1899] RE GENERA TION 3 1 1 



associated with any difference in the capacity for regeneration, since the 

 almost rudimentary first pair of appendages on the abdomen of the male 

 were renewed quite as often as those on the abdomen of the female, 

 although these last fulfil the important function of egg-carrying. 



These facts appear to tell very decidedly against the conception 

 of regeneration as a capacity regulated by adaptation, and the author 

 interprets his results in this way, and sums up as follows : " There 

 is no relation between the frequency of loss and the regenerative capacity 

 of a part : those who believe that there is such a relation overlook 

 an important part of the problem. Even if it had been found that the 

 parts most susceptible of injury were those most capable of regenera- 

 tion, it would not follow that this depended on so-called Natural 

 Selection. To assume this is to overlook the fact that unless these 

 animals had had from the beginning the power of replacing lost parts 

 they could not have survived at all, but would of necessity have be- 

 come extinct." 1 



These are astonishing views. One might just as well say that it 

 is impossible for Natural Selection to have brought about any change 

 in an important part or character in the course of phylogeny, because 

 the particular variation necessary to life must have been present from 

 the first, since otherwise the species must have died out ! It seems 

 not to have occurred to Morgan that the changes in the structure of 

 a species may have kept pace with the changes in the conditions of 

 its life — yet this is a presupposition of the hypothesis of Natural 

 Selection, and is indeed its conditio sine qua non. Hermit-crabs have 

 certainly possessed the power of regeneration " from the beginning," 

 but may they not have inherited it from their ancestors, the long- 

 tailed forms, which possess it to this day and have need of it for all 

 their appendages since all are liable to injury ? And cannot, nay, 

 must not, these in their turn have inherited it from their ancestors, 

 the sessile-eyed crustaceans, and so on through the whole crustacean- 

 pedigree back to the unknown annelid-like ancestors of the class ? 

 But doubtless even these possessed in a certain degree — probably even 

 in a higher degree — the power of regeneration, from which that of 

 the oldest crustaceans must have originated, and become localised 

 and transformed. We know that the lower worms have quite as high 

 a regenerative power, extending to all their parts, as the lower 

 Coelentera or polypes for instance. It seems almost as if Morgan 

 ascribed to me the view that the capacity for regeneration must be 

 built up anew for each species — must be inscribed so to speak on a 

 tabula rasa : my view, however, is that here, as in all transformations, 

 Nature started with what was already present, and by modifying it 

 brought about adaptation to new conditions. The assumed general 

 power of regeneration in the lowly ancestors of the crustaceans 



1 This quotation is translated from the German. We have been unable, at the moment, 

 to procure a copy of Mr. Morgan's paper.— [Tn.] 



