108 ZOOLOGY. 



young. These animals ai-e extremely prolific, and furnish food to the 

 aquatic larvge of insects. Cyclops setosa^ Ilald., Jour. Acad. IS'at. Sci. viii. 

 331, is the American analogue of the European G. quadricornis. 



Fam. 2. Cyjyrididce {Ostracoda of Latreille). In this family the animal 

 is inclosed in a bivalve shell with a dorsal hinge, and capable of being closed 

 when the antenna and feet are withdrawn. There are four antennte, those 

 of the second pair being large, elbowed, and adapted to assist in swimming. 

 Most of the species are minute, inhabiting fresh or salt water. The species 

 of the genus Cypris are abundant during the summer in puddles of stagnant 

 water, where they may be seen swimming about or walking upon objects 

 at the bottom. The eye is of a dark color, and the shell sufficiently trans- 

 lucent to allow it to be seen at the upper and anterior part. The eggs are 

 attached to extraneous bodies, and the young are not subject to metamor- 

 phosis. Their food is stated to be dead animal matter, and confervas. 

 Many of the species are beautifully marked with variations of color. The 

 followmg American species are indicated in the Proceed. Acad. ISTat. Sci. 

 vol. i. pp. 53 and ISi: Cypris agilis^ C. simplex^ and C. scabra^ Hald. 



Fam. 3. DaphnildiB (or Cladocera). Here a bivalve shell incloses the 

 body, with the exception of the head, wliich is distinctly exposed, and bears 

 a large compound eye capable of some motion. The inferior antennae are 

 very lai-ge, and generally two-branched. There are four, fi,ve, or six pair? 

 of feet, wliich afford characters for the sub-tamilies ; or families, if the 

 Cladocera are considered to constitute an order. Daphnia is abundant in 

 the stagnant pools where Cypris and Cyclops are found, and their locomotion 

 resembles that of the latter. The young are retained between the body and 

 shell posteriorly above, where they may be seen through the latter. 

 The Daphniae are so abundant as sometimes to discolor the water, the i-ed 

 species giving it somewhat the appearance of blood. Dr. W. Baird, in his 

 Natural History of the British Entomostraca, 1850, p. Y8, says he has 

 " frequently seen large patches of water in different ponds assume a ruddy 

 hue, like the red rust of iron, or as if blood had been mixed with it, and 

 ascertained the cause to be an immense number of D. pulex. The myriads 

 necessary to produce this effect are really astonishing, and it is extremely 

 interesting to watch their motions. On a sunshiny day, in a large pond, a 

 streak of red, a foot broad, and ten or twelve yards in length, will suddenly 

 appear in a particular spot, and this belt may be seen rapidly changing its 

 position, and in a very short time wheel completely round the pond. 

 Should the mass come near enougli the edge to allow the shadow of the 

 observer to fiiU upon them, or should a dark cloud suddenly obscure the 

 sun, the whole body immediately disappear, rising to the surface again when 

 they have reached beyond the shadow, or as soon as the cloud has passed over." 



At certain periods Daphnite, may be found with a black saddle-shaped 

 appendage (named the epTiippium) upon the back of the shell, which Strauss 

 discovered to be a receptacle for two eggs from which to reproduce the 

 species in the spring. At the fifth moult, the ephippium is cast off and 

 floats about at random, protecting its contents until the succeeding spring. 

 Daphnia abrupta and D.fenestrata^ Hald., Proceed. Acad, i. 184, 196, are 

 312 



