August 16, 1901.] 



SCIENCE. 



245 



forms it takes place more slowly, at least 

 in large forms having large legs. In pro- 

 teus the regeneration may extend over a 

 year and a half, and in necturus it takes 

 more than a year to make a new limb, at 

 least in animals in confinement. In the 

 large form, amphiuma, that has extremely 

 small legs regeneration takes place much 

 more rapidly tfian in a form like necturus 

 having much larger legs. 



In amphiuma the feet are not used 

 by the animal as organs of locomotion, 

 since they are too small and weak to sup- 

 port the heavy body. They can be moved 

 by the animal in the same way that the feet 

 are moved in other forms, and yet are use- 

 less for progression. It is said by Schrei- 

 ber that the regeneration of the legs of 

 Triton marmoratus is relatively very slight 

 as compared with that of other forms. 

 Fraisse also found in this form that an 

 amputated leg did not grow again, only a 

 deformed stump being produced. The tail, 

 also, is said to regenerate to only a slight 

 extent, but, so far as I know, there is noth- 

 ing peculiar in the life of this form that 

 makes it less liable to injury than other 

 large urodeles,^ Weismann cites the case 

 of proteus that is said also to regenerate less 

 well than do other forms. It lives in the 

 caves of Carniola, where there are few 

 other animals that could attack or injure 

 it, and to this immunity is ascribed its lack 

 of power of regeneration, yet Goette states 

 that he observed a regenerating leg in this 

 form, but that the process was not complete 

 after a year and a half. In necturus also, 

 which is not protected in any way, regenera- 

 tion is equally slow. Frogs are unable to 

 regenera.te their limbs, although they are 

 sometimes lost, but the larval tadpole can 

 regenerate at least its hind legs. In the rep- 

 tiles the tail regenerates, though this is ac- 



*I do not know ■whether this animal was kept 

 long enough to make it certain that the legs do not 

 regenerate. 



complished more readily in some groups 

 than in others, but at present we do not 

 know of any connection between this con- 

 dition and the liability of certain forms to 

 injury. Turtles and snakes do not re- 

 generate their tails. I do not know of any 

 observations on crocodiles. 



In birds, the legs and wings are not sup- 

 posed to have the power to regenerate,* but 

 in two forms f at least the beak has been 

 found to possess remarkable powers of re- 

 generation. There are a few very dubious 

 observations in regard to the regeneration 

 in man of superfluous digits that had been 

 cut off. X 



These examples might be added to 

 by others in the groups cited, and also 

 by examples taken from the smaller groups 

 of the animal kingdom, but those given will 

 suflSce, I think, to show that the power to 

 regenerate is characteristic of entire groups 

 rather than individual species. When ex- 

 ceptions occur, we do not find them to be 

 forms that are obviously protected, but 

 the lack of regeneration can rather be ac- 

 counted for by some peculiarity in the struc- 

 ture of the animal. If this is borne in 

 mind as well as the fact that protected and 

 unprotected parts of the same animal re- 

 generate equally well, there is established, 

 I think, a strong case in favor of the view 

 that there is no necessary connection be- 

 tween regeneration and liability to injury. 

 "We may, therefore, leave this side of the 

 question and turn our attention to another 

 consideration. 



It will be granted without argument that 

 the power of replacement of lost parts is of 

 use to the animal that possesses it, espe- 

 cially if the animal is liable to inj ury . Cases 

 of usefulness of this sort are generally 



* A statement to the contrary quoted in Darwin's 

 ' Animals and Plants under Domestication, 'is douhted 

 by Darwin himself. 



t The stork and the fighting cocks. 



J See Darwin, loc cit. 



