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Psyche 
[December 
Its presence in a region seemed, in general, to be correlated 
with the presence of food in that region, and not all the 
midgut cells appeared to be secreting it. This gave it a 
fragmentary appearance in most sections. 
In order to ascertain whether the membrane contained 
chitin, and could be called a peritrophic membrane, eight 
midguts of Ranatra which had been fed fifteen hours before 
were subjected to the chitosan test, as described by Richards 
(1951, pp. 32 and 33). Solid food was never observed in 
the Ranatra midgut, and thus use of this test seemed to be 
justified. The technique of Sutton (personal communica- 
tion) was employed; each individual was dissected in 
Ringer’s solution, the gut removed, and the midgut cut off 
just posterior to the esophageal valve and anterior to the 
point of entrance of the Malpighian tubules. The midgut 
was then placed in about 5 cc. of concentrated potassium 
hydroxide solution in a Bunsen tube and heated in a gly- 
cerine bath to 160 degrees C. for 20 minutes. If, after this 
treatment, any residue remained in the tube, it was tested 
with Lugol solution, zinc chloride, 1% sulfuric acid, and 3% 
acetic acid, following the methods prescribed by Richards 
(1951). In three of the eight individuals, positive reactions 
were obtained by this method; the small and very delicate 
strands of material which remained after the potassium 
hydroxide treatment in these three appeared, therefore, 
to be chitinous in nature, and to represent fragments of a 
peritrophic membrane. 
Explanation of Plate 9 
Figures 1-3. Fig. 1. Longitudinal section through part of the anterior, 
dilated portion of the midgut of Ranatra jusca, showing the secretion of 
a peritrophic membrane by the epithelial cells. Fixed in alcoholic Bouin’s; 
Mallory’s triple connective tissue stain. 240 X. Fig. 2. Longitudinal sec- 
tion through the posterior part of the midgut of H esperocorixa interrupta. 
Note the large fragment, presumably an ingested piece of arthropod exo- 
skeleton, within the food mass. Fixed in aqueous Bouin’s; Mallory’s triple 
connective tissue stain. 440 X. Fig. 3. Detail of the fragment shown in 
Figure 2. Note the sculpturing on the surface of the fragment. 720 X. 
Abbreviations Used in Figures. C-Fragment of exoskeleton within food 
mass. E-Midgut epithelium. F-Food material in gut. L-Lumen of gut. 
M-Peritrophic membrane. 
