IX CEPHALODISCUS 599 



also found in the stalk of the buccal shield, which radiate out from 

 the stalk into the shield. 



Body eavity. — In a young bud, the body appears to be divided 

 into three sections (anterior, middle, and posterior) by two circular 

 furrows. Each of these three sections possesses a separate body 

 cavity. The most anterior section, out of which the buccal shield 

 proceeds, has an unpaired body eavity, into which a short intestinal 

 diverticulum enters from the middle section. The body cavity in 

 both the middle and posterior sections is paired, the two lateral halves 

 being separated' by mesenteries. The boundary between the middle 

 and posterior sections, the latter of which becomes the greater part of 

 the body cavity in the adult, becomes more or less indistinct. The 

 body cavity of the middle section is retained in the adult in the 

 postoral lamella and in the region of the central nervous system and 

 of the feathered tentacles, into which it is continued. The body 

 cavity of the posterior section in the adult contains the whole of the 

 alimentary canal and the ovaries, these organs almost entirely filling it. 

 It is continued into the pedicle. 



The alimentary canal forms a loop in the body, with a ventral 

 section which runs backwards and into which the mouth leads, and a 

 dorsal section running forwards and opening anteriorly through the 

 anus. The mouth leads first into the "pharynx," which com- 

 municates with the exterior by means of the two gill-slits mentioned 

 above. A thin diverticulum runs out anteriorly from the pharynx 

 below the nervous system into the stalk of the oral disc. The 

 pharynx is followed first by an oesophagus and then by a very 

 spacious stomach or stomach intestine, which occupies by far the 

 greater part of the body cavity. At the point where the pedicle joins 

 the body, the stomach passes over into a narrower section of the 

 intestine, which, immediately behind the stomach, ascends, and then, 

 bending forward, runs along the dorsal side as the hind-gut to the 

 anus. 



Genital organs. — Male genital organs have not been observed. 

 The female organs consist of two ovaries, lying in the anterior 

 part of the body ; they are continued into two strongly pigmented 

 oviducts, which open outAvard through the apertures already men- 

 tioned (Fig. 470, 17). 



Reproduction. — Besides multiplying sexually by means of eggs, 

 Cephalodiscus also reproduces itself asexually by gemmation. The 

 buds always form on the pedicle, near to its free end. Almost all 

 adult individuals have from 1 to 3 buds. 



Many individuals of Cephalodiscus live together in a ramifying 

 and anastomosing system of tubes secreted by themselves, these tubes 

 having occasional apertures. The animals, throughout life, when 

 not disturbed, remain in the immediate vicinity of these apertures, 

 through which they protrude their unfolded crowns of tentacles. 



