WILD LIFE OF ORCHARD AND FIELD 



for pond-snails than the tule marshes of the Pacific 

 slope, where hundreds of the great, graceful Limnea 

 stagnalis lie among the rotting vegetation or float 

 upside down at the surface of the still water. But 

 some of the fresh-water mollusks remain most of 

 the time at the bottom, coming to the surface only 

 to breathe now and then; and to get their shells 

 it is necessary to use a sieve -bottomed dipper or 

 some sort of dredge. When the water becomes 

 low they bury themselves in the mud; it is there- 

 fore always profitable, late in the summer, to rake 

 out the bottom of mud-holes where, the water has 

 entirely disappeared. Another plan is gently to 

 pull up the water-weeds by the roots and cleanse 

 them in a basin of water. You will thus secure 

 many very small species. Experience will quick- 

 ly teach the collector where he may expect to find 

 this and that kind, and that some caution and 

 much sharpness of observation are necessary, 

 since some species by their naturally dead tints, 

 and others by a coating of mud, assimilate them- 

 selves so nearly to their surroundings as easily to 

 be overlooked by man as well as other enemies. 



The shell is increased rapidly for the first two or 

 three years, and the delicate lines of increment, 

 parallel with the outlines of the aperture, are readily 



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