and other Siliceous Bodies. 15 



sentcd appearances of an exceedingly singular nature. The sub- 

 stance of the sponge in this instance appears to have suffered 

 so much by decomposition as to prevent its being detected in 

 its original fibrous form. It has, in fact, become a confused 

 magma of disintegrated spongeous matter, only to be recog- 

 nised as such by the frequent occurrence of similar decom- 

 posed material in other bodies of the like description. Amid 

 these remains of the sponge there are an innumerable quan- 

 tity of globular vesicles of nearly a uniform size : many of 

 these are simple and transparent, and only to be recognised 

 as organized tissue by the regularity of their size and form, 

 and by having universally dispersed over their outer surfaces 

 minute irregular particles of an opake black matter : but by 

 far the greater number of them are furnished with a globular 

 opake body of about one-third their own diameter, which 

 usually occupies the vesicle, and which causes it, when in this 

 perfect state, and when seen with a linear power of about 150, 

 and represented by PL I. fig* 3, very strongly to resemble the 

 separated ova of the frog when immersed in water. Along 

 with these vesicular bodies, there are numerous small brown 

 fibrous masses which resemble very small keratose sponges : 

 the largest of these are about five or six times the diameter 

 of the vesicles, and they are seen decreasing gradually in size 

 until they may be traced to be identical with the nucleus con- 

 tained within the vesicles, but in a higher stage of develop- 

 ment, as represented at PL I. fig. 4. a, b, c and d. Upon 

 carefully examining the other specimens of this series, I found 

 in several of them similar vesicular bodies of a large size im- 

 bedded amid the fibrous tissue of the sponge. They were 

 more sparingly dispersed through the tissue in the latter 

 cases, but in every other respect they closely resembled those 

 first described. These curious vesicles h~ve evidently ex- 

 isted before the siliceous matter became solidified, as each of 

 them has become a base from which a mass of acicular calce- 

 donic crystals has radiated. 



From the whole of the circumstances attending these 

 interesting remains, their uniformity in size and shape, their 

 gradual development into small masses of sponge-like tissue, 

 and the great similarity that they bear to the ova of nume- 

 rous species of British sponges, described by Dr. Grant in 

 the valuable papers on these subjects published in the e New 

 Edinburgh Philosophical Journal' of 1827, little doubt re- 

 mains on my own mind that they are the fossilized gem- 

 mules of the sponges which have given form to the siliceous 

 masses in which they are imbedded. It is true they differ 

 from the gemmules of the British sponges described by 

 Dr. Grant, as the latter are oviform, while the former are 



