ANIMALS, Classification of. Classifi cation is simply sorting out — arranging differ ent things according to their likeness, putting them into groups. To these groups names are given for convenience in referring to them, and thus arises the terminology of this department of knowledge, which is the technical language of science broadly considered. In the present article, however, the writer purposes to confine himself to organic nature, and chiefly to zoology.
The alluded to above is very simple and easy at first. The child undertakes it in the kindergarten when he separates blue papers from red, square blocks from round ones, the long sticks from the short. But pres ently something combining more than one qual ity is encountered, and the question arises: Shall I put this on this pile or on that? An infant in a kindergarten who picked up a red ball might well hesitate whether to place it with the red things by virtue of its color, or on the spherical pile by virtue of its shape. This illustrates the cardinal difficulty that has em barrassed all classifiers, and has caused so great a diversity of schemes for the orderly arrangement of natural objects. Probably the only perfect classifier is nature herself, in the form of that mysterious and marvelous selector, chemical affinity. Human intelligence is less well informed as to the real constitution and affinities of the objects, animate and inanimate, that man's senses perceive, and, for the present, his arrangements of them must be imperfect and tentative. Hence classifications of the various groups, or even the limits of the groups themselves, may and do vary in at least two directions — first in the selection of a standard of comparisons, and second in knowledge or opinion of relationships.
At first, as was natural, superficial resem blances sufficed to group seemingly like objects. This brought worms, spiders and insects into one lot, classed bats with birds, whales with fishes and so on. But a closer examination soon revealed these and lesser incongruities. It
was ascertained that every known bird was clothed in feathers and reproduced itself by eggs. The hat, although it flew in the air, was covered with hair, brought forth its young alive and suckled them; those were the most conspicuous and universal characteristics of dcr oy mammals. So the bat was a mammal that flew.
Fishes were found to be always covered with a more or less scaly skin and breathed the air aer within the water by means of gills. The whales 4-d were found to breathe only atmospheric air, 4 brought forth living young and suckled them. me Plainly it was wrong to put them among the fishes, although they lived in the water — they were mammals. Thus arose the concept that are fundamental structure was a better criterion by tr., which to classify than external likeness.
r: Artificial Schemes.— In the early days 4 the knowledge of animal structure was very ti,t, limited. Comparative anatomy had hardly le b been thought of, and, indeed, arose into a defi m.t, nite science largely because of curiosity as to classification. Meanwhile naturalists wanted to group their facts, pigCon-hole and label their increasing information, which more and more was falling into coincidences and suggesting 3. new comparisons and contrasts. Hence the early attempts at classification were frankly for convenience, hardly more scientific than the 6,1pigeon-holes in a clerk's desk. The crowning tri example of probably, is the "system" by which Linne (Linnmus) arranged the plants of the world.
The makers of all these "artificial" arrange ments, as they were called, were ever seeking for the best, the most comprehensive features by which to work. Some were fantastic, as the I "circle" theory of Macleay and Vigors; others sensible and useful. An arrangement of birds - long in vogue was by the form of their feet, by which all birds were separated into several "orders" according as they were seizers, run. ners, climbers, etc. This was utilizing function as a criterion, and only hinted at structure.