The Shell-Collector’s Handbook. 9 
into two branches, one taking its course to the apex 
of the spire, and supplying the liver, intestine, and 
reproductive organs (posterior aorta); while the other 
(anterior aorta) runs forward, gives branches to the 
salivary glands, head, tentacles, and body-wall, and a 
large branch—the pedal artery—which passes back- 
wards along the foot to supply it. There are no 
capillaries, and the arteries end by funnel-shaped 
openings in the lacune of the interstices of the 
tissues. From these lacune the blood passes into the 
various sinuses of the body. Two of these sinuses 
run along the sides of the foot (pedal sinuses), one on 
either side, and another (visceral sinus) courses from 
the apex of the shell-cavity to the posterior end of the 
mantle-cavity, ending in a circular pulmonary sinus. 
From this pulmonary sinus efferent vessels carry the 
blood to the roof of the mantle-cavity to be aérated, 
and then coverge to form a pulmonary vein, which 
runs in a straight line along the roof of the respira- 
tory chamber back to the auricle, previously 
receiving the renal vein from the kidney. The pedal 
’ sinuses do not seem to be in direct communication 
with the pulmonary sinus, and any blood passing from 
one to the other must be transmitted by way of the 
lacune. According to the researches of Harless and 
Wicke, in the majority of the Pulmonata, the blood is 
bluish and richly corpusculated ; in others, whitish and 
opaline; while in the Genus Planorbis, it is red in 
colour. 
THe Respiratory Orcans.—In the Branchio- 
gasteropoda—where the organs are so formed as to 
breathe air dissolved in the watery medium in which 
