178 THE EVOLUTION OF MAN. 



lization. One party affirms that it is expelled from the 

 egg-cell, the other that it dissolves in the yelk. Some are 

 of opinion that it disappears entirely, others, that it only 

 does so partially. 



y We cannot here enter into the various views which have 

 recently been formed as to this remarkable incident in fertili- 

 zation, the examination of which presents great difficulties. 

 Those who are particularly interested in it may be referred 

 to valuable works on this subject by Auerbach, Biitschli, 

 Hertwig, Strasburger, and others. ^^ Here we can only 

 briefly indicate the view which at present appears most 

 probable. Most students of this point now assume as a 

 universal incident in fertilization that the germ-vesicle, the 

 original kernel of the egg-cell, disappears before fertilization, 

 being either expelled from the ^g^ or dissolved in the yelk. 

 Either no part of the egg-cell, or only the germ-spot 

 {nucleolus), remains as a defined part in the yelk. Accord- 

 ing to Hertwig and others, this germ-spot amalgamates with 

 the sperm-kernel, or the kernel of the intruding sperm-cell, 

 and this amalgamation gives rise to the kernel of the 

 parent-cell. On the contrary, according to other observers, 

 the parent-kernel (cytococcus) is an entirely new formation 

 in the protoplasm of the parent-cell (cytula, Fig. 21). 



At present, therefore, the majority of observers assume 

 that between the original nucleated egg- cell and the 

 known nucleated parent-cell there is a stage in which there 

 is no real cell-kernel or nucleus, and in which, therefore, the 

 form- value of the whole organic individual is no longer that 

 of a true nucleated cell, but that of a non-nucleated cytod, 

 i.e. a simple protoplasmic body in which no true cell-kernel 

 (nucleus) is to be found. (C£ p. 129.) Even if, with Hert- 



