THE CUMACEA 187 



males (Fig. 113) they are generally present on all save the last 

 pair of legs. 



The pleopods are always absent in the female and sometimes in 

 the male, but more usually in the latter sex from one to five pairs 

 are well developed and biramous. The uropods are always con- 

 spicuous, their slender rami furnished with comb-like rows of spines 

 apparently used in cleaning the anterior appendages, for which 

 purpose the abdomen can be flexed ventrally and sometimes also 

 dorsally. 



Internal Anatomy. The masticatory stomach is stated to 

 resemble closely that of the Tanaidacea. There are from one to 

 four pairs of hepatic caeca (Fig. 1 1 2, hep). In one genus (Platycuma) 

 the anterior part of the intestine is coiled, forming a spiral of 

 two and a half turns within the carapace, but it has not been 

 ascertained whether the coiled part belongs to the mesenteron or 

 to the proctodaeum. In this genus also the hepatic caeca appear 

 to be absent. The heart (h) is usually somewhat elongated, but 

 in Platycuma it is subglobular. There are three pairs of ostia. 

 Besides anterior and posterior median arteries, the heart gives off 

 a pair of antero-lateral vessels and an unpaired descending artery. 

 A well-developed maxillary gland is present, which, according to 

 Glaus, resembles closely that of Apseudes (Tanaidacea). The 

 ventral nerve -chain consists of ten thoracic and six abdominal 

 ganglia. 



The simple tubular paired ovaries are connected, at least in the 

 young, by a narrow transverse bridge. The openings of the 

 oviducts have not been seen. The testes are separate, tubular, with 

 four small caeca anteriorly. The short vasa deferentia open on 

 the sternal surface of the last thoracic somite. 



DEVELOPMENT. 



The development appears to resemble, in its main features, 

 that of the Isopoda. In the earlier stages the embryo is curved 

 dorsally. As in the Tanaidacea and Isopoda, the young leave the 

 brood-pouch with the last pair of legs still undeveloped. In certain 

 species this deficiency persists very late, and possibly in some 

 cases throughout life. 



REMARKS ON HABITS, ETC. 



The Cumacea are exclusively marine (including under this term 

 the group of peculiar species inhabiting the Caspian Sea), and are 

 generally found burrowing in sand or mud. No species appears to 

 be truly pelagic, although the actively swimming males of some 

 species, and less commonly the females, are found in the plankton 



