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diff --git a/22428.txt b/22428.txt new file mode 100644 index 0000000..55cd8e5 --- /dev/null +++ b/22428.txt @@ -0,0 +1,11627 @@ +The Project Gutenberg EBook of Contributions to the Theory of Natural +Selection, by Alfred Russel Wallace + +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: Contributions to the Theory of Natural Selection + A Series of Essays + +Author: Alfred Russel Wallace + +Release Date: August 29, 2007 [EBook #22428] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK THEORY OF NATURAL SELECTION *** + + + + +Produced by Marilynda Fraser-Cunliffe, LN Yaddanapudi and +the Online Distributed Proofreading Team at +http://www.pgdp.net (This file was made using scans of +public domain works from the University of Michigan Digital +Libraries.) + + + + + + + + + +_CONTRIBUTIONS TO_ THE THEORY OF NATURAL SELECTION. + +A Series of Essays. + + +BY + +ALFRED RUSSEL WALLACE, + +AUTHOR OF + +"THE MALAY ARCHIPELAGO," ETC., ETC. + + +_SECOND EDITION, WITH CORRECTIONS AND ADDITIONS._ + + +New York: + +MACMILLAN AND CO. + +1871. + +[_The Right of Translation and Reproduction is reserved._] + + +LONDON: + +PRINTED BY HEAD, HOLE & CO., FARRINGDON STREET, + +AND IVY LANE, E.C. + + + + +PREFACE. + + +The present volume consists of essays which I have contributed to +various periodicals, or read before scientific societies during the last +fifteen years, with others now printed for the first time. The two first +of the series are printed without alteration, because, having gained me +the reputation of being an independent originator of the theory of +"natural selection," they may be considered to have some historical +value. I have added to them one or two very short explanatory notes, and +have given headings to subjects, to make them uniform with the rest of +the book. The other essays have been carefully corrected, often +considerably enlarged, and in some cases almost rewritten, so as to +express more fully and more clearly the views which I hold at the +present time; and as most of them originally appeared in publications +which have a very limited circulation, I believe that the larger portion +of this volume will be new to many of my friends and to most of my +readers. + +I now wish to say a few words on the reasons which have led me to +publish this work. The second essay, especially when taken in connection +with the first, contains an outline sketch of the theory of the +origin of species (by means of what was afterwards termed by Mr. +Darwin--"natural selection,") as conceived by me before I had the least +notion of the scope and nature of Mr. Darwin's labours. They were +published in a way not likely to attract the attention of any but +working naturalists, and I feel sure that many who have heard of them, +have never had the opportunity of ascertaining how much or how little +they really contain. It therefore happens, that, while some writers give +me more credit than I deserve, others may very naturally class me with +Dr. Wells and Mr. Patrick Matthew, who, as Mr. Darwin has shown in the +historical sketch given in the 4th and 5th Editions of the "Origin of +Species," certainly propounded the fundamental principle of "natural +selection" before himself, but who made no further use of that +principle, and failed to see its wide and immensely important +applications. + +The present work will, I venture to think, prove, that I both saw at the +time the value and scope of the law which I had discovered, and have +since been able to apply it to some purpose in a few original lines of +investigation. But here my claims cease. I have felt all my life, and I +still feel, the most sincere satisfaction that Mr. Darwin had been at +work long before me, and that it was not left for me to attempt to write +"The Origin of Species." I have long since measured my own strength, and +know well that it would be quite unequal to that task. Far abler men +than myself may confess, that they have not that untiring patience in +accumulating, and that wonderful skill in using, large masses of facts +of the most varied kind,--that wide and accurate physiological +knowledge,--that acuteness in devising and skill in carrying out +experiments,--and that admirable style of composition, at once clear, +persuasive and judicial,--qualities, which in their harmonious +combination mark out Mr. Darwin as the man, perhaps of all men now +living, best fitted for the great work he has undertaken and +accomplished. + +My own more limited powers have, it is true, enabled me now and then to +seize on some conspicuous group of unappropriated facts, and to search +out some generalization which might bring them under the reign of known +law; but they are not suited to that more scientific and more laborious +process of elaborate induction, which in Mr. Darwin's hands has led to +such brilliant results. + +Another reason which has led me to publish this volume at the present +time is, that there are some important points on which I differ from Mr. +Darwin, and I wish to put my opinions on record in an easily accessible +form, before the publication of his new work, (already announced,) in +which I believe most of these disputed questions will be fully +discussed. + +I will now give the date and mode of publication of each of the essays +in this volume, as well as the amount of alteration they have undergone. + + +I.--ON THE LAW WHICH HAS REGULATED THE INTRODUCTION OF NEW SPECIES. + +First published in the "Annals and Magazine of Natural History," +September, 1855. Reprinted without alteration of the text. + + +II.--ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY FROM THE +ORIGINAL TYPE. + +First published in the "Journal of the Proceedings of the Linnaean +Society," August, 1858. Reprinted without alteration of the text, except +one or two grammatical emendations. + + +III.--MIMICRY AND OTHER PROTECTIVE RESEMBLANCES AMONG ANIMALS. + +First published in the "Westminster Review," July, 1867. Reprinted with +a few corrections and some important additions, among which I may +especially mention Mr. Jenner Weir's observations and experiments on the +colours of the caterpillars eaten or rejected by birds. + + +IV.--THE MALAYAN PAPILIONIDAE, OR SWALLOW-TAILED BUTTERFLIES, AS +ILLUSTRATIVE OF THE THEORY OF NATURAL SELECTION. + +First published in the "Transactions of the Linnaean Society," Vol. XXV. +(read March, 1864), under the title, "On the Phenomena of Variation and +Geographical Distribution, as illustrated by the Papilionidae of the +Malayan Region." + +The introductory part of this essay is now reprinted, omitting tables, +references to plates, &c., with some additions, and several corrections. +Owing to the publication of Dr. Felder's "Voyage of the Novara" +(Lepidoptera) in the interval between the reading of my paper and its +publication, several of my new species must have their names changed for +those given to them by Dr. Felder, and this will explain the want of +agreement in some cases between the names used in this volume and those +of the original paper. + + +V.--ON INSTINCT IN MAN AND ANIMALS. + +Not previously published. + + +VI.--THE PHILOSOPHY OF BIRDS' NESTS. + +First published in the "Intellectual Observer," July, 1867. Reprinted +with considerable emendations and additions. + + +VII.--A THEORY OF BIRDS' NESTS; SHOWING THE RELATION OF CERTAIN +DIFFERENCES OF COLOUR IN BIRDS TO THEIR MODE OF NIDIFICATION. + +First published in the "Journal of Travel and Natural History" (No. 2), +1868. Now reprinted with considerable emendations and additions, by +which I have endeavoured more clearly to express, and more fully to +illustrate, my meaning in those parts which have been misunderstood by +my critics. + + +VIII.--CREATION BY LAW. + +First published in the "Quarterly Journal of Science," October, 1867. +Now reprinted with a few alterations and additions. + + +IX.--THE DEVELOPMENT OF HUMAN RACES UNDER THE LAW OF NATURAL SELECTION. + +First published in the "Anthropological Review," May, 1864. Now +reprinted with a few important alterations and additions. I had intended +to have considerably extended this essay, but on attempting it I found +that I should probably weaken the effect without adding much to the +argument. I have therefore preferred to leave it as it was first +written, with the exception of a few ill-considered passages which never +fully expressed my meaning. As it now stands, I believe it contains the +enunciation of an important truth. + + +X.--THE LIMITS OF NATURAL SELECTION AS APPLIED TO MAN. + +This is the further development of a few sentences at the end of an +article on "Geological Time and the Origin of Species," which appeared +in the "Quarterly Review," for April, 1869. I have here ventured to +touch on a class of problems which are usually considered to be beyond +the boundaries of science, but which, I believe, will one day be brought +within her domain. + + * * * * * + +For the convenience of those who are acquainted with any of my essays in +their original form, I subjoin references to the more important +additions and alterations now made to them. + + +_ADDITIONS AND CORRECTIONS TO THE ESSAYS AS ORIGINALLY PUBLISHED_. + +Essays I. and II. are unaltered, but short notes are added at pp. 19, +24, 29, and 40. + + +III.--_Mimicry, and other Protective Resemblances among Animals._ + + PAGE + + 53 Additional illustration of protective colouring in the case of + the wood-dove and the robin. + + 63 On moths resembling bird's dung and mortar. + + 86 Correction of some names of African Papilios and a reference to + Mr. Trimen's observations. + + 89 Mr. Jenner Weir's observation on birds which refused to eat + _Spilosoma menthrasti_. + + 102 An additional case of snake mimicry in _Oxyrhopus trigeminus_. + + 107 Mr. Salvin's case of mimicry among hawks. + + 113 Name, _Diadema anomala_, added. + + 117 to 122. Use of gay colours in caterpillars, with an account of + Mr. Jenner Weir's and Mr. Butler's observations. + + +IV.--_The Malayan Papilionidae or Swallow-tailed Butterflies, as +illustrative of the Theory of Natural Selection._ + + 135 to 140. Additions to the discussion on the rank of the + Papilionidae, and on the principles which determine the + comparative rank of groups in the animal kingdom. + + 164 Illustration of variability from Mr. Baker's revision of the + British Roses. + + 173 Additional facts, on local variations of colour. + + 196 Additional genus of birds (Ceycopsis) peculiar to Celebes. + + 199, 200. Concluding remarks. + + +VI.--_The Philosophy of Birds' Nests._ + + 218 On nesting of Terns and Gulls, rewritten. + + 220 to 222. Daines Barrington, and others, on the song of birds. + + 223 On young birds learning to build, by memory and imitation. + + 224 Levaillant, on mode of nest-building. + + 229 On imperfect adaptation in birds' nests. + + +VII.--_A Theory of Birds' Nests._ + + 231, 232. Introductory passages modified, with some omissions. + + 233 How modifications of organization would affect the form of the + nest. + + 235 Illustration from the habits of children and savages. + + 235, 236. Objection to term "hereditary habit" answered. + + 237 Passage rewritten, on more or less variable characters in + relation to nidification. + + 248 On males choosing or rejecting females, and on the various modes + in which colour may be acquired by female birds. + + 249 On probable ancestral colours of female birds. + + 255 Protective colouring of the Waxwing. + + +VIII.--_Creation by Law._ + + 293 Amount of variation in dogs. + + 296, 297. The "Times" on Natural Selection. + + 298 to 300. On intermediate or generalized forms of extinct animals + as an indication of transmutation or development. + + 302 Tabular demonstration of the Origin of Species by Natural + Selection. + + +IX.--_The development of Human Races, under the law of Natural +Selection._ + + 316 On colour as perhaps correlated with immunity from disease in + man. + + 326, 327. On the probable future development of man. + + 330 Concluding paragraph rewritten. + +_London, March, 1870._ + + + + +PREFACE TO THE SECOND EDITION. + + +The flattering reception of my Essays by the public and the press having +led to a second edition being called for within a year of its first +publication, I have taken the opportunity to make a few necessary +corrections. I have also added a few passages to the 6th and 7th Essays, +and have given two notes, explanatory of some portions of the last +chapter which appear to have been not always understood. These additions +are as follows:-- + + +-------------------------------------------------------------------+ + | _To avoid altering the paging the additional pages now given have | + | been lettered._ | + +---------+---------+-----------------------------------------------+ + | 1st Ed. | 2nd Ed. | | + +---------+---------+ | + | 221 | 221 | Additional facts as to birds acquiring | + | | | the song of other species. | + | | | | + | 223 | 223A } | Mr. Spruce's remarks on young birds | + | | 223B } | pairing with old. | + | | | | + | 228 | 228A } | Pouchet's observations on a change | + | | 228B } | in the nests of swallows. | + | | | | + | 229 | -- | Passage omitted about nest of Golden | + | | | Crested Warbler, which had been | + | | | inserted on Rennie's authority, but | + | | | has not been confirmed by any later | + | | | observers. | + | | | | + | 261 | 261 | Daines Barrington, on importance of | + | | | protection to the female bird. | + | | | | + | | 372 | Note A. | + | | | | + | | 372B | Note B. | + +---------+---------+-----------------------------------------------+ + + + + +CONTENTS. + + + I.--_On the Law which has regulated the introduction of New + Species._ Pp. 1-25 + + Geographical distribution dependent on Geologic Changes + + A Law deduced from well-known Geographical and Geological facts + + The form of a true system of Classification determined by this Law + + Geographical Distribution of Organisms + + Geological Distribution of the forms of Life + + High Organization of very ancient Animals consistent with this Law + + Objections to Forbes' Theory of Polarity + + Rudimentary Organs + + Conclusion + + + II.--_On the Tendency of Varieties to depart indefinitely from the + Original Type._ Pp. 26-44 + + Instability of Varieties supposed to prove the permanent + distinctness of Species + + The Struggle for Existence + + The Law of Population of Species + + The Abundance or Rarity of a Species dependent upon its more or less + perfect Adaptation to the Conditions of Existence + + Useful Variations will tend to Increase, useless or hurtful + Variations to Diminish + + Superior Varieties will ultimately extirpate the Original Species + + The Partial Reversion of Domesticated Varieties explained + + Lamarck's Hypothesis very different from that now advanced + + Conclusion + + + III.--_Mimicry, and other Protective Resemblances among + Animals._ Pp. 45-129 + + Test of true and false Theories + + Importance of the Principle of Utility + + Popular Theories of Colour in Animals + + Importance of Concealment as influencing Colour + + Special modifications of Colour + + Theory of Protective Colouring + + Objection that Colour as being dangerous should not exist in Nature + + Mimicry + + Mimicry among Lepidoptera + + Lepidoptera mimicking other Insects + + Mimicry among Beetles + + Beetles mimicking other Insects + + Insects mimicking Species of other Orders + + Cases of Mimicry among the Vertebrata + + Mimicry among Snakes + + Mimicry among Birds + + Mimicry among Mammals + + Objections to Mr. Bates' Theory of Mimicry + + Mimicry by Female Insects only + + Cause of the dull Colours of Female Birds + + Use of the gaudy Colours of many Caterpillars + + Summary + + General deductions as to Colour in Nature + + Conclusion + + + IV.--_The Malayan Papilionidae, or Swallow-tailed Butterflies, as + illustrative of the Theory of Natural Selection._ Pp. 130-200 + + Special value of the Diurnal Lepidoptera for inquiries of this + Nature + + Question of the rank of the Papilionidae + + Distribution of the Papilionidae + + Definition of the word Species + + Laws and Modes of Variation + + Simple Variability + + Polymorphism or Dimorphism + + Local form or variety + + Co-existing Variety + + Race or Subspecies + + Species + + Variation as specially influenced by Locality + + Local Variation of Size + + Local Variation of Form + + Local Variations of Colour + + Remarks on the facts of Local Variation + + Mimicry + + Concluding Remarks on Variation in Lepidoptera + + Arrangement and Geographical Distribution of the Malayan Papilionidae + + Arrangement + + Geographical Distribution + + Range of the Groups of Malayan Papilionidae + + Remarkable peculiarities of the island of Celebes + + Concluding Remarks + + + V.--_On Instinct in Man and Animals._ Pp. 201-210 + + How Instinct may be best Studied + + Definition of Instinct + + Does Man possess Instincts? + + How Indians travel through unknown and trackless Forests + + + VI.--_The Philosophy of Birds' Nests._ Pp. 211-230 + + Instinct or Reason in the Construction of Birds' Nests + + Do Men build by Reason or by Imitation? + + Why does each Bird build a peculiar kind of Nest? + + How do young Birds learn to build their first Nest? + + Do Birds sing by Instinct or by Imitation? + + Man's Works mainly Imitative + + How young Birds may learn to build Nests. + + Birds do Alter and Improve their Nests when altered conditions + require it + + Conclusion + + + VII.--_A Theory of Birds' Nests; showing the relation of certain + differences of colour in female birds to their mode of + nidification._ Pp. 231-263 + + Changed Conditions and persistent Habits as influencing Nidification + + Classification of Nests + + Sexual differences of Colour in Birds + + The Law which connects the Colours of Female Birds with the mode of + Nidification + + What the Facts Teach us Colour more variable than Structure or + Habits, and therefore the Character which has generally been + modified + + Exceptional cases confirmatory of the above Explanation + + Real or apparent exceptions to the Law stated at p. 240 + + Various modes of Protection of Animals + + Females of some groups require and obtain more Protection than the + Males + + Conclusion + + + VIII.--_Creation by Law._ Pp. 264-301 + + Laws from which the Origin of Species may be deduced + + Mr. Darwin's Metaphors liable to Misconception + + A case of Orchis-structure explained by Natural Selection + + Adaptation brought about by General Laws + + Beauty in Nature + + How new Forms are produced by Variation and Selection + + The Objection that there are Limits to Variation + + Objection to the argument from Classification + + The _Times_ on Natural Selection + + Intermediate or generalized forms of Extinct Animals an indication + of Transmutation or Development + + Conclusion + + A Demonstration of the Origin of Species + + + IX.--_The Development of Human Races under the Law of Natural + Selection_. Pp. 302-331 + + Wide difference of Opinion as to Man's Origin + + Outline of the Theory of Natural Selection + + Different effects of Natural Selection on Animals and on Man + + Influence of External Nature in the development of the Human Mind + + Extinction of Lower Races + + The Origin of the Races of Man + + The Bearing of these views on the Antiquity of Man + + Their Bearing on the Dignity and Supremacy of Man + + Their Bearing on the future Development of Man + + Summary + + Conclusion + + + X.--_The Limits of Natural Selection as applied to Man._ Pp. 333--371 + + What Natural Selection can Not do + + The Brain of the Savage shown to be Larger than he Needs it to be + + Size of Brain an important Element of Mental Power + + Comparison of the Brains of Man and of Anthropoid Apes + + Range of intellectual power in Man + + Intellect of Savages and of Animals compared + + The use of the Hairy Covering of Mammalia + + The Constant absence of Hair from certain parts of Man's body a + remarkable Phenomenon + + Savage Man feels the want of this Hairy Covering + + Man's Naked Skin could not have been produced by Natural Selection + + Feet and Hands of Man considered as Difficulties on the Theory of + Natural Selection + + The Origin of Some of Man's Mental Faculties, by the preservation of + Useful Variations, not possible + + Difficulty as to the Origin of the Moral Sense + + Summary of the Argument as to the Insufficiency of Natural Selection + to account for the Development of Man + + The Origin of Consciousness + + The Nature of Matter + + Matter is Force + + All Force is probably Will-force + + Conclusion + + + + +I. + +ON THE LAW WHICH HAS REGULATED THE INTRODUCTION OF NEW SPECIES.[A] + + +--------------------------------------------------------------+ + | [A] Written at Sarawak in February, 1855, and published in | + | the "Annals and Magazine of Natural History," September, | + | 1855. | + +--------------------------------------------------------------+ + + +_Geographical Distribution dependent on Geologic Changes._ + +Every naturalist who has directed his attention to the subject of the +geographical distribution of animals and plants, must have been +interested in the singular facts which it presents. Many of these facts +are quite different from what would have been anticipated, and have +hitherto been considered as highly curious, but quite inexplicable. None +of the explanations attempted from the time of Linnaeus are now +considered at all satisfactory; none of them have given a cause +sufficient to account for the facts known at the time, or comprehensive +enough to include all the new facts which have since been, and are daily +being added. Of late years, however, a great light has been thrown upon +the subject by geological investigations, which have shown that the +present state of the earth and of the organisms now inhabiting it, is +but the last stage of a long and uninterrupted series of changes which +it has undergone, and consequently, that to endeavour to explain and +account for its present condition without any reference to those changes +(as has frequently been done) must lead to very imperfect and erroneous +conclusions. + +The facts proved by geology are briefly these:--That during an immense, +but unknown period, the surface of the earth has undergone successive +changes; land has sunk beneath the ocean, while fresh land has risen up +from it; mountain chains have been elevated; islands have been formed +into continents, and continents submerged till they have become islands; +and these changes have taken place, not once merely, but perhaps +hundreds, perhaps thousands of times:--That all these operations have +been more or less continuous, but unequal in their progress, and during +the whole series the organic life of the earth has undergone a +corresponding alteration. This alteration also has been gradual, but +complete; after a certain interval not a single species existing which +had lived at the commencement of the period. This complete renewal of +the forms of life also appears to have occurred several times:--That +from the last of the geological epochs to the present or historical +epoch, the change of organic life has been gradual: the first appearance +of animals now existing can in many cases be traced, their numbers +gradually increasing in the more recent formations, while other species +continually die out and disappear, so that the present condition of the +organic world is clearly derived by a natural process of gradual +extinction and creation of species from that of the latest geological +periods. We may therefore safely infer a like gradation and natural +sequence from one geological epoch to another. + +Now, taking this as a fair statement of the results of geological +inquiry, we see that the present geographical distribution of life upon +the earth must be the result of all the previous changes, both of the +surface of the earth itself and of its inhabitants. Many causes, no +doubt, have operated of which we must ever remain in ignorance, and we +may, therefore, expect to find many details very difficult of +explanation, and in attempting to give one, must allow ourselves to call +into our service geological changes which it is highly probable may have +occurred, though we have no direct evidence of their individual +operation. + +The great increase of our knowledge within the last twenty years, both +of the present and past history of the organic world, has accumulated a +body of facts which should afford a sufficient foundation for a +comprehensive law embracing and explaining them all, and giving a +direction to new researches. It is about ten years since the idea of +such a law suggested itself to the writer of this essay, and he has +since taken every opportunity of testing it by all the newly-ascertained +facts with which he has become acquainted, or has been able to observe +himself. These have all served to convince him of the correctness of his +hypothesis. Fully to enter into such a subject would occupy much space, +and it is only in consequence of some views having been lately +promulgated, he believes, in a wrong direction, that he now ventures to +present his ideas to the public, with only such obvious illustrations of +the arguments and results as occur to him in a place far removed from +all means of reference and exact information. + + +_A Law deduced from well-known Geographical and Geological Facts._ + +The following propositions in Organic Geography and Geology give the +main facts on which the hypothesis is founded. + + +Geography. + +1. Large groups, such as classes and orders, are generally spread over +the whole earth, while smaller ones, such as families and genera, are +frequently confined to one portion, often to a very limited district. + +2. In widely distributed families the genera are often limited in range; +in widely distributed genera, well marked groups of species are peculiar +to each geographical district. + +3. When a group is confined to one district, and is rich in species, it +is almost invariably the case that the most closely allied species are +found in the same locality or in closely adjoining localities, and that +therefore the natural sequence of the species by affinity is also +geographical. + +4. In countries of a similar climate, but separated by a wide sea or +lofty mountains, the families, genera and species of the one are often +represented by closely allied families, genera and species peculiar to +the other. + + +Geology. + +5. The distribution of the organic world in time is very similar to its +present distribution in space. + +6. Most of the larger and some small groups extend through several +geological periods. + +7. In each period, however, there are peculiar groups, found nowhere +else, and extending through one or several formations. + +8. Species of one genus, or genera of one family occurring in the same +geological time are more closely allied than those separated in time. + +9. As generally in geography no species or genus occurs in two very +distant localities without being also found in intermediate places, so +in geology the life of a species or genus has not been interrupted. In +other words, no group or species has come into existence twice. + +10. The following law may be deduced from these facts:--_Every species +has come into existence coincident both in space and time with a +pre-existing closely allied species._ + +This law agrees with, explains and illustrates all the facts connected +with the following branches of the subject:--1st. The system of natural +affinities. 2nd. The distribution of animals and plants in space. 3rd. +The same in time, including all the phaenomena of representative groups, +and those which Professor Forbes supposed to manifest polarity. 4th. The +phaenomena of rudimentary organs. We will briefly endeavour to show its +bearing upon each of these. + + +_The Form of a true system of Classification determined by this Law._ + +If the law above enunciated be true, it follows that the natural series +of affinities will also represent the order in which the several species +came into existence, each one having had for its immediate antitype a +closely allied species existing at the time of its origin. It is +evidently possible that two or three distinct species may have had a +common antitype, and that each of these may again have become the +antitypes from which other closely allied species were created. The +effect of this would be, that so long as each species has had but one +new species formed on its model, the line of affinities will be simple, +and may be represented by placing the several species in direct +succession in a straight line. But if two or more species have been +independently formed on the plan of a common antitype, then the series +of affinities will be compound, and can only be represented by a forked +or many branched line. Now, all attempts at a Natural classification and +arrangement of organic beings show, that both these plans have obtained +in creation. Sometimes the series of affinities can be well represented +for a space by a direct progression from species to species or from +group to group, but it is generally found impossible so to continue. +There constantly occur two or more modifications of an organ or +modifications of two distinct organs, leading us on to two distinct +series of species, which at length differ so much from each other as to +form distinct genera or families. These are the parallel series or +representative groups of naturalists, and they often occur in different +countries, or are found fossil in different formations. They are said to +have an analogy to each other when they are so far removed from their +common antitype as to differ in many important points of structure, +while they still preserve a family resemblance. We thus see how +difficult it is to determine in every case whether a given relation is +an analogy or an affinity, for it is evident that as we go back along +the parallel or divergent series, towards the common antitype, the +analogy which existed between the two groups becomes an affinity. We are +also made aware of the difficulty of arriving at a true classification, +even in a small and perfect group;--in the actual state of nature it is +almost impossible, the species being so numerous and the modifications +of form and structure so varied, arising probably from the immense +number of species which have served as antitypes for the existing +species, and thus produced a complicated branching of the lines of +affinity, as intricate as the twigs of a gnarled oak or the vascular +system of the human body. Again, if we consider that we have only +fragments of this vast system, the stem and main branches being +represented by extinct species of which we have no knowledge, while a +vast mass of limbs and boughs and minute twigs and scattered leaves is +what we have to place in order, and determine the true position each +originally occupied with regard to the others, the whole difficulty of +the true Natural System of classification becomes apparent to us. + +We shall thus find ourselves obliged to reject all these systems of +classification which arrange species or groups in circles, as well as +these which fix a definite number for the divisions of each group. The +latter class have been very generally rejected by naturalists, as +contrary to nature, notwithstanding the ability with which they have +been advocated; but the circular system of affinities seems to have +obtained a deeper hold, many eminent naturalists having to some extent +adopted it. We have, however, never been able to find a case in which +the circle has been closed by a direct and close affinity. In most cases +a palpable analogy has been substituted, in others the affinity is very +obscure or altogether doubtful. The complicated branching of the lines +of affinities in extensive groups must also afford great facilities for +giving a show of probability to any such purely artificial arrangements. +Their death-blow was given by the admirable paper of the lamented Mr. +Strickland, published in the "Annals of Natural History," in which he so +clearly showed the true synthetical method of discovering the Natural +System. + + +_Geographical Distribution of Organisms._ + +If we now consider the geographical distribution of animals and plants +upon the earth, we shall find all the facts beautifully in accordance +with, and readily explained by, the present hypothesis. A country having +species, genera, and whole families peculiar to it, will be the +necessary result of its having been isolated for a long period, +sufficient for many series of species to have been created on the type +of pre-existing ones, which, as well as many of the earlier-formed +species, have become extinct, and thus made the groups appear isolated. +If in any case the antitype had an extensive range, two or more groups +of species might have been formed, each varying from it in a different +manner, and thus producing several representative or analogous groups. +The Sylviadae of Europe and the Sylvicolidae of North America, the +Heliconidae of South America and the Euploeas of the East, the group of +Trogons inhabiting Asia, and that peculiar to South America, are +examples that may be accounted for in this manner. + +Such phaenomena as are exhibited by the Galapagos Islands, which contain +little groups of plants and animals peculiar to themselves, but most +nearly allied to those of South America, have not hitherto received any, +even a conjectural explanation. The Galapagos are a volcanic group of +high antiquity, and have probably never been more closely connected with +the continent than they are at present. They must have been first +peopled, like other newly-formed islands, by the action of winds and +currents, and at a period sufficiently remote to have had the original +species die out, and the modified prototypes only remain. In the same +way we can account for the separate islands having each their peculiar +species, either on the supposition that the same original emigration +peopled the whole of the islands with the same species from which +differently modified prototypes were created, or that the islands were +successively peopled from each other, but that new species have been +created in each on the plan of the pre-existing ones. St. Helena is a +similar case of a very ancient island having obtained an entirely +peculiar, though limited, flora. On the other hand, no example is known +of an island which can be proved geologically to be of very recent +origin (late in the Tertiary, for instance), and yet possesses generic +or family groups, or even many species peculiar to itself. + +When a range of mountains has attained a great elevation, and has so +remained during a long geological period, the species of the two sides +at and near their bases will be often very different, representative +species of some genera occurring, and even whole genera being peculiar +to one side only, as is remarkably seen in the case of the Andes and +Rocky Mountains. A similar phaenomenon occurs when an island has been +separated from a continent at a very early period. The shallow sea +between the Peninsula of Malacca, Java, Sumatra and Borneo was probably +a continent or large island at an early epoch, and may have become +submerged as the volcanic ranges of Java and Sumatra were elevated. The +organic results we see in the very considerable number of species of +animals common to some or all of these countries, while at the same time +a number of closely allied representative species exist peculiar to +each, showing that a considerable period has elapsed since their +separation. The facts of geographical distribution and of geology may +thus mutually explain each other in doubtful cases, should the +principles here advocated be clearly established. + +In all those cases in which an island has been separated from a +continent, or raised by volcanic or coralline action from the sea, or in +which a mountain-chain has been elevated in a recent geological epoch, +the phaenomena of peculiar groups or even of single representative +species will not exist. Our own island is an example of this, its +separation from the continent being geologically very recent, and we +have consequently scarcely a species which is peculiar to it; while the +Alpine range, one of the most recent mountain elevations, separates +faunas and floras which scarcely differ more than may be due to climate +and latitude alone. + +The series of facts alluded to in Proposition (3), of closely allied +species in rich groups being found geographically near each other, is +most striking and important. Mr. Lovell Reeve has well exemplified it in +his able and interesting paper on the Distribution of the Bulimi. It is +also seen in the Humming-birds and Toucans, little groups of two or +three closely allied species being often found in the same or closely +adjoining districts, as we have had the good fortune of personally +verifying. Fishes give evidence of a similar kind: each great river has +its peculiar genera, and in more extensive genera its groups of closely +allied species. But it is the same throughout Nature; every class and +order of animals will contribute similar facts. Hitherto no attempt has +been made to explain these singular phenomena, or to show how they have +arisen. Why are the genera of Palms and of Orchids in almost every case +confined to one hemisphere? Why are the closely allied species of +brown-backed Trogons all found in the East, and the green-backed in the +West? Why are the Macaws and the Cockatoos similarly restricted? Insects +furnish a countless number of analogous examples;--the Goliathi of +Africa, the Ornithopterae of the Indian Islands, the Heliconidae of South +America, the Danaidae of the East, and in all, the most closely allied +species found in geographical proximity. The question forces itself +upon every thinking mind,--why are these things so? They could not be as +they are had no law regulated their creation and dispersion. The law +here enunciated not merely explains, but necessitates the facts we see +to exist, while the vast and long-continued geological changes of the +earth readily account for the exceptions and apparent discrepancies that +here and there occur. The writer's object in putting forward his views +in the present imperfect manner is to submit them to the test of other +minds, and to be made aware of all the facts supposed to be inconsistent +with them. As his hypothesis is one which claims acceptance solely as +explaining and connecting facts which exist in nature, he expects facts +alone to be brought to disprove it, not _a priori_ arguments against its +probability. + + +_Geological Distribution of the Forms of Life._ + +The phaenomena of geological distribution are exactly analogous to those +of geography. Closely allied species are found associated in the same +beds, and the change from species to species appears to have been as +gradual in time as in space. Geology, however, furnishes us with +positive proof of the extinction and production of species, though it +does not inform us how either has taken place. The extinction of +species, however, offers but little difficulty, and the _modus operandi_ +has been well illustrated by Sir C. Lyell in his admirable +"Principles." Geological changes, however gradual, must occasionally +have modified external conditions to such an extent as to have rendered +the existence of certain species impossible. The extinction would in +most cases be effected by a gradual dying-out, but in some instances +there might have been a sudden destruction of a species of limited +range. To discover how the extinct species have from time to time been +replaced by new ones down to the very latest geological period, is the +most difficult, and at the same time the most interesting problem in the +natural history of the earth. The present inquiry, which seeks to +eliminate from known facts a law which has determined, to a certain +degree, what species could and did appear at a given epoch, may, it is +hoped, be considered as one step in the right direction towards a +complete solution of it. + + +_High Organization of very ancient Animals consistent with this Law._ + +Much discussion has of late years taken place on the question, whether +the succession of life upon the globe has been from a lower to a higher +degree of organization. The admitted facts seem to show that there has +been a general, but not a detailed progression. Mollusca and Radiata +existed before Vertebrata, and the progression from Fishes to Reptiles +and Mammalia, and also from the lower mammals to the higher, is +indisputable. On the other hand, it is said that the Mollusca and +Radiata of the very earliest periods were more highly organized than the +great mass of those now existing, and that the very first fishes that +have been discovered are by no means the lowest organised of the class. +Now it is believed the present hypothesis will harmonize with all these +facts, and in a great measure serve to explain them; for though it may +appear to some readers essentially a theory of progression, it is in +reality only one of gradual change. It is, however, by no means +difficult to show that a real progression in the scale of organization +is perfectly consistent with all the appearances, and even with apparent +retrogression, should such occur. + +Returning to the analogy of a branching tree, as the best mode of +representing the natural arrangement of species and their successive +creation, let us suppose that at an early geological epoch any group +(say a class of the Mollusca) has attained to a great richness of +species and a high organization. Now let this great branch of allied +species, by geological mutations, be completely or partially destroyed. +Subsequently a new branch springs from the same trunk, that is to say, +new species are successively created, having for their antitypes the +same lower organized species which had served as the antitypes for the +former group, but which have survived the modified conditions which +destroyed it. This new group being subject to these altered conditions, +has modifications of structure and organization given to it, and +becomes the representative group of the former one in another geological +formation. It may, however, happen, that though later in time, the new +series of species may never attain to so high a degree of organization +as those preceding it, but in its turn become extinct, and give place to +yet another modification from the same root, which may be of higher or +lower organization, more or less numerous in species, and more or less +varied in form and structure than either of those which preceded it. +Again, each of these groups may not have become totally extinct, but may +have left a few species, the modified prototypes of which have existed +in each succeeding period, a faint memorial of their former grandeur and +luxuriance. Thus every case of apparent retrogression may be in reality +a progress, though an interrupted one: when some monarch of the forest +loses a limb, it may be replaced by a feeble and sickly substitute. The +foregoing remarks appear to apply to the case of the Mollusca, which, at +a very early period, had reached a high organization and a great +development of forms and species in the testaceous Cephalopoda. In each +succeeding age modified species and genera replaced the former ones +which had become extinct, and as we approach the present aera, but few +and small representatives of the group remain, while the Gasteropods and +Bivalves have acquired an immense preponderance. In the long series of +changes the earth has undergone, the process of peopling it with organic +beings has been continually going on, and whenever any of the higher +groups have become nearly or quite extinct, the lower forms which have +better resisted the modified physical conditions have served as the +antitypes on which to found the new races. In this manner alone, it is +believed, can the representative groups at successive periods, and the +risings and fallings in the scale of organization, be in every case +explained. + + +_Objections to Forbes' Theory of Polarity._ + +The hypothesis of polarity, recently put forward by Professor Edward +Forbes to account for the abundance of generic forms at a very early +period and at present, while in the intermediate epochs there is a +gradual diminution and impoverishment, till the minimum occurred at the +confines of the Palaeozoic and Secondary epochs, appears to us quite +unnecessary, as the facts may be readily accounted for on the principles +already laid down. Between the Palaeozoic and Neozoic periods of +Professor Forbes, there is scarcely a species in common, and the greater +part of the genera and families also disappear to be replaced by new +ones. It is almost universally admitted that such a change in the +organic world must have occupied a vast period of time. Of this interval +we have no record; probably because the whole area of the early +formations now exposed to our researches was elevated at the end of the +Palaeozoic period, and remained so through the interval required for the +organic changes which resulted in the fauna and flora of the Secondary +period. The records of this interval are buried beneath the ocean which +covers three-fourths of the globe. Now it appears highly probable that a +long period of quiescence or stability in the physical conditions of a +district would be most favourable to the existence of organic life in +the greatest abundance, both as regards individuals and also as to +variety of species and generic group, just as we now find that the +places best adapted to the rapid growth and increase of individuals also +contain the greatest profusion of species and the greatest variety of +forms,--the tropics in comparison with the temperate and arctic regions. +On the other hand, it seems no less probable that a change in the +physical conditions of a district, even small in amount if rapid, or +even gradual if to a great amount, would be highly unfavourable to the +existence of individuals, might cause the extinction of many species, +and would probably be equally unfavourable to the creation of new ones. +In this too we may find an analogy with the present state of our earth, +for it has been shown to be the violent extremes and rapid changes of +physical conditions, rather than the actual mean state in the temperate +and frigid zones, which renders them less prolific than the tropical +regions, as exemplified by the great distance beyond the tropics to +which tropical forms penetrate when the climate is equable, and also by +the richness in species and forms of tropical mountain regions which +principally differ from the temperate zone in the uniformity of their +climate. However this may be, it seems a fair assumption that during a +period of geological repose the new species which we know to have been +created would have appeared; that the creations would then exceed in +number the extinctions, and therefore the number of species would +increase. In a period of geological activity, on the other hand, it +seems probable that the extinctions might exceed the creations, and the +number of species consequently diminish. That such effects did take +place in connexion with the causes to which we have imputed them, is +shown in the case of the Coal formation, the faults and contortions of +which show a period of great activity and violent convulsions, and it is +in the formation immediately succeeding this that the poverty of forms +of life is most apparent. We have then only to suppose a long period of +somewhat similar action during the vast unknown interval at the +termination of the Palaeozoic period, and then a decreasing violence or +rapidity through the Secondary period, to allow for the gradual +repopulation of the earth with varied forms, and the whole of the facts +are explained.[B] We thus have a clue to the increase of the forms of +life during certain periods, and their decrease during others, without +recourse to any causes but those we know to have existed, and to +effects fairly deducible from them. The precise manner in which the +geological changes of the early formations were effected is so extremely +obscure, that when we can explain important facts by a retardation at +one time and an acceleration at another of a process which we know from +its nature and from observation to have been unequal,--a cause so simple +may surely be preferred to one so obscure and hypothetical as polarity. + + +--------------------------------------------------------------+ + | [B] Professor Ramsay has since shown that a glacial epoch | + | probably occurred at the time of the Permian formation, | + | which will more satisfactorily account for the comparative | + | poverty of species. | + +--------------------------------------------------------------+ + +I would also venture to suggest some reasons against the very nature of +the theory of Professor Forbes. Our knowledge of the organic world +during any geological epoch is necessarily very imperfect. Looking at +the vast numbers of species and groups that have been discovered by +geologists, this may be doubted; but we should compare their numbers not +merely with those that now exist upon the earth, but with a far larger +amount. We have no reason for believing that the number of species on +the earth at any former period was much less than at present; at all +events the aquatic portion, with which geologists have most +acquaintance, was probably often as great or greater. Now we know that +there have been many complete changes of species; new sets of organisms +have many times been introduced in place of old ones which have become +extinct, so that the total amount which have existed on the earth from +the earliest geological period must have borne about the same proportion +to those now living, as the whole human race who have lived and died +upon the earth, to the population at the present time. Again, at each +epoch, the whole earth was no doubt, as now, more or less the theatre of +life, and as the successive generations of each species died, their +exuviae and preservable parts would be deposited over every portion of +the then existing seas and oceans, which we have reason for supposing to +have been more, rather than less, extensive than at present. In order +then to understand our possible knowledge of the early world and its +inhabitants, we must compare, not the area of the whole field of our +geological researches with the earth's surface, but the area of the +examined portion of each formation separately with the whole earth. For +example, during the Silurian period all the earth was Silurian, and +animals were living and dying, and depositing their remains more or less +over the whole area of the globe, and they were probably (the species at +least) nearly as varied in different latitudes and longitudes as at +present. What proportion do the Silurian districts bear to the whole +surface of the globe, land and sea (for far more extensive Silurian +districts probably exist beneath the ocean than above it), and what +portion of the known Silurian districts has been actually examined for +fossils? Would the area of rock actually laid open to the eye be the +thousandth or the ten-thousandth part of the earth's surface? Ask the +same question with regard to the Oolite or the Chalk, or even to +particular beds of these when they differ considerably in their +fossils, and you may then get some notion of how small a portion of the +whole we know. + +But yet more important is the probability, nay almost the certainty, +that whole formations containing the records of vast geological periods +are entirely buried beneath the ocean, and for ever beyond our reach. +Most of the gaps in the geological series may thus be filled up, and +vast numbers of unknown and unimaginable animals, which might help to +elucidate the affinities of the numerous isolated groups which are a +perpetual puzzle to the zoologist, may there be buried, till future +revolutions may raise them in their turn above the waters, to afford +materials for the study of whatever race of intelligent beings may then +have succeeded us. These considerations must lead us to the conclusion, +that our knowledge of the whole series of the former inhabitants of the +earth is necessarily most imperfect and fragmentary,--as much so as our +knowledge of the present organic world would be, were we forced to make +our collections and observations only in spots equally limited in area +and in number with those actually laid open for the collection of +fossils. Now, the hypothesis of Professor Forbes is essentially one that +assumes to a great extent the completeness of our knowledge of the whole +series of organic beings which have existed on the earth. This +appears to be a fatal objection to it, independently of all other +considerations. It may be said that the same objections exist against +every theory on such a subject, but this is not necessarily the case. +The hypothesis put forward in this paper depends in no degree upon the +completeness of our knowledge of the former condition of the organic +world, but takes what facts we have as fragments of a vast whole, and +deduces from them something of the nature and proportions of that whole +which we can never know in detail. It is founded upon isolated groups of +facts, recognizes their isolation, and endeavours to deduce from them +the nature of the intervening portions. + + +_Rudimentary Organs._ + +Another important series of facts, quite in accordance with, and even +necessary deductions from, the law now developed, are those of +rudimentary organs. That these really do exist, and in most cases have +no special function in the animal oeconomy, is admitted by the first +authorities in comparative anatomy. The minute limbs hidden beneath the +skin in many of the snake-like lizards, the anal hooks of the boa +constrictor, the complete series of jointed finger-bones in the paddle +of the Manatus and whale, are a few of the most familiar instances. In +botany a similar class of facts has been long recognised. Abortive +stamens, rudimentary floral envelopes and undeveloped carpels, are of +the most frequent occurrence. To every thoughtful naturalist the +question must arise, What are these for? What have they to do with the +great laws of creation? Do they not teach us something of the system of +Nature? If each species has been created independently, and without any +necessary relations with pre-existing species, what do these rudiments, +these apparent imperfections mean? There must be a cause for them; they +must be the necessary results of some great natural law. Now, if, as it +has been endeavoured to be shown, the great law which has regulated the +peopling of the earth with animal and vegetable life is, that every +change shall be gradual; that no new creature shall be formed widely +differing from anything before existing; that in this, as in everything +else in Nature, there shall be gradation and harmony,--then these +rudimentary organs are necessary, and are an essential part of the +system of Nature. Ere the higher Vertebrata were formed, for instance, +many steps were required, and many organs had to undergo modifications +from the rudimental condition in which only they had as yet existed. We +still see remaining an antitypal sketch of a wing adapted for flight in +the scaly flapper of the penguin, and limbs first concealed beneath the +skin, and then weakly protruding from it, were the necessary gradations +before others should be formed fully adapted for locomotion.[C] Many +more of these modifications should we behold, and more complete series +of them, had we a view of all the forms which have ceased to live. The +great gaps that exist between fishes, reptiles, birds, and mammals would +then, no doubt, be softened down by intermediate groups, and the whole +organic world would be seen to be an unbroken and harmonious system. + + +--------------------------------------------------------------+ + | [C] The theory of Natural Selection has now taught us that | + | these are not the steps by which limbs have been formed; and | + | that most rudimentary organs have been produced by abortion, | + | owing to disuse, as explained by Mr. Darwin. | + +--------------------------------------------------------------+ + + +_Conclusion._ + +It has now been shown, though most briefly and imperfectly, how the law +that "_Every species has come into existence coincident both in time and +space with a pre-existing closely allied species_," connects together +and renders intelligible a vast number of independent and hitherto +unexplained facts. The natural system of arrangement of organic beings, +their geographical distribution, their geological sequence, the +phaenomena of representative and substituted groups in all their +modifications, and the most singular peculiarities of anatomical +structure, are all explained and illustrated by it, in perfect +accordance with the vast mass of facts which the researches of modern +naturalists have brought together, and, it is believed, not materially +opposed to any of them. It also claims a superiority over previous +hypotheses, on the ground that it not merely explains, but necessitates +what exists. Granted the law, and many of the most important facts in +Nature could not have been otherwise, but are almost as necessary +deductions from it, as are the elliptic orbits of the planets from the +law of gravitation. + + + + +II. + +ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY FROM THE ORIGINAL +TYPE.[D] + + +--------------------------------------------------------------+ + | [D] Written at Ternate, February, 1858; and published in the | + | Journal of the Proceedings of the Linnaean Society for | + | August, 1858. | + +--------------------------------------------------------------+ + + +_Instability of Varieties supposed to prove the permanent distinctness +of Species._ + +One of the strongest arguments which have been adduced to prove the +original and permanent distinctness of species is, that _varieties_ +produced in a state of domesticity are more or less unstable, and often +have a tendency, if left to themselves, to return to the normal form of +the parent species; and this instability is considered to be a +distinctive peculiarity of all varieties, even of those occurring among +wild animals in a state of nature, and to constitute a provision for +preserving unchanged the originally created distinct species. + +In the absence or scarcity of facts and observations as to _varieties_ +occurring among wild animals, this argument has had great weight with +naturalists, and has led to a very general and somewhat prejudiced +belief in the stability of species. Equally general, however, is the +belief in what are called "permanent or true varieties,"--races of +animals which continually propagate their like, but which differ so +slightly (although constantly) from some other race, that the one is +considered to be a _variety_ of the other. Which is the _variety_ and +which the original _species_, there is generally no means of +determining, except in those rare cases in which the one race has been +known to produce an offspring unlike itself and resembling the other. +This, however, would seem quite incompatible with the "permanent +invariability of species," but the difficulty is overcome by assuming +that such varieties have strict limits, and can never again vary further +from the original type, although they may return to it, which, from the +analogy of the domesticated animals, is considered to be highly +probable, if not certainly proved. + +It will be observed that this argument rests entirely on the assumption, +that _varieties_ occurring in a state of nature are in all respects +analogous to or even identical with those of domestic animals, and are +governed by the same laws as regards their permanence or further +variation. But it is the object of the present paper to show that this +assumption is altogether false, that there is a general principle in +nature which will cause many _varieties_ to survive the parent species, +and to give rise to successive variations departing further and further +from the original type; and which also produces, in domesticated +animals, the tendency of varieties to return to the parent form. + + +_The Struggle for Existence._ + +The life of wild animals is a struggle for existence. The full exertion +of all their faculties and all their energies is required to preserve +their own existence and provide for that of their infant offspring. The +possibility of procuring food during the least favourable seasons, and +of escaping the attacks of their most dangerous enemies, are the primary +conditions which determine the existence both of individuals and of +entire species. These conditions will also determine the population of a +species; and by a careful consideration of all the circumstances we may +be enabled to comprehend, and in some degree to explain, what at first +sight appears so inexplicable--the excessive abundance of some species, +while others closely allied to them are very rare. + + +_The Law of Population of Species._ + +The general proportion that must obtain between certain groups of +animals is readily seen. Large animals cannot be so abundant as small +ones; the carnivora must be less numerous than the herbivora; eagles and +lions can never be so plentiful as pigeons and antelopes; and the wild +asses of the Tartarian deserts cannot equal in numbers the horses of the +more luxuriant prairies and pampas of America. The greater or less +fecundity of an animal is often considered to be one of the chief causes +of its abundance or scarcity; but a consideration of the facts will show +us that it really has little or nothing to do with the matter. Even the +least prolific of animals would increase rapidly if unchecked, whereas +it is evident that the animal population of the globe must be +stationary, or perhaps, through the influence of man, decreasing. +Fluctuations there may be; but permanent increase, except in restricted +localities, is almost impossible. For example, our own observation must +convince us that birds do not go on increasing every year in a +geometrical ratio, as they would do, were there not some powerful check +to their natural increase. Very few birds produce less than two young +ones each year, while many have six, eight, or ten; four will certainly +be below the average; and if we suppose that each pair produce young +only four times in their life, that will also be below the average, +supposing them not to die either by violence or want of food. Yet at +this rate how tremendous would be the increase in a few years from a +single pair! A simple calculation will show that in fifteen years each +pair of birds would have increased to nearly ten millions![E] whereas we +have no reason to believe that the number of the birds of any country +increases at all in fifteen or in one hundred and fifty years. With such +powers of increase the population must have reached its limits, and +have become stationary, in a very few years after the origin of each +species. It is evident, therefore, that each year an immense number of +birds must perish--as many in fact as are born; and as on the lowest +calculation the progeny are each year twice as numerous as their +parents, it follows that, whatever be the average number of individuals +existing in any given country, _twice that number must perish +annually_,--a striking result, but one which seems at least highly +probable, and is perhaps under rather than over the truth. It would +therefore appear that, as far as the continuance of the species and the +keeping up the average number of individuals are concerned, large broods +are superfluous. On the average all above _one_ become food for hawks +and kites, wild cats or weasels, or perish of cold and hunger as winter +comes on. This is strikingly proved by the case of particular species; +for we find that their abundance in individuals bears no relation +whatever to their fertility in producing offspring. + + +--------------------------------------------------------------+ + | [E] This is under estimated. The number would really amount | + | to more than two thousand millions! | + +--------------------------------------------------------------+ + +Perhaps the most remarkable instance of an immense bird population is +that of the passenger pigeon of the United States, which lays only one, +or at most two eggs, and is said to rear generally but one young one. +Why is this bird so extraordinarily abundant, while others producing two +or three times as many young are much less plentiful? The explanation is +not difficult. The food most congenial to this species, and on which it +thrives best, is abundantly distributed over a very extensive region, +offering such differences of soil and climate, that in one part or +another of the area the supply never fails. The bird is capable of a +very rapid and long-continued flight, so that it can pass without +fatigue over the whole of the district it inhabits, and as soon as the +supply of food begins to fail in one place is able to discover a fresh +feeding-ground. This example strikingly shows us that the procuring a +constant supply of wholesome food is almost the sole condition requisite +for ensuring the rapid increase of a given species, since neither the +limited fecundity, nor the unrestrained attacks of birds of prey and of +man are here sufficient to check it. In no other birds are these +peculiar circumstances so strikingly combined. Either their food is more +liable to failure, or they have not sufficient power of wing to search +for it over an extensive area, or during some season of the year it +becomes very scarce, and less wholesome substitutes have to be found; +and thus, though more fertile in offspring, they can never increase +beyond the supply of food in the least favourable seasons. + +Many birds can only exist by migrating, when their food becomes scarce, +to regions possessing a milder, or at least a different climate, though, +as these migrating birds are seldom excessively abundant, it is evident +that the countries they visit are still deficient in a constant and +abundant supply of wholesome food. Those whose organization does not +permit them to migrate when their food becomes periodically scarce, can +never attain a large population. This is probably the reasons why +woodpeckers are scarce with us, while in the tropics they are among the +most abundant of solitary birds. Thus the house sparrow is more +abundant than the redbreast, because its food is more constant and +plentiful,--seeds of grasses being preserved during the winter, and our +farm-yards and stubble-fields furnishing an almost inexhaustible supply. +Why, as a general rule, are aquatic, and especially sea birds, very +numerous in individuals? Not because they are more prolific than others, +generally the contrary; but because their food never fails, the +sea-shores and river-banks daily swarming with a fresh supply of small +mollusca and crustacea. Exactly the same laws will apply to mammals. +Wild cats are prolific and have few enemies; why then are they never as +abundant as rabbits? The only intelligible answer is, that their supply +of food is more precarious. It appears evident, therefore, that so long +as a country remains physically unchanged, the numbers of its animal +population cannot materially increase. If one species does so, some +others requiring the same kind of food must diminish in proportion. The +numbers that die annually must be immense; and as the individual +existence of each animal depends upon itself, those that die must be +the weakest--the very young, the aged, and the diseased--while those +that prolong their existence can only be the most perfect in health and +vigour--those who are best able to obtain food regularly, and avoid +their numerous enemies. It is, as we commenced by remarking, "a struggle +for existence," in which the weakest and least perfectly organized must +always succumb. + + +_The Abundance or Rarity of a Species dependent upon its more or less +perfect Adaptation to the Conditions of Existence._ + +It seems evident that what takes place among the individuals of a +species must also occur among the several allied species of a +group,--viz., that those which are best adapted to obtain a regular +supply of food, and to defend themselves against the attacks of their +enemies and the vicissitudes of the seasons, must necessarily obtain and +preserve a superiority in population; while those species which from +some defect of power or organization are the least capable of +counteracting the vicissitudes of food-supply, &c., must diminish in +numbers, and, in extreme cases, become altogether extinct. Between these +extremes the species will present various degrees of capacity for +ensuring the means of preserving life; and it is thus we account for the +abundance or rarity of species. Our ignorance will generally prevent us +from accurately tracing the effects to their causes; but could we become +perfectly acquainted with the organization and habits of the various +species of animals, and could we measure the capacity of each for +performing the different acts necessary to its safety and existence +under all the varying circumstances by which it is surrounded, we might +be able even to calculate the proportionate abundance of individuals +which is the necessary result. + +If now we have succeeded in establishing these two points--1st, _that +the animal population of a country is generally stationary, being kept +down by a periodical deficiency of food, and other checks_; and, 2nd, +_that the comparative abundance or scarcity of the individuals of the +several species is entirely due to their organization and resulting +habits, which, rendering it more difficult to procure a regular supply +of food and to provide for their personal safety in some cases than in +others, can only be balanced by a difference in the population which +have to exist in a given area_--we shall be in a condition to proceed to +the consideration of _varieties_, to which the preceding remarks have a +direct and very important application. + + +_Useful Variations will tend to Increase; useless or hurtful Variations +to Diminish._ + +Most or perhaps all the variations from the typical form of a species +must have some definite effect, however slight, on the habits or +capacities of the individuals. Even a change of colour might, by +rendering them more or less distinguishable, affect their safety; a +greater or less development of hair might modify their habits. More +important changes, such as an increase in the power or dimensions of the +limbs or any of the external organs, would more or less affect their +mode of procuring food or the range of country which they could inhabit. +It is also evident that most changes would affect, either favourably or +adversely, the powers of prolonging existence. An antelope with shorter +or weaker legs must necessarily suffer more from the attacks of the +feline carnivora; the passenger pigeon with less powerful wings would +sooner or later be affected in its powers of procuring a regular supply +of food; and in both cases the result must necessarily be a diminution +of the population of the modified species. If, on the other hand, any +species should produce a variety having slightly increased powers of +preserving existence, that variety must inevitably in time acquire a +superiority in numbers. These results must follow as surely as old age, +intemperance, or scarcity of food produce an increased mortality. In +both cases there may be many individual exceptions; but on the average +the rule will invariably be found to hold good. All varieties will +therefore fall into two classes--those which under the same conditions +would never reach the population of the parent species, and those which +would in time obtain and keep a numerical superiority. Now, let some +alteration of physical conditions occur in the district--a long period +of drought, a destruction of vegetation by locusts, the irruption of +some new carnivorous animal seeking "pastures new"--any change in fact +tending to render existence more difficult to the species in question, +and tasking its utmost powers to avoid complete extermination; it is +evident that, of all the individuals composing the species, those +forming the least numerous and most feebly organized variety would +suffer first, and, were the pressure severe, must soon become extinct. +The same causes continuing in action, the parent species would next +suffer, would gradually diminish in numbers, and with a recurrence of +similar unfavourable conditions might also become extinct. Tho superior +variety would then alone remain, and on a return to favourable +circumstances would rapidly increase in numbers and occupy the place of +the extinct species and variety. + + +_Superior Varieties will ultimately Extirpate the original Species._ + +The _variety_ would now have replaced the _species_, of which it would +be a more perfectly developed and more highly organized form. It would +be in all respects better adapted to secure its safety, and to prolong +its individual existence and that of the race. Such a variety _could +not_ return to the original form; for that form is an inferior one, and +could never compete with it for existence. Granted, therefore, a +"tendency" to reproduce the original type of the species, still the +variety must ever remain preponderant in numbers, and under adverse +physical conditions _again alone survive_. But this new, improved, and +populous race might itself, in course of time, give rise to new +varieties, exhibiting several diverging modifications of form, any of +which, tending to increase the facilities for preserving existence, +must, by the same general law, in their turn become predominant. Here, +then, we have _progression and continued divergence_ deduced from the +general laws which regulate the existence of animals in a state of +nature, and from the undisputed fact that varieties do frequently occur. +It is not, however, contended that this result would be invariable; a +change of physical conditions in the district might at times materially +modify it, rendering the race which had been the most capable of +supporting existence under the former conditions now the least so, and +even causing the extinction of the newer and, for a time, superior race, +while the old or parent species and its first inferior varieties +continued to flourish. Variations in unimportant parts might also occur, +having no perceptible effect on the life-preserving powers; and the +varieties so furnished might run a course parallel with the parent +species, either giving rise to further variations or returning to the +former type. All we argue for is, that certain varieties have a tendency +to maintain their existence longer than the original species, and this +tendency must make itself felt; for though the doctrine of chances or +averages can never be trusted to on a limited scale, yet, if applied to +high numbers, the results come nearer to what theory demands, and, as we +approach to an infinity of examples, become strictly accurate. Now the +scale on which nature works is so vast--the numbers of individuals and +the periods of time with which she deals approach so near to infinity, +than any cause, however slight, and however liable to be veiled and +counteracted by accidental circumstances, must in the end produce its +full legitimate results. + + +_The Partial Reversion of Domesticated Varieties explained._ + +Let us now turn to domesticated animals, and inquire how varieties +produced among them are affected by the principles here enunciated. The +essential difference in the condition of wild and domestic animals is +this,--that among the former, their well-being and very existence depend +upon the full exercise and healthy condition of all their senses and +physical powers, whereas, among the latter, these are only partially +exercised, and in some cases are absolutely unused. A wild animal has to +search, and often to labour, for every mouthful of food--to exercise +sight, hearing, and smell in seeking it, and in avoiding dangers, in +procuring shelter from the inclemency of the seasons, and in providing +for the subsistence and safety of its offspring. There is no muscle of +its body that is not called into daily and hourly activity; there is no +sense or faculty that is not strengthened by continual exercise. The +domestic animal, on the other hand, has food provided for it, is +sheltered, and often confined, to guard it against the vicissitudes of +the seasons, is carefully secured from the attacks of its natural +enemies, and seldom even rears its young without human assistance. Half +of its senses and faculties become quite useless, and the other half are +but occasionally called into feeble exercise, while even its muscular +system is only irregularly brought into action. + +Now when a variety of such an animal occurs, having increased power or +capacity in any organ or sense, such increase is totally useless, is +never called into action, and may even exist without the animal ever +becoming aware of it. In the wild animal, on the contrary, all its +faculties and powers being brought into full action for the necessities +of existence, any increase becomes immediately available, is +strengthened by exercise, and must even slightly modify the food, the +habits, and the whole economy of the race. It creates as it were a new +animal, one of superior powers, and which will necessarily increase in +numbers and outlive those which are inferior to it. + +Again, in the domesticated animal all variations have an equal chance of +continuance; and those which would decidedly render a wild animal unable +to compete with its fellows and continue its existence are no +disadvantage whatever in a state of domesticity. Our quickly fattening +pigs, short-legged sheep pouter pigeons, and poodle dogs could never +have come into existence in a state of nature, because the very first +step towards such inferior forms would have led to the rapid extinction +of the race; still less could they now exist in competition with their +wild allies. The great speed but slight endurance of the race horse, the +unwieldy strength of the ploughman's team, would both be useless in a +state of nature. If turned wild on the pampas, such animals would +probably soon become extinct, or under favourable circumstances might +each gradually lose those extreme qualities which would never be called +into action, and in a few generations revert to a common type, which +must be that in which the various powers and faculties are so +proportioned to each other as to be best adapted to procure food and +secure safety,--that in which by the full exercise of every part of its +organisation the animal can alone continue to live. Domestic varieties, +when turned wild, _must_ return to something near the type of the +original wild stock, _or become altogether extinct_.