The Pond Snails 



L. gracilis, Jay, has but four or five whorls, but is 

 seven times as long as broad. It might be called "the needle 

 pond snail." The aperture is elongately oval, and has no fold. 

 Colour, white. Length, i inch. 



Habitat. — Lake Champlain, Wisconsin and Ohio. 



THE POUCH SNAILS. BLADDER SNAILS 



Genus PHYSA, Drap. 



Shell sinistral, oblong, thin, polished, of few whorls; aper- 

 ture oval, anterior margin not dilated; outer lip acute; inner 

 lip reflexed over columella; foot long, pointed behind; mantle 

 margin fringed, reflected over shell edges; tentacles, long, thread- 

 like. Distribution world-wide. More active moUusks than the 

 Limnaeas, both in walking and in gliding with shell downward on 

 the surface of the water. They descend and ascend on threads 

 of mucus. 



The best way to study these little pouch snails is to get a 

 few full grown ones in spring, place them in a tumbler or fruit 

 jar of pond water, with a pebbly bottom, and a little pond weed 

 lying on the bottom. The spawn will be extruded, and the young 

 hatched. As they develop they constantly travel about on 

 threads. 



A writer in the Quarterly Journal of Conchology makes 

 some interesting observations upon these agile little "bladder 

 snails": 



Often when two Physae meet upon the same thread they 

 fight as only mollusks of this genus can, and the manoeuvres they 

 go through upon their fairy ladders outdo the cleverest human 

 gymnast that ever performed. I once saw one ascending, and 

 when it was halfway up the thread it was overtaken by another; 

 then came the "tug of war"; each tried to shake the other off 

 by repeated blows and jerks of its shell, at the same time creeping 

 over each others' shell and body in a most excited manner. 

 Neither being able to gain the mastery, one began to descend, 

 followed by the other, which overtook it, reaching the bottom 

 first. 



Yet they are not always bent on war, but pass and repass 

 each other in an amicable spirit. One of the most beautiful 

 sights in molluscan economy is to see these little "golden pippins" 

 gliding through the water by no visible means; and when they 



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