SPECIFICITY IN FERTILIZATION 199 



development might proceed to a late stage. Sooner or 

 later, however, the heterogenic hybrids proved to be 

 non- viable. 



There is, however, according to Newman, definite 

 evidence of specificity in teleosts in the sense that 

 species fertilization succeeds much more readily than 

 any hybrid fertilization. The percentage of hybrid fer- 

 tilized eggs is always less under given conditions and is 

 frequently extremely small. The more ready union of 

 the species sperm must depend upon some chemical rela- 

 tion between egg and sperm, more highly developed 

 between gametes of the same than between gametes of 

 different species. This obviously operates at the surface, 

 because the subsequent events of fertilization after pene- 

 tration appear to proceed with equal facility whether 

 the sperm belongs to the same or to a different species. 

 Moenkhaus (1910), on the other hand, believes that, in 

 the case of the teleosts studied by him, there is no evi- 

 dence of any specific adaptation of the egg for its own 

 spermatozoon. No adequate test of such a conclusion 

 appears to have been made. The dry method of insemi- 

 nation usually employed for teleosts exposes the egg to 

 the highest possible sperm concentration and thus ren- 

 ders a quantitative examination of the problem of 

 specificity impossible. 



Moenkhaus (1904), Giinther and Paula Hertwig 

 (1914), and Morris (1914) found normal penetration of 

 the spermatozoon, normal behavior of the germ nuclei, 

 and no evidence of chrornatin elimination in the hybrid 

 fertilization of the teleosts that they have studied cyto- 

 logically. However, Pinney (1918) reports chromatin 

 elimination in certain teleost crosses in the first and 



