THE PRINCIPLE OF CEPHALIZATION.
In the last of a series of papers on cephalization (or brain development) as a fundamental principle in the development of the system of animal life, Prof. Dana says ("American Journal," October, 1876): "I would refer to the case among mammals for an illustration of the principle that the lowest forms are those having their locomotive functions located in the posterior parts of the body; and that in the higher the forces, or force organs, are more and more forward in the structure. For example, in the whale the tail is the propelling organ, and is of enormous power and magnitude, and the brain is very small, and is situated far from the head extremity in a great mass of flesh and bone furnished with poor organs of sense; a grade up, in the horse or ox, the tail or posterior extremity is no longer an organ of locomotion, and is little more than a caudal whip lash, and locomotion is performed by organs situated more anteriorly, the legs, and a well-formed head carries a brain which is a vastly higher organ of intelligence than that of the whale, but the legs are simply organs of locomotion, and the hinder are the more powerful; and higher up, in the tiger or cat, the fore legs—not the hind legs—are the organs of chief muscular force, and these have higher functions than that of simple locomotion, and further, the body is proportionately shortened, and the head is shortened anteriorly, or in the jaws, and approximates thus toward the condition of man. The existence or not of a switch-like tail, as in ordinary quadrupeds, has little bearing on the question of the degree of cephalization, since the organ is not an organ of locomotion, or one indicating a large posterior development of muscular bone. But, approaching man in the system of life, even this seems to have significance."