150 
CLASS III.— ORDER I. 
able ; in the thickness of the fibres, for instance, some 
of them resemble the Antipathes, having their branches 
anastomosised, whilst others are composed of fibres 
as fine as the threads of silk, and wove as close as 
down, or the hair of beaver when formed into hats ; 
every intermediate gradation between these two ex- 
tremes is to be met with. 
In the texture of the Spongias it is also observable 
that they have their holes of different sizes and depths, 
sometimes regularly and sometimes irregularly dis- 
posed : of the use for which these holes (which hence- 
forth we shall denominate oscules ) are designed, we as 
yet remain ignorant ; but observation leads us to con- 
clude that they answer the purpose of introducing 
water into the central parts of the Polypidom ; so that 
if there are any polypi internally, they may be sup- 
plied with the necessary aliment. There are however 
many Spongias destitute of these oscules ; the absence 
or presence of which, together with their form and si- 
tuation, may assist in furnishing us with criteria for 
defining the several species : the same may be said of 
the variety in their texture. 
I can say nothing decisive as to their colours ; they 
appear varied, but fugitive ; those authors who have 
been enabled to observe them in a living state, men- 
tion the colours as being numerous and bright. The 
few I have seen on the coasts of Calvados, when 
first taken from the sea, exhibited a beautiful red, or a 
bright citron ; those dried, in collections, present us 
with every hue from a dirty white to a deep black, 
passing through fawn-colour and every intermediate 
shade. 
Their height varies from a millemetre to a complete 
