426 The Bird 
the motion is more abrupt than is the motion of a pendu- 
lum. The Mexican motmot is brilliantly coloured, yet in a 
densely foliaged tree, among the bright spots of sunlight, 
it becomes almost invisible. It is the motion of the tail 
which most often betrays the bird. 
In the tail marked a in Fig. 340 it will be noticed that, 
where the barbs have not yet been picked off, the unmu- 
tilated vane is considerably narrowed—an interesting fact 
for the consideration of evolutionists, as it offers strong 
circumstantial evidence, but by no means absolute proof, 
of a case of the inheritance of acquired characters, a much- 
mooted question not many years ago among scientists. If 
we choose to accept the evidence thus, we may presume 
that if this habit is continued through a sufficient number 
of generations, the vane will, at the point of continued 
denudation, ultimately become naturally bare. 
But, in any case, it is a fact which must hold the inter- 
est of the most superficial bird student that here is a 
bird which voluntarily tears away a portion of its plu- 
mage. To the best of our present knowledge this is solely 
to ornament itself, but the fact that both sexes equally 
possess this habit makes such an explanation the merest 
theory. The interest which this has for us here is not the 
ultimate psychological significance of the habit, but the 
fact that there is a bird which thus voluntarily mutilates 
its plumage. As in so many other cases, we must 
depend on future study of live birds in their natural 
haunts to clear up the difficulty. It is this very com- 
plexity of Nature’s problems which makes a naturalist’s 
life ever one of enthusiasm and zest. 
