468 THE CAUSES OF THE XI 
strong and muscular; such organic modification is 
a result of this particular action and exercise. 
Lamarck thought that by a very simple supposi- 
tion based on this truth he could explain the origin 
of the various animal species: he said, for ex- 
ample, 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 produced 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 hy- 
potheses, and when people tell you that Mr. Dar- 
win’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 ; 
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 
