VI 



PROTRACHEATA 



429 



It falls into the following divisions : buccal cavity, pharynx, oeso- 

 phagus, mid-gut or stomach-intestine, and rectum. The bueeal cavity, 

 in whose base the mouth proper lies, arises ontogenetically by the 

 growing together of a row of papillae surrounding the mouth ; the 

 mouth and jaws are thus enclosed within a circular Avail. In front 

 of the mouth, within the buceal cavity, lies a median prominence, the 

 tongue. At the back of the buceal cavity, where it passes into the 

 pharynx, i.e. at the posterior edge of the 

 mouth, is an invagination directed back- 

 wards, into which the unpaired terminal 

 portion of two salivary glands enters ; 



these 

 through 



glands 



are 



the 



long 



greater 



tubes 

 part of the 



running 



body 



longitudinally in the lateral divisions of 

 the body cavity. At the anterior end, 

 near the bend toAvards the common ter- 

 minal division, each salivary gland has 

 a ccecal vesicular appendage. The 

 pharynx, which reaches to the region 

 between the first and second pair of 

 legs, possesses a very thick muscular 

 wall : its lumen in a transverse section 

 is Y-shaped. The oesophagus is shorter. 

 Its wall, which consists of an outer 

 longitudinal and an inner circular mus- 



FIG. 2^-2. Anterior end of the body 



open (after Balfour). n, Antenna ; s, 

 tongue ; 7;, jaw ; dg, salivary gland ; gs, 

 common terminal portion of the twn 

 salivary glands; ph, pharynx; :, ceso- 

 phagus ; I, the lip papillre surrounding 

 the buceal cavity ; op, oral or slime 

 papilla 1 ; slil, duct or reservoir of the 



cular layer, is much thinner than that of of Peripatuscapensis, ventral side, laid 



... /M-win /"iffai- Ttal-fmil* 1 * rt A ii + ai-ino - 



the pharynx. These three divisions are 

 lined by the chitinous cuticle. 



The stomach - intestine stretches 

 from near the two pairs of legs almost 

 to the end of the body. Its wall is in 



i . 



folds, and its muscular layer (outer cir- 

 cular and inner longitudinal, i.e. the reverse of Avhat obtains in all 

 anterior sections of the canal) is exceedingly thin. It is nowhere 



o */ 



fastened to the body wall by mesenteries. The rectum, which is 

 distinctly separated from the mid-gut, is considerably narrower, with 

 a tolerably well-developed muscular wall. 



An endothelium (peritoneal epithelium) covers the outer muscular 

 Avail of the enteric canal and the other organs lying in or forming the 

 boundary of the body cavity. 



The nervous system of Peripatus (Fig. 293) consists of a large 

 brain placed in the head in front of and OA*er the pharynx (suprn- 

 cesophageal ganglion), and of two ventral longitudinal nerve trunks 

 proceeding from the brain, Avhich run far apart in the lateral diA'isions 

 of the body cavity to its posterior end. In each segment, i.e. in each 

 part of the body corresponding with a pair of extremities, the longi- 

 tudinal nerves are connected by seA r eral transverse commissures (9-10 in 



