Instinctive Behaviour of Worms 7 1 



fall on the animal, turn its head and jump 

 towards the source of light. 



There is a great contrast between the more 

 prominent instinctive movements displayed by 

 worms, and those of beings which possess 

 neither head nor tail, their central nervous 

 system consisting of two subdermal rings of 

 nerve cells and fibres, in place of a rudimentary 

 brain such as that which exists in the head of 

 an earth-worm. For example, the common 

 earth-worm displays remarkable purposive be- 

 haviour in the way it plugs the external opening 

 of its burrow. The animal emerges from its 

 burrow at night, and drags dry leaves, the petals 

 of flowers, paper, or other light materials, 

 squeezing them into its burrow. A leaf when 

 being dragged to the burrow often becomes 

 folded or crumpled. When another leaf is 

 drawn in, this is done exteriorly to the first one, 

 and so on with the succeeding leaves; and 

 finally they all become closely folded and 

 packed together; the interstices between the 

 leaves being filled up by means of a viscid 

 secretion ejected from the animal's body. 

 Darwin describes the way in which an earth- 



