84 ORGANIC EVOLUTION — THE FACTORS 



same time at the other end of the wood. It would be 

 a mere chance if they ever knew of each other's exist- 

 ence — a . still more unlikely chance that they should 

 resist on both sides all temptations to a less advan- 

 tageous alliance. But unless they did so the new 

 breed would never even begin, let alone the question of 

 its perpetuation after it had begun. I think Professor 

 Weismann is justified in saying that we cannot, either 

 with more or less ease, imagine the process of Natural 

 Selection." — Nature, August 9, 1894. 



I think we can with considerable ease imagine the 

 process of evolution. So far from being purely hypo- 

 thetical, geology and embryology render it certain. 

 No man has seen it at work among the higher species 

 of plants and animals to which the attention of Lord 

 Salisbury, like that of the rest of the general public, is 

 directed, for since it normally proceeds on lines of 

 minute variations, not on lines of great abnormalities, 

 no man is able to observe a sufficient number of 

 generations ; but any man may observe its operation 

 among the lower plants and animals {e.g. among the 

 short-lived microbes of disease), and scores of men, as 

 will be seen, have recorded their observations as regards 

 these latter. Even artificial selection usually proceeds 

 on lines of normal variations. For instance, among 

 cattle and pigeons, the domesticated animals Lord 

 Salisbury specially quotes, how many peculiarities that 

 are examples of evolution, not of retrogression, have 

 been otherwise developed. When he speaks of two 

 individuals accidentally blessed with the same variation, 

 he is alluding of course to abnormal inborn variations. 

 It is certainly improbable that two individuals should 

 exhibit the same abnormality at the same time ; it is 

 still more improbable that they should meet and inter- 

 breed if they do ; and even more improbable that the 

 abnormality should be of such a nature as to enable 



