=The Stomodaeum= consists of the pharynx, the oesophagus, and the sucking stomach. As we have said, the mouth is to be found between the rostrum and the labium. It opens into the pharynx, the anterior wall of which is formed by a chitinous plate on the inner surface of the rostrum, sometimes called the palate. As the inner surfaces of the rostrum and labium are practically flat, the cavity of the pharynx would be obliterated when they are pressed together, were it not for a groove running down the centre of the palate, which the apposed labium converts into a tube, up which the fluids of the prey are sucked. In the Theraphosidae there is a corresponding groove on the inner surface of the labium. 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 commencement of the oesophagus is the opening of a gland, probably salivary, which is situated in the rostrum. [Illustration: FIG. 185.—Diagram showing the anatomy of the cephalothorax of a Spider. The right alimentary diverticulum has been removed. _a_, Aorta; _c_, left diverticulum with secondary caeca; _e_, endosternite; _oes_, oesophagus, descending to the mouth; _s_, sucking stomach; _sh_, dorsal shield of sucking stomach. ] 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 cephalothorax 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 enlarged, and fluids from the pharynx are pumped up into it. The canal thus far is lined by chitin, like the exterior of the body, and forms a sort of complicated mouth-apparatus. The =Mesenteron= lies partly in 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 (_Epeira_) they continue 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 proceeds along the middle line till it ends in the proctodaeum.