20 ANIMAL LIFE 



CHAPTER IV 



MOVEMENT 



Movement, more than any other feature of animals, 

 brings to us the meaning and working of their life. 

 Activity is the sign of life, and as its manifestations 

 exhibit control and adaptation, so does the organism 

 that displays them rise in the scale of being. Begin- 

 ning with the animalcules and jelly-fish, which have 

 at best but feeble swimming movements, we pass to 

 the creeping things that cling to the ground or dart 

 spasmodically from one resting-place to another, and 

 then to the Crustacea and insects, in which the prob- 

 lems of walking on land and of flight through air are 

 first solved. 



The flight of insects is not only the most perfect 

 movement known, but it has also raised these animals 

 to the highest place amongst invertebrates. Their 

 flight may be only temporary, but it is upon the 

 superiority so gained that their life exhibits organisa- 

 tion, and even civilisation of the most complex kind. 



The movements of vertebrates in water, on land, 

 and through the air, bring home the same con- 

 clusion. Fish born and bred in the water are the 

 lowest members of the group ; and the most specialised 



