234 The Science of Life. 



since Darwin's day, but we have said enough to show 

 that Mr. Bateson has made an important step towards 

 reaching- solid ground, and a timely protest against 

 attempting to give a false appearance of simplicity to 

 the intricacies of nature. 



(c) Statistical Study of Variation. The application of 

 statistical methods to the study of variation may not 

 sound very attractive to the outsider, and yet if he take 

 the trouble to read Prof. Karl Pearson's essay on the 

 relative variability of man and woman he will find how 

 important the method is in regard to conclusions which 

 he cherishes or abhors. 



The statistical method measures a selected character 

 in man or crab, in buttercup's petals or sparrow's 

 egg and after a sufficiently wide survey plots out a 

 curve showing the amount of variation which occurs 

 and the proportionate number of variants on either side 

 of the average. 



If curves be constructed for individuals of different 

 age, it may be shown that there is a greater death-rate 

 among the variants on one side of the average than on 

 the other, and this leads on to a measurement of the 

 action of natural selection. 



Of course there are many difficulties in the use of 

 the method and in the interpretation of the results, 

 but what concerns us here is that Mr. Galton, Prof. 

 Weldon, Prof. Pearson, and others have introduced a 

 method of measurement into a domain where certainties 

 are few and platitudes many. 



(d) Isolation. A formidable objection to the Dar- 

 winian theory, first stated by Professor Fleeming 

 Jenkin, and often urged since, is that particular varia- 

 tions of small amount would tend to be lost or neutra- 

 lized by intercrossing. In artificial selection the breeder 

 takes measures to prevent this by isolation; but what 

 is the factor in natural conditions? 



The usual Darwinian answer to the difficulty is to 

 suppose that numerous similar variations occur at once. 

 Thus Weismann says, "The necessary variations, from 

 which transformations arise by means of selection, must 

 in all cases be exhibited over and over again by many 



