788 THE AMERICAN NATURALIST.  [Vou. XXXII. 
present the subject within a single volume, and in a manner which 
is both thorough and attractive. And by this same showing it is 
evident that the book which will be used by large numbers of 
English students has not yet appeared. 
The distinctive feature of Parker and Haswell’s work is the way 
in which the study of “types,” or “ examples ” as our authors prefer 
to call them, is united with the more usual methods of descriptive 
zoology. Believing that definitions and general descriptions can be 
useful only after the student has obtained some first-hand knowledge 
of the things described, our authors begin the study of every group 
with a description of some single example of that group, which should 
be thoroughly studied in the laboratory before undertaking the study 
of the group as a whole. ‘The value of this departure, no one who is 
a thorough believer in the laboratory method can for a moment 
doubt ; that it has its dangers none can deny. If the study stops 
with a few examples, it is narrow and misleading; if it covers the 
whole field by means of a text-book and a few museum specimens, it 
is superficial, A proper combination of the two methods, which 
would secure the advantages and avoid the disadvantages of both, 
would be ideally perfect. 
Such a combination our authors have attempted, and, as it seems 
to us, with signal success. ‘Every group which cannot be readily 
and intelligibly described in terms of another group” is represented 
by an example. The descriptions of these examples are concise and 
yet comprehensive, and this part of the work might well be used as 
a laboratory guide were it not for the fact that the authors have been 
so cosmopolitan in their choice of examples, some of which are 
peculiar to Australia, others to New Zealand, others to Great Britain, 
and still others to the Mediterranean. In most cases, however, © 
alternative forms are suggested which might serve in the place of 
the example described. 
Following the description of the examples there is given the classi- 
fication of the group which it represents, then a detailed description 
of its various subdivisions, and finally a general discussion of the 
organization, embryology, ethology (cecology), distribution, and affini- 
ties of the group as a whole. 
In accordance with the plan of presenting specific facts before the 
general ones, the discussion of distribution, the philosophy of zoology, 
and the history of zoology, with references to the general literature, 
is put at the end of the work. However, in order to render the body 
of the work intelligible to elementary students there is at the begin- 
