286 Theories Treating of Inheritance 
end the acceptance of these germs has led necessarily to 
systems which reject the inheritance of acquired char- 
acters concur to prove, although more proof is certainly 
no longer necessary after all the other considerations 
which we have developed in an earlier chapter, that the 
very idea of these preformistic germs is untenable, as is 
thus every theory founded upon them. 
However limited the number of theories or hypoth- 
eses selected by us, and however rapid and brief the 
critical exposition which we have made of them, it seems 
to us nevertheless that it is unnecessary to proceed further 
with our examination. For it has shown us that among 
the principal theories, which up to the present have been 
devised to explain the inheritance of acquired characters, 
none has accomplished this difficult task, and it has 
already served another purpose for which chiefly we 
undertook it. This purpose consisted on the one hand in 
bringing to light in other theories the most suggestive and 
fruitful ideas put forward; on the other hand in deter- 
mining the conditions which are necessary and sufficient 
to render possible the inheritance of acquired characters, 
and a critical examination of concrete theories already 
developed has certainly helped to put these conditions in 
evidence better than simple reflection upon them could 
have done. 
If we take a look over the road which we have thus far 
traveled we see that among these conditions those which 
have appeared to us as the essential and fundamental ones 
are the three following: 
1. All the manifold physical, chemical, morphologi- 
cal, and physiologic variations, which can appear in the 
most different parts of the organism, are to be ascribed 
