12 F. W. GAMBLE AND J. H. ASHWORTH. 



The position and relations of the three anterior septa or dia- 

 phragms, of the dorsal and ventral mesenteries between the 

 first two of these, and the presence of regularly arranged septa 

 in the tail region, have already been noted. It may be added 

 that a pair of outgrowths from the first diaphragm lie under 

 the oesophagus, opening anteriorly into the coelomic space in 

 front of the first septum. They are very vascular, and con- 

 tract rhythmically every three or four seconds during life, and 

 are doubtless of use in everting the proboscis (PI. 2 and 3, figs. 

 5 and 6, Dph. Ph.). 



In the caudal region the intestine is attached both above 

 and below to the body-wall by mesenteries, in which the dorsal 

 and ventral vessels lie. 



5. Alimentary Canal (PL 2). 



This consists (1) of an eversible buccal mass {Bucc, M.), 

 of a pinkish or greenish-brown colour, which lies in front of 

 the first septum ; (2) of an oesophagus, of a light brown colour, 

 provided with a pair of glandular pouches behind the third 

 diaphragm ; (3) of a gastric region, with yellow glandular walls, 

 extending from the level of the heart to about that of the 

 twelfth or thirteenth notopodiura ; and (4) of an intestine, of a 

 dark brown or almost black colour, folded in a concertina-like 

 manner by the caudal septa, and opening at the terminal anus. 



During life the buccal mass (or "proboscis") is constantly 

 being everted and withdrawn, carrying sand into the oesopha- 

 gus. During eversion several rows of curved, pointed, vascular 

 papillae {B. Pap.) are first extruded. These papillae (PI. 3, 

 fig. 7) in old specimens are tipped with chitin, and recall the 

 armature of the proboscis in certain Sipunculids (e. g. Phas- 

 colion collare^). Then the more globular portion of the 

 buccal mass, covered with minute rounded processes, is pro- 

 truded. Finally, when fully everted, the buccal aperture is 

 surrounded by a few pointed pigmented papillae, which are 

 continuous with the lining of the first part of the oesophagus. 



1 Selenka, ' Die Sipuuculiden,' 1883, pi. vi, fig. 74. 



