vi PREFACE 



zoology may be attained. The present manual does not 

 provide such instruction, but is intended to be used in 

 association with it, and the examples selected for de- 

 scription are such as may under most circumstances be 

 readily obtained. 



The general plan is similar to that followed in the Text- 

 Book of Zoology by the same authors, but the restricted 

 space has necessitated considerable modifications. We 

 have not adopted the method, followed in various recent 

 manuals, of beginning with one of the larger Invertebrata 

 or with a vertebrate, and working from that upwards and 

 downwards. The reasons given for such a mode of treat- 

 ment we understand to be that if we begin with the simplest 

 animals, the Protozoa, we discourage and embarrass the 

 beginner by introducing him at once into a world entirely 

 new to him, requiring him at the same time to learn the use 

 of an entirely unfamiliar instrument the microscope. But in 

 our opinion, the difficulty is much less than is alleged by the 

 advocates of the alternative method, and the advantage of 

 presenting the facts at the outset in a natural and logical 

 order by far outweigh any such disadvantages. We are con- 

 vinced that any general acquaintance which the student may 

 possess beforehand with a rabbit or a crayfish will be of little 

 real value to him when he begins to take up seriously the 

 study of its structure. Moreover an elementary knowledge 

 of the use of the microscope is absolutely essential to any 

 adequate study of Zoology as an intellectual discipline, and 

 this difficulty, such as it is, may as well be met first as last. 



