Divisions of Life and Time 



the fish, and the bat is more expert on the 

 wing than many birds, but the one is not a fish 

 nor is the other a bird ; both are equally mam- 

 mals. Dress, however, does count for some- 

 thing in the rest of the animal kingdom, if not 

 so much as it does with us, but it may not be 

 used as the basis of classification, only as a help 

 to distinguish species from one another. Most 

 mammals are clothed in hair or fur, but many 

 go naked, especially in warm climates, and so 

 do the whales, in order that they may slip 

 through the water readily.* The armadillos 

 are protected by an armor of bone, and their 

 cousins, the pangolins of Asia and Africa, by 

 an even more effective armor of sharp-edged, 

 overlapping horny scales. 



Birds are familiar to all, and even the kiwis 

 and penguins, which depart most in appearance 

 from their fellows, are easily recognized as 

 birds, so the class may be passed by with little 



* The reader will please bear in mind that in these cases the 

 animals have no choice in the matter, that they have not shed 

 their fur overcoats as we would take off our clothes, but that 

 their nakedness is the slow result of adaptation to their sur- 

 roundings. 



35 