[F] + + +--------------------------------------------------------------+ + | [F] That is, they will vary, and the variations which tend | + | to adapt them to the wild state, and therefore approximate | + | them to wild animals, will be preserved. Those individuals | + | which do not vary sufficiently will perish. | + +--------------------------------------------------------------+ + +We see, then, that no inferences as to the permanence of varieties in a +state of nature can be deduced from the observations of those occurring +among domestic animals. The two are so much opposed to each other in +every circumstance of their existence, that what applies to the one is +almost sure not to apply to the other. Domestic animals are abnormal, +irregular, artificial; they are subject to variations which never occur +and never can occur in a state of nature: their very existence depends +altogether on human care; so far are many of them removed from that just +proportion of faculties, that true balance of organisation, by means of +which alone an animal left to its own resources can preserve its +existence and continue its race. + + +_Lamarck's Hypothesis very different from that now advanced._ + +The hypothesis of Lamarck--that progressive changes in species have been +produced by the attempts of animals to increase the development of their +own organs, and thus modify their structure and habits--has been +repeatedly and easily refuted by all writers on the subject of varieties +and species, and it seems to have been considered that when this was +done the whole question has been finally settled; but the view here +developed renders such hypothesis quite unnecessary, by showing that +similar results must be produced by the action of principles constantly +at work in nature. The powerful retractile talons of the falcon-and the +cat-tribes have not been produced or increased by the volition of those +animals; but among the different varieties which occurred in the earlier +and less highly organized forms of these groups, _those always survived +longest which had the greatest facilities for seizing their prey_. +Neither did the giraffe acquire its long neck by desiring to reach the +foliage of the more lofty shrubs, and constantly stretching its neck for +the purpose, but because any varieties which occurred among its +antitypes with a longer neck than usual _at once secured a fresh range +of pasture over the same ground as their shorter-necked companions, and +on the first scarcity of food were thereby enabled to outlive them_. +Even the peculiar colours of many animals, more especially of insects, +so closely resembling the soil or leaves or bark on which they +habitually reside, are explained on the same principle; for though in +the course of ages varieties of many tints may have occurred, _yet those +races having colours best adapted to concealment from their enemies +would inevitably survive the longest_. We have also here an acting cause +to account for that balance so often observed in nature,--a deficiency +in one set of organs always being compensated by an increased +development of some others--powerful wings accompanying weak feet, or +great velocity making up for the absence of defensive weapons; for it +has been shown that all varieties in which an unbalanced deficiency +occurred could not long continue their existence. The action of this +principle is exactly like that of the centrifugal governor of the steam +engine, which checks and corrects any irregularities almost before they +become evident; and in like manner no unbalanced deficiency in the +animal kingdom can ever reach any conspicuous magnitude, because it +would make itself felt at the very first step, by rendering existence +difficult and extinction almost sure soon to follow. An origin such as +is here advocated will also agree with the peculiar character of the +modifications of form and structure which obtain in organized +beings--the many lines of divergence from a central type, the increasing +efficiency and power of a particular organ through a succession of +allied species, and the remarkable persistence of unimportant parts, +such as colour, texture of plumage and hair, form of horns or crests, +through a series of species differing considerably in more essential +characters. It also furnishes us with a reason for that "more +specialized structure" which Professor Owen states to be a +characteristic of recent compared with extinct forms, and which would +evidently be the result of the progressive modification of any organ +applied to a special purpose in the animal economy. + + +_Conclusion._ + +We believe we have now shown that there is a tendency in nature to the +continued progression of certain classes of _varieties_ further and +further from the original type--a progression to which there appears no +reason to assign any definite limits--and that the same principle which +produces this result in a state of nature will also explain why domestic +varieties have a tendency, when they become wild, to revert to the +original type. This progression, by minute steps, in various +directions, but always checked and balanced by the necessary conditions, +subject to which alone existence can be preserved, may, it is believed, +be followed out so as to agree with all the phaenomena presented by +organized beings, their extinction and succession in past ages, and all +the extraordinary modifications of form, instinct and habits which they +exhibit. + + + + +III. + +MIMICRY, AND OTHER PROTECTIVE RESEMBLANCES AMONG ANIMALS. + + +There is no more convincing proof of the truth of a comprehensive +theory, than its power of absorbing and finding a place for new facts, +and its capability of interpreting phaenomena which had been previously +looked upon as unaccountable anomalies. It is thus that the law of +universal gravitation and the undulatory theory of light have become +established and universally accepted by men of science. Fact after fact +has been brought forward as being apparently inconsistent with them, and +one after another these very facts have been shown to be the +consequences of the laws they were at first supposed to disprove. A +false theory will never stand this test. Advancing knowledge brings to +light whole groups of facts which it cannot deal with, and its advocates +steadily decrease in numbers, notwithstanding the ability and scientific +skill with which it may have been supported. The great name of Edward +Forbes did not prevent his theory of "Polarity in the distribution of +Organic beings in Time" from dying a natural death; but the most +striking illustration of the behaviour of a false theory is to be found +in the "Circular and Quinarian System" of classification propounded by +MacLeay, and developed by Swainson, with an amount of knowledge and +ingenuity that have rarely been surpassed. This theory was eminently +attractive, both from its symmetry and completeness, and from the +interesting nature of the varied analogies and affinities which it +brought to light and made use of. The series of Natural History volumes +in "Lardner's Cabinet Cyclopaedia," in which Mr. Swainson developed it in +most departments of the animal kingdom, made it widely known; and in +fact for a long time these were the best and almost the only popular +text-books for the rising generation of naturalists. It was favourably +received too by the older school, which was perhaps rather an indication +of its unsoundness. A considerable number of well-known naturalists +either spoke approvingly of it, or advocated similar principles, and for +a good many years it was decidedly in the ascendent. With such a +favourable introduction, and with such talented exponents, it must have +become established if it had had any germ of truth in it; yet it quite +died out in a few short years, its very existence is now a matter of +history; and so rapid was its fall that its talented creator, Swainson, +perhaps lived to be the last man who believed in it. + +Such is the course of a false theory. That of a true one is very +different, as may be well seen by the progress of opinion on the subject +of Natural Selection. In less than eight years "The Origin of Species" +has produced conviction in the minds of a majority of the most eminent +living men of science. New facts, new problems, new difficulties as they +arise are accepted, solved or removed by this theory; and its principles +are illustrated by the progress and conclusions of every well +established branch of human knowledge. It is the object of the present +essay to show how it has recently been applied to connect together and +explain a variety of curious facts which had long been considered as +inexplicable anomalies. + + +_Importance of the Principle of Utility._ + +Perhaps no principle has ever been announced so fertile in results as +that which Mr. Darwin so earnestly impresses upon us, and which is +indeed a necessary deduction from the theory of Natural Selection, +namely--that none of the definite facts of organic nature, no special +organ, no characteristic form or marking, no peculiarities of instinct +or of habit, no relations between species or between groups of +species--can exist, but which must now be or once have been _useful_ to +the individuals or the races which possess them. This great principle +gives us a clue which we can follow out in the study of many recondite +phaenomena, and leads us to seek a meaning and a purpose of some definite +character in minutiae which we should be otherwise almost sure to pass +over as insignificant or unimportant. + + +_Popular Theories of Colour in Animals._ + +The adaptation of the external colouring of animals to their conditions +of life has long been recognised, and has been imputed either to an +originally created specific peculiarity, or to the direct action of +climate, soil, or food. Where the former explanation has been accepted, +it has completely checked inquiry, since we could never get any further +than the fact of the adaptation. There was nothing more to be known +about the matter. The second explanation was soon found to be quite +inadequate to deal with all the varied phases of the phaenomena, and to +be contradicted by many well-known facts. For example, wild rabbits are +always of grey or brown tints well suited for concealment among grass +and fern. But when these rabbits are domesticated, without any change of +climate or food, they vary into white or black, and these varieties may +be multiplied to any extent, forming white or black races. Exactly the +same thing has occurred with pigeons; and in the case of rats and mice, +the white variety has not been shown to be at all dependent on +alteration of climate, food, or other external conditions. In many cases +the wings of an insect not only assume the exact tint of the bark or +leaf it is accustomed to rest on, but the form and veining of the leaf +or the exact rugosity of the bark is imitated; and these detailed +modifications cannot be reasonably imputed to climate or to food, since +in many cases the species does not feed on the substance it resembles, +and when it does, no reasonable connexion can be shown to exist between +the supposed cause and the effect produced. It was reserved for the +theory of Natural Selection to solve all these problems, and many others +which were not at first supposed to be directly connected with them. To +make these latter intelligible, it will be necessary to give a sketch of +the whole series of phaenomena which may be classed under the head of +useful or protective resemblances. + + +_Importance of Concealment as Influencing Colour._ + +Concealment, more or less complete, is useful to many animals, and +absolutely essential to some. Those which have numerous enemies from +which they cannot escape by rapidity of motion, find safety in +concealment. Those which prey upon others must also be so constituted as +not to alarm them by their presence or their approach, or they would +soon die of hunger. Now it is remarkable in how many cases nature gives +this boon to the animal, by colouring it with such tints as may best +serve to enable it to escape from its enemies or to entrap its prey. +Desert animals as a rule are desert-coloured. The lion is a typical +example of this, and must be almost invisible when crouched upon the +sand or among desert rocks and stones. Antelopes are all more or less +sandy-coloured. The camel is pre-eminently so. The Egyptian cat and the +Pampas cat are sandy or earth-coloured. The Australian kangaroos are of +the same tints, and the original colour of the wild horse is supposed to +have been a sandy or clay-colour. + +The desert birds are still more remarkably protected by their +assimilative hues. The stonechats, the larks, the quails, the +goatsuckers and the grouse, which abound in the North African and +Asiatic deserts, are all tinted and mottled so as to resemble with +wonderful accuracy the average colour and aspect of the soil in the +district they inhabit. The Rev. H. Tristram, in his account of the +ornithology of North Africa in the 1st volume of the "Ibis," says: "In +the desert, where neither trees, brush-wood, nor even undulation of the +surface afford the slightest protection to its foes, a modification of +colour which shall be assimilated to that of the surrounding country, is +absolutely necessary. Hence _without exception_ the upper plumage of +_every bird_, whether lark, chat, sylvain, or sand-grouse, and also the +fur of _all the smaller mammals_, and the skin of _all the snakes and +lizards_, is of one uniform isabelline or sand colour." After the +testimony of so able an observer it is unnecessary to adduce further +examples of the protective colours of desert animals. + +Almost equally striking are the cases of arctic animals possessing the +white colour that best conceals them upon snowfields and icebergs. The +polar bear is the only bear that is white, and it lives constantly among +snow and ice. The arctic fox, the ermine and the alpine hare change to +white in winter only, because in summer white would be more conspicuous +than any other colour, and therefore a danger rather than a protection; +but the American polar hare, inhabiting regions of almost perpetual +snow, is white all the year round. Other animals inhabiting the same +Northern regions do not, however, change colour. The sable is a good +example, for throughout the severity of a Siberian winter it retains its +rich brown fur. But its habits are such that it does not need the +protection of colour, for it is said to be able to subsist on fruits and +berries in winter, and to be so active upon the trees as to catch small +birds among the branches. So also the woodchuck of Canada has a +dark-brown fur; but then it lives in burrows and frequents river banks, +catching fish and small animals that live in or near the water. + +Among birds, the ptarmigan is a fine example of protective colouring. +Its summer plumage so exactly harmonizes with the lichen-coloured stones +among which it delights to sit, that a person may walk through a flock +of them without seeing a single bird; while in winter its white plumage +is an almost equal protection. The snow-bunting, the jer-falcon, and the +snowy owl are also white-coloured birds inhabiting the arctic regions, +and there can be little doubt but that their colouring is to some extent +protective. + +Nocturnal animals supply us with equally good illustrations. Mice, rats, +bats, and moles possess the least conspicuous of hues, and must be quite +invisible at times when any light colour would be instantly seen. Owls +and goatsuckers are of those dark mottled tints that will assimilate +with bark and lichen, and thus protect them during the day, and at the +same time be inconspicuous in the dusk. + +It is only in the tropics, among forests which never lose their foliage, +that we find whole groups of birds whose chief colour is green. The +parrots are the most striking example, but we have also a group of green +pigeons in the East; and the barbets, leaf-thrushes, bee-eaters, +white-eyes, turacos, and several smaller groups, have so much green in +their plumage as to tend greatly to conceal them among the foliage. + + +_Special Modifications of Colour._ + +The conformity of tint which has been so far shown to exist between +animals and their habitations is of a somewhat general character; we +will now consider the cases of more special adaptation. If the lion is +enabled by his sandy colour readily to conceal himself by merely +crouching down upon the desert, how, it may be asked, do the elegant +markings of the tiger, the jaguar, and the other large cats agree with +this theory? We reply that these are generally cases of more or less +special adaptation. The tiger is a jungle animal, and hides himself +among tufts of grass or of bamboos, and in these positions the vertical +stripes with which his body is adorned must so assimilate with the +vertical stems of the bamboo, as to assist greatly in concealing him +from his approaching prey. How remarkable it is that besides the lion +and tiger, almost all the other large cats are arboreal in their +habits, and almost all have ocellated or spotted skins, which must +certainly tend to blend them with the background of foliage; while the +one exception, the puma, has an ashy brown uniform fur, and has the +habit of clinging so closely to a limb of a tree while waiting for his +prey to pass beneath as to be hardly distinguishable from the bark. + +Among birds, the ptarmigan, already mentioned, must be considered a +remarkable case of special adaptation. Another is a South-American +goatsucker (Caprimulgus rupestris) which rests in the bright sunshine on +little bare rocky islets in the Upper Rio Negro, where its unusually +light colours so closely resemble those of the rock and sand, that it +can scarcely be detected till trodden upon. + +The Duke of Argyll, in his "Reign of Law," has pointed out the admirable +adaptation of the colours of the woodcock to its protection. The various +browns and yellows and pale ash-colour that occur in fallen leaves are +all reproduced in its plumage, so that when according to its habit it +rests upon the ground under trees, it is almost impossible to detect it. +In snipes the colours are modified so as to be equally in harmony with +the prevalent forms and colours of marshy vegetation. Mr. J. M. Lester, +in a paper read before the Rugby School Natural History Society, +observes:--"The wood-dove, when perched amongst the branches of its +favourite _fir_, is scarcely discernible; whereas, were it among some +lighter foliage, the blue and purple tints in its plumage would far +sooner betray it. The robin redbreast too, although it might be thought +that the red on its breast made it much easier to be seen, is in reality +not at all endangered by it, since it generally contrives to get among +some russet or yellow fading leaves, where the red matches very well +with the autumn tints, and the brown of the rest of the body with the +bare branches." + +Reptiles offer us many similar examples. The most arboreal lizards, the +iguanas, are as green as the leaves they feed upon, and the slender +whip-snakes are rendered almost invisible as they glide among the +foliage by a similar colouration. How difficult it is sometimes to catch +sight of the little green tree-frogs sitting on the leaves of a small +plant enclosed in a glass case in the Zoological Gardens; yet how much +better concealed must they be among the fresh green damp foliage of a +marshy forest. There is a North-American frog found on lichen-covered +rocks and walls, which is so coloured as exactly to resemble them, and +as long as it remains quiet would certainly escape detection. Some of +the geckos which cling motionless on the trunks of trees in the tropics, +are of such curiously marbled colours as to match exactly with the bark +they rest upon. + +In every part of the tropics there are tree-snakes that twist among +boughs and shrubs, or lie coiled up on the dense masses of foliage. +These are of many distinct groups, and comprise both venomous and +harmless genera; but almost all of them are of a beautiful green +colour, sometimes more or less adorned with white or dusky bands and +spots. There can be little doubt that this colour is doubly useful to +them, since it will tend to conceal them from their enemies, and will +lead their prey to approach them unconscious of danger. Dr. Gunther +informs me that there is only one genus of true arboreal snakes (Dipsas) +whose colours are rarely green, but are of various shades of black, +brown, and olive, and these are all nocturnal reptiles, and there can be +little doubt conceal themselves during the day in holes, so that the +green protective tint would be useless to them, and they accordingly +retain the more usual reptilian hues. + +Fishes present similar instances. Many flat fish, as for example the +flounder and the skate, are exactly the colour of the gravel or sand on +which they habitually rest. Among the marine flower gardens of an +Eastern coral reef the fishes present every variety of gorgeous colour, +while the river fish even of the tropics rarely if ever have gay or +conspicuous markings. A very curious case of this kind of adaptation +occurs in the sea-horses (Hippocampus) of Australia, some of which bear +long foliaceous appendages resembling seaweed, and are of a brilliant +red colour; and they are known to live among seaweed of the same hue, so +that when at rest they must be quite invisible. There are now in the +aquarium of the Zoological Society some slender green pipe-fish which +fasten themselves to any object at the bottom by their prehensile +tails, and float about with the current, looking exactly like some +simple cylindrical algae. + +It is, however, in the insect world that this principle of the +adaptation of animals to their environment is most fully and strikingly +developed. In order to understand how general this is, it is necessary +to enter somewhat into details, as we shall thereby be better able to +appreciate the significance of the still more remarkable phenomena we +shall presently have to discuss. It seems to be in proportion to their +sluggish motions or the absence of other means of defence, that insects +possess the protective colouring. In the tropics there are thousands of +species of insects which rest during the day clinging to the bark of +dead or fallen trees; and the greater portion of these are delicately +mottled with gray and brown tints, which though symmetrically disposed +and infinitely varied, yet blend so completely with the usual colours of +the bark, that at two or three feet distance they are quite +undistinguishable. In some cases a species is known to frequent only one +species of tree. This is the case with the common South American +long-horned beetle (Onychocerus scorpio) which, Mr. Bates informed me, +is found only on a rough-barked tree, called Tapiriba, on the Amazon. It +is very abundant, but so exactly does it resemble the bark in colour and +rugosity, and so closely does it cling to the branches, that until it +moves it is absolutely invisible! An allied species (O. concentricus) +is found only at Para, on a distinct species of tree, the bark of which +it resembles with equal accuracy. Both these insects are abundant, and +we may fairly conclude that the protection they derive from this strange +concealment is at least one of the causes that enable the race to +flourish. + +Many of the species of Cicindela, or tiger beetle, will illustrate this +mode of protection. Our common Cicindela campestris frequents grassy +banks, and is of a beautiful green colour, while C. maritima, which is +found only on sandy sea-shores, is of a pale bronzy yellow, so as to be +almost invisible. A great number of the species found by myself in the +Malay islands are similarly protected. The beautiful Cicindela gloriosa, +of a very deep velvety green colour, was only taken upon wet mossy +stones in the bed of a mountain stream, where it was with the greatest +difficulty detected. A large brown species (C. heros) was found chiefly +on dead leaves in forest paths; and one which was never seen except on +the wet mud of salt marshes was of a glossy olive so exactly the colour +of the mud as only to be distinguished when the sun shone, by its +shadow! Where the sandy beach was coralline and nearly white, I found a +very pale Cicindela; wherever it was volcanic and black, a dark species +of the same genus was sure to be met with. + +There are in the East small beetles of the family Buprestidae which +generally rest on the midrib of a leaf, and the naturalist often +hesitates before picking them off, so closely do they resemble pieces of +bird's dung. Kirby and Spence mention the small beetle Onthophilus +sulcatus as being like the seed of an umbelliferous plant; and another +small weevil, which is much persecuted by predatory beetles of the genus +Harpalus, is of the exact colour of loamy soil, and was found to be +particularly abundant in loam pits. Mr. Bates mentions a small beetle +(Chlamys pilula) which was undistinguishable by the eye from the dung of +caterpillars, while some of the Cassidae, from their hemispherical forms +and pearly gold colour, resemble glittering dew-drops upon the leaves. + +A number of our small brown and speckled weevils at the approach of any +object roll off the leaf they are sitting on, at the same time drawing +in their legs and antennae, which fit so perfectly into cavities for +their reception that the insect becomes a mere oval brownish lump, which +it is hopeless to look for among the similarly coloured little stones +and earth pellets among which it lies motionless. + +The distribution of colour in butterflies and moths respectively is very +instructive from this point of view. The former have all their brilliant +colouring on the upper surface of all four wings, while the under +surface is almost always soberly coloured, and often very dark and +obscure. The moths on the contrary have generally their chief colour on +the hind wings only, the upper wings being of dull, sombre, and often +imitative tints, and these generally conceal the hind wings when the +insects are in repose. This arrangement of the colours is therefore +eminently protective, because the butterfly always rests with his wings +raised so as to conceal the dangerous brilliancy of his upper surface. +It is probable that if we watched their habits sufficiently we should +find the under surface of the wings of butterflies very frequently +imitative and protective. Mr. T. W. Wood has pointed out that the little +orange-tip butterfly often rests in the evening on the green and white +flower heads of an umbelliferous plant, and that when observed in this +position the beautiful green and white mottling of the under surface +completely assimilates with the flower heads and renders the creature +very difficult to be seen. It is probable that the rich dark colouring +of the under side of our peacock, tortoiseshell, and red-admiral +butterflies answers a similar purpose. + +Two curious South American butterflies that always settle on the trunks +of trees (Gynecia dirce and Callizona acesta) have the under surface +curiously striped and mottled, and when viewed obliquely must closely +assimilate with the appearance of the furrowed bark of many kinds of +trees. But the most wonderful and undoubted case of protective +resemblance in a butterfly which I have ever seen, is that of the common +Indian Kallima inachis, and its Malayan ally, Kallima paralekta. The +upper surface of these insects is very striking and showy, as they are +of a large size, and are adorned with a broad band of rich orange on a +deep bluish ground. The under side is very variable in colour, so that +out of fifty specimens no two can be found exactly alike, but every one +of them will be of some shade of ash or brown or ochre, such as are +found among dead, dry, or decaying leaves. The apex of the upper wings +is produced into an acute point, a very common form in the leaves of +tropical shrubs and trees, and the lower wings are also produced into a +short narrow tail. Between these two points runs a dark curved line +exactly representing the midrib of a leaf, and from this radiate on each +side a few oblique lines, which serve to indicate the lateral veins of a +leaf. These marks are more clearly seen on the outer portion of the base +of the wings, and on the inner side towards the middle and apex, and it +is very curious to observe how the usual marginal and transverse striae +of the group are here modified and strengthened so as to become adapted +for an imitation of the venation of a leaf. We come now to a still more +extraordinary part of the imitation, for we find representations of +leaves in every stage of decay, variously blotched and mildewed and +pierced with holes, and in many cases irregularly covered with powdery +black dots gathered into patches and spots, so closely resembling the +various kinds of minute fungi that grow on dead leaves that it is +impossible to avoid thinking at first sight that the butterflies +themselves have been attacked by real fungi. + +But this resemblance, close as it is, would be of little use if the +habits of the insect did not accord with it. If the butterfly sat upon +leaves or upon flowers, or opened its wings so as to expose the upper +surface, or exposed and moved its head and antennae as many other +butterflies do, its disguise would be of little avail. We might be sure, +however, from the analogy of many other cases, that the habits of the +insect are such as still further to aid its deceptive garb; but we are +not obliged to make any such supposition, since I myself had the good +fortune to observe scores of Kallima paralekta, in Sumatra, and to +capture many of them, and can vouch for the accuracy of the following +details. These butterflies frequent dry forests and fly very swiftly. +They were never seen to settle on a flower or a green leaf, but were +many times lost sight of in a bush or tree of dead leaves. On such +occasions they were generally searched for in vain, for while gazing +intently at the very spot where one had disappeared, it would often +suddenly dart out, and again vanish twenty or fifty yards further on. On +one or two occasions the insect was detected reposing, and it could then +be seen how completely it assimilates itself to the surrounding leaves. +It sits on a nearly upright twig, the wings fitting closely back to +back, concealing the antennae and head, which are drawn up between their +bases. The little tails of the hind wing touch the branch, and form a +perfect stalk to the leaf, which is supported in its place by the claws +of the middle pair of feet, which are slender and inconspicuous. The +irregular outline of the wings gives exactly the perspective effect of a +shrivelled leaf. We thus have size, colour, form, markings, and habits, +all combining together to produce a disguise which may be said to be +absolutely perfect; and the protection which it affords is sufficiently +indicated by the abundance of the individuals that possess it. + +The Rev. Joseph Greene has called attention to the striking harmony +between the colours of those British moths which are on the wing in +autumn and winter, and the prevailing tints of nature at those seasons. +In autumn various shades of yellow and brown prevail, and he shows that +out of fifty-two species that fly at this season, no less than forty-two +are of corresponding colours. Orgyia antiqua, O. gonostigma, the genera +Xanthia, Glaea, and Ennomos are examples. In winter, gray and silvery +tints prevail, and the genus Chematobia and several species of Hybernia +which fly during this season are of corresponding hues. No doubt if the +habits of moths in a state of nature were more closely observed, we +should find many cases of special protective resemblance. A few such +have already been noticed. Agriopis aprilina, Acronycta psi, and many +other moths which rest during the day on the north side of the trunks of +trees can with difficulty be distinguished from the grey and green +lichens that cover them. The lappet moth (Gastropacha querci) closely +resembles both in shape and colour a brown dry leaf; and the well-known +buff-tip moth, when at rest is like the broken end of a lichen-covered +branch. There are some of the small moths which exactly resemble the +dung of birds dropped on leaves, and on this point Mr. A. Sidgwick, in a +paper read before the Rugby School Natural History Society, gives the +following original observation:--"I myself have more than once mistaken +Cilix compressa, a little white and grey moth, for a piece of bird's +dung dropped upon a leaf, and _vice versa_ the dung for the moth. +Bryophila Glandifera and Perla are the very image of the mortar walls on +which they rest; and only this summer, in Switzerland, I amused myself +for some time in watching a moth, probably Larentia tripunctaria, +fluttering about quite close to me, and then alighting on a wall of the +stone of the district which it so exactly matched as to be quite +invisible a couple of yards off." There are probably hosts of these +resemblances which have not been observed, owing to the difficulty of +finding many of the species in their stations of natural repose. +Caterpillars are also similarly protected. Many exactly resemble in tint +the leaves they feed upon; others are like little brown twigs, and many +are so strangely marked or humped, that when motionless they can hardly +be taken to be living creatures at all. Mr. Andrew Murray has remarked +how closely the larva of the peacock moth (Saturnia pavonia-minor) +harmonizes in its ground colour with that of the young buds of heather +on which it feeds, and that the pink spots with which it is decorated +correspond with the flowers and flower-buds of the same plant. + +The whole order of Orthoptera, grasshoppers, locusts, crickets, &c., are +protected by their colours harmonizing with that of the vegetation or +the soil on which they live, and in no other group have we such striking +examples of special resemblance. Most of the tropical Mantidae and +Locustidae are of the exact tint of the leaves on which they habitually +repose, and many of them in addition have the veinings of their wings +modified so as exactly to imitate that of a leaf. This is carried to the +furthest possible extent in the wonderful genus, Phyllium, the "walking +leaf," in which not only are the wings perfect imitations of leaves in +every detail, but the thorax and legs are flat, dilated, and leaf-like; +so that when tho living insect is resting among the foliage on which it +feeds, the closest observation is often unable to distinguish between +the animal and the vegetable. + +The whole family of the Phasmidae, or spectres, to which this insect +belongs, is more or less imitative, and a great number of the species +are called "walking-stick insects," from their singular resemblance to +twigs and branches. Some of these are a foot long and as thick as one's +finger, and their whole colouring, form, rugosity, and the arrangement +of the head, legs, and antennae, are such as to render them absolutely +identical in appearance with dead sticks. They hang loosely about shrubs +in the forest, and have the extraordinary habit of stretching out their +legs unsymmetrically, so as to render the deception more complete. One +of these creatures obtained by myself in Borneo (Ceroxylus laceratus) +was covered over with foliaceous excrescences of a clear olive green +colour, so as exactly to resemble a stick grown over by a creeping moss +or jungermannia. The Dyak who brought it me assured me it was grown over +with moss although alive, and it was only after a most minute +examination that I could convince myself it was not so. + +We need not adduce any more examples to show how important are the +details of form and of colouring in animals, and that their very +existence may often depend upon their being by these means concealed +from their enemies. This kind of protection is found apparently in every +class and order, for it has been noticed wherever we can obtain +sufficient knowledge of the details of an animal's life-history. It +varies in degree, from the mere absence of conspicuous colour or a +general harmony with the prevailing tints of nature, up to such a minute +and detailed resemblance to inorganic or vegetable structures as to +realize the talisman of the fairy tale, and to give its possessor the +power of rendering itself invisible. + + +_Theory of Protective Colouring._ + +We will now endeavour to show how these wonderful resemblances have most +probably been brought about. Returning to the higher animals, let us +consider the remarkable fact of the rarity of white colouring in the +mammalia or birds of the temperate or tropical zones in a state of +nature. There is not a single white land-bird or quadruped in Europe, +except the few arctic or alpine species, to which white is a protective +colour. Yet in many of these creatures there seems to be no inherent +tendency to avoid white, for directly they are domesticated white +varieties arise, and appear to thrive as well as others. We have white +mice and rats, white cats, horses, dogs, and cattle, white poultry, +pigeons, turkeys, and ducks, and white rabbits. Some of these animals +have been domesticated for a long period, others only for a few +centuries; but in almost every case in which an animal has been +thoroughly domesticated, parti-coloured and white varieties are produced +and become permanent. + +It is also well known that animals in a state of nature produce white +varieties occasionally. Blackbirds, starlings, and crows are +occasionally seen white, as well as elephants, deer, tigers, hares, +moles, and many other animals; but in no case is a permanent white race +produced. Now there are no statistics to show that the normal-coloured +parents produce white offspring oftener under domestication than in a +state of nature, and we have no right to make such an assumption if the +facts can be accounted for without it. But if the colours of animals do +really, in the various instances already adduced, serve for their +concealment and preservation, then white or any other conspicuous colour +must be hurtful, and must in most cases shorten an animal's life. A +white rabbit would be more surely the prey of hawk or buzzard, and the +white mole, or field mouse, could not long escape from the vigilant owl. +So, also, any deviation from those tints best adapted to conceal a +carnivorous animal would render the pursuit of its prey much more +difficult, would place it at a disadvantage among its fellows, and in a +time of scarcity would probably cause it to starve to death. On the +other hand, if an animal spreads from a temperate into an arctic +district, the conditions are changed. During a large portion of the +year, and just when the struggle for existence is most severe, white is +the prevailing tint of nature, and dark colours will be the most +conspicuous. The white varieties will now have an advantage; they will +escape from their enemies or will secure food, while their brown +companions will be devoured or will starve; and as "like produces like" +is the established rule in nature, the white race will become +permanently established, and dark varieties, when they occasionally +appear, will soon die out from their want of adaptation to their +environment. In each case the fittest will survive, and a race will be +eventually produced adapted to the conditions in which it lives. + +We have here an illustration of the simple and effectual means by which +animals are brought into harmony with the rest of nature. That slight +amount of variability in every species, which we often look upon as +something accidental or abnormal, or so insignificant as to be hardly +worthy of notice, is yet the foundation of all those wonderful and +harmonious resemblances which play such an important part in the economy +of nature. Variation is generally very small in amount, but it is all +that is required, because the change in the external conditions to which +an animal is subject is generally very slow and intermittent. When these +changes have taken place too rapidly, the result has often been the +extinction of species; but the general rule is, that climatal and +geological changes go on slowly, and the slight but continual +variations in the colour, form, and structure of all animals, has +furnished individuals adapted to these changes, and who have become the +progenitors of modified races. Rapid multiplication, incessant slight +variation, and survival of the fittest--these are the laws which ever +keep the organic world in harmony with the inorganic, and with itself. +These are the laws which we believe have produced all the cases of +protective resemblance already adduced, as well as those still more +curious examples we have yet to bring before our readers. + +It must always be borne in mind that the more wonderful examples, in +which there is not only a general but a special resemblance--as in the +walking leaf, the mossy phasma, and the leaf-winged butterfly--represent +those few instances in which the process of modification has been going +on during an immense series of generations. They all occur in the +tropics, where the conditions of existence are the most favourable, and +where climatic changes have for long periods been hardly perceptible. In +most of them favourable variations both of colour, form, structure, and +instinct or habit, must have occurred to produce the perfect adaptation +we now behold. All these are known to vary, and favourable variations +when not accompanied by others that were unfavourable, would certainly +survive. At one time a little step might be made in this direction, at +another time in that--a change of conditions might sometimes render +useless that which it had taken ages to produce--great and sudden +physical modifications might often produce the extinction of a race +just as it was approaching perfection, and a hundred checks of which we +can know nothing may have retarded the progress towards perfect +adaptation; so that we can hardly wonder at there being so few cases in +which a completely successful result has been attained as shown by the +abundance and wide diffusion of the creatures so protected. + + +_Objection that Colour, as being dangerous, should not exist in Nature._ + +It is as well here to reply to an objection that will no doubt occur to +many readers--that if protection is so useful to all animals, and so +easily brought about by variation and survival of the fittest, there +ought to be no conspicuously-coloured creatures; and they will perhaps +ask how we account for the brilliant birds, and painted snakes, and +gorgeous insects, that occur abundantly all over the world. It will be +advisable to answer this question rather fully, in order that we may be +prepared to understand the phenomena of "mimicry," which it is the +special object of this paper to illustrate and explain. + +The slightest observation of the life of animals will show us, that they +escape from their enemies and obtain their food in an infinite number of +ways; and that their varied habits and instincts are in every case +adapted to the conditions of their existence. The porcupine and the +hedgehog have a defensive armour that saves them from the attacks of +most animals. The tortoise is not injured by the conspicuous colours of +his shell, because that shell is in most cases an effectual protection +to him. The skunks of North America find safety in their power of +emitting an unbearably offensive odour; the beaver in its aquatic habits +and solidly constructed abode. In some cases the chief danger to an +animal occurs at one particular period of its existence, and if that is +guarded against its numbers can easily be maintained. This is the case +with many birds, the eggs and young of which are especially obnoxious to +danger, and we find accordingly a variety of curious contrivances to +protect them. We have nests carefully concealed, hung from the slender +extremities of grass or boughs over water, or placed in the hollow of a +tree with a very small opening. When these precautions are successful, +so many more individuals will be reared than can possibly find food +during the least favourable seasons, that there will always be a number +of weakly and inexperienced young birds who will fall a prey to the +enemies of the race, and thus render necessary for the stronger and +healthier individuals no other safeguard than their strength and +activity. The instincts most favourable to the production and rearing of +offspring will in these cases be most important, and the survival of the +fittest will act so as to keep up and advance those instincts, while +other causes which tend to modify colour and marking may continue their +action almost unchecked. + +It is perhaps in insects that we may best study the varied means by +which animals are defended or concealed. One of the uses of the +phosphorescence with which many insects are furnished, is probably to +frighten away their enemies; for Kirby and Spence state that a ground +beetle (Carabus) has been observed running round and round a luminous +centipede as if afraid to attack it. An immense number of insects have +stings, and some stingless ants of the genus Polyrachis are armed with +strong and sharp spines on the back, which must render them unpalatable +to many of the smaller insectivorous birds. Many beetles of the family +Curculionidae have the wing cases and other external parts so excessively +hard, that they cannot be pinned without first drilling a hole to +receive the pin, and it is probable that all such find a protection in +this excessive hardness. Great numbers of insects hide themselves among +the petals of flowers, or in the cracks of bark and timber; and finally, +extensive groups and even whole orders have a more or less powerful and +disgusting smell and taste, which they either possess permanently, or +can emit at pleasure. The attitudes of some insects may also protect +them, as the habit of turning up the tail by the harmless rove-beetles +(Staphylindidae) no doubt leads other animals besides children to the +belief that they can sting. The curious attitude assumed by sphinx +caterpillars is probably a safeguard, as well as the blood-red tentacles +which can suddenly be thrown out from the neck, by the caterpillars of +all the true swallow-tailed butterflies. + +It is among the groups that possess some of these varied kinds of +protection in a high degree, that we find the greatest amount of +conspicuous colour, or at least the most complete absence of protective +imitation. The stinging Hymenoptera, wasps, bees, and hornets, are, as a +rule, very showy and brilliant insects, and there is not a single +instance recorded in which any one of them is coloured so as to resemble +a vegetable or inanimate substance. The Chrysididae, or golden wasps, +which do not sting, possess as a substitute the power of rolling +themselves up into a ball, which is almost as hard and polished as if +really made of metal,--and they are all adorned with the most gorgeous +colours. The whole order Hemiptera (comprising the bugs) emit a powerful +odour, and they present a very large proportion of gay-coloured and +conspicuous insects. The lady-birds (Coccinellidae) and their allies the +Eumorphidae, are often brightly spotted, as if to attract attention; but +they can both emit fluids of a very disagreeable nature, they are +certainly rejected by some birds, and are probably never eaten by any. + +The great family of ground beetles (Carabidae) almost all possess a +disagreeable and some a very pungent smell, and a few, called bombardier +beetles, have the peculiar faculty of emitting a jet of very volatile +liquid, which appears like a puff of smoke, and is accompanied by a +distinct crepitating explosion. It is probably because these insects are +mostly nocturnal and predacious that they do not present more vivid +hues. They are chiefly remarkable for brilliant metallic tints or dull +red patches when they are not wholly black, and are therefore very +conspicuous by day, when insect-eaters are kept off by their bad odour +and taste, but are sufficiently invisible at night when it is of +importance that their prey should not become aware of their proximity. + +It seems probable that in some cases that which would appear at first to +be a source of danger to its possessor may really be a means of +protection. Many showy and weak-flying butterflies have a very broad +expanse of wing, as in the brilliant blue Morphos of Brazilian forests, +and the large Eastern Papilios; yet these groups are tolerably +plentiful. Now, specimens of these butterflies are often captured with +pierced and broken wings, as if they had been seized by birds from whom +they had escaped; but if the wings had been much smaller in proportion +to the body, it seems probable that the insect would be more frequently +struck or pierced in a vital part, and thus the increased expanse of the +wings may have been indirectly beneficial. + +In other cases the capacity of increase in a species is so great that +however many of the perfect insect may be destroyed, there is always +ample means for the continuance of the race. Many of the flesh flies, +gnats, ants, palm-tree weevils and locusts are in this category. The +whole family of Cetoniadae or rose chafers, so full of gaily-coloured +species, are probably saved from attack by a combination of characters. +They fly very rapidly with a zigzag or waving course; they hide +themselves the moment they alight, either in the corolla of flowers, or +in rotten wood, or in cracks and hollows of trees, and they are +generally encased in a very hard and polished coat of mail which may +render them unsatisfactory food to such birds as would be able to +capture them. The causes which lead to the development of colour have +been here able to act unchecked, and we see the result in a large +variety of the most gorgeously-coloured insects. + +Here, then, with our very imperfect knowledge of the life-history of +animals, we are able to see that there are widely varied modes by which +they may obtain protection from their enemies or concealment from their +prey. Some of those seem to be so complete and effectual as to answer +all the wants of the race, and lead to the maintenance of the largest +possible population. When this is the case, we can well understand that +no further protection derived from a modification of colour can be of +the slightest use, and the most brilliant hues may be developed without +any prejudicial effect upon the species. On some of the laws that +determine the development of colour something may be said presently. It +is now merely necessary to show that concealment by obscure or imitative +tints is only one out of very many ways by which animals maintain their +existence; and having done this we are prepared to consider the +phenomena of what has been termed "mimicry." It is to be particularly +observed, however, that the word is not here used in the sense of +voluntary imitation, but to imply a particular kind of resemblance--a +resemblance not in internal structure but in external appearance--a +resemblance in those parts only that catch the eye--a resemblance that +deceives. As this kind of resemblance has the same effect as voluntary +imitation or mimicry, and as we have no word that expresses the required +meaning, "mimicry" was adopted by Mr. Bates (who was the first to +explain the facts), and has led to some misunderstanding; but there need +be none, if it is remembered that both "mimicry" and "imitation" are +used in a metaphorical sense, as implying that close external likeness +which causes things unlike in structure to be mistaken for each other. + + +_Mimicry._ + +It has been long known to entomologists that certain insects bear a +strange external resemblance to others belonging to distinct genera, +families, or even orders, and with which they have no real affinity +whatever. The fact, however, appears to have been generally considered +as dependent upon some unknown law of "analogy"--some "system of +nature," or "general plan," which had guided the Creator in designing +the myriads of insect forms, and which we could never hope to +understand. In only one case does it appear that the resemblance was +thought to be useful, and to have been designed as a means to a definite +and intelligible purpose. The flies of the genus Volucella enter the +nests of bees to deposit their eggs, so that their larvae may feed upon +the larvae of the bees, and these flies are each wonderfully like the bee +on which it is parasitic. Kirby and Spence believed that this +resemblance or "mimicry" was for the express purpose of protecting the +flies from the attacks of the bees, and the connection is so evident +that it was hardly possible to avoid this conclusion. The resemblance, +however, of moths to butterflies or to bees, of beetles to wasps, and of +locusts to beetles, has been many times noticed by eminent writers; but +scarcely ever till within the last few years does it appear to have been +considered that these resemblances had any special purpose, or were of +any direct benefit to the insects themselves. In this respect they were +looked upon as accidental, as instances of the "curious analogies" in +nature which must be wondered at but which could not be explained. +Recently, however, these instances have been greatly multiplied; the +nature of the resemblances has been more carefully studied, and it has +been found that they are often carried out into such details as almost +to imply a purpose of deceiving the observer. The phenomena, moreover, +have been shown to follow certain definite laws, which again all +indicate their dependence on the more general law of the "survival of +the fittest," or "the preservation of favoured races in the struggle for +life." It will, perhaps, be as well here to state what these laws or +general conclusions are, and then to give some account of the facts +which support them. + +The first law is, that in an overwhelming majority of cases of mimicry, +the animals (or the groups) which resemble each other inhabit the same +country, the same district, and in most cases are to be found together +on the very same spot. + +The second law is, that these resemblances are not indiscriminate, but +are limited to certain groups, which in every case are abundant in +species and individuals, and can often be ascertained to have some +special protection. + +The third law is, that the species which resemble or "mimic" these +dominant groups, are comparatively less abundant in individuals, and are +often very rare. + +These laws will be found to hold good, in all the cases of true mimicry +among various classes of animals to which we have now to call the +attention of our readers. + + +_Mimicry among Lepidoptera._ + +As it is among butterflies that instances of mimicry are most numerous +and most striking, an account of some of the more prominent examples in +this group will first be given. There is in South America an extensive +family of these insects, the Heliconidae, which are in many respects very +remarkable. They are so abundant and characteristic in all the woody +portions of the American tropics, that in almost every locality they +will be seen more frequently than any other butterflies. They are +distinguished by very elongate wings, body, and antennae, and are +exceedingly beautiful and varied in their colours; spots and patches of +yellow, red, or pure white upon a black, blue, or brown ground, being +most general. They frequent the forests chiefly, and all fly slowly and +weakly; yet although they are so conspicuous, and could certainly be +caught by insectivorous birds more easily than almost any other +insects, their great abundance all over the wide region they inhabit +shows that they are not so persecuted. It is to be especially remarked +also, that they possess no adaptive colouring to protect them during +repose, for the under side of their wings presents the same, or at least +an equally conspicuous colouring as the upper side; and they may be +observed after sunset suspended at the end of twigs and leaves where +they have taken up their station for the night, fully exposed to the +attacks of enemies if they have any. These beautiful insects possess, +however, a strong pungent semi-aromatic or medicinal odour, which seems +to pervade all the juices of their system. When the entomologist +squeezes the breast of one of them between his fingers to kill it, a +yellow liquid exudes which stains the skin, and the smell of which can +only be got rid of by time and repeated washings. Here we have probably +the cause of their immunity from attack, since there is a great deal of +evidence to show that certain insects are so disgusting to birds that +they will under no circumstances touch them. Mr. Stainton has observed +that a brood of young turkeys greedily devoured all the worthless moths +he had amassed in a night's "sugaring," yet one after another seized and +rejected a single white moth which happened to be among them. Young +pheasants and partridges which eat many kinds of caterpillars seem to +have an absolute dread of that of the common currant moth, which they +will never touch, and tomtits as well as other small birds appear never +to eat the same species. In the case of the Heliconidae, however, we +have some direct evidence to the same effect. In the Brazilian forests +there are great numbers of insectivorous birds--as jacamars, trogons, +and puffbirds--which catch insects on the wing, and that they destroy +many butterflies is indicated by the fact that the wings of these +insects are often found on the ground where their bodies have been +devoured. But among these there are no wings of Heliconidae, while those +of the large showy Nymphalidae, which have a much swifter flight, are +often met with. Again, a gentleman who had recently returned from Brazil +stated at a meeting of the Entomological Society that he once observed a +pair of puffbirds catching butterflies, which they brought to their nest +to feed their young; yet during half an hour they never brought one of +the Heliconidae, which were flying lazily about in great numbers, and +which they could have captured more easily than any others. It was this +circumstance that led Mr. Belt to observe them so long, as he could not +understand why the most common insects should be altogether passed by. +Mr. Bates also tells us that he never saw them molested by lizards or +predacious flies, which often pounce on other butterflies. + +If, therefore, we accept it as highly probable (if not proved) that the +Heliconidae are very greatly protected from attack by their peculiar +odour and taste, we find it much more easy to understand their chief +characteristics--their great abundance, their slow flight, their gaudy +colours, and the entire absence of protective tints on their under +surfaces. This property places them somewhat in the position of those +curious wingless birds of oceanic islands, the dodo, the apteryx, and +the moas, which are with great reason supposed to have lost the power of +flight on account of the absence of carnivorous quadrupeds. Our +butterflies have been protected in a different way, but quite as +effectually; and the result has been that as there has been nothing to +escape from, there has been no weeding out of slow flyers, and as there +has been nothing to hide from, there has been no extermination of the +bright-coloured varieties, and no preservation of such as tended to +assimilate with surrounding objects. + +Now let us consider how this kind of protection must act. Tropical +insectivorous birds very frequently sit on dead branches of a lofty +tree, or on those which overhang forest paths, gazing intently around, +and darting off at intervals to seize an insect at a considerable +distance, which they generally return to their station to devour. If a +bird began by capturing the slow-flying, conspicuous Heliconidae, and +found them always so disagreeable that it could not eat them, it would +after a very few trials leave off catching them at all; and their whole +appearance, form, colouring, and mode of flight is so peculiar, that +there can be little doubt birds would soon learn to distinguish them at +a long distance, and never waste any time in pursuit of them. Under +these circumstances, it is evident that any other butterfly of a group +which birds were accustomed to devour, would be almost equally well +protected by closely resembling a Heliconia externally, as if it +acquired also the disagreeable odour; always supposing that there were +only a few of them among a great number of the Heliconias. If the birds +could not distinguish the two kinds externally, and there were on the +average only one eatable among fifty uneatable, they would soon give up +seeking for the eatable ones, even if they knew them to exist. If, on +the other hand, any particular butterfly of an eatable group acquired +the disagreeable taste of the Heliconias while it retained the +characteristic form and colouring of its own group, this would be really +of no use to it whatever; for the birds would go on catching it among +its eatable allies (compared with which it would rarely occur), it would +be wounded and disabled, even if rejected, and its increase would thus +be as effectually checked as if it were devoured. It is important, +therefore, to understand that if any one genus of an extensive family of +eatable butterflies were in danger of extermination from insect-eating +birds, and if two kinds of variation were going on among them, some +individuals possessing a slightly disagreeable taste, others a slight +resemblance to the Heliconidae, this latter quality would be much more +valuable than the former. The change in flavour would not at all prevent +the variety from being captured as before, and it would almost certainly +be thoroughly disabled before being rejected. The approach in colour and +form to the Heliconidae, however, would be at the very first a positive, +though perhaps a slight advantage; for although at short distances this +variety would be easily distinguished and devoured, yet at a longer +distance it might be mistaken for one of the uneatable group, and so be +passed by and gain another day's life, which might in many cases be +sufficient for it to lay a quantity of eggs and leave a numerous +progeny, many of which would inherit the peculiarity which had been the +safeguard of their parent. + +Now, this hypothetical case is exactly realized in South America. Among +the white butterflies forming the family Pieridae (many of which do not +greatly differ in appearance from our own cabbage butterflies) is a +genus of rather small size (Leptalis), some species of which are white +like their allies, while the larger number exactly resemble the +Heliconidae in the form and colouring of the wings. It must always be +remembered that these two families are as absolutely distinguished from +each other by structural characters as are the carnivora and the +ruminants among quadrupeds, and that an entomologist can always +distinguish the one from the other by the structure of the feet, just as +certainly as a zoologist can tell a bear from a buffalo by the skull or +by a tooth. Yet the resemblance of a species of the one family to +another species in the other family was often so great, that both Mr. +Bates and myself were many times deceived at the time of capture, and +did not discover the distinctness of the two insects till a closer +examination detected their essential differences. During his residence +of eleven years in the Amazon valley, Mr. Bates found a number of +species or varieties of Leptalis, each of which was a more or less exact +copy of one of the Heliconidae of the district it inhabited; and the +results of his observations are embodied in a paper published in the +Linnean Transactions, in which he first explained the phenomena of +"mimicry" as the result of natural selection, and showed its identity in +cause and purpose with protective resemblance to vegetable or inorganic +forms. + +The imitation of the Heliconidae by the Leptalides is carried out to a +wonderful degree in form as well as in colouring. The wings have become +elongated to the same extent, and the antennae and abdomen have both +become lengthened, to correspond with the unusual condition in which +they exist in the former family. In colouration there are several types +in the different genera of Heliconidae. The genus Mechanitis is generally +of a rich semi-transparent brown, banded with black and yellow; Methona +is of large size, the wings transparent like horn, and with black +transverse bands; while the delicate Ithomias are all more or less +transparent, with black veins and borders, and often with marginal and +transverse bands of orange red. These different forms are all copied by +the various species of Leptalis, every band and spot and tint of colour, +and the various degrees of transparency, being exactly reproduced. As if +to derive all the benefit possible from this protective mimicry, the +habits have become so modified that the Leptalides generally frequent +the very same spots as their models, and have the same mode of flight; +and as they are always very scarce (Mr. Bates estimating their numbers +at about one to a thousand of the group they resemble), there is hardly +a possibility of their being found out by their enemies. It is also +very remarkable that in almost every case the particular Ithomias and +other species of Heliconidae which they resemble, are noted as being very +common species, swarming in individuals, and found over a wide range of +country. This indicates antiquity and permanence in the species, and is +exactly the condition most essential both to aid in the development of +the resemblance, and to increase its utility. + +But the Leptalides are not the only insects who have prolonged their +existence by imitating the great protected group of Heliconidae;--a genus +of quite another family of most lovely small American butterflies, the +Erycinidae, and three genera of diurnal moths, also present species which +often mimic the same dominant forms, so that some, as Ithomia ilerdina +of St. Paulo, for instance, have flying with them a few individuals of +three widely different insects, which are yet disguised with exactly the +same form, colour, and markings, so as to be quite undistinguishable +when upon the wing. Again, the Heliconidae are not the only group that +are imitated, although they are the most frequent models. The black and +red group of South American Papilios, and the handsome Erycinian genus +Stalachtis, have also a few who copy them; but this fact offers no +difficulty, since these two groups are almost as dominant as the +Heliconidae. They both fly very slowly, they are both conspicuously +coloured, and they both abound in individuals; so that there is every +reason to believe that they possess a protection of a similar kind to +the Heliconidae, and that it is therefore equally an advantage to other +insects to be mistaken for them. There is also another extraordinary +fact that we are not yet in a position clearly to comprehend: some +groups of the Heliconidae themselves mimic other groups. Species of +Heliconia mimic Mechanitis, and every species of Napeogenes mimics some +other Heliconideous butterfly. This would seem to indicate that the +distasteful secretion is not produced alike by all members of the +family, and that where it is deficient protective imitation comes into +play. It is this, perhaps, that has caused such a general resemblance +among the Heliconidae, such a uniformity of type with great diversity of +colouring, since any aberration causing an insect to cease to look like +one of the family would inevitably lead to its being attacked, wounded, +and exterminated, even although it was not eatable. + +In other parts of the world an exactly parallel series of facts have +been observed. The Danaidae and the Acraeidae of the Old World tropics form +in fact one great group with the Heliconidae. They have the same general +form, structure, and habits: they possess the same protective odour, and +are equally abundant in individuals, although not so varied in colour, +blue and white spots on a black ground being the most general pattern. +The insects which mimic these are chiefly Papilios, and Diadema, a genus +allied to our peacock and tortoiseshell butterflies. In tropical Africa +there is a peculiar group of the genus Danais, characterized by +dark-brown and bluish-white colours, arranged in bands or stripes. One +of these, Danais niavius, is exactly imitated both by Papilio hippocoon +and by Diadema anthedon; another, Danais echeria, by Papilio cenea; and +in Natal a variety of the Danais is found having a white spot at the tip +of wings, accompanied by a variety of the Papilio bearing a +corresponding white spot. Acraea gea is copied in its very peculiar style +of colouration by the female of Papilio cynorta, by Panopaea hirce, and +by the female of Elymnias phegea. Acraea euryta of Calabar has a female +variety of Panopea hirce from the same place which exactly copies it; +and Mr. Trimen, in his paper on Mimetic Analogies among African +Butterflies, published in the Transactions of the Linnaean Society for +1868, gives a list of no less than sixteen species and varieties of +Diadema and its allies, and ten of Papilio, which in their colour and +markings are perfect mimics of species or varieties of Danais or Acraea +which inhabit the same districts. + +Passing on to India, we have Danais tytia, a butterfly with +semi-transparent bluish wings and a border of rich reddish brown. This +remarkable style of colouring is exactly reproduced in Papilio agestor +and in Diadema nama, and all three insects not unfrequently come +together in collections made at Darjeeling. In the Philippine Islands +the large and curious Idea leuconoee with its semi-transparent white +wings, veined and spotted with black, is copied by the rare Papilio +idaeoides from the same islands. + +In the Malay archipelago the very common and beautiful Euploea midamus +is so exactly mimicked by two rare Papilios (P. paradoxa and P. aenigma) +that I generally caught them under the impression that they were the +more common species; and the equally common and even more beautiful +Euploea rhadamanthus, with its pure white bands and spots on a ground of +glossy blue and black, is reproduced in the Papilio caunus. Here also +there are species of Diadema imitating the same group in two or three +instances; but we shall have to adduce these further on in connexion +with another branch of the subject. + +It has been already mentioned that in South America there is a group of +Papilios which have all the characteristics of a protected race, and +whose peculiar colours and markings are imitated by other butterflies +not so protected. There is just such a group also in the East, having +very similar colours and the same habits, and these also are mimicked by +other species in the same genus not closely allied to them, and also by +a few of other families. Papilio hector, a common Indian butterfly of a +rich black colour spotted with crimson, is so closely copied by Papilio +romulus, that the latter insect has been thought to be its female. A +close examination shows, however, that it is essentially different, and +belongs to another section of the genus. Papilio antiphus and P. +diphilus, black swallow-tailed butterflies with cream-coloured spots, +are so well imitated by varieties of P. theseus, that several writers +have classed them as the same species. Papilio liris, found only in the +island of Timor, is accompanied there by P. aenomaus, the female of +which so exactly resembles it that they can hardly be separated in the +cabinet, and on the wing are quite undistinguishable. But one of the +most curious cases is the fine yellow-spotted Papilio coeon, which is +unmistakeably imitated by the female tailed form of Papilio memnon. +These are both from Sumatra; but in North India P. coeon is replaced by +another species, which has been named P. doubledayi, having red spots +instead of yellow; and in the same district the corresponding female +tailed form of Papilio androgeus, sometimes considered a variety of P. +memnon, is similarly red-spotted. Mr. Westwood has described some +curious day-flying moths (Epicopeia) from North India, which have the +form and colour of Papilios of this section, and two of these are very +good imitations of Papilio polydorus and Papilio varuna, also from North +India. + +Almost all these cases of mimicry are from the tropics, where the forms +of life are more abundant, and where insect development especially is of +unchecked luxuriance; but there are also one or two instances in +temperate regions. In North America, the large and handsome red and +black butterfly Danais erippus is very common; and the same country is +inhabited by Limenitis archippus, which closely resembles the Danais, +while it differs entirely from every species of its own genus. + +The only case of probable mimicry in our own country is the +following:--A very common white moth (Spilosoma menthastri) was found by +Mr. Stainton to be rejected by young turkeys among hundreds of other +moths on which they greedily fed. Each bird in succession took hold of +this moth and threw it down again, as if too nasty to eat. Mr. Jenner +Weir also found that this moth was refused by the Bullfinch, Chaffinch, +Yellow Hammer, and Red Bunting, but eaten after much hesitation by the +Robin. We may therefore fairly conclude that this species would be +disagreeable to many other birds, and would thus have an immunity from +attack, which may be the cause of its great abundance and of its +conspicuous white colour. Now it is a curious thing that there is +another moth, Diaphora mendica, which appears about the same time, and +whose female only is white. It is about the same size as Spilosoma +menthastri, and sufficiently resembles it in the dusk, and this moth is +much less common. It seems very probable, therefore, that these species +stand in the same relation to each other as the mimicking butterflies of +various families do to the Heliconidae and Danaidae. It would be very +interesting to experiment on all white moths, to ascertain if those +which are most common are generally rejected by birds. It may be +anticipated that they would be so, because white is the most conspicuous +of all colours for nocturnal insects, and had they not some other +protection would certainly be very injurious to them. + + +_Lepidoptera mimicking other Insects._ + +In the preceding cases we have found Lepidoptera imitating other species +of the same order, and such species only as we have good reason to +believe were free from the attacks of many insectivorous creatures; but +there are other instances in which they altogether lose the external +appearance of the order to which they belong, and take on the dress of +bees or wasps--insects which have an undeniable protection in their +stings. The Sesiidae and AEgeriidae, two families of day-flying moths, are +particularly remarkable in this respect, and a mere inspection of the +names given to the various species shows how the resemblance has struck +everyone. We have apiformis, vespiforme, ichneumoniforme, scoliaeforme, +sphegiforme (bee-like, wasp-like, ichneumon-like, &c.) and many others, +all indicating a resemblance to stinging Hymenoptera. In Britain we may +particularly notice Sesia bombiliformis, which very closely resembles +the male of the large and common humble bee, Bombus hortorum; Sphecia +craboniforme, which is coloured like a hornet, and is (on the authority +of Mr. Jenner Weir) much more like it when alive than when in the +cabinet, from the way in which it carries its wings; and the currant +clear-wing, Trochilium tipuliforme, which resembles a small black wasp +(Odynerus sinuatus) very abundant in gardens at the same season. It has +been so much the practice to look upon these resemblances as mere +curious analogies playing no part in the economy of nature, that we have +scarcely any observations of the habits and appearance when alive of the +hundreds of species of these groups in various parts of the world, or +how far they are accompanied by Hymenoptera, which they specifically +resemble. There are many species in India (like those figured