To discuss this important paper in detail on the present occasion is quite unnecessary; and it will suffice to state that it has formed the basis on which all modern classifications of the group are framed. Indeed it has been accepted by most writers with little or no modification. In this scheme it was proposed to divide mammals into three primary groups, or sub-classes, namely, Prototheria, or Ornithodelphia, as represented only by the egg-laying group; Metatheria or Didelphia, including the pouched group, or marsupials; and Eutheria or Monodelphia, comprising the whole of the remaining or placental groups. Of late years, owing to the discovery of unexpected relationships between placentals and marsupials, it has been proposed to recognise only two sub-classes of mammals: the Eutheria, comprising the two groups last mentioned, and the Prototheria, or monotremes. The scheme chiefly differed from the one proposed some years earlier by Huxley in the inclusion of the Hyracoidea (klipdass) and Proboscidea (elephants) as sub-orders of the Ungulata, instead of their forming separate orders by themselves. In this instance Flower ranked the Artiodactyla, Perissodactyla, Hyracoidea, and Proboscidea as equivalent sub-orders of Ungulata, but later on he brigaded the two former together as Ungulata Vera, and the two latter as Subungulata. The above scheme was employed by Flower in the article “Mammalia,” written by him for the ninth edition of the _Encyclopædia Britannica_, the volume containing which appeared in 1883. This article, with others by himself and other authors, formed, as will be noticed later on, the basis of the _Study of Mammals_ published in 1891. Among other articles contributed by Flower to the _Encyclopædia_ were those on the Horse, Kangaroo, Lemur, Lion, Mastodon, Megatherium, Otter, Platypus, Rhinoceros, Seal, Swine, Tapir, Whale, and Zebra. The aforesaid scheme of classification was likewise used in the second part of the “Catalogue of Osteological Specimens in the Museum of the Royal College of Surgeons,” which was written with the assistance of Dr. Garson, and appeared in 1884. Since this valuable work has been already noticed at some length in the chapter devoted to Flower’s official connection with the College of Surgeons, it need not be further referred to in this place, except that the writer may again take the opportunity of expressing his regret that the views on nomenclature there enunciated have not met with acceptance among the modern school of naturalists. At the “Jubilee” meeting of the Zoological Society, held in June 1887, Flower, as President, read an address on the “Progress of Zoological Science” during the reign of Queen Victoria, which appeared in the _Report_ of the Council of that year, and to which reference has been made in an earlier chapter.