12 THE DARWINIAN HYPOTHESIS I 
the attempt to gratify such desires will result in an 
appropriate modification of the organs exerted. 
Make a man a blacksmith, and his brachial muscles 
will develop in accordance with the demands made 
upon them, and in like manner, says Lamarck, 
“the efforts of some short-necked bird to catch 
fish without wetting himself have, with time and 
perseverance, given rise to all our herons and! 
long-necked waders.” 
The Lamarckian hypothesis has long since been 
justly condemned, and it is the established prac- 
tice for every tyro to raise his heel against the 
carcase of the dead lion. But it is rarely either 
wise or instructive to treat even the errors of a 
really great man with mere ridicule, and in the 
present case the logical form of the doctrine stands 
on a very different footing from its substance. 
If species have really arisen by the operation 
of natural conditions, we ought to be able to find 
those conditions now at work; we ought to be 
able to discover in nature some power adequate 
to modify any given kind of animal or plant in 
such a manner as to give rise to another kind, 
which would be admitted by naturalists as a 
distinct species. Lamarck imagined that he had 
discovered this vera causa in the admitted facts. 
that some organs may be modified by exercise ; 
and that modifications, once produced, are capable 
of hereditary transmission. It does not seem to 
have occurred to him to inquire-whether there is 
