300 Explanation of Inheritance 
special cases of this reversibility, and all find their im- 
mediate explanation in this very simple hypothesis. 
In résumé: By this hypothesis of a nervous accumu- 
lator formed and deposited by the same specific current 
which it can afterward restore, the first of the two sub- 
conditions, included in the third condition, necessary and 
sufficient to account for the inheritance of acquired char- 
acters, are fulfilled. On the other side the localization of 
the germinal substance in the central zone, which con- 
stitutes the point of departure and the foundation for the 
hypothesis of centroepigenesis, has already satisfied com- 
pletely the second of these sub-conditions. As to the two 
other conditions, the first has already been satisfied by 
considering the nervous current with its numerous differ- 
ent specificities as the common denominator or as the 
basis of vital phenomena of the most diverse kinds which 
are in activity at each instant in the most varied points of 
the soma; the second was satished by assuming a con- 
tmuous action on the part of the germinal substance 
throughout the whole of ontogeny, by means of the 
steady activation of new specific potential elements pour- 
ing their discharges into the general circulatory system. 
It follows from this that centroepigenesis is able singly 
and alone to explain the inheritance of acquired char- 
acters, because it fulfills these conditions which we rightly 
regarded not only as necessary, but also as sufficient. 
For greater clearness, nevertheless, it will be worth 
while to institute, as we have indicated above, a compar- 
ison between this ontogenetic development, as it would be 
constituted according to the hypothesis of centro- 
epigenesis, and a very characteristic phenomenon, in some 
respects analogous, which is presented by the inorganic 
world. The reproduction of a sentence by a phonograph 
