PRINCIPAL SYSTEMS OF ZOOLOGY 211 



not easily be ascertained, he for the first time divided the animal 

 kingdom into distinct classes, characterized by definite features; he 

 also for the first time introduced orders into the system of Zoology 

 besides genera and species, which had been vaguely distinguished 

 before.^^ And though he did not even attempt to define the charac- 

 teristics of these different kinds of groups, it is plain from his nu- 

 merous writings that he considered them all as subdivisions of a 

 successively more limited value, embracing a larger or smaller num- 

 ber of animals, agreeing in more or less comprehensive attributes. 

 He expresses his views of these relations between classes, orders, gen- 

 era, species, and varieties, by comparisons, in the following manner.^^ 



Classis Ordo Genus Species Varietas 



Genus summum Genus intermedium Genus proximum Species Individuum 



Provinciae Territoria Paroeciae Pagi Domicilium 



Legiones Cohortes Manipuli Contubernia Miles 



His arrangement of the animal kingdom is presented in the fol- 

 lowing diagram, compiled from the twelfth edition, published in 

 1766. 



CLASSIFICATION OF LINN^US 



Cl. 1. Mammalia. Ord. Primates, Bruta, Ferae, Glires, Pecora, Belluae, Cete. 



Cl. 2. Aves. Ord. Accipitres, Picae, Anseres, Grallae, Gallinae, Passeres. 



Cl. 3. Amphibia. Ord. Reptiles, Serpentes, Nantes. 



Cl. 4. Pisces. Ord. Apodes, Jugulares, Thoracici, Abdominales. 



Cl. 5. Insecta. Ord. Coleoptera, Hemiptera, Lepidoptera, Neuroptera, Hymenoptera, 



Diptera, Aptera. 

 Cl. 6. Vermes. Ord. Intestina, Mollusca, Testacea, Lithophyta, Zoophyta. 



In the earlier editions, up to the tenth, the class of Mammalia 

 was called Quadrupedia and did not contain the Cetaceans, which 

 were still included among the Fishes. There seems never to have 

 existed any discrepancy among naturalists respecting the natural limits 

 of the class of Birds since it was first characterized by Linnaeus, in 

 a manner which excluded the Bats and referred them to the class 

 of Mammalia. In the early editions of the Systema Naturce the class 

 of Reptiles embraces the same animals as in the systems of the most 

 recent investigators; but since the tenth edition it has been en- 

 cumbered with the addition of the cartilaginous and semicartilagi- 



*^ The ykvT) fikyiffTa of Aristotle correspond, however, to the classes of Linnaeus; the 

 'ykrr] ixeya\a to his orders. 

 ^See Systema Naturce (12th ed.) p. 13. 



