EVOLUTION AND EPIGENESIS. 223 



explained in a grossly mechanical way that might excite the 

 envy of an ultra-epigenesist. On the other hand the old 

 epigenesis, instead of appealing to external mechanical influ- 

 ences as dominating development, invoked " ingenerate heat," 

 "vital force," "spirits," etc., as agencies, operating from within. 



The chief analogy between the old and the new evolution, — 

 which holds for epigenesis as well, only in a less degree, — lies 

 in what correspondence there is between predctermmation and 

 preforjnation. It seems to be believed by some that these two 

 things are essentially one and the same ; or at least that they 

 differ only as the more and the less of the same thing. That 

 is a mistake which the controversialist in epigenetics is partic- 

 ularly prone to make. He protests that this predetermination 

 is only the old preformation thinly disguised, and that it really 

 involves all the absurdities of emboitement. Grant that the 

 evolutionist claims too much organization or architecture in 

 the germ ; how does this ''too imicW differ from the less on 

 which epigenesis builds } Certainly not in kind. Carry the 

 "too much" to any excess exemplified in recent theories, and 

 it never loses its identity with the approved "less "; and never 

 comes any nearer the old idea of preformation. However ex- 

 tensively the features of the adult organism may be predeter- 

 mined, they are never predelineated. Predelineation views 

 organization as completed ; predetermination implies just the 

 contrary, setting the completion always at the end of a histo- 

 genetic building-process. 



// seems to be forgotten that determination from within may 

 proceed quite as cpigenetically as determination from zvithont. 

 From the old standpoints even Weismann's doctrine of deter- 

 minants would appear to be extravagant epigenesis. A theory 

 which begins with the claim that the entire body of the germ 

 outside the nucleus is isotropic, and starts developmental dif- 

 ferentiation with biophores emanating from the nucleus, and 

 generating new organizations at every step, — such a theory 

 certainly is wanting in none of the cardinal virtues ascribed to 

 epigenesis. The scheme is the acme of discontinuity in devel- 

 opment, for it builds not only de novo, but keeps on rebuilding, 

 organizing, and reorganizing to the end. 



