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 vertebre 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- 
