410 Bibliographical Notices. 
The fibre in the dry state is exceedingly rigid and brittle, and 
preserves much of its rigidity even after having been soaked 
many hours in water. The radiation of the fibres from the centre 
of the sponge towards the outer surface is in a series of straight 
lines, and the interstices rarely exceed half a line in length. 
The great excurrent canals are found only on the extreme edge 
of the sponge; they are few in number, and are disposed im a 
single line at unequal distances throughout the whole of the 
circumference of the sponge, the largest not exceeding two lines 
in diameter. 
This sponge is remarkable for its approximation, in the struc- 
ture of its skeleton, to the highest orders of animal organization. 
BIBLIOGRAPHICAL NOTICES. 
A History of the British Freshwater Algae, including descriptions of 
the Desmidex and Diatomacee, with upwards of 100 Plates. By 
A. H. Hassall, F.L.S. 2 vols. 8vo. London, 1845. 
We consider the publication of this work as likely to promote in a 
great degree the study of the freshwater Algee of Britain; a tribe 
which, owing to its great obscurity and the want of good magnified 
figures, has been almost universaJly neglected by our botanists. 
Whilst the Mosses, the Lichens, the Fungi, and even the marine Algze 
have had valuable and elaborate works devoted to their elucidation, 
we are not acquainted with any extensive English work on the fresh- 
water tribes since that of Dillwyn, which, although highly valuable, 
having appeared before the structure of the Algze was much under- 
stood, cannot be considered as supplying the deficiency. The figures 
contained in Mr. Hassall’s work will be found of the utmost value to 
the student of this curious tribe of plants, as they appear in most 
cases to have been carefully drawn and to be faithful representations 
of the species. It is unfortunate that the author has not pointed out 
the cases in which his figures are not the result of his own observa- 
tions, but copied from published plates. ‘The appearance of ‘‘ Hass. 
delt.” at the bottom of all the plates leads us to suppose that they 
are all of them original, but a more careful examination shows that 
not a fewarecopies. We shall notice some of these as we proceed, 
previously however reminding our readers that the parts of the book 
which it falls to our lot to blame are only a small portion of the 
whole. As a whole, there can be no doubt that it is a proof of its 
author being possessed of very considerable abilities ; more especially 
of extensive powers of discrimination, although not of definition. 
We consider these powers as quite distinct and frequently existing 
separately, although both are essential to a writer on descriptive 
natural history. 
In the preface we find it stated that ‘ the characters developed 
in the state of reproduction are relied upon in the framing not merely 
of the families and genera, but also in the definition of species” in the 
