I should, be disposed to interpret the facts of the embryological history and of the anatomy of the _Arthropoda_ in a different manner. The _Copepoda_, the _Ostracoda_, and the _Branchiopoda_ are the _Crustacea_ which have departed least from the embryonic or _Nauplius_-forms; and, of these, I imagine that the _Copepoda_ represent the hypothetical _Archicarida_ most closely. _Apus_ and _Sapphirina_ indicate the relations of these Archaeocarids with the _Trilobita_, and the _Eurypterida_ connect the _Trilobita_ and the _Copepoda_ with the _Xiphosura_. But the _Xiphosura_ have such close morphological relations with the _Arachnida_, and especially with the oldest known Arachnidan, _Scorpio_, that I cannot doubt the existence of a genetic connection between the two groups. On the other hand, the _Branchiopoda_ do, even at the present day, almost pass into the true _Podophthalmia_, by _Nebalia_. By the _Trilobita_, again, the _Archicarida_ are connected with such _Edriophthalmia_ as _Serolis_. The _Stomapoda_ are extremely modified _Edriophthalmia_ 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_.