26 Mr Harrison, A preliminary account of the 
buccal cavity and the pumping-pharynx, other than through its 
lumen, must be cut off. There can be no such communication 
ventrally, as the tube arises from the floor of the stomatodaeum. 
But a wide channel exists dorsal to the buccal tube, which is 
closed, as far as I can determine, by a pair of elastic folds, which 
lie at the base of the tube, and which pass obliquely upwards and 
backwards. When the two halves of the tube are brought 
together, the lips of these folds also come together, and shut off 
the pumping-pharynx from the buccal cavity. 
The function of the buccal tube is obviously that of the straw 
through which we take our lemon-squash. When the buccal 
eavity is protracted, its anterior end comes into contact with the 
skin, through which the piercers are already actively engaged in 
boring, and possibly its sharp chitinous edges also penetrate to 
some extent. Its lumen is in direct continuity with the pumping- 
pharynx, into which blood is drawn by the active pumping action 
of the dilatator muscles. From the appearance in cleared prepara- 
tions, a pair of ventral folds lying at the proximal ends of the 
pieces of the buccal tube would appear to act as valves closing its 
lumen during relaxation of the dilatators, but I am not able to 
make out the relations of these in sections. Me 
The prercer-sheath and piercing apparatus. 
The piercer-sheath is an invagination of the floor of the buccal 
cavity which runs backwards beneath the alimentary canal to the 
posterior margin of the sub-oesophageal ganglion, where it ends 
about the tendinous insertions of six muscles, the retractors of the 
piercing apparatus. In section these muscles appear as two lateral 
groups of three, one on either side of the middle line. Each group 
is composed of a dorsal and a ventral muscle nearer the middle line, 
with a lateral muscle lying outside and between them. Between 
the dorsal pair of muscles, and extending downwards in the middle 
line, lies a strand of tissue not of a muscular nature. Tracing these 
structures from behind forwards, it is found that the ventral pair 
of muscles is inserted into a pair of hollow chitinous ‘tendons,’ 
which run a short distance forwards and then join a thin chitinous 
plate which lies on the floor of the sheath. This plate runs through 
about two-thirds of the whole length of the sheath, the anterior 
third being separated by a suture from the posterior two-thirds. 
In dissections of potash-cleared specimens this posterior plate has 
broad punctate or granulate margins. The lateral pair also are 
inserted into tendons, which soon unite to give rise to a hollow 
chitinous structure, the ventral piercer, thyough the base of which 
a strand of muscle runs, but which, for the greater part of its length, 
is simply hollow chitin, apparently without cellular elements. It 
