60 NATURAL SCIENCE. Jan., 



great deal is talked about the educational value of science, and the 

 true inductive method of teaching by observation and experiment, 

 but we rarely find books that put their precepts so well into practice 

 as does Mr. Mitchell's " Outlines of Biology." 



The method of teaching by types, so much in vogue, often repels 

 the student by its absence of a connected story, and by a want of 

 relation between the different chapters. No such complaint can be 

 made here. The interest of the reader is caught at the outset, and is 

 kept to the close, by a series of admirable chapters on the broader 

 problems and conclusions of biology. All the earlier studies are thus 

 united by the central idea of protoplasm ; so that the thoughts of the 

 student are thrown back to the first chapter by such sentences as 

 "Ciliary motion, then, is a form of protoplasmic activity," and again, 

 " The development of the animal consists in the organisation and 

 specialisation of its protoplasm." Among these chapters we would 

 specially instance those on " The Building up of Protoplasm," " The 

 Differences between Plants and Animals," " Cell-structure and Cell- 

 division," " The Gastrula, Coelenterata, and Coelomata," and 

 " Embryology." But there are also interesting little excursus 

 scattered through the more descriptive chapters ; thus, Amoeba is 

 made the text for talks on subjects so different as genera and species 

 in general, and death and reproduction in single-celled animals. 



Our author's accuracy is shown in such cases as his careful dis- 

 tinction between Pvotococcus and Pleuvococcus on p. 16, or that between 

 Lumbvicus and Allobophova on pp. 138 and 152, since these are forms 

 too often confused by our writers of text-books. The lucid and 

 interesting qualities of his writing may best be gauged by the fact 

 that a person absolutely ignorant of biology has seriously incom- 

 moded the present reviewer by constantly borrowing the book to 

 read. The clearness of style is enhanced by a judicious use of solid 

 and spaced type, though it must be confessed that a whole page 

 of the latter is nearly as troublesome to read as bad type-writing. 

 An additional advantage to the book is that the numerous figures 

 have nearly all been drawn by the author himself. This proceeding 

 naturally has its defects, for not all scientific men have mastered the 

 difficulties of " process work." But it brings with it the counter- 

 balancing gain of clearness and accuracy. 



In a word, we know of no introduction to biology that we would 

 more willingly place in the hand of a beginner, whether he intended 

 to become a professed biologist, or merely to pass the examination of 

 " the conjoint board " ; while those who wish, not so much to study, 

 as to get a clear and up-to-date idea of the broader questions of 

 biology, may safely be advised to make themselves a Christmas 

 present of these attractive " Outlines." 



Rocks, Ancient and Modern. 



ElNLEITUNG IN DIE GeOLOGIE ALS HISTOKISCHE WlSSENSCHAFT ! BEOBACHTUNGEN 

 UBER DIE BlLDUNG DER GESTE1NE UND 1HREK ORGANISCHEN ElNSCHLUSSE. 



By Johannes Walther. Part III. Lithogenesis der Gegenwart. Beobachtungen 

 liber die Bildung der Gesteiae an der heutigen Erdoberflache. 8vo. Pp. viii., 

 and 535-1055. Jena : Fischer, 1894. 



Reference has been made on more than one occasion in the pages 

 of Natural Science to the many interesting points raised by Professor 

 Walther in the earlier parts of the above work. One is therefore 

 quite prepared to find that the more strictly geological part of the 

 book is treated in an original and unconventional manner. In the 



