"That I have not troubled myself to reply to the reiterated arguments in favour of the doctrine [of mineral origin] advanced by Professors King and Rowney on the strength of the occurrence of undoubted results of mineralization in the Canadian Ophite, and of still more marked evidences of the same action in other Ophites, has been simply because these arguments appeared to me, as I thought they must also appear to others, entirely destitute of logical force. Every scientific palæontologist I have ever been acquainted with has taken the _best_ preserved specimens, not the _worst_, as the basis of his reconstructions; and if he should meet with distinct evidence of characteristic organic structure in even a very small fragment of a doubtful form, he would consider the organic origin of that form to be thereby substantiated, whatever might be the evidence of purely mineral arrangement which the greater part of his specimen may present,--since he would regard that arrangement as a probable result of _subsequent_ mineralization, by which the original organic structure has been more or less obscured. If this is _not_ to be our rule of interpretation, a large part of the palæontological work of our time must be thrown aside as worthless. If, for example, Professors King and Rowney were to begin their study of Nummulites by the examination of their most mineralized forms, they would deem themselves justified (according to their canons of interpretation) in denying the existence of the tubulation and canalization which I described (in 1849) in the N. lævigata preserved almost unaltered in the London Clay of Bracklesham Bay.