8 GENERAL PRINCIPLES OF ZOOLOGY 



wolf, and fox are related to one another, since they belong to the same 

 genus, the genus of doglike animals, of which they are different species. 

 Linnxus's method was particularly valuable in the description of new 

 species, inasmuch as it at the onset informed the reader of the relationships 

 of the new species. 



In his characterization of the various groups Linnseus broke with the 

 prevailing custom. His predecessors (as Gessner, Aldrovandus) had 

 given a verbose and detailed description of each animal, from which the 

 beginner was scarcely able to see what was specially characteristic for that 

 animal, a matter which should have been emphasized in the definition. 

 Linnteus, on the other hand, introduced brief diagnoses, which in a few 

 words, never in sentence form, gave only what was necessary for recog- 

 nition, a matter of great importance, in view of the enormously increasing 

 number of known animals. 



Influence of the Linnean System. — But in the great superiority 

 of the Linnean System lay at the same time the germ of the one-sided 

 development which zoology came to take. The perfecting of the system, 

 which undoubtedly had become necessary, gave that a brilliant aspect, 

 and hid the fact that classification is not the ultimate purpose of investi- 

 gation, but only an important and indispensable aid to it. In the zeal for 

 naming and classifying animals, the higher goal, knowledge of the nature 

 of animals, was lost sight of, and the interest in anatomy, physiolog}', and 

 embryology flagged. 



From these reproaches we can scarcely spare LinnjEus himself, for 

 while in his "Sy sterna Naturae" he treated of a much larger number of 

 animals than any earlier zoologist, he brought about no deepening of our 

 knowledge. The manner in which he divided the animal kingdom is 

 rather a retrogression than an advance. He recognized six classes: 

 Mammalia, Aves, Amphibia, Pisces, Insecta, \'ermes. The first four 

 classes correspond to Aristotle's four groups of animals ■\\'ith blood. In 

 the division of the invertebrated animals into Insecta and Vermes Linmtus 

 stands undoubtedly below Aristotle, who set up a larger number of 

 groups. 



But in his successors, we see the damage wrought by the systematic 

 method. The diagnoses of Linnaeus were for the most part models, which, 

 mutatis mutandis, could be employed for new species with little trouble. 

 There was needed only some exchanging of adjectives to e.xpress the 

 differences. With the hundreds of thousands of different species of 

 animals there was no lack of material, and so the way was opened for 

 that spiritless species-making which in the first half of the last century 

 brought zoology into such discredit. 



