[38] I do not think it necessary to apologize for the apparent disposal of this _quaestio vexata_; because, from the wildness of the upland ridges to which the _D. obscuroguttatus_ is in Madeira exclusively confined, I deem it an absolute impossibility that it could ever have been _introduced_, through any chance agencies whatsoever. And hence, unless we reject the doctrine of specific centres _in toto_, I contend that it must have migrated, together with other insects similarly circumstanced, by ordinary means, and without natural impediments, from its own area of diffusion. [39] I am informed by Dr. Hooker, that the only two insects (belonging respectively to the orders Coleoptera and Lepidoptera) which he detected in Kerguelen's Land were wingless. [40] Insecta Maderensia, p. 6. [41] Insecta Maderensia, p. 36. [42] _Id._ p. 310. [43] Insecta Maderensia, p. 452. [44] Insecta Maderensia, p. 11. [45] Religion of Nature Delineated, p. 84. CHAPTER IV. ORGANS AND CHARACTERS OF VARIATION. Having in the preceding chapter briefly alluded to some of the principal causes by which the outward aspect of the insect tribes would seem to be in a large measure (though within definite specific limits) regulated, it may perhaps be desirable to gather into a small compass, from those remarks, what the chief organs and characters are which appear to be more peculiarly beneath the control of the various influences which we have been just discussing. To imagine that when an insect has become much altered in its general contour, all the parts of which it is composed are equally affected, is contrary to experience; since observation warns us that there are but few actual _members_ which are capable of change,--whilst even the external features, or secondary diagnostics, are only interfered with according to a fixed law, the workings of which are necessarily modified, in proportion as the constitutions of the several animals are differently organized and acted upon.