more than his sanction, is, likewise, a thing that can be proved. This discovery was first made in 1859 by Mr. Gosse, the naturalist, for up to that time it had always been imagined that the crab, at any rate, was indifferent. Mr. Gosse, however, by the simple expedient of detaching the anemone from the shell, demonstrated that this was not the case, for on each occasion that he did so the hermit-crab picked it up again in its two claws, and pressing it against its shell, held it there for about ten minutes, at the end of which time it was sticking fast, as before. The crab, therefore, must derive some advantage from the presence of the anemone in return for the protection which he perhaps affords the latter against certain enemies. Or possibly the constant change of locality, with its increased chances of procuring food, is the real or the principal benefit conferred. But how does the crab benefit? This, at first sight, is not quite so easy to see. The explanation usually given is that it is “masked” or concealed by the sea-anemone, which is by no means small in comparison with the size of the shell, but often almost and completely covers it, forming a sort of cloak round it at its base, and towering like a pillar above it, so that of the two it is by far the more conspicuous object, especially when the crab is withdrawn, or partly withdrawn, into its shell. Nor is it always one anemone only that is affixed to the shell; there may be as many as two or three, or even more, and in some cases not only the shell, but the crab’s own claws may be thus utilised. Certainly, therefore, if concealment is a gain to the crab, it obtains this advantage by the arrangement. If, too, it has any special enemies of its own—as it is very probable that it has—the stinging cells of its allies would be likely either to incapacitate them or keep them at a distance. Of one thing, at least, we may be certain, that some advantage is obtained—and, no doubt, it is a substantial one—by each of the individuals in this strange copartnership—for throughout nature, in associations of the kind, the principle expressed by the homely Scotch saying of “giff, gaff”—Anglicè, “nothing for nothing”—obtains. Apparent instances may indeed be found of one species doing something for the benefit of another, since the very nature of these arrangements is such as often to give them this appearance. But such instances are apparent only. Whatever it looks like, and whatever either or any of the parties concerned may do, they always do it for their own, and not for one another’s benefit.