No other ancient writer deserves much notice in a historic sketch of zoology. Tian and Pliny show no capacity for the scientific treatment of the subject, and in their writ ings facts are largely mingled with fables. During the middle ages zoology, like other kindred sciences, was almost completely neglected. For many centuries, the only name worth mentioning, in connection with the history of the science, is that of Albert, count of Bollstitdt, commonly called Albertus Magnus; whose knowledge, however, was entirely derived from Aristotle and other ancient authors, and all he did was merely to call attention to the forgotten science, without making any contribution to its advanco meat. From his time, in the first half of the 13th c., to the beginning of the 16th, zoology was again almost completely neglected; but the new activity of mind which then displayed itself soon sought this as well as other directions, and an impulse was more given to zoology as well as to some other branches of science, by the prog ress of geographical diseOvery; curiosity being awakened with regard to the strange productions of the new world, and of the eastern and southern regions, till then equally unknown. The names of Belon (q.v.) and Rondelet arc the two greatest in this department at this period, and by them zoology was enriched with many new facts, while attempts were also made at a more perfect classification. Aidro vandi and Gesner (q.v.) soon followed them, besides others who began to direct their attention niore specially to particular branches of zoology, some of whom greatly extended the science by their observations on the animals of newly discovered coun tries. It was not till after the middle of the 17th c., however, that any real prog ress was made in classification, founded upon a philosophical study and comparison of animals. The works of Ray (q.v.) are described by Cuvier as "the foundation of mod ern zoology." The materials, however, were in great part prepared, and the first out line of a system sketched by Willoughby, the friend of Ray, whom Ray long survived, and whose works he edited. From the days of Aristotle, zoology had never been prose cuted with such acuteness of observation, accuracy of description, and breadth of philo sophical generalization as it was by Willoughby and Ray. The progress of the science became very rapid. Buffon won for it, by his interesting descriptions and brilliant style, the general attention of the educated portion of society, not only in his own but in other countries, and was almost immediately followed by Linnaeus, who, extending his studies from botany to zoology, not only extended the science by his own observations and discoveries, but rendered it far greater service by gathering together the facts ascer tained by others, and by the improvement which he effected in classification. Some of the larger groups established by Linnaeus have been retained by all subsequent natur alists without essential modification of their characters, and even his smallest groups genera—have been very generally retained, although now regarded as constituting tribes or families. According to the •inntean system, the animal kingdom is divided into six great classes, which are further brought together in groups of two each, as follows: Heart bilocular, with two auricles, blood ? Viviparous. 1. Mammalia.
warm, red. r Oviparous. 2. Birds.
Heart unilocular, with one auricle, blood , With lungs. 3. Amphibia.
cold, red With gills. 4. Fishes. Heart unilocular, with one auricle, circu- With antenna. 5. Insects.
lating fluid (sanies) cold, white... With tentacula. 6. Vermes.
The orders into which Linnaeus divided these classes have, in the most important instances, been already noticed, either under the classes; or separately. i It was, how- ever, in constituting and, defining the genera that Linnaeus showed n the highest degree his powers both of observation and arrangement. His labors in the lower departments of the animal kingdom were much less perfect than in the higher; but others speedily entered upon the field, and while new species of animals and their habits continued to be described, the study of comparative anatomy was also diligently prosecuted, and thus preparation was made for a more complete and philosophical sys tem of zoology. The names of Pallas, Hunter, and Blumenboeli are particularly worthy to be noticed; but more than any other, the name of Cuvier, who, like Linnmns, took a comprehensive view of the whole subject of zoology, and carried forward the work of minute observation as well as of generalization. His system of classification is rather
an improvement of that of Linnteus than one fundamentally new, and it has formed a new starting-point for all further progress. The divisions, the classes, and many of the orders of Cuvier's system have already been noticed under their proper heads, so that it may be enough here to give the most general outline of the system, showing Cuvier's four great divisions of the animal kingdom, and the classes which he arranges under them.
The system of Cuvier has been modified by Lamarck, Virey, Dunteril, De Blairsville, F. Cuvier, and others; and in consequence of the progress of scientific discovery, more considerable changes have recently been proposed by eminent naturalists, some of them amounting almost to a reconstruction of the greater part of the system; while in particular departments, and especially those which contain the lower forms of animal life, Cuvier's arrangement, regarded by himself ds merely provisional, may be said to have already become completely antiquated.
A complete system of the animal kingdom has been proposed by Agassiz. He adopts the four great divisions of Cuvier, but makes much change in the subdivisions, acknowl edging, however, that much is 'still uncertain, and that a satisfactory arrangement must depend upon anatomical and embryological researches yet to be made. The following is an'outline of his system: The three Cuvierian divisions of vertebrata, mollusca, and articulata have been very generally retained .by systematic zoologists, without much change as to the classes or even orders of animals included in each, although it is now generally admitted that the eirrhopoda are not to be ranked among the mollusca, but, as crustaceans, among the artica. kik; and the polyzoa or bryowa, formerly placed with other " zoophytes" among the radi ata, have been removed by many naturalists to a place among the Inollusea. Among the radiata of Cuvier great changes have been made; and it may be well to indicate here some of the chief of the new groups which have been proposed, and pretty generally- ac cepted by naturalists, although their proper order and their relations to each other cannot be so well set forth as in those departments of the animal kingdom which have been more thoroughly studied. Greater importance has been assigned by recent naturalists than by their predecessors to the nervous system as a basis of classification. The lowest animals, those in which no trace of a nervous system has been discovered, have been formed into a separate division of the animal kingdom, under the names (write and protozoa (q.v.), the latter of which has obtained general preference. Higher in organization than the protozoa are the of Owen, having a nervous system distinctly traceable in a filament ary form, and including all the higher orders of Cuvier's radiata. Some groups, as antlio zoa (see ZOOPHYTE), still occupy a doubtful intermediate place between protozoa and nematoneura. To the articulata, Owen has, with regard to their nervous system, given the name homogangliata f), and to the mollusca the name heterogangliata (q.v.). In like manner, he has recently introduced in his classification of the vertebrate the terms hematothermal and harnatocryal, these being merely words formed from the Greek, and signifying respectively and the former in cl ud ing manynalia and birds, the latter, reptiles and fishes. Further information about the recent classification of some of the lower groups of animals will be found in the article WORMS.
In the study of zoology, far more attention has been paid recently than formerly to the relation which each part of the animal organization bears to the whole, as the respir atory system to the circulatory system, the digestive system, the nervous system, etc. The study of the science has thus become more philosophical, and the view obtained of nature more complete; and if the difficulty of classification is found greater than when characters derived from particular parts of the organization were more exclusively regarded, the result, when fairly wrought out, is a system at once more perfect and more natural.