At St. Paul's Rocks, once more, a mass of new volcanic peaks rising abruptly from the midst of the Atlantic, the naturalist of the 'Beagle' notes with interest that feather and dirt-feeding and parasitic insects or spiders are the first inhabitants to take up their quarters on recently formed oceanic islands. This problem of the peopling of new lands, indeed, so closely connected with the evolution of new species, necessarily obtruded itself upon his attention again and again during his five years' cruise; and in some cases, especially that of the Galapagos Islands, the curious insular faunas and floras which he observed upon this trip, composed as they were of mere casual straylings from adjacent shores, produced upon his mind a very deep and lasting impression, whose traces one may without difficulty discern on every second page of the 'Origin of Species.' On the last day of February, 1832, the 'Beagle' came to anchor in the harbour of Bahia, and young Darwin caught sight for the first time of the mutually strangling luxuriance of tropical vegetation. Nowhere on earth are the finest conditions of tropical life more fully realised than in the tangled depths of the great uncleared Brazilian forests, which everywhere gird round like a natural palisade with their impenetrable belt the narrow and laborious clearings of over-mastered man. The rich alluvial silt of mighty river systems, the immemorial manuring of the virgin soil, the fierce energy of an almost equatorial sun, and the universal presence of abundant water, combine to make life in that marvellous region unusually wealthy, varied, and crowded, so that the struggle for existence is there perhaps more directly visible to the seeing eye than in any other known portion of God's universe. 'Delight itself,' says Darwin in his journal, with that naive simplicity which everywhere forms the chief charm of his direct and unaffected literary style--'delight itself is a weak term to express the feelings of a naturalist who for the first time has wandered by himself in a Brazilian forest. The elegance of the grasses, the novelty of the parasitical plants, the beauty of the flowers, the glossy green of the foliage, but above all the general luxuriance of the vegetation, filled me with admiration.' In truth, among those huge buttressed trunks, overhung by the unbroken canopy of foliage on the vast spreading and interlacing branches, festooned with lianas and drooping lichens, or beautified by the pendent alien growth of perfumed orchids, Darwin's mind must indeed have found congenial food for apt reflection, and infinite opportunities for inference and induction. Prom the mere picturesque point of view, indeed, the naturalist enjoys such sights as this a thousand times more truly and profoundly than the mere casual unskilled observer: for it is a shallow, self-flattering mistake of vulgar and narrow minds to suppose that fuller knowledge and clearer