144 ^ 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. 



j. 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- 



