of the
amphipod type. On the other side, the _Isopoda_ lead to the
_Myriapoda_, and the latter to the _Insecta_. Thus the Arthropod
phylum, which suggests itself to me, is that the branches of the
_Podophthalmia_, of the _Insecta_ (with the _Myriapoda_), and of the
_Arachnida_, spring separately and distinctly from the Archaeocarid
root--and that the _Zoaea_-forms occur only at the origin of the
Podophthalmous branch.

The phylum of the _Vertebrata_ is the most interesting of all, and is
admirably discussed by Professor Haeckel. I can note only a few points
which seem to me to be open to discussion. The _Monorhina_, having
been developed out of the _Leptocardia_, gave rise, according to
Professor Haeckel, to a shark-like form, which was the common stock
of all the _Amphirhina_. From this "Protamphirhine" were developed, in
divergent lines, the true Sharks, Rays, and _Chimaerae_; the Ganoids,
and the _Dipneusta_. The _Teleostei_ are modified _Ganoidei_. The
_Dipneusta_ gave rise to the _Amphibia_, which are the root of all
other _Vertebrata_, inasmuch as out of them were developed the first
_Vertebrata_ provided with an amnion, or the _Protamniota_. The
_Protamniota_ split up into two stems, one that of the _Mammalia_, the
other common to _Reptilia_ and _Aves_.

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 Shark