37 



is more or less concealed, and not unfrequently entirely 

 hidden, by the overlapping of the outer whorl. 



The shape of Paludina vivipara is very produced, 

 having six convolutions, the last of vrhich is almost 

 obsolete. The colour is that of an olive-green, over 

 which are broad reddish-brovrn bands ; these bands 

 are so placed as to have three of them on the lowest 

 whorl, the bottom one of which becomes obsolete at the 

 commencement of the second whorl ; the other two 

 bands traverse the second and third whorls, and then 

 gradually fade away. 



The dimensions of the largest specimens procured 

 from the river Soar, near Thrumpton, and the canal 

 near Beeston Ryelands, are — the length, an inch and a 

 half J the breadth, one inch and one-sixth of an inch ; 

 the latter being the diameter of the lowest whorl. 



It grows to a much larger size in the south-eastern 

 parts of Germany than it does in England, 



Dr. Lister appears to have been the first conchologist 

 who described this shell, in a work which he published 

 in the year 1678. 



The young, as extracted from the parent before the 

 period at which they are brought forth, have very thin 

 transparent shells, and aro nearly spherical. If the 

 oviducts of Paludina vivapara are examined at the 

 commencement of summer, they will be found to con- 

 tain young from a quarter of an inch in diameter 

 downwards to a size which is nearly invisible to the 

 unassisted eye. Mr. Woodward, of the British 

 Museum, says, "Embryos scarcely visible to the naked 

 eye have a well-formed shell, ornamented with epi- 

 dermal fringes; a foot and operculum; and the head 

 has long delicate tentacula, and very distinct black 

 eyes." The young are not born until they are about a 

 quarter of an inch in diameter. 



