270 MENTAL EVOLUTION IN ANIMALS. 



historic priority, even if from the first these two principles 

 have not been in combination ; the important fact to be 

 shown is that even a fully formed instinct may prove itself, 

 under the influence of intelligence, variable or plastic. I 

 therefore demonstrated the plasticity of many existing 

 instincts, dwelling especially upon the cell-making instinct 

 of bees, and the incubating and maternal instinct of warm- 

 blooded animals — choosing these instincts for special con- 

 sideration because they must be of so ancient an origin, and 

 are so strongly inherited. 



Intelligence may operate in the modification of instinct, 

 either by perceiving the need of a change in the dictates of 

 heredity, by intelligent imitation of the habits of other 

 animals, or by parents intentionally teaching their young. 

 Copious facts on all these points were therefore given. But 

 the best evidence of the extreme modification which instincts 

 may be made to undergo by the combined effects of intelli- 

 gence and selection, is that which is afforded by the facts of 

 Domestication. These facts were therefore detailed at length, 

 and they showed that domestication has not merely a nega- 

 tive influence in eradicating natural instincts (witness the 

 loss of wildness in dogs, cats, horses, and cattle ; dogs not 

 attacking sheep, pigs, or poultry ; the latter having lost their 

 instinctive fear of dogs, so differing from pheasants; the 

 incubating instinct being lost in the Spanish hen, and the 

 maternal instinct in cows and sheep where the young have 

 for generations been habitually removed from their mothers 

 at birth ; Polynesian dogs having lost their natural intelli- 

 gence, together with their natural taste for flesh) ; but also a 

 positive influence in developing new instincts. In the case 

 of the Dog these new or " artificial " instincts were shown to 

 be strikingly exhibited in the sheep-dog, pointer, and re- 

 triever ; but perhaps still more remarkably in the instinctive 

 love of man shown by nearly all the breeds ; faithfulness to 

 and sense of dependence upon man ; inborn idea of protect- 

 ing his master's property and of himself as constituting a 

 part of that property ; barking being an acquired instinct, 

 and probably arising from this idea of protecting his master's 

 property. Indeed so fundamental has been this psychological 

 transformation in the dog, that the artificial instincts have 

 frequently become stronger than even the strongest of the 

 natural instincts, viz., the maternal — as is proved by cases in 



