Regeneration Not Exact Repetition 



141 



Finally, cases are not rare in which a regenerating 1 

 organ alters its form, as in the lizard in which the new 

 tail has a skeleton not formed of individual vertebrae at 

 all, but of a little continuous, cartilaginous cylinder. 



Now the epigenetic theories explain very easily how 

 it comes that the part amputated can follow in its regen- 

 eration a shorter road than in its ontogeny (caenogenetic 

 regeneration), and how in many cases after completion of 

 the process, it may have a form quite different from that 

 of the original part. For the remaining part of the body, 

 on which the morphologic determination of the ampu- 

 tated part depends, is now in the adult state while for- 

 merly it was in the embryonic state. 



The altered condition in which it now exerts its 

 formative action upon the part in process of regenera- 

 tion explains the diversity, not only of the earlier results 

 obtained, in which development and regeneration proceed 

 in different ways, but also of the final results, in which the 

 regenerated part is of abnormal conformation. For the 

 differences of conformation which are produced at the 

 commencement of the process of regeneration cannot 

 always be smoothed out and effaced when, at the end of 

 the regenerative process, the condition of the rest of the 

 organism from which the formative action is exerted 

 upon the part in process of regeneration becomes again 

 the same in relation to that latter as at the end of 

 normal ontogeny. 



Weismann on the contrary, whose above quoted ex- 

 planation is clearly no more adapted to these cases, is 

 forced to take refuge in the following subsidiary 

 hypothesis : 



vensystems. Zeitscher. f. wissensch. Zoologie. Bd., 65. Zw. Heft, 

 1898. P. 229235. 



