First lesson in zoology : adapted for use in schools . ate in the summer. Turtles do not layeggs until from eleven to thirteen years old. The land-tortoises, as probably all turtles, are long-lived,and often reach a great age. White, in his l^atural His-13 194 FIRST LESSONS IN ZOOLOGY. tory of Selborne;, relates that one was kept in a village tillit was supposed to be one hundred years old. When we see how few turtles are devoured by other ani-mals because of their thick shell, and also take into accounttheir vitality and the length of time it requires for them toarrive at maturity, the cause
First lesson in zoology : adapted for use in schools . ate in the summer. Turtles do not layeggs until from eleven to thirteen years old. The land-tortoises, as probably all turtles, are long-lived,and often reach a great age. White, in his l^atural His-13 194 FIRST LESSONS IN ZOOLOGY. tory of Selborne;, relates that one was kept in a village tillit was supposed to be one hundred years old. When we see how few turtles are devoured by other ani-mals because of their thick shell, and also take into accounttheir vitality and the length of time it requires for them toarrive at maturity, the cause of their great longevity is ex-plained. The Crocodiles.—In the crocodile, gavial, and alligator,we return again to a lizard-like form. They present a de-cided step in advance of other reptiles, the heart approach-ing that of birds, in having the ventricle completely di-vided by a partition into two chambers; the venous and ar-terial blood mingling outside of the heart, not in it, as in theforegoing orders. The brain is also more like that of Fig. 200.—Head of the Florida Crocodile. The nostrils are capable of closing, so that crocodiles andalligators draw their prey under the water and hold itthere until it is drowned; but they are obliged, to dragit ashore in order to devour it. The skin is coveredwith large bony, epidermal scales. The conical teeth arelodged in sockets in the jaws. The feet are partly crocodiles and gavials lay from twenty to thirty cylin-drical eggs in the sand on river-banks. The crocodiles aredistributed throughout the tropics, even Australia; the ga-vials are mostly confined to India and Malaysia, and alsoAustralia. It is among certain fossil reptiles that we find links con-necting the reptiles and birds, and thus the highest, best-developed reptiles are not those now in existence, but those THE LIZARDS, BWAKE8, AND OTHER REPTILES. 195 which flourished long ago, and whose tracks have, in somecases, been preserved in the New Eed Sand
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1894
