2O4 EDMUND IS. WILSON. 



ordinary conditions, the animal regenerates without reversal. For 

 example, from a male left-handed individual the large chela was 

 removed and twelve days later (a period long enough to effect a 

 complete reversal, as shown by other experiments) the remaining 

 small chela was also removed. The animal moulted nine days 

 later (twenty-one days after the first operation) and is not reversed - 

 showing a typical small chela on the right side and a large one 

 on the left, which however is less modified than usual. 



The absence of reversal in the seven cases in which the remain- 

 ing chela was cast may have been due to the same cause as in 

 the above experiment ; but two cases remain, that seem beyond 

 question, though one of these did. not moult quite normally and 

 the other not at all. The first case (Fig. 3, D-F), a right-handed 

 male, moulted nine days after the operation, but did not succeed 

 in extricating the small chela from the cast skin. The appen- 

 dage was, however, easily drawn out by hand, in an apparently 

 quite healthy condition, and fixed in formalin. From the right 

 stump of the large chela had been regenerated one of the same 

 type (Fig. 3, F], which though still small, shows clearly enough 

 all the characteristic features of the appendage. The appendage 

 drawn out of the cast (Fig. 3, E] is on the whole of the small 

 type but has lost the characteristic setose ridge of the dactylus, 

 and shows an indication of the hammer. It is, however, far less 

 modified than the uninjured appendage after the same period of 

 time (Fig. 3, B}. 



The second case, which did not moult, is shown in Fig. 3, G, 

 77, fourteen days after the operation. The appendage developed 

 on the stump of the large chela, though small, is plainly of the 

 large type. The small (left) chela, owing to the absence of a 

 moult, shows no change. 



The foregoing data are too meager to have a very high value, 

 yet they render it probable that the moulding of the small chela 

 into one of the large type, and the production of the small one 

 on the opposite side is controlled by the nervous system --a re- 

 sult in accord with Herbst's remarkable observations on the re- 

 generation of the eye in Palcemon and Morgan's on the regen- 

 eration of the head in Allolobophora. It is possible that the 

 failure of reversal in such operations in AlpJicus is due to a circu- 



