22 SPIDERS [CH. 



if it must," and is quite ignorant of the purpose to be 

 subserved. 



It is no doubt quite beyond our power to ascertain 

 accurately the mental condition of a spider, but it is 

 perfectly easy to make a few illuminating experiments 

 on two points which have a very decided bearing on 

 intelligence : the development of the senses, and the 

 degree of what has been called educability, or the 

 power of learning from experience. To what extent can 

 the spider see, hear, smell, feel, taste ? How far is it 

 capable of varying its action as the result of ex- 

 perience ? The senses, as far as we know, are the 

 principal if not the only avenues by which external 

 impressions can reach the seat of intelligence, and 

 there is no surer indication of the intelligence of an 

 animal than the degree to which it is susceptible of 

 education. Probably most readers know the immor- 

 tal story of the pike cited by Darwin in the Descent 

 of Man. The pike was in an aquarium, separated by 

 a sheet of glass from a tank in which were numerous 

 small fish. Not till three months had expired 

 did the pike cease to dash itself against the glass 

 partition in its attempts to seize the fish in the neigh- 

 bouring tank. It then desisted and had evidently 

 learnt something but what? After three months, 

 the glass partition was removed, but the pike refused 

 to attack those particular fish, though it immediately 

 seized any new specimens introduced to the tank. All 



