NATURAL SELECTION NOT A LAW 19 



theory that they no longer think it necessary to in- 

 voke the operation of natural selection at all. Yet 

 another school of zoological inquiry, consisting for 

 the most part of those who devote themselves to 

 examination of the fossil records of life, attaches 

 increasing importance to the existence of varia- 

 tions oriented in some direction, and think that the 

 evidence points to the branches of the tree of life 

 having been thrust in their diverging courses by 

 some inward directive force, instead of having been 

 trained and lopped by selection. 



It happens to be my own opinion that these 

 various views can be synthesized under the Dar- 

 winian principle, and that natural selection still holds 

 the field as the most credible hypothesis of the 

 cause of organic evolution. Nevertheless, in the 

 last sixty years, many distinguished biologists have 

 seen in natural selection the only probable agent 

 in effecting evolution, an agent competent to 

 account for all the changes that we know to have 

 taken place ; others have held that its probable 

 influence has been overrated ; others that it has 

 been only one of the many causes of organic evolu- 

 tion ; others again have doubted or denied its 

 efficacy. The scientific world is agreed about 

 evolution ; it is not agreed about natural selection. 

 It is merely ludicrous to assert that natural selection 

 and the struggle for existence have any claims to be 

 regarded as scientific law. The German claim that 

 " the natural law to which all the laws of nature can 

 be reduced, is the law of struggle " fails, first because, 

 even if it were a scientific law, it does not follow that 

 a law derived from a consideration of animals and 



