~I 
BS 
MR. P. R. AWATI ON THE MECHANISM 
The csophagus is lined with the layers of an epithelium, and, 
innermost of all,a soft chitin, which disappears posteriorly : from 
this point, the outer layer of the cesophagus is generally one cell 
thick, the cells being small. The inner layer consists of elongated 
cells which have vacuoles in them, and which are greatly developed 
in the stomach. Outside the outer epithelial layer are found the 
vonstrictor and the valvular muscles. (Text-fig. 2, Con.M., V.M.) 
The Cardiac Valve (text-figs. 2, 7, C.V.)—This is very short, 
and it seems that its position in the cesophagus varies in different 
insects. In Schizoneura lanigera it is present at the end of the 
cesophagus (Davidson (9)), but in Lygus the valve is in its middle. 
It is formed by the doubling of a part of the cesophagus upon 
itself. The valvular muscles are attached to the base of the valve. 
It remains closed in the normal position until the muscles contract, 
when it is opened. 
It prevents any return-flow of the sap from the stomach into 
the cesophagus. 
Tue Gustatory Oreans. (Text-figs. 26-28.) 
That these are a specialised part of the supracesophageal 
ganglia is proved beyond doubt. They are situated upon the 
Text-figure 26. 
Nucleus. 
Nerve fibre. 
Nerve from the brain Cribriform Plate 
to the G.Or. with pores. 
Lygus pabulinus. 
Longitudinal section, showing the histological structures of the gustatory 
organs with the cribriform plate, etc. Ob. 6 & Oc. 4. 
For explanation of the lettering see p. 693. 
operculum in the clypeo-labral region. There is a nerve running 
from the brain to these organs on the upper wall of the pharynx. 
Their histoiogical str uctures, though specialised, are similar to 
those of the brain, 
