799 ZOOLOGY THE branch of science to which the name zoology is strictly applicable may be defined as that portion of biology which relates to animals, as distinguished from that portion which is concerned with plants. elation The science of biology itself has been placed by Mr lj io- Herbert Spencer in the group of concrete sciences, the other groups recognized by that writer being the "abstract- iences. concrete " and the " abstract." The abstract sciences are logic and mathematics, and treat of the blank forms in which phenomena occur in relation to time, space, and number. The abstract -concrete sciences are mechanics, physics, and chemistry. The title assigned to them is justified by the fact that, whilst their subject-matter is found in a consideration of varied concrete phenomena, they do not aim at the explanation of complex concrete phenomena as such, but at the determination of certain "abstract" quantitative relations and sequences known as the "laws" of mechanics, physics, and chemistry, which never are manifested in a pure form, but always are inferred by observation and experiment upon complex phenomena in which the abstract laws are disguised by their simultaneous interaction. The group of concrete sciences includes astronomy, geology, biology, and socio logy. These sciences have for their aim to " explain " the concrete complex phenomena of () the sidereal system, (6) the earth as a whole, (c) the living matter on the earth s surface, (d) human society, by reference to the properties of matter set forth in the generalizations or laws of the abstract-concrete sciences, i.e., of mechanics, physics, and chemistry. The classification thus sketched exhibits, whatever its practical demerits, the most important fact with regard to biology, namely, that it is the aim or business of those occupied with that branch of science to assign living things, in all their variety of form and activity, to the one set of forces recognized by the physicist and chemist. Just as the astronomer accounts for the heavenly bodies and their movements by the laws of motion and the pro perty of attraction, as the geologist explains the present state of the earth s crust by the long-continued action of the same forces which at this moment are studied and treated in the form of " laws " by physicists and chemists, so the biologist seeks to explain in all its details the long process of the evolution of the innumerable forms of life now existing, or which have existed in the past, as a neces sary outcome, an automatic product, of these same forces. Science may be defined as the knowledge of causes; and, so long as biology was not a conscious attempt to ascertain the causes of living things, it could not be rightly grouped with other branches of science. For a very long period the two parallel divisions of biology, botany and zoology, were actually limited to the accumulation of observations, which were noted, tabulated, and contemplated by the students of these subjects with wonder and delight, but only to a limited extent and in restricted classes of facts with any hope or intention of connecting the phenomena observed with the great nexus of physical sequence or causation. A vague desire to assign the forms and the activities of living things in all their variety to general causes has always been present to thoughtful observers from the earliest times of which we have record, but the earlier attempts in this direction were fantastic in the extreme ; and it is the mere truth that, at the time when the phenomena of inorganic nature had been recognized as the outcome of uniform and constant properties capable of analysis and measurement, living things were still left hopelessly out of the domain of explanation, the earlier theories having been rejected and nothing as yet suggested in their place. The history of zoology as a science is therefore the his- Scope of tory of the great biological doctrine of the evolution of the his- living things by the natural selection of varieties in the tory of struggle for existence, since that doctrine is the one 20 medium whereby all the phenomena of life, whether of form or function, are rendered capable of explanation by the laws of physics and chemistry, and so made the subject-matter of a true science or study of causes. A history of zoology must take account of the growth of those various kinds of information with regard to animal life which have been arrived at in past ages through the labours of a long series of ardent lovers of nature, who in each succeeding period have more and more carefully and accurately tested, proved, arranged, and tabulated their knowledge, until at last the accumulated lore of centuries almost without the con sciousness of its latest heirs and cultivators took the form of the doctrine of descent and the filiation of the animal series. HISTORY. There is something almost pathetic in the childish wonder and delight with which mankind in its earlier phases of civilization gathered up and treasured stories of strange animals from distant lands or deep seas, such as are recorded in the Physiologus, in Albertus Magnus, and even at the present day in the popular treatises of Japan and China. That omnivorous universally credulous stage, which may be called the " legendary," was succeeded by the age of collectors and travellers, when many of the Era of strange stories believed in were actually demonstrated as collect- true by the living or preserved trophies brought to Europe rs a " d by adventurous navigators. The possibility of verification ^ established verification as a habit ; and the collecting of things, instead of the accumulating of reports, developed a new faculty of minute observation. The early collectors of natural curiosities were the founders of zoological science, and to this day the naturalist-traveller and his correlative, the museum curator and systematist, play a most important part in the progress of zoology. Indeed, the historical and present importance of this aspect or branch of zoological science is so great that the name "zoology" has until recently been associated entirely with it, to the exclusion of the study of minute anatomical structure and function which have been distinguished as anatomy and physiology. It is a curious result of the steps of the historical progress of the two divisions of biological science that, whilst the word " botany " has always been understood, and is at the present day understood, as embracing the study, not only of the external forms of plants, their systematic nomencla ture and classification, and their geographical distribution, but also the study of their minute structure, their organs of nutrition and reproduction, and the mode of action of the mechanism furnished by those organs, the word " zoology " has been limited to such a knowledge of ani mals as the travelling sportsman could acquire in making his collections of skins of beasts and birds, of dried insects and molluscs shells, and such a knowledge as the museum curator could acquire by the examination and classification of these portable objects. Anatomy and the study of ani mal mechanism, animal physics, and animal chemistry, all of which form part of a true zoology, have been excluded from the usual definition of the word by the mere accident that the zoologist of the last three centuries has had his museum but has not had his garden of living specimens as the botanist has had ; * and, whilst the zoologist has thus
1 The mediaeval attitude towards both plants and animals had no