Artificial Parthenogenesis 123 



7. When the experiments on artificial partheno- 

 genesis were first pubHshed they aroused a good deal 

 of antagonism not only among reactionaries in general 

 but also among a certain group of biologists. 0. 

 Hertwig had defined fertilization as consisting in the 

 fusion of two nuclei, the egg nucleus and the sperm 

 nucleus. No such fusion of two nuclei takes place in 

 artificial parthenogenesis since no spermatozoon enters 

 the eggy and it became necessary, therefore, to abandon 

 Hertwig's definition as wrong. The objection raised 

 that the phenomena are limited to a few species soon 

 became untenable since it has been possible to produce 

 artificial parthenogenesis in the egg of plants {Fuciis, 

 according to Overton) as well as of animals, from echino- 

 derms up to the frog; and it may possibly one day be 

 accomplished also in warm-blooded animals. A second 

 objection was that the eggs caused to develop by the 

 methods of artificial parthenogenesis could never reach 

 the adult stage and that hence the phenomenon was 

 merely pathological. There was no basis for such a 

 statement, except that it is extremely difficult to raise 

 marine invertebrates. Delage^ was courageous enough 



This is exactly what one should expect since the unfertilized egg is not 

 only surrounded by the cortical layer but also by a thick layer of jelly 

 both of which are lacking in the fertilized egg. It is difficult to under- 

 stand how this observation can throw any light on the mechanism of 

 development, since water diffuses rapidly enough into the unfertilized 



* Delage, Y., Compt. rend. Acad. Sc, 1909, cxlviii., 453. 



