EVOLUTION AS SEEN IN THE CLASSIFICATION OF ANIMALS 307 



mental object of any system of classifying — library books, stamps, or ani- 

 mals — is to arrange in orderly sequence, to place like with like. Thus in the 

 library the books on photography are side by side in one place, books on 

 ceramics in another, biographies in still a third. Similarity, then, of one 

 kind or another, is the basis of all classification. In the case of animals, 

 similarity of structure, morphology, has traditionally been the basis upon 

 which classifications have been built. More recently physiological and 

 serological similarities have begun to contribute to classification, but it 

 still remains true that most of the generally recognized classification is 

 firmly grounded in morphological similarity. Morphologically similar ani- 

 mals are placed near together in classification; morphologically dissimilar 

 animals are placed farther apart. 



Classifications of one kind or another are probably as old as man's 

 curiosity about his fellow inhabitants on this planet. During the centuries 

 of the infancy of biology many classifications were suggested. Indeed, so 

 many biologists created so many classifications that the resulting confusion 

 finally became a stumbling block in the way of further scientific progress. 

 It was the genius of the Swedish biologist, Linnaeus, born in 1707, that he 

 was able to devise a system of classification which all biologists would 

 agree to use and which was so logically developed that today, despite ex- 

 panding horizons of biological knowledge, it still serves the needs of sci- 

 ence. Addition and amplification have been necessary, but no fundamental 

 reorganization. Linnaeus laid the foundations well. 



Binomial System of Nomenclature 



The basis of the Linnaean system is the conferring of two names upon 

 each kind of animal. Hence this is a binomial system of nomenclature. 

 Thus Linnaeus named the domestic dog Canis familiaris. The second name 

 of the two designates a unit of classification called the species, while the 

 first name of the two designates a larger unit of classification, usually in- 

 cluding more than one species, called the genus. An analogy lies in the 

 practice of writing the name of a human individual with the surname first, 

 the given name second, e.g.. Smith, John. The individual named is one of 

 the Smiths, the particular one of them he is being John. Similarly the com- 

 mon dog belongs to the genus of dogs, Canis, his particular species being 

 familiaris. The prairie wolf or coyote belongs to the genus Canis also, but 

 not to the same species; his species is latrans. Thus he is known to science 

 as Canis latrans. Similarly, the jackal of Africa belongs to the same genus 

 but to a different species; he is Canis aureus. 



