ARACHNIDA—ARANEAE CHAP. 
At the top of the pharynx, which is nearly perpendicular, the 
canal continues backwards and upwards as a narrow tube, the 
oesophagus, passing right through the nerve-mass, which embraces 
it closely on all sides, to the sucking stomach. At the com- 
mencement of the oesophagus is the opening of a gland, probably 
salivary, which is situated in the rostrum. 
We now reach the sucking stomach, which occupies the centre of 
the cephalothorax. It is placed directly over a skeletal plate, the 
“ endosternite ” (Fig. 185, e), to which its lower surface is connected 
by powerful muscles, while its upper 
wall is protected by a hard plate 
or “buckler,’ which is similarly 
attached to the roof of the cephalo- 
thorax in the region of the “fovea 
media.” The walls of the stomach 
are not themselves muscular, but 
by the contraction of the muscles 
above mentioned its cavity is en- 
larged, and fluids from the pharynx 
are pumped up into it. 
The canal thus far is lned by 
chitin, like the exterior of the 
body, and forms a sort of compli- 
cated mouth-apparatus. 
The Mesenteron les partly in 
Fic. 185.—Diagram showing the ana- 
tomy of the cephalothorax of a 
Spider. Therightalimentary diverti- 
culum has been removed. a, Aorta ; 
c, left diverticulum with secondary 
caeca; e, endosternite ; oes, oeso- 
phagus, descending to the mouth ; 
s, sucking stomach ; sh, dorsal 
shield of sucking stomach. 
the cephalothorax and partly in 
the abdomen. The thoracic portion, 
shortly behind the sucking stomach, 
sends forward on either side a large 
branch or “diverticulum,” from each of which five secondary 
branches or “caeca” are given off (Fig. 185). Of these the 
anterior pair sometimes join, thus forming a complete ring; but 
usually, though adjacent, they remain distinct. The other four 
pairs of caeca curve downwards, protruding into the coxae of the 
legs, where they often terminate, but sometimes (Hpeir'a) they con- 
tinue their curve until they meet, though they never fuse, under the 
nerve-mass. Behind the origin of the diverticula the mesenteron 
continues as a widish tube, and shortly passes through the pedicle 
and enters the abdomen, where, curving slightly upwards, it pro- 
ceeds along the middle line till it ends in the proctodaeum. 
