Critiques and Addresses eBook

This eBook from the Gutenberg Project consists of approximately 350 pages of information about Critiques and Addresses.

Critiques and Addresses eBook

This eBook from the Gutenberg Project consists of approximately 350 pages of information about Critiques and Addresses.

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.

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Critiques and Addresses from Project Gutenberg. Public domain.