Now, it seems to me that, if we say, with Mr. Romanes, that the brown capuchin discovered the _principle of the screw_, we must also say that the dung-beetle that I observed in South Africa was acquainted with the _principle of the inclined plane_. Such an expression, I contend, involves an unsatisfactory misuse of terms. A mechanical principle is a concept,[GZ] and as such, in my opinion, beyond the reach of the brute--monkey or beetle. That of which the monkey is capable is the perceptual recognition of the fact that certain actions performed in certain ways produce certain results. Why they do so he neither knows nor cares to know. What the brown capuchin discovered was not the principle of the screw, but that the action of screwing produced the results he desired--a very different matter. My friend, Mr. S. H. Swayne, tells me that the elephant at the Clifton Zoo, having taking a tennis-racket from a boy who had been plaguing him, broke it by leaning it against a step and deliberately stepping on it in the middle, where it was unsupported. A most intelligent action. And it would have been a capital piece of exercise for the lad's reasoning power, had he been required to analyze the matter, to show why the elephant's action had the desired effect, and set forth the principle involved. I do not think the elephant himself possesses the faculty requisite for such a piece of reasoning. He is content with the practical success of his actions; principles are beyond him. I will now give two instances of intelligence in vertebrates which exemplify phases of inference somewhat different from those which we have so far considered. Mr. Watson, in his "Reasoning Power of Animals,"[HA] tells of an elephant which was suffering from eye-trouble, and nearly blind. A Dr. Webb operated on one eye, the animal being made to lie down for the purpose. The pain was intense, and the great beast uttered a terrific roar. But the effect was satisfactory, for the sight was partially restored. On the following day the elephant lay down of himself, and submitted quietly to a similar operation on the other eye. No doubt the elephant's action here was, in part, the result of its wonderful docility and training. But there was also probably the inference that, since Dr. Webb had already given him relief, he would do so again. The anticipation of relief outmastered the anticipation of immediate discomfort or pain. I do not think, however, that any one is likely to contend that any rational analysis of the phenomena is necessarily involved in the elephant's behaviour.