cucurbitacees,' pp. 36, 28, 30. + +[288] Loudon's 'Gard. Mag.,' vol. viii., 1832, p. 52. + +[289] 'Transact. Hort. Soc.,' vol. i. p. 25. + +[290] 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. vi. p. 189. + +[291] 'Philosophical Transactions,' 1799, p. 200. + +[292] 'Ueber die Bastarderzeugung,' 1828, s. 32, 33. For Mr. Chaundy's +case, _see_ Loudon's 'Gard. Mag.,' vol. vii., 1831, p. 696. + +[293] 'Gardener's Chron.,' 1846, p. 601. + +[294] 'Philosoph. Transact.,' 1799, p. 201. + +[295] Quoted in 'Bull. Bot. Soc. France,' vol. ii., 1855, p. 327. + +[296] Gaertner, 'Bastarderzeugung,' s. 259, 518, 526 _et seq._ + +[297] 'Fortsetzung,' 1763, s. 29; 'Dritte Fortsetzung,' s. 44, 96; 'Act. +Acad. St. Petersburg,' 1782, part ii., p. 251; 'Nova Acta,' 1793, pp. 391, +394; 'Nova Acta,' 1795, pp. 316, 323. + +[298] 'Die Bastardbefruchtung,' &c., 1865, s. 31, 41, 42. + +[299] Max Wichura fully accepts this view ('Bastardbefruchtung,' s. 43), as +does the Rev. M. J. Berkeley, in 'Journal of Hort. Soc.,' Jan. 1866, p. 70. + +[300] 'Bastarderzeugung,' s. 394, 526, 528. + +[301] Koelreuter,' Nova Acta,' 1795, p. 316. + +[302] Gaertner, 'Bastarderzeugung,' s. 430. + +[303] 'Botanische Zeitung,' Jan. 1864, s. 3. + +[304] 'Monatsbericht Akad. Wissen,' Berlin, 1866, s. 372. + +[305] International Hort. Congress, London, 1866. + +[306] 'Proc. Bot. Soc. of Edinburgh,' May, 1863: these observations are +given in abstract, and others are added, in the 'Journal of Proc. of Linn. +Soc.,' vol. viii. Bot., 1864, p. 162. + +[307] Prof. Lecoq, 'De la Fecondation,' 2nd edit., 1862, p. 76. + +[308] 'Bastarderzeugung,' s. 64, 357. + +[309] Idem, s. 357. + +[310] 'Zweite Fortsetzung,' s. 10; 'Dritte Fort.,' s. 40. + +[311] Duvernoy, quoted by Gaertner, 'Bastarderzeugung,' s. 334. + +[312] 'Gardner's Chronicle,' 1846, p. 183. + +[313] 'Transact. Hort. Soc.,' vol. vii., 1830, p. 95. + +[314] Prof. Lecoq, 'De la Fecondation,' 1845, p. 70; Gaertner, +'Bastarderzeugung,' s. 64. + +[315] 'Gardener's Chron.' 1866, p. 1068. + +[316] 'Journal of Proc. of Linn. Soc.,' vol. viii., 1864, p. 168. + +[317] 'Amaryllidaceae,' 1837, p. 371; 'Journal of Hort. Soc.,' vol. ii., +1847, p. 19. + +[318] Loudon's 'Gardener's Magazine,' vol. xi., 1835, p. 260. + +[319] 'Gardener's Chronicle,' 1850, p. 470. + +[320] 'Journal Hort. Soc., vol. v. p. 135. The seedlings thus raised were +given to the Hort. Soc.; but I find, on inquiry, that they unfortunately +died the following winter. + +[321] Mr. D. Beaton, in 'Journal of Hort.,' 1861, p. 453. Lecoq, however +('De la Fecond.,' 1862, p. 369), states that this hybrid is descended from +_G. psittacinus_ and _cardinalis_; but this is opposed to Herbert's +experience, who found that the former species could not be crossed. + +[322] This is the conclusion of Prof. Devay, 'Du Danger des Mariages +Consang.,' 1862, p. 97. Virchow quotes, in the 'Deutsche Jahrbuecher,' +1863, s. 354, some curious evidence on half the cases of a peculiar form of +blindness occurring in the offspring from near relations. + +[323] For England, _see_ below. For Germany, _see_ Metzger, +'Getreidearten,' 1841, s. 63. For France, Loiseleur-Deslongchamps ('Consid. +sur les Cereales,' 1843, p. 200) gives numerous references on this subject. +For Southern France, _see_ Godron, 'Florula Juvenalis,' 1854, p. 28. + +[324] 'A general Treatise of Husbandry,' vol. iii. p. 58. + +[325] 'Gardener's Chronicle and Agricult. Gazette,' 1858, p. 247; and for +the second statement, idem, 1850, p. 702. On this same subject, _see_ also +Rev. D. Walker's 'Prize Essay of Highland Agricult. Soc.,' vol. ii. p. 200. +Also Marshall's 'Minutes of Agriculture,' November, 1775. + +[326] Oberlin's 'Memoirs,' Eng. translat., p. 73. For Lancashire, _see_ +Marshall's 'Review of Reports,' 1808, p. 295. + +[327] 'Cottage Gardener,' 1856, p. 186. For Mr. Robson's subsequent +statements, _see_ 'Journal of Horticulture,' Feb. 18, 1866, p. 121. For Mr. +Abbey's remarks on grafting, &c., idem, July 18, 1865, p. 44. + +[328] 'Mem. de l'Acad. des Sciences,' 1790, p. 209. + +[329] 'On the Varieties of Wheat,' p. 52. + +[330] Mr. Spencer has fully and ably discussed this whole subject in his +'Principles of Biology,' 1864, vol. ii. ch. x. In the first edition of my +'Origin of Species,' 1859, p. 267, I spoke of the good effects from slight +changes in the conditions of life and from cross-breeding, and of the evil +effects from great changes in the conditions and from crossing widely +distinct forms, as a series of facts "connected together by some common but +unknown bond, which is essentially related to the principle of life." + +[331] 'Essais de Zoologie Generale,' 1841, p. 256. + +[332] Du Rut, 'Annales du Museum,' 1807, tom. ix. p. 120. + +[333] 'Saeugethiere von Paraguay,' 1830, s. 49, 106, 118, 124, 201, 208, +249, 265, 327. + +[334] 'The Naturalist on the Amazons,' 1863, vol. i. pp. 99, 193; vol. ii. +p. 113. + +[335] 'Embassy to the Court of Ava,' vol. i. p. 534. + +[336] 'Journal,' vol. i. p. 213. + +[337] 'Saeugethiere,' s. 327. + +[338] On the Breeding of the larger Felidae, 'Proc. Zoolog. Soc.,' 1861, p. +140. + +[339] Sleeman's 'Rambles in India,' vol. ii. p. 10. + +[340] Wiegmann's 'Archif fuer Naturgesch.,' 1837, s. 162. + +[341] Rengger, 'Saeugethiere,' &c., s. 276. On the parentage of the +guinea-pig, _see_ also Isid. Geoffroy St. Hilaire, 'Hist. Nat. Gen.' + +[342] Although the existence of the _Leporides_, as described by Dr. Broca +('Journal de Phys.,' tom. ii. p. 370), is now positively denied, yet Dr. +Pigeaux ('Annals and Mag. of Nat. Hist.,' vol. xx., 1867, p. 75) affirms +that the hare and rabbit have produced hybrids. + +[343] 'Quadrupeds of North America,' by Audubon and Bachman, 1846, p. 268. + +[344] Loudon's 'Mag. of Nat. Hist.,' vol. ix., 1836, p. 571; Audubon and +Bachman's 'Quadrupeds of North America,' p. 221. + +[345] Flourens, 'De l'Instinct,' &c., 1845, p. 88. + +[346] _See_ 'Annual Reports Zoolog. Soc.,' 1855, 1858, 1863, 1864; 'Times' +newspaper, Aug. 10th, 1847; Flourens, 'De l'Instinct,' p. 85. + +[347] 'Saeugethiere,' &c., s. 34, 49. + +[348] Art. Brazil, 'Penny Cyclop.,' p. 363. + +[349] 'The Naturalist on the River Amazon,' vol. i. p. 99. + +[350] 'Encyclop. of Rural Sports,' p. 691. + +[351] According to Sir A. Burnes ('Cabool,' &c., p. 51), eight species are +used for hawking in Scinde. + +[352] Loudon's 'Mag. of Nat. Hist.,' vol. vi., 1833, p. 110. + +[353] F. Cuvier, 'Annal. du Museum,' tom. ix. p. 128. + +[354] 'The Zoologist,' vol. vii.-viii., 1849-50, p. 2648. + +[355] Knox, 'Ornithological Rambles in Sussex,' p. 91. + +[356] 'The Zoologist,' vol. vii.-viii., 1849-50, p. 2566; vol. ix.-x., +1851-2, p. 3207. + +[357] Bechstein, 'Naturgesch. der Stubenvoegel,' 1840, s. 20. + +[358] 'Ornithological Biography,' vol. v. p. 517. + +[359] A case is recorded in 'The Zoologist,' vol. i.-ii., 1843-45, p. 453. +For the siskin breeding, vol. iii.-iv., 1845-46, p. 1075. Bechstein, +'Stubenvoegel,' s. 139, speaks of bullfinches making nests, but rarely +producing young. + +[360] Yarrell's 'Hist. British Birds,' 1839, vol. i. p. 412. + +[361] Loudon's 'Mag. of Nat. History,' vol. ix., 1836, p. 347. + +[362] 'Memoires du Museum d'Hist. Nat.,' tom. x. p. 314: five cases of +parrots breeding in France are here recorded. _See_, also, 'Report Brit. +Assoc. Zoolog.,' 1843. + +[363] 'Stubenvoegel,' s. 105, 83. + +[364] Dr. Hancock remarks ('Charlesworth's Mag. of Nat. Hist.,' vol. ii., +1838, p. 492), "it is singular that, amongst the numerous useful birds that +are indigenous to Guiana, none are found to propagate among the Indians; +yet the common fowl is reared in abundance throughout the country." + +[365] 'A Week at Port Royal,' 1855, p. 7. + +[366] Audubon, 'American Ornithology,' vol. v. pp. 552, 557. + +[367] Moubray on Poultry, 7th edit., p. 133. + +[368] Temminck, 'Hist. Nat. Gen. des Pigeons,' &c., 1813, tom. iii. pp. +288, 382; 'Annals and Mag. of Nat. Hist.,' vol. xii., 1843, p. 453. Other +species of partridge have occasionally bred; as the red-legged (_P. +rubra_), when kept in a large court in France (_see_ 'Journal de Physique,' +tom. xxv. p. 294), and in the Zoological Gardens in 1856. + +[369] Rev. E. S. Dixon, 'The Dovecote,' 1851, pp. 243-252. + +[370] Temminck, 'Hist. Nat. Gen. des Pigeons,' &c., tom. ii. pp. 456, 458; +tom. iii. pp. 2, 13, 47. + +[371] Bates, 'The Naturalist on the Amazons,' vol. i. p. 193; vol. ii. p. +112. + +[372] Temminck, 'Hist. Nat. Gen.,' &c., tom. iii. p. 125. For _Tetrao +urogallus_, _see_ L. Lloyd, 'Field Sports of North of Europe,' vol. i. pp. +287, 314; and 'Bull. de la Soc. d'Acclimat.,' tom. vii., 1860, p. 600. For +_T. Scoticus_, Thompson, 'Nat. Hist. of Ireland,' vol. ii., 1850, p. 49. +For _T. cupido_, 'Boston Journal of Nat. Hist.,' vol. iii. p. 199. + +[373] Marcel de Serres, 'Annales des Sci. Nat.,' 2nd series, Zoolog., tom. +xiii. p. 175. + +[374] Dr. Hancock, in 'Charlesworth's Mag. of Nat. Hist.' vol. ii., 1838, +p. 491; R. Hill, 'A Week at Port Royal,' p. 8; 'Guide to the Zoological +Gardens,' by P. L. Sclater, 1859, pp. 11, 12; 'The Knowsley Menagerie,' by +Dr. Gray, 1846, pl. xiv.; E. Blyth, 'Report Asiatic Soc. of Bengal,' May, +1855. + +[375] Prof. Newton, in 'Proc. Zoolog. Soc.,' 1860, p. 336. + +[376] 'The Dovecote and Aviary,' p. 428. + +[377] 'Ornithological Biography,' vol. iii. p. 9. + +[378] 'Geograph. Journal,' vol. xiii., 1844, p. 32. + +[379] Loudon's 'Mag. of Nat. Hist.,' vol. v., 1832, p. 153. + +[380] 'Zoologist,' vols. v.