LABORATORY WORK, X 353 



OBSERVATIONS ON THE LIVING ANIMAL. 



Each student should be provided with the following : (1) plate cov- 

 ered with moist filter paper; (2) hand lens; (3-5) vials containing 

 sugar solution, acetic acid, and beef extract ; (6) four new toothpicks ; 

 (7) pipette. 



1. Touch with a toothpick, first the head end, then the tail end of 

 the worm ; to which contact does it react more strongly ? 



2. Place the earthworm near the window. Does it move toward 

 or from the light ? 



3. With the breath blow upon the head end of the worm. Record 

 results. Are results due to the warmth of the breath or to the 

 current of air? To test, send a puff upon the head with a pipette. 



4. Bring near to the head end in succession the ends of toothpicks 

 dipped in water, in sugar solution, in acetic acid, and in beef extract. 

 How does the worm react to each fluid ? 



5. Place the earthworm on a piece of filter paper two-thirds of which 

 is wet. Reaction of worm at edge of wet part ? How do these reac- 

 tions of the earthworm accord with its ordinary movements out of 

 doors ? 



6. When the. head end is being thrust out forward, in what phase 

 (contraction or expansion) is the middle of the worm? The tail 

 end? In what direction does the contraction wave pass? 



TOPICS FOR FURTHER STUDY 



1. Habitat and food of the earthworm. 2. Economic importance 

 of earthworms. 3. Allies of the earthworm: Nais, Dero, Tubifex, 

 the leeches, the Gephyrea, the Bryozoa. 



X. NEREIS 



Nereis can be obtained at the sea-shore by digging in mud flats 

 between tide lines. It can be transported in damp sand or seaweed, 

 and will remain alive for several days in a shallow vessel filled with 

 sea-water and kept in a cool place. 



DRAWINGS 



{From alcoholic specimens) 

 1. Whole animal, dorsal view. Natural size. 

 2 A 



