2 THE MEASUREMENT OF VARIATION. 



portance as the corner stone of the whole fabric of Evo- 

 lution, that we shall briefly inquire in the following 

 pages. 



In his " Origin of Species," Darwin clearly recog- 

 nised the fundamental importance of the existence of 

 variation, for without it there could evidently be no 

 such thing as evolution. In his " Variation of Animals 

 and Plants," also, he brought together an enormous 

 mass of material concerning the facts of variation, 

 though unfortunately this dealt almost exclusively with 

 organisms in a condition of domestication. Still, there 

 was sufficient evidence even then to show that wild ani- 

 mals and plants are also subject to variation, though 

 Darwin probably did not fully recognise how consider- 

 able and universal this variation is. As to the causes 

 of variation, Darwin did not hazard many conjectures. 

 To do so would have been premature^ and from actual 

 lack of knowledge almost impossible. For many years 

 after the publication of Darwin's work, the additions to 

 our knowledge of the subject of variation were exceed- 

 ingly small. Scientists seemed to rest content with the 

 material he had collected, and to theorise on this alone, 

 rather than to test their theories by a search after fresh 

 facts and data. Within the last decade, however, the 

 importance of the scientific study of variation has be- 

 gun to be more thoroughly recognised, and has resulted 

 in its being attacked with considerable vigour from sev- 

 eral entirely different points of view. Investigations 

 from the mathematical side have shown that many of 

 the apparently disconnected facts of variation can be 

 expressed with ease and lucidity by exact mathematical 

 expressions, and that much material which has hitherto 



