Reptiles and amphibia are altogether unknown in the Polar Regions, but a large number of fish, chiefly marine, have taken their origin there. The Salmon family are of Arctic origin, as also are the Sticklebacks and the Perches, many of the Cod family, the Herrings, and several of the Flat fish. It would lead me too far to refer to the invertebrate fauna of the Polar Regions, but a few remarks on the Arctic plants may not be out of place. The principal Arctic genera are Salix, Ranunculus, Draba, Pedicularis, Potentilla, Saxifraga, Carex, Juncus, Luzula, Eriophorum, and others. Among the most characteristic Arctic plants may be mentioned _Dryas octopetala_, to which I have already referred as occurring in the west of Ireland; _Saxifraga oppositifolia_, another British species, occurs in the higher mountains of Scotland, Ireland, and Wales; _Braya alpina_, _Papaver nudicaule_, _Lychnis apetala_, _Diapensia lapponica_, and _Lobelia Dortmanna_, which is found in the lakes of Scotland and Ireland. The dwarf birch (_Betula nana_) also, which still occurs in Scotland and the North of England, and which had formerly a wider range in the British Islands, should be included among these; but there are other plants probably of Arctic origin, though not now occurring in the Arctic Regions, and to these may be classed the so-called American species of plants which are found on the northern and western coasts of Ireland, in the Hebrides, in Scotland, and in North America. These are no doubt the relics of an Arctic flora which flourished in high latitudes in past times when the climate there was more temperate. A list of these species will be found on page 166. As none of them occur in Siberia, they must either have found their way to North America and to Europe from the Arctic Regions, or have travelled from North America across the latter to Europe. In any case a former land-connection between the two continents must have existed. This becomes the more evident when we examine the remarkable results obtained by the late Professor Heer, who first described the Tertiary plant-beds in North Greenland. No less than 282 species of plants have been described by this eminent botanist from these deposits. A large number of the plants found were trees belonging to the genus _Sequoia_, _Thujopsis_, and _Salisburia_, besides beeches, oaks, planes, poplars, limes, and magnolias. That they grew on the spot is proved by the fruits, which have been obtained from these beds in various stages of growth.