That evolution may occur within a class seems to be quite certain. The case of the Porto Santo rabbits, one of many cited by Darwin or brought to knowledge since his time, will make clear what is meant. Porto Santo is a small island, not far from Madeira, on which a Portuguese navigator, named Zarco, let loose, somewhere about the year 1420, a doe and a recently born litter of rabbits, which we may feel quite sure belonged to one of those domestic breeds which have all been derived from the wild rabbit of Europe known to zoologists as _Lepus Cuniculus_. The island was a favourable spot for the rabbits, for there do not appear to have been any carnivorous beasts or birds to harry them, nor were there other land mammals competing with them for food; and, as a result, we are told that they had so far increased and multiplied in forty years as to be described as "innumerable." In four and a half centuries these rabbits had become so different from any European rabbits that Haeckel described them as a species apart, and named it _Lepus Huxlei_. This rabbit is much smaller than the European form, being described as more like a large rat than a rabbit. Its colour is very different from its European relatives; it has curious nocturnal habits; it is exceedingly wild and untamable. Most remarkable of all, and most conclusive as to specific difference, Mr. Bartlett, the highly skilled head keeper of the London Zoological Gardens, utterly failed to induce the two males which were brought over to those gardens to associate with or to breed with the females of various other breeds of rabbits which were repeatedly placed with them. If the history of these Porto Santo rabbits had been unknown to us, instead of being a matter as to which there can be no doubt, every naturalist would at once have accepted them as a separate species. We need not hesitate, it appears, to do so and to admit that it is a new species which has been produced within historic times and under conditions with which we are fully acquainted. It may, however, be argued, and quite fairly argued, that such a process of evolution, though definitely proved, is a very different thing from such an evolution as would permit of a common ancestry for animals so far apart, for example, as a whale and a rabbit, or perhaps even nearer in relationship, as between a lion and a seal. To discuss this further would require a dissertation on the highly involved question of species and varieties, and that is not now to be attempted. What, however, may be said is that the difficulties presented by what is called phylogeny--that is, the relationships of different classes to one another--are so great as to have led more than one man of science to proclaim his belief that evolution has been poly--and not mono--phyletic. Such is the view which has been enunciated by Father Wasmann, S.J., whose authority on a point of this kind is paramount. It has also been upheld by Professor Bateson, a man widely separated from