. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. 2l6 MANUAL OF ZOOLOGY. This division comprises the two orders Ostracoda and Copepoda. Order I. Ostracoda.—Small Crustaceans having the entire body enclosed in a shell or carapace, which is composed of two valves united along the back by a membrane. The branchiae are attached to the posterior jaws, and there are only two or three pairs of feet, which subserve locomotion, but are not adapted for swimming. A distinct heart is sometimes present {Cypridind), but is more usually wantin
. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. 2l6 MANUAL OF ZOOLOGY. This division comprises the two orders Ostracoda and Copepoda. Order I. Ostracoda.—Small Crustaceans having the entire body enclosed in a shell or carapace, which is composed of two valves united along the back by a membrane. The branchiae are attached to the posterior jaws, and there are only two or three pairs of feet, which subserve locomotion, but are not adapted for swimming. A distinct heart is sometimes present {Cypridind), but is more usually wanting (Cypris and Cythere). Little is known of the development of the Ostracoda, but the young of Cypris are said to be " shell-bearing Nauplius forms " (Claus), possessing only the three anterior pairs of limbs, but protected by a bivalve shell. As in other Nauplii, the third pair of limbs, though now locomotive, are ultimately transformed into the mandibles. They pass through several stages, with complete moults, before arriving at sexual maturity. The Cytherides, on the other hand, have at birth the two pairs of antennae and two pairs of jaws, with three pairs of rudimentary abdominal limbs. The order includes the Cyprides (fig. 66, a), which are of almost universal occurrence in fresh water. The common. Fig. 66.—Fresh-water Entotnostraca. a Cyfins tn's-siriata; b Daphnia pulexi c Cyclops quadriconiis. Cypris is completely protected from its enemies by a bivalve carapace, which it can open and shut at will, and out of which it can protrude its feet. Locomotion is mainly eifected by means of a pair of caudal appendages. The Cypris is ex- tremely prolific, and a single impregnation appears to last the female for its entire lifetime. It appears, also, that the young females, produced in this way, are capable for some generations of producing fresh individuals without the influence of a male (parthenogenesis).. Please note that these images are extracted from scanned p
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Keywords: ., bookauthorni, bookcentury1800, bookdecade1870, booksubjectzoology
