180 



FEESH-WATEE AQTJAEIA. 



cultivated in a snail. But I certainly have noticed that the 

 longer some of the Limnxse are kept in confinement, the less 

 they eat of growing plants and the more of confervse. These 

 snails are gregarious for the most part, and extremely prolific. 

 They are generally found in sluggish or stagnant water, 

 crawling upon the mud or adhering to and feeding upon 

 aquatic plants, or floating on the surface of the water. Each 

 individual is both male and female. 



Limnsea stagnalis (Mg. 119) is a very elegant snail, found in 

 slow-rmining and stagnant water nearly all over Britain, and 

 is sometimes called the "Fresh- water "Whelk." It is very 



Fig. 119. LiMNiEA stagnalis. 



useful in the aquarium as a consumer of conf ei-vae, but it is . 

 not always willing to confine itself to this food. It should 

 therefore be watched, and removed directly it is seen destroying 

 the aquatic plants. I have had some snails of this species 

 which lived almost entirely upon confervoid growth, but they 

 were those which I had had in confinement for a long time. 

 This snail, when irritated, sometimes discharges a violet- 

 coloured liquid. It is also occasionally carnivorous. L. stag- 

 nalis is not by any means difficult to recognise, on account of 

 its large size and elegant shape. Its body is yellowish-grey 

 with a bluish- green tinge and mottled with brown and white. 

 The tentacles are flat and triangular. The disc is broad and 

 has a yellowish margin. The sheU is about IJin. long, of 



