444 INTERNAL SECRETIONS 



general influence which leads to the first differentiation of the 

 soma." Champy (1922, p. 157) writes : " I accept for the tritons 

 and in a general way for vertebrates the hypothesis of Lipschiitz 

 on the asexuality of the embryonic form ; this hypothesis is the 

 expression of common sense. As long as I am unable to 

 distinguish the sex in the embryo I regard it as having no 

 sex.'' 



On the other hand certain facts have been related which do 

 not seem to conform with our hypothesis. Riddle (1920) finds 

 that there is from the beginning " a metabolic difference between 

 the ova {egg yolks) which give rise to the two sexes in doves"; 

 female-producing eggs appear to have a lower metabolism than 

 male-producing eggs. In accordance with this observation 

 Riddle stated that female-producing eggs are better able to 

 survive a decreased oxygen pressure than male-producing eggs. 

 But I do not find that such a statement is really opposed to 

 our hypothesis, which by no means denies, as will be made clear 

 in the next section, the existence of biochemical differences 

 between male- and female-producing eggs. Lillie (1923) 

 says that it is not evident as to whether the hypothesis that 

 the embryonic soma is primarily asexual is to be understood 

 to presuppose the zygotic determination of sex or not. But 

 the position is a clear one : the hypothesis that the soma is 

 primarily asexual refers only to the phenomena of sex differen- 

 tiation. This means that biochemical differences between 

 male and female eggs, as in Riddle's experiments, may be 

 present from the beginning without there being biochemical 

 differences between male and female somatic cells, the meta- 

 bolism of which may indeed be influenced by sex hormones 

 before sexual differentiation of the soma takes place. Certain 

 observations of Minoura (1921) do not, however, at first thought 

 fully agree with our conceptions in regard to fowls. He 

 describes a transformation of the original female gonad into a 

 male one under the influence of an engrafted testicle, but he 

 records at the same time the remains of the ]\Iiillerian ducts. 

 But the graft had to be made in the second week of 

 incubation, when sexual differentiation had already begun, and 

 it is easy to understand that some heterosexual characters 

 such as the Miillerian ducts might persist, though in a 

 rudimentary state. 



Goldschmidt (1920) argues that in birds the genetic position 



