144 A Homogeneous Germ Substance Inadmissable 
The first part has shown us that simple epigenesis is 
directly and decidedly controverted by a whole series of 
indubitable facts and results which no one now opposes. 
The second part, which refutes preformation, shows us 
on the contrary that the nature of every process of 
development is really epigenetic. 
And thus a correspondingly greater probability is es- 
tablished for those hypotheses which, concentrating the 
power of sending forth the controlling influences of 
development into a single well defined zone of the orga- 
nism, thereby explain quite as well as epigenesis the facts 
that are irreconcilable with preformation, and are at the 
same time in accord also with all the facts which simple 
epigenesis is incapable of explaining, 
3. Inadmissibility of a Homogeneous Germinal 
Substance 
It will not be necessary to give this question more 
than a very brief consideration, for it is sufficient to men- 
tion the chief argument which all the partisans of pre- 
formistic germs, the epigenesists as well as the preform- 
ists proper, have repeated incessantly and still repeat. 
The fact that in doing this each uses almost the same ex- 
pressions as the others shows how conclusive this 
argument is. 
“The considerations,” remarks Wilson, “which have 
led to the rehabilitation of the theory of pangenesis are 
based upon the facts of what Galton has called particu- 
late inheritance. The phenomena of atavism, the char- 
acters of hybrids, the facts of spontaneous variation, all 
show that even the most minute characteristics may ap- 
pear or disappear independently, may be modified inde- 
