SUPPLEMENTARY NOTES ON TWINS IN CATTLE. 71 



tion of the ovarian hormone the testicular hormone is antagonistic 

 to growth of the ovary. Presumably, therefore, the normal growth 

 of an ovary in the presence of a testis, as in the experiments of 

 Moore and Sand, depends upon a protective action that the elabo- 

 rated ovarian hormone exerts against the testicular hormone. I 

 do not think that Moore (1921, p. 168) is entirely correct in his 

 opinion that hormone action is never characterized by inhibition, 

 and that in the case of the free-martin the transformation of the 

 gonad is due solely to the stimulating action of the male hormone. 

 The gonad of the free-martin is unquestionably inhibited not only 

 in its total growth, but also in its histogenesis by the male hor- 

 mone; later yet the growth of the Miillerian duct is halted and 

 degeneration also sets in owing to the presence of the male hor- 

 mone. It is not until a still later period that the stimulating effects 

 of the male hormone on the sex cords and rete of the gonad and 

 on the epididymis and Wolffian duct of the free-martin become 

 apparent. There is certainly an element of truth in the contention 

 of Steinach, Lipschiitz, and others that the sex hormones inhibit 

 heterologous sex characters in addition to stimulating the homo- 

 logous ones. 



The great and important advances made in recent years in the 

 study of sex hormones have led certain authors to extreme posi- 

 tions concerning their economy in the organism. Lipschiitz (1919, 

 p. 390 ff.) has given the boldest statement in his theory that the 

 embryonic soma is primarily asexual, and that sex characters are 

 secondarily imposed upon it by the differentiation of a male or 

 female " puberty gland." In the discussion of this statement we 

 should no doubt run foul of definitions. Whether it is to be under- 

 stood under the presupposition of the zygotic determination of sex 

 or not is not clear. If so, it confines itself to the phenomena of 

 sex differentiation. The primary differentiation, therefore, which 

 itself requires explanation, would be presumably that of the mis- 

 named "puberty gland." This is, however, demonstrably not the 

 case (Lillie and Bascom, '22). Moreover, if there were no other 

 factor at work in determining the sex differentiation of embryonic 

 primordia than the specific sex hormone, it is difficult to understand 

 why the free-martin, which receives only male sex hormones, should 

 not become completely male. It is obvious that the male hormone 



