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This structure is common to these filaments and to all the 
silicious spicules of other sponges. 
The elegant lightness of the flower baskets, one would think, 
must render them very liable to accident, but the strength and 
rigidity of their structure offer much more resistance than one 
might expect, and that this is the case is proved by the very few 
cases of injury that are to be found in the specimens that have 
been submitted to my examination. The hooks on the free fila- 
ments that form the fringe round the base of the tube and 
which diverge in every direction must be a great protection, as 
they would catch hold of and tear any sea animal that might 
attempt to approach it. 
The thin elevated ridges which more or less completely and 
regularly encircle the outer surface of the tube, add very 
considerably to its general strength, and it is to be observed 
that the fringe round the apex of the tube can only be regarded 
as one of these transverse ribs that is more regular than the 
rest, and placed at the edge of the aperture of the tubular body 
to give strength and security to the vase. 
Indeed, the more we study the structure, the more one is 
struck with the lightness, beauty, and admirable manner in 
which it is formed for the purpose of resisting injury. 
When the filaments are chemically examined, they are found 
to consist of nearly pure silica, mixed with a quantity of animal 
matter that has been called kerasote in other sponges. If they 
are placed in the flame of a spirit lamp, they become black,, 
from the charring of the animal matter, and then split up into 
numerous very thin laminae, and if submitted to the action of 
the blow-pipe, or charcoal, they form a globule of glass. The 
filament is solid and hard. If the long fracture is examined 
with a magnifying glass, it will be found to be formed of an 
immense number of very thin concentric coats, placed one over 
the . other round a centre ; but the coats are best seen when the 
filaments are placed over the flame of a spirit lamp, when the 
filament splits and the coat of animal matter being burnt, the 
coats or layers of siliceous matter separate from each other, and 
are easier seen. . 
All the perfect specimens that I have examined, have a base 
consisting of a thick mass of filaments, which enclose a quantity 
of earth and fragments of shells, showing that the sponge grows 
on the mud of the sea shore. Mr. Cuming’s specimen shows 
this structure in the state in which it is generally brought to this 
country, see Linn . Trans, xiii. t. 13, f. 1 & 3. Professor Owen- 
calls this root “the apical extremity,” and speaks of it as “the 
small end where they (the longitudinal fibres) begin to resolve 
themselves; into ;their constituent filaments.” 
In the description of Dr. Farre’s specimen, Professor Owen 
