612 F. A. POTTS. 



stability of the effect produced here with the case recorded 

 byGiardof Phryxus paguri and Eupagurus bernhardi. 

 The parasite is fixed ou the abdomen of the hermit crab, 

 and it is comparatively easy to remove it from its host 

 without injury to the latter. Giard did this in the case of 

 a modified male crab, and when, after being kept for a 

 month, it moulted, he thought he could observe an incipient 

 return to the unmodified condition of the appendages, the 

 gonads being still of small size. It may, perhaps, be affirmed 

 that the two cases are fundamentally different, and that 

 Phryxus is purely an ectoparasite, its effect naturally passing 

 away after removal, while it is impossible to entirely nullify 

 the effect of the Peltogaster by operation, the roots con- 

 tinuing to live and play the same part as the complete 

 parasite, but the same results have been obtained with 

 Eupagurus meticulosus even in cases where the partial 

 recovery of the gonads showed that the parasitic stimulus 

 had finally ceased to act. 



(2) From regeneration. 



As in the American species on which T. H. Morgan espieri- 

 mented, the abdominal appendages of Eupagurus meticu- 

 losus are easily capable of regeneration. Various abdominal 

 appendages were cut off from crabs, in a large number of 

 which the Peltogaster was at the same time removed. In all 

 cases at the next moult the appendages were found to be 

 regenerating. When the appendage was cut off proximal to 

 the bifurcation the rami regenerated but feebly, but if the 

 cut was made at a level slightly distal to the bifurcation an 

 almost complete regeneration took place. Unfortunately the 

 number of operations of the latter class were but few, and in 

 those of the former it was difficult to see whether the degree 

 of modification in the old and new appendages exactly corre- 

 sponds. But the point which comes out clearly as a result 

 of these experiments is that females and modified males 

 (pi. 34, fig. 1), from which the Peltogaster has been removed, 

 regenerate appendages in which both rami are of approxi- 

 mately equal size, while unmodified and slightly modified 



