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1905. ] Anatomy of the Tsetse-fly (Glossina palpalis). 535 
course, till it finally enters with it the penis, the muscles of which it 
innervates. In the female a similar plexus appears to be formed, but owing 
to the dense tangle formed by the fat-body, uterine glands, and Malpighian 
tubules, I have not succeeded in dissecting out its finer details. 
2. The Digestive Tract—Since the proboscis, buccal cavity, and pharynx 
have been thoroughly described in Austen’s monograph by Hansen, whose 
account I can but confirm, I commence my description with the cesophagus. 
This portion of the alimentary canal (figs. 1 and 2, @s.) runs first of all in 
an upward direction from the pharynx (P4.), then bends sharply round and 
passes backwards through the brain. The first portion of the cesophagus 
is dilated, but slightly compressed, appearing of greater calibre in a dorsal 
than in a lateral view. After bending round, it narrows rapidly, and the 
portion which passes through the brain is of extreme tenuity, scarcely, if at 
all, of greater calibre than the salivary ducts. Behind the brain the 
cesophagus widens, at first very gradually, then, after entering the thorax, 
more rapidly, till it joins the stomach, into which it opens ventrally, 
breaking through the floor slightly in front of the point at which the thoracic 
intestine arises dorsally. From the point at which the cesophagus opens 
into the stomach, the duct of the sucking stomach arises. 
The stomach, which marks the commencement of the mesenteron, has 
a peculiar and very characteristic form (fig. 2, St.). Seen from the dorsal 
aspect, it appears roughly oblong in form, with a bevelled anterior edge, 
and the upper surface more or less saddle-shaped, ie, convex in the 
transverse section, concave in the longitudinal direction. Seen from below, 
its lateral edges appear wrapped round the cesophagus and the duct of the 
sucking stomach, on which it rides, as it were. From the dorsal side of 
the stomach, about the middle of its length, arises the intestine, the first 
part of which (Zh. £.) runs backwards through the thorax as a straight 
tube of even calibre, until it passes the waist. As soon as it enters the 
‘abdomen the intestine swells and becomes the strictly digestive portion of 
the alimentary canal. — 
The abdominal intestine is of great length, but until it reaches the 
proctodeum it cannot be divided into regions. It forms a number of 
complicated coils in the abdomen, and for purposes of description a number 
of limbs may be distinguished, each limb separated from the one next 
following by a more or less sharp bend (figs. 2 and 3). 
The first limb (1) runs backwards along the abdomen in a dorsal situation, 
curving first slightly to the right, then more strongly to the left, until it 
reaches the fifth segment, where a sharp bend takes place forwards in a 
ventral direction. The second limb (2) curves round from left to right, 
