diff options
Diffstat (limited to '57460-h')
| -rw-r--r-- | 57460-h/57460-h.htm | 5049 |
1 files changed, 2 insertions, 5047 deletions
diff --git a/57460-h/57460-h.htm b/57460-h/57460-h.htm index 09cb8c6..66c8b4b 100644 --- a/57460-h/57460-h.htm +++ b/57460-h/57460-h.htm @@ -130,44 +130,7 @@ background-color:#ffffff;font-variant:normal;font-style:normal;font-weight:norma <body> -<pre> - -The Project Gutenberg EBook of The Genetic and the operative evidence -relating to secondary sexual character, by Thomas Hunt Morgan - -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/license - - -Title: The Genetic and the operative evidence relating to secondary sexual characters - -Author: Thomas Hunt Morgan - -Release Date: July 7, 2018 [EBook #57460] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE GENETIC *** - - - - -Produced by Larry B. Harrison, Bryan Ness, Chuck Greif and -the Online Distributed Proofreading Team at -http://www.pgdp.net (This file was produced from images -generously made available by The Internet Archive/American -Libraries.) - - - - - - -</pre> +<div>*** START OF THE PROJECT GUTENBERG EBOOK 57460 ***</div> <hr class="full" /> @@ -1468,5015 +1431,7 @@ and black hens (2:1:1).</p> while the exponents stand for the factors involved, viz, B for barred and b for not-barred, which here means a black bird.</p> -<pre> - Barred♂ Black♀ - P₁ ZᴮZᴮ ZᵇbW - \ / - \ / - \ / - \ / - ZᴮZ ZᴮW - F₁ Barred♂ Barred♀ - \ / - \ / - ZᴮZᴮ ZᴮZᵇ ZᴮW ZᵇW - Barred♂ Barred♂ Barred♀ Black♀ - -</pre> - -<p>In the reciprocal cross, a black cock was mated to a barred hen. The -sons were barred, the daughters black (F₁). These inbred gave (F₂) -barred males and females, black males and females in the ratio of -1:1:1:1. The chromosome scheme of inheritance is as follows:</p> - -<pre> - Black♂ Barred♀ - P₁ ZᵇZᵇ ZᴮW - \ / - \ / - \ / - ZᴮZᵇ ZᵇW - F₁ Barred♂ Black♀ - \ / - \/ - ZᴮZᵇ ZᵇZᵇ ZᴮW ZᵇW - Barred♂ Black♂ Barred♀ Black♀ -</pre> - -<p><span class="pagenum"><a name="page_28" id="page_28">{28}</a></span></p> - -<p>One back-cross test consists in mating the F₁ barred males ZᴮZᵇ (from -both crosses) to a pure black female. The expectation is for equal -numbers of barred and black males and females, and the result was -realized. The F₁ barred hen of the first cross (ZᴮW) back-crossed to a -black cock is expected to give only barred males and black females, and -this result also was obtained. The explanation of the last cross, based -on the sex chromosomes, is as follows:</p> - -<pre> - - Black♂ F₁ Barred♀ - ZᵇZᵇ ZᴮW - \ / - \ / - \ / - ZᴮZᵇ ZᵇW - Barred♂ Black♀ -</pre> - -<p>Before these experiments were finished Goodale had made other crosses -involving the barring factor, and had obtained results that showed the -sex-linked inheritance of this factor (1909). For example, he crossed -Buff Rock male (not barred) to white Plymouth Rock females. The sons -were barred and the daughters not barred. The reciprocal cross gave -barred sons and daughters. A White Rock male (carrying barring) mated to -a Brown Leghorn female gave barred sons and daughters. Reciprocally, the -chicks were of two kinds as to their down, viz, black chicks and chicks -with the down pattern of the barred rock. All these results with Barred -Plymouth Rocks show that they carry a sex-linked dominant factor for -barring. Its wild-type allelomorph would be game-color (jungle-fowl), -but since, when the dominant barring is absent in some of the -individuals in these crosses, they are black, it would seem to follow -that another dominant factor, one for black, that is not sex-linked, is -also present.</p> - -<p>Pearl and Surface have also carried out crosses with Plymouth Rocks on a -much larger scale. Their results conformed in every way to the -foregoing. They crossed Barred Plymouth Rocks and Cornish Indian games. -The plumage of the male of the latter race is black with dark red on the -back and wing-bows; the females are also black laced with mahogany -ground-color on back, breast, wing, and tail coverts. When the male game -is mated to the barred hen the sons are barred and the daughters are -black. In the reciprocal cross both sons and daughters are barred. The -back-cross tests conformed to expectation. The results were the same as -those already stated above for the Langshan-Rock cross.</p> - -<p>Sturtevant crossed Columbian Wyandottes and Brown Leghorns. The F₁ sons -were alike, whichever way the cross was made. They were fairly typical -Wyandottes, which race carries therefore more of the dominant plumage -characters (two or three?). There were two types of daughters, depending -on the direction in which the cross was made.<span class="pagenum"><a name="page_29" id="page_29">{29}</a></span> When the father is -Wyandotte, the daughters are like him (except for stippling of the -Leghorn type). When the father is Brown Leghorn the daughters are -somewhat stippled red birds. In the former case the daughters getting -their Z chromosome from their Wyandotte father resemble him; in the -latter case the daughters getting their Z chromosome from their Leghorn -father look more like him. Their failure to look exactly like him must -be due to autosomal factors derived from the Wyandotte mother that -dominate other autosomal factors from the father.</p> - -<p>Hagedoorn crossed Black Breasted Game bantams (like those used in my -Sebright crosses) to Brown-Breasted bantams. In the latter the black -breast feathers of the male are bordered by lemon; the hens are nearly -black. Black-breasted male to “brown-red” female gave both -black-breasted sons and daughters. In the reciprocal cross all the sons -were black-breasted (like the mother) and all the daughters were brown -red like the father. Evidently the factor here for Brown Breasted game -is sex-linked and recessive. In this case the new mutant sex-linked -character is recessive to the wild type.</p> - -<p>Davenport (1912) crossed Brown Leghorns to Dark Brahmas. In the cross -and its reciprocal all the sons are alike. Two dominant sex-linked -factors were found,<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a> viz, the white background characteristic of the -Dark Brahmas and the red upper wing-coverts (and back) characteristic of -the Brown Leghorns. On the other hand, the <i>daughters</i> differ in the two -crosses, in each case resembling their father in their hackle color.</p> - -<p>When two sex-linked characters are involved in a cross it is possible to -determine by suitable matings whether an interchange between the -chromosomes that bear them has taken place. In the case of the sex -chromosomes only one sex, the male, has both like chromosomes, viz, ZZ, -and we expect from analogy with the <i>Drosophila</i> work that crossing-over -would be found between the sex chromosomes only in the male. Goodale has -recently (1917) made the important discovery that in poultry -crossing-over takes place between the sex chromosomes (ZZ) in the male, -but not in the female (ZW or ZO). This relation, therefore, is the -reverse in birds and flies, for, in the one, crossing-over takes place -in the female and in the other in the male. Whether this difference -extends also to the other chromosomes in birds as it does in flies is as -yet not known.</p> - -<p>Several years ago some crosses between gold and silver Campines were -reported by Rev. E. Lewis Jones. The results are consistent with the -view that a sex-linked factor pair is responsible for this difference in -color, although the author does not apply this view to his results. The -results may be seen in the table on page 16, to which Jones has<span class="pagenum"><a name="page_30" id="page_30">{30}</a></span> -prefixed the number of individuals. The cross also involved -hen-feathering <i>versus</i> cock-feathering, which appears here (as in other -cases) to be a non-sex-linked dominant factor. As stated above there are -in the results a few apparent inconsistencies with this interpretation, -due possibly to heterozygous females having been used in the crosses.</p> - -<p>Lefevre crossed Silver Spangled Hamburgs and Brown Leghorns. The -spangling was found to be a sex-linked dominant factor. A spangled cock -bred to a Leghorn hen gives spangled sons and daughters; a spangled hen -by a Leghorn male gave spangled sons and not spangled daughters. The -daughters do not transmit spangling. Other factors may obscure the -results, especially factors for black, or the localization of the -pattern. Lefevre says “it would seem probable that multiple factors for -black, introduced by the Brown Leghorns, are present, and that these -factors may have a cumulative effect, with the result that pigmentation -is developed to varying degrees of extension.” Whether the factors for -black spoken of as coming from the Leghorns are dominant wild-type -factors that have mutant allelomorphs in the Silver Spangled Hamburg is -not entirely clear from the quotation.</p> - -<p>Baur gives in his Introduction to the Study of Heredity (1914, pp. -202-203) some results (unpublished) that Hagedoorn had obtained by -crossing gold and silver races of Assendelver birds. The factor is -sex-linked and is no doubt the same factor reported by Jones for gold -and silver Campines and by Sturtevant for Columbian Wyandottes. Silver -dominates gold and the sex relations are the same as those already -reported by others for poultry, viz, the male is ZZ, the female ZW. Gold -hens by a heterozygous silver<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">[6]</a> gave 162 silver cocks, 163 silver hens, -168 gold cocks, 160 gold hens, expressed graphically (<i>g</i> for gold, <i>s</i> -for silver):</p> - -<table border="0" cellpadding="2" cellspacing="0" summary="" - class="sml"> -<tr class="c"><td colspan="4">Zᵍ—W♀ × Z—Zᵍ♂</td></tr> -<tr class="c"><td colspan="4" class="bt">ZˢZᵍ—ZᵍZᵍ—ZˢW—ZᵍW</td></tr> -<tr class="c"><td>Silver</td><td>Gold</td><td>Silver</td><td>Gold</td></tr> -<tr class="c"><td> male</td><td>male</td><td>female</td><td>female</td></tr> -</table> - -<p>When a silver hen was united to a gold cock there were 246 silver cocks -and 243 gold hens—crisscross inheritance.</p> - -<p class="c"><i>Summary.</i></p> - -<p>From the standpoint of the Brown Leghorn type representing the wild -type, the following colors and patterns represent dominant mutations -from that type:</p> - -<table border="0" cellpadding="1" cellspacing="0" summary=""> - -<tr><td class="c" colspan="2"><i>Dominants.</i></td></tr> - -<tr valign="top"><td>White of White Leghorn. <br /> -Silver of Dark Brahma.<br /> -Black of Minorca.<br /> -Lacing of Brahma.</td><td> -Barring of Plymouth Rock.<br /> -Black (?) of Plymouth Rock.<br /> -Buff (or red).</td></tr> -</table> - -<p> -<span class="pagenum"><a name="page_31" id="page_31">{31}</a></span></p> - -<p>Each of these (in heterozygous condition of course) is dominant; in some -cases completely so, in others incompletely dominant. At three different -loci in the sex chromosome a dominant mutation has occurred; at three -loci in other chromosomes dominant mutant changes have also occurred.</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> - -<tr><td class="c" colspan="2"><i>Recessives.</i></td></tr> -<tr valign="top"> -<td>White of Rose Comb bantam. <br /> -White of Silky.<br /> -White of White Rock.</td> -<td>Brown of Brown-breasted game.<br /> -Penciling.</td></tr> -</table> - -<p>Whether the recessive white that is sometimes found in dominant White -Rock stock is different from both of the other recessive whites is not -known. There are, then, 5 or 6 recessive characters that are not -sex-linked and 1 recessive sex-linked character.</p> - -<p>Owing to the relatively large number of color dominants in poultry, some -unnecessary confusion has arisen concerning the relation of the -dominants to the wild type, and especially to other mutant characters to -which they are said to be dominant, in the sense, however, of being -epistatic. An imaginary example will illustrate this. For example, if at -some locus in the wild type a mutation occurred that gave a dominant -black (<i>i. e.</i>, a black that shows up when one gene for it is present) -and at the same time this black also showed up even when other recessive -mutant characters were present in homozygous form, then F₁ birds would -be black when black is crossed to such pure recessive stocks. Such cases -have indeed been described as dominant, but a knowledge of F₂ would have -shown at once the error of such a system. For, if black had been a real -dominant, the F₂ would have given 3 blacks to 1 of the other type (such -as the wild type), but if the case were one of epistasis, then there -would have been 9:3:3:1 classes in F₂ (or some modification of that -ratio). In this sense, then, epistasis may be defined as a result that -appears when one member of the pair of genes produces its effect -regardless of the constitution of the individual with respect to another -gene (or other pairs of genes). It is curious at least to note that in -the case of dominant white the term epistatic has been much less often -used than in the case of black. Theoretically the two situations are -exactly alike, but because black could so obviously conceal things -beneath it, while white is not thought of as doing so, it seemed -“natural” to make such a distinction. In reality it is not a question of -covering up at all, but a case of a dominant character (white or black) -preventing other colors from appearing.</p> - -<p>In the case of recessive white the situation is somewhat different and -no one, so far as I know, has gone so far as to speak of such a white as -epistatic, although when the animal is white it certainly hides, when -completely effective, all the other effects of color-producing factors, -but allows them to “show through” in some of the cases. This means not -that they do “show through,” but that they only develop<span class="pagenum"><a name="page_32" id="page_32">{32}</a></span> to a “lower” -degree. The difference between dominant and recessive whites rests on -the fact that in one case one member of a pair of factors gives white -and in the other both members are necessary. But obviously such a -distinction is not important, and if it were worth while the case might -be argued for recessive whites being also epistatic. The whole tangle -goes back to a false interpretation of presence and absence of -characters and presence and absence of factors. As I have gone over this -ground recently in my paper on the Theory of the Gene, I need not repeat -here what I tried to make clear there.</p> - -<h3><a name="ENDOCRINE_CELLS_IN_OVARY_AND_TESTES_OF_BIRDS" id="ENDOCRINE_CELLS_IN_OVARY_AND_TESTES_OF_BIRDS"></a>ENDOCRINE CELLS IN OVARY AND TESTES OF BIRDS.</h3> - -<p>The occurrence of gland-like cells with an internal secretion in the -ovary and testes of fowls has been described by a number of writers and -denied, at least for the testes, by others. The work of Boring and Pearl -has done much to bring this question to a satisfactory solution, for -they have tested out and made use of the best reagents that their -predecessors had discovered and have used a much greater amount of -material. As they have reviewed very fully the literature of the -subject, it will not be necessary to go over the ground again in detail.</p> - -<p>In the follicles of the ovary there are present, according to Boring and -Pearl, groups or nests of cells lying among the connective tissue of the -inner theca. The cells are about three times as large as the ordinary -connective-tissue cells of the ovary. The cytoplasm is clear and -vacuolated, “only occasionally containing a few acidophile granules -which stain with the fuchsin in Mallory’s stain or the eosin of Mann’s -stain, while the real interstitial cells are crowded with granules.”</p> - -<p>When the egg is set free from its follicle, the latter collapses and the -rupture becomes closed. A mass of cells collects in the center of the -collapsed structure which develop yellow pigment. The cells, lying in -the puckered edge of the follicle, may also develop such yellow color. -The cells that produce the yellow pigment come from the nests of cells -that lay originally mainly in the theca interna. Either by migration or -by division they come to fill up the central cavity. The yellow -substance in the cells is not fat, since it does not dissolve in the -clearing oils, nor can it be protein, for it does not take acid stains -as normal secretion granules of protein. It does not dissolve in HCl, -HNO₃, or H₂SO₄, nor in strong KOH, although the latter turns the pigment -a bright red color. Many other substances were also tried by Boring and -Pearl, but none of them dissolved the yellow pigment, which reacts in -this respect in the same way as does the yellow pigment in the luteal -cells of the mammal. The similarity in the nature of the pigments in the -two cases is an argument in favor of the view that the cells that -produce the pigment are the same in both groups. In the<span class="pagenum"><a name="page_33" id="page_33">{33}</a></span> mammal the -yellow corpus luteum is a large, gland-like organ that develops after -the ovum is discharged; in the bird there is also a yellow spot on the -ovary, due to the pigment in the collapsed follicle, but it is smaller -and much less conspicuous than in the mammal. The evidence concerning -luteal cells in the testes of the bird is conflicting. One of the -difficulties in the situation is the identification of the cells, which -are sometimes regarded merely as the general connective-tissue stroma of -the testis that is undoubtedly present; at other times special secretory -cells are discerned embedded in the connective tissue, as individual -cells or in islands. Boring states (1912) that in newly hatched chicks -about half of the tissue of the testes is interstitial connective -tissue; the other half consists of tubes or cords whose principal -function is the development of the germ-cells. In the paper of 1912 -Boring reached the conclusion that there are no “interstitial cells in -the testes of the domesticated chicken in the sense that this term has -been previously used,” and states that no evidence has been found that -an internal secretion of any kind is formed by any cells of the -interstitial tissue.</p> - -<p>It is not necessary to discuss whether or not connective-tissue cells -are present in the testes of birds, for is it generally conceded that -they are found at least in certain stages, but it is important to look -into the question as to whether among these interstitial cells there are -others that have an endocrine function. Mazzetti gives pictures of such -gland-cells between the seminal tubules of the cock bird, but says that -they are rare, “even though this bird has very marked secondary sexual -characters” (Boring and Pearl). It may be remarked parenthetically that -if they had been more abundant the bird might have had no secondary -sexual plumage since it will be pointed out below that such glandular -cells may have as their special function the suppression of these -characters.</p> - -<p>According to Des Cilleuls, interstitial cells are first found in males -about 30 days old and at this time the secondary sexual characters put -in their appearance. If, as will be shown in the sequel, he means by -interstitial cells the endocrine cells that suppress the development of -the male plumage in the female, the appearance of these cells at this -time would be significant; but if he implies that their occurrence in -the male incites the development of the secondary sexual characters, his -interpretation is open to serious doubt. Reeves found interstitial cells -in testes of cocks 3, 5½, 9, and 18 months—more in the earlier stages.</p> - -<p>In a later communication by Boring and Pearl the whole question is taken -up again with improved methods, etc. Previously 21 male birds had been -studied, just hatched to 12 months old. More sections of this same -material were made which were stained according<span class="pagenum"><a name="page_34" id="page_34">{34}</a></span> to Mann’s and Mallory’s -methods. In addition, a whole new series of preparations was made. A few -interstitial cells, i. e., granule containing-cells were found in newly -hatched chicks, but not in any of the 60 mature birds examined.</p> - -<h3><a name="LUTEAL-CELLS_IN_THE_TESTES_OF_THE_MALE_SEBRIGHT" id="LUTEAL-CELLS_IN_THE_TESTES_OF_THE_MALE_SEBRIGHT"></a>LUTEAL-CELLS IN THE TESTES OF THE MALE SEBRIGHT.</h3> - -<p>Finding that the testes of F₂ hen-feathered birds were often flat and -pear-shaped instead of rounded and cylindrical, as in ordinary cocks, -and that they were often black in color, suggested, as already stated, -that the testes of the Sebright might be hermaphrodite in some element. -It seemed not impossible that egg-cells might be found. I made a -considerable number of sections of the testes of these birds and -examined them under the microscope; not finding any egg or egg-like -bodies, the slides were laid aside, but the idea that in some other way -the Sebright’s testes might correspond to the ovary of the female next -recurred to my mind. Consequently, when in the summer of 1918 I had some -new material derived from a castrated Sebright male that had partly -regenerated its testes and was again going back to hen-feathering, and -pieces from one of the old testes of a castrated bird, I asked Miss -Boring, who was then in Woods Hole, to make some preparations and -examine them to see if she could detect any such elements in them as she -had found in the female. Miss Boring reported the occurrence of luteal -cells in the testes from hen-feathered males, and the results have been -published in a brief preliminary paper (1918). The abundance of these -clear cells, supposedly gland-cells with endocrine influences, in the -testes of hen-feathered birds is in sharp contrast to their absence in -the normal adult cock birds. It seems to follow, therefore, that the -hen-feathering in the Sebrights is due to the presence of these cells, -whose function is the same as of the similar cells in the female, <i>i. -e.</i>, the suppression in both of cock-feathering. Castrating the Sebright -produces its effect by the removal of these cells that are responsible -for the suppression of cock-feathering.</p> - -<p>The occurrence of luteal cells in young stages of other races of poultry -raises the question as to whether in these races the first or juvenile -plumage, that resembles that of the hen rather than that of the cock, -may not also be due to an internal secretion from these cells, or -whether this juvenile plumage is only the plumage of a characteristic -stage in development. Castration of young chicks ought to settle this -point. Such castration experiments have been made by Goodale. The -absence of any reference to any effect on the juvenile plumage in these -early castrated birds probably meant that they did not develop -precociously cock-feathering, and he writes me that he examined them -carefully and that their plumage is like that of the normal chicks. -Geoffrey Smith has reported the occurrence of two kinds of males<span class="pagenum"><a name="page_35" id="page_35">{35}</a></span> in a -race of Leghorns, the males of one of which become cock-feathered before -the other. May not this difference depend on the length of time -endocrine cells remain or begin to develop? A histological study of the -two types would be of the greatest interest.</p> - -<h3><a name="ENDOCRINE_CELLS_IN_THE_TESTES_OF_MAMMALS" id="ENDOCRINE_CELLS_IN_THE_TESTES_OF_MAMMALS"></a>ENDOCRINE CELLS IN THE TESTES OF MAMMALS.</h3> - -<p>In man and other mammals it has long been recognized that in addition to -the germinal cells of the testis there are also present other cells, -sometimes called interstitial cells, that, so far as known, have no -immediate function in connection with the germ-cells, or at least that -have other important functions outside the relation to the reproductive -organ. That some internal secretion from these cells has an important -influence on the secondary sexual characters rather than anything done -by or produced by the germinal cells has been very clearly shown by -evidence derived from three separate sources, namely, from the operation -known as vasectomy, from an exceptional condition known as -cryptorchidism, and more indirectly from X-ray treatment. Vasectomy -involves either cutting the vasa deferentia in such a way that the cut -ends do not reunite. In consequence of the closure of the outlet of the -testis the germinal cells slowly degenerate, and finally completely -disappear. How such an effect is produced we do not know. That this -result does take place is borne out by the unanimous testimony of all -those who have successfully performed the operation. Ancel and Bouin -showed (1903) that breaking the continuity of the vas deferens -suppressed spermatogenesis in 8 to 12 months. Both the Sertoli cells -(the nourishing cells of the germinal epithelium) and the interstitial -cells persist. Such animals remain sexually active and their secondary -sexual characters are not affected. Marshall states that in the hedgehog -the remarkable periodic enlargement of the testis takes place even after -vasectomy, although the germ-cells have disappeared.</p> - -<p>In mammals the testes fail at times to pass through the inguinal canal, -and, in consequence of their retention in the body-cavity, the -germ-cells fail to develop. On the other hand, the interstitial cells of -the testis develop normally. Cryptorchid individuals show the normal -secondary sexual characters of their species. How retention of the sperm -should give rise to the same result as cutting the duct, viz, absorption -of the germinal cells, is not known. A possible solution may be found in -the pressure exerted on the testes, both when retained in the abdomen -and when their outlets are stopped by tying or cutting the ducts.</p> - -<p>Finally, it has been long known that continued or repeated exposure to -X-rays or to radium causes the destruction of the germ-cells, but leaves -the interstitial cells intact and presumably functional. Destruc<span class="pagenum"><a name="page_36" id="page_36">{36}</a></span>tion of -the germ-cell by X-rays has no effect on the secondary sexual -characters.</p> - -<p>This threefold evidence demonstrates that in the male of the mammalia -most, perhaps all, of the secondary sexual characters that are affected -by castration are not affected by the destruction of the germ-cells. -This conclusion supports very strongly the view that the interstitial -cells are the cellular element in the testes that influence through -internal secretion the development of the secondary sexual characters of -the male.</p> - -<p>Equally important are the results that relate to the accessory organs of -reproduction, such as the glands that open into the vas deferens -(prostate, Cowper’s gland, etc.) and the copulatory organs also. In the -castrated mammals these organs diminish in size. On the other hand, -after destruction of the germ-cells in the testes (or even when they -fail to develop as in cryptorchid individuals) these accessory parts are -unaffected. In birds, as will be shown, the situation is entirely -different.</p> - -<h3><a name="CYCLICAL_CHANGES_IN_THE_INTERSTITIAL_CELLS_IN_HIBERNATING_MAMMALS" id="CYCLICAL_CHANGES_IN_THE_INTERSTITIAL_CELLS_IN_HIBERNATING_MAMMALS"></a>CYCLICAL CHANGES IN THE INTERSTITIAL CELLS IN HIBERNATING MAMMALS.</h3> - -<p>The changes that take place in the interstitial cells in mammals that -hibernate and in which there is a definite rutting season following -hibernation have been examined by several workers. The mole has been -studied by Regaud (1904), Lécaillon (1909), Tandler and Grosz (1911); -the marmot by Hauseman (1895) and Gaugini (1903); the hedgehog by -Marshall (1911); and the woodchuck by Rasmussan (1917). In the mole the -interstitial cells are most abundant when the tubules in which the -spermatogenesis is taking place are least developed, and <i>vice versa</i>. -In the hedgehog the increase in both tissues takes place at the same -time. In the woodchuck both tissues increase rapidly after hibernation -(during March and April), after which the spermatogenesis continues -actively for the two following months (May and June), while the -interstitial cells retrograde rapidly during April and remain at a low -level for the rest of the year. Retrogression in the germinal epithelium -begins in July, after the rutting season is past. It appears from this -evidence that the activity of the two tissues does not always run the -same course. Since the secondary sexual characters of the male, which -are not well developed in these animals, are not so far as known -affected by the condition of the testes, the evidence does not have any -very direct bearing on our present topic. How far the sexual behavior of -these mammals is determined by the quantity or by the activity of the -interstitial cells is not very clear from the evidence, although there -is a very noticeable increase in the amount of this tissue just before -and during the rutting season. In the mole also the<span class="pagenum"><a name="page_37" id="page_37">{37}</a></span> interstitial cells -begin to increase just before the mating season, and the increase -continues for several months after mating has taken place. It is -difficult to judge how great or how little the change amounts to unless -the whole organ is considered, for the relative volumes of the seminal -tubes and the interstitial tissues does not give a measure of the total -volume of these tissues, since the testes may decrease greatly in size -when the seminal tubes retrograde, and the apparent increase of the -interstitial cells at the time may not increase the total amount of that -tissue present.</p> - -<p>Probably more important than the ratio of interstitial tissue to tubules -is the activity of the former. Rasmussan states that in the woodchuck -the interstitial cells not only increase in number immediately after -hibernation, but the increase in amount of this tissue is largely due to -increase in the cytoplasm, in which there appears an accumulation of -fatty globules in the more peripheral parts of the cells. In the central -cytoplasm an abundance of fine lipoid granules develops.</p> - -<p>Marshall has made some interesting experiments on the hedgehog at -different seasons. Castration in March prior to the breeding-season has -an influence on the accessory generative organs (vesiculæ seminales, -prostates, and Cowper’s glands). They remain in the same undeveloped -stage in which they were at the time of operation. If castration is -carried out very early in the breeding-season, when the accessory -reproductive organs are about half developed, their further enlargement -is prevented. In so far as the accessory organs rank as secondary sexual -organs, their complete development is thus shown to depend on the -testes. Transection of the vasa deferentia before the beginning of the -breeding-season affects somewhat the enlargement of the testes, but -produces no effect on the accessory organs.</p> - -<h3><a name="HERMAPHRODITISM_IN_POULTRY_AND_THE_SECONDARY_SEXUAL_CHARACTERS" id="HERMAPHRODITISM_IN_POULTRY_AND_THE_SECONDARY_SEXUAL_CHARACTERS"></a>HERMAPHRODITISM IN POULTRY AND THE SECONDARY SEXUAL CHARACTERS.</h3> - -<p>Several hermaphrodite birds have been described (Brandt, 1889; Shattock -and Seligman, 1906; Pearl and Curtis, 1909; Smith and Thomas, 1913; -Bond, 1914; etc.). The most recent and complete account of such birds is -that by Boring and Pearl. They examined in all 8 hermaphrodites, or at -least 8 birds that showed in their plumage, or other secondary sexual -characters, peculiarities of both sexes. Five of the birds came from -Herr Houwink in Meppel, Holland, who had a stock in which there -appeared, in 1911, two hermaphrodites out of 80 birds, and in 1912, -three out of 80 birds. These were the birds studied by Boring and Pearl. -In addition, when Pearl saw Herr Houwink’s birds in 1910, “there were -then on hand a considerable number of these supposed hermaphrodite -birds.” An anatomical study of the Holland birds showed that one of them -was nearly a normal female; three, the<span class="pagenum"><a name="page_38" id="page_38">{38}</a></span> authors say, were “evidently -undeveloped females. They have infantile oviducts and embryonic -ovaries.” It should be added that there was a tumor more than twice the -size of the ovary attached to or part of the ovary. If the ovary itself -was affected by the tumor, or the tumor was a part of the ovary, the -slightly unusual condition of the birds might be accounted for. Of the -other 3 birds, 2 are also suspected to have ovarian tumors, while in the -third bird streaks of a secretion which resembles the substance of the -tumor of the other two were found. The change towards male plumage in -these 5 birds is probably due either to the incomplete development of -ovary or to the effect of the tumor on the ovary. Although luteal cells -are described as present, it seems probable that their total number -might be less than in a normal bird, and hence their insufficient -secretion would fail to suppress the development of male plumage. From -this point of view these birds are no more hermaphrodites than is a hen -with her ovary taken out.</p> - -<p>The remaining Holland birds were entirely different. On the left side -there was an ovary in an inactive condition; on the right side there was -a testis, producing spermatozoa. Sections of the testis show that it is -normal, consisting of a mass of tubules with very little connective -tissue between them. In both ovary and testis there are “a few nests of -luteal cells near the surface. The ovary contains eggs, but is abnormal -to some extent.” The authors state:</p> - -<div class="blockquot"><p>“In external appearance it is more like a male than the others, -which fact correlates well with the active condition of the testis -and inactive diseased ovary, with only one corpus luteum scar. The -interstitial cells can scarcely be held accountable for the male -secondary sex characters, as the only ones in an active secreting -condition are a few in the ovary.”</p></div> - -<p>It is not quite clear what is meant in this quotation by the statement -that the interstitial cells can scarcely be held accountable for the -male secondary characters unless to suggest that they cause the -development of these characters in the male, as they are supposed to do -in mammals—a view that the authors do not seem at other times to hold.</p> - -<p>Another hermaphrodite (Atwood’s black) had an infantile oviduct and an -ovotestis. A second bird, too, had an ovotestis—mostly testis—as well -as a rather large oviduct. Collections of luteal cells are described -between the tubules of the testicular portion. If, as suggested by the -Sebright cases, these cells tend to suppress the female plumage, their -presence here in excess might at least be made to account for the female -part of the plumage of this bird. Comparing the last two birds (that -showed active sex-behavior as males) with the best of the Holland birds, -Boring and Pearl point out that the active sex behavior of the two -former can not be due to “interstitial cells that are absent in these -<span class="pagenum"><a name="page_39" id="page_39">{39}</a></span>but present to a slight extent in the former.” They then add” -...though the differences can not be laid to the lutear cells, as they -are present in all three.” That the relative amounts of the latter or -their activity might still be accountable for the difference would not -seem entirely excluded from the evidence so far as it is given.</p> - -<p>A fourth hermaphrodite (Dexter’s) laid 12 eggs and had a large coiled -oviduct. There was present “a large, lobulated reproductive organ on the -left,” which proved to be an ovotestis. Several ovarian tumors were -present and there was testicular tissue.</p> - -<p>It is fairly evident, then, that four of these birds described by Boring -and Pearl were females with abnormal ovaries. The incomplete development -of the latter, or their abnormal condition due to tumors, may -sufficiently explain the occurrence of male secondary sexual characters. -That these tumors affect, to different degrees, such characters is -expected from what is shown by imperfectly spayed females of normal -breeds.