Chap. I. THEIR SENSES. 23 



different occasions might be explained, either 

 by the degree of extension of their skin and 

 its consequent transparency, or by some 

 particular incidence of the light ; but I 

 could discover no such relation. One thing 

 was manifest, namely that when worms were 

 employed in dragging leaves into their 

 burrows or in eating them, and even during 

 the short intervals whilst they rested from 

 their work, they either did not perceive 

 the light or were regardless of it ; and this 

 occurred even when the light was concentrated 

 on them through a large lens. So, again, 

 whilst they are paired, they will remain for 

 an hour or two out of their burrows, fully 

 exposed to the morning light ; but it appears 

 from what Hoffmeister says that a light 

 will occasionally cause paired individuals to 

 se^Darate. 



When a worm is suddenly illuminated and 

 dashes like a rabbit into its burrow — to use 

 the expression employed by a friend — we are 

 at first led to look at the action as a reflex one. 

 The irritation of the cerebral ganglia appears 

 to cause certain muscles to contract in an 

 inevitable manner, independently of the will 



