Merrill Lynch's asset management fees increased less than 1% in the fourth quarter, but fees are up 29% from the same period in 1997. Total assets under management increased $34 billion during the quarter to just over $500 billion, up 7% from third quarter 1998 and up 53% compared with the fourth quarter of 1997. Merrill's Mercury Asset Management group raised more than $1 billion in mutual fund assets worldwide since July, the company stated in financial reports, released today. Due in part to reorganization costs, net earnings of $359 million were down 23% compared with 1997's fourth quarter, an improvement over the net earnings loss of $163 million for the third quarter ended Sept. 25. Earnings per share were 86 cents diluted, compared with -48 cents in the third quarter and $1.15 in fourth quarter 1997.