ORGANS OF DIGESTION. 



into clusters of small follicles, already forming lobules, like the 

 lobules of the tubuli biliferi in Crustacea. There are three pairs of 

 salivary glands, lengthened and complicated, in the scutellera 

 mgrolineata which feeds on the young seeds of growing corn. 

 The biliary tubes of this insect are very small, and they ter- 

 minate in a single median vesicular enlargement, forming a 

 minute gall-bladder. The chylific stomach, with its several 

 convolutions and enlargements, composes, as in most insects, 

 the greatest part of the alimentary canal. In the herbivorous 

 coreus marginatus, which feeds on the juices of several plants, 

 the digestive canal is more lengthened, but similar in 

 structure. There are four pairs of large elongated salivary 

 glands ; two pairs of short simple biliary follicles pour their 

 secretion into a single gall-bladder, and a pair of long 

 sacculated pancreatic follicles terminate separately in the 

 stomach above the entrance of the short cystic duct. This 

 simple form of the pancreas is seen also in the leptis, bomby- 

 liuSy chrysotoxum, and many other insects. In the cicada 

 orni (Fig. 118, B.) which appears to feed on the juices of the 

 pine, and not of the ash tree, the long narrow tubular 

 stomach (B. t), after forming numerous convolutions, returns 

 to terminate in itself, like the intestine of a vorticella or the 

 tubuli of many glands. In this, as in many other insects, 

 there are two distinct forms of salivary glands which unite 

 together to enter the mouth by a single duct on each side. 

 One of these glands is a simple convoluted follicle (Fig. 118. 

 B. p.) like the biliary and urinary tubuli, and the other gland 

 on each side of the oesophagus forms a posterior (B. o.) and 

 an anterior (B. n.) lobule, composed of small short follicles, 

 before terminating in the common duct. The long capillary 

 ossophagus dilates into a small crop (B. c.) before entering 

 the coecal cavity with which the chylific stomach (B. e. t.) 

 commences, and from which the intestinal canal (B. u.} 

 originates. The stomach (B. e.f, /.) in place of forming a 

 continuous canal, as usual, from the oesophagus to the in- 

 testine, here turns off suddenly from the direct course of the 

 alimentary canal, and, after forming numerous convolutions 

 as a small tube (B. t.), it returns, to terminate in its proximal 

 extremity (B./.), thus forming a circular elongated tubular 

 coecum. At the commencement of this long circular coecum, 

 the stomach receives the termitnaions of four isolated monili* 



PART IV. A A 



