360 Problems of Organic Adaptation 



tern, and again he invokes the aid of "entelechy." Finally, 

 he finds a third proof of vitalism in the field of behavior, 

 or what he calls the "individuality of correspondence be- 

 tween stimuli and responses." In such cases something non- 

 mechanistic interferes when the good of the organism re- 

 quires it, and this something, which resembles the "indwell- 

 ing soul" of Plato, he calls "psychoid." In short, Driesch's 

 three "proofs" of vitalism are all based upon adaptive re- 

 sponses. 



However, all the parts of living things, whether eggs, 

 embryos, or adults, are rarely, if ever, equipotential. Even 

 parts of the embryos of the sea-urchin, upon which Driesch 

 did much of his work and based most of his conclusions, 

 are not equipotential in the chief axis; that is, fragments 

 from the upper or lower poles are not capable of regenerat- 

 ing a whole embryo or larva. Fragments of the hydroid 

 Tubularia are not equipotential so far as proportionality is 

 concerned (Child). Regeneration in the ascidian Clavelina 

 is complicated by degeneration, regeneration, and budding 

 (ZurStrassen). The different cleavage cells of the eggs of 

 mollusks, annelids, and ascidians are not equipotential, and 

 when one of these cells is destroyed its function is not taken 

 by other cells, but the embryo remains incomplete (mosaic 

 development). 



When Driesch maintains that neither cytoplasm, nucleus, 

 nor medium is the cause of differentiation what can he 

 mean? All of these factors are in varying ways and de- 

 grees the causes of differentiation. And when he asserts 

 that it is inconceivable that any machine could be broken up 

 in the three dimensions of space and the fragments still be 

 capable of producing whole machines, or that it is absurd 

 to suppose that any machine could give rise to an equipoten- 

 tial system, it is evident that his conception of a machine is 



