INTRODUCTION 17 



the common cowbird is named Molothrus ater. The generic name is 

 always begun with a capital letter and at the present time all specific 

 names (of animals) with a small letter. From the use of two names for 

 each species, this system of naming is known as the Binomial Sj'^stem of 

 Nomenclature. 



Linnseus's great work, the Systema Naturce, contained the first note- 

 worthy appUcation of this system of naming, in the form of a catalog, 

 methodically arranged. The species were grouped into orders, and the 

 orders into classes. While these groupings have since been shown to be 

 artificial, and new groupings have been substituted, the binomial system 

 of names has been retained and many species still bear the names which 

 Linnaeus proposed for them. The changes introduced into the grouping 

 of species since Linnseus's time are intended to express ideas of the rela- 

 tionship of the groups to each other. But without a preliminary dis- 

 cussion of evolution it will not be profitable to pursue this matter further. 



The advantages of a comprehensive system of classification are 

 obvious. Any kind of arrangement is better than none. Such an 

 arrangement, applied to animals, is not only a convenient aid to the 

 other branches of zoology; it actually raises problems which would 

 otherwise scarcely be discovered. The development of even a slight 

 degree of order out of confusion always suggests the possibility of further 

 generalization. 



Comparative Anatomy. — The next great movement in zoological 

 progress was the development of comparative anatomy. Descriptive 

 anatomy dates back to the ancients. But as larger numbers of animals 

 became known, and especially under the influence of the Linnsean clas- 

 sification which placed similar animals in the same orders, it was inevi- 

 table that anatomy should become strongly comparative. Even as 

 early as 1555, Belon noted the close correspondence, "bone for bone," 

 between the skeleton of a bird and that of man. By 1645 there was poib- 

 lished, by Severino, a book expressly devoted to comparative anatomy. 

 Vicq d'Azyr, of France, made a brilliant beginning in comparison of the 

 arms and legs of man with those of other animals, and in the anatomy of 

 the brain, but he died at the early age of forty-six. 



The real founder of comparative anatomy was Georges Cuvier 

 (Fig. 8), a Frenchman (1769-1832). Not content to limit his observa- 

 tions to the vertebrates (back-boned animals) as the earlier comparative 

 anatomists were inclined to do, Cuvier made comparative studies through 

 the whole animal kingdom. From 1801 to 1805 he published a systematic 

 treatise on comparative anatomy, which included both invertebrates 

 and vertebrates. A few years later he published a great work on fossil 

 bones of the region about Paris, which was also comparative. From all 

 these comparative studies Cuvier came to the conclusion that animals 

 are built in accordance with four general types ; the vertebrate type, the 



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