150 mb. darwin's work and 



blacksmith, his arms will become strong and muscular; 

 such organic modification is a result of this particular 

 action and exercise. Lamarck thought that by a very- 

 simple supposition based on this truth he could explain 

 the origin of the various animal species : he said, for 

 example, that the short-legged birds which live on 

 fish, had been converted into the long-legged waders by 

 desiring to get the fish without wetting their feathers, 

 and so stretching their legs more and more through 

 successive generations. If Lamarck could have shown 

 experimentally, that even races of animals could be pro- 

 duced in this way, there might have been some ground 

 for his speculations. But he could show nothing of the 

 kind, and his hypothesis has pretty well dropped into 

 oblivion, as it deserved to do. I said in an earlier 

 lecture that there are hypotheses and hypotheses, and 

 when people tell you that Mr. Darwin's strongly- 

 based hypothesis is nothing but a mere modification 

 of Lamarck's, you will know what to think of their 

 capacity for forming a judgment on this subject. 



But you must recollect that when I say I think it 

 is either Mr. Darwin's hypothesis or nothing j that 

 either we must take his view, or look upon the whole of 

 organic nature as an enigma, the meaning of which 

 is wholly hidden from us ; you must understand that I 

 mean that I accept it provisionally, in exactly the same 

 way as I accept any other hypothesis. Men of science 

 do not pledge themselves to creeds ; they are bound by 

 articles of no sort ; there is not a single belief that it 

 is not a bounden duty with them to hold with a light 

 hand and to part with it, cheerfully, the moment it is 

 really proved to be contrary to any fact, great or small. 



