203] 



REGENERATION OF CRAYFISH APPENDAGES 



15 



ent, in part at least, upon the time of year and the age of the in- 

 dividual. 



The following table gives the record of a number of 

 crayfish, none of which exceeds three inches in length, the ma- 

 jority of them being smaller. It can be seen from the table that 

 the time required for regeneration is extremely variable, in 

 some cases all five new segments developing in less time than is 

 required for the appearance of the papilla in other cases. 



No. 



Regeneration. 



Date. 



Regeneration. Date. 



Number of 

 days 



days 



days 



23 days 



23 days 



days 



days 



5 days 



and 3 days. 

 7 and 3 days 



7 and 5 days. 



8 and 5 days. 

 8 and 5 days. 

 31 days 



In No. 2 the chela was broken off in the process of moult- 

 ing and it will be noticed that regeneration took place very rap- 

 idly in this case. The five new segments were formed within a 

 week. In No. 3 the time required to produce the same regenera- 

 tion was three weeks. Of course a part of this diflference may 

 have been due to a difference in the physiological condition of 

 the two animals, but there is no doubt that the fact that the one 

 had just moulted while the other had not is one of the most im- 

 portant factors in the question. In Nos. 10, 11, and 12 a chela 

 was removed at the same time, and No. 10 had moulted a few 

 days before. The papilla appeared a day earlier in the latter 

 case than in the other two, and the growth was more rapid af- 

 terwards. After the papilla once appears, it is difficult to see 

 why the growth should not proceed as rapidly in one case as in 

 the other. The difference must be due to physiological causes. 



On October 16, 1896, a large crayfish was obtained from 



