CLASSIFICATION OF SCIENCES 103 



still only an apprentice. In a lecture on Inher- 

 itance, the late Prof. W. F. R. Weldon put this 

 matter very clearly: "The ideal description of 

 every experience, the description which alone 

 makes further progress possible, is a description 

 of all the results obtained, and not a statement 

 which largely ignores the inconsistencies observed. 

 The reason why astronomers, and physicists, 

 and chemists can so often afford to neglect the 

 inconsistencies of their experience without making 

 themselves ridiculous is that by great labour 

 they have already succeeded in confining the 

 limits within which these inconsistencies occur, 

 so that the proportion of the whole experience 

 affected by them is very small. But biologists 

 have not yet advanced so far as this: The margin 

 of uncertainty in their experience is still so large 

 that they are obliged to take account of it in 

 every statement they make." 



Yet the work which Prof. Weldon himself 

 did in connection with variation, heredity, and 

 selection was symptomatic of the movement 

 towards exactness that has recently character- 

 ized even the most difficult departments of 

 Biology, those dealing with Evolution. There 

 has been for a long time much exact science in 

 comparative anatomy and physiology, but in 

 recent years the labours of the biometricians on 

 the one hand, and of the experimental zoologists 



