A HISTORY OF ESSEX The question of the food of the oysters in different localities is one of great importance, and may vary so much as to account for the difference in flavour, and why they become green in some localities and not in others, and lose that colour when moved elsewhere. This question of the food can be properly studied only on the spot, by examining the contents of the stomachs immediately after the animals have been taken out of the water in which they have lived, before the food has been digested. Large numbers of the French oysters and of the specifically distinct Portuguese and American have been laid down in particular localities. Mr. T. Newman, the manager of the Colne fishery, informs me that the Portu- guese have reproduced, though not in such a manner as to be of commercial value ; but the general temperature of the water is too low for the successful reproduction of the American or for that of the somewhat delicate French variety of our native species, which unfortunately for the same reason often fails to arrive at maturity, to the great loss of those interested in the fishery. 4. Scrobicularia plana (Da Costa). Occurs in great numbers in Pye Fleet and in some other estuaries. It is interesting to keep it alive in an aquarium at the bottom of which is a depth of 2 or 3 inches of mud, and to see how it projects its longer syphon to an extent of 5 inches and scoops up the mud, which it swallows and afterwards ejects. It may be killed with the syphons elongated by keeping it in a vessel from which all air is carefully excluded. 5. Macoma balthica (Linn.). Common in the mud of the estuaries. I have kept it alive in an aquarium with a mud bottom and bred hundreds of small ones, so that the surface of the mud seemed alive with the protruded syphons. Some grew to be
inch in diameter in three or four months.
6. Tellina tenuis (Da Costa) and 7. Tellina fabula, Gronovius. These also occur, but are not so common as Macoma balthica. 8. Mactra stultorum, Linn. Not common but has been seen. 9. Tapes aureus (Gmelin). This may be obtained alive from the mud off Mersea when left dry at low water, being fairly abundant. 10. Cardium edule, Linn. Common in many localities. Some years ago it was very abundant in the sandy mud off Foulness, but living individuals were com- paratively rare in 1894, after the previous very severe winters. 1 1 . Mya arenaria, Linn. This is very common in most of the estu- aries, and judging from the great number of dead shells in the living position it seems to have been still more common in some locali- ties than it now is. 12. Mya truncata, Linn. Probably lives off Mersea since the shells of recently dead individuals are not uncommon. 13. Borneo Candida (Linn.). Abundant in Blakestone Hole near Bright- lingsea and in the mud above Harwich. III. GASTROPODA PROSOBRANCHIA 1. Gibbula cineraria (Linn.). Common in various places. 2. Littorina littorea (Linn.). This is so extremely abundant on the mud flats left dry at low water that it must out- number all other associated mollusca com- bined. Many men and boys are employed in collecting it for food. 3. Littorina obtusata (Linn.). Found in sundry places, but not abun- dantly. Rissoa and Zippora. These small shells are common in the estuaries, and dead ones sometimes collect in vast numbers on the shores. My specimens seem to be chiefly 4. Rissoa inctmspicua, Alder. 5. Zippora membranacea, J. Adams. Probably others could be found by careful searching. 6. Buccinum undatum, Linn. This is more or less common all along the coast and dredged at almost every station. 7. Purpura lapillus (Linn.). This is commonly known as the 'dog whelk,' and is collected and destroyed on account of the damage it does in the oyster grounds, by killing the animals. 82
