. A manual of zoology. Zoology. /. CRUSTACEA: COPEPODA. 417 ?). EsTHERiiD.E. Body laterally compressed and enclosed in a bivalve shell, compound eyes fused; male very rare. Estheriu,'* Limnadln* in fresh water. Order II. Cladocera. Like the estheriids the small Cladocera have the body enclosed in a bivalve carapace, which, in some instances, is small and reaches back only over the first trunk segments, in others is large, enclosing the body, with a notch for the protrusion of the head, while behind it terminates in a sharp spine. The head bears a pair of large swimming antennse and a much smal
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. A manual of zoology. Zoology. /. CRUSTACEA: COPEPODA. 417 ?). EsTHERiiD.E. Body laterally compressed and enclosed in a bivalve shell, compound eyes fused; male very rare. Estheriu, '* Limnadln* in fresh water. Order II. Cladocera. Like the estheriids the small Cladocera have the body enclosed in a bivalve carapace, which, in some instances, is small and reaches back only over the first trunk segments, in others is large, enclosing the body, with a notch for the protrusion of the head, while behind it terminates in a sharp spine. The head bears a pair of large swimming antennse and a much smaller first pair bearing olfactory bristles and, in the male, hooks for. Fit;. iV-—Uran<:hij}U^ vonali.^, * fairy shrimp. (After Packard.) clasping the female. The body consists of few segments, the heart is a simple sac, and the fused faceted eyes, with paired optic nerves, are capa- l)le of motion in a special optic capsule. The young eggs in the sexual organs always occur in groups of four (tig. 4201. Of these but one grows into an egg, the others breaking down and serving this as nourishment. Larger eggs with more yolk occur wdien several of these groups (2-13 fuse to form a single egg. The summer eggs arise from a single group, the winter eggs from several groups of primordial ova. In all Cladocera the space between the back of the animal and the shell serves as a brood pouch. In some cases this pouch contains an albuminous fluid secreted by the mother, which nourishes the embryo. The larger winter eggs—one or two in number—frequently remain for awhile in the brood chamber and are there enveloped in a peculiar shell, the ephippium, consisting of two chitinous plates, like watch crystals, their edges closely appressed. Daphnid^. Shell well developed; Daplinia* (fig. 420j, Bosminn* Pdi.YPHEMiD^. Shell small, only funct;ioning as a brood case; head with an enormous eye and large swimming antenna; no phyllopodous feet; marine and lacustrine. Leptodora hyalina* appears a