</p> - -<p>There are a few statements in the summary of this paper that call for -comment. The statement that the “development of comb, spurs, and wattles -does not stand in direct quantitative relation to the sex of the gonad,” -appears to be only intended as a statement of fact based on the author’s -observation. But in what sense is there an expectation that they should -stand in such relation beyond the obvious fact that in the cock the comb -and wattles are larger than in the hen, and that spurs are generally -present only on the cock. But if the expression “sex of the gonad” -implies the germ-cells it is not at all certain that there is any -expectation of a quantitative relation, and there is some probability at -least that other cells than the sex-cells are involved in the -development of combs, wattles, and possibly spurs. A castrated cock has -a small comb resembling that of the female bird. On the other hand, -removal of the ovary sometimes leads to an increase in the comb and -wattles. Here we have, to say the least, a paradoxical situation, for -the result looks superficially as though something in the ovary keeps -down the hen’s comb, while something in the testes keeps up the cock’s -comb, yet when the ovary is removed the hen develops a cock’s comb; when -the testes are removed the cock develops a hen’s comb. The real meaning -is, I think, that the genetic complex for femaleness (one Z or else ZW) -stands in itself for a full-sized comb, while the genetic complex for -maleness (two Z’s) stands in itself for small comb.</p> - -<p>Boring and Pearl state that “body-shape and carriage have a genetic -relation to the sex of the gonad.” This statement means, I think, that -the amount of testicular matter present stands in some direct relation -to the shape of the body and carriage of the male. Castration, both of -the normal cock and the Sebright, seems to change the carriage somewhat -and perhaps the shape. Both lose something of the peculiar attitude of -the male, but I have not been able to my own<span class="pagenum"><a name="page_40" id="page_40">{40}</a></span> satisfaction to analyze -what this means. As has been pointed out, and as the pictures show, the -castrated Sebright changes his attitude, but whether this is a change -due to his new contour, or to a new balance resulting from a large tail, -or to a let-down resulting principally from effects on the nervous -system, is difficult to determine. The same statements apply in part to -the castrated cock of ordinary breeds, but not to the same degree, since -the change after castration, in feathering and in carriage at least, is -slight.</p> - -<p>The conclusions that the “amount of lutear cells or pigment (?) is in -precise correlation with the degree of external somatic femaleness -exhibited by the individual” is of especial interest in connection with -the Sebright evidence. It is difficult, however, to gather from the body -of the paper what the absolute amount of luteal cells is that is -present, for even in some of the more male-like birds with an ovotestis -the description leads one to suppose that there may be as much luteal -material present as in some of the more female birds with infantile -ovaries or cystic tumors.</p> - -<p>Pearl and Curtis (1909) described “a case of incomplete hermaphroditism” -in a Barred Plymouth Rock fowl. Externally the bird looked like a hen, -but “the head and neck resembled these parts in the cockerel,” -especially the comb and wattles. The bird was never seen to tread a hen, -nor did it ever crow normally. An ovary and oviduct were found on the -left side, the former no larger than that of a laying hen after removal -of the large yolks. No eggs were visible on its surface. On the right -side a testis (9 mm. by 6 mm.) and vas deferens were present. No eggs -were found in the ovary, and it gave every indication of being in a -degenerating condition, with no eggs or egg follicles in it. The testis -had no “normal seminiferous tubules”, but indications of cellular rods -were present. The organ is in all probability a degenerating testis.</p> - -<p>A Leghorn 2 years old has been described by Shattuck and Seligmann -(1906) that had the full-developed comb and wattles of the cock, but the -former drooped slightly to one side as in the hen. Well-developed spurs -were present. The plumage was mainly female, with neck-hackles -moderately developed, and with “saddle-hackles” practically absent. The -tail, though not typically female, lacks sickle feathers. The bird -excited no notice from other birds of either sex. A large left oviduct -and the distal end of a right oviduct were present. Two vasa deferentia -were also present. In the left side a flattened sex-gland (3 cm. high) -was found, made up of testicular tubules. Two small ova were found in -its posterior end. The right gonad was also tubular (testis).</p> - -<p>The occurrence of real testicular tissue in one of the Holland birds and -in three others described by Boring and Pearl, as well as in one<span class="pagenum"><a name="page_41" id="page_41">{41}</a></span> -described by Pearl and Curtis, and in another by Shattuck and Seligmann -calls for special comment, since the presence of both testicular and -ovarian tissue in the same bird is the essence of hermaphroditism. In -general there are two ways of looking at such a result. Either the -sex-determining factors have been changed so that in one part of the -body, where the reproductive organs are laid down, one condition can -prevail, in other parts other conditions; or a mixup of the sex -chromosomes has taken place. Until we get some more evidence concerning -such cases it is useless to speculate, although the former view might -seem the most probable of the two if the Holland birds of Herr Houwink’s -flock were in a high degree true hermaphrodites.</p> - -<p>But in fact three of the four described by Boring and Pearl were due to -tumors of the ovary, which, if they suppress the normal development of -this organ, would be expected to call forth the appearance of the -secondary sexual characters of the cock. If the likelihood of developing -a tumor were inherited, the frequent occurrence of hen-feathered birds -in this flock would be explained. However, one true hermaphrodite in 4 -birds is surprisingly high for a chance result, since hermaphrodite -birds are very rare.</p> - -<p>The second interpretation suggested above is one that has been advanced -and established by genetic evidence in <i>Drosophila</i>, viz., dislocation -of the sex chromosomes. In the case of birds the male is supposed to be -duplex for the sex factors (ZZ), the female simplex (ZW), and -consequently the chromosome-dislocation hypothesis must be worked out -contrawise in birds and insects. We should have to suppose that such -birds start as males (ZZ), and that at some division of the cells of the -embryo one of the Z’s became lost (left at the cell-wall for example). -All the cells that got ZZ would be male; all that got Z would be female. -If the reproductive region included cells of these two kinds, an -ovotestis would result. The rest of the body should be the same, or -nearly so, since the soma of male and female birds is alike whether ZZ -or Z, except in so far as it is affected by the secretions from the -ovaries (in most races of poultry), or from the testes if the race be -Sebright, Campines, or Hamburgs. Birds with ovotestis might, -nevertheless, be expected, on this view, to show at times an -intermediate condition of the secondary sexual characters, according to -how much internal secretion is produced in the ovotestis. In other -words, the chromosome loss might involve much more extensive regions -than the reproduction organs, but show its effects first in that organ -and then indirectly other parts of the body be affected by the luteal -cells of the testis. There is one rather good piece of evidence that -seems opposed to this interpretation. In the hermaphrodites the oviduct -is present in all cases. Its conspicuous presence in the four -hermaphrodites would seem, therefore, to indicate that the birds<span class="pagenum"><a name="page_42" id="page_42">{42}</a></span> -started as females (ZW), which is inconsistent with the dislocation -hypothesis. The alternate would be that in all these cases the Z part -always included the region of the oviduct, which seems improbable.</p> - -<p>There is another possibility, viz, that in birds a sex-factor is carried -by the W chromosome, and ZW is a female not because of one Z, but due to -the presence of W. If so, then one Z or two Z’s might give the same -result, viz, female. If a bird started as female, (ZW) and chromosomal -dislocation occurred, then the Z parts would be female and the male part -W. Until we get evidence on this point it is not worth elaborating. -Without genetic evidence from hybrids, the interpretation of -hermaphrodites in birds can have at present only a speculative interest. -We may hope some day to get the same kind of evidence as in the case of -<i>Drosophila</i>. Hermaphrodite hybrid pheasants that have been often -described might seem to furnish a hopeful field, for they appear to be -quite common and to show characteristics of both races. As yet, however, -no one has, I think, succeeded in finding a simple interpretation of the -results. It is also not unlikely that many of the pheasant cases are not -true hermaphrodites, but due to failure of normal development of the -reproductive gland, which gives an intermediate or mixed type of -secondary sexual characters.<span class="pagenum"><a name="page_43" id="page_43">{43}</a></span></p> - -<h2><a name="PART_II" id="PART_II"></a>PART II.</h2> - -<h3><a name="DARWINS_THEORY_OF_SEXUAL_SELECTION" id="DARWINS_THEORY_OF_SEXUAL_SELECTION"></a>DARWIN’S THEORY OF SEXUAL SELECTION.</h3> - -<p>Darwin seems to have felt the necessity of giving some other explanation -for the secondary sexual differences between the male and female than -that such differences were only a by-product or concomitant of sex -itself. His reason for searching further was probably a part of the -general point of view he had reached in regard to the utility of special -structures of animals, namely, that their presence finds its explanation -on the basis of utility. Believing as he did that most of the -adaptations of plants and animals have been built up by the accumulation -of small steps, it must have appeared to Darwin inconceivable that the -highly developed ornamentation exhibited in the secondary sexual -characters could have been simply the by-product of sex itself, -especially when the ornamentation may have been entirely absent in males -of closely related species. To-day we are not, I think, so oppressed -with the difficulties of the situation, for we have become familiar with -the fact that very slight genetic differences may cause very great -differences in the end-product. In a word, the problem seems less -formidable to us than it did to Darwin.</p> - -<p>Darwin appealed to three processes to account for the facts: (1) to -natural selection between the members of the same sex; (2) to choice on -the part of the “other” sex; (3) to the “inheritance of use.” Since each -of these appeals to a different procedure, let us take them up -separately.</p> - -<p>Competition of the males with each other for the female would, Darwin -said, lead to the survival of those males best endowed with organs of -offense and defense. The spurs of the cock are weapons dangerous for -other birds; the horns of the bull and those of deer are used for -offense and defense; the mane of the lion is a protection against the -teeth of other lions. It is true that these same weapons and shields -serve for attack and defense outside the species; but since the female -lacks them or has them less developed, they would not seem necessary for -survival of the individual against aggression from without. They have -developed, then, through competition within the species.</p> - -<p>Several objections of greater or less weight have been urged against -Darwin’s interpretation. It has been pointed out that the combats within -the species are seldom fatal and that the defeated rival finds another -mate. If, as a rule, there are as many females as males within the -species and monogamy is the rule, all males will find partners sooner or -later, all may have offspring, and the offspring have equally good -chances of survival. Under these circumstances it is not to be expected -that the combat would be likely to lead to the production of males with -longer spurs or larger horns.<span class="pagenum"><a name="page_44" id="page_44">{44}</a></span></p> - -<p>Darwin realized this difficulty and tried to meet it by another -assumption, viz, that the better endowed males would <i>also</i> be more -likely to have more offspring. How could this be made probable? Darwin -suggested that the strongest males would be in position to mate with the -first females to reach maturity, and if these were more likely to have -offspring, either because of maternal endowments that made them also -more prolific or because the earlier broods would have a better chance -of getting food, etc., then the successful competitor would sooner or -later impress his advantages on the race.</p> - -<p>At other times Darwin suggested that the exceptional vigor that led to -the greater development of the character in question would itself be of -value and through transmission to the offspring lead to advance in the -development of the other character in question. But here the argument -shifts to another field of inquiry and survival is ascribed to greater -vigor, while the secondary sexual character is carried along in its wake -as a sort of correlated effect.</p> - -<p>It will be conceded, I think, that such pleading does not help the -argument, but exposes rather its inherent weaknesses. There is, however, -a line of defense that is permissible. If monogamy is not the rule, if -the male captures or attracts several females and keeps a harem, as do -the fur seals and walruses, or rules a herd as does the bull, or has a -flock as does the cock, or mates more frequently with random females -than do some other males, then the advantage of his more developed -weapon might lead to more offspring. If it could be shown that such -intraspecific weapons prevail more frequently within polygamous species, -a fair argument for natural selection might be made. I do not know -whether such a census has been taken as yet, but it is true, I think, -that in most polygamous groups we find weapons of offense very highly -developed. The fur seal has a harem and the male is greater in size, in -strength, and in the development of his tusks than is the female. -Similarly for the walrus. The bull drives away rival bulls from the herd -until through age or injury, or through the development of a better -fighter, he is replaced. If the better endowment is due to a genetic -factor, we should expect natural selection to keep the race at the -highest possible level that variation supplies material for. If, then, -we confine the application of natural selection to cases of this sort, -the explanation is as valid as is the theory in other fields. Such a -conclusion becomes weakened when an attempt is made to apply it to other -groups of animals in which it appears improbable that the secondary -sexual characters of the male have any obvious value as organs of -offense. There are families of beetles, for example, in which the -development of the horns of the male are as striking as are those of the -ram or the stag. The males of these beetles are not known to fight with -each other, nor are they polygamous. It may seem that we must look here -for some other explanation, which, if found, might suffice to<span class="pagenum"><a name="page_45" id="page_45">{45}</a></span> cover -also the case of birds and mammals. In answer to this criticism it may -be argued that it is also possible that the other explanation when found -need not necessarily apply to the higher animals, where the laws of -combat may still give the true explanation. On the whole, I think that, -for our present purpose, it will suffice to state it is consistent with -the theory of natural selection to accept <i>provisionally</i> this part of -Darwin’s theory for those species in the higher groups in which polygamy -holds, conceding, however, that even here it may have to be altered when -fuller knowledge is gained.</p> - -<p>We are more concerned with that special feature of Darwin’s theory of -sexual selection that is applied to those cases where the characters are -supposed to owe their special development to selection by the -individuals of the opposite sex. It is assumed that the female <i>chooses</i> -the better endowed males, <i>because</i> of the strong appeal he makes to her -sense-organs. Here we must employ perforce or for brevity’s sake the -terms used in human psychology, and run the risk at every turn of -imputing to other animals the emotions and acquired associations which -man himself utilizes. Even granting that other animals possess somewhat -similar emotions to ours, there still remains always the danger, in the -absence of real evidence, of imputing to them the particular emotion -that we call “feeling for beauty”; and the greater danger of imputing an -esthetic sense so highly developed that the choice falls in the long run -on the suitor better ornamented than his rivals.</p> - -<h3><a name="OTHER_THEORIES_TO_ACCOUNT_FOR_SECONDARY_SEXUAL_CHARACTERS" id="OTHER_THEORIES_TO_ACCOUNT_FOR_SECONDARY_SEXUAL_CHARACTERS"></a>OTHER THEORIES TO ACCOUNT FOR SECONDARY SEXUAL CHARACTERS.</h3> - -<p>Wallace has always been an opponent of Darwin’s theory of sexual -selection in so far as it is based on female choice. As already stated, -he believes that the difference between the plumage of the male and -female in birds is due to natural selection keeping down the -ornamentation and high coloration in the female, because these would be -expected to expose the female while sitting on the nest to the attacks -of enemies, more especially of hawks. In support of this view he points -to a long series of species which build exposed nests and in them the -female is plainly and inconspicuously colored, while he also points out -that in such birds as parrots, toucans, woodpeckers, hangnests, and -starlings, which nest in holes or have covered nests, the female is -often as highly colored as the male. It can not be denied that he makes -out rather a strong case in support of this view, despite the fact that -there are other birds, like the Baltimore oriole, that have covered -nests and in which the sexes are very markedly different.</p> - -<p>Wallace tries to meet cases like the last one by assuming that the -covering keeps off the rain; but, if so, why are the sexes still so -different? In the case of other highly colored birds, such as jays, -magpies, hawks, and crows, Wallace believes that these birds are all -aggressive, hence<span class="pagenum"><a name="page_46" id="page_46">{46}</a></span> can protect their nests if attacked. As a further -support of his view, Wallace points out that in the few cases where the -female is more highly colored than the male (as the dotterel, species of -phalarope, an Australian creeper) the male incubates the eggs.</p> - -<p>Wallace’s suggestion still leaves unexplained the ornamentation of the -male, which he tries to account for as the direct result of the greater -vitality of the male. He tries to show that excessive ornaments and high -coloration develop especially in those parts of the body to which there -is an unusual supply of blood or where nerves and blood-vessels emerge -to go to the skin or to the muscles.</p> - -<div class="blockquot"><p>“If we have found a <i>vera causa</i> for the origin of ornamental -appendages of birds and other animals in a surplus of vital energy, -leading to abnormal growths in those parts of the integument where -muscular and nervous action are greatest, the continuous -development of these appendages will result from the ordinary -action of natural selection in preserving the most healthy and -vigorous individuals, and the still further selective agency of -sexual struggle in giving to the very strongest and most energetic -the parentage of the next generation. And, as all the evidence goes -to show that, so far as female birds exercise any choice, it is for -‘the most vigorous, defiant, and mettlesome male,’ this form of -sexual selection will act in the same direction, and help to carry -on the process of plume development to its culmination. That -culmination will be reached when the excessive length or abundance -of the plumes begins to be injurious to the bearer of them; and it -may be this check to the further lengthening of the peacock’s train -that has led to the broadening of the feathers at the ends, and the -consequent production of the magnificent eye-spots which now form -its crowning ornament.</p> - -<p>“The display of these plumes will result from the same causes which -led to their production. Just in proportion as the feathers -themselves increased in length and abundance, the skin-muscles -which serve to elevate them would increase also; and the nervous -development as well as the supply of blood to these parts being at -a maximum, the erection of the plumes would become a habit at all -periods of nervous or sexual excitement. The display of the plumes, -like the existence of the plumes themselves, would be the chief -external indication of the maturity and vigor of the male, and -would, therefore, be necessarily attractive to the female. We have, -thus, no reason for imputing to her any of those esthetic emotions -which are excited in us, by the beauty of form, color, and pattern -of these plumes; or the still more improbable esthetic tastes, -which would cause her to choose her mate on account of minute -differences in their forms, colors, or patterns.”</p></div> - -<p>Wallace says, referring to the immense tuft of golden plumage in the -best known birds of paradise (<i>Paradisea apoda</i> and <i>P. minor</i>) that -springs from a very small area on the side of the breast, that Mr. Frank -E. Beddard, who has kindly examined a specimen, says that “this area -lies upon the pectoral muscles, and near to the point where the fibers -of the muscle converge towards their attachment to the humerus. The -plumes arise, therefore, close to the most powerful muscle of the body, -and near to where the activities of that muscle would be at a maximum. -Furthermore, the area of attachment of the plumes is just<span class="pagenum"><a name="page_47" id="page_47">{47}</a></span> above the -point where the arteries and nerves for the supply of the pectoral -muscles, and neighboring regions, leave the interior of the body. The -area of attachment of the plume is, also, as you say in your letter, -just above the junction of the coracoid and sternum.” “Ornamental plumes -of considerable size rise from the same part in many other species of -paradise birds, sometimes extending laterally in front, so as to form -breast shields. They also occur in many hummingbirds, and in some sun -birds and honey-suckers; and in all these cases there is a wonderful -amount of activity and rapid movement, indicating a surplus of vitality, -which is able to manifest itself in the development of these accessory -plumes.”<a name="FNanchor_7_7" id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">[7]</a></p> - -<p>There are two serious defects in such an attempt to explain the facts. -In the first place, it has been shown in several cases that have been -studied that it is not the lessened “vitality” of the female but the -suppression caused by the ovary that keeps down the development of the -full plumage in that sex. In the second place, the anatomical influences -appealed to are imaginary rather than real, for it is by no means -apparent that the local exits of blood-vessels and nerves to muscles are -at all correlated with the location of the ornamental parts, in the -skin. Even when larger blood-vessels run to the region of excessive -development of feather ornaments it may well be that they go there -because the ornaments in question use them for their nourishment; in -other words, Wallace puts the cart before the horse. The top of the -head, where crests so often develop, the throat coloration and throat -shields of hummingbirds and birds of paradise, the two long tail -feathers of several species of hummingbirds, etc., do not arise, so far -as known, from regions which are conspicuous for a rich supply of blood -and nerves. Wallace’s appeal to underlying organs such as muscles that -supposedly influence the special development of the feathers in the skin -above does not strike one as a fortunate appeal to physiological -principles.</p> - -<p>Hudson, in his interesting book, “The Naturalist in La Plata,” has also -criticized Darwin’s theory of sexual selection. He has brought together -a considerable number of interesting observations that go to show that -the displays—dancing, singing, and combats—of males and females have -no relation to mating. Many of them involve birds already mated, -sometimes several males participating, sometimes males and females -together. Some of the tourneys he describes are more elaborate than the -mating instincts themselves, yet are not concerned with mating. He -attempts to explain them as overflow phenomena, <i>i. e.</i>, as expressions -of the high vitality of the males, especially at this time. If he is -right, then elaborate exhibitions of these kinds have evolved that have -no special connection with mating. Are we<span class="pagenum"><a name="page_48" id="page_48">{48}</a></span> called upon for a different -explanation for other differences that distinguish the sexes? One -example will suffice to bring out a curious emotional (?) display that, -elaborate as it is, has no apparent connection with mating (p. 269):</p> - -<div class="blockquot"><p>“The lapwing display, called by the natives its ‘dance’ or ‘serious -dance’—by which they mean square dance—requires three birds for -its performance, and is, so far as I know, unique in this respect. -The birds are so fond of it that they indulge in it all the year -round, and at frequent intervals during the day, also on moonlight -nights. If a person watches any two birds for some time—for they -live in pairs—he will see another lapwing, one of a neighboring -couple, rise up and fly to them, leaving his own mate to guard -their chosen ground; and instead of resenting this visit as an -unwarranted intrusion on their domain, as they would certainly -resent the approach of almost any other bird, they welcome it with -notes and signs of pleasure. Advancing to the visitor, they place -themselves behind it; then all three, keeping step, begin a rapid -march, uttering resonant drumming notes in time with their -movements; the notes of the pair behind being emitted in a stream, -like a drumroll, while the leader utters loud single notes at -regular intervals. The march ceases; the leader elevates his wings -and stands erect and motionless, still uttering loud notes; while -the other two, with puffed-out plumage and standing exactly -abreast, stoop forward and downward until the tips of their beaks -touch the ground, and sinking their rythmical voices to a murmur -remain for some time in this posture. The performance is then over -and the visitor goes back to his own ground and mate, to receive a -visitor himself later on.”<a name="FNanchor_8_8" id="FNanchor_8_8"></a><a href="#Footnote_8_8" class="fnanchor">[8]</a></p></div> - -<p>Cunningham, who has brought together many interesting cases of secondary -sexual differences in his book on “Sexual Dimorphism in the Animal -Kingdom,” attempts to show that the development of the secondary sexual -characters of the males are due directly to the use of certain parts of -the body during courtship—the use of the parts leading to the -enlargement and excessive growth of the parts. The effects are believed -by him to be inherited, and he tries, furthermore, to show the way in -which such acquired characters could be inherited. He makes use of the -modern idea of hormones—substances that are elaborated in many organs -of the body, whose effects are often most conspicuously produced in -other parts of the body. He imagines these hormones to be collected in -the germ-cells and transmitted to the next generation, where their -presence contributes to the further development of the special region -(when it develops) that corresponds to the region in its parent in which -the hormone was made. His speculation meets in the first place with the -general objections inherent in Lamarck’s theory—objections so well -recognized to-day that I need not go over them here. His special appeal -to the hormone theory makes use of that theory in a way to which it was -never intended to be put, by assuming that an internal secretion formed -in one organ can be stored up in another organ, eggs and sperm—an -assumption not only unsupported by any evidence, but, as I have stated, -one quite foreign to the hor<span class="pagenum"><a name="page_49" id="page_49">{49}</a></span>mone theory. In fact, Cunningham’s -suggestion is nothing more than Darwin’s old idea of pangens, which, -being imaginary, could be endowed with all desirable properties. But one -can not invoke a chemical substance, even a hormone, and then at the -critical moment endow it with special virtues.</p> - -<p>A rather unique explanation of the origin of secondary sexual characters -is made by Stolzmann. His argument runs as follows: (1) There is a great -excess of males in birds; (2) the males left over after mating are -useless to the species, since they can not propagate and they consume -food needed by the reproducing part of the population; (3) the -conspicuous coloration of the male has been evolved in order that he -could be seen more readily by birds of prey and the objectionable excess -of males removed; the comb of the cock has developed in order that he -may be the more easily killed by other cocks.</p> - -<p>Stolzmann’s account of the origin of the plumes of the birds of paradise -should be immortalized in the literature of the subject:</p> - -<div class="blockquot"><p>“Nous comprendrons aussi facilement la présence de longues plumes -chez les males de nombreuses espèces, comme p. e. chez les oiseaux -de paradis, chez les veuves (<i>Vidua</i>) et chez l’engoulevent -africain (<i>Cosmetornis</i>). Telles plumes ont probablement pour but -de relantir le vol des males. J’ai constate chez la <i>Loddigesia -mirabilis</i> (oiseaumouche péruvien), que le vieux male posséde -l’aile quelques millimetres plus courte que le jeune male ou la -femelle. Cet avortement des remiges provient assurément a cause de -développement extraordinaire de retrices externes chez le vieux -male de cet oiseaumouche. Si donc d’une part les retrices allongees -rendent le vol plus difficile et d’hautre les ailes plus petites -diminuent sa vélocité, le vol du male doit ètre plus lent que celui -de la femelle, le poids du corps restant la même. Le développement -extraordinaire soit des remiges soit des rectrices, en -<i>relantissant</i> le vol des males, rend leur rôle plus difficile, en -facilitant en même temps celui des femelles. Nous pouvons prendre -comme exemple le <i>Cosmetornis</i>, qui, comme tous les engoulevents, -se nourrit d’insectes, qu’il attrape au vol. Chez cet oiseau -quelques plumes des ailes se developpent extraordinairement pendant -l’époque de reproduction, en retardant visiblement son vol. Il est -donc facile a remarquer, qu’alors le male, ayant les mouvements -plus lourds, n’est pas en êtat de se procurer la même quantité -d’insectes qu’auparavant; ainsi donc la femelle a plus de chances -de trouver une nourriture plus abondante.”<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a></p></div> - -<p>Equally worthy of perpetuation is Stolzmann’s explanation of dancing and -singing birds:</p> - -<div class="blockquot"><p>“Toutes les réunions des males, leurs danses bizarres, leur chant, -enfin, ne servent pas probablement a séduire les femelles, mais -pour distraire les males, ce qui rend plus faciles les besognes -maternelles des femelles et au surplus les protege contre -l’assiduite nuisible des célibataires. Darwin lui-mème constate le -fait, qu’ordinairement pendant les réunions des males, quand ces -derniers sont trop occupes par le combat ou la danse, la femelle -s’echappe avec un d’eux pour copuler. Ainsi donc dans ce cas c’est -bien la selection naturelle et non la selection sexuelle, qui agit -pour la conservation d’équilibre sexuel.”<a name="FNanchor_9_9" id="FNanchor_9_9"></a><a href="#Footnote_9_9" class="fnanchor">[9]</a></p></div><p><span class="pagenum"><a name="page_50" id="page_50">{50}</a></span></p> - -<h3><a name="DISPLAY_OF_THE_MALE" id="DISPLAY_OF_THE_MALE"></a>DISPLAY OF THE MALE.</h3> - -<p>The antics of male birds at the mating season, their courtship -so-called, has played an important rôle in Darwin’s theory of sexual -selection. The behavior of many birds at this time is of such a kind as -to suggest that the male is exhibiting his plumage before the female for -the “purpose” of influencing her choice. The whole paraphernalia of -human psychology is imported into the situation and both the -consciousness of the male, his intentions so to speak, and the supposed -esthetic response or choice of the female is invoked. Even though it be -granted that the words that we must make use of, borrowed from human -behavior, are such as to imply much more in the direction of -consciousness and purpose than is desirable, and that most of the -behavior of animals should be stated in a more roundabout and objective -way, yet the theory will only work out on the assumption that the female -<i>chooses</i> in some sense the more brilliant or ornamental (or effective) -male, whether she is “conscious” or unconscious of intention. I doubt if -anyone to-day would care to defend seriously the theory on the grounds -of consciousness or esthetic value of the exhibition, despite the fact -that Darwin’s language often takes this turn and the less-guarded -statements of some of his disciples, such as Romanes, show little -hesitation in anthropo-morphologizing the entire situation. It is, -however, not necessary for the working out of the theory that this -complication be introduced into it, for if the female is more likely to -mate with a more brilliantly colored than a less brilliantly colored -male, the theory may be made to apply regardless of whether she is -“conscious” or not of the difference to which she responds.</p> - -<p>But there are weighty arguments against such an interpretation of the -behavior of the male and female during courtship. In the first place, -there is almost no direct evidence to show that the female mates with -the more ornamental male. As this is the all-essential requirement of -the theory, the almost complete absence of facts in its support leaves -the theory resting on a theoretical assumption. It can scarcely pass -unnoticed that while there exists a large mass of data describing the -secondary sexual characters, there is practically nothing in this -accumulation to show that the female makes her selection on differences -in coloration or ornamentation. And on the other hand, there is some -evidence showing that the female is ready to succumb to the -aggressiveness of the male rather than that she “chooses” him.</p> - -<p>The behavior of the male under sexual excitement is often described to -be of a kind to exhibit before the female his peculiar adornments. That -the “purpose” of his exhibition is to show himself off before the female -may be conceded, with reservations as to what is meant here by -“purpose.” That the male is conscious of the probable results of his -conduct is scarcely probable the first time he courted; but that he may<span class="pagenum"><a name="page_51" id="page_51">{51}</a></span> -have found out the most probable result after the first attempt through -“associative memory” is in accord with what the study of “animal -behavior” has shown to be possible. In this sense purpose would mean a -line of conduct that experience had shown to lead to a certain end. -Anticipation or far-sightedness would henceforth characterize such a -reaction. Here, however, we venture on very dubious grounds. But the -display of the male may be purposeful in a much simpler sense. His -activity may be an inborn reflex to visual or other sensory stimuli that -is a part of his attack on the female, or possibly a series of reflexes -that we may register under the old unanalyzed terms of “desire and -fear.” The action calls forth a responsive reflex in the female, for the -sexual act is not entirely active on one side, passive on the other, but -consists of a series of interreactions on the part of each sex, which, -if they pursue a given course, leads to the final mating. The mutual -responses appear to follow an automatic course in many cases if the -individuals are sexually ready to mate and the environment is -propitious. Types of behavior of this kind must be familiar to anyone -who has observed domesticated and semi-domesticated animals. The purpose -of the display may mean no more than a reaction that leads to a result -propitious to the perpetuation of the species if the situation is ripe -for such an outcome.