INSECTA. 217 



and wide chylitic stomach, with longitudinal folds, separated by a 

 circular linear constriction, in the posterior third of the body, from 

 the intestine : this is divided by a second constriction into two 

 equal parts, the first longitudinally folded like the stomach, the last 

 puckered into short transverse sacculi ; until w ithin a little distance 

 of the anus, which is protected by a pair of horny valves. 



In the Polydesmus the oesophagus gradually expands into the long 

 chylific stomach, which is separated by a short contracted pyloric 

 tube from the intestine. This suddenly swells out to equal width with 

 the stomach, is puckered up in its posterior half by short transverse 

 plicae, where it first gradually, and then suddenly, contracts to termi- 

 nate at the anus. 



The accessory glands of the digestive tract are slender tubes in the 

 Myriapod, as in the Hexapod tracheary Insects. In the Polydesmus 

 and lulus there are two such salivary glands at the sides of the oeso- 

 phagus, converging anteriorly to open into the pharynx. The more 

 compact and similarly situated poison glands, which terminate in the 

 large perforated hooked mandibles, in the Centipede, are superadded 

 to the simpler salivary glands of the Chilognatha. 



Slender biliary tubes creep upon the intestinal tunics in the Centi- 

 pede^ and pour their secretion into the canal close to the gizzard. 

 Excretory, probably urinary, tubes open into the terminal division 

 of the intestine ; and these are present in the lulidee. 



The alimentary tract in Hexapod Insects is divided into pharynx, 

 oesophagus, ingluvies or crop, gizzard, chylific stomach, small intes- 

 tine, caecum and rectum. All these parts rarely co-exist in the same 

 insect. The oesophagus is directly continued from the sucking ap- 

 paratus in Haustellate Inse"cts without a pharyngeal dilatation. 



In the carnivorous Dragon-fly * the alimentary tract is short and 

 straight: there is neither crop nor gizzard, the chylific stomach is 

 long, cylindrical, and is divided from the oesophagus by a slight con- 

 striction ; the short intestine which succeeds is dilated at its com- 

 mencement, and plicated longitudinally as far as the contracted 

 rectum. In other insects a duodenal and iliac tract of intestine may 

 be distinctly recognised. In the tiger-beetle {Cicendela) and the 

 carnivorous Carabidce^ there is a small gizzard, preceded by the usual 

 ingluvial dilatation of the oesophagus and followed by a long 

 chylific stomach, the external surface of which is beset with secerning 

 follicles. The small intestine makes a short turn before terminating 

 in the dilated colon. 



The alimentary canal of the browsing cockchafer is considerably 



* Prep. No. 589. 