-vi., 1847-48, p. 1660. + +[381] 'Transact. Entomolog. Soc.,' vol. iv., 1845, p. 60. + +[382] 'Transact. Linn. Soc.,' vol. vii. p. 40. + +[383] _See_ an interesting paper by Mr. Newman, in the 'Zoologist,' 1857, +p. 5764; and Dr. Wallace, in 'Proc. Entomolog. Soc.,' June 4th, 1860, p. +119. + +[384] Yarrell's 'British Birds,' vol. i. p. 506; Bechstein, 'Stubenvoegel,' +s. 185; 'Philosoph. Transact.,' 1772, p. 271. Bronn ('Geschichte der +Natur,' Band ii. s. 96) has collected a number of cases. For the case of +the deer, _see_ 'Penny Cyclop.,' vol. viii. p. 350. + +[385] 'Journal de Physiologie,' tom. ii. p. 347. + +[386] For additional evidence on this subject, _see_ F. Cuvier, in 'Annales +du Museum,' tom. xii. p. 119. + +[387] Numerous instances could be given. Thus Livingstone ('Travels,' p. +217) states that the King of the Barotse, an inland tribe which never had +any communication with white men, was extremely fond of taming animals, and +every young antelope was brought to him. Mr. Galton informs me that the +Damaras are likewise fond of keeping pets. The Indians of South America +follow the same habit. Capt. Wilkes states that the Polynesians of the +Samoan Islands tamed pigeons; and the New Zealanders, as Mr. Mantell +informs me, kept various kinds of birds. + +[388] For analogous cases with the fowl, _see_ Reaumur, 'Art de faire +Eclorre,' &c., 1749, p. 243; and Col. Sykes, in 'Proc. Zoolog. Soc.,' 1832, +&c. With respect to the fowl not breeding in northern regions, _see_ +Latham's 'Hist. of Birds,' vol. viii., 1823, p. 169. + +[389] 'Mem. par divers Savans, Acad. des Sciences,' tom. vi., 1835, p. 347. + +[390] Youatt on Sheep, p. 181. + +[391] J. Mills, 'Treatise on Cattle,' 1776, p. 72. + +[392] Bechstein, 'Stubenvoegel,' s. 242. + +[393] Crawfurd's 'Descriptive Dict. of the Indian Islands,' 1856, p. 145. + +[394] 'Bull. de la Soc. Acclimat., tom. ix., 1862, pp. 380, 384. + +[395] For pigeons, _see_ Dr. Chapuis, 'Le Pigeon Voyageur Belge,' 1865, p. +66. + +[396] 'Swedish Acts,' vol. i., 1739, p. 3. Pallas makes the same remark in +his Travels (Eng. translat.), vol. i. p. 292. + +[397] A. Kerner, 'Die Cultur der Alpenflanzen,' 1864, s. 139; Watson's +'Cybele Britannica,' vol. i. p. 131; Mr. D. Cameron, also, has written on +the culture of Alpine plants in 'Gard. Chronicle,' 1848, pp. 253, 268, and +mentions a few which seed. + +[398] 'Beitraege zur Kenntniss der Befruchtung,' 1844, s. 333. + +[399] 'Nova Acta Petrop.,' 1793, p. 391. + +[400] 'Cottage Gardener,' 1856, pp. 44, 109. + +[401] Dr. Herbert, 'Amaryllidaceae,' p. 176. + +[402] Gaertner, 'Beitraege zur Kenntniss,' &c., s. 560, 564. + +[403] 'Gardener's Chronicle,' 1844, p. 215; 1850, p. 470. + +[404] 'Beitraege zur Kenntniss,' &c., s. 252, 333. + +[405] 'Journal of Hort. Soc.,' vol. ii. 1847, p. 83. + +[406] 'Beitraege zur Kenntniss,' &c., s. 117 _et seq._; Koelreuter, 'Zweite +Fortsetzung,' s. 10, 121; 'Dritte Fortsetzung,' s. 57. Herbert, +'Amaryllidaceae,' p. 355. Wiegmann, 'Ueber die Bastarderzeugung,' s. 27. + +[407] 'Bastarderzeugung,' s. 356. + +[408] 'Teoria della Riproduzione,' 1816, p. 84; 'Traite du Citrus,' 1811, +p. 67. + +[409] Mr. C. W. Crocker, in 'Gard. Chronicle,' 1861, p. 1092. + +[410] Verlot, 'Des Varietes,' 1865, p. 80. + +[411] Verlot, idem, p. 88. + +[412] Prof. Allman, Brit. Assoc., quoted in the 'Phytologist,' vol. ii. p. +483. Prof. Harvey, on the authority of Mr. Andrews, who discovered the +plant, informed me that this monstrosity could be propagated by seed. With +respect to the poppy, _see_ Prof. Goeppert, as quoted in 'Journal of +Horticulture,' July 1st, 1863, p. 171. + +[413] 'Comptes Rendus,' Dec. 19th, 1864, p. 1039. + +[414] 'Gardener's Chronicle,' 1866, p. 681. + +[415] 'Theory of Horticulture,' p. 333. + +[416] Mr. Fairweather, in 'Transact. Hort. Soc.,' vol. iii. p. 406; Bosse, +quoted by Bronn, 'Geschichte der Natur,' B. ii. s. 77. On the effects of +the removal of the anthers, _see_ Mr. Leitner, in Silliman's 'North +American Journ. of Science,' vol. xxiii. p. 47; and Verlot, 'Des Varietes,' +1865, p. 84. + +[417] Lindley's 'Theory of Horticulture,' p. 333. + +[418] 'Gardener's Chronicle,' 1865, p. 626; 1866, pp. 290, 730; and Verlot, +'Des Varietes,' p. 75. + +[419] 'Gardener's Chronicle,' 1843, p. 628. In this article I suggested the +following theory on the doubleness of flowers. + +[420] Quoted by Gaertner, 'Bastarderzeugung,' s. 567. + +[421] 'Gardener's Chronicle,' 1866, p. 901. + +[422] Lindley, 'Theory of Horticulture,' p. 175-179; Godron, 'De l'Espece,' +tom. i. p. 106: Pickering, 'Races of Man;' Gallesio, 'Teoria della +Riproduzione,' 1816, p. 101-110. Meyen ('Reise um Erde,' Th. ii. s. 214) +states that at Manilla one variety of the banana is full of seeds; and +Chamisso (Hooker's 'Bot. Misc.,' vol. i. p. 310) describes a variety of the +bread-fruit in the Mariana Islands with small fruit, containing seeds which +are frequently perfect. Burnes, in his 'Travels in Bokhara,' remarks on the +pomegranate seeding in Mazenderan, as a remarkable peculiarity. + +[423] Ingledew, in 'Transact. of Agricult. and Hort. Soc. of India,' vol. +ii. + +[424] 'De la Fecondation,' 1862, p. 308. + +[425] Hooker's 'Bot. Misc.,' vol. i. p. 99; Gallesio, 'Teoria della +Riproduzione,' p. 110. + +[426] 'Transact. Linn. Soc.,' vol. xvii. p. 563. + +[427] Godron, 'De l'Espece,' tom. ii. p. 106; Herbert on Crocus, in +'Journal of Hort. Soc.,' vol. i., 1846, p. 254.--Dr. Wight, from what he +has seen in India, believes in this view; 'Madras Journal of Lit. and +Science,' vol. iv., 1836, p. 61. + +[428] Wahlenberg specifies eight species in this state on the Lapland Alps: +_see_ Appendix to Linnaeus' 'Tour in Lapland,' translated by Sir J. E. +Smith, vol. ii. pp. 274-280. + +[429] 'Travels in North America,' Eng. translat., vol. iii. p. 175. + +[430] With respect to the ivy and Acorus, _see_ Dr. Bromfield in the +'Phytologist,' vol. iii. p. 376. _See_ also Lindley and Vaucher on the +Acorus. + +[431] 'Annal. des Sc. Nat.,' 3rd series, Zool., tom. iv. p. 280. Prof. +Decaisne refers also to analogous cases with mosses and lichens near Paris. + +[432] Mr. Tuckerman, in Silliman's 'American Journal of Science,' vol. xlv. +p. 41. + +[433] Sir J. E. Smith, 'English Flora,' vol. i. p. 339. + +[434] G. Planchon, 'Flora de Montpellier,' 1864, p. 20. + +[435] On the non-production of seeds in England _see_ Mr. Crocker, in +'Gardener's Weekly Magazine,' 1852, p. 70; Vaucher, 'Hist. Phys. Plantes +d'Europe,' tom. i. p. 33; Lecoq, 'Geograph. Bot. de l'Europe,' tom. iv. p. +466; Dr. D. Clos, in 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. xvii., +1852, p. 129: this latter author refers to other analogous cases. On the +non-production of pollen by this Ranunculus _see_ Chatin, in 'Comptes +Rendus,' June 11th, 1866. + +[436] 'Bastarderzeugung,' s. 565. Koelreuter ('Dritte Fortsetzung,' s. 73, +87, 119) also shows that when two species, one single and the other double, +are crossed, the hybrids are apt to be extremely double. + +[437] 'Teoria della Riproduzione Veg.,' 1816, p. 73. + +[438] 'Bastarderzeugung,' s. 573. + +[439] Ibid., s. 527. + +[440] 'Transactions Phil. Soc.,' 1799, p. 202. For Koelreuter, _see_ 'Mem. +de l'Acad. de St. Petersbourg,' tom. iii., 1809 (published 1811), p. 197. +In reading C. K. Sprengel's remarkable work, 'Das entdeckte Geheimniss,' +&c., 1793, it is curious to observe how often this wonderfully acute +observer failed to understand the full meaning of the structure of the +flowers which he has so well described, from not always having before his +mind the key to the problem, namely, the good derived from the crossing of +distinct individual plants. + +[441] This abstract was published in the fourth edition (1866) of my +'Origin of Species;' but as this edition will be in the hands of but few +persons, and as my original observations on this point have not as yet been +published in detail, I have ventured here to reprint the abstract. + +[442] The term _unconscious selection_ has been objected to as a +contradiction: but _see_ some excellent observations on this head by Prof. +Huxley ('Nat. Hist. Review,' Oct. 1864, p. 578), who remarks that when the +wind heaps up sand-dunes it sifts and _unconsciously selects_ from the +gravel on the beach grains of sand of equal size. + +[443] Sheep, 1838, p. 60. + +[444] Mr. J. Wright