drously curious. I will describe each of these in turn. Behind the head, (or what for convenience may be so termed) the sides of the body are cut into nipple-like feet, about seven pairs in all, which are perforated, and carry so many bundles of fine, elastic, horny bristles, like the hairs of a camel's-hair pencil, each pencil carrying from twenty to thirty bristles. By means of suitable muscles, the pencils are pushed out to their full length, or withdrawn so as to be wholly sheathed in the foot.
Now let us look at the structure of these bristles. A few are simple hairs, but the majority are instruments of elaborate workmanship, though high powers of the microscope are needful to display them well. Each bristle consists of a transparent, yellow, horny shaft, the extremity of which dilates into a slightly enlarged knob. This is cleft into four points, three of which are minute, but the fourth is developed into a long, slightly divergent, highly elastic, tapering, and finely pointed spear.
These organs come into operation when the animal would extrude its body from the mouth of its tube. Their action is manifestly that of pushing against the walls of the interior, which on close examination are seen to be lined with a delicate membrane, exuded from the animal's skin. The opposite feet of one segment protrude the pencils of bristles, one on each side, the acute points of which penetrate and catch in the lining membrane; the segments behind this are now drawn up close, and extend their bristles; these catch in like manner; then an elongating movement takes place; the pencils of the anterior segments
