“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.”
“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.”
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.
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.
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.
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.
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.
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.
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.
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.
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 noapparentconnection 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.
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 characteristictraits 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.
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.
Probably a greater difference in the secondary sexual characters is shown in birds than in any other group. It is true that there arespecies, 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.
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:
“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.”[17]“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?“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.”
“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.”[17]
“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?
“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.”
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.
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:
“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:A whistling woman and a crowing henAre neither good for gods nor men.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:Poule qui chante, Prêtre qui danseEt Femme qui parle latin,N’arrivent jamais à belle fin.“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.“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.“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.“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.“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,* * * his big manly voiceTurning again toward childish treble, pipesAnd whistles in his sound.”
“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:
A whistling woman and a crowing henAre neither good for gods nor men.
A whistling woman and a crowing henAre neither good for gods nor men.
A whistling woman and a crowing henAre neither good for gods nor men.
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:
Poule qui chante, Prêtre qui danseEt Femme qui parle latin,N’arrivent jamais à belle fin.
Poule qui chante, Prêtre qui danseEt Femme qui parle latin,N’arrivent jamais à belle fin.
Poule qui chante, Prêtre qui danseEt Femme qui parle latin,N’arrivent jamais à belle fin.
“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.
“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.
“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.
“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.
“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,
* * * his big manly voiceTurning again toward childish treble, pipesAnd whistles in his sound.”
* * * his big manly voiceTurning again toward childish treble, pipesAnd whistles in his sound.”
* * * his big manly voiceTurning again toward childish treble, pipesAnd whistles in his sound.”
Gurney (1888) has recorded several cases in which female birds have assumed male plumage. For instance, he describes a female merganser,Mergus serrator, assuming male plumage that showed no signs of disease in the ovary. Mr. Cecil Smith had a female widgeon (Mareca penelope) 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.
“On May 16th, 1887, a chaffinch (Fringilla cœelebs) 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.“In the ‘Norwich Nat. Trans.,’ an enumeration was given of female Redstarts (Ruticilla phoenicurus) assuming male plumage (l.c.) to which the following may be added: a henR. phoenicurusassuming 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 (R. phoenicurus) in male plumage, which had the ovaries ‘quite perfect and full of eggs’ (cf.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 inRuticilla, but in other genera besides. Why it should happen inRuticilla phoenicurusoftener than in other Passerine birds is hard to explain, but such is evidently the case.”“The same is recorded to have happened five or six times with the female Red-backed Shrike (Lanius colluria); 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.“The following is a list of the species in which one or more instances of females assuming male plumage are ascertained to have occurred:Falco aesalon, fide Scully. (Cf. Sharpe, ‘Cat. Birds Brit. Mus.,’ i, p. 407).Tinnunculus alaudarius, fide Sharpe; col. fig. P. Z. S., 1874, p. 580.Lanius collurio, fide Hoy.Lanius vittatus, fide Blyth.Ruticilla phœnicurus, fide Millais, Clarke and others.Fringilla cœlebs, fide Clarke.Linota cannabina, fide Blyth.Linota rufescens, fide Blyth.Nectarinia asiatica, fide Blyth.Gallus (domestic fowl), fide Yarrell and others; col. fig. “B. of Sherwood,” p. 183.Pavo (peahen), fide Latham; fig. “Synopsis,” ii, pl. 60.Meleagris (Turkey), fide Bechstein.Phasianus colchicus, fide Edwards and others. Of common occurrence in a semi-domesticated state.Thaumalea picta, fide Edwards.Euplocamus nycthemerus, fide Yarrell.Pucrasia nipalensis, fide Blyth.Tetrao tetrix, fide Bond; col. fig. Dresser, “B. of Eur.,” vi, 205.Tetrao urogallus, fide Nilsson; col. fig. “Unser Auer-, Rackel- und Birkwild und seine Abarten,” by A. B. Meyer.Otis tarda, fide Tiedmann.Anas (domestic duck), fide Rowley; col. fig. “Orn. Misc.,” i, p. 118.Anas boschas, fide Hancock; fig. col. “Scandinavisk Fauna,” pl. 163.Fuligula marila, fide Blyth; see also P. Z. S., 1885, p. 246.Mergus serrator, fide Gurney.Mareca penelope, fide Cecil Smith.“Perhaps the Kestrel (Tinnunculus alaudarius) 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.“It is said that the females inOriolusgenerally become as bright as males in time (‘Ibis,’ 1864, p. 412; ‘Field,’ June 24th and July 8th, 1871).”“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 inAnas boschasand others of that tribe.”