on Shorthorn Cattle, in 'Journal of Royal Agricult. +Soc.,' vol. vii. pp. 208, 209. + +[445] H. D. Richardson on Pigs, 1817, p. 44. + +[446] 'Journal of R. Agricult. Soc.,' vol. i. p. 24. + +[447] Sheep, pp. 520, 319. + +[448] Loudon's 'Mag. of Nat. Hist.,' vol. viii., 1835, p. 618. + +[449] 'A Treatise on the Art of Breeding the Almond Tumbler,' 1851, p. 9. + +[450] 'Recreations in Agriculture,' vol. ii. p. 409. + +[451] Youatt on Cattle, pp. 191, 227. + +[452] Ferguson, 'Prize Poultry,' 1854, p. 208. + +[453] Wilson, in 'Transact. Highland Agricult. Soc.,' quoted in 'Gard. +Chronicle,' 1844, p. 29. + +[454] Simmonds, quoted in 'Gard. Chronicle,' 1855, p. 637. And for the +second quotation, _see_ Youatt on Sheep, p. 171. + +[455] Robinet, 'Vers a Soie,' 1848, p. 271. + +[456] Quatrefages, 'Les Maladies du Ver a Soie,' 1859, p. 101. + +[457] M. Simon, in 'Bull. de la Soc. d'Acclimat.,' tom. ix., 1862, p. 221. + +[458] 'The Poultry Chronicle,' vol. i., 1854, p. 607. + +[459] J. M. Eaton, 'A Treatise on Fancy Pigeons,' 1852, p. xiv., and 'A +Treatise on the Almond Tumbler,' 1851, p. 11. + +[460] 'Journal Royal Agricultural Soc.,' vol. vi. p. 22. + +[461] 'Poultry Chronicle,' vol. ii., 1855, p. 596. + +[462] Isid. Geoffroy St. Hilaire, 'Hist. Nat. Gen.,' tom. iii. p. 254. + +[463] 'Gardener's Chronicle,' 1850, p. 198. + +[464] 'Transact. Hort. Soc.,' vol. vi. p. 152. + +[465] 'Journal of Horticulture,' 1862, p. 369. + +[466] 'Transact. Hort. Soc.,' vol. iv. p. 381. + +[467] 'Transact. Hort. Soc.,' vol. iv. p. 285. + +[468] Rev. W. Bromehead, in 'Gard. Chronicle,' 1857, p. 550. + +[469] 'Gard. Chronicle,' 1862, p. 721. + +[470] Dr. Anderson, in 'The Bee,' vol. vi. p. 96; Mr. Barnes, in 'Gard. +Chronicle,' 1844, p. 476. + +[471] Godron, 'De l'Espece,' 1859, tom. ii. p. 69; 'Gard. Chronicle,' 1854, +p. 258. + +[472] On Sheep, p. 18. + +[473] Volz, 'Beitraege zur Kulturgeschichte,' 1852, s. 47. + +[474] Mitford's 'History of Greece,' vol. i. p. 73. + +[475] Dr. Dally, translated in 'Anthropological Review,' May 1864, p. 101. + +[476] Volz, 'Beitraege,' &c., 1852, s. 80. + +[477] 'History of the World,' ch. 45. + +[478] 'Gardener's Chronicle,' 1848, p. 323. + +[479] Reynier, 'De l'Economie des Celtes,' 1818, pp. 487, 503. + +[480] Le Couteur on Wheat, p. 15. + +[481] Michel, 'Des Haras,' 1861, p. 84. + +[482] Sir W. Wilde, an 'Essay on Unmanufactured Animal Remains,' &c., 1860, +p. 11. + +[483] Col. Hamilton Smith, 'Nat. Library,' vol. xii., Horses, pp. 135, 140. + +[484] Michel, 'Des Haras,' p. 90. + +[485] Mr. Baker, 'History of the Horse,' Veterinary, vol. xiii. p. 423. + +[486] M. l'Abbe Carlier, in 'Journal de Physique,' vol. xxiv., 1784, p. +181: this memoir contains much information on the ancient selection of +sheep; and is my authority for rams not being killed young in England. + +[487] 'Gardener's Chronicle,' 1843, p. 389. + +[488] Communications to Board of Agriculture, quoted in Dr. Darwin's +'Phytologia,' 1800, p. 451. + +[489] 'Memoire sur les Chinois,' 1786, tom. xi. p. 55; tom. v. p. 507. + +[490] 'Recherches sur l'Agriculture des Chinois,' par L. +D'Hervey-Saint-Denys, 1850, p. 229. With respect to Khang-hi, _see_ Huc's +'Chinese Empire,' p. 311. + +[491] Anderson, in 'Linn. Transact.,' vol. xii. p. 253. + +[492] 'Mem. de l'Acad.' (divers savans), tom. vi., 1835, p. 333. + +[493] 'Des Quadrupedes du Paraguay,' 1801, tom. ii. p. 333, 371. + +[494] 'The Great Sahara,' by the Rev. H. B. Tristram, 1860, p. 238. + +[495] Pallas, 'Act. Acad. St. Petersburg,' 1777, p. 249; Moorcroft and +Trebeck, 'Travels in the Himalayan Provinces,' 1841. + +[496] Quoted from Raffles, in the 'Indian Field,' 1859, p. 196; for Varro, +_see_ Pallas, _ut supra_. + +[497] Erman's 'Travels in Siberia,' Eng. translat., vol. i. p. 453. + +[498] _See_ also 'Journal of R. Geograph. Soc.,' vol. xiii. part i. p. 65. + +[499] Livingstone's 'First Travels,' pp. 191, 439, 565; _see_ also +'Expedition to the Zambesi,' 1865, p. 465, for an analogous case respecting +a good breed of goats. + +[500] Andersson's 'Travels in South Africa,' pp. 232, 318, 319. + +[501] Dr. Vavasseur, in 'Bull. de la Soc. d'Acclimat.,' tom. viii., 1861, +p. 136. + +[502] 'The Natural History of Dee Side,' 1855, p. 476. + +[503] 'Bull. de la Soc. d'Acclimat.,' tom. vii., 1860, p. 457. + +[504] 'Cattle,' p. 48. + +[505] Livingstone's Travels, p. 576; Andersson, 'Lake Ngami,' 1856, p. 222. +With respect to the sale in Kaffraria, _see_ 'Quarterly Review,' 1860, p. +139. + +[506] 'Memoire sur les Chinois' (by the Jesuits), 1786, tom. xi. p. 57. + +[507] F. Michel, 'Des Haras,' pp. 47, 50. + +[508] Col. Hamilton Smith, Dogs, in 'Nat. Lib.,' vol. x. p. 103. + +[509] Azara, 'Quadrupedes du Paraguay,' tom. ii. p. 324. + +[510] Sidney's edit. of Youatt, 1860, pp. 24, 25. + +[511] 'Rural Economy of Yorkshire,' vol. ii. p. 182. + +[512] Moll et Gayot, 'Du Boeuf,' 1860, p. 547. + +[513] 'The India Sporting Review,' vol. ii. p. 181; 'The Stud Farm,' by +Cecil, p. 58. + +[514] 'The Horse,' p. 22. + +[515] 'History of England,' vol. i. p. 316. + +[516] 'Uber Bestaendigkeit der Arten.' + +[517] Youatt on Sheep, p. 315. + +[518] 'Ueber Shorthorn Rindvieh,' 1857, s. 51. + +[519] Low, 'Domesticated Animals,' 1845, p. 363. + +[520] 'Quarterly Review,' 1849, p. 392. + +[521] H. von Nathusius, 'Vorstudien ... Schweineschaedel,' 1864, s. 140. + +[522] _See_ also Dr. Christ, in 'Ruetimeyer's Pfahlbauten,' 1861, s. 226. + +[523] The passage is given 'Bull. Soc. d'Acclimat.,' 1858, p. 11. + +[524] 'Journal of Horticulture,' 1862, p. 394. + +[525] 'Gardener's Chronicle,' 1857, p. 85. + +[526] _See_ Mr. Wildman's address to the Floricult. Soc., in 'Gardener's +Chronicle,' 1843, p. 86. + +[527] 'Journal of Horticulture,' Oct. 24th, 1865, p. 239. + +[528] Prescott's 'Hist. of Mexico,' vol. ii. p. 61. + +[529] Sageret, 'Pomologie Physiologique,' 1830, p. 47; Gallesio, 'Teoria +della Riproduzione,' 1816, p. 88; Godron, 'De l'Espece,' 1859, tom. ii. pp. +63, 67, 70. In my tenth and eleventh chapters I have given details on the +potato; and I can confirm similar remarks with respect to the onion. I have +also shown how far Naudin concurs in regard to the varieties of the melon. + +[530] Godron, 'De l'Espece,' tom. ii. p. 27. + +[531] 'The Anthropological Treatises of Blumenbach,' 1865, p. 292. + +[532] Mr. J. J. Murphy in his opening address to the Belfast Nat. Hist. +Soc., as given in the Belfast Northern Whig, Nov. 19, 1866. Mr. Murphy here +follows the line of argument against my views previously and more +cautiously given by the Rev. C. Pritchard, Pres. Royal Astronomical Soc., +in his sermon (Appendix, p. 33) preached before the British Association at +Nottingham, 1866. + +[533] On the Vision of Fishes and Amphibia, translated in 'Annals and Mag. +of Nat. Hist.,' vol. xviii., 1866, p. 469. + +[534] Fourth edition, 1866, p. 215. + +[535] Quoted by Youatt on Sheep, p. 325. _See_ also Youatt on Cattle, pp. +62, 69. + +[536] MM. Lherbette and De Quatrefages, in 'Bull. Soc. Acclimat.,' tom. +viii., 1861, p. 311. + +[537] 'The Poultry Book,' 1866, p. 123. + +[538] Youatt on Sheep, p. 312. + +[539] 'Treatise on the Almond Tumbler,' 1851, p. 33. + +[540] Dr. Heusinger, 'Wochenschrift fuer die Heilkunde,' Berlin, 1846, s. +279. + +[541] Youatt on the Dog, p. 232. + +[542] 'The Fruit-trees of America,' 1845, p. 270: for peaches, p. 466. + +[543] 'Proc. Royal Soc. of Arts and Sciences of Mauritius,' 1852, p. cxxxv. + +[544] 'Gardener's Chronicle,' 1856, p. 379. + +[545] Quatrefages, 'Maladies Actuelles du Ver a Soie,' 1859, pp. 12, 214. + +[546] 'Gardener's Chronicle,' 1851, p. 595. + +[547] 'Journal of Horticulture,' 1862, p. 476. + +[548] 'Gardener's Chronicle,' 1852, pp. 435, 691. + +[549] Bechstein, 'Naturgesch. Deutschlands,' 1801, B. i. s. 310. + +[550] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 224. + +[551] G. Lewis's 'Journal of Residence in West Indies,' 'Home and Col. +Library,' p. 100. + +[552] Sidney's edit. of Youatt on the Pig, p.24. + +[553] 'Journal of Horticulture,' 1862, pp. 476, 498; 1865, p. 460. With +respect to the heartsease, 'Gardener's Chronicle,' 1863, p. 628. + +[554] 'Des Jacinthes, de leur Culture,' 1768, p. 53: on wheat, 'Gardener's +Chronicle,' 1846, p. 653. + +[555] W. B. Tegetmeier, 'The Field,' Feb. 25, 1865. With respect to black +fowls, _see_ a quotation in Thompson's 'Nat. Hist. of Ireland,' 1849, vol. +i. p. 22. + +[556] 'Bull. de la Soc. d'Acclimat.,' tom. vii. 1860, p. 359. + +[557] 'Transact. Hort. Soc.,' vol. i. 2nd series, 1835, p. 275. For +raspberries, _see_ 'Gard. Chronicle,' 1855, p. 154, and 1863, p. 245. + +[558] 'Gardener's Chronicle,' 1843, p. 806. + +[559] Ibid., 1850, p. 732. + +[560] Ibid., 1860, p. 956. + +[561] J. De Jonghe, in 'Gard. Chronicle,' 1860, p. 120. + +[562] Downing, 'Fruit-trees of North America,' pp. 266, 501: in regard to +the cherry, p. 198. + +[563] 'Gardener's Chronicle,' 1849, p. 755. + +[564] 'Journal