. The origin and evolution of life, on the theory of action, reaction and interaction of energy. very stage of development and where advantageous or dis-advantageous chromatin predispositions in evolution come con-stantly under the operation of the law of selection. Thus in thebalance between the reptilian carnivora and herbivora we finda complete protophase of the more recent balance between themammalian carnivora and herbivora. The climax of defense was reached, however, in anotherline of Predentata, in the herbivorous dinosaurs, known asAnkylosaurus, in which there developed a close imitati
. The origin and evolution of life, on the theory of action, reaction and interaction of energy. very stage of development and where advantageous or dis-advantageous chromatin predispositions in evolution come con-stantly under the operation of the law of selection. Thus in thebalance between the reptilian carnivora and herbivora we finda complete protophase of the more recent balance between themammalian carnivora and herbivora. The climax of defense was reached, however, in anotherline of Predentata, in the herbivorous dinosaurs, known asAnkylosaurus, in which there developed a close imitation of thearmadillo or glyptodon type of mammal, with the head andentire body sheathed in a very dense, bony armature. Inthese animals not only is motion abandoned as a means ofescape, but the teeth become diminutive and feeble, as in mostother heavily armored forms of reptiles and mammals. Theherbivorous function of the teeth is replaced by the develop-ment of horny beaks. Thus these animals reach a ground-dwelling, slow-moving, heavily armored existence. 226 THE ORIGIN AND EVOLUTION OF LIFE. Pterosaurs There is no doubt that the pterosaurs, flying reptiles, wereadapted to fly far out to sea, for their remains are found min-gled with those of the mosasaurs in deposits far from theancient shore-lines. There is no relation whatever betweenthe feathered birds and these animals, whose analogies in theirmodes of flight are rather with the bats among the mammals. These flying reptiles areperhaps the most extraor-dinary of all extinct ani-mals. While some ptero-saurs were hardly largerthan sparrows, others sur-passed all living birds inthe spread of the wings,although inferior to manybirds in the bulk of thebody. It is believed thatthey depended almost entirely upon soaring for head in the largest types of the family {Pteranodon) isconverted into a great vertical fin, used, no doubt, in directingflight, with a long, backwardly projecting bony crest whichserved in the b
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