152 SOME REACTIONS AMONG ANIMALS 



4. Examine the ventral side with a hand lens and identify the project- 

 ing bristles (setce). 



Conclusions. 1. How are contractions and expansions concerned in 

 the forward motions of the worm ? 



2. What prevents a worm from slipping while crawling ? 



c. Nervous Responses to Stimuli 



Observations. 1. Gently touch various parts of the worm with a 

 blunt bristle. 



2. Observe a moving worm carefully. How does it find its way ? Is 

 the " lip " a sense organ ? 



3. Place the worm in a tray and partially cover it with the paste- 

 board cover. Observe whether the worm prefers light or darkness. 



4. Tap the tray with your pencil. Does the worm respond ? 

 Conclusions. 1. What do you think regarding its responses to touch ? 



2. What about its responses to light ? 



3. Does a worm hear or feel in responding to a jar ? 



4. Which portions of a worm are the most sensitive? 



d. Blood Tubes 



Observations. 1. Look for a dorsal red tube which pulsates. This is 

 the dorsal blood vessel which can be seen through the semitransparent 

 body wall. 



2. Examine the region about the girdle for several pairs of lateral red 

 vessels, the so-called "hearts." 



Conclusions. 1. Does the blood move in any definite direction as indi- 

 cated by the pulsations ? 



2. How might oxygen get into the blood tubes you can see ? 



Questions 



1. Why cannot earthworms live in a dry place ? 



2. How do earthworms enrich the soil ? 



3. Do they injure plants or animals ? 



4. How are earthworms protected from their enemies? 



5. What is the effect of the parasitic habit on such a worm as the 

 tapeworm ? 



6. In what different ways do worms get their food ? 



7. What is meant by the term u regeneration " as applied to worms ? 



8. What are some of the most dangerous worm parasites to man and 

 the domestic animals ? 



