The geographical distribution of animals, with a study of the relations ...

chap, xiii.] THE AUSTRALIAN REGION. 401fishes, as of plants and insects, has undoubtedly occurred, butthis has been effected by other means. If we look at a globewe see at once how this interchange may have taken place.Immediately south of Cape Horn we have the South ShetlandIslands and Graham's land, which is not improbably continuous,or nearly so, with South Victoria land immediately to the southof New Zealand. The intervening space is partly occupiedby the Auckland, Campbell, and Macquaries' Islands, which,there is reason to believe are the relics of a great southern extensionof New Zealand. At all events they form points whichwould aid the transmission of many organisms ;of the Macquaries' group, Emerald Island, isthe outlying islets of Victoria land.a considerable time in the air,and the farthestonly 600 miles fromThe ova of fish will surviveand the successful transmission ofsalmon ova to New Zealand packed in ice, shows how far theymight travel on icebergs. Now there is evidently some meansby which ova or young fishes are carried moderate distances, fromthe fact that remote alpine lakes and distinct river systems oftenhave the same species.of fresh water on their surfaces ;Glaciers and icebergs generally have poolsand whatever cause transmits fishto an isolated pond might occasionally stock these pools, and bythis means introduce the fishes of one southern island intoanother. Batrachians, which are equally patient of cold, mightbe transported by similar means ; while, as Mr. Darwin has sowell shown, {Origin of Species, 6th Ed. p. 345) there are variousknown modes by which plants might be transmitted, and weneed not therefore be surprised that botanists find a muchgreater similarity between the production of the several Southernlands and islands, than do zoologists. It is important to noticethat, however this intercommunication was effected, ithas continueddown to the epoch of existing species ; for Dr. Giintherfinds the same species of fresh-water fish (Galaxias attenuatus)inhabiting Tasmania, New Zealand, the Falkland Islands, andTemperate South America ; while another species is common toNew Zealand and the Auckland Islands. We cannot believethat a land connection has existed between all these remotelands within the period of existence of this one species of fish,