JOURNAL OF ENTOMOLOGY AND ZOOLOGY 89 
make out, owing to the extreme thinness of the walls of the 
arteries, which were usually collapsed, misplaced, or torn in 
places, so as to make their identification difficult. Consequently, 
only the main branches of the arterial circulation are shown in 
the drawing. 
The aorta leaves the ventricle at its anterior end, on the lower 
side. Almost immediately it divides into two parts, the posterior 
and anterior aorte. The posterior aorta runs back over the liver, 
dividing very soon into two parts, which branch and rebranch, 
the branches soon becoming indistinguishable from clefts be- 
tween the liver lobes. The anterior aorta runs forward below 
the upper body-wall and passes through the blood gland, which 
spreads in a flat, thin sheet above and posterior to the buccal 
mass. It is divided into a right and left portion and these are 
subdivided into numerous lobes. The substance of the gland is 
somewhat similar in its appearance to the pulp of lymph glands 
in vertebrates, as it consists of a mass of cells, among which are 
a few interlacing fibres. It communicates with the aorta by 
several branches. The aorta now divides into three parts. The 
first, the genital artery, runs down to the reproductive organs, 
where it opens into a network of sinuses; the second (N) runs 
through the blood gland and along the upper surface of the 
capsule surrounding the central ganglia; the third branch, or 
aorta proper, goes down on the right side of the buccal mass, 
curves under it, and gives off a large buceal artery, which sends 
two branches to the sinuses in the buccal mass. The remainder 
of the aorta enters the foot muscles as the pedal artery (Q), 
which can be traced forwards for some distance, but which I have 
been unable to trace backwards, although it probably has branch- 
es which run backwards. In any case, the blood would be carried 
back by the sinuses of the foot. 
The venous blood, with the exception of that coming from the 
posterior aorta, circulates through an elaborate system of irreg- 
ular, intercommunicating sinuses, chiefly in the foot and sides, 
which communicate with the main body cavity and the great 
lateral sinus. This lateral sinus forms a ring around the body 
at the level of the origin of the papille, to which it gives branches. 
