NOVEMBEB 27, 1896.] 



SCIENCE. 



79,7 



others, in developing this region along the 

 lines of classification marked out by the Con- 

 ference of 1889, are too well known to require 

 specific attention. That basin portion of the 

 continent is disclosing in striking characters and 

 in magnificent array the successive and con- 

 tinuous steps of progress through the great time 

 gap between the Archean complex and the 

 fully developed faunal conditions of the 

 early Combrian, in which gap, it is believed, 

 lies one-half the geologic history of the globe. 

 The Algqnkian seems to be a fact, and a large 

 one too, in North American geology ; yet this 

 period is not mentioned save in a single foot- 

 note (p. 296). In the four and one-half pages 

 devoted to the Archean, ten lines are, given to 

 the rocks of the period, of which ' there is 

 nothing very characteristic, ***** except 

 their extreme and. universal metamorphism.' 

 The word Huronian does not occur in these 

 pages. 



Perhaps a word of caution should be spoken 

 against the impression given by Figs. 264 and 

 265^ that iron ore is interstratified with its asso- 

 ciated rocks and hence may reach through to 

 the bottom of the earth's crust. Investigations 

 show that iron ore of the Lake Superior type 

 does not occur as interstratified formations and 

 does not appear to any workable extent in the 

 Archean of North America, as the term Archean 

 is understood among working geologists. In 

 giving 34 per cent, of his Archean space to evi- 

 dences of life the author says of the leading type 

 that its ' organic origin is not now generally ad- 

 mitted. ' 



To the writer it would seem that had fewer 

 pages been devoted to geysers and earthquakes, 

 topics of no great geologic significance so far as 

 past researches reveal, and more been given to 

 the subjects enumerated above, geologic science 

 would have been aided in its appeal to the in- 

 stincts of American students of geology. 



3. Finally, from a pedagogical standpoint, this 

 book is to be judged because the author calls it 

 a text-book for colleges. From this standpoint 

 it chief defect lies in the multiplicity of theories 

 advanced and discussed. A text-book should be 

 the exponent of a doctrine. It should be con- 

 structed on the definite and positive plan best 

 adapted, ip the mind of the author, to expound 



his body of principles. When several theories 

 are presented and the student practically told 

 to take his choice (p. 100 et seq.), or when he is 

 told that all are true (p. 65), the function of th.e 

 text-book disappears. The book in so far be- 

 comes a compilation of opinions. So far ,as the 

 development ; of geologic science goes, the 

 reader is in the dark as to what to believe, 

 unless he assumes that the chronological order 

 of the opinions expressed represents such devel- 

 opment. Geology is a science; it has passed the 

 stage of assumption. While much remains to he 

 discovered, worked out and established in geo- 

 logy, still the body of facts and well-understood 

 phenomena now clustering; around the subject 

 is sufficient to fill a book. By the presentation 

 of these facts and phenomena the student who 

 leans upon a text-book subjects himself to the 

 inspiration of positive ideas and, in his intel- 

 lectual processes,acquires that habit of decision 

 so essential to practical success. 



C. W. Hall. 

 The Uniyeesity of Minnesota. 



SCIENTIFIC LITEBATUBE. 

 Die Morphologic und Physiologic des Pflanzlichen 

 Zellkernes, eine kritische Litter atur. Studie 

 von Peof. Dr. a. Zimmeemann. Jena, Verlag 

 von G. Fischer. 1896. Pp. viii + 133. 

 This collection of literature and critical re- 

 view of the numerous scattered investigations 

 and comparatively few extended studies which 

 have been made upon the nucleus in plant cells 

 is very welcome to all plant cytologists. It is 

 indeed, an excellent and well prepared sum- 

 mary, and avoids the errors of classification, 

 ' which to* some extent impaired the usefulness 

 of the ' Botanisches Mikrotechnik ' by the same 

 author. 



The work is divided into a general part and a 

 special part. In the former, under the follow- 

 ing chapter heads, research methods, nomen- 

 clature and general considerations, chemical 

 structure, morphological differentiation of the 

 resting nucleus, nuclear division, nuclear fu- 

 sion and nuclear physiology, the various ob- 

 servations of a large number of "investigators 

 are collected. In this part the two most inter- 

 esting and useful chapters are those on karyo- 

 kinesis, in which Zimmermann's views upon 



