What my chief aim in the present treatise has been, will be easily perceived,--namely, to substantiate, as such, those _elements of disturbance_ (on the outward contour of the Annulose tribes) with which the physical world does everywhere abound: and, thereupon, to provoke the inquiry, whether entomologists, as a mass, have usually taken them into sufficient account, when describing as "species," from distant quarters of the globe, insects which recede in only minute particulars from their ordinary states. My own impression is, that they have not done so; and, moreover, that, if they had, our catalogues would have worn a very different appearance to what they now do: for, when once the subject is fairly looked into and analysed, it is impossible not to be convinced, that the _prima-facie_ aspect of these creatures is eminently beneath the control of the several conditions to which they have been long exposed. But let me not be misunderstood in the conclusion which I have been thus compelled to endorse, or be supposed to ignore the fact that truly _representative species_ may frequently occur in countries far removed from each other; which cannot therefore be regarded as modifications of a common type. I believe, however, that this doctrine of _representation_, whatever truth it may contain, has been too much relied upon; and that we have been over-ready to take advantage of it (unproved as it is) for the multiplication of our, so called, "specific novelties." I suspect, indeed, that _actual_ representative species (if they may be thus expressed) are more often to be recognized on the isolated portions of a formerly continuous tract, than in regions which have been widely separated since the last creative epoch; and that, in the instances where beings of a _nearly_ identical aspect are detected in opposite divisions of the earth, it is more often the case that members of them have been transported at a remote period (either by natural or artificial means) from their primaeval haunts, and have become gradually altered by the circumstances amongst which they have been placed, than that the respective phases were produced _in situ_ on patterns almost coincident.