by +Professor Westwood in his "Oriental Entomology") which have the hind +legs very broad and densely hairy, so as exactly to imitate the +brush-legged bees (Scopulipedes) which abound in the same country. In +this case we have more than mere resemblance of colour, for that which +is an important functional structure in the one group is imitated in +another whose habits render it perfectly useless. + + +_Mimicry among Beetles._ + +It may fairly be expected that if these imitations of one creature by +another really serve as a protection to weak and decaying species, +instances of the same kind will be found among other groups than the +Lepidoptera; and such is the case, although they are seldom so prominent +and so easily recognised as those already pointed out as occurring in +that order. A few very interesting examples may, however, be pointed out +in most of the other orders of insects. The Coleoptera or beetles that +imitate other Coleoptera of distinct groups are very numerous in +tropical countries, and they generally follow the laws already laid down +as regulating these phenomena. The insects which others imitate always +have a special protection, which leads them to be avoided as dangerous +or uneatable by small insectivorous animals; some have a disgusting +taste (analogous to that of the Heliconidae); others have such a hard and +stony covering that they cannot be crushed or digested; while a third +set are very active, and armed with powerful jaws, as well as having +some disagreeable secretion. Some species of Eumorphidae and Hispidae, +small flat or hemispherical beetles which are exceedingly abundant, and +have a disagreeable secretion, are imitated by others of the very +distinct group of Longicornes (of which our common musk-beetle may be +taken as an example). The extraordinary little Cyclopeplus batesii, +belongs to the same sub-family of this group as the Onychocerus scorpio +and O. concentricus, which have already been adduced as imitating with +such wonderful accuracy the bark of the trees they habitually frequent; +but it differs totally in outward appearance from every one of its +allies, having taken upon itself the exact shape and colouring of a +globular Corynomalus, a little stinking beetle with clubbed antennae. It +is curious to see how these clubbed antennae are imitated by an insect +belonging to a group with long slender antennae. The sub-family +Anisocerinae, to which Cyclopeplus belongs, is characterised by all its +members possessing a little knob or dilatation about the middle of the +antennae. This knob is considerably enlarged in C. batesii, and the +terminal portion of the antennae beyond it is so small and slender as to +be scarcely visible, and thus an excellent substitute is obtained for +the short clubbed antennae of the Corynomalus. Erythroplatis corallifer +is another curious broad flat beetle, that no one would take for a +Longicorn, since it almost exactly resembles Cephalodonta spinipes, one +of the commonest of the South American Hispidae; and what is still more +remarkable, another Longicorn of a distinct group, Streptolabis +hispoides, was found by Mr. Bates, which resembles the same insect with +equal minuteness,--a case exactly parallel to that among butterflies, +where species of two or three distinct groups mimicked the same +Heliconia. Many of the soft-winged beetles (Malacoderms) are excessively +abundant in individuals, and it is probable that they have some similar +protection, more especially as other species often strikingly resemble +them. A Longicorn beetle, Paeciloderma terminale, found in Jamaica, is +coloured exactly in the same way as a Lycus (one of the Malacoderms) +from the same island. Eroschema poweri, a Longicorn from Australia, +might certainly be taken for one of the same group, and several species +from the Malay Islands are equally deceptive. In the Island of Celebes I +found one of this group, having the whole body and elytra of a rich deep +blue colour, with the head only orange; and in company with it an insect +of a totally different family (Eucnemidae) with identically the same +colouration, and of so nearly the same size and form as to completely +puzzle the collector on every fresh occasion of capturing them. I have +been recently informed by Mr. Jenner Weir, who keeps a variety of small +birds, that none of them will touch our common "soldiers and sailors" +(species of Malacoderms), thus confirming my belief that they were a +protected group, founded on the fact of their being at once very +abundant, of conspicuous colours, and the objects of mimicry. + +There are a number of the larger tropical weevils which have the +elytra and the whole covering of the body so hard as to be a great +annoyance to the entomologist, because in attempting to transfix them +the points of his pins are constantly turned. I have found it necessary +in these cases to drill a hole very carefully with the point of a +sharp penknife before attempting to insert a pin. Many of the fine +long-antennaed Anthribidae (an allied group) have to be treated in the +same way. We can easily understand that after small birds have in vain +attempted to eat these insects, they should get to know them by sight, +and ever after leave them alone, and it will then be an advantage for +other insects which are comparatively soft and eatable, to be mistaken +for them. We need not be surprised, therefore, to find that there are +many Longicorns which strikingly resemble the "hard beetles" of their +own district. In South Brazil, Acanthotritus dorsalis is strikingly +like a Curculio of the hard genus Heiliplus, and Mr. Bates assures me +that he found Gymnocerus cratosomoides (a Longicorn) on the same tree +with a hard Cratosomus (a weevil), which it exactly mimics. Again, the +pretty Longicorn, Phacellocera batesii, mimics one of the hard +Anthribidae of the genus Ptychoderes, having long slender antennae. In the +Moluccas we find Cacia anthriboides, a small Longicorn which might be +easily mistaken for a very common species of Anthribidae found in the +same districts; and the very rare Capnolymma stygium closely imitates +the common Mecocerus gazella, which abounded where it was taken. Doliops +curculionoides and other allied Longicorns from the Philippine Islands +most curiously resemble, both in form and colouring, the brilliant +Pachyrhynchi,--Curculionidae, which are almost peculiar to that group of +islands. The remaining family of Coleoptera most frequently imitated is +the Cicindelidae. The rare and curious Longicorn, Collyrodes lacordairei, +has exactly the form and colouring of the genus Collyris, while an +undescribed species of Heteromera is exactly like a Therates, and was +taken running on the trunks of trees, as is the habit of that group. +There is one curious example of a Longicorn mimicking a Longicorn, like +the Papilios and Heliconidae which mimic their own allies. Agnia +fasciata, belonging to the sub-family Hypselominae, and Nemophas grayi, +belonging to the Lamiinae, were taken in Amboyna on the same fallen tree +at the same time, and were supposed to be the same species till they +were more carefully examined, and found to be structurally quite +different. The colouring of these insects is very remarkable, being rich +steel-blue black, crossed by broad hairy bands of orange buff, and out +of the many thousands of known species of Longicorns they are probably +the only two which are so coloured. The Nemophas grayi is the larger, +stronger, and better armed insect, and belongs to a more widely spread +and dominant group, very rich in species and individuals, and is +therefore most probably the subject of mimicry by the other species. + + +_Beetles mimicking other Insects._ + +We will now adduce a few cases in which beetles imitate other insects, +and insects of other orders imitate beetles. + +Charis melipona, a South American Longicorn of the family Necydalidae, +has been so named from its resemblance to a small bee of the genus +Melipona. It is one of the most remarkable cases of mimicry, since the +beetle has the thorax and body densely hairy like the bee, and the legs +are tufted in a manner most unusual in the order Coleoptera. Another +Longicorn, Odontocera odyneroides, has the abdomen banded with yellow, +and constricted at the base, and is altogether so exactly like a small +common wasp of the genus Odynerus, that Mr. Bates informs us he was +afraid to take it out of his net with his fingers for fear of being +stung. Had Mr. Bates's taste for insects been less omnivorous than it +was, the beetle's disguise might have saved it from his pin, as it had +no doubt often done from the beak of hungry birds. A larger insect, +Sphecomorpha chalybea, is exactly like one of the large metallic blue +wasps, and like them has the abdomen connected with the thorax by a +pedicel, rendering the deception most complete and striking. Many +Eastern species of Longicorns of the genus Oberea, when on the wing +exactly resemble Tenthredinidae, and many of the small species of +Hesthesis run about on timber, and cannot be distinguished from ants. +There is one genus of South American Longicorns that appears to mimic +the shielded bugs of the genus Scutellera. The Gymnocerous capucinus is +one of these, and is very like Pachyotris fabricii, one of the +Scutelleridae. The beautiful Gymnocerous dulcissimus is also very like +the same group of insects, though there is no known species that exactly +corresponds to it; but this is not to be wondered at, as the tropical +Hemiptera have been comparatively so little cared for by collectors. + + +_Insects mimicking Species of other Orders._ + +The most remarkable case of an insect of another order mimicking a +beetle is that of the Condylodera tricondyloides, one of the cricket +family from the Philippine Islands, which is so exactly like a +Tricondyla (one of the tiger beetles), that such an experienced +entomologist as Professor Westwood placed it among them in his cabinet, +and retained it there a long time before he discovered his mistake! Both +insects run along the trunks of trees, and whereas Tricondylas are very +plentiful, the insect that mimics it is, as in all other cases, very +rare. Mr. Bates also informs us that he found at Santarem on the Amazon, +a species of locust which mimicked one of the tiger beetles of the genus +Odontocheila, and was found on the same trees which they frequented. + +There are a considerable number of Diptera, or two-winged flies, that +closely resemble wasps and bees, and no doubt derive much benefit from +the wholesome dread which those insects excite. The Midas dives, and +other species of large Brazilian flies, have dark wings and metallic +blue elongate bodies, resembling the large stinging Sphegidae of the same +country; and a very large fly of the genus Asilus has black-banded +wings and the abdomen tipped with rich orange, so as exactly to resemble +the fine bee Euglossa dimidiata, and both are found in the same parts of +South America. We have also in our own country species of Bombylius +which are almost exactly like bees. In these cases the end gained by the +mimicry is no doubt freedom from attack, but it has sometimes an +altogether different purpose. There are a number of parasitic flies +whose larvae feed upon the larvae of bees, such as the British genus +Volucella and many of the tropical Bombylii, and most of these are +exactly like the particular species of bee they prey upon, so that they +can enter their nests unsuspected to deposit their eggs. There are also +bees that mimic bees. The cuckoo bees of the genus Nomada are parasitic +on the Andrenidae, and they resemble either wasps or species of Andrena; +and the parasitic humble-bees of the genus Apathus almost exactly +resemble the species of humble-bees in whose nests they are reared. Mr. +Bates informs us that he found numbers of these "cuckoo" bees and flies +on the Amazon, which all wore the livery of working bees peculiar to the +same country. + +There is a genus of small spiders in the tropics which feed on ants, and +they are exactly like ants themselves, which no doubt gives them more +opportunity of seizing their prey; and Mr. Bates found on the Amazon a +species of Mantis which exactly resembled the white ants which it fed +upon, as well as several species of crickets (Scaphura), which resembled +in a wonderful manner different sand-wasps of large size, which are +constantly on the search for crickets with which to provision their +nests. + +Perhaps the most wonderful case of all is the large caterpillar +mentioned by Mr. Bates, which startled him by its close resemblance to a +small snake. The first three segments behind the head were dilatable at +the will of the insect, and had on each side a large black pupillated +spot, which resembled the eye of the reptile. Moreover, it resembled a +poisonous viper, not a harmless species of snake, as was proved by the +imitation of keeled scales on the crown produced by the recumbent feet, +as the caterpillar threw itself backward! + +The attitudes of many of the tropical spiders are most extraordinary and +deceptive, but little attention has been paid to them. They often mimic +other insects, and some, Mr. Bates assures us, are exactly like flower +buds, and take their station in the axils of leaves, where they remain +motionless waiting for their prey. + + +_Cases of Mimicry among the Vertebrata._ + +Having thus shown how varied and extraordinary are the modes in which +mimicry occurs among insects, we have now to enquire if anything of the +same kind is to be observed among vertebrated animals. When we consider +all the conditions necessary to produce a good deceptive imitation, we +shall see at once that such can very rarely occur in the higher animals, +since they possess none of those facilities for the almost infinite +modifications of external form which exist in the very nature of insect +organization. The outer covering of insects being more or less solid +and horny, they are capable of almost any amount of change of form and +appearance without any essential modification internally. In many groups +the wings give much of the character, and these organs may be much +modified both in form and colour without interfering with their special +functions. Again, the number of species of insects is so great, and +there is such diversity of form and proportion in every group, that the +chances of an accidental approximation in size, form, and colour, of one +insect to another of a different group, are very considerable; and it is +these chance approximations that furnish the basis of mimicry, to be +continually advanced and perfected by the survival of those varieties +only which tend in the right direction. + +In the Vertebrata, on the contrary, the skeleton being internal the +external form depends almost entirely on the proportions and arrangement +of that skeleton, which again is strictly adapted to the functions +necessary for the well-being of the animal. The form cannot therefore be +rapidly modified by variation, and the thin and flexible integument will +not admit of the development of such strange protuberances as occur +continually in insects. The number of species of each group in the same +country is also comparatively small, and thus the chances of that first +accidental resemblance which is necessary for natural selection to work +upon are much diminished. We can hardly see the possibility of a mimicry +by which the elk could escape from the wolf, or the buffalo from the +tiger. There is, however, in one group of Vertebrata such a general +similarity of form, that a very slight modification, if accompanied by +identity of colour, would produce the necessary amount of resemblance; +and at the same time there exist a number of species which it would be +advantageous for others to resemble, since they are armed with the most +fatal weapons of offence. We accordingly find that reptiles furnish us +with a very remarkable and instructive case of true mimicry. + + +_Mimicry among Snakes._ + +There are in tropical America a number of venomous snakes of the genus +Elaps, which are ornamented with brilliant colours disposed in a +peculiar manner. The ground colour is generally bright red, on which are +black bands of various widths and sometimes divided into two or three by +yellow rings. Now, in the same country are found several genera of +harmless snakes, having no affinity whatever with the above, but +coloured exactly the same. For example, the poisonous Elaps fulvius +often occurs in Guatemala with simple black bands on a coral-red ground; +and in the same country is found the harmless snake Pliocerus equalis, +coloured and banded in identically the same manner. A variety of Elaps +corallinus has the black bands narrowly bordered with yellow on the same +red ground colour, and a harmless snake, Homalocranium semicinctum, has +exactly the same markings, and both are found in Mexico. The deadly +Elaps lemniscatus has the black bands very broad, and each of them +divided into three by narrow yellow rings; and this again is exactly +copied by a harmless snake, Pliocerus elapoides, which is found along +with its model in Mexico. + +But, more remarkable still, there is in South America a third group of +snakes, the genus Oxyrhopus, doubtfully venomous, and having no +immediate affinity with either of the preceding, which has also the same +curious distribution of colours, namely, variously disposed rings of +red, yellow, and black; and there are some cases in which species of all +three of these groups similarly marked inhabit the same district. For +example, Elaps mipartitus has single black rings very close together. It +inhabits the west side of the Andes, and in the same districts occur +Pliocerus euryzonus and Oxyrhopus petolarius, which exactly copy its +pattern. In Brazil Elaps lemniscatus is copied by Oxyrhopus trigeminus, +both having black rings disposed in threes. In Elaps hemiprichii the +ground colour appears to be black, with alternations of two narrow +yellow bands and a broader red one; and of this pattern again we have an +exact double in Oxyrhopus formosus, both being found in many localities +of tropical South America. + +What adds much to the extraordinary character of these resemblances is +the fact, that nowhere in the world but in America are there any snakes +at all which have this style of colouring. Dr. Gunther, of the British +Museum, who has kindly furnished some of the details here referred to, +assures me that this is the case; and that red, black, and yellow rings +occur together on no other snakes in the world but on Elaps and the +species which so closely resemble it. In all these cases, the size and +form as well as the colouration, are so much alike, that none but a +naturalist would distinguish the harmless from the poisonous species. + +Many of the small tree-frogs are no doubt also mimickers. When seen in +their natural attitudes, I have been often unable to distinguish them +from beetles or other insects sitting upon leaves, but regret to say I +neglected to observe what species or groups they most resembled, and the +subject does not yet seem to have attracted the attention of naturalists +abroad. + + +_Mimicry among Birds._ + +In the class of birds there are a number of cases that make some +approach to mimicry, such as the resemblance of the cuckoos, a weak and +defenceless group of birds, to hawks and Gallinaceae. There is, however, +one example which goes much further than this, and seems to be of +exactly the same nature as the many cases of insect mimicry which have +been already given. In Australia and the Moluccas there is a genus of +honeysuckers called Tropidorhynchus, good sized birds, very strong and +active, having powerful grasping claws and long, curved, sharp beaks. +They assemble together in groups and small flocks, and they have a very +loud bawling note, which can be heard at a great distance, and serves to +collect a number together in time of danger. They are very plentiful +and very pugnacious, frequently driving away crows, and even hawks, +which perch on a tree where a few of them are assembled. They are all of +rather dull and obscure colours. Now in the same countries there is a +group of orioles, forming the genus Mimeta, much weaker birds, which +have lost the gay colouring of their allies the golden orioles, being +usually olive-green or brown; and in several cases these most curiously +resemble the Tropidorhynchus of the same island. For example, in the +island of Bouru is found the Tropidorhynchus bouruensis, of a dull +earthy colour, and the Mimeta bouruensis, which resembles it in the +following particulars:--The upper and under surfaces of the two birds +are exactly of the same tints of dark and light brown; the +Tropidorhynchus has a large bare black patch round the eyes; this is +copied in the Mimeta by a patch of black feathers. The top of the head +of the Tropidorhynchus has a scaly appearance from the narrow +scale-formed feathers, which are imitated by the broader feathers of the +Mimeta having a dusky line down each. The Tropidorhynchus has a pale +ruff formed of curious recurved feathers on the nape (which has given +the whole genus the name of Friar birds); this is represented in the +Mimeta by a pale band in the same position. Lastly, the bill of the +Tropidorhynchus is raised into a protuberant keel at the base, and the +Mimeta has the same character, although it is not a common one in the +genus. The result is, that on a superficial examination the birds are +identical, although they have important structural differences, and +cannot be placed near each other in any natural arrangement. As a proof +that the resemblance is really deceptive, it may be mentioned that the +Mimeta is figured and described as a honeysucker in the costly "Voyage +de l'Astrolabe," under the name of Philedon bouruensis! + +Passing to the island of Ceram, we find allied species of both genera. +The Tropidorhynchus subcornutus is of an earthy brown colour washed with +yellow ochre, with bare orbits, dusky cheeks, and the usual pale +recurved nape-ruff. The Mimeta forsteni is absolutely identical in the +tints of every part of the body, the details of which are imitated in +the same manner as in the Bouru birds already described. In two other +islands there is an approximation towards mimicry, although it is not so +perfect as in the two preceding cases. In Timor the Tropidorhynchus +timoriensis is of the usual earthy brown above, with the nape-ruff very +prominent, the cheeks black, the throat nearly white, and the whole +under surface pale whitish brown. These various tints are all well +reproduced in Mimeta virescens, the chief want of exact imitation being +that the throat and breast of the Tropidorhynchus has a very scaly +appearance, being covered with rigid pointed feathers which are not +imitated in the Mimeta, although there are signs of faint dusky spots +which may easily furnish the groundwork of a more exact imitation by the +continued survival of favourable variations in the same direction. There +is also a large knob at the base of the bill of the Tropidorhynchus +which is not at all imitated by the Mimeta. In the island of Morty +(north of Gilolo) there exists the Tropidorhynchus fuscicapillus, of a +dark sooty brown colour, especially on the head, while the under parts +are rather lighter, and the characteristic ruff of the nape is wanting. +Now it is curious that in the adjacent island of Gilolo should be found +the Mimeta phaeochromus, the upper surface of which is of exactly the +same dark sooty tint as the Tropidorhynchus, and is the only known +species that is of such a dark colour. The under side is not quite light +enough, but it is a good approximation. This Mimeta is a rare bird, and +may very probably exist in Morty, though not yet found there; or, on the +other hand, recent changes in physical geography may have led to the +restriction of the Tropidorhynchus to that island, where it is very +common. + +Here, then, we have two cases of perfect mimicry and two others of good +approximation, occurring between species of the same two genera of +birds; and in three of these cases the pairs that resemble each other +are found together in the same island, and to which they are peculiar. +In all these cases the Tropidorhynchus is rather larger than the Mimeta, +but the difference is not beyond the limits of variation in species, and +the two genera are somewhat alike in form and proportion. There are, no +doubt, some special enemies by which many small birds are attacked, but +which are afraid of the Tropidorhynchus (probably some of the hawks), +and thus it becomes advantageous for the weak Mimeta to resemble the +strong, pugnacious, noisy, and very abundant Tropidorhynchus. + +My friend, Mr. Osbert Salvin, has given me another interesting case of +bird mimicry. In the neighbourhood of Rio Janeiro is found an +insect-eating hawk (Harpagus diodon), and in the same district a +bird-eating hawk (Accipiter pileatus) which closely resembles it. Both +are of the same ashy tint beneath, with the thighs and under +wing-coverts reddish brown, so that when on the wing and seen from below +they are undistinguishable. The curious point, however, is that the +Accipiter has a much wider range than the Harpagus, and in the regions +where the insect-eating species is not found it no longer resembles it, +the under wing-coverts varying to white; thus indicating that the +red-brown colour is kept true by its being useful to the Accipiter to be +mistaken for the insect-eating species, which birds have learnt not to +be afraid of. + + +_Mimicry among Mammals._ + +Among the Mammalia the only case which may be true mimicry is that of +the insectivorous genus Cladobates, found in the Malay countries, +several species of which very closely resemble squirrels. The size is +about the same, the long bushy tail is carried in the same way, and the +colours are very similar. In this case the use of the resemblance must +be to enable the Cladobates to approach the insects or small birds on +which it feeds, under the disguise of the harmless fruit-eating +squirrel. + + +_Objections to Mr. Bates' Theory of Mimicry._ + +Having now completed our survey of the most prominent and remarkable +cases of mimicry that have yet been noticed, we must say something of +the objections that have been made to the theory of their production +given by Mr. Bates, and which we have endeavoured to illustrate and +enforce in the preceding pages. Three counter explanations have been +proposed. Professor Westwood admits the fact of the mimicry and its +probable use to the insect, but maintains that each species was created +a mimic for the purpose of the protection thus afforded it. Mr. Andrew +Murray, in his paper on the "Disguises of Nature," inclines to the +opinion that similar conditions of food and of surrounding circumstances +have acted in some unknown way to produce the resemblances; and when the +subject was discussed before the Entomological Society of London, a +third objection was added--that heredity or the reversion to ancestral +types of form and colouration, might have produced many of the cases of +mimicry. + +Against the special creation of mimicking species there are all the +objections and difficulties in the way of special creation in other +cases, with the addition of a few that are peculiar to it. The most +obvious is, that we have gradations of mimicry and of protective +resemblance--a fact which is strongly suggestive of a natural process +having been at work. Another very serious objection is, that as mimicry +has been shown to be useful only to those species and groups which are +rare and probably dying out, and would cease to have any effect should +the proportionate abundance of the two species be reversed, it follows +that on the special-creation theory the one species must have been +created plentiful, the other rare; and, notwithstanding the many causes +that continually tend to alter the proportions of species, these two +species must have always been specially maintained at their respective +proportions, or the very purpose for which they each received their +peculiar characteristics would have completely failed. A third +difficulty is, that although it is very easy to understand how mimicry +may be brought about by variation and the survival of the fittest, it +seems a very strange thing for a Creator to protect an animal by making +it imitate another, when the very assumption of a Creator implies his +power to create it so as to require no such circuitous protection. These +appear to be fatal objections to the application of the special-creation +theory to this particular case. + +The other two supposed explanations, which may be shortly expressed as +the theories of "similar conditions" and of "heredity," agree in making +mimicry, where it exists, an adventitious circumstance not necessarily +connected with the well-being of the mimicking species. But several of +the most striking and most constant facts which have been adduced, +directly contradict both those hypotheses. The law that mimicry is +confined to a few groups only is one of these, for "similar conditions" +must act more or less on all groups in a limited region, and "heredity" +must influence all groups related to each other in an equal degree. +Again, the general fact that those species which mimic others are rare, +while those which are imitated are abundant, is in no way explained by +either of these theories, any more than is the frequent occurrence of +some palpable mode of protection in the imitated species. "Reversion to +an ancestral type" no way explains why the imitator and the imitated +always inhabit the very same district, whereas allied forms of every +degree of nearness and remoteness generally inhabit different countries, +and often different quarters of the globe; and neither it, nor "similar +conditions," will account for the likeness between species of distinct +groups being superficial only--a disguise, not a true resemblance; for +the imitation of bark, of leaves, of sticks, of dung; for the +resemblance between species in different orders, and even different +classes and sub-kingdoms; and finally, for the graduated series of the +phenomena, beginning with a general harmony and adaptation of tint in +autumn and winter moths and in arctic and desert animals, and ending +with those complete cases of detailed mimicry which not only deceive +predacious animals, but puzzle the most experienced insect collectors +and the most learned entomologists. + + +_Mimicry by Female Insects only._ + +But there is yet another series of phenomena connected with this +subject, which considerably strengthens the view here adopted, while it +seems quite incompatible with either of the other hypotheses; namely, +the relation of protective colouring and mimicry to the sexual +differences of animals. It will be clear to every one that if two +animals, which as regards "external conditions" and "hereditary +descent," are exactly alike, yet differ remarkably in colouration, one +resembling a protected species and the other not, the resemblance that +exists in one only can hardly be imputed to the influence of external +conditions or as the effect of heredity. And if, further, it can be +proved that the one requires protection more than the other, and that in +several cases it is that one which mimics the protected species, while +the one that least requires protection never does so, it will afford +very strong corroborative evidence that there is a real connexion +between the necessity for protection and the phenomenon of mimicry. Now +the sexes of insects offer us a test of the nature here indicated, and +appear to furnish one of the most conclusive arguments in favour of the +theory that the phenomena termed "mimicry" are produced by natural +selection. + +The comparative importance of the sexes varies much in different classes +of animals. In the higher vertebrates, where the number of young +produced at a birth is small and the same individuals breed many years +in succession, the preservation of both sexes is almost equally +important. In all the numerous cases in which the male protects the +female and her offspring, or helps to supply them with food, his +importance in the economy of nature is proportionately increased, +though it is never perhaps quite equal to that of the female. In +insects the case is very different; they pair but once in their lives, +and the prolonged existence of the male is in most cases quite +unnecessary for the continuance of the race. The female, however, must +continue to exist long enough to deposit her eggs in a place adapted for +the development and growth of the progeny. Hence there is a wide +difference in the need for protection in the two sexes; and we should, +therefore, expect to find that in some cases the special protection +given to the female was in the male less in amount or altogether +wanting. The facts entirely confirm this expectation. In the spectre +insects (Phasmidae) it is often the females alone that so strikingly +resemble leaves, while the males show only a rude approximation. The +male Diadema misippus is a very handsome and conspicuous butterfly, +without a sign of protective or imitative colouring, while the female is +entirely unlike her partner, and is one of the most wonderful cases of +mimicry on record, resembling most accurately the common Danais +chrysippus, in whose company it is often found. So in several species of +South American Pieris, the males are white and black, of a similar type +of colouring to our own "cabbage" butterflies, while the females are +rich yellow and buff, spotted and marked so as exactly to resemble +species of Heliconidae with which they associate in the forest. In the +Malay archipelago is found a Diadema which had always been considered a +male insect on account of its glossy metallic-blue tints, while its +companion of sober brown was looked upon as the female. I discovered, +however, that the reverse is the case, and that the rich and glossy +colours of the female are imitative and protective, since they cause her +exactly to resemble the common Euploea midamus of the same regions, a +species which has been already mentioned in this essay as mimicked by +another butterfly, Papilio paradoxa. I have since named this interesting +species Diadema anomala (see the Transactions of the Entomological +Society, 1869, p. 285). In this case, and in that of Diadema misippus, +there is no difference in the habits of the two sexes, which fly in +similar localities; so that the influence of "external conditions" +cannot be invoked here as it has been in the case of the South American +Pieris pyrrha and allies, where the white males frequent open sunny +places, while the Heliconia-like females haunt the shades of the forest. + +We may impute to the same general cause (the greater need of protection +for the female, owing to her weaker flight, greater exposure to attack, +and supreme importance)--the fact of the colours of female insects being +so very generally duller and less conspicuous than those of the other +sex. And that it is chiefly due to this cause rather than to what Mr. +Darwin terms "sexual selection" appears to be shown by the otherwise +inexplicable fact, that in the groups which have a protection of any +kind independent of concealment, sexual differences of colour are either +quite wanting or slightly developed. The Heliconidae and Danaidae, +protected by a disagreeable flavour, have the females as bright and +conspicuous as the males, and very rarely differing at all from them. +The stinging Hymenoptera have the two sexes equally well coloured. The +Carabidae, the Coccinellidae, Chrysomelidae, and the Telephori have both +sexes equally conspicuous, and seldom differing in colours. The +brilliant Curculios, which are protected by their hardness, are +brilliant in both sexes. Lastly, the glittering Cetoniadae and +Buprestidae, which seem to be protected by their hard and polished coats, +their rapid motions, and peculiar habits, present few sexual differences +of colour, while sexual selection has often manifested itself by +structural differences, such as horns, spines, or other processes. + + +_Cause of the dull Colours of Female Birds._ + +The same law manifests itself in Birds. The female while sitting on her +eggs requires protection by concealment to a much greater extent than +the male; and we accordingly find that in a large majority of the cases +in which the male birds are distinguished by unusual brilliancy of +plumage, the females are much more obscure, and often remarkably +plain-coloured. The exceptions are such as eminently to prove the rule, +for in most cases we can see a very good reason for them. In particular, +there are a few instances among wading and gallinaceous birds in which +the female has decidedly more brilliant colours than the male; but it is +a most curious and interesting fact that in most if not all these cases +the males sit upon the eggs; so that this exception to the usual rule +almost demonstrates that it is because the process of incubation is at +once very important and very dangerous, that the protection of obscure +colouring is developed. The most striking example is that of the gray +phalarope (Phalaropus fulicarius). When in winter plumage, the sexes of +this bird are alike in colouration, but in summer the female is much the +most conspicuous, having a black head, dark wings, and reddish-brown +back, while the male is nearly uniform brown, with dusky spots. Mr. +Gould in his "Birds of Great Britain" figures the two sexes in both +winter and summer plumage, and remarks on the strange peculiarity of the +usual colours of the two sexes being reversed, and also on the still +more curious fact that the "male alone sits on the eggs," which are +deposited on the bare ground. In another British bird, the dotterell, +the female is also larger and more brightly-coloured than the male; and +it seems to be proved that the males assist in incubation even if they +do not perform it entirely, for Mr. Gould tells us, "that they have been +shot with the breast bare of feathers, caused by sitting on the eggs." +The small quail-like birds forming the genus Turnix have also generally +large and bright-coloured females, and we are told by Mr. Jerdon in his +"Birds of India" that "the natives report that during the breeding +season the females desert their eggs and associate in flocks while the +males are employed in hatching the eggs." It is also an ascertained +fact, that the females are more bold and pugnacious than the males. A +further confirmation of this view is to be found in the fact (not +hitherto noticed) that in a large majority of the cases in which bright +colours exist in both sexes incubation takes place in a dark hole or in +a dome-shaped nest. Female kingfishers are often equally brilliant with +the male, and they build in holes in banks. Bee-eaters, trogons, +motmots, and toucans, all build in holes, and in none is there any +difference in the sexes, although they are, without exception, showy +birds. Parrots build in holes in trees, and in the majority of cases +they present no marked sexual difference tending to concealment of the +female. Woodpeckers are in the same category, since though the sexes +often differ in colour, the female is not generally less conspicuous +than the male. Wagtails and titmice build concealed nests, and the +females are nearly as gay as their mates. The female of the pretty +Australian bird Pardalotus punctatus, is very conspicuously spotted on +the upper surface, and it builds in a hole in the ground. The +gay-coloured hang-nests (Icterinae) and the equally brilliant tanagers +may be well contrasted; for the former, concealed in their covered +nests, present little or no sexual difference of colour--while the +open-nested tanagers have the females dull-coloured and sometimes with +almost protective tints. No doubt there are many individual exceptions +to the rule here indicated, because many and various causes have +combined to determine both the colouration and the habits of birds. +These have no doubt acted and re-acted on each other; and when +conditions have changed one of these characters may often have become +modified, while the other, though useless, may continue by hereditary +descent an apparent exception to what otherwise seems a very general +rule. The facts presented by the sexual differences of colour in birds +and their mode of nesting, are on the whole in perfect harmony with that +law of protective adaptation of colour and form, which appears to have +checked to some extent the powerful action of sexual selection, and to +have materially influenced the colouring of female birds, as it has +undoubtedly done that of female insects. + + +_Use of the gaudy Colours of many Caterpillars._ + +Since this essay was first published a very curious difficulty has been +cleared up by the application of the general principle of protective +colouring. Great numbers of caterpillars are so brilliantly marked and +coloured as to be very conspicuous even at a considerable distance, and +it has been noticed that such caterpillars seldom hide themselves. Other +species, however, are green or brown, closely resembling the colours of +the substances on which they feed, while others again imitate sticks, +and stretch themselves out motionless from a twig so as to look like one +of its branches. Now, as caterpillars form so large a part of the food +of birds, it was not easy to understand why any of them should have such +bright colours and markings as to make them specially visible. Mr. +Darwin had put the case to me as a difficulty from another point of +view, for he had arrived at the conclusion that brilliant colouration in +the animal kingdom is mainly due to sexual selection, and this could not +have acted in the case of sexless larvae. Applying here the analogy of +other insects, I reasoned, that since some caterpillars were evidently +protected by their imitative colouring, and others by their spiny or +hairy bodies, the bright colours of the rest must also be in some way +useful to them. I further thought that as some butterflies and moths +were greedily eaten by birds while others were distasteful to them, and +these latter were mostly of conspicuous colours, so probably these +brilliantly coloured caterpillars were distasteful, and therefore never +eaten by birds. Distastefulness alone would however be of little service +to caterpillars, because their soft and juicy bodies are so delicate, +that if seized and afterwards rejected by a bird they would almost +certainly be killed. Some constant and easily perceived signal was +therefore necessary to serve as a warning to birds never to touch these +uneatable kinds, and a very gaudy and conspicuous colouring with the +habit of fully exposing themselves to view becomes such a signal, being +in strong contrast with the green or brown tints and retiring habits of +the eatable kinds. The subject was brought by me before the +Entomological Society (see Proceedings, March 4th, 1867), in order that +those members having opportunities for making observations might do so +in the following summer; and I also wrote a letter to the _Field_ +newspaper, begging that some of its readers would co-operate in making +observations on what insects were rejected by birds, at the same time +fully explaining the great interest and scientific importance of the +problem. It is a curious example of how few of the country readers of +that paper are at all interested in questions of simple natural history, +that I only obtained one answer from a gentleman in Cumberland, who gave +me some interesting observations on the general dislike and abhorrence +of all birds to the "Gooseberry Caterpillar," probably that of the +Magpie-moth (Abraxas grossulariata). Neither young pheasants, +partridges, nor wild-ducks could be induced to eat it, sparrows and +finches never touched it, and all birds to whom he offered it rejected +it with evident dread and abhorrence. It will be seen that these +observations are confirmed by those of two members of the Entomological +Society to whom we are indebted for more detailed information. + +In March, 1869, Mr. J. Jenner Weir communicated a valuable series of +observations made during many years, but more especially in the two +preceding summers, in his aviary, containing the following birds of more +or less insectivorous habits:--Robin, Yellow-Hammer, Reed-bunting, +Bullfinch, Chaffinch, Crossbill, Thrush, Tree-Pipit, Siskin, and +Redpoll. He found that hairy caterpillars were uniformly rejected; five +distinct species were quite unnoticed by all his birds, and were allowed +to crawl about the aviary for days with impunity. The spiny caterpillars +of the Tortoiseshell and Peacock butterflies were equally rejected; but +in both these cases Mr. Weir thinks it is the taste, not the hairs or +spines, that are disagreeable, because some very young caterpillars of a +hairy species were rejected although no hairs were developed, and the +smooth pupae of the above-named butterflies were refused as persistently +as the spined larvae. In these cases, then, both hairs and spines would +seem to be mere signs of uneatableness. + +His next experiments were with those smooth gaily-coloured caterpillars +which never conceal themselves, but on the contrary appear to court +observation. Such are those of the Magpie moth (Abraxas grossulariata), +whose caterpillar is conspicuously white and black spotted--the Diloba +coeruleocephala, whose larvae is pale yellow with a broad blue or green +lateral band--the Cucullia verbasci, whose larvae is greenish white with +yellow bands and black spots, and Anthrocera filipendulae (the six spot +Burnet moth), whose caterpillar is yellow with black spots. These were +given to the birds at various times, sometimes mixed with other kinds of +larvae which were greedily eaten, but they were in every case rejected +apparently unnoticed, and were left to crawl about till they died. + +The next set of observations were on the dull-coloured and protected +larvae, and the results of numerous experiments are thus summarised by +Mr. Weir. "All caterpillars whose habits are nocturnal, which are dull +coloured, with fleshy bodies and smooth skins, are eaten with the +greatest avidity. Every species of green caterpillar is also much +relished. All Geometrae, whose larvae resemble twigs as they stand out +from the plant on their anal prolegs, are invariably eaten." + +At the same meeting Mr. A. G. Butler, of the British Museum, +communicated the results of his observations with lizards, frogs, and +spiders, which strikingly corroborate those of Mr. Weir. Three green +lizards (Lacerta viridis) which he kept for several years, were very +voracious, eating all kinds of food, from a lemon cheesecake to a +spider, and devouring flies, caterpillars, and humble bees; yet there +were some caterpillars and moths which they would seize only to drop +immediately. Among these the principal were the caterpillar of the +Magpie moth (Abraxas grossulariata) and the perfect six spot Burnet moth +(Anthrocera filipendulae). These would be first seized but invariably +dropped in disgust, and afterwards left unmolested. Subsequently frogs +were kept and fed with caterpillars from the garden, but two of +these--that of the before-mentioned Magpie moth, and that of the V. moth +(Halia wavaria), which is green with conspicuous white or yellow stripes +and black spots--were constantly rejected. When these species were first +offered, the frogs sprang at them eagerly and licked them into their +mouths; no sooner, however, had they done so than they seemed to be +aware of the mistake that they had made, and sat with gaping mouths, +rolling their tongues about until they had got quit of the nauseous +morsels. + +With spiders the same thing occurred. These two caterpillars were +repeatedly put into the webs both of the geometrical and hunting spiders +(Epeira diadema and Lycosa sp.), but in the former case they were cut +out and allowed to drop; in the latter, after disappearing in the jaws +of their captor down his dark silken funnel, they invariably reappeared, +either from below or else taking long strides up the funnel again. Mr. +Butler has observed lizards fight with and finally devour humble bees, +and a frog sitting on a bed of stone-crop leap up and catch the bees +which flew over his head, and swallow them, in utter disregard of their +stings. It is evident, therefore, that the possession of a disagreeable +taste or odour is a more effectual protection to certain conspicuous +caterpillars and moths, than would be even the possession of a sting. + +The observations of these two gentlemen supply a very remarkable +confirmation of the hypothetical solution of the difficulty which I had +given two years before. And as it is generally acknowledged that the +best test of the truth and completeness of a theory is the power which +it gives us of prevision, we may I think fairly claim this as a case in +which the power of prevision has been successfully exerted, and +therefore as furnishing a very powerful argument in favour of the truth +of the theory of Natural Selection. + + +_Summary._ + +I have now completed a brief, and necessarily very imperfect, survey of +the various ways in which the external form and colouring of animals is +adapted to be useful to them, either by concealing them from their +enemies or from the creatures they prey upon. It has, I hope, been shown +that the subject is one of much interest, both as regard a true +comprehension of the place each animal fills in the economy of nature, +and the means by which it is enabled to maintain that place; and also as +teaching us how important a part is played by the minutest details in +the structure of animals, and how complicated and delicate is the +equilibrium of the organic world. + +My exposition of the subject having been necessarily somewhat lengthy +and full of details, it will be as well to recapitulate its main points. + +There is a general harmony in nature between the colours of an animal +and those of its habitation. Arctic animals are white, desert animals +are sand-coloured; dwellers among leaves and grass are green; nocturnal +animals are dusky. These colours are not universal, but are very +general, and are seldom reversed. Going on a little further, we find +birds, reptiles, and insects, so tinted and mottled as exactly to match +the rock, or bark, or leaf, or flower, they are accustomed to rest +upon,--and thereby effectually concealed. Another step in advance, and +we have insects which are formed as well as coloured so as exactly to +resemble particular leaves, or sticks, or mossy twigs, or flowers; and +in these cases very peculiar habits and instincts come into play to aid +in the deception and render the concealment more complete. We now enter +upon a new phase of the phenomena, and come to creatures whose colours +neither conceal them nor make them like vegetable or mineral substances; +on the contrary, they are conspicuous enough, but they completely +resemble some other creature of a quite different group, while they +differ much in outward appearance from those with which all essential +parts of their organization show them to be really closely allied. They +appear like actors or masqueraders dressed up and painted for amusement, +or like swindlers endeavouring to pass themselves off for well-known and +respectable members of society. What is the meaning of this strange +travestie? Does Nature descend to imposture or masquerade? We answer, +she does not. Her principles are too severe. There is a use in every +detail of her handiwork. The resemblance of one animal to another is of +exactly the same essential nature as the resemblance to a leaf, or to +bark, or to desert sand, and answers exactly the same purpose. In the +one case the enemy will not attack the leaf or the bark, and so the +disguise is a safeguard; in the other case it is found that for various +reasons the creature resembled is passed over, and not attacked by the +usual enemies of its order, and thus the creature that resembles it has +an equally effectual safeguard. We are plainly shown that the disguise +is of the same nature in the two cases, by the occurrence in the same +group of one species resembling a vegetable substance, while another +resembles a living animal of another group; and we know that the +creatures resembled, possess an immunity from attack, by their being +always very abundant, by their being conspicuous and not concealing +themselves, and by their having generally no visible means of escape +from their enemies; while, at the same time, the particular quality that +makes them disliked is often very clear, such as a nasty taste or an +indigestible hardness. Further examination reveals the fact that, in +several cases of both kinds of disguise, it is the female only that is +thus disguised; and as it can be shown that the female needs protection +much more than the male, and that her preservation for a much longer +period is absolutely necessary for the continuance of the race, we have +an additional indication that the resemblance is in all cases +subservient to a great purpose--the preservation of the species. + +In endeavouring to explain these phenomena as having been brought about +by variation and natural selection, we start with the fact that white +varieties frequently occur, and when protected from enemies show no +incapacity for continued existence and increase. We know, further, that +varieties of many other tints occasionally occur; and as "the survival +of the fittest" must inevitably weed out those whose colours are +prejudicial and preserve those whose colours are a safeguard, we require +no other mode of accounting for the protective tints of arctic and +desert animals. But this being granted, there is such a perfectly +continuous and graduated series of examples of every kind of protective +imitation, up to the most wonderful cases of what is termed "mimicry," +that we can find no place at which to draw the line, and say,--so far +variation and natural selection will account for the phenomena, but for +all the rest we require a more potent cause. The counter theories that +have been proposed, that of the "special creation" of each imitative +form, that of the action of "similar conditions of existence" for some +of the cases, and of the laws of "hereditary descent and the reversion +to ancestral forms" for others,--have all been shown to be beset with +difficulties, and the two latter to be directly contradicted by some of +the most constant and most remarkable of the facts to be accounted for. + + +_General deductions as to Colour in Nature._ + +The important part that "protective resemblance" has played in +determining the colours and markings of many groups of animals, will +enable us to understand the meaning of one of the most striking facts in +nature, the uniformity in the colours of the vegetable as compared with +the wonderful diversity of the animal world. There appears no good +reason why trees and shrubs should not have been adorned with as many +varied hues and as strikingly designed patterns as birds and +butterflies, since the gay colours of flowers show that there is no +incapacity in vegetable tissues to exhibit them. But even flowers +themselves present us with none of those wonderful designs, those +complicated arrangements of stripes and dots and patches of colour, +that harmonious blending of hues in lines and bands and shaded spots, +which are so general a feature in insects. It is the opinion of Mr. +Darwin that we owe much of the beauty of flowers to the necessity of +attracting insects to aid in their fertilisation, and that much of the +development of colour in the animal world is due to "sexual selection," +colour being universally attractive, and thus leading to its propagation +and increase; but while fully admitting this, it will be evident from +the facts and arguments here brought forward, that very much of the +_variety_ both of colour and markings among animals is due to the +supreme importance of concealment, and thus the various tints of +minerals and vegetables have been directly reproduced in the animal +kingdom, and again and again modified as more special protection became +necessary. We shall thus have two causes for the development of colour +in the animal world, and shall be better enabled to understand how, by +their combined and separate action, the immense variety we now behold +has been produced. Both causes, however, will come under the general law +of "Utility," the advocacy of which, in its broadest sense, we owe +almost entirely to Mr. Darwin. A more accurate knowledge of the varied +phenomena connected with this subject may not improbably give us some +information both as to the senses and the mental faculties of the lower +animals. For it is evident that if colours which please us also attract +them, and if the various disguises which have been here enumerated are +equally deceptive to them as to ourselves, then both their powers of +vision and their faculties of perception and emotion, must be +essentially of the same nature as our own--a fact of high philosophical +importance in the study of our own nature and our true relations to the +lower animals. + + +_Conclusion._ + +Although such a variety of interesting facts have been already +accumulated, the subject we have been discussing is one of which +comparatively little is really known. The natural history of the tropics +has never yet been studied on the spot with a full appreciation of "what +to observe" in this matter. The varied ways in which the colouring and +form of animals serve for their protection, their strange disguises as +vegetable or mineral substances, their wonderful mimicry of other +beings, offer an almost unworked and inexhaustible field of discovery +for the zoologist, and will assuredly throw much light on the laws and +conditions which have resulted in the wonderful variety of colour, +shade, and marking which constitutes one of the most pleasing +characteristics of the animal world, but the immediate causes of which +it has hitherto been most difficult to explain. + +If I have succeeded in showing that in this wide and picturesque domain +of nature, results which have hitherto been supposed to depend either +upon those incalculable combinations of laws which we term chance or +upon the direct volition of the Creator, are really due to the action +of comparatively well-known and simple causes, I shall have attained my +present purpose, which has been to extend the interest so generally felt +in the more striking facts of natural history to a large class of +curious but much neglected details; and to further, in however slight a +degree, our knowledge of the subjection of the phenomena of life to the +"Reign of Law." + + + + +IV. + +THE MALAYAN PAPILIONIDAE OR SWALLOW-TAILED BUTTERFLIES, AS ILLUSTRATIVE +OF THE THEORY OF NATURAL SELECTION. + + +_Special Value of the Diurnal Lepidoptera for enquiries of this nature._ + +When the naturalist studies the habits, the structure, or the affinities +of animals, it matters little to which group he especially devotes +himself; all alike offer him endless materials for observation and +research. But, for the purpose of investigating the phenomena of +geographical distribution and of local, sexual, or general variation, +the several groups differ greatly in their value and importance. Some +have too limited a range, others are not sufficiently varied in specific +forms, while, what is of most importance, many groups have not received +that amount of attention over the whole region they inhabit, which could +furnish materials sufficiently approaching to completeness to enable us +to arrive at any accurate conclusions as to the phenomena they present +as a whole. It is in those groups which are, and have long been, +favourites with collectors, that the student of distribution and +variation will find his materials the most satisfactory, from their +comparative completeness. + +Pre-eminent among such groups are the diurnal Lepidoptera or +Butterflies, whose extreme beauty and endless diversity have led to +their having been assiduously collected in all parts of the world, and +to the numerous species and varieties having been figured in a series of +magnificent works, from those of Cramer, the contemporary of Linnaeus, +down to the inimitable productions of our own Hewitson.[G] But, besides +their abundance, their universal distribution, and the great attention +that has been paid to them, these insects have other qualities that +especially adapt them to elucidate the branches of inquiry already +alluded to. These are, the immense development and peculiar structure of +the wings, which not only vary in form more than those of any other +insects, but offer on both surfaces an endless variety of pattern, +colouring, and texture. The scales, with which they are more or less +completely covered, imitate the rich hues and delicate surfaces of satin +or of velvet, glitter with metallic lustre, or glow with the changeable +tints of the opal. This delicately painted surface acts as a register of +the minutest differences of organization--a shade of colour, an +additional streak or spot, a slight modification of outline continually +recurring with the greatest regularity and fixity, while the body and +all its other members exhibit no appreciable change. The wings of +Butterflies, as Mr. Bates has well put it, "serve as a tablet on which +Nature writes the story of the modifications of species;" they enable us +to perceive changes that would otherwise be uncertain and difficult of +observation, and exhibit to us on an enlarged scale the effects of the +climatal and other physical conditions which influence more or less +profoundly the organization of every living thing. + + +--------------------------------------------------------------+ + | [G] W. C. Hewitson, Esq., of Oatlands, Walton-on-Thames, | + | author of "Exotic Butterflies" and several other works, | + | illustrated by exquisite coloured figures drawn by himself; | + | and owner of the finest collection of Butterflies in the | + | world. | + +--------------------------------------------------------------+ + +A proof that this greater sensibility to modifying causes is not +imaginary may, I think, be drawn from the consideration, that while the +Lepidoptera as a whole are of all insects the least essentially varied +in form, structure, or habits, yet in the number of their specific forms +they are not much inferior to those orders which range over a much wider +field of nature, and exhibit more deeply seated structural +modifications. The Lepidoptera are all vegetable-feeders in their +larva-state, and suckers of juices or other liquids in their perfect +form. In their most widely separated groups they differ but little from +a common type, and offer comparatively unimportant modifications of +structure or of habits. The Coleoptera, the Diptera, or the Hymenoptera, +on the other hand, present far greater and more essential variations. In +either of these orders we have both vegetable and animal-feeders, +aquatic, and terrestrial, and parasitic groups. Whole families are +devoted to special departments in the economy of nature. Seeds, fruits, +bones, carcases, excrement, bark, have each their special and dependent +insect tribes from among them; whereas the Lepidoptera are, with but few +exceptions, confined to the one function of devouring the foliage of +living vegetation. We might therefore anticipate that their +species--population would be only equal to that of sections of the other +orders having a similar uniform mode of existence; and the fact that +their numbers are at all comparable with those of entire orders, so much +more varied in organization and habits, is, I think, a proof that they +are in general highly susceptible of specific modification. + + +_Question of the rank of the Papilionidae._ + +The Papilionidae are a family of diurnal Lepidoptera which have hitherto, +by almost universal consent, held the first rank in the order; and +though this position has recently been denied them, I cannot altogether +acquiesce in the reasoning by which it has been proposed to degrade them +to a lower rank. In Mr. Bates's most excellent paper on the Heliconidae, +(published in the Transactions of the Linnaean Society, vol. xxiii., p. +495) he claims for that family the highest position, chiefly because of +the imperfect structure of the fore legs, which is there carried to an +extreme degree of abortion, and thus removes them further than any other +family from the Hesperidae and Heterocera, which all have perfect legs. +Now it is a question whether any amount of difference which is exhibited +merely in the imperfection or abortion of certain organs, can establish +in the group exhibiting it a claim to a high grade of organization, +still less can this be allowed when another group along with perfection +of structure in the same organs, exhibits modifications peculiar to it, +together with the possession of an organ which in the remainder of the +order is altogether wanting. This is, however, the position of the +Papilionidae. The perfect insects possess two characters quite peculiar +to them. Mr. Edward Doubleday, in his "Genera of Diurnal Lepidoptera," +says, "The Papilionidae may be known by the apparently four-branched +median nervule and the spur on the anterior tibiae, characters found in +no other family." The four-branched median nervule is a character so +constant, so peculiar, and so well marked, as to enable a person to +tell, at a glance at the wings only of a butterfly, whether it does or +does not belong to this family; and I am not aware that any other group +of butterflies, at all comparable to this in extent and modifications of +form, possesses a character in its neuration to which the same degree of +certainty can be attached. The spur on the anterior tibiae is also found +in some of the Hesperidae, and is therefore supposed to show a direct +affinity between the two groups: but I do not imagine it can +counterbalance the differences in neuration and in every other part of +their organization. The most characteristic feature of the Papilionidae, +however, and that on which I think insufficient stress has been laid, is +undoubtedly the peculiar structure of the larvae. These all possess an +extraordinary organ situated on the neck, the well-known Y-shaped +tentacle, which is entirely concealed in a state of repose, but which is +capable of being suddenly thrown out by the insect when alarmed. When we +consider this singular apparatus, which in some species is nearly half +an inch long, the arrangement of muscles for its protrusion and +retraction, its perfect concealment during repose, its blood-red colour, +and the suddenness with which it can be thrown out, we must, I think, be +led to the conclusion that it serves as a protection to the larva, by +startling and frightening away some enemy when about to seize it, and is +thus one of the causes which has led to the wide extension and +maintained the permanence of this now dominant group. Those who believe +that such peculiar structures can only have arisen by very minute +successive variations, each one advantageous to its possessor, must see, +in the possession of such an organ by one group, and its complete +absence in every other, a proof of a very ancient origin and of very +long-continued modification. And such a positive structural addition to +the organization of the family, subserving an important function, seems +to me alone sufficient to warrant us in considering the Papilionidae as +the most highly developed portion of the whole order, and thus in +retaining it in the position which the size, strength, beauty, and +general structure of the perfect insects have been generally thought to +deserve. + +In Mr. Trimen's paper on "Mimetic Analogies among African Butterflies," +in the Transactions of the Linnaean Society, for 1868, he has argued +strongly in favour of Mr. Bates' views as to the higher position of the +Danaidae and the lower grade of the Papilionidae, and has adduced, among +other facts, the undoubted resemblance of the pupa of Parnassius, a +genus of Papilionidae, to that of some Hesperidae and moths. I admit, +therefore, that he has proved the Papilionidae to have retained several +characters of the nocturnal Lepidoptera which the Danaidae have lost, but +I deny that they are therefore to be considered lower in the scale of +organization. Other characters may be pointed out which indicate that +they are farther removed from the moths even than the Danaidae. The club +of the antennae is the most prominent and most constant feature by which +butterflies may be distinguished from moths, and of all butterflies the +Papilionidae have the most beautiful and most perfectly developed clubbed +antennae. Again, butterflies and moths are broadly characterised by their +diurnal and nocturnal habits respectively, and the Papilionidae, with +their close allies the Pieridae, are the most pre-eminently diurnal of +butterflies, most of them lovers of sunshine, and not presenting a +single crepuscular species. The great group of the Nymphalidae, on the +other hand (in which Mr. Bates includes the Danaidae and Heliconidae as +sub-families), contains an entire sub-family (Brassolidae) and a number +of genera, such as Thaumantis, Zeuxidia, Pavonia, &c., of crepuscular +habits, while a large proportion of the Satyridae and many of the +Danaidae are shade-loving butterflies. This question, of what is to be +considered the highest type of any group of organisms, is one of such +general interest to naturalists that it will be well to consider it a +little further, by a comparison of the Lepidoptera with some groups of +the higher animals. + +Mr. Trimen's argument, that the lepidopterous type, like that of birds, +being pre-eminently aerial, "therefore a diminution of the ambulatory +organs, instead of being a sign of inferiority, may very possibly +indicate a higher, because a more thoroughly aerial form," is certainly +unsound, for it would imply that the most aerial of birds (the swift and +the frigate-birds, for example) are the highest in the scale of +bird-organization, and the more so on account of their feet being very +ill adapted for walking. But no ornithologist has ever so classed them, +and the claim to the highest rank among birds is only disputed between +three groups, all very far removed from these. They are--1st. The +Falcons, on account of their general perfection, their rapid flight, +their piercing vision, their perfect feet armed with retractile claws, +the beauty of their forms, and the ease and rapidity of their motions; +2nd. The Parrots, whose feet, though ill-fitted for walking, are perfect +as prehensile organs, and which possess large brains with great +intelligence, though but moderate powers of flight; and, 3rd. The +Thrushes or Crows, as typical of the perching birds, on account of the +well-balanced development of their whole structure, in which no organ +or function has attained an undue prominence. + +Turning now to the Mammalia, it might be argued that as they are +pre-eminently the terrestrial type of vertebrates, to walk and run well +is essential to the typical perfection of the group; but this would give +the superiority to the horse, the deer, or the hunting leopard, instead +of to the Quadrumana. We seem here to have quite a case in point, for +one group of Quadrumana, the Lemurs, is undoubtedly nearer to the low +Insectivora and Marsupials than the Carnivora or the Ungulata, as shown +among other characters by the Opossums possessing a hand with perfect +opposable thumb, closely resembling that of some of the Lemurs; and by +the curious Galeopithecus, which is sometimes classed as a Lemur, and +sometimes with the Insectivora. Again, the implacental mammals, +including the Ornithodelphia and the Marsupials, are admitted to be +lower than the placental series. But one of the distinguishing +characters of the Marsupials is that the young are born blind and +exceedingly imperfect, and it might therefore be argued that those +orders in which the young are born most perfect are the highest, because +farthest from the low Marsupial type. This would make the Ruminants and +Ungulata higher than the Quadrumana or the Carnivora. But the Mammalia +offer a still more remarkable illustration of the fallacy of this mode +of reasoning, for if there is one character more than another which is +essential and distinctive of the class, it is that from which it derives +its name, the possession of mammary glands and the power of suckling +the young. What more reasonable, apparently, than to argue that the +group in which this important function is most developed, that in which +the young are most dependent upon it, and for the longest period, must +be the highest in the Mammalian scale of organization? Yet this group is +the Marsupial, in which the young commence suckling in a foetal +condition, and continue to do so till they are fully developed, and are +therefore for a long time absolutely dependent on this mode of +nourishment. + +These examples, I think, demonstrate that we cannot settle the rank of a +group by a consideration of the degree in which certain characters +resemble or differ from those in what is admitted to be a lower group; +and they also show that the highest group of a class may be more closely +connected to one of the lowest, than some other groups which have +developed laterally and diverged farther from the parent type, but which +yet, owing to want of balance or too great specialization in their +structure, have never reached a high grade of organization. The +Quadrumana afford a very valuable illustration, because, owing to their +undoubted affinity with man, we feel certain that they are really higher +than any other order of Mammalia, while at the same time they are more +distinctly allied to the lowest groups than many others. The case of the +Papilionidae seems to me so exactly parallel to this, that, while I admit +all the proofs of affinity with the undoubtedly lower groups of +Hesperidae and moths, I yet maintain that, owing to the complete and +even development of every part of their organization, these insects best +represent the highest perfection to which the butterfly type has +attained, and deserve to be placed at its head in every system of +classification. + + +_Distribution of the Papilionidae._ + +The Papilionidae are pretty widely distributed over the earth, but are +especially abundant in the tropics, where they attain their maximum of +size and beauty, and the greatest variety of form and colouring. South +America, North India, and the Malay Islands are the regions where these +fine insects occur in the greatest profusion, and where they actually +become a not unimportant feature in the scenery. In the Malay Islands in +particular, the giant Ornithopterae may be frequently seen about the +borders of the cultivated and forest districts, their large size, +stately flight, and gorgeous colouring rendering them even more +conspicuous than the generality of birds. In the shady suburbs of the +town of Malacca two large and handsome Papilios (Memnon and Nephelus) +are not uncommon, flapping with irregular flight along the roadways, or, +in the early morning, expanding their wings to the invigorating rays of +the sun. In Amboyna and other towns of the Moluccas, the magnificent +Deiphobus and Severus, and occasionally even the azure-winged Ulysses, +frequent similar situations, fluttering about the orange-trees and +flower-beds, or sometimes even straying into the narrow bazaars or +covered markets of the city. In Java the golden-dusted Arjuna may often +be seen at damp places on the roadside in the mountain districts, in +company with Sarpedon, Bathycles, and Agamemnon, and less frequently the +beautiful swallow-tailed Antiphates. In the more luxuriant parts of +these islands one can hardly take a morning's walk in the neighbourhood +of a town or village without seeing three or four species of Papilio, +and often twice that number. No less than 130 species of the family are +now known to inhabit the Archipelago, and of these ninety-six were +collected by myself. Thirty species are found in Borneo, being the +largest number in any one island, twenty-three species having been +obtained by myself in the vicinity of Sarawak; Java has twenty-eight +species; Celebes twenty-four, and the Peninsula of Malacca, twenty-six +species. Further east the numbers decrease; Batchian producing +seventeen, and New Guinea only fifteen, though this number is certainly +too small, owing to our present imperfect knowledge of that great +island. + + +_Definition of the word Species._ + +In estimating these numbers I have had the usual difficulty to +encounter, of determining what to consider species and what varieties. +The Malayan region, consisting of a large number of islands of generally +great antiquity, possesses, compared to its actual area, a great number +of distinct forms, often indeed distinguished by very slight +characters, but in most cases so constant in large series of specimens, +and so easily separable from each other, that I know not on what +principle we can refuse to give them the name and rank of species. One +of the best and most orthodox definitions is that of Pritchard, the +great ethnologist, who says, that "_separate origin and distinctness of +race, evinced by a constant transmission of some characteristic +peculiarity of organization_," constitutes a species. Now leaving out +the question of "origin," which we cannot determine, and taking only the +proof of separate origin, "_the constant transmission of some +characteristic peculiarity of organization_," we