No. 51 S J 



BEGENERA TION 



L01 



nature of the former, Boulenger finds no occasion for 

 applying the theory to the latter case. 



Barfurth finds that the axolotl often regenerates five 

 fingers on an amputated limb. Considering the complex- 

 ity of the regenerative mechanism, the frequent occur- 

 rence of abnormalities, and, as Barfurtli himself points 

 out, that " Modus und Product der Eegeneration von der 

 Art der Operation abliiingig sind" it would seem that the 

 regeneration of five fingers is of no more value from the 

 point of view of the salamander's phytogeny than the 

 double paw of a cat is for the appreciation of its phylog- 

 eny. Yet he is ready to believe that "die verhaltnis- 

 miissig hiiufigo Regeneration einer fiinffingerigen Hand 

 beim Axolotl ist ein Riicksehlag auf die urspriinglich 

 normalerweise fiinffingerige Hand der Amphibien." 



It will, perhaps, not be devoid of interest to note that 

 Ridewood, who studied the regeneration of the limb of 

 the toad, expresses himself quite differently upon this 

 question. "While in animals other than Anura," he 

 says, "structural differences between the regenerated 

 and the normal limb may be explained as phenomena of 

 atavism, there is no evidence of such phylogenetic re- 

 version in the regenerated limb-skeleton of the Anura 

 under consideration." 



It should be obvious that it is not sufficient to point to 

 some abstract ancestor, an imaginary conception, but 

 that the real ancestor must be known in order that the 

 genuineness of the reversion may be established beyond 

 doubt. It is absurd to apply the term "reversion" and 

 "atavism" to sporadic growths, not represented in the 

 normal development, of which the factors are, in most 

 cases, entirely unknown to us. 



The inconsistency ascribed to the theory may be 

 further exemplified by the following instances. Tn tra- 

 cheate insects, according to Brindley, the reproduced 

 portion of an amputated appendage is invariably unlike 

 the normal. In Blattidie fewer than five tarsi regenerate, 

 and the size of the parts is likewise different from the 



