530 



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. 



A Ye 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 lined by 

 chitin, like the exterior of the 

 FIG. 185. Pillar-urn showing the ana- body, and forms a sort of compli- 



toinv of the cephalothorax of a j .-, 



Spider. Therightalimentarydiverti- cated mouth-apparatus. 



cuium has been removed. , Aon.i ; xhe Mesenteron lies partly in 



c, left divcrtiriilum with secondary , i 



caeca; e, endosternite; oes, oeso- tne cephalothorax and partly 111 

 , descending to the mouth ; the abdomen. The thoracic portion, 



shortly behind the sucking stomach, 

 sends forward on either side a large 

 1 tranch or " diverticulum," from each of which five secondary 

 branches or " caeca " are given off (Fig. 185). Of these the 

 anterior p;iir sometimes join, thus forming a complete ring; but 

 usually, though adjacent, they remain distinct. The other four 

 ]tairs of caeca curve downwards, protruding into the coxae of the 

 legs, where they often terminate, but sometimes (JUpeira) 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 proctodaeuni. 



s, sucking stomach ; sh 

 shield of sucking stomach. 



dorsal 



