Chap, ii.] OF GENERATION IN THE TWO KINGDOMS. 313 



ment in the vegetal kingdom has been extended and apj)lied to 

 the animal kingdom. In truth, if we remount to the primordial 

 phenomenon of sexual generation, we find it nearly identical in 

 the two kingdoms. The animal ovulum and the vegetal pvulum 

 are rigorously comparable. 



The animsil ovulum is a cell, which, at first, is not distinguished 

 from many other histological elements by any observable 

 characteristic. This cell is composed essentially of an envelop- 

 ing wall, of a protoplasmic content, of a nucleus. It has been a 

 mistake therefore to give to these diverse plants of the ovular 

 cell special names, tending to give the notion that they represent 

 things without analogy, when in reality the differences are 

 purely virtual. The faculty of reproduction, of generation, 

 considered in a general manner, by no means specially appertains 

 to the ovular cell. It is merely developed more and more with 

 a longer range in the ovulum than in the other cells. 



Let this be as it may, it is indispensable to know the names 

 given by the embryologists to the diverse parts of the ovular 

 cell. The enveloping membrane, which is hyaline and trans- 

 parent, and whose projection has, in the microscope, the appear- 

 ance of a ring, has been called transparent zone, zona pellucida. 

 The content or cellular protoplasm of this envelopment, a 

 substance more or less viscous and granulous, has been called 

 mtelltis. The ovular protoplasm or vitellus contains a nucleus 

 which hollows for itself a way from a cavity and then bears the 

 names of germinative vesicle, vesicle of Purhinje. Finally, this 

 nucleus- contains a nucleole, which is the germinative spot. 



In the most perfect of the sexual vegetals, the phanerogams, 

 that which habitually is called ovulum is nearly equivalent to 

 the ovarium of animals. In the cellular tissue with polyhedrical 

 elements which this ovary contains, and which is called nucula, 

 is found the real ovulum, which has been called the emhryonary 

 sac. It is an oval cell, whose wall represents the vitelline membrane 

 of the animal ovulum. Its content is a mucous, granulous, and 

 greyish protoplasm, manifestly equivalent to the vitellus. Knally, 