</p> - -<p>This conclusion still leaves open the question as to whether the display -is more likely to be successful, if certain special characters possessed -by the species are exhibited. In the absence of any sufficient evidence -to show that this is so, and in the light of the very great danger of -projecting “our human standards” into the world of other animals, and in -view of the fact that related species without such marks are as -successful in maintaining themselves, I can not but think that at -present we have a good deal to lose in the way of scientific procedure -and nothing to gain of scientific value in accepting Darwin’s -interpretation of sexual selection based on the display of the male as -furnishing an opportunity to the female to make the “best” selection -amongst her suitors on the basis of his adornment.</p> - -<p>An excellent opportunity to study the problem as to “choosing” by the -female is furnished by the mutant races of <i>Drosophila</i>, some of which, -differing in a single mutant gene, have wings as different in coloration -as black, yellow, or gray, and eyes as differently colored as white, -vermilion, or red. Sturtevant put a yellow female with a gray -(wild-type) male and a yellow male. The male that first mated was noted -and the trio discarded. The female “chose” the gray males 25 times and -the yellow only 8 times. In the control combination, where a gray female -“chose” between the same two kinds of males, she took the gray male 60 -times and the yellow male 12 times. In both cases it “appears” that the -female “prefers” the gray male, but this deduction may give an entirely -wrong impression as to what is taking place, for<span class="pagenum"><a name="page_52" id="page_52">{52}</a></span> the result would be -the same in kind if the gray male were more active and mated quicker. -This was tested by putting a gray and a yellow female with a gray male -and then for control a gray and a yellow female with a yellow male. The -result was as follows:</p> - -<table border="0" cellpadding="4" cellspacing="0" summary="" - class="sml"> - -<tr><td rowspan="2" valign="middle">Red ♂ </td><td>{Gray ♀ </td><td> 25 </td><td rowspan="2"></td><td rowspan="2" valign="middle"> Yellow ♂ </td><td>{Gray ♀ </td><td> 12</td></tr> -<tr><td>{Yellow ♀ </td><td> 31 </td><td> {Yellow ♀ </td><td> 30 </td></tr> -</table> - -<p>Here the gray male mated slightly oftener with the yellow female than -with the other, whereas the yellow male mated much oftener with the -yellow female than with the gray one. Both results are explicable on the -view that the yellow female, being less active, is more easily captured -by the yellow male than is the gray female. This view fits in also with -the former experiment, where the yellow male is much less successful -than the more active gray male. Such a conclusion gives a more -consistent explanation of all the facts than does the theory of female -choice, for on the latter we must suppose that the yellow females prefer -the gray males and the yellow male prefers the yellow females, etc.</p> - -<p>The following results were obtained by Sturtevant when red and white -eyed flies were competing:</p> - -<table border="0" cellpadding="4" cellspacing="0" summary="" - class="sml"> - -<tr><td rowspan="2" valign="middle">Red ♂ </td> -<td> {Red ♀ </td><td> 54 </td> -<td rowspan="5"> </td> -<td rowspan="2" valign="middle"> Red ♀ </td> -<td> {Red ♂ </td><td> 53</td></tr> - -<tr><td>{White ♀ </td><td> 82 </td> -<td> {White ♂ </td><td> 14</td></tr> - -<tr><td> </td></tr> - -<tr><td rowspan="2" valign="middle">White ♂ </td> -<td> {Red ♀ </td><td> 40 </td> -<td rowspan="2" valign="middle"> White ♀</td> -<td> {Red ♂ </td><td> 62</td></tr> -<tr><td>{White ♀ </td><td> 93 </td> -<td> {White ♂ </td><td> 19</td></tr> -</table> - -<p>The outcome can be interpreted in the same way as the yellow-gray -competition. The red male wins by virtue of his greater activity, while -the white female is chosen more often, especially by the white male, -because of her passivity (or weaker resistance). It may be claimed that -these results do not show that the female does not choose, for such -choice, if made, would be swamped by another condition of the -experiment, viz, the greater aggressiveness of one kind of male and -greater passivity of the other kind of female. This, of course, is true, -but the experiment still shows that in these flies other influences are -so much greater than “choice” by the female, if it exists, that the -postulated effect of the latter practically disappears from the -situation.</p> - -<p>Mayer’s experiments with the large moth <i>Callosamia promethea</i> furnish -important information as to the factors involved in mating. The results -are all the more significant from our present point of view because the -colors of male and female are in this species markedly different. The -wings of the male are black, those of the female reddish brown; the -antennæ of the male are large and bushy, those of the female small and -slender. Mayer found that the males are attracted by the female from -some distance when the latter are put into a glass jar covered by only -coarse mosquito-netting, but if the same jars are turned upside down the -males are unable to find the female. Females<span class="pagenum"><a name="page_53" id="page_53">{53}</a></span> concealed in loose cotton -attracted males. Females were put into a box with an open chimney at one -end, the other open end being covered by mosquito-netting. A current of -air blew into the open end and out of the chimney. The males flew to the -end of the chimney from which the air came and fluttered about in the -neighborhood. Males are attracted to places where a female has been kept -even several hours after her removal. The male finds the female through -the sense-organs in his antennæ, for a male whose abdomen has been cut -off and the sides of whose thorax are covered with shellac will still -fly to the female, but if his antennæ he coated with any substance he no -longer seeks the female. If the eyes of the males are blackened they -will mate with females “in the normal manner.”</p> - -<p>Mayer cut off the wings of females and glued male wings in their places, -so that the female looked like a male. Males readily mated with these -females. The wings of males were cut off and female wings glued in their -place. Mating occurred “with normal frequency, and I was unable to -detect that the female displayed any unusual aversion” to such males. -Males with female wings pass unnoticed by other males.</p> - -<p>In a later paper (1901) Mayer and Soule describe how, when the wings of -the male were painted scarlet or green, the males were accepted as -readily as normals in competition with them. Experiments were also made -by them with the gipsy moth. Wingless males met with more “resistance” -from the female than do normal males, but when the eyes were covered the -wingless males succeeded as often as the normal males, but the number of -observations on which this statement is were far too few to be of any -value, and there are several other observations that make any such -conclusion from the evidence highly uncertain.</p> - -<p>That it is the odor of the females that attracts the male can not be -doubted. It might still be claimed that the female chooses amongst her -suitors the darkest males, but the evidence gives no grounds for -inferring such a choice, and since she will even accept males with -female wings when they attempt to mate with her, it does not appear -probable that the color of the male is a factor in the result, or at -least if it is, then it must be entirely subordinate to the sense of -smell in finding the female and of touch after he arrives. There is -little or nothing in the behavior of these moths, or in that of the -silkworm moth, according to Kellogg, to suggest that vision plays any -significant rôle in courtship.</p> - -<p>Concerning the genetic situation in insects, there are only a few cases -that have been studied. The most instructive are those in which more -than a single kind of male exists (two or three), one of which may be -like the female, the other quite different. The best worked out cases -are <i>Papilio memnon</i> and <i>P. polytes</i>. De Meijere and Punnett have<span class="pagenum"><a name="page_54" id="page_54">{54}</a></span> -shown from the breeding data that it is possible to frame an explanation -of such a sort that the aberrant female differs from the female -resembling the male in only a single genetic factor—one not sex-linked -(<i>i. e.</i>, not carried by an X chromosome), but autosomal. The gene would -be of such a sort that it affects the female only—producing no visible -effect on the male. Such a conclusion, if established, helps, -theoretically at least, toward simplifying the situation in other -species, for it shows that genetic factors occur whose influence is on -one sex alone; hence the difference between the male and one type of -female does in such cases result from a single gene present in both but -causing them to be differently colored. There would be no need, then, to -assume that the difference had been slowly built up by selection, but -rather that the difference arose at some time by a single mutant step. -The incorporation of the step in the species would then follow if the -effect of the gene were useful in mating or if it had some other primary -significance for the welfare of the species, the different effect -produced on the male and female being only an unimportant by-product of -its action. On the other hand, it should be emphasized that because a -single factor difference between the two kinds of females will explain -the genetic results, it does not necessarily follow that the difference -did arise as a single mutation. The foregoing argument does no more than -imply that the difference in question may have arisen in this way, and -if so, that the situation, as it exists, would be the more easily -comprehended.</p> - -<p>In insects and spiders, where dimorphism is as marked as in birds, the -mating habits have been studied by a number of naturalists. Here also -there are numerous accounts of the display of the male during courtship. -The account given by Dr. and Mrs. Peckham are particularly detailed and -call for careful consideration on account of their well-recognized -accuracy in observational work. Moreover, as a result of their -observations, along with those of Montgomery, Petrunkewitsch, and -others, we have really fuller information concerning the courtship of -spiders than of birds and of mammals.</p> - -<p>In the great majority of species where the sexes are different the male -is more brightly colored or more ornamental. For example, in a group -such as the Attidæ of France, where both sexes are known, the Peckhams -state that in 26 cases the male is more conspicuous than the female; in -55 cases the sexes are alike, or if they differ the male is more -conspicuous. It appears that in other genera there are cases where the -female is more conspicuous than the male. The Peckhams state that -possibly as many as 250 species are in this condition. Those females -with brighter colors than the males are usually well armed by strong -spines. When very young they are like the males and begin to assume the -adult form and color when they are a quarter to a third grown. Whether -the change depends on changes in the ovary is not known.<span class="pagenum"><a name="page_55" id="page_55">{55}</a></span></p> - -<p>The mating behavior of <i>Saitis pulex</i>, a species in which the males and -females are much alike, is described by the Peckhams as follows:</p> - -<div class="blockquot"><p>“On May 24th we found a mature female and placed her in one of the -larger boxes, and the next day we put a male in with her. He saw -her as she stood perfectly still, twelve inches away; the glance -seemed to excite him and he at once moved toward her; when some -four inches from her he stood still and then began the most -remarkable performances that an amorous male could offer to an -admiring female. She eyed him eagerly, changing her position from -time to time so that he might be always in view. He, raising his -whole body on one side by straightening out the legs, and lowering -it on the other by folding the first two pairs of legs up and -under, leaned so far over as to be in danger of losing his balance, -which he only maintained by sidling rapidly toward the lowered -side. The palpus, too, on this side was turned back to correspond -to the direction of the legs nearest it. (Fig. 13.) He moved in a -semi-circle for about two inches and then instantly reversed the -position of the legs and circled in the opposite direction, -gradually approaching nearer and nearer to the female. Now she -dashes toward him, while he, raising his first pair of legs, -extends them upward and forward as if to hold her off, but withal -slowly retreats. Again and again he circles from side to side, she -gazing toward him in a softer mood, evidently admiring the grace of -his antics. This is repeated until we have counted 111 circles made -by the ardent little male. Now he approaches nearer and nearer and -when almost within reach whirls madly around and around her, she -joining and whirling with him in a giddy maze. Again he falls back -and resumes his semi-circular motions, with his body tilted over; -she, all excitement, lowers her head and raises her body so that it -is almost vertical; both draw nearer; she moves slowly under him, -he crawling over her head, and the mating is accomplished.</p> - -<p>“After they have paired once, the preliminary courtship is not so -long. When this same pair mated a second time, there was no -whirling movement, nor did the female lift her body, as at first.” -(pp. 37-38).<a name="FNanchor_10_10" id="FNanchor_10_10"></a><a href="#Footnote_10_10" class="fnanchor">[10]</a></p></div> - -<p>The courtship of another species, <i>Dendryphantes capitatus</i>, in which -the sexes are entirely different, is described as follows:</p> - -<div class="blockquot"><p>“The males of <i>capitatus</i> are very quarrelsome, sparring whenever -they meet, chasing each other about, and sometimes clinching. It is -a very abundant spider with us, so that we often put eight or ten -males into a box to see them fight. It seemed cruel sport at first, -but it was soon apparent that they were very prudent little -fellows, and were fully conscious that ‘he who fights and runs away -will live to fight another day.’ In fact, after two weeks of hard -fighting we were unable to discover one wounded warrior. When the -males are approaching each other, they hold the first legs up in a -vertical direction. Sometimes they drop the body on to one side as -they jump about each other. These movement are very quick, and they -are always ready for a passage at arms. When courting the females -they have another movement. They approach her rapidly until within -two to five inches, when they stop and extend the first legs -directly forward, close to the ground, the legs being slightly -curved with the tips turned up. (Fig. 18). Whether it be -intentional or not, this position serves admirably to expose the -whole of the bronze and white face to the attentive female, who -watches him closely from a little distance. (Fig. 19.) The males -also give their palpi a circular movement, much as a person does -when washing his hands. As he grows more excited, he lies down<span class="pagenum"><a name="page_56" id="page_56">{56}</a></span> on -one side with his legs still extended. These antics are repeated -for a very long time, often for hours, when at last the female, -either won by his beauty or worn out by his persistence, accepts -his addresses.” (Pp. 45, 46.)</p></div> - -<p>In another species, <i>Dendryphantes elegans</i>, both sexes are brilliantly -colored.</p> - -<div class="blockquot"><p>“The male is covered with iridescent scales, his general color -being green; in the female the coloring is dark, but iridescent, -and in certain lights has lovely rosy tints. In the sunlight both -shine with the metallic splendor of hummingbirds. The male alone -has a superciliary fringe of hairs on either side of his head, his -first legs being also longer and more adorned than those of his -mate. The female is much larger, and her loveliness is accompanied -by an extreme irritability of temper which the male seems to regard -as a constant menace to his safety, but his eagerness being great, -and his manners devoted and tender, he gradually overcomes her -opposition. Her change of mood is only brought about after much -patient courting on his part. While from three to five inches -distant from her he begins to wave his plumy first legs in a way -that reminds one of a wind-mill. She eyes him fiercely and he keeps -at a proper distance for a long time. If he comes close she dashes -at him and he quickly retreats. Sometimes he becomes bolder and -when within an inch, pauses, with the first legs outstretched -before him, not raised as is common in other species; the palpi -also are held stiffly out in front with the points together. Again -she drives him off, and so the play continues. Now the male grows -excited as he approaches her, and while still several inches away -whirls completely around and around; pausing, he runs closer and -begins to make his abdomen quiver as he stands on tip-toe in front -of her. Prancing from side to side, he grows bolder and bolder, -while she seems less fierce, and yielding to the excitement lifts -up her magnificently iridescent abdomen, holding it at one time -vertically and at another sideways to him. She no longer rushes at -him, but retreats a little as he approaches. At last he comes close -to her, lying flat, with his first legs stretched out and -quivering. With the tips of his front legs he gently pats her; this -seems to arouse the old demon of resistance, and she drives him -back. Again and again he pats her with a caressing movement, -gradually creeping nearer and nearer, which she now permits without -resistance until he crawls over her head to her abdomen, far enough -to reach the epigynum with his palpus”. (Pp. 46-47.)</p></div> - -<p>If we lay no emphasis on the implied emotional elements in the behavior -of the spiders in this description—terms of emotion borrowed direct -from human psychology—there still remain the several types of -apparently significant reactions associated with courtship. The -statements leave no room for doubt that vision plays an important rôle -in the complex reflexes that lead gradually to successful mating. The -Peckhams insist that the display of the male is always of a kind to -bring before the female the special adornments of the male in whatever -part of the body they may lie. The chance of subjective interpretation -here is so great that unless the results are carefully checked up by -studies of the attitudes assumed by males in species in which the males -are without ornament, their interpretation must be taken with the -greatest reserve. Assigning, as our authors do, so much by gratuitous -implication to the emotional side of the picture prejudices<span class="pagenum"><a name="page_57" id="page_57">{57}</a></span> one, -perhaps too greatly, against accepting a special (even an implied -intentional) exhibition of the specially ornamented parts. On the other -hand, if it be conceded that the conspicuousness of the male is an -element in the reaction, the very special adornments visible from the -front might be supposed to enhance the effect produced in the female. -Similar displays of special ornamentation in the male have been -described both for birds and insects, but here, too, the question has -been raised as to whether such exhibitions are more than an accidental -accompaniment of the posturing of the male, for the same kind of -behavior is known to occur in other cases where the male is unornamented -and resembles the female. Had such a male special ornamentation it would -no doubt appear to us that his behavior was “calculated” to display his -ornaments.</p> - -<p>Dr. and Mrs. Peckham point out that their observations are entirely -inconsistent with Wallace’s interpretation of the origin of secondary -sexual characters. They find no evidence in favor of his view that the -male possesses greater “vital activity.” On the contrary, the female is -the more active and pugnacious of the two. They also object to Wallace’s -statement of a total absence of any evidence that the female notices the -display of the male. In spiders the females “<i>observe</i>” the males with -close attention during their courtship. They point out also that, in -spiders at least, as the female gradually becomes adult, a male if -preferred will have a chance of mating with several females, “and as the -mating season lasts for two or three weeks the more brilliant males may -easily be selected again and again.” In regard to Wallace’s argument as -to the distribution of accessory plumes in humming birds, the Peckhams -point out that—</p> - -<div class="blockquot"><p>“The pectoral muscles reach their highest development in the -hummingbirds, the diurnal birds of prey, and the swallows, and we -may, therefore, fairly use these groups to test Mr. Wallace’s -explanation of breast plumes. In the swallows and birds of prey we -find no such appendages, in spite of their further claim to them, -on the ground of great vigor and activity. As to the humming-birds, -we find in the genus <i>Aglæactis</i> six species with more or less -developed breast-plumes, which are also found in nine other -species, scattered through different genera—in all, only fifteen -species out of four hundred and twenty-six; while we find in -fifty-six species the lengthened and modified tail-feathers, which, -according to Mr. Wallace’s view, should be peculiar to the -Gallinaceæ.</p> - -<p>“Again, there are elongated feathers from the throat or from the -side of the neck in thirty-five species, while seventeen have -crests from the top of the head, and seventeen, downy puffs from -the tarsi.”<a name="FNanchor_11_11" id="FNanchor_11_11"></a><a href="#Footnote_11_11" class="fnanchor">[11]</a></p></div> - -<p>From this brief survey of the family we see that, contrary to what we -should expect from Mr. Wallace’s theory, although the breast muscles are -the seat of the highest activity, breast plumes are the least frequent -of all the forms of ornamental plumage.<span class="pagenum"><a name="page_58" id="page_58">{58}</a></span></p> - -<div class="blockquot"><p>“We may fairly say, then, that the humming-birds completely refute -the proposition that there is any relation between the development -of color and accessory plumes and ‘surfaces where muscular and -nervous development is considerable.’<span class="lftspc">”</span><a name="FNanchor_12_12" id="FNanchor_12_12"></a><a href="#Footnote_12_12" class="fnanchor">[12]</a></p></div> - -<p>What is true for birds is even more obvious for spiders where the -special ornaments are not confined to parts of the body with high -muscular development, etc. The writers make the very pertinent criticism -that while Wallace objects to assuming the emotional states in females, -he is less careful in regard to the males’ emotions when he speaks of -the display “under the influence of jealousy or sexual excitement.... -The males, in their rivalry with each other, <i>would see what plumes were -most effective; and each would endeavor to excel his enemy</i> as far as -voluntary exertion would enable him.”<a name="FNanchor_13_13" id="FNanchor_13_13"></a><a href="#Footnote_13_13" class="fnanchor">[13]</a></p> - -<div class="blockquot"><p>“If the males have so complex an emotion as jealousy, and further, -if they are conscious of the value of the plumes, may it not be -asked why the female is unable to ‘see what plumes are most -effective?’ The mental state in the male is without meaning unless -we suppose the female to be affected and pleased.” (Peckham, <i>loc. -cit.</i>, p. 144.)</p></div> - -<p>In regard to another interpretation of the courtship, the Peckhams point -out:</p> - -<div class="blockquot"><p>“Mr. Pocock has suggested that the attitude of observant interest -on the part of the female spider might be taken to indicate that -she was preparing to spring upon her mate and devour him; or that -it might simply mean that she was warily guarding herself from his -approach. Neither of these suppositions is admissible. In some -species the male is not attacked by the female, and when she does -wish, as frequently happens, either to avoid or to destroy him, her -attitude is totally different. In the former case she turns about -and runs rapidly away, or suspends herself by a thread of web. In -the second, there is a contraction of all the muscles, the legs are -drawn together, and in this crouching position she creeps slowly -toward him, as she might if he were a fly, only with something more -malignant in her aspect. When she takes this stand the male -incontinently flees. When, on the contrary, the female is -interested in the male display, she seems perfectly absorbed in -watching him, the muscles are all relaxed, unconscious of herself -she directs her glance now here, now there, as he moves about; as -he continues his mad antics, her appearance gives every indication -of pleasurable excitement, and as he comes closer and closer, she -yields herself to the impulses which he has awakened in her, and, -as in <i>pulex</i>, joins in his dance and whirls around and around as -though intoxicated. We claim, then, to have completely answered Mr. -Wallace’s first objection.” (Peckham, <i>loc. cit.</i>, pp. 145, 146.)</p></div> - -<p>Finally, in regard to the specific character of the display of the -males, the Peckhams make the following significant statement:<span class="pagenum"><a name="page_59" id="page_59">{59}</a></span></p> - -<div class="blockquot"><p>“The spider has four pairs of legs, and all are equally available -for display or locomotion, and since all the movements are slow and -on the ground they are entirely open to observation and study, and -we are thus in a position to decide by facts whether their activity -is simply an outlet for superfluous energy, and therefore -meaningless, or whether there is a purpose in it. If the purpose of -the antics is only to let off energy, then we should expect one -pair to be flourished around quite as often as another, and that -the pair flourished should as frequently be one that was not -ornamented as one that was; and, moreover, their movements ought -not to be of such a nature as to display the color or ornament, -more frequently than the law of chance would explain. If the spider -almost always moves the ornamented legs, and in such a way, too, as -to bring out their beauty, it would seem to us, to say the least, -highly improbable that the dance of the spider was merely a -meaningless overflow of surplus energy. Such an explanation leaves -much that needs explanation. The facts are, that the best foot is -put forward; and this is just what Darwin’s theory requires and -explains. Under Mr. Wallace’s view the facts are inexplicable. The -better to show that these movements are not simply meaningless -outlets of high vigor, we illustrate the several positions by -figures taken from nature (figs. 7-12). The figures would seem to -prove that the legs that are ornamented or contrasted in color are -also the legs that are usually flourished; that where none of the -legs have special ornament, then all are used; or, as sometimes -happens, when an unornamented leg is used the movements are of such -a character as to display some ornament that would otherwise have -been more or less hidden from the female.” (Peckham, <i>loc. cit.</i>, -p. 147.)</p></div> - -<p>In the tarantula, Petrunkewitsch finds that sight plays no rôle in -mating—that it is due entirely to accidental contact between the male -and female. Here the sexes are closely alike, except for a pair of hooks -on the front legs of the male, by means of which he grasps the mandibles -of the female, holding them during the elaborate process of transference -to her genital opening the sperm that he has already collected in the -genital spoon on his palpi. The hooks serve to guard the male against -injury or death, while at the same time they aid him in the act of -coitus.</p> - -<p>In a common spider, <i>Mœvia villata</i>, two kinds of males exist. Both have -been seen to mate with the same female. No preference is given to either -type. The difference between them, according to Painter, is connected -with or caused by an additional pair of chromosomes in the gray male. -The two types may therefore have no connection with sexual selection, -but be directly due to a difference in the chromosome group.</p> - -<p>Montgomery, who made observations on the courting habits of several -species of spiders, states that his “general theoretical conclusions -were quite different from those of the Peckhams.” It turns out, however, -that his objection to their view is based entirely on their assumption -that the male is conscious of his display and that the female is guided -by an esthetic sense in selecting the more beautiful male. It should be -pointed out that even after the removal of these<span class="pagenum"><a name="page_60" id="page_60">{60}</a></span> gratuitous assumptions -as to the cause of the evolution of the male and female, enough still -remains in Montgomery’s own observations to include his results on -courtship under Darwin’s theory of sexual selection. For example, -Montgomery says:</p> - -<div class="blockquot"><p>“The adult male is excited simultaneously by fear of and desire for -the female, and his courtship motions are for the most part -exaggerations of ordinary motions of fear and timidity. By such -motions he advertises himself to the female as a male, but there is -no proof that he consciously seeks to arouse her eagerness by -esthetic display—there seems to be no good reason to hold that the -female is actuated in her choice by sensations of beauty.... Thus -my opinion was opposed to Darwin’s theory.”</p></div> - -<p>Now, it is obvious that if a more brightly colored male has a better -chance of “advertising himself” to the female all the essential -requirements of Darwin’s theory are fulfilled, regardless of whether the -male is conscious of his ornamentation or the female makes use of an -“esthetic sense.” In another passage (p. 173) Montgomery concedes all -that any modern critical advocate of Darwin’s theory is likely to ask:</p> - -<div class="blockquot"><p>“We have previously seen that conscious aesthetic choice by the -female probably does not account for such male characters -[secondary sexual characters with their ‘conspicuous color -markings’]; that they are accordingly, probably not due to sexual -selection. These characters of the males may be most readily -explained as being conceived by simple natural selection. Peculiar -ornamentation would be selected because unusually greater sex -recognition therefore prompted mating.”</p></div> - -<p>It is evident that Montgomery has only shifted the situation, although -to advantage, I think, but is essentially in accord with Darwin’s theory -of sexual selection, despite his protest to the contrary. The difference -lies in Darwin’s and especially in the Peckhams’ use of the term -“choice,” “aesthetic sense,” etc., to stand for the fact that the female -more promptly mates (as Montgomery prefers to put it) with a male -peculiarly ornamental.</p> - -<p>The most critical observations on sexual selection that have been made -in the group of insects are those by Sturtevant on the pomace fly. The -courtship is described as follows:</p> - -<div class="blockquot"><p>“The first and most noticeable act in courtship occurs when the -male, being near the female, extends one wing at about right angles -to his body, and vibrates it for a few seconds. The wing is then -returned to the normal position and the process is repeated, -usually with the other wing. But between times there is a -scissors-like movement of the wings repeated several times. This -vibrating of the wings is often repeated many times, and may be -done in any position relative to the female, though the male always -faces her. Usually, in fact, he swings quickly around her in a -semicircle once, or oftener, during the process. Soon the male -begins to protrude his genitalia and, if the female remains quiet, -to lick her posterior end. Some white matter now protrudes from her -ovipositor, and other males in the same vial are usually observed -to become excited now and begin courting, indicating odor as a -cause of sexual excitement. If the female runs or flies away the -male is excited, moves his<span class="pagenum"><a name="page_61" id="page_61">{61}</a></span> wings jerkily, and walks around -rapidly, but seems unable to follow the female accurately or to -locate her quickly. The penis is directed forward by bending up the -abdomen underneath, towards the thorax, and is jerked toward the -female (the male always standing facing her at this stage), but not -always toward her genitalia, as I have seen it strike her in the -eye. (The male in this case, however, had white eyes, and so was -perhaps blind. Normally the aim is accurate.) If it does strike the -mark the male mounts on the female’s back, between her wings. -Mounting never takes place until after the actual copulation has -occurred, in which respect <i>Drosophila</i> differs from some related -flies (<i>e. g.</i>, Muscidæ, Anthomyidæ, Sepsidæ, Borboridæ, and -Ephydrichæ, so far as my observations go). In these forms the male -flies and lights on the female, after which copulation may or may -not take place, probably depending upon the way the female -responds.”<a name="FNanchor_14_14" id="FNanchor_14_14"></a><a href="#Footnote_14_14" class="fnanchor">[14]</a></p></div> - -<p>To test whether the wings have any significance in courtship, the wings -of a male were clipped off and he was put into competition with a normal -male of the same stock, age, and size. A virgin female sexually mature -was given to these two males. The normal male mated 72 times before the -other, the clipped male 53 times. It might appear that the female -selected the normal male in preference to the clipped one, or possibly -that the male with normal wings drove the other male away. That the -operation on the wings may have an influence on the male himself is -shown in McEwen’s results. He found that clipped males lost their -heliotropism. It was also possible that the courtship of the normal male -might make the female ready to copulate and then she would mate with -either male. Sturtevant tested the last supposition by placing single -pairs in vials, testing each day an equal number of normal and clipped -males. The length of time before copulation was noted. The clipped male -began to court as soon as the normal, but a larger number of normal -males mated in the first 12 minutes than clipped males (50 to 25). Had -the females discriminated against the clipped males to an equal extent -we would have expected a much greater excess than 72 to 53 when they -were in competition. It appears, then, that the wings are useful in -shortening the time between the meeting of the individuals and -copulation. The display acts, however, almost as favorably for the other -male as for the exhibitor himself. The results show, therefore, that -here an esthetic sense of the female need not be postulated, for she -actually shows little preference when she has been brought to the point -of mating between the male that aroused her and the other male that did -not. This critical test puts the problem in a different relation from -that which Darwin’s theory of female choice was meant to throw light -upon.</p> - -<p>The reverse experiment—a clipped and a normal female of the same age, -size, etc.—showed that the mate did not discriminate between them, for -in 52 first trials the normal female was paired with 25 times, the -clipped 27 times.<span class="pagenum"><a name="page_62" id="page_62">{62}</a></span></p> - -<h2><a name="PART_III" id="PART_III"></a>PART III.<br /><br /> -THE GENETIC AND THE OPERATIVE EVIDENCE.</h2> - -<p>The genetic and operative evidence shows that there has been included -under the general term “secondary sexual characters” a complex of cases -that are the outcome of diverse physiological processes. Sex-linked and -sex-limited characters have often been confused; some characters depend -on the gonad; some of these involve the ovary, others the testes. Still -other characters fall under none of these groups, but are the direct -product of the male or female genetic constitution. It is not -surprising, therefore, that theories proposed on the information derived -from certain of these data are controverted by information derived from -other data. The theory of sexual selection, in its attempt to bring all -the facts under one point of view, has not escaped these difficulties, -even although it may be said that neither natural selection nor sexual -selection is concerned with the origin or even the kind of variations -with which it works. Nevertheless, the latter theory, by ignoring the -origin or the physiological process concerned in the production of -secondary sexual characters, may make assumptions that are difficult to -harmonize with the facts in the case, and we shall find several -instances of this sort. For example, if the hen had selected the cock -for his fine plumage (which, as we have seen, depends in part on -autosomal genes producing their effect without the cooperation of the -testes), she would be expected to endow herself with the same adornments -(if her selection worked), unless her ovary were already producing some -substance inimical to those that she is “calling forth” by selection of -the male. The problem is evidently, then, more complex than appears on -the surface, and is not so simple as it seemed when these essential -facts were unknown or ignored.