X INTRODUCTION. 



To those whose notions of the faculties and economy of 

 animals are merely derived from popular belief, or supported 

 only by casual observation, the preceding most excellent advice 

 is particularly necessary to be observed when commencing 

 the study of natural history, respecting the objects of which 

 there have always been so many misconceptions, prejudices, 

 and superstitions afloat, that they have been great impediments 

 to the general diffusion of a correct knowledge of the subject. 



Although the Linnaean system of botany has still its admirers 

 and followers, despite the more philosophical system of Jussieu, 

 yet the Linnaean system of zoology may be said to have been 

 universally superseded by that of Cuvier. The Cuvierian 

 Classification of the first class of animals has therefore been 

 adopted here. It may be advisable, in this place, to quote 

 his prefatory observations on classification as applied to the 

 animal kingdom. " The essential characters in animals, on 

 which their primary divisions are to be founded, it is evident 

 should be those which are drawn from the animal functions, 

 that is, from the sensations and motions ; for both these not 

 only make the being an animal, but in a manner establish 

 its degree of animality. Observation confirms this position 

 by showing that the degrees of development and complication 

 accord with those of the organs of the vegetative functions. 

 The heart and the organs of the circulation form a kind of 

 centre for the vegetative functions, as the brain and the trunk 

 of the nervous system do for the animal functions. Now we 

 see these two systems become imperfect and disappear together. 

 In the lowest class of animals, where the nerves cease to be 

 visible, the fibres are no longer distinct, and the digestive 



