Synonym.—Trichostrongylus instabilis (Railliet, 1893).

Looss has described a very delicate nematode (Figs. 187-9) frequently encountered in Egyptian fellahs, and since found by

Ijima in Japan. Its habitat is the upper part of the small intestine. The male, which is provided with two spicules, is

Fig. 188.—T. subtilis, female.	Fig. 189.—T. subtilis, bursa. (After Looss.)

from 4 to 5 mm. in length by 0·07 mm. in breadth; the female is slightly larger and is much more abundant than the male. The eggs (Fig. 168, a) are oval, thin-shelled, with an unseg-