THE MONERULA. 51 



egg-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 faiis 

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

 after fertilization is accomplished ^at/a new cell-kernel 

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

 (Cytula, Fig. 166). The transitory kernel-less cy tod-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 ; we therefore 

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



PIG. 165. Monerula of Mammal (Rabbit). The fertilized egg-cell after 

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

 of the latter is formed by the modified zona pellucida, (*) together \\iili 

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

 sperm. cells are still visible (s). 



FIG. 166.-Parent.cell (Cytnla) of a Mammal (Rabbit): k, -parent- 

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

 mod.ftod zona pellucida ; s , sperm-cells ; h, outer albuminous covering. 