</p> - -<p>In the case of other theories, such as those of Wallace and of -Cunningham (that appeal more directly to the causes that are producing -the variation out of which the secondary sexual characters are built -up), the absence of information, physiological or genetic, has only too -often given these writers the opportunity to speculate without the -restraints which a more recent knowledge of the facts has imposed on us.</p> - -<p>It is obvious from what we have learned that we shall have to proceed -with more caution in disentangling the evidence before we can hope to -“explain” it. Despite the meagerness of our present information, enough -has been found out to indicate that we must be content for a while with -tentative and partial explanations even in the best-known cases, and we -must, I think, be prepared to admit that no one theory may be able to -account for all of the secondary sexual differences that exist between -the sexes.</p> - -<p>The genetic evidence shows, in the case of cock-feathering versus -hen-feathering in birds, that only one or two Mendelian factor -differ<span class="pagenum"><a name="page_63" id="page_63">{63}</a></span>ences are involved. The result may seem to mean that the -secondary sexual <i>characters</i> themselves have been acquired historically -by a single evolutionary step, and that in consequence the opportunity -for selection to have accomplished such a result has been enormously -facilitated. Such an argument rests, however, as we know to-day, on a -false interpretation of Mendelian heredity. What the evidence really -shows is that one or two genes if present cause the testes to produce -some substance that prevents the cock-feathering from developing. The -genetic complex may require a hundred or a thousand or more special -factors that are directly and indirectly concerned with the development -of the cock-feathering, but one or two other factors may suffice to -block this machinery; or, to change the metaphor, these dominant factors -may be no more than so much sand poured into the clock. The clock may -have been slowly built up historically by many contributory “factors,” -but a little sand may spoil its activity. Similarly in the hen something -produced by the ovary prevents the fullest possible genetic action from -taking place. Here at present we do not know whether a single factor or -a hundred “special” factors are necessary to produce such an inhibition, -but if, as one would like to suppose, it is the same or partly the same -genes involved in the ovary, and in the testes of hen-feathered males, -then a relatively few, one or two, factors will suffice to bar -cock-feathering from the female.</p> - -<p>In a case like the clover butterfly, where the genetic relations work -out on the theory of one pair of factors that produce two types of -females and one type of male, it seems more reasonable to infer that -such a difference has not been slowly acquired by many smaller -mutational changes, because the two types are not adapted to live under -two different environments for which their differences fit them -respectively, but to live in the same environment. It has never been -claimed, so far as I know, that these two types of females have arisen -through some males preferring one, some another kind of female, so that -even although it may seem probable that the genetic situation is simple, -the simplicity can not be turned to the advantage of the theory of -sexual selection. It is unnecessary to discuss further the origin of the -factor or factors suppressing the development of one type in the male or -the probability of the multiplicity of such factors. In the case of such -species as <i>Papilio memnon</i> and <i>P. polytes</i>, with three types of -females, the situation is the same as above, with the addition of the -theory of mimicry, that “explains” some advantage accruing to each type -of female. Since the latter is only a form of natural selection, we are -not further concerned with the change here. Punnett’s excellent -treatment of the problems involved in his recent book on mimicry brings -the subject down to date.</p> - -<p>Meager as is the genetic and surgical evidence at present, it is enough -to show that only by further work along these lines can we hope to lay<span class="pagenum"><a name="page_64" id="page_64">{64}</a></span> -a firm foundation for a scientific study of the subject. It is equally -important that critical evidence be obtained in regard to the effect on -the female of males of different types in competition. The instinctive -reactions of animals in these respects, their first reaction, the -associations that may or may not result, are practically an open field -for investigation. The entire equipment of human psychology of the -introspective school, that has been appealed to for help in a situation -itself little understood, reads often more like fiction than like -science.</p> - -<p>So far as one branch of the subject goes—the possible interpretation of -ornamentation in the male—there seem to be two ways at least in which -the subject calls for immediate investigation: First, if it can be shown -that, other things being equal, a more adorned male rouses the female to -prompter mating, it may be inferred with some probability that in the -long run such conduct would lead to the establishment of the more -effective individual, but this would not be true unless the males mate, -as a rule, more than once, for any advantage that might accrue to a more -ornamented male would not affect the course of evolution of the species -if every other male found a mate too. Second, if it could be shown that -the special ornamentation of the male is only one of several effects of -a gene whose main effect is in some other direction, then the advantage -gained through natural selection in this other direction would carry in -its wake the advance in ornamentation, and if the change affects one sex -more than the other, owing to the difference in the genetic complex of -the two sexes, it would be called a secondary sexual character.</p> - -<h4>A. <span class="smcap">Evidence from Mammals.</span></h4> - -<p>Owing to the differences in the secondary sexual characters of different -breeds of sheep, we have more genetic information about such characters -in this group than in other groups of mammals. Fortunately, also, in -some of the breeds both castration and ovariotomy have been performed, -and consequently we are in position to utilize both sources of -information for interpreting the situation. In certain breeds both males -and females have horns (Dorsets), in which case the horns of the male -are larger than those of the female. In other breeds neither males nor -females have horns (Suffolks). In still other breeds the males have -horns and the females are hornless (Merinos and Herdwicks). The clearest -evidence that we have, both genetic and operative, is that obtained by -Woods, as reported by Bateson, in which horned (Dorsets) and hornless -(Suffolks) breeds were crossed. In the Dorsets, where both sexes have -horns, those of the male are larger than those in the female. When the -young male is castrated the horns develop, but only as far as in the -female. It appears, therefore, that the presence of the testis, probably -through some secretion from it,<span class="pagenum"><a name="page_65" id="page_65">{65}</a></span> contributes to the development of the -horns. The other race, the Suffolks, have no horns in either sex. -Castration produces no change in their hornless condition.</p> - -<p>When a Dorset ram is crossed to a Suffolk ewe the sons have horns, the -daughters lack them. The reciprocal cross gives the same results. The -factor or factors involved are therefore not sex-linked. When the F₁’s -from the cross or from its reciprocal are inbred, four classes of -offspring are produced, namely: Horned male, 3; hornless male, 1; horned -female, 1; hornless female, 3. The ratios, as above, are approximately -3:1:1:3.</p> - -<p>A simple Mendelian explanation covers the results. If we assume that the -Dorsets, both male and female, are homozygous in a factor for horns, H, -that is not in the sex chromosome, and that the Suffolks “lack this -factor,” <i>i. e.</i>, that they have an allelemorphic factor for -hornlessness, the germ-cells are H-H and h-h, respectively. Only one -kind of individual, Hh, results in F₁. Since the male with this formula -develops horns, we must conclude that the presence of the testis -(through its secretions) causes horns to develop, while in the female of -this same composition horns are not produced because of the absence of -the testes. The sex-cells in these F₁ individuals are H-h and H-h. -Chance meeting of these gametes will give 3 classes of individuals, -irrespective of sex, namely, (1) HH, (2) Hh, (1) hh. The expectation for -the males is that those of the composition (1) HH and (2) Hh will -develop horns, while those of the composition hh will not develop horns. -There should be 3 horned to 1 hornless male. In the females we expect -those with the composition (1) HH to develop horns, since they have the -same formula as the pure Dorset; those with the formula Hh are not -expected to develop horns, because the F₁ females of this composition do -not have horns; those with the formula hh are not expected to develop -horns, because they have the same composition as have the pure Suffolk. -There should be 3 hornless to 1 horned female. Combining both sexes, the -expectation for F₂ is 4 horned to 4 hornless. Arranged according to sex, -these give the classes realized: Horned male, 3; hornless male, 1; -horned female, 1; hornless female, 3. That this is the correct -explanation is borne out by back-crossing the hornless F₁ female to a -hornless Suffolk ram. The former has two kinds of gametes, H and h, the -latter only gametes that bear the h factor. Half the sons should be -horned, half hornless, because half of them are Hh and half hh. But none -of the daughters should have horns, because neither the Hh nor the hh -females produce horns. This is the result realized, viz, 3 hornless -offspring to 1 horned.</p> - -<p>The preceding account of the inheritance of the factor for horns is -based on the combination of Dorsets and Suffolks used by Wood. That -other conditions may exist in other breeds and even in races of<span class="pagenum"><a name="page_66" id="page_66">{66}</a></span> the -same breed is claimed by Arkell as a result of a large number of crosses -that he has carried out. He states, for instance, that in the great -Merino class, with its various sub-breeds, there are flocks in which the -males only are horned, but even here there may be individual males that -are hornless “and at times the females may also show some signs of horn -growth.” In America, Arkell states, there are three types of -Merinos—the American, the Delaine, and the Rambouillet. He quotes Plumb -(Types and Breeds of Farm Animals, Boston, 1906) as stating that “the -American Merino ram carries heavy, spirally twisted horns, but the ewes -are hornless; ... that the rams of the National Standard or Victor-Beald -Delaines may or may not have horns; that the Dickinson Delaines may have -small horns, but a polled head is preferred,” etc. These conditions -suggest that there may be more than a single factor for horns in sheep -or that there may be modifying factors in certain breeds. In fact, -Arkell and Davenport attempt to cover the results of Arkell’s -experiments by assuming that there is an inhibiting factor for horns -that is carried by the sex chromosome. Such an inhibitor (I) would be -double in the XX female and single in the X male. It is assumed to be -incapable of preventing the development of horns in the heterozygous Hh -male, the inhibitor being there simplex (<i>i.e.</i>, one I), while the -double inhibitor is capable of preventing the horns in the heterozygous -(Hh) condition, but not of preventing the development of horns when the -homozygous (HH) condition occurs. There are several objections to this -scheme: first, that there is no evidence that a <i>sex-linked</i> inhibitor -is present that affects the hornless breeds, for the evidence indicates -rather that there is no factor for horns present in them, at least in -the Suffolks; second, the peculiar balance between the factors for horns -and the inhibitor seems an extremely artificial statement. Arkell and -Davenport intimate that races with horned males and hornless females do -not exist in a pure state. That breeds impure in these respects may -exist need not be denied, but that pure races for such a dimorphic -condition do exist seems probable. Castle states, for instance, that he -knows at first hand of such races of Merinos. Castle also states that -castrated Merino rams in this race do not develop horns, and this result -is in accordance with statements made by Marshall for Herdwicks (a race -with horned males and hornless females). Under the circumstances it is -certain that the presence of the testes is one of the factors in -determining whether horns develop at all (as in Merinos), or in -determining the extent to which they develop (as in the Dorsets), rather -than that the difference between the sexes is due only to an inhibiting -genetic factor. Nevertheless, it may be well to keep open the -possibility that there may be different factors for horns in different -races (allelomorphs or others), or conversely, that the genetic -composition of the races is different, the factor for horns remaining -the same, but producing a different effect.<span class="pagenum"><a name="page_67" id="page_67">{67}</a></span></p> - -<p>It may be pointed out in passing that if, as Arkell assumes, the -hornless races are due to the presence in them of an inhibitor for -horns, the results can be worked out without postulating that the -inhibitor is sex-linked. For example, if the hornless male and female be -HHII and the horned male and female HHii, the F₁ horned males and -hornless females will be HHIi. The germ-cells will be HI and Hi in each -sex, which, by chance meeting, as shown below, gives the results -obtained by Wood. Thus:</p> - -<table border="0" cellpadding="2" cellspacing="0" summary="" - class="sml"> -<tr><td>HI </td><td rowspan="2" class="c"><big>×</big></td><td> Hi.....female.</td></tr> -<tr><td>HI </td><td>Hi.....male.</td></tr> -<tr class="c"><td colspan="3" class="bt">1HIHI+2, HIHi+1, HiHi.</td></tr> - -</table> - -<p>These formulæ give 3 horned males, 1 hornless male, 1 horned female, 3 -hornless females. This formulation, while appealing apparently to a -different set of factors from those used by Arkell, is in reality the -same in principle, since the heterozygous condition is here represented -by Ii (instead of Hh) and sex determines that the heterozygous male is -horned and the female hornless.</p> - -<p>The genetic relations of the Merino with horned males and hornless -females to the Dorsets, in which both sexes are horned (but in the male -the horns are larger), must be different from the genetic relation in -the other cross. There are two theoretical possibilities, viz., that a -different factor for horns is present that is either an allelomorph or -another different factor; or second, that a modifier is present in the -Merino that keeps down the development of the horns in the female. An -answer could be obtained by breeding Merinos to horned and to hornless -and getting F₂ from both crosses. Arkell’s data is not sufficient to -settle the question, because his numbers are often too small, but -chiefly because it appears that there were two genetic types present in -his flock of Merinos, one of which is characterized by scurs (very short -horns) in the females, the other by hornlessness in the female. He found -in a cross between a hornless father and Merino mother (that had knobs -or scab-like growths) that the daughters had horns or scurs and carried -a determiner for horns (as subsequent generations showed). On the other -hand, in other cases where the Merino mother was without horns, her F₁ -daughters had no horns. In both cases the F₁ sons had horns. Arkell -cites this cross as “proving” that the knobs of Merino ewes depend for -their development upon two horn determiners (H´H´). It is not at all -evident that the results lead to such a conclusion, as other -explanations will cover the case as well.</p> - -<p>Arkell’s mating between Dorsets and Merinos (tables <small>IX</small> and <small>XVI</small>) -corroborates his view “that the knob of the Merino female is represented -in the germ-plasm by the double determiner.” The 5 F₁ sons had long -horns, 3 F₁ daughters had horns present, and 2 had them absent (table -<small>XVI</small>). If some of the Merino mothers used were homozygous for a factor -that inhibits the development of horns in the female<span class="pagenum"><a name="page_68" id="page_68">{68}</a></span> we can account for -the hornless daughters, and if other mothers did not have this factor -(or were heterozygous for it) we can account for the horned daughters. -Evidently more evidence is needed. Arkell himself assigns a -corresponding difference to the mothers in these cases, based on the -observed fact that the mother that had knobs or scurs were the ones that -gave birth to the horned daughters. If the above suggestion proves true, -it shows that the Merino condition dominates the Dorset condition. The -result is in harmony with the view that both have a common factor for -horns, but that in addition the Merinos have a non-sex-linked modifier -that holds down the development of the horns in the ewe.</p> - -<p>What bearing have these results on the theory of sexual selection? -Clearly the Merino male, as constituted at present, develops horns -because he is a male, but only in the sense that his testes secrete some -substance that makes his horns grow. That maleness does not in itself -necessarily produce horn is shown by the absence of horns in the Suffolk -breed. Is it the same factor, present in the Merino, that produces horns -in both sexes of Dorsets when homozygous and in the male only when -heterozygous? If originally the ancestral race had no horns, the -appearance of factors for horns would, even in a heterozygous condition, -have sufficed in the males for the development of horns. If this gave -them any advantage either over the enemies of the race or in the eyes of -the female, such factors might be perpetuated, and through transferrence -to the females ultimately become homozygous in both sexes. Both would -then have horns, whether horns were or were not of any advantage to the -female, which would have them because they have an advantage to the -other sex.</p> - -<p>Because the genetic evidence shows that a single factor difference -between the breeds with and without horns accounts for the horned -condition in one of them, it by no means follows that horns as they -exist arose as a single mutant factor change. True, they may have arisen -as a new single factor difference, but the Mendelian evidence can not be -claimed as evidence for this view. The <i>a priori</i> argument based on the -relation of horns in an adaptive sense to the rest of the body would -appear rather to indicate that they could not have arisen at a single -mutational step.</p> - -<p>Concerning the still broader bearing of this evidence on the theory of -sexual selection, two distinct questions are involved: first, how has -the present racial difference in horns arisen in domesticated sheep, and -secondly, what was the original condition of sheep. Reversing the order -of these questions, we find that sheep were domesticated in Asia and -Europe before the dawn of history. “Whether our well-known and useful -animal is derived from any one of the existing wild species, or from the -crossing of several, or from some now extinct species, is quite a matter -of conjecture” (Flower and Lydekker’s “Mammals”).<span class="pagenum"><a name="page_69" id="page_69">{69}</a></span> Most of the wild -species of the genus (of which about 12 are recognized) have horns in -both sexes, but larger in the male. There are 3 wild species in which -the horns are lacking in the female, according to Flower and Lydekker. -If these have been crossed into the domesticated breeds the condition -shown by the Merino may go back to the wild state. The third condition -found in domesticated races, viz, hornlessness, may have appeared under -domestication. Such a change might have arisen in either of the two -other types and would be comparable to well-known losses of characters -shown by domesticated animals and plants. These losses of characters are -usually ascribed to actual losses of genes; any lost gene in the complex -of factors necessary for the production of horns might cause such a -change. But there is no advantage, in fact, in ascribing the <i>loss</i> in -the character to a <i>loss</i> in one of the factors producing that -character, for any change of any kind in the factor complex might bring -about the same result and the evidence from multiple allelomorphs should -put us on our guard against the all too easy assumption that a loss in a -character involves necessarily loss of a factor in the real sense in -which loss is used in ordinary speech.</p> - -<p>The operative and genetic evidence for sheep shows that if the horns in -the male were developed through natural or sexual selection we should -expect them to develop also in the female. The greater development in -the male seems to be due to secretions from the testes which probably -are due to special factors that call them forth, but whether such -factors were also acquired to reinforce the effects being produced -through selection or were already present (reinforcement for horns being -only a by-product of their activity) can not of course be known. We can -suppose that special factors that suppress the development of horns in -the female may have arisen in the wild or in the domesticated races and -have been perpetuated because of some imagined benefit conferred; or -that in certain races factors were already present that kept down the -development of horns in the female. In any case such factors do not -cause their effects through secretions from the ovary, because after -ovariotomy horns do not develop; nor are they sex-linked factors. Any -speculation as to how natural or sexual selection has brought about the -evolution of the horns in sheep must reckon with the conditions imposed -on such speculation by the preceding information. So far as I can see, -it leaves the situation in this respect neither better nor worse off -than before.</p> - -<p>In deer the effects of castration are well known, but there is no -genetic evidence to show the kind of factors involved, since no crosses -have been made between species with differences in their horns. If the -young male deer is castrated before the antlers have appeared, no horns -develop. If castrated at the time when the antlers have begun to -develop, incomplete or imperfect development follows. The antlers<span class="pagenum"><a name="page_70" id="page_70">{70}</a></span> -remain covered with the velvet, and are said not to be thrown off -periodically as in the normal male. If the adult stag with antlers is -castrated, the horns are precociously dropped, and, if replaced at all, -the new antlers are imperfect and are not renewed. I do not know of any -cases in which females have been spayed, but no doubt the ovaries must -sometimes become diseased. There are, however, a few records of horns -developing in this sex in old age, or presumably after disease of the -ovaries. Both male and female reindeer are horned. Castration produces -no effect on the development of the horns.</p> - -<p>In the case of deer it is evident that the presence of the testes in the -male causes the horns to develop. The genetic factor, or factors, for -horns may be supposed to be carried by both sexes, but the effects of -the factor can be seen only when the testes are present. In the reindeer -and eland, on the other hand, the genetic factor for sex can produce -horns without the need of the environment produced by the testes.<a name="FNanchor_15_15" id="FNanchor_15_15"></a><a href="#Footnote_15_15" class="fnanchor">[15]</a> -Whether we are dealing here with the same factor or whether the rest of -the hereditary complex makes the result different can not be known -without breeding experiments.</p> - -<p>There is apparently a connection between the stage of development of the -horns and the age of the animal, as the following statement by -Yarrell<a name="FNanchor_16_16" id="FNanchor_16_16"></a><a href="#Footnote_16_16" class="fnanchor">[16]</a> (1858) indicates:</p> - -<div class="blockquot"><p>“The fallow-buck is at his best in his sixth, or at most in his -seventh year; after which, though the carcass may increase, the -horns become smaller, and irregularly going back annually through -something like their former stages of increase, a very old buck has -from the state of his horns been mistaken for a young one. In the -osteological department of the Museum at Paris there was, and may -be now, the skeleton of a female reindeer in which the horns were -reduced to little more than a rudiment of the beam and the -brow-antler; this animal was so old that the molar teeth were worn -down to the edges of the alveolar cavities.”</p></div> - -<p>At first sight these results in the fallow deer appear to be only an age -condition, but since in old age a reverse process sets in, it may appear -more probable that the amount of secretion by the testes or other glands -may be the conditioning agent. In the case of the reindeer one may -hesitate to ascribe the change to the ovary without further evidence.</p> - -<p>In cattle the effects of castration as seen in oxen have been studied. -There is little here that is useful for our present purpose. The horns -are not inhibited and may even be larger than in the bull. The absence -of horns in certain races of cattle is apparently a dominant character, -but as the character is neither sex-limited nor sex-linked, the evidence -has no further bearing on the present topic.<span class="pagenum"><a name="page_71" id="page_71">{71}</a></span></p> - -<p>The effect of removal of the ovary from female calves has been studied -by Tandler and Keller. The height of the ovariotomized female is less -than that of the cow. The same difference is found between bull and ox. -Tandler and Keller call attention to the similarity of the head in male -and female lacking the gonads. They conclude that the ovariotomized -female does not come to resemble the male, but that removal of the gonad -causes both sexes to converge to a common type.</p> - -<p>Castration is frequently performed in horses, dogs, and cats, but as the -secondary sexual differences, aside from size and behavior, are not very -well marked in these animals, the results need not be here considered.</p> - -<p>Steinach’s experiments with rats are important, because by grafting -ovarian tissue into the castrated male, the male was caused to assume -certain characteristics peculiar to the female. The mammary glands that -are rudimentary in the male became much enlarged—not only the glandular -tissue increased in amount, but the mammæ themselves were greatly -developed. The hair of the male is coarser than that of the female. In -the feminized male the hair was soft like that of the female. The size -was smaller than that of the male. The skeleton also was affected, and -Steinach thinks that it changed in the direction of a female skeleton. -Even more striking was the sexual behavior of the feminized rat. The -individual no longer reacted as male, but showed some of the reflexes -peculiar to the female. These results, that stand almost alone, appear -to show that several of the secondary sexual characters of the female -rat are due directly to the presence of the ovary.</p> - -<p>One of the most striking and definite results shown by castrated rats -(Steinach), guinea-pigs (Pirsche, Steinach), rabbits (Pauncet), hedgehog -(Marshall), and man is to be seen in the effect on the accessory glands -connected with the male ducts as well as on the penis. These remain -small and infantile. Some substances produced by the testes are -essential for the development of these parts. Natural selection rather -than sexual selection would be the agency that here comes into play.</p> - -<p>In man the effects of castration have been often described. Eunuchs have -had a commercial value in some countries, as in Turkey and China, and -castration has been deliberately practiced on young children. Certain -religious sects, such as the Skops of Russia, have advocated and carried -out the operation. Disease has also at times necessitated the removal of -the testis, more often in adults than in the young. The full effects are -shown only when the operation has been carried out before the secondary -sexual characters have developed. The more striking difference between -the sexes involve the beard, and the hair on other parts of the body, -the voice, the shape of the pelvis, and the mammary glands. For a -detailed account of the results, the publications of Tandler and Grosz -and Marshall’s book on the “Physiology of Reproduction” should be -consulted.<span class="pagenum"><a name="page_72" id="page_72">{72}</a></span></p> - -<p>The two most obvious changes in the eunuch are the absence of the beard -and mustache and the small larynx, which produces a high-pitched voice. -In both these respects man differs from woman; in both, however, the -eunuch is like the boy as much as he is like the woman. It is not -evident, therefore, whether the eunuch has retained the juvenile -condition or has become more like the female. Moreover, there is the -possibility that there is no difference in the present case between -these two conditions. The distribution of hair on the pubis of the -eunuch is often said to be more like that in the woman than that in the -man, but there is apparently no sufficient evidence to show that this is -more than the juvenile condition or an undeveloped condition of the -male. As to the voice, there is no way of determining whether the voice -of the eunuch is feminine or juvenile. The development of the mammæ in -the eunuch would be a better test, but it does not appear from the -literature on the subject that the mammary glands and the nipples of the -eunuch are changed toward the female type. On the contrary, it appears -rather that there is no such change. It is true that the tendency toward -the accumulation of fat may give the eunuch a somewhat feminine -appearance (since one of the foci of fat accumulation is in the region -of the breasts), but this in itself can scarcely be claimed to be -feminization, but due rather to the more slothful habit of the eunuch -that tends to obesity.</p> - -<p>A more suggestive resemblance is found in the narrowness of the shoulder -girdle and broadness of the hips in the eunuch, but even these -resemblances to the female should be regarded skeptically, since other -changes in the bones that result from castration are certainly not a -development toward the female type, but a peculiar specific effect of -the absence of testes on the growth of the bones. For instance, the -bones of the arms and legs are much longer in the eunuch than in either -the normal man or woman, in fact, more in the direction of the male, who -has longer legs than the female. The explanation usually given is that -the ossification at the ends of the bones and of the epiphyses does not -take place so soon as in normal men and women. The condition here is -that characteristic of the juvenile state that is carried over into the -adult, but whether the narrowness of the chest and shoulder girdle of -the eunuch is correlated in some way with the more prolonged growth of -the other bones has not, so far as I know, been determined. That there -is no <i>apparent</i> connection between the shortness of the one and the -greater length of the other does not necessarily lead to the conclusion -that there is no such connection. For the present I think we must hold -this point in reserve.</p> - -<p>Steinach’s evidence for the feminized rats, if it may be extended to -man, indicates that some of the female characteristics are due to the -presence of the ovary holding in check the genetic possibilities of the -female, as well as leading to the development of such characteristic<span class="pagenum"><a name="page_73" id="page_73">{73}</a></span> -traits as the mammæ, etc. In the case of the pelvis the female departs -from the juvenile type of both sexes, and here one might look for a -better criterion. It is stated that the pelvis of the ox is more like -that of the female than it is like that of the male, and it has been -said that this is true for the castrated rat and guinea-pig, but whether -a simple enlargement of the juvenile pelvis would make it resemble the -female type more than that of the male has not, so far as I know, been -carefully examined. Should it prove here that this is the case, the -evidence on this point would be no stronger than that for other -character differences. As has been stated, Tandler and Grosz think that -the changes in the skeleton of the ox, as well as those in the castrated -cow (skull, pelvis, and limb bones), are due directly to loss of the -gonads and are much the same in both. But their resemblance may possibly -be due more to an enlarged juvenile condition rather than that either of -them changes toward the normal skeleton of the other sex.</p> - -<p>The statements that have been published concerning the effects of -removal of the ovaries in woman are, on the whole, unsatisfactory and -often contradictory. That the uterus and oviducts become smaller is -expected from what is known to occur in other mammals, and is definitely -recorded in the human female. That the breasts become smaller is stated -to be the case, but whether because of an actual decrease in the -glandular portion has not, so far as I know, been shown. That hair is -likely to develop on the upper lip of woman without ovaries is also -claimed as likely to occur, and this, too, is sometimes seen in old -women, but if it is interpreted to mean an approach to the bearded -condition of man it should be admitted that the development is hardly -sufficient to invite such a comparison. Finally, it has been stated that -the voice becomes deeper, more, therefore, like the male, but this has -also been denied. If it could be established that the voice changes and -that it was brought about by an enlargement of the larynx, similar to -that which takes place when the larynx of the boy changes to that of the -man, it might seem not improbable that the change was toward that of the -opposite sex. This would mean that the ovary produces some substance -that prevents the enlargement of the larynx in the female. But since it -has been shown that the enlargement in the male is caused by the -development of the testes, and that this enlargement is prevented by -castration, a paradoxical situation would present itself, viz, that the -testes cause the larynx to enlarge in the male and the ovary prevents -the enlargement in the female. Until convincing evidence is forthcoming, -the question is better left undecided.</p> - -<h4>B. <span class="smcap">Evidence from Birds.</span></h4> - -<p>Probably a greater difference in the secondary sexual characters is -shown in birds than in any other group. It is true that there are<span class="pagenum"><a name="page_74" id="page_74">{74}</a></span> -species, such as the doves and pigeons, in which the plumage of the male -is much like that of the female, but this is the exception rather than -the rule. At the other extreme are species like birds of paradise, -hummingbirds, fowls, pheasants, ducks, and many passerines, in which the -plumage of the two sexes is entirely different. Our knowledge as to the -relation between the nuptial plumage of the male and the condition of -the sex-organs rests largely on information gained by castration in -poultry and ducks and on the assumption of the nuptial plumage in -several species only at the mating season.