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He perceived himself wordless, and Ethel was about to speak. He glared about him, seeking a prompt climax. Instant action was necessary. He perceived Huxley's Vertebrata upon the side-table. He clutched it, swayed it through a momentous arc, hurled it violently into the empty fireplace. For a second he seemed to be seeking some other missile.
Here the upright lines, 1, 2, 3, 4, 5, may represent the comparative height and grade of organization of both the five sub-kingdoms, and the five classes of each of these; 5 being the vertebrata in the one case, and the mammalia in the other.
Turning to the Vertebrata, the only palæozoic Elasmobranch Fish of which we have any complete knowledge is the Devonian and Carboniferous Pleuracanthus, which differs no more from existing Sharks than these do from one another.
In accordance with this view it seems, if we turn to geological evidence, that organisation on the whole has advanced throughout the world by slow and interrupted steps. In the great kingdom of the Vertebrata it has culminated in man.
"From these lowest Vertebrata to the highest, and to the highest forms among these, the comparison between the embryonic conditions of the higher animals and the adult states of the lower can be more completely and thoroughly instituted than if the survey is extended to the Invertebrata, inasmuch as the latter are in many respects constructed upon an altogether too dissimilar type; indeed they often differ from one another far more than the lowest vertebrate does from the highest mammal; yet the following pages will show that the comparison may also be extended to them with interest.
She certainly belonged to the same mammiferous division of vertebrata as Mrs. Beaudesart, but there the affinity ended with a jerk. In a word, she was the low-born daughter of a late poverty-stricken Victorian selector. Her father, after twelve years' manful struggle with a bad selection, had hanged himself in the stable; whereupon the storekeeper had sold the movables, and the mortgagee the farm.
"No," I told Conseil, "that's no mermaid, it's an unusual creature of which only a few specimens are left in the Red Sea. That's a dugong." "Order Sirenia, group Pisciforma, subclass Monodelphia, class Mammalia, branch Vertebrata," Conseil replied. And when Conseil has spoken, there's nothing else to be said. Meanwhile Ned Land kept staring.
When, however, we come to the Arthropoda and Vertebrata, even to the lowest classes in these two great Sub-Kingdoms, sexual selection has effected much. In the several great classes of the animal kingdom, in mammals, birds, reptiles, fishes, insects, and even crustaceans, the differences between the sexes follow nearly the same rules.
But no such reply can be made to the argument that whereas the marine vertebrata of the Palæozoic period consisted entirely of cartilaginous fishes, the marine vertebrata of later periods include numerous genera of osseous fishes; and that, therefore, the later marine vertebrate faunas are more heterogeneous than the oldest known one.
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.
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