238 AKTHROPODA [CH. 



being laid and fertilise the ova whilst they are in the genital sac. 

 Two glands, consisting of branching tubes, called colleterial 

 glands open separately behind the spermatheca. They secrete 

 a fluid which hardens to form the egg-capsule in which the eggs 

 are laid. This is moulded in the genital sac and may often be 

 seen half-protruding between the distended seventh sternum of the 

 mature female. 



When the sldn is removed from the dorsal surface of the cock- 

 roach the cavity laid open is not a coelom but a 

 internal haemocoele, and it is largely filled by a loose white 

 tissue, known as the fat-body, which surrounds the 

 various internal organs. If the alimentary canal be disentangled 

 from this it is at once evident that in Insects, unlike other Arthro- 

 pods, the intestine is longer than the body and the larger portion 

 of it which lies in the abdomen is coiled ia order to stow it away. 

 Like the digestive tube of other Arthropods a large part of its length 

 consists of the stoinodaeum and proctodaeum. The former consists 

 of an oesophagus which quickly passes into a large crop in which 

 the food is stored for a time. The lining of both these regions 

 bears hairs and the muscles in their walls are striped. The crop 

 is followed by a gizzard, which bears internally six hard chitinous 

 teeth, and behind them are fine hairs which act as strainers, so 

 that only finely divided food can pass on into the mesenteron or 

 chylific ventricle, as the part of the alimentary canal is called 

 which alone is lined by endoderm and is capable of absorbing 

 nourishment. This tube is produced in front into seven or eight 

 pouches, the so-called hepatic diverticula. The mesenteron, the 

 limit of which is marked by the insertion of the Malpighian tubules, 

 is succeeded by the intestine or proctodaeum, a long coiled tube 

 which enlarges posteriorly and opens by the anus. The enlarged 

 portion is called the rectum (Fig. 99), the anterior coiled portion 

 the colon. 



Lying along the crop on each side are a pair of branched glands 

 the salivary glands and a bladder termed the salivary 

 reservoir. All three are provided with long ducts. Those of the 

 two glands on each side unite to form a single tube which then 

 receives the duct of the reservoir, and the common ducts of the two 

 sides open behind the mouth but in front of the second maxillae. 

 The saliva converts starch into sugar. The secretion of the hepatic 

 diverticula emulsifies fats and turns insoluble proteids into the 

 soluble forms (peptones). This secretion seems to pass forward into 



