Chap. L 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 1 



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 



separate. 



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 manntjr, independently of the will 



