and other Siliceous Bodies. 13 



were seen in a fine state of preservation in several parts of the 

 specimen, and were very similar to the tubes described in the 

 former instances, both in their dimensions and mode of ar- 

 rangement. The substance of the tube is of an opake white, 

 while the interior is filled with the bright red pigment before 

 described. In this case also, as in the former ones, the fibrous 

 casts of the interior of the tubes occupy a great part of the 

 space within the agate, with an occasional intermixture of 

 what is evidently a disorganized or semi-decomposed mass of 

 the horny tubes. 



The fifth specimen is also a keratose sponge, the tubes of 

 which are very slight, and the points at which they anastomose 

 are more distant from each other than in the former cases that 

 have been described. The sides of the tubes are composed of 

 the red pigment which usually does not extend beyond the 

 boundary of the horny substance ; but in some parts of this 

 specimen it not only thus supplies the place of the horny 

 matter, but a quantity of it has also been deposited around 

 the tubes, greatly increasing in appearance their natural dia- 

 meters, and indicating the strong elective attraction that has 

 existed between it and the animal substance of the sponge : 

 and this is rendered the more evident by this red pigment 

 not being perceived in any other part of the siliceous mass 

 beside that occupied by the sponge-tubes, either in a state of 

 perfect preservation or of semi-decomposition ; the whole of 

 the spaces between these portions of animal matter being oc- 

 cupied with unstained and beautifully pellucid silex. 



The fibres of all the specimens hitherto described are truly 

 tubular, and in this respect strongly resemble in their struc- 

 ture the recent Spongia fistularis. In their arrangement of 

 their fibres and their mode of anastomosing they appear very 

 closely to resemble the sponges of commerce and many of the 

 Australian keratose species. 



Such are the prevailing characters of the sponge tissues to 

 be found in the German and Sicilian moss agates. I have 

 examined nearly 200 of these interesting bodies, and in the 

 whole of them I have been enabled to discern spongeous tis- 

 sue either in precisely similar states to those tissues that I 

 have described at length, or in some modification of them ; and 

 it is only in very few cases indeed that a careful and patient 

 examination of a specimen, however indistinct it might at first 

 have appeared, has not been rewarded by finding in some part 

 of it, not only the casts of the interior of the fibre, but por- 

 tions of the fibre itself in a sufficiently perfect state to leave 

 no doubt remaining upon my mind of the truth of its animal 

 nature. 



The green jaspers of India are also fruitful sources of 



