209] REGENERATION OF CRAYFISH APPENDAGES 21 



In the ambulatory appendages it is not so unusual to find 

 them broken at different levels and regeneration from these lev- 

 els taking place. Fig. 19, PI. I, shows a ventral view of the re- 

 generating right last leg of C. gracilis, 35 mm. in length. This 

 appendage was broken off between the third and fourth seg- 

 ments. The new portion is three days old. 



I have never known of a single instance occurring under 

 natural conditions, where an appendage was broken off at a level 

 proximal to the breaking- joint. My experiments with appenda- 

 ges removed below the second joint have never yielded positive 

 results. New tissue is formed, but in no case has it ever assumed 

 the appearance of a regenerating appendage. I have never seen 

 an individual moult, however, after an appendage had been re- 

 moved below the usual breaking-joint. I can not speak conclu- 

 sively on this point. 



Morgan ( :oo, pp. 2 and 3) states that in the hermit crab 

 regeneration takes place very readily at a point proximal to the 

 breaking-joint. In the crayfish, however, it is at least certain 

 that regeneration does not occur as readily, or in the usual man- 

 ner, proximal to the breaking-joint as at that point or distal to 

 it. 



In a collection of crayfish I once found an individual with 

 a double chela (Fig. 20, PI. I). This chela was evidently a re- 

 generated one, for it was very much smaller than the one on the 

 opposite side and was of less than the normal size for the cray- 

 fish which bore it. The two segments proximal to the breaking- 

 joint were of the same size as the corresponding segments on the 

 opposite side, thus indicating that the break had taken place at 

 the usual level. 



Deformed claws in lobsters seems to be a much more usual 

 occurrence than in crayfish. Herrick ('95, pp. 144-148) gives 

 some interesting notes on this phenomenon, and also mentions 

 the fact that these deformities have attracted the attention of 

 naturalists for more than two hundred years. Recent writers 



