Darwin named Lawson several times in his notes and diaries. When the "Beagle" survey expedition arrived at Charles Island (Floreana Island) in September 1835, Darwin noted in his diary: "An Englishman Mr Lawson is now acting as Governor. — By chance he came down to visit a Whaling Vessel &amp; in the morning accompanied us to the Settlement." Lawson described having seen a reduction in the numbers and size of Galápagos tortoises taken for meat by the whalers. In his zoological notes, Darwin recorded that "It is said that slight variations in the form of the shell are constant according to the Island which they inhabit — also the average largest size appears equally to vary according to the locality.— Mr Lawson states he can on seeing a Tortoise pronounce with certainty from which island it has been brought." This was one of the points which Darwin listed later in the voyage, between mid-June and August 1836, as arousing his first suspicion that "such facts would undermine the stability of Species". After the voyage, Darwin developed this idea during his investigations into transmutation of species, resulting in his theory of evolution.