176 Psyche [December 



the mesenteron, including the reservoir, is completed very shortly 

 — one or two days — before the nymph hatches out; but the oesoph- 

 agus and salivary glands, the rectum and malpighian tubes are 

 complete several days earlier. The chitinous intima of the 

 oesophagus and rectum is already secreted, though as yet in a 

 plastic condition, at the stage shown in figure 2. The dorsal wall 

 of the midgut and the anterior part of the reservoir are the last 

 portions of the mesenteron to close up and complete. The midgut 

 appears to proliferate from a small mass of cells at the inner 

 ends of the oesophagus and rectum respectively: it appears, there- 

 fore, to be of ectodermal origin. The basement-membrane of 

 the mesenteric epithelium is more or less chitinous and apparently 

 secreted by the epithelium itself. The peritoneal membrane is 

 largely developed in this insect (and many other Homoptera, 

 and more or less envelops the whole alimentary canal and its 

 appendages, and appears to be only deficient over the anterior 

 part of the oesophagus, a small posterior portion of the rectum 

 and the long loop (fig. 3, part outside line indicating peritoneal 

 membrane) of the midgut; but it is probable that it is merely 

 exceedingly delicate over this area, and, therefore, practically 

 invisible. In figures 3 and 4, however, the peritoneal membrane 

 is only shown over those parts where it is a really thick tissue, 

 and thus in figure 4a it appears to leave the oesophagus anteriorly 

 and continue only on the reservoir. The posterior part of the 

 oesophagus, the anterior part of the rectum, part of the midgut 

 and reservoir and the proximal portions of the malpighian tubes 

 lie alongside one another in close contact, and are also twisted 

 around each other. The whole tangle is closely invested by the 

 peritoneal membrane; in figure 3 the parts are not shown twisted, 

 in order to keep the figure clear. There is a constriction (fig. 4 

 frv.) around the reservoir, just in front of the oesophageal valve, 

 provided with extra annular muscles; this occasionally shows 

 as a slight invagination (similar to the oesophageal valve), but 

 in any case it forms a valve for the reservoir, to admit or prevent 

 the passage of food therein. 



Berlese supposes (in apparently similar cases of Coccidse) 

 that by this unusual arrangement of the alimentary canal and its 

 appendages, osmosis of the innutritious watery part of the food 

 and the excess of sugar therein, may take place through the various 



