122 Facts Compelling Us to Reject Pre formation 



of this objection by taking into consideration, besides 

 the architecture of the germ plasm itself, also the uneven 

 rapidity of multiplication of the different determinants 

 and the reciprocal forces of attraction exercised by these 

 latter upon one another, as factors which determine the 

 orderly division of each plasm or each id. 84 But, as 

 this author himself admits, the architecture of the germ 

 plasm remains necessarily the principal factor, and conse- 

 quently the objection of the incompatibility of this arbi- 

 trary architecture with constant complete division of the 

 plasm without alteration, remains in all its force. 



Another argument which presents itself likewise 

 against pre formation is, that with the exception of the 

 partial developments cited in the preceding section of 

 parts which each contained one very definite zone of the 

 organism, it has never been possible to obtain the devel- 

 opment or the continuation of development of somatic 

 parts, even though they are capable of living for some 

 time after they have been detached from the rest of the 

 organism. 



One would certainly not regard as a continuation of 

 normal development the mere increase in mass which 

 takes place in parts cut off from the fetal organism, 

 when they are transplanted upon tissues which on account 

 of their great richness in blood vessels are especially 

 capable of affording abundant nourishment to their new 

 guests. 



This simple increase in mass depends for the most 

 part on an actual multiplication of the respective cells, 

 which proceeds in directions determined either by nutri- 

 tion alone or by the path of least resistance in the environ- 



"Weismann: Das Keimplasma. Eine Theorie der Vererbung. 

 Jena, Fischer, 1892. P. 86. 



