cylindrical or flattened, varying according to the state of contraction. The body is dark (blackish or grayish with brownish stripes). It is marked by a series of rings, at least l00 in number. The dorsal surface is mottled by distinct rows of spots, whereas the ventral surface is irregularly mottled. At both ends of the body the worm is provided with a mouthpiece or sucker.
Fig. i. — Leech (Moeller).
With the posterior one the animal fastens himself, and then brings the triangular mouthpiece into play. This is provided with three sets of tooth plates, which by their muscular attachments move like a segment of a circular saw and make a triangular cut into the skin, through which the animal sucks the blood by means of its muscular pharynx. The clotting of the blood is prevented by a locally secreted ferment. The blood passes into a large
