J. G. WALLER ON CLIONA CELATA, ETC. 265 



Bowerbank ('* Brit. SiDongiaclge," Vol. i.), and I have also many 

 other examples. These developments therefore of the young Sponge 

 may assist in determining the possibility of such a creature com- 

 mencing life as an excavator. One example is figured in Plate XXE., 

 Fig. 6 (500 diam.). At Fig. 7, same plate, is a group of the gem- 

 mules (?) with buds developing, which are possibly the same, as 

 previously noted, but are here given from the dried state, the 

 others being from a specimen mounted in balsam. In all cases, 

 where these (Fig. 6) occur, the gemmule seems to be exhausted, 

 and its vesicles to have disappeared. 



Thus I have endeavoured to bring the subject from the dominion 

 of conjecture, and to place before you an issue, whence it may be 

 determined. In summing up I state these propositions. If it can 

 be shown, that the Sponge is not always in the burrows, even as a 

 whole or a part, there is an end of the theory of a " boring " Sponge. 

 If the limestone burrows at Babbicombe never exhibit traces of the 

 Sponge, the theory is also at an end, for no one can doubt but, that 

 a similar creature made these. If it can be demonstrated, that the 

 burrows are made by a hard and not a soft instrument, nor by a 

 solvent, the theory is also at an end, and its further prosecution 

 useless. These propositions, I have endeavoured to prove, in the 

 paper before you. 



It is my hope that the subject may now be definitely settled, for, 

 in this friendly warfare, both victor and vanquished are gainers 

 equally in the contest, when the struggle is not for victory but for 

 truth. 



Having through the courtesy of our President, Mr. Charters 

 White, and that of Mr. Charles Stewart, had an opportunity of 

 examining the slides on which each illustrated their respective 

 theory and analogy on this subject, viz., Dentine absorption and the 

 operation of Lactic Acid upon bone, I feel it necessary to give some 

 supplementary remarks. And I cannot but express myself thank- 

 ful to those gentlemen for their kindness in explaining their several 

 views. Especially is this due to Mr. Stewart, who took much pains 

 to explain an operation, with which I was unfamiliar, in that lucid 

 manner for which he is so distinguished. 



Now, at starting, there is a formidable objection to both theories. 

 Here are operations going on within a living creature, part of the 

 incidents of its life, destruction of material, waste, co-existent as it is 