</p> - -<p>John Hunter in 1780 described a pheasant with male plumage. His account -of a similar change in a pea fowl is so complete that I venture to quote -it in full:</p> - -<div class="blockquot"><p>“Lady Tynte had a favorite pyed pea-hen, which had produced -chickens eight several times; having moulted when she was about -eleven years old, she astonished the lady and her family by showing -the feathers peculiar to the other sex, and appearing like a pyed -peacock. In this process the tail, which was similar to that of a -cock, first appeared after moulting. In the following year she -moulted again, and produced the same feathers. In the third year -she did the same; at the same time she had spurs similar to those -of a cock. She died in the following winter during the hard frost, -namely, in the winter 1775-6. She never bred after this change in -her plumage. This bird is now preserved in the Museum of Sir Ashton -Lever.”<a name="FNanchor_17_17" id="FNanchor_17_17"></a><a href="#Footnote_17_17" class="fnanchor">[17]</a></p> - -<p>“From what has been related of these two birds, may it not -reasonably be inferred that it seems probable that all those wild -pheasants of the female sex, which are found with the feathers of -the cock, had changed the nature of their feathers, particularly at -a certain age?</p> - -<p>“If this idea be just, it shews that there is a disposition in the -female to come nearer and nearer to the male, at least in the -secondary properties; or it may rather be said that the female is -later in producing this change than the male is; for it has already -been observed that both sexes when young differ not from each other -in these respects, but that the male appears to be the one that by -degrees separates from the female in its secondary properties.”</p></div> - -<p>Statements in regard to the effect of castration on poultry go back, it -appears, to Aristotle. Yarrel in 1811 and again in 1850 has given an -excellent account of many of the effects produced. His account of the -effects on the cock seem to be based partly on hearsay, and while they -contain much accurate information, yet the statement that the plumage of -the capon is intermediate between that of the cock and hen is incorrect. -The further statement that by cutting the oviduct the hen assumes the -plumage of the capon has been shown by Sellheim to be erroneous. The -operation referred to by Yarrel must have been one in which the ovary -was removed.<span class="pagenum"><a name="page_75" id="page_75">{75}</a></span></p> - -<p>Yarrel described a female pheasant that had assumed some of the -characteristic colors of the male. On dissection he found that the ovary -was diseased as well as the oviduct. He correctly assigns the change in -plumage to the condition of the ovary. He states furthermore that most -of the female pheasants that he had examined that had male plumage had -not assumed the complete coloration of the male. In one case, however, a -complete change had taken place. The change in pheasants he thought was -due to old age accompanied by partial or complete loss of function of -the ovary. For poultry he states:</p> - -<div class="blockquot"><p>“In the imperfect female the comb increases; a short spur or spurs -appear; the plumage undergoes an alteration, getting what is -usually called ‘foul-feathered;’ she ceases to produce any eggs, -and makes an imperfect attempt to imitate the crow of the cock. -Being profitless in this state, she is usually made away with. The -proverb says:</p> - -<div class="poetry"> -<div class="poem"><div class="stanza"> -<span class="i0">A whistling woman and a crowing hen<br /></span> -<span class="i0">Are neither good for gods nor men.<br /></span> -</div></div> -</div> - -<p class="nind">Our neighbors and allies the French, who seem to take a wider range -in their prejudice against habits which they consider irregular, -have the following proverb, which says:</p> - -<div class="poetry"> -<div class="poem"><div class="stanza"> -<span class="i0">Poule qui chante, Prêtre qui danse<br /></span> -<span class="i2">Et Femme qui parle latin,<br /></span> -<span class="i2">N’arrivent jamais à belle fin.<br /></span> -</div></div> -</div> - -<p>“I have seen two instances in which females of the wild duck have -assumed to a considerable extent the appearance of the plumage of -the mallard, even to the curled feathers of the tail. One of these -birds, in my own collection, was given me when alive by my kind -friend the late John Morgan, esq. When this bird was examined after -death, the sexual organs were found to be diseased, as in the case -of the hen pheasants referred to, and figured in the 2d volume of -the History of our British Birds. In the published illustrations to -his Fauna of Scandinavia, M. Nilsson has given a colored figure of -a duck in this state of plumage (plate 163), which is called a -barren female, and in which the curled tail-feathers are made very -conspicuous.</p> - -<p>“From the general similarity in these females to the appearance -assumed for a time by healthy males in July, I am disposed to refer -this seasonal change in males, in this and in other species of -ducks, to a temporary exhausted state of the male generative -organs, and their consequent diminished constitutional influence on -the plumage.</p> - -<p>“A male shut up by himself from early spring to the end of July -undergoes no change in his plumage; but if he is allowed to -associate with females till their season of incubation commences, -he then goes through the change, and this appears to indicate the -cause of the partial summer moulting.</p> - -<p>“The appearance is somewhat different, but yet very interesting in -insects and crustacea. In these classes the sexual organs are -double and distinct, arranged one on each side of the elongated -mesial line. It sometimes happens, that a species in which the -sexes are of a different color, or markings, or form has one sexual -organ of each sort, male and female, in which case each half of the -same insect is developed under the exclusive influence of the -sexual organ on its own side. Instances are preserved among our -collections of butterflies, mothes and beetles; and I have seen it -twice in the common lobster.<span class="pagenum"><a name="page_76" id="page_76">{76}</a></span></p> - -<p>“Nor is the human race exempt from the operation of the law which -prevails in the Mammalia. In women, at an advanced age, hair -appears on the chin and upper lip, and the voice alters, becoming -deep in its tone. The beard in old men becomes thin and soft, and -our own inimitable Shakespeare has told us,</p> - -<div class="poetry"> -<div class="poem"><div class="stanza"> -<span class="i6">* * * his big manly voice<br /></span> -<span class="i0">Turning again toward childish treble, pipes<br /></span> -<span class="i0">And whistles in his sound.”<br /></span> -</div></div> -</div> -</div> - -<p>Gurney (1888) has recorded several cases in which female birds have -assumed male plumage. For instance, he describes a female merganser, -<i>Mergus serrator</i>, assuming male plumage that showed no signs of disease -in the ovary. Mr. Cecil Smith had a female widgeon (<i>Mareca penelope</i>) -on his ponds near Trenton, which assumed the male plumage some years -ago, and which, so far as he knew, had not had young nor laid eggs.</p> - -<div class="blockquot"><p>“On May 16th, 1887, a chaffinch (<i>Fringilla cœelebs</i>) in full male -plumage was shot at Chapel Town, near Leeds, in Yorkshire, by the -son of Mr. W. L. Jackson, M. P.; it was skinned by G. R. Grassham, -assistant to Mr. W. E. Clarke at the Museum, who, much to his -surprise, found that it was a female, and contained an egg, ready -for laying, of a pale blue, without markings, and another egg in a -less forward state. This chaffinch is in every way in perfect male -plumage, and I am indebted to Mr. Clarke for his kindness in -sending these particulars with the specimen, which he received from -Grassham a few hours after the latter had dissected the bird.</p> - -<p>“In the ‘Norwich Nat. Trans.,’ an enumeration was given of female -Redstarts (<i>Ruticilla phoenicurus</i>) assuming male plumage (<i>l.c.</i>) -to which the following may be added: a hen <i>R. phoenicurus</i> -assuming male plumage, and very like Mr. Millais’ described in the -‘Norwich Nat. Trans.’ iv., p. 182, was caught by Mr. W. E. Clarke -sitting upon her eggs, at Wike, near Leeds, in June, 1886; at the -same time Mr. Clarke saw the cock close by, which appeared to be in -the ordinary male plumage. The late Mr. Henry Doubleday’s -collection contained a hen Redstart (<i>R. phoenicurus</i>) in male -plumage, which had the ovaries ‘quite perfect and full of eggs’ -(<i>cf.</i> B. of Norf., i, p. 370, note), probably one of those alluded -to by Yarrell (Brit. B. 1st ed. i, p. 240) in the remarks made by -him on the plumage of this species. I have some recollection of -this Redstart at the dispersal of Mr. Doubleday’s collection, but -do not know who was the purchaser of it. There can be no doubt that -more would soon turn up if looked for; and now that attention has -been drawn to the subject, and the practice of dissection is -getting more general among bird stuffers, it is certain to be the -case, not only in <i>Ruticilla</i>, but in other genera besides. Why it -should happen in <i>Ruticilla phoenicurus</i> oftener than in other -Passerine birds is hard to explain, but such is evidently the -case.”</p> - -<p>“The same is recorded to have happened five or six times with the -female Red-backed Shrike (<i>Lanius colluria</i>); see ‘the Field,’ June -17, 1871, and April 25, 1885; Mag. N. H., iv, p. 344; ‘B. of -Suffolk,’ p. 45; ‘Ibis,’ 1863, p. 292; but the number of hen -Redstarts which have donned masculine attire is greater.</p> - -<p>“The following is a list of the species in which one or more -instances of females assuming male plumage are ascertained to have -occurred:</p> - -<ul> -<li>Falco aesalon, fide Scully. (Cf. Sharpe, ‘Cat. Birds Brit. Mus.,’ i, p. 407).</li> -<li>Tinnunculus alaudarius, fide Sharpe; col. fig. P. Z. S., 1874, p. 580.</li> -<li>Lanius collurio, fide Hoy.</li> -<li>Lanius vittatus, fide Blyth.</li> -<li><span class="pagenum"><a name="page_77" id="page_77">{77}</a></span>Ruticilla phœnicurus, fide Millais, Clarke and others.</li> -<li>Fringilla cœlebs, fide Clarke.</li> -<li>Linota cannabina, fide Blyth.</li> -<li>Linota rufescens, fide Blyth.</li> -<li>Nectarinia asiatica, fide Blyth.</li> -<li>Gallus (domestic fowl), fide Yarrell and others; col. fig. “B. of Sherwood,” p. 183.</li> -<li>Pavo (peahen), fide Latham; fig. “Synopsis,” ii, pl. 60.</li> -<li>Meleagris (Turkey), fide Bechstein.</li> -<li>Phasianus colchicus, fide Edwards and others. Of common occurrence in a semi-domesticated state.</li> -<li>Thaumalea picta, fide Edwards.</li> -<li>Euplocamus nycthemerus, fide Yarrell.</li> -<li>Pucrasia nipalensis, fide Blyth.</li> -<li>Tetrao tetrix, fide Bond; col. fig. Dresser, “B. of Eur.,” vi, 205.</li> -<li>Tetrao urogallus, fide Nilsson; col. fig. “Unser Auer-, Rackel- und Birkwild und seine Abarten,” by A. B. Meyer.</li> -<li>Otis tarda, fide Tiedmann.</li> -<li>Anas (domestic duck), fide Rowley; col. fig. “Orn. Misc.,” i, p. 118.</li> -<li>Anas boschas, fide Hancock; fig. col. “Scandinavisk Fauna,” pl. 163.</li> -<li>Fuligula marila, fide Blyth; see also P. Z. S., 1885, p. 246.</li> -<li>Mergus serrator, fide Gurney.</li> -<li>Mareca penelope, fide Cecil Smith.</li> -</ul> - -<p>“Perhaps the Kestrel (<i>Tinnunculus alaudarius</i>) ought not to be -included in this catalogue, for so many have been seen with the -lower part of the back blue or bluish, as to leave little doubt -that the female generally becomes so if she lives long enough.</p> - -<p>“It is said that the females in <i>Oriolus</i> generally become as -bright as males in time (‘Ibis,’ 1864, p. 412; ‘Field,’ June 24th -and July 8th, 1871).”</p> - -<p>“P. S.—Mr. W. Tegetmeier tells me he has known a barnyard cock -moult into hen’s plumage, which is the converse of the instances -narrated in this paper, and rather resembles the annual change -which takes place in <i>Anas boschas</i> and others of that tribe.”</p></div> - -<p>In a later notice Gurney makes the following statement:</p> - -<div class="blockquot"><p>“The bearded tit (<i>Panurus biarmicus</i>) may be added to the list of -female birds which are known to occasionally assume male plumage. -In the summer of 1882 a bearded tit, two years old, in Mr. J. G. -Keulemans’ aviary, hatched five eggs and moulted, during which -operation she suffered much from cold and stiffness, and when she -recovered her plumage it was partly that of the male (<i>cf.</i> ‘The -Field,’ Sept. 14, 1872).”</p></div> - -<p>Brandt, who has reviewed the literature very thoroughly, cites the -following cases:</p> - -<div class="blockquot"><p>“Galeinacei: Gallus bankiva domest., Phasianus pictus, torquatus, -colchicus, mongolicus and nycthemerus, Pavo cristatus domest., -Meleagris gallopave domest., Perdix einerea, Tetrao urogallus, -tetrix und bonasia.</p> - -<p>“Passeres: Fringilla coelebs, Pyrrhula vulgaris, coccinea, Loxia -chloris, Turdus merula, Ruticilla phoenicurus, ochrura, -chrysogastra, Cyanecula Wolfii, Sturnus vulgaris, Ampelis cotinga.</p> - -<p>“Scansores: Cuculus canorus, Edolius glandarius.</p> - -<p>“Grallatores: Machetes pugnax.</p> - -<p>“Natatores: Anas boschas domest.</p> - -<p>“Es ware denkbar, dass die Hahnenfedrigkeit, wenn auch in -verkapptem Grade, allen Vögeln, selbst denjenigen zukomme, deren -Gefieder uns geschlechtlich uniform zu sein scheint. Wie dem auch -sei, einzelne Genera und Species scheinen mehr, andere weniger zur -Arrhenoidie prädisponirt. So<span class="pagenum"><a name="page_78" id="page_78">{78}</a></span> bemerkt J. Geoffrey St. Hilaire (p. -511), dass Fasanen häufiger selbst als die Hühner hahnenfedrig -werden, während für den Pfau, den man doch stets eines natürlichen -Todes sterben lässt, ihm nur ein einziger Fall (der von Hunter) -bekannt geworden. Während Lorenz (vide Tichomirow) auf dem Moskauer -Markt häufiger hahnenfedrige Weibchen von Phasianus colchicus and -mongolicus aufgefunden, ist ihm dieses fur Ph. chrysomelas bisher -kein einziges Mal gelungen, obgleich die Zahl der jährlich in -Moskau feilgebotenen Exemplare dieser Art sich auf 8000 Stück -belaufen möchte.”</p></div> - -<p>The preceding cases relate to exceptional changes in the plumage as -observed in nature, or in birds kept under domestication. We may next -examine the cases where the ovary or the testis has been removed.</p> - -<p>The earlier observations of Berthold, Wagner, Hanau, Samuel, Sellheim, -Pirsche, Foges, Shattock, and Seligman are sufficiently covered by later -work quoted below. Sellheim’s work, however, is especially to be noted, -since he gives some measurements covering the weight of the brain, -heart, and body of the cock and capon, as well as observations on the -skull and skeleton. The weight of the brain is slightly less in the -capon, but the body-weight is greater. He questions whether the ovary -has ever been successfully removed, and he shows that the operation of -resecting the oviduct does not, as was supposed, lead to the -degeneration of the ovary. On the contrary, he found that after the -effects of the operation had been removed the ovary began again its -functions.</p> - -<p>From Goodale’s careful summing up of the effects of castration only the -following points need be recalled: The feathers are little changed; some -of them, the hackles especially, become longer. The lowermost tier of -wing coverts are elongated as compared with those of the cock. The spurs -are practically the same in the capon and cock. The capon is disinclined -to give voice, but at times he crows. The molting is not affected. The -size of the capon is larger. He pays little attention to the hens. He is -not pugnacious, and if attacked will not often fight. As a rule he does -not pursue the hens, but if a hen squats down as the capon approaches he -will mount and go through the characteristic mating reaction. The comb -is extremely small, much smaller than that of the female of the same -race; it is infantile rather than feminine.</p> - -<p>Comparing these results with those that I have observed in the castrated -Sebright, we find that aside from the assumption of the full plumage of -the cock-feathered bird the Sebright shows all of the characteristic -features of the capon. The spurs develop, perhaps even more fully than -in the normal Sebright cock. He seldom crows, and then weakly. The birds -appear large, but the excessive development of the feathers produces the -effect. I have not weighed them to show whether an actual increase in -size takes place. Two of my birds are notably large for Sebrights, but -the others are smaller. Both large and small cocks occur in the strain -that I have used. My Sebright and other capons neglect the hens, but I -have seen them tread the hens<span class="pagenum"><a name="page_79" id="page_79">{79}</a></span> on occasion. They will fight each other, -if two strangers meet, but the attacks are not violent or prolonged. A -normal male beats them easily, and afterwards they run away from such -birds. The combs and wattles are very small and pale. If a piece of the -testis is left in, the comb is a fair index of its size. In the birds -that changed back toward a Sebright the comb slowly enlarged. After the -second operation it decreased again as the plumage once more changed to -that of the cock.</p> - -<p>Goodale’s results with ovariotomized females are especially noteworthy, -since here for the first time we have definite information as to the -effects of the operation. By using a well-established breed, the brown -Leghorn, in which the dimorphism of the sexes is very striking, the -results are made all the more convincing. Goodale found that it was -possible to completely remove the ovary of young birds, for at an early -age the ovary is sufficiently compact to make its entire removal -possible. Later the ovary becomes more diffuse, and complete removal is -almost impossible. In a few successful cases, in which the ovary had -been completely removed, the bird assumed the full plumage of the -Leghorn cock, with red back, black breast, and long, pointed hackle and -saddle feathers. Spurs developed in all the operated females, even when -the ovary was not entirely removed. There can be little doubt that the -ovary holds back the development of the spurs, but as some hens -sometimes develop spurs, especially in certain breeds, it is not -entirely certain that in these cases the loss of the ovary is the cause -of the appearance. The comb (and wattles) developed to different -degrees; in some birds it was as large as in the cocks, in others no -larger than in the normal hen, but in all cases it was larger than in -the capon. What to conclude is doubtful. Tentatively it may be suggested -that the genetic complex that gives the female (ZW) produces a comb as -large as that shown by the female independently of the ovary, but beyond -this point the ovary inhibits the further development of the comb, -presumably by means of the same internal secretion that holds down the -cock plumage in the hen. In the male, on the other hand, the genetic -complex (ZZ) produces a comb much smaller than that of the female (no -more than that of the capon), and the testes produce a substance that -causes this comb to grow to the size of that of the cock. Possibly, -however, other internal secretions are involved.</p> - -<p>The operated hens are quiet and nearly voiceless. None of Goodale’s -birds were heard to crow, yet this seems to be a well-known peculiarity -of old hens that have become cock-feathered. The operated hens are not -larger than the normal hens of the same breed. Their legs remain short, -as in the normal hen; and in this respect and in size the ovariotomized -bird is externally a female. The poullards “never visit the nests, never -sing or cackle, show none of the normal female reactions, and few or -none of the male.<span class="pagenum"><a name="page_80" id="page_80">{80}</a></span>”</p> - -<p>The influence of the ovary in suppressing the cock plumage has been -convincingly shown in an experiment of Goodale’s, in which, after -removal of both testes from the young Leghorn cock, pieces of ovaries -were inserted into the body-cavity. As dissection showed later, several -of these implanted pieces grew onto the wall of the body-cavity. The -birds developed the plumage of a hen, although some traces of the male -plumage were at times present. The difference between the sexes is so -great in Brown Leghorns that the hen-feathering of the feminized -cockerels leaves no doubt that the presence of the ovary had produced -the female coloration.</p> - -<p>Geoffrey Smith and Mrs. Haig Thomas (1913) have examined a number of -hybrid pheasants, some of which were sterile. They found that the ovary -(and oviduct) was often small and degenerate. There was a more or less -corresponding tendency for such female hybrids to show male feathering, -at least in a part of the plumage. The degeneration of the sex element, -however, does not take place until after the time of synapsis, so that -the younger germ-cells may be normal. The later degeneration of these -cells is not likely to influence the secondary sexual characters, but -may be an index of changes in other parts of the ovary.</p> - -<p>Geoffrey Smith had a breed of White Leghorns with cocks of two -classes—those that assumed cock plumage at 6 months, and those that are -like the hens for 8 months, after which they slowly assume the -cock-feathering. The difference is hereditary and appears to segregate. -Possibly this breed had one factor at least for hen-feathering that is -more effective for young birds than for older ones.</p> - -<p>Smith states that birds and crabs (see <i>infra</i>) appear to give opposite -results, since removal of the ovary in the former leads to development -of secondary male characters and removal of testes in the latter to -secondary female characters. But he adds that he thinks the results are -really the same, because in the crab it is not the suppression of the -testis but the feminization of the male by the Sacculina that causes the -change.</p> - -<p>There are a number of observations on ducks. Several cases have been -recorded where in old age the female assumed the male plumage (Darwin, -Shattock, and Sellheim). Also a few cases in which the testes were -removed. Those of Goodale are the most complete and striking. The male -duck has two characteristic plumages, one called the nuptial, also -called the summer or breeding plumage that is assumed at the molt in the -autumn, and the other the eclipse plumage, which is not identical with -but much like that of the female. Here, then, we find a new situation, -and one that invites comparison with the condition in Sebrights, in so -far as the male becomes hen-feathered at certain seasons.<span class="pagenum"><a name="page_81" id="page_81">{81}</a></span></p> - -<p>Throughout the greater part of the year the Rouen drake has the nuptial -plumage. The head is green and the breast is claret. Two median tail -feathers are strongly curved; the next two are also often curved. These -four are called the sex feathers. At the close of the breeding-season -(July) both sexes molt. The male now has the same coat as the female, or -nearly so. The green head becomes brown to buff; the sex feathers are -straight. The change back again to the nuptial plumage begins at the end -of summer and is completed early in October. Thus in the race of Rouens -the eclipse plumage lasts only a very short time. In the mallard it -lasts longer. The eclipse plumage develops, therefore, only when the -testes are active, or, as Goodale puts it, “the presence of the active -testis is necessary for the drake to assume this plumage.” Conversely, -the nuptial plumage comes on in the late summer, when mating is over, -and when the testes have shrunken and are not active, at least as far as -the sex-cells are concerned. In some respects the situation is like that -in the fowls, for in both the testes are not necessary for the -development of the full plumage, but in other respects the situation is -different, because at the time in the ducks when the testes are active -the eclipse plumage develops. Are we to suppose that at the time of -sexual activity a substance is produced analogous to that produced by -the ovary of the female? This seems the most plausible assumption, for -we know that if the testis is removed the eclipse plumage does not -appear. Such a situation suggests a comparison with the Sebright, where -it has been shown that the testis must actively produce some substance -which, like that in the ovary, keeps down cock-feathering. It is -plausible, even if it can not be established, that the substance in the -duck and the inhibitory substance in the male Sebright are the same as -that produced in the female.</p> - -<p>Goodale’s results with females (ducks) are not so clear cut, because the -ovariotomized females turned out to be of two sorts. One sort is almost -identical with the male, the other is more intermediate. There are -sufficient reasons for thinking, he says, that these differences are not -due to defective operations. Goodale suggests a genetic difference in -the females used, but this is apparently even to Goodale himself not a -very satisfactory solution. For our present purpose the important fact -is that the ovariotomized female may assume the perfect male plumage. -Evidently the ovary produces some substance which, as in the hen, -suppresses the potential plumage of the male. One such female known to -have had all the ovary removed never assumed the summer (eclipse) -plumage of the drake. On the other hand, another female developed first -the nuptial plumage, but this was replaced by the summer coat “of the -male of this variety.” Again, in the summers of 1914 and 1915 the change -to the eclipse plumage was followed in the autumn by a return to the -nuptial plumage.<span class="pagenum"><a name="page_82" id="page_82">{82}</a></span></p> - -<p>How can we explain the apparent discrepancy of Goodale’s results? In one -case, the nuptial plumage was molted to nuptial plumage; in the other -case an eclipse plumage appeared at the breeding-season. Goodale regards -the latter case as a more perfect approach to the male than the former, -but this view undoubtedly offers serious theoretical difficulties. It -seems to me possible to suppose that in those cases where the summer -plumage appeared there was in reality enough ovarian tissue (or related -tissue) left after the operation to produce an effect at the normal -season for such ovarian tissue to become most active. It might then -suffice to eclipse the male plumage sufficiently to make it very similar -to the eclipse of the normal male. At any rate, on this basis we have a -consistent explanation of the entire complex of phenomena.</p> - -<p>What bearing have these results relating to castration and -transplantation on the theory of sexual selection? Granting, of course, -that selection takes the materials as it finds them, there may still be -restrictions imposed on the theory by the kind of material offered. For -instance, the development of the plumage of the cock is independent of -the condition of his testes. Hence, if the female selected the more -vigorous male, she would not necessarily obtain one more ornate than his -less vigorous rivals. If the taste of the hen has built up the plumage -of the cock, it has been carried out then independently of the vigor -resulting from the greater activity of the testis. In a word, the more -vigorous male is not necessarily the most highly colored one. Darwin -concedes that these two conditions, high color and vigor, must go -together to insure success, or at least that the most vigorous and -therefore the most highly colored male will have more offspring. -Wallace’s contention that the greater vigor of the male accounts for his -greater development of plumage gets scant support from the facts of -castration. One might rather contend that the female must be more -vigorous, since she is obliged to suppress plumage that is allowed to -run riot in the male.</p> - -<p>Wallace’s argument in favor of natural selection holding down the -plumage in the female as a protection to her while nesting might appear -to fit the facts better were it not that the quest for an explanation of -the male’s plumage is thereby abandoned. It should not be forgotten in -this connection that the nest is generally only partly concealed, that -bright color at rest need not be conspicuous, and that the male, exposed -as he is through a considerable part of the year, still manages to -maintain himself in about equal numbers with the female. Suppose, -however, for the sake of argument, that natural selection has kept under -the full possibilities of the female. The <i>modus operandi</i> would be -competition between the least adorned females, suppression being brought -about by the activity of the ovary; while the male is left therefore to -exhibit the full possibilities of the genetic complex of<span class="pagenum"><a name="page_83" id="page_83">{83}</a></span> his race -without restraint. The facts in the case are that the plumage of the -male is the direct result of his genetic composition; the female has the -same genetic composition (the sex-linked characters are duplex), but the -ovary produces a substance that holds them in restraint. Put in this -way, there is nothing further to be explained, unless we insist on -finding an explanation as to how the species came to have its genetic -constitution. In other words, if we are not satisfied with the statement -as to the actual situation, we must explain it by a utilitarian appeal -to a relation between the plumage and the world outside of the -individual or the species. To those who feel unsatisfied to leave the -case as it stands on a physiological basis, there is another -hypothetical means of escape. It may be assumed that the genetic factors -that are instrumental in producing the secondary sexual characters have -also other but unknown influences in the economy of the species, color -and ornamentation being by-products of these factors whose utility in -other directions accounts for their presence. Such a philosophy has -perhaps one redeeming feature, since it suggests the possibility of -searching for other influences—influences that only incidentally give -the striking coloration and ornamentation of the males.</p> - -<p>At first sight the absence of cock-feathering in the Sebright may seem -to furnish the occasion for such a quest. It might appear that since -only one or two genetic factor differences are responsible for the -“nuptial” plumage of the male, that this plumage may have originated in -one or two genetic changes. Such an argument is fallacious, however, for -very many genetic factors may historically have been necessary to build -up the nuptial plumage of the male. The breeding experiment shows no -more than that one or two other factors have appeared that counteract -the effect of all that the others are capable of producing; the -experiment throws no light upon how many or how few these other factors -may be. That the nuptial complex is still present in the Sebright is -evident after castration. Castration shows only that the testes in the -Sebright produce some material that keeps down the effects of all the -other factors combined. This conclusion, it is true, somewhat simplifies -the problem for those who appeal to natural selection as suppressing in -the female the feathering of the cock, because it shows that this could -have been accomplished by one or two Mendelian factors that appeared of -such a kind that they caused the ovary to produce a substance -antagonistic to the influences coming from the genetic complex of the -species.</p> - -<p>With this by way of provisional exposition, let us return to the -question as to whether the Sebright-game cross throws any other light on -the possibly useful character of the genetic factor or factors that -produce cock-feathering. It is obvious that the evidence gives us no -clue at all, for with the exception of the normal allelomorphs of the -dominant factor for hen-feathering, all the other factors are still<span class="pagenum"><a name="page_84" id="page_84">{84}</a></span> -present in the Sebright. The normal allelomorph in question need not -have had any relation to the other complex; in fact, it seems not to -have any, because the castrated Sebright (with both normal allelomorphs -replaced by genes for hen-feathering) still develops the characteristic -cock-feathering.</p> - -<p>The outcome in the duck with its double male plumage is still more -puzzling when we attempt to analyze the situation in the light of the -selection theory. At the height of the breeding-season, when his testes -are enlarged and functioning actively, a substance is being produced -that leads to the eclipse of the nuptial plumage. If the male were -selected by his partner for his plumage, he would be chosen for a -plumage that develops in the absence of the functioning testes. If the -male is chosen because of his greater aggressiveness or “activity” or -“vitality” due to the development of his testes, the result would be to -select males that would probably develop a better eclipse plumage. The -case is interesting because it gives an opportunity to distinguish -between a plumage that develops under the influence of the sexual organs -and one that does not; and the latter is paradoxically the nuptial -plumage. It is true that the male might be selected for his nuptial -suit, and, theoretically at least, female choice might still be made -responsible for this plumage, but this merely shifts the problem, for it -leaves “unexplained” the appearance historically of the effect of the -activity of the testes in suppressing this plumage for a short time -after maturity. No doubt an attempt might be made to show that natural -selection comes in at this time of the year in giving a protective color -to the male, but so long as any evidence is lacking as to the need of -this protection the argument serves rather to further complicate an -already difficult situation.</p> - -<p>Goodale has written to me that there is an account, in the Agricultural -Journal, Union of South Africa, <span class="smcap">IV</span>, 1912, of the effects of the removal -of the ovary of the female ostrich. I have not been able to see the -account, but according to my informant such female individuals assume -the male secondary characters.</p> - -<p>Of unusual interest in connection with the seasonal change of plumage in -males of dimorphic species are Beebe’s experiments with scarlet tanagers -and bobolinks. In both species the males in their nuptial plumage are -very different from the females. Full-plumaged males of both species, at -the height of their “vocal and physical condition,” were confined in -small cages. The supply of light was gradually cut off and a slight -increase of the amount of food was allowed them. The birds became less -active in consequence and increased in weight. “The time for the fall -molt came and passed and not a single feather was shed.” The birds had -skipped the autumn molt and remained in their nuptial plumage. The song -soon died away; “the birds seldom uttered even a chirp.” From time to -time a bird was gradually brought into<span class="pagenum"><a name="page_85" id="page_85">{85}</a></span> the light for a week or two and -meal-worms were added to the diet. This invariably resulted in a full -resumption of song.</p> - -<div class="blockquot"><p>“I found that a sudden alteration in temperature—either lower or -higher—wrought a radical change in the physical metabolism of the -birds. They would stop feeding almost altogether, and one tanager -lost weight rapidly. A few feathers on the neck fell out, and in -the course of some two weeks this bird moulted almost every feather -and came strongly into his normal winter plumage of olive green. -The metabolism set up by the change in temperature, in its intent -and rapidity, seems comparable only to the growth of a deer’s -antlers.</p> - -<p>“Early in the following spring individual tanagers and bobolinks -were gradually brought under normal conditions and activities, with -quick result; just as the wild birds in their winter haunts in -South America were at that time shedding their winter garb and -assuming the most brilliant hues of summer, so the birds under my -observation also moulted into the colors appropriate to the season. -The old scarlet and black feathers fell from the tanagers and were -replaced by others of the same color; from buff, cream, and black, -the bobolinks moulted into buff, cream, and black! There was no -exception; the moult was from nuptial to nuptial, not from nuptial -to winter plumage. The dull colors of the winter season had been -skipped.”