In the Madeiras, this diminution and enlargement of stature, accompanied for the most part respectively by the retention and annihilation of the powers of flight, is singularly traceable on the selfsame rocks, particularly the smaller ones of the group. Thus, on the Flat Deserta, or Ilheo Chao, the _Scarites abbreviatus_, Koll., _Laparocerus morio_, Schoen., and the _Helops Vulcanus_, Woll., attain a gigantic size; yet it is on that very island that the _Ptinus albopictus_, Woll., finds its minimum of development,--scarcely exceeding in dimensions some of the larger members of the _Trichopterygia_. The Deserta Grande has some special modifying capability of its own,--the _Eurygnathus Latreillei_, Lap., _Notiophilus geminatus_, Dej., _Zargus pellucidus_, Woll., _Calathus complanatus_, Koll., _Olisthopus Maderensis_, Woll., _Caulotrupis conicollis_, Woll., _Laparocerus morio_, Schoen., _Omias Waterhousei_, Woll., _Helops Vulcanus_, Woll., and the _Ellipsodes glabratus_, Fab., being also larger on that rock than is typical: all of them, however, with the exception of _Notiophilus geminatus_, are there, as elsewhere, apterous. Other qualifying results, from isolation, are equally apparent. Take _colour_, for instance; and we shall perceive that in the _Dromius sigma_, Rossi, it is sensibly affected. The normal state of that insect "does not occur at all in Madeira proper, but only in Porto Santo. True it is that the modifications in the several islands present but slight differences _inter se_; nevertheless, being constant, I would lay particular stress upon them, since they go very materially to prove that the effects of isolation on external insect form are even more important, if possible, than those of latitude. That this is the case in the present instance, appears clear from facts so minute as these. For, out of the many specimens which have come under my observation from various countries of Europe, if there is one point more constant than another in this otherwise variable species, it is, I believe, to all circumstances, its immaculate prothorax. Now, whilst this (we may almost say essential) character obtains in Porto Santo, in Madeira it does not hold good: the prothorax there is invariably infuscate in the centre; and on a small adjacent rock (the Ilheo de Fora) it is entirely dark. Nor let anyone suppose that details apparently so trivial are beneath our notice, or the mere result of chance, since it is by the observation of such-like points, and by marking their development according to the circumstances of the several localities in which they obtain, that we are alone able to appreciate their importance, and so to form, in a wider and geographical sense, a correct estimate of their value[40]." The _Olisthopus Maderensis_, Woll., is much paler, larger, and more opake, on the Dezerta Grande than it is in Madeira proper. So great indeed is the change which it has undergone through a long isolation