122 Facts Compelling Us to Reject Preformation 
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.8* 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 preformation 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. 
