CEUSTACEA 97 



segment of the protopodite has been named the coxopodite, 

 and the distal segment the basipodite. Similarly the five 

 segments of the endopodite have been called in succession, 

 beginning at the proximal end, ischiopodite, meropodite, 

 carpopodite, propodite, dactylopodite. The chelate condition 

 arises by the propodite being prolonged beyond the articula- 

 tion of the dactylopodite, so that the latter comes to be articu- 

 lated antero-laterally instead of distally. The first pair, the 

 claws, pincers, chelipeds or chelae, are much longer and stronger 

 than any other pair, and one is ordinarily rather larger than 

 the other. They are used for tearing the food, and also for 

 offence and defence. The basipodite and the ischiopodite are 

 fused together in the first pair. The oviduct of the female 

 opens on the basal segment of the third pereiopod, and the 

 vas deferens of the male on that of the fifth pereiopod. But 

 the openings are subject to variation, abnormal specimens 

 being occasionally obtained with more than one pair of 

 openings. For instance, in the male there may be additional 

 paired or unpaired openings on the fourth and even on the 

 third pereiopoda. In the female a fold between the third 

 pereiopods forms a chamber for storing spermatophores, and 

 is therefore a spermatheca. 



The first of the pleopoda, or abdominal appendages, is 

 modified in both sexes. In the male it is in the form of a 

 firm, irregularly cylindrical rod projecting forwards between 

 the bases of the last pair of pereiopoda. Each is formed of 

 the fused protopodite and endopodite, the exopodite being 

 absent. The endopodite is folded so as to form a gutter-like 

 groove. The posterior end of the groove can be applied to 

 the opening of the vas deferens, and the gutter serves to convey 

 the spermatophores to the spermatheca of the female. In the 

 female the first pair are long and thin, and each consists of a 

 two-jointed protopodite, and a jointed setose filament which 

 is believed to be the endopodite. They share the function, 

 with the next four appendages, of supporting the eggs during 

 the long incubatory period. The second pair of appendages 

 of the male are also modified and somewhat larger than those 

 of the female, the endopodite being produced on its inner 

 border into a long flat plate, doubtless of use in supporting 



