HERMIT CRAB AND PELTOGASTER. 619 



modified crabs and crabs which have almost entirely assumed 

 the female characters. 



(4) The apparent cases of modification in the female 

 toward the male type are probably due to unusually eai'ly 

 infection^ a retarding influence being exerted by the parasite 

 on the incompletely developed secondary sexual characters 

 causing them to remain in the less advanced male stage. 



(5) In Eupagurus prideauxi a similar development of 

 the female secondary sexual characters in the male was 

 observed. 



(6) Observations on the moulting and regeneration of the 

 abdominal appendages show that the final degree of modifi- 

 cation is attained early after the commencement of the 

 external stage of Peltogaster^ and is never afterwards altered 

 either by continued action of the parasite or by its extirpa- 

 tion. The great range of degree in modification is the 

 expression of individual variability in the hermit crabs. 



(7) The looseness of the correlation between the changes 

 in the primary and secondary sexual characters shows that 

 the latter ai'e not directly consequent upon the formei'^ but 

 rather that both are attributable to some change in the 

 general metabolism. 



Note. — In " Exped. Sci. Travailleur et du Talisman^ Crus- 

 tacea Decapoda^ pt. i, Brachyura et Anomura^ 1900^ p. 228," 

 A. Milne-Edwards and E. L. Bouvier assign the crabs here 

 called Eupagurus angulatus to Herbst's earlier species 

 E. excavatus, and that known as E. meticulosus to E. 

 excavatus var. meticulosus. 



September, 1906. F. A. P. 



BiBLIOGEAPHY. 



1. QiAKD, A. — "La castratiou parasitaire," 'Bull. Soc. Dep. du Nord,' 

 ser. 2, 10 Annee, 1887. 



