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 falls 

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

 after fertilization is accomplished that a new cell-kernel 

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

 (Cytula, Fig. 166). 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 ; we therefore 

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



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

 the loss of 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 (/i) secreted on to the outside of the latter. In this a few 

 sperm-cells are still visible (s). 



FIG. 166. Parent.cell (Cytula) of a Mammal (Babbit): fc, parent, 

 kernel; <n, nudeolus of the latter; p, protoplasm of the parent-cell; 2, 

 modified zona pellucida ; s, sperm-cells ; 7i, outer albuminouarcovering. 



