108 ZOOLOGY. 
young. These animals are extremely prolific,.and furnish food to the — 
aquatic larve of insects. Cyclops setosa, Hald., Jour. Acad. Nat. Sci. viii. 
331, is the American analogue of the European C. quadricornis. 
Fam. 2. Cypridide (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when the antennee and feet are withdrawn. There are four antenne, 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 conferve. 
Many of the species are beautifully marked with variations of color. The 
following American species are indicated in the Proceed. Acad. Nat. Sci. 
vol. i. pp. 53 and 184: Cypris agilis, C. simplex, and C. scabra, Hald. 
fam. 3. Daphniide (or Cladocera). Here a bivalve shell incloses the 
body, with the exception of the head, which is distinctly exposed, and bears 
a large compound eye capable of some motion. The inferior antenne are 
very large, and generally two-branched. There are four, five, or six pairs 
of feet, which afford characters for the sub-families; 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 Daphniz are so abundant as sometimes to discolor the water, the red 
species giving it somewhat the appearance of blood. Dr. W. Baird, in his 
Natural History of the British Entomostraca, 1850, p. 78, 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 enough the edge to allow the shadow of the 
observer to fall 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 Daphnie may be found with a black saddle-shaped 
appendage (named the ephippiwm) 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, Wald., Proceed. Acad. 1. 184, 196, are 
312 
