Knowledge and Authority 105 



greatest authorities in anatomy that the world has 

 seen, told us that it was so. We know it because, 

 Huxley having told us that it was so, we are able at 

 any time with a microscope and dissecting needles to 

 observe the fact for ourselves. It is true, that unless we 

 are making a special studj^ of the Medusae we do not 

 repeat the observation in the case of so many different 

 forms of Medusae as Huxley studied ; but it is part of 

 our training to observe for ourselves in a sufficient 

 number of cases to test the correspondence between 

 statement and fact before we accept the generalisation 

 of any authority. And we learn, or at least have the 

 opportunity of learning, in the whole habit of our lives 

 as naturalists, to distinguish carefully between know- 

 ledge of which personal observation is an essential part, 

 and opinion or belief which may or may not be based 

 upon authority, but which in any case is devoid of the 

 corroboration of personal observation. When a piece 

 of new anatomical or physiological work is published 

 in a technical journal, it is read by a large number of 

 anatomists and physiologists, and if the work is ap- 

 parently of an important kind, bearing on the general 

 problems that even specialists have to follow, they all 

 at once set to work in their laboratories to make cor- 

 roborative dissections or experiments, and it is part of 

 every modern account of a biological discovery to tell 

 exactly the methods by which results were got, in order 

 that this process of corroboration may be set about 

 easily. The question as to whether or no natural 

 selection were the sole or chief cause, or indeed a cause 

 at all, of evolution is not yet, and perhaps never will be, 

 a matter of knowledge in the scientific sense. At the 

 most, we can see for ourselves only that selection does 

 bring about changes at least as great as the differences 



