Geological Society. 463 



obscured by irregular patches of a substance which the author con- 

 ceives may have been glutinous animal matter. In another specimen 

 of green jasper the spiral course of this curious tissue was much less 

 obscure, and when examined with a power of 800 linear its tubular 

 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 opake or semi-pellucid spheres, and in different por- 

 tions of the agate were considerable numbers of larger, opake, 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 the vessels 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 crystallizing process of the as- 

 sociated mineral matter. 



