FAM. 1. _Syllidae._—These are small worms, the majority being less than an inch long, so that they are not easily observed. {307}The body consists of a fair number of segments.[368] In many genera a dorsal bundle of unjointed, natatory chaetae makes its appearance at maturity. The palps, which are grooved, are in some cases so united with one another and with the prostomium as to be scarcely recognisable. (For head see p. 262, and for feet see p. 264.) The pharynx is armed with one or more teeth. There is a special gizzard, following the pharynx, and provided with thick, muscular walls of peculiar structure. Following the gizzard, the oesophagus receives in many genera a pair of T-shaped diverticula, that are used for storing water, which is swallowed with food. These diverticula are absent in _Autolytus_ and other free-swimming forms. The reproduction of the members of this family is interesting, and has already been described (p. 278). [Illustration: FIG. 160.—_Syllis armillaris_ Müll. × 2. (From Johnston.) The head is towards the right.] _Syllis._—The tentacles and cirri are moniliform; the palps large; there is a single dorsal tooth, which is provided with a poison gland, the duct of which opens near its apex; it is used rather for stabbing its prey than for grasping and tearing. _S. krohnii_ Ehlers, is abundant under stones, and forms tubes of sand; it is nearly an inch long, and consists of some eighty-five to ninety-five segments marked with yellow bands. It may readily be identified by longer dorsal cirri, terminally dilated, alternating with shorter ones. _S. cornuta_ Rathke, has a translucent green body, about half an inch long; no alternation {308}of cirri. Mediterranean, Atlantic, on the Norwegian coast, off Spitzbergen, and on the Madeira coast. _S. armillaris_ Müll. is very common at low water; it is pale yellowish-brown, with a couple of dusky marks on each segment; and measures 2 inches. The dorsal cirri are quite short, consisting of only eight to ten joints. In _Pionosyllis_ the tentacles and cirri are not moniliform; a single dorsal tooth. _P. malmgreni_ M‘I. under stones. _Sphaerosyllis_.—The dorsal cirri are swollen at the base, and are not moniliform; the long palps are fused along nearly their whole extent. _S. hystrix_ Clap. is only about one-eighth of an inch in length. _Exogone_ Oerst. _Grubea_ Qfg. _Autolytus._—The small palps are entirely fused with the prostomium; the pharynx, which is bent upon itself, is armed with a circle of denticles. Dorsal cirri somewhat foliaceous. There are no ventral cirri. The male and female differ from one another and from the asexual "stock" (see p. 279). _A. pictus_ Ehl. is abundant under stones. It measures about two-thirds of an inch in length, is darkly coloured with a median lighter band; the anterior dorsal cirri are long. _A. prolifer_ Müll. is common.