THE MONERULA. 



51 



egor-cell of animals, oither before or after fertilization, the 

 original kernel disappeared. We explained this phenomenon 

 as a reversion or atavism, and assumed that the s^g-celL 

 in accordance with the law of latent heredity, first fails 

 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. vols i. pp. 178-183.) 



! P 



: | 



Fig. 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 peUucida (z) together with 



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 (Cytula) of a Mammal (Rabbit): I; parent, 

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

 modified zona pellucida ; s, sperm-cells ; ft, outer albuminous covering 



