OBJECTIONS TO THE THEORY OF NATURAL SELECTION 185 



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 oscillation, 

 of infinitesimal beginnings can ever build up a sufficiently appre- 

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

 ural selection to seize upon and perpetuate." 



But in all the foregoing cases the insects in their original state 

 no doubt presented some rude and accidental resemblance to an 

 object commonly found in the stations frequented by them. Nor 

 is this at all improbable, considering the almost infinite number 

 of surrounding objects and the diversity in form and color of the 

 hosts of insects which exist. As some rude resemblance is neces- 

 sary for the first start, we can understand how it is that the 

 larger and higher animals do not (with the exception, as far as I 

 know, of one fish) resemble for the sake of protection special ob- 

 jects, but only the surface which commonly surrounds them, and 

 this chiefly in color. Assuming that an insect originally happened 

 to resemble in some degree a dead twig or a decayed leaf, and that 

 it varied slightly in many ways, then all the variations which 

 rendered the insect at all more like any such object, and thus 

 favored its escape, would be preserved, while other variations 

 would be neglected and ultimately lost; or, if they rendered the 

 insect at all less like the imitated object, they would be eliminated. 

 There would indeed be force in Mr. Mivart's objection, if we were 

 to attempt to account for the above resemblances, independently 

 of natural selection, through mere fluctuating variability; but as 

 the case stands there is none. 



Nor can I see any force in Mr. Mivart's difficulty with respect 

 to "the last touches of perfection in the mimicry;'' as in the case 

 given by Mr. Wallace, of a walking-stick insect (Ceroxylus lacera- 

 tus), which resembles "a stick grown over by a creeping moss or 

 jungermannia." So close was this resemblance, that a native Dyak 

 maintained that the foliaceous excrescences were really moss. In- 

 sects are preyed on by birds and other enemies whose sight is 

 probably sharper than ours, and every grade in resemblance which 

 aided an insect to escape notice or detection, would tend toward 

 its preservation; and the more perfect the resemblance, so much 

 the better for the insect. Considering the nature of the differences 

 between the species in the group which includes the above Ceroxy- 

 lus, there is nothing improbable in this insect having varied in the 

 irregularities on its surface, and in these having become more or 

 less green-colored; for in every group the characters which differ 

 in the several species are the most apt to vary, while the generic 



