E. V. Wulff —166 — Historical Plant Geography 



in former periods of the earth's history was not the same as at present, 

 that where there are now continents, or at least over part of their 

 territory, there were deep oceans and where the latter now are there 

 were continents, then in the rocks of which our continents are composed 

 there should be, over considerable expanses of territory, deep-sea de- 

 posits, attesting that at one time the given continent was at the bot- 

 tom of the ocean. Such deep-sea deposits, however, are not to be 

 found on our continents. This serves as grounds for concluding that 

 our present continents were never covered by oceans and, in contrast 

 to the ocean depths, always constituted elevated land-masses. On 

 their surface in former geological periods, just as at present, there 

 existed relatively shallow seas, but a large part (at least one-third) of 

 their surface was always dry land (Soergel, 1917, p. 11). Slight vari- 

 ations in the level of the ocean, amounting to as much as several hun- 

 dred meters, accompanied by a depression or elevation of the strand 

 Hnes, may change considerably the contours of our continents, but they 

 cannot affect their permanence as a whole nor the permanence of the 

 ocean beds. 



To geophysical objections to the land-bridge theory there may be 

 added objections based on geological and paleontological data. These 

 bear witness to the absence of transitional forms between the fossil 

 marine faunas of the earlier geological periods and the sudden appear- 

 ance of whole groups of species not connected with those of the for- 

 mations preceding them in sequence of time, as would be required by the 

 theory of evolution. These facts indicate that the successive phases 

 of development of the inhabitants of the sea did not take place on the 

 surface of our continents but must have taken place within the boun- 

 daries of the oceans as at present constituted. Hence, the following 

 conclusions are drawn by the advocates of the theory of permanence 

 (Soergel, 1917, p. 15): — 



1. The great areas now occupied by oceans must have been thus 

 occupied always, at least ever since the Pre-Cambrian era. 



2. Fossil marine faunas have no roots on our present continents; 

 they merely represent the repeated inland migrations of sea animals. 

 (This is further confirmed by the absence in the faunas of present-day 

 inland seas of elements that have preserved features of a deep-sea 



origin). . . 



3. The territory occupied by our present contments has constituted 

 a habitat of marine fauna always in contrast to the territory of the 

 present oceans, a circumstance which is only understandable if one 

 assumes that the former was an elevated territory, subject to alternate 

 upheaval and depression, i.e., a territory of a continental character. 

 This means that the continents must have been permanent. 



These conclusions, however, leave entirely unexplained the bioge- 

 ographical data that indicate the need of assuming that the continents 

 were at one time connected. It is true that now even advocates of the 

 theory of permanence try to find a way out of the contradictions 

 created. They state that, though we cannot concede the existence of 

 large trans-oceanic land-bridges, we may concede the existence of some 

 sort of connection between the continents, e.g., narrow land-bridges 

 between North America and Europe, Australia and South America, 