of Horticulture,' Sept. 26th, 1865, p. 254; _see_ other +references given in chap. x. + +[565] Mr. Selby, in 'Mag. of Zoology and Botany,' Edinburgh, vol. ii., +1838, p. 393. + +[566] The Reine Claude de Bavay, 'Journal of Horticulture,' Dec. 27, 1864, +p. 511. + +[567] Mr. Pusey, in 'Journal of R. Agricult. Soc., vol. vi. p. 179. For +Swedish turnips, _see_ 'Gard. Chron.,' 1847, p. 91. + +[568] Godron, 'De l'Espece,' tom. ii. p. 98. + +[569] 'Gardener's Chron.,' 1866, p. 732. + +[570] 'Gardener's Chronicle,' 1862, pp. 820, 821. + +[571] 'On the Varieties of Wheat,' p. 59. + +[572] Mr. Hewitt and others, in 'Journal of Hort.,' 1862, p. 773. + +[573] 'Encyclop. of Rural Sports,' p. 405. + +[574] Col. Le Couteur, 'Journal Roy. Agricult. Soc.,' vol. iv. p. 43. + +[575] 'Gardener's Chronicle,' 1845, p. 273. + +[576] 'Journal of Horticulture,' 1862, p. 157. + +[577] 'Cottage Gardener,' 1860, p. 368. + +[578] 'A Review of Reports,' 1808, p. 406. + +[579] 'Gardener's Chronicle,' 1853, p. 45. + +[580] Isidore Geoffroy St. Hilaire, 'Hist. Nat. Gen.,' tom. iii. p. 49. On +the Cochineal Insect, p. 46. + +[581] Capt. Marryat, quoted by Blyth in 'Journ. Asiatic Soc. of Bengal,' +vol. xxviii. p. 229. + +[582] Mr. Oxley, 'Journal of the Indian Archipelago,' vol. ii., 1848, p. +645. + +[583] Mr. Abbey, in 'Journal of Horticulture,' Dec. 1, 1863, p. 430. + +[584] 'On Naval Timber,' 1831, p. 107. + +[585] Mr. Baily, in 'The Poultry Chronicle,' vol. ii., 1854, p. 150. Also +vol. i. p. 342; vol. iii. p. 245. + +[586] 'Cottage Gardener,' 1855, December, p. 171; 1856, January, pp. 248, +323. + +[587] 'Ueber Shorthorn Rindvieh,' 1857, s. 51. + +[588] 'The Veterinary,' vol. xiii. p. 720. For the Glamorganshire cattle, +_see_ Youatt on Cattle, p. 51. + +[589] J. M. Eaton, 'A Treatise on Fancy Pigeons,' p. 82; Ferguson, on 'Rare +and Prize Poultry,' p. 162; Mr. Brent, in 'Cottage Gardener,' Oct. 1860. p. +13. + +[590] 'Die Racen des Schweines,' 1860, s. 48. + +[591] _See_ some good remarks on this head by M. de Quatrefages, 'Unite de +l'Espece Humaine,' 1861, p. 119. + +[592] Verlot, 'Des Varietes,' 1865, p. 94. + +[593] Mr. Patrick Sheriff, in 'Gard. Chronicle,' 1858, p. 771. + +[594] 'Pomologie Physiolog.,' 1830, p. 106. + +[595] Youatt on Sheep, p. 521. + +[596] 'A Treatise on the Almond Tumbler,' p. i. + +[597] M. J. de Jonghe, in 'Gard. Chron.,' 1858, p. 173. + +[598] Max. Mueller, 'Science of Language,' 1861, p. 223. + +[599] Youatt on Cattle, pp. 116, 128. + +[600] 'Domesticated Animals,' p. 188. + +[601] Volz, 'Beitraege zur Kulturgeschichte,' 1852, s. 99 _et passim_. + +[602] Blaine, 'Encyclop. of Rural Sports,' p. 213. + +[603] 'Des Jacinthes,' &c., Amsterdam, 1768, p. 43; Verlot, 'Des Varietes,' +&c., p. 86. On the reindeer, _see_ Linnaeus, 'Tour in Lapland,' translated +by Sir J. E. Smith, vol. i. p. 314. The statement in regard to German +shepherds is given on the authority of Dr. Weinland. + +[604] Mueller's 'Physiology,' Eng. translation, vol. ii. p. 1662. With +respect to the similarity of twins in constitution, Dr. William Ogle has +given me the following extract from Professor Trousseau's Lectures +('Clinique Medicale,' tom. i. p. 523), in which a curious case is +recorded:--"J'ai donne mes soins a deux freres jumeaux, tous deux si +extraordinairement ressemblants qu'il m'etait impossible de les +reconnaitre, a moins de les voir l'un a cote de l'autre. Cette ressemblance +physique s'etendait plus loin: ils avaient, permettez-moi l'expression, une +similitude pathologique plus remarquable encore. Ainsi l'un d'eux que je +voyais aux neothermes a Paris malade d'une ophthalmie rhumatismale me +disait, 'En ce moment mon frere doit avoir une ophthalmie comme la mienne;' +et comme je m'etais recrie, il me montrait quelques jours apres une lettre +qu'il venait de recevoir de ce frere alors a Vienne, et qui lui ecrivait en +effet--'J'ai mon ophthalmie, tu dois avoir la tienne.' Quelque singulier +que ceci puisse paraitre, le fait non est pas moins exact: on ne me l'a pas +raconte, je l'ai vu, et j'en ai vu d'autres analogues dans ma pratique. Ces +deux jumeaux etaient aussi tous deux asthmatiques, et asthmatiques a un +effroyable degre. Originaires de Marseille, ils n'ont jamais pu demeurer +dans cette ville, ou leurs interets les appelaient souvent, sans etre pris +de leurs acces; jamais ils n'en eprouvaient a Paris. Bien mieux, il leur +suffisait de gagner Toulon pour etre gueris de leurs attaques de +Marseilles. Voyageant sans cesse et dans tous pays pour leurs affaires, ils +avaient remarque que certaines localites leur etaient funestes, que dans +d'autres ils etaient exempts de tout phenomene d'oppression." + +[605] Isid. Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. iii. p. 352; +Moquin Tandon, 'Teratologie Vegetale,' 1841, p. 115. + +[606] Metzger, 'Die Getreidearten,' 1841, s. 39. + +[607] On the date-palm, _see_ Vogel, 'Annals and Mag. of Nat. Hist.,' 1854, +p. 460. On Indian varieties, Dr. F. Hamilton, 'Transact. Linn. Soc.,' vol. +xiv. p. 296. On the varieties cultivated in Tahiti, _see_ Dr. Bennett, in +Loudon's 'Mag. of N. Hist.,' vol. v., 1832, p. 484. Also Ellis, 'Polynesian +Researches,' vol. i. pp. 375, 370. On twenty varieties of the Pandanus and +other trees in the Marianne Island, _see_ 'Hooker's Miscellany,' vol. i. p. +308. On the bamboo in China, _see_ Huc's 'Chinese Empire,' vol. ii. p. 307. + +[608] 'Treatise on the Culture of the Apple,' &c., p. 3. + +[609] Gallesio, 'Teoria della Riproduzione Veg.,' p. 125. + +[610] _See_ Dr. Hooker's Memoir on Arctic Plants in 'Linn. Transact.,' vol. +xxiii, part ii. Mr. Woodward, and a higher authority cannot be quoted, +speaks of the Arctic mollusca (in his 'Rudimentary Treatise,' 1856, p. 355) +as remarkably subject to variation. + +[611] Bechstein, in his 'Naturgeschichte der Stubenvoegel,' 1840, s. 238, +has some good remarks on this subject. He states that his canary-birds +varied in colour, though kept on uniform food. + +[612] 'The Plant,' by Schleiden, translated by Henfrey, 1848, p. 169. _See_ +also Alex. Braun, in 'Bot. Memoirs,' Ray. Soc., 1853, p. 313. + +[613] Messrs. Hardy and Son, of Maldon, in 'Gard. Chronicle,' 1856, p. 458. + +[614] 'Quadrupedes du Paraguay,' 1801, tom. ii. p. 319. + +[615] McClelland on Indian Cyprinidae, 'Asiatic Researches,' vol. xix. part +ii., 1839, pp. 266, 268, 313. + +[616] Quoted by Sageret, 'Pom. Phys.,' 1830, p. 43. + +[617] 'The Fruits of America,' 1845, p. 5. + +[618] M. Cardan, in 'Comptes Rendus,' Dec. 1848, quoted in 'Gard. +Chronicle,' 1849, p. 101. + +[619] M. Alexis Jordan mentions four excellent pears found in woods in +France, and alludes to others ('Mem. Acad. de Lyon,' tom. ii. 1852, p. +159). Poiteau's remark is quoted in 'Gardener's Mag.,' vol. iv., 1828, p. +385. _See_ 'Gard. Chronicle,' 1862, p. 335, for another case of a new +variety of the pear found in a hedge in France. Also for another case, +_see_ Loudon's 'Encyclop. of Gardening,' p. 901. Mr. Rivers has given me +similar information. + +[620] Duval, 'Hist. du Poirier,' 1849, p. 2. + +[621] I infer that this is the fact from Van Mons' statement ('Arbres +Fruitiers,' 1835, tom. i. p. 446) that he finds in the woods seedlings +resembling all the chief cultivated races of both the pear and apple. Van +Mons, however, looked at these wild varieties as aboriginal species. + +[622] Downing, 'Fruit-trees of North America,' p. 422; Foley, in 'Transact. +Hort. Soc.,' vol. vi. p. 412. + +[623] 'Gard. Chronicle,' 1847, p. 244. + +[624] 'Gardener's Chronicle,' 1841, p. 383; 1850, p. 700; 1854, p. 650. + +[625] 'Die Getreidearten,' 1843, s. 66, 116, 117. + +[626] Sabine, in 'Hort. Transact.,' vol. iii. p. 225; Bronn, 'Geschichte +der Natur,' b. ii. s. 119. + +[627] 'Journal of Horticulture,' 1861, p. 112; on Zinnia, 'Gardener's +Chronicle,' 1860, p. 852. + +[628] 'The Chrysanthemum, its History, &c.,' 1865, p. 3. + +[629] 'Gardener's Chron.,' 1855, p. 54; 'Journal of Horticulture,' May 9, +1865, p. 363. + +[630] Quoted by Verlot, 'Des Varietes,' &c., 1865, p. 28. + +[631] 'Examination of the Characteristics of Genera and Species:' +Charleston, 1855, p. 14. + +[632] Mr Hewitt, 'Journal of Hort.,' 1863, p. 39. + +[633] Devay, 'Mariages Consanguins,' pp. 97, 125. In conversation I have +found two or three naturalists of the same opinion. + +[634] Mueller has conclusively argued against this belief, 'Elements of +Phys.,' Eng. translat., vol. ii., 1842, p. 1405. + +[635] 'Act. Acad. St. Petersburg,' 1780, part ii. p. 84, &c. + +[636] 'Bastarderzeugung,' s. 249, 255, 295. + +[637] 'Nova Acta, St. Petersburg,' 1794, p. 378; 1795, pp. 307, 313, 316; +1787, p. 407. + +[638] 'De la Fecondation,' 1862, p. 311. + +[639] 'Amaryllidaceae,' 1837, p. 362. + +[640] Abstracted in 'Gard. Chronicle,' 1860, p. 1081. + +[641] This was the opinion of the elder De Candolle, as quoted in 'Dic. +Class. d'Hist. Nat.,' tom. viii. p. 405. Puvis, in his work, 'De