18701882] PANMIXIA 353 



{Nature, Vol. IX.) ; but it is more than once hinted at in the Letter 263 

 Origin, in the passages where rudimentary organs are said to 

 be more variable than others, because no longer under the 

 restraining influence of Natural Selection. And still more 

 distinctly is this principle recognised in p. 120. 



Thus, in sending you the enclosed letter, I do not imagine 

 that I am bringing any novel suggestions under your notice. 

 As I see that you have already applied the principle in 

 question to the case of artificially-bred structures, I cannot but 

 infer that you have pondered it in connection with naturally- 

 bred structures. What objection, however, you can have 

 seen to this principle in this latter connection, I am unable to 

 divine ; and so I think the best course for me to pursue is 

 the one I adopt viz., to send you my considerations in full. 



In the absence of express information, the most natural 

 inference is that the reason you refuse to entertain the prin- 

 ciple in question, is because you show the backward tendency 

 of indiscriminate variability [to be] inadequate to contend 

 with the conservative tendency of long inheritance. The 

 converse of this is expressed in the words " That the struggle 

 between Natural Selection on the one hand, and the tendency 

 to reversion and variability on the other hand, will in the 

 course of time cease ; and that the most abnormally developed 

 organs may be made constant, I see no reason to doubt ' 

 (Origin, p. 121). Certainly not, if, as I doubt not, the word 

 " constant " is intended to bear a relative signification ; but to 

 say that constancy can ever become absolute i.e., that any 

 term of inheritance could secure to an organ a total immunity 

 from the smallest amount of spontaneous variability to say 

 this would be unwarrantable. Suppose, for instance, that 

 for some reason or other a further increase in the size of a 

 bat's wing should now suddenly become highly beneficial to 

 that animal : we can scarcely suppose that variations would 

 not be forthcoming for Natural Selection to seize upon 

 (unless the limit of possible size has now been reached, which 

 is an altogether distinct matter). And if we suppose that 

 minute variations on the side of increase are thus even now 

 occasionally taking place, much more is it probable that 

 similar variations on the side of decrease are now taking 

 place i.e., that if the conservative influence of Natural 

 Selection were removed for a long period of time, more 



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