REPORT OF COMMISSIONERS OF INLAND FISHERIES. 147 



have any of these writers furnished positive experimental evidence 

 for their conclusions. I have been unable to fiml in their descrip- 

 tions any proof that double limbs or symmetrical crusher chela have 

 ever arisen in a congenital manner. While the theory of injuries 

 after moulting seems very plausible, proof still remains to be pro- 

 duced. Apparently the first case of double claws of which the origin 

 and history is positively known is the specimen recently discribed 

 by Zeleny ('05) ; who, in one of his experiments, obtained the regener- 

 ation of a double chela in the fiddler crab. It is evident, then, that 

 before we can hope to clear up this question, we need more accurate 

 data on the formation of these abnormal structures. 



Specimens Nos. 7, 8, 9, may be something of a contribution 

 toward this required data. Attention has been called to the fact that 

 all these cases are regeneration products. In these specimens we have 

 at least two authentic cases of the regeneration of similar crushing 

 chelae, and one case of the regeneration of a triple claw of the type 

 which both Faxon and Bateson were strongly inclined to be only 

 congenital in origin. These three cases, together with Zeleny's, 

 serve, therefore, to establish the process of regeneration as a factor in 

 the origin of abnormalities in crustacean limbs. 



h. Further Considerations Favoring the Regeneration Theory. 



1. That the Abnormal Crustacean Limbs Found so far have been only 

 on Adult Animals. 



If double or triple claws are congenital in their origin, we might 

 expect to occasionally meet such abnormalities in very young lob- 

 sters. The lobster hatchery at the experiment station of the Rhode 

 Island Commission of Inland Fisheries furnishes an excellent 

 opportunity for such observations. But among the hundreds of 

 thousands of lobsters reared yearly from the egg, no case of chela 

 repetition has yet been reported; and I have also personally exam- 

 ined with care something over 2,000 fourth and fifth-stage lobsters 

 without observing a single case of duplication of parts in the chelipeds. 



