THE LOCUST OR THE CRAYFISH. 57 



they jump, in terms of their own length? Place one in 

 water. Observe and describe the result. 



E. Other Activities. Do they make any noise at all? 

 Under what circumstances. 



How is feeding effected? Catch a large specimen and 

 try to feed him. Describe and interpret all the observed 

 phenomena. How do the jaws work? 



Do you find any evidence of egg laying? If so, what 

 are the conditions number, place of laying, arrange- 

 ment of eggs, etc.? 



F. Collections. Each student should collect and take 

 to the laboratory, for his own use, several specimens of 

 each sex the largest he can find. Some of these should 

 be preserved in alcohol or formaldehyde for dissection 

 later; the others should be properly cared for and studied 

 alive in the laboratory for further details of external 

 structure and behavior. 



74. Laboratory Studies. The time at the disposal of 

 the class must determine how much of these studies shall 

 be undertaken. If time is limited, they can be divided 

 among the members of the class. 



A. Activities. The great gain of the laboratory, in 

 studying the activities, is that one can control the condi- 

 tions and thus get exactness of results which cannot 

 come from more general observation. This use of con- 

 trolled conditions we call an experiment. In this way 

 the field observations can be extended and corrected. 

 This testing of one's result is an exceedingly valuable 

 training. 



