vi INSTINCT 85 



where simple patience is the method prescribed for over- 

 coming an obstacle : 



" Very young hermit-crabs, not long after leaving the egg, 

 rush with extraordinary animation for suitable shells that are 

 given to them in the water. They examine the opening at the 

 mouth, and take up their quarters inside with remarkable alacrity. 

 But, if it chances that the shells are still occupied by molluscs, 

 then they stay close by the opening, and wait till the snail 

 dies, which generally occurs soon after the beginning of the 

 imprisonment and the strict watch. Upon this the small crab 

 pulls out the carcass, devours it, and moves into the lodging 

 himself." 1 



On this Preyer remarks : 



" What foresight ! On account of the preference of the empty 

 shells, the whole proceeding cannot be hereditary. But the 

 young animals are not instructed. They were from the begin- 

 ning separated from their parents, and had no time or opportunity 

 for experiences of their own. They must, therefore, have in- 

 herited their practice of waiting from their ancestors, as a rule of 

 conduct for the case where the shell is occupied, and they can at 

 once distinguish such a one from an empty one." 2 



The element that is not hereditary seems to be supplied 

 by perception. The empty shell invites immediate entry. 

 The full one sets in motion a different train of actions, 

 equally hereditary, and also adapted in the end to give 

 possession of the shell. 



In the last illustration given, and in some of the others, 

 it will be seen that instinct overcomes its obstacle by 

 bringing up as it were a reserve method not ordinarily 

 employed. It has alternative methods. We may say if 

 we please that the reserve method is merely a response to 

 a special stimulus, but we must keep in mind that the 

 speciality of the stimulus lies precisely in this, that the 

 success of the instinct cannot be compassed by ordinary 

 means. The cat-like patience of the hermit-crab is only 

 called forth by the necessity of getting into a shell, and by 

 its finding the shell occupied. The same general explanation 

 would apply to the action of the vine weevil, which makes 

 a nest for its eggs by rolling up a young vine leaf. If 



1 Preyer, p. 240. 2 Ib. p. 241. 



