René-Antoine Ferchault de Réaumur
René-Antoine Ferchault de Réaumur (1683-1757) is better known today as the inventor of the alcohol thermometer, whose temperature scale is named after him. However, to most biologists Réaumur is known as the man who in 1712 presented to the French Academy a remarkable paper on crayfish limb regeneration ("Sur les diverses reproductions qui se font dans les Ecrevisse, les Omars, les Crabes, etc. et entr'autres sur celles de leurs Jambes et de leurs Ecailles". Mem. Acad. Roy. Sci., pp.223-245). The paper is beautifully illustrated by the author and clearly demonstrates the ability of these animals to regenerate missing limbs.
A very interesting recount of Réaumur's work can be found in Charles E. Dinsmore's "A History of Regeneration Research: Milestones in the Evolution of a Science". The book can also be purchased through Cambridge University Press.

Below, an excerpt from one of Réaumur's drawings is shown illustrating the successive stages of limb regeneration in the crayfish.