Especially characterized by their peregrinations and metamorphoses.

Distoma hepaticum, and D. lanceolatum, Liver-fluke; flat, melon-seed or lancet-shaped, soft worms, of a yellowish-white color, with two suction pores; one of which is seated at the head extremity; the other, which terminates caecally, at the belly. Between the two is the sexual orifice. They are hermaphrodites.

The Distoma hepaticum is the larger, being from four to eight or to fourteen lines long, and from one and a half to six broad, with a branched intestinal canal.

The Distoma lanceolatum, as the smaller, is from two to four lines long and about one broad. Its intestinal canal is bifurcated.

Both infest the liver of the herbivora, rarely of man. The D. lanceolatum has only once been met with in the latter. In brutes they occur in great multitudes, obstructing and dilating the gall-ducts.

Distoma Oculi Humani

A minute distoma, once met with in a child between the cataractous lens and its capsule.

Polystoma Pinguicola, Hexathyridium Pinguicola (Treutler)

An inch long and from two to three lines thick, oval, superiorly convex, in-feriorly depressed worm, with six pores at its head extremity, and a larger abdominal aperture anterior to the tail. Found once by Treutler in the fat of an ovarian fat-cyst.

Polystoma venarum, Hexathyridium venarum (Treutler), probably a pseudo-parasite.