CONSTITUENTS OF MONERULA. l8l 



future possibilities, is in this stage only a small, simple ball 

 of primitive slime (protoplasm, Fig. 19). The membrane 

 is still there, but seems to be an entirely passive part of the 

 egg, and takes no real share in the active processes of the 

 evolution of this egg. We may, therefore, for a time pass 

 over this membrane, for we shall afterwards enter into the 

 changes which it undergoes in a later stage ; as regards the 

 actual process of evolution, it is entirely without significance. 

 At present we need only concern ourselves with the contents 



FIG. 21. Parent-cell or cytula of a Mammal (Rabbit) : 7,-, parent- 

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

 modified zona peUucida ; s, sperm-cells; ft, external albuminous membrane. 



of the globular egg, the homogeneous yelk, which when 

 in this condition we call the Monerula, in allusion to the 

 Monera-fomi. 



Although morphologically we can see no denned con- 

 stituent parts in the Monerula, yet chemically we must 

 regard the latter as the complex product of at least four 

 different constituents ; these are : (1) the protoplasm of the 

 maternal egg-cell; (2) the protoplasm of the paternal 



