454 SCIENTIFIC THOUGHT. 



life has as an inevitable corollary come more and 

 more into prominence. It has been the subject of 

 much discussion, as a phenomenon which is felt to 

 require a mechanical explanation. 



The problem of the continuity in time of the forms 

 and properties of living matter forced itself on the great 

 propounder of the modern theory of Descent, on Darwin. 

 He looked upon the principle of "Reversion 1 this power 

 of calling back to life long-lost characters as the most 

 wonderful of all the attributes of inheritance." 

 si At the end of his second great work, ten years after 



P ", 7. 



(it, the appearance of the ' Origin of Species,' he ventured on 

 a hypothetical explanation, his theory of " Pangenesis," 

 " which implies that the whole organisation, in the sense 

 of every atom or unit, reproduces itself ; hence ovules and 

 pollen-grains, the fertilised seed or egg, as well as birds, 

 include and consist of a multitude of germs thrown off 

 from each separate atom of the organism." s This idea, 

 as the author himself admitted, and as has since fre- 

 quently been pointed out, was not fundamentally new : it 

 had been anticipated by Buffon in his celebrated "organic 

 molecules," and since Darwin it has been restated and 

 adapted in various modified forms. It is hardly an ex- 

 planation, but it is a statement which emphasises the 

 great fact of modern biology, the fact brought out by 

 the cellular theory, that the units of life are not the large 

 visible organisms which were formerly studied by prefer- 

 ence, but the innumerable, infinitesimal living beings 



1 ' Animal* and Plants under Domestication.' chap. 27, voL ii. p. 



3;*. 



Domestication/ voL ii. p. 372. 



1 ' Animals and Plants under 



