190 HOLISM AND EVOLUTION chap. 



was in the course of being generally accepted, and accepted 

 in the mechanical sense. 



This was the first phase of Darwinism, the phase during 

 which Natural Selection was chiefly stressed and was the 

 dominant note in the theory. Then came the second phase, 

 when attention began to be given to the other factor of 

 Variation. With this Neo-Darwinian phase the name of 

 Weismann is for ever honourably associated. Many great 

 labourers there have been in this field, but the name of 

 Weismann will ever stand out pre-eminent as the biologist 

 who, whatever his mistakes in detail, initiated and developed 

 the exploration of the germ-cell as the source of Variation 

 in Evolution. Weismann turned the gaze of Evolutionists 

 from the outside to the inside of the process, from the 

 apparent mechanism of external interaction and clash to 

 the mystery of the inner process. And what he taught was 

 not only most surprising, but remains one of the most 

 significant and important truths in the whole range of 

 biology. I shall deal with this matter just now. But be- 

 fore doing so I wish to point out that Weismann and his 

 fellow-workers were handicapped in their labours by the 

 mechanical view of Evolution which had already become a 

 fixed dogma in the earlier stage of Darwinism. If any- 

 where, the mechanistic conception should have received its 

 quietus in the domain of Variation, in the exploration of 

 the inner process or factor of Evolution. Unfortunately 

 Weismann and several of the most prominent biologists who 

 developed this second phase of Darwinism arrived at their 

 task not only as convinced Darwinians, but as mechanistic 

 Darwinians. 



The great battle in which Darwinism had won was tacitly 

 considered a victory for the mechanical view of it. And thus 

 the whole problem of Variation, as viewed by these leading 

 Neo-Darwinians, came to be one of investigating or finding 

 the mechanism of Variation. Their services have been 

 great, and the route they have opened up will in the years 

 to come lead to even greater results. But there is no doubt 

 that the mechanistic conception has been a grave handicap 



