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LIFE : OUTLINES OF GENERAL BIOLOGY 



on such a pace that "even on horseback one could scarce overtake 

 him. With great bounds he hurries on, jerking out his long hind-legs, 

 with his tail stretched out as a rudder; bound after bound he goes, 



Jerboas (Dipus). typical mammals of the desert and stcpjX's. The long hind- 

 Icgs are atlapted for rapid bij>cdal progression and astonishingly long 

 lcaf>s — an adaptation securing safety, 



and, Ix'forc one has rightly seen how he began or wliither he went, 

 he has disappeared in the darkness." 



The third sohition of the steppe problem is illustrated by the 

 larger mammals, such as antelopes, gazelles, the maral stag, and 



