1897] SOME NEW BOOKS 129 
in the slightly increased size, but in some extension of the parts 
dealing with the Sporozoa and the Vertebrata. 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 Ray Lankester in Natural Science for August 1896. 
Dr Hertwig has therefore done well to give them greater prominence. 
Among the Vertebrata, while Dr Hertwig has endeavoured to ac- 
commodate Boulenger’s classification of the Reptilia 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 
Neocrinoidea. 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 niust ultimately depend. 
ARTHROPODS FOR BEGINNERS 
TuroucH A Pocket-LENs. By Henry Scherren, F.Z.S. 8vo. Pp. 192. 
London: The Religious Tract Society. 1897. Price, 2s. 6d. 
Mr 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, ete., 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 
