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XLV] opens into the oral capsule with three slightly recurved teeth about 8 μ long, which fit into three corresponding indentures of the posterior border of the oral capsule. Posteriorly, it presents a three-lobed valve. The intestine rims almost in a straight line to the anus, which opens at 170-200 μ, from the posterior extremity. The vulva is placed anteriorly to the anus at 350-475 μ. from the caudal end. Neither anus nor vulva is marked by any prominence of the body wall. The ova of Œ. apiostomum, like those of other parasites belonging to this genus or to the closely allied genus Sclerostoma, probably hatch in water, and by this medium reach a fresh host, penetrating either through the œsophagus or the skin. They finally settle beneath the intestinal mucosa, usually between the ileo-cæcal valve and the anus, and here grow considerably in size, feeding on the blood of the host. Having practically reached the adult stage, they leave their cysts for the purpose of copulation and oviposition, and they and their eggs are expelled with the fæces. Life-history and pathogenesis.—The allied species, Œ. columbianum, which, according to Curtice, is frequent in adult sheep in the south of the United States and is more particularly observed in the autumn and winter, does not appear to cause any serious trouble except when present in great numbers. The parasite may be found in its adult state within the lumen of the cæcum or colon, but it is found more frequently in the larval stage lodged beneath the mucous membrane in cysts varying in size from that of a pin's head to that of a hazel-nut, each cyst containing a coiled-up worm. The species peculiar to apes and monkeys are likewise found during their larval stage within small hæmorrhagic cysts beneath the mucosa of the cæcum and large intestine. The parasites are blood-suckers; their intestines are crammed with erythrocytes. The larger cysts usually present a small perforation at their summit; through this the worm protrudes and escapes. Œ. dentatum, which inhabits the pig, the wild boar, and the white-lipped peccary (Dicotyles labiatus), is found not only in the cæcum and colon, but also farther up in the small intestine, and von Lin stow found it within the liver. According to Railliet, the eggs of this species hatch in water within three or four days, the liberated embryo measuring 200-250 μ.

This sclerostome (Fig. 184) is an intestinal parasite of monkeys inhabiting the large intestine. It has several times been found in natives, post mortem, by Turner in the Transvaal and by Stannus in Nyasaland. The worms are about the size and shape of a female ankylostome. The male is 9.5 mm. long and 0.56 mm. broad; the female, with a tapering pos- terior extremity, 14-16 mm. in length and 0.73 mm. broad.