1. Rangifer tarandus typicus. 2. " " spitzbergensis. 3. " " caribou. 4. " " terræ-novæ. 5. " " grœnlandicus. 6. " " arcticus.
I hardly think these can be considered of equal value; indeed, though there may be differences between _R. grœnlandicus_, _typicus_, _arcticus_, and _spitzbergensis_, the antlers exhibit a certain much closer relationship among one another than to _R. terræ-novæ_ and _caribou_. But the whole subject is by no means as well known as could be wished, and a very careful comparative study of recent and fossil remains of the Reindeer from various parts of the Old and New Worlds is much needed to put our views on a firmer basis.
The presence of the Arctic Hare in Ireland and the absence of the common European Hare (_Lepus europæus_) can be explained in a somewhat similar manner. The Arctic Hare is the older of the two species--corresponding with the Barren-ground Reindeer--and the European Hare the newer one, associating, like the Woodland Reindeer, in its westward migration with Siberian animals, though probably of Oriental origin.
Let us once more refer back again to the map on page 137 indicating the geographical distribution of the Arctic Hare. Its discontinuous range and its isolated position in the Alps, Pyrenees, and the Japanese mountains, all tend to show that it is an ancient species. Moreover, its presence in Ireland in the plain as well as in the mountains, clearly points to the fact that, in the British Islands at any rate, the Arctic Hare was the first comer, and that subsequently the European Hare invaded these countries. It probably found Ireland then no longer accessible, having since become separated from England. Again and again do we find the statement repeated, that the presence of the Arctic Hare in Europe is a clear proof of the former prevalence in our continent of an Arctic climate. But if so, why should this Hare at present live and thrive in Ireland, which has a particularly mild climate in winter, and be absent from so many continental stations where the temperature more resembles that of its native home? If we suppose that the European Hare migrated to Europe from the east, after the Arctic Hare had become established in Western Europe, and drove the latter into the mountains or northward whenever the two came into contact, we should have, it seems to me, a better explanation of the range presented by the two species. I was formerly of opinion that the European Hare had come with the Siberian animals from Siberia, but it appears to me more likely now, that it reached our continent with the Oriental migrants, and only then joined the Siberians in Eastern Europe.