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EVOLUTION OF ANIMALS 



Part V 



hunter. It prowls in the grass, waits, and pounces. If not too hungry, it brings 

 the mouse home still alive, sets it free to take a crippled run, then pounces 

 again. Cats catch and clutch and climb — the play of their foreshoulders is 

 something to see and remember. Their musdes are surpassingly supple, 

 elaborately developed on head, neck and shoulders. Their facial expressions 



Fig. 37.2. The flexibility of a mam- 

 mal. Gibbon, the acrobat of mammals. 

 At home in southeastern Asia these 

 long-armed apes leap and swing 

 through the treetops always depend- 

 ing greatly upon their arms. (After 

 Clark: History of the Primates. Cour- 

 tesy, British Museum Guide, 1949.) 



change. Their night "eyeshine" is momentarily reflected by the headlights as 

 the car approaches within twenty feet of them. Then it glitters and disappears. 

 The angle of reflection is limited as it is in the wayside signs. Cats walk on 

 their toes; the hind foot is bent at the heel with a downward sag, not upright as 

 it is in dogs, and their step is more elastic. They are famous for turning in 

 the air and landing "on all fours" when dropped. 



About 3000 B.C., the Egyptians tamed a certain variety of African wild cats 

 so that they might hunt and protect their grain. The cats did this so well that 

 they were for a time believed to represent one of the gods. Later, they were 

 exported and introduced into other countries. It is a comment on the cat's 

 subtlety that where a dog and cat are pets, the dog follows the owner, and the 

 owner follows the cat. 



Chief Types of Mammals 



Based on the provisions for the developing young, there are three types of 

 mammals: those which lay eggs; those which carry the young in a brood 

 pouch after a short period of internal development; and those in which the 

 developing young are attached by a placenta to the uterus of the mother. 



Egg-laying Mammals — Subclass 1, Monotremata. Monotremes are so called 

 because the single opening (L, monotrema, one opening) of the cloaca re- 



