Nature on the two continents. The union between the continents probably existed only in the north, perhaps above the fiftieth degree of latitude. If we follow the most eastern parts of Asia, northern Japan, Siberia, and Kamchatka, which are separated from America by Bering Strait, or if we proceed from the American side through the peninsula of Alaska and the chain of the Aleutian Islands, we shall comprehend at once that only very ordinary geological changes may have been sufficient to bring about the separation of lands which had been long united. Looking toward the extreme north, we find no other separation between the Old and New Worlds than a simple arm of the sea, Bering Strait.
The study of living Nature in the arctic regions of Asia and America is very instructive. Let us begin with examining the vegetation. Some anemones and a ranunculus[1] of Siberia are now common in North America. Another species of ranunculus[2] is common to Japan, Kamchatka, Alaska, and northern and eastern America. While we admire the tulip tree[3] in the parks of Europe, we recollect also that that beautiful exotic is one of the glories of the North American flora. But the tulip tree has recently been discovered in China. Then, there are the violets of Siberia and Japan,[4] which are mingled also with the vegetation of North America; and a vine (Vitus Labrusca), now well known, reputed American, which grows in Japan and a part of eastern Asia. A maple[5] is common to Japan and North America, as are also Spiræa betulifolia (birch-leaved spiræa) and Potentilla fragiformis of the rose family, some saxifrages, a crassula (Penthorum sedoides), various umbelliferous plants, the maritime alder, and a few orchids and lilies.
The animal world furnishes valuable evidences of our theory. Concerning insects I will cite only the facts most demonstrative of former communications. Some carnivorous beetles, the Carabs,[6] insects remarkable for their forms and colors, wingless, and having only their legs as means of locomotion, inhabitants of eastern Siberia, are also found in the cold countries of North America. I first saw collections made in California, after I had already become familiar with the faunas of Europe, Asia, and America. I was then surprised to see in those collections European and Asiatic forms which were believed to be entirely foreign to America. A little French butterfly, also occurring in Siberia, the valley of the Amoor, and Japan, was found on the western coast of America. It appears to be unique in the color of its wings, which are beautifully green on the lower sides. The like-
