Their Food, Sex and Spawning. 209 



off in numbers. Sometimes, through inclement weather or 

 other cause, the cocklers (who frequently " hunt in a pack ") 

 will considerably diminish the produce of a particular ground, 

 and fishing for them there becomes unprofitable, but after an 

 interval of a year or more, when the men return to the spot, 

 they find well grown material fit for market. Seldom indeed 

 has there been decided scarcity from over-fishing. Moreover, 

 it should be taken into account that the numbers of the 

 cocklers have been on the increase. 



As to the food of the cockle, of that there is no stint in our 

 District. Though not such a grazier as is the periwinkle, the 

 cockle nevertheless seems to live fully as much on marine 

 plants as on animal substances, sand likewise is not infrequent. 

 Herdman and Scott have found the cockles' stomachs often 

 empty.* In our examinations relatively not many were in this 

 condition. Some of ours were examined on the spot, others 

 shortly after they were taken off the sands. Their digestion is 

 active, so before long the alimentary canal exhibits scant traces 

 of food. This latter in many respects resembles that of oysters 

 and mussels, viz., fragments of algae, diminutive crustaceans 

 (ostracods, &c.), diatoms, foraminifers and so forth. Scott 

 mentions a copepod (Lichomolgus agilis) as resident (a mess- 

 mate) within cockles and mussels ; we cannot say whether this 

 is the case in the Thames specimens. 



Sex and Growth. Separation of the sexes occurs as in the 

 common mussel, but the Norwegian cockle is said by Lacaze 

 Duthiers to exhibit a hermaphrodite condition. On this score 

 we can give no information personally. 



The cocklers in our District find traces of spawning from 

 spring till end of June. By July in good seasons the adult 

 breeding cockle gets flabby, and by the end of this month 

 shows signs of recovery, and from August onwards they think 

 it is in best condition. We have not examined their repro- 



* Rep. Lancashire Sea Fish. Labor, for 1894., tabular statement. 



