154 Thomas Henry Huxley 



them the instinct for experimental investigation of 

 everything with wliich they are surrounded, and their 

 imitative faculties are pecuharly great. The import- 

 ance of this, from the point of view of Huxley's argu- 

 ment, is great. The difference between the instincts of 

 the lower animals and the intelligence of man is that 

 instincts are to a large extent fixed and mechanical. 

 The proper performance of an instinct demands the 

 presence of exactly the right external conditions for its 

 accomplishment. In the absence of these conditions, 

 the call to perform the instinctive action is equally great, 

 and results in useless performances. In many of the 

 higher animals these elaborate instincts are more gen- 

 eral in their character, and are supplemented bj^ a con- 

 siderable but varj'ing aptitude for modification of 

 instinctive action to suit varieties of surrounding cir- 

 cumstances. As this intelligence becomes more and 

 more developed, the blind, mechanical instinct becomes 

 weaker. A large number of instances might be given 

 of such instincts modified by dawning intelligence. The 

 chief factors in producing the change are, as has been 

 shewn by Professor Groos, the possession of a general 

 instinct to imitate and to experiment, and the existence 

 of a peiiod of 3-outh in which the 3'oung creature may 

 practise these instincts, and so prepare itself for the 

 more serious purposes of adult life. The anthropoid 

 apes seem to possess these experimental instincts to an 

 extent much greater than that observed in any other 

 class of animals, and, as they have a long period of 

 youth, they have the opportunity of putting them into 

 practice to the fullest possible extent. 



From the natural history of the anthropoid apes, 

 Huxley passed to consideration of their relation to man, 

 prefacing his observations with a passage defending the 



