The only modification which it occurs to me to suggest in this general view of the Phylogeny of the _Vertebrata_ is, that the "Protamphirhine" was possibly more ganoid than shark-like. So far as our present information goes the Ganoids are as old as the Sharks; and it is very interesting to observe that the remains of the oldest Ganoids, _Cephalaspis_ and _Pteraspis_, have as yet displayed no trace of jaws. It is just possible that they may connect the _Monorhina_, with the Sturgeons among the _Amphirhina_. On the other hand, the Crossopterygian Ganoids exhibit the closest connection with _Lepidosiren_, and thereby with the _Amphibia_. It should not be forgotten that the development of the Lampreys exhibits curious points of resemblance with that of the _Amphibia_, which are absent in the Sharks and Rays. Of the development of the _Ganoidei_ we have unfortunately no knowledge, but their brains and their reproductive organs are more amphibian than are those of the Sharks. On the whole, I am disposed to think that the direct stem of ascent from the _Monorhina_ to the _Amphibia_ is formed by the Ganoids and the Mudfishes; while the Osseous fishes and the Sharks are branches in different directions from this stem. What the _Protamniota_ were like, I do not suppose any one is in a position to say, but I cannot think that the thoroughly Lacertian _Protorosaurus_ had anything to do with them. The reptiles which are most amphibian in their characters, and therefore, probably, most nearly approach the _Protamniota_, are the _Ichthyosauria_ and the _Chelonia_. That the _Didelphia_ were developed out of some ornithodelphous form, as Professor Haeckel supposes, seems to be unquestionable; but the existing Opossums and Kangaroos are certainly extremely modified and remote from their ancestors the "_Prodidelphia_," of which we have not, at present the slightest knowledge. The mode of origin of the _Monodelphia_ from these is a very difficult problem, for the most part left open by Professor Haeckel. He considers the _Prosimiae_, or Lemurs, to be the common stock of the _Deciduata_, and the _Cetacea_ (with which he includes the _Sirenia_) to be modified _Ungulata_. As regards the latter question, I have little doubt that the _Sirenia_ connect the _Ungulata_ with the _Proboscidea_; and none, that the _Cetacea_ are extremely modified _Carnivora_. The passage between the Seals and the _Cetacea_ by _Zeuglodon_ is complete. I also think that there is much to be said for the opinion, that the _Insectivora_ represent the common stock of the _Primates_ (which passed into them by the _Prosimiae_), the _Cheiroptera_, the _Rodentia_, and the _Carnivora_. And I am greatly disposed to look for the common root of all the _Ungulata_, as well, in some ancient non-deciduate Mammals which were more like _Insectivora_ than anything else. On the other hand, the _Edentata_ appear to form a series by themselves.