No. 6.] LIABILITY TO INJURY. 297 



Two individuals (the same that regenerated the first append- 

 ages) regenerated the second appendages (Figs. 22, 24). Both 

 were males. Eleven others had not regenerated. The third 

 abdominal appendage of a male (belonging, therefore, to the 

 fifth abdominal segment) had regenerated (Fig. 25). This was 

 also on one of the individuals that had regenerated the first two 

 appendages. The same appendage had been removed from six 

 other males and from two females, and had not regenerated. 

 In three cases the third abdominal appendage (of the fourth 

 segment) of three females had been removed and had not 

 regenerated. 



How far the regeneration of these appendages is dependent 

 on an ecdysis I do not know. The more anterior appendages 

 of the body may develop quite far before the animal changes 

 its exoskeleton. 



Summary. - The experiment shows that the abdominal 

 appendages have the power of regeneration, although they do 

 not regenerate as readily as do the more anterior appendages, 

 or as do the last abdominal appendages. The positive evidence 

 showing that the anterior abdominal appendage regenerated in 

 several cases is, I think, of much greater weight than the 

 negative evidence that they did not do so as frequently as the 

 other appendages during the short time of the experiment. 



In regard to the relative usefulness of the abdominal append- 

 ages little can be said. In the male they are small and weak, 

 and one, the third, present in the female, is absent in the male. 

 In the female the first three abdominal appendages carry the 

 eggs. They are, therefore, essential for the existence of the 

 race; yet there is no difference found between the power of 

 regeneration of the three anterior egg-bearing appendages 

 of the female and the two corresponding appendages of the 

 male. 



IV. CONCLUSIONS. 



The results of the experiments show that the more anterior 

 appendages regenerate quickly. A large percentage of the 

 parts removed had begun to regenerate even during the short 



