708 MR, P. R. AWATI ON THE MECHANISM 
Great stresses have to be borne, and economy of skeletal material 
has been effected and a maximum of rigidity attained, by forming 
this material into hollow tubes instead of into solid rods. Many 
parallel cases may be instanced from the plant kingdom—of 
hollow stems which resist great stress. 
Text-figure 17. 
Lygus pabulinus. 
Transverse section, showing the clypeal folds, salivary ducts. Ob. 2 & Oc. 12. 
For explanation of the lettering see p. 693. 
The tentorium consists of the following parts :— 
(I.) The Body of the Tentorium, or Tentorium proper. (Text- 
es. A. 7, 9) es) 
This is formed by the fusion of the different arms of the endo- 
skeleton. It lies between the pump below and the pharynx 
above. It is found at the place where, if it were absent, there 
would be great probability of the pharynx on the one hand and 
the pump on the other, being dragged out of their positions 
by contractions of their powerful muscles. It furnishes a firm 
support for both these organs. 
Its structure is interesting ; both its surfaces (dorsal toward the 
pharynx, and ventral facing the pump) are curved and form two 
grooves. The groove facing the pharynx is V-shaped and corre- 
sponds exactly to the shape of the ventral wall of the pharynx, 
which fits closely into it. They are joined together by con- 
nective tissue. 
The shape of the other groove, 7.e. the ventral one, is roughly 
semicircular, and into it the pump is wedged, and kept there by 
connective tissue. 
