4 TADACHIKA MINOURA 



produced by the females in these cases correspond to the sex- 

 hormones of vertebrates, but their function is evidently much 

 like that of hormones. Goldschmidt ('16) has described inter- 

 sexual forms in hybrid gypsy-moths and attempted to account 

 for them by postulating a quantitative gradation in the value of 

 the sex-determining factors. In his materials there was further 

 a correlation between the degree of development of the secondary 

 sexual characters and the degree of development of the gonads. 



From investigations of this kind, two general conclusions may 

 be drawn: first, that the sex-glands secrete certain substances 

 which may conveniently be designated sex-hormones, which are 

 related in an important way to the sexual characters; secondly, 

 sexual differentiation is controllable, at least to some extent, 

 by non-genetic factors. 



The following experiments were carried out at the University 

 of Chicago during the years 1917 to 1919. I am deeply indebted 

 to Professor LUhe for his invaluable suggestions and criticisms 

 during the course of the work and for his generosity in supplying 

 me with numerous materials used in the experiments. I also 

 wish to express my thanks to Dr. L. H. Hyman for revising the 

 manuscript. 



GRAFTS 



1. Material 



The common fowl was the material selected for the experi- 

 ments, owing to the ease with w^hich it can be operated on in 

 embryonic stages. The white Wyandotte breed was employed 

 in the majority of the experiments. The chicks from which the 

 organs to be grafted were taken also belonged to this breed with 

 a few exceptions in which other varieties of fowls were used. 



2. Experimental method^ 



a. Operation. The surface of the developing egg selected for 

 operation was cleaned with dilute sublimate solution or 70 per 



1 This method was originally devised by Peebles ('08). It was later modified 

 in several particulars by Murphy, Rous ('11), and Kiyono ('17). 



