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PEEFACE TO THE FIRST EDITION 



IN spite of its bulk, the present work is strictly adapted to the 

 needs of the beginner. The mode of treatment of the subject is 

 such that no previous knowledge of Zoology is assumed, and 

 students of the first and second years should have no more 

 difficulty in following the accounts of the various groups than is 

 incidental to the first study of a complex and unfamiliar subject. 



There can be little doubt that the study of Zoology is most 

 profitably as well as most pleasantly begun in the field and by the 

 sea-shore, in the Zoological Garden and the Aquarium. In a 

 very real sense it is true that the best zoologist is he who knows 

 the most animals, and there can certainly be no better foundation 

 for a strict and scientific study of the subject than a familiarity 

 with the general appearance and habits of the common members 

 of the principal animal classes. But Zoology as a branch of 

 academical study can hardly be pursued on the broad lines of 

 general natural history, and must be content to lose a little in 

 breadth of view at least in its earlier stages while insisting upon 

 accurate observation, comparison, and induction, within the 

 limited field of Laboratory and Museum work. 



A not uncommon method of expounding the science of Zoology 

 is to begin the study of a given group by a definition, the very 

 terms of which it is impossible that the student should under- 

 stand ; then to take a general survey of the group, illustrated by 

 casual references to animals and to structures of which it is highly 

 unlikely he has ever heard ; and, finally, to descend to a survey of 

 the more important forms included in the group. It will probably 

 be generally agreed that, from the teacher's point of view, this 

 method begins at the wrong end, and is hardly more rational than 

 it would be to deliver a course on the general characteristics of 



