HIGHLY VARIABLE. 187 



prised at one of the blue species varying into red, or con- 

 versely ; but if all the species had blue flowers, the color 

 would become a generic character, and its variation would 

 be a more unusual circumstance. I have chosen this exam- 

 ple because the explanation which most naturalists would 

 advance is not here applicable, namely, that specific charac 

 ters are more variable than generic, because they are taken 

 from parts of less physiological importance than those com- 

 monly used for classing genera. I believe this explanation 

 is partly, yet only indirectly, true ; I shall, however, have 

 to return to this point in the chapter on Classification. It 

 would be almost superfluous to adduce evidence in support 

 of the statement, that ordinary specific characters are more 

 variable than generic ; but with respect to important char- 

 acters, I have repeatedly noticed in works on natural history, 

 that when an author remarks with surprise that some impor- 

 tant organ or part, which is generally very constant through- 

 out a large group of species, differs considerably in closely 

 allied species, it is often variable in the individuals of the 

 same species. And this fact shows that a character, which 

 is generally of generic value, when it sinks in value and 

 becomes only of specific value, often becomes variable, 

 though its physiological importance may remain the same. 

 Something of the same kind applies to monstrosities: at least 

 Is. Geoffroy Saint-Hilaire apparently entertains no doubt, 

 that the more an organ normally differs in the different 

 species of the same group, the more subject it is to anoma- 

 lies in the individuals. 



On the ordinary view of each species having been inde- 

 pendently created, why should that part of the structure, 

 which differs from the same part in other independently 

 created species of the same genus, be more variable than 

 those parts which are closely alike in the several species ? 

 I do not see that any explanation can be given. But on 

 the view that species are only strongly marked and fixed 

 varieties, we might expect often to find them still continuing 

 to vary in those parts of their structure which have varied 

 within a moderately recent period, and which have thus 

 come to differ. Or to state the case in another manner : the 

 points in which all the species of a genus resemble each 

 other, and in which they differ from allied genera, are called 

 generic characters ; and these characters may be attributed to 

 inheritance from a common progenitor, for it can rarely have 

 happened that natural selection will have modified several 



