120 MOLLUSC A. 



The testis is a large, white organ that extends, from the region 

 of the stomach, posteriorly to the end of the body, dorsal to the 

 visceral sac. 



Draw a figure of the male reproductive system. 



Open the base of the penis and remove a number of spennato- 

 phores. Place them in a watch-glass in water and examine 

 with a microscope. Notice: 



1. The sheath. 



2. The packet of spermatozoa. 



3. The spiral discharging portion. 

 Draw. 



Why are the spermatozoa contained in spermatophores? 



Female Reproductive System. — The opening of the oviduct 

 has already been noticed. Observe: 



(a) The large, swollen portion, the oviducal gland, that lies 

 dorsal to the left branchial heart. 



(6) The oviduct leaving the dorsal portion of the gland. The 

 oviduct is long and convoluted, and is frequently filled with eggs. 

 This depends on the season of the year. 



(c) The lighter colored, greatly lobulated ovary, also fre- 

 quently filled with eggs, lying dorsal to the oviduct and visceral 

 sac and extending from the region of the stomach to the end of 

 the body. The ovary is inclosed in a capsule from which the 

 oviduct leads. 



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-cavce that are intimately connected with 

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

 the kidneys and enter the corresponding branchial hearts. 



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



