 However , Darwin did have four live juvenile specimens to compare from different islands . These were pet tortoises taken by himself ( from San Salvador ) , his captain FitzRoy ( two from Española ) and his servant Syms Covington ( from Floreana ) . Unfortunately , they could not help to determine whether each island had its own variety because the specimens were not mature enough to exhibit morphological differences . Although the British Museum had a few specimens , their provenance within the Galápagos was unknown . However , conversations with the naturalist Gabriel Bibron , who had seen the mature tortoises of the Paris Natural History Museum confirmed to Darwin that distinct varieties occurred . 