la +Degeneration,' 1837, p. 37, has discussed this same point. + +[642] 'Comptes Rendus,' Novembre 21, 1864, p. 838. + +[643] 'Nova Acta, St. Petersburg,' 1794, p. 391. + +[644] 'Bastarderzeugung,' s. 507, 516, 572. + +[645] 'Die Bastardbefruchtung,' &c., 1865, s. 24. + +[646] 'Bastarderzeugung,' s. 452, 507. + +[647] 'Die Bastardbefruchtung,' s. 56. + +[648] 'Bastarderzeugung,' s. 423. + +[649] 'Dritte Fortsetzung,' &c., 1766, s. 85. + +[650] 'Die Bastardbefruchtung,' &c., 1865, s. 92; _see_ also the Rev. M. J. +Berkeley on the same subject, in 'Journal of Royal Hort. Soc.,' 1866, p. +80. + +[651] Dr. P. Lucas has given a history of opinion on this subject: 'Hered. +Nat.,' 1847, tom. i. p. 175. + +[652] 'Hist. des Anomalies,' tom. iii. p. 499. + +[653] Idem., tom. iii. pp. 392, 502. + +[654] _See_ his interesting work, 'Metamorphoses de l'Homme,' &c., 1862, p. +129. + +[655] 'Dritte Fortsetzung,' &c., s. 123; 'Bastarderzeugung,' s. 249. + +[656] 'Gardener's Chronicle,' 1853, p. 183. + +[657] Mr. Wildman, 'Floricultural Soc.,' Feb. 7, 1843, reported in 'Gard. +Chron.,' 1843, p. 86. + +[658] Mr. Robson, in 'Journal of Horticulture,' Feb. 13th, 1866, p. 122. + +[659] 'Journal of Horticulture,' 1861, p. 24. + +[660] Ibid., 1862, p. 83. + +[661] 'Gard. Chron.,' 1845, p. 660. + +[662] Ibid., 1863, p. 628. + +[663] 'Journal of Hort.,' 1861, pp. 64, 309. + +[664] 'Des Varietes,' &c., p. 76. + +[665] Engel, 'Sur les Prop. Medicales des Plantes,' 1860, pp. 10, 25. On +changes in the odours of plants, _see_ Dalibert's Experiments, quoted by +Beckman, 'Inventions,' vol. ii. p. 344; and Nees, in Ferussac, 'Bull. des +Sc. Nat.,' 1824, tom. i. p. 60. With respect to the rhubarb, &c., _see_ +also 'Gardener's Chronicle,' 1849, p. 355; 1862, p. 1123. + +[666] Hooker, 'Flora Indica,' p. 32. + +[667] Naudin, 'Annales des Sc. Nat.,' 4th series, Bot., tom. xi., 1859, p. +81. 'Gardener's Chronicle,' 1859, p. 464. + +[668] Moorcroft's 'Travels,' &c., vol. ii. p. 143. + +[669] 'Gardener's Chronicle,' 1861, p. 1113. + +[670] Royle, 'Productive Resources of India,' p. 59. + +[671] 'Personal Narrative,' Eng. translat., vol. v. p. 101. This statement +has been confirmed by Karsten ('Beitrag zur Kenntniss der Rhynchoprion:' +Moscow, 1864. s. 39), and by others. + +[672] 'Organic Chemistry,' Eng. translat., 1st edit., p. 369. + +[673] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 155. + +[674] Darwin, 'Journal of Researches,' 1845, p. 434. + +[675] These statements on disease are taken from Dr. Boudin's 'Geographie +et de Statistique Medicales,' 1857, tom. i. p. xliv. and lii.; tom. ii. p. +315. + +[676] E. Desor, quoted in the 'Anthrop. Rev.,' 1863, p. 180. For much +confirmatory evidence, _see_ Quatrefages, 'Unite de l'Espece Humaine,' +1861, p. 131. + +[677] 'Ceylon,' by Sir J. E. Tennent, vol. i., 1859, p. 89. + +[678] Godron, 'De l'Espece,' tom. ii. p. 52. + +[679] 'Journal of Horticultural Soc.,' vol. vii., 1852, p. 117. + +[680] 'Journal of Hort. Soc.,' vol. i. p. 160. + +[681] _See_ Lecoq on the Villosity of Plants, 'Geograph. Bot.,' tom. iii. +pp. 287, 291; Gaertner, 'Bastarderz.,' s. 261; Mr. Musters, on the Opuntia, +in 'Gard. Chronicle,' 1846, p. 444. + +[682] 'Pom. Phys.,' p. 136. + +[683] 'Ampelographie,' 1849, p. 19. + +[684] Gaertner, 'Bastarderz.,' s. 606, has collected nearly all recorded +facts. Andrew Knight (in 'Transact. Hort. Soc.,' vol. ii. p. 160) goes so +far as to maintain that few varieties are absolutely permanent in character +when propagated by buds or grafts. + +[685] Mr. Blyth, in 'Annals and Mag. of Nat. Hist.,' vol. xx., 1847, p. +391. + +[686] 'Natural History Review,' 1862, p. 113. + +[687] 'Journal of Roy. Geographical Soc.,' vol. ix., 1839, p. 275. + +[688] 'Travels in Bokhara,' vol. iii. p. 151. + +[689] _See_ also, on the influence of marshy pastures on the wool, Godron, +'L'Espece,' tom. ii. p. 22. + +[690] Isidore Geoffroy St. Hilaire, 'Hist. Nat. Gen.,' tom. iii. p. 438. + +[691] Azara has made some good remarks on this subject, 'Quadrupedes du +Paraguay,' tom. ii. p. 337. _See_ an account of a family of naked mice +produced in England, 'Proc. Zoolog. Soc.,' 1856, p. 38. + +[692] 'Die Fauna der Pfahlbauten,' 1861, s. 15. + +[693] 'Schweinschaedel,' 1864, s. 99. + +[694] 'Travels in Siberia,' Eng. translat., vol. i. p. 228. + +[695] A. R. Wallace, 'Travels on the Amazon and Rio Negro,' p. 294. + +[696] 'Naturgeschichte der Stubenvoegel,' 1840, s. 262, 308. + +[697] 'Hist. Nat. Gen.,' tom. iii. p. 402. + +[698] 'Bull. de la Soc. Imp. d'Acclimat.,' tom. viii. p. 351. + +[699] _See_ an account of Mr. Gregson's experiments on the _Abraxus +grossulariata_, 'Proc. Entomolog. Soc.,' Jan. 6th, 1862: these experiments +have been confirmed by Mr. Greening, in 'Proc. of the Northern Entomolog. +Soc.,' July 28th, 1862. For the effects of food on caterpillars, see a +curious account by M. Michely, in 'Bull. de la Soc. Imp. d'Acclimat.,' tom. +viii. p. 563. For analogous facts from Dahlbom on Hymenoptera, _see_ +Westwood's 'Modern Class. of Insects,' vol. ii. p. 98. _See_ also Dr. L. +Moeller, 'Die Abhaengigkeit der Insecten,' 1867, s. 70. + +[700] 'The Principles of Biology,' vol. ii. 1866. The present chapters were +written before I had read Mr. Herbert Spencer's work, so that I have not +been able to make so much use of it as I should otherwise probably have +done. + +[701] 'Proc. Acad. Nat. Soc. of Philadelphia,' Jan. 28th, 1862. + +[702] _See_ Mr. B. D. Walsh's excellent papers in 'Proc. Entomolog. Soc. +Philadelphia,' Dec. 1866, p. 284. With respect to the willow, _see_ idem, +1864, p. 546. + +[703] _See_ his admirable Histoire des Galles, in 'Annal. des Sc. Nat. +Bot.,' 3rd series, tom. xix., 1853, p. 273. + +[704] Kirby and Spence's 'Entomology,' 1818, vol. i. p. 450; +Lucaze-Duthiers, idem, p. 284. + +[705] 'Proc. Entomolog. Soc. Philadelphia,' 1864, p. 558. + +[706] Mr. B. D. Walsh, idem, p. 633; and Dec. 1866, p. 275. + +[707] Mr. B. D. Walsh, idem, 1864, p. 545, 411, 495; and Dec. 1866, p. 278. +_See_ also Lucaze-Duthiers. + +[708] Lucaze-Duthiers, idem, pp. 325, 328. + +[709] 'Linnaea,' vol. xvii., 1843; quoted by Dr. M. T. Masters, Royal +Institution, March 16th, 1860. + +[710] Hewett C. Watson, 'Cybele Britannica,' vol. i., 1847, p. 11. + +[711] 'Gardener's Chronicle,' 1857, p. 629. + +[712] 'Memoire sur la Production Artificielle des Monstrosites,' 1862, pp. +8-12; 'Recherches sur les Conditions, &c., chez les Monstres,' 1863, p. 6. +An abstract is given of Geoffroy's Experiments by his son, in his 'Vie, +Travaux, &c.,' 1847, p. 290. + +[713] Paget, 'Lectures on Surgical Pathology,' 1853, vol. i. p. 483. + +[714] 'Researches upon the Venom of the Rattle-snake,' Jan. 1861, by Dr. +Mitchell, p. 67. + +[715] Mr. Sedgwick, in 'British and Foreign Medico-Chirurg. Review,' July +1863, p. 175. + +[716] 'An Essay on Generation,' Eng. translat., p. 18; Paget, 'Lectures on +Surgical Pathology,' 1853, vol. i. p. 209. + +[717] 'An Essay on Animal Reproduction,' Eng. translat., 1769, p. 79. + +[718] Carpenter's 'Principles of Comp. Physiology,' 1854, p. 479. + +[719] Charlesworth's 'Mag. of Nat. Hist.,' vol. i., 1837, p. 145. + +[720] Paget, 'Lectures on Surgical Pathology,' vol. i. p. 239. + +[721] Quoted by Carpenter, 'Comp. Phys.,' p. 479. + +[722] Paget, 'Lectures,' &c., p. 257. + +[723] These cases are given by Blumenbach in his 'Essay on Generation,' pp. +52, 54. + +[724] 'Cellular Pathology,' trans. by Dr. Chance, 1860, pp. 27, 441. + +[725] Paget, 'Lectures on Pathology,' vol. i., 1853, p. 357. + +[726] Paget, idem, p. 150. + +[727] 'The Principles of Biology,' vol. ii., 1866, chap. 3-5. + +[728] 'Lectures on Pathology,' 1853, vol. i. p. 71. + +[729] 'Comptes Rendus,' Sept. 26th, 1864, p. 539. + +[730] 'The Principles of Biology,' vol. ii. p. 243. + +[731] Idem, vol. ii. p. 269. + +[732] Idem, vol. ii. p. 273. + +[733] Paget, 'Lectures on Pathology,' vol. ii. p. 209. + +[734] Mueller's 'Phys.,' Eng. translat., pp. 54, 791. Prof. Reed has given +('Physiological and Anat. Researches,' p. 10) a curious account of the +atrophy of the limbs of rabbits after the destruction of the nerve. + +[735] Quoted by Lecoq, in 'Geograph. Bot.,' tom. i., 1854, p. 182. + +[736] 'Das Abaendern der Voegel,' 1833, s. 74. + +[737] Nathusius, 'Die Racen des Schweines,' 1860, s. 53, 57; 'Vorstudien +... Schweineschaedel,' 1864, s. 103, 130, 133. + +[738] 'Journal of Agriculture of Highland Soc.,' July, 1860, p. 321. + +[739] 'Principles of Biology,' vol. ii. p. 263. + +[740] 'Natural History Review,' vol. iv., Oct. 1864, p. 617. + +[741] 'Lectures on Surgical Pathology,' 1853, vol. i. p. 27. + +[742] Andersson, 'Travels in South Africa,' p. 318. For analogous cases in +South America, _see_ Aug. St. Hilaire, 'Voyage dans le Province de Goyaz,' +tom. i. p. 71. + +[743] Brickell's 'Nat. Hist. of North Carolina,' 1739, p. 53. + +[744] Livingstone, quoted by Youatt on Sheep, p. 142. Hodgson, in 'Journal +of