ABTHROPODA. 53 



2. Do crabs swim backwards ? (You can answer this 



question about living crabs from the dead speci- 

 mens.) 



3. What changes would have to take place in the cray- 



fish in order for it to become a crab ? 



4. What changes would be necessary in the appendages ? 

 Which is the "higher form," the crab or the crayfish? 



3. THE PILL-BUG. 



1. Where is this animal found ? (Dem.) 



2. Describe, — 



(a) the color ; 

 (S) the shape. 



3. How many somites are there in the entire body ? 



4. How can you distinguish cephalo-thorax from abdo- 



men ? 



5. Are any of the appendages provided with pinchers ? 



6. Are the eyes on stalks ? 



7. Identify the antenna. 



8. Identify the plate-like gills on the abdomen. 



Why is this animal included in the same class with 



the crayfish ? 

 Do you think the pill-bug is a simpler or a more 



highly organized animal than the crayfish '! 

 What inappropriateness in the word " bug " when 



applied to this animal ? 



4. THE FAIRY SHRIMP. Branchipus. 

 A. The Living Shrimp. 



1. Habitat. 



a. What is its habitat ? 

 h. At what time of year is it found ? 

 e. How does it pass the winter ? 

 d. Where is it in midsummer ? 



