130 MOLLUSCA. 



The nidamental glands have been studied and removed. 



Draw a figure of the female reproductive system. 



Circulatory System. An injected specimen is desirable. The 

 blood that has been supplied to the body in general is collected 

 by veins and carried to the branchial hearts. The vessels that 

 collect the blood are: 



1. The pre-cavce. A single vessel carries the blood from the 

 head to the anterior ends of the kidneys. Here the vessel divides 

 into right and left pre-cavse that are intimately connected with 

 the kidneys. The pre-cavae diverge near the posterior ends of 

 the kidneys and enter the corresponding branchial hearts. 



2. The post-caves. A pair of very large vessels that return 

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

 sponding pre-cavae 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 



