190 SPECIFIC CHAEACTEES [Chap. Y. 



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

 trie species had blue flowers, the colour would become a 

 generic character, and its variation 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 

 characters, 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, diffi rs 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. Geoifroy 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 



