46 THE GENESIS OF SPECIES. [CHAP. 



extraordinary habit of stretching out their legs unsymmetri- 

 cally, so as to render the deception more complete." Now 

 let us suppose that the ancestors of these various animals 

 were all destitute of the very special protections they at 

 present possess, as on the Darwinian hypothesis we must 

 do. Let it also be conceded that small deviations from the 

 antecedent coloring or form would tend to make some of 

 their ancestors escape destruction by causing them more or 

 less frequently to be passed over, or mistaken by their 

 persecutors. Yet the deviation must, as the event has 

 shown, in each case be in some definite direction, whether 

 it be toward some other animal or plant, or toward some 

 dead or inorganic matter. But as, according to Mr. Dar- 

 win's theory, there is a constant tendency to indefinite vari- 

 ation, and as the minute incipient variations will be in all 

 directions, they must tend to neutralize each other, and at 

 first to form such unstable modifications that it is difficult, 

 if not impossible, to see how such indefinite oscillations of 

 infinitesimal beginnings can ever build up a sufficiently ap- 

 preciable resemblance to a leaf, bamboo, or other object, 

 for "Natural Selection" to seize upon and perpetuate. 

 This difficulty is augmented when we consider a point to 

 be dwelt upon hereafter how necessary it is that many in- 

 dividuals should be similarly modified simultaneously. This 

 has been insisted on in an able article in the North British 

 Review for June, 1867, p. 286, and the consideration of the 

 article has occasioned Mr. Darwin to make an important 

 modification in his views. 14 



In these cases of mimicry it seems difficult indeed to im- 

 agine a reason why variations tending in an infinitesimal 

 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 

 those variations might take, and the common preservation 



14 " Origin of Species.' 1 5th edit., p. 104. 



