180 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
An exceptional habit has been noted by R. D. Darbishire* 
when the cockles become anchored by the byssus threads 
of Mytilus and grow and develop freely in the water. 
Only on the posterior margin of the shell, from which the 
siphons protrude, are there any other attached animals or 
plants. Among these are green or brown Alege (Sphace- 
laria\, Zoophytes (Obelia), small anemones (Actinia), and 
rarely, barnacles (Balanus). In some places the cockles 
commonly bear a tuft of alge, and the position of the animal — 
in the sand can be determined by the presence of this 
projecting tuft. The animal, as a rule, remains in nearly 
the same position, but is able to shift about by means of 
the strongly developed muscular foot. Where the sand is 
not much disturbed by the tidal current, as round the 
stake of a net for instance, the cockles are generally more 
abundant. 
A current of water continually entering the mantle 
cavity by the lower, and passing out again by the upper 
siphon, bears the food supply in the form of suspended 
microscopic animals and plants. The cockle feeds on 
spores and other young stages of lower algex, fragments of 
filamentous alge, vegetable debris, Foraminifera, Diatoms, 
and probably also the smaller micro-crustacea. The 
animal exercises no selective action on the food taken in; 
all that is contained in the entering current of water, 
including a large quantity of sand and suspended inorganic 
matter, 1s carried in by the cilia of the labial palps and 
passed on into the stomach. The greater part, therefore, 
of the contents of stomach and intestine is sand and fine 
mud. 
The chief enemies of the cockle are fishes and birds. 
They also are eaten by starfish and bored by dog whelks. 
They form an important food for many fishes, chiefly 
* Fauna of Liverpool Bay. Report L., p. 241, 
