The Dispersal of Shells

Abstract

IT is strange that we have had to wait so long for a manual on dispersal. Many books have been written on the geographical distribution of animals and plants; and islands and even continents have been raised or lowered to account for the strange anomalies. Yet comparatively little attention has been paid to a study that must be undertaken before we are qualified to express an opinion on geographical distribution. Darwin and Lyell, however, thoroughly recognised the importance of the subject, and the former made many experiments on the vitality of seeds under trying circumstances—such as being immersed in sea-water, or eaten by birds. Direct observation of the species in transit, under natural conditions, has been less attended to, except in the case of flying animals and of certain plants. The cause of this neglect is easy to understand: dispersal, in the groups that are not specially modified to assist the process, is mainly the result of the accumulation of rare accidents, such as would only occasionally be noticed by some naturalist engaged in quite different observations. It is useless to go into the field on purpose to watch the dispersal of snails; the entomologist, ornithologist, fisherman, or sportsman may once in a season obtain a direct observation, and it is to such observers that we must principally trust.

The Dispersal of Shells: an Inquiry into the Means of Dispersal possessed by Fresh-water and Land Mollusca.

By Harry Wallis Kew With a Preface by Alfred Russel Wallace, LL.D., F.R.S. With Illustrations. Pp. xi. 291. International Scientific Series, Vol. lxxv. 8vo. (London: Kegan Paul, Trench, Trübner and Co., 1893.)