that there are real physical agents, independently of heat and cold, which are unfavourable in Ireland to the existence of these lower creatures. We may perhaps be told, by the advocates of Professor Forbes's theory, that it is the result of isolation,--the quondam land of passage having been broken up before the proper complement of species had reached this large portion of their western destination. But even this, although I believe it to contain much presumptive truth, will not altogether suffice to account for the phaenomena which we see; for Ireland is not only remarkable for the paucity of its _species_, but also for the paucity of its _individuals_,--and the latter fact cannot be explained by any stretch of the migration-hypothesis. We are compelled therefore to conclude, that Ireland, like the other countries to which we have already alluded, presents conditions (altogether irrespective of _latitude_) which must be regarded as adverse to the general prosperity of the insect races. And so it is with _localities_ (no less than with larger countries),--many of which are eminently unproductive, when compared with others situated at but a short distance from them. Thus, the south-western corner of England is by far the most unprofitable portion of our island, unless indeed I am much mistaken, for insect ascendency. I have made some remarks on this subject in the 'Zoologist,'--from which I extract the following: "Unlike the easy collecting to which we are accustomed in the more favoured East, miles of unprofitable country have often to be gone over, be it swampy moorland or iron-bound coast, where scarcely an insect is to be seen; or, at any rate, where the few which exist are so ordinary, and so sparingly dispersed, as to be scarcely worth the labour of obtaining them,--more especially since the identical species are many of them to be met with in the utmost profusion in more central, or eastern districts. Whether it be the moisture of the climate, or the violence of the south-west winds, which (continually sweeping, as they do, over the high central mass of Devonshire and the bleak, barren downs of Cornwall) present as great an obstacle to the development of animal, as they clearly do of vegetable life, I will not venture to suggest; yet certain it is, from observation, that insects not only become fewer in number in proportion as they are exposed to these external agencies of wind and water; but likewise, in many instances, diminish so considerably in stature as to be scarcely reconcileable with their normal types[20]."