Natural Selection in Cepaea

HE remarkable variation in colour and ornamentation of the shell which T is shown by certain gastropods has attracted the attention of collectors for many years. Recently, several studies of this variation have appeared, which unfortunately lead to very diverse conclusions on its mechanism of maintetenance and its significance in evolution. One of the commonest and most strikingly variable snails of Europe is Cepaea nemoralis, which has been studied in considerable detail by several workers, mainly in Europe but also in the U.S.A. where it has been successfully introduced. DIVER (1940) has concluded that its range of variation is wholly random, BOETTGER (1931) that on the contrary it is determined by natural selection, while LAMOTTE (1951) believes that for banding, at least, it is maintained in each colony primarily by mutation, and SCHILDER (1950) by gene flow.