NOTICES OF NEW BOOKS. 225 
The manipulation of the microscope and its accessories constitutes 
the larger portion of the book, and in that an exposition is given of the 
meaning of the term “ Critical Microscopy ” as laid down by Mr. Nelson. 
One of the main adjustments in accurate work with the microscope 
is the proper determination of tube length under any given conditions. 
This is very fully dealt with, and the various known methods to correct 
for different thicknesses of cover-glass, or different types of objects, are 
well set out. Dark-ground illumination is also fully described, beginning 
with the method of placing a stop in an ordinary sub -stage condenser. 
Little consideration is given to the modern type of concentric dark- 
ground illuminator ; in fact it is stated that the method of using a stop 
in a good sub-stage illuminator is superior in some respects to results 
obtained by using a concentric condenser, a statement that some, at 
least, may be inclined to controvert. 
A description is given of a method of observing stained preparation 
by means of dark-ground illumination, a method that the author 
apparently claims as his own. 
The care of the eyes is well dealt with, and it can be commended as 
one of the most useful sections, short as it is, in this book. 
A brief account of the author’s method of taking photo-micrographs, 
particularly that in which he takes a series on such a small size as a 
quarter-plate, is described. It would not be difficult to criticize many 
of the statements made in the book ; at the same time, the obvious 
and expressed intention of the writer is to help those who have occasion 
to use the micrograph. There is no doubt that if the methods described 
are followed, a much higher order of work would be accomplished than 
if reliance is placed on the very haphazard methods at present practised 
in most laboratories. From this point of view, therefore, the book 
thoroughly justifies itself. It suffers somewhat from the frequent 
abstracts from letters and from other published papers, but in general it 
may be commended to the student or to the medical research worker as 
a useful guide. J.E. B. 
Etudes sur les Infusoires d’eau Douce. By Dr. E. Penard. 1922. 
331 pp. Published by Georg and Cie, Geneva. 
A Handbook of the British Lichens. By Annie Lorrain Smith, F.L.S. 
1921. 159 pp. Published by the British Museum (Natural 
History), Cromwell Road, S.W.7. 
Catalogue of the Fossil Bryozoa (Polyzoa), in the Department of 
Geology, British Museum. Yol. III. The Cribrimorphs, 
Part 1. By W. D. Lang, Sc.D., F.G.S. 1921. 269 pp. and 
8 pis. Published by the British Museum (Natural History), 
Cromwell Road, S.W.7. 
Practical Plant Biology. By Henry H. Dixon, Sc.D., F.R.S. 1922. 
xii + 291 pp. Published by Longmans, Green and Co., 
39 Paternoster Row. E.C.4. Price 6s. 
The Microscope. How to choose it and use it. By S. E. Dowdy, 
M.P.S., F.R.M.S. 1921. 53 pp. and 1 pi. Published by 
A. E. Soman and Co., Norwich. Price 5s. 6d. 
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