Page:Mind (Old Series) Volume 12.djvu/257

 244 W. L. DAVIDSON : I do not indeed say that a system could not be formed, or has not been formed, to which the word arbitrary might not be strictly applied. On the contrary, when Theophrastus divided plants into trees and herbs, " referring the larger shrubs to the former, and undershrubs to the latter," he used a principle of division (namely, size) which cannot be designated as other than frivolous notwithstanding that it long kept its ground, being accepted so late as the beginning of last century by Bay in our own country and Tournefort in France. And much the same may be said of Pliny the Elder's grouping of animals according to the element they lived in : those that fly in the air (wlatilia), those that live on the land (terrestria), and those that swim in the water (aquatilia}. But the Linnaean system (which is that com- monly known as Artificial) differs from the Natural mainly in degree ; and the accurate plan would be to drop the desig- nations " natural " and " artificial," and to replace them by the terms " more natural " and " less natural ". What, then, is the distinction between the Natural and the Artificial so-called ; and how can the former legitimately claim the pre-eminence ? This question will be answered by referring to the objects that biological classing has in view. In the first place, it has all the objects of classifica- tion in general viz., helping the memory, aiding the under- standing and displaying coexistences. But, in the next place, it has the peculiarity of dealing with living beings and of aiming at presenting these in the mutual relations that they actually bear in Nature. Now, in order to do this, it is not sufficient to rest content with mere superficial resem- blances, but we must go deep down and fix upon those that are significant and important : and the test of importance and significance is, that they are constant and prolific of corre- lated properties. It is the main objection to the Artificial system that it fails in this respect, or fails to a far greater extent than the Natural system does. It is too ready to proceed upon the more obvious and easily ascertainable points of animals and plants, and it does not make the fact of correlated properties a prime consideration. Notwith- standing its one great recommendation viz., that it facili- tates identification it is deficient in the very points that are most imperative ; and its leading principle of arrange- ment e.g., in Botany, the number of stamens and pistils lands us in natural groups only, as it were, by accident and very occasionally. Let us take as an example the classifying of Animals. In the Linnsean. system, the classifying organ that determined