106 REGENERATION 



In the teleostean fishes the fins of a number of forms are known to 

 regenerate. It is probable that this takes place in most members of 

 the group. 



In the amphibia we find a large number of forms that regenerate 

 their limbs and tail, and other parts of the body, but limitations appear 

 in certain forms. The rapid regeneration of the legs in the smaller 

 urodeles has been often described. In larger forms it takes place 

 more slowly, at least in large forms having large legs. In proteus 

 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 than in a form like 

 "necturus having much larger legs (Fig. 39). 



In amphiuma the feet are not used by the animal as organs of 

 locomotion, since they are too small and weak to support 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 useless for progression. 

 It is said by Schreiber 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 nothing peculiar in the life of this form that makes it less 

 liable to injury than other large urodeles. 1 Weismann cites the case of 

 proteus, which 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 regen- 

 erating 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, regeneration is equally slow. Frogs are unable to regenerate 

 their limbs, although they are sometimes lost, but the larval tadpole 

 can regenerate at least its hind legs. In the lizards the tail regen- 

 erates, but at present we do not know of any connection between 

 this condition and the liability of certain forms to injury. Turtles 

 and snakes do not regenerate their tails. I do not know of any 

 observations on crocodiles. 



In birds, the legs and wings are not supposed to have the power 

 to regenerate, 2 but in two forms 3 at least the beak has been found to 



1 I do not know whether this animal was kept long enough to make it certain that the 

 legs do not regenerate. 



2 A statement to the contrary quoted in Darwin's Animals and Plants under Domesti- 

 cation is doubted by Darwin himself. 



8 The stork and the fighting cocks. 



