H2 PHILOSOPHY OF ZOOLOGY. 



PART II. 



THE METHOD OF INVESTIGATING THE 

 CHARACTERS OF ANIMALS. 



In order to render complete the history of any species of 

 animal, it is necessary to examine the peculiar character of 

 all those systems of organs which have been noticed in the 

 first volume of this Work, and to ascertain those laws which 

 regulate its physical and geographical distribution. As this 

 method of investigation is both laborious and difficult, it 

 has been successfully practised by few. The greater num- 

 ber of naturalists have rested satisfied with an examination 

 of the external characters of animals, and have overlooked 

 those which are furnished by their internal structure. In 

 order to form a correct opinion of the merits of these dif- 

 ferent methods of investigation, Ave ought to bear in mind, 

 that the history of a species is incomplete, when its external 

 characters only have been determined ; that many of these 

 characters are liable to change, and are, consequently, apt 

 to mislead. The characters, on the other hand, furnished by 

 structure are more permanent, yield more certain results, 

 and are more engaging to a philosophical mind. On this 

 important subject, however, it will be necessary to go more 

 into detail, and to consider what those different characters 

 are, and how they are ascertained. 



