The Story of Evolution 87 



only a small family, and this may tend to the evolution of parental 

 care and the kindly emotions. Thus it may be understood that 

 from the conquest of the land many far-reaching consequences 

 have followed. 



Finally, it is worth dwelling on the risks of terrestrial life, 

 because they enable us better to understand why so many land 

 animals have become burro wers and others climbers of trees, why 

 some have returned to the water and others have taken to the air. 

 It may be asked, perhaps, why the land should have been colo- 

 nised at all when the risks and difficulties are so great. The 

 answer must be that necessity and curiosity are the mother and 

 father of invention. Animals left the water because the pools 

 dried up, or because they were overcrowded, or because of inveter- 

 ate enemies, but also because of that curiosity and spirit of 

 adventure which, from first to last, has been one of the spurs of 

 progress. 



Conquering the Air 



6. The last great haunt of life is the air, a mastery of which 

 must be placed to the credit of insects, Pterodactyls, birds, and 

 bats. These have been the successes, but it should be noted that 

 there have been many brilliant failures, which have not attained 

 to much more than parachuting. These include the Flying 

 Fishes, which take leaps from the water and are carried for many 

 yards and to considerable heights, holding their enlarged pec- 

 toral fins taut or with little more than a slight fluttering. There is 

 a so-called Flying Frog (Rhacophorus) that skims from branch 

 to branch, and the much more effective Flying Dragon (Draco 

 volans) of the Far East, which has been mentioned already. 

 Among mammals there are Flying Phalangers, Flying Lemurs, 

 and more besides, all attaining to great skill as parachutists, and 

 illustrating the endeavour to master the air which man has realised 

 in a way of his own. 



The power of flight brings obvious advantages. A bird feed- 



