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Show LAWS OF VARIATION. CHAP. v. 154 f t . e cease. and that the most abnormally course o 1m ' developed organs may be made constant, I can see no t d bt Hence when an organ, however reason o ou · · d · · b 1 •t may be has been transmltte In approxl-a norma 1 ' · d d mately the same condition to many modified .escen - t an s, as 1·n the case of the wing of the bat, . It must have existed, according to my theory, for an ~mmense period in nearly the same state; and thus It comes to be no more variable than any other s!ruct~re. It · 1 in those cases in which the mod1ficat1on has lS on y a· .1 . t been comparatively recent and extraor ~na:1. y gre~ that we ought to find the g~nerati~e var~ab~l~ty, as .1t may be called, still present 1n a h1gh degree. For 1n 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 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, t~e colour would become a generic character, and its variation would be a more unusual circumstance. I have chosen this example because an explanation is not in this case applicable, which most naturalists would advance, 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- CHAP. V. LAWS OF VARIATION. 155 turn to this subject in our chapter on Classification. It would be almost superfluous to adduce evidence in support of the above statement, that specific characters are. mor~ variable than generic ; but I have repeatedly notwed In works on natural history, that when an author has remarked with surprise that some important organ or part, which is generally very constant throughout large gro.ups of ~pecies, has dijfered considerably in closely-allied species, that it has, also, been variable in the individuals of some of the species. And this fact shows that a character, which is generally of generic v~lue, when it sinks in value and becomes only of spec~ fic ~alue, often becomes variable, though its physiologwalimportance may remain the same. Something of the same kind applies to monstrosities: at least Is. Geoffroy St. Hilaire seems to entertain no doubt, that the more an organ normally differs in the different species of the same group, the more subject it is to individual anomalies. . On the ordinary view of each species having been mdependently created, why should that part of the .~tructure, which differs from the same part in other Ind~pendently-created species of the same genus, be more variable than those parts which are closely alike in the several s~ecies? I do not see that any explanation can be given. But on the view of species being only strongly marked and fixed varieties, we might surely expect to find them still often continuing to vary in those parts of their structure which have varied within a moderately recent 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 the species of some othe; genus, are called generic characters· and these characters in common I attribute to inherit~nce from a common |