have a definition which +will compel us to neglect altogether the _amount_ of difference between +any two forms, and to consider only whether the differences that present +themselves are _permanent_. The rule, therefore, I have endeavoured to +adopt is, that when the difference between two forms inhabiting separate +areas seems quite constant, when it can be defined in words, and when it +is not confined to a single peculiarity only, I have considered such +forms to be species. When, however, the individuals of each locality +vary among themselves, so as to cause the distinctions between the two +forms to become inconsiderable and indefinite, or where the differences, +though constant, are confined to one particular only, such as size, +tint, or a single point of difference in marking or in outline, I class +one of the forms as a variety of the other. + +I find as a general rule that the constancy of species is in an inverse +ratio to their range. Those which are confined to one or two islands are +generally very constant. When they extend to many islands, considerable +variability appears; and when they have an extensive range over a large +part of the Archipelago, the amount of unstable variation is very large. +These facts are explicable on Mr. Darwin's principles. When a species +exists over a wide area, it must have had, and probably still possesses, +great powers of dispersion. Under the different conditions of existence +in various portions of its area, different variations from the type +would be selected, and, were they completely isolated, would soon become +distinctly modified forms; but this process is checked by the dispersive +powers of the whole species, which leads to the more or less frequent +intermixture of the incipient varieties, which thus become irregular and +unstable. Where, however, a species has a limited range, it indicates +less active powers of dispersion, and the process of modification under +changed conditions is less interfered with. The species will therefore +exist under one or more permanent forms according as portions of it have +been isolated at a more or less remote period. + + +_Laws and Modes of Variation._ + +What is commonly called variation consists of several distinct phenomena +which have been too often confounded. I shall proceed to consider these +under the heads of--1st, simple variability; 2nd, polymorphism; 3rd, +local forms; 4th, co-existing varieties; 5th, races or subspecies; and +6th, true species. + +1. _Simple variability._--Under this head I include all those cases in +which the specific form is to some extent unstable. Throughout the whole +range of the species, and even in the progeny of individuals, there +occur continual and uncertain differences of form, analogous to that +variability which is so characteristic of domestic breeds. It is +impossible usefully to define any of these forms, because there are +indefinite gradations to each other form. Species which possess these +characteristics have always a wide range, and are more frequently the +inhabitants of continents than of islands, though such cases are always +exceptional, it being far more common for specific forms to be fixed +within very narrow limits of variation. The only good example of this +kind of variability which occurs among the Malayan Papilionidae is in +Papilio Severus, a species inhabiting all the islands of the Moluccas +and New Guinea, and exhibiting in each of them a greater amount of +individual difference than often serves to distinguish well-marked +species. Almost equally remarkable are the variations exhibited in most +of the species of Ornithoptera, which I have found in some cases to +extend even to the form of the wing and the arrangement of the nervures. +Closely allied, however, to these variable species are others which, +though differing slightly from them, are constant and confined to +limited areas. After satisfying oneself, by the examination of numerous +specimens captured in their native countries, that the one set of +individuals are variable and the others are not, it becomes evident that +by classing all alike as varieties of one species we shall be obscuring +an important fact in nature; and that the only way to exhibit that fact +in its true light is to treat the invariable local form as a distinct +species, even though it does not offer better distinguishing characters +than do the extreme forms of the variable species. Cases of this kind +are the Ornithoptera Priamus, which is confined to the islands of Ceram +and Amboyna, and is very constant in both sexes, while the allied +species inhabiting New Guinea and the Papuan Islands is exceedingly +variable; and in the island of Celebes is a species closely allied to +the variable P. Severus, but which, being exceedingly constant, I have +described as a distinct species under the name of Papilio Pertinax. + +2. _Polymorphism or dimorphism._--By this term I understand the +co-existence in the same locality of two or more distinct forms, not +connected by intermediate gradations, and all of which are occasionally +produced from common parents. These distinct forms generally occur in +the female sex only, and their offspring, instead of being hybrids, or +like the two parents, appear to reproduce all the distinct forms in +varying proportions. I believe it will be found that a considerable +number of what have been classed as _varieties_ are really cases of +polymorphism. Albinoism and melanism are of this character, as well as +most of those cases in which well-marked varieties occur in company with +the parent species, but without any intermediate forms. If these +distinct forms breed independently, and are never reproduced from a +common parent, they must be considered as separate species, contact +without intermixture being a good test of specific difference. On the +other hand, intercrossing without producing an intermediate race is a +test of dimorphism. I consider, therefore, that under any circumstances +the term "variety" is wrongly applied to such cases. + +The Malayan Papilionidae exhibit some very curious instances of +polymorphism, some of which have been recorded as varieties, others as +distinct species; and they all occur in the female sex. Papilio Memnon +is one of the most striking, as it exhibits the mixture of simple +variability, local and polymorphic forms, all hitherto classed under the +common title of varieties. The polymorphism is strikingly exhibited by +the females, one set of which resemble the males in form, with a +variable paler colouring; the others have a large spatulate tail to the +hinder wings and a distinct style of colouring, which causes them +closely to resemble P. Coon, a species having the two sexes alike and +inhabiting the same countries, but with which they have no direct +affinity. The tailless females exhibit simple variability, scarcely two +being found exactly alike even in the same locality. The males of the +island of Borneo exhibit constant differences of the under surface, and +may therefore be distinguished as a local form, while the continental +specimens, as a whole, offer such large and constant differences from +those of the islands, that I am inclined to separate them as a distinct +species, to which the name P. Androgeus (Cramer) may be applied. We +have here, therefore, distinct species, local forms, polymorphism, and +simple variability, which seem to me to be distinct phenomena, but which +have been hitherto all classed together as varieties. I may mention that +the fact of these distinct forms being one species is doubly proved. The +males, the tailed and tailless females, have all been bred from a single +group of the larvae, by Messrs. Payen and Bocarme, in Java, and I myself +captured, in Sumatra, a male P. Memnon, and a tailed female P. Achates, +under circumstances which led me to class them as the same species. + +Papilio Pammon offers a somewhat similar case. The female was described +by Linnaeus as P. Polytes, and was considered to be a distinct species +till Westermann bred the two from the same larvae (see Boisduval, +"Species General des Lepidopteres," p. 272). They were therefore classed +as sexes of one species by Mr. Edward Doubleday, in his "Genera of +Diurnal Lepidoptera," in 1846. Later, female specimens were received +from India closely resembling the male insect, and this was held to +overthrow the authority of M. Westermann's observation, and to +re-establish P. Polytes as a distinct species; and as such it +accordingly appears in the British Museum List of Papilionidae in 1856, +and in the Catalogue of the East India Museum in 1857. This discrepancy +is explained by the fact of P. Pammon having two females, one closely +resembling the male, while the other is totally different from it. A +long familiarity with this insect (which replaced by local forms or by +closely allied species, occurs in every island of the Archipelago) has +convinced me of the correctness of this statement; for in every place +where a male allied to P. Pammon is found, a female resembling P. +Polytes also occurs, and sometimes, though less frequently than on the +continent, another female closely resembling the male: while not only +has no male specimen of P. Polytes yet been discovered, but the female +(Polytes) has never yet been found in localities to which the male +(Pammon) does not extend. In this case, as in the last, distinct +species, local forms, and dimorphic specimens, have been confounded +under the common appellation of varieties. + +But, besides the true P. Polytes, there are several allied forms of +females to be considered, namely, P. Theseus (Cramer), P. Molanides (De +Haan), P. Elyros (G. R. Gray), and P. Romulus (Linnaeus). The dark female +figured by Cramer as P. Theseus seems to be the common and perhaps the +only form in Sumatra, whereas in Java, Borneo, and Timor, along with +males quite identical with those of Sumatra, occur females of the +Polytes form, although a single specimen of the true P. Theseus taken at +Lombock would seem to show that the two forms do occur together. In the +allied species found in the Philippine Islands (P. Alphenor, Cramer = P. +Ledebouria, Eschscholtz, the female of which is P. Elyros, G. R. Gray,) +forms corresponding to these extremes occur, along with a number of +intermediate varieties, as shown by a fine series in the British Museum. +We have here an indication of how dimorphism may be produced; for let +the extreme Philippine forms be better suited to their conditions of +existence than the intermediate connecting links, and the latter will +gradually die out, leaving two distinct forms of the same insect, each +adapted to some special conditions. As these conditions are sure to vary +in different districts, it will often happen, as in Sumatra and Java, +that the one form will predominate in the one island, the other in the +adjacent one. In the island of Borneo there seems to be a third form; +for P. Melanides (De Haan) evidently belongs to this group, and has all +the chief characteristics of P. Theseus, with a modified colouration of +the hind wings. I now come to an insect which, if I am correct, offers +one of the most interesting cases of variation yet adduced. Papilio +Romulus, a butterfly found over a large part of India and Ceylon, and +not uncommon in collections, has always been considered a true and +independent species, and no suspicions have been expressed regarding it. +But a male of this form does not, I believe, exist. I have examined the +fine series in the British Museum, in the East India Company's Museum, +in the Hope Museum at Oxford, in Mr. Hewitson's and several other +private collections, and can find nothing but females; and for this +common butterfly no male partner can be found except the equally common +P. Pammon, a species already provided with two wives, and yet to whom we +shall be forced, I believe, to assign a third. On carefully examining P. +Romulus, I find that in all essential characters--the form and texture +of the wings, the length of the antennae, the spotting of the head and +thorax, and even the peculiar tints and shades with which it is +ornamented--it corresponds exactly with the other females of the Pammon +group; and though, from the peculiar marking of the fore wings, it has +at first sight a very different aspect, yet a closer examination shows +that every one of its markings could be produced by slight and almost +imperceptible modifications of the various allied forms. I fully +believe, therefore, that I shall be correct in placing P. Romulus as a +third Indian form of the female P. Pammon, corresponding to P. +Melanides, the third form of the Malayan P. Theseus. I may mention here +that the females of this group have a superficial resemblance to the +Polydorus group of Papilios, as shown by P. Theseus having been +considered to be the female of P. Antiphus, and by P. Romulus being +arranged next to P. Hector. There is no close affinity between these two +groups of Papilio, and I am disposed to believe that we have here a case +of mimicry, brought about by the same causes which Mr. Bates has so well +explained in his account of the Heliconidae, and which has led to the +singular exuberance of polymorphic forms in this and allied groups of +the genus Papilio. I shall have to devote a section of my essay to the +consideration of this subject. + +The third example of polymorphism I have to bring forward is Papilio +Ormenus, which is closely allied to the well-known P. Erechtheus, of +Australia. The most common form of the female also resembles that of P. +Erechtheus; but a totally different-looking insect was found by myself +in the Aru Islands, and figured by Mr. Hewitson under the name of P. +Onesimus, which subsequent observation has convinced me is a second form +of the female of P. Ormenus. Comparison of this with Boisduval's +description of P. Amanga, a specimen of which from New Guinea is in the +Paris Museum, shows the latter to be a closely similar form; and two +other specimens were obtained by myself, one in the island of Goram and +the other in Waigiou, all evidently local modifications of the same +form. In each of these localities males and ordinary females of P. +Ormenus were also found. So far there is no evidence that these +light-coloured insects are not females of a distinct species, the males +of which have not been discovered. But two facts have convinced me this +is not the case. At Dorey, in New Guinea, where males and ordinary +females closely allied to P. Ormenus occur (but which seem to me worthy +of being separated as a distinct species), I found one of these +light-coloured females closely followed in her flight by three males, +exactly in the same manner as occurs (and, I believe, occurs only) with +the sexes of the same species. After watching them a considerable time, +I captured the whole of them, and became satisfied that I had discovered +the true relations of this anomalous form. The next year I had +corroborative proof of the correctness of this opinion by the discovery +in the island of Batchian of a new species allied to P. Ormenus, all the +females of which, either seen or captured by me, were of one form, and +much more closely resembling the abnormal light-coloured females of P. +Ormenus and P. Pandion than the ordinary specimens of that sex. Every +naturalist will, I think, agree that this is strongly confirmative of +the supposition that both forms of female are of one species; and when +we consider, further, that in four separate islands, in each of which I +resided for several months, the two forms of female were obtained and +only one form of male ever seen, and that about the same time, M. +Montrouzier in Woodlark Island, at the other extremity of New Guinea +(where he resided several years, and must have obtained all the large +Lepidoptera of the island), obtained females closely resembling mine, +which, in despair at finding no appropriate partners for them, he mates +with a widely different species--it becomes, I think, sufficiently +evident this is another case of polymorphism of the same nature as those +already pointed out in P. Pammon and P. Memnon. This species, however, +is not only dimorphic, but trimorphic; for, in the island of Waigiou, I +obtained a third female quite distinct from either of the others, and in +some degree intermediate between the ordinary female and the male. The +specimen is particularly interesting to those who believe, with Mr. +Darwin, that extreme difference of the sexes has been gradually produced +by what he terms sexual selection, since it may be supposed to exhibit +one of the intermediate steps in that process, which has been +accidentally preserved in company with its more favoured rivals, though +its extreme rarity (only one specimen having been seen to many hundreds +of the other form) would indicate that it may soon become extinct. + +The only other case of polymorphism in the genus Papilio, at all equal +in interest to those I have now brought forward, occurs in America; and +we have, fortunately, accurate information about it. Papilio Turnus is +common over almost the whole of temperate North America; and the female +resembles the male very closely. A totally different-looking insect both +in form and colour, Papilio Glaucus, inhabits the same region; and +though, down to the time when Boisduval published his "Species General," +no connexion was supposed to exist between the two species, it is now +well ascertained that P. Glaucus is a second female form of P. Turnus. +In the "Proceedings of the Entomological Society of Philadelphia," Jan., +1863, Mr. Walsh gives a very interesting account of the distribution of +this species. He tells us that in the New England States and in New York +all the females are yellow, while in Illinois and further south all are +black; in the intermediate region both black and yellow females occur in +varying proportions. Lat. 37 deg. is approximately the southern limit of the +yellow form, and 42 deg. the northern limit of the black form; and, to +render the proof complete, both black and yellow insects have been bred +from a single batch of eggs. He further states that, out of thousands +of specimens, he has never seen or heard of intermediate varieties +between these forms. In this interesting example we see the effects of +latitude in determining the proportions in which the individuals of each +form should exist. The conditions are _here_ favourable to the one form, +_there_ to the other; but we are by no means to suppose that these +conditions consist in climate alone. It is highly probable that the +existence of enemies, and of competing forms of life, may be the main +determining influences; and it is much to be wished that such a +competent observer as Mr. Walsh would endeavour to ascertain what are +the adverse causes which are most efficient in keeping down the numbers +of each of these contrasted forms. + +Dimorphism of this kind in the animal kingdom does not seem to have any +direct relations to the reproductive powers, as Mr. Darwin has shown to +be the case in plants, nor does it appear to be very general. One other +case only is known to me in another family of my eastern Lepidoptera, +the Pieridae; and but few occur in the Lepidoptera of other countries. +The spring and autumn broods of some European species differ very +remarkably; and this must be considered as a phenomenon of an analogous +though not of an identical nature, while the Araschnia prorsa, of +Central Europe, is a striking example of this alternate or seasonal +dimorphism. Among our nocturnal Lepidoptera, I am informed, many +analogous cases occur; and as the whole history of many of these has +been investigated by breeding successive generations from the egg, it is +to be hoped that some of our British Lepidopterists will give us a +connected account of all the abnormal phenomena which they present. +Among the Coleoptera Mr. Pascoe has pointed out the existence of two +forms of the male sex in seven species of the two genera Xenocerus and +Mecocerus belonging to the family Anthribidae, (Proc. Ent. Soc. Lond., +1862); and no less than six European Water-beetles, of the genus +Dytiscus, have females of two forms, the most common having the elytra +deeply sulcate, the rarer smooth as in the males. The three, and +sometimes four or more, forms under which many Hymenopterous insects +(especially Ants) occur, must be considered as a related phenomenon, +though here each form is specialized to a distinct function in the +economy of the species. Among the higher animals, albinoism and melanism +may, as I have already stated, be considered as analogous facts; and I +met with one case of a bird, a species of Lory (Eos fuscata), clearly +existing under two differently coloured forms, since I obtained both +sexes of each from a single flock, while no intermediate specimens have +yet been found. + +The fact of the two sexes of one species differing very considerably is +so common, that it attracted but little attention till Mr. Darwin showed +how it could in many cases be explained by the principle of sexual +selection. For instance, in most polygamous animals the males fight for +the possession of the females, and the victors, always becoming the +progenitors of the succeeding generation, impress upon their male +offspring their own superior size, strength, or unusually developed +offensive weapons. It is thus that we can account for the spurs and the +superior strength and size of the males in Gallinaceous birds, and also +for the large canine tusks in the males of fruit-eating Apes. So the +superior beauty of plumage and special adornments of the males of so +many birds can be explained by supposing (what there are many facts to +prove) that the females prefer the most beautiful and perfect-plumaged +males, and that thus, slight accidental variations of form and colour +have been accumulated, till they have produced the wonderful train of +the Peacock and the gorgeous plumage of the Bird of Paradise. Both these +causes have no doubt acted partially in insects, so many species +possessing horns and powerful jaws in the male sex only, and still more +frequently the males alone rejoicing in rich colours or sparkling +lustre. But there is here another cause which has led to sexual +differences, viz., a special adaptation of the sexes to diverse habits +or modes of life. This is well seen in female Butterflies (which are +generally weaker and of slower flight), often having colours better +adapted to concealment; and in certain South American species (Papilio +torquatus) the females, which inhabit the forests, resemble the AEneas +group of Papilios which abound in similar localities, while the males, +which frequent the sunny open river-banks, have a totally different +colouration. In these cases, therefore, natural selection seems to have +acted independently of sexual selection; and all such cases may be +considered as examples of the simplest dimorphism, since the offspring +never offer intermediate varieties between the parent forms. + +The phenomena of dimorphism and polymorphism may be well illustrated by +supposing that a blue-eyed, flaxen-haired Saxon man had two wives, one a +black-haired, red-skinned Indian squaw, the other a woolly-headed, +sooty-skinned negress--and that instead of the children being mulattoes +of brown or dusky tints, mingling the separate characteristics of their +parents in varying degrees, all the boys should be pure Saxon boys like +their father, while the girls should altogether resemble their mothers. +This would be thought a sufficiently wonderful fact; yet the phenomena +here brought forward as existing in the insect-world are still more +extraordinary; for each mother is capable not only of producing male +offspring like the father, and female like herself, but also of +producing other females exactly like her fellow-wife, and altogether +differing from herself. If an island could be stocked with a colony of +human beings having similar physiological idiosyncrasies with Papilio +Pammon or Papilio Ormenus, we should see white men living with yellow, +red, and black women, and their offspring always reproducing the same +types; so that at the end of many generations the men would remain pure +white, and the women of the same well-marked races as at the +commencement. + +The distinctive character therefore of dimorphism is this, that the +union of these distinct forms does not produce intermediate varieties, +but reproduces the distinct forms unchanged. In simple varieties, on the +other hand, as well as when distinct local forms or distinct species are +crossed, the offspring never resembles either parent exactly, but is +more or less intermediate between them. Dimorphism is thus seen to be a +specialized result of variation, by which new physiological phenomena +have been developed; the two should therefore, whenever possible, be +kept separate. + +3. _Local form, or variety._--This is the first step in the transition +from variety to species. It occurs in species of wide range, when groups +of individuals have become partially isolated in several points of its +area of distribution, in each of which a characteristic form has become +more or less completely segregated. Such forms are very common in all +parts of the world, and have often been classed by one author as +varieties, by another as species. I restrict the term to those cases +where the difference of the forms is very slight, or where the +segregation is more or less imperfect. The best example in the present +group is Papilio Agamemnon, a species which ranges over the greater part +of tropical Asia, the whole of the Malay archipelago, and a portion of +the Australian and Pacific regions. The modifications are principally of +size and form, and, though slight, are tolerably constant in each +locality. The steps, however, are so numerous and gradual that it would +be impossible to define many of them, though the extreme forms are +sufficiently distinct. Papilio Sarpedon presents somewhat similar but +less numerous variations. + +4. _Co-existing Variety._--This is a somewhat doubtful case. It is when +a slight but permanent and hereditary modification of form exists in +company with the parent or typical form, without presenting those +intermediate gradations which would constitute it a case of simple +variability. It is evidently only by direct evidence of the two forms +breeding separately that this can be distinguished from dimorphism. The +difficulty occurs in Papilio Jason, and P. Evemon, which inhabit the +same localities, and are almost exactly alike in form, size, and +colouration, except that the latter always wants a very conspicuous red +spot on the under surface, which is found not only in P. Jason, but in +all the allied species. It is only by breeding the two insects that it +can be determined whether this is a case of a co-existing variety or of +dimorphism. In the former case, however, the difference being constant +and so very conspicuous and easily defined, I see not how we could +escape considering it as a distinct species. A true case of co-existing +forms would, I consider, be produced, if a slight variety had become +fixed as a local form, and afterwards been brought into contact with the +parent species, with little or no intermixture of the two; and such +instances do very probably occur. + +5. _Race or subspecies._--These are local forms completely fixed and +isolated; and there is no possible test but individual opinion to +determine which of them shall be considered as species and which +varieties. If stability of form and "_the constant transmission of some +characteristic peculiarity of organization_" is the test of a species +(and I can find no other test that is more certain than individual +opinion) then every one of these fixed races, confined as they almost +always are to distinct and limited areas, must be regarded as a species; +and as such I have in most cases treated them. The various modifications +of Papilio Ulysses, P. Peranthus, P. Codrus, P. Eurypilus, P. Helenus, +&c., are excellent examples; for while some present great and +well-marked, others offer slight and inconspicuous differences, yet in +all cases these differences seem equally fixed and permanent. If, +therefore, we call some of these forms species, and others varieties, we +introduce a purely arbitrary distinction, and shall never be able to +decide where to draw the line. The races of Papilio Ulysses, for +example, vary in amount of modification from the scarcely differing New +Guinea form to those of Woodlark Island and New Caledonia, but all seem +equally constant; and as most of these had already been named and +described as species, I have added the New Guinea form under the name of +P. Autolycus. We thus get a little group of Ulyssine Papilios, the whole +comprised within a very limited area, each one confined to a separate +portion of that area, and, though differing in various amounts, each +apparently constant. Few naturalists will doubt that all these may and +probably have been derived from a common stock, and therefore it seems +desirable that there should be a unity in our method of treating them; +either call them all _varieties_ or all _species_. Varieties, however, +continually get overlooked; in lists of species they are often +altogether unrecorded; and thus we are in danger of neglecting the +interesting phenomena of variation and distribution which they present. +I think it advisable, therefore, to name all such forms; and those who +will not accept them as species may consider them as subspecies or +races. + +6. _Species._--Species are merely those strongly marked races or local +forms which when in contact do not intermix, and when inhabiting +distinct areas are generally believed to have had a separate origin, and +to be incapable of producing a fertile hybrid offspring. But as the test +of hybridity cannot be applied in one case in ten thousand, and even if +it could be applied would prove nothing, since it is founded on an +assumption of the very question to be decided--and as the test of +separate origin is in every case inapplicable--and as, further, the test +of non-intermixture is useless, except in those rare cases where the +most closely allied species are found inhabiting the same area, it will +be evident that we have no means whatever of distinguishing so-called +"true species" from the several modes of variation here pointed out, and +into which they so often pass by an insensible gradation. It is quite +true that, in the great majority of cases, what we term "species" are +so well marked and definite that there is no difference of opinion about +them; but as the test of a true theory is, that it accounts for, or at +the very least is not inconsistent with, the whole of the phenomena and +apparent anomalies of the problem to be solved, it is reasonable to ask +that those who deny the origin of species by variation and selection +should grapple with the facts in detail, and show how the doctrine of +the distinct origin and permanence of species will explain and harmonize +them. It has been recently asserted by Dr. J. E. Gray (in the +Proceedings of the Zoological Society for 1863, page 134), that the +difficulty of limiting species is in proportion to our ignorance, and +that just as groups or countries are more accurately known and studied +in greater detail the limits of species become settled. This statement +has, like many other general assertions, its portion of both truth and +error. There is no doubt that many uncertain species, founded on few or +isolated specimens, have had their true nature determined by the study +of a good series of examples: they have been thereby established as +species or as varieties; and the number of times this has occurred is +doubtless very great. But there are other, and equally trustworthy +cases, in which, not single species, but whole groups have, by the study +of a vast accumulation of materials, been proved to have no definite +specific limits. A few of these must be adduced. In Dr. Carpenter's +"Introduction to the Study of the Foraminifera," he states that "_there +is not a single specimen of plant or animal of which the range of +variation has been studied by the collocation and comparison of so large +a number of specimens as have passed under the review of Messrs. +Williamson, Parker, Rupert Jones, and myself, in our studies of the +types of this group_;" and the result of this extended comparison of +specimens is stated to be, "_The range of variation is so great among +the Foraminifera as to include not merely those differential characters +which have been usually accounted_ SPECIFIC, _but also those upon which +the greater part of the_ GENERA _of this group have been founded, and +even in some instances those of its_ ORDERS" (Foraminifera, Preface, x). +Yet this same group had been divided by D'Orbigny and other authors into +a number of clearly defined _families_, _genera_, and _species_, which +these careful and conscientious researches have shown to have been +almost all founded on incomplete knowledge. + +Professor DeCandolle has recently given the results of an extensive +review of the species of Cupuliferae. He finds that the best-known +species of oaks are those which produce most varieties and subvarieties; +that they are often surrounded by provisional species; and, with the +fullest materials at his command, two-thirds of the species he considers +more or less doubtful. His general conclusion is, that "_in botany the +lowest series of groups,_ SUBVARIETIES, VARIETIES, _and_ RACES _are very +badly limited; these can be grouped into_ SPECIES _a little less vaguely +limited, which again can be formed into sufficiently precise_ GENERA." +This general conclusion is entirely objected to by the writer of the +article in the "Natural History Review," who, however, does not deny its +applicability to the particular order under discussion, while this very +difference of opinion is another proof that difficulties in the +determination of species do not, any more than in the higher groups, +vanish with increasing materials and more accurate research. + +Another striking example of the same kind is seen in the genera Rubus +and Rosa, adduced by Mr. Darwin himself; for though the amplest +materials exist for a knowledge of these groups, and the most careful +research has been bestowed upon them, yet the various species have not +thereby been accurately limited and defined so as to satisfy the +majority of botanists. In Mr. Baker's revision of the British Roses, +just published by the Linnaean Society, the author includes under the +single species Rosa canina, no less than twenty-eight named _varieties_, +distinguished by more or less constant characters and often confined to +special localities; and to these are referred about seventy of the +_species_ of Continental and British botanists. + +Dr. Hooker seems to have found the same thing in his study of the Arctic +flora. For though he has had much of the accumulated materials of his +predecessors to work upon, he continually expresses himself as unable to +do more than group the numerous and apparently fluctuating forms into +more or less imperfectly defined species. In his paper on the +"Distribution of Arctic Plants," (Trans. Linn. Soc. xxiii., p. 310) Dr. +Hooker says:--"The most able and experienced descriptive botanists vary +in their estimate of the value of the 'specific term' to a much greater +extent than is generally supposed." ... "I think I may safely affirm +that the 'specific term' has three different standard values, all +current in descriptive botany, but each more or less confined to one +class of observers." ... "This is no question of what is right or wrong +as to the real value of the specific term; I believe each is right +according to the standard he assumes as the specific." + +Lastly, I will adduce Mr. Bates's researches on the Amazons. During +eleven years he accumulated vast materials, and carefully studied the +variation and distribution of insects. Yet he has shown that many +species of Lepidoptera, which before offered no special difficulties, +are in reality most intricately combined in a tangled web of affinities, +leading by such gradual steps from the slightest and least stable +variations to fixed races and well-marked species, that it is very often +impossible to draw those sharp dividing-lines which it is supposed that +a careful study and full materials will always enable us to do. + +These few examples show, I think, that in every department of nature +there occur instances of the instability of specific form, which the +increase of materials aggravates rather than diminishes. And it must be +remembered that the naturalist is rarely likely to err on the side of +imputing greater indefiniteness to species than really exists. There is +a completeness and satisfaction to the mind in defining and limiting +and naming a species, which leads us all to do so whenever we +conscientiously can, and which we know has led many collectors to reject +vague intermediate forms as destroying the symmetry of their cabinets. +We must therefore consider these cases of excessive variation and +instability as being thoroughly well established; and to the objection +that, after all, these cases are but few compared with those in which +species can be limited and defined, and are therefore merely exceptions +to a general rule, I reply that a true law embraces all apparent +exceptions, and that to the great laws of nature there are no real +exceptions--that what appear to be such are equally results of law, and +are often (perhaps indeed always) those very results which are most +important as revealing the true nature and action of the law. It is for +such reasons that naturalists now look upon the study of _varieties_ as +more important than that of well-fixed species. It is in the former that +we see nature still at work, in the very act of producing those +wonderful modifications of form, that endless variety of colour, and +that complicated harmony of relations, which gratify every sense and +give occupation to every faculty of the true lover of nature. + + +_Variation as specially influenced by Locality._ + +The phenomena of variation as influenced by locality have not hitherto +received much attention. Botanists, it is true, are acquainted with the +influences of climate, altitude, and other physical conditions, in +modifying the forms and external characteristics of plants; but I am not +aware that any peculiar influence has been traced to locality, +independent of climate. Almost the only case I can find recorded is +mentioned in that repertory of natural-history facts, "The Origin of +Species," viz. that herbaceous groups have a tendency to become arboreal +in islands. In the animal world, I cannot find that any facts have been +pointed out as showing the special influence of locality in giving a +peculiar _facies_ to the several disconnected species that inhabit it. +What I have to adduce on this matter will therefore, I hope, possess +some interest and novelty. + +On examining the closely allied species, local forms, and varieties +distributed over the Indian and Malayan regions, I find that larger or +smaller districts, or even single islands, give a special character to +the majority of their Papilionidae. For instance: 1. The species of the +Indian region (Sumatra, Java, and Borneo) are almost invariably smaller +than the allied species inhabiting Celebes and the Moluccas; 2. The +species of New Guinea and Australia are also, though in a less degree, +smaller than the nearest species or varieties of the Moluccas; 3. In the +Moluccas themselves the species of Amboyna are the largest; 4. The +species of Celebes equal or even surpass in size those of Amboyna; 5. +The species and varieties of Celebes possess a striking character in the +form of the anterior wings, different from that of the allied species +and varieties of all the surrounding islands; 6. Tailed species in India +or the Indian region become tailless as they spread eastward through the +archipelago; 7. In Amboyna and Ceram the females of several species are +dull-coloured, while in the adjacent islands they are more brilliant. + +_Local variation of Size._--Having preserved the finest and largest +specimens of Butterflies in my own collection, and having always taken +for comparison the largest specimens of the same sex, I believe that the +tables I now give are sufficiently exact. The differences of expanse of +wings are in most cases very great, and are much more conspicuous in the +specimens themselves than on paper. It will be seen that no less than +fourteen Papilionidae inhabiting Celebes and the Moluccas are from +one-third to one-half greater in extent of wing than the allied species +representing them in Java, Sumatra, and Borneo. Six species inhabiting +Amboyna are larger than the closely allied forms of the northern +Moluccas and New Guinea by about one-sixth. These include almost every +case in which closely allied species can be compared. + + Species of Papilionidae of the Closely allied species of Java and + Moluccas and Celebes (large). the Indian region (small). + + Expanse. Expanse. + Inches. Inches. + Ornithoptera (Helena { O. Pompeus 5.8 + Amboyna) 7.6 { O. Amphrisius 6.0 + Papilio Adamantius } + (Celebes) 5.8 } + P. Lorquinianus } P. Peranthus 3.8 + (Moluccas) 4.8 } + P. Blumei (Celebes) 5.4 P. Brama 4.0 + P. Alphenor (Celebes) 4.8 P. Theseus 3.6 + P. Gigon (Celebes) 5.4 P. Demolion 4.0 + P. Deucalion (Celebes) 4.6 P. Macareus 3.7 + P. Agamemnon, var. + (Celebes) 4.4 P. Agamemnon, var. 3.8 + P. Eurypilus (Moluccas) 4.0 } P. Jason 3.4 + P. Telephus (Celebes) 4.3 } + P. AEgisthus (Moluccas) 4.4 P. Rama 3.2 + P. Milon (Celebes) 4.4 P. Sarpedon 3.8 + P. Androcles (Celebes) 4.8 P. Antiphates 3.7 + P. Polyphontes (Celebes) 4.6 P. Diphilus 3.9 + Leptocircus Ennius + (Celebes) 2.0 L. Meges 1.8 + + Species inhabiting Amboyna Allied species of New Guinea and + (large). the North Moluccas (smaller). + + Papilio Ulysses 6.1 { P. Autolycus 5.2 + { P. Telegonus 4.0 + P. Polydorus 4.9 P. Leodamas 4.0 + P. Deiphobus 6.8 P. Deiphontes 5.8 + P. Gambrisius 6.4 { P. Ormenus 5.6 + { P. Tydeus 6.0 + P. Codrus 5.1 P. Codrus, var. + papuensis 4.3 + Ornithoptera Priamus, Ornithoptera Poseidon, + (male) 8.3 (male) 7.0 + +_Local variation of Form._--The differences of form are equally clear. +Papilio Pammon everywhere on the continent is tailed in both sexes. In +Java, Sumatra, and Borneo, the closely allied P. Theseus has a very +short tail, or tooth only, in the male, while in the females the tail is +retained. Further east, in Celebes and the South Moluccas, the hardly +separable P. Alphenor has quite lost the tail in the male, while the +female retains it, but in a narrower and less spatulate form. A little +further, in Gilolo, P. Nicanor has completely lost the tail in both +sexes. + +Papilio Agamemnon exhibits a somewhat similar series of changes. In +India it is always tailed; in the greater part of the archipelago it has +a very short tail; while far east, in New Guinea and the adjacent +islands, the tail has almost entirely disappeared. + +In the Polydorus-group two species, P. Antiphus and P. Diphilus, +inhabiting India and the Indian region, are tailed, while the two which +take their place in the Moluccas, New Guinea, and Australia, P. +Polydorus and P. Leodamas, are destitute of tail, the species furthest +east having lost this ornament the most completely. + + Western species, Tailed. Allied Eastern species not Tailed. + + Papilio Pammon (India) P. Thesus (Islands) minute tail. + P. Agamemnon, var. (India) P. Agamemnon, var. (Islands). + P. Antiphus (India, Java) P. Polydorus (Moluccas). + P. Diphilus (India, Java) P. Leodamas (New Guinea). + +The most conspicuous instance of local modification of form, however, is +exhibited in the island of Celebes, which in this respect, as in some +others, stands alone and isolated in the whole archipelago. Almost every +species of Papilio inhabiting Celebes has the wings of a peculiar shape, +which distinguishes them at a glance from the allied species of every +other island. This peculiarity consists, first, in the upper wings being +generally more elongate and falcate; and secondly, in the costa or +anterior margin being much more curved, and in most instances exhibiting +near the base an abrupt bend or elbow, which in some species is very +conspicuous. This peculiarity is visible, not only when the Celebesian +species are compared with their small-sized allies of Java and Borneo, +but also, and in an almost equal degree, when the large forms of Amboyna +and the Moluccas are the objects of comparison, showing that this is +quite a distinct phenomenon from the difference of size which has just +been pointed out. + +In the following Table I have arranged the chief Papilios of Celebes in +the order in which they exhibit this characteristic form most +prominently. + + Papilios of Celebes, having the Closely allied Papilios of the + wings falcate or with abruptly surrounding islands, with less + curved costa. wings and slightly falcate curved costa. + + 1. P. Gigon P. Demolion (Java). + 2. P. Pamphylus P. Jason (Sumatra). + 3. P. Milon P. Sarpedon (Moluccas, Java). + 4. P. Agamemnon, var. P. Agamemnon, var. (Borneo). + 5. P. Adamantius P. Peranthus (Java). + 6. P. Ascalaphus P. Deiphontes (Gilolo). + 7. P. Sataspes P. Helenus (Java). + 8. P. Blumei P. Brama (Sumatra). + 9. P. Androcles P. Antiphates (Borneo). + 10. P. Rhesus P. Aristaeus (Moluccas). + 11. P. Theseus, var. (male) P. Thesus (male) (Java). + 12. P. Codrus, var. P. Codrus (Moluccas). + 13. P. Encelades P. Leucothoe (Malacca). + +It thus appears that every species of Papilio exhibits this peculiar +form in a greater or less degree, except one, P. Polyphontes, allied to +P. Diphilus of India and P. Polydorus of the Moluccas. This fact I +shall recur to again, as I think it helps us to understand something of +the causes that may have brought about the phenomenon we are +considering. Neither do the genera Ornithoptera and Leptocircus exhibit +any traces of this peculiar form. In several other families of +Butterflies this characteristic form reappears in a few species. In the +Pieridae the following species, all peculiar to Celebes, exhibit it +distinctly:-- + + 1. Pieris Eperia compared with P. Coronis (Java). + 2. Thyca Zebuda " " Thyca Descombesi + (India). + 3. T. Rosenbergii " " T. Hyparete (Java). + 4. Tachyris Hombronii " " T. Lyncida. + 5. T. Lycaste " " T. Lyncida. + 6. T. Zarinda " " T. Nero (Malacca). + 7. T. Ithome " " T. Nephele. + 8. Eronia tritaea " " Eronia Valeria + (Java). + 9. Iphias Glaucippe, var. " " Iphias Glaucippe + (Java). + +The species of Terias, one or two Pieris, and the genus Callidryas do +not exhibit any perceptible change of form. + +In the other families there are but few similar examples. The following +are all that I can find in my collection:-- + + Cethosia AEole compared with Cethosia Biblis (Java). + Eurhinia megalonice " " Eurhinia Polynice + (Borneo). + Limenitis Limire " " Limenitis Procris + (Java). + Cynthia Arsinoe, var. " " Cynthia Arsinoe (Java, + Sumatra, Borneo) + +All these belong to the family of the Nymphalidae. Many other genera of +this family, as Diadema, Adolias, Charaxes, and Cyrestis, as well as the +entire families of the Danaidae, Satyridae, Lycaenidae, and Hesperidae, +present no examples of this peculiar form of the upper wing in the +Celebesian species. + +_Local variations of Colour._--In Amboyna and Ceram the female of the +large and handsome Ornithoptera Helena has the large patch on the hind +wings constantly of a pale dull ochre or buff colour, while in the +scarcely distinguishable varieties from the adjacent islands of Bouru +and New Guinea, it is of a golden yellow, hardly inferior in brilliancy +to its colour in the male sex. The female of Ornithoptera Priamus +(inhabiting Amboyna and Ceram exclusively) is of a pale dusky brown +tint, while in all the allied species the same sex is nearly black with +contrasted white markings. As a third example, the female of Papilio +Ulysses has the blue colour obscured by dull and dusky tints, while in +the closely allied species from the surrounding islands, the females are +of almost as brilliant an azure blue as the males. A parallel case to +this is the occurrence, in the small islands of Goram, Matabello, Ke, +and Aru, of several distinct species of Euploea and Diadema, having broad +bands or patches of white, which do not exist in any of the allied +species from the larger islands. These facts seem to indicate some local +influence in modifying colour, as unintelligible and almost as +remarkable as that which has resulted in the modifications of form +previously described. + + +_Remarks on the facts of Local variation._ + +The facts now brought forward seem to me of the highest interest. We see +that almost all the species in two important families of the Lepidoptera +(Papilionidae and Pieridae) acquire, in a single island, a characteristic +modification of form distinguishing them from the allied species and +varieties of all the surrounding islands. In other equally extensive +families no such change occurs, except in one or two isolated species. +However we may account for these phenomena, or whether we may be quite +unable to account for them, they furnish, in my opinion, a strong +corroborative testimony in favour of the doctrine of the origin of +species by successive small variations; for we have here slight +varieties, local races, and undoubted species, all modified in exactly +the same manner, indicating plainly a common cause producing identical +results. On the generally received theory of the original distinctness +and permanence of species, we are met by this difficulty: one portion of +these curiously modified forms are admitted to have been produced by +variation and some natural action of local conditions; whilst the other +portion, differing from the former only in degree, and connected with +them by insensible gradations, are said to have possessed this +peculiarity of form at their first creation, or to have derived it from +unknown causes of a totally distinct nature. Is not the _a priori_ +evidence in favour of an identity of the causes that have produced such +similar results? and have we not a right to call upon our opponents for +some proofs of their own doctrine, and for an explanation of its +difficulties, instead of their assuming that they are right, and laying +upon us the burthen of disproof? + +Let us now see if the facts in question do not themselves furnish some +clue to their explanation. Mr. Bates has shown that certain groups of +butterflies have a defence against insectivorous animals, independent of +swiftness of motion. These are generally very abundant, slow, and weak +fliers, and are more or less the objects of mimicry by other groups, +which thus gain an advantage in a freedom from persecution similar to +that enjoyed by those they resemble. Now the only Papilios which have +not in Celebes acquired the peculiar form of wing, belong to a group +which is imitated both by other species of Papilio and by Moths of the +genus Epicopeia. This group is of weak and slow flight; and we may +therefore fairly conclude that it possesses some means of defence +(probably in a peculiar odour or taste) which saves it from attack. Now +the arched costa and falcate form of wing is generally supposed to give +increased powers of flight, or, as seems to me more probable, greater +facility in making sudden turnings, and thus baffling a pursuer. But the +members of the Polydorus-group (to which belongs the only unchanged +Celebesian Papilio), being already guarded against attack, have no need +of this increased power of wing; and "natural selection" would therefore +have no tendency to produce it. The whole family of Danaidae are in the +same position: they are slow and weak fliers; yet they abound in species +and individuals, and are the objects of mimicry. The Satyridae have also +probably a means of protection--perhaps their keeping always near the +ground and their generally obscure colours; while the Lycaenidae and +Hesperidae may find security in their small size and rapid motions. In +the extensive family of the Nymphalidae, however, we find that several of +the larger species, of comparatively feeble structure, have their wings +modified (Cethosia, Limenitis, Junonia, Cynthia), while the large-bodied +powerful species, which have all an excessively rapid flight, have +exactly the same form of wing in Celebes as in the other islands. On the +whole, therefore, we may say that all the butterflies of rather large +size, conspicuous colours, and not very swift flight have been affected +in the manner described, while the smaller sized and obscure groups, as +well as those which are the objects of mimicry, and also those of +exceedingly swift flight have remained unaffected. + +It would thus appear as if there must be (or once have been) in the +island of Celebes, some peculiar enemy to these larger-sized butterflies +which does not exist, or is less abundant, in the surrounding islands. +Increased powers of flight, or rapidity of turning, was advantageous in +baffling this enemy; and the peculiar form of wing necessary to give +this would be readily acquired by the action of "natural selection" on +the slight variations of form that are continually occurring. + +Such an enemy one would naturally suppose to be an insectivorous bird; +but it is a remarkable fact that most of the genera of Fly-catchers +of Borneo and Java on the one side (Muscipeta, Philentoma,) and of +the Moluccas on the other (Monarcha, Rhipidura), are almost entirely +absent from Celebes. Their place seems to be supplied by the +Caterpillar-catchers (Graucalus, Campephaga, &c.), of which six or seven +species are known from Celebes and are very numerous in individuals. We +have no positive evidence that these birds pursue butterflies on the +wing, but it is highly probable that they do so when other food is +scarce. Mr. Bates has suggested to me that the larger Dragonflies +(AEshna, &c.) prey upon butterflies; but I did not notice that they were +more abundant in Celebes than elsewhere. However this may be, the fauna +of Celebes is undoubtedly highly peculiar in every department of which +we have any accurate knowledge; and though we may not be able +satisfactorily to trace how it has been effected, there can, I think, be +little doubt that the singular modification in the wings of so many of +the butterflies of that island is an effect of that complicated action +and reaction of all living things upon each other in the struggle for +existence, which continually tends to readjust disturbed relations, and +to bring every species into harmony with the varying conditions of the +surrounding universe. + +But even the conjectural explanation now given fails us in the other +cases of local modification. Why the species of the Western islands +should be smaller than those further east,--why those of Amboyna should +exceed in size those of Gilolo and New Guinea--why the tailed species +of India should begin to lose that appendage in the islands, and retain +no trace of it on the borders of the Pacific,--and why, in three +separate cases, the females of Amboyna species should be less gaily +attired than the corresponding females of the surrounding islands,--are +questions which we cannot at present attempt to answer. That they +depend, however, on some general principle is certain, because analogous +facts have been observed in other parts of the world. Mr. Bates informs +me that, in three distinct groups, Papilios which on the Upper Amazon +and in most other parts of South America have spotless upper wings +obtain pale or white spots at Para and on the Lower Amazon; and also +that the AEneas-group of Papilios never have tails in the equatorial +regions and the Amazons valley, but gradually acquire tails in many +cases as they range towards the northern or southern tropic. Even in +Europe we have somewhat similar facts; for the species and varieties of +butterflies peculiar to the island of Sardinia are generally smaller and +more deeply coloured than those of the mainland, and the same has +recently been shown to be the case with the common tortoiseshell +butterfly in the Isle of Man; while Papilio Hospiton, peculiar to the +former island, has lost the tail, which is a prominent feature of the +closely allied P. Machaon. + +Facts of a similar nature to those now brought forward would no doubt be +found to occur in other groups of insects, were local faunas carefully +studied in relation to those of the surrounding countries; and they +seem to indicate that climate and other physical causes have, in some +cases, a very powerful effect in modifying specific form and colour, and +thus directly aid in producing the endless variety of nature. + + +_Mimicry._ + +Having fully discussed this subject in the preceding essay, I have only +to adduce such illustrations of it, as are furnished by the Eastern +Papilionidae, and to show their bearing upon the phenomena of variation +already mentioned. As in America, so in the Old World, species of +Danaidae are the objects which the other families most often imitate. But +besides these, some genera of Morphidae and one section of the genus +Papilio are also less frequently copied. Many species of Papilio mimic +other species of these three groups so closely that they are +undistinguishable when on the wing; and in every case the pairs which +resemble each other inhabit the same locality. + +The following list exhibits the most important and best marked cases of +mimicry which occur among the Papilionidae of the Malayan region and +India:-- + + Mimickers. Species mimicked. Common habitat. + + DANAIDAE. + + 1. Papilio paradoxa Euploea Midamus } Sumatra, &c. + (male & female) (male & female) } + 2. P. Caunus E. Rhadamanthus Borneo and + Sumatra. + 3. P. Thule Danais sobrina New Guinea. + 4. P. Macareus D. Aglaia Malacca, Java + 5. Papilio Agestor Danais Tytia Northern India. + 6. P. Idaeoides Hestia Leuconoe Philippines. + 7. P. Delessertii Ideopsis daos Penang. + + MORPHIDAE. + + 8. P. Pandion Drusilla bioculata New Guinea + (female) + + PAPILIO (POLYDORUS- and COON-groups). + + 9. P. Pammon (Romulus, Papilio Hector India. + female) + 10. P. Theseus, var. P. Antiphus Sumatra, Borneo. + (female) + 11. P. Theseus, var. P. Diphilus Sumatra, Java. + (female) + 12. P. Memnon, var. P. Coon Sumatra. + (Achates, female) + 13. P. Androgeus, var. P. Doubledayi Northern India. + (Achates, female) + 14. P. Oenomaus P. Liris Timor. + (female) + +We have, therefore, fourteen species or marked varieties of Papilio, +which so closely resemble species of other groups in their respective +localities, that it is not possible to impute the resemblance to +accident. The first two in the list (Papilio paradoxa and P. Caunus) are +so exactly like Euploea Midamus and E. Rhadamanthus on the wing, that +although they fly very slowly, I was quite unable to distinguish them. +The first is a very interesting case, because the male and female differ +considerably, and each mimics the corresponding sex of the Euploea. A +new species of Papilio which I discovered in New Guinea resembles Danais +sobrina, from the same country, just as Papilio Marcareus resembles +Danais Aglaia in Malacca, and (according to Dr. Horsfield's figure) +still more closely in Java. The Indian Papilio Agestor closely imitates +Danais Tytia, which has quite a different style of colouring from the +preceding; and the extraordinary Papilio Idaeoides from the Philippine +Islands, must, when on the wing, perfectly resemble the Hestia Leuconoe +of the same region, as also does the Papilio Delessertii imitate the +Ideopsis daos from Penang. Now in every one of these cases the Papilios +are very scarce, while the Danaidae which they resemble are exceedingly +abundant--most of them swarming so as to be a positive nuisance to the +collecting entomologist by continually hovering before him when he is in +search of newer and more varied captures. Every garden, every roadside, +the suburbs of every village are full of them, indicating very clearly +that their life is an easy one, and that they are free from persecution +by the foes which keep down the population of less favoured races. This +superabundant population has been shown by Mr. Bates to be a general +characteristic of all American groups and species which are objects of +mimicry; and it is interesting to find his observations confirmed by +examples on the other side of the globe. + +The remarkable genus Drusilla, a group of pale-coloured butterflies, +more or less adorned with ocellate spots, is also the object of mimicry +by three distinct genera (Melanitis, Hyantis, and Papilio). These +insects, like the Danaidae, are abundant in individuals, have a very +weak and slow flight, and do not seek concealment, or appear to have any +means of protection from insectivorous creatures. It is natural to +conclude, therefore, that they have some hidden property which saves +them from attack; and it is easy to see that when any other insects, by +what we call accidental variation, come more or less remotely to +resemble them, the latter will share to some extent in their immunity. +An extraordinary dimorphic form of the female of Papilio Ormenus has +come to resemble the Drusillas sufficiently to be taken for one of that +group at a little distance; and it is curious that I captured one of +these Papilios in the Aru Islands hovering along the ground, and +settling on it occasionally, just as it is the habit of the Drusillas to +do. The resemblance in this case is only general; but this form of +Papilio varies much, and there is therefore material for natural +selection to act upon, so as ultimately to produce a copy as exact as in +the other cases. + +The eastern Papilios allied to Polydorus, Coon, and Philoxenus, form a +natural section of the genus resembling, in many respects, the +AEneas-group of South America, which they may be said to represent in the +East. Like them, they are forest insects, have a low and weak flight, +and in their favourite localities are rather abundant in individuals; +and like them, too, they are the objects of mimicry. We may conclude, +therefore, that they possess some hidden means of protection, which +makes it useful to other insects to be mistaken for them. + +The Papilios which resemble them belong to a very distinct section of +the genus, in which the sexes differ greatly; and it is those females +only which differ most from the males, and which have already been +alluded to as exhibiting instances of dimorphism, which resemble species +of the other group. + +The resemblance of P. Romulus to P. Hector is, in some specimens, very +considerable, and has led to the two species being placed following each +other in the British Museum Catalogues and by Mr. E. Doubleday. I have +shown, however, that P. Romulus is probably a dimorphic form of the +female P. Pammon, and belongs to a distinct section of the genus. + +The next pair, Papilio Theseus, and P. Antiphus, have been united as one +species both by De Haan and in the British Museum Catalogues. The +ordinary variety of P. Theseus found in Java almost as nearly resembles +P. Diphilus, inhabiting the same country. The most interesting case, +however, is the extreme female form of P. Memnon (figured by Cramer +under the name of P. Achates), which has acquired the general form and +markings of P. Coon, an insect which differs from the ordinary male P. +Memnon, as much as any two species which can be chosen in this extensive +and highly varied genus; and, as if to show that this resemblance is not +accidental, but is the result of law, when in India we find a species +closely allied to P. Coon, but with red instead of yellow spots (P. +Doubledayi), the corresponding variety of P. Androgeus (P. Achates, +Cramer, 182, A, B,) has acquired exactly the same peculiarity of having +red spots instead of yellow. Lastly, in the island of Timor, the female +of P. Oenomaus (a species allied to P. Memnon) resembles so closely P. +Liris (one of the Polydorus-group), that the two, which were often seen +flying together, could only be distinguished by a minute comparison +after being captured. + +The last six cases of mimicry are especially instructive, because they +seem to indicate one of the processes by which dimorphic forms have been +produced. When, as in these cases, one sex differs much from the other, +and varies greatly itself, it may happen that occasionally individual +variations will occur having a distant resemblance to groups which are +the objects of mimicry, and which it is therefore advantageous to +resemble. Such a variety will have a better chance of preservation; the +individuals possessing it will be multiplied; and their accidental +likeness to the favoured group will be rendered permanent by hereditary +transmission, and, each successive variation which increases the +resemblance being preserved, and all variations departing from the +favoured type having less chance of preservation, there will in time +result those singular cases of two or more isolated and fixed forms, +bound together by that intimate relationship which constitutes them the +sexes of a single species. The reason why the females are more subject +to this kind of modification than the males is, probably, that their +slower flight, when laden with eggs, and their exposure to attack while +in the act of depositing their eggs upon leaves, render it especially +advantageous for them to have some additional protection. This they at +once obtain by acquiring a resemblance to other species which, from +whatever cause, enjoy a comparative immunity from persecution. + + +_Concluding remarks on Variation in Lepidoptera._ + +This summary of the more interesting phenomena of variation presented by +the eastern Papilionidae is, I think, sufficient to substantiate my +position, that the Lepidoptera are a group that offer especial +facilities for such inquiries; and it will also show that they have +undergone an amount of special adaptive modification rarely equalled +among the more highly organized animals. And, among the Lepidoptera, the +great and pre-eminently tropical families of Papilionidae and Danaidae +seem to be those in which complicated adaptations to the surrounding +organic and inorganic universe have been most completely developed, +offering in this respect a striking analogy to the equally +extraordinary, though totally different, adaptations which present +themselves in the Orchideae, the only family of plants in which mimicry +of other organisms appears to play any important part, and the only one +in which cases of conspicuous polymorphism occur; for as such we must +class the male, female, and hermaphrodite forms of Catasetum +tridentatum, which differ so greatly in form and structure that they +were long considered to belong to three distinct genera. + + +_Arrangement and Geographical Distribution of the Malayan Papilionidae_. + +_Arrangement._--Although the species of Papilionidae inhabiting the +Malayan region are very numerous, they all belong to three out of the +nine genera into which the family is divided. One of the remaining +genera (Eurycus) is restricted to Australia, and another (Teinopalpus) +to the Himalayan Mountains, while no less than four (Parnassius, +Doritis, Thais, and Sericinus) are confined to Southern Europe and to +the mountain-ranges of the Palaearctic region. + +The genera Ornithoptera and Leptocircus are highly characteristic of +Malayan entomology, but are uniform in character and of small extent. +The genus Papilio, on the other hand, presents a great variety of forms, +and is so richly represented in the Malay Islands, that more than +one-fourth of all the known species are found there. It becomes +necessary, therefore, to divide this genus into natural groups before we +can successfully study its geographical distribution. + +Owing principally to Dr. Horsfield's observations in Java, we are +acquainted with a considerable number of the larvae of Papilios; and +these furnish good characters for the primary division of the genus into +natural groups. The manner in which the hinder wings are plaited or +folded back at the abdominal margin, the size of the anal valves, the +structure of the antennae, and the form of the wings are also of much +service, as well as the character of the flight and the style of +colouration. Using these characters, I divide the Malayan Papilios into +four sections, and seventeen groups, as follows:-- + +Genus ORNITHOPTERA. + + a. Priamus-group. } Black and Green. + c. Brookeanus-group.