JOUENAXi OF ENTOMOLOGY AND ZOOLOGY 35 



majority of the sections were cut 10 microns thick, though a few 

 were cut 5 microns. 



II. Morphology of the Proventriculus 



A. External. The alimentary canal of the Hydropsychid 

 larva is a straight tube. The fore-intestine, which extends to the 

 middle of the metathorax, is divided into the following parfs: 

 Pharynx, oesophagus, proventriculus, and the oesophageal valve, 

 which is an invagination of the fore-intestine into the mid-intestine. 

 The proventriculus is the region just before the mid-intestine, and 

 is confined to the meso- and metathoracic segments. (Fig. 1, P. ). 

 When there is little or no food in the canal, this region is clearly 

 defined and is barrel shaped. The coat of circular muscles is very 

 thicic and the intima greatly modified. The latter is armed with 

 numerous dark brown teeth, which, unlike those of some of the 

 forms which have been previously studied, are plainly visible 

 through the muscular layers. A series of yellow spines caudad 

 of the teeth, and two valves armed with spines on their outer sur- 

 face, may also be seen without dissection. (Fig. 1.) 



B. Internal. On dissecting the proventriculus. It is seen to 

 differ from the forms already described, in the large number of 

 strong teeth, anc^ the presence of two well developed valves In the 

 posterior region of the organ. These valves are connected with 

 the oesophageal valve and, so far as I know, have not been figured 

 in literature before. 



The intima of the oesophagus Is thrown Into six primary folds 

 (Fig. 2, Fd. 1), which become clothed with caudally-directed spines 

 as they near the proventriculus. Each of these folds becomes sub- 

 divided caudally into six secondary folds (Fig. 2, Fd. 2) which pass 

 Into the teeth of the proventriculus. The thirty-six chitlnous teeth 

 are arranged in six groups — five large teeth (Figs. 2 and 3, Tl.) in 

 each group, separated by a smaller lower tooth (Figs. 2 and .3, Ts.) . 

 The large teeth viewed from the side are, roughly speaking, tri- 

 angular In shape. Just caudad of the apex Is a sinus, and in many 

 cases the apex itself has a slight concavity. (Fig. 3, Ts.) Caudad 

 of these teeth are typically twelve rows of closely set yellow spines, 

 arranged in parallel lines and directed forward. (Fig. 2, Sp.) 



