THE BIOLOGY OF TWINS 165 



mammals which were kept from earliest youth in 

 peculiar conditions of artificial nurture and took on 

 the ways and habits of their unrelated comrades; 

 that many cases are known among children where 

 those transplanted early from deteriorative to 

 wholesome conditions have developed well ; and that 

 the changes of nurture in Gal ton's cases were within 

 very narrow limits. Hereditary " nature " is 

 indeed the seed-corn; nurture is the sunshine and 

 the soil, the wind and the rain. When both com- 

 ponents of a resultant are essential, it does not seem 

 to matter very much which we call the more im- 

 portant. The fundamental factors of all sorts of 

 characters are in the germ, but the precise expres- 

 sion they find in development depends in some 

 measure on the nurture. 



