Gerald Tsai Jr., a fund manager and financier who pioneered the creation of performance funds in the 1950s and '60s and later turned a canning company into the financial services giant Primerica, died Wednesday in Manhattan. He was 79.

The cause was multiple organ failure, said his son Christopher.

Primerica and a subsidiary Tsai once led eventually became building blocks of Citigroup. But Tsai was perhaps most famous for his skill in building mutual funds.

He was not yet 30 when he started Fidelity Investments' first aggressive growth fund in 1958, riding it to great success and a large personal fortune. Tsai spurred the popularity of "momentum investing," as his funds swiftly moved money from one hot growth stock to another. He joined the Fidelity Management and Research Co. in 1952 as a security analyst. By 1963, he was an executive vice president.

At Fidelity, Tsai "showed himself to be a shrewd and decisive picker of stocks for short-term appreciation," John Brooks wrote in the book "The Go-Go Years: The Drama and Crashing Finale of Wall Street's Bullish 60s" in 1973. "So swift and nimble in getting into and out of specific stocks that his relations with them, far from resembling a marriage or even a companionate marriage, were more often like that of a roue with a chorus line."

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