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 tra l ne rve 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 



