268 SCIENCE PROGRESS 



superstructure erected on them by some theorists appears to me 

 to be unsound. Here, however, it is only possible to note the 

 inference that has been made from modern ideas of geologic 

 time. That inference falls entirely to the ground. There is 

 now no recognised maximum limit to geologic time. There are 

 no valid arguments which enable us to limit the time for organic 

 evolution to less than a thousand million of years. And that 

 period would suffice for any known theory of evolution. Conse- 

 quently, whatever may be said for or against the neo-Mendelian 

 theory of sports, this particular argument is invalid. It is 

 desirable also to state that the argument from geologic time is 

 not available for the neo-Lamarckian as against the neo-Dar- 

 winian. I am not aware that any recognised neo-Lamarckian 

 controversialist has made use of it, but if he has, it is invalid. 

 Our knowledge of geologic time is equally consistent with any 

 and every theory of evolution. The conclusion of this aspect of 

 our subject is purely negative. Biologists and others who have 

 made use of the geologic argument must abandon it, and must 

 reconsider their theories, in view of the fact that recent and 

 current speculations on geologic time have broken down. 



C. . A Suggestion concerning Physiological Infertility 



Although the first crude and obvious arguments that arise 

 from attempts to correlate the sciences of geology and biology 

 are of little value, it does not therefore follow that the use of 

 biological data is impossible. But the data must be used more 

 fully and more carefully than has yet been done. Many ways 

 of combining our data are, no doubt, theoretically possible. For 

 our present purpose, however, it will suffice if we call attention 

 to one aspect of evolution — on which Darwin, in his Origin of 

 Species, and Spencer, in the Principles of Biology, laid consider- 

 able stress, yet which has been overlooked in recent biological 

 speculation. We have already noted the problem of the time 

 required for the making of new species. As we have already 

 seen, nothing of the kind has been observed. Nor is this state- 

 ment an example of reasoning in a circle. It might be contended 

 that changes which we have produced by breeding and cultiva- 

 tion are not called species changes, for the simple reason that 

 we have observed them. With regard to some forms of life 

 there is substance in the argument. Darwin, in his famous 

 investigations on cirripedes, found great difficulty in deciding 



