with descriptions of new Species. °° 829 
tial in determining that of the chambers it inhabits. The test 
then can be easily applied; and were the secretion of an acid nature, 
there could be little difficulty, one would think, in detecting it ; 
particularly as Cliona appears to work perpetually—at least so 
long as it continues to grow. I have completely failed, however, 
in detecting an acid. 
I took C. gorgonioides alive fresh from the sea, and breaking 
up the stone in which it was lodged removed the creature by 
piecemeal, and placing each portion on litmus-paper pressed. 
the fluids out of it between plates of glass; but not the slightest 
alteration occurred. I continued tryimg piece after piece for 
several hours, and contrived to remove portions of the animal 
with the surface entire ; but all was in vain,—no indications of 
an acid solvent could be obtained. 
In a specimen of the Strombus gigas in the Newcastle Museum 
penetrated by a species of Cliona, the papille have passed through 
the strong horny epidermis, drilling it with great precision ; the 
holes are quite circular, and of the same size as those in the shell. 
This could hardly be achieved by an acid solvent. 
When a portion of the fresh C. celata is carefully removed 
- from the chambers and placed in a little acetic acid, a distinct 
effervescence takes place as if calcareous matter mingled with the 
tissue. The same result occurs when a little of the dried sub- 
stance adhering to the sides of the excavations of 7hoosa is re- 
moved and treated with the same acid. From these facts we 
may conclude, perhaps, that no acid solvent had been employed ; 
while it is likely, were the excavations effected by mechanicai 
means, that the surface and tissue would be charged with cal- 
careous particles. Indeed such particles may generally be ob- 
served strewed along the branched channels in the shell of the 
oyster when inhabited by C. celata. I have also seen similar 
ealcareous particles adhering to the animal of C. gorgonioides 
when removed from its chambers in limestone. These particles 
are large enough to be detected with a pocket lens, and 
will be more fully described further on. At present they are 
alluded to, as they afford a pretty strong proof of mechanical 
agency. 
The excavations would then appear to be effected by mechanical, 
and not by chemical means. What is the instrument, and how 
is it applied ? 
With respect to Cliona, it is well known to possess siliceous 
spicula; some of the points of which penetrate the surface of 
the animal, and might be supposed capable of reducing the cal- 
earcous bodies in which these creatures bury themselves. But 
other and apparently more efficient agents have been discovered, 
eovering the surface of the sponge. 
