vi INSTINCT 87 



bit to make room for another, it will often use the same 

 object a second or third time over, while it will throw 

 away objects much better suited for its "purpose/' in 

 favour of bits of glass which do not conceal it at all. 1 

 On the other hand, a crab described by Mr. Bateson 2 

 shows more capacity for adjustment. It takes the weed 

 in its chelae, tears it across, puts one end in its mouth and 

 chews it, and finally rubs it on its head and legs until it 

 is caught by the hairs. If however the hairs do not catch 

 the piece, the crab puts it back into its mouth and chews 

 it up again. Here the non-fulfilment of the function 

 has a direct influence. The crab persists or repeats the 

 necessary steps. Whether this implies intelligence or not is 

 a question on which opinions may differ. We may content 

 ourselves with noting the fact that, whatever the means 

 employed, special actions are brought to bear by which the 

 ends of the instinct are achieved. Still more instructive 

 is Schneider's 3 experiment on some " sea-spiders " to 

 which he gave pieces of paper and linen as well as bits of 

 algae, which they generally use. The paper and linen 

 were at first utterly neglected, but when Schneider removed 

 the algae, a divergence appeared. Of the five crabs, three 

 grubbed in the sand, and so covered their backs with bits 

 of shell and pebble, while the other two betook them- 

 selves to the paper and the linen. In the former case, a 

 second kind of habitual reaction is evoked. In the latter, 

 one object is substituted for another. The paper does not, 

 as long as algae are present, excite the crab to seize it ; 

 but the algae being gone, the paper steps into their place 

 so that the instinct may still be fulfilled. The instinct is 

 thus in part independent of stimulus. It needs objects in 

 order to work itself out, but it is not entirely set in 

 motion by the influence of those objects. 



7. At this point it may be asked how far we are justified 

 in referring well-devised adaptations of hereditary methods 

 to mere instinct. An alternative explanation suggests 

 itself. It is possible that within the sphere of instinct, 

 intelligence plays a certain subordinate part. Though the 



1 Op. tit. p. 210. 2 Journal of Marine Biology, 1889-90, p. 213. 



3 Op. tit. p. 318. 



