5 | ae Notices of Memoirs—Dr. R. F. Scharff— 
formation of the continental shelves. The latter consequently have 
been dry land after their formation.’ 
The remarkable circumstance that the submarine fjord-valleys on 
the European and on the American side, and likewise the submarine 
ridges connecting the two continents, are situated at about the same 
depth makes it probable that the whole area had once been raised 
simultaneously, and had thus become connected by land. Dana long 
ago urged that the refrigeration of the climate at the close of the 
Tertiary era was connected with a period of high-latitude elevation,” 
and I cannot refrain from expressing my opinion, that the Glacial 
period was primarily due to the diversion of oceanic currents produced 
by changes in the distribution of land and water. With every respect 
for the views of those who hold different opinions, it seems to me that 
the peculiar phenomena connected with the Ice Age in Western Europe, 
and especially the apparent survival of southern species of plants and 
animals in Ireland through the Glacial period, are best explained by 
such a theory as that just stated. 
It is especially the teachings of Edward Forbes and A. R. Wallace 
that led to the recognition of the significance of the present geographical 
distribution of animals and plants as an indicator of the changes which 
have taken place in the arrangement of land and water. They believed 
that many terrestrial animals and plants require a continuous land- 
surface for their dispersal. Yet the diversity and comparative richness 
of the fauna and flora of some of the oceanic islands, and the depth of 
water intervening between them and the mainland, had to be accounted 
for in some other manner. Neither Wallace nor Darwin was inclined 
to admit extensive geographical changes within the period of existing 
species. The distribution of plants and animals by ‘ accidental’, or 
what Darwin called ‘ occasional’, means of dispersal seemed to furnish 
them with a clue to the worldwide dissemination of certain species. 
Darwin’s experiments have found many imitators; and valuable 
observations tending to show that at any rate some of the more 
minute animals and plants are liable to be conveyed by occasional 
means of dispersal, have been made. 
It would be idle to deny that the seeds of certain plants are carried 
to great distances by wind; that many others are undoubtedly trans- 
ported by ocean currents; that some seeds are even scattered here and 
there by birds. My contention is, and, I concur in this opinion with 
many eminent botanists, that only a small percentage of plants are 
disseminated and actually established in that manner. Most of them 
require for their dispersal a solid and continuous expanse of soil. 
Sir Joseph Hooker evidently believed that the flora of Greenland 
had travelled across from Europe by a land-bridge in Pre-Glacial 
times. He considered the existing plants of the country as certainly 
older than the Glacial period; for he argued that the severity of the 
climate destroyed many species, while the remainder took refuge and 
survived in the southern parts of Greenland.’ Professor James Geikie 
1 F. Nansen, Norwegian North Polar Expedition, 1904, iv, p. 192. 
2 J.D. Dana, Manual of Geology, 3rd ed., p. 540. 
3 J. D. Hooker, ‘‘ Distribution of Arctic Plants’’: Trans. Linn. Soc., 1860, 
XXili, pp. 252-5. 
