312 TRANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



'^ runs round the edge of the mantle, giving off branches on 



both sides. Very small vessels leave the aorta at intervals 

 and pass to the alimentarj' canal. The next two vessels 

 which arise are asymmetrically placed. Thej' leave the 

 aorta lateralh', but the left one is somewhat posteriorly 

 situated. These vessels (fig. 3G, A. cut.), after passing 

 out laterally, run up the walls of the body cavity and 

 break up into small vessels innervating the roof (the floor 

 of the mantle cavity). The vessel on the right side, 

 however, gives off an additional branch (hg. 3G, A. cut.'), 

 whieh bores into the wall and passes to the tissues below 

 the ovary and rectum. 



The Cephalic Aorta passes forwards until the Nerve 

 Collar is reached and then breaks up at one jx>int into 

 several vessels. The point where this division takes place 

 is hidden by the salivary glands and by connective tissue. 



One large vessel runs down at right angles to the 

 course of the Cephalic Artery. This is the Pedal Artery 

 (figs. 36 and 35, A. -ped.). After a short course, it divides 

 into two branches which make their way into the foot, 

 branch again (each in a similar way) and supply the 

 musculature. These blood vessels are of considerable size. 

 Here they branch, but must of their small branches, which 

 form almost a capillary network, are not shown in the 

 figures. It is by means of this network, and the forcible 

 action of the blood, that the great expansion of the foot 

 is effected. 



Returning to the nerve collar region, it will be seen 

 that another large vessel runs dorsally, also at right 

 angles to the aorta. This aitery, the lUiccal (fig. 30, 

 A. hue), goes forward ai <hc sule of the oesophagus, and 

 after giving off two siiuill xcssels to the ])rol)os('is, enters 

 the latter with the aJiniciitary canal. Here it breaks uj) 

 into a complicated series of br;iiicii('s supplying the 



