. Beginners' Zoology . whales do not cut the gum, but are reabsorbed and are replaced by horny platesof whalebone, which act as strainers. Give evidence,from the flippers, lungs, and other organs, that the whaleis descended from a land mammal (Fig. 397). Comparethe whale with a typical land mammal, as the dog, andenumerate the specializations of the whale for living inwater. What change took place in the general form of thebody .-• It is believed that on account of scarcity of foodthe land ancestors of the whale, hundreds of thousands ofyears ago, took to living upon fish, etc., an
. Beginners' Zoology . whales do not cut the gum, but are reabsorbed and are replaced by horny platesof whalebone, which act as strainers. Give evidence,from the flippers, lungs, and other organs, that the whaleis descended from a land mammal (Fig. 397). Comparethe whale with a typical land mammal, as the dog, andenumerate the specializations of the whale for living inwater. What change took place in the general form of thebody .-• It is believed that on account of scarcity of foodthe land ancestors of the whale, hundreds of thousands ofyears ago, took to living upon fish, etc., and, gradually be-coming swimmers and divers, lost the power of locomotion on land. Order Why ? Elephants are rapidly becoming extinct because of thevalue of their ivory alsofurnish valua-ble products,but they willprobably existmuch The manatees and dugongs (sea cows) are a closely re-lated order living upon water plants, and hence living closeto shore and in the mouths of rivers. Order. Why ?. Fig. 380. — Manatee, or sea cow; it lives near the shoreand eats seaweed. (Florida to Brazil.) 210 BEGINNERS ZOOLOGY Hoofed Mammals. — All the animals in this order walkon the tips of their toes, which have been adapted to thisuse by the claws having developed into hoofs. The orderis subdivided into the odd-toed (such as the horse with onetoe and the rhinoceros with three) and the even-toed (asthe ox with two toes and the pig with four). All the even-toed forms except the pig and hippopotamus chew the cudand are given the name of rtiminants. Horse and Man Compared. — To which finger and toeon mans hand and foot does a horses foot correspond? (Figs. 381, iZi, 399.) Has the horse kneecaps ?Is its heel bone large orsmall ? Is the fetlock ontoe, instep, or ankle?Does the part of a horseshind leg that is most elon-gated correspond to thethigh, calf, or foot inman ? On the fore leg,is the elongated part theupper arm, forearm, orhand? (Figs. 395, 399.)Does the mo
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