Answer by taking a quote from the following article:

Sir Julian Sorell Huxley FRS (22 June 1887 - 14 February 1975) was a British evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern synthesis. He was secretary of the Zoological Society of London (1935-1942), the first Director of UNESCO, a founding member of the World Wildlife Fund and the first President of the British Humanist Association. Huxley was well known for his presentation of science in books and articles, and on radio and television.

Huxley's humanism came from his appreciation that mankind was in charge of its own destiny (at least in principle), and this raised the need for a sense of direction and a system of ethics. His grandfather T. H. Huxley, when faced with similar problems, had promoted agnosticism, but Julian chose humanism as being more directed to supplying a basis for ethics. Julian's thinking went along these lines: "The critical point in the evolution of man... was when he acquired the use of [language]... Man's development is potentially open... He has developed a new method of evolution: the transmission of organized experience by way of tradition, which... largely overrides the automatic process of natural selection as the agent of change". Both Huxley and his grandfather gave Romanes Lectures on the possible connection between evolution and ethics. (see evolutionary ethics) Huxley's views on god could be described as being that of an agnostic atheist.  Huxley had a close association with the British rationalist and secular humanist movements. He was an Honorary Associate of the Rationalist Press Association from 1927 until his death, and on the formation of the British Humanist Association in 1963 became its first President, to be succeeded by AJ Ayer in 1965. He was also closely involved with the International Humanist and Ethical Union. Many of Huxley's books address humanist themes. In 1962 Huxley accepted the American Humanist Association's annual "Humanist of the Year" award.  Huxley also presided over the founding Congress of the International Humanist and Ethical Union and served with John Dewey, Albert Einstein and Thomas Mann on the founding advisory board of the First Humanist Society of New York.

What else did he do
Both Huxley and his grandfather gave Romanes Lectures on the possible connection between evolution and ethics.