420 



ZOOLOGY 



circularly arranged fibres (circ. mus.) situated externally, imme- 

 diately below the dermis, and a layer of longitudinally arranged 

 fibres (long, mus.) situated internally. The circular layer is in- 

 terrupted at arl' the in- 

 tervals between the seg- 

 ments ; the longitudinal 

 layer is interrupted along 

 a series of longitudinal 

 lines, so as to be divided 

 into seven bundles. 



The setae are lodged 

 in sacs, the setigerous sacs 

 (see Fig. 339), lined by 

 a continuation of the 

 epidermis. In the re- 

 gion of the body in whJch 

 the reproductive organs 

 are lodged some of these 

 sacs are -enlarged and 

 glandular, and receive 

 the special name of the 

 capsulogenous rilun<h. 



The enteric canal 

 (Fig. 33 3) is, as in 

 Nereis, a tube which 

 runs through the entire 

 I length of the body from 

 the mouth at the an- 

 'terior to the anas at the 

 posterior end. As in the 

 case of Nereis, it. lies in 

 a cavity, th< lined 



by a thin cellular mem- 

 brane, the petition 

 and filled with a fluid, 

 the caelomic fluid, con- 

 taining colourless cor- 

 puscles. It is divided. 

 into a series of cham- 

 bers corresponding to 

 the segments by a series 

 of delicate transvers 

 partitions, the x/'j'ta or 

 mesenteries, consisting of folds of the peritoneal membrane en- 

 closing muscular fibres. 



The mouth leads into a small lnn'cnl cml ij. This is followed by 

 ;i much kirger thick- walled, rounded chamber, tlu JM//'V///M.- (ph.\ 



