Notwithstanding the enormous numbers, these beds are often completely exhausted in a few seasons. When the beds are first discovered, men will take as much as 1500 to 2000 pounds of shell each, in a day's fishing. In one hundred pounds of shells as they are taken, the average number of valves or half shells will be, nigger-heads, about one thousand; sand-shells, nine hundred; muckets, eight hundred, which would be an average of nine thousand mussels per ton. The meat in a ton of nigger-heads weighs over three hundred pounds. This is usually removed by the fishermen by boiling the mussels for ten or fifteen minutes in crude sheet iron tanks when the shells open and the fleshy part falls out or may be easily removed by hand. To show how little the pearls they may contain enter into the calculations of these fishermen, it may be stated here that the shell-buyers pay about twenty-five per cent. less for the mussels as taken from the river than they do for the shells when cleaned. On the Californian coast when the divers worked independently, they preferred to sell the oysters unopened. They received about $4.50 per thousand on an average for the shells and double for the oysters complete. The fishing season for pearlers is from August to December. The large operations for shell, in the early days of the industry, were confined to the same period, but of late, fishing is carried on throughout the year, immense quantities being taken through the ice. The shells are better in cold weather, being less brittle than when exposed in the boats during warm weather. Fishing through the ice is very wasteful however, as the undersized, which are dropped back from the scoops and rakes in the summer, when thrown out on the ice are allowed to remain there and die. The price of shells varies considerably from season to season. An average price for nigger-heads is about ten dollars per ton; sand-shells bring about twice as much, muckets half that price, and the other varieties together will average about twenty-five per cent. more than nigger-heads, though among these the deer-horn is worth about four times as much as the nigger-head. In the first six months of 1898 nearly four thousand tons of mussel shells were sold by mussel fishermen on the Mississippi. They brought about thirty-nine thousand dollars, 94 per cent. of these were nigger-heads. The spawning time of the unio varies with different species. In the central Mississippi basin it is normally February, March and April for nigger-head, and summer and early fall for the mucket and sand-shell.