Of much more importance than either of the foregoing were two contributions to mammalian anatomy made by Sir William during the year last mentioned. The one, which appeared in the _Medical Times and Gazette_, was the report of “Lectures on the Comparative Anatomy of the Organs of Digestion in the Mammalia, delivered at the Royal College of Surgeons in February and March, 1872.” In this article, which is well illustrated, will be found descriptions of the various forms assumed by the stomach in a large number of the ordinal and family groups; especial attention being directed to the remarkable complexity of that organ in the porpoise. The other, which was published in _Nature_, and in abstract in the _Report_ of the British Association, dealt with the arrangement and nomenclature of the lobes of the mammalian liver. It is, perhaps, one of the most valuable of the author’s contributions to visceral anatomy; and introduced order and precision where confusion had previously reigned. The names then given to the different lobes of the liver have been very generally adopted in zoological and anatomical literature. In 1873 Flower delivered before the Royal Institution a lecture on palæontological evidence of gradual modification of animal forms, which is published in the _Proceedings_ of that body for the same year. In this he touched on the important evidence afforded by the discoveries which had then been recently made in North America in favour of the derivation of one animal form from another, directing particular attention to the case for the evolution of the horse. Another paper on the same subject appears in the _British Medical Journal_ for 1874; while, as noticed below, Sir William again lectured on palæontological evolution in 1876. The year 1874 was noteworthy, so far as palæontology is concerned, by the appearance in the _Philosophical Transactions_ of the Royal Society of a paper by Flower on part of a remarkable mammalian skull from Patagonia, described under the name of _Homalodontotherium cunninghami_. In justice to the author, it should be said that he was not responsible for the undue length of the generic name, which had been bestowed by his friend Huxley four years previously in the Geological Society’s _Journal_, and which Flower was therefore compelled to employ. It refers to the fact that the jaws of the new animal are remarkable for the even and unbroken wall formed by the teeth, which show no enlarged tusks. At the time the geological age of this interesting fossil was quite unknown; but it formed the forerunner of the marvellous discoveries of the remains of fossil mammals of middle tertiary age in Patagonia, which have been made of late years, and have done so much to increase our knowledge of the past life and history of the South American Continent.