248 LESSONS FROM NATUIiE. [CHAP. V11I. 



they must tend to neutralise each other, and at first to form 

 such unstable modifications that it is difficult, if not im 

 possible, to see how such indefinite oscillations of insig 

 nificant beginnings can ever build up a sufficiently appre 

 ciable resemblance to a leaf, bamboo, or other object, for 

 Natural Selection to seize upon and perpetuate. This 

 difficulty is augmented when we consider how necessary it is 

 that many individuals should be modified simultaneously &quot; 

 and similarly in order that slightly favourable variations 

 may hold their own against the overwhelming force and 

 influence of mere number. A consideration insisted on in 

 the &amp;lt; North British Keview for June 1867, p. 286 ; a con 

 sideration of which review has compelled Mr. Darwin to 

 modify his views very importantly, and he has himself 

 confessed that until reading this article he did not &quot; appre 

 ciate how rarely single variations, whether slight or strongly 

 marked, could be perpetuated.&quot; 



&quot; In these cases of mimicry it seems difficult indeed to 

 imagine a reason why variations tending in a minute degree 

 in any special direction should be preserved. All variations 

 would be preserved which tended to obscure the perception 

 of an animal by its enemies, whatever direction these varia 

 tions might take, and the common preservation of conflicting 

 tendencies would greatly favour their mutual neutralisation 

 and obliteration, if we may rely on the many cases which 

 have been brought forward by Mr. Darwin with regard to 

 domestic animals.&quot; 



As to the last cited examples of the imitation of mildew, 

 &c., I added :* &quot; How this double mimicry can importantly 

 aid in the struggle for life seems puzzling indeed, but much 

 more so how the first faint beginnings of the imitation of 

 such injuries in the leaf can be developed in the animal into 

 such a complete representation of them a fortiori, how 

 simultaneous and similar first beginnings of imitations of 

 such injuries could ever have been developed in several 



* Op. cit, p. 41. 



