APPARENT EXCEPTIONS. 183 



culty, it may be well to consider this subject a 

 little nearer. 



There is one explanation which it cannot be 

 doubted applies to many cases, and this is the 

 simple explanation, that we often mistake the pur- 

 pose of particular structures in Nature, and connect 

 them with intentions which are not and never were 

 the intentions really in view. The best naturalists 

 are liable to such mistakes. A very curious illus- 

 tration is afforded by an observation of Mr Darwin, 

 in his " Origin of Species." He says that " if green 

 Woodpeckers alone had existed, and we did not 

 know that there were any black and pied kinds, I 

 daresay we should have thought that the green 

 colour was a beautiful adaptation to hide this tree- 

 frequenting bird from its enemies." Now, this in- 

 troduces us to a very curious subject, and one as 

 well adapted as any other to illustrate the relation 

 in which Law stands to Purpose in the economy of 

 Nature. 



There can be no doubt that the principle of 

 adapted colouring with the effect and for the pur- 

 pose of concealment, prevails extensively in various 

 branches of the Animal Kingdom. It arises pro- 