} + b. Pompeus-group. Black and yellow. + +Genus PAPILIO. + + A. Larvae short, thick, with numerous fleshy tubercles; + of a purplish colour. + + a. Nox-group. Abdominal fold in male very large; + anal valves small, but swollen; antennae moderate; + wings entire, or tailed; includes the Indian + Philoxenus-group. + b. Coon-group. Abdominal fold in male small; anal + valves small, but swollen; antennae moderate; + wings tailed. + c. Polydorus-group. Abdominal fold in male small, + or none; anal valves small or obsolete, hairy; + wings tailed or entire. + + B. Larvae with third segment swollen, transversely or + obliquely banded; pupa much bent. Imago with + abdominal margin in male plaited, but not reflexed; + body weak; antennae long; wings much + dilated, often tailed. + + d. Ulysses-group. + {Protenor-group (Indian) is + e. Peranthus-group. {somewhat intermediate between + f. Memnon-group. {these, and is nearest + {to the Nox-group. + g. Helenus-group. + h. Erectheus-group. + i. Pammon-group. + k. Demolion-group. + + C. Larvae subcylindrical, variously coloured. Imago with + abdominal margin in male plaited, but not reflexed; + body weak; antennae short, with a thick + curved club; wings entire. + + l. Erithonius-group. Sexes alike, larva and pupa + something like those of P. Demolion. + m. Paradoxa-group. Sexes different. + n. Dissimilis-group. Sexes alike; larva bright-coloured; + pupa straight, cylindric. + + D. Larvae elongate, attenuate behind, and often bifid, with + lateral and oblique pale stripes, green. Imago + with the abdominal margin in male reflexed, + woolly or hairy within; anal valves small, hairy; + antennae short, stout; body stout. + + o. Macareus-group. Hind wings entire. + p. Antiphates-group. Hind wings much tailed (swallow-tails). + q. Eurypylus-group. Hind wings elongate or tailed. + +Genus LEPTOCIRCUS. + +Making, in all, twenty distinct groups of Malayan Papilionidae. + +The first section of the genus Papilio (A) comprises insects which, +though differing considerably in structure, having much general +resemblance. They all have a weak, low flight, frequent the most +luxuriant forest-districts, seem to love the shade, and are the objects +of mimicry by other Papilios. + +Section B consists of weak-bodied, large-winged insects, with an +irregular wavering flight, and which, when resting on foliage, often +expand the wings, which the species of the other sections rarely or +never do. They are the most conspicuous and striking of eastern +Butterflies. + +Section C consists of much weaker and slower-flying insects, often +resembling in their flight, as well as in their colours, species of +Danaidae. + +Section D contains the strongest-bodied and most swift-flying of the +genus. They love sunlight, and frequent the borders of streams and the +edges of puddles, where they gather together in swarms consisting of +several species, greedily sucking up the moisture, and, when disturbed, +circling round in the air, or flying high and with great strength and +rapidity. + +_Geographical Distribution._--One hundred and thirty species of Malayan +Papilionidae are now known within the district extending from the Malay +peninsula, on the north-west, to Woodlark Island, near New Guinea, on +the south-east. + +The exceeding richness of the Malayan region in these fine insects is +seen by comparing the number of species found in the different tropical +regions of the earth. From all Africa only 33 species of Papilio are +known; but as several are still undescribed in collections, we may raise +their number to about 40. In all tropical Asia there are at present +described only 65 species, and I have seen in collections but two or +three which have not yet been named. In South America, south of Panama, +there are 150 species, or about one-seventh more than are yet known from +the Malayan region; but the area of the two countries is very different; +for while South America (even excluding Patagonia) contains 5,000,000 +square miles, a line encircling the whole of the Malayan islands would +only include an area of 2,700,000 square miles, of which the land-area +would be about 1,000,000 square miles. This superior richness is partly +real and partly apparent. The breaking up of a district into small +isolated portions, as in an archipelago, seems highly favourable to the +segregation and perpetuation of local peculiarities in certain groups; +so that a species which on a continent might have a wide range, and +whose local forms, if any, would be so connected together that it would +be impossible to separate them, may become by isolation reduced to a +number of such clearly defined and constant forms that we are obliged to +count them as species. From this point of view, therefore, the greater +proportionate number of Malayan species may be considered as apparent +only. Its true superiority is shown, on the other hand, by the +possession of three genera and twenty groups of Papilionidae against a +single genus and eight groups in South America, and also by the much +greater average size of the Malayan species. In most other families, +however, the reverse is the case, the South American Nymphalidae, +Satyridae, and Erycinidae far surpassing those of the East in number, +variety, and beauty. + +The following list, exhibiting the range and distribution of each group, +will enable us to study more easily their internal and external +relations. + + +_Range of the Groups of Malayan Papilionidae._ + +Ornithoptera. + + 1. Priamus-group. Moluccas to Woodlark Island 5 species. + 2. Pompeus-group. Himalayas to New Guinea, + (Celebes, maximum) 11" + 3. Brookeana-group. Sumatra and Borneo 1" + +Papilio. + + 4. Nox-group. North India, Java, and Philippines 5 species + 5. Coon-group. North India to Java 2" + 6. Polydorus-group. India to New Guinea + and Pacific 7" + 7. Ulysses-group. Celebes to New Caledonia 4" + 8. Peranthus-group. India to Timor and + Moluccas (India, maximum) 9" + 9. Memnon-group. India to Timor and Moluccas + (Java, maximum) 10" + 10. Helenus-group. Africa and India to New + Guinea 11" + 11. Pammon-group. India to Pacific and Australia 9" + 12. Erectheus-group. Celebes to Australia 2" + 13. Demolion-group. India to Celebes 2" + 14. Erithonius-group. Africa, India, Australia 1" + 15. Paradoxa-group. India to Java (Borneo, + maximum) 5" + 16. Dissimilis-group. India to Timor (India, + maximum) 2" + 17. Macareus-group. India to New Guinea 10" + 18. Antiphates-group. Widely distributed 8" + 19. Eurypylus-group. India to Australia 15" + +Leptocircus. + + 20. Leptocircus-group. India to Celebes 4" + +This Table shows the great affinity of the Malayan with the Indian +Papilionidae, only three out of the twenty groups ranging beyond, into +Africa, Europe, or America. The limitation of groups to the Indo-Malayan +or Austro-Malayan divisions of the archipelago, which is so well marked +in the higher animals, is much less conspicuous in insects, but is shown +in some degree by the Papilionidae. The following groups are either +almost or entirely restricted to one portion of the archipelago:-- + + _Indo-Malayan Region._ _Austro-Malayan Region._ + + Nox-group. Priamus-group. + Coon-group. Ulysses-group. + Macareus-group (nearly). Erechtheus-group. + Paradoxa-group. + Dissimilis-group (nearly). + Brookeanus-group. + LEPTOCIRCUS (genus). + +The remaining groups, which range over the whole archipelago, are, in +many cases, insects of very powerful flight, or they frequent open +places and the sea-beach, and are thus more likely to get blown from +island to island. The fact that three such characteristic groups as +those of Priamus, Ulysses, and Erechtheus are strictly limited to the +Australian region of the archipelago, while five other groups are with +equal strictness confined to the Indian region, is a strong +corroboration of that division which has been founded almost entirely on +the distribution of Mammalia and Birds. + +If the various Malayan islands have undergone recent changes of level, +and if any of them have been more closely united within the period of +existing species than they are now, we may expect to find indications of +such changes in community of species between islands now widely +separated; while those islands which have long remained isolated would +have had time to acquire peculiar forms by a slow and natural process of +modification. + +An examination of the relations of the species of the adjacent islands, +will thus enable us to correct opinions formed from a mere consideration +of their relative positions. For example, looking at a map of the +archipelago, it is almost impossible to avoid the idea that Java and +Sumatra have been recently united; their present proximity is so great, +and they have such an obvious resemblance in their volcanic structure. +Yet there can be little doubt that this opinion is erroneous, and that +Sumatra has had a more recent and more intimate connexion with Borneo +than it has had with Java. This is strikingly shown by the mammals of +these islands--very few of the species of Java and Sumatra being +identical, while a considerable number are common to Sumatra and Borneo. +The birds show a somewhat similar relationship; and we shall find that +the distribution of the Papilionidae tells exactly the same tale. Thus:-- + + Sumatra has 21 species } + Borneo " 30 " } 20 sp. common to both islands; + + Sumatra " 21 " } + Java " 28 " } 11 sp. common to both islands; + + Borneo " 30 " } + Java " 28 " } 20 sp. common to both islands; + +showing that both Sumatra and Java have a much closer relationship to +Borneo than they have to each other--a most singular and interesting +result, when we consider the wide separation of Borneo from them both, +and its very different structure. The evidence furnished by a single +group of insects would have had but little weight on a point of such +magnitude if standing alone; but coming as it does to confirm deductions +drawn from whole classes of the higher animals, it must be admitted to +have considerable value. + +We may determine in a similar manner the relations of the different +Papuan Islands to New Guinea. Of thirteen species of Papilionidae +obtained in the Aru Islands, six were also found in New Guinea, and +seven not. Of nine species obtained at Waigiou, six were New Guinea, and +three not. The five species found at Mysol were all New Guinea species. +Mysol, therefore, has closer relations to New Guinea than the other +islands; and this is corroborated by the distribution of the birds, of +which I will only now give one instance. The Paradise Bird found in +Mysol is the common New Guinea species, while the Aru Islands and +Waigiou have each a species peculiar to themselves. + +The large island of Borneo, which contains more species of Papilionidae +than any other in the archipelago, has nevertheless only three peculiar +to itself; and it is quite possible, and even probable, that one of +these may be found in Sumatra or Java. The last-named island has also +three species peculiar to it; Sumatra has not one, and the peninsula of +Malacca only two. The identity of species is even greater than in birds +or in most other groups of insects, and points very strongly to a recent +connexion of the whole with each other and the continent. + + +_Remarkable Peculiarities of the Island of Celebes._ + +If we now pass to the next island (Celebes), separated from those last +mentioned by a strait not wider than that which divides them from each +other, we have a striking contrast; for with a total number of species +less than either Borneo or Java, no fewer than eighteen are absolutely +restricted to it. Further east, the large islands of Ceram and New +Guinea have only three species peculiar to each, and Timor has five. We +shall have to look, not to single islands, but to whole groups, in order +to obtain an amount of individuality comparable with that of Celebes. +For example, the extensive group comprising the large islands of Java, +Borneo, and Sumatra, with the peninsula of Malacca, possessing +altogether 48 species, has about 24, or just half, peculiar to it; the +numerous group of the Philippines possess 22 species, of which 17 are +peculiar; the seven chief islands of the Moluccas have 27, of which 12 +are peculiar; and the whole of the Papuan Islands, with an equal number +of species, have 17 peculiar. Comparable with the most isolated of these +groups is Celebes, with its 24 species, of which the large proportion of +18 are peculiar. We see, therefore, that the opinion I have elsewhere +expressed, of the high degree of isolation and the remarkable +distinctive features of this interesting island, is fully borne out by +the examination of this conspicuous family of insects. A single +straggling island with a few small satellites, it is zoologically of +equal importance with extensive groups of islands many times as large +as itself; and standing in the very centre of the archipelago, +surrounded on every side with islets connecting it with the larger +groups, and which seem to afford the greatest facilities for the +migration and intercommunication of their respective productions, it yet +stands out conspicuous with a character of its own in every department +of nature, and presents peculiarities which are, I believe, without a +parallel in any similar locality on the globe. + +Briefly to summarize these peculiarities, Celebes possesses three genera +of mammals (out of the very small number which inhabit it) which are of +singular and isolated forms, viz., Cynopithecus, a tailless Ape allied +to the Baboons; Anoa, a straight-horned Antelope of obscure affinities, +but quite unlike anything else in the whole archipelago or in India: and +Babirusa, an altogether abnormal wild Pig. With a rather limited bird +population, Celebes has an immense preponderance of species confined to +it, and has also six remarkable genera (Meropogon, Ceycopsis, +Streptocitta, Enodes, Scissirostrum, and Megacephalon) entirely +restricted to its narrow limits, as well as two others (Prioniturus and +Basilornis) which only range to a single island beyond it. + +Mr. Smith's elaborate tables of the distribution of Malayan Hymenoptera +(see "Proc. Linn. Soc." Zool. vol. vii.) show that out of the large +number of 301 species collected in Celebes, 190 (or nearly two-thirds) +are absolutely restricted to it, although Borneo on one side, and the +various islands of the Moluccas on the other, were equally well explored +by me; and no less than twelve of the genera are not found in any other +island of the archipelago. I have shown in the present essay that, in +the Papilionidae, it has far more species of its own than any other +island, and a greater proportion of peculiar species than many of the +large groups of islands in the archipelago--and that it gives to a large +number of the species and varieties which inhabit it, 1st, an increase +of size, and, 2nd, a peculiar modification in the form of the wings, +which stamp upon the most dissimilar insects a mark distinctive of their +common birth-place. + +What, I would ask, are we to do with phenomena such as these? Are we to +rest content with that very simple, but at the same time very +unsatisfying explanation, that all these insects and other animals were +created exactly _as_ they are, and originally placed exactly _where_ +they are, by the inscrutable will of their Creator, and that we have +nothing to do but to register the facts and wonder? Was this single +island selected for a fantastic display of creative power, merely to +excite a childlike and unreasoning admiration? Is all this appearance of +gradual modification by the action of natural causes--a modification the +successive steps of which we can almost trace--all delusive? Is this +harmony between the most diverse groups, all presenting analogous +phenomena, and indicating a dependence upon physical changes of which we +have independent evidence, all false testimony? If I could think so, the +study of nature would have lost for me its greatest charm. I should +feel as would the geologist, if you could convince him that his +interpretation of the earth's past history was all a delusion--that +strata were never formed in the primeval ocean, and that the fossils he +so carefully collects and studies are no true record of a former living +world, but were all created just as they now are, and in the rocks where +he now finds them. + +I must here express my own belief that none of these phenomena, however +apparently isolated or insignificant, can ever stand alone--that not the +wing of a butterfly can change in form or vary in colour, except in +harmony with, and as a part of the grand march of nature. I believe, +therefore, that all the curious phenomena I have just recapitulated, are +immediately dependent on the last series of changes, organic and +inorganic, in these regions; and as the phenomena presented by the +island of Celebes differ from those of all the surrounding islands, it +can, I conceive, only be because the past history of Celebes has been, +to some extent, unique and different from theirs. We must have much more +evidence to determine exactly in what that difference has consisted. At +present, I only see my way clear to one deduction, viz., that Celebes +represents one of the oldest parts of the archipelago; that it has been +formerly more completely isolated both from India and from Australia +than it is now, and that amid all the mutations it has undergone, a +relic or substratum of the fauna and flora of some more ancient land has +been here preserved to us. + +It is only since my return home, and since I have been able to compare +the productions of Celebes side by side with those of the surrounding +islands, that I have been fully impressed with their peculiarity, and +the great interest that attaches to them. The plants and the reptiles +are still almost unknown; and it is to be hoped that some enterprising +naturalist may soon devote himself to their study. The geology of the +country would also be well worth exploring, and its newer fossils would +be of especial interest as elucidating the changes which have led to its +present anomalous condition. This island stands, as it were, upon the +boundary-line between two worlds. On one side is that ancient Australian +fauna, which preserves to the present day the facies of an early +geological epoch; on the other is the rich and varied fauna of Asia, +which seems to contain, in every class and order, the most perfect and +highly organised animals. Celebes has relations to both, yet strictly +belongs to neither: it possesses characteristics which are altogether +its own; and I am convinced that no single island upon the globe would +so well repay a careful and detailed research into its past and present +history. + + +_Concluding Remarks._ + +In writing this essay it has been my object to show how much may, under +favourable circumstances, be learnt by the study of what may be termed +the external physiology of a small group of animals, inhabiting a +limited district. This branch of natural history had received little +attention till Mr. Darwin showed how important an adjunct it may become +towards a true interpretation of the history of organized beings, and +attracted towards it some small share of that research which had before +been almost exclusively devoted to internal structure and physiology. +The nature of species, the laws of variation, the mysterious influence +of locality on both form and colour, the phenomena of dimorphism and of +mimicry, the modifying influence of sex, the general laws of +geographical distribution, and the interpretation of past changes of the +earth's surface, have all been more or less fully illustrated by the +very limited group of the Malayan Papilionidae; while, at the same time, +the deductions drawn therefrom have been shown to be supported by +analogous facts, occurring in other and often widely-separated groups of +animals. + + + + +V. + +ON INSTINCT IN MAN AND ANIMALS. + + +The most perfect and most striking examples of what is termed instinct, +those in which reason or observation appear to have the least influence, +and which seem to imply the possession of faculties farthest removed +from our own, are to be found among insects. The marvellous constructive +powers of bees and wasps, the social economy of ants, the careful +provision for the safety of a progeny they are never to see manifested +by many beetles and flies, and the curious preparations for the pupa +state by the larvae of butterflies and moths, are typical examples of +this faculty, and are supposed to be conclusive as to the existence of +some power or intelligence, very different from that which we derive +from our senses or from our reason. + + +_How Instinct may be best Studied._ + +Whatever we may define instinct to be, it is evidently some form of +mental manifestation, and as we can only judge of mind by the analogy of +our own mental functions and by observation of the results of mental +action in other men and in animals, it is incumbent on us, first, to +study and endeavour to comprehend the minds of infants, of savage men, +and of animals not very far removed from ourselves, before we pronounce +positively as to the nature of the mental operations in creatures so +radically different from us as insects. We have not yet even been able +to ascertain what are the senses they possess, or what relation their +powers of seeing, hearing, and feeling have to ours. Their sight may far +exceed ours both in delicacy and in range, and may possibly give them +knowledge of the internal constitution of bodies analogous to that which +we obtain by the spectroscope; and that their visual organs do possess +some powers which ours do not, is indicated by the extraordinary +crystalline rods radiating from the optic ganglion to the facets of the +compound eye, which rods vary in form and thickness in different parts +of their length, and possess distinctive characters in each group of +insects. This complex apparatus, so different from anything in the eyes +of vertebrates, may subserve some function quite inconceivable by us, as +well as that which we know as vision. There is reason to believe that +insects appreciate sounds of extreme delicacy, and it is supposed that +certain minute organs, plentifully supplied with nerves, and situated in +the subcostal vein of the wing in most insects, are the organs of +hearing. But besides these, the Orthoptera (such as grasshoppers, &c.) +have what are supposed to be ears on their fore legs, and Mr. Lowne +believes that the little stalked balls, which are the sole remnants of +the hind wings in flies, are also organs of hearing or of some analogous +sense. In flies, too, the third joint of the antennae contains thousands +of nerve-fibres, which terminate in small open cells, and this Mr. Lowne +believes to be the organ of smell, or of some other, perhaps new, sense. +It is quite evident, therefore, that insects may possess senses which +give them a knowledge of that which we can never perceive, and enable +them to perform acts which to us are incomprehensible. In the midst of +this complete ignorance of their faculties and inner nature, is it wise +for us to judge so boldly of their powers by a comparison with our own? +How can we pretend to fathom the profound mystery of their mental +nature, and decide what, and how much, they can perceive or remember, +reason or reflect! To leap at one bound from our own consciousness to +that of an insect's, is as unreasonable and absurd as if, with a pretty +good knowledge of the multiplication table, we were to go straight to +the study of the calculus of functions, or as if our comparative +anatomists should pass from the study of man's bony structure to that of +the fish, and, without any knowledge of the numerous intermediate forms, +were to attempt to determine the homologies between these distant types +of vertebrata. In such a case would not error be inevitable, and would +not continued study in the same direction only render the erroneous +conclusions more ingrained and more irremovable. + + +_Definition of Instinct._ + +Before going further into this subject, we must determine what we mean +by the term instinct. It has been variously defined as--"disposition +operating without the aid of instruction or experience," "a mental power +totally independent of organization," or "a power enabling an animal to +do that which, in those things man can do, results from a chain of +reasoning, and in things which man cannot do, is not to be explained by +any efforts of the intellectual faculties." We find, too, that the word +instinct is very frequently applied to acts which are evidently the +result either of organization or of habit. The colt or calf is said to +walk instinctively, almost as soon as it is born; but this is solely due +to its organization, which renders walking both possible and pleasurable +to it. So we are said instinctively to hold out our hands to save +ourselves from falling, but this is an acquired habit, which the infant +does not possess. It appears to me that instinct should be defined +as--"the performance by an animal of complex acts, absolutely without +instruction or previously-acquired knowledge." Thus, acts are said to be +performed by birds in building their nests, by bees in constructing +their cells, and by many insects in providing for the future wants of +themselves or their progeny, without ever having seen such acts +performed by others, and without any knowledge of why they perform them +themselves. This is expressed by the very common term "blind instinct." +But we have here a number of assertions of matters of fact, which, +strange to say, have never been proved to be facts at all. They are +thought to be so self-evident that they may be taken for granted. No +one has ever yet obtained the eggs of some bird which builds an +elaborate nest, hatched these eggs by steam or under a quite distinct +parent, placed them afterwards in an extensive aviary or covered garden, +where the situation and the materials of a nest similar to that of the +parent birds may be found, and then seen what kind of nest these birds +would build. If under these rigorous conditions they choose the same +materials, the same situation, and construct the nest in the same way +and as perfectly as their parents did, instinct would be proved in their +case; now it is only assumed, and assumed, as I shall show further on, +without any sufficient reason. So, no one has ever carefully taken the +pupae of a hive of bees out of the comb, removed them from the presence +of other bees, and loosed them in a large conservatory with plenty of +flowers and food, and observed what kind of cells they would construct. +But till this is done, no one can say that bees build without +instruction, no one can say that with every new swarm there are no bees +older than those of the same year, who may be the teachers in forming +the new comb. Now, in a scientific inquiry, a point which can be proved +should not be assumed, and a totally unknown power should not be brought +in to explain facts, when known powers may be sufficient. For both these +reasons I decline to accept the theory of instinct in any case where all +other possible modes of explanation have not been exhausted. + + +_Does Man possess Instincts._ + +Many of the upholders of the instinctive theory maintain, that man has +instincts exactly of the same nature as those of animals, but more or +less liable to be obscured by his reasoning powers; and as this is a +case more open to our observation than any other, I will devote a few +pages to its consideration. Infants are said to suck by instinct, and +afterwards to walk by the same power, while in adult man the most +prominent case of instinct is supposed to be, the powers possessed by +savage races to find their way across a trackless and previously unknown +wilderness. Let us take first the case of the infant's sucking. It is +sometimes absurdly stated that the new-born infant "seeks the breast," +and this is held to be a wonderful proof of instinct. No doubt it would +be if true, but unfortunately for the theory it is totally false, as +every nurse and medical man can testify. Still, the child undoubtedly +sucks without teaching, but this is one of those _simple_ acts dependent +upon organization, which cannot properly be termed instinct, any more +than breathing or muscular motion. Any object of suitable size in the +mouth of an infant excites the nerves and muscles so as to produce the +act of suction, and when at a little later period, the will comes into +play, the pleasurable sensations consequent on the act lead to its +continuance. So, walking is evidently dependent on the arrangement of +the bones and joints, and the pleasurable exertion of the muscles, which +lead to the vertical posture becoming gradually the most agreeable one; +and there can be little doubt that an infant would learn of itself to +walk, even if suckled by a wild beast. + + +_How Indians travel through unknown and trackless Forests._ + +Let us now consider the fact, of Indians finding their way through +forests they have never traversed before. This is much misunderstood, +for I believe it is only performed under such special conditions, as at +once to show that instinct has nothing to do with it. A savage, it is +true, can find his way through his native forests in a direction in +which he has never traversed them before; but this is because from +infancy he has been used to wander in them, and to find his way by +indications which he has observed himself or learnt from others. Savages +make long journeys in many directions, and, their whole faculties being +directed to the subject, they gain a wide and accurate knowledge of the +topography, not only of their own district, but of all the regions round +about. Every one who has travelled in a new direction communicates his +knowledge to those who have travelled less, and descriptions of routes +and localities, and minute incidents of travel, form one of the main +staples of conversation round the evening fire. Every wanderer or +captive from another tribe adds to the store of information, and as the +very existence of individuals and of whole families and tribes, depends +upon the completeness of this knowledge, all the acute perceptive +faculties of the adult savage are devoted to acquiring and perfecting +it. The good hunter or warrior thus comes to know the bearing of every +hill and mountain range, the directions and junctions of all the +streams, the situation of each tract characterized by peculiar +vegetation, not only within the area he has himself traversed, but for +perhaps a hundred miles around it. His acute observation enables him to +detect the slightest undulations of the surface, the various changes of +subsoil and alterations in the character of the vegetation, that would +be quite imperceptible to a stranger. His eye is always open to the +direction in which he is going; the mossy side of trees, the presence of +certain plants under the shade of rocks, the morning and evening flight +of birds, are to him indications of direction, almost as sure as the sun +in the heavens. Now, if such a savage is required to find his way across +this country in a direction in which he has never been before, he is +quite equal to the task. By however circuitous a route he has come to +the point he is to start from, he has observed all the bearings and +distances so well, that he knows pretty nearly where he is, the +direction of his own home and that of the place he is required to go to. +He starts towards it, and knows that by a certain time he must cross an +upland or a river, that the streams should flow in a certain direction, +and that he should cross some of them at a certain distance from their +sources. The nature of the soil throughout the whole region is known to +him, as well as all the great features of the vegetation. As he +approaches any tract of country he has been in or near before, many +minute indications guide him, but he observes them so cautiously that +his white companions cannot perceive by what he has directed his course. +Every now and then he slightly changes his direction, but he is never +confused, never loses himself, for he always feels at home; till at last +he arrives at a well-known country, and directs his course so as to +reach the exact spot desired. To the Europeans whom he guides, he seems +to have come without trouble, without any special observation, and in a +nearly straight unchanging course. They are astonished, and ask if he +has ever been the same route before, and when he answers "No," conclude +that some unerring instinct could alone have guided him. But take this +same man into another country very similar to his own, but with other +streams and hills, another kind of soil, with a somewhat different +vegetation and animal life; and after bringing him by a circuitous route +to a given point, ask him to return to his starting place, by a straight +line of fifty miles through the forest, and he will certainly decline to +attempt it, or, attempting it, will more or less completely fail. His +supposed instinct does not act out of his own country. + +A savage, even in a new country, has, however, undoubted advantages, +from his familiarity with forest life, his entire fearlessness of being +lost, his accurate perception of direction and of distance, and he is +thus able very soon to acquire a knowledge of the district that seems +marvellous to a civilized man; but my own observation of savages in +forest countries has convinced me, that they find their way by the use +of no other faculties than those which we ourselves possess. It appears +to me, therefore, that to call in the aid of a new and mysterious power +to account for savages being able to do that which, under similar +conditions, we could almost all of us perform, although perhaps less +perfectly, is almost ludicrously unnecessary. + +In the next essay I shall attempt to show, that much of what has been +attributed to instinct in birds, can be also very well explained by +crediting them with those faculties of observation, memory, and +imitation, and with that limited amount of reason, which they +undoubtedly exhibit. + + + + +VI. + +THE PHILOSOPHY OF BIRDS' NESTS. + + +_Instinct or Reason in the Construction of Birds' Nests._ + +Birds, we are told, build their nests by _instinct_, while man +constructs his dwelling by the exercise of _reason_. Birds never change, +but continue to build for ever on the self-same plan; man alters and +improves his houses continually. Reason advances; instinct is +stationary. + +This doctrine is so very general that it may almost be said to be +universally adopted. Men who agree on nothing else, accept this as a +good explanation of the facts. Philosophers and poets, metaphysicians +and divines, naturalists and the general public, not only agree in +believing this to be probable, but even adopt it as a sort of axiom that +is so self-evident as to need no proof, and use it as the very +foundation of their speculations on instinct and reason. A belief so +general, one would think, must rest on indisputable facts, and be a +logical deduction from them. Yet I have come to the conclusion that not +only is it very doubtful, but absolutely erroneous; that it not only +deviates widely from the truth, but is in almost every particular +exactly opposed to it. I believe, in short, that birds do _not_ build +their nests by instinct; that man does _not_ construct his dwelling by +reason; that birds do change and improve when affected by the same +causes that make men do so; and that mankind neither alter nor improve +when they exist under conditions similar to those which are almost +universal among birds. + + +_Do Men build by Reason or by Imitation?_ + +Let us first consider the theory of reason, as alone determining the +domestic architecture of the human race. Man, as a reasonable animal, it +is said, continually alters and improves his dwelling. This I entirely +deny. As a rule, he neither alters nor improves, any more than the birds +do. What have the houses of most savage tribes improved from, each as +invariable as the nest of a species of bird? The tents of the Arab are +the same now as they were two or three thousand years ago, and the mud +villages of Egypt can scarcely have improved since the time of the +Pharaohs. The palm-leaf huts and hovels of the various tribes of South +America and the Malay Archipelago, what have they improved from since +those regions were first inhabited? The Patagonian's rude shelter of +leaves, the hollowed bank of the South African Earthmen, we cannot even +conceive to have been ever inferior to what they now are. Even nearer +home, the Irish turf cabin and the Highland stone shelty can hardly have +advanced much during the last two thousand years. Now, no one imputes +this stationary condition of domestic architecture among these savage +tribes to instinct, but to simple imitation from one generation to +another, and the absence of any sufficiently powerful stimulus to +change or improvement. No one imagines that if an infant Arab could be +transferred to Patagonia, or to the Highlands, it would, when it grew +up, astonish its foster-parents by constructing a tent of skins. On the +other hand, it is quite clear that physical conditions, combined with +the degree of civilization arrived at, almost necessitate certain types +of structure. The turf, or stones, or snow--the palm-leaves, bamboo, or +branches, which are the materials of houses in various countries, are +used because nothing else is so readily to be obtained. The Egyptian +peasant has none of these, not even wood. What, then, can he use but +mud? In tropical forest-countries, the bamboo and the broad palm-leaves +are the natural material for houses, and the form and mode of structure +will be decided in part by the nature of the country, whether hot or +cool, whether swampy or dry, whether rocky or plain, whether frequented +by wild beasts, or whether subject to the attacks of enemies. When once +a particular mode of building has been adopted, and has become confirmed +by habit and by hereditary custom, it will be long retained, even when +its utility has been lost through changed conditions, or through +migration into a very different region. As a general rule, throughout +the whole continent of America, native houses are built directly upon +the ground--strength and security being given by thickening the low +walls and the roof. In almost the whole of the Malay Islands, on the +contrary, the houses are raised on posts, often to a great height, with +an open bamboo floor; and the whole structure is exceedingly slight and +thin. Now, what can be the reason of this remarkable difference between +countries, many parts of which are strikingly similar in physical +conditions, natural productions, and the state of civilization of their +inhabitants? We appear to have some clue to it in the supposed origin +and migrations of their respective populations. The indigenes of +tropical America are believed to have immigrated from the north--from a +country where the winters are severe, and raised houses with open floors +would be hardly habitable. They moved southwards by land along the +mountain ranges and uplands, and in an altered climate continued the +mode of construction of their forefathers, modified only by the new +materials they met with. By minute observations of the Indians of the +Amazon Valley, Mr. Bates arrived at the conclusion that they were +comparatively recent immigrants from a colder climate. He says:--"No one +could live long among the Indians of the Upper Amazon without being +struck with their constitutional dislike to the heat ... Their skin is +hot to the touch, and they perspire little ... They are restless and +discontented in hot, dry weather, but cheerful on cool days, when the +rain is pouring down their naked backs." And, after giving many other +details, he concludes, "How different all this is with the Negro, the +true child of tropical climes! The impression gradually forced itself on +my mind that the Red Indian lives as an immigrant or stranger in these +hot regions, and that his constitution was not originally adapted, and +has not since become perfectly adapted, to the climate." + +The Malay races, on the other hand, are no doubt very ancient +inhabitants of the hottest regions, and are particularly addicted to +forming their first settlements at the mouths of rivers or creeks, or in +land-locked bays and inlets. They are a pre-eminently maritime or +semi-aquatic people, to whom a canoe is a necessary of life, and who +will never travel by land if they can do so by water. In accordance with +these tastes, they have built their houses on posts in the water, after +the manner of the lake-dwellers of ancient Europe; and this mode of +construction has become so confirmed, that even those tribes who have +spread far into the interior, on dry plains and rocky mountains, +continue to build in exactly the same manner, and find safety in the +height to which they elevate their dwellings above the ground. + + +_Why does each Bird build a peculiar kind of Nest?_ + +These general characteristics of the abode of savage man will be found +to be exactly paralleled by the nests of birds. Each species uses the +materials it can most readily obtain, and builds in situations most +congenial to its habits. The wren, for example, frequenting hedgerows +and low thickets, builds its nest generally of _moss_, a material always +found where it lives, and among which it probably obtains much of its +insect food; but it varies sometimes, using hay or feathers when these +are at hand. Rooks dig in pastures and ploughed fields for grubs, and +in doing so must continually encounter _roots_ and _fibres_. These are +used to line its nest. What more natural! The crow feeding on carrion, +dead rabbits, and lambs, and frequenting sheep-walks and warrens, +chooses _fur_ and _wool_ to line its nest. The lark frequents cultivated +fields, and makes its nest, on the ground, of grass lined with +_horsehair_--materials the most easy to meet with, and the best adapted +to its needs. The kingfisher makes its nest of the _bones_ of the fish +which it has eaten. Swallows use clay and mud from the margins of the +ponds and rivers over which they find their insect food. The materials +of birds' nests, like those used by savage man for his house, are, then, +those which come first to hand; and it certainly requires no more +special instinct to select them in one case than in the other. + +But, it will be said, it is not so much the materials as the form and +structure of nests, that vary so much, and are so wonderfully adapted to +the wants and habits of each species; how are these to be accounted for +except by instinct? I reply, they may be in a great measure explained by +the general habits of the species, the nature of the tools they have to +work with, and the materials they can most easily obtain, with the very +simplest adaptations of means to an end, quite within the mental +capacities of birds. The delicacy and perfection of the nest will bear a +direct relation to the size of the bird, its structure and habits. That +of the wren or the humming-bird is perhaps not finer or more beautiful +in proportion than that of the blackbird, the magpie, or the crow. The +wren, having a slender beak, long legs, and great activity, is able with +great ease to form a well-woven nest of the finest materials, and places +it in thickets and hedgerows which it frequents in its search for food. +The titmouse, haunting fruit-trees and walls, and searching in cracks +and crannies for insects, is naturally led to build in holes where it +has shelter and security; while its great activity, and the perfection +of its tools (bill and feet), enable it readily to form a beautiful +receptacle for its eggs and young. Pigeons having heavy bodies and weak +feet and bills (imperfect tools for forming a delicate structure) build +rude, flat nests of sticks, laid across strong branches which will bear +their weight and that of their bulky young. They can do no better. The +Caprimulgidae have the most imperfect tools of all, feet that will not +support them except on a flat surface (for they cannot truly perch) and +a bill excessively broad, short, and weak, and almost hidden by feathers +and bristles. They cannot build a nest of twigs or fibres, hair or moss, +like other birds, and they therefore generally dispense with one +altogether, laying their eggs on the bare ground, or on the stump or +flat limb of a tree. The clumsy hooked bills, short necks and feet, and +heavy bodies of Parrots, render them quite incapable of building a nest +like most other birds. They cannot climb up a branch without using both +bill and feet; they cannot even turn round on a perch without holding on +with their bill. How, then, could they inlay, or weave, or twist the +materials of a nest? Consequently, they all lay in holes of trees, the +tops of rotten stumps, or in deserted ants' nests, the soft materials of +which they can easily hollow out. + +Many terns and sandpipers lay their eggs on the bare sand of the +sea-shore, and no doubt the Duke of Argyll is correct when he says, that +the cause of this habit is not that they are unable to form a nest, but +that, in such situations, any nest would be conspicuous and lead to the +discovery of the eggs. The choice of _place_ is, however, evidently +determined by the habits of the birds, who, in their daily search for +food, are continually roaming over extensive tide-washed flats. Gulls +vary considerably in their mode of nesting, but it is always in +accordance with their structure and habits. The situation is either on a +bare rock or on ledges of sea-cliffs, in marshes or on weedy shores. The +materials are sea-weed, tufts of grass or rushes, or the _debris_ of the +shore, heaped together with as little order and constructive art as +might be expected from the webbed feet and clumsy bill of these birds, +the latter better adapted for seizing fish than for forming a delicate +nest. The long-legged, broad-billed flamingo, who is continually +stalking over muddy flats in search of food, heaps up the mud into a +conical stool, on the top of which it lays its eggs. The bird can thus +sit upon them conveniently, and they are kept dry, out of reach of the +tides. + +Now I believe that throughout the whole class of birds the same general +principles will be found to hold good, sometimes distinctly, sometimes +more obscurely apparent, according as the habits of the species are more +marked, or their structure more peculiar. It is true that, among birds +differing but little in structure or habits, we see considerable +diversity in the mode of nesting, but we are now so well assured that +important changes of climate and of surface have occurred within the +period of existing species, that it is by no means difficult to see how +such differences have arisen. Simple habits are known to be hereditary, +and as the area now occupied by each species is different from that of +every other, we may be sure that such changes would act differently upon +each, and would often bring together species which had acquired their +peculiar habits in distinct regions and under different conditions. + + +_How do Young Birds learn to Build their First Nest?_ + +But it is objected, birds do not _learn_ to make their nest as man does +to build, for all birds will make exactly the same nest as the rest of +their species, even if they have never seen one, and it is instinct +alone that can enable them to do this. No doubt this would be instinct +if it were true, and I simply ask for proof of the fact. This point, +although so important to the question at issue, is always assumed +without proof, and even against proof, for what facts there are, are +opposed to it. Birds brought up from the egg in cages do not make the +characteristic nest of their species, even though the proper materials +are supplied them, and often make no nest at all, but rudely heap +together a quantity of materials; and the experiment has never been +fairly tried, of turning out a pair of birds so brought up, into an +enclosure covered with netting, and watching the result of their +untaught attempts at nest-making. With regard to the songs of birds, +however, which is thought to be equally instinctive, the experiment has +been tried, and it is found that young birds never have the song +peculiar to their species if they have not heard it, whereas they +acquire very easily the song of almost any other bird with which they +are associated. + + +_Do Birds sing by Instinct or by Imitation?_ + +The Hon. Daines Barrington was of opinion that "notes in birds are no +more innate than language is in man, and depend entirely on the master +under which they are bred, _as far as their organs will enable them to +imitate_ the sounds which they have frequent opportunities of hearing." +He has given an account of his experiments in the "Philosophical +Transactions" for 1773 (Vol. 63); he says: "I have educated nestling +linnets under the three best singing larks--the skylark, woodlark, and +titlark, every one of which, instead of the linnet's song, adhered +entirely to that of their respective instructors. When the note of the +titlark linnet was thoroughly fixed, I hung the bird in a room with two +common linnets for a quarter of a year, which were full in song; the +titlark linnet, however, did not borrow any passage from the linnet's +song, but adhered stedfastly to that of the titlark." He then goes on +to say that birds taken from the nest at two or three weeks old have +already learnt the call-note of their species. To prevent this the birds +must be taken from the nest when a day or two old, and he gives an +account of a goldfinch which he saw at Knighton in Radnorshire, and +which sang exactly like a wren, without any portion of the proper note +of its species. This bird had been taken from the nest at two or three +days old, and had been hung at a window opposite a small garden, where +it had undoubtedly acquired the notes of the wren without having any +opportunity of learning even the call of the goldfinch. + +He also saw a linnet, which had been taken from the nest when only two +or three days old, and which, not having any other sounds to imitate, +had learnt almost to articulate, and could repeat the words "Pretty +Boy," and some other short sentences. + +Another linnet was educated by himself under a _vengolina_ (a small +African finch, which he says sings better than any foreign bird but the +American mocking bird), and it imitated its African master so exactly +that it was impossible to distinguish the one from the other. + +Still more extraordinary was the case of a common house sparrow, which +only chirps in a wild state, but which learnt the song of the linnet and +goldfinch by being brought up near those birds. + +The Rev. W. H. Herbert made similar observations, and states that the +young whinchat and wheatear, which have naturally little variety of +song, are ready in confinement to learn from other species, and become +much better songsters. The bullfinch, whose natural notes are weak, +harsh, and insignificant, has nevertheless a wonderful musical faculty, +since it can be taught to whistle complete tunes. The nightingale, on +the other hand, whose natural song is so beautiful, is exceedingly apt +in confinement to learn that of other birds instead. Bechstein gives an +account of a redstart which had built under the eaves of his house, +which imitated the song of a caged chaffinch in a window underneath, +while another in his neighbour's garden repeated some of the notes of a +blackcap, which had a nest close by. + +These facts, and many others which might be quoted, render it certain +that the peculiar notes of birds are acquired by imitation, as surely as +a child learns English or French, not by instinct, but by hearing the +language spoken by its parents. + +It is especially worthy of remark that, for young birds to acquire a new +song correctly, they must be taken out of hearing of their parents very +soon, for in the first three or four days they have already acquired +some knowledge of the parent notes, which they will afterwards imitate. +This shows that very young birds can both hear and remember, and it +would be very extraordinary if, after they could see, they could neither +observe nor recollect, and could live for days and weeks in a nest and +know nothing of its materials and the manner of its construction. +During the time they are learning to fly and return often to the nest, +they must be able to examine it inside and out in every detail, and as +we have seen that their daily search for food invariably leads them +among the materials of which it is constructed, and among places similar +to that in which it is placed, is it so very wonderful that when they +want one themselves they should make one like it? How else, in fact, +should they make it? Would it not be much more remarkable if they went +out of their way to get materials quite different from those used in the +parent nest, if they arranged them in a way they had seen no example of, +and formed the whole structure differently from that in which they +themselves were reared, and which we may fairly presume is that which +their whole organization is best adapted to put together with celerity +and ease? It has, however, been objected that observation, imitation, or +memory, can have nothing to do with a bird's architectural powers, +because the young birds, which in England are born in May or June, will +proceed in the following April or May to build a nest as perfect and as +beautiful as that in which it was hatched, although it could never have +seen one built. But surely the young birds _before_ they left the nest +had ample opportunities of observing its _form_, its _size_, its +_position_, the _materials_ of which it was constructed, and the manner +in which those materials were arranged. Memory would retain these +observations till the following spring, when the materials would come in +their way during their daily search for food, and it seems highly +probable that the older birds would begin building first, and that those +born the preceding summer would follow their example, learning from them +how the foundations of the nest are laid and the materials put +together.[H] + + +--------------------------------------------------------------+ + | [H] It has been very pertinently remarked by a friend, that, | + | if young birds did observe the nest they were reared in, | + | they would consider it to be a natural production like the | + | leaves and branches and matted twigs that surrounded it, and | + | could not possibly conclude that their parents had | + | constructed the one and not the other. This may be a valid | + | objection, and, if so, we shall have to depend on the mode | + | of instruction described in the succeeding paragraphs, but | + | the question can only be finally decided by a careful set of | + | experiments. | + +--------------------------------------------------------------+ + +Again, we have no right to assume that young birds generally pair +together. It seems probable that in each pair there is most frequently +only one bird born the preceding summer, who would be guided, to some +extent, by its partner. + +My friend, Mr. Richard Spruce, the well-known traveller and botanist, +thinks this is the case, and has kindly allowed me to publish the +following observations, which he sent me after reading my book. + + +_How young Birds may learn to build Nests._ + +"Among the Indians of Peru and Ecuador, many of whose customs are relics +of the semi-civilisation that prevailed before the Spanish conquest, it +is usual for the young men to marry old women, and the young women old +men. A young man, they say, accustomed to be tended by his mother, would +fare ill if he had only an ignorant young girl to take care of him; and +the girl herself would be better off with a man of mature years, capable +of supplying the place of a father to her. + +"Something like this custom prevails among many animals. A stout old +buck can generally fight his way to the doe of his choice, and indeed of +as many does as he can manage; but a young buck 'of his first horns,' +must either content himself with celibacy, or with some dame +well-stricken in years. + +"Compare the nearly parallel case of the domestic cock and of many other +birds. Then consider the consequences amongst birds that pair, if an old +cock sorts with a young hen and an old hen with a young cock, as I think +is certainly the case with blackbirds and others that are known to fight +for the youngest and handsomest females. One of each pair being already +an 'old bird,' will be competent to instruct its younger partner (not +only in the futility of 'chaff,' but) in the selection of a site for a +nest and how to build it; then, how eggs are hatched and young birds +reared. + +"Such, in brief, is my idea of how a bird on its first espousals may be +taught the Whole Duty of the married state." + +On this difficult point I have sought for information from some of our +best field ornithologists, but without success, as it is in most cases +impossible to distinguish old from young birds after the first year. I +am informed, however, that the males of blackbirds, sparrows, and many +other kinds fight furiously, and the conqueror of course has the choice +of a mate. Mr. Spruce's view is at least as probable as the contrary one +(that young birds, _as a rule_, pair together), and it is to some extent +supported by the celebrated American observer, Wilson, who strongly +insists on the variety in the nests of birds of the same species, some +being so much better finished than others; and he believes _that the +less perfect nests are built by the younger, the more perfect by the +older, birds_. + +At all events, till the crucial experiment is made, and a pair of birds +raised from the egg without ever seeing a nest are shown to be capable +of making one exactly of the parental type, I do not think we are +justified in calling in the aid of an unknown and mysterious faculty to +do that which is so strictly analogous to the house-building of savage +man. + +Again, we always assume that because a nest appears to us delicately and +artfully built, that it therefore requires much special knowledge and +acquired skill (or their substitute, instinct) in the bird who builds +it. We forget that it is formed twig by twig and fibre by fibre, rudely +enough at first, but crevices and irregularities, which must seem huge +gaps and chasms in the eyes of the little builders, are filled up by +twigs and stalks pushed in by slender beak and active foot, and that the +wool, feathers, or horsehair are laid thread by thread, so that the +result seems a marvel of ingenuity to us, just as would the rudest +Iinand hut to a native of Brobdignag. Levaillant has given an account +of the process of nest-building by a little African warbler, which +sufficiently shows that a very beautiful structure may be produced with +very little art. The foundation was laid of moss and flax interwoven +with grass and tufts of cotton, and presented a rude mass, five or six +inches in diameter, and four inches thick. This was pressed and trampled +down repeatedly, so as at last to make it into a kind of felt. The birds +pressed it with their bodies, turning round upon them in every +direction, so as to get it quite firm and smooth before raising the +sides. These were added bit by bit, trimmed and beaten with the wings +and feet, so as to felt the whole together, projecting fibres being now +and then worked in with the bill. By these simple and apparently +inefficient means, the inner surface of the nest was rendered almost as +smooth and compact as a piece of cloth. + + +_Man's Works mainly Imitative._ + +But look at civilised man! it is said; look at Grecian, and Egyptian, +and Roman, and Gothic, and modern Architecture! What advance! what +improvement! what refinements! This is what reason leads to, whereas +birds remain for ever stationary. If, however, such advances as these +are required, to prove the effects of reason as contrasted with +instinct, then all savage and many half-civilized tribes have no reason, +but build instinctively quite as much as birds do. + +Man ranges over the whole earth, and exists under the most varied +conditions, leading necessarily to equally varied habits. He +migrates--he makes wars and conquests--one race mingles with +another--different customs are brought into contact--the habits of a +migrating or conquering race are modified by the different circumstances +of a new country. The civilized race which conquered Egypt must have +developed its mode of building in a forest country where timber was +abundant, for it is not probable, that the idea of cylindrical columns +originated in a country destitute of trees. The pyramids might have been +built by an indigenous race, but not the temples of El Uksor and Karnak. +In Grecian architecture, almost every characteristic feature can be +traced to an origin in wooden buildings. The columns, the architrave, +the frieze, the fillets, the cantelevers, the form of the roof, all +point to an origin in some southern forest-clad country, and strikingly +corroborate the view derived from philology, that Greece was colonised +from north-western India. But to erect columns and span them with huge +blocks of stone, or marble, is not an act of reason, but one of pure +unreasoning imitation. The arch is the only true and reasonable mode of +covering over wide spaces with stone, and therefore, Grecian +architecture, however exquisitely beautiful, is false in principle, and +is by no means a good example of the application of reason to the art of +building. And what do most of us do at the present day but imitate the +buildings of those that have gone before us? We have not even been able +to discover or develope any definite style of building best suited for +us. We have no characteristic national style of architecture, and to +that extent are even below the birds, who have each their characteristic +form of nest, exactly adapted to their wants and habits. + + +_Birds do Alter and Improve their Nests when altered Conditions require +it._ + +The great uniformity in the architecture of each species of bird which +has been supposed to prove a nest-building instinct, we may, therefore, +fairly impute to the uniformity of the conditions under which each +species lives. Their range is often very limited, and they very seldom +permanently change their country, so as to be placed in new conditions. +When, however, new conditions do occur, they take advantage of them just +as freely and wisely as man could do. The chimney and house-swallows are +a standing proof of a change of habit since chimneys and houses were +built, and in America this change has taken place within about three +hundred years. Thread and worsted are now used in many nests instead of +wool and horsehair, and the jackdaw shows an affection for the church +steeple which can hardly be explained by instinct. In the more thickly +populated parts of the United States, the Baltimore oriole uses all +sorts of pieces of string, skeins of silk, or the gardener's bass, to +weave into its fine pensile nest, instead of the single hairs and +vegetable fibres it has painfully to seek in wilder regions; and Wilson, +a most careful observer, believes that it improves in nest-building by +practice--the older birds making the best nests. The purple martin takes +possession of empty gourds or small boxes, stuck up for its reception in +almost every village and farm in America; and several of the American +wrens will also build in cigar boxes, with a small hole cut in them, if +placed in a suitable situation. The orchard oriole of the United States +offers us an excellent example of a bird which modifies its nest +according to circumstances. When built among firm and stiff branches the +nest is very shallow, but if, as is often the case, it is suspended from +the slender twigs of the weeping willow, it is made much deeper, so that +when swayed about violently by the wind the young may not tumble out. It +has been observed also, that the nests built in the warm Southern States +are much slighter and more porous in texture than those in the colder +regions of the north. Our own house-sparrow equally well adapts himself +to circumstances. When he builds in trees, as he, no doubt, always did +originally, he constructs a well-made domed nest, perfectly fitted to +protect his young ones; but when he can find a convenient hole in a +building or among thatch, or in any well-sheltered place, he takes much +less trouble, and forms a very loosely-built nest. + +A curious example of a recent change of habits has occurred in Jamaica. +Previous to 1854, the palm swift (Tachornis phaenicobea) inhabited +exclusively the palm trees in a few districts in the island. A colony +then established themselves in two cocoa-nut palms in Spanish Town, and +remained there till 1857, when one tree was blown down, and the other +stripped of its foliage. Instead of now seeking out other palm trees, +the swifts drove out the swallows who built in the Piazza of the House +of Assembly, and took possession of it, building their nests on the tops +of the end walls and at the angles formed by the beams and joists, a +place which they continue to occupy in considerable numbers. It is +remarked that here they form their nest with much less elaboration than +when built in the palms, probably from being less exposed. + +A still more curious example of change and improvement in nest building +was published by Mr. F. A. Pouchet, in the tenth number of the _Comptes +Rendus_ for 1870, just as the first edition of this work appeared. Forty +years ago M. Pouchet had himself collected nests of the House-Martin or +Window-Swallow (_Hirundo urbica_) from old buildings at Rouen, and +deposited them in the museum of that city. On recently obtaining some +more nests he was surprised, on comparing them with the old ones, to +find that they exhibited a decided change of form and structure. This +led him to investigate the matter more closely. The changed nests had +been obtained from houses in a newly erected quarter of the city, and he +found that all the nests in the newly-built streets were of the new +form. But on visiting the churches and older buildings, and some rocks +where these birds build, he found many nests of the old type along with +some of the new pattern. He then examined all the figures and +descriptions of the older naturalists, and found that they invariably +represented the older form only. + +The difference between the two forms he states to be as follows. In the +old form the nest is a portion of a globe--when situated in the upper +angle of a window one-fourth of a hemisphere--and the opening is very +small and circular, being of a size just sufficient to allow the body of +the bird to pass. In the new form the nest is much wider in proportion +to its height, being a segment of a depressed spheroid, and the aperture +is very wide and shallow, and close to the horizontal surface to which +the nest is attached above. + +M. Pouchet thinks that the new form is an undoubted improvement on the +old. The nest has a wider bottom and must allow the young ones to have +more freedom of motion than in the old narrower, and deeper nests, and +its wide aperture allows the young birds to peep out and breathe the +fresh air. This is so wide as to serve as a sort of balcony for them, +and two young ones can often be seen on it without interfering with the +passage in and out of the old birds. At the same time, by being so close +to the roof, it is a better protection against rain, against cold, and +against enemies, than the small round hole of the old nests. Here, then, +we have an improvement in nest building, as well marked as any +improvement that takes place in human dwellings in so short a time. + +But perfection of structure and adaptation to purpose, are not universal +characteristics of birds' nests, since there are decided imperfections +in the nesting of many birds which are quite compatible with our present +theory, but are hardly so with that of instinct, which is supposed to be +infallible. The Passenger pigeon of America often crowds the branches +with its nests till they break, and the ground is strewn with shattered +nests, eggs, and young birds. Rooks' nests are often so imperfect that +during high winds the eggs fall out; but the Window-Swallow is the most +unfortunate in this respect, for White, of Selborne, informs us that he +has seen them build, year after year, in places where their nests are +liable to be washed away by a heavy rain and their young ones destroyed. + + +_Conclusion._ + +A fair consideration of all these facts will, I think, fully support the +statement with which I commenced, and show, that the mental faculties +exhibited by birds in the construction of their nests, are the same in +kind as those manifested by mankind in the formation of their dwellings. +These are, essentially, imitation, and a slow and partial adaptation to +new conditions. To compare the work of birds with the highest +manifestations of human art and science, is totally beside the question. +I do not maintain that birds are gifted with reasoning faculties at all +approaching in variety and extent to those of man. I simply hold that +the phenomena presented by their mode of building their nests, when +fairly compared with those exhibited by the great mass of mankind in +building their houses, indicate no essential difference in the kind or +nature of the mental faculties employed. If instinct means anything, it +means the capacity to perform some complex act without teaching or +experience. It implies innate ideas of a very definite kind, and, if +established, would overthrow Mr. Mill's sensationalism and all the +modern philosophy of experience. That the existence of true instinct may +be established in other cases is not impossible, but in the particular +instance of birds' nests, which is usually considered one of its +strongholds, I cannot find a particle of evidence to show the existence +of anything beyond those lower reasoning and imitative powers, which +animals are universally admitted to possess. + + + + +VII. + +A THEORY OF BIRDS' NESTS; + +SHOWING THE RELATION OF CERTAIN DIFFERENCES OF COLOUR IN FEMALE +BIRDS, TO THEIR MODE OF NIDIFICATION. + + +The habit of forming a more or less elaborate structure for the +reception of their eggs and young, must undoubtedly be looked upon as +one of the most remarkable and interesting characteristics of the class +of birds. In other classes of vertebrate animals, such structures are +few and exceptional, and never attain to the same degree of completeness +and beauty. Birds' nests have, accordingly, attracted much attention, +and have furnished one of the stock arguments to prove the existence of +a blind but unerring instinct in the lower animals. The very general +belief that every bird is enabled to build its nest, not by the ordinary +faculties of observation, memory, and imitation, but by means of some +innate and mysterious impulse, has had the bad effect of withdrawing +attention from the very evident relation that exists between the +structure, habits, and intelligence of birds, and the kind of nests they +construct. + +In the preceding essay I have detailed several of these relations, and +they teach us, that a consideration of the structure, the food, and +other specialities of a bird's existence, will give a clue, and +sometimes a very complete one, to the reason why it builds its nest of +certain materials, in a definite situation, and in a more or less +elaborate manner. + +I now propose to consider the question from a more general point of +view, and to discuss its application to some important problems in the +natural history of birds. + + +_Changed Conditions and persistent Habits as influencing Nidification._ + +Besides the causes above alluded to, there are two other factors whose +effect in any particular case we can only vaguely guess at, but which +must have had an important influence in determining the existing details +of nidification. These are--changed conditions of existence, whether +internal or external, and the influence of hereditary or imitative +habit; the first inducing alterations in accordance with changes of +organic structure, of climate, or of the surrounding fauna and flora; +the other preserving the peculiarities so produced, even when changed +conditions render them no longer necessary. Many facts have been already +given which show that birds do adapt their nests to the situations in +which they place them, and the adoption of eaves, chimneys, and boxes, +by swallows, wrens, and many other birds, shows that they are always +ready to take advantage of changed conditions. It is probable, +therefore, that a permanent change of climate would cause many birds to +modify the form or materials of their abodes, so as better to protect +their young. The introduction of new enemies to eggs or young birds, +might introduce many alterations tending to their better concealment. A +change in the vegetation of a country, would often necessitate the use +of new materials. So, also, we may be sure, that as a species slowly +became modified in any external or internal characters, it would +necessarily change in some degree its mode of building. This effect +would be produced by modifications of the most varied nature; such as +the power and rapidity of flight, which must often determine the +distance to which a bird will go to obtain materials for its nest; the +capacity of sustaining itself almost motionless in the air, which must +sometimes determine the position in which a nest can be built; the +strength and grasping power of the foot in relation to the weight of the +bird, a power absolutely essential to the constructor of a +delicately-woven and well-finished nest; the length and fineness of the +beak, which has to be used like a needle in building the best textile +nests; the length and mobility of the neck, which is needful for the +same purpose; the possession of a salivary secretion like that used in +the nests of many of the swifts and swallows, as well as that of the +song-thrush--peculiarities of habits, which ultimately depend on +structure, and which often determine the material most frequently met +with or most easily to be obtained. Modifications in any of these +characters would necessarily lead, either to a change in the materials +of the nest, or in the mode of combining them in the finished +structure, or in the form or position of that structure. + +During all these changes, however, certain specialities of nest-building +would continue, for a shorter or a longer time after the causes which +had necessitated them had passed away. Such records of a vanished past +meet us everywhere, even in man's works, notwithstanding his boasted +reason. Not only are the main features of Greek architecture, mere +reproductions in stone of what were originally parts of a wooden +building, but our modern copyists of Gothic architecture often build +solid buttresses capped with weighty pinnacles, to support a wooden roof +which has no outward thrust to render them necessary; and even think +they ornament their buildings by adding sham spouts of carved stone, +while modern waterpipes, stuck on without any attempt at harmony, do the +real duty. So, when railways superseded coaches, it was thought +necessary to build the first-class carriages to imitate a number of +coach-bodies joined together; and the arm-loops for each passenger to +hold on by, which were useful when bad roads made every journey a +succession of jolts and lurches, were continued on our smooth +macadamised mail-routes, and, still more absurdly, remain to this day in +our railway carriages, the relic of a kind of locomotion we can now +hardly realize. Another good example is to be seen in our boots. When +elastic sides came into fashion we had been so long used to fasten them +with buttons or laces, that a boot without either looked bare and +unfinished, and accordingly the makers often put on a row of useless +buttons or imitation laces, because habit rendered the appearance of +them necessary to us. It is universally admitted that the habits of +children and of savages give us the best clue to the habits and mode of +thought of animals; and every one must have observed how children at +first imitate the actions of their elders, without any regard to the use +or applicability of the particular acts. So, in savages, many customs +peculiar to each tribe are handed down from father to son merely by the +force of habit, and are continued long after the purpose which they +originally served has ceased to exist. With these and a hundred similar +facts everywhere around us, we may fairly impute much of what we cannot +understand in the details of Bird-Architecture to an analogous cause. If +we do not do so, we must assume, either that birds are guided in every +action by pure reason to a far greater extent than men are, or that an +infallible instinct leads them to the same result by a different road. +The first theory has never, that I am aware of, been maintained by any +author, and I have already shown that the second, although constantly +assumed, has never been proved, and that a large body of facts is +entirely opposed to it. One of my critics has, indeed, maintained that I +admit "instinct" under the term "hereditary habit;" but the whole course +of my argument shows that I do not do so. Hereditary habit is, indeed, +the same as instinct when the term is applied to some simple action +dependent upon a peculiarity of structure which is hereditary; as when +the descendants of tumbler pigeons tumble, and the descendants of pouter +pigeons pout. In the present case, however, I compare it strictly to the +hereditary, or more properly, persistent or imitative, habits of +savages, in building their houses as their fathers did. Imitation is a +lower faculty than invention. Children and savages imitate before they +originate; birds, as well as all other animals, do the same. + +The preceding observations are intended to show, that the exact mode of +nidification of each species of bird is probably the result of a variety +of causes, which have been continually inducing changes in accordance +with changed organic or physical conditions. The most important of these +causes seem to be, in the first place, the structure of the species, +and, in the second, its environment or conditions of existence. Now we +know, that every one of the characters or conditions included under +these two heads is variable. We have seen that, on the large scale, the +main features of the nest built by each group of birds, bears a relation +to the organic structure of that group, and we have, therefore, a right +to infer, that as structure varies, the nest will vary also in some +particular corresponding to the changes of structure. We have seen also, +that birds change the position, the form, and the construction of their +nest, whenever the available materials or the available situations, vary +naturally or have been altered by man; and we have, therefore, a right +to infer that similar changes have taken place, when, by a natural +process, external conditions have become in any way permanently altered. +We must remember, however, that all these factors are very stable during +many generations, and only change at a rate commensurate with those of +the great physical features of the earth as revealed to us by geology; +and we may, therefore, infer that the form and construction of nests, +which we have shown to be dependent on them, are equally stable. If, +therefore, we find less important and more easily modified characters +than these, so correlated with peculiarities of nidification as to +indicate that one is probably the cause of the other, we shall be +justified in concluding that these variable characters are dependent on +the mode of nidification, and not that the form of the nest has been +determined by these variable characters. Such a correlation I am now +about to point out. + + +_Classification of Nests._ + +For the purpose of this inquiry it is necessary to group nests into two +great classes, without any regard to their most obvious differences or +resemblances, but solely looking to the fact of whether the contents +(eggs, young, or sitting bird) are hidden or exposed to view. In the +first class we place all those in which the eggs and young are +completely hidden, no matter whether this is effected by an elaborate +covered structure, or by depositing the eggs in some hollow tree or +burrow underground. In the second, we group all in which the eggs, +young, and sitting bird are exposed to view, no matter whether there is +the most beautifully formed nest, or none at all. Kingfishers, which +build almost invariably in holes in banks; Woodpeckers and Parrots, +which build in hollow trees; the Icteridae of America, which all make +beautiful covered and suspended nests; and our own Wren, which builds a +domed nest, are examples of the former; while our Thrushes, Warblers, +and Finches, as well as the Crowshrikes, Chatterers, and Tanagers of the +tropics, together with all Raptorial birds and Pigeons, and a vast +number of others in every part of the world, all adopt the latter mode +of building. + +It will be seen that this division of birds according to their +nidification, bears little relation to the character of the nest itself. +It is a functional not a structural classification. The most rude and +the most perfect specimens of bird-architecture are to be found in both +sections. It has, however, a certain relation to natural affinities, for +large groups of birds, undoubtedly allied, fall into one or the other +division exclusively. The species of a genus or of a family are rarely +divided between the two primary classes, although they are frequently +divided between the two very distinct modes of nidification that exist +in the first of them. + +All the Scansorial or climbing, and most of the Fissirostral or +wide-gaped birds, for example, build concealed nests; and, in the latter +group, the two families which build open nests, the Swifts and the +Goat-suckers, are undoubtedly very widely separated from the other +families with which they are associated in our classifications. The +Tits vary much in their mode of nesting, some making open nests +concealed in a hole, while others build domed or even pendulous covered +nests, but they all come under the same class. Starlings vary in a +similar way. The talking Mynahs, like our own starlings, build in holes, +the glossy starlings of the East (of the genus Calornis) form a hanging +covered nest, while the genus Sturnopastor builds in a hollow tree. One +of the most striking cases in which one family of birds is divided +between the two classes, is that of the Finches; for while most of the +European species build exposed nests, many of the Australian finches +make them dome-shaped. + + +_Sexual differences of Colour in Birds._ + +Turning now from the nests to the creatures who make them, let us +consider birds themselves from a somewhat unusual point of view, and +form them into separate groups, according as both sexes, or the males +only, are adorned with conspicuous colours. + +The sexual differences of colour and plumage in birds are very +remarkable, and have attracted much attention; and, in the case of +polygamous birds, have been well explained by Mr. Darwin's principle of +sexual selection. We can, to a great extent, understand how male +Pheasants and Grouse have acquired their more brilliant plumage and +greater size, by the continual rivalry of the males both in strength and +beauty; but this theory does not throw any light on the causes which +have made the female Toucan, Bee-eater, Parroquet, Macaw and Tit, in +almost every case as gay and brilliant as the male, while the gorgeous +Chatterers, Manakins, Tanagers, and Birds of Paradise, as well as our +own Blackbird, have mates so dull and inconspicuous that they can hardly +be recognised as belonging to the same species. + + +_The Law which connects the Colours of Female Birds with the mode of +Nidification._ + +The above-stated anomaly can, however, now be explained by the influence +of the mode of nidification, since I find that, with but very few +exceptions, it is the rule--_that when both sexes are of strikingly gay +and conspicuous colours, the nest is of the first class, or such as to +conceal the sitting bird; while, whenever there is a striking contrast +of colours, the male being gay and conspicuous, the female dull and +obscure, the nest is open and the sitting bird exposed to view_. I will +now proceed to indicate the chief facts that support this statement, and +will afterwards explain the manner in which I conceive the relation has +been brought about. + +We will first consider those groups of birds in which the female is +gaily or at least conspicuously coloured, and is in most cases exactly +like the male. + +1. Kingfishers (Alcedinidae). In some of the most brilliant species of +this family the female exactly resembles the male; in others there is a +sexual difference, but it rarely tends to make the female less +conspicuous. In some, the female has a band across the breast, which is +wanting in the male, as in the beautiful Halcyon diops of Ternate. In +others the band is rufous in the female, as in several of the American +species; while in Dacelo gaudichaudii, and others of the same genus, the +tail of the female is rufous, while that of the male is blue. In most +kingfishers the nest is in a deep hole in the ground; in Tanysiptera it +is said to be in a hole in the nests of termites, or sometimes in +crevices under overhanging rocks. + +2. Motmots (Momotidae). In these showy birds the sexes are exactly alike, +and the nest in a hole under ground. + +3. Puff-birds (Bucconidae). These birds are often gaily coloured; some +have coral-red bills; the sexes are exactly alike, and the nest is in a +hole in sloping ground. + +4. Trogons (Trogonidae). In these magnificent birds the females are +generally less brightly coloured than the males, but are yet often gay +and conspicuous. The nest is in a hole of a tree. + +5. Hoopoes (Upupidae). The barred plumage and long crests of these birds +render them conspicuous. The sexes are exactly alike, and the nest is in +a hollow tree. + +6. Hornbills (Bucerotidae). These large birds have enormous coloured +bills, which are generally quite as well coloured and conspicuous in the +females. Their nests are always in hollow trees, where the female is +entirely concealed. + +7. Barbets (Capitonidae). These birds are all very gaily-coloured, and, +what is remarkable, the most brilliant patches of colour are disposed +about the head and neck, and are very conspicuous. The sexes are +exactly alike, and the nest is in a hole of a tree. + +8. Toucans (Rhamphastidae). These fine birds are coloured in the most +conspicuous parts of their body, especially on the large bill, and on +the upper and lower tail coverts, which are crimson, white, or yellow. +The sexes are exactly alike, and they always build in a hollow tree. + +9. Plaintain-eaters (Musophagidae). Here again the head and bill are most +brilliantly coloured in both sexes, and the nest is in a hole of a tree. + +10. Ground cuckoos (Centropus). These birds are often of conspicuous +colours, and are alike in both sexes. They build a domed nest. + +11. Woodpeckers (Picidae). In this family the females often differ from +the males, in having a yellow or white, instead of a crimson crest, but +are almost as conspicuous. They all nest in holes in trees. + +12. Parrots (Psittaci). In this great tribe, adorned with the most +brilliant and varied colours, the rule is, that the sexes are precisely +alike, and this is the case in the most gorgeous families, the lories, +the cockatoos, and the macaws; but in some there is a sexual difference +of colour to a slight extent. All build in holes, mostly in trees, but +sometimes in the ground, or in white ants' nests. In the single case in +which the nest is exposed, that of the Australian ground parrot, +Pezoporus formosus, the bird has lost the gay colouring of its allies, +and is clothed in sombre and completely protective tints of dusky green +and black. + +13. Gapers (Eurylaemidae). In these beautiful Eastern birds, somewhat +allied to the American chatterers, the sexes are exactly alike, and are +adorned with the most gay and conspicuous markings. The nest is a woven +structure, _covered over_, and suspended from the extremities of +branches over water. + +14. Pardalotus (Ampelidae). In these Australian birds the females differ +from the males, but are often very conspicuous, having brightly-spotted +heads. Their nests are sometimes dome-shaped, sometimes in holes of +trees, or in burrows in the ground. + +15. Tits (Paridae). These little birds are always pretty, and many +(especially among the Indian species) are very conspicuous. They always +have the sexes alike, a circumstance very unusual among the smaller +gaily-coloured birds of our own country. The nest is always covered over +or concealed in a hole. + +16. Nuthatches (Sitta). Often very pretty birds, the sexes alike, and +the nest in a hole. + +17.