378 



SCIENCE 



[N. S. Vol. XXVIII. No. 716 



even cross the equator. On the other side of 

 the equator they may come down gradually 

 from the mountains. . . . Close investigation 

 always discloses the fact that the original 

 starting point of these migrations was on the 

 Schwingungskreis." 



Still another useful function of the Reibisch 

 theory is the explanation of the common arc- 

 shaped (Bogenformig) life-area. This type 

 of distribution is assumed to be due to the 

 effect of the organism's meeting the " Kul- 

 minationskreis " in its eastward or westward 

 migration. It should be explained that the 

 Kulminationskreis is a great circle which 

 passes through Ecuador and Sumatra at 

 right angles to the equator, and is so named 

 because it marks the position of nearest ap- 

 proach to the rotational poles that can be 

 attained by any point on the globe's surface 

 during pendulation. In an eastward or west- 

 ward movement of a species, when the Kul- 

 minationskreis is reached, a halt and change 

 of direction is likely to be made, since at this 

 point opposite conditions of climate set in. 

 For example, an organism passing northwest- 

 ward through that portion of North America 

 lying in the Atlantic-Indic North Quadrant 

 (which is in equatorial phase) enters, when it 

 crosses longitude 80° west, a quadrant which 

 is in its polar phase. The turn southward 

 follows and the " Bogenformig Areal " is the 

 result. 



Especially interesting is Professor Simroth's 

 very brief discussion of the character of the 

 fauna of the swing-pole regions themselves. 

 Here, where pendulation has been so little as 

 to be practically negligible as an agent of 

 climatic change, we might expect to find the 

 homes of many very ancient forms of life, 

 such as have never experienced the necessity 

 of moving. That a comparison of the faunas 

 of both east and west swing-pole regions with 

 that of extra-polar areas reveals a gratifying 

 number of primitive forms is held to be true 

 by the author. And the existence is asserted 

 of a mass of botanical writings whose purpose 

 has been to establish how little the recent flora 

 of both swing-pole regions differs from that of 

 the Tertiary. 



Tlse preceding brief review of the effects on 



the movements and evolutionary changes in 

 species and faunas that might be expected 

 through the operation of pendulation has been 

 without reference to the effects of the land 

 upheavals and submergences that are a neces- 

 sary consequence of the pendulation principle. 

 Of these latter and their effects, so largely 

 speculative, little is offered by the author or 

 could be expected. As further examples of 

 equatorial sinkings are mentioned the Caspian 

 area, the Dead Sea, North Africa and North 

 Australia. Such broad low flat areas as the 

 Sahara, in particular, because of their lack of 

 defensive or refuge-furnishing barriers, are 

 believed to have been of high importance as 

 factors in the initiation of evolutionary 

 changes. Animals and plants originating in 

 such a place must make more than ordinary 

 effort to keep in an equable climate. For such 

 pendulation has the mandate : move or vary. 

 In considering the eventuality that some 

 might stay, it is ventured that " only the 

 strongest mutations would suffice " those that 

 did. To those that move several alternatives 

 are open. They may go east or west on their 

 own meridian. If there are mountains, they 

 may ascend them. In a polar movement they 

 may attain greater warmth, perhaps, by volun- 

 tarily descending into the sea; while in an 

 equatorial movement which involves a stretch 

 of continent already low, many will be forced 

 into the sea with the gradual submergence. 



Estimates of the value of as purely spec- 

 ulative a piece of work as this are so apt to 

 vary with individual temperament or scien- 

 tific interest that they are little better than 

 gratuitous. When the issue between the 

 author and his public (for the book is con- 

 fessedly a brief) is so largely one of inter- 

 pretation, the pointing of minor errors of 

 fact, unavoidable in so great a massing of 

 material from so wide a field, has scant 

 relevance. Beside the conception in defense 

 of which the author's thesis has been written, 

 even a vaster compilation of biological data 

 than Professor Simroth has brought together 

 might well have for many an appearance of 

 comparative insignificance. So it will doubt- 

 less be easier for most readers to admit a 

 considerable measure of explaining value in 



