I. SIMULTANEOUS INFLUENCE OF NUTRI- 

 TION AND SELECTION ON VARIOUS 

 CHARACTERS. 



§ I. VARIABILITY AS A NUTRITIONAL PHENOMENON. 



When a new science comes into the field, it usually 

 happens that certain groups of phenomena, which uj) to 

 then had been dealt with under other heads, are found 

 to come within its ken. This is happening at the present 

 moment, with the study of variability and that of the 

 dependence of the growth and development of particular 

 organs and characters on nutrition. This connection with 

 nutrition has been studied chiefly from the experimental 

 and biological point of view ; whilst the same phenomena 

 have been dealt with by statistical methods from another 

 point of view. 



New boundaries are difficult to defiihe, and it will be 

 a long time before an agreement will l)e reached as to 

 which sections of the theory of nutrition should be in- 

 cluded in the science of variability. 



In the historical and critical part (Part I, i)p. L^3 and 

 137 etc.) I have urged that we had no right to give up the 

 attempt to provide an answer to the question as to the 

 causes of the fluctuating dififerences between individuals 

 and between homologous organs of one and the same 

 individual. The science of variabilitv must not be satis- 



