x SCIENCE PROGRESS. 



An important feature of this book is the series of illustrative 

 problems which are worked out fully in the text. 



Large collections of examples are appended to several of the 

 chapters. These examples are carefully grouped, and afford consider- 

 able opportunities of choice to teachers and students making this their 

 text-book. 



Untersuchungen ucber Ban Keruthcilung mid Bewegung dcr Diatomeen, 

 von Robert Lauterborn. Mit i Figur im Text und 10 Tafeln. 

 Leipzig: Verlag von Wilhelm Engelmann, 1896. 



This splendidly got up work reflects credit no less on the author 

 than the publisher. The Diatoms have been too long the almost 

 exclusive property of the amateur, but the important results which have 

 been obtained by Dr. Lauterborn can hardly fail to direct new attention 

 to this group of organisms. 



After a brief historical account of the work of previous investigators, 

 followed by a general description of the methods which he employed, 

 the author passes on to the results of his researches on various members 

 of the Diatomaceas, and these results are as surprising as they are novel. 

 Dr. Lauterborn has wisely checked his investigations on the killed and 

 fixed plants, by observations made on living material, and he has also 

 applied the microtome methods with great success in his endeavours to 

 elucidate the anatomical structure, often very complicated, of the Dia- 

 tom cell. Thus in Pinnul'aria, the " raphe " is shown to represent an 

 open slit which places the protoplasm in communication with the ex- 

 ternal world, and in Surirella calcarata the same end is attained by 

 means of slits which occur at the edges of the four wing-like outgrowths 

 so characteristic of this species. 



As regards the structural characters exhibited by the living con- 

 tents of the cell, Dr. Lauterborn has arrived at several remarkable 

 conclusions and his results will, if confirmed, prove of great im- 

 portance. For in these organisms, representing a somewhat isolated 

 phylum, only joining the main line somewhere amongst the lower algae, 

 we meet with a protoplasmic complexity for which we seek in vain 

 amongst the higher animals and plants, finding at most a faint degree of 

 resemblance amongst the protozoa. And, indeed, it is a remarkable 

 fact, if we take a general survey of organic life, that we find the 

 mechanism of cell-division so extremely complex amongst these lower 

 forms, often far more so than is the case with plants or animals far 

 higher up in the evolutionary scale. 



Amongst the observations recorded on the mode of nuclear division, 

 Lauterborn mentions that he was able to recognise cross fibrils of pro- 

 toplasm connecting the aster rays, and he adduces a considerable body 

 of evidence in favour of Biitschli's theory as to the foam-structure of 

 protoplasm. Even in the nucleus, in some instances, he asserts that 

 a foam-stucture can be distinguished, the chromatin particles occurring 

 in the angles where the foam-walls meet. The centrosomes are stated 



