iv PREFACE 



depend not only on the teacher's training in zoology and his 

 pedagogical skill, but also 011 the age and previous training of 

 the pupils. The problem is a special one for each teacher to 

 solve for himself. The directions given in the accompanying 

 pamphlet, therefore, are to be regarded merely as suggestive. 



The inductive method of presentation, in a necessarily modified 

 form, has been followed in the earlier chapters of the text-book, 

 as being the natural mode of approach to a new subject based 

 upon laboratory work. After the study of the red-legged locust, 

 for example, another animal that has easily recognizable rela- 

 tionship to this form is considered. Not until all the selected 

 representatives of the Orthoptera have been described, are the 

 characters of the order mentioned. By that time the pupil's 

 mind is ready for the definition of Orthoptera. The conceptions 

 of the larger groups of invertebrate classes and phyla are devel- 

 oped in the same manner. 



It has been our earnest endeavor to present all the important 

 aspects of zoology in a well-balanced account. The basis of the 

 subject-matter in a text-book on zoology is necessarily morpho- 

 logical. The pupil must have some understanding of the appear- 

 ance of animals and their organs before he can be supposed to 

 think clearly regarding the uses of the organs or the relation of 

 the animals to their environment. We have described the appear- 

 ance of nearly all the animals mentioned. In certain selected 

 cases we have described the structure and the functions of the 

 systems of internal organs, and the development of the individ- 

 ual ; and in appropriate connections we have spoken of the 

 economic importance of animals, and have given brief sketches 

 of the geographical distribution and the geological history of 

 races. The rapidly developing science of comparative psychology 

 is now sufficiently precise to justify the inclusion in a work of 

 this kind of some of the important studies of the mental behavior 

 of animals. We hope that the facts selected will give a general 

 notion of the increasing complexity of the mental life in the 

 higher animals. We have also presented in as simple a way 