“On May 16th, 1887, a chaffinch (Fringilla cœelebs) 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.
“In the ‘Norwich Nat. Trans.,’ an enumeration was given of female Redstarts (Ruticilla phoenicurus) assuming male plumage (l.c.) to which the following may be added: a henR. phoenicurusassuming 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 (R. phoenicurus) in male plumage, which had the ovaries ‘quite perfect and full of eggs’ (cf.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 inRuticilla, but in other genera besides. Why it should happen inRuticilla phoenicurusoftener than in other Passerine birds is hard to explain, but such is evidently the case.”
“The same is recorded to have happened five or six times with the female Red-backed Shrike (Lanius colluria); 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.
“The following is a list of the species in which one or more instances of females assuming male plumage are ascertained to have occurred:
“Perhaps the Kestrel (Tinnunculus alaudarius) 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.
“It is said that the females inOriolusgenerally become as bright as males in time (‘Ibis,’ 1864, p. 412; ‘Field,’ June 24th and July 8th, 1871).”
“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 inAnas boschasand others of that tribe.”
In a later notice Gurney makes the following statement:
“The bearded tit (Panurus biarmicus) 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 (cf.‘The Field,’ Sept. 14, 1872).”
“The bearded tit (Panurus biarmicus) 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 (cf.‘The Field,’ Sept. 14, 1872).”
Brandt, who has reviewed the literature very thoroughly, cites the following cases:
“Galeinacei: Gallus bankiva domest., Phasianus pictus, torquatus, colchicus, mongolicus and nycthemerus, Pavo cristatus domest., Meleagris gallopave domest., Perdix einerea, Tetrao urogallus, tetrix und bonasia.“Passeres: Fringilla coelebs, Pyrrhula vulgaris, coccinea, Loxia chloris, Turdus merula, Ruticilla phoenicurus, ochrura, chrysogastra, Cyanecula Wolfii, Sturnus vulgaris, Ampelis cotinga.“Scansores: Cuculus canorus, Edolius glandarius.“Grallatores: Machetes pugnax.“Natatores: Anas boschas domest.“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. Sobemerkt 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.”
“Galeinacei: Gallus bankiva domest., Phasianus pictus, torquatus, colchicus, mongolicus and nycthemerus, Pavo cristatus domest., Meleagris gallopave domest., Perdix einerea, Tetrao urogallus, tetrix und bonasia.
“Passeres: Fringilla coelebs, Pyrrhula vulgaris, coccinea, Loxia chloris, Turdus merula, Ruticilla phoenicurus, ochrura, chrysogastra, Cyanecula Wolfii, Sturnus vulgaris, Ampelis cotinga.
“Scansores: Cuculus canorus, Edolius glandarius.
“Grallatores: Machetes pugnax.
“Natatores: Anas boschas domest.
“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. Sobemerkt 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.”
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.
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.
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.
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 henson 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.
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.
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.”
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.
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.
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.
Smith states that birds and crabs (seeinfra) 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.
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.
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.
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.
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.
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.
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. Themodus operandiwould 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 ofhis 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.
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.
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 stillpresent 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.
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.
Goodale has written to me that there is an account, in the Agricultural Journal, Union of South Africa,IV, 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.
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 intothe light for a week or two and meal-worms were added to the diet. This invariably resulted in a full resumption of song.
“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.“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.”
“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.
“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.”
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.
Until further information is obtained judgment must be suspended. If, as Beebe’s statements strongly suggest, the external conditions,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.
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 forRana fuscathat 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.
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.