DIMORPHISM AND POLYMORPHISM 369 



occurs ; and in the case of the Rotifera, it is not to be expected 

 that any influence could cause a male to produce female char- 

 acters. 



In the part treating of sexual reproduction — including the 

 section on the struggle of the paternal and maternal hereditary 

 tendencies which takes place during the development of the 

 offspring — no mention was made of a very general, and, in my 

 opinion, erroneous conception of sex ; and it will be as well to 

 explain this omission before proceeding further. 



The transference of sex has hitherto usually been looked upon 

 as an act of transmission. This cannot be the case, inasmuch 

 as every germ-plasm contains the primary constituents for both 

 sexes, and the process of transmission itself has evidently nothing 

 to do with the determination of sex. As already mentioned, 

 it does not by any means follow that because a child is a female, 

 its secondary or primary sexual characters will resemble those 

 of its mother. This, indeed, has long been known, but has not 

 led to a general recognition of the fact that sex is not trans- 

 mitted at all ; and that, on the contrary, the primary consti- 

 tuents of both sexes are always passed on from both sides : the 

 decision as to which of them are to become active depends on 

 secondary factors, which have not yet been clearly recognised 

 in any case. The male halves of the sexual double-determinants 

 of the mother are just as capable of undergoing development as 

 are the female halves, and vice versd : — the ' law of sexual trans- 

 mission,' * which was propounded by Haeckel some time ago. is 

 not tenable. Expressed in a purely empirical manner, the facts 

 have been more correctly formulated by Dejerine f according 

 to Darwin's ( ?) views, in his valuable work on the heredity of 

 nervous complaints : — ' the prepotency of one of the parents in 

 transmission may be direct, and follow the sex, or may cross 

 over, and become manifest in the opposite sex.' 



For this reason the so-called 'transmission of sex' was entirely 

 left aside in the section on the struggle of the parental char- 

 acters during the formation of the child ; transmission of the 

 primary and secondary sexual characters occurs, but sex itself 

 cannot be transmitted. 



* Ernst Haeckel, ' Generelle Morphologie der Organismen,' Bd. II., 

 Berlin, 1866, p. 183. 



t J. Dejerine, ' L'Heredite dans les maladies du syst^me nerveux,' Paris, 

 1886, p. 17. 