Asiatic Soc. of Bengal,' vol. xvi., 1847, p. 1006, &c. &c. + +[745] 'Naturalist Library,' Dogs, vol. ii. 1840, p. 104. + +[746] 'De l'Espece,' tom. i., 1859, p. 367. + +[747] 'Ceylon,' by Sir J. E. Tennent, 1859, vol. ii. p. 531. + +[748] For the foregoing statements, _see_ Hunter's 'Essays and +Observations,' 1861, vol. ii. p. 329; Dr. Edmondston, as quoted in +Macgillivray's 'British Birds,' vol. v. p. 550; Menetries, as quoted in +Bronn's 'Geschichte der Natur,' B. ii. s. 110. + +[749] These statements on the intestines are taken from Isidore Geoffroy +St. Hilaire, 'Hist. Nat. Gen.,' tom. iii. pp. 427, 441. + +[750] Gilbert White, 'Nat. Hist. Selbourne,' 1825, vol. ii. p. 121. + +[751] Burdach, 'Traite de Phys.,' tom. ii. p. 267, as quoted by Dr. P. +Lucas, 'L'Hered. Nat.,' tom. i. p. 388. + +[752] This and several other cases are given by Colin, 'Physiologie Comp. +des Animaux Dom.,' 1854, tom. i. p. 426. + +[753] M. Michely de Cayenne, in 'Bull. Soc. d'Acclimat.,' tom. viii., 1861, +p. 563. + +[754] Quatrefages, 'Unite de l'Espece Humaine,' 1861, p. 79. + +[755] 'Flora,' 1835, B. ii. p. 504. + +[756] Alph. De Candolle, 'Geograph. Bot.,' tom. ii. p. 1078. + +[757] Royle, 'Illustrations of the Botany of the Himalaya,' p. 19. + +[758] 'Gardener's Chronicle,' 1850, pp. 204, 219. + +[759] Rev. R. Everest, 'Journal As. Soc. of Bengal,' vol. iii. p. 19. + +[760] Youatt on Sheep, 1838, p. 491. + +[761] Royle, 'Prod. Resources of India,' p. 153. + +[762] Tegetmeier, 'Poultry Book,' 1866, p. 102. + +[763] Dr. R. Paterson, in a paper communicated to Bot. Soc. of Canada, +quoted in the 'Reader,' 1863. Nov. 13th. + +[764] _See_ remarks by Editor in 'Gard. Chronicle,' 1848, p. 5. + +[765] 'Gard. Chronicle,' 1860, p. 938. Remarks by Editor and quotation from +Decaisne. + +[766] J. de Jonghe, of Brussels, in 'Gard. Chronicle,' 1857, p. 612. + +[767] Ch. Martius, 'Voyage Bot. Cotes Sept. de la Norvege,' p. 26. + +[768] 'Journal de l'Acad. Hort. de Gand,' quoted in 'Gard. Chron.,' 1859, +p. 7. + +[769] 'Gard. Chronicle,' 1851, p. 396. + +[770] Idem., 1862, p. 235. + +[771] On the authority of Labat, quoted in 'Gard. Chron.,' 1862, p. 235. + +[772] MM. Edwards and Colin, 'Annal. des Sc. Nat.,' 2nd series, Bot., tom. +v. p. 22. + +[773] 'Geograph. Bot.,' p. 337. + +[774] 'Swedish Acts,' Eng. translat., 1739-40, vol. i. Kalm, in his +'Travels,' vol. ii. p. 166, gives an analogous case with cotton-plants +raised in New Jersey from Carolina seed. + +[775] De Candolle, 'Geograph. Bot.,' p. 339. + +[776] 'Gard. Chronicle,' 1862, p. 235. + +[777] Gallesio, 'Teoria della Riproduzione Veg.,' 1816, p. 125; and 'Traite +du Citrus,' 1811, p. 359. + +[778] 'Essai sur l'Hist. des Orangers,' 1813, p. 20, &c. + +[779] Alph. De Candolle, 'Geograph. Bot.,' p. 882. + +[780] 'Ch. Darwin's Lehre von der Entstehung,' &c., 1862, s. 87. + +[781] Decaisne, quoted in 'Gard. Chronicle,' 1865, p. 271. + +[782] For the magnolia, _see_ Loudon's 'Gard. Mag.,' vol. xiii., 1837, p. +21. For camellias and roses, _see_ 'Gard. Chron.,' 1860, p. 384. For the +yew, 'Journal of Hort.,' March 3rd, 1863, p. 174. For sweet potatoes, _see_ +Col. von Siebold, in 'Gard. Chron.,' 1855, p. 822. + +[783] The Editor, 'Gard. Chron.,' 1861, p. 239. + +[784] Loudon's 'Gard. Mag.,' vol. xii., 1836, p. 378. + +[785] 'Gardeners Chron.,' 1865, p. 699. + +[786] 'Arboretum et Fruticetum,' vol. iii. p. 1376. + +[787] Mr. Robson, in 'Journal of Horticulture,' 1861, p. 23. + +[788] Dr. Bonavia, 'Report of the Agri.-Hort. Soc. of Oudh,' 1866. + +[789] 'Cottage Gardener,' 1860, April, 24th, p. 57. + +[790] 'Gardener's Chronicle,' 1841, p. 291. + +[791] Mr. Beaton, in 'Cottage Gardener,' March 20th, 1860, p. 377. Queen +Mab will also stand stove heat, _see_ 'Gard. Chronicle,' 1845, p. 226. + +[792] 'Gardener's Chronicle,' 1841, p. 439. + +[793] Quoted by Asa Gray, in 'Am. Journ. of Sci.,' 2nd series, Jan. 1865, +p. 106. + +[794] For China, _see_ 'Memoire sur les Chinois,' tom, xi., 1786, p. 60. +Columella is quoted by Carlier, in 'Journal de Physique,' tom. xxiv. 1784. + +[795] Messrs. Hardy and Son, in 'Gard. Chronicle,' 1856, p. 589. + +[796] Isid. Geoffroy St. Hilaire, 'Hist. Nat. des Anomalies,' 1836, tom. +ii. pp. 210, 223, 224, 395; 'Philosoph. Transact.,' 1775, p. 313. + +[797] Pallas, quoted by Youatt on Sheep, p. 25. + +[798] Youatt on Cattle, 1834, p. 174. + +[799] 'Encyclop. Method.,' 1820, p. 483: _see_ p. 500, on the Indian zebu +casting its horns. Similar cases in European cattle were given in the third +chapter. + +[800] Pallas, 'Travels,' Eng. translat., vol. i. p. 243. + +[801] Mr. Beaton, in 'Journal of Horticulture,' May 21, 1861, p. 133. + +[802] Lecoq, 'De la Fecondation,' 1862, p. 233. + +[803] 'Annales du Museum,' tom. vi. p. 319. + +[804] 'Hist. des Anomalies,' tom. iii. p. 392. Prof. Huxley applies the +same principle in accounting for the remarkable, though normal, differences +in the arrangement of the nervous system in the Mollusca, in his great +paper on the Morphology of the Cephalous Mollusca, in 'Phil. Transact.,' +1853, p. 56. + +[805] 'Elements de Teratologie Veg.,' 1841, p. 113. + +[806] Prof. J. B. Simonds, on the Age of the Ox, Sheep, &c., quoted in +'Gard. Chronicle,' 1854, p. 588. + +[807] 'Hist. des Anomalies,' tom. i. p. 674. + +[808] Quoted by Isid. Geoffroy, idem, tom. i. p. 635. + +[809] 'The Poultry Book,' by W. B. Tegetmeier, 1866, p. 250. + +[810] A. Walker on Intermarriage, 1838, p. 160. + +[811] 'The Farrier and Naturalist,' vol. i., 1828, p. 456. + +[812] Godron, 'Sur l'Espece,' tom. ii. p. 217. + +[813] 'Quadrupedes du Paraguay,' tom. ii. p. 333. + +[814] On Sheep, p. 142. + +[815] 'Ueber Racen, Kreuzungen, &c.,' 1825, s. 24. + +[816] Quoted from Conolly, in 'The Indian Field,' Feb. 1859, vol. ii. p. +266. + +[817] 'Domesticated Animals of the British Islands,' pp. 307, 368. + +[818] 'Proceedings Zoolog. Soc.,' 1833, p. 113. + +[819] Sedgwick, 'Brit. and Foreign Medico-Chirurg. Review,' April 1863, p. +453. + +[820] 'Gard. Chronicle,' 1849, p. 205. + +[821] 'Embassy to the Court of Ava,' vol. i. p. 320. + +[822] 'Narrative of a Mission to the Court of Ava in 1855,' p. 94. + +[823] Those statements are taken from Mr. Sedgwick, in the 'Medico-Chirurg. +Review,' July 1861, p. 198; April 1863, pp. 455 and 458. Liebreich is +quoted by Professor Devay, in his 'Mariages Consanguins,' 1862, p. 116. + +[824] Loudon's 'Mag. of Nat. Hist.,' vol. i., 1829, pp. 66, 178. _See_ also +Dr. P. Lucas, 'L'Hered. Nat.,' tom. i. p. 428, on the inheritance of +deafness in cats. + +[825] 'Annales des Sc. Nat.' Zoolog., 3rd series, 1847, tom. viii. p. 239. + +[826] 'Gardener's Chron.,' 1864, p. 1202. + +[827] Verlot gives several other instances, 'Des Varietes,' 1865, p. 72. + +[828] 'Arbres Fruitiers,' 1836, tom. ii. pp. 204, 226. + +[829] 'Annales du Museum,' tom. xx. p. 188. + +[830] 'Gardener's Chron.,' 1843, p. 877. + +[831] Ibid., 1845, p. 102. + +[832] 'Hist. des Anomalies,' tom. iii. p. 402. _See_ also M. Camille +Dareste, 'Recherches sur les Conditions,' &c., 1863, pp. 16, 48. + +[833] Rev. E. S. Dixon, 'Ornamental Poultry,' 1848, p. 111; Isidore +Geoffroy, 'Hist. Anomalies,' tom. i. p. 211. + +[834] 'On the Breeding of Domestic Animals,' 1829, p. 6. + +[835] Youatt on Cattle, 1834, p. 283. + +[836] Mr. Herbert Spencer ('Principles of Biology,' 1864, vol. i. pp. 452, +468) takes a different view; and in one place remarks: "We have seen reason +to think that, as fast as essential faculties multiply, and as fast as the +number of organs that co-operate in any given function increases, indirect +equilibration through natural selection becomes less and less capable of +producing specific adaptations; and remains fully capable only of +maintaining the general fitness of constitution to conditions." This view +that natural selection can do little in modifying the higher animals +surprises me, seeing that man's selection has undoubtedly effected much +with our domesticated quadrupeds and birds. + +[837] Dr. Prosper Lucas apparently disbelieves in any such connexion, +'L'Hered. Nat.,' tom. ii. pp. 88-94. + +[838] 'British Medical Journal,' 1862, p. 433. + +[839] Boudin, 'Geograph. Medicale,' tom. i. p. 406. + +[840] This fact and the following cases, when not stated to the contrary, +are taken from a very curious paper by Prof. Heusinger, in 'Wochenschrift +fuer Heilkunde,' May 1846, s. 277. + +[841] Mr. Mogford, in the 'Veterinarian,' quoted in 'The Field,' Jan. 22, +1861, p. 545. + +[842] 'Edinburgh Veterinary Journal,' Oct. 1860, p. 347. + +[843] 'Hist. des Anomalies,' 1832, tom. i. pp. 22, 537-556; tom. iii. p. +462. + +[844] 'Comptes Rendus,' 1855, pp. 855, 1029. + +[845] Carpenter's 'Comp. Phys.,' 1854, p. 480; _see_ also Camille Dareste, +'Comptes Rendus,' March 20th, 1865, p. 562. + +[846] 'Elements of Physiology,' Eng. translat, vol. i., 1838, p. 412. With +respect to Vrolik, _see_ Todd's 'Cyclop. of Anat. and Phys.,' vol. iv., +1849-52, p. 