The Life of the Fly 



on a sheet of blotting-paper, which will absorb 

 the excess of liquid unfavourable to successful 

 observation. Outside its natural environment, 

 the animal moves about violently and rest- 

 lessly. With its body half out of the scab- 

 bard, this time composed entirely of fibrous 

 matter, it clutches with its feet at the support- 

 ing plane. Then, contracting itself, it draws 

 the scabbard towards it, half-raising it and 

 sometimes even making it assume a vertical 

 position. Even so do the Bulimi move along, 

 lifting their shell as they complete each crawl- 

 ing step. 



After a couple of minutes in the free air, 

 I replace the Caddis-worm in the water. This 

 time, it floats, but like a cylinder with too 

 much weight below. The sheath remains 

 vertical, with its hinder orifice level with the 

 water. Soon, an air-bubble escapes from the 

 orifice. Deprived of this buoy, the skiff at 

 once goes down. 



The result is the same with the Caddis- 

 worms in shell casings. At first, they float, 

 straight up on end, and then dip under and 

 sink, faster than the others, after sending out 

 an air-bubble or two through the back-window. 



That is enough : the secret is out. When 



cased in wood or in shells, the Caddis-worms, 



206 



