The whole of these ultimate assortments, however, are dependent, as it were, for their outline, upon contingency or chance; and we must not deduce our ideas of genera from the examples which _they_ supply. We should rather reflect, that it is no matter of mere speculation, that many organic links, now absent, have, through the crises and occurrences to which we have just drawn attention, become lost. On the contrary, indeed, we know that, in the common course of things, it _must_ have been so; and therefore we are induced to regard those cases as exceptional, and as in no way expository of Nature's universal scheme. The more we look into the question, whether by the light of analogy or the evidence of facts, the more are we convinced that lines of rigid demarcation (either between genera or species, though especially the former) do not anywhere, except through accident, exist. And hence it is that we ascend, by degrees, to a comprehension of that _unity_ at which I have already glanced; and are led to believe that, could the entire living panorama, in all its magnificence and breadth, be spread out before our eyes, with its long-lost links (of the past and present epochs) replaced, it would be found, from first to last, to be complete and continuous throughout,--a very marvel of perfection, the work of a Master's hand. FOOTNOTES: [78] "Nullo modo fieri potest, ut axiomata per argumentationem constituta ad inventionem novorum operum valeant; quia subtilitas naturae subtilitatem argumentandi multis partibus superat. Sed axiomata a particularibus rite et ordine abstracta, nova particularia rursus facile indicant et designant; itaque scientias reddunt activas."--_Novum Organum_, Aphoris. xxiv. [79] In selecting this simple method to illustrate the _principle_ of a binomial system of nomenclature, it is scarcely necessary to remind the reader that I do not intend to imply that every man is _specifically distinct_ from his neighbour! [80] Considerations sur un Nouveau Systeme de Nomenclature, par C. J. B. Amyot (_Rev. Zool._, p. 133, A.D. 1838). [81] I may add, that this suggestion, as to the evenly balanced state of generic types, is in accordance with the views of Mr. Waterhouse,--whose extensive knowledge in the higher departments of zoological science gives a value to his opinion, especially on questions such as these, which I am glad to have an opportunity of acknowledging. [82] Annals of Nat. Hist. (2nd series), xiv., p. 199.