Distribution of Moths of the Sub-family Bistonine. 379 
that is the rock upon which the rival theories of geologists, 
botanists and zoologists are shipwrecked. Did, or did not 
the coast line of Pleistocene ‘ Western Britain’ approximate 
that of to-day ? It seems to me we are all inclined to make 
a fetish of the 100 fathom line on the one hand, and of the 
1,000 fathom line on the other, and that the resul: is chaos. 
If we argue from the accepted glacial geology of to-day, most 
of Great Britain and all of Ireland were overwhelmed with ice 
and incapable of supporting life. If we take the views of 
the botanists and zoologists, they can produce long lists of 
plants common to the British Isles and America, of plants, 
insects and slugs peculiar to Ireland and the Spanish Peninsula, 
and of bryophytes found only in the west of our islands and 
in various isolated localities in Africa and America; such, 
they urge, must have survived. Examples of such are :— 
the Irish Ladies’ Tresses (Spivanthes romanzoffiana), Ireland 
and America; Blue-eyed Grass (Sisyrinchium angustifolium), 
Ireland and N. America; the Pipewort (Eviocaulon septangu- 
lave), Ireland, Scotland and America; the London Pride 
(Saxifraga umbrosa), Ireland, Pyrennes, Spain and Portugal ; 
the weevil, Otiorrhynchus auropunctatus, Ireland, France, Spain ; 
the caddisfly, Tinodes maculicornis, the Kerry Slug (Geoma- 
lacus maculosus), and the following mosses :—Philonotis 
wilsont, Wales, Scotland, Ireland, Fernando Po, Myurium 
hebridarum, Scotland, Azores and Canary Islands, Daltonia 
splachnoides, Ireland, West Indies and Mexico, Sematophyllum 
micans, Ireland, Scotland, England and America. 
The two views are incompatible and, of a certainty, that 
of the botanist and zoologist, as emphasised by the above 
selection from many available examples, is on firmer ground. 
Either, then, the Glacial Period was not so rigorous as pictured, 
or the British Isles of Pleistocene times extended far to the 
South West and to more favoured localities. And, for- 
tunately, direct evidence can be brought to bear on this. It 
is generally conceded that, just after the Ice Age, steppe 
conditions obtained in Europe as far west as East Anglia. 
Now, if it requires a distance from the Atlantic to South Russia 
to bring into being the steppes of to-day, surely this argues 
that, for an extension of these conditions to England, Western 
Europe possessed a configuration differing widely from its 
present one: and this, in turn, demands that Pleistocene 
Europe should stretch far to the west of our present limits. 
There, then, cut off from the rest of the habitable globe by 
leagues of ice, on low islands and coasts, kept warm by the 
Gulf Stream (probably) and by the Atlantic Ocean (certainly), 
favoured species survived ; amongst them was N. zonaria. 
At length the glaciers waned, and as they did so, the atten- 
uated band of survivors attempted to spread, retreating as 
1916 Dec. 1. 
