While on the "Erebus", Hooker had read proofs of Charles Darwin's "The Voyage of the Beagle" provided by Charles Lyell and had been very impressed by Darwin's skill as a naturalist. They had met once, before the Antarctic voyage started. After Hooker's return to England, he was approached by Darwin who invited him to classify the plants that Darwin had collected in South America and the Galápagos Islands. Hooker agreed and the pair began a life-long friendship. On 11 January 1844 Darwin mentioned to Hooker his early ideas on the evolution and natural selection, and Hooker showed interest. In 1847 he agreed to read Darwin's "Essay" explaining the theory, and responded with notes giving Darwin calm critical feedback. Their correspondence continued throughout the development of Darwin's theory and in 1858 Darwin wrote that Hooker was "the one living soul from whom I have constantly received sympathy".