The Pond Snails 



The spire of this snail tapers above the large body whorl to a 

 needle-pointed apex. The whorls are rounded and separated by 

 a deep suture. The outer lip is thin and does not flare. The 

 columella is somewhat callous, and bears a strong oblique fold. 

 The yellowish brown surface is coated with an epidermis, which is 

 usually worn off on the spire, and the shell substance corroded by 

 carbonic acid in the water. 



The body is yellowish gray; the broad foot is edged with 

 yellow. The large square head bears pointed tentacles that 

 broaden toward their bases. The largest specimens are two 

 inches long. Half-grown shells are transparent and more slender 

 than the adults. 



L. stagnalis is a general feeder, exhibiting decided carni- 

 vorous tastes, though it is generally rated a vegetarian. In the 

 fresh-water aquarium this bloodthirsty snail attacks newts and 

 sticklebacks and contentedly picks their bones. Larvae of water 

 beetles and other insects have also been its victims, and even its 

 own young are not exempt. These depredations are not justified 

 on the grounds of hunger. Plenty of its favourite vegetable food 

 was in the jar. It is strange that a snail is able to capture crea- 

 tures so strong, so agile and in some instances so well armed. 

 In a pond in England an old newspaper was found to be covered 

 with snails which were hungrily feeding upon its substance. 



The eggs are laid in cylindrical masses, counting from fifty 

 to one hundred or more. The young grow most lustily in large 

 ponds and streams. It is a fact well established by scientific 

 tests that "rate of development and ultimate size attained are 

 in direct proportion to the volume of water in which the individuals 

 have lived." It is not surprising that so susceptible and so 

 cosmopolitan a species should exhibit infinite variations. 



The Dwarfed Limneea (L. truncatula, Mull.) means no harm 

 at all, but it probably works more harm to the human race than 

 any other mollusk. And this by being the innocent victim of 

 one of Nature's cruel conspiracies, which gives the victory to a 

 disgusting parasite. 



Our little truncatula has a pointed, conical shell not over 

 half an inch high, with shiny, deeply sutured whorls, and a distinct 

 umbilicus. It scrapes the yellow-green algae from the surface 

 of ditches and ponds, "askin' nothin' f 'm nobody." But around 

 it swim the ciliated embryos of Fasciola hefatica: a single adult 



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