1897] THE PROBLEMS OF BRITISH FAUNA 379 
‘ British, ‘ English’ and ‘ Germanic” types—to have entered the 
country from the east and south-east across the dry area of the 
North Sea and the Straits of Dover during the subsequent period 
when the British territory had emerged from the Glacial sea, England 
being united to the Continent, and Ireland to Great Britain. 
At the time when Forbes wrote, the glacial deposits were 
believed to have been laid down on the bed of a sea covered with 
floating ice. The subsequent adoption by the majority of geologists 
of the theory that the Boulder Clay represents the ground moraine 
of vast sheets of land ice has led most recent writers on the British 
fauna and flora to regard most if not the whole of the living things 
in our area as post-glacial immigrants. Whatever animals and 
plants lived in these islands during Pliocene times are presumed 
by Professor James Geikie, and those who share his views, to 
have been exterminated by the terrible rigour of the glacial condi- 
tions during the Pleistocene age. And the general view at present 
is that it was not until the climate improved in later Pleistocene 
times that the country again became the abode of animal and 
vegetable life. On this theory it would seem certain that the 
arctic and alpine species were the first to establish themselves in our 
area. 
Now, the results to which Dr Scharff’s studies have led him are - 
in startling opposition to the current opinion just mentioned. He 
believes that, with the exception of the ‘Siberian’ section, the 
whole of the British fauna entered the country in Pliocene or the 
earliest Pleistocene times. With regard specially to the Irish 
fauna, he considers that all the animals which now inhabit Ireland 
must have passed into that island in the Pliocene, or, at latest, 
about the opening of the Pleistocene period, there being, in his view, 
no evidence of any land-connection between England and Ireland 
after that date. It is hardly necessary to recall the fact that the 
absence of so many British animals and plants from Ireland has 
led naturalists without exception to regard that country as an older 
island than Great Britain, whatever geological age they may ascribe 
to the fauna and flora. 
It is specially the study of the past and present distribution of 
the British mammals that has led Dr Scharff to his results. The 
‘ Siberian’ mammals which are found—living or extinct—in Great 
Britain, but not in Ireland, furnish, as has been said, the key to his 
argument. Remains of these mammals, preserved in the continental 
Pleistocene deposits, enable the course of their migration from east 
to west to be traced in considerable detail. They lived in Siberia in 
Pliocene times, but in Europe their remains are not found except in 
beds later than the Lower Boulder Clay, which Dr Scharff suggests 
was laid down in the northern part of a sea connecting the 
