102 REPORT OF COMMISSIONERS OF INLAND FISHERIES, 



The importance of a careful study of abnormal structures is well 

 emphasized by Bateson: " To collect and codify the facts of varia- 

 tion is, I submit, the first duty of the naturalist. This work should 

 be undertaken if only to rid our science of that excessive burden of 

 contradictory assumptions by which it is now oppressed. V/hat- 

 ever be our views of descent, variation is the common basis of them 

 all. As the first step towards the systematic study of variation, we 

 need a compact catalogue of the known facts, a list which shall 

 contain, as far as possible, all cases of variation observed" (p. vi). 

 The following data may be valuable as contributing something to 

 such a list, and further — since some of these variations are authentic 

 regeneration products — they may serve in determining one source of 

 origin for such structures. 



Much of the material about to be described was obtained by 

 experiments made at the experiment station of the Rhode Island 

 Commission of Inland Fisheries, and from the commission's collec- 

 tion at the State House, in charge of Secretary Morton. Mr. Cart- 

 land kindly aided me in securing drawings from his collection at 

 Pemaquid Beach, Maine. And through the courtesy of the United 

 States Fish Commission, we were able to obtain possession of a most 

 rare specimen of triple chelse. The use of the epidiascope at the 

 anatomical laboratory of Brown University has also greatly facili- 

 tated the production of accurate drawings.* 



II. 

 ABNORMAL APPENDAGES. 

 A. Explanation of Terms. 



The following terms will be used in the sense indicated below: 

 Chelce: The pair of appendages which carry the " great forceps " 



or claws. 



Chelipeds: The appendages, including both the chelse and the 



thoracic limbs, or walking legs. 



* A method, it may be added, which is not only equally as accurate as the camera lucida, 

 but makes it possible to draw objects of such a large size as would be practically impossible by 

 means of the latter instrument. 



