3505. Body cylindrical with branchiæ in or upon the tegument, blood red; two ganglionic nervous threads run along the ventral surface of the body, as in Insects; all are indeed androgynous.
Here belong the Red-blooded Worms, as Hirudines, Lumbrici, Nereides, and Serpulæ.
Fam. 4. Tubularial Worms—Dermatobranchiata.
Body cylindrical. The branchiæ are only a vascular network in the tegument.
Here belong the Hirudines and Lumbrici.
The Hirudines have a perfectly naked body, without filaments and bristles, a perfect network of vessels containing red blood within the tegument, an intestine with an anus, both sexual parts androgynoid; posteriorly they have a pad or sucker; in the mouth there are mostly maxillæ, and upon the head simple eyes.
The Naiades and Lumbrici have bristles in longitudinal rows upon the sides of the body. The latter are androgynous. The Naiades increase by division.
The Thalassemæ have a protuberant white body; red blood-vessels only upon the intestine; mouth rostriform.
These Worms stick in the mud, and are nourished by it. They have here and there bristles, but which do not form any longitudinal rows. They appear to absorb water through the skin, and respire by the intestine. They cannot, by reason of their red blood, range with the Holothuriæ.
Fam. 5. Alcyonioid Worms—Notobranchiata.