500 



SCIENCE 



[N. S. Vol. XLIII. No. 1110 



from the general Paleozoic discussion, William 

 Dawson from the Devonian, Dana is given 

 Tinder the consideration of the permanency of 

 continents and ocean basins, while Darwin, 

 Wallace, Huxley and Lamarck are seen among 

 the statements of evolution. 



As was to be expected from one of the 

 world's foremost paleogeographers not the 

 least of the many excellent features of the 

 book are the discussions of the past geog- 

 raphy of the earth and the many original maps 

 to illustrate it. There are usually several 

 paleographic maps of ISTorth America for each 

 period. 



The book is so filled with interesting mat- 

 ter that it is difB.cult to pick out topics for 

 special remark. It is, however, noteworthy 

 that the text-book issuing from the university 

 which saw the birth of Dana's " Manual of 

 Geology " should advocate, though in a less 

 rigid form than did Dana, the permanency of 

 the oceanic and continental areas, the theory 

 propounded by him. " Since the beginning of 

 Paleozoic times the oceanic basins and the 

 continental masses have been more or less 

 permanent." This permanency is more flex- 

 ible in the continental masses whose domi- 

 nant movement is upward, for portions of 

 these are at times invaded by the ocean or 

 have parts of their masses faulted off into the 

 oceanic basins. 



The author's discussion of the early life of 

 this globe must also be mentioned. " At the 

 very base of the geologic record, in the 

 Archeozoic," he says, " the rocks testify to a 

 world with about the same physical environ- 

 ment as that of subsequent time." The pres- 

 ence of life in the marine waters at this time 

 is shown by the carbonaceous shales and the 

 large amount of graphite. No fossils are 

 known. It is assumed that the Archeozoic 

 was the " age of unicellular life," both plant 

 and animal. By the close of this long era it is 

 postulated that small multicellular plants and 

 animals had also been evolved. Among the 

 latter were morulas, gastrulse and planulsE, 

 known at present as early embryonic stages in 

 the development of existing animals. From 

 the Proterozoic a small number of fossil spe- 



cies are known. These are " an abundance of 

 marine algae, some radiolarians and tubes and 

 burrows made by annelids." The presence of 

 annelids implies the existence of the more 

 lowly organized sponges, coelenterates and 

 worms. So likewise the presence here of such 

 other invertebrate phyla as the echinoderms, 

 molluscoids, moUusks and arthropods is indi- 

 cated by the highly evolved state of all these 

 phyla at the opening of the Paleozoic. The 

 author thus rejects Walcott's theory that the 

 Proterozoic fossils thus far known are most 

 probably non-marine and that in the at pres- 

 ent unknown Proterozoic oceans developed the 

 life which made so sudden an appearance in 

 the lowest Paleozoic sediments. He agrees 

 with Daly and Lane that the early marine 

 waters had a different chemical content but 

 objects that this alone could cause animals to 

 so largely secrete chitinous, instead of cal- 

 careous skeletons, while the plant organisms, 

 especially algse, at the same time formed great 

 thicknesses of limestone through their cal- 

 careous secretions. 



As to the evolution of insects " it is thought 

 that out of some Silurian or Devonian tri- 

 lobite that habituated itself to the land-waters 

 and became amphibious was derived the stem 

 stock of insects." 



That modern necessity, a good working in- 

 dex, is here well met. Only a few examples of 

 oversight were noted. One was the failure to 

 refer to the discussions of pre-Cambrian and 

 late Paleozoic occurrences under the word 

 glaciation. All references are to the Pleisto- 

 cene. 



An excellent generalization of the TJ. S. 

 Geologic map, 14 by 17 inches, is inserted im- 

 mediately before the index. It is thus easily 

 accessible for reference without interfering 

 with the usefulness of the index. It would be 

 of still greater aid to the student if it had a 

 blank base so that when unfolded the entire 

 map would be visible though the back were 

 closed. This would enable the map to be con- 

 stantly before the student, no matter what part 

 of the book he was reading. It is unfortunate 

 that in the legend of this map the author uses 

 the " ic " endings to the period names without 



