NEE]) OF 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 assoctations of char- 
acters, as when one individual is red and white and another is 
black and white ; and, second, by different degrees of develop- 
Fic. 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 74 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 is 
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 
