It is, perhaps, one of the most interesting discoveries of modern geology, that certain races of animals now extinct have in various ways assumed some of the characteristics presented by animals much higher in the scale of being, that flourish in the present day. It seems as if there had been some strange law of anticipation at work, if we may venture so to formulate the idea. It has already been shown how the great saurians Ichthyosaurus and Plesiosaurus presumed to put on some of the characters of whales, and to play their _rôle_ in nature, though they were only reptiles; how the carnivorous Dinosaurs acquired teeth like those now possessed by lions and tigers, which also are mammals; and now we find herbivorous Dinosaurs imitating the Glyptodon, an armadillo that lived in South America almost down to the human period. We shall not lose sight of this very interesting and curious discovery, for other cases will present themselves to our view in future chapters. The reader might ask, "If reptiles were able in these and other ways to imitate the mammals of to-day, or of yesterday, why should they not have been able to go a few steps further, and actually _become_ mammals?" The Evolutionist, if confronted with such a question, would say, that there is no evidence of Dinosaurs turning into mammals, but that both may have branched off at an early geological period (say the Permian) from a primitive group of reptiles, or even of amphibians. It must be borne in mind that, during the "age of reptiles" (Mesozoic period), the mammalian type was but feebly represented by certain small and humble forms, probably marsupials. As far as we know, there were no big quadrupeds such as flourish to-day; therefore reptiles played their part, and in so doing acquired some of their habits and structural peculiarities. It is difficult for us, living in an age of quadrupeds, to realise this, and to picture to ourselves reptilian types posing as "lords of creation," or, to use a homely phrase, "strutting in peacock's feathers." * * * * *