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.