PREFACE. 



THE present volume is intended as an introduction to 

 the serious study of zoology. It embraces directions for 

 laboratory work upon a selected series of animal types and 

 a general account of related forms. Laboratory guides 

 are somewhat numerous, but general outlines of zoology 

 adapted to beginners are few. By combining the two, 

 it has been possible to emphasize the comparative side of 

 the subject. A knowledge of isolated facts, no matter how 

 extensive, is of little value in education, excepting as the 

 powers of observation are trained in ascertaining those 

 facts. Nature studies are truly educational only when the 

 student is trained to correlate and classify facts. A con- 

 siderable experience with students of different ages has 

 resulted in the conviction that it is not sufficient to ask one 

 to compare a grasshopper and a beetle, pointing out their 

 resemblances and points of difference; leading questions 

 must be asked. When the student has answered the ques- 

 tions under the headings " Comparisons" in the following 

 pages, he has a tolerably complete statement of the princi- 

 pal characters of the larger groups of the animal kingdom. 



Several considerations have had weight in the selection 

 of types to be studied in detail. In the first place, so far 

 as possible, these should be such as are readily obtainable 

 in any locality. But there are certain important groups, 

 all the members of which are marine. The forms of these 

 which have been used can be purchased of dealers in labor- 



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