the present day, I cannot but put the existence of the common stock from which they sprang far back in the Palaeozoic epoch; and I should apply a similar argumentation to all other groups of animals. IV. Professor Haeckel proposes a number of modifications in Taxonomy, all of which are well worthy of consideration. Thus he establishes a third primary division of the living world, distinct from both animals and plants, under the name of the _Protista_, to include the _Myxomycetes_, the _Diatomaceae_, and the _Labyrinthulae_, which are commonly regarded as plants, with the _Noctilucae_, the _Flagellata_, the _Rhizopoda_, the _Protoplasta_, and the _Monera_, which are most generally included within the animal world. A like attempt has been made, by other writers, to escape the inconvenience of calling these dubious organisms by the name of plant or animal; but I confess, it appears to me, that the inconvenience which is eluded in one direction, by this step, is met in two others. Professor Haeckel himself doubts whether the _Fungi_ ought not to be removed into his _Protista_. If they are not, indeed, the _Myxomycetes_ render the drawing of every line of demarcation between _Protista_ and Plants impossible. But if they are, who is to define the _Fungi_ from the _Algae_? Yet the sea-weeds are surely, in every respect, plants. On the other hand, Professor Haeckel puts the sponges among the _Coelenterata_ (or polypes and corals), with the double inconvenience, as it appears to me, of separating the sponges from their immediate kindred, the _Protoplasta_, and destroying the definition of the _Coelenterata_. So again, the _Infusoria_ possess all the characters of animality, but it can hardly be said that they are as clearly allied to the worms as they are to the _Noctilucae_. On the whole, it appears to me to be most convenient to adhere to the old plan of calling such of these low forms as are more animal in habit, _Protozoa_, and such as are more vegetal, _Protophyta_. Another considerable innovation is the proposition to divide the class Pisces into the four groups of _Leptocardia, Cyclostomata, Pisces_, and _Dipneusta_. As regards the establishment of a separate class for the Lancelet _(Amphioxus)_, I think there can be little doubt of the propriety of so doing, inasmuch as it is far more different from all other fishes than they are from one another. And there is much to be said in favour of the same promotion of the _Cyclostomata_, or Lampreys and Hags. But considering the close relation of the Mudfish with the _Ganoidei_, and the wide differences between the _Elasmobranchii_ and the _Teleostei_, I greatly doubt the propriety of separating the _Dipneusta_, as a class, from the other _Pisces_.