The advent of the Woodland form of the Reindeer in Europe took place at a much later stage. It came, as I indicated, with the hordes of Siberian migrants which invaded Europe during what is known as the Inter-glacial phase of the Glacial period. Scandinavia, not being then directly connected with continental Europe, was not accessible to it; neither was Ireland, which had by that time become disconnected from Great Britain. None of the Siberian migrants seem to have been able to cross the River Garonne, and we therefore find neither the Woodland Reindeer nor any of the typical Siberian species represented in the Pyrenean deposits. [Illustration: Fig. 12.--Map of Europe, indicating the parts which were probably submerged (shaded) at the commencement of the Glacial period. The light portions represent, approximately, the extent of the land at that time.] The Woodland Reindeer persisted in continental Europe until comparatively recent times, and it has since made its way into Scandinavia across Northern Russia, and probably mingled with the older stock of the Barren-ground form. In the same way, it may have come about that in the English pleistocene deposits the remains of the two races occur. In a recent contribution to our knowledge of the deer tribe (_c_, p. 88), Mr. Lydekker suggests that the former division of the Reindeer races into the two forms of Woodland and Barren-ground Caribou, no longer holds good. He now recognises no less than six races, as follows:-- 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.