FAM. 3. _Chaetopteridae._—The family is represented on our coasts by _Chaetopterus variopedatus_ Ren.,[383] which is found at the Channel Islands, the Scilly Isles, the Isle of Man, and the west Scottish coast, and probably at various other places, at low water and down to a depth of some 15 fathoms. It occurs in all European seas. The animal builds a long tube, the basis of which is a tough, parchment-like substance; this is coated externally with sand, small pebbles, and other débris: it is of considerable length and about ¾ inch in diameter, is U-shaped and open at both ends, the greater part of it being embedded in sand or in crevices of rocks. The animal, whose body-wall is thin and delicate, never leaves its tube. The body has a bizarre appearance; three regions are readily {324}distinguishable, which may be denoted by the letters A, B, and C. The most anterior region, A, is flattened, and carries nine pairs of conical lobes with delicate chaetae, though the fourth lobe possesses special stouter chaetae (as in _Polydora_). The anterior end of the body terminates in a wide funnel, the boundary of which is formed chiefly by the peristomium; on its dorsal surface is a pair of tentacle-like processes (peristomial cirri); the region between which represents the prostomium. [Illustration: FIG. 173.—_Chaetopterus._ (From Panceri.) Natural size of a young specimen. A is the anterior region of the body; B, the middle region; C, the hinder region. _c_, Peristomial cirri; _d_, "sucker"; _e_, the great "wings"; _f_, the first of the three "fans"; _m_, mouth.] The second region, B, is very curiously modified; it is formed of five segments. The most anterior is produced on either side into a great wing-like process, which in life is directed forwards above the region A. Each is grooved on its inner side, the ciliated grooves being continuous with a median groove running forwards along the back of A; this apparatus serves to bring food to the great funnel-like mouth. The next segment (twelfth) carries a dorsal and ventral "sucker," representing the parapodia. Each of the segments 13, 14, 15 carries a membranous fold encircling the body. By the constant movement of these "fans," which have nearly the same diameter as the tube, a current of water is constantly washed over the animal. The fans represent the notopodia; the neuropodia are bilobed rounded knobs. The region C consists in the adult of about thirty segments, all alike, and less modified than the preceding. The animal is the most truly tubicolous of the Polychaetes, and is much modified on this account. No locomotor chaetae are present, though the great wings and notopodial processes of region C contains chitinous bristles, which, however, do not project;[384] the anterior region with its stiff chaetae, and the neuropodial uncinal plates of the rest of the body serve in its movements up and down the tube, while the "suckers" fix the worm temporarily to the wall of its house.