THE LOCUST OR THE CRAYFISH. 67 



Discover their burrows in low moist places. What 

 becomes of the dirt from the burrows? How are the 

 burrows formed? Dig out one and follow its course. 

 How deep? Does it contain water? or crayfish? Do 

 you ever find any empty shells of crayfish? What may 

 they mean? 



2. Activities. In field and laboratory find all the facts 

 obtainable with respect to methods and efficiency of loco- 

 motion; feeding; reproduction; respiration. 



3. Sensitiveness, Kinds of. Experiments (similar to 

 those suggested for the locust) should be devised to prove 

 whether they are sensitive, and, if so, what special senses 

 they possess and the location of the organs. 



4. General Form. Work out its symmetry as indi- 

 cated for the locust. How do the general body regions 

 compare with those of the locust? Has it head, thorax, 

 and abdomen? Does it show segmentation? How does 

 it compare in this respect with the locust? Study with 

 care the external evidences of segmentation, the number 

 of segments, their freedom and degree of fusion in the 

 various regions. 



Make outline drawings of the body from dorsal and 

 ventral views. 



5. The Appendages. How do these compare with 

 those of the locust in number and variety? How many, 

 and how many kinds, do you find on first examination? 



The adaptation of the appendages. After this much 

 of study go back to the living specimen and w r atch the 

 natural action of each type of appendage. Which seem 

 to be least used? Which seem most used? Describe 

 carefully the uses of all so far as you can make them out. 

 Note the particulars in which the form and structure of 