973. + +[847] 'Teratologie Veg.,' 1841, livre iii. + +[848] 'Hist. des Anomalies,' tom. iii. pp. 4, 5, 6. + +[849] 'Teratologie Veg.,' p. 156. _See_ also my paper on climbing plants in +'Journal of Linn. Soc. Bot.,' vol. ix., 1865, p. 114. + +[850] 'Memoires du Museum,' &c., tom. viii. p. 178. + +[851] Loudon's 'Encyclop. of Gardening,' p. 829. + +[852] Prichard, 'Phys. Hist. of Mankind,' 1851, vol. i. p. 324. + +[853] 'Annales des Sc. Nat.,' 1st series, tom. xix. p. 327. + +[854] 'Comptes Rendus,' Dec. 1864, p. 1039. + +[855] Ueber Foetale Rachites, 'Wuerzburger Medicin. Zeitschrift,' 1860, B. +i. s. 265. + +[856] 'Teratologie Veg.,' p. 192. Dr. M. Masters informs me that he doubts +the truth of this conclusion; but the facts to be given seem to be +sufficient to establish it. + +[857] 'Journal of Horticulture,' July 2nd, 1861, p. 253. + +[858] It would be worth trial to fertilise with the same pollen the central +and lateral flowers of the pelargonium, and of some other highly cultivated +plants, protecting them of course from insects: then to sow the seed +separately, and observe whether the one or the other lot of seedlings +varied the most. + +[859] Quoted in 'Journal of Horticulture,' Feb. 24, 1863, p. 152. + +[860] 'Gardener's Chronicle,' 1866, p. 612. For the Phalaenopsis, _see_ +idem, 1867, p. 211. + +[861] Memoires ... des Vegetaux,' 1837, tom. ii. p. 170. + +[862] 'Journal of Horticulture,' July 23, 1861, p. 311. + +[863] 'Nouvelles Archives du Museum,' tom. i. p. 137. + +[864] Hugo von Mohl, 'The Vegetable Cell,' Eng. tr., 1852, p. 76. + +[865] The Rev. H. H. Dombrain, in 'Journal of Horticulture,' 1861, June +4th, p. 174; and June 25th, p. 234; 1862, April 29th, p. 83. + +[866] 'Transact. Linn. Soc.,' vol. xxiii., 1861, p. 360. + +[867] 'Die Getreidearten,' 1843, s. 208, 209. + +[868] 'Gardener's Chronicle,' 1850, p. 198. + +[869] Quoted in 'Gardener's Chron.,' 1866, p. 74. + +[870] 'Ueber den Begriff der Pflanzenart,' 1834, s. 14. + +[871] 'Domesticated Animals,' 1845, p. 351. + +[872] Bechstein, 'Naturgeschichte Deutschlands,' Band iv., 1795, s. 31. + +[873] 'Proc. Entomolog. Soc. of Philadelphia,' Oct. 1863, p. 213. + +[874] Quoted by Paget, 'Lectures on Pathology,' 1853, p. 159. + +[875] Dr. Lachmann, also, observes ('Annals and Mag. of Nat. History,' 2nd +series, vol. xix., 1857, p. 231) with respect to infusoria, that "fissation +and gemmation pass into each other almost imperceptibly." Again, Mr. W. C. +Minor ('Annals and Mag. of Nat. Hist.,' 3rd series, vol. xi. p. 328) shows +that with Annelids the distinction that has been made between fission and +budding is not a fundamental one. _See_ Bonnet, 'Oeuvres d'Hist. Nat.,' +tom. v., 1781, p. 339, for remarks on the budding-out of the amputated +limbs of Salamanders. _See_, also, Professor Clark's work 'Mind in Nature,' +New York, 1865, pp. 62, 94. + +[876] Paget, 'Lectures on Pathology,' 1853, p. 158. + +[877] Idem, pp. 152, 164. + +[878] On the Asexual Reproduction of Cecydomyide Larvae, translated in +'Annals and Mag. of Nat. Hist.,' March 1866, pp. 167, 171. + +[879] _See_ some excellent remarks on this head by Quatrefages, in 'Annales +des Sc. Nat.,' Zoolog., 3rd series, 1850, p. 138. + +[880] 'Annals and Mag. of Nat. Hist.,' 2nd series, vol. xx., 1857, pp. +153-455. + +[881] 'Annales des Sc. Nat.,' 3rd series, 1850, tom. xiii. + +[882] 'Transact. Phil. Soc.,' 1851, pp. 196, 208, 210; 1853, p. 245, 247. + +[883] 'Beitrage zur Kenntniss,' &c., 1844, s. 345. + +[884] 'Nouvelles Archives du Museum,' tom. i. p. 27. + +[885] As quoted by Sir J. Lubbock in 'Nat. Hist. Review,' 1862, p. 345. + +[886] 'Transact. Linn. Soc.,' vol. xxiv., 1863, p. 62. + +[887] 'Parthenogenesis,' 1849, pp. 25-26. Prof. Huxley has some excellent +remarks ('Medical Times,' 1856, p. 637) on this subject, in reference to +the development of star-fishes, and shows how curiously metamorphosis +graduates into gemmation or zoid-formation, which is in fact the same as +metagenesis. + +[888] Prof. J. Reay Greene, in Guenther's 'Record of Zoolog. Lit.,' 1865, +p. 625. + +[889] Fritz Mueller's 'Fuer Darwin,' 1864, s. 65, 71. The highest authority +on crustaceans, Prof. Milne Edwards, insists ('Annal. des Sci. Nat.,' 2nd +series, Zoolog., tom. iii. p. 322) on their metamorphoses differing even in +closely allied genera. + +[890] Prof. Allman, in 'Annals and Mag. of Nat. Hist.,' 3rd series, vol. +xiii., 1864, p. 348; Dr. S. Wright, idem, vol. viii., 1861, p. 127. _See_ +also p. 358 for analogous statements by Sars. + +[891] 'Tissus Vivants,' 1866, p. 22. + +[892] 'Cellular Pathology,' translat. by Dr. Chance, 1860, pp. 14, 18, 83, +460. + +[893] Paget, 'Surgical Pathology,' vol. i., 1853, pp. 12-14. + +[894] Idem, p. 19. + +[895] Mantegazza, quoted in 'Popular Science Review,' July 1865, p. 522. + +[896] 'De la Production Artificielle des Os,' p. 8. + +[897] Isidore Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. ii. pp. +549, 560, 562; Virchow, idem, p. 484. + +[898] For the most recent classification of cells, _see_ Ernst Haeckel's +'Generelle Morpholog.,' Band ii., 1866, s. 275. + +[899] 'The Structure and Growth of Tissues,' 1865, p. 21, &c. + +[900] Dr. W. Turner, 'The present Aspect of Cellular Pathology,' 'Edinburgh +Medical Journal,' April, 1863. + +[901] This term is used by Dr. E. Montgomery ('On the Formation of +so-called Cells in Animal Bodies,' 1867, p. 42), who denies that cells are +derived from other cells by a process of growth, but believes that they +originate through certain chemical changes. + +[902] Prof. Huxley has called my attention to the views of Buffon and +Bonnet. The former ('Hist. Nat. Gen.,' edit. of 1749, tom. ii. pp. 54, 62, +329, 333, 420, 425) supposes that organic molecules exist in the food +consumed by every living creature; and that these molecules are analogous +in nature with the various organs by which they are absorbed. When the +organs thus become fully developed, the molecules being no longer required +collect and form buds or the sexual elements. If Buffon had assumed that +his organic molecules had been formed by each separate unit throughout the +body, his view and mine would have been closely similar. + +Bonnet ('Oeuvres d'Hist. Nat.,' tom. v., part i., 1781, 4to edit., p. 334) +speaks of the limbs having germs adapted for the reparation of all possible +losses; but whether these germs are supposed to be the same with those +within the buds and sexual organs is not clear. His famous but now exploded +theory of _emboitement_ implies that perfect germs are included within +germs in endless succession, pre-formed and ready for all succeeding +generations. According to my view, the germs or gemmules of each separate +part were not originally pre-formed, but are continually produced at all +ages during each generation, with some handed down from preceding +generations. + +Prof. Owen remarks ('Parthenogenesis,' 1849, pp. 5-8), "Not all the progeny +of the primary impregnated germ-cell are required for the formation of the +body in all animals: certain of the derivative germ-cells may remain +unchanged and become included in that body which has been composed of their +metamorphosed and diversely combined or confluent brethren: so included, +any derivative germ-cell, or the nucleus of such, may commence and repeat +the same processes of growth by imbibition, and of propagation by +spontaneous fission, as those to which itself owed its origin;" &c. By the +agency of these germ-cells Prof. Owen accounts for parthenogenesis, for +propagation by self-division during successive generations, and for the +repairs of injuries. His view agrees with mine in the assumed transmission +and multiplication of his germ-cells, but differs fundamentally from mine +in the belief that the primary germ-cell was formed within the ovarium of +the female and was fertilised by the male. My gemmules are supposed to be +formed, quite independently of sexual concourse, by each separate cell or +unit throughout the body, and to be merely aggregated within the +reproductive organs. + +Lastly, Mr. Herbert Spencer ('Principles of Biology,' vol. i., 1863-4, +chaps. iv. and viii.) has discussed at considerable length what he +designates as physiological units. These agree with my gemmules in being +supposed to multiply and to be transmitted from parent to child; the sexual +elements are supposed to serve merely as their vehicles; they are the +efficient agents in all the forms of reproduction and in the repairs of +injuries; they account for inheritance, but they are not brought to bear on +reversion or atavism, and this is unintelligible to me; they are supposed +to possess polarity, or, as I call it, affinity; and apparently they are +believed to be derived from each separate part of the whole body. But +gemmules differ from Mr. Spencer's physiological units, inasmuch as a +certain number, or mass of them, are, as we shall see, requisite for the +development of each cell or part. Nevertheless I should have concluded that +Mr. Spencer's views were fundamentally the same with mine, had it not been +for several passages which, as far as I understand them, indicate something +quite different. I will quote some of these passages from pp. 254-256. "In +the fertilised germ we have two groups of physiological units, slightly +different in their structures."