154 LAWS OF VARIATION. Chap. V. 



course of time cease ; and that the most abnormally 

 developed organs may be made constant, I can see no 

 reason to doubt. Hence when an organ, however 

 abnormal it may be, has been transmitted in approxi- 

 mately the same condition to many modified descend- 

 ants, as in the case of the wing of the bat, it must 

 have existed, according to my theory, for an immense 

 period in nearly the same state; and thus it comes 

 to be no more variable than any other structure. It 

 is only in those cases in which the modification has 

 been comparatively recent and extraordinarily great 

 that we ought to find the generative variability, as it 

 may be called, still present in a high degree. For in 

 this case the variability will seldom as yet have been 

 fixed by the continued selection of the individuals vary- 

 ing in the required manner and degree, and by the con- 

 tinued rejection of those tending to revert to a former 

 and less modified condition. 



The principle included in these remarks may be 

 extended. It is notorious that specific characters are 

 more variable than generic. To explain by a simple 

 example what is meant. If some species in a large genus 

 of plants 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 an explanation is not in 

 this case applicable, which most naturalists would ad- 

 vance, 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 re- 



