544- Geological Society : — Mr. Bowerbank 



specimens the fibres were not disposed in the same manner as in the 

 sponge of commerce, but in a series of thin plates, resembling very 

 much the macerated woody fibres of the leaves of some endogenous 

 plants. Only one recent species, from Australia, is known to Mr. 

 Bowerbank to exhibit this structure. 



No spicula are mentioned by the author in either the agates or jas- 

 pers, and but one instance of the occurrence of foraminifera. The whole 

 of the sponges contained in the green jaspers, Mr. Bowerbank refers 

 to that division of the keratose which he has called Fistularia. 



2. Gemmules. — A specimenof Indian green jasper, which had under- 

 gone so great decomposition as to prevent the original fibrous structure 

 from being detected, presented innumerable globular vesicles of nearly 

 uniform size. Many of them were simple and transparent, and could 

 be recognised as organic only by the regularity of their size and form, 

 and by having universally dispersed over their outer surface minute 

 irregular black particles ; but by far the greater number of them 

 had in their interior a globular opake body, about one-third their 

 own diameter. Associated with these vesicles were numerous small 

 fibrous masses resembling minute keratose sponges, the largest of 

 which were five or six times the diameter of the vesicles ; but the 

 smallest were identical in nature with the nucleus, though in a higher 

 state of development. In other specimens from the same mass of 

 jasper, larger vesicles were found more sparingly imbedded amidst 

 the fibrous tissue of the sponge. From these characters and their 

 resemblance to those of the ova of some recent sponges, Mr. Bower- 

 bank has little doubt that the vesicles are the fossilized gemmules of 

 the sponges which gave the form to the siliceous masses in which they 

 are imbedded. An agate supposed to have come from Oberstein, 

 presented characters which, Mr. Bowerbank is of opinion, indicated 

 gemmules in an immature state, or in different stages of development, 

 fixed to the fibre of the sponge ; and in another specimen, believed to 

 have been received from the same locality, gemmules in different 

 conditions were sparingly scattered amid the tissue. 



If this idea of the development of the gemmules in situ be correct, 

 it will account, the author thinks, for the frequent occurrence of small 

 detached patches of minute sponge-fibre in well- developed and large- 

 sized tissue. Several other specimens, considered by Mr. Bower- 

 bank to contain gemmules in different stages of development or de- 

 composition, are described in the paper, particularly an agate from 

 Antigua in the possession of Mr. R. Brown ; and one from Ober- 

 stein, which contained vast numbers of small, pellucid, yellow glo- 

 bules, bearing a strong resemblance to the minute granules which 

 occur in the gelatinous or fleshy sheath surrounding the fibres of the 

 sponge of commerce, and which are probably incipient germs. In 

 accounting for the preservation of the gemmules in a fossil state, 

 Mr. Bowerbank refers to the covering of the ova of birds, fishes and 

 reptiles ; and he says, it is natural to expect that the gemmules of 

 the sponge should be similarly protected, and therefore preserved 

 after the decay of the sponge from which they derived their origin. 



3. Vascular structure. — In a species of recent Turkey sponge, and 



