( 137 ) 



the intervening sea declines to I51JI) and 20U0 fathoms, and is ahuost devoid of 

 shallows and smaller islands towards the mainland. Geological evidence, therefore, is 

 entirely opposed to a former land-connection of the Galapagos Islands with America. 

 The flora has an undoubted American character, although the proportion of species 

 confined to tlie islands in question is enormous.* The fauna represents most 

 difficulties. Darwin t says : " Bnt it is the circumstauce that several of the islands 

 possess their own species of the tortoise, mockiug-thrush, finches, and numerous 

 plants, these species having the same general habits, occupying analogous situations, 

 and obviously filling the same place in the natural economy of this archipelago, that 

 strikes me with wonder." Indeed, a wonder it may be called, that islands so close 

 together, and aj)parently with the same natural conditions, have so many repre- 

 sentative forms. Such facts were almost unknown, or at least not properly 

 understood, at the time of Darwin's exploration ; but nowadays they are well 

 known to every naturalist. A similar differentiation of forms — one form representing 

 other closely allied ones on different islands — is now known to exist in every group 

 of islands, apparently more pronounced in groups of greater age than in geologically 

 younger groups of islands. Let us take for e.xamples the Drepanidae, Phaeornis, 

 Chuskmpis, and Moho in the Hawaiian arcliipelago, the whole fauna of the Malayan 

 and Papuan archipelago, especially the birds, marsupials, lepidoptera, the fauna of 

 Antilles and the Philippines, the parrots of Curasao, Arnba, and Bonaire, the birds 

 of the Marianne and Caroline Islands — in fact, the fauna of almost every archi- 

 pelago or of any detached islands on the earth's surface. Only the fact that the 

 various islands are so very close to each other | makes the case of the Galapagos 

 more striking. 



Dr. Baur § discusses the question how this " harmonic distribution " has come 

 about. He maintains that there is only one explanation — namely, that the islands 

 were in former times connected, forming a large and continuous mass of land, the 

 volcanic rocks which now form the islands having been elevated on the latter. At 

 that time, ho says, the number of species found there was small. Then this mass 

 of land became submerged, and the few original species which inhabited the whole 

 area, having become restricted to the former mountain-tops, now islands, became 

 diflerentiated in many different forms through isolation. This theory sounds very 

 sensible and probable, but, if applied to the Galapagos Islands it must equally be 

 applied to most other island-groups where similar phenomena exist, as we have 

 explained before. Dr. Baur is convinced that the differentiation of so many forms 

 on the various islands could never have taken 2)lace through the accidental arrival of 

 individuals. The necessity of this deduction, however, we cannot see. It is doubtless, 

 in our opinion, quite as intelligible, that the various islands have been populated 

 from one island, where an ancestral form was living. Thus, they were reached 

 at various times, and b3'-and-by, through isolation, the separated colonies became 

 slightly changed, without the necessity of assuming a submergence of a great area, 

 the existence of which is opposed to geological observations and theories. In 

 fact, the differentiation, as found in the various forms, seems more explainable if 

 we accept that they have reached their present home at various times, because their 



* Darwin, Journal nf Rrsearch'Sy p. 419 (Edit. 1890). 

 t t.e. p. 423. 

 X «.<!. p. 423. 



§ "The Differentiation of Species in the G.alapagos Islands and tlie Orit^in of the Group." liostun 

 (in liinhig. Led.) IS9o, and in American XatHrali.it, 1891, p]i. 217-29 and 307-30), 