---- (Sittella). The female of these Australian nuthatches is often +the most conspicuous, being white-and black-marked. The nest is, +according to Gould, "completely concealed among upright twigs connected +together." + +18. Creepers (Climacteris). In these Australian creepers the sexes are +alike, or the female most conspicuous, and the nest is in a hole of a +tree. + +19. Estrelda, Amadina. In these genera of Eastern and Australian finches +the females, although more or less different from the males, are still +very conspicuous having a red rump, or being white spotted. They differ +from most others of the family in building domed nests. + +20. Certhiola. In these pretty little American creepers the sexes are +alike, and they build a domed nest. + +21. Mynahs (Sturnidae). These showy Eastern starlings have the sexes +exactly alike. They build in holes of trees. + +22. Calornis (Sturnidae). These brilliant metallic starlings have no +sexual differences. They build a pensile covered nest. + +23. Hangnests (Icteridae). The red or yellow and black plumage of most of +these birds is very conspicuous, and is exactly alike in both sexes. +They are celebrated for their fine purse-shaped pensile nests. + +It will be seen that this list comprehends six important families of +Fissirostres, four of Scansores, the Psittaci, and several genera, with +three entire families of Passeres, comprising about twelve hundred +species, or about one-seventh of all known birds. + + * * * * * + +The cases in which, whenever the male is gaily coloured, the female is +much less gay or quite inconspicuous, are exceedingly numerous, +comprising, in fact, almost all the bright-coloured Passeres, except +those enumerated in the preceding class. The following are the most +remarkable:-- + +1. Chatterers (Cotingidae). These comprise some of the most gorgeous +birds in the world, vivid blues, rich purples, and bright reds, being +the most characteristic colours. The females are always obscurely +tinted, and are often of a greenish hue, not easily visible among the +foliage. + +2. Manakins (Pipridae). These elegant birds, whose caps or crests are of +the most brilliant colours, are usually of a sombre green in the female +sex. + +3. Tanagers (Tanagridae). These rival the chatterers in the brilliancy of +their colours, and are even more varied. The females are generally of +plain and sombre hues, and always less conspicuous than the males. + +In the extensive families of the warblers (Sylviadae), thrushes +(Turdidae), flycatchers (Muscicapidae), and shrikes (Laniadae), a +considerable proportion of the species are beautifully marked with gay +and conspicuous tints, as is also the case in the Pheasants and Grouse; +but in every case the females are less gay, and are most frequently of +the very plainest and least conspicuous hues. Now, throughout _the whole +of these families the nest is open_, and I am not aware of a single +instance in which any one of these birds builds a _domed nest_, or +places it in a _hole of a tree_, or _underground_, or in any place where +it is effectually concealed. + +In considering the question we are now investigating, it is not +necessary to take into account the larger and more powerful birds, +because these seldom depend much on concealment to secure their safety. +In the raptorial birds bright colours are as a rule absent; and their +structure and habits are such as not to require any special protection +for the female. The larger waders are sometimes very brightly coloured +in both sexes; but they are probably little subject to the attacks of +enemies, since the scarlet ibis, the most conspicuous of birds, exists +in immense quantities in South America. In game birds and water-fowl, +however, the females are often very plainly coloured, when the males are +adorned with brilliant hues; and the abnormal family of the Megapodidae +offers us the interesting fact of an identity in the colours of the +sexes (which in Megacephalon and Talegalla are somewhat conspicuous), in +conjunction with the habit of not sitting on the eggs at all. + + +_What the Facts Teach us._ + +Taking the whole body of evidence here brought forward, embracing as it +does almost every group of bright-coloured birds, it will, I think, be +admitted that the relation between the two series of facts in the +colouring and nidification of birds has been sufficiently established. +There are, it is true, a few apparent and some real exceptions, which I +shall consider presently; but they are too few and unimportant to weigh +much against the mass of evidence on the other side, and may for the +present be neglected. Let us then consider what we are to do with this +unexpected set of correspondences between groups of phenomena which, at +first sight, appear so disconnected. Do they fall in with any other +groups of natural phenomena? Do they teach us anything of the way in +which nature works, and give us any insight into the causes which have +brought about the marvellous variety, and beauty, and harmony of living +things? I believe we can answer these questions in the affirmative; and +I may mention, as a sufficient proof that these are not isolated facts, +that I was first led to see their relation to each other by the study of +an analogous though distinct set of phenomena among insects, that of +protective resemblance and "mimicry." + +On considering this remarkable series of corresponding facts, the first +thing we are taught by them seems to be, that there is no incapacity in +the female sex among birds, to receive the same bright hues and strongly +contrasted tints with which their partners are so often decorated, since +whenever they are _protected and concealed_ during the period of +incubation _they are similarly adorned_. The fair inference is, that it +is chiefly due to the absence of protection or concealment during this +important epoch, that gay and conspicuous tints are withheld or left +undeveloped. The mode in which this has been effected is very +intelligible, if we admit the action of natural and sexual selection. It +would appear from the numerous cases in which both sexes are adorned +with equally brilliant colours (while both sexes are rarely armed with +equally developed offensive and defensive weapons when not required for +individual safety), that the normal action of "sexual selection" is to +develop colour and beauty in both sexes, by the preservation and +multiplication of all varieties of colour in either sex which are +pleasing to the other. Several very close observers of the habits of +animals have assured me, that male birds and quadrupeds do often take +very strong likes and dislikes to individual females, and we can hardly +believe that the one sex (the female) can have a general taste for +colour while the other has no such taste. However this may be, the fact +remains, that in a vast number of cases the female acquires as brilliant +and as varied colours as the male, and therefore most probably acquires +them in the same way as the male does; that is, either because the +colour is useful to it, or is correlated with some useful variation, or +is pleasing to the other sex. The only remaining supposition is that it +is transmitted from the other sex, without being of any use. From the +number of examples above adduced of bright colours in the female, this +would imply that colour-characters acquired by one sex are generally +(but not necessarily) transmitted to the other. If this be the case it +will, I think, enable us to explain the phenomena, even if we do not +admit that the male bird is ever influenced in the choice of a mate by +her more gay or perfect plumage. + +The female bird, while sitting on her eggs in an uncovered nest, is much +exposed to the attacks of enemies, and any modification of colour which +rendered her more conspicuous would often lead to her destruction and +that of her offspring. All variations of colour in this direction in the +female, would therefore sooner or later be eliminated, while such +modifications as rendered her inconspicuous, by assimilating her to +surrounding objects, as the earth or the foliage, would, on the whole, +survive the longest, and thus lead to the attainment of those brown or +green and inconspicuous tints, which form the colouring (of the upper +surface at least), of the vast majority of female birds which sit upon +open nests. + +This does not imply, as some have thought, that all female birds were +once as brilliant as the males. The change has been a very gradual one, +generally dating from the origin of genera or of larger groups, but +there can be no doubt that the remote ancestry of birds having great +sexual differences of colour, were nearly or quite alike, sometimes +(perhaps in most cases) more nearly resembling the female, but +occasionally perhaps being nearer what the male is now. The young birds +(which usually resemble the females) will probably give some idea of +this ancestral type, and it is well known that the young of allied +species and of different sexes are often undistinguishable. + + +_Colour more variable than Structure or Habits, and therefore the +Character which has generally been Modified._ + +At the commencement of this essay, I have endeavoured to prove, that the +characteristic differences and the essential features of birds' nests, +are dependent on the structure of the species and upon the present and +past conditions of their existence. Both these factors are more +important and less variable than colour; and we must therefore conclude +that in most cases the mode of nidification (dependent on structure and +environment) has been the cause, and not the effect, of the similarity +or differences of the sexes as regards colour. When the confirmed habit +of a group of birds, was to build their nests in holes of trees like the +toucans, or in holes in the ground like the kingfishers, the protection +the female thus obtained, during the important and dangerous time of +incubation, placed the two sexes on an equality as regards exposure to +attack, and allowed "sexual selection," or any other cause, to act +unchecked in the development of gay colours and conspicuous markings in +both sexes. + +When, on the other hand (as in the Tanagers and Flycatchers), the habit +of the whole group was to build open cup-shaped nests in more or less +exposed situations, the production of colour and marking in the female, +by whatever cause, was continually checked by its rendering her too +conspicuous, while in the male it had free play, and developed in him +the most gorgeous hues. This, however, was not perhaps universally the +case; for where there was more than usual intelligence and capacity for +change of habits, the danger the female was exposed to by a partial +brightness of colour or marking might lead to the construction of a +concealed or covered nest, as in the case of the Tits and Hangnests. +When this occurred, a special protection to the female would be no +longer necessary; so that the acquisition of colour and the modification +of the nest, might in some cases act and react on each other and attain +their full development together. + + +_Exceptional Cases confirmatory of the above Explanation._ + +There exist a few very curious and anomalous facts in the natural +history of birds, which fortunately serve as crucial tests of the truth +of this mode of explaining the inequalities of sexual colouration. It +has been long known, that in some species the males either assisted in, +or wholly performed, the act of incubation. It has also been often +noticed, that in certain birds the usual sexual differences were +reversed, the male being the more plainly coloured, the female more gay +and often larger. I am not, however, aware that these two anomalies had +ever been supposed to stand to each other in the relation of cause and +effect, till I adduced them in support of my views of the general theory +of protective adaptation. Yet it is undoubtedly the fact, that in the +best known cases in which the female bird is more conspicuously coloured +than the male, it is either positively ascertained that the latter +performs the duties of incubation, or there are good reasons for +believing such to be the case. The most satisfactory example is that of +the Gray Phalarope (Phalaropus fulicarius), the sexes of which are alike +in winter, while in summer the female instead of the male takes on a gay +and conspicuous nuptial plumage; but the male performs the duties of +incubation, sitting upon the eggs, which are laid upon the bare ground. + +In the Dotterell (Eudromias morinellus) the female is larger and more +brightly coloured than the male; and here, also, it is almost certain +that the latter sits upon the eggs. The Turnices of India also, have the +female larger and often more brightly coloured; and Mr. Jerdon states, +in his "Birds of India," that the natives report, that, during the +breeding season, the females desert their eggs and associate in flocks, +while the males are employed in hatching the eggs. In the few other +cases in which the females are more brightly coloured, the habits are +not accurately known. The case of the Ostriches and Emeus will occur to +many as a difficulty, for here the male incubates, but is not less +conspicuous than the female; but there are two reasons why the case does +not apply;--the birds are too large to derive any safety from +concealment, from enemies which would devour the eggs they can defend +themselves by force, while to escape from their personal foes they trust +to speed. + +We find, therefore, that a very large mass of facts relating to the +sexual colouration and the mode of nidification of birds, including some +of the most extraordinary anomalies to be found in their natural +history, can be shown to have an interdependent relation to each other, +on the simple principle of the need of greater protection to that parent +which performs the duties of incubation. Considering the very imperfect +knowledge we possess of the habits of most extra-European birds, the +exceptions to the prevalent rule are few, and generally occur in +isolated species or in small groups; while several apparent exceptions +can be shown to be really confirmations of the law. + + +_Real or apparent Exceptions to the Law stated at page 240._ + +The only marked exceptions I have been able to discover are the +following:-- + +1. King crows (Dicrourus). These birds are of a glossy black colour with +long forked tails. The sexes present no difference, and they build open +nests. This apparent exception may probably be accounted for by the fact +that these birds do not need the protection of a less conspicuous +colour. They are very pugnacious, and often attack and drive away crows, +hawks, and kites; and as they are semi-gregarious in their habits, the +females are not likely to be attacked while incubating. + +2. Orioles (Oriolidae). The true orioles are very gay birds; the sexes +are, in many Eastern species, either nearly or quite alike, and the +nests are open. This is one of the most serious exceptions, but it is +one that to some extent proves the rule; for in this case it has been +noticed, that the parent birds display excessive care and solicitude in +concealing the nest among thick foliage, and in protecting their +offspring by incessant and anxious watching. This indicates that the +want of protection consequent on the bright colour of the female makes +itself felt, and is obviated by an increased development of the mental +faculties. + +3. Ground thrushes (Pittidae). These elegant and brilliantly-coloured +birds are generally alike in both sexes, and build an open nest. It is +curious, however, that this is only an apparent exception, for almost +all the bright colours are on the under surface, the back being usually +olive green or brown, and the head black, with brown or whitish stripes, +all which colours would harmonize with the foliage, sticks, and roots +which surround the nest, built on or near the ground, and thus serve as +a protection to the female bird. + +4. Grallina Australis. This Australian bird is of strongly contrasted +black and white colours. The sexes are exactly alike, and it builds an +open clay nest in an exposed situation on a tree. This appears to be a +most striking exception, but I am by no means sure that it is so. We +require to know what tree it usually builds on, the colour of the bark +or of the lichens that grow upon it, the tints of the ground, or of +other surrounding objects, before we can say that the bird, when sitting +on its nest, is really conspicuous. It has been remarked that small +patches of white and black blend at a short distance to form grey, one +of the commonest tints of natural objects. + +5. Sunbirds (Nectarineidae). In these beautiful little birds the males +only are adorned with brilliant colours, the females being quite plain, +yet they build covered nests in all the cases in which the nidification +is known. This is a negative rather than a positive exception to the +rule, since there may be other causes besides the need for protection, +which prevent the female acquiring the gay colours of her mate, and +there is one curious circumstance which tends to elucidate it. The male +of Leptocoma zeylanica is said to assist in incubation. It is possible, +therefore, that the group may originally have used open nests, and some +change of conditions, leading the male bird to sit, may have been +followed by the adoption of a domed nest. This is, however, the most +serious exception I have yet found to the general rule. + +6. Superb warblers (Maluridae). The males of these little birds are +adorned with the most gorgeous colours, while the females are very +plain, yet they make domed nests. It is to be observed, however, that +the male plumage is nuptial merely, and is retained for a very short +time; the rest of the year both sexes are plain alike. It is probable, +therefore, that the domed nest is for the protection of these delicate +little birds against the rain, and that there is some unknown cause +which has led to the development of colour in the males only. + +There is one other case which at first sight looks like an exception, +but which is far from being one in reality, and deserves to be +mentioned. In the beautiful Waxwing, (Bombycilla garrula,) the sexes are +very nearly alike, and the elegant red wax tips to the wing-feathers are +nearly, and sometimes quite, as conspicuous in the female as in the +male. Yet it builds an open nest, and a person looking at the bird would +say it ought according to my theory to cover its nest. But it is, in +reality, as completely protected by its colouration as the most plainly +coloured bird that flies. It breeds only in very high latitudes, and the +nest, placed in fir-trees, is formed chiefly of lichens. Now the +delicate gray and ashy and purplish hues of the head and back, together +with the yellow of the wings and tail, are tints that exactly harmonize +with the colours of various species of lichens, while the brilliant red +wax tips exactly represent the crimson fructification of the common +lichen, Cladonia coccifera. When sitting on its nest, therefore, the +female bird will exhibit no colours that are not common to the materials +of which it is constructed; and the several tints are distributed in +about the same proportions as they occur in nature. At a short distance +the bird would be indistinguishable from the nest it is sitting on, or +from a natural clump of lichens, and will thus be completely protected. + +I think I have now noticed all exceptions of any importance to the law +of dependence of sexual colour on nidification. It will be seen that +they are very few in number, compared with those which support the +generalization; and in several cases there are circumstances in the +habits or structure of the species that sufficiently explain them. It is +remarkable also that I have found scarcely any _positive_ exceptions, +that is, cases of very brilliant or conspicuous female birds in which +the nest was not concealed. Much less can there be shown any group of +birds, in which the females are all of decidedly conspicuous colours on +the upper surface, and yet sit in open nests. The many cases in which +birds of dull colours in both sexes make domed or concealed nests, do +not, of course, affect this theory one way or the other; since its +purpose is only to account for the fact, that brilliant females of +brilliant males are _always_ found to have covered or hidden nests, +while obscure females of brilliant males _almost always_ have open and +exposed nests. The fact that all classes of nests occur with dull +coloured birds in both sexes merely shows, as I have strongly +maintained, that in most cases the character of the nest determines the +colouration of the female, and not _vice versa_. + +If the views here advocated are correct, as to the various influences +that have determined the specialities of every bird's nest, and the +general colouration of female birds, with their action and reaction on +each other, we can hardly expect to find evidence more complete than +that here set forth. Nature is such a tangled web of complex relations, +that a series of correspondences running through hundreds of species, +genera, and families, in every part of the system, can hardly fail to +indicate a true casual connexion; and when, of the two factors in the +problem, one can be shown to be dependent on the most deeply seated and +the most stable facts of structure and conditions of life, while the +other is a character universally admitted to be superficial and easily +modified, there can be little doubt as to which is cause and which +effect. + + +_Various modes of Protection of Animals._ + +But the explanation of the phenomenon here attempted does not rest alone +on the facts I have been able now to adduce. In the essay on "Mimicry," +it is shown how important a part the necessity for protection has +played, in determining the external form and colouration, and sometimes +even the internal structure of animals. + +As illustrating this latter point, I may refer to the remarkable hooked, +branched, or star-like spiculae in many sponges, which are believed to +have the function chiefly, of rendering them unpalatable to other +creatures. The Holothuridae or sea-cucumbers possess a similar +protection, many of them having anchor-shaped spicules embedded in their +skin, as the Synapta; while others (Cuviera squamata) are covered with a +hard calcareous pavement. Many of these are of a bright red or purple +colour, and are very conspicuous, while the allied Trepang, or +Beche-de-mer (Holothuria edulis), which is not armed with any such +defensive weapons, is of a dull sand-or mud-colour, so as hardly to be +distinguished from the sea bed on which it reposes. Many of the smaller +marine animals are protected by their almost invisible transparency, +while those that are most brightly coloured will be often found to have +a special protection, either in stinging tentacles like Physalia, or in +a hard calcareous crust, as in the star fishes. + + +_Females of some Groups require and obtain more Protection than the +Males._ + +In the struggle for existence incessantly going on, protection or +concealment is one of the most general and most effectual means of +maintaining life; and it is by modifications of colour that this +protection can be most readily obtained, since no other character is +subject to such numerous and rapid variations. The case I have now +endeavoured to illustrate is exactly analogous to what occurs among +butterflies. As a general rule, the female butterfly is of dull and +inconspicuous colours, even when the male is most gorgeously arrayed; +but when the species is protected from attack by a disagreeable odour, +as in the Heliconidae, Danaidae and Acroeidae, both sexes display the same +or equally brilliant hues. Among the species which gain a protection by +imitating these, the very weak and slow-flying Leptalides resemble them +in both sexes, because both sexes alike require protection, while in the +more active and strong-winged genera--Papilio, Pieris, and Diadema--it +is generally the females only that mimic the protected groups, and in +doing so often become actually more gay and more conspicuous than the +males, thus reversing the usual and in fact almost universal characters +of the sexes. So, in the wonderful Eastern leaf-insects of the genus +Phyllium, it is the female only that so marvellously imitates a green +leaf; and in all these cases the difference can be traced to the greater +need of protection for the female, on whose continued existence, while +depositing her eggs, the safety of the race depends. In Mammalia and in +reptiles, however brilliant the colours may be, there is rarely any +difference between that of the sexes, because the female is not +necessarily more exposed to attack than the male. It may, I think, be +looked upon as a confirmation of this view, that no single case is known +either in the above-named genera--Papilio, Pieris, and Diadema--or in +any other butterfly, of a male _alone_, mimicking one of the Danaidae or +Heliconidae. Yet the necessary colour is far more abundant in the males, +and variations always seem ready for any useful purpose. This seems to +depend on the general law, that each species and each sex can only be +modified just as far as is absolutely necessary for it to maintain +itself in the struggle for existence, not a step further. A male insect +by its structure and habits is less exposed to danger, and also requires +less protection than the female. It cannot, therefore, alone acquire any +further protection through the agency of natural selection. But the +female requires some extra protection, to balance the greater danger to +which she is exposed, and her greater importance to the existence of the +species; and this she always acquires, in one way or another, through +the action of natural selection. + +In his "Origin of Species," fourth edition, p. 241, Mr. Darwin +recognises the necessity for protection as sometimes being a cause of +the obscure colours of female birds; but he does not seem to consider it +so very important an agent in modifying colour as I am disposed to do. +In the same paragraph (p. 240), he alludes to the fact of female birds +and butterflies being sometimes very plain, sometimes as gay as the +males; but, apparently, considers this mainly due to peculiar laws of +inheritance, which sometimes continue acquired colour in the line of one +sex only, sometimes in both. Without denying the action of such a law +(which Mr. Darwin informs me he has facts to support), I impute the +difference, in the great majority of cases, to the greater or less need +of protection in the female sex in these groups of animals. + +This need was seen to exist a century ago by the Hon. Daines Barrington, +who, in the article already quoted (see p. 220), after alluding to the +fact that singing birds are all small, and suggesting (but I think +erroneously) that this may have arisen from the difficulty larger birds +would have in concealing themselves if they called the attention of +their enemies by loud notes, goes on thus:--"I should rather conceive it +is for the same reason no hen bird sings, because this talent would be +still more dangerous during incubation, which _may possibly also account +for the inferiority in point of plumage_." This is a curious +anticipation of the main idea on which this essay is founded. It has +been unnoticed for near a century, and my attention was only recently +called to it by Mr. Darwin himself. + + +_Conclusion._ + +To some persons it will perhaps appear, that the causes to which I +impute so much of the external aspect of nature are too simple, too +insignificant, and too unimportant for such a mighty work. But I would +ask them to consider, that the great object of all the peculiarities of +animal structure is to preserve the life of the individual, and to +maintain the existence of the species. Colour has hitherto been too +often looked upon as something adventitious and superficial, something +given to an animal not to be useful to itself, but solely to gratify man +or even superior beings--to add to the beauty and ideal harmony of +nature. If this were the case, then, it is evident that the colours of +organised beings would be an exception to most other natural phenomena. +They would not be the product of general laws, or determined by +ever-changing external conditions; and we must give up all enquiry into +their origin and causes, since (by the hypothesis) they are dependent on +a Will whose motives must ever be unknown to us. But, strange to say, no +sooner do we begin to examine and classify the colours of natural +objects, than we find that they are intimately related to a variety of +other phenomena, and are, like them, strictly subordinated to general +laws. I have here attempted to elucidate some of these laws in the case +of birds, and have shown how the mode of nidification has affected the +colouring of the female sex in this group. I have before shown to how +great an extent, and in how many ways, the need of protection has +determined the colours of insects, and of some groups of reptiles and +mammalia, and I would now call particular attention to the fact that the +gay tints of flowers, so long supposed to be a convincing proof that +colour has been bestowed for other purposes than the good of its +possessor, have been shown by Mr. Darwin to follow the same great law of +utility. Flowers do not often need protection, but very often require +the aid of insects to fertilize them, and maintain their reproductive +powers in the greatest vigour. Their gay colours attract insects, as do +also their sweet odours and honeyed secretions; and that this is the +main function of colour in flowers is shown by the striking fact, that +those flowers which can be perfectly fertilized by the wind, and do not +need the aid of insects, _rarely or never have gaily-coloured flowers_. + +This wide extension of the general principle of utility to the colours +of such varied groups, both in the animal and vegetable kingdoms, +compels us to acknowledge that the "reign of law" has been fairly traced +into this stronghold of the advocates of special creation. And to those +who oppose the explanation I have given of the facts adduced in this +essay, I would again respectfully urge that they must grapple with the +whole of the facts, not one or two of them only. It will be admitted +that, on the theory of evolution and natural selection, a wide range of +facts with regard to colour in nature have been co-ordinated and +explained. Until at least an equally wide range of facts can be shown to +be in harmony with any other theory, we can hardly be expected to +abandon that which has already done such good service, and which has led +to the discovery of so many interesting and unexpected harmonies among +the most common (but hitherto most neglected and least understood), of +the phenomena presented by organised beings. + + + + +VIII. + +CREATION BY LAW. + + +Among the various criticisms that have appeared on Mr. Darwin's +celebrated "Origin of Species," there is, perhaps, none that will appeal +to so large a number of well educated and intelligent persons, as that +contained in the Duke of Argyll's "Reign of Law." The noble author +represents the feelings and expresses the ideas of that large class, who +take a keen interest in the progress of Science in general, and +especially that of Natural History, but have never themselves studied +nature in detail, or acquired that personal knowledge of the structure +of closely allied forms,--the wonderful gradations from species to +species and from group to group, and the infinite variety of the +phenomena of "variation" in organic beings,--which are absolutely +necessary for a full appreciation of the facts and reasonings contained +in Mr. Darwin's great work. + +Nearly half of the Duke's book is devoted to an exposition of his idea +of "Creation by Law," and he expresses so clearly what are his +difficulties and objections as regards the theory of "Natural +Selection," that I think it advisable that they should be fairly +answered, and that his own views should be shown to lead to conclusions, +as hard to accept as any which he imputes to Mr. Darwin. + +The point on which the Duke of Argyll lays most stress, is, that proofs +of Mind everywhere meet us in Nature, and are more especially manifest +wherever we find "contrivance" or "beauty." He maintains that this +indicates the constant supervision and direct interference of the +Creator, and cannot possibly be explained by the unassisted action of +any combination of laws. Now, Mr. Darwin's work has for its main object, +to show, that all the phenomena of living things,--all their wonderful +organs and complicated structures, their infinite variety of form, size, +and colour, their intricate and involved relations to each other,--may +have been produced by the action of a few general laws of the simplest +kind, laws which are in most cases mere statements of admitted facts. +The chief of these laws or facts are the following:-- + +1. _The Law of Multiplication in Geometrical Progression._--All +organized beings have enormous powers of multiplication. Even man, who +increases slower than all other animals, could under the most favourable +circumstances double his numbers every fifteen years, or a hundred-fold +in a century. Many animals and plants could increase their numbers from +ten to a thousand-fold every year. + +2. _The Law of Limited Populations._--The number of living individuals +of each species in any country, or in the whole globe, is practically +stationary; whence it follows that the whole of this enormous increase +must die off almost as fast as produced, except only those individuals +for whom room is made by the death of parents. As a simple but striking +example, take an oak forest. Every oak will drop annually thousands or +millions of acorns, but till an old tree falls, not one of these +millions can grow up into an oak. They must die at various stages of +growth. + +3. _The Law of Heredity, or Likeness of Offspring to their +Parents._--This is a universal, but not an absolute law. All creatures +resemble their parents in a high degree, and in the majority of cases +very accurately; so that even individual peculiarities, of whatever +kind, in the parents, are almost always transmitted to some of the +offspring. + +4. _The Law of Variation._--This is fully expressed by the lines:-- + + "No being on this earthly ball, + Is like another, all in all." + +Offspring resemble their parents very much, but not wholly--each being +possesses its individuality. This "variation" itself varies in amount, +but it is always present, not only in the whole being, but in every part +of every being. Every organ, every character, every feeling is +individual; that is to say, _varies_ from the same organ, character, or +feeling in every other individual. + +5. _The Law of unceasing Change of Physical Conditions upon the Surface +of the Earth._--Geology shows us that this change has always gone on in +times past, and we also know that it is now everywhere going on. + +6. _The Equilibrium or Harmony of Nature._--When a species is well +adapted to the conditions which environ it, it flourishes; when +imperfectly adapted it decays; when ill-adapted it becomes extinct. If +_all_ the conditions which determine an organism's well-being are taken +into consideration, this statement can hardly be disputed. + + * * * * * + +This series of facts or laws, are mere statements of what is the +condition of nature. They are facts or inferences which are generally +known, generally admitted--but in discussing the subject of the "Origin +of Species"--as generally forgotten. It is from these universally +admitted facts, that the origin of all the varied forms of nature may be +deduced by a logical chain of reasoning, which, however, is at every +step verified and shown to be in strict accord with facts; and, at the +same time, many curious phenomena which can by no other means be +understood, are explained and accounted for. It is probable, that these +primary facts or laws are but results of the very nature of life, and of +the essential properties of organized and unorganized matter. Mr. +Herbert Spencer, in his "First Principles" and his "Biology" has, I +think, made us able to understand how this may be; but at present we may +accept these simple laws without going further back, and the question +then is--whether the variety, the harmony, the contrivance, and the +beauty we perceive in organic beings, can have been produced by the +action of these laws alone, or whether we are required to believe in the +incessant interference and direct action of the mind and will of the +Creator. It is simply a question of how the Creator has worked. The +Duke (and I quote him as having well expressed the views of the more +intelligent of Mr. Darwin's opponents) maintains, that He has personally +applied general laws to produce effects, which those laws are not in +themselves capable of producing; that the universe alone, with all its +laws intact, would be a sort of chaos, without variety, without harmony, +without design, without beauty; that there is not (and therefore we may +presume that there could not be) any self-developing power in the +universe. I believe, on the contrary, that the universe is so +constituted as to be self-regulating; that as long as it contains Life, +the forms under which that life is manifested have an inherent power of +adjustment to each other and to surrounding nature; and that this +adjustment necessarily leads to the greatest amount of variety and +beauty and enjoyment, because it does depend on general laws, and not on +a continual supervision and re-arrangement of details. As a matter of +feeling and religion, I hold this to be a far higher conception of the +Creator and of the Universe than that which may be called the "continual +interference" hypothesis; but it is not a question to be decided by our +feelings or convictions, it is a question of facts and of reason. Could +the change, which Geology shows us has ever taken place in the forms of +life, have been produced by general laws, or does it imperatively +require the incessant supervision of a creative mind? This is the +question for us to consider, and our opponents have the difficult task +of proving a negative, if we show that there are both facts and +analogies in our favour. + + +_Mr. Darwin's Metaphors liable to Misconception._ + +Mr. Darwin has laid himself open to much misconception, and has given to +his opponents a powerful weapon against himself, by his continual use of +metaphor in describing the wonderful co-adaptations of organic beings. + +"It is curious," says the Duke of Argyll, "to observe the language +which this most advanced disciple of pure naturalism instinctively +uses, when he has to describe the complicated structure of this curious +order of plants (the Orchids). 'Caution in ascribing intentions to +nature,' does not seem to occur to him as possible. Intention is the one +thing which he does see, and which, when he does not see, he seeks for +diligently until he finds it. He exhausts every form of words and of +illustration, by which intention or mental purpose can be described. +'Contrivance'--'curious contrivance,'--'beautiful contrivance,'--these +are expressions which occur over and over again. Here is one sentence +describing the parts of a particular species: 'the Labellum is developed +into a long nectary, _in order_ to attract Lepidoptera, and we shall +presently give reason for suspecting that the nectar is _purposely_ so +lodged, that it can be sucked only slowly _in order_ to give time for +the curious chemical quality of the viscid matter setting hard and +dry.'" Many other examples of similar expressions are quoted by the +Duke, who maintains that no explanation of these "contrivances" has +been or can be given, except on the supposition of a personal contriver, +specially arranging the details of each case, although causing them to +be produced by the ordinary processes of growth and reproduction. + +Now there is a difficulty in this view of the origin of the structure of +Orchids which the Duke does not allude to. The majority of flowering +plants are fertilized, either without the agency of insects or, when +insects are required, without any very important modification of the +structure of the flower. It is evident, therefore, that flowers might +have been formed as varied, fantastic, and beautiful as the Orchids, and +yet have been fertilized without more complexity of structure than is +found in Violets, or Clover, or Primroses, or a thousand other flowers. +The strange springs and traps and pitfalls found in the flowers of +Orchids cannot be necessary _per se_, since exactly the same end is +gained in ten thousand other flowers which do not possess them. Is it +not then an extraordinary idea, to imagine the Creator of the Universe +_contriving_ the various complicated parts of these flowers, as a +mechanic might contrive an ingenious toy or a difficult puzzle? Is it +not a more worthy conception that they are some of the results of those +general laws which were so co-ordinated at the first introduction of +life upon the earth as to result necessarily in the utmost possible +development of varied forms? + +But let us take one of the simpler cases adduced and see if our general +laws are unable to account for it. + + +_A Case of Orchis-structure explained by Natural Selection._ + +There is a Madagascar Orchis--the Angraecum sesquipedale--with an +immensely long and deep nectary. How did such an extraordinary organ +come to be developed? Mr. Darwin's explanation is this. The pollen of +this flower can only be removed by the base of the proboscis of some +very large moths, when trying to get at the nectar at the bottom of the +vessel. The moths with the longest probosces would do this most +effectually; they would be rewarded for their long tongues by getting +the most nectar; whilst on the other hand, the flowers with the deepest +nectaries would be the best fertilized by the largest moths preferring +them. Consequently, the deepest nectaried Orchids and the longest +tongued moths would each confer on the other an advantage in the battle +of life. This would tend to their respective perpetuation, and to the +constant lengthening of nectaries and probosces. Now let it be +remembered, that what we have to account for, is only the unusual length +of this organ. A nectary is found in many orders of plants and is +especially common in the Orchids, but in this one case only is it more +than a foot long. How did this arise? We begin with the fact, proved +experimentally by Mr. Darwin, that moths do visit Orchids, do thrust +their spiral trunks into the nectaries, and do fertilize them by +carrying the pollinia of one flower to the stigma of another. He has +further explained the exact mechanism by which this is effected, and +the Duke of Argyll admits the accuracy of his observations. In our +British species, such as Orchis pyramidalis, it is not necessary that +there should be any exact adjustment between the length of the nectary +and that of the proboscis of the insect; and thus a number of insects of +various sizes are found to carry away the pollinia and aid in the +fertilization. In the Angraecum sesquipedale, however, it is necessary +that the proboscis should be forced into a particular part of the +flower, and this would only be done by a large moth burying its +proboscis to the very base, and straining to drain the nectar from the +bottom of the long tube, in which it occupies a depth of one or two +inches only. Now let us start from the time when the nectary was only +half its present length or about six inches, and was chiefly fertilized +by a species of moth which appeared at the time of the plant's +flowering, and whose proboscis was of the same length. Among the +millions of flowers of the Angraecum produced every year, some would +always be shorter than the average, some longer. The former, owing to +the structure of the flower, would not get fertilized, because the moths +could get all the nectar without forcing their trunks down to the very +base. The latter would be well fertilized, and the longest would on the +average be the best fertilized of all. By this process alone the average +length of the nectary would annually increase, because, the +short-nectaried flowers being sterile and the long ones having abundant +offspring, exactly the same effect would be produced as if a gardener +destroyed the short ones and sowed the seed of the long ones only; and +this we know by experience would produce a regular increase of length, +since it is this very process which has increased the size and changed +the form of our cultivated fruits and flowers. + +But this would lead in time to such an increased length of the nectary +that many of the moths could only just reach the surface of the nectar, +and only the few with exceptionally long trunks be able to suck up a +considerable portion. + +This would cause many moths to neglect these flowers because they could +not get a satisfying supply of nectar, and if these were the only moths +in the country the flowers would undoubtedly suffer, and the further +growth of the nectary be checked by exactly the same process which had +led to its increase. But there are an immense variety of moths, of +various lengths of proboscis, and as the nectary became longer, other +and larger species would become the fertilizers, and would carry on the +process till the largest moths became the sole agents. Now, if not +before, the moth would also be affected, for those with the longest +probosces would get most food, would be the strongest and most vigorous, +would visit and fertilize the greatest number of flowers, and would +leave the largest number of descendants. The flowers most completely +fertilized by these moths being those which had the longest nectaries, +there would in each generation be on the average an increase in the +length of the nectaries, and also an average increase in the length of +the probosces of the moths; and this would be a _necessary result_ from +the fact that nature ever fluctuates about a mean, or that in every +generation there would be flowers with longer and shorter nectaries, and +moths with longer and shorter probosces than the average. No doubt there +are a hundred causes that might have checked this process before it had +reached the point of development at which we find it. If, for instance, +the variation in the quantity of nectar had been at any stage greater +than the variation in the length of the nectary, then smaller moths +could have reached it and have effected the fertilization. Or if the +growth of the probosces of the moths had from other causes increased +quicker than that of the nectary, or if the increased length of +proboscis had been injurious to them in any way, or if the species of +moth with the longest proboscis had become much diminished by some enemy +or other unfavourable conditions, then, in any of these cases, the +shorter nectaried flowers, which would have attracted and could have +been fertilized by the smaller kinds of moths, would have had the +advantage. And checks of a similar nature to these no doubt have acted +in other parts of the world, and have prevented such an extraordinary +development of nectary as has been produced by favourable conditions in +Madagascar only, and in one single species of Orchid. I may here mention +that some of the large Sphinx moths of the tropics have probosces nearly +as long as the nectary of Angraecum sesquipedale. I have carefully +measured the proboscis of a specimen of Macrosila cluentius from South +America, in the collection of the British Museum, and find it to be nine +inches and a quarter long! One from tropical Africa (Macrosila morganii) +is seven inches and a half. A species having a proboscis two or three +inches longer could reach the nectar in the largest flowers of Angraecum +sesquipedale, whose nectaries vary in length from ten to fourteen +inches. That such a moth exists in Madagascar may be safely predicted; +and naturalists who visit that island should search for it with as much +confidence as Astronomers searched for the planet Neptune,--and I +venture to predict they will be equally successful! + +Now, instead of this beautiful self-acting adjustment, the opposing +theory is, that the Creator of the Universe, by a direct act of his +Will, so disposed the natural forces influencing the growth of this one +species of plant as to cause its nectary to increase to this enormous +length; and at the same time, by an equally special act, determined the +flow of nourishment in the organization of the moth, so as to cause its +proboscis to increase in exactly the same proportion, having previously +so constructed the Angraecum that it could only be maintained in +existence by the agency of this moth. But what proof is given or +suggested that this was the mode by which the adjustment took place? +None whatever, except a feeling that there is an adjustment of a +delicate kind, and an inability to see how known causes could have +produced such an adjustment. I believe I have shown, however, that such +an adjustment is not only possible but inevitable, unless at some point +or other we deny the action of those simple laws which we have already +admitted to be but the expressions of existing facts. + + +_Adaptation brought about by General Laws._ + +It is difficult to find anything like parallel cases in inorganic +nature, but that of a river may perhaps illustrate the subject in some +degree. Let us suppose a person totally ignorant of Modern Geology to +study carefully a great River System. He finds in its lower part, a deep +broad channel filled to the brim, flowing slowly through a flat country +and carrying out to the sea a quantity of fine sediment. Higher up it +branches into a number of smaller channels, flowing alternately through +flat valleys and between high banks; sometimes he finds a deep rocky bed +with perpendicular walls, carrying the water through a chain of hills; +where the stream is narrow he finds it deep, where wide shallow. Further +up still, he comes to a mountainous region, with hundreds of streams and +rivulets, each with its tributary rills and gullies, collecting the +water from every square mile of surface, and every channel adapted to +the water that it has to carry. He finds that the bed of every branch, +and stream, and rivulet, has a steeper and steeper slope as it +approaches its sources, and is thus enabled to carry off the water from +heavy rains, and to bear away the stones and pebbles and gravel, that +would otherwise block up its course. In every part of this system he +would see exact adaptation of means to an end. He would say, that this +system of channels must have been designed, it answers its purpose so +effectually. Nothing but a mind could have so exactly adapted the slopes +of the channels, their capacity, and frequency, to the nature of the +soil and the quantity of the rainfall. Again, he would see special +adaptation to the wants of man, in broad quiet navigable rivers flowing +through fertile plains that support a large population, while the rocky +streams and mountain torrents, were confined to those sterile regions +suitable only for a small population of shepherds and herdsmen. He would +listen with incredulity to the Geologist, who assured him, that the +adaptation and adjustment he so admired was an inevitable result of the +action of general laws. That the rains and rivers, aided by subterranean +forces, had modelled the country, had formed the hills and valleys, had +scooped out the river beds, and levelled the plains;--and it would only +be after much patient observation and study, after having watched the +minute changes produced year by year, and multiplying them by thousands +and ten thousands, after visiting the various regions of the earth and +seeing the changes everywhere going on, and the unmistakable signs of +greater changes in past times,--that he could be made to understand that +the surface of the earth, however beautiful and harmonious it may +appear, is strictly due in every detail to the action of forces which +are demonstrably self-adjusting. + +Moreover, when he had sufficiently extended his inquiries, he would +find, that every evil effect which he would imagine must be the result +of non-adjustment does somewhere or other occur, only it is not always +evil. Looking on a fertile valley, he would perhaps say--"If the channel +of this river were not well adjusted, if for a few miles it sloped the +wrong way, the water could not escape, and all this luxuriant valley, +full of human beings, would become a waste of waters." Well, there are +hundreds of such cases. Every lake is a valley "wasted by water," and in +some cases (as the Dead Sea) it is a positive evil, a blot upon the +harmony and adaptation of the surface of the earth. Again, he might +say--"If rain did not fall here, but the clouds passed over us to some +other regions, this verdant and highly cultivated plain would become a +desert." And there are such deserts over a large part of the earth, +which abundant rains would convert into pleasant dwelling-places for +man. Or he might observe some great navigable river, and reflect how +easily rocks, or a steeper channel in places, might render it useless to +man;--and a little inquiry would show him hundreds of rivers in every +part of the world, which are thus rendered useless for navigation. + +Exactly the same thing occurs in organic nature. We see some one +wonderful case of adjustment, some unusual development of an organ, but +we pass over the hundreds of cases in which that adjustment and +development do not occur. No doubt when one adjustment is absent another +takes its place, because no organism can continue to exist that is not +adjusted to its environment; and unceasing variation with unlimited +powers of multiplication, in most cases, furnish the means of +self-adjustment. The world is so constituted, that by the action of +general laws there is produced the greatest possible variety of surface +and of climate; and by the action of laws equally general, the greatest +possible variety of organisms have been produced, adapted to the varied +conditions of every part of the earth. Tho objector would probably +himself admit, that the varied surface of the earth--the plains and +valleys, the hills and mountains, the deserts and volcanoes, the winds +and currents, the seas and lakes and rivers, and the various climates of +the earth--are all the results of general laws acting and re-acting +during countless ages; and that the Creator does not appear to guide and +control the action of these laws--here determining the height of a +mountain, there altering the channel of a river--here making the rains +more abundant, there changing the direction of a current. He would +probably admit that the forces of inorganic nature are self-adjusting, +and that the result necessarily fluctuates about a given mean condition +(which is itself slowly changing), while within certain limits the +greatest possible amount of variety is produced. If then a "contriving +mind" is not necessary at every step of the process of change eternally +going on in the inorganic world, why are we required to believe in the +continual action of such a mind in the region of organic nature? True, +the laws at work are more complex, the adjustments more delicate, the +appearance of special adaptation more remarkable; but why should we +measure the creative mind by our own? Why should we suppose the machine +too complicated, to have been designed by the Creator so complete that +it would necessarily work out harmonious results? The theory of +"continual interference" is a limitation of the Creator's power. It +assumes that he could not work by pure law in the organic, as he has +done in the inorganic world; it assumes that he could not foresee the +consequences of the laws of matter and mind combined--that results would +continually arise which are contrary to what is best, and that he has to +change what would otherwise be the course of nature, in order to produce +that beauty, and variety, and harmony, which even we, with our limited +intellects, can conceive to be the result of self-adjustment in a +universe governed by unvarying law. If we could not conceive the world +of nature to be self-adjusting and capable of endless development, it +would even then be an unworthy idea of a Creator, to impute the +incapacity of our minds to him; but when many human minds can conceive, +and can even trace out in detail some of the adaptations in nature as +the necessary results of unvarying law, it seems strange that, in the +interests of religion, any one should seek to prove that the System of +Nature, instead of being above, is far below our highest conceptions of +it. I, for one, cannot believe that the world would come to chaos if +left to Law alone. I cannot believe that there is in it no inherent +power of developing beauty or variety, and that the direct action of the +Deity is required to produce each spot or streak on every insect, each +detail of structure in every one of the millions of organisms that live +or have lived upon the earth. For it is impossible to draw a line. If +any modifications of structure could be the result of law, why not all? +If some self-adaptations could arise, why not others? If any varieties +of colour, why not all the varieties we see? No attempt is made to +explain this, except by reference to the fact that "purpose" and +"contrivance" are everywhere visible, and by the illogical deduction +that they could only have arisen from the direct action of some mind, +because the direct action of our minds produces similar "contrivances"; +but it is forgotten that adaptation, however produced, must have the +appearance of design. The channel of a river looks as if made _for_ the +river, although it is made _by_ it; the fine layers and beds in a +deposit of sand, often look as if they had been sorted, and sifted, and +levelled, designedly; the sides and angles of a crystal exactly resemble +similar forms designed by man; but we do not therefore conclude that +these effects have, in each individual case, required the directing +action of a creative mind, or see any difficulty in their being produced +by natural Law. + + +_Beauty in Nature._ + +Let us, however, leave this general argument for a while, and turn to +another special case, which has been appealed to as conclusive against +Mr. Darwin's views. "Beauty" is, to some persons, as great a +stumbling-block as "contrivance." They cannot conceive a system of the +Universe, so perfect, as necessarily to develop every form of Beauty, +but suppose that when anything specially beautiful occurs, it is a step +beyond what that system could have produced, something which the Creator +has added for his own delectation. + +Speaking of the Humming Birds, the Duke of Argyll says: "In the first +place, it is to be observed of the whole group, that there is no +connection which can be traced or conceived, between the splendour of +the humming birds and any function essential to their life. If there +were any such connection, that splendour could not be confined, as it +almost exclusively is, to only one sex. The female birds are, of course, +not placed at any disadvantage in the struggle for existence by their +more sombre colouring." And after describing the various ornaments of +these birds, he says: "Mere ornament and variety of form, and these for +their own sake, is the only principle or rule with reference to which +Creative Power seems to have worked in these wonderful and beautiful +birds.... A crest of topaz is no better in the struggle for existence +than a crest of sapphire. A frill ending in spangles of the emerald is +no better in the battle of life than a frill ending in spangles of the +ruby. A tail is not affected for the purposes of flight, whether its +marginal or its central feathers are decorated with white.... Mere +beauty and mere variety, for their own sake, are objects which we +ourselves seek when we can make the Forces of Nature subordinate to the +attainment of them. There seems to be no conceivable reason why we +should doubt or question, that these are ends and aims also in the forms +given to living organisms" ("Reign of Law," p. 248). + +Here the statement that "no connection can be conceived between the +splendour of the humming birds and any function essential to their +life," is met by the fact, that Mr. Darwin has not only conceived but +has shown, both by observation and reasoning, how beauty of colour and +form may have a direct influence on the most important of all the +functions of life, that of reproduction. In the variations to which +birds are subject, any more brilliant colour than usual would be +attractive to the females, and would lead to the individuals so adorned +leaving more than the average number of offspring. Experiment and +observation have shown, that this kind of sexual selection does actually +take place; and the laws of inheritance would necessarily lead to the +further development of any individual peculiarity that was attractive, +and thus the splendour of the humming birds is directly connected with +their very existence. It is true that "a crest of topaz may be no better +than a crest of sapphire," but either of these may be much better than +no crest at all; and the different conditions under which the parent +form must have existed in different parts of its range, will have +determined different variations of tint, either of which were +advantageous. The reason why female birds are not adorned with equally +brilliant plumes is sufficiently clear; they would be injurious, by +rendering their possessors too conspicuous during incubation. Survival +of the fittest, has therefore favoured the development of those dark +green tints on the upper surface of so many female humming birds, which +are most conducive to their protection while the important functions of +hatching and rearing the young are being carried on. Keeping in mind the +laws of multiplication, variation, and survival of the fittest, which +are for ever in action, these varied developments of beauty and +harmonious adjustments to conditions, are not only conceivable but +demonstrable results. + +The objection I am now combating is solely founded on the supposed +analogy of the Creator's mind to ours, as regards the love of Beauty for +its own sake; but if this analogy is to be trusted, then there ought to +be no natural objects which are disagreeable or ungraceful in our eyes. +And yet it is undoubtedly the fact that there are many such. Just as +surely as the Horse and Deer are beautiful and graceful, the Elephant, +Rhinoceros, Hippopotamus, and Camel are the reverse. The majority of +Monkeys and Apes are not beautiful; the majority of Birds have no beauty +of colour; a vast number of Insects and Reptiles are positively ugly. +Now, if the Creator's mind is like ours, whence this ugliness? It is +useless to say "that is a mystery we cannot explain," because we have +attempted to explain one-half of creation by a method that will not +apply to the other half. We know that a man with the highest taste and +with unlimited wealth, practically does abolish all ungraceful and +disagreeable forms and colours from his own domains. If the beauty of +creation is to be explained by the Creator's love of beauty, we are +bound to ask why he has not banished deformity from the earth, as the +wealthy and enlightened man does from his estate and from his dwelling; +and if we can get no satisfactory answer, we shall do well to reject the +explanation offered. Again, in the case of flowers, which are always +especially referred to, as the surest evidence of beauty being an end of +itself in creation, the whole of the facts are never fairly met. At +least half the plants in the world have not bright-coloured or beautiful +flowers; and Mr. Darwin has lately arrived at the wonderful +generalization, that flowers have become beautiful solely to attract +insects to assist in their fertilization. He adds, "I have come to this +conclusion from finding it an invariable rule, that when a flower is +fertilized by the wind it never has a gaily-coloured corolla." Here is a +most wonderful case of beauty being _useful_, when it might be least +expected. But much more is proved; for when beauty is of no use to the +plant it is not given. It cannot be imagined to do any harm. It is +simply not necessary, and is therefore withheld! We ought surely to have +been told how this fact is consistent with beauty being "an end in +itself," and with the statement of its being given to natural objects +"for its own sake." + + +_How new Forms are produced by Variation and Selection._ + +Let us now consider another of the popular objections which the Duke of +Argyll thus sets forth:-- + +"Mr. Darwin does not pretend to have discovered any law or rule, +according to which new Forms have been born from old Forms. He does not +hold that outward conditions, however changed, are sufficient to account +for them.... His theory seems to be far better than a mere theory--to be +an established scientific truth--in so far as it accounts, in part at +least, for the success and establishment and spread of new Forms _when +they have arisen_. But it does not even suggest the law under which, or +by or according to which, such new Forms are introduced. Natural +Selection can do nothing, except with the materials presented to its +hands. It cannot select except among the things open to selection.... +Strictly speaking, therefore, Mr. Darwin's theory is not a theory on the +Origin of Species at all, but only a theory on the causes which lead to +the relative success or failure of such new forms as may be born into +the world." ("Reign of Law," p. 230.) + +In this, and many other passages in his work, the Duke of Argyll sets +forth his idea of Creation as a "Creation by birth," but maintains that +each birth of a new form from parents differing from itself, has been +produced by a special interference of the Creator, in order to direct +the process of development into certain channels; that each new species +is in fact a "special creation," although brought into existence through +the ordinary laws of reproduction. He maintains therefore, that the laws +of multiplication and variation cannot furnish the right kinds of +materials at the right times for natural selection to work on. I +believe, on the contrary, that it can be logically _proved_ from the six +axiomatic laws before laid down, that such materials would be furnished; +but I prefer to show there are abundance of _facts_ which demonstrate +that they are furnished. + +The experience of all cultivators of plants and breeders of animals +shows, that when a sufficient number of individuals are examined, +variations of any required kind can always be met with. On this depends +the possibility of obtaining breeds, races, and fixed varieties of +animals and plants; and it is found, that any one form of variation may +be accumulated by selection, without materially affecting the other +characters of the species; each _seems_ to vary in the one required +direction only. For example, in turnips, radishes, potatoes, and +carrots, the root or tuber varies in size, colour, form, and flavour, +while the foliage and flowers seem to remain almost stationary; in the +cabbage and lettuce, on the contrary, the foliage can be modified into +various forms and modes of growth, the root, flower, and fruit remaining +little altered; in the cauliflower and brocoli the flower heads vary; in +the garden pea the pod only changes. We get innumerable forms of fruit +in the apple and pear, while the leaves and flowers remain +undistinguishable; the same occurs in the gooseberry and garden currant. +Directly however, (in the very same genus) we want the flower to vary in +the Ribes sanguineum, it does so, although mere cultivation for hundreds +of years has not produced marked differences in the flowers of Ribes +grossularia. When fashion demands any particular change in the form or +size, or colour of a flower, sufficient variation always occurs in the +right direction, as is shown by our roses, auriculas, and geraniums; +when, as recently, ornamental leaves come into fashion sufficient +variation is found to meet the demand, and we have zoned pelargoniums, +and variegated ivy, and it is discovered that a host of our commonest +shrubs and herbaceous plants have taken to vary in this direction just +when we want them to do so! This rapid variation is not confined to old +and well-known plants subjected for a long series of generations to +cultivation, but the Sikim Rhododendrons, the Fuchsias, and Calceolarias +from the Andes, and the Pelargoniums from the Cape are equally +accommodating, and vary just when and where and how we require them. + +Turning to animals we find equally striking examples. If we want any +special quality in any animal we have only to breed it in sufficient +quantities and watch carefully, and the required variety is _always_ +found, and can be increased to almost any desired extent. In Sheep, we +get flesh, fat, and wool; in Cows, milk; in Horses, colour, strength, +size, and speed; in Poultry, we have got almost any variety of colour, +curious modifications of plumage, and the capacity of perpetual +egg-laying. In Pigeons we have a still more remarkable proof of the +universality of variation, for it has been at one time or another the +fancy of breeders to change the form of every part of these birds, and +they have never found the required variations absent. The form, size, +and shape of bill and feet, have been changed to such a degree as is +found only in distinct genera of wild birds; the number of tail feathers +has been increased, a character which is generally one of the most +permanent nature, and is of high importance in the classification of +birds; and the size, the colour, and the habits, have been also changed +to a marvellous extent. In Dogs, the degree of modification and the +facility with which it is effected, is almost equally apparent. Look at +the constant amount of variation in opposite directions that must have +been going on, to develop the poodle and the greyhound from the same +original stock! Instincts, habits, intelligence, size, speed, form, and +colour, have always varied, so as to produce the very races which the +wants or fancies or passions of men may have led them to desire. Whether +they wanted a bull-dog to torture another animal, a greyhound to catch +a hare, or a bloodhound to hunt down their oppressed fellow-creatures, +the required variations have always appeared. + +Now this great mass of facts, of which a mere sketch has been here +given, are fully accounted for by the "Law of Variation" as laid down at +the commencement of this paper. Universal variability--small in amount +but in every direction, ever fluctuating about a mean condition until +made to advance in a given direction by "election," natural or +artificial,--is the simple basis for the indefinite modification of the +forms of life;--partial, unbalanced, and consequently unstable +modifications being produced by man, while those developed under the +unrestrained action of natural laws, are at every step self-adjusted to +external conditions by the dying out of all unadjusted forms, and are +therefore stable and comparatively permanent. To be consistent in their +views, our opponents must maintain that every one of the variations that +have rendered possible the changes produced by man, have been determined +at the right time and place by the will of the Creator. Every race +produced by the florist or the breeder, the dog or the pigeon fancier, +the ratcatcher, the sporting man, or the slave-hunter, must have been +provided for by varieties occurring when wanted; and as these variations +were never withheld, it would prove, that the sanction of an all-wise +and all-powerful Being, has been given to that which the highest human +minds consider to be trivial, mean, or debasing. + +This appears to be a complete answer to the theory, that variation +sufficient in amount to be accumulated in a given direction must be the +direct act of the Creative Mind, but it is also sufficiently condemned +by being so entirely unnecessary. The facility with which man obtains +new races, depends chiefly upon the number of individuals he can procure +to select from. When hundreds of florists or breeders are all aiming at +the same object, the work of change goes on rapidly. But a common +species in nature contains a thousand-or a million-fold more individuals +than any domestic race; and survival of the fittest must unerringly +preserve all that vary in the right direction, not only in obvious +characters but in minute details, not only in external but in internal +organs; so that if the materials are sufficient for the needs of man, +there can be no want of them to fulfil the grand purpose of keeping up a +supply of modified organisms, exactly adapted to the changed conditions +that are always occurring in the inorganic world. + + +_The Objection that there are Limits to Variation._ + +Having now, I believe, fairly answered the chief objections of the Duke +of Argyll, I proceed to notice one or two of those adduced in an able +and argumentative essay on the "Origin of Species" in the _North British +Review_ for July, 1867. The writer first attempts to prove that there +are strict limits to variation. When we begin to select variations in +any one direction, the process is comparatively rapid, but after a +considerable amount of change has been effected it becomes slower and +slower, till at length its limits are reached and no care in breeding +and selection can produce any further advance. The race-horse is chosen +as an example. It is admitted that, with any ordinary lot of horses to +begin with, careful selection would in a few years make a great +improvement, and in a comparatively short time the standard of our best +racers might be reached. But that standard has not for many years been +materially raised, although unlimited wealth and energy are expended in +the attempt. This is held to prove that there are definite limits to +variation in any special direction, and that we have no reason to +suppose that mere time, and the selective process being carried on by +natural law, could make any material difference. But the writer does not +perceive that this argument fails to meet the real question, which is, +not whether indefinite and unlimited change in any or all directions is +possible, but whether such differences as do occur in nature could have +been produced by the accumulation of variations by selection. In the +matter of speed, a limit of a definite kind as regards land animals does +exist in nature. All the swiftest animals--deer, antelopes, hares, +foxes, lions, leopards, horses, zebras, and many others, have reached +very nearly the same degree of speed. Although the swiftest of each must +have been for ages preserved, and the slowest must have perished, we +have no reason to believe there is any advance of speed. The possible +limit under existing conditions, and perhaps