Adaptations to Environment 129 



beginning of better brains, more controlled activities, and higher 

 expressions of family life. 



VI. THE AIR 



There are no animals thoroughly aerial, but many insects 

 spend much of their adult life in the free air, and the swift 

 hardly pauses in its flight from dawn to dusk of the long sum- 

 mer day, alighting only for brief moments at the nest to deliver 

 insects to the young. All the active life of bats certainly deserves 

 to be called aerial. 



The air was the last haunt of life to be conquered, and it is 

 interesting to inquire what the conquest implied. ( 1 ) It meant 

 transcending the radical difficulty of terrestrial life which con- 

 fines the creatures of the dry land to moving on one plane, the 

 surface of the earth. But the power of flight brought its pos- 

 sessors back to the universal freedom of movement which water 

 animals enjoy. When we watch a sparrow rise into the air just 

 as the cat has completed her stealthy stalking, we see that flight 

 implies an enormous increase of safety. (2) The power of flight 

 also opened up new possibilities of following the prey, of explor- 

 ing new territories, of prospecting for water. (3) Of great im- 

 portance too was the practicability of placing the eggs and the 

 young, perhaps in a nest, in some place inaccessible to most ene- 

 mies. When one thinks of it, the rooks' nests swaying on the tree- 

 tops express the climax of a brilliant experiment. (4) The 

 crowning advantage was the possibility of migrating, of conquer- 

 ing time (by circumventing the arid summer and the severe 

 winter) and of conquering space (by passing quickly from one 

 country to another and sometimes almost girdling the globe). 

 There are not many acquisitions that have meant more to their 

 possessors than the power of flight. It was a key opening the 

 doors of a new freedom.. 



The problem of flight, as has been said in a previous chapter, 



