From the amphibians (probably from extinct forms, not from living) there arose the highest three classes of vertebrates—the true reptiles, the birds, and the mammals—all of whom have lungs and breathe air from the beginning to the end of their days. Gills, as organs of breathing, disappear forever, being changed, as has been said, into parts of the organs of mastication and hearing. In the reptiles first appear those organs which in the highest races overflow on occasions of tenderness and grief, the tear glands. These organs are, however, in our cold-blooded antecedents, organs of ocular lubrication rather than of weeping. There are but four small orders of existing reptiles—snakes, turtles, lizards, and crocodilians. These are the pygmean descendants of a mighty line, the last of a dynasty which during the greater part of the Mesozoic ages was represented by the most immense and powerful monsters that have ever lived upon the earth. Mesozoic civilisation was pre-eminently saurian. Reptiles were supreme everywhere—on sea and land and in the air. Their rulership of the world was not so bloody and masterful as man’s, but quite as remorseless. Imagine an aristocracy made up of pterosaurs (flying reptiles), with teeth, and measuring 20 feet between wing-tips; great plesiosaurs (serpent reptiles) and ichthyosaurs (fish reptiles), enormous bandits of the seas; and dinosaurs and atlantosaurs, giant land lizards, 30 feet high and from 50 to 100 feet in length. A government of demagogs is bad enough, as king-ridden mankind well know, but dragons would be worse, if possible. The atlantosaurs were the largest animals that have ever walked upon the earth. They were huge plant-eaters inhabiting North America. It has been surmised that one of these behemoths ‘may have consumed a whole tree for breakfast.’ It was the mighty saurians of the Mesozoic time who brought into everlasting subordination the piscatorial civilisation of the Devonian and carboniferous ages.