under possible terrestrial +conditions, has been long ago reached. In cases, however, where this +limit had not been so nearly reached as in the horse, we have been +enabled to make a more marked advance and to produce a greater +difference of form. The wild dog is an animal that hunts much in +company, and trusts more to endurance than to speed. Man has produced +the greyhound, which differs much more from the wolf or the dingo than +the racer does from the wild Arabian. Domestic dogs, again, have varied +more in size and in form than the whole family of Canidae in a state of +nature. No wild dog, fox, or wolf, is either so small as some of the +smallest terriers and spaniels, or so large as the largest varieties of +hound or Newfoundland dog. And, certainly, no two wild animals of the +family differ so widely in form and proportions as the Chinese pug and +the Italian greyhound, or the bulldog and the common greyhound. The +known range of variation is, therefore, more than enough for the +derivation of all the forms of Dogs, Wolves, and Foxes from a common +ancestor. + +Again, it is objected that the Pouter or the Fan-tail pigeon cannot be +further developed in the same direction. Variation seems to have reached +its limits in these birds. But so it has in nature. The Fan-tail has not +only more tail feathers than any of the three hundred and forty existing +species of pigeons, but more than any of the eight thousand known +species of birds. There is, of course, some limit to the number of +feathers of which a tail useful for flight can consist, and in the +Fan-tail we have probably reached that limit. Many birds have the +oesophagus or the skin of the neck more or less dilatable, but in no +known bird is it so dilatable as in the Pouter pigeon. Here again the +possible limit, compatible with a healthy existence, has probably been +reached. In like manner the differences in the size and form of the beak +in the various breeds of the domestic Pigeon, is greater than that +between the extreme forms of beak in the various genera and sub-families +of the whole Pigeon tribe. From these facts, and many others of the same +nature, we may fairly infer, that if rigid selection were applied to any +organ, we could in a comparatively short time produce a much greater +amount of change than that which occurs between species and species in a +state of nature, since the differences which we do produce are often +comparable with those which exist between distinct genera or distinct +families. The facts adduced by the writer of the article referred to, of +the definite limits to variability in certain directions in domesticated +animals, are, therefore, no objection whatever to the view, that all the +modifications which exist in nature have been produced by the +accumulation, by natural selection, of small and useful variations, +since those very modifications have equally definite and very similar +limits. + + +_Objection to the Argument from Classification._ + +To another of this writer's objections--that by Professor Thomson's +calculations the sun can only have existed in a solid state 500,000,000 +of years, and that therefore _time_ would not suffice for the slow +process of development of all living organisms--it is hardly necessary +to reply, as it cannot be seriously contended, even if this calculation +has claims to approximate accuracy, that the process of change and +development may not have been sufficiently rapid to have occurred within +that period. His objection to the Classification argument is, however, +more plausible. The uncertainty of opinion among Naturalists as to which +are species and which varieties, is one of Mr. Darwin's very strong +arguments that these two names cannot belong to things quite distinct in +nature and origin. The Reviewer says that this argument is of no weight, +because the works of man present exactly the same phenomena; and he +instances patent inventions, and the excessive difficulty of determining +whether they are new or old. I accept the analogy though it is a very +imperfect one, and maintain that such as it is, it is all in favour of +Mr. Darwin's views. For are not all inventions of the same kind directly +affiliated to a common ancestor? Are not improved Steam Engines or +Clocks the lineal descendants of some existing Steam Engine or Clock? Is +there ever a new Creation in Art or Science any more than in Nature? Did +ever patentee absolutely originate any complete and entire invention, no +portion of which was derived from anything that had been made or +described before? It is therefore clear that the difficulty of +distinguishing the various classes of inventions which claim to be new, +is of the same nature as the difficulty of distinguishing varieties and +species, because neither are absolute new creations, but both are alike +descendants of pre-existing forms, from which and from each other they +differ by varying and often imperceptible degrees. It appears, then, +that however plausible this writer's objections may seem, whenever he +descends from generalities to any specific statement, his supposed +difficulties turn out to be in reality strongly confirmatory of Mr. +Darwin's view. + + +_The "Times," on Natural Selection._ + +The extraordinary misconception of the whole subject by popular writers +and reviewers, is well shown by an article which appeared in the _Times_ +newspaper on "The Reign of Law." Alluding to the supposed economy of +nature, in the adaptation of each species to its own place and its +special use, the reviewer remarks: "To this universal law of the +greatest economy, the law of natural selection stands in direct +antagonism as the law of 'greatest possible waste' of time and of +creative power. To conceive a duck with webbed feet and a spoon-shaped +bill, living by suction, to pass naturally into a gull with webbed feet +and a knife-like bill, living on flesh, in the longest possible time and +in the most laborious possible way, we may conceive it to pass from the +one to the other state by natural selection. The battle of life the +ducks will have to fight will increase in peril continually as they +cease (with the change of their bill) to be ducks, and attain a +_maximum_ of danger in the condition in which they begin to be gulls; +and ages must elapse and whole generations must perish, and countless +generations of the one species be created and sacrificed, to arrive at +one single pair of the other." + +In this passage the theory of natural selection is so absurdly +misrepresented that it would be amusing, did we not consider the +misleading effect likely to be produced by this kind of teaching in so +popular a journal. It is assumed that the duck and the gull are +essential parts of nature, each well fitted for its place, and that if +one had been produced from the other by a gradual metamorphosis, the +intermediate forms would have been useless, unmeaning, and unfitted for +any place, in the system of the universe. Now, this idea can only exist +in a mind ignorant of the very foundation and essence of the theory of +natural selection, which is, the preservation of _useful_ variations +only, or, as has been well expressed, in other words, the "survival of +the fittest." Every intermediate form which could possibly have arisen +during the transition from the duck to the gull, so far from having an +unusually severe battle to fight for existence, or incurring any +"_maximum_ of danger," would necessarily have been as accurately +adjusted to the rest of nature, and as well fitted to maintain and to +enjoy its existence, as the duck or the gull actually are. If it were +not so, it never could have been produced under the law of natural +selection. + + +_Intermediate or generalized Forms of extinct Animals, an indication of +Transmutation or Development._ + +The misconception of this writer illustrates another point very +frequently overlooked. It is an essential part of Mr. Darwin's theory, +that one existing animal has not been derived from any other existing +animal, but that both are the descendants of a common ancestor, which +was at once different from either, but, in essential characters, +intermediate between them both. The illustration of the duck and the +gull is therefore misleading; one of these birds has not been derived +from the other, but both from a common ancestor. This is not a mere +supposition invented to support the theory of natural selection, but is +founded on a variety of indisputable facts. As we go back into past +time, and meet with the fossil remains of more and more ancient races of +extinct animals, we find that many of them actually are intermediate +between distinct groups of existing animals. Professor Owen continually +dwells on this fact: he says in his "Palaeontology," p. 284: "A more +generalized vertebrate structure is illustrated, in the extinct +reptiles, by the affinities to ganoid fishes, shown by Ganocephala, +Labyrinthodontia, and Icthyopterygia; by the affinities of the +Pterosauria to Birds, and by the approximation of the Dinosauria to +Mammals. (These have been recently shown by Professor Huxley to have +more affinity to Birds.) It is manifested by the combination of modern +crocodilian, chelonian, and lacertian characters in the Cryptodontia +and the Dicnyodontia, and by the combined lacertian and crocodilian +characters in the Thecodontia and Sauropterygia." In the same work he +tells us that, "the Anoplotherium, in several important characters +resembled the embryo Ruminant, but retained throughout life those marks +of adhesion to a generalized mammalian type;"--and assures us that he +has "never omitted a proper opportunity for impressing the results of +observations showing the more generalized structures of extinct as +compared with the more specialized forms of recent animals." Modern +palaeontologists have discovered hundreds of examples of these more +generalized or ancestral types. In the time of Cuvier, the Ruminants and +the Pachyderms were looked upon as two of the most distinct orders of +animals; but it is now demonstrated that there once existed a variety of +genera and species, connecting by almost imperceptible grades such +widely different animals as the pig and the camel. Among living +quadrupeds we can scarcely find a more isolated group than the genus +Equus, comprising the horses, asses, and Zebras; but through many +species of Paloplotherium, Hippotherium, and Hipparion, and numbers of +extinct forms of Equus found in Europe, India, and America, an almost +complete transition is established with the Eocene Anoplothorium and +Paleotherium, which are also generalized or ancestral types of the Tapir +and Rhinoceros. The recent researches of M. Gaudry in Greece have +furnished much new evidence of the same character. In the Miocene beds +of Pikermi he has discovered the group of the Simocyonidae intermediate +between bears and wolves; the genus Hyaenictis which connects the hyaenas +with the civets; the Ancylotherium, which is allied both to the extinct +mastodon and to the living pangolin or scaly ant-eater; and the +Helladotherium, which connects the now isolated giraffe with the deer +and antelopes. + +Between reptiles and fishes an intermediate type has been found in the +Archegosaurus of the Coal formation; while the Labyrinthodon of the +Trias combined characters of the Batrachia with those of crocodiles, +lizards, and ganoid fishes. Even birds, the most apparently isolated of +all living forms, and the most rarely preserved in a fossil state, have +been shown to possess undoubted affinities with reptiles; and in the +Oolitic Archaeopteryx, with its lengthened tail, feathered on each side, +we have one of the connecting links from the side of birds; while +Professor Huxley has recently shown that the entire order of +Dinosaurians have remarkable affinities to birds, and that one of them, +the Compsognathus, makes a nearer approach to bird organisation than +does Archaeopteryx to that of reptiles. + +Analogous facts to those occur in other classes of animals, as +an example of which we have the authority of a distinguished +paleontologist, M. Barande, quoted by Mr. Darwin, for the statement, +that although the Palaeozoic Invertebrata can certainly be classed under +existing groups, yet at this ancient period the groups were not so +distinctly separated from each other as they are now; while Mr. Scudder +tells us, that some of the fossil insects discovered in the Coal +formation of America offer characters intermediate between those of +existing orders. Agassiz, again, insists strongly that the more ancient +animals resemble the embryonic forms of existing species; but as the +embryos of distinct groups are known to resemble each other more than +the adult animals (and in fact to be undistinguishable at a very early +age), this is the same as saying that the ancient animals are exactly +what, on Darwin's theory, the ancestors of existing animals ought to be; +and this, it must be remembered, is the evidence of one of the strongest +opponents of the theory of natural selection. + + +_Conclusion._ + +I have thus endeavoured to meet fairly, and to answer plainly, a few of +the most common objections to the theory of natural selection, and I +have done so in every case by referring to admitted facts and to logical +deductions from those facts. + +As an indication and general summary of the line of argument I have +adopted, I here give a brief demonstration in a tabular form of the +Origin of Species by means of Natural Selection, referring for the +_facts_ to Mr. Darwin's works, and to the pages in this volume, where +they are more or less fully treated. + + +_A Demonstration of the Origin of Species by Natural Selection_. + + ___________________________________________________________________ + | | | + |_PROVED FACTS_. |_NECESSARY CONSEQUENCES_ | + | |(_afterwards taken as Proved | + | |Facts_). | + |_________________________________|_________________________________| + | | | + |RAPID INCREASE OF ORGANISMS, | | + |pp. 29, 265; ("Origin |STRUGGLE FOR EXISTENCE, | + |of Species," p. 75, 5th Ed.) |the deaths equalling the | + | |births on the average, p. 30; | + |TOTAL NUMBER OF INDIVIDUALS |("Origin of Species," chap. | + |STATIONARY, pp. 30, |III.) | + |266. | | + |_________________________________|_________________________________| + | | | + |STRUGGLE FOR EXISTENCE. |SURVIVAL OF THE FITTEST, | + | |or Natural Selection; meaning | + |HEREDITY WITH VARIATION, |simply, that on the | + |or general likeness with |whole those die who are | + |individual differences of parents|least fitted to maintain their | + |and offspring, pp. |existence; ("Origin of Species," | + |266, 287-291, 308; ("Origin |chap. IV.) | + |of Species," chap. I., II., V.) | | + |_________________________________|_________________________________| + | | | + |SURVIVAL OF THE FITTEST. |CHANGES OF ORGANIC FORMS, | + | |to keep them in harmony | + |CHANGE OF EXTERNAL CONDITIONS, |with the Changed Conditions; | + |universal and unceasing.--See |and as the changes | + |"Lyell's |of conditions are permanent | + |Principles of Geology." |changes, in the sense | + | |of not reverting back to | + | |identical previous conditions, | + | |the changes of organic | + | |forms must be in the | + | |same sense permanent, and | + | |thus originate SPECIES. | + |_________________________________|_________________________________| + + + + +IX. + +THE DEVELOPMENT OF HUMAN RACES UNDER THE LAW OF NATURAL SELECTION. + + +Among the most advanced students of man, there exists a wide difference +of opinion on some of the most vital questions respecting his nature and +origin. Anthropologists are now, indeed, pretty well agreed that man is +not a recent introduction into the earth. All who have studied the +question, now admit that his antiquity is very great; and that, though +we have to some extent ascertained the minimum of time during which he +_must_ have existed, we have made no approximation towards determining +that far greater period during which he _may_ have, and probably _has_ +existed. We can with tolerable certainty affirm that man must have +inhabited the earth a thousand centuries ago, but we cannot assert that +he positively did not exist, or that there is any good evidence against +his having existed, for a period of ten thousand centuries. We know +positively, that he was contemporaneous with many now extinct animals, +and has survived changes of the earth's surface fifty or a hundred times +greater than any that have occurred during the historical period; but we +cannot place any definite limit to the number of species he may have +outlived, or to the amount of terrestrial change he may have witnessed. + + +_Wide differences of opinion as to Man's Origin._ + +But while on this question of man's antiquity there is a very general +agreement,--and all are waiting eagerly for fresh evidence to clear up +those points which all admit to be full of doubt,--on other, and not +less obscure and difficult questions, a considerable amount of dogmatism +is exhibited; doctrines are put forward as established truths, no doubt +or hesitation is admitted, and it seems to be supposed that no further +evidence is required, or that any new facts can modify our convictions. +This is especially the case when we inquire,--Are the various forms +under which man now exists primitive, or derived from pre-existing +forms; in other words, is man of one or many species? To this question +we immediately obtain distinct answers diametrically opposed to each +other: the one party positively maintaining, that man is a _species_ and +is essentially _one_--that all differences are but local and temporary +variations, produced by the different physical and moral conditions by +which he is surrounded; the other party maintaining with equal +confidence, that man is a genus of _many species_, each of which is +practically unchangeable, and has ever been as distinct, or even more +distinct, than we now behold them. This difference of opinion is +somewhat remarkable, when we consider that both parties are well +acquainted with the subject; both use the same vast accumulation of +facts; both reject those early traditions of mankind which profess to +give an account of his origin; and both declare that they are seeking +fearlessly after truth alone; yet each will persist in looking only at +the portion of truth on his own side of the question, and at the error +which is mingled with his opponent's doctrine. It is my wish to show how +the two opposing views can be combined, so as to eliminate the error and +retain the truth in each, and it is by means of Mr. Darwin's celebrated +theory of "Natural Selection" that I hope to do this, and thus to +harmonise the conflicting theories of modern anthropologists. + +Let us first see what each party has to say for itself. In favour of the +unity of mankind it is argued, that there are no races without +transitions to others; that every race exhibits within itself variations +of colour, of hair, of feature, and of form, to such a degree as to +bridge over, to a large extent, the gap that separates it from other +races. It is asserted that no race is homogeneous; that there is a +tendency to vary; that climate, food, and habits produce, and render +permanent, physical peculiarities, which, though slight in the limited +periods allowed to our observation, would, in the long ages during which +the human race has existed, have sufficed to produce all the differences +that now appear. It is further asserted that the advocates of the +opposite theory do not agree among themselves; that some would make +three, some five, some fifty or a hundred and fifty species of man; some +would have had each species created in pairs, while others require +nations to have at once sprung into existence, and that there is no +stability or consistency in any doctrine but that of one primitive +stock. + +The advocates of the original diversity of man, on the other hand, have +much to say for themselves. They argue that proofs of change in man have +never been brought forward except to the most trifling amount, while +evidence of his permanence meets us everywhere. The Portuguese and +Spaniards, settled for two or three centuries in South America, retain +their chief physical, mental, and moral characteristics; the Dutch boers +at the Cape, and the descendants of the early Dutch settlers in the +Moluccas, have not lost the features or the colour of the Germanic +races; the Jews, scattered over the world in the most diverse climates, +retain the same characteristic lineaments everywhere; the Egyptian +sculptures and paintings show us that, for at least 4000 or 5000 years, +the strongly contrasted features of the Negro and the Semitic races have +remained altogether unchanged; while more recent discoveries prove, that +the mound-builders of the Mississippi valley, and the dwellers on +Brazilian mountains, had, even in the very infancy of the human race, +some traces of the same peculiar and characteristic type of cranial +formation that now distinguishes them. + +If we endeavour to decide impartially on the merits of this difficult +controversy, judging solely by the evidence that each party has brought +forward, it certainly seems that the best of the argument is on the +side of those who maintain the primitive diversity of man. Their +opponents have not been able to refute the permanence of existing races +as far back as we can trace them, and have failed to show, in a single +case, that at any former epoch the well marked varieties of mankind +approximated more closely than they do at the present day. At the same +time this is but negative evidence. A condition of immobility for four +or five thousand years, does not preclude an advance at an earlier +epoch, and--if we can show that there are causes in nature which would +check any further physical change when certain conditions were +fulfilled--does not even render such an advance improbable, if there are +any general arguments to be adduced in its favour. Such a cause, I +believe, does exist; and I shall now endeavour to point out its nature +and its mode of operation. + + +_Outline of the Theory of Natural Selection._ + +In order to make my argument intelligible, it is necessary for me to +explain very briefly the theory of "Natural Selection" promulgated by +Mr. Darwin, and the power which it possesses of modifying the forms of +animals and plants. The grand feature in the multiplication of organic +life is, that close general resemblance is combined with more or less +individual variation. The child resembles its parents or ancestors more +or less closely in all its peculiarities, deformities, or beauties; it +resembles them in general more than it does any other individuals; yet +children of the same parents are not all alike, and it often happens +that they differ very considerably from their parents and from each +other. This is equally true, of man, of all animals, and of all plants. +Moreover, it is found that individuals do not differ from their parents +in certain particulars only, while in all others they are exact +duplicates of them. They differ from them and from each other, in every +particular: in form, in size, in colour; in the structure of internal as +well as of external organs; in those subtle peculiarities which produce +differences of constitution, as well as in those still more subtle ones +which lead to modifications of mind and character. In other words, in +every possible way, in every organ and in every function, individuals of +the same stock vary. + +Now, health, strength, and long life, are the results of a harmony +between the individual and the universe that surrounds it. Let us +suppose that at any given moment this harmony is perfect. A certain +animal is exactly fitted to secure its prey, to escape from its enemies, +to resist the inclemencies of the seasons, and to rear a numerous and +healthy offspring. But a change now takes place. A series of cold +winters, for instance, come on, making food scarce, and bringing an +immigration of some other animals to compete with the former inhabitants +of the district. The new immigrant is swift of foot, and surpasses its +rivals in the pursuit of game; the winter nights are colder, and require +a thicker fur as a protection, and more nourishing food to keep up the +heat of the system. Our supposed perfect animal is no longer in harmony +with its universe; it is in danger of dying of cold or of starvation. +But the animal varies in its offspring. Some of these are swifter than +others--they still manage to catch food enough; some are hardier and +more thickly furred--they manage in the cold nights to keep warm enough; +the slow, the weak, and the thinly clad soon die off. Again and again, +in each succeeding generation, the same thing takes place. By this +natural process, which is so inevitable that it cannot be conceived not +to act, those best adapted to live, live; those least adapted, die. It +is sometimes said that we have no direct evidence of the action of this +selecting power in nature. But it seems to me we have better evidence +than even direct observation would be, because it is more universal, +viz., the evidence of necessity. It must be so; for, as all wild animals +increase in a geometrical ratio, while their actual numbers remain on +the average stationary, it follows, that as many die annually as are +born. If, therefore, we deny natural selection, it can only be by +asserting that, in such a case as I have supposed, the strong, the +healthy, the swift, the well clad, the well organised animals in every +respect, have no advantage over,--do not on the average live longer +than, the weak, the unhealthy, the slow, the ill-clad, and the +imperfectly organised individuals; and this no sane man has yet been +found hardy enough to assert. But this is not all; for the offspring on +the average resemble their parents, and the selected portion of each +succeeding generation will therefore be stronger, swifter, and more +thickly furred than the last; and if this process goes on for thousands +of generations, our animal will have again become thoroughly in harmony +with the new conditions in which it is placed. But it will now be a +different creature. It will be not only swifter and stronger, and more +furry, it will also probably have changed in colour, in form, perhaps +have acquired a longer tail, or differently shaped ears; for it is an +ascertained fact, that when one part of an animal is modified, some +other parts almost always change, as it were in sympathy with it. Mr. +Darwin calls this "correlation of growth," and gives as instances, that +hairless dogs have imperfect teeth; white cats, when blue-eyed, are +deaf; small feet accompany short beaks in pigeons; and other equally +interesting cases. + +Grant, therefore, the premises: 1st. That peculiarities of every kind +are more or less hereditary. 2nd. That the offspring of every animal +vary more or less in all parts of their organization. 3rd. That +the universe in which these animals live, is not absolutely +invariable;--none of which propositions can be denied; and then +consider, that the animals in any country (those at least which are not +dying out) must at each successive period be brought into harmony with +the surrounding conditions; and we have all the elements for a change of +form and structure in the animals, keeping exact pace with changes of +whatever nature in the surrounding universe. Such changes must be slow, +for the changes in the universe are very slow; but just as these slow +changes become important, when we look at results after long periods of +action, as we do when we perceive the alterations of the earth's surface +during geological epochs; so the parallel changes in animal form become +more and more striking, in proportion as the time they have been going +on is great; as we see when we compare our living animals with those +which we disentomb from each successively older geological formation. + +This is, briefly, the theory of "natural selection," which explains the +changes in the organic world as being parallel with, and in part +dependent on, those in the inorganic. What we now have to inquire +is,--Can this theory be applied in any way to the question of the origin +of the races of man? or is there anything in human nature that takes him +out of the category of those organic existences, over whose successive +mutations it has had such powerful sway? + + +_Different effects of Natural Selection on Animals and on Man._ + +In order to answer these questions, we must consider why it is that +"natural selection" acts so powerfully upon animals; and we shall, I +believe, find, that its effect depends mainly upon their self-dependence +and individual isolation. A slight injury, a temporary illness, will +often end in death, because it leaves the individual powerless against +its enemies. If an herbivorous animal is a little sick and has not fed +well for a day or two, and the herd is then pursued by a beast of prey, +our poor invalid inevitably falls a victim. So, in a carnivorous animal, +the least deficiency of vigour prevents its capturing food, and it soon +dies of starvation. There is, as a general rule, no mutual assistance +between adults, which enables them to tide over a period of sickness. +Neither is there any division of labour; each must fulfil _all_ the +conditions of its existence, and, therefore, "natural selection" keeps +all up to a pretty uniform standard. + +But in man, as we now behold him, this is different. He is social and +sympathetic. In the rudest tribes the sick are assisted, at least with +food; less robust health and vigour than the average does not entail +death. Neither does the want of perfect limbs, or other organs, produce +the same effects as among animals. Some division of labour takes place; +the swiftest hunt, the less active fish, or gather fruits; food is, to +some extent, exchanged or divided. The action of natural selection is +therefore checked; the weaker, the dwarfish, those of less active limbs, +or less piercing eyesight, do not suffer the extreme penalty which falls +upon animals so defective. + +In proportion as these physical characteristics become of less +importance, mental and moral qualities will have increasing influence on +the well-being of the race. Capacity for acting in concert for +protection, and for the acquisition of food and shelter; sympathy, which +leads all in turn to assist each other; the sense of right, which checks +depredations upon our fellows; the smaller development of the combative +and destructive propensities; self-restraint in present appetites; and +that intelligent foresight which prepares for the future, are all +qualities, that from their earliest appearance must have been for the +benefit of each community, and would, therefore, have become the +subjects of "natural selection." For it is evident that such qualities +would be for the well-being of man; would guard him against external +enemies, against internal dissensions, and against the effects of +inclement seasons and impending famine, more surely than could any +merely physical modification. Tribes in which such mental and moral +qualities were predominant, would therefore have an advantage in the +struggle for existence over other tribes in which they were less +developed, would live and maintain their numbers, while the others would +decrease and finally succumb. + +Again, when any slow changes of physical geography, or of climate, make +it necessary for an animal to alter its food, its clothing, or its +weapons, it can only do so by the occurrence of a corresponding change +in its own bodily structure and internal organization. If a larger or +more powerful beast is to be captured and devoured, as when a +carnivorous animal which has hitherto preyed on antelopes is obliged +from their decreasing numbers to attack buffaloes, it is only the +strongest who can hold,--those with most powerful claws, and formidable +canine teeth, that can struggle with and overcome such an animal. +Natural selection immediately comes into play, and by its action these +organs gradually become adapted to their new requirements. But man, +under similar circumstances, does not require longer nails or teeth, +greater bodily strength or swiftness. He makes sharper spears, or a +better bow, or he constructs a cunning pitfall, or combines in a hunting +party to circumvent his new prey. The capacities which enable him to do +this are what he requires to be strengthened, and these will, therefore, +be gradually modified by "natural selection," while the form and +structure of his body will remain unchanged. So, when a glacial epoch +comes on, some animals must acquire warmer fur, or a covering of fat, or +else die of cold. Those best clothed by nature are, therefore, preserved +by natural selection. Man, under the same circumstances, will make +himself warmer clothing, and build better houses; and the necessity of +doing this will react upon his mental organization and social +condition--will advance them while his natural body remains naked as +before. + +When the accustomed food of some animal becomes scarce or totally fails, +it can only exist by becoming adapted to a new kind of food, a food +perhaps less nourishing and less digestible. "Natural selection" will +now act upon the stomach and intestines, and all their individual +variations will be taken advantage of, to modify the race into harmony +with its new food. In many cases, however, it is probable that this +cannot be done. The internal organs may not vary quick enough, and then +the animal will decrease in numbers, and finally become extinct. But +man guards himself from such accidents by superintending and guiding the +operations of nature. He plants the seed of his most agreeable food, and +thus procures a supply, independent of the accidents of varying seasons +or natural extinction. He domesticates animals, which serve him either +to capture food or for food itself, and thus, changes of any great +extent in his teeth or digestive organs are rendered unnecessary. Man, +too, has everywhere the use of fire, and by its means can render +palatable a variety of animal and vegetable substances, which he could +hardly otherwise make use of; and thus obtains for himself a supply of +food far more varied and abundant than that which any animal can +command. + +Thus man, by the mere capacity of clothing himself, and making weapons +and tools, has taken away from nature that power of slowly but +permanently changing the external form and structure, in accordance with +changes in the external world, which she exercises over all other +animals. As the competing races by which they are surrounded, the +climate, the vegetation, or the animals which serve them for food, are +slowly changing, they must undergo a corresponding change in their +structure, habits, and constitution, to keep them in harmony with the +new conditions--to enable them to live and maintain their numbers. But +man does this by means of his intellect alone, the variations of which +enable him, with an unchanged body, still to keep in harmony with the +changing universe. + +There is one point, however, in which nature will still act upon him as +it does on animals, and, to some extent, modify his external characters. +Mr. Darwin has shown, that the colour of the skin is correlated with +constitutional peculiarities both in vegetables and animals, so that +liability to certain diseases or freedom from them is often accompanied +by marked external characters. Now, there is every reason to believe +that this has acted, and, to some extent, may still continue to act, on +man. In localities where certain diseases are prevalent, those +individuals of savage races which were subject to them would rapidly die +off; while those who were constitutionally free from the disease would +survive, and form the progenitors of a new race. These favoured +individuals would probably be distinguished by peculiarities of +_colour_, with which again peculiarities in the texture or the abundance +of _hair_ seem to be correlated, and thus may have been brought about +those racial differences of colour, which seem to have no relation to +mere temperature or other obvious peculiarities of climate. + +From the time, therefore, when the social and sympathetic feelings came +into active operation, and the intellectual and moral faculties became +fairly developed, man would cease to be influenced by "natural +selection" in his physical form and structure. As an animal he would +remain almost stationary, the changes of the surrounding universe +ceasing to produce in him that powerful modifying effect which they +exercise over other parts of the organic world. But from the moment +that the form of his body became stationary, his mind would become +subject to those very influences from which his body had escaped; every +slight variation in his mental and moral nature which should enable him +better to guard against adverse circumstances, and combine for mutual +comfort and protection, would be preserved and accumulated; the better +and higher specimens of our race would therefore increase and spread, +the lower and more brutal would give way and successively die out, and +that rapid advancement of mental organization would occur, which has +raised the very lowest races of man so far above the brutes (although +differing so little from some of them in physical structure), and, in +conjunction with scarcely perceptible modifications of form, has +developed the wonderful intellect of the European races. + + +_Influence of external Nature in the development of the Human Mind._ + +But from the time when this mental and moral advance commenced, and +man's physical character became fixed and almost immutable, a new series +of causes would come into action, and take part in his mental growth. +The diverse aspects of nature would now make themselves felt, and +profoundly influence the character of the primitive man. + +When the power that had hitherto modified the body had its action +transferred to the mind, then races would advance and become improved, +merely by the harsh discipline of a sterile soil and inclement seasons. +Under their influence, a hardier, a more provident, and a more social +race would be developed, than in those regions where the earth produces +a perennial supply of vegetable food, and where neither foresight nor +ingenuity are required to prepare for the rigours of winter. And is it +not the fact that in all ages, and in every quarter of the globe, the +inhabitants of temperate have been superior to those of hotter +countries? All the great invasions and displacements of races have been +from North to South, rather than the reverse; and we have no record of +there ever having existed, any more than there exists to-day, a solitary +instance of an indigenous inter-tropical civilization. The Mexican +civilization and government came from the North, and, as well as the +Peruvian, was established, not in the rich tropical plains, but on the +lofty and sterile plateaux of the Andes. The religion and civilization +of Ceylon were introduced from North India; the successive conquerors of +the Indian peninsula came from the North-west; the northern Mongols +conquered the more Southern Chinese; and it was the bold and adventurous +tribes of the North that overran and infused new life into Southern +Europe. + + +_Extinction of Lower Races._ + +It is the same great law of "the preservation of favoured races in the +struggle for life," which leads to the inevitable extinction of all +those low and mentally undeveloped populations with which Europeans come +in contact. The red Indian in North America, and in Brazil; the +Tasmanian, Australian, and New Zealander in the southern hemisphere, die +out, not from any one special cause, but from the inevitable effects of +an unequal mental and physical struggle. The intellectual and moral, as +well as the physical, qualities of the European are superior; the same +powers and capacities which have made him rise in a few centuries from +the condition of the wandering savage with a scanty and stationary +population, to his present state of culture and advancement, with a +greater average longevity, a greater average strength, and a capacity of +more rapid increase,--enable him when in contact with the savage man, to +conquer in the struggle for existence, and to increase at his expense, +just as the better adapted, increase at the expense of the less adapted +varieties in the animal and vegetable kingdoms,--just as the weeds of +Europe overrun North America and Australia, extinguishing native +productions by the inherent vigour of their organization, and by their +greater capacity for existence and multiplication. + + +_The Origin of the Races of Man._ + +If these views are correct; if in proportion as man's social, moral, and +intellectual faculties became developed, his physical structure would +cease to be affected by the operation of "natural selection," we have a +most important clue to the origin of races. For it will follow, that +those great modifications of structure and of external form, which +resulted in the development of man out of some lower type of animal, +must have occurred before his intellect had raised him above the +condition of the brutes, at a period when he was gregarious, but +scarcely social, with a mind perceptive but not reflective, ere any +sense of _right_ or feelings of _sympathy_ had been developed in him. He +would be still subject, like the rest of the organic world, to the +action of "natural selection," which would retain his physical form and +constitution in harmony with the surrounding universe. He was probably +at a very early period a dominant race, spreading widely over the warmer +regions of the earth as it then existed, and in agreement with what we +see in the case of other dominant species, gradually becoming modified +in accordance with local conditions. As he ranged farther from his +original home, and became exposed to greater extremes of climate, to +greater changes of food, and had to contend with new enemies, organic +and inorganic, slight useful variations in his constitution would be +selected and rendered permanent, and would, on the principle of +"correlation of growth," be accompanied by corresponding external +physical changes. Thus might have arisen those striking characteristics +and special modifications which still distinguish the chief races of +mankind. The red, black, yellow, or blushing white skin; the straight, +the curly, the woolly hair; the scanty or abundant beard; the straight +or oblique eyes; the various forms of the pelvis, the cranium, and other +parts of the skeleton. + +But while these changes had been going on, his mental development had, +from some unknown cause, greatly advanced, and had now reached that +condition in which it began powerfully to influence his whole existence, +and would therefore become subject to the irresistible action of +"natural selection." This action would quickly give the ascendency to +mind: speech would probably now be first developed, leading to a still +further advance of the mental faculties; and from that moment man, as +regards the form and structure of most parts of his body, would remain +almost stationary. The art of making weapons, division of labour, +anticipation of the future, restraint of the appetites, moral, social, +and sympathetic feelings, would now have a preponderating influence on +his well being, and would therefore be that part of his nature on which +"natural selection" would most powerfully act; and we should thus have +explained that wonderful persistence of mere physical characteristics, +which is the stumbling-block of those who advocate the unity of mankind. + +We are now, therefore, enabled to harmonise the conflicting views of +anthropologists on this subject. Man may have been, indeed I believe +must have been, once a homogeneous race; but it was at a period of which +we have as yet discovered no remains, at a period so remote in his +history, that he had not yet acquired that wonderfully developed brain, +the organ of the mind, which now, even in his lowest examples, raises +him far above the highest brutes;--at a period when he had the form but +hardly the nature of man, when he neither possessed human speech, nor +those sympathetic and moral feelings which in a greater or less degree +everywhere now distinguish the race. Just in proportion as these truly +human faculties became developed in him, would his physical features +become fixed and permanent, because the latter would be of less +importance to his well being; he would be kept in harmony with the +slowly changing universe around him, by an advance in mind, rather than +by a change in body. If, therefore, we are of opinion that he was not +really man till these higher faculties were fully developed, we may +fairly assert that there were many originally distinct races of men; +while, if we think that a being closely resembling us in form and +structure, but with mental faculties scarcely raised above the brute, +must still be considered to have been human, we are fully entitled to +maintain the common origin of all mankind. + + +_The Bearing of these Views on the Antiquity of Man._ + +These considerations, it will be seen, enable us to place the origin of +man at a much more remote geological epoch than has yet been thought +possible. He may even have lived in the Miocene or Eocene period, when +not a single mammal was identical in form with any existing species. +For, in the long series of ages during which these primeval animals were +being slowly changed into the species which now inhabit the earth, the +power which acted to modify them would only affect the mental +organization of man. His brain alone would have increased in size and +complexity, and his cranium have undergone corresponding changes of +form, while the whole structure of lower animals was being changed. This +will enable us to understand how the fossil crania of Denise and Engis +agree so closely with existing forms, although they undoubtedly existed +in company with large mammalia now extinct. The Neanderthal skull may be +a specimen of one of the lowest races then existing, just as the +Australians are the lowest of our modern epoch. We have no reason to +suppose that mind and brain and skull modification, could go on quicker +than that of the other parts of the organization; and we must therefore +look back very far in the past, to find man in that early condition in +which his mind was not sufficiently developed, to remove his body from +the modifying influence of external conditions and the cumulative action +of "natural selection." I believe, therefore, that there is no _a +priori_ reason against our finding the remains of man or his works in +the tertiary deposits. The absence of all such remains in the European +beds of this age has little weight, because, as we go further back in +time, it is natural to suppose that man's distribution over the surface +of the earth was less universal than at present. + +Besides, Europe was in a great measure submerged during the tertiary +epoch; and though its scattered islands may have been uninhabited by +man, it by no means follows that he did not at the same time exist in +warm or tropical continents. If geologists can point out to us the most +extensive land in the warmer regions of the earth, which has not been +submerged since Eocene or Miocene times, it is there that we may expect +to find some traces of the very early progenitors of man. It is there +that we may trace back the gradually decreasing brain of former races, +till we come to a time when the body also begins materially to differ. +Then we shall have reached the starting point of the human family. +Before that period, he had not mind enough to preserve his body from +change, and would, therefore, have been subject to the same +comparatively rapid modifications of form as the other mammalia. + + +_Their Bearing on the Dignity and Supremacy of Man._ + +If the views I have here endeavoured to sustain have any foundation, +they give us a new argument for placing man apart, as not only the head +and culminating point of the grand series of organic nature, but as in +some degree a new and distinct order of being. From those infinitely +remote ages, when the first rudiments of organic life appeared upon the +earth, every plant, and every animal has been subject to one great law +of physical change. As the earth has gone through its grand cycles of +geological, climatal, and organic progress, every form of life has been +subject to its irresistible action, and has been continually, but +imperceptibly moulded into such new shapes as would preserve their +harmony with the ever-changing universe. No living thing could escape +this law of its being; none (except, perhaps, the simplest and most +rudimentary organisms), could remain unchanged and live, amid the +universal change around it. + +At length, however, there came into existence a being in whom that +subtle force we term _mind_, became of greater importance than his mere +bodily structure. Though with a naked and unprotected body, _this_ gave +him clothing against the varying inclemencies of the seasons. Though +unable to compete with the deer in swiftness, or with the wild bull in +strength, _this_ gave him weapons with which to capture or overcome +both. Though less capable than most other animals of living on the herbs +and the fruits that unaided nature supplies, this wonderful faculty +taught him to govern and direct nature to his own benefit, and make her +produce food for him, when and where he pleased. From the moment when +the first skin was used as a covering, when the first rude spear was +formed to assist in the chase, when fire was first used to cook his +food, when the first seed was sown or shoot planted, a grand revolution +was effected in nature, a revolution which in all the previous ages of +the earth's history had had no parallel, for a being had arisen who was +no longer necessarily subject to change with the changing universe--a +being who was in some degree superior to nature, inasmuch as he knew how +to control and regulate her action, and could keep himself in harmony +with her, not by a change in body, but by an advance of mind. + +Here, then, we see the true grandeur and dignity of man. On this view of +his special attributes, we may admit, that even those who claim for him +a position as an order, a class, or a sub-kingdom by himself, have some +show of reason on their side. He is, indeed, a being apart, since he is +not influenced by the great laws which irresistibly modify all other +organic beings. Nay more; this victory which he has gained for himself, +gives him a directing influence over other existences. Man has not only +escaped "natural selection" himself, but he is actually able to take +away some of that power from nature which before his appearance she +universally exercised. We can anticipate the time when the earth will +produce only cultivated plants and domestic animals; when man's +selection shall have supplanted "natural selection;" and when the ocean +will be the only domain in which that power can be exerted, which for +countless cycles of ages ruled supreme over all the earth. + + +_Their Bearing on the future Development of Man._ + +We now find ourselves enabled to answer those who maintain, that if Mr. +Darwin's theory of the Origin of Species is true, man too must change in +form, and become developed into some other animal as different from his +present self as he is from the Gorilla or the Chimpanzee; and who +speculate on what this form is likely to be. But it is evident that such +will not be the case; for no change of conditions is conceivable, which +will render any important alteration of his form and organization so +universally useful and necessary to him, as to give those possessing it +always the best chance of surviving, and thus lead to the development +of a new species, genus, or higher group of man. On the other hand, we +know that far greater changes of conditions and of his entire +environment have been undergone by man, than any other highly organized +animal could survive unchanged, and have been met by mental, not +corporeal adaptation. The difference of habits, of food, clothing, +weapons, and enemies, between savage and civilized man, is enormous. +Difference in bodily form and structure there is practically none, +except a slightly increased size of brain, corresponding to his higher +mental development. + +We have every reason to believe, then, that man may have existed and may +continue to exist, through a series of geological periods which shall +see all other forms of animal life again and again changed; while he +himself remains unchanged, except in the two particulars already +specified--the head and face, as immediately connected with the organ of +the mind and as being the medium of expressing the most refined emotions +of his nature,--and to a slight extent in colour, hair, and proportions, +so far as they are correlated with constitutional resistance to disease. + + +_Summary._ + +Briefly to recapitulate the argument;--in two distinct ways has man +escaped the influence of those laws which have produced unceasing change +in the animal world. 1. By his superior intellect he is enabled to +provide himself with clothing and weapons, and by cultivating the soil +to obtain a constant supply of congenial food. This renders it +unnecessary for his body, like those of the lower animals, to be +modified in accordance with changing conditions--to gain a warmer +natural covering, to acquire more powerful teeth or claws, or to become +adapted to obtain and digest new kinds of food, as circumstances may +require. 2. By his superior sympathetic and moral feelings, he becomes +fitted for the social state; he ceases to plunder the weak and helpless +of his tribe; he shares the game which he has caught with less active or +less fortunate hunters, or exchanges it for weapons which even the weak +or the deformed can fashion; he saves the sick and wounded from death; +and thus the power which leads to the rigid destruction of all animals +who cannot in every respect help themselves, is prevented from acting on +him. + +This power is "natural selection;" and, as by no other means can it be +shown, that individual variations can ever become accumulated and +rendered permanent so as to form well-marked races, it follows that the +differences which now separate mankind from other animals, must have +been produced before he became possessed of a human intellect or human +sympathies. This view also renders possible, or even requires, the +existence of man at a comparatively remote geological epoch. For, during +the long periods in which other animals have been undergoing +modification in their whole structure, to such an amount as to +constitute distinct genera and families, man's _body_ will have +remained generically, or even specifically, the same, while his _head_ +and _brain_ alone will have undergone modification equal to theirs. We +can thus understand how it is that, judging from the head and brain, +Professor Owen places man in a distinct sub-class of mammalia, while as +regards the bony structure of his body, there is the closest anatomical +resemblance to the anthropoid apes, "every tooth, every bone, strictly +homologous--which makes the determination of the difference between +_Homo_ and _Pithecus_ the anatomist's difficulty." The present theory +fully recognises and accounts for these facts; and we may perhaps claim +as corroborative of its truth, that it neither requires us to depreciate +the intellectual chasm which separates man from the apes, nor refuses +full recognition of the striking resemblances to them, which exist in +other parts of his structure. + + +_Conclusion._ + +In concluding this brief sketch of a great subject, I would point out +its bearing upon the future of the human race. If my conclusions are +just, it must inevitably follow that the higher--the more intellectual +and moral--must displace the lower and more degraded races; and the +power of "natural selection," still acting on his mental organization, +must ever lead to the more perfect adaptation of man's higher faculties +to the conditions of surrounding nature, and to the exigencies of the +social state. While his external form will probably ever remain +unchanged, except in the development of that perfect beauty which +results from a healthy and well organized body, refined and ennobled by +the highest intellectual faculties and sympathetic emotions, his mental +constitution may continue to advance and improve, till the world is +again inhabited by a single nearly homogeneous race, no individual of +which will be inferior to the noblest specimens of existing humanity. + +Our progress towards such a result is very slow, but it still seems to +be a progress. We are just now living at an abnormal period of the +world's history, owing to the marvellous developments and vast practical +results of science, having been given to societies too low morally and +intellectually, to know how to make the best use of them, and to whom +they have consequently been curses as well as blessings. Among civilized +nations at the present day, it does not seem possible for natural +selection to act in any way, so as to secure the permanent advancement +of morality and intelligence; for it is indisputably the mediocre, if +not the low, both as regards morality and intelligence, who succeed best +in life and multiply fastest. Yet there is undoubtedly an advance--on +the whole a steady and a permanent one--both in the influence on public +opinion of a high morality, and in the general desire for intellectual +elevation; and as I cannot impute this in any way to "survival of the +fittest," I am forced to conclude that it is due, to the inherent +progressive power of those glorious qualities which raise us so +immeasurably above our fellow animals, and at the same time afford us +the surest proof that there are other and higher existences than +ourselves, from whom these qualities may have been derived, and towards +whom we may be ever tending. + + + + +X. + +THE LIMITS OF NATURAL SELECTION AS APPLIED TO MAN. + + +Throughout this volume I have endeavoured to show, that the known laws +of variation, multiplication, and heredity, resulting in a "struggle for +existence" and the "survival of the fittest," have probably sufficed to +produce all the varieties of structure, all the wonderful adaptations, +all the beauty of form and of colour, that we see in the animal and +vegetable kingdoms. To the best of my ability I have answered the most +obvious and the most often repeated objections to this theory, and have, +I hope, added to its general strength, by showing how colour--one of the +strongholds of the advocates of special creation--may be, in almost all +its modifications, accounted for by the combined influence of sexual +selection and the need of protection. I have also endeavoured to show, +how the same power which has modified animals has acted on man; and +have, I believe, proved that, as soon as the human intellect became +developed above a certain low stage, man's body would cease to be +materially affected by natural selection, because the development of his +mental faculties would render important modifications of its form and +structure unnecessary. It will, therefore, probably excite some +surprise among my readers, to find that I do not consider that all +nature can be explained on the principles of which I am so ardent an +advocate; and that I am now myself going to state objections, and to +place limits, to the power of "natural selection." I believe, however, +that there are such limits; and that just as surely as we can trace the +action of natural laws in the development of organic forms, and can +clearly conceive that fuller knowledge would enable us to follow step by +step the whole process of that development, so surely can we trace the +action of some unknown higher law, beyond and independent of all those +laws of which we have any knowledge. We can trace this action more or +less distinctly in many phenomena, the two most important of which +are--the origin of sensation or consciousness, and the development of +man from the lower animals. I shall first consider the latter difficulty +as more immediately connected with the subjects discussed in this +volume. + + +_What Natural Selection can Not do._ + +In considering the question of the development of man by known natural +laws, we must ever bear in mind the first principle of "natural +selection," no less than of the general theory of evolution, that all +changes of form or structure, all increase in the size of an organ or in +its complexity, all greater specialization or physiological division of +labour, can only be brought about, in as much as it is for the good of +the being so modified. Mr. Darwin himself has taken care to impress +upon us, that "natural selection" has no power to produce absolute +perfection but only relative perfection, no power to advance any being +much beyond his follow beings, but only just so much beyond them as to +enable it to survive them in the struggle for existence. Still less has +it any power to produce modifications which are in any degree injurious +to its possessor, and Mr. Darwin frequently uses the strong expression, +that a single case of this kind would be fatal to his theory. If, +therefore, we find in man any characters, which all the evidence we can +obtain goes to show would have been actually injurious to him on their +first appearance, they could not possibly have been produced by natural +selection. Neither could any specially developed organ have been so +produced if it had been merely useless to him, or if its use were not +proportionate to its degree of development. Such cases as these would +prove, that some other law, or some other power, than "natural +selection" had been at work. But if, further, we could see that these +very modifications, though hurtful or useless at the time when they +first appeared, became in the highest degree useful at a much later +period, and are now essential to the full moral and intellectual +development of human nature, we should then infer the action of mind, +foreseeing the future and preparing for it, just as surely as we do, +when we see the breeder set himself to work with the determination to +produce a definite improvement in some cultivated plant or domestic +animal. I would further remark that this enquiry is as thoroughly +scientific and legitimate as that into the origin of species itself. It +is an attempt to solve the inverse problem, to deduce the existence of a +new power of a definite character, in order to account for facts which +according to the theory of natural selection ought not to happen. Such +problems are well known to science, and the search after their solution +has often led to the most brilliant results. In the case of man, there +are facts of the nature above alluded to, and in calling attention to +them, and in inferring a cause for them, I believe that I am as strictly +within the bounds of scientific investigation as I have been in any +other portion of my work. + + +_The Brain of the Savage shown to be Larger than he Needs it to be._ + +_Size of Brain an important Element of Mental Power._--The brain is +universally admitted to be the organ of the mind; and it is almost as +universally admitted, that size of brain is one of the most important of +the elements which determine mental power or capacity. There seems to be +no doubt that brains differ considerably in quality, as indicated by +greater or less complexity of the convolutions, quantity of grey matter, +and perhaps unknown peculiarities of organization; but this difference +of quality seems merely to increase or diminish the influence of +quantity, not to neutralize it. Thus, all the most eminent modern +writers see an intimate connection between the diminished size of the +brain in the lower races of mankind, and their intellectual +inferiority. The collections of Dr. J. B. Davis and Dr. Morton give the +following as the average internal capacity of the cranium in the chief +races:--Teutonic family, 94 cubic inches; Esquimaux, 91 cubic inches; +Negroes, 85 cubic inches; Australians and Tasmanians, 82 cubic inches; +Bushmen, 77 cubic inches. These last numbers, however, are deduced from +comparatively few specimens, and may be below the average, just as a +small number of Finns and Cossacks give 98 cubic inches, or considerably +more than that of the German races. It is evident, therefore, that the +absolute bulk of the brain is not necessarily much less in savage than +in civilised man, for Esquimaux skulls are known with a capacity of 113 +inches, or hardly less than the largest among Europeans. But what is +still more extraordinary, the few remains yet known of pre-historic man +do not indicate any material diminution in the size of the brain case. A +Swiss skull of the stone age, found in the lake dwelling of Meilen, +corresponded exactly to that of a Swiss youth of the present day. The +celebrated Neanderthal skull had a larger circumference than the +average, and its capacity, indicating actual mass of brain, is estimated +to have been not less than 75 cubic inches, or nearly the average of +existing Australian crania. The Engis skull, perhaps the oldest known, +and which, according to Sir John Lubbock, "there seems no doubt was +really contemporary with the mammoth and the cave bear," is yet, +according to Professor Huxley, "a fair average skull, which might have +belonged to a philosopher, or might have contained the thoughtless +brains of a savage." Of the cave men of Les Eyzies, who were undoubtedly +contemporary with the reindeer in the South of France, Professor Paul +Broca says (in a paper read before the Congress of Pre-historic +Archaeology in 1868)--"The great capacity of the brain, the development +of the frontal region, the fine elliptical form of the anterior part of +the profile of the skull, are incontestible characteristics of +superiority, such as we are accustomed to meet with in civilised races;" +yet the great breadth of the face, the enormous development of the +ascending ramus of the lower jaw, the extent and roughness of the +surfaces for the attachment of the muscles, especially of the +masticators, and the extraordinary development of the ridge of the +femur, indicate enormous muscular power, and the habits of a savage and +brutal race. + +These facts might almost make us doubt whether the size of the brain is +in any direct way an index of mental power, had we not the most +conclusive evidence that it is so, in the fact that, whenever an adult +male European has a skull less than nineteen inches in circumference, or +has less than sixty-five cubic inches of brain, he is invariably +idiotic. When we join with this the equally undisputed fact, that great +men--those who combine acute perception with great reflective power, +strong passions, and general energy of character, such as Napoleon, +Cuvier, and O'Connell, have always heads far above the average size, we +must feel satisfied that volume of brain is one, and perhaps the most +important, measure of intellect; and this being the case, we cannot fail +to be struck with the apparent anomaly, that many of the lowest savages +should have as much brains as average Europeans. The idea is suggested +of a surplusage of power; of an instrument beyond the needs of its +possessor. + +_Comparison of the Brains of Man and of Anthropoid Apes._--In order to +discover if there is any foundation for this notion, let us compare the +brain of man with that of animals. The adult male Orang-utan is quite as +bulky as a small sized man, while the Gorilla is considerably above the +average size of man, as estimated by bulk and weight; yet the former has +a brain of only 28 cubic inches, the latter, one of 30, or, in the +largest specimen yet known, of 341/2 cubic inches. We have seen that the +average cranial capacity of the lowest savages is probably not less than +_five-sixths_ of that of the highest civilized races, while the brain of +the anthropoid apes scarcely amounts to _one-third_ of that of man, in +both cases taking the average; or the proportions may be more clearly +represented by the following figures--anthropoid apes, 10; savages, 26; +civilized man, 32. But do these figures at all approximately represent +the relative intellect of the three groups? Is the savage really no +farther removed from the philosopher, and so much removed from the ape, +as these figures would indicate? In considering this question, we must +not forget that the heads of savages vary in size, almost as much as +those of civilized Europeans. Thus, while the largest Teutonic skull in +Dr. Davis' collection is 112.4 cubic inches, there is an Araucanian of +115.5, an Esquimaux of 113.1, a Marquesan of 11O.6, a Negro of 105.8, +and even an Australian of 104.5 cubic inches. We may, therefore, fairly +compare the savage with the highest European on the one side, and with +the Orang, Chimpanzee, or Gorilla, on the other, and see whether there +is any relative proportion between brain and intellect. + +_Range of intellectual power in Man._--First, let us consider what this +wonderful instrument, the brain, is capable of in its higher +developments. In Mr. Galton's interesting work on "Hereditary Genius," +he remarks on the enormous difference between the intellectual power and +grasp of the well-trained mathematician or man of science, and the +average Englishman. The number of marks obtained by high wranglers, is +often more than thirty times as great as that of the men at the bottom +of the honour list, who are still of fair mathematical ability; and it +is the opinion of skilled examiners, that even this does not represent +the full difference of intellectual power. If, now, we descend to those +savage tribes who only count to three or five, and who find it +impossible to comprehend the addition of two and three without having +the objects actually before them, we feel that the chasm between them +and the good mathematician is so vast, that a thousand to one will +probably not fully express it. Yet we know that the mass of brain might +be nearly the same in both, or might not differ in a greater proportion +than as 5 to 6; whence we may fairly infer that the savage possesses a +brain capable, if cultivated and developed, of performing work of a kind +and degree far beyond what he ever requires it to do. + +Again, let us consider the power of the higher or even the average +civilized man, of forming abstract ideas, and carrying on more or less +complex trains of reasoning. Our languages are full of terms to express +abstract conceptions. Our business and our pleasures involve the +continual foresight of many contingencies. Our law, our government, and +our science, continually require us to reason through a variety of +complicated phenomena to the expected result. Even our games, such as +chess, compel us to exercise all these faculties in a remarkable degree. +Compare this with the savage languages, which contain no words for +abstract conceptions; the utter want of foresight of the savage man +beyond his simplest necessities; his inability to combine, or to +compare, or to reason on any general subject that does not immediately +appeal to his senses. So, in his moral and aesthetic faculties, the +savage has none of those wide sympathies with all nature, those +conceptions of the infinite, of the good, of the sublime and beautiful, +which are so largely developed in civilized man. Any considerable +development of these would, in fact, be useless or even hurtful to him, +since they would to some extent interfere with the supremacy of those +perceptive and animal faculties on which his very existence often +depends, in the severe struggle he has to carry on against nature and +his fellow-man. Yet the rudiments of all these powers and feelings +undoubtedly exist in him, since one or other of them frequently manifest +themselves in exceptional cases, or when some special circumstances call +them forth. Some tribes, such as the Santals, are remarkable for as pure +a love of truth as the most moral among civilized men. The Hindoo and +the Polynesian have a high artistic feeling, the first traces of which +are clearly visible in the rude drawings of the palaeolithic men who were +the contemporaries in France of the Reindeer and the Mammoth. Instances +of unselfish love, of true gratitude, and of deep religious feeling, +sometimes occur among most savage races. + +On the whole, then, we may conclude, that the general moral and +intellectual development of the savage, is not less removed from that of +civilized man than has been shown to be the case in the one department +of mathematics; and from the fact that all the moral and intellectual +faculties do occasionally manifest themselves, we may fairly conclude +that they are always latent, and that the large brain of the savage man +is much beyond his actual requirements in the savage state. + +_Intellect of Savages and of Animals compared._--Let us now compare the +intellectual wants of the savage, and the actual amount of intellect he +exhibits, with those of the higher animals. Such races as the Andaman +Islanders, the Australians, and the Tasmanians, the Digger Indians of +North America, or the natives of Fuegia, pass their lives so as to +require the exercise of few faculties not possessed in an equal degree +by many animals. In the mode of capture of game or fish, they by no +means surpass the ingenuity or forethought of the jaguar, who drops +saliva into the water, and seizes the fish as they come to eat it; or of +wolves and jackals, who hunt in packs; or of the fox, who buries his +surplus food till he requires it. The sentinels placed by antelopes and +by monkeys, and the various modes of building adopted by field mice and +beavers, as well as the sleeping place of the orang-utan, and the +tree-shelter of some of the African anthropoid apes, may well be +compared with the amount of care and forethought bestowed by many +savages in similar circumstances. His possession of free and perfect +hands, not required for locomotion, enable man to form and use weapons +and implements which are beyond the physical powers of brutes; but +having done this, he certainly does not exhibit more mind in using them +than do many lower animals. What is there in the life of the savage, but +the satisfying of the cravings of appetite in the simplest and easiest +way? What thoughts, ideas, or actions are there, that raise him many +grades above the elephant or the ape? Yet he possesses, as we have seen, +a brain vastly superior to theirs in size and complexity; and this brain +gives him, in an undeveloped state, faculties which he never requires to +use. And if this is true of existing savages, how much more true must +it have been of the men whose sole weapons were rudely chipped flints, +and some of whom, we may fairly conclude, were lower than any existing +race; while the only evidence yet in our possession shows them to have +had brains fully as capacious as those of the average of the lower +savage races. + +We see, then, that whether we compare the savage with the higher +developments of man, or with the brutes around him, we are alike driven +to the conclusion that in his large and well-developed brain he +possesses an organ quite disproportionate to his actual requirements--an +organ that seems prepared in advance, only to be fully utilized as he +progresses in civilization. A brain slightly larger than that of the +gorilla would, according to the evidence before us, fully have sufficed +for the limited mental development of the savage; and we must therefore +admit, that the large brain he actually possesses could never have been +solely developed by any of those laws of evolution, whose essence is, +that they lead to a degree of organization exactly proportionate to the +wants of each species, never beyond those wants--that no preparation can +be made for the future development of the race--that one part of the +body can never increase in size or complexity, except in strict +co-ordination to the pressing wants of the whole. The brain of +pre-historic and of savage man seems to me to prove the existence of +some power, distinct from that which has guided the development of the +lower animals through their ever-varying forms of being. + + +_The Use of the Hairy Covering of Mammalia._ + +Let us now consider another point in man's organization, the bearing of +which has been almost entirely overlooked by writers on both sides of +this question. One of the most general external characters of the +terrestrial mammalia is the hairy covering of the body, which, whenever +the skin is flexible, soft, and sensitive, forms a natural protection +against the severities of climate, and particularly against rain. That +this is its most important function, is well shown by the manner in +which the hairs are disposed so as to carry off the water, by being +invariably directed downwards from the most elevated parts of the body. +Thus, on the under surface the hair is always less plentiful, and, in +many cases, the belly is almost bare. The hair lies downwards, on the +limbs of all walking mammals, from the shoulder to the toes, but in the +orang-utan it is directed from the shoulder to the elbow, and again from +the wrist to the elbow, in a reverse direction. This corresponds to the +habits of the animal, which, when resting, holds its long arms upwards +over its head, or clasping a branch above it, so that the rain would +flow down both the arm and fore-arm to the long hair which meets at the +elbow. In accordance with this principle, the hair is always