More Beetles 



ditional resistance in the substance traversed 

 will cause the Beetle to turn aside slightly, 

 now hither, now thither. Consequently the 

 glass wall will be completely denuded at sun- 

 dry points; windows will be formed, chinks 

 upon which I rely to make observation pos- 

 sible, but which will be hateful to the dark- 

 ness-loving workers. 



To make sure of these windows and save 

 the insect from them, I sheath the tube in a 

 few cardboard sheaths which can be gently 

 slipped up and down and which fit inside one 

 another. With this arrangement, I shall be 

 able, when required, and without distracting 

 the insect from its work, to create alter- 

 nately, by a simple movement of the thumb, 

 a little light for myself and darkness for the 

 Beetle. The distribution of the movable 

 sheaths, which slip up or down as needed, 

 will allow the tube to be examined from end 

 to end as and when the accidents of boring 

 open up new windows. 



A last precaution is necessary. If I 

 merely put the couple simply in the dish 

 surmounted by the bell-glass, it Is probable 

 that the prisoners will not realize what a 

 small portion of the soil Is available for dlg- 



102 



