INTRODUCTION. 



XXlll 



leisurely, as no important duties of incubation are pressing irresistibly 

 upon them), and they are once more amongst the dates and pomegranates 

 of the Saharan oasis, the annual cycle is finished, to be repeated with 

 scarcely a variation for thousands of years to come, as it has been for 

 thousands of years in the past. 



Some such story as this is the true history of a bird, divined by the keen 

 poetic insight of Kingsley and Butler, and no doubt ten years hence will 

 be accepted by every man of science. The evolution of scientific thought 

 will not come to an end because Darwin did not live long enough to 

 chronicle it. 



The pre-Darwinian philosophers regarded man and birds as separate 

 creations, the former endowed with reason and the latter with instinct. 

 Instinct and reason were regarded by them as distinct from each other, as 

 arms were looked upon as being perfectly distinct from wings. Modern 

 biologists have discovered a close affinity between the latter; they have 

 discovered that the arms of a man and the wings of a bird are only modi- 

 fications of the fore legs of their common ancestor, and there can be little 

 doubt that the reason of man and the instinct of birds are likewise only 

 modifications of some mental power possessed by their common ancestor. 

 If instinct be regarded as distinct from reason, it must be admitted that 

 both faculties are possessed both by man and by birds. The difference 

 between the two faculties would then chiefly lie in this, that if the operator 

 were conscious of the motive for performing an action in a certain manner, 

 it would be regarded as an act of reason; but if the action had been 

 repeated so often that the cause of its performance was forgotten in the 

 fact that it had been so often repeated as to have become a habit, it would 

 be regarded as memory, and where the habit was inherited from an ancestor 

 as instinct. Instinct would thus become a synonym of inherited habit, 

 inherited memory, or, to be still more precise, inherited association of 

 ideas a faculty common to man and other animals. 



