294 Explanation of Inheritance 
is likewise proportional to the mass of the substance of 
the accumulator, (because it is proportional to its nervo- 
motive force, which also is in its turn proportional to this 
mass, according to the preliminary hypothesis), then the 
quantity of work required to effect the change under con- 
sideration, must be regarded as equivalent to a resistance 
R, which opposes the discharge. 
If now we assume that in nearly all cases, which come 
into consideration here, the quantity of work, requisite 
for effecting a given change in the dynamic equilibrium 
of the whole circulatory system, is proportionately 
greater the more considerable (if we may be pardoned 
for this much too indefinite expression) in quantity and 
quality this change is, it becomes at once conceivable why 
each specific potential element of the central zone can 
becomes activated only when the embryo has reached 
the ontogenetic stage, corresponding to the particular 
phylogenetic stage at which this element was acquired by 
the germinal substance. For then first will the change 
which the dynamic system of the embryo undergoes, as 
a result of the activation of this specific potential element, 
be the very least possible, and therefore usually also the 
only one whose resistance can be surmounted by the very 
weak nervo-motor force of this specific potential element. 
The following general rule can thus be established: 
The smaller the mass and therefore the nervo-motor 
force of a specific accumulator, so much the more 
closely is its discharge dependent upon the condition 
that the whole dynamic system, above all and very 
especially in the immediate neighborhood of the ac- 
cumulator, find itself again in exactly the same state in 
which it was when the accumulator was formed. Con- 
versely, the greater the mass of the accumulator, the 
