The accepted scientific name of a species is a binomial phrase consisting of the generic name, which is placed first, and a trivial name proper to the species. The whole compound is the specific name. The terms employed should be formed from Latin or Greek roots, and the whole is regarded as Latin, so far as the termination, and agreement between the adjectival trivial and nominal generic name are concerned. (See ZOOLOGICAL NOMEN CLATURE.) The Sub-Family.—The next highest group, the sub-family, includes a group of genera, held together by structural resem blances. Its name is always made by adding to the root of the name of one of the genera included in it, the termination -inae.
Sub-families are grouped into families, whose names, formed as are those of sub-families, are characterized by the termination -idae.
Neither of these groups has a definite connotation, each, except in so far as it is bounded by morphological gaps between neigh bouring genera, gaps which depend on our very- incomplete knowl edge of fossil forms, is of the nature of an artificially circum scribed assemblage.
The primary division of the animal kingdom is into phyla. Each phylum is sharply characterized by the possession of a plan of structure in the adult which is peculiar to it, differing from that proper to every other phylum in such ways that it is, in general, incapable of derivation from any other. As the adult structure of an animal represents a condition finally arrived at, at the end of a developmental history which begins with a single fertilized egg cell or zygote it necessarily follows that in certain fundamental features, at any rate, the modes of development of all the members of a phylum will agree with one another and differ from those of representatives of other phyla. This is indeed the
case, but there do exist resemblances in the early development between members of different phyla which have led zoologists to discuss the possibility of relationship between one phylum and another of a kind which must have existed in the early stages of evolution, at a time when the first fundamental branching out of the animal kingdom took place.
Thus a study of animal development (see EMBRYOLOGY) is necessary for the establishment of a natural classification.
The labours of zoologists have now resulted in the establish ment of a classification of animals, based entirely on morphology, which is unlikely to be seriously modified in its broad outlines by further work. The minor classification, into orders and smaller groups, is still disputed, although even here the differences be tween taxonomists lie more largely in the minor points of the grade to which a group belongs, or the position of its boundaries, than in a real clash of opinion as to mutual relationships.
This classification makes it possible for any competent zoologist to determine an animal, which is unknown to him, at any rate so far as its family or genus is concerned. It is thus of immense practical value, not only to the pure, academic zoologist, but also to those whose work has a direct economic bearing. The first thing which has to be done in an attempt to control an injurious insect is to discover its name, because only when this is known is it possible to find out whether the pest is imported or of local origin, and whether it is known and controlled in other parts of the world.
National museums exist in order that they may play the part of dictionaries, ensuring the accurate determination of all animals which may prove of interest either scientifically or commercially.