Beginning with the skull--and, indeed, for present aim, limiting myself thereto--I have found that a vertical longitudinal section brings to light in greatest number and of truest value the differential characters between lowest _Homo_ and highest _Simia_. Those truly and indifferently interested in the question may not think it unworthy their time--if it has not already been so bestowed--to give attention to the detailed discussions and illustrations of the characters in question in the second and third volumes of the "Transactions of the Zoological Society."[2] The concluding memoir, relating more especially to points of approximation in cranial and denial structure of the highest _Quadrumane_ to the lowest _Bimane_, has been separately published. [Footnote 2: "Oseteological Contributions to the Natural History of the Orangs (_Pithecus_) and Chimpanzees (_Troglodites niger_ and _Trog. gorilla_)."] I selected from the large and instructive series of human skulls of various races in the Museum of the Royal College of Surgeons that which was the lowest, and might be called most bestial, in its cranial and dental characters. It was from an adult of that human family of which the life-characters are chiefly but truly and suggestively defined in the narrative of Cook's first voyage in the Endeavor.[3] [Footnote 3: Hawkesworth's 4th ed., vol. iii., 1770, pp. 86, 137, 229. The skull in question is No 5,394 of the "Catalogue of the Osteology" in the above Museum, 4to, vol. ii, p. 823, 1853.] Not to trespass further on the patience of my readers, I may refer to the "Memoir on the Gorilla," 4to, 1865. Plate xii. gives a view, natural size, of the vertical and longitudinal section of an Australian skull; plate xi. gives a similar view of the skull of the gorilla. Reduced copies of these views may be found at p. 572, figs. 395, 396, vol. ii, of my "Anatomy of Vertebrates." As far as my experience has reached, there is no skull displaying the characters of a quadrumanous species, as that series descends from the gorilla and chimpanzee to the baboon, which exhibits differences, osteal or dental, on which specific and generic distinctions are founded, so great, so marked, as are to be seen, and have been above illustrated, in the comparison of the highest ape with the lowest man.