Distribution of Energy Explains Ontogeny 51 
“in which nature destroys in a manner which may seem 
to us cruel, cells which have just been produced.” The 
hypothesis of the distribution of trophic nervous energy 
seems to us the only one which can give a satisfactory ex- 
planation of this phenomenon. 
The struggle of the parts of the organism cannot in 
fact be the exclusive cause of this involution of young 
tissues. This struggle is not sufficient by itself to explain 
the exactness of the epoch and of the stage of develop- 
ment at which this physiological involution takes place. 
Even if we were willing to admit that this struggle has 
some effective participation in the production of this 
phenomenon, we must nevertheless admit that in addition 
an inciting ontogenetic stimulus, as Roux would say, 
must at the appointed time exert its trophic action upon 
the parts destined to victory, while it abandons others 
previously favored, but which now are devoted to destruc- 
tion. The distribution of trophic nervous energy with its 
changes would thus always remain the only cause of the 
phenomenon. 
But if ontogenetic physiological involutions are due to 
the fact that the distribution of trophic nervous energy 
abandons one region to turn to another, similar changes 
and shifting of this distribution must then be likewise 
the cause of all invaginations and evaginations, of all 
morphological phenomena in general and, with much 
probability, consequently, of those ontogenetic phenomena 
also which are not exclusively morphological in nature. 
To produce each one of these serial ontogenetic mod- 
ifications in the distribution of trophic nervous energy it 
would suffice theoretically that at the required moment 
there become active, were it only upon one certain point 
of the circulatory system, a single new definite specific 
