410 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
over the surface of the gland along its posterior lateral 
margins, providing numerous branches, and eventually 
plunging below the surface into the substance of the 
gland. Other small branches are given off, on each side, 
from the aorta, and pass through the gland to supply the 
stomach. 
Approaching the pit wherein the ligament rests, the 
aorta curves to the right of the median line so as to bend 
round the pit, and on reaching its anterior edge plunges 
down into the midst of the digestive gland, bending 
slightly to the right, so as to pass the oesophagus on that 
side. It gives oft two vessels, which arise close together 
on the left side. Both of these leave the gland and pass 
into the mantle, one curving back to supply the region of 
the ligamental pit; whilst the other, the anterior pallial 
artery (fig. 14, 4. p.a.), which is larger, passes forwards 
to the anterior dorsal corner of the mantle, where it 
bifurcates to form the circumpallial arteries running 
round the margin of the mantle lobes. It also gives off 
sinaller vessels before dividing, which supply this area of 
the mantle on both sides. 
The main branch of the aorta passes, as we have seen, 
into the midst of the digestive gland (fig. 14), and gives 
off very close to the two vessels above described a small 
branch which, passing through the gland, reaches the 
surface again on the left side and passes into the mantle. 
This will be easily seen (in injections with lard) on the 
left side of the gland. 
At about the level of the upper lip, a small vessel 1s 
given off, passes to the anterior surface, and breaks 
up to supply the external labial palps and the upper lip 
(fig. 17, A.Z.). The capillaries, or very small vessels, can 
be followed out on the palps if the injection is successfully 
carried out. 
