20 INTRODUCTION. 



" Instinct by itself ought always to guide individuals of the- 

 same kind to the same work. But suppose there are dif- 

 ficulties in the way of the completion of the work ? The 

 individual removes the hindrance ; he selects the best place 

 for his dwelling ; he guards against accident, he meets 

 danger. Sometimes he gives way to sloth, and builds no 

 house, but steals someone else's, and scarcely ever improves 

 it. The insect, believed by man to act as a machine, gives 

 proof at every moment that it takes note of the situation in 

 which it finds itself, and of a crowd of accidental circum- 

 stances which it was impossible to foresee. But to take 

 note of a difficult position, to improve it, to make a choice, 

 to take a thing in order to save oneself trouble, to be 

 lazy when one is made for industry, is this instinct ? 

 Impossible ! " 



In the same way speaks C. Menault, in his admirable book 

 on " Intelligence in Animals" (Paris, 1872, p. 114): '" What ! 

 creatures that have faculties, that feel, remember, and com- 

 pare their feelings, that express themselves in a more or less 

 distinct fashion, but ever in sympathy with their emotions 

 of joy, grief, auger, or passion such creatures have no 

 intelligence ? By God, I should then like to know what 

 intelligence is ! " 



Note also what Wallace, the thought-colleague of Dar- 

 win, brings forward in his " Natural and Sexual Selection " 

 (1870), on the many changes and alterations of a very 

 powerful instinct, namely the nestbuilding instinct of birds, 

 in consequence of change of circumstances. " The orchard 

 oriole of the United States," says Wallace, " offers us an 

 excellent example of a bird which modifies its nest according 

 to circumstances. When built among firm and stiff 

 branches the nest is very shallow, but if, as is often the 

 case, it is suspended from the slender twigs of the weeping 

 willow, it is made much deeper, so that when swayed 

 about violently by the wind the young may not tumble out. 

 It has been observed also, that the nests built in the warm 

 southern states are much slighter and more porous in texture 

 than those in the colder regions of the north. Our own 

 house-t-parrow equally well adapts himself to circumstances; 

 when he builds in trees, as he, no doubt, always did 

 originally, he constructs a well-made domed nest, perfectly 

 fitted to protect his young ones ; but when he can find a 



