168 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 innumcrable 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 
enly to prove inadequate. But if it be steadfastly borne 
in mind that in Protoplasm, as Rollet*’ 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 gencral laws 
shewn 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 docs heredity display itself. These 
