154 
LAWS OF VAEIATION, 
Chap. Y. 
course of time cease; and tliat the most abnormally 
developed organs may be made constant, I can see no 
reason to doubt. Hence when an organ, however ab¬ 
normal 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 varying in 
the required manner and degree, and by the continued 
rejection of those tending to revert to a former and less 
modified condition. 
The principle included in these remarks may be ex¬ 
tended. 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- 
