In 1868, the Biological department of the Academy, through union with the Microscopical Society of Philadelphia became the Biological and Microscopical Section of the Academy. This continued to 1924, when the Section became the Leidy Microscopical Club. The minutes of the Club are contained in Coll. 295, relating to the Biological and Microscopical Section.

This collection contains correspondence, a list of the Club's property (1930), an account of a meeting, and 5 letterpress annual programs of expeditions (1923-1927), prepared by joint committees including George L. Pennock, Eva B. Gadsby, Frank J. Keeley and Chalkley T. Palmer. The first two of these programs are for the Biological and Microscopical Section in collaboration with the Mineralogical and Geological Section.