THE CRUSTACEA OF NEW JERSEY. 243 



different from adult animals. Probably in most forms even a 

 third intermediate larval stage (the micronisciis stage) occurs. 

 Sexual dimorphism very pronounced in all forms. Sometimes 

 the parasite penetrates to the inner organs of its host, looking 

 merely like an endoparasite, and in all such cases the body of 

 the female is found to be greatly deformed. 



The resemblance of certain of the Cymothoidea to these ani- 

 mals was thoug-ht by some to express relationship. As now 

 generally contended, their similarity is more likely due to para- 

 sitic habits, their structural characters indicating them of but 

 remote relation, and no trace of annectant forms has been dis- 

 covered. 



No less than seven families have been proposed, ])ut as several 

 of these are said to represent only different transitorv larval 

 stages, thus only four families are all Sars admits. These 

 families were framed originally more with reference to the 

 host on which the bopyroid was parasitic, as Microniscidcne on 

 Copepoda, Cyproniscid?e on Ostracoda. Dajidse on Schizopoda, 

 CabiropsidcX on Isopoda and Amphipoda, Cryptoniscidse on 

 Cirripedia, Entoniscidae on Brachyura and Bopyridae on deca- 

 podous Crustacea. 



Family BOPYRID^. 



Body of female distinctly segmented, more or less asym- 

 metrical, twisted now to right, now to left, and dorsal face flat- 

 tened. Cephalon deeply sunk into mesosome. carries in front 

 two pairs of rudimentary antennae. Eyes, when present, dorsal. 

 Maxillipeds lamellar, biarticulate, obtecting oral area below, 

 more frecjuently showing small terminal joint, and at base two 

 curved lanceolate appendages (epignaths). Legs seven pairs, 

 sometimes obsolete on one side, and all of same structure, short, 

 prehensile. Coxal plates obsolete or distinctly defined. In- 

 cubatory plates five pairs, more or less arching over ventral face 

 of mesosome. First pair usually concealed by second and di- 

 vided by transversal fold into two segments, of which distal 

 one projects freely within incubatory cavity. Metasome more 

 or less distinctly segmented, pleopoda, forming simple or double 



