Chap. I. THEIR SENSES. 21 



illuminated by a candle, or even by a bright 

 paraffin lamp, they were not usually affected 

 at first. Nor were they when the light was 

 alternately admitted and shut off. Some- 

 times, however, they behaved very differ- 

 ently, for as soon as tlie light fell on them, 

 they withdrew into their burrows with 

 almost instantaneous rapidity. This occurred 

 perhaps once out of a dozen times. When 

 they did not withdraw instantly, they often 

 raised the anterior tapering ends of their 

 bodies from the ground, as if their attention 

 was aroused or as if surprise was felt ; or 

 they moved their bodies from side to side as 

 if feeling for some object. They appeared 

 distressed by the light ; but I doubt whether 

 this was really the case, for on two occasions 

 after withdrawing slowly, they remained for 

 a long time with their anterior extremities 

 protruding a little from the mouths of their 

 burrows, in which position they were ready 

 for instant and complete withdrawal. 



When the light from a candle was con- 

 centrated by means of a large lens on the 

 anterior extremity, they generally withdrew 

 instantly ; but this concentrated light failed 



