210 ESSAY ON CLASSIFICATION 



Aristotle cannot be said to have proposed any regular classification. 

 He speaks constantly of more or less extensive groups, under a com- 

 mon appellation, evidently considering them as natural divisions; 

 but he nowhere expresses a conviction that these groups may be ar- 

 ranged methodically so as to exhibit the natural affinities of animals. 

 Yet he frequently introduces his remarks respecting different animals 

 in such an order and in such connections as clearly to indicate that 

 he knew their relations. When speaking of Fishes, for instance, he 

 never includes the Selachians. 



After Aristotle, the systematic classification of animals makes no 

 progress for two thousand years, until Linnaeus introduces new dis- 

 tinctions and assigns a more precise meaning to the terms class 

 (genus summum), order (genus intermedium), genus (genus proxi- 

 mum), and species, the two first of which are introduced by him for 

 the first time as distinct groups under these names in the system of 

 Zoology. 



SECTION III 

 PERIOD OF LINNiEUS 



When looking over the Systema Natures of Linnaeus, taking as the 

 standard of our appreciation even the twelfth edition, which is the 

 last he edited himself, it is hardly possible in our day to realize how 

 great was the influence of that work upon the progress of Zoology .^° 

 And yet it acted like magic upon the age and stimulated exertions 

 far surpassing anything that had been done in preceding centuries. 

 Such a result must be ascribed partly to the circumstance that he was 

 the first man who ever conceived distinctly the idea of expressing 

 in a definite form what he considered to be a system of nature, 

 and partly also to the great comprehensiveness, simplicity, and clear- 

 ness of his method. Discarding in his system everything that could 



^''To appreciate correctly the successive improvements of the classification of Lin- 

 naeus, we need only compare the first edition of the Systerria Naturce (1735), with the 

 second (1740), the sixth (1748), the tenth (1758), and the twelfth (1766-1768), as they 

 are the only editions he revised himself. The third is only a reprint of the first, the 

 fourth and fifth are reprints of the second; the seventh, eighth, and ninth are reprints 

 of the sixth; the eleventh is a reprint of the tenth; and the thirteenth, published after 

 his death by Gmelin (1783-1793), is a mere compilation, deserving little confidence. 



