An excellent example of this is offered by the development of “cannon-bones” in the lower portion of the limbs of the members of the horse tribe on the one hand and those of the deer and antelopes on the other; the object of this lengthening and strengthening of this part of the limb being in both instances the attainment of increased speed. Whereas, however in the one instance the cannon-bone is formed from one original element, in the other it is the result of the fusion of two such elements. In this case, indeed, the difference in the structure of this part of the skeleton in the two groups is so apparent as to leave no reasonable doubt as to the remoteness of the affinity between their respective ancestors. There is, however, a certain group of extinct South American hoofed mammals in which the cannon-bone corresponds exactly in origin and structure with that of the horse, from which it might be assumed that the two animals were closely related, whereas, from other evidence, we know that they are widely sundered. Approximately similar structures are therefore in many instances far from being indications of genetic affinity between the animals in which they respectively occur. Before the occurrence of this parallelism was recognised by naturalists as an important factor in their development, such resemblances were, however, frequently regarded as indications of a common parentage, so that animals which had comparatively little to do with one another were brigaded as members of the same assemblage. With these preliminary remarks, we may proceed to a general survey of Sir William’s zoological work. It has, however, been found convenient to relegate the consideration of his numerous memoirs on the Cetacea to the next chapter, by which means their connection will be made more apparent than if they were discussed among those on other sections of zoology. The first zoological paper (and indeed the first scientific work of any description) published by Flower seems to have been that on the dissection of one of the African lemurs belonging to the genus _Galago_, which appeared in the Zoological Society’s _Proceedings_ for 1852, and serves to prove, as mentioned in the first chapter, that the author was at that time holding the post of Curator of the Museum of the Middlesex Hospital. The paper itself is of little importance, dealing only with the structure of the muscles and viscera of the species in question. The next paper on the list, which appeared in the same journal for 1860, was also written during this part of Flower’s career; it is one of the few devoted to the anatomy of birds, and describes the gizzard of the Nicobar pigeon and other graminivorous species.