on Moss Agates and other Siliceous Bodies. 545 



in some others from Australia*, Mr. Bowerbank detected in the horny 

 sheath which invested the solid fibre, minute anastomosing vessels ; 

 but he has not observed a similar vascular covering on the external sur- 

 face of the two specimens of Spongia fistularis which he has examined. 

 The co-existence, however, of this sheath with a tubular fibre, he 

 states, he has discovered in specimens of Indian green jasper. On 

 examining with a power of 60 linear a thin polished slice, he 

 found that some well-preserved tubes, of greater size than the rest, 

 had, on their external surface, a coating of a darker colour than the 

 other parts of the fibre, and were evidently analogous to the vascular 

 sheath of the keratose sponges of commerce. On employing a power 

 of 500 linear, the presence of a reticulated vascular structure was 

 exhibited as distinctly as in the recent sponge, particularly where a 

 portion of the originally horny or fleshy part of the sheath had un- 

 dergone a slight degree of decomposition. This structure Mr. 

 Bowerbank has also detected in two fragments of flint-pebbles. 



The characters exhibited by this external coating are not the 

 only evidences of vascular structure which the author found during 

 his examination of the organic remains inclosed in moss agates and 

 Indian green jaspers, for he discovered in the centre of the tube 

 which exhibited the sheath, a dark thread penetrating the cavity for 

 a considerable distance, and when examined with a power of 500 

 linear, it assumed the appearance of a spiral tubular thread, frequently 

 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 



* Microscopic Journal, vol. i. No. 1, p. 10. 



