72 Instinct and Intelligence 



worm almost invariably lays hold of leaves by 

 their tips, so that the thin part of the leaf can 

 be easily drawn into the burrow, leaving the 

 thick foot-stalk projecting outwards from the 

 mouth of the hole. He observes : " Although 

 the habit of dragging leaves into their burrows 

 is undoubtedly instinctive with worms," never- 

 theless these purposive movements are so 

 accurately adapted to fulfil their ends, that it 

 is difficult to distinguish them from movements 

 guided by intelligence. 1 



Darwin refers to the fact that the instinctive 

 behaviour of earth-worms is hereditary, for he 

 had watched a very young one born in one of 

 his pots, dragging for some distance a Scotch fir 

 leaf, one needle of which was as long and almost 

 as thick as its own body. No species of pine 

 was endemic in the part of England where this 

 incident occurred; it is therefore incredible 

 that the proper manner of dragging pine-leaves 

 into the burrow could have been learnt by this 

 worm ; its behaviour was clearly instinctive or 

 innate, for so young an individual could not 



1 The Formation of Vegetable Mould, by Charles Darwin, 

 pp. 27, 56, 



