Origin of Species Variorum

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 advanced or retrograded in organisation. To attempt to compare in the scale of highness members of distinct types seemed hopeless: who will decide whether a cuttle-fish be higher than a bee— that insect which the great Von Baer believed to be "in fact more highly organised than a fish, although upon another type"? In the complex struggle for life it is quite credible that crustaceans, .. not very high in their own class, might beat .. cephalopods, the highest molluscs; and such crustaceans, though not highly developed, would stand very high in the scale of invertebrate animals if judged by the most decisive of all trials— the law of battle. Besides these inherent difficulties in deciding which forms are the most advanced in organisation, we ought not solely to compare the highest members of a class at any two .. periods— though undoubtedly this is one and perhaps the most important element in striking a balance— but we ought to compare all the members, high and low, at the two periods. At an ancient epoch the highest and lowest molluscs, namely, cephalopods and brachiopods, swarmed in numbers: at the present time both orders are greatly reduced, whilst other orders, intermediate in .. organisation, have largely increased; consequently some naturalists .. maintain that molluscs were formerly more highly developed than at present; but a stronger case can be made out on the opposite side, by considering the vast reduction of the lowest molluscs, and the fact that our existing cephalopods, though .. few in number, are more highly organised than their ancient representatives. We ought also to compare