is in favour of the view that the succession of life-forms upon the globe has been to a large extent regulated by some orderly and constantly-acting law of modification and evolution.  Upon no other theory can we comprehend how the fauna of any given formation is more closely related to that of the formation next below in the series, and to that of the formation next above, than to that of any other series of deposits.  Upon no other view can we comprehend why the Post-Tertiary Mammals of South America should consist principally of Edentates, Llamas, Tapirs, Peccaries, Platyrhine Monkeys, and other forms now characterising this continent; whilst those of Australia should be wholly referable to the order of Marsupials.  On no other view can we explain the common occurrence of “intermediate” or “transitional” forms of life, filling in the gaps between groups now widely distinct.

On the other hand, there are facts which point clearly to the existence of some law other than that of evolution, and probably of a deeper and more far-reaching character.  Upon no theory of evolution can we find a satisfactory explanation for the constant introduction throughout geological time of new forms of life, which do not appear to have been preceded by pre-existent allied types; The Graptolites and Trilobites have no known predecessors, and leave no known successors.  The Insects appear suddenly in the Devonian, and the Arachnides and Myriapods in the Carboniferous, under well-differentiated and highly-specialised types.  The Dibranchiate Cephalopods appear with equal apparent suddenness in the older Mesozoic deposits, and no known type of the Palaeozoic period can be pointed to as a possible ancestor.  The Hippuritidoe of the Cretaceous burst into a varied life to all appearance almost immediately after their first introduction into existence.  The wonderful Dicotyledonous flora of the Upper Cretaceous period similarly surprises us without any prophetic annunciation from the older Jurassic.

Many other instances could be given; but enough has been said to show that there is a good deal to be said on both sides, and that the problem is one environed with profound difficulties.  One point only seems now to be universally conceded, and that is, that the record of life in past time is not interrupted by gaps other than those due to the necessary imperfections of the fossiliferous series, to the fact that many animals are incapable of preservation in a fossil condition, or to other causes of a like nature.  All those who are entitled to speak on this head are agreed that the introduction of new and the destruction of old species have been slow and gradual processes, in no sense of the term “catastrophistic.”  Most are also willing to admit that “Evolution” has taken place in the past, to a greater or less extent, and that a greater or less number of so-called species of fossil animals are really the modified descendants of pre-existent forms. How this