150 The Bible of Nature 



which it is the loyal endeavor of each pair to 

 leave after them not their worse, but their bet- 

 tered selves. 



Fourthly, the most important impression we 

 get is that of the gradual ascent of life. As the 

 ages passed, higher and higher^ animals are seen. 

 Fishes were on the scene before Amphibians, 

 Reptiles before Birds. 



All theory apart, in the course of the ages life 



has been slowly creeping upward, finding finer 



and finer expression, and not along one line only, 



but along many fines. It is not among backboned 



animals only that we find the creature reaching 



toward a greater fulness of life, a greater richness 



of experience, and an increased freedom from the 



grip of the environment. Notably there is along 



many lines an increasing complexity of nervous 



system, and a correlated liberation of the Psyche. 



' This is not an anthropomorphic impression. We do 

 not mean by "higher" merely liker man; we use the two- 

 fold standard of differentiation and integration. Differ- 

 entiation is the structural side of division of labor, it 

 means increased complexity and specialization of parts. 

 Integration means the consolidation, harmonizing, and 

 regulation of the body into a more and more perfect unity. 

 Thus just as a modern locomotive is a finer product than 

 Stephenson's "Puffing Billy," in being much more differ- 

 entiated and integrated, so the bird is a much higher ani- 

 mal than the earthworm. That we do not mean liker man 

 is obvious when we say that the grass is a much higher 

 plant than the seaweed. It is much more differentiated 

 and integrated, but it is not any nearer man. 



