Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 UEPHYJREA. 387 Te and an inner layer of longitudinal fibres. The latter are connected with the former and also amongst themselves by net-like anastomoses. These dermal muscles cause the folds of the cuticle. Internally to the longitudinal muscles there is another layer of circular muscles. In the <'li«'t(fera two hooked seta? ai'e present near the genital opening (tig. 311); these assist locomotion. There may also be present one or two circles of setse at the posterior end of the body
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 UEPHYJREA. 387 Te and an inner layer of longitudinal fibres. The latter are connected with the former and also amongst themselves by net-like anastomoses. These dermal muscles cause the folds of the cuticle. Internally to the longitudinal muscles there is another layer of circular muscles. In the <'li«'t(fera two hooked seta? ai'e present near the genital opening (tig. 311); these assist locomotion. There may also be present one or two circles of setse at the posterior end of the body (Echiurus). In the Chcetifera (fig. 311), the ante- rior part of the body is elongated to form a kind of proboscis, which projects im- movably and cor- responds to the prseoral lobe (pr?e- stomixim) of the A i' nelida. The mouth is placed ventrally at the base of the probos- cis. In the Ac/ueta (Sipuncudidce) this proboscis is want- ing ; the mouth is placed at the ex- tremity of the an- terior region of the body, which is sur- rounded with cili- ated tentacles and FlG- 312.—.SV//»Mc»/»s niulim, laid open from the side (after W. Kefersteiu). 2V. Tentacles ; G, cerebral ganglion ; VG, vru- Can be retracted by tral nerve cord; Z», intestine; A, anus ; BD brown tubes means of retractor (ventral glands), muscles (fig. 312). Alimentary canal.—The mouth opens into a pharynx, which is sometimes furnished with teeth; this is followed by a ciliated intes- tinal canal, which is usually longer than the body and disposed in coils in the body cavity. The terminal portion of the intestine is
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