The common freshwater Unio (Unio tumidus), and also Unio pictorum, both produce pearls, but they are generally small, and of a bad colour; sometimes I have found several in one shell, and again, I have opened many, and not been successful.
* 'The Scotch Pearl Fishery' ('The Wesleyan and Methodist Magazine,' January, 1865, from the 'Times' and the 'Scotsman'), † Camden's 'Britannia,' p. 962.
A species of freshwater mussel, Anodonta cygnea, is said to be eaten in the county of Leitrim by the peasantry, and Unionidoe are eaten in the south of Europe, either roasted in their shells and drenched with oil, or covered with bread-crumbs, and scalloped; and, according to Dr. Wilhelm Gottlob Rosenhauer, Unio Requienii, and Unio litoralis, which are found near Granada, in the river Jenil, are often brought to the market; but when the fish are taken out of their shells and cooked, they are described as very tough food. Anodontoe and Unionidoe (Anodontes et Mulettes), are employed by the fishermen in the neighbourhood of Nantes for bait; * and I have occasionally used Dreis-sena polymorpha, for the same purpose, which seemed to be greatly appreciated by the fish in the pond where I was fishing, as they greedily sucked off the bait as fast as it was put on the hook. The Dreissenoe were brought from the canal at Sawley, Leicestershire, and turned into the ponds, where they have thriven wonderfully, and are the favourite food of water-rats, if one may judge from the number of empty shells deposited on the banks, amongst the rushes, in small heaps sometimes two or three inches deep. In some countries the shells of the large Anodontoe are used for skimming milk. In China, in the province of Nanking, Anodonta edulis (Heude) is said by M. R. P. Heude to be cultivated in the large canals of Song-kiang-fou for eating purposes,† and in the Chinese market at Ta-kou Anodontoe are brought in basketfuls from the Pei-ho river and sold as food.* The valves of Unio tientsi-nensis, the Ko-fen of the Chinese, are used by them as a powder in medicine, and occasionally as one of the ingredients in pills, as a substitute for pearls.†
* 'Catalogue des Radiaires,' etc., par Frederic Cailliaud, de Nantes. † 'Diagnoses Molluscorum in fluminibus provinciae Nankingensis.
The pearl-mussels Dipsa plicatus, and the Alasmo-dontoe, both belonging to the family Unionidoe, are used for the artificial production of pearls in China. The art of artificial pearl-making is of great antiquity. The Chinese attribute it to a native of Hutchefu, named Yé-jin-Yang, who lived in the thirteenth century. His memory is still honoured by those who practise the art, and there is a temple especially dedicated to him. There is a large manufactory of these artificial pearls in the neighbourhood of Canton, and at Hutchefu, near the river Ning-Po. In the months of April and May the Dipsas, and Alasmodontoe, are furnished with matrices of metal, placed between the shell and the mantle of the fish. In one year they are incrustated with the nacre; but sometimes they are left longer to obtain a thicker coating. Thus are produced the little figures of idols with which the Chinese ornament their hats and caps.‡ The valves of Dipsa plicatus are used also for weighing grains of rice, etc.
In the north-western part of Australia, a freshwater mussel forms a staple article of food, while in the south-western part of the continent the natives will not touch them, but regard them with a superstitious dread and abhorrence. In Grey's 'Australia' he gives an account of a native, Kaiber by name, whom he ordered to gather some of these shellfish for food, as they were nearly dying from hunger; but the man steadfastly refused, as he affirmed that by touching them, the native sorcerer, or " Boyl-yas," would acquire a mysterious influence over him, which would end in his death. At last, however, he was ordered to bring some instantly, as Mr. Grey intended eating them. After thinking for a moment or so, Kaiber walked away for this purpose, but bitterly lamented his fate whilst occupied with his task. It was true, he said, he had not died of hunger or thirst, but this was all owing to his courage and strong sinews; yet, what would these avail against the supernatural powers of the Boyl-yas. " They will eat me at night, whilst worn-out by fatigue I must sleep". However, the mussels were brought, and Mr. Grey made a meal of them.* It is not only of late years that Mytilus edulis has been thought worthy to grace our table, for in 1390 we have the following recipes given in a "role" of ancient English cookery, compiled by the master cooks of King Richard II., called the 'Forme of Cury :' -
Collectorum,' auctore, R. P. Heude, S. J. 'Journal de Conchyliologie,' tome xxii. 1874.
* 'Notice sur la Malacologie de quelques points du littoral de l'Empire Chinois,' par Odon Delbeaux, 'Journal de Conch'.
† 'Essai sur la Pharmacie et la Matiére Médicale des Chinois,' par J. O. Delbeaux.
‡ 'Journal de Conchyliologie,' P. Fischer, tome xiii. 1865.