130 



not expanded as in some insects, forming a gullet, but is practically 

 the same diameter throughout its entire extent. It is lined with 

 chitin, surrounded by a delicate basement membrane. 



The gizzard is a mushroom-shaped organ, opening into the stomach 

 and receiving the contents of the oesophagus and the aspiratory 

 pharynx. From its anterior concave inner surface project a number 

 of finger-like processes that arise from a basement membrane. They 

 are lined with chitiu, and each one near its base contains an elongated 

 nucleus. These processes reach to the center of the gizzard and in a 

 general way point towards the opening into the stomach. The giz- 

 zard is surrounded by circular bands of muscle fibers. Its function 

 is not entirely imderstood. Wagner (5) has pointed out that these 

 processes may act as whips to defibrinate the blood. It is more 

 probable that their action is mainly valvular, preventing regurgita- 

 tion of blood from the stomach. 



The stomach of a flea is large and is capable of great distention. 

 It is composed of a layer of secretory cells, resting on a basement mem- 

 brane, the organ being surrounded by muscle fibers passing in 

 different directions. The epithelial surface is thrown into little 

 projections like villi. As absorption occurs in the stomach, these 

 villi, or projections of the epithelial cells, may serve to increase the 

 absorptive surface as well as serving a glandular function. At the 

 anterior end of the stomach are the cecal glands. 



The intestine is short, receives the excretion from the Malpighian 

 tubules, and ends in the rectum. In the rectum may be seen the 

 so-caUed "rectal glands." All of the alimentary canal, with the ex- 

 ception of the stomach, is lined , with chitin. The stomach and the 

 rectum are capable of peristaltic movement. 



The salivary glands, four in number, two on each side of the anterior 

 part of the stomach, are simple acinous glands, lined with a single layer 

 of secreting cells. The lumen of the glands is large and acts as a 

 reservoir for the salivary secretion. The ducts from these glands 

 unite to form a single duct which passes beneath the subcesophagal 

 ganglion and empties into the salivary pump. This duct is lined on 

 its inner surface by a spiral arrangement of chitin, giving it a very 

 characteristic appearance. 



DESCRIPTION OF FIGURE SHOWING MOUTH PARTS. 



1. Epiphaiynx. 



2. Mandibles. 



3. Rostrum, paired portion. 



4. Rostrum, unpaired portion. 



5. Maxilla. 



6. Maxillary palpus. 



7. Salivary grooves. 



