tube alone (the animal having deserted it) was held up full of water, the fluid ran out rapidly at the same aperture. The animal, also, which voluntarily crawled out of its habitation, displays no such reversion of the tail as is described by Dr. Williams. This organ is a little leaf-shaped body, formed by the union of several short segments, and slightly bent downward, but not reverted.
The quitting of its tenement by the Worm enabled me to see and admire some other points in its structure, and their subservience to its economy. On each side of the neck, just below the edge of the flat cork-like head, are seen two little scarlet gills, resembling in structure those of fishes. Each consists of a free leaflet, formed of numerous thin plates set face to face: in health these little pointed gills are thrown about with agility in various directions, and their points alternately coiled up and unfolded. Behind these, along each side of the body, are placed prominent fleshy warts, to the number of fifteen pairs; each of which consists of two portions, the hinder part being dilated into a soft transverse mop, and the fore part perforated to give exit to a brush of fine spears of elaborate construction. They are about twelve in each bundle, each formed of a long and slender, highly elastic, glassy shaft, terminated by a bent blade, the edge of which is of the most delicate thinness, and the point of which is drawn out to great length and tenuity. Some of the blades appear to be simple and knife-like, but others have the edge cut with oblique slits, parallel to each other, and pointing from the base. They do not form saw-teeth, but are
