LINN.EUS AND THE LINNEAN CLASSIFICATION. 47 



necessarily, altogether of what is called an c artificial ' 

 character ; and we may here explain briefly what is meant 

 by an ' artificial ' as opposed to a ' natural ' classification. 



Classification is simply the arrangement of a series of 

 objects in some kind of order, and its most obvious pur- 

 pose is to supply a means of identifying and finding any 

 given object in the series. When naturalists first came to 

 investigate the vast series of the animal kingdom, they 

 were at once confronted with the necessity of establishing 

 some arrangement of these, so that they might be able to 

 find out what any new animal was, and to place it in some 

 group. As, however, their knowledge was very imperfect, 

 they naturally adopted obvious and conspicuous characters 

 as the basis of their arrangement, regardless of the fact 

 that such characters are often of little real importance, and 

 may be quite outweighed by other much less readily 

 recognisable features. Ray's classification of animals, 

 which, in a slightly modified form, is here subjoined, is 

 based in this way on a few obvious characters. Ray 

 divided all animals as follows : 



I. RED-BLOODED ANIMALS (= Vertebrata). 



1. Respiring by lungs, and having a heart furnished with two 



ventricles 



A. Viviparous 



a. Aquatic Cetacea (whales, &c.). 



b. Terrestrial Ordinary Mammals. 



B. Oviparous Birds. 



2. Having a heart with a single ventricle 



A. Air-breathers, with lungs Reptiles. 



B. Breathing by means of gills Fishes. 



II. WHITE-BLOODED ANIMALS (= Invertebrate animals). 



i Malacia, or Mollusca. 



1. Of large size 3 Malacostraca, or Crustacea. 



( Ostracoderma, or Testacea. 



2. Of small size Insecta. 



