The still-living varieties of the oyster are a miserable remnant of the 255 fossil species from the chalk described in Coquand’s recent work. Professor Flower, in reviewing this monograph, remarks, that ‘with these mollusks, numerous as they are, there are no forms that can fairly be recognized as transitional.’ But inasmuch as the succession in time of these species is well-established by the different zones of the chalk in which they are found, we must either accept some nine or ten successive creations concerned in the production of oysters, or we must allow the various fossil species to be connected with one another by descent. Upon the latter alternative, a whole chain of transitional links must once have existed between the earliest form of oyster and the latest; and though many of these links have been preserved, still more must have been lost, or deprived of their distinctive features; so that here, where the geological record is, to all appearance, unusually perfect, its actual imperfection is more clearly than ever established.
To conclude, then, in few words:—The majority of dead creatures never become fossils at all.
The majority of fossils perish miserably in their hiding-places.
Of those that are saved, the majority cannot be got at by man.
Of those that can be, the majority never are.
Of those that are, a large number prove illegible; a large number are fragments; a large number duplicates; and, lastly, a large number fall into hands which again lose or destroy them.
We cannot therefore argue, because fossils of such-and-such forms of life have never been found, that such-and-such forms never existed. They may have existed, and left no fossils. The fossils may have been left, and subsequently destroyed. The fossils may be undestroyed, but never have been found. The sum-total of acquisitions is small, but precious; it never can make a complete record, but it may make one sufficiently ample to establish the Darwinian Theory, or to replace it by some still wider and still simpler generalization.