Page:Tropical Diseases.djvu/874

818 at the beginning of the posterior third of the body. The tail of the male is provided with a large, umbrella-like, trilobate bursa (Fig. 178, ) possessing eleven ribs. Two long and very delicate spicules project from the cloaca, which opens at the bottom of the bursa. Owing to the relative positions of the sexual openings, the worms in conjugation look like the Greek $$\gamma$$.

Reproduction and mode of infection.—The female ankylostomes produce a prodigious and never-ending stream of eggs (Fig. 168, b), which pass out in the fæces. As already stated, while in the body of the host the development of the embryo does not advance very far; but on leaving the human host it proceeds, in suitable circumstances, so rapidly that in one to two days a rhabditiform embryo (0·2 mm. by 0·014 mm.) is born. This minute organism (Fig. 179) is very active, voraciously devouring what organic matter it can find and, for a week, growing rapidly, to 0·56 mm. by 0·024 mm. (Fig. 180).