8 INTRODUCTION 



that creepeth upon the earth". Solomon is represented (i Kings 

 iv. 33) as using the same fourfold division, except that the word 

 " beast" is used instead of "cattle". The creatures included 

 under the former term are evidently those which are popularly 

 called " quadrupeds " at the present day, while scientifically they 

 are known as " mammals ". The lower terrestrial forms of life are 

 embraced by the comprehensive term " creeping things ". The 

 word " insect " was used in English till comparatively recently 

 much in the same way. This crude classification is clearly based 

 on the nature of the media in which the various animals live, i.e. it 

 is a division into animals living respectively on the land, in the 

 water, and in the air, land animals being* further subdivided into 

 higher and lower forms. Such a grouping is of necessity very 

 superficial, for habitat is a very misleading guide to affinity or 

 likeness. Whales, porpoises, and seals are as much " beasts" as 

 cows and sheep, though to this day we speak of whale and seal 

 ''fisheries". And further, such a group as " creeping things" 

 or " insects " (in the old sense) contains such a miscellaneous 

 assortment of creatures that it may be looked upon as a mere 

 receptacle for forms finding no place in the other three sub- 

 divisions. 



The first man to place zoology on a scientific basis was the 

 Greek philosopher Aristotle (384-322 B.C.), "perhaps the greatest 

 and most truly scientific man in the highest sense of the word 

 that the world has ever known " (Milnes Marshall), who, though 

 the study of animals was not the one to which most of his 

 time was devoted, has nevertheless been styled the " Father 

 of Natural History". Aristotle had a very considerable know- 

 ledge of the habits and structure of the animals known to him, 

 about 500 in number; he was impressed by the fact that the 

 animal kingdom exhibits a transition from lower to higher, and 

 devised a scientific system of classification based on structure. 

 His great merit here lies in the fact that he divided the animal 

 kingdom into two groups, (A) Animals with red blood and a 

 backbone, and (B) Animals without red blood and no backbone, 

 a division which corresponds precisely with the modern one into 

 Vertebrata (Backboned animals) and Invertebrata (Backboneless 

 animals), though we now know that the distinction as to blood is 

 not quite so absolute as Aristotle supposed. He further recog- 

 nized five classes among the backboned animals (viviparous 



