It seems that Nucella lapillus may follow the pattern described for certain other gastropods, of greater color variation toward the extremes of the geographic range. Ross described colorful populations way up there in Nova Scotia. I have seen similar populations in central Maine, with shells showing various shades of orange, yellow, grey, black, tan and brown, and often banded with a contrasting color, or with white. There are virtually no all-white shells in these populations. Only a hundred or so miles south, in central Massachusetts, north of Cape Cod, the species looks radically different. Around Plymouth are stretches of rocky shoreline with tens of thousands of Nucella, virtually every one of them pure white - in some areas, maybe a few brown ones mixed in, less than 1%. No bright colors, no banding at all. The shore structure, vegetation, and water temperature in these areas are very similar to those in Maine. However, south of Cape Cod, in southern Massachusetts, and moving down into Rhode Island, colorful and banded populations are again encountered, though not showing as much variation as the northernmost populations. The reference cited by Aydin is very interesting, as it suggests that the shell structure of these animals is environmentally, not genetically controlled. It is easy to see how populations in different habitats might evolve different phenotypes, but if artificially transplanting a population to a new habitat brings about such changes in next generation offspring, it is obvious the change is produced by environmental factors, not heredity. What might the actual mechanism(s) be? Any ideas? A stronger, thicker shell might provide protection from predators (though even "thin-shelled" Nucella lapillus still have a very strong shell), but certainly the presence of predators is not the stimulus that actually produces the change. Has anyone tried transplanting individuals from the central geographic range into habitats near the extremes of the range (or vice versa), to see if the observed color variations are environmentally induced? (Probably not, given that the environmental conditions at the two extremes of a species' range are often very different, while the conditions in the central range typically fall between those at the two extremes). Not likely that both cold and warm water could stimulate production of colored shells, while intermediate temperatures would cause white shells. Paul M.