16 Mr. J. S. Bowerbank on Moss Agates 



spberical ; but this variation is of no moment, as we shall 

 hereafter find that in other cases the fossilized gemmules are 

 oviform like those of various species of British Halichondria ; 

 while in the recent sponge from Australia, which I have de- 

 scribed in the c Annals and Magazine of Natural History 5 for 

 April 1841, the gemmules are precisely of the same form as 

 those occurring in the green jasper described above. It is a 

 singular circumstance that the mode of propagation of the 

 sponge should be thus capable of demonstration from the 

 fossil specimens, but the case which I have just described is 

 by no means rare in its occurrence. In an agate which is said 

 to have come from Oberstein, the gemmules are seen appa- 

 rently in an immature state attached in considerable numbers 

 to the fibre of the sponge ; and in the two portions of this 

 specimen, which is represented by figures 5 and 6, and which 

 are drawn to the same scale, it is apparent from the variation 

 in their size that they are in different stages of development. 

 In another agate in my possession, which I believe to be from 

 Oberstein, and in which the spongeous fibre is in a most per- 

 fect and beautiful state of preservation, the gemmules are 

 seen sparingly scattered amid the tissue. Some of these have 

 the usual form of round compact globules pellucid for a small 

 space inwards from the circumferential line, but dense and 

 opake thence to the centre ; while others appear to have been 

 partially developed without having been ejected from the pa- 

 rent body, as they present the appearance of well-defined glo- 

 bular sponges, whose diameters are three or four times that of 

 the undeveloped gemmules, as represented by PI. I. fig. 7. 

 If this idea of their development in situ be correct, it will per- 

 haps account for the frequent occurrence of the small detached 

 patches of minute sponge-fibre that are so often found im- 

 bedded amid the w 7 ell-developed and large-sized tissue of the 

 sponge which is especially characteristic of the various masses 

 alluded to. 



In a fourth agate, which probably came from the same 

 place as the last, the fibre of the sponge has suffered so much 

 by decomposition as to leave but few pieces of it in so fine 

 a state of preservation as that represented by PL II. fig. 1. 

 There are none of the gemmules in this specimen which are 

 adhering to the fibres ; but although not seen in actual attach- 

 ment, they are dispersed in great numbers throughout the 

 whole of the mass, and are seen in various stages of develop- 

 ment, as represented in PL II. fig. 2. Among them are inter- 

 spersed vast numbers of small pellucid yellow globules, which 

 bear a striking resemblance to similar minute granular bodies 

 that are observed in great abundance imbedded in the gelati- 

 nous or fleshy sheath that is found surrounding the fibres of 



