ix ANIMAL BEHAVIOUR 169 



equally inferior one. It must not be supposed, indeed, 

 that instinctive capacities may not show variability ; the 

 point is that they are much more uniform than intellectual 

 endowments. Perhaps one may venture to say that 

 while intelligence is as much made as born, instinctive 

 capacity is much more inborn than made. 



(4) Instinctive behaviour is always adaptive in the 

 normal conditions of the animal's life, though it may 

 prove ineffective or misleading in face of peculiar exi- 

 gencies. It has to do with particular external circum- 

 stances, particular stimuli and configurations, which 

 frequently recur, or, if not, are of vital moment (as in the 

 young bird's escape from the imprisoning egg-shell) ; and 

 a slight change in the conditions is likely to result in 

 extraordinary nonplussing. 



The apartness of purely instinctive behaviour, as con- 

 trasted with that experimental, inferential, or reflective 

 kind of behaviour which we call intelligent, is strongly 

 suggested by it 3 limitations. The French naturalist 

 Fabre (whom Darwin called " that inimitable observer") 

 relates that he induced numerous procession-caterpillars 

 to move round the circular parapet of a fountain in his 

 garden, and by adjusting the length of the procession got 

 the head of the leader to touch the tail of the last member 

 of the file. The living circle continued for days in futile 

 circumambulation, obeying the instinctive follow-my- 

 leader predisposition, which in natural conditions serves 

 them well in their search for a suitable place in which to 

 undergo their metamorphosis. 



The grub of one of the mason-bees is hatched in a 

 mortar-cradle, with a lid through which it has to cut its 

 way. If the lid be artificially thickened by glueing on 

 a piece of stout paper, this makes no difference to the 

 success of the boring. But if a little empty paper-box 

 be placed over the lid, the grub emerges into this, and 

 having completed the boring part of its inborn routine 

 cannot recommence it, and dies in its paper prison. 



It is too soon to come to a conclusion in regard to the 

 nature of instinct, for we have not the facts fully before 

 us. (a) Some investigators regard instinctive behaviour 



