SEVENTEENTH AND EIGHTEENTH CENTURIES ^13 



and, finally, in making a number of observations of life in nature and the 

 interrelation of its different phenomena. 



The binary nomenclature 

 The most important purely formal improvement of the system which Lin- 

 naeus effected was the binary nomenclature, introduced in 1753 into the 

 classification of the vegetable kingdom and somewhat later into that of the 

 animal kingdom. Previously he had followed the example of Tournefort in 

 characterizing every genus by a single term, while the character of the species 

 was designated by a short diagnosis of some few words. Now he introduced 

 instead one single character word for the species also, so that every plant 

 or animal received its character and its fixed place in the system by means 

 of only two words. This reform is certainly the most important of his con- 

 tributions in the purely formal sphere. Thanks to this alone biology has 

 been able to master the vast amount of form-material that has been col- 

 lected up to the present day, which could certainly never have been handled 

 if it had been necessary to employ diagnoses in order to denote the species. 

 His other reforms in connexion with the system applied not so much to 

 botany as to zoology; he left his botanical sexual system for the most 

 part undisturbed and contented himself with incorporating into it the new 

 species which were sent to him from all over the world. Of the improve- 

 ments which he introduced into the animal system the most worthy of 

 mention is the fact that he at last associated whales with the quadrupeds, 

 which resulted in the latter's receiving the name they have since borne — 

 Mammalia — that is, animals which feed their young. The orders into which 

 he divided this class, mainly after the dental structure, were, however, still 

 somewhat artificial and were long ago rearranged; on the other hand, his 

 method of associating man with the apes in the order Primates has been 

 retained. Birds, which were essentially classified according to their beaks, 

 have, as is well known, been still further regrouped. His transfer in the last 

 editions of Sy sterna natures of the Cartilaginei to the amphibians, which was 

 at variance with Artedi's system, was extremely unfortunate, based as it 

 was on a misconception of those fishes' gills. On the whole, Linnasus dis- 

 liked cold-blooded animals; as a motto for the amphibians he chose the 

 words: "Terrible are Thy works, O Lord," and he assures us that there 

 are not many who would wish to collect these animals. In regard to the inver- 

 tebrate animals he let his system stand unaltered; only the species, in par- 

 ticular the insects, were reduplicated like the plants. 



The ' ' natural method of -plants 

 In spite of the enormous amount of work entailed in describing these new 

 animals and plants from all parts of the world, Linnasus found time to apply 

 himself to theoretical problems of great importance. Chief among these 

 should be mentioned his work on the natural vegetable system. As early 



