This section of the Academy had its origin in the union of the Philadelphia Biological Society (1857-58) with a biological group of the Academy in 1858, forming the Biological Dept. of the Academy. Some members, wishing to emphasize microscopy, engineered a change in 1868, when, by agreement with the Academy, the name was changed to the Biological and Microscopical Department of the Academy.

In 1866 the Academy established “sections”. Soon after, apparently in 1868, the department became the Biological and Microscopical Section of the Academy. Sections were discontinued in 1924, when the organization united with the Geological and Paleontological Section to become the Leidy Microscopical Club.

In 1956, Mrs. W. Hersey Thomas, a member of long standing in the Club, undertook to make an index to the minutes. The work was interrupted when her eyes failed, so that only the time between 1857-1885 is covered by this index.

The minute books have been deposited in the library, only the one currently used remaining in the possession of the Club's secretary.