INTRODUCTION. 



were a greater uniformity in the constitution of the human mind. 

 And, for the same reason, neither of the labourers should despise 

 or undervalue the labours of the rest ; since each department has 

 its peculiar value, and the pursuit of it cannot be rendered use- 

 less by any advance in the rest. Thus, the mere collection of 

 specimens, and the arrangement of them according to their external 

 characters, is, in fact, laying the foundation for the operations of 

 the scientific Naturalist. Even in districts which have been 

 most completely explored, it will be rare for the diligent collector 

 to find himself unrewarded by the discovery of some species new 

 to that locality, if not previously altogether unknown. But in 

 those which have been as yet comparatively little examined, it 

 cannot be doubted that a rich harvest of discovery awaits every 

 one who will devote himself to the search for it. We need not 

 leave our own island for this purpose. To the number of the 

 larger animals which tenant the land we cannot expect any con- 

 siderable addition ; but not a year passes without many new 

 species of insects being discovered ; and there are several parts of 

 our coasts that are rich in marine tribes, of which very little is 

 yet known, and which, consequently, hold out the most tempting 

 prospect to the collector. In all such researches, the locality, 

 and the other circumstances in which the specimen is found 

 should be carefully noted ; for the collection then has a double 

 value, not only on its own account, but as affording information 

 on a most interesting and important department of zoology the 

 geographical distribution of animals. 



As to the importance of the study of the Anatomy and of the 

 Habits of the ani mals brought together by the collector, it 

 would seem unnecessary to say anything here. It will be shown 

 in the course of the present Treatise, that the classification of 

 Animals must be founded iipon their general structure, not upon 

 a few external characters ; and that the value of these last in 

 Zoology is, chiefly that they serve as a ready key or index to the 

 internal organisation, when the connexion between them has been 



