[Revised entry by Roberta L. Millstein on March 13, 2026.
Changes to: Main text, Bibliography]
In the 1950s, a lively debate broke out among biologists that continues to this day, over what might seem like the most unlikely of organisms: the land snail, Cepaea nemoralis. Yet, there are in fact some interesting aspects to C. nemoralis. This species of snail is polymorphic; the snail’s shell varies in color (pink, brown, and yellow) as well as the number of visible bands (anywhere from 0 – 5). But the colors and bands are not equally distributed across populations. In some populations, pink…

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