Edward B. Lewis ( May 20 , 1918 â `` July 21 , 2004 ) was an American geneticist . He shared the 1995 Nobel Prize in Physiology or Medicine . Edward B. Lewis ( May 20 , 1918 â `` July 21 , 2004 ) was an American geneticist , a corecipient of the 1995 Nobel Prize in Physiology or Medicine .