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Crass ANNELIDA.

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Ornvrr SUCTORIA.

Hievpo.—The Leech.

The creatures forming this genus are mostly aquatic,
some being inhabitants of fresh water, others of the sea, and
a small number preferring moist situations near stagnant
water. Their eggs are enveloped in a kind of cocoon, of a
texture much resembling sponge. The H. medicinahe is
the most familiar example, and needs no lengthened de-
scription, though the mouth may claim a short notice, as
being remarkably adapted to the food on which it subsists,
the fluids of frogs, fish, etc. It is placed in the centre of
the cavity formed by the anterior sucker, and is composed
of three little cartilaginous bodies, or jaws, so disposed that
the three edges form three radii of a circle: each of these is
furnished with two rows of minute teeth, so as to resemble