4. PREFATORY NOTE 



example, a grasshopper, crayfish, or bird. To meet this 

 view, each of the laboratory exercises practically stands 

 as a unit, and any one of the above animals may be used 

 to introduce the subject if desired; but the exercise on 

 the grasshopper is designed especially for introductory 

 work. Moreover, there is sufficient unity in the treat- 

 ment in the text of the groups of animals represented by 

 the foregoing examples to make such a method perfectly 

 feasible. 



GLENN W. HERRICK. 



