THE MONElirLA. 



^T 



eo^g-cell of animals, either before or after fertilization, the 

 original kernel disappeared. We explained this phenomenon 

 as a reversion or atavism, and assumed that the egg-cell, 

 in accordance with the law of latent heredity, first falls 

 back into the kernel-less, cytod stage (Fig. 165). It is on]y 

 after fertilization is accomplished that a new cell-kernel 

 arises in this cytod, which thus becomes the parent-cell 

 {Cytula, Fig. 1G6). The transitory kernel-less cytod-con- 

 dition, intermediate between the egg-cell and the parent- 

 cell, is an interesting germ-form, because, in accordance 

 with the fundamental law of Biogeny, it reproduces the 

 original, oldest parent-form of the Moneron ; w^e therefore 

 call it the Monerula. (Cf vol. i. pp. 178-183.) 



Fig. 1G5.— Monerula of M.ammal (Rabbit). The fertilized egg-cell after 

 the loss or the nucleus is a simple ball of protoplasm (d). The outer covering 

 of the latter is formed by the modified zona pellucida (z) together with 

 a mucous layer (h) secreted on to the outside of the latter. In this a few 

 s^jerm -cells are still visible (.5). 



Fig. 166.— Parent.cell (Cytulo) of a Mammal (Eabbit) : Tc, parent, 

 kernel; n, nucleolus of the latter; p, protoplasm of the parent-cell; z, 

 modified zona pellucida ; s, sperm-cells ; h, outer albuminou3 covering. 



