Question: Which founder and retired chief executive of The Vanguard Group was hired by Walter L. Morgan in 1951 and became his heir at his company?

full_context: Document 1: Paul Tudor Jones: Paul Tudor Jones II (born September 28, 1954) is an American investor, hedge fund manager, and philanthropist. In 1980, he founded his hedge fund, Tudor Investment Corporation, an asset management firm headquartered in Greenwich, Connecticut. Soon after, he created the Tudor Group, a hedge fund holding company that specializes in fixed income, currencies, equities, and commodities.
Document 2: Whitehall Securities: Whitehall Securities Corporation Ltd was formed in 1907 By Weetman Dickinson Pearson MP who became Viscount Cowdray in 1917 together with Harold Pearson MP. Sir Weetman was nominated as President as well as being a founding director. The company was capitalised at £1,000,000. On 12th December 1990 the company name was changed to Pearson Management Services Ltd. The company formed part of what is now the Pearson PLC group of business interests which were initially amongst the world's leading oil and construction contractors.
Document 3: Thomas Welton Stanford: Thomas Welton Stanford (1832 - 1918), also known as Welton Stanford, was an American-born Australian businessman, spiritualist and philanthropist, most notably toward Stanford University, which was founded by his older brother Leland Stanford. Although living most of his adult life in Australia, he kept his American citizenship and served intermittently as honorary American vice consul-general in Melbourne.
Document 4: Morgan Morgan: Colonel Morgan Morgan (November 1, 1688 — November 17, 1766) was an American pioneer. He was thought to have founded the first permanent settlement in present-day West Virginia at Cool Spring Farm.
Document 5: Walter L. Morgan: Walter L. Morgan (July 23, 1898 – September 2, 1998) was the founder of the Wellington Fund, the first balanced mutual fund in the United States and one of the oldest surviving mutual funds. Morgan was born in Wilkes-Barre, Pennsylvania where he prepared at the Hillman Academy. He graduated from Princeton University in 1920, and shortly thereafter became the youngest CPA in Pennsylvania. In the 1920s Morgan raised $100,000 from relatives and business people to create what he believed to be a stable investment portfolio. The Industrial and Power Securities Company was established in 1928. It was later renamed the Wellington Fund in honor of the Duke of Wellington. Wellington Management Company was incorporated in Philadelphia in 1933. In 1951 Morgan hired John C. Bogle who became his heir at the company.
Document 6: Lowell Milken: Lowell Milken, the younger brother of Michael Milken, is co-founder of Knowledge Universe, a provider of early childhood education (ECE). He is also the founder of the TAP System for Teacher and Student Advancement, co-founder and chairman of the Milken Family Foundation, and a former senior vice president in the junk bond trading operation of Drexel Burnham Lambert,
Document 7: George Soros: George Soros ( or ; Hungarian: "Soros György" , ] ; born György Schwartz, August 12, 1930) is a Hungarian-American investor, business magnate, philanthropist, and author. Soros is one of the world's most successful investors. As of May 2017, he had a net worth of $25.2 billion, ranking among the 30 richest people in the world.
Document 8: Wellington Fund: The Wellington Fund was the first balanced mutual fund in the United States, and is one of the oldest surviving mutual funds. It was established in 1928 by Walter L. Morgan with $100,000 raised from relatives and business people in Morgan's home state of Pennsylvania. It was originally called the Industrial and Power Securities Company, but was later renamed after the Duke of Wellington. Wellington Management Company was incorporated in 1933, and while it still manages the Wellington Fund, is a private firm, independent of Vanguard.
Document 9: Harold Stanley: Harold Stanley (October 2, 1885 – May 14, 1963) was an American businessman and one of the founders of Morgan Stanley in 1935. For 20 years, he ran Morgan Stanley until he left the firm in 1955.
Document 10: John C. Bogle: John Clifton "Jack" Bogle (born May 8, 1929) is an American investor, business magnate, and philanthropist. He is the founder and retired chief executive of The Vanguard Group.
Document 11: Kenneth C. Griffin: Kenneth C. Griffin (born October 15, 1968) is an American investor, hedge fund manager, and philanthropist. He is the founder and chief executive of the global investment firm Citadel, founded in 1990. s of March 2015 , Citadel is one of the world's largest alternative investment management firms with an estimated $25 billion in investment capital. Citadel's group of hedge funds rank among the largest and most successful hedge funds in the world. "Forbes" identified Griffin as one of 2012's highest earning hedge fund managers as well as one of the Forbes 400.
Document 12: John Morgan (lawyer): John Morgan (born March 31, 1956) is an American lawyer. He is the founder of the nationwide personal injury law firm Morgan & Morgan.
Document 13: Charles R. Schwab: Charles Robert Schwab (born July 29, 1937) is an American investor, financial executive, and philanthropist. He is the founder and chairman of the Charles Schwab Corporation. He pioneered discount sales of equity securities starting in 1975. His company became by far the largest discount securities dealer in the United States. He retired as CEO in 2008, but remains chairman and is the largest shareholder.
Document 14: Mortimer J. Buckley: Mortimer J. "Tim" Buckley (born 1969) is an American executive at The Vanguard Group. The Vanguard Board elected him unanimously to succeed F. William McNabb III as chief executive officer upon McNabb's retirement at the end of December 2017.
Document 15: Jeffrey Gundlach: Jeffrey Edward Gundlach (born October 30, 1959) is the founder of DoubleLine Capital LP, an investment firm. He was formerly the head of the $9.3 billion TCW Total Return Bond Fund.
ground_truth: John Clifton "Jack" Bogle