gO THE AMERICAN NATURALIST. [VoL. XXXV. 
supposition upon which rests the whole theory of the Arctic 
immigration, in so far as such terrestrial animals are concerned, 
which require a continuous land connection, consists in the 
assumption that. America and Europe were connected far north 
between Scandinavia, Spitsbergen, and Greenland until toward 
the end of the glacial period, while Norway again was continu- 
ous with Scotland across the North Sea, and England (and 
Ireland) with France. The earliest traces of such an immigra- 
tion he finds in certain so-called American plants and fresh- 
water sponges which are found on the northern and western 
coasts of Ireland, in the Hebrides, in Scotland, and in North 
America. “The geographical distribution of some of the 
Arctic species is referred to in greater detail," to use Dr. 
Scharff's own words in his summary of this chapter, “to show 
how the relative age of their entry into Europe can be deter- 
mined. Two forms of reindeer, resembling the Barren-Ground 
and Woodland varieties, have been met with in European 
deposits, but only the former occurs in Ireland and the south 
of France, whilst eastward the other becomes more common, 
and finally is the only one found. It is believed that the 
Barren-Ground is the older form as far as Europe is concerned, 
and that it came to us with the Arctic migration, and that the 
other reindeer reached Europe much later from Siberia, when 
Ireland had already become detached from England. The 
range of the Arctic hare is equally instructive. It must have 
been a native of Europe since early glacial or preglacial times 
— before the common English hare had made its appearance 
in central Europe. Along with other Arctic forms it entered 
northern Europe directly from the Arctic regions by means of 
the former land connection which joined, as I remarked, Lap- 
land with Spitsbergen, Greenland, and North America.” The 
stoat, or ermine, is another distinctly northern animal which 
Dr. Scharff regards as having reached Ireland and England at 
two different times; the one from the Arctic regions as a 
northern migrant, the other with the Siberian fauna from the 
east, and its range is made to include 
Greenland and Spits- 
bergen. 
rg He also thinks that there can be no doubt that the 
British grouse belongs to the northern migration, and the 
