188 LAND AND FRESH-WATER MOLLUSKS. 
this variety is intermediate in form between the 
typical L . peregra and L . glutinosa . 
3. Var. Burnetii (PL X., fig. 116) differs from 
the type in its involute spire, placed more 
obliquely, in being regularly striated, and in the 
darker colour of the animal. This variety was 
detected by Mr. Burnett, in 1848, in the 
stomachs of trout caught in Loch Shene, and 
on a second visit he obtained many living ex¬ 
amples. It occurs in a few other Scottish lakes 
and also in North Wales. 
This species shows greater activity than the 
others of the genus; as implied by the specific 
name—from the Latin peregrinor, “ to travel 
through strange places ”—it is widely dispersed, 
everywhere abundant in ponds, ditches, and slow 
running water, and is not unfrequently found 
at some distance from the water, or walking on 
the moist mud. It attains an elevation of 1742 
feet on the Aberdeenshire mountains. 
It is very prolific, and lays upwards of a thou¬ 
sand eggs in a season; these are contained in 
clusters of from 12 to 100; the gelatinous mass 
in which they are imbedded is of an elongated 
oval form. 
The dispersion of the fresh-water mollusks is 
chiefly effected by the agency of streams and 
and-floods; but wherever a pool of water is 
formed, L . peregra is the first to make its ap- 
