MR. C. REID ON THE NATURAL HISTORY OF ISOLATED PONDS. 279 
since they placed a number of young ones in this pond to fatten. 
They fattened, but became very unwholesome, and the men had 
reason to remember the hunt they made when the Eels were full 
grown. If this account is true, I do not know of any instance of 
Eels having travelled a long distance. 
Passing next to the Mollusca, we obtain some curious results ; 
for while among the gasteropods, Limmeids of various species are 
abundant in isolated ponds, there is an almost entire absence of the 
operculated pond-snails, generally so common in stagnant water. 
I have never seen either of our species of Paludina, and our two v-**' 
species of Bytkinia , and two of Valvata have only been observed 
in ponds closely adjoining rivers or extensive marshes. Neritina 
wo can scarcely expect to find in a small pond. Sucrinea put r is 
and S. elegans both occur occasionally ; when found at all they 
are abundant, so have evidently no difficulty in living in these 
ponds when once introduced. 
Limncea peregra is the mollusc most commonly found in isolated 
ponds ; indeed, its occurrence is so habitual that where found 
without other species I have long ceased to note it — the number of 
occurrences observed must now bo at least one hundred. Limnaa 
truncatula is fairly common, and has a curious tendency to turn up 
in horse-troughs and stone basins. In one instance a number of 
specimens were found in a raised stone cattle-trough on the marshes 
of the Humber. The dykes in this marsh contain water much too 
salt for cattle to drink, and it is necessary to provide a supply of 
water by deep borings, one of which overflowed from the tube into 
this cattle-trough. Thus a small colony of L. truncatula was found 
living in a cattle-trough in the middle of a salt-marsh, where the 
surrounding dykes were too salt for this snail to live in. Limncea 
auricularia is seldom found in isolated ponds, but possibly the 
species has sometimes been overlooked among L. peregra. Stunted 
varieties might easily escape observation, and the unfavourable 
conditions make dwarf forms of common occurrence among the 
mollusca in small ponds. Limncea palmtris, though so abundant 
in our marshes, is a rare species in isolated ponds ; I have only 
noticed it two or three times. Limncea stagnalis has been found 
twice ; in one case in a dew-pond on the dry South Downs. 
Limncea glabra , our last species of the genus, is a rare form 
which we could scarcely expect to find in artificial ponds ; but 
u 
VOL. v. 
