 Gulick (1873) points out that with natural selection, one can assume that where different forms are found, different external conditions will also be found (with the different forms having adapted over the course of generations to the different external conditions). However, there seem to be cases (e.g., among snails) where the external conditions are very similar, yet the organismic forms are very different. He notes that these species tend to occupy very small areas, even though there is reason to believe it is not because they lack the ability to migrate further. He then postulates a scenario: Suppose some members of a species migrate to a new area where they are free from competition and largely separated from the original population. New variations will arise in the new population, but unless they are “decidedly malformed”, they will persist. The new population will thus come to differentiate itself from the original population (e.g., with new shades of color or with variations of shape), perhaps rapidly if there is a “preexisting tendency to rapid variation”.