October 13, 1923] 



NA TURE 



535. 



found in summer riding on the weaker sex. Among 

 the Bryozoa^ treated by the same author^ we find the 

 beautiful Memhranipora membranacea var. erecta, which 

 is very common in brackish water in Holland. 



Echinoderms and tunicates must be passed here 



for lack of space. Dr. Redeke's account of the fishes 



^will be of special interest, not only to ichthyologists, 



)ut also to others, for here the different zones of 



^alinity are separately described. Last comes Prof. 



[ax Weber, who treats of ten species of cetaceans, of 



^-which specimens of all but one, the common Phocsena, 



have stranded on the banks of the Zuiderzee at different 



times. 



A systematic index, more than eight pages in three 

 columns, increases the utility of this important mono- 

 graph of a brackish- water area. 



W. G. N. VAN DER SlEEN. 



Geology for Canadian Students. 



Elementary Geology : with special reference to Canada. 

 By Prof. A. P. Coleman and Prof. W. A. Parks. 

 Pp. XX -I- 363. (London and Toronto: J. M. Dent 

 and Sons, Ltd., 1922.) 155. net. 



^HE issue of treatises on general geology specially 

 adapted to readers and observers in the units 

 )f our federal commonwealth is a sign of healthy auto- 

 lomy in the domain of natural history. Colleges in the 

 )ominions have long been troubled with the details 

 )f the English Oligocene, a poor thing at the best, or 

 the Llandovery sequence on the Shropshire border, 

 spirants in South Africa have been well served by 

 ir. A. L. Du Toit's " Physical Geography " and 

 'rof. E. PL L. Schwarz's " South African Geology," 

 ince the latter includes a short general introduction 

 to the science. 



Profs. A. P. Coleman and W. A. Parks of Toronto 

 low provide Canadian students with a sound elementary 

 text-book based primarily on what may be seen in 

 mada or in the adjacent United States. The account 

 )f the Grenville and Keewatin series, the former con- 

 listing of altered shales (garnet-sillimanite gneisses) and 

 rystalline limestones, and the latter of volcanic tuffs 

 lavas, is very valuable for European students who 

 Irish to realise the nature of the oldest known rocks 

 svealed to us in the accessible crust. The eastern 

 [Series, the Grenville, may prove to be somewhat 

 )lder than the Keewatin of the west ; but both are 

 ivaded by the great batholitic intrusions which have 

 jiven rise, often by interaction with their surroundings, 

 to what may still be styled the Laurentian gneiss. 

 Prof. Coleman's work among the glacial beds of early 

 Iluronian age adds greatly to the interest of the pages 

 on Pre-Caml)rian rocks. 



NO. 2815, VOL. I I 2] 



While European types of fossils are in places very 

 justly figured, such as the Jurassic Trigonias and 

 ammonites of England, we are introduced to the 

 Cambrian trilobites of British Columbia, to Devonian 

 fishes from Canada described by Traquairand Whiteaves, 

 to the Permian reptile Dimetrodon of Texas, with 

 its amazing dorsal spines, and to a Lower Cretaceous 

 Stegosaurus from the province of All3erta. The 

 Cainozoic era, styled also in this book the Tertiary 

 period, is dealt with slightly ; yet the thicknesses 

 of its strata in many localities show that its duration 

 was equal to that of Mesozoic times. The spelling 

 " Cenozoic," adopted by the authors, though it follows 

 Lyell's nomenclature of the systems, is etymologically 

 misleading and should be synonymous with azoic. 

 We greet on p. 353 an ancestor of the national maple 

 leaf, culled from interglacial deposits in Toronto. 



The book is finely printed and is handsomely illus- 

 trated throughout. Too much may have been attempted 

 in one volume, and the definitions of divisions of the 

 animal and vegetable kingdoms on pp. 155-160 are 

 necessarily unsatisfying and incomplete. Some of 

 these divisions are further treated in the chapters on 

 stratigraphy ; but where are the radiolaria, which have 

 a significance as rock-formers } Five or six pages 

 more would have made the description of mineral 

 characters almost adequate. As it is, we have a not 

 too accurate summary of the crystallographic systems 

 (the principal axis, for example, in the tetragonal 

 and hexagonal systems is said to be " long "), while 

 we are led to suppose that quartz is hexagonal. Are 

 the micas, again (p. 12), of different crystal systems ? 

 " Mont Pelee," an error sanctioned by Angelo Heilprin, 

 appears under the fine photograph on p. 54. These 

 are small details, and to point them out implies that 

 we know that new editions will be required, and that 

 the next one will still further enlighten us by the 

 possession of an index. Grenville A. J. Cole. 



Mental Athleticism. 



Principles of Psychology : the Foundation Work of the 

 AUtheian System of Philosophy. By Arthur Lynch. 

 Pp. xxiii-f-408. (London : G. Bell and Sons, Ltd., 

 1923.) 215. net. 



MR. LYNCH some years ago published a book in 

 two volumes entitled " Psychology : a New 

 System." Whether, like a famous work of a famous 

 predecessor — the Scots philosopher Hume — his book 

 fell still-born from the press, or whether for other more 

 personal reasons, he has decided to recast it. He 

 now presents it in one volume and describes it as the 

 foundation work of the Aletheian system of philosophy. 

 (Why the first e in the word is given the French acute 



