SEXUAL HORMONES AND MORPHOGENESIS 473 



no sharp boundary lines between (a) and {b) or between (b) and 

 (c). To the group of '' functional sex characters'' there belong 

 all the differences between the sexes which are not morpho- 

 logical, such as differences in the body temperature or in the 

 intensity of the metaboHsm. Sex differences relating to 

 nervous and psychical reactions are included in the fifth group. 



Such a classification does not collide with the genetic system 

 given above. It is intended to serve only for practical ends. 



Various authors such as /. 5. Huxley (1912), Champy (1922, 

 p. 121), de la Vaulx (1922) and Maranon (1922), recognizing the 

 drawbacks of the old classification of the sex characters into 

 primary and secondary ones, have proposed others for practical 

 use. Champy (pp. 65, 123) speaks of permanent and temporary 

 sex characters in amphibians; Maranon (p. 90) groups the sex 

 characters as somatic and functional ones, including in each 

 group primary and secondary characters according to their 

 importance for propagation. Other classifications might very 

 well be made to satisfy special practical requirements. 



It is desirable to define closely the terms sex gland and 

 gonad for mammals especially. I propose to restrict the term 

 gonad to the generative part of the ovary or testicle. The 

 hormone-producing part, even though generative elements may 

 be involved in it, might be called "puberty gland," as proposed 

 by Steinach, or, as Sand suggested, "sex hormonic gland"; but 

 sex-endocrine gland is the better term. The *' gonad" and 

 'sex-endocrine gland" together form the "sex 



H. THE HORMONIC ACTIVITY OF THE SEX GLANDS 

 WHICH IS NOT SEX SPECIFIC. 



We have already mentioned that there is evidence that the 

 secretions of the testicle and the ovary may in certain circum- 

 stances produce similar effects. The growth of the pad in the 

 frog and that of the comb in the fowl is promoted not only by 

 the testicle, but to a certain degree also by the ovary (see 

 p. 285). Other observations also have been made on the fowl 

 (see p. 396). These can be explained by assuming that the 

 ovary may produce male hormones. But, on the other hand, 

 one might suppose that both sex glands may produce identical 

 substances or hormones which do not act in a sex specific 

 manner 



