of the Flints of the Upper Chalk. 293 



akin to such definition as would be found in Johnson's Dictionary; 

 at any rate, not exactly the opposite. Thus, when I named 

 "peculiar affinity'^ (p. 3), I meant ^'^ belonging to one to the ex- 

 clusion of others" [Johnson's Dictionary]. When I used the 

 word " envelope/-' I meant inwrapping and surrounding, and not 

 mere attachment to, or growing upon, as Mr. Bowerbank under- 

 stands it (see p. 255). 



I nowhere deny the predisposition of sponges for silex; on 

 the contrary, I expressly allude to it several times (see p. 10, &c.). 

 I deny the "peculiar'' and "special" affinity only, which the 

 sponge theory requires. The very next clause to that quoted is, 

 " Such facts disprove the alleged special affinity." Mr. Bower- 

 bank himself admits (p. 259) that I do not deny what on p. 251 

 he says that I do deny ; thus admitting that the whole discussion 

 raised on the latter page is immaterial and unfounded. 



Again, it is said that 1 do " not offer the slightest explanation 

 of the cause of the suspension in all parts alike of the masses of 

 siliceous spiculse, the remains of polythalamous shells, small 

 branched corals, and numerous other animal bodies ; nor account 

 for the continually recurring presence of that tissue which he 

 (Mr. Bowerbank) has described as, and still believes to be, por- 

 tions of the skeleton of the sponge, to which the great mass of 

 chalk flints owe their origin." Now any one who has read my 

 former paper will find every one of these questions discussed, 

 both as to the fact of their alleged presence, and as to the pro- 

 bable explanation where present (see pp. 4, 15, 16, &c.). The 

 explanation ofibred by Mr. Bowerbank himself, in his paper in 

 the ' Geol. Trans.,' p. 183, is clearly untenable, requiring as it 

 does the integrity of the entire sponge tissue, an integrity which 

 has never yet been found to exist in a single instance. On the 

 same page (252) I am represented to have described two speci- 

 mens quite difi'erently from my actual expressions, arising from 

 inattention to the grammatical connexion of my sentences ; and 

 am further said to offer no explanation of the fact of the position 

 of certain shells on flint, while on the very page referred to I 

 make an express reference, by note, to an explanation in a later 

 page, which explanation is consistent with all known facts, though 

 it happens to be in direct antagonism with the sponge theory. 

 On the same page I am said to speak of a " nodule of water," 

 an absurdity which is certainly nowhere to be found in my 

 paper. 



On page 253 I am represented to consider as " very impro- 

 bable," and to indulge in certain "fallacies of imagination" 

 respecting, certain habits of sponges, which are so familiar to 

 every one that it never occurred to me to be necessary even to 

 allude to them ; much less did I doubt them. 



