No. 626] 



ADAPTATION 



205 



set, an ''accidental" one. In those cases where the cor- 

 rect response appears to ensue unhesitatingly, we have 

 had to suppose either (1) that the observer has overlooked 

 ''trial and error" stages preceding the response in ques- 

 tion, or (2) that the response is the outcome of an inher- 

 ited mechanism, based upon racial experience, and there- 

 fore ultimately upon some form of selection. 



III. Vitalism^ 



Let us now consider the claims of a school of thinkers 

 who argue for the existence of a primary purposefulness 

 in living things, and who deny that any conceivable mech- 

 anism can account for certain of the phenomena ob- 

 served. As the most conspicuous representative of this 

 school we naturally turn to Hans Driesch, who has made 

 a more determined attempt than any other vitalist to 

 reduce his beliefs to a unified system of philosophy. 



Driesch 's three "proofs" of vitalism may be summar- 

 . ized as follows : 



1. In the earlier development of some organisms, 

 rather low^ in the scale of life, any part of the embryo, 

 provided that it be of a sufficient size, will, if artificially 

 detached, produce the entire organism. This he regards 

 as conclusive disproof of the supposition that the spa- 

 tially arranged diversities of the adult organism depend 

 for their origin upon diversities of a spatial sort in the 

 embryo. Such a spatial prearrangement of the parts as 

 is postulated by the Weismannian "germ plasm" theory, 

 and other preformationist hypotheses, he assumes to be 

 essential to any mechanical theory w^hatever. 



But, Driesch claims, the spatial diversities of the adult 

 organism must depend upon preexisting diversities of 

 some sort, therefore he invokes a non-spatial airent, "en- 

 telech}'-," to account for them. Now "eiitrltn liy " imisT 

 be a manifoldness, ^ince it is conjured u\) to txi'laiii 

 other manifoldness, but this manifoldness is infoisi rc, 



