ANIMAL BEHAVIOUR 201 



one. The capacity is often very markedly sex-linked, the 

 one sex doing with perfect finish what the other does not do at 

 all; thus the drones of the bee-hive take no part in comb- 

 making. One must not, of course, suppose that instinctive 

 capacities are not variable; the point is rather that instinc- 

 tive equipment is much more uniform than intellectual en- 

 dowment. It may be admitted that part of the individuality 

 of intelligence is due to the fact that intelligence is as much 

 made as born, which brings us back to the contrast that 

 instinctive capacity is much more inborn than made. 



(4) Instinctive behaviour is always adaptive to the nor- 

 mal conditions of the animal's life, though it may prove in- 

 effective or misleading in face of peculiar exigencies. It 

 has to do with particular events and circumstances, particular 

 stimuli and configurations, which frequently recur, or, if not, 

 are of vital moment (as in the escape from the imprisoning 

 egg-shell) ; and a slight change in the conditions is likely 

 to result in extraordinary nonplussing. 



A study of these limitations tends to. impress us with the 

 difference between purely instinctive behaviour, and that 

 experimental, inferential, or reflective kind of behaviour 

 which we call intelligent. Let us illustrate. 



The veteran French naturalist Fabre, who died in 1915 

 at the age of ninety-two, relates that he induced a long file 

 of procession caterpillars to move round the circular parapet 

 of a fountain, and by making the head of the leader touch 

 the tail of the last member formed a living circle which 

 continued for days circumambulating futilely. " They knew 

 nothing about anything." The grub of the mason-bee is 

 hatched in a mortar-cradle with a lid through which it has 

 to cut its way. This it does without difficulty. If the 

 lid be artificially thickened by gluing on a piece of stout 



