1 86 THE LIVING WORLD. 



in the later geological ages has consisted simply 

 in the expansion of groups appearing long before, 

 we must conclude that the power of the undifferen- 

 tiated forms to expand into different lines of devel- 

 opment disappears very early in their history. 

 While then we cannot deny the possibility of an 

 indefinite future development from the existing 

 generalized types, it is certainly improbable that 

 any new great groups will arise. Man, seizing upon 

 the last undifferentiated faculty, the intellect, is 

 developing this to the extreme. With him, the 

 animal world proper has ended and the intellectual 

 world begun. 



If there is anything further needed to convince us 

 that the evolution of animals ceases with man, we 

 have only to notice his influence upon the rest 

 of the animal kingdom. We cannot yet compute 

 that influence, but it will doubtless be the death- 

 blow to the evolution of animals. Man is rapidly 

 causing the extinction of almost all land animals, at 

 least the larger ones. As the frontiers of civilization 

 are being extended farther and farther into the 

 uninhabited regions, he is driving out of existence 

 all of the large animals and many of the smaller 

 ones. We have only to look ahead a comparatively 

 short time to see the extinction of nearly all land 

 animals, except such as may strike man's fancy to 

 use or preserve. To what extent this may apply to 

 other animals to insects, marine animals, etc. is 

 not clear. But in the highest group of animals, the 

 vertebrates, it is pretty clear that man is eventually 

 to bring about not only the end of advance, but also 



