The female of the last species has two outward receptacles for the eggs; in this there is but one, and that is placed on the under part of the animal near the tail.
The Hairy Cypris, ([Cypris pubera].)
These singular little creatures are found in stagnant fresh water: they are very small, and, at first sight, appear like a bivalve shell. The animal which is enclosed in this two-valved case, opens and shuts it at will; when it does this, it throws out from one end of the shell numerous whitish hair-like members; it is by moving these that it is enabled to swim with considerable celerity, and it never stops until it meets with some object on which it can rest. Its two antennæ, which issue from the fore part of the shell, are long, very flexible, and bent backwards; their articulations are numerous, which gives them great freedom of motion. The movements of these antennæ contribute materially to the swimming powers of the creature.
At the place where the head is united to the body, a small black point is seen,—this is the eye of the animal.
Cypris pubera. (Fig. 1, highly magnified; fig. 2, natural size.)
The Cypris changes its shell like the rest of the Crustacea; it is found in marshes where vegetable substances are growing. Sometimes they are so numerous, that the water appears covered with them; they are more usually found in Spring and Autumn than at any other part of the year; from this it is inferred that there are two broods in the course of the year.
The drying up of marshes during the Summer heats, destroys immense numbers every season. It appears, however, from observation, that in this case, some of these tiny creatures manage to bury themselves in the mud, where they hermetically close their shells, and remain in a kind of dormant state, until rain or other causes have again filled the marshes with water.
A species nearly allied to this, the Artemia Salina, the Lymington shrimp, or brine-worm, is able to live in the brine of the salt-pans, which is so strongly impregnated with salt, as to destroy any other Crustaceous animal.