Cyclops

Cyclops, a genus of small fresh-water crustaceans, type of a family (Cyclopidae) in the order Copepoda. They are popularly included under the wide title of 'water-fleas.' Various species are common as active swimmers in fresh-water pools or slow-flowing brooks, and a few forms have been recorded from the sea. Like other copepods, cyclops has an elongated body, without a shell, with four forked thoracic feet and a five-jointed abdomen. The head-region is not distinct from the first ring of the thorax; there is a pear-shaped segmented body and a long abdomen; both pairs of antennæ are long, and in the male the anterior pair form claspers; the mandibular and maxillary palps are degenerate; and a heart is said to be absent. The average length of the commonest species is from 2 to 3 millimetres; the males are generally smaller than the females. A very marked feature, to which the name refers, is the single median eye, usually bright crimson and sparkling like a gem; and not less noticeable are the two large egg-bags carried by the females. They eat both animal and vegetable matter, and are very prolific. See CRUSTACEA, WATER-FLEA.