THE ORIGIN OF GYNANDROMORPHS. 103 



was not dissected. He records, apparently also on the authority of 

 Cabanis, another bilateral gynandromorph in the species Colaptes 

 mexicanus. Here, curiously enough, the right half was female, the 

 left male, but Weber suggests that possibly the bird had the adult 

 male plumage on the left side, while on the right the plumage was juve- 

 nile; in other words, the bird was a male, but with the full plumage only 

 on one side, and that the left side, which normally contains the ovary. 



Brandt states that Lorenz found in the markets of Moscow, in the 

 course of fifteen years, three male Tetrao tetrix with female plumage; 

 one of these had a testis on one side and an ovary on the other. 



Bond has described a pheasant with the plumage of the left side 

 preponderantly male, that of the right side preponderantly female. 

 On the left side there was an ovary, and this is the normal position of 

 the ovary in birds. It contained both ovarian and testicular tissue. 

 There was no trace of a gonad on the right side. In the last three cases 

 there is no stated correspondence between the external and the 

 internal division of the sexes. 



Setting aside the two rather doubtful cases (that of Cabanis and the 

 uncertain reference to Lorenz's case), there remain the two well- 

 established cases of Poll and Weber, where dissection was made, and 

 Bond's case, that is like the last, but not so clear, since the ovary 

 contained also testicular tissue. 



It is very difficult to explain these cases by chromosomal elimina- 

 tion, even if the male and female plumage differences were supposed 

 to be due to two or one (Z) chromosomes in the parts affected. Start- 

 ing as a male with two Z chromosomes, if one were lost at an early 

 division one half of the bird would be female, Z, and the other male, 

 ZZ. This possibility could be established only by finding a bilateral 

 gynandromorph in a hybrid that was heterozygous for sex-linked 

 factors. Such factors have been described for pigeons (Cole and 

 Staples-Browne) and for doves (Strong, R. M.,and Riddle), for canaries, 

 and for fowls, but no cases of gynandromorphs hi them have yet been 

 met with in which these characters were involved. 



An attempt to bring the avian results in line with the Drosophila 

 runs counter to the evidence from gonadectomy, since it assumes 

 that the differences involved are due directly to the chromosomal 

 composition of the male and the female parts, and are not due to 

 ovarian extract, which, in poultry and ducks at least, has been shown 

 to suppress in the female her potentiality of developing the full cock 

 plumage. It may be interesting to review briefly this situation, since 

 Goodale's results with ducks show that the relation of the plumage 

 to the gonad is not so simple as appeared at first. 



It has long been known in poultry that the removal of the testes 

 does not interfere with the development of the secondary sexual 

 plumage of the cock. In color, shape, and size of the feathers the capon 



