HUXLEY AND NATURAL SELECTION. 143 



safest of all guides into the unknown, when it has 

 brought him success many times and in very different 

 directions, when he knows that many other workers 

 in other fields of biological inquiry have had a simi- 

 larly happy experience, he gradually comes to feel a 

 profound confidence in the permanent truth and the 

 far-reaching importance of the great theory which has 

 served him so well. 



