vi SCIENCE PROGRESS. 



Integrals are just touched upon, also spherical harmonics, Bessel's 

 function, hyberbolic functions and gamma functions. The chapter closes 

 with a problem on the conduction of heat, and a tabulated list of in- 

 tegrals. 



The book is printed in clear, good-sized type, on good paper, an- 

 swers are in nearly all cases given to the exercises, and an index is 

 provided. 



To the teacher of the Calculus, no less than to the Engineer, this 

 book will prove of great value as a rich storehouse of practical illustra- 

 tive examples, by means of which he may impart to his students a real 

 useful working knowledge of the subject. 



Vorlesuiigen ueber Bakterien. Von Dr. Alfred Fischer, a.o. Professor 

 der Botanik in Leipzig. Mit 29 Abbildungen. Jena : Verlag 

 von Gustav Fischer, 1897. 



All who have followed Prof. Fischer's work on Bacteria will 

 open his new book on these organisms with anticipatory pleasure. 

 Nor will they be disappointed. Since the publication of Dr. Bary's 

 fascinating lectures, nothing has been written concerning Bacteria, 

 which gives so clear and interesting a sketch of the present state 

 of our knowledge in this department of Botany as does Dr. Fischer's 

 new book. With the advance of knowledge, much of what we used to 

 accept as fact has been found to require revision, and not only have 

 many of the old puzzles been gradually solved, but many new paths of 

 inquiry have been opened up. Winogradsky's magnificent researches 

 are ably summarised, and the results, showing that some bacteria 

 possess the power of assimilating the carbon dioxide from the atmos- 

 phere, others again that of obtaining their energy by oxidising sulphur- 

 etted hydrogen, first to water and sulphur and finally to sulphur 

 dioxide, instead of relying on the oxidation of carbohydrates, are pre- 

 sented in a clear and readable form. 



The bacteria concerned in the fixation of nitrogen and the relation 

 of the process to the carbohydrates obtained from the leguminous plants, 

 in which they engender the formation of tubercles, receives a clear 

 though somewhat brief exposition. 



Some of the other instances of symbiosis however are not so 

 happily chosen. In a book of this kind, a discussion on the symbiotic 

 relat ons of fungus and alga in lichens seems to be somewhat out of 

 place, and the beautiful case of the gingerbeer plant, so thoroughly 

 investigated by Marshall Ward, might with advantage have been sub- 

 stituted. As it is, this, perhaps the most striking example of symbiosis 

 of its kind, finds no mention at the hands of our author. The later 

 chapters, dealing with the relation of bacteria to disease are perhaps less 

 interesting than many of the preceding ones, but within the compass of 

 a short course of lectures, such as that of which the volume before us 

 is made up, possibly this is not easily avoidable. 



