94 THE FOUNDATIONS OF ZOOLOGY 



selection, they are fortuitous, so far as their fitness is in question. 

 The mere fact that species change is no more remarkable than the 

 change of seasons, or the melting of a snowdrift ; nor do I suppose 

 that any one believes that any change ever takes place in nature 

 without those antecdent changes which we call physical causes. 

 The thing to be explained is not that species change, but how the 

 changes of species tend to establish harmony between them and 

 the world in which they live. Since many species, many more in 

 fact than all that now exist, have disappeared during the long 

 history of life without leaving descendants ; and since the early 

 extinction of the blood of the vast majority of the individual 

 organisms which now exist can be demonstrated, the adjustments 

 of these which survive cannot be accounted for by any law of 

 " necessary " or " universal " progress or evolution. 



Living things, like everything else, act in accordance with the 

 laws of matter and motion. Animals, like clouds, grow lighter as 

 they ascend a mountain, and their volume increases as their 

 temperature rises ; but changes of this sort are all that external 

 changes can produce prior to selection, unless they tend to bring 

 about responsive modification, or adjustr^ent; and it is begging the 

 question to attribute the origin of this tendency to the inheritance 

 of modifications in the right direction unless some reason why the 

 right ones should be the ones which are inherited is pointed out. 



I have tried to show, page 66, that instead of a preliminary 

 condition to selection, the adaptive influence of the environment, 

 so far as this influence is adaptive, is the result of past selection, 

 and Darwin's explanation of the origin of species by selection is 

 the only one worth considering. 



It scarcely seems necessary, at this late day, to point out that 

 by foytnitons variations, Darwin means those differences between 

 individuals which stand in no discoverable relation to the use to 

 which they are turned by selection ; for Darwin admits, as every 

 one must, that if there were no changes in the external world we 

 should have no reason to expect any difference between individual 

 living things; but, whatever may be our opinion of the nature of 

 those "variations" which are said to be a necessary preliminary to 

 selection, it seems clear that the effects of the conditions of life 

 cannot be transmitted to future generations, unless the organisms 



