VARIATION 41 



shrimp, on the other hand, which may, for instance, be 

 either eight or nine but cannot be halfway between, 

 illustrates what is meant by discontinuous variation. 

 The widespread occurrence of this later category of 

 variations has been pointed out by Bateson in his 

 encyclopedic volume "On Materials for the Study 

 of Variation." 



h. With respect to their character variations may be 

 quantitative or qualitative. A six-rayed starfish 

 represents a quantitative variation from the normal 

 number of five rays, whereas a red variety of a flower 

 may differ chemically from a blue variety, or a bitter 

 fruit may differ from a sweet fruit in a qualitative 

 way dependent upon the chemical constitution of 

 the fruit in question. 



i. With respect to their relation to an average stand- 

 ard variations may have a fluctuating distribution 

 around an arithmetical mean, as when some of the 

 offspring have more and some less of the parental 

 character, or the variations in the progeny may all 

 center about a new average quite distinct from the 

 parental standard and consequently come under the 

 head of mutations, 



j. Finally, and most important in the present 

 connection, with respect to heritability, variations may 

 possess the power to reappear in subsequent genera- 

 tions, or they may lack that power. It is this aspect 

 of variability which bears most directly upon genetics. 



Other possible categories might be mentioned, but 

 a suflicient number have been cited to show the 

 great diversity of variations in general. 



