appearance of the Primates. At that period, there existed lemurs in Europe and America, of a transitional type, showing points of resemblance to the hoofed animals of the same age, the ancestors of our own horses and tapirs. The Eocene was the epoch of the first great placental mammalian population, and we know that in such early epochs of each main class, when the class is assuming a dominant position, it always possesses an immense plasticity, rapidly dividing and subdividing into more and more definitely specialized types. Accordingly, it was probably as early as this period that the ancestors of the higher apes began to differentiate themselves from the ancestors of the modern lemurs. All analogy shows us that these divisions begin a long way down in time, proceed rapidly at first, and grow less rapid as the various creatures become more and more specialized, so losing their original plasticity.
In the Miocene, the specialization of the Primates must have continued very fast; for as early as the mid-Miocene strata we find in Continental Europe a large anthropoid ape, identified by good authorities as a close relation of the modern gibbons. Other apes of the same date are similarly identified as nearly allied with other living genera. Hence the question naturally arises—if the bifurcation of the Primates had already proceeded so far in the mid-Miocene period that even existing genera of higher apes had been fairly well demarkated, must not the ancestors of man have already begun to be generically distinct from the ancestors of the other anthropoids? Is it not consonant with analogy to suppose that the monkey group should have separated from the lemur group in the Eocene; that the anthropoid apes should have separated from the monkeys in the lower Miocene; and that the human genus (as distinct from the fully developed human species) should have separated from the anthropoid apes in the mid-Miocene? There seems to be good reason for this conclusion.
In mid-Miocene strata at Thenay, the Abbé Bourgeois has found certain split flints, some of them bearing traces of fire, which he believes to be of artificial origin; and in this belief he is upheld by M. de Mortillet, Dr. Hamy, MM. de Quatrefages, Worsaae, and Capellini, and other distinguished anthropologists. Specimens may be seen in the Musée de St. Germain, almost as obviously human in their workmanship as any of the St. Acheul type. M. Delaunay has similarly found a rib of an extinct manatee, which seems to have been notched or cut with a sharp instrument; and M. Ribeiro, of the Portuguese geological survey, has noted wrought flints in the Miocene deposits of the Tagus, which he exhibited in Paris in 1879. On the evidence of these and other facts M. de Mortillet pronounces in favor of what he calls Tertiary man. But as he carefully distinguishes him from Quaternary man, "l'homme de St. Acheul"—the river-drift man of Professor Dawkins—I suppose he means to imply that this species, though belonging to the same genus as ourselves, was yet so far unlike us, so
