A SUMMER AT HOME. 241 



Not in a great variety, it is time, but in individuals, 

 literally countless. ^i 



These mollusks were elongate and twisted to the right ; 

 oval and twisted to the left; flat and rolled on them- 

 selves, like an old-fashioned ginger-cake. They crawled 

 over the stems of the lilies, the projecting trunks of 

 the trees, stones, mud, dead leaves, and even came a 

 little way out of the water, at times, although strictly 

 aquatic animals. 



These shells were not beautiful, and I can scarcely say 

 why I hunted them so eagerly ; unless to be able to de- 

 termine just how many kinds were to be found. This 

 I by no means accomplished, but was content to have 

 a fine series of three genera, which were found in one 

 limited spot. It is hard to describe their differences, 

 except by giving anatomical details; so suffice it to say, 

 I had Limngeas that were twisted to the right, and 

 Physas, twisted to the left, and Planorbes, that were 

 flat and curled like a watch-spring. Collectively we can 

 call them " water-snails." 



" These snails have the power of crawling or floating 

 along the surface of the water, the creeping disk being 

 just level with the surface and the shell hanging be- 

 neath. When they wish to sink, a portion of the air 

 contained in the lung-cavity is expelled, and a sliglit 

 clicking sound is heard accompanying this movement." 



I had almost forgotten a fourth form. From blades of 

 broad grass that were waving in the current I gathered 

 a quantity of little shells, that had no twist about them, 

 but were more like little bowls turned bottom upward. 

 They are water-snails too, but let us say Ancylns, and be 



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