  Privately, Darwin early on decided he could not practice medicine. But his already serious inclination toward science was considerably strengthened at Edinburgh both by some fine scientific lectures in chemistry, geology and anatomy and by the mentoring of Dr. Robert Grant. Grant certainly knew that young Charles was Erasmus Darwin’s grandson; Grant expounded evolutionary ideas derived from Jean-Baptiste Lamarck and Charles’ grandfather. But his primary gift to Charles was introducing him to marine invertebrate anatomy and the use of the microscope as a scientific tool and as an aid to dissecting extremely small creatures dredged out of the Firth of Forth. Darwin joined an Edinburgh scientific society, the Plinean society, of which Grant was a prominent member, and presented two lectures that reported discoveries he had made while working with Grant. This interest in marine invertebrates was to be a life long obsession, climaxing in his massive four-volume contribution to the comparative anatomy and systematics of fossil and living Cirripedia or ‘barnacles’ (Barrett &amp; Freeman 1988, vols. 11–13).