82 Charles Zeleny. 



not entirely satisfactory. Twenty specimens, ten with the large 

 chela on the right side, and ten with it on the left, were treated 

 in this way. Five specimens had moulted at the end of 62 days 

 after the operation when the experiment was closed. The first 

 one moulted 54 days after the operation and in this the regen- 

 erated chela ( = former large one) was as yet smaller than the 

 other ( = former small one). The old small one had no pro- 

 nounced change as a result of the moult. In the four other 

 specimens, one of which moulted 59 and the other three 62 

 days after the operation, the new regenerated chela was in each 

 case larger than the opposite old one, though it had not as yet 

 attained the full size and characteristics of the typical large one. 



It may be safely concluded from the above observation that no 

 reversal of the chelae in the sense of the reversal of opercula in 

 Hydroides takes place in the males of Gelasimus after removal 

 of the large chela, for it seems evident that in the first case men- 

 tioned, where the regenerated chela was as yet smaller than the 

 old small one of the opposite side, it had not yet reached its full 

 growth. In further support of this view is the fact that no pro- 

 nounced change in the old chela was noticed. 



b. Small Chela Alone Removed. The following results were 

 obtained when the small chela alone was removed: Only four 

 of the ten specimens moulted before the end of the 62 days, con- 

 stituting the limit of the experiments. In all of these the newly 

 regenerated chelae were much smaller than the opposite large ones 

 and approached in character the ordinary small chelae. The four 

 specimens mentioned moulted, respectively, 48, 61,61 and 62 days 

 after the operation. Therefore, here also there is no reversal of 

 the chelae. 



e. Both ChelcB Removed. In this set of experiments both 

 chelae were autotomized. Ten specimens were kept for 62 days 

 and eighteen for 42 days. Seven of the former moulted and 

 showed the characters of the regenerated chelae. In each of the 

 seven a large chela was regenerated in place of the former large 

 one and a small chela in place of the former small one. There 

 was no reversal. The chelae after the first moult did not of course 

 as yet have the full size of the old ones but the difference in size 

 was very evident. 



In one of the seven cases mentioned here as having moulted so as 

 to show the characters of the regenerated "chelae one specimen 



