EAETHWOEM 133 



Make a diagram of tlie part of the nervous system 

 studied isolated from the body. 



D. The Excretory System. 



Examine in a drop of water under a low power a sep- 

 tum which has been removed from near the CBSophagus, 

 and find 



a. The segmental organs ornephridia. — Position? 

 Number in each segment? Structure? "Why called 

 " segmental " ? Do they open into the body-cavity ? 

 To the exterior ? Is the internal opening in the 

 same segment as the body of the nephridial 

 tubule? On a septum removed from a living 

 earthworm and examined in a drop of water look 

 for the nephrostome or nephridial funnel at 

 the inner extremity of the tubule. ]S"ote the large 

 size of the cells forming the funnel ; also the cilia 

 with which they are covered. Do the cilia move ? 

 If so, of what use is their movement ? 



E. The Reproductive System. 



On septa nine-ten, ten-eleven, and eleven-twelve find 



a. The seminal vesicles. — "What is their position? 

 Shape ? Are all of the same size ? Do they vary 

 much in size in different specimens taken at the 

 same time of the year ? In specimens taken at 

 different times of the year ? "What is their color ? 

 Carefully remove the oesophagus and notice that 

 the lateral vesicles communicate with a median 

 vesicle in segment ten and with another in seg- 

 ment eleven. 



There wiU. be seen projecting into the front 

 of each median seminal vesicle, after removing 

 the roof of the same, 



