[Professor Huxley as a naturalist, educator, and controversialist was one of the commanding figures of the nineteenth century. To physiology and morphology his researches added much of importance: as an expositor he stood unapproached. As the bold and witty champion of Darwinism he gave natural selection an acceptance much more early and wide than it would otherwise have enjoyed. In 1876 he delivered in America three lectures on Evolution: the third of the series is here given. All three are copyrighted and published by D. Appleton & Co., New York, in a volume which also contains a lecture on the study of biology. Since 1876 the arguments of Professor Huxley have been reinforced by the discovery of many fossils connecting not only the horse, but other quadrupeds, with species widely different and now extinct. The most comprehensive collection illustrating the descent of the horse is to be seen at the American Museum of Natural History, New York, where also the evolution of tapirs, camels, llamas, rhinoceroses, dinosaurs, great ground sloths and other animals are clearly to be traced--in most cases by remains discovered in America. A capital book on the theme broached by Professor Huxley is "Animals of the Past," by Frederic A. Lucas, Curator of the Division of Comparative Anatomy, United States National Museum, Washington, D. C., published by McClure, Phillips & Co., New York. "The Life and Letters of Professor Huxley," edited by his son, Leonard Huxley, is a work of rare interest: it is published by D. Appleton & Co., New York.] The occurrence of historical facts is said to be demonstrated, when the evidence that they happened is of such a character as to render the assumption that they did not happen in the highest degree improbable; and the question I now have to deal with is, whether evidence in favour of the evolution of animals of this degree of cogency is, or is not, obtainable from the record of the succession of living forms which is presented to us by fossil remains. Those who have attended to the progress of palaeontology are aware that evidence of the character which I have defined has been produced in considerable and continually-increasing quantity during the last few years. Indeed, the amount and the satisfactory nature of that evidence are somewhat surprising, when we consider the conditions under which alone we can hope to obtain it.