NEED OE IMPROVEMENT 



47 



and every botanist will tell you that we may hunt forever with- 

 out finding two plants exactly alike, so mightily are the materials 

 mixed out of which races and individuals are made. This is 

 variation or variability, and upon this fact are selection and 

 improvement based. 



Variability in a single character. Variability arises in two 

 distinctly different ways : first, by different associatioris of char- 

 acters, as when one individual is red and white and another is 

 black and white ; and, second, by different degrees of develop- 



Fig. 7. Jersey cow, Figgis 76106, property of C. I. Hood & Company, 



Lowell, Massachusetts. Champion and Grand Champion, World's Fair, 



St. Louis, 1904. 547 lbs. 6 oz. butter in 7 J months. Such a cow is worth 



perhaps a dozen of the ordinary kind that make 125 lbs. in a year 



ment of the separate characters, as when one individual ic 

 simply larger or fleeter or darker-colored than another. Either 

 gives rise to what is known as variation, and either may afford 

 the basis for natural selection. 



However the racial characters may be mixed in different in- 

 dividuals, it will be found on close inspection that the separate 

 characters are themselves highly variable ; that is to say, varia- 

 bility is not confined to individuals but is a property of each and 



