1897] SOME NEW BOOKS 129 



in the slightly increased size, but in some extension of the parts 

 dealing with the Sporozoa and the Vertebrate. The Sporozoa have of 

 late years assumed great economic importance, especially in reference 

 to the breeding of fish and to certain diseases of man, as was insisted 

 on by Professor Eay Lankester in Natural Science for August 1896. 

 I)r Hertwig has therefore done well to give them greater prominence. 

 Among the Vertebrate, while Dr Hertwig has endeavoured to ac- 

 commodate Boulenger's classification of the Keptilia to the restricted 

 needs and limits of a text-book, he has found himself still unable to 

 introduce the modifications in the classification of birds that have 

 been held necessary by certain recent anatomists. 



In our former review we alluded to the weakness of the palaeonto- 

 logical part of this otherwise admirable book, and we regret to find 

 that weakness just as conspicuous. It leads to sins, not merely of 

 omission, as the passing over of all the differences between an 

 ammonoid and a nautiloid shell, and the absence of any account of 

 the shell in the decapodous cephalopods, but also of commission, as 

 the long obsolete division of the crinoids into Palaeocrinoidea and 

 Xeocrinoidea. A knowledge of palaeontology, too, would have saved 

 Dr Hertwig from devoting space to the views of Haeckel on the 

 Cystidea, when that space is so valuable that this most important 

 class of all the echinoderms has to be dealt with in a dozen lines. 

 We trust that the fifth edition, which is sure to be called for, will 

 show some consideration to those extinct animals on the knowledge 

 of which our classifications must ultimately depend. 



Aethropods for Beginners 



Through a Pocket-Lens. By Henry Schcrren, F.Z.S. 8vo. Pp. 192. 

 London : The Religious Tract Society. 1897. Price, 2s. 6d. 



Me Scherren is well known as a writer of attractive little books on 

 natural history for beginners, and his reputation in this respect is not 

 likely to suffer from the volume that is now under notice. Its object 

 is to show how much may be learnt with an ordinary pocket-lens and 

 simple appliances ; but it is surely somewhat of a pity that the title is 

 not more indicative of its contents. For the purpose could have been 

 carried out with equal satisfaction if minerals, or any group of the 

 smaller plants or animals, had been selected for study. As a matter of 

 fact Mr Scherren's choice fell, and fell wisely, upon the Arthropoda, a 

 group to which he has devoted much of his spare time, and which is 

 peculiarly suitable for the purpose in hand on account of the abund- 

 ance and obtrusiveness of its species, its attractiveness to young 

 naturalists and collectors, and the extent of the variation in structure 

 and habits that it displays. 



The first chapter contains much useful advice on the question of 

 lenses, needles, forceps, beakers, etc., showing that all needful ap- 

 pliances for the investigations illustrated in the following chapters of 

 the book may be obtained by the expenditure of a small sum of 

 money. In the way of lenses, however, there is one object which 

 seems to have escaped Mr Scherren's notice, and to which he will 

 perhaps be glad to have his attention drawn. This is the ordinary 

 watchmaker's lens, which will be found invaluable for dissecting 



