Page:A History of Land Mammals in the Western Hemisphere.djvu/75

Rh without devising an artificial terminology, drawn chiefly from Greek and Latin.

In dealing with fossils, the difficulty of nomenclature becomes formidable indeed. The larger and more conspicuous mammals of the modern world are more or less familiar to all educated people, and such names as rhinoceros, hippopotamus, elephant, kangaroo, will call up a definite and fairly accurate image of the animal in question. For the strange creatures that vanished from the earth ages before the appearance of Man there are no vernacular names and it serves no good purpose to coin such terms. To the layman names like Uintatherium or Smilodon convey no idea whatever, and all that can be done is to attempt to give them a meaning by illustration and description, using the name merely as a peg upon which to hang the description.

The system of zoölogical classification which is still in use was largely the invention of the Swedish naturalist Linnaeus, who published it shortly after the middle of the eighteenth century. As devised by Linnaeus, the scheme was intended to express ideal relationships, whereas now it is employed to express real genetic affinities, so far as these can be ascertained. The Linnaean system is an organized hierarchy of groups, arranged in ascending order of comprehensiveness. In this scheme, what may be regarded as the unit is the species, a concept around which many battles have been waged and concerning which there is still much difference of opinion and usage. Originally a term in logic, it first received a definite meaning in Zoölogy and Botany from John Ray (1628 [sic]—1705) who applied it to indicate a group of animals, or plants, with marked common characters and freely interbreeding. Linnaeus, though not always consistent in his expressions on the subject, regarded species as objective realities, concrete and actual things, which it was the naturalist's business to discover and name, and held that they were fixed entities which had been separately created. This belief in the fixity and objective