earliest remains of fossilised vertebrates, Silurian primitive fishes (selachii) and ganoids. These are followed, in the Devonian system, by the first dipneust fishes (a transitional form from the fishes to the amphibia). In the next, the Carboniferous system, we find the first terrestrial or four-footed vertebrates--amphibians of the order of the stegocephala. A little later, in the Permian rocks, the earliest amniotes, lowly, lizard-like reptiles (tocosauria), make their appearance; the warm-blooded birds and mammals are still wanting. We have the first traces of the mammals in the Triassic, the earliest sedimentary rocks of the mesozoic age; these are of the monotreme sub-class (pantotheria and allotheria). They are succeeded by the first marsupials (prodidelphia) in the Jurassic, the ancestral forms of the placentals (mallotheria), in the Cretaceous. See p. 115. But the richest development of the mammal class takes place in the next or Tertiary age. In the course of its four periods--the eocene, oligocene, miocene, and pliocene--the mammal species increase steadily in number, variety, and complexity, down to the present time. From the lowest common ancestral group of the placentals proceed four divergent branches, the legions of the carnassia, rodents, ungulates, and primates. The primate legion surpasses all the rest. In this Linné long ago included the lemurs, apes, and man. The historical order in which the various stages of vertebrate development make their successive appearance corresponds entirely to the morphological order of their advance in organisation, as we have learned it from the study of comparative anatomy and embryology. These paleontological facts are among the most important proofs of the descent of man from a long series of higher and lower vertebrates. There is no other explanation possible except evolution for the chronological succession of these classes, which is in perfect harmony with the morphological and systematic distribution. The anti-evolutionists have not even attempted to give any other explanation. The fishes, dipneusts, amphibians, reptiles, monotremes, marsupials, placentals, lemurs, apes, anthropoid apes, and ape-men (pithecanthropi), are inseparable links of a long ancestral chain, of which the last and most perfect link is man. (_Cf._ the tables pp. 116-118.)