REVIEWS. 
159 
acquired a special interest in consequence of the direction taken of late years 
by biological research. Under each species, besides the descriptions and 
remarks on the characters, we find a full synonymy, a statement of the 
mode of occurrence of the species, a list of the British localities where it 
occurs, a full indication of its geographical distribution, and in the case of 
those species which occur fossil, of its range in geological time. In fact, 
Mr. Hincks seems to have aimed successfully at making the systematic 
portion of his work as complete as possible. The student who makes use 
of this book for the systematic investigation of our Marine Polyzoa will 
doubtless find his work comparatively easy, but the subject in itself is by 
no means an easy one; the researches necessary for the production of the 
present volume must have been long-continued and environed with many 
special difficulties, and we may heartily congratulate Mr. Hincks on the 
results of his long and arduous labours. 
In his Introduction, which extends to over 1 40 pages, and deals with the 
generalities of the class, its structural characters in general, the production of 
special parts, such as the curious avicularia, or ‘ bird’s heads,’ and the vibra- 
cula, and the physiology of the animals, including their reproduction and em- 
bryology, we find evidences of the same conscientious care on the part of the 
author, who cites and discusses the statements contained in all the most 
recent publications on these points, selecting and supplementing them by the 
light of his own researches. This portion of the work is as admirably done 
in its way as the systematic part, and will serve, not only as a necessary 
guide to the proper understanding of the latter, but also as a good summary 
of the anatomy and physiology of the class. 
The illustrations consist of 83 plates, forming the second volume of 
the book, and of numerous woodcuts scattered through the text of the 
first volume. The Introduction is almost entirely illustrated with wood- 
engravings, although here and there a plate is referred to, but for the 
elucidation of the development of the Bryozoa the author has given a plate 
of beautiful figures, copied from the magnificent work of Dr. J. Barrois, of 
Lille, on the embryology of these animals. The rest of the plates, illustrative 
of the systematic section of the book, have been beautifully executed in 
lithography by Mr. Hollick, and with the aid of these and the author’s clear 
and precise descriptions, the determination of the species of British Marine 
Polyzoa ought certainly henceforward to present little difficulty. All the 
woodcuts, which are distributed more or less abundantly throughout the 
volume of text, are most delicate and beautiful specimens of the art. 
THE CRAYFISH.* 
T HE Crayfish is one of the type animals described by Professor Huxley 
and Mr. Martin in their Elementary Biology, and it is also, we believe, 
one of those the structure of which is always investigated by the former 
* The Crayfish , an Introduction to the Study of Zoology. By T. II. 
Huxley, F.R.S. Small 8vo. C. Kegan, Paul & Co. (International Scientific 
Series), London, 1880. 
