CHAPTER 18 

 PRINCIPLES OF TAXONOMY 



Objects of all kinds that have ever interested civilized man have been 

 classified by him as soon as they became numerous enough to show simi- 

 larities amid differences. Animals have not escaped this human pro- 

 pensity for cataloguing. Classification was not necessary when chiefly 

 the large, conspicuous animals were known, and when travel and com- 

 munication between regions was so meager that each naturalist knew 

 only the beasts of his own land. But as knowledge enlarged through 

 travel, and as microscopes increased the range of size of animals that 

 could be observed, the method of describing animals and their habits 

 and modes of life singly, without reference to other animals, became 

 cumbersome. It was then that classification began. 



The classification of living things is known as taxonomy (from the 

 Greek taxis arrangement and nomos law), which means literally an orderly 

 arrangement. Both animals and plants are classified, and the principle 

 on which their grouping is based is the same in both; but the schemes 

 adopted for these two great kingdoms are somewhat different. Tax- 

 onomy of animals is often called systematic zoology, that of plants sys- 

 tematic botany. Only the plan adopted for zoology is considered in 

 this book. 



Conceptions of Taxonomy. — An orderly arrangement of objects or 

 facts presupposes a system of classification. The same objects or facts 

 can usually be classified in different ways by the use of different charac- 

 ters, qualities, or relations as a basis. What qualities are chosen to form 

 the basis of classification depends on the importance attached to those 

 qualities. If their importance is not known, the classification depends on 

 the purpose or bent of mind of the classifier. It thus happened that 

 in the early taxonomy of animals there were likely to be various schemes 

 of classification, because no settled convictions existed regarding the sig- 

 nificance of such grouping. Some of the first schemes arc described 

 below, but it may be pointed out in advance that all but one of the sys- 

 tems of classification that have ever been in use have been essentially 

 devices to save confusion. Things were put upon shelves, figuratively, 

 and labeled and catalogued. As long as prevention of confusion was 

 the chief aim, classification might be artificial and arbitrary. The one 

 exception to this arbitrary basis of arrangement is found in the system of 



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