Page:The New International Encyclopædia 1st ed. v. 04.djvu/927

CLASSIFICATION OF ANIMALS. extinct forms. Tliese grades or degrees of kinship we speak of as sju'cies, genera, families, ■orders, classes, etc. S|)ecies arc more nearly re- lated than genera, genera than families, etc. The total number of the kinds of animals, or species, that are recognized is not far from 400,- OOO. In order to think of them all. it is neces- sary that they should be grouped into cate- irories of larger size than species, and these, in turn, into still larger ones. This is rendered possible by the fact that animals show nearer and remoter affinities. The ordinary lowest category is species: but tliis may be subdivided into nets or varieties: several similar species are grouped into a genus; related genera con- stitute a faniH}/: several families may make up an order. Orders constitute a class: classes a phylum. For example see table preceding. A particular species receives a composite name, embracing first that of the genus, and, second, that of the species; thus, the common cat is Felis donicstica. Scientific yomenclature. — The custom, above stated, of giving to each animal a double name, that of its genus and its species, arose with Linnaeus, and is called 'binomial nomenclature.' It answers to a man's family and individual or 'Christian' name, as Smith, John, It always consists of Greek or Latin words, or of words put Into Latinized form, partly because of a traditional custom descended from the early au- thors, who wrote only in Latin, but mainly be- cause it is thus made comprehensible to readers in all languages. Furthermore, great confusion •nould follow the attempted use of vernacular names alone, since many different animals are given the same name in popular speech, while the same animal is known by various names in different localities. 'Robin' means several very diverse birds to persons living in America. Great Britain, India, or Australia, but Turdiis niigriitorius is unmistakably the American thrush, locally called the robin. Theoretically, these names are supposed to be suitably applied. Thus, 1 Urdus is the old Latin terra for a thrush- like bird, and mipratorius, the Latin adjective 'migratory.' It often happens, however, through the misapprehension or ignorance of the person who first applies the name, that unsuitable or positively erroneous appellations have been given, or wrong collocations have been made. A subsequent student, discovering this error, or taking a different view of the animal's relation- ship, endeavors to correct it by giving it a new, and, in his opinion, better name; or he may transfer it to another genus, but retain the specific name. A third writer, not knowing that the same animal has l>een previously de- scribed and named, may name it something en- tirely different. These changes and duplications went on almost unchecked until the middle of the nineteenth century, when the British Asso- ciation for the Advancement of Science and other influential bodies of naturalists devised means of regulating the matter, which resulted in certain now generally accepted rules, the sub- stance of which is as follows: A name for a new species is not recognized in science, unless it is in the customary' binomial form (the two parts agreeing in numlier and gender), and has In'en accompanied by a description by which the ani- mal may be satisfactorily identified, and which is published in some book or periodical accessible 817 CLASSIFICATION OF ANIMALS. to students in general; and when this has been done, no other person may give the animal a different specific name. This is called the rule of priority — that is, the first name legally aj)- plied must remain (as a mere lal)el), whether it is subsequently found to have been well chosen, or not, A limit, however, was found necessary to this rule, and it is therefore agreed that no name previous to the one made or sanctioned by Limia-us in the tenth edition of his Systenia yaturrv (17.5S) shall be recognized. Certain minor limitations arc also made for local needs — as. for example, with reference to Rafinesque in the United States. In zoological or botanical nomenclature, a generic name can be applied only to one group of organisms. If it is subse- quently given to something else the new applica- tion will not hold. According to one code, at least, a generic name that has disappeared by fusion of genera or the splitting of a gentis can- not be used again. In scientific works, the tech- nical name of an animal is often followed by the name (usually abbreviated) of the man who named it as a whole, as Turdus miyratorius, Linn. ; but if the generic name was made by one man and the specific by another, both authorities may be given, in order to avoid any mistake, thus: Bluebird, Sialia sialis (Linn.). Halde- mann. Latterly, the recognition of subdivisions within species, called subspecies, races, or varie- ties, has led to the addition of a third name in many cases, especially among birds — for ex- ample, Falco peregrinus nnatum means the (American) variety aiiatum of the European peregrine falcon, or our duck-hawk. Another custom is that all specific and varietal names shall begin with a small letter, even when 'prop- er' adjectives or nouns. Similar rules and ex- planations apply to the names of the higher groups, whicii are capitalized, always in the plural, and, in the case of the family, take the termination idee, which in zoiilogj" invariably in- dicates a group of family rank. {Xote. — In the present work the nile of technical books is not followed as to the initial of specific names, which are capitalized as they would be in English.) Categobies of Ci.assificatiox. The number of known species of living animals is perhaps .■J.iO.OOO, to which must be added over .iO,000 fos- sil described species, making over 400.000 in all. To contain all these forms it is necessary to pro- vide a complicated system of categories of vary- ing ranks. We recognize the fact that, in beast as well as in man. no two individuals are exact- ly alike. But just as the various members of the B. Smith family more nearly resemble each other than they do the .Tones or Brown families, so certain other animals, while showing slight individual differences, possess so many common, constant qualities that we put them in the same species. Likewise, several species have certain qualities in common, while they differ in other respects so markedly from all other species that we class them together in one genus. In the same way, a number of related genera fall nat- urally into the same family. Species. — A term applied in biology to the tinit of classification — that is, the lowest group that receives a name. (For the exceptional usage in respect to 'varieties,' see below.) Al- though the term 'species' is almost universally employed l)y biologists to-day, a precise defini- tion cannot be applied to it; for there is abso-