</p></div> - -<p>How are these results to be interpreted? Obviously the environment -prevented the autumn molting; hence the birds necessarily retained their -nuptial plumage. But is this the whole story? Did they not also remain -sexually active with their testes producing sperm as in the mating -season? In other words, if feathers had been plucked from them, would -not the new feathers have been like those already present? Despite the -author’s statement that not a single feather was molted, is it not -likely that occasionally a feather must have been accidentally lost. If -even one had been lost and an eclipse feather had replaced it, the -effect would not have escaped so keen an observer as Dr. Beebe. It seems -to me not unlikely that an occasional feather may have been lost and -replaced by a nuptial one. If so, then the results are most probably -interpreted as due to the birds having remained sexually active. This -condition suppressed the autumn molt, and at the same time would cause -any single feather lost to be like those still present. In support of -such a conclusion I can appeal to Beebe’s statement that after a week in -the light a full resumption of the song took place. It is unlikely that -sexual maturity would be attained in so short a time unless the birds -were already in the condition of sexual vigor. Perhaps one can appeal -also to Beebe’s other statement, viz, that after a sudden change in -temperature, followed by a changed metabolism and loss of weight, the -birds molted and assumed the eclipse (winter) plumage. Here I should -interpret the facts cited possibly to mean that the males lost their -sexual activity and in consequence developed the eclipse plumage.</p> - -<p>Until further information is obtained judgment must be suspended. If, as -Beebe’s statements strongly suggest, the external conditions,<span class="pagenum"><a name="page_86" id="page_86">{86}</a></span> acting -directly on the “metabolism,” cause the changes observed, then the -experiments mean that environmental conditions affect directly the -development of the nuptial and the eclipse plumage; but if, as I suggest -here, the effects observed are due directly to the environmental action -through its effects on the testes, then the results fall more nearly -into line with those of Goodale on ducks, etc.</p> - -<h4>C. <span class="smcap">Evidence from Amphibia.</span></h4> - -<p>The thumbs of frogs enlarge at the breeding-season and shrink -afterwards. The enlarged thumb is used by the male in clasping the -female during copulation, and the rough papillæ that appear over its -surface at this time may also help to anchor the male in his precarious -position on the back of the female. Since the pads and their papillæ are -used in copulation, they belong rather in the class of accessory organs -of reproduction than in the class of secondary sexual characters. Smith -and Schuster state for <i>Rana fusca</i> that the testes are at their -smallest size in March and April after the breeding-season. From that -time until August they steadily increase in size and reach their maximum -size in September. From September to March they are inactive and full -size, until the shedding of the sperm in March brings them soon -afterward to their lowest point again. It is to be noted that the -increase after March is associated with the increase in division rate of -the spermatogonia. The ripening of the sperm is finished in October.</p> - -<p>The thumb-pads with their pigmented papilla are “cast off” immediately -after the breeding-season, the thumb remaining smooth from May to -September. The reduction of the pad is usually due to the reduction of -the glands and the disappearance of the papillæ. Smith and Schuster -state: “During the months when the most active growth of the testis is -taking place the thumb-pads remain inactive and smooth.” The -implication, apparently, is that one ought to expect the growth in the -thumb to take place when the germ-cells are most actively dividing, if -its growth is connected with their activity; but there are no grounds -for such expectations, because the influence of the gonad may have -nothing to do with the division rate of the germ-cells, but rather with -interstitial or other cells, and even here less with their division rate -than with their period of greater secretive activity.</p> - -<div class="blockquot"><p>“In August and September the epidermal papillæ begin to be obvious, -and from this time onwards until about February a continuous -increase of the epidermal papillæ and pigmentation occurs. During -the greater part of this time, when the thumb-pads are attaining -their characteristic rough and pigmented appearance, the testes -remain inactive and unchanged—a fact which has been too readily -overlooked by writers on the correlation of the primary and -secondary sexual characters.”</p></div> - -<p>Nussbaum (1909) and later Meisenheimer (1911) found that after -castration the thumb-pads disappear. Smith confirms this report in all -essential respects, although in certain details concerning the papillæ<span class="pagenum"><a name="page_87" id="page_87">{87}</a></span> -he does not agree with the two former observers. His results show that -castration at the breeding-season is rapidly followed by the loss of the -outer papillated layer of the thumb-pads, but castration at any other -season does not have “any marked effect,” the papillæ remaining for 5 -months and more in the same condition as at the time of castration. The -essential point here, however, is that the excessive and even special -development at the breeding-season does not take place nor is again -assumed (apparently), if castration has taken place at some other time -of the year.</p> - -<p>Smith and Schuster’s attempts to transplant the testes into other males -or females were unsuccessful, as the testes degenerate after a time. -Auto-transplantation of the testes were more successful.</p> - -<p>Removal of the ovary had no effect on the thumbs of the female, and even -the injection of testes extracts into such females did not cause them to -develop pads. Nussbaum and Meisenheimer had found that transplantation -of pieces of the testes, and even injection of testes extract, into -castrated frogs caused an enlargement of the thumb-pads. Smith shows -that this conclusion rests on uncritical evidence. At any rate, his own -more carefully planned experiments extending over the year show that the -results obtained by Nussbaum and by Meisenheimer may be accounted for on -other grounds than the effect of the injection or implantation.</p> - -<p>The following statement by Smith is not without interest, since it bears -directly on an important question as to how internal secretions may -produce their effects.</p> - -<div class="blockquot"><p>“The deduction, therefore, which has been unduly based on -Nussbaum’s experiments, that the testis of the frog contains an -internal secretion, which, on being circulated in the blood, calls -for the development of the secondary sexual characters, either with -or without the mediation of the nervous system, is without -experimental foundation.... The fact that the developmental cycle -of the thumb depends for its normal course on the presence of -normal living testicular tissue can be equally well explained on -the theory that the testicular cells enter into a chain of -metabolic processes in the body which do not pursue their normal -course in the absence of the testicular cells. This disturbance of -the normal metabolic processes of the body, resulting in the -failure of the metabolic organs of the body to give rise to their -normal products in normal quantities, may have the result of -inhibiting the further development of the secondary sexual -characters. The development of these latter characters may depend, -therefore, not directly on the action of an internal secretion or -hormone derived from the gonad, but on the elaboration of other -products in other organs of the body in their due proportions. -These substances may be tentatively called ‘sexual formative -substances,’ but we have no reason for supposing that they are -entirely devoted to sexual or reproductive purposes, and that they -take no part in the ordinary metabolic processes of the body.”</p></div> - -<p>The arbitrary distinctions that Smith here sets up do not seem to me to -contribute anything to the situation, and in fact in the end it amounts -to practically the same thing whether the hormone acts<span class="pagenum"><a name="page_88" id="page_88">{88}</a></span> directly on some -specific part of the body or whether in doing so it acts on other parts -as well. While it is more or less customary to limit the term “hormone” -to substances that do produce specific effects in a particular organ, no -one would, I suppose, deny that a substance was acting as a hormone if -at the same time it acted on other parts of the body also, or even if -its immediate action were on some part and its ultimate action on -another part of the animal. Moreover, there is nothing in the evidence -appealed to by Smith that supports one rather than the other contention. -It is not apparent that the simpler idea of hormone action may not still -apply. Failure to implant the testes in castrated male or female, and -failure of injections to produce the results sought for, may mean no -more than that the experimenter failed to fulfill some one of the -conditions present in the normal frog at the breeding-season. Granting -that the results recorded by Nussbaum and Meisenheimer are open to the -serious objections, pointed out by Smith and Schuster, the facts -recorded by all three writers indicate that the maximum development of -the pad takes place when the testes are at their greatest development -and that the pad suddenly decreases if at this time the testes are -removed. It would seem to follow that since the swelling is connected -with the presence of a certain condition of the testes, its enlargement -is to be referred directly to the latter, and the case comes under the -general category of “secondary sexual differences,” depending on the -gonad.</p> - -<p>The secondary sexual characters of <i>Triton cristatus</i> can not, as can -those of the frog, be supposed to be mechanically useful in mating, but -seem to be comparable in every respect with the secondary sexual -ornaments of higher animals. The work of Bresca has shown that their -development is under the influence of the testes. The most important -secondary sexual characters of the male are the dorsal comb and the -white stripes of the tail. The comb extends along the dorsal surface of -the body and of the tail (with a slight dip in the pelvic region). It is -fully developed during the breeding-season, when it reaches a height of -1.5 cm. In winter it is only 0.66 mm. high, or even less. The white -stripes also are fully developed in the breeding-season. They extend on -each side from the cloaca to the end of the tail. In the female the -white stripe is sometimes faintly seen. The angles of the tail and of -the cloaca thickening are black-brown or black. The belly of the male is -bright orange or “Ziegel rot”; that of the female sulphur-yellow or -orange, but the difference is not constant. The upper surface of the -head of the male is marbled, especially during the breeding-season -almost disappearing during the rest of the year. Bresca found, when the -testes were removed from sexually mature males, that in the course of a -year all the important secondary sexual characters disappeared, -including the comb, the white tail stripes, and the marbling of the -upper surface. Removal of the ovaries did not affect the characters of<span class="pagenum"><a name="page_89" id="page_89">{89}</a></span> -the female. The black lower corner of the tail in the male is not -changed by castration.</p> - -<p>When the skin along the middle line of the back of the female is -transplanted upon the back of a normal male (in place of his own comb) -the transplanted tissue develops into a comb. In other words, under the -influence of the testis, the dorsal mid-line tissues of the female -change into those characteristic of the male. When pieces of skin of a -male with the white tail stripes are grafted on the side of the tail of -another male, the stripe remains, but when grafted similarly on a female -the stripe slowly disappears. The result shows that its presence depends -on the testis.</p> - -<p>A remarkably clear case of hermaphroditism in amphibians was found by V. -la Vallette St. George. He found an individual of <i>Triton tæniatus</i> that -was outwardly a male with well-formed dorsal comb. In the interior were -two large testes in normal position and just lateral to these on each -side a large ovary. Sections showed ripe sperm in the testes and typical -ova in the ovary. Sperm-ducts were present, but no oviducts. The -presence of the testes will, of course, account for the development of -the secondary sexual characters of the male.</p> - -<p>Other cases amongst the Anura have been recorded by Loisel and by -Marshall, Spengel, and Knappe. In the early stages of the gonad in frogs -there appears to be an hermaphroditic stage in which egg mother-cells -and sperm mother-cells are both present, at least in those individuals -that will later become males (Kusakowitsch).</p> - -<p>The normal hermaphroditism of certain fish (<i>Serranus</i>) and its rare -occurrence in other species (recorded by Shattuck and Seligmann) need -not be recorded here.<a name="FNanchor_18_18" id="FNanchor_18_18"></a><a href="#Footnote_18_18" class="fnanchor">[18]</a></p> - -<h4>D. <span class="smcap">Evidence from Crustaceans.</span></h4> - -<p>In the Crustacea the secondary sexual characters are not marked, except -in a few cases. In the amphipods, Holmes has shown direct contact plays -the chief rôle in mating, and in the crayfish it has been shown by -Dearborn, Andrews, and Pearse that sex recognition is largely tactile. -Chidester also has shown this in crayfish. Even in crabs, and especially -those living on land which have well-developed eyes and good vision, -secondary sexual differences are as a rule slight and the mating -instincts simple. On the other hand, the enormous chela of the male of -the fiddler is supposed to be a secondary sexual difference (mainly -because no other use for it has been found). Pearse suggests that the -waving of this claw by the male is used as a sex signal, although he is -disinclined to accept Alcock’s view that it has become “conspicuous and -beautiful in order to attract the female.”</p> - -<p>The most remarkable case known of a change in the secondary sexual -characters of one sex into those of the other was discovered by<span class="pagenum"><a name="page_90" id="page_90">{90}</a></span> Giard -in 1886. As a result of infection by parasitic crustacea (<i>e. g.</i>, -<i>Sacculina</i>), the male crab develops the secondary sexual characters of -the female. It has been generally supposed, following Giard, that this -result is due to the destruction of the testes of the male by the roots -of the parasite that invades the spaces between the organs of the host, -and, in the case of the testis, ultimately brings about its partial or -complete destruction. Not unnaturally the results here were supposed to -be parallel to those of castration in vertebrates, and received in fact -the name of “parasitic castration.” More recently Geoffrey Smith has -studied this phenomenon in the crab <i>Inachus</i>, infected by the parasite -<i>Sacculina</i>, and has reached the conclusion that the change is not due -to injury or to destruction of the testes, but to a change in the -metabolism of the crab brought about by the parasite.</p> - -<p>Taking Geoffrey Smith’s case of <i>Inachus-Sacculina</i> as typical, the -changes brought about are as follows: The parasites attach themselves to -the young crabs before the external secondary sexual differences have -appeared. In the females, the effect is to cause them to develop -prematurely the distinctively female characters. In the male, on the -other hand, the narrow abdomen of the male changes after a molt into the -broad abdomen of the female, which also develops ovigerous appendages on -its ventral surface like those of the female in every detail. The larger -claw of the male changes into that of the female, which is different in -form as well as in size. Some years ago I ventured to raise the question -as to whether these effects on the male might not be interpreted as -retention of the juvenile characters rather than development of the -female characters in the male. This might appear more especially the -case in the somewhat more juvenile shape of the anterior abdominal -appendages and possibly also in the shape of the broader abdomen; but -Smith has later shown that the results can not be interpreted as -juvenile, for when the changed organs are examined in detail they are -found to differ from the same organs in the juvenile condition, and to -be identical with those of the adult female. I think, therefore, that we -must accept this interpretation of Giard and of Smith as correct. But -Smith goes further and believes that the effects may be carried so far -that eggs develop in the old testes; in other words, that the testis -changes to an ovary. It seems to me that the evidence to support this -last point should be much stronger than that advanced by Smith before we -can accept this interpretation, for we lack the essential control for -this evidence. In only a single case were eggs found—in the testis of a -male that had been infected, but from which the parasite had fallen off, -and which was presumably recovering from the effects of its presence. -Now, it is known that in the testes of some male animals a few eggs may -occasionally be found where there is no suspicion that the animal has -changed its sex. In some crustacea, in scorpions, and in insects, -isolated instances of this kind have been found. Abnormal division<span class="pagenum"><a name="page_91" id="page_91">{91}</a></span> of a -spermatogonial cell, of such a kind that both sex chromosomes (in the -case of insects at least) got into the same cell might be expected to -cause such a cell to become, even in the male, an egg-cell rather than a -sperm-cell. The degenerative changes of the testes in the hermit crab -caused by the parasite might be imagined to favor such abnormal division -with its consequences. More significant, however, is the fact that the -parasite causes the absorption of the ovary when it infects a young -female, so that even all its eggs disappear. In other words, the -parasite is as injurious to the peculiarly female organ as it is to the -testis. Why then, one can not but ask, should an influence that causes -such effects on the ovary first change a male into a female so long as -it is present and then when the parasite has disappeared leave an -influence behind of a kind that causes the ovary to develop—an organ -which the parasite destroys when the parasite is present? Is it not more -probable that only the secondary sexual organs were changed, without -change in sex, the single case of eggs observed being caused in another -way? This point can only be settled by direct experimentation either by -removal of the testis, by injuring it, or by injection, grafting, or -feeding experiments. The extent of the testis and its position make it -impossible to remove it by an operation, as I have found after repeated -attempts. It seemed easier to destroy it by radium. This I have tried to -do, using very powerful tubes, treating the crab (fiddler crabs) for -several hours. The crabs had had one claw removed—the enormously large -one—and were kept until the next molt, that occurred from a week to six -weeks later. In none of the cases was any change produced. The large -claw of the male regenerated, of course, not full size after only one -molt, but after several nearly full size and always with the -peculiarities of the male crab. The abdomen and the appendages were not -changed. Whether the significant cells of the testes, if there are such -cells apart from the germ-cells, were destroyed, can not be told, for as -yet the histological examination of the material has not been made. -Until a successful operation has been done, I think we must hesitate to -accept Smith’s argument, although based as it is on a series of -interesting observations. His speculation is as follows:</p> - -<div class="blockquot"><p>“The reason why <i>Sacculina</i> causes the assumption of the adult -female state in <i>Inachus</i> is found in the facts: (1) that the roots -of <i>Sacculina</i> elaborate a yolk-substance from the blood of -<i>Inachus</i> of a similar nature to that which is elaborated in the -ovaries of an adult <i>Inachus</i>; (2) that in order to elaborate this -yolk-substance the roots take up from the blood of <i>Inachus</i> the -female sexual formation substance, which is the necessary material -for forming the yolk; (3) that the female sexual formative -substance being absorbed by the <i>Sacculina</i> roots is regenerated in -excess; (4) that the presence of the female formative substance -continually circulating in large quantities in the body-fluids of -the infected crabs causes the production of adult female secondary -sexual characters, and, when the parasite dies, of yolk-containing -eggs.”</p></div> - -<p>In brief, the evidence consists in showing that in the parasite a -yolk-substance appears, which Smith says comes from the blood of the -crab<span class="pagenum"><a name="page_92" id="page_92">{92}</a></span> that produces it under the influence of the parasite. -Incidentally, as it were, this is said to be the same yolk-substance -(but no sufficient evidence that it is the same is given) that the egg -stores up inside itself, and it is <i>assumed</i> that it is a formative -substance that causes the cell that gets it (or contains it or secretes -it—details are wanting) to become an egg-cell. It is the excess of this -substance produced by the male crab, while still a male, under the -influence of the parasite, that affects the abdomen and its appendages -in such a way that they assume the female condition. There are too many -assumptions in the argument, some of which are scarcely of a kind that -our knowledge of development, incomplete as it is, can allow us to -accept without more direct evidence in their support, to make this view -very plausible. Until better evidence is forthcoming, I fail to be -convinced by Smith’s interpretation of his facts.</p> - -<p>Into Smith’s and Robson’s interesting observations on the blood of -crabs, described in Smith’s later paper (part 7, 1911), it is not -necessary to enter here, since the evidence taken as a whole offers -little further in support of his view than had been already assumed. The -argument on page 263 should not, however, pass unchallenged. Smith says:</p> - -<div class="blockquot"><p>“It is clear that the old and familiar idea of an internal -secretion produced by the gonad being the stimulus for the -development of the secondary sexual character could not be applied -here, since at the time that the alterations in the secondary -sexual characters take place no ovary is present to give rise to -the required stimulus. It is suggested, therefore, that in some way -the stimulus must reside in the roots of the <i>Sacculina</i>,” etc.</p></div> - -<p>The argument seems to imply that, since the secondary sexual characters -of the female can not be produced by an ovary in the infected male, -therefore the <i>Sacculina</i> must take the place of the ovary. But why make -such a supposition, for if the testes simply keep down the development -of the female characters, as Giard supposes, there is no need either for -an ovary or for a <i>Sacculina</i> to develop them. One might as well argue -that since the cock does not develop the secondary sexual characters of -the hen that an ovary is essential for their development—which is true, -but not in the sense implied.</p> - -<p>Stamati (1888) states that he attempted to remove the testes of adult -crayfish and apparently succeeded, but since no effects are expected -until after a molt occurs (that may not take place for two years or -more), no results were obtained. Injections of the gonads with an acid -failed, since the animals died.</p> - -<h4>E. <span class="smcap">Evidence from Insects.</span></h4> - -<p>In 1899 Oudemans succeeded in finding a method of removing the testes -and ovaries from caterpillars, using a dimorphic species, <i>Ocneria -dispar</i>, the gipsy moth. The results were negative; none of the -secondary sexual characters of the male or female moths or the accessory -organs of copulation were in the least affected by the operation. The -castrated male copulated as readily with the female as did the normal<span class="pagenum"><a name="page_93" id="page_93">{93}</a></span> -male, while the spayed females also behaved as normal individuals of -that sex behave. Kellogg, in 1904, repeated the same operation in the -silkworm moth on a small scale with the same results. Kopec and -Meisenheimer, in 1909, repeated in a more detailed way Oudemans’s work. -A further important addition was made by Kopec and by Meisenheimer. They -transplanted ovaries into a castrated male and testes into a spayed -female. Neither gonad produced any effect on the characters of the other -sex. It is interesting to note that the testes underwent their normal -development in the body of a spayed female, and even in one with the -ovaries present, and that the ovary also underwent normal development in -the body of the male. In other words, there is no intolerance of the -tissue of one sex to the gonad of the other. This result is all the more -unexpected, because other observations have shown that the color of the -blood, and its chemical properties, is quite different in the male and -female moths of certain species.</p> - -<p>In the case of moths, therefore, if these cases be regarded as typical, -the situation from the point of view of sexual selection is much simpler -than in birds in the sense that the secondary sexual characters are -directly the product of the genetic constituents of all the cells, and -not influenced indirectly by the secretions from the testes or the -ovaries. Sexual selection, therefore, if it is an agent in the evolution -of the differences between males and females, has acted on the genetic -complex to produce these effects on either sex without the result being -involved in the condition of the ovary or the testes.</p> - -<p>Regen castrated crickets, <i>Gryllus campestris</i>, in the larval stages and -found no effects on the adult structures. The castrated males chirped -like normal males and mated with the females. Spayed females were like -normal females; they bored holes in the ground, but laid no eggs in -them, of course, as the ovary had been completely removed.</p> - -<p>The only genetic evidence in the group of insects, outside of the -vinegar fly, relating to the secondary sexual inheritance of the -secondary sexual characters is the following important experiments made -by Foot and Strobell:</p> - -<p>The male of one of the bugs, <i>Euchistus variolarius</i>, has a black spot -on the end of the abdomen—a spot that is not present in the female. -Foot and Strobell crossed a female of this species to another bug, <i>E. -servus</i>, that lacks the spot in both sexes. The daughters had no spot, -the sons a faint spot less developed than in <i>variolarius</i>. These inbred -gave (in F₂) 249 females without a spot, 107 males with a spot, and 84 -males without a spot. The results are explicable on the view that a -single dominant Mendelian factor, not-sex-linked, causes the spot in the -males, but the presence of the gene in the female produces no effect. -The effect, therefore, is sex-limited, <i>i. e.</i>, its expression is -determined by the rest of the complex male or female.</p> - -<p>The very important breeding experiments carried out by Goldschmidt on -varieties of the gipsy moth should be referred to in this<span class="pagenum"><a name="page_94" id="page_94">{94}</a></span> connection, -but as I have recently reviewed these results in the paper on -gynandromorphs written in collaboration with C. B. Bridges,<a name="FNanchor_19_19" id="FNanchor_19_19"></a><a href="#Footnote_19_19" class="fnanchor">[19]</a> I need -only refer to that account here.</p> - -<div class="blockquot"><p class="c">[Note added April 21, 1919.]</p> - -<p>Shortly after the preceding paper was finished a theses by A. -Pézard on the secondary sexual characters of birds reached me. In -it the author gives an account of a number of experiments that he -has made with poultry and with pheasants. His description of the -changes that take place after castration are more exact and more -detailed than any other so far recorded; but in general the results -obtained by Pézard, through castration, are the same as those that -had been obtained by others. Castration of 4 male silver pheasants -are reported. No change in the plumage results, although the -changes that take place in the comb and wattles are the same in -kind as those observed in fowls. The sexual instincts and -peculiarities of the voice and their belligerency are also lost. -Similarly 4 golden pheasants that were operated on gave the same -results.</p> - -<p>Three pheasants with mixed plumage (<i>Phasianus colchicus</i>) were -examined. Their testes proved, on histological examination, to be -imperfectly developed. It is not evident what relation existed -between the facts and the mixed plumage. The suggestions made by -Pézard seem inadequate to cover the cases.</p> - -<p>Testicular tissue transplanted into castrated cocks whose comb, -wattles, etc., had undergone retrogressive changes brought about a -return to the normal conditions after an interval during which the -implanted nodules had begun to regenerate.</p> - -<p>Testicular extract from the cryptorchid testes of swine was -injected into castrated cocks. In one case this resulted in a rapid -growth in size of the comb, which, after 2 months, had reached its -full size. Cessation of the injections led immediately to a -cessation of growth. Before injection the bird exhibited the -pacifistic characteristics of the capon, but the injections brought -out little by little the aggressive behavior of the normal male. -The voice reappeared and “nous assistons á une véritable crise de -puberte.”</p> - -<p>A histological study of the testes of the fowl and of pheasants -showed that much connective tissue is characteristic of young -birds. In the adult cock, and during the mating season of the -pheasant, the connective tissue becomes largely crowded out by the -enlargement of the tubules. Pézard concludes that the -“interstitial” cells in birds have nothing to do with the secondary -sexual characters, but that these come rather under the influence -of the germinal cycle of cells of the testes. The submergence of -the connective-tissue cells of pheasants during the breeding-season -and their reappearance during the rest of the year might appear to -have some relation to the facts that I have recently described in -Sebrights, but as the nuptial plumage of the male remains the same -throughout the year we can not ascribe any direct influence to this -tissue. Nevertheless, the different tissues of the testes in birds -that show seasonal dimorphism of plumage should be carefully -examined.</p> - -<p>Pézard made a few observations on hens whose ovary had been -removed. His results are in accord with those of Goodale, except -that he thinks that the ovary has no influence on the erectile -organs (comb, etc.) which acquire in the spayed bird the same -<i>length</i> as that of the normal female.</p> - -<p>Two hens showing male characteristics and a pheasant similarly -affected are described. In all three cases an examination of the -ovary was found to be undeveloped or abnormal.</p></div><p><span class="pagenum"><a name="page_95" id="page_95">{95}</a></span></p> - -<h2><a name="PART_IV" id="PART_IV"></a>PART IV.<br /><br /> -SUMMARY AND CONCLUSIONS.</h2> - -<p>1. The two principal results obtained were: (<i>a</i>) that castration of -hen-feathered Sebright males causes them to develop the full plumage -characteristic of the cock-bird; (<i>b</i>) that complete hen-feathering is -due to two dominant Mendelian genes.</p> - -<p>2. A striking change takes place when the Sebright male is castrated -(<a href="#plt_1">plate 1</a>, figs. 3, 4; <a href="#plt_3">plate 3</a>, fig. 1). The new feathers on the upper -surface of the head, neck, back, wings, rump, and tail-coverts assume a -different color and distribution of their pigment; they take on a new -shape, and in those regions where in the cock the barbules are absent -from a part of the margin of the feather, the same absence occurs in the -castrated birds. Such feathers are present on the neck, back, wing-bow, -and rump. The transition is shown in the figures in <a href="#plt_6">plate 6</a>, where for -comparison one of the old and one of the new feathers lie side by side. -The tail-coverts in the hen-feathered bird are short, and like those in -the hen do not cover the true tail. After castration they become -excessively long—longer, in fact, than in many cocks—and cover the -true tail feathers. The tail feathers themselves, moreover, become -increased in length, as do the posterior row of feathers of the -wing-coverts. On the breast and sides the change is less marked. The -castrated Sebright loses his erect carriage, but how far this is due to -the changes in his plumage and how far is real (as a result of a new -balance due possibly to the lengthening tail and its coverts) I can not -decide.</p> - -<p>3. While castration causes the hen-feathered male to make additions in -color, length, and size of many feathers, it causes at the same time the -other retrogressive changes characteristic of the capon (a castrated -cock-feathered bird); the comb and wattles shrink and become pale, the -birds almost cease crowing, and become timid. They do not make much -effort to mate with the hens, but when they do they show the usual -copulatory reactions.</p> - -<p>4. If feathers are removed at the time of castration, the new feathers -show the full effect of the removal of the testes, although they must -have begun to develop immediately afterward. It is suggested that by -means of this delicate test the time relations of the internal secretion -can be profitably studied.</p> - -<p>5. Feathers that may have started their development at the time of the -operation show the old influence at the tip of the feathers (<a href="#plt_10">plate 10</a>) -and the new one in the rest of the feather. The change is abrupt, -although the transition is perfect.</p> - -<p>6. Incomplete castration of the hen-feathered male leads to smaller -changes in the same direction than those following complete castration.</p> - -<p>Where such small pieces of the testis were left that complete -cock-feathering followed, the bird slowly changed back to -hen-feathering<span class="pagenum"><a name="page_96" id="page_96">{96}</a></span> as the testes began to regenerate. When the regenerated -pieces were removed the bird became cock-feathered again.</p> - -<p>7. One Sebright male whose testes appear to have been completely removed -did not change the character of the plumage. No testes were found on -autopsy. It is suggested that some other endocrine organs have taken -over the function of the testes, but as yet none such can be indicated.</p> - -<p>8. In one case an old hen-feathered (F₁) male began to change over to -cock-feathering. It was found that his testes had dwindled (probably -through disease) to very small size (10 by 5 mm.).</p> - -<p>9. The F₁ male of the cross between the Sebright and game is also -hen-feathered (<a href="#plt_2">plate 2</a>, fig. 1). After castration he becomes -cock-feathered (<a href="#plt_2">plate 2</a>, fig. 4) and shows thereby the genetic type of -the heterozygous cock-feathered class in which his hen belongs. The -change in this male is even more striking than that in the Sebright. The -change in the individual feathers is shown in <a href="#plt_7">plate 7</a>, figs. 1 and 1<i>a</i>.</p> - -<p>10. Three types of F₂ hen-feathered castrated males are shown in plate -2, figure 3, and <a href="#plt_3">plate 3</a>, figure 3 and figure 4. The first was a dark -bird that changed to a lighter red above. The third a gray bird that -became bright red; the second was a light yellow that became deep -yellow, etc. The class of hens to which such males belong, as -cock-feathered birds, can thus be found out by castration. In this way -the F₂, and back-cross, hen-feathered cocks can be classified with the -corresponding F₂ cock-feathered males.</p> - -<p>11. In the F₂ generation, made up of birds from the direct and -reciprocal crosses taken together, there were 29 hen-feathered and 26 -cock-feathered males. In the back-cross (F₁ hen by game male) the -classes were 2 and 7. The results seem in better accord with the -assumption that two factors are present in the Sebright that stand for -hen-feathering; that either alone will give hen-feathered birds -(intermediate type?), but that both together give the extreme type of -hen-feathering seen in the Sebright.