104 THE TRIUMPH OF THE MAMMALvS 



have to keep our eyes wide open in studying evolu- 

 tion, as there are numbers of different influences at 

 work all the time. The changes of land and water 

 continued. All through the time of the evolution of 

 the mammals the land was rising. It made a great 

 difference to many of them. Vegetation also, as we 

 saw, was changing. The fruit-bearing trees were 

 coming in, and there were presently immense stores 

 of rich food, apart from insects, in the shape of nuts. 

 Until carnivores learned to climb trees, this was a 

 very safe and satisfactory world to live in. A very 

 large family of the primitive insect-eating and tree- 

 climbing mammals remained in the trees, and 

 prospered. While the horse was developing on the 

 plains of America, and the hippopotamus in the 

 swamps of Africa, the monkey family was evolving in 

 the trees, all unconscious of the remarkable destiny 

 of one of its branches. Here we naturally open a 

 new chapter. 



