54 
Psyche 
[June 
brane probably when the first food breaks through the sack 
on its passage down the intestine. The muscular wall (m) 
of the oesophagus (oes) that was a simple layer of cells at 
the ninetieth hour (fig. 3), expands into a bulb-like ring at 
the end of the oesophageal valve. Inside this ring is an open 
space which Wigglesworth (30) calls a blood sinus (bl s). 
This muscle with its blood sinus is a sphincter which, when 
expanded, closes off the mid-intestine to the entrance of 
food. When contracted, the passageway through the oeso- 
phageal valve is open. The ectodermal cells, lining the sto- 
modseum, that were so large in the embryo, have thinned 
out and disappeared over the end of the bulbous ring, their 
place being taken by a thin membrane, the chitinous intima 
(c in) . The cells secreting the peritrophic membrane (pc) 
which have now assumed a very regular appearance with 
smooth inner and outer walls, are very large and vacuolated. 
At the sides of the mid-intestine lie the two gastric coeca 
(coec) which discharge their contents into the intestine 
near the oesophageal valve. Their contents are prevented 
from bathing the oesophageal valve by the peritrophic mem- 
brane (m) which is forced together by the fluid and ex- 
tends down into the mid-gut. 
Nelson (’15) states that the stomodseum in the honey-bee 
is closed at its inner end by cells of the anterior mesenteron 
rudiment. He does not mention any embryonic origin for 
the peritrophic membrane. Snodgrass (’25) refers to Nel- 
son in regard to the stomodseal membrane and says, “the 
old idea that the peritrophic membrane of insects is a back- 
ward prolongation of the chitinous intima of the proventri- 
culus has been discredited in all recent investigations on its 
origin.” He finds that it is formed in the adult bee from 
protoplasmic bodies given off from the epithelial cells of 
the mid-intestine. These fill in the granular layer. Wig- 
glesworth (’30) is of the opinion that the peritrophic mem- 
brane is of two-fold origin: a chitinous basis, secreted at 
the anterior end of the mid-gut and a series of indefinite 
membranes which condense on the outside of this as it pro- 
ceeds down the gut. Having access to some slides of the 
