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mates. Well then, affection of the endocrine organs asserts its influ- 
ence in the first place on these specifically human characteristics. 
From an a posteriori point of view, this is really quite natural 
and perfectly logical. The endocrine organs regulate the development 
of the form up to the most trifling details, and least considerable 
properties, they control the morphogenesis. In the man of to-day 
they co-operate in such a manner as to originate the Homo recens. 
But in the ancestor of man, with his rather pithecoid characters, 
their co-operation was such as to originate a more primitive form. 
During evolution the activity of the endocrine organs must therefore 
have undergone a modification, a morpbological character that in a 
primitive form acquired a certain degree of development, in a higher 
form must have altered its development. That alteration may be 
either a regressive one — so retardation. or suppression of the 
development -— or a progressive one, so a more forcible develop- 
ment. What I will call the architectonic function of the endocrine 
organs in man must be somewhat different from, say, that of Gorilla, 
or Chimpanzee. If the endocrine organs control the morphogenesis, 
then they must also adapt themselves in their function to the phy- 
logenetic metamorphoses. Is it, however, really beyond all doubt, 
that we have to speak of adaptation in this case? Did the endocrine 
organs indeed play only the passive part of adaptation, in this 
process, or was that part rather an active one, if not a directing, 
then, at least, a regulating one? The question is one of biological 
principle, for it is immediately related to the question of even 
wider bearing, whether evolution has only been brought about by 
the influence of external circumstances, or rather by such influence 
in connection with an internal agent. In a former publication I 
wrote in favour of the last named opinion and [ then pointed out 
the possibility that the endocrine organs have played an important 
part in evolution, It was then impossible to me to arrive at any 
notion as to the nature of that relation between their function and 
evolution. I believe now to have advanced a step, as it has become 
evident to me, that, at least in the bringing about of the specifically 
human characteristics, that influence has always acted in the same 
direction. 
The differences in form between related species may be brought 
about either by something existant developing more strongly, or 
being suppressed in its development. In this latter case, therefore. 
the influence of the endocrine organs must have been a retardative 
one. Well then, I propose to demonstrate that the development of 
the specifically human characteristics is the result of a retardative 
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