INTRODUCED SPECIES. 79 
INTRODUCED SPECIES. 
UNSUCCESSFUL attempts have been made from time to time 
to introduce Helix pomatia into Somerset. Mr. Francis Knight 
informs me that he brought specimens from Bavaria in 1878 
and turned them out in three places on Mendip. In his “ Sea- 
board of Mendip” he observes that H. pomatia was “found in 
1902 on Callow and near Cross. Perhaps descendants of 
specimens introduced in 1878.” Specimens in the museum at 
Weston-super-Mare are said to have been taken in Weston 
W ood, but it cannot be doubted that they had been introduced 
there. 
-Many years ago I brought many specimens of H. pomatia 
and H. cantiana from Doddington, Kent, and turned them out 
on the Inferior Oolite at Bratton St. Maur. None of the 
latter were observed the following year or afterwards, and two 
years later only a dead shell of ey. pomatia was forthcoming 
from the hedgebank in which they were placed. It is curious 
that AH. cantiana did not survive, as it is abundant in some 
parts of the county. 
Miss Hele informed Mr. John Taylor in 1881 that Helici- 
gona arbustorum “is a difficult species to introduce into a fresh 
district,—I have again and again taken them from Bath and 
liberated them in different hedges round Bristol, but always 
unsuccessfully.” 
Mr. F. Knight brought Unis tumidus and Unis pictorum 
from Langport : and turned them out on Western and at Max- 
mills; he also brought Neritina fluviatilis from the Brue to 
Weston Moor, and informs me that Vivipara vivipara is 
naturalised at Winscombe. 
There are examples of Physa heterostropha, Say, in the 
Jenyns Collection at Bath Museum, which were taken from a 
pond near that city. This species is an alien closely allied to 
if not identical with Physa acuta, Draparnaud, another alien 
which flourishes in one of the lily tanks at Kew, in warm 
water from a mill at Aberdeen, and a few other localities. 
Concerning unsuccessful attempts at colonisation, Mr. H. 
Wallis Kew observes (‘ Dispersal of Shells,” p. 183) :—* It 
must be remembered that when thus carried by man they are 
generally put down in districts already well stocked, and the 
creatures in such cases are obviously less likely to survive than 
those which happen to be transported by natural means to 
poorly stocked regions or to newly formed and unoccupied 
islands.” 
