Della Femina's Agency to Merge With Ketchum: Outspoken adman Jerry Della Femina said he will combine his 16-month-old agency with the New York office of Ketchum Communications, which has been seeking a higher profile on Madison Avenue. Della Femina, 57, has long been one of the most colorful figures in advertising. He severed 25-year ties to the Della Femina McNamee Inc. agency in June, 1992, after clashing with the French agency that had acquired control of it. Six months later, he founded Jerry Inc. That agency will be merged in a stock swap. The partners will each own 50% of Jerry & Ketchum Inc.