In the History of Zoology, four eras are marked by the names of four great cultivators of that science. All knowledge of nature must have commenced in the observation of individuals, or in an intuitive perception of their properties bestowed upon the first man. We may suppose, however, that at some period not remote from the creation of the human race men were left to their own resources, when they were necessarily forced to examine the nature and qualities of plants and animals, as well as of all natural objects with which they came into contact. The son would learn from the father, and impart to his descendants a certain degree of knowledge acquired by observation. Where the art of writing was unknown, science would advance but slowly; and even where it was practised, the privilege would probably belong to individuals or families, so that the mass would still be left to their ordinary resources. Those who lived in the remote ages antecedent to the Christian era probably knew as much of natural history as the unlettered peasant of our own age and country. Whatever may have been the acquirements of the priests, the sole depositaries of science in ancient India, Chaldea, and Egypt, they perished amid the revolutions of empires. The Sacred Scriptures, however, show that Moses, who was learned in all the wisdom of the Egyptians, had bestowed considerable attention on the animal world; but as these writings were not intended for our instruction in natural knowledge, the observations which they contain on the subject have no reference to systematic arrangement. In short, whatever may have been the knowledge possessed by the subjects of the Pharaohs, or the Hebrews and Greeks of the earlier ages, we do not find that it had assumed any definite form, or constituted a body of doctrine, until the time of Alexander the Great. At this epoch the illustrious Aristotle collected the observations of his predecessors; added to them those, more extensive and more important, which were made by himself; and, although deeply engaged in the study of other subjects, succeeded in collecting a mass of facts, and in eliciting from them general principles, the accuracy of many of which might surprise us, did we not reflect that, in this department at least, he followed the true method by which the physical sciences have in our times received so vast an augmentation. He, however, stands alone among the writers of remote antiquity in this field; for, if others followed in his steps, their works have been lost.