iv] SENSE ORGANS AND SENSES 67 



certainly lacking in the Eudrilidae, whatever may be 

 the function of the cellular epidermic bodies here 

 briefly referred to. 



While there is thus nothing very positive to be 

 gleaned from an examination of the structure of the 

 Oligochaeta as to the senses which they may possess, 

 experiment has done something towards an elucida- 

 tion of their behaviour under stimuli and their 

 reaction to light and to other forces which come into 

 play during their lives. There is some evidence that 

 earthworms can see, using that expression of course 

 in a very broad way. At any rate they react to 

 changes in the intensity of light. The gross experi- 

 ment of flashing a lantern upon earthworms which 

 are reaching out from their burrows with the tail 

 end inserted in those burrows shows that they have 

 an appreciation of light. More refined experiments 

 have been conducted upon the sense of light. 

 Dr Graber used a box with two compartments, the 

 one of which was dark and the other illuminated 

 with diffused daylight, i.e. not direct sunlight. The 

 worms were allowed equally free access to both and 

 were examined at the close of every hour, and their 

 positions noted. The investigator found that on the 

 average the dark half of the box contained 5*2 times 

 as many worms as the light chamber, thus indicating 

 a very marked preference for absence of light. 



Not only is this the case, but the same observer 



52 



