264 J. G. WALLER ON CLIOXA CELATA, ETC. 



My argument is tlms complete. I rest upon it, well knowing 

 that, as yet, it has never been so taken up. The analogy which 

 exists with the borings of the larvae of the Scolytus is shown 

 throughout. The orifices are identical (PI. XX., Figs. 1, 2), so are 

 the burrows, as seen in sections (Figs. 4, 6), and again in the 

 minute workings (as in Figs. 7, 8, 9). 



As I have been alluding to Annelids, I may observe that 

 several forms, apparently of such, I have recently observed upon 

 one of my mounted portions of shell. The diameter of these is 

 the 2,000th of an inch, which I find to be the same as the smallest 

 excavated channels. Assuming therefore an Annelid to be the 

 factor, these forms, if of such, present no difficulty on the score of 

 dimensions. Moreover, we may fitly compare the size of the larva 

 of Scolytus as quoted, which has a diameter of about the 500th of an 

 inch, and its sub-circular excavations about the 250th in diameter ; 

 full double that seen in those of shell or limestone, and thence infer 

 a still more minute creature to be the factor, in the view that an 

 Annelid makes the burrow. 



In my previous paper on this subject ('' Q.C.J.," Vol. ii., 1871) 

 I believe, I was the first to figure the so-called gemmule of this 

 Sponge, as Dr. Bowerbank makes no mention of it. Besides this I 

 also figured other forms, apparently connected with reproduction. In 

 examining with higher power amongst these gemmules, I discovered 

 above them groups of spicular bundles, which mark the early 

 growth of siliceous Sponges. Many similar ones are given by Dr. 



features, and is so far extremely interesting; but it is anything but an 

 example which gives evidence in favour of the Sponge being the excavator. 

 The most patent fact exhibited is the entire absence of Sponge from minute 

 channels, where, had it ever been, it must, at least have left some spicules. 

 In PI. XXL, Fig. 5, I give a drawing of one of the long channels of the 

 smallest kind, and have brought from another part, where remains of Sponge 

 are seen, a group of spicules to contrast the size together. The channel has 

 a diameter of 2,000th of an inch, the section of the arc of the spicules' curve is 

 the same, so had they ever been developed within this channel, no or.linary 

 means could remove them. As the same fact is seen throughout, it has a 

 great significance. But it exhibits a still more important piece of evidence, 

 for the large excavated channel, out of which the small tubular channels 

 proceed, itself has no remains of Sponge, or even a spicule, although the 

 greater part has escaped being uncovered by grinding the section. In fact, 

 the spicules are very fev/ in any part of the section, and are the sole repre- 

 sentatives of the Sponge : where they do appear is in the most open parts, 

 and where most exposed to washing away ; they are entirely wanting in all the 

 ramifications. The form of the spicules are shown in the drawing, and are 

 all of the same kind — accrate — totally unlike those of CUona celata, i\.x\d 

 probably belonging to an entirely different species. The evidence of excava- 

 tion differs iu no way from the familiar lorms. 



