CHAPTER SIX 



THE MOST IMPORTANT OF THE EXISTING BIOGENETIC 

 THEORIES IN RELATION TO THE INHERITANCE OF 

 ACQUIRED CHARACTERS. 



We believe it is unnecessary to discuss here in an 

 exhaustive way the fact that the question of the admis- 

 sibility or inadmissibility of the Lamarckian principle re- 

 mains always distinct from, and entirely independent of 

 the question of the evolutionary or epigenetic nature of 

 development. Darwin in his evolutionary theory with 

 preformistic germs, a true theory of preformation, 

 accepts inheritance ; Galton limits it to a few cases ; Weis- 

 mann excludes it unconditionally. Hertwig accepts it in 

 his epigenetic theory, although he does not exclude some 

 sort of preformistic germs; DeVries excludes it. Roux 

 who was inclined at first to believe that this inheritance 

 might exist in combination with the chemical develop- 

 ment of the egg, a theory frankly evolutionary without 

 preformistic germs, has finally regarded the two theories 

 as irreconcilable. The only theories which appear es- 

 pecially inclined toward the complete acceptance of the 

 Lamarckian conception, are the epigenetic theories with- 

 out preformistic germs, for example that of Spencer. 



We can now pass on to the rapid review of the 

 principal biogenetic theories current today, with especial 

 reference to their direct or indirect relation to the ques- 



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