The Caddis- Worm 



almost the whole of the sheath is constructed 

 at the bottom of the pond, whither all the ma- 

 terials picked up at random, having descended 

 once before, are likely to descend again. In 

 the sheaths, the parts capable of floating are 

 very rare. Without taking their specific levity 

 into account, simply so as not to remain idle, 

 the Caddis-worm fixed them to its bundle 

 when sporting on the surface of the water. 



We have our submarines, in which hy- 

 draulic ingenuity displays its highest resources. 

 The Caddis-worms have theirs, which emerge, 

 float on the surface, dip down and even stop at 

 mid-depth by releasing gradually their surplus 

 air. And this apparatus, so perfectly bal- 

 anced, so skilful, requires no knowledge on 

 the part of its constructor. It comes into be- 

 ing of itself, in accordance with the plans of 

 the universal harmony of things. 



211 



