Cliuialic Changes in Japan since Pliocene Epoch. 15 



Oil the other, and vice versa. This, I think, can only be explained 

 by the movement of the poles to and fro. We may assume that 

 during the earlier Pliocene, the North Pole was more to the 

 Asiatic side. Then it began to move to the Atlantic side until 

 the Diluvial, when that side fell into ice-age and the Asiatic side 

 into coralline age ; after that it may be taken as having made a 

 backward movement, that is to say, back again to the Asiatic side. 

 So far as I know, this mode of explanation meets with no serious 

 objection. Therefore, if theories are made to explain a phenome- 

 non whose cause is unknown, and if, among these theories, the 

 one which explains it in the easiest and most unconstrained way is 

 the most plausible, then the movement of the poles to and fro must be 

 regarded as the most plausible explanation of the climatic changes 

 of the Northern Hemisphere since the Pliocene Epoch. 



It is a singular coincidence that Prof. Simroth of Leipsic, led 

 by a peculiar geographical distribution of the organisms in the 

 present creation, had already tried to explain it also by the so- 

 called " Theory of the Oscillation of the Poles," first propounded 

 by Reibisch to account for the displacement of the beach-line. In 

 tliis theory, '-^ the North and South Poles are made to swing to and 

 fro on the meridian of 10° E.L. which corresponds to 170° W.L. 

 on the Pacific side, a line just passing through the Bering Strait. 

 This meridian has been calletl by Reibisch the circle of oscillation. 

 Now Simroth had recognized a more or less symmetrical distribu- 

 tion of similar or vicarious foi'ms either east or west of this circle or, 

 if under the same circle, north and south of the equator. The first 

 is called by Simroth the transversal sijininetrtf, and is said to be 

 caused by the organisms diverting to the east or the west as the 

 quickest means of evasion of the approach of a pole or of the 

 equator. The second is called by him meridial s)jmmetrij, and is 

 thought to be caused by organisms on the approach of the equator, 

 climbing up high mountains on which they can wander south and 

 even cross the equator beyond which they can again come dow^n to 

 the low-land, where the climate is suited for their existence. As 



1 ) Simroth. Die Peadnlationstheorie, 1907. 



