I AM glad to be able to assure Mr. Searles Wood that I have long been familiar with the specimen called Palœocetus sedgwicki, preserved in the Woodwardian Museum at Cambridge, and have repeatedly examined it with much interest. It is undoubtedly Cetacean, and allied to the genus Balœnoptera, as Mr. Seeley demonstrated, though differing in smaller size and some other characters from any existing species. As, however, the light it throws upon the evolution of the Cetacea is very small compared to the time that would have been taken up in discussing its bearings, I did not think it worth while to allude to it in a lecture of which the length was necessarily limited. It is, after all, a most unsatisfactory fragment, as its geological age is, and probably always will remain, a matter of doubt. Allowing, however, the utmost antiquity assigned to it, my argument would rather be strengthened than weakened. Mr. Searles Wood seems to have missed the fact that my chief contention was against the prevalent view that the Cetacea have been derived from the Carnivora through the Seals. Any evidence which throws back their origin in time and derives them from some more generalised type of mammals would militate against this view. No one can suppose that the Ungulata originated at the commencement of the Tertiary period, as we know that they were then already differentiated into great and distinet sections. Their primitive ancestry must therefore be looked for far back in Mesozoic times. That I thought the Cetacea existed before the Tertiary periad I distinctly intimated by suggesting, as an explanation of the absence of their remains in the chalk, that they might then have been inhabitants of great inland waters, but having had so many warnings of the fallacy of negative evidence in geology, I do not yet despair of the discovery of a veritable Cretaceous whale.