Yet though entomologists may be in reality as well qualified as any other natural historians for drawing general conclusions from the result of their researches, it is impossible to conceal the fact, that, as a body, they have not ordinarily done so. Whether this has happened through an accidental disinclination on their part to occupy themselves in such matters, or (which is more probable) from their whole time having been engrossed by the dry routine of their science, I do not pretend to determine: be the solution, however, what it may, the inference is practically the same,--that the Annulosa have not hitherto been sufficiently regarded, in the great questions of zoological geography. But especially have they been ignored during that most significant of considerations which has been so ably brought forward of late years by some of our keenest observers,--namely, the distribution of animals, as affected by geological changes, on the earth's surface. It would be well if the collector of insects would devote at least a tithe of his energies to the speculative branch of his subject. Certain it is that much would probably be advanced, at first, on slender premises; and would, as a consequence, fall to the ground, leaving no record behind it. Yet such must inevitably be the case, at the outset, in every region of inquiry; and we are prepared to expect it. It does not however follow that _good_ would not be developed also; whilst we are confident of the fact, that unless the trial be made, it cannot possibly arise. No question has ever yet been mooted without beneficial results: it has either been shown to be absurd, and has received its death-blow on the spot, or else truth has been elicited (indirectly perhaps), which has at once shed a new ray of light on some of its obscurest bearings. And so, assuredly, it would be in the present instance. We cannot doubt that there is much to be discovered in the past history of insect dissemination, which would tend, when rightly interpreted, to explain many of the occult phaenomena of the present day; and we may be equally satisfied that this cannot by any possibility be attempted without the assistance of geology. Let us therefore glance hastily at a few of those more undeniable convulsions which we are aware have, at various epochs, taken place; and endeavour to catch a glimpse of how, in the common course of things, that portion of the insect world would be affected which was exposed to their influence.