Pearls are yet found in the river mussels in all parts of eastern Asia, from Siberia to the Indian Ocean, and from the Himalayas to the Pacific. It is represented that they are not from the _Unio margaritifera_, the common river-mussel of Europe, but from other species, such as _Unio mongolicus_, _U. dahuricus_, _Dipsas plicatus_, etc. It is quite impossible to obtain a reliable estimate of the total number of persons employed, or the output of pearls in China, but these items are certainly very much larger than the average Occidental believes. In the vicinity of Canton the _Dipsas plicatus_ has been used for centuries by the Chinese in the production of artificial pearls, this industry giving employment to thousands of persons.[172] The pearl-mussel fishery is of importance in Manchuria, where it has been carried on for hundreds of years, not only by the citizens, but by the military department on account of the government, and especially in the streams which flow into the Songari, a tributary of the Amur. Jacinth relates that in case of a deficit, the officers and subalterns were punished by a deduction from their pay, and also by corporal chastisement.[173] Witsen speaks of the pearls from the River Gan, a tributary of the Amur, and also from the islands of the Amur, the boundary river of Manchuria. Pearl fisheries were established at these places by the Russians nearly two centuries ago.[174] Pearls become finer and more plentiful the further we penetrate into Manchuria; and they are numerous in the lake of Heikow or Hing-chou-men, “Black Lake” or “Gate of Precious Gems,” where they have long been exploited for the account of the emperor of China. The occurrence of pearls in many parts of Asiatic Russia was noted by Von Hessling. In northern Siberia, according to Witsen, writing in 1705,[175] pearls were found in the waters about the town of Mangasea on the Turuchan; and Von Middendorf notes that they were found in the Tunguska River, which flows into the Yenisei. Whether, however, they come from the _Unio margaritifera_ is considered doubtful by Von Middendorf. Witsen referred to their occurrence in the rivers and streams of Irkutsk and Onon, and this is confirmed by several writers of more recent times. Pallas says that the mussels found there are quite large, and speaks of the Ilim, which flows into the Angara, as another river where they occur. Ancient books relating to Japan repeatedly allude to the occurrence of pearls on the coasts of that country. They are mentioned in the Nihonki, of the eighth century, the oldest Japanese history.