THE MONERULA. 



179 



wig, we assume tliat the germ-vesicle does not completely 

 disappear, but that the germ-spot (^nucleolus) remains and 

 amalo'amates at the moment of fertilization with the 

 nucleus (or nucleolus ?) of the sperm-cell, we may say that 

 the kernel of the parent-cell arises anew in that act, and 

 that, therefore, a non-nucleated germ-stage, in which the 

 form-value of the germ is only that of a cytod, precedes the 

 one-celled germ-stage (the parent-cell). For reasons which 

 we shall presently recognize, we shall call this simplest 

 (non-nucleated) stage, the Monerula.^^ (Fig. 19.) 



Fig, 19. — Monerula of a Mammal (Rabbit). The fertilized egg-cell, after 

 the disappearance of the germ-vesicle, is a simple globe of protoplasm (tZ). 

 The outer membrane is formed by the modified zona pellucida (z), together 

 with a mucous layer (h) secreted on the outside of the zona. A few single 

 sperm-cells (s) are still visible in the membrane. 



We regard it as a fact of the greatest interest that the 

 human child, like that of every other animal, is, in this 

 first stage of its individual existence, a non-nucleated ball 

 of protoplasm, a true cytod, a homogeneous, structureless 

 body, without different constituent parts. For in this 

 " Monerula-form " the structure of the animal, and thus of 



