Long Island Sound snail, the channeled and knobbed whelks. Crustaceans include crabs, shrimp and lobsters. In the Sound there are the green crab (a non-native species first reported in Boston around 1900, but a common crab found on the shore, where it feeds on eastern oysters and soft-shell clams), blue crab, red crab, Jonah crab in deepwater areas, and the Atlantic rock crab, which settles in large numbers along rocky shores, especially around Millstone Point, Niantic Bay and Fishers Island Sound. Other crabs found include the lady crab, spider crabs, and fiddler crabs; hermit crabs and mole crabs are also found. By the
On the Origin of Species an incipient species" and that "species are only strongly marked and permanent varieties". He argues for the ubiquity of variation in nature. Historians have noted that naturalists had long been aware that the individuals of a species differed from one another, but had generally considered such variations to be limited and unimportant deviations from the archetype of each species, that archetype being a fixed ideal in the mind of God. Darwin and Wallace made variation among individuals of the same species central to understanding the natural world. In Chapter III, Darwin asks how varieties "which I have called incipient species"