It is generally said in natural history books, that the relations existing between the shark and the pilot-fish are not quite understood: but since it must be an inestimable privilege to a little weakly fishlet that any large fish might snap up, to have a shark for a protector, and a shark-cavern to go into—not in the way that other creatures go into it—and since there is nothing which the shark eats that his friend may not have a share of, if he wants to, I really do not see what more one need understand, as far, at least, as the pilot-fish is concerned. Then, too, if—as there seems little doubt is the case—the pilot-fish acts as a scout for the shark, and brings him to anything eatable that he may find floating about in the sea, this fully explains the part which the shark plays in this little amicable arrangement. He protects his little guide and purveyor, not only by his presence but also by offering him an asylum, and the habit of seeking such an asylum has, no doubt, been acquired by the pilot-fish through his seeing the young sharks do so. He has lived in the nursery with them, and they have taught him the trick. Of course, as the pilot-fish shares in anything the shark gets, his wish to guide the latter to whatever he may be the first to find, as well as the trouble he takes to find it, is easily explained. It is not an unselfish act, but one in his own interests, and thus all the requisites of an association of this sort, between two different species of animals, are fulfilled.[13] When a shark is caught at sea, the poor little pilot-fish, as he is hauled up on deck, will leap up after him out of the water, in a vain endeavour to follow his life’s companion. It is no use; he falls back again, the blue and golden bands with which his bright little body is decorated glittering in the sun—for there generally is a sun in the regions where these things take place. This certainly looks as though the pilot-fish were genuinely attached to the shark. It seems like the act of a faithful little friend, but it need imply no more than does his habitual following and keeping company with the shark in the sea. To be with the great fish has become an instinct with the little one, and so when the latter sees his convoy going somewhere where he has never gone before, he endeavours to go with him. Still, that a really friendly feeling may, through long association, have arisen between the two companions, though differing so from one another in size and appearance, does not seem impossible, or even unlikely. Of course, in considering a question of this sort, we should first get clear ideas of what friendship really is—the essential elements of which it consists. To do this is not, perhaps, so easy a matter as it may seem. At any rate, it is too difficult to be attempted in a work like this.