  In the same vein of instinct vs. reason, Darwin in the Origin of Species wrote, “It is a significant fact, that the more the habits of any particular animal are studied by a naturalist, the more he attributes to reason, and the less to unlearnt instinct” (1871, Book I, p.46). He devoted considerable attention in both the Origin and in the Descent of Man to animal behavior, with the obvious goal of demonstrating mental continuity among the species. To make his case, Darwin relied heavily on anecdotes provided by his correspondents — a project infamously pursued after Darwin's death by his protégé George Romanes (1882). Darwin also carried out experiments and was a keen observer, however. In his final work he describes experiments on the flexibility of earthworm behavior in manipulating leaves, which he took to show considerable intelligence (Darwin 1881; see also Crist 2002).