The facts and ideas with which the animal ecologist needs to become acquainted are so widely scattered that a large amount of selective reading is necessary. The ecologist must read, select, and become an organizing center of things ecological. All of the facts and conceptions which he needs are not even confined to zoölogical or biological literature. In seeking an understanding of any problem, conventional groupings of the sciences and their arbitrary boundaries must not bar one from fertile fields. Many of the conceptions of the physical sciences, due to their more advanced stage of development, anticipate the future development of biology. This is particularly true of their dynamic conceptions. For this reason we should not hesitate to utilize and deliberately strive to secure development along similar lines in animal ecology. Elsewhere I have stated (An Ecological Survey in Northern Michigan, 1906, pp. 11, 12) that: “It is thus very apparent that as soon as ecological phenomena are investigated dynamically and expressed in terms of processes, this science will of necessity become more closely correlated with those allied sciences which have already availed themselves of such methods.... It seems a very simple matter to give assent to the idea of the law of change, yet in its practical application this simplicity often vanishes at once when it is seen that it involves the relation of cause and effect.... As this method of thinking is not generally understood, it is occasionally applied in such a crude and general sense that its bearing cannot be grasped when applied to special or concrete problems. There can be no question as to the general validity of this method, but what is now needed is to know how these processes are combined and related to produce particular environmental conditions or situations. That these difficulties are not confined to the ecologist alone, but are obstacles which arise in any attempt at scientific interpretation, is worthy of special notice. We are thus able to see why certain naturalists, apparently not recognizing or understanding the developmental processes which scientific ideas undergo, nor being acquainted with the tendencies of interpretation, dynamically considered, now making such rapid headway in ecological botany, geography, physiography, geology, and psychology, are inclined to look upon such attempts in biology as merely a fad or personal peculiarity of the student, and not of any particular consequence. Such ideas confuse the incidental with the essential and suggest a complete failure to grasp the situation or to realize the fundamental importance of stating explanations in terms of processes. Furthermore, in several of the allied sciences, the methods of dynamical interpretation have already made considerable advance. Here, then, is a resource, at present largely unworked by many biologists, where a wealth of ideas and explanations lies strewn over the surface and only need to be