PRINCIPLES OF TAXONOMY 245 



classification that prevails at the present time. The modern system 

 serves two purposes instead of but one. It has fitted admirably the 

 modern evolution doctrine, according to which species of animals are 

 related to one another through common descent. Classification may 

 now afford the convenience that was desired in the earliest attempts at 

 organization and at the same time express the kinship which the evolution 

 doctrine implies. It is rather by accident than by design that the 

 modern system is both a convenience and an expression of the course of 

 evolution, because the author of it did not subscribe to the evolution 

 doctrine. The system of classification is a branching one, and evolution 

 results in a branching scheme of kinship. When the evolution idea was 

 adopted, therefore, it was easy to adapt the branching classification to 

 the portrayal of evolution. The scheme had the further advantage of 

 being capable of expansion; the successive branchings could be as numer- 

 ous as was required in any line of descent. A classification which 

 expresses evolutionary development is called a genetic or natural sys- 

 tem — genetic because ancestries are involved, natural because the basis 

 of it exists in nature, not just in the minds of men. 



Ray and Linnaeus in Taxonomy. — It has been said that John Ray 

 (1627-1705), an Englishman, was the first true systematist. Ray pro- 

 posed a dichotomous systematic table of the animal kingdom, that is, 

 a system which branched by twos. He used anatomical likenesses as the 

 basis on which animals were grouped, and the soundness of his judgment 

 of these characters is shown by the fact that several of his groups are still 

 recognized as natural ones. It is Carolus Linnaeus (Fig. 205), 1707- 

 1778, however, who is considered to be the real founder of classification. 

 Linnaeus's most important work was the "Systema Naturae," which 

 appeared in 12 editions between 1735 and 1768 and, after his death, in a 

 thirteenth, edited by Gmelin. In this work Linnaeus completed a classi- 

 fication which Ray had established in part, giving names to important 

 groups that Ray had left without appellations and describing animals in 

 language which, unlike many of the writings of his time, could not be 

 misunderstood. Linnaeus also had the courage to defy prejudice in such 

 details as removing the whales from the group of fishes, to which Ray also 

 knew they did not belong, and placing them with the terrestrial hairy 

 animals called mammals. For, in the Linnaean classification, structural 

 characters, rather than habits or external forms, were used as a basis. 

 Six classes were employed, four of them vertebrate (borrowed from Ray) 

 and two invertebrate. These classes were divided into orders, the orders 

 into genera, and the genera into species. The lesser groups were usually 

 much more inclusive than the groups now given these same ranks. Thus, 

 a Linnaean genus occasionally includes three or four orders, as these 

 groups are now reckoned. Moreover, the genus often contained animals 



