435 
nature was evident. The same tissue also lined the cavity of almost 
every fibre of the sponge which was stated to exhibit a structure com- 
posed of foliaceous plates, like the skeletons of the leaves of some 
endogenous plants. In an agate, probably from Oberstein, Mr. 
Bowerbank says, he detected other evidences of tissue of an exceed- 
ingly remarkable character. The fibre, which was very large, had 
been apparently surrounded. by a villose coat, and wherever, by po- 
lishing, a longitudinal section had been exposed, one or two minute 
vessels of uniform diameter and simple structure were visible in the 
centre of the fibre, and ranging in the direction of its axis. At irre- 
gular distances within these vessels the author discovered pellucid 
round globules, the diameter of which varied from the 1000th to the 
2380th of an inch, the diameter of the vessels ranging from the 
1000th to the 2000th of an inch. In other parts of the interior of 
the fibre were opaque or semi-pellucid spheres, and in different por- 
tions of the agate were considerable numbers of larger, opaque, round 
bodies, the whole of which Mr. Bowerbank considers to be gemmules 
in various states of development ; and he thinks it is extremely pro- 
bable that thevessels containing the globules were true ovarian ducts. 
In support of this inference Mr. Bowerbank describes another agate, 
in which there were no appearances of well-defined anastomosing 
fibres, but which exhibited numerous long and simple thread-like 
fibres apparently much decomposed, as their substance consisted 
sometimes of a congeries of minute separate particles, and sometimes 
of straight or curved lines composed of minute black bodies. In 
other cases these strings of incipient gemmules were contained 
within the boundaries of the tubes, and then presented rarely more 
than a row of single gemmules; but occasionally the diameter of the 
vessels appeared to have been much enlarged, and the gemmules 
were indiscriminately dispersed within its cavity. In some instances 
also they exceeded in diameter the vessel or its remains, as if they 
had outgrown and burst their natural boundary, or the walls of the 
latter had contracted. From the close resemblance in the structure 
and contents of these vessels to those contained in the large sponge- 
fibre first described, Mr. Bowerbank has little doubt, whatever may 
have been their original nature, that they are the same kind of tissue, 
under somewhat different conditions. 
In all the agates and jaspers which have been microscopically in- 
vestigated by the author, the spaces not occupied by remains of 
spongeous texture were filled with silex or chalcedony arranged in 
bands which conformed more or less to the outline of the enclosed 
fossil. Where, however, the matrix consisted of radiating crystals, 
the decayed animal remains frequently appeared to have been impelled 
forward, in the same manner as the decomposed cellular portions of 
fossil wood have often yielded to the erystallizing process of the as- 
sociated mineral matter. 
Egyptian jaspers, Mocha stones, &c.—The author has examined 
also numerous specimens of polished Egyptian jaspers, which, when 
viewed as opaque objects, by direct light and with a power of 150 
linear, were found to consist of finely comminuted light buff or brown 
irregular granules, cemented by semi-transparent silex, very much 
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