The Life of the Fly 



protected above by the layer through which 

 they have passed and on every side by the 

 thickness of the vessel's contents. Satisfied 

 with the site, they have stopped there. 



It is a very different matter in the tube. 

 The least buried of the pupae are half a yard 

 down. Others are lower still; most of them 

 even have reached the bottom of the tube and 

 are touching the cork stopper, an insuperable 

 barrier. These last, we can see, would have 

 gone yet deeper if the apparatus had allowed 

 them. Not one of the score of grubs has 

 settled at the customary halting-place; all have 

 travelled farther down the column, until their 

 strength gave way. In their anxious flight, 

 they have dug deeper and ever deeper. 



What were they flying from? The light. 

 Above them, the column traversed forms a 

 more than sufficient shelter; but, at the sides, 

 the irksome sensation is still felt through a 

 coat of earth half an inch thick if the descent 

 is made perpendicularly. To escape the dis- 

 turbing impression, the grub therefore goes 

 deeper and deeper, hoping to obtain lower 

 down the rest which is denied it above. It 

 only ceases to move when worn out with the 

 effort or stopped by an obstacle. 



Now, in a soft diffused light, what can be the 



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