268 MENTAL EVOLUTION IN ANIMALS 



by idiots; also by animals, as in dogs barking round a 

 carriage, differences of individual disposition and idiosyn- 

 cracies, forming strange companionships, &c. Next, that 

 automatic and useless or fortuitous habits are inherited, was 

 amply proved by cases in which this has been observed of the 

 tricks of manner displayed by men and animals ; in disposi- 

 tion, as among the island races of monkeys described by 

 Humboldt ; in the paces of the horse in different parts of the 

 world ; in the remarkable and wholly useless habits of the 

 tumbler and pouter pigeons, &c. Further, that such inherited, 

 non-intelligent, or purposeless habits should vary, is a matter 

 of certainty ; seeing that, as was subsequently shown, useful 

 habits may do so, and that even fully formed instincts are 

 plastic ; much more, then, must these fortuitous sports of 

 habit be variable. Lastly, that when they vary in profitable 

 directions the variations will be seized upon and fixed by 

 natural selection is no less a matter of certainty, and will not 

 be questioned by any one who believes in natural selection 

 as a principle concerned in the evolution of organic structures. 

 Thus only can we explain the instincts of many low animals 

 (such as the caddis-worm), and certain instincts of the higher 

 (such as that of incubation). Coming next to secondary 

 instincts, it was first shown that intelligent adjustments when 

 frequently performed become automatic in the individual, 

 and next that they are inherited till they become automatic 

 habits in the race. The former fact is familiar to every one ; 

 the latter was proved by such cases as those of hereditary 

 handwriting, family aptitudes for particular pursuits, race 

 characteristics of psychology in man, good breeding, and 

 sense of modesty. In animals the same principle is seen in 

 an hereditary tendency to " beg " in dogs, and even in cats ; 

 ponies from Norway not having " mouths ;" Dr. Huggins's 

 dog presenting an inherited antipathy to butchers ; wild 

 animals showing an instinctive fear of their particular 

 enemies, such fear being lost as regards man in domesticated 

 animals (notably in the rabbit and duck, where selection is 

 not likely to have had any part in obliterating natural wild- 

 ness) ; animals living on oceanic islands showing no fear of 

 man for several generations after his first advent among 

 them, then acquiring instinctive dread of him, and even 

 learning what constitutes safe distance from fire-arms ; 



