I9 o 9 ] CURRENT LITERATURE 75 



and equatorial. According to this theory, past variations in climate in any given 

 place have been due to pendulation. 



Glacial periods, such as the Permian and Pleistocene, have been developed 

 through a poleward swing of regions now temperate; while warm periods, such 

 as the Cretaceous and Eocene, have been developed by means of a swing toward 

 the equator. At the present time Europe and eastern North America are supposed 

 to be swinging southward and getting warmer, while western North America is 

 swinging northward. Pendulation causes constant redistribution in the oceanic 

 waters, by reason of the earth's oblateness, thus accounting for the submergence 

 of coast lines. 



The major portion of the volume is devoted to the presentation of the facts of 

 distribution in animals as related to the pendulation theory. It is claimed that 

 the various groups are more or less symmetrically distributed with reference to the 

 fixed poles, owing to the control exerted on migration by the swinging of the earth 

 on its axis of pendulation. One chapter only is given to plants, and in this chapter 

 chief attention is paid to the conifers and Campanulaceae. Three maps are 

 presented, showing the distribution of the conifers. In these and other maps 



figu 



sym 



metrically from that region. 



The volume as a whole has a strangely medieval atmosphere. Students of 

 geographic distribution in these days are so accustomed to look carefully for 

 facts that they have largely ceased to care for hypothetical disquisitions such as 

 that of Simroth. One feels that the author regards the pendulation theory as a 

 panacea, and that he selects for consideration those facts of distribution which 

 fit it best. Certainly the problems of migration are vastly more than the sym- 

 metrical movement of organisms from a center under the control of the direction 

 of pendulation. And the idea of pendulation itself seems more like an iridescent 

 fancy than a reality. Biologists may well wait until there is some astronomic or 

 geologic basis for such a hypothesis before they attempt to readjust their facts to 

 the new theory.-H. C. Cowles. 



MINOR NOTICES 



Purple bacteria.— A monograph on Rhodobacteria* is the natural outcome 

 °f the results of shorter studies on the subject which have been presented from 

 time to time by Molisch. After a discussion, partly historical, of methods of 

 culture, the author describes eleven new species recognized by him and gives a 

 ^cation, based upon those of Winogradsky and Migula, in which he divides 

 ier Rhodobacteria, containing all known purple bacteria, into two families: 

 vhich do and those which do not show sulphur granules in the cell substance. 



12 to thf» hirtrl^™:. — 1 „:j~ _r j.i ^.j_. n/r — «~*w« Avnm ; n oc tV»^ relation of 



theoi 

 those 

 Turn 



MOLISCH examines 



1 



3 Molisch, Hans, Die Purpurbacterien nach neuen Untersuchungen. pp. 95- P ls - 

 4- Jena: G. Fischer. 1907. 



