ZOOLOGY

(Yunanca köken — orijinale bakınız.) The science of animals. It teaches their nature and properties,their cla ification, and their order of succe ion upon, and their distribution over the earth. A know ledge of the nature of animals, as it implies that of their organization, and of the functions and interde pendencies of their component parts, constitutes the two great branches of zoology, called Zootomy, or comparative anatomy, and Physiology. The doctrine of the succe ion of species of animals upon the earth, as it relates principally to such as no longer exist, is included in a third branch of the science of animals, called Palaeontology, with which is closely connected that which treats of the geographical distribution of existing spi cies. The term Zoology!s practically restricted to the science of the outward characters, habits, properties, and cla ification of animals. As the forms of living animals, the parts they play in the theatre of nature, their good and evil relations to man, cannot be profitably treated of in the space a igned to this article,it will be limited to the exposition of the principles of the cla ification of animals, and of the characters and relative value of those groups which have not been already treated of in the present wotk. A cla ification is e entially based on the ideas of likene , unlikene , and proportion in its subjects. When it is ent purposed degrees to define,of resemblance,in a cla ification a natural of animals,system istheiraimeddiii'er-at. When a cla ification is restricted to the enunciation of a few likene es which may be most readily detected and most easily retained in the memory, it becomes an artificial system. A likene extends as far as a character is com mon; and the more extended or common the property or structure on which such character is founded, the more im portant and e ential it becomes as an element of the cla ification. Zoologists having ascertained as many of the characters common to all animals as served to form their complex idea of an animal, have, in the next place, endeavoured to discover the difl'ereiice, which, added to the idea or definition of the animal, would form the most extended species of that genus, logically speaking. Such a difference or character is not to be detected by a superficial examination. Aristotle thought he had found it in the blood, recognizing as blood only the red-coloured nu trient fluid, like that which flows in the arteries and veins of man. His primary division of animals was therefore into Sanguineous and Exsanguineous animals; the Enaima and the Anaima. The Enaima were the beasts, birds, reptiles, and fishes; and the Anaima, or bloodle animals, included all the lower species. Nothing, perhaps, can show more forcibly the nature and amount of observation required to frame a good cla iflcn tion, and the value of the information concentrated in ita exposition, than the great and long-continued deference paid to this early step in the cla ificatory branch of zoology, and the minute and extended researches required for the elimination of its erroneous element. First, it was found that many of the Exsanguineous animals of Aristotle did actually po e blood, differing only in colour from that of the so called Sanguineous species. This discovery, however, led only to a nominal improvement in the primary division of animals; the Enaima being " red-blooded," and the Anaima "white-blooded" animals. It was reserved for Cuvier, in the course of his minute di ections of the lower animals to discover that an extensive cla of worms had red blood circulating in a closed system of arteries and veins; and thi? discovery first materially affected the value of the charactei adopted by Aristotle for the primary groups of the animal kingdom. Now, if scientific cla ification were really based on the idea of likene alone, and the grouping together of individ [s. 1364]