Chap. L THEIE 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 ^hem, 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 manner, independently of the will 



