122 Specific Characters Chap. v. 



in this case the variability will seldom as yet have been fixed by 

 the continued selection of the individuals varying in the required 

 manner and degree, and by the continued rejection of those tending 

 to revert to a former and less-modified condition. 



Specific Characters more Variable than Generic Characters. 



The principle discussed under the last heading may be applied to 

 our present subject. It is notorious that specific characters are 

 more fsdz&e than generic. To explain by a simple example what 

 is meant : if in a large genus of plants some species had blue 

 flowers and some had red, the colour would be only a specific 

 character, and no one would be surprised at one of the blue species 

 varying into red, or conversely; but if all the species had blue 

 flowers, the colour would become a generic character, and its varia- 

 tion would be a more unusual circumstance. I have chosen this 

 example because the explanation which most naturalists would 

 advance is not here applicable, namely, that specific characters are 

 more variable than generic, because they are taken from parts of less 

 physiological importance than those commonly 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 charac- 

 ters, I have repeatedly noticed in works on natural history, that 

 when an author remarks with surprise that some important organ 

 or part, which is generally very constant throughout 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. Some- 

 thing of the same kind applies to monstrosities : at least Is. Geoffroy 

 St. 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 anomalies in the individuals. 



On the ordinary view of each species having been independently 

 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 



