310 ANIMAL INTELLIGENCE. 



ground, which are thus wasted. A third species, the M. precius 

 of North America, has acquired instincts as perfect as those of 

 the cuckoo, for it never lays more than an egg in a foster-nest, 

 so that the young bird is securely reared. Mr. Hudson is a 

 strong disbeliever in evolution, but he appears to have been so 

 much struck by the imperfect instincts of the Melothrus Canari- 

 ensis that he quotes my words, and asks, ' Must we consider these 

 habits not as especially endowed or created instincts, but as 

 small consequences of one general law, namely transition ? ' J 



Such are all the facts and considerations which I have 

 to present with reference to the curious instinct in ques- 

 tion. It will be seen that with one doubtful or not suffi- 

 ciently investigated exception, viz., that of cuckoos adapt- 

 ing the colour of their eggs to that of the eggs of the 

 foster-parents there is nothing connected with these 

 instincts that presents any difficulty to the theory of evo- 

 lution. We may, perhaps, at first sight wonder why some 

 counteracting instinct should not have been developed by 

 the same agency in the birds which are liable to be thus 

 duped ; but here we must remember that the deposition 

 of a parasitic egg is, comparatively speaking, an exceed- 

 ingly rare event, and therefore not one that is likely to 

 lead to the development of a special instinct to meet it. 



General Intelligence. 



Under this heading I shall here, as in tne case of this 

 heading elsewhere, string together all the instances which 

 I have met with, and which I deem trustworthy, of the 

 display of unusually high intelligence in the class, family, 

 order, or species of animals under consideration the ob- 

 ject of this heading in all cases being that of supplying, 

 by the facts mentioned beneath it, a general idea of the 

 upper limit of intelligence which is distinctive of each 

 group of animals. 



That birds recognise their own images in mirrors as 

 birds there can be no question. Houzeau, who records 

 observations of his own in this connection with parrots,* 

 adds that dogs are more difficult to deceive by mirrors in 



1 Origin of Species, p. 215. 2 Tom. i., p. 130. 



