For 25 years, from 1831 into 1856, the English zoologist William Yarrell was both a friend and adviser to Charles Darwin. He was regarded by Darwin as a wise and eminent naturalist of the older generation. Yarrell was part of a small group of naturalists, including Leonard Jenyns and John Stevens Henslow, whose interests in ornithology, entomology and geology expanded over the years. Their knowledge helped to support publication of the results of the HMS Beagle voyage and to inform Darwin while he was developing his hypotheses on evolution before the publication of On the Origin of Species, first published in 1859.
: Symposium on Evolution, Held at Duquesne University, April 4, 1959, in Commemoration of the Centenary of Charles Darwin's The Origin of Species . Frederick C. Bawden, Gottfried O. Lang, Andrew G. van Melsen, Cyril Vollert, Charles Darwin. ; Evolution and Christian Thought Today . Russell L. Mixter.
