which runs in a straight course to the vent at the posterior end of the body. The intestine presents a remarkable structure, the typhosolis, or, as the old anatomists called it, an intestine within an intestine; and Claparède[1] has shown that this consists of a deep longitudinal involution of the walls of the intestine, by which means an extensive absorbent surface is gained.
The circulatory system is well developed. Worms breathe by their skin, as they do not possess any special respiratory organs. The two sexes are united in the same individual, but two individuals pair together. The nervous system is fairly well developed; and the two almost confluent cerebral ganglia are situated very near to the anterior end of the body.
Senses.—Worms are destitute of eyes, and at first I thought that they were quite insensible to light; for those kept in confinement were repeatedly observed by the aid of a candle, and others out of doors by the aid of a lantern, yet they were rarely alarmed, although extremely timid animals. Other
- ↑ Histolog. Untersuchungen über die Regenwürmer. 'Zeitschrift für wissenschaft. Zoologie,' B. xix., 1869, p. 611.
