48 Sterile and Hybrid Pheasants 



There is a certain amount of experimental evidence on other birds 

 which confirms this result. Thus Guthrie (4) records the case of a hen 

 which assumed cock's plumage after the removal of the ovary, and 

 Goodale (5) observed the developement of Drake's plumage in some 

 Ducks from which he had removed the ovaries. 



We must suppose that the ovary in a female bird normally exerts 

 an influence on the developement of the typical female plumage, but 

 we are not in a position to say how this influence is exerted, whether 

 by means of a specific hormone, or by entering into a chain of metabolic 

 processes and stimulating the production in excess of substances which 

 are formed elsewhere. In previous studies the latter mode of action of 

 the gonad upon the body has been advocated in opposition to the ordi- 

 nary hormone theory, and it may be suggested that in the cases before 

 us the wide range of variation in the degree to which the secondary 

 sexual characters are altered when the gonad shows no corresponding 

 variations in its degree of degeneracy, points to other organs of the 

 body, in addition to the gonad, taking part in the correlation. 



It will be noticed that these cases of assumption of male characters 

 by the female as the result of ovarian degeneracy are the converse of 

 the case of the crabs infected by SaccuUna where the males under the 

 influence of the parasite assume female characters. 



The two cases are not, however, completely parallel, because in the 

 birds we are dealing with a mere suppression of the ovary, while in the 

 crabs it is not merely a suppression of the testis but the active feminis- 

 ing of the SaccuUna which brings about the changes. 



Nevertheless the two cases are parallel, in so far as they prove that 

 certain male secondary sexual characters are latent in the body of the 

 female bird which can be made patent by the removal of the influence 

 of the ovary, and that certain female secondary sexual characters are 

 latent in the body of the male crab which can be called forth by appro- 

 priate stimuli. 



It would be possible to use these facts in favour of that particular 

 Mendelian theory of sex which looks upon one sex as heterozygous for 

 sex and the other homozygous, and to urge that in Birds the female 

 sex is heterozygous, the male homozygous, and in certain Crustacea the 

 male is heterozygous and the female homozygous. It is certainly a 

 remarkable fact that on the one hand in Birds the assumption of male 

 characters by the female is frequently associated with abnormality of 

 the ovary, while the assumption of female characters by the male is 

 independent of any reproductive abnormality but is due to hereditary 



