This usually extends into the abdomen, and is a 

 prominent object in dissections and sections (Fig. 



38)- 



The Homologue of the Proventriculus. There is no 

 true proventriculus as in many insects. There is, 

 however, an interesting fold of the fore-gut into the 

 mid-gut which represents this organ. The muscular 

 bundles are here increased, and the whole forms a 

 valvular muscular organ (Fig. 38). 



The Mechanism of Feeding. The powerful pump- 

 ing action which must result from a drawing asunder 

 of the three large chitinous plates of the pumping 

 organ is very evident. These plates, also, when drawn 

 apart must, by reason of their spring-like shape, revert 

 to their original positions close together, without any 

 muscular aid. Posteriorly the valve-like arrangement 

 mentioned before prevents regurgitation. Further, 

 when the blood reaches the junction of the oesophagus 

 and mid-gut the invaginated portion is withdrawn, and 

 is distended by the entering blood into a distinct 

 4 crop,' the valvular function is suspended, and the 

 blood flows onward. 



The Mid-gut. The mid-gut extends from the 

 proventriculus to the origin of the malpighian tubes. 



The anterior narrow portion of the mid-gut lies 

 in the thorax, and does not become distended with 

 blood. The posterior poition when fully dilated fills 

 the greater portion of the abdomen, the viscera being 

 pushed into the last few segments. 



The Hind-gut. The hind-gut is short and passes 

 in one or two bends from the pylorus to the anus. 

 Immediately beyond the pylorus there is a considerable 

 dilatation which is poorly supplied with muscular fibres : 

 into this open the five malpighian tubules. For a short 

 distance beyond this the lumen is narrow (ileum), but 



