38 



I have also alluded to this shell in my introduction, 

 at page 3. 



An inhabitant of slow rivers, canals, and ditches, 

 fiourishing best where the water is still and not liable 

 to be frequently disturbed by strong currents. 



It is very readily kept in confinement, in any small 

 vessel which contains water. The year before last I 

 myself kept one in this manner throughout the winter, 

 giving it occasionally fresh water; under these circum- 

 stances it flourished and increased its size considerably. 



A curious fact with respect to this shell, as well as 

 to many others (especially Bithinia tentaculata, Cyclas 

 cornea, Planorbis cornea, Pianorbis marginata, Pla- 

 norbis carinatus, Valvata piscinalis, Limuseus pereger, 

 &c.,) is worth recording. In cold weather these mol- 

 luscs require a much greater degree of heat to destroy 

 them than in hot weather, a circumstance probably 

 accounted for by their animal heat being greater in 

 cold than' in hot weather, and also probably by their 

 being somewhat torpid at a lower temperature. This 

 phenomenon is so apparent that it requires a tempera- 

 ture about 20° higher to kill them in autumn to what it 

 does in the middle of the summer. Physa fontinalis, 

 Planorbis albus, and Neritina fluvialiiis are an excep- 

 tion to the rule, as a similar temperature will destroy 

 them at all seasons of the year. Amongst the land 

 shells several of the Helices also require an increase of 

 heat for an increase of cold in the weather to destroy 

 life. 



Our localities for Paludina vivipara are, the river 

 Soar at Thrumpton and the canal near Beeston, in 

 both of which places it is abundant. Also the Trent, 

 at Beeston Ryelands, and below the Nottingham bridge, 

 and the canal and a ditch at Lenton. 



It is found in the Thames (Forbes), at Birmingham 



