J. G. WALLER ON CLIOXA CELATA, ETC. 253 



Their views are always changing, and never agree one with another. 

 This is inevitable, when the mind convinces itself first, and after- 

 wards seeks for proof for its conviction. When such is the case, to 

 begin by evidence is distasteful, for it is apt to disturb the pre- 

 conception and the bond of faith. So it is, that they refuse to look 

 at opposing evidence, but cling to whatever aids their own views, 

 however remote it maybe. It is hardly possible to find any subject 

 in which the opinions have been more varied, and least consistent 

 one with another. Not that any want of good faith exists ; all may 

 be credited by desiring a true solution ; but a large number of those 

 who mention the facts of Cliona burrows, and ascribe them to the 

 work of a Sponge, have never studied the question at all, but taken 

 upon trust the views of others. 



We want evidence — which way it leads is unimportant, so that it 

 be not to follow an ignis fatuus. Bring facts before us, and on those 

 build. The only facts which appear to me to take the form of evi- 

 dence are those given by Dr. Bowerbank, and, strangely enough, 

 never alluded to, though every one should see how important is the 

 bearing upon this question. He says. Vol. ii., p. 218, " Brit. 

 Spongiadse," " Some naturalists have promulgated the idea that 

 this species of Sponge has the power of excavating the canals and 

 other spaces which it usually occupies. My own intimate knowledge 

 of the species has led me to a contrary conclusion. When located 

 in oyster or other shells, it usually fills entirely the cavities between 

 the two surfaces, but when the canals excavated in the limestone 

 extend to the depth of two or more inches, it frequently occurs that 

 the Sponge terminates at the depth of less than an inch, and the 

 remaining part of the canal is quite empty and clean, without the 

 slightest indication of ever having been occupied by Sponge.* And 

 in one of these perforated stones from Tenby, which I broke through 

 its centre, although it abounded with the sinuous canals, none of 

 them presented the slightest traces of having ever contained Sponge ; 

 and occasionally oyster shells full of perforations may be found in 

 the same condition — one such I have in my possession. These facts 

 militate strongly against the idea that the excavations are produced 

 by the Sponge." Again — " In an oyster shell from which I have 

 thin sections, the perforations in its substance consist of nearly 

 straight tubes, of about the same diameter throughout, and each 



* Precisely the same facts occur in the burrows in the limestone at Babbi- 

 combe. 



