THE FACTORS WHICH DETERMINE SEX 699 



The effects on growth are noteworthy. After early removal of the 

 gonad the growth curve of the determined male was always higher 

 than that of the determined female. But the difference was 

 accentuated by the presence of an ovary, which thus inhibited the 

 growth. 1 



Pezard's 2 experiments with fowls show that castration and 

 ovariotomy lead to the development of a neutral type. The removal 

 of the testis inhibits the growth of the comb and other erectile 

 structures (wattles and auricular appendages), the capacity to crow 

 and the combative instincts, but it does not affect the spurs on the 

 characteristically male plumage. The latter are inhibited in the hen 

 by the ovarian influence, and as Goodale also has shown, if the 

 ovaries be removed the spurs grow and a brilliantly developed type 

 of plumage is produced, such as one ordinarily associates with the 

 male, but is in reality of a neutral type. 



In view of these and other experiments (such as those of Tandler 

 and Keller on oxen, in which the shape of the head is said to be 

 similar in male and female " castrates "), Lipschlitz 3 has elaborated 

 the idea of an indifferent or asexual embryonic form which becomes 

 male or female according to whether it is acted on by male or female 

 internal secretions. It will have been seen that whereas in Mammals 

 the fully developed neutral or indifferent type is in its somatic 

 characters much nearer to the female, in birds it is closer to the 

 male. Whether or not this is correlated with the apparent fact 

 that in Mammals the male is heterozygous as regards sex, while in 

 birds the female is heterozygous, is an open question. 



GENERAL CONCLUSIONS 



If it be true that all individuals are potentially bisexual (one of 

 the two sexes being recessive or latent excepting in hermaphrodites), 

 and that changed circumstances, leading to a changed metabolism, 

 may, in exceptional cases, even in adult life, cause the development 

 of the recessive characteristics (as in the case of the Crustaceans 

 mentioned above), it would seem extremely probable that the 

 dominance of one set of sexual characters over the other may be 

 determined in some cases at an early stage of development in response 



1 Cf. Stotsenburg who found with rats that the testis had no effect on the 

 growth, but that ovariotomy caused an increase of growth by 17-33 per cent. 

 (Anat. Rec., vol. iii., 1909, vol. vii., 1913, and vol. xii., 1917). 



2 Pezard, " Secondary Sexual Characters and Endocrinology," Endocrinology, 

 vol. iv., 1920. "Modifications Periodiques ou Definitives des Caracteres 

 Sexuels Secondaires et du Comportment chez les Gallinacees," Annales des Sci. 

 Nat. (Sees. Sot. et Zool.\ Paris, 1922. 



3 Lipschiitz, " L' Action sp6cifique de la Secretion interne des Glandes 

 Sexuelles, etc.," La Revue Scientifique, Paris, 1921. 



