76 THOMPSON YATES LABORATORIES REPORT 
At the proximal end the chitinous lamella of the labrum ends within the 
clypeus, projecting upwards for a considerable distance as a flattened rod-shaped piece, 
which affords attachment to fan-shaped muscles, arising from the roof of the clypeus. 
The hypopharynx. Savigny (1816); lingua, Westwood ; ligula, Kirby 
and Spence (1828); or tongue, is formed by a prolongation of the chitinous lower wall 
ot the pharynx. It is a thin, flattened lamella of chitin, closely applied to the under 
surface of the labrum-epipharynx. Its lateral edges are turned upwards slightly, and 
upon these rest the inner edges of the mandibles and the convex basal borders of the 
epipharynx. The tip of the hypopharynx is simple and lanceolate. In the centre of 
the hypopharynx the chitin is thickened and deeply hollowed out on its upper surface, 
to form an almost completely closed gutter running down the whole length of the 
organ, and approximated to the slit on the under surface of the epipharynx. The 
hypopharynx consists of an upper thick flattened plate of chitin, hollowed at its 
centre to form the gutter, and a lower thin plate ; the intermediate space being filled 
with delicate connective tissue, and is lined with chitin forming cells : well seen in a 
section at the base of the proboscis (plate XVI, fig. 1). Throughout the distal two- 
thirds the two plates are fused together, the space remaining as a core of cells, imbedded 
in the chitin on each side of the salivary gutter. This gutter commences as a V-shaped 
opening (plate XIX, fig. 1) at the point of origin ot the hypopharynx. Connected with 
this aperture is the salivary receptacle (plate XVIII, fig. 1 j.r), a hollow, cone-shaped 
organ, lying applied to the ventral wall ot the pharynx. The base of the cone points 
backward and slightly upwards; the apex, after a slight curve upwards, opens on to 
the salivary gutter at the V-shaped slit. The sides of the receptacle are of thick 
opaque chitin, except on its dorsal surface, which is somewhat flattened and composed 
of thin membranous transparent chitin. The lateral walls of the receptacle are 
strengthened by chitinous bands from the lateral portions of the clypeus. The base 
ot the receptacle is distinctly membranous in character, very faintly staining with 
haematein : a little below its centre the common duct of the salivary glands is 
inserted. Above and around the insertion of the duct are attached the fine tendons 
of two muscles, one from each side (plate XVIII, fig. 1 f.m. and XIX, fig. 1 r.m.). 
These muscles arise together from the ventral surface of the lower chitinous plate of 
the pharynx, but more especially from a chitinous ridge on each side, which is concave 
anteriorly and also from above down, and projects from its under surface near the 
junction of the first and second portions of the pharynx (plate XVIII, fig. 1), The 
mechanism of the receptacle is probably as follows : — When the muscles contract, 
dilatation of the cavity of the receptacle is produced by pulling of the membranous 
base outwards ; saliva then flows in and fills the cavity. On relaxation of the 
muscles, the membrane springs back into its original position, thus expelling the saliva 
down the channel of the hypopharynx. 
The mandibles, two in number, are extremely delicate, transparent scroll-like 
rods of chitin, applied, one on each side of the base and sides of the epipharynx, 
