From my position at the Zoological Society and from the aid received from numerous correspondents in all parts of the world, I had little difficulty from the first in providing my much-esteemed friend with materials for his studies, and in the beginning of 1871 had the pleasure of putting at his disposal some notes and materials concerning the Antelopes of the genus _Tragelaphus_. Upon these was based the excellent paper on that genus read by Sir Victor before the Zoological Society on the 16th of May of that year, the first of a series of essays on this and kindred subjects. Four similar papers, as will be seen by reference to the Zoological Society’s ‘Proceedings,’ followed in 1872, three in 1874, and others in succeeding years, until 1878, when, I regret to say, they came to an abrupt conclusion. The last of the series was one of an extremely useful and important character, containing, as it did, a complete essay on the classification of the Deer-family and a synopsis of the existing species, which, until recently, has remained our leading authority upon this difficult group of Mammals. During the whole of this time also Sir Victor had been engaged in collecting specimens, and in having drawings made by Wolf and put upon the stone by Smit, for a complete work on the Bovine animals which he had planned out and proposed to write. After 1878, however, other matters intervened and sadly interfered with my friend’s studies in Natural History. Sir Victor changed his habitual residence to Pau, and though I now saw him occasionally in London on his way from France to his home in Ireland, I could never induce him to continue his former researches, although he always assured me that he was still devoted to Natural Science and was determined to return to it eventually. Circumstances, however, prevented him from carrying his wishes into effect. In November 1891, when still in the prime of life, Sir Victor died, leaving his great work still unfinished, and represented mainly by a series of over a hundred lithographic plates, which, as already mentioned in the Introduction, have formed the basis of the present work. The MSS. which were also kindly placed at my disposal by the family, not having been touched for nearly fifteen years, were in such an incomplete state that it was impossible to utilize them. Upon pointing out this to his son, the present Sir Douglas Brooke, he was good enough to assure me that his only wish was that the best possible use for Science should be made of the whole of the materials accumulated by his father. Acting upon this understanding I undertook to prepare the letterpress of an entirely new work on the Antelopes, using such of Sir Victor’s plates as I could employ for its illustration.