This collection includes correspondence on natural history and evolution, and especially on his collection and study of shells from Japan and the Pacific islands. Principal correspondents include Louis Agassiz, Charles Robert Darwin, Sir William Henry Flower, Alpheus Hyatt, George Newbold Lawrence, George J. Romanes, Alfred R. Wallace, and the Linnean Society of London.

There are 153 letters in this collection, many addressed to Aubrey Lackington Moore, an English writer who tried to reconcile evolution and traditional Christianity. Some letters discuss scientific questions of the day, while others are formal social notes. Also includes 24 clipped signatures, inlcuding those of Sir Henry Wentworth Acland; Goerge Bentham; H. A. Bruce; S. H. Butcher; Matthewss Duncan; Percy Gardner; George Gritchett; G. Grote; Alfred Cort Haddon; Sir Prescott Gardner Hewitt; William Guyer Hunter; Thomas Henry Huxley; John Lingard; Thomas Babington Macauley; Miss K. Aubrey Moore; Louis Pasteur; Sir John Russell Reynolds, bart.; Thomas Smith; James Leigh Strachan-Davidson; Agnes Strickland; and Arthur Thomason.

Thomas Henry Huxley (1825-1895) was an eminent Victorian-era biologist, best known as a passionate defender and popularizer of Darwin's theory of evolution. His partisanship earned him the nickname of "Darwin's Bulldog," although he did not accept the theory uncritically. In addition to his work in biology, he performed original research in zoology and paleontology. He is also remembered as the progenitor of a family of highly successful scientists and thinkers. This collection is made up of letters, primarily written by Huxley, on a variety of topics including the age of man, evolution, education, natural history, science, geology, spiritualism, and vivisection. The most voluminous correspondence is with Sir James Thomas Knowles (30 letters) and with Huxley's daughter, Ethel Huxley Collier, "Babs," (44 items). The 30 letters to Knowles appear in neither the Life and Letters, nor are they listed in Dawson's guide to the Huxley Papers at the Imperial College. The other major correspondents include Charles Edward C. Appleton, Matthew Arnold, William B. Carpenter, Sir Henry Cole, George Dixon, Sir John Donnelly, Thomas Campbell Eyton, Sir William Henry Flower, Sir Joseph Dalton Hooker, Leonard Huxley, Sir William Jenner, Sir Charles Lyell, Louis Compton Miall, Alphonse Milne-Edwards, Sir James Paget, Harry Quilter, Harry Govier Seeley, Alfred R. Wallace, and William Crawford Williamson.

The collection is a miscellaneous group of letters of mainly British scientists and physicians, purchased as an existing autograph collection. There are a few American signatures. The letters are primarily from the nineteenth century and focus on medical and geological topics, but also there are some earlier and later dates. In addition to the letters are anatomical drawings of surgery, sketches of bones, and one geological notebook.

These are primarily letters to Gray on various aspects of natural history, with many references to collections at the British Museum of Natural History. There are numerous letters from British scientists and from European colleagues. There are letters from Americans too, such as those from Agassiz which relate to his Florida expeditions and the creation of natural history collections.

One of the most important natural historians in nineteenth century Britain, Charles Darwin provided the first compelling mechanism to account for organismal evolutionary change. Although lacking a coherent model of heredity, Darwin's natural selection has exerted an enormous influence over the biological sciences and since the introduction of Mendelian genetics, had remained the key unifying principle in the discipline. The APS Darwin Papers are a large a valuable assemblage of Darwin's correspondence with scientific colleagues, including Charles Lyell and George J. Romanes. They are included in the print version of the Correspondence of Charles Darwin (Cambridge Univ. Press).

There is correspondence concerning geology, botany, natural history, natural selection, evolution, British science and scientists, and other scientific topics. Most of the letters are written by Lyell, with a very few items by others.