Bell was at the heart of the scientific establishment and when Charles Darwin returned to London from the "Beagle" expedition on 2 December 1836, Bell was quick to take on the task of describing the reptile specimens. He was also entrusted with the specimens of Crustacea collected on the voyage. He was the authority in this field; his book "British Stalke-eyed Crustacea" is a masterwork. He played a significant part in the inception of Darwin's theory of natural selection in March 1837 when he confirmed that the giant Galápagos tortoises were native to the islands, not brought in by buccaneers for food as Darwin had thought. He supported the arrangements for publication of "Zoology of the Voyage of H.M.S. Beagle", but then was very slow to make progress on the work, and though the first parts of work were published in 1838, Bell's contribution on reptiles ("Part 5") was published in two numbers, in 1842 and 1843, and he subsequently failed to take any action on the Crustacea.