ARRANGEMENT AND CLASSIFICATION 61 



•divisions that may be established in the series which they constitute. 

 This it behoves us to recognise ; it would indeed be difficult to dispute. 

 Let us now pass to the actual arrangement and classification of 

 animals. 



The Tkue Aerangement and Classification of Animals. 



Since the purpose and principles both of a general arrangement 

 and of a classification of living animals were not at first perceived 

 when these subjects were studied, the works of naturalists long suffered 

 from this imperfection of our ideas. The same thing happened in 

 the science of natural history as has happened in all others to which 

 much attention was given, before any principles had been thought out 

 to constitute a basis and to guide their labours. 



Instead of subjecting the classification which had to be made in 

 €ach kingdom of living bodies to an arrangement which should be quite 

 unfettered, attention was entirely devoted to disposing objects in 

 convenient classes, so that their arrangement" was thus abandoned 

 to arbitrary opinion. 



The affinities among the larger groups in the vegetable kingdom, 

 for example, were very difficult to grasp ; and artificial systems were 

 long made use of in botany. They faciUtated the making of convenient 

 classifications based upon arbitrary principles, so that every author drew 

 up a new one according to his fancy. Thus the proper arrangement of 

 plants according to the natural method was then always sacrificed. It 

 is only since we have recognised the importance of the parts concerned 

 with fruiting, and the greater importance of some than others that the 

 general arrangement of plants began to make progress towards perfection. 



As the case of animals is different, the general affinities which 

 characterise the main groups are much easier to perceive : so that 

 several of these groups were identified at the very beginning of the 

 study of natural history. 



Aristotle indeed divided animals primarily into two main divisions 

 or, as he called it, two classes, viz. : 



1. Animals that have blood : 



Viviparous quadrupeds. 

 Oviparous quadrupeds. 

 Fishes. 

 Birds. 



2. Animals that have no blood : 



Molluscs. 

 Crustaceans. 

 Testaceans. 

 Insects. 



