Before coming to a decision on the part played by flotsam and jetsam in the constitution of an island fauna, those who have studied the problem on the spot should, however, have a voice in the matter. And though, from my experience in northern latitudes, I feel sure that island faunas there are but slightly affected by occasional dispersal of species, Mr. Hedley, who has made the fauna of the Pacific Islands his special study, assures me that drift migration plays an important _rôle_ in that region. I hope we may soon have a more detailed account of his particular observation bearing on this interesting subject. On the other hand, Mr. Simpson, who has gained considerable experience of oceanic dispersal in the West Indian region, though he acknowledges having often noticed bamboo rafts, which would be suitable in the transportal of invertebrates, nevertheless does not attach much importance to this means of distribution. "The fact," he remarks, "that the operculates (operculate land-shells) form so large a proportion of the Antillean land-snail fauna, that a majority of the genera are found on two or more of the islands and the mainland, while nearly every species is absolutely restricted to a single island, appears to me to be very strong testimony in favour of a former general land connection" (p. 428). Amphibians are affected in the same manner by sea-water as slugs are. The accidental transportal of an amphibian from the mainland to an island is therefore almost inconceivable. And the presence of frogs, toads, and newts in the British Islands, in Corsica and Sardinia, indicates, if nothing else did, that all these islands were at no distant date united with the continent of Europe. As regards the terrestrial reptiles, the case is somewhat different. Many of them readily take to the sea, and, as probably all snakes and some lizards are able to swim, it is possible that sometimes, though very rarely, they might reach islands if not too far from a continent. Instances of accidental transportal of land-reptiles to islands have actually been observed. But the fact of the occurrence of such instances by no means proves that reptiles thus conveyed are able to establish themselves permanently in their new home. Sir Charles Lyell records in his _Principles of Geology_ that a large boa-constrictor was once seen floating to the island of St. Vincent, twisted round the trunk of a tree. It appeared so little injured by its long voyage from South America, that it captured some sheep before it was killed.