The eggs of _Cypris_ (Pl. IX. fig. 35) are often found in glasses of water containing the animals. They are rounded or oblong, of a red colour, glued together by an amorphous jelly, and adherent to pieces of stick or the sides of the glass. They are enclosed in a thick shell, which exhibits a cellular appearance in the surface view, and is striated in the side view; so that the structure of the shell is prismatic, as in that of the oyster. When the eggs escape from the shell, they present the appearance represented in fig. 35 _a_, the body of the young animal being enclosed in a transparent envelope, one end of which forms a blunt protrusion; there is also a separate slender process enclosing the superior antennæ. After a time, the envelope is cast off (fig. 35 _b_), when the animal begins its active stage of life. The cast-off envelopes (fig. 35 _c_), with the protruded portions wrinkled, are often found in the sediment of water containing the animals. The structure of these ova is that of what are called winter ova, which agree with the resting-spores of the lower plants or the Algæ. _Cy´clops quadricor´nis_ (Pl. IX. fig. 30) is another common species. In this the body is closely surrounded by the jointed shell, as in a lobster. The superior antennæ (_a_) are very long and many-jointed, each joint having short bristles arising from it, while the inferior antennæ are short and four-jointed. There is no separate head, this being united to or consolidated with the first joint of the thor´ax or chest, the head and thorax together comprising four joints. The remaining joints enclose the belly, or abdómen, which has the appearance of a tail; but the tail is constituted by the two last parallel pieces, which are furnished with fine feathery filaments. The female is most commonly met with, and is easily known by having the egg-pouch, or ovary (_o_) external on each side, and filled with eggs or ova. The little _Cyclops_ is readily recognized by its form and jerking motion through the water.