(86) 



526 0. GORDON HEWITT. 



figure (fig. 25), it is rather similar to the proventriculus of the 

 imago in general structure. The cesophageal epithelium 

 penetrates a central core which is composed of large clear 

 cells (c. c.) ; its lumen, being oesophageal, is lined with chitin. 

 This core is surrounded by an outer sheath, the cells (e. v.) of 

 which are continuous with those of the ventriculus. At the 

 junction of the central core with the outer sheath of cells 

 there is a ring of small more deeply-staining cells (i.e.). 

 This ring was regarded by Kowalevski (1887) as the rudi- 

 ment of the stornodaeum of the nymph, but Lowne is of the 

 opinion that it develops in the nymph into the proventriculus 

 of the imago. I believe that it forms a portion, at least, of 

 the proventriculus of the imago, as it exhibits a very close 

 resemblance to the ring of cells in this region figured in the 

 section of the proventriculus of the imago (fig. 20 of Part I). 

 The mesenteron of the mature larva is of very great 

 length, and is not divisible into the two regions of 

 ventriculus and small proximal intestine as in the imago, but 

 appears to have the same character throughout; hence Lowne 

 calls it the " chyle-stomach," which term, or ventriculus (fig. 

 29, v.) } may be used to designate the whole region from the pro- 

 ventriculus to the point at which the malpighian tubes arise. 

 It is very much convoluted and twisted upon itself. The 

 course of the ventriculus is almost constant, and can be better 

 understood from the figure than from any detailed description. 

 At the anterior end four tubular caeca (c. v.) arise. Their 

 walls consist of large cells whose inner faces project into the 

 lumen of the glands ; these glands were not present in the 

 imago. The epithelium of the ventriculus (fig. 30) is com- 

 posed of large cells (e. v.), which project into the lumen of 

 the alimentary tract ; they possess large nuclei and the sides 

 of the cells facing the lumen have a distinct striated appear- 

 ance, which is absent in those epithelial cells covered with a 

 chitinous intima. This striated appearance may be related 

 in some way to the production of the mucous intima which 

 is generally present in the ventriculus, and which appears to 

 take the place of the loose chitinous intima* or peritrophic 



