SOME REACTIONS AMONG ANIMALS 163 



3. Name an animal that is active ; one that is sluggish. 



4. Is the crayfish an active or a sluggish animal ? 



5. Note its large pinching claws. 



Conclusions. 1. Can it be easily seen when at rest between water 

 weeds or rocks. 



2. What do you think is meant by the term 'protective coloration' ? 



3. What is evidently one use of the large claws ? 



b. Locomotion 



1. WALKING 



Method. Place the crayfish on the laboratory table, and observe its 

 movements. 



Observations. 1 . What is its attitude when you are trying to seize it ? 



2. Are the pincers (chelipeds) used in walking ? 



3. Notice the appendages used in walking. How many are there ? 

 (They are called walking legs.) 



4. Do the walking legs on opposite parts of the body move together ? 



5. What seems to be the use of the long feelers (antennae) during the 

 locomotion of the crayfish ? 



Conclusion. Write a paragraph telling how the legs are adapted 

 (fitted) for their uses. 



2. SWIMMING 



Method. Place specimen in a tray of water. 



Observations. 1 . How does the specimen swim ? (The organ used 

 in swimming is called the caudal Jin.} 



2. Does the fin change its shape for either stroke ? 



3. Just how is the caudal fin used in swimming ? 



Conclusions. 1 . What can you say of the differences in function of 

 the appendages just studied ? 



2. Would it be easy for the crayfish to swim forwards instead of back- 

 wards ? Explain your answer. (How are ships retarded at sea ?) 



3. How is the shape of the caudal fin adapted for swimming ? Com- 

 pare with a paddle or oar. 



4. Write a paragraph showing just how a crayfish is fitted or adapted 

 for life in the water. 



c. Surroundings (Reasons for Sense Organs) 



Observations. 1. Touch various parts of the body lightly with a pen- 

 cil or bristle, and note the results. Try especially the joints and other thin 

 parts of the body, the eyes, feelers, and mouth parts. 



