134 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
time to time in the shallow waters of our district require 
further investigation. At times Shrimps are very scarce, 
having apparently either migrated to deeper water or 
buried themselves in the sand.* This seems to be largely 
the result of temperature variations. Periodic observations 
at fixed stations, the Shrimp trawl being down for the 
same time, and at the same state of the tide, say once a 
week, should, supplemented by our work in the laboratory, 
give us a good deal of information in regard to the life- 
history of the Shrimp throughout the year. 
I have suggested above, in connection with the des- 
truction of immature fish, that Shrimp culture might be 
carried on in our estuaries. At any rate the matter ought 
to be tried on a small scale experimentally. A sheltered 
creek or bend in one of the estuaries should be closed in 
by stakes and wattling, like a fishing weir, so as to keep 
out Skates, Codling, Crabs, and other enemies. This 
preserve could then be stocked with Shrimps—which 
might be fed with any fish refuse—and if it were found 
that the youug stages when hatched out could be kept 
inside the enclosure and reared, the probability is that in 
the absence of enemies and with abundance of food the 
numbers would increase very greatly. 
EDIBLE MOLLUSCA. 
The edible mollusca of chief importance here are the 
Cockle (Cardiwm edule), and the Mussel (Mytilus edulis), 
and a certain amount of work has been done on both of 
these shell-fish in the laboratory. 
THE COCKLE. 
In examining for food, specimens sent by the bailiffs the 
first thing noticed was the very large proportion of indi- 
viduals in which the stomach was quite empty, the reason 
* See Trans, Liverpool Biological Society, vol. V. p, 49; and vol. VI. p. 32. 
