Origin of Species Variorum

objections as the above would be fatal to any view which included advance in organisation as a necessary contingent. They would be fatal to my view if Foraminifera, for instance, could be proved to have first come into existence during the Laurentian epoch, or Brachiopods during the lower Silurian formations; for if this were proved, there would not have been time sufficient for the development of these organisms up to the standard which they had then reached. When once advanced up to any given point, there is no necessity on the theory of natural selection for their further continued progress; though they will, during each successive age, have to be slightly modified, so as to hold their places in relation to their changing conditions of life. All such objections hinge on the question whether we have any sufficient knowledge of the antiquity of the world and of the periods when the various forms of life first appeared; and this may be boldly disputed.

The problem whether organisation on the whole has advanced is in many ways excessively intricate. The geological record, at all times imperfect, does not extend far enough back, as I believe, to show with unmistakeable clearness that within the known history of the world organisation has largely advanced. Even at the present day, looking to members of the same class, naturalists are not unanimous which forms are to be ranked as highest: thus, some look at the selaceans or sharks, from their approach in some important points of structure to reptiles, as the highest fish; others look at the teleosteans as the highest. The ganoids stand intermediate between the selaceans and teleosteans; the latter at the present day are largely preponderant in number; but formerly selaceans and ganoids alone existed; and in this case, according to the standard of highness chosen, so will it be said that fishes have