The polymath of Rennes -- Discoveries and losses -- Ramón y Cajal's hunting case watch -- Beneath the faceted eye -- In the air and under the water : the olfactory brain -- The mushroom body enigma -- The brain within the brain -- Eight legs and more : chelicerates, myriapods, and some distant relatives -- Reiterations, appendages, and the ancient brain -- Philosophical anatomy, Swedish pioneers, and neuronal systematics -- Convergence or common descent? -- The origin of insects