1 68 THE DOCTRINE OF DESCENT. 



is not incomprehensible, and seems inexplicable only if 

 we make the naturally futile attempt to bring sensibly 

 before us the infinitely minute agencies which operate 

 both mechanically and chemically. In the " Variation of 

 Plants and Animals," Darwin has set up a provisional 

 hypothesis of Pangenesis. He says that all phenomena 

 of heredity and reversion would thereby be rendered 

 possible, that in every elementary or cellular portion of 

 the organism innumerable gemmules are produced, which 

 are hoarded up in the reproductive elements, in every 

 ovum, in every sperm corpuscule, and might remain 

 latent during hundreds of generations, and only then 

 exhibit their powers in reversion.^*' This hypothesis, it 

 appears, has met with no ready approbation, probably, 

 as it seems to us, because, in the attempt to meditate 

 upon it, the sensible representation forces itself forward 

 only to prove inadequate. But if it be steadfastly borne 

 in mind that in Protoplasm, as RoUet " appropriately 

 terms it, the most complex phenomenal forms of life 

 possess a most persistent witness of their connection 

 with the simplest, it follows that the general laws 

 shown to be true or probable with reference to the 

 simplest organisms, must be applicable to the most 

 perfect also. This holds good also in reproduction, 

 which, in its fundamental phenomena, offers nothing 

 that cannot be based upon molecular physics applied 

 to colloidal living substance capable of imbibition, and 

 thus divested of vitalistic dualism. 



The more highly complex is an organism, that is, the 

 greater the differentiation in the development from the 

 protoplasm of the germ-cell to maturity, the more 

 heterogeneously does heredity display itself. These 



