NATURAL HISTORY. 73 



worm, which is to be found sometimes in 

 ponds, and very often in springs of fresh 

 water. There are several sorts of them, but 

 the one I am thinking of now, builds a stone 

 house to live in. These worms are in the 

 habit of making a little tube, sometimes of 

 sand, or shell, or wood, or leaves, or stones, 

 to live in ; and their skill consists in joining 

 these perfectly, and making them stick to- 

 gether. But we are talking now of the caddis- 

 worm that uses stone. What the worm has 

 to do is to make a tube out of small stones, 

 that shall have a hollow about as large as a 

 wheat straw, and be perfectly smooth inside. 

 This is a pretty hard task at least it would 

 be very hard to us. When the stone-mason 

 wishes a stone of a particular size or shape, 

 and cannot find it, he takes his hammer and 

 breaks one until it will suit ; but the caddis- 

 worm has no hammer, and must take the 

 stones just as it finds them. The little in- 

 sect then has to pick out a great many stones 

 before he gets the right one, because they 

 have so many little rough points about them 

 that it is very difficult to get those which will 

 make the tube perfectly smooth inside. Re- 

 member, tooj that the bottom or lower side of 



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