OSTEACODA. 427 



pose. In addition a large copulatory organ, which may be derived 

 from a modified pair of appendages and often possesses a very compli- 

 cated structure, is always present. The male genital organs consist 

 on either side of several elongated or globular testes, of a vas def erens 

 and the copulatory organ ; the presence in Cypris of a very peculiar 

 paired mucous gland and the size and form of the spermatozoa seem to 

 be worthy of notice (Zenker). The female of Cypris possesses two 

 ovarian tubes which project into the reduplicature of the carapace, 

 two receptaoula seminis, and the same number of genital openings at 

 the base of the abdomen. 



Development. The greater number of Ostracoda lays eggs, which 

 they either attach to water-plants (Cypris}, or, as in Cypridina, 

 carry about with them between the shell valves until the young are 

 hatched. The free development of Cypris consists of a complicated 

 metamorphosis. The larvae, when hatched, possess, like the Nauplius 

 form, only three pairs of appendages, 

 but are strongly compressed laterally, and 

 are already enclosed in a thin bivalve 

 shell (fig. 338). In the marine Ostracoda 

 the development is simplified, so that the 

 metamorphosis is entirely absent. 



The Ostracoda feed altogether on ani- 

 mal matter, as it seems especially on the 

 carcasses of different aquatic animals. FIG. 338. Very youn;? larva of 



Numerous fossil forms are known from ^ )n> - N'mpUtM stage, with 



three fairs of appendages. 



almost all formations, but, unfortunately, M, stomach; D, intestine; 

 only the remains of their shells are pre- j^f ' ** 



served. mandible. 



Cypridina. "With heart and large movable paired eye. With deep excava- 

 tion in the edges of the shell for the passage of the antennae. The anterior 

 antennas are bent, furnished with strong seta:, and have olfactory hairs at their 

 extremity. The posterior antenna; are biramous swimming feet. The biting 

 part of the mandible is weak or entirely aborted ; palp is five-jointed, pediform, 

 and of considerable length. The seventh pair of appendages is represented by 

 a cylindrical ringed appendage (Putzfuss). Cypridina meditcrranca Costa. 

 Astcropc olilonga Gr., Trieste. Haloeypris Dana. 



Cytlicre O. Fr. Mull. Without heart. The anterior antennas are bent at 

 their base and beset with short seta;. The posterior antennas arc strongly 

 developed, with hooks on the terminal joint. Three pairs of legs, of which the 

 last is the most strongly developed. The abdomen has only the caudal fork, of 

 which the two branches are small and lobe-like. The testes and ovaries do not 

 project between the lamella? of the carapace. The male genital apparatus has 

 no mucous eland. They are all marine animals. The females often carry the 



