216 THE ORIGIN OF SPECIES 



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 important organ or part, which is generally very 

 constant throughout a large group of species, differs con- 

 siderably 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 mcy remain the same. Something of the 

 same kind applies to monstrosities: at least Is. Geol- 

 froy St.-Hilaire apparently entertains no doubt that the 

 more an organ normally diflEers in the di/ferent 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 frori 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 I 

 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 charac- 

 ters; and these characters may be attributed to inheri- 



