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[December 
Psyche 
boundary between foregut and midgut. It is from the midgut 
cells directly posterior to this groove that the Type II 
peritrophic membrane is secreted, and the sillon marks 
its anteriormost point of insertion. This secretory group 
of midgut cells, the “massif des cellules-meres de la peri- 
trophique” of Aubertot, is histologically distinct from the 
rest of the midgut in som(e insects. 
ANNULAR CELLS 
Fig. 4. Detail of the annular cell region in Sigara ornata. Heavy line 
indicates the cuticular intima of the foregut, with which the entonnoir 
is continuous. Orientation same as that of Figure B (Plate 12) ; the eso- 
phagus and inner cell layer are not shown. The midgut epithelium is 
stippled. 850 X. 
It appears, however, that Sutton has mistaken the an- 
nular cells, which are definitely of foregut origin, for mid- 
gut epithelium, perhaps believing them to represent a 
“massif”. In so doing, she has taken the groove between the 
annular cells and the esophageal invagination to be the 
sillon; this appears to be the case in her figure 10. In the 
present study, however, the intima was seen to cover the 
annular cells and to end at a point more posteriorly located 
than the sillon of Sutton’s diagram. This area is quite com- 
plicated in corixids, since the annular cells which are closest 
to the migut bend inwards, towards the lumen, forming a 
whorl. The true sillon lies at the apices of these curved 
annular cells, and the terminal part of the intima therefore 
extends up into the whorl (see Text-fig. 4). There is rarely 
