Instincts 413 
characters present themselves exactly in the order of 
their phylogenetic acquisition. 
If the capacity which centroepigenesis possesses of 
explaining the Lamarckian principle extends so far as to 
account, without needing any subordinate hypothesis, for 
the inheritance of those characters also’ which either sex 
has acquired separately and at different times and each 
on its own account, it shows itself still more especially 
and completely adapted to explaining the inheritance of 
those characters common to both sexes as well as those 
belonging only to one sex which, in consequence of their 
excessive complexity and of the circumstance that they 
are located not simply in definite parts of the organism 
but rather in numberless places at the same time, have 
so far always constituted the greatest difficulty for every 
theory which has attempted to explain the inheritance 
of them. We refer to the instincts. 
It is evident in fact that we can regard every instinct 
as due to a special relative mode of being of the different 
psychic centers and of the nervous network connecting 
them. For it depends upon this relative mode of being 
that to certain definite sensations which arrive at certain 
perceptive centers there correspond necessarily certain 
reflex movements induced by the motor centers which 
are in definite communication with these perceptive 
centers. Now, however, every deposition of new psychic 
centers, perceptive or motor, mnemonic or volitional, 
and every new connection of these by means of nervous 
communications more or less direct or indirect, more 
or less conductive or resistant, would be, according to 
the centroepigenetic hypothesis, only the effect of as 
many special modes of being of nervous circulation in 
the limited territory of the nervous system alone. It 
