36 



An exceptional habit has been noted by E. D. Darbi shire* 

 when the cockles become anchored by the byssns 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 Algae (Sphace- 

 laria), Zoophytes (Obelia), small anemones (Actinia), and 

 rarely, barnacles (Balaniis). In some places the cockles 

 commonly bear a tuft of algae, 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 algae, fragments of 

 filamentous algae, 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, is 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 Liverjiool Bay. Report I., p. 241. 



