The suggestion advanced by Darwin (p. 353), that young snails just hatched might sometimes adhere to the feet of birds roosting on the ground and thus be transported, appears to me so extremely improbable as to be scarcely worth serious consideration. Indeed, as Darwin himself acknowledged later on, it does not help us very much to suggest possible modes of transport. What we require is direct evidence. How far we are, however, from obtaining it, may be inferred from Mr. Kew's remark (p. 119), that "we have little or no actual evidence of precise modes of dispersal even for short distances on land." A very curious statement was made by a well-known French conchologist, the late M. Bourguignat, with regard to introductions of mollusca. Whether he had any actual facts collected in support of it, I cannot say, but he maintained that species accidentally transported, with the exception of those under maritime influence, can only be acclimatised from north to south, and not from south to north--from east to west, but not from west to east (p. 353). The whole theory of the accidental or abnormal dispersal of mollusca appears to have been originated by Darwin, in order to account for their presence on so-called _Oceanic islands_. His views were strongly supported by Wallace, who defines these islands (p. 243) as those which are of volcanic or coralline formation usually far from continents, entirely without indigenous land mammals or amphibians, but with a fair number of birds and insects, and usually with some reptiles. I do not wish it to be understood that I am in any way undervaluing the great works of these distinguished naturalists. Darwin's views have had more influence in advancing Zoology than those of any man, and his fame is unassailable. Nevertheless, I feel that his theories regarding the origin of the faunas of oceanic islands require revision.