longer or +more dense along the spine or middle of the back from the nape to the +tail, often rising into a crest of hair or bristles on the ridge of the +back. This character prevails through the entire series of the mammalia, +from the marsupials to the quadrumana, and by this long persistence it +must have acquired such a powerful hereditary tendency, that we should +expect it to reappear continually even after it had been abolished by +ages of the most rigid selection; and we may feel sure that it never +could have been completely abolished under the law of natural selection, +unless it had become so positively injurious as to lead to the almost +invariable extinction of individuals possessing it. + + +_The constant absence of Hair from certain parts of Man's Body a +remarkable Phenomenon._ + +In man the hairy covering of the body has almost totally disappeared, +and, what is very remarkable, it has disappeared more completely from +the back than from any other part of the body. Bearded and beardless +races alike have the back smooth, and even when a considerable quantity +of hair appears on the limbs and breast, the back, and especially the +spinal region, is absolutely free, thus completely reversing the +characteristics of all other mammalia. The Ainos of the Kurile Islands +and Japan are said to be a hairy race; but Mr. Bickmore, who saw some of +them, and described them in a paper read before the Ethnological +Society, gives no details as to where the hair was most abundant, merely +stating generally, that "their chief peculiarity is their great +abundance of hair, not only on the head and face, but over the whole +body." This might very well be said of any man who had hairy limbs and +breast, unless it was specially stated that his back was hairy, which +is not done in this case. The hairy family in Birmah have, indeed, hair +on the back rather longer than on the breast, thus reproducing the true +mammalian character, but they have still longer hair on the face, +forehead, and inside the ears, which is quite abnormal; and the fact +that their teeth are all very imperfect, shows that this is a case of +monstrosity rather than one of true reversion to the ancestral type of +man before he lost his hairy covering. + + +_Savage Man feels the Want of this Hairy Covering._ + +We must now enquire if we have any evidence to show, or any reason to +believe, that a hairy covering to the back would be in any degree +hurtful to savage man, or to man in any stage of his progress from his +lower animal form; and if it were merely useless, could it have been so +entirely and completely removed as not to be continually reappearing in +mixed races? Let us look to savage man for some light on these points. +One of the most common habits of savages is to use some covering for the +back and shoulders, even when they have none on any other part of the +body. The early voyagers observed with surprise, that the Tasmanians, +both men and women, wore the kangaroo-skin, which was their only +covering, not from any feeling of modesty, but over the shoulders to +keep the back dry and warm. A cloth over the shoulders was also the +national dress of the Maories. The Patagonians wear a cloak or mantle +over the shoulders, and the Fuegians often wear a small piece of skin on +the back, laced on, and shifted from side to side as the wind blows. +The Hottentots also wore a somewhat similar skin over the back, which +they never removed, and in which they were buried. Even in the tropics +most savages take precautions to keep their backs dry. The natives of +Timor use the leaf of a fan palm, carefully stitched up and folded, +which they always carry with them, and which, held over the back, forms +an admirable protection from the rain. Almost all the Malay races, as +well as the Indians of South America, make great palm-leaf hats, four +feet or more across, which they use during their canoe voyages to +protect their bodies from heavy showers of rain; and they use smaller +hats of the same kind when travelling by land. + +We find, then, that so far from there being any reason to believe that a +hairy covering to the back could have been hurtful or even useless to +pre-historic man, the habits of modern savages indicate exactly the +opposite view, as they evidently feel the want of it, and are obliged to +provide substitutes of various kinds. The perfectly erect posture of +man, may be supposed to have something to do with the disappearance of +the hair from his body, while it remains on his head; but when walking, +exposed to rain and wind, a man naturally stoops forwards, and thus +exposes his back; and the undoubted fact, that most savages feel the +effects of cold and wet most severely in that part of the body, +sufficiently demonstrates that the hair could not have ceased to grow +there merely because it was useless, even if it were likely that a +character so long persistent in the entire order of mammalia, could have +so completely disappeared, under the influence of so weak a selective +power as a diminished usefulness. + + +_Man's Naked Skin could not have been produced by Natural Selection._ + +It seems to me, then, to be absolutely certain, that "Natural Selection" +could not have produced man's hairless body by the accumulation of +variations from a hairy ancestor. The evidence all goes to show that +such variations could not have been useful, but must, on the contrary, +have been to some extent hurtful. If even, owing to an unknown +correlation with other hurtful qualities, it had been abolished in the +ancestral tropical man, we cannot conceive that, as man spread into +colder climates, it should not have returned under the powerful +influence of reversion to such a long persistent ancestral type. But the +very foundation of such a supposition as this is untenable; for we +cannot suppose that a character which, like hairiness, exists throughout +the whole of the mammalia, can have become, in one form only, so +constantly correlated with an injurious character, as to lead to its +permanent suppression--a suppression so complete and effectual that it +never, or scarcely ever, reappears in mongrels of the most widely +different races of man. + +Two characters could hardly be wider apart, than the size and +development of man's brain, and the distribution of hair upon the +surface of his body; yet they both lead us to the same conclusion--that +some other power than Natural Selection has been engaged in his +production. + + +_Feet and Hands of Man, considered as Difficulties on the Theory of +Natural Selection._ + +There are a few other physical characteristics of man, that may just be +mentioned as offering similar difficulties, though I do not attach the +same importance to them as to those I have already dwelt on. The +specialization and perfection of the hands and feet of man seems +difficult to account for. Throughout the whole of the quadrumana the +foot is prehensile; and a very rigid selection must therefore have been +needed to bring about that arrangement of the bones and muscles, which +has converted the thumb into a great toe, so completely, that the power +of opposability is totally lost in every race, whatever some travellers +may vaguely assert to the contrary. It is difficult to see why the +prehensile power should have been taken away. It must certainly have +been useful in climbing, and the case of the baboons shows that it is +quite compatible with terrestrial locomotion. It may not be compatible +with perfectly easy erect locomotion; but, then, how can we conceive +that early man, _as an animal_, gained anything by purely erect +locomotion? Again, the hand of man contains latent capacities and powers +which are unused by savages, and must have been even less used by +palaeolithic man and his still ruder predecessors. It has all the +appearance of an organ prepared for the use of civilized man, and one +which was required to render civilization possible. Apes make little use +of their separate fingers and opposable thumbs. They grasp objects +rudely and clumsily, and look as if a much less specialized extremity +would have served their purpose as well. I do not lay much stress on +this, but, if it be proved that some intelligent power has guided or +determined the development of man, then we may see indications of that +power, in facts which, by themselves, would not serve to prove its +existence. + +_The voice of man._--The same remark will apply to another peculiarly +human character, the wonderful power, range, flexibility, and sweetness, +of the musical sounds producible by the human larynx, especially in the +female sex. The habits of savages give no indication of how this faculty +could have been developed by natural selection; because it is never +required or used by them. The singing of savages is a more or less +monotonous howling, and the females seldom sing at all. Savages +certainly never choose their wives for fine voices, but for rude health, +and strength, and physical beauty. Sexual selection could not therefore +have developed this wonderful power, which only comes into play among +civilized people. It seems as if the organ had been prepared in +anticipation of the future progress of man, since it contains latent +capacities which are useless to him in his earlier condition. The +delicate correlations of structure that give it such marvellous powers, +could not therefore have been acquired by means of natural selection. + + +_The Origin of some of Man's Mental Faculties, by the preservation of +Useful Variations, not possible._ + +Turning to the mind of man, we meet with many difficulties in attempting +to understand, how those mental faculties, which are especially human, +could have been acquired by the preservation of useful variations. At +first sight, it would seem that such feelings as those of abstract +justice and benevolence could never have been so acquired, because they +are incompatible with the law of the strongest, which is the essence of +natural selection. But this is, I think, an erroneous view, because we +must look, not to individuals but to societies; and justice and +benevolence, exercised towards members of the same tribe, would +certainly tend to strengthen that tribe, and give it a superiority over +another in which the right of the strongest prevailed, and where +consequently the weak and the sickly were left to perish, and the few +strong ruthlessly destroyed the many who were weaker. + +But there is another class of human faculties that do not regard our +fellow men, and which cannot, therefore, be thus accounted for. Such are +the capacity to form ideal conceptions of space and time, of eternity +and infinity--the capacity for intense artistic feelings of pleasure, in +form, colour, and composition--and for those abstract notions of form +and number which render geometry and arithmetic possible. How were all +or any of these faculties first developed, when they could have been of +no possible use to man in his early stages of barbarism? How could +"natural selection," or survival of the fittest in the struggle for +existence, at all favour the development of mental powers so entirely +removed from the material necessities of savage men, and which even now, +with our comparatively high civilization, are, in their farthest +developments, in advance of the age, and appear to have relation rather +to the future of the race than to its actual status? + + +_Difficulty as to the Origin of the Moral Sense._ + +Exactly the same difficulty arises, when we endeavour to account for the +development of the moral sense or conscience in savage man; for although +the _practice_ of benevolence, honesty, or truth, may have been useful +to the tribe possessing these virtues, that does not at all account for +the peculiar _sanctity_, attached to actions which each tribe considers +right and moral, as contrasted with the very different feelings with +which they regard what is merely _useful_. The utilitarian hypothesis +(which is the theory of natural selection applied to the mind) seems +inadequate to account for the development of the moral sense. This +subject has been recently much discussed, and I will here only give one +example to illustrate my argument. The utilitarian sanction for +truthfulness is by no means very powerful or universal. Few laws enforce +it. No very severe reprobation follows untruthfulness. In all ages and +countries, falsehood has been thought allowable in love, and laudable in +war; while, at the present day, it is held to be venial by the majority +of mankind, in trade, commerce, and speculation. A certain amount of +untruthfulness is a necessary part of politeness in the east and west +alike, while even severe moralists have held a lie justifiable, to elude +an enemy or prevent a crime. Such being the difficulties with which this +virtue has had to struggle, with so many exceptions to its practice, +with so many instances in which it brought ruin or death to its too +ardent devotee, how can we believe that considerations of utility could +ever invest it with the mysterious sanctity of the highest +virtue,--could ever induce men to value truth for its own sake, and +practice it regardless of consequences? + +Yet, it is a fact, that such a mystical sense of wrong does attach to +untruthfulness, not only among the higher classes of civilized people, +but among whole tribes of utter savages. Sir Walter Elliott tells us (in +his paper "On the Characteristics of the Population of Central and +Southern India," published in the Journal of the Ethnological Society of +London, vol. i., p. 107) that the Kurubars and Santals, barbarous +hill-tribes of Central India, are noted for veracity. It is a common +saying that "a Kurubar _always_ speaks the truth;" and Major Jervis +says, "the Santals are the most truthful men I ever met with." As a +remarkable instance of this quality the following fact is given. A +number of prisoners, taken during the Santal insurrection, were allowed +to go free on parole, to work at a certain spot for wages. After some +time cholera attacked them and they were obliged to leave, but every man +of them returned and gave up his earnings to the guard. Two hundred +savages with money in their girdles, walked thirty miles back to prison +rather than break their word! My own experience among savages has +furnished me with similar, although less severely tested, instances; and +we cannot avoid asking, how is it, that in these few cases "experiences +of utility" have left such an overwhelming impression, while in so many +others they have left none? The experiences of savage men as regards the +utility of truth, must, in the long run, be pretty nearly equal. How is +it, then, that in some cases the result is a sanctity which overrides +all considerations of personal advantage, while in others there is +hardly a rudiment of such a feeling? + +The intuitional theory, which I am now advocating, explains this by the +supposition, that there is a feeling--a sense of right and wrong--in our +nature, antecedent to and independent of experiences of utility. Where +free play is allowed to the relations between man and man, this feeling +attaches itself to those acts of universal utility or self-sacrifice, +which are the products of our affections and sympathies, and which we +term moral; while it may be, and often is, perverted, to give the same +sanction to acts of narrow and conventional utility which are really +immoral,--as when the Hindoo will tell a lie, but will sooner starve +than eat unclean food; and looks upon the marriage of adult females as +gross immorality. + +The strength of the moral feeling will depend upon individual or racial +constitution, and on education and habit;--the acts to which its +sanctions are applied, will depend upon how far the simple feelings and +affections of our nature, have been modified by custom, by law, or by +religion. + +It is difficult to conceive that such an intense and mystical feeling of +right and wrong, (so intense as to overcome all ideas of personal +advantage or utility), could have been developed out of accumulated +ancestral experiences of utility; and still more difficult to +understand, how feelings developed by one set of utilities, could be +transferred to acts of which the utility was partial, imaginary, or +altogether absent. But if a moral sense is an essential part of our +nature, it is easy to see, that its sanction may often be given to acts +which are useless or immoral; just as the natural appetite for drink, is +perverted by the drunkard into the means of his destruction. + + +_Summary of the Argument as to the Insufficiency of Natural Selection to +account for the Development of Man._ + +Briefly to resume my argument--I have shown that the brain of the lowest +savages, and, as far as we yet know, of the pre-historic races, is +little inferior in size to that of the highest types of man, and +immensely superior to that of the higher animals; while it is +universally admitted that quantity of brain is one of the most +important, and probably the most essential, of the elements which +determine mental power. Yet the mental requirements of savages, and the +faculties actually exercised by them, are very little above those of +animals. The higher feelings of pure morality and refined emotion, and +the power of abstract reasoning and ideal conception, are useless to +them, are rarely if ever manifested, and have no important relations to +their habits, wants, desires, or well-being. They possess a mental organ +beyond their needs. Natural Selection could only have endowed savage man +with a brain a little superior to that of an ape, whereas he actually +possesses one very little inferior to that of a philosopher. + +The soft, naked, sensitive skin of man, entirely free from that hairy +covering which is so universal among other mammalia, cannot be explained +on the theory of natural selection. The habits of savages show that they +feel the want of this covering, which is most completely absent in man +exactly where it is thickest in other animals. We have no reason +whatever to believe, that it could have been hurtful, or even useless to +primitive man; and, under these circumstances, its complete abolition, +shown by its never reverting in mixed breeds, is a demonstration of the +agency of some other power than the law of the survival of the fittest, +in the development of man from the lower animals. + +Other characters show difficulties of a similar kind, though not perhaps +in an equal degree. The structure of the human foot and hand seem +unnecessarily perfect for the needs of savage man, in whom they are as +completely and as humanly developed as in the highest races. The +structure of the human larynx, giving the power of speech and of +producing musical sounds, and especially its extreme development in the +female sex, are shown to be beyond the needs of savages, and from their +known habits, impossible to have been acquired either by sexual +selection, or by survival of the fittest. + +The mind of man offers arguments in the same direction, hardly less +strong than those derived from his bodily structure. A number of his +mental faculties have no relation to his fellow men, or to his material +progress. The power of conceiving eternity and infinity, and all those +purely abstract notions of form, number, and harmony, which play so +large a part in the life of civilised races, are entirely outside of the +world of thought of the savage, and have no influence on his individual +existence or on that of his tribe. They could not, therefore, have been +developed by any preservation of useful forms of thought; yet we find +occasional traces of them amidst a low civilization, and at a time when +they could have had no practical effect on the success of the +individual, the family, or the race; and the development of a moral +sense or conscience by similar means is equally inconceivable. + +But, on the other hand, we find that every one of these characteristics +is necessary for the full development of human nature. The rapid +progress of civilization under favourable conditions, would not be +possible, were not the organ of the mind of man prepared in advance, +fully developed as regards size, structure, and proportions, and only +needing a few generations of use and habit to co-ordinate its complex +functions. The naked and sensitive skin, by necessitating clothing and +houses, would lead to the more rapid development of man's inventive and +constructive faculties; and, by leading to a more refined feeling of +personal modesty, may have influenced, to a considerable extent, his +moral nature. The erect form of man, by freeing the hands from all +locomotive uses, has been necessary for his intellectual advancement; +and the extreme perfection of his hands, has alone rendered possible +that excellence in all the arts of civilization which raises him so far +above the savage, and is perhaps but the forerunner of a higher +intellectual and moral advancement. The perfection of his vocal organs +has first led to the formation of articulate speech, and then to the +development of those exquisitely toned sounds, which are only +appreciated by the higher races, and which are probably destined for +more elevated uses and more refined enjoyment, in a higher condition +than we have yet attained to. So, those faculties which enable us to +transcend time and space, and to realize the wonderful conceptions of +mathematics and philosophy, or which give us an intense yearning for +abstract truth, (all of which were occasionally manifested at such an +early period of human history as to be far in advance of any of the few +practical applications which have since grown out of them), are +evidently essential to the perfect development of man as a spiritual +being, but are utterly inconceivable as having been produced through the +action of a law which looks only, and can look only, to the immediate +material welfare of the individual or the race. + +The inference I would draw from this class of phenomena is, that a +superior intelligence has guided the development of man in a definite +direction, and for a special purpose, just as man guides the development +of many animal and vegetable forms. The laws of evolution alone would, +perhaps, never have produced a grain so well adapted to man's use as +wheat and maize; such fruits as the seedless banana and bread-fruit; or +such animals as the Guernsey milch cow, or the London dray-horse. Yet +these so closely resemble the unaided productions of nature, that we may +well imagine a being who had mastered the laws of development of organic +forms through past ages, refusing to believe that any new power had been +concerned in their production, and scornfully rejecting the theory (as +my theory will be rejected by many who agree with me on other points), +that in these few cases a controlling intelligence had directed the +action of the laws of variation, multiplication, and survival, for his +own purposes. We know, however, that this has been done; and we must +therefore admit the possibility that, if we are not the highest +intelligences in the universe, some higher intelligence may have +directed the process by which the human race was developed, by means of +more subtle agencies than we are acquainted with. At the same time I +must confess, that this theory has the disadvantage of requiring the +intervention of some distinct individual intelligence, to aid in the +production of what we can hardly avoid considering as the ultimate aim +and outcome of all organized existence--intellectual, ever-advancing, +spiritual man. It therefore implies, that the great laws which govern +the material universe were insufficient for his production, unless we +consider (as we may fairly do) that the controlling action of such +higher intelligences is a necessary part of those laws, just as the +action of all surrounding organisms is one of the agencies in organic +development. But even if my particular view should not be the true one, +the difficulties I have put forward remain, and I think prove, that some +more general and more fundamental law underlies that of "natural +selection." The law of "unconscious intelligence" pervading all organic +nature, put forth by Dr. Laycock and adopted by Mr. Murphy, is such a +law; but to my mind it has the double disadvantage of being both +unintelligible and incapable of any kind of proof. It is more probable, +that the true law lies too deep for us to discover it; but there seems +to me, to be ample indications that such a law does exist, and is +probably connected with the absolute origin of life and organization. +(_Note A._) + + +_The Origin of Consciousness._ + +The question of the origin of sensation and of thought can be but +briefly discussed in this place, since it is a subject wide enough to +require a separate volume for its proper treatment. No physiologist or +philosopher has yet ventured to propound an intelligible theory, of how +sensation may possibly be a product of organization; while many have +declared the passage from matter to mind to be inconceivable. In his +presidential address to the Physical Section of the British Association +at Norwich, in 1868, Professor Tyndall expressed himself as follows:-- + +"The passage from the physics of the brain to the corresponding facts of +consciousness is unthinkable. Granted that a definite thought, and a +definite molecular action in the brain occur simultaneously, we do not +possess the intellectual organ, nor apparently any rudiment of the +organ, which would enable us to pass by a process of reasoning from the +one phenomenon to the other. They appear together, but we do not know +why. Were our minds and senses so expanded, strengthened, and +illuminated as to enable us to see and feel the very molecules of the +brain; were we capable of following all their motions, all their +groupings, all their electric discharges, if such there be, and were we +intimately acquainted with the corresponding states of thought and +feeling, we should be as far as ever from the solution of the problem, +'How are these physical processes connected with the facts of +consciousness?' The chasm between the two classes of phenomena would +still remain intellectually impassable." + +In his latest work ("An Introduction to the Classification of Animals,") +published in 1869, Professor Huxley unhesitatingly adopts the "well +founded doctrine, that life is the cause and not the consequence of +organization." In his celebrated article "On the Physical Basis of +Life," however, he maintains, that life is a property of protoplasm, and +that protoplasm owes its properties to the nature and disposition of its +molecules. Hence he terms it "the matter of life," and believes that all +the physical properties of organized beings are due to the physical +properties of protoplasm. So far we might, perhaps, follow him, but he +does not stop here. He proceeds to bridge over that chasm which +Professor Tyndall has declared to be "intellectually impassable," and, +by means which he states to be logical, arrives at the conclusion, that +our "_thoughts are the expression of molecular changes in that matter of +life which is the source of our other vital phenomena_." Not having been +able to find any clue in Professor Huxley's writings, to the steps by +which he passes from those vital phenomena, which consist only, in their +last analysis, of movements of particles of matter, to those other +phenomena which we term thought, sensation, or consciousness; but, +knowing that so positive an expression of opinion from him will have +great weight with many persons, I shall endeavour to show, with as much +brevity as is compatible with clearness, that this theory is not only +incapable of proof, but is also, as it appears to me, inconsistent with +accurate conceptions of molecular physics. To do this, and in order +further to develop my views, I shall have to give a brief sketch of the +most recent speculations and discoveries, as to the ultimate nature and +constitution of matter. + + +_The Nature of Matter._ + +It has been long seen by the best thinkers on the subject, that +atoms,--considered as minute solid bodies from which emanate the +attractive and repulsive forces which give what we term matter its +properties,--could serve no purpose whatever; since it is universally +admitted that the supposed atoms never touch each other, and it cannot +be conceived that these homogeneous, indivisible, solid units, are +themselves the ultimate _cause_ of the forces that emanate from their +centres. As, therefore, none of the properties of matter can be due to +the atoms themselves, but only to the forces which emanate from the +points in space indicated by the atomic centres, it is logical +continually to diminish their size till they vanish, leaving only +localized centres of force to represent them. Of the various attempts +that have been made to show how the properties of matter may be due to +such modified atoms (considered as mere centres of force), the most +successful, because the simplest and the most logical, is that of Mr. +Bayma, who, in his "Molecular Mechanics," has demonstrated how, from the +simple assumption of such centres having attractive and repulsive forces +(both varying according to the same law of the inverse squares as +gravitation), and by grouping them in symmetrical figures, consisting of +a repulsive centre, an attractive nucleus, and one or more repulsive +envelopes, we may explain all the general properties of matter; and, by +more and more complex arrangements, even the special chemical, +electrical, and magnetic properties of special forms of matter.[I] Each +chemical element will thus consist of a molecule formed of simple atoms, +(or as Mr. Bayma terms them to avoid confusion, "material elements") in +greater or less number and of more or less complex arrangement; which +molecule is in stable equilibrium, but liable to be changed in form by +the attractive or repulsive influences of differently constituted +molecules, constituting the phenomena of chemical combination, and +resulting in new forms of molecule of greater complexity and more or +less stability. + + +--------------------------------------------------------------+ + | [I] Mr. Bayma's work, entitled "The Elements of Molecular | + | Mechanics," was published in 1866, and has received less | + | attention than it deserves. It is characterised by great | + | lucidity, by logical arrangement, and by comparatively | + | simple geometrical and algebraical demonstrations, so that | + | it may be understood and appreciated with a very moderate | + | knowledge of mathematics. It consists of a series of | + | Propositions, deduced from the known properties of matter; | + | from these are derived a number of Theorems, by whose help | + | the more complicated Problems are solved. Nothing is taken | + | for granted throughout the work, and the only valid mode of | + | escaping from its conclusions is, by either disproving the | + | fundamental Propositions, or by detecting fallacies in the | + | subsequent reasoning. | + +--------------------------------------------------------------+ + +Those organic compounds of which organized beings are built up, consist, +as is well known, of matter of an extreme complexity. and great +instability; whence result the changes of form to which it is +continually subject. This view enables us to comprehend the +_possibility_, of the phenomena of vegetative life being due to an +almost infinite complexity of molecular combinations, subject to +definite changes under the stimuli of heat, moisture, light, +electricity, and probably some unknown forces. But this greater and +greater complexity, even if carried to an infinite extent, cannot, of +itself, have the slightest tendency to originate consciousness in such +molecules or groups of molecules. If a material element, or a +combination of a thousand material elements in a molecule, are alike +unconscious, it is impossible for us to believe, that the mere addition +of one, two, or a thousand other material elements to form a more +complex molecule, could in any way tend to produce a self-conscious +existence. The things are radically distinct. To say that mind is a +product or function of protoplasm, or of its molecular changes, is to +use words to which we can attach no clear conception. You cannot have, +in the whole, what does not exist in any of the parts; and those who +argue thus should put forth a definite conception of matter, with +clearly enunciated properties, and show, that the necessary result of a +certain complex arrangement of the elements or atoms of that matter, +will be the production of self-consciousness. There is no escape from +this dilemma,--either all matter is conscious, or consciousness is +something distinct from matter, and in the latter case, its presence in +material forms is a proof of the existence of conscious beings, outside +of, and independent of, what we term matter. (_Note B._) + +_Matter is Force._--The foregoing considerations lead us to the very +important conclusion, that matter is essentially force, and nothing but +force; that matter, as popularly understood, does not exist, and is, in +fact, philosophically inconceivable. When we touch matter, we only +really experience sensations of resistance, implying repulsive force; +and no other sense can give us such apparently solid proofs of the +reality of matter, as touch does. This conclusion, if kept constantly +present in the mind, will be found to have a most important bearing on +almost every high scientific and philosophical problem, and especially +on such as relate to our own conscious existence. + +_All Force is probably Will-Force._--If we are satisfied that force or +forces are all that exist in the material universe, we are next led to +enquire what is force? We are acquainted with two radically distinct or +apparently distinct kinds of force--the first consists of the primary +forces of nature, such as gravitation, cohesion, repulsion, heat, +electricity, &c.; the second is our own will-force. Many persons will at +once deny that the latter exists. It will be said, that it is a mere +transformation of the primary forces before alluded to; that the +correlation of forces includes those of animal life, and that _will_ +itself is but the result of molecular change in the brain. I think, +however, that it can be shown, that this latter assertion has neither +been proved, nor even been proved to be possible; and that in making it, +a great leap in the dark has been taken from the known to the unknown. +It may be at once admitted that the _muscular force_ of animals and men, +is merely the transformed energy derived from the primary forces of +nature. So much has been, if not rigidly proved, yet rendered highly +probable, and it is in perfect accordance with all our knowledge of +natural forces and natural laws. But it cannot be contended that the +physiological balance-sheet has ever been so accurately struck, that we +are entitled to say, not one-thousandth part of a grain more of force +has been exerted by any organized body or in any part of it, than has +been derived from the known primary forces of the material world. If +that were so, it would absolutely negative the existence of will; for if +will is anything, it is a power that _directs_ the action of the forces +stored up in the body, and it is not conceivable that this _direction_ +can take place, without the exercise of some force in some part of the +organism. However delicately a machine may be constructed, with the most +exquisitely contrived detents to release a weight or spring by the +exertion of the smallest possible amount of force, _some_ external force +will always, be required; so, in the animal machine, however minute may +be the changes required in the cells or fibres of the brain, to set in +motion the nerve currents which loosen or excite the pent up forces of +certain muscles, _some force_ must be required to effect those changes. +If it is said, "those changes are automatic, and are set in motion by +external causes," then one essential part of our consciousness, a +certain amount of freedom in willing, is annihilated; and it is +inconceivable how or why there should have arisen any consciousness or +any apparent will, in such purely automatic organisms. If this were so, +our apparent WILL would be a delusion, and Professor Huxley's +belief--"that our volition counts for something as a condition of the +course of events," would be fallacious, since our volition would then be +but one link in the chain of events, counting for neither more nor less +than any other link whatever. + +If, therefore, we have traced one force, however minute, to an origin in +our own WILL, while we have no knowledge of any other primary cause of +force, it does not seem an improbable conclusion that all force may be +will-force; and thus, that the whole universe, is not merely dependent +on, but actually _is_, the WILL of higher intelligences or of one +Supreme Intelligence. It has been often said that the true poet is a +seer; and in the noble verse of an American poetess, we find expressed, +what may prove to be the highest fact of science, the noblest truth of +philosophy: + + God of the Granite and the Rose! + Soul of the Sparrow and the Bee! + The mighty tide of Being flows + Through countless channels, Lord, from thee. + It leaps to life in grass and flowers, + Through every grade of being runs, + While from Creation's radiant towers + Its glory flames in Stars and Suns. + + +_Conclusion._ + +These speculations are usually held to be far beyond the bounds of +science; but they appear to me to be more legitimate deductions from the +facts of science, than those which consist in reducing the whole +universe, not merely to matter, but to matter conceived and defined so +as to be philosophically inconceivable. It is surely a great step in +advance, to get rid of the notion that _matter_ is a thing of itself, +which can exist _per se_, and must have been eternal, since it is +supposed to be indestructible and uncreated,--that force, or the forces +of nature, are another thing, given or added to matter, or else its +necessary properties,--and that mind is yet another thing, either a +product of this matter and its supposed inherent forces, or distinct +from and co-existent with it;--and to be able to substitute for this +complicated theory, which leads to endless dilemmas and contradictions, +the far simpler and more consistent belief, that matter, as an entity +distinct from force, does not exist; and that FORCE is a product of +MIND. Philosophy had long demonstrated our incapacity to prove the +existence of matter, as usually conceived; while it admitted the +demonstration to each of us of our own self-conscious, ideal existence. +Science has now worked its way up to the same result, and this agreement +between them should give us some confidence in their combined teaching. + +The view we have now arrived at seems to me more grand and sublime, as +well as far simpler, than any other. It exhibits the universe, as a +universe of intelligence and will-power; and by enabling us to rid +ourselves of the impossibility of thinking of mind, but as connected +with our old notions of matter, opens up infinite possibilities of +existence, connected with infinitely varied manifestations of force, +totally distinct from, yet as real as, what we term matter. + +The grand law of continuity which we see pervading our universe, would +lead us to infer infinite gradations of existence, and to people all +space with intelligence and will-power; and, if so, we have no +difficulty in believing that for so noble a purpose as the progressive +development of higher and higher intelligences, those primal and general +will-forces, which have sufficed for the production of the lower +animals, should have been guided into new channels and made to converge +in definite directions. And if, as seems to me probable, this has been +done, I cannot admit that it in any degree affects the truth or +generality of Mr. Darwin's great discovery. It merely shows, that the +laws of organic development have been occasionally used for a special +end, just as man uses them for his special ends; and, I do not see that +the law of "natural selection" can be said to be disproved, if it can be +shown that man does not owe his entire physical and mental development +to its unaided action, any more than it is disproved by the existence of +the poodle or the pouter pigeon, the production of which may have been +equally beyond its undirected power. + +The objections which in this essay I have taken, to the view,--that the +same law which appears to have sufficed for the development of animals, +has been alone the cause of man's superior physical and mental +nature,--will, I have no doubt, be over-ruled and explained away. But I +venture to think they will nevertheless maintain their ground, and that +they can only be met by the discovery of new facts or new laws, of a +nature very different from any yet known to us. I can only hope that my +treatment of the subject, though necessarily very meagre, has been clear +and intelligible; and that it may prove suggestive, both to the +opponents and to the upholders of the theory of Natural Selection. + + + + +NOTES. + + +_NOTE A._ (_Page_ 360.) + +Some of my critics seem quite to have misunderstood my meaning in this +part of the argument. They have accused me of unnecessarily and +unphilosophically appealing to "first causes" in order to get over a +difficulty--of believing that "our brains are made by God and our lungs +by natural selection;" and that, in point of fact, "man is God's +domestic animal." An eminent French critic, M. Claparede, makes me +continually call in the aid of--"_une Force superieure_," the capital F, +meaning I imagine that this "higher Force" is the Deity. I can only +explain this misconception by the incapacity of the modern cultivated +mind to realise the existence of any higher intelligence between itself +and Deity. Angels and archangels, spirits and demons, have been so long +banished from our belief as to have become actually unthinkable as +actual existences, and nothing in modern philosophy takes their place. +Yet the grand law of "continuity," the last outcome of modern science, +which seems absolute throughout the realms of matter, force, and mind, +so far as we can explore them, cannot surely fail to be true beyond the +narrow sphere of our vision, and leave an infinite chasm between man and +the Great Mind of the universe. Such a supposition seems to me in the +highest degree improbable. + +Now, in referring to the origin of man, and its possible determining +causes, I have used the words "some other power"--"some intelligent +power"--"a superior intelligence"--"a controlling intelligence," and +only in reference to the origin of universal forces and laws have I +spoken of the will or power of "one Supreme Intelligence." These are the +only expressions I have used in alluding to the power which I believe +has acted in the case of man, and they were purposely chosen to show, +that I reject the hypothesis of "first causes" for any and every +_special_ effect in the universe, except in the same sense that the +action of man or of any other intelligent being is a first cause. In +using such terms I wished to show plainly, that I contemplated the +possibility that the development of the essentially human portions of +man's structure and intellect may have been determined by the directing +influence of some higher intelligent beings, acting through natural and +universal laws. A belief of this nature may or may not have a +foundation, but it is an intelligible theory, and is not, _in its +nature_, incapable of proof; and it rests on facts and arguments of an +exactly similar kind to those, which would enable a sufficiently +powerful intellect to deduce, from the existence on the earth of +cultivated plants and domestic animals, the presence of some intelligent +being of a higher nature than themselves. + + +_NOTE B._ (_Page_ 365.) + +A friend has suggested that I have not here explained myself +sufficiently, and objects, that _life_ does not exist in matter any more +than _consciousness_, and if the one can be produced by the laws of +matter, why may not the other? I reply, that there is a radical +difference between the two. Organic or vegetative life consists +essentially in chemical transformations and molecular motions, occurring +under certain conditions and in a certain order. The matter, and the +forces which act upon it, are for the most part known; and if there are +any forces engaged in the manifestation of vegetative life yet +undiscovered (which is a moot question), we can conceive them as +analogous to such forces as heat, electricity, or chemical affinity, +with which we are already acquainted. We can thus clearly _conceive_ of +the transition from dead matter to living matter. A complex mass which +suffers decomposition or decay is dead, but if this mass has the power +of attracting to itself, from the surrounding medium, matter like that +of which it is composed, we have the first rudiment of vegetative life. +If the mass can do this for a considerable time, and if its absorption +of new matter more than replaces that lost by decomposition, and if it +is of such a nature as to resist the mechanical or chemical forces to +which it is usually exposed, and to retain a tolerably constant form, we +term it a living organism. We can _conceive_ an organism to be so +constituted, and we can further conceive that any fragments, which may +be accidentally broken from it, or which may fall away when its bulk has +become too great for the cohesion of all its parts, may begin to +increase anew and run the same course as the parent mass. This is growth +and reproduction in their simplest forms; and from such a simple +beginning it is possible to conceive a series of slight modifications of +composition, and of internal and external forces, which should +ultimately lead to the development of more complex organisms. The LIFE +of such an organism may, perhaps, be nothing added to it, but merely the +name we give to the result of a balance of internal and external forces +in maintaining the permanence of the form and structure of the +individual. The simplest conceivable form of such life would be the +dewdrop, which owes its existence to the balance between the +condensation of aqueous vapour in the atmosphere and the evaporation of +its substance. If either is in excess, it soon ceases to maintain an +individual existence. I do not maintain that vegetative life _is_ wholly +due to such a complex balance of forces, but only that it is +_conceivable_ as such. + +With CONSCIOUSNESS the case is very different. Its phenomena are not +comparable with those of any kind of _matter_ subjected to any of the +known or conceivable _forces_ of nature; and we cannot _conceive_ a +gradual transition from absolute unconsciousness to consciousness, from +an unsentient organism to a sentient being. The merest rudiment of +sensation or self-consciousness is infinitely removed from absolutely +non-sentient or unconscious matter. We can conceive of no physical +addition to, or modification of, an unconscious mass which should create +consciousness; no step in the series of changes organised matter may +undergo, which should bring in sensation where there was no sensation +or power of sensation at the preceding step. It is because the things +are utterly incomparable and incommensurable that we can only conceive +of _sensation_ coming to matter from without, while _life_ may be +conceived as merely a specific combination and co-ordination of the +matter and the forces that compose the universe, and with which we are +separately acquainted. We may admit with Professor Huxley that +_protoplasm_ is the "matter of life" and the cause of organisation, but +we cannot admit or conceive that _protoplasm_ is the primary source of +sensation and consciousness, or that it can ever of itself become +_conscious_ in the same way as we may perhaps conceive that it may +become _alive_. + + + + +INDEX. + + + _ABRAXAS grossulariata_, 119. + + _Acanthotritus dorsalis_, 94. + + _Accipiter pileatus_, 107. + + ACRAEIDAE, the subjects of mimicry, 85, 86. + + _Acronycta psi_, protective colouring of, 62. + + ADAPTATION brought about by general laws, 276; + looks like design, 281. + + AEGERIIDAE mimic Hymenoptera, 90. + + AGASSIZ, or embryonic character of ancient animals, 301. + + _Agnia fasciata_, mimics another Longicorn, 95. + + _Agriopis aprilina_, protective colouring of, 62. + + ALCEDINIDAE, sexual colouring and nidification of, 240. + + AMADINA, sexual colouring and nidification of, 243. + + AMPELIDAE, sexual colouring and nidification of, 243. + + ANCYLOTHERIUM, 300. + + ANDRENIDAE, 98. + + _Angraecum sesquipedale_, 272; + its fertilization by a large moth, 275. + + ANIMALS, senses and faculties of, 127; + intellect of, compared with that of savages, 341. + + ANISOCERINAE, 92. + + ANOA, 196. + + ANOPLOTHERIUM, 299. + + ANTHRIBIDAE, mimicry of, 94; + dimorphism in, 155. + + _Anthrocera filipendulae_, 120. + + ANTHROPOLOGISTS, wide difference of opinion among, as to origin of + human races, 304; + conflicting views of, harmonized, 321. + + ANTIQUITY of man, 303, 322. + + APATHUS, 98. + + APPARENT exceptions to law of colour and nidification, 253. + + AQUATIC BIRDS, why abundant, 32. + + _Araschnia prorsa_, 154. + + ARCHEGOSAURUS, 300. + + ARCHAEOPTERYX, 300. + + ARCHITECTURE of most nations derivative, 228; + Grecian, false in principle, 226. + + ARCTIC animals, white colour of, 50, 51. + + ARGYLL, Duke of, on colours of Woodcock, 53; + on mind in nature, 265; + criticism on Darwin's works, 269; + on humming birds 282; + on creation by birth, 287. + + ASILUS, 97. + + ASPECTS of nature as influencing man's development, 317. + + + BABIRUSA, 196. + + BALANCE in nature, 42. + + BARRINGTON, Hon. Daines, on song of birds, 220. + + BASILORNIS, 196. + + BATES, Mr., first adopted the word "mimicry," 75; + his observations on Leptalis and Heliconidae, 82; + his paper explaining the theory of mimicry, 83; + objections to his theory, 108; + on variation, 165; + on recent immigration of Amazonian Indians, 214. + + BAYMA, Mr., on "Molecular Mechanics," 363, 364. + + BEAUTY in nature, 282; + not universal, 284; + of flowers useful to them, 285; + not given for its own sake, 285. + + BIRDS, possible rapid increase of, 29; + numbers that die annually, 30; + mimicry among, 103; + dull colour of females, 114; + nidification as affecting colour of females, 116; + refusing the gooseberry caterpillar, 119; + the highest in rank and organization, 137; + dimorphism in, 155; + why peculiar nest built by each species, 215-219; + build more perfect nests as they grow older, 224, 227; + alter and improve their nests, 226; + sexual differences of colour in, 239. + + _Bombus hortorum_, 90. + + _Bombycilla, garrula_, colours and nidification of, 255. + + BOMBYLIUS, 98. + + BRAIN of the savage but slightly less than that of civilized man, 336; + size of, an important element of mental power, 335; + of savage races larger than their needs require, 338, 343; + of man and of anthropoid apes compared, 338. + + BROCA, Professor Paul, on the fine crania of the cave men, 337. + + _Bryophila glandifera_ and _B. perla_ protectively coloured, 63. + + BUCEROTIDAE, sexual colouring and nidification of, 241. + + BUCCONIDAE, sexual colouring and nidification of, 241. + + BUFF-TIP moth, resembles a broken stick, 62. + + BUILDINGS of various races do not change, 213. + + BUPRESTIDAE, resembling bird's dung, 57; + similar colours in two sexes, 114. + + BUTTERFLIES, value of, in studying "natural selection," 131; + varieties of, in Sardinia and Isle of Man, 178. + + + _CACIA anthriboides_, 94. + + _Callizona acesta_, protective colouring of, 59. + + CALORNIS, 239. + + CAPITONIDAE, sexual colouring and nidification of, 241. + + _Capnolymma stygium_, 94. + + CARABIDAE, special protection among, 72; + similar colouring of two sexes, 114. + + CASSIDAE, resemble dew drops, 58. + + CATERPILLARS, mimicking a poisonous snake, 99; + gaudy colours of, 117; + various modes of protection of, 118; + gooseberry caterpillar, 119; + Mr. Jenner Weir's observations on, 119; + Mr. A. G. Butler's observations on, 121. + + CELEBES, local modifications of form in, 170; + probable cause of these, 176; + remarkable zoological peculiarities of, 195-199. + + CENTROPUS, sexual colouring and nidification of, 242. + + _Cephalodonta spinipes_, 92. + + _Ceroxylus laceratus_, imitates a moss-covered stick, 64. + + CERTHIOLA, sexual colouring and nidification of, 244. + + _Cethosia aeole_, 172; + _biblis_, 172. + + CETONIADAE, how protected, 73; + similar colours of two sexes, 114. + + CEYCOPSIS, 196. + + _Charis melipona_, 96. + + CHEMATOBIA, wintry colours of this genus, 62. + + _Chlamys pilula_, resembles dung of caterpillars, 58. + + CHRYSIDIDAE, how protected, 72. + + CHRYSOMELIDAE, similar colouring of two sexes, 114. + + CICINDELA, adaptive colour of various species of, 57. + + _Cilix compressa_, resembles bird's dung, 63. + + CLADOBATES, mimicking squirrels, 107. + + CLASSIFICATION, form of true, 6; + circular, inadmissible, 8; + quinarian and circular, of Swainson, 46; + argument from, against Mr. Darwin, 295. + + CLIMACTERIS, sexual colouring and nidification of, 243. + + COCCINELLIDAE, how protected, 72; + similar colouring of sexes, 114. + + COEXISTING varieties, 159. + + _Collyrodes lacordairei_, 95. + + COLOUR, in animals, popular theories of, 47; + frequent variations of, in domesticated animals, 48; + influenced by need of concealment, 49; + in deserts, 49, 50; + in Arctic regions, 50, 51; + nocturnal, 51; + tropical, 52; + special modifications of, 52; + different distribution of, in butterflies and moths, 58; + of autumnal and winter moths, 62; + white, generally dangerous and therefore eliminated, 66; + why it exists so abundantly although often injurious, 69; + influenced by need of protection, 113; + of female birds, 114; + in relation to nidification of birds, 116; + gaudy colours of many caterpillars, 117; + in nature, general causes of, 126; + local variations of, 173; + sexual differences of, in birds, 239; + in female birds, how connected with their nidification, 240, 246; + more variable than structure or habits, and therefore more easily + modified, 249; + of flowers, as explained by Mr. Darwin, 262; + often correlated with disease, 316. + + COMPSOGNATHUS, 300. + + _Condylodera tricondyloides_, 97. + + CONSCIOUSNESS, origin of, 360; + Professor Tyndall on, 361; + not a product of complex organization, 365. + + CORRELATION of growth, 310. + + _Corynomalus sp._, 92. + + COTINGIDAE, sexual colouring and nidification of, 244. + + CRATOSOMUS, a hard weevil, 94. + + CRICKETS mimicking sand wasps, 98. + + CRYPTODONTIA, 299. + + _Cucullia verbasci_, 120. + + CURCULIONIDAE, often protected by hard covering, 71; + similar colours of two sexes, 114. + + _Cuviera squamata_, 258. + + _Cyclopeplus batesii_, 92. + + CYNOPITHECUS, 196. + + _Cynthia arsinoe_, 172. + + + DANAIDAE, the subjects of mimicry, 85, 86. + + _Danais erippus_, 88; + _chysippus_, 112; + _sobrina_, 179; + _aglaia_, 179; + _tytia_, 180. + + DARWIN, Mr., his principle of utility, 47; + on cause of colour in flowers, 127, 262; + on colours of caterpillars, 118; + on sexual colouration, 260; + his metaphors liable to misconception, 269; + criticism of, in _North British Review_, 291. + + DESERT animals, colours of, 49, 50. + + DIADEMA, species of, mimic Danaidae, 86, 87; + female with male colouration, 112. + + _Diadema misippus_, 112; + _D. anomala_, 113. + + _Diaphora mendica_, 89. + + DICNYODONTIA, 299. + + DICROURUS, 253. + + _Diloba coeruleocephala_, 120. + + DIMORPHISM, 145; + in beetles, 155; + in birds, 155; + illustrated, 157. + + DINOSAURIA, 298. + + DIPTERA mimicking wasps and bees, 97. + + _Doliops curculionides_, 94. + + DOMESTICATED animals, their essential difference from wild + ones, 38-41. + + DOTTERELL, 251. + + DRUSILLA, mimicked by three genera, 181. + + _Drusilla bioculata_, 180. + + DYTISCUS, dimorphism in, 155. + + + EGYPTIAN architecture, introduced, 225. + + _Elaps fulvius_, _E. corallinus_, _E. lemniscatus_, 101; + _E. mipartitus_, _E. lemniscatus_, _E. hemiprichii_, 102. + + ENODES, 196. + + ENNOMUS, autumnal colours of this genus, 62. + + _Eos fuscata_, dimorphism of, 155. + + EQUUS, 299. + + _Eronia tritaea_, 172; + _valeria_, 172. + + _Eroschema poweri_, 93. + + ERYCINIDAE mimic Heliconidae, 84. + + _Erythroplatis corallifer_, 92. + + ESTRELDA, sexual colouring and nidification of, 243. + + EUCNEMIDAE, mimicking a Malacoderm, 93. + + _Eudromias morinellus_, 251. + + _Euglossa dimidiata_, 98. + + EUMORPHIDAE, a protected group 72; + imitated by Longicorns, 92. + + EUPLOEA, local modifications of colour in, 173. + + _Euploea midamus_, 87-113, 179; + _E. rhadamanthus_, 87, 179. + + _Eurhinia megalonice_, 172; + _polynice_, 172. + + EURYLAEMIDAE, sexual colouring and nidification of, 243. + + EXTINCT animals, intermediate forms of, 298. + + EXTINCTION of lower races, 318. + + + FEMALE birds, colours of, 114; + sometimes connected with their mode of nidification, 240; + more exposed to enemies than the males, 248. + + FEMALE butterflies generally dull-coloured, 259. + + FEMALE insects, mimicry by, 110, 259; + colours of, 113. + + FEMALE sex, has no incapacity for as brilliant colouration as the + male, 247; + in some groups requires more protection than the male, 258. + + FISHES, protective colouring of, 55. + + FISSIROSTRAL birds, nests of, 238. + + FLOWERS, causes of colour in, 127. + + FLYCATCHERS, genera of, absent from Celebes, 177. + + FORBES, EDWARD, objections to his theory of Polarity, 17-23. + + FORCE is probably all Will-force, 366. + + + GALAPAGOS, 10. + + GALTON, Mr., on range of intellectual power, 339. + + GANOCEPHALA, 298. + + _Gastropacha querci_, protective colour and form of, 62. + + GAUDRY, M., on fossil mammals of Greece, 299. + + GEOGRAPHICAL distribution, dependent on geologic changes, 1; + its agreement with law of introduction of new species, 9; + of allied species and groups, 12. + + GEOLOGICAL distribution analogous to geographical, 13. + + GEOLOGY, facts proved by, 2-5. + + GIRAFFE, how it acquired its long neck, 42. + + GLAEA, autumnal colours of this genus, 62. + + GOULD, Mr., on sexual plumage of Gray Phalarope, 115; + on incubation by male Dotterell, 115. + + _Grallina australis_, 254. + + GREEN birds almost confined to the tropics, 52. + + _Gymnocerus cratosomoides_, 94. + + _Gymnocerous capucinus_, 96. + + _Gymnocerous dulcissimus_, 97. + + GUNTHER, Dr., on arboreal snakes, 55; + on colouring of snakes, 102. + + _Gynecia dirce_, 59. + + + HABITS, often persistent when use of them has ceased, 234; + of children and savages analogous to those of animals, 235; + if persistent and imitative may be termed hereditary, 235, 236. + + HAIRY covering of Mammalia, use of, 344; + absence of, in man remarkable, 345; + the want of it felt by savages, 346; + could not have been abolished by natural selection, 348. + + _Harpagus diodon_, 107. + + HEILIPLUS, a hard genus of Curculionidae, 94. + + HELICONIDAE, the objects of mimicry, 77; + their secretions, 88; + not attacked by birds, 79; + sometimes mimicked by other Heliconidae, 85. + + HELLADOTHERIUM, 300. + + HEMIPTERA, protected by bad odour, 72. + + HERBERT, Rev. W., on song of birds, 221. + + HESPERIDAE, probable means of protection of, 176. + + HESTHESIS, longicorns resembling ants, 96. + + _Hestia leuconoe_, 180. + + HEWITSON, Mr., 131. + + HIPPARION, 299. + + HIPPOTHERIUM, 299. + + HISPIDAE, imitated by Longicorns, 92. + + HOLOTHURIDAE, 258. + + _Homalocranium semicinctum_, 101. + + HOOKER, Dr., on the value of the "specific term," 165. + + HOUSES of American and Malay races contrasted, 213. + + HUXLEY, Professor, on "Physical Basis of Life," 362; + on volition, 368. + + HYAENICTIS, 300. + + HYBERNIA, wintry colours of this genus, 62. + + HYMENOPTERA, large number of, peculiar to Celebes, 196. + + + ICTERIDAE, sexual colouring and nidification of, 244. + + ICTHYOPTERYGIA, 298. + + _Ideopsis daos_, 180. + + IMITATION, the effects of, in man's works, 212. + + INDIANS, how they travel through trackless forests, 207. + + INSECTS, protective colouring of, 56; + mimicking species of other orders, 97; + senses of, perhaps different from ours, 202, 203. + + INSTINCT, how it may be best studied, 201; + definition of, 203; + in many cases assumed without proof, 205; + if possessed by man, 206; + supposed, of Indians, 207; + supposed to be shown in the construction of birds' nests, 211. + + INTELLECT of savages compared with that of animals, 341. + + INTELLECTUAL power, range of, in man, 339. + + _Iphias glaucippe_, 172. + + ITHOMIA, mimicked by Leptalis, 83. + + _Ithomia ilerdina_, mimicked by four groups of Lepidoptera, 84. + + + JAVA, relations of, to Sumatra and Borneo, 193. + + JAMAICA swift altering position of nest, 228. + + JERDON, Mr., on incubation by males in Turnix, 115. + + + _Kallima inachis_ and _Kallima paralekta_, wonderful resemblance of, + to leaves, 59-61. + + + LABYRINTHODONTIA, 298, 300. + + LAKES as cases of imperfect adaptation, 278. + + LANIADAE, sexual colouring and nidification of, 245. + + LAMARCK'S hypothesis very different from the author's, 41. + + _Larentia tripunctaria_, 63. + + LAW which has regulated the introduction of new species, 5; + confirmed by geographical distribution, 9; + high organization of ancient animals consistent with, 14; + of multiplication in geometrical progression, 265; + of limited populations, 265; + of heredity, 266; + of variation, 266; + of change of physical conditions, 266; + of the equilibrium of nature, 266; + as opposed to continual interference, 268. + + LAYCOCK, Dr., on law of "unconscious intelligence," 360. + + LEAF BUTTERFLY, appearance and habits of, 59-61. + + LEPIDOPTERA, especially subject to variation, 132. + + LEPTALIS, species of mimic Heliconidae, 82; + gain a protection thereby, 259. + + LESTER, Mr. J. M., on wood-dove and robin, 53. + + LEVAILLANT, on formation of a nest, 224. + + _Limenitis archippus_, 88. + + _Limenitis limire_, 172; + _procris_, 172. + + LIZARDS refusing certain moths and caterpillars, 121; + devouring bees, 121. + + LOCAL FORMS, 158. + + LOCAL variation of form, 169; + of colour, 173; + general remarks on, 174; + in Celebesian butterflies, probable use of, 175. + + LOCUSTIDAE, adaptive colouring of, 64. + + LUMINOUSNESS of some insects a protection, 71. + + LYCAENIDAE, probable means of protection of, 176. + + + MAMMALS, mimicry among, 107. + + MAN, does he build by reason or imitation, 212; + his works mainly imitative, 225; + antiquity of, 303, 322; + difference of opinion as to his origin, 304; + unity or plurality of species, 305; + persistence of type of, 306; + importance of mental and moral characters, 312; + his dignity and supremacy, 324; + his influence on nature, 326; + his future development, 326; + range of intellectual power in, 339; + rudiments of all the higher faculties in savage, 341; + his feet and hands, difficulties on the theory of natural + selection, 349; + his voice, 350; + his mental faculties, 351; + difficulty as to the origin of the moral sense in, 352; + development of, probably directed by a superior intelligence, 359. + + MANTIDAE, adaptive colouring of, 64; + mimicking white ants, 98. + + MALACODERMS, a protected group, 93. + + MALURIDAE, 255. + + MATTER, the nature of, 363; + Mr. Bayma on, 363; + is force, 365. + + MECHANITIS and Methona, mimicked by _Leptalis_, 83. + + MECOCERUS, dimorphism of, 155. + + _Mecocerus gazella_, 94. + + MEGACEPHALON, 196. + + MEGAPODIDAE, sexual colouring and nidification of, 246. + + MEROPOGON, 196. + + _Midas dives_, 97. + + MIMETA, mimicking Tropidorhynchus, 104. + + MIMICRY, meaning of the word, 74; + theory of, 76; + among Lepidoptera, 77; + how it acts as a protection, 80, 81; + of other insects by Lepidoptera, 89; + among beetles, 91; + of other insects by beetles, 95; + of insects by species of other orders, 97; + among the vertebrata, 99; + among snakes, 101; + among tree frogs, 103; + among birds, 103; + among mammals, 107; + objections to the theory of, 108; + by female insects, 110; + among Papilionidae, 179; + never occurs in the male only, 260. + + MOMOTIDAE, sexual colouring and nidification of, 241. + + MONTROUZIER, M., on butterflies of Woodlark Island, 152. + + MORAL sense, difficulty as to the origin of, 352. + + MORPHOS, how protected, 73. + + MURRAY, Mr. Andrew, objections to theory of mimicry, 108. + + MUSCICAPIDAE, sexual colouring and nidification of, 245. + + MUSOPHAGIDAE, sexual colouring and nidification of, 242. + + + NAPEOGENES, all the species are mimickers, 85. + + NATURAL selection, the principle stated, 41-43; + general acceptance of the theory of, 46; + tabular demonstration of, 302; + outline of theory of, 307; + its effects on man and animals different, 311; + hardly acts among civilized societies, 330; + what it can not do, 333; + cannot produce injurious or useless modifications, 334. + + NECTARINEIDAE, 254. + + NECYDALIDAE, mimic Hymenoptera, 96. + + _Nemophas grayi_, a Longicorn mimicked by a Longicorn, 95. + + NESTS of Birds, why different, 215; + of young birds, how built, 219; + construction of, described by Levaillant, 224; + imperfections in, 229; + influenced by changed conditions and persistent habits, 232; + classification of, according to function, 237. + + NEW FORMS, how produced by variation and selection, 286. + + NEW GUINEA, relation of the several Papuan islands to, 194. + + NOCTURNAL animals, colours of, 51. + + NOMADA, 98. + + + OBEREA, species resemble Tenthredinidae, 96. + + _Odontocera odyneroides_, 96. + + ODONTOCHEILA, 97. + + _Odyncrus sinuatus_, 90. + + _Onthophilus sulcatus_, like a seed, 58. + + _Onychocerus scorpio_, resembles bark, 56. + + ORANGE-TIP butterfly, protective colouring of, 59. + + ORCHIS, structure of an, explained by natural selection, 271. + + _Orgyia antiqua_ and _O. gonostigma_, autumnal colours of, 62. + + ORIOLIDAE, 253. + + _Ornithoptera priamus_, 145, 173; + _O. helena_, 173. + + _Oxyrhopus petolarius_, _O. trigeminus_, _O. formosus_, 102. + + OWEN, Professor, on more generalized structure of extinct + animals, 298. + + + _Pachyotris fabricii_, 96. + + PACHYRHYNCHI, weevils mimicked by Longicorns, 95. + + PALEOTHERIUM, 299. + + PALOPLOTHERIUM, 299. + + PAPILIO, black and red group imitated, 84. + + _Papilio achates_, 147; + _P. adamantius_, 171; + _P. aenigma_, 87; + _P. agamemnon_, 141, 158, 170, 171; + _P. agestor_, 180; + _P. alphenor_, 148, 169; + _P. amanga_, 151; + _P. androcles_, 171; + _P. androgeus_, 88, 147, 180, 183; + _P. antiphates_, 141, 171; + _P. antiphus_, 87, 150, 170, 180, 183; + _P. aristaeus_, 171; + _P. arjuna_, 141; + _P. ascalaphus_, 171; + _P. autolycus_, 160; + _P. bathycles_, 141; + _P. blumei_, 171; + _P. brama_, 171; + _P. caunus_, 87, 179; + _P. codrus_, 160, 171; + _P. coeon_, 88, 146, 180, 182; + _P. deiphobus_, 140; + _P. deiphontes_, 171; + _P. delessertii_, 180; + _P. demolion_, 171; + _P. diphilus_, 87, 170, 180, 183; + _P. doubledayi_, 88, 180; + _P. elyros_, 148; + _P. encelades_, 171; + _P. erectheus_, 151; + _P. euripilus_, 160; + _P. evemon_, 159; + _P. gigon_, 171; + _P. glaucus_, 152; + _P. hector_, 87, 150, 180, 183; + _P. helenus_, 160, 171; + _P. hospiton_, 178; + _P. idaeoides_, 180; + _P. jason_, 159, 171; + _P. ledebouria_, 148; + _P. leucothoe_, 171; + _P. leodamas_, 170; + _P. liris_, 87, 180, 184; + _P. macareus_, 179; + _P. machaon_, 178; + _P. melanides_, 148, 150; + _P. memnon_, 88, 140, 146, 147, 152, 180, 183; + _P. milon_, 171; + _P. nephelus_, 140; + _P. nicanor_, 170; + _P. oenomaus_, 88, 180, 184; + _P. onesimus_, 151; + _P. ormenus_, 150, 152, 182; + _P. pammon_, 147, 152, 170, 180; + _P. pamphylus_, 171; + _P. pandion_, 152, 180; + _P. paradoxa_, 87, 179; + _P. peranthus_, 160, 171; + _P. pertinax_, 145; + _P. philoxenus_, 182; + _P. polydorus_, 88, 170, 182; + _P. polytes_, 147, 148; + _P. rhesus_, 171; + _P. romulus_, 87, 148, 150, 183; + _P. sarpedon_, 141, 158, 171; + _P. sataspes_, 171; + _P. severus_, 140, 144; + _P. theseus_, 87, 148, 150, 169, 170, 171, 180, 183; + _P. thule_, 179; + _P. torquatus_, 156; + _P. turnus_, 152; + _P. ulysses_, 140, 160, 173; + _P. varuna_, 88. + + PAPILIONIDAE, the question of their rank, 133; + peculiar characters possessed by, 134; + peculiarly diurnal, 136; + compared with groups of mammalia, 138; + distribution of, 140; + large forms of Celebes and Moluccas, 168; + large forms of Amboyna, 169; + local variation of form, 169; + arrangement of, 186; + geographical distribution of, 189; + of Indo-Malay and Austro-Malay regions, 192; + of Java, Sumatra, and Borneo, 193. + + PARIDAE, sexual colouring and nidification of, 243. + + PASSENGER pigeon, cause of its great numbers, 308. + + PATENT inventions, as illustrating classification, 295. + + _Phacellocera batesii_, mimics one of the Anthribidae, 94. + + _Phalaropus fulicarius_, 115, 251. + + PHASMIDAE, imitate sticks and twigs, 64; + females resembling leaves, 112. + + PHYLLIUM, wonderful protective colour and form of, 64. + + PHYSALIA, 258. + + PIERIDAE, local modification of form in, 172. + + PIERIS, females only imitating Heliconidae, 112. + + _Pieris coronis_, 172; + _eperia_, 172. + + _Pieris pyrrha_, 113. + + PICIDAE, sexual colouring and nidification of, 242. + + PIPRIDAE, sexual colouring and nidification of, 245. + + PITTIDAE, 253. + + _Pliocerus equalis_, 101; + _P. elapoides, P. euryzonus_, 102. + + _Paeciloderma terminale_, 93. + + POLARITY, Forbes' theory of, 17, 45. + + POLYMORPHISM, 145; + illustration of, 157. + + POPULATION of species, law of, 28; + does not permanently increase, 29; + not determined by abundance of offspring, 29; + checks to, 30; + difference in the case of cats and rabbits explained, 32. + + PREVISION, a case of, 122. + + PRIONITURUS, 196. + + PROTECTION, various modes in which animals obtain it, 69-71, 258; + greater need of, in female insects and birds, 113. + + PROTECTIVE colouring, theory of, 65. + + PSITTACI (Parrots), sexual colouring and nidification of, 242. + + PTEROSAURIA, 298. + + PTYCHODERES, 94. + + + RACES, or subspecies, 160; + of man, origin of, 319. + + REDBREAST and woodpigeon, protective colouring of, 53, 54. + + REPRESENTATIVE groups, 9; + of Trogons, butterflies, &c., 12. + + REPTILES, protective colouring of, 54. + + RHAMPHASTIDAE, sexual colouring and nidification of, 242. + + RHINOCEROS, 299. + + RIVER system, as illustrating self-adaptation, 276. + + ROSES, Mr. Baker on varieties of, 165. + + RUDIMENTARY organs, 23. + + + SALVIN, Mr. Osbert, on a case of bird mimicry, 107. + + _Saturnia pavonia-minor_, protective colouring of larva of, 63. + + SATYRIDAE, probable means of protection of, 176. + + SAUROPTERYGIA, 299. + + SAVAGES, why they become extinct, 319; + undeveloped intellect of, 339, 341; + intellect of, compared with that of animals, 341, 343; + protect their backs from rain, 346. + + SCANSORIAL birds, nests of, 238. + + SCAPHURA, 98. + + SCISSIROSTRUM, 165. + + SCOPULIPEDES, brush-legged bees, 91. + + SCUDDER, Mr., on fossil insects, 301. + + SCUTELLERIDAE, mimicked by Longicorns, 96. + + _Sesia bombiliformis_, 90. + + SESIIDAE, mimic Hymenoptera, 90. + + SEXES, comparative importance of, in different classes of + animals, 111; + diverse habits of, 156. + + SEXUAL SELECTION, 156; + its normal action to develop colour in both sexes, 247; + among birds, 283. + + SIDGWICK, Mr. A., on protective colouring of moths, 62. + + SIMOCYONIDAE, 300. + + SITTA, sexual colouring and nidification of, 243. + + SITTELLA, sexual colouring and nidification of, 243. + + SNAKES, mimicry among, 101. + + SONG of birds, instinctive or imitative, 220. + + SPECIES, law of population of, 28; + abundance or rarity of, dependent on the adaptation to + conditions, 33; + definition of, 141, 161; + the range and constancy of, 143; + extreme variation in, 163, 164. + + SPEED of animals, limits of, 292. + + _Sphecia craboniforme_, 90. + + _Sphecomorpha chalybea_, 96. + + SPHEGIDAE, mimicked by flies, 97. + + SPIDERS, which mimic ants, 98; + and flower buds, 99. + + _Spilosoma menthastri_, 88. + + STAINTON, Mr., on moths rejected by turkeys, 78, 88. + + STALACHTIS, a genus of Erycinidae, the object of mimicry, 84. + + STINGING insects generally conspicuously coloured, 72. + + STREPTOCITTA, 196. + + STURNIDAE, sexual colouring and nidification of, 244. + + STURNOPASTOR, 239. + + ST. HELENA, 10. + + _Streptolabis hispoides_, 93. + + STRUGGLE for existence, 28, 33. + + SURVIVAL of the fittest, law of, stated, 33; + its action in determining colour, 67. + + SWAINSON'S circular and quinarian theory, 45. + + SYLVIADAE, sexual colouring and nidification of, 245. + + SYNAPTA, 258. + + + _TACHORNIS phoenicobea_, 228. + + _Tachyris hombronii_, 172; + _ithome_, 172; + _lycaste_, 172; + _lyncida_, 172; + _nephele_, 172; + _nero_, 172; + _zarinda_, 172. + + TANAGRIDAE, sexual colouring and nidification of, 245. + + TAPIR, 299. + + TELEPHORI, similar colouring of two sexes, 114. + + TEMPERATE and cold climates favourable to civilization, 318. + + THECODONTIA, 299. + + THERATES, mimicked by Heteromera, 95. + + _Thyca descombesi_, 172; + _hyparete_, 172; + _rosenbergii_, 172; + _zebuda_, 172. + + TIGER, adaptive colouring of, 52. + + TIMES newspaper on Natural Selection, 296. + + TOOLS, importance of, to man, 314. + + TREE FROGS, probable mimicry by, 103. + + TRICONDYLA, 97. + + TRIMEN, Mr., on rank of the Papilionidae, 136. + + TRISTRAM, Rev. H., on colours of desert animals, 50. + + _Trochilium tipuliforme_, 90. + + TROGONIDAE, sexual colouring and nidification of, 241. + + TROPICAL birds often green, 52. + + TROPICS, most favourable to production of perfect adaptation among + animals, 68; + not favourable to growth of civilization, 318. + + TROPIDORHYNCHUS mimicked by orioles, 104. + + TRUTHFULNESS of some savages, 353; + not to be explained on utilitarian hypothesis, 354. + + TURDIDAE, sexual colouring and nidification of, 245. + + TURNIX, 115, 251. + + TYNDALL, Professor, on origin of consciousness, 361. + + + UPUPIDAE, sexual colouring and nidification of, 241. + + USEFUL and useless variations, 34. + + UTILITY, importance of the principle of, 47, 127. + + + VARIABILITY, simple, 144. + + VARIATIONS, useful and useless, 34; + laws of, 143, 266; + as influenced by locality, 166; + of size, 168; + universality of, 287-291; + are there limits to, 291; + of domestic dogs, 293; + of pigeons, 293. + + VARIETIES, instability of, supposed to prove the permanent + distinctness of species, 26; + if superior will extirpate original species, 36; + its reversion then impossible, 37; + of domesticated animals may partially revert, 38, 40; + inconvenience of using the term, 161. + + VERTEBRATA, mimicry among, 99. + + VOICE of man, not explained by natural selection, 350. + + VOLUCELLA, species of mimic bees, 75, 98. + + + WALSH, Mr., on dimorphism, of _Papilio turnus_, 153. + + WEAPONS and tools, how they affect man's progress, 314. + + WEEVILS often resemble small lumps of earth, 58. + + WEIR, Mr. Jenner, on a moth refused by birds, 89; + on beetles refused by birds, 93; + on caterpillars eaten and rejected by birds, 119. + + WESTWOOD, Professor, objections to theory of mimicry, 108. + + WHITE colour in domesticated and wild animals, 66. + + WILD and domesticated animals, essential differences of, 38-41. + + WILL really exerts force, 367; + probably the primary source of force, 368. + + WOOD, Mr. T. W., on orange-tip butterfly, 59. + + WOODCOCKS and Snipes, protective colouring of, 53. + + WOODPECKERS, why scarce in England, 32. + + + _XANTHIA_, autumnal colours of these moths, 62. + + + ZEBRAS, 299. + + +--------------------------------------------------------------+ + | Transcriber's Notes & Errata | + | | + | The following entries were added to the Table of Contents. | + | | + | In Chapter IV.--_The Malayan Papilionidae, or Swallow-tailed | + | Butterflies, as illustrative of the Theory of Natural | + | Selection._: | + | | + | Arrangement and Geographical Distribution of the Malayan | + | Papilionidae | + | | + | Range of the Groups of Malayan Papilionidae | + | | + | | + | In Chapter VI.--_The Philosophy of Birds' Nests._: | + | | + | How young Birds may learn to build Nests. | + | | + | | + | Missing page number 94 supplied for the entry "_Phacellocera | + | batesii_, mimics one of the Anthribidae," in the index. | + | | + | The following words were found in both hyphenated and | + | unhyphenated forms (incidence in parentheses). | + | | + | |Co-existing (2) |Coexisting (1) | | + | |Fly-catcher (1) |Flycatcher (2) | | + | |sea-weed (2) |seaweed (1) | | + | |bull-dog (1) |bulldog (1) | | + | | + | The following typographical errors have been corrected: | + | | + | |Error |Correction | | + | | | | | + | |sparrrow |sparrow | | + | |unwieldly |unwieldy | | + | |it |its | | + | |Perphaps |Perhaps | | + | |confimation |confirmation | | + | |Pharoahs |Pharaohs | | + | |receptable |receptacle | | + | |occured |occurred | | + | |that that |than that | | + +--------------------------------------------------------------+ + + + + + +End of the Project Gutenberg EBook of Contributions to the Theory of Natural +Selection, by Alfred Russel Wallace + +*** END OF THIS PROJECT GUTENBERG EBOOK THEORY OF NATURAL SELECTION *** + +***** This file should be named 22428.txt or 22428.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/2/2/4/2/22428/ + +Produced by Marilynda Fraser-Cunliffe, LN Yaddanapudi and +the Online Distributed Proofreading Team at +http://www.pgdp.net (This file was made using scans of +public domain works from the University of Michigan Digital +Libraries.) + + +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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