WORMS 



43 



it avoids or seeks a bright light, as a window ; also whether any 

 parts of the body are especially sensitive to touch, or all equally 

 sensitive. What effect when a bright light is brought suddenly near 

 it at night ? 



Is red blood visible through the skin ? Can you notice 

 any pulsations in a vessel along the back ? Do all earth- 

 worms have the same number of divisions or rings ? Com- 

 pare the size of the rings or segments. Can it crawl faster 

 on glass or on paper ? 



A magnifying glass will show on most species tiny bristle- 

 like projections called seta. How are the setae arranged ? 

 (d, Fig. 70.) How many on 

 one ring of the. worm ? How 

 do they point ? Does the worm 

 feel smoother when it is pulled 

 forward or backward between 



FIG. 70. MOUTH AND 



the fingers ? Why ? Are setae on the lower sur- 

 face ? Upper surface ? The sides ? What is the 

 use of the setae ? Are they useful below ground ? 

 Does the worm move at a uniform 'rate ? What 

 change in form occurs as the front part of the 

 body is pushed forward ? As the hinder part is 

 pulled onward ? How far does it go at each 

 movement ? At certain seasons a broad band, 

 or ring, appears, covering several segments and 

 making them seem enlarged (Fig. 71). This is 

 the clitellnm^ or reproductive girdle. Is this girdle 

 nearer the mouth or the tail ? 



Draw the exterior of an earthworm. 

 Dorsal and Ventral Surfaces. - The earthworm 

 always crawls with the same surface to the ground ; this 

 is called the ventral surface, the opposite surface is the 

 dorsal surface. This is the first animal studied to which 



FIG. 71. 

 EARTH- 

 WORM, 



mouth end 

 above. 



