38 DARWINISM AND THE PROBLEMS OF LIFE 



and therefore we may safely conclude that they have 

 been evolved from these, and that in the course of 

 generations the children have diverged more and 

 more from their parents. 



If we go further back in the story of the earth's 

 growth, we find that each period of geology has its 

 characteristic animals, which must be the parents of 

 the later and the offspring of the earlier forms. When, 

 moreover, we pass in review before the eye of the 

 mind the animals of the succeeding epochs, we notice 

 something else besides the unceasing changes of form. 

 The older the period we take, the simpler we find the 

 shapes of living things ; and the nearer the period 

 approaches to our own time, the more intricate and 

 the higher is the organisation. In the earlier periods, 

 for instance, we find only the lowest forms of vertebrates, 

 and these only very sparingly. Gradually, the number 

 of species increases. Lizards, birds, and mammals 

 appear ; and amongst these the higher species come 

 in succession, the carnivores, the apes, and, finally, at 

 the last moment from the geological point of view, 

 we find unmistakable proofs of man's existence and 

 activity. 



Hence geology drives us to the conclusion that the 

 animals of our time descend from simpler forms, these 

 from yet simpler ones, and so on, so that only the very 

 simplest organisms can have arisen at the first creation 

 of living things. There was, for instance, a time when 

 only the very lowest types of vertebrates, the fishes, 

 were present on the earth ; and while a good many of 

 these fishes were modified in the following epochs 



