124 Facts Compelling Us to Reject Pre formation 



histologically differentiated in an approximately normal 

 way. It follows that the differentiation of these parts 

 is not a function of reciprocal actions between these 

 parts and other parts. Therefore there is thus already 

 proven a certain histologic and morphologic self -differ- 

 entiation of many parts of the developing egg." 88 



This is not correct. For these experiments show, 

 we repeat, only a mere increase in mass of these tissues, 

 which is morphologically without any specific character; 

 and the continuation of the histologic differentiation 

 which had already commenced or was on the point of 

 commencing at the moment of amputation, is explicable 

 by the simple accumulation of the effects of the same 

 vital process which merely persists exactly as it was 

 before the amputation. 



Another argument against pre formation is the great 

 capacity of modification of the organism while it is 

 undergoing development, as well as when fully developed, 

 to which it owes its remarkable power of adapting itself 

 to quite abnormal conditions. For the preformation 

 theory with its determinants, which are bound up with 

 one another into a solid structure, and of which each 

 determines the formation even of the smallest particles 

 and their most minute variations, implies undeniably a 

 great morphological rigidity, which is not reconcilable 

 with the great mutability of the organism. 



"Galls," says Oscar Hertwig, for example, "are 

 valuable witnesses against the germ theory of Weismann. 

 They teach us that cells of plant bodies can serve quite 

 other purposes than could have been foreseen during 



8ft Wilhelm Roux : Zur Orientierung iiber einige Probleme der 

 embryonalen Entwicklung. Zeitschrift fur Biologic; Bd. XXI. July 

 1885. P. 480482. Gcsammelte Abhandlungen. II, P. 206207. 



