72 SECRETS OF ANIMAL LIFE 



adaptations is a whale! Think of the torpedo-like 

 shape, suited for cleaving the water; the shiny, 

 frictionless, almost naked skin; the horizontally 

 flattened tail-flukes, which serve as propellers; 

 the transformation of the fore-limbs into paddle- 

 like flippers, which are moved en bloc and are mainly 

 used in balancing; the thick layer of blubber (an 

 exaggeration of the subcutaneous fat found in most 

 mammals), which retains the warmth of the body, 

 compensating for the almost entire absence of hair, 

 and also helps to make the whale's great bulk more 

 buoyant, and by its elasticity to resist the great 

 pressure involved in deep diving; the shortening 

 of the neck and the welding of the vertebrae of that 

 region; the superficial reduction of friction, illus- 

 trated in the absence of external ears; the dorsal 

 position of the valved, automatically-closing blow- 

 hole or nostril (single in the adult toothed whales, 

 strangely remaining in the primitive double con- 

 dition in the more specialized baleen whales) ; the 

 sponginess of most of the bones, making for buoy- 

 ancy; the remarkable networks of blood-vessels, 

 which probably help respiration during the prolonged 

 submersion; the relatively huge chest-cavity and 

 the spacious (though simple) lungs, which are 

 hydrostatic as well as breathing organs; the usual 

 reduction of the offspring to one at a time; and the 

 special milk-reservoirs which give the baby a big 

 mouthful at a gulp. These are more or less obvious 

 adaptations, but for one that is obvious there are ten 

 that are subtle. There is, for example, the arrange- 



