Summary of This Chapter 223 
chapter, we are able to affirm that although no fact or 
argument is capable by itself alone of affording an ir- 
refutable and unconditional proof either direct or indirect, 
of the inheritance of acquired characters, nevertheless the 
sum total of the facts and the arguments which are fa- 
vorable to it is so weighty that one is not only justified in 
believing but is even compelled to believe that the 
Lamarckian principle is in all probability correct. 
But the difficulties of explaining the mechanism of 
inheritance are so great, that many investigators may 
have thought them to be insurmountable. It is conceiv- 
able that many others, like Roux, have been led to dis- 
pute its existence, just in order to free themselves in that 
way froma veritable nightmare. But this position is no 
longer possible. 
The objective examination of the question leads to 
the conviction that the inheritance of acquired characters 
is to be considered as in all probability a reality, there- 
fore we are in duty bound to seek an explanation of this 
phenomenon by some hypothesis, even if it be only a 
provisional one. 
So in the following chapter we propose to examine 
comparatively a few of the most recent and most im- 
portant -hypotheses which have been devised for the 
explanation of inheritance. After that in the penultimate 
chapter we shall set forth more thoroughly the explana- 
tion of the Lamarckian principle which the centro- 
epigenetic hypothesis can give. 
Further evidence that somatic changes induced in animals by 
envircnmental influences may be repeated in their descendants as 
a result of germinal influences is furnished by Sumner and by 
Kammerer. See Archiv fiir Entwicklungs—Mechanik der Organ- 
ismen, Leipzig, June and September, Ig10. (Translator. ) 
