Thomas Henry Huxley PC FRS FLS ( 4 May 1825 - 29 June 1895 ) was an English biologist ( comparative anatomist ) , known as `` Darwin 's Bulldog '' for his advocacy of Charles Darwin 's theory of evolution .
Thomas Henry Huxley PC PRS ( 4 May 1825 - 29 June 1895 ) was an English biologist .