In Darwin's second year at the university, he joined the Plinian Society, a student natural-history group featuring lively debates in which radical democratic students with materialistic views challenged orthodox religious concepts of science. He assisted Robert Edmond Grant's investigations of the anatomy and life cycle of marine invertebrates in the Firth of Forth, and on 27 March 1827 presented at the Plinian his own discovery that black spores found in oyster shells were the eggs of a skate leech. One day, Grant praised Lamarck's evolutionary ideas. Darwin was astonished by Grant's audacity, but had recently read similar ideas in his grandfather Erasmus' journals. Darwin was rather bored by Robert Jameson's natural-history course, which covered geology—including the debate between Neptunism and Plutonism. He learned the classification of plants, and assisted with work on the collections of the University Museum, one of the largest museums in Europe at the time.