REGENERATION IN CAMBARUS. 309 



it not be an index of the comparative plasticity of the two parts? 

 The more rapid regeneration of the thoracic appendages than 

 of the swimmerets in the adult crayfish, may be due to a longer 

 retention of the plastic embryonic condition of the cells in the 

 region of the breaking joint by the former, certainly not to any pro- 

 portionate difference in the food supply of the two series of organs. 



The important point in Morgan's results which he properly 

 emphasized, was that regeneration did take place, however slight 

 it might be. While we cannot say that the abdominal append- 

 ages of crayfishes are never injured, yet injuries to them are rare 

 in nature. Examination of hundreds of individuals has shown 

 that there is a remarkable uniformity of size and structure in 

 these organs, a condition which could not exist if mutilations 

 were frequent. Yet these appendages possess as high a power 

 of regeneration in youthful stages as any of the appendages 

 which are so frequently torn away. My experiments strengthen 

 very much the evidence in favor of Morgan's statement that 

 there is no relation between power of regeneration and liability 

 to injury. 



CONCLUSIONS. 



The following conclusions may be drawn from the study of 

 abnormalities, and the results of the experiments described in 

 this paper. 



1 . The abdominal swimmerets of C. (Bartonius) bartoni Fabr. 

 all possess a high power of regeneration in immature specimens. 

 Since regeneration of swimmerets has been noted in Cambarus 

 propingnus, Palcsmonetes vn/garns, Homarus americanns and Eu- 

 pagurus longicarpus, it is probable that the decapods generally 

 possess this power, especially in young individuals. 



2. This regeneration usually cannot be seen till after one, and 

 sometimes two, moults have occurred, due to masking of the 

 regeneration by the exoskeleton. 



3. Slow regenerative processes in the swimmerets of.the older 

 individuals are due probably to a lower degree of plasticity in the 

 protoplasm rather than to insufficiency of the food supply. 



4. Injuries may occur, but they are rare in swimmerets, and 

 the power of regeneration and liability of the parts to injury are 

 apparently independent. 



