Regeneration and Generation 139 



also that which is capable of regenerating all three pha- 

 langes; or the distal part of the second phalanx should 

 contain, besides the accessory idioplasm capable of regen- 

 erating the distal portions of the second phalanx and the 

 whole of the third phalanx, also that which is capable of 

 regenerating both the third phalanx and the entire second 

 phalanx itself. Why, then, should only that accessory 

 idioplasm become activated which is capable of regenerat- 

 ing just the particular part cut off? 



Further, Weismann himself recognizes that when dif- 

 ferent tissues and organs are cut through, "it is only the 

 harmonious equipment of the cells of a definite cross sec- 

 tion with groups of determinants, different but mutually 

 adaptable, in accord among themselves and compliment- 

 ary, that could make regeneration of the higher type pos- 

 sible." 112 But really it is not easy to conceive how this 

 harmonious equipment of reserve idioplasm could be 

 guaranteed in the great number of different cells of a 

 complex section. 



Roux has seen so clearly this impossibility of explain- 

 ing the phenomena of regeneration by pre formation 

 theories, that he asserts that in "direct" or "typical" gen- 

 eration self-differentiation may have the preponderance 

 over differentiation due to reciprocal actions among the 

 parts without nevertheless entirely excluding it; but in 

 regeneration, which he calls "indirect" or "atypical" 

 generation, he admits that differentiation of epigenetic 

 nature must necessarily prevail over pre formation. 113 



Weismann has rightly been unwilling to fall into the 

 contradiction of imagining two different natures for two 



112 Weisann: Ibid. P. 297298. 



113 Roux: Uber Mosaikarbeit usw. Anat. Hefte. P. 279331. 

 Gesamm. Abhandl. II. P. 819870. 



