The Growth of Zoology,—Let us now look at some general phases in the growth of zoology. In its first stages of growth we find a period devoted to descriptions. In the time of Linnæus, for illustration, emphasis was placed on collecting, describing and systematically arranging all the different kinds of animals. This resulted in giving naturalists a knowledge of the form and appearance of the chief animals that inhabit the globe, and formed the basis upon which further progress could be made.
We can not, however, reach general conclusions without the examination of many facts, and there was naturally a long period devoted merely to the accumulation of facts about animals.
The next great step in advance was that of comparison. The contrast between description and comparison is brought out so clearly by I. P. Whipple in his essay on Louis Agassiz that I quote from it. He says:
My first impression of the genius of Agassiz was gained when he was in the full vigor of his mental and physical powers. Some thirty-five years ago (now sixty-five years), at a meeting of a literary and scientific club of which I happened to be a member, a discussion sprang up concerning Dr. Hitchcock's book on fossil "Bird-tracks," and plates were exhibited representing his geological discoveries. After much time had been consumed in describing the bird-tracks as isolated phenomena, and in lavishing compliments on Dr. Hitchcoock, a man suddenly rose, who, in five minutes, dominated the whole assembly. He was, he said, much interested in the specimens before them, and he would add that he thought highly of Dr. Hitchcock's book, as far as it accurately described the curious and interesting facts he had unearthed; but, he added, the defect in Dr. Hitchcock's volume is this, that it is "dees-creep-teeve," and not "compar-a-teeve." It was evident throughout that the native language of the critic was French, and that he found some difficulty in forcing his thoughts into English words, but I can never forget the intense emphasis he put on the words "descriptive" and "comparative," and by this emphasis flashing into the minds of the whole company the difference between an enumeration of strange, unexplained facts and the same facts as interpreted and put into relation with other facts more generally known.
The moment he contrasted "dees-creep-teeve" with "com-par-a-teeve" one felt the vast gulf that yawned between mere scientific observation and scientific intelligence, between eyesight and insight, between minds that doggedly perceive and describe and minds that instinctively compare and combine.
The descriptive and comparative stages in zoology, of course, overlapped. It was in the early part of the nineteenth century that Cuvier, the great French zoologist and legislator, founded the science of comparative anatomy, and this brought the comparative method into the study of zoology. The beneficent results of this were notable, and zoological knowledge broadened and deepened.
In the last part of the nineteenth century zoologists added another method to the investigation of animal life; they began to study processes by the experimental method. This was not merely the extension of physiology into zoology. The new method involved experiments upon
