Correspondence, 1887-1925, mainly between Dendy and fellow academics relating to the morphology and classification of sponges, notably with George Parker Bidder, President of the Marine Biological Association of the UK; Professor William John Dakin, Professor of Zoology, University of Liverpool; Francisco Ferrer Hernandez, Musea de Gencias Naturales, Madrid, Spain; Professor William A Haswell, Emeritus Professor of Biology, University of Sydney, Australia; Ernst Hentschel, Zoologisches Museum, Hamburg, Germany; William Abbott Herdman, University of Liverpool; Professor Sydney John Hickson, Emeritus Professor of Zoology, University of Liverpool; Randolph Kirkpartick, Natural History Museum, London; Professor James Herbert Orton, Emeritus Professor of Zoology, University of Liverpool; Joseph Pearson, Director of the Columbo Museum, Ceylon; and Edgar Thurston, Superintendent of the Government Museum, Madras, India. The correspondence also includes letters, 1919-1921, relating to the establishment of a research grant in memory of Harold Row, Dendy's assistant. Papers, 1886-1899, relating to sponge collections, particularly specimens in Australia and New Zealand, and including the dredging records for Port Phillip, Victoria, Australia, 1887-1890. Lecture notes written by Dendy, [1903-1925], including handwritten texts of lectures on 'Echinodermata', 'The development of starfish', 'Holothurioidea', 'Class Gastropoda', 'Mytilus', 'Anodarta cygnea', 'Helix', 'Mollusca', and 'Merozoa', and typescript texts of public lectures including 'The stream of life', given at a Citizens' Lecture in Edinburgh, 1921, and 'The evolution theory today', given at the Liverpool Meeting of the British Association for the Advancement of Science, 1923. Working notebooks, [1886]-1912, mainly containing scientific experiments and observations relating to sponges, notably the Challenger Amphipoda and the Grantia Compressa, and notes on the topographical distribution of, and biographical references to, sponge specimens. Two notebooks, 1917-1919, recording experiments and observations during Dendy's membership of the Royal Society's Committee for the Investigation of Grain Pests. Papers, 1892, relating to The Victorian land planarians [1894] by Dendy, comprising a volume of annotated and revised extracts from that work, and a letter to Dendy from Thomas Steel concerning flatworm species. Printed obituaries of Dendy, 1925-1926. Papers relating to the study of lizard-like reptiles commonly known as Tuatara (the scientific name being Sphenodon), [1897]-1910, including correspondence, 1908-1910, between Dendy and Edward Bles, Elliot Smith, Annie Howes and [William Thompson] Sedgwick, and catalogues, notes and photographs of Tuatara embryos.

The collection centres on Wallich's work on biology, particularly marine biology, and his belief that other figures in the field were ignoring or plagiarising his discoveries. As well as his notes, it includes a collection of offprints by Wallich (MS.4969) and a collection of offprints by other scientists, with Wallich's comments (MS.4970).