</p> - -<p>12. The difference in color in the two races (Sebright and Black -Breasted Game bantams) is very great. The former have almost uniformly -laced feathers, while the latter has the varied plumage of the -jungle-fowl. The game is strongly dimorphic in color and color-pattern; -the Sebright has the same type of coloration and pattern both in the -male and female, but this is deceptive, as castration shows, because the -castrated male is as strikingly different from the normal Sebright -female as is the cock of other birds from the hen. The resemblance of -male and female in this race is due to the suppression of the true male -plumage by something produced in the testes. Therefore the heredity of -dimorphism resolves itself here into the problem of the heredity of -hen-feathering. That the female Sebright has the same genetic factors as -the male is shown by the fact that she trans<span class="pagenum"><a name="page_97" id="page_97">{97}</a></span>mits hen-feathering in the -same way as does the male, and also by the fact, as Darwin pointed out, -that an old female Sebright whose ovaries had degenerated developed not -the hen-feathered plumage of her own cock, but cock-feathered plumage -like that of most male poultry.</p> - -<p>13. The color of the F₁ birds is shown in <a href="#plt_2">plate 2</a>, figs. 1 and 2. In -general, the feathers are stippled, black and light yellow being the two -most conspicuous ingredients. Since hen-feathering dominates, the -dimorphism is absent, or at least is so slight as to not attract -attention—little more, in fact, than in the Sebright race. The carriage -of the male is like that of the Sebright male. The F₁ male and female -are alike in the direct cross and the reciprocal, or at least no -conspicuous difference is found between the two classes of hens, -indicating that no important sex-linked factors are involved in the -cross.</p> - -<p>14. The F₂ birds show a great variety of color and pattern, but those -obtained can be approximately grouped into 16 classes. The classes are, -however, admittedly not uniform, indicating minor factors not here -reckoned with. The classification of the hens is easiest; the F₂ -hen-feathered males can then in many cases be referred to the proper -classes; the F₂ cock-feathered males can not be accurately classified -with their corresponding hens, except in the case of those that resemble -the two P₁ males, the F₁ male, and those that castration experiments of -the hen-feathered males have shown to belong to certain hen types.</p> - -<p>15. Despite the admitted difficulties of classification, it is suggested -that three factor-pairs of differences will cover the main color classes -seen in the F₂ and in the back-cross. One or two of these seem to be -incompletely dominant, since the F₁ birds are not like either parent in -any single character, nor are they like the wild type in so far as this -is represented by the game.</p> - -<p>16. A histological examination of the testis of the male Sebright by -Boring and Morgan has shown that it contains cells like those present in -the ovary of all breeds of poultry. These cells are called luteal cells -by Pearl and Boring, from their resemblance to the cells of that name -found in the corpora lutea of mammals. In the mammals similar cells are -supposed to produce internal secretions that act as hormones. Their -function in the female bird is unknown, but the fact that after the -removal of the ovary the female develops the secondary sexual plumage of -the male suggests that some secretion from these cells performs this -function. Their occurrence in the male Sebright and their complete -absence, or paucity, in the males of other races supports strongly the -view that these cells are concerned with the suppression of the -secondary sexual plumage.</p> - -<p>17. While in mammals the interstitial cells have been supposed to -produce an internal secretion that causes the development of some of the -secondary sexual characters of the male, and the fuller elaboration of -others, in birds no such connection exists, if we except the case<span class="pagenum"><a name="page_98" id="page_98">{98}</a></span> of -the Sebright. Castration of ordinary males does not affect deleteriously -the secondary sexual plumage (although it does the comb, behavior, -etc.), in fact may even enhance their effects. But, while in the mammal -a secretion is necessary for the full development of the secondary -sexual characters, in the Sebright a secretion inhibits certain of them. -What element in the ordinary bird and in the Sebright causes the full -development of the comb, wattles, sexual behavior, etc., is not known. -Possibly it is the sexual elements themselves, but possibly it is a -secondary influence of the luteal cells producing a contrary effect on -these parts from its effects on the feathers; but possibly more than one -kind of secretory cell is present in the testis of the cock.</p> - -<p>18. The causes of the development of the secondary sexual characters are -seen to be of such diverse physiological kinds that one may well -hesitate to apply the same explanation as to their evolution. In fact, -it is pointed out that several of the theories that have been suggested -run counter to the conditions that bring about the development of the -secondary sexual characters.</p> - -<p>19. An attempt is made to give a critical review of Darwin’s theory of -sexual selection in the light of the modern genetic and operative -results on the secondary sexual characters of the vertebrates. It is -pointed out that far from extending the general theory in its -applications, the modern work has shown in the first place that the -underlying conditions that call forth the development of the secondary -sexual differences are so diverse in the different groups of animals -that it is a priori very unlikely that this evolution can have been -directed by the same external agent, such as the choice of the female, -for such an assumption carries with it in several cases other -implications concerning the causes of the suppression of these same -characters in the female herself, etc. In the second place, it is -pointed out that the problem of the excessive development of certain -characters in the male whose genes are present in both sexes no longer -oppresses us as it did Darwin, for it has been shown both by the genetic -and by the operative work that a single factorial difference may be at -the root of exceedingly great differences in the individual. Such -results, while they admittedly do not <i>in most cases</i> tell us that the -differences involved have arisen at a single progressive step, show us -nevertheless that such differences may depend on very simple initial -differences, and if so, the entire problem becomes enormously -simplified. To Darwin the excessive development of color and -ornamentation appeared due to a long, slow process of evolution -laboriously brought about by the female through selection of those males -a little more ornamented than their fellows. To-day we have found out -that in many cases the genetic composition of a male with such -ornamentation and of a female without it may be almost identical, except -that the genes in one chromosome are duplex in one sex and simplex in -the other. Owing to this initial difference, the<span class="pagenum"><a name="page_99" id="page_99">{99}</a></span> female in birds -produces an internal secretion that suppresses in her the ornamentation -shown by the male, and in the mammal an internal secretion produced by -the testes causes the full development in the male of the secondary -sexual characters. If, as seems probable, these secretions are some -particular kind of substance, the condition that led to their appearance -historically need not have been very complex; and if not, the problem -appears simplified. It still remains to give some reasonable explanation -as to why such substances should continue to be produced if their -products—the secondary sexual characters—possess no “beauty” for the -female. Here more work is necessary, but the modern genetic point of -view may possibly give an important clue. We are coming to realize more -fully that the hereditary genes generally have more than a single effect -on the characters of the animal. The secondary sexual characters may, -then, be only by-products of genes whose important function lies in some -other direction. If, for example, the secretion produced by the cells of -the male have an important influence on his output of energy, or -strength, or activity, their secondary influence over certain parts of -the body would not call for any further explanation on the modern view -of natural selection. If the secretions of the ovary of the female bird -have some direct relation to her physiological processes that are -important in the development of the oviduct, for instance, it would be a -matter of no importance from an evolutionary point of view if that same -secretion suppresses in her the development of the high color shown by -the male.<span class="pagenum"><a name="page_100" id="page_100">{100}</a></span></p> - -<h2><a name="BIBLIOGRAPHY" id="BIBLIOGRAPHY"></a>BIBLIOGRAPHY.</h2> - -<div class="blockquott"><p><span class="smcap">Alcock, A.</span>, 1892. On the habits of <i>Galasimus annulipes</i>. An. Mag. -Nat. Hist., VI.</p> - -<p><span class="smcap">Ancel, P., et Bouin</span>, 1906. Sur l’effet des injections d’extrait de -glande interstitielle du testicule sur la croissance. Compt. Rend. -Acad. Sc. Paris, CXLII.</p> - -<p><span class="smcap">Arkell, T. R.</span>, 1912. Some data on the inheritance of horns in -sheep. N. H. Agr. Exp. Sta. Bull., 160.</p> - -<p>—— ——, 1912. The nature of the inheritance in sheep. Science, n. -s., XXXV.</p> - -<p>—— ——, and <span class="smcap">C. B. Davenport</span>, 1912. Horns in sheep as a typical -sex-limited character. Science, n. s., XXXV.</p> - -<p><span class="smcap">Bateson, W.</span>, and <span class="smcap">E. R. Saunders</span>, 1902. Experiments with poultry. -Reports Evol. Committee, I, Part II.</p> - -<p>—— ——, <span class="smcap">E. R. Saunders</span>, and <span class="smcap">R. C. Punnett</span>, 1905. Experimental -studies in the physiology of heredity. Reports Evol. Committee, II.</p> - -<p>—— ——, 1906. Poultry. Reports Evol. Committee, III.</p> - -<p>—— ——, 1908. Experimental studies in the physiology of heredity. -Reports Evol. Committee, IV.</p> - -<p>—— ——, and <span class="smcap">R. C. Punnett</span>, 1911. The inheritance of the peculiar -pigmentation of the silky fowl. Jour. of Genetics, III.</p> - -<p>—— ——, 1913. Mendel’s principles of heredity. Cambridge.</p> - -<p><span class="smcap">Baur, E.</span>, 1914. Einführung in die experimentelle Vererbungslehre, -Berlin.</p> - -<p><span class="smcap">Beebe, C. W.</span>, 1908. Preliminary report on an investigation of the -seasonal changes of color in birds. Amer. Nat., XLII.</p> - -<p><span class="smcap">Bergendal, D.</span>, 1888. Über abnorme Formen der ersten abdominalen -Anhänge bei einigen Krebsweibschen. Bihang till K. Svenska -Vet.-Akad. Handlingar, XIV.</p> - -<p><span class="smcap">Bertkau, P.</span>, 1891. Beschreibung eines Arthropodenzwitters. Arch. f. -Nat. ges., LVII.</p> - -<p><span class="smcap">Bond, C. J.</span>, 1913. Some points of genetic interest in regeneration -of the testis after experimental orchectomy in birds. Jour. of -Gen., III.</p> - -<p>—— ——, 1914. On a case of unilateral development of secondary -male characters in a pheasant, with remarks on the influence of -hormones in the production of secondary sexual characters. Jour. of -Gen., III.</p> - -<p><span class="smcap">Boring, Alice M.</span>, 1912. The interstitial cells and the supposed -internal secretion of the chicken testis. Biol. Bull., XXIII.</p> - -<p>—— ——, and <span class="smcap">Raymond Pearl</span>, 1917. Sex studies, IX. Interstitial -cells in the reproductive organs of the chicken. Anat. Record, -XIII.</p> - -<p>—— ——, 1918. Sex studies, X. Hermaphrodite birds. Jour. Exp. -Zool., XXV.</p> - -<p>—— ——, and <span class="smcap">T. H. Morgan</span>, 1918. Lutear cells and hen-feathering. -Jour. of General Physiology, I.</p> - -<p><span class="smcap">Bourne, A. G.</span>, 1884. On certain abnormalities of the common frog. -Quart. Jour. Micro. Science, XXIV.</p> - -<p><span class="smcap">Brandt, A.</span>, 1889. Anatomisches und Allgemeines über die sogenannte -Hahnenfedrigkeit und über anderweitige Geschlechtsanomalien bei -Vögeln. Zeits. f. wiss. Zool., XLVIII.</p> - -<p><span class="smcap">Bresca, G.</span>, 1910. Experimentelle Untersuchungen über die sekundären -Sexualcharaktere der Tritonen. Arch. Entw.-mech., XXIX.</p> - -<p><span class="smcap">Castle, W. E.</span>, 1912. Are horns in sheep a sex-limited character? -Science, n. s., XXXV.</p> - -<p><span class="smcap">Chidester, F. E.</span>, 1911. The mating habits of four species of the -Brachyura. Biol. Bull., XXI.</p> - -<p><span class="smcap">Cholodowsky, N.</span>, 1908. Über den Hermaphroditismus bei -Chermes-Arten. Zool. Anz., XXV.<span class="pagenum"><a name="page_101" id="page_101">{101}</a></span></p> - -<p><span class="smcap">Cilleuls des, J.</span>, 1912. A propos du determinisme des caractères -sexual secondaires chez les oiseaux. Compt. Rend. Soc. Biol., -LXXIII.</p> - -<p><span class="smcap">Cunningham, J. T.</span>, 1908. The heredity of secondary sexual -characters in relation to hormones, a theory of the heredity of -somatogenic characters. Arch. Ent. Med., XXVI.</p> - -<p><span class="smcap">Darwin, Charles</span>, 1868. Animals and plants under domestication.</p> - -<p><span class="smcap">Davenport, C. B.</span>, 1906. Inheritance in poultry. Carnegie Inst. -Wash. Pub. No. 52, 1908.</p> - -<p>—— ——, 1909. Inheritance of characteristics in domestic fowl. -Carnegie Inst. Wash. Pub. No. 121, 1909.</p> - -<p>—— ——, 1911. Another case of sex-limited heredity in poultry. -Proc. Soc. Exp. Biol., Med., IX.</p> - -<p>—— ——, 1912. Sex-limited inheritance in poultry. Jour. Exp. -Zool., XIII. 1912.</p> - -<p><span class="smcap">Dittrich, V. R.</span>, 1888. Über Andrena praecox ♀ und <i>Astacus -fluviatilis</i> ♀ mit teilweise männlichen Kennzeichen. Zeit. f. Ent., -XIII.</p> - -<p><span class="smcap">Durham, F. M.</span>, and <span class="smcap">D. C. E. Marryat.</span>, 1908. Note on the inheritance -of sex in canaries. Reports Evol. Committee, IV.</p> - -<p><span class="smcap">Foges, Arthur</span>, 1903. Zur Lehre von den secundären -Geschlechtscharakteren. Arch. f. Phys., 93.</p> - -<p><span class="smcap">Fowler, C. H.</span>, 1894. Notes on some specimens of antlers of the -fallow deer, showing continuous variation and the effects of total -or partial castration. Proc. Zool. Soc. London.</p> - -<p><span class="smcap">Geddes, A. C.</span>, 1910. Abnormal bone growth in the absence of -functioning testicles. Proc. Roy. Soc. of Edinburgh, XXXI.</p> - -<p><span class="smcap">Giard, A.</span>, 1904. Comme la castration agit-elle sur les caractères -sexuels secondaires? Compt. Rend. Soc. Biol., LVI.</p> - -<p><span class="smcap">Gissler, C. F.</span>, 1881. Description of a hermaphroditic phyllopod -crustacean (<i>Eubranchipus</i>). Am. Nat., XV.</p> - -<p><span class="smcap">Goodale, H. D.</span>, 1909. Sex and its relation to the barring factor in -poultry. Science, XXIX.</p> - -<p>—— ——, 1910. Some results of castration in ducks. Biol. Bull., -XX.</p> - -<p>—— ——, 1910. Breeding experiments with poultry. Proc. Soc. Exp. -Biol. Med., VII.</p> - -<p>—— ——, 1911. Studies in hybrid ducks. Journ. Exp. Zool., XX.</p> - -<p>—— ——, 1913. Castration in relation to the secondary sexual -characters of Brown Leghorns. Am. Nat., XLVII.</p> - -<p>—— ——, 1916. A feminized cockerel. Journ. Exp. Zool., XX.</p> - -<p>—— ——, 1916. Gonodectomy. Carnegie Inst. Wash. Pub. No. 243.</p> - -<p>—— ——, 1917. Crossing-over in the sex chromosome of the male -fowl. Science, XLVI.</p> - -<p><span class="smcap">Gurney, J. H.</span>, 1888. On the occasional assumption of the male -plumage by female birds. Ibis, VI.</p> - -<p><span class="smcap">Guyer, M. F.</span>, 1909. The spermatogenesis of the domestic guinea -(<i>Numida meleagris</i> dom.) Anat. Anz., XXXIV.</p> - -<p>—— ——, 1909. The spermatogenesis of the domestic chicken -(<i>Gallus gallus</i> dom.). Anat. Anz., XXXIV.</p> - -<p>—— ——, 1909. On the sex of hybrid birds. Biol. Bull., XVI.</p> - -<p>—— ——, 1909. La livré e du plumage chez les hybrids de pinta de -et de poule. Bull. du Museum. d’hist. Nat. No. 1.</p> - -<p>—— ——, 1910. Accessory chromosome in man. Biol. Bull., XIX.</p> - -<p><span class="smcap">Guthrie, C. C.</span>, 1911. On evidence of some influence in offspring -from engrafted ovarian tissue. Science, XXXIII.</p> - -<p><span class="smcap">Hadley, P. B.</span>, 1913. Studies on inheritance in poultry. 1. The -constitution of the White Leghorn breed. Bull. Agr. Exp. Station of -the Rhode Island State College, No. 155.</p> - -<p>—— ——, 1914. 11. The factor for the black pigmentation in the -White Leghorn breed. Bull. Agr. Exp. Station of the Rhode Island -State College, No. 161.</p> - -<p><span class="smcap">Halban, J.</span>, 1903. Die Entstehung der Geschlechtscharaktere. Arch. -f. Gynäkologie, LXX.<span class="pagenum"><a name="page_102" id="page_102">{102}</a></span></p> - -<p><span class="smcap">Hanau, A.</span>, 1897. Versuche über den Einfluss der Geschlechtsdrüsen -und die secundären Sexualcharactere. Arch. f. ges. Phys., LXV.</p> - -<p><span class="smcap">Harris, J. A.</span>, <span class="smcap">A. F. Blakeslee</span>, and <span class="smcap">W. E. Kirkpatrick</span>, 1918. The -correlation between egg production during various periods of the -year in domestic fowl. Genetics, III.</p> - -<p><span class="smcap">Hegar, A.</span>, 1903. Korrelation der Keimdrüsen und -Geschlechtsbestimmung. Beiträge zur Geburtshilfe und Gynäkologie, -VII.</p> - -<p><span class="smcap">Heinroth, O. Von</span>, 1909. Ein lateral hermaphroditisch gefärbter -Gimpel (<i>Pyrrhula pyrrhula europaea</i>). Ges. Nat. Freunde zu Berlin.</p> - -<p><span class="smcap">Herbst, C.</span>, 1901. Formative Reize in der tierischen Ontogenese. -Leipzig.</p> - -<p><span class="smcap">Herlitzka, A.</span>, 1899. Sul trapiantamento dei testicoli. Arch. f. -Ent.-mec., IX.</p> - -<p><span class="smcap">Holmes, S. J.</span>, 1908. Phototaxis in fiddler crabs and its relation -to theories of orientation. Journ. Comp. Neurol., XVIII.</p> - -<p><span class="smcap">Hudson, W. H.</span>, 1892. The naturalist in La Plata. London.</p> - -<p><span class="smcap">Hull, J. E.</span>, 1918. Gynandry in arachnids. Jour. of Genetics, VII.</p> - -<p><span class="smcap">Hunter, John</span>, 1780. Account of an extraordinary pheasant. Phil. -Trans. Royal Soc. London., LXX.</p> - -<p><span class="smcap">Hurst, C. C.</span>, 1905. Experiments with poultry. Reports Evol. -Committee, II.</p> - -<p><span class="smcap">Jones, E. L.</span>, 1914. The Campine Club, 1914, Year Book (see also -Farm Poultry, June, 1914, page 113).</p> - -<p><span class="smcap">Kellogg, V. L.</span>, 1904. Influence of the primary reproductive organs -on the secondary sexual characters. Jour. Exp. Zool., I.</p> - -<p><span class="smcap">Knappe, E.</span>, 1886. Das biddersche Organ. Morph. Jahrb., XI.</p> - -<p><span class="smcap">Kopěc, S.</span>, 1913. Nochmals über die Unabhängigkeit der Ausbildung -sekundärer Geschlechtscharaktere von den Gonaden bei Lepidopteren. -Zool. Anz., XLIII.</p> - -<p><span class="smcap">Kurz, W.</span>, 1874. Über androgyne Missbildung bei Cladoceren. Sitz. d. -math.-nat.-wiss. Klasse. d. Akadem. Wissensch., Wien., LXIX.</p> - -<p><span class="smcap">Lefevre, G.</span> Sex-limited inheritance in poultry. Aust. Record, XI, -p. 499, 1916-17.</p> - -<p><span class="smcap">Lillie, F. R.</span>, 1917. The free-martin; a study of the action of -sex-hormones in the fœtal life of cattle. Jour. Exp. Zool., XXIII.</p> - -<p><span class="smcap">Lippincott, W. A.</span>, 1918. The case of the blue Andalusian. Amer. -Nat., LII.</p> - -<p><span class="smcap">Loewy, A.</span>, 1903. Neuere Untersuchungen zur Physiologie der -Geschlechtsorgane. Ergebn. d. Phys. II. Jabrg., 1. Abt., Biochemie.</p> - -<p><span class="smcap">Loibel</span>, 1901. Grenouille femelle presentent toutes les caractères -sexuels secondaires du male. Comptes Rend. Soc. Biol.</p> - -<p><span class="smcap">McEwen, R. S.</span>, The reactions to light and to gravity in -<i>Drosophila</i> and its mutants. Jour. Exp. Zool., XXV.</p> - -<p><span class="smcap">Marshall, A. M.</span>, 1884. On certain abnormal conditions of the -reproductive organs of the frog. Jour. Anat. and Physiol., VIII.</p> - -<p><span class="smcap">Marshall, F. H. A.</span>, 1910. The physiology of reproduction. London.</p> - -<p>—— ——, 1910. Physiology of Reproduction. New York.</p> - -<p><span class="smcap">de Meijere, J. C. H.</span>, 1911. Über getrennte Vererbung der -Geschlechter. Arch. Rass. Gesell. VIII.</p> - -<p><span class="smcap">Mayer, A. G.</span>, 1897. A new hypothesis of seasonal-dimorphism in -Lepidoptera. Psyche, VIII.</p> - -<p>—— ——, 1900. On the mating instinct in moths. Psyche, IX.</p> - -<p><span class="smcap">Mazzetti, L.</span>, 1916. I Caretteri sessuali secondari e le cellule -interstitiali del testicolo. Anat. Anz. XXXVIII.</p> - -<p><span class="smcap">Meisenheimer, J.</span>, 1909. Experimentelle Studien zur Soma- und -Geschlechtsdifferenzierung. Jena.</p> - -<p>—— ——, 1911. Über die Wirkung von Hoden-und Ovarial-substanz auf -die sekundären Geschlechtsmerkmale des Frosches. Zool. Anz., -XXXVIII.</p> - -<p><span class="smcap">Möbius, P. J.</span>, 1906. Über die Wirkungen der Kastration. Halle.</p> - -<p><span class="smcap">Montgomery, T. H., Jr.</span>, 1909. Further studies on the activities of -Araneads, II. Proc. Acad. Nat. Sci., Philadelphia.<span class="pagenum"><a name="page_103" id="page_103">{103}</a></span></p> - -<p><span class="smcap">Montgomery, T. H.</span>, Jr., 1910. The significance of the courtship and -secondary sexual characters of Araneads. Amer. Nat., XLIV.</p> - -<p><span class="smcap">Morgan, T. H.</span>, 1905. An alternative interpretation of the origin of -gynandromorphous insects. Science, XXI.</p> - -<p>—— ——, 1907. Experimental Zoology. New York.</p> - -<p>—— ——, 1909. A biological and cytological study of sex -determination in phylloxerans and aphids. Journ. Expr. Zool., VII.</p> - -<p>—— ——, 1913. Heredity and sex. New York.</p> - -<p>—— ——, 1914. Mosaics and gynandromorphs in <i>Drosophila</i>. Proc. -Soc. Biol. and Med., XI.</p> - -<p>—— ——, 1914. Sex-limited and sex-linked inheritance. Amer. -Natur., XLVIII.</p> - -<p>—— ——, 1915. Demonstration of the appearance after castration of -cock-feathering in a hen-feathered cockerel. Proc. Soc. Exp. Biol. -and Med., XIII.</p> - -<p>—— ——, 1917. The theory of the gene. Amer. Natur., LI.</p> - -<p>—— ——, 1918. A critique of the theory of evolution. New York.</p> - -<p>—— ——, 1918. Concerning the mutation theory. Scientific Monthly, -May.</p> - -<p>—— ——, 1918. Changes in factors through selection. Scientific -Monthly, June.</p> - -<p>—— ——, 1918. Evolution by mutation. Scientific Monthly, July.</p> - -<p><span class="smcap">Morgan, T. H.</span>, and <span class="smcap">H. D. Goodale</span>, 1912. Sex-linked inheritance in -poultry. Annals New York Acad. Science, XXII.</p> - -<p><span class="smcap">Müller, R.</span>, 1907. Sexualbiologie. Berlin.</p> - -<p>—— ——, 1908. Das Problem der sekundären Geschlechtsmerkmale und -die Tierzucht.</p> - -<p><span class="smcap">Myers, B. D.</span>, 1916. Histological changes in testes following -vasectomy. Anat. Record X, 1916.</p> - -<p><span class="smcap">Nicholls, F.</span>, 1731. An account of the hermaphrodite lobster. Phil. -Trans. London, XXXVI.</p> - -<p><span class="smcap">Nussabaum, M.</span>, 1905. Einfluss des Hodensekrets auf die Entwicklung -der Brunstorgane des Landfrosches. Verhandl. d. Naturhist. Vereins. -f. Rheinl.-Westfalen, LXII.</p> - -<p>—— ——, 1905. Innere Sekretion und Nerveneinfluss. Ergebn. Anat. -und Ent.-ges., XV.</p> - -<p>—— ——, 1909, Hoden und Brunstorgane des braunen Landfrosches -(<i>Rana fusca</i>). Arch. f. d. gesamte Phys., CXXVI.</p> - -<p><span class="smcap">Oudemans, H. Th.</span>, 1899. Falter aus kastrierten Raupen, wie sie -aussehen und wie sie sich benehmen. Zoolog. Jahrb., Abt. Syst., -XII.</p> - -<p><span class="smcap">Packard, A. S.</span>, 1875. On gynandromorphism in the Lepidoptera. Mem. -Boston Soc. Nat. Hist., II.</p> - -<p><span class="smcap">Painter, T. S.</span>, 1913. On the dimorphism of the males of <i>Mœvia -vittata</i>, a jumping spider. Zool. Jahrb. Abt., Syst., XXXV.</p> - -<p><span class="smcap">Pearl, R.</span>, and <span class="smcap">M. R. Curtis</span>, 1909. Studies on the physiology of -reproduction in the domestic fowl. Biol. Bull., XVII.</p> - -<p>—— ——, 1910. Studies on hybrid poultry. Rept. Maine Agri. Exp. -Station.</p> - -<p>—— ——, and <span class="smcap">F. M. Surface</span>, 1910. On the inheritance of the barred -color pattern in poultry. Arch. Ent.-mech., XXX.</p> - -<p>—— ——,—— ——, 1910. Further data regarding the sex-limited -inheritance of the barred colored pattern in poultry. Science, -XXXII.</p> - -<p>—— ——, and <span class="smcap">A. M. Boring</span>, 1917. Sex studies. Anat. Rec., XIII.</p> - -<p>—— ——, 1917. The corpus luteum in the ovary of the domestic -fowl. Am. Journ. of Anat., XXIII.</p> - -<p><span class="smcap">Pearse, A. S.</span>, 1912. The habits of fiddler crabs. Philippine Journ. -Science, VII.</p> - -<p>—— ——, 1914. On the habits of <i>Uca pugna</i> and <i>Uca pugilator</i>. -Wiscon, Acad. Sci., XVII.</p> - -<p><span class="smcap">Petrunkewitch, A.</span>, 1911. Sense of sight, courtship, and mating in -<i>Dugesiella hentzi</i>, a theraphosid spider from Texas. Zool. Jahrb., -Abst. Syst., XXXI.</p> - -<p><span class="smcap">Pocock, R. I.</span>, 1905. The effects of castration on the horns of the -prongbuck. Proc. Zool. Soc., London.<span class="pagenum"><a name="page_104" id="page_104">{104}</a></span></p> - -<p><span class="smcap">Poll, H.</span>, 1909. Zur Lehre von den sekundären Sexualcharakteren. -Sitz. Ges. Nat. Fr. zu Berlin.</p> - -<p><span class="smcap">Poncet, A.</span>, 1903. De l’influence de la castration sur le -developpement du squelette. Compt. Rend. Soc. Biol., LV.</p> - -<p><span class="smcap">Porter, J. P.</span>, 1906. The habits, instincts and mental powers of -spiders. Jour. Phys., XVII.</p> - -<p><span class="smcap">Potts, F. A.</span>, 1906. The modification of the sexual characters of -the hermit crab caused by the parasite <i>Peltogaster</i>. Q. J. M. Sc., -L.</p> - -<p><span class="smcap">Punnett, R. C.</span>, 1915. Mimicry in butterflies. Cambridge.</p> - -<p><span class="smcap">Punnett, R. C.</span>, and <span class="smcap">P. G. Bailey</span>, 1914. On inheritance of weight in -poultry. Journ. of Genetics, IV.</p> - -<p><span class="smcap">Rasmussen, A. T.</span>, 1917. Seasonal changes in the interstitial cells -of the testis in the woodchuck, <i>Marmota monax</i>. Am. Jour. of -Anat., XXII.</p> - -<p><span class="smcap">Reagan, E. P.</span>, 1916. Some results and possibilities of early -embryonic castration. Anat. Record, II.</p> - -<p><span class="smcap">Reeves, T. P.</span>, 1915. On the presence of interstitial cells in the -chicken’s testis. Anat. Record, IX, 1915.</p> - -<p><span class="smcap">Rogen, J.</span>, 1909. Kastration und ihre Folgeerscheinungen bei -<i>Gryllus campestris</i> L. Zool. Anz., XXXIV.</p> - -<p>—— ——, 1910. Kastration und ihre Folgeerscheinungen bei <i>Gryllus -campestris</i> L. Zool. Anz., XXXV.</p> - -<p><span class="smcap">Ribbert</span>, 1897. Über Veränderungen transplantierter Gewebe. Arch. f. -Ent.-mec., VI.</p> - -<p>—— ——, 1898. Über Transplantation von Ovarium, Hoden und Mamma. -Arch. f. Ent. mech., VII.</p> - -<p><span class="smcap">Romanes, G. J.</span>, 1892. Darwin, and after Darwin, Chicago.</p> - -<p><span class="smcap">Rörig, A.</span>, 1899. Welche Beziehungen bestehen zwischen den -Reproduktionsorganen der Cerviden and der Geweihbildung derselben? -Arch. Entw.-mech., VIII.</p> - -<p>—— ——, 1901. Korrelationen zwischen gewissen Organen der -Cerviden und den Geweihen derselben. Verhandl. internat. Zoolog. -Kongress, Berlin.</p> - -<p><span class="smcap">Shattock, S. G.</span>, and <span class="smcap">C. G. Seligmann</span>, 1906. An example of true -hermaphroditism in the domestic fowl with remarks on the phenomenon -of allopterotism. Trans. Pathol. Soc. of London.</p> - -<p><span class="smcap">Smith, Geoffrey</span>, 1910-1912. Studies in the experimental analysis of -sex. Q. J. Micro. Sci., LIV-LVIII.</p> - -<p>—— ——, 1913. On the effect of castration on the thumb of the -frog, <i>Rana fusca</i>. Zool. Anz., XLI.</p> - -<p><span class="smcap">Smith, Geoffrey</span> and Mrs. <span class="smcap">Haig Thomas</span>, 1913. On sterile and hybrid -pheasants. Jour. Gen., III.</p> - -<p><span class="smcap">Spengel, J. W.</span>, 1876. Das Urogenitalsystem der Amphibien. Arbeit. -Zool. Zootom. in Würzburg, III.</p> - -<p><span class="smcap">Spengel, J. W.</span>, 1889. Zwitterbildung bei Amphibien. Biol. -Centralbl., IV.</p> - -<p><span class="smcap">Spillman, W. J.</span>, 1908. Spurious allelomorphism. Am. Nat., XLII.</p> - -<p>—— ——, 1909. Barring in barred Plymouth Rocks. Poultry, V.</p> - -<p><span class="smcap">Stamati, G.</span>, 1888. Sur l’opération de la castration chez -l’écrevisse. Bull. Soc. Zool. France, XIII.</p> - -<p><span class="smcap">Steinach, E.</span>, 1910. Geschlechtstrieb und echt sekundäre -Geschlechtsmerkmale als Folge der innersekretorischen Funktion der -Keimdrüsen. Zeit. f. Phys., XXIV.</p> - -<p>—— ——, 1912. Willkürliche Umwandlung von Säugetier-Männchen in -Tieren mit ausgeprägt weiblichen Geschlechtscharakteren und -weiblicher Psyche. Archiv. ges. Phys., CXXXXIIII.</p> - -<p><span class="smcap">Stephan, P.</span>, 1902. De l’hermaphoditisme chez les vertébrés. Annal. -de la faculté des sciences de Marseille, XII.<span class="pagenum"><a name="page_105" id="page_105">{105}</a></span></p> - -<p><span class="smcap">Stockard, C. R.</span>, 1911. The fate of the ovarian tissues when planted -on different organs. Arch. f. Ent. Mech., XXXII.</p> - -<p>—— ——, and <span class="smcap">G. N. Papanicolau</span>, 1917. The existence of a typical -œstrous cycle in the guinea-pig. With a study of its histological -and physiological changes. Am. Jour. of Anat., XXII.</p> - -<p><span class="smcap">Stotsenburg, J. M.</span>, 1913. The effect of spaying and semi-spaying -young albino rats (<i>Mus norvegicus albinus</i>) on the growth in body -weight and body length. Anat. Rec., VII.</p> - -<p><span class="smcap">Sturtevant, A. H.</span>, 1911. Another sex-limited character in fowls, -Science, XXXIII.</p> - -<p>—— ——, 1912. An experiment dealing with sex-linkage in fowls. -Journ. Exp. Zool., XII.</p> - -<p>—— ——, 1915. Experiments on sex recognition and the problem of -sexual selection in <i>Drosophila</i>. Journ. of Animal Behav., V.</p> - -<p><span class="smcap">Swift, C. H.</span>, 1914. Origin and early history of the germ cells of -the chick. Amer. Jour, of Anat., XV.</p> - -<p><span class="smcap">Tandler, J.</span>, und <span class="smcap">K. Kellar</span>. Die Körperform der weiblichen -Fruehkastraten des Rindes. Archiv Entw-mech., XXXI.</p> - -<p>—— ——, und <span class="smcap">S. Grosz</span>, 1909, 1910. Ueber den Einfluss der -Castration auf den Organismus. Archiv f. Entw-mech., XXVII, XXIX, -XXX, 1909.</p> - -<p>—— ——, und <span class="smcap">S. Grosz</span>, 1913. Die biologischen Grundlagen der -sekundären Geschlechtscharaktere. Berlin.</p> - -<p><span class="smcap">V. la Valette St. George</span>, 1895. Zwitterbildung beim kleinen -Wassermolch. Arch. Mik. Anat., XLV.</p> - -<p><span class="smcap">Walker, C. E.</span>, 1908. The influence of the testis upon the secondary -sexual characters of fowls. Proc. Royal Soc. of Med.</p> - -<p><span class="smcap">Wallace, A. R.</span>, 1891. Darwinism: An exposition of the theory of -natural selection. London.</p> - -<p>—— ——, 1891. Natural selection and tropical nature. London.</p> - -<p><span class="smcap">Weber, M.</span>, 1890. Über einen Fall von Hermaphroditismus bei -<i>Fringilla coelebs</i>, Zool. Anz., XIII.</p> - -<p><span class="smcap">Yarrell, W.</span>, 1827. On the changes in the plumage of some -hen-pheasants, Phil. Trans., 117.</p> - -<p>—— ——, 1857. On the influence of the sexual organ in modifying -external character. Journ. Proc. Linn. Soc., I.</p></div><p><span class="pagenum"><a name="page_106" id="page_106">{106}</a></span></p> - -<h2><a name="DESCRIPTION_OF_PLATES" id="DESCRIPTION_OF_PLATES"></a>DESCRIPTION OF PLATES.</h2> - -<table border="0" cellpadding="0" cellspacing="0" summary="" -style="border: 2px black solid;margin:auto auto;max-width:50%; -padding:1%;"> -<tr><td><p class="c"><span class="nonvis">In certain versions of this etext [in certain browsers] -clicking on the image of the plate will bring up a larger version.</span></p> - -<p class="c">(etext transcriber's note)</p></td></tr> -</table> - -<p class="c"><span class="smcap"><a href="#plt_1">Plate 1.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Fig. 1.</span> Black-Breasted Game bantam cock. He is typically -cock-feathered, but, as in all games, his hackles and tail-coverts -are shorter than in the cocks of other breeds. The comb was dubbed -by the breeder.</p> - -<p><span class="smcap">Fig. 2.</span> Black-Breasted Game bantam hen. The great contrast in color -between the cock and hen is practically the same as that in the -Brown Leghorn, in most races of Tosa fowls, and in the wild type -<i>Gallus bankiva</i>.</p> - -<p><span class="smcap">Fig. 3.</span> Sebright cock, “hen-feathered.” The short hackles, the -rounded feathers of the back and saddle, and the shortness of the -tail-coverts are characteristic features of these males. For -details of individual feathers from different regions see <a href="#plt_6">plate 6</a> -and <a href="#plt_8">plate 8</a>.</p> - -<p><span class="smcap">Fig. 4.</span> A castrated Sebright male. The drawing was made about a -year after the operation. This particular bird developed a lighter -color than did other castrated Sebrights (see <a href="#plt_3">plate 3</a>, fig. 1). The -entire dorsal region has changed its color, and the feathers have -also changed in shape, length, etc. Note especially the very long -hackle and saddle feathers (for details see <a href="#plt_6">plate 6</a>, fig. 1<i>a</i>) and -the change in the wing-bow. The tail-coverts have also grown long.</p></div> - -<p class="c"><span class="smcap"><a href="#plt_2">Plate 2.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Fig. 1.</span> F₁ hen-feathered male out of Game by Sebright. The -hen-feathering in this bird is as complete as in the Sebright.</p> - -<p><span class="smcap">Fig. 2.</span> F₁ female out of Game by Sebright.</p> - -<p><span class="smcap">Fig. 3.</span> Castrated male originally hen-feathered (292), nearly black -in color, as shown by the individual feathers of <a href="#plt_7">plate 7</a>, figure 2. -After castration the bird has become red above, with black -iridescent tail-coverts, and deeper yellow (or red) below.</p> - -<p><span class="smcap">Fig. 4.</span> Castrated F₁ male, originally like figure 1. Note -especially the change in color of the whole upper surface that has -become red, like that of the jungle-fowl. The tail-coverts have -grown long and are now iridescent black. The breast has changed -least, but is a richer yellow. The comb and wattles and ear lobes -are shrunken, as in all capons.</p></div> - -<p class="c"><span class="smcap"><a href="#plt_3">Plate 3.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Fig. 1.</span> A castrated Sebright male. The operation was performed on a -juvenile bird; the drawing was made a year later. The bird is -typical as to the change in color that takes place in the Sebright. -He was darker red than the bird shown in <a href="#plt_1">plate 1</a>, figure 4. The red -was more mahogany than the picture shows. The original feathers -were like those in <a href="#plt_6">plate 6</a>, fig. 2 (there erroneously referred to -as those of light-colored Sebright).</p> - -<p><span class="smcap">Fig. 2.</span> An F₂ hen-feathered very dark male. The condition of his -plumage at the time of the operation is shown in this figure. The -change that took place after castration is shown in the next -figure.</p> - -<p><span class="smcap">Fig. 3.</span> The change that took place in the bird drawn in figure 2 is -shown here. The whole upper surface has become red, except the -tail-coverts, which are iridescent black. Note also the change in -color on the wing-bow. For the details of the feathers see <a href="#plt_9">plate 9</a>, -figures 1, 1<i>a</i>.</p> - -<p><span class="smcap">Fig. 4.</span> A castrated F₂ bird that had been hen-feathered and had -changed over to cock-feathering, as shown here. The color and the -details of the original hen-feathering are shown in <a href="#plt_9">plate 9</a>, -figures 2 and 2<i>a</i>.</p></div><p><span class="pagenum"><a name="page_107" id="page_107">{107}</a></span></p> - -<p class="c"><span class="smcap"><a href="#plt_4">Plate 4.