488 



SCIENCE 



[N. S. Vol. XL VI. No. 1194 



formed of rows of integumental scales, and 

 that they are thus the same sort of organ as 

 are the bands of the armadillo carapace, which 

 Newman finds so convenient for the compari- 

 son of individuals. 



The last and longest chapter. Chapter VII., 

 gives a detailed study of the results of both 

 lines of investigation, and presents, with nu- 

 merous illustrations the strange correspond- 

 ences in detail in the external characters of 

 monozygotic twins, whether found in the cara- 

 pace of the armadillo, or in the palm and sole 

 ridges of man. These two series of studies 

 serve to strengthen each other, and are shown 

 to be essentially similar phenomena, of great 

 biological significance. In the facility with 

 which embryonic material of every stage may 

 be obtained the armadillo has a decided ad- 

 vantage over man as a Versuchstier, although 

 in the enormous amount of detail presented by 

 human palms and soles, and the readiness with 

 which they may be compared in the form of 

 prints, there are certain distinct advantages 

 in the study of man. If once the essential 

 identity of the phenomenon of polyembryony 

 in Dasypus and Homo be generally recognized, 

 those parts of the history of human duplicate 

 twins (and perhaps, of double monsters as 

 well) which are beyond our power to observe 

 directly, may be satisfactorily supplied through 

 the study of the corresponding stages in the 

 armadillo; while the correspondences in the 

 friction-skin configuration of human monozy- 

 gotic twins may be added to those observed in 

 the carapace of the armadillo to show the 

 amount of power possessed by the germ- 

 plasm, or some other element or elements of 

 the egg, to determine the details of the adult 

 soma. H. H. W. 



Economic Geology. By Heinbich Eies, A.M., 

 Ph.D. Fourth edition. John Wiley and 

 Sons. 



The appearance of the fourth edition of this 

 excellent and standard book on the subject, in 

 the midst of a year of battle largely as to sup- 

 plies of war materials, deserves attention, since 

 the change of publishers has been marked by 

 thorough rewriting and extensive additions. 



The statistics and references are brought 

 down to 1914-15, showing the first effect of the 

 war, but not the rebound. ISTot only are there 

 25 per cent, more illustrations, but many of the 

 less legible ones are redrawn and greatly im- 

 proved. Compare, for instance, those on pages 

 529 and 545 of the new with the corresponding 

 figures on pages 367 and 378 of the old. A 

 large number of half tones taken by the author 

 show that the descriptions of the various ore 

 deposits are not mere compilations. This is 

 perhaps the main use of some of them, for un- 

 dated views of a mine do not show what now 

 is. Would it not be well if in scientific works 

 the date of views were always given? 



The main improvement of the book, how- 

 ever, is that it now includes descriptions, in 

 but slightly smaller type, of the chief rival ore 

 deposits in other countries, and thus makes 

 possible a much more comprehensive handling 

 of the great question of ore deposits. For in- 

 stance, the Swedish deposits of Kiruna receive 

 first-hand treatment, and there is a plate of a 

 section of Luxembourg iron ores. While the 

 treatment is and must be brief, there are al- 

 ways one or two recent references to start one 

 on further search. The summaries of different 

 views as to the origin of ores, for instance, 

 Cuban ores, though brief, are well done. 

 While the author does not hesitate at times to 

 express his own views, yet he gives rival views. 

 The account, for instance, of the oolitic iron- 

 ore deposits could hardly be improved for so 

 brief a statement. 



While of course the publications of the 

 United States Geological Survey have been 

 largely used, they are by no means the exclu- 

 sive source, and the various publications of the 

 mining engineering societies have been also 

 duly consulted. 



The table of geographic and geologic dis- 

 tribution of coal in the United States is a new 

 and valuable feature, and the general subject 

 of coal receives very satisfactory treatment. 

 If the source of the analyses of coal on pages 

 8 and 9 is given it has been overlooked by the 

 reviewer. 



The treatment of copper has been brought 

 to date by reference to the Nonesuch Lode. 



