i88o.] 
Analyses of Boohs, 
337 
A History of the British Marine Polyzoa. By Thomas Hincks, 
B.A., F.R.S. London : John Van Voorst. 
We have here a most elaborate and admirable monograph, drawn 
up by an author whose prolonged and successful researches in 
this department of biology specially qualify him for the task. In 
the Introduction Mr. Hincks treats of the structure of the 
Polyzoa, their embryology, distribution, and classification, and 
discusses the meaning of some parts whose function is obscure. 
Among these is the so-called “brown body” which has given 
scope to much controversy. Setting aside less probable views, 
it has been regarded as a mere lifeless residuum of the dead 
polypide, or as a special structure having a reproductive function. 
In common with Prof. F. A. Smitt, the author has held the 
former view, and has supported it by means of original observa- 
tions. He now, however, considers that the evidence tallies 
better with the “residuary” theory of Joliet and Nitschke. 
Still no very satisfactory explanation seems to have been given 
of the observations of Prof. Smitt and of the author’s own. 
Another subject of dispute is the funaion of the “ avicula- 
rium,” which in some genera — Bugula and Bicellaria — appears 
as an “articulated assemblage attached to the zooecium with a 
formidable hooked beak and a mandible worked by powerful 
muscles, perpetually snapping its jaws with monotonous energy, 
and swaying to and fro with vigorous swing on its jointed base 
— grotesque both in form and movement.” Mr. Hincks, who 
traces the development of this “ bird’s head ” through a long 
series of gradationa.1 forms, considers that its funClion is de- 
fensive rather than subservient to the capture of nourishment. 
Further observations will here be useful. The passage of the 
ova into the ooecium or ovicell has not been witnessed, nor is 
the author aware of any observations showing how it is effected. 
Mr. Hincks seems to believe not merely that the ooecium aCts as 
a marsupium, but that, under circumstances not explained, ova 
are produced within it. 
On the distribution of the Polyzoa the author remarks that 
pending the publication of the results of the Challenger Expedi- 
tion generalisation would be premature. 
The remainder of the work is devoted to a systematic account 
of the Polyzoa, and will prove a most useful guide to the student 
of marine zoology. The work is not merely illustrated with 
woodcuts introduced in the text, but with eighty-three plates, 
forming a companion volume. The bibliography of the subject 
is given in an Appendix. 
Biologists will feel greatly indebted to Mr. Hincks for thus 
placing before them the observations of a lifetime, and will not 
be slow in acknowledging the merit of the publisher, already so 
honourably known in the department of Natural History. 
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