148 A Homogencous Germ Substance Inadmissible 
those parts of the body which are independently and 
hereditarily variable, we have thus an exact measure for 
determining the number of the little vital particles which 
must compose the germ plasm: they cannot be fewer.” 
“We are then logically forced to assume that a special 
element exists in the germ plasm for each of these pecul- 
iarities, not because the inheritance of even the smallest 
details is possible, but because each of these parts of the 
body can have its variations inherited individually, each 
by itself. If all men possessed a certain depression in 
front of the ear, one could not conclude that because it 
was hereditary, it must be represented in the germ plasm 
by a special element * * * the fact which forces us 
to accept this hypothesis is that all men do not possess this 
depression, that we can imagine two people who resemble 
each other in all other respects but of whom one pos- 
sesses this depression and the other does not.” 1°? 
This is then the great and only argument of all the 
theories of preformistic germs. 
One cannot fail to see that it really possesses a very 
great value against such theories as that of Spencer, who 
supposes the germ plasm to be constituted by a homogene- 
ous substance. In the almost complete darkness in which 
we still find ourselves in respect to the nature and causes 
of ontogenetic phenomena, there are very few things 
which we can venture to call impossible. Nevertheless 
the supposition which is implied in the epigenetic theories 
of the Spencer type, namely, that a homogeneous germ 
substance a little different chemically from an other, is 
able to give rise to an individual quite identical with that 
which the other substance produces, except for one little 
**°Weismann: Das Keimplasma. P. 72—74. 
