342 THE ORIGIN OF SPECIES 



migration of a marine fauna, which, during the Pliocene or even 

 a somewhat earher period, was nearly uniform along the con- 

 tinuous shores of the Polar Circle, will account, on the theory of 

 modification, for many closely allied forms now living in marine 

 areas completely sundered. Thus, I think, we can understand the 

 presence of some closely allied, still existing and extinct tertiary 

 forms, on the eastern and western shores of temperate North 

 America; and the still more striking fact of many closely allied 

 crustaceans (as described in Dana's admirable work), some fish 

 and other marine animals, inhabiting the Mediterranean and the 

 seas of Japan — these two areas being now completely separated 

 by the breath of a whole continent and by wide spaces of ocean. 

 These cases of close relationship in species either now or 

 formerly inhabiting the seas on the eastern and western shores of 

 North America, the Mediterranean and Japan, and the temperate 

 lands of North America and Europe, are inexplicable on the theory 

 of creation. We cannot maintain that such species have been 

 created alike, in correspondence with the nearly similar physical 

 conditions of the areas; for if we compare, for instance, certain 

 parts of South America with parts of South Africa or Australia, 

 we see countries closely similar in all their physical conditions, 

 with their inhabitants utterly dissimilar. 



ALTERNATE GLACIAL PERIODS IN THE NORTH AND SOUTH 



But we must return to our more immediate subject. I am con- 

 vinced that Forbes' view may be largely extended. In Europe we 

 meet with the plainest evidence of the Glacial period, from the 

 western shores of Britain to the Ural range, and southward to 

 the Pyrenees. We may infer from the frozen mammals and nature 

 of the mountain vegetation, that Siberia was similarly affected. 

 In the Lebanon, according to Dr. Hooker, perpetual snow formerly 

 covered the central axis, and fed glaciers which rolled 4,000 feet 

 down the valleys. The same observer has recently found great 

 moraines at a low level on the Atlas range in North Africa. Along 

 the Himalaj''a, at points 900 miles apart, glaciers have left the 

 marks of their former low descent; and in Sikkim, Dr. Hooker 

 saw maize growing on ancient and gigantic moraines. Southward 

 of the Asiatic continent, on the opposite side of the equator, we 

 know, from the excellent researches of Dr. J. Haast and Dr. Hec- 

 tor, that in New Zealand immense glaciers formerly descended to 

 a low level; and the same plants found by Dr. Hooker on widely 

 separated m.ountains in this island tell the same story of a former 

 cold period. From facts communicated to me by the Rev. W. B. 



