QUATREFAGE’S HISTOIRE NATURELLE. 47 
ness in leaving many genera as “‘incerte sedis,’ rather than 
force them into a position which he did not feel sure naturally 
was theirs. 
We now come to the chief part of the work, the systematic 
description of the families, genera, and species. ‘There are 
many new genera introduced, and new arrangements of spe- 
cies advocated, which we cannot here examine; and, indeed, 
they will be best appreciated by a study of the work itself. 
M. Claparéde has already criticised some points in the arrange- 
ment of genera very fully, which has given rise to a rather 
sharp contest in the ‘ Comptes Rendus’ of the French Academy, 
‘The family of Syllidea appear to be the great cause of dis- 
cussion, which present great difficulties to the naturalist by 
their metamorphoses and alternation of generations, the same 
species appearing under very different phases. Many new 
species are described and figured in the work from the collec- 
tion of the museum; and here we must object to the frequent 
insufficiency of descriptions and figures. In several cases— 
e.g. Polynoé setosissima and Aphrodita talpa—the most cha- 
racteristic parts of the worm are not figured, but merely a 
general view of the animal is given; and, moreover, in a large 
number of cases no figure at all is given of the worm de- 
scribed. This cannot but cause difficulty to other zoologists, 
and is much to be regretted. The figures of species, we 
notice, moreover, are not infrequently over-coloured—e. g. 
Hermione hystrix and Chetopterus Valencinti. With regard 
to the Cheetopterus of our coasts, M. de Quatrefages re-names 
it without any compunction, though it has been described 
and figured most fully in the ‘ Linnean Transactions’ by Dr. 
Baird as Chetopterus insignis. The author was, however, 
most probably, not aware of this, since these descriptions of 
species have been in hand for some years. At the same time, 
there is no evidence in the book of any careful bibliographical 
research, with a view to reducing the confusion of names at 
present existing, or even avoiding its increase. 
The class Gephyrea, which owes its establishment to the 
labours of M. de Quatrefages, is treated of in the last 114 
pages of the second volume, and in proportion to the size of 
the group this part of the work will, perhaps, be more valu- 
able to the naturalist than that on the Annelida. This class 
of Vermes, at present so little known, is discussed in much 
the same manner as the Annelida, through which we have 
just passed, and is illustrated in the same way. 
Before taking leave of this book we wish again to express 
our conviction that it will be found of great value to the 
zoologist and anatomist, since it contains nearly all the 
