1914] Kershaw—The Alimentary Canal of a Cercopid 67 
muscle connecting the cesophagus and top of the sac may—by 
pulling the pouch and sac still more askew—contract the opening 
further, or by relaxing open it wider. The pouch lies ventrally 
and medianly within the mesothorax. The sac lies more dorsally 
and chiefly within the meta-thorax, but projects at times into the 
abdomen. The cesophagus runs through the pro-thorax. In 
figures 2 and 8 the anterior end of the pouch is not quite in a natural 
position, since it is usually more pulled over and downwards to 
the top of the sac by the large muscle attached to the latter and to 
the cesophagus. Figures 2 and 3 are slightly diagrammatic to 
avoid confusion of parts. The lines of the organs in the transverse 
section if projected to the longitudinal view (fig. 3) would not all 
agree as they strictly should; for instance the ascending midgut, 
to agree with the transverse section strictly, should have been 
dotted in right behind the malpighian tubes, instead of being 
shown just clearing them, but this would altogether have confused 
the sketch. The epithelium of the pouch not only tucks in longi- 
tudinally between the malpighian tubes, midgut, etc. (fig. 3, trans. 
sec.), but also—in a plane at right angles to the longitudinal tucks 
—between the several zigzags of the various tubes (fig. 3, i, k). 
This is only just indicated for the longitudinal tucks in the trans- 
verse section; in reality the epithelium follows all the interspaces 
of the organs very closely indeed, and more or less adheres to, but 
does not fuse with, the latter. Thus it presents a very large area 
for filtration or osmotic action. 
The total length of the alimentary canal is about fifty mm., 
made up as follows:—the cesophagus is about 1 mm.; the pouch 
and sac together 3 mm.; the tubular part of the midgut from the 
sac to the constriction or midgut sphincter ! 10 mm.; from thence 
to its entrance into the pouch 15 mm.; the zigzag portion within 
the pouch 11 mm.; from the anterior end of the zigzag to the origin 
of the malpighian tubes (rectal valve) 1 mm.; thence to the anus 
9mm. The length of the lobulate portion of the malpighian tubes 
is about 7 mm.; the smooth portion to their entrance into the 
pouch 3 mm.; the zigzag portion within the pouch 7 mm.; the 
straight portion to the origin of the tubes 1 mm.; total length 
about 18 mm. All measurements were taken with the organs 
straightened out but not unduly stretched. 
1 This constriction is provided with annular muscles. 
