102 INSTINCTS 



inferences in choosing one or other of them. There 

 are, in fact, occasions when they are free from the 

 dominating influence of directive instinct. In 

 some cases, indeed, reason appears to have actually 

 modified instinct. Caterpillars that have pro- 

 tected themselves by rolling up leaves have, 

 under different circumstances, taken to burrowing 

 within them : beetles that rolled up balls of dung 

 (for the deposit of their eggs) have taken advan- 

 tage of sheep droppings : a New Zealand parrot 

 (Pastor mutabilis) has within recent years become 

 carnivorous, and causes much loss to farmers by 

 wounding sheep. Birds and insects will occa- 

 sionally alter the customary form and situation of 

 their nests, and will make shift to economize 

 materials. A crucial case, quoted by Romanes, 

 is that of a flycatcher which nested in a conserva- 

 tory and, appreciating the heat maintained by 

 the furnace, left its eggs to hatch of themselves. 

 In all these cases there must have been some dis- 

 tinguishing of properties, and inferring from ex- 

 perience. A familiar illustration is that of a dog 

 which has been shut into a garden. At first he 

 will endeavour to scrape himself under the gate, 

 or through the bars, but if he fails to get past and 

 is an intelligent animal, he will attempt to jump 

 the gate. He notices that the gate has the pro- 

 perty of being surmounted by a jump, and infers 

 from past experience that he can leap over it. 

 He would not try to jump a high wall. Man 

 has been assisted in outdistancing the most 

 intelligent quadrupeds by his almost total loss 

 of directive instinct : he must rely upon his 

 reason, whereas the dog or the monkey is subject 

 to instinctive promptings which confuse its 

 reasoning faculties. Habit, it is true, similarly 

 enables man to dispense with his reason : but 

 habit is less imperious than instinct, and may 



