94 Thomas Henry Huxley 



existence and resulting survival of the fittest, v^^as the 

 actual cause of the present assured position of evolution 

 as a first principle of science, it by no means follows 

 that the survival of the fittest has become similarly a 

 first principle of science. At cross roads a traveller 

 may choose the right path from a quite unsatisfactory 

 reason. Darwin himself, in the act of bringing forward 

 his own theory of natural selection, admitted the possi- 

 bility of the co-operation of many other agencies in 

 evolution, and at various times during the course of his 

 life he was inclined to attach, now more now less, im- 

 portance to these additional agencies. Huxley, as we 

 shall soon come to see, never wavered in his adhesion 

 to the facts of evolution after 1859; but, from first to 

 last, regarded natural selection as only the most prob- 

 able cause of the occurrence of evolution. Other 

 naturalists, of whom the best-known are Weismann 

 in Germany, Ray Lankester in England, and W. K. 

 Brooks in America, have come to attach a continually 

 increasing importance to the purely Darwinian factor 

 of natural selection ; while others again, such as Her- 

 bert Spencer in England, and the late Professor Cope 

 and a large American school, have advocated more and 

 more strongly the importance of what may be called the 

 Ivamarckian factors of evolution, — the inherited effects 

 of increased or diminished use of organs, the direct in- 

 fluence of the environment, and so forth. From the 

 fact that Darwin has persuaded the world of the truth 

 of evolution, evolution is often called Darwinism ; and 

 in this historically just though scientifically inaccurate 

 sense of the term, Huxley was a strict Darwinian, a 

 Darwinian of the Darwinians. From the facts that, 

 although natural selection had been formulated by 

 several writers before Darwin, and had been simul- 



