December 11, 1914] 



SCIENCE 



859 



proliferation, abnormal inter-actions, and to 

 cancer formation. 



The abnormal activities of cancer cells, to- 

 gether with the products of necrosis present 

 in every cancer, may induce cell division and 

 the formation of cells veith the right chromo- 

 some complex for cancer origin, in neighbor- 

 ing tissues, and so start up secondary or ter- 

 tiary growths from the primary, thus giving 

 rise to the phenomenon occasionally met with 

 in transplanted tumors of change in type, car- 

 cinoma into sarcoma, for example, as Bash- 

 ford has found. 



The varying frequency of cancer in different 

 organs or tissues depends, according to this 

 theory, upon the frequency of mitotic divisions 

 in the normal tissues; the age incidence of 

 cancer, upon the abnormal divisions which ac- 

 company physiologically weakened cells, as in 

 the case of protozoa in " depression " periods. 



In his treatment of the theory Boveri gives 

 its application to most of the well-known phe- 

 nomena met with in cancer growth, and meets 

 some of the arguments which have been 

 brought against it. Erom the nature of the 

 ease the theory is difficult if not impossible to 

 analyze by direct experiment, and for this rea- 

 son, as well as for its impracticability, it is 

 probable that the hypothesis will not be favor- 

 ably received by the medical profession. 



Gary N. Calkins 

 Columbia University, 

 Department of Zoology 



A Text-hooh of Geology, for use in mining 

 schools, colleges and secondary schools. By 

 James Park, Professor of Mining in the 

 University of Otago, New Zealand. Lon- 

 don, Charles Griffin & Co. 1914. 8vo. Pp. 

 xvi 4- 598, Pigs. 263, Pis. 10. 

 Professor Park has already become well- 

 known to teachers and students of geology in 

 America by his writings upon mining geology. 

 His cosmopolitan attitude and broad sym- 

 pathies are attested in the present text-book 

 by a frontispiece from the Grand Canyon of 

 the Colorado, and by acknowledgments, in his 

 preface, to the director of the U. S. Geological 

 Survey for aid kindly extended. A reader on 



this side of the world would naturally antici- 

 pate a text-book specially prepared for Aus- 

 tralasia, but one is pleasantly surprised to find 

 that the anticipations are not borne out by the 

 facts. European and American geological sec- 

 tions and remains of life are discussed with 

 the same fulness as Australasian. One can 

 not help wishing that for readers on this side 

 of the world a little more emphasis had been 

 laid on the latter. 



Professor Park's text-book is of about the 

 same size and scope as Scott's " Introduction 

 to Geology," or LeConte's " Elements." It 

 will furnish the material, along with labora- 

 tory study and suitable field trips, for one 

 year's work in a college or scientific school. 

 It impresses the reviewer as too advanced for 

 secondary schools, despite its title. 



There are, of course, several lines along 

 which the subject of geology may be attacked 

 or expounded. Broad, general processes such 

 as erosion and deposition, elevation and sub- 

 sidence, may be set forth in advance of the 

 handling and learning of minerals and rocks. 

 Or the teacher, as seems best to the writer, 

 may begin with actual rocks and discuss these 

 first; passing later to their large forms and 

 their erosion, disturbance and order in time. 

 A third start is possible if one considers the 

 earth in its astronomical relations and later 

 comes down to the terrestrial details. Pro- 

 fessor Park begins with a summary of the 

 science in all its bearings, and in his first 

 chapter outlines the general astronomical re- 

 lations, history, structure and the play of 

 modifying processes. The chapter closes with 

 seventeen summarizing propositions. Chap- 

 ter II. in two pages blocks out the subdivisions 

 of the subject and briefly reviews the teach- 

 ings of several of its founders. Passing then 

 to denudation and the destructive and con- 

 structive effects of streams, oceans, and the 

 resulting general rock structures, nine chap- 

 ters, or about one third the work, are utilized 

 before the rock-forming minerals and the 

 rocks themselves are specifically taken up. 

 One may question if it would not be clearer 

 to a student if the rock-making minerals and 

 the rocks themselves, as formed of them, could 



