Stocks ended mostly lower in a volatile session Tuesday. A few notable stocks were active in extended trading after reporting quarterly results. At the closing bell, the Nasdaq fell 0.5%. It had been up as much as 0.3% and down as much as 1.1% intraday. The S&P 500 slipped 0.2%. But the Dow Jones industrial average ticked up a fraction. Volume jumped across the board in the stock market today.