with descriptions of some new genera. 401 
racters than those which have hitherto designated the numerous 
and extraordinary species of these singular animals. 
Lamouroux, in his ‘Histoire des Polipiers Coralligénes Flex- 
ibles,’ has described 163 species of Spongiade under the common 
generic designation of Spongia, basing his descriptive characters 
principally upon form and colour. It is almost unnecessary for 
me to say, that there is scarcely one of these descriptions which 
can be applied with any degree of certainty when we attempt to 
identify specimens of recent sponges. 
Dr. Fleming, in his ‘ History of British Animals,’ taking ad. 
vantage of the valuable labours of Dr. Grant, has divided the 
Spongiade into a series of genera founded, to a certain extent, 
upon their anatomical structure, and takmg the common officmal 
sponges as his type, has described the characters of the genus 
Spongia mm the following words :— Porous, the cartilagimous 
skeleton simple or destitute of earthy spicula.” 
Dr. Johnston, mm his admirable ‘History of the British Sponges 
and Lithophytes, has added considerably to these characters, 
and has thus designated the genus :—“ Body multiform, very 
porous, elastic, composed of a network of corneous fibres inos- 
culating in every direction, and traversed by tortuous canals 
opening on the surface by ‘wider orifices ; the fibres often con- 
tain imbedded spicula: gelatine fugacious: marine.” This se-~ 
ries of characters would perhaps be sufficiently definite if we 
had to consider the British species of the Spon giade only, but 
when we launch into the wide field of exotic species, it ceases to 
be sufficiently descriptive and definite to enable us to hope to 
arrange these extraordinary and protean forms of animal life in 
such a manner as to allow the student to recognise a species, or 
to refer it to its proper genus with anything approaching to the 
same degree of certainty that we find the constant practice in 
the science of botany. 
It is true that in the latter science we have a much more ex- 
tended series of determinate structural characters than we can 
ever hope to find among the Spongiade, and that among plants 
these characters are of such a nature as to be readily available 
either to the unassisted vision or by the aid of a low microsco- 
pical power; while among the Spongiade, from the minuteness 
of many of the most essential organs, we can scarcely hope to 
make any great degree of progress in the knowledge and deve- 
lopment of such characters without the aid of the best modern 
microscopical powers ; but with such assistance there is little doubt 
in my own mind, from the great and permanent varieties of the 
structures of the skeleton especially, that we shall be enabled to 
establish such a series of well-defined new genera, and to subdi- 
vide and arrange those already established, as very materially to 
as 