... "It is not obvious that change in the +form of the part, caused by changed action, involves such change in the +physiological units throughout the organism, that these, when groups of +them are thrown off in the shape of reproductive centres, will unfold into +organisms that have this part similarly changed in form. Indeed, when +treating of Adaptation, we saw that an organ modified by increase or +decrease of function can but slowly so react on the system at large as to +bring about those correlative changes required to produce a new +equilibrium; and yet only when such new equilibrium has been established, +can we expect it to be _fully_ expressed in the modified physiological +units of which the organism is built--only then can we count on a complete +transfer of the modification to descendants."... "That the change in the +offspring must, other things equal, be in the same direction as the change +in the parent, we may dimly see is implied by the fact, that the change +propagated throughout the parental system is a change towards a new state +of equilibrium--a change tending to bring the actions of all organs, +reproductive included, into harmony with these new actions." + +[903] M. Philipeaux ('Comptes Rendus,' Oct. 1, 1866, p. 576, and June, +1867) has lately shown that when the entire fore-limb, including the +scapula, is extirpated, the power of regrowth is lost. From this he +concludes that it is necessary for regrowth that a small portion of the +limb should be left. But as in the lower animals the whole body may be +bisected and both halves be reproduced, this belief does not seem probable. +May not the early closing of a deep wound, as in the case of the +extirpation of the scapula, prevent the formation or protrusion of the +nascent limb? + +[904] 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. xiv., 1850, p. 244. + +[905] _See_ some very interesting papers on this subject by Prof. Lionel +Beale, in 'Medical Times and Gazette,' Sept. 9th, 1865, pp. 273, 330. + +[906] Third Report of the R. Comm. on the Cattle Plague, as quoted in +'Gard. Chronicle,' 1866, p. 446. + +[907] In a cod-fish, weighing 20 lb., Mr. F. Buckland ('Land and Water,' +1867, p. 57) calculated the above number of eggs. In another instance, +Harmer ('Phil. Transact.,' 1767, p. 280) found 3,681,760 eggs. For the +Ascaris, _see_ Carpenter's 'Comp. Phys.,' 1854, p. 590. Mr. J. Scott, of +the Royal Botanic Garden of Edinburgh, calculated, in the same manner as I +have done for some British orchids ('Fertilisation of Orchids,' p. 344), +the number of seeds in a capsule of an Acropera, and found the number to be +371,250. Now this plant produces several flowers on a raceme and many +racemes during a season. In an allied genus, Gongora, Mr. Scott has seen +twenty capsules produced on a single raceme: ten such racemes on the +Acropera would yield above seventy-four millions of seed. I may add that +Fritz Mueller informs me that he found in a capsule of a Maxillaria, in +South Brazil, that the seed weighed 42-1/2 grains: he then arranged half a +grain of seed in a narrow line, and by counting a measured length found the +number in the half-grain to be 20,667, so that in the capsule there must +have been 1,756,440 seeds! The same plant sometimes produces half-a-dozen +capsules. + +[908] 'Annals and Mag. of Nat. Hist.,' 3rd series, vol. viii., 1861, p. +490. + +[909] Paget, 'Lectures on Pathology,' p. 27; Virchow, 'Cellular Pathology,' +translat. by Dr. Chance, pp. 123, 126, 294; Claude Bernard, 'Des Tissus +Vivants,' pp. 177, 210, 337; Mueller's 'Physiology,' Eng. translat., p. +290. + +[910] Virchow, 'Cellular Pathology,' trans. by Dr. Chance, 1860, pp. 60, +162, 245, 441, 454. + +[911] Idem, pp. 412-426. + +[912] _See_ Rev. J. M. Berkeley, in 'Gard. Chron.,' April 28th, 1866, on a +bud developed on the petal of the Clarkia. _See_ also H. Schacht, 'Lehrbuch +der Anat.,' &c., 1859, Theile ii. s. 12, on adventitious buds. + +[913] Mr. Herbert Spencer ('Principles of Biology,' vol. ii. p. 430) has +fully discussed the antagonism between growth and reproduction. + +[914] The male salmon is known to breed at a very early age. The Triton and +Siredon, whilst retaining their larval branchiae, according to Filippi and +Dumeril ('Annals and Mag. of Nat. Hist.,' 3rd series, 1866, p. 157), are +capable of reproduction. Ernst Haeckel has recently ('Monatsbericht Akad. +Wiss. Berlin,' Feb. 2nd, 1865) observed the surprising case of a medusa, +with its reproductive organs active, which produces by budding a widely +different form of medusa; and this latter also has the power of sexual +reproduction. Krohn has shown ('Annals and Mag. of Nat. Hist.,' 3rd series, +vol. xix., 1862, p. 6) that certain other medusae, whilst sexually mature, +propagate by gemmae. + +[915] _See_ his excellent discussion on this subject in 'Nouvelles Archives +du Museum,' tom. i. p. 151. + +[916] Various physiologists have insisted on this distinction between +growth and development. Prof. Marshall ('Phil. Transact.,' 1864, p. 544) +gives a good instance in microcephalous idiots, in which the brain +continues to grow after having been arrested in its development. + +[917] 'Compte Rendu,' Nov. 14, 1864, p. 800. + +[918] As previously remarked by Quatrefages, in his 'Metamorphoses de +l'Homme,' &c., 1862, p. 129. + +[919] Guenther's 'Zoological Record,' 1864, p. 279. + +[920] Sedgwick, in 'Medico-Chirurg. Review,' April 1863, p. 454. + +[921] Isid. Geoffroy St. Hilaire, 'Hist. des Anomalies,' tom. i., 1832, pp. +435, 657; and tom. ii. p. 560. + +[922] Virchow, 'Cellular Pathology,' 1860, p. 66. + +[923] Moquin-Tandon, 'Teratologie Veg.,' 1841, pp. 218, 220, 353. For the +case of the pea, _see_ 'Gardener's Chron.,' 1866, p. 897. + +[924] Mueller's 'Physiology,' Eng. translat., vol. i. p. 407. + +[925] _See_ some remarks to this effect by Sir H. Holland in his 'Medical +Notes,' 1839, p. 32. + +[926] This is the view taken by Prof. Haeckel, in his 'Generelle +Morphologie' (B. ii. s. 171), who says: "Lediglich die partielle Identitaet +der specifischconstituirten Materie im elterlichen und im kindlichen +Organismus, die Theilung dieser Materie bei der Fortpflanzung, ist die +Ursache der Erblichkeit." + +[927] In these remarks I, in fact, follow Naudin, who speaks of the +elements or essences of the two species which are crossed. See his +excellent memoir in the 'Nouvelles Archives du Museum,' tom. i. p. 151. + +[928] Godron, 'De l'Espece,' 1859, tom. ii. p. 44, &c. + +[929] Journal Proc. Linn. Soc., 1858, vol. iii. p. 60. + +[930] 'The Quarterly Journal of Science,' Oct. 1867, p. 486. + +[931] M. Rufz de Lavison, in 'Bull. Soc. Imp. d'Acclimat.,' Dec. 1862, p. +1009. + +[932] 'Races of Man,' 1850, p. 315. + +[933] 'Travels in Peru,' Eng. translat., p. 177. + +[934] Youatt on Cattle, 1834, p 200: on Pigs; _see_ 'Gard. Chronicle,' +1854, p. 410. + +[935] 'Die Pflanzen der Pfahlbauten,' 1865. + +[936] Morlot, 'Soc. Vaud. des Scien. Nat,' Mars 1860, p. 298. + +[937] Ruetimeyer, 'Die Fauna der Pfahlbauten,' 1861, s. 30. + +[938] Godron, 'De l'Espece,' tom. i., 1859, p. 368. + +[939] 'Geographie Botan.,' 1855, p. 989. + +[940] Pickering, 'Races of Man,' 1850, p. 318. + +[941] 'Journal of a Horticultural Tour,' by a Deputation of the Caledonian +Hist. Soc., 1823, p. 293. + + + + + + * * * * * + + + + + +Corrections made to printed original. + +p. iii. "APPEARANCE WITH ADVANCING AGE": 'ARPEARANCE' in original. + +p. vi. "SLIGHT CHANGES SUFFICIENT": 'SUFFICENT' in original. + +p. 61. "bearing in mind what has been said": 'bearnig' in original. + +p. 78. "not attached to any particular period": 'particuliar' in original. + +p. 243. "it permits innumerable individuals to be born": 'permitts' in +original. + +p. 294. "liable to complete absorption": 'absortion' in original. + +p. 297. "found that when the animal was compelled ...": 'found than ...' in +original. + +p. 318. "branches in a rudimentary condition": 'rudimentry' in original. + +p. 384. "force themselves into a minute orifice": 'into' was printed on +next line in original, after 'must'. + + + +***END OF THE PROJECT GUTENBERG EBOOK THE VARIATION OF ANIMALS AND PLANTS +UNDER DOMESTICATION, VOLUME II (OF 2)*** + + +******* This file should be named 28897.txt or 28897.zip ******* + + +This and all associated files of various formats will be found in: +http://www.gutenberg.org/dirs/2/8/8/9/28897 + + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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