The Animal Organism and its Germ-Layers 71 



or to ultimate chemical elements endowed with, homing in- 

 stincts and the rest. Surely if either of these sub-alterna- 

 tives be accepted the analysis which goes no farther than 

 that of ascribing to the sex-cells power and instinct suffi- 

 cient to enable them to do what they do, would have gone 

 but a short way on its course and ought not to make any 

 pretence of being a complete explanation of the phenomena. 

 On the other hand, if we conceive that the sex-cells move 

 through the agency of their elements and are not merely 

 moved by means of these elements, why not as well allow that 

 the developing organism as such may move its cells to meet 

 its needs? As a purely logical matter there would be no 

 more hesitancy in admitting that the organism moves its 

 parts than in contending that the cell moves its parts, for 

 the difficulty of conceiving how the thing is done is no greater 

 in the one case than in the other. The only reason why the 

 conception that the cells migrate wholly by their own pow- 

 ers seems less vague, that is more analyzed, than the concep- 

 tion that the cells are moved by the growing organism, is 

 that in the first case a whole set of inevitable collateral phe- 

 nomena, that is those pertaining to the parts 'of the cells 

 themselves, is unconsciously excluded from the view. In 

 other words, the satisfaction felt by analysis of this sort 

 is an entirely spurious and illegitimate satisfaction begot- 

 ten of the fact that the analysis is false. It is a process 

 of searching for the factors involved in the complex of 

 phenomena under contemplation, but ignoring all excepting 

 a few of these factors. And this criticism of Weismann's 

 attempt to explain fully the migration of the sex-cells holds 

 for the attempt to explain on elementalist principles any 

 biological phenomena whatever. 



I remarked above that as a "purely logical matter" there 

 is no more ground for refusing to believe the organism directs 

 the movements of the sex-cells than for refusinir to believe 

 the cells direct their own movements. It will not do to let 



