THE EARTHWORM 33 



find where it divides near the anterior end. One branch 

 goes up one side of the gullet and the other up the opposite 

 side, after which they meet on top of the alimentary canal 

 to form the brain. 



In most of the segments will be seen a small, much con- 

 voluted tube, the nephridium. The nephridia are the or- 

 gans of secretion. Each one opens outward on the ventral 

 side of the body through a pore. They carry off the waste 

 products of the body. 



The earthworm is hermaphroditic and has both the male 

 and female reproductive organs. Beneath the seminal 

 vesicles already noted will be found the testes. These open 

 outward through a pair of ducts that extend backward to 

 the fifteenth segment. 



The ovaries may be found, with difficulty, in segment 18. 

 They are a pair of small white bodies. The ova pass from 

 the ovaries into funnel-shaped oviducts that open on the 

 ventral side of the body through segment 14. 



Make a drawing showing these points. 



D. FIELD STUDY OF THE EARTHWORM. Study the 

 earthworm in the field. When is it found on top of the 

 ground, during the night or day, when the air is dry or 

 moist? What is the shape of its burrow? How deep is 

 the burrow ? What is often found piled around the mouth 

 of the burrow ? These are pellets of earth and refuse food 

 that have passed through the alimentary canal and are 

 termed castings. Note the ease and quickness with which 

 an earthworm can retreat into its burrow. Note how 

 difficult it is to pull one out of its burrow. Why is this ? 



E. TOPICS FOR FURTHER STUDY. Write out the chief 

 characteristics of the earthworm, remembering the division 

 of the body into definite segments. Make a diagrammatic 



HERRICK LAB. EX. 3 



