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serious students in the various subjects. Certain parts 

 have the character of a work of reference. 



Although the Vertebrate animals will receive adequate 

 treatment in the latter volumes, the first six will be 

 devoted to the Invertebrates. The space has been 

 apportioned with due regard to the size and importance 

 of the several groups of animals, and the editors have 

 endeavoured not to overlook entirely any of the less 

 conspicuous divisions, whose Natural History may be no 

 less interesting than that of more familiar animals. The 

 habits and external features of each group will be con- 

 sidered in conjunction with its classification, geographical, 

 distribution, anatomical structure, development, and 

 palaeontology. Especial attention will in most cases be 

 paid to the members of the British Fauna. 



Complete uniformity of treatment has not been aimed 

 at. It has been thought of the first importance to secure 

 the help of contributors who are thoroughly acquainted 

 with the groups on which they are writing, and to allow 

 them to a large extent to handle their subject in the way 

 in which they can do it and themselves the most justice. 

 In some cases it is impossible to treat a class of animals 

 adequately without paying considerable attention to in- 

 ternal structure. In other cases, the purposes of the 

 work can be better met by devoting most of the allotted 

 space to habits and external structure. 



Although it is neither possible nor desirable altogether 

 to avoid copying figures which have previously been 

 published, a special feature of the work will be that the 

 illustrations are, where possible, drawn from nature. 

 Chapters on geographical distribution will in many cases 

 be illustrated by maps. 



