126 MIND IN EVOLUTION CHAP. 



at birth to stimuli of a highly general instead of a defi- 

 nitely particularised character, and this is the first step in 

 the conversion of an instinct into a general tendency 

 capable of being directed by experience. The instinctive 

 tendency as such becomes more general, and experience 

 makes it definite. 



7. Retrogressive Assimilation. 



In the cases hitherto discussed, there was to begin with 

 a reaction, random or instinctive, to a certain stimulus, and 

 the effect of experience was to modify this reaction. We 

 pass now to cases in which a reaction is acquired to which 

 there is no initial tendency. In the former cases, the reaction 

 had to be modified ; in these it has to be as it were created. 



The sight of a man or the sound of a human voice 

 cannot under ordinary circumstances stimulate a wild 

 animal that does not prey upon man to expect food or 

 prepare to receive it. But if the same animal is caught 

 and kept in captivity, it will soon "get to know" its 

 keeper and perhaps its feeding time. If it is an intelligent 

 animal it may itself be readily trained to make conventional 

 signs of its desire for food, as I have seen an elephant ring- 

 ing a bell and turning a rattle, while a smaller elephant in 

 the next stall would knock with its trunk against the sides 

 of its cage to win back to itself the attention and the buns 

 which were being unfairly attracted by its neighbour. But 

 in its simpler form, this operation of experience is seen 

 very much lower down in the intellectual scale. Fish, for 

 example, which are accustomed to be fed, will come to the 

 surface and be ready to snap as soon as any one approaches 

 their tank. Mr. Bateson 1 describes a rockling which 

 under these circumstance would lift its head above water 

 and snap at the fingers. According to Brehm 2 tortoises 

 and turtles in general become accustomed to men who 

 treat them well though it is probably the human form or 

 voice to which they react, as it is elsewhere said that the 

 most easily tameable of Chelonia do not distinguish indi- 

 viduals. 3 Watersnakes we learn on the same authority, 4 

 get excited when the keeper bringing food opens the door 



1 Journal of Marine Biology, p. 238. 



2 Thicrleben, VII. p. 547. ' 3 2 b. p. 562. 4 Ib. p. 471. 



