112 ANNELIDA 



opening is not in the somite in which the most of the tube 

 lies, but in the somite anterior to it. That is, the nephridium 

 that occupies the space in somite twenty opens externally on 

 somite twenty, but internally perforates the septum directly 

 anterior and opens into somite nineteen. 



2. Remove a nephridium with your forceps and examine 

 it with your microscope. Notice that it consists of a coiled 

 tube of varying diameter. The funnel is not easy to find 

 and is hard to remove. It may be found by removing the 

 portion of the septum through which the nephridium passes 

 and examining it with a microscope. 



Draw the nephridia into your previous figure. 



Cut the stomach-intestine behind the gizzard and pull it 

 forward, carefully separating the tissue from it as it is drawn 

 forward, so underlying organs will not be disturbed. In this 

 way free the alimentary canal to the position of the pharynx. 



You can now see the extent of the nephridia, and pos- 

 sibly see where they perforate the septa. 



Reproductive System. — 1. The seminal vesicles are large 

 white bodies, united in the median line. They send three 

 lobes on either side, that normally overlap the posterior part 

 of the esophagus. In what somites do the lobes occur? 



2. Carefully open the seminal vesicles near the median 

 dorsal line and examine their contents microscopically. 



3. With a pipette wash out the contents and notice the 

 two pairs of convoluted funnels, the inner openings of the 

 vasa deferentia. The testes are hard to find, as they are the 

 same color as the coagulated mass that filled the seminal 

 vesicles. They are attached to the septa just anterior to the 

 funnels. The narrow tubes of the vasa deferentia may some- 

 times be seen leaving the seminal vesicles. They open ex- 

 ternally on somite fifteen. 



4. The ovaries are a pair of very small organs attached 

 to the posterior surface of the septum that separates the 

 twelfth from the thirteenth somite, near the mid ventral line. 

 They may sometimes be found with a lens, but usually are 



