352 Fecundation 
phenomenon, be it only in so far as a phenomenon of 
assimilation, is itself essentially a rhythmic phenomenon. 
In regard to fecundation we know that it was Spencer 
who first recognized what has been more or less explicitly 
accepted by others, that it consisted probably in a per- 
turbation of an equilibrium which tended toward a 
stability unfavorable to vital activity.2°° 
Now we have already seen how our hypothesis set 
forth above is able to make at once conceivable in what 
this equilibrium unfavorable to vital activity may consist. 
According to this hypothesis, it would consist in the 
equalization toward which the masses, and the corres- 
ponding potentials, of the coupled accumulators of each 
mnemonic element would tend, and which they would 
eventually attain, and this equilibrium would be disturbed 
by the substitution for one of these accumulators of an- 
other specifically equal to it but differing in mass and 
potential. And it is precisely in this function of fecunda- 
tion, of replacing in each couple one of the specific 
accumulators by another differing quantitatively as 
widely as possible, that we find an explanation of the fact 
that the rejuvenation of the germ and the consequent 
vitality of the progeny to which fecundation tends, are 
proportionally greater when fecundation occurs not be- 
tween individuals too closely related but rather between 
individuals which belong indeed to the same species but 
are somewhat dissimilar. 
According to the same hypothesis, this equilibrium 
could also be deranged by the extra-nuclear discharge of 
one of the two coupled accumulators, and this is just what 
*s*Spencer: Principles of Biology. I, P. 340—341, and II. P. 
614—616. 
