C. Hay Murray 
299 
noticed that frequently, but not always, the bug stores blood in 
the anterior end of the intestine long before the stomach is full. 
In nearly every case when a partially fed bug was dissected, it was 
found that, although some of the blood imbibed had been stored 
in the first portion of the intestine, there was a clear empty space 
immediately after the stomach separating the blood in the stomach 
from that in the intestine. This is due to a sphincter which, one would 
be tempted to think, must be overstrained when the bug feeds to reple¬ 
tion, as the junction between stomach and intestine-is then not clearly 
defined. It is quite possible that the effect is the result of the peri¬ 
staltic action of the alimentary tract forcing the blood onward in 
portions, while the sphincter may not begin to act until there is some 
slight strain on it. Considering the suction that must be created when 
the pump pulls, it is rather curious that there is no trace of a 
mechanical valve between the pump and the stomach to prevent regur¬ 
gitation of what has already been imbibed, there being no sphincter 
muscle between pump and oesophagus. The function of a valve may, 
however, be undertaken by the very thin-walled oesophagus being 
occluded by the pressure of the surrounding tissues when the pump 
sucks, or it may be that the muscles work peristaltically from anterior 
to posterior, and the see-saw movement of the roof of the pump may 
thus act as a valve which is alternately closed and opened. In favour 
of the first suggestion is the fact that the stomach always contains 
some air, which expanding under the reduced pressure would tend to 
occlude the thin-walled oesophagus. On dissecting a bug under fluid, 
the stomach always becomes very prominent when the dorsal body wall 
is opened, because of the air contained in it. Among the Diptera 
large volumes of air are also found in the alimentary tract, though the 
purpose is not apparent. In the bug, the presence of this air would 
seem to be due to the creature commencing to work the pump ere the 
lancets were imbedded, or else continuing to work it after they were 
withdrawn. As the bug imbibes blood it is mixed with saliva from the 
salivary receptacles. These are two in number and lie on the dorsal 
surface of the thorax on either side of the oesophagus just before it 
branches out into the crop. When freshly dissected out, the colour is 
found to vary in different specimens. Landois, in speaking of these 
receptacles, calls them the “large spherical salivary glands,” and says 
they are of an exquisite “yellow green” colour. In the writer’s 
experience the colour varies very much, but never has he seen them 
“ yellow green.” Whatever be the nature of the colour it is soluble 
