REGENERATION AND LIABILITY TO INJURY 97 



important data. Furthermore, a comparison may be made between 

 different parts of the same animal, or between the same parts of 

 different animals living under similar or dissimilar conditions. 



There are only a few cases known in which a systematic exami- 

 nation has been carried out of the power of regeneration of the dif- 

 ferent parts of the body of the same animal. Spallanzani's results 

 show that those salamanders that can regenerate their fore legs can 

 regenerate their hind legs also. Towle, who has examined in my 

 laboratory the regeneration of a number of American newts and sala- 

 manders, finds also that both the fore and hind legs regenerate in the 

 same forms. The tail and the external gills, in those newts with 

 gills, also regenerate. It has also been shown in triton that the eye 

 regenerates if a portion of the bulb is left. Broussonet first showed 

 (1786) that the fins of fish have the power to regenerate, although, 

 strangely enough, Fraisse and Weismann state that very little power 

 of regeneration is present in the fins of fish. I have found that the 

 fins of several kinds of fish regenerate, belonging to widely different 

 families. 1 In Fnndnlns heteroclitus I have found that the pectoral, 

 pelvic, caudal, anal, and dorsal fins have the power of regeneration. 

 In reptiles the feet do not regenerate, at least no cases are known, 

 but the tail of lizards has this power well developed. In birds neither 

 the wings nor the feet regenerate, but Fraisse has described the case 

 of a stork in which, the lower jaw being broken off, and the upper 

 being cut off at the same level, both regenerated. Bordage has 

 recorded the regeneration of the beak of the domesticated fighting 

 cocks (of the Malay breed) of Mauritius. In the mammals neither 

 the legs, nor the tail, nor the jaws regenerate, although several of 

 the internal organs, as described in the next chapter, have extensive 

 powers of regeneration. 



The best opportunity to examine the regenerative power in simi- 

 lar organs of the same animal is found in forms like the Crustacea, 

 myriapods, and insects, in which external appendages are repeated in 

 each or many segments of the body. In decapod Crustacea, includ- 

 ing shrimps, lobsters, crayfish, crabs, hermit-crabs, etc., regeneration 

 takes place in the walking legs of all the forms that have been exam- 

 ined, and this includes members of many genera and families. I have 

 made an examination of the regeneration of the appendages (Fig. 37) 

 of the hermit-crab. In this animal, which lives in an appropri- 

 ated snail's shell, only the anterior part of the body projects from the 

 shell. The part that protrudes is covered by a hard cuticle, while the 

 part of the body covered by the shell is quite soft. Three pairs of 

 legs are protruded from the shell. The first pair with large claws 



1 Fundulus heteroclitus, Stenopus chrysops, Decapterus macrella, l\fenticirrhus macre/la, 

 Carassins miralus, Phoxinus fundtdoides, Noturus s/>., arrl a few others. 

 H 