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Fig. 1.</span> One of the original Black-Breasted Game males used in the -breeding experiments. Compare with colored drawing, <a href="#plt_1">plate 1</a>, figure -1.</p> - -<p><span class="smcap">Fig. 2.</span> A Black-Breasted Game hen used in the breeding experiments. -Compare with colored drawing, <a href="#plt_1">plate 1</a>, figure 2.</p> - -<p><span class="smcap">Fig. 3.</span> A Sebright male. The bird was used in the later -back-crosses and not in the original experiments. He is typical of -his breed.</p> - -<p><span class="smcap">Fig. 4.</span> A Sebright female. One of the birds used in the original -experiments.</p> - -<p><span class="smcap">Fig. 5.</span> An F₁ male. This bird had just reached maturity and was -younger than the one drawn in <a href="#plt_2">plate 2</a>, figure 1.</p> - -<p><span class="smcap">Fig. 6.</span> An F₁ hen of the same age as the last. The pattern changed -a little as the bird became older.</p></div> - -<p class="c"><span class="smcap"><a href="#plt_5">Plate 5.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Fig. 1.</span> An adult Sebright male for comparison with the next figure.</p> - -<p><span class="smcap">Fig. 2.</span> A castrated Sebright male. This photograph shows the same -bird from which the drawing, <a href="#plt_1">plate 1</a>, figure 4, was made. It is the -lighter colored bird referred to in the text.</p> - -<p><span class="smcap">Fig. 3.</span> One of the two F₁ castrated birds. For comparison see the -colored drawing in <a href="#plt_2">plate 2</a>, figure 4.</p> - -<p><span class="smcap">Fig. 4.</span> A castrated Sebright. This bird is darker, and in this -sense more typical than figure 2.</p> - -<p><span class="smcap">Fig. 5.</span> One of the castrated Sebright males which at one time after -castration was as extremely cock-feathered as figure 2, but slowly -“went back” towards hen-feathering, as the figure shows especially -in the hackle and saddle. The details are much better shown in the -feathers photographed in <a href="#plt_8">plate 8</a>, figures 1, 2, 3, 4, 1<i>a</i>, 2<i>a</i>, -3<i>a</i>, 4<i>a</i>, 1<i>b</i>, 2<i>b</i>, 3<i>b</i>, 4<i>b</i>.</p> - -<p><span class="smcap">Fig. 6.</span> The same bird was opened and the regenerated pieces of the -testis removed. He returned later, as shown here, to full -cock-feathering.</p></div> - -<p class="c"><span class="smcap"><a href="#plt_6">Plate 6.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Figs. 1, 1a.</span> Typical old (1) and new (1<i>a</i>) feathers (after -castration) of the same bird. This is the “lighter” male drawn in -<a href="#plt_1">plate 1</a>, figure 4, and photographed in <a href="#plt_5">plate 5</a>, figure 2.</p> - -<p><span class="smcap">Figs. 2, 2a.</span> Typical old (2) and new (2<i>a</i>) (after castration) -feathers of another Sebright. This bird developed after castration -darker feathers than did the last bird. Its feathers were more like -those that other castrated Sebrights developed. Legend on <a href="#plt_6">plate 6</a> -erroneous as far as 2 and 2a are concerned.</p></div> - -<p class="c"><span class="smcap"><a href="#plt_7">Plate 7.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Figs. 1, 1a.</span> Typical old (1) and new (1<i>a</i>) (after castration) -feathers of an F₁ bird. (See <a href="#plt_2">plate 2</a>, figures 1 and 4.)</p> - -<p><span class="smcap">Figs. 2, 2a.</span> Typical old (2) and new (2<small>A</small>) (after castration) -feathers of bird shown in <a href="#plt_3">plate 3</a>, figures 2 and 3 (No. 292).</p></div> - -<p class="c"><span class="smcap"><a href="#plt_8">Plate 8.</a></span></p> - -<div class="blockquott"><p>Typical feathers of “dark” Sebright (1, 2, 3, 4) that after -incomplete castration changed to cock-feathering (1<i>a</i>, 2<i>a</i>, 3<i>a</i>, -4<i>a</i>), then later, as pieces of the testes that had been left -behind in the old situs regenerated, began to go back towards -hen-feathering (1<i>b</i>, 2<i>b</i>, 3<i>b</i>, 4<i>b</i>). The bird was then opened -again, and the regenerated pieces removed, when it again became -cock-feathered (1<i>c</i>, 2<i>c</i>, 3<i>c</i>, 4<i>c</i>), and has so remained for -more than a year.</p></div><p><span class="pagenum"><a name="page_108" id="page_108">{108}</a></span></p> - -<p class="c"><span class="smcap"><a href="#plt_9">Plate 9.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Figs. 1, 1a.</span> Typical feathers of hackle and saddle from -hen-feathered bird (No. 68) <a href="#plt_3">plate 3</a>, figure 2, that changed over to -the cock-feathered bird of <a href="#plt_3">plate 3</a>, figure 3.</p> - -<p><span class="smcap">Figs. 2, 2a.</span> Typical feathers of an F₁ male (2) that changed over -partly as a result of degeneration of his testes, into a -cock-feathered bird (2<small>A</small>). The change was not so great as it is -after castration.</p> - -<p><span class="smcap">Figs. 3, 3a.</span> Typical feathers of Sebright male that slightly -changed towards cock-feathering (old hackle feather missing).</p></div> - -<p class="c"><span class="smcap"><a href="#plt_10">Plate 10.</a></span></p> - -<div class="blockquott"><p><span class="smcap">Figs. 1, 1a.</span> Old (1) and new (1<small>A</small>) wing-coverts of normal Sebright -(1) and castrated (1<small>A</small>).</p> - -<p><span class="smcap">Figs. 2a, 2b.</span> Upper row, to right, “Transitional” hackle feathers -(2<small>A</small>), and a slightly later changed-over feather from wing-bow (2<small>A</small>), -and from back (2<span class="smcap">B</span>). Second row, to left, old (2), transitional -(2<i>a</i>), and changed-over feather (2<i>b</i>), from saddle of Sebright.</p> - -<p><span class="smcap">Fig. 3.</span> Three feathers (tail-covert, wing-bow, and saddle) of an F₂ -hen-feathered game-like male.</p> - -<p><span class="smcap">Fig. 4.</span> A series of breast feathers from an F₂ bird. At one end of -the series (the left) the feather is spangled, at the other barred.</p> - -<p><span class="smcap">Fig. 5.</span> A series of breast feathers from another F₂ bird. At one -end of the series (the left) the feathers are penciled, at the -other end they are barred.</p></div><p><span class="pagenum"><a name="page_109" id="page_109">{109}</a></span></p> - -<div class="figcenter"> -<a name="plt_1" id="plt_1"></a> -<br /> -<a href="images/i_plate01_lg.jpg"> -<img src="images/i_plate01_sml.jpg" width="374" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 1</p> - -<table border="0" cellpadding="0" cellspacing="0" summary="" -style="text-align:left;"> - -<tr><td>1. Black Breasted Game Bantam male. <br /> -2. Female.<br /></td> -<td>3. Sebright male.<br /> -4. Castrated Sebright male.</td></tr> -</table> -</div> -</div> - -<p><span class="pagenum"><a name="page_111" id="page_111">{111}</a></span></p><p><span class="pagenum"><a name="page_110" id="page_110">{110}</a></span></p> - -<div class="figcenter"> -<a name="plt_2" id="plt_2"></a> -<br /> -<a href="images/i_plate02_lg.jpg"> -<img src="images/i_plate02_sml.jpg" width="365" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 2<br /></p> -<table border="0" cellpadding="0" cellspacing="0" summary="" -style="text-align:left;"> - -<tr><td> -1. Hen-feathered F₁ male. <br /> -2. F₁ female.<br /></td><td> -3. Castrated F₂ male.<br /> -4. Castrated F₁ male (Fig. 1).<br /></td> -</tr> -</table> -</div> -</div> - -<p><span class="pagenum"><a name="page_113" id="page_113">{113}</a></span></p><p><span class="pagenum"><a name="page_112" id="page_112">{112}</a></span></p> - -<div class="figcenter"> -<a name="plt_3" id="plt_3"></a> -<br /> -<a href="images/i_plate03_lg.jpg"> -<img src="images/i_plate03_sml.jpg" width="366" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 3<br /></p> - -<table border="0" cellpadding="0" cellspacing="0" summary="" -style="text-align:left;"> - -<tr><td> -1. Castrated Sebright male. <br /> -2. F₂ Hen-feathered male.<br /></td><td> -3. Same castrated.<br /> -4. F₂ Castrated male.<br /></td></tr> -</table> -</div> -</div> - -<p><span class="pagenum"><a name="page_115" id="page_115">{115}</a></span></p><p><span class="pagenum"><a name="page_114" id="page_114">{114}</a></span></p> - -<div class="figcenter"> -<a name="plt_4" id="plt_4"></a> -<br /> -<a href="images/i_plate04_lg.jpg"> -<img src="images/i_plate04_sml.jpg" width="374" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 4<br /></p> - -<table border="0" cellpadding="0" cellspacing="0" summary="" -style="text-align:left;"> - -<tr><td> -1. Black-Breasted Game male.<br /> -2. Black-Breasted Game female. <br /> -3. Sebright male.<br /></td><td> -4. Sebright female.<br /> -5. Hybrid male.<br /> -6. Hybrid female.<br /></td></tr> -</table></div> -</div> - -<p><span class="pagenum"><a name="page_117" id="page_117">{117}</a></span></p><p><span class="pagenum"><a name="page_116" id="page_116">{116}</a></span></p> - -<div class="figcenter"> -<a name="plt_5" id="plt_5"></a> -<br /> -<a href="images/i_plate05_lg.jpg"> -<img src="images/i_plate05_sml.jpg" width="394" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 5<br /></p> -<table border="0" cellpadding="0" cellspacing="0" summary="" -style="text-align:left;"> - -<tr><td> -1. Adult Sebright male.<br /> -2. Castrated Sebright male. <br /> -3. Castrated F₁ male.<br /></td><td> -4. Another castrated Sebright male.<br /> -5. Castrated Sebright male with testes regenerating.<br /> -6. Same as 5 after second removal of testes.</td></tr> -</table> -</div> -</div> - -<p><span class="pagenum"><a name="page_119" id="page_119">{119}</a></span></p><p><span class="pagenum"><a name="page_118" id="page_118">{118}</a></span></p> - -<div class="figcenter"> -<a name="plt_6" id="plt_6"></a> -<br /> -<a href="images/i_plate06_lg.jpg"> -<img src="images/i_plate06_sml.jpg" width="366" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 6<br /></p> - -<p class="c">Feathers of “light” colored Sebright (1, 2) that changed to -cock-feathers after castration (1ªa, 2ª).</p></div> -</div> - -<p><span class="pagenum"><a name="page_121" id="page_121">{121}</a></span><span class="pagenum"><a name="page_120" id="page_120">{120}</a></span></p> - -<div class="figcenter"> -<a name="plt_7" id="plt_7"></a> -<br /> -<a href="images/i_plate07_lg.jpg"> -<img src="images/i_plate07_sml.jpg" width="366" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 7<br /></p> - -<p class="c">Feathers of F₁ hen-feathered male before (1), and after (1ª) castration.</p> - -<p class="c">Feathers of a darker hen-feathered male before (2), and after (2ª) -castration.</p></div> -</div> - -<p><span class="pagenum"><a name="page_123" id="page_123">{123}</a></span><span class="pagenum"><a name="page_122" id="page_122">{122}</a></span></p> - -<div class="figcenter"> -<a name="plt_8" id="plt_8"></a> -<br /> -<a href="images/i_plate08_lg.jpg"> -<img src="images/i_plate08_sml.jpg" width="365" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 8<br /></p> - -<p>Feathers from hen-feathered male Sebright (1, 2, 3, 4) that changed to -cock-feathered male (1ª, 2ª, 3ª, 4ª) after castration; and then began to -go back as the testes regenerated (1ᵇ, 2ᵇ, 3ᵇ, 4ᵇ); then changed again -to cock-feathering after castration (1ᶜ, 2ᶜ, 3ᶜ, 4ᶜ).</p></div> -</div> - -<p><span class="pagenum"><a name="page_125" id="page_125">{125}</a></span><span class="pagenum"><a name="page_124" id="page_124">{124}</a></span></p> - -<div class="figcenter"> -<a name="plt_9" id="plt_9"></a> -<br /> -<a href="images/i_plate09_lg.jpg"> -<img src="images/i_plate09_sml.jpg" width="358" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 9<br /></p> - -<p class="c">Feathers showing complete (1) or incomplete (2 and 3) change from -hen-feathering to cock-feathering (1ª, 2ª, 3ª) after castration.</p></div> -</div> - -<p><span class="pagenum"><a name="page_127" id="page_127">{127}</a></span><span class="pagenum"><a name="page_126" id="page_126">{126}</a></span></p> - -<div class="figcenter"> -<a name="plt_10" id="plt_10"></a> -<br /> -<a href="images/i_plate10_lg.jpg"> -<img src="images/i_plate10_sml.jpg" width="359" height="550" alt="[Image unavailable.]" /></a> -<div class="caption"><p class="c">PLATE 10<br /></p> - -<p class="c">Normal. 1, 2; transitional, 1ª, 2ª, and changed-over feathers, 2ᵇ, of -Sebright, 3, 4 and 5. Feathers from F₂ birds.</p></div> -</div> - -<div class="footnotes"><p class="cb">FOOTNOTES:</p> - -<div class="footnote"><p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> The expectation for 1 dominant and 1 recessive factor is so -nearly the same as for 1 dominant alone that for the numbers obtained no -difference between the two cases could be detected.</p></div> - -<div class="footnote"><p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> There is one other bird, not given in the above list, that -is pure Sebright except that his legs are yellow. Until I find out by -further breeding of the Sebright stock whether yellow legs are present -in it, this case must remain doubtful. On the basis of a two factor -color-difference one Sebright (as to color) is expected in 16 birds, and -one in 64 on a three factor basis. Some Sebrights had been raised along -with the back cross, hence the possibility of contamination.</p></div> - -<div class="footnote"><p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> Provided that the blue classification was based on the -adult plumage and not on down color.</p></div> - -<div class="footnote"><p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">[4]</span></a> If the recessive mutation occurs first in the Z chromosome -of an egg of the female it will not appear in the next generation; then -if it has passed into a male, half his daughters will show it. The -single factor-pair involved is carried by the sex chromosomes ZZ.</p></div> - -<div class="footnote"><p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> One may be either sex-linked or sex-limited so far as the -evidence goes.</p></div> - -<div class="footnote"><p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">[6]</span></a> No mention is made by Baur that a heterozygous male instead -of a pure silver male was used, although the male is made heterozygous -in the formulæ.</p></div> - -<div class="footnote"><p><a name="Footnote_7_7" id="Footnote_7_7"></a><a href="#FNanchor_7_7"><span class="label">[7]</span></a> For activity and pugnacity in hummingbirds, see Tropical -Nature, pp. 130, 213.</p></div> - -<div class="footnote"><p><a name="Footnote_8_8" id="Footnote_8_8"></a><a href="#FNanchor_8_8"><span class="label">[8]</span></a> The Naturalist in La Plata, W. H. Hudson, London, 1892, pp. -269-270.</p></div> - -<div class="footnote"><p><a name="Footnote_9_9" id="Footnote_9_9"></a><a href="#FNanchor_9_9"><span class="label">[9]</span></a> Proceedings of the Zoological Society of London, 1885, p. -431, Quelques remarques sur le dimorphisme sexuel. Jean Stolzmann.</p></div> - -<div class="footnote"><p><a name="Footnote_10_10" id="Footnote_10_10"></a><a href="#FNanchor_10_10"><span class="label">[10]</span></a> George W. and Elizabeth G. Peckham. Observations on Sexual -Selection in Spiders of the Family Attidæ. Nat. Hist. Soc. of Wisconsin, -Vol. I, 1889, pp, 46, 47.</p></div> - -<div class="footnote"><p><a name="Footnote_11_11" id="Footnote_11_11"></a><a href="#FNanchor_11_11"><span class="label">[11]</span></a> <i>Loddigesia mirabilis</i> has the tail about three times as -long as the body. Similar modifications are found in the genera -<i>Sappho</i>, <i>Cynanthus</i>, <i>Lesbia</i>, <i>Stegnura</i>, <i>Discura</i>, <i>Gouldia</i>, <i>et -al.</i></p></div> - -<div class="footnote"><p><a name="Footnote_12_12" id="Footnote_12_12"></a><a href="#FNanchor_12_12"><span class="label">[12]</span></a> Among the most remarkable of this wonderful family are the -nine species of coquettes (<i>Lophornis</i>), which have elongated feathers, -with metallic tips, springing from the sides of the neck; some have also -beautiful crests. (George W. and Elizabeth G. Peckham, Additional -Observations on Sexual Selection in Spiders of the Family Attidæ, Nat. -Hist. Soc. of Wisconsin, 1889, vol. I, pp. 141, 142.)</p></div> - -<div class="footnote"><p><a name="Footnote_13_13" id="Footnote_13_13"></a><a href="#FNanchor_13_13"><span class="label">[13]</span></a> Tropical Nature, p. 210. The italics are ours.</p></div> - -<div class="footnote"><p><a name="Footnote_14_14" id="Footnote_14_14"></a><a href="#FNanchor_14_14"><span class="label">[14]</span></a> A. H. Sturtevant, Experiments on Sex Recognition and the -Problem of Sexual Selection in <i>Drosophila</i>. Journ. Animal Behavior, -Sept.-Oct. 1915, vol. 5, No. 5, pp. 352, 353.</p></div> - -<div class="footnote"><p><a name="Footnote_15_15" id="Footnote_15_15"></a><a href="#FNanchor_15_15"><span class="label">[15]</span></a> In the eland as well as in the reindeer, in which both -sexes have horns that begin in the latter at least to develop before the -gonads ripen, it is stated that castration does not prevent the -development of the horns in the male, but whether they are as large as -in the normal male is apparently not definitely stated.</p></div> - -<div class="footnote"><p><a name="Footnote_16_16" id="Footnote_16_16"></a><a href="#FNanchor_16_16"><span class="label">[16]</span></a> Yarrell also states that after the fallow buck has reached -the height of its maturity and has 6 prongs in its antler, removal of -one testis causes the next antler to have but 5 prongs.</p></div> - -<div class="footnote"><p><a name="Footnote_17_17" id="Footnote_17_17"></a><a href="#FNanchor_17_17"><span class="label">[17]</span></a> It might be supposed that this bird was really a cock -which had been changed for a hen; but the following facts put this -matter beyond a doubt: First, there was no other pyed pea-fowl in the -country. Secondly, the hen had knobs on her toes, which were the same -after her change. Thirdly, she was as small after the change as before, -therefore too small for a cock. Fourthly, she was a favorite bird, and -was generally fed by the lady, and used to come for her meat, which she -still continued to do after the change in the feathers.</p></div> - -<div class="footnote"><p><a name="Footnote_18_18" id="Footnote_18_18"></a><a href="#FNanchor_18_18"><span class="label">[18]</span></a> See the latter also for references to <i>Lacertilia</i> and -<i>Chelonia</i>.</p></div> - -<div class="footnote"><p><a name="Footnote_19_19" id="Footnote_19_19"></a><a href="#FNanchor_19_19"><span class="label">[19]</span></a> Carnegie Inst. Wash. Pub. No. 278, 1918.</p></div> - -</div> - -<hr class="full" /> - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of The Genetic and the operative evidence -relating to secondary sexual character, by Thomas Hunt Morgan - -*** END OF THIS PROJECT GUTENBERG EBOOK THE GENETIC *** - -***** This file should be named 57460-h.htm or 57460-h.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/5/7/4/6/57460/ - -Produced by Larry B. Harrison, Bryan Ness, Chuck Greif and -the Online Distributed Proofreading Team at -http://www.pgdp.net (This file was produced from images -generously made available by The Internet Archive/American -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. Special rules, -set forth in the General Terms of Use part of this license, apply to -copying and distributing Project Gutenberg-tm electronic works to -protect the PROJECT GUTENBERG-tm concept and trademark. Project -Gutenberg is a registered trademark, and may not be used if you -charge for the eBooks, unless you receive specific permission. If you -do not charge anything for copies of this eBook, complying with the -rules is very easy. You may use this eBook for nearly any purpose -such as creation of derivative works, reports, performances and -research. They may be modified and printed and given away--you may do -practically ANYTHING with public domain eBooks. Redistribution is -subject to the trademark license, especially commercial -redistribution. - - - -*** START: FULL LICENSE *** - -THE FULL PROJECT GUTENBERG LICENSE -PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK - -To protect the Project Gutenberg-tm mission of promoting the free -distribution of electronic works, by using or distributing this work -(or any other work associated in any way with the phrase "Project -Gutenberg"), you agree to comply with all the terms of the Full Project -Gutenberg-tm License (available with this file or online at -http://gutenberg.org/license). - - -Section 1. General Terms of Use and Redistributing Project Gutenberg-tm -electronic works - -1.A. By reading or using any part of this Project Gutenberg-tm -electronic work, you indicate that you have read, understand, agree to -and accept all the terms of this license and intellectual property -(trademark/copyright) agreement. If you do not agree to abide by all -the terms of this agreement, you must cease using and return or destroy -all copies of Project Gutenberg-tm electronic works in your possession. -If you paid a fee for obtaining a copy of or access to a Project -Gutenberg-tm electronic work and you do not agree to be bound by the -terms of this agreement, you may obtain a refund from the person or -entity to whom you paid the fee as set forth in paragraph 1.E.8. - -1.B. "Project Gutenberg" is a registered trademark. It may only be -used on or associated in any way with an electronic work by people who -agree to be bound by the terms of this agreement. There are a few -things that you can do with most Project Gutenberg-tm electronic works -even without complying with the full terms of this agreement. See -paragraph 1.C below. There are a lot of things you can do with Project -Gutenberg-tm electronic works if you follow the terms of this agreement -and help preserve free future access to Project Gutenberg-tm electronic -works. See paragraph 1.E below. - -1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" -or PGLAF), owns a compilation copyright in the collection of Project -Gutenberg-tm electronic works. Nearly all the individual works in the -collection are in the public domain in the United States. If an -individual work is in the public domain in the United States and you are -located in the United States, we do not claim a right to prevent you from -copying, distributing, performing, displaying or creating derivative -works based on the work as long as all references to Project Gutenberg -are removed. Of course, we hope that you will support the Project -Gutenberg-tm mission of promoting free access to electronic works by -freely sharing Project Gutenberg-tm works in compliance with the terms of -this agreement for keeping the Project Gutenberg-tm name associated with -the work. You can easily comply with the terms of this agreement by -keeping this work in the same format with its attached full Project -Gutenberg-tm License when you share it without charge with others. - -1.D. The copyright laws of the place where you are located also govern -what you can do with this work. Copyright laws in most countries are in -a constant state of change. If you are outside the United States, check -the laws of your country in addition to the terms of this agreement -before downloading, copying, displaying, performing, distributing or -creating derivative works based on this work or any other Project -Gutenberg-tm work. The Foundation makes no representations concerning -the copyright status of any work in any country outside the United -States. - -1.E. Unless you have removed all references to Project Gutenberg: - -1.E.1. The following sentence, with active links to, or other immediate -access to, the full Project Gutenberg-tm License must appear prominently -whenever any copy of a Project Gutenberg-tm work (any work on which the -phrase "Project Gutenberg" appears, or with which the phrase "Project -Gutenberg" is associated) is accessed, displayed, performed, viewed, -copied or distributed: - -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/license - -1.E.2. If an individual Project Gutenberg-tm electronic work is derived -from the public domain (does not contain a notice indicating that it is -posted with permission of the copyright holder), the work can be copied -and distributed to anyone in the United States without paying any fees -or charges. If you are redistributing or providing access to a work -with the phrase "Project Gutenberg" associated with or appearing on the -work, you must comply either with the requirements of paragraphs 1.E.1 -through 1.E.7 or obtain permission for the use of the work and the -Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or -1.E.9. - -1.E.3. If an individual Project Gutenberg-tm electronic work is posted -with the permission of the copyright holder, your use and distribution -must comply with both paragraphs 1.E.1 through 1.E.7 and any additional -terms imposed by the copyright holder. Additional terms will be linked -to the Project Gutenberg-tm License for all works posted with the -permission of the copyright holder found at the beginning of this work. - -1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm -License terms from this work, or any files containing a part of this -work or any other work associated with Project Gutenberg-tm. - -1.E.5. Do not copy, display, perform, distribute or redistribute this -electronic work, or any part of this electronic work, without -prominently displaying the sentence set forth in paragraph 1.E.1 with -active links or immediate access to the full terms of the Project -Gutenberg-tm License. - -1.E.6. You may convert to and distribute this work in any binary, -compressed, marked up, nonproprietary or proprietary form, including any -word processing or hypertext form. However, if you provide access to or -distribute copies of a Project Gutenberg-tm work in a format other than -"Plain Vanilla ASCII" or other format used in the official version -posted on the official Project Gutenberg-tm web site (www.gutenberg.org), -you must, at no additional cost, fee or expense to the user, provide a -copy, a means of exporting a copy, or a means of obtaining a copy upon -request, of the work in its original "Plain Vanilla ASCII" or other -form. Any alternate format must include the full Project Gutenberg-tm -License as specified in paragraph 1.E.1. - -1.E.7. Do not charge a fee for access to, viewing, displaying, -performing, copying or distributing any Project Gutenberg-tm works -unless you comply with paragraph 1.E.8 or 1.E.9. - -1.E.8. You may charge a reasonable fee for copies of or providing -access to or distributing Project Gutenberg-tm electronic works provided -that - -- You pay a royalty fee of 20% of the gross profits you derive from - the use of Project Gutenberg-tm works calculated using the method - you already use to calculate your applicable taxes. The fee is - owed to the owner of the Project Gutenberg-tm trademark, but he - has agreed to donate royalties under this paragraph to the - Project Gutenberg Literary Archive Foundation. Royalty payments - must be paid within 60 days following each date on which you - prepare (or are legally required to prepare) your periodic tax - returns. Royalty payments should be clearly marked as such and - sent to the Project Gutenberg Literary Archive Foundation at the - address specified in Section 4, "Information about donations to - the Project Gutenberg Literary Archive Foundation." - -- You provide a full refund of any money paid by a user who notifies - you in writing (or by e-mail) within 30 days of receipt that s/he - does not agree to the terms of the full Project Gutenberg-tm - License. You must require such a user to return or - destroy all copies of the works possessed in a physical medium - and discontinue all use of and all access to other copies of - Project Gutenberg-tm works. - -- You provide, in accordance with paragraph 1.F.3, a full refund of any - money paid for a work or a replacement copy, if a defect in the - electronic work is discovered and reported to you within 90 days - of receipt of the work. - -- You comply with all other terms of this agreement for free - distribution of Project Gutenberg-tm works. - -1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm -electronic work or group of works on different terms than are set -forth in this agreement, you must obtain permission in writing from -both the Project Gutenberg Literary Archive Foundation and Michael -Hart, the owner of the Project Gutenberg-tm trademark. Contact the -Foundation as set forth in Section 3 below. - -1.F. - -1.F.1. Project Gutenberg volunteers and employees expend considerable -effort to identify, do copyright research on, transcribe and proofread -public domain works in creating the Project Gutenberg-tm -collection. Despite these efforts, Project Gutenberg-tm electronic -works, and the medium on which they may be stored, may contain -"Defects," such as, but not limited to, incomplete, inaccurate or -corrupt data, transcription errors, a copyright or other intellectual -property infringement, a defective or damaged disk or other medium, a -computer virus, or computer codes that damage or cannot be read by -your equipment. - -1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right -of Replacement or Refund" described in paragraph 1.F.3, the Project -Gutenberg Literary Archive Foundation, the owner of the Project -Gutenberg-tm trademark, and any other party distributing a Project -Gutenberg-tm electronic work under this agreement, disclaim all -liability to you for damages, costs and expenses, including legal -fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT -LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE -PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE -TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE -LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR -INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH -DAMAGE. - -1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a -defect in this electronic work within 90 days of receiving it, you can -receive a refund of the money (if any) you paid for it by sending a -written explanation to the person you received the work from. If you -received the work on a physical medium, you must return the medium with -your written explanation. The person or entity that provided you with -the defective work may elect to provide a replacement copy in lieu of a -refund. If you received the work electronically, the person or entity -providing it to you may choose to give you a second opportunity to -receive the work electronically in lieu of a refund. If the second copy -is also defective, you may demand a refund in writing without further -opportunities to fix the problem. - -1.F.4. Except for the limited right of replacement or refund set forth -in paragraph 1.F.3, this work is provided to you 'AS-IS' WITH NO OTHER -WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO -WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE. - -1.F.5. Some states do not allow disclaimers of certain implied -warranties or the exclusion or limitation of certain types of damages. -If any disclaimer or limitation set forth in this agreement violates the -law of the state applicable to this agreement, the agreement shall be -interpreted to make the maximum disclaimer or limitation permitted by -the applicable state law. The invalidity or unenforceability of any -provision of this agreement shall not void the remaining provisions. - -1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the -trademark owner, any agent or employee of the Foundation, anyone -providing copies of Project Gutenberg-tm electronic works in accordance -with this agreement, and any volunteers associated with the production, -promotion and distribution of Project Gutenberg-tm electronic works, -harmless from all liability, costs and expenses, including legal fees, -that arise directly or indirectly from any of the following which you do -or cause to occur: (a) distribution of this or any Project Gutenberg-tm -work, (b) alteration, modification, or additions or deletions to any -Project Gutenberg-tm work, and (c) any Defect you cause. - - -Section 2. Information about the Mission of Project Gutenberg-tm - -Project Gutenberg-tm is synonymous with the free distribution of -electronic works in formats readable by the widest variety of computers -including obsolete, old, middle-aged and new computers. It exists -because of the efforts of hundreds of volunteers and donations from -people in all walks of life. - -Volunteers and financial support to provide volunteers with the -assistance they need, are critical to reaching Project Gutenberg-tm's -goals and ensuring that the Project Gutenberg-tm collection will -remain freely available for generations to come. In 2001, the Project -Gutenberg Literary Archive Foundation was created to provide a secure -and permanent future for Project Gutenberg-tm and future generations. -To learn more about the Project Gutenberg Literary Archive Foundation -and how your efforts and donations can help, see Sections 3 and 4 -and the Foundation web page at http://www.pglaf.org. - - -Section 3. Information about the Project Gutenberg Literary Archive -Foundation - -The Project Gutenberg Literary Archive Foundation is a non profit -501(c)(3) educational corporation organized under the laws of the -state of Mississippi and granted tax exempt status by the Internal -Revenue Service. The Foundation's EIN or federal tax identification -number is 64-6221541. Its 501(c)(3) letter is posted at -http://pglaf.org/fundraising. Contributions to the Project Gutenberg -Literary Archive Foundation are tax deductible to the full extent -permitted by U.S. federal laws and your state's laws. - -The Foundation's principal office is located at 4557 Melan Dr. S. -Fairbanks, AK, 99712., but its volunteers and employees are scattered -throughout numerous locations. Its business office is located at -809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887, email -business@pglaf.org. Email contact links and up to date contact -information can be found at the Foundation's web site and official -page at http://pglaf.org - -For additional contact information: - Dr. Gregory B. Newby - Chief Executive and Director - gbnewby@pglaf.org - - -Section 4. Information about Donations to the Project Gutenberg -Literary Archive Foundation - -Project Gutenberg-tm depends upon and cannot survive without wide -spread public support and donations to carry out its mission of -increasing the number of public domain and licensed works that can be -freely distributed in machine readable form accessible by the widest -array of equipment including outdated equipment. Many small donations -($1 to $5,000) are particularly important to maintaining tax exempt -status with the IRS. - -The Foundation is committed to complying with the laws regulating -charities and charitable donations in all 50 states of the United -States. Compliance requirements are not uniform and it takes a -considerable effort, much paperwork and many fees to meet and keep up -with these requirements. We do not solicit donations in locations -where we have not received written confirmation of compliance. To -SEND DONATIONS or determine the status of compliance for any -particular state visit http://pglaf.org - -While we cannot and do not solicit contributions from states where we -have not met the solicitation requirements, we know of no prohibition -against accepting unsolicited donations from donors in such states who -approach us with offers to donate. - -International donations are gratefully accepted, but we cannot make -any statements concerning tax treatment of donations received from -outside the United States. U.S. laws alone swamp our small staff. - -Please check the Project Gutenberg Web pages for current donation -methods and addresses. Donations are accepted in a number of other -ways including checks, online payments and credit card donations. -To donate, please visit: http://pglaf.org/donate - - -Section 5. General Information About Project Gutenberg-tm electronic -works. - -Professor Michael S. Hart is the originator of the Project Gutenberg-tm -concept of a library of electronic works that could be freely shared -with anyone. For thirty years, he produced and distributed Project -Gutenberg-tm eBooks with only a loose network of volunteer support. - - -Project Gutenberg-tm eBooks are often created from several printed -editions, all of which are confirmed as Public Domain in the U.S. -unless a copyright notice is included. Thus, we do not necessarily -keep eBooks in compliance with any particular paper edition. - - -Most people start at our Web site which has the main PG search facility: - - http://www.gutenberg.org - -This Web site includes information about Project Gutenberg-tm, -including how to make donations to the Project Gutenberg Literary -Archive Foundation, how to help produce our new eBooks, and how to -subscribe to our email newsletter to hear about new eBooks. - - -</pre> +<div>*** END OF THE PROJECT GUTENBERG EBOOK 57460 ***</div> </body> </html> |