JOTJKNAL 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 hrauches 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 aortae. The posterior aorta runs back over the liver, 

 dividing very soon into two ]iarts, 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 buccal 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, l)ut which I have 

 been unable to trace backwards, although it probably has branch- 

 es which run backwards. In any case, the l)lood 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 papillae, to which it gives branches. 



