Box 1: Obituary and biographical material; photographs; letters of Bidder to his wife and daughter Anna Bidder; and a list of holidays, dates, and companions, 1926-46.
Box 2: Poems; scientific notes and notebook; letters including 'Social life, mostly Naples'; coal crisis, 1915; and personal papers.
Box 3: Anna Bidder, family and personal correspondence; letters from Adolphe Portmann; letters and documents about Anna Bidder's work; testamentary papers on the Greenwood family; and family history.
Box 4: Notes on physiology and botany; letters from Naples, 1895; and 14 scientific notebooks.
Box 5: 30 scientific notebooks; experiments, drafts of papers.
Box 6: Scientific notebooks, mostly on sponges, 1886-92 and 1920-38.
Box 7: Letters to Bidder on science and from scientists, and essays on sponges, 1898 and 1922-25.
Box 8: Notes on sponges and a lecture on sponges, 1925; personal letters mostly to Bidder from his wife; and letters of other family and friends.
Box 9: The Danish Gas Company, 1853-1953, illustrated history; notes and drafts on sponges; and 'The ancient history of sponges and animals', BAAS address, 1927.
Box 10: Classification of sponges and notes on sponges; letters to and from Bogoslaw Dohrn, Naples, 1921.
Box 11: 18 scientific notebooks; drafts and proofs.
Box 12: Scientific notes; commonplace book with philosophical notes; sketchbook; and notebooks of poetry, c.1899-1902.
Box 13: 5 scientific notebooks; Guide to the aquarium of the Zoological Station, Naples, with MS notes; and correspondence with the Zoological Station, Naples, 1880s.
Box 14: Early, pre-1900 scientific papers; obituaries of W.H. Caldwell, E.J. Allen; and papers by E. Topsent.
Box 15: Address to the Marine Biological Association; miscellaneous notebooks and letters; and letters A-Z.
Box 16: Notes on sponges, c.1891; incomplete dissertation, 1888, on the physiology of sponges.
Box 17: University lectures, 1920-27; speech 'The management of capital'; notes on Altenburg's theory of the compound eye, c.1926; and letters from Bidder.
Box 18: Letters to Marion Greenwood Bidder (wife of G.P. Bidder), c.1887-1932, especially from pupils at Newnham College, 1896-1904.
Cambridge University Science Club, c.1885, photograph.