Huxley on Charles Darwin's dog. Humorous notes on the ancestry and evolution of Charles Darwin's dog Polly, written in around 1870 by British biologist Thomas Henry Huxley (1825-1895), one of the leading proponents and supporters of Darwin's theory of evolution. Huxley has labelled Polly (bottom) the ur-hound, and given her an evolutionary tree that is part pig (left) and part cat (right). Polly was a terrier who originally belonged to Darwin's daughter Henrietta. Polly was devoted to Darwin, sleeping in a basket in his study while he wrote. Polly also appeared in Darwin's 'The Expression of the Emotions in Man and Animals' (1872).