S92 THE ORIGIN OF SPECIES 



given in this chapter strengthen in any great degree my 

 theory; but none of the cases of difficulty, to the best 

 of my judgment, annihilates it. On the other hand, the 

 fact that instincts are not always absolutely perfect and 

 are liable to mistakes; that no instinct can be shown 

 to have been produced for the good of other animals, 

 though animals take advantage of the instincts of others; 

 that the canon in natural history, of "Natur non facit 

 saltum," is applicable to instincts as well as to corporeal 

 structure, and is plainly explicable on the foregoing 

 views, but is otherwise inexplicable — all tend to cor- 

 roborate the theory of natural selection. 



This theory is also strengthened by some few other 

 facts in regard to instincts; as by that common case of 

 closely allied, but distinct, species, when inhabiting dis- 

 tant parts of the world and living under considerably 

 difierent conditions of life, yet often retaining nearly the 

 same instincts. For instance, we can understand, on 

 the principle of inheritance, how it is that the thrush 

 of tropical South America lines its nest with mud, in 

 the same peculiar manner as does our British thrush; 

 how it is that the Hornbills of Africa and India have 

 the same extraordinary instinct of plastering up and 

 imprisoning the females in a hole in a tree, with only 

 a small hole left in the plaster through which the males 

 feed them and their young when hatched; how it is that 

 the male wrens (Troglodytes) of North America build 

 "cock-nests," to roost in, like the males of our Kitty- 

 wrens — a habit wholly unlike that of any other known 

 bird. 



Finally, it may not be a logical deduction, but to 

 my imagination it is far more satisfactory to look at 



