126 MIMICRY, AND OTHER PROTECTIVE 
examples of every kind of protective imitation, up to 
the most wonderful cases of what is termed “mimicry,” 
that we can find no place at which to draw the line, 
and say,—so far variation and natural selection will 
account for the phenomena, but for all the rest we 
require a more potent cause. The counter theories 
that have been proposed, that of the ‘‘ special creation ” 
of each imitative form, that of the action of “similar 
conditions of existence” for some of the cases, and of 
the laws of “hereditary descent and the reversion to 
ancestral forms” for others,—have all been shown 
to be beset with difficulties, and the two latter to be 
directly contradicted by some of the most constant and 
most remarkable of the facts to be accounted for. 
General. deductions as to Colour in Nature. 
The important part that “ protective resemblance” 
has played in determining the colours and markings 
of many groups of animals, will enable us to under- 
stand the meaning of one of the most striking facts 
in nature, the uniformity in the colours of the vege- 
table as compared with the wonderful diversity of the ~ 
animal world. There appears no good reason why 
trees and shrubs should not have been adorned with 
as many varied hues and as strikingly designed pat- 
terns as birds and butterflies, since the gay colours 
of flowers show that there is no incapacity in vege- 
table tissues to exhibit them. But even flowers them- 
selves present us with none of those wonderful designs, 
those complicated arrangements of stripes and dots 
