PREFACE 



The students in our American colleges who take up the 

 elementary study of zoology fall for the most part into 

 two classes : on the one hand those who purpose to become 

 specialists in some one of the zoological branches, and on the 

 other those who pursue the subject merely as a part of a liberal 

 education, or as an adjunct to the more complete study of other 

 sciences in which some knowledge of the phenomena of animal 

 life is desirable. As a rule, the method of instruction employed 

 for these two groups of students is, from practical necessity, 

 nearly the same, although the second group is much the larger. 

 Our college students have had very diverse preparations for this 

 subject. All presumably have at least some slight knowledge 

 of elementary chemistry and physics, and all probably know a 

 few biological facts, but their knowledge of plants and animals 

 is apt to be fragmentary and not very systematically arranged, 

 and they have but little conception of the fundamental principles 

 of biology, of the relationships of various types of organisms to 

 one another, or of the broader problems of ecology and theoreti- 

 cal biology. These students are, however, of some maturity, 

 they are beginning to form rudimentary conceptions, at least, 

 of the significance of life and of the simpler philosophical 

 problems. 



The up-to-date text-books at present available in English 

 seem to be designed either exclusively for pupils of our high 

 schools and academies, or else for college students who intend 

 to become specialists in zoology, so that the college professor 

 must refer his students to books either too elementary for them, 

 or too unreliable because antiquated, or to such as enter into 

 details which belong more properly to the specialist or to the 

 subject of comparative anatomy studied with extensive dissecting 

 in the laboratory. 



