124 Facts Compelling Us to Reject Preformation 
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.” *8 
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 preformation 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 
Wilhelm Roux: Zur Orientierung iiber einige Probleme der 
embryonalen Entwicklung. Zeitschrift fiir Biologie; Bd. XXI. July 
1885. P. 480—482. Gesammelte Abhandlungen. II, P. 206—207. 
