50 THE EVOLUTION OF MAN. 



sea. raises many different inqniries and thoughts. Spon- 

 taneous generation, especially, is naturally suggested by the 

 Bathybius. We have already found that, for the origin of 

 first Monera upon our globe, the assumption of spontaneous 

 generation is a necessary hypothesis. We shall be all the 

 more inclined to confirm it now that, in the Monera, we have 

 recognized those simplest organisms, the origin of which 

 by spontaneous generation, in the present condition of our 

 science, no longer involves very great difficulties. For the 

 Monera actually stand on the very boundary between 

 organic and inorganic natural bodics.^^ 



Next to the simple cytod-bodies of the Monera, as the 

 second ancestral stage in the human pedigree (as in that of 

 all other animals), comes the simple cell, that most undifferen- 

 tiated cell-form, which, at the present time, still leads an 

 independent solitary life, as the Amoeba. For the first and 

 oldest process of organic differentiation, which affected tlie 

 homogeneous and structureless plasson-body of the Monera, 

 caused the separation of the latter into two diilei'ent sub- 

 stances ; an inner firmer substance, the kernel, or nucleus, 

 and an outer, softer substance, the cell-substance, or 

 j)rof()p!<csin(t. By this extremely important separative pro- 

 cess, by the diil'erentiation of the plasson into nucleus and 

 protoplasm, the organized cell originated from the sti-ucture- 

 less cytod, the nucleolated from the non-nucleolated plastid. 

 'J"hat the cells which first appeared upon the eaith origin- 

 ated in Liiis manner, by the difierentiation of the Monera, i« 

 a conception w^hich in the present condition of histological 

 knowledge seems quite allowable ; for we can even yet 

 directly observe this oldest histological process of differ- 

 entiati(>>Ji in Ontogeny. It will be I'emenibcrud that in the 



