LOLIGO PEALII. 121 



blood from the posterior end of the body. They join the corre- 

 sponding pre-cavse near the anterior borders of the branchial 

 hearts. 



3. The mantle-veins. These return blood to the branchial 

 hearts from the anterior portion of the mantle. 



The blood that is received by each branchial heart is sent 

 into the corresponding gill through a vessel that leaves the heart 

 near the opening of the mantle vein, and runs along the side of 

 the gill that is attached to the mantle. 



The blood is collected from each gill by a large branchial vein 

 that runs along the ventral side of the gill, and enters the sys- 

 temic heart. 



Draw a figure showing the vessels connected with the branchial 

 hearts. 



Expose the systemic heart by carefully removing the superfi- 

 cial tissue between the branchial hearts, and notice that it is not 

 symmetrical. Its lateral angles receive the branchial veins and 

 it gives rise to an artery from each of the other two angles. 



The posterior aorta divides almost immediately into three 

 large vessels. These are: 



(a) The median mantle artery which follows the edge of the 

 ventral mesentery to the mantle. 



(6) A pair of lateral mantle arteries which diverge posteriorly 

 and supply the two sides of the mantle. Besides these large 

 vessels there is a small vessel that runs anteriorly over the ven- 

 tral surface of the heart and supplies the ink gland and rectum, 

 and another one that runs dorsally and posteriorly to supply part 

 of the reproductive system. 



(c) From the dorsal surface of the heart, near its anterior 

 end, a small vessel passes over the anterior and dorsal surfaces 

 of the stomach and finally passes into the gonad. 



The anterior aorta is larger than the posterior aorta. From 

 the anterior angle of the heart, which is to the right of the median 

 line, it follows a straight course alongside the esophagus to the 

 head. A number of small vessels are given off along its course, 

 and it is finally distributed to the head and arms. 



